Note: Descriptions are shown in the official language in which they were submitted.
1043497 9133
This invention i9 concerned wlth the manufacture o~
thermo~ettlng molding compositions, methods ~or using them,
and novel reslns to be employed in the moldlng composltions.
More particularly this lnvention is concerned with thermo-
setting molding compositions which contain resins that can
be heat cured in "one-step", l.e., cured wlthout the addltion
of curlng or crosslinking agents, and which possess a
oombination of unique characterlstlcs making them most
desirable ~or use ln lnJection molding processeY, as well as
ror transfer and compression moldlng processes.
The molding arts have long desired a "one-step"
curing thermosettlng resin which can be compounded lnto a
moldlng materlal or compound having or producing the
~ollowing oharacterlstics and/or results:
1. A~ initial llght color and the ablllty to
be pigmented to pastel shades. :
2. ~ood color stab$11ty even when heated and
exposed to ultravlolet ( W) llght.
3. Excellent moldlng prQperties such as~
(a) me abillty to sufficlently maintain
plastlclty and flow characterlstics while residlng in j;
warm runner molds, at about 120C., which are used in
many inJectlon molding apparatus.
1,"..,. . ,... ~., .
(b) Have the abillty to rapldly cure ln the
mold when brought to a selected moldlng temperature; and j -
(c) Possess the approprlate ~luidity ln the
mold sùch that it will ~111 the mold so as to preclude -~
~ormation of vold3 and allow the fabrlcatlon o~ intricately ---
shaped articles.
4. Mlnlmum shrlnkage durlng curing in the mold and
a~ter aelng at ambient room temperature (e.g., 20-25C.).
5. The molded artlcle should be very rlgld and
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2- ~
,. , . ~ , ,:, ,, , , , ,., . , . .. ., - . . . . . . ..
1043497 9133
retain its shape at elevated temperatures 80 that the
article can be withdrawn from the mold while hot. This
avoids the t~me consuming need to cool the mold before
withdrawing the article. This characteristic is technically
called "hot rigidity" or high modulus at elevated tempera-
tures.
6. The shaped molded article should possess a
low degree of deformation at high temperatures, e.g., over
200C.
7, Since molded articles made from compounded
thermosetting resins are suppQ$ed to be heat resistant
they should also pos~ess the ability to withstand stresses
induced by humidity and temperature differentials across
the walls of the articles. This may be defined as a
high steam crack resistance and articles possessing such
can be used in appliances which are expected to be ex-
po8ed to heat and steam, for example, iron handles.
8. Since thermosetting resins are fre~uently
used in making molded articles used in electrical and
electronic applications, excellent electrical properties
are most desirable.
The molder has a number of "one-step" thermosetting
resins which he can use in making useful molding materials --
and the ~uestion presented is whether any of them when
properly compounded, provide a molding material which can
eventually satisfy all of the desirable criteria recited
above.
First, there are the "one-step" phenol-formaldehyde
resin containing molding materials. They fail to meet a
number of the criteria, for example: -
1, They possess a dark initial color and --~
3. ;
9133
~043497
cannot be pigmented to pastel shades;
2. They possess poor color stability when
heated and/or exposed to W light;
3. They are viscosity sensitive at elevated ~i;
temperatures and increase in viscosity too
rapidly when held in warm runners, as used
in in~ection molding, and when the visco~ity
or flow is adjusted by reformulation of the
material, a 1088 of hot rigidity in the
molded article occurs;
4. They shrink to an undesirable extent though
they are better in this property than most
other thermosets; and
5. The steam crack resistance of a phenolic
molding material having good molding - -
latitude is not adequate.
Therefore, molding materials containing one-step
phenol-formaldehyde resins, though desirable, fail to meet
very important molding criteria and product requirements
Next, the molder can compound "one-step" melamine
or urea-formaldehyde resins. These molding materials are
known to possess good light-color characteristics because ~ -
the resias are not deficient in this regard. However
these molding materials fail in the following respects:
1, The materials have a high degree of shrinkage
in the mold and continue to shrink upon
aging at room temperature;
2, A melamine or urea molding material which
ha8 good molding latitude is deficient in
hot rigidity properties; and
3, They possess inferior steam crack resistance,
,:
4.
1043497 9133
PolyeYter res~n~ are popular thermosetting resins
but are not "one-step" resins and when compounded in a
molding material, the molding material significantly shrinks
in the mold and when otherwise exposed to high temperatures.
To minimize this deficiency, the molder must add a low pro-
file additive to the material which tends to expand the
resin's surface at the mold surface to thereby create an
article more closely approximating the mold's capacity
and configuration.
There i8 described herein a molding material con-
taining at least an inert filler which can satisfy, in a
superior manner, each of the desirable characteristics 1-8
recited above.
STATEMENT OF THE INVENTION : -
The molding material of this invention contains
about 20 to about 70 weight percent, based on the weight
of the material of a light colored resin formed by the re-
action of Bisphenol A (hereinafter called Bis-A), chemically
known as 2,2-bis(4-hydroxyphenyl)propane, and formaldehyde,
and about 30 to about 80 weight percent, based on the weight
of the material, of a reinforcing filler for the resin, The
resin comprises the product of the reaction of formaldehyde
and Bis-A at the mole ratio of about 2 to about 3.75 in the
presence of an alkali metal or barium hydroxide condensation
cataly~t to produce a one-step, heat convertible resin, It
has a pH of about 3 to about 8. The reinforcing filler may
be a particulate, such as powdery or fibrous, solid which
when mixed with the resin and the resin is cured to the solid
state, at least one of the following properties for the resin :
i8 increased: tensile strength, tensile modulus, Izod impact
strength (notched), flexural strength and flexural modulus.
