TW202033630A - Method for manufacturing acrylic film - Google Patents

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

Manufacturing method of acrylic film

The present invention relates to a method of manufacturing an acrylic film, and more specifically, to a method of manufacturing a transparent and high-quality acrylic film with improved brittleness by using specific acrylic rubber particles and methacrylic resin.

The demand for liquid crystal display devices in LCD TVs and liquid crystal displays of personal computers has expanded. The liquid crystal display device is usually composed of a liquid crystal cell formed by sandwiching a transparent electrode, a liquid crystal layer, a color filter, etc. by glass plates, and two polarizing plates arranged on both sides of the liquid crystal cell. Two optical films (protective films for polarizing plates) sandwich a polarizer (also called polarizing film, polarizing film). For this polarizing plate protective film, a cellulose triacetate film is usually used.

On the other hand, due to technological advances in recent years, the increase in size of liquid crystal display devices has accelerated, and the uses of liquid crystal display devices have also diversified. Examples include the use as a large display installed on the street or in a store, and the use of a display device called a digital signage for advertising displays in public places.

For such applications, it is assumed to be used outdoors. Therefore, deterioration due to moisture absorption of the polarizing film becomes a problem, and higher moisture resistance is required for the polarizing plate protective film. However, it is difficult to obtain sufficient moisture resistance for cellulose ester films such as cellulose triacetate films used in the past. If the film is thickened in order to obtain moisture resistance, the optical influence becomes larger. . In addition, in recent years, thinner devices have also been required, so thickening of the polarizing plate itself has also become a problem.

On the other hand, for optical film materials with low moisture absorption, methacrylic resins are suitable for use in optical films because they exhibit excellent transparency and dimensional stability in addition to low moisture absorption.

However, when compared with cellulose ester films and the like, optical films containing methacrylic resins are easily broken and brittle, and are difficult to handle. In particular, it is difficult to stably manufacture optical films for large liquid crystal display devices.

Furthermore, in recent years, acrylic films used for optical applications have become extremely demanding in terms of transparency and appearance. However, in the conventional melt film forming method, there are film foreign matter caused by gel polymer etc., birefringence caused by flow alignment, resin coloration and haze value increase caused by retention deterioration, etc. The problem is that it is difficult to produce an acrylic film with high transparency and good appearance required for optical applications.

On the other hand, in the solution casting method, the viscosity of the solution can be reduced by adjusting the type of solvent and solid content. Therefore, compared with the melt film forming method, high-precision filtration is possible, and an acrylic film with excellent transparency and appearance can be obtained. In the solution casting method, the technique of adding acrylic rubber particles in order to eliminate the brittleness of the acrylic film has been disclosed. (Patent Documents 1～3) In Patent Document 1, as a method for obtaining an optical film with improved brittleness, a cellulose ester film is mixed with acrylic rubber particles and produced by a solution casting method. However, the film obtained by this method contains cellulose ester, and therefore, sufficient improvement in moisture resistance cannot be obtained.

Patent Document 2 proposes a cast film containing acrylic resin and acrylic rubber particles. However, it does not describe the solubility of acrylic rubber particles in solvents, and it is hard to say that they are excellent in solvent dispersibility.

In Patent Document 3, an acrylic rubber particle with improved dispersibility is proposed, but there is no description about the impact resistance of the obtained acrylic film. It is difficult to say that a film with sufficient impact resistance is obtained. [Prior Technical Literature] [Patent Literature]

Patent Document 1: WO2009/047924 Patent Document 2: JP 2009-209295 Patent Document 3: JP 2016-043494

[The problem to be solved by the invention]

Therefore, the present invention was made in view of the above-mentioned problems, and its object is to provide an acrylic film which has low moisture absorption, is transparent and has high heat resistance, and has significantly improved brittleness, and is particularly suitable for use as a large liquid crystal Polarizer protective film in display devices or liquid crystal display devices for outdoor use. [Means to solve the problem]

The inventors of the present invention have completed the present invention including the following aspects as a result of studies to achieve the above-mentioned object.

That is, the present invention provides the following [1] to [6]. [1] A method of producing an acrylic film, characterized in that it is a method of producing an acrylic film comprising the steps of including acrylic rubber particles (C) obtained by an emulsion polymerization method and a methacrylic resin (D) and the step of evaporating the aforementioned organic solvent after the dope of organic solvent is cast on the casting support; the methacrylic resin (D) contains 60% by mass or more methyl methacrylate The unit is a non-crosslinked polymer with a weight average molecular weight of 70,000 or more; The acrylic rubber particles (C) have a two-layer structure or more of an outer layer (b) and an inner layer (a) inscribed therewith, and the thickness of the outer layer (b) is 7.5 nm or more; the outer layer (b) includes non-crossing The non-crosslinked hard polymer contains more than 70% by mass of methyl methacrylate units and has a weight average molecular weight of 45,000 or more; the inner layer (a) contains an elastic copolymer, and the elastic copolymer The material system contains 60 to 99.8% by mass of alkyl acrylate units and 0.2 to 10% by mass of structural units derived from copolymerizable crosslinkable monomers. [2] The method for producing an acrylic film as described in [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 as described in [1] or [2], characterized in that a part of the hard polymer constituting the outer layer (b) of the acrylic rubber particles (C) is internally copolymerized with elastic Covalent bonding. [4] The method for producing an acrylic film as described in any one of [1] to [3], which is characterized by: 100 parts by mass relative to the total of acrylic rubber particles (C) and methacrylic resin (D) The mass ratio of the acrylic rubber particles (C) is in the range of 2 to 90 parts by mass. [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], characterized in that it is used for optical applications. [Effects of Invention]

