Note: Descriptions are shown in the official language in which they were submitted.
- ~692~1
-- 1 --
This application is a division of Serial No. 334,619,
filed August 27, 1979.
The present invention relates ~o hollow microspheres
formed from organic film forming materials. Preferably, the
organic ~ilm forming material is plastic and the invention is
hereinafter described in that context.
The present invention also relates to hollow plastic
microsphereshaving a thin t~ansparent metal coating deposited
on the inner wall surface of the microsphere.
The present invention also relates to hollow
plastic microspheres having a thin re1ective
metal coating deposited on the inner wall sur-
face of the microsphere.
The present invention furt~er relates
to the use o ~he hollow plastic microspheres in
the manufacture of improved insulation materials
for use in construction of homes, factories
and of~ice buildings and in the manufacture o~
products in which heat baxriers are desired or
necessary.
The present invention furth~r relates
; to the use o~ the hollow plastic microspheres as
filler materials in s~ntactic foam systems.
The hollow plastic microspheres of the pre-
sen~ invention, depending on their diame~er anà
the,r wall ~hickness and the particular compo-
sition from which they are made, are capable o
withstanding rela~ively hign e~ternal pressures
and/or weigh~. Hollow plastic microspheres can
be made tnat are -esistant to re~tively ~ign tem~eratures
and stable to many chemical agents and wea~hering
conditions. These characteristics make the
microspheres suitable for a wide variety of uses.
~,
3 2 ~ 1
BACKGROUND OF THE INVENTION
_
In recent years the substantial increases in
costs of basic materials such as plastics, cement,
asphalt and the li'~e has encouraged development and
use of filler materials to reduce the amount and
cost of the basic materials used and the weight
of the finished materials.
The substantial increases in the energy costs
of hea~ing and cooling has encouraged the develop-
ment of new and be~ter insulation materials andmany new insulation materials and insulating
systems usin~ the new materials have been developed
in an attempt to satisfy these needs.
One o~ the newly suggested filler materials
and insulating materials utilizes hollow plastic
microspheres. The known me~hods for producing
hollow plastic microspheres, however, have not
been.successful in producing microspheres of
uniorm size or uniform thin walls which makes
it very difficult to produce filler and insu-
lation materials of controlled and predictable
physical and chemical characteristics and
quality. Also, the relatively high cost and the
re~latively small size of tne prior art microspheres
25 has limi~ed their use.
One of the existing methods o producing
hollow plastic microspheres, for example, as
disclosed i~ ~he Veatch et al U.S. Patent
2,797,201, is to disperse a liquid or solid gas-
phase precursor material ~n a plastic material~o be blown to form the microspheres. The plastic
material containing the solid or liquid
gas-phase precursor enclosed therein is
then neated to convert the solid or
liquid gas-phase precursor material into a
gas and is ~urther heated to expand the gas
9211
- 3
and produce the hollow plastic microsphere con-
taining therein the e~panded gas. This process
is, understandably, difficul~ to control and
inherently produces plastic microspheres of
random size and wall thickness, microsphPres
with walls that have sections or portions of
the walls ~ha~ are rela~ively thin, walls that
have hole~, small trapped bubbles, trapped or
dissolved solvents or gases, any one or more
of which will result in a substantial weakening
of the microspheres~ and a substantial pro-
portion o~ the microspheres which are not
suitable for use and must be scrapped or recycled.
. Further, the use o~ conven~ional fiberglass
insulation is being ques~ioned in the light of
the recently discovered possibili~y that~riber-
glass of certain particle size may be carcino-
genic in the same or similar manner as asbestos.
The use of polyurethane foams, urea~formaldehyde
foams and oolystyrene oams as insulating ma~erials
have recently been criticized because of their
dimensional and chemical instability, for
example, a tendency to shrink and to evolve
the biowing gases such as Freon and to evolve
unreacted gases such as formaldehyde.
In addition, in some applications, the use
of low density microspheres presents a serious
problem because they are difficult to handle
since they are readily elutriated and tend to
blow about. In situations of this type, the
filamented microspheres of the presen~ invention
provide a convenient and safe method o~ handling
the microspheres.
g~l ~
-- 4
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention, there are provided
hollow organic film forming material microspheres of substantially
uniform diameter of 200 to 10,000 microns and of substantially
uniform wall thickness of 0.1 to 1,000 microns, wherein said
microspheres are free of latent solid or liquid blowing gas
materials or gases and the walls of said microspheres are
substantially free of holes, relatively thinned wall portions
or sections and bubbles.
According to a further aspect of the present invention,
there are provided filamented, hollow inorganic film forming
material microspheres having a diameter of 200 to 10,000 microns,
having a wall thickness of 0.1 to 1,000 microns, wherein said
microspheres are connected to each other by filament portions
which are continuous with the microspheres and are of the same
organic film forming material from which the microspheres are
made.
Preferably the organic film forming material is plastic
and, as stated above, the invention i5 discussed herein in that
context.
~ ~92~ 1
The microspheres can be made ro~ a low heat
conductivity plascic composi~lon and can contain
a low heat cond~ctivity gas. The micros?heres
can also be made to contain a thin metal coating
deposited on the inner wall surface of the micro-
spheres. The metal coating, depending on i~s
thic~ness, can be transparent or reflective. The
use of a reflective metal coating i~proves the
insulating and heat reflecting characteristies
of the microspheres.
The plastic microspheres of tne present inven-
tion can be used to form a heat barrier by using
them to ill void spaces between existing walls
or o~her spaces and by forming them into sheets
or other shaped forms ~o be used as insulation
barriers. When used to form insulation barriers,
the interstices between the microspheres can be
filled wi~h a low hea~ conductivity gas, a foam
or other material all of which increase the heat
~ 20 insulation characteristics of ~he materials ~ade
`~ from the microspheres.
In one embodiment of the invention, the micro-
spheres are coated with an adhesîve or Loam filler
and flat~ened to an oblate spheroid or a generally
cellular shape. The microspheres are held in the
~latt~ned position until the adhesive hardens
and/or cures after which the microspheres retain
-- their fla~tened shape. The use of the flattened
microspheres substan~ially reduces the -volume of
the interstices between ~he microspheres and
significantly improves the ~hermal insulating
characteristics of the microspheres.
ne microspheres can be made from plastic
composi~ions selected for their desired optical
and chemical properties and for the particular
gaseous material to be contained therein.
2 1 1
-- 6 --
Where a gas con~aining dispersed metal
particles i5 used to blow ~he microspheres, a
metal layer is deposited on the inner wall sur-
ace of the microsphere as a thin metal coating.
Where a gaseous organo metal compound is used
to deposit the me~al layers, a gaseous organo
metal compound is used as or wi~h the blowing gas
to blow the microspheres. The organo metal com-
pound can be decomposed just prior ~o blowing the
microspheres or after the microsphe~es are for~ed
by, or example, subjecting the blowing gas or the
mie~osp~eres to heat and/or an elect~iczl ~ischarge.
The ilamented microspheres are made in a
manner such that they are connec~ed or atta~ed to each
other by a thin cont;nuous plastic ~ament. ~ne .ilamented
microspheres can be flat~ened to produce the
oblate spheroids. The filaments interrupt and
reduce the area of wall to wall con~act be~een
the microspheres and reduce ~he thermal conducti~
vity between the walls of the microspheres. The
~ilamented microspheres also assist in handling
and preventing scatterin~ of m:icrospheres, particu-
larly whers very small diamete~ microspheres or
low density mic~ospheres are produced. The fila-
mented microspheres have a distinc~ advancage
~ver th~ simple addition of ilaments in ~nat the
continu~us filamen~s do not tend to se~tle in ~e systems in
which they are used.
~ E ADVANTAGES
The present invention overcomes many of the
problems associated with prior at~empts to produce
hollow plastic microspheres- The invention allows the
production of hollow plastic microspheres having
1 1~9?,1 1
predetermined characteristics such ~haL improved
- filler materials and insulating materials and
insulating sys~ems can be designed, manuactured
and tailor made to suit a par~icular desired use7
The diameter and wall thickness uniformity, and
the ther~al, strength and chemical resistance
characteristics of the plastic microspheres can
be determined by carefully selecting the plastic
and constituents of ~he plastic composition and
con~rolling the blowing gas pressure and tempera-
: ture, and the temperature, viscosity and thickness
of the liquid plastic film from which the micro-
spheres are formed. The inner volume of the
microspheres may con~ain an inert low heat con-
ductivity gas used ~o blow the ~icros~here. The
; hollow plastic microspheres of ~he presen~ inven-
tion can have a transparent metal co2ting de~osited
: on the inner wall surface ~hereof which allows
visual light to pass ~hrougn ~he microspheres
but reflects and traps infrared radiations. The
holl QW plas~ic microspheres can also h2~e a low
:: emissivi~y reflec~ive metal coating depo~ited on
: the inner wall surface of ~he microsphere whicn
effectively re~l~.cts visual light and radiant
: hea~ energy.
The invention ~rovides a practical and economical
means by which hollow plastic microspheres having a
: high heat insulation eficiency can be utilized
to prepare a relatively low cos~ e ficient insu-
lating material for common every day uses. The
present in~ention also allows the economic pro-
. duction of hollow plas~ic microspheres from plas-
: ~ic compositions which incor~orates a metallic
ra ~ ticn barrier and can be used as an ~sula~lon ~a~erial.
~l ~6(~2
-- 8
The process and apparatus aspects of the present
invention, as compared to the prior art processes
of using a latent liquid or .solid blowing agent,
can be conducted at higher temperatures sin~e
there is no included expandible and/or decom-
posable blowing agent used. The ability ~o use
higher blowing ~empera~ures resul~s in for
particular plastic composi~ions a lower vis-
cosity or ~he plastic composition which allows
surface tension forces to produce significantly
greater uniformi~y in wall thickness, sp~ericity
and diameter o the microspheres produced.
The presen~ invent~on also allows the
use of a wide variety of blowing gases and/or
blowing gas materials. In accordance wiLh the
present invention, a wide variety of gaseous
material blowing gas can be encapsulated, i.e.
i~ is no longer requir~d to use a latent liquid
or solid blowing agent as the blowing gas.
The invention provides for the production of
hollow plastic microspheres at economic prices and in
: large quantities. The invention allows the production
o hollow plastic microspheres having predetermined
diameters, wall thicknesses, strength and resistance to
chemical agents and weathering and gas permeability
such that superior systems can be designed, manufactured
and tailor made to suit a particular desired use.
3~
9~ 92~1
B~IEF DESCRIPTION OF THE DR4WINGS
The attached drawings illustrate exemplary forms of
a method and apparatu~ for making microspheres
for use in and às filler materials and for use
in and as insulating materials.
The Figure 1 o~ the drawings shows in
cross-sec~ion an apparatus having mult-iple
coa~ial blowing nozzle means for supplying the
gaseous material for blowing hollow plastic
mierospheres, a ~rans~erse ~et providing an
entraining fluid to assist in the form~tion
and de~ac~ent OL ~he microspheres from the
blowing nozzles, and means for supplying
a quench or heating LlUid tc cool or heat
;he microspheres.
T'ne Figure 2 of the drawings is an.enlarged
de~ailed c_oss-sec~ion of the nozzle means o
apparatus sho~-n in Figure L.
`
,:.
~ 1~92~ 1
-- 10 --
The Figure 3 of the drawings is a detailed
cross-section of a modified form o the nozzle
means shown in Figure 2 in which the lower end
of the nozzle means is ~apered inwardl~.
