Methacrylic resin composition and molded article

Abstract

To provide a methacrylic resin composition and a molded body that have excellent light transparency and allow sufficient diffusion of light and have high resistance to heat distortion and long-term service characteristics.SOLUTION: A methacrylic resin composition contains 0.5-6 pts.mass of a light-diffusing filler with an average particle size of 0.2-10 μm and 0.005-0.3 pt.mass of an ultraviolet light absorber relative to 100 pts.mass of a methacrylic resin and has a midpoint glass transition temperature of 105°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a methacrylic resin composition and a molded article. [Background technology]

[0002] Conventionally, light-diffusing materials used in lighting covers, various displays, signs, etc. have been investigated as materials molded from a transparent base resin containing inorganic or organic fine particles dispersed therein. A widely used method for producing such light-diffusing materials is to scatter or reflect light at the interface between the transparent base resin and the fine particles dispersed therein, due to the difference in refractive index between the base resin and the fine particles. In this case, methacrylic resins, polycarbonate resins, styrene resins, cyclic olefin resins, etc. are typically used as transparent resins.

[0003] Since there is a strong demand for brighter and more uniform products such as the above-mentioned lighting covers, various displays, and signs, the light-diffusing materials used in these products must have the ability to transmit light more effectively and diffuse it sufficiently. In addition, the recent shift to LED light sources has resulted in longer product lifespans, creating a demand for materials that are suitable for longer-term use and for long-term outdoor use. Furthermore, in recent years, the output of internal light sources has increased compared to conventional methods in order to create light-emitting devices that are brighter and more visible from a distance, creating a strong demand for light-diffusing materials with good thermal deformation resistance.

[0004] Patent Document 1 discloses a methacrylic resin composition in which a crosslinked silicone resin is added to a methacrylic resin, which achieves good light transmission and good light diffusion, but is not suitable for long-term use in Patent Document 1. In addition, the productivity of the methacrylic resin composition is poor, its heat distortion resistance is not sufficient, and when used as a vehicle component, it is not possible to obtain a good molded article. Patent Document 2 discloses fine particles suitable for achieving good light transmission and good light diffusion, but when used, the heat distortion resistance is still insufficient and the material is not suitable for long-term use. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-207743 [Patent Document 2] Japanese Patent Application Publication No. 10-67829 Summary of the Invention [Problem to be solved by the invention]

[0006] On the other hand, for applications such as vehicle emblems, shift levers, interior light covers, and lamp covers located inside combination lamps, the environmental temperatures used are relatively high. Therefore, a technique has been used in which transparent resins with good heat deformation resistance are used and a textured surface is applied to the surface of the transparent resin molded product to diffuse transmitted light. However, surface texture application has been difficult for large molded products or molded products with long molding flow lengths, resulting in internal light sources showing through, which has limited the shape of the molded product. Furthermore, texture application, particularly in injection molding, can cause the mold surface irregularities to become smaller over long periods of molding, allowing the internal light source to show through, which poses problems in terms of maintaining quality. There is a strong demand for light-diffusing materials that can solve these problems, have good heat deformation resistance, and are suitable for long-term use in vehicles such as automobiles.

[0007] Therefore, an object of the present invention is to provide a methacrylic resin composition and a molded article that have excellent light transmission and sufficient light diffusion properties, as well as good heat distortion resistance and long-term usage properties. [Means for solving the problem]

[0008] As a result of extensive research conducted by the present inventors to solve the above-mentioned problems of the conventional art, they found that the above-mentioned problems of the conventional art can be solved by a methacrylic resin composition having a specific composition, and thus completed the present invention.

[0009] That is, the present invention is as follows. [1] The copolymer contains a monomer unit derived from a methacrylic acid ester and a monomer unit derived from a monomer copolymerizable with the methacrylic acid ester but not containing an aromatic ring. The composition contains 0.5 to 6 parts by mass of a light-diffusing filler having an average particle size of 0.2 to 10 μm and 0.005 to 0.3 parts by mass of an ultraviolet absorber relative to 100 parts by mass of methacrylic resin, and has a midpoint glass transition temperature of 105°C or higher. and meets one of the following conditions i) to iii): A methacrylic resin composition comprising: i) The viscosity at 260°C shear rate of 100 (1 / sec) is 1000 Pa·s or more and 1500 Pa·s or less, and the midpoint glass transition temperature is 111°C or more and 130°C or less ii) The viscosity at 260°C and a shear rate of 100 (1 / sec) is 500 Pa·s or more and less than 1000 Pa·s, and the midpoint glass transition temperature is 113°C or more and 130°C or less. iii) The viscosity at 260°C and a shear rate of 100 (1 / sec) is 200 Pa·s or more and less than 500 Pa·s, and the midpoint glass transition temperature is 115°C or more and 130°C or less. [2] The methacrylic resin composition according to [1], wherein the light-diffusing filler is organic particles. [3] The methacrylic resin composition according to [1] or [2], wherein the light-diffusing filler is a cross-linked styrene-MMA resin or a cross-linked silicone resin. [4] The methacrylic resin composition according to any one of [1] to [3], wherein the light-diffusing filler has an average particle size of 1.2 to 9 μm. [5] The methacrylic resin composition according to any one of [1] to [4], wherein the methacrylic resin has a weight average molecular weight of 75,000 to 230,000. [6] The methacrylic resin composition according to any one of [1] to [5], wherein the methacrylic resin contains 6 to 50% of a molecular weight component having a peak molecular weight (Mp) of 1 / 5 or less in a GPC elution curve measured by gel permeation chromatography (GPC). [7] The methacrylic resin composition according to any one of [1] to [6], wherein the amount of terminal unsaturated double bonds in the methacrylic resin is 0.013 mol % or less. [8] The methacrylic resin composition according to any one of [1] to [7], wherein the ultraviolet absorber has a maximum absorption wavelength of 300 nm or more and 350 nm or less in the wavelength range of 300 nm to 830 nm. [9] Further containing additives, [1] to [2], wherein the combined mass ratio of additives excluding rubber components to 100 parts by mass of the methacrylic resin is 0.15 parts by mass or less. [8] 1. The methacrylic resin composition according to claim 1 . [ 10 ] Residual monomer is 8000 mass ppm or less, [1] [9] 1. The methacrylic resin composition according to claim 1 . [ 11 ] Contains no yellow dyes, [1]~[ 10 10. The methacrylic resin composition according to claim 1, wherein the methacrylic resin composition is a methacrylic resin. [ 12 ] [1]~[ 11 2. A molded article obtained by molding the methacrylic resin composition according to any one of claims 1 to 11. [ 13 ] The thickness t is 1 to 5 mm, 12 ] A molded article according to the present invention. [ 14 ] The molding is injection molding, 12 ] or [ 13 ] A molded article according to the present invention. [ 15 ] The length L and thickness t satisfy the following conditions (1), (2), and (3): 12 ] A molded article according to the present invention. 1mm≦t≦5mm...Condition (1) L≧130mm···Condition (2) L / t≧65 · · Condition (3) [ 16 ] Used in vehicle components, 12 ]~[ 15 ] The molded article according to any one of the preceding items. [ 17 ] Used in vehicle lighting components, 12 ]~[ 15 ] The molded article according to any one of the preceding items. [ 18 ] Used as a lamp cover placed inside a vehicle combination lamp. 12 ]~[ 15 ] The molded article according to any one of the preceding items. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a methacrylic resin composition and a molded article which have excellent light transmission and sufficient light diffusion properties, good heat distortion resistance, and long-term use properties. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, we will explain in detail the form for implementing the present invention (hereinafter referred to as the ``present embodiment''), but the present invention is not limited to the following description and can be implemented in various modifications within the scope of its gist.

[0012] In the following, a structural unit that constitutes a polymer may be referred to as a "monomer unit" and / or a "structural unit" that includes a plurality of such "monomer units." Furthermore, the constituent material of such a "monomer unit" may be referred to simply as "monomer" without the "unit" part.

[0013] [Methacrylic resin composition] The methacrylic resin composition of this embodiment contains 0.5 to 6 parts by mass of a light-diffusing filler having an average particle size of 0.2 to 10 μm and 0.005 to 0.3 parts by mass of an ultraviolet absorber per 100 parts by mass of methacrylic resin, and has a midpoint glass transition temperature of 105° C. or higher. In particular, by setting the midpoint glass transition temperature to 105° C. or higher and not blending a yellow dye, it is possible to impart better heat distortion resistance to a molded article, making it more suitable for use in applications in proximity to an internal light source such as a high-power LED.

[0014] <Methacrylic resin> The methacrylic resin is one of the components of the methacrylic resin composition of this embodiment. The inclusion of the methacrylic resin improves the appearance, and provides good heat distortion resistance and long-term usage properties.

[0015] The methacrylic resin is preferably a homopolymer of methyl methacrylate or a copolymer containing repeating units derived from methyl methacrylate in order to improve fluidity, transparency, yellowness, and heat distortion resistance. Among them, from the viewpoint of ensuring excellent long-term use properties, a copolymer containing a monomer unit derived from a methacrylic acid ester (e.g., methyl methacrylate) and a monomer unit derived from a monomer copolymerizable with the methacrylic acid ester and not containing an aromatic ring (e.g., a monomer not containing an aromatic ring among the other monomers described below) is preferred, and a copolymer consisting only of a monomer unit derived from a methacrylic acid ester (e.g., methyl methacrylate) and a monomer unit derived from a monomer copolymerizable with the methacrylic acid ester and not containing an aromatic ring (e.g., a monomer not containing an aromatic ring among the other monomers described below) is more preferred. The copolymer preferably has a mass ratio of repeating monomer units derived from methyl methacrylate of 75% by mass or more relative to 100% by mass of the methacrylic resin. The copolymer more preferably contains 75% by mass or more but less than 100% by mass of methyl methacrylate monomer units and more than 0% but 25% by mass or less of repeating monomer units derived from other monomers relative to 100% by mass of the methacrylic resin. A copolymer containing 80% by mass or more but less than 100% by mass of methyl methacrylate monomer units and more than 0% but 20% by mass or less of repeating monomer units derived from other monomers is even more preferred. A copolymer containing 90% by mass or more but less than 99.5% by mass of methyl methacrylate monomer units and more than 0.5% but 10% by mass or less of repeating monomer units derived from other monomers is particularly preferred.

[0016] The other monomer is preferably a monomer copolymerizable with a methacrylic acid ester (preferably methyl methacrylate). Examples of other monomers constituting the repeating monomers derived from the other monomers contained in the methacrylic resin include, but are not limited to, acrylic ester monomers having one acrylate group, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, and lauryl acrylate (preferably, acrylic ester monomers having one acrylate group that do not contain an aromatic ring). Methyl acrylate, ethyl acrylate, and butyl acrylate are preferred because of their easy availability. Furthermore, from the viewpoint of long-term usability, it is preferable to use a monomer that does not contain an aromatic ring. When an acrylic acid ester monomer having one acrylate group (for example, an acrylic acid ester monomer having one acrylate group and not containing an aromatic ring) is used, the mass proportion of repeating units derived from the acrylic acid ester monomer having one acrylate group relative to 100% by mass of the methacrylic resin is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, to improve fluidity. To improve heat distortion resistance, the methacrylic resin preferably contains 8% by mass or less of repeating units derived from the acrylic acid ester monomer having one acrylate group, more preferably 5% by mass or less, and even more preferably 4% by mass or less, relative to 100% by mass of the methacrylic resin. In particular, when a methyl acrylate monomer is used as the other monomer, it is preferable that the repeating monomer units derived from methyl acrylate be contained in an amount of 1.5 to 3.8% by mass relative to 100% by mass of the methacrylic resin, and when an ethyl acrylate monomer is used, it is preferable that the repeating monomer units derived from ethyl acrylate be contained in an amount of 5 to 7% by mass relative to 100% by mass of the methacrylic resin.