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

[Form to implement the invention]

The dopant used for casting in the manufacturing method of the present invention includes (1) acrylic rubber particles (C) obtained by emulsion polymerization, (2) methacrylic resin (D), and (3) organic solvent And the methacrylic resin (D) is a non-crosslinked polymer containing 60% by 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 have a two-layer structure or more of an outer layer (b) and an inner layer (a) inscribed therewith, and the outer layer (b) has a thickness of 7.5 nm or more; the outer layer ( b) Contains a non-crosslinked hard polymer, the non-crosslinked hard polymer contains more than 70% by mass of methyl methacrylate units; the inner layer (a) contains an elastic copolymer, and the elastic copolymer contains It is composed of 60-99.8% by mass of alkyl acrylate units and 0.2-10% by mass of structural units derived from copolymerizable crosslinkable monomers. 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)" is sometimes described as "grafting agent", and "copolymerizable crosslinkable monomer (crosslinking agent)" is sometimes described as " Crosslinking agent".

The acrylic rubber particles (C) used in the present invention may be in any form of powder, granular, agglomerate, and coagulum.

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, still more preferably 0.1 μm; the upper limit of the average particle diameter It is preferably 0.35 μm, more preferably 0.3 μm, still more 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 size of the granular material increases. In addition, the average particle diameter of the acrylic rubber particles (C) is a value obtained by a light scattering method.

The composition in the case where the acrylic rubber particles (C) used in the present invention are composed of three layers of the core layer (a-1), the intermediate layer (a-2), and the outer layer (b) will be described below. In addition, the intermediate layer (a-2) composed of three layers is inscribed with the outer layer (b), which can correspond to the inner layer (a) of the present invention. The core layer (a-1) is an arbitrary layer. A preferable core layer (a-1) contains a polymer containing a structural unit derived from methyl methacrylate (hereinafter sometimes referred to as "methyl methacrylate unit"), a polymer derived from alkyl acrylate Structural units (hereinafter sometimes referred to as "alkyl acrylate units") and structural units derived from crosslinkable monomers (grafting agents) (hereinafter sometimes referred to as "crosslinkable monomers (grafting agents) Units''), as well as structural units derived from crosslinkable monomers (crosslinkers) (sometimes referred to as “crosslinkable monomer (crosslinker) units”) and copolymerizable Structural units of other monomers (hereinafter sometimes referred to as "copolymerizable other monomer units").

The amount of methyl methacrylate units in the core layer (a-1) relative to all the structural units of the core layer (a-1) is preferably 40 to 98.99 mass%, more preferably 90 to 96.9 mass% . The smaller the amount of methyl methacrylate units, the more the weather resistance of the film tends to decrease; the more the amount of methyl methacrylate units, the more the impact resistance of the film tends to decrease.

The amount of alkyl acrylate units in the core layer (a-1) relative to all the structural units of the core layer (a-1) is preferably 1 to 60% by mass, more preferably 3 to 10% by mass. The carbon number of the alkyl group in the alkyl acrylate is preferably 1-8. The smaller the amount of alkyl acrylate units, the more the thermal decomposition resistance of the multi-layer structure acrylic polymer tends to decrease; the larger the amount of alkyl acrylate units, the more the film’s resistance to warm water or boiling water whitening will decrease. tendency.

The amount of the copolymerizable crosslinkable monomer (grafting agent) unit in the core layer (a-1) relative to all the structural units of the core layer (a-1) is preferably 0.01-1% by mass , 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 force between the core layer (a-1) and the intermediate layer (a-2); The greater the amount of the linking monomer (grafting agent) unit, the more the impact resistance of the film tends to decrease.

The amount of the copolymerizable crosslinkable monomer (crosslinker) unit in the core layer (a-1) relative to all the structural units of the core layer (a-1) is preferably 0 to 0.5% by mass, More preferably, it is 0 to 0.2% by mass. The greater the amount of the copolymerizable crosslinkable monomer (crosslinker) unit, the more the impact resistance of the film tends to decrease.

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

The intermediate layer (a-2) contains the following polymers: alkyl acrylate units and copolymerizable crosslinkable monomer (grafting agent) units, as well as methyl methacrylate units, copolymerizable Crosslinkable monomer (crosslinker) unit and other monomer units that can be copolymerized.

The amount of alkyl acrylate units in the intermediate layer (a-2) is 60-99.8% by mass, preferably 70-99.5% by mass, more preferably 80% relative to all the structural units of the intermediate layer (a-2) ～99% by mass. The carbon number of the alkyl group in the alkyl acrylate is preferably 1-8. The smaller the amount of alkyl acrylate units, the more the impact resistance of the film tends to decrease; the more the amount of alkyl acrylate units, the more the stress whitening resistance and transparency of the film tend to decrease.

