Note: Descriptions are shown in the official language in which they were submitted.
l~SS~i3~ `
The present invention relates to a process for pre-
paring unsaturated polyester resin in the form of a mouldable
paste which is transparent, non-sticky and which has a shelf-
life of up to about 6 months. More particularly the improved
process of the present invention is particularly suited to
provide an unsaturated polyester resin for the moulding of
transparent or coloured objects such as buttons or other
ornamentations.
PRIOR ART
Unsaturated polyester resins in gel form are well
known in the art. Such gels are in the unpolymerized state or
in a partially polymerized state and can be molded at tempera-
tures of from 100 to 150C under pressure within a few minutes
whereby cross-linking polymerization occurs to produce a hard
finished article.
It is also known that transparent unsaturated poly-
ester resins in the partially polymerized state whether filler
are incorporated or not are sticky or tacky when handled, they
have a relatively short shelf-life, about 4 to 6 weeks, and
3 20 they are highly sensitive to temperature variations. They also
have a high shrinkage coefficient resulting in breakage of the
molded article having a non-uniform section. Further, such
products can only be used in compression molding since
injection, transfermolding, extrusion and similar shaping
techniques are inapplicable. Some of these disadvantages have ~ -
been overcome by incorporation of filler or reinforcement
fillers such as fiber glass, but of course when this is done a
non-transparent product can only be obtained.
As can be readily appreciated by those skilled in the
30 art it would be advantageous for ornemental industries such as
the button industry to have available an unsaturated polyester ;
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resin in the form of a mouldable paste which is transparent,
non-sticky and which has a relatively long shelf-life and which
could provide various consistent coloured patterns by the use
of separately coloured pastes.
TH~ INVENTION
In accordance with the present invention, there is
now provided an improved process whereby an unsaturated poly-
ester resin which is transparent, non-sticky and which has a
shelf-life of from about 5 to about ~ months is obtained.
Broadly, the improved process of the present
invention comprises d;srupt;ng the polymerization processus of
an unsaturated polyester gel at the stage B by mechanically
breaking the gel ~nto small gel particles, adding a further
amount of unsatured polyes'ter resin and, after thorough mixing,
the compositlon is allowed to mature whereby a mouldable paste
is obtained, the paste being transparent, non-sticky and is
surprisingly stable for periods of up to about 6 months.
More specifically, the improved process of the
present invention comprises preparing an unsaturated polyester
~` 20 resin gel contain;ng an initiator effective at a temperature of
at least 80C, mechanically break;ng up said gel into fine
particles thereby to disrupt the polymerization process of the
gel, mixing the particles thus obtained with less than 50 parts
per hundred of the same unsaturated polyester resin as used in
preparing the starting gel and containing an oxide or hydroxide
of a metal of Group II and an initiator effective a~ a tempera-
ture of at least 80C, and allowing the mixture thus obta;ned
to mature at a temperature of from 35 to ~0C for a period of
from 2 to 4 days. The unsaturated polyester resin paste thus
obtained can then be formed into sheets by passing through a
roll-mill or in the form of extruded rods for future use in
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lOS5638
compression, transfer or injection moulding.
The preparation of the unsaturated polyester resin
gel is known in the art and can be obtained by any of three
different methods. One method involves the addition of an
ionic polymerization catalyst to a stage A unsaturated poly-
ester resin whereby gellification is obtained. Another method
comprises the addition of polyisocyanate to a stage A unsatu-
rated polyester resin. Finally gellification is obtained by
incorporation of organic quaternary ammonium compounds and
mercaptan into the unsaturated polyester resin.
Gelling is carried out at a temperature varying
between room temperature and 40C. and the time requlred will
vary between a few minutes to a few hours depending on the
system used, react~vity of the resin and temperature used, as
is well known to those skilled in the art. The gelling is
carried out in such a way that no more the 25~ of the polymer-
ization takes place.
It is important that prior to the gelling that an
initiator be incorporated into the resin to induce complete
cross-linking in the partially polymerized unsaturated poly-
ester resin paste obtained by the present invention upon appli-
cation of heat and pressure.
