JP6114459B1 - Methacrylic resin - Google Patents

Abstract

An object of the present invention is to provide a methacrylic resin having high heat resistance, highly controlled birefringence, excellent color tone and transparency, and excellent moldability. The main unit includes a structural unit (B) having a ring structure in the main chain, and the (B) structural unit is an N-substituted maleimide structural unit (B-1) and a lactone ring structural unit (B-2). A methacrylic resin containing at least one structural unit selected from the group consisting of: a glass transition temperature of more than 120 ° C. and 160 ° C. or less; The yellowness index (YI) measured using a 10 cm optical path length cell for a 20 w / v% chloroform solution of methanol insolubles is 5% by mass or less with respect to 100% by mass of the total amount of methanol insolubles. A methacrylic resin characterized in that it is 7. [Selection figure] None

Description

The present invention has high heat resistance, highly birefringent is controlled, is excellent in color tone and transparency, relates to a methacrylic resin excellent in moldability.

  In recent years, methacrylic resins have excellent transparency, surface hardness, etc., and low birefringence, which is an optical property, and therefore, for example, various optical products such as liquid crystal displays, plasma displays, and organic EL displays. As an optical resin for optical materials such as optical disks, optical films, plastic substrates, etc., such as flat panel displays, small infrared sensors, micro optical waveguides, ultra-small lenses, DVD / BlueRayDisk pickup lenses that handle short-wavelength light, etc. The market is expanding greatly.

  In particular, methacrylic resins having a ring structure in the main chain and compositions containing the methacrylic resins are known to have excellent performance in both heat resistance and optical properties (for example, patents). Ref. 1), the demand is growing rapidly year by year. However, methacrylic resins having a ring structure in the main chain with improved heat resistance and optical properties as described above are sometimes colored due to absorption in the visible light region due to the ring structure, etc. Such a problem has arisen. Therefore, a method for reducing unreacted cyclic monomers remaining in the methacrylic resin has been disclosed in order to obtain a methacrylic resin having a ring structure in the main chain with little coloring and high transparency.

  For example, in Patent Document 2, a monomer component containing an N-substituted maleimide (a) and a methacrylic acid ester (b) is used, and a part of the monomer component is supplied to initiate polymerization, followed by polymerization. In the production method of supplying the remainder of the monomer component in the middle, the ratio of N-substituted maleimide (a) in the unreacted monomer component present in the reaction system at the end of the supply of the monomer component is simply The amount of residual N-substituted maleimide monomer is reduced by controlling it to be less than the proportion of N-substituted maleimide (a) in the total supply amount of the monomer component, and it is excellent in transparency and heat resistant with little coloring. A method for obtaining a functional methacrylic resin has been proposed.

  Further, in Patent Document 3, in a methacrylate ester monomer / maleimide monomer polymerization system using a sulfur chain transfer agent such as mercaptan, an acidic substance is allowed to exist in the reaction system, thereby remaining maleimide. There has been proposed a method for reducing coloring and suppressing maleimide monomers generated by heating at the time of molding and the like.

International Publication No. 2011/149088 Japanese Patent Laid-Open No. 9-324016 JP 2001-233919 A

  However, in recent years, the use has expanded from optical film applications to thick molded object applications such as lenses and molded plates. For example, even for molded object applications having a long optical path length, and less coloring, and It has been eagerly desired to provide a resin that can exhibit high transparency.

  In Patent Documents 2 and 3, as a method for reducing coloring, attention is paid to N-substituted maleimide having strong coloring property as the monomer itself, and the amount of N-substituted maleimide remaining in the methacrylic resin is reduced, molding processing, or the like. A method has been proposed in which the amount of N-substituted maleimide due to the thermal history is reduced and the amount is reduced.

  However, as described above, it has been found that, for example, as a methacrylic resin for coping with expansion to a molded product having a long optical path length, the coloring degree and transparency are insufficient.

  Therefore, it is strongly desired not only to control the remaining coloring monomers such as N-substituted maleimide but also to further improve the coloring property and transparency of the methacrylic resin by paying attention to the polymer itself. ing.

  An object of the present invention is to provide a methacrylic resin having high heat resistance, highly controlled birefringence, excellent color tone and transparency, and excellent moldability.

  As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventors, for example, in order to develop high transparency with less coloring even in a molded product having a long optical path length. It has been clarified that the above-mentioned problems can be solved by separating the methacrylic resin into a methanol-soluble component and a methanol-insoluble component and controlling the characteristics of the respective components.

  If the polymer itself can be improved, as a methacrylic resin having a ring structure in the main chain, not only a resin having a ring structure derived from an N-substituted maleimide monomer, but also, for example, a resin having a lactone ring structural unit Etc.

That is, the present invention is as follows.
[1]
Look-containing structural unit (B) having a ring structure in its main chain, (B) the structural unit, the group consisting of N- substituted maleimide structural unit (B-1), and a lactone ring structure unit (B-2) It is more including methacrylic resin at least one structural unit selected,
The glass transition temperature is over 120 ° C. and below 160 ° C.,
The amount of methanol-soluble component of the methacrylic resin is 5% by mass or less with respect to 100% by mass of the total amount of methanol-soluble component and methanol-insoluble component,
The yellowness index (YI) measured using a 10 cm optical path length cell for a 20 w / v% chloroform solution of the methanol insoluble matter is 0 to 7,
A methacrylic resin characterized by that.
[2]
The methacrylic resin according to [1], wherein a 20 w / v% chloroform solution insoluble in methanol has a transmittance at 680 nm measured using a 10 cm optical path length cell of 90% or more.
[3]
The methacrylic resin according to [1] or [2], wherein the methacrylic resin contains 50 to 97% by mass of the methacrylic ester monomer unit (A) based on 100% by mass of the methacrylic resin.
[4]
The methacrylic resin is 100% by mass of the methacrylic resin, the structural unit (B) having a ring structure in the main chain: 3 to 30% by mass, and other vinyls copolymerizable with the methacrylic acid ester monomer The methacrylic resin according to any one of [1] to [3], containing a monomeric unit (C): 0 to 20% by mass.
[5]
[1] to [4] The content of the (B) structural unit is 45 to 100% by mass, where the total amount of the (B) structural unit and the (C) monomer unit is 100% by mass. ] The methacrylic resin in any one of.
[ 6 ]
[1] to (C) wherein the monomer unit (C) includes at least one structural unit selected from the group consisting of an acrylate monomer, an aromatic vinyl monomer, and a vinyl cyanide monomer. [ 5 ] The methacrylic resin according to any one of [ 5 ].
[ 7 ]
The methacrylic resin according to any one of [1] to [ 6 ], which has a photoelastic coefficient of −2 × 10 ⁻¹² to + 2 × 10 ⁻¹² Pa ⁻¹ .
[ 8 ]
The ratio (Mz / Mw) of the Z average molecular weight (Mz) and the weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) is 1.3 to 2.0 [1] to [ 7 ] The methacrylic resin in any one of .

Effects of the present invention

  According to the present invention, a methacrylic resin having high heat resistance, highly controlled birefringence, excellent color tone and transparency, and excellent moldability can be provided.

  Hereinafter, although the form for implementing this invention (henceforth "this embodiment") is demonstrated in detail, this invention is not limited to the following description, In the range of the summary Various modifications can be made.

(Methacrylic resin)
The methacrylic resin in this embodiment is a group consisting of a methacrylic acid ester monomer unit (A), a structural unit (B-1) derived from an N-substituted maleimide monomer, and a lactone ring structural unit (B-2). Including a structural unit (B) having at least one ring structure selected from the main chain, and optionally including other vinyl monomer units (C) copolymerizable with a methacrylic acid ester monomer. .

  Hereinafter, each monomer structural unit will be described.

-Structural unit derived from methacrylic acid ester monomer (A)-
First, the structural unit (A) derived from a methacrylic acid ester monomer will be described.
The structural unit (A) derived from a methacrylic acid ester monomer is formed from, for example, a monomer selected from methacrylic acid esters shown below.
Examples of the methacrylate ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, and methacrylic acid. Cyclopentyl, cyclohexyl methacrylate, cyclooctyl methacrylate, tricyclodecyl methacrylate, dicyclooctyl methacrylate, tricyclododecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, 1-phenylethyl methacrylate, methacrylic acid Examples include 2-phenoxyethyl, 3-phenylpropyl methacrylate, 2,4,6-tribromophenyl methacrylate, and the like.
These monomers may be used alone or in combination of two or more.
Of the above methacrylic acid esters, methyl methacrylate and benzyl methacrylate are preferred in that the obtained methacrylic resin is excellent in transparency and weather resistance.
The structural unit (A) derived from the methacrylic acid ester monomer may contain only one kind or two or more kinds.

  As the content of the structural unit (A) derived from the methacrylic acid ester monomer, from the viewpoint of sufficiently imparting heat resistance to the methacrylic resin by the structural unit (B) having a ring structure to be described later in the main chain, The methacrylic resin is defined as 100% by mass, preferably 50 to 97% by mass, more preferably 55 to 97% by mass, even more preferably 55 to 95% by mass, still more preferably 60 to 93% by mass, and particularly preferably 60%. It is -90 mass%.

  Hereinafter, the structural unit (B) having a ring structure in the main chain will be described.

-Structural unit derived from N-substituted maleimide monomer (B-1)-
Next, the structural unit (B-1) derived from the N-substituted maleimide monomer will be described.
The structural unit (B-1) derived from the N-substituted maleimide monomer is at least selected from a monomer represented by the following formula (1) and / or a monomer represented by the following formula (2). One may be formed, and it is preferably formed from both monomers represented by the following formula (1) and the following formula (2).

式（１）中、Ｒ^１は、炭素数７〜１４のアリールアルキル基、炭素数６〜１４のアリール基のいずれかを示し、Ｒ^２及びＲ^３は、それぞれ独立に、水素原子、炭素数１〜１２のアルキル基、炭素数６〜１４のアリール基のいずれかを示す。
また、Ｒ^２がアリール基の場合には、Ｒ^２は、置換基としてハロゲンを含んでいてもよい。
また、Ｒ^１は、ハロゲン原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、ニトロ基、ベンジル基等の置換基で置換されていてもよい。

In Formula (1), R ¹ represents any of an arylalkyl group having 7 to 14 carbon atoms and an aryl group having 6 to 14 carbon atoms, and R ² and R ³ each independently represent a hydrogen atom or a carbon number. One of an alkyl group having 1 to 12 and an aryl group having 6 to 14 carbon atoms is shown.
When R ² is an aryl group, R ² may contain halogen as a substituent.
R ¹ may be substituted with a substituent such as a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a nitro group, or a benzyl group.

式（２）中、Ｒ^４は、水素原子、炭素数３〜１２のシクロアルキル基、炭素数１〜１２のアルキル基のいずれかを示し、Ｒ^５及びＲ^６は、それぞれ独立に、水素原子、炭素数１〜１２のアルキル基、炭素数６〜１４のアリール基のいずれかを示す。

In Formula (2), R ⁴ represents any one of a hydrogen atom, a cycloalkyl group having 3 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms, and R ⁵ and R ⁶ are each independently a hydrogen atom. Or an alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 14 carbon atoms.

Specific examples will be shown below.
Examples of the monomer represented by the formula (1) include N-phenylmaleimide, N-benzylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromo Phenyl) maleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N- (2-methoxyphenyl) maleimide, N- (2-nitrophenyl) maleimide, N- (2,4 , 6-trimethylphenyl) maleimide, N- (4-benzylphenyl) maleimide, N- (2,4,6-tribromophenyl) maleimide, N-naphthylmaleimide, N-anthracenylmaleimide, 3-methyl-1 -Phenyl-1H-pyrrole-2,5-dione, 3,4-dimethyl-1-phenyl-1H-pyrrole-2,5- One, 1,3-diphenyl -1H- pyrrole-2,5-dione, 1,3,4-triphenyl -1H- pyrrole-2,5-dione, and the like.
Among these monomers, N-phenylmaleimide and N-benzylmaleimide are preferable because the obtained methacrylic resin has excellent heat resistance and optical properties such as birefringence.
These monomers may be used alone or in combination of two or more.

Examples of the monomer represented by the formula (2) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-laurylmaleimide, N-stearyl Maleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, 1-cyclohexyl-3-methyl-1-phenyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1-phenyl-1H- Pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1 - pyrrole-2,5-dione, and 1-cyclohexyl-3,4-diphenyl -1H- pyrrole-2,5-dione can be cited.
Among these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferable because the weather resistance of the methacrylic resin is excellent. N-cyclohexylmaleimide is particularly preferable because of its excellent hygroscopicity.
These monomers can be used alone or in combination of two or more.

