FI66890B - PIGMENTERBAR FOEGA KRYMPANDE POLYESTERPRESSMASSA - Google Patents

Description

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Patent- och raghterttjrralaan # Amekm utl ^ d eehutUkrWtw pwt # emd 31.08.84 (32) (33) (31) Pyr> «« y «uotfc« «Btglrd prtortMt (71) 0wens-Corning Fiberglas Corporation, Fiberglas Tower, Toledo, Ohio 43659, USA (72) Donald R. Stevenson, Brunswick, Ohio, USA (74) Oy Kolster Ab (54) Pigmentable, low shrink polyester compression mass -Pigmenterbar, föga krympande polyesterpressmass

Unsaturated polyester polymers blended with vinyl monomers such as styrene are well known casting resins that can be vulcanized at room temperature or under heat and / or pressure to form a molded thermoplastic member. These casting resins often contain inert fillers, glass fibers, glass flakes, talc, etc. for the purpose of imparting impact strength, flexural strength, and stiffness to cast parts. However, most conventional disposable plastic resins typically shrink by about 8-10% by volume and are distorted during the molding process, so the shrinkage of these conventional molding resins is unsatisfactory despite the many favorable intrinsic properties of polyester molding compositions. To provide a low shrinkage property, several low shrinkage resin systems have been proposed and mainly contain a thermosetting polyester resin, a thermoplastic resin and a reactive unsaturated monomer mixed together with various fillers. Conventional low shrinkage resin systems 2 66890 are one-component or two-component systems. A particularly desirable # low shrinkage casting composition is described in U.S. Patent 3,883,612, which provides a stabilized emulsion containing a modified dicyclopentadiene polyester resin mixed with a thermoplastic polymer that reacts like an acid to form a uniform emulsion mixture.

Although known resin systems produce the desired low profile, pigmentable castings, such resins are difficult to pigment and tend to produce non-uniform pigmentation and incompatible discoloration such as streaking, spotting and light color due to the casting properties of the resin system.

Thus, it has now been found that a substantially improved, pigmentable, low shrinkage polyester resin system can be produced by providing a thermoplastic casting resin system containing slightly crosslinked polymer particles.

The present invention relates to a pigmented, low-shrinkage, thermoplastic, unsaturated polyester resin molding compound containing dyeing pigments containing at least 25% by weight of a disposable plastic, ethylenically unsaturated polyester prepared by reacting oi, β-unsaturated polyic acid with -25% by weight of lightly crosslinked, pre-formed and polymer particles and about 30-70% by weight of ethylenically unsaturated monomer copolymerizable with said thermoplastic polyester.

The composition is characterized in that the average particle size of the preformed polymer particles is between n.

15-100 μm and are made of a linear polymer crosslinked with minor amounts of a polyfunctional monomer that provides crosslinking sites to the preformed polymer particles, said crosslinked polymer particles having a crosslinking density of about 0.005-2 equivalents per said crosslinking site per kg .

The low shrinkage casting resin systems of this invention contain three main components, namely: lightly crosslinked polymer particles; unsaturated polyester polymer and monomer 3,66890 (usually styrene). Low shrinkage blends contain fillers, thickeners and other additives in addition to pigments.

The polymer particles preformed in accordance with the present invention are slightly crosslinked, reactive polymer particles having an average particle size of between about 15 and 100, and preferably between 20 and 50. The particle size of the slightly crosslinked, reactive polymer particles appears to effectively control the pores in the cast body, where pores below about 2000 nm clearly cause undesired light scattering and consequent spotting and streaks in the molded body. In addition to the light scattering effect, preformed polymer particles below about 15 microns cause an increase in the viscosity of the polyester resin casting mixture, while a size above about 1000 microns causes undesired surface porosity in the casting. The crosslinking density of the lightly crosslinked polymer particles is broadly between about 0.0005-2.0 and preferably between 0.01-1.0 depending on the polymer.

According to one aspect of the present invention, the preformed polymer particles may be slightly crosslinked linear polymers formed from ethylenically unsaturated monomers by addition copolymerization via a double bond and crosslinking small amounts of bifunctional or polyfunctional monomer. The slightly crosslinked polymer particles have an average particle size of at least about 15 and between about 15 and 100, and preferably between about 20 and 50. The particle size of the slightly crosslinked polymer particles appears to effectively control the pores in the cast body, where pores below about 2000 nm clearly cause unwanted light scattering and consequent spotting and streaking in the molded body. The crosslinking density of the lightly crosslinked polymer particles is between n.

0.005 -2.0 equivalents of crosslinking site per 1 kg of polymer. Greater crosslinking improves pigmentation but increases shrinkage. The recommended crosslinking range is between about 0.01 and 1.0 equivalent crosslinking point per kg of polymer. The crosslinking density is determined by first calculating the equivalent crosslinking sites in a monomer having at least two reactive functionalities for crosslinking vinyl monomers. For example, the ethylenically unsaturated functionality of divinylbenzene is two and has one crosslinking site, as the second double bond is considered to be in the copolymerized polymer chain. For specific purposes, the crosslinking density of a polymer is the number of equivalent crosslinking sites per gram mole of polyfunctional monomer per kg of polymer. A polymer containing 10 g of divinylbenzene copolymerized with 999 g of a monofunctional monomer (styrene) has, for example, 10/130 crosslinking points, i.e. a crosslinking density of 0.0769 equivalents of crosslinking point per kg of polymer. In terms of weight percentages, the polymer particles generally contain 0.1-10% crosslinking monomers, depending heavily on the molecular weight of the crosslinking monomers.

Slightly crosslinked polymer particles are prepared by Addi thiopolymerization via an ethylene double bond of monofunctional unsaturated monomers. Monofunctional monomer complexes consist of one or more ethylenically unsaturated monomers and include butadiene, styrene, vinyl acetate, vinyl toluene, vinyl chloride, carbonyl styrene, 1-acrylamide, acrylonitrile and acrylonitrile, acrylonitrile, acrylonitrile and acrylonitrile. methyl acrylate, ethyl acrylate and polyether acrylate. Acid groups can be incorporated into the polymer particles by incorporating unsaturated aliphatic carboxylic acids having sufficient double bond reactivity to react with other unsaturated monomers to form a copolymer or slightly crosslinked polymer particles. Preferred unsaturated carboxylic acids are aliphatic monocarboxylic or dicarboxylic acids having 3 to 12 carbon atoms and include, for example, monocarboxylic acids such as acrylic, methacrylic and cinnamic acid, and further include dicarboxylic acids such as itaconic, maleic and fumaric acids. The acid number of the slightly crosslinked polymer particles can range from about 0-40.

