Resin composition, molding material, method for producing the molding material, thermosetting matrix resin raw material, and use of unsaturated polyester in resin composition

Abstract

To provide a novel resin composition containing an unsaturated polyester suitable for use with a reactive diluent containing a (meth)acrylate.SOLUTION: A resin composition according to one embodiment of the present invention comprises an unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct, and a (meth)acrylate as a reactive diluent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates primarily to resin compositions, methods for making the resin compositions, molding materials, methods for making the molding materials, thermosetting matrix resin feedstocks, and the use of unsaturated polyesters in resin compositions. [Background technology]

[0002] FRP (fiber reinforced plastic) is a composite material in which fiber reinforcing materials are impregnated with a polymer matrix, and is widely used in parts for aircraft, automobiles, ships, and other types of transportation equipment, as well as sporting and leisure goods. One of the manufacturing methods for FRP products is to use molding materials such as sheet molding compound (SMC) and bulk molding compound (BMC), which are made of discontinuous fibers and a thermosetting matrix resin.

[0003] It has been pointed out that SMC and BMC, which contain styrene in the thermosetting matrix resin, have a strong odor, which can cause problems in the working environment where molding is carried out (Patent Documents 1 and 2). In an SMC having a thermosetting matrix resin containing a vinyl ester, an unsaturated polyester, a thickener, a polymerization initiator, a polymerization inhibitor, and an ethylenically unsaturated monomer, it has been proposed to use an ethylenically unsaturated monomer whose homopolymer has a glass transition temperature of 55°C or higher in order to improve the heat resistance of an FRP product obtained by curing the SMC (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. WO2018 / 070076 [Patent Document 2] International Publication No. WO2020 / 213414 [Patent Document 3] International Publication No. WO2019 / 017254 Summary of the Invention [Problem to be solved by the invention]

[0005] Regarding the thermosetting matrix resin of a molding material using a (meth)acrylate as a reactive diluent, there has not yet been sufficient research focusing on the unsaturated polyester to be blended with the matrix resin. The present invention was made in the course of investigations conducted by the present inventors in light of the current situation, and a main object of the present invention is to provide a novel resin composition containing an unsaturated polyester suitable for use together with a reactive diluent containing a (meth)acrylate. In this specification, problems to be solved by each embodiment of the present invention may be explicitly or implicitly disclosed. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a resin composition containing an unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct, and a (meth)acrylate as a reactive diluent. Effect of the Invention

[0007] In accordance with one preferred embodiment of the present invention, there is provided a novel resin composition comprising an unsaturated polyester suitable for use with a reactive diluent comprising a (meth)acrylate. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an SMC manufacturing apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In this specification, unless otherwise specified, "A to B" expressing a numerical range means "A or more, and B or less." In this specification, unless otherwise specified, "viscosity" refers to a value measured using a B-type viscometer in accordance with JIS Z8803:2011. The techniques according to the embodiments of the present invention can be advantageously used for the production of thermosetting molding materials containing fibre reinforcement made of discontinuous fibres, such as SMC and BMC. Hereinafter, the embodiment of the present invention will be described in detail with reference to an example of manufacturing an SMC.

[0010] 1. Manufacturing method of SMC A typical manufacturing method for SMC is described below with reference to FIG. A continuous fiber bundle 10 is drawn from the fiber package P and sent to a chopper 1. The continuous fiber bundle 10 is, for example, a carbon fiber tow consisting of 1,000 to 100,000 filaments per bundle, and may be partially split. Instead of the carbon fiber tow, a glass fiber bundle or an aromatic polyamide fiber bundle may also be used. The chopped fiber bundle 20 is formed by cutting the continuous fiber bundle 10 with the chopper 1. The fiber length of the discontinuous fibers constituting the chopped fiber bundle 20 is, for example, within a range of 5 mm to 100 mm, preferably 10 to 60 mm, and more preferably 10 to 30 mm.

[0011] Chopper 1 is disposed above the running path of first carrier film 51. Resin paste 41 is applied to the surface of first carrier film 51 by a first coater 2a equipped with a doctor blade. The viscosity of resin paste 41 at 25°C is, for example, 0.05 to 10 Pa·s, preferably 0.1 to 5 Pa·s, more preferably 0.1 to 2 Pa·s, and even more preferably 0.1 to 1 Pa·s, and may be 0.2 Pa·s or more. The chopped fiber bundles 20 fall onto the surface, on which the resin paste 41 is applied, of the traveling first carrier film 51. The fallen chopped fiber bundles 20 are piled up on the first carrier film 51 to form a random mat 30.

[0012] A second coater 2b equipped with a doctor blade applies another resin paste 42 to the surface of the second carrier film 52. The resin paste 41 and the resin paste 42 have the same composition, and both contain a thickener. A first carrier film 51 and a second carrier film 52 are bonded together with the random mat 30 sandwiched between them so that the surfaces coated with the resin pastes 41 and 42 face each other, thereby forming a laminate 60.

[0013] By pressing the laminate 60 with the impregnating machine 3, the random mat 30 is impregnated with the resin pastes 41 and 42 to become an impregnated random mat. The laminate 60 is wound onto a bobbin. Instead of being wound onto a bobbin, the laminate 60 may be folded and placed into a container. The impregnated random mat is aged to complete the SMC. During the aging period, the resin pastes 41 and 42 contained in the impregnated random mat thicken due to the action of the thickener contained therein. The thickened resin pastes 41 and 42 are the matrix resin of the SMC. The viscosity of the thickened resin pastes 41 and 42 contained in the SMC is usually within a range of 1000 Pa·s or more and less than 100,000 Pa·s at 25°C.