[0017] Other examples of the other monomer include acrylic acid ester monomers such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate, which have two or more (meth)acrylate groups and in which both terminal hydroxyl groups of ethylene glycol or its oligomers are esterified with acrylic acid or methacrylic acid; neopentyl glycol di(meth)acrylate, di(meth)acrylate, and other such esters in which two alcohol hydroxyl groups are esterified with acrylic acid or methacrylic acid; and polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol are esterified with acrylic acid or methacrylic acid. Among these, acrylic acid ester monomers that do not contain aromatic rings are preferred from the viewpoint of long-term use properties. From the viewpoint of ensuring fluidity during injection molding and maintaining transparency, it is preferable that the repeating monomer units derived from the monomer having two (meth)acrylate groups be 0.4% by mass or less relative to 100% by mass of the above methacrylic resin when a monomer having two (meth)acrylate groups is used, 0.25% by mass or less when a monomer having three (meth)acrylate groups is used, and 0.15% by mass or less when a monomer having four or more (meth)acrylate groups is used.

[0018] Furthermore, examples of the other monomers other than the acrylic acid ester monomer include, but are not limited to, α,β-unsaturated acids such as acrylic acid and methacrylic acid; unsaturated group-containing dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and cinnamic acid, and alkyl esters thereof; styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, o-ethylstyrene, p-tert-butylstyrene, and isopropenylbenzene (α-methylstyrene); 1-vinylnaphthalene, 2-vinylnaphthalene Examples of suitable monomers include aromatic vinyl compounds such as 1,1-diphenylethylene, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, and isopropenyloctylbenzene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; maleimide, and N-substituted maleimides such as N-methylmaleimide, N-ethylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide; amides such as acrylamide and methacrylamide; and polyfunctional monomers such as divinylbenzene. Among these, N-substituted maleimides are preferred from the viewpoint of heat distortion resistance, and it is preferable to use a monomer that does not contain an aromatic ring from the viewpoint of long-term usage properties. The content of other vinyl monomer units copolymerizable with the above-mentioned methacrylic acid ester monomers constituting the methacrylic resin is preferably 0.1% by mass or more and 20% by mass in the methacrylic resin.

[0019] By setting the mass proportion of the repeating monomer units derived from the other vinyl monomer copolymerizable with methyl methacrylate to 0.1% by mass or more relative to 100% by mass of the methacrylic resin, fluidity and heat resistance can be improved, and by setting it to 20% by mass or less, heat resistance can be increased. The mass proportion is preferably 0.1 to 17% by mass, more preferably 0.2 to 15% by mass, and even more preferably 0.3 to 12% by mass. The other monomers may be used singly or in combination of two or more.

[0020] (Properties of methacrylic resin) -Weight average molecular weight, molecular weight distribution- The weight average molecular weight and molecular weight distribution of the methacrylic resin will now be described. The methacrylic resin preferably has a weight-average molecular weight (Mw) of 300,000 or less as measured by GPC (gel permeation chromatography). To achieve excellent mechanical strength and solvent resistance, the weight-average molecular weight (Mw) of the methacrylic resin is preferably 50,000 or more, more preferably 60,000 or more, even more preferably 70,000 or more, even more preferably 75,000 or more, and particularly preferably 80,000 or more. To ensure good fluidity, the methacrylic resin preferably has a weight-average molecular weight (Mw) of 300,000 or less, more preferably 250,000 or less, even more preferably 230,000 or less, even more preferably 210,000 or less, and even more preferably 180,000 or less. A weight-average molecular weight of 110,000 to 175,000 provides an excellent balance of molding fluidity, diffusivity, long-term use properties, and impact resistance. This is more preferable because molding can be performed well to produce moldings of the size used in automobile parts applications. When the weight-average molecular weight of the methacrylic resin is within the above-mentioned range, a balance between fluidity, mechanical strength, and solvent resistance can be achieved, and good molding processability can be maintained. In particular, when the Mw is 75,000 or more, the strength is even better. Furthermore, when the Mw is 18,500 or less, the molding fluidity is even better.

[0021] The molecular weight distribution (Mw / Mn) of the methacrylic resin is preferably 1.7 to 6.0, more preferably 1.8 to 5.0, even more preferably 1.9 to 5.0, and even more preferably 2.0 to 5.0. When the molecular weight distribution of the methacrylic resin is 1.6 or more and 6.0 or less, an excellent balance between molding flowability and mechanical strength is obtained. In particular, when the molecular weight distribution is 3.0 to 5.0, an even better balance between molding flowability, diffusivity, long-term use properties, and impact resistance is obtained.

[0022] The weight average molecular weight (Mw) and number average molecular weight (Mn) of the methacrylic resin can be measured by gel permeation chromatography (GPC), specifically, by the method described in the examples below. Specifically, a calibration curve is created from the elution time and weight-average molecular weight using a standard methacrylic resin whose monodisperse weight-average molecular weight is known and available as a reagent, and an analytical gel column that elutes high molecular weight components first.The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the methacrylic resin to be measured can then be determined based on the resulting calibration curve, and the molecular weight distribution can be calculated from these. The number average molecular weight (Mn) is simply the average molecular weight per molecule and is defined as the total weight of the system divided by the number of molecules in the system. Weight average molecular weight (Mw) is defined as the average of molecular weights by weight fraction.

[0023] -Amount of molecular weight components less than 1 / 5 of the peak top molecular weight (Mp)- To improve moldability and impact resistance, the methacrylic resin preferably contains 5 to 50% of molecular weight components having a molecular weight of 1 / 5 or less of the peak top molecular weight (Mp), more preferably 6 to 50%, even more preferably 7 to 45%, even more preferably 8 to 43%, and particularly preferably 10 to 30%. In particular, when the content of molecular weight components having a molecular weight of 1 / 5 or less of the peak top molecular weight (Mp) is 20 to 30%, the resin has an excellent balance of molding flowability, diffusivity, long-term use properties, and impact resistance. Here, the abundance (%) of molecular weight components having a molecular weight of 1 / 5 or less of the peak top molecular weight (Mp) refers to the proportion of the area of ​​the area corresponding to molecular weight components having a molecular weight of 1 / 5 or less of the peak top molecular weight (Mp) when the total area of ​​the GPC elution curve is taken as 100%, and can be measured by the method described in the Examples below. The peak top molecular weight (Mp) refers to the weight molecular weight that shows a peak in a GPC elution curve. When there are multiple peaks in a GPC elution curve, the molecular weight at the peak indicated by the most abundant weight molecular weight is taken as the peak top molecular weight (Mp). When the amount of molecular weight components present in the methacrylic resin that are 1 / 5 or less of the peak top molecular weight (Mp) is 6% or more, the light-diffusing filler effectively prevents gas in the mold from being entrained and exploding during molding flow, resulting in molding defects, thereby achieving good moldability. Good molding flowability is also achieved. When the amount is 50% or less, good impact resistance is achieved. Furthermore, it is preferable that the amount of methacrylic resin components having a molecular weight of 500 or less is as small as possible in order to prevent the occurrence of foam-like appearance defects known as silver during molding.

[0024] - Midpoint glass transition temperature measured using a differential scanning calorimeter - The methacrylic resin preferably has a midpoint glass transition temperature (°C) of 105°C or higher, as determined from a glass transition curve obtained by heating from 40°C to 210°C at a heating rate of 10°C / min in a nitrogen gas atmosphere using a differential scanning calorimeter (DSC) in accordance with JIS-K-7121 with α-alumina as a reference. The midpoint glass transition temperature (°C) obtained by the measurement method described in the Examples below indicates that the higher the value, the better the thermal distortion resistance of the resin, and affects the temperature at which the molded body begins to deform when a light source is brought close to it. Therefore, the higher the midpoint glass transition temperature, the closer a high-power light source can be brought. Furthermore, even in applications using a nearby high-power LED light source, the molded body can be used stably in the desired shape. The above-mentioned methacrylic resin preferably has a midpoint glass transition temperature of 107°C or higher, more preferably 109°C or higher, even more preferably 111°C or higher, even more preferably 113°C or higher, and even more preferably 118°C or higher. Furthermore, a midpoint glass transition temperature of 140°C or lower is preferred to maintain a good balance between the strength and fluidity of the methacrylic resin.

[0025] -Unsaturated double bond terminal amount- To prevent molding defects known as silver strix caused by the generation of pyrolysis gas, the amount of unsaturated double bond terminals in the methacrylic resin is preferably 0.015 mol % or less, more preferably 0.013 mol % or less, and even more preferably 0.009 mol % or less, relative to 100 mol % of the methacrylic resin. The amount of unsaturated double bond terminals can be controlled by controlling the polymerization temperature or by using a chain transfer agent. The amount of unsaturated double bond terminals can be measured by the method described in the Examples below.

[0026] (Methacrylic resin manufacturing method) The methacrylic resin can be produced by, but is not limited to, solution polymerization, bulk polymerization, cast polymerization, or suspension polymerization. Bulk polymerization, solution polymerization, and suspension polymerization are preferred, and suspension polymerization is more preferred. By selecting suspension polymerization, small spherical polymers with sizes of 0.5 μm to 5 mm can be obtained, which allows for good dispersion of additives when producing the methacrylic resin composition of this embodiment.

[0027] The polymerization temperature may be appropriately selected optimally depending on the polymerization method, but when suspension polymerization is performed, the temperature is preferably 50° C. or higher and 100° C. or lower, more preferably 60° C. or higher and 90° C. When solution polymerization is performed, the temperature is preferably 180° C. or lower, more preferably 160° C. or lower.

[0028] When producing the methacrylic resin, a polymerization initiator may be used. The polymerization initiator is not limited to the following, but in the case of radical polymerization, for example, di-t-butyl peroxide, lauroyl peroxide, stearyl peroxide, benzoyl peroxide, t-butyl peroxyneodecanate, t-butyl peroxypivalate, dilauroyl peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylsilyl peroxide, Examples of the initiator include organic peroxides such as methylcyclohexane and 1,1-bis(t-butylperoxy)cyclohexane, and common azo-based radical polymerization initiators such as azobisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis(1-cyclohexanecarbonitrile), 2,2'-azobis-4-methoxy-2,4-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, and 2,2'-azobis-2-methylbutyronitrile. These initiators may be used alone or in combination of two or more. These radical polymerization initiators may also be used in combination with an appropriate reducing agent as a redox initiator. These radical polymerization initiators and / or redox initiators are generally used in the range of 0 to 1 part by mass per 100 parts by mass of the total amount of all monomers used in the polymerization of the methacrylic resin, and can be appropriately selected taking into consideration the temperature at which the polymerization is carried out and the half-life of the polymerization initiator.

[0029] When bulk polymerization, cast polymerization, or suspension polymerization is selected as the polymerization method for the methacrylic resin, it is preferable to carry out the polymerization using a peroxide polymerization initiator from the viewpoint of preventing coloration of the methacrylic resin. The peroxide polymerization initiator is not limited to the following, but examples thereof include lauroyl peroxide, decanoyl peroxide, and t-butylperoxy-2-ethylhexanoate, with lauroyl peroxide being more preferred.

[0030] When the methacrylic resin is polymerized by a solution polymerization method at a high temperature of 90°C or higher, it is preferable to use as the polymerization initiator a peroxide, an azobis initiator, or the like, which has a 10-hour half-life temperature of 80°C or higher and is soluble in the organic solvent used. Examples of the peroxides and azobis initiators include, but are not limited to, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 1,1-azobis(1-cyclohexanecarbonitrile), and 2-(carbamoylazo)isobutyronitrile.

[0031] When producing the methacrylic resin, the molecular weight of the methacrylic resin may be controlled within a range that does not impair the object of the present invention. Methods for controlling the molecular weight of the methacrylic resin include, but are not limited to, methods for controlling the molecular weight by using chain transfer agents such as alkyl mercaptans, dimethylacetamide, dimethylformamide, and triethylamine, and iniferters such as dithiocarbamates, triphenylmethylazobenzene, and tetraphenylethane derivatives. It is also possible to adjust the molecular weight by adjusting the amount of these additives added.

