Note: Descriptions are shown in the official language in which they were submitted.
BLOW MOLDED CONTAINER AND METHOD OF MANUFACTURE
The invention is concerned with plastic con-
tainers produced by blow molding. Of particular inter-
est is blow molding as carried out over the lower range
of permissible temperature so as to result in biaxial
orientation.
o
~$~ Z
BACKGROUND OF THE INVENTION
Plastic containers, that is, containers con-
structed primarily of substituted or unsubstituted hydro-
carbons have, for some time, been in prevalent use. In-
creased popularity, as compared with inorganic glasses,is due to a variety of factors--inter alia, improved
impact resistance, reduced weight, and, perhaps most
significantly, reduced cost.
As would be expected, procedures for producing
so popular a commodity have been in continuing transi-
tion. What started as a simple operation, analogous to
that used for inorganic glass has evolved through a
variety of stages. Today, most contaillers are produced
by procedures which involve a first formation of a pre-
form, sometimes denoted a parison, followed by expansionof the preform to produce the final container. Preforms
are commonly produced by any of the various molding opera-
tions with extrusion and inJection being predominant~
Expansion is commonly by means of gas pressure with final
form being determined by a mold specifically designed for
this operation.
A most sophisticated form of blow molding is
now becoming commercially significant. It differs from
earlier procedures in that the parison is first stretched
and then blown while its temperature is much lower than
wlth conventional processes--generally, within the 100E
(ca, 4QC~ range above T (the temperature at which the
plastic material passes from the glass phase to the rub-
ber phase), This procedure, which is known as stretch-
blow molding,or orientation blow molding, is not onlyreplacing more conventional procedures,~ but is opening up
new markets. Advantages of the new procedures are all
related to biaxial orientation of the polymer material.
Regardless of how the parison is initially formed--e-g-,
whether by extrusion or injection, regardless of whether
-- 3 --
o
the procedure is two-stage or in-line, the parison ?
while at a temperature insufficient to permit free plastic
f~w is expanded biaxially to conform with the blow mold.
The temperature of operation generally within the 100~
(ca. 40C) range immediately above T is such that
expansion introduces true strain into the material. The
strain translated into a definable polymer orientation
resuIts in a number of attributes.
Alignment of polymer molecules results in in-
creased tensile strength, as well as increased clarity,
increased impact strength, and reduced creep. A vast
market for carbonated soft drink containers is a direct
result of significantly improved gas barrier properties.
Suitable container materials are substituted
and unsubstituted thermoplastic hydrocarbons. Commonly
used materials at this time include acrylonitrile, poly-
ethylene terephthalate, and polypropylene. The described
prOcedures are well known--descriptions are included in
standard reference texts, See, for example, Modern
Plastics Encyclopedia, Vol. 54, NQ. lOA, 197i-1978,
McGraW-Hill Publishing Co. (e.g., sections on "Blow
Molding" at page 230 et seq.; "Injection-Blow Molding"
at page 232 et seq.; and "Stretch-Blow Molding" at page
233 et seq.). It is well known that the various types of
stretch-blow molding procedures, as well as conventional
injection blow molding procedures, have not been success-
fully adapted to the production of a container including
an integral handle. Commercially, plastic containers
with handles have been made exclusively by extrusion-
blow molding procedures wherein a large diameter parison
is pinched in such a way as to define a handle area which
is subsequently blown with the rest of the container to
its final dimensions. This process depends onthe use of
high plastic temperatures to proyide satisfactory fusion
of the plastic in the blow mold when it is pinched prior
82
4 -
O
to expansion with the pressurizing medium. It also de-
pends on the use of large diameter parisons and forming
the neck finish in the blow mold. ~ further limiting
feature is that such handles are hollow and interconnected
with the cavity of the coiltainer so that the handle must
also act to contain product. This and other design limi-
tations preclude consideration of such processes for
certain important markets.
