JP2017145410A - Methacrylic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a methacrylic resin composition which is excellent in birefringence, is less likely to contaminate a mold surface during molding, and gives a molded article excellent in appearance.PROBLEM TO BE SOLVED: The methacrylic resin composition of the present invention contains: a methacrylic resin containing a structural unit (X) having a ring structure in the main chain, the structural unit (X) being at least one selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide-based structural unit, and a lactone ring structural unit; and an organophosphorus compound. The glass transition temperature of the methacrylic resin composition is higher than 120°C and equal to or lower than 160°C. In the methacrylic resin composition, the content of phosphorus element is 143-1,000 mass ppm and the content of a hindered phenol compound having a molecular weight of less than 300 is 5-120 mass ppm.SELECTED DRAWING: None

Description

  The present invention relates to a methacrylic resin composition.

  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, a methacrylic resin having a ring structure in the main chain and a composition containing the methacrylic resin are known to have excellent performance in both heat resistance and optical properties. Demand is expanding rapidly. However, when a methacrylic resin having a ring structure in the main chain with improved heat resistance and optical properties as described above is heated and melted and processed into a film or other molded article to obtain a member for optical applications Because of its high glass transition temperature, there is a drawback that it is forced to be melt-processed at a relatively high temperature and is liable to undergo thermal decomposition. Also, in recent years, as demand grows and demands for higher quality progress, it is easy to generate heat with a higher discharge rate and various filters attached for the purpose of removing foreign matter, and the residence time is compared. Increasingly, melt molding using long and large extruders is increasing. Providing a methacrylic resin excellent in optical properties and heat resistance and a composition containing the same, which is excellent in molding process stability and can provide a member with higher quality for optical applications even under such severe molding conditions. Expected.

  Conventionally, specific phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants have been added to methacrylic resins for the purpose of improving the thermal stability of methacrylic resins and suppressing color change associated with heat melting. Many compositions containing at least one antioxidant selected from antioxidants such as agents, and molded articles and films using the same are known.

  In addition to the above-mentioned purpose, a methacrylic resin having a ring structure in the main chain and a high glass transition temperature and a composition containing the methacrylic resin are mainly used for suppressing the coloring of the polymerization product and for the cyclization reaction. At the time of adopting a production method that introduces a ring structure into the chain, attempts to formulate organophosphorus compounds containing phosphorus antioxidants as stabilizers for cyclization catalysts and intermolecular crosslinking inhibition, and production of the resin composition Attempts to improve the thermal stability by adding the antioxidant in any of the steps for achieving this are in progress.

  For example, in Patent Document 1, a composition containing a maleimide monomer in an amount of 10% by weight or more and a compound having a phosphorus atom in an amount of 0.001 to 1% by weight with respect to all monomers is a long time at a high temperature. It has been proposed that high transparency can be achieved without yellowing even when exposed.

  In Patent Document 2, methyl methacrylate 10 to 70% by weight, N-substituted maleimide 5 to 30% by weight, cyclohexyl methacrylate 15 to 85% by weight, and other copolymerizable monomers 0 to 30%. A resin composition containing a hindered amine light stabilizer, a hindered phenolic antioxidant, and a phosphite antioxidant has been proposed for a copolymer consisting of% by weight. In addition, it has been proposed to obtain a molded article excellent in heat resistance and low birefringence, having little coloration during molding and less coloring under a high temperature atmosphere (around 100 ° C.).

  Moreover, in patent document 3, when superposing | polymerizing the monomer which can be radically polymerized containing N-substituted maleimide, at least 1 sort (s) of antioxidant chosen from the group which consists of a phenolic antioxidant and phosphorus antioxidant By using this method, a part of the monomer component is allowed to coexist during the polymerization of the monomer component, and the remaining antioxidant is added after the polymerization of the monomer component is completed. A manufacturing method has been proposed.

  Furthermore, in Patent Document 4, a monomer mixture containing, as a component, a methacrylic acid ester or acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms, methyl methacrylate, and a monomer having a maleimide structure. By including a specific compound having a hindered phenol skeleton, particularly a compound having a molecular weight of 600 or more, in a resin obtained by polymerizing a polymer, the transmittance change is small even when exposed to ultraviolet rays having a wavelength of 350 to 410 nm for a long time. Optical elements have been proposed.

  Further, in Patent Document 5, an antioxidant such as a phosphorus antioxidant is added to a resin composition containing a methacrylic resin having a ring structure in the main chain and elastic organic fine particles having a conjugated diene monomer structural unit as an essential component. A method for improving the stability of the optical properties of a retardation film obtained by molding has been proposed. At that time, the antioxidant may be mixed together when mixing the methacrylic resin and the elastic organic fine particles, specifically, kneaded by a twin screw extruder, or may be contained in the methacrylic resin or elastic organic. It is said that the fine particles may be mixed together with their constituent monomer components at the time of preparation of the fine particles.

JP-A-6-116331 JP-A-8-217944 JP 10-45850 A JP 2006-188623 A JP 2013-83907 A

  In recent years, methacrylic resins having a ring structure in the main chain have been studied for wide use not only as optical films but also for light guide plates and injection molding applications. With increasing demand, there is a tendency to increase the number of cases where melt processing is performed under conditions of high temperature molding or a long molding cycle time, but even higher demands for molded product quality are required. For example, even when a methacrylic resin composition having a high glass transition temperature and excellent optical properties is used for injection molding, a new proposal that can reduce streaks and silver streaks appearing on the surface of the molded product is expected. Yes. However, in the proposals found in the prior literature, for example, a sufficient effect cannot be obtained for solving problems such as contamination of the mold surface in injection molding and streaks and silver streaks generated on the surface of the obtained molded product. There is a present situation.

  Accordingly, an object of the present invention is to provide a methacrylic resin composition that is excellent in birefringence, hardly contaminates the mold surface during molding, and provides a molded product having an excellent appearance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have a relatively high glass transition temperature and a methacrylic resin composition containing an antioxidant such as a phosphorus-based antioxidant. In the above, the decomposition of the antioxidant described above generates a highly volatile product that does not contain phosphorus element, and this decomposition product causes defects such as mold contamination during molding and streaks on the surface of the molded product. It turned out to be conducive.

  As a result of further earnest studies, the present inventors have found that in a methacrylic resin composition containing an organic phosphorus compound in its composition and having a relatively high glass transition temperature, the content of phosphorus element and less than a specific molecular weight. The inventors have found that the above problem can be solved by controlling the amount of a decomposition product having a hindered phenol structural unit not containing a certain phosphorus element, and have completed the present invention.

That is, the present invention is as follows.
[1]
The structural unit (X) includes a structural unit (X) having a ring structure in the main chain, and the structural unit (X) is composed of a structural unit derived from an N-substituted maleimide monomer, a glutarimide-based structural unit, and a lactone ring structural unit. Including at least one selected methacrylic resin and an organophosphorus compound,
The glass transition temperature is over 120 ° C. and below 160 ° C.,
The phosphorus element content is 143 to 1000 ppm by mass,
The content of a hindered phenol compound having a molecular weight of less than 300 is 5 to 120 mass ppm or less, and a methacrylic resin composition.

[2]
The methacrylic resin composition according to [1], wherein the organic phosphorus compound includes an organic phosphorus compound having a trivalent phosphorus element.

[3]
The methacrylic resin composition according to [1] or [2], wherein the polymethyl methacrylate-converted weight average molecular weight (Mw) measured by GPC measurement method is 80,000 to 170,000.

[4]
The R value of the following formula derived from the weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) in terms of polymethyl methacrylate measured by GPC is 1.0 to 1.5. The methacrylic resin composition according to any one of [1] to [3], which is a range.
R value = [Mw / Mn] / [Mz / Mw]

[5]
The methacrylic resin composition according to any one of [1] to [4], wherein the absolute value of the photoelastic coefficient is 3.0 × 10 ⁻¹² Pa ⁻¹ or less.

[6]
The methacrylic resin composition according to [5], wherein the absolute value of the photoelastic coefficient is 1.0 × 10 ⁻¹² Pa ⁻¹ or less.

  ADVANTAGE OF THE INVENTION According to this invention, the methacrylic resin composition which is excellent in birefringence, cannot contaminate the metal mold surface at the time of shaping | molding, and can obtain the molded article excellent in an external appearance 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 composition)
The methacrylic resin composition of this embodiment contains a methacrylic resin and an organic phosphorus compound, and if necessary, contains other thermoplastic resins and additives. In the methacrylic resin composition of the present embodiment, the content of a hindered phenol compound having a molecular weight of less than 300 is 300 ppm by mass or less.

