WO2021033768A1

WO2021033768A1 - Copolymer and method for producing same, copolymer mixture, dope resin composition, and resin molded body and method for producing same

Info

Publication number: WO2021033768A1
Application number: PCT/JP2020/031644
Authority: WO
Inventors: 慎也井本; 倫明北村; 健介寳來; 中西　秀高
Original assignee: 株式会社日本触媒
Priority date: 2019-08-22
Filing date: 2020-08-21
Publication date: 2021-02-25
Also published as: JP7474771B2; CN114341210A; KR20220042168A; JPWO2021033768A1

Abstract

The present invention discloses a method for producing a copolymer which contains a constituent unit derived from α-methylenelactone and a constituent unit derived from an alkyl (meth)acrylate that has an alkyl group having from 1 to 6 carbon atoms. This method for producing a copolymer comprises a step for polymerizing monomers containing α-methylenelactone and an alkyl (meth)acrylate in the presence of a solvent. The solvent satisfies either the condition (A) (at least one solvent selected from the group consisting of cyclic amides and cyclic esters) or the condition (B) (a mixed solvent which is composed of a first solvent having a boiling point of less than 100°C and a second solvent having a boiling point of 100°C or more, wherein: the first solvent is at least one substance selected from the group consisting of ketones and alkyl chlorides; the second solvent is at least one substance selected from the group consisting of cyclic ketones, cyclic esters, amides and sulfoxides; and the mixed solvent has a boiling point of from 70°C to 120°C).

Description

Copolymer and its production method, copolymer mixture, dope resin composition, resin molded product and its production method

The present invention relates to a copolymer and a method for producing the same, a copolymer mixture, a dope resin composition, and a resin molded product and a method for producing the same.

Copolymers containing structural units derived from α-methylene lactone are excellent in transparency, heat resistance, and optical isotropic properties, and are expected to be applied to optical applications. For example, Patent Document 1 describes that a film or the like, which is a molded product of a copolymer (resin) containing a constituent unit derived from a predetermined α-methylene lactone, is suitable for use as an optical member.

Japanese Unexamined Patent Publication No. 2008-179813

By the way, in general, a copolymer containing a structural unit derived from α-methylene lactone tends to have low solubility in a solvent, so that polymerization is carried out without a solvent or in a dimethyl sulfoxide (DMSO) solvent. However, the heat of polymerization cannot be removed by polymerization without a solvent, and the solvent itself is decomposed by heating to generate harmful substances in polymerization with a DMSO solvent, and it has explosiveness under specific conditions. Therefore, there is a problem in terms of safety and it is not suitable for industrialization. Further, according to the study by the present inventors, when the polymerization is carried out in a DMSO solvent, the obtained copolymer containing a structural unit derived from α-methylene lactone is colored, and the transparency tends to be lowered. I found that.

Therefore, the present invention provides a method for producing a copolymer containing a structural unit derived from α-methylenelactone by polymerization using a solvent, which can improve the transparency of the obtained copolymer. The main purpose is to provide.

The present invention relates to the following methods for producing a copolymer according to [1] to [8], the copolymer according to [9] to [11], and the copolymer according to [12] to [14]. Provided are a mixture, a dope resin composition according to [15], a resin molded product according to [16], and a method for producing the resin molded product according to [17] and [18].
[1] A method for producing a copolymer containing a structural unit derived from α-methylenelactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, which is α in the presence of a solvent. -Production of a copolymer comprising a step of polymerizing a monomer containing methylene lactone and alkyl (meth) acrylate, wherein the solvent is a solvent satisfying either the following condition (A) or the following condition (B). Method.
Condition (A): At least one solvent selected from the group consisting of cyclic amides and cyclic esters.
Condition (B): A mixed solvent consisting of a first solvent having a boiling point of less than 100 ° C. and a second solvent having a boiling point of 100 ° C. or higher, and the first solvent is selected from the group consisting of ketones and alkyl chlorides. The second solvent is at least one selected from the group consisting of cyclic ketones, cyclic esters, amides, and sulfoxides, and is a mixed solvent having a boiling point of 70 to 120 ° C.
[2] The method for producing a copolymer according to [1], wherein the solvent is a solvent that satisfies the condition (A).
[3] The method for producing a copolymer according to [1], wherein the solvent is a solvent that satisfies the condition (B).
[4] The method for producing a copolymer according to [3], wherein the first solvent is acetone.
[5] The method for producing a copolymer according to [3] or [4], wherein the second solvent is a cyclic ketone.
[6] The method for producing a copolymer according to [5], wherein the cyclic ketone is cyclohexanone.
[7] The method for producing a copolymer according to [3] or [4], wherein the second solvent is at least one selected from the group consisting of cyclic esters, amides, and sulfoxides.
[8] The second solvent is γ-butyrolactone, γ-valerolactone, δ-valerolactone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N, N'-dimethylimidazolidinone. The method for producing a copolymer according to [7], which is at least one selected from the group consisting of dimethyl sulfoxide and dimethyl sulfoxide.
[9] Containing a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, the internal haze per 100 μm thickness when made into a film is 2. Copolymer, less than 5%.
[10] A copolymer containing a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms and having a weight average molecular weight of 200,000 or more and 1,000,000 or less. ..
[11] The copolymer according to [9] or [10], wherein ^{the L *} a ^* b ^* color system has an internal b ^* value of less than 1.6 per 100 μm of thickness when formed into a film.
[12] A copolymer mixture containing the copolymer according to any one of [9] to [11] and at least one compound selected from the group consisting of cyclic amides, cyclic esters, and cyclic ketones. ..
[13] Consists of a copolymer containing a structural unit derived from α-methylene lactone and a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, a cyclic amide, a cyclic ester, and a cyclic ketone. A copolymer mixture containing at least one compound selected from the group.
[14] The copolymer mixture according to [12] or [13], wherein the content of the compound is 10 to 3000 mass ppm based on the total amount of the copolymer.
[15] A dope resin composition containing the copolymer according to any one of [9] to [11] and a dispersion medium, wherein the content of the copolymer is the total amount of the dope resin composition. As a reference, a dope resin composition of 5% by mass or more.
[16] A resin molded product containing the copolymer according to any one of [9] to [11] or the copolymer mixture according to any one of [12] to [14].
[17] A resin composition containing the copolymer according to any one of [9] to [11] or the copolymer mixture according to any one of [12] to [14] is molded into a resin molded product. A method for producing a resin molded product, comprising a step of obtaining the above.
[18] Production of a resin molded product comprising a step of applying the dope resin composition according to [15] and a step of removing a dispersion medium from the coated dope resin composition to obtain a resin molded product. Method.

According to the present invention, there is a method for producing a copolymer containing a structural unit derived from α-methylenelactone by polymerization using a solvent, which can improve the transparency of the obtained copolymer. Provided. The method for producing a copolymer according to some forms facilitates a polymerization reaction under reflux. Further, according to the present invention, there is provided a copolymer obtained by such a production method and a copolymer mixture containing the copolymer. The copolymer mixture according to some forms tends to be excellent in reducing the processing load on the formed film, the strength of the formed film, and the like. Further, according to the present invention, there is provided a dope resin composition using the copolymer or the copolymer mixture, a resin molded product, and a method for producing the same.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

In the present specification, "resin (composition)" is a broader concept than "(co) polymer". The resin may be composed of, for example, one kind or two or more kinds of (co) polymers, or may contain an additive such as an antioxidant other than the (co) polymer, if necessary. May be good.

[Method for producing copolymer]
The method for producing a copolymer according to an embodiment is a method for producing a copolymer containing a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms. Is.

The structural unit derived from α-methylene lactone is formed by the polymerization of α-methylene lactone in which a methylene group is bonded to the carbon at the α position. The specific structure of the structural unit derived from α-methylene lactone is not particularly limited. The number of ring members of the lactone is not particularly limited, but is preferably a 5-membered ring (γ-lactone) or a 6-membered ring because the ring structure is highly stable and higher surface strength can be obtained based on this high stability. (Δ-Lactone).

Specific examples of the α-methylene lactone having a 5-membered ring or a 6-membered ring are α-methylene-γ-butyrolactone and α-methylene-δ-valerolactone. These may have substituents.

The structural unit derived from α-methylene lactone is preferably a structural unit having a structure represented by the following formula (1).

^{R 1} to R ⁴ in the formula (1) are hydrogen atoms or hydrocarbon groups having 1 to 18 carbon atoms independently of each other.

The structural unit having the structure represented by the formula (1) can be formed by polymerizing a monomer containing α-methylene-γ-butyrolactone represented by the following formula (2).

^{R 1} to R ⁴ in the formula (2) are hydrogen atoms or hydrocarbon groups having 1 to 18 carbon atoms independently of each other.

The hydrocarbon group is an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group is, for example, an alkyl group. The alkyl group preferably has 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, a cyclopentyl group, a cyclohexyl group and the like. Can be mentioned.

The aromatic hydrocarbon group is not particularly limited, and may contain, for example, a heterocyclic structure. Examples of the aromatic hydrocarbon group include a phenyl group, a tolyl group, a benzyl group and the like.

R ¹ to R ⁴ are preferably hydrogen atoms or alkyl groups having 1 to 10 carbon atoms, more preferably all hydrogen atoms, independently of each other.

The content of the constituent unit derived from α-methylene lactone in the copolymer is preferably 5 to 40% by mass, more preferably 7.5 to 35% by mass, and further preferably 10 from the viewpoint of further improving heat resistance and the like. ~ 30% by mass. The content of each structural unit in the copolymer can be obtained by dissolving the copolymer in a ^{deuterated solvent, measuring 1 1} H-NMR, and calculating the area ratio of the peak corresponding to each structural unit. ..

The structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms is formed by polymerization of alkyl (meth) acrylate. Examples of the alkyl group having 1 to 6 carbon atoms in the alkyl (meth) acrylate include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group and an n-pentyl group. , N-hexyl group, cyclopentyl group, cyclohexyl group and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The number of carbon atoms of the alkyl group in the alkyl (meth) acrylate is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

The number of carbon atoms of the alkyl group in alkyl methacrylate is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

The content of the structural unit derived from alkyl (meth) acrylate in the copolymer is preferably 95 to 60% by mass, more preferably 92.5 to 65% by mass from the viewpoint of further improving heat resistance, transparency and the like. , More preferably 90 to 70% by mass.

The copolymer may contain a structural unit derived from α-methylene lactone and a structural unit of other monomers other than the structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms. .. Specific examples thereof include benzyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, styrene, vinyltoluene, α-methylstyrene, acrylonitrile, methyl vinylketone, ethylene, and propylene. Examples thereof include structural units derived from monomers such as vinyl acetate. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of other structural units in the copolymer is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less.

The method for producing a copolymer according to the present embodiment includes a step of polymerizing a monomer containing α-methylenelactone and alkyl (meth) acrylate in the presence of a solvent. The solvent is a solvent that satisfies either the following condition (A) or the following condition (B).
Condition (A): At least one solvent selected from the group consisting of cyclic amides and cyclic esters.
Condition (B): A mixed solvent consisting of a first solvent having a boiling point of less than 100 ° C. and a second solvent having a boiling point of 100 ° C. or higher, and the first solvent is selected from the group consisting of ketones and alkyl chlorides. The second solvent is at least one selected from the group consisting of cyclic ketones, cyclic esters, amides, and sulfoxides, and is a mixed solvent having a boiling point of 70 to 120 ° C.

According to the method for producing a copolymer according to the present embodiment, it is possible to improve the transparency of the obtained copolymer. The reason why such an effect is exerted is not always clear, but the present inventors consider that the cause of coloring (decrease in transparency) is the formation of a homopolymer of α-methylene lactone. There is. The homopolymer is soluble in the DMSO solvent alone, but tends to be insoluble or difficult to dissolve in the solvent satisfying the condition (A) or the solvent satisfying the condition (B). Therefore, by polymerizing the monomer containing α-methylenelactone with a solvent satisfying the condition (A) or a solvent satisfying the condition (B), the formation of a homopolymer of α-methylenelactone is suppressed. It is believed that this can reduce the coloring of the copolymer and improve the transparency.

Further, by using a solvent satisfying the condition (B), the method for producing a copolymer according to the present embodiment polymerizes under reflux when producing a copolymer containing a structural unit derived from α-methylenelactone. The reaction becomes easy, and for example, the polymerization can be carried out in a reflux state at a general polymerization temperature (for example, 70 to 120 ° C.). When the polymerization is carried out in the reflux state, the heat of polymerization at the time of polymerization can be slowed down and the polymerization temperature can be controlled near the boiling point, so that the polymerization can proceed safely and stably. When the boiling point of the mixed solvent is 120 ° C. or lower, it is advantageous in that the polymerization rate can be easily controlled, by-products are suppressed, and the polymerization temperature does not become too high than the boiling point of the (meth) alkyl acrylate monomer. Is. Further, when the boiling point of the mixed solvent is 70 ° C. or higher, it is advantageous in terms of productivity such as the viscosity of the polymer solution and the polymerization rate.

The solvent represented by the condition (A) is at least one solvent selected from the group consisting of cyclic amides and cyclic esters, and may be one single solvent or a mixed solvent in which two or more are combined. It may be present, but it is preferably one kind of single solvent. The boiling point of the solvent (the boiling point of the single solvent or the boiling point of the mixed solvent) is preferably more than 200 ° C. and 300 ° C. or lower because the content of the solvent (compound) in the copolymer mixture can be easily controlled.

Examples of the cyclic amide include N-methylpyrrolidone (NMP), N, N'-dimethylimidazolidinone (DMI) and the like. Among these, the cyclic amide is preferably NMP because of its high versatility.

Examples of the cyclic ester include γ-butyrolactone (GBL), γ-valerolactone, δ-valerolactone and the like. Among these, the cyclic ester is preferably GBL from the viewpoint of high versatility.

When the solvent represented by the condition (A) is used, the polymerization temperature and the polymerization time vary depending on the type of the monomer used, the ratio of use and the like, but the polymerization temperature is preferably 0 to 150 ° C., more preferably 50. It is about 150 ° C., more preferably 60 to 140 ° C. The polymerization time is preferably 0.5 to 20 hours, more preferably 1 to 10 hours.

The solvent represented by the condition (B) is a mixed solvent composed of a first solvent having a boiling point of less than 100 ° C. and a second solvent having a boiling point of 100 ° C. or higher, and the first solvent is a ketone and chloride. At least one selected from the group consisting of alkyl, the second solvent is at least one selected from the group consisting of cyclic ketones, cyclic esters, amides, and sulfoxides, with a boiling point (of the mixed solvent) of 70-120. It is a mixed solvent at ° C.

The first solvent is a solvent having a boiling point of less than 100 ° C., and is at least one solvent selected from the group consisting of ketones and alkyl chlorides. Examples of such a first solvent include ketones such as acetone (ACE) and methyl ethyl ketone (MEK), and alkyl chlorides such as dichloromethane, chloroform, 1,2-dichloroethane, and 1,1-dichloroethane. As the first solvent, one type may be used alone, or two or more types may be used in combination. Among these, the first solvent is preferably acetone.

The second solvent is a solvent having a boiling point of 100 ° C. or higher, and is at least one solvent selected from the group consisting of cyclic ketones, cyclic esters, amides, and sulfoxides. Examples of such a second solvent include cyclic ketones such as cyclohexanone (anone) and cyclopentanone, cyclic esters such as γ-butyrolactone (GBL), γ-valerolactone and δ-valerolactone, N, N-. Examples thereof include amides such as dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone (NMP), N, N'-dimethylimidazolidinone (DMI), and sulfoxides such as dimethyl sulfoxide. As the second solvent, one type may be used alone, or two or more types may be used in combination. One aspect of the second solvent is preferably cyclic ketones, more preferably cyclohexanone. Another aspect of the second solvent is preferably at least one selected from the group consisting of cyclic esters, amides, and sulfoxides, more preferably γ-butyrolactone, γ-valerolactone, δ-valerolactone, N, N. -Dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N, N'-dimethylimidazolidinone, and at least one selected from the group consisting of dimethyl sulfoxide.

The combination of the first solvent and the second solvent may be a combination of acetone and cyclohexanone. According to the studies by the present inventors, it has been found that acetone and cyclohexanone tend to be difficult to dissolve the copolymers by themselves, but the above-mentioned copolymers are very easily dissolved. Therefore, by using such a mixed solvent, it becomes easy to carry out the polymerization reaction under reflux, and it becomes possible to improve the transparency of the obtained copolymer.

The above-mentioned copolymer consists of an alkyl chloride having a boiling point of less than 100 ° C. as a first solvent and a group consisting of a cyclic ester, an amide, and a sulfoxide having a boiling point of 100 ° C. or higher as a second solvent. It tends to be easily soluble in at least one solvent of choice. Therefore, the combination of the first solvent and the second solvent is an alkyl chloride having a boiling point of less than 100 ° C. and a solvent having a boiling point of 100 ° C. or higher, from cyclic ketones, cyclic esters, amides, and sulfoxides. It may be a combination with at least one solvent selected from the above group, a solvent having a boiling point of less than 100 ° C., and at least one solvent selected from the group consisting of ketone and alkyl chloride, and a cyclic ester. It may be a combination with at least one solvent selected from the group consisting of, amide, and sulfoxide.

The boiling point of the mixed solvent is 70 to 120 ° C, preferably 75 to 115 ° C, and more preferably 80 to 110 ° C. When the boiling point of the mixed solvent is in such a range, it becomes easy to carry out the polymerization reaction under reflux. In this specification, the boiling point of the mixed solvent means a value measured by the method described in Examples.

The mixing ratio of the first solvent and the second solvent is not particularly limited as long as the boiling point of the mixed solvent is 70 to 120 ° C., and can be adjusted at any ratio. By adjusting the first solvent and the second solvent at an arbitrary ratio and adjusting the boiling point of the mixed solvent in the range of 70 to 120 ° C., it becomes easy to carry out the polymerization reaction under reflux, and the obtained copolymer can be obtained. It is possible to improve the transparency of the polymer. For example, the mass ratio of the first solvent to the second solvent (mass of the first solvent / mass of the second solvent) is preferably 1/9 or more, more preferably 2/8 or more, and preferably 2/8 or more. It is 9/1 or less, more preferably 8/2 or less, further preferably 7/3 or less, particularly preferably 6/4 or less, and most preferably 5/5 or less.

When the solvent represented by the condition (B) is used, the polymerization temperature and the polymerization time differ depending on the type of the monomer used, the ratio of use, etc., but the polymerization temperature is easy to control the polymerization rate and is a by-product. From the viewpoint that the polymerization temperature does not become too high above the boiling point of the (meth) alkyl acrylate monomer, the temperature is preferably 120 ° C. or lower, and from the viewpoint of productivity such as the viscosity of the polymerization solution and the polymerization rate, it is preferable. It is 70 ° C. or higher. The polymerization temperature is more preferably 75 to 115 ° C, still more preferably 80 to 110 ° C. The polymerization time is preferably 0.5 to 20 hours, more preferably 1 to 10 hours.

In the polymerization step, the method of charging each monomer component (α-methylenelactone, alkyl (meth) acrylate, other monomer, etc.) into the reactor is not particularly limited, and before charging the polymerization initiator. A method in which the entire amount of the monomer is added, a method in which the entire amount of the monomer is continuously added dropwise at the same time as the polymerization initiator is added, and a part of the monomer is first added and the remaining monomer is added after the polymerization is started. The method of dropping and adding, changing the content ratio of α-methylene lactone in the monomer composition to be added first and the content ratio of α-methylene lactone in the monomer composition to be added after the start of polymerization. The method of doing this can be mentioned.

