JPWO2019004083A1 - Methacrylic copolymers and molded products - Google Patents

Abstract

The present invention provides a methacrylic copolymer containing 5 to 50 mass% of structural units derived from a monomer represented by the following formula (1) and 50 to 95 mass% of structural units derived from methyl methacrylate. [Chemical Formula 1] (In the formula (1), R1 represents a hydrogen atom or a methyl group. R2 and R3 each independently represent a linear, branched or cyclic monovalent hydrocarbon group having 1 to 15 carbon atoms, or , R2 and R3 may be bonded to each other to form an aliphatic hydrocarbon ring together with the carbon atom to which they are bonded.

Description

  The present invention relates to methacrylic copolymers and moldings containing such copolymers.

  In general, methacrylic resin is excellent in optical properties such as transparency and weather resistance, and thus has been conventionally used in various applications such as display members used for lighting equipment, signboards, electronic / electrical members, medical members, and the like. ing. In these applications, thermal decomposition resistance and the like may be required in addition to optical properties and weather resistance.

  As a method for improving the physical properties of the methacrylic resin, there is a method of copolymerizing a monomer having a specific structure. For example, in Patent Document 1, there is little coloring, high transparency, low haze, high impact strength, low saturated water absorption, and size by copolymerizing with a monomer derived from methacrylic acid cycloalkyl ester. It is disclosed that a molded product having a small change and a good appearance can be obtained.

  On the other hand, copolymerization of a monomer having a functional group such as a hydroxyl group is expected to improve the physical properties of the resin. However, Patent Document 2 discloses that gelation occurs during the reaction when methyl methacrylate and a monomer having a hydroxyl group are copolymerized, and in order to obtain a copolymer for a molding material, There were challenges.

WO2013-161267 Japanese Patent No. 3550152

  Therefore, an object of the present invention is to provide a copolymer in which a proper amount of a polymerizable monomer having a hydroxyl group is used, which is difficult to thermally decompose, has excellent chemical resistance, and suppresses gel-butting during melt molding. is there.

According to the present invention, the above object is achieved by the following aspects.
[1]
A methacrylic copolymer containing 5 to 50 mass% of structural units derived from the monomer represented by the following formula (1) and 50 to 95 mass% of structural units derived from methyl methacrylate.

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ are each independently a linear, branched or cyclic monovalent hydrocarbon group having 1 to 15 carbon atoms, or R ² and R ³ may combine with each other to form an aliphatic hydrocarbon ring together with the carbon atom to which they are bonded.)
[2]
The methacrylic copolymer according to [1], wherein the monomer represented by the formula (1) has a sum of carbon numbers of R ² and R ³ of 2 to 9.
[3]
The methacrylic copolymer according to [1] or [2], which has a weight average molecular weight of 40,000 to 300,000.
[4]
The methacrylic copolymer according to any one of [1] to [3], wherein the weight average molecular weight / number average molecular weight ratio is 1.01 to 3.0.
[5]
Regarding the ratio Mw / Mn of the weight-average molecular weight Mw to the number-average molecular weight Mn calculated on the basis of the chromatogram obtained by gel permeation chromatography, the value after the heat treatment at 260 ° C. for 1 hour is The methacrylic copolymer according to any one of [1] to [4], which is 1.4 times or less the value before treatment.
[6]
The copolymer according to any one of [1] to [5], wherein Mw / Mn after the heat treatment at 260 ° C. for 1 hour is 1.2 times or less the value before the treatment.
[7]
A molded body containing 80% by mass or more of the copolymer according to any one of [1] to [6].
[8]
The molded product according to [7], which is a melt-molded product.
[9]
The molded product according to [7] or [8], which is a sheet having a thickness of 0.5 mm or more.
[10]
The molded product according to [7] or [8], which is a film having a thickness of 1 μm to 500 μm.

  The methacrylic copolymer of the present invention has excellent chemical resistance and suppresses the generation of gel spots during melt molding.

  The methacrylic copolymer of the present invention (hereinafter sometimes simply referred to as “copolymer”) contains a structural unit derived from the monomer represented by the formula (1).

The monomer represented by the formula (1) has a hydroxyl group and can give chemical resistance when it is copolymerized. Further, improvement of mechanical strength and improvement of adhesion to different materials such as metal can be expected. By having the substituents R ² and R ³ , high heat resistance can be imparted to the resulting copolymer. In addition, the carbon atom at the site where the (meth) acryloyloxymethyl group and the hydroxymethyl group are bonded is a quaternary carbon atom due to the substituents R ² and R ³ , and the (meth) acryloyloxy group and the hydroxyl group are bonded via a methylene group. By being bonded together, desorption due to heating does not occur easily, and it has excellent thermal decomposition resistance. When the carbon atom is a secondary or tertiary carbon atom, the thermal decomposition resistance of the obtained copolymer is lowered and the molding temperature is limited.

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ are each independently a linear, branched or cyclic monovalent hydrocarbon group having 1 to 15 carbon atoms, or R ² and R ³ may combine with each other to form an aliphatic hydrocarbon ring together with the carbon atom to which they are bonded.)

The copolymer of the present invention contains the structural unit derived from the monomer represented by the formula (1) in an amount of 5 to 50% by mass, preferably 8 to 40% by mass based on the mass of the copolymer. , And more preferably 10 to 20% by mass. When the content of the structural unit derived from the monomer represented by the formula (1) is within this range, the copolymer of the present invention is excellent in thermal decomposition resistance. In a preferred embodiment of the present invention, the monomer represented by the formula (1) preferably has a sum of carbon numbers of R ² and R ³ of 2 to 9.

