POLYESTER MOULDING COMPOSITIONS

Abstract: The present invention is concerned with a moulding composition having improved surface appearance and im­ pact strength and comprising an unsaturated, crosslinkable thermosetting resin, an ethylenicallly unsaturated monomer, a reinforcing agent and/or a filler and a normally solid, carboxy-containing styrene-butadiene block copolymer, pre­ pared by contacting a monolithium terminated block copoly­ mer with dry gaseous carbon dioxide at a temperature of from 20-100°C, a pressure of from 103-793 kPa (abs) and at a molar ratio of carbon dioxide added to lithium terminated block copolymer of from 0.75:1 to 3.0:1 and having a 1,2-vinyl content of from 30 to 40 mol percent.

Description: MOULDING COMPOSITIONS The present invention is concerned with a moulding composition comprising: a) an unsaturated, crosslinkable thermosetting resin; b) an ethylenically unsaturated monomer; c) a reinforcing agent,-a filler or mixtures thereof as additive and d) a normally solid, carboxy-containing styrene-butadiene block copolymer. Such a composition is useful e.g. as bulk moulding composition (BMC) or sheet moulding composition (SMC), which should exhibit a high impact strength, a smooth surface and low shrinkage/low profile characteristics. USP 4,020,036 discloses a moulding composition comprising an unsaturated polyester, a normally solid carboxy-contaihing styrene-butadiene block copolymer, a vinyl monomer, a catalyst, a reinforcing agent and a filler. Although this reference discloses a composition comprising a normally solid, carboxy-containing styrenebutadiene block copolymer, it does not specify how to prepare these carboxy-containing block copolymers. Furthermore, the vinyl content in the butadiene part of the block copolymer may vary over a wide range of from 5 to 76 percent according to this preference. It has now been found that a moulding composition, comprising an unsaturated, crosslinkable thermosetting resin, an ethylenically unsaturated monomer, a reinforcing agent and/or a filler and a normally solid carboxy-containing styrene-butadiene block copolymer, exhibits an improved impact strength and an improved surface gloss together with low profile/low shrinkage characteristics as BMC or SMC, provided the carboxy-containing styrene-butadiene block copolymer has been prepared in a specific way and provided the 1,2-vinyl content of the butadiene part of the block copolymer corresponds to specific values. Accordingly, the present invention is concerned with a moulding composition comprising: a) an unsaturated, crosslinkable thermosetting resin; b) an ethylenically unsaturated monomer; c) a reinforcing agent, a filler or mixtures thereof as additive and d) a normally solid, carboxy-containing styrene-butadiene block copolymer, characterized in that the moulding composition comprises a normally solid, carboxy-containing styrene-butadiene block copolymer prepared by contacting a monolithium terminated styrene-butadiene block copolymer solution with carbon dioxide by introducing dry gaseous carbon dioxide into said polymer solution at a temperature of from 200C to 100µC, at a pressure of from 103 kPa(abs) to 793 kPa(abs) and at a molar ratio of carbon dioxide added to lithium terminated block copolymer of from 0.75:1 to 3.0: :1, the butadiene portion of the monolithium terminated styrene-butadiene block copolymer having prior to the contact of this block copolymer with carbon dioxide a micro structure of between 30 and 40 mol percent 1,2-vinyl, between 20 and 30 mol percent 1,4-cis and between 30 and 50 mol percent 1,4-trans. A key aspect of the present invention is the microstructure of the butadiene block of the styrene-butadiene block copolymer (abbreviated SB block copolymer). This microstructure, as determined by conventional infra-red analysis using the 910 cm 1 band, is as follows (expressed in mol percent): Preferred 1,2-vinyl 30 to 40 35 1,4-cis 20 to 30 25 1,4-trans 30 to 50 40 The desired weight average molecular weights of the styrene block and butadiene block of each block copolymer arm are: Preferred Styrene block 8,000 to 20,000 11,000 to 15,000 Butadiene block 30,000 to 100,000 60,000 to 80,000 The carboxy-containing polymer is typically prepared by anionic polymerization employing an organomonolithium initiator. The first step of the process involves contacting the styrene monomer and the organo-monolithium compound in the presence of an inert diluent therein forming a living polymer compound having the simplified structure S-Li. The inert diluent may be an aromatic or naphthenic hydrocarbon, e.g., benzene or cyclohexane, which may be modified by the presence of an alkene