The problem of producing plastic containers
with handles using stretch-blow processes derive from the
nature of the process and the condition of the plastic at
the time it is biaxially oriented. It is not possible to
produce handles by the aforementioned parison pinch-off
technique because the plastic temperature required for
suitable molecular orîentation is much too low to permit
adequate fusion of the plastic. ~o form the handle and
ne~k finish first at elevated temperatures and then cool
to biorientation temperatures before stretching and blowing
would yield handles and substantial other unoriented por-
tions of the container with inferior containment andother properties. Additionaliy, the prime current market
for bioriented containers is for soft drinks where its
success depends onthe use of a bottle shape optimally
designed for pressurized use. Such designs are not pos-
sible in the processes heretofore considered.
And so the common assessment of the marketplace has been that stretch-blow molding processes are
incompatible with the production of integral handles and
attempts to overcome this problem have generally taken the
form of mechanical fixtures. A variety of discrete handle
configurations have been attached by means of bands and
the like. Such attachments have been suitable for car-
rying but not for pouring with a one-handed grip.
An approach described in French Patent No.
1,192,475 has apparently not found commercial use, The
4BZ
-- 5
procedure described in conjunction with FIGS,12 and 13
of that reference as applied to conventional (not stretch~
blow molding makes use of a completely formed return handle
attached at both upper and lower extremities to a parison
portion not subjected to blow molding. While permitting
undisturbed blowing in the bottom portion of the parison,
this approach is undesirable because an excessive portion
of the length of the parison cannot be blown resulting
in inefficient material utilization, container shape and
size restrictions even when a small, one-finger, jug-style
handle is cont~mplated. Additionally, such an approach
when translated to stretch-blow processes leaves substan-
tial portions of the container between the extremities
of the handle in a non-oriented, and therefore inferior?
state.
~6~
6 --
SUMMA~Y OF THE INVENTION
Blown containers of the invention include han-
dles integral with the container. Handles are an inte-
gral part of the parison or preform being affixed at a
single plane normal to the major axis of the parison
outside the region to be blown. Material waste is thereby
minimized and container design freedom maximized. In
addition, such handle regions may serve as gripping re-
gions during blowing and for support during filling and
capping, Stretch-blow processes in accordance with the
invention provide opportunity to biorient a maximum por-
tion of the parison and container.
The teaching is of sufficient breadth to include
final blown containers in which handle form and joinder
are independent of blowing. Handle configurations may
be simple bar-shaped, L-shaped, T-shaped, or may even
return to result in double joinder on the same parison
plane. They may serve for pouring or carrying~
Preferred embodiments of the invention are
directed to handles with lower extremities somehow affixed
to a blown portion of the container. Species include
those in which such second joinder is accomplished me-
chanically as by use of encircling hands. labels and the
like but also include embodiments in which joinder at
least partially results from handle-interlocklng and/or
bonding with a blown region.
While the keyed or interlocked configuration is
believed suitable for most uses, an alternative, in which
joinder is accomplished by fusion or bonding is certainly
a desirable embodiment. The nature of the blowing opera-
tion generally precludes sufficient heat in the blowing
region to accomplish fusion. A variety of bonding opera-
tions including, inter alia, welding and adhesive bonding
serve. Bonding may be independent of, or ancillary to,
interlocking.
48~?f
7 --
BRIEF DESCRIP~ION QF THE`DRAWrNG
FIGS. lA and lB are perspective views, res-
pectively, of a parison and a broken section in perspec-
tive of the corresponding blown container pr~vide with a
T" bar.
FIGS 2, 3, and 4 are perspective views of
handle portions of blown structures alternate to that of
FIG, lB and are provided, respectively, with a single
joinder loop, a double joinder loop, and an "L~' carrier.
FIGS. 5A and 5F are plan views and 5B through
SE sectional views, all views of preferred embodiments in
accordance with which a handle molded in a portion outside
the blown portion of the parison is attached to a blown
region during blowing. Reference is made to these views
in the fabrication of such embodiments.
