Method for producing masterbatch, method for producing acrylic resin composition, and masterbatch

Abstract

To provide a method for producing masterbatch that makes it possible to reduce the number of poorly dispersed particles.SOLUTION: A method for producing masterbatch comprises producing masterbatch by feeding a raw resin composition into an extruder having a barrel and a screw, wherein the barrel temperature is 200°C or less and the following expression (1) is satisfied. The raw resin composition contains an acrylic resin and acrylic crosslinked particles with an average particle diameter of 1 μm or less, the content of the acrylic crosslinked particles being 5 wt.% or more. Q / N / (D / 40)3≤0.11 (1) (in the formula, Q denotes the supply rate [kg / h] of the raw resin composition, N denotes the screw rotational speed [rpm], and D denotes the bore diameter [mm] of the extruder).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a masterbatch, a method for producing an acrylic resin composition, and a masterbatch. [Background technology]

[0002] A liquid crystal display device typically has two polarizing plates arranged on both sides of a liquid crystal cell. Here, a polarizer protective film is bonded to the surface of the polarizer of the polarizing plate. Triacetyl cellulose (TAC) film is typically used as the polarizer protective film, but acrylic film has been proposed for the purpose of improving durability. However, acrylic film has a high surface smoothness, making it prone to blocking. To prevent blocking, a known method is to pass a resin composition containing an amorphous acrylic resin (A) having a ring structure in the main chain and particles (B) with an average particle size of 0.1 to 1 μm through a polymer filter in a molten state, and then melt-extrude the resin composition into a film (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2010 / 061917 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inventors' investigations revealed that the optical film manufacturing method described in Patent Document 1 results in a large number of poorly dispersed particles, which may result in an increase in the differential pressure between the outlet and inlet of the polymer filter.

[0005] An object of the present invention is to provide a method for producing a masterbatch that can reduce poorly dispersed particles. [Means for solving the problem]

[0006] [1] A method for producing a masterbatch by supplying a raw material resin composition to an extruder equipped with a barrel and a screw, wherein the temperature of the barrel is 200°C or less, the following formula (1) is satisfied, the raw material resin composition contains an acrylic resin and acrylic crosslinked particles having an average particle size of 1 μm or less, and the content of the acrylic crosslinked particles is 5 wt% or more. Q / N / (D / 40) 3 ≦0.11 (1) (In the formula, Q is the feed rate [kg / h] of the raw material resin composition, N is the rotation speed [rpm] of the screw, and D is the diameter [mm] of the extruder.)

[0007] [2] The method for producing a masterbatch according to [1], wherein the raw material resin composition further contains an additive having a melting point of 200°C or less.

[0008] [3] The method for producing a masterbatch according to [2], wherein the additive is a lubricant or an ultraviolet absorber.

[0009] [4] The method for producing a masterbatch according to any one of [1] to [3], wherein the acrylic resin has a glass transition temperature of 120°C or higher.

[0010] [5] The method for producing a masterbatch according to [4], wherein the acrylic resin has a ring structure in the main chain.

[0011] [6] A method for producing an acrylic resin composition, comprising: obtaining a masterbatch by the method for producing a masterbatch according to any one of [1] to [5]; and mixing the masterbatch with an acrylic resin having a ring structure in its main chain.

[0012] [7] A masterbatch comprising an acrylic resin and acrylic crosslinked particles having an average particle size of 1 μm or less, wherein the content of the acrylic crosslinked particles is 5% by weight or more, and wherein the number of particles having a particle size of 10 μm or more per 1 mg of the masterbatch measured after dissolving or dispersing the masterbatch in methylene chloride to a solids concentration of 40 ppm by weight is 200 or less.

[0013] [8] A masterbatch comprising an acrylic resin having a glass transition temperature of 120°C or higher and acrylic crosslinked particles, wherein the content of the acrylic crosslinked particles is 5% by weight or higher, and wherein the number of particles having a particle size of 10 μm or larger per 1 mg of the masterbatch measured after dissolving or dispersing the masterbatch in methylene chloride to a solids concentration of 40 ppm by weight is 200 or less.