[0014] 2.Resin composition One aspect of the present invention relates to a resin composition. A resin composition according to one embodiment contains a specific unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct, and a (meth)acrylate as a reactive diluent.

[0015] In the following description, the resin composition used as the resin pastes 41 and 42 in the above-mentioned SMC production method will be referred to as a second resin composition for convenience. The second resin composition is prepared by adding a thickener to the first resin composition, which contains the specific unsaturated polyester, a (meth)acrylate as a reactive diluent, a radical polymerization initiator, and preferably further contains an epoxy vinyl ester. In the above-mentioned SMC production method, the second resin composition is used as the resin paste 41, 42 immediately after the thickener is added to the first resin composition to obtain the second resin composition.

[0016] Although epoxy vinyl ester is not an essential component in the first resin composition, its incorporation is recommended since it has the effect of improving the heat resistance and mechanical properties of the cured product of the second resin composition (which is the polymer matrix of the FRP obtained by curing the SMC). Although the type of epoxy vinyl ester is not particularly limited, a typical example is a bisphenol A type epoxy vinyl ester, which is produced by esterifying a bisphenol A type epoxy resin (an epoxy resin mainly composed of bisphenol A diglycidyl ether) with an unsaturated monocarboxylic acid. The unsaturated monocarboxylic acid is typically acrylic acid or methacrylic acid.

[0017] Polyester is a polymer having a structure formed by polycondensation of dicarboxylic acid R1(COOH)2 and diol R2(OH)2, and has units derived from dicarboxylic acid: -CO-R1-CO-, and units derived from diol: -O-R2-O-. The specific unsaturated polyester at least partially contains, as a unit derived from a dicarboxylic acid, a unit derived from fumaric acid or maleic acid: -CO-CH=CH-CO-. It should be noted that in addition to fumaric acid and maleic acid, maleic anhydride can also be used as a raw material in the synthesis of unsaturated polyesters containing units derived from fumaric or maleic acid. As is well known to those skilled in the art, in the synthesis of unsaturated polyesters using maleic acid or maleic anhydride as a raw material, a cis-to-trans transformation called fumarate formation can occur. Therefore, even if an unsaturated polyester has a trans -CO-CH=CH-CO- group, the dicarboxylic acid raw material used in the synthesis does not necessarily contain fumaric acid.

[0018] The specific unsaturated polyester may contain units derived from unsaturated dicarboxylic acids other than units derived from fumaric acid or maleic acid, and may also contain units derived from saturated acids such as phthalic anhydride, isophthalic acid, and terephthalic acid, as units derived from unsaturated dicarboxylic acids. From the viewpoint of improving the heat resistance of the cured product of the second resin composition, in the above-mentioned specific unsaturated polyester, the amount of units derived from fumaric acid or maleic acid, based on the total amount of units derived from dicarboxylic acid, is preferably 50% or more, more preferably 75% or more, even more preferably 90% or more, and most preferably 100%, in terms of the number of moles.

[0019] At least a part of the units derived from a diol contained in the specific unsaturated polyester is a unit derived from a bisphenol A-propylene oxide adduct. Bisphenol A-propylene oxide adduct is a type of bisphenol A-alkylene oxide adduct.

[0020] The following formula (I) is a general formula representing the structure of a bisphenol A-alkylene oxide adduct. [ka] In formula (I), R is an ethylene group or an alkyl-substituted ethylene group. When R is a methylethylene group, formula (I) represents a bisphenol A-propylene oxide adduct. When R is an ethylene group, formula (I) represents a bisphenol A-ethylene oxide adduct. x and y are each independently 0 or a positive number, and x+y is a positive number indicating the average number of moles of alkylene oxide added. The average number of moles of alkylene oxide added is the average number of alkylene oxide units RO contained in the bisphenol A-alkylene oxide adduct per molecule.

[0021] In the above specific unsaturated polyester, the average number of propylene oxide units contained in the units derived from the bisphenol A-propylene oxide adduct is preferably 1 to 4, more preferably 2 to 3. The average number reflects the average number of moles of propylene oxide added in the bisphenol A-propylene oxide adduct used as a synthetic raw material for the unsaturated polyester.

[0022] By introducing units derived from a bisphenol A-propylene oxide adduct as units derived from a diol, the specific unsaturated polyester exhibits favorable solubility in (meth)acrylates. In the above specific unsaturated polyester, the amount of units derived from bisphenol A-propylene oxide adduct relative to the total amount of units derived from diol is preferably 20% or more in terms of moles, and may be 50% or more, 75% or more, 95% or more, or may be 100%. In particular, in order to increase the solubility in isobornyl (meth)acrylate, it is preferred to increase the ratio of units derived from bisphenol A-propylene oxide adduct to the units derived from diol.

[0023] Examples of units derived from diols that the specific unsaturated polyester may contain in addition to the units derived from bisphenol A-propylene oxide adducts include units derived from bisphenol A-ethylene oxide adducts, propylene glycol, ethylene glycol, dipropylene glycol, diethylene glycol, neopentyl glycol, polypropylene glycol, or polyethylene glycol. These may be contained alone or in combination. In one example, only a portion of the diol-derived units may be replaced with units derived from a low molecular weight polyol having three or more hydroxyl groups per molecule, such as trimethylolpropane.