-Methacrylic resin-
The methacrylic resin in this embodiment is a structural unit having at least one ring structure selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer, a glutarimide structural unit, and a lactone ring structural unit in the main chain. (X) and a structural unit derived from a methacrylic acid ester monomer.

  Hereinafter, each monomer structural unit will be described.

-Structural unit derived from methacrylic acid ester monomer-
First, a structural unit derived from a methacrylic acid ester monomer will be described.
The structural unit derived from a methacrylic acid ester monomer is formed from, for example, a monomer selected from the following methacrylic acid esters.
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 derived from a methacrylic acid ester monomer may contain only 1 type, or may contain 2 or more types.

  Hereinafter, the structural unit (X) in the methacrylic resin including the structural unit (X) having a ring structure in the main chain will be described in particular.

-Structural unit derived from N-substituted maleimide monomer-
Next, the structural unit derived from the N-substituted maleimide monomer will be described.

  The structural unit derived from the N-substituted maleimide monomer may be at least one selected from a monomer represented by the following formula (1) and / or a monomer represented by the following formula (2), Preferably, it is 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。

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.

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 formula (1) to the content (B2) of the structural unit derived from the monomer represented by 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. Expresses photoelastic properties.

  The content of the structural unit 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 the methacrylic resin is 100% by mass. , Preferably it is the range of 5-40 mass%, More preferably, it is the range of 5-35 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 unreacted monomer. This is effective in preventing deterioration in physical properties of the methacrylic resin.

The methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the present embodiment can be copolymerized with a methacrylic acid ester monomer and an N-substituted maleimide monomer as long as the object of the present invention is not impaired. It may contain structural units derived from other monomers.
For example, other copolymerizable monomers include aromatic vinyl; unsaturated nitrile; cyclohexyl group, benzyl group, or acrylate ester having an alkyl group having 1 to 18 carbon atoms; glycidyl compound; unsaturated carboxylic acid Etc. Examples of the aromatic vinyl include styrene, α-methylstyrene, divinylbenzene, and the like. Examples of the unsaturated nitrile include acrylonitrile, methacrylonitrile, ethacrylonitrile and the like. Examples of the acrylate ester include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, and butyl acrylate. Examples of the glycidyl compound include glycidyl (meth) acrylate and allyl glycidyl ether. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and half-esterified products or anhydrides thereof.
The structural unit derived from the other copolymerizable monomer may have only one type, or may have two or more types.

The content of structural units derived from these other copolymerizable monomers is preferably 0 to 20% by mass, preferably 0.1 to 15% by mass, based on 100% by mass of the methacrylic resin. Is more preferable, and it is still more preferable that it is 0.1-10 mass%.
When the content of the structural unit derived from another monomer is within this range, it is preferable because the processability and mechanical properties of the resin can be improved without impairing the original effect of introducing a ring structure into the main chain.

As a method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer in the main chain, any polymerization method of bulk polymerization, solution polymerization, suspension polymerization, precipitation polymerization, and emulsion polymerization Preferred are bulk polymerization and solution polymerization, and more preferred is solution polymerization.
In the production method in the present embodiment, for example, any of a batch polymerization method and a continuous polymerization method can be used as the polymerization format.
In the production method in the present embodiment, it is preferable to polymerize the monomer by radical polymerization.

  Hereinafter, as an example of a method for producing a methacrylic resin having a structural unit derived from an N-substituted maleimide monomer (hereinafter, sometimes referred to as “maleimide copolymer”), a radical is produced in a batch manner using a solution polymerization method. The case of producing by polymerization will be specifically described.

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 solvent at the time of polymerization is not particularly limited as long as the polymerization proceeds and the copolymer or used monomer does not precipitate 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 50 to 200 ° C., more preferably 80 to 200 ° C. from the viewpoint of productivity. More preferably, it is 90-200 degreeC, More preferably, it is 100-180 degreeC, More preferably, it is 110-170 degreeC.

  Further, the polymerization time is not particularly limited as long as the required degree of polymerization can be obtained at the required conversion rate, but it is 0.5 to 10 hours from the viewpoint of productivity and the like. Preferably, it is 1 to 8 hours.

  During the polymerization reaction, polymerization may be performed by adding a polymerization initiator or a chain transfer agent as necessary.

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.

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.

  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. When this temperature is 150 ° C. or higher, it is effective to prevent the residual volatile matter from increasing. On the contrary, when this temperature is 350 ° C. or lower, there is little possibility that coloring or decomposition of the resulting methacrylic resin occurs.
The degree of vacuum in the devolatilizer may be in the range of 10 to 500 Torr, and in particular, the range of 10 to 300 Torr is preferable. When the degree of vacuum is 500 Torr or less, volatile components tend not to remain, and when the degree of vacuum is 10 Torr or more, industrial implementation is easier.
The treatment time is appropriately selected depending on the amount of residual volatile matter, but is preferably as short as possible in order to suppress coloring and decomposition of the resulting methacrylic 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.

上記一般式（３）において、好ましくはＲ^７及びＲ^８は、それぞれ独立して、水素又はメチル基であり、Ｒ^９は、水素、メチル基、ブチル基、シクロヘキシル基のいずれかであり、より好ましくは、Ｒ^７は、メチル基であり、Ｒ^８は、水素であり、Ｒ^９は、メチル基である。 --Glutarimide structural unit--
For example, methacrylic resins having glutarimide-based structural units in the main chain are disclosed in JP-A-2006-249202, JP-A-2007-009182, JP-A-2007-009191, JP-A-2011-186482, It is a methacrylic resin having a glutarimide-based structural unit described in Japanese Patent Publication No. 2012/114718, and can be formed by the method described in the publication.
The glutarimide-based structural unit constituting the methacrylic resin of this embodiment may be formed after resin polymerization.
Specifically, the glutarimide-based structural unit may be represented by the following general formula (3).

In the above general formula (3), preferably R ⁷ and R ⁸ are each independently hydrogen or a methyl group, R ⁹ is any one of hydrogen, a methyl group, a butyl group, and a cyclohexyl group, and more Preferably, R ⁷ is a methyl group, R ⁸ is hydrogen, and R ⁹ is a methyl group.

  The glutarimide-based structural unit may include only a single type or a plurality of types.

In the methacrylic resin having a glutarimide-based structural unit, the content of the glutarimide-based structural unit is not particularly limited as long as it satisfies the glass transition temperature range preferable as the composition of the present embodiment. 100 mass% of resin, Preferably it is the range of 5-70 mass%, More preferably, it is the range of 5-60 mass%.
When the content of the glutarimide-based structural unit is in the above range, a resin having good moldability, heat resistance, and optical properties is preferable.

The methacrylic resin having a glutarimide-based structural unit may further contain an aromatic vinyl monomer unit as necessary.
Although it does not specifically limit as an aromatic vinyl monomer, Styrene and (alpha) -methylstyrene are mentioned, Styrene is preferable.

The content of the aromatic vinyl unit in the methacrylic resin having a glutarimide structural unit is not particularly limited, but is preferably 0 to 20% by mass with respect to 100% by mass of the methacrylic resin having a glutarimide structural unit.
When the content of the aromatic vinyl unit is in the above range, it is preferable because both heat resistance and excellent photoelastic characteristics can be achieved.

Next, an example of a method for producing a methacrylic resin having a glutarimide structural unit will be described.
First, a meta (a) acrylate polymer is produced by polymerizing a meta (a) acrylate such as methyl methacrylate. When an aromatic vinyl unit is included in a methacrylic resin having a glutarimide-based structural unit, a meth (a) acrylic acid ester is copolymerized with a meth (a) acrylic acid ester and an aromatic vinyl (for example, styrene). -Manufacture aromatic vinyl copolymers.

  Next, an imidization reaction is performed by reacting the meth (a) acrylic acid ester polymer or the methacrylic acid ester-aromatic vinyl copolymer with an imidizing agent (imidation step). Thereby, a methacrylic resin having a glutarimide-based structural unit can be produced.

The imidizing agent is not particularly limited as long as it can generate the glutarimide-based structural unit represented by the general formula (3).
Specifically, ammonia or a primary amine can be used as the imidizing agent. Examples of the primary amine include aliphatic hydrocarbon group-containing primary amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, and n-hexylamine; And alicyclic hydrocarbon group-containing primary amines such as cyclohexylamine; and the like.
Among the imidizing agents, ammonia, methylamine, and cyclohexylamine are preferably used, and methylamine is particularly preferably used from the viewpoints of cost and physical properties.

  In this imidization step, the content of the glutarimide structural unit in the methacrylic resin having the resulting glutarimide structural unit can be adjusted by adjusting the ratio of the imidizing agent added.

