Unsaturated polyester resin composition for RTM molding

Abstract

The present invention provides an unsaturated polyester resin for RTM molding that exhibits stable curing time regardless of storage period and can suppress the occurrence of warping in molded products obtained by RTM molding. [Solution] An unsaturated polyester resin composition comprising an unsaturated polyester resin (A) and an unsaturated monomer (B), wherein the unsaturated polyester resin (A) consists of constituent units derived from an acid component and an alcohol component, the acid component contains an unsaturated dibasic acid such as phthalic anhydride and maleic anhydride, the alcohol component contains at least one of ethylene glycol and diethylene glycol and propylene glycol, the unsaturated monomer (B) is a styrene monomer, and the unsaturated polyester resin composition contains formic acid (C), the content of which is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of resin (A) and monomer (B), an unsaturated polyester resin composition for RTM molding.

Description

Technical Field

[0001] The present invention relates to an unsaturated polyester resin composition for RTM molding, a molding material, a method for manufacturing a molded body, and a molded body.

Background Art

[0002] Unsaturated polyester resin compositions are used as resins for decorative materials such as artificial marble, sealing materials, paints, or adhesives because their cured products are excellent in water resistance, chemical resistance, and further in appearance. They are also used as materials (FRP) having high strength by being compounded with reinforcing materials. As one of the molding methods for such unsaturated polyester resin compositions, the RTM (Resin Transfer Molding) molding method has been conventionally known. Since the RTM molding method is a closed molding method, the volatilization of organic solvents is small and the working environment is good. In addition, the RTM molding method does not require dedicated equipment such as an autoclave, and does not require as much skill as the hand lay-up (HLU) method, and has the characteristic that molded products can be produced with high reliability and reproducibility. Therefore, the RTM molding method is widely used as a molding method for FRP, and the development of unsaturated polyester resin compositions suitable for the RTM molding method has also been promoted.

[0003] For example, Patent Document 1 discloses an unsaturated polyester resin composition for RTM molding comprising an unsaturated polyester containing a dicyclopentadiene component, a terephthalic acid-based unsaturated polyester, and a vinyl polymerizable monomer for the purpose of improving water resistance and mold release properties from an FRP mold.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Unsaturated polyester resin compositions for RTM molding may require long-term storage depending on the application and manufacturing / sales method. However, when RTM molding is performed using unsaturated polyester resin compositions that have been stored for a long time, there is a problem of slow curing speed. Furthermore, when using unsaturated polyester resin compositions that have been stored for a long time, there is a problem of warping occurring in the molded product. Therefore, there is a need for an unsaturated polyester resin composition for RTM molding that has a stable curing time regardless of the storage period and can suppress warping of molded products obtained by RTM molding. Therefore, the object of the present invention is to provide an unsaturated polyester resin composition for RTM molding that has a stable curing time regardless of the storage period and can suppress the occurrence of warping in molded products obtained by RTM molding. [Means for solving the problem]

[0006] As a result of diligent research to solve the above problems, the present inventors have found that a composition containing an unsaturated polyester resin, an unsaturated monomer, and formic acid can solve the above problems. The present invention relates to the following: [1] An unsaturated polyester resin composition for RTM molding comprising an unsaturated polyester resin (A) and an unsaturated monomer (B), wherein the unsaturated polyester resin (A) consists of constituent units derived from an acid component and constituent units derived from an alcohol component, the acid component comprises phthalic anhydride and an unsaturated dibasic acid, the alcohol component comprises at least one of ethylene glycol and diethylene glycol and propylene glycol, the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid, the unsaturated monomer (B) is at least one selected from the group consisting of styrene monomers and acrylic monomers, and the unsaturated polyester resin composition for RTM molding contains formic acid (C), the content of which is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B), [2] The unsaturated polyester resin composition for RTM molding according to [1], further comprising at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2). [3] The unsaturated polyester resin composition for RTM molding according to [1] or [2], further comprising a transition metal catalyst (D1) and an aromatic tertiary amine (D2). [4] The unsaturated polyester resin composition for RTM molding according to [2] or [3], wherein the transition metal catalyst (D1) is at least one selected from the group consisting of organic salts of cobalt and organic salts of copper. [5] An unsaturated polyester resin composition for RTM molding according to any one of [1] to [4], wherein the total content of phthalic anhydride and the unsaturated dibasic acid in the acid component is 90 to 100 mol%. [6] An unsaturated polyester resin composition for RTM molding according to any one of [1] to [5], wherein the total content of ethylene glycol, diethylene glycol, and propylene glycol in the alcohol component is 90 to 100 mol%. [7] An unsaturated polyester resin composition for RTM molding according to any one of [1] to [6], wherein the molar ratio of phthalic anhydride to an unsaturated dibasic acid [phthalic anhydride / unsaturated dibasic acid] is 55 / 45 to 65 / 35. [8] An unsaturated polyester resin composition for RTM molding according to any one of [1] to [7], wherein the molar ratio [alcohol component / acid component] of constituent units derived from the alcohol component to constituent units derived from the acid component is 1.0 to 1.2. [9] The unsaturated polyester resin composition for RTM molding according to any one of [1] to [8], wherein the viscosity of the unsaturated polyester resin composition for RTM molding at 25°C is 30 to 2000 mPa·s.

[10] An unsaturated polyester resin composition for RTM molding according to any one of [2] to [9] above, wherein the mass ratio of formic acid (C) to the metal equivalent amount of the transition metal catalyst (D1) [(C) / (D1)(metal equivalent amount)] is 0.1 to 15.

[11] The unsaturated polyester resin composition for RTM molding according to any one of [2] to

[10] , wherein the content of the transition metal catalyst (D1) is 0.001 to 3 parts by mass, in terms of metal, per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B).

[12] An unsaturated polyester resin composition for RTM molding according to any one of [1] to

[11] , wherein the mass ratio of the unsaturated polyester resin (A) to the unsaturated monomer (B) [(A) / (B)] is 50 / 50 to 70 / 30.

[13] An unsaturated polyester resin composition for RTM molding according to any one of [1] to

[12] above, which is for L-RTM molding.

[14] A molding material comprising an unsaturated polyester resin composition for RTM molding according to any one of [1] to

[13] above, and a curing agent.

[15] A method for producing a molded article, comprising the steps of blending a curing agent into an unsaturated polyester resin composition for RTM molding described in any one of [1] to

[13] above, injecting it into a mold, and impregnating a reinforcing substrate placed inside the mold.

[16] A method for producing a molded article, comprising the steps of storing an unsaturated polyester resin composition for RTM molding described in any one of [2] to [4] above for three weeks or more, and blending a curing agent into the stored unsaturated polyester resin composition for RTM molding, injecting it into a mold, and impregnating a reinforcing substrate placed inside the mold.

