WO2020067218A1

WO2020067218A1 - Method for manufacturing acrylic film

Info

Publication number: WO2020067218A1
Application number: PCT/JP2019/037710
Authority: WO
Inventors: 坂本　滋; 竹友山下; 宙小澤
Original assignee: 株式会社クラレ
Priority date: 2018-09-28
Filing date: 2019-09-25
Publication date: 2020-04-02
Also published as: JPWO2020067218A1; TW202033630A; CN112752640B; TWI825183B; CN112752640A; KR20210063356A; JP7248700B2

Abstract

The present provides a method for manufacturing an acrylic film, the method comprising a step in which a dope containing an acrylic rubber particle (C) obtained by an emulsion polymerization method, a methacrylic resin (D) which is a non-crosslinked polymer containing at least 60 mass% of a methyl methacrylate unit and has a weight average molecular weight of at least 70,000, and an organic solvent is cast on a flow casting support, and then the solvent is vaporized. The acrylic rubber particle (C) has a structure of two or more layers including: an outer layer (b) which contains a non-crosslinked hard polymer containing 70 mass% or more of a methyl methacrylate unit and having a weight average molecular weight of at least 45,000; and an inner layer (a) which is inscribed with the outer layer (b) and contains an elastic copolymer containing 60-99.8 mass% of an alkyl acrylate unit and 0.2-10 mass% of a structural unit derived from a copolymerizable crosslinkable monomer, wherein the thickness of the outer layer (b) is at least 7.5 nm.

Description

Acrylic film manufacturing method

The present invention relates to a method for producing an acrylic film, and more particularly, to a method for producing a transparent and high-quality acrylic film having improved brittleness by using specific acrylic rubber particles and methacrylic resin.

需要 Demand for liquid crystal display devices is expanding for applications such as liquid crystal televisions and liquid crystal displays for personal computers. Normally, a liquid crystal display device includes a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, and the like are sandwiched between glass plates, and two polarizing plates provided on both sides of the liquid crystal cell. In this configuration, the optical element (also referred to as a polarizing film or a polarizing film) is sandwiched between two optical films (a polarizing plate protective film). Usually, a cellulose triacetate film is used as the polarizing plate protective film.

On the other hand, recent technological advances have accelerated the size of liquid crystal display devices, and diversified the applications of liquid crystal display devices. For example, there is a use as a large display installed in a street or a shop, a use as an advertisement display in a public place using a display device called digital signage, and the like.

ため In such applications, since it is assumed that the polarizing film is used outdoors, deterioration of the polarizing film due to moisture absorption becomes a problem, and higher moisture resistance is required for the polarizing plate protective film. However, it is difficult to obtain sufficient moisture resistance with a conventionally used cellulose ester film such as a cellulose triacetate film, and there is a problem that when the film is thickened to obtain the moisture resistance, the optical effect is increased. . Furthermore, since the thickness of the device has recently been required to be reduced, the thickness of the polarizing plate itself has also become a problem.

On the other hand, as a low hygroscopic optical film material, a methacrylic resin has been suitably used for an optical film because it exhibits excellent transparency and dimensional stability in addition to low hygroscopicity.

However, an optical film made of a methacrylic resin has a fragile and brittle property as compared with a cellulose ester film or the like, and is difficult to handle. In particular, it is necessary to stably produce an optical film for a large-sized liquid crystal display device. Was difficult.

アクリル Furthermore, acrylic films used for optical applications have recently been required to have extremely high transparency and appearance. However, in the conventional melt film forming method, there are problems such as film foreign matter due to gel polymer, birefringence due to flow orientation, coloring of resin due to stagnation and increase in haze value, and high transparency and good quality required for optical applications. It was difficult to produce an acrylic film having a good appearance.

On the other hand, in the solution casting method, the viscosity of the solution can be reduced by adjusting the type of the solvent, the solid content, and the like. Therefore, as compared with the melt film forming method, high-precision filtration is possible, and an acrylic film excellent in transparency and appearance is obtained. In the solution casting method, a technique in which acrylic rubber particles are added to dissolve the fragility of an acrylic film is disclosed. (Patent Documents 1 to 3)
Patent Document 1 proposes, as a method for obtaining an optical film with improved brittleness, a film produced by mixing an acrylic rubber particle with a cellulose ester film and producing the film by a solution casting method. However, since the film obtained by this method contains a cellulose ester, sufficient improvement in moisture resistance has not been obtained.

Patent Document 2 proposes a cast film comprising an acrylic resin and acrylic rubber particles. However, there is no description of the solubility of the acrylic rubber particles in a solvent, and it is said that the film has excellent dispersibility in a solvent. hard.

Patent Document 3 proposes acrylic rubber particles having improved dispersibility. However, there is no description about the impact resistance of the obtained acrylic film, and it is said that a film having sufficient impact resistance is obtained. Hard to say.

WO2009 / 047924 JP 2009-209295 A JP 2016-043494

Therefore, the present invention has been made in view of the above problems, the object is low hygroscopic, transparent, high heat resistance, significantly improved brittleness, particularly, a large liquid crystal display device, An object of the present invention is to provide an acrylic film suitably used as a polarizer protective film in a liquid crystal display device for outdoor use.

The present inventors have studied to achieve the above object, and as a result, have completed the present invention including the following embodiments.