In the methacrylic resin of the present embodiment, using the monomer represented by the formula (1) and the monomer represented by the formula (2) in combination provides highly controlled birefringence characteristics. It is particularly preferable because it can be expressed.
The molar ratio of the content (B1) of the structural unit derived from the monomer represented by the formula (1) to the content (B2) of the structural unit derived from the monomer represented by the formula (2) (B1 / B2) is preferably more than 0 and 15 or less, more preferably more than 0 and 10 or less.
When the molar ratio B1 / B2 is in this range, the methacrylic resin of the present embodiment maintains transparency, does not cause yellowing, and does not impair the environmental resistance, and has good heat resistance and good photoelasticity. Express characteristics.

The content of the structural unit (B-1) derived from the N-substituted maleimide monomer is not particularly limited as long as the obtained composition satisfies the glass transition temperature range of the present embodiment, but a methacrylic resin. Is 100% by mass, preferably 5 to 40% by mass, and more preferably 5 to 35% by mass.
When it is within this range, the methacrylic resin can obtain a more sufficient heat resistance improving effect, and more preferable effects of improving weather resistance, low water absorption, and optical properties. It should be noted that the content of the structural unit derived from the N-substituted maleimide monomer being 40% by mass or less reduces the reactivity of the monomer component during the polymerization reaction and increases the amount of monomer remaining unreacted. This is effective in preventing deterioration in physical properties of the methacrylic resin.

-Lactone ring structural unit (B-2)-
Examples of the methacrylic resin having a lactone ring structural unit in the main chain include, for example, JP-A No. 2001-151814, JP-A No. 2004-168882, JP-A No. 2005-146084, JP-A No. 2006-96960, and JP-A No. 2006-96960. It can be formed by the methods described in JP-A No. 2006-171464, JP-A No. 2007-63541, JP-A No. 2007-297620, JP-A No. 2010-180305, and the like.

上記一般式（３）において、Ｒ^１０、Ｒ^１１及びＲ^１２は、互いに独立して、水素原子、又は炭素数１〜２０の有機残基である。
有機残基としては、例えば、メチル基、エチル基、プロピル基等の炭素数１〜２０の飽和脂肪族炭化水素基（アルキル基等）；エテニル基、プロペニル基等の炭素数２〜２０の不飽和脂肪族炭化水素基（アルケニル基等）；フェニル基、ナフチル基等の炭素数６〜２０の芳香族炭化水素基（アリール基等）；これら飽和脂肪族炭化水素基、不飽和脂肪族炭化水素基、芳香族炭化水素基における水素原子の一つ以上が、ヒドロキシ基、カルボキシル基、エーテル基、エステル基からなる群から選ばれる少なくとも１種の基により置換された基；等が挙げられる。 The lactone ring structural unit constituting the methacrylic resin of this embodiment may be formed after resin polymerization.
The lactone ring structural unit in the present embodiment is preferably a 6-membered ring because it is excellent in the stability of the ring structure.
As the lactone ring structural unit which is a 6-membered ring, for example, a structure represented by the following general formula (3) is particularly preferable.

In the general formula (3), R ¹⁰ , R ¹¹ and R ¹² are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms.
Examples of the organic residue include saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms such as methyl group, ethyl group, and propyl group (alkyl groups and the like); non-carbon atoms having 2 to 20 carbon atoms such as ethenyl group and propenyl group. Saturated aliphatic hydrocarbon group (alkenyl group etc.); C6-C20 aromatic hydrocarbon group (aryl group etc.) such as phenyl group, naphthyl group; These saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbons Group, a group in which one or more hydrogen atoms in the aromatic hydrocarbon group are substituted with at least one group selected from the group consisting of a hydroxy group, a carboxyl group, an ether group, and an ester group.

  The lactone ring structure is obtained by, for example, copolymerizing an acrylic acid-based monomer having a hydroxy group and a methacrylic acid ester monomer such as methyl methacrylate to form a hydroxy group and an ester group or a carboxyl group in the molecular chain. After the introduction, it can be formed by causing dealcoholization (esterification) or dehydration condensation (hereinafter also referred to as “cyclization condensation reaction”) between these hydroxy groups and ester groups or carboxyl groups.

  Examples of the acrylic acid-based monomer having a hydroxy group used for polymerization include 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, 2- (hydroxymethyl) alkyl acrylate (for example, 2- (Hydroxymethyl) methyl acrylate, 2- (hydroxymethyl) ethyl acrylate, 2- (hydroxymethyl) isopropyl acrylate, 2- (hydroxymethyl) acrylate n-butyl, 2- (hydroxymethyl) acrylate t- Butyl), 2- (hydroxyethyl) alkyl acrylate, and the like, preferably 2- (hydroxymethyl) acrylic acid and 2- (hydroxymethyl) alkyl acrylate which are monomers having a hydroxyallyl moiety. , Particularly preferably methyl 2- (hydroxymethyl) acrylate 2- (hydroxymethyl) acrylate.

The content of the lactone ring structural unit in the methacrylic resin having a lactone ring structural unit in the main chain is not particularly limited as long as it satisfies the glass transition temperature range of the methacrylic resin of the present embodiment, but the methacrylic resin It is preferable that it is 5-40 mass% with respect to 100 mass%, More preferably, it is 5-35 mass%.
When the content of the lactone ring structural unit is within this range, effects of introducing a ring structure such as improvement in solvent resistance and improvement in surface hardness can be exhibited while maintaining moldability.
In addition, the content rate of the lactone ring structure in a methacrylic resin can be determined using the method of the above-mentioned patent document description.

  The content of the structural unit (B) having a ring structure in the main chain is 3% from the viewpoint of heat resistance, thermal stability, strength, and fluidity of the methacrylic resin of the present embodiment, with the methacrylic resin being 100% by mass. The lower limit is more preferably 5% by mass or more, still more preferably 7% by mass or more, still more preferably 8% by mass or more, and the upper limit is more preferably It is 30% by mass or less, more preferably 28% by mass or less, still more preferably 25% by mass or less, particularly preferably 20% by mass or less, particularly preferably 18% by mass or less, and most preferably less than 15% by mass.

-Other vinyl monomer units (C) copolymerizable with methacrylate monomers-
Other vinyl monomer units (C) (hereinafter referred to as (C) monomer units) copolymerizable with methacrylic acid ester monomers that can constitute the methacrylic resin of this embodiment. .) Are aromatic vinyl monomer units (C-1), acrylate monomer units (C-2), vinyl cyanide monomer units (C-3), and other single units. A monomer unit (C-4) is mentioned.
As for other vinyl monomer units (C) copolymerizable with the methacrylic acid ester monomer, only one kind may be used alone, or two or more kinds may be combined.

  The monomer unit (C) can be appropriately selected depending on the properties required for the methacrylic resin of the present embodiment, but the thermal stability, fluidity, mechanical properties, chemical resistance, etc. When the characteristics are particularly necessary, it consists of an aromatic vinyl monomer unit (C-1), an acrylate monomer unit (C-2), and a vinyl cyanide monomer unit (C-3). At least one selected from the group is preferred.

[Aromatic vinyl-based monomer unit (C-1)]
Although it does not specifically limit as a monomer which makes the aromatic vinyl monomer unit (C-1) which comprises the methacrylic resin of this embodiment, It represents with following General formula (4). Aromatic vinyl monomers are preferred.

In the general formula (4), R ¹ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with a hydroxyl group, for example.
R ² is selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 8 carbon atoms, and an aryloxy group having 6 to 8 carbon atoms. Any one selected and R ² may be the same group or different groups. Further, R ² may form a ring structure.
n represents an integer of 0 to 5.

Specific examples of the monomer represented by the general formula (4) are not particularly limited, but styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethyl. Styrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene, о-ethylstyrene, p-tert-butylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenyl benzene (α-methylstyrene), isopropenyl toluene, isopropenyl ethyl benzene, isopropenyl propyl benzene, isopropenyl butyl benzene, isopropenyl pentyl benzene, isopropenyl hexyl benzene, Isopropenyl octylben Zen, α-hydroxymethylstyrene, α-hydroxyethylstyrene and the like.
Among these, styrene and isopropenylbenzene are preferable, and styrene is more preferable from the viewpoints of imparting fluidity and reducing unreacted monomers by improving the polymerization conversion rate.
These may be appropriately selected according to required characteristics in the methacrylic resin of the present embodiment.

  The content in the case of using the aromatic vinyl monomer unit (C-1) is (A) the monomer unit and (B) in consideration of the balance between heat resistance, reduction of residual monomer species, and fluidity. When the total amount with the structural unit is 100% by mass, it is preferably 23% by mass or less, more preferably 20% by mass or less, further preferably 18% by mass or less, still more preferably 15% by mass or less, More preferably, it is 10 mass% or less.

When the aromatic vinyl monomer unit (C-1) is used in combination with the maleimide structural unit (B-1) described above, the (C-1) monomer relative to the content of the structural unit (B-1) As the ratio (mass ratio) of the content of units (that is, (C-1) content / (B-1) content), the processing fluidity at the time of molding the film and the silver streak due to the reduction of residual monomer From the viewpoint of the effect of reducing the resistance, it is preferably 0.3 to 5.
Here, from the viewpoint of maintaining good color tone and heat resistance, the upper limit value is preferably 5 or less, more preferably 3 or less, and even more preferably 1 or less. From the viewpoint of reducing the residual monomer, the lower limit is preferably 0.3 or more, more preferably 0.4 or more.
The aromatic vinyl monomer (C-1) described above may be used alone or in combination of two or more.

[Acrylic acid ester monomer unit (C-2)]
Although it does not specifically limit as a monomer which makes the acrylate ester monomer unit (C-2) which comprises the methacrylic resin of this embodiment, The acryl represented by following General formula (5) Acid ester monomers are preferred.

In the general formula (5), R ¹ represents a hydrogen atom or an alkoxy group having 1 to 12 carbon atoms, and R ² represents an alkyl group having 1 to 18 carbon atoms.

As a monomer for forming the acrylate ester monomer unit (C-2), in the methacrylic resin for a film of the present embodiment, weather resistance, heat resistance, fluidity, and thermal stability are improved. From the viewpoint, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, and the like are preferable. More preferred are methyl acrylate, ethyl acrylate, and n-butyl acrylate, and methyl acrylate and ethyl acrylate are more preferred from the viewpoint of availability.
The acrylate monomer unit (C-2) may be used alone or in combination of two or more.

  In the case of using the acrylate monomer unit (C-2), the total content of the (A) monomer unit and the (B) structural unit is 100 from the viewpoints of heat resistance and thermal stability. In the case of mass%, it is preferably 5 mass% or less, more preferably 3 mass% or less.

[Vinyl cyanide monomer unit (C-3)]
The monomer constituting the vinyl cyanide monomer unit (C-3) constituting the methacrylic resin of the present embodiment is not particularly limited, and examples thereof include acrylonitrile, methacrylonitrile, and ethacrylo. Nitrile, vinylidene cyanide and the like can be mentioned, and among them, acrylonitrile is preferable from the viewpoint of easy availability and imparting chemical resistance.
The vinyl cyanide monomer unit (C-3) may be used alone or in combination of two or more.

  The content when using the vinyl cyanide monomer unit (C-3) is the total amount of the (A) monomer unit and the (B) structural unit from the viewpoint of solvent resistance and heat resistance. Is preferably 15% by mass or less, more preferably 12% by mass or less, and still more preferably 10% by mass or less.

[Monomer units other than (C-1) to (C-3) (C-4)]
Although it does not specifically limit as a monomer which makes monomeric units (C-4) other than (C-1)-(C-3) which comprises the methacrylic resin of this embodiment, For example, Amides such as acrylamide, methacrylamide; glycidyl compounds such as glycidyl (meth) acrylate and allyl glycidyl ether; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid, and half esters thereof Unsaturated alcohols such as methallyl alcohol and allyl alcohol; olefins such as ethylene, propylene and 4-methyl-1-pentene; vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, Vinyl compounds other than those mentioned above, such as N-vinylpyrrolidone and N-vinylcarbazole, or vinylidene formation Thing, and the like.
Furthermore, as a crosslinkable compound having a plurality of reactive double bonds, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, etc. Esterification of both terminal hydroxyl groups of ethylene glycol or its oligomer with acrylic acid or methacrylic acid; hydroxyl groups of two alcohols such as neopentyl glycol di (meth) acrylate and di (meth) acrylate with acrylic acid or methacrylic acid Esterified; esterified polyhydric alcohol derivatives such as trimethylolpropane and pentaerythritol with acrylic acid or methacrylic acid; polyfunctional monomers such as divinylbenzene.