The amount of the copolymerizable crosslinkable monomer (grafting agent) unit in the intermediate layer (a-2) is 0.2-10% by mass relative to all the structural units of the intermediate layer (a-2), preferably It is 0.5 to 5% by mass, more preferably 1 to 3% by mass. The smaller the amount of copolymerizable crosslinkable monomer (grafting agent) units, the more the stress whitening resistance of the film tends to decrease; the amount of copolymerizable crosslinkable monomer (grafting agent) units The more it is, the more the impact resistance of the film tends to decrease.

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

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

The outer layer (b) contains a polymer containing methyl methacrylate units and optionally alkyl acrylate units. 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% by mass or more of methyl methacrylate units. The amount of methyl methacrylate units in the outer layer (b) relative to all the structural units of the outer layer (b) is preferably 80 to 99% by mass, more preferably 95 to 98% by mass. The less the amount of methyl methacrylate units, the more the stress whitening resistance of the film tends to decrease; the more the amount of methyl methacrylate units, the more the thermal decomposition resistance of the multi-layer acrylic polymer decreases. tendency.

The amount of alkyl acrylate units that may be contained in the outer layer (b) relative to all structural units of the outer layer (b) is preferably 1-20% by mass, more preferably 2-5% by mass. The carbon number of the alkyl group in the alkyl acrylate is preferably 1-8. The smaller the amount of alkyl acrylate units, the more the thermal decomposition resistance of the multi-layer structure acrylic polymer tends to decrease; the more the amount of alkyl acrylate units, the more 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, more preferably 60,000 or more and 100,000 or less. If the weight average molecular weight is within this range, the impact resistance of the obtained film will be excellent. The glass transition temperature of the outer layer (b) is preferably 80°C or higher, more preferably 90°C or higher, and still more preferably 100°C or higher. The higher the glass transition temperature of the outer layer (b), the more the hot water resistance or boiling water whitening resistance of the film tends to improve.

In this specification, the "alkyl acrylate" includes alkyl acrylates having an alkyl group of 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, Secondary butyl acrylate, tertiary butyl acrylate, n-butyl methyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, etc. These alkyl acrylates can be used individually by 1 type or in combination of 2 or more types. Among these, methyl acrylate and/or n-butyl acrylate are preferred.

In this specification, the "copolymerizable crosslinkable monomer" is a monomer having two or more polymerizable groups, for example: allyl methacrylate, allyl acrylate, maleic mono- or diene Propyl ester, mono- or diallyl fumarate, crotonyl acrylate, crotonyl methacrylate and other copolymerizable crosslinkable monomers (grafting agents) with different types of polymerizable groups, diacrylic compounds, Copolymerizable crosslinking monomers (crosslinking agents) having the same type of polymerizable groups, such as dimethacrylic acid compounds, diallyl compounds, divinyl compounds, diene compounds, and trivinyl compounds. As the copolymerizable crosslinking monomer (or crosslinking agent) having the same type of polymerizable group, for example, ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, Propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, trivinylbenzene, ethylene glycol diallyl ether, propylene glycol diallyl ether, butadiene Wait. The copolymerizable crosslinkable monomer can be used alone or in combination of two or more.

In this specification, "other copolymerizable monomers" include, for example, aromatic vinyl monomers such as styrene, p-methylstyrene, o-methylstyrene, vinyl naphthalene, and acrylonitrile Unsaturated nitrile monomers, olefin monomers such as ethylene, propylene, vinyl chloride, vinylidene chloride (vinylidene chloride), vinylidene fluoride (vinylidene fluoride) and other halogenated vinyl monomers, acrylic acid, methacrylic acid , Maleic anhydride and other unsaturated carboxylic acid monomers, vinyl acetate, N-propyl maleimide, N-cyclohexyl maleimide, N-o-chlorophenyl maleimide, etc. Leximine-based monomers can be used alone or in combination of two or more types.

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) are composed of two layers, the inner layer (a) and the outer layer (b) are sequentially formed by the seed emulsion polymerization method to obtain an acrylic polymer with a core-shell multilayer structure . For example, when the acrylic rubber particles (C) are composed of three layers, the core layer (or the first layer, a-1), the intermediate layer (or the second layer, a-2) are sequentially made by seed emulsion polymerization. ) And the outer layer (3rd layer/shell, b) are formed to obtain an acrylic polymer with a core-shell multilayer structure.

The preferred method for producing acrylic rubber particles (C) used in the present invention includes the following steps: emulsification polymerization of acrylic monomers to obtain a latex containing a multilayer acrylic polymer; The latex of is coagulated to obtain a slurry containing acrylic rubber particles (C); the slurry is washed and dehydrated; and the dehydrated slurry is dried.