[17] A molded article obtained by RTM molding an unsaturated polyester resin composition for RTM molding described in any one of [1] to

[13] above. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an unsaturated polyester resin composition for RTM molding that has a stable curing time regardless of the storage period and can suppress the occurrence of warping in molded products obtained by RTM molding. [Modes for carrying out the invention]

[0008] [Unsaturated polyester resin composition for RTM molding] The unsaturated polyester resin composition for RTM molding of the present invention is An unsaturated polyester resin composition for RTM molding comprising an unsaturated polyester resin (A) and an unsaturated monomer (B), wherein the unsaturated polyester resin (A) consists of constituent units derived from an acid component and constituent units derived from an alcohol component, the acid component comprises phthalic anhydride and an unsaturated dibasic acid, the alcohol component comprises at least one of ethylene glycol and diethylene glycol and propylene glycol, the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid, the unsaturated monomer (B) is at least one selected from the group consisting of styrene monomers and acrylic monomers, and the RTM molding unsaturated polyester resin composition contains formic acid (C), the content of formic acid (C) is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). The unsaturated polyester resin composition for RTM molding of the present invention (hereinafter also simply referred to as "unsaturated polyester resin composition") has the above-described structure, which allows for stable curing time regardless of storage period and suppresses the occurrence of warping in molded products obtained by RTM molding. Here, "stable curing time regardless of storage period" means that even when the unsaturated polyester resin is stored for a long period of time, the change in curing time between the unsaturated polyester resin composition immediately after preparation and the unsaturated polyester resin composition after storage is small, that is, the difference in curing time between the unsaturated polyester resin composition immediately after preparation and after storage is small. Furthermore, because the unsaturated polyester resin composition of the present invention exhibits little change in curing time before and after storage, using this composition makes it easier to adjust the timing of demolding during RTM molding, thereby improving product yield. Moreover, because the unsaturated polyester resin composition of the present invention contains formic acid, the change in curing time of the unsaturated polyester resin composition between immediately after preparation and after long-term storage can be reduced, making it possible to improve productivity without delaying the demolding timing even after long-term storage.

[0009] The unsaturated polyester resin composition for RTM molding of the present invention is used in a state in which a curing accelerator (including a curing co-accelerator) is included at the time of use (curing) to promote curing. Such a curing accelerator only needs to be included by the time of use (curing), and may be added immediately before use, but it is preferable to include the curing accelerator in advance from the viewpoint of reducing the workload at the time of use. For this reason, it is usually stored after the curing accelerator has been added until it is used. However, with conventional unsaturated polyester resin compositions, when a curing accelerator is included in the composition, a problem arises in that the curing rate slows down after long-term storage, making it difficult to store for a long period of time after the curing accelerator has been added. However, because the unsaturated polyester resin composition for RTM molding of the present invention contains formic acid, even when the curing accelerator is added before use and then stored for a long period of time, the change in the curing time of the unsaturated polyester resin composition before and after storage is small, and the occurrence of warping of molded products obtained by RTM molding can be suppressed. Therefore, the unsaturated polyester resin composition for RTM molding of the present invention is suitably used for long-term storage.

[0010] From the viewpoints of ease of injection into a mold and ease of impregnation into a reinforcing base material such as a fiber reinforcing material used as necessary, the viscosity of the unsaturated polyester resin composition at 25°C is preferably 30 to 2000 mPa·s, more preferably 50 to 1000 mPa·s, and still more preferably 50 to 500 mPa·s. The unsaturated polyester resin composition of the present invention has a stable curing time regardless of the storage period and can suppress the occurrence of warpage of the obtained molded product, and thus is particularly preferably used for L-RTM (Light Resin Transfer Molding) molding.

[0011] (Unsaturated polyester resin (A)) The unsaturated polyester resin (A) used in the present invention is composed of a structural unit derived from an acid component and a structural unit derived from an alcohol component, the acid component includes phthalic anhydride and an unsaturated dibasic acid, the alcohol component includes at least one of ethylene glycol and diethylene glycol and propylene glycol, and the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid. <Structural unit derived from acid component> The structural unit derived from the acid component that constitutes the unsaturated polyester resin (A) refers to the portion derived from the acid component of the ester bond formed by the condensation of the acid component and the alcohol component. The acid component that provides the structural unit includes phthalic anhydride and an unsaturated dibasic acid, and the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid.

[0012] The ratio (mol) of the total amount of the structural unit derived from phthalic anhydride and the structural unit derived from the unsaturated dibasic acid in the structural unit derived from the acid component is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, still more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol% in terms of the number of carboxyl groups. The structural unit derived from the acid component may consist only of the structural unit derived from phthalic anhydride and the structural unit derived from the unsaturated dibasic acid. That is, the total content of phthalic anhydride and the unsaturated dibasic acid in the acid component is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, still more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%. The acid component may consist only of phthalic anhydride and the unsaturated dibasic acid. The unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid, and fumaric acid, preferably at least one selected from the group consisting of maleic anhydride and maleic acid, and more preferably maleic anhydride.

[0013] The ratio (mol) of the structural unit derived from phthalic anhydride in the structural unit derived from the acid component is preferably 20 to 90 mol%, more preferably 30 to 80 mol%, still more preferably 40 to 70 mol%, and even more preferably 55 to 65 mol% in terms of the number of carboxyl groups. The ratio (mol) of the structural unit derived from the unsaturated dibasic acid in the structural unit derived from the acid component is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, still more preferably 30 to 60 mol%, and even more preferably 35 to 45 mol% in terms of the number of carboxyl groups. The molar ratio of phthalic anhydride to the unsaturated dibasic acid [phthalic anhydride / unsaturated dibasic acid] is preferably 20 / 80 to 90 / 10, more preferably 30 / 70 to 80 / 20, still more preferably 40 / 60 to 70 / 30, and even more preferably 55 / 45 to 65 / 35. By setting the molar ratio of phthalic anhydride to unsaturated dibasic acid within the aforementioned range, the resulting molded product exhibits an excellent balance of rigidity and flexibility, resulting in good mechanical strength.

[0014] The aforementioned acid component may include other acid components besides phthalic anhydride and the aforementioned unsaturated dibasic acid. Examples of other acid components include saturated dibasic acids other than phthalic anhydride, and unsaturated dibasic acids other than maleic anhydride, maleic acid, and fumaric acid. Examples of saturated dibasic acids include aromatic dibasic acids, alicyclic dibasic acids, and aliphatic dibasic acids. Examples of aromatic dibasic acids include 2,6-naphthalenedicarboxylic acid and 4,4'-biphenyldicarboxylic acid. Examples of alicyclic dibasic acids include 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and endomethylenehexahydrophthalic anhydride. Examples of aliphatic dibasic acids include succinic acid, adipic acid, sebacic acid, azelaic acid, succinic acid substituted with alkyl groups having 16 to 18 carbon atoms, and dimer acids. You may use one or more saturated dibasic acids other than phthalic anhydride.

[0015] Examples of unsaturated dibasic acids other than maleic anhydride, maleic acid, and fumaric acid include itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and endomethylenetetrahydrophthalic anhydride. Unsaturated dibasic acids other than maleic anhydride, maleic acid, and fumaric acid may be used individually or in combination of two or more.

[0016] <Constituent units derived from alcohol components> In unsaturated polyester resin (A), the constituent units derived from the alcohol component refer to the portion of the ester bond formed by the condensation of the acid component and the alcohol component that originates from the alcohol component. The alcohol component that provides the aforementioned structural units includes at least one of ethylene glycol and diethylene glycol, and propylene glycol. From the viewpoint of ease of adjusting the balance between the flexibility and rigidity of the polyester resin, ease of penetration of the unsaturated polyester resin composition into the reinforcing material used as needed during RTM molding, and economic efficiency, the alcohol component that provides the structural units preferably contains ethylene glycol and propylene glycol, and more preferably consists of ethylene glycol and propylene glycol. Furthermore, a constituent unit derived from at least one of ethylene glycol and diethylene glycol includes cases where the constituent unit is derived from ethylene glycol, cases where the constituent unit is derived from diethylene glycol, and cases where the constituent unit consists of a constituent unit derived from ethylene glycol and a constituent unit derived from diethylene glycol.

[0017] The ratio (moles) of the total amount of constituent units derived from ethylene glycol, diethylene glycol, and propylene glycol in the constituent units derived from the alcohol component is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%, in terms of the number of hydroxyl groups, and the constituent units derived from the alcohol component may consist only of constituent units derived from at least one of ethylene glycol and diethylene glycol and constituent units derived from propylene glycol.