  Among the monomers constituting the monomer unit (C) described above, at least one selected from the group consisting of methyl acrylate, ethyl acrylate, styrene, and acrylonitrile is preferable from the viewpoint of availability.

The content of the other vinyl monomer unit (C) copolymerizable with the methacrylic acid ester monomer is 100% by mass of the methacrylic resin from the viewpoint of enhancing the effect of imparting heat resistance by the structural unit (B). As, it is 0-20 mass%, it is preferable that it is 0-18 mass%, and it is more preferable that it is 0-15 mass%.
In particular, when a crosslinkable polyfunctional (meth) acrylate having a plurality of reactive double bonds is used as the monomer unit (C), the content of the monomer unit (C) is the fluidity of the polymer. In view of the above, it is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and still more preferably 0.2% by mass or less.

  In particular, in this embodiment, from the viewpoint of heat resistance and optical properties of the methacrylic resin, when the total amount of (B) structural unit and (C) monomer unit is 100% by mass, (B) structural unit Is 45 to 100% by mass. At this time, content of (C) structural unit is 0-55 mass%. And content of (B) structural unit becomes like this. Preferably it is 50-100 mass%, More preferably, it is 50-90 mass%, More preferably, it is 50-80 mass%.

  Hereinafter, the characteristics of the methacrylic resin of this embodiment will be described.

The glass transition temperature (Tg) of the methacrylic resin in this embodiment is more than 120 ° C. and 160 ° C. or less.
When the glass transition temperature of the methacrylic resin exceeds 120 ° C., necessary and sufficient heat resistance can be obtained more easily as a recent lens molded body and film molded body optical film for liquid crystal display. The glass transition temperature (Tg) is more preferably 125 ° C. or higher, and still more preferably 130 ° C. or higher, from the viewpoint of dimensional stability under the use environment temperature.
On the other hand, when the glass transition temperature (Tg) of the methacrylic resin is 160 ° C. or lower, melt processing at an extremely high temperature can be avoided, thermal decomposition of the resin or the like can be suppressed, and a good product can be obtained. The glass transition temperature (Tg) is preferably 150 ° C. or lower for the reasons described above.
In addition, a glass transition temperature (Tg) can be determined by measuring based on JIS-K7121. Specifically, it can measure using the method described in the Example mentioned later.

In the present embodiment, the ratio of the amount of the methanol-soluble component of the methacrylic resin to the total amount of 100% by mass of the methanol-soluble component and the methanol-insoluble component is 5% by mass or less, preferably 4.5%. % Or less, more preferably 4% by mass or less, still more preferably 3.5% by mass or less, preferably 3% by mass or less, and more preferably 2.5% by mass or less.
By setting the proportion of the soluble component to 5% by mass or less, it is possible to suppress problems during molding such as cast roll contamination during film molding and silver streak generation during injection molding.
For methanol-soluble and methanol-insoluble components, methacrylic resin is used as a chloroform solution, and then the solution is dropped into methanol to reprecipitate, and the filtrate and filtrate are separated, and then each is dried. Specifically, it can be obtained by the method described in Examples below.

  The methacrylic resin in this embodiment has a yellowness index (YI) measured using a 10 cm optical path length cell of a 20 w / v% chloroform solution in a methanol-insoluble portion, 0 to 7, preferably 0.5 to 6, More preferably, it is 0.8-5, More preferably, it is 1-4.

In the methacrylic resin in this embodiment, the transmittance at 680 nm measured under the same conditions as in the above YI measurement is preferably 90% or more, more preferably 91% or more, and 92 % Or more is more preferable.
When the yellowness index (YI) and the transmittance are within this range, a molded product suitable for optical use can be obtained.
The yellowness index (YI) and transmittance can be measured by the methods described in the examples below.

In the methacrylic resin in this embodiment, the weight average molecular weight (Mw) in terms of polymethyl methacrylate measured by gel permeation chromatography (GPC) is preferably in the range of 65,000 to 300,000, more preferably. It is in the range of 100,000 to 220,000, more preferably in the range of 120,000 to 180,000.
When the weight average molecular weight (Mw) is in the above range, the balance between mechanical strength and fluidity is excellent.
Further, regarding the ratio among the Z average molecular weight (Mz), the weight average molecular weight (Mw), and the number average molecular weight (Mn) as parameters representing the molecular weight distribution, in the methacrylic resin in this embodiment, fluidity and mechanical Considering the balance with the strength, Mw / Mn is preferably 1.5 to 3.0, more preferably 1.6 to 2.5, and 1.6 to 2.3. Mz / Mw is preferably 1.3 to 2.0, more preferably 1.3 to 1.8, and still more preferably 1.4 to 1.7.
In particular, when Mz / Mw is within this range, a methacrylic resin excellent in color tone can be obtained.
In addition, about the Z average molecular weight of a methacrylic resin, a weight average molecular weight, and a number average molecular weight, it can measure by the method of the below-mentioned Example description.

The absolute value of the photoelastic coefficient _{C R} of methacrylic resin containing a structural unit (X) in the main chain of the present embodiment has a ring structure, is preferably 3.0 × ¹⁰ -12 ^{Pa -1} or less, 2 more preferably .0 × ¹⁰ -12 ^{Pa -1} or less, further preferably 1.0 × ¹⁰ -12 ^{Pa -1} or less.
The photoelastic coefficient is described in various documents (see, for example, Chemical Review, No. 39, 1998 (published by the Academic Publishing Center)) and is defined by the following formulas (ia) and (ib). It is. As the value of photoelastic coefficient C _R is close to zero, it can be seen that change in birefringence due to an external force is small.
C _R = | Δn | / σ _R (i−a)
| Δn | = | nx−ny | (i−b)
(In the formula, _CR is a photoelastic coefficient, σ _R is an extension stress, | Δn | is an absolute value of birefringence, nx is a refractive index in the extension direction, and ny is in-plane perpendicular to the extension direction. Refractive index in direction is shown respectively.)
If the absolute value is 3.0 × 10 ^-12 Pa ^-1 or less in photoelastic coefficient C _R of the methacrylic resin of the present embodiment, even when used in a liquid crystal display device with a film, or unevenness in retardation occurs Further, it is possible to suppress or prevent the contrast at the periphery of the display screen from being lowered or light leakage from occurring.
Photoelastic coefficient C _R of the methacrylic resin, specifically, can be determined by the method described in Examples described later.

(Method for producing methacrylic resin)
Hereinafter, it describes about the manufacturing method of the methacrylic resin of this embodiment.

As for the manufacturing method of the methacrylic resin of this embodiment, the manufacturing method of the following 1st aspect and 2nd aspect is mentioned.
In the first aspect, in a method of radical polymerization of two or more monomers including a methacrylic acid ester monomer in a batch or semi-batch manner in a solvent, the radical polymerization initiator is reduced by half at the polymerization temperature. Using the one whose period is 1 minute or more and less than 60 minutes, the radical polymerization initiator is added into the reactor while gradually decreasing the amount of addition per unit time, and the polymerization of the monomer proceeds. And the addition amount of the radical polymerization initiator added after the time when the polymerization conversion rate reaches 85% is 10 to 25% by mass, with the total addition amount of the radical polymerization initiator being 100% by mass. .
In the first aspect, the radical polymerization initiator may be added continuously or intermittently. When intermittently added, the addition amount per unit time is not considered for the time not added. Shall.
In the second aspect, in a method of radical polymerization of two or more monomer components including a methacrylic acid ester monomer in a batch or semi-batch mode in a solvent, as a radical polymerization initiator, at a polymerization temperature. Using those having a half-life of 60 minutes or more, adding 30% by mass or more of the total amount of the radical polymerization initiator within 30 minutes from the start of the addition of the polymerization initiator, and of the polymerization initiator After 30 minutes from the start of addition, 25% by mass or more of the total addition amount of the monomer is added.
When the temperature fluctuates during the polymerization, the time average of the polymerization temperature until the polymerization conversion rate reaches 95% is regarded as the polymerization temperature.

  Hereinafter, a method for producing a methacrylic resin containing an N-substituted maleimide structural unit (B-1) as the structural unit (B) having a ring structure in the main chain will be described in detail.

A solution polymerization method is used as a method for producing a methacrylic resin having a structural unit (B-1) derived from an N-substituted maleimide monomer in the main chain in the present embodiment.
In the production method of the present embodiment, a batch (batch) type or a semi-batch (semi-batch) type can be used as the polymerization format. Here, the batch type is a process in which the reaction starts and proceeds after all the raw materials are charged into the reactor, and the product is recovered after completion. The semi-batch type is either the raw material input or the product recovery. This is a process in which one of them is performed simultaneously while the reaction is in progress. As a method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the main chain in the present embodiment, a semi-batch method in which a part of raw materials is charged after the reaction starts is preferable.
In the manufacturing method in the present embodiment, polymerization of monomers by radical polymerization is used.

The polymerization solvent to be used is not particularly limited as long as the solubility of the maleimide copolymer obtained by polymerization is increased and the viscosity of the reaction solution can be appropriately maintained for the purpose of preventing gelation.
Specific polymerization solvents include, for example, aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and isopropylbenzene; ketones such as methyl isobutyl ketone, butyl cellosolve, methyl ethyl ketone, and cyclohexanone; polar solvents such as dimethylformamide and 2-methylpyrrolidone. Can be used.
Moreover, you may use together alcohol, such as methanol, ethanol, and isopropanol, as a polymerization solvent in the range which does not inhibit melt | dissolution of the polymerization product at the time of superposition | polymerization.

  The amount of the solvent at the time of polymerization is not particularly limited as long as the polymerization proceeds and precipitation of the copolymer and the used monomer does not occur during production and can be easily removed. When the total amount is 100 parts by mass, it is preferably 10 to 200 parts by mass. More preferably, it is 25-200 mass parts, More preferably, it is 50-200 mass parts, More preferably, it is 50-150 mass parts.

  The polymerization temperature is not particularly limited as long as the polymerization proceeds, but is preferably 70 to 180 ° C, more preferably 80 to 160 ° C. More preferably, it is 90-150 degreeC, More preferably, it is 100-150 degreeC. From the viewpoint of productivity, the temperature is preferably 70 ° C. or higher, and is preferably 180 ° C. or lower in order to suppress side reactions during polymerization and obtain a polymer having a desired molecular weight and quality.

  The polymerization time is not particularly limited as long as the required degree of polymerization can be obtained at the required conversion rate, but from the viewpoint of productivity and the like, it is preferably 2 to 15 hours, More preferably, it is 3-12 hours, More preferably, it is 4-10 hours.

The polymerization conversion rate at the end of polymerization of a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the main chain in this embodiment is preferably 93 to 99.9%, and 95 to 99.5. % Is more preferable, and 97 to 99% is more preferable.
Here, the polymerization conversion rate is a monomer added in the polymerization system, which is a value obtained by subtracting the total mass of monomers remaining at the end of the polymerization from the total mass of monomers added in the polymerization system. It is a ratio to the total mass of.
Further, the amount of N-substituted maleimide monomer remaining in the solution after polymerization (N-substituted maleimide remaining amount) is preferably 100 to 7000 mass ppm or less, and 200 to 5000 mass ppm or less. It is more preferable, and it is further more preferable that it is 300-3000 mass ppm or less.
Although the higher the polymerization conversion rate and the smaller the residual amount of N-substituted maleimide, the less monomer that can be used in the solvent recovery system, the load on the purification system is reduced, and the basic unit is increased and economical. If the polymerization conversion rate is excessively increased or the residual amount of N-substituted maleimide is excessively reduced, the amount of low molecular weight components and the amount of methanol-soluble components increase, which may adversely affect the color tone and molding processability. There is.

  During the polymerization reaction, a chain transfer agent may be added and polymerized as necessary.

As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used, for example, n-butyl mercaptan, n-octyl mercaptan, n-decyl mercaptan, n-dodecyl mercaptan, 2-ethylhexyl thioglycolate and the like. Mercaptan compounds; halogen compounds such as carbon tetrachloride, methylene chloride and bromoform; unsaturated hydrocarbon compounds such as α-methylstyrene dimer, α-terpinene, dipentene and terpinolene;
These may be used alone or in combination of two or more.
These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.
The addition amount of the chain transfer agent may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of monomers used for polymerization is 100 parts by mass.

In solution polymerization, it is important to reduce the dissolved oxygen concentration in the polymerization solution as much as possible. For example, the dissolved oxygen concentration is preferably 10 ppm or less.
The dissolved oxygen concentration can be measured using, for example, a dissolved oxygen meter DO meter B-505 (manufactured by Iijima Electronics Co., Ltd.). As a method for lowering the dissolved oxygen concentration, a method of bubbling an inert gas in the polymerization solution, and an operation of releasing the pressure after pressurizing the container containing the polymerization solution with an inert gas to about 0.2 MPa before the polymerization are repeated. A method such as a method and a method of passing an inert gas in a container containing a polymerization solution can be appropriately selected.

