WO1999054377A1

WO1999054377A1 - Unsaturated polyester resin composition and cured article thereof

Info

Publication number: WO1999054377A1
Application number: PCT/JP1999/002081
Authority: WO
Inventors: Shigeru Murata; Toshio Yamauchi; Ryoichi Fujitani
Original assignee: Kyowa Yuka Co., Ltd.
Priority date: 1998-04-22
Filing date: 1999-04-20
Publication date: 1999-10-28
Also published as: AU3172199A

Abstract

An unsaturated polyester resin composition which comprises an unsaturated polyester resin having specific structural units in the molecule and a monomer copolymerizable therewith having a double bond; and a cured article obtained by curing the unsaturated polyester resin composition. The cured article has pliability or flexibility, is excellent in resistance to water, hot water, and alkalis, and withstands use in severe environments. The composition has good handleability. The cured article has extremely high mechanical properties. The composition is suitable for use in producing bathtubs, sewage purifier tanks, water storage tanks, etc.

Description

Description. Unsaturated polyester resin composition and cured product thereof

The present invention relates to an unsaturated polyester resin composition having excellent flexibility, flexibility, hot water resistance and alkali resistance, and a cured product thereof.

This application is based on a patent application to Japan (Japanese Patent Application No. 10-112125), and the contents of the Japanese application are incorporated herein by reference. Background art

Generally, the unsaturated polyester resin composition is easy to handle because it is liquid at room temperature, has good miscibility with glass fiber, good adhesion, and its cured product has good mechanical properties. Is often used.

For example, an unsaturated polyester resin composed of a dicarboxylic acid component containing a vinyl dicarboxylic acid and a diol component, a styrene monomer, an acryl monomer, an acryl monomer or a methacryl monomer. Unsaturated polyester resin compositions containing a crosslinking agent such as those described above are used in bathtubs, septic tanks, water storage tanks, etc. in combination with glass fibers.

In recent years, molded articles of the unsaturated polyester resin composition are often used under severe environments. Therefore, there is a strong demand for molded articles of the unsaturated polyester resin composition to have improvements in water resistance, hot water resistance, alkali resistance, inorganic salt resistance, oxidation resistance, and the like.

Therefore, in order to improve the performance of the unsaturated polyester resin composition such as water resistance, hot water resistance, and alkali resistance, for example, the diol component of the raw material is composed of neopentyl diol alcohol and bisphenol A alkyl. Unsaturated polyester resin such as lenoxide adduct, xylylene glycol, hydrogenated bisphenol. A, or vinyl dicarboxylic acid component as raw material is fumaric acid alone, or fumaric acid and isophthalic acid, terephthalic acid There has been proposed an unsaturated polyester resin which is used in combination with an aromatic dicarboxylic acid or the like.

Further, as a crosslinking agent, a monomer having a copolymerizable double bond, for example, α-methylstyrene, 4-t-butylstyrene, glycidyl acrylate, glycidyl methacrylate, methacrylic acid A method using a polyhydric ester of a polyhydric alcohol with a polyhydric alcohol, for example, ethylene glycol dimethacrylate has been proposed.

In particular, when the unsaturated polyester resin composition is used for surface layers such as bathtubs, septic tanks, water tanks, etc., it is necessary to have excellent water resistance, and isophthalic acid, fumaric acid, hydrogenated bisphenol A, etc. Used.

A casting plate obtained by curing an unsaturated polyester resin composition obtained by blending the above-mentioned unsaturated polyester resin with a crosslinking agent such as styrene is excellent in hot water resistance.

However, the laminated plate obtained by laminating and curing glass fiber on the casting plate has cracks, blisters, etc. on the surface in hot water, and practically has a problem in terms of hot water resistance. Not satisfied.

