Fiber-reinforced unsaturated copolyester

Abstract: A fiber-reinforced unsaturated polyester resin composition comprising an unsaturated polyester (A) obtained from, as acid component, 40 to 100 mole % of an unsaturated dicarboxylic acid or anhydride thereof and at most 60 mole % of a saturated dicarboxylic acid or anhydride thereof and, as alcohol component, a polyhydric alcohol having a primary hydroxyl group, and having a hydroxyl value of 115 to 210 mgKOH/g and an acid value of not more than 5 mgKOH/g, a polyisocyanate compound (B) having a terminal group of formula and a viscosity, at 25°C, of 0.01 to 2 Pas (10 to 2,000 cps) and being in the liquid state, a polymerizable vinyl monomer (C) and a fiber (D), said composition satisfying the following conditions (i), (ii) and (iii); (i) the proportion of (A) is 50 to 70% by weight of the total weight of (A) and (C), (ii) the molar ratio of the isocyanate group of (B) to the hydroxyl group of (A) is 0.75 to 1.2, and (iii) the proportion of (D) is 50 to 70% by weight of the total weight of (A), (B), (C) and (D).

Description: This invention relates to a novel fiber-reinforced unsaturated polyester resin composition giving molded articles having excellent impact resistance and improved moldability. Unsaturated polyester resins can be obtained by dissolving an unsaturated polyester formed by a polycondensation reaction between a mixture of an unsaturated dicarboxylic acid or its anhydride with a saturated dicarboxylic acid or its anhydride and a polyhydric alcohol, together with a polymerizable vinyl monomer and a polymerization inhibitor and the resultant unsaturated resins are in the liquid form. Cured products of such unsaturated polyester resins have excellent mechanical strength, chemical resistance and heat resistance. By utilizing these properties, unsaturated polyester resins are now in use as a casting, coating or decorative sheet-forming material. Since, however, unsaturated polyester resins are lacking in stiffness and toughness, they have to be used in combination with a fiber when used as a structural material. That is, it is in the form of a fiber-reinforced unsaturated polyester resin that they are widely and effectively used in various molded articles such as boat, ship, bathtub, water tank, septic tank and chemicals storage tanks. The use of unsaturated polyester resins in combination with a fiber to obtain fiber-reinforced unsaturated polyester resin composition giving molded articles having excellent impact resistance a is well-known method. However, such fiber-reinforced unsaturated polyester resins are not sufficient for use in applications requiring higher impact resistance, for example, member for automobile outer structure, bumper, beam or helmet. As a method of obtaining molded articles having higher impact resistance from fiber-reinforced unsaturated polyester resin compositions, methods of using an unsaturated polyester resin having a comparatively high molecular weight, of using an unsaturated polyester resin having excellent flexibility and tenacity and of using a larger amount of a reinforcing fiber are known. However, a high molecular weight, unsaturated polyester resin has a high viscosity, and causes a problem with fiber impregnation, although it has a liquid-like appearance at room temperature, and therefore it does not have satisfactory molding workability. The appearances, strengths and elastic moduli of the resulting molded articles are not satisfactory, either. The use of conventionally known urethane-modified unsaturated polyester resin having excellent flexibility and tenacity can provide a fiber-reinforced unsaturated polyester resin composition giving molded articles having improved impact resistance. However, such a polyester resin has a defect that it cannot always provide a composition which has satisfactory molding workability. For producing molded articles of excellent impact resistance by preparing a non-sticky sheet-like molding material having excellent flowability upon molding in a heat press, there is a proposal, for example, to prepare a sheet molding compound from a high molecular weight unsaturated polyester resin, a metal oxide or a metal hydroxide, and a fiber. However, the resultant compound does not have sufficient impact resistance. In order to improve the