WO2025205813A1 - Maleimide-based copolymer - Google Patents

Abstract

The present invention addresses the problem of providing a maleimide-based copolymer that is, even when used for a recycled resin, capable of imparting heat resistance to the resin while suppressing any reduction in impact resistance of the resin, and that has a favorable appearance when molded.　One embodiment of the present invention is a maleimide-based copolymer containing an aromatic vinyl-based monomeric unit and a maleimide-based monomeric unit. The glass transition temperature of the maleimide-based copolymer is 160°C-210°C. The maleimide-based copolymer has a weight-average molecular weight of 50,000 to 170,000. The content of a component of the maleimide-based copolymer is less than 3 mass%, the component having a molecular weight of at least 500,000.

Description

Maleimide copolymer

The present invention relates to a maleimide copolymer.

ABS resin is a thermoplastic resin whose main components are acrylonitrile, butadiene, and styrene. Taking advantage of its excellent mechanical strength, appearance, chemical resistance, and moldability, it is widely used in automobiles, home appliances, office equipment, housing construction materials, and everyday items. However, in applications that require heat resistance, such as automobile interior materials, its heat resistance can be insufficient. One technique for improving the heat resistance of ABS resin is to melt-knead maleimide copolymers or α-methylstyrene copolymers using an extruder or similar device (Patent Documents 1 and 2).

Meanwhile, climate change is causing increasingly severe weather disasters such as wildfires, floods, droughts, extreme heat, and heavy rain, making the development of environmentally friendly products all the more important. Material recycling of styrene-based resins such as ABS resin is also becoming more active.

Japanese Patent Application Laid-Open No. 2003-41080 WO2010/082617 publication

However, recycled resins are prone to deterioration, and when mixing them with heat-resistance additives such as those mentioned above, kneading them at high temperatures can cause the recycled resin itself to deteriorate, resulting in a loss of physical properties. On the other hand, kneading them at low temperatures can result in a poor appearance of the molded product.

The present invention was made in light of these circumstances, and aims to provide a maleimide-based copolymer that, even when used in recycled resins, can impart heat resistance to the resin while minimizing a decrease in the resin's impact resistance, and also provides a good appearance when molded.

After extensive research, the inventors discovered that the above-mentioned problems can be solved when the glass transition temperature of the maleimide copolymer is within a specific range and the molecular weight distribution is also within a specific range, leading to the completion of the present invention.

According to the present invention, the following is provided:
[1] A maleimide copolymer comprising an aromatic vinyl monomer unit and a maleimide monomer unit, wherein the maleimide copolymer has a glass transition temperature of 160 to 210°C, a weight average molecular weight of 50,000 to 170,000, and a content of components having a molecular weight of 500,000 or more in the maleimide copolymer is less than 3 mass%.
[2] The maleimide copolymer according to [1], wherein Mw/Mn is 2.8 or less, where Mw is the weight-average molecular weight and Mn is the number-average molecular weight.
[3] The maleimide copolymer according to [1] or [2], wherein the glass transition temperature is 170 to 195°C.
[4] The maleimide copolymer according to any one of [1] to [3], wherein the maleimide copolymer has a melt mass-flow rate of 15 to 100 g/10 min at 265°C under a load of 98 N, as measured by a method in accordance with JIS K 7210-1:2014.
[5] The maleimide copolymer according to any one of [1] to [4], which is used to impart heat resistance to recycled resins.
[6] The maleimide copolymer according to [5], wherein the recycled resin comprises at least one resin selected from the group consisting of ABS resin, ASA resin, AES resin, and SAN resin.

The present invention provides a maleimide-based copolymer that, even when used in recycled resins, can impart heat resistance to the resin while suppressing a decrease in the resin's impact resistance, and also provides a good appearance when molded.

The present invention is described in detail below. However, the present invention is not limited to these descriptions. The features of the embodiments described below can be combined with each other. Furthermore, each feature can be an independent invention. Furthermore, elements of the following embodiments that are not specified in the claims are optional and can be omitted.

<Terminology>
In this specification, for example, the description "X to Y" means that the number is equal to or greater than X and equal to or less than Y. In this specification, any number of "0"s (for example, one or two) may be added to the end of a numerical value. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400."

1. Maleimide-Based Copolymer The maleimide-based copolymer according to this embodiment is a copolymer including an aromatic vinyl-based monomer unit and a maleimide-based monomer unit. In this embodiment, the maleimide-based copolymer may further include one or more of a vinyl cyanide-based monomer unit and an unsaturated dicarboxylic acid anhydride-based monomer unit.

1.1 Aromatic vinyl monomer unit The aromatic vinyl monomer unit is a structural unit derived from the aromatic vinyl monomer used in the polymerization of the maleimide copolymer according to this embodiment. Examples of aromatic vinyl monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, and α-methyl-p-methylstyrene. These aromatic vinyl monomers may be used alone or in combination of two or more. As the aromatic vinyl monomer according to this embodiment, styrene is preferred because the resulting resin composition has good moldability and is easily available.

The maleimide-based copolymer of this embodiment preferably contains 30 to 70 mass% of aromatic vinyl-based monomer units, and more preferably 40 to 60 mass% of aromatic vinyl-based monomer units, when the total of the aromatic vinyl-based monomer units, maleimide-based monomer units, vinyl cyanide-based monomer units, and unsaturated dicarboxylic acid anhydride-based monomer units is taken as 100 mass%. The content of aromatic vinyl-based monomer units is, for example, 30, 35, 40, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 60, 61, 62, 63, 64, 65, or 70 mass%, and may be within a range between any two of the values exemplified here. The content of aromatic vinyl-based monomer units in the maleimide-based copolymer can be measured using C-13 NMR. When the content of aromatic vinyl-based monomer units is equal to or greater than the lower limit, the resulting resin composition exhibits good fluidity and moldability. When the content of aromatic vinyl monomer units is equal to or less than the upper limit, the content of the heat resistance-imparting component can be ensured, and the effect of imparting heat resistance to the resin composition is further enhanced.