or alkane such as pentenes or pentanes. Specific examples of suitable diluents include n-pentane, n-hexane, isooctane, cyclohexane, toluene, benzene and xylene. The organomonolithium compounds are represented by the formula RLi; wherein R is an aliphatic, cycloaliphatic, or aromatic radical, or combinations thereof, preferably containing from 2 to 20 carbon atoms per molecule. A much preferred initiator is sec-butyllithium. The concentration of the initiator can be regulated to control the molecular weight of the polymer. Generally, the initiator concentration is in the range of about 0.25 to 50 millimoles per 100 grams of monomer although both higher and lower initiator levels can be used if desired. The required initiator level frequently depends upon the solubility of the initiator in the hydrocarbon diluent. These polymerization reactions are usually carried out at a temperature in the range of -51 C to 1490C and at pressures which are sufficient to maintain the reaction mixture in the liquid phase. Next, the living polymer in solution is contacted with a butadiene monomer. The resulting living polymer has a simplified structure S-B-Li. The medium vinyl polybutadiene block is readily obtained by employing a small amount of a polar material as a vinyl promoter. The vinyl promoter conveniently is added to the hydrocarbon diluent at the appropriate time in the polymerization sequence. These promoters can be selected from ethers, tertiary amines, and other promoters. Preferred are dimethoxybenzene, tetrahydrofuran, 1,2-dimethoxyethane, dimethyl ether, diethyl ether, methyl ethyl ether, ethyl propyl ether, di-n-propyl ether, di-n-octyl ether, anisole, dibenzyl ether, diphenyl ether, dimethylethylamine, tri-n-propylamine, tri-nbutylamine, trimethylamine, triethylamine, N ,N-dimethylaniline, N-ethylpiperidine, N-methyl-N-ethylaniline, N-methylmorpholine and N,N,N',N'-tetramethylethylenediamine. The amount of polar compound employed will vary widely with the choice of vinyl promoter, but should be that amount necessary to prdmote the degree of vinylization desired. An exemplary amount would be in the range of about 0.01 to 25 parts by weight per hundred parts monomer. The average molecular weights of the polystyrene blocks of the block copolymer are determined by gel permeation chromatography, whereas the polystyrene content of the polymer is measured by infra-red spectroscopy of the finished polymer. After formation of the butadiene block, the living polymer is contacted with carbon dioxide, by introducing dry gaseous carbon dioxide in the living polymer solution. A second key aspect of the present invention is that said contact is carried out at a temperature between 20iC and 100iC and at a pressure between 103 and 793 kPa(abs.) and that the amount of C02 added is such that the molar ratio of C02 added to SB-Li is between 0.75:1 and 3.0:1, preferably between 1.0:1 and 2.0:1. Under these circumstances a mixture of block copolymer structures is obtained comprising 20-80 preferably 40-60 percent weight of uncoupled block copolymer, 10-40 preferably 15-25 percent weight of coupled linear block copolymer and 10-40 preferably 25-35 percent weight of coupled radial block copolymer, comprising a minor amount of radial block copolymers having four arms. The uncoupled block copolymer probably comprisesla mixture of block copolymer structures differing with respect to the terminating group only, Next the polymer is recovered by known finishing techniques. The unsaturated, crosslinkable thermosetting resins include both unsaturated vinyl ester resins and unsaturated polyester resins. The vinyl ester resins are typically prepared by the esterification of polyepoxides with ethylenically unsaturated monocarboxylic acids in the presence of onium salts of inorganic acids. The vinyl ester resins have a typical formula: EMI5.1 and are prepared by reacting a glycidyl polyether of a polyhydric phenol with an acrylic acid in the presence of an onium salt. The composition of the polymerizable unsaturated polyester resin component of the moulding compositions of this invention may be varied widely. The polymerizable unsaturated polyester portion thereof is ordinarily prepared by the reaction of an alpha, betaethylenically unsaturated dicarboxylic acid, or an admixture of such an acid with a saturated dicarboxylic acid, and a dihydric alcohol. Among the ethylenically unsaturated dicarboxylic acids which may be used are maleic acid, fumaric acid, mesaconic acid, aconitic acid, citraconic acid, ethyl maleic acid, xeronic acid and itaconic acid. Halogen substituted derivatives of these acids may also be utilized. The anhydrides of these acids, where