When polymerizing the monomer, a polymerization initiator may be added if necessary. Examples of the polymerization initiator include cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, and t-amylperoxy-2. Organic peroxides such as -ethylhexanoate, t-butylperoxy-2-ethylhexanoate; 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), Examples thereof include azo compounds such as 2,2'-azobis (2,4-dimethylvaleronitrile) and dimethyl-2,2'-azobis (2-methylpropionate). The content ratio of the polymerization initiator may be appropriately set according to the combination of the monomers used, the reaction conditions, etc., and is not particularly limited, but is preferably 10 to 10000% by mass, more preferably, with respect to all the monomers. Is 100 to 3000 mass ppm, more preferably 300 to 2000 mass ppm.

When polymerizing the monomer, a chain transfer agent may be added if necessary. Examples of the chain transfer agent include monofunctional thiol compounds such as n-dodecyl mercaptoethanol and β-mercaptopropionic acid; bifunctional thiol compounds such as biterminal mercapto-modified polysiloxane; side chain polyfunctional mercapto having mercapto-modified side chains. Examples include modified polysiloxane. The content ratio of the chain transfer agent may be appropriately set according to the combination of monomers to be used, reaction conditions, etc., and is not particularly limited, but is preferably 10 to 10000 mass ppm, more preferably, with respect to all the monomers. Is 100 to 3000 mass ppm.

When polymerizing the monomer, in order to suppress the increase in viscosity of the reaction solution, it is preferable to control the concentration of the copolymer in the polymerization reaction mixture to be 90% by mass or less, more preferably 70. It is mass% or less, more preferably 50 mass% or less. Further, if the concentration of the copolymer in the polymerization reaction mixture is too low, the productivity is lowered. Therefore, it is preferable to control the concentration of the polymer in the polymerization reaction mixture to be 10% by mass or more, more preferably. It is 20% by mass or more.

The polymerization reaction mixture obtained through the polymerization step usually contains a solvent in addition to the target copolymer. The method for separating the copolymer from the solvent is not particularly limited, and examples thereof include a method by reprecipitation, a devolatilizer consisting of a heat exchanger and a devolatilization tank, and a method of desolving the copolymer using a vented extruder. Be done.

[Copolymer]
The copolymer according to one embodiment contains a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, and has a thickness of 100 μm when formed into a film. The internal haze per hit is less than 2.5%. The copolymer of this embodiment can be a copolymer obtained by the above-mentioned production method. Since the above-mentioned production method can improve the transparency of the obtained copolymer, by using the production method, the internal haze per 100 μm thickness of the film and the time of the film are obtained. It may be possible to set the ^{internal b *} value or the like per 100 μm of the thickness of the ^{L *} a ^* b ^{* color system within a predetermined range.}

The copolymer has an internal haze of less than 2.5% per 100 μm thickness when made into a film. The internal haze is preferably 2.0% or less, more preferably 1.5% or less, still more preferably 1.0% or less, and particularly preferably 0.8% or less. The internal haze per 100 μm thickness of the copolymer as a film can be measured by, for example, the method described in Examples. Further, the temperature at which the copolymer is hot-press molded may be, for example, 200 to 270 ° C., more specifically 240 ° C.

The copolymer according to another embodiment contains a structural unit derived from α-methylene lactone and a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, and has a weight average molecular weight (Mw). Is 200,000 or more and 1,000,000 or less. By using the copolymer of the present embodiment, it is possible to form a film having excellent transparency, heat resistance, and flexibility.

The copolymer is in a state in which the solvent used in the above production method is substantially free. Here, "substantially free" means that the content of the solvent may be less than 10 parts by mass based on the total amount of the copolymer. The solvent content can be measured by, for example, the method described in Examples using a film formed from a copolymer or a copolymer mixture.

^{In the copolymer, the internal b *} value per 100 μm of the thickness ^{of the L *} a ^* b ^* color system when formed into a film is preferably less than 1.6. The internal b ^* value is more preferably 1.2 or less, further preferably 0.8 or less, particularly preferably 0.6 or less, and most preferably 0.4 or less. ^{The internal b *} value per 100 μm of the thickness ^{of the L *} a ^* b ^* color system when made into a film of a copolymer can be measured by, for example, the method described in Examples. Further, the temperature at which the copolymer is hot-press molded may be, for example, 200 to 270 ° C., more specifically 240 ° C.

The weight average molecular weight (Mw) of the copolymer is preferably 100,000 or more, more preferably 150,000 or more, further preferably 200,000 or more, particularly preferably 220,000 or more, and most preferably 240000 or more. The weight average molecular weight (Mw) of the copolymer is preferably 1,000,000 or less, more preferably 750000 or less, still more preferably 500,000 or less. When the Mw of the copolymer is in the above-mentioned predetermined range, the flexibility of the film can be further improved. The Mw of the copolymer can be measured, for example, by the method described in Examples.

The number average molecular weight (Mn) of the copolymer is preferably 20,000 or more, more preferably 50,000 or more, and further preferably 100,000 or more. The number average molecular weight (Mn) of the copolymer is preferably 500,000 or less, more preferably 400,000 or less, still more preferably 300,000 or less. The Mn of the copolymer can be measured by, for example, the method described in Examples. The dispersity (Mw / Mn) of the copolymer is preferably 3.0 or less, more preferably 2.8 or less, and further preferably 2.5 or less.

The copolymer has a yellowness (YI) measured in accordance with JIS Z 8729 when a 15% chloroform solution of the copolymer is used, preferably 5 or less, more preferably 3 or less, still more preferable. Is less than or equal to 1. When the YI of the copolymer is in such a range, a low-colored resin molded product can be obtained.

The glass transition temperature (Tg) measured in accordance with JIS K 7121 of the copolymer is preferably 110 ° C. or higher, more preferably 115 ° C. or higher, still more preferably 115 ° C. or higher, from the viewpoint of further improving heat resistance and the like. It is 120 ° C. or higher. The upper limit of the glass transition temperature of the copolymer is not particularly limited, but can be, for example, 160 ° C. or lower.

The 5% weight loss temperature of the copolymer is preferably 280 ° C. or higher, more preferably 290 ° C. or higher, still more preferably 300 ° C. or higher, from the viewpoint of further improving heat resistance and the like. The upper limit of the 5% weight loss temperature of the copolymer is not particularly limited, but can be, for example, 400 ° C. or lower. The 5% weight loss temperature can be measured, for example, by the method described in Examples.

[Copolymer mixture]
The copolymer mixture according to one embodiment includes a copolymer containing a structural unit derived from α-methylenelactone and a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, and a cyclic amide. It contains a cyclic ester and at least one compound selected from the group consisting of cyclic ketones. One aspect of the copolymer mixture contains the above-mentioned copolymer and at least one compound selected from the group consisting of cyclic amides, cyclic esters, and cyclic ketones.

As at least one compound selected from the group consisting of a cyclic amide, a cyclic ester, and a cyclic ketone, those exemplified as a solvent in the above-mentioned method for producing a copolymer can be used. The content of the compound is preferably 10 to 3000 mass ppm based on the total amount of the copolymer. The content of the compound is more preferably 200 mass ppm or more, further preferably 300 mass ppm or more, still more preferably 2500 mass ppm or less, still more preferably 2000 mass ppm or less, based on the total amount of the copolymer. is there. When the content of the compound is in such a range, the processability of the resin, the reduction of the processing load on the formed film, the strength of the formed film and the like tend to be excellent. The content of the compound can be measured by, for example, the method described in Examples using a film formed from a copolymer or a mixture of copolymers.

The copolymer mixture is obtained by leaving the solvent (compound) so that the content of the compound is within a predetermined range when the copolymer is separated from the solvent in the above-mentioned method for producing a copolymer. It can also be obtained by adding a compound so that the content of the compound is within a predetermined range in the copolymer after isolation.

[Doping resin composition]
The doped resin composition according to one embodiment contains the above-mentioned copolymer and a dispersion medium. The doped resin composition can be suitably used for producing a resin molded product.

As one aspect of the dispersion medium, for example, an alkyl chloride solvent such as chloroform and dichloromethane; an aromatic solvent such as toluene, xylene and benzene; and an alcohol solvent such as methanol, ethanol, isopropanol, n-butanol and 2-butanol. ; Methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone, ethyl acetate, diethyl ether, NMP, GBL and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type. However, when two or more kinds are used in combination, the solvent represented by the above condition (B) is excluded.

Another aspect of the dispersion medium is the solvent represented by the above condition (B). The boiling point of the mixed solvent (solvent represented by the condition (B)) is preferably 70 to 120 ° C. The combination of the first solvent and the second solvent of the mixed solvent, the boiling point of the mixed solvent, the mixing ratio of the first solvent and the second solvent, and the like are determined by the above-mentioned first solvent and the second solvent. The combination is the same as the boiling point of the mixed solvent, the mixing ratio of the first solvent and the second solvent, and the like. Therefore, a duplicate description will be omitted here. The first solvent may be further added to the above-mentioned mixed solvent. The boiling point of the dispersion medium when the first solvent is further added to the above-mentioned mixed solvent is preferably 30 to 110 ° C, more preferably 40 to 100 ° C.

The content of the copolymer in the dope resin composition is 5% by mass or more, preferably 10% by mass or more, more preferably 10% by mass or more, based on the total amount of the dope resin composition, from the viewpoint of efficiently producing the resin molded product. Is 15% by mass or more, more preferably 20% by mass or more. The content of the copolymer is preferably 60% by mass or less, more preferably 50% by mass, based on the total amount of the doped resin composition, from the viewpoint of ensuring fluidity in order to stably produce in the production equipment. Hereinafter, it is more preferably 40% by mass or less.