FIGS, 6A, 6B, and 6C are a broken plan view
and sectional views, respecti~ely, of configurations
alternative to those of FIGS. 5.
FIGS. 7A, 7B and 7C are a broken plan view and
sectional views, respectively, which depict another
alternative to those of FIGS, 5,
FIGS. 8A, 8B, 8C, and FIGS. 9A, 9B, 9C of the
same general form as FIGS. 6A, 6B, and 6C, depict yet
addltional alternatives to those of FIGS, 5.
FIGS. lOA and lOE are plan views and lOB, lOC
and lOD are sectional views all depicting an embodiment
in which a pouring handle is formed on a blown bottle
with the lower extremity being attached by spin-welding.
FIGS. llA, llB, llC? and 12A, 12B, all section
except llA in plan, are views illustrative of spin-
welding attachment of lower handle extremity alternative
to that of FIGS. lOA through lOE.
FIGS, 13A in section, 13B in plan, and 13C in
section, are views illustrative of embodiments in which a
handle, part of the upper region of the parison before
~9`f~8%
blQwi:ng, is. return-bonded to a blown region of a contain-
er by~ any of a variety of bonding techniques alternative
to s~pin~welding.
FIG$. 14A, 14B, 14C, and 14D are, respectively,
a top, a front, and sectional view of a pariscn including
a pro~ecting l'L~' handle and, finally, of the corresponding
portion of the blown container,
FI:GS, 15A and 15B are sectional views of a
paris~.n. at two stages during processing in which a
handle is deformed from a straight bar to an ~'L".
FI.G$. 16A, 16B and 16C are top front and sec-
tional Views oP a parison corresponding with 14A, 14B, and
14C, and 16D a section view of a blown container corres-
ponding with 14D but in which the ~'L~' handle i8 provided
with a shaped extremity whi.ch.facilitates bonding to a
blown region of the containeri and
FIGS, 17A through 17C are sectional and plan
views of blow molding and ancillary apparatus suitable for
th.e fabrication of the configuration of FIG. 16D.
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`DETAILED D~C _RI~TION
1. The Drawing
The following figure descriptions are concerned
with configuration, although views illustrative of appro-
5 priate processing steps and apparatus are sometimes in-
cluded, All embodiments depicted and all others within
the inventive teaching share in common the pre-blown
molding which contains a completed or inchoate handle as
an integral part. This handle is invariably attached
over a locali~ed region ideally corresponding with but a
single plane normal to the ma;or axis of the pre-blown
molding. In each instance, the pre-blown molding, how-
ever, produced (sometimes characterized as a parison or
preform) is blow molded to conform with an appropriate
blowing mold. ~hile not explicitly discussed, molding
may take the traditional form with temperature signifi-
cantly above the glass-rubber transition temperature or it
may be carried out at reduced temperature, generally
within the range of from T to T plus 100F (ca. 40C)
to result in biaxial orientation. The latter procedure,
the preferred embodiment of the invention, results so
long as the temperature of the plastic material is suf-
ficiently low to result in biaxial orientation sometime
during--not necessarily throughout--expansion.
PIGS. lA and lB are a perspective view of a
parison l and of a broken portion of blow molded container
2 produced f~om such parison 1~ The ~T" bar carrying
handle 3 is an integral portion of parison 1, being molded
as a portion of a ring 4 about the entire periphery of
parison 15 Ring 4 may serve for gripping during blowing.
FIG. 2 is a view of a blown container illustra-
tive of a carrying handle configuration alternative to
that depicted in FIG.lB. In this instance, the "T'l is
replaced by a loop which is a part of ring portlo~ 11
of a parison which when blown results in a container of
B~
-- 10--
which 12 is a port~on.
FIG. 3, again of a form corresponding with
FIG.lB, is illustrative of a form of carrying handle 20
of loop configuration which returns to ring section 21
at two regions, 22 and 23. The entire loop configura-
tion, an integral part of the parison, i5 unaffected in
the blowing operation which results in the blown container
of which 24 is a section.
