KR20210063356A - Method for manufacturing acrylic film - Google Patents

Abstract

The present invention is a non-crosslinked polymer containing acrylic rubber particles (C) obtained by emulsion polymerization and 60 mass% or more of methyl methacrylate units, and a methacrylic resin (D) having a weight average molecular weight of 70,000 or more and an organic solvent. A method for producing an acrylic film comprising a step of evaporating the organic solvent after casting the dope contained on a support for casting, wherein the acrylic rubber particles (C) contain 70% by mass or more of methyl methacrylate units, an outer layer (b) containing a non-crosslinked hard polymer having a weight average molecular weight of 45,000 or more, 60 to 99.8 mass% of an alkyl acrylate unit inscribed therewith, and 0.2 to 0.2 to structural units derived from a copolymerizable crosslinkable monomer To provide a method for producing an acrylic film having a two-layer structure or more having an inner layer (a) containing an elastic copolymer containing 10 mass%, wherein the outer layer (b) has a thickness of 7.5 nm or more.

Description

Method for manufacturing acrylic film

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 a methacrylic resin.

Demand for liquid crystal display devices is expanding in applications such as liquid crystal televisions and liquid crystal displays of personal computers. In general, a liquid crystal display device is composed of a liquid crystal cell with a transparent electrode, a liquid crystal layer, a color filter, etc. sandwiched by a glass plate, and two polarizing plates formed on both sides thereof, and each polarizing plate is a polarizer (polarizing film, polarizing film, polarizing film). Film) is sandwiched between two optical films (polarizing plate protective film). As this polarizing plate protective film, a cellulose triacetate film is used normally.

On the other hand, the use of a liquid crystal display device is diversified while enlargement of a liquid crystal display device is accelerated|stimulated by the progress of recent technology. For example, use as a large display installed in a street or storefront, use to the display for advertisements in a public place using the display device called a digital signage, etc. are mentioned.

In such a use, since use outdoors is assumed, deterioration by moisture absorption of a polarizing film becomes a problem, and higher moisture resistance is calculated|required by a polarizing plate protective film. However, it was difficult to obtain sufficient moisture resistance with cellulose ester films, such as a cellulose triacetate film used conventionally, and there existed a problem that an optical influence became large when it thickened in order to acquire moisture resistance. Furthermore, since thickness reduction of an apparatus is also calculated|required in recent years, it also became a problem that polarizing plate itself becomes thick.

On the other hand, as a low hygroscopic optical film material, in addition to low hygroscopicity, methacryl-type resin was used suitably for the optical film from the point which showed the outstanding transparency and dimensional stability.

However, compared with a cellulose ester film, an optical film made of a methacrylic resin is prone to cracking and has a brittle property, making it difficult to handle, and it is particularly difficult to stably produce an optical film for a large-sized liquid crystal display device. did.

Moreover, very high transparency and external appearance are calculated|required by the acrylic film used for an optical use in recent years. However, in the conventional melt film forming method, there are problems such as film foreign material due to gel polymer, birefringence due to flow orientation, and increase in coloring and soaking of the resin due to retention deterioration, high transparency 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, solution viscosity can be made low by adjusting the kind, solid content, etc. of a solvent. Therefore, compared with the melt film forming method, highly accurate filtration is possible, and the acrylic film excellent in transparency and an external appearance is obtained. In the solution casting method, in order to eliminate the weakness of the acrylic film, a technique in which acrylic rubber particles are added is disclosed (Patent Documents 1 to 3).

In patent document 1, as a method of obtaining the optical film which improved brittleness, with respect to a cellulose-ester film, the acrylic rubber particle was mixed, and the film manufactured by the solution casting method is proposed. However, by this method, since the obtained film contains the cellulose ester, sufficient improvement of moisture resistance was not acquired.

In patent document 2, although the flexible film which consists of an acrylic resin and an acrylic rubber particle is proposed, there is no description of the solubility with respect to the solvent of an acrylic rubber particle, and it is hard to say that it is excellent in the dispersibility with respect to a solvent.

In patent document 3, although the acrylic rubber particle with improved dispersibility is proposed, there is no description regarding the impact resistance of the obtained acrylic film, and it is hard to say that a film with sufficient impact resistance was obtained.

WO2009/047924 Japanese Patent Laid-Open No. 2009-209295 Japanese Patent Laid-Open No. 2016-043494

Therefore, this invention has been made in view of the said subject, and the objective is low hygroscopicity, transparency, high heat resistance, and remarkably improves brittleness, and especially a large sized liquid crystal display device and a liquid crystal display device for outdoor use. It is to provide the acrylic film used suitably as a polarizer protective film in.

MEANS TO SOLVE THE PROBLEM The present inventors came to complete this invention including the following forms, as a result of examining in order to achieve the said objective.