The Figure 3a of the drawings is a detailed
cross-section of a modified transverse jet
entraining means having a 1attened ori~ice
opening and the Figure 3 nozzle means.
The Figur~ 3b of the drawings is a top
plane view of the modified transvexse jet
entraining means and the nozæle means illus~rated
in Figure 3a o the drawings.
The Figure 3c of the drawings illustrates
the use of the apparatus of Figure 3b to make
filamented hollow plastic microspheres.
The Figu~e 4 of the drawings is; a detailed
cross-section of a modified form of the nozzIe
means shown in Figure 2 in which the lower por-
tion OL the nozzle i9 enlarge~
~;~ 20 The~Figure 5 of the d~awings shows a cross-
section of an en~ view of a flat plate solar
energy~collector using the~hollow plastic ~icro-~
spheres of the present in~en~ion.
~ ~ The Figure 6 of the drawings shows a c. oss-
;~ section of an end view of a tubular solar energv
collector using;the hoilow plastic microspheres
of the present invention.
The Figure 7 of the drawings shows a cross-
section of spherical shaped hollow plastic micro-
spheres ~ade into a ormed panel.
The Figure 7a of the drawings shows a cross-
sec~ion of oblate spheroid shaped hollow plastlc
microspheres made into a Eormed panel.
The Figure 7b o the drawings shows a cross-
section of oblate spheroid shaped hollow plastic
2 1 ~
filamented microspheres made into a formed panel
in which the ilaments interrupt the microsphere
wall to wall contact.
DETAILED DISCUSSION
OF THE DRAWINGS
The invention will be described with reference
to the accompanying Figures of ~he drawings where-
in like numbers designate li~e parts throughout
the se~eral views.
Referring to Figures 1 and 2 of ~he drawings,
there is illustrated a vessel 1, made or suitable
container material heated, as necessary, by means
not shown for holding a liquid plastic 2. The
bot~om floor 3 o~ vessel 1 contains a plurality
of openings 4 ~hrough whi~ch liquid plastic 2 is
fed to coaxial blowing nozzles 5. T-ne coaxial
blowing nozzle 5 can be made sepa~ately or can be
formed by a downwa-.d extension o the Dottom 3
of vesseI 1. The coaxial blowing nozzle 5 consists
of an inner nozzle 6 having an ori~ice 6a for a
blowing gas and an outer nozzle 7 having an ori ice
7a ~or liquid plastic. T'ne inner nozzle 6 is
disposed within and coa~ial to outer nozzle 7 to
form annular space 8 be~ween nozzles 6 ~nd 7,
which annular space provides a flow path for
liquid plas~ic. The ori~ice 6a of inner nozzle
6 terminates at or a short distance above ~he
plane of orifice 7a of outer nozzle 7
The liquid plas~ic 2 a~ about at~ospheric
pressure or a~ elevated pressure flows downwardly
through annular space 8 and fllls the area be~ween
orifice 6a and 7a. The surface tension orces
in the liquid plastic 2 from a thin liquid
plas~ic ilm 9 across orifices 6a and 7a.
2 ~ ~
- 12 -
A blowing gas 10 and/or blowing gas containing
dispersed metal particles, which is a~ or below
ambient temperature or which is heated by means
not shown to about the temperature o~ the liquid
plastic and which is at a pressure above the
liquid plastic pressure at the blowing nozzle,
is fed through distribution condui~ 11 and inner
coaxial nozzle 6 and brought into contact with
the inner surace of the liquid plastic film 9.
The blowing.gzs exerts a positive pressure on
the liquid ~lastic film to blow and distend the
~: film outwardly to orm an elongated cylinder
shaped liquid film 12 of plastic filled with the
: blowing gas. The elonga~ed cylinder 12 is
closed at its outer end and is connected at its
;~ inner end to outer nozzle 7 at the peripheral
edge of orifice 7a. A balancing pressure of a
gas or of an inert gas, i.eO a slightly lower
: pressure, is provided in the area of the blowing
nozzle into which the elongated cylinder shaped
liquid ilm is blown. The il~ustrated coaxial
nozzle can be used to produce~microspheres naving
~: : diameters three to :five times the size o~ the
: inside diameter of orifice 7a and is useful in
biowing low viscosity plastic materials.
: A transverse jet 13 is used to direc~ an
iner~ entraining fluid 14, which is at about,
below or above the temperature of the liquid
plastic 2. The entraining fluid 14 is fed
through distribution conduit 15, nozzle 13 and
transverse jet nozzle orifice 13a and directed
at the coaxial blowing nozæle 5. The transverse
jet 13 is aligned to direct the flow of entraining
fluid 14 over and around blowing nozzle 7 in the
~ ~921 1
- 13 -
microsphere forming region at and behind the
orifice 7a. The entraining fluid 14 as it
passes over and around blowing nozzle 5 fluid
dynamically induces a pulsating or fluctuating
pressure field in the entraining 1uid 14 at ~he
opposite or lee side of blowing nozzle 5 in its
wake or shadow.
The entraining fluid 14 envelops and acts
on ~he elongated cylinder 12 in such a manner as
~o and causes ~he cylinder ~o flap, fold, pinch
and close-of at its inner end at a point 16
proximate to the ori~ice 7a of outer nozzle 7.
The continued movement of the entraining fluid 14
over the elongated cylinder 12 produces fluid
drag forces on the cylinder 12 and detaches it
rom the orifice 7a o the outer nozzle 7 to
2110w the cylinder to ~all. The surface tension
forces of the liquid plastic act on the entrained,
ralling elongated cylinder L2 and cause ~he
cylinder to seeX a minimum surace area and ~o
form a spherical shape hollow plastic microsphere
: . 17.
Quench or heating nozzles 18 having oriices
18a are disposed below and on bo~h sides of
coaxial blowing nozzle 5 and direct cooling or
heating'fluid l9 at and in~o contact wi~h the
liquid plastic microsphere 17 ~.o rapidly cool or
; heat and cure and solidify the liquid plas~ic and
form a smooth, hardened, hollow plastic micro-.
sphere. The quench or heating fluid 19 also
serves ~o carry the hollow plastic microspheres
away from the coaxial blowin~ nozzle 5, Su~icient
heating and curing time can be provided by using
a heated fluidized bed, heated liquid carrier
~ ~g2~ 1
- 14 -
or belt carrier system for the thermosetting hollow plastic micro-
spheres to cure and harden ~he microspheres with substantially
little or no distortion or effect on the size or shape of the
microspheres. Where the plastic is thermosetting, the heated
and cured plastic microsphexes can be subsequently cooled. The
solidified and harden~d hollow plastic microspheres are collected
by suitable ~eans not shown.
. In Fi~ure 3 of the drawings, the lower portion of the
outer coaxial nozzle 7 is tapered downwardly and inwardly at 21.
This embodiment as in ~he previous embodiment comprises coaxial
blowing nozzle 5 which consists of inner nozzle 6 wi~h orifice
6a and outer nozzle 6 with orifice 7a'. The figure of the draw-
ings also shows elonga~ed cylinder shaped liquid film 12 with a
pinched portion 16.
The use of ~he tapered nozzle 21 construction was found
to substantially assist in the formation of a thin plas~ic film
9' in the area between ori~ice 6a of inner nozzle 6 and orifice
: 7a' of outer nozzle 7~ The inner wall surface 22 of the taper
portion 21 of the outer nozzle 7 when pressure is applied to
liquid plastic 2 orces the liquid p:Lastic 2 to squeeze through
a fine gap formed between the outer edge of orifice 6a, i.e.,
the ou~ex edge of inner nozzle 6, and the inner surface 22 to
form the thin liquid plastic film 9' across orifices 6a and 7a'.
The ormation of the liquid plastic film 9' ~oes not in this
embodiment rely solely on the surface tension properties of the
liquid plas~icO The illustrated coaxial nozzle can be used to
produce
- 15 - 1~9211
microspheres having diameters three to five times
the size of the diameter of oriice 7a of coaxial
nozzle 7 and allows making microspheres of s~aller
diameter than thosR made using the Figure 2
apparatus and is particularly useful in blowing
high viscosity plastic materials.
. The diame~er of the microsphere is determined
by the diameter of orifice 7a'. This apparatus
allows the use of larger inner diameters of outer
nozzle 7 and larger inner diame~ers Oc inner
nozzle 6, bo~h of which reduce the possibility
o~ plugging of the coaxial nozzles when in use.
These ~eatures are particularl~ advantageous when
the blowing gas contains dispersed metal particles
andlor the plastic compositions contain additive
material par~icles.
In Figures 3a and 3b of the drawings
the outer portion of the transvers~
jet 13 is flattened to form a ~enerally rectangular
or oval shaped orifice opening 13a. The ori~ice
opening 13a can be disposed at an angle relative
~:o a line dra~n ~hrough ~he central axis o~
coa~ial nozzle 5. The preferred angie, however,
is that as illustrated in the drawing. Thac is,
at an angle of about 90 to the central a~is of
the coa-.~ial nozzle 5.
The use of the flattened transverse jet
entraining fluid was found, at a given velocity,
to concentrate the ef~ect of the fluctuating
pressure field and to increase the ampl~ude
of tne pressure fluctuations induced in the region
o the ~ormation of the hollow microspheres at
the opposite or lee side of the blowing nozz7 e 5.
1 ~92~ ~L
- 16 -
By the use of ~he fla~tened transverse je~ and
increasing ~he amplitude oE the pressure fluc-
tuations, the pinching action exerted on the
cylinder 12 is increased. This action facili-
tates the closing of of the cylinder 12 at i~s
inner pinched end 1~ and detaching o the cylinder
13 from ~he oriice 7a o the cent~er nozzle 7.
The Figure 3c of the drawings illustra~es apparatus
in which a hi~h viscosity plastic material
is used to blow 'nollow olas~ic filamented micro-
spheres. In this Figure, the eiong~ted shaped
cyLinder 12 and plastic microspheres 17a, 17b
and 17c are connec~ed to each other by thin
plastic filaments 17d. As can be seen in the
drawin~, as ~he micros?heres 17a, i7b and 17c
progress zway from blowing nozzle ~ surace
tension forces act on the elonga~ed cylinder 12
to effect the gradual change of the elongated
shaped cylinder 12 to t~e generally spherical
shape 17a, more spherical~shape 17b and finally
the spheri~al shape microsphere 17c. The same
surface tension ~orces cause a gradual reduction
- in the diameter Oc the connecting filaments
L7d, as the distance between the microspheres
and filaments and the blowing nozzle 5 increases.
The hollow plastic microspheres 17a, 17b and
17c that are obtai~ed are con~ected by thln
filament portions 17d that are substantially of
~qual length and that are continuous wi~h the
plastic microsphere.
The operation of the apparatus illustra~ed
in Figures 3, 3a, 3b and 3c otnerwise ;han dis-
cussed above is similar to that discussed ~ h
17 ~ 921~
regard to Figures 1 and 2 o ~he drawings.
The Figure 4 of the draw~ngs illustrates
apparatus in which the lower
portion of the coaxial nozzle 7 is provided with
a bulbous member 23 which imparts to the outer
nozzle 7 an expanded spherical shape. This embo-
diment as in the previous embodiments comprises
coaxial blowing nozzle 5 which consists of inner
nozzle 6 with orifice 6a and outer nozzle 7 wi~h
orifice 7a. The Figure of ~he drawings also shows
elonga~ed cylinder shaped liquid film 1~ with
the pinched ~ortion 16.