[0014] [9] The masterbatch according to [7] or [8], wherein the number of particles having a particle diameter of 10 μm or more and 20 μm or less per 1 mg of the masterbatch measured after dissolving or dispersing the masterbatch in methylene chloride to a solids concentration of 40 ppm by weight is 120 or less. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a method for producing a masterbatch that can reduce poorly dispersed particles. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described.

[0017] [Masterbatch manufacturing method] The method for producing a masterbatch according to the present embodiment is a method for producing a masterbatch by supplying a raw resin composition to an extruder equipped with a barrel and a screw. The extruder is not particularly limited, but examples thereof include a single-screw extruder and a twin-screw extruder. An example of the method for producing a masterbatch according to the present embodiment will be described below.

[0018] First, the raw resin composition is fed from the main feeder of the twin-screw extruder and melted. Next, the strands extruded from the die of the twin-screw extruder are cooled in a water tank and then cut with a pelletizer to obtain a masterbatch.

[0019] Here, the barrel temperature is 200°C or less, and preferably 180°C or less. If the barrel temperature is 200°C or less, the melt viscosity of the raw resin composition is maintained within a certain range, and sufficient shear stress is applied to the raw resin composition, thereby reducing the number of poorly dispersed particles in the masterbatch. As a result, even if the acrylic resin composition described below is produced for a long period of time by adding the masterbatch, the differential pressure between the outlet and inlet of the polymer filter installed upstream of the die of the extruder is less likely to increase. The barrel temperature is, for example, 150°C or more.

[0020] The method for producing a masterbatch according to this embodiment satisfies the following formula (1). Therefore, sufficient shear stress is applied to the raw resin composition, reducing the number of poorly dispersed particles in the masterbatch. As a result, even when the acrylic resin composition described below is produced for a long period of time by adding the masterbatch, the differential pressure between the outlet and inlet of the polymer filter installed upstream of the die of the extruder is less likely to increase. Q / N / (D / 40) 3 ≦0.11 (1) (In the formula, Q is the feed rate of the raw material resin composition [kg / h], N is the screw rotation speed [rpm], and D is the extruder bore [mm].)

[0021] Note that (D / 40) is the extruder diameter normalized (non-dimensionalized) by a normalization constant of 40 [mm]. Here, Q / N / (D / 40) 3 It is more preferable that Q / N / (D / 40) is 0.1 [kg / h / rpm] or less. 3 is, for example, 0.03 [kg / h / rpm] or more.

[0022] The raw resin composition contains an acrylic resin and crosslinked acrylic particles having an average particle size of 1 μm or less. The content of the crosslinked acrylic particles in the raw resin composition is 5 wt % or more, preferably 8 wt % or more, and preferably 10 wt % or more. When the content of the crosslinked acrylic particles in the raw resin composition is 5 wt % or more, the amount of masterbatch added decreases when producing an acrylic resin composition used to produce a polarizer protective film with excellent blocking resistance. The content of the crosslinked acrylic particles in the raw resin composition is, for example, 30 wt % or less, or may be 25 wt % or less, or may be 20 wt % or less.

[0023] The raw resin composition preferably further contains an additive having a melting point of 200°C or lower. This allows the acrylic crosslinked particles to be sufficiently wetted before the raw resin composition is kneaded in the extruder, thereby reducing the number of poorly dispersed particles in the masterbatch. As a result, even if the acrylic resin composition described below is produced for a long period of time by adding the masterbatch, the differential pressure between the outlet and inlet of the polymer filter installed upstream of the die of the extruder is less likely to increase.