In addition, molded products of unsaturated polyester resin used for bathtubs, vats, water tanks, or other glass fiber reinforced applications, the outer layer is water resistant in consideration of the mechanical strength and economics of the molded product. In general, a resin having properties such as hot water resistance and alkali resistance is used, and a relatively inexpensive laminating resin (reinforcing resin) having high mechanical strength is used for the inner layer. Therefore, the unsaturated polyester resin used as the outer layer has good adhesion to the laminating resin as the inner layer, has flexibility and flexibility that can follow a temperature change, and has water resistance, hot water resistance, A resin having characteristics such as alkali resistance is desired. Disclosure of the invention

The present invention has been made to solve the above problems, and provides an unsaturated polyester resin composition having excellent flexibility, flexibility, water resistance, hot water resistance, alkali resistance, and the like.

The unsaturated polyester resin composition of the present invention has a general formula

An unsaturated polyester resin having a structural unit represented by (I) (wherein R ¹ and R ² represent the same or different lower alkyl groups) and a monomer having a double bond copolymerizable therewith It is characterized by containing a body.

R ¹ R ²

—— 0— CH ₂ -CH-CH ₂ — CH—— CH Factory 0—

... (I) In particular, in the formula (I), it is preferable that both R ¹ and R ² are ethyl groups.

Further, in this composition, the proportion of the monomer having a copolymerizable double bond is preferably from 10 to 60% by weight.

Here, the unsaturated polyester resin is composed of a diol component containing 2,4-dialkyl-1,5-pentanediol, a vinyl dicarboxylic acid (a dicarboxylic acid having at least one vinyl group in a molecule) or a dicarboxylic acid. An unsaturated polyester resin having a number average molecular weight of 1,000 to 3,000 obtained by subjecting a dicarboxylic acid component containing an alkyl ester to an esterification reaction or a transesterification reaction is preferable. In this case, examples of the alkyl portion of the alkyl ester include alkyl having 1 to 8 carbon atoms described below, and methyl or ethyl is preferable.

In addition, 2,4-dialkyl-1,5-pentane in the raw material diol component It is preferable that the ratio of the evening gas is 30 to 100 mol%.

Further, the dicarboxylic acid component preferably contains at least one of phthalic acid, terephthalic acid, and isophthalic acid, or an alkyl ester thereof, or phthalic anhydride. In this case, examples of the alkyl portion of the alkyl ester include alkyl having 1 to 8 carbon atoms described below, and methyl or ethyl is preferable.

As the beer dicarboxylic acid, fumaric acid or maleic acid or its anhydride is preferably used.

Further, a polymerization initiator is preferably contained.

The unsaturated polyester resin cured product of the present invention is obtained by curing the above-mentioned unsaturated polyester resin composition. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plan view showing the JIS No. 1 dumbbell. BEST MODE FOR CARRYING OUT THE INVENTION

In the definition of the formula (I), the lower alkyl group represents a straight-chain or branched alkyl having 1 to 8 carbon atoms. Examples include groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isoamyl, neopentyl, 21-pentyl, 3-pentyl, hexyl, heptyl, octyl and the like. Among them, those in which both R ¹ and R ² are ethyl groups are preferred.

The unsaturated polyester resin which is a constituent component of the unsaturated polyester resin composition of the present invention includes, for example, 2,4-dialkyl-1,5-pentene which is a structural unit component represented by the general formula (I). Reaction between a diol component containing a diene diol and a dicarboxylic acid component containing a vinyl dicarboxylic acid or an alkyl ester thereof, or It can be obtained by subjecting it to a tell exchange reaction.

Further, a non-vinyl dicarboxylic acid may be used in combination as a raw material, and in that case, the method may be carried out in one step or two or more steps as follows. For example, when the dicarboxylic acid component contains a vinyl dicarboxylic acid, a diol component containing a 2,4-dialkyl-1,5-pentendiol and a dicarboxylic acid component containing a vinyl dicarboxylic acid and a non-vinyl dicarboxylic acid are used. May be simultaneously subjected to an esterification reaction, or a non-vinyl dicarboxylic acid and a diol component are first subjected to an esterification reaction (first-stage reaction), and then a vinyl dicarboxylic acid is added. If necessary, a diol component may be added and the mixture may be subjected to an esterification reaction (second-stage reaction).

