Abstract: Aromatic polyamide compositions with improved electrostatic properties, formed structures produced therefrom, and use and production thereof.Described are compositions comprising an aromatic polyamide which is soluble in organic solvents and from 0.01 to 30% by weight, based on the weight of the composition, of an organic or organometallic charge control agent.The compositions can be used for producing formed structures, in particular fibers; these fibers are preferably used for producing webs which can be used for producing dust filters.

Abstract: Light-stabilized polymer microparticles, which contain at least one light stabilizer, and processes for the preparation of these microparticles by polymerization of suitable monomers, at least a part of the polymerization being carried out in the presence of at least one light stabilizer, are described. The polymer microparticles can be used in coating compositions which comprise a disperse phase containing these particles and a liquid continuous phase.Coatings and finishes based on the compositions according to the invention are distinguished by improved weathering resistance, in particular by a high light stability.

Abstract: A method of preparing a lass of PPV derivatives includes preparing a soluble precursor of a PPV derivative and converting the soluble precursor to a PPV derivative. The converting includes performing either a thermal treatment in a range of temperatures from approximately 25.degree. C. to 400.degree. C. at a reduced pressure or an acid-catalyzed ultraviolet radiation treatment.

Abstract: A pultrusion processing method for long fiber-reinforced nylon which combines the nylon anionic ring-opening polymerization technology and the pultrusion processing method to manufacture long fiber-reinforced thermoplastic nylon composites. The method comprises the steps of forming an active caprolactam sodium salt catalyst composition by reacting melt nylon 6 monomer raw material, i.e., caprolactum, with sodium hydride, forming co-catalyst composition by melting caprolactam and a polymeric co-catalyst, then mixing the active caprolactum sodium salt catalyst composition and the co-catalyst composition in a continuous mixing device to obtain a reaction mixture with low viscosity. The mixture is then charged into a closed impregnating tank to impregnate preheated and dried reinforced fiber, which is immediately pulled into a hot mold for composite molding processing to form a finished product of long fiber-reinforced nylon composites.

Abstract: Disclosed is a polyester-imide prepared from a condensation polymerization of aromatic diacid, diimide diacid, and diol, having a carboxy to hydroxy equivalent molar ratio of 0.9:1 to 1.1:1. The disclosed polyester-imide has outstanding heat-resistance, remarkable filming ability, and high solubility in both phenol series and amide series solvents.

Abstract: Novel cyclic imino ether compositions containing one or more mesogenic moieties, when polymerized, result in products having improved properties.

Abstract: The present invention relates to plastics that can be obtained by reacting unsaturated and/or hydroxyl-group-containing fatty acids or their esters or mixtures of various such fatty acids and esters with bifunctional ester-forming and/or amide-forming compounds and, if necessary, subsequently converting ethylenic double bonds, to give difatty acid diamides, difatty acid diesters, difatty acid amide esters, monofatty acid amide amines or monofatty acid amide alcohols as monomer components which contain at least two reactive groups suited for linkage to give polymers, in particular ethylenic double bonds, hydroxyl groups, epoxy groups or amino groups, and by linking the said compounds in the known way via a second group of bifunctional compounds that are capable of reacting with these free reactive groups to give the desired plastics.

Abstract: A method for the polymerization of Nylon 6 from caprolactam and water using a catalyst composition comprising a primary catalyst, which can be an alkali metal hypophosphite or an alkali-earth metal hypophosphite, and an amine cocatalyst. The amine cocatalyst can be selected from the group consisting of phenylene diamines, hindered amines, poly(hindered amines), Group I benzotriazoles, and Group II benzotriazoles. The catalyst composition used in this invention is most useful when used in conjunction with the reactive extrusion technology which requires a very fast polymerization rate to take full advantage of this evolving technology.

Abstract: The present invention discloses new polymers which can assume an accordion-like conformation of the backbone. These polymers are prepared by the copolymerization of two difuntional, chemically precoupled precursors to chromophoric units. The resulting polymers have a head-to-head, tail-to-tail topology (a syndioregic arrangement of rigid units along the polymer backbone), and the molecular units are designed to fold into an "accordion" conformation. This useful microstructure (a three-dimensional conformation) forms spontaneously (self-assembles); or, it can be brought about by field-assisted processing. Films and fibers of these polymers have useful second-order nonlinear optical properties, and may be used for the modulation and switching of optical communications signals.