  During the polymerization reaction, a polymerization initiator is added.

As the polymerization initiator, any initiator generally used in radical polymerization can be used. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide Organic peroxides such as oxide, t-butylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexanoate, t-amylperoxyisononanoate, 1,1-di-t-butylperoxycyclohexane; 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis Azo compounds such as isobutyrate; it can.
These may be used alone or in combination of two or more.
These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.
The addition amount of the polymerization initiator may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass, when the total amount of monomers used for polymerization is 100 parts by mass.

  During polymerization of a methacrylic resin having a cyclic structural unit derived from an N-substituted maleimide monomer in this embodiment, methanol can be produced by controlling the concentration of each comonomer present in the reaction system and the radical having polymerization activity. The amount of the solute is 5% by mass or less with respect to 100% by mass of the total amount of the methanol-soluble component and the methanol-insoluble component, and the 10 cm optical path length cell is used for the 20 w / v% chloroform solution of the methanol-insoluble component. A methacrylic resin having a yellowness index (YI) measured in this manner of 0 to 7 can be produced.

In a general batch-type radical polymerization, when it is attempted to increase the conversion rate at the end of the polymerization, the amount of the oligomer component increases at the end of the polymerization, which is considered to adversely affect the moldability. In addition, when copolymerizing a methacrylic acid ester monomer and an N-substituted maleimide monomer, the N-substituted maleimide monomer generally tends to remain, and a low molecular weight with a high N-substituted maleimide content at the end of the polymerization. It is considered that a polymer is produced and itself exhibits colorability, or a polymer that becomes a coloring component upon heating is produced.
In the polymerization of a methacrylic resin having a ring structural unit derived from an N-substituted maleimide monomer in the present embodiment, a polymerization initiator and / or a monomer is added during the polymerization, and the addition amount is controlled. It is possible to reduce the fluctuation of the concentration ratio between the monomer and radical in the system during polymerization, suppress the formation of low molecular weight components at the end of the polymerization, and improve the colorability and molding processability.

The first polymerization method is a batch polymerization or semi-batch polymerization, using a radical polymerization initiator having a half-life of 1 minute or more and less than 60 minutes as a radical polymerization initiator, While gradually adding the added amount per unit time, it is added into the reactor, and the polymerization of the monomer proceeds.
The second polymerization method uses a batch polymerization or a semi-batch polymerization with a radical polymerization initiator that has a half-life of 60 minutes or more at the polymerization temperature. A part of the radical polymerization initiator is added within the time, and a part of the monomer is added after a predetermined time after the start of the polymerization to advance the polymerization.

  Each polymerization method will be described below.

As described above, the first polymerization method uses a radical polymerization initiator having a half-life of 1 minute or more and less than 60 minutes as the radical polymerization initiator, and the radical polymerization initiator is added in an amount per unit time. While gradually decreasing, it is added to the reactor, and the polymerization of the monomer proceeds.
Here, the radical polymerization initiator having a half-life at a polymerization temperature of 1 minute or more and less than 60 minutes is a radical polymerization initiator having a polymerization temperature of 1 minute half-life temperature or less and higher than the 1-hour half-life temperature. In other words.

  If the initiator has a half-life of 1 minute or more at the polymerization temperature, the initiator can be added to the polymerization reactor, mixed well with the contents liquid, and then decomposed to initiate polymerization, preferable. In addition, by adding an initiator having a half-life significantly shorter than the polymerization time during the polymerization, the variation in the ratio of the residual monomer concentration to the radical concentration in the reaction system is kept small, and the residual monomer concentration at the end of the polymerization It is possible to keep the radical concentration at a stage where the amount of water is lowered, thereby suppressing the generation of low molecular weight components during the polymerization.

  The half-life of the radical polymerization initiator at the polymerization temperature is preferably 3 minutes or more and less than 60 minutes, more preferably 5 minutes or more and less than 60 minutes.

  The above 1 minute half-life temperature and 1-hour half-life temperature are described in the literature and technical data of peroxide manufacturers, etc., and further by using data of activation energy of decomposition reaction, The half-life temperature can also be calculated.

  Examples of half-life temperatures for some radical initiators are listed in Table 1.

  In the first polymerization method, the addition amount of the initiator added after the polymerization conversion rate reaches 85%, the total addition amount of the radical polymerization initiator added during the polymerization period is 100% by mass, It is preferable to set it as 10-25 mass%, and it is more preferable that it is 10-20 mass%.

Furthermore, in the first polymerization method, the one having a half-life at the polymerization temperature of 1 minute or more and less than 60 minutes is used, and the radical polymerization initiator is gradually added to the reactor while the amount of addition per unit time is gradually reduced. In addition, when the polymerization of the monomer proceeds, it is preferable that the addition rate of the initiator when the polymerization conversion rate reaches 85% is 1/10 to 1/3 of the maximum addition rate, More preferably, it is 1/10 to 1/4.
It is preferable from the viewpoint of obtaining a sufficient conversion rate that it is at least the lower limit, and it is preferable from the viewpoint of suppressing the production of polymer components that adversely affect the color tone and workability.

  Further, in the first polymerization method, a part of the monomer is charged into the reactor before the polymerization is started, and the remainder of the monomer is supplied after the polymerization initiator is added and the polymerization is started. Since the generation of the ultra-high molecular weight component is suppressed together with the generation of the molecular weight component, the molecular weight distribution can be narrowed, and Mw / Mn and Mz / Mw can be adjusted to a desired range. In addition, the amount of N-substituted maleimide monomer remaining at the end of the polymerization can be reduced, and the color tone can be improved.

  The ratio of the amount of the initially charged monomer and the amount of the monomer added after the start of polymerization is preferably 1: 9 to 8: 2, more preferably 2: 8 to 7.5: 2.5. Yes, more preferably from 3: 7 to 5: 5.

  In the first polymerization method, the amount of the methacrylic acid ester monomer that tends to be polymerized first at the time of copolymerization is reduced at the initial charging and increased at the additional addition, so that the N-substituted maleimide monomer at the end of the polymerization is increased. The residual amount of the monomer can be reduced, which is preferable from the viewpoint of improving the color tone.

  Further, the remaining amount of the N-substituted maleimide monomer can be reduced by adding a monomer such as styrene having high alternating copolymerization with the N-substituted maleimide monomer during the polymerization.

  As described above, the second polymerization method uses a radical polymerization initiator having a half-life of 60 minutes or more at the polymerization temperature as described above. A part of the monomer is added, and a part of the monomer is added after a predetermined time after the start of the polymerization to advance the polymerization.

When a radical initiator having a half-life that cannot be said to be significantly shorter than the polymerization time is used, the radical concentration is kept relatively high even at the end of the polymerization.
Here, by adding the monomer at the end of the polymerization, the fluctuation of the ratio of the residual monomer concentration to the radical concentration can be reduced during the polymerization period. In addition, by adding a large amount of radical initiator at the initial stage of polymerization, the radical concentration at the stage where the residual monomer concentration at the end of the polymerization is lowered can be kept low, thereby generating a low molecular weight component during the polymerization. Can be suppressed.

In the second polymerization method, the radical initiator is added in an amount of 25% by mass or more of the total addition amount within 30 minutes from the start of the addition of the polymerization initiator, preferably 33% by mass or more of the total addition amount. More preferably, 50% by mass or more is added.
Further, the monomer is added at least 25% by mass of the total addition amount after 30 minutes from the start of addition of the polymerization initiator, preferably at least 33% by mass of the total addition amount, more preferably 50 mass% or more is added, More preferably, 66 mass% or more is added.

  Further, in the second polymerization method, preferably within 4 hours from the start of addition of the polymerization initiator, more preferably within 3 hours from the start of addition of the polymerization initiator, and more preferably 2 hours from the start of addition of the polymerization initiator. Within the total amount of radical initiator added.

In the first production method and the second production method of the methacrylic resin containing the N-substituted maleimide structural unit (B-1) as the structural unit (B) having a ring structure in the main chain, radical initiation An agent can be used in combination of 2 or more types.
In all of the two or more radical initiators, when the half-life at the polymerization temperature is 1 minute or more and less than 60 minutes, or when the half-life at the polymerization temperature is 60 minutes or more, The addition amount and the addition rate of the radical initiator in the polymerization method and the second polymerization method may be the total addition amount and addition rate of two or more kinds of radical initiators.
In the case of using a combination of a half-life at the polymerization temperature of 1 minute or more and less than 60 minutes and a half-life at the polymerization temperature of 60 minutes or more, the second polymerization method is adopted. That is, within 30 minutes from the start of addition of the polymerization initiator, 25% by mass or more of the total addition amount of the radical polymerization initiator is added, and after 30 minutes from the start of addition of the polymerization initiator, Add 25% by mass or more of the total addition amount.

  The method for recovering the polymer from the polymerization solution obtained by solution polymerization is not particularly limited. For example, a poor solvent such as a hydrocarbon solvent or alcohol solvent that does not dissolve the polymerization product obtained by polymerization. After adding the polymerization liquid in the presence of an excessive amount, the homogenizer is treated (emulsified and dispersed), and the unreacted monomer is subjected to pretreatment such as liquid-liquid extraction and solid-liquid extraction. Examples include a method of separating from a polymerization solution; or a method of separating a polymerization solvent and unreacted monomers via a step called a devolatilization step and recovering a polymerization product.

Here, the devolatilization step refers to a step of removing volatile components such as a polymerization solvent, a residual monomer, and a reaction by-product under heating and reduced pressure conditions.
As an apparatus used for the devolatilization process, for example, a devolatilization apparatus composed of a tubular heat exchanger and a devolatilization tank; thin film evaporators such as Wibren and Exeva manufactured by Shinko Environmental Solution Co., Ltd., Hitachi contra, and inclined blade contra; And a vented extruder having sufficient residence time and surface area to exhibit volatility.
A devolatilization process using a devolatilizer in which any two or more of these apparatuses are combined can also be used.

The treatment temperature in the devolatilizer is preferably 150 to 350 ° C, more preferably 170 to 300 ° C, and further preferably 200 to 280 ° C. Residual volatile matter can be suppressed by setting the temperature to the lower limit temperature or higher, and coloring and decomposition of the acrylic resin obtained by setting the temperature to the upper limit temperature or lower can be suppressed.
The degree of vacuum in the devolatilizer is preferably 10 to 500 Torr, and more preferably 10 to 300 Torr. By setting the degree of vacuum below the upper limit, the remaining amount of volatile matter can be suppressed. Moreover, the vacuum degree more than a lower limit is realistic on industrial implementation.
The treatment time is appropriately selected depending on the amount of residual volatile matter, but a shorter time is preferable in order to suppress coloring and decomposition of the resulting acrylic resin.

  The polymer recovered through the devolatilization process is processed into a pellet in a process called a granulation process.

  In the granulation step, the molten resin is extruded into a strand shape from a perforated die and processed into pellets by a cold cut method, an air hot cut method, an underwater strand cut method, and an underwater cut method.

  In addition, when an extruder with a vent is employ | adopted as a devolatilization apparatus, you may serve as a devolatilization process and a granulation process.

  Hereinafter, a method for producing a methacrylic resin containing a lactone ring structural unit (B-2) as the structural unit (B) having a ring structure in the main chain will be described in detail.

  As a method for producing a methacrylic resin having a lactone ring structural unit (B-2) in the main chain in the present embodiment, solution polymerization using a solvent is preferable for promoting the cyclization reaction. Here, the lactone ring structure may be formed by a cyclization reaction after polymerization.

Examples of the polymerization solvent to be used include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone;
These solvents may be used alone or in combination of two or more.

  The amount of solvent at the time of polymerization is not particularly limited as long as the polymerization proceeds and gelation can be suppressed. For example, when the total amount of monomers to be blended is 100 parts by mass, 50 to 200 masses Part, preferably 100 to 200 parts by mass.

In order to sufficiently suppress the gelation of the polymerization solution and promote the cyclization reaction after the polymerization, the polymerization is performed so that the concentration of the produced polymer in the reaction mixture obtained after the polymerization is 50% by mass or less. It is preferable.
Moreover, it is preferable to control so that it may become 50 mass% or less by adding a polymerization solvent suitably to a reaction mixture. The method for appropriately adding the polymerization solvent to the reaction mixture is not particularly limited, and for example, the polymerization solvent may be added continuously or the polymerization solvent may be added intermittently. The polymerization solvent to be added may be only one kind of single solvent or two or more kinds of mixed solvents.