Preferred results are obtained when the initiator is
selected from those which are effective at temperatures above
80C. As an example of suitable initiators there may be
mentioned benzoyl peroxide, t-butyl per~enzoate, dicumyl
peroxide, 2,5-dimethyl-2,5-(t-butylperoxy)hexane, di-t-butyl-
diperphthalate, 2,5-dimethyl-2,5 dihydroperoxyde hexane, bis- -
(t-butylperoxy~diisopropylbenzene~ di~t~butylperoxy~3,3,5-
trimethylcyclohexane or azo initiators for example 2-t butyl-
azocyanobutane, l-t-butylazo-l-cyanocyclohexane.
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When a coloured resin is desired, colouring agents or
pigments are incorporated in the starting unsaturated polyester
- resin, but caution must be exercised to select those which will
not effect the gelling of the resin or il;s shelf~ e. For
example it is known that chromophthalic pigments ~ill acceler-
ate gelling and then decrease the stability of the gel whereas
carbon black will tend to completely inhibit gelling.
When a transparent gel is desired fillers having a
refractive index approximating that of the resins are prefer-
able used. The use fillers is somewhat restricted to colloidalsilica and certain types of micronized asbestos, but because
of their strong trixotropic effects, the amount should be
reskr~cted to less than 2%. On the other hand dehydrated
potato starch having a particle size of from 10 to 40 microns
does not effect the transparency of the polyester resin and
may be used in amounts of up to 30%.
Since the final polyester resin will be molded under
heat in a metallic mold, it is recommended to incorporate a
mold releasing agent such as an alkyl phosphate Por example
under the trademark ZELEC~ or metallic stearates such as zinc
stearate or calcium stearate ~n concentration oF from 1~5 to
2.0%. These can be incorporated into the polyester resin
before the gelling step.
After initial gelling has taken place, that is, that
a stage B unsaturated polyester resin has 6een obtained, the
gel is then finely divided so as to disrupt or arrest the
polymerization process of the gel. This is done 6y passing the
gel through any apparatus which will cause the gel mass to be
finely divided. As an example of such an apparatus there may
be mentioned a grinder somewhat resembling a meat grinder where
the openings through which the gel will be forced will vary
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1~55~38
between 1 to 3 millimeters, with a diameter of 1 mm being pre-
ferred. The finely divided mass of gel thus obtained cannot be
defined in terms of particle size, since the mass is in gel
form, other than to say that it is finely divided as opposed to
the original gel and in order to give an idea of what the fine
particles look like, the mass obtained would resemble whatever
would be obtained when passing solid gelatine through a meat
grinder.
The thus extruded material has the consistency of a
paste, is very sticky but is very stable due to the fact that
the growth of the polymeric chain has been interrupted and due
to the action of the oxygen of the air which stabilizes the
free radicals.
To this paste, which is difficult to manipulate
becaus~ it is sticky, there is added in a mixer a further
amount of unsaturated polyester resin, (stage A~ less than 50%
but prefera61y from 10 to 25% by weight of the stage B resin.
The added unsaturated polyester resin has incorporated therein
from 2 to 10% by weight of stage A resin of an oxide or
hydroxide of a metal of the Group TI, along with an inhibitor
and an initiator effectiye at a temperature above 80C. Also
if desired there may also be added some fillers.
The oxide or hydroxide of a metal of Group II is
added to reduce stickiness and as an example of such oxides
there may be mentioned magnesium oxide, calcium oxide or
magnesium hydroxide. The initiator is the same as the one
added in the preparation of the stage B resin. There is also
incorporated from 0.05 to 0~1% by weight of stage A resin of an
inhibitor~ The "inhibitor" as employed in this invention is
such an agent or mixture thereof which acts to inhibit free
radical polymerization of said resin and monomer in course of
gelation, and is selected from:
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(a) phenols such as hydroquinone, para-tertiary-butylcatechol,
pyrogallol, trin;trophenol, 4-ethylcatechol, 3-phenylcatechol,
3-isobutylcatechol, etc., (b) quinones such as quinone, tetra-
chloro-p-quinone, toluquinone, quinhydrone, etc., (c) aromatic
amines such as N,N'-di-beta-naphthyl-p-phenylenediamine, N,N'-
diphenyl-p-phenylenediamine, p-hydroquinone-diphenylamine, p-
methyl-p-sulphonamide phenylamine, etc., (d~ amine salts such
as tributylamine hydrochloride, etc., (e) ascorbic acid, (f)
trinitrobenzene.
