JP7460464B2 - METHACRYLIC RESIN COMPOSITION AND METHOD FOR PRODUCING SAME - Google Patents

Description

The present invention relates to a methacrylic resin composition and a method for producing the same.

Methacrylic resins have excellent optical properties such as transparency and weather resistance, and their molded articles have beautiful appearances. Therefore, they have been used in a variety of applications, including lighting fixtures, display components such as signs, optical components such as display parts, interior components, building components, electronic and electrical components, and medical components. In particular, acrylic resins containing acrylic crosslinked rubber particles have excellent impact resistance and are widely used.

The above acrylic resins have problems in that poor dispersion of the crosslinked rubber particles impairs impact resistance when molded into a sheet, or causes defects on the surface, resulting in poor appearance. Patent Document 1 discloses a method for producing acrylic resin pellets that has good resin dispersion and can produce molded products with excellent appearance. However, it does not disclose an appropriate combination of acrylic crosslinked rubber particles and a methacrylic polymer as a base material.

JP2014-156511

The object of the present invention is to provide a methacrylic resin composition in which surface defects are reduced by dispersing acrylic crosslinked rubber particles in a methacrylic polymer.

In order to achieve the above object, the present invention provides a resin composition containing a methacrylic polymer (A) and acrylic crosslinked rubber particles (B) that satisfy the following conditions, and a method for producing the same.
[1]
A methacrylic resin composition comprising 10 to 90% by mass of a methacrylic polymer (A) and 90 to 10% by mass of acrylic crosslinked rubber particles (B), wherein the melt viscosity ratio (ηB/ηA) of the melt viscosity (ηB) of the acrylic crosslinked rubber particles (B) at 240°C to the melt viscosity (ηA) of the methacrylic polymer (A) at 200°C is 0.1 to 5.
[2]
A method for producing the methacrylic resin composition according to [1], comprising a step of melt-kneading the methacrylic polymer (A) and the acrylic crosslinked rubber particles (B).
[3]
The method for producing a methacrylic resin composition according to [2], wherein the methacrylic polymer (A) contains a dispersion particle (A1) and a methacrylic polymer (A2), and the melt viscosity (ηA2) of the methacrylic polymer (A2) at 200°C is 1000 to 30000 Pa s.
[4]
a step of mixing the acrylic crosslinked rubber particles (B) and the dispersion particles (A1) to obtain a coagulated powder (B2) having a melt viscosity (ηB2) at 240° C. of 100 to 10,000 Pa s;
a step of melt-kneading the obtained coagulated powder (B2) and the methacrylic polymer (A2);
and a melt viscosity ratio of the ηB2 to the ηA2 (ηB2/ηA2) is 0.005 to 0.12.
[5]
The methacrylic resin composition comprises a coagulated powder (B2) having as its constituent elements acrylic crosslinked rubber particles (B) and dispersing particles (A1), and a methacrylic polymer (A2), the total of the dispersing particles (A1) and the methacrylic polymer (A2) being 10 to 90 mass %, and the acrylic crosslinked rubber particles (B) being 90 to 10 mass %, respectively, and the melt viscosity ratio (ηB/ηA) of the melt viscosity (ηB) of the acrylic crosslinked rubber particles (B) at 240°C to the melt viscosity (ηA) of the methacrylic polymer (A2) at 200°C is 0.1 to 5.
[6]
A molded article comprising the methacrylic resin composition according to [1] or [5].
[7]
The molded article according to [6], which is a film.

According to the present invention, it is possible to provide a methacrylic resin composition having good dispersibility of the acrylic crosslinked rubber particles (B) and excellent impact resistance and appearance.

The methacrylic resin composition of the present invention contains a methacrylic polymer (A) and acrylic crosslinked rubber particles (B). The content of the methacrylic polymer (A) in the methacrylic resin composition is 10 to 90% by mass, preferably 15 to 85% by mass. The content of the acrylic crosslinked rubber particles (B) in the methacrylic resin composition is 90 to 10% by mass, preferably 85 to 15% by mass.

The methacrylic polymer (A) is a resin containing a structural unit derived from a methacrylic acid ester. Examples of the methacrylic acid ester include methacrylic acid alkyl esters such as methyl methacrylate (hereinafter referred to as "MMA"), ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, and dodecyl methacrylate; 1-methylcyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, and tricyclo[5.2.1.0 ^2,6] methacrylate; methacrylic acid cycloalkyl esters such as dec-8-yl (hereinafter referred to as "TCDMA"); methacrylic acid aryl esters such as phenyl methacrylate; methacrylic acid aralkyl esters such as benzyl methacrylate; and the like. From the viewpoint of availability, MMA, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and tert-butyl methacrylate are preferred, with MMA being the most preferred. The content of structural units derived from methacrylic acid esters in the methacrylic resin is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, and may be only structural units derived from methacrylic acid esters.