method, there is proposed the use of an unsaturated polyester resin and a polyisocyanate compound in combination with a fiber to obtain a high impact-resistant composition. Thus, US-A-4,327,145 describes an easily shaped sheet molding compound comprising a resin composition composed of an unsaturated polyester having a hydroxyl value of 20 to 55 mgKOH/g and an acid value of 5 to 20 mgKOH/g in which the ratio of the hydroxyl value to the acid value is 1.7/1 to 10/1, a polymerizable vinyl monomer and a polyisocyanate compound, and a glass fiber. Since, however, the molecular weight of the unsaturated polyester is comparatively high, the unsaturated polyester resin in the liquid form, dissolved in the vinyl monomer, has a high viscosity and therefore impregnates the fiber insufficiently. Further, residual isocyanate groups in the sheet molding compound and carboxyl groups of the unsaturated polyester react at the time of heat press molding, and produce carbon dioxide gas. For this reason and some others, drawbacks such as whitening and blisters are likely to occur in molded articles. Whitening is one of the causes of variability in the mechanical strength of molded articles. EP-A-0072024 and EP-A-0016248 disclose fiber-reinforced unsaturated polyester resin compositions comprising (A) an unsaturated polyester, (B) polyisocyanate, (C) a polymerizable vinyl monomer and (D) a fiber. However, these resin compositions do not have satisfactory impact strength. US-A-4,067,845 describes a process for producing a press-molding sheet molding compound which comprises an unsaturated polyester having an acid value of not less than 14 mgKOH/g, a molar ratio of hydroxyl group to carboxyl group in the range of 0.8 to 5.7 and a molecular weight of 800 to 5,000, a polyisocyanate compound, a metal oxide or a metal hydroxide, a polymerizable vinyl monomer and a fiber and which thickens by maturing. In order to obtain a press-molding sheet molding compound, the above process utilizes, for the thickening, a reaction between the hydroxyl group of the polyisocyanate compound and the isocyanate group of the polyisocyanate, a decarbonation-involved reaction between the carboxyl group of the unsaturated polyester and the isocyanate group of the polyisocyanate compound and a reaction between said carboxyl group and the metal oxide or metal hydroxide, thus being likely to cause whitening and blisters in the molded articles due to carbonic acid gas. This invention provides a fiber-reinforced unsaturated polyester resin composition comprising an unsaturated polyester (A) having a hydroxyl value of 115 to 210 mgKOH/g and an acid value of not more than 5 mgKOH/g obtained from, as acid component, 40 to 100 mole % of an unsaturated dicarboxylic acid or anhydride thereof and at most 60 mole % of a saturated dicarboxylic acid or anhydride thereof and, as alcohol component, a polyhydric alcohol the hydroxyl groups of which are primary hydroxyl groups or a mixture of said polyhydric alcohol with not more than 5 mole % of a polyhydric alcohol having a secondary hydroxy group, a polyisocyanate compound (B) a terminal group of which is of formula and having a viscosity, at 25°C, of 0.01 to 2 Pas (10 to 2,000 cps) and being in the liquid state, a polymerizable vinyl monomer (C), a fiber (D) and a polyhydric alcohol (E) having at least 2 hydroxyl groups in the molecule and having a hydroxyl value of 35 to 1,100, mgKOH/g, said composition satisfying the following conditions, (i), (ii), (iii) and (iv); (i) the proportion of (E) is not more than 50% by weight of the total weight of (A) and (E), (ii) the total weight of (A) and (E) is 50 to 85% by weight of the total of (A), (E) and (C), (iii) the molar ratio of the isocyanate group of (B) to the hydroxyl group of (A) and (E) is 0.75 to 1.2, and (iv) the proportion of (D) is 50 to 70% by weight of the total weight of (A), (B), (C), (D) and (E). The unsaturated polyester (A) used in the composition of this invention is a polycondensate obtained by a polycondensation reaction known per se between a mixture, as an acid component, of 40 to 100 mole % of an unsaturated dicarboxylic acid or anhydride thereof with not more than 60 mole % of a saturated dicarboxylic acid or anhydride thereof and, as an alcohol component, a polyhydric alcohol the hydroxyl groups of which