Although the method for implementing the said imidation reaction is not specifically limited, A conventionally well-known method can be used, for example, an imidation reaction can be advanced by using an extruder or a batch-type reaction tank.
Although it does not specifically limit as said extruder, For example, a single screw extruder, a twin screw extruder, a multi screw extruder etc. can be used.
Among these, it is preferable to use a twin screw extruder. According to the twin screw extruder, the mixing of the raw material polymer and the imidizing agent can be promoted.
Examples of the twin-screw extruder include a non-meshing type same direction rotating type, a meshing type same direction rotating type, a non-meshing type different direction rotating type, and a meshing type different direction rotating type.
The above-exemplified extruders may be used alone, or a plurality of the extruders may be connected in series.

  In addition, since it is possible to remove a by-product such as an imidizing agent, methanol, or monomers of the reaction, it is particularly possible to attach a ben mouth that can be depressurized below atmospheric pressure to the extruder used. preferable.

In producing a methacrylic resin having a glutarimide-based structural unit, in addition to the imidization step, an esterification step of treating the carboxyl group of the resin with an esterifying agent such as dimethyl carbonate can be included. At that time, a catalyst such as trimethylamine, triethylamine, or tributylamine can be used in combination.
An esterification process can be advanced by using an extruder or a batch-type reaction tank similarly to the said imidation process, for example.
In addition, for the purpose of removing excess esterifying agent, by-products such as methanol, or monomers, it is preferable that the apparatus to be used is equipped with a vent that can be reduced to atmospheric pressure or lower.

  A methacrylic resin that has undergone an imidization step and, if necessary, an esterification step, is melted and extruded into a strand form from an extruder attached with a porous die, cold cut method, air hot cut method, underwater strand cut method, under It is processed into pellets by a water cut method.

  Also, in order to reduce the number of foreign substances in the resin, the methacrylic resin is dissolved in an organic solvent such as toluene, methyl ethyl ketone, methylene chloride, the resulting methacrylic resin solution is filtered, and then the organic solvent is devolatilized. It is also preferred to use the method.

--Lactone ring structural unit--
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（４）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 in 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 (4) is particularly preferable.

In the general formula (4), 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 preferable as the composition of the present embodiment. 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 methacrylic resin having a lactone ring structural unit may have a structural unit derived from another monomer copolymerizable with the above-mentioned methacrylic acid ester monomer and an acrylic acid monomer having a hydroxy group. Good.
Examples of such other copolymerizable monomers include styrene, vinyl toluene, α-methyl styrene, α-hydroxymethyl styrene, α-hydroxyethyl styrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl. Monomers having a polymerizable double bond such as alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, N-vinyl carbazole Examples include the body.
These other monomers (structural units) may have only one type or two or more types.

The content of structural units derived from these other copolymerizable monomers is preferably 0 to 20% by mass with respect to 100% by mass of the methacrylic resin, and 10% by mass from the viewpoint of weather resistance. % Is more preferable, and it is more preferable that the content is less than 7% by mass.
The methacrylic resin in this embodiment may have only one type of structural unit derived from the above copolymerizable other monomer, or may have two or more types.

  As a method for producing a methacrylic resin having a lactone ring structural unit, a method of forming a lactone ring structure by a cyclization reaction after polymerization is used, but solution polymerization using a solvent is preferable for promoting the cyclization reaction. .

Examples of the solvent used for the polymerization 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 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 to add a polymerization solvent to the reaction mixture as appropriate and control it to be 50% by mass or less.
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.

  During the polymerization reaction, polymerization may be performed by adding a polymerization initiator or a chain transfer agent as necessary.

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 amount of the polymerization initiator used 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 is good as 0.05-1 mass part.

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 amount of chain transfer agent used 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 polymerization is 100 parts by mass. In this case, it may be 0.05 to 1 part by mass.

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.
When the amount of the catalyst used is 0.01 parts by mass or more, it is effective for improving the reaction rate of the cyclization condensation reaction, and when the amount of the catalyst used is 3 parts by mass or less, the obtained polymer is colored. In addition, it is effective to prevent the polymer from cross-linking and difficult to be melt-molded.

  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. When the reaction treatment temperature is 150 ° C. or higher, it is effective to prevent the cyclization condensation reaction from being insufficient and the residual volatile content to increase, and when the reaction treatment temperature is 350 ° C. or less, it was obtained. It is effective in suppressing the coloring and decomposition of the polymer.
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 is 500 Torr or less, volatile components tend not to remain. Conversely, when the degree of vacuum is 10 Torr or more, industrial implementation is relatively easy.

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 imidization for forming the above-mentioned glutarimide-based structural unit and the lactonization for forming the above-mentioned lactone ring structural unit may be performed after the production of the resin and before the production of the resin composition (described later). In addition, during the production of the resin composition, it may be performed together with melt kneading of the resin and components other than the resin.

  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, a glutarimide structural unit, and a lactone ring structural unit. Among these, 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 a photoelastic coefficient without blending with other thermoplastic resins.

-Organic phosphorus compounds-
As an organic phosphorus compound contained in the methacrylic resin composition of the present embodiment, phosphorus having an organic substituent (including those having a P—C bond and a P—O—C bond in this embodiment). Although it is not particularly limited as long as it is a compound, it contains at least one trivalent phosphorus selected from phosphites (hereinafter also referred to as “phosphites”), phosphonites, and hydrolysis products thereof. An organic phosphorus compound as its constituent element; and at least one selected from phosphoric acid esters (hereinafter also referred to as “phosphates”), oxidation products of the phosphites, and oxidation products of the phosphonites And those containing both an organic phosphorus compound containing pentavalent phosphorus as a constituent element thereof, and the like.
The organic phosphorus compound includes an organic phosphorus compound having a hindered phenol moiety (for example, a compound in which a hindered phenol skeleton unit is ester-bonded to a phosphorus atom, or a hindered phenol skeleton unit having a phosphorus atom via an alkyl group). And a compound in which at least two hindered phenol skeleton units are ester-bonded to a phosphorus atom and two hindered phenol skeleton units are bonded to each other through an alkyl chain). When a compound in which a hindered phenol skeleton unit is ester-bonded to a phosphorus atom is used as the organic phosphorus compound, the hindered phenol compound having a molecular weight of less than 300 is hydrolyzed during melt kneading of the methacrylic resin composition of the present embodiment. Tend to occur.

  The phosphites, phosphonites, and phosphates have an aromatic ring and are preferably bulky compounds. For example, phosphites, phosphonites, and phosphates having an aryl substituent or a pentaerythritol structure are preferable.

In general, it is known that phosphites and phosphonites, which are trivalent organophosphorus compounds, are easily oxidized by applying heat in the presence of oxygen and are also prone to hydrolysis.
It is known that acidic P—OH and PH═O protons are generated by hydrolysis and react directly with oxygen and hydroperoxide to form pentavalent organophosphorus compounds.
The organophosphorus compound defined in the present specification includes a hydrolysis product and an oxidation product generated by the hydrolysis and the oxidation reaction.

Specific examples of phosphites (phosphites) include phosphite monoesters, diesters, or triesters (eg, phenyl phosphite, diphenyl phosphite, triphenyl phosphite), tris ( 2,4-di-t-butylphenyl) phosphite, tris (2,6-di-t-butylphenyl) phosphite, tris (2,4-di-t-butyl-5-methylphenyl) phosphite, Bis (2,4-di-t-butyl-6-methylphenyl) ethyl phosphite, 2,2′-methylenebis (4,6-di-t-butylphenyl) octyl phosphite, bis (2,6-di -T-butyl-4-methylphenyl) pentaerythritol diphosphite, (6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2, 4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphine, cyclic neopentanetetraylbis (2,6-di-t-butyl-4-methyl Phenyl) phosphite and hydrolysis products of these phosphites.
Commercially available phosphorus-based antioxidants may be used. For example, Irgafos 168 (Irgafos 168: Tris (2,4-di-t-butylphenyl) phosphite, manufactured by BASF), Irgafos 12 (Irgafos 12: Tris [2- [ [2,4,8,10-tetra-t-butyldibenzo [d, f] [1,3,2] dioxaphosphin-6-yl] oxy] ethyl] amine (manufactured by BASF), Irgaphos 38 ( Irgafos 38: bis (2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite, manufactured by BASF), Adekastab HP-10 (ADKSTAB HP-10: 2,2′-methylenebis (4,6-di-) tert-butylphenyl) octyl phosphite (manufactured by ADEKA Corporation), ADK STAB PEP24G (AD KASTAB PEP24G: cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite: manufactured by ADEKA Corporation, ADK STAB PEP36 (ADKSTAP PEP36: bis (2,6-di-t-butyl-4) -Methylphenyl) pentaerythritol diphosphite: manufactured by ADEKA Corporation), ADK STAB PEP36A (ADKSTAB PEP36A: bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite: manufactured by ADEKA Corporation) , ADK STAB PEP-8 (ADKSTAP PEP-8: cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl phosphite: manufactured by ADEKA Corporation), Sumilizer GP (Sumiliz) rGP: (6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3 2] Dioxaphosphepine, manufactured by Sumitomo Chemical Co., Ltd.).