[0024] The additives are not particularly limited as long as they have a melting point of 200°C or less, and examples thereof include lubricants, ultraviolet absorbers, and antioxidants. Examples of lubricants include fatty acid amide lubricants, fatty acid ester lubricants, metal soap lubricants, polymer lubricants, aliphatic hydrocarbon lubricants, aliphatic alcohol lubricants, and aliphatic acid lubricants. Specific examples of lubricants include stearic acid amide and palmitic acid amide. Examples of ultraviolet absorbers include triazine compounds, benzotriazole compounds, benzophenone compounds, and benzoxazine compounds. Specific examples of ultraviolet absorbers include 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol. Examples of antioxidants include phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. Specific examples of antioxidants include 2,6-di-t-butyl-p-cresol, tocopherol, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, triphenyl phosphite, and tris(2,4-di-t-butylphenyl) phosphite.

[0025] (acrylic resin) In this specification and claims, acrylic resin refers to a polymer of a monomer having an acryloyl group and / or a monomer having a methacryloyl group. In this case, the acrylic resin may be either a homopolymer or a copolymer. When the acrylic resin is a copolymer, it may also be a copolymer of a monomer not having an acryloyl group or a methacryloyl group.

[0026] The glass transition temperature of the acrylic resin is preferably 120°C or higher, more preferably above 120°C, even more preferably 121°C or higher, even more preferably 123°C or higher, and particularly preferably 125°C or higher. When the glass transition temperature of the acrylic resin is 120°C or higher, dimensional change of the acrylic film in a high-temperature environment is small, which is practically preferable. The glass transition temperature of the acrylic resin is, for example, 150°C or lower.

[0027] The acrylic resin having a glass transition temperature of 120° C. or higher is not particularly limited, but examples thereof include acrylic resins having a ring structure in the main chain.

[0028] Here, the ring structure is preferably at least one selected from the group consisting of a glutarimide ring, a lactone ring, a maleic anhydride ring, a maleimide ring, and a glutaric anhydride ring.

[0029] The acrylic resin having a glutarimide ring in the main chain has, for example, a structural unit represented by the following formula (1) as a structural unit having a ring structure in the main chain.

[0030] [ka] (In the formula, R 1 and R 2 are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 3 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

[0031] The content of the structural unit represented by formula (1) in the acrylic resin is preferably 2% by weight or more and 30% by weight or less. When the content of the structural unit represented by formula (1) in the acrylic resin is 2% by weight or more, the dimensional change of the acrylic film in a high-temperature environment is small, and when it is 30% by weight or less, the retardation of the acrylic film is small.

[0032] The content of the structural unit represented by formula (1) in the acrylic resin can be expressed as, for example, R 3 is a methyl group, 1 It is determined based on the molar ratio calculated from the area of the peak at around 3.5 to 3.8 ppm in the H-NMR spectrum, which is attributable to the protons constituting the O-CH3 of methyl methacrylate, and the area of the peak at around 3.0 to 3.3 ppm, which is attributable to the protons constituting the N-CH3 of the glutarimide ring.

[0033] The acrylic resin having the structural unit represented by formula (1) can be produced by a known method. An example of the method for producing the acrylic resin having the structural unit represented by formula (1) will be described below.

[0034] First, a twin-screw extruder is used to melt methyl methacrylate resin, and then an imidizing agent is injected to imidize the methyl methacrylate resin. Next, strands discharged from the die of the twin-screw extruder are cooled in a water bath and then cut with a pelletizer to obtain an imidized acrylic resin. Next, a twin-screw extruder is used to melt imidized methyl methacrylate resin, and then an esterifying agent is injected to esterify the imidized acrylic resin. Next, strands discharged from the die of the twin-screw extruder are cooled in a water bath and then cut with a pelletizer to obtain an acrylic resin having a structural unit represented by formula (1).

[0035] Examples of the imidizing agent include ammonia and primary amines represented by the following formula (2): Among these, monomethylamine is preferred.

[0036] R 3 NH2(2) (In the formula, R 3 is the same as formula (1).

[0037] Examples of the esterifying agent include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluene sulfonate, methyl trifluoromethyl sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Of these, dimethyl carbonate is preferred.

