Monomer composition, methacrylic resin, and method for producing methacrylic resin

Abstract

The present invention provides a methacrylic resin that maintains the excellent heat resistance of methacrylic resins, has excellent weather resistance, and is inhibited from yellowing; a monomer composition for obtaining the methacrylic resin; and a method for producing the methacrylic resin using the monomer composition. [Solution] A monomer composition comprising methyl methacrylate and at least one α-olefin selected from the group consisting of 2-ethyl-1-hexene, 1-octene, and 1-dodecene, wherein the content of the α-olefin is 10,000 mass ppm or less relative to the total mass of the monomer composition.

Description

Technical Field

[0001] The present invention relates to a monomer composition, a methacrylic resin, and a method for producing a methacrylic resin. This application claims priority based on Japanese Patent Application No. 2021-041292 filed in Japan on March 15, 2021, the content of which is incorporated herein by reference.

Background Art

[0002] Methacrylic resins are excellent in transparency, heat resistance, and weather resistance, and have balanced performance in resin physical properties such as mechanical strength, thermal properties, and moldability. In particular, methacrylic resin plates made of methacrylic resins are used in applications such as tanning beds, lighting equipment, skin therapy equipment, medical equipment, devices for curing or reacting with ultraviolet rays (hereinafter referred to as "UV"), equipment for growing animals and plants, skylights, and transparent members used in HID lamps.

[0003] In the above applications, when a methacrylic resin plate is installed in an environment exposed to UV such as direct sunlight or a UV lamp, the methacrylic resin plate has a problem that a yellowish color (yellowing) occurs. Therefore, there has been a demand for a methacrylic resin that does not develop a yellowish color even when exposed to UV for a long time, that is, a methacrylic resin having excellent weather resistance.

[0004] As a technique for improving the weather resistance of methacrylic resins, Patent Document 1 discloses a methacrylic resin obtained by polymerizing a monomer such as methyl methacrylate in the presence of a hindered amine-based compound (HALS) having a specific structure, which is one of the light stabilizers.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, the methacrylic resin described in Patent Document 1 had a problem in that, while its weather resistance improved with increasing amounts of HALS added during polymerization, the resulting methacrylic resin became discolored because HALS itself is colored. Furthermore, increasing the amount of HALS added reduced polymerization efficiency and increased the amount of residual monomers in the methacrylic resin, which led to a problem of reduced weather resistance in the resulting methacrylic resin.

[0007] In view of the above circumstances, the present invention aims to provide a methacrylic resin that ensures the excellent heat resistance of methacrylic resins, has excellent weather resistance and suppresses yellowing, a monomer composition for obtaining the methacrylic resin, and a method for producing the methacrylic resin using the monomer composition. [Means for solving the problem]

[0008] To achieve the above objectives, the present invention employs the following configuration. [1] A monomer composition comprising methyl methacrylate and α-olefin. [2] The content of at least one compound selected from the group consisting of transition metal compounds and group 13 element compounds is 0 ppm or more by mass, relative to the total mass of the α-olefin, and is 7 × 10 4 The monomer composition described in [1], wherein the mass is less than or equal to ppm. [3] The monomer composition according to [1] or [2], comprising 0.1 ppm by mass or more of the α-olefin with respect to the total mass of the monomer composition. [4] The monomer composition according to any one of [1] to [3], wherein the α-olefin is a liquid or solid at room temperature and pressure. [5] The monomer composition according to any one of [1] to [4], wherein the α-olefin comprises an α-olefin having 6 to 12 carbon atoms. [6] The monomer composition according to any one of [1] to [5], wherein the α-olefin comprises 1-octene or 1-dodecene. [7] A methacrylic resin obtained by radical polymerization of a monomer mixture containing the monomer composition described in any of [1] to [6]. [8] A methacrylic resin containing an α-olefin monomer. [9] The methacrylic resin according to [8], comprising 0.1 ppm by mass or more of the α-olefin monomer.

[10] The methacrylic resin according to [8] or [9], wherein the α-olefin monomer is liquid or solid at room temperature and pressure.

[11] The methacrylic resin according to any one of [8] to

[10] , wherein the α-olefin monomer comprises an α-olefin having 6 to 12 carbon atoms.