FIG. 4, depicts another structure alternative
to that of lB, this time produced from a parison molded
in a form to include "L" handle 30 attached to ring portion
31 resulting in a blown container 32.
FIGS. 5A and 5B depict a parison 4Q including
an "L" handle region 41 of the general configuration of
that shown in FIG. 4. The lower extremity of that "L"
handle 41, how-ever, is of such configuration as to ex-
pedite attachment to the blown container 42,
In FIGS. 5B and 5C the configuration provides
for a notches extremity 43 to facilitate bonding. The
blow mold, not shown, may have provislqn fQr insertion
of the notched region of handle 41 so that it, in effect,
becomes a portion of the innér surface of the blow mold
during blowing. In this manner, the sidewall is blown
against, into and around the configuration of the handle
end to secure a gripping attachment. To facilitate the
molding of the sidewall into such configurations, it
may be desirable to vibrate the handle end to p~omote
slippage and~or generate heat.
FIG. 5D is a detailed view of this arrangement.
FIG. 5E is a detailed view of the same region
shown in FIG. 5D but showing a section through a plane
or orthogonal to that of FIG. 5D. The undercut notch of
extremity 43 is clearly seen. The distorted region of
blown container 42 conforming to the notch is also visible.
FIG. 5F is a top plane view showing handle 41,
-11 --
as well as the neck region of paris-an 40 and tbe ~lown
container 42.
FIGS. 6A, 6B, and 6C are illustrative of a COII=
figuration in which a handle region 50, again, facilitates
connection with blown container wall 51 by interlocking,
but which, in contradistinction to handle extremity 43
of FIG. 5, constitutes the male rather than female memb.er
of the pair. Again, wall 51 is distorted to meet with 50
with distortion being produced during blowing7 Male pro-
~ecting region 52 is shown in phantom in elevational view6A. FIGS. 6B and 6C are, again representations on planes
orthogonal one to the other.
FIGS, 7A through 7C corres.pond in form with
those of FIGS 6A through 6C and depict a structure in
which a lower extremity of handle 60 is shaped at 62 to
mate with blown wall 61,
~ IGS 8A through 8C are vi.ews corresponding with
those of FIGS. 6 and 7. The handle, in this instance
designated as member 7a7 is provided with an undercut
configuration 71 which results in firm mating resistant
of all anticipated stress directions contemplated during
a normal pouring operation.
FIGS. 9A through 9C depict handle 80 which.
mates with blown container wall 81 at region 82, again,
with a shaped pattern designed to result in a high integri-
ty joinder,
FIGS. lOA through lOE are illustrative of a
joinder procedure for welding a handle which may otherwise
be of the general configuration shown in any of the figures
lmmediately preceding. Welding is due to friction pro-
duced upon rotation of a plast.ic member~ the procedure
being known as spin-welding, In accordance with this
procedure, the parison here denoted 90 is provided with a
handle 91 which is injection molded to include a button
region 92 which is attached to the remainder of handle 91
12 -
only by regi`ons 93, easily severed to be s.~un hy an a,ppro~
priate tool to produce a friction to blown si,de, wall 24
at weld area 95,
~IGS. llA through llC depict a structure al-
ternative to that of FIG. lOA through. lOE, again, a
parison, not shown, includes a handle lQl which, in this
instance, is bonded by means of ~ separate button 102 SQ
as to bond to blown side wall 103 in the region of wéld
area 104.
In ~IGS. 12A and 12B, a handle, end 111 is bonded
to a blown side wal.l 112 over a weld region 113 by means
of a,n at~ached button 114 which is e.asily severed. As
in FIGS, 10 a,nd 11, bonding is by friction produced by
means of a rotating tool, n~t shown. Temperature is at~
taine.d only locally and only over an appropri.ate surface
region of side.wall 112~ The ope.ration carried out subse-,
quent to blowing is controlled so as to result only in
local surface heating and thereb.y prevents substantial
impairment of blown properties.