1.2 Maleimide Monomer Unit The maleimide monomer unit is a structural unit derived from the maleimide monomer used in the polymerization of the maleimide copolymer according to this embodiment (or a structural unit obtained by imidizing a structural unit derived from an unsaturated dicarboxylic acid anhydride monomer). Examples of maleimide monomers include N-alkylmaleimides such as N-methylmaleimide, N-butylmaleimide, and N-cyclohexylmaleimide, and N-arylmaleimides such as N-phenylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide, N-methoxyphenylmaleimide, and N-tribromophenylmaleimide. These maleimide monomers may be used alone or in combination of two or more. As the maleimide monomer according to this embodiment, N-arylmaleimide is preferred, and N-phenylmaleimide is more preferred. When the maleimide monomer is of such a type, the effect of imparting heat resistance to the resin composition is enhanced.

To incorporate maleimide monomer units into a maleimide copolymer, for example, a raw material consisting of an unsaturated dicarboxylic anhydride monomer can be copolymerized with another monomer, and the resulting copolymer can be imidized with ammonia or a primary amine to produce structural units similar to those obtained by polymerizing a maleimide monomer. Alternatively, a raw material consisting of a maleimide monomer can be copolymerized with another monomer.

The maleimide-based copolymer of this embodiment preferably contains 30 to 60 mass% of maleimide-based monomer units, and more preferably 35 to 50 mass% of maleimide-based monomer units, when the total of the aromatic vinyl-based monomer units, maleimide-based monomer units, vinyl cyanide-based monomer units, and unsaturated dicarboxylic acid anhydride-based monomer units is taken as 100 mass%. The maleimide-based monomer unit content is, for example, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, or 60 mass%, and may be within a range between any two of the values exemplified here. The maleimide-based monomer unit content in the maleimide-based copolymer can be measured using C-13 NMR. When the content of the maleimide-based monomer units is equal to or greater than the lower limit, the effect of imparting heat resistance to the resin composition is enhanced. When the content of the maleimide-based monomer units is equal to or less than the upper limit, dispersibility in the resin composition is improved.

1.3 Vinyl cyanide monomer unit The vinyl cyanide monomer unit is a structural unit derived from the vinyl cyanide monomer used in the polymerization of the maleimide copolymer according to this embodiment. Examples of vinyl cyanide monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, and fumaronitrile. These vinyl cyanide monomers may be used alone or in combination of two or more. As the vinyl cyanide monomer according to this embodiment, acrylonitrile is preferred because of its good copolymerizability and easy availability.

The maleimide copolymer of this embodiment preferably contains 0 to 30% by mass of vinyl cyanide monomer units, more preferably 0.5 to 25% by mass, and even more preferably 5 to 20% by mass, of vinyl cyanide monomer units, assuming the total of aromatic vinyl monomer units, maleimide monomer units, vinyl cyanide monomer units, and unsaturated dicarboxylic anhydride monomer units to be 100% by mass. The content of vinyl cyanide monomer units is, for example, 0, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, or 30% by mass, and may be within a range between any two of the values exemplified here. The content of vinyl cyanide monomer units in the maleimide copolymer can be measured using C-13 NMR. When the content of vinyl cyanide monomer units is equal to or greater than the lower limit, the fluidity and chemical resistance of the resulting resin composition are improved. When the content of vinyl cyanide monomer units is below the upper limit, a resin composition with good color can be obtained.

1.4 Unsaturated dicarboxylic acid anhydride monomer unit The unsaturated dicarboxylic acid anhydride monomer unit is a structural unit derived from the unsaturated dicarboxylic acid anhydride monomer used in the polymerization of the maleimide copolymer according to this embodiment. Examples of unsaturated dicarboxylic acid anhydride monomers include maleic anhydride, itaconic anhydride, citraconic anhydride, and aconitic anhydride. These unsaturated dicarboxylic acid anhydride monomers may be used alone or in combination of two or more. As the unsaturated dicarboxylic acid anhydride monomer according to this embodiment, maleic acid anhydride is preferred because of its good copolymerizability and easy availability.

The maleimide-based copolymer of this embodiment preferably contains 0 to 15% by mass of unsaturated dicarboxylic acid anhydride-based monomer units, when the total of aromatic vinyl-based monomer units, maleimide-based monomer units, vinyl cyanide-based monomer units, and unsaturated dicarboxylic acid anhydride-based monomer units is taken as 100% by mass, more preferably 0.1 to 15% by mass, even more preferably 0.2 to 10% by mass, and particularly preferably 0.5 to 5% by mass. The content of the unsaturated dicarboxylic acid anhydride monomer unit is, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15% by mass, and may be within a range between any two of the values exemplified here. The content of the unsaturated dicarboxylic acid anhydride monomer unit in the maleimide copolymer can be measured using a C-13 NMR method. When the content of the unsaturated dicarboxylic acid anhydride monomer unit is equal to or greater than the lower limit, the effect of imparting heat resistance to the resin composition is enhanced, and further, when the resulting resin composition is applied to a molded article, the adhesion to the coating film is improved. When the content of unsaturated dicarboxylic acid anhydride monomer units is below the upper limit, a resin composition with good thermal stability is obtained.