[12] The methacrylic resin according to any one of [8] to

[11] , wherein the α-olefin monomer comprises 1-octene or 1-dodecene. A resin molded article obtained by molding a methacrylic resin as described in any of

[13] [8] to

[12] .

[14] A compound comprising methyl methacrylate and α-olefin, wherein the content of at least one compound selected from the group consisting of transition metal compounds and group 13 element compounds is 7 × 10 with respect to the total mass of the α-olefin. 4 A method for producing a methacrylic resin, comprising radical polymerization of a monomer mixture containing a monomer composition with a mass of ppm or less. [Effects of the Invention]

[0009] According to the present invention, these problems can be solved. Specifically, the present invention provides a methacrylic resin that ensures the excellent heat resistance of methacrylic resins, has excellent weather resistance and suppresses yellowing, a monomer composition for obtaining the methacrylic resin, and a method for producing the methacrylic resin using the monomer composition. [Modes for carrying out the invention]

[0010] The following terms used in this specification and in the claims are defined as follows: A "monomer" refers to a compound that has a polymerizable carbon-carbon double bond. A "monomer-based unit" is a general term for atomic groups that are directly formed by the polymerization of one monomer molecule, and atomic groups that are obtained by chemically transforming a part of the aforementioned atomic group. "(Meth)acrylate" is selected from "acrylate" and "methacrylate". "(Meth)acrylic acid" is selected from "acrylic acid" and "methacrylic acid". "α-olefin" refers to an olefin hydrocarbon that has a carbon-carbon double bond at the α-position. The term "α-olefin monomer" refers to an olefin hydrocarbon having a carbon-carbon double bond at the α-position, but it is used to specify that it is an unreacted monomer. "Conjugation" refers to the overlap of p orbitals beyond the sigma bond between them. "Non-conjugated" means that conjugation does not occur. "The obtained methacrylic resin" refers to a resin obtained by radical polymerization of a monomer mixture containing the monomer composition of the present invention. "The obtained resin molded article" means a molded article obtained by molding the methacrylic resin of the present invention. "Mass %" indicates the percentage of a given component contained in 100% of the total amount by mass. "Mass-average molecular weight" is a value measured using gel permeation chromatography with standard polystyrene as the standard sample. "Room temperature" means a temperature between 5 and 35 degrees Celsius. "Normal pressure" refers to a range of 900 to 1100 hPa. "Transition metal" means a metallic element located in Groups 3 to 11 of the periodic table. Typically, scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and mercury (Hg), etc. "Group 13 element" means an element located in Group 13 of the periodic table. Typically, boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). "Periodic table" means "Periodic Table of Elements" (URL https: / / pubchem.ncbi.nlm.nih.gov / periodic-table / ).

[0011] <Monomer composition> The monomer composition of the present invention contains methyl methacrylate and an α-olefin. Also, other components may be included as long as the effects of the present invention are not impaired.

[0012] By containing methyl methacrylate, the monomer composition of the present invention provides good weather resistance and suppressed yellowing of the resulting methacrylic resin. [[ID=​​

[0014] The methyl methacrylate content in the monomer composition of the present invention is not particularly limited, but is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass, based on the total mass of the monomer composition.

[0015] However, the content of methyl methacrylate relative to 100% of the total mass of the monomer composition of the present invention is less than 100% by mass. Furthermore, the total content of methyl methacrylate and α-olefin relative to 100% of the total mass of the monomer composition of the present invention does not exceed 100% by mass.

[0016] The lower limit of the α-olefin content in the monomer composition of the present invention is not particularly limited, but since the weather resistance of the resulting methacrylic resin is better, it is preferably 0.1 ppm by mass or more, more preferably 10 ppm by mass or more, even more preferably 60 ppm by mass or more, and particularly preferably 80 ppm by mass or more, relative to the total mass of the monomer composition.

[0017] The upper limit of the α-olefin content in the monomer composition of the present invention is not particularly limited, but it is preferably 10,000 ppm by mass or less, more preferably 5,000 ppm by mass or less, even more preferably 4,000 ppm by mass or less, and particularly preferably 3,000 ppm by mass or less, in order to better maintain the heat resistance of the resulting methacrylic resin.