[0018] That is, the total content of ethylene glycol, diethylene glycol, and propylene glycol in the alcohol component is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%, and the alcohol component may consist of at least one of ethylene glycol and diethylene glycol and propylene glycol alone. Here, "total amount of ethylene glycol (or its derived constituent units), diethylene glycol (or its derived constituent units), and propylene glycol (or its derived constituent units)" means the total content of that one type and propylene glycol (or its derived constituent units) if only one of ethylene glycol (or its derived constituent units) and diethylene glycol (or its derived constituent units) is included. In this specification, similar descriptions shall have the same meaning. The molar ratio of propylene glycol to the total of ethylene glycol and diethylene glycol [propylene glycol / ethylene glycol and diethylene glycol] is 35 / 65 to 75 / 25, preferably 50 / 50 to 75 / 25, more preferably 55 / 45 to 75 / 25, even more preferably 55 / 45 to 70 / 30, and even more preferably 60 / 40 to 65 / 35. Here, "total of ethylene glycol and diethylene glycol" refers to the content of only one of ethylene glycol and diethylene glycol if only one is included. In this specification, similar descriptions shall have the same meaning. By setting the molar ratio of propylene glycol to the total of ethylene glycol and diethylene glycol within the aforementioned range, the resulting molded article exhibits an excellent balance of rigidity and flexibility, resulting in good mechanical strength.

[0019] The molar ratio of propylene glycol-derived components to the total of ethylene glycol-derived components and diethylene glycol-derived components [propylene glycol / ethylene glycol and diethylene glycol] is 35 / 65 to 75 / 25, preferably 50 / 50 to 75 / 25, more preferably 55 / 45 to 75 / 25, even more preferably 55 / 45 to 70 / 30, and even more preferably 60 / 40 to 65 / 35. The ratio (moles) of propylene glycol-derived structural units in the structural units derived from the alcohol component is preferably 35 to 75 mol%, more preferably 50 to 75 mol%, even more preferably 55 to 75 mol%, even more preferably 55 to 70 mol%, and even more preferably 60 to 65 mol%, in terms of the number of hydroxyl groups. The ratio (moles) of the total constituent units derived from ethylene glycol and diethylene glycol in the constituent units derived from the alcohol component is preferably 25 to 65 mol%, more preferably 25 to 50 mol%, even more preferably 25 to 45 mol%, even more preferably 30 to 45 mol%, and even more preferably 35 to 40 mol%, in terms of the number of hydroxyl groups.

[0020] The aforementioned alcohol component may include other alcohol components besides ethylene glycol, diethylene glycol, and propylene glycol. Examples of other alcohol components include aliphatic diols other than ethylene glycol, diethylene glycol, and propylene glycol, alicyclic diols, bisphenol alkylene oxide adducts, and polyalkylene glycols. Aliphatic diols include 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,4-butenediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 2-ethyl-2-methylpropane-1,3-diol, 2-butyl-2-ethylpropane-1,3-diol, 1,6-hexanediol, 3-methyl-1,5- Examples include pentanediol, 2-ethyl-1,3-hexanediol, 2,4-dimethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropanoate, triethylene glycol, and dipropylene glycol.

[0021] Examples of alicyclic diols include 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F. Examples of bisphenol alkylene oxide adducts include bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Alcohol components other than ethylene glycol, diethylene glycol, and propylene glycol may be used individually or in combination of two or more types.

[0022] The unsaturated polyester resin (A) may contain other structural units besides those described above. Examples of components that provide other structural units include monobasic acids, trivalent or higher polycarboxylic acids, monoalcohols, trivalent or higher polyhydric alcohols, and hydroxycarboxylic acids. Furthermore, lower alkyl esters and anhydrides of the acid component may also be used. Furthermore, the unsaturated polyester resin (A) may contain constituent units derived from compounds that do not have a carboxyl group or a hydroxyl group, but the constituent units derived from compounds that do not have a carboxyl group or a hydroxyl group are preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0% by mass. In particular, it is preferable that the unsaturated polyester resin (A) does not contain constituent units substantially derived from dicyclopentadiene, and the constituent units derived from dicyclopentadiene are preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0% by mass.

[0023] The molar ratio [alcohol component / acid component] of constituent units derived from the alcohol component to constituent units derived from the acid component is preferably 0.9 to 1.3, more preferably 0.95 to 1.25, even more preferably 1.0 to 1.2, and even more preferably 1.05 to 1.15. The above molar ratio is calculated based on the molar ratio of hydroxyl groups contained in the alcohol component to carboxyl groups contained in the acid component. Therefore, hydroxycarboxylic acids are contained in both the acid component and the alcohol component, and the number of hydroxyl groups and carboxyl groups they contain contributes to the molar ratio of the constituent units.

[0024] The acid value of the unsaturated polyester resin (A) of the present invention is preferably 2 to 40 mg KOH / g, more preferably 10 to 40 mg KOH / g, even more preferably 10 to 35 mg KOH / g, even more preferably 10 to 20 mg KOH / g, and even more preferably 12 to 20 mg KOH / g. When the acid value of the unsaturated polyester resin (A) is within the above range, it tends to reduce the change in curing time before and after storage.

[0025] The content of the unsaturated polyester resin (A) is preferably 35 to 85% by mass, more preferably 40 to 80% by mass, even more preferably 50 to 75% by mass, even more preferably 55 to 70% by mass, and even more preferably 55 to 65% by mass, based on 100% by mass of the unsaturated polyester resin composition.

[0026] <Method for producing unsaturated polyester resin (A)> As long as an unsaturated polyester resin (A) used in the present invention is obtained, that is, as described above, an unsaturated polyester resin consisting of constituent units derived from an acid component and constituent units derived from an alcohol component, wherein the acid component includes phthalic anhydride and an unsaturated dibasic acid, the alcohol component includes at least one of ethylene glycol and diethylene glycol and propylene glycol, and the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid, there are no particular restrictions on the method of production, and it can be produced by conventionally known methods.

[0027] For example, the unsaturated polyester resin (A) can be obtained by heating and dehydrating condensation (esterification reaction) using the acid component and alcohol component described above, under an inert gas atmosphere such as nitrogen, preferably at a reaction temperature of 160 to 280°C, more preferably 200 to 260°C. An esterification catalyst may be used in the esterification reaction as needed. Examples of esterification catalysts include at least one metal compound selected from the group consisting of antimony, germanium, titanium, tin, zinc, aluminum, and manganese. The amount of esterification catalyst added is preferably 0.01 to 1.5 moles per 100 moles of saturated dibasic acid component containing phthalic anhydride. Furthermore, a polymerization inhibitor may be added as needed to suppress the reaction of unsaturated bonds contained in the unsaturated dibasic acid. Examples of polymerization inhibitors include polyhydric phenol-based polymerization inhibitors such as methylhydroquinone, hydroquinone, toluhydroquinone, trimethylhydroquinone, and tert-butylcatechol; and quinone-based polymerization inhibitors such as parabenzoquinone and toluquinone. The amount of polymerization inhibitor added is preferably 0.002 to 1.0 parts by mass, and more preferably 0.005 to 0.3 parts by mass, per 100 parts by mass of the total amount of the acid component and alcohol component. The endpoint of the reaction can be determined by the acid value of the reaction mixture, the amount of condensation water (or alcohol in the case of lower alkyl esters as raw materials), and the viscosity of the resulting polyester or reaction mixture.