[0032] As the chain transfer agent, alkyl mercaptans are preferred from the viewpoints of handleability and stability. Examples of the alkyl mercaptans include, but are not limited to, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris(thioglycolate), and pentaerythritol tetrakis(thioglycolate). The chain transfer agent and iniferter can be added appropriately depending on the molecular weight of the target methacrylic resin, but are generally used in an amount of 0.001 to 5 parts by mass per 100 parts by mass of the total amount of all monomers used in the polymerization of the methacrylic resin.

[0033] Other methods for controlling the molecular weight include changing the polymerization method, adjusting the amounts of the polymerization initiator, the chain transfer agent, the iniferter, etc., and changing various polymerization conditions such as the polymerization temperature. These molecular weight control methods may be used alone or in combination of two or more.

[0034] <Light diffusing filler> The light-diffusing filler is one of the components of the methacrylic resin composition of this embodiment. By incorporating 0.5 to 6 parts by mass of the light-diffusing filler with an average particle size of 0.2 to 10 μm per 100 parts by mass of the methacrylic resin, it is possible to effectively reduce the image of the light source in products with an internal light source, particularly vehicle components, while maintaining brightness that allows clear visibility.

[0035] Preferred examples of the light-diffusing filler include inorganic particles such as titanium dioxide, aluminum trioxide, zinc oxide, and barium sulfate, and organic particles such as crosslinked silicone resins, crosslinked methacrylic resins, crosslinked styrene-methyl methacrylate resins, and crosslinked styrene resins. Among these, organic particles are more preferred in order to increase the amount of transmitted light and improve the brightness and visibility when light enters a molded product, crosslinked silicone resins and crosslinked styrene-methyl methacrylate resins are even more preferred in order to further improve the balance between light diffusibility and the brightness and visibility when light enters a molded product, as well as the long-term usage characteristics, and it is even more preferred to use a porous body in order to further improve light diffusibility. The methacrylic resin refers to a resin with a crosslinking degree (%) of 0.5 or less, and the organic particles in the light-diffusing filler refer to a resin with a crosslinking degree of 2 or more. The crosslinking degree refers to a value measured in the same manner as ASTM D6725, by adding 29 g of N,N-dimethylformamide and 1 g of sample to a glass container, shaking for 24 hours to make a swollen liquid, removing the supernatant by centrifugation, evaporating the gel fraction to dryness in a vacuum dryer at 130°C, and measuring the weight of the residue.

[0036] The average particle size of the light-diffusing filler is more preferably 1.2 μm or more and 9 μm or less, even more preferably 1.7 μm or more and 8 μm or less, and even more preferably 2 μm or more and 6 μm or less. The average particle size can be measured by dissolving 2 g of a methacrylic resin composition sample cut out from a molded body in 100 ml of acetone, precipitating insoluble matter by centrifugation, drying the precipitate, dispersing the resultant in 3 mL of a 0.1 mass % aqueous solution of sodium hexametaphosphate, dropping the resulting dispersion into a Beckman Coulter LS13320 while gently shaking the dispersion to a degree that does not generate bubbles, and calculating the cumulative 50% particle size on a volume basis by adjusting the reading of the concentration meter to an appropriate range. The content of the light-diffusing filler is more preferably 1 part by mass or more and 5 parts by mass or less relative to 100 parts by mass of the methacrylic resin.

[0037] When organic fine particles having a refractive index higher than that of the base resin are used as the light-diffusing filler, the difference in refractive index between the methacrylic resin and the light-diffusing filler is preferably 0.06 or less, more preferably 0.05 or less, and even more preferably 0.04 or less, in order to obtain a methacrylic resin composition with good weather resistance. Furthermore, the difference in refractive index is preferably 0.005 or more, more preferably 0.01 or more, and even more preferably 0.02 or more, in order to obtain good light diffusion properties. When organic fine particles having a refractive index lower than that of the base resin are used, the difference in refractive index between the methacrylic resin and the light-diffusing filler is preferably 0.1 or less, more preferably 0.08 or less, in order to obtain good weather resistance and total light transmittance and a molded article that is bright and has good visibility when light from a light source is incident. Furthermore, the difference in refractive index is preferably 0.005 or more, more preferably 0.01 or more, and even more preferably 0.02 or more, in order to obtain good light diffusion properties. When inorganic fine particles are used as the light-diffusing filler, the difference in refractive index between the methacrylic resin and the light-diffusing filler is preferably 1.5 or less, and more preferably 1.1 or less, in order to improve the total light transmittance and to produce a molded product that is bright and has good visibility when light from a light source is incident. The refractive index difference is a value determined by setting the refractive index of polymethyl methacrylate exceeding the limit molecular weight to 1.491, and the light-diffusing filler refers to one having a refractive index difference of 0.003 or more with respect to polymethyl methacrylate.

[0038] (ultraviolet absorber) The methacrylic resin composition of this embodiment contains 0.005 to 0.3 parts by mass of an ultraviolet absorber per 100 parts by mass of the methacrylic resin. The inclusion of an ultraviolet absorber not only improves weather resistance and long-term usage characteristics, resulting in a molded article suitable for long-term use, but also effectively prevents discoloration when exposed to ultraviolet light contained in a light source, as well as a decrease in the amount of transmitted light due to absorption of LED light resulting from discoloration. In the methacrylic resin composition containing the light-diffusing filler of this embodiment, the optical path length of light passing through the molded article is longer than the thickness of the molded article due to light diffusion, which accentuates discoloration. Therefore, preventing discoloration is extremely important. The ultraviolet absorber may directly absorb light in the ultraviolet range or may prevent reactions that cause ultraviolet-induced resin degradation, as long as the energy of ultraviolet light is absorbed in some form. In order to fully utilize the performance of the UV absorber, the UV absorber must be contained in an amount of 0.005 parts by mass or more, preferably 0.01 parts by mass or more, more preferably 0.015 parts by mass or more, and even more preferably 0.02 parts by mass or more, per 100 parts by mass of the methacrylic resin. In addition, in order to prevent mold contamination and resin sticking to metal rolls due to precipitation of the UV absorber during molding, the UV absorber must be contained in an amount of 0.3 parts by mass or less, preferably 0.19 parts by mass or less, more preferably 0.15 parts by mass or less, even more preferably 0.1 parts by mass or less, still more preferably 0.07 parts by mass or less, and particularly preferably 0.04 parts by mass or less, per 100 parts by mass of the methacrylic resin.

[0039] Examples of the ultraviolet absorber include, but are not limited to, benzotriazole-based compounds, benzotriazine-based compounds, benzoate-based compounds, benzophenone-based compounds, oxybenzophenone-based compounds, hindered amine-based compounds, phenol-based compounds, oxazole-based compounds, malonic acid ester-based compounds, cyanoacrylate-based compounds, lactone-based compounds, salicylic acid ester-based compounds, and benzoxazinone-based compounds, with benzotriazole-based compounds, benzotriazine-based compounds, and hindered amine-based compounds being preferred. The above ultraviolet absorbents may be used alone or in combination of two or more. In the methacrylic resin composition of this embodiment containing a light-diffusing filler, the optical path length of light passing through the molded body is longer than the thickness of the molded body due to light diffusion, thereby enhancing the color tone. Therefore, to avoid affecting the color of the methacrylic resin composition in the visible light wavelength range, the UV absorber preferably has an absorption maximum wavelength of 300 to 350 nm in the wavelength range of 300 to 830 nm, or does not have an absorption maximum wavelength in the visible light range of 380 to 780 nm, and more preferably has an absorption maximum wavelength of 300 to 350 nm in the wavelength range of 300 to 830 nm. If the UV absorber has an absorption maximum wavelength of 350 nm or less, or does not have an absorption maximum in the visible light range, when used, for example, as an automotive component, it can diffuse white LED light sources while maintaining a closer white color, resulting in excellent nighttime visibility.

[0040] The vapor pressure (P) of the above ultraviolet absorber at 20°C is 1.0 x 10 -4 Pa or less, and more preferably 1.0 × 10 -6 Pa or less, and more preferably 1.0 × 10 -8 Pa or less.

[0041] Excellent moldability means, for example, that the ultraviolet absorber adheres less to the surface of the mold during injection molding, or that the ultraviolet absorber adheres less to the roll during film formation. If the resin adheres to the roll, it may adhere to the surface of the molded article, for example, and deteriorate the appearance and optical properties, which is undesirable when the molded article is used as an optical material.

[0042] The melting point (Tm) of the ultraviolet absorber is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 130°C or higher. A melting point of 80°C or higher can prevent the ultraviolet absorber from volatilizing during molding, allowing the ultraviolet absorber to fully exhibit its performance. In addition, contamination of the mold by the volatilized ultraviolet absorber can be effectively prevented.

[0043] The ultraviolet absorber preferably exhibits a weight loss rate of 50% or less when heated from 23°C to 260°C at a rate of 20°C / min, more preferably 30% or less, even more preferably 15% or less, even more preferably 10% or less, and still more preferably 5% or less.

[0044] <Other additives> The methacrylic resin composition of this embodiment may contain additives other than the methacrylic resin, the light-diffusing filler, and the UV absorber, as long as the object of the present invention is not impaired. As the other additives, it is preferable to add a heat stabilizer, a strength modifier, etc. It is preferable not to use a rubber component as the other additives. In this specification, the other additives may be simply referred to as "additives."

[0045] (heat stabilizer) Examples of the heat stabilizer include, but are not limited to, hindered phenol-based antioxidants and phosphorus-based processing stabilizers, with hindered phenol-based antioxidants being preferred.

[0046] Specifically, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, thiodiethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, 3,3',3'',5,5',5''-hexa-tert-butyl-a,a',a''-(mesitylene-2,4,6-triyl)tri-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, 4,6-bis(dodecylthiomethyl)-o-cresol, ethylenebis(oxyethylene)bis[3-(5-tert -butyl-4-hydroxy-m-tolyl)propionate, hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6 -xylin)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamine)phenol, etc., and pentaerythritol terakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is a preferred heat stabilizer.

[0047] When a heat stabilizer is used, to fully exert its effect, the amount added is preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, relative to 100 parts by mass of the methacrylic resin. Also, to prevent mold contamination such as mold deposits, the amount of heat stabilizer added is preferably 0.5% by mass or less, more preferably 0.2 parts by mass or less, even more preferably 0.15% by mass or less, and particularly preferably 0.12 parts by mass or less.

[0048] (Other resins) The other resins used as the other additives are not particularly limited as long as they do not impair the effects of the present invention, and known thermoplastic resins are suitably used.

[0049] Examples of the thermoplastic resin include, but are not limited to, polypropylene resins, polyethylene resins, polystyrene resins, syndiotactic polystyrene resins, ABS resins (acrylonitrile-butadiene-styrene copolymers), AS resins (acrylonitrile-styrene copolymers), BAAS resins (butadiene-acrylonitrile-acrylonitrile rubber-styrene copolymers), AAS resins (acrylonitrile-acrylonitrile rubber-styrene copolymers), thermoplastic polyurethane resins, biodegradable resins, polycarbonate-ABS resin alloys, polyalkylene arylate resins such as polybutylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polytrimethylene terephthalate, and polyethylene naphthalate, polyamide resins, polyphenylene ether resins, polyphenylene sulfide resins, and phenolic resins. In particular, AS resin, BAAS resin, and thermoplastic polyurethane resin are preferred for improving fluidity, ABS resin and thermoplastic polyurethane resin are preferred for improving impact resistance, and polyester resin is preferred for improving chemical resistance. Furthermore, polyphenylene ether resins, polyphenylene sulfide resins, phenolic resins, etc. are expected to have the effect of improving flame retardancy. These resins may be used singly or in combination of two or more.

[0050] When other resins are used, in order to maintain good total light transmittance and weather resistance, the amount is preferably more than 0 mass% and not more than 40 mass%, more preferably not more than 30 mass%, and even more preferably not more than 20 mass%, relative to 100 mass% of the methacrylic resin composition.