For example, a more preferable method of producing acrylic rubber particles (C) composed of three layers includes the following steps: in the presence of an emulsifier, 40 to 98.99 mass% (more preferably 90 to 96.9 mass%) of methyl Methyl acrylate, 1 to 60% by mass (more preferably 3 to 10% by mass) alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, 0.01 to 1% by mass (more preferably 0.1 to 0.5% by mass) The grafting agent and the crosslinking agent of 0-0.5% by mass (more preferably 0-0.2% by mass) are polymerized (first polymerization) to obtain the latex (I) containing the core layer (a-1); in the latex In the presence of (I), 70-99.5 mass% (more preferably 80-99 mass%) of alkyl acrylate with carbon number of 1-8, 0-30 mass% (more preferably 0-20 Mass%) methyl methacrylate, 0.5-5 mass% (more preferably 1-3 mass%) grafting agent and 0-5 mass% (more preferably 0-2 mass%) crosslinking agent Perform polymerization (second polymerization) to obtain latex (II) containing core layer (a-1) and intermediate layer (a-2); in the presence of latex (II), 80-99% by mass (more preferably 95～98% by mass) of methyl methacrylate and 1～20% by mass (more preferably 2～5% by mass) of alkyl and alkyl acrylate with carbon number of 1～8 for polymerization (third polymerization ) To obtain a latex (III) containing a core layer (a-1), an intermediate layer (a-2) and an outer layer (b); solidify the latex (III) to obtain a slurry; wash the slurry And dehydration; and drying the dehydrated slurry.

The polymerization can be performed by a known method. In the polymerization carried out in the presence of latex, in order to obtain a core-shell multilayer structure acrylic polymer, seed emulsion polymerization can be preferably used. Emulsion polymerization or seeding polymerization is a method well known in the technical field, and therefore can be carried out according to a common method.

The polymerization initiator used in each polymerization is not particularly limited. The polymerization initiator includes, for example, water-soluble inorganic initiators such as potassium persulfate and ammonium persulfate; oxidation-reduction of inorganic initiators combined with sulfite or thiosulfate, etc. Initiator; a redox initiator made of organic peroxides and ferrous salts or sodium sulfoxylate. The polymerization initiator may be added to the reaction system at the beginning of the polymerization at one time, or may be added to the reaction system separately at the beginning of the polymerization and during the polymerization in consideration of the reaction speed. The amount of the polymerization initiator used can be appropriately set, for example, so that the average particle diameter of the core-shell multilayer structure acrylic rubber particles (C) falls within the aforementioned range.

From the viewpoint of controlling the polymerization rate and adjusting the molecular weight, the polymerization initiator amount used in each polymerization is preferably 0.05 to 0.15 parts by mass relative to 100 parts by mass of the total amount of methyl methacrylate and alkyl acrylate , More preferably 0.08 to 0.12 parts by mass. By setting the polymerization starting dose to this range, it becomes an industrially suitable polymerization rate from the viewpoint of polymerization heat removal and polymerization time. Furthermore, 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 polymerization is not particularly limited. Examples of emulsifiers include anionic emulsifiers such as long-chain alkyl sulfonates, alkyl sulfosuccinates, and alkylbenzene sulfonates; polyoxyethylene alkyl ethers, polyoxyethylene nonyl Non-ionic emulsifiers such as phenyl ether; polyoxyethylene nonylphenyl ether sulfate such as polyoxyethylene nonylphenyl ether sodium sulfate, polyoxyethylene alkyl ether sulfate such as polyoxyethylene alkyl ether sodium sulfate, Nonionic and anionic emulsifiers such as alkyl ether carboxylates such as polyoxyethylene tridecyl ether sodium acetate. The amount of the emulsifier used can be suitably set, for example, so that the average particle diameter of the granular material contained in the core-shell multilayer acrylic polymer will fall within the aforementioned range.

In the present invention, the first polymerization, the second polymerization, and the third polymerization can be carried out sequentially in a polymerization tank, and the polymerization can also be changed every time in the first polymerization, the second polymerization and the third polymerization. Slot and proceed in sequence. In the present invention, it is preferable to carry out each polymerization sequentially in one polymerization tank. In addition, the temperature of the reaction system during polymerization is preferably 30 to 120°C, more preferably 50 to 100°C.

In addition, in any of the first polymerization, the second polymerization, and the third polymerization, a reactive ultraviolet absorber, such as 2-[2-hydroxy-5-(2-methacrylic acid) can be added as needed. (Oxyethyl)phenyl]-2H-1,2,3-benzotriazole and the like. The reactive ultraviolet absorber is introduced into the molecular chain of the acrylic polymer of the multilayer structure, and the ultraviolet resistance of the acrylic polymer of the multilayer structure is improved. The addition amount of the reactive ultraviolet absorber is preferably 0.05 to 5 parts by mass relative to 100 parts by mass of the total amount of monomers used in the polymerization.

The chain transfer agent can be used in each polymerization in order to adjust the molecular weight. The chain transfer agent used in each polymerization is not particularly limited. As for the chain transfer agent, for example, alkyl mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, tertiary dodecyl mercaptan, n-hexadecyl mercaptan; disulfide Xanthogen disulfide such as dimethylxanthogen disulfide and diethylxanthogen disulfide; thiuram disulfide such as tetramethylamine disulfide; four Halogenated hydrocarbons such as carbon chloride and ethylene bromide. The amount of the chain transfer agent used can be appropriately set in a range in which the polymer can be adjusted to a specified 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, etc. However, the monomer used in the third polymerization is specifically It is preferably 0.05 to 2 parts by mass, and more preferably 0.08 to 1 part by mass with respect to 100 parts by mass of the total amount of methyl methacrylate and alkyl acrylate.

