Modified unsaturated polyesters and process for the preparation therefor

Abstract: An unsaturated polyester modified by having an elastomeric polymer segment chemically bonded thereto, the chemical bond comprising a cyclic member containing six carbon atoms, and process for the preparation therefor by incorporating a conjugated diolefin group into an elastomeric polymer, reacting the conjugated diolefin group with an ethylenically unsaturated group in an unsaturated polyester so as to chemically combine the elastomeric polymer and the polyester through a cyclic hydrocarbon structure comprising 6 C atoms and recovering a modified unsaturated polyester.

Description: The invention relates to a modified unsaturated polyester, to a thermosetting unsaturated polyester resin composition containing the same and to a process for the preparation of said modified unsaturated polyester. The use of unsaturated polyesters in thermosetting resin compositions is, of course, well known in the prior art. Generally, these compositions comprise an unsaturated polyester, a vinyl monomer, a curing agent and a filler. The thermal setting resin composition may also comprise other additives, such as reinforcing agents, anti-shrinking agents and thickeners. In this regard, it should be noted that anti-shrinking agents are commonly used to improve surface characteristics whereas thickeners are used to increase the viscosity of the uncured composition prior to moulding. In general, unsaturated polyester resin compositions exhibit excellent rigidity, heat resistance and electrical characteristics when used in thermosetting applications. In some applications, however, such as bulk moulding and sheet moulding applications, improved impact resistance and improved surface characteristics (less shrinkage) are required or at least desired. As indicated in the background section of U.S.-A-4,329,438 several methods have, heretofore, been proposed for improving the impact resistance and the surface characteristics of such unsaturated polyester resin compositions. These methods include the addition of either a diolefin rubber or a styrene-diolefin block copolymer to the resin compositions. Moreover, it is known to use carboxylated derivatives of styrene-butadiene block copolymers as additives in polyester resin compositions for this same purpose. As indicated in the background section of said U.S.-A-4,329,438, however, these methods have not been completely successful due, primarily, to the incompatibility of the rubber polymer in the composition and the resulting destructive phase separation and bleeding of the rubber to the surface. Another difficulty with the proposed prior art solutions to the problem, particularly in those cases where a block copolymer is used, is solubility of the block copolymer in the vinyl monomer which functions both as a crosslinking agent and as a solvent in the composition. U.S.-A-4,329,438 teaches yet another method for solving the destructive phase separation problem wherein a carboxylated derivative of a styrene-butadiene block copolymer is used. Specifically, the styrene-butadiene block copolymer is modified by grafting an unsaturated dicarboxylic acid and/or an unsaturated dicarboxylic acid derivative onto the block copolymer. According to the disclosure, significant improvement is realized but destructive phase separation and the associated rubber bleeding is apparently not completely eliminated since the block copolymer and the unsaturated polyester remain as a physical admixture in the thermosetting resin composition. U.S.-A-3,892,819 teaches still another method of solving a compatibility problem in a vinyl ester composition wherein a carboxylated derivative of a polydiene rubber is used. Particularly, this patent specification teaches that when a polydiene rubber is first treated so as to contain terminal carboxyl groups, the carboxyl groups may then be reacted with epoxy groups contained in the backbone of a polyvinyl ester. The polydiene rubber is, then, chemically bonded to the polyvinyl ester and, therefore, not subject to destructive phase separation so long as the chemical bond remains intact. The ester bond actually used in the thus modified polyvinyl ester is, of course, relatively weak and may be broken under certain conditions. Should this occur prior to curing of the resin composition destructive phase separation and the associated rubber bleeding would again surface. There is, then, a need for a still better way for incorporating a rubber or a thermoplastic elastomeric polymer into a thermosetting polyester resin composition. It has now been discovered that the foregoing and other disadvantages of the prior art polyester resin compositions can be overcome or at least significantly reduced with the modified unsaturated polyester of this invention and an improved thermosetting unsaturated polyester resin composition provided therewith. It is, therefore, an object of the present invention to provide a modified polyester, methods of preparing the same and a thermosetting polyester resin composition containing the same. It is another object of this invention to provide such a modified polyester which when formulated into a thermosetting polyester resin composition will not be subject to destructive phase separation. It is a still further object of the present invention to provide such a modified polyester which, when formulated into a thermosetting polyester resin composition and cured, will yield a moulded product having improved impact resistance. It is yet another object of this invention to provide such a modified unsaturated polyester which, when formulated into a thermal setting unsaturated polyester resin composition and cured, will yield a moulded product exhibiting less shrinkage, and hence, better surface characteristics. The foregoing and other objects and advantages will become apparent from the description set forth hereinafter. Accordingly, the invention provides a modified unsaturated polyester which unsaturated polyester is modified by having at least one elastomeric polymer segment chemically bonded thereto via a 6 carbon cyclic member obtained via a Diels Alder reaction. The unsaturated polyester of this invention is modified by chemically incorporating a treated elastomeric homopolymer or copolymer into the backbone of said polyester through a relatively stable chemical bond, which elastomeric homopolymer or