[0051] Examples of the other additives include, but are not limited to, plasticizers such as phthalate esters, fatty acid esters, trimellitate esters, phosphate esters, and polyesters; lubricants such as higher fatty acids, higher fatty acid esters, and higher fatty acid mono-, di-, or triglycerides; antistatic agents such as polyethers, polyether esters, polyether ester amides, alkyl sulfonates, and alkyl benzene sulfonates, flame retardant aids, conductivity imparting agents, stress relaxation agents, crystallization accelerators, hydrolysis inhibitors, lubricants, strength modifiers, sliding property improvers, compatibilizers, nucleating agents, reinforcing agents, reinforcing agents, flow adjusters, sensitizers, thickeners, anti-settling agents, anti-sagging agents, fillers, antifoaming agents, coupling agents, rust inhibitors, antibacterial and anti-fungal agents, antifouling agents, conductive polymers, and dyes and pigments.

[0052] In the methacrylic resin composition of this embodiment, the content of the other additives per 100 parts by mass of the methacrylic resin composition is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, to improve mold releasability when a lubricant is used. To prevent molding defects such as bleed-out, the content is preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, even more preferably 0.2 parts by mass or less, and particularly preferably 0.12 parts by mass or less. When a dye or pigment is used, organic dyes are preferred to improve total light transmittance. Furthermore, anthraquinone-based, perinone-based, methine-based, and quinophthalone-based organic dyes are more preferred to improve weather resistance. The use of dyes not only allows for the production of a light-diffusing molded article of the desired color, but also allows for the adjustment of the color of the diffused light. The amount of dye added is preferably 0.000002 parts by mass or more, more preferably 0.000005 parts by mass or more, to achieve a dyeing effect. To prevent mold contamination, the amount is preferably 0.6 parts by mass or less, more preferably 0.3 parts by mass or less, even more preferably 0.2 parts by mass or less, and particularly preferably 0.12 parts by mass or less.

[0053] The methacrylic resin composition of this embodiment preferably does not contain a yellow dye. A yellow dye refers to a dye with a maximum absorption wavelength in the 380-495 nm range. The absence of a yellow dye allows for effective diffusion of the 420-430 nm wavelength light, which is present at high intensity in white LED light. Conversely, the inclusion of a yellow dye results in the absorption of light with a wavelength of 420-430 nm, which causes heat accumulation in the material and increases the resin temperature, making it difficult to use the material in close proximity to an LED light source or to increase the output of the LED light source to ensure good visibility from a distance. Furthermore, the yellowing of the methacrylic resin composition reduces the visibility of white LEDs at night. Furthermore, this accelerates resin degradation and additive bleed-out.

[0054] When a strength modifier is used, the amount is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the methacrylic resin, in order to effectively modify the strength, and is preferably 35 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, in order to ensure good heat distortion resistance and flowability.

[0055] In order to suppress bleed-out of the additives and stabilize the light transmission and diffusion characteristics even when the resin is used in a hot and humid space such as the inside of an automobile lamp housing, the total mass ratio of the additives excluding the rubber component is preferably 0.15 parts by mass or less, more preferably 0.14 parts by mass or less, and even more preferably 0.13 parts by mass or less, per 100 parts by mass of the methacrylic resin. By including the other additives in the above-mentioned ranges, the functions of each material can be exhibited.

[0056] <Method for producing methacrylic resin composition> The methacrylic resin composition of the present embodiment can be produced, for example, by mixing the above-mentioned methacrylic resin, the above-mentioned light-diffusing filler, and the above-mentioned ultraviolet absorber. The mixing method is not particularly limited, but may be a melt kneading method, a solvent kneading method, a dry blending method, or the like, and from the viewpoint of productivity, the melt kneading method and the dry blending method are preferred. The equipment used for mixing may be a common kneader or mixer, and specific examples include a single-screw extruder, a twin-screw extruder, a variable shell mixer, a Banbury mixer, and a tumbler. As a method of melt kneading, it is preferable to use a twin-screw extruder, since this allows the light diffusing agent to be uniformly dispersed without agglomeration, thereby improving the light diffusibility and uniformity of the light diffusibility of the resulting resin molded body.

[0057] In the case of melt kneading, the production temperature is preferably 200° C. or higher and 320° C. or lower. From the viewpoint of productivity, it is more preferably 210° C. or higher, and even more preferably 220° C. or higher, and from the viewpoint of preventing yellowing of the methacrylic resin composition due to decomposition of the resin, it is more preferably 300° C. or lower, and even more preferably 290° C. or lower.

[0058] <Characteristics of methacrylic resin composition> The methacrylic resin composition of this embodiment has a midpoint glass transition temperature (Tg) of 105° C. or higher. The higher the midpoint glass transition temperature, the better the thermal distortion resistance of the resin composition, and it affects the temperature at which the molded article begins to deform when a light source is placed close to it. Therefore, the higher the midpoint glass transition temperature, the closer a high-power light source can be placed. Furthermore, even in applications where a high-power LED light source is placed close to the molded article, the molded article can be used stably in the desired shape. The midpoint glass transition temperature is preferably 107°C or higher, more preferably 109°C or higher, even more preferably 111°C or higher, even more preferably 113°C or higher, even more preferably 115°C or higher, and particularly preferably 118°C or higher. Furthermore, in order to achieve a good balance between the strength and flowability of the methacrylic resin composition, the midpoint glass transition temperature is preferably 140°C or lower, more preferably 130°C or lower. Having a midpoint glass transition temperature within this range allows the methacrylic resin composition to exhibit good heat distortion resistance while achieving a good balance with other physical properties such as the strength and molding flowability of the methacrylic resin composition. The midpoint glass transition temperature can be measured by the method described in the Examples below. The midpoint glass transition temperature can be adjusted by using the above-mentioned methacrylic resin in a preferred embodiment, adjusting the amount of light-diffusing filler added to fall within the range of the preferred embodiment, and adjusting the amount of other additive components added to fall within the range of the preferred embodiment.

[0059] - Viscosity and Tg - The viscosity of the methacrylic resin composition of this embodiment at 260° C. and a shear rate of 100 (1 / sec) is preferably 200 to 1500 Pa·s. In the methacrylic resin composition of the present embodiment, the viscosity of the methacrylic resin composition at 260°C and a shear rate of 100 (1 / sec) and the midpoint glass transition temperature (Tg) of the methacrylic resin composition preferably satisfy any one of the following relationships i) to iii). i) The viscosity at 260°C shear rate of 100 (1 / sec) is 1000 Pa·s or more and 1500 Pa·s or less, and the midpoint glass transition temperature is 111°C or more and 130°C or less ii) A viscosity of 500 Pa·s or more and less than 1000 Pa·s at 260°C and a shear rate of 100 (1 / sec) and a midpoint glass transition temperature of 113°C or more and 130°C or less iii) A viscosity of 200 Pa·s or more and less than 500 Pa·s at 260°C and a shear rate of 100 (1 / sec) and a midpoint glass transition temperature of 115°C or more and 130°C or less In methacrylic resin compositions with a relatively high viscosity of 1000 Pa·s to 1500 Pa·s, the movement of methacrylic resin molecules is slow even at resin temperatures near the Tg. Therefore, if the Tg is 111°C or higher (preferably 111°C to 130°C), bleed-out of additives in the methacrylic resin composition can be effectively suppressed, and bleed-out of additives can be suppressed and light transmission and diffusion properties can be stabilized even when used in hot and humid spaces such as the inside of an automobile lamp housing. When the viscosity of the methacrylic resin composition is 500 Pa·s to 1000 Pa·s, the Tg is preferably 113°C or higher (preferably 113°C to 130°C) in order to suppress bleed-out of additives and stabilize light transmission and diffusion properties when used in hot and humid spaces. When the viscosity is 200 Pa·s or more but less than 500 Pa·s, the viscosity is relatively low and the molecules move actively. Therefore, when used in a hot and humid space, it is preferable that the Tg be 115°C or more (preferably 115°C or more and 130°C or less) in order to suppress bleed-out of additives and stabilize the light transmission and diffusion characteristics. The greater the viscosity at 260°C and a shear rate of 100 (1 / sec) and / or the higher the Tg, the slower the movement of the methacrylic resin molecules even when exposed to the same high temperature, and the more effectively the bleed-out of additives in the methacrylic resin composition can be suppressed, and even when used in a hot and humid space such as the inside of an automobile lamp housing, the bleed-out of additives can be suppressed and the light transmission and diffusion properties can be stabilized. The viscosity and Tg at 260°C and a shear rate of 100 (1 / sec) can be adjusted by the monomer composition, molecular weight, molecular weight distribution, and type and amount of additives of the methacrylic resin in the methacrylic resin composition. The viscosity at 260°C and a shear rate of 100 (1 / sec) can be measured by the method described in the Examples below.

[0060] -Residual monomer amount- The total amount of residual monomers contained in the methacrylic resin composition of this embodiment is preferably 9000 ppm by mass or less, and more preferably 8000 ppm by mass or less. By keeping the total amount of residual monomers at 8000 ppm by mass or less, problems such as vent-up can be effectively prevented when producing the methacrylic resin composition by melt kneading. Furthermore, even with a resin material such as that of this embodiment, in which the inclusion of a light-diffusing filler disrupts the resin flow front during molding and makes molding defects due to molding gas more likely to occur, it is possible to successfully mold a molded article having a long length L. This characteristic is particularly useful when injection molding a molded article having a long length L, such as an automotive component. The total amount of residual monomers contained in the methacrylic resin composition can be measured by analyzing the monomer component species analyzed in the procedure described below (Analysis of structural units of methacrylic resin) and the monomer component species of other resins used using a gas chromatogram (GC) as described below. The amount of total residual monomers contained in the methacrylic resin composition is more preferably 6000 ppm by mass or less, even more preferably 5000 ppm by mass or less, even more preferably 4000 ppm by mass or less, and particularly preferably 3000 ppm by mass or less. In the production of methacrylic resins, the amount of total residual monomers contained in the methacrylic resin composition can be reduced, for example, by continuing the suspension polymerization until an exothermic peak is observed, or by raising the temperature to 88°C or higher after the exothermic peak is observed and maintaining the temperature for 30 minutes or more. In solution polymerization, the amount can be reduced by setting the polymerization temperature at a temperature 20°C or higher than the 1-minute half-life temperature. In the production of methacrylic resin compositions, residual monomers can be reduced by using melt kneading and removing volatiles using a vacuum vent during melt kneading.

[0061] The mass proportion of the above methacrylic resin in 100 mass% of the methacrylic resin composition of this embodiment is preferably 80 to 99 mass%, more preferably 90 to 99 mass%, even more preferably 94 to 99 mass%, still more preferably 95 to 99 mass%, and particularly preferably 95 to 98 mass%. The mass proportion of the light-diffusing filler in 100% by mass of the methacrylic resin composition of this embodiment is preferably 0.9 to 6% by mass, more preferably 1 to 6% by mass, and even more preferably 1 to 5% by mass. The mass proportion of the ultraviolet absorber in 100 mass% of the methacrylic resin composition of this embodiment is preferably 0.01 to 0.3 mass%, and more preferably 0.015 to 0.19 mass%. The proportion of the total mass of the methacrylic resin, the light-diffusing filler, and the ultraviolet absorber in 100% by mass of the methacrylic resin composition of the present embodiment is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, and is preferably 100% by mass or less, more preferably 99.9% by mass or less, and even more preferably 99.8% by mass or less.

[0062] The methacrylic resin composition of this embodiment has even better moldability and processability, and in order to be able to fill large molded bodies and fine flow paths, the spiral length measured using an injection molding machine (Shibaura Machine EC-100SX) under the conditions of a resin temperature of 250°C, a mold temperature of 60°C, an injection pressure of 75 MPa, and an injection time of 20 seconds is preferably 24 cm or more, more preferably 25 cm or more, even more preferably 28 cm or more, and particularly preferably 31 cm or more. The spiral length can be measured by the method described in the Examples below. The spiral length can be adjusted by using the methacrylic resin of the preferred embodiment, adjusting the amount of light-diffusing filler added to fall within the range of the preferred embodiment, and adjusting the amount of other additive components added to fall within the range of the preferred embodiment.