1.5 Copolymerizable Monomer Units The maleimide copolymer according to this embodiment may be copolymerized with a copolymerizable monomer other than an aromatic vinyl monomer, a maleimide monomer, a vinyl cyanide monomer, and an unsaturated dicarboxylic anhydride monomer, as long as the effects of the present invention are not impaired. Examples of monomers copolymerizable with the maleimide copolymer include acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, and butyl acrylate, methacrylic acid ester monomers such as methyl methacrylate and ethyl methacrylate, vinyl carboxylic acid monomers such as acrylic acid and methacrylic acid, acrylic acid amide, and methacrylic acid amide. These monomers copolymerizable with the maleimide copolymer may be used alone or in combination of two or more.

The monomers copolymerizable with the maleimide-based copolymer described above are copolymerizable to the extent that the effects of the present invention are not impaired. However, the structural units derived from these monomers preferably account for 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, of the maleimide-based copolymer taken as 100% by mass. In other words, when the maleimide-based copolymer of this embodiment is taken as 100% by mass, the total content of aromatic vinyl-based monomer units, maleimide-based monomer units, vinyl cyanide-based monomer units, and unsaturated dicarboxylic acid anhydride-based monomer units is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. It is particularly preferable that the maleimide-based copolymer of this embodiment consists solely of aromatic vinyl-based monomer units, maleimide-based monomer units, vinyl cyanide-based monomers, and unsaturated dicarboxylic acid anhydride-based monomer units.

From the perspective of further reducing the environmental impact, the monomers used in the maleimide copolymer of this embodiment can be monomers produced from conventional petroleum-derived raw materials, as well as monomers produced from biomass raw materials as defined by ISCC PLUS certification, circular raw materials including those derived from biomass, and chemically recycled raw materials in which used resins are converted into oil and reused.

2. Physical Properties of Maleimide-Based Copolymer 2.1 Glass Transition Temperature The glass transition temperature of the maleimide-based copolymer according to this embodiment is 160 to 210°C, and more preferably 170 to 195°C. The glass transition temperature of the maleimide-based copolymer is, for example, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, or 210°C, and may be within a range between any two of the values exemplified here. The glass transition temperature can be measured, for example, by a method conforming to JIS K 7121:2012. When the glass transition temperature is equal to or higher than the lower limit, the effect of imparting heat resistance to the resin composition is enhanced. When the glass transition temperature is equal to or lower than the upper limit, the copolymer can be easily kneaded with the resin composition even at low temperatures. The glass transition temperature of the maleimide-based copolymer can be adjusted by the type and content of the monomer unit, molecular weight distribution, etc., and can particularly be adjusted by the content and/or weight average molecular weight of the maleimide-based monomer.

2.2 Weight Average Molecular Weight The weight average molecular weight of the maleimide copolymer according to this embodiment is 50,000 to 170,000, more preferably 60,000 to 150,000, and even more preferably 70,000 to 130,000. The weight average molecular weight of the maleimide copolymer is, for example, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, 120,000, 130,000, 140,000, 150,000, 160,000, or 170,000, and may be within a range between any two of the values exemplified here. The weight average molecular weight can be, for example, a polystyrene-equivalent value measured using gel permeation chromatography (GPC). Specifically, it can be a value measured under the following conditions.
Apparatus: SYSTEM-21 Shodex (manufactured by Resonac Co., Ltd.)
Column: Three PL gel MIXED-B (Polymer Laboratories) in series Temperature: 40°C
Solvent: tetrahydrofuran Concentration: 0.4% by mass
Calibration curve: Prepared using standard polystyrene (PS) (manufactured by Polymer Laboratories). When the weight-average molecular weight is equal to or greater than the lower limit, the effect of imparting heat resistance to the resin composition is enhanced, and the impact resistance of the resin composition is improved. When the weight-average molecular weight is equal to or less than the upper limit, the copolymer is easily kneaded with the resin composition even at low temperatures. The weight-average molecular weight of the maleimide copolymer can be adjusted by the polymerization conditions, particularly by the amount of polymerization initiator and/or chain transfer agent used.

2.3 Molecular Weight Distribution In the maleimide copolymer according to this embodiment, where Mw is the weight-average molecular weight and Mn is the number-average molecular weight, Mw/Mn is 2.8 or less, more preferably 2.7 or less, and even more preferably 2.5 or less. The lower limit of Mw/Mn is not particularly limited, but is, for example, 1.0. The number-average molecular weight can be, for example, a polystyrene-equivalent value measured using gel permeation chromatography (GPC) in the same manner as the weight-average molecular weight described above. The smaller the Mw/Mn, the more improved the dispersibility in the resin composition, and ultimately the better the appearance during molding. The Mw/Mn of the maleimide copolymer can be adjusted by the polymerization conditions and is affected by the uniformity of the polymerization reaction system. In the case of solution polymerization, it can be adjusted, for example, by the rotation speed of the stirrer.

In the maleimide-based copolymer of this embodiment, the content of components having a molecular weight of 500,000 or more is less than 3% by mass, more preferably 2% by mass or less, and even more preferably 1.5% by mass or less. The content of components having a molecular weight of 500,000 or more in the maleimide-based copolymer is, for example, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, or 0% by mass, and may be within a range between any two of the values exemplified here. The content of components having a molecular weight of 500,000 or more in a maleimide-based copolymer can be, for example, the proportion of molecular weights of 500,000 or more in an integrated molecular weight distribution curve measured using gel permeation chromatography (GPC), similar to the weight-average molecular weight described above. The lower the content of components having a molecular weight of 500,000 or more in a maleimide-based copolymer, the better the dispersibility in the resin composition, and ultimately the better the appearance during molding. The content of components having a molecular weight of 500,000 or more in a maleimide-based copolymer can be adjusted by the polymerization conditions; in the case of solution polymerization, for example, it can be adjusted by the amount of chain transfer agent used and/or the rotation speed of the stirrer.

