Methyl methacrylate-based polymer and method for producing the same

Abstract

To provide a resin composition containing a methacrylic polymer using chemically recycled methyl methacrylate which enables provision of a resin molding that has high flexural modulus and excellent durability to flexural stress.SOLUTION: A resin composition contains a methacrylic polymer (P) including a repeating unit derived from methyl methacrylate (A), wherein the methyl methacrylate (A) contains chemically recycled methyl methacrylate (A1), when a ratio (%) of a peak area to an end point having a molecular weight of 1,000 or more to a peak area from a start point to the end point, which is obtained from a molecular weight distribution curve by gel permeation chromatography, is represented by W, W is 50.0% or more and less than 99.3%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition and a method for producing the same. More specifically, the present invention relates to a resin composition containing a methacrylic polymer using methyl methacrylate derived from chemical recycling, which can provide a resin molded article having a high flexural modulus and excellent durability against bending stress, and a method for producing this resin composition. [Background technology]

[0002] Among synthetic resins, methacrylic resin (PMMA) has excellent transparency and weather resistance, a high modulus of elasticity, and excellent surface hardness. As a result, it is widely used in a variety of applications, including display front panels for liquid crystal displays and organic electroluminescence (EL) displays, signage, lighting equipment, home appliances, vehicle interior and exterior materials, industrial materials, construction materials, lenses, light guide plates, light-collecting components, and optical components used in liquid crystal displays and organic electroluminescence (EL) displays. Furthermore, with the recent rise in awareness of environmental issues, demand for plastics derived from biomass raw materials is increasing in all fields. Among these, recycling of waste materials is particularly important, and recycled products are being used for a variety of purposes. Methacrylic resins are materials that can be chemically recycled relatively easily and with high yields. Therefore, in response to the recent increase in societal demand for plastic recycling, attempts are being made to expand the scope of application of chemically recyclable methacrylic resins to various product fields. Specifically, active research is being conducted into the recovery of methacrylic resins from various components of scrapped vehicles, particularly tail lamps, building materials, lighting supplies, signboards, display components, etc., and their chemical recycling and reuse.

[0003] In PMMA chemical recycling, PMMA is thermally decomposed to generate a gas containing methyl methacrylate (MMA gas), which is then cooled to recover MMA as a liquid. Because chemical recycling of PMMA requires a huge amount of energy, reusing chemically recycled methyl methacrylate poses the issue of increased manufacturing costs. To address this cost issue, chemically recycled methyl methacrylate is mixed with methyl methacrylate derived from fossil materials.

[0004] This is also the reason why the mass balance (MB) method has become popular. As disclosed in Non-Patent Document 1, the mass balance method (MB) refers to a technique for allocating a certain characteristic to a portion of a product in accordance with the amount of raw material input when raw materials with a certain characteristic (e.g., biomass-derived raw materials) are mixed with raw materials without that characteristic (e.g., fossil-derived raw materials). This approach is becoming a global trend to mix raw materials in any ratio and allocate the amount of biomass-derived components contained in the raw materials to the final product using the mass balance method. In other words, biomass-derived methyl methacrylate and fossil-derived methyl methacrylate are mixed in specific proportions, and some of the product is sold as biomass-derived methyl methacrylate or as a resin product using such methyl methacrylate. Therefore, adopting this mass balance method (MB) and mastering the use of chemically recycled methyl methacrylate in monomers and resin products has become increasingly important in recent years.

[0005] On the other hand, resin molded articles obtained by polymerizing methyl methacrylate derived from fossil raw materials have insufficient flexural modulus, and there is a demand for improved durability against bending stress. Conventionally, Patent Document 1 has proposed a methacrylic resin composition capable of producing molded articles with excellent Charpy impact strength, in which, in a differential molecular weight distribution curve of the methacrylic resin composition, the ratio (%) W1 of the peak area from the starting point to a molecular weight of 30,000 to the peak area from the starting point to the end point is 10 to 25, and the ratio (%) W2 of the peak area from a molecular weight of 300,000 to the peak area from the starting point to the end point is 3 to 15. However, Patent Document 1 does not contain any description or suggestion regarding chemical recycling of methacrylic resins, and the molecular weight of the resin composition is different from the specified range of the present invention. Furthermore, the effect of the resin composition is impact resistance, which is different from the flexural modulus and flexural stress resistance.