In this method, the order of addition of the non-Biel dicarboxylic acid and the vinyl dicarboxylic acid may be reversed.

Usually, these reactions are carried out at a temperature of from 120 to 250, normal pressure or reduced pressure.

The reaction is terminated when the acid value of the unsaturated polyester resin reaches preferably 30 (KOHmg / g) or less, more preferably 20 (KOHmg / g) or less.

When the esterification reaction is carried out, a catalyst such as lead oxide, zinc acetate, tetrabutyltinate, or zirconium naphthenate may be used, if necessary.

The use amount of such a catalyst is not particularly limited, but is usually 0.01 to 5.0% by weight based on the dicarboxylic acid component.

When the dicarboxylic acid component contains an alkyl ester of a vinyl dicarboxylic acid, such as methyl or ethyl, the unsaturated polyester resin is composed of an alkyl ester of the dicarboxylic acid such as methyl or ethyl, and 2,4-dialkyl-1,5- It can also be obtained by subjecting it to a transesterification reaction with a diol component containing pentanediol by a well-known method. Also, when an alkyl ester of a non-vinyl dicarboxylic acid is used, it can be subjected to a transesterification reaction in the same manner as described above.

The number average molecular weight of the unsaturated polyester resin is not uniform depending on the type of raw materials, reaction conditions, etc. However, when assuming applications such as molding, it is generally about 1,000 to 3,500. preferable.

Specific examples of 2,4-dialkyl-1,5-pentanediol include 2,4-dimethyl-1,5-pentanediol, 2-ethyl-4-methyl-1,5-pentanediol, and 2-methyl-4-. Propyl-1,5—pentanediol, 2—isopropyl_4—methyl—1,5—pentandiol, 2,4—Jetyl-1,5—Pentyldiol, 2—ethyl—4_propyl—1, 5 — pentanediol, 2 — ethyl 4-, isopropyl-1, 5, 5-pentanediol, 2, 4-dipropyl — 1, 5 — pentanediol, 2 — isopropyl-1, 4- propyl — 1, 5 — pentanediol, 2, 4 —Diisopropyl-1,5—pentanediol, 2,4-dibutyl-1,5—pentanediol, 2,4-dipentyl—1,5—pentanediol, 2,4—dihexyl1,5— Pen evening And diols. Among them, 2,4-diethyl-1,5-pentanediol is preferred.

2,4-Dialkyl-1,5-pentendiol can be prepared in a known manner, for example, as described in Japanese Patent Application Laid-Open (A) No. Hei 8 — 48642 or EP807617A. It can be manufactured according to the method described.

Other diols that may be used in combination with 2,4-dialkyl-1,5-pentenediol include, for example, ethylene glycol, propylene glycol, 1,3-butanediol, neopentyl glycol, 1,3_ Propanediol, 1,5-pentenediol, 1,6-hexanediol, bisphenol A hydride, 2-butyl_2-ethylethyl 1,3-propanediol, 3-methyl-1,5-pentene Diol, 1, 9—nonanediol, 2—methyl—1,8—oct Tangyl etc. can be mentioned. These can be used alone or in combination of two or more.

The proportion of 2,4-dialkyl-1,5-pentenediol in all diol components is preferably at least 30 mol%, more preferably at least 50 mol%. If the ratio of 2,4-dialkyl-1,5-pentanedole in the total diol component is less than 30 mol%, the water resistance and hot water resistance of the cured product obtained from the unsaturated polyester resin composition are reduced.

Examples of the vinyl dicarboxylic acid include maleic acid or its anhydride, fumaric acid, itaconic acid or its anhydride, citraconic acid or its anhydride, and the like. Among them, maleic acid or its anhydride or fumaric acid is preferred.