[0028] (Unsaturated monomer (B)) The unsaturated polyester resin composition of the present invention contains an unsaturated monomer (B) selected from the group consisting of styrene monomers and acrylic monomers. The unsaturated monomer (B) contained in the unsaturated polyester resin composition of the present invention is preferably a styrene monomer. The unsaturated polyester resin composition of the present invention exhibits excellent room-temperature reactivity, availability, and mechanical strength of the resulting molded articles when the unsaturated monomer (B) is at least one selected from the group consisting of styrene monomers and acrylic monomers. Furthermore, when the unsaturated monomer (B) is a styrene monomer, the composition exhibits excellent room-temperature reactivity, availability, and mechanical strength of the resulting molded articles.

[0029] Examples of styrene monomers include styrene, vinyltoluene, and α-methylstyrene, with styrene being preferred. Acrylic monomers include methyl (meth)acrylate, (meth)acrylic acid, benzyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl ( Examples include meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and diethylene glycol di(meth)acrylate. Here, "(meth)acrylic acid" refers to both "methacrylic acid" and "acrylic acid," and "(meth)acrylate" refers to both "methacrylate" and "acrylate." The unsaturated monomer (B) may be used alone or in a mixture of two or more types as appropriate.

[0030] The content of the unsaturated monomer (B) is preferably 10 to 64% by mass, more preferably 15 to 59% by mass, even more preferably 20 to 49% by mass, even more preferably 25 to 43% by mass, and even more preferably 30 to 43% by mass, based on 100% by mass of the unsaturated polyester resin composition. The total content of the unsaturated polyester resin (A) and unsaturated monomer (B) in the unsaturated polyester resin composition is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more. The upper limit is preferably 99.99% by mass or less, more preferably 99.9% by mass or less, even more preferably 99.7% by mass or less, and even more preferably 99.5% by mass or less. The total content of all components in the unsaturated polyester resin composition does not exceed 100% by mass. The mass ratio of the unsaturated polyester resin (A) to the unsaturated monomer (B) [unsaturated polyester resin (A) / unsaturated monomer (B)] is preferably 35 / 65 to 85 / 15, more preferably 40 / 60 to 80 / 20, even more preferably 50 / 50 to 75 / 25, even more preferably 50 / 50 to 70 / 30, and even more preferably 55 / 45 to 65 / 35.

[0031] (Formic acid (C)) The unsaturated polyester resin composition of the present invention contains formic acid (C), and the formic acid (C) content is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). The unsaturated polyester resin composition for RTM molding according to the present invention contains formic acid in the above-mentioned amount, which allows for a stable curing time regardless of the storage period and suppresses the occurrence of warping in the resulting molded product.

[0032] The formic acid (C) content is 0.01 to 0.1 parts by mass, preferably 0.015 to 0.09 parts by mass, more preferably 0.02 to 0.085 parts by mass, even more preferably 0.03 to 0.08 parts by mass, and even more preferably 0.05 to 0.08 parts by mass, based on 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). If the formic acid (C) content is less than 0.01 parts by mass, the curing time will not be sufficiently stabilized, and if it exceeds 0.1 parts by mass, the curing time will become unstable. The formic acid (C) content is preferably 0.01 to 0.1% by mass, more preferably 0.015 to 0.09% by mass, even more preferably 0.02 to 0.085% by mass, even more preferably 0.03 to 0.08% by mass, and even more preferably 0.05 to 0.08% by mass, based on 100% by mass of the unsaturated polyester resin composition. When the formic acid (C) content is within the aforementioned range, the curing time of the unsaturated polyester resin composition is stable before and after storage, and the occurrence of warping of molded products can be suppressed. The mass ratio of formic acid (C) to the metal equivalent amount (transition metal content) of the transition metal catalyst (D1) described later [formic acid (C) / transition metal catalyst (D1) (metal equivalent amount)] is preferably 0.1 to 15, more preferably 0.5 to 10, even more preferably 1 to 8, and even more preferably 2 to 5. When the ratio of the transition metal catalyst (D1) to formic acid (C) is within the aforementioned range, the curing time of the unsaturated polyester resin composition is stable before and after storage, and the occurrence of warping of the molded product can be suppressed.

[0033] The unsaturated polyester resin composition of the present invention preferably further comprises at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2), and more preferably further comprises at least a transition metal catalyst (D1). Furthermore, the unsaturated polyester resin composition of the present invention more preferably further comprises a transition metal catalyst (D1) and an aromatic tertiary amine (D2). Each of these is described below.

[0034] (Transition metal catalyst (D1)) The unsaturated polyester resin composition of the present invention preferably contains a transition metal catalyst (D1). The transition metal catalyst (D1) acts as a curing accelerator when the unsaturated polyester resin composition for RTM molding of the present invention is subjected to RTM molding and cured. Furthermore, even if the unsaturated polyester resin composition of the present invention contains a transition metal catalyst (D1), the inclusion of formic acid (C) together makes it possible to stabilize the curing time before and after storage. The transition metal catalyst (D1) is not particularly limited as long as it can function as a curing accelerator, but examples include metal soaps such as cobalt naphthenate, cobalt octoate (2-ethylhexanoate cobalt), zinc octoate (2-ethylhexanoate zinc), vanadium octoate (2-ethylhexanoate vanadium), cobalt caprylate, zinc caprylate, vanadium caprylate, copper naphthenate, and barium naphthenate; and metal chelates such as vanadium acetylacetate, cobalt acetylacetate, and iron acetylacetonate. Among these, the transition metal catalyst (D1) is preferably a metal soap, from the viewpoint of stabilizing the curing time of the unsaturated polyester resin composition before and after storage and suppressing the occurrence of warping of the molded product.

[0035] The organic acids constituting the metal soaps are preferably at least one of octic acid (2-ethylhexanoic acid), n-caprylic acid, and neodecanoic acid, more preferably at least one of octic acid (2-ethylhexanoic acid) and neodecanoic acid, and even more preferably octic acid (2-ethylhexanoic acid) and neodecanoic acid. The transition metal constituting the metal soaps (transition metal catalyst (D1)) is preferably at least one of cobalt, zinc, vanadium, copper, and barium, and more preferably at least one of cobalt and copper. Even more preferably, the transition metal constituting the metal soaps (transition metal catalyst (D1)) includes both cobalt and copper. Among these, the transition metal catalyst (D1) is preferably a salt of an organic acid and a transition metal, which is at least one of cobalt and copper (i.e., at least one selected from the group consisting of organic salts of cobalt and organic salts of copper), from the viewpoint of stabilizing the curing time of the unsaturated polyester resin composition before and after storage and suppressing the occurrence of warping of the molded product. More preferably, it is a salt of an organic acid, which is at least one of octic acid (2-ethylhexanoic acid) and neodecanoic acid, and a transition metal, which is at least one of cobalt and copper. Even more preferably, it is cobalt octoate (cobalt 2-ethylhexanoate) and copper neodecanoate.