2.4 Melt Mass-Flow Rate The melt mass-flow rate of the maleimide-based copolymer according to this embodiment is preferably 5 to 120 g/10 min, more preferably 10 to 110 g/10 min, and even more preferably 15 to 100 g/10 min. The melt mass-flow rate of the maleimide-based copolymer can be measured, for example, by a method conforming to JIS K 7210-1:2014, specifically, under conditions of 265°C and a load of 98 N. When the melt mass-flow rate of the maleimide-based copolymer is equal to or greater than the lower limit, the fluidity of the resulting resin composition is improved. When the melt mass-flow rate of the maleimide-based copolymer is equal to or less than the upper limit, the impact resistance of the resulting resin composition is improved.

3. Method for Producing Maleimide-Based Copolymer Polymerization methods for the maleimide-based copolymer according to this embodiment include, for example, solution polymerization and bulk polymerization. Solution polymerization is preferred from the viewpoint that polymerization while performing fractional addition or the like can yield a maleimide-based copolymer with a more uniform copolymer composition. The solvent for solution polymerization is preferably non-polymerizable from the viewpoint that by-products are less likely to be produced and adverse effects are minimal. Examples of solvents for solution polymerization include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; ethers such as tetrahydrofuran and 1,4-dioxane; aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Methyl ethyl ketone and methyl isobutyl ketone are preferred because of the ease of solvent removal during devolatilization and recovery of the maleimide-based copolymer. The polymerization process can be a continuous polymerization method, a batch method (batch method), or a semi-batch method.

In the method for producing a maleimide copolymer according to this embodiment, the rotation speed of the stirrer during solution polymerization is, for example, preferably 200 rotations per minute or more, more preferably 300 rotations per minute or more, and even more preferably 400 rotations per minute or more. When the rotation speed of the stirrer during solution polymerization is within this range, a favorable molecular weight distribution is achieved, and the amount of components with a molecular weight of 500,000 or more in the maleimide copolymer is reduced.

The maleimide copolymer according to this embodiment can be produced by any method, but is preferably obtained by radical polymerization, with the polymerization temperature preferably in the range of 80 to 150°C. The polymerization initiator is also not particularly limited, but examples include known azo compounds such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile, azobismethylpropionitrile, and azobismethylbutyronitrile, and known organic peroxides such as benzoyl peroxide, t-butylperoxybenzoate, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexanoate, di-t-butylperoxide, dicumyl peroxide, and ethyl-3,3-di-(t-butylperoxy)butyrate. These may be used alone or in combination. From the perspective of polymerization reaction rate and polymerization rate control, it is preferable to use an azo compound or organic peroxide with a 10-hour half-life at 70 to 120°C. The amount of polymerization initiator used is not particularly limited, but is preferably 0.01 to 1.5% by mass, and more preferably 0.1 to 1.0% by mass, based on 100% by mass of all monomer units. A polymerization initiator used in an amount of 0.01% by mass or more is preferable because a sufficient polymerization rate can be achieved. A polymerization initiator used in an amount of 1.5% by mass or less can suppress the polymerization rate, making it easier to control the reaction and achieve the target molecular weight.

A chain transfer agent can be used in the production of the maleimide-based copolymer of this embodiment. The chain transfer agent that can be used is not particularly limited, but examples include n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, α-methylstyrene dimer (2,4-diphenyl-4-methyl-1-pentene), ethyl thioglycolate, limonene, and terpinolene. The amount of chain transfer agent used is not particularly limited as long as it is within the range that achieves the target molecular weight, but is preferably 0.001 to 2.0% by mass, and more preferably 0.01 to 1.5% by mass, relative to 100% by mass of all monomer units. The target molecular weight can be easily achieved if the amount of chain transfer agent used is 0.01 to 1.5% by mass.

Methods for introducing maleimide monomer units into the maleimide copolymer of this embodiment include copolymerizing an aromatic vinyl monomer, a maleimide monomer, and optionally a vinyl cyanide monomer and an unsaturated dicarboxylic acid anhydride monomer (direct method), or a method in which an aromatic vinyl monomer, an unsaturated dicarboxylic acid anhydride monomer, and optionally a vinyl cyanide monomer are first copolymerized, and then the unsaturated dicarboxylic acid anhydride groups are reacted with ammonia or a primary amine to convert the unsaturated dicarboxylic acid anhydride groups into maleimide monomer units (post-imidization method). The post-imidization method is preferred because it reduces the amount of maleimide monomer remaining in the copolymer.

Primary amines used in the post-imidization method include, for example, alkylamines such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, n-pentylamine, n-hexylamine, n-octylamine, cyclohexylamine, and decylamine, as well as chlorine- or bromine-substituted alkylamines, and aromatic amines such as aniline, toluidine, and naphthylamine. Of these, aniline and cyclohexylamine are preferred. These primary amines may be used alone or in combination of two or more. The amount of primary amine added is not particularly limited, but is preferably 0.7 to 1.1 molar equivalents, more preferably 0.85 to 1.05 molar equivalents, relative to the unsaturated dicarboxylic acid anhydride monomer units in the maleimide copolymer. A primary amine addition amount of 0.7 molar equivalents or more relative to the unsaturated dicarboxylic acid anhydride monomer units in the maleimide copolymer is preferred because it provides good thermal stability. Furthermore, adding a primary amine in an amount of 1.1 molar equivalents or less is preferable because it reduces the amount of primary amine remaining in the maleimide copolymer.