9133
1043497
STATE OF THE ART
The first phenolic molding compounds produced
by Dr Leo H. Baekeland in 1910 were compression molded
using e~uipment originally designed for molding rubber.
Compress~on molding, typically with a cavity and a top
force or plug section, uses cold powder or heated preforms.
Compression molding remains a ma30r method of producing
thermoset parts,
The transfer or plunger molding process was later
developed In that process, the preheated molding compound
is placed in a separate plunger or well, and then trans-
ferred (or injected) into the mold. The process is ideal ~ -
for molding around inserts and for molding intricate
parts or to close tolerances.
Injection molding with reciprocating screw type
presses is the most recent advance in the molding of ther-
mosetting materials, an advance that has triggered a re-
surgence of interest in 60-year old phenolic molding mate-
rials as well as other thermosetting molding materials.
The in-line reciprocating screw machine has been used for
thermoplastics and only more recently modified to handle --
thermosetting materials. Basically, the machine conveys
the molding material as a powder from the hopper, heats,
melts and plasticizes the material in the screw flights,
and then the screw, acting as a ram, injects the material - -
directly into the mold,
Advantages of injection molding on reciprocating
screw machines include a high degree o automation and
control, elimination of preheated preforms, very fast - -
cure cycles and vertical discharge of the molded part.
Molds and e~uipment are eqùivalent in cost and complexity
of design to those used for transfer molding.
,. . ~ .
6 ;
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9133
1043497
The newly-developed ability to injection mold
thermosetting molding materials has led to a reevaluation
of the materials being used in many applications of injec-
tion molding. Cure cycles for phenolic thermosetting mold-
ing materials are frequently shorter than the cooling cycles
for engineering thermoplastics, especially in thick or large
parts. Molded thermosets are rigid on curing and can be
discharged hot from the mold whereas thermoplastics must be
cooled in the mold. The costs of producing parts from
thermosetting molding materials now compare much more ~i
favorably with competing materials. For example, the
properties of molded phenolic parts (especially their heat
resistance and dimensional stability) stack up well against
the properties of parts made from die cast metals. Of
course, the heat resistance and dimensional stability of
thermosets have always been superior to those of the
so-called engineered thermoplastics.
Concurrent with the development of the injection
molding process was the development of improved thermo-
setting molding material, e.g~, phenolic molding com- -- -
pounds, which are more suited for the particular require~
ments of in~ection molding. Characteristics that were ~-
improved include: density and granulation that allow
steady feed in both the machine hopper and screw flights,
lubricity of the material for better control of frictional ~
heat in the barrel and better mold release, and melt and ~ -
flow properties which permit the materials to be us0d
on the most critical applications. Unique resin
D-9133
~0434~7
developments have permitted molding compounds to be held
in the heated barrel of the injection machine for longer
periods of time with little loss of flow. In addition,
once the material enters the mold, its high hot rigidity,
when combined with the use of hotter molds (in the range
of about 175 to 200C.) yields more distortion-free
parts on extremely fast molding cycles.
It is expected that in the next few years, the
"warm runner" technique for processing thermosets w~ll
become very popular with many molders, particularly
those who are currently utilizing multi-cavity molds and
discarding sprue and runner systems that are 20-50 per
cent of the total shot size. Warm runner molding is
also sometimes referred to as "cold runner", "hot mani-
fold", or "runnerless" molding.
In the standard mold for injection m~lding of
thermosets, the material in the sprue and runner system
is cured along with the parts, and is discarded when the
entire molding is discharged from the mold. In a warm
runner mold, the material in the sprue and a major por- - -
tion of the runner system is maintained at a temperature
where it will flow but not cure by locating the sprue
and runner system in a separate insulated portion of the
ld. Thus, when cured parts are removed from the mold,
the material in the sprue and runner becomes part of
, . . -
the next molding instead of being discarded. - --
The figure is a cross-sectional -view of the
mold and runner section of an injection molding apparatus
~. .
'": ~' :,
-8- ~
'. ' '
.A `
~, . . . . ..
D-9133
1043497
adapted for use in warm runner molding.
The drawing shows a cross-sectional view, with ~;
self-explanatory legends, of a typical warm runner mold.
As can be seen, the runner, sprue, and nozzles are sep-
arated from the hot portion of the mold by a piece of
transite, and are surrounded by water channel~ that
maintain the manifold and nozzle temperatures at approxi-
mately 90-110C. With efficient temperature control of
these regions, molding material actually remains fluid
3/8 inch or less away from another region in the mold
where parts are curing at mold temperatures up to 205C.
From the above discussion, the most obvious
advantage to the use of the warm runner molding method
is the savings in molding material which is not discarded,
but rather is effectively used. However, additional ad-
vantages can be obtained by this invention such as ~-
better dimensional control, improved cycles, and a higher - -
degree of automation.
The characteristics of the mold~ng material
used in a warm runner mold are critical. The compound
must have exceptional "life"; that is, it must ~ose
flow at a very slow rate when held at the elevated
manifold temperature. At the same time, once it enters
the ld, which is significantly higher in temperature,
the material must cure as rapidly as possible.
In the in~ection molding process, granular
molding compound is poured directly into the hopper of
the injection machine. The screw then rotates and moves
rearward, drawing material in from the hopper and, at
_g_ , .