The doped resin composition may contain other polymers in the resin molded product described later. The content of the other polymer is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, still more preferably 0 to 30% by mass, and particularly preferably 0 to 0 to 50% by mass based on the total amount of the doped resin composition. It is 20% by mass, most preferably 0 to 10% by mass.

The doped resin composition may contain other additives in the resin molded product described later. The doped resin composition can contain one or more other additives. The content of the other additives is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, still more preferably 0 to 0.5% by mass, based on the total amount of the doped resin composition.

The yellowness (YI) measured in accordance with JIS Z 8729 of the doped resin composition is preferably 5 or less, more preferably 3 or less, still more preferably 1 from the viewpoint of obtaining a low-colored resin molded product. It is as follows.

The viscosity of the doped resin composition at 25 ° C. is preferably 0.001 Pa · s or more, more preferably 0.01 Pa · s or more, still more preferably 0.1 Pa · s, from the viewpoint of improving the productivity of the resin molded product. The above is preferably 10 Pa · s or less, more preferably 5 Pa · s or less, still more preferably 1 Pa · s or less. The viscosity at 25 ° C. can be measured by, for example, the method described in Examples.

The haze measured in accordance with JIS K7136 of the doped resin composition is preferably 5 or less, more preferably 3 or less, and further preferably 1 or less from the viewpoint of obtaining a highly transparent resin molded product.

[Resin molded product and its manufacturing method]
The resin molded product according to one embodiment contains the above-mentioned copolymer or the above-mentioned copolymer mixture as a main component. The resin molded product according to the present embodiment is a resin composition containing the above-mentioned copolymer or the above-mentioned copolymer mixture, or a dope resin composition containing the above-mentioned copolymer or the above-mentioned copolymer mixture. Can be manufactured using.

The content of the copolymer or the copolymer mixture is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, still more preferably 70 to 100% by mass, particularly preferably 70 to 100% by mass, based on the total amount of the resin molded product. Is 80 to 100% by mass, most preferably 90 to 100% by mass. When the content of the copolymer or the copolymer mixture in the resin molded product is 50% by mass or more, a resin molded product having better transparency can be obtained.

The resin molded product may contain a polymer (other polymer) other than the above-mentioned copolymer. Examples of other polymers include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and vinyl chlorinated resin; Acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate, polybutylene terephthalate, Polyesters such as polyethylene naphthalate; polyamides such as nylon 6, nylon 66, nylon 610; polyacetals; polycarbonates; polyphenylene oxides; polyphenylene sulfides; polyether ether ketones; polysulphons; polyether salphons; polyoxybenzylene; polyamideimide; polybutadienes Elastic organic fine particles such as based rubber and acrylic rubber; rubbery polymers such as polybutadiene rubber, ABS resin containing acrylic rubber, and ASA resin can be mentioned. The content of the other polymer is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, still more preferably 0 to 30% by mass, particularly, based on the total amount of the resin molded product (resin composition). It is preferably 0 to 20% by mass, and most preferably 0 to 10% by mass.

The resin molded product may contain other additives. Other additives include, for example, antioxidants such as hindered phenol-based, phosphorus-based and sulfur-based; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers. Ultraviolet absorbers such as phenylsalicylate, (2,2'-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as; Antistatic agents such as anionic, cationic and nonionic surfactants; Colorants such as inorganic pigments, organic pigments and dyes; Organic fillers or inorganic fillers; Resin modifiers; Organic fillers or Inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; fluidizing agents; compatibilizers and the like. The resin molded product may contain one or more other additives. The content of the other additives is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, still more preferably 0 to 0.5% by mass, based on the total amount of the resin molded product.

The resin molded body is preferably a film-shaped resin molded body or a sheet-shaped resin molded body and a planar resin molded body. In the present specification, the film-shaped resin molded body (film) means that the film thickness is less than 350 μm, and the sheet-shaped resin molded body (sheet) means that the film thickness is 350 μm or more. ..

One aspect of the method for producing a resin molded product includes a step of molding a resin composition containing the above-mentioned copolymer or the above-mentioned copolymer mixture to obtain a resin molded product. The method for molding the resin composition is not particularly limited, and examples thereof include conventionally known methods such as a melt extrusion method, a calendar method, and a compression molding method. Among these, the method for molding the resin composition is preferably a melt extrusion method.

The resin composition may contain the above-mentioned other polymer, the above-mentioned other additive, etc. in addition to the above-mentioned copolymer or the above-mentioned copolymer mixture according to the desired resin molded product. Good. The content of the copolymer or copolymer mixture, other polymer, other additives, etc. in the resin composition may be the same as the content of each component exemplified in the resin molded product.

Specific examples of the melt extrusion method include a T-die method, an inflation method, and the like. The molding temperature of the resin molded product is preferably 150 to 350 ° C., more preferably 200 to 300 ° C.

Another aspect of the method for producing a resin molded product includes a step of applying the above-mentioned dope resin composition and a step of removing a dispersion medium from the coated dope resin composition to obtain a resin molded product. .. The method for applying the doped resin composition is not particularly limited, and examples thereof include conventionally known methods such as a solution casting method (solution casting method). As the solution casting method (solution casting method), for example, an apparatus such as a drum type casting machine, a band type casting machine, or a spin coater can be used.

The method for removing the dispersion medium from the doped resin composition is not particularly limited, and examples thereof include a method of heating the doped resin composition to volatilize the dispersion medium. The heating temperature can be appropriately set according to the dispersion medium used.

The film-shaped resin molded body (film) can be made into a stretched film by stretching. The film is preferably a stretched film because of its excellent flexibility and, in some cases, the ability to impart a phase difference.

As a method for stretching the film, a conventionally known stretching method can be applied, and examples thereof include uniaxial stretching such as free width uniaxial stretching and constant width uniaxial stretching; biaxial stretching such as sequential biaxial stretching and simultaneous biaxial stretching. Be done. The method of stretching the film is preferably biaxial stretching in that the bending resistance in any two orthogonal directions in the film plane is improved.

The stretching temperature when stretching the film is preferably near the glass transition temperature of the above-mentioned copolymer. More specifically, it is preferably (glass transition temperature -30) ° C to (glass transition temperature +100) ° C, more preferably (glass transition temperature -20) ° C to (glass transition temperature +50) ° C, and even more preferably (glass). The transition temperature is −10) ° C. to (glass transition temperature +30) ° C.

The stretching ratio when stretching the film may be, for example, in the range of 1.05 to 10 times in each of the vertical and horizontal directions.

The film thickness of the film-shaped resin molded product (film) is preferably 1 μm or more and less than 350 μm, and more preferably 10 μm or more and 300 μm or less. The film thickness of the sheet-shaped resin molded product (sheet) is preferably 350 μm or more and 10 mm or less, and more preferably 350 μm or more and 5 mm or less.

When the resin molded product is a film, the total light transmittance of the film measured by a method according to JIS K7136 is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more, and particularly preferably 90% or more. It is 92% or more. The total light transmittance is a measure of transparency, and when it is 85% or more, the transparency of the film can be sufficient.

When the resin molded product is a film, the elastic modulus of the film is preferably 4 GPa or more, more preferably 4.5 GPa or more, and further preferably 5 GPa or more from the viewpoint of further improving the strength of the film. The upper limit of the elastic modulus of the film is not particularly limited, but can be, for example, 15 GPa or less. The elastic modulus of the film can be measured, for example, by the method described in Examples.

When the resin molded product is a film, the Young's modulus of the film is preferably 4 GPa or more, more preferably 4.5 GPa or more, and further preferably 5 GPa or more from the viewpoint of further improving the strength of the film. The upper limit of the Young's modulus of the film is not particularly limited, but can be, for example, 15 GPa or less. The Young's modulus of the film can be measured, for example, by the method described in Examples.

When the resin molded product is a film, the pencil hardness of the film is preferably H or more, more preferably 2H or more, and further preferably 3H or more from the viewpoint of further improving the strength of the film.

When the resin molded body is a film, the film breaks into the bent portion even if the number of times of bending exceeds 100,000 in a bending test (foldable test) in which the film is repeatedly bent and returned in a U shape under predetermined conditions. It is preferable that The predetermined condition can be, for example, the condition described in the embodiment.

The resin molded product of the present embodiment can be applied to various uses, for example, it can be suitably applied to optical applications. Specific examples of applications include light guide members, film applications, lenses (optical lenses, etc.), covers, foam applications (for example, cushioning materials, heat insulating / heat insulating materials, vibration damping materials, soundproofing materials, sealing materials). , Packing material, etc.).

The resin molded product of the present embodiment (particularly, a film-shaped resin molded product) can be suitably used for optical applications. Further, since the resin molded product of the present embodiment (particularly, a film-shaped resin molded product) is excellent in transparency, heat resistance, flexibility, and surface hardness, it can be suitably used for flexible display applications, and in particular, It can be more preferably used as the outermost cover window. Specific examples of the flexible display include a thin and bendable flexible type organic EL display, a smartphone that can be folded or rolled up, and the like. Further, since the film-shaped resin molded body has a low phase difference, it can also be used as a protective film or the like for each layer of a flexible display. Further, it is possible to manufacture a polarizing plate or a touch panel using a film-shaped resin molded body.

When a film-shaped resin molded body (film) is applied as a cover window for a flexible display, it may be used as a laminated body having another layer such as a hard coat layer, for example. Further, the cover window for the flexible display formed from the film can be arranged on the surface of the flexible display via, for example, an adhesive layer or the like.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples. In the following, unless otherwise specified, "part" means "part by mass". In addition, various physical properties were measured and evaluated as follows.

<Example A>
[Polymerization reaction rate and polymer composition analysis]
For the reaction rate during the polymerization reaction and the content of the specific monomer unit in the copolymer, the amount of unreacted monomer in the obtained polymerization reaction solution was gas chromatographed (manufactured by Shimadzu Corporation, device name: GC). -2014) was used for measurement and determination.