Suitable bifunctional cross-linking vinyl monomers such as diallyl phthalate, divinylbenzene, divinyl ether, neopentyl, diallyylifenyylifosfaatti, diallyl isopropylideenija 1,6-heksaanidiakrylaatti and similar diacrylates, as well as other bifunctional vinyl 5 66 890 monomers having a reactive bifunctional etylee-up process unsaturation, which capable of crosslinking other ethylenically unsaturated vinyl monomers. Crosslinkable unsaturated monomers may further include, for example, a polyfunctional ethylenically unsaturated polymer, such as an ethylenically unsaturated polyester prepolymer, which can effectively crosslink styrene, which polymerizes to polystyrene. Triallyl cyanurate and other triacrylates are trifunctional monomers containing two crosslinking sites per mole of polyfunctional monomer.

According to a further aspect of this invention, the polymer particles may be substantially slightly crosslinked linear condensation polymers, such as polyester polymers, with minor amounts of ethylenic unsaturation that can be crosslinked with ethylenically unsaturated vinyl monomer. The lightly crosslinked condensation polymer particles have an average particle size of about 15-100 and preferably between about 20-50, which appears to effectively control pores in the molded article and prevent unwanted light scattering and consequent spotting and streaking in the molded article. The crosslinking density of the lightly crosslinked condensation polymer particles is between about 0.0073 and 1.2 equivalents of crosslinking point per 1 kg of polymer. Greater crosslinking improves pigmentation but increases shrinkage. The preferred crosslinking range for the condensation polymer particles is between about 0.14 and 0.58 equivalents of crosslinking point per kg of polymer.

The crosslinking density of the condensation polymer particles is determined by first calculating the ratio of ethylenically unsaturated double bonds available in a polymer such as a polyester backbone to the utility of ethylenically unsaturated double bonds in the crosslinking monomer, with one equivalent double bond in the polyester in the monomer crosslinking the single The number of crosslinking sites in the final polyester particles is substantially limited to a smaller number of equivalent double bonds present in the polyester polymer backbone or equivalent double bonds in the crosslinking monomer. Thus, a polyester polymer containing 0.3 equivalents of double bond available for crosslinking with 6,66890 double bond in 0.25 equivalents of monomer produces 1 kg of lightly crosslinked polyester with a crosslinking density of 0.25 crosslinking points per 1 kg. polymer. Similarly, a polyester polymer having 0.3 equivalents of double bond available for crosslinking with 0.35 equivalents of double bond in the monomer produces 1 kg of lightly crosslinked polyester having a crosslinking density of 0.3 crosslinking points per kilogram of polymer. Similarly, excess styrene relative to the equivalent can be crosslinked with smaller amounts of crosslinkable unsaturated polyester polymer. It is recommended that the equivalent unsaturation in the polyester polymer be approximately equivalent to the equivalent unsaturated double bonds in the monomer, although a significant excess of equivalent monomeric unsaturation may be present to produce the linear polystyrene polymer crosslinked with the unsaturated polyester.

Slightly crosslinked condensation polymer particles are pseudo-thermoplastic polymers including polyurethanes, polyamides, polyamines, epoxides, alkyd polyesters, DRS polymers, polyethers, polycarbonates and other equivalents. a per polymer. Slightly crosslinked polyester polymer particles are typically esterification products of polyols and dicarboxylic acids in which the polyester polymer contains higher amounts of saturated dicarboxylic acid and minor amounts of unsaturated dicarboxylic acids. Saturated dicarboxylic acids (or anhydride forms) typically include, e.g., adipic, iso-phthalic, orthophthalic, terephthalic, sebacic, sorbic acid, and other similar dicarboxylic acids. According to the present invention, the lightly crosslinked polyester polymer contains minor amounts of alpha, beta-unsaturated dicarboxylic acid (or anhydride) and may be e.g. maleic, fumaric, mesaconic, itaconic, ditraconic, dimeric methacrylic acid or other alpha, beta-ethyl unsaturated dicarboxylic acid. Typical glycols esterified with dicarboxylic acids include, for example, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, butane diols and hexanediols. Smaller amounts of higher polyols, 66890 such as pentaerythritol, triethylene glycol, trimethylene propane and glycerol as well as polyalkylene glycol ethers and hydroxyalkyl ethers can be used.

The unsaturated dicarboxylic acids esterified in the polyester backbone are adapted to crosslink ethylenically with an unsaturated vinyl monomer such as styrene, methylstyrene, chlorostyrene, vinyltoluene, divinylbenzene, vinylacetate, acrylic acid and methacrylic acid and methacrylic acid.

The preformed, slightly crosslinked polymer particles dispersed in the thermoplastic resin solution apparently allow the preformed polymer particles to be absorbed from the low shrinkage resin system and yet prevent the lightly crosslinked polymer particles from dissolving in the styrene monomer of the resin. The preformed crosslinked polymer particles contain sufficient bridges to prevent them from dissolving, but are not so crosslinked that they would completely resist swelling. As a result, the preformed, slightly crosslinked polymer particles are not thermoplastic, but rather pseudo-thermoplastic and retain their shape when dispersed in the polyester resin, although swell to some extent. The preformed, slightly crosslinked polymer particles tend to swell, thereby achieving a solution density that is approximately the solution density of a disposable plastic polyester resin (polymer and monomer). Thus, the dry preformed, slightly crosslinked polymer particles have a specific gravity of between about 1.10 and 1.50, and preferably between about 1.25 and 1.35, although the solution density of the particles decreases somewhat due to the absorption of the monomer when dispersed in the polyester resin. The swollen polymer particles increase in volume but do not solvate into monomers such as styrene, where the polymer particles swell in a volume of 1 sow to a height of 6 sms when immersed in the styrene in the test tube.

An even further improvement can be realized by providing the preformed, slightly crosslinked polymer particles with smaller amounts of reactive amino or oxirane groups. The reactive amino or oxirane groups in the lightly crosslinked, preformed polymer particles are grafted onto the polymer particle by an in situ reaction to form polyethylenically unsaturated double bonds in the poly- containing primary, secondary or tertiary amino groups. The monomer containing an amino or oxirane group is addition copolymerized through ethylenic unsaturation in the polymer chain to provide reactive amino or oxirane groups on the surface of the polymer particles. For example, about 15% of t-butylaminoethyl methacrylate or 15% of Ν, Ν'-dimethylaminoethyl acrylate or 1% of neopentyl glycolide acrylate or about 10% of glycidal acrylate can be copolymerized with the methyl methacrylate to be copolymerized by suspension polymerization. 100 μm. Heating the reactive polymer particles in a low shrinkage resin system at about 90 ° C for about one hour effectively causes the dispersed polymer particles to react with the free carboxyl groups attached to the thermoset unsaturated polyester polymer, as will be seen below.