The use of the bulbous spherical shaped member
23 is found ror a given veloeity o ent~aining
fluid 14 (Figure 2) to subs~antially increase the
amplitude of ~ne pressure 1uctuations included in
the region of the formation of ~he hollow micro-
sPneres 2t the opposi~e or lee side of the blowing
~ozzle ~. By the use of the bulbous member 23
and increasing ~he amplitude of the pressure fluc-
~uations, the pinching action exerted on ~he
elongated cylinder 12 is increased. This action
~acilitates ~he closing of of the cylinder 12 at
its inner pinched end 16 and detaching the cylinder
12 from the orifice 7a of ~he outer noz~le 7.
Referring again to Fi~ure 4 of the
drawings, a beater bar 24 can be used to assist in
detaching the c~Jlinder 12 from ori~ice 7a. The
beater bar 24 is attached to a spindle, not shown,
which is caused to ro~a~e in a manner such that
the beater bar 24 is brought to bear upon the
pinched portion 16 of the elongated cylinder 12
and to thus facilitate ~he closing off of the
92~ 1
- 18 -
cylinder 12 at its inner pinched end 16 and
detaching the cylinder 12 from the orifice 7a o
outer nozzle 7.
The ~p~aratus illustrated
in the Figures 2 to 4 can be used singly or in
various eombinations as the situation may rea,uire.
The en~ire apparatus can be enclosed in a high
pressure containment vessel, no~ shown, which
allows the process to be carried out at elevated
10 pressures.
The Figure ; of the drawings illustrates Lhe
use of the hollo~ plastic microspheres of the
present invention in the cons~ruc~ion of a fla~
pla~e solar energy collector 29. The drawing
shows a cross-section taken ,rom an end view OL
the solar collector. The ~uter cover member 30
rotects the solar collector from the weather
elements. The cover 30 can be made ,rom cle~r
giass or plastic. The cover member 30 can also
be made ~rom several layers of light ~ransparent
hollow plastic microspheres of this inventian
; bonded together with a transparen~ polyacrylate
or polymethyl acrylate resin to ~orm a trans-
parent co~er. There is disposed below and ?arallel
~: tO cover 30 a black coated fla~ metal plate
absorber 31 to which there is bonded ~o the
bottom surface thereof a mul~iplicitY or eYenly
spaced heat exchanae medium 32 containin~ tubes
33. The heat exchange medium can, .or example,
be water and the tubes 33 are in~erconnected by
conven~ional means not shown ~o allow for the
flow of ;he heat exchange medium 32 ~hrough ~hn
tubes 33. ~n order to minimize heat loss from
the solar collector and increase its eficiency,
~he space between ~he outer cover 30 and ~'ne rlat
11~92~1
- 19 -
plate absorber 31 can also be filled with a bed
o li~ht transparent hollow plastic microspheres
34 of the present invention. The solar coll~ctor
29 has an inner cover member 35 by means of which
the collector can be at~ached to a roof 36 of a
home. To ~urther decrease the heat loss o~ the
solar collector and increase its efficiency, the
space between the lower surace of the flat plate
absorber 31 and the inner cover member 35 can be
~illed with reflective hollow plast~c microspheres
39 containing on the inner wall surface thereof
a visible light and infrared radiation reflective
metal coating. The end members 37 and 38 of the
solar collec~or 29 close-off the top and bottom
edges of the collector.
The construc~ion and operation of the flat
plate solar collector are other~-ise essentially
the same as the know flat plate solar collector.
~; ~ The Figure 6 or the drawings illustrates the
; 20 use of the hollow plastic microspheres of the
prese~t invention in the construction of a tubular
solar energy collector 43. The drawing shows a
c~oss~section taken ~rom an end view of the solar
collector. The outer cover member 44 can be made
rom clea~ gl~ss or plastic. The cover member 44
can als,o be made from several layers of light
transparent hollow plastic microspheres o~ this
invention bonded toge~her wi~h a trans~parent
polyester or polyolefin resin to form a trans-
parent cover. There is disposed below and paralleIto cover 30 a double pipe tubular member 45.
The tubular member 45 consists of an inner feed
tube 46 and an outer return ~ube 47. The heat
exchange medium 48, for example water, is fed
through inner feed tube 46, passes to one end of
2 ~ ~
the tube where it reverses its direction of flow,
by means not shown, and ~he heat exchange medium
49 (return) passes back through the return tube
47. The inner feed tube 46 is coaxial to ~he
outer return tube 47. The outer return tube 47
has on its outer surface a black heat absorbing
coating. The heat exchange medium in passing
through feed tube 46 and return tube 47 is heated.
The tubular collector 43 has outer parallel
side covers 50 and a lower outer curved cover
portion 51. The lower curved cover portion 5L
is concentric with the inner tube 46 and outer
tube 47. The inner surface of the lower portion
51 is coated with a reflecting material 52 such
that ~he sun's rays are re~lec~ed and~concentrated
in the direction of the~black heat absorbing
surface coating of return tube 47. In order to
minimiæe heat loss from the solar collector and
increase its erficiency, the entire area between
the outer covers 44, 50 and 51 and the return
tube 47 can be filled with a bed of the visible
ligh~ transparent hollow~plas~ic microspheres 54
of the present invention.
The tubular solar collector 43 is normally
mounted in groups in a manner such tha~ they
intercept the movement of the sun across the sky.
The sun's rays pass through the tra~sparent micro-
spneres 54 and impinged directly on the outer side
of the return tube 47 and are reflected by
reflector 52 and impin~ed on the lower side of
; return tube 47.
The construction and operation of the tubular
solar collector are othe~ise essentially the same
as the known tubular solar collectors.
~ ~692~ 1
- 21
The Figure 7 o~ the drawings illustrates the
use of the hollow plastic microspheres of the
present invention in the construction of a formed
panel 61. The panel contains mul~iple layers of
uniform sized plastic microspheres 62. The micro-
spheres can have a thin deposi~ed layer 63 o~ a
re1ecting me~al deposited on their inner wall
surface. The internal volume of the microspheres
can be filled with a low heat conductivity gas 64
and the interstices 65 between the microspheres
can be filled with the same gas or 2 low heat
conductivity foam containing a low heat conductivi~y
gas. The acing surface 66 can be coated with a
thin layer of plaster suitable for subsequent
sizing and painting and/or covering wi~h wall
paper. The backing surface 67 can be coated ~ith
the same or different plastic from wh~ch the
microspheres are made ~o form a vapor barrier
or with plaster or with both materials.
The Figure 7a of the drawings illustrates
the use o~ the hollow plastic microspheres OL- the
present invention in the construction of a for~ed
panel 71. The panel contains multiple layers of
uniform sized 1at~ened obla~e spheroid or rec-
tangular shaped microspheres 72. The oblate
spheroid shaped microspheres can have an inner
thin deposi~ed layer 73 of a re~lective me~al.
The internal volume of the microsphere can be
filled with a low heat conductivity ~as 74. The
Llattened coni~uration of the microspheres sub-
stantially reduces ~he volume o the inters~ices
~etween the microspheres which can be filled with
a low hea~ conductivi~y foam 75. The facing 76
can be coated with a thin Layer of plaster
suitable for subsequent sizing and painting
~ ~6921 ~
-22
and/or covering with wall paper. The backing sur-
face 77 can be coated with the same or different
plastic from which the microspheres are made to
; ~orm a vapor barrier or with plaster or with both
; materials.
The Figure 7b of the drawings illustrates an
e~bodiment of the formed wall panel of Figure 7a
in which fil~ted hollow plastic microspheres connected by very
thin plastic filamen~s 78 are used. The thi.n
plastic filaments 78 are formed bet-~een adjacent
microspheres when and as the microspheres are
blown and jo~n the microspheres together. T'ne
connecting il~ments 78 in ~he formed panel
interrupt the wall tQ wall contact, i.e. ~he contact
between ~he microspheres and serve to substantially
reduce the conduction heat transfer between adja-
; cent microspheres. The use of filamented micro-
spheres to provide the interrupting filaments
is particularly ad~antageous and preferred
becausa the filaments are posl~ivel-r evenly
dist~ibuted, cannot settle, are supplied in the
desired con~rolled amountJ and in the formed
panel provide an interloc~ing structure which
serves to strengthen the formed panel. The
~acing 76, as before, can be coated with a
thin layer o~ plaster suitable ror subsequent
sizing znd painting and/or covering with wall
~ paper. The backing surface 77 can be coa~ed
; ~ith the same or diferent plas~ic fro~ which
30 the microspheres are made to form a vapor
barrier or with plaster or with both materials.
:~692:L1
23
ORGANIC FILM FO~MING ~ATERIAL
AND PLASTIC COMPOSITIONS
The organic film forming material and compositions
and particularly the plastic composi~ions rom which
the hollow plastic microspheres of ~he present
invention are made can be widely varied to obtain
the desired physical characteristics for blowing
and forming, cooling or heating and curing the
microspheres and the desired neat ins~la~ing,
strength, gas permeability and light trasmission
characteristics o~ the plastic microspheres ~roduced.
The plastic composi~ions can be selected to
have a low heat conductivity and sufficient strength
when hardened, solidified and cured to support a
substantial amount of external pressure or weight.
The constituents of the plastic compositions c2n
vary widely, depending on their intended use and
can inolude naturally occu~ring resins as well
as synthetically produced plas~ic materials.
The cons~ituents of the plastic com~ositions
can be selected and blended to have 'nigh resis-
tance to orrosive gaseous materlals, hign
resistance to gaseous chemical agen~s,~ high
resistance to alkali and weather, low suscepti-
bility to diffusion of gaseous materials into
; ~nd out of the plastic microspheres, and to be
substantially free of trapped gas bubbIes or
dissolved gases in the walls or the microspheres
which can form bubbles and to have suficient
strength when cured, hardened and solidified
to withstand external ?ressure and/or weight.
The microspheres of the present invention are
capable of contacting adjacent microspheres with-
out signi~icant wear or deterioration at the
points of contact and are resistant to deterior-
ation from e.~posure to moisture, heat
11692~ 1
- 24 -
and/or weathering.
The plastic compositions that can be used to
form microspheres of the present invention include
thermosetting and thermoplastic materials such as
polyethylene, polypropylene, polystyrene, poly-
es~ers, polyurethanes, plychloro-trifluoro
ethylene, polyvinyl fluoride, polyvinylidene,
polymethyl me~hacrylate acetyl, phenol-formaldehyde
resins and silicone and polycarbonate resins.
The plastic compositions also inclu~e organic
materials such as cellulose ace~ate, cellulose
ace~ate-butyra~e, and cellulose acetate-propiona~e.
The plastic compositions may consist essentially
of the plas~ic material or may contain the
plasti~ material dissolved or dispersed in a
suitable solvent.
Thermoplastic synthetic resins that can ~e
used are polyvinyl resins, i.e. polyvinyl alcohol
(wa~er- or organic solvent-soluble)~ polyvinyl
chloride, copolymers of vinyl chloride and vinyl
acetate, polyvinyl b~tyral, pol.ystyrene, poly-
~inylidene chloride, acrylic resins such as
polymethyl methacrylate, polyallyL, polye~hylene,
and polyamide (nylon~ resins.
Ther~osetting resins ~hat can be used are
those in ~he thermoplastic water- or organic
solven~-soluble stage of partial polymerization,
the resins being converted after or during
formation of the microspheres into a more or
less fully polymeri7ed solvent-insoluble sLage.