  The polymerization temperature is not particularly limited as long as the polymerization proceeds, but is preferably 50 to 200 ° C., more preferably 80 to 180 ° C. from the viewpoint of productivity.

  The polymerization time is not particularly limited as long as the target conversion rate is satisfied, but is preferably 0.5 to 10 hours, more preferably 1 to 8 hours from the viewpoint of productivity and the like.

  The polymerization conversion rate at the end of the polymerization of the methacrylic resin having a lactone ring structural unit in the main chain in this embodiment is the polymerization conversion disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer. It can be a rate.

  During the polymerization reaction, if necessary, a chain transfer agent may be added for polymerization.

As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used. For example, the chain transfer agent disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer is used. it can.
These may be used alone or in combination of two or more.
These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.
The addition amount of the chain transfer agent is not particularly limited as long as a desired degree of polymerization can be obtained under the polymerization conditions used, but preferably the total amount of monomers used for the polymerization is 100 parts by mass. In this case, the content may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass.

  The dissolved oxygen concentration in the polymerization solution may be, for example, the value disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer.

  During the polymerization reaction, polymerization is performed by adding a polymerization initiator.

Although it does not specifically limit as a polymerization initiator, For example, the polymerization initiator etc. which were disclosed by the preparation method of the methacryl resin which has a structural unit derived from the said N-substituted maleimide monomer can be utilized.
These polymerization initiators may be used alone or in combination of two or more.
The addition amount of the polymerization initiator may be appropriately set according to the combination of monomers and reaction conditions, and is not particularly limited. However, when the total amount of monomers used for polymerization is 100 parts by mass Furthermore, it may be 0.01 to 1 part by mass, preferably 0.05 to 0.5 part by mass.

  In the polymerization of the methacrylic resin having a lactone ring structural unit in the present embodiment, a polymerization initiator and, if necessary, a monomer are added during the polymerization, and the addition amount is controlled to control the polymerization system. It is possible to reduce the fluctuation of the ratio between the monomer concentration and the radical concentration, suppress the formation of low molecular weight components at the end of polymerization, and improve the colorability and moldability.

The first polymerization method is a batch polymerization or semi-batch polymerization, using a radical polymerization initiator having a half-life of 1 minute or more and less than 60 minutes as a radical polymerization initiator, While gradually adding the added amount per unit time, it is added into the reactor, and the polymerization of the monomer proceeds.
The second polymerization method uses a batch polymerization or a semi-batch polymerization with a radical polymerization initiator that has a half-life of 60 minutes or more at the polymerization temperature. A part of the radical polymerization initiator is added within the time, and a part of the monomer is added after a predetermined time after the start of the polymerization to advance the polymerization.

  Each polymerization method will be described below.

As described above, the first polymerization method uses a radical polymerization initiator having a half-life of 1 minute or more and less than 60 minutes as the radical polymerization initiator, and the radical polymerization initiator is added in an amount per unit time. While gradually decreasing, it is added to the reactor, and the polymerization of the monomer proceeds.
Here, the radical polymerization initiator having a half-life at a polymerization temperature of 1 minute or more and less than 60 minutes is a radical polymerization initiator having a polymerization temperature of 1 minute half-life temperature or less and higher than the 1-hour half-life temperature. In other words.
If the initiator has a half-life of 1 minute or more at the polymerization temperature, the initiator can be added to the polymerization reactor, mixed well with the contents liquid, and then decomposed to initiate polymerization, preferable. In addition, by adding an initiator having a half-life significantly shorter than the polymerization time during the polymerization, the variation in the ratio of the residual monomer concentration to the radical concentration in the reaction system is kept small, and the residual monomer concentration at the end of the polymerization It is possible to keep the radical concentration at a stage where the amount of water is lowered, thereby suppressing the generation of low molecular weight components during the polymerization.

  The half-life of the radical polymerization initiator at the polymerization temperature is preferably 3 minutes or more and less than 60 minutes, more preferably 5 minutes or more and less than 60 minutes.

  The meaning and calculation method of the half-life temperature and examples of the half-life temperature of the radical initiator are as disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer.

  In the first polymerization method, the addition amount of the initiator added after the polymerization conversion rate reaches 85%, the total addition amount of the radical polymerization initiator added during the polymerization period is 100% by mass, It is preferable to set it as 10-25 mass%, and it is more preferable that it is 10-20 mass%.

Furthermore, in the first polymerization method, the one having a half-life at the polymerization temperature of 1 minute or more and less than 60 minutes is used, and the radical polymerization initiator is gradually added to the reactor while the amount of addition per unit time is gradually reduced. In addition, when the polymerization of the monomer proceeds, it is preferable that the addition rate of the initiator when the polymerization conversion rate reaches 85% is 1/10 to 1/3 of the maximum addition rate, More preferably, it is 1/10 to 1/4.
It is preferable from the viewpoint of obtaining a sufficient conversion rate that it is at least the lower limit, and it is preferable from the viewpoint of suppressing the production of polymer components that adversely affect the color tone and workability.

  Further, in the first polymerization method, a part of the monomer is charged into the reactor before the polymerization is started, and the remainder of the monomer is supplied after the polymerization initiator is added and the polymerization is started. Since the generation of the ultra-high molecular weight component is suppressed together with the generation of the molecular weight component, the molecular weight distribution can be narrowed, and Mw / Mn and Mz / Mw can be adjusted to a desired range. In addition, by introducing an acrylic acid-based monomer having a hydroxy group uniformly and as little as possible into the molecule, the intramolecular cyclization rate is increased, gelation is suppressed, and color tone is further deteriorated. In view of this, it is preferable to add a monomer after the start of polymerization.

  The ratio of the amount of the initially charged monomer and the amount of the monomer added after the start of polymerization is preferably 1: 9 to 8: 2, more preferably 2: 8 to 7.5: 2.5. Yes, more preferably from 3: 7 to 5: 5.

  As described above, the second polymerization method uses a radical polymerization initiator having a half-life of 60 minutes or more at the polymerization temperature as described above. A part of the monomer is added, and a part of the monomer is added after a predetermined time after the start of the polymerization to advance the polymerization.

When a radical initiator having a half-life that cannot be said to be significantly shorter than the polymerization time is used, the radical concentration is kept relatively high even at the end of the polymerization.
Here, by adding the monomer at the end of the polymerization, the fluctuation of the ratio of the residual monomer concentration to the radical concentration can be reduced during the polymerization period. In addition, by adding a large amount of radical initiator at the initial stage of polymerization, the radical concentration at the stage where the residual monomer concentration at the end of the polymerization is lowered can be kept low, thereby generating a low molecular weight component during the polymerization. Can be suppressed.

In the second polymerization method, the radical initiator is added in an amount of 25% by mass or more of the total addition amount within 30 minutes from the start of the addition of the polymerization initiator, preferably 33% by mass or more of the total addition amount. More preferably, 50% by mass or more is added.
Further, the monomer is added at least 25% by mass of the total addition amount after 30 minutes from the start of addition of the polymerization initiator, preferably at least 33% by mass of the total addition amount, more preferably 50 mass% or more is added, More preferably, 66 mass% or more is added.

  Further, in the second polymerization method, preferably within 4 hours from the start of addition of the polymerization initiator, more preferably within 3 hours from the start of addition of the polymerization initiator, and more preferably 2 hours from the start of addition of the polymerization initiator. Within the total amount of radical initiator added.

In the first production method and the second production method of the methacrylic resin production method containing the lactone ring structural unit (B-2) as the structural unit (B) having a ring structure in the main chain, the radical initiator is 2 More than one species can be used in combination.
In all of the two or more radical initiators, when the half-life at the polymerization temperature is 1 minute or more and less than 60 minutes, or when the half-life at the polymerization temperature is 60 minutes or more, The addition amount and the addition rate of the radical initiator in the polymerization method and the second polymerization method may be the total addition amount and addition rate of two or more kinds of radical initiators.
In the case of using a combination of a half-life at the polymerization temperature of 1 minute or more and less than 60 minutes and a half-life at the polymerization temperature of 60 minutes or more, the second polymerization method is adopted. That is, within 30 minutes from the start of addition of the polymerization initiator, 25% by mass or more of the total addition amount of the radical polymerization initiator is added, and after 30 minutes from the start of addition of the polymerization initiator, Add 25% by mass or more of the total addition amount.

The methacrylic resin having a lactone ring structural unit in the present embodiment can be obtained by performing a cyclization reaction after completion of the polymerization reaction. Therefore, it is preferable to use the lactone cyclization reaction in a state containing a solvent without removing the polymerization solvent from the polymerization reaction solution.
The copolymer obtained by polymerization undergoes a heat treatment to cause a cyclization condensation reaction between a hydroxyl group (hydroxyl group) present in the molecular chain of the copolymer and an ester group, resulting in a lactone ring structure. Form.

  During the heat treatment for forming the lactone ring structure, a vacuum apparatus or a reaction apparatus equipped with a devolatilization apparatus for removing alcohol that may be by-produced by cyclization condensation, an extruder equipped with a devolatilization apparatus, or the like can be used. .

When forming the lactone ring structure, heat treatment may be performed using a cyclization condensation catalyst, if necessary, in order to promote the cyclization condensation reaction.
Specific examples of the cyclization condensation catalyst include, for example, methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, trimethyl phosphite, Phosphorous acid monoalkyl ester, dialkyl ester or triester such as triethyl phosphate; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate, lauryl phosphate, stearyl phosphate, phosphoric acid Isostearyl, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, Trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate Phosphoric acid monoalkyl esters and the like, dialkyl ester or trialkyl esters; and the like are.
These may be used alone or in combination of two or more.
The amount of the cyclization condensation catalyst is not particularly limited, but is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 100 parts by mass with respect to 100 parts by mass of the methacrylic resin. 1 part by mass.
There exists a possibility that the reaction rate of a cyclization condensation reaction may not fully improve that the usage-amount is less than 0.01 mass part. On the other hand, when the amount of the catalyst used exceeds 3 parts by mass, the obtained polymer may be colored, or the polymer may be cross-linked to make melt molding difficult.

  The addition timing of the cyclization condensation catalyst is not particularly limited. For example, it may be added at the initial stage of the cyclization condensation reaction, may be added during the reaction, or may be added both. Good.

It is also preferable to perform devolatilization at the same time when the cyclization condensation reaction is performed in the presence of a solvent.
There are no particular limitations on the equipment used when the cyclization condensation reaction and the devolatilization step are performed simultaneously, but a devolatilizer comprising a heat exchanger and a devolatilization tank, an extruder with a vent, and devolatilization are also included. A device in which an apparatus and an extruder are arranged in series is preferable, and a twin screw extruder with a vent is more preferable.

The vented twin screw extruder is preferably a vented extruder having a plurality of vent ports.
The reaction treatment temperature when using an extruder with a vent is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. If the reaction treatment temperature is less than 150 ° C., the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. Conversely, when the reaction treatment temperature exceeds 350 ° C., the obtained polymer may be colored or decomposed.
The degree of vacuum when using an extruder with a vent is preferably 10 to 500 Torr, more preferably 10 to 300 Torr. When the degree of vacuum exceeds 500 Torr, volatile matter may remain easily. Conversely, when the degree of vacuum is less than 10 Torr, industrial implementation may be difficult.

It is also preferable to add an alkaline earth metal and / or amphoteric metal salt of an organic acid during granulation for the purpose of deactivating the remaining cyclization condensation catalyst when performing the cyclization condensation reaction.
As the alkaline earth metal and / or amphoteric metal salt of an organic acid, for example, calcium acetyl acetate, calcium stearate, zinc acetate, zinc octylate, zinc 2-ethylhexylate and the like can be used.

  After passing through the cyclocondensation reaction step, the methacrylic resin is melted and extruded in a strand form from an extruder attached with a porous die, and is cold-cut, air-hot cut, underwater strand-cut, and underwater-cut. Process into pellets.

  The lactonization for forming the lactone ring structural unit described above may be performed after the production of the resin and before the production of the resin composition (described later), and during the production of the resin composition, components other than the resin and the resin It may be performed in combination with melt kneading.

  The methacrylic resin in this embodiment preferably has at least one ring structural unit selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer and a lactone ring structural unit. It is particularly preferable to have a structural unit derived from an N-substituted maleimide monomer from the viewpoint of highly controlling optical properties such as photoelastic coefficient without blending a thermoplastic resin.

