WO2020241822A1

WO2020241822A1 - Methacrylic copolymer and molded article

Info

Publication number: WO2020241822A1
Application number: PCT/JP2020/021319
Authority: WO
Inventors: 伸崇平岡; 広大松橋; 英孝田村
Original assignee: 株式会社クラレ
Priority date: 2019-05-29
Filing date: 2020-05-29
Publication date: 2020-12-03
Also published as: JPWO2020241822A1; JP7442520B2; TW202106732A

Abstract

A methacrylic copolymer which comprises 85.0-95.0 mass% monomer units derived from methyl methacrylate and 5.0-15.0 mass% monomer units derived from an acrylic ester and has a weight-average molecular weight Mw of 48,000-59,000 and in which the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn, Mw/Mn, is 2.1 or less and the ratio of the glass transition temperature Tg to the melt flow rate R measured under the conditions of 230°C and a load of 3.8 kg, Tg/R, is 5.0-1.5 °C·10-min/g.

Description

Methacrylic copolymer and molded article

The present invention relates to methacrylic copolymers and molded articles. More specifically, the present invention relates to a methacrylic copolymer having excellent fluidity during heat molding and less mold stain, and a molded product having high heat resistance and high mechanical strength.

Methacrylic resin has high transparency and is useful as a material for molded products used for optical members, lighting members, signboard members, decorative members and the like. In some fields where molded products of methacrylic resin are used, there is a demand for weight reduction or thinning of molded products.
In order to obtain a thin-walled molded product, it is necessary for the methacrylic resin to have high fluidity when melted. As measures for increasing the fluidity of the resin, it is generally known to lower the softening temperature or the glass transition temperature, lower the molecular weight, widen the molecular weight distribution, and the like. However, when these measures are applied to methacrylic resin, the heat resistance is lowered and the mechanical strength is lowered. In consideration of such a situation, Cited Documents 1 to 3 propose various methacrylic resins and methods for producing the same.

WO 2013/161265 A1 Japanese Unexamined Patent Publication No. 2017/178975 WO 2017/146169 A1

An object of the present invention is to provide a methacrylic copolymer having excellent fluidity during heat molding and less mold stain, and a molded product having high heat resistance and high mechanical strength.

As a result of repeated studies to solve the above problems, the present invention including the following forms has been completed.

[1] Containing 85.0 to 95.0% by mass of a monomer unit derived from methyl methacrylate and 5.0 to 15.0% by mass of a monomer unit derived from an acrylic acid ester.
Weight average molecular weight Mw is 48,000-59000,
The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn is 2.1 or less, and the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R under the conditions of 230 ° C. and a 3.8 kg load is 5.0. A methacrylic copolymer at ~ 1.5 ° C. for 10 minutes / g.
[2] The methacrylic according to [1], wherein the amount of bound sulfur atoms with respect to the monomer unit derived from methyl methacrylate is 0.4 mol% or less, and the melt flow rate R is 25 g / 10 minutes or more. Polymer.

[3] A thermoplastic resin composition containing the methacrylic copolymer according to [1] or [2] and acrylic rubber particles.
[4] The thermoplastic resin composition according to [3], which further contains an acrylic block copolymer.
[5] The amount of the acetone-insoluble content contained in the thermoplastic resin composition is 59% by mass or less, and the acetone-soluble content contained in the thermoplastic resin composition is under the conditions of 230 ° C. and a load of 3.8 kg. The thermoplastic resin composition according to [3] or [4], wherein the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R in the above is 6.0 to 1.5 ° C. for 10 minutes / g.

[6] Pellet-shaped molding material containing the methacrylic copolymer according to [1] or [2] [7] A molded product containing the methacrylic copolymer according to [1] or [2]. ..
[8] The molded product according to [7], which is in the form of a plate having a thickness of 0.5 mm or less.
[9] A housing for a mobile phone terminal containing the methacrylic copolymer according to [1] or [2].
[10] A housing for a mobile phone terminal having a portion having a thickness of 0.8 mm or less and containing the methacrylic copolymer according to [1] or [2].
[11] An optical member containing the methacrylic copolymer according to [1] or [2].

[12] The method for producing a methacrylic copolymer according to claim 1 or 2, which comprises subjecting a monomer containing methyl methacrylate and an acrylic acid ester to a polymerization reaction by a massive polymerization method.

[13] 100 parts by mass of a monomer containing at least 81.0 to 94.2% by mass of methyl methacrylate and 5.8 to 19.0% by mass of an acrylic acid ester, 0.42 to 0.52 parts by mass of a chain transfer agent. , And the polymerization initiator was supplied to a continuous flow reactor with an average residence time of 1.5 to 3 hours and polymerized at a temperature of 110 to 140 ° C. without using a solvent and having a polymerization conversion rate of 35 to 65%.
It then comprises removing unreacted monomers by heating and devolatile at 220-260 ° C.
Containing 85-95.0% by mass of structural units derived from methyl methacrylate and 5.0-15.0% by mass of structural units derived from acrylic ester.
Weight average molecular weight Mw is 48,000-59000,
The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn is 2.1 or less, and the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R under the conditions of 230 ° C. and a 3.8 kg load is 5.0. A method for producing a methacrylic copolymer at ~ 1.5 ° C. for 10 minutes / g.

The methacrylic copolymer of the present invention has excellent fluidity and is unlikely to cause molding defects such as silver streaks, cracks, sink marks, flow marks, resin burns, gas stains, and coloring. The molding material containing the methacrylic copolymer of the present invention is suitable for injection molding. The molding material containing the methacrylic copolymer of the present invention is suitable for obtaining a thin-walled molded product, for example, a plate having a thickness of 0.5 mm or less. The molded product containing the methacrylic copolymer of the present invention has high heat resistance and mechanical strength, and has no appearance defects such as coloring. The molding material containing the methacrylic copolymer of the present invention has low heat generation due to shearing, and an injection-molded product having a good appearance can be obtained even at a low temperature and a high injection pressure.

The methacrylic copolymer of the present invention comprises a monomer unit derived from methyl methacrylate and a monomer unit derived from an acrylic acid ester.
The content of the monomer unit derived from methyl methacrylate is 85.0 to 95.0% by mass, preferably 85.0 to 93.5% by mass, and more preferably 87.5 to 93.5% by mass. More preferably, it is 88 to 93.5% by mass. The content of the monomer unit derived from the acrylic acid ester is 5.0 to 15.0% by mass, preferably 6.5 to 15.0% by mass, and more preferably 6.5 to 12.5% by mass. More preferably, it is 6.5 to 12% by mass. In the methacrylic copolymer of the present invention, the total of the monomer unit derived from methyl methacrylate and the monomer unit derived from the acrylic acid ester is preferably 99% by mass or more, preferably 100% by mass. Is more preferable.

Acrylate esters include acrylic acids such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, myristyl acrylate, dodecyl acrylate, palmityl acrylate, stearyl acrylate, and behenyl acrylate. Linear alkyl ester; Acrylic acid branched alkyl ester such as isopropyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate; Acrylic acid cyclic alkyl ester such as cyclohexyl acrylate; Acrylic acid aryl ester such as phenyl acrylate; benzyl acrylate and the like Acrylate aralkyl ester; etc. Of these, acrylic acid linear, branched or cyclic alkyl esters are preferred, and acrylic acid linear alkyl esters are more preferred. The alkyl group in the acrylic acid alkyl ester preferably has 1 to 18, more preferably 1 or 2, and even more preferably 1.