Suitable amino group-containing ethylenically unsaturated monomers which can be copolymerized with ethylenically unsaturated polymers include, for example: 2-aminoethyl methacrylate; m-aminostyrene; t-butylaminoethyl acrylate; T-butyyliaminometakrylaatti; Ν, Ν-diethylaminoethyl; Ν, Ν-diethylaminoethyl; allylamines; and divinylamines. The aminopolymer particles preferably contain about 0.02-5% nitrogen (N) by weight. Suitable oxirane group-containing ethylenically unsaturated monomers containing oxirane groups which can be copolymerized with ethylenically unsaturated polymers include, for example, glycidyl methacrylate; allyl glycidal ether and glycidyl acrylate. The preferred oxirane-containing lightly crosslinked polymer contains about 0.2-15% by weight of reactive oxirane (CH ~ - CH-)

V

Preformed, lightly crosslinked polymer particles which are addition polymers or condensation polymers according to the present invention or which have reactive amino or 9 66890 oxirane groups according to preferred aspects of this invention may be bead polymers prepared by suspension polymerization with polymerization in which polymerization is carried out. . In suspension polyolation, droplets of a monomer or mixtures of monomers containing a polymerization initiator are formed by rapid mixing in a non-soluble liquid (usually water) containing a hydrophobic surfactant. Each drop is bulk polymerized and the resulting exotherm is adjusted with the surrounding non-soluble water. The suspending agent prevents these droplets from accumulating and regulates this particle size. The particle size obtained depends on the suspending agent and its concentration, the ratio of monomer to water, the mixing rate and other process variables. The desired suspending agent is a 0.8% aqueous solution of hydroxyethylcellulose. Other suitable suspending agents include, for example, carboxymethylcellulose, polyacrylic acid, polyvinyl alcohol, and others set forth in the Examples. Suspension polymerization is described in more detail in U.S. Patent Nos. 2,694,700 and 3,488,745. The average particle sizes of a preformed crosslinked polymer particle can be determined with an optical microscope. The preformed, slightly crosslinked polymer particles produced by suspension polymerization are then precipitated from solution, filtered and dried before being used in a low shrinkage system. Although suspension polymerization is preferred, lightly crosslinked polymer particles can be prepared by grinding the lightly crosslinked polymers described above to provide a particle size of about 15 to 100 microns.

Referring now to an ethylenically unsaturated thermoplastic polyester polymer, unsaturated polyester polymers are obtained by polycondensation of an alpha, beta-unsaturated dicarboxylic acid with a polyol. Examples of alpha, beta-unsaturated dicarboxylic acids include: maleic, fumaric, mesaconic, ita-cononic, citraconic, dimeric methacrylic acid, etc. whose dicarboxylic acids can be reacted in anhydride or ester form instead of the acid form. The thermoplastic polyester preferably contains only unsaturated dicarboxylic acids, but may additionally contain minor molar amounts of saturated dicarboxylic acids or their anhydrides up to a substitution rate of about 20 mol% with saturated dicarboxylic acids. Examples of 6689090 saturated dicarboxylic acids that can be used in this regard include adipic, isophthalic, orthophthalic, terephthalic, sebacic, succinic acid, etc.

Polyols commonly used to form thermoplastic polyester polymers and conventionally esterified with dicarboxylic acids include glycols such as ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, dipropylene glycol, butanediol, and hexanediol, but , trimethylolpropane and glycerol. Also polyalkylene glycol ethers and hydroxyalkyl ethers; e.g., 2,2-bis- (4-beta-hydroxyalkoxyphenyl) alkanes and 2,2-bis- (hydroxycyclohexyl) alkanes may be used and are referred to as "polyols" for the purposes of this specification. Dipropylene glycol and propylene glycol are preferably included as the main component of the polyol and often form all of the polyols required for the preparation of the preferred disposable plastic polyester resin.

A particularly preferred polyester is the dicyclopentadiene-modified polyester described in U.S. Patent No. 3,883,612. acid. The preferred thermoplastic polyester is prepared by esterifying primarily dicyclopentadiene with an unsaturated dicarboxylic acid to minimize esterification with hydroxyl groups. At about 153 ° C, esterification of dicyclopentadiene with hydroxyl groups is a competitive reaction to esterification of dicyclopentadiene with carboxyl groups. Therefore, it is preferred to react only a portion of the glycol feed with a large molar excess of unsaturated dicarboxylic acid, primarily to form a partial polymer of the acid-terminated glycolic dibasic acid first. The acid-terminated partial polymer is then reacted with dicyclopentadiene to form a dicyclopentadiene-esterified polyester prepolymer. In practice, the preferred dicyclopentadiene-terminated polyester is prepared by first feeding 2 molar equivalents of unsaturated 11,66890 dicarboxylic acids per molar equivalent to glycol. The mixture of glycol and dicarboxylic acid is then heated and allowed to react at esterification temperatures of about 143-154 ° C until substantially all of the glycol is esterified with an excess of unsaturated dibasic acids relative to the molar equivalent. Completion of glycol esterification can be measured by the acid number of the reagents, which becomes substantially constant, indicating that no more hydroxyl groups are available for esterification. Dicyclopentadiene is then added to the reactor and reacted with the glycolide carboxylic acid partial polymer at temperatures below 160 ° C and preferably at a reaction temperature between 143-154 ° C. After the dicyclopentadiene is completely charged to the reactor, the reagent mixture is maintained at about 153 ° C until the acid number of the reagents becomes substantially constant, with the dicyclopentadiene being primarily esterified with the available terminal acid groups of the partial polymer. The remainder of the glycol feed can then be added to the reactor, after which the reaction is continued at about 199 ° C to complete the formation of the dicyclopentadiene-terminated polyester polymer.

