Methyl methacrylate polymer and its manufacturing method

Abstract

The present invention provides a resin composition that contains a methacrylic polymer using methyl methacrylate derived from chemical recycling, and that can provide a resin molded article that has a high flexural modulus and excellent durability against bending stress. [Solution] 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 the resin composition has a molecular weight distribution curve by gel permeation chromatography, and when W is the ratio (%) of the peak area from the start point to the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point, W is 50.0% or more and less than 99.3%.

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 the resin composition. [Background technology]

[0002] Among synthetic resins, methacrylic resin (PMMA) has excellent transparency and weather resistance, a high elastic modulus, and excellent surface hardness, and is therefore widely used in display front panels such as LCD and OLED, signage, lighting, home appliances, vehicle interior and exterior materials, industrial materials, construction materials, lenses, light guide plates, light collecting components, and optical components used in LCD and OLED displays. In addition, with the growing awareness of environmental issues in recent years, the demand for plastics derived from biomass raw materials is increasing in all fields. Among them, recycling of waste materials is particularly important, and recycled products are used for various purposes. Methacrylic resins are materials that can be chemically recycled relatively easily and with a high yield. Therefore, in response to the increasing social demand for plastic recycling in recent years, 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 parts of scrapped vehicles, particularly tail lamps, building materials, lighting supplies, signboards, display parts, and the like, 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 an enormous amount of energy, reusing chemically recycled methyl methacrylate poses the problem of increased manufacturing costs. To solve the cost issue, methyl methacrylate derived from chemical recycling is mixed with methyl methacrylate derived from fossil raw materials.

[0004] This is also the reason why the mass balance (MB) method has become widespread. As disclosed in Non-Patent Document 1, the mass balance method (MB) refers to a method for allocating a certain characteristic to a part of a product according to the input amount of raw materials 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). As a result, the idea of ​​mixing raw materials in any ratio and allocating the amount of biomass-derived components contained in the raw materials to the final product by the mass balance method is becoming a global trend. In other words, methyl methacrylate derived from biomass raw materials and methyl methacrylate derived from fossil raw materials are mixed in specific amounts, and some of the products are sold as methyl methacrylate derived from biomass raw materials or as resin products using such methyl methacrylate. Therefore, adopting such a mass balance method (MB) and making full use of monomers and resin products containing methyl methacrylate derived from chemical recycling has become 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 end point is 3 to 15 to the peak area from the starting point to the end point. 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 of the present invention is different from the specified range. Furthermore, the effect of the resin composition is impact resistance, which is an effect different from the flexural modulus and flexural stress resistance.

[0006] Patent Document 2 proposes a methacrylic resin having excellent fluidity, heat resistance, and surface hardness, in which the proportion of molecular weight components having a molecular weight of 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 also does not contain any description or suggestion regarding chemical recycling of methacrylic resins, and the effects it describes 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] JP 2021-155698 A [Patent Document 2] JP 2020-012072 A [Non-patent literature]

[0008] [Non-Patent Document 1] Ministry of the Environment, "Concept of plastics with biomass-derived characteristics assigned 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] As a result of extensive investigations aimed at solving the above-mentioned problems, the present inventors have found that, for a resin composition containing a methacrylic polymer using methyl methacrylate derived from chemical recycling, when the ratio of the peak area from the start point to the end point of a molecular weight distribution curve measured by gel permeation chromatography falls within a specific range, the resin composition exhibits a high flexural modulus. That is, the present invention relates to the following.

[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 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 start point to the end point having a molecular weight of 1000 or more to the peak area from the start point to 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 content of repeating units derived from methyl methacrylate (A) in the methacrylic polymer (P) is 50 mass% or more.