O~her useful resins are alkyd, polysilo~ane,
phenol-~ormaldehyde, urea-formaldehyde and
melamine-~ormaldehyde resins.
~ ~9~ 1
- 25 -
Natural ilm forming materials are also included within
the scope of the form, including soybean pro~ein, zein protein,
alginates, and cel~.ulose in solution as cellulose Xanthate or
cuprammonium cellulose.
The plastic compositions disclosed in Veatch et al
U~S. Patent 2,797,201 and the Morehouse, Jr. U.S. Patent
3,615,972 can also ba used in carrying out the present invention.
There may be added to ~he plastic compositions chemical
agents or addi~ives which effect the viscosity o the compositions
or of the surface film of the microsphere in ordex to obtain the
desired viscosities needed to obtain a s~ahle film for blowing
the microspheres. Suitable chemical agents are materials that
act as sol~ents for the plastic compositions. The solvents that
are used will, of course, depend on the solubility in the solvent
of the plastic composition used. Water, al~ohols, ethers, esters,
organlc acids, hydrocarbons and chlorinated hydrocarbons can be
used as solvents. To assist in the blowing and formation of the
plastic microspheres, surface active agents, such as colloidal
particles of insoluble substances and viscQsity stabilizers can
be added to the plastic composition as additives. These additives
can afPect the viscosity of the surface film of the microsphere
to stabilize the film during film formation.
A distinct and advantageous feature o the present
invention is that latent solid or latent liquid blowing gases
are not used or required and that the microspheres that
2 1 ~
- 26 -
are produced are Xree of latent solid or latent liquid blowing
gas materials or gases.
Additlonal plastic compositions suitable for use in
the present inven~ion are:
Thermoplastic resins: Epoxy resins, phenol~ormaldehyde
resins, and ~elmac;
Other resin compositions are: Elvanol, silicones, and
Te10n.
For a more speaific description of ~he above plastic
and resin compositions see Zimmerman and Lavine, "Handbook of
Material Trade Names", Vols. I-IV, 1953-1965.
The plastic compositions of the present invention are
formulated to have a relatively narrow temperature difference
between ~he liquid ~emperature and the plastic hardening tempera-
ture (thenmoplastic) or a relatively narrow temperature difference
betwe~n the liquid temperature and the ~hermosetting and cuxing
temperature. The plastic compositions are formulated such that
they have a high rate of viscosity increase with the haxdening
temperature or the *hermosetting emperature such that the micro-
sphere walls will solidify, harden and strengthen before theblowing gas within the sphere decreases in volume and pressure
a sufficient amount to cause the microsphere to collapse. Where
it is desirous to maintain a positive pressure in the contained
vo~ume of the microspheres, the permeabili~y of the contained
gases can be decreased in the manner discussed below.
The use o~ Saran plastic compositions is found to pro-
duce microspheres ~hat are useful as filler materials. The poly-
s~yrene plastic compositions can be used to make microspheres for
.
* Trademark
2 1 :1
-27
use as improved insulating materials. The poly-
ethylene plastic compositions can be advantageously
used to make microspheres for use as filler
materials in plasti~ molding compositions. The
polypropylene plastic compositions can be used
to make microspheres for use as aggregate in
concrete.
The plas~ic compositions from which the hollow
plastic microsphere can~be made are, depending on
the particular plastic materials used, to some
degree permeable to the gas materials used to
blow the microspheres and/or to the gases prese~t
in the medium surrounding the microspheres. The
gas permeability of the plastic compositions can
be reduced and~or substantially eliminated by the
addition, prior to blowing ~he ~icrospheres, to
the plas~ic composition of very small inert
lam;nar plane-orientable additive material parti-
cles. Suitable additive partlcles are mica,
graphite and aluminum leaf powders. When any
one or more OL these laminar plane orientable
additive material particles are added to a
plastic composir.ion prior to the blowing and
formation of the hollol~ plastic microspheres,
the process of making the microsphere aligns the
laminar particles, as the plastic film is
stretched in passing, i.e. extruded, through the
conical blowing nozzle, with the walls of the
hollo~ plastic microsphere and normal to the gas
diffusion direction. The presence of the laminar
plane particles in ~he mic-osphere walls substan-
tiallv diminishes the gas permeability of the
plastic f~lm. The sizes of .he additive particles are
92~ ~
- 28 -
advantageously selected to be less than one-half the thickness of
the wall of the microspheres. The gas permeability of certain
plastics may be further diminished or reduced by subjecting the
microspheres to ionization radiation to promote cross-linking
of the plastic molecules.
BL~WING ~S
The hollow plastic microspheres used to make insulating
materials can ~e blown with an inert gas or gas containing dis-
persed me~al particles or a mixture ~hereof. The ya~es that are
used to blow the microspheres are selected to have a low heat
conductivity and generally involve heavy molecules which do not
transfer heat readily. Suitable blowing gases can be argon,
xenon, Freon yases, nitrogen, sulfur and sulfur dioxide. The
~lowing gas is selected to have the desired internal pressure
when cooled to ambient ~emperatures. Blowing gases can also be
selected that react with the plastic microspheres, e.g. to assist
in the hardening and/or curing of the microspheres or to make
the microsphere less permeable to the contained blowing gases~
For certain uses, oxygen or air can be used as or added to the
blowing gas.
A blowing gas containing di~persed metal par~icles can
be used to obtain in ~he contained volume of the microsphere a
deposit of a ~hin metal coating on the inner wall surface of
the hollow p~astic microsphexe. The thickness of metal coating
deposited will determine whe~her the metal coating is trans-
parent or reflective
~ ~&92~:1
_ 29 _
of visible light. The blowing gases can also be
selected to react with ~he deposited thin metal
layer to obtain desired characteristics in the
me~al layer. For example, to reduce the thermal
conductivi~y of the metal layer.
The rnetal used to coat the inner wall surface
of the hollow plastic microspheres is.selected
to have the desired emissivity, low heat conduc-
~ion characteristics, and ~o adhere to the inner
wall surface of the plastic microspheres. The
thickness and the nature of the deposited metal
coating will depend to some extent upon ~.he metal,
the particle size o~ the metal used, the size of
the microsp~ere and the amount of dispersed metal
particles used.
The dispersed metal particle size can be 25A
O O O
to lO,OOOA, preferably 50A to 5,000A and more pre-
ferably lOOA to l,OOOA. A suf~icient amount of
the metal is dispersed in the blowing gas to ob-
~0 tain the desired ~hickness of the deposited metal.The dispersed metal particles can advantageously
be p~ovided with an electrost~tic char~e to
assist in depositing them on the inner wall
surface of the microsp~eres.
Metal particXes such as aluminum, silver,
nickel, zinc, antimony, barium, cadmium, cesîum,
bismuth, selenium, lithium, magnesium, potassium,
and gold can be used. Aluminum, zinc and
nickel, however, are preferred. Dispersed me~al
oxide particles can in a similar manner be used
to obtain similar effects to that or the metals.
In addition, ~he metal oxide particles can be
used to produce a deposited film of lower heat
conductivity characteristics.
- 30 -
The ~hin metal coating can also be deposited
on the inner wall surface of the microsphere by
using as or with blowing gas organo metal
compounds tha~ are gases at ambient temperatures
or that become gases on heating. 0~ the organo
metal compounds available, the organo carbonyl
compounds are pre~erred. Suitable organo metal
carbonyl compounds are nickel and iron.
The organo metal compounds can be decomposed
by heating just prior to blowing the microspheres
to obtain finelv dis~ersed me~al particles and a
decomposi~ion gas or product. The deccmposition gas, if
present, can be used to assist in blowing the micro-
spheres. The dispersed metal particles from
decomposition of the organo me~al compound, as
before, deposit to form the thin me~al layer.
Alternatively, the microsphere, a~ter being formed
and containing the gaseous organo metal compound
blowing gas, can be subjected to "electrlcal
dischar~e" means which deco~poses the organo metai
compound to form the rinely dispersed metal
particles and the decomposition ga~s or product.
The thickness of the deposited metal layer
will depend primarily on the partial pressure of
the gaseous organo metal blowing gas and the
inside dia~eter o~ the microsphere.
An auxiliar~ blowing gas, e.g. an inert
blowing gas, can be used to dilute the gaseous
organo metal compound blowing gas in order to
control ~he thickness o~ the deposi~ed metal
layer. There can also be used as an auxiliarv
blowing gas~a gas that acts as a catalyst or
1~;92
-31
hardening agent for the plastic compositions. The
addition of the catalyst or hardening agent to
the blowing gas prevents contact of the catalyst
or hardening agent with the plastic composition
until a time just before the microsphere is formed.
The entraining fluid, e.g. an inert entraining
fluid, can be a Oas a~ a high or low temperature
and can be selected to react wi~h or be inert to
the plastic compo~ition. Suitable entraining
fluids are nitrogen, air, steam and argon. A
gaseous catalyst for the plastic can also be
included in the entrainin~ fluid.
The quench or heating fluid can be a llquid,
a liquid dispersion or a gas. Suitable quencn or
heating fluids are steam, a fine water spray, air,
nitrogen or mixtures thereof. The selection of
a specific quench or heating fluid and quench or
'neating temperature depends to some e~tent on
the plastic composition ~rom which the microspheres
are made and the blowing gas temperature and
pressure.
PROCESS CONDITIONS
__ _
The orga~ic film forming materials and/or plastic
compositions o the presen~ invention are in 2
liquid-fluid form at the desired blowing temper-
ature and during the blowing operation. The
liquid plastic composition can be at a temperature
of about 0C. to about 400C., preferably 10C.
to 300C. and more preferably 20C. to 200C.,
depending on the constituents and state of poly-
merization of, for example, the plastic composition.
The plas~ic composition at the blowing temperature
is liquid, fluid and flows easily. The liauid
: 3.692~ ~ -
-32
plastic just prior to the blowing operation can
have a viscosity 5f 0 . 10 to 600 poises, usually
10 to 350 poises and more usually 30 to 200 poises.
Where the process is used to make non-fila-
mented microspheres, the liquid plastic just prior
to the blowing operation can ha~e a viscosity
of ~.1 to 200 poises, preferably 0.5 to 100 poises,
and more preferably S.0 ~o 50 poises.
Where the process is used to make filamented
microspheres, the liquid plastic just prior to
the blowing operation can have a viscosity of 50
to 600 poises, preferably 100 to 400 poises, and
more preferably 150 to 300 poises. The viscosity
can be measured by conventional means, e.g. using
a Broofield viscometer.
A critical feature of ~he present invention
is ~hat the formation of the hollow plastic micro-
spheres can be carried out at low viscosities
relative to the viscosities her?tofore used in
the prior art processes that utilized latent
liquid or solid blowing agents dispersed throughout
or contained in the plastic compositions used to
blow the microspheres. Because of the abili~y ~o
utilize comparatively low viscosities, applicant
is able to obtain hollow plastic microspheres,
the walls o which are ~ree of any entrapped or
dissolved gases or bubbles. With the low vis-
cosities used by appIicant, any entrapped or
dissolved gases diffuse out and escape from the
plastic film surface during the btbble formation.
With the high viscosities required to be used
in the prior are processes, any dissolved gaseous
bubbles are trapped in the ~alls of the plastic
microspheres as they are formed because of the
high viscosities required to be used.