That is, the present invention provides the following [1] to [6].
[1] Acrylic rubber particles (C) obtained by an emulsion polymerization method, a non-crosslinked polymer containing 60% by mass or more of methyl methacrylate units, and a methacrylic resin (D) having a weight average molecular weight of 70,000 or more; After casting a dope containing an organic solvent on a casting support, a method for producing an acrylic film including a step of evaporating the organic solvent,
An outer layer (b) containing a non-crosslinked hard polymer having a weight average molecular weight of 45,000 or more, wherein the acrylic rubber particles (C) contain 70% by mass or more of methyl methacrylate units, and an alkyl inscribed therein. 2 having an inner layer (a) containing an elastic copolymer comprising 60 to 99.8% by mass of an acrylate unit and 0.2 to 10% by mass of a structural unit derived from a copolymerizable crosslinkable monomer; A method for producing an acrylic film having a layer structure or more, wherein the thickness of the outer layer (b) is 7.5 nm or more.
[2] The method for producing an acrylic film according to [1], wherein the alkyl acrylate unit used in the elastic copolymer of the acrylic rubber particles (C) is n-butyl acrylate.
[3] The method according to [1] or [2], wherein a part of the hard polymer constituting the outer layer (b) of the acrylic rubber particles (C) is covalently bonded to the insulated elastic copolymer. The method for producing an acrylic film according to the above.
[4] The mass ratio of the acrylic rubber particles (C) is in the range of 2 to 90 parts by mass with respect to the total of 100 parts by mass of the acrylic rubber particles (C) and the methacrylic resin (D). The method for producing an acrylic film according to any one of [1] to [3].
[5] The method for producing an acrylic film according to any one of [1] to [4], wherein the thickness of the film after drying is 20 μm or more and 200 μm or less.
[6] The method for producing an acrylic film according to any one of [1] to [5], which is used for optical applications.

According to the present invention, it is possible to provide an acrylic film that has low moisture absorption, is transparent, has high heat resistance, and has remarkably improved brittleness.

The dope used for casting in the production method of the present invention contains (1) an acrylic rubber particle (C) obtained by an emulsion polymerization method, (2) a methacrylic resin (D), and (3) an organic solvent. The resin (D) is a non-crosslinked polymer containing 60% by mass or more of a methyl methacrylate unit, and has a weight average molecular weight (Mw) of 70,000 or more.
(1) Acrylic rubber particles (C) obtained by emulsion polymerization
The acrylic rubber particles (C) used in the present invention comprise an outer layer (b) containing a non-crosslinked hard polymer containing 70% by mass or more of methyl methacrylate units, and 60 to 99.8% by mass of an alkyl acrylate unit inscribed therein. % Or more and an inner layer (a) containing an elastic copolymer containing 0.2 to 10% by mass of a structural unit derived from a copolymerizable crosslinkable monomer, (B) has a thickness of 7.5 nm or more.
In the present specification, “copolymerizable crosslinkable monomer” includes “copolymerizable crosslinkable monomer (grafting agent)” and “copolymerizable crosslinkable monomer (crosslinking agent)”. including. Further, the “copolymerizable crosslinkable monomer (grafting agent)” may be described as “grafting agent”, and the “copolymerizable crosslinkable monomer (crosslinking agent)” may be referred to as “crosslinking agent”. ".

アクリル The acrylic rubber particles (C) used in the present invention may be in any form of powder, granules, aggregates, and coagulates.

The lower limit of the average particle diameter of the acrylic rubber particles (C) used in the present invention is preferably 0.01 μm, more preferably 0.04 μm, further preferably 0.05 μm, and still more preferably 0.1 μm. The upper limit of the particle diameter is preferably 0.35 μm, more preferably 0.3 μm, further preferably 0.2 μm, and still more preferably 0.15 μm. The stress whitening resistance of the acrylic film of the present invention tends to decrease as the average particle diameter of the granular material increases. The average particle diameter of the acrylic rubber particles (C) is a value obtained by a light scattering method.

組成 The composition in the case where the acrylic rubber particles (C) used in the present invention have a three-layer structure of a core layer (a-1), an intermediate layer (a-2), and an outer layer (b) will be described below. The three-layered intermediate layer (a-2) is inscribed in the outer layer (b), and can correspond to the inner layer (a) of the present invention. The core layer (a-1) is an optional layer. Preferred core layer (a-1) is a structural unit derived from methyl methacrylate (hereinafter sometimes referred to as "methyl methacrylate unit"), a structural unit derived from alkyl acrylate (hereinafter referred to as "alkyl acrylate unit") And a structural unit derived from a crosslinkable monomer (grafting agent) (hereinafter sometimes referred to as a “crosslinkable monomer (grafting agent) unit”), and if necessary Derived from a crosslinkable monomer (crosslinking agent) (hereinafter sometimes referred to as a “crosslinkable monomer (crosslinking agent) unit”) and other copolymerizable monomers The polymer includes a structural unit (hereinafter, sometimes referred to as “another copolymerizable monomer unit”).

The amount of the methyl methacrylate unit in the core layer (a-1) is preferably 40 to 99.99% by mass, more preferably 90 to 96.9% by mass, based on all structural units of the core layer (a-1). It is. The smaller the amount of methyl methacrylate units, the lower the weather resistance of the film tends to be, and the larger the amount of methyl methacrylate units, the lower the impact resistance of the film tends to be.

量 The amount of the alkyl acrylate unit in the core layer (a-1) is preferably 1 to 60% by mass, more preferably 3 to 10% by mass, based on all the structural units of the core layer (a-1). The alkyl group in the alkyl acrylate preferably has 1 to 8 carbon atoms. The smaller the amount of the alkyl acrylate unit, the lower the thermal decomposition resistance of the multi-layer acrylic polymer tends to be. The larger the amount of the alkyl acrylate unit, the lower the warm water resistance or boiling water whitening resistance of the film.