Ethylenically unsaturated monomers are vinyl monomers that are copolymerizable with unsaturated polyester polymers and are used to disperse or dissolve the unsaturated thermoplastic polyester polymer of this invention to form an unsaturated polyester resin blend. Vinyl monomers are well known and include, for example: styrene, methylstyrene, chlorostyrene, vinyltoluene, divinylbenzene, vinyl acetate, acrylic and methacrylic acid, acrylic and methacrylic acid lower alkyl esters, vinyl ethers, vinyl esters, vinyl esters, vinyl esters, vinyl esters, vinyl esters. or mixtures thereof. For reasons of efficiency and economy, the most preferred vinyl monomers in forming the low profile casting resin of this invention are styrene and vinyl toluene.

The above stabilized resin emulsion preferably comprises a mixture of at least about 25% by weight of a thermoplastic polyester polymer, about 5-25% by weight of lightly crosslinked polymer particles, and about 30-70% by weight of styrene or other ethylenically unsaturated monomer. Preferred ranges are 8-20% crosslinked poly (12,66890) polymer particles, 40-55% monomer and 35-45% unsaturated polyester polymer. The ratios of unsaturated thermoplastic polyester, monomer and slightly crosslinked polymer particles can be varied within the scope of this invention to provide a one-component, uniform and stabilized dispersion system that is particularly suitable for pigmented, low shrinkage castings.

The low shrinkage casting composition of the present invention can be effectively pigmented by dispersing conventional pigment particles in a low shrinkage resin mixture with a Cowles mixer and a similar instant mixer. Suitable opacifying pigments that may be used include, for example, titanium dioxide, lithophone, zinc sulfide, lead titanate, antimony oxide, zirconia, calcium titanium, lead white, sodium titanium, zinc oxide and leaded zinc oxide. Tinting pigments may include, for example, yellow ferritic oxide, ferric oxide, brown iron oxide, tan brown iron oxide, crude Sienna, burnt Sienna, chromium oxide green, copper-phthalonitrile blue, phthalocyanine blue, phthalocyanine blue, ultramarine blue, carbon black, soot black organic phthalamine blue and green.

The low shrinkage casting resin of this invention is suitably blended with additives known as chemical thickeners which are blended with physically unsaturated thermoplastic polyester polymers, ethylenically unsaturated monomer and polymer particles. Chemical thickeners generally include Group II metal oxides, hydroxides and alkoxides. Alkali earth metal oxides and hydroxides are preferred. For reasons of efficiency and economy, low-shrinkage castings are most often used with calcium oxide and magnesium oxide or similar hydroxides.

Catalysts and catalyst accelerators are often incorporated in small amounts into thermoplastic polyester resins containing ethylenically unsaturated monomer to vulcanize or crosslink the unsaturated polyester with the monomer. Such catalysts and accelerators are well known and can likewise be used in the present invention for vulcanizing a thermoplastic polyester polymer and monomer mixed with slightly crosslinked polymer particles. Typical catalysts include, for example, organic peroxides and peracids such as tertiary butyl benzoate, tertiary butyl peroctoate, benzoyl peroxide, etc. Examples of conventional promoters include cobalt octoate, cobalt naphthenate, and amines such as diethylaniline. The amounts of catalysts and accelerators can be varied depending on the casting process, as well as the number and type of inhibitors used, in a manner well known in the art. Fibers and fillers can be added by mixing a suitable casting mixture and include, for example, glass fibers, cut fibers, chalk, kaolin, asbestos, calcium carbonate, talc, ceramic spheres, quartz, and the like.

The following examples illustrate preferred embodiments of this invention. Examples 1-9, both inclusive, relate to addition polymers for crosslinked polymer particles. Examples 11-13 describe condensation polymers and Examples 14-15 describe polymer particles having amino or oxirane groups.

Example 1

1000 g of a 0.8% aqueous solution of hydroxyethylcellulose was placed in a 3-liter grooved resin kettle equipped with an N 2 feed tube, a thermometer, a paddle stirrer and a condenser. After blowing through the solution for 15 minutes, a solution of 198 g of methyl methacrylate, 2 g of neopentyl glycol diacrylate and 1.5 g of 2,2'-azobisisobutyronitrile was added to the aqueous phase, stirred vigorously and heated to 80 ° C. After about 20-30 monutes, exotherm occurred and was adjusted by adding cold water through the condenser. The stirring rate was then reduced and, after about one hour at 80 ° C, the suspension was cooled. Excess methanol was added to the suspension and this mixture was filtered, rinsed with methanol and dried in a vacuum oven at 80 ° C. The yield was almost quantitative. The average particle size was 70-100 μια and the crosslinking density of the polymer particles was 0.0543 equivalents of crosslinking point per kg of polymer.

Example 2a. Several copolymers of styrene and methyl methacrylate, 14,66890 shown in Table 1 below, were prepared according to the method of Example 1. The average particle size ranged from 20 to 100 μm. The crosslinking density ranged from about 0.0054 to 1.15 equivalents of crosslinking point per kg of polymer. Preferred results were obtained at a crosslinking density of 0.016 to 0.38 equivalents of crosslinking point per kg of polymer when blended into a pigmented, low shrinkage polyester resin system.

b. The particulate vinyl acetate polymer was prepared in a three liter grooved resin flask containing 1000 g of a 0.8% aqueous solution of hydroxyethylcellulose. The solution was stirred vigorously with the addition of a solution containing 98 g of vinyl acetate, 2 g of triallyl isocyanurate and 1 g of isopropyl peroxycarbonate. The temperature was raised to 50 ° C and maintained there. After 30 minutes, the reaction generated heat to about 65 ° C and was maintained at this temperature for 4 hours. The mixture was cooled and the suspension particles were allowed to settle. The water was decanted and the product was vacuum filtered and dried to give particle sizes of about 15-60 μm with an average particle size between about 30-40 μm. Several of the vinyl acetate polymers shown in Table 1 were prepared according to this procedure and had an average particle size of about 20-50. The crosslinking density ranged from about 0.01 to 2.0 equivalents of crosslinking point per kg of polymer. The recommended results were obtained at a crosslinking density of 0.05-1.0 equivalents of crosslinking point per kg of polymer when blended into a pigmented low shrinkage polyester resin system.

table 1

Suspension polymers Molar equivalent- Average Acid per 1 kg Particle size number of polymer a) 99 parts methyl methacrylate 0.0543 60-100 0 1 part neopentyl glycol diacrylate b) 99 parts styrene 0.0543 80-100 0 1 oea neopentyl glycol diacrylate ) 49.5 parts of styrene 0.0543 70-100 0 49.5 parts of methyl methacrylate 1.0 part of neopentyl glycol diacrylate 66890 15