Further, the methacrylic polymer (A) may contain a structural unit derived from a monomer other than methacrylic acid ester. Examples of such other monomers include methyl acrylate (hereinafter referred to as "MA"), ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and tert-acrylate. Butyl, hexyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, acrylic Cyclohexyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, trifluoromethyl acrylate, trifluoroethyl acrylate, pentafluoroethyl acrylate, glycidyl acrylate, allyl acrylate, phenyl acrylate, toluyl acrylate , benzyl acrylate, isobornyl acrylate, 3-dimethylaminoethyl acrylate, and other acrylic esters. Acrylic acid esters such as -butyl, isobutyl acrylate, and tert-butyl acrylate are preferred, MA and ethyl acrylate are more preferred, and MA is most preferred. The total content of structural units derived from these other monomers in the methacrylic resin is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and The derived structural unit may not be included.

The methacrylic resin can be obtained by polymerizing the above-mentioned methacrylic acid ester and other optional monomers. In such polymerization, when a plurality of types of monomers are used, the plurality of types of monomers are usually mixed to prepare a monomer mixture, and then subjected to the polymerization. Although there are no particular limitations on the polymerization method, from the viewpoint of productivity, radical polymerization is preferably carried out by methods such as bulk polymerization, suspension polymerization, solution polymerization, and emulsion polymerization.

The methacrylic polymer (A) of the present invention preferably has a weight average molecular weight (Mw) of 40,000 to 200,000, more preferably 50,000 to 180,000, and even more preferably 55,000 to 160,000. When the Mw is 40,000 or more, the strength and toughness of the molded article of the present invention are improved. When the Mw is 200,000 or less, the fluidity of the methacrylic polymer of the present invention is improved, and molding processability is improved.

The weight average molecular weight (Mw) is a value calculated by converting a chromatogram measured by gel permeation chromatography into the molecular weight of standard polystyrene.

The methacrylic polymer (A) may be a commercially available product. Examples of commercially available methacrylic polymers include "PARAPET H1000B" (MFR: 22 g/10 min (230°C, 37.3 N)), "PARAPET GF" (MFR: 15 g/10 min (230°C, 37.3 N)), "PARAPET EH" (MFR: 1.3 g/10 min (230°C, 37.3 N)), "PARAPET HRL" (MFR: 2.0 g/10 min (230°C, 37.3 N)), "PARAPET HRS" (MFR: 2.4 g/10 min (230°C, 37.3 N)), and "PARAPET G" (MFR: 8.0 g/10 min (230°C, 37.3 N)) [all trade names, manufactured by Kuraray Co., Ltd.].

The acrylic crosslinked rubber particles (B) are particles containing an acrylic crosslinked rubber polymer obtained by an emulsion polymerization method, and preferably include an outermost layer made of a thermoplastic polymer (P), and an outermost layer in contact with and covering the outermost layer. These are multilayer structure rubber particles containing a crosslinked rubber polymer (Q). For example, the multilayer structure rubber particles have a two-layer structure (Q-P) in which the core is a crosslinked rubber polymer (Q) and the outer shell (outermost layer) is a thermoplastic polymer (P), and the core is a crosslinked polymer (R). - Three-layer structure (R-Q-P) with inner shell made of crosslinked rubber polymer (Q) - outer shell (outermost layer) thermoplastic polymer (P), core made of crosslinked rubber polymer (Q) - First Four-layer structure (QR-Q-P): inner shell is crosslinked polymer (R) - second inner shell is crosslinked rubber polymer (Q) - outer shell (outermost layer) is thermoplastic polymer (P) particles, etc.

A layer other than the outermost layer in a multilayer structure rubber particle (hereinafter, a layer other than the outermost layer may be referred to as an "inner layer"; for example, the above Q, R+Q, Q+R+Q each correspond to an inner layer) and the outermost layer The mass ratio is preferably 60/40 to 95/5, more preferably 70/30 to 90/10. In the inner layer, the proportion of the layer containing the crosslinked rubber polymer (Q) is preferably 20 to 70% by mass, more preferably 30 to 50% by mass.

The multilayered rubber particles preferably have an average particle size of 0.05 to 0.3 μm, more preferably 0.1 to 0.27 μm, and even more preferably 0.2 to 0.25 μm. By using multilayered crosslinked rubber particles having an average particle size within this range, particularly an average particle size of 0.2 to 1 μm, toughness can be achieved with a small amount of compounding, and therefore the rigidity and surface hardness of the molded product are not impaired. In this specification, the average particle size is the average value in the volume-based particle size distribution measured by the light scattering method, or the average particle size measured from an electron microscope photograph.