Abstract: A composition comprising a 1,2-dialkylidenecyclobutane such as 1,2-dimethylenecyclobutane, a bisbenzocyclobutene and a polyimide such as a bismaleimide can be thermally cured to a tough copolymer having a high glass transition temperature.

Abstract: Novel imido copolymers having improved thermal properties and well adapted for the production, e.g., of molded and cellular shaped articles, and laminates, are formed from (a) at least one N,N'-bis(maleimide), (b) at least one hindered diprimary diamine, e.g., of 4,4'-diamino-3,3',5,5'-tetraalkyldiphenylmethane or 1,3- or 1,4-(diamino)trialkylbenzene type, and, optionally, either (c.sub.1) at least one N-[(meth)allyloxyphenyl]maleimide or (c.sub.2) admixture of at least one N-[(meth)allyloxyphenyl]maleimide with at least one N-[(meth)allyloxymono/di(meth)allylphenyl]maleimide.

Abstract: An improved liquid crystal-aligning coating composed mainly of a specified high molecule, mainly a polyether polyimide or a polyimide, and capable of controlling the alignment and pretilt angle of liquid crystals; a liquid crystal display element using the coating; and a dinitro compound and a diol compound each as an intermediate of a diamino compound constituting the polyimide ether, are provided, which specified high molecule contains in its molecular long chain, a substituted cyclohexylidene group or a cyclohexylidene group expressed by the formula ##STR1## wherein R.sub.1 to R.sub.6 of the cyclohexyl group each represent H, 1-15C alkyl group, a cyclohexyl group or a cyclohexyl group having 1-15C alkyl group, and may be each the same or partly or totally different.

Abstract: Hydroxypolyamides can be obtained in a simple and economical way in a chloride-free manner when(a) aromatic amino hydroxy carboxylic acids or(b) aromatic diaminodihydroxy compounds and aromatic dicarboxylic acids or(c) aromatic diaminodihydroxy compounds, aromatic dicarboxylic acids and aromatic amino hydroxy carboxylic acids are converted in the presence of 1-ethoxycarbonyl-2-ethoxy-1.2-dihydroquinoline, 1-1'-carbonyldioxy-di-1.2.3-benzotriazole or dicyclohexyl carbodiimide/1-hydroxy-1.2.3-benzotriazole.

Abstract: A denatured bismaleimide resin of repeating units represented by the following formula (I) and process for preparing same which comprises the Michael addition reaction of a bismaleimide and an aromatic secondary diamine: ##STR1## wherein, n represents an integer of 1 to 3, A represents a divalent group having from 2 to 20 carbon atoms,A' represents a divalent group having less than 20 carbon atoms which includes at least one or more aromatic groups, andR represents aliphatic having from 1 to 10 carbon atoms.

Abstract: High molecular weight aromatic polyamides with pendant carboxyl groups.

Abstract: The invention relates to high molecular weight (co)polyamides and to a process for the accelerated production of polyamides during melt polycondensation using a combination of aminocaprolactam (ACL) and/or lysine components and polycarboxylic acids and known catalysts and also, if desired, for the accelerated solid-phase post-condensation of the catalyst-containing (co)polyamides and to the polyamides produced by the processes.

Abstract: The invention relates to a process for the production of poly-(1,4-benzamide) in admixture with SiO.sub.2 by polycondensation of 4-aminobenzoic acid in the presence of SiCl.sub.4 in 1,3-dimethyltetrahydro-2(1H)-pyrimidinone in the presence of salts, such as lithium chloride or calcium chloride.

Abstract: A method for synthetizing polyanhydrides in solution using coupling agents and a removable acid acceptor to effect a one-step polymerization of dicarboxylic acids. As used in the method, these coupling agents include phosgene, diphosgene, and acid chlorides. Insoluble acid acceptors include insoluble polyamines and crosslinked polyamines such as polyethyleneimine and polyvinylpyridine and inorganic bases such as K.sub.2 CO.sub.3, Na.sub.2 CO.sub.3, NaHCO.sub.3, and CaCO.sub.3. The only byproduct formed is a removable hydrochloric acid-acid acceptor.Examples are provided of the polymerization of highly pure polyanhydrides using phosgene, diphosgene or an acid chloride as the coupling agent, in combination with either an insoluble acid acceptor or a soluble acid acceptor in a solvent wherein the polymerizaiton byproduct or polymer is insoluble.A particularly important application of these polyanhydrides is in the formation of drug delivery devices containing bioactive compounds.

