Rosin-modified unsaturated polyester, rosin-modified unsaturated polyester composition, and molded body

Abstract

The purpose of the present invention is to provide a rosin-modified unsaturated polyester capable of forming a cured product having excellent surface hardness and water resistance. A rosin-modified unsaturated polyester according to the present invention is characterized by having a methanol tolerance at 25°C of 100 g or less. As the rosin-modified unsaturated polyester, a polycondensate of raw material compounds including a polyol (Y) and carboxylic acids (X) containing rosins (a) and α,β-unsaturated dicarboxylic acids (b) is preferably used. According to the present invention, it is possible to provide a rosin-modified unsaturated polyester capable of forming a cured product having excellent surface hardness and water resistance.

Description

Rosin-modified unsaturated polyester, rosin-modified unsaturated polyester composition, and molded article

[0001] The present invention relates to a rosin-modified unsaturated polyester, a rosin-modified unsaturated polyester composition, and a molded article.

[0002] BACKGROUND ART Cured products of unsaturated polyester compositions have been widely used as molded articles in a variety of applications, such as buildings, automobiles, aircraft, ships, and electronic devices, because of their excellent moldability and appearance.

[0003] In recent years, from the viewpoint of environmental issues, there has been an increasing demand for fiber-reinforced plastics (FRPs) that are lightweight and have excellent mechanical strength, for example, in fields such as ship hulls, bathtubs, construction materials, and industrial equipment. In fiber-reinforced plastics, unsaturated polyester compositions are used as binders for integrating reinforcing fibers. Fiber-reinforced plastics are produced by impregnating reinforcing fibers with the unsaturated polyester composition and then curing the composition.

[0004] The unsaturated polyester composition contains an unsaturated polyester, a radically polymerizable monomer, and, if necessary, a polymerization initiator or a curing agent. The unsaturated polyester is generally obtained by polycondensation of a carboxylic acid, including an α,β-unsaturated dicarboxylic acid, with a polyol. The unsaturated polyester composition can be cured by copolymerizing the unsaturated polyester and the radically polymerizable monomer, thereby obtaining a molded article.

[0005] Patent Document 1 discloses an unsaturated polyester composition containing an unsaturated polyester and a polymerizable monomer. The unsaturated polyester is composed of an acid component containing an aromatic dicarboxylic acid, a monocarboxylic acid, and an unsaturated dicarboxylic acid, and an alcohol component containing a trihydric or higher polyhydric alcohol and a dihydric alcohol. The monocarboxylic acid used may be a rosin-based compound or an aliphatic monocarboxylic acid having 4 to 36 carbon atoms derived from biomass.

[0006] JP 2010-235777 A

[0007] However, conventional unsaturated polyester compositions do not have sufficiently excellent surface hardness and water resistance after curing, and further improvements are desired.

[0008] Therefore, an object of the present invention is to provide a rosin-modified unsaturated polyester capable of forming a cured product excellent in both surface hardness and water resistance. A further object of the present invention is to provide a rosin-modified unsaturated polyester composition containing the rosin-modified unsaturated polyester and a molded article thereof.

[0009] The present inventors have conducted various studies in view of the above problems and have found that the above problems can be solved by the following rosin-modified unsaturated polyester.

[0010] The present invention has the following embodiments. [1] A rosin-modified unsaturated polyester having a methanol tolerance of 100 g or less at 25°C. [2] The rosin-modified unsaturated polyester according to [1] above, having a softening point of 60°C or higher. [3] The rosin-modified unsaturated polyester according to [1] or [2] above, which is a polycondensate of raw material compounds containing rosins (a), carboxylic acids (X) including α,β-unsaturated dicarboxylic acids (b), and polyol (Y). [4] The rosin-modified unsaturated polyester according to [3] above, wherein the rosins (a) contain at least one of disproportionated rosin and hydrogenated rosin. [5] The rosin-modified unsaturated polyester according to [3] or [4] above, wherein the polyol (Y) contains a trihydric or higher polyol (d). [6] A rosin-modified unsaturated polyester composition comprising the rosin-modified unsaturated polyester according to any one of [1] to [5] above, and a polymerization inhibitor. [7] A rosin-modified unsaturated polyester composition comprising the rosin-modified unsaturated polyester described in any one of [1] to [5] above and a radical-polymerizable monomer. [8] The rosin-modified unsaturated polyester composition described in [7] above, wherein the radical-polymerizable monomer comprises at least one of styrene and methylstyrene. [9] A molded article comprising a cured product of the rosin-modified unsaturated polyester composition described in [7] or [8] above.

[0011] According to the present invention, it is possible to provide a rosin-modified unsaturated polyester capable of forming a cured product having both excellent surface hardness and water resistance. The cured product is suitably used as a molded article having a desired shape.

[0012] <Rosin-modified unsaturated polyester> The present invention relates to a rosin-modified unsaturated polyester, which is preferably characterized by having a methanol tolerance at 25°C of 100 g or less.

[0013] The rosin-modified unsaturated polyester of the present invention is modified using a rosin (a) as a raw material compound, which can improve the surface hardness after curing. However, simply using the rosin (a) not only fails to sufficiently improve the surface hardness after curing, but also sometimes results in reduced water resistance.

[0014] In view of these circumstances, the present inventors have conducted extensive research and have found that, by adjusting the methanol tolerance of a rosin-modified unsaturated polyester modified with a rosin (a) to 100 g or less, a cured product having excellent surface hardness and water resistance can be formed.

[0015] In the present invention, "methanol tolerance" is measured by, as described below, measuring the amount of methanol required to precipitate and turn cloudy when methanol is added dropwise as a poor solvent to a reference solution prepared by dissolving a rosin-modified unsaturated polyester in toluene. The more hydrophilic polar groups, such as carboxyl groups and hydroxyl groups, contained in the rosin-modified unsaturated polyester, the greater the polarity of the rosin-modified unsaturated polyester. Thus, the greater the polarity, the more difficult it becomes for the rosin-modified unsaturated polyester to precipitate in the reference solution to which methanol has been added dropwise, and the greater the methanol tolerance tends to be. Therefore, methanol tolerance can be used as an indicator of the degree of esterification of a rosin-modified unsaturated polyester.

[0016] Furthermore, by setting the methanol tolerance to 100 g or less, the carboxy groups of the carboxylic acid component containing the rosin (a) constituting the rosin-modified unsaturated polyester are sufficiently esterified with the hydroxyl groups of the polyol component, thereby increasing the degree of esterification. Thus, a rosin-modified unsaturated polyester modified with rosin (a) and having a methanol tolerance of 100 g or less and thus a high degree of esterification can be provided, which makes it possible to provide a rosin-modified unsaturated polyester composition capable of forming a cured product that is excellent in both surface hardness and water resistance. The cured product is suitably used as a molded article molded into a desired shape.

[0017] The methanol tolerance of the rosin-modified unsaturated polyester at 25°C is preferably 100 g or less, more preferably 80 g or less, more preferably 75 g or less, more preferably 70 g or less, more preferably 60 g or less, and more preferably 45 g or less.

[0018] The methanol tolerance of the rosin-modified unsaturated polyester at 25° C. is preferably 25 g or more. By making the methanol tolerance 25 g or more, the oil resistance (oil repellency) of the rosin-modified unsaturated polyester can be improved so that penetration of oil into the cured product of the rosin-modified unsaturated polyester can be reduced.

[0019] The methanol tolerance of a rosin-modified unsaturated polyester at 25°C can be measured according to the following procedure. First, 5 g of rosin-modified unsaturated polyester is dissolved in 50 mL of toluene in a transparent glass Erlenmeyer flask (volume 100 mL, preferably conforming to JIS R3503 (1994)) to obtain a reference solution. Methanol is added dropwise to the reference solution while stirring it at 25°C, and the mass (g) of methanol added until the reference solution becomes cloudy is determined. This mass (g) of methanol is defined as the methanol tolerance of the rosin-modified unsaturated polyester at 25°C. The Erlenmeyer flask is placed on a newspaper, and with the newspaper and the Erlenmeyer flask in contact, characters (10-point) printed on the newspaper are visually observed through the reference solution in the Erlenmeyer flask. The point at which the characters become indistinguishable due to the cloudiness of the reference solution is deemed to be the "clouding of the reference solution."