,~
D-9133
lU43497
the same time, plasticating it to a soft putty-like mass.
When the required weight of material has been plasti-
cized, the screw stops rotating and then moves forward
acting as a ram and forcing the molding compound through
the sprue, runners, and gates into the mold cavities.
After the required cure time, the mold opens, discharg-
ing the finished parts, and the cycle begins again.
Most thermoplastic in~ection machines can be
converted for the molding of thermosets by the instal-
lation of a new screw and barrel (pasticizing unit)especially designed for these materials. The screw
length-to-diameter ratio for thermosets is normally 14:1
. . .
and smaller than the 20:1 to 24:1 for thermoplastics.
.
The compression ratio (compression volume between flights
of screw between feed end and injection end) is normally
1:1 for thermosets as compared to approximately 2-1/2:1
for thermopla~tic~
With thermoplastics, the cylinder i~ heated to
about 200 to about 320C. Temperature control on the
mold is in the range of about 35 to about 95C. With ~ ~
thermosets, the barrel temperature is normally in the : -
range of about 60 to about 110C. Mold temperatures ~;
are about 150 to about 205C.
Screw speed in rpm (revolutions per minute)
is an important factor in proper plasticization of the --
-10-
.
D-9133
1043~97
material passing over the flights. Faster screw speed
results in shorter plasticizing time for a given shot.
Thermosets are usually processed with a screw speed
between 50 and 75 rpm. which is lower than the 90 to
220 rpm. normally used for thermoplastic.
Screw back pressure is pressure developed
on the material as the screw moves rearward against
applied hydraulic resistance during the plasticizing
step. This hydraulic resistance is controlled by
the back pressure injection cylinder flow valve, and
normal plasticizing pressures range from 400-3,000 psi.
in the material.
DISCUSSION OF THE INVENTION
The resins of this invention are produced - ~ -
by reacting about 2 to about 3.75 moles of formaldehyde
with one mole of Bis-A. Though the reaction of
formaldehyde with bis-A is described in the literature,
there is no descriptîon of a resin possessing all of ~ -
the above properties when properly compounded. Many
have described novolak (2-step) resins from these
reactants. Such reaction products have been suggested
as tackifiers in adhesives. The resole (l-step) ~ -
resins descrlbed by others are mainly rec~mmended for
-11- ~' '''
D-9133
~Q43497
varnish applications. None have sugges~ed the reaction
of these two reactants in the manner described herein
whereby to produce the unique resins of this invention.
It has been determined that the reaction
between formaldehyde and bis-phenol A should be
carried out by mixing them with an alkali metal or
barium hydroxide or oxide catalyst to achieve an initial
mixture having a pH of about 8 to about 11. The -
resin is thereafter treated with an acid to reduce
the pH of the resin solution to below about 8,
desirably between about 3 to about 8, and preferably
between 5 to 8. The preferred acids are the mineral
acids, such as sulfuric, phosphoric, phosphorous acids, ~ -
and the like, and carboxylic acids such as lactic acid,
citric acid, acetic acid, trichloroacetic acid, -~
monochloroacetic acid, oxalic acid, and thR like.
The most preferred acids for neutralization are ~ -
phosphoric acid, sulfuric acid, lactic acid and citric -
acid.
The initial mixture of the bis-A and formal- -
dehyde i8 achieved at a temperature below rapid conden- -
sation and the mixture is brought to condensation
'
, -
-12-
,
~ 434g7 9133
temperature, with stirring. Usually, the reaction
temperature is at least 80C., preferably the reactlon
i9 carried out at about 90 - 100~. Preferably, tempPr-
ature is ¢ontrolled by operating the reaction under reflux
and reduced or atmospheric pressure may be employed. The
reaction i~ contlnued untll the deslred degree of
reaction i~ achieved; this can ra~ge from about 30
minutes to one hour, or longer. Generally, the degree Or
reaotlon is predicated upon the polydi~perslty soughtO
Once the degree of thiQ reactlon is completed, the
product is cooled, neutralized with acid, and then stripped,
with heat and reduced pressure, of water and unreacted
materials. These are conventional practlces in the
art.
In some lnstances, one may flnd that the
- strlpped resln contalns unreacted formaldehyde. If
the quantlty o~ unreacted formaldehyde creates an
obnoxlous odor problem during the molding o~ the resin,
then lt may prove desirable to add a formaldehyde
scavenger to the resln, during its manufacture, before
- or after strlpping or as part of the molding material
~ormulatlon. The scavenger is any compound capable
Or reacting wlth ~ormaldehyde such as amides, amines
and alcohols; illustrated by melamine, urea, n-butanol,
sec-butanol, n-hexanol, polyvinyl alcohol,
ethylene glycol, glycerine, and the like~ The a~ount ;``
Or ~cavenger employed may range ~rom O to 25 weight
percent, based on the weight of the re~ln, and is
mostly dependent upon the amount of free formaldehyde
: .
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13,
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9133
1043497
present. However, ln most cases lt 1B desirable not
to employ more than about 15 wel~ht per cent o~ the
scavenger ba~ed upon the weight Or the resin.
The resin produced will usually have a
vl~coslty Or not more than about 30 centlstokes at
25 C., determined as a 35 weight per cent 801utlon in
ethanol. A Vi8C08ity Or 7-15 centistoke~ at 25 C.
i8 ~requently pre~erred ror most compounding and mold- -
lng operations. However, these viscos~tios are not
critical to the practice o~ thic inventlon.