copolymer is frequently referred to herein as an elastomeric polymer. The elastomeric homopolymer or copolymer may be chemically bonded to the unsaturated polyester by reacting the polyester with an elastomeric homopolymer or copolymer, which copolymer may be either random or block, comprising a conjugated diolefin linkage or by grafting the polyester onto such an elastomeric homopolymer or copolymer. The chemical bonding is accomplished by reacting the conjugated diolefin group of the elastomeric homopolymer or copolymer with an ethylenic unsaturation contained in a preformed polyester or with an ethylenic unsaturation of a monomer useful in preparing such a polyester via a Diels Alder condensation or cyclization. The Diels Alder addition reaction will be accomplished at typical Diels Alder reaction conditions. The modified unsaturated polyester thus produced will exhibit good impact resistance and may be used in a thermosetting composition. The thermosetting resin composition may also comprise a vinyl monomer, a curing agent and other additives as desired or required. As indicated hereinbefore, the present invention relates to a modified polyester, to methods for preparing said modified polyester and to an improved unsaturated polyester resin composition, which improved unsaturated polyester resin composition exhibits good impact strength when cured and, therefore, may be used with advantage in various moulding applications and particularly sheet moulding and bulk moulding applications. The improved unsaturated polyester is, in effect, a conventional unsaturated polyester modified by chemically incorporating an elastomeric homopolymer or copolymer containing a conjugated diolefin linkage. The chemical incorporation is through a Diels Alder addition reaction between the conjugated diolefin linkage of the elastomeric homopolymer or copolymer with a vinyl unsaturation in the unsaturated polyester or in a monomer subsequently used to prepare such a polyester. The modified unsaturated polyester of this invention may be prepared in at least two ways. Firstly, both an unsaturated polyester and an elastomeric homopolymer or copolymer may be separately produced, the elastomeric homopolymer or copolymer then chemically treated so as to incorporate a conjugated diolefin structure and the thus treated elastomeric homopolymer or copolymer then reacted with the unsaturated polyester at Diels Alder reaction conditions. Alternatively, the elastomeric homopolymer or copolymer may be first produced, chemically treated so as to incorporate a conjugated diolefin linkage, reacted with a suitable monomeric dienophile and then incorporated into the unsaturated polyester by grafting the polyester onto the elastomeric homopolymer or copolymer at the site of said dienophile. The unsaturated polyesters which may be modified in the present invention include: those polyesters prepared through the condensation of an unsaturated dicarboxylic acid, an unsaturated dicarboxylic anhydride or a mixture thereof with a dihydric alcohol or mixture thereof and those prepared by condensing an unsaturated monocarboxylic acid with a polyepoxide. Since the modification consists of a 4+2 Diels-Alder cycloaddition reaction, however, it is essential to the present invention that the unsaturated polyester contain at least one dienophile group; i.e., a polar group or a substituted polar group, preferably a carboxyl group, adjacent to a carbon-carbon double bond in the unsaturated polyester structure. Most preferably, the unsaturated polyester will contain at least one group having a carboxyl group adjacent to each of the carbon atoms in a carbon carbon double bond. Suitable unsaturated polyesters prepared from an unsaturated dicarboxylic acid and/or an anhydride thereof and a polyhydric alcohol include unsaturated polyesters obtained by replacing up to 90 %mol of the unsaturated dicarboxylic acid or anhydride thereof with a saturated dicarboxylic acid or an anhydride thereof. Suitable dicarboxylic acids or anhydrides include, for example, maleic, fumaric, itaconic, citraconic, chloromaleic, mesaconic and glutaconic. Suitable saturated dicarboxylic acids or anhydrides which may be substituted for a part of the unsaturated dicarboxylic acid or anhydride include, but are not 2 necessarily limited to, for example phthalic, succinic, adipic, azelaic, isophthalic, terephthalic and tetrafluorophthalic. Suitable dihydric alcohols include, but are not limited to, linear glycols such as ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, 1,3-butanediol, neopentyl glycol, 1,4-cyclohexane dimethanol mixtures of these glycols and cyclohexane dimethanol with hydroxy-alkyl ethers of bisphenol A. Suitable unsaturated polyesters include those described in U.S.-A-3,925,299, 3,925,300, and 3,489,707. In general, these polyesters are produced by condensing the dicarboxylic acid or anhydride or mixture thereof with a dihydric alcohol or mixture thereof at a temperature within the range of from 30°C to 205°C. The condensation reaction is usually terminated when an acid number less than 100 is reached most frequently by use of an indicator such as, for example, toluhydroquinone, hydroquinone, a methyl ester of hydroquinone and m-dinitrobenzene. Suitable polyvinyl esters include those described in U.S.-A-Nos. 3,179,623; 3,256,266; 3,301,743; 3,317,465; 3,367,992 and 3,377,406. In general, unsaturated monocarboxylic acids useful in such polyvinyl esters include, for example, acrylic acid, methacrylic acid, halogenated acrylic or methacrylic acids, cinnamic acid and various half esters of dicarboxylic acids such as the half esters of hydroxyalkyl acrylate or methacrylate wherein the hydroxyalkyl group preferably has from 2 to 6 carbon atoms. Polyepoxides which may be used in polyvinyl esters include, but are not necessarily limited to, for example, glycidyl polyethers of both polyhydric alcohols and polyhydric phenols, flame retardant epoxy resins based on tetrabromo bisphenol A, epoxy novolacs, epoxidized fatty acids or drying oil acids, epoxidized diolefins, epoxidized diunsaturated acid esters and epoxidized unsaturated polyesters containing more than one oxirane group per molecule. The polyepoxides may be monomeric or polymeric. In general, any elastomeric polymer known in the prior art may be chemically treated to incorporate a conjugated diolefin linkage and then used to modify a polyester in accordance with