The thermoplastic polymer (P) constituting the outermost layer preferably contains a methacrylic acid alkyl ester unit having an alkyl group having 1 to 8 carbon atoms and, if necessary, a monofunctional monomer unit other than the methacrylic acid alkyl ester. It is a polymer containing It is preferable that the thermoplastic polymer (P) does not contain a polyfunctional monomer unit.

The amount of methacrylic acid alkyl ester units having an alkyl group having 1 to 8 carbon atoms constituting the thermoplastic polymer (P) is preferably 80 to 100% by mass, more preferably 85 to 95% by mass, based on the mass of the thermoplastic polymer (P).

As the methacrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms (hereinafter sometimes referred to as methacrylic acid C _1-8 alkyl ester), for example, methyl methacrylate is preferable.
The amount of monofunctional monomer units other than methacrylic acid C _1-8 alkyl ester constituting the thermoplastic polymer (P) is preferably 0 to 20% by mass based on the mass of the thermoplastic polymer (P). , more preferably 5 to 15% by mass.

Monofunctional monomers other than methacrylic acid C _1-8 alkyl esters include acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and prol acrylate, and aromatic monomers such as styrene. Vinyl compounds can be mentioned.

The outermost layer may be a single layer made of one type of thermoplastic polymer (P), or a multilayer made of two or more types of thermoplastic polymers (P).

In one preferred embodiment of the present invention, the inner layer has an intermediate layer made of a crosslinked rubber polymer (Q) and a core made of a crosslinked polymer (R) that is in contact with and covered by the intermediate layer (inner layer = R + Q).

The crosslinked polymer (R) consists of methyl methacrylate units, monofunctional monomer units other than methyl methacrylate, and polyfunctional monomer units.

The amount of methyl methacrylate units constituting the crosslinked polymer (R) is preferably 40 to 98.5% by mass, more preferably 45 to 95% by mass, based on the mass of the crosslinked polymer (R).

The amount of monofunctional monomer units other than methyl methacrylate constituting the crosslinked polymer (R) is 1 to 59.5% by mass, preferably 5 to 55% by mass based on the mass of the crosslinked polymer (R). %.
Examples of monofunctional monomers other than methyl methacrylate include acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and propyl acrylate, and aromatic vinyl compounds such as styrene. Can be done.

The amount of the polyfunctional monomer unit constituting the crosslinked polymer (R) is preferably 0.05 to 0.4% by mass, more preferably 0.1 to 0.3% by mass, based on the mass of the crosslinked polymer (R).

The amount of the crosslinked polymer (R) is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass, relative to the amount of the multilayered rubber particles.

The crosslinked rubber polymer (Q) consists of an acrylic ester unit having an alkyl group having 1 to 8 carbon atoms, a monofunctional monomer unit other than an acrylic ester, and a polyfunctional monomer unit.

The acrylic acid ester unit having an alkyl group having 1 to 8 carbon atoms in the crosslinked rubber polymer (Q) is preferably 10 to 100% by mass, more preferably 20 to 100% by mass, based on the mass of the crosslinked rubber polymer (Q). It is 90% by mass.

The polyfunctional monomer unit in the crosslinked rubber polymer (Q) is preferably 0.01 to 1% by mass, more preferably 0.1 to 0.5% by mass based on the mass of the crosslinked rubber polymer (Q). %.

Examples of acrylic esters used in the thermoplastic polymer (P), crosslinked rubber polymer (Q), and crosslinked polymer (R) include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, Acrylic acid alkyl esters such as s-butyl acrylate, t-butyl acrylate, n-butyl methyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate can be mentioned. These acrylic esters can be used alone or in combination of two or more. Among these, methyl acrylate and/or n-butyl acrylate are preferred.

Examples of the polyfunctional monomer units used in the crosslinked rubber polymer (Q) and the crosslinked polymer (R) include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, triethylene glycol dimethacrylate, hexanediol dimethacrylate, and ethylene glycol. Examples include diacrylate, propylene glycol diacrylate, triethylene glycol diacrylate, allyl methacrylate, and triallyl isocyanurate.
The monofunctional monomer units other than methyl methacrylate in the crosslinked polymer (R) and the monofunctional monomer units other than acrylic ester in the crosslinked rubber polymer (Q) can be used together with methacrylic ester or acrylic ester. Any polymerizable vinyl monomer may be used, such as aromatic vinyl monomers such as styrene, p-methylstyrene, o-methylstyrene, vinylnaphthalene, and unsaturated nitrile monomers such as acrylonitrile. , olefinic monomers such as ethylene and propylene, halogenated vinyl monomers such as vinyl chloride, vinylidene chloride, and vinylidene fluoride, and unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, and maleic anhydride. , vinyl acetate, N-propylmaleimide, N-cyclohexylmaleimide, N-chlorophenylmaleimide, and other maleimide monomers, and these compounds can be used alone or in combination of two or more types. .