Examples of phosphonites include tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphonite, tetrakis (2,4-di-tert-butyl-5-methylphenyl) 4,4. Examples thereof include '-biphenylene diphosphonite and hydrolysis products of these phosphonites.
Commercially available phosphorus antioxidants may be used, for example, Hostanox P-EPQ (P-EPQ: tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylene diphosphonite: Clariant Co. Ltd. And GSY P101 (tetrakis (2,4-di-t-butyl-5methylphenyl) 4,4′-biphenylenediphosphonite: manufactured by Sakai Chemical Co., Ltd.).

  Specific examples of phosphate esters (phosphates) include 2-ethylhexyl acid phosphate, isodecyl acid phosphate, oleyl acid phosphate, bis (2-ethylhexyl) hydrogen phosphate, ethylene bis (diphenyl phosphate), propylene bis ( Diphenyl phosphate), phenylene bis (diphenyl phosphate), naphthylene bis (ditoluyl phosphate), bisphenol A bis (diphenyl phosphate), 3,5-di-t-butyl-4-hydroxybenzyl phosphate diethyl ester, and their hydrolyzed products Thing etc. are mentioned.

(Method for producing methacrylic resin composition)
The method for producing the methacrylic resin composition of the present embodiment is not particularly limited as long as a composition satisfying the requirements of the present invention can be obtained.
For example, a method in which an organophosphorus compound is allowed to coexist with a monomer during polymerization, a method in which an organophosphorus compound is blended before a devolatilization step for removing a monomer or a polymerization solvent remaining after completion of solution polymerization, a devolatilization step Pellet using a method that is added when granulating the polymerization product collected later (including when other thermoplastic resins are blended at the same time), an extruder attached with a side feed device and a vent port after the devolatilization step And when granulating again using a melt-kneading apparatus such as an extruder (including the case where other thermoplastic resins are blended at the same time), a method of adding directly or as a master batch pellet may be mentioned.
When the melt extrusion method is employed as a method for preparing the composition, it is preferable to employ a method of preparing the composition while using a vented extruder and removing residual volatile components as much as possible.

  Further, when the methacrylic resin composition of the present embodiment is used for a film application or the like, for the purpose of reducing foreign matter, a polymerization reaction step, a liquid-liquid separation step, a liquid-solid separation step, a devolatilization step, granulation In any one or a plurality of steps of the step and the molding step, for example, a sintered filter, a pleated filter, a leaf disk type polymer filter or the like having a filtration accuracy of 1.5 to 20 μm is added to the filtration device and prepared. This is also a preferred method.

Regardless of which method is selected, in preparing the composition of this embodiment containing an organophosphorus compound in its composition, it is possible to prepare the composition after reducing oxygen and water as much as possible. preferable.
For example, the oxygen concentration is preferably less than 300 ppm in the polymerization step, and in the preparation method using an extruder or the like, the oxygen concentration in the extruder is preferably less than 1% by volume, and 0.8% by volume. More preferably, it is less.
The water content of the methacrylic resin is preferably adjusted to 1000 ppm by mass or less, more preferably 500 ppm by mass or less.
Within these ranges, it is relatively easy and advantageous to prepare a composition that satisfies the requirements of the present invention.

For example, when a production method using an extruder is adopted, the raw material pelletized methacrylic resin and organophosphorus compound are heated under reduced pressure or dehumidified air, and dried sufficiently in advance to obtain moisture. Is preferably removed as much as possible, mixed and fed to the extruder.
Furthermore, in order to reduce oxygen contamination in the extruder as much as possible and prevent oxidation of the composition in the molten state, an inert gas such as nitrogen gas is allowed to flow into the extruder and a vented extruder is used. It is preferable to carry out while evacuating under reduced pressure.
As drying temperature of the raw material in that case, 40-120 degreeC is preferable, More preferably, it is 70-100 degreeC.
The degree of reduced pressure is not particularly limited, but in particular, when using a powdered organic phosphorus compound, the organic phosphorus compound is adhered to the methacrylic resin by using an additive or the like in advance so as not to be scattered. The degree of decompression may be selected as appropriate while taking measures such as

Using an extruder, the methacrylic resin composition melt-kneaded and brought into a molten state is melt-extruded from a porous die and pelletized.
In this case, examples of the granulation method that can be used include an aerial hot cut method, a watering hot cut method, a cold cut method, an underwater strand cut method, an underwater cut method, and the like.

In order to obtain a methacrylic resin composition in which the presence state of the organophosphorus compound contained is highly controlled as in this embodiment, the composition in a molten state at high temperature is exposed to air as much as possible. It is preferable to adopt a granulation method that can be quickly cooled and solidified.
For this purpose, for example, a watering hot cut method, a cold cut method, an underwater strand cut method, an underwater cut method, and the like are preferable. A cut method is more preferable.
In that case, the molten resin temperature is lowered as much as possible, the residence time from the perforated die outlet to the cooling water surface is reduced as much as possible, and the cooling water temperature is as high as possible within the possible range. More preferably, granulation is performed.
For example, the molten resin temperature is preferably 240 to 300 ° C, more preferably 250 to 290 ° C, and the residence time from the porous die outlet to the cooling water surface is preferably within 5 seconds, more preferably within 3 seconds. The temperature of the cooling water is preferably 30 to 80 ° C, more preferably 40 to 60 ° C.

(Characteristics of methacrylic resin composition)
Hereinafter, the characteristics of the methacrylic resin composition of the present embodiment will be described in detail.

-Phosphorus element content-
In the methacrylic resin composition of the present embodiment, the phosphorus element content is 10 to 1000 ppm by mass, preferably 20 to 500 ppm by mass, and more preferably 50 to 300 ppm by mass.
If the phosphorus element content is less than 10 mass ppm, the decomposition of the methacrylic resin composition having a high glass transition temperature as in the present embodiment due to heat and oxygen may not be sufficiently suppressed.
Further, when the content of the phosphorus element exceeds 1000 mass ppm, the volatile matter that is generated when melt kneading is performed at a high temperature using a methacrylic resin composition having a high glass transition temperature as in this embodiment. Decomposition products are present in a large amount in the composition, and cooling rolls and mold dirt during melt molding increase, and a large amount of streaks and silver streaks are generated on the surface of the resulting molded product. There is a fear.
The content of the phosphorus element contained in the composition can be measured using a fluorescent X-ray analyzer, and can be determined by an SQX order analysis method using, for example, Rigaku fluorescent X-ray: ZSX Primus II.

In addition, the organophosphorus compound contained in the methacrylic resin composition of the present embodiment preferably contains an organophosphorus compound having at least a trivalent phosphorus element. When an organic phosphorus compound having a trivalent phosphorus element is contained, mold contamination is improved.
Whether or not the organophosphorus compound contained in the methacrylic resin composition contains an organophosphorus compound having a trivalent phosphorus element as its constituent element is attributed to trivalent phosphorus in ³¹ P-NMR measurement. It can be confirmed from the spectrum peak.

-Weight average molecular weight-
In the methacrylic resin composition of the present embodiment, the polymethylmethacrylate conversion weight average molecular weight (Mw) measured by GPC measurement method is preferably in the range of 80,000 to 170,000, more preferably 80, 000 to 150,000, more preferably 100,000 to 150,000.
When the weight average molecular weight (Mw) is in this range, the balance between mechanical strength and moldability is excellent, which is preferable.

-R value-
In addition, the methacrylic resin composition of the present embodiment has an R value of the following formula derived from the weight average molecular weight Mw, the number average molecular weight Mn, and the Z average molecular weight Mz in terms of polymethyl methacrylate measured by the GPC measurement method. It is preferable to be in the range of 0.8 to 1.5.
R value = [Mw / Mn] / [Mz / Mw]
R obtained by the above formula represents a ratio between Mw / Mn, which is an index focused on the low molecular weight side, and Mz / Mw, which is an index focused on the high molecular weight side, and is an index related to the spread of the molecular weight distribution.
Therefore, an R value smaller than 1 means that the resin composition has a higher molecular weight spread, and conversely an R value larger than 1 has a lower molecular weight spread. It means a resin composition. The R value of the methacrylic resin composition of the present embodiment is preferably in the range of 0.8 to 1.5, more preferably 1.0 to 1.5, still more preferably 1.0 to 1.4. Particularly preferably, it is 1.1 to 1.4. When the R value is within this range, the melt time is maintained and the mechanical strength is maintained, while the residence time is longer and the molded product of good quality is maintained even when subjected to melt molding at a higher temperature. This is preferable.
In addition, about the weight average molecular weight of this methacrylic-type resin composition, a number average molecular weight, and a Z average molecular weight, it can measure by the method of the below-mentioned Example description.