Abstract: Acetylene terminated aspartimides are prepared using two methods. In the first, an amino-substituted aromatic acetylene is reacted with an aromatic bismaleimide in a solvent of glacial acetic acid and/or m-c=resol. In the second method, an aromatic diamine is reacted with an ethynyl containing maleimide, such as N-(3-ethynylphenyl) maleimide, in a solvent of glacial acetic acid and/or m-cresol. In addition, acetylene terminated aspartimides are blended with various acetylene terminated oligomers and polymers to yield composite materials exhibiting improved mechanical properties.

Abstract: Thermosetting mixtures which contain (a) 10 to 90% by weight of at least one aromatic di- or polycyanate compound or a prepolymer thereof,(b) 90 to 10% by weight of at least one compound of the formula I or II ##STR1## or of a prepolymer of a compound of the formula I or II and, based on the sum of (a) and (b),(c) 0 to 50% by weight of at least one compound of the formula III ##STR2## in which R.sub.1, R.sub.2 and R.sub.3 independently of one another are each a hydrogen atom or methyl, n is 1 or 2 and m is 2 or 3, R is hydrogen or an aliphatic, cycloaliphatic or aromatic radical, R' is an aliphatic radical, m- or p-phenylene or m- or p-phenylenoxy and R" is an m-valent organic radical with 2-14 30 C atoms, are suitable for the production of shaped articles, such as prepregs or laminates, coatings and glueings.

Abstract: This invention relates to a curable resin composition comprising (a) a component selected from the group consisting of a dicyanate-terminated aromatic polysulfone oligomer, a dicyanate-terminated aromatic polyketone oligomer and mixtures thereof, (b) a cyanate ester component selected from the group consisting of polyfunctional aromatic cyanate ester monomers having at least two cyanate groups bonded to their aromatic ring, prepolymers of the cyanate esters and prepolymers of the cyanate ester monomers and amines, and (c) a bismaleimide component selected from the group consisting of bismaleimides, bismaleimides prepolymers and prepolymers of the bismaleimides and amines.

Abstract: This invention relates to the use of compositions of the formula: ##STR1## wherein n is 2 to 4 and X is --O--, --S-- or ##STR2## wherein R.sub.1 is an aliphatic or aromatic moiety as a curing agent for epoxy resins to form a thermoset material which has a reduced shrinkage.

Abstract: Compositions comprising an organotin mercaptide, organotin sulfide, organotin carboxylate or mixtures thereof and a diester of an ethylenically unsaturated dicarboxylic acid having one carboxyl group on each carbon atom of the ethenylene group are useful for stabilizing halogen-containing organic polymers against the deteriorative effects of heat, light and weathering.

Abstract: Thermoplastic polyamides with improved stability against reduction in molecular weight due to the effect of light, which have maleic imides as end groups.

Abstract: An improved method of molding involves utilizing as the catalyst and initiator components of a polymerizable composition, a Grignard catalyst and a dual initiator system.

Abstract: Unsaturated polyamide polymers are provided which are comprised of a polyamide chain terminated at one end by a group containing at least one double bond. The polymers are particularly useful in the preparation of molded object coatings, water tight joints, grafting onto thermoplastic polymers or copolymers, and the like.

Abstract: Heat-curable mixtures, containing (a) an epoxide resin having on average more than one epoxide group in the molecule, (b) an allyl-substituted or methallyl-substituted imide of the formula I ##STR1## in which E is allyl or methallyl, G is hydrogen or methyl, n is 1 or 2, and R is hydrogen, alkyl, alkenyl, cycloalkyl, aryl, benzyl or arylene, and (c) a curing catalyst, have good storage stability and processability and produce moulded materials having high mechanical strength values and good resistance to heat.

Abstract: Polyalkylpiperidinesulfonic acid esters of the formulae I and IIB--X--O--SO.sub.2 --A).sub.m (I)(B'--X--O--SO.sub.2).sub.2 A' (II),in which A, A', B, B', X and m are as defined in claim 1, the polyalkylpiperidine group being present in each of the substituents B and B'. These esters are suitable for use as curing catalysts for acid-curable resins and act therein, at the same time, as light stabilizers.