[0036] The content of the transition metal catalyst (D1) is preferably 0.001 to 3 parts by mass, more preferably 0.005 to 1 part by mass, even more preferably 0.008 to 0.1 parts by mass, and even more preferably 0.01 to 0.04 parts by mass, based on a metal equivalent, per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). Here, the metal equivalent content of the transition metal catalyst (D1) refers to the total metal equivalent amounts of the two or more transition metal catalysts if two or more transition metal catalysts are included. In this specification, similar descriptions shall have the same meaning. The content of the transition metal catalyst (D1) in the unsaturated polyester resin composition is preferably 0.001 to 3% by mass, more preferably 0.005 to 1% by mass, even more preferably 0.008 to 0.1% by mass, and even more preferably 0.01 to 0.04% by mass, in terms of metal. When the content of the transition metal catalyst (D1) is within the aforementioned range, the curing time of the unsaturated polyester resin composition is stable before and after storage, and the occurrence of warping of the molded product can be suppressed. Furthermore, when the transition metal catalyst (D1) is a cobalt organic acid salt and a copper organic acid salt, the mass ratio [cobalt / copper] of the cobalt organic acid salt to the copper equivalent amount of the copper organic acid salt (copper content in the copper organic acid salt) is preferably 5 to 25, more preferably 10 to 20, and even more preferably 12 to 18. When the mass ratio [cobalt / copper] of the cobalt-equivalent amount

[0037] (Aromatic tertiary amine (D2)) The unsaturated polyester resin composition of the present invention preferably contains an aromatic tertiary amine (D2). The aromatic tertiary amine (D2) acts as a curing accelerator or curing co-accelerator when the RTM molding unsaturated polyester resin composition of the present invention is subjected to RTM molding and cured. Furthermore, together with formic acid (C), the aromatic tertiary amine (D2) also contributes to stabilizing the curing time of the unsaturated polyester resin composition before and after storage. Examples of aromatic tertiary amines (D2) include, preferably, N,N-substituted anilines such as N,N-dimethylaniline and N,N-diethylaniline; N,N-substituted p-toluidines such as N,N-dimethyl-p-toluidine, N,N-bis(2-hydroxyethyl)-p-toluidine, and N,N-bis(2-hydroxypropyl)-p-toluidine; and 4-(N,N-substituted amino) benzaldehydes such as 4-(N,N-dimethylamino)benzaldehyde, 4-[N,N-bis(2-hydroxyethyl)amino]benzaldehyde, and 4-(N-methyl-N-hydroxyethylamino)benzaldehyde. Among these, at least one of N,N-dimethylaniline and N,N-diethylaniline is preferred, and N,N-dimethylaniline is more preferred. The content of aromatic tertiary amine (D2) is preferably 0.01 to 1 part by mass, 0.05 to 0.5 parts by mass, more preferably 0.06 to 0.2 parts by mass, and even more preferably 0.07 to 0.1 parts by mass, based on 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). The content of aromatic tertiary amine (D2) in the unsaturated polyester resin composition is preferably 0.01 to 1% by mass, 0.05 to 0.5% by mass, more preferably 0.06 to 0.2% by mass, and even more preferably 0.07 to 0.1% by mass. When the content of aromatic tertiary amine (D2) is within the aforementioned range, the curing time of the unsaturated polyester resin composition is stable before and after storage, and the occurrence of warping of molded articles can be suppressed. The mass ratio of aromatic tertiary amine (D2) to formic acid (C) [aromatic tertiary amine (D2) / formic acid (C)] is preferably 0.1 to 10, more preferably 0.5 to 5, and even more preferably 1 to 3. When the ratio of formic acid (C) to aromatic tertiary amine (D2) is within the aforementioned range, the curing time of the unsaturated polyester resin composition is stable before and after storage, and the occurrence of warping in molded products tends to be suppressed.

[0038] (Other ingredients) The unsaturated polyester resin composition of the present invention may contain other components as long as they do not interfere with the effects of the present invention. Other such components include, for example, colorants such as pigments and dyes, polymerization inhibitors, defoamers, and drying agents. These other components may be included in the unsaturated polyester resin composition during use (RTM molding), depending on the application. Polymerization inhibitors are added to prevent gelation during manufacturing, ensure pot life during molding, and improve storage stability. Polymerization inhibitors may be added during the synthesis of unsaturated polyester resins, mixed simultaneously when mixing unsaturated polyester resins and unsaturated monomers, or added immediately before use. In particular, it is preferable to mix them during the synthesis of unsaturated polyester resins or when mixing unsaturated polyester resins and unsaturated monomers. Suitable polymerization inhibitors include polyhydric phenol-based polymerization inhibitors such as methylhydroquinone, hydroquinone, toluhydroquinone, trimethylhydroquinone, and tert-butylcatechol, and quinone-based polymerization inhibitors such as parabenzoquinone and toluquinone. The content of the polymerization inhibitor in the unsaturated polyester resin composition is preferably 0.001 to 0.5% by mass, and more preferably 0.005 to 0.15% by mass.

[0039] Antifoaming agents are added to prevent foam from being mixed in when blending resins, unsaturated monomers, etc., or during molding. It is preferable to mix the antifoaming agent at the same time as mixing the unsaturated polyester resin and the unsaturated monomers. Suitable defoaming agents include silicone-based defoaming agents, and more preferably dimethylsiloxane. The content of the defoaming agent in the unsaturated polyester resin composition is preferably 0.0005 to 0.05% by mass, and more preferably 0.001 to 0.01% by mass.

[0040] The drying agent is added to completely cure surfaces that come into contact with air. It is preferable to mix the drying agent at the same time as mixing the unsaturated polyester resin and the unsaturated monomer, and depending on its melting point, it is preferable to mix it while heating. Paraffin is preferred as the drying agent, and paraffin wax is more preferred. The drying agent content is preferably 0.05 to 0.5% by mass, and more preferably 0.1 to 0.3% by mass, in the unsaturated polyester resin composition.

[0041] (Method for producing unsaturated polyester resin composition for RTM molding) As described above, the unsaturated polyester resin composition for RTM molding of the present invention contains an unsaturated polyester resin for RTM molding (A), an unsaturated monomer (B), and formic acid (C). There are no particular restrictions on the method of manufacturing the composition, but it is preferable to manufacture it by the method shown below.

[0042] The unsaturated polyester resin (A) and the unsaturated monomer (B) are mixed. Since the unsaturated polyester resin (A) is solid at room temperature, it is dissolved in the unsaturated monomer (B), which is a diluent, to obtain a uniform, high-viscosity liquid. Next, formic acid (C), and optionally a transition metal catalyst (D1), aromatic tertiary amine (D2), and other components (hereinafter also referred to as optional components) are mixed into the resulting liquid (mixture). Furthermore, if the RTM molding unsaturated polyester resin composition contains optional components, the mixing order of formic acid and the optional components is not particularly limited. The mixture of the unsaturated polyester resin (A) and the unsaturated monomer (B) may be mixed with formic acid (C) and the optional components simultaneously, or the optional components may be mixed after the formic acid (C), or the formic acid (C) may be mixed after the optional components. Furthermore, when incorporating components with a high melting point, such as paraffin wax, heating may be added as necessary to dissolve the components. The heating temperature is not particularly limited as long as it does not hinder the effects of the present invention, but is preferably 40 to 70°C. Furthermore, when a polymerization inhibitor is included and the unsaturated polyester resin composition is heated during production, it is preferable to mix the components that require heating first, then return them to room temperature (for example, 10 to 40°C, preferably 15 to 35°C) before mixing. The unsaturated polyester resin composition obtained in this way has a stable curing time regardless of the storage period and can suppress the occurrence of warping in molded products obtained by RTM molding.

[0043] [Molding material] The molding material of the present invention comprises the above-described unsaturated polyester resin composition for RTM molding and a curing agent.

[0044] The hardening agent is used during molding to quickly obtain a homogeneous hardened product. Examples of curing agents include ketone peroxides such as methyl ethyl ketone peroxide and acetylacetone peroxide, diacyl peroxides such as benzoyl peroxide, peroxyesters such as t-butyl peroxybenzoate, hydroperoxides such as cumene hydroperoxide, and dialkyl peroxides such as dicumyl peroxide. The curing agent may be used alone or in combination of two or more types. The type and amount of curing agent can be varied depending on the application, but among these, ketone peroxide-based curing agents are preferred from the viewpoint of room-temperature curing. The curing agent content is preferably 0.05 to 5 parts by mass per 100 parts by mass of the unsaturated polyester resin composition.