The methacrylic copolymer of the present invention may have a monomer unit other than a monomer unit derived from methyl methacrylate and a monomer unit derived from an acrylic acid ester, and such a single amount may be present. As the body, an alkyl ester of acyclic C2 or more of methacrylic acid such as ethyl methacrylate, butyl butyl methacrylate, hexyl methacrylate, and heptyl methacrylate, preferably an alkyl ester of acyclic C2 or more and C7 or less of methacrylic acid; bicyclo methacrylate [3]. .2.1] Octyl, Tricyclo Methacrylic Acid [3.2.1.0 ^2,7 ] Octyl, Tricyclo Methacrylic Acid [5.2.1.0 ^2,6 ] Decyl, 3,9: 8,10 Methacrylic Acid -Methacrylic acid cyclic alkyl ester such as dimethanotricyclo [4.2.1.1 ^2,5 ] decyl; aromatic vinyl such as styrene and methylstyrene can be mentioned. The content of these monomer units is preferably 1% by mass or less. In addition, "C2 or more and C7 or less" means that the number of carbon atoms constituting the alkyl group is 2 or more and 7 or less.

From the viewpoint of toughness, surface hardness, etc., the methacrylic copolymer of the present invention has a weight average molecular weight Mw and a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn, both of which are within the following ranges. That is, the methacrylic copolymer of the present invention has a weight average molecular weight Mw of 48,000 to 59000, preferably 48,000 to 55,000, and more preferably 49000 to 53000, and the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is Mw / Mn. However, it is 2.1 or less, preferably 1.7 or more and 2.0 or less. The weight average molecular weight Mw and the number average molecular weight Mn are values calculated by converting the chart measured by gel permeation chromatography into the molecular weight of standard polystyrene.

In the methacrylic copolymer of the present invention, the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R under the conditions of 230 ° C. and a 3.8 kg load is preferably 5.0 to 1.5 ° C. for 10 minutes / g. Is 4.0 to 1.5 ° C. for 10 minutes / g, more preferably 3.5 to 1.5 ° C. for 10 minutes / g, and even more preferably 3.3 to 1.5 ° C. for 10 minutes / g. ..
The glass transition temperature is once raised to 230 ° C. using a differential scanning calorimetry device (manufactured by Shimadzu Corporation, DSC-50 (product number)) in accordance with JIS K7121, then cooled to room temperature, and then to room temperature. The DSC curve was measured under the condition that the temperature was raised from 1 to 230 ° C. at 10 ° C./min. It is an intermediate point glass transition temperature (Tmg) determined based on the DSC curve measured at the time of the second temperature rise. The melt flow rate is a value measured under the conditions of 230 ° C., 3.8 kg load, and 10 minutes in accordance with JIS K7210.

The lower limit of the melt flow rate R of the methacrylic copolymer of the present invention measured at 230 ° C. and a load of 3.8 kg is preferably 15 g / 10 minutes, more preferably 25 g / 10 from the viewpoint of moldability, toughness and the like. Minutes, with an upper limit of preferably 60 g / 10 minutes.

In the methacrylic copolymer of the present invention, the amount of bound sulfur atom with respect to the monomer unit derived from methyl methacrylate is preferably 0.4 mol% or less, more preferably 0.3 to 0.38 mol%, still more preferably. It is 0.31 to 0.36 mol%. The amount of sulfur bond is related to imparting good moldability, low mold stain, and high fluidity to the methacrylic copolymer.
The amount of bound sulfur atom is a value S _p which is determined as follows.
The methacrylic copolymer is dissolved in chloroform to obtain a solution. This solution is added to n-hexane to give a precipitate. The precipitate is dried at 80 ° C. for 12 hours or longer under vacuum. An appropriate amount of the obtained dried product is precisely weighed, set in a sulfur combustion device, decomposed in a reactor having a temperature of 400 ° C., and the generated gas is passed through a furnace having a temperature of 900 ° C., and then 0.3% hydrogen peroxide solution is used. Absorb with. The obtained liquid (decomposition gas aqueous solution) is appropriately diluted with pure water, and sulfate ions are quantified by ion chromatography (ICS-1500 manufactured by DIONEX, column: AS12A). From the mass W _p (mass%) of sulfur atoms per mass of the dried product, the amount of bound sulfur atoms (mol%) with respect to the monomer unit derived from methyl methacrylate is calculated.

The method for producing the methacrylic copolymer of the present invention is not particularly limited. For example, it can be produced by a known polymerization reaction such as a radical polymerization reaction or an anionic polymerization reaction. In the present invention, a radical polymerization reaction is preferable. The polymerization reaction can be carried out by a suspension polymerization method, a bulk polymerization method, a solution polymerization method, or an emulsion polymerization method. Of these polymerization methods, the massive polymerization method is preferable because it contains less impurities. In the massive polymerization method, the polymerization conversion rate is preferably 35 to 65%. The bulk polymerization method is preferably carried out by a continuous flow method. In the continuous flow type massive polymerization method, the average residence time in the reactor is preferably 1.5 to 3 hours.

A preferred method for producing the methacrylic copolymer of the present invention is a monomer containing methyl methacrylate and an acrylic acid ester, preferably methyl methacrylate 81.0 to 94.2% by mass and an acrylic acid ester 5.8 to 19. A monomer containing at least 0% by mass, more preferably a monomer containing 81.0 to 91.9% by mass of methyl methacrylate and 8.1 to 19.0% by mass of an acrylic acid ester are polymerized by a massive polymerization method. Including that. Acrylic acid esters are involved in imparting high fluidity and high melt flow rate R to methacrylic copolymers. In addition to methyl methacrylate and acrylic acid ester, the monomers used for polymerization include methacrylic acid acyclic C2 or more alkyl ester (preferably methacrylic acid acyclic C2 or more and C7 or less alkyl ester), methacrylic acid cyclic alkyl ester; Aromatic vinyl such as styrene and methylstyrene may be contained. The content of these monomers other than methyl methacrylate and acrylic acid ester is preferably 1% by mass or less. In the production method of the present invention, the total amount of methyl methacrylate and acrylic acid ester contained in the monomer to be polymerized is preferably 99% by mass or more, and more preferably 100% by mass.

The polymerization reaction is carried out using a polymerization initiator, a predetermined monomer, and if necessary, a chain transfer agent or the like. The temperature at the time of polymerization is preferably 100 to 150 ° C, more preferably 110 to 140 ° C, and even more preferably 120 to 140 ° C. The lower the polymerization temperature, the higher the heat resistance of the methacrylic copolymer of the present invention tends to be.

The polymerization initiator used in the present invention is not particularly limited. For example, an azo-based polymerization initiator such as azobisisobutyronitrile; a peroxide-based polymerization initiator such as t-hexyl peroxyisopropyl monocarbonate and the like can be mentioned. The polymerization initiator used in the present invention preferably has a half-life of 1 second to 1 minute at the temperature at the time of polymerization. When the amount of the polymerization initiator used is small, the methacrylic copolymer of the present invention tends to have less mold stain. From the viewpoint of reducing mold stains, for example, azobisisobutyronitrile is preferably 0.02 parts by mass or less, more preferably 0 parts by mass, based on a total of 100 parts by mass of the monomers to be polymerized. It can be used in an amount of .002 parts by mass or more and 0.01 parts by mass or less.