-Other thermoplastic resins-
Other thermoplastic resins can be blended with the methacrylic resin of this embodiment for the purpose of adjusting birefringence and improving flexibility without impairing the object of the present invention.
Examples of the other thermoplastic resins include polyacrylates such as polybutyl acrylate; polystyrene, styrene-methyl methacrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene. Styrenic polymers such as block copolymers; and further, for example, JP-A-59-202213, JP-A-63-27516, JP-A-51-129449, JP-A-52-56150 Acrylic rubber particles having a three- to four-layer structure; rubber polymers disclosed in JP-B-60-17406 and JP-A-8-245854; described in International Publication No. 2014-002491 , Methacrylic rubber-containing graph copolymer particles obtained by multistage polymerization; It is.
Among these, from the viewpoint of obtaining good optical properties and mechanical properties, from a composition compatible with a styrene-acrylonitrile copolymer and a methacrylic resin containing a structural unit (X) having a ring structure in the main chain. The rubber-containing graft copolymer particles having a graft portion on the surface layer are preferable.
The average particle diameter of the acrylic rubber particles, the methacrylic rubber-containing graph copolymer particles, and the rubbery polymer described above is a viewpoint of improving the impact strength, optical characteristics, etc. of the film obtained from the composition of the present embodiment. Therefore, it is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm.

  The content of the other thermoplastic resin is preferably 0 to 50 parts by mass, more preferably 0 to 25 parts by mass when the methacrylic resin is 100 parts by mass.

-Additives-
The methacrylic resin according to this embodiment may contain various additives as long as the effects of the present invention are not significantly impaired.
Additives are not particularly limited, but include, for example, inorganic fillers; pigments such as iron oxides; lubricants and release agents such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bisstearamide. Molding agents: Softeners and plasticizers such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, mineral oil, hindered phenolic antioxidants, sulfurous antioxidants, etc. Antioxidants; Hindered amine light stabilizers; Benzotriazole ultraviolet absorbers; Flame retardants; Antistatic agents; Reinforcing agents such as organic fibers, glass fibers, carbon fibers, and metal whiskers; Colorants; Phosphites and phosphonites , Organophosphorus compounds such as phosphate esters; other additives; or these Mixtures thereof, and the like.

  Hereinafter, the contents of the present invention will be specifically described with reference to Examples and Comparative Examples. In addition, this invention is not limited to the following Example.

<1. Measurement of polymerization conversion>
A part of the polymerization solution in Examples and Comparative Examples was collected, and the amount of monomer remaining in this polymerization solution sample was dissolved in chloroform to prepare a 5 mass% solution, and n was used as an internal standard substance. -Decane was added, the concentration of the monomer remaining in the sample was measured using gas chromatography (GC-2010, manufactured by Shimadzu Corporation), and the total mass (a) of the monomer remaining in the polymerization solution was determined. Asked. Then, the total mass (a), the total mass (b) when it is assumed that all of the monomer added up to the time when the sample is taken remain in the polymerization solution, and the single mass added by the end of the polymerization step. From the total mass (c) of the monomer, the polymerization conversion rate (%) was calculated by the calculation formula (ba) / c × 100.

<2. Analysis of structural units>
Unless otherwise specified in each production example described later, the structural unit of the methacrylic resin produced in the production example described later was identified by ¹ H-NMR measurement and ¹³ C-NMR measurement, and the abundance thereof was calculated. The measurement conditions for ¹ H-NMR measurement and ¹³ C-NMR measurement are as follows.
・ Measurement equipment: DPX-400 manufactured by Bruker
Measurement solvent: CDCl ₃ or DMSO-d ₆
・ Measurement temperature: 40 ℃
In addition, when the ring structure of methacrylic resin was a lactone ring structure, it confirmed by the method of Unexamined-Japanese-Patent No. 2001-151814 and Unexamined-Japanese-Patent No. 2007-297620.

<3. Measurement of molecular weight and molecular weight distribution>
The Z-average molecular weight (Mz), weight-average molecular weight (Mw), and number-average molecular weight (Mn) of the methacrylic resin produced in the production examples described later were measured using the following apparatus and conditions.
Measurement device: manufactured by Tosoh Corporation, gel permeation chromatography (HLC-8320GPC)
·Measurement condition:
Column: One TSKguardcolumn SuperH-H, two TSKgel SuperHM-M, and one TSKgel SuperH2500 were connected in series in this order. Column temperature: 40 ° C
Developing solvent: Tetrahydrofuran, Flow rate: 0.6 mL / min, 0.16 g / L of 2,6-di-t-butyl-4-methylphenol (BHT) was added as an internal standard.
Detector: RI (differential refraction) detector, detection sensitivity: 3.0 mV / min Sample: 0.02 g of methacrylic resin or 20 mL of a methacrylic resin in tetrahydrofuran. Injection volume: 10 μL
Standard sample for calibration curve: The following 10 polymethyl methacrylates (manufactured by Polymer Laboratories; PMMAC calibration Kit M-M-10) having different molecular weights but known monodisperse weight peak molecular weights were used.
Weight peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 85,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity with respect to the elution time of the methacrylic resin was measured.
Based on the calibration curve obtained by the measurement of the standard sample for the calibration curve, the Z average molecular weight (Mz), the weight average molecular weight (Mw), and the number average molecular weight (Mn) of the methacrylic resin and the methacrylic resin are obtained. It was.

<4. Glass transition temperature>
Based on JIS-K7121, the glass transition temperature (Tg) (degreeC) of the methacrylic resin was measured.
First, 4 pieces (about 4 places) of about 10 mg each were cut out as test pieces from a sample that was conditioned (left at 23 ° C. for 1 week) under standard conditions (23 ° C., 65% RH).
Next, a differential scanning calorimeter (Diamond DSC manufactured by PerkinElmer Japan Co., Ltd.) was used under the condition of a nitrogen gas flow rate of 25 mL / min, where the temperature rose from room temperature (23 ° C.) to 200 ° C. at 10 ° C./min. Temperature (primary temperature increase), held at 200 ° C. for 5 minutes to completely melt the sample, then cooled to 10 ° C./minute from 200 ° C. to 40 ° C., held at 40 ° C. for 5 minutes, Of the DSC curve drawn during the temperature rise (secondary temperature rise) again under the above temperature rise conditions, the stepwise change partial curve at the time of the secondary temperature rise and the respective base line extension lines are equidistant in the vertical axis direction. The intersection (intermediate glass transition temperature) with a certain straight line was measured as the glass transition temperature (Tg) (° C.). Four points were measured per sample, and the arithmetic average of four points (rounded off after the decimal point) was taken as the measured value.

<5. Measurement of photoelastic coefficient _{C R>}
The methacrylic resin obtained in Examples and Comparative Examples was used as a measurement sample by using a vacuum compression molding machine as a press film.
As specific sample preparation conditions, using a vacuum compression molding machine (manufactured by Shinfuji Metal Industry Co., Ltd., SFV-30 type), preheating at 260 ° C. under reduced pressure (about 10 kPa) for 10 minutes, After compressing at about 10 MPa for 5 minutes and releasing the reduced pressure and the press pressure, it was transferred to a cooling compression molding machine and solidified by cooling. The obtained press film was cured for 24 hours or more in a constant temperature and humidity chamber adjusted to 23 ° C. and a humidity of 60%, and then a test specimen (thickness: about 150 μm, width: 6 mm) was cut out.
The photoelastic coefficient C _R (Pa ⁻¹ ) was measured using a birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357.
The film-shaped test piece was similarly arrange | positioned so that it might become 50 mm between chuck | zippers on the film tension apparatus (made by Imoto Seisakusho) installed in the constant temperature and humidity chamber. Next, the apparatus was arranged so that the laser beam path of the birefringence measuring apparatus (manufactured by Otsuka Electronics, RETS-100) was positioned at the center of the film, and the strain rate was 50% / min (between chucks: 50 mm, chuck moving speed: The birefringence of the test piece was measured while applying an extensional stress at 5 mm / min.
From the relationship between the absolute value of birefringence (| Δn |) and the tensile stress (σ _R ) obtained from the measurement, the slope of the straight line is obtained by least square approximation, and the photoelastic coefficient (C _R ) (Pa ⁻¹ ) is obtained. Calculated. For the calculation, data with an extensional stress between 2.5 MPa ≦ σ _R ≦ 10 MPa was used.
C _R = | Δn | / σ _R
Here, the absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | nx−ny |
(Nx: refractive index in the stretching direction, ny: refractive index in the direction perpendicular to the stretching direction in the plane)

<6. Measurement of the amount of methanol soluble matter and the amount of methanol insoluble matter>
After 5 g of the methacrylic resin obtained in Examples and Comparative Examples was dissolved in 100 mL of chloroform, the solution was put into a dropping funnel and dropped into 1 L of methanol stirred with a stir bar over about 1 hour. Then, reprecipitation was performed. After dropping the whole amount, the mixture was allowed to stand for 1 hour, and then suction filtration was performed using a membrane filter (T050A090C, manufactured by Advantech Toyo Co., Ltd.) as a filter.
The filtrate was vacuum-dried at 60 ° C. for 16 hours to make methanol insoluble. In addition, the filtrate may be left in the eggplant-shaped flask after removing the solvent using a rotary evaporator at a bath temperature of 40 ° C. and gradually lowering the vacuum from the initial setting of 390 Torr to 30 Torr. Soluble was recovered and used as methanol soluble.
Each of the mass of the methanol-insoluble part and the mass of the methanol-soluble part is weighed, and the ratio of the amount of methanol-soluble part to the total amount (100% by mass) of the amount of methanol-soluble part and the amount of methanol-insoluble part (mass) %) (Methanol soluble fraction) was calculated.

<7. Measurement of Yellowness Index (YI) and 680 nm transmittance>
The methanol-insoluble content of the methacrylic resin obtained in the above-mentioned Examples and Comparative Examples is a 20 w / v% chloroform solution (that is, a solution prepared in such a ratio that a 10 g sample is dissolved in chloroform to form a 50 mL solution). And used as a measurement sample. Using a UV-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-2500PC), measuring wavelength 380-780 nm, slit width 2 nm, 10 cm optical path length cell with viewing angle 10 °, auxiliary illuminant C, reference object: chloroform The transmittance was measured.
According to JIS K 7373, using the XYZ color system, the following formula YI = 100 (1.2769X−1.0592Z) / Y
YI (Yellowness Index) was calculated.
Further, the transmittance (%) at a wavelength of 680 nm was also recorded under the same conditions as in the above YI measurement.

<8. Evaluation of film formation of methacrylic resin>
A methacrylic resin obtained in Examples and Comparative Examples described below was dried at 90 ° C. for 24 hours with dehumidified air to reduce the moisture content to 300 ppm by mass or less, and then formed into a film by the following method. Went.
A film was prepared using a 15 mmφ twin-screw extruder (manufactured by Technobel) with a 300-mm wide T-die installed at the tip of the extruder. The film forming conditions at that time were as follows: extruder tip set temperature 260 ° C., T die temperature set 255 ° C., discharge rate 1 kg / hour, cooling roll set temperature: glass transition temperature −10 ° C., and a film with a film thickness of 80 μm. Obtained. After continuously operating for 6 hours under these conditions, a film for evaluation was collected in a length of 1 m.
Then, using a roll that was thoroughly cleaned before the start of film formation, the surface of the roll after 6 hours was visually observed for dirt. "A" means that the roll surface is slightly soiled, and "X" means that the roll surface is completely soiled and needs to be cleaned again.