[0018] The preferred upper and lower limits mentioned above can be combined in any way. Specifically, the α-olefin content in the monomer composition of the present invention is preferably 0.1 ppm by mass or more and 10,000 ppm by mass or less, more preferably 10 ppm by mass or more and 5,000 ppm by mass or less, even more preferably 60 ppm by mass or more and 4,000 ppm by mass or less, and particularly preferably 80 ppm by mass or more and 3,000 ppm by mass or less.

[0019] It is presumed that α-olefins exhibit excellent radical scavenging effects because the coupling products of olefin hydrocarbons to which radicals generated by ultraviolet light are attached are stable. Chain-type α-olefins are preferred as the α-olefin.

[0020] The α-olefin preferably includes an α-olefin having 6 to 12 carbon atoms. The proportion of the α-olefin having 6 to 12 carbon atoms in the α-olefin is not particularly limited, but is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 99% by mass or more. The α-olefin is particularly preferably composed of an α-olefin having 6 to 12 carbon atoms.

[0021] The number of carbon atoms in the α-olefin having 6 to 12 carbon atoms is not particularly limited as long as it is between 6 and 12 carbon atoms, but it is preferably between 8 and 10 carbon atoms. Because the number of carbon atoms in the α-olefin is above the lower limit of the range, it tends to remain in the methacrylic resin obtained without volatilizing due to heating during polymerization. Therefore, it can contribute significantly to improving weather resistance.

[0022] Examples of α-olefins having 6 to 12 carbon atoms include 2-ethyl-1-hexene, 2-methyl-1-heptene, 4-methyl-1-heptene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. Among these, at least one selected from the group consisting of 2-ethyl-1-hexene, 1-octene, and 1-dodecene is preferred, 1-octene or 1-dodecene is more preferred, and 1-octene is even more preferred because it tends to remain in the methacrylic resin. The proportion of 1-octene in the α-olefin is not particularly limited, but is preferably 50% by mass or more, and more preferably 80% by mass or more, relative to the total mass of the α-olefin.

[0023] In the monomer composition of the present invention, the content of at least one compound selected from the group consisting of transition metal compounds and group 13 element compounds is 0 ppm or more by mass, relative to the total mass of α-olefin, and is 7 × 10⁻¹⁶ ppm or more. 4 It is preferable that the mass be less than or equal to ppm. In this invention, the α-olefin does not exhibit resonance stabilization effects and has significantly lower reactivity compared to methyl methacrylate, which is a conjugated monomer. Therefore, unless a specific polymerization catalyst is used, such as at least one compound selected from the group consisting of transition metal compounds and group 13 element compounds, and special conditions are met to exhibit catalytic effects, unreacted α-olefins (hereinafter also referred to as "α-olefin monomers") remain in the resulting methacrylic resin. It is believed that the presence of these α-olefin monomers in the methacrylic resin results in good weather resistance and suppression of yellowing of the resulting methacrylic resin. In other words, because the at least one compound does not exhibit catalytic effects, the content of the at least one compound is 7 × 10¹⁶ of the total mass of the α-olefin. 4 Preferably, the mass is ppm or less, 1 × 10 4 It is more preferable that the concentration be less than or equal to ppm by mass, even more preferable that it be less than or equal to 1000 ppm by mass, and particularly preferable that it is not present at all. Here, "not present" means that it is below the detection limit.

[0024] Examples of the at least one compound include compounds of transition metals from Group 5 to Group 11 having a chelating ligand, and Lewis acid catalysts. Specific examples of the transition metals include vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, platinum, ruthenium, cobalt, rhodium, nickel, palladium, and copper. Among these, transition metals from groups 8 to 11 are preferred, transition metals from group 10 are more preferred, and nickel (Ni) or palladium (Pd) is even more preferred. These transition metals may be used individually or in combination of two or more.

[0025] The chelating ligand contains at least two atoms selected from the group consisting of P, N, O, and S, and is bidentate or multidentate, and is electronically neutral or anionic. The structure of the chelating ligand is illustrated in a review by Ittel et al. (Ittel et al., "Late-Metal Catalysts for Ethylene Homo- and Copolymerization", Chemical Reviews, March 25, 2000, Vol. 100, No. 4, pp. 1169-1204). Examples of the chelating ligands include bidentate anionic P,O ligands. Examples of the bidentate anionic P,O ligands include phosphosulfonic acid, phosphocarboxylic acid, phosphorusphenol, and phosphorus enolate. Examples of chelating ligands other than the bidentate anionic P,O ligands include bidentate anionic N,O ligands. Examples of the bidentate anionic N,O ligands include salicylaldehyde and pyridinecarboxylic acid. Examples of chelating ligands other than the bidentate anionic P,O ligands and bidentate anionic N,O ligands include diimine ligands, diphenoxide ligands, and diamide ligands.