2Q FIGS. 13A through 13C are i,ncluded to depict
a procedure for bonding a lower handle extremity to a
blown container by any of several bonding'procedures in-
cluding gas welding, ultrasonic we,lding, high frequency
bonding, ~,tc~ In this embodiment, a h.andle end 121 is
bonded to a blown container side wall 122 via a thin
wafer 123 which serves as the bonding medium. The thin
wafer may simply be a lower melting poi,nt material (than
that of the material from wh.ich handle 121 and s.ide wall
122 are composed) or may be provided with filler which
increases the absorption crpss-section for some form of
energy utilized for bonding. Bonding procedures which
may be utilized may inclu~ si,~ple heating~ or may take
the form of ultrasonic vibration, or of high frequency
electric or magnetic fields designed to produce heating
in wafer 123 or at its interface with the sidewall.
8;2
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Alternatively, using tbe configuration Qf FIGS,
13A through 13C, suitable bonding agents may be applie.d
between the wafer 123 and sidewall 122 which may be acti-
vated by the various energy sources described above.
' Alternatively, the configuration of ~IGS. 13h
thro'ugh 130 may be used where adhesive bondlng is achieved
without activation by energy source.s such as may be
achieved with water-based, solvent-b.ased or other adhe-
sives which cure at ambient conditions.
FIGS. 14A through 14D are, re.spective.ly, plane
front and side views in section of a parison handle 131
whi:ch is an integral portion of ring region 132 of paris.~n
133~ The inal blown con~iguration shown in FTG. 14D
show-s the blown side wall 134 and handle and ring regions
131 and 132, respectively, unchanged, The final confi-
guration is generally that depicted in FIG. 4~
FIGS. 15A and 15B are included as illustrative
of an expedient procedure for producing an ~L"-shaped
handle. In these figures, a bar handle 141 attached to
ring portion 142 of parison 143 is deformed by me~ns n.ot
shown by deforming bar handle 141 to produce orthogonal
handle region 144. Deformation produced by simple pres-
sure during or subsequent to any otherwise orthodox
molding step is expedited by enlarged handle region 145
which, due to residual heat, is selectively deformedt
Alternatively, region 145 may be of lesser
thickn'ess and heated to achieve localiæed deformation in
order to achieve the desired i'L" shape~
In FIGS. 16A through 16D, a handle region 151,
again, part of a ring section 152 of preform 153 forms
an "L" configuration, this time with a lower extremity
region 154 which is, itself, reduced in cross-section so
as to facilitate insertion and sealing of the handle end
in a suitab.le slot in the blow mold (:shown in FIGS. 17A
through 17C~, The reduce.d cross-section creates shoulders
4B~
-14 ~
around the periphery of the handle. end which seal the
slot against "blow outs" o$ containe.r wall 155 ~h.ich can
result in rçgion 156 from a desirable loose fit in the
slot and the high pressures of the Bl~wing gas,
. FIG5. 17A through 17C depict apparatus and
operation suitable for the preparation of the configura-
ti~n of FIG~ 16D. Here the handle regi.on 161 with reduced
extremity 162, again, forming a po~tion of ring region 163
is forced-into an aperture 164 provided in blow mold 165
by handle depressor 166 prior to e.xpansion of preform 167
resulting from pressure introduced by blow air iholo 168.
2, The Proc~ess
Processing in accordance with the invention
inya~iably contemplates a blowing ste.p in which a pre~
form is expanded to conform with a mold, The general
procedure is well known and is describ.e.d, for example,
in the reference set forth. under prior art, The type of
blowing operation of primary concern from the inventive
standpoint results in biorientation of polymer molecules.
Biorientation can only occur oyer a range. of temperature$
within which some part of the stre.ss applied during blow-
ing produces strain in the polymer, It has been indica~ted
that this requirement is met in many polymer materials
if blowing is carried out within a finite temperature
range above T . For these purposes~ T is assigned its
conventional meaning of the temperature representing the
transition from the glass phase to the rubber phase p~o-
duced upon heating of the polymer. An acceptable range
for biorientation--i.e., for stretch blow molding in the
usual case, does not exceed 100F (caz 40C) above T .