The amount of the copolymerizable crosslinkable monomer (grafting agent) unit in the core layer (a-1) is preferably 0.01 to 1 mass based on all structural units in the core layer (a-1). %, More preferably 0.1 to 0.5% by mass. The smaller the amount of the copolymerizable crosslinkable monomer (grafting agent) unit, the lower the bonding strength between the core layer (a-1) and the intermediate layer (a-2) tends to be. As the amount of the crosslinking monomer (grafting agent) unit increases, the impact resistance of the film tends to decrease.

The amount of the copolymerizable crosslinkable monomer (crosslinking agent) unit in the core layer (a-1) is preferably 0 to 0.5% by mass based on all structural units in the core layer (a-1). , More preferably 0 to 0.2% by mass. As the amount of the copolymerizable crosslinking monomer (crosslinking agent) unit increases, the impact resistance of the film tends to decrease.

The amount of other copolymerizable monomer units in the core layer (a-1) is preferably from 0 to 20% by mass, more preferably from 0 to 20% by mass, based on all structural units of the core layer (a-1). 10% by mass.

The intermediate layer (a-2) includes an alkyl acrylate unit, a copolymerizable crosslinking monomer (grafting agent) unit, and, if necessary, a methyl methacrylate unit and a copolymerizable crosslinking monomer (crosslinked monomer). Agent) unit and a polymer comprising other copolymerizable monomer units.

The amount of the alkyl acrylate unit in the intermediate layer (a-2) is 60 to 99.8% by mass, preferably 70 to 99.5% by mass, based on all structural units of the intermediate layer (a-2). More preferably, it is 80 to 99% by mass. The alkyl group in the alkyl acrylate preferably has 1 to 8 carbon atoms. The smaller the amount of the alkyl acrylate unit, the lower the impact resistance of the film tends to be, and the larger the amount of the alkyl acrylate unit, the lower the stress whitening resistance and transparency of the film tend to be.

The amount of the copolymerizable crosslinking monomer (grafting agent) unit in the intermediate layer (a-2) is 0.2 to 10% by mass based on all the structural units in the intermediate layer (a-2). And preferably 0.5 to 5% by mass, more preferably 1 to 3% by mass. The smaller the amount of the copolymerizable crosslinking monomer (grafting agent) unit, the lower the stress whitening resistance of the film tends to be, and the amount of the copolymerizable crosslinking monomer (grafting agent) unit. As the content increases, the impact resistance of the film tends to decrease.

量 The amount of methyl methacrylate units in the intermediate layer (a-2) is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, based on all structural units of the intermediate layer (a-2). The greater the amount of methyl methacrylate units, the lower the impact resistance of the film tends to be.

The amount of the copolymerizable crosslinkable monomer (crosslinking agent) unit in the core layer (a-2) is preferably 0 to 0.5% by mass based on all structural units in the core layer (a-1). , More preferably 0 to 0.2% by mass. As the amount of the copolymerizable crosslinking monomer (crosslinking agent) unit increases, the impact resistance of the film tends to decrease.
The amount of other copolymerizable monomer units in the intermediate layer (a-2) is preferably 0 to 40% by mass, more preferably 0 to 40% by mass, based on all structural units of the intermediate layer (a-2). 30% by mass.

The outer layer (b) contains a polymer containing a methyl methacrylate unit and, if necessary, an alkyl acrylate unit. The thickness of the outer layer is at least 7.5 nm, preferably 7.6 to 40 nm.

The outer layer (b) is a non-crosslinked hard polymer containing 70% by mass or more of methyl methacrylate units. The amount of the methyl methacrylate unit in the outer layer (b) is preferably from 80 to 99% by mass, more preferably from 95 to 98% by mass, based on all the structural units in the outer layer (b). The smaller the amount of the methyl methacrylate unit, the lower the stress whitening resistance of the film tends to be. The larger the amount of the methyl methacrylate unit, the lower the thermal decomposition resistance of the multi-layer acrylic polymer.

量 The amount of the alkyl acrylate unit which may be contained in the outer layer (b) is preferably 1 to 20% by mass, more preferably 2 to 5% by mass, based on all structural units of the outer layer (b). The alkyl group in the alkyl acrylate preferably has 1 to 8 carbon atoms. As the amount of the alkyl acrylate unit is smaller, the thermal decomposition resistance of the multi-layer acrylic polymer tends to decrease, and as the amount of the alkyl acrylate unit increases, the stress whitening resistance of the film tends to decrease.

(4) The weight average molecular weight of the non-crosslinked hard polymer constituting the outer layer (b) is 45,000 or more, preferably 50,000 or more, more preferably 60,000 or more and 100,000 or less. When the weight average molecular weight is within this range, the resulting film will have excellent impact resistance. The glass transition temperature of the outer layer (b) is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, and further preferably 100 ° C. or higher. The higher the glass transition temperature of the outer layer (b), the more the warm water resistance or boiling water whitening resistance of the film tends to be improved.

In the present specification, the “alkyl acrylate” includes an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, and s-butyl. Examples include acrylate, t-butyl acrylate, n-butylmethyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate. These alkyl acrylates can be used alone or in combination of two or more. Of these, methyl acrylate and / or n-butyl acrylate are preferred.