[0026] Here, typical catalysts that are compounds of transition metals from groups 5 to 11 having the aforementioned chelating ligand include so-called SHOP catalysts and Drent catalysts. The SHOP catalyst is a catalyst in which a phosphorus ligand having an aryl group, which may have substituents, is coordinated to nickel metal. The Drent catalyst is a catalyst in which a phosphorus ligand having an aryl group, which may have substituents, is coordinated to palladium metal.

[0027] Furthermore, typical Lewis acid catalysts include cationic complexes of divalent palladium or platinum. These cationic complexes of divalent palladium or platinum exhibit Lewis acidity and are useful as Lewis acid catalysts for reactions such as the Diels-Alder reaction. Compounds of group 13 elements boron and aluminum, the fourth transition metal titanium, and the fifth transition metal zirconium are also preferred because they exhibit Lewis acidity.

[0028] Examples of the other components mentioned above include the following monomers and additives.

[0029] (monomer) 1) Methacrylic acid ester: For example, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, or benzyl methacrylate. 2) Acrylate esters: For example, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, or 2-ethylhexyl acrylate. 3) Unsaturated carboxylic acids: For example, acrylic acid, methacrylic acid, maleic acid, or itaconic acid. 4) Unsaturated carboxylic acid anhydrides: For example, maleic anhydride or itaconic anhydride. 5) Maleimide: For example, N-phenylmaleimide or N-cyclohexylmaleimide. 6) Hydroxyl group-containing vinyl monomers: For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. 7) Vinyl ester: For example, vinyl acetate or vinyl benzoate. 8) Vinyl chloride, vinylidene chloride and their derivatives. 9) Nitrogen-containing vinyl monomers: For example, methacrylamide or acrylonitrile. 10) Epoxy group-containing monomers: For example, glycidyl acrylate or glycidyl methacrylate. 11) Aromatic vinyl monomers: For example, styrene, or alpha-methylstyrene.

[0030] 12) Alkanediolic di(meth)acrylate: For example, ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, or 1,6-hexanediol di(meth)acrylate. 13) Polyoxyalkylene glycol di(meth)acrylate: For example, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, or neopentyl glycol di(meth)acrylate. 14) Vinyl monomers having two or more ethylenically unsaturated bonds in the molecule: For example, divinylbenzene. 15) An unsaturated polyester prepolymer obtained from at least one polycarboxylic acid containing an ethylenically unsaturated polycarboxylic acid and at least one diol. 16) A vinyl ester prepolymer obtained by modifying the terminals of epoxy groups with acrylic.

[0031] (Additives) Examples of known additives include mold release agents, lubricants, plasticizers, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, flame retardants, flame retardant aids, polymerization inhibitors, fillers, pigments, dyes, silane coupling agents, leveling agents, defoaming agents, and fluorescent agents.

[0032] The monomers and additives can be used individually or in combination of two or more as the other components. Among the above, from the viewpoint of having an excellent balance of transparency, heat resistance, and moldability of the resulting methacrylic resin, at least one monomer selected from the group consisting of methyl acrylate, ethyl acrylate, and n-butyl acrylate is preferred as the other component. In addition to the monomers mentioned above, other components include the following monomers.

[0033] Examples of known additives include mold release agents, lubricants, plasticizers, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, flame retardants, flame retardant aids, polymerization inhibitors, fillers, pigments, dyes, silane coupling agents, leveling agents, defoamers, and fluorescent agents. Furthermore, the monomeric composition of the present invention may contain compounds that inevitably become mixed with methyl methacrylate, such as methacrolein or methanol.

[0034] <Monomer mixture> The monomer mixture of the present invention is a raw material for the methacrylic resin of the present invention, which will be described later. The monomer mixture contains 60% by mass or more of the monomer composition of the present invention described above. Here, "containing 60% by mass or more of the monomer composition of the present invention" means that the monomer mixture contains 100% by mass of the monomer composition of the present invention described above, based on 100% by mass of the total mass of the monomer mixture, or that it contains 60% by mass or more but less than 100% by mass of the monomer composition of the present invention and more than 0% by mass and 40% by mass or less of "other monomers copolymerizable with the monomer composition of the present invention" (also simply referred to as "other monomers"), and the sum of the monomer composition and the other monomers does not exceed 100% by mass.