[0020] The softening point of the rosin-modified unsaturated polyester is preferably 50°C or higher, more preferably 55°C or higher, more preferably 60°C or higher, and even more preferably 81°C or higher. The softening point of the rosin-modified unsaturated polyester is more preferably 130°C or lower. By adjusting the softening point of the rosin-modified unsaturated polyester to 50°C or higher, the rosin-modified unsaturated polyester can exhibit higher surface hardness after curing. By adjusting the softening point of the rosin-modified unsaturated polyester to 130°C or lower, the solubility of the rosin-modified unsaturated polyester in radically polymerizable monomers in the rosin-modified unsaturated polyester composition can be improved.

[0021] The softening point of the rosin-modified unsaturated polyester is a value measured in accordance with ASTM D6090 (1997). For the measurement, a measuring device such as a "Dropping Point System DP70" manufactured by Mettler Toledo can be used. When using the measuring device, the softening point can be measured, for example, as follows. First, a stainless steel cup having a top diameter of 10 mm, a bottom hole having a diameter of 6.35 mm, and a depth of 10 mm is filled with the rosin-modified unsaturated polyester, and the cup is placed in the measuring device. The temperature is then increased from 40°C at a rate of 3°C / min. The temperature at which the rosin-modified unsaturated polyester is detected by a detector installed 19 mm vertically below the hole in the bottom of the cup is measured, and this temperature can be taken as the softening point.

[0022] The rosin-modified unsaturated polyester is preferably a polycondensate (reaction product) of raw material compounds including rosins (a), carboxylic acids (X) including α,β-unsaturated dicarboxylic acids (b), and a polyol (Y). The rosin-modified unsaturated polyester is obtained by an esterification reaction between a carboxy group of the carboxylic acid (X) and a hydroxyl group of the polyol (Y). The raw material compounds constituting the rosin-modified unsaturated polyester are described below in order.

[0023] [Carboxylic Acids (X)] The raw material compounds constituting the rosin-modified unsaturated polyester include carboxylic acids (X). The carboxylic acids (X) preferably include rosins (a) and α,β-unsaturated dicarboxylic acids (b).

[0024] (Rosins (a)) Examples of the rosins (a) include unmodified rosin (unmodified rosin) and modified rosin (rosin derivative). The rosins (a) may be used alone or in combination of two or more.

[0025] Examples of unmodified rosins include natural rosins such as gum rosin, tall oil rosin, and wood rosin; and purified rosins obtained by purifying natural rosin. Gum rosin is preferred as the natural rosin. Refined rosin can be obtained by purifying natural rosin using known purification methods such as distillation, extraction, recrystallization, and adsorption. Unmodified rosins may be used alone or in combination of two or more.

[0026] Natural rosin is a natural resin whose main component is resin acid. Natural rosin contains resin acids having conjugated double bonds. Natural rosin may also contain resin acids having no conjugated double bonds. Examples of resin acids having conjugated double bonds include abietic acid, palustric acid, neoabietic acid, and levopimaric acid. Examples of resin acids having no conjugated double bonds include dehydroabietic acid, dihydroabietic acid, and tetrahydroabietic acid. Resin acids having conjugated double bonds and resin acids having no conjugated double bonds may be used alone or in combination of two or more.

[0027] Modified rosin is a modified form of the unmodified rosin described above. Examples of modified rosin include acid-modified rosin and stabilized rosin.

[0028] Acid-modified rosin can be obtained, for example, by adding an α,β-unsaturated carboxylic acid to unmodified rosin by Diels-Alder reaction or the like. Examples of the α,β-unsaturated carboxylic acid include α,β-unsaturated carboxylic acids and their anhydrides. Specific examples include fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, citraconic anhydride, acrylic acid, and methacrylic acid. The α,β-unsaturated carboxylic acids may be used alone or in combination of two or more.

[0029] Stabilized rosin is a modified rosin obtained by subjecting unmodified rosin to a stabilization treatment. The stabilization treatment is carried out in order to reduce or eliminate the conjugated double bonds in the resin acid having the conjugated double bonds. Examples of the stabilization treatment include hydrogenation, disproportionation, and polymerization.

[0030] Therefore, examples of stabilized rosins include hydrogenated rosin, disproportionated rosin, polymerized rosin, etc. The stabilized rosins may be used alone or in combination of two or more.

[0031] Hydrogenated rosin can be obtained, for example, by hydrogenating unmodified rosin in the presence of a hydrogenation catalyst. Hydrogenated rosin can also be obtained by hydrogenating polymerized rosin. Disproportionated rosin can be obtained, for example, by disproportionating unmodified rosin in the presence of a disproportionation catalyst. Polymerized rosin is a polymer of unmodified rosin. Polymerized rosin can be obtained by polymerizing unmodified rosin in the presence of a polymerization catalyst.

[0032] The rosin (a) is preferably a modified rosin, more preferably a hydrogenated rosin or a disproportionated rosin, and more preferably a disproportionated rosin, which makes it possible to obtain a rosin-modified unsaturated polyester having a sufficient number of unsaturated bonds copolymerizable with the radically polymerizable monomer described below, and which can exhibit higher surface hardness and water resistance after curing.

[0033] For example, when an α,β-unsaturated dicarboxylic acid (b) is used as the carboxylic acid (X) to sufficiently introduce unsaturated bonds into a rosin-modified unsaturated polyester, the α,β-unsaturated dicarboxylic acid (b) may undergo a Diels-Alder reaction to add to the rosin (a), resulting in the loss of the unsaturated bonds of the α,β-unsaturated dicarboxylic acid (b). As a result, the opportunity for copolymerization between the rosin-modified unsaturated polyester and a radically polymerizable monomer is reduced, and the surface hardness of the cured product of the rosin-modified unsaturated polyester composition containing the rosin-modified unsaturated polyester may be insufficient. However, by using a modified rosin as the rosin (a), the occurrence of the Diels-Alder reaction described above can be reduced, and the loss of the unsaturated bonds of the α,β-unsaturated dicarboxylic acid (b) can be suppressed. Therefore, the double bonds derived from the α,β-unsaturated dicarboxylic acid (b) can remain in the rosin-modified unsaturated polyester. This allows the rosin-modified unsaturated polyester to be copolymerized with the radically polymerizable monomer more reliably, thereby improving the surface hardness after curing.

[0034] The content of the modified rosin in the rosins (a) is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass or more, and particularly preferably 100% by mass.

[0035] The content of the rosin (a) in the raw material compound is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more, relative to 100 parts by mass of the total amount of the carboxylic acid (X) and the polyol (Y). The content of the rosin (a) in the raw material compound is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, relative to 100 parts by mass of the total amount of the carboxylic acid (X) and the polyol (Y). By setting the content of the rosin (a) to 20 parts by mass or more, the rosin-modified unsaturated polyester can exhibit higher surface hardness and water resistance after curing. By setting the content of the rosin (a) to 70 parts by mass or less, raw material compounds other than the rosin (a) can be used in sufficient amounts.

[0036] As will be described later, the rosins (a) may contain metal atoms as unavoidable impurities. However, by setting the content of the rosins (a) to 70 parts by mass or less, it is possible to prevent the content of metal atoms from becoming unintentionally high during the production of the rosin-modified unsaturated polyester.

[0037] (α,β-Unsaturated Dicarboxylic Acids (b)) The raw material compounds constituting the rosin-modified unsaturated polyester include carboxylic acids (X). The carboxylic acids (X) preferably include α,β-unsaturated dicarboxylic acids (b) in addition to the above-mentioned rosins (a). By using the α,β-unsaturated dicarboxylic acids (b), a sufficient amount of unsaturated bonds can be introduced into the rosin-modified unsaturated polyester.