this invention. Useful elastomeric polymers, then, include those prepared in bulk, suspension, solution or emulsion. As is well known, polymerization of monomers to produce an elastomer may be accomplished using free-radical, cationic and anionic initiators or polymerization catalyst. As indicated more fully hereinafter, however, it is important to the present invention that the elastomic polymer comprise at least one active group containing an alkali metal atom when it is treated to incorporate the conjugated diolefin linkage. As a result elastomeric polymers prepared with free-radical or cationic initiators as well as those produced with an anionic initiator and then treated to deactivate the active site must be metallated to incorporate at least one such active site prior to treatment to incorporate the conjugated diolefin linkage. Metallization may, of course, be accomplished using techniques well known in the prior art such as the method taught in U.S.-A-4,145,298. Polyolefin elastomers containing ethylenic unsaturation could, of course, be easily metallated using these techniques. Notwithstanding that any elastomeric polymer may be used in the present invention, elastomers prepared with an anionic initiator and then treated to incorporate a conjugated diolefin linkage before deactivation of the active site are preferred and the invention will be described in greater detail by reference to such polymers. Any metallated polymer containing an alkali-metal atom may, however, be sustituted for such active, living polymers. In general the elastomeric homopolymers and copolymers most useful in this invention will be prepared by contacting the monomer or monomers with an organo alkali metal compound in a suitable solvent at a temperature within the range from -150°C to 300°C. Particularly effective polymerization initiators are organo lithium compounds having the general formula RLi n wherein R is an aliphatic, cycloaliphatic or aromatic hydrocarbon radical having from 1 to 20 carbon atoms and n is an integer of 1 to 4. In general, the elastomeric polymers useful in the present invention will have a molecular weight within the range from 2,000 to 200,000 and when the elastomeric polymer is a copolymer of one or more diolefins and one or more other monomers, the elastomeric polymer will comprise from 20 to 99 wt% monomeric diolefin units. At this point, it should again be noted, that it is essential to the present invention that the elastomeric homopolymer or copolymer be a living polymer; i.e., contain at least one active group, such as an alkali metal atom bonded to a carbon atom, which can be treated so as to incorporate a conjugated diolefin group by the process of this invention. Elastomeric homopolymers and copolymers useful in the present invention include those terminally reactive homopolymers and copolymers described in U.S.-A-3,135,716; 3,150,209; 3,496,154; 3,498,960; 4,145,298 and 4,238,202, particularly those homopolymers and copolymers having only one terminal lithium atom and described in U.S.-A-3,150,209; 3, 496,154; 3,498,960; 4,145,298 and 4,238,202. In general, the elastomers taught by these patent specifications may be polymers of one or more conjugated dienes containing from 4 to 12 carbon atoms such as, for example, 1,3-butadiene, isoprene, piperylene, 2- and 3-methylpentadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene and 4,5-diethyl-1,3-octadiene, preferably those containing 4 to 8 carbon atoms. Moreover, one or more of the hydrogen atoms in these conjugated diolefins may be substituted with halogen atoms. The elastomeric polymers may also be copolymers of one or more of the aforementioned conjugated diolefins and one or more other monomers. Other monomers which may be used include aryl substituted olefins such as, for example, styrene, various alkylstyrenes, paramethoxystyrene, vinylnaphthalene and vinyltoluene, heterocyclic nitrogen-containing monomers, such as pyridine and quinoline derivatives containing at least one vinyl or alphamethylvinyl group such as, for example, 2-vinylpyridine, 3-vinylpyridine and 4-vinylpyridine. In addition to the forgoing polymers, other block copolymers useful in the present invention may be prepared in accordance with the methods described in U.S.-A-Nos. 3,231,635; 3,265,765 and 3,322,856. In practicing these methods, however, care should be exercised to produce block copolymers having the general formula B x -(A-B) y or A x -(B-A) y wherein x is a number equal to 0 or 1 and y is a whole number from 1 to 15. A and B are as defined in the aforementioned patent numbers 3,231,635; 3,265,765 and 3,322,856, A being a polymer block of an alkenyl-substituted aromatic hydrocarbon and B a polymer block. In one process embodiment of the present invention and as indicated hereinbefore, the elastomeric homopolymer or copolymer useful in the present invention may be first treated so as to comprise a conjugated diolefin group, as taught in copending U.S. Patent Application Serial No. 948,336 (US-A-4 839 431) which copending application was filed 31st December 1986, and then reacted with a preformed unsaturated polyester. Treatment of the elastomeric homopolymer or copolymer to incorporate a conjugated diolefin structure may be accomplished by reacting a so called living elastomeric homopolymer or copolymer first with a 2,3-ethylenically unsaturated aldehyde or ketone having, respectively, one of the following general formulae: 1. wherein R₁ represents a hydrogen atom or an aliphatic, cycloaliphatic, aryl or alkyl-substituted aryl hydrocarbon group having 1 to 10 carbon atoms; or 2. wherein R₁ is as defined hereinbefore and R₂ represents an aliphatic, cycloaliphatic, aryl or alkyl-substituted aryl hydrocarbon group having 1 to 10 carbon atoms; and thereafter converting the resulting alkali metal salt to the corresponding alcohol and then dehydrating the alcohol. As is known in the prior art, the latter two steps may be accomplished, in effect, simultaneously when an acid is used in excess of the stoichiometric amount to convert the alkali metal salt to the corresponding alcohol at an elevated temperature. In general, reaction of the 2,3-ethylenically unsaturated aldehyde or ketone with the living elastomeric homopolymer or copolymer will be accomplished in a suitable solvent at a temperature within the range from 10°C to 150°C. Nominal holding times at reaction conditions will, generally, range