The method for producing acrylic crosslinked rubber particles (B) can be, for example, emulsion-polymerizing a monomer (r) for constituting a crosslinked polymer (R) to obtain a latex containing a crosslinked polymer (RI), adding a monomer (q) for constituting a crosslinked rubber polymer (Q) to the latex and performing seed emulsion polymerization of the monomer (q) to obtain a latex containing the crosslinked polymer (R) and the crosslinked rubber polymer (q), and adding a monomer (p) for constituting a thermoplastic polymer (P) to the latex and performing seed emulsion polymerization of the monomer (p) to obtain a latex containing multilayered crosslinked rubber particles. Emulsion polymerization is a known method used to obtain a latex containing a polymer. Seed emulsion polymerization is a method in which a polymerization reaction of a monomer is carried out on the surface of a seed particle. Seed emulsion polymerization is preferably used to obtain core-shell structured polymer particles.

The methacrylic resin composition of the present invention can be obtained by melt-kneading a methacrylic polymer (A) and acrylic crosslinked rubber particles (B).

From the viewpoint of dispersibility of the acrylic crosslinked rubber particles (B), the melt viscosity ratio of the melt viscosity ηA of the methacrylic polymer (A) at 200°C and the melt viscosity ηB of the acrylic crosslinked rubber particles (B) at 240°C ηB/ηA is preferably 0.1 to 5, more preferably 0.1 to 4.

The methacrylic polymer (A) according to the present invention may contain dispersing particles (A1) and a methacrylic polymer (A2).

The dispersing particles (A1), like the methacrylic polymer (A), are resins containing structural units derived from methacrylic acid esters, and can be obtained as a latex containing the dispersing particles (A1) by emulsion polymerization. can.

Like the methacrylic polymer (A), the methacrylic polymer (A2) is a resin containing structural units derived from methacrylic acid ester, and can be processed by suspension polymerization, bulk polymerization, solution polymerization, and emulsion polymerization. It can be obtained as pellets or powder by any polymerization method. Further, the melt viscosity (ηA2) at 200°C is 1000 to 30000 Pa·s.

In the method for producing a resin composition of the present invention, a latex containing crosslinked acrylic rubber particles (B) and a latex containing dispersible particles (A1) are mixed and coagulated to obtain a coagulated powder (B2). It may include a step. The melt viscosity (ηB2) of the solidified powder (B2) at 240°C is 100 to 10,000 Pa·s. The coagulated powder (B2) has dispersible particles (A1) around the acrylic crosslinked rubber particles (B), so that when melt-kneaded with the methacrylic polymer (A2), the acrylic crosslinked rubber particles ( B) Aggregation is further suppressed. Note that the melt viscosity can be measured using a flow tester or a capillograph.
The average particle diameter can be determined by measuring the latex of the dispersing particles (A1) or the acrylic crosslinked rubber particles (B) using a light scattering method. In the light scattering method, latex can be sampled and the average particle size can be measured using a laser diffraction/scattering particle size distribution analyzer LA-950V2 manufactured by Horiba, Ltd.

The resin composition of the present invention can be produced by melt-kneading the coagulated powder (B2) and the methacrylic polymer (A2).
From the viewpoint of resin dispersibility, the melt viscosity ratio ηB2/ηA2 of the melt viscosity ηA2 of the methacrylic polymer (A2) at 200°C and the melt viscosity ηB2 of the acrylic crosslinked rubber particles (B2) at 240°C is 0. 005 to 0.12 is preferable, 0.01 to 0.1 is more preferable, and 0.01 to 0.06 is even more preferable.

Although the method for producing the resin composition of the present invention is not particularly limited, a method of melt-kneading is preferred in order to improve the dispersibility of each component constituting the resin composition. The kneading operation can be carried out using known mixing or kneading equipment, such as a kneader-ruder, extruder, mixing roll, Banbury mixer, or the like.

The kneading device used for melt kneading is preferably a single screw extruder or a twin screw extruder. The molded article containing the methacrylic resin composition of the present invention is also useful as a film, and the film obtained by melt kneading in a single screw extruder using the T-die extrusion method has good dispersion of crosslinked rubber particles and has excellent appearance. The thickness of the film is preferably 20 to 100 μm, more preferably 40 to 70 μm.

The cylinder temperature during melt-kneading in an extruder is preferably 200°C or higher, more preferably 220°C or higher, still more preferably 240°C or higher. Further, from the viewpoint of deterioration and coloring of the resin composition, the cylinder temperature is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 260°C or lower.