The monovalent hydrocarbon group represented by R ² and R ³ has 1 to 15, preferably 1 to 12, more preferably 1 to 8, still more preferably 1 to 6, and particularly preferably 1 to 4 carbon atoms. is there. As the monovalent hydrocarbon group having 1 to 15 carbon atoms represented by R ² and R ³ , specifically, each independently a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, and a sec-butyl group. Group, tert-butyl group, amyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, Cyclopentylmethyl group, cyclopentylethyl group, cyclopentylbutyl group, cyclohexyl group, cyclohexylmethyl group, cyclohexylethyl group, cyclohexylbutyl group, methylcyclohexylmethyl group, ethylcyclohexylmethyl group, ethylcyclohexylethyl group, bicyclo [2.2.1] Heptyl group, bicyclo [2.2.1] heptylmethyl group, Bicyclo [2.2.1] heptylethyl group, bicyclo [2.2.1] heptylbutyl group, methylbicyclo [2.2.1] heptylmethyl group, ethylbicyclo [2.2.1] heptylmethyl group, Ethylbicyclo [2.2.1] heptylethyl group, bicyclo [2.2.2] octyl group, bicyclo [2.2.2] octylmethyl group, bicyclo [2.2.2] octylethyl group, bicyclo [ 2.2.2] Octylbutyl group, methylbicyclo [2.2.2] octylmethyl group, ethylbicyclo [2.2.2] octylmethyl group, ethylbicyclo [2.2.2] octylethyl group, tricyclo [5.2.1.0 ^2,6 ] decyl group, tricyclo [5.2.1.0 ^2,6 ] decylmethyl group, tricyclo [5.2.1.0 ^2,6 ] decylethyl group, tricycle B [5.2.1.0 ^{2, 6]} Deshirubuchiru group, methyltricyclo [5.2.1.0 ^{2, 6]} Deshirumechiru group, ethyl tricyclo [5.2.1.0 ^{2, 6]} Deshirumechiru Group, ethyltricyclo [5.2.1.0 ^2,6 ] decylethyl group, adamantyl group, adamantylmethyl group, adamantylethyl group, adamantylbutyl group, methyladamantylmethyl group, ethyladamantylmethyl group, ethyladamantylethyl group, Tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecyl group, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecylmethyl group, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecylethyl group, tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecylbutyl group, ethyltetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecylmethyl group, ethyltetracyclo [4.4.0.1 ^2,5 . Examples include linear, branched or cyclic monovalent hydrocarbon groups such as [ ^17,10 ] dodecylethyl group, phenyl group, tolyl group and naphthyl group. Of these monovalent hydrocarbon groups, methyl group, ethyl group, n-propyl group, isopropyl group and n-butyl group are preferred. When R ² and R ³ are different, the carbon atom to which R ² and R ³ are bonded becomes an asymmetric carbon, and R ² and R ³ may have an asymmetric carbon. When the monomer represented by the formula (1) of the present invention is an optically active compound having one or more asymmetric carbons, R or S is a pure enantiomer or an R-isomer for each asymmetric carbon. It includes all monomers (including a racemic mixture) in which S-isomers are mixed in an arbitrary ratio.

R ² and R ³ may be bonded to each other to form an aliphatic hydrocarbon ring together with the carbon atom to which they are bonded, and in this case, the aliphatic hydrocarbon ring may be cyclopropane, cyclobutane, cyclopentane, cyclohexane, bicyclo. [2.2.1] heptane, bicyclo [2.2.2] octane, tricyclo [5.2.1.0 ^2,6 ] decane, adamantane, tetracyclo [4.4.0.1 ^2,5 . Examples of the alicyclic hydrocarbon having 3 to 12 carbon atoms, such as [ ^17,10 ] dodecane, may be a condensed ring containing these, and some of the hydrogen atoms of these alicyclic hydrocarbons are linear or branched. It may be substituted with a cyclic or cyclic monovalent hydrocarbon group having 1 to 15 carbon atoms. Of these aliphatic hydrocarbon rings, cyclopentane, cyclohexane, bicyclo [2.2.1] heptane, bicyclo [2.2.2] octane, tricyclo [5.2.1.0 ^2,6 ] decane, Adamantane and the like are preferable, and among these, cyclopentane and cyclohexane are particularly preferable.

  More specific examples of the monomer represented by the formula (1) of the present invention include the following, but the present invention is not limited to these.

（式中、Ｒ^１は上記と同様である。）

(In the formula, R ¹ is the same as above.)

  The copolymer of the present invention contains 50% by mass to 95% by mass of a structural unit derived from methyl methacrylate in addition to the monomer represented by the above formula (1) with respect to the mass of the copolymer. The content of the structural unit derived from methyl methacrylate is more preferably 60% by mass to 92% by mass, and particularly preferably 80% by mass to 90% by mass.

The copolymer of the present invention is derived from a monomer represented by the formula (1) and a radical-polymerizable monomer other than methyl methacrylate (hereinafter sometimes referred to as a radical-polymerizable monomer (2)). It may have a structural unit that Examples of the radical polymerizable monomer (2) include
Methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, s-butyl acrylate, t-butyl acrylate, amyl acrylate, isoamyl acrylate, acrylic acid Acrylic acid alkyl esters such as n-hexyl, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate; 2-hydroxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, allyl acrylate, acrylic Acrylic acid derivatives such as benzyl acidate; vinyl aromatic hydrocarbons such as styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene; vinylcyclohexane, vinylcyclopentane, vinylcyclohexene, vinylcyclohepta Vinyl cycloaliphatic hydrocarbons such as vinylcycloheptene and vinyl norbornene; ethylenically unsaturated carboxylic acids such as maleic anhydride, maleic acid and itaconic acid; ethylene, propylene, 1-butene, isobutylene, 1-octene, etc. Olefin: Conjugated diene such as butadiene, isoprene, myrcene; acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl ketone, vinyl chloride, vinylidene chloride, vinylidene fluoride; 2-vinylfuran, 2-isopropenylfuran, 2 -Vinylbenzofuran, 2-isopropenylbenzofuran, 2-vinyldibenzofuran, 2-vinylthiophene, 2-isopropenylthiophene, 2-vinyldibenzothiophene, 2-vinylpyrrole, N-vinylindole, N -Vinylcarbazole, 2-vinyloxazole, 2-isopropenyloxazole, 2-vinylbenzoxazole, 3-vinylisoxazole, 3-isopropenylisoxazole, 2-vinylthiazole, 2-vinylimidazole, 4 (5) -vinyl Imidazole, N-vinylimidazole, N-vinylimidazoline, 2-vinylbenzimidazole, 5 (6) -vinylbenzimidazole, 5-isopropenylpyrazole, 2-isopropenyl 1,3,4-oxadiazole, vinyltetrazole, 2-vinylpyridine, 4-vinylpyridine, 2-isopropenylpyridine, 3-vinylpyridine, 3-isopropenylpyridine, 2-vinylquinoline, 2-isopropenylquinoline, 4-vinylquinoline, 4-vinylpyrimidine, , 4-Dimethyl-6-vinyl-S-triazine, 3-methylidenedihydrofuran-2 (3H) -one, 4-methyl-3-methylidenedihydrofuran-2 (3H) -one, 4-decyl-3. Ethylenically unsaturated heterocyclic compounds such as methylidene dihydrofuran-2 (3H) -one; phosphoric acid having an ethylenically unsaturated group such as dimethylmethacryloyloxymethylphosphate, 2-methacryloyloxy-1-methylethylphosphate Examples thereof include esters.

  The amount of the structural unit derived from the radically polymerizable monomer (2) contained in the copolymer of the present invention is based on the balance of heat resistance, low water absorption, melt moldability, etc., relative to the mass of the copolymer. , Preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 5% by mass or less. The amount of the structural unit derived from the radically polymerizable monomer (2) contained in the copolymer of the present invention may be 0.5% by mass or more.

  The weight average molecular weight of the copolymer of the present invention is preferably 40,000 to 300,000, more preferably 60,000 to 250,000, and particularly preferably 80,000 to 200,000. When the weight average molecular weight is within this range, the strength and moldability are excellent.

