Methacrylic resin and method for producing the same, methacrylic resin composition, and molded body

Abstract

To provide a methacrylic resin that exhibits superior heat resistance and thermal decomposition resistance (thermal stability), achieves suppressed discoloration such as yellowing, and offers superior moldability, and a method for producing the same.SOLUTION: A methacrylic resin according to the present disclosure comprises a methacrylic copolymer (A) having 40-99 mass% of a methyl methacrylate (MMA) unit, 1-40 mass% of one or more isopropenyl aromatic compound units (UI) and 0-30 mass% of one or more other units (UO), further comprising 1-1000 ppm of one or more organic disulfide compounds (D), wherein the total residual amount of the raw material monomer of the methacrylic copolymer (A) is 1.00 mass% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a methacrylic resin, a method for producing the same, a methacrylic resin composition, and a molded article. [Background technology]

[0002] Methacrylic resins such as polymethyl methacrylate (PMMA) have excellent transparency, scratch resistance, and moldability, and are widely used as materials for optical components such as light guide plates and lenses; components for vehicles such as automobiles (vehicle interior materials and vehicle exterior materials, etc.); and various components for buildings, household goods, office equipment, and lighting equipment. Methacrylic resins are required to have heat resistance depending on the application. For example, in the backlight of a liquid crystal display including a light source and a light guide plate, the use of high-power light-emitting diodes (LEDs) (e.g., LEDs with an output of 1 W or more) as light sources has been increasing along with the increase in the length of the light path of the light guide plate and the increase in functionality such as improved brightness. In general, in order to prevent light leakage from the light-entering end face of the light guide plate, it is preferable that the light-emitting surface of the LED and the light-entering end face of the light guide plate are as close as possible. However, particularly when using high-power LEDs that generate a large amount of heat, the closer the light-emitting surface of the LED and the light-entering end face of the light guide plate are to the light that is exposed to the heat emitted from the LED, and therefore higher heat resistance is required.

[0003] As one of the methacrylic resins with improved heat resistance, a methacrylic copolymer containing methyl methacrylate (MMA) units and isopropenyl aromatic compound units such as α-methylstyrene (αMSt) units is known. For example, Patent Document 1 discloses a method for producing a methacrylic copolymer by adding a polyfunctional organic peroxide having a 10-hour half-life temperature in the range of 60 to 110°C as a polymerization initiator to a monomer mixture containing methyl methacrylate (MMA) and α-methylstyrene (αMSt) and bulk-polymerizing the mixture (claim 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-218515 [Patent Document 2] Japanese Patent Application Publication No. 3-281648 [Patent Document 3] Japanese Patent Application Publication No. 7-292202 [Patent Document 4] Japanese Patent Application Publication No. 6-345932 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the methacrylic copolymer containing MMA units and isopropenyl aromatic compound units such as αMSt units tends to have a relatively low thermal decomposition temperature. Therefore, in the methacrylic resin mainly containing this copolymer, the copolymer is thermally decomposed during heating and melting during resin production and molding, etc., and the amount of residual monomers in the resin increases, which may cause a decrease in heat resistance. In addition, if the residence time in a heated and melted state during resin production and molding is long, the thermal decomposition of the methacrylic copolymer may cause poor appearance such as foaming.

[0006] As a method for improving the thermal decomposition resistance of the above-mentioned methacrylic copolymer, a method of adding various antioxidants has been proposed. For example, Patent Documents 2 and 3 disclose methacrylic resins in which a hindered phenol compound and a phosphite compound are added as antioxidants to a methacrylic copolymer containing MMA units and αMSt units (claim 1 of Patent Document 2, claim 1 of Patent Document 3). Patent Document 4 discloses a methacrylic resin in which a phenol-acrylate bifunctional compound and a hindered phenol compound are added as antioxidants to a methacrylic copolymer containing MMA units and αMSt units (claim 1 of Patent Document 4).

[0007] The antioxidants used in Patent Documents 2 and 3 cannot effectively capture alkyl radicals generated by thermal decomposition of the main chain of a methacrylic copolymer containing MMA units and isopropenyl aromatic compound units such as αMSt units, and therefore cannot be said to have a sufficient effect of improving thermal decomposition resistance. The antioxidant used in Patent Document 4 has an alkyl radical capturing ability, but its effect of improving thermal decomposition resistance is insufficient, and if the amount added is increased, the resin may discolor (e.g., turn yellow, etc.).

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a methacrylic resin that has good heat resistance and thermal decomposition resistance (thermal stability), is inhibited from discoloring such as yellowing, and has good moldability, and a method for producing the same. [Means for solving the problem]

[0009] The present disclosure provides the following [1] to

[14] methacrylic resins, production methods thereof, methacrylic resin compositions, and molded articles. [1] A methacrylic copolymer (A) comprising 40 to 99 mass% of methyl methacrylate (MMA) units, 1 to 40 mass% of one or more isopropenyl aromatic compound units (UI), and 0 to 30 mass% of one or more other units (UO); Further, it contains 1 to 1000 ppm of one or more organic disulfide compounds (D), A methacrylic resin, in which the total residual amount of raw material monomers of the methacrylic copolymer (A) is 1.00 mass% or less.

[0010] [2] The methacrylic resin of [1], wherein one or more of the isopropenyl aromatic compound units (UI) contain an α-methylstyrene unit. [3] The methacrylic resin according to [1] or [2], wherein the methacrylic copolymer (A) contains, as the other units (UO), an aromatic vinyl compound unit other than an isopropenyl aromatic compound unit.

[0011] [4] The methacrylic resin according to any one of [1] to [3], wherein the one or more organic disulfide compounds (D) include di-tert-dodecyl disulfide (DDS) and / or dibenzyl disulfide (DBS). [5] The methacrylic resin according to any one of [1] to [4], further comprising 0.0001 to 1.0 mass% of one or more organic phosphorus compounds (P). [6] Any of the methacrylic resins [1] to [5] further containing 1000 to 5000 ppm of one or more lubricants (L).

[0012] [7] Any of the methacrylic resins [1] to [6], having a glass transition temperature of 120°C or higher. [8] Any of the methacrylic resins according to [1] to [7], having a 1% weight loss temperature of 270°C or higher, as measured by thermogravimetric analysis under an inert gas atmosphere.

[0013] [9] A methacrylic resin composition comprising the methacrylic resin according to any one of [1] to [8].

[10] A molded article comprising the methacrylic resin according to any one of [1] to [8] or the methacrylic resin composition according to [9].

[0014]

[11] A step (S1) of preparing a polymerization raw material containing, as raw material monomers, 30 to 99 mass% of methyl methacrylate (MMA), 1 to 59 mass% of one or more isopropenyl aromatic compounds (I), and 0 to 49 mass% of one or more other monomers (O), and further containing a polymerization initiator; A step (S2) of polymerizing the polymerization raw material under conditions of a polymerization conversion rate of 30 to 60 mass% to obtain a resin solution containing the methacrylic resin; and (S3) removing by volatilization at least a portion of the raw material monomers present in the resin solution in one or more steps to obtain the methacrylic resin having a total residual amount of raw material monomers of 1.00 mass% or less. The method for producing a methacrylic resin according to any one of [1] to [8], wherein one or more organic disulfide compounds (D) are added to at least one of the polymerization raw material, the resin solution obtained after completion of step (S2), and the resin solution during which step (S3) is being carried out, so that the one or more organic disulfide compounds (D) are present in an amount of 1 to 1000 ppm in the methacrylic resin obtained after step (S3).

[0015]

[12] The method for producing a methacrylic resin according to

[11] , wherein one or more organic disulfide compounds (D) are added to at least the polymerization raw materials among the polymerization raw materials, the resin solution obtained after completion of step (S2), and the resin solution during step (S3).

[13] The method for producing a methacrylic resin according to

[11] or

[12] , further comprising adding one or more organic phosphorus compounds (P) to at least one of the polymerization raw materials, the resin solution obtained after completion of step (S2), and the resin solution during step (S3).

[14] The method for producing a methacrylic resin according to any one of

[11] to

[13] , further comprising adding one or more lubricants (L) to at least one of the polymerization raw materials, the resin solution obtained after completion of step (S2), and the resin solution during step (S3). Effect of the Invention

[0016] According to the present disclosure, it is possible to provide a methacrylic resin having good heat resistance and resistance to thermal decomposition (thermal stability), suppressed discoloration such as yellowing, and good moldability, and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In this specification, unless otherwise specified, a "unit" contained in a polymer is a repeating unit contained in the polymer, and is a monomer unit derived from a raw material monomer or a derived unit derived from one or more types of monomer units. In this specification, (meth)acrylic is a general term for acrylic and methacrylic, and the same applies to (meth)acrylonitrile and the like.