The chain transfer agent used in the present invention is not particularly limited. For example, mercaptan chain transfer agents such as n-octyl mercaptan and n-dodecyl mercaptan; α-methylstyrene dimer; terpinolene and the like can be mentioned. The amount of the chain transfer agent used is preferably 0.42 to 0.52 parts by mass with respect to a total of 100 parts by mass of the monomers to be polymerized. As the amount of the mercaptan chain transfer agent used increases, the amount of bound sulfur atoms with respect to the monomer unit derived from methyl methacrylate increases. From the viewpoint of good injection moldability, less mold contamination, and high fluidity, for example, n-octyl mercaptan is preferably 0.3 mass by mass with respect to 100 parts by mass of the total amount of the monomers to be polymerized. It can be used in an amount of 0.6 parts by mass or more, more preferably 0.41 parts by mass or more and 0.50 parts by mass or less.

After the polymerization reaction, it is preferable to remove the unreacted monomer from the reaction product. The unreacted monomer is preferably removed by a thermal devolatile method at a temperature of 220 to 260 ° C. In the addition / volatilization method, volatile components are removed from a device for heating a liquid containing a reaction product discharged from a reactor, for example, a heat exchanger and a liquid heated to a predetermined temperature by the device for heating. An extruder with a vent for removal is preferably used. A vented extruder usually consists of a cylinder and a screw. The cylinder is provided with a hopper (introduction port for liquid including reaction products), a rear vent on the upstream side of the hopper, a front vent on the downstream side of the hopper, and a polymer discharge port on the most downstream side. Then, it is preferable to set the temperature and pressure in the hopper and the cylinder so that the liquid heated in the hopper evaporates in a flash. The removed volatile matter is discharged from the rear vent and the front vent. Then, it is preferable to add an inert gas such as nitrogen gas at the rear vent and / or the front vent to the volatile matter discharged through the rear vent and / or the front vent. Further, the screw may be either a single shaft type or a biaxial type. The screw may, for example, have a smaller shaft diameter of the screw in that portion than that of the other portion so as to release pressure at the portion corresponding to the front vent. Further, a valve mechanism for providing a dynamic valve immediately before the front vent, or a bypass mechanism for providing a reverse screw portion on the screw immediately before the front vent and providing a bypass connecting immediately before and after the front vent in the cylinder may be provided.

The thermoplastic resin composition of the present invention contains the methacrylic copolymer of the present invention and acrylic rubber particles.

Examples of the acrylic rubber particles include those composed of an outer layer made of a thermoplastic polymer (P) and an inner layer made of a crosslinked elastic body in contact with and covered with the outer layer, and the inner layer and the outer layer are a core and a shell. It is preferable that the above is formed. The inner layer consists of a core and an inner shell. In the acrylic rubber particles, for example, the core (inner layer) is a crosslinked rubber polymer (Q) -the outer shell (outer layer) is a thermoplastic polymer (P), and the core (inner layer) is a crosslinked polymer (R). ) -Inner shell (inner layer) is a crosslinked rubber polymer (Q) -Outer shell (outer layer) is a three-layer polymer of thermoplastic polymer (P), core (inner layer) is a crosslinked rubber polymer (Q) -First A four-layer polymer in which the inner shell (inner layer) is a crosslinked polymer (R) -the second inner shell (inner layer) is a crosslinked rubber polymer (Q) -the outer shell (outer layer) is a thermoplastic polymer (P). be able to.

From the viewpoint of transparency, the polymer contained in each layer so that the difference in refractive index between adjacent layers is preferably less than 0.005, more preferably less than 0.004, and even more preferably less than 0.003. It is preferable to select.

The mass ratio of the inner layer to the outer layer of the acrylic rubber particles is preferably 60/40 to 95/5, more preferably 70/30 to 90/10. In the inner layer, the ratio of the layer containing the crosslinked rubber polymer (Q) is preferably 20 to 70% by mass, more preferably 30 to 50% by mass.

The acrylic rubber particles have an average particle diameter of preferably 0.05 to 3 μm, more preferably 0.1 to 1 μm, and even more preferably 0.15 to 0.2 μm. By having an average particle size within such a range, particularly an average particle size of 0.15 to 0.2 μm, toughness can be exhibited with a small amount of compounding, and therefore rigidity and surface hardness are not impaired. .. The average particle size in the present specification is an average value in a volume-based particle size distribution measured by a light scattered light method.

The thermoplastic polymer (P) is a polymer composed of 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. The thermoplastic polymer (P) preferably does not contain a polyfunctional monomer unit.

The amount of the methacrylic acid alkyl ester unit having an alkyl group having 1 to 8 carbon atoms constituting the thermoplastic polymer (P) is preferably 80 to 100% by mass with respect to the mass of the thermoplastic polymer (P). More preferably, it is 85 to 95% by mass.

As the methacrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms (hereinafter, may be referred to as methacrylic acid C1-8 alkyl ester), for example, methyl methacrylate is preferable.

The amount of the monofunctional monomer unit other than the methacrylic acid C1-8 alkyl ester constituting the thermoplastic polymer (P) is preferably 0 to 20% by mass with respect to the mass of the thermoplastic polymer (P). More preferably, it is 5 to 15% by mass.
Examples of monofunctional monomers other than methacrylic acid C1-8 alkyl ester include acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and prol acrylate; aromatic vinyl such as styrene. Compounds can be mentioned.

The amount of the thermoplastic polymer (P) is preferably 40 to 75% by mass, more preferably 45 to 70% by mass, and further preferably 50 to 65% by mass with respect to the acrylic rubber particles.

The crosslinked elastic layer, which is an inner layer, has an intermediate layer made of a crosslinked rubber polymer (Q) and an inner layer made of a crosslinked polymer (R) and covered in contact with the intermediate layer.

The crosslinked polymer (R) is composed of a methyl methacrylate unit, a monofunctional monomer unit other than methyl methacrylate, and a polyfunctional monomer unit.

The amount of the methyl methacrylate unit 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 the monofunctional monomer unit 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 the monofunctional monomer other than methyl methacrylate include acrylic acid 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 0.1, based on the mass of the crosslinked polymer (R). It is 0.3% by mass.
Examples of the polyfunctional monomer include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, triethylene glycol dimethacrylate, hexanediol dimethacrylate, ethylene glycol diacrylate, propylene glycol diacrylate, triethylene glycol diacrylate, allyl methacrylate, and triallyl. Isocyanurate and the like can be mentioned.

The amount of the crosslinked polymer (R) is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and further preferably 10 to 30% by mass with respect to the acrylic rubber particles.

The crosslinked rubber polymer (Q) is composed of an acrylic acid alkyl ester unit having an alkyl group having 1 to 8 carbon atoms and / or a conjugated diene unit, and a polyfunctional monomer unit.

The amount of the acrylic acid alkyl ester unit and / or the conjugated diene unit having an alkyl group having 1 to 8 carbon atoms constituting the crosslinked rubber polymer (Q) is preferable with respect to the mass of the crosslinked rubber polymer (Q). It is 85 to 99% by mass, more preferably 95 to 98% by mass.