  The measurement by gel permeation chromatography can be performed as follows. Tetrahydrofuran is used as an eluent, and two columns of TSKgelSuperMultiporeHZM-M manufactured by Tosoh Corporation and SuperHZ4000 are connected in series as a column. As an analyzer, HLC-8320 (product number) manufactured by Tosoh Corporation equipped with a differential refractive index detector (RI detector) is used. A resin material to be tested, that is, 4 mg of a methacrylic copolymer is dissolved in 5 ml of tetrahydrofuran and filtered through a filter of 0.1 μm to prepare a solution to be tested. The column oven temperature is set to 40 ° C., 20 μl of the test solution is injected at an eluent flow rate of 0.35 ml / min, and the chromatogram is measured. The chromatogram is a chart in which the electric signal value (intensity Y) derived from the refractive index difference between the test solution and the reference solution is plotted against the retention time X.

  A standard polystyrene having a molecular weight of 400 to 5,000,000 was measured by gel permeation chromatography to prepare a calibration curve showing the relationship between the retention time and the molecular weight. The baseline connecting the points where the slope on the high molecular weight side of the chromatogram changes from zero to plus and the points where the slope on the low molecular weight side changes from negative to zero. If the chromatogram shows multiple peaks, connect the line connecting the point where the slope of the highest molecular weight peak changes from zero to plus and the point where the slope of the lowest molecular weight peak changes from negative to zero. Use as a baseline.

  The copolymer of the present invention preferably has a weight average molecular weight / number average molecular weight ratio (hereinafter, this ratio is referred to as “molecular weight distribution”) in a state before heat treatment at 260 ° C. for 1 hour. It is 1.01 to 3.0, more preferably 1.05 to 2.7, and further preferably 1.10 to 2.5. When the molecular weight distribution is within such a range, a copolymer having good moldability can be obtained. The weight average molecular weight and the number average molecular weight are values in terms of standard polystyrene measured by GPC (gel permeation chromatography).

  The weight average molecular weight and the molecular weight distribution can be controlled by adjusting the types and amounts of the polymerization initiator and the chain transfer agent during the polymerization reaction.

  The copolymer of the present invention preferably has a Mw / Mn value after heat treatment at 260 ° C. for 1 hour of 1.0 to 1.4 times the value before treatment, and 1.0 to 1.4 times. It is more preferably 1.2 times, further preferably 1.0 to 1.15 times, and particularly preferably 1.0 to 1.1 times. The smaller this value is, the more likely the occurrence of gel lumps during melt molding is suppressed.

  The heat treatment at 260 ° C. for 1 hour is to evaluate the gelation of the methacrylic copolymer, and by this treatment, a copolymer whose Mw / Mn value exceeds 1.4 times the value before the treatment is molded. A part of the gel may be formed inside the machine to cause gel lumps.

  The methacrylic copolymer of the present invention includes molding materials having various shapes such as powder and pellets. For example, a pellet-shaped molding material can be obtained, for example, by cooling and cutting the resin extruded in a strand form from the die plate of the methacrylic copolymer of the present invention that has been melted by an extruder. As a method of cutting the strands into pellets, methods such as underwater cutting, hot cutting, and strand cutting can be adopted.

  The methacrylic copolymer undergoes a thermal history when molded into a shape such as pellets, but the methacrylic copolymer of the present invention polymerizes a monomer containing a (meth) acrylic acid ester having a hydroxyl group and methyl methacrylate. However, it may be in the form of a powder that has been purified by reprecipitation or the like and dried and has a low heat history, or it may be molded into various shapes such as pellets and subjected to a heat history.

  The copolymer of the present invention has a glass transition temperature of preferably 100 to 350 ° C, more preferably 110 to 250 ° C. If the glass transition temperature is too low, the heat resistance of the copolymer will be insufficient and the usable applications will be limited. If the glass transition temperature is too high, the copolymer becomes brittle and easily broken. The glass transition temperature is a value measured according to JIS K7121. That is, the copolymer of the present invention is heated to 270 ° C. once, cooled to room temperature, and then heated from room temperature to 270 ° C. at a rate of 10 ° C./min by a differential scanning calorimetry DSC curve. The glass transition temperature of the present invention can be defined as the midpoint glass transition temperature obtained from the DSC curve measured during the second heating.

  The thermal decomposition temperature of the copolymer of the present invention is preferably 270 ° C or higher, more preferably 290 ° C or higher, even more preferably 295 ° C or higher, and particularly preferably 300 ° C or higher. The thermal decomposition temperature may be 320 ° C. or lower. The thermal decomposition temperature can be measured by the method described in the examples.

  There is no particular limitation on the method for producing the copolymer of the present invention. Usually, from the viewpoint of productivity, a radical polymerization method is adopted to produce a copolymer by adjusting the polymerization temperature, the polymerization time, the type and amount of the chain transfer agent, the type and amount of the polymerization initiator, and the like. The method is preferred. Further, since the monomer represented by the formula (1) is also capable of anionic polymerization, the anionic polymerization method should be adopted when a block copolymer or a copolymer having high stereoregularity is desired. Is also possible.

  The radical polymerization method for producing the copolymer of the present invention is preferably carried out without a solvent or in a solvent, and is preferably carried out without a solvent from the viewpoint of obtaining a copolymer having a low impurity concentration. From the viewpoint of suppressing the occurrence of silver or coloring in the molded body, it is preferable to carry out the polymerization reaction with a low amount of dissolved oxygen in the polymerization reaction raw material. The polymerization reaction is preferably performed in an atmosphere of an inert gas such as nitrogen gas.

  The polymerization initiator used in the radical polymerization method for producing the copolymer of the present invention is not particularly limited as long as it generates a reactive radical. For example, t-hexyl peroxyisopropyl monocarbonate, t-hexyl peroxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butylperoxypivalate. , T-hexyl peroxypivalate, t-butyl peroxy neodecanoate, t-hexyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1 , 1-bis (t-hexylperoxy) cyclohexane, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'- Azobis (2-methylbutyronitrile), dimethyl 2,2'-azobis (2-methylpro) Onato), and the like. Of these, t-hexylperoxy 2-ethylhexanoate, 1,1-bis (t-hexylperoxy) cyclohexane and dimethyl 2,2'-azobis (2-methylpropionate) are preferable.

  The 1-hour half-life temperature of such a polymerization initiator is preferably 60 to 140 ° C, more preferably 80 to 120 ° C. The polymerization initiator used for producing the copolymer has a hydrogen abstraction ability of preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. Such polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator used is preferably 0.0001 to 0.02 parts by mass, more preferably 0.001 to 0.01 parts by mass, and still more preferably 100 parts by mass of the monomer used in the polymerization reaction. Is 0.005 to 0.007 parts by mass.