[0024] When polyisocyanate is used as a thickener to be added to the first resin composition to obtain the second resin composition, the hydroxyl value of the specific unsaturated polyester is preferably 1 mgKOH / g or more, more preferably 5 mgKOH / g or more, even more preferably 10 mgKOH / g or more, and particularly preferably 15 mgKOH / g or more, from the viewpoint of imparting suitable thickening properties to the second resin composition. The hydroxyl value is not limited, but may be, for example, 150 mgKOH / g or less, or 100 mgKOH / g or less. The hydroxyl value can be controlled, for example, by adjusting the molar ratio of the dicarboxylic acid raw material and the diol raw material used in the synthesis of the unsaturated polyester, or the molecular weight of the synthesized unsaturated polyester.

[0025] From the viewpoint of improving the heat resistance and / or mechanical properties of the cured product of the second resin composition, the weight average molecular weight of the specific unsaturated polyester is preferably 2000 or more, more preferably 4000 or more, and may even be 6000 or more. From the viewpoint of making it easy to dissolve in (meth)acrylate and / or reducing the viscosity of the first resin composition, the weight average molecular weight of the specific unsaturated polyester is preferably 50000 or less, more preferably 25000 or less. The weight average molecular weight here is a polystyrene-equivalent value, and is measured by GPC (gel permeation chromatography).

[0026] From the viewpoint of imparting suitable thickening properties to the second resin composition and / or improving the heat resistance and / or mechanical strength of the cured product of the second resin composition, the amount of the specific unsaturated polyester in the first resin composition is preferably 2% or more, more preferably 4% or more, and may even be 6% or more, based on the mass of the first resin composition. From the viewpoint of shortening the time required for producing the first resin composition and / or reducing the viscosity of the first resin composition, the amount of the specific unsaturated polyester in the first resin composition is preferably 60% or less, more preferably 30% or less, and even more preferably 10% or less, based on the mass of the first resin composition.

[0027] The (meth)acrylate is contained in the first resin composition as a reactive diluent. The reactive diluent has a function of lowering the viscosity of the first resin composition. Therefore, the (meth)acrylate contained in the first resin composition as a reactive diluent has a viscosity lower than that of the specific unsaturated polyester. More specifically, the viscosity of the (meth)acrylate contained in the first resin composition as a reactive diluent is preferably 500 mPa·s or less at 25°C, more preferably 100 mPa· or less, even more preferably 50 mPa· or less, and most preferably 10 mPa·s or less. The (meth)acrylate may be a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate. A plurality of (meth)acrylates having the above-mentioned preferred viscosity may be used in combination.

[0028] Examples of (meth)acrylates contained in the first resin composition as a reactive diluent include, but are not limited to, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, 1,3-butanediol dimethacrylate, ethylene glycol dimethacrylate, 1,6-hexamethyl ...1,3-butanediol dimethacrylate, 1,6-hexamethylmethacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexamethylmethacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, 1,6-hexamethylmethacrylate, 1,3-butanediol dimethacrylate, 1,3-butanediol dimeth Examples of suitable acrylates include hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, methyl acrylate, ethyl methacrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, phenoxyethyl acrylate, cyclohexyl acrylate, isobornyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and trimethylolpropane triacrylate. The (meth)acrylate contained in the first resin composition as a reactive diluent may be one type or two or more types.

[0029] One suitable example of the (meth)acrylate contained in the first resin composition as a reactive diluent is isobornyl (meth)acrylate. When isobornyl (meth)acrylate is used as a reactive diluent, the cured product of the second resin composition exhibits good heat resistance. The use of a bifunctional (meth)acrylate such as ethylene glycol di(meth)acrylate as a reactive diluent is also advantageous in improving the heat resistance of the cured product of the second resin composition. Compared to isobornyl (meth)acrylate, bifunctional (meth)acrylates also have the advantage that the specific unsaturated polyester is more easily dissolved in them.

[0030] In a preferred embodiment, isobornyl (meth)acrylate and bifunctional (meth)acrylate can be used in combination. In this case, from the viewpoint of making the specific unsaturated polyester easily soluble, the ratio of the bifunctional (meth)acrylate to the total of isobornyl (meth)acrylate and bifunctional (meth)acrylate is preferably 0.05 or more by mass, more preferably 0.1 or more, and even more preferably 0.2 or more. From the viewpoint of improving the heat resistance and / or mechanical properties of the cured product of the second resin composition, the ratio of the bifunctional (meth)acrylate to the total of isobornyl (meth)acrylate and bifunctional (meth)acrylate is preferably 0.6 or less by mass, more preferably 0.3 or less.

[0031] The amount of (meth)acrylate contained in the first resin composition as a reactive diluent is determined so that the second resin composition obtained by adding a thickener to the first resin composition has a viscosity suitable for use as resin pastes 41, 42. When the thickener is liquid, the amount of (meth)acrylate contained in the first resin composition as a reactive diluent may be determined so that the viscosity ratio between the thickener and the resin composition at the temperature (e.g., 15 to 28°C) when the thickener is added to the first resin composition is preferably 1000 or less, more preferably 100 or less. This is because different liquids tend to mix with each other more easily as the viscosity ratio between them becomes smaller. From the viewpoint of improving the toughness of the cured product of the second resin composition, the amount of (meth)acrylate contained in the first resin composition as a reactive diluent is preferably 80% or less, more preferably 60% or less, and even more preferably 50% or less, of the mass of the first resin composition.