As used herein, the term “copolymerizable crosslinkable monomer” refers to a monomer having two or more polymerizable groups, for example, allyl methacrylate, allyl acrylate, mono- or di-allyl maleate, -Or di-allyl fumarate, crotyl acrylate, crotyl methacrylate and other copolymerizable crosslinkable monomers having different polymerizable groups (grafting agents), diacrylic compounds, dimethacrylic compounds, diallyl compounds, divinyl Copolymerizable crosslinkable monomers (crosslinking agents) having the same type of polymerizable group, such as compounds, diene compounds, and trivinyl compounds. Examples of the copolymerizable crosslinking monomer (or crosslinking agent) having the same type of polymerizable group include ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, Examples include polyethylene glycol di (meth) acrylate, divinylbenzene, trivinylbenzene, ethylene glycol diallyl ether, propylene glycol diallyl ether, and butadiene. The copolymerizable crosslinking monomer can be used alone or in combination of two or more.

In the present specification, “other copolymerizable monomers” include, for example, aromatic vinyl monomers such as styrene, p-methylstyrene, o-methylstyrene, and vinylnaphthalene, and unsaturated nitriles such as acrylonitrile. Monomers, olefin monomers such as ethylene and propylene, vinyl halide monomers such as vinyl chloride, vinylidene chloride, and vinylidene fluoride, and unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic anhydride Maleimide monomers such as vinyl acetate, vinyl acetate, N-propylmaleimide, N-cyclohexylmaleimide, and No-chlorophenylmaleimide, and these monomers may be used alone or in combination of two or more. They can be used in combination.

製造 The method for producing the acrylic rubber particles (C) used in the present invention is not particularly limited. For example, when the acrylic rubber particles (C) have a two-layer structure, the inner layer (a) and the outer layer (b) may be sequentially formed by a seed emulsion polymerization method to obtain a core-shell multilayer acrylic polymer. it can. For example, when the acrylic rubber particles (C) have a three-layer structure, a core layer (or first layer, a-1), an intermediate layer (or second layer, a-2), and an outer layer (third layer / shell). , B) are successively formed by a seed emulsion polymerization method to obtain an acrylic polymer having a core-shell multilayer structure.

A preferred method for producing the acrylic rubber particles (C) used in the present invention is to carry out emulsion polymerization of an acrylic monomer to obtain a latex containing a multilayer acrylic polymer; Coagulating the latex to obtain a slurry containing the acrylic rubber particles (C); {washing and dewatering the slurry;} drying the dewatered slurry.

For example, a more preferred method for producing the acrylic rubber particles (C) having a three-layer structure is that, in the presence of an emulsifier, methyl methacrylate is 40 to 99.99% by mass, more preferably 90 to 96.9% by mass, 1 to 60% by mass, more preferably 3 to 10% by mass, an alkyl acrylate having 1 to 8 carbon atoms, 0.01 to 1% by mass, more preferably 0.1 to 0.5% by mass of a grafting agent and crosslinking 0 to 0.5% by mass, more preferably 0 to 0.2% by mass of the agent is polymerized (1st polymerization) to obtain a latex (I) containing a core layer (a-1); {Presence of latex (I) Below, 70 to 99.5% by mass, more preferably 80 to 99% by mass, alkyl methacrylate having 1 to 8 carbon atoms of the alkyl group, 0 to 30% by mass, more preferably 0 to 20% by mass, Grafting agent 0. 5 to 5% by mass, more preferably 1 to 3% by mass, and 0 to 5% by mass, more preferably 0 to 2% by mass of the crosslinking agent are polymerized (2nd polymerization) to form the core layer (a-1) and the intermediate layer ( a-2) and (2) in the presence of latex (II), 80 to 99% by weight, more preferably 95 to 98% by weight, of methyl methacrylate and 1 to 8 carbon atoms in the alkyl group. (3rd polymerization) of 1 to 20% by mass, more preferably 2 to 5% by mass of an alkyl acrylate containing a core layer (a-1), an intermediate layer (a-2) and an outer layer (b). Latex (III) comprising: coagulating latex (III) to obtain a slurry; washing and dewatering the slurry; and drying the dewatered slurry.

The polymerization can be performed by a known method. Among the polymerizations performed in the presence of latex, seed emulsion polymerization is preferably used to obtain a core-shell multi-layer acrylic polymer. Emulsion polymerization or seed polymerization is a method well known in the art, and can be carried out according to a conventional method.

重合 The polymerization initiator used in each polymerization is not particularly limited. Examples of the polymerization initiator include water-soluble inorganic initiators such as potassium persulfate and ammonium persulfate; redox initiators obtained by using sulfites or thiosulfates in combination with inorganic initiators; and organic peroxides. Redox initiators and the like, which are used in combination with ferrous salts or sodium sulfoxylate, may be mentioned. The polymerization initiator may be added to the reaction system all at once at the start of polymerization, or may be added to the reaction system at the start of polymerization and during the polymerization in consideration of the reaction rate and the like. The amount of the polymerization initiator to be used can be appropriately set, for example, so that the average particle size of the core-shell multilayer acrylic rubber particles (C) falls within the above-mentioned range.

The amount of the polymerization initiator used in each polymerization is preferably 0.05 to 0.15 parts by mass, based on 100 parts by mass of the total amount of methyl methacrylate and alkyl acrylate, from the viewpoint of controlling the polymerization rate and adjusting the molecular weight. Preferably it is 0.08 to 0.12 parts by mass. By setting the amount of the polymerization initiator in this range, the polymerization rate becomes industrially appropriate from the viewpoints of heat removal of polymerization and polymerization time. Furthermore, it becomes easy to set the molecular weight of the outer layer (b) of the core-shell multilayer acrylic rubber particles (C) to a desired range.