Suspension polymers Molar equivalents Average Acids 1 kg kchti particle size number polymer d) 48.5 parts styrene 0.0543 60-70 7.56 48.5 parts methyl methacrylate 2.0 parts cinnamic acid 1.0 part neopentyl glycol diacrylate e) 95.0 parts methyl .0543 50-60 17.00 4.5 parts cinnamic acid 0.5 parts neopentyl glycol diacrylate f) 98 parts vinyl acetate q-jgg 30-50 0 2 parts triallyl 1 i-isocyanurate 'g) 97 parts vinyl acetate 0.298 50- 60 0 3 parts triallyl isocyanurate h) 95 parts vinyl acetate 0.1988 80-100 0 3 parts acrylic-terminated polyester 2 parts triallyl isocyanurate i) 49.5 parts methyl methacrylate 0.0543 60-80 0 49.5 parts chlorostyrene 1.0 parts of neopentyl glycol diacrylate j) 91 parts of methyl methacrylate 0.0543 50-70 0 8 parts of hydroxyethyl acrylate losa neopentyl glycol diacrylate k) 91.6 parts of methyl methacrylate 0.0543 40-60 0 7.4 parts of acrylonitrile l-acylonitrile 1.0 part of neopentyl part a methyl methacrylate 0 132g 70-90 0 3 parts 1,6-hexanediol diacrylate 'm) 99.5 parts methyl methacrylate 0.0221 70-90 0 0.5 parts 1,6-hexanediol diacrylate n) 39 parts methyl methacrylate 0.0543 40 -60 0 60 parts of methyl acrylate 1 part of neopentyl glycolide acrylate 16 6 6890

Suspension polymers Molar equivalents Average Acids per kg Particle size number of polymer o) 60 parts methyl methacrylate 0.0543 40-60 0 39 parts methyl 1 acrylate 1 part neopentyl glycol diacrylate p) 93 parts vinyl acetate 0.519 80-100 17.9 5 parts allyl maleate 2 parts triallyl isocyanurate q) 51 parts methyl methacrylate 0.0543 80-100 0 48 parts vinylidene chloride 1 part neopentyl glycol diacrylate r) 94 parts styrene 0.0769 30-50 18.9 5 parts cinnamic acid 1 part divinylbenzene parts of methyl methacrylate 0.2172 50-70 0 4 parts of neopentyl glycolide acrylate t) 96 parts of vinyl acetate 0.2917 70-90 10.76 3 parts of allyl maleate 1 part of triallyl isocyanurate u) 95.5 parts of vinyl acetate 0.3591 30-40 8 .97 2.5 parts allyl maleate 2.0 parts triallyl isocyanurate v) 66.0 parts vinyl acetate 0.2359 90-110 11.66 30.0 parts methyl methacrylate 1.5 parts acrylic acid 2.0 parts triallyl isocyanurate 0.5 parts neepentyl glycol glycol di-acrylate

Example 3

The dicyclopentadiene-modified polyester polymer was synthesized from the following raw materials: 9.9 grams of propylene glycol (752 g) 2.0 grams of dicyclopentadiene (264 g) 17,66890 10.0 grams of maleic anhydride (980 g)

The polymer synthesis was performed in a standard reaction vessel suitable for the polyester batch process and including a stirrer, heater, condenser, and inert gas stream.

First phase; The formation of an acid-terminated partial copolymer of propylene glycol and maleic acid ester was performed by charging anhydride and 3% xylene (based on the charge) to a reaction vessel and heating in an inert gas at 149 ° C and maintaining at 149 ° C until the acid number of the charge became constant. The acid number became constant at about 412, after which the second stage began.

Second step: A prepolymer was prepared by adding all 2.0 moles of dicyclopentadiene to the propylene-maleic acid partial copolymer at a reaction temperature of 153 ° C. To this 2.0 moles of dicyclopentadiene was mixed with 3% xylene and added to the reaction vessel at a constant and constant rate for 30 minutes, and then the reaction was continued until the acid number of the charge dropped to about 276.

Step Three: A dicyclopentadiene-terminated polyester was prepared by feeding the remaining 4.9 moles of propylene glycol to the prepolymer in the above reaction vessel, along with 0.3 g of hydroquinone. The batch temperature was gradually raised to about 199 ° C and allowed to react further until an acid number of 30 was reached. A test sample of 7 parts of a resin mixed with 3 parts of styrene gave a viscosity of 3600 cP at 25 ° C, 0.5 g of hydroquinone was added to a polymer which was then diluted with styrene to give a dicyclopentadiene polyester resin having a ratio of 70 parts by weight of dicyclopentadiene polyester and 30 parts by weight of styrene monomer. About 1 g of ionol was then added and the resin was discharged into a container.

Example 4

The polymer particles of Example 1 were mixed into the resin mixture of Example 3 at room temperature by charging them to a mixing vessel to obtain the following final composition: 15 parts by weight of the polymer particles of Example 1 40 parts by weight of the polyester polymer of Example 3 (solid) 45 parts by weight of styrene

The mixture was gently stirred to form a uniform dispersion of stabilized resin. The resulting resin had a viscosity of 1600 3 cP, a weight of 4.546 dm, 9.9 and an SPI gel time of 9 minutes, an SPI reaction time of 12 minutes and an exothermic SPI peak of 202 ° C with 1% BPO benzoyl peroxide 82 ° C. (SPI = "Society of the Plastics Industry", defines different testing methods.)

Example 5

A bulk casting mixture was prepared by mixing together the following materials (by weight) in a Baker-Perkins kneading mixer:

CaCO 3 53.0

Zinc stearate 1.5

Example 4 casting resin mixture 27.0 t-butyl perbenzoate 0.5 6.4 mm glass fibers 20.0

Iron oxide pigment 325 mesh (0.044 mm) 2.0

Mg (OH) 2 0.5

Three-quarters of the amount of calcium carbonate and zinc stearate were first dry blended in a blender. The t-butyl perbenzoate catalyst, the pigment and the remaining calcium carbonate were mixed into the liquid casting resin mixture, and the mixture was slowly added to the material in the kneading mixer while stirring was continued. After thorough wetting of the calcium carbonate was achieved, magnesium hydroxide was added and stirring was continued for about two minutes. The cut fiberglass reinforcement was added and stirring was continued for about 2 minutes until the glass was thoroughly moistened. The mixing period after the addition of the glass was kept as short as possible in line with the wetting of the glass and the achievement of uniform dispersion of the glass and thickener so as not to cause excessive glass breakage into shorter fibers which would result in less consolidation in bulk castings. The bulk cast mixture was finally removed from the mixer and stored overnight (before casting) to ensure that the thickening process was substantially complete.