the anhydrides exist, are embraced under the term "acid" since the reaction products or polyesters obtained by utilizing such acids and anhydrides are the same, and, in fact, in many instances it is preferred to utilize the anhydride rather than the free acid. The dihydric alcohol component of the polyester includes such compounds as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, 1,2-propanediol, di-1,3propanediol, butylene glycol and halogen substituted glycols. Small amounts of polyols with a functionality greater than two may be utilized in conjunction with the dihydric component. As indicated hereinabove, in many instances it is desirable to utilize a portion of a saturated dicarboxylic acid in conjunction with the ethylenically unsaturated dicarboxylic acid component. Examples of useful saturated acids include phthalic acid, isophthalic acid, terephathalic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dimethyl succinic acid, as well as halogenated derivatives of the above acids. The inclusion of a saturated dicarboxylic acid, such as described hereinabove, in an unsaturated polyester resin does not alter the beneficial effects realized from the addition of a small quantity of the carboxy-containing polymer. Generally, a saturated dicarboxylic acid is included as one of the components utilized in the preparation of an unsaturated polyester resin as some physical properties are improved by such inclusion. The term "unsaturated polyester resin" as used in the resin industry is interpreted as a resin utilizing an unsaturated dicarboxylic acid as at least a portion of the acid component of the polyester; therefore, the term embraces those resins which also utilize a saturated dicarboxylic acid as a portion of the acid component. The cross-linkable polyester resins and vinyl ester resins obtained can be readily cross-linked by uniting them with ethylenically unsaturated monomers, i.e., monomeric compounds containing a Cz s Croup. Styrene and vinyl toluene are most frequently utilized as the cross-linking monomer, although many other monomers may also be employed. Styrene is the most preferred monomer. Such other monomers include divinyl benzene, ethyl alpha-methyl styrene, chloro- and fluoro-styrenes, diallyl phthalate, triallyl cyanurate, allyl diglycolate, diallyl phenyl phosphonate, diethylene glycol bis (allyl carbonate), 1,2-propylene glycol bis (allyl carbonate), bis (allyl lactate) carbonate, allyl succinyl allyl glycolate, allyl maleate, methallyl maleate, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate, vinyl acetate and allyl acetate. The catalysts used in this invention are conventional free radical polymerization initiators selected from among organic peroxides and the hydroperoxides such as benzoyl peroxide dicumyl peroxide, methyl ethyl ketone peroxide, lauryl peroxide, cyclohexanone peroxide, t-butyl perbenzoate, t-butyl hydroperoxide, t-butylbenzene hydroperoxide, cumune hydroperoxide and t-butyl peroctoate. In addition, azo compounds such as azobis isobutyronitrile can be employed. A presently preferred catalyst is t-butyl perbenzoate. The reinforcing agents used in this invention comprise fibres selected from glass, asbestos, carbon, graphite, metal, synthetic polymers such as polyamides, polyesters, polyolefins and natural fibres such as cotton, jute, hemp, sisal, flax, wood, paper and the like. A preferred fibre is glass. The fibres can be used in the form of mats, fabrics, threads and chopped fibres. Another typical component in SMC and BMC is a thickening agent. These agents are usually oxides or hydroxides of a Group II metal. These agents include specifically oxides and hydroxides of magnesium, calcium, strontium, barium and zinc. In addition to the previously named components of the compositions of this invention other optional additives can be used. These include fillers, pigments, colorants, lubricants, stabilizers and silane coupling agents. Fillers include calcium carbonate, calcium silicate, talc, clay, alumina, aluminium hydroxide, antimony trioxide, silica, mica, barium sulphate, calcium sulphate and mixtures thereof. Preferred fillers include calcium carbonate, clay, talc and surface-treated fillers. A lubricant such as aluminium, barium, calcium, magnesium or zinc stearate can be used to impart mould release properties to the compositions. Conventional colorants and pigments such as Ti02, carbon black, phthalocyanine pigments and mixtures thereof can be employed in amounts sufficient to give the desired colour to the final moulded product. The ingredients are incorporated by a milling technique which involves moderate to high shear. This can be accomplished by