[0032] When the first resin composition contains an epoxy vinyl ester, from the viewpoint of improving the mechanical properties of the cured product of the second resin composition, the amount of the epoxy vinyl ester is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more of the mass of the first resin composition. From the viewpoint of imparting an appropriate thickening property to the second resin composition, the amount of the epoxy vinyl ester is preferably 70% or less, more preferably 50% or less of the mass of the first resin composition.

[0033] The radical polymerization initiator contained in the first resin composition may be an organic peroxide that is commonly used as a curing agent in a thermosetting resin composition for SMC using an unsaturated polyester. Suitable examples of such organic peroxides include, but are not limited to, ketone peroxides, hydroperoxides, diacyl peroxides, dialkyl peroxides, peroxyketals, alkyl peresters, and percarbonates.

[0034] The radical polymerization initiator preferably has a 10-hour half-life temperature in the range of 70 to 120° C., more preferably in the range of 80 to 110° C., and further preferably in the range of 90 to 100° C. The 10-hour half-life temperature is a temperature at which the half-life of a polymerization initiator dissolved in benzene when thermally decomposed at a constant temperature is 10 hours, and a benzene solution containing the polymerization initiator at a concentration of 0.2 mol / L is used. For examples of organic peroxides having a 10-hour half-life temperature within the above preferred range, reference can be made to the above-mentioned Patent Document 3.

[0035] The first resin composition may contain only one type of radical polymerization initiator, or may contain multiple types of radical polymerization initiators. The amount of the radical polymerization initiator contained in the first resin composition is preferably within the following range, from the viewpoint of imparting appropriate curing properties to the molding material using the second resin composition: That is, when the total amount of the radically polymerizable group-containing components in the first resin composition, which contains the specific unsaturated polyester, the (meth)acrylate as a reactive diluent, and the epoxy vinyl ester optionally contained therein, is taken as 100 parts by mass, the amount of the radical polymerization initiator is preferably 0.2 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.8 to 2 parts by mass. Reducing the amount of the radical polymerization initiator as much as possible within the above range is advantageous in terms of reducing VOCs contained in an FRP product produced from a molding material using the second resin composition.

[0036] The first resin composition may contain optional components in addition to the unsaturated polyester, the (meth)acrylate as a reactive diluent, and the radical polymerization initiator. Examples of the optional components include a radical polymerization inhibitor, an antioxidant, a light stabilizer, an internal mold release agent, a low-shrinkage agent, a drying agent, a colorant, a low-shrinkage agent, a dispersant, a filler, and a flame retardant. The radical polymerization inhibitor is well known, and suitable examples thereof include catechol, hydroquinone, benzoquinone, and nitroso compounds.

[0037] In a most desirable example, the first resin composition does not contain any reactive diluent other than (meth)acrylate, such as styrene or diallyl phthalate. When the first resin composition contains a reactive diluent other than (meth)acrylate, the amount of the reactive diluent is preferably 20% or less, more preferably 10% or less, and even more preferably 2% or less, of the total mass of the reactive diluent contained in the first resin composition.

[0038] The first resin composition can be prepared by mixing all of the components to be blended together, for example, using a dynamic mixer. The first resin composition is not suitable for long-term storage because it contains both a radical polymerizable group-containing component and a radical polymerization initiator. Therefore, from the viewpoint of increasing production efficiency, it is desirable to prepare a large amount of a semi-finished composition that contains all of the radical polymerizable group-containing components to be blended into the first resin composition and does not contain a radical polymerization initiator, and prepare the first resin composition using the unfinished composition in only the required amount when needed. The other components except for the radical polymerizable group-containing component and the radical polymerization initiator may be contained in the semi-finished composition, or may be added to the semi-finished composition together with the radical polymerization initiator when preparing the first resin composition using the semi-finished composition.

[0039] A suitable example of the thickener added to the first resin composition to obtain the second resin composition is polyisocyanate. Polyisocyanate is an organic compound having two or more isocyanate groups (-NCO) in the molecule, and typical examples include diisocyanate, which is a compound having two isocyanate groups in the molecule, and polymeric MDI (also called crude MDI). Suitable examples of diisocyanates include, but are not limited to, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate. The polyisocyanate may be used alone or in combination of two or more kinds. Examples of thickeners other than polyisocyanates include alkaline earth metal oxides or hydroxides such as magnesium oxide, magnesium hydroxide, calcium hydroxide, and the like.

[0040] When a polyisocyanate is used as a thickener, the amount of the thickener is, from the viewpoint of imparting appropriate thickening properties to the second resin composition, preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass, relative to 100 parts by mass of the total amount of the radically polymerizable group-containing component in the first resin composition containing the specific unsaturated polyester, the (meth)acrylate as a reactive diluent, and the optionally contained epoxy vinyl ester.

[0041] When an alkaline earth metal oxide or hydroxide is used as the thickener, the amount of the thickener is, from the viewpoint of imparting appropriate thickening properties to the second resin composition, preferably 0.5 parts by mass or more and 5 parts by mass or less, and more preferably 0.7 parts by mass or more and 2 parts by mass or less, when the total amount of the radically polymerizable group-containing components in the first resin composition containing the specific unsaturated polyester, the (meth)acrylate as a reactive diluent, and the optionally contained epoxy vinyl ester is taken as 100 parts by mass.