[0035] Examples of the other monomers include the monomers 1) to 16) listed above in the description of the monomer composition of the present invention as monomers that may be included as other compounds. The monomers described in 1) to 16) above can be used individually or in combination of two or more as the other monomers.

[0036] Among the monomers 1) to 16) above, ethylene glycol dimethacrylate or neopentyl glycol dimethacrylate is preferred from the viewpoint of having an excellent balance between the heat resistance and transparency of the resulting methacrylic resin.

[0037] A polymerization initiator can be added to the monomer mixture. Examples of the polymerization initiator include organic oxides and compounds similar to azo compounds. The amount of polymerization initiator added to the monomer mixture is not particularly limited, but is preferably 0.005 to 5% by mass relative to 100% by mass of radical polymerizable monomers in the monomer mixture.

[0038] Various additives such as mold release agents, lubricants, plasticizers, antioxidants, antistatic agents, light stabilizers, ultraviolet absorbers, flame retardants, flame retardant aids, polymerization inhibitors, fillers, pigments, dyes, silane coupling agents, leveling agents, defoamers, fluorescent agents, or chain transfer agents may be added to the monomer mixture as needed.

[0039] <Methacrylic resin> The methacrylic resin of the present invention is obtained by radical polymerization of a monomer mixture containing 60% by mass or more of the monomer composition of the present invention described above. The mass-average molecular weight (Mw) of the methacrylic resin is not particularly limited, but can be appropriately set in the range of 100,000 to 1,000,000 depending on the intended use of the methacrylic resin. By appropriately increasing the mass-average molecular weight, solvent resistance and chemical resistance can be improved.

[0040] <Methacrylic resin manufacturing method> The methacrylic resin of the present invention can be obtained, for example, by polymerizing a monomer mixture containing 100% by mass of the monomer composition of the present invention described above, or a monomer mixture containing 60% by mass or more but less than 100% by mass of the monomer composition of the present invention described above and more than 0% by mass and 40% by mass or less of "other monomers copolymerizable with the monomer composition of the present invention" (also simply referred to as "other monomers"), wherein the total amount of each component of the monomer composition and the other monomers (including polymerization initiators and various additives) does not exceed 100% by mass.

[0041] The polymerization method for the monomer composition is not particularly limited, but examples include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization. From the viewpoint of the transparency of the methacrylic resin, the environmental burden due to the use of solvents, and the productivity and manufacturing cost of the resin laminate, bulk polymerization is preferred as the polymerization method for the monomer mixture. The specific methods for bulk polymerization are not particularly limited, but they can be produced using known casting polymerization methods such as the cell casting method or the continuous casting method. The mass-average molecular weight (Mw) of the methacrylic resin can be controlled by adjusting the polymerization temperature, polymerization time, amount of polymerization initiator added, and the type and amount of serial transfer agent added.

[0042] Cast polymerization is a method for obtaining a methacrylic resin by injecting a monomer mixture for obtaining a methacrylic resin or the syrup described later into a mold consisting of two inorganic glass plates or metal plates (for example, SUS plates) that are placed opposite each other at a predetermined distance and sealed around the periphery with a gasket such as a flexible resin tube, and polymerizing the mixture. The obtained methacrylic resin is then peeled from the mold to obtain a resin molded body.

[0043] As the syrup, a syrup can be used that contains a polymer (partial polymer) and the unreacted monomer mixture obtained by polymerizing a portion of the monomer mixture. Furthermore, a syrup of the type obtained by dissolving the methacrylic resin of the present invention in the monomer mixture can also be used.

[0044] The molecular weight of the partial polymer in the syrup or the dissolved methacrylic resin in the syrup is not particularly limited, but the mass-average molecular weight can be 50,000 or more and 300,000 or less. Furthermore, the mixing ratio of the partial polymer in the syrup or the dissolved methacrylic resin to the monomer mixture is not particularly limited, but the mass ratio can be 2:98 to 50:50.