Examples of the acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and propyl acrylate.

The amount of the polyfunctional monomer unit constituting the crosslinked rubber polymer (Q) is preferably 1 to 1.7% by mass, more preferably 1.2 to 1% by mass, based on the mass of the crosslinked rubber polymer (Q). It is 1.6% by mass, more preferably 1.3 to 1.5% by mass.
Examples of the polyfunctional monomer include those mentioned in the crosslinked polymer (R).

From the viewpoint of improving bending resistance, the ratio of the mass of the polyfunctional monomer unit in the crosslinked rubber polymer (Q) to the mass of the polyfunctional monomer unit in the crosslinked polymer (R) is preferable. It is 0.05 to 0.25, more preferably 0.1 to 0.2. The glass transition temperature of the crosslinked rubber polymer (Q) is preferably lower than the glass transition temperature of the crosslinked polymer (R).

The amount of the crosslinked rubber polymer (Q) is preferably 20 to 55% by mass, more preferably 25 to 45% by mass, and further preferably 30 to 40% by mass with respect to the amount of acrylic rubber particles.

The average diameter of the inner layer of the acrylic rubber particles is preferably 60 to 110 nm, more preferably 65 to 105 nm, and further preferably 70 to 100 nm. The average diameter of the inner layer can be determined as follows. Using a hydraulic press molding machine, mold size 50 mm x 120 mm, press temperature 250 ° C, preheating time 3 minutes, press pressure 50 kg / cm ² , press time 30 seconds, cooling temperature 20 ° C, cooling pressure 50 kg / cm ^{2. Under} the condition that the cooling time is 10 minutes, the resin composition containing the acrylic rubber particles is molded into a flat plate having a thickness of 3 mm. Using a microtome, the obtained flat plate is cut at −100 ° C. in a direction parallel to the long side to obtain a slice having a thickness of 40 nm, and the slice is dyed with ruthenium. The dyed flakes are observed with a scanning transmission electron microscope (JSM7600F manufactured by JEOL Ltd.) at an accelerating voltage of 25 kV and a photograph is taken. Measure the minor axis and major axis of the ruthenium-stained part (exposed part of the crosslinked elastic layer), set (minor axis + major axis) / 2 as the diameter of the inner layer, measure 20 or more, and then average the number. Calculate (average diameter).

The acrylic rubber particles are not particularly limited depending on the production method thereof. For example, emulsion polymerization and the like can be mentioned.
In the case of emulsion polymerization, for example, the monomer (r) for forming the crosslinked polymer (R) is emulsion-polymerized to obtain a latex containing the crosslinked polymer (R), and the crosslinked rubber polymer (R) is obtained. A monomer (q) for constituting Q) is added, and the monomer (q) is seed-emulsified polymerized to obtain a latex containing a crosslinked polymer (R) and a crosslinked rubber polymer (q). , A monomer (p) for forming a thermoplastic polymer (P) is added thereto, and the monomer (p) is seed-emulsified polymerized to obtain a latex containing acrylic 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 monomer polymerization reaction is carried out on the surface of seed particles. Seed emulsion polymerization is preferably used to obtain core-shell structural polymer particles.

The thermoplastic resin composition of the present invention can further contain an acrylic block copolymer.

The acrylic block copolymer is preferably composed of a polymer block (b1) having a methacrylic acid ester unit as a main component and a polymer block (b2) having an acrylic acid ester unit as a main component. The number of polymer blocks (b1) in one molecule of the acrylic block copolymer may be 1, or may be 2 or more. Further, the number of polymer blocks (b2) in one molecule of the acrylic block copolymer may be 1, or may be 2 or more.

The amount of the methacrylic acid ester unit contained in the polymer block (b1) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 98% by mass or more. .. As the methacrylic acid ester, for example, methyl methacrylate is preferable. The methacrylic acid ester can be used alone or in combination of two or more for the polymer block (b1).

The amount of the polymer block (b1) contained in the acrylic block copolymer is preferable from the viewpoints of transparency, flexibility, bending resistance, impact resistance, flexibility, molding processability, surface smoothness, and the like. Is 40% by mass or more and 90% by mass or less, more preferably 45% by mass or more and 80% by mass or less.

The glass transition temperature of the polymer block (b2) is preferably 20 ° C. or lower, more preferably −20 ° C. or lower.

The amount of the acrylic ester unit contained in the polymer block (b2) is preferably 90% by mass or more. Examples of the acrylic acid ester include n-butyl acrylate and benzyl acrylate. These acrylic acid esters can be used alone or in combination of two or more for the polymer block (b2).

The polymer block (b2) may contain monomer units other than the acrylic acid ester as long as it does not interfere with the object and effect of the present invention.

The polymer block (b2) is preferably composed of an acrylic acid alkyl ester unit and a (meth) acrylic acid aromatic ester unit from the viewpoint of transparency and the like. The mass ratio of the acrylic acid alkyl ester unit / (meth) acrylic acid aromatic ester is preferably 50/50 to 90/10, more preferably 60/40 to 80/20.

The bond form between the polymer block (b1) and the polymer block (b2) contained in the acrylic block copolymer is not particularly limited. For example, one end of a polymer block (b1) connected to one end of a polymer block (b2) (b1-b2 diblock copolymer); a polymer at both ends of a polymer block (b2). A block (b1) in which one end is connected (b1-b2-b1 triblock copolymer) is preferable.

The weight average molecular weight of the acrylic block copolymer is preferably 52,000 or more and 400,000 or less, and more preferably 60,000 or more and 300,000 or less. Further, in the acrylic block copolymer, the ratio of the weight average molecular weight to the number average molecular weight is preferably 1.01 or more and 2.00 or less, and more preferably 1.05 or more and 1.60 or less. The weight average molecular weight and the number average molecular weight of the acrylic block copolymer can be appropriately set from the viewpoints of moldability, tensile strength, appearance and the like. The weight average molecular weight and the number average molecular weight are standard polystyrene-equivalent values measured by GPC (gel permeation chromatography).

The acrylic block copolymer is not particularly limited depending on the production method thereof, and can be obtained by a known method. For example, a method including living polymerization of the monomers constituting each polymer block is generally used. As a living polymerization method, a method including anionic polymerization in the presence of an organoalkali metal compound and an organoaluminum compound is a method in which the molecular weight and composition ratio can be easily controlled, the production cost, and the obtained acrylic block copolymer. It is preferable from the viewpoint of purity.

The amount of acetone insoluble matter contained in the thermoplastic resin composition of the present invention is preferably 59% by mass or less, more preferably 50% by mass or less, and further preferably 45% by mass.

The amount of acetone insoluble matter contained in the thermoplastic resin composition is determined as follows. 2 g (w0) of the precisely weighed thermoplastic resin composition is added to 50 ml of acetone, and the mixture is stirred at room temperature for 24 hours. The obtained liquid is placed in a centrifuge tube and centrifuged at 0 ° C. and 20000 rpm for 180 minutes. The supernatant is then removed by decantation. Acetone is added to the centrifuge tube and stirred. Centrifuge at 5 ° C. and 20000 rpm for 120 minutes. The supernatant is then removed by decantation. The centrifuge is taken out from the bottom of the centrifuge tube, dried at 50 ° C. under reduced pressure, and its mass w1 is measured.
The amount (percentage) of acetone insoluble matter is calculated by the formula: 100 × w1 / w0.
The amount (percentage) of the acetone-soluble component is calculated by the formula: 100 × (w0-w1) / w0.