[0042] When a thickener is added to a first resin composition to obtain a second resin composition, a mixer that is usually used for mixing liquids (a dynamic mixer or a static mixer) is used. The viscosity of the second resin composition during preparation is, for example, 10 Pa s or less, preferably 5 Pa s or less, more preferably 2 Pa s or less, and even more preferably 1 Pa or less at 25° C. There is no particular lower limit to the viscosity, but it may be 0.05 Pa s or more, or 0.1 Pa s or more at 25° C. The viscosity at the time of preparation referred to here is the viscosity when the second resin composition obtained by the addition of the thickener to the first resin composition is kept at 25°C for 30 minutes from the time when the addition of the thickener to the first resin composition is completed. The glass transition temperature of the cured product obtained by thermally curing the second resin composition is, for example, 100° C. or higher, preferably 140° C. or higher, more preferably 160° C. or higher, and may be 180° C. or higher or even 200° C. or higher. There is no particular upper limit to the glass transition temperature, but it is, for example, 215° C. or lower. The glass transition temperature of the cured product can be measured by the method described in the Examples below.

[0043] The second resin composition can be used not only as a matrix resin for SMC but also as a matrix resin for BMC. When producing BMC, the second resin composition is mixed with discontinuous fibers using a kneader. When used to produce BMC, the composition of the second resin composition can be adjusted to have a viscosity suitable for kneading.

[0044] 3. Experimental Results The following are the results of experiments carried out by the present inventors. 3.1.Experiment 1 Five types of unsaturated polyesters, UP1 to UP6, shown in Table 1 below, were synthesized.

[0045] [Table 1]

[0046] The bisphenol A-propylene oxide 2.3 mole adduct (hereinafter referred to as BPP) in Table 1 is a bisphenol A-propylene oxide adduct having an average added mole number of propylene oxide of 2.3.

[0047] In the synthesis of the unsaturated polyesters UP1 to UP6, fumaric acid was used as the dicarboxylic acid. The types and amounts of the diols used in the synthesis of the unsaturated polyesters UP1 to UP6 are as follows: In the synthesis of UP1, 1.05 times the molar amount of BPP as fumaric acid was used as the diol. In the synthesis of UP2, 0.76 times the molar amount of BPP and 0.25 times the molar amount of propylene glycol (hereinafter referred to as PG) were used as diols relative to fumaric acid. In the synthesis of UP3, 0.51 times the molar amount of BPP and 0.50 times the molar amount of fumaric acid were used as diols.

[0048] In the synthesis of UP4, 0.25 times the molar amount of BPP and 0.76 times the molar amount of fumaric acid were used as diols. In the synthesis of UP5, 0.49 times the molar amount of BPP, 0.50 times the molar amount of PG, and 0.02 times the molar amount of trimethylolpropane were used as diols relative to fumaric acid. In the synthesis of UP6, PG was used as the diol in an amount 1.01 times that of fumaric acid in terms of molar amount.

[0049] In the synthesis of the unsaturated polyester UP7, equimolar amounts of fumaric acid and isophthalic acid were used as the dicarboxylic acids, and 1.01 times the molar amount of BPP as the dicarboxylic acid was used as the diol.

[0050] In the synthesis of each unsaturated polyester, dicarboxylic acid and diol were charged into the reaction vessel of a distillation reactor together with tetra-n-butoxytitanium (hereinafter referred to as TBT) in an amount of 0.1% by mass of the dicarboxylic acid and an antioxidant (ADEKA STAB AO-60) in an amount to give a concentration of 400 ppm in the reaction mixture, and heated while stirring with a stirring blade. TBT is a polymerization catalyst. The temperature of the reaction mixture was maintained at 250° C. until distillation of water ceased. After distillation of water ceased, the temperature of the reaction mixture was lowered to 230° C., and the pressure inside the reaction vessel was reduced to 133 Pa over about 20 minutes, and heating was continued to distill off the diol.

[0051] The torque required to rotate the stirring blades increased with time due to the increase in viscosity of the reaction mixture accompanying the increase in the molecular weight of the produced unsaturated polyester. In order to control the molecular weight of the unsaturated polyester, the stirring was stopped when the torque reached a predetermined value, and the reaction vessel was returned to normal pressure by introducing nitrogen gas, and the reaction mixture was removed. The acid value and hydroxyl value of UP1 were measured, and the acid value was 10.9 mg KOH / g and the hydroxyl value was 29.5 mg KOH / g.

[0052] 3.2.Experiment 2 The solubility of the unsaturated polyesters UP1 to UP6 in liquid methacrylate monomers was examined under the following three conditions. Condition 1: Unsaturated polyester and isobornyl methacrylate were mixed in a 1:1 ratio by mass. Condition 2: Unsaturated polyester and ethylene glycol dimethacrylate were mixed in a 1:1 ratio by mass. Condition 3: Unsaturated polyester, isobornyl methacrylate, and ethylene glycol dimethacrylate were mixed in a ratio by mass of 2:2:3 (unsaturated polyester:isobornyl methacrylate:ethylene glycol dimethacrylate). The results are shown in Table 2.

[0053] [Table 2]

[0054] The meanings of the symbols 〇, △, and × in Table 2 are as follows: ◯: When stirred at 40°C, the unsaturated polyester completely dissolved within 3 hours. △: When stirred at 40°C, it took more than 3 hours, but the unsaturated polyester was completely dissolved. ×: The unsaturated polyester was not completely dissolved even after stirring at 40°C for 7 hours. Thus, ◯ indicates good solubility in liquid methacrylate monomers, Δ indicates some solubility in liquid methacrylate monomers, and × indicates poor solubility in liquid methacrylate monomers.