-Glass transition temperature-
The glass transition temperature (Tg) of the methacrylic resin composition in this embodiment is more than 120 ° C. and 160 ° C. or less.
If the glass transition temperature (Tg) of the methacrylic resin composition exceeds 120 ° C., necessary and sufficient heat resistance can be obtained more easily as a recent lens molded body and a film molded body optical film for a 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 composition exceeds 160 ° C., the temperature at the time of melt processing must be set to a considerably high temperature, which tends to cause thermal decomposition of the resin, etc. It may be difficult to obtain a good product.
The glass transition temperature (Tg) is preferably 150 ° C. or lower for the reasons described above.
The glass transition temperature (Tg) can be determined by measuring in accordance with JIS-K7121. Specifically, it can measure using the method described in the Example mentioned later.

-Photoelastic coefficient-
The absolute value of the photoelastic coefficient C _R of the methacrylic resin composition comprising a methacrylic resin containing a structural unit (X) having a main chain in the ring structure of the present embodiment, 3.0 × 10 ^-12 Pa ^-1 or less is preferably, more preferably 2.0 × at 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 of the photoelastic coefficient C _R of the methacrylic resin composition of the present embodiment is 3.0 × 10 ^-12 Pa ^-1 or less, be used in a liquid crystal display device with a film, a retardation unevenness occurs And the contrast of the peripheral portion of the display screen does not decrease and light leakage does not occur.
Photoelastic coefficient C _R of the methacrylic resin composition, specifically, can be determined by the method described in Examples described later.

-Content of a hindered phenol compound having a molecular weight of less than 300-
Conventionally, as a hindered phenolic antioxidant blended in a methacrylic resin having a relatively high glass transition temperature, for example, those having a molecular weight exceeding 500 are known, and further, the thermal decomposition starting temperature is higher. Many examples have been disclosed where things are selected.

In addition, the present inventors have found that hindered phenol compounds having a molecular weight of less than 300 such as 2,6-di-tert-butyl-p-cresol, which are often used in general-purpose resins such as polyethylene, have excellent antioxidant ability. However, in a methacrylic resin composition having a relatively high glass transition temperature due to its high volatility, various members of the melt molding machine are soiled, the appearance of the resulting molded product is impaired, and the molded product We paid attention to the concern of causing yellowing.
As a result, it has been found that even when a hindered phenol compound having a molecular weight of less than 300 is not used, the resulting resin composition may contain a hindered phenol compound having a molecular weight of less than 300.

  As a result of the study by the present inventors, when a methacrylic resin composition having a relatively high glass transition temperature is melt-kneaded at a high temperature, a phosphorus compound having a hindered phenol moiety is blended as its structural unit. It has been found that a hindered phenol compound having a molecular weight of less than 300 may be produced as a decomposition product thereof. In addition, the hindered phenol compound having a molecular weight of less than 300 has a low melting point, and it has become clear that various adverse effects are produced on the melt processing characteristics of the resulting methacrylic resin composition.

  The hindered phenol compound having a molecular weight of less than 300 in the present invention refers to a phenol compound having at least one bulky substituent, such as a tert-butyl group, and is generally classified as a hindered phenol, a hindered phenol, and a hindered phenol. All the dophenols are comprehensively defined as hindered phenol compounds. Examples of the bulky substituent include a tert-butyl group, and more specifically, a decomposition product of an organophosphorus compound having a hindered phenol moiety, and the like. 4-dimethyl-6-tert-butylphenol, 2-methyl-6-tert-butyl-p-cresol, 2,4-di-tert-butylphenol, 2,6-di-tert-butylphenol, 2,6-di- Examples thereof include tert-butyl-p-cresol, 2,4-di-tert-butyl-o-cresol, 2,4-di-tert-butyl-m-cresol and the like.

The content of the hindered phenol compound having a molecular weight of less than 300 contained in the methacrylic resin composition of the present embodiment is 300 mass ppm or less, preferably 200 mass ppm or less, more preferably 120 mass ppm or less. Moreover, as a minimum of content, it is preferable that it is 5 mass ppm or more from a viewpoint which prevents the process to remove from becoming complicated, More preferably, it is 10 mass ppm or more. When the content is in this range, roll contamination during film formation, mold contamination during injection molding, and the like are not increased, which is preferable.
The structure and content of the hindered phenol compound having a molecular weight of less than 300 contained in the methacrylic resin composition can be measured using a gas chromatograph mass spectrometer, and specifically, the method described in the examples below. It can ask for.

-Other thermoplastic resins-
When preparing the methacrylic resin composition of the present embodiment, other thermoplastic resins may be blended for the purpose of adjusting the birefringence and improving flexibility without impairing the purpose of the present embodiment. it can.
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.
As the average particle diameter of the acrylic rubber particles, methacrylic rubber-containing graph 卜 copolymer particles, and rubbery polymer, the impact strength and optical characteristics of the film obtained from the methacrylic resin composition of the present embodiment, etc. From the viewpoint of increasing the thickness, 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 composition 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 agent: Softening agent / plasticizer such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, mineral oil; hindered phenolic antioxidant (preferably containing phosphorus atom) Not hindered phenol antioxidants), antioxidants such as sulfur antioxidants; hindered amine light stabilizers; benzotriazole ultraviolet absorbers; higher alcohols such as cetyl alcohol and stearyl alcohol; stearic acid monoglyceride, stearic acid Such as diglyceride Flame retardants; antistatic agents; mold releasing agents such as glycerin higher fatty acid ester organic fibers, glass fibers, carbon fibers, reinforcing agents such as metal whisker; coloring agents; Other additives; or mixtures thereof.

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.
Examples 8, 9, and 14 are described as reference examples.

(1. 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 Co., Ltd.
Measurement conditions Measurement solvent: CDCl ₃ or d ₆ -DMSO
Measurement temperature: 40 ° C
In addition, when the ring structure of methacrylic resin is a lactone ring structure, it confirms by the method of Unexamined-Japanese-Patent No. 2001-151814, and when the ring structure of methacrylic resin is a glutarimide ring structure It was confirmed by the method described in the republished patent WO2012 / 114718.

(2. Molecular weight and R value)
The weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) of the methacrylic resin produced in the production examples described later and the methacrylic resin compositions produced in the examples and comparative examples described later are Measured with the following apparatus and conditions.
Measuring apparatus: manufactured by Tosoh Corporation, gel permeation chromatography (HLC-8320GPC)
Column: One TSK guard column SuperH-H, two TSK gel Super HM-M, and one TSK gel Super H 2500 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 methacrylic resin composition in 20 mL of tetrahydrofuran, injection amount: 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 or methacrylic resin composition was measured.
Based on the area area in the GPC elution curve and a calibration curve of a seventh-order approximation, the weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) of the methacrylic resin and methacrylic resin composition And Mw / Mn and Mz / Mw were determined using these values. And R value was computed from the following formula | equation.
R value = [Mw / Mn] / [Mz / Mw]

(3. Glass transition temperature)
Based on JIS-K7121, the glass transition temperature (Tg) (degreeC) of the methacrylic resin composition 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.

(4. Phosphorus element content)
The phosphorus element content (mass ppm) of the methacrylic resin compositions produced in Examples and Comparative Examples described below was measured using the following apparatus and conditions.
・ Measurement equipment: X-ray fluorescence analyzer (ZSX Primus II) manufactured by Rigaku Corporation
Measurement method: SQX order analysis method 3 g of freeze-pulverized sample was filled in a 30 mm diameter PVC ring, solidified by a pressure molding machine, and used for measurement.

(5. Presence or absence of trivalent organophosphorus compound)
The valence of the organophosphorus compound contained in the methacrylic resin compositions produced in Examples and Comparative Examples described later was determined by ³¹ P-NMR.
^{The 31} P-NMR measurement apparatus and measurement conditions are as follows.
Measurement device: Bruker Biospin's Fourier transform nuclear magnetic resonance apparatus (AVANCE III 500HD Prodigy)
·Measurement condition:
Observation frequency: 202 MHz, number of integrations: 50,000 times Detection pulse flip angle: 30 °, delay time: 2 seconds Pulse program: zg30
Measurement temperature: room temperature Solvent used: CDCl ₃ , hexamethylphosphoric triamide was added as an internal standard substance.
A 200 mg sample was dissolved in 1 mL of CDCl ₃ previously added with the internal standard substance, filled in a 5 mmφ sample tube, and used for measurement.
From the obtained spectrum, it was confirmed that the spectrum peak observed between 90 ppm and 140 ppm was derived from an organic phosphorus compound having a trivalent phosphorus element.
And the case where the organic phosphorus compound which has a trivalent phosphorus element was contained was set as "(circle)", and the case where it was not included was set as "x".