[0045] Furthermore, the molding material of the present invention may further include a photoradical initiator to adjust the curing rate. Examples of photoradical initiators include benzophenone-based compounds such as benzophenone, benzyl, and methyl orthobenzoyl benzoate; benzoin ether-based compounds such as benzoin alkyl ethers; acetophenone-based compounds such as benzyl dimethyl ketal, 2,2-diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, and 1,1-dichloroacetophenone; and thioxanthone-based compounds such as 2-chlorothioxanthone, 2-methylthioxanthone, and 2-isopropylthioxanthone. Photoradical initiators may be used individually or in combination of two or more. The content of the photoradical initiator is preferably 0.1 to 5 parts by mass per 100 parts by mass of the unsaturated polyester resin composition.

[0046] [Molded articles and methods for manufacturing molded articles] The molded article of the present invention is a molded article obtained by RTM molding of the unsaturated polyester resin composition. Preferably, the molded article of the present invention is a molded article obtained by RTM molding using a molding material comprising the unsaturated polyester resin composition and a curing agent. Because the molded article of the present invention uses the aforementioned unsaturated polyester resin composition, the occurrence of warping is suppressed. Furthermore, the unsaturated polyester resin composition for RTM molding used in the molded article of the present invention is suitable for RTM molding, and therefore can be molded under any molding conditions when used in an RTM molding method. RTM molding can typically be performed by mixing a curing agent into the unsaturated polyester resin composition for RTM molding, injecting it into a mold, and heating it as needed to form the resin. The RTM molding methods used to form the molded articles of the present invention include L-RTM molding methods, VaRTM (Vacuum Assisted Resin Transfer Molding) molding methods, and HP-RTM (High Pressure Resin Transfer Molding) molding methods. However, from the viewpoint of fully demonstrating the warping suppression effect of the present invention, the L-RTM molding method is particularly preferred.

[0047] A method for manufacturing a molded article according to one aspect of the present invention will be described below. The present invention provides a method for producing a molded article, comprising the steps of blending a curing agent into the unsaturated polyester resin composition, injecting it into a mold, and impregnating a reinforcing substrate placed inside the mold. More specifically, when the method for manufacturing the molded article of the present invention is performed by L-RTM molding, it is usually carried out by the following operations. First, prepare a mold consisting of a clampable upper and lower mold (male and female), and apply gel coat or the like to the lower mold as needed. Place the reinforcing substrate in this lower mold. Note that the lower mold can be made of resin or the like. Next, an upper mold made of resin or the like is placed over the lower mold so as to cover the reinforcing substrate which is placed as needed, and the mold is clamped under reduced pressure inside the mold. After that, an unsaturated polyester resin composition (corresponding to the molding material) containing a curing agent is injected into the mold under reduced pressure inside the mold, impregnated into the reinforcing substrate, and cured to obtain a molded body. The conditions for L-RTM molding are not particularly limited as long as they are generally known conditions. The mold temperature can be adjusted as appropriate depending on the type of curing agent, but is preferably 10 to 40°C (more preferably 15 to 35°C), and the pressure inside the mold is preferably 100 kPa or less. When heating and curing during L-RTM molding, it is preferable to maintain the mold temperature at a predetermined temperature for a certain period of time, cure it, then slowly cool it, and demold it. The curing time during L-RTM molding can be adjusted as appropriate depending on the size of the molded body, the type of curing agent, etc., but is preferably 10 to 100 minutes.

[0048] Suitable reinforcing materials include, for example, fiber-reinforced materials such as glass fibers, carbon fibers, and aramid fibers. As the fiber-reinforced material, at least one selected from the group consisting of glass fibers and carbon fibers is preferred. The form of the reinforcing material is not particularly limited; woven fabrics, nonwoven fabrics, etc., can be used, and these may also be used in the form of a preform formed by laminating and shaping them as needed. Furthermore, a core material may be used along with the reinforcing substrate to ensure the fluidity of the resin. When a core material is used, the reinforcing substrate may be laminated on one side of the core material or on both sides of the core material. Examples of such core materials include carbon fibers, glass fibers, aramid fibers, metal fibers, nylon fibers, polyester fibers, and polypropylene fibers, but polypropylene fibers are preferred. The form of the core material is not particularly limited and may include woven fabrics, nonwoven fabrics, etc., but nonwoven fabrics are preferred.

[0049] The method for manufacturing a molded article of the present invention may include a step of storing the unsaturated polyester resin composition for a long period of time before the step of injecting it into the mold described above. This is preferable because the effects of the present invention can be more significantly exhibited by including the long-term storage step. The unsaturated polyester resin composition is usually stored at room temperature or ambient temperature. The storage period is not particularly limited, but from the viewpoint of more significantly demonstrating the effects of the present invention, it is, for example, one week or more, preferably two weeks or more, more preferably three weeks or more, and even more preferably one month or more. Furthermore, there is no particular upper limit to the storage period as long as the effects of the present invention can be achieved, but it is preferably within three months. The starting point for calculating the storage period is as follows: if the RTM molding unsaturated polyester resin composition does not contain a transition metal catalyst (D1) and an aromatic tertiary amine (D2), the starting point is the time when at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2) is mixed into the RTM molding unsaturated polyester resin composition (if both the transition metal catalyst (D1) and the aromatic tertiary amine (D2) are mixed, the starting point is the time when both the transition metal catalyst (D1) and the aromatic tertiary amine (D2) are mixed into the RTM molding unsaturated polyester resin composition); if the RTM molding unsaturated polyester resin composition contains at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2), the starting point is immediately after the preparation (immediately after manufacturing) of the RTM molding unsaturated polyester resin composition. Furthermore, it is preferable to have a step after the storage step in which a curing agent is added to the stored composition, injected into a mold, and impregnated into the reinforcing substrate placed inside the mold. In other words, the method for manufacturing a molded article according to the present invention is The process includes the steps of storing an unsaturated polyester resin composition for RTM molding for three weeks or more, and after storage, blending a curing agent into the unsaturated polyester resin composition for RTM molding, injecting it into a mold, and impregnating a reinforcing substrate placed inside the mold. The RTM molding unsaturated polyester resin composition comprises an unsaturated polyester resin (A), an unsaturated monomer (B), formic acid (C), and at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2). The unsaturated polyester resin (A) comprises a constituent unit derived from an acid component and a constituent unit derived from an alcohol component, wherein the acid component includes phthalic anhydride and an unsaturated dibasic acid, the alcohol component includes at least one of ethylene glycol and diethylene glycol and propylene glycol, and the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid. The unsaturated monomer (B) is at least one selected from the group consisting of styrene monomers and acrylic monomers. Preferably, the method for producing a molded article is such that the formic acid (C) content is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B).

[0050] Furthermore, when manufacturing the unsaturated polyester resin composition for RTM molding, the order of addition of formic acid (C) and at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2) is not particularly limited. Formic acid (C) and at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2) may be added simultaneously. Formic acid (C) may be added first, followed by at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2). Formic acid (C) may be added after at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2). The present invention's method for manufacturing molded articles utilizes a specific unsaturated polyester resin composition containing formic acid, thereby stabilizing the curing time regardless of the storage period. This facilitates adjustment of the demolding timing, improving product yield. Because it is possible to suppress significant changes in the curing time of the unsaturated polyester resin composition between immediately after preparation and after long-term storage, it is possible to improve production efficiency without delaying the demolding timing even after long-term storage of the composition. Furthermore, it is possible to suppress the occurrence of warping in the resulting molded articles.