[Weight average molecular weight and number average molecular weight]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the copolymer were determined by polystyrene conversion using gel permeation chromatography (GPC). The equipment and measurement conditions used for the measurement are as follows.
System: Tosoh GPC system HLC-8220
Measurement side column configuration:
・ Guard column (manufactured by Tosoh, TSKguardcolum SuperHZ-L)
-Separation column (manufactured by Tosoh, TSKgel SuperHZM-M) 2 series connection Reference side column configuration:
・ Reference column (manufactured by Tosoh, TSKgel SuperH-RC)
Developing solvent: Chloroform (manufactured by Wako Pure Chemical Industries, Ltd., special grade)
Flow rate of developing solvent: 0.6 mL / min Standard sample: TSK standard polystyrene (Tosoh, PS-oligomer kit)
Column temperature: 40 ° C

[ML content in copolymer]
The ML content (content of the structural unit derived from α-methylene lactone) in the copolymer ^{was determined by 1 1} H-NMR. ^{Specifically, using deuterated DMSO or deuterated chloroform as a deuterated solvent, 1} H-NMR measurement was performed using a nuclear magnetic resonance spectrometer (AV300M manufactured by BRUKER), and the area ratio of the ^{obtained 1 H-NMR profile was obtained.} I asked for it.

[Glass transition temperature (Tg)]
The glass transition temperature of the copolymer was determined in accordance with the provisions of JIS K 7121. Specifically, using a differential scanning calorimeter (manufactured by Rigaku, Thermo plus EVO DSC-8230), a sample of about 10 mg was heated from room temperature to 200 ° C. (heating rate 20 ° C./min) under a nitrogen gas atmosphere. The DSC curve obtained was evaluated by the starting point method. As a reference, α-alumina was used.

[5% weight loss temperature]
The 5% weight loss temperature of the copolymer was determined in accordance with JIS K 7120. Specifically, using a differential differential thermal balance device (manufactured by Rigaku, Thermo plus2 Tg-8120), a sample of about 10 mg was heated from room temperature to 400 ° C. at 10 ° C./min under a nitrogen gas atmosphere. At this time, it was determined by measuring the temperature at the time when the mass of the sample being heated decreased by 5%.

[Film thickness]
The thickness of the film was determined by a digital micrometer (manufactured by Mitutoyo).

[Total light transmittance of film]
The total light transmittance of the film was determined in accordance with the regulations of JIS K7361. Specifically, the measurement was performed using a haze meter (NDH-1001DP, manufactured by Nippon Denshoku Kogyo Co., Ltd.).

[Film tensile test (modulus measurement)]
The stretched film is cut into a size of 90 mm × 20 mm to make a test piece, and is tensioned using an autograph (manufactured by Shimadzu Corporation: AG-X) in an atmosphere of a temperature of 25 ° C. and a relative humidity of 50% in accordance with JIS K7127. The test was carried out. The conditions are that the tensile speed is 0.25 mm / min up to a strain of 0.5%, then 1 mm / min, the distance between the chucks is 55 mm, the marked line interval measured by the displacement meter is 25 mm, and the test is performed three times at 25 ° C. Was performed, and the average value was used as the measured value. The displacement was measured using a non-contact elongation width meter (manufactured by Shimadzu Corporation: TRViewX), and the elastic modulus was evaluated as a slope between 0.05% and 0.25% of strain.

[Young's modulus of film]
The Young's modulus of the film was evaluated with respect to the stretched film (thickness 4 μm) by a method compliant with ISO-14577-1 using an ultrafine hardness tester (Fisher Instruments HM-2000). The evaluation was carried out with the unstretched film fixed to the glass substrate. The measurement conditions were a square cone-shaped Vickers indenter (face-to-face angle a = 136 °), maximum test load 3 mN; application time 20 seconds when load was applied; creep time 5 seconds; application time 20 seconds when load was reduced; The measurement temperature was room temperature (25 ° C.), and the values measured three times were averaged and obtained.

[Pencil hardness of film]
For the pencil hardness of the film, use a test pencil specified by JIS-S-6006, and use a pencil scratch hardness tester No. 1 manufactured by Yasuda Seiki Seisakusho. Evaluation was performed using 533 under a load of 750 g in accordance with JIS K5600-5-4 (1999), and the highest hardness of the pencil that was not scratched was defined as the pencil hardness.

[Film foldable test]
The stretched film was cut into a size of 15 mm × 80 mm to obtain a test piece, and taped to Tension-FreeFolding Clamshell-type (manufactured by Yuasa System Co., Ltd., DMLHP-CS). Further, the test piece is bent at the half position of the long side so that the distance between both ends of the long side of the folded test piece is 5 mm and the radius of curvature of the bent portion of the test piece is 2.5 mm. The folded state was set. Then, in an environment of 25 ° C., changing from a flat open state to a folded state was regarded as one bending, and bending was repeated 100,000 times with 30 bending times per minute. The case where the film in the folded portion after the test was not broken was evaluated as "good", and the case where the film was broken was evaluated as "bad".

(Example A1)
A reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube, 9 parts of methyl methacrylate (MMA), 0.75 parts of α-methylene-γ-butyrolactone (ML), and N-methylpyrrolidone as a solvent ( 10 parts of NMP) was charged, and the temperature was raised to 105 ° C. through nitrogen. Then, 0.003 parts of t-amylperoxyisononanoate (manufactured by Alchema Yoshitomi, Luperox (registered trademark) 570, hereinafter also referred to as “initiator 570”) was added as a polymerization initiator, and 0.2 parts of NMP. Solution polymerization was carried out at 105-115 ° C. for 6 hours while dropping 0.005 part of the initiator 570 and 0.25 part of ML diluted in 1 at a constant rate over 2 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 98.8% and 99.3%, respectively. Next, the obtained polymerization reaction solution was vacuum dried (1 mmHg) at 240 ° C. for 2 hours to obtain a white copolymer. Table 1 shows the physical characteristics of the obtained copolymer. Next, the obtained copolymer was heat-press molded at 240 ° C. to obtain an unstretched press film having a thickness of about 160 μm, and then the obtained unstretched cast film was cut into a size of 96 mm × 96 mm and sequentially. Using a biaxial stretching machine (manufactured by Toyo Seiki Seisakusho, X6-S), the stretching speed is 300% / min at a stretching temperature of 140 ° C. (Tg + 18 ° C.) in the longitudinal direction (MD direction) and the transverse direction (TD direction). Biaxial stretching was carried out in sequence so that the stretching ratio was 2.0 times, and the film was cooled to obtain a stretched film having a thickness of 40 μm. Table 1 shows the physical characteristics of the obtained stretched film.

<Test Example B, Example B, and Comparative Example B>
[Polymerization reaction rate in static polymerization]
The polymerization reaction rate in the static polymerization was determined by diluting the polymerization solution with chloroform, dropping it in methanol, removing the copolymer by reprecipitation, and drying the copolymer at 240 ° C. for 1 hour. It was simply calculated by the amount.

[Polymerization reaction rate in agitation polymerization and composition analysis of copolymer]
For the reaction rate during the polymerization reaction in the stirring polymerization and the content of the specific monomer unit in the copolymer, the amount of unreacted monomer in the obtained polymerization reaction solution was gas chromatographed (manufactured by Shimadzu Corporation, apparatus). Name: GC-2014) was used for measurement.

[Weight average molecular weight and number average molecular weight of copolymer]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the copolymer were determined in the same manner as the weight average molecular weight and the number average molecular weight of the copolymer of <Example A>.

[ML content in copolymer]
The ML content in the copolymer (content of the structural unit derived from α-methylenelactone) was determined in the same manner as the ML content in the copolymer of <Example A>.

[Copolymer glass transition temperature (Tg)]
The glass transition temperature of the copolymer was determined in the same manner as the glass transition temperature of the copolymer of <Example A>.

[5% weight loss temperature of copolymer]
The 5% weight loss temperature of the copolymer was determined in the same manner as the 5% weight loss temperature of the copolymer of <Example A>.

[Internal haze of copolymer]
The internal haze of the copolymer was determined in accordance with JIS K7136. Specifically, an unstretched film obtained by hot-press molding the copolymer at 240 ° C. and 40 MPa for 10 minutes was prepared, and an optical path length was prepared using a haze meter (NDH-1001DP, manufactured by Nippon Denshoku Kogyo Co., Ltd.). A 10 mm quartz cell was filled with 1,2,3,4-tetrahydronaphthalene (tetralin), and a film was immersed therein for measurement, and the internal haze value per 100 μm was calculated.

[Internal b ^* value of copolymer]
An unstretched film obtained by hot-press molding the copolymer at 240 ° C. and 40 MPa for 10 minutes was prepared, and a spectrophotometer (Colormeter ZE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used to form a quartz cell having an optical path length of 10 mm. It was filled with 1,2,3,4-tetrahydronaphthalene (tetralin), and the film was immersed in the film for measurement, and calculated as ^{the b *} value per 100 μm of the thickness of the ^{L *} a ^* b ^{* color system.}

[Solvent (compound) content in copolymer or copolymer mixture]
The solvent (compound) content in the copolymer or the copolymer mixture is determined by gas chromatography (manufactured by Shimadzu Corporation, device name: GC-2014) after dissolving the copolymer or the copolymer mixture in dimethylacetamide. It was determined by measuring using.

[Viscosity of Doping Resin Composition]
The viscosity of the doped resin composition was measured at 25 ° C. using a BHII type viscometer (manufactured by Toki Sangyo).

[Yellowness (YI) of Doping Resin Composition]
The yellowness (YI) of the doped resin composition was determined in accordance with the provisions of JIS Z 8729. Specifically, the measurement was performed using a quartz cell having an optical path length of 10 mm in a transmission mode of a spectrocolor difference meter (manufactured by Nippon Denshoku Kogyo: Coloreter ZE6000).