A catalyst may be used when introducing maleimide-based monomer units via post-imidization. The catalyst can enhance the dehydration ring-closure reaction in the reaction between ammonia or a primary amine and an unsaturated dicarboxylic acid anhydride group, particularly in the reaction converting the unsaturated dicarboxylic acid anhydride group to a maleimide group. The type of catalyst is not particularly limited, but tertiary amines can be used, for example. Examples of tertiary amines include, but are not limited to, trimethylamine, triethylamine, tripropylamine, tributylamine, N,N-dimethylaniline, and N,N-diethylaniline. The amount of tertiary amine added is not particularly limited, but preferably 0.01 molar equivalents or more relative to the unsaturated dicarboxylic acid anhydride monomer units. The temperature of the imidization reaction in this embodiment is preferably 100 to 250°C, more preferably 120 to 200°C. An imidization reaction temperature of 100°C or higher is preferred from the perspective of productivity, as the reaction rate is sufficiently fast. It is preferable for the imidization reaction temperature to be 250°C or less, as this can prevent the deterioration of physical properties of the maleimide copolymer due to thermal degradation.

A known method can be used to remove volatile components (devolatilization method), such as the solvent used in solution polymerization and unreacted monomers, from the solution after solution polymerization of a maleimide copolymer or the solution after post-imidization. For example, a vacuum devolatilization tank equipped with a heater or a devolatilization extruder equipped with a vent can be used. The devolatilized molten maleimide copolymer is transferred to the granulation process, extruded into strands through a multi-hole die, and processed into pellets using the cold cut method, in-air hot cut method, or underwater hot cut method.

4. Method of Using Maleimide-Based Copolymer The maleimide-based copolymer according to this embodiment can be suitably used in applications for imparting heat resistance to resin compositions. The maleimide-based copolymer according to this embodiment can be kneaded even at low temperatures, and therefore can be particularly suitably used as a heat resistance imparting agent for recycled resins. Therefore, one aspect of the present invention is a maleimide-based copolymer used in applications for imparting heat resistance to recycled resins.

4.1 Resin Composition The resin composition according to this embodiment contains a resin and the maleimide-based copolymer described above. The resin according to this embodiment may be a virgin resin (virgin material), a recycled resin, or a combination of these. In the case of the maleimide-based copolymer according to this embodiment, the resin preferably contains a recycled resin. The content of the recycled resin in the resin according to this embodiment can be appropriately selected depending on the desired physical properties. The content of the recycled resin in the resin according to this embodiment may be, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% by mass, where the resin is taken as 100% by mass, and may be within a range between any two of the values exemplified here. The maleimide-based copolymer according to this embodiment can impart heat resistance to a resin containing (or consisting solely of) a recycled resin without impairing the physical properties of the resin.

The resin according to this embodiment preferably contains one or more resins selected from the group consisting of ABS resin, ASA resin, AES resin, and SAN resin, and the recycled resin according to this embodiment preferably contains one or more resins selected from the group consisting of ABS resin, ASA resin, AES resin, and SAN resin. When the resin according to this embodiment is taken as 100% by mass, the total content of ABS resin, ASA resin, AES resin, and SAN resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. It is particularly preferable that the resin according to this embodiment consists solely of one or more resins selected from the group consisting of ABS resin, ASA resin, AES resin, and SAN resin.

In this embodiment, the resin composition preferably contains 60 to 95% by mass of resin and 5 to 40% by mass of maleimide copolymer, more preferably 70 to 95% by mass of resin and 5 to 30% by mass of maleimide copolymer, and even more preferably 80 to 90% by mass of resin and 10 to 20% by mass of maleimide copolymer, in a total of 100% by mass of the resin composition. When the resin and maleimide copolymer contents in the resin composition are within these ranges, the effect of improving the heat resistance of the resin composition is obtained.

4.2 Physical Properties of Resin Composition 4.2.1 Melt Mass-Flow Rate The melt mass-flow rate of the resin composition according to this embodiment is preferably 5 to 40 g/10 min, and more preferably 10 to 35 g/10 min. The melt mass-flow rate of the resin composition can be measured, for example, by a method conforming to JIS K 7210-1:2014, specifically, under conditions of 220°C and a load of 98 N. When the melt mass-flow rate of the resin composition is equal to or greater than the lower limit, moldability is improved, reducing the molding defect rate and improving productivity by improving the molding cycle. When the melt mass-flow rate of the resin composition is equal to or less than the upper limit, the molding defect rate is reduced.

4.2.2 Charpy Impact Strength The Charpy impact strength of the resin composition according to this embodiment is preferably 5.0 kJ/ ^m² or more, and more preferably 6.0 kJ/ ^m² or more. The Charpy impact strength can be measured, for example, by a method in accordance with JIS K 7111-1:2012. Specifically, the Charpy impact strength can be measured using a notched test piece and edgewise impact. The maleimide copolymer according to this embodiment can impart heat resistance to the resin while suppressing a decrease in impact resistance. Therefore, in this embodiment, when the Charpy impact strength (unit: kJ/ ^m² ) of the resin before mixing with the maleimide copolymer is taken as 100%, the Charpy impact strength (unit: kJ/ ^m² ) of the resin composition containing the maleimide copolymer is preferably 30% or more, and more preferably 40% or more.

4.2.3 Deflection Temperature Under Load The deflection temperature under load of the resin composition according to this embodiment is preferably 79°C or higher, and more preferably 81°C or higher. The deflection temperature under load can be measured, for example, by a method in accordance with Method A of JIS K 7191-1:2015. Specifically, the deflection temperature under load can be measured using a test piece measuring 80 mm x 80 mm and 4 mm thick under a load of 1.8 MPa. The maleimide copolymer according to this embodiment can impart heat resistance to the resin. When the deflection temperature under load (unit: °C) of the resin before mixing with the maleimide copolymer is taken as 100%, the proportion of the deflection temperature under load (unit: °C) of the resin composition containing the maleimide copolymer is preferably 110% or higher.