[0051] Furthermore, the aforementioned RTM molding unsaturated polyester resin composition is suitable for long-term storage (preservation) because its curing time is stable regardless of the storage period. In other words, the storage method for the RTM molding unsaturated polyester resin composition of the present invention is: The process includes storing the unsaturated polyester resin composition for RTM molding for three weeks or more. The RTM molding unsaturated polyester resin composition comprises an unsaturated polyester resin (A), an unsaturated monomer (B), formic acid (C), and at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2). The unsaturated polyester resin (A) comprises a constituent unit derived from an acid component and a constituent unit derived from an alcohol component, wherein the acid component includes phthalic anhydride and an unsaturated dibasic acid, the alcohol component includes at least one of ethylene glycol and diethylene glycol and propylene glycol, and the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid. The unsaturated monomer (B) is at least one selected from the group consisting of styrene monomers and acrylic monomers. The storage method is such that the formic acid (C) content is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). The storage period for the RTM molding unsaturated polyester resin composition may be, for example, one week or more, two weeks or more, preferably three weeks or more, and more preferably one month or more. There is no upper limit, but preferably three months or less. By having a long-term storage process, the effect of the present invention, which is that the curing time is stable regardless of the storage period, can be exhibited more significantly.

[0052] According to the storage method for the unsaturated polyester resin composition for RTM molding of the present invention, since the unsaturated polyester resin composition is used, the curing time of the composition can be stabilized regardless of the storage period. Therefore, the timing of demolding can be easily adjusted, and the product yield can be improved. Since it is possible to suppress a large change in the curing time of the unsaturated polyester resin composition between immediately after preparation and after long-term storage, it is possible to improve production efficiency without delaying the timing of demolding even after long-term storage. Furthermore, when using an unsaturated polyester resin composition stored by this storage method, the occurrence of warping of molded articles obtained by RTM molding can be suppressed. [Examples]

[0053] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The measurements and evaluations in these examples were performed by the following methods.

[0054] <Evaluation of curvature> [Warpage of unsaturated polyester resin composition immediately after manufacturing] Following the preparation of unsaturated polyester resin compositions according to the examples and comparative examples, immediately afterward, 1 part by mass of Permec N (manufactured by NOF Corporation, methyl ethyl ketone peroxide, purity 55% by mass, diluted with dimethyl phthalate) was added as a curing agent to 100 parts by mass of the unsaturated polyester resin composition and mixed to obtain a molding material (unsaturated polyester resin composition mixed with curing agent). Then, L-RTM molding was performed promptly as described below, and the resulting molded product (molded body) was evaluated for warpage. (L-RTM molding) Gel coat was applied to the lower mold. Next, chopped strand mat (300g / m²) was applied. 2 (Weight), glass roving cloth (570g / m²) 2 (Balance weight), and polypropylene nonwoven fabric (manufactured by F.R.P. Service Co., Ltd., product name: Robicore, 300g / m²). 2 Chopped strand mat with a weight of 180g / m² 2(Mat made of polypropylene nonwoven fabric), glass surface mat (30g / m²) 2 The material (based on the weight) was placed on the lower mold in this order from bottom to top. Next, the upper mold was placed over the lower mold so as to cover the side of the lower mold where the chopped strand mat and polypropylene nonwoven fabric were placed, and then fixed in place. The molding material was injected into the mold at room temperature (29°C) while reducing the pressure inside the mold to 0.5 kPa until the molding material filled the entire inside of the mold. After 90 minutes, the mold was opened to the atmosphere and demolded to obtain a molded product (a plate-like object measuring 1 m x 3 m x 1 cm thick).

[0055] (Method for evaluating warping) The molded parts were left at room temperature after demolding, and their warping was visually inspected the day after demolding. Specifically, when warping occurs in a molded plate-like object, the warping occurs at the periphery, resulting in a concave shape (a shape in which the cross-section in the thickness direction is curved like an arc). Therefore, the plate-like object was placed on a horizontal table with the concave side facing upwards and the convex central part in contact with the table (placed so that the periphery of the plate-like object is slightly elevated). The distance h (the maximum vertical distance between the upper surface of the plate-like object and the horizontal surface of the table at the periphery of the plate-like object) was measured, and the value obtained by subtracting the thickness of the plate-like object (1.0 cm) from distance h (h - [thickness of plate-like object]) was used as the amount of warping and evaluated according to the following criteria. The results are shown in Table 1. ◎: Warpage of the molded product is less than 1 cm (Excellent, judged to maintain the shape upon demolding) ○: The amount of warping of the molded product is 1 cm or more but less than 2 cm (judged as not posing a practical problem). ×: The amount of warping of the molded product is 2 cm or more (the molded product is curved and deemed unusable).

[0056] [Warpage of unsaturated polyester resin composition one month after manufacturing] After producing unsaturated polyester resin compositions according to the examples and comparative examples, the obtained unsaturated polyester resin compositions were filled into square cans, sealed with lids, and stored at 40°C for one month. The unsaturated polyester resin compositions after storage were subjected to L-RTM molding in the same manner as described above (L-RTM molding), and the warpage of each molded product the day after demolding was evaluated using the same criteria as described above (Warpage Evaluation Method). The results are shown in Table 1.

[0057] <Evaluation of changes over time in gelling time and minimum curing time> Following the production of unsaturated polyester resin compositions according to the examples and comparative examples, the gelation time (hereinafter also referred to as the initial gelation time) and minimum curing time (hereinafter also referred to as the initial minimum curing time) of each unsaturated polyester resin composition immediately after production were measured. Furthermore, 333g of each obtained unsaturated polyester resin composition was filled into 300mL square cans, which were then sealed with lids. These square cans were stored at 40°C for one month, and the gelation time (hereinafter also referred to as the gelation time after one month) and minimum curing time (hereinafter also referred to as the minimum curing time after one month) were measured for each unsaturated polyester resin composition after one month. Here, the initial gelation time and initial minimum curing time, as well as the gelation time and minimum curing time after one month, were measured according to JIS K 6901:2008 (exothermic method, curing characteristics at 25°C). Permec N (manufactured by NOF Corporation, methyl ethyl ketone peroxide, purity 55% by mass, diluted with dimethyl phthalate) was added as a curing agent at a rate of 1 part by mass per 100 parts by mass of the unsaturated polyester resin composition. The change in gelation time over time was evaluated by calculating the difference between the initial gelation time and the gelation time after one month, and evaluating it according to the following criteria. The results are shown in Table 1. If the difference in gelation time was less than 10 minutes, it was marked as "◎" (very good); if the difference in gelation time was 10 minutes or more but less than 20 minutes, it was marked as "〇" (good); and if the difference in gelation time was 20 minutes or more, it was marked as "×" (poor). Similarly, the change in minimum curing time over time was evaluated by calculating the difference between the initial minimum curing time and the minimum curing time after one month, and evaluating it according to the following criteria. The results are shown in Table 1. If the difference in minimum curing time was less than 10 minutes, it was marked as "◎" (very good); if the difference in minimum curing time was 10 minutes or more but less than 20 minutes, it was marked as "〇" (good); and if the difference in minimum curing time was 20 minutes or more, it was marked as "×" (poor).

[0058] <Manufacturing of unsaturated polyester resin> Manufacturing Example 1 In a four-necked flask equipped with a stirrer, thermometer, inert gas inlet tube, and reflux condenser, 60.0 moles of phthalic anhydride, 40.0 moles of maleic anhydride, 69.0 moles of propylene glycol, and 40.0 moles of ethylene glycol were charged and heated at 215°C to dehydrate and condense, yielding an unsaturated polyester resin (A1) with an acid value of 18 mg KOH / g. Manufacturing Example 2 In a four-necked flask equipped with a stirrer, thermometer, inert gas inlet tube, and reflux condenser, 56.0 moles of phthalic anhydride, 44.0 moles of maleic anhydride, 65.3 moles of propylene glycol, and 43.5 moles of diethylene glycol were charged and heated at 215°C to dehydrate and condense, yielding an unsaturated polyester resin (A2) with an acid value of 12 mg KOH / g.