[0038] The acrylic resin having a lactone ring in the main chain can be obtained, for example, by polymerizing a monomer represented by the following formula (3) and then heat treating it to form a lactone ring.

[0039] [ka] (In the formula, R 4 and R 5 are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0040] Examples of the monomer represented by formula (3) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, and t-butyl 2-(hydroxymethyl)acrylate, and two or more of them may be used in combination. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is particularly preferred.

[0041] The acrylic resin may further have a structural unit derived from a (meth)acrylic acid ester. Examples of the (meth)acrylic acid ester include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate. Two or more of these may be used in combination. Among these, alkyl methacrylates are preferred, and methyl methacrylate is particularly preferred.

[0042] The acrylic resin may further contain structural units derived from other monomers, including, but not limited to, aromatic monomers such as styrene and methylstyrene, and nitrile monomers such as acrylonitrile and methacrylonitrile.

[0043] Examples of acrylic resins having maleic anhydride rings in the main chain include styrene-N-phenylmaleimide-maleic anhydride copolymers. Examples of acrylic resins having maleimide rings in the main chain include the olefin-maleimide copolymers described in JP 2004-45893 A. Examples of acrylic resins having glutaric anhydride rings in the main chain include the heat-resistant copolymers described in JP 2003-137937 A.

[0044] (acrylic cross-linked particles) In this specification and claims, the term "acrylic crosslinked particles" refers to crosslinked particles containing a polymer of a monomer having an acryloyl group and / or a monomer having a methacryloyl group. In this case, the polymer may be either a homopolymer or a copolymer. When the polymer is a copolymer, it may be a copolymer of a monomer not having an acryloyl group or a methacryloyl group.

[0045] The shape of the acrylic crosslinked particles is not particularly limited, but in consideration of the blocking resistance of the polarizer protective film, a spherical shape is preferred.

[0046] The ratio of the refractive index of the crosslinked acrylic particles to the refractive index of the acrylic resin is preferably 98% or more and 102% or less, and more preferably 99% or more and 101% or less. When the ratio of the refractive index of the crosslinked acrylic particles to the refractive index of the acrylic resin is 98% or more and 102% or less, a polarizer protective film with excellent transparency can be obtained. The refractive index of the crosslinked acrylic particles is preferably 1.47 or more and 1.55 or less, more preferably 1.47 or more and 1.53 or less, and particularly preferably 1.48 or more and 1.52 or less. When the refractive index of the crosslinked acrylic particles is 1.47 or more and 1.55 or less, a polarizer protective film with excellent transparency can be obtained.

[0047] The monofunctional monomer used in producing the acrylic crosslinked particles is not particularly limited, but examples thereof include (meth)acrylic acid esters and other monofunctional monomers copolymerizable with (meth)acrylic acid esters. Among these, methyl methacrylate is preferred from the viewpoints of compatibility with acrylic resins and refractive index. The content of methyl methacrylate units in the acrylic crosslinked particles is not particularly limited, but is, for example, 80% by weight or more and 99% by weight or less.

[0048] A polyfunctional monomer may be used when producing the crosslinked acrylic particles. The weight ratio of the polyfunctional monomer to the monofunctional monomer is preferably 0.5% by weight or more and 30% by weight or less. When the weight ratio of the polyfunctional monomer to the monofunctional monomer is 0.5% by weight or more, the heat resistance and dispersibility of the crosslinked acrylic particles are improved, and when it is 30% by weight or less, the particles are less likely to coalesce during production of the crosslinked acrylic particles, and irregularly shaped particles are less likely to be formed.

[0049] The raw material resin composition contains crosslinked acrylic particles having an average particle size of 1 μm or less, and preferably contains first crosslinked acrylic particles having an average particle size of 0.5 μm to 1.0 μm and second crosslinked acrylic particles having an average particle size of 0.1 μm to 0.3 μm. When the raw material resin composition contains crosslinked acrylic particles having an average particle size of 1 μm or less, a polarizer protective film having excellent transparency and anti-blocking properties can be obtained. The weight ratio of the second crosslinked acrylic particles to the first crosslinked acrylic particles is not particularly limited, but is, for example, 0.10 to 0.50.