The resins Or this lnvention are character- -
lzed by a relatively narrow molecular weight dl~trlbu-
tlon and low molecular weight. For example, the
"polydlsperslty" o~ these reolns 18 low, ranging rrom ~ -
about 1.5, or sllghtly lower, to about 5, or 811ghtly
hlgher. Most typlcally, the "polydisper~lty" i~
about 1.7 to about 3. "Polydl~perslty" i~ the ratio
o~ the welght average molecular welght to the
number average molecular welght, ~he re~in 18
typlcally a mlxture Or dimer~, trlmers and tet~ame~
as the prevalent components and contains a
methylol cohtent capable o~ condens~ng durlng the
curlng reactlon.
As 18 typlcal wlth thermosetting resln~,
they are compounded wlth reln~orclng materiala ~o -
enhance the Physlcal strength propertle~ rererred
to above. The ~lller materlals may be ln the
rorm Or non-~lbrous partlcles and ~lbrouo partlcle~
They may bo lnorganlc or organic, and ~hoy may
range ~rom materlal~ such as cotton rlber~ or
14,
9133
1043497
fabrics to glass fibers, from asbestos to wood flour,
from silica filler to hydrated alumina, from sisal
to ground nut shells (e.g., walnut), from carbon
ibers to zirconium or boron fibers, from poly-
propylene ibers to polyvinyl alcohol fibers, and
the like.
For example, boron fibers are used in
amounts up to about 50 weight per cent of the molding
compound. They are lightweight and strength impart-
ing Ibers. Carbon and graphite f~bers are used inam~unts up to about 50 weight per c~nt to provide
high mechanical strength retained at high temperatues.
Asbestos, either of the chrysotile, anthophylite,
crocidolite, tre lite or octinolite varieties, is-a
fibrous filler which is employed in amounts of rom about
5 to about 50 weight per cent, basis weight of molding
compound, to impart strength improvement and heat-
resistance. Alumina and zirconium oxide fibrous fillers
are used in amounts up to about 60 weight per cent to
provide enhanced physical properties, a high strength
to weight ratio, and resistance to elevated temperature.
Glsss ibers are particularly desirable, in amoun~s of
fro~ about 30 to about 45 weight per cent, to provide -~
high ~tren8th and resistance to water, alcohols and other
chemical8. Polyvinyl àlcohol ibers are uniquely desirable ~ -
in the molding compositions o this invention in a unts
o from about 10 to about 50 weight per cent to pro-
vide exceptionally high impact strengths. Shredded
15.
.. . ~
9133
1043497
cotton 15 desirable, partlcularly i~ the moldlng
compound i5 UBed in appllcations whlch do not requlre
notched Izod impact strength~ greater than about
0.45.
Particulate rlller~, o~ the pi~mentary
and non-pl~mentary (l.e., doe~ or does not provlde color)
type~, are most de~lrable and range rrOm sànd, quartz, ;~
trlpoll slllca, dlatomaceous earth, a~uminum ~
cates (e.g., clays), mlca, talo (magne~lum ~ lcate),
altered novaculite, ~umed colloldal slllca, nephellne
syenite, wollastonite (cal~ium sili¢ate), glass
spheres, kaolln clay, calcium oarbonate) zinc oxlde,
alumlnum oxlde, ~agneslum oxlde, tltanlum dloxlde,
b~ryllium oxlde, barlum~#ul~ate, wood rlour, shell
rlour, ~oron carblde, hollow carbon Mlcroballoon~TM,
hollow phenoll¢ resln Mlcroballoon~TM. Such klnds
or~r111ers are used ln amounts as low as ~ welght
per cent up to about 70 weig~t per ¢~nt, based on
the welght Or the moldlng oompound. Frequently,
mlxtures Or ~uch ~iller~ are used to impart ~pecial
propertle~ such as molding materlal ~low, ele~rlcal
propertles ln the molded resin, stren~th pr~pertles,
lmpact reslstance, and the llke.
In this regard, re~erence i8 made to SPE
Journal, Volume 28, No. 6, June 1972, pagee 21-36, -
lncluslve, publlshed by the 90clety o~ Pla~tlcc
En~lneers, Inc., ~reenwlch, Connecticut, U.S.A. ~he
SPE Journal artlcle al~o dlscusses a wide variety
o~ other ~dditivos, many o~ which may be used ln the
16.
9133
1043497
practice of this invention, such as antioxidants,
colorants, optical brighteners, lubricants and ultraviolet
light absorbers. ProcesQing and molding aids, such as
lubricants (e.g., stearic acid) may be added to the resin
prior to formulation into a molding compound, and/or they
may be added during the compounding of the resin to`form
the molding compound, and/or they may be added to both
the resin per se and the molding compound.
An opt ~ nal aid which may be added during the
compounding step to make the molding compoùnd is calcium
oxide and/or calcium hydroxide, It serves the function
of enhancin~ the hot rigidity characteristico of the
campound. C~lcium oxide or hydroxide may be added in
amounts up to 11 weight per cent, preferably about 2-7
weigbt per cent, based on the weight of the compound.
The combinations 8uitable for effective
molding compounds pursuant to this invention are
innumerable and desirable compounded compositions
are depicted in the designated examples below.
Compounding is effected in the usual manner
except that certain obviou8 factors should be con-
8idered. If the ob~ect i8 to produce a light colored ~ ~ -
molded article, then the reinforcing component8
should be light colored and should t add undesired
¢olor upon curing of the molding material. If the
molding material i8 to be employed in in~ection
molding oper~tion8, then the viscosity of the resin
17.