[0059] <Manufacturing of unsaturated polyester resin compositions> Example 1 The unsaturated polyester resin (A1) obtained in Production Example 1, styrene, formic acid, 8% cobalt octoate (manufactured by Nippon Chemical Industries, Ltd., Nikka Octix® Cobalt, cobalt content: 8% by mass), 5% copper neodecanoate (manufactured by Nippon Chemical Industries, Ltd., copper neodecanoate, copper content: 5% by mass), N,N-dimethylaniline, trimethylsiloxane-terminated dimethylsiloxane (manufactured by Dow Toray Industries, Ltd., SH-200), paraffin wax (manufactured by Nippon Seiro Co., Ltd., WAX-125), and hydroquinone were placed in a container in the amounts shown in Table 1 and heated and mixed until uniform to obtain an unsaturated polyester resin composition (viscosity 250 mPa·s at 25°C).

[0060] Example 2 and Comparative Example 2 An unsaturated polyester resin composition was obtained in the same manner as in Example 1, except that the types and amounts of raw materials for the unsaturated polyester resin composition were as shown in Table 1. The viscosity of the unsaturated polyester resin composition in Example 2 at 25°C was 250 mPa·s.

[0061] Comparative Example 1 The unsaturated polyester resin (A2) obtained in Production Example 2, styrene, 12% cobalt octoate (manufactured by Nippon Chemical Industrial Co., Ltd., Nikka Octix® Cobalt, cobalt content: 12% by mass), N,N-dimethylaniline, and methylhydroquinone were placed in a container in the amounts shown in Table 1 and heated and mixed until uniform to obtain an unsaturated polyester resin composition.

[0062] [Table 1] *1 In Table 1, 8% cobalt octoate refers to cobalt octoate with a Co concentration of 8% by mass (manufactured by Nippon Chemical Industrial Co., Ltd.), and the Co equivalent amount for Examples 1 and 2 and Comparative Example 2 is 0.024 parts by mass. *2 In Table 1, 5% copper neodecanoate refers to copper neodecanoate with a copper concentration of 5% (manufactured by Nippon Chemical Industrial Co., Ltd.), and the copper equivalent amount for Examples 1 and 2 and Comparative Example 2 is 0.0015 parts by mass. *3 In Table 1, 12% cobalt octoate refers to cobalt octoate with a Co concentration of 12% by mass (manufactured by Nippon Chemical Industrial Co., Ltd.), and the Co equivalent amount for Comparative Example 1 is 0.018 parts by mass. *4 In Table 1, "PG" represents propylene glycol, "EG" represents ethylene glycol, and "DEG" represents diethylene glycol. *5 In Table 1, "PAN" represents phthalic anhydride and "MAN" represents maleic anhydride.

[0063] As shown in Table 1, the unsaturated polyester resin compositions of the examples showed the same curing time as the unsaturated polyester resin compositions immediately after manufacture, even after being stored for one month. Furthermore, no warping was observed in the molded products obtained by RTM molding using the unsaturated polyester resin compositions of the examples. Thus, the unsaturated polyester resin composition for RTM molding of the present invention can reduce the change in curing time before and after storage, and stabilize the curing time to a constant time. Furthermore, by performing RTM molding using the unsaturated polyester resin composition for RTM molding of the present invention, warping of the molded product can be suppressed, and production efficiency can be improved.

Claims

1. An unsaturated polyester resin composition for RTM molding comprising an unsaturated polyester resin (A) and an unsaturated monomer (B), The unsaturated polyester resin (A) comprises a constituent unit derived from an acid component and a constituent unit derived from an alcohol component, wherein the acid component includes phthalic anhydride and an unsaturated dibasic acid, the alcohol component includes at least one of ethylene glycol and diethylene glycol and propylene glycol, and the unsaturated dibasic acid is at least one selected from the group consisting of maleic anhydride, maleic acid and fumaric acid. The unsaturated monomer (B) is at least one selected from the group consisting of styrene monomers and acrylic monomers. The aforementioned unsaturated polyester resin composition for RTM molding contains formic acid (C), The formic acid (C) content is 0.01 to 0.1 parts by mass per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B). Unsaturated polyester resin composition for RTM molding.

2. The unsaturated polyester resin composition for RTM molding according to claim 1, further comprising at least one selected from the group consisting of a transition metal catalyst (D1) and an aromatic tertiary amine (D2).

3. The unsaturated polyester resin composition for RTM molding according to claim 1, further comprising a transition metal catalyst (D1) and an aromatic tertiary amine (D2).

4. The unsaturated polyester resin composition for RTM molding according to claim 2 or 3, wherein the transition metal catalyst (D1) is at least one selected from the group consisting of organic salts of cobalt and organic salts of copper.

5. The unsaturated polyester resin composition for RTM molding according to claim 1 or 2, wherein the total content of phthalic anhydride and the unsaturated dibasic acid in the acid component is 90 to 100 mol%.

6. The unsaturated polyester resin composition for RTM molding according to claim 1 or 2, wherein the total content of ethylene glycol, diethylene glycol, and propylene glycol in the alcohol component is 90 to 100 mol%.

7. The unsaturated polyester resin composition for RTM molding according to claim 1 or 2, wherein the molar ratio of phthalic anhydride to an unsaturated dibasic acid [phthalic anhydride / unsaturated dibasic acid] is 55 / 45 to 65 / 35.

8. The unsaturated polyester resin composition for RTM molding according to claim 1 or 2, wherein the molar ratio [alcohol component / acid component] of constituent units derived from the alcohol component to constituent units derived from the acid component is 1.0 to 1.

2.

9. The unsaturated polyester resin composition for RTM molding according to claim 1 or 2, wherein the viscosity of the RTM molding unsaturated polyester resin composition at 25°C is 30 to 2000 mPa·s.

10. The unsaturated polyester resin composition for RTM molding according to claim 2 or 3, wherein the mass ratio of formic acid (C) to the metal equivalent amount of the transition metal catalyst (D1) [(C) / (D1)(metal equivalent amount)] is 0.1 to 15.

11. The unsaturated polyester resin composition for RTM molding according to claim 2 or 3, wherein the content of the transition metal catalyst (D1) is 0.001 to 3 parts by mass, in terms of metal, per 100 parts by mass of the total amount of the unsaturated polyester resin (A) and the unsaturated monomer (B).

12. The unsaturated polyester resin composition for RTM molding according to claim 1 or 2, wherein the mass ratio [(A) / (B)] of the unsaturated polyester resin (A) to the unsaturated monomer (B) is 50 / 50 to 70 / 30.

13. An unsaturated polyester resin composition for RTM molding according to claim 1 or 2, which is for L-RTM molding.

14. A molding material comprising the unsaturated polyester resin composition for RTM molding according to claim 1 or 2, and a curing agent.

15. A method for producing a molded article, comprising the steps of blending a curing agent into the RTM molding unsaturated polyester resin composition according to claim 1 or 2, injecting it into a mold, and impregnating a reinforcing substrate placed inside the mold.

16. A method for producing a molded article, comprising the steps of storing the unsaturated polyester resin composition for RTM molding described in claim 2 or 3 for three weeks or more, and blending a curing agent into the stored unsaturated polyester resin composition for RTM molding, injecting it into a mold, and impregnating a reinforcing substrate placed inside the mold.

17. A molded article obtained by RTM molding the unsaturated polyester resin composition for RTM molding described in claim 1 or 2.

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