[0006] Patent Document 2 proposes a methacrylic resin that has excellent fluidity, heat resistance, and surface hardness, and in which the proportion of molecular weight components that are 1 / 5 or less of the peak molecular weight obtained from an elution curve by gel permeation chromatography is less than 7%. However, Patent Document 2 does not describe or suggest anything about chemical recycling of methacrylic resins, and the effects it provides are different from those of the present invention, such as the flexural modulus and bending stress resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2021-155698 [Patent Document 2] Japanese Patent Publication No. 2020-012072 [Non-patent literature]

[0008] [Non-Patent Document 1] Ministry of the Environment, "Concept of plastics that have been assigned biomass-derived characteristics using the mass balance method, Study Group on the Mass Balance Method, 2022," Internet<URL:https: / / www.env.go.jp / content / 000142721.pdf> Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a resin composition containing a methacrylic polymer using methyl methacrylate derived from chemical recycling, which can provide a resin molded article having a high flexural modulus and excellent durability against bending stress, and a method for producing the resin composition. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that resin compositions containing a methacrylic polymer using methyl methacrylate derived from chemical recycling, in which the ratio of the peak area from the start point to the end point for molecular weights of 1000 or more to the peak area from the start point to the end point, obtained from a molecular weight distribution curve measured by gel permeation chromatography, falls within a specific range, exhibit a high flexural modulus. That is, the present invention is summarized as follows.

[0011] [1] A resin composition comprising a methacrylic polymer (P) containing a repeating unit derived from methyl methacrylate (A), wherein the methyl methacrylate (A) comprises methyl methacrylate (A1) derived from chemical recycling, and wherein the resin composition has a molecular weight distribution curve obtained by gel permeation chromatography, and W is the ratio (%) of the peak area from the starting point to the end point for a molecular weight of 1,000 or more to the peak area from the end point, where W is 50.0% or more and less than 99.3%.

[0012] [2] The resin composition according to [1], wherein the end point has a molecular weight of 5 million or more and 10 million or less.

[0013] [3] The resin composition according to [1] or [2], wherein W is 60.0% or more and less than 99.3%.

[0014] [4] The resin composition according to [3], wherein W is 70.0% or more and less than 99.3%.

[0015] [5] The resin composition according to [4], wherein W is 90.0% or more and less than 99.3%.

[0016] [6] The resin composition according to any one of [1] to [5], wherein the methacrylic polymer (P) contains repeating units derived from methyl methacrylate (A) in an amount of 50 mass % or more.

[0017] [7] The resin composition according to [6], wherein the methacrylic polymer (P) contains repeating units derived from methyl methacrylate (A) in an amount of 70 mass % or more.

[0018] [8] The resin composition according to any one of [1] to [7], wherein the methacrylic polymer (P) contains a repeating unit derived from methyl methacrylate (A) and a repeating unit derived from an acrylic acid ester.

[0019] [9] The resin composition according to any one of [1] to [7], wherein the methacrylic polymer (P) contains a repeating unit derived from methyl methacrylate (A) and a repeating unit derived from styrene.

[0020]

[10] The resin composition according to any one of [1] to [9], wherein the methyl methacrylate (A) further contains methyl methacrylate (A2) derived from a fossil raw material.

[0021]

[11] The resin composition according to

[10] , wherein the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) is 5% by mass or more and 95% by mass or less.

[0022]

[12] The resin composition according to

[11] , wherein the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) is 10% by mass or more and 90% by mass or less.

[0023]

[13] The resin composition according to

[12] , wherein the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) is 15% by mass or more and 80% by mass or less.

[0024]

[14] A resin molded product comprising the resin composition according to any one of [1] to

[13] .