(Measurement of 6. photoelastic coefficient _{C R)}
The methacrylic resin compositions obtained in Examples and Comparative Examples were used as measurement samples by using a vacuum compression molding machine as a press film.
As specific sample preparation conditions, a vacuum compression molding machine (manufactured by Shin-Fuji Metal Industry Co., Ltd., SFV-30 type) was used, and after preheating at 260 ° C. under reduced pressure (about 10 kPa) for 10 minutes, After compressing at about 10 MPa at 5 ° C. for 5 minutes and releasing the reduced pressure and the pressing 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 |
(In the formula, nx represents the refractive index in the stretching direction, and ny represents the refractive index in the direction perpendicular to the stretching direction in the plane.)

(7. Content of hindered phenol compound having a molecular weight of less than 300)
Gas chromatograph mass spectrometry analysis of the content (mass ppm) of hindered phenol compounds having a molecular weight of less than 300 remaining in the methacrylic resins obtained in the production examples described later and in the methacrylic resin compositions obtained in the examples and comparative examples. The total was measured using GC-7890C / МSD-5975 (manufactured by Agilent).
A sample is dissolved in chloroform to prepare a 5% by mass solution. The obtained solution is put into 6 times amount of methanol in a volume ratio with respect to chloroform, the polymer part is precipitated, and solid-liquid separation is performed by filtration. The liquid phase was collected. The resulting solution was slowly air-dried at room temperature and concentrated to a liquid volume of less than 0.5 mL, and chloroform was added to the resulting concentrate to make a 1 mL solution. As an internal standard substance, Adeka AO-60 (n-octadecyl-beta- (4′-hydroxy-3 ′, 5′-di-t-butylphenyl) propionate: manufactured by ADEKA) was 0.025% by mass. 1 mL of chloroform solution containing it was added. The content of the hindered phenol compound having a molecular weight of less than 300 was converted into the content (mass ppm) by weight conversion from the peak area of the target substance using a calibration curve prepared in advance using an internal standard substance.
In addition, the structure and molecular weight of the hindered phenol compound contained in the sample can be specified by an MS library using GC / MS.
Column used: HP-5МS L30M
Carrier gas: helium (flow rate 1mL / min)
Oven temperature: held at 50 ° C. for 5 minutes, then raised to 325 ° C. at a rate of 10 ° C./minute Transfer temperature: 325 ° C.
Mass spectral range: 20-800
Split ratio: 10: 1

(8. Injection molding evaluation)
The pellet-shaped resin compositions obtained in Examples and Comparative Examples described later were dried with dehumidified air at 90 ° C. for 6 hours, and injection molded by the following two methods A method and B method.
Method A: An ISO dumbbell type test piece using an Autoshot C15A manufactured by Fanuc as an injection molding machine under the conditions of a cylinder temperature of 260 ° C., a mold temperature of 70 ° C., a screw rotation speed of 80 rpm, an injection time of 10 seconds, and a cooling time of 20 seconds. Using a metal mold, the molded product was molded into 100 shots.
The adhesion state of the mold after molding was confirmed visually to evaluate the adhesion state. When there is no deposit, the adhesion status is “Good”, and when the mold surface is cloudy, the adhesion status is usually “△”, and there is a liquid or solid deposit on the mold surface. In this case, the adhesion state was judged as “x”.
Moreover, the adhesion and / or cloudiness of the mold after molding were wiped off with ethanol, and the ease of wiping was evaluated. And, when wiping off deposits and / or cloudiness is easy, wiping is good, and when wiping off deposits and / or fogging is difficult (when wiping off several times), wiping is normal. In the case where “Δ”, adhering matter and / or cloudiness cannot be wiped off, the wiping property was judged as “poor”.
In addition, in the injection molding of the methacrylic resin composition, in addition to the hindered phenol compound having a molecular weight of less than 300, a low molecular weight oligomer component generated from the methacrylic resin may contaminate the mold. A hindered phenol compound having a molecular weight of less than 300 is often a crystalline compound having a melting point near the mold temperature at the time of molding, and is a major cause of mold contaminants.
Method B: An Autoshot C15A manufactured by Fanuc was used as an injection molding machine, and a mold for an ISO dumbbell type test piece was used for 10 minutes at a cylinder temperature of 280 ° C. under conditions of a mold temperature of 70 ° C. and a screw rotation speed of 80 rpm. The injection molding of 10 shots was performed under the conditions, the appearance of the obtained test piece was visually confirmed, and the number of silver streaks generated was measured.

[material]
It shows below about the raw material used in the Example and comparative example which are mentioned later.
[Monomer]
・ Methyl methacrylate: manufactured by Asahi Kasei Chemicals Corporation ・ N-phenylmaleimide (phMI): manufactured by Nippon Shokubai Co., Ltd. ・ N-cyclohexylmaleimide (chMI): manufactured by Nippon Shokubai Co., Ltd. : Combi Block manufactured monomethylamine: Mitsubishi Gas Chemical Co., Ltd. [Organic phosphorus compound]
A-1: Tris (2,4-di-t-butylphenyl) phosphite A-2: Stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemical Industry Co., Ltd.)
A-3: Bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite A-4: 6- [3- (3-t-butyl-4-hydroxy-5 Methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] dioxaphosphine A-5: 2,2′-methylenebis (4 6-di-tert-butylphenyl) octyl phosphite A-6: tetrakis (2,4-di-t-butyl-5-methylphenyl) 4,4′-biphenylenediphosphonite A-7: tetrakis (2 , 4-Di-tert-butylphenyl) 4,4′-biphenylenediphosphonite A-8: 3,5-di-tert-butyl-4-hydroxybenzyl phosphate diethyl ester [additive]
2,6-di-tert-butyl-p-cresol (manufactured by Wako Pure Chemical Industries, Ltd.)

[Production Example 1-1] Production of methacrylic resin having structural unit derived from N-substituted maleimide monomer 450.7 kg of methyl methacrylate (hereinafter referred to as “MMA”), N-phenylmaleimide (hereinafter referred to as “phMI”) 39.8 kg, N-cyclohexylmaleimide (hereinafter referred to as “chMI”) 59.7 kg, chain transfer agent n-octyl mercaptan 0.41 kg, polymerization solvent metaxylene (hereinafter referred to as “mXy”) 450 kg was weighed and added to a 1.25 m ³ reactor previously purged with nitrogen, and these were stirred to obtain a mixed monomer solution.
The mixed monomer solution was then bubbled with nitrogen for 6 hours at a rate of 100 mL / min to remove dissolved oxygen and raise the temperature to 124 ° C.
Next, polymerization was started by adding a polymerization initiator solution in which 0.30 kg of 1,1-di-t-butylperoxycyclohexane as a polymerization initiator was dissolved in 3.85 kg of mXy at a rate of 1 kg / hour. did.
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.
This polymerization solution was supplied to a tubular heat exchanger preliminarily heated to 170 ° C. and a concentrating device consisting of a vaporization tank, 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 to perform devolatilization. At this time, the temperature inside the apparatus was 280 ° C., the supply rate was 30 L / hour, the rotation speed was 400 rpm, and the degree of vacuum was 30 Torr.
When the composition of the obtained polymer (1-1) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.9% by mass, and 10.8% by mass, respectively. %Met. The weight average molecular weight was 145,000.

[Production Example 1-2]
In Production Example 1-1, polymerization was performed in the same manner as in Production Example 1-1 except that the amount of the polymerization initiator used was 0.23 kg and no chain transfer agent was used, and the polymer was recovered.
The obtained polymer (1-2) had a weight average molecular weight of 235,000.

[Production Example 1-3]
In Production Example 1-1, polymerization was performed in the same manner as in Production Example 1-1 except that the amount of chain transfer agent used was changed to 0.80 kg, and the polymer was recovered.
The obtained polymer (1-3) had a weight average molecular weight of 89,000.

[Production Example 1-4]
In Production Example 1-1, the amount of methyl methacrylate used was changed to 503.5 kg, the amount of N-phenylmaleimide used was changed to 17.2 kg, the amount of N-cyclohexylmaleimide used was changed to 29.5 kg, and polymerization was started. Polymerization was performed in the same manner as in Production Example 1-1 except that the amount of the agent used was changed to 0.49 kg and the amount of the chain transfer agent used was changed to 0.62 kg.
When the composition of the obtained polymer (1-4) was confirmed, structural units derived from MMA, phMI, and chMI monomers were 90.3% by mass, 4.0% by mass, and 5.7% by mass, respectively. %Met. The weight average molecular weight was 115,000.