[0045] The mold for casting polymerization is not particularly limited, and known molds can be used. Examples of molds for obtaining plate-shaped resin molded products include molds for cell casting and molds for continuous casting. Examples of molds for cell casting include those in which two plate-like bodies, such as inorganic glass plates, chrome-plated metal plates, or stainless steel plates, are placed opposite each other at a predetermined distance, and a gasket is placed on the edge thereof, thereby forming a sealed space between the plate-like bodies and the gasket.

[0046] Examples of molds for continuous casting include those in which a sealed space is formed by the opposing surfaces of a pair of endless belts traveling in the same direction at the same speed, and gaskets traveling at the same speed as the endless belts on both sides of the endless belts. The spacing of the voids in the mold is adjusted as needed to obtain a resin plate of the desired thickness, but it is generally between 1 and 30 mm.

[0047] <Effects and Effects> The monomer composition of the present invention contains an α-olefin, and the methacrylic resin obtained by radical polymerization of a monomer mixture containing the monomer composition of the present invention ensures excellent heat resistance, good weather resistance, and suppressed yellowing. Although the reason why the monomer composition of the present invention contains α-olefins, thereby ensuring excellent heat resistance, good weather resistance, and suppressed yellowing, is not entirely clear, it is presumed to be as follows.

[0048] Polymers containing units based on methyl methacrylate (methacrylic resins) undergo cleavage of the main chain or side chains upon exposure to light or heat, generating radical species. Typically, these generated radical species cause yellowing of the methacrylic resin and a decrease in mechanical strength due to a reduction in molecular weight.

[0049] However, as mentioned above, the α-olefin in the present invention does not exhibit resonance stabilization effect and has significantly lower reactivity compared to methyl methacrylate, which is a conjugated monomer. Therefore, unless a specific polymerization catalyst such as a transition metal compound or a Group 13 compound is used and special conditions are met to exhibit catalytic effect, unreacted α-olefin (also referred to as "α-olefin monomer") remains in the resulting methacrylic resin. The α-olefin monomer remains in the methacrylic resin. And it is thought that the α-olefin monomer functions as a radical scavenger.

[0050] Specifically, a hydrogen atom bonded to a carbon atom adjacent to the double bond site of the α-olefin monomer is abstracted by the aforementioned radical species. The olefin hydrocarbon from which the hydrogen atom (hydrogen radical) has been abstracted then captures other radical species as described above. As a result, it is believed that the excellent heat resistance of the methacrylic resin is ensured, its weather resistance is superior, and yellowing is suppressed. [Examples]

[0051] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples described later. In the following explanation, "part" refers to the "mass part". In Table 1, "Amount (parts by mass)" represents the total amount of MMA and BA as 100 parts by mass, expressed in parts by mass and ppm, while "Amount (percentage by mass)" represents the total mass of the monomer composition as 100% by mass, expressed in percent by mass and ppm. "-" indicates that the compound in question is not included.

[0052] The abbreviations and names of the compounds used in the examples and comparative examples are as follows: • MMA: Methyl methacrylate (manufactured by Mitsubishi Chemical Corporation). BA: n-butyl acrylate (manufactured by Mitsubishi Chemical Corporation). • OCT:1 - Octene (manufactured by Tokyo Chemical Industry Co., Ltd.). • HEX:1 - Hexene (manufactured by Tokyo Chemical Industry Co., Ltd.). • 2E1H: 2-ethyl-1-hexene (manufactured by Tokyo Chemical Industry Co., Ltd.). HALS: 1,2,3,4-butanetetracarboxylic acid tetrakis(2,2,6,6-tetramethyl-4-piperidinyl) (product name: LA-57, manufactured by ADEKA Corporation).