Abstract: An improved process for the anionic polymerization of lactams is described. Particular azetidinedione compounds are employed as promoters and their use not only permits low polymerization temperatures but gives rise to faster polymerization reactions than prior art procedures allow.The rapid polymerization of caprolactam in accordance with the present invention makes the process particularly suited to RIM procedures for preparing molded polyamides.

Abstract: High molecular weight block copolyamides useful in the production of fibers of high strength and modulus, having the following formula: ##STR1## wherein X is --CH.sub.2 --.sub.m, wherein m is 0 to 12, ##STR2## wherein Z is C(CH.sub.3).sub.2, zero, oxygen or SO.sub.2, are prepared from N,N'-bis(4-aminophenyl) terephthalamide having the formula: ##STR3## which is itself prepared by condensing aniline with dimethyl terephthalate or terephthalic acid, nitrating the product produced thereby and finally hydrogenating the resultant compound.

Abstract: A block copolyamide having effectively improved impact strength is obtained by polymerizing a mixture comprising substantially from about 50 to about 95 parts by weight of lactam and from about 50 to about 5 parts by weight of polyol in the presence of catalyst for an anionic polymerization and activator represented by the following formula (I); ##STR1## wherein A denotes a bifunctional organic residue having at least one kind of heteroatoms selected from the group consisting of N, O, S, F, Cl, Br and I, and Y and Y' denote an acyl group selected from the group consisting of ##STR2## respectively, and n and n' denote an integer of 3 to 11 respectively, or by polymerizing, in the presence of catalyst for anionic polymerization, a mixture comprising substantially from about 50 to about 95 parts by weight of lactam and from about 5 to about 50 parts by weight of prepolymer obtained by a reaction of polyol and activator represented by the above formula (I), wherein A denotes a bifunctional aromatic residue having

Abstract: Polyimide resins suitable for use as composite matrix materials are formed by copolymerization of maleic and norbornenyl end-capped monomers and oligomers. The copolymers can be cured at temperatures under about 300.degree. C. by controlling the available concentration of the maleic end-capped reactant. This control can be achieved by adding sufficient amounts of said maleic reactant, or by chemical modification of either copolymer, so as to either increase Diels-Alder retrogression of the norbornenyl-capped reactant and/or holding initiation and polymerization to a rate compatible with the availability of the maleic-capped reactant.

Abstract: Impact modified polyamide/polyether block copolymers have increased impact strength for corresponding polyol concentration, which can be achieved using certain difunctional and tri-functional symmetrical triazine derivatives as the co-catalyst/coupling agent, and lactamyl salts as the catalyst. Also disclosed is an improved anionic polymerization process, especially suitable for reaction injection molding.

Abstract: Polyamides from lactams are prepared by the reaction of an initiator compound, a liquid hydroxy containing nitrile copolymer and a lactam using as a catalyst a minor amount of a lactam anionic polymerization catalyst. The resulting polyamides exhibit high impact strength and improved dimensional stability or reduced sensitivity to dimensional change upon exposure to a high humidity environment.

Abstract: An aromatic and/or heterocyclic polyamide-amide type polar solvent composition is prepared by prepolymerizing an aromatic or heterocyclic diamine with an aromatic or heterocyclic or heterocyclic dicarboxylic acid chloride in a smaller molar equivalent than that of the diamine to prepare a prepolymer solution having a solution viscosity of 20 poise or less; by removing a by-product, hydrochloric acid, from the resultant prepolymer solution by neutralizing it with ammonia to such an extent that the pH of a mixture of 10 g of the neutralized mixture with 200 ml of water becomes 3.7 to 8.0; by high polymerizing the prepolymer with an additional amount of aromatic or heterocyclic dicarboxylic acid chloride, and; finally, by converting the entire amount of hydrochloric acid and 10 to 70% NH.sub.

Abstract: Poly(.epsilon.-caprolactam) is prepared with less than 3 percent water-extractable material by carrying out the polymerization reaction in a vessel, the interior surfaces of which are coated with an inert adherent coating of an organic polymer.