[0038] The α,β-unsaturated dicarboxylic acids (b) include α,β-unsaturated dicarboxylic acids and anhydrides thereof. The α,β-unsaturated dicarboxylic acid preferably means a chain dicarboxylic acid having two carboxy groups in one molecule and an unsaturated bond between the α- and β-carbons of at least one carboxy group.

[0039] Examples of the α,β-unsaturated dicarboxylic acid (b) include α,β-unsaturated dicarboxylic acids and their anhydrides, and α,β-unsaturated aliphatic dicarboxylic acids and their anhydrides are preferred. Specific examples include fumaric acid, itaconic acid, maleic acid, mesaconic acid, citraconic acid, glutaconic acid, and their anhydrides. Of these, fumaric acid, maleic acid, and their anhydrides are preferred, with maleic acid and maleic anhydride being more preferred, and maleic anhydride being even more preferred. The α,β-unsaturated dicarboxylic acids (b) may be used alone or in combination of two or more.

[0040] The content of the α,β-unsaturated dicarboxylic acid (b) in the raw material compounds is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and more preferably 10 parts by mass or more, relative to 100 parts by mass of the total amount of the carboxylic acid (X) and the polyol (Y). The content of the α,β-unsaturated dicarboxylic acid (b) in the raw material compounds is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, more preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and more preferably 18 parts by mass or less, relative to 100 parts by mass of the total amount of the carboxylic acid (X) and the polyol (Y). By ensuring that the content of the α,β-unsaturated dicarboxylic acid (b) is 5 parts by mass or more, a sufficient amount of unsaturated bonds can be introduced into the rosin-modified unsaturated polyester. This allows a rosin-modified unsaturated polyester composition containing the rosin-modified unsaturated polyester to exhibit higher surface hardness and water resistance after curing. On the other hand, as the content of the rosin (a) increases, polymerization of the α,β-unsaturated dicarboxylic acids (b) may occur, resulting in gelation of the rosin-modified unsaturated polyester. In order to reduce such gelation, it is preferable to set the content of the α,β-unsaturated dicarboxylic acids (b) to 50 parts by mass or less.

[0041] Furthermore, as described below, rosins (a) may contain metal atoms as unavoidable impurities, but when the rosins (a) are contained in a high content, for example, 50 parts by mass or more, relative to 100 parts by mass of the total of the carboxylic acids (X) and the polyol (Y), the content of the α,β-unsaturated dicarboxylic acids (b) in the raw material compounds is preferably 15 parts by mass or less, relative to 100 parts by mass of the total of the carboxylic acids (X) and the polyol (Y). This makes it possible to reduce gelation of the rosin-modified unsaturated polyester, which is caused by metal atoms acting as a polymerization catalyst to promote polymerization of the α,β-unsaturated dicarboxylic acids (b) themselves, in the second esterification step described below.

[0042] (Other Carboxylic Acids (c)) The raw material compounds constituting the rosin-modified unsaturated polyester include carboxylic acids (X). The carboxylic acids (X) preferably further include other carboxylic acids (c) in addition to the above-mentioned rosins (a) and α,β-unsaturated dicarboxylic acids (b). Note that the above-mentioned other carboxylic acids (c) exclude the rosins (a) and α,β-unsaturated dicarboxylic acids (b).

[0043] Examples of the other carboxylic acids (c) include monocarboxylic acids (c1) and polycarboxylic acids (c2). The other carboxylic acids (c) may be used singly or in combination of two or more. Note that the rosins (a) are excluded from the monocarboxylic acids (c1). Furthermore, the rosins (a) and α,β-unsaturated dicarboxylic acids (b) are excluded from the polycarboxylic acids (c2).

[0044] Examples of the monocarboxylic acid (c1) include aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, lauric acid, stearic acid, 2-ethylhexanoic acid, cyclohexanoic acid, and anhydrides thereof; and aromatic monocarboxylic acids such as benzoic acid, methylbenzoic acid, para-t-butylbenzoic acid, orthobenzoylbenzoic acid, naphthoic acid, and anhydrides thereof. Among these, aliphatic monocarboxylic acids and aromatic monocarboxylic acids are preferred, with stearic acid, para-t-butylbenzoic acid, and benzoic acid being more preferred. Furthermore, aromatic monocarboxylic acids are preferred, with para-t-butylbenzoic acid and benzoic acid being more preferred. The monocarboxylic acid (c1) may be used alone or in combination of two or more types.

[0045] The polycarboxylic acids (c2) are preferably polycarboxylic acids that do not contain linear unsaturated hydrocarbon chains, and anhydrides thereof.

[0046] Examples of the polycarboxylic acids (c2) include: chain saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, oxaloacetic acid, methylmalonic acid, dimethylmalonic acid, methylsuccinic acid, 2,2-dimethylsuccinic acid, methylglutaric acid, dimethylglutaric acid, 1,3-acetonedicarboxylic acid, ketoglutaric acid, 2-oxoadipic acid, 4-oxoheptanedioic acid, 5-oxoazelaic acid, and anhydrides thereof; cyclic aliphatic dicarboxylic acids such as tetrahydrophthalic acid, cyclopropane-1,1-dicarboxylic acid, cyclobutane-1,1-dicarboxylic acid, cyclohexane-1,1-dicarboxylic acid, cyclohexanedicarboxylic acid, and anhydrides thereof; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, phenylenedioxydiacetic acid, indan-2,2-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, and anhydrides thereof; and aromatic tricarboxylic acids or aromatic tetracarboxylic acids such as trimellitic acid, pyromellitic acid, and anhydrides thereof.

[0047] The polycarboxylic acids (c2) are preferably isophthalic acid, adipic acid, tetrahydrophthalic acid, and anhydrides thereof, more preferably adipic acid, tetrahydrophthalic acid, and anhydrides thereof. The polycarboxylic acids (c2) may be used singly or in combination of two or more.

[0048] The other carboxylic acids (c) may contain only the monocarboxylic acids (c1) among the monocarboxylic acids (c1) and the polycarboxylic acids (c2), or may contain both the monocarboxylic acids (c1) and the polycarboxylic acids (c2).

[0049] [Polyol (Y)] The raw material compounds constituting the rosin-modified unsaturated polyester preferably contain a polyol (Y). The polyol (Y) is a polyhydric alcohol having two or more hydroxyl groups in one molecule.

[0050] Examples of the polyol (Y) include a trihydric or higher polyol (d) and a diol (e). The polyol (Y) preferably contains at least the trihydric or higher polyol (d). For example, the polyol (Y) may contain only the trihydric or higher polyol (d), or may contain the trihydric or higher polyol (d) and the diol (e) in combination.

[0051] (Polyol (d)) The polyol (Y) preferably contains a trihydric or higher polyol (d). The polyol (d) is a polyhydric alcohol having three or more hydroxyl groups in one molecule. By using a trihydric or higher polyol (d), the amount of rosins (a) introduced into the molecule of the rosin-modified unsaturated polyester can be increased, and this allows the rosin-modified unsaturated polyester to exhibit higher surface hardness and water resistance after curing.

[0052] Examples of the trivalent or higher polyol (d) include trivalent polyols such as glycerin, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane (also simply referred to as "trimethylolpropane"), trioxyisobutane, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2,3,4-pentanetriol, and 1,2,5-hexanetriol; tetravalent polyols such as pentaerythritol; pentavalent or higher polyols such as dipentaerythritol, glucose, sucrose, and sorbitol; and alkylene oxide (ethylene oxide, propylene oxide, etc.) adducts thereof. The trivalent or higher polyol (d) may be used alone or in combination of two or more.

[0053] As the trivalent or higher polyol (d), from the viewpoint of reactivity, a trivalent polyol and a tetravalent polyol are preferred. As the trivalent polyol, glycerin and trimethylolpropane are preferred, and glycerin is more preferred. Furthermore, as the tetravalent polyol, pentaerythritol is preferred.