That is, the present invention provides the following [1] to [6].

[1] A non-crosslinked polymer containing acrylic rubber particles (C) obtained by emulsion polymerization and 60 mass% or more of methyl methacrylate units, containing a methacrylic resin (D) having a weight average molecular weight of 70,000 or more and an organic solvent A method for producing an acrylic film comprising a step of evaporating the organic solvent after casting the dope to be cast on a support for casting,

The acrylic rubber particles (C) contain 70 mass% or more of methyl methacrylate units, and an outer layer (b) containing a non-crosslinked hard polymer having a weight average molecular weight of 45,000 or more, and an alkyl acrylate inscribed therewith A two-layer or more structure having an inner layer (a) containing an elastic copolymer comprising 60 to 99.8 mass% of units and 0.2 to 10 mass% of structural units derived from a copolymerizable crosslinkable monomer, wherein the outer layer (b) A method for producing an acrylic film, characterized in that the thickness 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 for producing an acrylic film 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 inscribed elastic copolymer. .

[4] [1] to, wherein the mass ratio of the acrylic rubber particles (C) is in the range of 2 to 90 parts by mass relative to 100 parts by mass in total of the acrylic rubber particles (C) and the methacrylic resin (D) [3] The method for producing the acrylic film according to any one of [3].

[5] The method for producing an acrylic film according to any one of [1] to [4], wherein the film thickness 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], wherein the method is used for an optical use.

ADVANTAGE OF THE INVENTION By this invention, it is low hygroscopicity, it is transparent, it is high heat resistance, and the acrylic film which improved brittleness remarkably can be provided.

Dope used for casting in the manufacturing method of this invention contains (1) acrylic rubber particle (C) obtained by emulsion polymerization method, (2) methacrylic resin (D), and (3) organic solvent, Methacryl The system resin (D) is a non-crosslinked polymer containing 60 mass% or more of methyl methacrylate units, and is a resin having a weight average molecular weight (Mw) of 70,000 or more.

(1) Acrylic rubber particles obtained by emulsion polymerization (C)

The acrylic rubber particles (C) used in the present invention include an outer layer (b) containing a non-crosslinked hard polymer containing 70 mass% or more of methyl methacrylate units, and 60 to 99.8 alkyl acrylate units inscribed therewith. A two-layer structure or more having an inner layer (a) containing an elastic copolymer comprising mass% and 0.2 to 10 mass% of structural units derived from a copolymerizable crosslinkable monomer, wherein the outer layer (b) has a thickness of 7.5 more than nanometers.

In this specification, "copolymerizable crosslinkable monomer" includes "copolymerizable crosslinkable monomer (grafting agent)" and "copolymerizable crosslinkable monomer (crosslinking agent)." In addition, "copolymerizable crosslinkable monomer (grafting agent)" may be described as "grafting agent", and "copolymerizable crosslinkable monomer (crosslinking agent)" may be described as "crosslinking agent".

The acrylic rubber particle (C) used for this invention may be any form of a powder form, a granular body, an aggregate, and a coagulated material.

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, still more preferably 0.05 μm, even more preferably 0.1 μm, The upper limit is preferably 0.35 µm, more preferably 0.3 µm, still more preferably 0.2 µm, even 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. In addition, the average particle diameter of an acrylic rubber particle (C) is a value obtained by the light scattering method.

The composition in the case where the acrylic rubber particle (C) used for this invention has a three-layer structure of a core layer (a-1), an intermediate|middle layer (a-2), and an outer layer (b) is demonstrated below. In addition, the intermediate|middle layer (a-2) of a three-layer structure is in contact with the outer layer (b), and can respond|correspond to the inner layer (a) of this invention. The core layer (a-1) is an arbitrary 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, “alkyl acrylate unit"), and a structural unit derived from a crosslinkable monomer (grafting agent) (hereinafter, may be described as "crosslinkable monomer (grafting agent) unit"), and if necessary Structural units derived from a crosslinkable monomer (crosslinking agent) (hereinafter, may be referred to as "crosslinkable monomer (crosslinking agent) units") and structural units derived from other copolymerizable monomers (hereinafter, "other copolymerizable monomer units") may be described).

The amount of the methyl methacrylate unit in the core layer (a-1) is preferably 40 to 98.99 mass%, more preferably 90 to 96.9 mass%, based on all the structural units of the core layer (a-1). to be. As the amount of the methyl methacrylate unit decreases, the weather resistance of the film tends to decrease, and as the amount of the methyl methacrylate unit increases, the impact resistance of the film tends to decrease.