Abstract: A curable resin composition comprising (i) a catalytic composite comprising a peroxide and other catalytic component and (ii) a mixture or a preliminary reaction product of (a) a polyfunctional cyanate ester, prepolymer of the cyanate ester or coprepolymer of the cyanate ester and an amine and (b) a polyfunctional maleimide, prepolymer of the maleimide or coprepolymer of the maleimide and an amine and optionally (c) other component is disclosed. The composition cures rapidly at a low temperature and is preferable from view point of quantity production and workability. The composition is excellent in respect of adhering property, heat-resistance, moisture-resistance and chemical-resistance, and is useful for preparing laminated products, molded products, paint, powder paint, adhesive or varnish.

Abstract: A process for producing flame retardant polyamide molding resin containing melamine cyanurate which is formed from melamine and cyanuric acid in the molten polyamide and which has a fine crystallite size of less than 250 A. The polyamide molding resin produced by this process provides shaped articles having excellent mechanical properties as well as flame retardant properties without blooming.

Abstract: A new type of poly-2-pyrrolidone suitable for melt spinning and a process for its preparation. The new poly-2-pyrrolidone is characterized in that the polymer in the virgin state has a relative viscosity (1 gram of polymer in 100 ml of 96% sulphuric acid at 20.degree. C.) of between 2.2 and 7.0, shows a weight loss of less than 5% by weight when heated from 20.degree. C. to the onset temperature of thermal degradation at a rate 4.degree. C. per minute, the ratio between the relative viscosities after and before melt spinning ranges between 0.50:1 and 0.95:1, and the relative viscosity after melt spinning is at least 1.90. The new poly-2-pyrrolidone is prepared by polymerization of 2-pyrrolidone in the presence of an anionic catalyst and an accelerator wherein N-(2-caprolactim)-caprolactam is used as the accelerator in an amount of between 0.05 and 5.0 mole percent relative to the monomer, and the polymerization is carried out at a temperature of between about 25.degree. and 70.degree. C.

Abstract: A method for producing flame resistant synthetic polyamides, suitable for inning is described, wherein melamine and isocyanuric acid are reacted in an aqueous environment at the melamine isocyanurate formation temperature. An aqueous suspension of melamine isocyanurate is obtained having a maximum granule size not exceeding 2 microns, substantially free from agglomerates. The suspension is admixed with the monomeric material and the whole is submitted to polymerization. The invention provides a successful method for obtaining flame-resisting polyamide fibers and yarns owing to the presence therein of the melamine isocyanurate additive.

Abstract: Novel compositions comprising polymerization products of polyimide derivatives having terminal acetylenic amide groups and processes for their preparation are disclosed herein. These new compositions are primarily polymers of derivatives of anhydride-terminated aromatic polyimides from which these derivatives are prepared by amidation to provide acetylenic amide groups having terminal --C.tbd.CH groups as hemi-amic acid groups or their derivatives. These derivative compositions are more tractable than the original anhydride-terminated polyimides and can be converted at appropriate lower temperatures and in accordance with the practice of this invention to crosslinked, insoluble, infusible polymers without by-product formation thereby extending greatly the applications for which the aromatic polyimides can be employed. Also included are polymers from monomeric compounds containing acetylenic amide groups derived from monomeric tetracarboxylic dianhydrides.

Abstract: A flame-retardant polyamide composition comprising 98 to 60% by weight of a polyamide and, uniformly dispersed therein, 2 to 40% by weight of melamine cyanurate, characterized in that nearly 100% of the latter particles have a particle size of at most 35.mu. and at least 80% by weight of the particles have a particle size of at most 10.mu.; and a process for producing said composition.

Abstract: Low hardness and scratch resistance in direct-cast diethylene glycol bis(allyl carbonate) (CR-39.RTM. plastic surface laminae in glass-plastic lenses are analyzed and new plastic formulations, preferably comprising the monomer catalyzed with a mixed isopropyl percarbonate-benzoyl peroxide polymerization catalyst, are disclosed, offering improved hardness and scratch resistance for laminated lenses and also for CR-39.RTM. plastic articles generally.

Abstract: A method for the production of blocked isocyanate-and isocyanurate group-containing compounds which comprises:transforming a monomeric aliphatic or cycloaliphatic polyisocyanate or a mixture thereof into an intermediate mixture comprising an isocyanurate containing at least 2 free isocyanate groups; andblocking said intermediate isocyanurate mixture with dimethylketoxime at 50.degree.-120.degree. C.;wherein the amount of said dimethylketoxime is such that one equivalent of NCO group reacts with one equivalent of said dimethylketoxime.The mixtures of the present invention are particularly suited as co-catalysts for the anionic polymerization of epsilon-caprolactam, as well as hardeners for higher functional thermoplastic compounds which contain Zerewitinoff-active hydrogen atoms.