[0054] The trivalent or higher polyol (d) preferably contains a trivalent polyol, and more preferably contains a trivalent polyol and a tetravalent polyol, which allows the amount of hydroxyl groups to be supplied to the esterification reaction to be increased, and the amount of rosin (a) to be introduced into the structure of the rosin-modified unsaturated polyester to be increased.

[0055] When the trihydric or higher polyol (d) contains both a trihydric polyol and a tetrahydric polyol, the content of the rosin (a) can be set to a high value, preferably 50 parts by mass or more, per 100 parts by mass of the total amount of the carboxylic acid (X) and the polyol (Y). As a result, the rosin-modified unsaturated polyester can exhibit higher surface hardness and water resistance after curing.

[0056] The content of the trivalent or higher polyol (d) in the raw material compounds is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of the total amount of the carboxylic acids (X) and the polyol (Y). The content of the trivalent or higher polyol (d) in the raw material compounds is preferably 30 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the total amount of the carboxylic acids (X) and the polyol (Y).

[0057] (Diol (e)) The polyol (Y) preferably further contains a diol (e). The diol (e) is a polyhydric alcohol (dihydric polyol) having two hydroxyl groups per molecule. By using the diol (e), the carboxy groups of the carboxylic acids (X) can be sufficiently esterified, and the amount of excess carboxy groups not subjected to the esterification reaction can be reduced, thereby lowering the methanol tolerance of the rosin-modified unsaturated polyester.

[0058] Examples of the diol (e) include methylene glycol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 4,4'-dihydroxyphenylpropane, 4,4'-dihydroxymethylmethane, diethylene glycol, triethylene glycol, polyethylene glycol (PEG), dipropylene glycol, polytetramethylene glycol (PTMG), polypropylene glycol (PPG), 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, bisphenol A, bisphenol F, and alkylene oxide (ethylene oxide, propylene oxide, etc.) adducts thereof. The diol (e) may be used alone or in combination of two or more.

[0059] The number of carbon atoms in the diol (e) is preferably 6 or less, more preferably 4 or less. The number of carbon atoms in the diol (e) is preferably 1 or more, more preferably 2 or more. The smaller the number of carbon atoms in the diol (e), the higher the softening point of the rosin-modified unsaturated polyester can be, and as a result, the rosin-modified unsaturated polyester can exhibit higher surface hardness after curing.

[0060] As the diol (e), 1,2-propanediol, 1,3-propanediol, 1,6-hexanediol, and neopentyl glycol are preferred, and 1,3-propanediol and neopentyl glycol are more preferred.

[0061] The polyol (Y) preferably contains a trihydric or higher polyol (d), and more preferably contains a trihydric or higher polyol (d) and a diol (e), which allows the rosin-modified unsaturated polyester to exhibit higher surface hardness and water resistance after curing.

[0062] When the polyol (Y) contains a trihydric or higher polyol (d) and a diol (e), the content of the trihydric or higher polyol (d) in the polyol (Y) is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 55 mol% or more. When the polyol (Y) contains a trihydric or higher polyol (d) and a diol (e), the content of the trihydric or higher polyol (d) in the polyol (Y) is preferably 70 mol% or less, more preferably 65 mol% or less. By making the content of the trihydric or higher polyol (d) 40 mol% or more, the amount of rosin (a) introduced into the molecule of the rosin-modified unsaturated polyester can be increased, thereby allowing the rosin-modified unsaturated polyester to exhibit higher surface hardness and water resistance after curing. By making the content of the trihydric or higher polyol (d) 70 mol% or less, the amount of excess hydroxyl groups not subjected to the esterification reaction can be reduced, thereby reducing the methanol tolerance.

[0063] The content of polyol (Y) in the raw material compound is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, per 100 parts by mass of the total amount of carboxylic acids (X) and polyol (Y). The content of polyol (Y) in the raw material compound is preferably 60 parts by mass or less, more preferably 35 parts by mass or less, per 100 parts by mass of the total amount of carboxylic acids (X) and polyol (Y). By setting the content of polyol (Y) to 10 parts by mass or more, the carboxy groups of the carboxylic acids (X) can be sufficiently esterified, and the methanol tolerance of the rosin-modified unsaturated polyester can be reduced. By setting the content of polyol (Y) to 60 parts by mass or less, the amount of excess hydroxyl groups not subjected to the esterification reaction can be reduced, and the methanol tolerance can be reduced.

[0064] The molecular structure of the rosin-modified unsaturated polyester is not particularly limited. For example, when the polyol (Y) contains a trihydric or higher polyol (d) and a diol (e), the rosin-modified unsaturated polyester is preferably a polycondensate obtained by esterifying an esterified product (I) having a hydroxyl group, which is an esterification reaction product of a rosin (a) and a trihydric or higher polyol (d), with an α,β-unsaturated dicarboxylic acid (b) and a diol (e). In such a rosin-modified unsaturated polyester, the esterification reaction of each raw material compound has progressed sufficiently, making it possible to reduce the amount of unreacted carboxyl groups and hydroxyl groups contained in the rosin-modified unsaturated polyester. This reduces the methanol tolerance of the rosin-modified unsaturated polyester. That is, the methanol tolerance of the rosin-modified unsaturated polyester at 25°C can be set to preferably 100 g or less.

[0065] When the carboxylic acids (X) further contain other carboxylic acids (c), the rosin-modified unsaturated polyester is preferably a polycondensate obtained by esterifying an ester (I) having a hydroxyl group, which is an esterification reaction product of a rosin (a), other carboxylic acids (c), and a trivalent or higher polyol (d), with an α,β-unsaturated dicarboxylic acid (b) and a diol (e). In such a rosin-modified unsaturated polyester, the esterification reactions of the raw material compounds have progressed sufficiently, which can reduce the methanol tolerance of the rosin-modified unsaturated polyester.

[0066] In the raw material compounds, the ratio of the total number of moles of hydroxyl groups in the polyol (Y) to the total number of moles of carboxyl groups in the carboxylic acids (X) [total number of moles of hydroxyl groups in the polyol (Y) / total number of moles of carboxyl groups in the carboxylic acids (X)] is preferably 0.95 or more, more preferably 1.00 or more. In the raw material compounds, the ratio of the total number of moles of hydroxyl groups in the polyol (Y) to the total number of moles of carboxyl groups in the carboxylic acids (X) [total number of moles of hydroxyl groups in the polyol (Y) / total number of moles of carboxyl groups in the carboxylic acids (X)] is preferably 1.30 or less, more preferably 1.15 or less. By keeping this ratio within the above range, the hydroxyl groups in the polyol (Y) are sufficiently esterified with the carboxyl groups of the carboxylic acids (X) containing the rosins (a), thereby increasing the degree of esterification. This makes it easier to adjust the methanol tolerance of the rosin-modified unsaturated polyester to 100 g or less. As a result, the surface hardness and water resistance of cured products made using the rosin-modified unsaturated polyester can be improved. Furthermore, it is also possible to reduce the occurrence of azeotropy due to dehydration of the polyol (Y) during the esterification reaction for producing the rosin-modified unsaturated polyester.

[0067] As described above, the carboxylic acids (X) include a plurality of types of carboxylic acids, such as rosins (a) and α,β-unsaturated dicarboxylic acids (b). Therefore, the total number of moles of carboxy groups in the carboxylic acids (X) can be calculated as follows. First, for each of the carboxylic acids (X), the number of moles of the carboxylic acids (X) contained in the raw material compound is multiplied by the number of carboxy groups in one molecule of the carboxylic acid (X) to obtain the number of moles of the carboxy groups (M COOH Next, the mole number of carboxy groups (M COOH ) are summed, and the value obtained is defined as the "total number of moles of carboxy groups in the carboxylic acid (X)."