[0055] Comparing UP2 to UP4, the time required for UP2 to completely dissolve in isobornyl methacrylate was the shortest, followed by UP3, and the longest by UP4. The time required for UP5 to completely dissolve in isobornyl methacrylate was similar to that of UP3.

[0056] 3.3.Experiment 3 Three types of resin pastes were prepared by mixing the following materials in the mass ratios shown in Table 3. VE solution: A solution obtained by mixing bisphenol A type epoxy diacrylate (SARTOMER CN104 by Arkema) and isobornyl methacrylate in a 1:1 ratio by mass. UP solution A: A solution obtained by mixing UP1 and isobornyl methacrylate in a mass ratio of 1:1. UP solution B: A solution obtained by mixing UP3, isobornyl methacrylate, and ethylene glycol dimethacrylate in a mass ratio of 2:2:3. UP solution C: A solution obtained by mixing UP5, isobornyl methacrylate, and ethylene glycol dimethacrylate in a mass ratio of 2:2:3. Additional reactive diluent: ethylene glycol dimethacrylate. Polymerization initiator: Kayacarvon BIC-75 from Kayaku Akzo, containing t-butylperoxyisopropyl carbonate (10-hour half-life temperature: 97°C). Thickener: Cosmonate LL from Mitsui Chemicals Fine Co., Ltd., a partially modified mixture of bis(4-isocyanatophenyl)methane (modified MDI).

[0057] [Table 3]

[0058] When preparing each resin paste, a primary paste was first prepared by mixing all the components except for the thickener, and finally the thickener was mixed into the primary paste. Table 3 also shows the measurement results of the viscosity at 25°C of each of the three types of resin pastes prepared when they were prepared and after thickening, as well as the glass transition temperature of the cured products obtained by heating each of them.

[0059] Here, the viscosity at the time of preparation is the viscosity when the resin paste is kept at 25° C. for 30 minutes from the time when all the raw materials of the resin paste are mixed together, and the viscosity after thickening is the viscosity when the resin paste is kept at 25° C. for one week from the time of preparation. All of these viscosities were measured at a sample temperature of 25°C using a B-type viscometer (Toki Sangyo's digital viscometer TVB-10 model) in accordance with JIS Z8803:2011.

[0060] The test pieces for measuring the glass transition temperature were prepared as follows. That is, first, the resin paste was kept at 25°C for one week after preparation to thicken it. Next, the thickened resin paste was placed in a die for panel molding and heated and cured at 140°C for 10 minutes using a press machine to mold a square resin plate with a thickness of 2 mm and dimensions of approximately 30 cm. A test piece measuring 57 mm x 12.7 mm x 2 mm was cut out from this resin plate.

[0061] The loss modulus and storage modulus of the prepared test specimens were measured using a dynamic viscoelasticity measuring device (DMA-Q800, manufactured by TA Instruments), and the temperature at which Tan δ, expressed as the ratio (loss modulus / storage modulus), showed a peak was determined as the glass transition temperature. The conditions for the dynamic viscoelasticity measurement were as follows, in accordance with ASTM D7028. Heating rate: 5℃ / min Chuck span: 35mm Distortion: 0.02% Frequency: 1Hz

[0062] 3.4.Experiment 4 In experiment 4, a resin paste was prepared using styrene as a reactive diluent, which easily dissolves unsaturated polyester. Specifically, a resin paste was prepared by mixing the following materials in the ratios shown in Table 4 below. VE solution: a mixture of bisphenol A type epoxy diacrylate and styrene containing 68% by weight of bisphenol A type epoxy diacrylate (SARTOMER CN104 from Arkema). UP solution: A mixture of unsaturated polyester and styrene containing any one of UP1 to UP6 synthesized in Experiment 1 at a concentration of 68 mass%. Polymerization initiator: Kayacarvon BIC-75 from Kayaku Akzo, containing t-butylperoxyisopropyl carbonate. Thickener: Cosmonate LL from Mitsui Chemicals Fine Co., Ltd., a partially modified mixture of bis(4-isocyanatophenyl)methane (modified MDI).

[0063] [Table 4]

[0064] The glass transition temperature of the cured product obtained by heating each resin paste was measured. The procedure for preparing the test specimens for measurement and measuring the glass transition temperature was the same as in Experiment 3. The results are shown in Table 5.

[0065] [Table 5]

[0066] Comparing the examples using UP1 to UP6, it was observed that the glass transition temperature of the cured resin obtained from the resin paste tended to increase as the amount of BPP used in the unsaturated polyester was reduced and the amount of PG was increased. Furthermore, when comparing the examples using UP1 and UP7, the resin paste containing UP1, which uses only fumaric acid as the dicarboxylic acid, had a higher glass transition temperature of the cured product than the resin paste containing UP7, which uses fumaric acid and isophthalic acid as the dicarboxylic acids.

[0067] As described above, the results of Experiment 4 show that it is advantageous to use an unsaturated polyester with a small double bond equivalent in order to increase the glass transition temperature of the cured resin obtained from the resin paste. However, the results of Experiment 3, which used an acrylate as a reactive diluent, were in contrast to those of Experiment 4, and no effect of the double bond equivalent of the unsaturated polyester on the glass transition temperature of the cured resin was observed.