[Production Example 1-5]
Production Example 1-1 Production Example 1-1 except that the amount of methyl methacrylate used was changed to 351.2 kg, the amount of N-phenylmaleimide used was changed to 79.6 kg, and the amount of N-cyclohexylmaleimide used was changed to 119.4 kg. Polymerization was performed in the same manner as in 1-1, and a polymer was recovered.
When the composition of the obtained polymer (1-5) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 63.3 mass%, 15.8 mass%, and 20.9 mass%, respectively. %Met. The weight average molecular weight of the obtained polymer was 127,000.

[Production Example 1-6]
In Production Example 1-1, the polymerization solvent used was changed from metaxylene to methyl isobutyl ketone, and the addition amount of n-octyl mercaptan was changed to 0.35 kg in the same manner as in Production Example 1-1. Polymerization was performed and the polymer was recovered.
When the composition of the obtained polymer (1-6) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.9% by mass, and 10.8% by mass, respectively. %Met. The weight average molecular weight was 218,000.

[Production Example 1-7]
In Production Example 1-1, the amount of methyl methacrylate used is 405.6 kg, the amount of N-phenylmaleimide used is 35.8 kg, the amount of N-cyclohexylmaleimide used is 53.7 kg, and the chain transfer agent n -Polymerization was carried out in the same manner as in Production Example 1-1 except that the amount of octyl mercaptan added was changed to 0.05 kg and the amount of metaxylene used was changed to 500 kg, and the polymer was recovered.
When the composition of the obtained polymer (1-7) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.9% by mass, and 10.8% by mass, respectively. %Met. Moreover, the weight average molecular weight was 123,000.

[Production Example 1-8]
When the polymer solution obtained in Production Example 1-1 is supplied to a thin film evaporator, 0.6 part by mass of tetrakis (2,4-di-) with respect to 100 parts by mass of the polymer contained in the solution. tert-Butylphenyl) 4,4′-biphenylenediphosphonite (A-7) is added and stirred to obtain a resin composition pellet in the same manner as in Production Example 1-1, except that the solution is homogeneous. It was.
The weight average molecular weight of the obtained resin composition (1-8) was 168,000. Further, it contained 278 mass ppm of phosphorus element and 76 mass ppm of a hindered phenol compound having a molecular weight of less than 300.

[Production Example 2-1] Production of methacrylic resin having a lactone ring structural unit Methyl methacrylate 40 was placed in an autoclave equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen gas introduction pipe. 10 parts by mass of methyl 2- (hydroxymethyl) acrylate, 50 parts by mass of toluene, 0.025 part by mass of tris (2,4-di-t-butylphenyl) phosphite (A-1) as an organic phosphorus compound Was 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%. While a toluene solution containing parts by mass was added dropwise over 2 hours, solution polymerization was performed at about 105 to 110 ° C. under reflux, and the polymerization was further continued for 4 hours.
To the obtained polymer solution, 0.05 part by mass of stearyl phosphate / distearyl phosphate mixture (A-2), which is an organic phosphorus compound, is added as a cyclization catalyst, and the mixture is refluxed at about 90 to 102 ° C. for 2 hours. Cyclocondensation reaction was performed for a time.
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. At that time, the catalyst deactivator (octyl zinc) and AS resin (acrylonitrile-styrene resin) (manufactured by Asahi Kasei Chemicals Co., Ltd., product name: Stylac) from the two side feeds provided in the latter half of the twin screw extruder AS783) was introduced. AS resin was added at a feed rate of 1.65 kg / hr.
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 (2-1).
When the composition of the obtained resin composition was confirmed, the content of the lactone ring structural unit was 28.3% by mass. In addition, 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 129,000.

[Production Example 3-1]: Production of methacrylic resin having a glutarimide-based structural unit Methyl methacrylate-styrene copolymer (MS resin) (manufactured by Nippon Steel Chemical Co., Ltd., product name: MS-800) as a raw material resin ), Monomethylamine is used as an imidizing agent, and a methacrylic resin having a glutarimide-based structural unit is produced using a meshing type co-rotating twin screw extruder having a diameter of 15 mm and L / D = 90 did.
At that time, the oxygen concentration in the extruder was reduced to 1% by volume or less by flowing nitrogen gas from the popper. The set temperature of each temperature control zone of the extruder was 250 ° C., the screw rotation speed was 300 rpm, MS resin was supplied at 1 kg / hour, and the supply amount of monomethylamine was 20 parts by mass with respect to 100 parts by mass of MS resin.
MS resin was introduced from the hopper, and the resin was melted and filled with a kneading block, and then monomethylamine was injected from the nozzle. A seal ring was placed at the end of the reaction zone to fill the resin. By-products and excess methylamine after the reaction were removed by reducing the pressure at the vent port to 60 Torr. The resin that came out as a strand from a die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer.
Next, in a meshing type co-rotating twin screw extruder with a bore of 15 mm and L / D = 90, from a hopper under the conditions of 230 ° C. and a screw rotation speed of 150 rpm in each temperature control zone of the extruder The pellet obtained above was charged at a supply rate of 1 kg / hour, and the resin was melted and filled with a kneading block, and then 0.8 mass from the nozzle to 100 mass parts of the pellet-shaped resin. Part of the dimethyl carbonate was injected to reduce the carboxyl groups in the resin. A reverse flight was placed at the end of the reaction zone to fill the resin. By-products and excess dimethyl carbonate after the reaction were removed by reducing the pressure at the vent port to 100 Torr.
The resin coming out as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized again with a pelletizer to obtain a methacrylic resin (3-1) having a glutarimide-based structural unit.
When the content of the glutarimide-based structural unit of the obtained resin (3-1) was measured according to the re-published patent WO2012 / 114718, the content of the glutarimide-based structural unit was 58% by mass, derived from the styrene monomer. The content of the structural unit was 19% by mass. The weight average molecular weight (Mw) was 119,000.

[Production Example 3-2]
The glutarimide system was the same as in Production Example 3-1, except that the MS resin supply rate was changed to 0.5 kg / hour and the monomethylamine supply amount was changed to 40 parts by mass with respect to 100 parts by mass of the MS resin. A methacrylic resin (3-2) having a structural unit was obtained.
When the content of the glutarimide-based structural unit of the obtained resin (3-2) was measured according to the re-published patent WO2012 / 114718, the content of the glutarimide-based structural unit was 72% by mass, derived from the styrene monomer. The content of the structural unit was 19% by mass, and the weight average molecular weight (Mw) was 98,000.

[Production Example 4]
In Production Example 1-1, 0.05 kg of tris (2,4-di-t-butylphenyl) phosphite (A-1) was added in addition to the monomer, the chain transfer agent, and the polymerization initiator during the polymerization. A resin composition (4) was obtained in the same manner as in Production Example 1-1 except that the polymerization was performed.
When the composition of the obtained resin composition was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.9% by mass, and 10.8% by mass, respectively. .
The weight average molecular weight (Mw) was 145,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ . .

[Example 1]
(Preparation of methacrylic resin composition)
The methacrylic resin (1-1) obtained in Production Example 1-1 was vacuum dried at 90 ° C. for 5 hours, cooled to 30 ° C. under a nitrogen atmosphere, and used for the preparation of the composition.
As the organic phosphorus compound, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite (A-3) was used and dried under reduced pressure before use.
Using a tumbler mixer previously substituted with nitrogen, a mixture of 100 parts by mass of the methacrylic resin (1-1) and 0.2 parts by mass of (A-3) was prepared.
Using dehumidified air whose dew point was adjusted to −30 ° C. and temperature adjusted to 80 ° C., the resulting mixture was supplied to a 58 mmφ vented twin screw extruder and melt kneaded. At that time, a nitrogen introduction line was provided below the raw material popper attached to the twin-screw extruder, and nitrogen was introduced into the extruder. When the oxygen concentration under the raw material hopper was measured, it was about 1% by volume.
As operating conditions, the lower part of the extruder and the die set temperature of 270 ° C., the rotation speed of 200 rpm, the degree of vacuum at the vent part was 200 Torr, and the discharge rate was 120 kg / hour.
The melt-kneaded resin composition is extruded in a strand form through a perforated die, introduced into a cooling bath filled with cooling water preheated to 50 ° C., cooled and solidified, cut by a cutter, and formed into a pellet-like composition I got a thing.
When the temperature of the molten resin composition at the outlet of the porous die was measured, it was 280 ° C., and the arrival time from the outlet of the porous die to the cooling water surface was about 2 seconds.
The obtained composition contained 192 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 82 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 142,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 2]
A composition was prepared in the same manner as in Example 1 except that 0.2 parts by mass of (A-3) and 0.3 parts by mass of (A-4) were used as the organophosphorus compound.
The obtained composition contained 346 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing trivalent phosphorus element was confirmed from the analysis using ³¹ P-NMR. Moreover, 96 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 142,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 3]
A composition was prepared in the same manner as in Example 1, except that 0.2 parts by mass of (A-3) and 0.8 parts by mass of (A-6) were used as the organophosphorus compound.
The obtained composition contained 567 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 89 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 142,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 4]
A composition was prepared in the same manner as in Example 1, except that 0.1 part by mass of (A-3) and 0.1 part by mass of (A-7) were used as the organophosphorus compound.
The obtained composition contained 143 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 68 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 142,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ^−1. The composition was evaluated for injection molding. The results are shown in Table 1.