[0068] In addition, in the "total number of moles of carboxy groups in the carboxylic acids (X)", the number of moles of carboxy groups in the rosins (a) (M COOH) is calculated as follows. First, the acid value of the rosin (A) contained in the raw material compound is measured, and the amount of carboxy groups contained in the rosin (A) per unit mass is calculated. Based on this amount of carboxy groups, the average molecular weight of the rosin (A) is determined. Then, the number of moles of carboxy groups in the rosin (a) (M COOH ) is obtained.

[0069] The acid value of the rosin (A) can be measured in accordance with JIS K5601-2-1 (1999).

[0070] The total number of moles of hydroxyl groups in the polyol (Y) can be calculated as follows. The polyol (Y) may contain a plurality of types of polyols, such as a trivalent or higher polyol (d) and a diol (e). Therefore, for each polyol (Y), the number of moles of polyol (Y) contained in the raw material compound is first multiplied by the number of hydroxyl groups in one molecule of this polyol (Y) to obtain the number of moles of hydroxyl groups (M OH Next, the mole number of hydroxyl groups (M OH ) are summed, and the value obtained is defined as the "total number of moles of hydroxyl groups in polyol (Y)."

[0071] The raw material compounds constituting the rosin-modified unsaturated polyester may further contain a monohydric alcohol. The monohydric alcohol is a compound having one hydroxyl group per molecule. Examples of the monohydric alcohol include methanol, ethanol, propanol, and isopropanol. The monohydric alcohol may be used alone or in combination of two or more.

[0072] The weight-average molecular weight of the rosin-modified unsaturated polyester is preferably 3,000 or more, more preferably 4,000 or more. The weight-average molecular weight of the rosin-modified unsaturated polyester is preferably 50,000 or less, more preferably 20,000 or less. When the weight-average molecular weight of the rosin-modified unsaturated polyester is 3,000 or more, the water resistance and surface hardness of a cured product obtained using the rosin-modified unsaturated polyester can be improved. When the weight-average molecular weight of the rosin-modified unsaturated polyester is 50,000 or less, gelation and excessive increase in molecular weight of the rosin-modified unsaturated polyester are reduced, and the solubility of the rosin-modified unsaturated polyester in radical polymerizable monomers described below can be improved.

[0073] Furthermore, by setting the weight-average molecular weight of the rosin-modified unsaturated polyester to 20,000 or less, the heating temperature required to dissolve the rosin-modified unsaturated polyester in a radical polymerizable monomer during production of the rosin-modified unsaturated polyester composition can be lowered, making it possible to suitably use radical polymerizable monomers with relatively low boiling points, such as styrene.

[0074] The weight-average molecular weight of a rosin-modified unsaturated polyester refers to the value calculated by converting the molecular weight measured by gel permeation chromatography (GPC) into polystyrene equivalents. For example, it can be measured under the following measurement conditions. The rosin-modified unsaturated polyester is dissolved in tetrahydrofuran to obtain a measurement sample with a rosin-modified unsaturated polyester concentration of 0.5% by mass. Using this measurement sample, the weight-average molecular weight of the rosin-modified unsaturated polyester can be measured using a gel permeation chromatograph (GPC) equipped with a refractive index detector (RID) under the following measurement apparatus and measurement conditions. Measurement equipment: "Shodex GPC-101" manufactured by Showa Denko K.K. Column: "KF-802" + "KF-806L" x 2 manufactured by Showa Denko K.K. Detector: Shodex RI-71 (differential refractive index detector) Data processing: "480IIXP", ​​Standard polystyrene ("S-0.5", "S-1.0", "S-1.2", "S-1.9", "S-2.9", "S-3.1", "S-4.4", "S-5.1", "S-7.2", "S-19.6", "S-49.2", "S-114", "S-257", "S-778", "S-1320", "S-7450" manufactured by Showa Denko K.K.) Column temperature: 40°C Solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 0.5% by mass Injection volume: 100 μm

[0075] (Method for Producing Rosin-Modified Unsaturated Polyester) The rosin-modified unsaturated polyester can be produced by polycondensing raw material compounds including rosins (a), carboxylic acids (X) including α,β-unsaturated dicarboxylic acids (b), and polyol (Y). The rosin-modified unsaturated polyester is obtained by polycondensation (esterification reaction) of the carboxylic acids (X) and the polyol (Y) accompanied by dehydration.

[0076] The polycondensation of the raw material compounds can be carried out by a known method, for example, a method in which the raw material compounds are mixed and heated, if necessary in the presence of a solvent, to cause a reaction.

[0077] The solvent is not particularly limited, but examples thereof include petroleum hydrocarbon solvents such as hexane and mineral spirits; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, γ-butyrolactone, and propylene glycol monomethyl ether acetate; and organic solvents such as aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, and pyridine. The solvents may be used alone or in combination. The blending ratio of the solvents is not particularly limited and may be appropriately determined depending on the purpose and application.

[0078] For example, by heating the raw material compound in the presence of a solvent that can form an azeotropic distillate with water (for example, an azeotropic dehydrating agent such as xylene or toluene), an esterification reaction can be initiated and the water produced by the reaction can be distilled off. After completion of the reaction, the solvent may be removed as necessary. Alternatively, for example, the raw material compound can be heated in the absence of a solvent to initiate the esterification reaction and the produced water can be distilled off by a known method.

[0079] The polycondensation of the raw material compounds is preferably carried out in the presence of an esterification catalyst. The esterification catalyst is not particularly limited, but examples include organic sulfonic acids such as benzenesulfonic acid, p-toluenesulfonic acid, p-dodecylbenzenesulfonic acid, methanesulfonic acid, and ethanesulfonic acid; mineral acids such as sulfuric acid and hydrochloric acid; metal catalysts such as tetrabutyl zirconate, tetraisopropyl titanate, tetraisobutyl titanate, aluminum oxide, titanium oxide, magnesium oxide, magnesium hydroxide, magnesium acetate, calcium oxide, calcium hydroxide, calcium acetate, zinc oxide, and zinc acetate; trifluoromethylsulfuric acid, trifluoromethylacetic acid, and the like. The esterification catalyst may be used alone or in combination of two or more. The addition ratio of the esterification catalyst is not particularly limited and may be appropriately determined depending on the purpose and application.

[0080] The polycondensation of the raw material compounds is preferably carried out under atmospheric pressure in an inert gas atmosphere. In the polycondensation of the raw material compounds, the heating temperature of the raw material compounds is preferably 150 to 280° C., and more preferably 200 to 250° C. The heating time is preferably 4 to 20 hours, and more preferably 6 to 15 hours.

[0081] In the polycondensation of the raw material compounds, the order in which the raw material compounds are reacted, i.e., the order in which the raw material compounds are mixed, is not particularly limited. All of the raw material compounds may be mixed simultaneously and polycondensed, or the raw material compounds may be mixed in any order and polycondensed. For example, when the carboxylic acids (X) include a rosin (a) and an α,β-unsaturated dicarboxylic acid (b) and the alcohol (Y) includes a trivalent or higher polyol (d) and a diol (e), the raw material compounds can be polycondensed in any order, but it is preferable to polycondense them in the order shown below.

[0082] That is, the method for producing a rosin-modified unsaturated polyester preferably includes: a first esterification step in which a rosin (a) and a trivalent or higher polyol (d) are heated at a heating temperature of 230°C or higher to cause an esterification reaction, thereby obtaining an esterified product (I) having a hydroxyl group; and a second esterification step in which, after the first esterification step, the esterified product (I), an α,β-unsaturated dicarboxylic acid (b), and a diol (e) are heated at a heating temperature of 180°C or higher and lower than 230°C to cause an esterification reaction, thereby obtaining a rosin-modified unsaturated polyester.

[0083] In the above method, after the esterification reaction of the rosin (a) and the trivalent or higher polyol (d) is carried out in the first esterification step, the esterification reaction of the α,β-unsaturated dicarboxylic acid (b) is carried out in the second esterification step. As a result, even when the rosin (a) contains a resin acid having a conjugated double bond, addition of the α,β-unsaturated dicarboxylic acid (b) to the resin acid via the Diels-Alder reaction can be reduced, and unsaturated bonds derived from the α,β-unsaturated dicarboxylic acid (b) can be sufficiently introduced into the rosin-modified unsaturated polyester.