[Haze of Doping Resin Composition]
The haze of the doped resin composition was determined in accordance with the regulations of JIS K7136. Specifically, it was measured using a haze meter (NDH-1001DP, manufactured by Nippon Denshoku Kogyo Co., Ltd.) using a quartz cell having an optical path length of 10 mm.

[Film thickness]
The film thickness was determined in the same manner as the film thickness of <Example A>.

[Total light transmittance of film]
The total light transmittance of the film was determined in the same manner as the total light transmittance of the film of <Example A>.

[Film tensile test (modulus measurement)]
A tensile test (measurement of elastic modulus) of the film was performed in the same manner as the tensile test of the film of <Example A>, and the elastic modulus was measured.

[Pencil hardness of film]
The pencil hardness of the film was determined in the same manner as the pencil hardness of the film of <Example A>.

[Film foldable test]
The film foldable test was performed in the same manner as in the film foldable test of <Example A>, and the presence or absence of breakage of the film in the folded portion after the test was evaluated in the same manner as in <Example A>.

[Film phase difference]
The in-plane retardation Re and the thickness direction retardation Rth with respect to light having a wavelength of 589 nm of the stretched film were measured using a fully automatic birefringence meter (“KOBRA-WR” manufactured by Oji Measuring Instruments) under the condition of an incident angle of 40 °. .. Specifically, the refractive index in the slow axis direction in the plane of the film is nx, the refractive index in the phase advance axis direction in the plane of the film is ny, the refractive index in the thickness direction of the film is nz, and the thickness of the film. In-plane retardation Re and thickness direction retardation Rth were obtained from the following equations, respectively. In the following examples, the in-plane retardation Re and the thickness direction retardation Rth were determined with the film thickness d being 40 μm.
In-plane phase difference Re = (nx-ny) x d
Thickness direction phase difference Rth = [(nx + ny) /2-nz] × d

<Synthesis of copolymer by static polymerization>
(Test Example B1)
In a hermetically sealed reaction vessel, 7 parts of methyl methacrylate (MMA), 3 parts of α-methylene-γ-butyrolactone (ML), 10 parts of N-methylpyrrolidone (NMP) as a solvent, and azobisisobutyro as an initiator. 0.03 part of nitrile (AIBN) was charged, nitrogen was bubbled to this for 2 minutes, the inside of the container was replaced with nitrogen, and the lid was closed to seal the container. Then, the reaction vessel was immersed in an oil bath at 75 ° C. for 2 hours for polymerization. After the polymerization, it was diluted with chloroform, added to methanol and reprecipitated, and a white solid was taken out. Then, it was vacuum dried at 240 ° C. for 1 hour to obtain about 6 parts of a white copolymer. Table 2 shows the physical characteristics of the obtained copolymer.

(Test Example B2)
Polymerization, reprecipitation, and drying were carried out in the same manner as in Test Example B1 except that the solvent was changed from NMP to γ-butyrolactone (GBL) to obtain 6.5 parts of a white copolymer. Table 2 shows the physical characteristics of the obtained copolymer.

(Test Example B3)
Polymerization, reprecipitation, and drying were carried out in the same manner as in Test Example B1 except that the solvent was changed from NMP to dimethyl sulfoxide (DMSO) to obtain 6 parts of a white copolymer. Table 2 shows the physical characteristics of the obtained copolymer.

(Test Example B4)
Polymerization was carried out in the same manner as in Test Example B1 except that the solvent was changed from NMP to toluene. However, the polymerization was terminated because the solid was precipitated and solidified during the polymerization.

(Test Example B5)
Polymerization was carried out in the same manner as in Test Example B1 except that a solvent such as NMP was not used. However, the polymerization was terminated because the solid was precipitated and solidified during the polymerization.

From Test Examples B1 to B5, NMP, GBL, and DMSO having a polymerization reaction rate of 50% or more were judged to be good, and the following stirring polymerization was carried out using these solvents.

<Synthesis of copolymer by stirring polymerization and preparation of film>
(Example B1-1)
In a reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction tube, 8 parts of methyl methacrylate (MMA), 1.5 parts of α-methylene-γ-butyrolactone (ML), and n- as a chain transfer agent. 0.005 part of dodecyl mercaptan (nDM) and 10 parts of N-methylpyrrolidone (NMP) as a solvent were charged, and the temperature was raised to 105 ° C. through nitrogen. Then, 0.003 parts of t-amylperoxyisononanoate (manufactured by Alchema Yoshitomi, Luperox (registered trademark) 570, hereinafter also referred to as “initiator 570”) was added as a polymerization initiator, and 0.2 parts of NMP. 0.005 part of the initiator diluted with 570 and 0.5 part of ML were added dropwise at 105 to 115 ° C. over 2 hours at a constant rate. After the dropping, 4 parts of NMP was added, and solution stirring polymerization was further carried out at 105 to 115 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 99.1% and 99.5%, respectively. The obtained polymerization reaction solution was vacuum dried (133 Pa (1 mmHg)) at 240 ° C. for 2 hours to obtain a white copolymer. Table 3 shows the physical characteristics of the obtained copolymer.

Next, the obtained copolymer of Example B1-1 was hot press molded at 240 ° C. to obtain an unstretched press film having a thickness of about 160 μm. The obtained unstretched film was cut into a size of 96 mm × 96 mm, and 300% / min at a stretching temperature (146 ° C.) of Tg + 18 ° C. using a sequential biaxial stretching machine (X6-S manufactured by Toyo Seiki Seisakusho). A stretched film having a thickness of 40 μm is obtained by sequentially biaxially stretching the film so that the stretching ratio becomes 2.0 times in the vertical direction (MD direction) and the horizontal direction (TD direction) at the stretching speed of. Obtained. Table 3 shows the physical characteristics of the obtained stretched film.

(Example B1-2)
A copolymer and a stretched film having a thickness of 40 μm were obtained in the same manner as in Example B1-1 except that the solvent was changed from NMP to γ-butyrolactone (GBL). The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 98.5% and 99.0%, respectively. Table 3 shows the physical characteristics of the obtained copolymer and the physical characteristics of the stretched film.

(Example B1-3)
A reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube was charged with 9 parts of MMA, 0.75 parts of ML, 0.005 parts of nDM, and 10 parts of GBL as a solvent. The temperature was raised to 105 ° C. through nitrogen. After that, 0.003 parts of the initiator 570 was added, and 0.005 parts of the initiator 570 diluted with 0.2 parts of GBL and 0.25 parts of ML were added dropwise at 105 to 115 ° C. over 2 hours at a constant rate. did. After the dropping, 4 parts of GBL was added, and solution stirring polymerization was further carried out at 105 to 115 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 98.4% and 99.2%, respectively. The obtained polymerization reaction solution was used in the same manner as in Example B1-1 to obtain a copolymer and a stretched film having a thickness of 40 μm. Table 3 shows the physical characteristics of the obtained copolymer and the physical characteristics of the stretched film.

(Example B1-4)
The same as in Example B1-3 except that nDM was changed from 0.005 part to 0.03 part, GBL was changed from 10 part to 15 part as a solvent, and 4 parts of GBL added after the dropping was not added. , A copolymer and a stretched film having a thickness of 40 μm were obtained. The conversion rates of MMA and ML calculated from the amount of unreacted monomer in the polymerization reaction solution were 98.0% and 98.5%, respectively. Table 3 shows the physical characteristics of the obtained copolymer and the physical characteristics of the stretched film.

(Example B1-5)
A reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube was charged with 7 parts of MMA, 2.2 parts of ML, and 10 parts of GBL as a solvent, and the temperature was raised to 105 ° C. through nitrogen. I warmed it up. After that, 0.003 parts of the initiator 570 was added, and 0.005 parts of the initiator 570 diluted with 0.2 parts of GBL and 0.8 parts of ML were added dropwise at 105 to 115 ° C. over 2 hours at a constant rate. did. After the dropping, 4 parts of GBL was added, and solution stirring polymerization was further carried out at 105 to 115 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 99.1% and 99.2%, respectively. The obtained polymerization reaction solution was used in the same manner as in Example B1-1 to obtain a copolymer and a stretched film having a thickness of 40 μm. Table 3 shows the physical characteristics of the obtained copolymer and the physical characteristics of the stretched film.

(Comparative Example B1-1)
A reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube is charged with 7 parts of MMA, 3 parts of ML, and 10 parts of DMSO as a solvent, and the temperature is raised to 105 ° C. through nitrogen. It was. Then, 0.02 part of the initiator 570 was added, and solution stirring polymerization was carried out at 105 to 115 ° C. for 6 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 99.1% and 99.5%, respectively. The obtained polymerization reaction solution was used in the same manner as in Example B1-1 to obtain a copolymer and a stretched film having a thickness of 40 μm. Table 3 shows the physical characteristics of the obtained copolymer and the physical characteristics of the stretched film.

<Preparation of Doping Resin Composition and Preparation of Film>
(Example B2-1)
A dope resin composition having a solid content of 12.5% by mass is mixed with 1 part of the copolymer obtained in Example B1-2 and 7 parts of dichloromethane as a dispersion medium, shaken for 1 minute, and then stirred and mixed for 60 minutes. Was produced. The viscosity of the doped resin composition was 0.3 Pa · s, YI was 0.9, and haze was 0.3%. When the dope resin composition was visually confirmed, it was uniformly dispersed, and no change was observed in the appearance of the dope resin composition even after being allowed to stand overnight.

Next, the doped resin composition was dropped onto the PET film and spread over a film thickness of 800 μm using an applicator. Then, the PET film was placed in a dryer and dried at 40 ° C. for 30 minutes and 60 ° C. for 30 minutes, and then the applied film was peeled off from PET. Wide mountain-shaped clips were attached vertically so that the obtained film would not curl, and the film was hung in a dryer and then dried at 100 ° C. for 12 hours to obtain an unstretched cast film having a thickness of 160 μm. The obtained unstretched cast film was sequentially stretched using a biaxial stretching machine in the same manner as in Example B1-1 to obtain a stretched film having a thickness of 40 μm. Table 3 shows the physical characteristics of the obtained stretched film.