from 1 to 120 minutes. Suitable solvents include any of the solvents known in the prior art to be effective for use during preparation of the elastomeric homopolymer or copolymer. These include hydrocarbons such as paraffins, cycloparaffins, aromatics and alkyl-substituted aromatics containing from 4 to 10 carbon atoms per molecule. Suitable solvents include, for example, benzene, toluene, cyclohexane, methyl cyclohexane, n-butane, n-hexane and n-heptane. Since the reaction between the living elastomeric homopolymer or copolymer and the 2,3-ethylenically unsaturated aldehyde or ketone proceeds stoichiometrically, it will, generally, be sufficient to use 1 mol of 2,3-ethylenically unsaturated aldehyde or ketone per mol of alkali metal active sites in the living elastomeric polymer to be treated although lesser amounts as well as excess amounts of either the aldehyde or ketone may be used. The alkali metal salt produced by reacting the living elastomeric homopolymer or copolymer with a 2,3-ethylenically unsaturated aldehyde or ketone is next converted to the corresponding alcohol. Any of the methods known in the prior art to be effective for such conversion may be used in the present invention. One such method is to simply react the alkali metal salt with an acid. In general, this reaction will be accomplished in a suitable solvent such as those solvents heretofore mentioned as useful for the aldehyde or ketone reaction with the elastomeric polymer. In general, any acid, organic or inorganic, may be used. Suitable acids, then include, but are not limited to, the series of aliphatic carboxylic acids starting with formic acid the series of aromatic carboxylic acids starting with benzoic acid and the various mineral acids such as, for example, hydrochloric acid, nitric acid and sulphuric acid. After the corresponding alcohol has been produced, the same will then be dehydrated, while still in solution, to yield the desired conjugated diolefin structure. Generally, this may be accomplished simply by heating the alcohol. More expediently, however, this may be accomplished by effecting the acid treatment at an elevated temperature. In a preferred embodiment of the present invention, then, the acid treatment will be accomplished at a temperature within the range of from 40°C to 205°C. Generally, nominal holding times at a temperature within the foregoing range within the range of from 1 to 120 minutes will be sufficient to permit both conversion of the lithium salt to the corresponding alcohol and dehydration of the alcohol. Again, conversion of the alkali metal salt to the alcohol will occur on a stoichiometric basis, however, an excess of acid will catalyze the dehydration reaction. Generally, then, a slightly greater than stoichiometric amount of acid will be used to effect the conversion. The elastomeric homopolymer or copolymer containing the conjugated diolefin structure may be recovered as a crumb from solution using conventional technology well known in the prior art or the same may be used directly in the next step in the preparation of a modified unsaturated polyester. In this one process embodiment the elastomeric homopolymer or copolymer containing the conjugated diolefin structure is next reacted with a preformed unsaturated polyester. In general, the reaction between the preformed polymers will be accomplished in a suitable solvent such as those solvents heretofore described as useful in the previous steps. As indicated hereinbefore, the reaction will constitute a 4 + 2 Diels Alder addition involving the conjugated diolefin group incorporated into the elastomeric polymer and an ethylenically unsaturated linkage having a polar group on at least one adjacent carbon atom in the unsaturated polyester. In general, and when the modified unsaturated polyester is to be used in a moulding composition, it will not be necessary to incorporate more than an average of about one elastomeric segment into the unsaturated polyester. Moreover, when the unsaturated polyester has been preformed using vinyl substituted monocarboxylic acids, care should be exercised to ensure that no more than about one vinyl group is reacted with an elastomeric segment containing a conjugated diolefin group. Notwithstanding this, it is contemplated in the present invention to incorporate more than one treated elastomeric segment per polyester segment, particularly when relatively high molecular weight unsaturated polyesters containing unsaturated dicarboxylic acid monomer units are used. In general, reaction between the conjugated diolefin group of the treated elastomeric polymer and an ethylenically unsaturated linkage in an unsaturated polyester will be accomplished at a temperature within the range from 10°C to 205°C. In this regard, and as is well known in the prior art, higher temperatures within this range will be required to effect reaction between the conjugated diolefin group and the ethylenic unsaturation when the ethylenic unsaturation has only one adjacent active polar group. Moreover, higher temperatures within this range will be required if the ethylenic unsaturation is hindered. The lower temperatures within this range are, of course, effective when the ethylenic unsaturation has two adjacent active groups and said ethylenic unsaturation is otherwise unhindered. In general, the pH will be maintained at a value within the range of from 1 to 7 during the Diels Alder addition reaction. Nominal holding times within the range from 1 to 240 minutes will be sufficient to permit the reaction to proceed to completion. Again, the 4 + 2 Diels Alder addition will proceed on a stoichiometric basis. In general, and in moulding compositions comprising such modified polyester, the modified polyester will comprise from 10 to 100 %mol of the total polyester used in the composition. As a result, at least two methods may be used to produce the desired blend of modified unsaturated polyester and the unmodified unsaturated polyester. For example, when the unsaturated polyester resin composition is to comprise less than 100 %mol of modified unsaturated polyester a sufficient amount of treated elastomeric polymer may be added to an unsaturated polyester to convert the desired percentage thereof, less than 100 %mol, to a modified unsaturated polyester. Alternatively, the unsaturated polyester may be modified on a stoichiometric basis and the thus modified unsaturated polyester then