In addition, as the non-vinyl dicarboxylic acid, those conventionally used for improving the physical properties such as water resistance of unsaturated polyester resin can be used. For example, phthalic anhydride, phthalic acid, terephthalic acid, isophthalic acid, tetrahydrophthalic anhydride, tetrahydrofluoric acid, tetraclophthalic anhydride, tetrachlorophthalic anhydride, succinic acid , Adipic acid, azelaic acid, sebacic acid and the like. Among them, dicarboxylic acids having an aromatic ring, such as phthalic anhydride, phthalic acid, terephthalic acid, and isophthalic acid, increase the water resistance and hot water resistance after curing the polyester resin composition. It is a particularly preferred raw material. Further, an alkyl ester such as the above-mentioned methyl or ethyl ester of dicarboxylic acid can also be used as a raw material.

In the unsaturated polyester resin, the vinyl dicarboxylic acid as a raw material is preferably 40 to 70 mol% of all dicarboxylic acid components. Further, it is preferable that 50 mol% or more of the non-vinyl dicarboxylic acid is phthalic acid, terephthalic acid, isophthalic acid, an alkyl ester thereof, or phthalic anhydride. In addition, purpose, use Depending on the application, a small amount of a monocarboxylic acid or a trivalent or higher polycarboxylic acid may be added to the raw material for the esterification reaction. %. The molar ratio of the diol component to the dicarboxylic acid component, which is the raw material of the unsaturated polyester resin, is preferably from 0.9 to 1.2, and more preferably from 1.0 to 1.1. Excess diol component may be generally removed by a reduced pressure treatment or the like immediately before the end of the reaction or after the end of the reaction.

The unsaturated polyester resin composition of the present invention can be obtained by mixing the above-mentioned unsaturated polyester resin with a monomer having a copolymerizable double bond. Since the above-mentioned unsaturated polyester resin has extremely good compatibility with a monomer having a copolymerizable double bond, it can be easily made uniform by stirring and mixing both. In order to prevent the homopolymerization of a monomer having a copolymerizable double bond, a polymerization inhibitor, for example, a quinone such as a hide opening is added to the monomer in an amount of 0.05 to 0.5. % By weight may be added.

As the monomer having a double bond capable of copolymerization (vinyl monomer), a monomer used as a crosslinking agent for a conventional unsaturated polyester resin composition can be similarly used. For example, styrene, a-methylstyrene, t-butylstyrene, chlorostyrene, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, Glycidyl acrylate, methacrylic acid, methyl methacrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, glycidyl methacrylate, acetic acid Vinyl, acrylamide, acrylonitrile, diacetone acrylamide, etc. may be used alone or in combination of two or more. Also, bifunctional biel monomers such as divinylbenzene, diaryl phthalate and ethylene glycol dimethacrylate can be used. In particular, styrene is inexpensive and has good physical properties and is often used. The proportion of the monomer having a double bond in the unsaturated polyester resin composition is preferably from 10 to 60% by weight, and more preferably from 30 to 50% by weight. When the proportion of the monomer is less than 10% by weight, the water resistance, hot water resistance and mechanical strength of the cured product are reduced. When the proportion is more than 60% by weight, the homopolymer of the monomer is Generates in large quantities, and reduces the flexibility, flexibility, and mechanical strength of the cured product.

The unsaturated polyester resin composition of the present invention is a liquid having fluidity at room temperature, and can be stored at room temperature for a long period of time.

The unsaturated polyester resin composition of the present invention can be used as a one-pack or two-pack kit composed of a monomer having a double bond copolymerizable with the unsaturated polyester resin.

The unsaturated polyester resin composition of the present invention is cured alone or, if necessary, after addition of a polymerization initiator, a polymerization accelerator, etc., under conditions such as room temperature, heating, or light irradiation. Thereby, a solid unsaturated polyester resin cured product is obtained. The thermosetting of the composition of the present invention can be carried out under various temperature conditions by selecting a polymerization initiator, a polymerization accelerator and the like.