2 1 ~
The liquid plastic fed to the coaxial blowing
nozzle can be at about ambient pressure or can be
at an elevated pressure. The liquid plastic feed
can be at a pressure of 1 to 20,000 p.s.i~g.,
usually 3 to 10,000 p.s.i.g. and more usually
5 to 5,000 p.s.i.g.
Where the process is used to make microspheres
for use as insulating materials and in insulating
systems, for use in syntactic foam `systems and
as filler materials in general, the li~uid plastic
fed to the coaxial blowing nozzle can be at a
pressure of 1 to' 1,000 p.s.i.g., preerabl~ at 3
to 100 p.s.i.g., and more preferably at 5 to 50
p . s . i . g .
The liquid plastic is continuously fed to the
coa~ial blowing nozzle during the blowing operation
to prevent ?remature breaking and detaching of
tne elonga~ed cylinder shaped liquid plastic film
as it is being formed by the blowing gas.
20 The blowing gas or gaseous material blowing
gas will be at about the same temperature as the
liquid plastic being blown. T'ne blowing gas or
gaseous ma~erial blowing gas te~perature can,
however, be at a hioher temperature than the
liquid plastic to assist in maintaining the
fluidity of the hollow liquid plastic ~icrosphere
: durin~ the blowing operation or can be at a
lower temperature than the liquid plastic to
assist in the solidiication and hardening of
the hollow liquid plastic microsphere as it is
formed. The pressure of the blowing gas or
gaseous material blowing gas is sufficient to
- 1 ~692 1 1
)
- ~4 -
blow the microsphere and will be slightly above
the pressure of liquid plastic film at the oriice
7a of the outer nozzle 7. The blowing gas pres-
sure will also depend on and be slightly above the
ambient pressure external to the blowing nozzle.
The temperatures of the gaseous material
blowing gases will depend on the blowing gas used
and ~he viscosity-temperature-shear relationship
f~r the plastic materials used to make the micro-
spheres.
The pressure of the blowing gas or gaseous
material blowing gas is sufricient to blow the
microsphere and will be sligh~ly above ~he pres-
sure of liquid plastic at the orifice 7a of the
ou~er nozzle 7. Depending on the gaseous materiai
to be encapsulated within the hollow plastic
microspheres, the blowing gas or the gaseous
material can be at a pressure of 1 to 20,000
p.s.i.g.j usually 3 to 10,000 p.s.i.g. and more
usually 5 to 5,000 p.s.i.g.
The blowing gas or gaseo~s material blowing
gas can also be at a pressure of 1 to 1,000
p.s.i.g., prefer~bly 3 to 100 p.s.i.g. and more
preferably 5 to 50 p.s.i.g.
~1692
Where the process is used to make microspheres
for use as insula~ing materials and in insulating
systems, for use in syntactic foam systems and
as filler materials in general, the blowing gas
or gaseous material blowing gas can be at a pres-
sure of 1 to 125 p.s.i.g., preferably at 2 to
lOO p.s.i.g. and more preferably at 5 .to 30
p . s . i . g .
The pressure of the blowing gas containing
dispersed mecal particles alone and/or in combi-
nation with the principle blowing gas is sufficient
~o blow the microsphere and the combined gas pres-
sure will be slightly above the pressure of the
liq~id plastic at the oriflce 7a of the outer
2 1 ~
_36
nozzle 7. The pressure o the combined mixture
of the blo~ing gases will also depend on and be
slightly above the ambient pressure external to
the blowing nozzle.
The ambient pressure external to the blowing
nozzle can be at about atmospheric pressure or
can be a~ suba~mospheric or super-~mospheric
pressure. The ambient pressure external to the
blowing nozzle will be such that it substantially
balances, but is slightly less than ~he blowing
gas pressure.
The transverse jet ~ntraining fluid which is
~ directed over and around the coaxial blowing
;~ nozzle to assist in ~he formation and detaching
of the hoIlow liquid plastic microsphere rrom
the coaxial blowing nozzle can have a linear
velocity in the region of microsphere formation
of 1 to 120 ft/sec, usually 5 to 80 ,~/sec and
more usually 10 to 60 ft/sec.
Where the process if~used to make non-fila-
~ented~microspheres, ~he linea~ velocity o the
transverse j.et fluid in the region of microsphere
formation c~n be 30 to 120 ft/sec, preer~ablv
40 to 100 ft/sec and more preferably 50 to 80
ft/sec.
Where the process is used to make filamented
microspheres, the linear velocity of the trans-
verse je~ fluid in the region o microspher2
rormation can be I to 50 ~/sec, preferably~5
to 40 ft/sec and more preferably 10 to 30 ft/sec.
Further, it is found (Figures 2 to 4) ~hat
pulsing the transverse jet entraining fluid at
a ra~e of 2 to lS00 pulses/sec, preferably 50 ~o
1000 pulses/sec and more preferably 100 ~o S00
6921 ~
pulses/sec assists in controlling the diameter
of the microspheres and detaching the micro-
spheres ~rom.the coaxial blowing nozzle.
The distance between filamented microspheres
depends to some extent on the viscosity of the
plastic and the linear velocity of the transverse
jet entraining fluid.
The entraining fluid can be at the same
temperature as the liquid plastic being blown.
The entraining fluid can, however, be at a higher
~empexa~ure ~han the liquid plastic to assis~
in maintaining ~he fluidity of the hollow liquid
plas~ic microsphere during ~he blowing operation
or can be at a lower tempera~ure than the liquid
plastic to assist in the stabilization of the
forming film and the solidification and hardening
o the hollow liquid plastic microsphere as -it
is formed.
The quench or heating 1uid:is at a tempera-
ture such that i~ rapidly cools or heats the~micro- ~
spheres to solidify, harden and streng~hen t~e ~ :
liquid plastic before the inner gas pressure
decreases to a value at which the plastic micro-
sphere would collapse or Durst the microsphere
The quench cooling fluid can be at a tem~erature
of 0 to 200F., ~sually 40 to 200F. and more
usually 50 ~o 100F. The heating fluid can be
at a temperature OL 100 to 800F., usually 200
to 600F. and more usually 300 to 500F,,
depending on the plastic composition.
The quench cooling fluid very rapidly cools
the outer liquid plastic surface of the micro-
sphere with which it is in direct contact and
more slowly cools the blowing gas enclosed within
~6~21 ~
the microsphere because of ~he lower thermal
conductivity of the gas. This cooling process
allows sufficient ~ime for the plastic walls
of the microspheres to strengthen before the gas
is cooled and ~he pressùre within the plastic
microsphere is substantially reduced.
The time elapsed from commencement of the
blowing of the plastic microspheres to the
cooling and ~nitial hardening o the ~icrospheres can
be .0001 to 60.0 seconds, preferably .0010 to
30.0 seconds and more preferably 0.10 to 10.0
seconds.
Where a ther~osetting plastic com~osition is
used to ~orm the microsphere, the time elapsed
from co~mencement o the blowing of the plas~ic
~icrosphere to the heating and curing of the
microsphere for i~ to have suf~icient strength
to maintain its size and shape can be 0.10 second
to 30 minutes, preferably 1 second to 20 minutes
and more preferably 10 seconds to 10 minutes.
The filamented microspnere embodiment of
the~in~ention provides a means by which the
mi-crospheres may be suspended and allowed to
harden and/or cure without being brought into
contact with any surface. The ilamented
microspheres are simply drawn on a blanket
or drum and are suspended between the blowing
nozzle and ~he blanket or drum for a sufficien~
period or time for them to harden andlor cure.
~ g21~
39
APPARATUS
Referring to Figures 1 and 2 o the drawings,
the vessel 1 is constructed to maintain the
liquid plastic at thP desired operating tempera-
tures. The liquid plas~ic 2 is fed to coaxial
blowing nozzle S. The coaxial blowing nozzle 5
consists o an inner nozzle 6 having an outside
diameter of 0.32 ~o 0.010 inch, preferably 0.20
to 0.015 inch and more preferably 0.10 to 0.020
inch and an outer nozzle 7 having an inside
diameter of 0.420 to 3.020 inch, preferablv
0.260 to 0.025 and more preferably 0.130 to 0.030
inch. The inner nozzle 5 and outer nozzle 7
form annular space 8 which provides a 1OW path
~hrough-~hi~h the liqu:i~ piastic 2 is ex~n~ed. The ois- ;
~nce be~Jee~ ~he ~ner nozzle 6 and outer nozzle 7 can be
0.050 to 0.004, preferably 0.030 to 0.005 and
more preerably 0.015 to 0.008;inch.
The orlfice 6a of inner nozzle 6 ter~inates
a short distance above the plane of orifice 7a
of outer nozzle 7. The orifice 6a can be
spaced above oriice 7a at a dis~ance of 0.001
to 0.125 inch, prefe~ably 0.00~ to 0.050 incn
and more preferably 0.003 to 0.025 inch. The
liquid plas~ic 2 ~lows ~nwardly and is ~x~ed ~rough arnular
space 8 and fills the area between orifice 6a
and 7a. The orifices 6a and 7a can be made from
~ stainless steel, pla~tinum allo~s, glass or
; fused aiumina. S~ainless steel, however, is
preferred. The surface tension forces in the
liquid plastic 2 form a thin liquid plastic
.ilm 9 across orifices 6a and 7a which has
about the same or a smaller thickness as the
distance of orifice 6a is spaced above orifice 7a.
:~ 16~2 ~ ~
- 40 -
The liquid plastic film 9 can be 25 ~o 3175
microns, prefe~abiy 50 to 1270 microns, and mo~e
preferably 76 to 635 microns thick.
The Figure 2 blowing nozzle can be used to blow
liquid plastic at relatively low viscosities, for
example, of 10 to 60 poises and to blow hollow
plastic micropsheres of relatively thick wall
size, for example, o 20 to 100 microns or more.
A blowing gas or gaseous material blowing
gas is fed ~hrough inner coaxial nozzle 6 and
brought into COtltaC L with the inner su~face of
liquid plastic film 9. The blowing gas or gaseous
material blowing gas e~erts a positive pressure
on the li~ui.d plastic film to blow and distend
the film outwardly and downwardly to form-an
elo~gated cylinder shaped liquid film 12 of
liquid plastic filled with the inert blowing gas
or gaseous material blowing gas 10. T'ne elongated
cylinder 12 is closed at its outer end and is
connected to outer nozzle 7 at the peripheral
edge of orifice 7a.
; The transverse jet 13 is used to direct an
inert entraini~g fluid 14 through nozzle 13 and
transverse jet nozzle orifice 13a at the coaxial
blowing nozzle 5. The coaxial blowing nozzle 5
, has an outer diameter OL 0.52 to 0.030 inch,
preferabl,y 0.36 to 0.035 inch and more preferably
0.140 to 0.040 inch.
The process wa~ found
to be very sensitive to the distance of the trans~
verse jet 13 ~rom the orifice 7a of ou~er nozzle
7, the angle at which the transverse jet was
directed at coaxial blowing nozzle ; and the
g21~
-41
point at which a line drawn through the center
axis of trans~erse jet 13 intersected with a line
drawn through the center a~is of coaxial nozzle
5. The transverse jet 13 is aligned to direct
the flow of entraining fluid 14 over and around
outer nozzle 7 in the microsphere forming region
o the orifice 7a. The oriice 13a o transverse
jet 13 is located a distance of 0.5 to 14 times,
preferably 1 to 10 times and more preferably 1.5
to 8 times and s~ill more preferably 1.5 to 4
times the outside dizmeter oL coaxial blowing
nozzl~ 5 away from the poin~ of intersect of a
line drawn along the center axis o~ transverse
jet 13 and a line drawn along the center axis
o~ coaxial blowing nozzle S. The center axis
of transverse jet 13 is aligned at an angle of
15 to 85, pre~erably 25 to 75 and more preferably
35 to 55 relative to the center axi~s o~ the
coaxial blowing nozzle 5. The orifice 13a can
be circular in shape and have an inside diameter
of 0.32 to 0.010 inch, preferably 0.20 to 0.015
inch and more preferably 0.10 to 0.020 inch.