combined with the desired amount of unmodified unsaturated polyester. This latter method does, of course, permit the use of an unsaturated polyester different from the one that was modified. In a second process embodiment of the present invention, the elastomeric homopolymer or copolymer which has been treated so as to contain a conjugated diolefin group will first be reacted with a monomeric dienophile and then, in effect, used as a monomer in the preparation of an unsaturated polyester. In this regard, it should be noted that the treated elastomeric polymer may be reacted with any one of the dicarboxylic acids heretofore mentioned as well as any one of the vinyl monocarboxylic acids identified above. The elastomeric polymer which will now contain at least one terminal carboxyl group may then be substituted for a portion of the unsaturated dicarboxylic acid monomer or a portion of the vinyl substituted monocarboxylic acid monomer in any one of the aforementioned processes for producing an unsaturated polyester. The conditions used to react the treated elastomeric polymer with the monomeric dienophile will, of course, be identical to those used in reacting the treated elastomeric polymer with a preformed unsaturated polyester. The conditions used in the preparation of the unsaturated polyester, when using the treated elastomeric polymer containing at least one carboxyl group as a monomer, will also be identical to the conditions used in the afore-identified processes for preparing such polyesters. Again, when a thermosetting polyester resin composition containing polyester which is less than 100% modified polyester is prepared, two methods may be used to prepare a mixture of modified polyester and unmodified polyester suitable for use in a thermosetting resin composition. In one such method, the amount of monomer comprising an elastomeric polymer segment actually substituted for acid in the condensation reaction may be controlled so as to yield a polyester resin mixture comprising the desired amount of modified polyester and the desired amount of unmodified polyester. In a second such method, a sufficient amount of treated elastomeric polymer will be substituted for unsaturated dicarboxylic acid monomer or vinyl substituted monocarboxylic acid monomer to produce a polyester containing the desired number of appendant elastomeric homopolymer or copolymer segments per polyester segment and the thus produced modified polyester then added to a sufficient amount of unmodified polyester to yield the desired composition for use in a thermosetting polyester resin. In either of these methods, the polyester is, in effect, reacted with or grafted onto one or more of the treated elastomeric polymers at the site of the monomeric dienophile. As indicated hereinbefore, the modified unsaturated polyesters of this invention are particularly useful in thermosetting polyester resin compositions. The modified unsaturated polyesters of this invention contain at least one elastomeric segment which imparts impact resistance to the moulded product. Since the elastomeric segment is chemically bonded in the modified unsaturated polyester the improved impact resistance is achieved without destructive phase separation or rubber bleeding to the surface during formation of the moulded article. In general, the modified polyester of this invention will comprise from 1 to 95 wt% of the thermosetting polyester composition. The composition may also comprise from 0 to 95 wt% of an unmodified unsaturated polyester, which unmodified unsaturated polyester may be the same or different than the one which was modified. The thermosetting unsaturated polyester resin composition will also comprise a vinyl monomer which acts both as a solvent and as a crosslinking agent. In general, the vinyl monomer will comprise from 5 to 50 wt% of the thermosetting composition. The thermosetting composition will, generally, also comprise a curing agent. In general, the curing agent will comprise from 0.001 to 1 wt% of the thermosetting composition. The thermosetting composition may also comprise a filler, a reinforcing agent and a thickener. When a filler is used, the same will, generally, comprise from 5 to 70 wt% of the thermosetting composition. When a reinforcing agent is used, the same will, generally, comprise from 5 wt% to 90 wt% of the composition. When a thickener is used, the same will, generally, comprise from 0.1 to 5 wt% of the thermosetting composition. In general, any of the vinyl monomers known to be useful in the prior art for crosslinking mouldable compositions may be used in the thermosetting resin composition of the present invention. Suitable vinyl monomers include the styrene monomers and substituted derivatives thereof such as, for example, styrene, α-methylstyrene, aminostyrene, methylethylaminostyrene, methoxystyrene, chlorostyrene, dichlorostyrene, dimethylstyrene, trimethylstyrene, t-butylstyrene, sodium styrenesulfonate, p-benzylstyrene, p-phenoxystyrene and similar aryl-substituted styrenes. Suitable monomers also include β-hydrocarbyl-substituted derivatives of acrylic acid in which the alkyl group has 1 to 8 carbon atoms such as, for example, ethylacrylic acid, propylacrylic acid, butylacrylic acid, amylacrylic acid, hexylacrilic acid, heptylacrylic acid, octylacrylic acid, phenylacrylic acid and vinylacrylic acid. Suitable vinyl monomers also include various acrylates and substituted acrylates such as, for example methylacrylate, methyl methacrylate, ethyl acrylate, butyl methacrylate and butyl acrylate. In addition to the foregoing vinyl compounds, any CH=C< group containing monomers may be utilized if desired. In general, any of the curing agents known in the prior art to be effective for use in thermosetting unsaturated polyester resins may be used in the composition of the present invention. Generally, curing agents are conventional free radical polymerization initiators, particularly organic peroxides and hydroperoxides. Suitable curing agents then, include, for example, benzoyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, lauryl peroxide, cyclohexanone peroxide, t-butyl perbenzoate, t-butyl hydroperoxide and t-butyl benzene hydroperoxide, cumene hydroperoxide and t-butyl peroctoate. In addition, various azo compounds such as azobisisobutyronitrile may be used. A particularly preferred curing agent is t-butyl perbenzoate. In general, any of the fillers