Abstract: A process for the anionic polymerization or copolymerization of olefinic monomers, dienic monomers, vinyl monomers and heterocyclic monomers is described which comprises reacting at least one monomer which is an olefinic monomer, a vinyl monomer or an heterocyclic monomer with a catalyst capable of inducing anionic polymerization and an aprotic macroheterocyclic cryptant, said at least one monomer being the only medium for the reaction.The macroheterocyclic complexing agent has general formula ##STR1## in which: R.sub.1 is hydrogen, a hydrocarbon radical or alkoxycarbonyl, or the two R.sub.1 together can form a group of the general formula: ##STR2## in which A is a hydrocarbon radical,D is oxygen, sulfur, or a hydrocarbon radical, with the proviso that at leat two of the D groups are oxygen or sulfur and that if R.sub.1 is hydrogen, a hydrocarbon radical or alkoxycarbonyl, one of these two D groups is oxygen or sulfur and the other is oxygen, andn and p are integers from 1 to 3 and m is 2 or 3.

Abstract: Novel polyamides are prepared having end groups especially selected to impart special properties to the polymer. These polyamides are prepared by utilizing anionic polymerization processes and the end groups can be of a type that, under existing methods, normally will hinder or completely stop the anionic polymerization reaction. The hindering effect of these end groups is largely overcome through the formation of novel initiator compounds that enables the polymerization reaction to proceed with extreme rapidity at comparatively low temperatures despite the presence of these end groups.

Abstract: An aromatic polyamide having a high degree of polymerization is produced by polymerizing(A) a mixture of an aromatic diamine of the formula (1):H.sub.2 N--Ar.sub.1 --NH.sub.2 (1)and an aromatic dicarboxylic acid dihalide of the formula (2):XOC--Ar.sub.2 --COX (2)(b) a mixture of the aromatic diamine of the formula (1), the aromatic dicarboxylic acid dihalide of the formula (2) and a hydrogen halide salt of an aromatic amino carboxylic acid halide of the formula (3):XH.multidot.H.sub.2 N--Ar.sub.3 --COX (3)or(C) the hydrogen halide salt of the aromatic amino carboxylic acid halide of the formula (3) alone,Wherein Ar.sub.1, Ar.sub.2 and Ar.sub.

Abstract: The invention relates to antistatic polyamide compositions comprising a polyamide and as an antistatic agent from 0.1 to 20%, preferably from 1.5 to 15%, by weight based on the total weight of the composition of urethanes with ether groups. The urethanes with ether groups are stable in melts of aliphatic polyamides for prolonged periods at temperatures of up to about 300.degree. C. and filaments and fibers of such polyamides or woven fabrics, knitted fabrics, non-woven or pile fabrics produced from these filaments or fibers show outstanding antistatic properties.

Abstract: A method of forming white polymers of controlled molecular weight when polymerizing 2-pyrrolidone using an alkaline catalyst and sulfur dioxide as the chain initiator is disclosed. The temperature at which the polymerization is carried out is critical and is carefully controlled. The SO.sub.2 which must also be controlled within limits is diluted with an inert gas to diminish its activity and make it easier to measure the small amounts involved. The viscosity and thermal stability of the polymers formed are as good as or better than those formed when CO.sub.2 is used as the initiator.

Abstract: The invention relates to a method for manufacturing of anionic polycaprolactam with a low content of water extractables and high stability of the degree of polymerization during melting by a two-stage polymerization using known basic initiators and known activators of the following types: ##STR1## where R is ##STR2## R.sup.1 = R or C.sub.1-4 alkyl, cycloalkyl or allyl, R.sup.2 = C.sub.1-4 alkyl or H atom, n is an integer 3-11 and x is an integer >3. The ratio of activator to initiator (e.g. sodium dihydromethoxyethoxyaluminate) ranges between 2.6 and 4.2, advantageously 2.8-3.5 The first polymerization stage proceeds at 150.degree.-200.degree. C. for .ltoreq.10 min, the polymer is then shaped and postpolymerized at 150.degree.-200.degree. C. for .ltoreq.90 min to achieve a monomer content near to the equilibrium content corresponding to the 2nd stage temperature.