[0025]

[15] A method for producing a resin composition, comprising: a step of thermally decomposing waste materials containing a methacrylic polymer to obtain chemically recycled methyl methacrylate (A1); a step of mixing the chemically recycled methyl methacrylate (A1) with fossil raw material-derived methyl methacrylate (A2) to obtain methyl methacrylate (A); and a step of radically polymerizing a polymerizable raw material containing the methyl methacrylate (A) to obtain a resin composition, A method for producing a resin composition, wherein the resin composition has a molecular weight distribution curve obtained by gel permeation chromatography, and W is the ratio (%) of the peak area from the starting point to the end point with a molecular weight of 1000 or more to the peak area from the starting point to the end point, and W is 50.0% or more and less than 99.3%. [Effects of the Invention]

[0026] According to the present invention, there is provided a resin composition containing a methacrylic polymer using methyl methacrylate derived from chemical recycling, which can provide a resin molded article having a high flexural modulus and excellent durability against bending stress. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be described in detail below. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the following description as long as it does not go beyond the gist of the present invention. The present invention can be implemented by modifying it as desired within the scope of the gist of the present invention. In the present invention, when "~" is used to express a numerical value or a physical property value, the values ​​before and after the "~" are included. In the present invention, "(meth)acrylic" refers to either or both of "acrylic" and "methacrylic".

[0028] [Resin composition] The resin composition of the present invention comprises a methacrylic polymer (P) (hereinafter, sometimes referred to as "the methacrylic polymer (P) of the present invention") containing repeating units derived from methyl methacrylate (A), wherein the methyl methacrylate (A) comprises methyl methacrylate (A1) derived from chemical recycling. The resin composition is characterized in that, when W is the ratio (%) of the peak area from the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point, obtained from a molecular weight distribution curve by gel permeation chromatography (hereinafter, sometimes simply referred to as "the ratio W of the peak area from the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point" or "W"), W is 50.0% or more and less than 99.3%. The molecular weight of the end point is not particularly limited, but is preferably in the range of 5 million to 10 million. The specific method for measuring the molecular weight by gel permeation chromatography (GPC) in the present invention is as described in the Examples section below.

[0029] When the ratio W of the peak area from the molecular weight of 1000 or more to the peak area from the start point to the end point of the resin composition of the present invention is less than 99.3%, a resin molded article with a high flexural modulus can be obtained. On the other hand, when the ratio W of the peak area from the molecular weight of 1000 or more to the peak area from the start point to the end point of the resin composition of the present invention is less than 50%, the heat resistance, impact resistance, and mechanical properties of the resulting resin molded article are reduced. From this viewpoint, W of the resin composition of the present invention is less than 99.3%, preferably 99.25% or less, particularly 99.2% or less, 50.0% or more, preferably 60.0% or more, more preferably 70.0% or more, even more preferably 80.0% or more, particularly preferably 90.0% or more, and most preferably 95.0% or more.

[0030] A resin composition in which the ratio W of the peak area from the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point is in the range of 50.0% to less than 99.3% indicates that the resin composition contains a polymer having a molecular weight of 1000 or more to the end point within a specific range, as described below, and has an excellent flexural modulus while maintaining the inherent physical properties of PMMA. To obtain a resin composition in which the ratio W of the peak area from the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point is in the range of 50.0% to less than 99.3%, a person skilled in the art can adjust the ratio by appropriately selecting the amount of chemically recycled methyl methacrylate (A1) in the resin composition, the thermal decomposition temperature of the chemically recycled methyl methacrylate (A1), the selected thermal decomposition apparatus, the purification method, and the purity of the chemically recycled methyl methacrylate (A1).

[0031] Such a resin composition of the present invention can be obtained by including methyl methacrylate (A) derived from chemical recycling in the methyl methacrylate (A) (hereinafter, sometimes referred to as "methyl methacrylate (A) of the present invention" or simply "methyl methacrylate (A)") constituting the repeating units derived from methyl methacrylate (A) contained in the methacrylic polymer (P) in the resin composition. Specifically, chemically recycled methyl methacrylate (A1) contains impurities generated or mixed in during the thermal decomposition process. Even after chemical recycling, purification such as distillation cannot completely remove these impurities, and they remain in the chemically recycled methyl methacrylate (A1). The impurities remaining in the chemically recycled methyl methacrylate (A1) act as polymerization retarders in the polymerization reaction of the chemically recycled methyl methacrylate (A1), lowering the average molecular weight of the resulting PMMA. Therefore, by using chemically recycled methyl methacrylate (A1), the resulting methacrylic polymer (P) contains low-molecular-weight components, such as those with a molecular weight of less than 1,000. This results in a higher content of low-molecular-weight components, such as those with a molecular weight of less than 1,000, compared to PMMA that does not use chemically recycled methyl methacrylate (A1). These low-molecular-weight components are thought to function similarly to plasticizers in the resin composition, improving the flexural modulus of the resulting resin molded product. In the resin composition of the present invention, when the ratio W of the peak area from the end point of a molecular weight of 1000 or more to the peak area from the start point to the end point is less than 99.3%, this indicates the presence of low molecular weight components, and a W of less than 99.3% allows for a high flexural modulus to be obtained. On the other hand, a W of 50.0% or more indicates the presence of a large amount of high molecular weight components, which is essential for maintaining the inherent physical properties of PMMA. The content of the chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) of the present invention will be described later.