The amount of the alkyl acrylate unit in the core layer (a-1) is preferably 1 to 60 mass%, more preferably 3 to 10 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. As the amount of the alkyl acrylate unit decreases, the thermal decomposition resistance of the multilayer structure acrylic polymer tends to decrease, and as the amount of the alkyl acrylate unit increases, the hot water or non-water whitening resistance of the film tends to decrease.

The amount of the copolymerizable crosslinkable monomer (grafting agent) unit in the core layer (a-1) is preferably 0.01 to 1 mass%, more preferably 0.01 to 1 mass%, based on all the structural units of the core layer (a-1). is 0.1 to 0.5 mass%. As the amount of the copolymerizable crosslinkable monomer (grafting agent) unit decreases, the bonding strength between the core layer (a-1) and the intermediate layer (a-2) tends to decrease, and the copolymerizable crosslinkable monomer (grafting agent) unit tends to decrease. As the amount of the film 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 mass%, more preferably 0 to 0.5 mass%, based on all the structural units of the core layer (a-1). It is 0-0.2 mass %. The higher the amount of the copolymerizable crosslinkable monomer (crosslinking agent) unit, the lower the impact resistance of the film tends to be.

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

The intermediate layer (a-2) includes an alkyl acrylate unit, a copolymerizable crosslinkable monomer (grafting agent) unit, and, if necessary, a methyl methacrylate unit, a copolymerizable crosslinkable monomer (crosslinking agent) unit, and a copolymerizable unit. It is a polymer composed of other monomer units.

The amount of the alkyl acrylate unit in the intermediate layer (a-2) is 60 to 99.8 mass%, preferably 70 to 99.5 mass%, more preferably 80 to all the structural units of the intermediate layer (a-2). -99 mass %. The alkyl group in the alkyl acrylate preferably has 1 to 8 carbon atoms. As the amount of the alkyl acrylate unit decreases, the impact resistance of the film tends to decrease, and as the amount of the alkyl acrylate unit increases, the stress whitening resistance and transparency of the film tend to decrease.

The quantity of the copolymerizable crosslinkable monomer (grafting agent) unit in an intermediate|middle layer (a-2) is 0.2-10 mass % with respect to all the structural units of an intermediate|middle layer (a-2), Preferably it is 0.5-5 mass %, more preferably 1-3 mass %. As the amount of the copolymerizable crosslinkable monomer (grafting agent) unit is small, the stress whitening resistance of the film tends to decrease, and as the amount of the copolymerizable crosslinkable monomer (grafting agent) unit is large, the impact resistance of the film decreases. tends to be

The amount of the methyl methacrylate unit in the intermediate layer (a-2) is preferably 0 to 30 mass%, more preferably 0 to 20 mass%, based on all the structural units of the intermediate layer (a-2). As the amount of the methyl methacrylate 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-2) is preferably 0 to 0.5 mass%, more preferably 0 to 0.5 mass%, based on all the structural units of the core layer (a-1). It is 0-0.2 mass %. The higher the amount of the copolymerizable crosslinkable monomer (crosslinking agent) unit, the lower the impact resistance of the film tends to be.

The amount of other copolymerizable monomer units in the intermediate layer (a-2) is preferably 0 to 40 mass%, more preferably 0 to 30 mass%, based on all the structural units of the intermediate layer (a-2).

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

The outer layer (b) is a non-crosslinked hard polymer containing 70 mass% or more of methyl methacrylate units. The amount of the methyl methacrylate unit in the outer layer (b) is preferably 80 to 99 mass%, more preferably 95 to 98 mass%, based on all the structural units of the outer layer (b). As the amount of the methyl methacrylate unit decreases, the stress whitening resistance of the film tends to decrease, and as the amount of the methyl methacrylate unit increases, the thermal decomposition resistance of the multilayer structure acrylic polymer tends to decrease.

The amount of the alkyl acrylate unit which you may have in the outer layer (b) is preferably 1 to 20 mass%, more preferably 2 to 5 mass%, based on all the 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 decreases, the thermal decomposition resistance of the multilayer structure 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.

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, and more preferably 60,000 or more and 100,000 or less. It will be excellent in the impact resistance of the film obtained as a weight average molecular weight is in this range. The glass transition temperature of the outer layer (b) is preferably 80°C or higher, more preferably 90°C or higher, still more preferably 100°C or higher. There exists a tendency for the warm water or non-water whitening resistance of a film to improve, so that the glass transition temperature of an outer layer (b) is high.

In this specification, as "alkyl acrylate", the C1-C8 alkyl acrylate of an alkyl group is mentioned, For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acryl a rate, s-butyl acrylate, t-butyl acrylate, n-butylmethyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, etc. are mentioned. These alkyl acrylates can be used individually by 1 type or in combination of 2 or more type. Among these, methyl acrylate and/or n-butyl acrylate are preferable.