The line dra~n through the center axis of
: trans~erse jet 13 intersects the line drawn
through the center axis of coaxial blowing
noæzle S at a point above the oririce 7a of
outer nozzle 7 which is .5 to 4 ti~es, preferably
1.0 to 3.5 times and more pre~erably 2 to 3
times the outside diameter of the coaxial blowing
nozzle 5. The transverse jet entraining fluid
acts on the elongated shaped cylinder 12 to
flap and pinch i~ closed and to detach it rom
the orifice 7a o~ the outer nozzle 7 to allow
the cvlinder to fall, i.e. be trànsported away from
the outer nozzle 7 by the entraining fluid.
~ ~g2~ ~ ~
- 42 -
The transverse jet entraining fluid as it
passes over and around the blowing nozzle 1uid
dynamically induces a periodic pulsating or
fluctuating pressure field at ~he opposite or
lee side of the blowing nozzle in the wake or
shadow of the coaxial blowing nozzle. A similar
periodic pulsating or fluctuating pressure field
can be produced by a pulsating sonic pressure
field directed at the coaxial blowing nozzle.
The entraining fluid assists in ~he ormation
- and detaching of the hollow plastic microsphere
from tke coaxial blowing nozzle. The use of
the transverse jet and entraining 1uid in the
manner described also discourages wetting of
the ou~er wall surface of the coaxi.al blowing
nozzle S by the fluid plastic being blow~. The
wetting of the outer wall disrupts and in~erfers
with blowing the microspheres.
The quench or heating nozzles 18 are dis-
posed below and on both sides of the coaxial
blowing nozzle 5 a su~licient distance apart, o
allow the microspheres 17 to fall between the
quench nozzles 18. The inside diameter of quench
nozzlP orifice 18a can be 0.1 to 0.75 inch,
prefe~ably 0.2 to 0.6 inch and more preferably
0.3 to 0.5 inch. The quench nozzles 18 direct
cooling or hea~ing fluid 19 at and into contact
with the liquid plastic microspheres 17 at a
velocity of 2 to 14, preferably 3 to 10 and more
preferably 4 to 8 ft/sec to rapidly cool o. heat
and solldi~y the liquid plastic and form a nerd,
smooth hollow plastic microsphere.
- 43 - ~ 9 2 ~ ~
Referrin~ to Figure 3 of the ~raw-n~s, it is found
that in blowing high viscosity liquid plastic
compositions that it is advantageous to immediately
prior to blowing the liquid plastic to provide
: by extrllsion a very thin Liquid plastic film for
blowing into ~he elongated cylinder shape liquid
film 12. The thin liquid film 9' is provided
by having the lower portion of the outer coaxial
nozzle 7 tapered downwardly and inwardly a~ 21.
: 10 The tapered portion 21 a~d inner wall surace 22
: thereof can be at an angle o 15 to 75, 30 to 60
and pref erably abou~ 45~ relative to the center
axis or coaxial blowing nozzle 5. The oriice
7a' can be 0.19 to l.S times, preerably 0.20
to 1.1 times and more preferably 0.25 to .8 times
the inner diameter of orifice 6a of inner nozzle
: 6.
: The thickness of the liqtlid plas~ic film 9' :
i ~ can be varied by adjusti.ng the distance of or fice
2~0 6a of inner nozzle 6 above orifice 7a o~ o~ter ~ :
: nozzle 7 such that:the distance between the
~ : periDheral edge of orifice~68 and the~inner wall
:~ ~ surface 22 of tapered nozzle 21 can be varied.
By control~ing the distance bet~een the peripheral
edge of orifice 6a and the inner wall surface 22
of the tapered nozzle to form a very fine~gap
and~by controlling the pressure applied to feed
: ~he liauid plastic 2 through annula~space 8 tne
liquid plastic 2 can be squeezed or extruded
through the very fine gap to form a relatively
thin liquid plastic fil~ 9'.
.
_ 44 ~ 9~1~
The proper gap can best be determined by
pressing ~he inner coaxial nozzle 6 downward with
sufficien~ pressure to completely block-of the
~low of plastic, and to then very slowly raise
the inne~ coaxial nozzle 6 until a stable system
is obtained, i.e. un~il the microspheres are
being ~ormed.
When blowing high or low viscosity plastic
compositions, it was found to be advantageous to
obtain the very ~hin liquid plastic film and to
continue durlng the blowing operation to supply
liquid plastic to the elongated cylinder shaped
liquid film as it was formed. Where a high pres-
sure is used ~o squeeze, i.e. ex~rude, the liquid
plasLic thr,ough the very thin gap, the pressure
of the inert blowing gas or gaseous material
blowing ~as is gene~ally less than the liquid
plastic feed pressure, but slightly abcve che
pressure of ~he liquid plastic at ~he coaxial
blowing nozzle.
T'ne tapered nozzle coniguration of Figure 3
is also par~icularly useful in aligning the~
la~inar pl ane orientable plastic addtivie materials .
The passage of the plastic material through the
fine or narrow gap se:rves ~o align the additive
materials wi~h the walls of the microspheres as
the microspheres are being formed.
_ 45 ~ g211
In Figures 3a and 3b of the drawings, the transverse
jet 13 can be flattened to form a generally rectangular or
oval shape. The orifice 13a can also be flattened to
form a generally oval or rectangular shape. The width
of the orifice can be 0.96 too.030 inch, preferably
0. 60 to 0. 045 inch and more preferably 0.030 to 0.060
inch. The height of the orifice can be 0.32 to 0.010 inch,
preferably 0.020 to 0.015 inch and more preferably 0.10 to
0.20 inch.
With reference to Figure 3c of the drawings, there
is shown the formation of the uniform diameter filamented
microspheres spaced about equal distances apart. The
numbered items in this drawing have the same means as
discussed above with reference ~o Figures 1, 2, 3, 3a
and 3b.
With reference to Figure 4 of the drawings, it
was found that in blowing the liquid plastic to
form the elongated cylinder shaped liquid film
12 that it was advantageous to increase the
.
,
- 4~ 9211
outer diame~er of the lower portion coa~ial blowing
nozzle 5. One me~hod of increasing the outer
diameter of coaxial blowing nozzle 5 is by pro-
~iding the lower portion of outer nozzle 7 with
a bulbous member 23 which imparts to the lower
portion of outer nozzle 7 a spherical shape. The
use o ~he bulbous spherical shaped member 23 is
found for a given velocity of the entraining fluid
to substantially increase the amplitude o~ the
~ pressure f~uctuations induced in the region or the
formation of the hollow microspheres. The diame~er
of the bulbous member 23 can be l.25 to 4 times,
pre~erably 1.5 to 3 times and more preferably l.75
~o 2.75 times ~he diameter of the outer diameter
of coaxial blowing nozzle 5. When using a hulbous
member 23, the transverse jet 13 is generally aligned
such that a line drawn through the center axis
of trans~erse je~ i3 will pass through the cen~er
of bulbous member 23.
- Referriny again to Figure 4, a beater bar 24 is
used to facilitate detaching of ~he elongated
cylinder shaped liquid fiLm 12 from the ori,ice
7a of outer nozzle 7. The ~eater ~ar 24 is attached
to a spindle, no~ sho~n, which is caused to rotate
in a manner such that the beater bar 24 is brought
to bear upon the pinched portion 16 of che
elonga~ed c~linder 12. The beater bar 24 is set
; to spin at about the same rzte as tne for~ation
of hollow microspheres and can be 2 to 1500,
preferably 10 to 800 and more preferably 20 to
400 revolutions per second. The bea~er bar 24
can thus be used to facilitate the closing o~
of t~e cylinder 12 at i~s inner pinched end 16
and to detacn the cylinder 12 from the oririce
7a o outer nozzle 7.
~ 16921~
~ 47
DESCRIPTIO~ OF THE M_ ROSPHERES
The hollow microspheres made in accordance
with the present invention can be made from a wide
variety of organic film forming materials and co~-
positions particularly plastic compositions.
The hollow plastic microspheres made in
accordance with the presen~ invention can be
made from suitable organic film forming compositions
which are resistant to high temperatures and
ohemical attack and resistant to weathering as
the situation may require.
The organic film forming composi~ions that can
be used are those that have the necessary ~is-
cosities, as mentioned above, when being blown
to form stable ~ilms and ~hich have a rapid change
from the molten or liquid state to the solid or
hard state with a relatively narrow temperature
change or within a rela~ively short cure time.
That is, they change from liquid to solid within
a relative narrowly defined temperature range
and/or cure in a rela.ively short time.
The hollow plastic microspheres are sub-
stant ally uniform ln diameter and wall thickness,
and depending on their composi~ion and the
blowing conditions are light transparent, trans-
lucent or opaque, sof~ or hard, and smooth or
rough. The walls of the microspheres are free or
substantially free of any holes, rela~ively
thinned wall portions or sections, trapped gas
bubbles, or suficient amounts of dissolved
gases or solvents to form bubbles. The micro-
spheres are 2190 free of any latent solid or
9~
-48
liquid blowing gas materials or gases. The pre-
ferred plastic compositions are those that are
resistant to chemical attack, elevated temperatures,
weatherlng and diffusion of gases into and/or
out of the microspheres. Where the blowing gases
may decompose at elevated temperatures, plastic
compositions th~t are liquid below the decompositlon
temperatures of the gases can be used.
The plastic microspheres can be made in
various diameters and wall thickness, depending
upon the desired end use of the microspheres. The
microspheres can have an outer diameter of 200 to
10,000 microns, preferably 500 to 6,000 microns
and more preferably 1,000 to 4,000 microns. The
microspheres can have a wall thickness of 0.1 to
1,000 microns, preferably 0.5 to 400 microns and
more preferably 1 to 100 microns.
The diameter and wall thic'~ness of the
hollow microspheres will of course affect the
average bulk density of the microspheres. The
microspheres can have an average bulk density of 0.2
to 15 lblft3, usually 0.5 to 12 lb/ft3 and more
usually 0.75 to 9 lb/ft3. For use in a preferred
embodiment to ma~e low density insulating
materials, the hollow plastic microspheres can
have an average bul:~ density as low as 0.5 to 1.5,
for example, about 1.0 lb/ft3.
116921~
- 49 -
The microspheres, because the walls are
free or substantially free of any holes, thinned
sections, trapped gas bubbles, and/or suficient
amo~nts of dissol~ed gases or solve~ts to form
bubbles and are substantially stronger than the
microspheres heretofore produced.
The microspheres made from thermoplastic
compositions ater being formed can be reheated
to soften the plastic and enlarge .he microspheres
andlor to impro~e the surface smoo~hness of the
microspheres. On reheating, ~he internal gas
pressure will increase and cause tne microspnere
to increase in size. After reheating to the
des,ired size~ for example, in a "shot tower",
the microspheres are rapidly cooled to -eeai~
.