The unsaturated polyester resin composition of the present invention can be combined with glass fiber and used as a glass fiber reinforced plastic.

In this case, it is also possible to impregnate the glass fiber or to mix it with various fillers, reinforcing agents, coloring agents, etc. before starting the curing.

As the polymerization initiator and the polymerization accelerator, those used for curing a conventional unsaturated polyester resin composition can be used. Examples of the polymerization initiator include, for example, benzoyl peroxide, decanol peroxide, 3,3,5-trimethylhexanoyl peroxide, methylethylketone peroxide, cyclohexanone peroxide, and acetylacetate. Ton oxide, cumene hide mouth Organic peroxides such as xide, t-butyl hydroperoxide, lauroyl peroxide, t-butyl peroxide, t-butyl peroxide, and t-butyl peroxide are exemplified. Of these, methylethylketone peroxyside is preferred.

Examples of the polymerization accelerator include cobalt naphthenate, cobalt octoate, manganese naphthenate, dimethylaniline, and dimethyl balatoluidine. The polymerization initiator and the polymerization accelerator are each preferably used in an amount of 0.01 to 5.00% by weight, more preferably 0.05 to 3.00% by weight, based on the unsaturated polyester resin composition.

Since the unsaturated polyester resin composition of the present invention is excellent in flexibility, flexibility, hot water resistance and alkali resistance, it is extremely useful for molding materials such as bathtubs, purification tanks, and water storage tanks.

The unsaturated polyester resin composition of the present invention can be applied to paints, decorative boards, adhesives, putty for automobiles, cast products, and the like, in addition to the above uses. Example

[Example 1]

In a reaction vessel equipped with a cooler, a rotary stirrer, a thermometer, and an inert gas inlet tube, 5.6 g of terephthalic acid and 705.3 g of 2,4-dimethyl-1,5-pentanediol were charged, and the mixture was stirred under a nitrogen stream. The reaction was carried out at a reaction temperature of 210 ° C. and normal pressure for 4 hours (first-stage reaction). When the acid value of the reaction product reached 9.5 (KO Hmg / g), it was cooled until the temperature reached 160 ° C. Further, 59.2 g of hydrofluoric anhydride and 196.2 g of maleic anhydride were added, and the mixture was reacted at a reaction temperature of 210 ° C. with stirring (second-stage reaction). After that, the sample was kept at 200 ° C under a reduced pressure of 20 mm of mercury for 1 hour, and the acid value was 15.4 (KOHmg / g). 1073 g of a Japanese polyester resin was obtained. Cool the unsaturated polyester resin to 100 ° C and stir well with 0.15 g of hydroquinone as a polymerization inhibitor and styrene 7 as a crosslinking agent (monomer having a double bond). 15 g was immediately added to obtain a uniform liquid unsaturated polyester resin composition. The viscosity of the unsaturated polyester resin composition at 25 ° C. was 5.3 voids.

[Examples 2 to 5, Comparative Examples 1 to 3]

An unsaturated polyester resin composition was produced in the same manner as in Example 1.

The raw material compositions used in Examples 2 to 5, the first-stage and second-stage reaction conditions are shown in Tables 1 and 2, the composition and viscosity of the unsaturated polyester resin composition are shown in Table 3, and the same as in Comparative Examples 1 to 3. Tables 4 to 6 show the items in (4).

Each of the unsaturated polyester resin compositions of this example has a low viscosity, and can be favorably used for spraying work when used for gel coating.