In the present specification, the "copolymerizable crosslinkable monomer" is a monomer having two or more polymerizable groups, for example, allyl methacrylate, allyl acrylate, mono- or di-allyl maleate, mono- or A copolymerizable crosslinkable monomer having a heterogeneous polymerizable group such as di-allyl fumarate, crotyl acrylate, and crotyl methacrylate (grafting agent), diacrylic compound, dimethacrylic compound, diallyl compound, divinyl and copolymerizable crosslinkable monomers (crosslinking agents) having a polymerizable group of the same type as a compound, a diene compound, and a trivinyl compound. Examples of the copolymerizable crosslinkable 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, Polyethylene glycol di(meth)acrylate, divinylbenzene, trivinylbenzene, ethylene glycol diallyl ether, propylene glycol diallyl ether, butadiene, etc. are mentioned. The copolymerizable crosslinkable monomer can be used individually by 1 type or in combination of 2 or more type.

In the present specification, as "other copolymerizable monomers", for example, aromatic vinyl monomers such as styrene, p-methylstyrene, o-methylstyrene, and vinylnaphthalene, unsaturated nitrile monomers such as acrylonitrile, ethylene, propylene Olefin-based monomers such as vinyl chloride, vinylidene chloride, and vinylidene fluoride halogenated monomers, unsaturated carboxylic acid-based monomers such as acrylic acid, methacrylic acid, maleic anhydride, vinyl acetate, N-propyl maleimide, N and maleimide-based monomers such as -cyclohexylmaleimide and No-chlorophenylmaleimide, and these monomers can be used alone or in combination of two or more.

The manufacturing method of the acrylic rubber particle (C) used for this invention is not specifically limited. For example, when the acrylic rubber particles (C) have a two-layer structure, the inner layer (a) and the outer layer (b) are sequentially formed by a seed emulsion polymerization method to obtain an acrylic polymer having a core-shell multilayer structure. . For example, when the acrylic rubber particles (C) have a three-layer configuration, a core layer (or first layer, a-1), an intermediate layer (or second layer, a-2), and an outer layer (third layer/shell) , b) can be sequentially formed by a seed emulsion polymerization method to obtain an acrylic polymer having a core-shell multilayer structure.

A preferable manufacturing method of the acrylic rubber particle (C) used for this invention performs emulsion polymerization of an acrylic monomer, and obtains the latex containing a multilayer structure acrylic polymer; coagulating the latex containing the multilayer structure acrylic polymer to obtain a slurry containing the acrylic rubber particles (C); Washing and dehydrating the slurry; It will include a step of drying the dehydrated slurry.

For example, a more preferable manufacturing method of the acrylic rubber particle (C) having a three-layer structure is 40 to 98.99 mass% of methyl methacrylate, more preferably 90 to 96.9 mass%, in the presence of an emulsifier, the number of carbon atoms in the alkyl group 1 to 8 alkyl acrylate 1 to 60 mass%, more preferably 3 to 10 mass%, 0.01 to 1 mass% of grafting agent, more preferably 0.1 to 0.5 mass% and 0 to 0.5 mass% of crosslinking agent, more preferably Preferably, 0-0.2 mass % is superposed|polymerized (1st polymerization), and latex (I) containing a core layer (a-1) is obtained; In the presence of latex (I), 70 to 99.5 mass% of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, more preferably 80 to 99 mass%, and 0 to 30 mass% of methyl methacrylate, more preferably 0 -20 mass %, grafting agent 0.5-5 mass %, More preferably 1-3 mass % and crosslinking agent 0-5 mass %, More preferably, 0-2 mass % is superposed|polymerized (2nd polymerization), and the core layer (a Obtaining latex (II) containing -1) and an intermediate|middle layer (a-2); In the presence of latex (II), 80 to 99 mass% of methyl methacrylate, more preferably 95 to 98 mass%, and 1 to 20 mass% of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, more preferably 2 to obtain a latex (III) comprising a core layer (a-1), an intermediate layer (a-2), and an outer layer (b) by polymerizing 5% by mass (3rd polymerization); coagulating latex (III) to obtain a slurry; washing and dewatering the slurry; It will include a step of drying the dehydrated slurry.

Polymerization can be performed by a well-known method. Seed emulsion polymerization during polymerization carried out in the presence of latex is preferably used in order to obtain a core-shell multilayer structure acrylic polymer. Since emulsion polymerization or seed polymerization is a method well known in the art, it can be carried out according to a conventional method.