The acetone-soluble component contained in the thermoplastic resin composition of the present invention can be obtained by drying the supernatant at 50 ° C. under reduced pressure. As for the acetone-soluble content, the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R under the conditions of 230 ° C. and a 3.8 kg load is preferably 6.0 to 1.5 ° C. for 10 minutes / g, more preferably. Is 5.6 to 2.0 ° C. for 10 minutes / g.

The acetone-soluble component contained in the thermoplastic resin composition of the present invention has a glass transition temperature of preferably 90 to 115 ° C, more preferably 95 to 110 ° C.

The acetone-soluble component contained in the thermoplastic resin composition of the present invention has a melt flow rate R of preferably 15 to 60 g / 10 minutes, more preferably 20 to 55 g / 10 under the conditions of 230 ° C. and a load of 3.8 kg. Minutes.

The molding material of the present invention contains the methacrylic copolymer (or thermoplastic resin composition) of the present invention. The molding material of the present invention is an antioxidant, a heat deterioration inhibitor, an ultraviolet absorber, a light stabilizer, a lubricant, a mold release agent, a polymer processing aid, an antistatic agent, as long as the effects of the present invention are not impaired. Additives such as flame retardant, dye pigment, light diffusing agent, organic dye, matting agent, impact resistance modifier, and phosphor may be further contained.

The antioxidant is effective in preventing oxidative deterioration of the resin by itself in the presence of oxygen. For example, phosphorus-based antioxidants, hindered phenol-based antioxidants, thioether-based antioxidants, and the like can be mentioned. Of these, phosphorus-based antioxidants and hindered phenol-based antioxidants are preferable from the viewpoint of the effect of preventing deterioration of optical properties due to coloring, and the combined use of phosphorus-based antioxidants and hindered phenol-based antioxidants is more preferable. preferable.
When a phosphorus-based antioxidant and a hindered phenol-based antioxidant are used in combination, it is recommended to use a phosphorus-based antioxidant / hindered phenol-based antioxidant in a mass ratio of 0.2 / 1 to 2/1. It is preferably used at 0.5 / 1/1 to 1/1, more preferably.

Phosphorus antioxidants include 2,2-methylenebis (4,6-di-t-butylphenyl) octylphosphite (manufactured by ADEKA; trade name: ADEKA STAB HP-10), tris (2,4-di-). t-butylphenyl) phosphite (manufactured by BASF; trade name: IRUGAFOS168), 3,9-bis (2,6-di-t-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa 3 , 9-Diphosphaspiro [5.5] Undecan (manufactured by ADEKA; trade name: ADEKA STAB PEP-36) and the like.

As hindered phenolic antioxidants, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by BASF; trade name IRGANOX1010), octadecyl-3- (3,5-Di-t-butyl-4-hydroxyphenyl) propionate (manufactured by BASF; trade name IRGANOX1076) and the like are preferable.

As the heat deterioration inhibitor, the heat deterioration of the resin can be prevented by capturing the polymer radicals generated when exposed to high heat under a substantially oxygen-free state.
Examples of the heat deterioration inhibitor include 2-t-butyl-6- (3'-t-butyl-5'-methyl-hydroxybenzyl) -4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name: Sumilyzer GM). 2,4-dit-amyl-6- (3', 5'-di-t-amyl-2'-hydroxy-α-methylbenzyl) phenylacrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumilyzer GS) and the like are preferable. ..

The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays, and is said to have a function of mainly converting light energy into heat energy.
Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, oxalic acid anilides, malonic acid esters, formamidines and the like. Among these, benzotriazoles, triazines, and ultraviolet absorbers having a maximum molar extinction coefficient ε _max of 100 dm ³ · mol ^-1 cm ^-1 or less at a wavelength of 380 to 450 nm are preferable.

Benzotriazoles are highly effective in suppressing deterioration of optical properties such as coloring due to exposure to ultraviolet rays, and are therefore preferable as an ultraviolet absorber used when the molded product of the present invention is applied to optical applications. Examples of benzotriazoles include 2- (2H-benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (manufactured by BASF; trade name TINUVIN329), 2- (2H-). Benzotriazole-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (manufactured by BASF; trade name TINUVIN234), 2,2'-methylenebis [6- (2H-benzotriazole-2) -Il) -4-t-octylphenol] (manufactured by ADEKA; LA-31) and the like are preferable.

Further, an ultraviolet absorber having a maximum molar extinction coefficient ε _max of 1200 dm ³ · mol ^-1 cm ^-1 or less at a wavelength of 380 to 450 nm can suppress discoloration of the obtained molded product. Examples of such an ultraviolet absorber include 2-ethyl-2'-ethoxy-oxalanilide (manufactured by Clariant Japan Co., Ltd .; trade name: Sandeuboa VSU).
Among these UV absorbers, benzotriazoles are preferably used from the viewpoint of suppressing resin deterioration due to UV exposure.

Further, when it is desired to efficiently absorb a short wavelength having a wavelength of 380 nm or less, a triazine-type ultraviolet absorber is preferably used. Examples of such an ultraviolet absorber include 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine (manufactured by ADEKA; LA-F70). Examples thereof include hydroxyphenyltriazine-based ultraviolet absorbers (manufactured by BASF; TINUVIN 477 and TINUVIN 460), which are related thereto.

The maximum value ε _max of the molar extinction coefficient of the ultraviolet absorber is measured as follows. 10.00 mg of an ultraviolet absorber is added to 1 L of cyclohexane and dissolved so that there is no undissolved substance by visual observation. This solution is injected into a quartz glass cell of 1 cm × 1 cm × 3 cm, and the absorbance at a wavelength of 380 to 450 nm and an optical path length of 1 cm is measured using a U-3410 spectrophotometer manufactured by Hitachi, Ltd. The maximum value ε _max of the molar extinction coefficient is calculated from the molecular weight ( _MVV ) of the ultraviolet absorber and the maximum value (A _max ) of the measured absorbance by the following equation.
ε _max = [A _max / (10 × 10 ^-3 )] × M _UV

The light stabilizer is a compound that is said to have a function of capturing radicals mainly generated by oxidation by light. Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

Examples of the lubricant include stearic acid, behenic acid, stearoamic acid, methylene bisstearoamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, and hydrogenated oil. Increasing the amount of lubricant used tends to increase the melt flow rate R of the molding material of the present invention and increase the fluidity.

The mold release agent is a compound having a function of facilitating separation of a molded product from a mold. Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; and glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride. In the present invention, it is preferable to use higher alcohols and glycerin fatty acid monoester in combination as a release agent. When the higher alcohols and the glycerin fatty acid monoester are used in combination, the mass ratio of the higher alcohols / glycerin fatty acid monoester is preferably in the range of 2.5 / 1 to 3.5 / 1, 2.8. It is more preferable to use it in the range of / 1 to 3.2 / 1.