乳化 The emulsifier used in each polymerization is not particularly limited. Examples of the emulsifier include anionic emulsifiers such as long-chain alkyl sulfonates, alkyl sulfosuccinates, and alkylbenzene sulfonates; nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene nonylphenyl ether; polyoxyethylene Polyoxyethylene nonylphenyl ether sulfates such as sodium nonylphenyl ether sulfate, polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene alkyl ether sulfate, and alkyl ether carboxylate salts such as sodium polyoxyethylene tridecyl ether acetate Nonionic and anionic emulsifiers can be mentioned. The amount of the emulsifier to be used can be appropriately set, for example, so that the average particle diameter of the granular material contained in the core-shell multi-layer acrylic polymer is in the above-mentioned range.

において In the present invention, the first polymerization, the second polymerization, and the third polymerization may be sequentially performed in one polymerization tank, or the polymerization may be performed sequentially by changing the polymerization tank every time the first polymerization, the second polymerization, and the third polymerization are performed. In the present invention, each polymerization is preferably performed sequentially in one polymerization tank. The temperature of the reaction system during the polymerization is preferably 30 to 120 ° C, more preferably 50 to 100 ° C.

In any of the first polymerization, the second polymerization, and the third polymerization, a reactive ultraviolet absorber such as 2- [2-hydroxy-5- (2-methacryloyloxyethyl) phenyl] -2H-1, 2,3-benzotriazole and the like can be added. The reactive ultraviolet absorber is introduced into the molecular chains of the multilayer acrylic polymer, and the ultraviolet resistance of the multilayer acrylic polymer is improved. The amount of the reactive ultraviolet absorber added is preferably 0.05 to 5 parts by mass based on 100 parts by mass of the total amount of the monomers used for the polymerization.

A chain transfer agent can be used in each polymerization for controlling the molecular weight. The chain transfer agent used for each polymerization is not particularly limited. Examples of the chain transfer agent include alkyl mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan and n-hexadecyl mercaptan; xanthogen disulfides such as dimethyl xanthogen disulfide and diethyl xanthogen disulfide; tetratetrauram disulfide Thiuram disulfides; and halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide. The amount of the chain transfer agent to be used can be appropriately set within a range where the polymer can be adjusted to a predetermined molecular weight in each polymerization. The amount of the chain transfer agent used in the third polymerization varies depending on the amount of the polymerization initiator used in the third polymerization, but the total amount of the monomers used in the third polymerization, specifically, methyl methacrylate and alkyl acrylate The amount is preferably 0.05 to 2 parts by mass, more preferably 0.08 to 1 part by mass, per 100 parts by mass.

In the present invention, the acrylic rubber particles (C) are recovered from the emulsified latex by coagulating the emulsified latex. The coagulation of the latex can be performed by a known method. Examples of the coagulation method include a freeze coagulation method, a salting out coagulation method, and an acid precipitation coagulation method. Among these, the salting out coagulation method capable of continuously producing high-quality coagulated material is preferable.
The coagulant that can be used in the present invention may be an aqueous solution of an inorganic acid or a salt thereof, or an organic acid or a salt thereof having a property of coagulating and coagulating the emulsion polymerization latex.

The emulsified latex is a three-layer acrylic polymer latex consisting of a core layer (a-1), an intermediate layer (a-2), and an outer layer (b) alone or as a mixture of two or more, or a core layer (a -1), a mixture of a multi-layer acrylic polymer latex comprising an intermediate layer (a-2) and an outer layer (b) and at least one single-layer acrylic polymer latex, by adding a coagulant. Can be solidified.

(2) Methacrylic resin (D)
The methacrylic resin (D) is a non-crosslinked polymer containing 60% by mass or more of methyl methacrylate units, and has a weight average molecular weight of 70,000 or more.

The methacrylic resin (D) preferably contains 60 to 99.8% by mass of a methyl methacrylate unit and 0.2 to 40% by mass of an alkyl acrylate unit.

量 The amount of the alkyl acrylate unit contained in the methacrylic resin (D) is preferably from 0.3 to 30% by mass, more preferably from 0.4 to 20% by mass. The alkyl group in the alkyl acrylate preferably has 1 to 8 carbon atoms. The smaller the amount of the alkyl acrylate unit, the lower the impact resistance of the film tends to be, and the larger the amount of the alkyl acrylate unit, the lower the stress whitening resistance and transparency of the film tend to be.

(4) The weight average molecular weight of the methacrylic resin (D) is 70,000 or more, for example, 75,000 to 2,000,000, and preferably 80,000 to 1800000. The weight average molecular weight can be measured by gel permeation chromatography. The measurement by gel permeation chromatography can be performed as described in Examples below.

(3) Organic Solvent The organic solvent can be used without any limitation as long as it dissolves the acrylic rubber particles (C) and the methacrylic resin (D) and additives that are added as needed.

For example, a chlorine-based organic solvent includes methylene chloride and chloroform; non-chlorine-based organic solvents include methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, 1,3-dioxolan, and 1,4. -Dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3 1,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1- Propanol, nitroethane, etc. can be mentioned, and methylene chloride, methyl acetate, ethyl acetate, acetone, methyl Ketone and can be preferably used. Further, these solvents may be used as a mixture of plural kinds.