[0018] [Methacrylic resin] The methacrylic resin of the present disclosure contains a methacrylic copolymer (A) consisting of 40 to 99 mass% of methyl methacrylate (MMA) units, 1 to 40 mass% of one or more isopropenyl aromatic compound units (UI), and 0 to 30 mass% of one or more other units (UO). The content of the methacrylic copolymer (A) in the methacrylic resin of the present disclosure is not particularly limited, and is preferably 97.0 mass% or more. The lower limit is more preferably 97.5 mass%, further preferably 98.0 mass%, particularly preferably 98.5 mass%, and most preferably 99.0 mass%. The upper limit is 99.9999 mass%. In the methacrylic resin of the present disclosure, the total residual amount of raw material monomers of the methacrylic copolymer (A) is 0 to 1.00% by mass. The methacrylic resin of the present disclosure contains 1 to 1000 ppm of one or more organic disulfide compounds (D). The methacrylic resin of the present disclosure can further include one or more optional components, as needed.

[0019] (Methacrylic copolymer (A)) The content of methyl methacrylate (MMA) units in the methacrylic copolymer (A) is 40 to 99% by mass. The lower limit is preferably 45% by mass, more preferably 50% by mass, even more preferably 55% by mass, even more preferably 60% by mass, even more preferably 65% ​​by mass, particularly preferably 70% by mass, and most preferably 75% by mass. The upper limit is preferably 95% by mass, more preferably 90% by mass, and particularly preferably 85% by mass. The content of one or more isopropenyl aromatic compound units (UI) in the methacrylic copolymer (A) (the total amount when there are multiple types, unless otherwise specified) is 1 to 40 mass%. The lower limit is preferably 5 mass%, more preferably 10 mass%, and particularly preferably 15 mass%. The upper limit is preferably 35 mass%, more preferably 30 mass%, particularly preferably 25 mass%, and most preferably 20 mass%.

[0020] The content of one or more other units (UO) in the methacrylic copolymer (A) (the total amount when there are multiple units, unless otherwise specified) is 0 to 30% by mass. The upper limit is preferably 25% by mass, more preferably 20% by mass, even more preferably 15% by mass, particularly preferably 10% by mass, and most preferably 5% by mass. In the methacrylic copolymer (A), the total of the content of MMA units, the content of one or more isopropenyl aromatic compound units (UI), and the content of one or more other units (UO) is 100 mass%.

[0021] If the content of the isopropenyl aromatic compound unit (UI) is less than the lower limit, the heat resistance of the methacrylic copolymer (A) may be insufficient. If the content of the isopropenyl aromatic compound unit (UI) is more than the upper limit, the polymerizability (productivity), thermal decomposition resistance, and moldability of the methacrylic copolymer (A) may be reduced. If the content of the isopropenyl aromatic compound unit (UI) is more than the upper limit, it becomes difficult to control the copolymerization of the isopropenyl aromatic compound (I), and it may be difficult to stably produce a methacrylic copolymer (A) having a uniform composition, such as the content of the isopropenyl aromatic compound unit (UI). Variation in the composition, such as the content of the isopropenyl aromatic compound unit (UI), may lead to a decrease in heat resistance and mechanical properties, such as rigidity and surface hardness.

[0022] If the content of MMA unit and the content of isopropenyl aromatic compound unit (UI) are within the above range, the methacrylic copolymer (A) can have good transparency, heat resistance, thermal decomposition resistance, polymerizability (productivity), and moldability. In addition, if the content of MMA unit and the content of isopropenyl aromatic compound unit (UI) are within the above range, the copolymerization of isopropenyl aromatic compound (I) is relatively easy to control, and the methacrylic copolymer (A) having a uniform composition such as the content of isopropenyl aromatic compound unit (UI) can be stably produced, and the methacrylic copolymer (A) having good heat resistance and mechanical properties such as rigidity and surface hardness can be stably produced.

[0023] The methacrylic copolymer (A) can be obtained by copolymerizing methyl methacrylate (MMA), one or more isopropenyl aromatic compounds (I), and, if necessary, one or more other monomers (O). Examples of the isopropenyl aromatic compound (I) include alkyl-substituted isopropenylbenzenes such as isopropenylbenzene (α-methylstyrene (αMSt)), isopropenylnaphthalene, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, and isopropenyloctylbenzene. From the viewpoint of availability of raw materials, etc., the one or more isopropenyl aromatic compounds (I) preferably contain one or more alkyl-substituted isopropenylbenzenes, and particularly preferably contain isopropenylbenzene (α-methylstyrene (αMSt)).

[0024] The other monomer (O) may be a vinyl monomer (V) having one polymerizable unsaturated bond in one molecule other than methyl methacrylate (MMA) and the isopropenyl aromatic compound (I). Examples of the vinyl monomer (V) include (meth)acrylic acid esters other than MMA, such as methyl acrylate; (meth)acrylic acid alkyl esters such as ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate; and (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate and norbornenyl (meth)acrylate. Other examples of the vinyl monomer (V) include (meth)acrylic acid, (meth)acrylamide, and (meth)allylonitrile. Other examples of the vinyl monomer (V) include aromatic vinyl compounds other than the isopropenyl aromatic compound (I), such as styrene (St); alkyl-substituted styrenes such as o-, m-, or p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, o-, m-, or p-ethylstyrene; and 1,1-diphenylethylene. The methacrylic copolymer (A) may contain, for example, aromatic vinyl compound units (such as styrene (St) units) other than the isopropenyl aromatic compound units (UI) as other units (UO).

[0025] The methacrylic copolymer (A) may contain one or more ring structural units (UR) as one or more other units (UO). Other monomers (O) capable of introducing a ring structure into the main chain by radical polymerization reaction include acid anhydrides such as maleic anhydride (Mah) and itaconic anhydride; N-alkylmaleimides such as N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide, and N-cyclohexylmaleimide (ChMI); N-arylmaleimides such as N-phenylmaleimide, N-methylphenylmaleimide, and N-chlorophenylmaleimide; and cycloolefins such as norbornene, ethylidenenorbornene, dicyclopentadiene, and tetracyclododecene. Among them, maleic anhydride (Mah), N-cyclohexylmaleimide (ChMI), and N-phenylmaleimide are preferred. The content of the ring structural unit (UR) in the methacrylic copolymer (A) (the total amount when there are multiple types, unless otherwise specified) is 0 to 30% by mass. The upper limit is preferably 25% by mass, more preferably 20% by mass, even more preferably 15% by mass, particularly preferably 10% by mass, and most preferably 5% by mass.

[0026] (Organic disulfide compounds (D)) The methacrylic resin of the present disclosure contains one or more organic disulfide compounds (D) as an additive at 1 to 1000 ppm. The lower limit is preferably 10 ppm, more preferably 50 ppm, even more preferably 80 ppm, even more preferably 100 ppm, even more preferably 150 ppm, particularly preferably 200 ppm, and most preferably 250 ppm. The upper limit is preferably 800 ppm, more preferably 750 ppm, even more preferably 700 ppm, even more preferably 650 ppm, even more preferably 600 ppm, particularly preferably 550 ppm, and most preferably 500 ppm.

[0027] As explained in the section [Problems to be Solved by the Invention], conventionally, methacrylic copolymers containing MMA units and isopropenyl aromatic compound units (UI) such as αMSt units tend to have a relatively low thermal decomposition temperature. Therefore, when a methacrylic resin mainly contains this copolymer, the copolymer is thermally decomposed during heating and melting during resin production and molding, etc., and the amount of residual monomer in the resin increases, which may reduce heat resistance. In addition, when the residence time in a heated and melted state during resin production and molding is long, the thermal decomposition of the methacrylic copolymer may cause poor appearance such as foaming.

[0028] In the methacrylic resin of the present disclosure containing an appropriate amount of organic disulfide compound (D), the presence of the appropriate amount of organic disulfide compound (D) effectively suppresses thermal decomposition of the methacrylic copolymer (A) during resin production, and as a result, a methacrylic resin having a small amount of residual monomer and excellent heat resistance and thermal decomposition resistance (thermal stability) can be stably produced. In addition, in the production of the resin, the presence of an appropriate amount of the organic disulfide compound (D) makes it relatively easy to control the copolymerization of the isopropenyl aromatic compound (I), and enables the stable production of a methacrylic copolymer (A) having a uniform composition, such as the content of isopropenyl aromatic compound units (UI), and thus enables the stable production of a methacrylic copolymer (A) having good heat resistance and mechanical properties, such as rigidity and surface hardness.

[0029] The methacrylic resin of the present disclosure containing an appropriate amount of the organic disulfide compound (D) has excellent heat resistance and resistance to thermal decomposition (thermal stability) because the presence of the appropriate amount of the organic disulfide compound (D) effectively suppresses thermal decomposition of the methacrylic copolymer (A) even when heated and melted during molding or other processing after the production of the resin.

[0030] In the methacrylic resin of the present disclosure containing an appropriate amount of the organic disulfide compound (D), even if the residence time in a heated and molten state is long during resin production, molding, etc., poor appearance such as foaming due to thermal decomposition of the methacrylic copolymer (A) is suppressed. When the content of the organic disulfide compound (D) in the methacrylic resin of the present disclosure is equal to or less than the upper limit above, discoloration such as yellowing and odor during resin production and molding can be suppressed.