[material]
It shows below about the raw material used in the Example and comparative example which are mentioned later.
[[Monomer]]
・ Methyl methacrylate: Asahi Kasei Chemicals Corporation ・ N-Phenylmaleimide (phMI): Nippon Shokubai Co., Ltd. ・ N-cyclohexylmaleimide (chMI): Nippon Shokubai Co., Ltd. ・ Styrene: Asahi Kasei Chemicals Corporation Methyl acrylate (MHMA): manufactured by Combi Bloks [[polymerization initiator]]
1,1-di (t-butylperoxy) cyclohexane: NOF Corporation "Perhexa C"
・ 1,1-di (t-hexylperoxy) cyclohexane: “Perhexa HC” manufactured by NOF Corporation
T-Butyl peroxyisopropyl monocarbonate: “Perbutyl I” manufactured by NOF Corporation
T-amyl peroxyisononanoate: “Lupelox 570” manufactured by Arkema Yoshitomi Corporation
T-Butylperoxy-2-ethylhexanoate: NOF Corporation "Perbutyl O"
[[Chain transfer agent]]
・ N-octyl mercaptan: manufactured by Kao Corporation ・ n-dodecyl mercaptan: manufactured by Kao Corporation

[Example 1] Production of methacrylic resin (A) having N-substituted maleimide structural units Methyl methacrylate (hereinafter referred to as MMA) 146.0 kg, N-phenylmaleimide 14.6 kg (hereinafter referred to as phMI), N-cyclohexyl Maleimide (hereinafter referred to as “chMI”) 22.0 kg, chain transfer agent n-octyl mercaptan 0.174 kg, meta-xylene 147.0 kg (hereinafter referred to as “mXy”) are weighed, and equipped with a temperature control device by a jacket and a stirring blade Was added to the 1.25 m ³ reactor and stirred to obtain a mixed monomer solution.
Next, 271.2 kg of MMA, 27.1 kg of phMI, 40.9 kg of chMI, and 273.0 kg of mXy were weighed, added to tank 1 and stirred to obtain a mixed monomer solution for addition.
Further, MMA 58.0 kg was weighed in the tank 2.
Bubbling with nitrogen is performed for 1 hour for the contents of the reactor at a rate of 30 L / min, and bubbling with nitrogen is performed for 30 minutes for each of tank 1 and tank 2 for 10 minutes to remove dissolved oxygen. did.
Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 124 ° C., while stirring at 50 rpm, 0.348 kg of 1,1-di (t-butylperoxy) cyclohexane was dissolved in 4.652 kg of mXy. The polymerization was started by adding the polymerization initiator solution at a rate of 2 kg / hour.
During polymerization, the temperature of the solution in the reactor was controlled at 124 ± 2 ° C. by adjusting the temperature with a jacket. 30 minutes after the start of polymerization, the addition rate of the initiator solution was reduced to 1 kg / hour, and the additional monomer solution for addition was added from tank 1 at 306.1 kg / hour for 2 hours.
Then, 2 hours and 45 minutes after the start of polymerization, MMA was added from tank 2 at a rate of 116 kg / hour over 30 minutes.
Furthermore, the initiator solution decreased the addition rate to 0.5 kg / hour after 3.5 hours of polymerization, 0.25 kg / hour after 4.5 hours, and 0.125 kg / hour after 6 hours, and 7 hours after the start of polymerization. The addition was stopped.
After 10 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.
The 1-hour half-life temperature of 1,1-di (t-butylperoxy) cyclohexane used as an initiator is 111 ° C., the half-life temperature of 1 minute is 154 ° C., and the half-life at 124 ° C. of the polymerization temperature is 16 minutes.
After 4 hours, 6 hours, 8 hours and 10 hours (at the end of polymerization), the polymer solution was sampled, and the polymerization conversion was analyzed from the remaining monomer concentration. It was 84.8% after 4 hours, 93.3% after 6 hours, 95.7% after 8 hours, and 96.0% after 10 hours.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass.
The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized.
At this time, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. Thus, a methacrylic resin (A) having an N-substituted maleimide structural unit was obtained.
As a result of confirming the composition of the obtained pellet-like polymer, the structural units derived from MMA, phMI, and chMI monomers were 81.3 mass%, 7.9 mass%, and 10.8 mass%, respectively. there were. Moreover, the weight average molecular weight was 141,000, Mz / Mw was 1.54, and Mw / Mn was 1.94. Other physical properties are shown in Table 2.

[Example 2] Production of methacrylic resin (B) having N-substituted maleimide structural unit MMA 176.2 kg, phMI 6.0 kg, chMI 10.3 kg, chain transfer agent n-octyl mercaptan 0.168 kg, mXy 153.7 kg Were weighed and added to a 1.25 m ³ reactor equipped with a temperature control device using a jacket and a stirring blade to obtain a mixed monomer solution.
Next, MMA 327.1 kg, phMI 11.2 kg, chMI 19.2 kg, mXy 285.3 kg were weighed and added to tank 1 and stirred to obtain a mixed monomer solution for addition.
Furthermore, 11.0 kg of styrene was weighed in the tank 2. Bubbling with nitrogen is performed for 1 hour for the contents of the reactor at a rate of 30 L / min, and bubbling with nitrogen is performed for 30 minutes for each of tank 1 and tank 2 for 10 minutes to remove dissolved oxygen. did.
Thereafter, steam was blown into the jacket to raise the solution temperature in the reactor to 124 ° C., and 0.337 kg of 1,1-di (t-hexylperoxy) cyclohexane was dissolved in 4.663 kg of mXy while stirring at 50 rpm. The polymerization was started by adding the polymerization initiator solution at a rate of 2 kg / hour.
During polymerization, the temperature of the solution in the reactor was controlled at 124 ± 2 ° C. by adjusting the temperature with a jacket. 30 minutes after the start of polymerization, the addition rate of the initiator solution was reduced to 1 kg / hour, and the additional monomer solution for addition was added at 257.1 kg / hour from tank 1 for 2.5 hours.
Next, 3 hours and 30 minutes after the start of polymerization, styrene was added from tank 2 at a rate of 44 kg / hour over 15 minutes.
Furthermore, the initiator solution decreased the addition rate to 0.5 kg / hour after 3.5 hours of polymerization, 0.25 kg / hour after 4.5 hours, and 0.125 kg / hour after 6 hours, and 7 hours after the start of polymerization. The addition was stopped.
After 10 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.
The 1-hour half-life temperature of 1-di (t-hexylperoxy) cyclohexane used as the initiator is 107 ° C., the 1-minute half-life temperature is 149 ° C., and the half-life at a polymerization temperature of 124 ° C. is 11 Minutes.
After 4 hours, 6 hours, 8 hours and 10 hours (at the end of polymerization), the polymer solution was sampled, and the polymerization conversion was analyzed from the remaining monomer concentration. It was 84.5% after 4 hours, 92.2% after 6 hours, 95.2% after 8 hours, and 95.5% after 10 hours.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass. The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized.
At this time, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. Thus, a methacrylic resin (B) having an N-substituted maleimide structural unit was obtained.
When the composition of the obtained pellet-like polymer was confirmed, the structural units derived from MMA, phMI, chMI, and styrene monomers were 89.8% by mass, 3.5% by mass, and 5.1% by mass, respectively. %, 1.6% by mass. Moreover, the weight average molecular weight was 133,000, Mz / Mw was 1.58, and Mw / Mn was 2.07. Other physical properties are shown in Table 2.

[Example 3] Production of methacrylic resin (C) having N-substituted maleimide structural unit MMA 500 kg, phMI 39.6 kg, chMI 10.4 kg, chain transfer agent n-octyl mercaptan 0.275 kg, mXy 450 kg, The mixture was added to a 1.25 m ³ reactor equipped with a temperature controller using a jacket and a stirring blade, and stirred to obtain a mixed monomer solution.
Nitrogen was bubbled through the solution in the reactor at a rate of 30 L / min for 1 hour to remove dissolved oxygen. Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 120 ° C, and while stirring at 50 rpm, 0.175 kg of 1,1-di (t-butylperoxy) cyclohexane was dissolved in 3.000 kg of mXy. Polymerization was started by adding the polymerization initiator solution at a rate of 1.5 kg / hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 120 ± 2 ° C. by adjusting the temperature with a jacket. 30 minutes after the start of the polymerization, the addition rate of the initiator solution is decreased to 0.75 kg / hour, then the addition rate is decreased to 0.5 kg / hour 2 hours after the start of polymerization and 0.2 kg / hour after 3 hours. The addition was stopped 7 hours after the start of polymerization.
After 10 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.
The 1-hour half-life temperature of 1,1-di (t-butylperoxy) cyclohexane used as the initiator is 111 ° C., the half-life temperature of 1 minute is 154 ° C., and the half-life at 120 ° C. of the polymerization temperature is 24 minutes.
Sampling of the polymer solution was performed at 5 hours, 8 hours and 10 hours (at the end of the polymerization), respectively, and the polymerization conversion was analyzed from the remaining monomer concentration. It was 85.0%, 93 hours after 8 hours, and 94.0% after 10 hours.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass.
The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized.
At this time, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. Thus, a methacrylic resin (C) having an N-substituted maleimide structural unit was obtained.
As a result of confirming the composition of the obtained pellet-like polymer, the structural units derived from MMA, phMI, and chMI monomers were 91.1% by mass, 7.3% by mass, and 1.6% by mass, respectively. there were. Moreover, the weight average molecular weight was 151,000, Mz / Mw was 1.75, and Mw / Mn was 2.29. Other physical properties are shown in Table 2.

[Example 4] Production of methacrylic resin (D) having N-substituted maleimide structural unit MMA 112.5 kg, phMI 12.5 kg, chain transfer agent n-octyl mercaptan 0.50 kg, toluene 125 kg were weighed, jacket Were added to a 1.25 m ³ reactor equipped with a temperature control device and a stirring blade to obtain a mixed monomer solution. Next, 337.5 kg of MMA, 37.5 kg of phMI, and 375 kg of toluene were weighed, added to tank 1 and stirred to obtain a mixed monomer solution for addition.
Bubbling with nitrogen was performed for 1 hour for the content liquid in the reactor at a rate of 30 L / min, and bubbling with nitrogen was performed for 30 minutes for the content liquid in the tank 1 at a rate of 10 L / min to remove dissolved oxygen.
Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 110 ° C., and a polymerization initiator solution in which 0.5 kg of t-butylperoxyisopropyl monocarbonate was dissolved in 1 kg of toluene while stirring at 50 rpm. Polymerization was started by addition. Further, a polymerization initiator solution prepared by dissolving 0.75 kg of t-butylperoxyisopropyl monocarbonate in 1.5 kg of toluene was added at a constant speed for 1 hour.
During the polymerization, the temperature of the solution in the reactor was controlled at 110 ± 2 ° C. by adjusting the temperature with a jacket. After 12 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.
The 1-hour half-life temperature of t-butylperoxyisopropyl monocarbonate used as an initiator is 118 ° C., and the half-life at 110 ° C. of the polymerization temperature is 153 minutes. The polymer solution was sampled at 5.5 hours, 7 hours, 10 hours and 12 hours (at the end of polymerization) after the start of the polymerization, and the polymerization conversion rate was analyzed from the remaining monomer concentration. However, it was 84.2% after 5.5 hours, 90.0% after 7 hours, 95% after 10 hours, and 97.3% after 12 hours.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass.
The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized. At this time, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. Thus, a methacrylic resin (D) having an N-substituted maleimide structural unit was obtained.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from MMA and phMI monomers were 90.1% by mass and 9.9% by mass, respectively. Moreover, the weight average molecular weight was 145,000, Mz / Mw was 1.65, and Mw / Mn was 2.16. Other physical properties are shown in Table 2.

[Example 5]: Production of methacrylic resin (E) having a lactone ring structural unit Methacrylic acid was added to an autoclave equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen gas introduction pipe, the interior of which was previously substituted with nitrogen. 20 parts by mass of methyl, 5 parts by mass of methyl 2- (hydroxymethyl) acrylate, 25 parts by mass of toluene, and 0.025 part by mass of tris (2,4-di-t-butylphenyl) phosphite as an organic phosphorus compound were charged. .
Thereafter, the temperature was raised to 100 ° C. while introducing nitrogen gas, and 0.05 parts by mass of t-amylperoxyisonononanoate as a polymerization initiator was added at the same time. The dropping of the toluene solution containing parts by mass was started, and while dropping this over 1.5 hours, solution polymerization was performed at about 105 to 110 ° C. under reflux, and the polymerization was further continued for 5.5 hours. Further, 20 parts by mass of methyl methacrylate, 5 parts by mass of methyl 2- (hydroxymethyl) acrylate, and 25 parts by mass of toluene were added at a constant rate over 2 hours after 30 minutes from the start of polymerization.
To the obtained polymer solution, 0.05 part by mass of a stearyl phosphate / distearyl phosphate mixture, which is an organophosphorus compound, is added as a cyclization catalyst, and the cyclization condensation is performed at about 90 to 102 ° C. for 2 hours under reflux. Reaction was performed.
The 1-hour half-life temperature of t-amylperoxyisononanoate used as an initiator is 114 ° C., the half-life at 110 ° C. of the polymerization temperature is 101 minutes, and the half-life at 105 ° C. is 180 minutes. The polymer solution was sampled 4 hours and 7.5 hours after the start of polymerization, and the polymerization conversion rate was analyzed from the remaining monomer concentration. It was 94.8% after time. The time average of the polymerization temperature from 0 hour to 7.5 hours after the start of polymerization was 105 ° C.
Next, the obtained polymer solution is heated to 240 ° C. with a heater composed of a multitubular heat exchanger, and a biaxial shaft equipped with a plurality of vent ports and a plurality of downstream side feed ports for devolatilization. By introducing into an extruder, the cyclization reaction was allowed to proceed while devolatilization.
In the twin screw extruder, the obtained copolymer solution was supplied so as to be 15 kg / hour in terms of resin, and the conditions were a barrel temperature of 250 ° C., a rotation speed of 100 rpm, and a vacuum degree of 10 to 300 Torr.
The resin composition melt-kneaded with a twin screw extruder was extruded from a strand die, cooled with water, and pelletized to obtain a resin composition.
When the composition of the obtained resin composition was confirmed, the content of the lactone ring structural unit was 32.8% by mass. About content of the lactone ring structural unit, it calculated | required according to the method of Unexamined-Japanese-Patent No. 2007-297620. Moreover, the weight average molecular weight of the obtained resin composition was 124,000, Mz / Mw was 1.62, and Mw / Mn was 2.13. Other physical properties are shown in Table 2.