- 10 After thorough mixing at room temperature the final
paste is then al1Owed to mature For a few days after which it
is dry and easy to handle. The paste is then extruded into
rods which are cut into small discs of 3 to 4 mm in thickness
and stored for future use. Subsequently, these discs can be
placed in the cavities of a metallic mold heated to 125-135C
under a pressure of 200-300 psi for two minutes to provide
buttons.
When a coloured pattern is desired sheet of clifferent
thicknesses are formed and rolled together to form a rod having
a large dlameter wherein the various colours are evenly dis-
persed to provide a coloured pattern on subsequent cutting into
discs of 3 to 4 mm. depending on the shape of the mold.
The term unsaturated polyester resin as employed in
this invention is the kind of unsaturated polyester resin that
is formed by the esterification of polybasic acids including an
alpha,beta-olefinically unsaturated dibasic acid with mono-
and/or polyvalent alcohols comprising mainly divalent alcohols.
Typical saturated polybasic acids are the dibasic
acids including phthalic acid, terephthalic acid, adipic acid,
sebacic acid and the like. Typical unsaturated dibasic acids
are maleic acid, fumaric acid, citraconic acid, chloromaleic
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~IL05S638
acid and the like. Examples of divalent alcoho1s are ethylene
glycol, diethylene glycol, polyethylene glycols, propylene
glycol, mixed ethylenepropylene glycols, l,6-hexanediol, 1,3-
butylene glycol, 2,3-dimethylpropane-1,3-diol and the like.
The resin then is dissolved in a monomer having an
unsaturated double bond which is copolymerizable with alpha,
beta-unsaturated double bonds of the polyester resin. In this
instance the monomer is usually added with a polymerization
- inhibiting agent or mixture thereof.
Typical unsaturated monomers copolymerizable with the
unsaturated polyester resins are styrene, acrylonitrile, ethyl-
vlnylbenzene, isopropenyl toluene, vinyl benzoate, methyl
acrylate, methyl methacrylate, acrolein, dimethylstyrene and
the like.
The unsaturated polyester resin at this point is
referred to as a stage A unsaturated polyester resin by those
skilled in the art. ; `
To exemplify, a typical unsaturated polyester resin
is obtained in the following manner; anhydrous maleic acid,
anhydrous phthalic acid, ethylene glycol, and propylene glycol
in amounts corresponding to a respective mole ratio of
0.5:0.5:0.55:0.55 are reacted at 180C. until the acid value
of the mixture reaches 50, and unsaturated polyester resin
thus formed (100 parts) is then dissolved in 50 parts of
styrene monomer to which 0.05 part of hydroquinone has been
added as an inhibitor.
After partial polymerization of the stage A unsatu-
rated polyester resin there is obtained a gel which is also
; referred to in the art as a stage B unsaturated polyester
resin.
As an example of suitable unsaturated polyester
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1~)5563~3
resins which can be used as starting material there may be
mentioned products such as those sold on the market under the
trademarks POLYLITE 31000 (Reichold Chemical Co.), PALATAL~
P-6 and P-70 (BASF~ of LEGUVAL~ W-21 (Bayer Co.).
The present invention will be more fully understood
by referring to the following examples which are given tn
illustrate the invention rather than to limit its scope.