[0032] <Methacrylic polymer (P)> The methacrylic polymer (P) of the present invention contains repeating units derived from the methyl methacrylate (A) of the present invention. The methacrylic polymer (P) of the present invention may be a homopolymer consisting only of repeating units derived from methyl methacrylate (A), or may be a copolymer of methyl methacrylate (A) and another monomer such as a (meth)acrylic acid ester other than methyl methacrylate (A).

[0033] When the methacrylic polymer (P) of the present invention is a copolymer containing repeating units derived from methyl methacrylate (A) and repeating units derived from other monomers, the content of repeating units derived from methyl methacrylate (A) in the methacrylic polymer (P) of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. When the content of repeating units derived from methyl methacrylate (A) is equal to or higher than the above lower limit, the inherent transparency, chemical resistance, heat resistance, weather resistance, etc. of methyl methacrylate are improved. As described above, the methacrylic polymer (P) of the present invention may be a homopolymer containing 100% by mass of repeating units derived from methyl methacrylate (A).

[0034] When the methacrylic polymer (P) of the present invention is a copolymer containing repeating units derived from methyl methacrylate (A) and repeating units derived from another monomer, the other monomer is not particularly limited as long as it is copolymerizable with methyl methacrylate (A), and examples thereof include the following:

[0035] a) (meth)alkyl alkyl esters other than methyl methacrylate, in which the alkyl group has 1 to 5 carbon atoms. Examples include (meth)acrylic acid esters such as methyl acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, and t-butyl (meth)acrylate. These (meth)acrylic acid esters may be used alone or in combination of two or more. Among these, methyl acrylate and ethyl acrylate are more preferred because they have excellent copolymerizability with methyl methacrylate (A) and the resulting methacrylic polymer (P) has excellent heat resistance and thermal decomposition resistance.

[0036] b) (Meth)acrylic acid esters other than the above a) such as n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, lauryl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, cyclohexyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, 2-naphthyl (meth)acrylate, and phenoxymethyl (meth)acrylate. c) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. d) Aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p-methoxystyrene, p-acetoxystyrene, α-vinylnaphthalene, and 2-vinylfluorene. e) Unsaturated nitrile compounds such as acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, and vinylidene cyanide. f) Ethylenically unsaturated ether compounds such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, and ethyl allyl ether. g) Vinyl halide compounds such as vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, and 1,2-dibromoethylene. h) Aliphatic conjugated diene compounds such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, substituted linear conjugated pentadiene, linear and side chain conjugated hexadienes.

[0037] Among these, the other monomers constituting the repeating units derived from other monomers contained in the methacrylic polymer (P) of the present invention are preferably the acrylic acid esters listed above in a) and b) and aromatic vinyl compounds such as styrene, from the viewpoint of improving transparency, heat resistance, and mechanical strength. The methacrylic polymer (P) of the present invention may contain only one type of repeating unit derived from these other monomers, or may contain two or more types.

[0038] <Methyl methacrylate (A1) derived from chemical recycling and methyl methacrylate (A2) derived from fossil fuels> The methyl methacrylate (A) of the present invention is characterized by containing methyl methacrylate (A1) derived from chemical recycling.