[0031] For the reasons described above, the methacrylic resin of the present disclosure, the methacrylic resin composition containing the methacrylic resin of the present disclosure, and the molded article containing the methacrylic resin of the present disclosure can have excellent heat resistance, thermal decomposition resistance (thermal stability), mechanical properties such as rigidity and surface hardness, moldability, and appearance. It is considered that the organic disulfide compound (D) can effectively suppress the thermal decomposition of the methacrylic copolymer (A) by effectively capturing alkyl radicals generated by the thermal decomposition of the methacrylic copolymer (A) with thiyl radicals generated by cleavage of disulfide bonds.

[0032] Examples of the organic disulfide compound (D) include diethyl disulfide, di-n-propyl disulfide, di-n-butyl disulfide, di-sec-butyl disulfide, di-tert-butyl disulfide, di-n-amyl disulfide, di-tert-amyl disulfide, di-tert-hexyl disulfide, di-n-octyl disulfide, di-tert-octyl disulfide, di-n-dodecyl disulfide, di-tert-dodecyl disulfide (DDS), di-n-stearin disulfide, ethyl-n-propyl disulfide, ethyl-tert-butyl disulfide, ethyl-sec-butyl disulfide, and n-propyl- Examples of the dialkyl disulfide compounds include isopropyl disulfide; aromatic disulfide compounds such as diphenyl disulfide, dibenzyl disulfide (DBS), and di-p-tolyl disulfide; cyclic disulfide compounds such as ditrimethylene disulfide, ditetramethylene disulfide, and dicyclohexyl disulfide; amino group-containing disulfide compounds such as cystine and diaminodiphenyl disulfide; disulfides of carboxylic acids or derivatives thereof such as dithiodiclycolic acid, dithiodipropionic acid, and dithiodiclycolic acid-2-ethylhexyl; and unsaturated bond-containing disulfide compounds such as diallyl disulfide. Among them, dialkyl disulfide compounds and / or aromatic disulfide compounds are preferred. From the viewpoint of the cleavage temperature of the disulfide bond, the dialkyl disulfide compound is preferably a di-tert-alkyl disulfide such as di-tert-dodecyl disulfide (DDS). The aromatic disulfide compound is preferably dibenzyl disulfide (DBS) or the like. The timing of adding the organic disulfide compound (D) is not particularly limited, and it may be added either before polymerization of the methacrylic copolymer (A) or during the production of the methacrylic resin.

[0033] (Organophosphorus compounds (P)) The methacrylic resin of the present disclosure may contain one or more organic phosphorus compounds (P) as additives. The organic phosphorus compounds (P) are believed to be capable of effectively suppressing thermal discoloration caused by decomposition products of the organic disulfide compounds remaining in the methacrylic copolymer (A). The organic phosphorus compound (P) can be a compound having one or more phosphorus atom-containing organic groups (e.g., an organic group containing a PC bond and / or a POC bond). Specific examples include organic phosphorus compounds containing trivalent phosphorus, such as phosphorous acid esters (also called phosphites), phosphonites, and hydrolysis products thereof; organic phosphorus compounds containing pentavalent phosphorus, such as phosphoric acid esters (also called phosphates), oxidation products of the above phosphorous acid esters, and oxidation products of the above phosphonites; and combinations thereof. As the phosphites, phosphonites, and phosphates, relatively bulky compounds having an aromatic ring are preferred, and for example, compounds having an aryl substituent and a pentaerythritol structure are preferred.

[0034] Examples of phosphorous esters (phosphites) include monoesters, diesters, and triesters of phosphorous acid (e.g., phenyl phosphite, diphenyl phosphite, and triphenyl phosphite, etc.), tris(2,4-di-t-butylphenyl)phosphite, tris(2,6-di-t-butylphenyl)phosphite, tris(2,4-di-t-butyl-5-methylphenyl)phosphite, bis(2,4-di-t-butyl-6-methylphenyl)ethyl phosphite, 2,2'-methylenebis(4,6-di-t-butylphenyl)ethyl phosphite, t-butylphenyl)octyl phosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, (6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]dioxaphosphepine, cyclic neopentanetetraylbis(2,6-di-t-butyl-4-methylphenyl)phosphite, and hydrolysis products of these phosphites.

[0035] The phosphites may be commercially available as phosphorus-based antioxidants. Specific examples include tris(2,4-di-t-butylphenyl)phosphite (BASF's "Irgafos 168" and the like), tris[2-[[2,4,8,10-tetra-t-butyldibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]ethyl]amine (BASF's "Irgafos 12" and the like), bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite (BASF's "Irgafos 38" and the like), 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite (ADEKA's "Adekastab HP-10" and the like), and cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl)phosphite (ADEKA's "Adekastab HP-10" and the like). tert-butyl-4-methylphenyl)pentaerythritol diphosphite (ADEKA's "ADEKA STAB PEP36", etc.), bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite (ADEKA's "ADEKA STAB PEP36A", etc.), cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl phosphite (ADEKA's "ADEKA STAB PEP-8", etc.), and 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]dioxaphosphepine (Sumitomo Chemical's "Sumilizer GP", etc.).

[0036] Examples of the phosphonites include tetrakis(2,4-di-tert-butylphenyl)4,4'-biphenylene diphosphonite, tetrakis(2,4-di-tert-butyl-5-methylphenyl)4,4'-biphenylene diphosphonite, and hydrolysis products of these phosphonites. The phosphonites may be commercially available phosphorus-based antioxidants, and specific examples include tetrakis(2,4-di-tert-butylphenyl)4,4'-biphenylene diphosphonite (Clariant's "HostanoxP-EPQ" and the like) and tetrakis(2,4-di-t-butyl-5-methylphenyl)4,4'-biphenylene diphosphonite (Sakai Chemical Industry's "GSY P101" and the like).

[0037] Examples of phosphoric esters (phosphates) include 2-ethylhexyl acid phosphate, isodecyl acid phosphate, oleyl acid phosphate, bis(2-ethylhexyl)hydrogen phosphate, ethylene bis(diphenyl phosphate), propylene bis(diphenyl phosphate), phenylene bis(diphenyl phosphate), naphthylene bis(ditoluyl phosphate), bisphenol A bis(diphenyl phosphate), 3,5-di-t-butyl-4-hydroxybenzyl phosphate diethyl ester, and hydrolysis products thereof.

[0038] The content of the organic phosphorus compound (P) in the methacrylic resin of the present disclosure (total amount in the case of a plurality of types, unless otherwise specified) is not particularly limited, and is preferably 0.0001% by mass (1 ppm) to 1.0% by mass from the viewpoints of thermal decomposition resistance (thermal stability) and suppression of discoloration during heat melting. The lower limit is more preferably 5 ppm, even more preferably 10 ppm, even more preferably 20 ppm, even more preferably 50 ppm, particularly preferably 80 ppm, and most preferably 100 ppm. The upper limit is more preferably 0.5% by mass, particularly preferably 0.2% by mass, and most preferably 0.1% by mass.

[0039] If the content of the organic phosphorus compound (P) is too low, the effect of suppressing discoloration during heat melting due to the addition of the organic phosphorus compound (P) may not be effectively obtained. If the content of the organic phosphorus compound (P) is too high, the organic phosphorus compound (P) may suppress the effect of improving the thermal decomposition resistance (thermal stability) due to the organic disulfide compound (D), and the organic phosphorus compound (P) may bleed out during molding processing of the methacrylic resin of the present disclosure. The timing of adding the organic phosphorus compound (P) is not particularly limited, and it may be added either before polymerization of the methacrylic copolymer (A) or during the production of the methacrylic resin.

[0040] In the methacrylic resin of the present disclosure, the molar ratio of the organic phosphorus compound (P) to the organic disulfide compound (D) (organic phosphorus compound (P) / organic disulfide compound (D) molar ratio) is not particularly limited, and is preferably 0.01 to 100 from the viewpoint of effectively improving thermal decomposition resistance (thermal stability) and suppressing discoloration during heat melting. The lower limit of this molar ratio is more preferably 0.05, particularly preferably 0.1, and most preferably 1.0. The upper limit of this molar ratio is more preferably 50, particularly preferably 10.

[0041] (Lubricant (L)) The methacrylic resin of the present disclosure may contain one or more lubricants (L) as additives, if necessary. The methacrylic resin of the present disclosure containing one or more lubricants (L) may improve mold releasability during molding. Examples of the lubricant (L) include stearic acid, behenic acid, stearamidic acid, and methylene bisstearamide; waxes such as paraffin wax and ketone wax; aliphatic alcohols (preferably alcohols having 8 to 30 carbon atoms) such as octyl alcohol, cetyl alcohol, and stearyl alcohol; hydrogenated oils; and glycerin fatty acid esters (preferably glycerin carboxylates having 8 to 30 carbon atoms) such as hydroxystearic acid triglyceride, stearic acid monoglyceride, and stearate diglyceride. As the lubricant (L), an aliphatic alcohol and a glycerin fatty acid monoester can be used in combination. In this case, the mass ratio of the aliphatic alcohol / glycerin fatty acid monoester is preferably 2.5 / 1 to 3.5 / 1, more preferably 2.8 / 1 to 3.2 / 1. The content of the lubricant (L) in the methacrylic resin of the present disclosure (the total amount when there are multiple types, unless otherwise specified) is not particularly limited, and is preferably 1000 to 5000 ppm. The upper limit is more preferably 4500 ppm, particularly preferably 4000 ppm, and most preferably 3500 ppm. The timing of adding the lubricant (L) is not particularly limited, and it may be added before polymerization of the methacrylic copolymer (A), during production of the methacrylic resin, or after production of the methacrylic resin.