To a significant extent, the degree oftbiorientation and,
in conseguence, the improvement in physical properties
attendant upon this parameter increases fQr a given de-
gree of expansion as temperature is decreasedl A sig-
nificant improvement in properties is generally found to
~ \
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result in those procedures in which the average wall
thickness is reduced by a factor of at least two, while
the plastic is at a temperature within lOO~F (ca. 40C?
or preferably 50F tca. 10C) above T . This is con-
sidered to be preferred from the standpoint of stretchblow molding, per se, and in similar fashion is considered
to define a preferred embodiment in accordance ~ith tbe
invention~
Formation of handles as integral portions of
plastic bottles requires attainment of adequate fusion
temperature. In conventionalmolding, handles have been
produced by parison pinch-off necessarily requi~ring
attai~nment of fusion temperature~ In alternative proce-
dures, projections have been molded by appropriately
shaped molds as an integral part of the operation~
The complexity of blow molding operations, as
commercially practiced, have attained a high degree of
sophistication and options are available to produce con-
tainers of varied shape, However? imposition of the
further requirement of complex blow molds or of local
welding or of additional molding or forming sequences or
Qf extenuated container neck portions have, in the
general view, been considered impractical means for pro-
ducing handleware, especially for bioriented containers.
The inventive process seeks to avoid the prob-
lem by an alternative route.
3, The Parison
In accordance with the inventive approach, a
preform (or parison) is somehow provided with an integral
projection generally of the same mate~ial of which the
parison is constructed. In the usually contemplated case,
the preferred embodiment, the projection is the result of
a unitary molding operation--generally, an injection
molding operation, Known preferred alternatives may re-
sult of a unitary molding operation--generally, an in-
82
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jection molding operation, Known preferred alternatives
may result in such pro~ection attached by welding or
otber means~ for example, to an extruded preform~
As seen from the drawings, the projection,
eventually to serve as a handle, may expeditiously be
ateached at a thickened region ultimately to serve as a
gripping section for subsequent hlow molding. The thick-
ened portion generally required for the blow molding
operation offers the additional structural integrity
desired for a stress point resulting from handle usage.
Such gripping sections are necessarily close to an ex-
tremity of the preform and inherently meet the first re-
quirement of the invention--i~e., that preform-handle
attachment be at a region outside of the main section of
the blow mold and that the blown container shape and/or
size be essentially unaffected by the inclusion of the
handle.
A variety of embodiments are shown, for example,
in FIGS, 1 through 4. All such embodiments share the
common feature of preform-handle attachment being re-
stricted to a region approximately corresponding with but
a single plane which is normal to the major axis of the
preform, In certain embodiments, handle attachment may
be made to more than one point onthe plane, One such,
depicted in FIG. 3, serves as a carrying handle.
From a commercial standpoint, a significant area
is considered and directed to blow molding of containers
with handles, an extremity of which is on a second plane
normal to the major axis of the container--a plane now
corresponding with a blown region, For purposes of this
description, this portion is referred to as the lower
handle extremity, This preferred embodiment, generally
serving as a pour handle, is accomplished by a varietY of
prDcedures,
A si~ple expedient description, represented,
;4~
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for example, by the structure of ~IG, 4, contemplates
simple forming or other distortion to produce a handle,
perhaps an L-shaped configuration. The lower extremity?
while on a plane corresponding with a blown region, i8
not attached to the blown wall. Integrity of such a
structure is dependent upon the sti$fness of the handle
material, itself.
Another embodiment provides for mechanical
attachment of the lower handle extremity. This may take
the form of a band or even a label which may contain the
printed matter identifying the contentsof the container.
Embodiments represented, for example, by FIGS.