  The hydrogen abstraction capacity can be known from the technical data of the polymerization initiator manufacturer (for example, technical data of NOF Corporation “hydrogen abstraction capacity and initiator efficiency of organic peroxide” (created in April 2003)). .. Further, it can be measured by a radical trapping method using α-methylstyrene dimer, that is, an α-methylstyrene dimer trapping method. The measurement is generally performed as follows. First, the polymerization initiator is cleaved in the presence of α-methylstyrene dimer as a radical trapping agent to generate radical fragments. Among the generated radical fragments, radical fragments having a low hydrogen abstraction ability are added to the double bond of α-methylstyrene dimer and captured. On the other hand, a radical fragment having a high hydrogen abstraction ability abstracts hydrogen from cyclohexane to generate a cyclohexyl radical, and the cyclohexyl radical is added to and captured by the double bond of α-methylstyrene dimer to produce a cyclohexane captured product. Therefore, the ratio (mol fraction) of radical fragments having a high hydrogen abstraction ability to the theoretical radical fragment generation amount, which is obtained by quantifying cyclohexane or a cyclohexane trapped product, is defined as the hydrogen abstraction ability.

  As the chain transfer agent used when the radical polymerization method is selected for producing the copolymer of the present invention, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1 , 6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris- ( β-thiopropionate), alkyl mercaptans such as pentaerythritol tetrakisthiopropionate, and the like. Of these, monofunctional alkyl mercaptans such as n-octyl mercaptan and n-dodecyl mercaptan are preferable. These chain transfer agents may be used alone or in combination of two or more.

  The amount of the chain transfer agent used is preferably 0.1 to 1 part by mass, more preferably 0.15 to 0.8 part by mass, and still more preferably 0, based on 100 parts by mass of the monomer used in the polymerization reaction. .2 to 0.6 parts by mass, most preferably 0.2 to 0.5 parts by mass. The amount of the chain transfer agent used is preferably 2500 to 10000 parts by mass, more preferably 3000 to 9000 parts by mass, and further preferably 3500 to 6000 parts by mass with respect to 100 parts by mass of the polymerization initiator. When the amount of the chain transfer agent used is in the above range, the molecular weight of the obtained copolymer can be controlled, so that the obtained copolymer can have good moldability and high mechanical strength.

  When a solvent is used when a radical polymerization method is selected for producing the copolymer of the present invention, it is not limited as long as it can dissolve the monomer and the copolymer, but is not limited to benzene, toluene, ethylbenzene, and other aromatic compounds. Group hydrocarbons are preferred. These solvents may be used alone or in combination of two or more. The amount of the solvent used can be appropriately set from the viewpoint of the viscosity of the reaction solution and the productivity. The amount of the solvent used is, for example, preferably 100 parts by mass or less, more preferably 90 parts by mass or less, relative to 100 parts by mass of the polymerization reaction raw material.

  When the radical polymerization method is selected for producing the copolymer of the present invention, the temperature during the polymerization reaction is preferably 100 to 200 ° C, more preferably 110 to 180 ° C. When the polymerization temperature is 100 ° C. or higher, the productivity tends to be improved due to the improvement of the polymerization rate, the decrease in viscosity of the polymerization liquid, and the like. Further, when the polymerization temperature is 200 ° C. or lower, the control of the polymerization rate is facilitated and the production of by-products is suppressed, so that the coloring of the copolymer of the present invention can be suppressed. The polymerization reaction time is preferably 0.5 to 4 hours, more preferably 1.5 to 3.5 hours, still more preferably 1.5 to 3 hours. In the case of a continuous flow reactor, the polymerization reaction time is the average residence time in the reactor. When the temperature during the polymerization reaction and the time for the polymerization reaction are within the above ranges, a copolymer having excellent transparency can be produced with high efficiency.

  The radical polymerization may be carried out using a batch reactor, but it is preferably carried out using a continuous flow reactor from the viewpoint of productivity. In the continuous flow reaction, for example, in a nitrogen atmosphere or the like, a polymerization reaction raw material (a monomer (a monomer represented by the formula (1), methyl methacrylate, a radical-polymerizable monomer (if necessary)) (Meaning 2)), a mixed solution containing a polymerization initiator, a chain transfer agent, etc.) is prepared, and it is supplied to the reactor at a constant flow rate, and the solution in the reactor is withdrawn at a flow rate corresponding to the supply rate. .. As the reactor, it is possible to use a tubular reactor that can bring the state close to a plug flow and / or a tank reactor that can bring the state close to complete mixing. Further, continuous flow polymerization may be carried out in one reactor, or continuous flow polymerization may be carried out by connecting two or more reactors.

  In the present invention, it is preferable to employ a continuous flow tank reactor for at least one reactor. The liquid amount in the tank reactor during the polymerization reaction is preferably 1/4 to 3/4, more preferably 1/3 to 2/3, with respect to the volume of the tank reactor. The reactor is usually equipped with a stirrer. Examples of the stirring device include a static stirring device and a dynamic stirring device. Examples of the dynamic stirrer include a Maxblend stirrer, a stirrer having a lattice-shaped blade rotating around a vertical rotary shaft arranged in the center, a propeller stirrer, a screw stirrer and the like. Of these, the Maxblend stirring device is preferably used from the viewpoint of uniform mixing.

  The polymerization conversion in the case of selecting the radical polymerization method for producing the copolymer of the present invention is preferably 50 to 100% by mass, more preferably 70% by mass when suspension polymerization is carried out using a batch reactor. Is about 99% by mass.

  The polymerization conversion rate when using a continuous flow tank reactor is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and further preferably 35 to 65% by mass. When the polymerization conversion rate is 20% by mass or more, it is easy to remove the remaining unreacted monomer, and the appearance of the molded article made of the copolymer tends to be good. When the polymerization conversion rate is 80% by mass or less, the viscosity of the polymerization liquid tends to be low and the productivity tends to be improved.

In the methacrylic copolymer of the present invention, the ratio (% by mass) of the structural unit derived from the monomer represented by the formula (1) and the structural unit derived from methyl methacrylate is the amount of the raw material monomer charged. Is almost equal to the ratio. The ratio of each structural unit can be determined by ¹ H-NMR.

  After completion of the polymerization, volatile components such as unreacted monomers are removed, if necessary. The removal method is not particularly limited, but heating devolatilization is preferable. Examples of the devolatilization method include an equilibrium flash method and an adiabatic flash method. The devolatilization temperature by the adiabatic flash method may be lower than the thermal decomposition temperature of the methacrylic copolymer, preferably 200 to 280 ° C, more preferably 220 to 260 ° C. The time for heating the resin by the adiabatic flash method is preferably 0.3 to 5 minutes, more preferably 0.4 to 3 minutes, and further preferably 0.5 to 2 minutes. When devolatilized in such a temperature range and heating time, it is easy to obtain a copolymer with little coloring. The removed unreacted monomer can be recovered and used again in the polymerization reaction. Since the yellow index of the recovered monomer may be high due to the heat applied during the recovery operation, the recovered monomer should be purified by an appropriate method to reduce the yellow index. Is preferred.