[0042] (Additives other than those mentioned above) The methacrylic resin of the present disclosure may contain, as necessary, one or more additives other than the organic disulfide compound (D), the organic phosphorus compound (P), and the lubricant (L). Other additives include crosslinked polymer particles, impact resistance agents, processing aids, light stabilizers, light diffusing agents, ultraviolet absorbers, colorants (organic dyes, inorganic dyes, pigments, etc.), antioxidants other than phosphorus-based, antistatic agents, plasticizers, surfactants, foaming agents, defoamers, and fillers. The content of additives other than the organic disulfide compound (D), the organic phosphorus compound (P), and the lubricant (L) in the methacrylic resin of the present disclosure (total amount in the case of a plurality of types unless otherwise specified) is preferably 0.5 mass% or less, more preferably 0.2 mass% or less. If the content of additives is too high, the molded product may have poor appearance such as silver. The timing of addition of additives other than the organic disulfide compound (D) and the lubricant (L) is not particularly limited, and may be any of before polymerization of the methacrylic copolymer (A), during production of the methacrylic resin, and after production of the methacrylic resin.

[0043] (Total remaining amount of raw material monomers) In the methacrylic resin of the present disclosure, at least a portion of at least one of the raw material monomers of the methacrylic copolymer (A) (specifically, methyl methacrylate (MMA), one or more isopropenyl aromatic compounds (I), and, as necessary, one or more other monomers (O)) may remain unreacted. As described above, the methacrylic resin of the present disclosure contains one or more organic disulfide compounds (D) in an amount of 1 to 1000 ppm. In the method for producing the methacrylic resin of the present disclosure, one or more organic disulfide compounds (D) can be added to the polymerization raw materials and / or intermediate products so that the one or more organic disulfide compounds (D) are present in an amount of 1 to 1000 ppm in the finally obtained methacrylic resin of the present disclosure. According to the methacrylic resin and the method for producing the same of the present disclosure, the thermal decomposition of the methacrylic copolymer (A) during the resin production is effectively suppressed, and the amount of the residual monomer in the resin is effectively reduced. As a result, the decrease in the heat resistance of the methacrylic resin due to the presence of the residual monomer can be effectively suppressed. The organic disulfide compound (D) can effectively suppress the thermal decomposition of the methacrylic copolymer (A) even when used in a small amount, so that discoloration such as yellowing of the methacrylic resin due to the addition of the organic disulfide compound (D) can be suppressed.

[0044] In the methacrylic resin of the present disclosure, the total residual amount of raw material monomers of the methacrylic copolymer (A) is 0 to 1.00 mass%. The upper limit of the total residual amount of raw material monomers is preferably 0.80 mass%, more preferably 0.75 mass%, even more preferably 0.70 mass%, even more preferably 0.65 mass%, even more preferably 0.60 mass%, particularly preferably 0.55 mass%, and most preferably 0.50 mass%.

[0045] The amount of methyl methacrylate (MMA) remaining in the methacrylic resin of the present disclosure is 1.00% by mass or less. The upper limit is preferably 0.80% by mass, more preferably 0.70% by mass, even more preferably 0.60% by mass, even more preferably 0.50% by mass, even more preferably 0.40% by mass, even more preferably 0.30% by mass, particularly preferably 0.20% by mass, and most preferably 0.10% by mass.

[0046] The content of the isopropenyl aromatic compound (I) remaining in the methacrylic resin of the present disclosure (when multiple types are present, the total amount) is 1.00 mass% or less. The upper limit is preferably 0.80 mass%, more preferably 0.70 mass%, more preferably 0.60 mass%, more preferably 0.50 mass%, more preferably 0.40 mass%, particularly preferably 0.30 mass%, and most preferably 0.20 mass%.

[0047] The content of other monomers (O) remaining in the methacrylic resin of the present disclosure (the total amount in the case of multiple types) is 1.00 mass% or less. The upper limit is preferably 0.80 mass%, more preferably 0.70 mass%, even more preferably 0.60 mass%, even more preferably 0.50 mass%, even more preferably 0.40 mass%, even more preferably 0.30 mass%, particularly preferably 0.20 mass%, and most preferably 0.10 mass%.

[0048] In this specification, unless otherwise specified, the "weight average molecular weight (Mw)" is the weight average molecular weight calculated based on standard polymethyl methacrylate (PMMA) determined by gel permeation chromatography (GPC) analysis using a differential refractive index detector. Similarly, the "number average molecular weight (Mn)" is the number average molecular weight calculated based on standard polymethyl methacrylate (PMMA) determined by gel permeation chromatography (GPC) analysis using a differential refractive index detector.

[0049] The weight average molecular weight (Mw) of the methacrylic resin of the present disclosure is not particularly limited, and is preferably 50,000 to 150,000. The lower limit is more preferably 55,000, more preferably 60,000, more preferably 65,000, more preferably 70,000, particularly preferably 75,000, and most preferably 80,000. The upper limit is more preferably 120,000, and particularly preferably 100,000. If Mw is equal to or greater than the lower limit, the methacrylic resin of the present disclosure tends to have excellent mechanical properties, and if Mw is equal to or less than the upper limit, the methacrylic resin of the present disclosure tends to have excellent moldability.

[0050] The molecular weight distribution (Mw / Mn) of the methacrylic resin of the present disclosure is not particularly limited, and is preferably 1.5 to 2.5. The lower limit is more preferably 1.8, and the upper limit is more preferably 2.3. If Mw / Mn is equal to or greater than the lower limit, the methacrylic resin of the present disclosure tends to have excellent melt fluidity and moldability, and if Mw / Mn is equal to or less than the upper limit, the methacrylic resin of the present disclosure tends to have excellent mechanical properties such as impact resistance and toughness.

[0051] The glass transition temperature (Tg) of the methacrylic resin of the present disclosure is not particularly limited, and is preferably 120°C or higher. The lower limit is more preferably 123°C, particularly preferably 125°C, and most preferably 130°C. The upper limit is not particularly limited, and is, for example, 150°C. The higher the Tg, the higher the heat resistance of the methacrylic resin of the present disclosure, and is preferable. A molded article containing the methacrylic resin of the present disclosure having a high Tg is less likely to deform and / or shrink due to heat, and is therefore preferable. In this specification, the "glass transition temperature (Tg)" can be measured in accordance with JIS K7121 by the method described in the section [Examples] below.

[0052] As described above, the methacrylic resin of the present disclosure has excellent thermal decomposition resistance. For example, the thermal decomposition resistance can be measured by performing thermogravimetric analysis (TGA) under an inert gas atmosphere as an index of 1% thermal weight loss temperature. The 1% thermal weight loss temperature of the methacrylic resin of the present disclosure can be, for example, 270°C or higher, 280°C or higher, 285°C or higher, or 290°C or higher. The upper limit of the 1% thermal weight loss temperature is not particularly limited, and can be, for example, 320°C or 310°C. The 1% thermal weight loss temperature can be measured using a thermogravimetric analyzer and is the temperature at which the weight loss rate is 1% relative to 100% weight before heating. For example, a TG curve can be obtained by performing thermogravimetric analysis (TGA) under conditions of heating from room temperature (20 to 25°C) to 500°C at a heating rate of 10°C / min in a nitrogen atmosphere, and the 1% thermal weight loss temperature can be obtained from this TG curve.

[0053] The methacrylic resin of the present disclosure can have excellent heat resistance and rigidity even under load. A test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm obtained by molding the methacrylic resin of the present disclosure can have a deflection temperature under load (HDT) of 105°C or more or 110°C or more, as measured in accordance with JIS K7191 after conditioning in accordance with JIS K6712-2. The upper limit is not particularly limited, and is, for example, 130°C or 125°C.

[0054] The methacrylic resin of the present disclosure is one that is inhibited from discoloring, such as yellowing. The yellow index (YI) value of a square test piece having a side length of 50 mm and a thickness of 3 mm obtained by molding the methacrylic resin of the present disclosure, measured in accordance with JIS K-7105, may be 5.0 or less or 4.0 or less. The lower limit is not particularly limited, and is, for example, 1.0.

[0055] The methacrylic resin of the present disclosure can have excellent moldability. The moldability can be measured using the melt flow rate (MFR). From the viewpoint of stability in hot melt molding, the MFR of the methacrylic resin of the present disclosure is preferably 1 to 20 g / 10 min. The lower limit is more preferably 2 g / 10 min., and particularly preferably 3 g / 10 min. The upper limit is more preferably 15 g / 10 min., and particularly preferably 10 g / 10 min. or less. In this specification, unless otherwise specified, the MFR of a methacrylic resin is a value measured using a melt indexer at a temperature of 230° C. and a load of 3.8 kg in accordance with JIS K7210.