[0039] Methyl methacrylate (A1) derived from chemical recycling is recovered during the chemical recycling of waste methacrylic resin (waste PMMA). In chemical recycling of waste PMMA, waste PMMA is thermally decomposed to generate a gas containing methyl methacrylate (MMA gas), which is then cooled to recover the methyl methacrylate as a liquid. The chemical recycling method is not particularly limited, but it is known that PMMA undergoes thermal decomposition at a relatively low temperature of around 300°C. From the viewpoint of productivity and monomer purity, thermal decomposition is preferably carried out at a temperature in the range of 300 to 700°C, more preferably in the range of 300 to 500°C, and even more preferably in the range of 300 to 450°C. The thermal decomposition device is not particularly limited as long as it is a conventionally known device, and examples thereof include a microwave decomposition device, an extruder, a kneader, and a fluidized bed.

[0040] The recovered methyl methacrylate contains impurities, and can be purified as needed by conventional methods such as distillation and crystallization. The purity of methyl methacrylate after recovery and purification is preferably 95% or more, more preferably 98% or more, and even more preferably 99% or more.

[0041] As described above, since chemically recycled methyl methacrylate (A1) increases the production cost, the methyl methacrylate (A) of the present invention is preferably a mixture of chemically recycled methyl methacrylate (A1) and fossil raw material-derived methyl methacrylate (A2). In this case, the content of the methyl methacrylate (A1) derived from chemical recycling in the methyl methacrylate (A) of the present invention is not particularly limited as long as it is an amount that causes the resin composition of the present invention to have a W value in the range of 50.0% or more and less than 99.3%. Generally, however, when the content of the methyl methacrylate (A1) derived from chemical recycling in the methyl methacrylate (A) of the present invention is low, W tends to be large, and the content of the methyl methacrylate (A1) derived from chemical recycling is high, W tends to be small. Therefore, the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) (the total of chemically recycled methyl methacrylate (A1) and fossil-derived methyl methacrylate (A2)) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. If the content of chemically recycled methyl methacrylate (A1) is equal to or greater than the above lower limit, the W of the resin composition of the present invention becomes less than 99.3%, and a specific amount of low-molecular-weight components is contained, which improves the flexural modulus and the recycling effect of waste methacrylic resin, which is preferable. On the other hand, the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) (the total of chemically recycled methyl methacrylate (A1) and fossil-derived methyl methacrylate (A2)) is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. When the content of the chemically recycled methyl methacrylate (A1) is equal to or less than the above upper limit, the W of the methyl methacrylate (A) of the present invention is 50.0% or more, the increase in cost due to the use of the chemically recycled methyl methacrylate (A1) can be suppressed, and the inherent physical properties of PMMA can be maintained due to the large content of high molecular weight components.

[0042] <Other ingredients> The resin composition of the present invention may contain, in addition to the methacrylic polymer (P) of the present invention, other conventionally known components within the scope of the intended effects of the present invention, such as impact modifiers, release agents, ultraviolet absorbers, polymerization inhibitors, antioxidants, flame retardants, lubricants, plasticizers, antistatic agents, light stabilizers, fillers, pigments, dyes, fluorescent agents, silane coupling agents, leveling agents, and antifoaming agents, within the scope of the present invention. However, from the viewpoint of ensuring excellent transparency, chemical resistance, heat resistance, and the like due to the repeating units derived from methyl methacrylate (A), the resin composition of the present invention is preferably prepared so that the content of the repeating units derived from methyl methacrylate (A) in the resin composition is 85 mass% or more.

[0043] [Method of producing resin composition] The resin composition of the present invention can be produced according to the method for producing a resin composition of the present invention through the steps of: pyrolyzing waste materials containing a methacrylic polymer to obtain chemically recycled methyl methacrylate (A1); mixing the chemically recycled methyl methacrylate (A1) with fossil raw material-derived methyl methacrylate (A2) to obtain methyl methacrylate (A); and radically polymerizing a polymerizable raw material containing the methyl methacrylate (A) to obtain a resin composition that satisfies the above-mentioned W.

[0044] The step of obtaining chemically recycled methyl methacrylate (A1) by thermally decomposing a waste material containing a methacrylic polymer is as described above, and as described above, the method may include a purification step of purifying the obtained chemically recycled methyl methacrylate (A1). The radical polymerization of the polymerizable raw material containing methyl methacrylate (A) is not particularly limited, but can be carried out, for example, as follows.