  In the production of the molded product of the present invention, the copolymer of the present invention may be mixed with another polymer and molded, as long as the effects of the present invention are not impaired. Examples of such other polymers include polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene ionomers; polystyrene, styrene-maleic anhydride copolymers, high-impact polystyrene. , AS resin, ABS resin, AES resin, AAS resin, ACS resin, MBS resin and other styrene resins; methyl methacrylate polymer, methyl methacrylate-styrene copolymer; polyethylene terephthalate, polybutylene terephthalate and other polyester resins; nylon 6, polyamide such as nylon 66, polyamide elastomer; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polya Tar, polyvinylidene fluoride, polyurethane, modified polyphenylene ether, polyphenylene sulfide, silicone modified resin; acrylic rubber, acrylic thermoplastic elastomer, silicone rubber; styrene thermoplastic elastomer such as SEPS, SEBS, SIS; IR, EPR, EPDM, etc. The olefin rubbers of

  The molded product of the present invention preferably contains the copolymer of the present invention in an amount of 80% by mass or more, more preferably 90% by mass or more. The method for producing the molded article of the present invention is not particularly limited. The copolymer of the present invention or a molding material containing the copolymer of the present invention is prepared, for example, by a T-die method (lamination method, co-extrusion method, etc.), inflation method (co-extrusion method, etc.), compression molding method, blow molding. Examples of the molding method include a melt molding method such as a method, a calendar molding method, a vacuum molding method, and an injection molding method (insert method, two-color method, pressing method, core back method, sandwich method, etc.), and a solution casting method. Among these, the T-die method, the inflation method or the injection molding method is preferable in terms of high productivity and cost. The molded product of the present invention is preferably a melt molded product obtained by a melt molding method.

  The copolymer of the present invention may be in the form of pellets or the like for the convenience of storage, transportation, or molding. Moreover, in obtaining the molded product of the present invention, the molding may be performed plural times. For example, the copolymer of the present invention can be molded to obtain a pellet-shaped molded body, and then the pellet-shaped molded body can be further molded into a molded body having a desired shape. The molded product of the present invention includes pellets.

  In the copolymer of the present invention, if necessary, an antioxidant, a heat deterioration inhibitor, an ultraviolet absorber, a light stabilizer, a lubricant, a release agent, a polymer processing aid, an antistatic agent, a flame retardant, a dye. Various additives such as pigments, light diffusers, organic dyes, matting agents, and phosphors may be added. The blending amount of such various additives is preferably 7% by mass or less, more preferably 5% by mass or less, and further preferably 4% by mass or less, based on the copolymer of the present invention.

  Various additives may be added to the polymerization reaction solution at the time of producing the copolymer, may be added to the copolymer produced by the polymerization reaction, or added at the time of producing the molded body Is also good.

  The antioxidant alone has an effect of preventing oxidative deterioration of the resin in the presence of oxygen. Examples thereof include phosphorus-based antioxidants, hindered phenol-based antioxidants and thioether-based antioxidants. These antioxidants may be used alone or in combination of two or more. Among them, from the viewpoint of preventing deterioration of optical properties due to coloring, phosphorus-based antioxidants and hindered phenol-based antioxidants are preferable, and combined use of phosphorus-based antioxidants and hindered phenol-based antioxidants is more preferable.

  When the phosphorus-based antioxidant and the hindered phenol-based antioxidant are used in combination, the usage amount of the phosphorus-based antioxidant: hindered phenol-based antioxidant is 1: 5 to 2: by mass ratio. 1 is preferable, and 1: 2 to 1: 1 is more preferable.

  As the phosphorus-based antioxidant, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite (manufactured by ADEKA; trade name: ADEKA STAB HP-10), tris (2,4-dit). -Butylphenyl) phosphite (manufactured by BASF; trade name: IRGAFOS168), 3,9-bis (2,6-di-t-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3. 9-diphosphaspiro [5.5] undecane (manufactured by ADEKA; trade name: ADEKA STAB PEP-36) and the like are preferable.

  As hindered phenolic antioxidants, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by BASF; trade name IRGANOX1010), octadecyl-3-. (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by BASF; trade name IRGANOX1076) and the like are preferable.

  The heat deterioration inhibitor is capable of preventing heat deterioration of the resin by trapping polymer radicals generated when exposed to high heat under a substantially oxygen-free condition.

  As the thermal deterioration inhibitor, 2-t-butyl-6- (3'-t-butyl-5'-methyl-hydroxybenzyl) -4-methylphenyl acrylate (Sumitomo Chemical Co .; trade name Sumilizer GM), 2,4-di-t-amyl-6- (3 ′, 5′-di-t-amyl-2′-hydroxy-α-methylbenzyl) phenyl acrylate (Sumitomo Chemical Co., Ltd .; trade name Sumilizer GS) and the like are available. preferable.

  The ultraviolet absorber is a compound having the ability to absorb ultraviolet rays, and is said to have a function of mainly converting light energy into heat energy.

  Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, oxalic acid anilides, malonic acid esters and formamidines. These may be used alone or in combination of two or more.

  Benzotriazoles have a high effect of suppressing deterioration of optical properties such as coloring due to exposure to ultraviolet rays, and therefore are preferable as ultraviolet absorbers used when the film of the present invention is applied to optical applications. As benzotriazoles, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (manufactured by BASF; trade name TINUVIN329), 2- (2H- Benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (manufactured by BASF; trade name TINUVIN234), 2,2′-methylenebis [6- (2H-benzotriazole-2 -Yl) -4-t-octylphenol] (made by ADEKA; LA-31), 2- (5-octylthio-2H-benzotriazol-2-yl) -6-tert-butyl-4-methylphenol and the like are preferable. ..

  Further, as an ultraviolet absorber for triazines, 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine (ADEKA Co .; LA-F70) is used. And its analogues, hydroxyphenyltriazine-based UV absorbers (manufactured by BASF; TINUVIN477 and TINUVIN460), 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5- Examples thereof include triazine.

  Furthermore, when it is desired to absorb light having a wavelength of 380 to 400 nm particularly effectively, International Publication No. 2011/089794, International Publication No. 2012/124395, JP 2012-012476 A, JP 2013-023461 A, Arrangement of a heterocyclic structure disclosed in JP 2013-112790 A, JP 2013-194037 A, JP 2014-62228 A, JP 2014-88542 A, JP 2014-88543 A, or the like. It is preferable to use a metal complex having a ligand as an ultraviolet absorber.