[0056] [Methacrylic resin manufacturing method] The methacrylic resin of the present disclosure can be produced by known methods. One embodiment of the method for producing a methacrylic resin according to the present disclosure includes: A step (S1) of preparing a polymerization raw material including raw material monomers such as methyl methacrylate (MMA), one or more isopropenyl aromatic compounds (I), and one or more other monomers (O), and further including a polymerization initiator; A step (S2) of polymerizing the polymerization raw material under conditions of a polymerization conversion rate of 30 to 60 mass% to obtain a resin solution containing a methacrylic resin; The method may include a step (S3) of volatilizing and removing at least a portion of the raw material monomers present in the resin solution in one or more steps to obtain a methacrylic resin having a total residual amount of raw material monomers of 1.00 mass% or less.

[0057] (Process (S1)) A polymerization raw material containing the above-mentioned multiple raw material monomers and a polymerization initiator is prepared. The content of MMA in the polymerization raw material is preferably from 30 to 99% by mass, more preferably from 45 to 95% by mass, and particularly preferably from 50 to 87% by mass. The content of one or more isopropenyl aromatic compounds (I) in the polymerization raw material is preferably from 1 to 59 mass %, more preferably from 5 to 40 mass %, and more preferably from 10 to 30 mass %. The content of one or more other monomers (O) in the polymerization raw materials is preferably from 0 to 49% by mass, more preferably from 0 to 30% by mass, and particularly preferably from 0 to 25% by mass.

[0058] As the polymerization initiator, one or more known radical polymerization initiators can be used. Specific examples include t-hexylperoxyisopropyl monocarbonate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1,1-bis(t-hexylperoxy)cyclohexane, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, 2,2'-azobis(2-methylpropionitrile) (AIBN), 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionate). Among these, 2,2'-azobis(2-methylpropionitrile) (AIBN), t-hexylperoxy 2-ethylhexanoate, 1,1-bis(t-hexylperoxy)cyclohexane, and dimethyl 2,2'-azobis(2-methylpropionate) are preferred.

[0059] The polymerization raw material may contain one or more chain transfer agents as necessary. The chain transfer agent may be used for the purpose of adjusting the molecular weight of the methacrylic copolymer (A). Examples of the chain transfer agent include alkyl mercaptans such as n-octyl mercaptan (n-OM), n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris-(β-thiopropionate), and pentaerythritol tetrakisthiopropionate; α-methylstyrene (αMSt) dimer; and terpinolene. Among these, monofunctional alkyl mercaptans such as n-octyl mercaptan (n-OM) and n-dodecyl mercaptan are preferred. The amount of chain transfer agent used (total amount when multiple types are used, unless otherwise specified) is not particularly limited, and is preferably 0 to 1 part by mass relative to 100 parts by mass of the total amount of multiple types of raw material monomers. The upper limit is more preferably 0.5 parts by mass, particularly preferably 0.4 parts by mass, and most preferably 0.3 parts by mass.

[0060] The polymerization raw material may contain one or more additives other than those mentioned above, if necessary. The polymerization raw materials can be prepared by mixing multiple raw material monomers, one or more polymerization initiators, one or more chain transfer agents as required, and one or more additives as required under an inert gas atmosphere such as nitrogen gas or in the presence of oxygen. They may be mixed all at once or in portions, and the blending procedure in the case of portion mixing is not particularly limited. The water content in the polymerization raw material is preferably 1000 ppm or less, more preferably 700 ppm or less, particularly preferably 280 ppm or less. The polymerization raw material can be dehydrated by a known method, if necessary. The amount of dissolved oxygen in the polymerization raw material is preferably adjusted to 10 ppm or less by nitrogen purging, etc. The amount of dissolved oxygen is more preferably 5 ppm or less, particularly preferably 4 ppm or less, and most preferably 3 ppm or less.

[0061] (Process (S2)) The polymerization can be carried out by a known method, and a bulk polymerization method is preferred. For example, a continuous bulk polymerization method is preferred in which the polymerization raw materials prepared in step (S1) are continuously fed to a tank reactor, bulk polymerization is carried out in the tank reactor under conditions of a polymerization conversion rate of 30 to 60%, a resin solution containing a methacrylic resin is obtained, and the resulting resin solution is continuously withdrawn from the tank reactor. The polymerization is preferably carried out under an atmosphere of an inert gas such as nitrogen gas. The polymerization temperature is not particularly limited, and is preferably 110 to 160°C, more preferably 120 to 155°C, and particularly preferably 130 to 150°C. The average residence time in the tank reactor is not particularly limited, and is preferably 1.5 to 6 hours, more preferably 2 to 5.5 hours, and particularly preferably 2.5 to 5 hours. The average concentration of the radical polymerization initiator in the liquid in the tank reactor is not particularly limited, and is preferably 1.0×10 -6 ~2.0×10 -5 It is in mol / L. The polymerization conversion rate is more preferably 35 to 58%, particularly preferably 35 to 55%, and most preferably 35 to 50%.

[0062] (Process (S3)) At least a portion of the unreacted raw material monomers present in the resin solution is removed by volatilization in one or more stages. Examples of the volatilization method include an adiabatic flash evaporation method, an equilibrium flash evaporation method, and a combination thereof, and an adiabatic flash evaporation method is preferred. The unreacted raw material monomers present in the resin solution can be removed by volatilization in a known manner using a heat exchanger, a vented extruder, or a combination of these, and the combined use of a heat exchanger and a vented extruder is preferred.

[0063] The heating temperature by the heat exchanger (also referred to as the set temperature of the heat exchanger or the heat exchanger temperature) is not particularly limited, and is preferably 180 to 280° C. The lower limit is more preferably 190° C., and particularly preferably 200° C. The upper limit is more preferably 270° C., particularly preferably 260° C., and most preferably 250° C. Examples of the extruder include a single-screw extruder, a twin-screw extruder, and a multi-screw extruder. The extruder has a resin inlet into which the resin solution is introduced, a cylinder with a built-in screw, and a die including a resin outlet for discharging the methacrylic resin obtained after the step (S3), and may have an additive supply port as necessary. The number of vents included in the vented extruder is one or more, and preferably multiple. The molten resin temperature in the die (also referred to as the die resin temperature) is not particularly limited, and is preferably 230 to 260°C. The lower limit is more preferably 235°C, and particularly preferably 240°C. The upper limit is more preferably 255°C, and particularly preferably 250°C.

[0064] If the heating temperature by the heat exchanger and the molten resin temperature in the die are within the above ranges, thermal decomposition of the methacrylic copolymer (A) is suppressed, and a methacrylic resin having excellent heat resistance and thermal decomposition resistance (thermal stability) can be produced. In addition, a methacrylic copolymer (A) having a uniform composition, such as the content of isopropenyl aromatic compound units (UI), can be stably produced, and a methacrylic copolymer (A) having good heat resistance and mechanical properties, such as rigidity and surface hardness, can be stably produced. The unreacted raw material monomer removed from the resin solution may be recovered and reused as the raw material monomer.

[0065] In the method for producing a methacrylic resin according to the present disclosure, one or more organic disulfide compounds (D) are added to at least one of the polymerization raw materials, the resin solution obtained after completion of step (S2), and the resin solution being processed in step (S3) so that the one or more organic disulfide compounds (D) are present in an amount of 1 to 1000 ppm in the methacrylic resin obtained after step (S3). Of the polymerization raw materials, the resin solution obtained after the end of step (S2), and the resin solution during step (S3), it is preferable to add one or more organic disulfide compounds (D) at least to the polymerization raw materials. The amount of one or more organic disulfide compounds (D) added to the polymerization raw material is preferably 10 to 2000 ppm. The lower limit is more preferably 20 ppm, even more preferably 30 ppm, even more preferably 50 ppm, even more preferably 80 ppm, particularly preferably 100 ppm, and most preferably 200 ppm. The upper limit is more preferably 1500 ppm, particularly preferably 1200 ppm, and most preferably 1000 ppm.

[0066] In the method for producing a methacrylic resin according to the present disclosure, one or more organic phosphorus compounds (P) may be added to at least one of the polymerization raw materials, the resin solution obtained after the end of step (S2), and the resin solution during step (S3), as necessary. The one or more organic phosphorus compounds (P) may be supplied, for example, from an additive supply port of an extruder.

[0067] In the method for producing a methacrylic resin according to the present disclosure, one or more lubricants (L) may be added to at least one of the polymerization raw materials, the resin solution obtained after the end of step (S2), and the resin solution during step (S3), as necessary. The one or more lubricants (L) may be supplied, for example, from an additive supply port of an extruder.

[0068] The methacrylic resin of the present disclosure obtained after step (S3) can be processed into a form suitable for use as a molding material, such as pellets or powder, by a known method.

[0069] As described above, according to the present disclosure, it is possible to provide a methacrylic resin having good heat resistance and thermal decomposition resistance (thermal stability), suppressing discoloration such as yellowing, and having good moldability, and a method for producing the same.