4.3 Manufacturing Method of Resin Composition The manufacturing method of the resin composition according to this embodiment is not particularly limited as long as it can knead and mix the resin and the maleimide-based copolymer. Known melt-kneading methods can be used as a method for kneading and mixing the resin and the maleimide-based copolymer. Examples of melt-kneading devices include screw extruders such as single-screw extruders, intermeshing co-rotating or intermeshing counter-rotating twin-screw extruders, and non- or partially intermeshing twin-screw extruders, Banbury mixers, co-kneaders, and mixing rolls. When kneading and mixing, additives such as stabilizers, UV absorbers, flame retardants, plasticizers, lubricants, glass fibers, inorganic fillers, colorants, and antistatic agents may also be added.

In this embodiment, the resin temperature when kneading and mixing the resin and maleimide copolymer is preferably less than 300°C, and more preferably 240 to 290°C. At such a resin temperature, even if the resin contains recycled resin (or is made only of recycled resin), heat resistance can be imparted without impairing the physical properties of the resin. Furthermore, the maleimide copolymer according to this embodiment can be sufficiently mixed with the resin even at such a temperature, resulting in a good appearance when molded.

The resin composition can be molded using known methods, such as injection molding, sheet extrusion, vacuum molding, blow molding, foam molding, and profile extrusion. It is preferable that molded articles made from the resin composition of this embodiment are free of streaks that would clearly cause a poor appearance, and have a surface condition that compares favorably with molded articles made from resins that do not contain maleimide copolymers. Articles molded from the resin composition of this embodiment can be suitably used in automobiles, home appliances, office automation equipment, housing materials, daily necessities, etc.

The present invention will be described in more detail below based on examples. Note that the examples described below are representative examples of the present invention, and should not be construed as narrowing the scope of the present invention.

<Maleimide-based copolymer A-1>
An autoclave equipped with a stirrer was charged with 65 parts by mass of styrene, 7 parts by mass of maleic anhydride, 0.2 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 25 parts by mass of methyl ethyl ketone. The stirrer rotation speed was set to 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 28 parts by mass of maleic anhydride and 0.18 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 100 parts by mass of methyl ethyl ketone was continuously added over 7 hours. After the addition, 0.03 parts by mass of t-butylperoxy-2-ethylhexanoate was added, the temperature was raised to 120°C, and the reaction was continued for another 1 hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 32 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the reaction was continued at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer A-1. The analytical results of the obtained maleimide copolymer A-1 are shown in Table 1.

<Maleimide-based copolymer A-2>
An autoclave equipped with a stirrer was charged with 65 parts by mass of styrene, 7 parts by mass of maleic anhydride, 0.3 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 25 parts by mass of methyl ethyl ketone. The stirrer rotation speed was set to 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 26 parts by mass of maleic anhydride and 0.18 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 100 parts by mass of methyl ethyl ketone was continuously added over 7 hours. After the addition, 0.03 parts by mass of t-butylperoxy-2-ethylhexanoate was added, the temperature was raised to 120°C, and the reaction was continued for another 1 hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 32 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the reaction was continued at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer A-2. The analytical results of the obtained maleimide copolymer A-2 are shown in Table 1.

<Maleimide-based copolymer A-3>
An autoclave equipped with a stirrer was charged with 42 parts by mass of styrene, 10 parts by mass of acrylonitrile, 4 parts by mass of maleic anhydride, 0.03 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 27 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 21 parts by mass of maleic anhydride and 0.15 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 85 parts by mass of methyl ethyl ketone and 20 parts by mass of styrene were continuously added over 4.5 hours. After the addition, 0.02 parts by mass of t-butylperoxy-2-ethylhexanoate and 3 parts by mass of styrene were added, the temperature was raised to 120°C, and the mixture was allowed to react for an additional hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 23 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the mixture was allowed to react at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer A-3. The analytical results of the obtained maleimide copolymer A-3 are shown in Table 1.

<Maleimide Copolymer A-4>
An autoclave equipped with a stirrer was charged with 42 parts by mass of styrene, 10 parts by mass of acrylonitrile, 4 parts by mass of maleic anhydride, 0.5 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 27 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 21 parts by mass of maleic anhydride and 0.3 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 85 parts by mass of methyl ethyl ketone was continuously added over 4.5 hours. After the addition, 0.02 parts by mass of t-butylperoxy-2-ethylhexanoate and 3 parts by mass of styrene were added, the temperature was raised to 120°C, and the mixture was allowed to react for an additional hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 23 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the mixture was allowed to react at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer A-4. The analytical results of the obtained maleimide copolymer A-4 are shown in Table 1.

<Maleimide-based copolymer A-5>
An autoclave equipped with a stirrer was charged with 62 parts by mass of styrene, 8 parts by mass of maleic anhydride, 0.3 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 25 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 rpm. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 30 parts by mass of maleic anhydride and 0.18 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 100 parts by mass of methyl ethyl ketone was continuously added over 7 hours. After the addition, 0.03 parts by mass of t-butylperoxy-2-ethylhexanoate was added, the temperature was raised to 120°C, and the reaction was continued for another 1 hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 35 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the reaction was continued at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer A-5. The analytical results of the obtained maleimide copolymer A-5 are shown in Table 1.