[0050] The raw resin composition may contain a plurality of acrylic crosslinked particles having different average particle sizes, and may further contain acrylic crosslinked particles having an average particle size of more than 1 μm, as long as the effects of the present invention are not impaired.

[0051] [Method of producing acrylic resin composition] The method for producing an acrylic resin composition of this embodiment includes the steps of obtaining a masterbatch by the method for producing a masterbatch of this embodiment, and mixing the masterbatch with an acrylic resin having a ring structure in its main chain. Here, the acrylic resin having a ring structure in its main chain that is mixed with the masterbatch is the same as the acrylic resin having a ring structure in its main chain that is contained in the raw resin composition described above. Note that the acrylic resin having a ring structure in its main chain that is mixed with the masterbatch may be the same as or different from the acrylic resin having a ring structure in its main chain that is contained in the raw resin composition. An example of a method for producing an acrylic resin composition will be described below.

[0052] First, an acrylic resin having a ring structure in its main chain is fed from the main feeder of a twin-screw extruder and melted. Next, a masterbatch is fed from the side feeder of the twin-screw extruder and mixed with the acrylic resin having a ring structure in its main chain while being melted. Next, the strands extruded from the die of the twin-screw extruder are cooled in a water tank and then cut with a pelletizer to obtain an acrylic resin composition.

[0053] [Masterbatch] A first aspect of the masterbatch of this embodiment includes an acrylic resin and crosslinked acrylic particles having an average particle size of 1 μm or less, and the content of the crosslinked acrylic particles is 5 wt % or more. A second aspect of the masterbatch of this embodiment includes an acrylic resin having a glass transition temperature of 120° C. or higher and crosslinked acrylic particles, and the content of the crosslinked acrylic particles is 5 wt % or more. The masterbatch of this embodiment is produced by the masterbatch production method of this embodiment.

[0054] The masterbatch of this embodiment is dissolved or dispersed in methylene chloride to a solids concentration of 40 ppm by weight, and the number of particles having a particle size of 10 μm or more per 1 mg of the masterbatch is measured. The number is 200 or less, preferably 180 or less, and more preferably 160 or less. When the masterbatch of this embodiment is dissolved or dispersed in methylene chloride to a solids concentration of 40 ppm by weight, and the number of particles having a particle size of 10 μm or more per 1 mg of the masterbatch is measured ... number of particles having a particle size of 10 μm or more per 1 mg of the masterbatch is measured., the masterbatch of this embodiment has few poorly dispersed particles. Therefore, even when an acrylic resin composition is produced for a long period of time by adding the masterbatch, the differential pressure between the outlet and inlet of the polymer filter installed upstream of the die of the extruder is unlikely to increase.

[0055] The masterbatch of this embodiment is dissolved or dispersed in methylene chloride to a solids concentration of 40 ppm by weight, and the number of particles having a particle size of 10 μm or more and 20 μm or less per 1 mg of the masterbatch, as measured, is preferably 120 or less. As a result, the masterbatch of this embodiment has few poorly dispersed particles. Therefore, even when an acrylic resin composition is produced for a long period of time by adding the masterbatch, the differential pressure between the outlet and inlet of the polymer filter installed upstream of the die of the extruder is unlikely to increase.

[0056] [Method of manufacturing polarizer protective film] The polarizer protective film can be produced by a known method using the acrylic resin composition of the present embodiment. An example of a method for producing a polarizer protective film will be described below.

[0057] First, the acrylic resin composition of the present embodiment is fed from the main feeder of a twin-screw extruder and melted. Next, a sheet is extruded from the T-die of the twin-screw extruder and cooled with a cooling roll to obtain an acrylic film. Next, the acrylic film is biaxially stretched to obtain a polarizer protective film. In this case, the biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching.