Table 1 First-stage reaction

* Acid value of the reaction solution reached in the first stage reaction

IPA: Isophthalic acid

E P D: 2, 4-Jetyl-1, 5-Penn diol G: Propylene glycol

MTA: dimethyl terephthalate

TPA: Terephthalic acid

Table 2

Second stage reaction

* Acid value of the reaction solution reached in the second stage reaction

E P D: 2 4 -Jetil-1,5 -Pentangil

F A: Fumaric acid

M A A: Maleic anhydride

PAA: Furic anhydride

3 Composition and physical properties of unsaturated polyester resin composition

H Q: Yakirokinon

Table 4 First-stage reaction

* Acid value of the reaction solution reached in the first stage reaction

IPA: Isofuric acid

HBP: hydrogenated bisphenol A

T P A: Terephthalic acid

N P G: Neopentyl glycol

PG: Propylene glycol Table 5

Second stage reaction

* Acid value of the reaction solution reached in the second stage reaction

P A A: phthalic anhydride

F A: Fumaric acid

N P G: neopentyl recall Table 6

Composition and physical properties of unsaturated polyester resin composition

H Q: Eight Drokinone

[Test Example 1; Various physical properties of cured product, hot water resistance, alkali resistance test]

Each unsaturated polyester obtained in Example 15 and Comparative Example 13 To 100 g of the resin composition, 1.5 g of methylethylketone peroxide [trade name: "Permec N" manufactured by Nippon Oil & Fats Co., Ltd.] and 0.5 g of 6% cobalt naphthenate were added and mixed.

Thereafter, the mixture was filled between two glass plates having a 3 mm-thick spacer and left in an air bath at 25 ° C. for 16 hours to be cured. Further, the cured product was cured in air at 120 ° C. for 2 hours to prepare a casting plate having a thickness of 3 mm.

Using each casting plate, the breaking strength, the breaking elongation, and the bending strength were measured. In addition, hot water resistance and alkali resistance were tested. Each test method is as follows.

• For rupture strength, rupture elongation, and bending strength, a JIS No. 1 dumbbell was prepared by cutting the above cast plate, and this was used as a test sample. The JIS No. 1 dumbbell has the shape shown in Fig. 1. For measurement of breaking strength, breaking elongation and bending strength, refer to JIS (Japanese

Industrial Standards) k 6 9 19

• The hot water resistance was evaluated by the retention of breaking strength after the dumbbell was immersed in boiling water for 400 hours.

• Alkali resistance was evaluated by the retention of breaking strength after immersing the dumbbell in a 5 wt% aqueous sodium hydroxide solution for one year.

Table 7 shows the physical properties of the cured product and the test results for hot water resistance and alkali resistance.

7

Physical properties of cured unsaturated polyester resin

Breaking strength Breaking elongation Bending strength Hot water Water resistant Alkali Strength retention rate Strength retention rate

(kgf / cm ² ) (%) (kgf / cm (%) (%)

1 丄 6 0 0 4 .2 Ηπ ^ Re Q 9 real

9 5 9 0 4 .5 ο Q 0 w ο Li Q

(~ 8 m 3 5 9 4 .3 8 0 0 8 3 9 0 Example 4 5 9 5 3 .8 8 2 6 7 9 8 6

5 5 9 0 3 .9 8 2 0 8 0 8 5 ratio 1 5 8 0 1 .8 8 3 5 3 8 4 3 comparison 2 5 6 5 1 .5 8 1 0 5 2 5 2 Example 3 5 9 5 1 3 8 4 0 6 4 6 8 Table 7 shows that the cured product of the unsaturated polyester resin of this example has the same breaking strength and bending strength as the cured product of the unsaturated polyester resin of the comparative example. Approximately 2 to 3 times, indicating excellent flexibility and flexibility. Further, the unsaturated polyester resin cured product of this example has extremely good hot water strength retention and alkaline strength retention.

[Test Example 2; Suitability test as gel coat film]

To 100 g of each of the unsaturated polyester resin compositions of Examples 1 and 5 and Comparative Examples 1 and 3, 3.5 g of rutile-type titanium oxide and silica fine powder [trade name: “Air Port Jill” Nippon Aerosil Co., Ltd. 4.0 g, 6 wt% cobalt naphthenate 0.6 g was kneaded with three rolls to produce a gel coat.