Example 6

The piece was cast in the following shape: a square of about 23 cm and a thickness of 19,66890 3.2 mm, with one surface having: (1) a straight reinforcement, about 12.7 mm deep, tapering to about 18.6 cm from long and 14.3 mm wide to about 18.3 cm long and 9.5 mm wide in a flat outer end with rounded ends and a longitudinal centerline about 25.4 mm from the edge of a 23 cm square; (2) L-shaped reinforcement about 12.7 mm deep with branches 19 cm long and 44.4 mm wide, with center lines about 25.4 mm from the edges of a 23 cm square, long branch parallel to the straight reinforcement (1) above and close to the opposite edge of the square, with a width narrowing from about 7.9 mm at the bottom to about 6.4 mm at its flat outer end and with rounded ends tapered at approximately the same angle than the direct reinforcement (1) above; and three circular protrusions centered at intervals of about 5 cm along a line about 6.4 cm from the edge of the square adjacent to the long branch of the above-mentioned L-shaped reinforcement (2), which were in order (a) about 12.7 mm deep and tapered from about 25.4 mm in diameter at the bottom to about 23.8 mm at its flat end, (b) about 6.4 mm deep and tapered to about 25 mm in diameter , 4 mm at the bottom to about 24.6 mm at its flat end, and (c) about 6.4 mm deep and tapered from about 15.8 mm in diameter at the bottom to about 14.3 mm at the flat end. at its head, of which all cones were approximately flat except 3 (c), where the cone was more pronounced near the base and more obscure near the apex.

About 350 g of the bulk cast from Example 5 was placed as a dense mass in a steel mold preheated to 146 ° C from the inside and 141 ° C from the core, the mold was quickly sealed in a press and held closed for two minutes. The press was then opened and the casting was removed from the mold. An excellent evenly pigmented body was obtained.

Example 7

A cast composition in the form of a thin sheet was prepared by mixing together the following materials (parts by weight) in the order shown in successive additions:

Casting resin mixture of Example 4 100.0 t-butyl perbenzoate 2.0 zinc stearate 3.7

CaCO 3 180.0 20 66890

Mg (OH) 2 5.0 25.4 Other hard glass fibers 96.9 Carbon black: 400 mesh (0.037 nun) 7.5

The casting resin mixture was fed to a Cowles instant mixer running at about 1000 rpm. The rate was gradually increased with successive additions of benzoate to maintain vortex, but without excessive air entrainment and magnesium hydroxide thickener was not added until the dry substances added above were thoroughly wetted and uniformly dispersed at a temperature of about 38 ° C. After the addition of magnesium hydroxide, stirring was continued for about 2 minutes. This mixture was then removed from the mixer and fed immediately (before excessive thickening, i.e., an increase in viscosity) to a Brenner SMC machine where it was applied to two sheets of polyethylene film to a thickness of about 1.6 mm on both sheets, one inch of glass fibers was applied to another on the bare surface of the plate and the bare surfaces of the two plates were then brought together by passing them through a pair of rollers. (SMC = "sheet molding compound", a perfectly formulated compression mass in the form of a thin sheet.) Thorough wetting of the glass was then carried out by passing the laminated sheet through successive pairs of brushed rollers to provide a kneading effect. The cast composition thus prepared was about 3.2 mm thick and was stored for about 5 days before casting to ensure substantial completion of the thickening process. An excellent evenly pigmented plate was obtained.

Example 8

Unsaturated thermoplastic polyester resins were prepared in a conventional manner by esterifying glycol components with dicarboxylic components at temperatures as low as about 149 ° C to produce a disposable, ethylenically unsaturated polyester polymer by a condensation reaction while removing water. The raw materials for each private thermoset unsaturated polyester polymer are listed in Table 2 below.

a) 4.51 mol of propylene glycol, 1.0 moles of dipropylene glycol, 5.1 mol of maleic anhydride, acid number = 30 66 890 21 b) 1 mole of propylene glycol, 8 mol of maleic anhydride, 2 mol of phthalic anhydride 10 mol of propylene oxide acid number = 28 C) for 1 mole of trimethylolpropane 8 moles of maleic anhydride, 1 mole of phthalic anhydride to 9 moles of propylene oxide acid number = 29

Example 9

The thermoplastic polyesters of Example 8 and the lightly crosslinked polymer particles of Table 1 formed a two-component, low-shrink casting resin that was combined just prior to making the BMC or SMC molding compositions. Excellent pigmentation was obtained for the final cast body. (BMC = "bulk molding compound", a perfectly formulated bulk compression mass containing the necessary particulate and / or fibrous fillers.) Example 10

Slightly crosslinked polymer particles were prepared by conventional latex treatment techniques to produce poor quality polymer particles that produced poorly pigmented, low shrinkage castings. Table 3 shows polymer particles with undesired particle sizes and / or undesired crosslinking densities. The parts indicated are parts by weight, the crosslinking density is equivalent to the crosslinking points per 1 kg of polymer, and the average particle size is in pm. Larger particle size polymer particles were prepared by the suspension technique.

Table 3

Polymer blend Crosslinking- Medium, particle- Acid density tell the number (microns) a) 99.5 parts styrene 0.0385 0.25 0 0.5 parts divinylbenzene b) 96.0 parts styrene 0.3077 0.25 0 4, 0 parts of divinylbenzene 66890

Polymer blend Crosslinking Average particle- Acid density tell the number (microns) c) 99.5 parts styrene 0.0385 0.09 0 0.5 parts divinylbenzene d) 96.0 parts styrene 0.3077 0.09 0 4.0 parts of divinylbenzene e) 98.5 parts of styrene 0.1154 9-11 0 1.5 parts of divinylbenzene f) 97.5 parts of styrene 0.30 0.2 8 1.0 parts of acrylic acid 1.5 parts of divinylbenzene g) 40 parts of methyl methacrylate 0 40-50 0 60 parts of styrene h) 85 parts of methyl methacrylate 0 40-60 0 15 parts of vinylidene chloride i) 66.5 parts of vinyl acetate 0 30-50 0 32.5 parts of methyl methacrylate 1.5 parts of acrylic acid j) 94 parts of styrene 0.077 3 19 5 parts of cinnamic acid 1 part of divinylbenzene ) 96 parts methyl methacrylate 0.22 2.7 0 4 parts neopentyl glycolide acrylate l) 74 parts vinyl acetate 2.6 30-40 0 26 parts triallyl isocyanurate m) 87 parts vinyl acetate 2.1 30-50 18 5 parts allyl maleate 8 part of triallyl isocyanurate

The above polymer particles produced poorly pigmented low profile bodies when blended, cast and tested according to the above examples, showing that the size of the preformed polymer particles as well as the crosslinking density must be controlled. The small particle size produced a moderately low profile but poor pigmentation such as speckles, streaks, and non-uniform color. Non-crosslinked particles similarly produced moderate low-profile bodies, but 66890 poor pigmentation. Large polymer particles produced acceptable pigmentation, but caused considerable porosity and non-uniformity on cast surfaces.