<Maleimide-based copolymer A-6>
An autoclave equipped with a stirrer was charged with 42 parts by mass of styrene, 10 parts by mass of acrylonitrile, 4 parts by mass of maleic anhydride, 1 part by mass of 2,4-diphenyl-4-methyl-1-pentene, and 27 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 21 parts by mass of maleic anhydride and 0.35 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 85 parts by mass of methyl ethyl ketone was continuously added over 4.5 hours. After the addition, 0.02 parts by mass of t-butylperoxy-2-ethylhexanoate and 3 parts by mass of styrene were added, the temperature was raised to 120°C, and the mixture was allowed to react for an additional hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 23 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the mixture was allowed to react at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer A-6. The analytical results of the obtained maleimide copolymer A-6 are shown in Table 1.

<Maleimide Copolymer A-7>
An autoclave equipped with a stirrer was charged with 65 parts by mass of styrene, 7 parts by mass of maleic anhydride, 0.025 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 25 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 26 parts by mass of maleic anhydride and 0.18 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 100 parts by mass of methyl ethyl ketone was continuously added over 7 hours. After the addition, 0.03 parts by mass of t-butylperoxy-2-ethylhexanoate was added, the temperature was raised to 120°C, and the reaction was continued for another 1 hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 32 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the reaction was continued at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile matter was removed to obtain pellets of maleimide copolymer A-7. The analytical results of the obtained maleimide copolymer A-7 are shown in Table 1.

<Maleimide-based copolymer B-1>
An autoclave equipped with a stirrer was charged with 65 parts by mass of styrene, 7 parts by mass of maleic anhydride, 0.3 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 25 parts by mass of methyl ethyl ketone. The stirrer rotation speed was set to 150 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 28 parts by mass of maleic anhydride and 0.18 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 100 parts by mass of methyl ethyl ketone was continuously added over 7 hours. After the addition, 0.03 parts by mass of t-butylperoxy-2-ethylhexanoate was added, the temperature was raised to 120°C, and the reaction was continued for another 1 hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 32 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the reaction was continued at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer B-1. The analytical results of the obtained maleimide copolymer B-1 are shown in Table 2.

<Maleimide-based copolymer B-2>
An autoclave equipped with a stirrer was charged with 42 parts by mass of styrene, 10 parts by mass of acrylonitrile, 4 parts by mass of maleic anhydride, 0.03 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 27 parts by mass of methyl ethyl ketone. The stirrer rotation speed was set to 150 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 21 parts by mass of maleic anhydride and 0.15 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 85 parts by mass of methyl ethyl ketone and 20 parts by mass of styrene were continuously added over 4.5 hours. After the addition, 0.02 parts by mass of t-butylperoxy-2-ethylhexanoate and 3 parts by mass of styrene were added, the temperature was raised to 120°C, and the mixture was allowed to react for an additional hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 23 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the mixture was allowed to react at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer B-2. The analytical results of the obtained maleimide copolymer B-2 are shown in Table 2.

<Maleimide-based copolymer B-3>
An autoclave equipped with a stirrer was charged with 65 parts by mass of styrene, 8 parts by mass of acrylonitrile, 2 parts by mass of maleic anhydride, 0.1 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 10 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 16 parts by mass of maleic anhydride and 0.3 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 80 parts by mass of methyl ethyl ketone was continuously added over 7 hours. After the addition, 0.01 parts by mass of t-butylperoxy-2-ethylhexanoate and 2 parts by mass of styrene were added, the temperature was raised to 120°C, and the reaction was continued for another 3 hours to obtain a styrene-maleic anhydride copolymer. Thereafter, 16 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the reaction was continued for 7 hours at 140°C. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer B-3. The analytical results of the obtained maleimide copolymer B-3 are shown in Table 2.

<Maleimide-based copolymer B-4>
An autoclave equipped with a stirrer was charged with 42 parts by mass of styrene, 10 parts by mass of acrylonitrile, 4 parts by mass of maleic anhydride, 2 parts by mass of 2,4-diphenyl-4-methyl-1-pentene, and 27 parts by mass of methyl ethyl ketone. The stirrer rotation speed was 450 revolutions per minute. After purging the system with nitrogen gas, the temperature was raised to 92°C, and a solution of 21 parts by mass of maleic anhydride and 0.35 parts by mass of t-butylperoxy-2-ethylhexanoate dissolved in 85 parts by mass of methyl ethyl ketone and 20 parts by mass of styrene were continuously added over 4.5 hours. After the addition, 0.02 parts by mass of t-butylperoxy-2-ethylhexanoate and 3 parts by mass of styrene were added, the temperature was raised to 120°C, and the mixture was allowed to react for an additional hour to obtain a styrene-maleic anhydride copolymer. Thereafter, 23 parts by mass of aniline and 0.4 parts by mass of triethylamine were added to the resin solution, and the mixture was allowed to react at 140°C for 7 hours. After the reaction was completed, the imidization reaction solution was charged into a vent-type screw extruder, and the volatile components were removed to obtain pellets of maleimide copolymer B-4. The analytical results of the obtained maleimide copolymer B-4 are shown in Table 2.