means of twin-rotor mixers designed to give moderate shear to the paste-like ingredients. It is essential to provide some shear and because of the viscosity of the materials being mixed, proper mixing cannot be obtained simply by stirring or by using a conventional impeller mixer. On the other hand, high intensity mixing would generate excessive heat (above 35 C) and activation of the catalyst which must be avoided. Sheet moulding compounding line mixing equipment can also be used. This mixing under sufficient shear to achieve good dispersion of the ingredients without heat build-up activating the catalyst insures a good blend and is necessitated by the fact that the carboxyl polymer is a normally solid material. Shear which gives a hat build-up of 1-50, preferably 2-30iC is satisfactory. Low shear is preferred for BMC to avoid glass degradation. The curing can be don at a tmpratut known in the art for the particular catalyst utilized. Generally a temperature of 100*C to 290'C and a time of 1 to 15 minutes in a press is sufficient. The relative amounts of each component are readily determined and adjusted by one skilled in the art. Relative amounts of various components are expressed below in parts by weight: Typical BMC Formulation unsaturated thermosetting 30 to 50 42 resin ethylenically unsaturated 35 to 60 46 monomer filler 100 to 200 150 glass fibres 75 to 150 100 carboxy-containing 8 to 20 12 polymer thickening agent 1 to 4 2 mould release agent 2 to 6 4 catalyst 0.5 to 3 1 The invention is further illustrated by means of the following examples. EXAMPLE 1 Various bulk moulding compositions (BMC) were prepared with varying types of rubbers, The formulation for the BMC was as follows (expressed in parts by weight): Component Amount Unsaturated polyester 42 Rubber additive 12 Styrene monomer 46 Glass roving 100 Calcium carbonate 150 Zinc stearate 4 T-butyl perbenzoate (TBPB) 1 M & negium oxide 2 In the formulations1 the polyester employed was a propyl glycol-maleate polyester resin. Zn actual practice, the polyester was combined with 18 parts of the styrene monomer while the rubber additive was separately combined with the remaining 28 parts styrene monomer. The various components were mixed under standard conditions. Then plaques were compression moulded from each component for 2 minutes at 1750C (peak exotherm) and 6894 kPa. Each plaque was then evaluated to determine its physical properties. All the rubber components employed in the BMC are based on alkyl lithium-prepared styrene-butadiene block copolymers. Three of the polymers are uncoupled diblocks (block copolymers 1, 9 and 10), with one (block copolymer 9) having a higher vinyl content for the butadiene portion. The other polymers are coupled with various coupling agents. The degree of coupling is shown in Table 1 by reference to the various species - SB1, SB2, SB3, SB4. For example, SB2 signifies a polymer species having the structure SB-x-BS while SB3 signifies a polymer species having the structure EMI10.1 where x is the coupling residue. Some of the polymers were coupled or reacted with C02. These are block copolymers 7, 8 and 11. Only block copolymer 7 is according to the invention; the 1,2-vinyl content of the butadiene portion in the other two polymers is too low. The description of the polymer and the impact value (unnotched Izod determined by ASTM 256) are presented in Table 1: : TABLE I Rubber Component BMC Block SB Molecular Percent weight of species Percent Percent Unnotched copolymer Weight 1,2 vinyl weight Izod number x 1000 SB1 SB2 SB3 SB4 of butadiene Styrene (kg#m/m) portion 1 130 100 - - - 10 25 44 2 56 15 5 30 50 10 21 49.5 3 52 15 85 - - 10 31 55 4 35 15 85 - - 10 28 44 5 95 15 5 30 50 10 15 44 6 92 15 5 30 50 35 14 49.5 7 83 46 23 31 - 35 14 60.5 8 104 39 35 26 - 10 14 44 9 83 100 - - - 35 14 38.5 10 104 100 - - - 10 14 44 11 85 59 21 17 3 14 15 49.5 EXAMPLE II Two different sheet moulding compositions (SMC) were prepared with two different rubbers. One rubber was block copolymer 11-and the other was a polymer according to the present invention designated block copolymer 12. Block copolymer 12 was prepared by 1) polymerizing 8,154 g. styrene in 73,386 g. cyclohexane in the presence of 479.3 ml. sec-butyllithium for 15 minutes at 500C; 2) preparing the living styrene-butadiene block copolymer by polymerizing 22,831 g. butadiene in 114,880 g. cyclohexane and 43,488 g. of the solution obtained in step 1 in the presence of 16.75 ml. orthodimethoxybenzene; 3) reacting the living block copolymer with 16 g. gaseous carbon dioxide, which is introduced in'15 seconds beneath the surface of the polymer solution, at 450C during 2 minutes and 4) terminating the reaction with 20 ml methanol. A comparison between the two polymers is given in Table 2. TABLE 2 Styrene S-B Percent Block Block Percent 1,2 vinyl Molecular Molecular Weight Species of Weight Weight SB1 Sub 2 SB3 SB4 butadiene x 1000 x 1000 portion Block Co- 12 85 44 22 30 4 35 polymer 12 Block Co- 13 85 59 21 17 3 . 