Methyl ethyl ketone peroxide [Product name: N, manufactured by Nippon Oil & Fats Co., Ltd.], stirred and then, using a spray gun on a chromed metal plate, use a spray gun to reduce the thickness of the gel coat to 0.4 to 0.6 mm. Spraying was performed so that the film was formed. After the film was gelled, it was kept in air at 55-60 ° C for 2 hours. Next, using a chopped strand mat as a reinforcing material, an unsaturated polyester resin for general lamination [trade name: “Polylight FH”] to a thickness of about 3 mm and a glass content of about 35% by weight. — 10 3 — N ”manufactured by Dainippon Ink and Chemicals, Inc.]. After standing for 24 hours, 2 hours at 120 ° C, and after curing, they were peeled off from the metal plate to make a test sample of 10 cm x 10 cm.

The test sample was immersed in a water bath that repeated a cooling and heating cycle of boiling for 16 hours and 25 ° C for 8 hours, and the surface state of the gel coat film was observed after 65 cycles (156 hours). . Table 8 shows the results. Table 8

Physical properties of gel coat film

As is evident from the results in Table 8, the unsaturated polyester resin composition of this example has excellent water resistance and hot water resistance even when used in combination with a general laminating resin. Industrial applicability

The cured product obtained by curing the unsaturated polyester resin composition of the present invention has flexibility and flexibility, and is excellent in water resistance, hot water resistance and alkali resistance, and is used in a severe environment. Can withstand. Even if the unsaturated polyester resin composition for general lamination is used for a laminated and cured laminate, no cracks or blister (scratch) force S will be generated on the surface, and the resin will not react with other lamination resins. It has good adhesion and can follow temperature changes, and is particularly suitable for bathtubs, septic tanks, water storage tanks and the like. It is easy to handle and has extremely high mechanical properties.

Claims

The scope of the claims

1. An unsaturated polyester resin having a structural unit represented by the following general formula (I) in the molecule (wherein R ¹ and R ² represent the same or different lower alkyl groups) and An unsaturated polyester resin composition comprising a monomer having a polymerizable double bond.

R ^{1 2}

— 0— CH ₂ — CH-CH Factory CH— CH ₂ — 0——

… (I)

2. The unsaturated polyester resin composition according to claim 1, wherein the proportion of the copolymerizable monomer having a double bond is 10 to 60% by weight.

3. The unsaturated polyester resin is an esterification reaction or a transesterification reaction between a diol component containing 2,4-dialkyl-1,5-pentenediol and a dicarboxylic acid component containing a vinyl dicarboxylic acid or a dicarboxylic acid alkyl ester. The unsaturated polyester resin composition according to claim 1, which is an unsaturated polyester resin having a number average molecular weight of 1,000 to 3,000 obtained by the reaction.

4. The unsaturated polyester resin composition according to claim 3, wherein the proportion of 2,4-dialkyl-1,5-pentanediol in the diol component is 30 to 100 mol%.

5. The method according to claim 3, wherein the dicarboxylic acid component contains at least one of phthalic acid, terephthalic acid, isophthalic acid, or an alkyl ester thereof, or phthalic anhydride. A saturated polyester resin composition.

6. The unsaturated polyester resin composition according to claim 3, wherein the vinyl dicarboxylic acid is fumaric acid, maleic acid, or an anhydride thereof.

7. The unsaturated polyester resin composition according to any one of claims 1 to 6, wherein in the formula (I), R ′ and R ² are both ethyl groups.

8. The unsaturated polyester resin composition according to claim 1, further comprising a polymerization initiator.

9. A cured unsaturated polyester resin, wherein the unsaturated polyester resin composition according to claim 1 is cured.

10. Unsaturated polyester resin having a structural unit represented by the following general formula (I) in the molecule (wherein R ¹ and R ² represent the same or different lower alkyl groups) and copolymerized therewith A two-pack kit comprising a monomer having a possible double bond.

R ¹ R ²

— 0— CH ₂ -CH-CH ₂ — CH—— CH ₂ — 0——

… (I)