[0063] [Molded body] The molded article of the present embodiment contains the methacrylic resin composition of the present embodiment described above. For example, it is a molded article obtained by molding the methacrylic resin composition of the present embodiment described above. In particular, the molded article of the present embodiment is preferably an injection-molded article obtained by injection molding.

[0064] Examples of methods for obtaining a resin molded body include known molding methods such as injection molding, extrusion molding, and pressure molding, and the obtained molded body may be subjected to secondary molding using known molding methods such as pressure molding and vacuum molding.

[0065] In the case of injection molding, the molding temperature is preferably 200° C. or higher and 320° C. or lower. From the viewpoint of productivity, it is more preferably 210° C. or higher, and even more preferably 220° C. or higher, and from the viewpoint of preventing yellowing of the methacrylic resin composition due to decomposition of the resin, it is more preferably 300° C. or lower, and even more preferably 290° C. or lower.

[0066] The molded article of this embodiment is preferably a thin, elongated molded article. Here, "thin, elongated shape" refers to a molded product in which the thickness of the thinnest part other than the part having the channel structure is less than 4 mm, and the length in the flow direction of the molded product, i.e., the flow length of the resin (N), is longer than the length in the direction perpendicular to the flow direction of the resin (V).

[0067] In the above-mentioned thin, elongated molded body, the relationship between the flow length N (mm) and the length V (mm) perpendicular to the resin flow direction is more preferably N / V>1.2, and even more preferably N / V>1.3.

[0068] (thickness t) As described above, the thickness t refers to the thickness of the thinnest part of the molded body other than the part having the channel structure, that is, the thinnest part of the flow cross section that appears when the molded body of this embodiment is cut in a direction perpendicular to its flow direction. In some molded articles, a leaf-vein-like channel structure may be partially provided to aid flow, or a channel structure may be provided for welding, joining, screwing, or tapping with other components. However, the thickness t of the molded article in this embodiment does not refer to the thickness of the portion having the channel structure, but rather to the thickness of the thinnest portion other than the portion having the channel structure. To effectively reduce the light source image of an internal light source, the thickness t is preferably 1 mm or more, more preferably 1.3 mm or more, and even more preferably 1.5 mm or more. Furthermore, to ensure bright and highly visible light when incident on the molded article, the thickness t is preferably 5 mm or less, more preferably 4.5 mm or less, even more preferably 4 mm or less, and even more preferably 3.5 mm or less.

[0069] (Length L) In this embodiment, the length L of the molded body refers to the length from the gate on the molded body to the farthest point from the gate. When two gates are used, the midpoint between gate 1 and gate 2 is defined as midpoint 1, and the longest length among the length from the farthest point U from midpoint 1 to the gate closest to location U, or the length from gate 1 or gate 2 to midpoint 1, is defined as length L. When three gates are used, the midpoint between gate 1 and gate 2 is defined as midpoint 1, the midpoint between gate 1 and gate 3 is defined as midpoint 2, and the midpoint between gate 2 and gate 3 is defined as midpoint 3. The longest length among the length from the farthest point W from midpoint 1 to the gate closest to location W, the length from the farthest point X from midpoint 2 to the gate closest to location X, the length from the farthest point Y from midpoint 3 to the gate closest to location Y, the length from gate 1 or gate 2 to midpoint 1, the length from gate 1 or 3 to midpoint 2, and the length from gate 2 or gate 3 to midpoint 3, is defined as length L. Measurements are similar when four or more gates are used. The midpoint between the gates and the length L can be measured along the surface of the molded body using an radius gauge, pin gauge, digital caliper, micrometer, etc. If the molded body is spherical or has multiple midpoints, any one of these can be used as the midpoint to determine the farthest point and length L. For the purpose of arranging a large internal light source or multiple internal light sources to make the molded product bright and highly visible when light enters the molded product, to prevent the gas trapped in the light-diffusing filler from exploding when the resin flows join together, and to reduce the number of locations where weld lines occur when the resin flows join together to make a molded product in which light is diffused uniformly, L is preferably 130 mm or more, more preferably 150 mm or more, even more preferably 180 mm or more, even more preferably 210 mm or more, even more preferably 240 mm or more, and particularly preferably 270 mm or more. It is necessary to use a mold having a final filling portion within the mold in order to measure the length L. By using a mold having a final filling portion within the mold, it is possible to evaluate whether a molded product having L within the above-mentioned suitable range can be obtained, taking into account the force that inhibits the flow of the resin composition, which acts in the opposite direction to the flow direction of the resin composition, due to the generation of gas from the resin composition being filled and the release of gas entrapped in the light-diffusing filler.

[0070] (Ratio of length L to thickness t of molded body L / t) In order to arrange an appropriate internal light source and make the molded body bright and highly visible when light enters the molded body, the ratio L / t of length L to thickness t is preferably 65 or more, more preferably 70 or more, even more preferably 75 or more, even more preferably 90 or more, and even more preferably 110 or more. In particular, the injection molded article of this embodiment preferably has a thickness t of 1 to 5 mm, a length L of 130 mm or more, and an L / t ratio of 65 or more.

[0071] (Diffusion rate of molded body) In the case of an injection-molded article, the diffusivity of the molded article of this embodiment is preferably stable regardless of the distance from the gate. Particularly when used in vehicle components, a stable diffusivity is required regardless of the location of the molded article, leading to stable visibility. The greater the distance from the gate, the less the injection molding pressure is transmitted, and the diffusivity tends to vary from that in the vicinity of the gate. To stabilize this, the diffusivity can be stabilized by adjusting the type and amount of diffusive material, the fluidity of the base methacrylic resin, and the molding conditions. Regarding the change in diffusivity, it is preferable that the difference between the diffusivity D at 30 mm from the gate and the diffusivity DH at 150 mm from the gate is small. It is more preferable that the difference between the diffusivity D and the diffusivity DT at 200 mm from the gate is small. It is even more preferable that the difference between the diffusivity D and the diffusivity DG at 240 mm from the gate is small. The difference between the diffusivity D and the diffusivities DH, DT, and DG is preferably 5% or less, more preferably 3% or less, and even more preferably 2% or less. Such a molded article can be suitably used as a vehicle member. The diffusivities D, DH, DT, and DG can be measured at lengths of 30 mm, 150 mm, 200 mm, and 240 mm measured from the gate along the surface of the molded body, using, for example, a diffusivity meter as described below. Considering that mounting holes for other components will be provided in the molded body, it is sufficient for parts of the molded body to have small differences in diffusivity, and small differences in diffusivity are preferred as they lead to stable visibility.

[0072] (Application) The molded article of this embodiment has excellent heat deformation resistance and long-term properties, and exhibits excellent light transmission and light diffusion properties, and therefore can be suitably used for architectural components, vehicle components, electrical and electronic components, lighting components, etc. Specifically, it is suitable for vehicle interior and exterior components such as lighting covers, signs, vehicle lighting components, emblems, shift levers, switch panels, and light guide portions of buttons. In particular, it can maintain its shape even when placed in close proximity to high-power LEDs, and is bright and has excellent visibility while sufficiently reducing the light source image, making it particularly suitable for light source image reducing components such as vehicle lighting components and lamp covers arranged inside combination lamps (particularly rear combination lamps). [Example]

[0073] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0074] [Raw materials] (Methacrylic resin) The raw materials of the methacrylic resin used in the production of the methacrylic resin composition are as follows. Methyl methacrylate (MMA): manufactured by Asahi Kasei (containing 2.5 ppm of 2,4-dimethyl-6-t-butylphenol manufactured by Chugai Boeki as a polymerization inhibitor) Methyl acrylate (MA): manufactured by Mitsubishi Chemical (containing 14 ppm of 4-methoxyphenol manufactured by Kawaguchi Chemical Industry Co., Ltd. as a polymerization inhibitor) Ethyl acrylate (EA): manufactured by Mitsubishi Chemical Cyclohexylmaleimide (CMI): Nippon Shokubai n-Octyl mercaptan: Arkema 2-Ethylhexyl thioglycolate: Tokyo Chemical Industry Co., Ltd. t-Butylperoxy-2-ethylhexanoate: NOF Corporation Perhexa 22: NOF Corporation Metaxylene: manufactured by Tokyo Chemical Industry Co., Ltd., used as a polymerization solvent Lauroyl peroxide: Made by Nippon Oil & Fats - Tricalcium phosphate: Made by Nippon Chemical Industry, used as a suspending agent Calcium carbonate: manufactured by Shiraishi Kogyo, used as a suspending agent Sodium lauryl sulfate: manufactured by Wako Pure Chemical Industries, used as a suspension aid

[0075] (Light diffusing filler) Cross-linked silicone resin: Momentive Japan (average particle size 2 μm, refractive index 1.42) ·Crosslinked styrene-MMA resin: Sekisui Plastics (average particle size 5μm, refractive index 1.53) Barium sulfate: Takehara Chemical Industry Co., Ltd. (average particle size 5 μm, refractive index 1.64) Titanium dioxide: Ishihara Sangyo Kaisha (average particle size 0.21 μm, refractive index 2.71)

[0076] (ultraviolet absorber) Tinuvin P: BASF, melting point 128°C, benzotriazole-based UV absorber (maximum absorption wavelength 345nm) Seesorb 703: Made by Shipro Chemicals. Melting point: 138°C. Benzotriazole-based UV absorber (maximum absorption wavelength: 355 nm). Tinuvin 770DF: BASF, melting point 137°C, hindered amine light stabilizer (maximum absorption wavelength 340nm)

[0077] (heat stabilizer) Adeka Stab 2112: Made by Adeka, melting point 180°C Irganox 1010: BASF, melting point 110°C Adeka Stab AO-80: Made by Adeka, melting point 110°C

[0078] (strength modifier) Kane Ace M-210: Made by Kaneka, refractive index 1.491

[0079] (lubricant) Kalcol 8098: Kao Chemical

[0080] (dye) Macrolex Red EG: LANXESS (CI Solvent Red 135)

[0081] [Measurement and evaluation methods] (Molecular weight measurement of methacrylic resin) The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) (Mn is the number average molecular weight) of the methacrylic resin were measured using the following apparatus and conditions. Measurement equipment: Tosoh Corporation gel permeation chromatography (HLC-8320GPC) Measurement conditions: Columns: One TSKguardcolumn SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 connected in series. With this column, high molecular weights elute early, while low molecular weights elute slowly. Detector: RI (differential refractive index) detector Detection sensitivity: 3.0mV / min Column temperature: 40℃ Sample: 0.02 g of methacrylic resin in 20 mL of tetrahydrofuran solution Injection volume: 10μL Developing solvent: tetrahydrofuran, flow rate: 0.6 mL / min, 0.1 g / L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard. As standard samples for the calibration curve, the following ten types of polymethyl methacrylate (PMMA Calibration Kit MM-10, manufactured by Polymer Laboratories) with known monodisperse peak molecular weights and different molecular weights were used. Since the polymethyl methacrylate standards used for the calibration curve standard samples each had a single peak, the corresponding peak was expressed as the weight peak molecular weight Mp, which was distinguished from the peak top molecular weight calculated when a sample had multiple peaks. Weight peak molecular weight (Mp) Standard sample 1 1,916,000 Standard sample 2 625,500 Standard sample 3 298,900 Standard sample 4 138,600 Standard sample 5 60,150 Standard sample 6 27,600 Standard sample 7 10,290 Standard sample 8 5,000 Standard sample 9 2,810 Standard Material 10,850 Under the above conditions, the RI detection intensity was measured against the elution time of the methacrylic resin. Based on the area in the GPC elution curve and a calibration curve of a third-order approximation equation, the weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and amount of molecular weight components present that are 1 / 5 or less of the peak top molecular weight (Mp) of the methacrylic resin were determined.