  The light stabilizer is a compound which is said to have a function of trapping radicals mainly generated by oxidation by light. Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

  Examples of the lubricant include stearic acid, behenic acid, stearamic acid, methylenebisstearamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, hardened oil and the like.

  Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride. In the present invention, it is preferable to use higher alcohols and glycerin fatty acid monoester together as a release agent. When higher alcohols and glycerin fatty acid monoesters are used in combination, the ratio is not particularly limited, but the amount of higher alcohols used: the amount of glycerin fatty acid monoesters used is 2.5: 1 to 3. 5: 1 is preferable, and 2.8: 1 to 3.2: 1 is more preferable.

  As the polymer processing aid, polymer particles having a particle diameter of 0.05 to 0.5 μm, which can be produced by an emulsion polymerization method, are usually used. The polymer particles may be single-layer particles composed of a polymer having a single composition ratio and a single intrinsic viscosity, or may be multi-layer particles composed of two or more polymers having a different composition ratio or an intrinsic viscosity. May be. Among these, particles having a two-layer structure having a polymer layer having a low intrinsic viscosity as an inner layer and a polymer layer having a high intrinsic viscosity of 5 dl / g or more as an outer layer are preferable. The polymer processing aid preferably has an intrinsic viscosity of 3 to 6 dl / g. If the intrinsic viscosity is too small, the effect of improving moldability tends to be low. If the intrinsic viscosity is too high, the molding processability of the copolymer tends to decrease.

  As the antistatic agent, sodium heptyl sulfonate, sodium octyl sulfonate, sodium nonyl sulfonate, sodium decyl sulfonate, sodium dodecyl sulfonate, sodium cetyl sulfonate, sodium octadecyl sulfonate, sodium diheptyl sulfonate, heptyl sulfonate Potassium, potassium octyl sulfonate, potassium nonyl sulfonate, potassium decyl sulfonate, potassium dodecyl sulfonate, potassium cetyl sulfonate, potassium octadecyl sulfonate, potassium diheptyl sulfonate, lithium heptyl sulfonate, lithium octyl sulfonate, nonyl sulfonate Lithium acid, lithium decyl sulfonate, lithium dodecyl sulfonate, lithium cetyl sulfonate, octadecyl sulfonate Lithium, alkyl sulfonates lithium diheptyl acid and the like, and the like.

  As a flame retardant, Magnesium hydroxide, Aluminum hydroxide, Hydrated aluminum silicate, Hydrated magnesium silicate, A metal hydrate having a hydroxyl group such as hydrotalcite or water of crystallization, Amine polyphosphate, Phosphoric acid compounds such as phosphate ester, Silicone compounds and the like, Trimethyl phosphate, Triethyl phosphate, Tripropyl phosphate, Tributyl phosphate, Tripentyl phosphate, Trihexyl phosphate, Tricyclohexyl phosphate, Triphenyl phosphate, Tricresyl phosphate, Trixylenyl phosphate, Dimethyl ethyl phosphate, Methyl dibutyl phosphate, Ethyldipropyl phosphate, Phosphate ester flame retardants such as hydroxyphenyl diphenyl phosphate are preferred.

  As dyes and pigments, red organic pigments such as Para Red, Fire Red, Pyrazolone Red, Thioindico Red, and Perylene Red, blue organic pigments such as Cyanine Blue and Indanthrene Blue, cyanine Green, green organics such as Naphthol Green. Pigments may be used, and one or more of these may be used.

  As the organic dye, a compound having a function of converting ultraviolet rays into visible rays is preferably used.

  Examples of the fluorescent substance include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent whitening agents and fluorescent bleaching agents.

  Examples of the light diffusing agent and matting agent include glass fine particles, polysiloxane-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, barium sulfate and the like. The copolymer of the present invention preferably contains no acid generator.

  The molded product of the present invention contains the copolymer of the present invention. The molding of the present invention is not particularly limited in its manufacturing method. The molded product of the present invention is, for example, a T-die method (laminating method, coextrusion method, etc.), inflation method (coextrusion method, etc.), compression molding method, blow molding method, calender molding method, vacuum molding method, injection molding method. Obtained by molding the copolymer of the present invention by a melt molding method such as an insert method, a dichroic method, a pressing method, a core back method, a sandwich method, etc. and a reaction molding method such as a cell cast polymerization method. be able to. Among these molding methods, the T-die method, the inflation method, the injection molding method, and the cell cast polymerization method are preferable from the viewpoints of high productivity and cost.

  Moreover, in obtaining the molded product of the present invention, the molding may be performed plural times. For example, after the methacrylic resin composition of the present invention is molded to obtain a pellet-shaped molded body, the pellet-shaped molded body can be further molded into a molded body having a desired shape.

  The sheet or film which is one form of the molded article of the present invention is preferably subjected to an extrusion molding method or a cell cast polymerization method. The thickness of the obtained sheet is preferably 0.5 mm or more, for example, 0.5 to 20 mm. The thickness of the obtained film is preferably 1 μm to 500 μm, more preferably 10 μm to 300 μm, and further preferably 15 to 50 μm.

  Applications of the molded product of the present invention include, for example, billboard members such as advertising towers, stand billboards, sleeve billboards, railroad billboards, and rooftop billboards; display parts such as showcases, partition boards, store displays; fluorescent light covers, mood lighting covers. Lighting components such as lamp shades, light ceilings, light walls, chandeliers; interior parts such as pendants and mirrors, doors, domes, safety window glass, partitions, stair wainscots, balcony wainscots, roofs of leisure buildings, etc. Parts: Aircraft windshields, visors for pilots, motorcycles, windshields for motorboats, light shields for buses, side visors for cars, rear visors, head wings, headlight covers, and other transportation means parts; audiovisual nameplates, stereo covers, protective masks for TVs. Electronic parts such as vending machine display covers Medical equipment parts such as incubators and X-ray parts; equipment-related parts such as machine covers, instrument covers, laboratory equipment, rulers, dials, observation windows; LCD protective plates, light guide plates, light guide films, Fresnel lenses, lenticular lenses, Optical parts such as front plates and diffusers of various displays; traffic related parts such as road signs, guide plates, curve mirrors, sound barriers; surface materials for automobile interiors, surface materials for mobile phones, film materials such as marking films; Parts for home appliances such as canopy materials and control panels for washing machines and roof panels for rice cookers; Others such as greenhouses, large water tanks, box water tanks, clock panels, bathtubs, sanitaries, desk mats, game parts, toys and welding Examples include face protection masks.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In addition, the measurement of physical properties and the like were performed by the following methods.