[0017] [7] The resin composition according to [6], wherein the content of repeating units derived from methyl methacrylate (A) in the methacrylic polymer (P) is 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 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 the 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 the 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 the 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 obtaining methyl methacrylate (A1) derived from chemical recycling by thermally decomposing a waste material containing a methacrylic polymer; a step of obtaining methyl methacrylate (A) by mixing the methyl methacrylate (A1) derived from chemical recycling with methyl methacrylate (A2) derived from a fossil raw material; 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 the ratio (%) of the peak area from the start point to the end point with a molecular weight of 1000 or more to the peak area from the start point to the end point is W, and W is 50.0% or more and less than 99.3%. Effect 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 product having a high flexural modulus and excellent durability against bending stress. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 contents of the following description as long as it does not exceed the gist of the present invention. The present invention can be modified and implemented as desired without departing from the gist of the present invention. In the present invention, when "~" is used with a numerical value or a physical property value before and after it, the values ​​before and after it 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 is a resin composition containing a methacrylic polymer (P) containing a repeating unit derived from methyl methacrylate (A) (hereinafter, sometimes referred to as "methacrylic polymer (P) of the present invention"). The methyl methacrylate (A) contains methyl methacrylate (A1) derived from chemical recycling, and the resin composition is characterized in that W is 50.0% or more and less than 99.3%, where W is the ratio of the peak area from the end point 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 to the molecular weight of 1000 or more to the peak area from the start point to the end point" or "W"). The molecular weight of the end point is not particularly limited, but is preferably in the range of, for example, 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] If the ratio W of the peak area from the starting point to the end point of the resin composition of the present invention to the peak area from the starting point to the end point of the molecular weight of 1000 or more is less than 99.3%, a resin molded product with a high bending modulus can be obtained. On the other hand, if the ratio W of the peak area from the starting point to the end point of the peak area from the starting point to the end point of the molecular weight of 1000 or more is less than 50%, the heat resistance, impact resistance and mechanical properties of the obtained resin molded product 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 preferably 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 molecular weight 1000 or more to the end point 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 excellent bending modulus while maintaining the inherent physical properties of PMMA. In order to obtain a resin composition in which the ratio W of the peak area from the molecular weight 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 amount of methyl methacrylate (A1) derived from chemical recycling in the resin composition, the pyrolysis temperature of methyl methacrylate (A1) derived from chemical recycling, the selected pyrolysis apparatus, the purification method, and the purity of methyl methacrylate (A1) derived from chemical recycling, as appropriate.

[0031] Such a resin composition of the present invention can be obtained by including methyl methacrylate (A) derived from chemical recycling in methyl methacrylate (A) (hereinafter, sometimes referred to as "methyl methacrylate (A) of the present invention" or simply "methyl methacrylate (A)") constituting a repeating unit derived from methyl methacrylate (A) contained in the methacrylic polymer (P) in the resin composition. That is, by chemically recycling the methyl methacrylate (A1) derived from chemical recycling, it contains impurities that are generated or mixed in during the thermal decomposition process. Even if purification such as distillation is performed after chemical recycling, these impurities cannot be completely removed, and remain in the methyl methacrylate (A1) derived from chemical recycling. The impurities remaining in the methyl methacrylate (A1) derived from chemical recycling act as polymerization retarders in the polymerization reaction of the methyl methacrylate (A1) derived from chemical recycling, lowering the average molecular weight of the PMMA produced. As a result, by using the methyl methacrylate (A1) derived from chemical recycling, the methacrylic polymer (P) obtained contains low molecular weight components such as those with a molecular weight of less than 1000, and the amount of low molecular weight components such as those with a molecular weight of less than 1000 is greater than that of PMMA that does not use the methyl methacrylate (A1) derived from chemical recycling. It is believed that these low molecular weight components exert a function similar to that of a plasticizer in the resin composition and improve the flexural modulus of the resulting resin molded body. In the resin composition of the present invention, the ratio W of the peak area from the molecular weight 1000 or more to the end point to the peak area from the start point to the end point is less than 99.3%, which indicates the presence of this low molecular weight component, and a high bending modulus can be obtained if W is less than 99.3%. On the other hand, 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 methyl methacrylate (A1) derived from chemical recycling 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 a repeating unit derived from methyl methacrylate (A) and a repeating unit derived from another monomer, the content of the repeating unit 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. If the content of the repeating unit derived from methyl methacrylate (A) is equal to or more 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 a repeating unit derived from methyl methacrylate (A) and a repeating unit 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 acid alkyl esters other than methyl methacrylate, in which the alkyl group has 1 to 5 carbon atoms. Examples of (meth)acrylic acid esters include 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 them, 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, as the other monomer constituting the repeating unit derived from the other monomer contained in the methacrylic polymer (P) of the present invention, the acrylic acid esters listed in a) and b) above and aromatic vinyl compounds such as styrene are preferred 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 derived from chemical recycling (A1) and methyl methacrylate derived from fossil raw materials (A2)> The methyl methacrylate (A) of the present invention is characterized in that it contains 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), and this MMA gas is cooled to recover the methyl methacrylate as a liquid. The method of chemical recycling is not particularly limited, but it is known that PMMA undergoes thermal decomposition at a relatively low temperature of about 300°C. From the viewpoints 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 pyrolysis 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 necessary. As the purification method, a conventionally known method such as distillation or crystallization can be used. 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 the methyl methacrylate (A1) derived from chemical recycling increases the production cost, the methyl methacrylate (A) of the present invention is preferably a mixture of the methyl methacrylate (A1) derived from chemical recycling and the methyl methacrylate (A2) derived from fossil raw materials. 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%. In general, 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 methyl methacrylate (A1) derived from chemical recycling in methyl methacrylate (A) (total of methyl methacrylate (A1) derived from chemical recycling and methyl methacrylate (A2) derived from fossil raw materials) 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 methyl methacrylate (A1) derived from chemical recycling is equal to or more than the above lower limit, the W of the resin composition of the present invention is less than 99.3%, a specific amount of low molecular weight components is contained, and the bending modulus is improved and the recycling effect of waste methacrylic resin is improved, which is preferable. On the other hand, the content of methyl methacrylate (A1) derived from chemical recycling in methyl methacrylate (A) (total of methyl methacrylate (A1) derived from chemical recycling and methyl methacrylate (A2) derived from fossil raw materials) 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 methyl methacrylate (A1) derived from chemical recycling is equal to or less than the above upper limit, W of the methyl methacrylate (A) of the present invention is 50.0% or more, the increase in cost due to the use of methyl methacrylate (A1) derived from chemical recycling 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 further contain other conventionally known components in addition to the methacrylic polymer (P) of the present invention within the range in which the effects of the present invention are achieved. For example, known additives such as impact strength 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 defoamers may be contained within the range in which the effects of the present invention are not impaired. 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), it is preferable to prepare the composition of the resin composition of the present invention 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 a waste material containing a methacrylic polymer to obtain methyl methacrylate (A1) derived from chemical recycling; mixing the methyl methacrylate (A1) derived from chemical recycling with methyl methacrylate (A2) derived from fossil raw materials 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 pyrolyzing 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 necessary, a known polymerization initiator, and the above-mentioned other components used as necessary are mixed together to prepare a polymerizable composition.