In the present invention, the recovery of acrylic rubber particles (C) from the emulsified latex is carried out by coagulating the emulsified latex. The coagulation of the latex can be performed by a known method. The coagulation method includes freeze coagulation method, salt precipitation coagulation method, acid precipitation coagulation method, and the like. Among these, the salting-out coagulation method capable of continuously producing high-quality coagulum is preferred. The coagulant that can be used in the present invention may be an aqueous solution of an inorganic acid or its salt, or an organic acid or its salt, which can coagulate and coagulate the emulsified polymer latex.

The emulsified latex can add a coagulant to the three-layer structure acrylic polymer latex including the core layer (a-1), the middle layer (a-2), and the outer layer (b) alone or in a mixture of two or more, or it can be added to The multi-layer acrylic polymer latex containing the core layer (a-1), the middle layer (a-2), and the outer layer (b) is mixed with at least one single-layer acrylic polymer latex. A coagulant is added, by This makes it solidify.

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

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

The amount of the alkyl acrylate unit contained in the methacrylic resin (D) is preferably 0.3 to 30% by mass, more preferably 0.4 to 20% by mass. The carbon number of the alkyl group in the alkyl acrylate is preferably 1-8. The smaller the amount of alkyl acrylate units, the more the impact resistance of the film tends to decrease; the more the amount of alkyl acrylate units, the more 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, 75,000 to 2,000,000, preferably 80,000 to 1,800,000. The weight average molecular weight can be measured by gel permeation chromatography. The measurement by the gel permeation chromatography method can be performed as described in the Examples described later.

(3) Organic solvent The organic solvent can be used without limitation as long as it can dissolve acrylic rubber particles (C), methacrylic resin (D), and additives added as needed.

(dioxolane)、1,4-二

烷、環己酮、甲酸乙酯、2,2,2-三氟乙醇、2,2,3,3-六氟-1-丙醇、1,3-二氟-2-丙醇、1,1,1,3,3,3-六氟-2-甲基-2-丙醇、1,1,1,3,3,3-六氟-2-丙醇、2,2,3,3,3-五氟-1-丙醇、硝乙烷等；較佳可使用二氯甲烷、乙酸甲酯、乙酸乙酯、丙酮、甲乙酮。又，亦可將此等溶媒混合多種而使用。For example, the chlorine-based organic solvents include dichloromethane and chloroform; the non-chlorine-based organic solvents include methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, and methyl isobutyl. Ketone, tetrahydrofuran, 1,3-di

(dioxolane), 1,4-two

Alkane, cyclohexanone, ethyl formate, 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.; preferably, dichloromethane, methyl acetate, ethyl acetate, acetone, methyl ethyl ketone can be used. In addition, multiple types of these solvents may be mixed and used.

○ Preparation of adulterants (dissolution step) The dopant used for casting in the manufacturing method of the present invention includes: acrylic rubber particles (C), methacrylic resin (D), and organic solvent obtained by emulsion polymerization, and methacrylic resin ( D) It is a non-crosslinked polymer containing 60% by mass or more of methyl methacrylate units and a resin having a weight average molecular weight (Mw) of 70,000 or more.

The dopant can be prepared by a general method including processing at a temperature (normal temperature or high temperature) above 0°C. The preparation of the dopant can be implemented using a method and apparatus for preparing the dopant in a usual solvent casting method. In addition, in the case of a general method, it is preferable to use halogenated hydrocarbons (especially dichloromethane) and alcohols (especially methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-propanol) as the organic solvent. Butanol, tertiary butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol).

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

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

The content of the organic solvent in the dopant is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and still more preferably 50 to 85% by mass. Any additives described later may be added to the dopant beforehand.

The dopant system can be prepared by stirring acrylic rubber particles (C), methacrylic resin (D), an organic solvent, and additives as required. At this time, the mixture of each component can be added to the stirring organic solvent to dissolve it, or each component can be sequentially added to the stirring organic solvent and dissolved, or it can be prepared by pre-preparing each component The solutions are mixed with these solutions to form dopants. The dissolution of acrylic rubber particles (C) and methacrylic resin (D) can be carried out using a method performed under normal pressure, a method performed below the boiling point of the main solvent, and pressure above the boiling point of the main solvent. The method of cooling and dissolving is described in Japanese Patent Application Publication No. 9-95544, Japanese Patent Application Publication No. 9-95557, or Japanese Patent Application Publication No. 9-95538, such as in Japanese Patent Application Publication No. 11-21379 The publication describes various dissolution methods such as a high-pressure method, but it is particularly preferable to use a method in which pressure is performed at a temperature higher than the boiling point of the main solvent.