(Chromatogram measurement by GPC and determination of molecular weight distribution based on the chromatogram)
4 mg of the resin material to be tested was dissolved in 5 ml of tetrahydrofuran and filtered with a 0.1 μm filter to prepare a solution to be tested. A test target solution is attached to a GPC device (HLC-8320, manufactured by Tosoh Corp.) having a column in which two TSKgel SuperMultipore HZM-M manufactured by Tosoh Corp. and SuperHZ4000 are connected in series, and a detection unit is a differential refractive index detector. 20 μl was injected and the chromatogram was measured. Tetrahydrofuran was used as an eluent at a flow rate of 0.35 ml / min, and the column temperature was set to 40 ° C.

  The calibration curve was created using the data of 10 points of standard polystyrene. A standard polystyrene having a molecular weight of 400 to 5,000,000 was measured by gel permeation chromatography to prepare a calibration curve showing the relationship between the retention time and the molecular weight. The line connecting the point where the slope on the high molecular weight side of the chromatogram changes from zero to plus and the point where the slope on the low molecular weight side changes from negative to zero was used as the baseline. If the chromatogram shows multiple peaks, connect the line connecting the point where the slope of the highest molecular weight peak changes from zero to plus and the point where the slope of the lowest molecular weight peak changes from negative to zero. The baseline was used.

  Further, the weight average molecular weight Mw and the number average molecular weight Mn in terms of polystyrene and the molecular weight distribution (Mw / Mn) were calculated from the chromatogram by a known calculation method.

( ¹ H-NMR measurement)
The structure of the compound synthesized in Production Example and the copolymerization composition in the copolymers of Examples and Comparative Examples were confirmed by ¹ H-NMR. ^{The 1} H-NMR spectrum was measured using a nuclear magnetic resonance apparatus (ULTRA SHIELD 400 PLUS manufactured by Bruker) using 1 mL of deuterated chloroform as a solvent for 10 mg of a sample at room temperature under the condition of 64 times of integration, It was measured.

(Pyrolysis temperature)
The thermal mass spectrometry (TG) of the copolymer was performed at a temperature rising rate of 10 ° C./min in accordance with JIS K7120 under a nitrogen atmosphere. The weight at 250 ° C. was set as the origin, and the temperature at which the weight was reduced by 2.5% was set as the thermal decomposition temperature. Shimadzu TGA-50 (product number) was used as a measuring device.

(Heating retention test)
The copolymer was heated at 260 ° C. for 1 hour using a melt indexer (L-220 manufactured by Tateyama Kagaku Kogyo). GPC measurement was performed on the samples before and after heating, Mw / Mn was determined, and the change rate (change rate of Mw / Mn in the heating test) was calculated.

(Chemical resistance test (methanol resistance))
The copolymer was hot press molded to obtain a test piece of 80 mm × 10 mm × thickness of 1.0 mm. The test piece was allowed to stand for 16 hours or more under the condition of 23 ° C. and 50% RH to control the humidity. Using a microsyringe, 10 mL of a solvent (methanol) was dropped on the test piece, and the appearance was visually observed.
A: No change B: Thin traces of droplets C: White turbidity D: Swelling / dissolution

  The following monomers were prepared as the monomers used in Examples and Comparative Examples.

-Methyl methacrylate (hereinafter referred to as "MMA")
-Methyl acrylate (hereinafter referred to as "MA")
-(3-Hydroxy-2,2-dimethyl) propyl methacrylate (see Formula (2), hereinafter referred to as "NPGMA".)
-(3-Hydroxy-2-cyclohexyl) propyl methacrylate (see Formula (3), hereinafter referred to as "CHDMA".)
-(3-Hydroxy-2,2-diethyl) propyl methacrylate (see Formula (4), hereinafter referred to as "PRDMA".)
-(3-Hydroxy-2-butyl-2-ethyl) propyl methacrylate (see Formula (5), hereinafter referred to as "BEPMA".)
-Methacrylic acid (2-hydroxyethyl) (hereinafter referred to as "HEMA")
The NPGMA obtained in Production Example 1 described below, the PRDMA obtained in Production Example 2 described below, the BEPMA used in Production Example 3 described below, and the CHDMA obtained in Production Example 4 described below were used.

<Production Example 1>
Synthesis of (3-hydroxy-2,2-dimethyl) propyl methacrylate (NPGMA) In a four-necked flask equipped with a thermometer, a stirrer and a dropping funnel, 644 parts by mass of toluene, 313 parts by mass of 2,2-dimethyl-. 1,3-Propanediol, 12 parts by mass of sodium methoxide (28% methanol solution), and 0.75 parts by mass of hydroquinone were charged and stirred. The temperature was raised to 60 ° C., and 180 parts by mass of methyl methacrylate was added dropwise from the dropping funnel over 1 hour. Thereafter, the pressure was reduced to 600 Torr, and the reaction was carried out for 4 hours while distilling off the by-product methanol. After completion of the reaction, it was washed twice with 750 parts by mass of ion-exchanged water. After concentrated by vacuum distillation, the residue was purified by column chromatography to obtain 113 parts by mass of (3-hydroxy-2,2-dimethyl) propyl methacrylate (NPGMA, see formula (2)).

<Production Example 2>
Synthesis of (3-hydroxy-2-cyclohexyl) propyl methacrylate (CHDMA) Using 2-cyclohexyl-1,3-propanediol instead of 2,2-dimethyl-1,3-propanediol and reacting at 70 ° C. Otherwise in the same manner as in Production Example 1, 98 parts by mass of (3-hydroxy-2-cyclohexyl) propyl methacrylate (CHDMA, see formula (3)) was obtained.

<Production Example 3>
Synthesis of (3-hydroxy-2,2-diethyl) propyl methacrylate (PRDMA) Other than using 2,2-diethyl-1,3-propanediol instead of 2,2-dimethyl-1,3-propanediol In the same manner as in Production Example 1, 105 parts by mass of (3-hydroxy-2,2-diethyl) propyl methacrylate (PRDMA, see formula (4)) was obtained.

<Production Example 4>
Synthesis of (3-hydroxy-2-butyl-2-ethyl) propyl methacrylate (BEPMA) 2-butyl-2-ethyl-1,3-propanediol instead of 2,2-dimethyl-1,3-propanediol In the same manner as in Production Example 1 except that was used, 110 parts by mass of (3-hydroxy-2-butyl-2-ethyl) propyl methacrylate (BEPMA, see formula (5)) was obtained. It was confirmed by ¹ H-NMR that the methacrylic acid esters of the formulas (2) to (5) were obtained.

<Example 1>
The inside of the pressure-resistant container with a stirrer that had been sufficiently dried was replaced with nitrogen. The pressure vessel was charged with 7.9 parts by mass of MMA, 2.0 parts by mass of NPGMA, 0.1 parts by mass of MA and 0.012 parts by mass of n-octyl mercaptan.