Hereinafter, production examples and examples according to the present invention, and comparative examples will be described.
[material]
The methacrylic resin (A2) used in Examples and Comparative Examples is as follows.
Methacrylic polymer (A2)-1: "Parapet EH" manufactured by Kuraray Co., Ltd., melt viscosity at 200°C 20000 Pa・s
Methacrylic polymer (A2)-2: “Parapet HRL” manufactured by Kuraray Co., Ltd., melt viscosity at 200°C 17,000 Pa・s”
Methacrylic polymer (A2)-3: “Parapet G” manufactured by Kuraray Co., Ltd., melt viscosity at 200°C 3400 Pa・s
Methacrylic polymer (A2)-4: "Parapet GF" manufactured by Kuraray Co., Ltd., melt viscosity at 200°C 1500 Pa・s
In addition, in the following, "part" means "part by mass".

(Production Example 1)
In a reactor equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a monomer inlet tube and a reflux condenser, 145 parts of ion-exchanged water, 1.25 parts of Pelex SS-H (manufactured by Kao Corporation), and 0.05 parts of sodium carbonate were charged and stirred to dissolve. The temperature was raised to 80°C, and 0.2 parts of a 2% aqueous potassium persulfate solution was added, and then a monomer mixture consisting of 9 parts of methyl methacrylate, 1 part of methyl acrylate and 0.037 parts of n-octyl mercaptan was quickly added and held for 60 minutes. Next, 2 parts of a 2% aqueous potassium persulfate solution was charged into this latex, and a monomer mixture consisting of 81 parts of methyl methacrylate, 9 parts of methyl acrylate and 0.33 parts of n-octyl mercaptan was continuously added over 2 hours, and after the dropwise addition was completed, the polymerization reaction was continued for another 60 minutes so that the polymerization conversion rate was 98% or more. By the above operations, a latex containing dispersion particles (A1)-1 was obtained. The melt viscosity of the dispersing particles (A1)-1 at 200° C. was 3,000 Pa·s.

(Manufacturing example 2)
In a reactor equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a monomer inlet tube, and a reflux condenser, 1050 parts by mass of ion-exchanged water, 0.44 parts by mass of polyoxyethylene tridecyl ether sodium acetate, and sodium carbonate were placed. 0.7 parts by mass was charged, and the inside of the reactor was sufficiently purged with nitrogen gas. Then, the internal temperature was brought to 80°C. 0.25 parts by mass of potassium persulfate was added thereto, and the mixture was stirred for 5 minutes. To this, 245 parts by mass of a monomer mixture consisting of 95.4% by mass of methyl methacrylate, 4.4% by mass of methyl acrylate, and 0.2% by mass of allyl methacrylate was continuously added dropwise over 60 minutes. After the dropwise addition was completed, the polymerization reaction was further carried out for 30 minutes so that the polymerization conversion rate was 98% or more.
Next, 0.32 parts by mass of potassium persulfate was added into the reactor and stirred for 5 minutes. Thereafter, 315 parts by mass of a monomer mixture consisting of 80.5% by mass of butyl acrylate, 17.5% by mass of styrene, and 2% by mass of allyl methacrylate was continuously added dropwise over 60 minutes. After the dropwise addition was completed, the polymerization reaction was further carried out for 30 minutes so that the polymerization conversion rate was 98% or more.
Next, 0.14 parts by mass of potassium persulfate was added into the same reactor and stirred for 5 minutes. Thereafter, 140 parts by mass of a monomer mixture consisting of 95.2% by mass of methyl methacrylate, 4.4% by mass of methyl acrylate and 0.4% by mass of n-octylmercaptan was continuously added dropwise over 30 minutes. After completion of the dropwise addition, the polymerization reaction was further carried out for 60 minutes so that the polymerization conversion rate was 98% or more. By the above operations, a latex containing acrylic crosslinked rubber particles (B)-1 was obtained. The average particle diameter was 0.23 μm.
An aqueous magnesium sulfate solution was added to the latex for salting out and coagulation. The coagulated product was washed with water, dehydrated, and dried to obtain a coagulated powder of acrylic crosslinked rubber particles (B)-1 alone. The melt viscosity at 240°C was 56,000 Pa·s.