known in the prior art to be useful in thermosetting polyester resins may be used in the thermosetting resin composition of the present invention. Suitable fillers include, for example, calcium carbonate, calcium silicate, silica, calcined clay, chalk, talc, limestone, anhydrous calcium sulphate, barium sulphate, asbestos, powdered glass, quartz, aluminium hydrate, aluminium oxide and antimony oxide. Similarly, any of the reinforcing agents known to be useful in thermosetting polyester resins may be used in the thermosetting composition of this invention. Suitable reinforcing agents, then, include, for example, fibres of glass, metal silicates, asbestos, celluose, carbon, graphite, polyesters, polyacryls, polyamides and polyolefins. Chopped glass fibres are particularly effective for use as reinforcing agents. In general, any of the thickening agents known in the prior art to be effective for use in thermosetting polyester resin compositions may be used in the composition of the present invention. Suitable thickeners include oxides and/or hydroxides of metals of Group II of the Periodic Table and are selected from oxides and hydroxides of magnesium, calcium, strontium, barium and zinc. The hydroxides of magnesium and/or calcium are particularly effective thickening agents. In addition to the previous named components, the thermosetting unsaturated polyester resin composition may also comprise, for example, pigments, colorants, lubricants, stabilizers and silane coupling agents. In this regard, it should be noted that conventional colorants and pigments such as, for example, TiO₂, carbon black and phthalocyanide pigment and mixtures thereof, are employed as desired in amounts sufficient to give the desired colour to the final moulded product. It should also be noted that lubricants such as, for example, aluminium, barium, calcium, magnesium or zinc stearate may be used to impart mould release properties to the composition. The ingredients of the thermosetting resin composition of this invention may be combined by a mixing technique which involves moderate to high shear agitation. 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 which would generate excessive heat (above 35°C) and activate the catalyst 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 buildup sufficient to activate the catalyst insures a good blend and is necessitated by the fact that the resin composition may contain normally solid material. Shear which gives a heat buildup of, preferably, 2-30°C is particularly satisfactory. Low shear is preferred for BMC to avoid glass degradation. The modified unsaturated polyester and the unmodified unsaturated polyester may be blended before incorporation into the moulding composition or each may be added separately during the mixing. Preferably, however, the polyesters will be blended before incorporation in the moulding composition. The thermosetting polyester resin composition of this invention may be cured at conditions known to be effective for this purpose in the prior art. Generally, temperatures within the range of from 100°C to 200°C and a time of 1 to 15 minutes is sufficient. In a preferred embodiment of the present invention, a preformed polyester comprising unsaturated dicarboxylic acid or anhydride and dihydric alcohol monomeric units will be modified by reaction with a block copolymer comprising a single alkenyl-substituted aromatic hydrocarbon block and a single diolefin block and having a conjugated diolefin linkage on or in the diolefin block. In a most preferred embodiment, the preformed polyester will comprise from 5 to 50 %mol of maleic acid or maleic anhydride monomer units and 50 %mol of propylene glycol monomer units. The preferred polyester may also comprise from 0 to 45 %mol of saturated dicarboxylic acid or anhydride monomeric units. The block copolymer will be prepared with an organo lithium compound using the method described in U.S. patent specification 3,231,635 and may be represented by the general formula A-B, wherein A and B are, respectively, polymer blocks of an alkenyl substituted aromatic hydrocarbon and a conjugated diolefin. In the preferred embodiment, the alkenyl-substituted aromatic hydrocarbon block will have a weight average molecular weight within the range of from 2,000 to 30,000 and the conjugated diene block will have a weight average molecular weight within the range from 2,000 to 90,000. In a most preferred embodiment, the alkenyl-substituted aromatic hydrocarbon will be styrene and the conjugated diolefin will be either butadiene or isoprene. In the preferred embodiment, the block copolymer will be treated so as to incorporate a conjugated diolefin group by first contacting the living polymer obtained from the polymerization process with acrolein to produce the lithium salt and then with sulphuric acid at an elevated temperature to, in effect, simultaneously form the corresponding alcohol and dehydrate the same. The thus treated block copolymer is next reacted with a preformed polyester. In the preferred embodiment, the treated block copolymer will be mixed with a molar excess of the preformed polyester and the reaction carried substantially to completion such that the resulting modified polyester will contain an average of roughly one block copolymer (elastomeric) segment per polyester segment. In the preferred embodiment, the treatment of the block copolymer will be accomplished in the same solvent as was used during the preparation of the block polymer. The reaction between the conjugated diene group and an ethylenically unsaturated group in the polyester will be accomplished at a temperature within the range from 25 to 125°C. As indicated hereinbefore, the reaction is a 4 + 2 Diels Alder addition and results, in effect, in the grafting of the block copolymer to the polyester through a cyclic structure comprising 6 carbon atoms. The preferred modified unsaturated polyesters of this invention are particularly effective, when used in thermosetting unsaturated polyester resin compositions, in imparting improved surface characteristics (less shrinkage) and improved impact resistance to the moulded products. Moreover, these improved properties are realized without the risk of destructive phase separation which has heretofore been experienced when elastomeric polymers were incorporated into a themosetting unsaturated polyester composition. In a preferred thermosetting unsaturated