[0082] (Analysis of structural units of methacrylic resins) 1 The monomer units were identified by H-NMR measurement, and their abundance (mass %) was calculated. 1 The measurement conditions for H-NMR measurement are as follows: Equipment: JEOL-ECA500 Solvent: CDCl3-d1 (deuterated chloroform) Sample: 1 g of methacrylic resin was dissolved in 10 ml of acetone, 20 ml of methanol was added dropwise, and the mixture was filtered. The insoluble matter was dried in vacuum at 40°C for 15 hours, and 15 mg of the resulting solution was dissolved in 0.75 mL of CDCl3-d to prepare the sample for measurement.

[0083] (Amount of unsaturated double bond terminals in methacrylic resin) 1 The monomer units were identified by H-NMR measurement, and the amount (mol %) present in the methacrylic resin was calculated. The amount of unsaturated double bond terminals was calculated from the integrated value (5.4 to 5.6 ppm) of the unsaturated double bond terminal peak and the integrated value (3.6 ppm) of the peak of the methyl group bonded to the oxygen atom of the ester group of the methacrylic resin. 1 The measurement conditions for H-NMR measurement are as follows: Equipment: JEOL-ECA500 Number of scans: 5000 Measurement temperature: room temperature Observation kernel: 1 H(500MHz) Solvent: CDCl3-d1 (deuterated chloroform) Sample: 1 g of methacrylic resin was dissolved in 10 ml of chloroform, 20 ml of methanol was added dropwise, and the mixture was filtered. The insoluble matter after filtration was dissolved again in 10 ml of chloroform, and 20 ml of methanol was added dropwise and the filtration process was repeated twice. The remaining insoluble matter was vacuum dried at 40°C for 15 hours, and 75 mg of the remaining insoluble matter was dissolved in 0.75 mL of CDCl3-d to prepare the sample for measurement. If the amount of insoluble matter after the final filtration was less than 75 mg, the above procedure was repeated until it reached 75 mg.

[0084] (Elemental analysis) The monomer units of methacrylic resin 9 in Production Example 9 described below were identified by elemental analysis. Sample: 1 g of methacrylic resin was dissolved in 10 ml of acetone, 20 ml of methanol was added dropwise, and the mixture was filtered. The insoluble matter was vacuum dried at 40°C for 15 hours, leaving 7.5 mg of the sample. This was placed in a platinum pan and measured using a Mitsubishi Chemical Analytech TN-110 under the following measurement conditions. The average of two measurements was taken as the total nitrogen content. The sample container (platinum pan) used had been previously introduced into the instrument and pre-baked. The CMI monomer unit content (wt%) and MMA monomer unit content (wt%) in the polymer were calculated from the measured total nitrogen content according to the following formulas (A) and (B). Measurement conditions Temperature: Pyrolysis furnace 800℃, oxidation furnace 900℃ Carrier gas: O2 (300 mL / min.), Ar / O2 (400 mL / min.) Standard sample: Pyridine / toluene solution Detector: Reduced pressure chemiluminescence detector Range: Low [Total nitrogen content] × (CMI molecular weight: 179 / nitrogen molecular weight: 14) = [CMI monomer unit content (wt%)] Equation (A) 100 (wt%) - [CMI monomer unit content (wt%)] = [MMA monomer unit content (wt%)] Equation (B)

[0085] (Measurement of Residual Monomer Amount in Methacrylic Resin Composition) Measurement was carried out using GC with a calibration curve method. More specifically, a portion of the resulting methacrylic resin composition was sampled and weighed, and the sample was dissolved in chloroform to prepare a 0.5% by mass solution. Nonane was added as an internal standard. A Shimadzu FID gas chromatograph (product number: GC2025) was used, along with a 0.32 mm inner diameter, 30 m long capillary column (Phenomenex, product number: ZB-1). The sample was held at 45°C for 5 minutes, then heated to 110°C at a rate of 10°C / min, then to 200°C at a rate of 30°C / min, then to 240°C at a rate of 10°C / min, then to 300°C at a rate of 50°C / min, and held at 300°C for 10 minutes.

[0086] (Total light transmittance) The total light transmittance of the 2 mm thick portion of the plate-shaped sample was measured using a Nippon Denshoku NDH7000 in accordance with JIS K7361. The plate-shaped sample used was a 100 mm × 100 mm × 2 mm plate-shaped sample B manufactured by injection molding, as described below. The total light transmittance was rated as ◎ (excellent) for 60% or more, ◯ (good) for 40% or more, △ (sufficient for practical use) for 30% or more, △△ (no practical problems) for 5% or more, and × (poor) for less than 5%.

[0087] (Diffusion rate) The transmittance diffusivity of the 2 mm thick portion of the plate-shaped sample was measured using a Nippon Denshoku GC5000 to measure the luminance (transmitted light intensity) at angles of 5°, 20°, and 70°, and the diffusivity was calculated using the following formula in accordance with DIN 5036. The plate-shaped sample used was plate-shaped sample B, measuring 100 mm x 100 mm x 2 mm and manufactured by injection molding, as described below. (Diffusion rate calculation formula) Diffusion factor = (20° transmitted light intensity + 70° transmitted light intensity) ÷ (2 × 5° transmitted light intensity) × 100 The diffusion rate was rated as ◎ (excellent) for 30% or more, ◯ (good) for 10% or more, △ (no practical problems) for 5% or more, and × (poor) for less than 5%.

[0088] (Long term usage characteristics) Using a Suga Test Instruments Sunshine Carbon Arc Weather Meter, a 2000-hour test was conducted under conditions of a black panel temperature of 63°C and 18 minutes of rainfall over a 120-minute period. The long-term usage characteristics were evaluated by measuring the color difference (ΔE) before and after the test at a thickness of 3 mm using a Nippon Denshoku TC8600 under a C-type light source and a 10° field of view in transmission mode. The flat plate sample used was a 100 mm x 100 mm x 3 mm flat plate sample A manufactured by injection molding, as described below. If ΔE was 0.5 or less, it was rated as ◎ (excellent), if it was 1.4 or less, it was rated as ○ (good), if it was 1.8 or less, it was △ (sufficient for practical use), and if ΔE was more than 1.8, it was rated as × (poor).

[0089] (Moldability) An evaluation mold with pin gates 50 mm from the left and top edges was used, capable of molding a molded body measuring 350 mm x 100 mm x 2 mm thick. The conditions were set to a Shibaura Machine EC-100SX: cylinder temperature 280°C, mold temperature 50°C, injection speed 130 mm / sec, and primary hold pressure 50 MPa. The presence or absence of molding defects was evaluated in the region from the end of the flow to 20 mm above the flat sample. When the evaluation mold was used and the resin was completely filled, a molded body measuring 350 mm x 100 mm x t = 2 mm, length L = 304 mm, and L / t = 152 was obtained. If the resin was filled to the very edge of the mold and no molding defects were observed, the result was rated as ◯ (excellent); if slight molding defects were observed regardless of the degree of resin filling but could be improved by changing molding conditions other than temperature and injection speed, the result was △ (level that is not problematic for practical use); and if molding defects were observed and could not be improved by changing molding conditions other than temperature and injection speed, the result was rated as × (poor).

[0090] (molding fluidity) -Measuring spiral length- A test was conducted to determine the relative flowability of each resin based on the distance it flowed through a spiral cavity with a constant cross-sectional area. Injection molding machine: Shibaura Machine EC-100SX Measurement mold: A mold with a groove 2 mm deep and 12.7 mm wide carved into the surface in the shape of an Archimedes spiral from the center of the surface Injection conditions Resin temperature: 250℃ Mold temperature: 60℃ Injection pressure: 75MPa Injection time: 20 seconds The resin was injected into the center of the mold surface under the above conditions. The spiral molded product was removed 20 seconds after the end of injection, and the length (cm) of the spiral portion was measured, which was used as an index for evaluating the flowability during molding processing. If the SFD (spiral length) was 31 cm or more, it was rated as ◎ (particularly excellent), if it was 28 cm or more, it was rated as 〇 (good), if it was 25 cm or more, it was △ (sufficient for practical use), and if it was 24 cm or less, it was △△ (practical but slightly inferior). The mold used to measure the spiral length was engraved in an Archimedes spiral shape up to a spiral length of 107 cm, and from 107 cm onwards, a flow path 0.5 mm deep on the surface of the mold extended to the outside of the mold, and there was no final filling section inside the mold.

[0091] (heat deformation resistance) As an index of heat distortion resistance, the midpoint glass transition temperature of a methacrylic resin composition sample cut from the molded article was measured. Using a differential scanning calorimeter (Diamond DSC, manufactured by PerkinElmer Japan Co., Ltd.), approximately 10 mg of the sample was heated from 40°C to 210°C at a heating rate of 10°C / min in accordance with JIS-K-7121 under a nitrogen gas atmosphere using α-alumina as a reference. The sample was then cooled to 40°C and heated again from 40°C to 210°C at a heating rate of 10°C / min. The midpoint glass transition temperature was determined from the second DSC curve. Midpoint glass transition temperatures of 118°C or higher were rated as excellent (excellent), 111°C or higher as good (good), 105°C or higher as fair (no practical problems), and less than 105°C as poor. When multiple inflection points were observed in the glass transition curve, the value of the largest inflection point was used. The midpoint glass transition temperature of the methacrylic resin can also be measured in the same manner as above.

[0092] (Heat decomposition resistance) A 10 mg sample of the methacrylic resin composition cut out from the molded body was placed on a differential thermobalance (Rigaku Thermo PlusEvo2) and heated from room temperature at 20°C / min under a nitrogen atmosphere. After being held at 100°C for 5 minutes, the temperature was again raised at 20°C / min to 290°C and held there for 30 minutes. The amount of thermal decomposition after being held at 290°C for 30 minutes was evaluated. A weight loss of less than 1.5% was rated as ⊚ (excellent), less than 3% as ◯ (good), less than 4% as △ (sufficient for practical use), and 4% or more as × (poor).

[0093] (shock resistance) The result of the unnotched Charpy impact test conducted in accordance with JIS K7111-1 was 20kJ / m 2 If it is above 17kJ / m, it is ◎ (excellent). 2 Above 0 (good), 15kJ / m 2 Above 15kJ / m 2 If it was less than 15kJ / m, it was marked as × (bad). 2 If the above is the case, a molded article having a good strength at the attachment portion to other members can be obtained.

[0094] (Bleed-out resistance) Plate-shaped sample A was suspended in an Espec thermo-hygrostat and left to stand for 1000 hours under conditions of 85°C x 85% RH. After removing it from the tester, the transmitted light intensity was measured at a measurement angle of 5° and compared with the value before the test. If the change in transmitted light intensity was within 10%, it was rated as ◯ (good); if it was within 15%, it was △ (no practical problem); and if it exceeded 15%, it was rated × (poor). If the change in transmitted light intensity was small, the change in transmitted light intensity due to bleed-out of the additive was small, and the sample can be used well in high-temperature, high-humidity environments such as inside an automobile lamp housing or the inside of a car.

[0095] (viscosity measurement) The viscosity of the methacrylic resin composition was measured at 260°C and a shear rate of 100 (1 / sec) using a twin capillary rheometer. The long die had a length of 16 mm, a diameter of 1φmm, and an incidence angle of 180°, while the short die had a length of 0.25 mm, a diameter of 1φmm, and an incidence angle of 180°. The results were corrected using the Bagley correction.

[0096] (yellowish) A flat plate sample B, which will be described later, was placed 30 mm from a white LED light source (TSPA22x8-57W), the light source was turned on in a dark room, and the color of the diffused light was confirmed through the flat plate sample B. If the color of the plate when viewed visually through the flat plate sample B was only slightly different from the color of the light source, it was rated as ◯ (good). If the color of the plate when viewed visually through the flat plate sample B was significantly different from the color of the light source and the plate appeared yellowish, it was rated as △ (no problem in practical use, but issues with use in automotive components, etc.). Note that Example 3 was intentionally dyed red using a coloring dye, so no evaluation was performed.