[0045] First, methyl methacrylate (A) as a polymerizable raw material, other monomers used as needed, a known polymerization initiator, and the other components described above that are further used as needed are mixed together to prepare a polymerizable composition.

[0046] The known polymerization initiator is not particularly limited, but for example, known azo initiators and peroxide initiators used in the production of methacrylic resins can be used, and the amount used is usually preferably about 100 to 50,000 ppm per 100 parts by mass of the raw material monomer. Furthermore, it is preferable to add a mercaptan compound such as n-octyl mercaptan or n-butyl mercaptan as a chain transfer agent to the polymerizable composition, since this allows for better control of the weight average molecular weight of the methacrylic polymer and the peak area ratio in the GPC molecular weight distribution curve.

[0047] The polymerization method for the polymerizable composition is not particularly limited as long as it is a conventionally known polymerization method, but examples include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. Among these, bulk polymerization is particularly preferred. Furthermore, known cast polymerization methods such as cell casting and continuous casting can be used. In the cast polymerization method, the outer peripheries of two opposing inorganic glass plates or metal plates (SUS plates) are sealed with a gasket such as a soft resin tube to form a mold. Subsequently, the polymerizable composition is injected into the mold and polymerized to form a sheet-like resin composition. The resulting resin composition is then peeled from the mold to obtain a plate-like resin molded product.

[0048] The shape of the mold for cast polymerization is not particularly limited, and any known mold can be used, such as a mold for cell casting and a mold for continuous casting. Examples of cell casting molds include two plates such as inorganic glass plates, chrome-plated metal plates, and stainless steel plates, arranged opposite each other at a predetermined distance, with a gasket placed on the edges to form a sealed space between the plates and the gasket. An example of a mold for continuous casting is one in which a sealed space is formed by the opposing surfaces of a pair of endless belts running in the same direction at the same speed and gaskets running at the same speed as the endless belts on both side edges of the endless belts.

[0049] The polymerization method when using the cast polymerization method is not particularly limited, and for example, a known polymerization method used in the production of methacrylic resins or styrene resins can be used. Specifically, a so-called bulk polymerization method using a monomer as a polymerization solvent can be carried out under known radical polymerization conditions.

[0050] When polymerization is performed using the cast polymerization method, the following steps (1) to (3) can be carried out in sequence. Step (1): A polymerizable composition is poured into a reaction vessel, and the reaction vessel is introduced into a polymerization apparatus. Step (2): The polymerizable composition in the reaction vessel is heated to a temperature range of 50°C or higher and 100°C or lower in the first heating zone of the polymerization apparatus, and also heated to a temperature range of 100°C or higher and 150°C or lower in the second heating zone to polymerize the composition and obtain a polymer. Step (3): The obtained polymer is removed from the reaction vessel to obtain a resin composition.

[0051] Prior to the above step (1), a part of the monomer raw material containing methyl methacrylate (A) as a main component may be prepolymerized to obtain a syrup containing a polymer and a monomer, and the remainder of the monomer raw material containing methyl methacrylate (A) as a main component may be added to this syrup to obtain a polymerizable composition.

[0052] After molding by cast polymerization in this manner, the resin molded article of the present invention can be obtained by cutting into a desired shape as needed. As the cutting method, known cutting methods such as NC cutting, laser cutting, circular saw cutting, band saw cutting, etc. can be used. Furthermore, the resin molded body can be molded into a desired shape by heat molding as needed. In this case, the resin molded body can be heated and softened using a known heating method such as heater heating, furnace heating, etc. Furthermore, the resin molded body that has been heated and softened can be molded using a known molding method such as vacuum molding, press molding, pressure molding, blow molding, etc.

[0053] [Resin molding] The resin molded article of the present invention is a molded article made of a resin composition. The resin molded article of the present invention, which uses the resin composition of the present invention, exhibits a high flexural modulus and has excellent bending stress resistance, and is therefore useful for applications such as display front panels for liquid crystal displays, organic EL displays, etc., signage, lighting supplies, home appliances, vehicle interior and exterior materials, industrial materials, construction materials, lenses, light guide plates, light collecting members, and optical members used in liquid crystal displays, organic EL displays, etc., and is particularly useful for applications such as vehicle members, construction materials, lighting supplies, signage, and display members that require bending resistance. [Example]

[0054] The features of the present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. In the following, "parts" means "parts by mass."