polyester resin composition, a modified unsaturated polyester within the scope of the present invention will, in effect, be substituted for from 50 to 100 wt% of the conventional unsaturated polyester normally used in such compositions. A preferred thermosetting unsaturated polyester resin composition will, then, comprise from 40 to 80% by weight of a modified unsaturated polyester within the scope of the present invention and from 0 to 40% by weight of an unmodified or conventional unsaturated polyester. As used herein, the recitation "unmodified unsaturated polyester" is intended to mean any unsaturated polyester known in the prior art which is not chemically combined with an elastomeric homopolymer or copolymer through a 6-member ring. The recitation "conventional unsaturated polyesters" is intended to mean any of those commercially available unsaturated polyesters which are commonly used in thermosetting polyester resin compositions. It will, of course, be appreciated that incorporation of the modified unsaturated polyester into the composition effectively incorporates from 1 to 50 wt% of an elastomeric polymer into said composition. In addition to the modified and unmodified unsaturated polyesters, a preferred thermosetting unsaturated polyester resin will also comprise from 5 to 50% by weight of an ethylenically unsaturated monomer capable of functioning as both a solvent and as a crosslinking agent. In a most preferred composition, the vinyl monomer will be styrene. A preferred thermosetting composition will also comprise from 0.1 to 0.5% by weight of a curing agent. The following Examples further illustrate the invention. Example 1 Preparation of styrene-butadiene block copolymer The block copolymer was prepared under anhydrous and anaerobic conditions in a closed, glass reaction vessel. Initially, styrene (13.1 g) dissolved in cyclohexane (170 g) was charged to the reaction vessel along with n-butoxy- t-butoxy-ethane (100 µl) and a 0.25N solution of s-butyllithium (3 ml). The reaction vessel was heated to 50°C and when the polymerization of styrene was substantially complete polymerization grade butadiene monomer (24.1 g) was added to the vessel. Polymerization of the diene monomer was allowed to proceed substantially to completion and the resulting styrene-butadiene diving block copolymer was quenched by the addition of an excess of methyl alcohol. The nonfunctionalized styrene-butadiene block copolymer was then recovered as crumb by coagulation with and excess of methyl alcohol. Analysis of the recovered product indicated that the block copolymer contained a single block of styrene having a weight average molecular weight of 13,400 and a single butadiene block having a weight average molecular weight of 29,400. Preparation of three styrene-butadiene block copolymers containing a single acrolein end group For convenience, these polymer samples have been identified as A, B and C. Each sample was prepared by repeating the polymerization steps summarized in this Example hereinbefore but before deactivating the lithium atom with methyl alcohol the living diblock copolymer was titrated with acrolein until the pale yellow colour of the living anionic polymer had disappeared. The end-capped block copolymer was then contacted with an aliquot of ammonium chloride in methyl alcohol to deactivate the lithium atom. Each of the three samples were recovered by coagulating with an excess of methyl alcohol. After recovery, each sample was analyzed to determine the weight average molecular weight of each block and the amount of coupled products in each sample. These results are shown in the following table: Acrolein Capped Block Copolymers A B C Molecular Weight of Styrene Block (x10⁻³) 14.4 13.3 13.3 Molecular Weight of Butadiene Block (x10⁻³) 29.1 29.1 29.5 Coupled Product (% by weight) 4 5 5 Preparation of styrene-butadiene block copolymer containing a cyclic anhydride moiety The acrolein capped polymers identified as A and B in this Example hereinbefore were combined and dissolved in cyclohexane (600 ml). The solution was then divided into two equal sized aliquots and each aliquot treated with an excess of maleic anhydride to produce an elastomer having a cyclic anhydride moiety chemically bonded thereto through a 6-carbon atom cyclic structure containing one carbon-carbon double bond and to dehydrate the alcohol which was produced in this Example hereinbefore. The treatment was accomplished by adding maleic anhydride (0.25g) to each aliquot and then heating both to reflux and holding each at this temperature for four hours. The resulting reaction products were then recovered as a crumb by coagulating in excess methyl alcohol. The elastomer thus produced could be substituted for a portion of the unsaturated dicarboxylic acid or anhydride monomer in any of the polyester resin operations hereinbefore discussed. Example 2 - Preparation of modified unsaturated polyester The acrolein capped polymer identified as C in Example 1 was dissolved in xylene (215ml) and combined with 10g of a maleate/propylene glyclol unsaturated polyester resins (known under the trade name Koppers 3702-5 unsaturated polyester resin). Three drops of concentrated H₂S0₄ were then added to this solution and the solution heated to reflux temperature and held at this temperature for four hours. The H₂SO₄, inter alia, acted as a catalyst for the Diels Alder reaction. As a result of this treatment, the alcohol produced in Example 1 was dehydrated and the conjugated diolefin group produced then reacted with the maleate/propylene glyclol unsaturated polyester resin. The product was contacted with an excess of methyl alcohol, a good solvent for the polyester resin. As a result of the contacting with methyl alcohol, the reaction product of the end-capped elastomer and the polyester and any unreacted end-capped elastomer were precipitated while any unreacted polyester remained in solution. After separation, the coagulated product was subjected to infrared (IR) analysis to confirm the presence of grafted polyester therein. This was confirmed by a peak occurring at 1640 cm⁻¹. Signals in the IR spectrum at 690 cm⁻¹ and 920 cm¹ also indicated that the coagulated product contained styrene-butadiene block copolymer. The relative intensities of the IR signals indicated that the modified polyester contained significant amounts of both of the polymeric reactants. Example 3 and Comparative Experiment