[0097] <Production Example 1 (Production of Methacrylic Resin 1)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 26 kg of ion-exchanged water was charged into a 60 L reactor, and the temperature was raised to 80°C. The entire mixed liquid, 21.2 kg of methyl methacrylate, 0.43 kg of methyl acrylate, 27 g of lauroyl peroxide, and 55 g of n-octyl mercaptan were then charged. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80°C, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C, and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 1). The resulting resin had a weight-average molecular weight of 108,000, a molecular weight distribution (Mw / Mn) of 1.85, a molecular weight component content of 4.4% with a molecular weight less than 1 / 5 of the peak top molecular weight (Mp), a monomer unit content of MMA / MA of 98 / 2 by mass, and an unsaturated bond terminal content of 0.008 mol%.

[0098] <Production Example 2 (Production of Methacrylic Resin 2)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 26 kg of ion-exchanged water was added to a 60 L reactor, and the temperature was raised to 80°C. The entire mixture, 20.5 kg of methyl methacrylate, 1.32 kg of ethyl acrylate, 33 g of lauroyl peroxide, and 27.5 g of n-octyl mercaptan were then added. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80°C, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min. Thereafter, the mixture was aged for 60 minutes to essentially complete the polymerization reaction. Next, the mixture was cooled to 50°C and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 2). The resulting resin had a weight-average molecular weight of 189,000, a molecular weight distribution (Mw / Mn) of 1.85, a molecular weight component content of 4.3% with a molecular weight less than 1 / 5 of the peak top molecular weight (Mp), a monomer unit content of MMA / EA of 94 / 6% by mass, and an unsaturated bond terminal content of 0.009 mol%.

[0099] <Production Example 3 (Production of Methacrylic Resin 3)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 26 kg of ion-exchanged water was added to a 60 L reactor, and the temperature was raised to 80°C. The entire mixed liquid, 21.2 kg of methyl methacrylate, 0.43 kg of methyl acrylate, 27 g of lauroyl peroxide, and 88 g of n-octyl mercaptan were then added. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80°C, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C, and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 3). The weight-average molecular weight of the obtained resin was 73,000, the molecular weight distribution (Mw / Mn) was 1.85, and the abundance of molecular weight components less than 1 / 5 of the peak top molecular weight (Mp) was 4.7%. The monomer units were MMA / MA = 98 / 2 mass%, and the amount of unsaturated bond terminals was 0.007 mol%.

[0100] <Production Example 4 (Production of Methacrylic Resin 4)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 23 kg of ion-exchanged water was placed in a 60 L reactor, and the temperature was raised to 80° C., and the entire mixture, 5.1 kg of methyl methacrylate, 36 g of lauroyl peroxide, and 94 g of 2-ethylhexyl thioglycolate were placed in the reactor. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80 ° C. After observing an exothermic peak, the temperature was raised to 92 ° C. at a rate of 1 ° C. / min and maintained at 92 ° C. to 94 ° C. for 30 minutes. After that, the temperature was lowered to 80 ° C. at a rate of 1 ° C. / min, and then 15.3 kg of methyl methacrylate, 360 g of methyl acrylate, 15 g of lauroyl peroxide, and 41.8 g of n-octyl mercaptan were added, and suspension polymerization was continued while maintaining the temperature at about 80 ° C. After observing the exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and then the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 4). The resulting methacrylic resin had an Mw of 83,000, a molecular weight distribution (Mw / Mn) of 2.3, a molecular weight component content of 1 / 5 or less of the peak top molecular weight (Mp) of 11.5%, a monomer unit content of MMA / MA of 98.3 / 1.7 mass%, and an unsaturated bond terminal content of 0.002 mol%.

[0101] <Production Example 5 (Production of Methacrylic Resin 5)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 23 kg of ion-exchanged water was added to a 60 L reactor, and the temperature was raised to 80°C. The entire mixed liquid, 4.95 kg of methyl methacrylate, 50 g of methyl acrylate, 36 g of lauroyl peroxide, and 110 g of 2-ethylhexyl thioglycolate were then added. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80 ° C. After observing the exothermic peak, the temperature was raised to 92 ° C. at a rate of 1 ° C. / min and maintained at 92 ° C. to 94 ° C. for 30 minutes. After that, the temperature was lowered to 80 ° C. at a rate of 1 ° C. / min, and then 15.0 kg of methyl methacrylate, 0.3 kg of methyl acrylate, 21 g of lauroyl peroxide, and 26 g of n-octyl mercaptan were added, and suspension polymerization was continued while maintaining the temperature at about 80 ° C. After observing the exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and then the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 5). The resulting methacrylic resin had an Mw of 119,000, a molecular weight distribution (Mw / Mn) of 3.4, and a molecular weight component content of 23.1% with a molecular weight less than 1 / 5 of the peak top molecular weight (Mp).The monomer unit content was MMA / MA = 98.1 / 1.9 mass%, and the amount of unsaturated bond terminals was 0.003 mol%.

[0102] <Production Example 6 (Production of Methacrylic Resin 6)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 23 kg of ion-exchanged water was placed in a 60 L reactor, and the temperature was raised to 80° C., and the entire mixture, 5.5 kg of methyl methacrylate, 40 g of lauroyl peroxide, and 90 g of 2-ethylhexyl thioglycolate were placed in the reactor. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80° C. An exothermic peak was observed 80 minutes after the raw materials were added. The temperature was then raised to 92°C at a rate of 1°C / min, and the temperature was maintained at 92-94°C for 30 minutes. The temperature was then lowered to 80°C at a rate of 1°C / min, after which 16.2 kg of methyl methacrylate, 0.75 kg of methyl acrylate, 19 g of lauroyl peroxide, and 18.7 g of n-octyl mercaptan were added, and suspension polymerization was continued while maintaining the temperature at approximately 80°C. An exothermic peak was observed 105 minutes after the raw materials were added. Thereafter, the temperature was raised to 92°C at a rate of 1°C / min, and the mixture was aged for 60 minutes to essentially complete the polymerization reaction. Next, the mixture was cooled to 50°C and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 6). The obtained polymer microparticles were melt-kneaded in a φ30 mm twin-screw extruder set at 240° C., and the strands were cooled and cut to obtain resin pellets (methacrylic resin 6). The weight-average molecular weight of the obtained resin pellets was 169,000, and the molecular weight distribution (Mw / Mn) was 3.7. Furthermore, the abundance (%) of molecular weight components with a molecular weight less than 1 / 5 of the Mp value was 24.3%. The monomer units were MMA / MA = 96.5 / 3.5 mass%, and the amount of unsaturated bond terminals was 0.003 mol%.

[0103] <Production Example 7 (Production of Methacrylic Resin 7)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 26 kg of ion-exchanged water was charged into a 60 L reactor, and the temperature was raised to 80°C. The entire mixed liquid, 21.3 kg of methyl methacrylate, 2.3 kg of methyl acrylate, 65 g of lauroyl peroxide, and 70 g of n-octyl mercaptan were then charged. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80°C, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C, and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 7). The resulting methacrylic resin had an Mw of 92,000, a molecular weight distribution (Mw / Mn) of 1.86, and a content (%) of molecular weight components with a molecular weight of 1 / 5 or less of the Mp value of 4.6%. The monomer units were MMA / MA = 90 / 10 mass%, and the content of unsaturated double bond terminals was 0.008 mol%.

[0104] <Production Example 8 (Production of Methacrylic Resin 8)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 23 kg of ion-exchanged water was added to a 60 L reactor, and the temperature was raised to 80°C. The entire mixed liquid, 6.7 kg of methyl methacrylate, 0.07 kg of methyl acrylate, 40 g of lauroyl peroxide, and 115 g of 2-ethylhexyl thioglycolate were then added. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 80°C, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min and maintained at 92°C to 94°C for 30 minutes. After that, the temperature was lowered to 80°C at a rate of 1°C / min, and then 13.4 kg of methyl methacrylate, 0.56 kg of methyl acrylate, 10 g of lauroyl peroxide, and 15 g of n-octyl mercaptan were added, and suspension polymerization was continued while maintaining the temperature at about 80°C. After observing the exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and then the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 8). The resulting methacrylic resin had an Mw of 151,000, a molecular weight distribution (Mw / Mn) of 4.4, and a content (%) of molecular weight components less than 1 / 5 of the Mp value of 28.5%. The monomer units were MMA / MA = 97 / 3 mass%, and the content of unsaturated double bond terminals was 0.004 mol%.

[0105] <Production Example 9 (Production of Methacrylic Resin 9)> Into a vessel equipped with a stirrer, 2 kg of ion-exchanged water, 65 g of tribasic calcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were placed to obtain a mixed liquid. Next, 26 kg of ion-exchanged water was charged into a 60 L reactor, and the temperature was raised to 80°C. The entire mixed liquid, 20.9 kg of methyl methacrylate, 0.88 kg of cyclohexylmaleimide, 40 g of t-butylperoxy-2-ethylhexanoate, and 66 g of n-octyl mercaptan were charged. Thereafter, suspension polymerization was carried out while maintaining the temperature at about 75°C, and after observing an exothermic peak, the temperature was raised to 92°C at a rate of 1°C / min, and the mixture was aged for 60 minutes, after which the polymerization reaction was essentially completed. Next, the mixture was cooled to 50°C, and 20% by mass of sulfuric acid was added to dissolve the suspending agent. The polymerization reaction solution was then passed through a 1.68 mm mesh sieve to remove aggregates, and the resulting bead-like polymer was washed, dehydrated, and dried to obtain polymer microparticles (methacrylic resin 8). The resulting methacrylic resin had an Mw of 95,000, a molecular weight distribution (Mw / Mn) of 1.95, and a content (%) of molecular weight components with a molecular weight of 1 / 5 or less of the Mp value of 5.2%. The monomer units were MMA / CMI = 96.1 / 3.9% by mass, and the content of unsaturated double bond terminals was 0.007 mol%.

[0106] (Production Example 10 (Production of Methacrylic Resin 10)) A pressure-resistant polymerization reactor equipped with a stirrer was charged with 950 g of methyl methacrylate, 9.8 g of methyl acrylate, 0.18 g of Perhexa 22 as a polymerization initiator, 2.8 g of n-octyl mercaptan, and 240 g of meta-xylene. After replacing the atmosphere inside the reaction vessel with nitrogen and sealing it, the temperature was raised to 185°C and a polymerization reaction was carried out for 90 minutes. The contents were removed, the reactor was washed, and the above reaction was repeated seven times. The removed contents were freeze-pulverized and then pelletized using a φ42 mm degassing extruder set at 230°C to obtain methacrylic resin 9. The weight-average molecular weight of the resulting resin was 76,000, the molecular weight distribution (Mw / Mn) was 1.96, the abundance (%) of molecular weight components less than 1 / 5 of the Mp value was 5.1%, the monomer unit was MMA / MA = 99 / 1 mass%, and the amount of unsaturated double bond terminals was 0.014 mol%.

[0107] [Examples 1 to 26] [Comparative Examples 1 to 4] The methacrylic resin, light-diffusing filler, UV absorber, and other additives were weighed out to the blending ratios shown in Tables 1 and 2, then placed in a tumbler and mixed. After thorough mixing, the mixed raw materials were fed into a φ26 mm twin-screw extruder and melt-kneaded (compounded) to form strands. The strands were cooled in a water bath and then cut into pellets using a pelletizer. During compounding, a vacuum line was connected to the vent of the extruder, and volatile components such as moisture and monomer components were removed under conditions of -0.08 MPa. Thus, methacrylic resin compositions were obtained. The kneading temperatures for the resin compositions were 220°C for Examples 9, 10, and 23, 260°C for Example 8, and 240°C for the others. The values ​​in Tables 1 and 2 represent the blending parts (parts by mass) when the mass of the methacrylic resin is 100 parts by mass.