As the polymer processing aid, for example, polymer particles having a particle size of 0.05 to 0.5 μm can be used. The polymer particles may be single-layer particles composed of polymers having a single composition ratio and a single ultimate viscosity, or multilayer particles composed of two or more kinds of polymers having different composition ratios or ultimate viscosities. You may. Among these, particles having a two-layer structure having a polymer layer having a low ultimate viscosity in the inner layer and a polymer layer having a high ultimate viscosity of 5 dl / g or more in the outer layer are preferable. The polymer processing aid preferably has an ultimate viscosity of 3 to 6 dl / g. Specific examples thereof include the Metabren-P series manufactured by Mitsubishi Rayon and the Pararoid series manufactured by Dow Chemical. The amount of the polymer processing aid used is preferably 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the methacrylic copolymer. Good processing characteristics are obtained when the amount of the polymer processing aid used is 0.1 parts by mass or more, and surface smoothness is good when the amount of the polymer processing aid used is 5 parts by mass or less.

Examples of the impact resistance modifier include a core-shell type modifier containing acrylic rubber or diene rubber as a core layer component; and a modifier containing a plurality of rubber particles.
As the organic dye, a compound having a function of converting ultraviolet rays, which are considered to be harmful to the resin, into visible light is preferably used.
Examples of the light diffusing agent and the matting agent include glass fine particles, polysiloxane-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, barium sulfate and the like.
Examples of the phosphor include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent whitening agents, and fluorescent bleaching agents.

These additives may be used alone or in combination of two or more. These additives may be added at the time of producing the methacrylic copolymer, or may be added to the produced methacrylic copolymer. The total amount of the additives contained in the methacrylic copolymer of the present invention is preferably 1% by mass or less, more preferably 0.% by mass, based on the methacrylic copolymer resin, from the viewpoint of suppressing poor appearance of the molded product. It is 8% by mass or less, more preferably 0.5% by mass or less.

The methacrylic copolymer or thermoplastic resin composition of the present invention can be used as a molding material in any form such as pellets, granules, and powder in order to enhance convenience such as transportation and storage.

The molded product of the present invention can be obtained by molding the methacrylic copolymer (or thermoplastic resin composition or molding material) of the present invention. Molding can be performed by a known method such as an injection molding method, a compression molding method, an extrusion molding method, a vacuum forming method, or a cast molding method. Of these, the injection molding method is preferable. The methacrylic copolymer of the present invention can provide a thin-walled and wide-area molded product with little residual strain and almost no coloring even when injection-molded at a low cylinder temperature and a high injection pressure with high production efficiency. it can. In the methacrylic copolymer of the present invention, the maximum value of the ratio of the resin flow length to the thickness of the mold that can be used in injection molding is preferably 450 or more. When the maximum value of the ratio of the resin flow length to the thickness is large as described above, the methacrylic copolymer of the present invention is suitable for producing a thin-walled molded product. The molded product of the preferred form of the present invention has a plate shape, and the thickness thereof is preferably 0.5 mm or less, more preferably 0.45 mm or less, still more preferably 0.4 mm or less, still more preferably 0.35 mm. It is as follows.

The methacrylic copolymer (or thermoplastic resin composition or molding material) of the present invention is suitable for manufacturing a housing of a mobile phone terminal. A mobile phone terminal is a terminal used for a telephone service (that is, a mobile phone) capable of making a call while moving. A mobile phone terminal consists of at least an antenna, a speaker, a microphone, an input / output device, a display device, an electronic circuit and a power supply, and a housing for accommodating them. There is a high demand for miniaturization and weight reduction of mobile phone terminals. Therefore, the housing for mobile phone terminals is required to be thinned while ensuring the strength at a practical level.

The methacrylic copolymer (or thermoplastic resin composition or molding material) of the present invention can secure the strength at a practical level even if it is thinned. The housing for the mobile phone terminal of the present invention is made of the methacrylic copolymer (or thermoplastic resin composition or molding material) of the present invention, and has, for example, a thickness of preferably 0.8 mm. Below, more preferably 0.7 mm or less, still more preferably 0.6 mm or less, the portion is composed of the methacrylic copolymer (or thermoplastic resin composition or molding material) of the present invention.

Examples of the molded product of the present invention include signboard parts such as advertising towers, stand signs, sleeve signs, column signboards, and roof signboards; display parts such as showcases, dividers, and store displays; fluorescent lamp covers, mood lighting covers, etc. Lighting parts such as lamp shades, light ceilings, light walls, chandeliers; Interior parts such as pendants and mirrors; Building parts such as doors, dome, safety window glass, partitions, staircase wainscots, balcony wainscots, roofs of leisure buildings Transport equipment related parts such as aircraft windshields, pilot visors, motorcycles, motor boat windshields, bus shading plates, automobile side visors, rear visors, head wings, headlight covers; audiovisual nameplates, stereo covers, TV protective masks, Electronic equipment parts such as vending machines; Medical equipment parts such as incubators and roentgen parts; Equipment-related parts such as machine covers, instrument covers, experimental equipment, rulers, dials, observation windows; LCD protective plates, light guide plates, guides Optical parts such as optical films, frennel lenses, lenticular lenses, front plates of various displays, diffusers, polarizer protective films, polarizing plate protective films, retardation films, housings for mobile phones; road signs, information boards, Traffic-related parts such as curved mirrors and soundproof walls; Surface materials for automobile interiors, surface materials for mobile phones, film materials such as marking films; For home appliances such as canopy materials and control panels for washing machines, and top panels for rice cookers Members; Other examples include greenhouses, large water tanks, box water tanks, clock panels, bathtubs, sanitary, desk mats, game parts, toys, and face protection masks during welding. Of these, the methacrylic copolymer of the present invention is suitable for an optical member, and among the optical members, it is suitable for a light guide body and a housing for a mobile phone.

The light guide is used, for example, as a member of the backlight of the liquid crystal display element. It guides the light from the light source on the side or back so that the light can be radiated uniformly from the entire plate surface. The plate surface of the light guide may be provided with micron-sized irregularities for uniformly radiating light. By using the methacrylic copolymer of the present invention, a thin (0.5 mm or less) and wide area light guide can be obtained. Further, by using the methacrylic copolymer of the present invention, it is possible to faithfully reproduce the micron-sized uneven fine shape engraved on the mold stamper on the surface of the molded product.

Next, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the examples.

Examples 1 to 7 and Comparative Examples 1 to 4
Purified methyl methacrylate (MMA), methyl acrylate (MA), 2,2'-azobis (2-methylpropionitrile) (AIBN) and n-octyl mercaptan (n-OM) in an autoclave with a stirrer. Was charged at the ratio shown in Table 1 and uniformly dissolved to obtain a polymerization raw material.
The polymerization raw material is continuously supplied from the autoclave to a tank reactor controlled at a temperature of 140 ° C. at 1.5 kg / hr, and the polymerization reaction is carried out by a massive polymerization method with an average residence time of 120 minutes, and the polymerization reaction is carried out from the tank reactor. The liquid containing the methacrylic copolymer was continuously discharged. The polymerization conversion rate was 57% by mass.
Then, the liquid discharged from the reactor was heated to 230 ° C. and supplied to a twin-screw extruder controlled to 240 ° C. In the twin-screw extruder, the volatile matter containing the unreacted monomer as a main component was separated and removed, and the methacrylic copolymer was extruded as a strand. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic copolymer.

The physical properties of the methacrylic copolymer were measured by the following method. The results are shown in Table 1. In this example and the comparative example, the amount of the unit derived from MMA is the amount of the unit other than the MA unit, so the description in the table is omitted.