[0053] [Measurement Methods and Evaluation Methods] <Method for measuring the remaining amount of α-olefin monomers in methacrylic resins> (1) Procedure for preparing samples and test solutions The obtained resin molded body was finely crushed, and 0.2 g of the crushed resin was dissolved in 10 mL of acetone for residual pesticide testing (hereinafter simply referred to as "acetone"). After the resin was dissolved, 1 mL of the internal standard solution was added using a volumetric pipette. A 0.1 vol% methyl salicylate / acetone solution was used as the internal standard solution. Three different concentrations of test solutions were prepared by diluting the target standard reagent with acetone, and a three-level calibration curve was created by gas chromatography-mass spectrometry (GC / MS) measurement described later, and the concentration of each target substance in the sample was quantified. A 0.1 vol% methyl salicylate / acetone solution was used as the internal standard solution. (GC / MS measurement conditions) Equipment: GC HP6890 / MS HP5973 (manufactured by Agilent) Ionization method: EI (Electron Ionization) method Column: DB-WAX 60m x 250μm x 0.5μm (manufactured by Agilent) Heating conditions: 70°C (5 min) → 200°C (5 min) Rate = 10°C / min Inlet temperature: 220℃ AUX temperature: 230℃ Ion source temperature: 230℃ Split ratio: 10:1 Flow rate: 2.0mL / min Average linear velocity: 37cm / sec Injection volume: 1μL Measurement mode: SIM

[0054] <Method for evaluating heat resistance> As an indicator of the heat resistance of the methacrylic resins obtained in the examples and comparative examples, the temperature of deflection under load (hereinafter referred to as "HDT") (°C) was measured for test specimens (length 127 mm × width 12.7 mm × thickness 3 mm) of the resin molded articles obtained in the examples and comparative examples, in accordance with JIS K 7191.

[0055] <Method for evaluating weather resistance> The weather resistance of the methacrylic resins obtained in the examples and comparative examples was evaluated by the following method. A UV exposure test was conducted using a metal weather accelerated weathering tester (manufactured by Daipla Wintes Co., Ltd., model: KU-R5CI-A) equipped with a metal halide lamp (manufactured by Daipla Wintes Co., Ltd., model: MW-60W) and a light cut filter (manufactured by Daipla Wintes Co., Ltd., model: KF-1). The yellowness (YI) and its change (ΔYI) from before the start of the UV exposure test to 200 hours after the start were measured according to the method described below.

[0056] Specifically, test pieces (50mm x 50mm square, 5mm thick) obtained by cutting the resin molded bodies obtained in the examples and comparative examples into squares were placed in the evaluation chamber of the metal weather accelerated weathering tester. The irradiation intensity of ultraviolet (UV) light irradiated onto the test specimen from the metal halide lamp was 80 mW / cm² at wavelengths of 330-390 nm, as measured by an ultraviolet irradiometer (Ushio Inc., model: UIT-101). 2 The values ​​were corrected accordingly. The evaluation chamber of the metal weather accelerated weathering tester was set to an environment with a temperature of 63°C and a humidity of 50 RH, and ultraviolet light (irradiation intensity 80 mW / cm²) from a metal halide lamp was used. 2 The test specimen was irradiated with ).

[0057] As an indicator of weather resistance, a spectrophotometer (manufactured by Nippon Denshoku Industries, Ltd., model name: SE-7700) was used to measure the yellowness (yellow index: YI) of the test specimens in accordance with ASTM D1925. One test specimen was measured before the start of the UV exposure test, and another test specimen was measured 200 hours after the start of the test. The change in the measured value was defined as the change in yellowness (ΔYI).

[0058] [Example 1] (1) Preparation of monomer composition A monomer composition was prepared by adding 98.0 parts by mass of MMA and 2.0 parts by mass of BA to a reactor (polymerization vessel) equipped with a condenser, thermometer, and stirrer, so that the 1-octene content was 500 ppm by mass.

[0059] (2) Production of syrup The prepared monomer composition was supplied to the reactor, stirred, and bubbled with nitrogen gas before heating was started. When the internal temperature of the reactor reached 80°C, 0.12 parts by mass of 2,2'-azobis-(2,4-dimethylvaleronitrile) was added as a radical polymerization initiator and 0.075 parts by mass of 1-dodecanethiol was added as a chain transfer agent to form a monomer mixture. The reactor was further heated until the internal temperature reached 100°C and held for 9 minutes. The reactor was then cooled to room temperature to obtain syrup. The polymer content in the syrup was 25% by mass and the unreacted monomer composition content was 75% by mass, relative to 100% of the total mass of the syrup.

[0060] (3) Casting polymerization To 100 parts by mass of the above syrup, 0.15 parts by mass of t-hexylperoxypivared 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 6.5 mm between two opposing SUS plates, where a soft resin gasket was placed at the edge of the SUS plates. The polymerizable composition was cured by heating at 80°C for 30 minutes, and then at 130°C for 30 minutes, to obtain a methacrylic resin. After the methacrylic resin and the SUS plates were cooled, the SUS plates were removed to obtain a 5 mm thick plate-shaped resin molded body. The evaluation results of the obtained resin molded body are shown in Table 1.