○ Production of dope (dissolution process)
The dope used for casting in the production method of the present invention contains acrylic rubber particles (C), a methacrylic resin (D), and an organic solvent obtained by an emulsion polymerization method, and the methacrylic resin (D) contains a methyl methacrylate unit. It is a non-crosslinked polymer containing 60% by mass or more, and a resin having a weight average molecular weight (Mw) of 70,000 or more.

The dope can be prepared by a general method comprising treating at a temperature of 0 ° C. or higher (normal temperature or high temperature). The dope can be prepared using a dope preparation method and apparatus in a usual solvent casting method. In the case of a general method, halogenated hydrocarbons (particularly dichloromethane) and alcohols (particularly methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, and t-butanol) are used as organic solvents. -Pentanol, 2-methyl-2-butanol and cyclohexanol) are preferably used.

The content of the acrylic rubber particles (C) in the dope is preferably 0.1 to 33% by mass, more preferably 0.2 to 28% by mass, and 0.3 to 24% by mass. Is more preferred.

The content of the methacrylic resin (D) in the dope is preferably from 4.9 to 37% by mass, more preferably from 9.8 to 32% by mass, and preferably from 14.7 to 26% by mass. More preferred.

The content of the organic solvent in the dope is preferably from 30 to 95% by mass, more preferably from 40 to 90% by mass, and still more preferably from 50 to 85% by mass.
An optional additive described later may be added to the dope.

The dope can be prepared by stirring the acrylic rubber particles (C), the methacrylic resin (D), the organic solvent and, if necessary, the additives. At this time, a mixture of each component may be added and dissolved in the stirred organic solvent, or each component may be sequentially added and dissolved in the stirred organic solvent, or a solution of each component may be added in advance. A dope may be formed by mixing these solutions after preparation. For dissolving the acrylic rubber particles (C) and the methacrylic resin (D), a method of dissolving at normal pressure, a method of dissolving at a temperature not higher than the boiling point of the main solvent, a method of dissolving at a pressure of not less than the boiling point of the main solvent, Various dissolution methods such as a method performed by a cooling dissolution method as described in JP-A-95544, JP-A-9-95557, or JP-A-9-95538, and a method performed at a high pressure as described in JP-A-11-21379. Although a method can be used, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

○ Casting Step In the casting step, the dope prepared as described above is cast on a casting support to form a film, which is dried to form a casting film. In this casting step, the dope is fed to a pressure die through a liquid feed pump, and the dope is cast from a pressure die slit to a casting position on a support such as an endless metal belt that transfers infinitely. It is a process. Structure of casting die, decompression chamber, support, etc., co-casting, peeling method, stretching, drying conditions in each step, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method Until now, paragraphs [0617] to [0889] of JP-A-2005-104148 are described in detail.

In the production method of the present invention, when an unstretched acrylic film is produced, the acrylic film is cast so that the film thickness is preferably 20 to 200 μm, more preferably 25 to 100 μm, and still more preferably 30 to 80 μm. The doping amount to be adjusted is adjusted. If the film thickness is smaller than this range, the strength of the cast film decreases and the workability deteriorates. On the other hand, if the thickness is larger than this range, the organic solvent may remain in the acrylic film.

○ Organic solvent evaporation step Next, the casting film thus obtained is dried. At that time, the casting film is usually heated on a metal support, and the organic solvent is evaporated until the casting film can be separated from the metal support.

の後 After the above steps, a peeling step, a preheating step, a heat treatment step, a stretching step, and the like are performed as required, whereby an acrylic film is produced by the production method of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples, but these are merely examples, and the present invention is not limited thereto.

(Particle size)
The emulsion containing the acrylic rubber particles (C) is diluted with ion-exchanged water to a solid concentration of 0.05% by mass, spread on a glass plate, and dried, whereby the individual particles are aggregated. But on a glass plate. Platinum / palladium was vapor-deposited on this surface, an electron micrograph was obtained with a scanning electron microscope, and the particle diameters of 100 particles were randomly measured and averaged to obtain an average particle diameter. On the other hand, the emulsion containing the acrylic rubber particles (C) was diluted to a solid content concentration of 0.05% by mass, placed in a quartz cell having a measurement length of 10 mm, and the absorbance at 500 nm was measured. The above operation was performed using particles having different particle diameters, and a calibration curve between the average particle diameter and 500 nm absorbance observed by an electron microscope was prepared. The average particle diameter of the acrylic rubber particles (C) was determined by measuring the absorbance using this calibration curve.

(Outer layer thickness)
The outer layer thickness was calculated from the following equation using the total value of the particle diameter of the acrylic rubber particles (C) obtained by the above-described method and the monomer composition ratio of the inner layer a as the elastic copolymer ratio.

(Measurement of molecular weight of methacrylic resin (D))
The molecular weight of the methacrylic resin (D) was calculated from a value obtained by measuring a chromatogram by gel permeation chromatography (GPC) under the following conditions and converting it to the molecular weight of standard polystyrene. The baseline shows that the slope of the peak on the high molecular weight side of the GPC chart changes from zero to plus when viewed from the earlier retention time, and that the slope of the peak on the low molecular weight side is negative to zero when viewed from the earlier retention time. A line connecting the points changing to.

GPC device: Tosoh Corporation, HLC-8320
Detector: Differential refractive index detector Column: Two TSKgel SuperMultipore HZM-M manufactured by Tosoh Corporation and Super HZ4000 connected in series were used.