[0068] 4. Summary of the embodiment The embodiments of the present invention include at least the following: [Embodiment 1] A resin composition comprising an unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct, and a (meth)acrylate as a reactive diluent. [Embodiment 2] In the unsaturated polyester, the amount of the units derived from the fumaric acid or maleic acid is 50% or more, preferably 75% or more, more preferably 90% or more, and may be 100%, in terms of the number of moles, based on the total amount of the units derived from the dicarboxylic acid. [Embodiment 3] The resin composition according to embodiment 1 or 2, wherein the average number of propylene oxide units contained in the units derived from the bisphenol A-propylene oxide adduct is 1 to 4, and preferably 2 to 3. [Embodiment 4] The resin composition according to any one of embodiments 1 to 3, wherein the (meth)acrylate has a viscosity, measured with a Brookfield viscometer, of 500 mPa·s or less at 25°C, preferably 100 mPa· or less, more preferably 50 mPa· or less, and even more preferably 10 mPa·s or less. [Embodiment 5] The resin composition according to any one of embodiments 1 to 4, wherein the (meth)acrylate is a bifunctional (meth)acrylate. [Embodiment 6] The resin composition according to embodiment 5, wherein the bifunctional (meth)acrylate is ethylene glycol di(meth)acrylate. [Embodiment 7] The resin composition according to any one of embodiments 1 to 6, wherein the (meth)acrylate is isobornyl (meth)acrylate. [Embodiment 8] The resin composition according to any one of embodiments 1 to 7, wherein the (meth)acrylate is isobornyl (meth)acrylate and ethylene glycol di(meth)acrylate. [Embodiment 9] The resin composition according to any one of embodiments 1 to 8, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 20% or more, 50% or more, 75% or more, 95% or more, or 100% by mole based on the total amount of units derived from the diol. [Embodiment 10] A resin composition according to embodiment 7, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 50% or more, preferably 75% or more, more preferably 95% or more, and may be 100% by mole, based on the total amount of units derived from the diol. [Embodiment 11] The resin composition according to any one of embodiments 1 to 10, further comprising an epoxy vinyl ester which may be a bisphenol A type epoxy vinyl ester. [Embodiment 12] The resin composition according to any one of embodiments 1 to 11, further comprising a radical polymerization initiator. [Embodiment 13] The resin composition according to embodiment 12, further comprising a thickener. [Embodiment 14] 14. The resin composition according to embodiment 13, wherein the thickener is a polyisocyanate. [Embodiment 15] A raw material for a thermosetting matrix resin of SMC or BMC, which contains an unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct, and which contains at least a (meth)acrylate as a reactive diluent in addition to the unsaturated polyester. [Embodiment 16] A molding material comprising the resin composition according to embodiment 13 or 14 and discontinuous fibers. [Embodiment 17] 17. The molding material according to embodiment 16, wherein the discontinuous fibers are carbon fibers. [Embodiment 18] 18. The molding material according to embodiment 16 or 17, which is a sheet molding compound. [Embodiment 19] A method for producing a sheet molding compound, comprising: providing a resin composition according to embodiment 13 or 14; impregnating a random mat of discontinuous fibers with the resin composition to obtain an impregnated random mat; and maturing the impregnated random mat. [Embodiment 20] 20. The method according to embodiment 19, wherein the discontinuous fibers comprise carbon fibers.

[0069] [Embodiment 21] 1. Use of an unsaturated polyester in a resin composition, the resin composition containing a (meth)acrylate as a reactive diluent in addition to the unsaturated polyester, the unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct. [Embodiment 22] 22. The use according to embodiment 21, wherein in the unsaturated polyester, the amount of units derived from fumaric acid or maleic acid is 50% or more, preferably 75% or more, more preferably 90% or more, and may be 100%, in terms of the number of moles, based on the total amount of units derived from dicarboxylic acids. [Embodiment 23] Use according to embodiment 21 or 22, wherein the average number of propylene oxide units contained in the units derived from the bisphenol A-propylene oxide adduct is 1 to 4, preferably 2 to 3. [Embodiment 24] The use according to any one of embodiments 21 to 23, wherein the resin composition contains, as the (meth)acrylate, a (meth)acrylate having a viscosity, measured with a Brookfield viscometer, at 25°C of 500 mPa s or less, preferably 100 mPa s or less, more preferably 50 mPa s or less, and even more preferably 10 mPa s or less. [Embodiment 25] The use according to any one of embodiments 21 to 24, wherein the resin composition contains a bifunctional (meth)acrylate as the (meth)acrylate. [Embodiment 26] The use according to embodiment 25, wherein the resin composition contains ethylene glycol di(meth)acrylate as the bifunctional (meth)acrylate. [Embodiment 27] The use according to any one of embodiments 21 to 26, wherein the resin composition contains isobornyl (meth)acrylate as the (meth)acrylate. [Embodiment 28] The use according to any one of embodiments 21 to 27, wherein the resin composition contains isobornyl (meth)acrylate and ethylene glycol di(meth)acrylate as the (meth)acrylate. [Embodiment 29] The use according to any one of embodiments 21 to 28, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 20% or more, 50% or more, 75% or more, 95% or more, or 100% by mole based on the total amount of units derived from the diol. [Embodiment 30] The use according to embodiment 27, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 50% or more, preferably 75% or more, more preferably 95% or more, or may be 100%, based on the total amount of units derived from the diol, in terms of the number of moles. [Embodiment 31] The use according to any one of embodiments 21 to 30, wherein the resin composition further comprises an epoxy vinyl ester, which may be a bisphenol A type epoxy vinyl ester. [Embodiment 32] The use according to any one of embodiments 21 to 31, wherein the resin composition further comprises a radical polymerization initiator. [Embodiment 33] The use according to any one of embodiments 21 to 32, wherein the resin composition further comprises a thickener.