[0055] [Methods for measuring various physical properties] <Measurement and evaluation of flexural modulus> As an index of the mechanical strength of the resin composition and resin molded article of the present invention, the bending stress (MPa) was measured at a support distance of 48 mm for test pieces (length 60 mm × width 25 mm × thickness 3 mm) of the resin molded articles obtained in the examples and comparative examples in accordance with JIS K7171. A bending modulus of 2600 MPa or more is evaluated as excellent in bending stress (○), A flexural modulus of less than 2600 MPa was evaluated as poor in flexural stress (×).

[0056] <Measurement and evaluation of heat resistance> As an index of the heat resistance of the resin composition and resin molded article of the present invention, test pieces (length 60 mm x width 25 mm x thickness 3 mm) of the resin molded articles obtained in the examples and comparative examples were crushed and the 5% mass loss temperature was measured. Measurement was carried out using TG / DTA6200 (manufactured by Seiko Instruments Inc.) under nitrogen atmosphere while increasing the temperature from 40 °C to 500 °C at a rate of 10 °C / min. When the sample mass at the start of measurement was taken as 100% by mass, the temperature at which the sample mass became 95% by mass was defined as the 5% mass loss temperature.

[0057] <Measurement of molecular weight by GPC> The molecular weight of the resin composition by GPC measurement was analyzed (measured) as follows. Specifically, 10 mL of tetrahydrofuran (THF) was added to 0.01 g of the resin molded body sample to prepare a sample solution. The molecular weight of this sample solution was measured by analyzing it under the following equipment and analysis conditions. Standard polystyrene was used as the standard sample. (Equipment) GPC analyzer: manufactured by Tosoh Corporation, model: HLC - 8420 Data analyzer: manufactured by Tosoh Corporation, model: EcoSEC Elite - WS (Column) Guard column: manufactured by Tosoh Corporation, model: TSKguardcolumnSuperMP(HZ)-H 4.6 mm I.D×15 cm, 1 piece Sample column: manufactured by Tosoh Corporation, model: TSKGEL SuperMultipore HZ - H 4.6 mm I.D.×15 cm, 2 pieces Reference column: manufactured by Tosoh Corporation, model: TSKGEL SuperH - RC 6.0 mm I.D.×15 cm, 1 piece (Analysis conditions) INLET temperature: 40 °C Column temperature: 40 °C RI temperature: 40 °C Solvent flow rate: 0.35 mL / min Detector: RI (Refractive Index) Sample solution injection volume: 10 μL (loop tube) (Data processing conditions) START TIME (min): 0.00 STOP TIME (min): 15.00 The weight average molecular weight (Mw) and number average molecular weight (Mn) were determined by the above GPC measurement, and the ratio W (%) of the peak area from the molecular weight of 1000 or more to the end point to the peak area from the start point to the end point was calculated from the obtained molecular weight distribution curve.

[0058] [Production Example 1: Production of methyl methacrylate derived from chemical recycling] A resin composition containing 86% by mass of repeating units derived from methyl methacrylate was depolymerized using a twin-screw extruder (TEM-26SS) at a barrel temperature of 370° C. The resulting chemically recycled methyl methacrylate was purified by batch distillation to obtain chemically recycled methyl methacrylate with a purity of 99.06% by mass.

[0059] [Example 1] A polymerizable composition was obtained by adding 0.24 parts of t-hexyl peroxypivalade as a radical polymerization initiator to 100 parts of raw material monomers, which were 41 parts of the above-mentioned chemically recycled methyl methacrylate and 59 parts of fossil-derived methyl methacrylate (manufactured by Mitsubishi Chemical Corporation). The polymerizable composition was then poured into a space with a gap of 5 mm between two opposing SUS plates, which were provided with soft resin gaskets at the ends of the SUS plates, and heated at 73°C for 2.5 hours and then at 115°C for 1 hour to cure the polymerizable composition and obtain a resin composition. Next, the resin composition was cooled together with the SUS plate, and then the SUS plate was removed to obtain a plate-shaped resin molding having a thickness of 3 mm. The obtained resin molded product was subjected to GPC measurement to determine Mw, Mn, and W, and the flexural modulus and 5% mass loss temperature were also measured. The results are shown in Table 1.