are primary hydroxyl groups or a mixture of said polyhydric alcohol with not more than 5 mole % of a polyhydric alcohol having a secondary hydroxyl group. The unsaturated polyester (A) used in this invention has an acid value of not more than 5 mgKOH/g and a hydroxyl value in the range of 115 to 210 mgKOH/g. The molecular weight thereof according the end-group method is, preferably, 500 to 1,000. A fiber-reinforced unsaturated polyester composition prepared by using an unsaturated polyester having an acid value of more than 5 mgKOH/g causes whitening and blisters upon hot press molding and gives rise to a decrease in impact resistance. When the hydroxyl value is less than 115 mgKOH/g, the molecular weight of an unsaturated polyester becomes more than 1,000 (according to the end-group method) and the unsaturated polyester impregnates fibers less well. When the hydroxyl value is more than 210 mgKOH/g, the molecular weight of an unsaturated polyester becomes less than 500 (according to the end-group method), and the impact resistance is insufficient although the unsaturated polyester readily impregnates fibers. Examples of suitable unsaturated dicarboxylic acids or anhydrides thereof include maleic acid, maleic anhydride and fumaric acid, and examples of the saturated dicarboxylic acid or anhydride thereof include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, HET acid (chlorendic acid) and tetrahydrophthalic anhydride. Examples of the polyhydric alcohol the hydroxyl groups of which are primary hydroxyl groups include ethylene glycol, diethylene glycol, 1,4-butanediol and neopentyl glycol. Examples of the optional polyhydric alcohol having a secondary hydroxyl group include propylene glycol, dipropylene glycol and an adduct of bisphenol-A with propylene oxide. The use of an unsaturated polyester prepared using more than 5 mole % of a polyhydric alcohol having a secondary hydroxyl group gives molded articles only low impact resistance. Examples of the polymerizable vinyl monomer (C) include styrene, chlorostyrene, vinyl toluene, (meth)acrylic acid and derivatives thereof. With regard to proportions of the unsaturated polyester and the polymerizable vinyl monomer, when an unsaturated polyester resin composition is prepared in accordance with the method of this invention, the unsaturated polyester can be used in an amount of 50 to 70% by weight, and the polymerizable vinyl monomer can be used in an amount of 30 to 50 % by weight. The polyisocyanate compound (B) usable in the composition of this invention has a terminal group of formula and a viscosity, at 25°C, of 0.01 to 2 Pas (10 to 2,000 cps), preferably 0.03 to 1.5 Pas (30 to 1,500 cps), and is in the liquid state. Examples of said polyisocyanate compound (B) include carbodiimide-modified 4,4'-diphenylmethanediisocyanate (e.g. a commercially available compound called "Isonate 143L"), polyether-type prepolymer of 4,4'-diphenylmethanediisocyanate (e.g. a commercially available compound called "Isonate 181"), and a polyester-type prepolymer of 4,4'-diphenylmethanediisocyanate (e.g. a commercially available compound called "Isonate 240"). Examples of the fiber (D) are, preferably, a glass fiber, carbon fiber and aramid fiber, in view of strength, affinity with resin and price and a glass fiber is particularly preferable. Examples of the polyhydric alcohol (E) include diethylene glycol, triethylene glycol, dipropylene glycol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol and polypropylene glycol having a molecular weight of 200 to 3,000 and polytetramethylene glycol having a molecular weight of 200 to 3,000. In general, glycol having a primary hydroxyl group is preferable, and particularly, polyethylene glycol and polytetramethylene glycol are preferable. The unsaturated polyester resin composition may also contain customarily used polymerization inhibitors such as hydroquinone, parabenzoquinone and methyl hydroquinone, customarily used curing catalysts such as benzoylperoxide, methylethylketoneperoxide, cumene hydroperoxide and t-butylperbenzoate, customarily used curing promoters such as dimethyl aniline and cobalt naphthenate, and customarily used urethane-forming catalysts such as cobalt octoate and dibutyltindilaurate. The unsaturated polyester resin composition of this invention can be used for press