○Casting steps In the casting step, the dopant prepared as described above is cast on the casting support to form a film, and dried to form a cast film. This casting step is a step in which the dopant is sent to the pressurizing die by a liquid feeding pump, and the dopant is cast from the slit of the pressurizing die to the casting position on a support such as an endless metal belt, etc. . From the structure of casting die, decompression chamber, support, co-casting, peeling method, stretching, drying conditions of each step, processing method, crimping, winding method after flatness correction, solvent recovery method, film recovery The method has been described in detail in paragraphs [0617] to [0889] of JP 2005-104148 A.

In the manufacturing method of the present invention, when an unstretched acrylic film is produced, the amount of dopant for casting is adjusted so that the thickness of the acrylic film is preferably 20 to 200 μm, more preferably 25 to 100 μm, and more preferably 30～80μm. When the film thickness is thinner than this range, the strength of the cast film decreases and the workability deteriorates. On the other hand, if the film thickness is thicker than this range, the organic solvent may remain in the acrylic film.

○Organic solvent evaporation step Next, the cast film obtained in this way is dried. At this time, usually the cast film is heated on the metal support, and the organic solvent is evaporated until the cast film becomes peelable from the metal support.

After the above steps, a peeling step, a preheating step, a heat treatment step, a stretching step, etc. are carried out as needed, thereby manufacturing the acrylic film according to the manufacturing method of the present invention. [Example]

Hereinafter, the present invention will be specifically explained with examples, but these are only examples, and the present invention is not limited to these.

(Particle size) The emulsion containing acrylic rubber particles (C) is diluted with ion-exchanged water to have a solid content concentration of 0.05% by mass, spread on the glass plate, and dried to make the individual particles exist on the glass plate without agglomeration . Platinum and palladium were vapor-deposited on this surface, and electron micrographs were obtained with a scanning electron microscope, and the particle diameters of 100 particles were randomly measured and averaged as the average particle diameter. On the other hand, the emulsion containing acrylic rubber particles (C) was diluted to a solid content concentration of 0.05% by mass and taken to a quartz cell with a measurement length of 10 mm, and the absorbance at 500 nm was measured. Perform the above operations with particles with different particle sizes to create a calibration curve based on the average particle size observed by the electron microscope and the absorbance at 500 nm. Using this calibration curve and measuring the absorbance, the average particle diameter of the acrylic rubber particles (C) is determined.

(Outer layer thickness) The thickness of the outer layer is 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.

(Molecular weight determination of methacrylic resin (D)) The molecular weight of the methacrylic resin (D) was calculated from the value converted into the molecular weight of standard polystyrene by measuring the chromatogram by gel permeation chromatography (GPC) under the following conditions. The baseline is set as a line connecting the following two points: from the earlier side of the residence time, the point where the slope of the peak on the high molecular weight side of the GPC chart changes from zero to a positive value, and from the earlier side of the residence time Look at the point where the slope of the peak on the low molecular weight side changes from a negative value to zero.

GPC device: manufactured by Tosoh Co., Ltd., HLC-8320 Detector: Differential refractive index detector Column: Use the two TSKgel SuperMultipore HZM-M and SuperHZ4000 made by Tosoh Co., Ltd. connected in series.

Eluent: Tetrahydrofuran Eluent flow rate: 0.35ml/min Column temperature: 40℃ Calibration curve: Use standard polystyrene 10-point data to create

(Measurement of the molecular weight of the outer layer (b) of acrylic rubber particles (C)) Acrylic rubber particles (C) are separated into the supernatant (acetone solution: outer layer component (b) by adding acetone, leaving it at room temperature for one day, stirring and centrifuging (20,000 rpm, 200 minutes)) ) And sediment (acetone swelling material: inner layer component (a)). After that, the solid content obtained by drying the acetone solution was measured by the same method as the molecular weight measurement 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 dichloromethane so that the content of the acrylic rubber particles (C-1) was 10% by weight, and the solution was shaken and dissolved at room temperature for 8 hours. The solution was filtered with a 50-mesh metal mesh, and the gel-like substance remaining on the metal mesh was dried at 80°C for 8 hours with a dryer, and the remaining amount was measured. The evaluation was performed based on the following judgment criteria. ○: The remaining amount is less than 1wt% △: The remaining amount is 1 or more and less than 5wt% ×: The remaining amount is more than 5wt%

(Heat resistance) Measured with a dynamic viscoelasticity measuring device (REOGEL-E4000 manufactured by UBM) at a frequency of 1 Hz, and read the peak temperature of the loss tangent (tanδ) derived from the methacrylic resin (D) on the high temperature side as the heat resistance Indicators for evaluation.

(Film impact resistance) The acrylic film was cut at 100 mm (longitudinal) × 10 mm (width), and bent once in a mountain fold at the center of the longitudinal direction. This evaluation was measured 3 times, and the evaluation was performed based on the following criteria. In addition, the fractured system evaluated here means broken and separated into two or more pieces. ○: 3 times without breaking ×: It will break at least 1 out of 3 times

[Manufacturing Example 1] [Production of acrylic rubber particles (C-1)] In a reactor equipped with a stirrer, a thermometer, a nitrogen introduction part, a monomer introduction tube and a reflux condenser, 1050 parts by mass of deionized water, 1 part by mass of sodium dodecylbenzene sulfonate and 0.05 parts by mass of sodium carbonate are fed into it, After the inside of the container was sufficiently replaced with nitrogen to make it into a substantially oxygen-free state, the internal temperature was set to 80°C. After adding 0.01 parts by mass of potassium persulfate and stirring for 5 minutes, 26.3 parts by mass of the monomer mixture with the composition described in the first layer of Table 1 below was continuously dropped and supplied over 20 minutes. After the dropping was completed, another 30 parts were added. Minute polymerization reaction makes the polymerization conversion rate become 98% or more.