[0061] [Examples 2-6] Except for changing the monomer composition as shown in Table 1, methacrylic resins and resin molded articles were produced in the same manner as in Example 1. The evaluation results of the obtained resin molded articles are shown in Table 1.

[0062] [Example 7] The monomer composition was changed as shown in Table 1, and methacrylic resins and resin molded articles were produced in the same manner as in Example 1, except that 1-octene was replaced with 1-hexene. The evaluation results of the obtained resin molded articles are shown in Table 1.

[0063] [Example 8] The monomer composition was changed as shown in Table 1, and the methacrylic resin and resin molded articles were produced in the same manner as in Example 1, except that 1-octene was replaced with 2-ethyl-1-hexene. The evaluation results of the obtained resin molded articles are shown in Table 1.

[0064] [Comparative Examples 1-3] Except for the monomer composition being as shown in Table 1, methacrylic resins and resin molded articles were produced in the same manner as in Example 1. The evaluation results of the obtained resin molded articles are shown in Table 1.

[0065] [Table 1]

[0066] The resin molded articles obtained in Examples 1 to 8 maintained excellent heat resistance, good weather resistance, and suppressed yellowing. This is thought to be because the monomer composition contained methyl methacrylate and α-olefin, and the α-olefin monomer remained in the methacrylic resin.

[0067] The resin molded articles obtained in Comparative Examples 1 and 3 did not contain α-olefins in the monomer composition, and no α-olefin monomers remained in the methacrylic resin, resulting in yellowing and insufficient weather resistance.

[0068] The resin molded article obtained in Comparative Example 2 exhibited yellowing and somewhat insufficient weather resistance because the monomer composition contained a hindered amine compound instead of α-olefin.

Claims

1. A monomer composition comprising methyl methacrylate and at least one α-olefin selected from the group consisting of 2-ethyl-1-hexene, 1-octene, and 1-dodecene, wherein the content of the α-olefin is 10,000 ppm by mass or less based on the total mass of the monomer composition.

2. The monomer composition according to claim 1, comprising the α-olefin in an amount of 0.1 ppm by mass or more based on the total mass of the monomer composition.

3. The content of at least one compound selected from the group consisting of transition metal compounds and Group 13 element compounds is 0 ppm by mass or more and 7×10 ppm by mass or more based on the total mass of the α-olefin. ４ The monomer composition according to claim 1 or 2, which has a mass ppm or less.

4. A methacrylic resin obtained by polymerizing a monomer mixture containing the monomer composition according to any one of claims 1 to 3.

5. A methacrylic resin, The methacrylic resin contains at least one α-olefin monomer selected from the group consisting of 2-ethyl-1-hexene, 1-octene, and 1-dodecene, The methacrylic resin has an α-olefin monomer content of 1,300 ppm by mass or less based on the total mass of the methacrylic resin.

6. The methacrylic resin described in claim 5, wherein the content of the α-olefin monomer is 0.1 mass ppm or more relative to the total mass of the methacrylic resin.

7. A resin molded body obtained by molding the methacrylic resin according to any one of claims 4 to 6.

8. A method for producing a methacrylic resin by radical polymerization of a monomer mixture containing a monomer composition. So, The monomer composition comprises methyl methacrylate and at least one α-olefin selected from the group consisting of 2-ethyl-1-hexene, 1-octene, and 1-dodecene; The content of the α-olefin in the monomer composition is 10,000 ppm by mass or less based on the total mass of the monomer composition.

9. A method for producing a methacrylic resin, comprising radically polymerizing a monomer mixture containing a monomer composition, the method comprising the steps of: The monomer composition comprises methyl methacrylate and at least one α-olefin selected from the group consisting of 2-ethyl-1-hexene, 1-octene, and 1-dodecene; The content of at least one compound selected from the group consisting of transition metal compounds and Group 13 element compounds in the monomer composition is 7×10 based on the total mass of the α-olefin. ４ and the content of the α-olefin is 10,000 ppm by mass or less relative to the total mass of the monomer composition.