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9133
1043497
compound ~hould be approprlate at khe molding con-
dition~ to achieve the de~lred rlow.
If the moldlng materlal 1B Por use ln trans-
~er or inJectlon molding operationsJ then it is
deslrable that the compound have rlows oP at least
15 inches, and typically`not greater than 45 lnche~,
determined by the ~ollowlng proccdure~ the mold-
ing behavior Or thermosetting resin comPoslte~ is
characterlzed by a rlow test ~imilar to tbat des-
crlbed by K. R. Horrman and E. R. Fiala in paperXXIV-2 Prom the Annual Te¢hnlcal Conrorence oP the
Soclety Or Pla~tics Englneers, Vol. 12, ~ en-
tltled "A Simple Ram Followlng Apparatus Applled to
Spiral Flow 0~ Plastlc Molding Compounds" wlth the
Pollowlng modl~idatlons~ (a) the oro~s-sectlo~
Or the Plow channel l~ 0.125" x 0.375"; (b) the
moldlng material is charged to the apparatus as a
prerorm preheated to 121 C.; (¢) a mold temperature
oP 168C. 18 used and (d) ~he trans~er pres~ure 18
8,800 psi on the ram. For the purpose oP this ln-
vention, the "moldabllltyl' Or a therm~setting co~-
pound 18 characterized by the ,numbor o~ ln¢,he~ the
materlal le capable Or rlowlng wlthin the mold
channel berore settlng up under tho conditlons Or
this test~ It has been emplrl¢ally establi~hed
that good perPorman¢e ln lnJectlon moldlng requires
a test ~low equal to or greater than 24 lnahes, and
good tran~er moldlng requlre~ a test rlow equal
to or greater than 18 ln¢hes in this teJt. Materlals
havlng spiral to~t ~low~ below 15 inches are gonerally
18.
D-9133
1043497
suitable only for the less demanding compression molding
techniques.
A desirable attribute of the molding materials
of this invention is the fact that they may be kept at
flow temperatures, e.g., about 90C. to about 125C.,
in the mold barrel and runners for long periods of i~
time, e.g., one hour or more without being cured,
yet when brought to cure temperature, e.g., about
175C., they rapidly cure to a rigid product, essentially
free of deformation and mold shrinkage, at least 30 per
cent faster than a comparable "one-step" phenol-formalde-
hyde resin molding material similarly compounded. -
Compounding may be effected in a variety of
equipment, such as a "Banbury"* mixer, an extruder, - -
a kneader, a two or three roll mill, and the like. ; -
It is important in the practice of this invention that
the componen¢s of the molding compound be intimately
~ :-
and thoroughly dispersed such that a~y portion thereof
has essentially the composition of any other portion
thereof.
Cne aspect of the resin of this invention
appears to be an anomoly to the excellent hot rigidity
properties of the products molded from the molding mater-
ials of this invention. The resin of this invention pro-
vides a molding material which appears fully cured when
removed from the mold on fast cycles, possesses a high
heat distortion temperature of about 130C., and the
molted resin article possesses electrical
.
*"Banbury" is a trade mark.
19 .
i r~
. . . . - . . - . .. . . .
~ 043497 9133
properties equivalent to those obtained from most phenolic
molding materials, but if the article is post cured, it
will possess superior electrical properties. This
sugge8ts that the apparently cured molded article which
possesses so many excellent properties still has unreacted
methylol groups which adversely affects the potential of
reaching optimum electrical properties. It is believed
that the post cure condenses those remaining groups and
this causes the electrical properties of the article to
be significantly enhanced. Post curing may be achieved
at temperatures exceeding the reaction temperature
o'f the methylol groups. Usually, it is at least about
35C. and preferably at least 90C. After the post cure,
the molted article of the compounded resin of this inven-
tion possesses exceptionally good electrical properties,
at least equal to the best obtained with lded phenol-
orma1dehyde resin which are comparably compounded.
T~e following examples are ofered to
illustrate this invention and are not intended for
the purpose of limiting this invention. In the
examples which follow, the ormulation is listed - -
prior to the procedure used in making the resin.
20.
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1043497
EXAMPLE I
Formulatlon Parte by Weight, grams
Blsphenol A 6000
Formaldehyde (40%) 3000
Sodlum Hydroxlde (25%) 72 -
Phosphorlc Acld (75%) 18
Water 18
Procedure
Into a reactor, equipped wlth a conden~er,
stlrrer and temperature recordlng devlce there was placed
6000 grams (26.4 moles) o~ blsphenol A~ and 3000 grams
(40 mole~) Or 40% by weight aqueous 801utlon o~ rormal~
dehyde. The pH Or the mlxture was ad~,ted/ tJo 9.8 by
_~ the addltlon thereto Or 72 grams ~4,5 mOlo~or a 25%
by welght aqueous eolutlon o~ ~odlum hydroxlde. The
mlxture was then heated to 95C. and malntained at 95C,
ror one hour whlle being stirred, The reaction mixture
was then cooled to 55C. and its pH wa~ adJu~ted to 6.o
by the addltlon theroto Or an aqueous eolutlon prepared
20 by admixing 18 grams Or a 75% phosphorlc acld solutlon ~ -
wlth 18 grams o~ water. ~he contents o~ the roactor -,
were then sub~ected to a vacuum o~ 28" (Hg) at a temper-
ature o~ be~we-n 95-100C, and controlled to a l50C,
,-, .