<Test Example C, Example C, and Comparative Example C>
[Measurement of boiling point of mixed solvent]
500 ml of a mixed solvent was added to a 1 L separable flask equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube, and the temperature was raised while stirring while passing nitrogen through the flask, and reflux was applied from the cooling tube. The internal temperature at that time was measured as the boiling point of the mixed solvent.

[Polymerization reaction rate in static polymerization]
The polymerization reaction rate in the static polymerization was simply determined in the same manner as the polymerization reaction rate in the static polymerization of <Test Example B, Example B, and Comparative Example B>.

[Polymerization reaction rate in agitation polymerization and composition analysis of copolymer]
The reaction rate at the time of the polymerization reaction in the stirring polymerization and the content of the specific monomer unit in the copolymer are the reaction rate at the time of the polymerization reaction in the stirring polymerization of <Test Example B, Example B, and Comparative Example B> and It was determined in the same manner as the content of the specific monomer unit in the copolymer.

[Weight average molecular weight and number average molecular weight of copolymer]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the copolymer were determined in the same manner as the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the copolymer of <Example A>.

[Internal haze of copolymer]
The internal haze of the copolymer was determined in the same manner as the internal haze of the copolymer of <Test Example B, Example B, and Comparative Example B>.

[Internal b ^* value of copolymer]
Internal b ^* values of the copolymers were determined in the same manner as the internal b ^* value of the copolymer of <Test Example B, Example B, and Comparative Example B>.

[Solvent (compound) content in copolymer]
The solvent (compound) content in the copolymer was determined in the same manner as the solvent (compound) content in the copolymer of <Test Example B, Example B, and Comparative Example B>.

[Viscosity of Doping Resin Composition]
The viscosity of the doped resin composition was determined in the same manner as the viscosity of the doped resin composition of <Test Example B, Example B, and Comparative Example B>.

[Yellowness (YI) of Doping Resin Composition]
The yellowness (YI) of the doped resin composition was determined in the same manner as the yellowness (YI) of the doped resin composition of <Test Example B, Example B, and Comparative Example B>.

[Haze of Doping Resin Composition]
The haze of the doped resin composition was determined in the same manner as the haze of the doped resin composition of <Test Example B, Example B, and Comparative Example B>.

[Film phase difference]
The phase difference of the film was determined in the same manner as the phase difference of the films of <Test Example B, Example B, and Comparative Example B>.

<Synthesis of copolymer by static polymerization>
(Test Example C1)
In a hermetically sealed reaction vessel, 7 parts of methyl methacrylate (MMA), 3 parts of α-methylene-γ-butyrolactone (ML), 10 parts of toluene (tor) as the solvent, and azobisisobutyronitrile (AIBN) as the initiator. ) Was charged, and nitrogen was bubbled to this for 2 minutes to replace the inside of the container with nitrogen, and then the lid was closed to seal the container. Then, the reaction vessel was immersed in an oil bath at 75 ° C. for 2 hours for polymerization. However, the polymerization was terminated because the solid was precipitated and solidified during the polymerization. After the polymerization, it was diluted with chloroform, added to methanol and reprecipitated, and a white solid was taken out.

(Test Example C2)
Polymerization was carried out in the same manner as in Test Example C1 except that the solvent was changed from toluene to acetone (ACE). However, the polymerization was terminated because the solid was precipitated and solidified during the polymerization.

(Test Example C3)
Polymerization was carried out in the same manner as in Test Example C1 except that the solvent was changed from toluene to cyclohexanone (anone). However, the polymerization was terminated because the solid was precipitated and solidified during the polymerization.

(Test Example C4)
Polymerization was carried out in the same manner as in Test Example C1 except that the solvent was changed from toluene to a mixed solvent (1: 1 (mass ratio)) of acetone (ACE) and cyclohexanone (anone). After the polymerization, it was diluted with chloroform, added to methanol and reprecipitated, and a white solid was taken out. Then, it was vacuum dried at 240 ° C. for 1 hour to obtain about 6 parts of a white copolymer. Table 4 shows the physical characteristics of the obtained copolymer.

From Test Examples C1 to C4, the mixed solvent of Test Example C4 in which no solid was precipitated during the polymerization was judged to be good, and the following stirring polymerization was examined centering on such a mixed solvent.

<Synthesis of copolymer by stirring polymerization and preparation of film>
(Example C1-1)
In a reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction tube, 7.5 parts of methyl methacrylate (MMA), 2 parts of α-methylene-γ-butyrolactone (ML), and n- as a chain transfer agent. 0.005 part of dodecyl mercaptan (nDM) and 10 parts of a mixed solvent in which acetone (ACE) and cyclohexanone (anone) were mixed at a ratio of 1: 1 (mass ratio) were charged, and the temperature was raised to 70 ° C. through nitrogen. I warmed it up. Then, 0.004 parts of AIBN was added as a polymerization initiator, and 0.011 parts of the initiator AIBN and 0 were diluted with a mixed solvent in which 0.2 parts of ACE and anon were mixed at a ratio of 1: 1 (mass ratio). .5 parts of ML was added dropwise at 70-75 ° C. over 3 hours at a constant rate. After the dropping, a mixed solvent in which 4 parts of ACE and Anon were mixed at a ratio of 1: 1 (mass ratio) was added, and solution stirring polymerization was further carried out at 70 to 75 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 92.1% and 95.5%, respectively. The obtained polymerization reaction solution was vacuum dried (133 Pa (1 mmHg)) at 240 ° C. for 2 hours to obtain a white copolymer. Table 5 shows the physical characteristics of the obtained copolymer.

Next, the obtained copolymer of Example C1-1 was heat-press molded at 240 ° C. to obtain an unstretched press film having a thickness of about 160 μm. The obtained unstretched film was cut into a size of 96 mm × 96 mm, and 300% / min at a stretching temperature (146 ° C.) of Tg + 18 ° C. using a sequential biaxial stretching machine (X6-S manufactured by Toyo Seiki Seisakusho). A stretched film having a thickness of 40 μm is obtained by sequentially biaxially stretching the film so that the stretching ratio becomes 2.0 times in the vertical direction (MD direction) and the horizontal direction (TD direction) at the stretching speed of. Obtained. Table 5 shows the physical characteristics of the obtained stretched film.

(Example C1-2)
In a reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction tube, 6 parts of methyl methacrylate (MMA), 3 parts of α-methylene-γ-butyrolactone (ML), and n-dodecyl mercaptan as a chain transfer agent. 0.005 part of (nDM) and 10 parts of a mixed solvent prepared by mixing acetone (ACE) and cyclohexanone (anone) as a solvent at a ratio of 3: 7 (mass ratio) were charged, and the temperature was raised to 85 ° C. through nitrogen. It was. Then, 0.004 parts of t-amylperoxy2-ethylhexanoate (manufactured by Alchema Yoshitomi, Luperox® 575, hereinafter also referred to as "initiator 575") was added, and 0.2 parts of ACE were added. 0.009 parts of initiator 575 and 1 part of ML diluted with a mixed solvent mixed with anon at a ratio of 3: 7 (mass ratio) were added dropwise at 85 to 90 ° C. over 3 hours at a constant rate. After the dropping, a mixed solvent in which 4 parts of ACE and Anon were mixed at a ratio of 3: 7 (mass ratio) was added, and solution stirring polymerization was further carried out at 85 to 90 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 93.1% and 95.5%, respectively. The obtained polymerization reaction solution was vacuum dried (133 Pa (1 mmHg)) at 240 ° C. for 2 hours to obtain a white copolymer. Table 5 shows the physical characteristics of the obtained copolymer.

Next, the obtained copolymer of Example C1-2 was heat-press molded at 240 ° C. to obtain an unstretched press film having a thickness of about 160 μm. The obtained unstretched film was cut into a size of 96 mm × 96 mm, and 300% / min at a stretching temperature (146 ° C.) of Tg + 18 ° C. using a sequential biaxial stretching machine (X6-S manufactured by Toyo Seiki Seisakusho). A stretched film having a thickness of 40 μm is obtained by sequentially biaxially stretching the film so that the stretching ratio becomes 2.0 times in the vertical direction (MD direction) and the horizontal direction (TD direction) at the stretching speed of. Obtained. Table 5 shows the physical characteristics of the obtained stretched film.

(Example C1-3)
A reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube, containing 6 parts of methyl methacrylate (MMA), 3 parts of α-methylene-γ-butyrolactone (ML), and acetone (ACE) as a solvent. 10 parts of a mixed solvent in which γ-butyrolactone (GBL) was mixed at a ratio of 2: 8 (mass ratio) was charged, and the temperature was raised to 100 ° C. while passing nitrogen through the mixed solvent. After that, 0.004 parts of t-amylperoxyisononanoate (manufactured by Alchema Yoshitomi, Luperox (registered trademark) 570, hereinafter also referred to as “initiator 570”) was added as a polymerization initiator, and 0.2 parts of ACE was added. And GBL were diluted in a mixed solvent mixed at a ratio of 2: 8 (mass ratio), and 0.009 parts of the initiator 570 and 1 part of ML were added dropwise at 100 to 110 ° C. over 3 hours at a constant rate. After the dropping, a mixed solvent in which 4 parts of ACE and GBL were mixed at a ratio of 2: 8 (mass ratio) was added, and solution stirring polymerization was further carried out at 100 to 110 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 92.2% and 96.5%, respectively. The obtained polymerization reaction solution was vacuum dried (133 Pa (1 mmHg)) at 240 ° C. for 2 hours to obtain a white copolymer. Table 5 shows the physical characteristics of the obtained copolymer.