[0058] The temperature at which the acrylic film is biaxially stretched is preferably (Tg + 5)°C or higher (Tg + 30)°C or lower, more preferably (Tg + 6)°C or higher (Tg + 25)°C or lower, and even more preferably (Tg + 7)°C or higher (Tg + 20)°C or lower, where Tg is the glass transition temperature of the acrylic resin. The areal stretching ratio when the acrylic film is biaxially stretched is not particularly limited, but is, for example, 2 times or higher and 10 times or lower. The stretching speed when the acrylic film is biaxially stretched is not particularly limited, but is, for example, 1.1 times / min or higher and 100 times / min or lower. When the acrylic film is sequentially biaxially stretched, the stretching speeds in the first stage and the second stage may be the same or different. In sequential biaxial stretching, the first stage stretching is usually stretching in the longitudinal direction (MD), and the second stage stretching is usually stretching in the transverse direction (TD).

[0059] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Example]

[0060] The present invention will be described in more detail below based on examples and comparative examples. Although examples of the present invention will be described, the present invention is not limited to the examples.

[0061] [Examples 1 to 11, Comparative Examples 1 to 5] (Acrylic resin manufacturing) Acrylic resin (I) was produced using a 40 mm diameter, co-rotating, intermeshing twin-screw extruder (L / D = 90). Here, L and D are the length and diameter of the extruder, respectively. The barrel temperature was set to 250-280°C, and the screw rotation speed was set to 85 rpm. Next, using a loss-in-weight feeder CE-T-2E (Kubota), polymethyl methacrylate resin (Mw = 105,000) was fed into the main feeder at a feed rate of 42.4 kg / h. The resin was melted and filled using a kneading block, and then 1.8 wt% monomethylamine (Mitsubishi Gas Chemical Company) was injected into the resin through a nozzle. A reverse flight was inserted at the end of the reaction zone to fill the resin. The pressure at the vent port was reduced to -0.092 MPa to remove reaction by-products and excess monomethylamine. Next, the strands discharged from the die of the extruder were cooled in a water tank and then cut with a pelletizer to obtain pelletized acrylic resin (I).

[0062] Acrylic resin (A1) was produced using a 40 mm diameter, co-rotating, intermeshing twin-screw extruder (L / D = 90). The barrel temperature was set to 240-260°C, and the screw rotation speed was set to 102 rpm. Next, using a loss-in-weight feeder CE-T-2E (Kubota), acrylic resin (I) was fed to the main feeder at a feed rate of 41 kg / hr. The resin was melted and filled using a kneading block, and then 0.56 wt.% dimethyl carbonate was injected into the resin through a nozzle to reduce the carboxyl groups in the resin. A reverse flight was inserted at the end of the reaction zone to fill the resin. The pressure at the vent port was reduced to -0.092 MPa to remove reaction by-products and excess dimethyl carbonate. The strand extruded from the extruder die was cooled in a water bath and then cut using a pelletizer to obtain pelletized acrylic resin (A1). The acrylic resin (A1) had a glutarimide ring in the main chain, the content of structural units having a glutarimide ring was 6% by weight, the glass transition temperature was 125° C., and the average refractive index was 1.50.

[0063] (Masterbatch manufacturing) A masterbatch was produced using a 40 mm diameter, co-rotating, intermeshing twin-screw extruder (L / D = 90). The raw resin composition was a dry blend of 85 parts by weight of acrylic resin (A1), 9 parts by weight of crosslinked acrylic particles with an average particle size of 0.8 μm, 4 parts by weight of crosslinked acrylic particles with an average particle size of 0.15 μm, and a predetermined amount of additives (see Table 1). The barrel temperature and screw rotation speed were set to predetermined values (see Table 1). Next, a loss-in-weight feeder CE-T-2E (manufactured by Kubota) was used to feed the raw resin composition to the main feeder at a predetermined feed rate (see Table 1), and the resin was melted using a kneading block. The strand extruded from the extruder die was cooled in a water bath and then cut using a pelletizer to obtain a pelletized masterbatch.