The following examples illustrate the preformed condensation polymer particles of this invention, but are not intended to limit the scope of this invention.

Example 11

The slightly unsaturated polyester polymer with minor amounts of unsaturation was prepared by conventional polyester fusion cooking from the following components:

0.886 moles of coconut oil

3.91 moles of trimethylolpropane

2.45 moles of maleic anhydride

8.15 moles of phthalic anhydride

5.90 moles of propylene glycol

Step 1: The above feedstocks were charged to the reactor and slowly heated to 149 ° C to esterify the dicarboxylic acid components with polyol components, removing the reaction water and maintaining the reaction until an acid number of 20 was reached. The slightly unsaturated polyester polymer was dissolved in monomeric styrene to obtain a 67 wt% styrene solution of unsaturated polyester.

Step 2: A three-liter grooved resin boiler equipped with a nitrogen supply tube, thermometer, vane stirrer and condenser containing 1000 g of a 0.8% aqueous solution of hydroxyethylcellulose was used for the polymerization of the polyester monomer mixture. After nitrogen was blown through the aqueous solution for 15 minutes, 200 g of the polyester-styrene mixture from Step 1 together with 2 g of lauroyl peroxide and 0.15% sodium lauroyl sulfate were added to the aqueous solution preheated to about 80 ° C. Stir vigorously for 10 minutes. After about 30 minutes, the stirring speed was reduced and after 1 hour the suspension was cooled. The suspended, slightly crosslinked polyester polymer was then dried by centrifugation to remove most of the water. The lightly crosslinked polyester particles had an average particle size of about 80-100 and a crosslinking density of 0.359 equivalents per crosslink per kg of polymer.

66890 24

Example 12

Several lightly crosslinked polyester polymer particles were prepared according to Example 11 by adding 55 g of a polyester polymer monomer solution containing 40% monomer, as shown in Table 4 below. About 5% lauroyl peroxide, based on the polymer-monomer solution, was added to the polymer-monomer and then charged to a resin kettle containing n.

650 ml of an 0.8% aqueous solution of hydroxyethylcellulose containing 0.15% sodium lauroyl sulfate. The addition of polyester-styrene was completed in about 10 minutes while maintaining the solution at 88 ° C with vigorous stirring. The resulting lightly crosslinked polyester polymer particles were filtered and dried with an average particle size of about 70-100 and the crosslinking density shown in Table 4 below. The crosslinking density is the crosslinking target per 1 kg of polymer and the particle size is in yum.

Table 4

Properties of polymer particles

Moles Crosslinking- Acid- Particulate- reagents density figure heap a) Rock nut oil 0.966

Trimethylolpropane 3.91

Maleic anhydride 2.45

Phthalic anhydride 8.15

Propylene glycol 5.9 0.3222 17.69 80-100

Styrene b) Phthalic anhydride 6.0

Propylene glycol 5.6 Glycidyl acrylate added to terminal acids 1.3

Styrene 0.1216 21.60 70-90 c) Mipic acid 6.0

Propylene glycol 5.6 Glycidyl acrylate added to terminal acids 1.3

Methyl methacrylate 0.1216 18.00 44-70 25 668 90

Anines of polymer particles

Moles Crosslinking- Acid- Particle- reagents density figure size d) Phthalic anhydride 8.0

Propylene glycol 1.0

Propylene disidia 10.0

Maleic anhydride 2.0

Styrene 0.2950 12.6 20-40 e) Hazelnut oil 0.866

Trimethylolpropane 3.91

Maleic anhydride 2.45

Tetrachlorophthalic acid 4.15

Phthalic anhydride 4.0

Propylene glycol 5.9

Styrene 0.2685 6.92 60-90

Example 13

Several lightly crosslinked polyester polymer particles were prepared as described in Example 11, but with smaller particle sizes or no crosslinking or too much crosslinking. The preformed polymer particles produced poorly pigmented and / or poor low profile castings when mixed, molded and tested according to the above examples. Small particle size polymer particles less than about 10 microns (average) produced a moderately low profile but poor pigmentation such as spots, streaks, and non-uniform color. The uncrosslinked polymer particles also produced poor pigmentation. Large particle size polymer particles larger than about 150 μτο. (on average) produced irregularities on the cast surface.

The following examples illustrate a preferred embodiment of the present invention in which the preformed polymer particles further contain reactive amino and oxirane groups.

Example 14

1000 g of a 0.8% aqueous solution of hydroxyethylcellulose was placed in a 3-liter grooved resin kettle equipped with an Nj feed tube, a thermometer, a paddle stirrer and a condenser. After N2 was blown through the solution for 15 minutes, a solution of 10 g of Nt-butylaminoethyl methacrylate, 2 g of neopenyl glycol acrylate and 188 g of methyl methacrylate and 2 g of BPO (benzoyl peroxide) was added to the aqueous phase at a temperature of about 67 ° C and a bath. stirred vigorously. The bath was then heated to about 80 ° C. After about 20 minutes, exotherm occurred and was adjusted by cooling with cold water. The stirring speed was then reduced and after approximately one hour at 80 ° C the suspension was cooled. The resulting suspended polymer particles were dried by centrifugation to remove most of the water. Methanol was added to the particles, which were then filtered and dried in a vacuum oven at 60 ° C. The yield was almost quantitative. The average particle size was 45-50 μm and the crosslinking density of the polymer particles was 0.0543. The amine content of the polymer was 0.16 wt% N.

Example 15

Several polymer particles listed in Table 5 below were prepared according to the procedure of Example 14, having an average particle size of about 20-100 μm and a crosslinking density ranging from 0.05 to 2 equivalents of crosslinking site per kg of polymer. Polymer particles were synthesized from monomers expressed by weight and containing reactive amino groups or oxirane groups. The ammonium groups are N by weight and the oxirane groups are (-CH-CH9) groups by weight.