5, 6, 7, 8, and 9, involve a procedure in which only a
minor modification is required in the blowing mold. Here
an aperture in the mold is filled by the lower handle
extremity so that the expanding preform conforms to such
extremity in the same manner as it does to the mold. In
general, temperatures attained during blowing, particular-
ly during stretch blowing, are insufficient to result in
adequate bond strength, The approach $ollowed to overcome
this problem in accordance with the invention may take the
form of a complex shaped lower handle extremity to result
in a mated pair with the corresponding wall region.
Undercut configurations are considered particularly ad-
vantageous. For many purposes ? undercutting takes the
form of opposing surface regions including a mate portion
haying a thickness decrease in an outward direction of at
least 10 percent within the region intruding into the mold.
~ corresponding configuration makes use o$ opposing inner
wall regions defining at least a lQ percent increase in a
void dimension over the length of handle extremity intrud-
ing into the mold. Such keyed configurations are consi-
dered to define a particularly valuable embodiment in
accordance with the invention.
Keying intimacy may be assured by providing
_ 18_
Keying intimacy may be ass~ured by pro~iding
means for vibrating the handle extremity during the blow-
ing operation. This is especially true in biorientation
processes where temperatures are ]ow and plastic stretching
and moldability is more difficult to achieve. Such vi-
bration promoteæ slippage of the side wall into the keyed
configurations as well as generates localized heating
inthe sidewall to promote stretch and moldaBility.
Integrity of joinder, whether keyed or not,
may be improved by a variety of bonding techniques.
These include welding operations generally accomplished by
frictional heating, as by spin welding or by other pro-
cedures in which contacting surfaces are placed in relative
movement, Vibration may be at sufficiently high frequency
and producing sufficient frictional heat to result in
ultrasonic welding. A variety of alternative heating
means may utilize external fields: magnetic, electric,
or electromagnetic, As ordinarily practiced, electromag-
netic welding~ induction welding, as well as radiation
welding may make use ~ intrinsic properties of the plastic
material or may depend upon fillers which are designed
to convert field energy to thermal energy. Such fillers
may take the form of magnetically or electrically polar
particles or may have larger absorption cross-section for
radiation,
An expeditious form of bonding may involve
chemical modification of the plastic, for example, by
cross-linking. This cross-linking or curing whi~h may
be induced by radiation of suitable quantum energy may
result from polymer cross-linking, for example, by inclu-
sion of a difunctional curing medium--or for that matter,
by any medium of greater polyfunctionality.
Local conductive heating is generally not ~re-
ferred, particularly as practiced in stretch blow molding~
since excessive heat conducted through the stretched side-
B2
- 19-
wall results in degradation of those properties. de.pendent
upon biaxial orientation and release of orientation stress
may result in collapse of the sidewall, possibly with its
rupture. However, the handle extremity shown in FIGS. 13A
through 13C represents a valuable embodiment in accordance
with the invention which ena~les the use of local conduc-
tive heating. In this case, the handle extre.mity posses-
ses a very thin section abutting the sidewall. Th.is
section may be heated sufficiently to fuse itself to the
sidewall without generating sufficient heat content to
substantially effect a deterioration of the thicker side-
wall.
In some instances, honding may result by use of
a separate adhesive, for example, by use of a hot melt
adh.esive. This, too, while sometimes suitable, may be
nonpreferred, since (a) effectire ~dhesives for many suit-
able blow molding plastics are unavailable and (.b) since.
use of an adhesive increases fabrication cost.
Bonding by whateve.r means may serve, its.elf ? to
result in ~oining of the lower handle extremity or may be
used in con~unction with other emhodiments, for example?
with many of the undercut mating embodiments described
abovè.