Next, the obtained copolymer of Example C1-3 was heat-press molded at 240 ° C. to obtain an unstretched press film having a thickness of about 160 μm. The obtained unstretched film was cut into a size of 96 mm × 96 mm, and 300% / min at a stretching temperature (146 ° C.) of Tg + 18 ° C. using a sequential biaxial stretching machine (X6-S manufactured by Toyo Seiki Seisakusho). A stretched film having a thickness of 40 μm is obtained by sequentially biaxially stretching the film so that the stretching ratio becomes 2.0 times in the vertical direction (MD direction) and the horizontal direction (TD direction) at the stretching speed of. Obtained. Table 5 shows the physical characteristics of the obtained stretched film.

(Example C1-4)
A reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction tube, 5 parts of methyl methacrylate (MMA), 3.2 parts of α-methylene-γ-butyrolactone (ML), and acetone (ACE) as a solvent. ) And N, N-dimethylacetamide (DMAc) in a ratio of 3: 7 (mass ratio), 10 parts of a mixed solvent was charged, and the temperature was raised to 85 ° C. while passing nitrogen through the mixed solvent. Then, 0.004 parts of the initiator 575 was added, and 0.009 parts of the initiator 575 and 1.8 were diluted with a mixed solvent in which 0.2 parts of ACE and DMAc were mixed at a ratio of 3: 7 (mass ratio). The ML of the part was added dropwise at a constant rate at 85 to 90 ° C. over 3 hours. After the dropping, a mixed solvent in which 4 parts of ACE and DMAc were mixed at a ratio of 3: 7 (mass ratio) was added, and solution stirring polymerization was further carried out at 85 to 90 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 90.2% and 95.5%, respectively. The obtained polymerization reaction solution was vacuum dried (133 Pa (1 mmHg)) at 240 ° C. for 2 hours to obtain a white copolymer. Table 5 shows the physical characteristics of the obtained copolymer.

Next, the obtained copolymer of Example C1-4 was hot press molded at 240 ° C. to obtain an unstretched press film having a thickness of about 160 μm. The obtained unstretched film was cut into a size of 96 mm × 96 mm, and 300% / min at a stretching temperature (146 ° C.) of Tg + 18 ° C. using a sequential biaxial stretching machine (X6-S manufactured by Toyo Seiki Seisakusho). A stretched film having a thickness of 40 μm is obtained by sequentially biaxially stretching the film so that the stretching ratio becomes 2.0 times in the vertical direction (MD direction) and the horizontal direction (TD direction) at the stretching speed of. Obtained. Table 5 shows the physical characteristics of the obtained stretched film.

(Comparative Example 1-1)
A reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction tube is charged with 7 parts of MMA, 3 parts of ML, and 10 parts of DMSO as a solvent, and the temperature is raised to 105 ° C. through nitrogen. It was. Then, 0.02 part of the initiator 570 was added, and solution stirring polymerization was carried out at 105 to 110 ° C. for 6 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 99.1% and 99.5%, respectively. The obtained polymerization reaction solution was used in the same manner as in Example C1-1 to obtain a copolymer and a stretched film having a thickness of 40 μm. Table 5 shows the physical characteristics of the obtained copolymer and the physical characteristics of the stretched film.

<Preparation of Doping Resin Composition and Preparation of Film>
(Example C2-1)
In a reactor equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introduction tube, 7.5 parts of methyl methacrylate (MMA), 2 parts of α-methylene-γ-butyrolactone (ML), and n- as a chain transfer agent. 0.005 part of dodecyl mercaptan (nDM) and 10 parts of a mixed solvent in which acetone (ACE) and cyclohexanone (anone) were mixed at a ratio of 3: 7 (mass ratio) were charged, and the temperature was raised to 85 ° C. through nitrogen. I warmed it up. Then, 0.004 parts of the initiator 575 was added, and 0.009 parts of the initiator 575 and 0.5 were diluted with a mixed solvent in which 0.2 parts of ACE and anon were mixed at a ratio of 3: 7 (mass ratio). The ML of the part was added dropwise at 85 to 90 ° C. over 3 hours at a constant rate. After the dropping, a mixed solvent in which 4 parts of ACE and Anon were mixed at a ratio of 3: 7 (mass ratio) was added, and solution stirring polymerization was further carried out at 85 to 90 ° C. for 4 hours. The conversion rates of MMA and ML calculated from the amount of unreacted monomers in the polymerization reaction solution were 93.1% and 97.5%, respectively. The obtained polymerization reaction solution was diluted with 55 parts of a mixed solvent in which ACE and anon were mixed at a ratio of 3: 7 (mass ratio) to prepare a dope resin composition having a copolymer content of 12.5% by mass. The doped resin composition was pressure filtered through a 3 μm membrane filter. The physical characteristics of the doped resin composition are shown in Table 5. When the dope resin composition was visually confirmed, it was uniformly dispersed, and no change was observed in the appearance of the dope resin composition even after being allowed to stand overnight.

Next, the doped resin composition of Example C2-1 was applied to a glass substrate and vacuum dried at 150 ° C. for 2 hours to obtain an unstretched cast film having a thickness of 120 μm. The obtained unstretched cast film was sequentially stretched using a biaxial stretching machine in the same manner as in Example C1-1 to obtain a stretched film having a thickness of 30 μm. Table 5 shows the physical characteristics of the obtained stretched film.

(Example C2-2)
A dope resin composition having a solid content of 12.5% by mass is mixed with 1 part of the copolymer obtained in Example C1-2 and 7 parts of dichloromethane as a dispersion medium, shaken for 1 minute, and then stirred and mixed for 60 minutes. Was produced. The physical characteristics of the doped resin composition are shown in Table 5. When the dope resin composition was visually confirmed, it was uniformly dispersed, and no change was observed in the appearance of the dope resin composition even after being allowed to stand overnight.

Next, the doped resin composition of Example C2-2 was added dropwise to the PET film, and the film was spread over a film thickness of 800 μm using an applicator. Then, the PET film was placed in a dryer and dried at 40 ° C. for 30 minutes and 60 ° C. for 30 minutes, and then the applied film was peeled off from PET. Wide mountain-shaped clips were attached vertically so that the obtained film would not curl, and the film was hung in a dryer and then dried at 100 ° C. for 12 hours to obtain an unstretched cast film having a thickness of 160 μm. The obtained unstretched cast film was sequentially stretched using a biaxial stretching machine in the same manner as in Example C1-1 to obtain a stretched film having a thickness of 40 μm. Table 5 shows the physical characteristics of the obtained stretched film.

Claims

A method for producing a copolymer containing a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms.
A step of polymerizing a monomer containing the α-methylene lactone and the alkyl (meth) acrylate in the presence of a solvent is provided.
A method for producing a copolymer, wherein the solvent is a solvent that satisfies either the following condition (A) or the following condition (B).
Condition (A): At least one solvent selected from the group consisting of cyclic amides and cyclic esters.
Condition (B): A mixed solvent composed of a first solvent having a boiling point of less than 100 ° C. and a second solvent having a boiling point of 100 ° C. or higher, from the group in which the first solvent is composed of a ketone and an alkyl chloride. It is at least one selected, and the second solvent is at least one selected from the group consisting of cyclic ketones, cyclic esters, amides, and sulfoxides, and is a mixed solvent having a boiling point of 70 to 120 ° C.
The method for producing a copolymer according to claim 1, wherein the solvent is a solvent that satisfies the condition (A).
The method for producing a copolymer according to claim 1, wherein the solvent is a solvent that satisfies the condition (B).
The method for producing a copolymer according to claim 3, wherein the first solvent is acetone.
The method for producing a copolymer according to claim 3 or 4, wherein the second solvent is a cyclic ketone.
The method for producing a copolymer according to claim 5, wherein the cyclic ketone is cyclohexanone.
The method for producing a copolymer according to claim 3 or 4, wherein the second solvent is at least one selected from the group consisting of cyclic esters, amides, and sulfoxides.
The second solvent is γ-butyrolactone, γ-valerolactone, δ-valerolactone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, N, N'-dimethylimidazolidinone, and The method for producing a copolymer according to claim 7, which is at least one selected from the group consisting of dimethyl sulfoxide.
It contains a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms.
A copolymer having an internal haze of less than 2.5% per 100 μm thickness when made into a film.
A copolymer containing a structural unit derived from α-methylene lactone and a structural unit derived from alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms and having a weight average molecular weight of 200,000 or more and 1,000,000 or less.
The copolymer according to claim 9 or 10, wherein the L * a * b * color system has an internal b * value of less than 1.6 per 100 μm of thickness when made into a film.
A copolymer mixture containing the copolymer according to any one of claims 9 to 11 and at least one compound selected from the group consisting of cyclic amides, cyclic esters, and cyclic ketones.
Selected from the group consisting of a copolymer containing a structural unit derived from α-methylene lactone and a structural unit derived from an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms, a cyclic amide, a cyclic ester, and a cyclic ketone. A copolymer mixture containing at least one compound.
The copolymer mixture according to claim 12 or 13, wherein the content of the compound is 10 to 3000 mass ppm based on the total amount of the copolymer.
A dope resin composition containing the copolymer according to any one of claims 9 to 11 and a dispersion medium.
A dope resin composition in which the content of the copolymer is 5% by mass or more based on the total amount of the dope resin composition.
A resin molded product containing the copolymer according to any one of claims 9 to 11 or the copolymer mixture according to any one of claims 12 to 14.
A step of molding a resin composition containing the copolymer according to any one of claims 9 to 11 or the copolymer mixture according to any one of claims 12 to 14 to obtain a resin molded product. A method for producing a resin molded product.
The step of applying the doped resin composition according to claim 15, and
A method for producing a resin molded product, comprising a step of removing the dispersion medium from the coated dope resin composition to obtain a resin molded product.