[0060] [Examples 2 and 3, Comparative Example 2] A resin molded product was produced in the same manner as in Example 1, except that the ratio of chemically recycled methyl methacrylate to fossil raw material-derived methyl methacrylate was changed to the values ​​shown in Table 1. Mw, Mn, and W were determined by GPC measurement, and the flexural modulus and 5% mass loss temperature were also measured. The results are shown in Table 1.

[0061] [Comparative Example 1] A resin molded product was produced in the same manner as in Example 1, except that 100 parts of methyl methacrylate derived from fossil raw materials was used as the raw material monomer. Mw, Mn, and W were determined by GPC measurement, and the flexural modulus and 5% mass loss temperature were also measured. The results are shown in Table 1.

[0062] [Table 1]

[0063] Table 1 shows that a resin composition containing a methacrylic polymer using methyl methacrylate derived from chemical recycling, in which the ratio W of the peak area from the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point is 50.0% or more and less than 99.3%, can have a high flexural modulus and excellent resistance to bending stress.

Claims

1. A resin composition comprising a methacrylic polymer (P) containing a repeating unit derived from methyl methacrylate (A), The methyl methacrylate (A) contains methyl methacrylate (A1) derived from chemical recycling, The resin composition has a molecular weight distribution curve obtained by gel permeation chromatography, and W is the ratio (%) of the peak area from the starting point to the end point with a molecular weight of 1000 or more to the peak area from the starting point to the end point, where W is 50.0% or more and less than 99.3%.

2. The resin composition according to claim 1, wherein the end point has a molecular weight of 5 million or more and 10 million or less.

3. The resin composition according to claim 1, wherein the W is 60.0% or more and less than 99.3%.

4. The resin composition according to claim 3, wherein the W is 70.0% or more and less than 99.3%.

5. The resin composition according to claim 4, wherein the W is 90.0% or more and less than 99.3%.

6. The resin composition according to claim 1, wherein the methacrylic polymer (P) contains repeating units derived from methyl methacrylate (A) in an amount of 50 mass% or more.

7. The resin composition according to claim 3, wherein the methacrylic polymer (P) contains repeating units derived from methyl methacrylate (A) in an amount of 70 mass% or more.

8. The resin composition according to claim 1, wherein the methacrylic polymer (P) contains a repeating unit derived from methyl methacrylate (A) and a repeating unit derived from an acrylic ester.

9. The resin composition according to claim 1, wherein the methacrylic polymer (P) contains a repeating unit derived from methyl methacrylate (A) and a repeating unit derived from styrene.

10. The resin composition according to claim 1, wherein the methyl methacrylate (A) further contains methyl methacrylate (A2) derived from fossil raw materials.

11. The resin composition according to claim 10, wherein the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) is 5% by mass or more and 95% by mass or less.

12. The resin composition according to claim 11, wherein the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) is 10% by mass or more and 90% by mass or less.

13. The resin composition according to claim 12, wherein the content of chemically recycled methyl methacrylate (A1) in the methyl methacrylate (A) is 15% by mass or more and 80% by mass or less.

14. A resin molded article comprising the resin composition according to any one of claims 1 to 13.

15. A step of pyrolyzing a waste material containing a methacrylic polymer to obtain chemically recycled methyl methacrylate (A1); a step of mixing the chemically recycled methyl methacrylate (A1) with the fossil raw material-derived methyl methacrylate (A2) to obtain methyl methacrylate (A); and a step of radically polymerizing a polymerizable raw material containing the methyl methacrylate (A) to obtain a resin composition, A method for producing a resin composition, wherein the resin composition has a molecular weight distribution curve obtained by gel permeation chromatography, and W is the ratio (%) of the peak area from the starting point to the end point of a peak having a molecular weight of 1000 or more to the peak area from the starting point to the end point, and W is 50.0% or more and less than 99.3%.

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