[0070] [Methacrylic resin composition] The methacrylic resin composition of the present disclosure can contain the above-described methacrylic resin of the present disclosure and one or more optional components. The methacrylic resin composition of the present disclosure may contain one or more other polymers. Examples of other polymers include methacrylic resins other than the above-mentioned methacrylic resins of the present disclosure; polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; other styrene resins such as polystyrene, high impact polystyrene, methyl methacrylate-styrene copolymer (MS resin), styrene-maleic anhydride copolymer (SMA resin), styrene-maleic anhydride-methyl methacrylate copolymer (SMM resin), acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-ethylene-propylene-diene-styrene (AES) resin, acrylic-acrylonitrile-styrene (AAS) resin, acrylonitrile-chlorinated ethylene-styrene (ACS) resin, and methacrylic butadiene styrene (MBS) resin; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamide resins such as nylon 6, nylon 66, and polyamide elastomer. polycarbonate-based resins; other thermoplastic resins such as polyphenylene sulfide, polyether ether ketone, polysulfone, polyphenylene oxide, polyimide, polyetherimide, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, ethylene-vinyl acetate copolymer, phenoxy-based resins, and ethylene-based ionomers; thermosetting resins such as phenol-based resins, melamine-based resins, silicone-based resins, and epoxy-based resins; polyurethane and chlorinated polyurethane resins; modified polyphenylene ether; silicone-modified resins; acrylic rubber, silicone rubber; acrylic rubber, silicone rubber; acrylic thermoplastic elastomers such as diblock copolymers and triblock copolymers of methyl methacrylate polymer block-n-butyl acrylate polymer block; styrene-based thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin-based rubbers such as IR, EPR, and EPDM. The methacrylic resin composition of the present disclosure may contain one or more optional additives. The timing of adding the additives contained in the methacrylic resin composition of the present disclosure may be during or after the production of the methacrylic resin of the present disclosure.

[0071] [Molded body] The molded article of the present disclosure can contain the above-described methacrylic resin of the present disclosure or the above-described methacrylic resin composition of the present disclosure. Molding can be performed by known molding methods such as injection molding, compression molding, extrusion molding, and vacuum molding. Examples of molded products include single-layer or laminated planar objects such as films, sheets, and plates; any three-dimensional structures, and the like. The molded product may be a laminate or composite containing a layer or member made of the methacrylic resin of the present disclosure or the methacrylic resin composition of the present disclosure and a layer or member made of other resins or various materials other than resins. Generally, the terms "film", "sheet", or "plate" are used for thin film molded products depending on the thickness, but there is no clear definition of these terms, and there is no clear distinction between them.

[0072] [Application] The methacrylic resin of the present disclosure can be used for any application. The methacrylic resin of the present disclosure has the characteristics of having good heat resistance and resistance to thermal decomposition (thermal stability) and being suppressed in discoloration such as yellowing, and is therefore suitable for optical components; components for electronic devices such as mobile phones and personal computers; components for transportation equipment such as vehicles (automobiles, etc.); and the like. Examples of optical members include displays such as liquid crystal displays, plasma displays, organic electroluminescence (EL) displays, field emission displays, and rear projection televisions; and display members such as touch panel displays that combine a touch panel with a display. Examples of optical members for displays include polarizer protective films, retardation plates (such as quarter-wave plates and half-wave plates), liquid crystal optical compensation films (such as viewing angle control films), display front panels, display substrates, transparent conductive substrates for touch panels, light guide plates, and lenses (arrays). In this specification, unless otherwise specified, "lens (array)" is a general term for lenses and lens arrays. Other optical components include optical components for solar cells (transparent substrates, back films, front films, etc.); optical components used in fields such as optical communications, optical switching, and optical measurement (waveguides, lenses (arrays), optical fibers, and optical fiber coating materials, etc.); and optical components for light-emitting elements such as light-emitting diodes (LEDs) (lenses, lens covers, etc.).

[0073] The methacrylic resin of the present disclosure is also suitable for films such as surface protection films and marking films for electronic devices such as mobile phones and personal computers.

[0074] Examples of optical components for vehicles include rear lamp outer covers and optical components inside rear lamps; inner lenses for headlights (also called projector lenses or PES lenses); front panels or molded bodies for in-vehicle meter panels and car navigation systems; door mirror housings, pillar covers (sash covers), license garnishes, front grilles, fog garnishes, emblems, light guiding rods; optical components for head-up displays such as optical cover components; and optical components for DMS (driver monitoring systems), OMS (occupant monitoring systems), gesture control, and LiDAR (light detection and ranging). Other examples of transportation equipment components include aircraft windshields, pilot visors, motorcycle windshields, motorboat windshields, bus shades, automobile side visors, rear visors, head wings, headlight covers, automobile interior components, and automobile exterior components such as bumpers.

[0075] Other applications of the methacrylic resin of the present disclosure include interior components such as furniture, wallpaper, pendant lights, and mirrors; architectural components such as doors, sashes, domes, safety window glass, partitions, staircase wainscoting, balcony wainscoting, and roofs of leisure buildings; sign components or marking films such as advertising towers, stand signs, side signs, transom signs, and rooftop signs; display components such as showcases, partitions, and store displays; lighting components such as fluorescent light covers, mood lighting covers, lampshades, lighted ceilings, lighted walls, and chandeliers; Examples of suitable applications include various home appliance parts such as TV protective masks; audio-visual nameplates, stereo covers; vending machines; medical equipment parts such as incubators and X-ray parts; equipment-related parts such as clock panels, machine covers, instrument covers, laboratory equipment, dial faces, and observation windows; traffic-related parts such as road signs, guide boards, convex mirrors, and soundproof walls; bathroom and sanitary parts such as bathtubs; greenhouses, large aquariums, box aquariums; stationery such as rulers and desk mats; game parts, toys, musical instruments; and decorative and protective films that are applied to the surface of face protection masks during welding. EXAMPLES

[0076] Examples and comparative examples according to the present invention will be described. [Evaluation items and evaluation methods] The evaluation items and evaluation methods are as follows. (Polymerization conversion rate) The polymerization conversion rate was determined by gas chromatography analysis. A column, INERTCAP1 (film thickness 0.4 μm, inner diameter 0.25 mmφ, length 60 m), manufactured by GL Sciences Inc., was connected to a gas chromatograph GC-14A manufactured by Shimadzu Corporation. The analysis was carried out under the following conditions, and the polymerization conversion rate was calculated from the obtained data. Injection temperature: 250℃, Detector temperature: 250℃, Temperature profile: Hold at 60°C for 5 minutes → Heat to 250°C at a rate of 10°C / min → Hold at 250°C for 10 minutes.

[0077] (Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn)) The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the resin were determined by gel permeation chromatography (GPC). The measurement device used was a GPC device "HLC-8320" manufactured by Tosoh Corporation. The separation column used was a series connection of "TSKguardcolumSuperHZ-H", "TSKgelHZM-M" and "TSKgelSuperHZ4000" manufactured by Tosoh Corporation. The detector used was a differential refractive index detector (RI detector). A sample solution was prepared by dissolving 4 mg of the resin to be measured in 5 ml of tetrahydrofuran. The temperature of the column oven was set to 40°C. Tetrahydrofuran was used as the eluent, the eluent flow rate was set to 0.35 ml / min, and 20 μl of the sample solution was injected into the device to measure the chromatogram. GPC measurements were performed on 10 standard polymethyl methacrylate (PMMA) points with molecular weights in the range of 400 to 5,000,000, and a calibration curve showing the relationship between retention time and molecular weight was created. Based on this calibration curve, the Mw and Mw / Mn of the resin to be measured, calculated in terms of standard PMMA, were determined.

[0078] (Monomer unit composition of methacrylic resin) 1 H-NMR spectrum or 13 The C-NMR spectrum was measured, and the monomer unit composition of the methacrylic resin was calculated from the ratio of the integral values ​​of the peaks derived from each monomer unit. Regarding methyl methacrylate-α-methylstyrene copolymer (MMA-αMSt copolymer), 1 The H-NMR spectrum was measured to identify the peaks derived from the protons of the methoxy groups of the methyl methacrylate (MMA) units and the peaks derived from the protons of the phenyl groups of the α-methylstyrene (αMSt) units, and the monomer unit composition was calculated from the ratio of the integral values ​​of each peak.

[0079] For methyl methacrylate-α-methylstyrene-styrene copolymer (MMA-αMSt-St copolymer), measurement mode: reverse gated decoupling method, 13The C-NMR spectrum was measured to identify the peaks derived from the carbon of the carbonyl group of the methyl methacrylate (MMA) unit, the peaks derived from the carbon of the phenyl group of the α-methylstyrene (αMSt) unit, and the peaks derived from the carbon of the phenyl group of the styrene (St) unit, and the monomer unit composition was calculated from the ratio of the integral values ​​of each peak.

[0080] For methyl methacrylate-α-methylstyrene-maleic anhydride copolymer (MMA-αMSt-Mah copolymer), the measurement mode was set to the reverse gated decoupling method. 13 The C-NMR spectrum was measured to identify the peaks derived from the carbon of the carbonyl group of the methyl methacrylate (MMA) unit, the peaks derived from the carbon of the phenyl group of the α-methylstyrene (αMSt) unit, and the peaks derived from the carbon of the carbonyl group of the maleic anhydride (Mah) unit, and the monomer unit composition was calculated from the ratio of the integral values ​​of each peak.