(Ratio of units (MA units) derived from methyl acrylate)
1 g of the resin pellet was dissolved in 40 ml of dichloromethane. 25 μl of the obtained solution was collected on a platinum board. Remove dichloromethane and pyrolyze gas chromatograph (GC-14A manufactured by Shimadzu Corporation, pyrolysis furnace temperature: 500 ° C, column: SGE BPX-5, temperature condition: hold at 40 ° C for 5 minutes → 280 ° C at 5 ° C / min The ratio of MA units was calculated based on the chromatogram recorded by heating up to.

(Polymerization conversion rate, residual volatile matter)
GL Sciences Inc. was used as a column on a gas chromatograph GC-14A manufactured by Shimadzu Corporation. INERTCAP1 manufactured by INERTCAP1 (df = 0.4 μm, 0.25 mm ID × 60 m) was connected, and analysis was performed under the following conditions, and calculation was performed based on the analysis.
injection temperature = 250 ° C
detector temperature = 250 ° C
Temperature conditions: Hold at 60 ° C for 5 minutes → Raise to 250 ° C at 10 ° C / min → Hold at 250 ° C for 10 minutes

(Molecular weight distribution Mw / Mn)
From the chromatogram measured by GPC (gel permeation chromatography), the value corresponding to the molecular weight of standard polystyrene was taken as the molecular weight of the copolymer.
Equipment: Tosoh GPC equipment HLC-8320
Separation column: Tosoh's TSKguardcoIumSuperHZ-H, TSKgeIHZM-M and TSKgeISuperHZ4000 are connected in series. Eluent: tetrahydrofuran Eluent flow rate: 0.35 mI / min Column temperature: 40 ° C
Detection method: Differential refractometer (RI)

(Amount of bonded sulfur atom (bond S))
The amount of the bonded sulfur atom of the methacrylic copolymer is a value determined as follows. The methacrylic copolymer is dissolved in chloroform to obtain a solution. This solution is added to n-hexane to give a precipitate. The precipitate is dried at 80 ° C. for 12 hours or longer under vacuum. An appropriate amount of the obtained dried product is precisely weighed, set in a sulfur combustion device, decomposed in a reactor having a temperature of 400 ° C., and the generated gas is passed through a furnace having a temperature of 900 ° C., and then 0.3% hydrogen peroxide solution is used. Absorb with. The obtained liquid (decomposition gas aqueous solution) is appropriately diluted with pure water, and sulfate ions are quantified by ion chromatography (ICS-1500 manufactured by DIONEX, column: AS12A). Calculate the mass W _p (mass%) of sulfur atoms per mass of the dried product. Using the mass _WMMA (mass%) of the structural unit derived from methyl methacrylate with respect to the methacrylic copolymer, the amount _Sp (mol%) of the bound sulfur atom with respect to the structural unit derived from methyl methacrylate is calculated by the following equation. calculate.
_{_{S p = W p × (100/32}} ) / (W MMA / 100)

2 g of the test sample was placed in 50 mL of acetone and stirred at room temperature for 24 hours. The entire amount of the obtained liquid was centrifuged using a centrifuge (CR20GIII manufactured by Hitachi Koki Co., Ltd.) under the conditions of a rotation speed of 20000 rpm, a temperature of 0 ° C., and 180 minutes. The supernatant and the precipitate were separated and dried at 50 ° C. for 8 hours under vacuum to obtain an acetone-insoluble component (A) and an acetone-soluble component (B).

(Melt flow rate R)
According to JIS K7210, the measurement was carried out under the conditions of 230 ° C., 3.8 kg load and 10 minutes.

(Glass transition temperature Tg)
The acetone-insoluble content of the methacrylic copolymer and the thermoplastic resin obtained in the examples was 250 using a differential scanning calorimetry device (manufactured by Shimadzu Corporation, DSC-50 (product number)) in accordance with JIS K7121. The DSC curve was measured under the condition that the temperature was raised once to ° C., then cooled to room temperature, and then the temperature was raised from room temperature to 200 ° C. at 10 ° C./min. The midpoint glass transition temperature obtained from the DSC curve measured at the time of the second temperature rise was defined as the glass transition temperature in the present invention.

(Bending strength)
Bending strength of the methacrylic copolymer obtained in Examples and Comparative Examples. Using this test piece, the measurement was performed with a test piece thickness of 4 mm in accordance with JIS K7171.

(Injection moldability)
Using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd .: SE-180DU-HP), injection molding is performed in a cylinder temperature of 280 ° C., a mold temperature of 75 ° C., and a molding cycle of 1 minute, and the long side is 205 mm and the short side is 160 mm. A flat plate S having a thickness of 0.4 mm was manufactured. The flat plate S has a ratio of the resin flow length from the gate to the thickness of 475 (= 190 mm / 0.4 mm).
The appearance of the flat plate S was observed and evaluated by the following indexes.
A: There are no cracks or sink marks.
B: There is a sink mark.
C: There is a crack.

(Die stain)
Using a "M-100C" injection molding machine manufactured by Meiki Co., Ltd., a flat plate mold (molded product dimensions: 40 mm x 200 mm x 2 mm), molding temperature 260 ° C, mold temperature 60 ° C, molding cycle 26 seconds and maintenance 40 shots of injection molding were performed under the condition of no pressure (short shot). The degree of dirt on the mold surface was examined and evaluated using the following indexes.
A: No mold stains.
C: There is dirt on the mold.

(Liquidity)
In the SE-180DU-HP molding machine manufactured by Sumitomo Heavy Industries, Ltd., a spiral flow mold (product thickness 0.4 mm, width) under the conditions of a mold temperature of 50 ° C., a molding temperature of 300 ° C., an injection speed of 100 mm / sec, and a filling pressure of 150 MPa. Injection molding was performed on 10 mm). The spiral flow length at that time was measured, and the fluidity was evaluated by the following indexes.
A: 125 mm or more B: 115 mm or more and less than 125 mm C: less than 115 mm

As the above results show, the methacrylic copolymer of the present invention has high fluidity, excellent injection moldability, and is less likely to cause mold stains.

Production Example 1 (Acrylic rubber particles)
In a reactor equipped with a stirrer, thermometer, nitrogen gas introduction tube, monomer introduction tube and reflux condenser, 1050 parts by mass of ion-exchanged water, 0.44 parts by mass of polyoxyethylene tridecyl ether sodium acetate and sodium carbonate 0. .7 parts by mass was charged and the inside of the reactor was replaced with nitrogen gas. Then, the internal temperature was adjusted 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 composed 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 completion of the dropping, 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 to the reactor and stirred for 5 minutes. Then, 315 parts by mass of a monomer mixture composed 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 completion of the dropping, 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 to the reactor and stirred for 5 minutes. Then, 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-octyl mercaptan was continuously added dropwise over 30 minutes. After completion of the dropping, a polymerization reaction was further carried out for 60 minutes so that the polymerization conversion rate was 98% or more.
By the above operation, a latex containing acrylic rubber particles was obtained. The latex was frozen and solidified. Then, it was washed with water and dried to obtain acrylic rubber particles. The average particle size of the acrylic rubber particles was 0.2 μm.