<Analysis of maleimide copolymer>
(composition analysis)
For each maleimide copolymer, the components and their contents were measured using C-13 NMR under the following conditions and with the following apparatus.
Device name: FT-NMR AVANCE300 (manufactured by BRUKER)
Solvent: deuterated chloroform Concentration: 14% by mass
Temperature: 27℃
Accumulation count: 8,000 times

(glass transition temperature)
The glass transition temperature of each maleimide copolymer was measured in accordance with JIS K 7121:2012 using the following apparatus and conditions.
Device name: Robot DSC6200 (Seiko Instruments Inc.)
Temperature increase rate: 10°C/min

(Weight average molecular weight, molecular weight distribution)
The weight-average molecular weight (Mw), number-average molecular weight (Mn), and content of components with a molecular weight of 500,000 or more of each maleimide copolymer were measured using gel permeation chromatography (GPC) under the following conditions:
Apparatus: SYSTEM-21 Shodex (manufactured by Resonac Co., Ltd.)
Column: Three PL gel MIXED-B (Polymer Laboratories) in series Temperature: 40°C
Solvent: tetrahydrofuran Concentration: 0.4% by mass
Calibration curve: Created using standard polystyrene (PS) (manufactured by Polymer Laboratories)

(Melt Mass-Flow Rate (MFR))
Each maleimide copolymer was measured under conditions of 265°C and a load of 98N by a method in accordance with JIS K 7210-1:2014.

<Examples 1 to 10, Comparative Examples 1 to 5, Reference Examples 1 to 4>
Resin compositions were prepared by melt-kneading each maleimide copolymer, each resin, and additives (each resin in Reference Examples 1 to 4) using an extruder under the formulations and production conditions shown in Tables 3 and 4. The extruder used was a twin-screw extruder (TEM-26SX, manufactured by Toshiba Machine Co., Ltd.) with an L/D ratio of 48 and a screw depth ratio of 1.56.

The resins and additives used are as follows:
resin:
C-1: Recycled ABS resin (manufactured by BAGE Plastics, "RFRI 8580 C9005 (R200540) UL94HB")
C-2: Recycled ABS resin (BAGE Plastics "R200680 ABS RFHI RAL7035 light gray")
C-3: ABS resin (virgin material; "GR-3000" manufactured by Denka Co., Ltd.)

Additives:
D-1: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ("Irganox (registered trademark) 1010" manufactured by BASF Japan Ltd.)
D-2: Tris(2,4-di-tert-butylphenyl)phosphite ("Irgafos (registered trademark) 168" manufactured by BASF Japan Ltd.)

<Analysis of Resin Composition>
(Melt Mass-Flow Rate (MFR))
For each resin composition, measurement was performed under conditions of 220°C and a load of 98N according to a method in accordance with JIS K 7210-1:2014.

(Charpy impact strength)
For each resin composition, the impact strength was measured using a notched test piece in an edgewise impact direction according to JIS K 7111-1: 2012. The measuring machine used was a digital impact tester (manufactured by Toyo Seiki Seisakusho, Ltd.).
In addition, for each example and comparative example, the percentage (%) of the Charpy impact strength (kJ/m ² ) was calculated, assuming that the Charpy impact strength (kJ/m ² ) of the corresponding Reference Examples 1 to 4 using the same resin was 100%.

(deflection temperature under load)
For each resin composition, measurements were performed using a test piece of 80 mm x 80 mm and 4 mm thick under a load of 1.8 MPa in accordance with Method A of JIS K 7191-1:2015. The measuring machine used was an HDT & VSPT tester (manufactured by Toyo Seiki Seisakusho, Ltd.).
Furthermore, for each Example and Comparative Example, the percentage (%) of the deflection temperature under load (°C) was calculated, assuming that the deflection temperature under load (°C) of the corresponding Reference Examples 1 to 4 using the same resin was 100%.

(exterior)
For each resin composition, an injection molding machine ("JSW-J5OADS" manufactured by The Japan Steel Works, Ltd.) was used to produce a mirror-finished plate measuring 90 mm in length, 55 mm in width, and 2 mm in thickness, molded under molding conditions of a cylinder temperature of 220°C and a mold temperature of 60°C, and the appearance was evaluated. The evaluation was carried out according to the following criteria, in comparison with the corresponding Reference Examples 1 to 4, which used the same resin as each Example and Comparative Example.
A: The surface condition is comparable to that of the corresponding reference example.
B: Slightly smaller streaks are observed compared to the corresponding reference example. C: Smaller streaks are observed compared to the corresponding reference example. D: Streaks that clearly cause a poor appearance are observed in some areas compared to the corresponding reference example. E: Streaks that clearly cause a poor appearance are observed all over the surface compared to the corresponding reference example.

The results in Table 3 show that the examples of the present invention, even when used with recycled resin, are able to impart heat resistance to the resin while suppressing a decrease in the resin's impact resistance, and also result in a good appearance when molded. The results in Table 4 show that Comparative Examples 1 to 4, which do not satisfy the configuration of the present invention, are inferior in at least one of the resin's impact resistance, heat resistance, and appearance. Furthermore, the results in Table 4 show that Comparative Example 5, in which the maleimide copolymer and recycled resin were kneaded and mixed at high temperature, produced a resin with poor impact resistance.

Claims (6)

A maleimide copolymer,
an aromatic vinyl-based monomer unit and a maleimide-based monomer unit;
Including,
The maleimide copolymer has a glass transition temperature of 160 to 210°C,
The maleimide copolymer has a weight average molecular weight of 50,000 to 170,000;
The maleimide copolymer has a content of components having a molecular weight of 500,000 or more of less than 3% by mass. The maleimide copolymer according to claim 1, wherein Mw/Mn is 2.8 or less, where Mw is the weight average molecular weight and Mn is the number average molecular weight. The maleimide copolymer according to claim 1, wherein the glass transition temperature is 170 to 195°C. The maleimide copolymer according to claim 1, having a melt mass-flow rate of 15 to 100 g/10 min at 265°C under a load of 98 N, as measured according to a method in accordance with JIS K 7210-1:2014. The maleimide copolymer according to claim 1 is used to impart heat resistance to recycled resins. The maleimide-based copolymer according to claim 5, wherein the recycled resin comprises one or more selected from the group consisting of ABS resin, ASA resin, AES resin, and SAN resin.