21. --
9133
1~43497
hot plate gel of 120 seconds, The resin was then
discharged to coolers to immediately stop condensation
reactions, The molding material composition made with
this resin could not be cured,
EXAMP$E II
Fo D lation Parts bY Wei~h~ rams
BisphQnol A 6000
Formaldehyde (40%) 9000
Sodium Hydroxide, (25%) 72
10 Phosphoric Acid (75%) 18
Water 18
Procedure
Into a reactor, equipped with a condenssr,
stirrer and temperature recording device there was placed
6000 grams (26,4 moles) of bisphenol A and 9000 grams
(120 moles) of 4070 by weight aqueous solution of formal-
dehyde. The pH of the m~xture was ad~usted to pH 9,5
r~ ~ O~ ~r,ol~sJ
~_J by the addition thereto of 72 grams ~4.5-~w~6~ o~ a
25% by weight aqueous solution of sodium hydroxide.
The m~xture was then heated to 95C, and maintsined at
95C, for one hour while being stlrred, The reactLon
mixture was then cooled to 55C. and its pH was ad~usted
to 6.5 by the addition thereto of an aqueous solution ~-
prepared by admixing 18 grams of a 75% phoaphor~ acid
solution with 18 grams of water. The c~ntents of the
reactor were then sub~ected to a ~ -
vacuum o~ 28" (Hg) whlle applylng heat, At about -
75C, the viscosity of the resin became extremely high
... . ...
9133
10 4 3 ~ 97
and as a re~ult the agitator klcked out. By raising
the temperature to 95C. the agitator started but it dit -
~kick-out ag~in because of the very high viscosity.
~e~
Formulation Parts bX Wei~ht~ ~rams
Bisphenol A 6000
Formaltehyde (4070) 5220
Barium hydroxide Monohydrate ?2
Phosphoric acid (8770) 18
10 Water 18
Procedure
Into a re~ctor, equipped with a condenser,
stirrer ~nd temperature recording d~vice, there was
placed 6000 grams (26.4 les) of bisphenol A and 5220
8rams (69.6 moles) of a 40% by weight aqueous solution
of formaldehyde. The pH of the mixture was at~usted to
9.2 by the addition thereto of 72 gram~ (0.38 moles) ~-,
of barium hydroxide monohydrate.
The mixture was then heated to 95C. and
maintained at 95C. for one hour while being continuously
stirred. The reaction mixture was then cooled to a
temperature of 55C. and its pH ad~uated to 6 by the
; ~- .
addition thereto of an aqueous solution prepared by
admixing 18 grams of water w~th 18 grams of 87% by
weight aqueous solution of phosphorlc acid. The
contents of the reactor were sub~ected to a vacuum of
27" (Hg) while applying hoat. In the proce~s o~ heating
,.
.
9133
1043497
the resin to 90C-100C., the ~gitator k*ked-out
at 70C. because of the very high viscosity o the resin.
The resin was immediately di~charged to coolers and
its 150C, hot plate gel was 58 seconds.
EXAMPJE ~`
Formulation Parts by Weight~ ~rams
Bisphenol A 6000
Fon~ldehyde (40%) 5220
Potassium Hydroxide (25Z) 72
Phosphoric Acid (87%) 18
Water `18
Procedure
Into a reactor, equipped with a condenser,
stirrer and temperature recordin8 device, there was - -
placed S000 gram~ (26,4 moles) of bisphenol A and 5220
grams (69.60 moles) of a 40% by wei~ht aqueous solution --
of formaldehyde. The pH of t~e mixture was ad~usted to
9.3 by the addition thereto o 72 grams (0.32 moles)
of 25Z by weight aqueous solution of potassium hydroxide.
20 The mixture was then heated to 95C. and maintsined at
95C. for one hour while bein~ continuously stirred.
The reaction mixture was th n cooled to a temperature
of 55C. and its pH ad~usted to 6.0 by the addition ` -
thereto of an aqueous solution prepared by ad~cing 18
grams of water with 18 grams of 87% by weigh~ aqueous
solution of phosphoric acid. The contents of the reactor
were sub~ected to a vacuum of 27" (Hg) at a temperature
bet~een 98C. and 110C. The re~n was controlled to a
r~J~
9133
10434~7 - ~ -
150C, hot plate gel of 110 seconds and then it was
discharged to coolers.
EXAMPLE V
Formulation Parts_bY Weight, ~rams
Bisphenol A 6000
Formalin (40qO) 5220
Sodium Hydroxlde (25~) 72
Phosphoric acid 18
Water 18 `
Procedure ;
Into a reactor equipped with a condenser,
stirrer and temperature recording device there was ~,
placed 6,000 gram~ (26.4 les) of Bis-A, and ~-
5220 grams (69.60 moles) of 40% by weight aqueous solution
of formaldehyde. The pH of the mixture was ad~usted ~to
~ lf~ ,mD/t5 J
~_J 9.5 by the addition thereto o 72 8rams ~i.5 mol~) of
a 25X by weight aqueous solution o~ sodiu~ hydroxide.
The mixture was then heated to 95C, and maintained
at 95C. for one hour while bein~ stlrred.