The polymerization initiator used in each polymerization is not restrict|limited in particular. As a polymerization initiator, For example, Water-soluble inorganic type initiators, such as a potassium persulfate and an ammonium persulfate; a redox initiator obtained by using a sulfite or thiosulfate in combination with an inorganic initiator; and a redox initiator obtained by using a ferrous salt or sodium sulfoxylate in combination with an organic peroxide. The polymerization initiator may be added to the reaction system collectively at the start of polymerization, or may be added to the reaction system separately at the time of polymerization initiation and during polymerization in consideration of the reaction rate and the like. The usage-amount of a polymerization initiator can be suitably set so that the average particle diameter of the core-shell multilayer structure acrylic rubber particle (C) may become the above-mentioned range, for example.

The amount of polymerization initiator used in each polymerization is preferably 0.05 to 0.15 parts by mass, more 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 polymerization rate control and molecular weight adjustment. It is 0.08-0.12 mass part. By making the amount of polymerization initiator into this range, it becomes an industrially appropriate polymerization rate from a viewpoint of polymerization heat removal and polymerization time. Moreover, it becomes easy to set the molecular weight of the outer layer (b) of the core-shell multilayer structure acrylic rubber particle (C) to a desired range.

The emulsifier used in each superposition|polymerization is not restrict|limited in particular. As an emulsifier, For example, Anionic emulsifiers, such as a long-chain alkylsulfonate, a sulfosuccinic acid alkylester salt, and an alkylbenzenesulfonate; nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene nonylphenyl ether; Polyoxyethylene nonylphenyl ether sulfate such as sodium polyoxyethylene nonylphenyl ether sulfate, polyoxyethylene alkyl ether sulfate such as sodium polyoxyethylene alkyl ether sulfate, and alkyl ether carboxylate such as sodium polyoxyethylene tridecyl ether acetate An ionic/anionic emulsifier is mentioned. The amount of the emulsifier to be used can be appropriately set, for example, so that the average particle diameter of the particles contained in the core-shell multilayer structure acrylic polymer falls within the range described above.

In the present invention, 1st polymerization, 2nd polymerization, and 3rd polymerization may be sequentially carried out in one polymerization tank, or the polymerization tank may be sequentially changed for every 1st polymerization, 2nd polymerization, and 3rd polymerization. In the present invention, it is preferable to sequentially carry out each polymerization in one polymerization tank. Moreover, the temperature of the reaction system while superposing|polymerizing becomes like this. Preferably it is 30-120 degreeC, More preferably, it is 50-100 degreeC.

Moreover, in any one of 1st polymerization, 2nd polymerization, and 3rd polymerization, if necessary, a reactive ultraviolet absorber, for example, 2-[2-hydroxy-5-(2-methacryloyloxyethyl) phenyl]-2H -1,2,3-benzotriazole and the like may be added. A reactive ultraviolet absorber is introduced into the molecular chain of the multilayer structure acrylic polymer, and the UV resistance of the multilayer structure acrylic polymer is improved. Preferably the addition amount of a reactive ultraviolet absorber is 0.05-5 mass parts with respect to 100 mass parts of total amounts of the monomer used for superposition|polymerization.

A chain transfer agent can be used in each superposition|polymerization for adjustment of molecular weight. The chain transfer agent used for each superposition|polymerization is not specifically limited. As a chain transfer agent, For example, Alkyl mercaptans, such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-hexadecyl mercaptan; xanthogen disulfide, such as dimethyl xanthogen disulfide and diethyl xanthogen disulfide; Thiuram disulfides, such as tetrathiuram disulfide; Halogenated hydrocarbons, such as carbon tetrachloride and ethylene bromide, etc. are mentioned. The usage-amount of a chain transfer agent can be suitably set in the range which can control a polymer to a predetermined molecular weight in each polymerization. Although the amount of the chain transfer agent used in the 3rd polymerization varies depending on the amount of the polymerization initiator used in the 3rd polymerization, etc., the monomer used in the 3rd polymerization, specifically, in 100 parts by mass of the total amount of methyl methacrylate and alkyl acrylate To this, Preferably it is 0.05-2 mass parts, More preferably, it is 0.08-1 mass part.

In this invention, collection|recovery of the acrylic rubber particle (C) from the said emulsion latex is performed by coagulating the emulsion latex. Coagulation of latex can be performed by a well-known method. Examples of the coagulation method include a freeze coagulation method, a salt-out coagulation method, and an acid stone coagulation method. Among these, the salting-out coagulation method capable of continuously producing a high-quality coagulated product 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 structure acrylic polymer latex composed of a core layer (a-1), an intermediate layer (a-2), and an outer layer (b) alone or a mixture of two or more, or a core layer (a-1) , an intermediate layer (a-2), and an outer layer (b) can be coagulated by adding a coagulant to a mixture of a multilayer structure acrylic polymer latex and at least one single layer acrylic polymer latex.

(2) methacrylic resin (D)

Methacrylic resin (D) is a non-crosslinked polymer containing 60 mass % or more of methyl methacrylate units, Comprising: It is resin with a weight average molecular weight of 70,000 or more.