[0064] Table 1 shows the conditions for producing the masterbatch.

[0065] [Table 1]

[0066] Here, the additives A1 to A3 are as follows. A1: Lubricant with a melting point of 101°C; stearic acid amide A2: Lubricant with melting point of 100°C; palmitic acid amide A3: UV absorber with a melting point of 144 to 150°C; 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine; Adekastab LA-F70 (manufactured by ADEKA)

[0067] (number of particles) 0.6 g of the masterbatch was dissolved or dispersed in 20 g of methylene chloride to obtain a masterbatch dispersion. Then, 0.22 g of the masterbatch dispersion was diluted with 160 g of methylene chloride to obtain a dilute masterbatch solution with a solids concentration of 40 ppm by weight. The methylene chloride used was filtered through a membrane filter with a mesh size of 0.22 μm. Next, the number of particles in 20 ml of the dilute masterbatch solution was measured using a liquid particle counter KS-42D (manufactured by Rion).

[0068] (poorly dispersed particles) The diluted solution used to measure the particle count was filtered through a membrane filter with a mesh size of 2 μm, and the particles collected on the membrane filter were observed under SEM to evaluate dispersibility. Dispersibility was evaluated according to the following criteria. 1: There are five or more poorly dispersed particles within the field of view 2: When there are 2 or more but less than 5 poorly dispersed particles within the field of view 3: When there are 0 to 2 poorly dispersed particles in the field of view

[0069] (Production of acrylic resin composition) An acrylic resin composition was produced using a tandem extrusion reactor consisting of a first extruder and a second extruder arranged in series. Both the first and second extruders were 75 mm diameter, intermeshing co-rotating twin-screw extruders (L / D = 74). The die of the first extruder and the main feeder of the second extruder were connected by a 38 mm diameter, 2 m long pipe, and a constant flow pressure valve was used to control the pressure inside the pipe.

[0070] A loss-in-weight feeder CE-T-2E (Kubota) was used to supply the raw resin to the main feeder of the first extruder. The pressure at each vent port of the first and second extruders was reduced to -0.095 MPa. Acrylic resin 1 was produced using polymethyl methacrylate resin (Mw = 105,000) as the raw resin and monomethylamine as the imidizing agent. The set temperature of the hottest part of the barrel of the first extruder was 280°C, the screw rotation speed was 55 rpm, the raw resin feed rate was 150 kg / h, and the amount of monomethylamine added was 2.0 wt% relative to the raw resin. A constant flow pressure valve was installed immediately before the main feeder of the second extruder, and the pressure at the monomethylamine injection section of the first extruder was adjusted to 8 MPa. The strand discharged from the die of the second extruder was cooled on a cooling conveyor and then cut using a pelletizer to produce a pelletized acrylic resin composition. Here, in order to adjust the pressure in the pipe connecting the die of the first extruder and the main feeder of the second extruder and to identify extrusion fluctuations, resin pressure gauges were installed in the die of the first extruder, the center of the pipe, and the die of the second extruder.

[0071] After the remaining imidization reagents and by-products were devolatilized through the rear vent and vacuum vent of the second extruder, a mixed solution of dimethyl carbonate and triethylamine was added as an esterifying agent to produce acrylic resin 2. The set temperature of each barrel of the second extruder was 260°C, and the screw rotation speed was 55 rpm. The amount of dimethyl carbonate added was 3.2 wt% relative to the raw resin. The amount of triethylamine added was 0.8 wt% relative to the raw resin. After removing the esterifying agent through the vent port, 1 wt% of masterbatch was added to the raw resin from the side feeder. The strand was then filtered through a leaf disk-type polymer filter (filtration accuracy: 5 μm) via a gear pump, discharged from the die, cooled in a water tank, and cut using a pelletizer to obtain a pelletized acrylic resin composition.