(Production Example 3)
200 parts of ion-exchanged water was placed in a glass-lined reaction vessel equipped with a condenser, a thermometer, and a stirrer, and then 1.3 parts of sodium dodecylbenzenesulfonate and 0.05 parts of sodium carbonate were added and dissolved. The atmosphere in the reaction vessel was replaced with nitrogen gas to make it substantially oxygen-free. The reaction vessel was then heated to bring the aqueous solution to 80°C.
0.01 parts of potassium persulfate was added to the aqueous solution, and the mixture was stirred for 5 minutes. Then, a mixture c consisting of 2.50 parts of methyl methacrylate (MMA), 2.50 parts of butyl acrylate (BA) and 0.01 parts of allyl methacrylate (ALMA) was continuously added dropwise over 15 minutes. After the addition of the mixture c, the mixture was held for 25 minutes, and emulsion polymerization was carried out to obtain latex c.
Next, 0.095 parts of potassium persulfate was added to the latex c, and further, a mixture i consisting of 1.5 parts of methyl methacrylate (MMA), 28.5 parts of butyl acrylate (BA) and 0.90 parts of allyl methacrylate (ALMA) was continuously added dropwise over 60 minutes. After the addition of the mixture i was completed, the mixture was held for 30 minutes and seed emulsion polymerization was carried out to obtain latex i.
Next, a mixture o consisting of 56.9 parts of methyl methacrylate (MMA), 8.1 parts of butyl acrylate (BA) and 0.0196 parts of n-octyl mercaptan (OM) was continuously added dropwise to the latex i over 100 minutes. After the addition of the mixture o was completed, the mixture was held for 60 minutes and seed emulsion polymerization was carried out to obtain a latex containing acrylic crosslinked rubber particles (B)-2. The average particle size was 0.11 μm.
A magnesium sulfate aqueous solution was added to the latex to cause salting out and coagulation. The coagulated product was washed with water, dehydrated, and dried to obtain a coagulated powder of acrylic crosslinked rubber particles (B)-2 alone. The melt viscosity at 240°C was 2300 Pa·s.

(Production Example 4)
The latexes were mixed so that the ratio of dispersion particles (A1)-1 and acrylic crosslinked rubber particles (B)-1 was 20:80. An aqueous magnesium sulfate solution was added to the latex to cause salting-out coagulation. The coagulated product was washed with water, dehydrated, and dried to obtain coagulated powder (B2)-1. The melt viscosity of coagulated powder (B2 )-1 at 240°C was 910 Pa s.

(Manufacturing example 5)
Coagulated powder (B2)-2 was obtained in the same manner as in Production Example 4, except that the ratio of dispersion particles (A1)-1 and acrylic crosslinked rubber particles (B)-1 was changed to 33:67. The melt viscosity of the solidified powder (B2)-2 at 240°C was 500 Pa·s.

(Manufacturing example 6)
Latex was mixed so that the ratio of dispersion particles (A1)-1 and acrylic crosslinked rubber particles (B)-2 was 40:60. An aqueous magnesium sulfate solution was added to the latex for salting out and coagulation. The coagulated product was washed with water, dehydrated, and dried to obtain a coagulated powder (B2)-3. The melt viscosity of the solidified powder (B2)-3 at 240°C was 360 Pa·s.

(Manufacturing example 7)
Coagulated powder (B2)-4 was obtained in the same manner as in Production Example 7, except that the ratio of dispersion particles (A1)-1 and acrylic crosslinked rubber particles (B)-2 was changed to 20:80. The melt viscosity of the solidified powder (B2-4) at 240°C was 450 Pa·s.

Measurements of physical property values in Examples and Comparative Examples were carried out by the following methods.
[Melt viscosity]
Using a flow tester (CFT-500D model manufactured by Shimadzu Corporation), the resin sufficiently dried in an oven was transferred to methacrylic polymers (A) and (A2) through a Φ1 mm x 2 mm capillary at a load of 50 kgf/ ^cm2 . was measured at 200°C, and acrylic crosslinked rubber particles (B) and coagulated powder (B2) were measured at 240°C.

[Number of film defects]
The number of defects on the films produced under the conditions described in the Examples was visually evaluated.
For the latex containing acrylic crosslinked rubber particles, the volume average particle size (referred to as "average particle size" in this specification) was measured by a light scattering method using a laser diffraction/scattering type particle size distribution measuring device LA-920V2 manufactured by HORIBA, Ltd.

Example 1
75% by mass of the methacrylic polymer (A2)-1 and 25% by mass of the coagulated powder (B2)-1 described in Production Example 4 were melted in a Φ20 mm single screw extruder and extruded from a 150 mm wide die at an extrusion temperature of 260° C. to produce a film with a thickness of 60 μm. The number of defects in the obtained film was measured and evaluated.

(Example 2)
A film was produced in the same manner as in Example 1, except that the composition in Example 1 was changed to that shown in Table 1, and the film was evaluated in the same manner.

(Example 3)
40% by mass of methacrylic polymer (A2)-1 and 60% by mass of coagulated powder (B2)-2 described in Production Example 5 were melted in a Φ20mm single-screw extruder and extruded through a die with a width of 150mm at a temperature of 260°C. A film with a thickness of 60 μm was produced by extrusion. The number of defects in the obtained film was measured and evaluated.