molding or reaction injection molding, which are customarily used in the field of unsaturated polyester resin compositions. The resin composition of this invention can be used, for example, in the following modes. One mode comprises uniformly mixing an unsaturated polyester resin in the liquid form at ambient temperature, which is obtained by mutually dissolving the unsaturated polyester (A), the polyhydric alcohol (E), the polymerizable vinyl monomer (C) and the polymerization inhibitor, with the polyisocyanate compound (B) in the liquid form at ambient temperature and a thermally decomposing-type radical polymerization initiator, and then using the mixture to impregnate the fiber (D) to preeffect an urethane-forming reaction for the thickening (so-called B-stage formation), thereby to prepare a non-sticky sheet-like or mass-like molding material which flows during hot press molding. The resulting sheet-like or mass-like molding material can be processed into molded articles having excellent impact resistance by heat press molding to effect a radical polymerization reaction. Another mode comprises filling the fiber (D) into a mold of desired shaped, and pouring an unsaturated polyester resin in the liquid form at ordinary temperature obtained from (A) and (C) as above, the polyhydric alcohol (E), and the polyisocyanate compound (B) in the liquid form at ambient temperature (to which a radical polymerization initiator has been added) into the mold kept at a predetermined temperature while these components are uniformly mixed, thereby to effect an urethane-forming reaction and a radical polymerization reaction simultaneously. This mode thus makes it possible to produce molded articles having excellent impact resistance. In this invention, it is made possible to obtain a fiber-reinforced unsaturated polyester resin composition having improved molding processability and giving molded articles having excellent impact resistance, strength and elastic modulus, by formulating the specified components (A), (B), (C), (D) and (E) in the specified proportions. It is possible to obtain a composition suitable, for example, for use in the preparation of automobile outer structures, bumper beams or helmets requiring higher impact resistance. Examples This invention will be explained according to Examples hereinbelow. In the Examples, the hydroxyl values [mgKOH/g] of unsaturated polyesters were measured by the acetylation method, and the acid values [mgKOH/g] and viscosities [Pas or cps] thereof were measured according to JIS K6901. The flexural strengths and flexural moduli of molded articles made of fiber-reinforced unsaturated polyester resin compositions were measured in accordance with JIS K6919 and the Izod impact strengths thereof (with a notch, in the edge direction) were measured in accordance with JIS K6911. The falling weight (dart) impact test was carried out by using a falling weight impact tester with a computer data analyzer, made by CEAST of Italy. In the test, a test piece having a size of 10 cm x 10 cm and a thickness of 3 mm was fixed with a force of 0.59 MPa (6 kg/cm²), onto a bearer having a 50 mm diameter-hole, and then a striker having a roundness formed, with its diameter of 20 mm, on the falling end was fallen at a speed of 10.0 m/second to punch through the test piece. An impact wave generated was detected by a distortion gauge equipped inside the striker, and the detected information was transmitted to a microcomputer to calculate a maximum impact load (Fmax) [kg], a break initiation energy (Ei) [0.0981J or kg.cm] and a break propogation energy (Ep) [0.0981 J or kg.cm]. The test was carried out three times to determine an average value. Fmax and Ei are important factors for evaluation of impact resistance property. Larger values of Fmax and Ei show excellence in impact resistance property. Ep shows a behaviour after broken, and larger values of Ep show that the complete breakage of a material is less likely. (Synthesis of unsaturated polyester resin) Synthesis Example (I), Synthesis of "A-I" 13480 g of isophthalic acid, 16570 g of neopentyl glycol, 9880g of ethylene glycol and 18840 of fumaric acid were charged into a reactor equipped with a stirrer, a thermometer, a nitrogen gas-introducing tube and partial condenser with a thermometer in its column