[0072] (Differential pressure increase) After producing the acrylic resin composition for 12 hours, the differential pressure between the outlet and inlet of the polymer filter was measured and the increase in differential pressure was evaluated. At this time, the increase in differential pressure was evaluated according to the following criteria. 1: When the differential pressure rise is 0.3 MPa or more 2: When the differential pressure increase is less than 0.3 MPa

[0073] The evaluation results of poorly dispersed particles in the masterbatch and the increase in differential pressure during production of the acrylic resin composition are shown in Table 2. Here, PC(≧10 μm) and PC(10-20 μm) mean the number of particles with a particle size of 10 μm or more per 1 mg of masterbatch and the number of particles with a particle size of 10 μm or more and 20 μm or less per 1 mg of masterbatch, respectively.

[0074] [Table 2]

[0075] From Table 2, it can be seen that in Examples 1 to 11, there were few poorly dispersed particles in the master batch, and the increase in differential pressure during the production of the acrylic resin composition was small. In contrast, in Comparative Examples 1 to 4, the barrel temperature was 210 to 250°C, so there were many poorly dispersed particles in the master batch, and the increase in differential pressure during the production of the acrylic resin composition was large. In particular, in Comparative Example 1, Q / N / (D / 40) 3 In Comparative Example 5, the ratio Q / N / (D / 40) was 0.268 [kg / h / rpm], resulting in a large number of poorly dispersed particles in the master batch. 3 Since the speed is 0.133 [kg / h / rpm], there are many poorly dispersed particles in the master batch, and the increase in differential pressure during production of the acrylic resin composition is large.

Claims

1. A method for producing a masterbatch by feeding a raw resin composition to an extruder equipped with a barrel and a screw, The temperature of the barrel is 200°C or less, The following formula (1) is satisfied: the raw material resin composition contains an acrylic resin and crosslinked acrylic particles having an average particle diameter of 1 μm or less, and the content of the crosslinked acrylic particles is 5 wt % or more. Q / N / (D / 40) ３ ≦0.11・・・(1) (In the formula, Q is the feed rate [kg / h] of the raw material resin composition, N is the rotation speed [rpm] of the screw, and D is the diameter [mm] of the extruder.)

2. The method for producing a masterbatch according to claim 1 , wherein the raw material resin composition further contains an additive having a melting point of 200° C. or less.

3. The method for producing a masterbatch according to claim 2 , wherein the additive is a lubricant or an ultraviolet absorber.

4. The method for producing a masterbatch according to claim 1 , wherein the acrylic resin has a glass transition temperature of 120° C. or higher.

5. The method for producing a masterbatch according to claim 4 , wherein the acrylic resin has a ring structure in the main chain.

6. A step of obtaining a masterbatch by the method for producing a masterbatch according to any one of claims 1 to 3; and mixing the masterbatch with an acrylic resin having a ring structure in its main chain.

7. A masterbatch comprising an acrylic resin and acrylic crosslinked particles having an average particle size of 1 μm or less, wherein the content of the acrylic crosslinked particles is 5 wt % or more, The masterbatch has a solid content of 40 ppm by weight and a measured result obtained by dissolving or dispersing the masterbatch in methylene chloride. The measured result shows that the number of particles having a particle size of 10 μm or more per 1 mg of the masterbatch is 200 or less.

8. A masterbatch comprising an acrylic resin having a glass transition temperature of 120°C or higher and acrylic crosslinked particles, the content of the acrylic crosslinked particles being 5% by weight or higher, The masterbatch has a solid content of 40 ppm by weight and a measured result obtained by dissolving or dispersing the masterbatch in methylene chloride. The measured result shows that the number of particles having a particle size of 10 μm or more per 1 mg of the masterbatch is 200 or less.

9. 9. The masterbatch according to claim 7 or 8, wherein the number of particles having a particle size of 10 μm or more and 20 μm or less per 1 mg of the masterbatch, as measured after dissolving or dispersing the masterbatch in methylene chloride to a solids concentration of 40 ppm by weight, is 120 or less.

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