[Comparative Example 1] Production of methacrylic resin (F) having N-substituted maleimide structural unit MMA 445.5 kg, phMI 44.0 kg, chMI 60.5 kg, chain transfer agent n-octyl mercaptan 0.55 kg, mXy 450 kg Then, the mixture was added to a 1.25 m ³ reactor equipped with a temperature controller using a jacket and a stirring blade, and stirred to obtain a mixed monomer solution.
Nitrogen was bubbled through the solution in the reactor at a rate of 30 L / min for 1 hour to remove dissolved oxygen. Thereafter, steam was blown into the jacket to raise the solution temperature in the reactor to 130 ° C., and 1.10 kg of t-butylperoxy-2-ethylhexanoate was dissolved in 4.9 kg of mXy while stirring at 50 rpm. Polymerization was initiated by adding a polymerization initiator solution at a rate of 1 kg / hour for 6 hours.
During the polymerization, the temperature of the solution in the reactor was controlled at 130 ± 2 ° C. by adjusting the temperature with a jacket. After 8 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained. The 1-hour half-life temperature of t-butylperoxy-2-ethylhexanoate used as an initiator is 92 ° C., the 1-minute half-life temperature is 134 ° C., and the half-life at 130 ° C. of the polymerization temperature is 1. .4 minutes. After 3.3 hours, 6 hours and 8 hours (at the end of the polymerization), the polymer solution was sampled and the polymerization conversion was analyzed from the remaining monomer concentration. It was 84.9% after 3 hours, 96.7% after 6 hours, and 96.8% after 8 hours.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass. The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized. At this time, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. Thus, a methacrylic resin (F) having an N-substituted maleimide structural unit was obtained.
When the composition of the obtained pellet-like polymer was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.7% by mass, and 11% by mass, respectively. It was. Moreover, the weight average molecular weight was 143,000, Mz / Mw was 1.85, and Mw / Mn was 2.75. Other physical properties are shown in Table 2.

[Comparative Example 2] Production of methacrylic resin (G) having N-substituted maleimide structural unit MMA 450.0 kg, phMI 50.0 kg, chain transfer agent n-dodecyl mercaptan 0.50 kg, toluene 500 kg were weighed, jacket Were added to a 1.25 m ³ reactor equipped with a temperature control device and a stirring blade to obtain a mixed monomer solution.
Nitrogen was bubbled through the solution in the reactor at a rate of 30 L / min for 1 hour to remove dissolved oxygen. Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 110 ° C., and 1.50 kg of t-butylperoxyisopropyl monocarbonate was dissolved in 4.5 kg of toluene while stirring at 50 rpm. Polymerization was initiated by adding the solution into the reactor.
During the polymerization, the temperature of the solution in the reactor was controlled at 110 ± 2 ° C. by adjusting the temperature with a jacket. After 12 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.
The 1-hour half-life temperature of t-butylperoxyisopropyl monocarbonate used as an initiator is 118 ° C., and the half-life at 110 ° C. of the polymerization temperature is 153 minutes.
After 4 hours, 8 hours, and 12 hours (at the end of polymerization), the polymer solution was sampled and the polymerization conversion was analyzed from the remaining monomer concentration. It was 90.4%, 96.5% after 6 hours, and 98.0% after 8 hours.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass.
The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized. At this time, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. Thus, a methacrylic resin (G) having an N-substituted maleimide structural unit was obtained.
When the composition of the obtained pellet-shaped polymer was confirmed, the structural units derived from the MMA and phMI monomers were 90.3% by mass and 9.7% by mass, respectively. Moreover, the weight average molecular weight was 155,000, Mz / Mw was 1.82, and Mw / Mn was 2.63. Other physical properties are shown in Table 2.

[Comparative Example 3] Production of methacrylic resin (H) having N-substituted maleimide structural units MMA 140.0 kg, chMI 100.0 kg, toluene 250 kg were weighed and 1.25 m ³ equipped with a temperature control device by a jacket and a stirring blade. The mixture was added to the reactor and stirred to obtain a mixed monomer solution.
Next, 82.5 kg of MMA, 25.0 kg of chMI, 35.0 kg of styrene, and 200.0 kg of toluene were weighed and added to the tank 1 and stirred to obtain a mixed monomer solution for addition.
Further, 82.5 kg of MMA, 35.0 kg of styrene, and 50.0 kg of toluene were weighed and added to the tank 2 and stirred to obtain a mixed monomer solution for addition.
The reactor liquid was bubbled with nitrogen at a rate of 30 L / min for 1 hour, and the inner solution of each of tank 1 and tank 2 was bubbled with nitrogen at a rate of 10 L / min for 30 minutes. Was removed.
Thereafter, steam was blown into the jacket to raise the temperature of the solution in the reactor to 110 ° C., and a polymerization initiator in which 0.20 kg of t-butylperoxyisopropyl monocarbonate was dissolved in 0.8 kg of toluene while stirring at 50 rpm. Polymerization is started by adding the solution into the reactor, and a polymerization initiator solution in which 2.30 kg of t-butylperoxyisopropyl monocarbonate is dissolved in 4.70 kg of toluene is added at a rate of 3.5 kg at a rate of 2 kg / hour. Added for hours.
Further, the content liquid in tank 1 was added at a constant rate for 3.5 hours after the start of polymerization, and then the content liquid in tank 2 was added at a constant rate for 3.5 hours thereafter.
During the polymerization, the temperature of the solution in the reactor was controlled at 110 ± 2 ° C. by adjusting the temperature with a jacket. After 10 hours from the start of polymerization, a polymerization solution containing a methacrylic resin having a ring structure in the main chain was obtained.
The 1-hour half-life temperature of t-butylperoxyisopropyl monocarbonate used as an initiator is 118 ° C., and the half-life at 110 ° C. of the polymerization temperature is 153 minutes.
The polymer solution was sampled 7 hours after the start of the polymerization and 10 hours after the end of the polymerization (at the end of the polymerization), and the polymerization conversion rate was analyzed from the remaining monomer concentration. After 10 hours, it was 97.3%.
This polymerization solution was supplied to a concentrating device consisting of a tubular heat exchanger and a vaporization tank preliminarily heated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass.
The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² and devolatilized. In this case, the temperature inside the apparatus was 280 ° C., the supply amount was 30 L / hr, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr. The polymer after devolatilization was pressurized with a gear pump, extruded from a strand die, cooled with water, and pelletized. Thus, a methacrylic resin (H) having an N-substituted maleimide structural unit was obtained.
When the composition of the obtained pellet-like polymer was confirmed, the structural units derived from MMA, chMI and styrene monomers were 60.3% by mass, 25.5% by mass and 14.2% by mass, respectively. there were. Moreover, the weight average molecular weight was 102,000, Mz / Mw was 1.90, and Mw / Mn was 2.84. Other physical properties are shown in Table 2.

[Comparative Example 4]: Production of methacrylic resin (I) having a lactone ring structural unit Methacrylic acid was added to an autoclave equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen gas introduction pipe. 40 parts by mass of methyl, 10 parts by mass of methyl 2- (hydroxymethyl) acrylate, 50 parts by mass of toluene, and 0.025 part by mass of tris (2,4-di-t-butylphenyl) phosphite as an organophosphorus compound were charged. .
Thereafter, while introducing nitrogen gas, the temperature was raised to 100 ° C., and 0.05 parts by mass of t-amylperoxyisonononanoate was added as a polymerization initiator, and at the same time, t-amylperoxyisonononate 0.1%. Dropping of the toluene solution containing parts by mass was started, and solution polymerization was performed at about 105 to 110 ° C. under reflux while dripping this over 2 hours, and the polymerization was further continued for 4 hours.
To the obtained polymer solution, 0.05 part by mass of a stearyl phosphate / distearyl phosphate mixture, which is an organophosphorus compound, is added as a cyclization catalyst, and the cyclization condensation is performed at about 90 to 102 ° C. for 2 hours under reflux. Reaction was performed.
The 1-hour half-life temperature of t-amylperoxyisononanoate used as an initiator is 114 ° C., the half-life at 110 ° C. of the polymerization temperature is 101 minutes, and the half-life at 105 ° C. is 180 minutes.
The polymer solution was sampled 4 hours and 6 hours after the start of the polymerization, and the polymerization conversion rate was analyzed from the remaining monomer concentration. As a result, 89.8% after 4 hours and 95 after 6 hours. 2%.
Next, the obtained polymer solution is heated to 240 ° C. with a heater composed of a multitubular heat exchanger, and a biaxial shaft equipped with a plurality of vent ports and a plurality of downstream side feed ports for devolatilization. By introducing into an extruder, the cyclization reaction was allowed to proceed while devolatilization.
In the twin screw extruder, the obtained copolymer solution was supplied so as to be 15 kg / hour in terms of resin, and the conditions were a barrel temperature of 250 ° C., a rotation speed of 100 rpm, and a vacuum degree of 10 to 300 Torr.
The resin composition melt-kneaded with a twin screw extruder was extruded from a strand die, cooled with water, and pelletized to obtain a resin composition.
When the composition of the obtained resin composition was confirmed, the content of the lactone ring structural unit was 31.5% by mass. About content of the lactone ring structural unit, it calculated | required according to the method of Unexamined-Japanese-Patent No. 2007-297620. Moreover, the weight average molecular weight of the obtained resin composition was 121,000, Mz / Mw was 1.78, and Mw / Mn was 2.52. Other physical properties are shown in Table 2.

The methacrylic resin of the present invention has high heat resistance, highly controlled birefringence, excellent color tone and transparency, and excellent moldability.
The methacrylic resin of the present invention is an optical material, for example, a polarizing plate protective film used for displays such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, rear projection televisions, etc .; / Retardation plates such as two-wavelength plates; liquid crystal optical compensation films such as viewing angle control films; display front plates; display substrates; lenses; transparent substrates used in solar cells, transparent conductive substrates such as touch panels; In the field of optical switching systems and optical measurement systems, it can be suitably used as waveguides, lenses, lens arrays, optical fibers, optical fiber coating materials; LED lenses;

Claims (8)

Look-containing structural unit (B) having a ring structure in its main chain, (B) the structural unit, the group consisting of N- substituted maleimide structural unit (B-1), and a lactone ring structure unit (B-2) It is more including methacrylic resin at least one structural unit selected,
The glass transition temperature is over 120 ° C. and below 160 ° C.,
The amount of methanol-soluble component of the methacrylic resin is 5% by mass or less with respect to 100% by mass of the total amount of methanol-soluble component and methanol-insoluble component,
The yellowness index (YI) measured using a 10 cm optical path length cell for a 20 w / v% chloroform solution of the methanol insoluble matter is 0 to 7,
A methacrylic resin characterized by that.   2. The methacrylic resin according to claim 1, wherein a 20 w / v% chloroform solution insoluble in methanol has a transmittance at 680 nm of 90% or more measured using a 10 cm optical path length cell.   The methacrylic resin according to claim 1 or 2, wherein the methacrylic resin contains 50 to 97% by mass of the methacrylic acid ester monomer unit (A) based on 100% by mass of the methacrylic resin.   The methacrylic resin is 100% by mass of the methacrylic resin, the structural unit (B) having a ring structure in the main chain: 3 to 30% by mass, and other vinyls copolymerizable with the methacrylic acid ester monomer The methacrylic resin according to any one of claims 1 to 3, comprising a monomeric unit (C): 0 to 20% by mass.   The content of the (B) structural unit is 45 to 100% by mass, where the total amount of the (B) structural unit and the (C) monomer unit is 100% by mass. The methacrylic resin according to any one of the above. The (C) monomer unit includes at least one structural unit selected from the group consisting of an acrylate monomer, an aromatic vinyl monomer, and a vinyl cyanide monomer. The methacrylic resin according to any one of 5 . The methacrylic resin according to any one of claims 1 to 6 , wherein the photoelastic coefficient is -2 × 10 ^-12 to + 2 × 10 ^-12 Pa ^-1 . The ratio of Z-average molecular weight measured by gel permeation chromatography (GPC) and (Mz) weight average molecular weight (Mw) (Mz / Mw) is 1.3 to 2.0, of claims 1 to 7 The methacrylic resin according to any one of the above.