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Table 5

Suspended Iopolymer Particles Crosslinking Amino- Xirirane- Particle Group Rg-nlgx, (microns) a) 89 parts of methyl methacrylate 0.0543 0.978 45-55 10 parts of N, N-dimethylaminoethyl acrylate 1 part of neopentyl glycol acylate acylate acrylate acrylate acrylate acrylate 0.0271 0.507 35-45 12 parts of 2-aminoethyl methacrylate 27 66890

Suspension polymer particles Crosslinking Amino- Cirirane- Particle density tendon groups size x) xx) xxx) (microns) 1 part neopentyl glycol acrylate c) 49 parts methyl methacrylate 0.0543 0.82 30-40 40 parts styrene 1 part t-butyl 1 part t-ethyl methacrylate 1 part non-pentyl glycol diacrylate d) 89 parts vinyl acetate 0.0994 0.845 20-30 10 parts 2-aminoethyl methacrylate 1 part triallyl isocyanurate e) 89 parts styrene 0.0769 0.978 50-60 10 parts N, N- dinethylaminoethyl 1 acrylate 1 part divinylbenzene f) 89 parts styrene 0.0769 1.176 40-50 10 parts m-aminostyrene 1 part divinylbenzene g) 85 parts styrene 0.0769 1.36 20-30 14 parts N, N-dimethylamino ethyl acrylate 1 part divinylbenzene h) 80 parts styrene 0.0769 1.858 20-30 19 parts N, N-dimethylaminoethyl acrylate 1 part divinylbenzene i) 80 parts methyl methacrylate 0.0543 2.234 20-30 19 parts n-aminostyrene 1 part nepenty diacrylate j) 45 parts of methyl methacrylate a 0.0543 1.24 20-30 40 parts of methyl acrylate 14 parts of N, N-dimethylaminoethyl lime acrylate 1 part of neepentyl glycol diacrylate 28 66890

Suspension polymer particles Crosslinking Amino- Xirirane- Particle density groups groups size x) xx) xxx) (microns) k) 94 parts of methyl ethyl methacrylate 0.0543 0.44100 45-55 5 parts of t-butylaminoethyl methacrylate 1 part of neopentyl glycol 97 parts methyl methacrylate 0.0543 1.1640 50-60 2 parts t-butylaminoethyl methacrylate 1 part neopentyl glycol diacrylate m) 98.5 parts methyl methacrylate 0.0543 0.0410 55-65 0.5 parts t-butylamino ethyl methacrylate 1.0 part neopentyl glycol diacrylate n) 95 parts vinyl acetate 0.1898 0.7363 20-25 3 parts allylamine 2 parts triallyl isocyanurate o) 89 parts methyl methacrylate 0.0543 3.36 40-50 10 parts glycidyl acrylate ] part neopentyl glycol diacrylate p) 89 parts methyl methacrylate 0.0543 3.02 45-50 10 parts glycidyl methacrylate 1 part neopentyl glycol diacrylate q) 89 parts styrene 0.0769 3.36 50-60 10 parts glycidyl acrylate 1 part divinylbenzene part of styrene 0.05 43 3.36 45-55 49 parts methyl methacrylate 10 parts glycidyl acrylate 1 part naphthyl glycol diacrylate s) 49 parts methyl methacrylate 0.0543 3.36 40-50 40 parts methyl methacrylate 29 66890

Suspended polymer particles Crosslinking Amino Oxirane Particle density groups gutters pile x) xx) xxx) (microns) 10 parts glycidyl acrylate 1 part neopentyl glycol diacrylate t) 80 parts methyl ethyl acrylate diacylate diacidate 0.0543 6,384 u) 70 parts of methyl methacrylate 0.0543 8.758 40-50 29 parts of glycidyl methacrylate 1 part of neopentyl glycol diacrylate v) 60 parts of methyl methacrylate 0.0543 11.77 40-50 39 parts of glycidyl methacrylate 1 part of neopentyl glycol diacrylate w / o diacrylate 2.7 20-30 9 parts glycidyl methacrylate 1 part triallyl isocyanurate x) 85 parts vinyl acetate 0.0994 4.22 20-30 14 parts glycidyl methacrylate 1 part triallyl isocyanurate y) 90 parts vinyl acetate 0.0994 3.393 30 -40 9 parts allyl glycidyl ether 1 part triallyl isocyanurate x) crosslinking point per kilogram of polymer xx) Weight% amino group in the polymer measured as N xxx) Weight % xirirane group as measured in the polymer as (-CH-Cl 2) groups

O

Claims (11)

1. Pigmented, low-shrinkable, heat-curable, unsaturated polyester resin press pulp containing dye pigment comprising at least 25% by weight of a thermosetting, ethylenically unsaturated polyester prepared by reacting an OC-unsaturated dicarboxylic acid with a polyol 5 * 25% by weight of slightly cross-linked, preformed polymer particles, and approx. 30-70% by weight of an ethylenically unsaturated monomer which can be copolymerized with said thermosetting polyester, characterized in that the preformed polymer particles have an average particle size of between approx. 15 and 100 µm and they are made from a linear polymer which has been crosslinked with smaller amounts of a multifunctional monomer, which provides crosslinking sites in the preformed polymer particles, said preformed polymer particles having a crosslink density between 0.005 to 2 equivalent cross-linking sites per 1 kg of said preformed polymer. 2. A composition according to claim 1, characterized in that the preformed polymer particles are essentially linear addition polymers which are a copolymerized monofunctional ethylenically unsaturated monomer which has been cross-linked with a bifunctional ethylenically unsaturated monomer. Composition according to Claim 2, characterized in that the preformed polymer particles have a cross-linking density of between approx. 0.01 to 1.0 equivalent of crosslinking sites per 1 kg of the preformed polymer. k. Composition according to any one of the preceding claims, characterized in that the average particle size of said preformed polymer particles is between approx. 20 and 50 µm. 5. A composition according to claim 1, characterized in that the slightly crosslinked, preformed polymer particles are a substantially linear condensation polymer which has been crosslinked with a bifunctional monomer, said polymer particles having a crosslink density between 0.0073 and 1.200. per 1 kg of the preformed polymer. Composition according to claim 5, characterized in that the polymer particles are an unsaturated polyester polymer which has been cross-linked with a vinyl monomer. Composition according to claim 5 or 6, characterized in that the cross-linking density in said preformed polyester polymer particles is between 0.1 * + and 0.58 equivalent cross-linking sites per 1 kg of the preformed polymer.