Then, in the same reactor, add 0.05 parts by mass of potassium persulfate 3% aqueous solution and stir for 5 minutes, and then continuously drip and supply 157.4 parts by mass of the monomer mixture described in the second layer of Table 1 below over 40 minutes. . After completion of the dropping, the polymerization reaction was further performed for 30 minutes so that the polymerization conversion rate became 98% or more.

Next, in the same reactor, 0.5 parts by mass of potassium persulfate 3% aqueous solution was added and stirred for 5 minutes, and 341 parts by mass of the monomer mixture was continuously dripped and supplied over 100 minutes. The monomer mixture contained the third in Table 1 below. The monomer of the composition described in the layer and 0.295 parts by mass of n-octyl mercaptan (nOM, chain transfer agent) relative to 100 parts by mass in total. After the dropping is completed, the polymerization reaction is further carried out for 60 minutes so that the polymerization conversion rate becomes 98% or more, an emulsion containing acrylic rubber particles (C-1) with an average particle diameter of 0.1 μm was obtained.

Next, the emulsion containing acrylic rubber particles (C-1) was frozen at -30°C for 4 hours. Put the frozen emulsion into 80°C warm water twice the amount of the frozen emulsion, dissolve it to make a slurry, keep it at 80°C for 20 minutes, dehydrate, and dry at 70°C to obtain acrylic rubber particles (C-1) Powder of coagulum.

[Manufacturing Example 2] [Production of acrylic rubber particles (C-2)] Except that sodium alkyl diphenyl ether disulfonate was used as the emulsifier and the monomer composition in Table 1 below was changed, it was carried out in the same manner as in Production Example 1 to obtain the coagulum of acrylic rubber particles (C-2) powder.

[Manufacturing Example 3] [Production of acrylic rubber particles (C-3)] Except having changed to the monomer composition of the following Table 1, it carried out similarly to manufacture example 1, and obtained the powder of the acrylic rubber particle (C-3) coagulum.

[Manufacturing Example 4] [Production of acrylic rubber particles (C-4)] Except having changed to the monomer composition of the following Table 1, it carried out similarly to manufacture example 1, and obtained the powder of acrylic rubber particle (C-4).

[Manufacturing Example 5] [Production of acrylic rubber particles (C-5)] Except having changed to the monomer composition of the following Table 1, it carried out similarly to manufacture example 1, and obtained the powder of acrylic rubber particle (C-5).

[Manufacturing Example 6] [Production of acrylic rubber particles (C-6)] Except having changed to the monomer composition of following Table 1, it carried out similarly to manufacture example 1, and obtained the powder of acrylic rubber particle (C-6).

[Manufacturing Example 7] [Production of acrylic rubber particles (C-7)] Except that sodium polyoxyethylene lauryl ether sulfate was used as the emulsifier and the monomer composition in Table 1 below was changed, the same procedure as in Production Example 1 was carried out to obtain a powder of acrylic rubber particles (C-4) coagulum .

[Manufacturing Example 8] [Production of acrylic rubber particles (C-8)] Except having changed to the monomer composition of the following Table 1, it carried out similarly to manufacture example 1, and obtained the powder of acrylic rubber particle (C-8).

[Table 1] Manufacturing example 1 Manufacturing example 2 Manufacturing example 3 Manufacturing example 4 Manufacturing example 5 Manufacturing example 6 Manufacturing example 7 Manufacturing example 8 C-1 C-2 C-3 C-4 C-5 C-6 C-7 C-8 Level 1 MMA quality% 49.9 93.7 49.9 50.0 49.9 28.1 49.9 MA quality% 6.1 BA quality% 49.9 41.0 50.0 49.9 59.8 49.9 Styrene quality% 8.9 11.7 ALMA quality% 0.2 0.2 0.2 0.2 0.4 0.2 Level 2 MMA quality% 4.9 4.9 5.1 4.9 4.9 4.1 4.9 MA quality% BA quality% 92.2 79.1 75.8 94.9 92.2 92.2 79.7 92.2 Styrene quality% 17.1 16.4 15.9 ALMA quality% 2.9 3.8 2.9 2.9 2.9 0.4 2.9 Level 3 MMA quality% 87.5 94.0 87.5 87.5 50.0 95.0 87.5 MA quality% 6.0 5.0 BA quality% 12.5 12.5 12.5 50.0 12.5 nOM phr 0.295 0.300 0.295 0.295 0.295 1.10 0.600 Layer ratio 1/2/3 layer quality% 5/30/65 10/50/40 35/45/20 5/30/65 unformed layer no 5/30/65 50/25/25 5/30/65