[0084] Furthermore, in the above method, the heating temperature during the esterification reaction can be increased by first carrying out the esterification reaction of the rosin (a) and the trihydric or higher polyol (d) prior to the reaction of the α,β-unsaturated dicarboxylic acid (b) and the diol (e) in the first esterification step. This allows the esterification reaction of the rosin (a) and the trihydric or higher polyol (d) to proceed sufficiently, and even when the content of the rosin (a) is high, the methanol tolerance of the finally obtained rosin-modified unsaturated polyester can be reduced.

[0085] The heating temperature in the first esterification step is preferably 230° C. or higher, more preferably 240° C. or higher. The heating temperature in the first esterification step is preferably 280° C. or lower, more preferably 250° C. or lower.

[0086] When the carboxylic acids (X) further contain other carboxylic acids (c), it is preferable to carry out an esterification reaction of the other carboxylic acids (c) in the first esterification step, i.e., it is preferable to carry out an esterification reaction of the rosin (a) and the other carboxylic acids (c) with the trivalent or higher polyol (d) in the first esterification step.

[0087] In the first esterification step, rosins (a) and, if necessary, other carboxylic acids (c) are esterified with an excess amount of a trivalent or higher polyol (d) to obtain an esterified product (I) having a hydroxyl group. In order to ensure that the esterification reaction proceeds sufficiently, the acid value of the esterified product (I) having a hydroxyl group obtained in the first esterification step is preferably 10 mgKOH / g or less.

[0088] In the second esterification step, the esterified product (I) obtained in the first esterification step, an α,β-unsaturated dicarboxylic acid (b), and a diol (e) are heated at a relatively low heating temperature to further cause an esterification reaction, thereby obtaining a rosin-modified unsaturated polyester.

[0089] The heating temperature in the second esterification step is preferably 180°C or higher, more preferably 190°C or higher, and even more preferably 200°C or higher. The heating temperature in the second esterification step is preferably less than 230°C, more preferably 220°C or lower, and even more preferably 210°C or lower. By carrying out the esterification reaction at such a relatively low heating temperature, the esterification reaction between the hydroxyl group-containing ester (I) obtained in the first esterification step and the α,β-unsaturated dicarboxylic acids (b) and diol (e) can be sufficiently promoted, and the methanol tolerance of the final rosin-modified unsaturated polyester can be reduced. Furthermore, by setting the reaction temperature in the second esterification step within the above range, even when unmodified rosin is used as the rosin (a), the unsaturated bonds derived from the α,β-unsaturated dicarboxylic acids (b) can be retained in the rosin-modified unsaturated polyester at a high residual rate, thereby enabling the final rosin-modified unsaturated polyester to be copolymerized with a radically polymerizable monomer more reliably.

[0090] In the second esterification step, it is preferable to cool the esterified product (I) obtained in the first esterification step to 180°C or lower, particularly 150 to 180°C, and then heat the esterified product (I) with the α,β-unsaturated dicarboxylic acids (b) and the diol (e) at the above-mentioned heating temperature to carry out the esterification reaction.

[0091] In the second esterification step, the esterification reaction of the esterified product (I), the α,β-unsaturated dicarboxylic acid (b), and the diol (e) is preferably carried out in the presence of a polymerization inhibitor.

[0092] Rosins (a) may contain rosin metal salts as unavoidable impurities. The metal atoms contained in such rosin metal salts can act as catalysts for the esterification reaction in the first esterification step. Meanwhile, in the second esterification step, the metal atoms may act as polymerization catalysts that promote the polymerization of α,β-unsaturated dicarboxylic acids (b). As a result, the rosin-modified unsaturated polyester may become too high in molecular weight and gel. Therefore, by using a polymerization inhibitor, the polymerization of α,β-unsaturated dicarboxylic acids (b) in the second esterification step can be suppressed, thereby reducing the gelation of the rosin-modified unsaturated polyester.

[0093] Examples of the metal atom of the rosin metal salt include at least one of iron, copper, zinc, aluminum, and magnesium. The content of the rosin metal salt in the rosin (a) is extremely small.

[0094] Examples of polymerization inhibitors include phenolic polymerization inhibitors such as (alkyl)phenols, p-methoxyphenols, o-isopropylphenols, catechol, resorcinol, t-butylcatechol, pyrogallol, dibutylcresol, and guaiacol; nitroso-based polymerization inhibitors such as nitrosobenzene, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, picric acid, cupferron, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime; quinone-based polymerization inhibitors such as hydroquinone, t-butylhydroquinone (TBHQ), p-benzoquinone, and 2,5-di-tert-butyl-p-benzoquinone; and piperidine-based polymerization inhibitors such as phenothiazine. Of these, nitroso-based polymerization inhibitors and quinone-based polymerization inhibitors are preferred, with aluminum N-nitrosophenylhydroxylamine and t-butylhydroquinone being more preferred. The polymerization inhibitors may be used alone or in combination of two or more.

[0095] The amount of the polymerization inhibitor is preferably 0.001 to 5 parts by mass, and more preferably 0.01 to 1 part by mass, relative to 100 parts by mass of the total amount of the carboxylic acids (X) and the polyol (Y). By setting the amount of the polymerization inhibitor within the above range, polymerization of the α,β-unsaturated dicarboxylic acids (b) in the second esterification step can be sufficiently suppressed.

[0096] The acid value of the rosin-modified unsaturated polyester obtained in the second esterification step is preferably 30 mgKOH / g or less, and more preferably 20 mgKOH / g or less, which allows the esterification reaction to proceed sufficiently in the second esterification step, thereby reducing the methanol tolerance of the finally obtained rosin-modified unsaturated polyester.

[0097] The acid value of the esterified product (I) obtained in the first step and the acid value of the rosin-modified unsaturated polyester obtained in the second esterification step can be measured in accordance with JIS K5601-2-1 (1999), and the hydroxyl value of the rosin-modified unsaturated polyester can be measured in accordance with JIS K 0070 (1992).

[0098] When a polymerization inhibitor is used in the second esterification step, the rosin-modified unsaturated polyester obtained by the method of the present invention described above is obtained in the form of a mixture with the polymerization inhibitor. That is, when a polymerization inhibitor is used in the second esterification step, a composition containing the rosin-modified unsaturated polyester and the polymerization inhibitor is obtained. Then, by adding the radical polymerizable monomer described below, and, if necessary, a polymerization initiator and a curing accelerator, etc. to this composition, a rosin-modified unsaturated polyester composition can be obtained. Furthermore, if necessary, a polymerization inhibitor may be further added to the rosin-modified unsaturated polyester composition.

[0099] <Rosin-modified unsaturated polyester composition> The rosin-modified unsaturated polyester described above is suitably used as a rosin-modified unsaturated polyester composition containing the same. The rosin-modified unsaturated polyester composition contains a rosin-modified unsaturated polyester and a radically polymerizable monomer. By using the rosin-modified unsaturated polyester of the present invention described above, the rosin-modified unsaturated polyester composition can form a cured product having excellent surface hardness and water resistance. This cured product is suitably used as a molded product molded into a desired shape.

[0100] The rosin-modified unsaturated polyester contains an unsaturated bond in the molecule. Examples of the unsaturated bond include a carbon-carbon double bond and a carbon-carbon triple bond. Of these, a carbon-carbon double bond is preferred.

