JP2023140062A - Copolymer and resin composition - Google Patents

Abstract

To provide a copolymer and a resin composition which are excellent in hydrolysis characteristics.SOLUTION: A copolymer includes a structural unit (a1) derived from a compound represented by formula (I), and a structural unit (a2) derived from at least one compound selected from the group consisting of butyl acrylate, butyl methacrylate, N-vinyl-2-pyrrolidone and acrylonitrile, wherein a value Mn2/Mn1 obtained by dividing a number average molecular weight Mn2 after hydrolysis treatment for two hours in a potassium hydroxide solution with a concentration of 5 mass% at 25°C by a number average molecular weight Mn1 before the hydrolysis treatment is 0.4 or less.SELECTED DRAWING: None

Description

The present invention relates to copolymers and resin compositions.

The use of degradable resin materials for disposable food containers, packaging materials, etc. is widespread for the purpose of environmental protection. The required performance of a degradable resin material is that it does not decompose during use, but decomposes immediately after use. To this end, it is necessary to appropriately select the degradable monomer and the monomer to be copolymerized and to control the decomposition characteristics.

Patent Document 1 discloses a resin composition containing a copolymer obtained by copolymerizing a degradable cyclic monomer with methyl methacrylate or the like.

International Publication No. 2021/071432

However, the decomposition characteristics of the copolymer disclosed in Patent Document 1 are not sufficient, and even after 24 hours of hydrolysis treatment, the decrease in molecular weight is low.

An object of the present invention is to provide a copolymer and a resin composition with excellent hydrolysis properties.

式（Ｉ）中、Ｘは炭素原子、窒素原子及び酸素原子からなる群から選択されるいずれか１種であり、Ｒ^１及びＲ^２は、それぞれ独立に、水素原子又は炭化水素基である。
［２］ 前記式（Ｉ）においてＸが酸素原子である、［１］に記載の共重合体。
［３］ 前記式（Ｉ）においてＲ^１及びＲ^２がいずれもメチル基である、［１］又は［２］に記載の共重合体。
［４］ 前記式（Ｉ）で表される化合物に由来する構成単位（ａ１）の全構成単位に対する割合が１～５０質量％である、［１］～［３］のいずれかに記載の共重合体。
［５］ ２５℃において５質量％濃度の水酸化カリウム水溶液下での２時間の加水分解処理によって、前記加水分解処理後の数平均分子量Ｍ_ｎ２を前記加水分解処理前の数平均分子量Ｍ_ｎ１で除した値Ｍ_ｎ２／Ｍ_ｎ１が０．２以下である、［１］～［４］のいずれかに記載の共重合体。
［６］ ［１］～［５］のいずれかに記載の共重合体を含む樹脂組成物。 [1] Structural unit (a1) derived from the compound represented by formula (I) and at least one compound selected from the group consisting of butyl acrylate, butyl methacrylate, N-vinyl-2-pyrrolidone and acrylonitrile. The number average molecular weight M _n 2 after the hydrolysis treatment is reduced by hydrolysis treatment for 2 hours under a potassium hydroxide solution with a concentration of 5% by mass at 25° C. A copolymer whose value M _n 2/M _n 1 divided by the number average molecular weight M _n 1 before decomposition treatment is 0.4 or less.

In formula (I), X is any one selected from the group consisting of carbon atoms, nitrogen atoms, and oxygen atoms, and R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group.
[2] The copolymer according to [1], wherein in the formula (I), X is an oxygen atom.
[3] The copolymer according to [1] or [ ² ], wherein in the formula (I), both R ¹ and R 2 are methyl groups.
[4] The compound according to any one of [1] to [3], wherein the proportion of the structural unit (a1) derived from the compound represented by formula (I) to the total structural units is 1 to 50% by mass. Polymer.
[5] The number average molecular weight M _n 2 after the hydrolysis treatment is changed to the number average molecular weight M n before the hydrolysis treatment by hydrolysis treatment for 2 hours under an aqueous potassium hydroxide solution having a concentration of 5% by mass at 25 _° C. The copolymer according to any one of [1] to [4], wherein the value M _n 2/M _n 1 divided by 1 is 0.2 or less.
[6] A resin composition comprising the copolymer according to any one of [1] to [5].

According to the present invention, it is possible to provide a copolymer and a resin composition with excellent hydrolysis properties.

Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not limited to the following description, and can be implemented with various modifications within the scope of the gist.

The following definitions of terms apply throughout the specification and claims.
Numerical ranges expressed using "~" include numbers at both ends.
"Structural unit" means a structural unit derived from a monomer, that is, a structural unit formed by polymerization of a monomer, or a part of a structural unit converted into a different structure by processing a polymer. means a constituent unit that has been
"Vinyl monomer" means a compound containing at least one vinyl group (carbon-carbon unsaturated double bond).
"(Meth)acrylate" refers to "acrylate" or "methacrylate".
"(Meth)acrylonitrile" refers to "acrylonitrile" or "methacrylonitrile".
"(Meth)acrylic acid" refers to "acrylic acid" or "methacrylic acid."
"(Meth)acryloyl" refers to "acryloyl" or "methacryloyl".

[Copolymer]
The copolymer of the present invention comprises a structural unit (a1) derived from the monomer (A1) described below, and at least one component selected from the group consisting of butyl acrylate, butyl methacrylate, N-vinyl-2-pyrrolidone, and acrylonitrile. A structural unit (a2) derived from a species compound.

<Structural unit (a1), monomer (A1)>
The structural unit (a1) is a structural unit based on the monomer (A1) described below. The number of structural units (a1) contained in the copolymer of the present invention may be one, or two or more.
Monomer (A1) is a compound represented by formula (I).

In formula (I), X, R ¹ and R ² are as follows.
X is any one selected from the group consisting of a carbon atom, a nitrogen atom, and an oxygen atom, preferably a nitrogen atom or an oxygen atom, and more preferably an oxygen atom. When X is a carbon atom, a methylene group (>CH ₂ ) in which two hydrogen atoms are bonded to a carbon atom is preferred. When X is nitrogen, an imino group (>NH) in which one hydrogen atom is bonded to a nitrogen atom is preferable.
R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group. The hydrocarbon group is preferably an alkyl group or an aryl group.
The alkyl group is preferably an alkyl group having 3 or less carbon atoms, and more preferably a methyl group. Moreover, it is preferable that both R ¹ and R ² are methyl groups.
The aryl group is preferably an aryl group having 10 or less carbon atoms, and more preferably a phenyl group.

The copolymer of the present invention has hydrolyzability by having the structural unit (a1) derived from the monomer (A1) represented by formula (I).

Specific examples of monomer (A1) include 5,5-dimethyl-2-methylene-1, where in formula (I), X is an oxygen atom and R ¹ and R ² are both methyl groups; Examples include 3-dioxolan-4-one.

The number average molecular weight M _n of the copolymer of the present invention is not particularly limited, but is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 500,000, even more preferably from 50,000 to 300,000. When the number average molecular weight M _n of the copolymer of the present invention is 1000 or more, the copolymer has better handling properties. Moreover, when the number average molecular weight M _n of the copolymer of the present invention is 1,000,000 or less, the hydrolyzability becomes more excellent.

In the copolymer of the present invention, the number average molecular weight M _n 2 after the hydrolysis treatment is reduced to that before the hydrolysis treatment by hydrolysis treatment for 2 hours at 25° C. under a potassium hydroxide solution with a concentration of 5% by mass. The value M _n 2 /M _n 1 divided by the number average molecular weight M _n 1 is 0.4 or less, preferably 0.3 or less, and more preferably 0.2 or less. Note that the number average molecular weight M _n 1 before the hydrolysis treatment is equal to the number average molecular weight M _n described above. If M _n 2/M _n 1 is 0.4 or less, the copolymer of the present invention has excellent hydrolyzability.

The proportion (mol%) of the structural unit (a1) in all the structural units of the copolymer of the present invention is not particularly limited, but is preferably 1 to 50 mol%, more preferably 10 to 50 mol%, and 25 to 50 mol%. More preferred is mole %. When the proportion of the structural unit (a1) in all the structural units of the copolymer of the present invention is 1 mol % or more, the copolymer of the present invention has better hydrolyzability. Further, when the proportion of the structural unit (a1) in all the structural units of the copolymer of the present invention is 50 mol% or less, the copolymer of the present invention has better durability during use.