After sufficiently replacing the pressure vessel with nitrogen gas, the temperature was raised to 140 ° C. with stirring. 0.00015 parts by mass of di-t-butyl peroxide (Perbutyl D, manufactured by NOF CORPORATION) was added to the pressure resistant vessel to initiate polymerization. After 4 hours from the start of polymerization, the polymerization was stopped by cooling to room temperature. After 50 parts by mass of toluene was added to the obtained solution to dilute it, the solution was poured into 4000 parts by mass of methanol to precipitate a solid. The precipitated solid was filtered off and dried sufficiently to obtain 7.4 parts by mass of copolymer (A1). When the ¹ H-NMR of the copolymer (A1) was measured, the content of structural units derived from MMA was 81.6% by mass, the content of structural units derived from NPGMA was 17.7% by mass, and derived from MA. The content of structural units was 0.8% by mass. The weight average molecular weight (Mw) of the copolymer (A1) was 209,000, and the molecular weight distribution (Mw / Mn) was 2.09. Other evaluation results are shown in Table 1.

<Example 2>
In the same manner as in Example 1 except that the pressure vessel was charged with 7.9 parts by mass of MMA, 2.0 parts by mass of CHDMA, 0.1 parts by mass of MA and 0.012 parts by mass of n-octyl mercaptan. Thus, 7.2 parts by mass of copolymer (A2) was obtained. When ¹ H-NMR of the copolymer (A2) was measured, the content of structural units derived from MMA was 83.3% by mass, the content of structural units derived from CHDMA was 16.1% by mass, and derived from MA. The content of structural units was 0.7% by mass. The copolymer (A2) had a weight average molecular weight (Mw) of 165,000 and a molecular weight distribution (Mw / Mn) of 1.99. Other evaluation results are shown in Table 1.

<Example 3>
In the same manner as in Example 1 except that the pressure vessel was charged with 5.9 parts by mass of MMA, 4.1 parts by mass of CHDMA, 0.1 parts by mass of MA, and 0.012 parts by mass of n-octyl mercaptan. Thus, 7.4 parts by mass of copolymer (A3) was obtained. When ¹ H-NMR of the copolymer (A3) was measured, the content of structural units derived from MMA was 65.3% by mass, the content of structural units derived from CHDMA was 35.5% by mass, and it was derived from MA. The content of structural units was 0.8% by mass. The copolymer (A3) had a weight average molecular weight (Mw) of 158,000 and a molecular weight distribution (Mw / Mn) of 2.08. Other evaluation results are shown in Table 1.

<Example 4>
7.9 parts by mass of MMA, 2.0 parts by mass of PRDMA, 0.1 parts by mass of MA and 0.012 parts by mass of n-octyl mercaptan were charged into the pressure vessel, and cooled 2 hours after the initiation of polymerization. Except for this, the same procedure as in Example 1 was carried out to obtain 7.4 parts by mass of the copolymer (A4). When ¹ H-NMR of the copolymer (A4) was measured, the content of structural units derived from MMA was 83.3% by mass, the content of structural units derived from PRDMA was 16.0% by mass, and derived from MA. The content of structural units was 0.7% by mass. The copolymer (A4) had a weight average molecular weight (Mw) of 186,000 and a molecular weight distribution (Mw / Mn) of 1.68. Other evaluation results are shown in Table 1.

<Example 5>
The pressure vessel was charged with 7.9 parts by mass of MMA, 2.0 parts by mass of BEPMA, 0.1 parts by mass of MA and 0.012 parts by mass of n-octyl mercaptan and cooled 2 hours after the initiation of polymerization. 7.2 parts by mass of copolymer (A5) were obtained in the same manner as in Example 1 except for the above. When ¹ H-NMR of the copolymer (A5) was measured, the content of the structural unit derived from MMA was 83.7% by mass, the content of the structural unit derived from BEPMA was 15.5% by mass, and the content was derived from MA. The content of structural units was 0.8% by mass. The copolymer (A5) had a weight average molecular weight (Mw) of 187,000 and a molecular weight distribution (Mw / Mn) of 1.73. Other evaluation results are shown in Table 1.

<Comparative Example 1>
In the same manner as in Example 1 except that the pressure vessel was charged with 7.9 parts by mass of MMA, 2.0 parts by mass of HEMA, 0.1 parts by mass of MA, and 0.012 parts by mass of n-octyl mercaptan. To obtain a copolymer (B1). Most of them were insolubilized (gelled) at the bottom of the container, so only the soluble components were collected and the physical properties were evaluated. The evaluation results are shown in Table 1.

<Comparative example 2>
In the same manner as in Example 1 except that the pressure vessel was charged with 5.9 parts by mass of MMA, 4.1 parts by mass of HEMA, 0.1 parts by mass of MA and 0.012 parts by mass of n-octyl mercaptan. To obtain a copolymer (B2). Most of them were insolubilized (gelled) at the bottom of the container, so only the soluble components were collected and the physical properties were evaluated. The evaluation results are shown in Table 1.

  As can be seen from Table 1, the copolymers (A1) to (A5) containing the structural unit derived from the monomer represented by the formula (1) do not cause gelation during polymerization. Further, it can be seen that the thermal decomposition temperature is high and therefore the thermal decomposition resistance is excellent. Furthermore, since the rate of change in Mw / Mn before and after the heating test is small, it can be seen that the generation of gel spots during melt molding is suppressed. It is also found that the chemical resistance is excellent.

Claims (10)

A methacrylic copolymer containing 5 to 50 mass% of structural units derived from the monomer represented by the following formula (1) and 50 to 95 mass% of structural units derived from methyl methacrylate.

(In the formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² and R ³ are each independently a linear, branched or cyclic monovalent hydrocarbon group having 1 to 15 carbon atoms, or R ² and R ³ may combine with each other to form an aliphatic hydrocarbon ring together with the carbon atom to which they are bonded.) The methacrylic copolymer according to claim 1, wherein the monomer represented by the formula (1) has a sum of carbon numbers of R ² and R ³ of 2 to 9.   The methacrylic copolymer according to claim 1 or 2, having a weight average molecular weight of 40,000 to 300,000.   The methacrylic copolymer according to any one of claims 1 to 3, wherein the weight average molecular weight / number average molecular weight ratio is 1.01 to 3.0.   Regarding the ratio Mw / Mn of the weight-average molecular weight Mw to the number-average molecular weight Mn calculated on the basis of the chromatogram obtained by gel permeation chromatography, the value after the heat treatment at 260 ° C. for 1 hour is The methacrylic copolymer according to any one of claims 1 to 4, which is 1.4 times or less the value before treatment.   The copolymer according to any one of claims 1 to 5, wherein Mw / Mn after heat treatment at 260 ° C for 1 hour is 1.2 times or less of a value before treatment.   A molded product containing 80% by mass or more of the copolymer according to any one of claims 1 to 6.   The molded product according to claim 7, which is a melt-molded product.   The molded product according to claim 7 or 8, which is a sheet having a thickness of 0.5 mm or more.   The molded product according to claim 7 or 8, which is a film having a thickness of 1 μm to 500 μm.