14 polymer 11 The two rubbers were employed in identical SMC formulations. The formulations had the following components (expressed in parts by weight): SMC Formulation Unsaturated polyester resin solution 420 Rubber 126 Styrene monomer 294 TBPB 9 Pigment 3 Zinc stearate 39 Calcium carbonate 1,260 Magnesium oxide 21 Glass fibres 840 Total 3,011 About 300 pounds of each formulation was prepared according to standard conditions. A portion of the SMC was then compression moulded into flat. plaques and the plaques were analyzed according to standard tests. These test results are presented in Table 3. TABLE 3 Hard- Shrinkage, Density, Initial Tensile, % Flex, Flex Notched Unnotched ness, mm g/cm Viscosi- kg/mê Strain kg/mê Mod., Izod, Izod, Barcol ty, Pa.s kg/mê kg#m/m kg#m/m Block co- 35 4.32 x 10-3 1.80 54 8.19 x 106 1.58 16.80 x 106 963.11 x 106 81.78 101.64 polymer 11 Block co- 20 6.35 x 10-3 1.78 48 7.32 x 106 1.46 16,53 x 106 1012.32 x 106 80.55 110.66 polymer 12 The physical properties were determined in accordance with the test procedures as follows: Flexural modulus and flexural strength, ASTM D790 Tensile and elongation, ASTM D256 Shrinkage, ASTM D955 Hardness, Barcol In addition, truck doors were also fabricated from the SMC's. Results are presented below in Table 4: TABLE 4 Tensile, Flex, Flex Mod. kg/m3 kg/m2 kg/m2 Block co- 5.09 x 106 15.37 x 106 913.9 x 106 polymer 11 Block Co- s.34 x 106 19.16 x 106 1054.5 x 106 polymer 12 In addition to having the best property balance, the doors made with SMC according to the present invention also had the best surface appearance.

Claims: CLAIMS 1. A moulding composition comprising: a) an unsaturated, crosslinkable thermosetting resin; b) an ethylenically unsaturated monomer; c) a reinforcing agent, a filler or mixtures thereof as additive and d) a normally solid, carboxy-containing styrene-butadiene block copolymer, characterized in that the moulding composition comprises a normally solid, carboxy-containing styrene-butadiene block copolymer prepared by contacting a monolithium terminated styrene-butadiene block copolymer solution with carbon dioxide by introducing dry gaseous carbon dioxide into said polymer solution at a temperature of from 20"C to 1O00C, at a pressure of from 103 kPa(abs) to 793 kPa(abs) and at a molar ratio of carbon dioxide added to lithium terminated block copolymer of from 0.75:1 to 3.0: :1, the butadiene portion of the monolithium terminated styrene-butadiene block copolymer having prior to the contact of this block copolymer with carbon dioxide a micro structure of between 30 and 40 mol percent 1,2-vinyl, between 20 and 30 mol percent 1,4-cis and between 30 and 50 mol percent 1,4-trans. 2. The composition of claim 1, characterized in that the preparation of the normally solid carboxy-containing block copolymer has been carried out at a molar ratio of carbon dioxide added to lithium terminated block copolymer of from 1.0:1 to 2.0:1. 3. The composition of claim 1, characterized in that said thermosetting resin is a polyester resin. 4. The composition of claim 3, characterized in that said polyester resin has been prepared by reacting an unsaturated dicarboxylic acid and a polyol. 5. The composition of claim 1 or claim 3, characterized in that said unsaturated monomer is styrene. 6. The composition of claim 1, characterized in that said additive is calcium carbonate. 7. The composition of claim 1, characterized in that said additive is a mixture of calcium carbonate and chopped fibre glass. 8. The composition of claim 1, characterized in that the composition additionally comprises a catalyst. 9. The composition of claim 8, characterized in that said catalyst is an organic peroxide. 10. The composition of claim 1, characterized in that the weight average molecular weight of each styrene block in the block copolymer prior to the reaction with carbon dioxide is between 8,000 and 20,000 and the weight average molecular weight of each butadiene block in said block copolymer prior to the reaction with carbon dioxide is between 30,000 and 100,000.

Inventors: GERGEN, WILLIAM PETER, HALPER, WALTER MARVIN
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1983
Main classification: C08L67
IPC codes: C08F8, C08F299, C08F2, C08L67, C08F285, C08L101, C08F297, C08L23, C08C19, C08F287, C08L51, C08L13, C08L77, C08L63, C08F290, C08G59