[0046] The known polymerization initiator is not particularly limited, but for example, a known azo initiator or peroxide initiator used in the production of methacrylic resins can be used. The amount of the initiator used is 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 makes it possible to further control 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 of the polymerizable composition is not particularly limited as long as it is a conventionally known polymerization method, and examples thereof include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and the like. Among them, bulk polymerization is particularly preferred. In particular, known cast polymerization methods such as cell casting and continuous casting can be used. In the cast polymerization method, the outer periphery of two inorganic glass plates or metal plates (SUS plates) arranged opposite each other is sealed with a gasket such as a soft resin tube to form a mold, and then the polymerizable composition is injected into the mold and polymerized to form a sheet-like resin composition. Next, the obtained resin composition is peeled off from the mold to obtain a plate-like resin molded body.

[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. An example of a mold for cell casting is one in which two plate-like bodies, such as inorganic glass plates, chrome-plated metal plates, stainless steel plates, etc., are arranged opposite each other at a predetermined distance, and a gasket is placed on the edges of the plates to form a sealed space by 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 adopted. 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 the polymerization is carried out using the cast polymerization method, the following steps (1) to (3) can be carried out in this order. 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 more and 100°C or less in a first heating zone in a polymerization apparatus, and is also heated to a temperature range of 100°C or more and 150°C or less in a 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 portion of the monomer raw material mainly composed of methyl methacrylate (A) may be prepolymerized to obtain a syrup containing a polymer and a monomer, and the remainder of the monomer raw material mainly composed of methyl methacrylate (A) 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 required. The cutting method may be a known cutting method such as NC cutting, laser cutting, circular saw cutting, or band saw cutting. Furthermore, the resin molded article can be molded into a desired shape by heating as necessary. In this case, the resin molded body can be heated and softened using a known heating method such as heater heating, furnace heating, etc. In addition, as a method for molding the resin molded body softened by heating, a known molding method such as vacuum molding, press molding, pressure molding, blow molding, etc. can be used.

[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 exhibits a high flexural modulus by using the resin composition of the present invention, and has excellent resistance to bending stress. Therefore, the article is useful for applications such as display front panels for liquid crystal or organic electroluminescence (EL) displays, signboards, lighting products, 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 or organic electroluminescence (EL) displays, and is particularly useful for applications such as vehicle members, construction materials, lighting products, signboards, and display members that require bending resistance. EXAMPLES

[0054] The features of the present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing contents, 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" refers to "parts by mass".

[0055] [Measurement methods for various physical properties] <Measurement and evaluation of bending modulus> As an index of the mechanical strength of the resin composition and resin molded article of the present invention, the bending stress (MPa) at a support distance of 48 mm was measured 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 bending modulus of less than 2600 MPa was evaluated as poor bending stress (×).