[0101] Examples of radically polymerizable monomers include vinyl compounds such as styrene, chlorostyrene, dichlorostyrene, t-butylstyrene, vinylnaphthalene, ethyl vinyl ether, methyl vinyl ketone, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylonitrile, and methacrylonitrile; allyl compounds such as diallyl phthalate, diallyl terephthalate, diallyl succinate, and triallyl cyanurate; and oligomers thereof. Styrene, methylstyrene, and diallyl phthalate are preferred, with styrene and methylstyrene being more preferred. These radically polymerizable monomers can be easily copolymerized with the rosin-modified unsaturated polyester, thereby enabling the rosin-modified unsaturated polyester composition to be cured more reliably. As a result, the surface hardness and water resistance of the cured rosin-modified unsaturated polyester composition can be further improved. The radically polymerizable monomers may be used alone or in combination of two or more.

[0102] The content of the radical polymerizable monomer may be adjusted as appropriate depending on the viscosity and intended use of the rosin-modified unsaturated polyester composition. The content of the radical polymerizable monomer in the rosin-modified unsaturated polyester composition is preferably 10 to 200 parts by mass, more preferably 30 to 150 parts by mass, per 100 parts by mass of the rosin-modified unsaturated polyester.

[0103] The viscosity of the rosin-modified unsaturated polyester composition at 25° C. is preferably 10 to 10,000 mPa·s, and more preferably 50 to 5,000 mPa·s.

[0104] The viscosity of the rosin-modified unsaturated polyester composition at 25°C is the viscosity measured using a rheometer (for example, a rheometer manufactured by Thermo Haake under the trade name "HAAKE RheoStress 600") at a temperature of 25°C and a frequency of 1.0 Hz.

[0105] The rosin-modified unsaturated polyester composition preferably contains a polymerization initiator. A thermal polymerization initiator is preferably used as the polymerization initiator. Examples include organic peroxides such as methyl ethyl ketone peroxide, acetylacetone peroxide, t-butyl peroxybenzoate, benzoyl peroxide, dicumyl peroxide, and cumene hydroperoxide. The content of the polymerization initiator in the rosin-modified unsaturated polyester composition is preferably 0.1 to 5 parts by mass per 100 parts by mass of the total amount of the rosin-modified unsaturated polyester and the radical-polymerizable monomer.

[0106] The rosin-modified unsaturated polyester composition preferably contains a curing accelerator. Examples of the curing accelerator include cobalt naphthenate, cobalt octoate, N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, acetylacetone, and acetic acid ethyl ester. The content of the curing accelerator in the rosin-modified unsaturated polyester composition is preferably 0.05 to 5 parts by mass per 100 parts by mass of the total amount of the rosin-modified unsaturated polyester and the radical polymerizable monomer.

[0107] The rosin-modified unsaturated polyester composition preferably contains a polymerization inhibitor, which can reduce unnecessary polymerization of the rosin-modified unsaturated polyester or the radical-polymerizable monomer during storage of the rosin-modified unsaturated polyester composition, thereby improving storage stability.

[0108] The polymerization inhibitor may be the same as the polymerization inhibitor used in the second esterification step of the method of the present invention. The content of the polymerization inhibitor is preferably 0.05 to 5 parts by mass per 100 parts by mass of the total amount of the rosin-modified unsaturated polyester and the radical-polymerizable monomer.

[0109] The method for producing the rosin-modified unsaturated polyester composition is not particularly limited. For example, the rosin-modified unsaturated polyester composition can be obtained by dissolving the rosin-modified unsaturated polyester in a radical polymerizable monomer. If necessary, a polymerization initiator, a curing accelerator, and a polymerization inhibitor may be added.

[0110] The rosin-modified unsaturated polyester composition is cured by copolymerizing the rosin-modified unsaturated polyester with a radical-polymerizable monomer. The polymerization temperature of the rosin-modified unsaturated polyester and the radical-polymerizable monomer can be adjusted depending on the type of polymerization initiator, and is preferably 20 to 150°C, more preferably 25 to 120°C. The polymerization time is preferably 2 to 30 hours, more preferably 3 to 10 hours. The polymerization reaction is preferably carried out in an inert gas atmosphere such as nitrogen gas.

[0111] By using a rosin-modified unsaturated polyester, the rosin-modified unsaturated polyester composition can be used to form a cured product (molded article) with high surface hardness. Such a cured product has excellent scratch resistance and can maintain a beautiful appearance for a long period of time. When the rosin-modified unsaturated polyester composition contains a thermal polymerization initiator, the rosin-modified unsaturated polyester composition can be sufficiently cured to the inside. Therefore, the cured product has even better scratch resistance.

[0112] Furthermore, by using the rosin-modified unsaturated polyester, the rosin-modified unsaturated polyester composition can form a cured product (molded article) having high water resistance. Such a cured product can reduce the decrease in mechanical strength due to contact with water. Therefore, even if the cured product comes into contact with water such as rainwater or humidity for a long period of time, the cured product can maintain high mechanical strength.

[0113] As described above, the rosin-modified unsaturated polyester composition can form a cured product having both high surface hardness and water resistance. Therefore, the rosin-modified unsaturated polyester composition can be used for various applications. The application of the rosin-modified unsaturated polyester composition is not particularly limited. For example, the rosin-modified unsaturated polyester composition can be cured into a desired shape and used as a molded product.

[0114] The rosin-modified unsaturated polyester composition is also suitable for use as a binder for bonding and integrating adherends. This allows the formation of a molded article in which adherends are bonded and integrated by a cured product of the rosin-modified unsaturated polyester composition. Even when the rosin-modified unsaturated polyester composition is used in this manner, a molded article with excellent surface hardness and water resistance can be obtained. Examples of the adherend include particles such as inorganic particles and synthetic resin particles, and fibers such as reinforcing fibers.

[0115] The rosin-modified unsaturated polyester composition can be used as a fiber-reinforced plastic (FRP).

[0116] The fiber-reinforced plastic contains a cured product of a rosin-modified unsaturated polyester composition and reinforcing fibers. The cured product of the rosin-modified unsaturated polyester composition can act as a binder to integrate the reinforcing fibers. That is, in the fiber-reinforced plastic, the cured product of the rosin-modified unsaturated polyester composition can function as a binder (sizing agent) to bond the reinforcing fibers together. In this way, by using a cured product of the rosin-modified unsaturated polyester composition, a fiber-reinforced plastic having high surface hardness and water resistance can be provided.

[0117] Examples of reinforcing fibers include inorganic fibers such as glass fibers, carbon fibers, metal fibers, and ceramic fibers; organic fibers such as polyvinyl alcohol fibers, polyester fibers, polyamide fibers, fluororesin fibers, and phenolic fibers; and natural fibers such as hemp and kenaf. Inorganic fibers are preferred, carbon fibers and glass fibers are preferred, and glass fibers are more preferred. The reinforcing fibers may be used alone or in combination of two or more types. The reinforcing fibers are preferably used as a reinforcing fiber substrate processed into a desired shape.

[0118]

[0003] A known method can be used to produce a fiber-reinforced plastic. For example, a fiber-reinforced plastic can be obtained by impregnating a reinforcing fiber with a rosin-modified unsaturated polyester composition to obtain a prepreg, and then curing the rosin-modified unsaturated polyester composition. Applications of the fiber-reinforced plastic are not particularly limited, and examples thereof include ship hulls, bathtubs, construction materials, and industrial equipment.

[0119] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0120] [Examples 1 to 5, Comparative Examples 1 and 2] (Synthesis of Rosin-Modified Unsaturated Polyester) A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with raw material compounds: disproportionated rosin (manufactured by Harima Chemicals, Inc., product name "G-100F"), adipic acid, tetrahydrophthalic anhydride, isophthalic acid, stearic acid, benzoic acid, glycerin, and pentaerythritol, in the amounts shown in Table 1. The mixture was heated to 250°C to carry out a dehydration condensation reaction of the raw material compounds, thereby forming an esterified product (I) having a hydroxyl group (first esterification step). The dehydration condensation reaction was carried out until the acid value of the final esterified product (I) reached 10 mgKOH / g or less.