[0070] Although the present invention has been described above with reference to specific embodiments, each embodiment is presented as an example and does not limit the scope of the present invention. Each embodiment described in this specification can be modified in various ways within the scope of the effects of the invention, and can be combined with features described in other embodiments within the scope of feasibility. [Explanation of symbols]

[0071] 1. Chopper 2a First coating machine 2b Second Coating Machine 3 Impregnation machine 10 Continuous fiber bundle 20 Chopped fiber bundles 30 Random Mat 41, 42 Resin paste 51 Daiichi Carrier Film 52 Second Carrier Film 60 Laminate P Fiber Package

Claims

1. A resin composition containing an unsaturated polyester having units derived from fumaric acid or maleic acid and units derived from bisphenol A-propylene oxide adduct, and a (meth)acrylate as a reactive diluent.

2. The resin composition according to claim 1, wherein the amount of units derived from fumaric acid or maleic acid in the unsaturated polyester is 50% or more in moles relative to the total amount of units derived from dicarboxylic acid.

3. The resin composition according to claim 1 or 2, wherein the average number of propylene oxide units contained in the unit derived from the bisphenol A-propylene oxide adduct is 1 to 4.

4. The resin composition according to claim 1 or 2, wherein the (meth)acrylate contains a (meth)acrylate whose viscosity, as measured by a B-type viscometer, is 500 mPa·s or less at 25°C.

5. The resin composition according to claim 1 or 2, wherein the (meth)acrylate contains a bifunctional (meth)acrylate.

6. The resin composition according to claim 5, wherein the aforementioned bifunctional (meth)acrylate contains ethylene glycol di(meth)acrylate.

7. The resin composition according to claim 1 or 2, wherein the (meth)acrylate contains isobornyl (meth)acrylate.

8. The resin composition according to claim 1 or 2, wherein the (meth)acrylate contains isobornyl (meth)acrylate and ethylene glycol di(meth)acrylate.

9. The resin composition according to claim 1 or 2, wherein the amount of units derived from the bisphenol A-propylene oxide adduct in the unsaturated polyester is 20% or more in moles relative to the total amount of units derived from the diol.

10. The resin composition according to claim 7, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 50% or more in moles relative to the total amount of units derived from the diol.

11. Furthermore, the resin composition according to claim 1 or 2, further containing an epoxy vinyl ester.

12. Furthermore, the resin composition according to claim 1 or 2 contains a radical polymerization initiator.

13. Furthermore, the resin composition according to claim 12, further containing a thickening agent.

14. The resin composition according to claim 13, wherein the thickening agent is polyisocyanate.

15. A raw material for a thermosetting matrix resin of SMC or BMC, comprising an unsaturated polyester containing units derived from fumaric acid or maleic acid and units derived from a bisphenol A-propylene oxide adduct, wherein the thermosetting matrix resin contains at least (meth)acrylate as a reactive diluent in addition to the unsaturated polyester.

16. A molding material comprising the resin composition according to claim 13 and discontinuous fibers.

17. The molding material according to claim 16, wherein carbon fibers are contained as the discontinuous fibers.

18. The molding material according to claim 16, which is a sheet molding compound.

19. A method for producing a sheet molding compound, comprising: providing the resin composition described in claim 13; impregnating a random mat made of discontinuous fibers with the resin composition to obtain an impregnated random mat; and aging the impregnated random mat.

20. The manufacturing method according to claim 19, wherein carbon fibers are contained as the discontinuous fibers.

21. Use of an unsaturated polyester in a resin composition, wherein the resin composition contains (meth)acrylate as a reactive diluent in addition to the unsaturated polyester, and the unsaturated polyester comprises units derived from fumaric acid or maleic acid and units derived from bisphenol A-propylene oxide adducts.

22. The use according to claim 21, wherein the amount of units derived from fumaric acid or maleic acid in the unsaturated polyester is 50% or more in moles relative to the total amount of units derived from dicarboxylic acid.

23. The use according to claim 21 or 22, wherein the average number of propylene oxide units contained in the unit derived from the bisphenol A-propylene oxide adduct is 1 to 4.

24. The use according to claim 21 or 22, wherein the resin composition contains, as the (meth)acrylate, a (meth)acrylate having a viscosity of 500 mPa·s or less as measured by a B-type viscometer at 25°C.

25. The use according to claim 21 or 22, wherein the resin composition contains a difunctional (meth)acrylate as the (meth)acrylate.

26. The use according to claim 25, wherein the resin composition contains ethylene glycol di(meth)acrylate as the difunctional (meth)acrylate.

27. The use according to claim 21 or 22, wherein the resin composition contains isobornyl (meth)acrylate as the (meth)acrylate.

28. The use according to claim 21 or 22, wherein the resin composition contains isobornyl (meth)acrylate and ethylene glycol di(meth)acrylate as the (meth)acrylate.

29. The use according to claim 21 or 22, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 20% or more in moles relative to the total amount of units derived from the diol.

30. The use according to claim 27, wherein in the unsaturated polyester, the amount of units derived from the bisphenol A-propylene oxide adduct is 50% or more in moles relative to the total amount of units derived from the diol.

31. The use according to claim 21 or 22, wherein the resin composition further contains an epoxy vinyl ester.

32. The use according to claim 21 or 22, wherein the resin composition further contains a radical polymerization initiator.

33. The use according to claim 21 or 22, wherein the resin composition further contains a thickening agent.

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