(Example 4)
50% by mass of methacrylic polymer (A2)-2 and 50% by mass of coagulated powder (B2)-1 described in Production Example 4 were melted in a Φ20mm single-screw extruder and extruded through a die with a width of 150mm at a temperature of 260°C. A film with a thickness of 60 μm was produced by extrusion. The number of defects in the obtained film was measured and evaluated.

Example 5
10 parts by mass of methacrylic polymer (A2)-1 and 50 parts by mass of acrylic crosslinked rubber particles (B)-1 were melt-kneaded at 260°C in a twin-screw extruder and pelletized. The pellets and 50 parts by mass of methacrylic polymer (A2)-1 were melted in a Φ20 mm single-screw extruder and extruded from a die with a width of 150 mm at an extrusion temperature of 260°C to produce a film with a thickness of 60 μm. The number of defects in the obtained film was measured and evaluated. The results are shown in Table 1. A film was produced in the same manner as in Example 1 and evaluated in the same manner.

(Example 6)
50% by mass of methacrylic polymer (A2)-1 and 50% by mass of coagulated powder (B2)-3 described in Production Example 6 were melted in a Φ20mm single screw extruder and extruded through a die with a width of 150mm at a temperature of 260°C. A film with a thickness of 60 μm was produced by extrusion. The number of defects in the obtained film was measured and evaluated.

(Example 7)
50% by mass of the methacrylic polymer (A2)-1 and 50% by mass of the coagulated powder (B2)-4 described in Production Example 7 were melted in a Φ20 mm single screw extruder and extruded through a 150 mm wide die at an extrusion temperature of 260° C. to produce a film with a thickness of 60 μm. The number of defects in the obtained film was measured and evaluated.

(Example 8)
50% by mass of the methacrylic polymer (A2)-2 and 50% by mass of the coagulated powder (B2)-3 described in Production Example 6 were melted in a Φ20 mm single screw extruder and extruded through a 150 mm wide die at an extrusion temperature of 260° C. to produce a film with a thickness of 60 μm. The number of defects in the obtained film was measured and evaluated.

(Example 9)
50% by mass of methacrylic polymer (A2)-3 and 50% by mass of coagulated powder (B2)-3 described in Production Example 6 were melted in a Φ20mm single-screw extruder and extruded through a die with a width of 150mm at a temperature of 260°C. A film with a thickness of 60 μm was produced by extrusion. The number of defects in the obtained film was measured and evaluated.

(Comparative example 1)
In Example 2, a film was produced in the same manner as in Example 2, except that methacrylic polymer (A2)-1 was changed to (A2)-3, and evaluated in the same manner.

(Comparative Example 2)
In Comparative Example 2, except that the formulation was changed to that shown in Table 4, a film was produced in the same manner as in Comparative Example 2, and evaluation was performed in the same manner.

(Comparative example 3)
In Example 3, a film was produced in the same manner as in Example 3, except that methacrylic polymer (A2)-1 was changed to (A2)-3, and evaluated in the same manner.

(Comparative Example 4)
In Comparative Example 3, except that the formulation was changed to that shown in Table 4, a film was produced in the same manner as in Comparative Example 3, and evaluation was performed in the same manner.

(Comparative example 5)
10% by mass of methacrylic polymer (A2)-1 and 50% by mass of crosslinked acrylic rubber particles (B)-1 were melt-kneaded at 260°C in a twin-screw extruder and pelletized. Further, the pellets and 50 parts by mass of methacrylic polymer (A2-3) were melted in a Φ20 mm single screw extruder and extruded through a die with a width of 150 mm at an extrusion temperature of 260°C to produce a film with a thickness of 60 μm. The number of defects in the obtained film was measured and evaluated.

(Comparative example 6)
50% by mass of methacrylic polymer (A2)-4 and 50% by mass of coagulated powder (B2)-1 described in Production Example 4 were melted in a Φ20mm single-screw extruder and extruded through a die with a width of 150mm at a temperature of 260°C. A film with a thickness of 60 μm was produced by extrusion. The number of defects in the obtained film was measured and evaluated.

(Comparative Example 7)
40% by mass of the methacrylic polymer (A2)-4 and 60% by mass of the coagulated powder (B2)-2 described in Production Example 4 were melted in a Φ20 mm single screw extruder and extruded through a 150 mm wide die at an extrusion temperature of 260° C. to produce a film with a thickness of 60 μm. The number of defects in the obtained film was measured and evaluated.

*1 Number of film defects: Defects in an A4 size film: 〇: Very few, △: Not noticeable, ×: Noticeable

*1 Number of film defects: Defects in the A4 area film are: 〇: Extremely few, △: Not noticeable, ×: Conspicuous

The films obtained in Examples 1 to 4 had fewer defects than the films obtained in Comparative Examples 1 to 2, and the resin composition of the present invention had good dispersibility of crosslinked rubber particles and produced molded products with good appearance. It can be seen that the following can be obtained.