portion, and the mixture was heated up to 205°C with a nitrogen gas being introduced, to carry out a polycondensation reaction according to customary manner. Steam at 100°C was flowed in the partial condenser to reflux the glycols and distil condensed water out of the reaction system. When the acid value of the reaction mixture reached 4.4, the heating was stopped, and the mixture was cooled to 120°C. Then, maleic anhydride was charged. The temperature of the mixture was again elevated to carry out a polycondensation reaction with a care that the reaction temperature did not exceed 225°C and to obtain an unsaturated polyester having an acid value of 2.6 and a hydroxyl value of 151.9. And then the system was cooled to 170°C, and 1.15g of hydroquinone and 0.25 g of p-benzoquinone were added and mixed sufficiently. A part of the resultant unsaturated polyester was dissolved in styrene to obtain a 34.5% styrene-containing unsaturated polyester resin ("A-I"). The viscosity of "A-I" measured at 25°C, was 0.263 Pas (263 cps). Comparative Synthesis Example, Synthesis of "A" Using the same reactor as that used in Synthesis Example (I), 1,846 g of isophthalic acid, 1,635 g of maleic anhydride and 2,220 g of propylene glycol were reacted in the same way as in Synthesis Example (I) to synthesize an unsaturated polyester having an acid value of 25.3, and then the synthesized polyester was dissolved in styrene to obtain an unsaturated polyester resin ("A") having a styrene content of 40.0% and a viscosity, at 25°C, of 1.280 Pas (1,280 cps). Example 1 1,727 g of the unsaturated polyester resin "A-I" obtained in Synthesis Example (I), 740 g of polyethylene glycol having a hydroxyl value of 369 mgKOH/g and 25 g of t-butyl perbenzoate were uniformly mixed, and then a polyisocyanate compound (Isonate 143L) was added and promptly mixed therewith uniformly. Then, the mixture was continuously supplied onto a polypropylene sheet using sheet-shaped material ("SMC" hereafter) manufacturing machine to prepare a roll-shaped SMC having a glass content of 65% by weight, a width of 45 cm and a thickness of 2 mm. The resultant SMC was wrapped with a cellophane film in order to prevent emanation of styrene, and aged in a chamber at a constant temperature of 23°C for 3 days. After the aging, the polypropylene sheet was peeled off to give a non-sticky, flexible SMC having a good ability to impregnate glass fiber. Thereafter, the SMC was cut to a size of 27 cm x 27 cm (500 g), set on a 30 cm x 30 cm plane plate mold mounted on a 100 ton press molding machine, and maintained at a molding temperature of 140°C and a molding pressure of 9.8 MPa (100 kg/cm²) for 5 minutes to obtain a shaped article having a size of 30 cm x 30 cm and a thickness of 3 mm. The appearance of the resultant shaped article was uniform and the flowability of the SMC was good although its glass content was high. The resultant molded article as cut to a size of 10 cm x 10 cm, and then evaluated by carrying out the falling weight impact test. As Table 1 shows, it is clear that the addition of polyethylene glycol improves the impact resistance further. Example 2 Example 1 was repeated except for the use of 1,910 g of the unsaturated polyester resin "A-I" obtained in Synthesis Example (I), 818 g of polytetramethylene glycol having a hydroxyl value of 173 mgKOH/g, 27 g of t-butyl perbenzoate and 772 g of an isocyanate compound (Isonate 143L), and the impact resistance was evaluated in the same way as in Example 1. The results of the evaluation are shown also in Table 1. Comparative Example 1 Example 1 was repeated except for the use of 2,842 g of the unsaturated polyester resin "A-I" obtained in Synthesis Example (I), 28 g of t-butyl perbenzoate and 658 g of an isocyanate compound (Isonate 143L), and the impact resistance was evaluated in the same way as in Example 1. The results of the evaluation are shown also in Table 1. Comparative Example 2 Example 1 was repeated except for the use of 3,500 g of the unsaturated polyester resin "A" obtained in the Comparative Synthesis Example, 105 g of zinc stearate, 70 g of magnesium oxide, 35 g of t-butyl perbenzoate and the content of glass fiber is 60 weight %, and the impact resistance was evaluated in the same way as in Example 1. The results of the evaluation are shown also in Table 1.