[0108] <Flat sample> (injection molding) The pellets of the obtained methacrylic resin composition were put into an injection molding machine (EC-100SX manufactured by Shibaura Machine), and flat samples A (100 mm × 100 mm × 3 mm, thickness t = 3 mm, length L = 110 mm, L / t = 37) and flat samples B (100 mm × 100 mm × 2 mm, thickness t = 2 mm, length L = 110 mm, L / t = 55) were molded to obtain flat samples for evaluation. The mold used had a mold surface (inner surface of the mold cavity) polished to a finish number of 8000. The molding conditions for this flat sample for evaluation were set as follows. Molding temperature (cylinder temperature): 250 °C Injection speed: 20 mm / second Holding pressure: 70 MPa Mold temperature: 65 °C Also, in order to enhance the transferability of the mold surface polished to a finish number of 8000 during injection molding, it is important to keep the mold temperature at a higher level. If the mold temperature is too high, the cooling time will be too long, which is not practical. The temperature range of the mold to make them quality is 50 °C or higher and 100 °C or lower, more preferably 60 °C or higher and 90 °C or lower, still more preferably 60 °C or higher and 85 °C or lower. This time, 65 °C was selected from among them.

[0109] <ISO dumbbell test piece> (Injection molding) The pellets of the obtained methacrylic resin composition were put into an injection molding machine (EC-100SX manufactured by Shibaura Machine), and ISO No. 1 dumbbell test pieces (thickness t = 4 mm, length L = 175 mm, L / t = 44) were molded, and samples for Charpy impact test were cut out. The molding conditions conformed to ISO K6717-2.

[0110] <Molding of plate-shaped molded body> (Injection molding) Additionally, for Examples 8, 10-16, and 20, pellets of the methacrylic resin composition were placed in an injection molding machine (Shibaura Machine EC-100SX) and injection molded using a plate-shaped mold (220 mm x 10 mm x 3 mm, two-cavity) with a side gate 10-19 mm from the top edge under conditions of a molding temperature (cylinder temperature) of 230 °C, a mold temperature of 60 °C, a primary dwell pressure of 80 MPa (5 seconds), and an injection speed of 20 mm / s to obtain plate-shaped molded bodies. In Examples 12 and 16, the methacrylic resin composition was filled to the final filling point of the mold, resulting in molded bodies with a defect-free appearance of 220 mm x 10 mm x 3 mm thick, L = 201 mm long, and L / t = 67 mm. In Example 8, there were some unfilled areas of resin, and a molded body with a dimension of 189 mm x 10 mm x 3 mm thick, L = 178 mm long, and L / t = 59 mm was obtained. (injection molding 2) An evaluation mold with a pin gate positioned 50 mm from the top and left edges was used, capable of molding a molded article measuring 350 mm × 100 mm × 2 mm thick. The mold conditions were a Shibaura Machine EC-100SX, with a cylinder temperature of 270°C, a mold temperature of 70°C, an injection speed of 140 mm / sec, and a primary hold pressure of 90 MPa. For Examples 1 to 26, which demonstrated sufficient moldability for practical use, injection-molded articles S measuring 350 mm × 100 mm × t = 2 mm, length L = 304 mm, and L / t = 152 mm were obtained. The diffusivities D, DH, DT, and DG of the injection-molded articles S were measured. The results are shown in Table 3. For each of the diffusivities D, DT, and DG, a difference from the diffusivity D was evaluated as excellent (◎) if it was within 2%, good (◯) if it was within 3%, △ (sufficient for practical use) if it was within 5%, and △△ (practical, but issues with use depending on the size of the molded article) if it exceeded 5%. It was found that Examples 1, 17, and 19 have issues with stabilizing diffusivity depending on the size of the molded body when used in applications requiring stable diffusivity, such as vehicle components, even when the molded body has a long length L. In Example 8, DG was slightly inferior. In Example 20, DT and DG were slightly inferior. It was also found that the molded bodies S obtained by injection molding Examples 2 to 7, 9 to 16, 18, and 21 to 26 are injection molded bodies that can be suitably used, regardless of the length L of the molded body, even in applications requiring stable diffusivity, such as vehicle components.

[0111] [Table 1]

[0112] [Table 2]

[0113] [Table 3]

[0114] As shown in Tables 1-3, in Examples 12 to 16, methacrylic resin compositions were produced that not only exhibited excellent total light transmittance, diffusivity, long-term use properties, and heat distortion resistance, but also exhibited favorable moldability, molding fluidity, thermal decomposition resistance, strength, and bleed-out resistance. In Comparative Example 1, the amount of light-diffusing filler added was small, resulting in poor light diffusion. In Comparative Example 2, the amount of light-diffusing filler added was too high, resulting in poor total light transmittance and a molded article that did not appear bright even when light was incident. Furthermore, the amount of light-diffusing filler added was too high, resulting in poor weather resistance, moldability, and thermal decomposition resistance. In Comparative Example 3, no ultraviolet absorber was added, resulting in poor long-term use properties. The molded article produced in Comparative Example 3 is not suitable for long-term use. In Comparative Example 4, the heat distortion resistance was poor. The molded article produced in Comparative Example 4 deformed due to the heat from the light source and could not maintain the desired shape. Although Example 1 was at a practically sufficient level, it was slightly inferior to Examples 12 and 16 in weather resistance, moldability, and molding flowability. Although Example 2 was at a practically sufficient level, it was slightly inferior to Examples 12 and 16 in moldability and molding flowability. Although Example 3 was at a practically sufficient level, it was slightly inferior in moldability, molding fluidity, and bleed-out resistance compared to Examples 12 and 16. Furthermore, although it was at a practically acceptable level, the total light transmittance was low because it was dyed with a red dye. This product was intentionally colored red, and although the total light transmittance was low, it can be used for vehicle stop lamp components where red light must be diffused. Although Example 4 was at a practically sufficient level, it was slightly inferior to Examples 12 and 16 in long-term use properties, moldability, molding flowability, and bleed-out resistance. Although Examples 5 to 7 were at a level sufficient for practical use, compared with Examples 12 and 16, the moldability and molding flowability were slightly inferior. Although Example 8 was at a practically sufficient level, it was slightly inferior in moldability, heat distortion resistance, and bleed-out resistance compared to Examples 12 and 16, and although it was at a practically acceptable level, it was slightly inferior in molding flowability. Although Example 9 was at a practically sufficient level, it was slightly inferior to Examples 12 and 16 in strength and bleed-out resistance. Although Examples 10, 11, and 13 to 15 were at a practically sufficient level, they were slightly inferior to Examples 12 and 16 in bleed-out resistance. Although Examples 17 and 18 were at a level sufficient for practical use, they were slightly inferior to Examples 12 and 16 in light transmittance and weather resistance. Although Example 19 was at a level sufficient for practical use, it was slightly inferior to Examples 12 and 16 in molding flowability and bleed-out resistance. Although Example 20 was at a practically sufficient level, it was slightly inferior to Examples 12 and 16 in terms of resistance to break-out. Although Examples 21 and 22 were at a level sufficient for practical use, they were slightly inferior to Examples 12 and 16 in moldability and bleed-out resistance. Although Example 23 was at a practically sufficient level, it was slightly inferior to Examples 12 and 16 in moldability and thermal decomposition resistance. In Example 24, the moldability and molding flowability were slightly inferior to those of Examples 12 and 16, although they were at a level sufficient for practical use. In Example 25, although the moldability, molding flowability and bleed-out resistance were at a level sufficient for practical use, they were somewhat inferior. In Example 26, when a white LED was viewed through the molded article, it appeared yellow, and the yellowness was somewhat inferior. The moldability, molding flowability, and bleed-out resistance were somewhat inferior. [Industrial Applicability]

[0115] The methacrylic resin composition of this embodiment has excellent heat distortion resistance and long-term properties, and can produce a resin molded product that transmits light well and has excellent light diffusion properties, making it suitable for use in architectural components, vehicle components, electrical and electronic components, lighting components, and the like. Specifically, the composition has industrial applicability as, for example, interior and exterior vehicle components such as lighting covers, signs, vehicle lighting components, emblems, shift levers, switch panels, and light guides for buttons. In particular, the composition can maintain the shape of the molded product even when placed near high-power LEDs, and is bright and highly visible while sufficiently reducing the light source image. Therefore, the composition is particularly suitable and industrially applicable as a vehicle lighting component or a light source image reducing component to be placed inside a rear combination lamp.

Claims

1. A methacrylic resin composition characterized by comprising, per 100 parts by mass of a methacrylic resin containing monomer units derived from a methacrylic acid ester and monomer units derived from a monomer not containing an aromatic ring copolymerizable with the methacrylic acid ester, 0.5 to 6 parts by mass of a light-diffusing filler having an average particle size of 0.2 to 10 μm and 0.005 to 0.3 parts by mass of an ultraviolet absorber, and having a midpoint glass transition temperature of 105°C or higher, and satisfying any one of the following conditions i) to iii): i) The viscosity at 260°C and a shear rate of 100 (1 / sec) is 1000 Pa·s or more and 1500 Pa·s or less, and the midpoint glass transition temperature is 111°C or more and 130°C or less. ii) The viscosity at 260°C and a shear rate of 100 (1 / sec) is 500 Pa·s or more and less than 1000 Pa·s, and the midpoint glass transition temperature is 113°C or more and 130°C or less. iii) The viscosity at 260°C and a shear rate of 100 (1 / sec) is 200 Pa·s or more and less than 500 Pa·s, and the midpoint glass transition temperature is 115°C or more and 130°C or less.

2. The methacrylic resin composition according to claim 1 , wherein the light-diffusing filler is organic particles.

3. 3. The methacrylic resin composition according to claim 1, wherein the light-diffusing filler is a crosslinked styrene-MMA resin or a crosslinked silicone resin.

4. The methacrylic resin composition according to any one of claims 1 to 3, wherein the light-diffusing filler has an average particle size of 1.2 to 9 µm.

5. The methacrylic resin composition according to any one of claims 1 to 4, wherein the weight average molecular weight of the methacrylic resin is 75,000 to 230,000.

6. The methacrylic resin composition according to any one of claims 1 to 5, wherein the methacrylic resin contains 6 to 50% of a molecular weight component having a peak molecular weight (Mp) or less in a GPC elution curve measured by gel permeation chromatography (GPC).

7. The methacrylic resin composition according to any one of claims 1 to 6, wherein the amount of terminal unsaturated double bonds in the methacrylic resin is 0.013 mol% or less.

8. The methacrylic resin composition according to any one of claims 1 to 7, wherein the ultraviolet absorber has a maximum absorption wavelength of 300 nm or more and 350 nm or less in the wavelength range of 300 nm to 830 nm.

9. Further containing additives, The methacrylic resin composition according to any one of claims 1 to 8, wherein the combined mass ratio of additives excluding rubber components to 100 parts by mass of the methacrylic resin is 0.15 parts by mass or less.

10. The methacrylic resin composition according to any one of claims 1 to 9, wherein a residual monomer content is 8000 ppm by mass or less.

11. The methacrylic resin composition according to any one of claims 1 to 10, which does not contain a yellow dye.

12. A molded article obtained by molding the methacrylic resin composition according to any one of claims 1 to 11.

13. The molded body according to claim 12, having a thickness t of 1 to 5 mm.

14. The molded article according to claim 12 or 13, wherein the molding is injection molding.

15. The molded body according to claim 12, wherein the length L and the thickness t satisfy the following conditions (1), (2), and (3). 1mm≦t≦5mm...condition (1) L≧130mm...Condition (2) L / t≧65...Condition (3)

16. The molded article according to any one of claims 12 to 15, which is used for a vehicle member.

17. The molded article according to any one of claims 12 to 15, which is used as a vehicle lighting component.

18. The molded article according to any one of claims 12 to 15, which is used as a lamp cover disposed inside a vehicle combination lamp.

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