EXAMPLE I
100 parts of POLYLITE~ 31000 (a liquid unsaturated
alkyl resin dissolved in styrene and manufactured by Reichold
Chemicals, Inc.), 0.1 part of 1% cobalt octoate, 0.2 part of
dodecylmercaptan, 1.0 part of PERCADOX~ 29B75, 0.5 park of
ZELEC~ EN (a mixture of alkyl phosphates used as a mold release
agent and manufactured by E.I. DuPont de Nemours & Co.) and 2.0
parts of mother of pearl are mixed for a few minutes and then
0.1 part of methyl ethyl ketone peroxide is added. The mixture
thus obtained is poured in a rectangular container placed on a
shaking table to eliminate the air incorporated in the mixture.
After resting for 45 minutes the polyester resin has
gelled and the gel is removed, cut in strips as passed through
i a grinder having orifices of at 1 mm.
To 100 parts of the paste thus obtained there is
added 15 parts of POLYLITE~ 31000, 0.5 part of magnesium oxide,
0.05 part of 2,6-di-t-butyl-p-cresol, 0.15 part of PERCADOX~
29B75, 0.10 part of ZELEC~ EN, 1 part of CAB-O-SIL~ M-5 (a
colloidal silica manufactured by Godfrey L. Cabot, Inc.) and
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0.30 part of mother of pearl, and mixing is carried out for
about 20 minutes in a Z type mixer.
The composition is then wrapped in polyethylene
sheets and stored for about 3 days after which the paste is
dry, transparent non-sticky and has a shelf-life of about 6
months. The composition is then extruded in rods which are cut
into discs of 3-4 mm in thickness. The individuals discs are
then placed in a button mold heated to 125-135C for 2 minutes
under a pressure of 200 psi to form button.
EXAMPLE~
The following ingredients are mixed for a few
minutes:
parts
POLYL ITE~ 31000 100
Cobalt octoate 1% 0.1
Cobalt acetylacetonate 1% 1.0
i Dibutylthiourea 0.25
PERCADOX~ 29B75 1.0
ZELEC~ UN Q.5
Colouring paste 0.2
Potato starch (20 - 40 microns~ 30.
After mixing there is then added 0.1 part oF cyclohexanone
peroxide. The mixture is allowed to rest for 2 to 3 hours in
a ~lat container to yield a transparent and coloured gel. The
gel is then passed through a grinder and lQO parts of the
finely divided gel thus obtained are placed in a sigma mixer
and the following are added:
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- parts
POLYLITE~ 31000 20
Magnesium hydroxide 1.0
PERCADOX~ 29B75 0.2
ZELEC UN 0.1
Colouring paste 0.04
Potato starch 6.
After thorough mixing the composition is stored in a container
for 3 to 4 days after which time the composition is dry, non-
sticky, transparent and has a shelf-life of 6 months. The
composition can then be used as in Example I.
EXAMPLE III
The following ingredients are mixed for a Few
minutes:
Ingredients parts
POLYLITE~ 31000 100
Cobalt octoate 1% 0.6
Dicumyl peroxide 1.0
Titanium dioxide paste 1.0
2,5-di-t-butyl-p-benzoquinone 0.45
Potato starch 30.
~ELEC~ UN 0.5
After mixing there is added 1 part of methyl ethyl ketone
peroxide. The mixture is allowed to rest for 2 to 3 hours in
a flat container to yield a transparent white gel. The gel is
then passed through a grinder and 100 parts of the finely
divided gel thus obtained are placed in a sigma mixer and the
following are added:
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1~55~3~
parts
POLYLITE~ 31000 15
Titanium dioxide 0.15
Calcium oxide 0.5
2,6-di-t-butyl-p-cresol 0.05
After thorough mixing the composition is stored in a container
for 3 to 4 days after which time the composition is dry, non-
sticky, transparent and has a shelf-life of 6 months.
- It is noted in the examples that the unsaturated
polyester resin which is added to the unsaturated polyester
resin gel is the same, but a different unsaturated polyester
resin could be also added instead of the same. The important
thing is that the unsaturated polyester resin which is to be
~ added must not be in gel form, but in the unpolymerized form.
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