Claims (7)

Contains 10 to 90% by mass of a methacrylic polymer (A) and 90 to 10% by mass of acrylic crosslinked rubber particles (B),
The load of the acrylic crosslinked rubber particles (B) is 50 kgf/cm ² and the melt viscosity (ηA) measured using a flow tester at 200 °C and the methacrylic polymer (A) is 50 kgf/cm ² and 240 A method for producing a methacrylic resin composition having a melt viscosity ratio (ηB/ηA) of melt viscosity (ηB) measured using a flow tester at 0.1 to 5,
The methacrylic polymer (A) is
Dispersion particles (A1) consisting of methyl methacrylate units and acrylic ester units and having a weight average molecular weight of 55,000 to 160,000, and
Contains a methacrylic polymer (A2) whose melt viscosity (ηA2) measured using a flow tester at a load of 50 kgf/cm2 and ²⁰⁰ °C is 1000 to 30000 Pa・s and whose weight average molecular weight is 55000 to 160000. death,
The acrylic crosslinked rubber particles (B) are
A crosslinked polymer (R) whose core consists of a methyl methacrylate unit, a monofunctional monomer unit other than methyl methacrylate, and a polyfunctional monomer unit;
A crosslinked rubber polymer (Q) consisting of an acrylic ester unit whose inner shell has an alkyl group having 1 to 8 carbon atoms, a monofunctional monomer unit other than an acrylic ester, and a polyfunctional monomer unit;
A thermoplastic polymer (P) whose outer shell (outermost layer) consists of methyl methacrylate units and acrylic ester units;
the mass ratio of the layers other than the outermost layer to the outermost layer is 60/40 to 95/5, and the average particle diameter is 0.1 to 0.27 μm. rubber particles,
The melt viscosity (melt viscosity ⁽ A step of obtaining a coagulated powder (B2) with ηB2) of 100 to 10,000 Pa·s; and
Melting and kneading the obtained coagulated powder (B2) and the methacrylic polymer (A2);
The melt viscosity ratio (ηB2/ηA2) of the ηB2 to the ηA2 is 0.01 to 0.06.
A method for producing a methacrylic resin composition. The method for producing a methacrylic resin composition according to claim 1, comprising: 15 to 85% by mass of the methacrylic polymer (A); and 85 to 15% by mass of the acrylic crosslinked rubber particles (B). 2. The method for producing a methacrylic resin composition according to claim 1, wherein a mass ratio of the layer other than the outermost layer of the acrylic crosslinked rubber particles (B) to the outermost layer is 70/30 to 90/10. The method for producing a methacrylic resin composition according to claim 1, wherein the average particle size of the acrylic crosslinked rubber particles (B) is 0.2 to 0.25 μm. A coagulated powder (B2) comprising acrylic crosslinked rubber particles (B) , dispersing particles (A1) consisting of methyl methacrylate units and acrylic ester units and having a weight average molecular weight of 55,000 to 160,000;
A methacrylic polymer (A2) having a weight average molecular weight of 55,000 to 160,000 ;
A methacrylic resin composition comprising:
The acrylic crosslinked rubber particles (B) are
A crosslinked polymer (R) whose core consists of a methyl methacrylate unit, a monofunctional monomer unit other than methyl methacrylate, and a polyfunctional monomer unit;
A crosslinked rubber polymer (Q) consisting of an acrylic ester unit whose inner shell has an alkyl group having 1 to 8 carbon atoms, a monofunctional monomer unit other than an acrylic ester, and a polyfunctional monomer unit;
A thermoplastic polymer (P) whose outer shell (outermost layer) consists of methyl methacrylate units and acrylic ester units;
the mass ratio of the layers other than the outermost layer to the outermost layer is 60/40 to 95/5, and the average particle diameter is 0.1 to 0.27 μm. rubber particles,
Contains 10 to 90% by mass of a methacrylic polymer (A) consisting of the dispersible particles (A1) and the methacrylic polymer (A2), and 90 to 10% by mass of the acrylic crosslinked rubber particles (B). death,
The melt viscosity (ηA) of the methacrylic polymer ( A) measured using a flow tester under the conditions of a load of 50 kgf/cm ² and 200°C of the acrylic crosslinked rubber particles (B) and a temperature of 50 kgf/cm ² and 240°C A methacrylic resin composition having a melt viscosity ratio (ηB/ηA) of melt viscosity (ηB) measured using a flow tester under the following conditions : 0.1 to 5. A molded article comprising the methacrylic resin composition according to claim 5 . The molded article of claim 6 which is a film.