Claims: A fibre-reinforced unsaturated polyester resin composition comprising an unsaturated polyester (A) having a hydroxyl value of 115 to 210 mgKOH/g and an acid value of not more than 5 mgKOH/g obtained from, as acid component, 40 to 100 mole % of an unsaturated dicarboxylic acid or anhydride thereof and at most 60 mole % of a saturated dicarboxylic acid or anhydride thereof and, as alcohol component, a polyhydric alcohol the hydroxyl groups of which are primary hydroxyl groups or a mixture of said polyhydric alcohol with not more than 5 mole % of a polyhydric alcohol having a secondary hydroxy group, a polyisocyanate compound (B) a terminal group of which is of formula and having a viscosity, at 25°C, of 0.01 to 2 Pas (10 to 2,000 cps) and being in the liquid state, a polymerizable vinyl monomer (C), a fiber (D) and a polyhydric alcohol (E) having at least 2 hydroxyl groups in the molecule and having a hydroxyl value of 35 to 1,100 mgKOH/g, said composition satisfying the following conditions (i), (ii), (iii) and (iv); (i) the proportion of (E) is not more than 50 % by weight of the total weight of (A) and (E), (ii) the total weight of (A) and (E) is 50 to 85% by weight of the total of (A), (E) and (C), (iii) the molar ratio of the isocyanate group of (B) to the hydroxyl group of (A) and (E) is 0.75 to 1.2, and (iv) the proportion of (D) is 50 to 70% by weight of the total weight of (A), (B), (C), (D) and (E). A composition according to claim 1 wherein the unsaturated dicarboxylic acid or anhydride is at least one of maleic acid, maleic anhydride and fumaric acid. A composition according to claim 1 or 2 wherein the polyhydric alcohol the hydroxyl groups of which are primary hydroxyl groups is at least one of ethylene glycol, diethylene glycol, 1,4-butanediol and neopentyl glycol. A composition according to claim 1, 2 or 3 wherein the polyisocyanate compound (B) has a viscosity, at 25°C, of 0.03 to 1.5 Pas (30 to 1,500 cps). A composition according to any one of the preceding claims wherein the polyisocyanate compound (B) is at least one of carbodiimide-modified 4,4'-diphenylmethane-diisocyanate, polyether-type prepolymer of 4,4'-diphenyl-methanediisocyanate and polyester-type prepolymer of 4,4'-diphenyl-methanediisocaynate. A composition according to any one of the preceding claims wherein the polymerizable vinyl monomer (C) is at least one of styrene, chlorostyrene, vinyltoluene and (meth)acrylic acid and derivatives thereof. A composition according to any one of the preceding claims wherein the fibre (D) is at least one of glass fibre, carbon fibre, and aramid fibre. A composition according to any one of the preceding claims wherein the polyhydric alcohol (E) is a glycol the hydroxy groups of which are primary hydroxy groups A composition according to any one of the preceding claims where the polyhydric alcohol (E) is at least one of polyethylene glycol and polytetramethylene glycol. A composition according to any one of the preceding claims wherein the total weight of (A) and (E) is 60 to 80% by weight of the total weight of (A), (E) and (C). A composition according to any one of the preceding claims wherein the molar ratio of the isocyanate group of (B) to the hydroxyl groups of (A) and (E) is 0.85 to 1.0.

Inventors: ABE TOSHIAKI, ISHIKAWA MASATO, NAMIKAWA AKIRA, OKUMURA HIROYUKI, TANISAKA HIROKA, ABE, TOSHIAKI, ISHIKAWA, MASATO, NAMIKAWA, AKIRA, OKUMURA, HIROYUKI, TANISAKA, HIROKA
Applicants: MITSUBISHI GAS CHEMICAL CO, MITSUBISHI GAS CHEMICAL COMPANY, INC.
Application year: 1988
Main classification: C08G18
IPC codes: C08G18, C08K7