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

The amount of the alkyl acrylate unit contained in methacrylic resin (D) becomes like this. Preferably it is 0.3-30 mass %, More preferably, it is 0.4-20 mass %. The alkyl group in the alkyl acrylate preferably has 1 to 8 carbon atoms. As the amount of the alkyl acrylate unit decreases, the impact resistance of the film tends to decrease, and as the amount of the alkyl acrylate unit increases, the stress whitening resistance and transparency of the film tend to decrease.

The weight average molecular weight of the methacrylic resin (D) is 70,000 or more, for example, 75000-20000, Preferably it is 80000-1800000. A weight average molecular weight can be measured by gel permeation chromatography. Measurement by gel permeation chromatography can be carried out as described in Examples to be described later.

(3) organic solvents

The organic solvent can be used without limitation as long as it dissolves the acrylic rubber particles (C), the methacrylic resin (D), and an additive to be added as needed.

For example, as a chlorine-type organic solvent, methylene chloride and chloroform; Non-chlorine organic solvents include methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, formic acid Ethyl, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3 ,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. are mentioned, Methylene chloride, methyl acetate, ethyl acetate, acetone, and methyl ethyl ketone can be used preferably. Moreover, you may mix and use two or more types of these solvents.

○ Preparation of dope (dissolution process)

Dope used for casting in the production method of the present invention contains acrylic rubber particles (C) obtained by emulsion polymerization, methacrylic resin (D) and an organic solvent, and methacrylic resin (D) is methylmethacrylic It is a non-crosslinked polymer containing 60 mass % or more of rate units, Comprising: It is resin with a weight average molecular weight (Mw) of 70,000 or more.

Dope can be prepared by the general method which consists of processing at the temperature (normal temperature or high temperature) of 0 degreeC or more. Preparation of dope can be performed using the preparation method and apparatus of dope in a normal solvent casting method. In addition, in the case of the general method, halogenated hydrocarbons (especially dichloromethane) and alcohols (especially methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol) as an organic solvent , 2-methyl-2-butanol and cyclohexanol).

It is preferable that content of the acrylic rubber particle (C) in dope is 0.1-33 mass %, It is more preferable that it is 0.2-28 mass %, It is still more preferable that it is 0.3-24 mass %.

It is preferable that content of the methacrylic resin (D) in dope is 4.9-37 mass %, It is more preferable that it is 9.8-32 mass %, It is more preferable that it is 14.7-26 mass %.

It is preferable that content of the organic solvent in dope is 30-95 mass %, It is more preferable that it is 40-90 mass %, It is more preferable that it is 50-85 mass %.

You may add the arbitrary additives mentioned later to dope.

Dope can be prepared by stirring an acrylic rubber particle (C), a methacrylic resin (D), an organic solvent, and an additive as needed. At this time, the mixture of each component may be added to and dissolved in the organic solvent during stirring, or each component may be sequentially added and dissolved in the organic solvent during stirring, and the solution of each component is prepared in advance and the solution is mixed by mixing the dope. may be formed. The dissolution of the acrylic rubber particles (C) and the methacrylic resin (D) is performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed by pressurization above the boiling point of the main solvent, JP-A A method carried out by a cooling melting method as described in Hei 9-95544, Hei 9-95557, or Hei 9-95538, as described in Japanese Patent Laid-Open No. Hei 11-21379 Although various dissolution methods, such as the method of carrying out at high pressure, can be used, The method of carrying out by pressurizing especially at the temperature more than the boiling point of a main solvent is preferable.

○ Flexible process

At a casting process, dope prepared as mentioned above is cast|flow_spreaded on the support body for casting|flow_spread, it is made into a film|membrane, this is dried and a cast film is formed. This casting process is a process of casting|flow_spreading dope from a pressurization die slit to the casting|flow_spreading position on support bodies, such as an endless metal belt which liquid-feeds dope to a pressurization die via a liquid feeding pump, and conveys it infinitely. Structures such as casting die, decompression chamber, support, co-spanning, peeling method, stretching, drying conditions for each step, handling method, curling method, winding method after flatness correction, solvent recovery method, film recovery method, Japanese Patent Application Laid-Open It is described in detail in paragraphs [0617] to [0889] of 2005-104148.

In the production method of the present invention, when an unstretched acrylic film is produced, the film thickness of the acrylic film is preferably 20 to 200 μm, more preferably 25 to 100 μm, still more preferably 30 to 80 μm. Controls the amount of flexible dope. In a film thickness thinner than this range, the intensity|strength of a cast film falls and workability deteriorates. On the other hand, in the film thickness thicker than this range, the organic solvent may remain|survive in an acrylic film.