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

[Example 1] The acrylic rubber particles (C-1) obtained in Production Example 1 were dissolved in dichloromethane so that the content of the acrylic rubber particles (C-1) was 30% by weight, and the solution was shaken and dissolved at room temperature for 8 hours. The solution was filtered with a 50-mesh metal mesh, and the gel-like substance remaining on the metal mesh was dried at 80° C. for 8 hours with a dryer, and the residual amount was measured to evaluate the solubility of acrylic rubber particles. The evaluation results are shown in Table 2. To 70 parts by mass of dichloromethane, 15 parts by mass of acrylic rubber particles (C-1) and 15 parts by mass of methacrylic resin (D) obtained in Production Example 1 were added, and the mixture was shaken and dissolved for 8 hours to obtain polymerization物solution. The solution was homogeneous, 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 with a thickness of 100 μm. Table 2 shows the physical properties of this film.

[Example 2] Except having used the acrylic rubber particle (C-2) obtained in the manufacturing 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] In addition to using the 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 were used relative to 70 parts by mass of dichloromethane (D) Except for dissolution, the same procedure as in Example 1 was carried out to obtain an 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 the 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] Except having used the acrylic rubber particle (C-5) obtained in the manufacturing example 5, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Comparative Example 3] Except having used the acrylic rubber particle (C-6) obtained in the manufacture example 6, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Comparative Example 4] Except for reducing the molecular weight of the methacrylic resin (D), the same procedure as in Example 1 was carried out to obtain an acrylic film. Table 2 shows the physical properties of this film.

[Comparative Example 5] Except having used the acrylic rubber particle (C-7) obtained in manufacture example 7, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Comparative Example 6] Except having used the acrylic rubber particle (C-8) obtained in the manufacturing example 8, it carried out similarly to Example 1, and obtained the acrylic film. Table 2 shows the physical properties of this film.

[Table 2] Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Methacrylic resin D composition MMA quality% 99.0 99.0 99.0 99.0 99.0 99.0 99.0 99.0 99.0 MA quality% 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 MW 80,000 80,000 80,000 80,000 80,000 80,000 40,000 80,000 80,000 Acrylic rubber particles C composition Mw of outer layer (b) 80,000 63,000 80,000 80,000 - 80,000 80,000 20,000 40,000 Final particle size nm 100 110 250 - 100 100 100 100 100 Outer layer thickness nm 14.8 8.6 37 - - 14.8 14.8 4.6 14.8 Acrylic rubber particles C solubility ○ ○ ○ ○ × ○ ○ △ ○ Adulterant composition Methacrylic resin D ratio % 15 15 twenty four 15 - 15 15 15 15 Acrylic rubber particles C ratio % 15 15 6 15 - 15 15 15 15 Solvent % 70 70 70 70 - 70 70 70 70 Film evaluation Heat resistance 117 124 121 130 - 91 117 124 117 Shock proof ○ ○ ○ × - ○ × ○ × Haze % 0.5 0.5 0.5 0.5 - 2.2 0.5 0.5 0.5 thickness μm 100 100 100 100 - 100 100 100 100

In Examples 1 and 3, compared with Comparative Examples 1, 4, and 6, the impact resistance was improved and the solubility was good; compared with Comparative Example 3, the heat resistance and haze were reduced. In Example 2, it is also excellent in solubility, heat resistance, and impact resistance, and the haze is suppressed to a low level. On the other hand, in Comparative Example 2, the acrylic rubber particle system is composed of only cross-linked particles and does not have an outer layer, so the solubility is low. In addition, in Comparative Example 5, although the acrylic rubber particles have an outer layer, the outer layer has a thickness of 7.5 nm or less, so the solubility is low.

no.

no.

no.

Claims (6)

A method for producing an acrylic film, characterized in that it is a method for producing an acrylic film comprising the following steps: acrylic rubber particles (C) and methacrylic resin (D) obtained by emulsion polymerization are contained , And the organic solvent dopant is cast on the casting support, the step of evaporating the aforementioned organic solvent; the methacrylic resin (D) is a non-crosslinked methyl methacrylate unit containing 60% by mass or more Polymer with a weight average molecular weight of 70,000 or more; The acrylic rubber particles (C) have a two-layer structure of an outer layer (b) and an inner layer (a) inscribed therewith, and the thickness of the outer layer (b) is 7.5 nm or more; the outer layer (b) includes a The non-crosslinked hard polymer contains more than 70% by mass of methyl methacrylate units and has a weight average molecular weight of 45,000 or more; the inner layer (a) contains an elastic copolymer, and the elastic copolymer The material system contains 60 to 99.8% by mass of alkyl acrylate units and 0.2 to 10% by mass of structural units derived from copolymerizable crosslinkable monomers. 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. The method for producing an acrylic film according to claim 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 internal elastic copolymer. The method for producing an acrylic film according to any one of claims 1 to 3, wherein the acrylic rubber particles (C) are based on 100 parts by mass of the acrylic rubber particles (C) and the methacrylic resin (D) in total The mass ratio of is in the range of 2 to 90 parts by mass. 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. Such as the manufacturing method of the acrylic film of any one of claims 1 to 5, which is used for optical applications.