1 l6921 ~
- 50 -
the increase in size.
Where the microspheres are formed in a manner
such that they are ccnnected by continuous ~in plastic
ilaments, that is they are made in the form of
filamented microspheres, the length of the con-
necting filaments can be 1 to 40, usually 2 to
20 and more usually 3 to 15 times the diameter
of ~he microspheres. The diame~er~ that is the
thickness o~ the connecting filaments, can be
1/~000 to 1/10, usually 1/2500 to 1/20 and more
usually 1/1000 to l/30 of the diameter of the
microspheres.
The microspheres can contain a gas a~ super-
atmospheric pressure, about ambient pressure or
at par~ial vacuum.
Where the microspheres are used as insu-
lating materials and in insulating sys~ems, or
in syntactic foam systems, or 2S filler material
in general, the microspheres can have an outer
diameter o~ ~00 to 5,000, preferably 500 to 3,000 and
more preferably 7~ to 2000 microns. These micro-
spheres can have a wall thickness o~ 0.1 to 500
microns, preferably 0.5 to 200 microns and more
preferably 1 to 50 microns. These microspheres
can have an average bulk density of 0. 3 to 15
: 1~D/ft3~ preferably l~.5 to 1~ lb/C~ and more
preferably ~.75 LO 5.0 lbJ~3. These microspheres
can have a contained gas pressure of 12 tO 100
p.s.i.a., preferably 15,o 75 p.s.i.a. and more
preferably 18 to 25 p.s.i.a.
In a preferred embodiment of the invention,
the ratio of the diameter to the wall thickness
OL the microspheres is selected such that the
microspheres are fle~ible, i.e. can be deformed
under pressure without breaking.
692
51
The microspheres can contain a thin metal
layer deposited on the inner wall surface of ~he
microsphere where the blowing gas contains dis-
persed metal particles. The thickness of the thin
metal coa~ing deposited on the inner wall surface
of the microsphere will depend on the amount and
particle size of the dispers~d metal particles
or partial ~ressure of organo metal blowing gas
that are used and the diameter of the microsphere.
The thickness of the thin metal coating can be
25 to lO,OOOA, preferably 50 to 5,000A and more pre-
ferably 109 to l,OOOA.
When it is desired that the deposited metal
coa~ing be transparent to light, the coating should
be less than lOOA and preerably less than 80A.
The transparent metal coated microspheres can have
a deposi~ed me~al coating 25 to 95A and ?referably
50 to 80A thick. These microspheres, though trans-
paren~ to visible light, are substantially reflec-
tive of infrared radlation.
~ en it is desired that the deposited metalcoating be reflective to light, the coating can De
more than lOOA and preferably more than 150A thick.
The reflective metal coated microspheres can have
a depositea metal coating 105 to 600A, preferably
150 to 400A.and more preferably 150 to 250A thick.
The thermal heat conductivity characteristics
o~ heat barriers made rrom the microspheres can
be further lmproved by partially flattening the
microspheres into an oblate spheroid or generaily
rectangular shape. The ~hermal conductivi~y o~ the
~ 16g21 '~
-52
oblate spheroids is further improved by mixing
with the obla~e spheroids thin plastic filaments.
The filaments are preferably provided in ~he form
of the filamented microspheres.
The filamented microspheres can as they are
formed be drawn and laid on a conveyor belt or drum.
A sufficient amount of tension can be maintained
on the filamented microspheres as they are drawn
to stretch them into the oblate spheroid shape.
The filamented microspheres are maintained in that
shape for a sufficient period of time to harden
and cure. A~er hardening of the filamen~ed oblate
spheroids, they can be laid in a bed, an adhesive
and/or foam can be added and the filamented
microspheres can be made into, e.g. a fou- by
eigh~ formed panel. The panel can be 1/4 to 3
inches in thickness, ~or example, 1/2, 1, 1 l/2
or 2 inches in thickness.
The thermal properties of the microspheres
: can also be improved by filling the interstices
between the microspheres with a low thermal con-
ductlvity gas, finely divided inert particles,
e.g. lamp black, a low conductivity foam, e.g.
polyurethane, or polyolefin resin foam.
~ ~6921 ~
The hollow plastic microspheres of the present
invention can be used to design systems having
improved insulating characteristics. Where
hollow microspheres are used in which the contained
volume has a low hea~ conductivity gas, systems
can be designed in which the thermal conductivity
can be R5 to R9, for example, R8 per inch.
Where hollow plastic microspheres are used
~aving a low heat conductivity gas and a low emissivity,
reflective metal coating deposited on the inner
wall suriace thereof are used, systems can be
designed in which the ther~al conductivi~y c2n ~e
R7 to R12, for example, R10 per inch .
Where an insula~ing system containing fila-
mented oblate spheroids and a reflective metal
coating deposited on the inner wall surface or
the microsphere are used, systems can ~e designed
in which ~he thermal conductivity can be R9 to
R16,~for e~ample R14 ?er inch.
The microspheres can also be used as heat
barriers by Lilling spaces between e~isting walls
or other void spaces or can be m2de in,o sheets
or other shaped forms b~ cementinO the micro-
spheres toge~her with a suitable resin or other
a &esive or by fusing the microspheres together
and can be used in new construction.
When the hollow plastic microspheres are
massed together to form a 'neat b~rrier, there is
reduced heat ~ransfer by solid conduction because
o the point to point contact be~ween adjacent
spheres and the low conductivity of the plastic
material used to form the spheres. There is
little heat transer hy convectior. because the
characteristic di~,ensions of the voids between
~g21 1
_ 54 -
the packed spheres are below that necessary to
initiate convection. There is little heat trans-
fer by gas conduction within the spheres when
there is a low heat conductivity gas in the
enclosed volume. Where there is a low emissivity,
highly reflective metal layer deposited on the
inner wall surace of the microspheres, ~here is
substantialiy llt~le radiant heat trans~er because
of the highly rerlective metal layer on the inner
; 10 wall surface of the spheres. A primary mode of
heat transfer remainlng, therefore, is by gas
conduction ln the interstices or voids be~een
the microspheres. The overall conductivi~y of
the system is lo~-er than that of the volds gas
because t'ne voids gas occuples only ~ frac~ion
o the volume of ~he total sys~em, and because
conductlon paths through the voids gas are
attentuated by ~he presence of the low conductivity
microspheres and the filaments. The use of a low
heat conductivity gas and/or a foam containing
a low heat conductivity gas to fill the interstices
bet~een the microspheres fur~her reduces the
then~al conductivity of a bed of the mic~ospheres.
The hollow plastlc microspheres Oc the ~resent
inve~ion have a distinct adv~ntage o$ being
s~rong and capabie of su?porting a substanLial
amount of weight. They can thus be used to make
simple inexpensive self-suppor~ing or load bearing
systems.
The following e~amples are used to illustrate
the invention.
.~692~ ~
- 55 -
EXAMPLES
The ~amples 1-7 are illus~rative of the use
of the present invention to make insulating materials
and~or systems.
Example 1
A thermoplastic composition comprising the
. following constituents is used to make hollow
plastic microspheres:
Polyethylene polymer.
rne plastic composition is heated to
~; form a fluid ?lastic having a viscosity of
10 to 20 poises at the blowing nozzle.
The liquid plastic is fed to the aDparatus of
Figures 1 and 2 of the drawings. The liquid
lastic passes through annular space 8 o~ blowing
nozzle 5 and rorms a thin liquid plastic fil~
across the orlfices 6a and 7a. The blowing nozzle
i has an outside diameter of 0.040 incn anâ
orifice 7a has an inside diameter o~ 0.030 inch.
The thin liquid molten plastic Lilm has a diameter
or 9. a30 inch and a thickness of a . 005;inch.
A heated blowing gas consisting of argon or a low
heat conductivity.gas 2t a positive pressure
is applied to ~he inner surface of the liquid
plastic film causing the film ~o distend do~-n~.~ardlt
into a elongated cylinder shape with its outer
end closed and its inner end attached LO the
outer edge of orifice 7a,
The transverse jet is used ~o direct an
entraining fluid which consists of heated
nitrogen over and around the blowing
nozzle 5. The transverse je~ is aligned at an
angle of 35 to 50 relative to ~he blowin~ nozzle
~ ~92~ ~
5~
and a line drawn through the center axis of the
transverse jet intersects a line drawn through
the center axis of the blowing nozzle 5 at a
point 2 to 3 times the outside diameter of the
coaxial blowing nozzle 5 above the orifice 7a.
. The entrained falling elonga~ed cylinders
assume a spherical shape, are cooled to about
zmbient temperature by a cool quench fluid
consisting o~ a fine -~ater spray which quic~ly
cools, solidifies and hardens the plastic
microspheres.
Uniform sized, smoo~h, hollow plastic
microspheres having a 2000 to 3000 mlcron
aiameter, a 20 ~o 40 micron wall thickness znd
filled with arCon or a low hea~ conductivitv gas
are obtained. The mic.ospheres are closely
e~amined and the walls are .ound to be free of
any trapped gas bubbles.
ExamPle 2
A thermose~ting plas~ic composition comprisinG
a mi~ture of 50% by weight acrylonitrile and 50%
by weight vinylidene chloride and a suitable
catalyst is used to ~ake hollow plas~ic microspheres.
The plas~ic composition mixture at the blowing
nozzle has a viscosity of ten poises.
The liquid plastic mixture is hezted
and is fed to the apparatus of Fi~ures
1 and 3 o the drawlngs. The liquid plastic
is passed through annular space 3 of blowing
nozzle S and into tapered ?ortion 21 or outer
nozzle 7. The liquid plastic under ?ressure is
squeezed and extruded through a fine gap formed
between ~he outer edge of orifice 6a and the inner
surace 22 of the tapered po ~ion 21 of outer nozzle
7 and forms a thin liquid p7astiC film across ~he
~ :16~21 ~
- 57 -
orifices 6a and 7a'. The blowing nozzle 5 has an
outside diameter of 0.04 inch and orifice 7a' has
an inside diameter of 0.01 inch. The thin liquid
plastic film has a diameter of 0.01 inch and
thickness of 0.003 inch. A heated blowing gas con-
sisting of argon or a low heat conductivity gas at
a positive pressure is applied to the inner surface
of the liquid plastic film causlng the film to
distend outwardly into an elonga~ed cylinder shape
with its outer end closed and its inner end
attached to the outer edge of orifice 7a'.
The transverse jet is used to direct an
entraining fluid which consists of heated nitrogen
over and around the blowing nozzle. The transverse
jet is aligned at an angle OL 35 ot 50 relative
to the blowing noz le and a line dr2wn th_ough
the center axls of the transverse jet intersects
a line drawn through the center axis of the blowin~
nozzle ~ at a point 2 to 3 times the outside
diameter of the~coaxial blowing noz21e 5 above
; or~fic~ 7a'.
The e~trained falling elongated cylinders filled
with .he blowing gas quickly assume a spherical
shape. The micros~heres are contacted with a
'neating rluid consisting of heated nitrogen
whlch solidifies, harder.s and begins ~o cure the
liquid plastic.
Unifor~ sized, smooth, hollow plastic micro-
spheres having an about 800 to 900 micron diamete~,
a 8 to 20 micron wall thickness and an lnternal
pressure Oc 12 p.s.i.a. are obtained. The micro-
spheres are examined and are found to be fLee of
~ ~92:~ 1
58 -
any trapped gas bubbles.