The reaction mixtuxe was ehen cooled to
55C. and it~ p~ was ad~usted to 6.5 by the ~ddition
thereto of an aqueous solution preparet by admixing
18 8rams of a 75% phosphoric acid so1ution with 18
grams of water. -- The contents of the re~ctor were then sub~ected
to a vacuum of 28" (Hg) at a temper~ture between 95-100C.
and controlled to a 150C. hot plate gel o 190 seconds,
Tho resln was then ti~ch~rged to coolers to immediately
stop the contens~tion reactions,
25-.
9133
1043497
EXAMPLE VI
Formulatlon Per cent by weight
Bis-A formaldehyde resin of Example V 45.75
Zinc stearate 3.50
Behenlc acid 0.75
Dibutyl phthalate l.OO
Calcium hydroxlde 2.00
Asbestos (Chrysotile) 18.50
Cellulose filler 11.25
lO Tltanium dioxide lO.OO
Zinc Oxide 7.00
Stearic acid 0.25
Ingredients, totaling 2500 grams) were weighed
as per above formulation and blended in a mill with
stone balls for fifteen mlnutes.
After blending for fifteen minute~, a five
undred gram charge of the raw mlx wa~ put on a two
roll mill. The front roll was kept at 88C-95C
and the back roll was at 138C-144C. The material
then formed a sheet and was further compounded for
seventy se¢onds on the mlll. It was then taken off
the rolls to cool and became rigid for grinding to a
deslred granulation particle size. --~
Then the granules were mixed with the balance of
the raw mix and re-rolled in the same manner deRcrlbed
above, cooled and ground. ~
: .
26.
9133
1043497
It was tested ror lnJection moldlng latltude
and hot rlgidlty.
Compresslon molded ~haker CUp8 have been
on test ~or steam crack re~tance ~or more than one
year To date, the CUp8 have shown no ¢racks.
In~ection Moldlng Pro~ertles
Moldlng Latltude 86 minutes
Hot Rlgidlty 2 1/8 lnches
Li~ted below are the phy~lcal ln~ectlon molded
properties. The moldln~ temperature wa~ 171C. wlth a
90 seconds cure time.
Notched Izod Impact Strength, 0.32
rt.-poundo/lnch o~ notch
(ASTM D 256)
Flexura~ Strength, p~l. 10,500
(AST~ D 790)
Modulu~ Or Elastlclty, pel. 0.95 x 106 -
(ASTM D 790)
Flexural Work to Break, rt-lbs/ln2 0.37 ~ -
(ASTM D 790)
Maxlmum Do~lectlon, lnches 0.144
(A8TM D 790) -
Ten~llo Strength, pai 8170 --
- (ASTM D 651)-
Compres~ive Strength, p~i 26,200
(ASTM D 695)
Rockwell Hardnes~ "E" 29
(ASTM D 785)
Heat Dlstortion Temperature 203C.
(ASTM D 648)
Wator Ab~orption 0.89%
(ASTM D 570)
.
-
9133
~ 43497
~XAMPLE VII
Repeating the procedure of Example VI, a molding
material from the following ingredients was made.
Formulation Per cent~
Bis-~ formaldehyde resin of Example V 50.00
Melamine 10.00
Calcium Hydroxide 4.50
10 Calcium Stearate ` 3.00
Asbestos 18.00
Pulp Flock 6.00
Ni8ro~ine 1.50
Clay 7 00
100. 00
The resulting molding material had a flow of
18.25 inches, measured at 168~C, according to the flow
procedure described at page 18 suPra. The molding
material was transfer molded to produce ASTM spec~mens
whlch were cured for two minutes at a mold temperature
of 168C - 171C. As shown in the table which foliows
the spec~mens were post-baked for ei8ht hours at 177C
and the post-baked or post-cured specimens were compared ~i
agalnst the first cured specimens as recited in the table.
.'-.-.
.
:
28.
1043497 9133
TABLE
ASTM
Method As Molded Postbaked *
Flexural Strength, psi (D 790) 10,100 12,100
Tensile Strength, p~i (D 651) 7,140 6,710
Compressive Strength (D 695) 26,900 28,800
p8i
Izod Impact, (ft-lbs/ (D 256) 330 .320
inch of notch)
Heat Distortion (D 648) 450 490
Temperature, F
Speclfic Gravity (D 792) 1.46 1.43 - ~ ~
Rockwell Hardness "E" (D 785) 69 80 . .
Dielectric Strength, (D 149) 395 406
S/T, volts/mil
Arc Resistance, sec. (D 495 173 184
Volume Resistivity, (D 257) 9.3x1012 2.9x1012
ohm cm
Dielectric Constant ~D 150)
60 cycles 10.1 5.5
1 KC 8.1. 5.2
1 NC 5.7 4.5
Dissip~tion Factor (D 150)
60 cycles 0,18 0.04
1 RC 0.11 0,04
1 MC 0,07 0.03 ~-
* 8 hrs, at 177C.
2gv
In the ta~le~ e~ow 1B R comparl80n Or the er~ects
o~ the u~e o~ short poly(~lngl alcohol) ~lb~rs (PV-OH),
wood flour, pulp flock and a~be~tos flo~ts as impact
relnforcement for the bi~phenol A-form-ldehyde resin
of Example V. me fiber~ ~nd flllers us-d are listed
below togcther wlth ths lmpact properties of compression
molded compo~ites:
TAB~E
C~mDo8$,tes
Filler System, Wt. X A B C
Woodflour - - 23
Pulp flock - 8
10 A~bestos floats - 30
PV-OH fibers (1/25", 6 denier) 20 ~ ' ~
Notched Izod Impact Strength,
ft-lb~/ln. 1,.6 0.35 0.25
8all-Drop Impact Strength, ln. 40 15 14
In the preceiing, moldln~ lat~tude was
d-term~ned by pl-cing-the molding maeorlal in the barrel
of a reciprocating screw ln~ecti,on machine while in the
plasticized state and sub~ecting it to a series of
increasing delay timos between in~ections following the
plasticizing step. The maximum delay time it will
still allow bottoming of the screw within the barrel
within a 30 second period i8 reported as the inJection
molding latitude in terms of the barrel re~idence time.