<Structural unit (a2), monomer (A2)>
The structural unit (a2) is based on at least one compound (hereinafter also referred to as "monomer (A2)") selected from the group consisting of butyl acrylate, butyl methacrylate, N-vinyl-2-pyrrolidone, and acrylonitrile. It is a constituent unit. The number of structural units (a2) contained in the copolymer of the present invention may be one, or two or more.

The copolymer of the present invention has more excellent hydrolyzability by containing the structural unit (a2).

The proportion (mol%) of the structural unit (a2) in all the structural units of the copolymer of the present invention is not particularly limited, but is preferably 50 to 99 mol%, more preferably 50 to 90 mol%, and 50 to 75 mol%. More preferred is mole %. When the proportion of the structural unit (a2) in all the structural units of the copolymer of the present invention is 50 mol % or more, the copolymer of the present invention has better durability during use. Further, when the proportion of the structural unit (a2) in all the structural units of the copolymer of the present invention is 99 mol % or less, the copolymer of the present invention has better hydrolyzability.

<Method for producing copolymer>
The method for producing the copolymer of the present invention is not particularly limited, and examples thereof include a method of polymerizing a polymerizable composition containing monomer (A1) and a monomer other than monomer (A1). .

(Polymerizable composition)
The polymerizable composition preferably contains a monomer (A1), a monomer (A2), and a polymerization initiator (B). The polymerizable composition may contain a solvent and other additives as necessary. Each component will be explained in detail below.

- Monomer (A1) and monomer (A2)
Monomer (A1) and monomer (A2) are as described above.

・Polymerization initiator (B)
The polymerization initiator (B) is a radical polymerization initiator. This improves the polymerization rate of the copolymer. As the radical polymerization initiator, for example, an organic peroxide or an azo compound can be used. The number of polymerization initiators (B) contained in the polymerizable composition may be one or two or more.

Examples of the organic peroxide include 2,4-dichlorobenzoyl peroxide, t-butyl peroxypivalate, o-methylbenzoyl peroxide, bis-3,5,5-trimethylhexanoyl peroxide, and octanoyl peroxide. Peroxide, t-butyl peroxy-2-ethylhexanoate, cyclohexanone peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, and di-t-butyl peroxide.

Examples of the azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethyl-4- methoxyvaleronitrile).

Among these radical polymerization initiators, benzoyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2 , 4-dimethyl-4-methoxyvaleronitrile).

The content of the polymerization initiator (B) in the polymerizable composition is not particularly limited, but is 0.001 to 0.05 per mole of the total of monomer (A1) and monomer (A2). The amount is preferably mol, more preferably 0.002 to 0.02 mol. When the content of the polymerization initiator (B) in the polymerizable composition is 0.001 mol or more per 1 mol of the monomer (A1) and the monomer (A2) in total, polymerization of the copolymer is prevented. Speed is further improved. Further, when the content of the polymerization initiator (B) in the polymerizable composition is 0.05 mol or less per 1 mol of the monomer (A1) and the monomer (A2) in total, Side reactions are sufficiently suppressed, and the molecular weight distribution of the copolymer becomes narrower.

・Solvent Examples of solvents include hydrocarbon solvents such as toluene; ether solvents such as diethyl ether, tetrahydrofuran, and diglyme; halogenated hydrocarbon solvents such as dichloromethane and chloroform; ketone solvents such as acetone; Alcohol solvents; nitrile solvents such as acetonitrile; vinyl ester solvents such as ethyl acetate; carbonate solvents such as ethylene carbonate; and supercritical carbon dioxide. The number of solvents may be one, or two or more.
The content of the solvent in the polymerizable composition is not particularly limited, but is preferably 20 to 90% by mass.

-Other additives Examples of other additives include chain transfer agents such as mercaptans.

(Polymerization of polymerizable composition)
The method for polymerizing the polymerizable composition is not particularly limited, and examples include emulsion polymerization, suspension polymerization, and solution polymerization.

The polymerization of the polymerizable composition may be performed in the presence of air, but from the viewpoint of polymerization efficiency, it is preferably performed under conditions in which air is replaced with an inert gas such as nitrogen gas or argon gas.

The temperature of the polymerizable composition during polymerization of the polymerizable compound is not particularly limited, but from the viewpoint of polymerization rate and polymerization control, it is preferably 0 to 150°C, more preferably 20 to 120°C.

The polymerization time of the polymerizable compound is not particularly limited, but is generally preferably 0.5 to 72 hours, more preferably 0.5 to 60 hours.