[0121] Next, the contents of the four-neck flask were cooled to 180°C. The raw materials, 1,3-propanediol, 1,6-hexanediol, neopentyl glycol, and maleic anhydride, as well as the polymerization inhibitors aluminum N-nitrosophenylhydroxylamine (manufactured by FUJIFILM Corporation, trade name "Q1305") and tertiary butyl hydroquinone (TBHQ), were added to the flask in the amounts shown in Table 1. The mixture was heated to 200°C to carry out a dehydration condensation reaction between the ester (I) and the raw materials, thereby forming a rosin-modified unsaturated polyester (second esterification step). This resulted in a mixture containing the rosin-modified unsaturated polyester and the polymerization inhibitor. The dehydration condensation reaction was carried out until the acid value of the resulting rosin-modified unsaturated polyester reached 20 mgKOH / g or less.

[0122] (Production of Rosin-Modified Unsaturated Polyester Composition) A rosin-modified unsaturated polyester composition was obtained by mixing 60.06 parts by mass of the above mixture (60 parts by mass of rosin-modified unsaturated polyester and 0.06 part by mass of polymerization inhibitor) with 40 parts by mass of 4-methylstyrene, 1 part by mass of cobalt naphthenate, and 2 parts by mass of a solution containing 55% by mass of methyl ethyl ketone peroxide (MEKP). In the rosin-modified unsaturated polyester composition, the rosin-modified unsaturated polyester was dissolved in 4-methylstyrene.

[0123] The disproportionated rosin used in the first esterification step contained a trace amount of rosin metal salt as an unavoidable impurity. The metal atom contained in the rosin metal salt was at least one of iron, copper, zinc, aluminum, and magnesium atoms.

[0124] The ratio of the total number of moles of hydroxyl groups in the polyol (Y) to the total number of moles of carboxy groups in the carboxylic acids (X) in all of the raw material compounds used in the first esterification step and the second esterification step [total number of moles of hydroxyl groups in polyol (Y) / total number of moles of carboxy groups in carboxylic acids (X)] is shown in the column "Ratio [total number of moles of hydroxyl groups / total number of moles of carboxy groups]" in Table 1.

[0125] [Evaluation] The rosin-modified unsaturated polyesters and rosin-modified unsaturated polyester compositions obtained in the Examples and Comparative Examples were evaluated as follows.

[0126] The methanol tolerance at 25° C., softening point, acid value, and hydroxyl value of the rosin-modified unsaturated polyester were measured according to the procedures described above. The results are shown in Table 1.

[0127] (Ease of synthesis) The weight average molecular weight of the rosin-modified unsaturated polyester was measured according to the procedure described above and evaluated based on the following criteria. The evaluation results are shown in Table 1. <Evaluation criteria> A: The weight average molecular weight of the rosin-modified unsaturated polyester was 20,000 or less. B: The weight average molecular weight of the rosin-modified unsaturated polyester was more than 20,000 and less than 50,000, and is considered to be no problem in practical use. X: The weight average molecular weight of the rosin-modified unsaturated polyester exceeded 50,000.

[0128] Considering factors such as solubility in radically polymerizable monomers, the weight-average molecular weight of the rosin-modified unsaturated polyester is preferably relatively low; for example, 50,000 or less, particularly 20,000 or less, is preferred. However, adjusting the weight-average molecular weight during the synthesis of the rosin-modified unsaturated polyester can be difficult. Specifically, as the reaction of the raw materials begins, the molecular weight of the reactants gradually increases. However, by the end of the reaction, the molecular weight of the reactants of the raw materials has increased considerably. Reaction between these reactants can lead to a rapid increase in molecular weight or gelation, making it difficult to obtain a rosin-modified unsaturated polyester with a relatively low weight-average molecular weight. However, the method of the present invention can reduce the occurrence of the aforementioned rapid increase in molecular weight or gelation, thereby easily producing a rosin-modified unsaturated polyester with a relatively low weight-average molecular weight. Therefore, even when producing a large amount of rosin-modified unsaturated polyester in a factory, the method of the present invention eliminates the need for strict control of reaction conditions, such as the reaction time of the raw materials, thereby reducing the burden of controlling reaction conditions and enabling the reproducible production of a rosin-modified unsaturated polyester with a relatively low weight-average molecular weight.

[0129] (Surface Hardness) The rosin-modified unsaturated polyester composition was poured into a cylindrical plastic container with a diameter of 65 mm, and cured by being left at room temperature for 3 hours under a nitrogen atmosphere and then at 80° C. for another 2 hours under a nitrogen atmosphere, thereby obtaining a cured product (thickness: 3 mm) of the rosin-modified unsaturated polyester composition.

[0130] The surface hardness of the cured product was evaluated using a pendulum hardness tester (manufactured by BYK under the trade name "Pendulum Hardness tester") in accordance with ASTM D4366 (2014). Specifically, a pendulum was swung around a metal ball (5 nm in diameter) in contact with the cured product as a fulcrum, and the time it took for the amplitude of the pendulum to decay from 6° to 3° was measured. This decay time was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1. Note that a longer decay time indicates a higher surface hardness of the cured product. The following evaluation criteria preferably have a rating of 3 or higher. This indicates that the cured product is at a level suitable for practical use. <Evaluation Criteria> 5: The decay time was 120 seconds or more. 4: The decay time was 100 seconds or more but less than 120 seconds. 3: The decay time was 80 seconds or more but less than 100 seconds. 2: The decay time was 60 seconds or more but less than 80 seconds. 1: The decay time was less than 60 seconds.

[0131] (Water Resistance) A cured product (thickness: 3 mm) of the rosin-modified unsaturated polyester composition was obtained using the same method as described above for evaluating surface hardness. The cured product was immersed in ion-exchanged water at 50°C for one month. The mass change rate of the cured product before and after immersion was calculated using the following formula and evaluated according to the following criteria. The evaluation results are shown in Table 1. Note that a score of 3 or higher on the following criteria is preferred. This is considered to be a level at which the cured product is suitable for practical use.

[0132] Mass change rate of cured product [%] = 100 × (W0 - W1) / W0 (where W0 is the mass [g] of the cured product before immersion, and W1 is the mass [g] of the cured product after immersion.)

[0133] <Evaluation criteria> 5: The mass change of the cured product was 0.2% or less. 4: The mass change of the cured product was more than 0.2% and 0.4% or less. 3: The mass change of the cured product was more than 0.4% and 0.6% or less. 2: The mass change of the cured product was more than 0.6% and 0.8% or less. 1: The mass change of the cured product was more than 0.8%.

[0134]

[0135] The rosin-modified unsaturated polyester and the rosin-modified unsaturated polyester composition containing the same of the present invention exhibit high surface hardness and water resistance after curing, and are therefore suitable for use in molded articles such as fiber-reinforced plastics.

[0136] (Cross-reference to related applications) This application claims priority to Japanese Patent Application No. 2024-11972, filed on January 30, 2024, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A rosin-modified unsaturated polyester having a methanol tolerance of 100 g or less at 25°C.

2. The rosin-modified unsaturated polyester according to claim 1, characterized in that the softening point is 60°C or higher.

3. The rosin-modified unsaturated polyester according to claim 1, which is a polycondensate of raw material compounds including rosins (a), carboxylic acids (X) including α,β-unsaturated dicarboxylic acids (b), and polyol (Y).

4. The rosin-modified unsaturated polyester according to claim 3, wherein the rosins (a) include at least one of disproportionated rosin and hydrogenated rosin.

5. The rosin-modified unsaturated polyester according to claim 3, wherein the polyol (Y) contains a trihydric or higher polyol (d).

6. A rosin-modified unsaturated polyester composition comprising the rosin-modified unsaturated polyester of claim 1 and a polymerization inhibitor.

7. A rosin-modified unsaturated polyester composition comprising the rosin-modified unsaturated polyester according to claim 1 and a radically polymerizable monomer.

8. The rosin-modified unsaturated polyester composition according to claim 7, characterized in that the radical polymerizable monomer contains at least one of styrene and methylstyrene.

9. A molded article comprising a cured product of the rosin-modified unsaturated polyester composition according to claim 8.

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