○ Organic solvent evaporation process

Next, the cast film thus obtained is dried. In that case, a cast film is usually heated on a metal support body, and the organic solvent is evaporated until a cast film becomes peelable from a metal support body.

After the above process, a peeling process, a preheating process, a heat treatment process, an extending process; The acrylic film by the manufacturing method of this invention is manufactured by passing through etc. as needed.

Example

Hereinafter, although an Example demonstrates this invention concretely, these are mere illustrations, and this invention is not limited to these.

(Particle diameter)

The emulsion containing the acrylic rubber particles (C) was diluted with ion-exchanged water so as to have a solid content concentration of 0.05% by mass, spread on a glass plate, and dried to make the individual particles exist on the glass plate without aggregation. Platinum and palladium were deposited on this surface, electron micrographs were 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 mass%, placed in a quartz cell with a measurement length of 10 mm, and the absorbance at 500 nm was measured. In the particle|grains from which a particle diameter differs, the above operation was performed, and the analytical curve of the average particle diameter and 500 nm absorbance by electron microscope observation was created. The average particle diameter of the acrylic rubber particle (C) was calculated|required by measuring the absorbance using this analytical curve.

(outer layer thickness)

The outer layer thickness was calculated by the following formula using the total value of the particle diameter of the acrylic rubber particles (C) obtained by the above 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 methacryl resin (D) was computed from the value converted into the molecular weight of standard polystyrene by measuring the chromatogram on the following conditions by gel permeation chromatography (GPC). The baseline is the point where the slope of the peak on the high molecular weight side of the GPC chart changes from zero to positive when viewed from the side with the faster holding time, and the slope of the peak on the low molecular weight side changes from negative to zero when viewed from the side with the fast holding time The points were connected by a line.

GPC device: HLC-8320 manufactured by Tosoh Corporation

Detector: Differential refractive index detector

Column: What connected two of TSKgel SuperMultipore HZM-M by Tosoh Corporation and SuperHZ4000 in series was used.

Eluent: tetrahydrofuran

Eluent flow rate: 0.35 ml/min

Column temperature: 40℃

Calibration curve: created using data from standard polystyrene 10 points

(Measurement of molecular weight of outer layer (b) of acrylic rubber particles (C))

Acrylic rubber particles (C) are obtained by adding acetone, standing at room temperature for one day, stirring, and centrifuging (200 minutes at 20,000 rotations) to obtain a supernatant (acetone solution: outer layer component (b)) and sediment (acetone swelling material: inner layer) isolate as component (a)). Then, the solid content obtained by drying the acetone solution was measured by the method similar to the molecular weight measurement of the said methacrylic resin (D).

(Solubility of Acrylic Rubber Particles (C))

It was dissolved in methylene chloride so that the content of the acrylic rubber particles (C-1) obtained in Production Example 1 was 10 wt%, and the mixture was dissolved with shaking at room temperature for 8 hours. The solution was filtered through a 50-mesh wire mesh, and the gelatinous substance remaining on the wire mesh was dried in a dryer at 80 DEG C for 8 hours, and the residual amount was measured.

It evaluated by the following judgment criteria.

○: Residual amount less than 1 wt%

△: residual amount of 1 or more and less than 5 wt%

x: residual amount is 5 wt% or more

(Heat resistance)

In a dynamic viscoelasticity measuring apparatus (REOGEL-E4000 manufactured by UBM), the measurement is performed at a frequency of 1 Hz, the peak temperature of the loss tangent (tanδ) derived from the methacrylic resin (D) on the high temperature side is read, and the It was evaluated as an index.

(Film impact resistance)

The acrylic film was cut out to 100 mm (length) x 10 mm (width), and it was folded once by mountain fold at the central part of the longitudinal direction, this evaluation was measured 3 times, and the following reference|standard evaluated. Incidentally, the folding in the evaluation herein indicates that it has been cracked and separated into two or more pieces.

○: Does not fold all 3 times

×: Fold at least 1 time out of 3 times

[Production Example 1]

[Preparation of acrylic rubber particles (C-1)]

1050 parts by mass of deionized water, 1 part by mass of sodium dodecylbenzenesulfonate and 0.05 parts by mass of sodium carbonate are injected into a reactor equipped with a stirrer, a thermometer, a nitrogen gas introduction part, a monomer introduction tube and a reflux condenser, and the inside of the container is sufficiently substituted with nitrogen gas After making the state substantially free of oxygen, the internal temperature was set to 80°C. There, 0.01 mass part of potassium persulfate was thrown in, and after stirring for 5 minutes, 26.3 mass parts of monomer mixtures of the composition described in the 1st layer of Table 1 below were continuously dripped and supplied over 20 minutes, and after completion|finish of dripping, the polymerization conversion rate was Polymerization reaction was further performed for 30 minutes so that it might become 98% or more.