4, Definitions
Terms utilized inthe description of this inven-
tion are used canventionally, ~or example, as described
above, particularly useful embodiments depend upon injec-
tion mol.ding to produce a preform and blow molding to
produce the final container, These and other terms used
in the description are briefly defined:
Plastic: a category of organic materials,
generally thermoplastic? substituted or unsubstituted,
hydrocarbons--examples are polyolefin ? such as polypropy-
lene, and polyesters? such as polye.thylene terephthalate~
T : (glass transition~ temperature at which the
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plastlc changes from a glassy state to a rubbe.ry state,
Molding operations are invariably carried out substan-
tially above T --generally at temperatures at least 100F
(ca. 40C) in excess. Preferred e.mbodiments herein which
depend upon biaxial orientation are carried out wlth the
plastic in the rubbery s*ate but over a lower
range, generally within 100F (ca. 40~C) of Tc~
Molding: that category of procedure.s in which
plastic material is caused to flow into the interstices
of the mold to result in a formed object which becomes
rigid upon cooling.
Preform: (occasionally re.ferred to as pariSon)
the molded form which, in the procedures of the invention ?
is formed preliminary to expansion to produce. the final
object and, therefore, a form somewhat smaller than that
of the final object. As generally contemplated, the pre-
form is produced with the plastic at an elevated tempera-.
ture in excess of 100F (ca, 4QC2 above Tc~
Injection molding: that molding procedure
generally utilized to produce the preform. In the us.ual
com~ercial process, plastic materials introduced as par=
ticulate matter by a screw or ram with or without external
heating is brought to elevated temperature so that it is
introduced as a flowing plastic condition under pressure
into a mold to produce the preform~ Connecting passages.
known as runners are common,
~ ompression or Transfer molding; One of the
more common alternatives to injection molding to produce
the handle in which a mass of plastic is h.eated and is
introduced into a mold portion. Whereafter, an additional
mold portion, such as a plunge.r, disto~ts the mass to cau$e
it to conform, again, with the interstices of the new
completed mold.
Blow molding: This term contemplates expansion
of the preform to its final configuration by the use of
21
O
gas under pressure. This requires use of a blow mold.
As practiced in the past, no effortwas made to change the
temperature of the preformed plastic before or during the
blowing operation. Some reduction in temperature natural-
ly results from contact with the preform mold.
Iniection blow moldin~: Procedure in which the
preform is molded by injection,
Stretch blow molding: Blow-molding in whichthe
preform is stretched often by means of an inserted plunger
prior to blowing. The procedure is recognized as advan-
tageously practiced with the plastic material within a
temperature range close to but above T so as to result
in extension of the polymer molecules from their natural
twisted state to an extended state with the major mole-
cular axis as resolved lying in the direction of stretch.
Blowing is carried outwithin the same temperature range
designed to result in retained orientation and produces
orientation in the blow direction so that the resulting
final configuration is "biaxially oriented.~'
Injection stretch blow molding: A procedure by
which the preform is produced by injection molding with
subsequent stretch blow molding to ~orm the final confi-
guration.
It has been stated that greatest commercial
impact is believed to obtain in conjunction with biaxial
orientation. ~hile the process is well understood and
while it has been procedurally defined in terms of tem-
perature, it may be useful to define the term as applied
to the finished product. The existence of biaxial orienta-
tion may be detected, destructively, by heating. Heating
the blown section to temperatures well below that required
for flow of unoriented material--temperatures as low as
50~F (ca, 10C) above T results in distortion of the
plastic in a direction approaching that of the preform~
5, ~aterial
i4~
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Materials satisfactory for the practice of the
invention are those satisfactory for blow molding--in a
preferred embodiment those sati,sfactory for stretch blow
molding. Both contemplate polymeric materials which at
least during the blowing operation are thermoplastic.
Compositionally, polymeric (,or plastic~, material ~atisfac-
tory for use are hydrocarbons or substituted hydrocarbons,
Materials include the simple unsubstituted homopolymers,
polypropylene and polystyrene, substituted polymers, such
as, acrylonitriles, and polyesters, such as polyethylene
terephthalate, Biaxial orientation implies a suitable
average polymer weight, Sufficient polymer weight (mole=
cular size), generally, inherent in the specification of a
normally solid room temperature polymer of satisfactory
mechanical properties is likely to average at least 10.,0~00
and is unlikely to exceed one or a few million molecular
weight.