Eluent: tetrahydrofuran Eluent flow rate: 0.35 ml / min Column temperature: 40 ° C
Calibration curve: Created using data of 10 standard polystyrenes

(Measurement of molecular weight of outer layer (b) of acrylic rubber particles (C))
Acrylic rubber particles (C) are added with acetone, left at room temperature for one day, stirred and centrifuged (20,000 rpm for 200 minutes) to precipitate with the supernatant (acetone solution: outer layer component (b)). (Acetone swelled product: inner layer component (a)). Thereafter, the solid content obtained by drying the acetone solution was measured in the same manner as in the measurement of the molecular weight of the methacrylic resin (D).

(Solubility of acrylic rubber particles (C))
The acrylic rubber particles (C-1) obtained in Production Example 1 were dissolved in methylene chloride so as to have a content of 10 wt%, and shaken at room temperature for 8 hours. The solution was filtered through a 50-mesh wire gauze, and the gel-like substance remaining on the wire gauze was dried at 80 ° C. for 8 hours with a drier, and the remaining amount was measured.
Evaluation was made according to the following criteria.
：: Residual amount is less than 1 wt% 残存: Residual amount is 1 to less than 5 wt% X: Residual amount is 5 wt% or more

(Heat-resistant)
Using a dynamic viscoelasticity measuring device (REOGEL-E4000 manufactured by UBM), measurement was performed at a frequency of 1 Hz, and the peak temperature of the loss tangent (tan δ) derived from the methacrylic resin (D) on the high temperature side was read, and the heat resistance was measured. It was evaluated as an index.

(Film impact resistance)
The acrylic film was cut out at 100 mm (vertical) × 10 mm (width), folded in a mountain at the center in the vertical direction, folded once, and this evaluation was measured three times and evaluated according to the following criteria. In addition, broken evaluation here means that it was broken and separated into two or more pieces.
：: not broken three times ×: broken at least once out of three times

[Production Example 1]
[Production of acrylic rubber particles (C-1)]
In a reactor equipped with a stirrer, thermometer, nitrogen gas inlet, monomer inlet tube and reflux condenser, 1050 parts by weight of deionized water, 1 part by weight of sodium dodecylbenzenesulfonate and 0.05 part by weight of sodium carbonate Then, the inside temperature of the vessel was set to 80 ° C. after the inside of the vessel was sufficiently replaced with nitrogen gas to make it substantially free of oxygen. Then, 0.01 part by mass of potassium persulfate was added thereto, and the mixture was stirred for 5 minutes. Then, 26.3 parts by mass of the monomer mixture having the composition shown in the first layer of Table 1 below was continuously added over 20 minutes. The mixture was supplied dropwise, and after the completion of the dropwise addition, the polymerization reaction was further performed for 30 minutes so that the polymerization conversion rate became 98% or more.

Next, 0.05 parts by mass of a 3% aqueous solution of potassium persulfate was charged into the reactor and stirred for 5 minutes, and then 157.4 parts by mass of a monomer mixture having the composition shown in the second layer of Table 1 below Was continuously added dropwise over 40 minutes. After the completion of the dropwise addition, the polymerization reaction was further performed for 30 minutes so that the polymerization conversion rate became 98% or more.

Next, after 0.5 parts by mass of a 3% aqueous solution of potassium persulfate was charged into the reactor and stirred for 5 minutes, a monomer having the composition shown in the third layer of Table 1 below and a total of 100 parts by mass were added. 341 parts by mass of a monomer mixture containing 0.295 parts by mass of n-octyl mercaptan (nOM, chain transfer agent) were continuously added dropwise to the mixture over 100 minutes, and after the completion of the dropwise addition, the polymerization conversion was 98%. The polymerization reaction was further carried out for 60 minutes as described above to obtain an emulsion containing acrylic rubber particles (C-1) having an average particle diameter of 0.1 μm.

Subsequently, the emulsion containing the acrylic rubber particles (C-1) was frozen at −30 ° C. for 4 hours. The frozen emulsion was poured into hot water of 80 ° C. twice as much as the frozen emulsion, dissolved and made into a slurry, kept at 80 ° C. for 20 minutes, dehydrated, dried at 70 ° C., and dried with acrylic rubber particles (C- 1) A solidified powder was obtained.

[Production Example 2]
[Production of acrylic rubber particles (C-2)]
A powder of coagulated acrylic rubber particles (C-2) was obtained in the same manner as in Production Example 1, except that sodium alkyldiphenyletherdisulfonate was used as the emulsifier, and the monomer composition was changed to the one shown in Table 1 below.

[Production Example 3]
[Production of acrylic rubber particles (C-3)]
A powder of coagulated acrylic rubber particles (C-3) was obtained in the same manner as in Production Example 1 except that the composition was changed to the monomer composition shown in Table 1 below.

[Production Example 4]
[Production of acrylic rubber particles (C-4)]
Except for changing to the monomer composition shown in Table 1 below, a powder of acrylic rubber particles (C-4) was obtained in the same manner as in Production Example 1.

[Production Example 5]
[Production of acrylic rubber particles (C-5)]
Except for changing to the monomer composition shown in Table 1 below, a powder of acrylic rubber particles (C-5) was obtained in the same manner as in Production Example 1.

[Production Example 6]
[Production of acrylic rubber particles (C-6)]
Except for changing to the monomer composition shown in Table 1 below, a powder of acrylic rubber particles (C-6) was obtained in the same manner as in Production Example 1.

[Production Example 7]
[Production of acrylic rubber particles (C-7)]
A powder of coagulated acrylic rubber particles (C-4) was obtained in the same manner as in Production Example 1, except that sodium polyoxyethylene lauryl ether sulfate was used as an emulsifier, and the composition was changed to the monomer composition shown in Table 1 below. .