X A portion of the styrene-butadiene block copolymer produced in Example 1 and a portion of the acrolein modified block copolymer produced in Example 1 and identified as C were dissolved in styrene monomer at a concentration of 30% by weight of polymer in said solution. A 50g aliquot of each solution was then treated with three drops of sulphuric acid and blended with an equal weight of solution (about 70% by weight of unsaturated polyester) containing Koppers 3702-5 unsaturated polyester, the same polyester which was modified in Example 2, in styrene. The blending was accomplished at 500 revolutions per minute (rpm) for three minutes using a 2.54 cm jiffy blade positioned in a 0.23 kg jar. Each of the blends were then set aside and observed to determine whether gross phase separation would occur. The observations are summarized in the following table: Blend Phase Separation Comparative Exp. X with styrene-butadiene block copolymer of example 1 complete after 2 days Example 3 with acrolein modified block copolymer of example 1 no separation after 7 days Example 4 and Comparative Experiment Y Blends were prepared with the polymers described in example 1 under "Preparation of styrene-butadiene block copolymer" and Example 2 and Koppers 3702-5 polyester. These resin blends were then used in the preparation of Sheet Moulding Compound pastes. Each of the pastes were prepared according to the following recipe: 100g Block Copolymer in Styrene Monomer (30wt% polymer) 100g Koppers 3702-5 Unsaturated Polyester Resin (70wt% in styrene) 300g Calcium Carbonate 6g Zinc Stearate 0.5g Black pigment 2.6g t-Butyl perbenzoate 0.5g PEP-100 Cure Promoter 7.8g Marinco H Thickening Agent Each paste was blended in an 800ml plastic beaker using a 2.54cm Jiffy Mixer blade at 500rpm. The fully blended pastes were then transferred to 0.46kg jars, sealed and set aside to age. After 18 days, the paste were inspected to access the homogeneity of the blend. The paste samples were evaluated for (1) the lack of exudate formation, (2) the absence of chalkiness and (3) smoothness. Each criteria was rated on a scale from 1 (worst) to 5 (best) so that a superior paste would get a combined score of 15, and the worst possible score would be 3. The results of each of the paste are summarized in the following table: Paste Numerical Rating Comparative Exp. Y with polymer of example 1 3 Example 4 with polymer of example 2 9

Claims: A modified unsaturated polyester which unsaturated polyester is modified by having at least one elastomeric polymer segment chemically bonded thereto via a 6 carbon cyclic member obtained via a Diels Alder reaction. A polyester as claimed in claim 1 wherein said unsaturated polyester comprises unsaturated dicarboxylic acid or unsaturated dicarboxylic anhydride monomer units. A polyester as claimed in claim 1 or 2 wherein said elastomeric polymer segment is a homopolymer of a conjugated diolefin having in the range of from 4 to 12 carbon atoms per molecule. A polyester as claimed in claim 1 or 2 wherein said elastomeric polymer segment is a copolymer of an alkenyl-substituted aromatic hydrocarbon and a conjugated diolefin having in the range of from 4 to 12 carbon atoms per molecule. A polyester as claimed in claim 4 wherein said copolymer is a block copolymer. A thermosetting unsaturated polyester resin composition comprising a modified unsaturated polyester as claimed in any one of the preceding claims and a vinyl monomer. A thermosetting unsaturated polyester resin composition as claimed in claim 6 which also contains an unmodified unsaturated polyester. A thermosetting unsaturated polyester resin composition as claimed in claim 6 or 7 wherein said unmodified unsaturated polyester comprises unsaturated dicarboxylic acid or anhydride monomer units. A curable composition containing a curing agent and a modified unsaturated polyester as claimed in any one of claims 1 to 5. An article containing a composition obtained by curing a curable composition as claimed in claim 9. A process for the preparation of a modified unsaturated polyester as claimed in any one of claims 1 to 5, which process comprises:- a) treating a preformed elastomeric polymer so as to incorporate a conjugated diolefin group; b) reacting said conjugated diolefin group with an ethylenically unsaturated group in an unsaturated polyester so as to chemically combine said elastomeric polymer and said unsaturated polyester through a cyclic hydrocarbon structure comprising 6 carbon atoms; and c) recovering a modified polyester. A process as claimed in claim 11 wherein said elastomeric polymer contains a lithium atom bonded to a terminal carbon atom and said diolefin group is produced by first reacting the lithium alkyl with a 2,3-ethylenically unsaturated aldehyde or ketone and thereafter neutralizing the resulting salt with an acid to produce an alcohol which is then dehydrated. A process as claimed in claims 12 wherein said lithium alkyl is reacted with a 2,3-ethylenically unsaturated aldehyde. A process as claimed in claim 13 wherein said aldehyde is acrolein. A process for grafting an unsaturated polyester onto an elastomeric polymer comprising the steps of: a) treating a preformed elastomeric polymer so as to incorporate a conjugated diolefin group; b) reacting said elastomeric polymer containing said conjugated diolefin with an unsaturated dicarboxylic acid or a vinyl substituted monocarboxylic acid via a 2 + 4 Diels-Alder addition; and c) using the reaction product from step b) as a monomer in a polyester polymerization process. A process as claimed in claim 15 wherein said elastomeric polymer is reacted with an unsaturated dicarboxylic acid and the reaction product then substituted for a portion of unsaturated dicarboxylic acid used in a process to produce a polyester by condensing an unsaturated dicarboxylic acid with a polyhydric alcohol. A process as claimed in claim 15 wherein said elastomeric polymer is reacted with a vinyl-substituted monocarboxylic acid and the reaction product then substituted for a portion of vinyl-substituted monocarboxylic acid monomer in a process wherein a polyester is produced by condensing a vinyl-substituted monocarboxylic acid with a polyepoxide.

Inventors: BROEKHUIS ANTONIUS AUGUSTINUS, BROEKHUIS, ANTONIUS AUGUSTINUS
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1987
Main classification: C08G63
IPC codes: C08F297, C08G81, C08G63, C08F299, C08F8