Subsequently, after adding 0.05 mass parts of potassium persulfate 3% aqueous solution into the reactor and stirring for 5 minutes, 157.4 mass parts of monomer mixtures of the composition described in the 2nd layer of Table 1 below were continuously dripped and supplied over 40 minutes. After completion|finish of dripping, the polymerization reaction was further implemented for 30 minutes so that the polymerization conversion ratio might become 98 % or more.

Next, 0.5 parts by mass of a 3% potassium persulfate aqueous solution was added into the reactor and stirred for 5 minutes, and then n-octylmercaptan ( nOM, chain transfer agent) 341 parts by mass of a monomer mixture containing 0.295 parts by mass are continuously dropwise supplied over 100 minutes, and after completion of the dropwise addition, polymerization is performed for an additional 60 minutes so that the polymerization conversion rate is 98% or more, the average particle diameter is 0.1 An emulsion containing acrylic rubber particles (C-1) having a size of mu m was obtained.

Then, the emulsion containing the acrylic rubber particles (C-1) was frozen at -30°C for 4 hours. After pouring and dissolving the frozen emulsion into twice the amount of the frozen emulsion at 80°C hot water to make a slurry, keeping it at 80°C for 20 minutes, dehydrating and drying at 70°C to obtain a coagulated product of acrylic rubber particles (C-1) got powder.

[Production Example 2]

[Preparation of acrylic rubber particles (C-2)]

As an emulsifier, sodium alkyldiphenyl ether disulfonate was used, except for changing the monomer composition shown in Table 1 below, in the same manner as in Production Example 1 to obtain a powder of a coagulated product of acrylic rubber particles (C-2).

[Production Example 3]

[Preparation of acrylic rubber particles (C-3)]

Except having changed to the monomer composition of Table 1 below, it carried out similarly to manufacture example 1, and obtained the powder of the coagulated material of acrylic rubber particle (C-3).

[Production Example 4]

[Preparation of acrylic rubber particles (C-4)]

A powder of acrylic rubber particles (C-4) was obtained in the same manner as in Production Example 1 except for changing the monomer composition shown in Table 1 below.

[Production Example 5]

[Preparation of acrylic rubber particles (C-5)]

A powder of acrylic rubber particles (C-5) was obtained in the same manner as in Production Example 1 except for changing the monomer composition shown in Table 1 below.

[Production Example 6]

[Preparation of acrylic rubber particles (C-6)]

A powder of acrylic rubber particles (C-6) was obtained in the same manner as in Production Example 1 except for changing the monomer composition shown in Table 1 below.

[Production Example 7]

[Preparation of acrylic rubber particles (C-7)]

As an emulsifier, sodium polyoxyethylene lauryl ether sulfate was used, except for changing to the monomer composition shown in Table 1 below, in the same manner as in Production Example 1 to obtain a powder of a coagulated product of acrylic rubber particles (C-7).

[Production Example 8]

[Preparation of acrylic rubber particles (C-8)]

A powder of acrylic rubber particles (C-8) was obtained in the same manner as in Production Example 1 except for changing the monomer composition shown in Table 1 below.

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

[Example 1]

It was dissolved in methylene chloride so that content of the acrylic rubber particle (C-1) obtained in manufacture example 1 might be set to 30 wt%, and it was shake-dissolved at room temperature for 8 hours. The dissolved solution was filtered through a 50-mesh wire mesh, and the gelatinous substance remaining on the wire mesh was dried in a dryer at 80°C for 8 hours, and the residual amount was measured to evaluate the solubility of the acrylic rubber particles. 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) and 15 parts by mass of the methacrylic resin (D) obtained in Production Example 1 were added, followed by shaking and dissolving for 8 hours to obtain a polymer solution. This solution was uniform, and no gel-like foreign matter was observed.

This solution was cast|flow_spread and air-dried on the release paper, it dried under reduced pressure at 80 degreeC for 8 hours, and obtained the 100-micrometer-thick acrylic film. Table 2 shows the physical properties of this film.

[Example 2]

Except having used the acrylic rubber particle (C-2) obtained in manufacture example 2, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Example 3]

Using the acrylic rubber particles (C-3) obtained in Production Example 3, and dissolving 24 parts by mass of the acrylic rubber particles (C-3) and 6 parts by mass of the methacrylic resin (D) with respect to 70 parts by mass of methylene chloride Except it, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Comparative Example 1]

Except having used the acrylic rubber particle (C-4) obtained in manufacture example 4, it carried out similarly to Example 1, and obtained the acrylic film. 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]

Except having reduced the molecular weight of the methacryl resin (D), it carried out similarly to Example 1, and obtained the acrylic film. 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.

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

Claims (6)

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