[0081] For methyl methacrylate-α-methylstyrene-cyclohexylmaleimide copolymer (MMA-αMSt-ChMI copolymer), measurement mode: reverse gated decoupling method, 13 The C-NMR spectrum was measured to identify the peaks derived from the carbon of the carbonyl group of the methyl methacrylate (MMA) unit, the peaks derived from the carbon of the phenyl group of the α-methylstyrene (αMSt) unit, and the peaks derived from the carbon of the carbonyl group of the cyclohexylmaleimide unit, and the monomer unit composition was calculated from the ratio of the integral values ​​of each peak.

[0082] (Residual amount of each monomer in methacrylic resin) The remaining amount of each monomer in the methacrylic resin was evaluated in the same manner as in the evaluation of the "monomer unit composition of the methacrylic resin" above. 1 H-NMR spectrum or 13 It was determined from C-NMR spectrum.

[0083] (Residual amount of organic disulfide compound (D) in methacrylic resin) 2 g of methacrylic resin was dissolved in 10 mL of dichloromethane, and then 30 mL of hexane was added to cause reprecipitation. The supernatant obtained after this reprecipitation process was separated, and the solvent in the supernatant was removed by vacuum distillation to concentrate. The concentrate obtained was dissolved again in 1 mL of dichloromethane, and then 4 mL of hexane was added to cause reprecipitation. 25 μL of the supernatant obtained after this reprecipitation process was collected on a platinum board as a measurement sample, and after removing the dichloromethane, pyrolysis gas chromatography analysis was performed. An Agilent Technologies "AgIlent J&W Series DB-5" column (inner diameter: 0.25 mm, film thickness: 0.25 μm, length: 30.0 m) was connected to a Shimadzu Corporation "Gas Chromatograph GC-14A". The analysis was carried out under the following conditions. The remaining amount of organic disulfide compound (D) was determined based on a calibration curve obtained from pyrolysis gas chromatography analysis of standard solutions of multiple organic disulfide compounds with different concentrations. Vaporization chamber temperature: 260℃, Column oven temperature: 100°C, Temperature profile: Heat up to 320°C at a rate of 20°C / min. → Hold at 320°C for 30 minutes.

[0084] (Glass transition temperature (Tg)) The glass transition temperature (Tg) of the resin to be measured was measured using a differential scanning calorimeter (Shimadzu Corporation's "DSC-50") in accordance with JIS K7121. 10 mg of the resin to be measured was placed in an aluminum pan and set in the above-mentioned device. After nitrogen replacement for 30 minutes or more, the temperature was raised from room temperature (20 to 25°C) to 250°C at a rate of 20°C / min in a nitrogen flow of 10 ml / min, held for 5 minutes, and cooled to room temperature (first scan). Next, the temperature was raised to 200°C at a rate of 10°C / min (second scan), and a DSC curve was measured. The midpoint glass transition temperature obtained from the DSC curve obtained by the second scan was taken as the glass transition temperature (Tg).

[0085] (1% thermogravimetric reduction temperature) Using a thermogravimetric analyzer (Shimadzu Corporation "TGA-50"), approximately 5 mg of the resin to be measured was heated from room temperature (20-25°C) to 500°C at a heating rate of 10°C / min in a nitrogen atmosphere to obtain a TG curve. The temperature at which the weight loss rate was 1% relative to the weight before heating of 100% was determined as the 1% thermal weight loss temperature.

[0086] (Melt Flow Rate (MFR)) The melt flow rate (MFR) of the methacrylic resin was measured under conditions of 230°C and a load of 3.8 kg in accordance with JIS K7210.

[0087] (Stability during heating and storage) Injection molding was performed using an injection molding machine (Meiki Seisakusho "M-100C"). After the methacrylic resin was allowed to reside in the cylinder set at 260°C for 30 minutes, 10 shots were molded to produce flat plates with a length of 200 mm, width of 50 mm, and thickness of 2 mm, at a mold temperature of 60°C and an injection speed of 50 mm / sec. The appearance of each flat plate was visually observed and evaluated according to the following criteria. A (Excellent): No foaming was observed from the first shot. B (Good): A slight amount of foaming was observed between the first and third shots, but no foaming was observed after the fourth shot. C (Fair): A large amount of foaming was observed between the 1st and 3rd shots. D (Not acceptable): The sprue broke between the 1st and 10th shots.

[0088] (Heavy Deflection Temperature (HDT)) Using an injection molding machine (M-100C manufactured by Meiki Seisakusho Co., Ltd.), methacrylic resin was injection molded under the conditions of cylinder temperature 230°C, mold temperature 60°C, and injection speed 50 mm / sec to obtain test pieces with a length of 80 mm, width of 10 mm, and thickness of 4 mm. The obtained test pieces were conditioned in accordance with JIS K6712-2. The deflection temperature under load (HDT) of the test pieces was measured in accordance with JIS K7191.

[0089] (Yellow Index (YI) value) Using an injection molding machine (M-100C manufactured by Meiki Seisakusho Co., Ltd.), methacrylic resin was injection molded under the conditions of cylinder temperature 230°C, mold temperature 60°C, and injection speed 50 mm / sec to obtain a square test piece with a side of 50 mm and a thickness of 3 mm. The yellow index (YI) value of this test piece was measured under the following conditions. The test piece was set in a spectrophotometer (PC-2200 manufactured by Shimadzu Corporation), and the light transmittance was measured at 1 nm intervals within the wavelength range of 340 to 700 nm using a C light source. From the obtained data, the XYZ values ​​were obtained in accordance with JIS Z-8722, and the yellow index (YI) value was calculated in accordance with JIS K-7105.

[0090] [Additives] The additives used are as follows: <Organic disulfide compounds (D)> (DDS) di-tert-dodecyl disulfide,

[0091] <Organophosphorus compounds (P)> (PEP-36) Phosphite antioxidant, ADEKA "ADEKA STAB PEP-36", (TPP) Triphenylphosphine.

[0092] <Antioxidants other than phosphorus-based> (GS) Phenolic antioxidant, "Sumilizer GS" manufactured by Sumitomo Chemical Co., Ltd.

[0093] <Lubricant (L)> (StMg) glycerol monostearate, (StOH) Stearyl alcohol.

[0094] [Example E1] In an autoclave equipped with a stirrer and a collection tube, 85 parts by mass of purified methyl methacrylate (MMA), 15 parts by mass of α-methylstyrene (αMSt), 400 ppm of n-octyl mercaptan (n-OM) as a chain transfer agent, and 300 ppm of di-tert-dodecyl disulfide (DDS) were charged and mixed uniformly. 500 ppm of 2,2'-azobis(2-methylpropionitrile) (AIBN) was added as a polymerization initiator and mixed uniformly to obtain a polymerization raw material. Nitrogen gas was blown into this polymerization raw material to set the dissolved oxygen concentration to 3 ppm. This composition of the polymerization raw material is also called the charge composition.

[0095] Next, a continuous flow tank reactor equipped with a brine cooling condenser was prepared, and the inside of the reactor was replaced with nitrogen gas. The above polymerization raw materials were continuously fed into the reactor at a constant flow rate so that the average residence time was 3.3 hours, and bulk polymerization was carried out at a polymerization temperature of 120°C, and a resin solution containing the methacrylic resin, which was the reaction product, was continuously discharged from the reactor. The pressure inside the reactor was regulated by a pressure regulating valve connected to the brine cooling condenser. The polymerization conversion rate was 30%.

[0096] A twin-screw extruder was prepared that had a resin inlet for introducing the resin solution discharged from the reactor and a die including a resin outlet for discharging the produced resin, and further had a first vent (also called a rear vent) located relatively close to the resin inlet, a second vent (also called a front vent) located relatively close to the resin outlet, and an additive supply port located between the second vent (front vent) and the resin outlet.

[0097] The resin solution discharged from the reactor was heated using a heat exchanger, and then supplied from the resin inlet into the extruder. The set temperature of the heat exchanger was 200°C, and the set temperature of the cylinder of the extruder was 245°C. Volatiles mainly composed of unreacted monomers were flash evaporated from the resin solution supplied into the cylinder of the extruder, and discharged from the first vent (rear vent). Furthermore, the resin was transported in the axial direction of the cylinder by the screw, and the volatiles evaporated during that time were discharged from the second vent (front vent). The screw rotation speed was 164 rpm. The resin was extruded in the form of strands from the resin outlet of the extruder. The temperature of the molten resin in the die was 244°C. The obtained strands were cut with a pelletizer to obtain pellets of a methacrylic resin containing a methacrylic copolymer (A-1) containing methyl methacrylate (MMA) units and α-methylstyrene (αMSt) units.

[0098] The main production conditions and the evaluation results are shown in Table 1. In Tables 1 to 3, conditions not shown in the tables are common conditions. In the tables, the "raw material composition" is a composition combining the charged composition and the post-added additives. In the tables, the amounts of the polymerization initiator, the chain transfer agent, and the organic disulfide compound (D) in the raw material composition are the amounts added relative to 100% by mass of the total amount of the raw material monomers.

[0099] [Examples E4 to E6, E8, E10, Comparative Examples EC2 to EC5] Except for changing the charged composition and / or polymerization conditions, the same method as in Example E1 was used to obtain methacrylic resins containing any of the methacrylic copolymers (A-4) to (A-6), (A-8), (A-10), and (C-2) to (C-5) containing methyl methacrylate (MMA) units and α-methylstyrene (αMSt) units. The main production conditions and evaluation results are shown in Tables 1 to 3.