<Hydrolysis treatment method of copolymer>
The hydrolysis treatment of the copolymer of the present invention is carried out as follows.
First, potassium hydroxide is dissolved in an arbitrary solvent to a concentration of 5% by mass. The solvent in which potassium hydroxide is dissolved is not particularly limited as long as it dissolves in the solvent in which the copolymer of the present invention is dissolved, but examples include water; alcohols such as methanol, alcohol, and isopropyl alcohol; acetone and methyl ethyl ketone, etc. ketones; ethers such as tetrahydrofuran and dimethyl ether; and alkyl halides such as chloroform and methylene chloride.

Next, the copolymer of the present invention is dissolved in a solvent. The solvent for dissolving the copolymer of the present invention is not particularly limited, but includes, for example, water; alcohols such as methanol, alcohol, and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; aromatic hydrocarbons such as toluene and benzene. ethers such as tetrahydrofuran and dimethyl ether; alkyl halides such as chloroform and methylene chloride; dimethylformamide, dimethyl sulfoxide, and diethylene glycol dimethyl ether.

The concentration of the copolymer of the present invention during the hydrolysis treatment is not particularly limited, but is preferably 1 to 90% by weight, more preferably 10 to 50% by weight. When dissolving the copolymer of the present invention in the solvent, heat treatment or the like may be performed.

To the mass of the solution in which the copolymer is dissolved, the temperature of which is controlled at 25°C, is added 10% by mass of the potassium hydroxide solution prepared above, whose temperature is controlled to 25°C, to start a hydrolysis reaction. Stirring is continued with an arbitrary stirring device during the reaction, and after 2 hours, the solvent is removed by vacuum treatment to obtain a product.

The value M _n 2 /M _n 1 obtained by dividing the number average molecular weight M _n 2 of the obtained product after the hydrolysis treatment by the number average molecular weight M _n 1 of the copolymer before hydrolysis is 0.4 or less. , preferably 0.3 or less, more preferably 0.2 or less.

<Method for measuring number average molecular weight>
The number average molecular weight of the copolymer of the present invention and its hydrolysis product is measured by GPC measurement described below.
The elution curve of the copolymer dissolved in tetrahydrofuran (THF) was measured by gel permeation chromatography (GPC) using tetrahydrofuran as the eluent at a column temperature of 40°C, and the number average molecular weight was determined based on the calibration curve with standard polymethyl methacrylate. calculate.

[Resin composition]
The copolymer according to the present invention may be mixed with any other resin or additive and used as a resin composition. The mixture can be obtained by dissolving each in an arbitrary solvent, stirring, and removing the solvent, or can be produced by melt-kneading.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited by the following description.

[Method for measuring number average molecular weight]
The elution curve of the copolymer dissolved in tetrahydrofuran (THF) was measured by gel permeation chromatography (GPC) using tetrahydrofuran as the eluent at a column temperature of 40°C, and the number average molecular weight was determined based on the calibration curve with standard polymethyl methacrylate. Calculated. Hereinafter, the measurement of number average molecular weight using GPC may be referred to as GPC measurement.

[Production Example 1: Synthesis of 5,5-dimethyl-2-methylene-1,3-dioxolan-4-one]
25 g of 2-acetoxy-2-methylpropionyl chloride and 18.4 g of triethylamine were dissolved in 100 mL of dichloromethane, and the mixture was heated and stirred under a nitrogen atmosphere for 5 hours to react. After 5 hours, the reaction solution was cooled and diluted into a mixed solvent of ether and hexane. The solvent in the diluted solution was evaporated to obtain 5,5-dimethyl-2-methylene-1,3-dioxolan-4-one.

In addition, in 5,5-dimethyl-2-methylene-1,3-dioxolan-4-one, in the above-mentioned formula (I), X is an oxygen atom, and R ¹ and R ² are both methyl groups. It is a compound.