[0056] <Measurement and evaluation of heat resistance> As an index of the heat resistance of the resin composition and the resin molded body of the present invention, the 5% mass loss temperature was measured for test pieces (length 60 mm × width 25 mm × thickness 3 mm) of the resin molded bodies obtained in the examples and comparative examples that were crushed. 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 was set to 100 mass% at the start of the measurement, the temperature at which the sample mass became 95 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, and 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] To 100 parts of raw material monomers, which were 41 parts of methyl methacrylate derived from the above chemical recycling and 59 parts of methyl methacrylate derived from fossil raw materials (manufactured by Mitsubishi Chemical Corporation), 0.24 parts of t-hexyl peroxy pivalade was added as a radical polymerization initiator to obtain a polymerizable composition. Next, the polymerizable composition was poured into a space with a gap of 5 mm provided by disposing a soft resin gasket at the end of the SUS plate between two opposing SUS plates, and heated at 73 ° C for 2.5 hours and then at 115 ° C for 1 hour to harden 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 was also subjected to measurement of flexural modulus and 5% mass loss temperature. 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 methyl methacrylate derived from chemical recycling to methyl methacrylate derived from fossil raw materials 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, and 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] From Table 1, it can be seen 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 molecular weight of 1000 or more to the end point to the peak area from the start point to the end point is 50.0% or more and less than 99.3%, can be obtained that has a high flexural modulus and excellent resistance to bending stress.

Claims

1. A methyl methacrylate polymer comprising a methacrylic polymer (P) containing 70 mass% or more of a repeating unit derived from methyl methacrylate (A), The methyl methacrylate (A) contains methyl methacrylate (A1) derived from chemical recycling, The methyl methacrylate polymer has a molecular weight distribution curve obtained by gel permeation chromatography, and the ratio (%) of the area of ​​a peak having a molecular weight of 1000 or more to the area of ​​a peak having a molecular weight of 1000 or more to the area of ​​a peak having a molecular weight of 1000 or more from the start point to the end point is defined as W, and W is 90.0% or more and less than 99.3%; A methyl methacrylate-based polymer, the 5% mass loss temperature of a resin molded product obtained by molding the methyl methacrylate-based polymer is lower than the 5% mass loss temperature of a resin molded product obtained by molding a methyl methacrylate-based polymer obtained using only methyl methacrylate (A) derived from a fossil raw material. The method for measuring the 5% mass loss temperature of the resin molded body is as follows. A test piece of the resin molding (length 60 mm × width 25 mm × thickness 3 mm) was pulverized and measured using a TG / DTA6200 (Seiko Instruments Inc.) under nitrogen while heating from 40° C. to 500° C. at a rate of 10° C. / min. The sample mass at the start of the measurement was taken as 100% by mass, and the temperature at which the sample mass reached 95% by mass was defined as the 5% mass reduction temperature.

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

3. The methyl methacrylate polymer 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.

4. The methyl methacrylate polymer 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.

5. The methyl methacrylate polymer according to claim 1, wherein the methyl methacrylate (A) further contains methyl methacrylate (A2) derived from a fossil raw material.

6. The methyl methacrylate polymer according to claim 5, wherein the content of the methyl methacrylate (A1) derived from chemical recycling in the methyl methacrylate (A) is 5% by mass or more and 95% by mass or less.

7. The methyl methacrylate polymer according to claim 6, wherein the content of the methyl methacrylate (A1) derived from chemical recycling in the methyl methacrylate (A) is 10% by mass or more and 90% by mass or less.

8. The methyl methacrylate polymer according to claim 7, wherein the content of the methyl methacrylate (A1) derived from chemical recycling in the methyl methacrylate (A) is 15% by mass or more and 80% by mass or less.

9. A resin molded article comprising the methyl methacrylate polymer according to any one of claims 1 to 8.

10. A step of pyrolyzing a waste material containing a methacrylic polymer to obtain methyl methacrylate (A1) derived from chemical recycling; A step of mixing the chemically recycled methyl methacrylate (A1) and the fossil raw material derived methyl methacrylate (A2) to obtain methyl methacrylate (A); and a step of radically polymerizing a polymerizable raw material containing methyl methacrylate (A) to obtain a methyl methacrylate polymer containing a methacrylic polymer (P) containing 70 mass% or more of a repeating unit derived from the methyl methacrylate (A), The methyl methacrylate polymer has a molecular weight distribution curve obtained by gel permeation chromatography, and the ratio (%) of the area of ​​a peak having a molecular weight of 1000 or more to the area of ​​a peak having a molecular weight of 1000 or more to the area of ​​a peak having a molecular weight of 1000 or more from the start point to the end point is defined as W, and W is 90.0% or more and less than 99.3%; The 5% mass loss temperature of a resin molded product obtained by molding the methyl methacrylate polymer is lower than the 5% mass loss temperature of a resin molded product obtained by molding a methyl methacrylate polymer obtained using only methyl methacrylate (A) derived from a fossil raw material. The method for measuring the 5% mass loss temperature of the resin molded body is as follows. A test piece of the resin molding (length 60 mm × width 25 mm × thickness 3 mm) was pulverized and measured using a TG / DTA6200 (Seiko Instruments Inc.) under nitrogen while heating from 40° C. to 500° C. at a rate of 10° C. / min. The sample mass at the start of the measurement was taken as 100% by mass, and the temperature at which the sample mass reached 95% by mass was defined as the 5% mass reduction temperature.

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