Hot ri~iditY is determinsd by taking a molded test sample
and promptly placing it horizontally upon a vertical rod
and the deflection of the part 80 positioned is measured. ~-
The inJection mold hot rigidity i reported as deflection
30.
.
9133
lV43497
in inches of the part from the horizontal. The steam
crack resistance.is measured by placing a compression
molded shaker cup (7" x 3" diameter x 1/4" in thickness,
molded at 168-177C. with a cure time of 60-120 seconds
and cond;itioned for 72 hours at 22C., at 50% relative
bumidity) over a steam ~et with cool air flow on the
outside surface 80 that the steam contacts the interior
of the cup. The steam crack r~sistance is méasured
as that period of time up to and including the formation
of visible cracks in the cup.
. 31~
9133-C
10434~7
Supple~e~tarY Disclosure
It has ~een determined that the reaction between
formaldehyde and bisphenol-A should be carried out by mixing
them w~th a catalytic amount of an alkali metal or barium
hydroxide or ox~de catalyst, The alkali metal hydroxide or
barium ~droxide catalyst is employed in a catalytic amount
such that the reaction mixture has a pH of from about 8 to
about 10. To ~eld a pH within this range, it has been found
that the alkali metal hydroxide or barium hydroxide catalyst
should be employed in amounts from about 0.005 to about 0.2
equivalents of hydroxyl, i,e., OH(-~, per mole of bisphenol-A.
T~e resin is thereafter treated with an acid to reduce the pH
of the resin solution below about 8, desirably between about
3 to about 8, an~ preferably between 4 and 5. The preferred
acids are the mineral acids, such as sulfuric, phosphoric, ~-
phosphorous acids, and the like, and carboxylic acids such as
lactic zcid, citric acid, acetic acid, trichloroacetic acid, ~'?
monochloroacetic acid, oxalic acid, and the like. The most
preferred acids for neutralization are phosphoric acid, sulfuric
acid, lactic acid and citric acid.
The initial mixture of the bis-A formaldehyde is
achieved at a temperature below rapid condensation and the mix-
ture is brought to condensation temperature, with stirring.
Usually, the reaction temperature is at least 80C., preferably
the reaction is carried out at about 90 - 100C., although ~ -
sl~ghtly lower temperatures, e.g., down to about 70C., can
be used in some cases, especially when higher proportions of
catalyst are used. Preferably, temperature is controlled by
operatlng the reaction under reflux and reduced or atmospheric
pressure may be employed, The reaction is continued until the
desired degree of reaction is achieved; this can range from -
a~ 32.
9133-C
1043497
about 30 minutes to on~ hou~, or lo~ger. Ge~eral~y, the degree
of reaction is predicated upon the pol~dispersity sought.
Once the reaction is completed, the product is cooled,
neutral~zed with acid Cw~en this is needed~, and then stripped,
with heat and reduced pressure, of water and unreacted materials.
These are conventional practices in the art.
Example IX
By procedures analogous to that described in
Example I, bisphenol-A/formaldehyde resins were made from the
formulations shown below in the Table, using the reaction
conditions indîcated therein:
Table
Component and _ Run No
Reaction Conditiohs 1 ~ 2 ~3 - - -
. _
Grams Bisphenol-A 6000 6000 6000
Grams of 40% Formaldehyde 4200 4200 4200
Grams of 25% NaOH 720 14.4(1) 27 ~ - .
Equivalents of OH(-~ per
mole Bisphenol-A 0.171 0.00342 0.0064 --~ -
Grams Phosphoric Acid 300
Grams Water 300 - -
Stearic acid, grams 240 240 - -
Reaction temp., C. 70 97-104 95
Reaction time 30 min. 12+ hrs. 3 hrs.
150 Gel time, Seconds 238 850 250
Yield, grams 7947 6970 7802
Methylol content, wt.% 17.97 8.73 14.44
Reactîon pH 10.1 8.3 8.3
Final pH 6 3 4.3
Cl) Added in two portions of 7.2 grams each. pH prior to
second portion was 4.5. -
. : .
A satisfactory molding material was made using
the resin from Run No. 1. T~e proportion of catalyst used in
Run No. 1 i8 about the upper limit for the particular formula- -
tion used.
The resin from Run ~o. 2 was too unreactive to be -
used.
.
a~ 33 ~
9133-C
~3~97
T~e proportio~ of catalyst i~ ~un ~o, 3 is slightly
above the lo~er limit that ca~ be used,
The reason that the proport~on of catalyst employed
in Run No, l is about the upper limit that should be employed
is that: :
(a~ the resin will contain a relatively large amount
of salt (from the neutralized catalyst~, whic~ will have a detri-
mental effect on steam crack resistance and electrical properties;
(b~ the reaction mixture employed in making the resin
was close to the limit in reactivity for convenient handling;
and
Cc~ because of the high reactivity of the resin, it
is difficult to remove enough water to prevent a severe tendency
to sinter.
34,
` , , . . , . , . , 1,:,