[Example 1]
50 parts by mass of 5,5-dimethyl-2-methylene-1,3-dioxolan-4-one produced in Production Example 1 as monomer (A1) and 50 parts by mass of butyl acrylate as monomer (A2). 1 part and 400 parts by mass of toluene as a solvent were charged into a reaction vessel, and the reaction vessel was purged with nitrogen for 30 minutes. After 30 minutes, 0.18 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) was added as an initiator, the reaction solution was heated to 70°C, and the reaction was stirred for 105 minutes under a nitrogen atmosphere. I let it happen. After the reaction solution was cooled, it was reprecipitated in a large amount of hexane to obtain a copolymer. The obtained copolymer was measured by GPC, and the number average molecular weight M _n 1 before hydrolysis treatment was calculated. In addition, ¹ H NMR measurement was performed, and the composition ratio of the obtained copolymer was structural unit (a1): structural unit (a2) = 35 mol%: 65 mol%.
Furthermore, 0.02 g of the obtained copolymer was stirred and dissolved in 1 mL of tetrahydrofuran. A solution of 0.005 g of potassium hydroxide in 0.1 mL of methanol was added to this copolymer solution, and the mixture was stirred at 25° C. for 2 hours to perform a hydrolysis treatment. The solution after the hydrolysis treatment was treated under reduced pressure using an evaporator to remove the solvent, and a reaction product was obtained. The obtained reaction product was measured by GPC, and the number average molecular weight M _n 2 after the hydrolysis treatment was calculated.
The charging ratio of monomers, the composition ratio (mol%) of the structural unit (a1) of the obtained copolymer, the number average molecular weight before hydrolysis treatment (M _n 1), the number average molecular weight after hydrolysis treatment ( M _n 2), M _n 2/M _n 1, shown in Table 1.

[Examples 2 to 12]
Example 1 except that the monomer (A1) and monomer (A2) were of the type and preparation ratio shown in Table 1 (Examples 2 to 6) or Table 2 (Examples 7 to 12). A copolymer was produced in the same manner. The composition ratio (mol%) of the structural unit (a1) of the obtained copolymer, the number average molecular weight before hydrolysis treatment (M _n 1), the number average molecular weight after hydrolysis treatment (M _n 2), and M _n 2 /M _n 1 is shown in Table 1 (Examples 2 to 6) or Table 2 (Examples 7 to 12, Comparative Example 1).

[Comparative example 1]
A copolymer was produced in the same manner as in Example 1, except that other monomers were used in place of monomer (A1) and monomer (A2), and the types and charging ratios were as shown in Table 2. Manufactured. The composition ratio (mol%) of the structural unit (a1) of the obtained copolymer, the number average molecular weight before hydrolysis treatment (M _n 1), the number average molecular weight after hydrolysis treatment (M _n 2), and M _n 2 /M _n 1, as shown in Table 1 (Examples 2 to 6) or Table 2 (Examples 7 to 12, Comparative Example 1).

As can be seen from Tables 1 and 2, the copolymers of Examples 1 to 12 had excellent hydrolyzability, but the copolymer of Comparative Example 1 had poor hydrolyzability.

The copolymer and resin composition of the present invention can be used for various packaging materials, food containers, beverage containers, microcapsules, capsules for fertilizers, and the like.

Claims (6)

A structural unit (a1) derived from a compound represented by formula (I) and a structure derived from at least one compound selected from the group consisting of butyl acrylate, butyl methacrylate, N-vinyl-2-pyrrolidone, and acrylonitrile. The number average molecular weight M _n 2 after the hydrolysis treatment is equal to that before the hydrolysis treatment by hydrolysis treatment for 2 hours under a potassium hydroxide solution with a concentration of 5% by mass at 25° C. A copolymer whose value M _n 2 /M _n 1 divided by the number average molecular weight M _n 1 is 0.4 or less.

In formula (I), X is any one selected from the group consisting of carbon atoms, nitrogen atoms, and oxygen atoms, and R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group. The copolymer according to claim 1, wherein in the formula (I), X is an oxygen atom. The copolymer according to claim ^{1 or 2, wherein in the formula (I), both R 1} and R ² are methyl groups. The copolymer according to any one of claims 1 to 3, wherein the proportion of the structural unit (a1) derived from the compound represented by the formula (I) to the total structural units is 1 to 50% by mass. The number average molecular weight M _n 2 after the hydrolysis treatment is divided by the number average molecular weight M _n 1 before the hydrolysis treatment by hydrolysis treatment for 2 hours at 25 ° C. under a potassium hydroxide aqueous solution with a concentration of 5% by mass. The copolymer according to any one of claims 1 to 4, wherein the value M _n 2/M _n 1 is 0.2 or less. A resin composition comprising the copolymer according to any one of claims 1 to 5.