Exam~
A ther~osetting composition comprising a mi~-
ture o 90% by wei~ht methyl methacrylate and 10%
by weight styrene and a suitable catalyst is used
to make low emissivity, reflective hollow plastic
microspheres.
The plastic composition mix~ure has a visco-
sity of ten poises at the blowing nozzle.
The liquid plastic mixture is fed to the appara-
tus of Figures 1 and 3 of the drawings. The liquid
plastic is heated to and is passed through annular
; space 8 of the blowing nozzle 5 and into tapered
: portion 21 of outer nozzle 7. The liquid plastic
; under pressure is squeezed through a fine gap
formed bet~reen the outer edge of oriice 6a and
the inner surace 22 of the tapered portion 21
of outer nozzle 7 and orms a thin liquid plastic
: fil~ across the orifices 6a and 7a'. The blowing
nozzle S has an out~side diameter o:E O.OS inch and
orifice 7a' has an inside diameter of 0.03 inch.
: rne thin li~uid plastic film has a diameter of
0.03 ,nch and a thickness of 0.01 inch. A heated
blowing gas consisting of argon or a low heat
conductivit.~ gas and containing finely dispersed
aluminum particles 0.03 to 0.05 micron size and
at a positive pressure is applied to the inner
surface of the liquid plastic film causing the
film to distend outwardly into an elongated c~linder
shape with its outer end closed and its inner end
attached to the outer edge of orifice 7a'.
The transverse jet is used to direct an inert
entraining fluid which consists or 'neated
nitrogen gas over and around the biowing ~ozzle.
The t~ansverse jet is aligned at an angle Oc
35 to 50 relative to the b!.owing nozzle and a
2 :~ 1
- 59 -
line drawn ~hrough the center axis of the trans-
verse jet intersects a line drawn through the
center axis of the blowing nozzle 5 at a point 2
to 3 times the outside diameter of the coaxial
blowing nozzle 5 above orifice 7a'.
The entrained falling elongated cylinders
filled with the blowing gas containing ~he dis-
persed aluminum par~icles quickly ass~me a spheri-
cal shape. The microspheres are contacted with
a heating fluid consisting of heated nitrogen
which quickly solidifies, hardens and begins to
cure the liquid plastic. The dispersed aluminum
particles are deposited on and adhere to ~he
inner wall surface o the plastic microsphere.
Uniform sized, smooth, hollow plas~lc micro-
spheres having an about 3000 to 4000 micLon diameter7
a 30 to 40 micron wall thicl~ness and having a low
emissivity, reflective aluminum metal coating 600A
to lOOOA thick and an internal contained pressure
of 12 p.s.i.a. are obtained. The ~icros~heres
- are examined and are found to be free of any
~rapped ga5 bubbles.
Example 4
An efficient flat plate solar energy collector,
as illustrated in Figure 5 of the drawings, is
constructed using the plastic microspnere of the
present invention as an improved insulating material.
In accordance with the present invention, the
area between the outer cover and the upper sur~ace
of the black coated metal absorber plate is filled
to a dep~h of about one inch with transparent
plastic microspheres made by the method of Example 2
of about 800 ~icron diameter, 10 micron wall thickness
and having an internal contained ~ressure of iO
2 ~ 1
-60
p.s.i.a. These microspheres are transparent to
visible light.
The area between the lower surface of the black
coated metal absorber plate and the inner cover
member is filled to a depth of about 1 1/2 inches
with the reflective plastic microspheres made by
the method of Example 3 of about 3000 micron
diameter, 30 micron wall thickness and having a
thin low emissivity, reflective aluminum metal
coating 700A thick and an internal contained
pressure of 12 p.s.i.a.
E~amPle 5
--
An efficient tubular solar energy collector,
as illus~rated in Figure 6 or the drawings, is
constructed using the ?las~ic microspheres OL
the present inven~ion as an improved insulating
material.
In accordance with the present invention, the
vol~lme between the outer cover, the sides and the
lower curved portion and the double ?ipÇ tubular
member is filled with transparent plastic micro-
spheres made by the me~hod o Example 2 tO provide
an about one inch layer of transparent p}astic
microsphe~es completely around ~he double p~?e
tubular member. The transparent plastic micro-
spheres are 800 microns in diameter, have a -.~all
thickness of 10 microns and an internal contained
pressure of 12 p.s.i.a. These microspheres are
transparent to visible light.
~ ~92~
- 61 -
E~ample 6
The Figure 7 OLC the drawings illustrates the
use of the hollow plastic microspheres of the pre-
sent invention in the construction of a one-inch
thick formed wall panel. The wall panel contains
multiple layers o uniform size plastic micro-
spheres made by the method OLC Example 3 of the
invention. The microspheres have an about 3000
micron diame~er~ 30 micron wali thickness and a
thin, low emissivity aluminum metal coating 700A
thic~ deposi~ed on the inner wall surface o~ the
microsphere. The internal volume of ~he micro-
spheres is ~illed with a low heat conductivity
gas, e.g. Freon-ll, 2nd the interstices between ~e micro-
spheres is filled wit~ a low heat conductivit~ f~oam con~ain~ng
Fre~n-ll gas. The microspheres are treated with a thin adnesl~e
coating of a similar composition to that 'ro~
which the pl2stic microspheres were made and ~ -
for~ed into a 7/8 inch~thick layer. The ad'nesi~-e
is aliowed~to cure to form a semi-rigid wallboard.
The ~2cing surface of the wall~joard is co2ted with
an~about 1/8 i~ch~hick plaster which i-s suitable
for subsequent~ sizir.g and painting and/or co-~éring
with wall DaDer. The backing surace of the
panel is coated with an 2bout 1/~1~ inch coating
OL ~he s~ame plastic composition rro~ which ~he
microspneres are made. The final panels are
allowed to cure. The cured panel.s form strong
wall panels which can be sawed and nailed ar.d
readily used in construction of new homes.
Several sections of the panels are ,ested and
found to have a R value of 12 per inch.
~ 1~921 ~
- 62 -
Example 7
-
The Figure 7b of the drawings illustrates the
use of the hollow plastic microspheres of the
~resent inven~ion in the construction of a formed
wall panel one-inch thick. The wall panel con-
tains hoLlow plastic microspheres made by the
method of Example 3. The microspheres have a
diame~er of about 3000 micron, 30 micron wall
thickness and a low emissivity aluminum met~l
coating 700A thick deposi~ed on the inner wall
surface of the microsphere. The microspheres
are coated with an adhesive of si~ilar composition
to that from whlch the microspheres are made.
A layer of microspheres about two inches thick
is pressed and flattened between two flat pl2tes
to form the microspheres into an oblate spheroid
or a general rec~angular shape in which the ra~io
oS the height to length of the flattened micro-
sprteres is 1:3. The Llattened microsprteres for~t
a layer :about 7l~8 inch thick and a~e neld in
th:is~position until ~he adhesive coating on the
mic.ospheres cure after which micros?heres retain
their flattened~shape. The in~ernal volume o
the microspheres.is filled with a low hezt con-
ductivitY gas, e.g. Freon-ll. The flattened
configur2tion of the microspheres subs.antially
reduces the volume of the interstices between the
~ic~ospheres and any-~l~me that rema;ns is r-ill2d~ h a low
neat concu tivitv ~02m contai~ing Freon-ll gas. The ~2cing surface
of the -~allboard is about 1/8 inch plaster
which is suitable for subsequent sizing and
painting and/or covering with wall paper. The
backing of the wall panel is about 2 1/16 inch
coating of the plastic from which the microspneres
2 ~ 1
63 -
are made. The panels are cured and form s~rong
wall panels which can be sawed and nailed and
readily used in construction of new homes. One
of the important effects of compressing the
microspheres is to significantly reduce the volume of
the interstices between the microspheres to sub-
stantially reduce the heat loss by convection.
Several sections of the pa~el are tested and
found to have a R value of 1~- per inch.
The formed panel of E~amples 6 and 7 can also
be made to have a density gradient in the di~ec-
tion of t'ne front to bac~ o~ the panel. Where
the panel is used indoors the surface .acing
the room can be made to have a relatively high
densiLy and high stre~gth, by increasing the ?rO-
por~ion of resin or otner binder to microspneres.
The sur~ace Lacinc the outside can ~e made to
have relatively low density and a high insulation
barrier efect by having a high proportion of
mlcrospheres to résin or binder. For e~m?le, the
front one ~hird of the panel can 'nave an average
density o about two to three Limes that OL the
average density of the center Lhird OL the panel.
The density of the back one ~hird of the panel
~; ~ can be about one-hal to one-third tha~ of the
center third of the panel. r~here ~he panels are
used on the outside of a house,~ the sides of the
panel can be reversed, i.e. the high density side
can face ou~ard.
.
~ ~6g~ ~
~ 64
UTILITY
The hol~ow plastlc microspheres of the present
inven~ion have many uses including the manu acture
of improved insulating materials and the use of
the microspheres as a filler or aggregate in
cement, plaster and asphalt and synthetic construc-
tion board materials. The microspheres czn also
be used in the manuacture of insulated louvers
and molded objects or forms.
The microsphere can be used to form thermal
insulation barriers merely by filling spaces
between the walls of refrigera~or ~rucks or train
cars, household refrigera~crs, cold storage
building facilities, homes, factories and office
buildings.
The hollow microsph res can be produced lrom
high melting temperature and/or ire resistant
plas.ic comoositions and whe~ used as~ a component
in building construction retard the development
and eYpansion o fires. The hollow plastic ~icro-
spheres, depending on the plastic co~position,
are stable ~o many chemical~agen~s and -~ea~hering
condit~ons. ~
The microspheres can be bonded together by
sintering o~ resin adhesives and molded into
sheets or other forms and used in new constructions
which requlre thermal insulation including homes,
factories and office buildings. Th~-~ constr~uction
~aterials made from the microspheres can oe pre-
formed or made at the construction si~e.
The ~icrospneres may be adhered together withknown adhesives or binders to produce semi- or
rigi.d cellular type materials or use in manu-
facturing various products or in construction.
T:~e microspheres, becauce they can be ~ade from
~1~92~.~
very stable plastic compositions, are not subject
to degradation by outgassing, aging, moisture,
weathering or biological at~ack. The hollow plas-
tic microspheres when uscd in manurac~ure of
improved insulating materials can advantageously
be used alone or in combina~ion with fiberglass,
styrooam, polyu~e~hane ~pam, phenol-formaldehyde
foam, organic and inorganic binders.
The ~icrospheres of the present invention can
be used to make insulating ma~erial tapes and insu-
la~ing, ~allboard and ceiling tiles. The micro-
spheres can also 2dvantageously be used in ?lastic
o~ resin boat construction to produce high strength
hulls and/or hulls which ~hemselves ~re buoyant.
The plastic compositions can also De selected
to produce microspheres that will be selecti-vely
permeaDle to speciic gases andjor organic mole-
cules. These micros?heres can then be used as
semi-pe~meable ~embranes to separate gaseous or
liquid mi~tures.
The ~lastic composition.~ can be ~ransparent,
translucent or opaque. A suitable coloring
material can be added to the pl.astic co~posi~ions
~o aid in identifica~ion of microspheres of
specified size andlor ~all thickness.
These and other uses of the present invention will
become apparent to those skilled in the art and from
the foregoing description and the following appended claims.
It will be understood that various changes and
modifications may be made in the invention and that the
scope thereof is not to be limited except as set forth
in the claims