[Production Example 8]
[Production of acrylic rubber particles (C-8)]
Except for changing to the monomer composition shown in Table 1 below, a powder of acrylic rubber particles (C-8) was obtained in the same manner as in Production Example 1.

As the methacrylic resin (D), a methyl methacrylate copolymer having a weight average molecular weight and a methyl acrylate copolymerization ratio as shown in Table 2 was used.

[Example 1]
The acrylic rubber particles (C-1) obtained in Production Example 1 were dissolved in methylene chloride so as to have a content of 30% by weight, and shaken at room temperature for 8 hours. The solution was filtered through a 50-mesh wire mesh, and the gel-like substance remaining on the wire mesh was dried at 80 ° C. for 8 hours with a drier, and the remaining amount was measured to determine the solubility of the acrylic rubber particles. evaluated. Table 2 shows the evaluation results. To 70 parts by mass of methylene chloride, 15 parts by mass of the acrylic rubber particles (C-1) obtained in Production Example 1 and 15 parts by mass of the methacrylic resin (D) were added and shaken for 8 hours to obtain a polymer solution. . This solution was uniform, and no gel-like foreign matter was observed.

This solution was cast on release paper, air-dried, and dried under reduced pressure at 80 ° C. for 8 hours to obtain an acrylic film having a thickness of 100 μm. Table 2 shows the physical properties of this film.

[Example 2]
An acrylic film was obtained in the same manner as in Example 1, except that the acrylic rubber particles (C-2) obtained in Production Example 2 were used. Table 2 shows the physical properties of this film.

[Example 3]
Using acrylic rubber particles (C-3) obtained in Production Example 3, 24 parts by mass of acrylic rubber particles (C-3) and 6 parts by mass of methacrylic resin (D) based on 70 parts by mass of methylene chloride Except having melt | dissolved a part, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Comparative Example 1]
An acrylic film was obtained in the same manner as in Example 1, except that the acrylic rubber particles (C-4) obtained in Production Example 4 were used. Table 2 shows the physical properties of this film.

[Comparative Example 2]
An acrylic film was obtained in the same manner as in Example 1, except that the acrylic rubber particles (C-5) obtained in Production Example 5 were used. Table 2 shows the physical properties of this film.

[Comparative Example 3]
An acrylic film was obtained in the same manner as in Example 1, except that the acrylic rubber particles (C-6) obtained in Production Example 6 were used. Table 2 shows the physical properties of this film.

[Comparative Example 4]
An acrylic film was obtained in the same manner as in Example 1 except that the molecular weight of the methacrylic resin (D) was reduced. Table 2 shows the physical properties of this film.

[Comparative Example 5]
An acrylic film was obtained in the same manner as in Example 1, except that the acrylic rubber particles (C-7) obtained in Production Example 7 were used. Table 2 shows the physical properties of this film.

[Comparative Example 6]
An acrylic film was obtained in the same manner as in Example 1, except that the acrylic rubber particles (C-8) obtained in Production Example 8 were used. Table 2 shows the physical properties of this film.

例 In Examples 1 and 3, the impact resistance was improved and the solubility was good as compared with Comparative Examples 1, 4 and 6, and the heat resistance and haze were reduced as compared with Comparative Example 3. Also in Example 2, the solubility, heat resistance and impact resistance are excellent, and the haze is suppressed to a low level. On the other hand, in Comparative Example 2, the acrylic rubber particles are composed of only the crosslinked particles, and have low solubility since they have no outer layer. In Comparative Example 5, although the acrylic rubber particles had an outer layer, the solubility was low because the outer layer thickness was 7.5 nm or less.

Claims

An acrylic rubber particle (C) obtained by an emulsion polymerization method, a non-crosslinked polymer containing 60% by mass or more of a methyl methacrylate unit, a methacrylic resin (D) having a weight average molecular weight of 70,000 or more and an organic solvent. After casting the dope containing on a casting support, a method for producing an acrylic film comprising a step of evaporating the organic solvent,
An outer layer (b) containing a non-crosslinked hard polymer having a weight average molecular weight of 45,000 or more, wherein the acrylic rubber particles (C) contain 70% by mass or more of methyl methacrylate units, and an alkyl inscribed therein. 2 having an inner layer (a) containing an elastic copolymer comprising 60 to 99.8% by mass of an acrylate unit and 0.2 to 10% by mass of a structural unit derived from a copolymerizable crosslinkable monomer; A method for producing an acrylic film having a layer structure or more, wherein the thickness of the outer layer (b) is 7.5 nm or more.
The method for producing an acrylic film according to claim 1, wherein the alkyl acrylate unit used in the elastic copolymer of the acrylic rubber particles (C) is n-butyl acrylate.
3. The acrylic film according to claim 1, wherein a part of the hard polymer constituting the outer layer (b) of the acrylic rubber particles (C) is covalently bonded to an inscribed elastic copolymer. 4. Production method.
The mass ratio of the acrylic rubber particles (C) is in the range of 2 to 90 parts by mass with respect to the total of 100 parts by mass of the acrylic rubber particles (C) and the methacrylic resin (D). 4. The method for producing an acrylic film according to any one of items 3 to 3.
The method for producing an acrylic film according to any one of claims 1 to 4, wherein the film thickness after drying is 20 μm or more and 200 μm or less.
The method for producing an acrylic film according to any one of claims 1 to 5, wherein the method is used for optical applications.