Production Example 2 (Acrylic block copolymer)
It consists of [methyl methacrylate (MMA) polymer block (b1-1)]-[n-butyl acrylate (BA) polymer block (b2)]-[methyl methacrylate (MMA) polymer block (b1-2)]. The weight average molecular weight (Mw) is 65,000, the total mass ratio of the polymer blocks (b1-1) :( c2) :( b1-2) is 15:70:15, and the mass ratio of each monomer ( A triblock copolymer having MMA: BA) = (30:70) was produced according to a conventional method.

Examples 8 to 13 and Comparative Examples 5 to 7
The methacrylic copolymer, the acrylic rubber particles, and the acrylic block copolymer are mixed at the ratios shown in Table 2, melt-kneaded at 250 ° C. with a twin-screw extruder having a shaft diameter of 20 mm, extruded, and thermoplastic. A resin composition was obtained.

The physical properties of the thermoplastic resin composition were measured by the following method. The results are shown in Table 2.

(transparency)
Thermoplastic resin obtained in Examples and Comparative Examples using an injection molding machine (M-100C, manufactured by Meiki Co., Ltd.) under the conditions of a cylinder temperature of 260 ° C., a mold temperature of 50 ° C., and an injection speed of 50 mm / sec. The composition was injection molded to obtain a square injection molded piece having a thickness of 3 mm and a side of 50 mm.
Each test piece was evaluated by the following indexes by measuring the total light transmittance Tt and haze H using a spectrocolor difference meter SE5000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with the method described in JIS K7361-1. Was done.
A: Tt is 90% or more and H is 5% or less B: Tt is 80% or more and less than 90% or H is 10% or less C: Tt is less than 80% or H is greater than 10%

(surface hardness)
Thermoplastic resin obtained in Examples and Comparative Examples using an injection molding machine (M-100C, manufactured by Meiki Co., Ltd.) under the conditions of a cylinder temperature of 260 ° C., a mold temperature of 50 ° C., and an injection speed of 50 mm / sec. The composition was injection molded to obtain a square injection molded piece having a thickness of 3 mm and a side of 50 mm.
Using a table-movable pencil scratching tester (model P) (manufactured by Toyo Seiki Co., Ltd.), press the pencil lead against the surface of the thermoplastic resin composition on one side of the injection molded piece at an angle of 45 degrees and a load of 750 g. However, the presence or absence of scratches was confirmed. The hardness of the pencil lead gradually increased, and the hardness of the lead, which was one step softer than the time when the scar was generated, was defined as the pencil hardness, and the obtained pencil hardness was evaluated by the following index.
A: Pencil hardness is 2H or more B: Pencil hardness is F or more and less than 2H C: Pencil hardness is less than F

(Impact resistance)
Thermoplastic resin obtained in Examples and Comparative Examples using an injection molding machine (M-100C, manufactured by Meiki Co., Ltd.) under the conditions of a cylinder temperature of 260 ° C., a mold temperature of 50 ° C., and an injection speed of 50 mm / sec. The composition was injection-molded to obtain a strip-shaped injection-molded piece having a thickness of 4 mm, a long side of 80 mm, and a short side of 10 mm.
The flatwise method measured by performing a Charpy impact test on each test piece in accordance with the method described in ISO179-1, and the Charpy impact strength without a notch is defined as the Charpy impact strength, and the obtained Charpy impact strength is obtained. The evaluation was performed using the following indicators.
A: Charpy impact strength is 60 kJ / m ² or more B: Charpy impact strength is 40 kJ / m ² or more and less than 60 kJ / m ² C: Charpy impact strength is less than 40 kJ / m ²

(Liquidity)
Spiral flow mold (product) using an injection molding machine (M-100C, manufactured by Meiki Co., Ltd.) under the conditions of mold temperature 50 ° C, molding temperature 250 ° C, injection speed 100 mm / sec, and filling pressure 100 MPa. Injection molding was performed on a thickness of 1 mm and a width of 10 mm). The spiral flow length at that time was measured, and the fluidity was evaluated by the following indexes.
A: Spiral flow length is 350 mm or more B: Spiral flow length is 300 mm or more and less than 350 mm C: Spiral flow length is less than 300 mm

As shown in the above results, the thermoplastic resin composition of the present invention can provide a thin-walled molded product having excellent transparency, surface hardness, and impact resistance.

Claims

It comprises 85.0 to 95.0% by mass of a monomer unit derived from methyl methacrylate and 5.0 to 15.0% by mass of a monomer unit derived from an acrylic acid ester.
Weight average molecular weight Mw is 48,000-59000,
The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn is 2.1 or less, and the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R under the conditions of 230 ° C. and a 3.8 kg load is 5.0. A methacrylic copolymer at ~ 1.5 ° C. for 10 minutes / g.
The methacrylic copolymer according to claim 1, wherein the amount of bound sulfur atoms with respect to the monomer unit derived from methyl methacrylate is 0.4 mol% or less, and the melt flow rate R is 25 g / 10 minutes or more.
A thermoplastic resin composition containing the methacrylic copolymer according to claim 1 or 2 and acrylic rubber particles.
The thermoplastic resin composition according to claim 3, further containing an acrylic block copolymer.
The amount of acetone-insoluble matter contained in the thermoplastic resin composition is 59% by mass or less, and the amount of acetone-soluble matter contained in the thermoplastic resin composition is melt flow under the conditions of 230 ° C. and a 3.8 kg load. The thermoplastic resin composition according to claim 3 or 4, wherein the ratio Tg / R of the glass transition temperature Tg to the rate R is 6.0 to 1.5 ° C. for 10 minutes / g.
Pellet-shaped molding material containing the methacrylic copolymer according to claim 1 or 2.
A molded product containing the methacrylic copolymer according to claim 1 or 2.
The molded product according to claim 7, which is in the form of a plate having a thickness of 0.5 mm or less.
A housing for a mobile phone terminal, which contains the methacrylic copolymer according to claim 1 or 2.
A housing for a mobile phone terminal having a portion having a thickness of 0.8 mm or less and containing the methacrylic copolymer according to claim 1 or 2.
An optical member containing the methacrylic copolymer according to claim 1 or 2.
The method for producing a methacrylic copolymer according to claim 1 or 2, which comprises subjecting a monomer containing methyl methacrylate and an acrylic acid ester to a polymerization reaction by a massive polymerization method.
100 parts by mass of a monomer containing at least 81.0 to 94.2% by mass of methyl methacrylate and 5.8 to 19.0% by mass of an acrylic acid ester, 0.42 to 0.52 parts by mass of a chain transfer agent, and polymerization. The initiator was supplied to a continuous flow reactor with an average residence time of 1.5 to 3 hours and polymerized at a temperature of 110 to 140 ° C. without using a solvent and having a polymerization conversion rate of 35 to 65%.
It then comprises removing unreacted monomers by heating and devolatile at 220-260 ° C.
Containing 85-95.0% by mass of structural units derived from methyl methacrylate and 5.0-15.0% by mass of structural units derived from acrylic ester.
Weight average molecular weight Mw is 48,000-59000,
The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn is 2.1 or less, and the ratio Tg / R of the glass transition temperature Tg to the melt flow rate R under the conditions of 230 ° C. and a 3.8 kg load is 5.0. A method for producing a methacrylic copolymer at ~ 1.5 ° C. for 10 minutes / g.