[0100] [Examples E2, E3, E7, E9, E11, E12, Comparative Examples EC1, EC6, EC7] A methacrylic resin containing any one of methacrylic copolymers (A-2), (A-3), (A-7), (A-9), (A-11), (A-12), (C-1), (C-6), and (C-7) containing methyl methacrylate (MMA) units and α-methylstyrene (αMSt) units was obtained in the same manner as in Example E1, except that the feed composition and / or polymerization conditions were changed and one or more additives were added later as follows.

[0101] One or more additives were added to the additive preparation tank, and the pressure was increased to 0.2 MPa and then released to atmospheric pressure, a total of four times, to remove oxygen and moisture, and the oxygen concentration in the additive preparation tank was set to 0%. Next, the one or more additives added to the additive preparation tank were heated to a temperature higher than the melting point and melted by stirring for two hours. The obtained liquid additive was filtered using a metal filter with a mesh size of 0.2 μm (PALL Corporation, "FLHF200-10M3F"), and injected into the extruder from the additive inlet using a metering pump. For example, in Example E2, the types of one or more additives added later and the amounts of each additive added relative to 100% by mass of the resin are as follows: (PEP-36) 1000ppm, (StMg) 1000ppm, (StOH) 2000ppm. The main production conditions and the evaluation results are shown in Tables 1 to 3. In the tables, the amount of additives added after polymerization in the raw material composition is the amount added relative to 100% by mass of the resin.

[0102] [Table 1]

[0103] [Table 2]

[0104] [Table 3]

[0105] [Summary of results] In Examples E1 to E12, methacrylic resins were obtained that contained methacrylic copolymers (A) consisting of 40 to 99 mass% methyl methacrylate (MMA) units, 1 to 40 mass% isopropenyl aromatic compound units (UI), and 0 to 30 mass% other units (UO). In these Examples, an appropriate amount of the organic disulfide compound (D) was added to the polymerization raw material, and a methacrylic resin containing 1 to 1000 ppm of the organic disulfide compound (D) was finally obtained. In all of the methacrylic resins obtained in these Examples, the total amount of residual raw material monomers was 1.00% by mass or less. All of the methacrylic resins obtained in these examples had a Tg of 120°C or higher, a 1% thermal weight loss temperature of 270°C or higher (280°C or higher), and good heat resistance and thermal decomposition resistance (thermal stability). All of the methacrylic resins obtained in these Examples had a good melt flow rate (MFR), and also had good thermal stability even when retained in a heated state during molding, and thus had good molding processability. All of the methacrylic resins obtained in these Examples had a deflection temperature under load (HDT) of 105° C. or higher (110° C. or higher), and had good heat resistance and rigidity under load. The methacrylic resins obtained in these Examples all had a yellow index (YI) value of 5.0 or less (4.0 or less), and discoloration such as yellowing was suppressed. All of the methacrylic resins obtained in these Examples were suitable for use as optical components, vehicle components for automobiles and the like, and the like.

[0106] In Comparative Examples EC1 to EC3, EC6, and EC7, methacrylic resins were obtained that contained a methacrylic copolymer (C) consisting of 40 to 99 mass% methyl methacrylate (MMA) units, 1 to 40 mass% isopropenyl aromatic compound units (UI), and 0 to 30 mass% other units (UO). In these Comparative Examples, the amount of the organic disulfide compound (D) added to the polymerization raw material was 0 ppm or insufficient, so that the content of the organic disulfide compound (D) in the finally obtained methacrylic resin was 0 ppm. In all of the methacrylic resins obtained in these Comparative Examples, the total amount of remaining raw material monomers of the methacrylic copolymer (C) exceeded 1.00% by mass. All of the methacrylic resins obtained in these comparative examples had poor heat resistance and / or thermal decomposition resistance (thermal stability), and were poor in the evaluation results of one or more of Tg, 1% weight loss temperature, heat deflection temperature (HDT), and stability during heating and dwell.

[0107] In Comparative Example EC4, a methacrylic resin was obtained that contained a methacrylic copolymer (C) containing methyl methacrylate (MMA) units and isopropenyl aromatic compound units (UI), in which the content of methyl methacrylate (MMA) units was less than 40 mass% and the content of isopropenyl aromatic compound units (UI) was more than 40 mass%. In this comparative example, an appropriate amount of an organic disulfide compound (D) was added to the polymerization raw material, and a methacrylic resin containing 1 to 1000 ppm of the organic disulfide compound (D) was finally obtained. In the methacrylic resin obtained in this Comparative Example, the total residual amount of the raw material monomers of the methacrylic copolymer (C) exceeded 1.00% by mass. The methacrylic resin obtained in this comparative example had poor heat resistance and / or thermal decomposition resistance (thermal stability), and was poor in Tg, 1% weight loss temperature, deflection temperature under load (HDT), and stability during heating and retention.

[0108] In Comparative Example EC5, a methacrylic resin was obtained that contained a methacrylic copolymer (C) consisting of 40 to 99 mass% of methyl methacrylate (MMA) units, 1 to 40 mass% of isopropenyl aromatic compound units (UI), and 0 to 30 mass% of other units (UO). In this comparative example, an organic disulfide compound (D) was added to the polymerization raw material, and a methacrylic resin containing more than 1000 ppm of the organic disulfide compound (D) was finally obtained. The methacrylic resin obtained in this comparative example had a total residual amount of raw material monomers of 1.00 mass% or less and had good heat resistance and thermal decomposition resistance (thermal stability). However, the yellow index (YI) value of the obtained methacrylic resin was poor, exceeding 10.0.

[0109] The present invention is not limited to the above-described embodiment and examples, and appropriate design changes are possible without departing from the spirit of the present invention.

Claims

1. A methacrylic copolymer (A) comprising 40 to 99% by mass of methyl methacrylate units, 1 to 40% by mass of one or more isopropenyl aromatic compound units (UI), and 0 to 30% by mass of one or more other units (UO); Further, it contains 1 to 1000 ppm of one or more organic disulfide compounds (D), A methacrylic resin, in which the total residual amount of raw material monomers of the methacrylic copolymer (A) is 1.00 mass% or less.

2. The methacrylic resin according to claim 1, wherein the one or more isopropenyl aromatic compound units (UI) include α-methylstyrene units.

3. The methacrylic resin according to claim 1, wherein the methacrylic copolymer (A) contains, as the other units (UO), aromatic vinyl compound units other than isopropenyl aromatic compound units.

4. The methacrylic resin according to claim 1, wherein the one or more organic disulfide compounds (D) include di-tert-dodecyl disulfide (DDS) and / or dibenzyl disulfide (DBS).

5. The methacrylic resin according to claim 1, further comprising 0.0001 to 1.0 mass% of one or more organic phosphorus compounds (P).

6. The methacrylic resin according to claim 1, further comprising 1000 to 5000 ppm of one or more lubricants (L).

7. The methacrylic resin according to claim 1, having a glass transition temperature of 120° C. or higher.

8. The methacrylic resin according to claim 1, which has a 1% thermal weight loss temperature of 270°C or higher as measured by thermogravimetric analysis under an inert gas atmosphere.

9. A methacrylic resin composition comprising the methacrylic resin according to claim 1.

10. A molded article comprising the methacrylic resin according to claim 1 or the methacrylic resin composition according to claim 9.

11. A step (S1) of preparing a polymerization raw material containing 30 to 99 mass% of methyl methacrylate, 1 to 59 mass% of one or more isopropenyl aromatic compounds (I), and 0 to 49 mass% of one or more other monomers (O) as raw material monomers, and further containing a polymerization initiator; A step (S2) of polymerizing the polymerization raw material under conditions of a polymerization conversion rate of 30 to 60 mass% to obtain a resin solution containing the methacrylic resin; and (S3) removing by volatilization at least a portion of the raw material monomers present in the resin solution in one or more steps to obtain the methacrylic resin having a total residual amount of raw material monomers of 1.00 mass% or less. The method for producing a methacrylic resin according to any one of claims 1 to 8, wherein one or more organic disulfide compounds (D) are added to at least one of the polymerization raw material, the resin solution obtained after completion of step (S2), and the resin solution being carried out in step (S3) so that the one or more organic disulfide compounds (D) are present in an amount of 1 to 1000 ppm in the methacrylic resin obtained after step (S3).

12. The method for producing a methacrylic resin according to claim 11, wherein one or more organic disulfide compounds (D) are added to at least the polymerization raw materials among the polymerization raw materials, the resin solution obtained after the completion of the step (S2), and the resin solution during the step (S3).

13. 12. The method for producing a methacrylic resin according to claim 11, wherein one or more organic phosphorus compounds (P) are added to at least one of the polymerization raw material, the resin solution obtained after the completion of step (S2), and the resin solution during the execution of step (S3).

14. 12. The method for producing a methacrylic resin according to claim 11, wherein one or more lubricants (L) are added to at least one of the polymerization raw material, the resin solution obtained after the completion of step (S2), and the resin solution during the execution of step (S3).

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