[Example 5]
A composition was obtained in the same manner as in Example 1 except that the resin composition obtained in Production Example 2-1 was used as the methacrylic resin, and 0.2 part by mass of (A-3) was used as the organic phosphorus compound. Prepared.
The obtained composition contained 215 mass ppm of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 79 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 122,000, the R value as an index of molecular weight distribution was 1.4, the glass transition temperature was 124 ° C., and the photoelastic coefficient was 1.5 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 6]
A composition was prepared in the same manner as in Example 1 except that the polymer obtained in Production Example 3-1 was used as the methacrylic resin and 0.3 part by mass of (A-6) was used as the organic phosphorus compound. did.
The obtained composition contained 145 mass ppm of the phosphorus element, and the presence of the organic phosphorus compound containing the trivalent phosphorus element was confirmed from the analysis using ³¹ P-NMR. Moreover, 12 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 112,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 140 ° C., and the photoelastic coefficient was 3.0 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 7]
A composition was prepared in the same manner as in Example 2 except that the polymer obtained in Production Example 1-2 was used as the methacrylic resin.
The obtained composition contained 355 mass ppm of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 112 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 216,000, the R value as an index of molecular weight distribution was 1.9, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 8]
The composition was obtained in the same manner as in Example 1 except that the polymer obtained in Production Example 1-3 was used as the methacrylic resin, and 0.1 part by mass of (A-3) was used as the organic phosphorus compound. Prepared.
The obtained composition contained 98 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 21 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 86,000, the R value as an index of molecular weight distribution was 1.2, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 9]
The polymer obtained in Production Example 1-4 was used as the methacrylic resin, and 0.05 part by mass of (A-1) and 0.05 part by weight of (A-6) were used as the organic phosphorus compound. A composition was prepared in the same manner as in Example 1 except that.
The obtained composition contained 42 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 10 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 108,000, the R value as an index of molecular weight distribution was 1.2, the glass transition temperature was 121 ° C., and the photoelastic coefficient was 0.4 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 10]
The polymer obtained in Production Example 1-5 was used as the methacrylic resin, and 0.1 part by mass of (A-3) and 0.2 part by mass of (A-5) were used as the organic phosphorus compound. A composition was prepared in the same manner as in Example 1 except that.
The obtained composition contained 192 mass ppm of the phosphorus element, and the presence of the organic phosphorus compound containing the trivalent phosphorus element was confirmed from the analysis using ³¹ P-NMR. Moreover, 36 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 112,000, the R value as an index of molecular weight distribution was 1.1, the glass transition temperature was 157 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 11]
The polymer obtained in Production Example 1-6 was used as the methacrylic resin, and 0.1 part by mass of (A-3) and 0.2 part by mass of (A-4) were used as the organic phosphorus compound. A composition was prepared in the same manner as in Example 1 except that.
The obtained composition contained 188 mass ppm of the phosphorus element, and the presence of the organic phosphorus compound containing the trivalent phosphorus element was confirmed from the analysis using ³¹ P-NMR. Further, it contained 49 mass ppm of a hindered phenol compound having a molecular weight of less than 300.
The weight average molecular weight (Mw) was 197,000, the R value as an index of molecular weight distribution was 0.8, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 12]
A composition was prepared in the same manner as in Example 11 except that the polymer obtained in Production Example 1-7 was used as the methacrylic resin.
The obtained composition contained 189 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 63 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 116,000, the R value as an index of molecular weight distribution was 1.7, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 13]
The composition was the same as in Example 1 except that the resin composition obtained in Production Example 1-8 was used as the methacrylic resin, and 0.2 part by mass of (A-6) was used as the organic phosphorus compound. Was prepared.
The obtained composition contained 480 mass ppm of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 79 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 155,000, the R value as an index of molecular weight distribution was 1.2, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Example 14]
As an organophosphorus compound, the same procedure as in Example 1 was performed except that 0.3 part by mass of (A-8) was used and 0.05 part by weight of 2,6-di-tert-butyl-p-cresol was newly added. A composition was prepared.
The obtained composition contained 256 mass ppm of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element could not be confirmed from the analysis using ³¹ P-NMR. Moreover, 190 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight was 142,000, the R value as an index of the molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

[Comparative Example 1]
The resin composition obtained in Production Example 4 contained 8 mass ppm of phosphorus element, and the presence of an organophosphorus compound containing trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 8 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 145,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
The obtained resin composition was used as it was without adding a new organic phosphorus compound and without being melt kneaded and granulated by a twin screw extruder, and was subjected to injection molding evaluation. The results are shown in Table 1.
From this result, it can be seen that when the phosphorus element content is extremely low, the mold contamination is deteriorated due to the decomposition of the resin composition.

[Comparative Example 2]
A composition was prepared in the same manner as in Example 1 except that 2.0 parts by mass of (A-3) was used as the organophosphorus compound.
The obtained composition contained 1870 mass ppm of the phosphorus element, and the presence of the organic phosphorus compound containing the trivalent phosphorus element was confirmed from the analysis using ³¹ P-NMR. Moreover, the hindered phenol compound of molecular weight less than 300 was contained 690 mass ppm.
The weight average molecular weight (Mw) was 142,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.
From this result, when the composition is prepared under the condition that a large amount of hindered phenol compound having a molecular weight of less than 300, which is a decomposition product of the used organic phosphorus compound, is left, it causes a problem in melt molding such as injection molding. I understand.

[Comparative Example 3]
In advance, 94 parts by mass of the polymer obtained in Production Example 1-1 and 6 parts by mass of (A-3) as an organophosphorus compound were mixed, and melt-kneaded in the same manner as in Example 1 to obtain an organophosphorus compound. A masterbatch composition containing a high concentration was prepared.
Using 5 parts by mass of this composition and 95 parts by mass of the polymer obtained in Production Example 1-1, the same composition as in Example 1 was melt-kneaded again using a twin screw extruder to prepare a composition. did.
The obtained composition contained 287 ppm by mass of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Further, the hindered phenol compound having a molecular weight of less than 300 was contained at 570 mass ppm.
The weight average molecular weight (Mw) was 142,000, the R value as an index of molecular weight distribution was 1.3, the glass transition temperature was 135 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.
Also from this result, when the composition is prepared under the condition that a large amount of hindered phenol compound having a molecular weight of less than 300, which is a decomposition product of the used organophosphorus compound, remains, it causes a problem in melt molding such as injection molding. I understand that.

[Comparative Example 4]
A composition was prepared in the same manner as in Example 5 except that the vent port of the twin screw extruder with vent used for preparing the composition was closed.
The obtained composition contained 215 mass ppm of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Further, the hindered phenol compound having a molecular weight of less than 300 was contained at 635 mass ppm.
The weight average molecular weight (Mw) was 123,000, the R value as an index of molecular weight distribution was 1.4, the glass transition temperature was 124 ° C., and the photoelastic coefficient was 1.5 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.
Also from this result, when the composition is prepared under the condition that a large amount of hindered phenol compound having a molecular weight of less than 300, which is a decomposition product of the used organophosphorus compound, remains, it causes a problem in melt molding such as injection molding. I understand that.

[Comparative Example 5]
The polymer obtained in Production Example 3-2 was used as the methacrylic resin, and 0.1 part by mass of (A-3) and 0.2 part by mass of (A-4) were used as the organic phosphorus compound. A composition was prepared in the same manner as in Example 1 except that.
The obtained composition contained 186 ppm by mass of phosphorus element, and the presence of an organic phosphorus compound containing a trivalent phosphorus element was confirmed by analysis using ³¹ P-NMR. Moreover, 190 mass ppm of hindered phenol compounds with a molecular weight of less than 300 were contained.
The weight average molecular weight (Mw) was 96,000, the R value as an index of molecular weight distribution was 1.6, the glass transition temperature was 166 ° C., and the photoelastic coefficient was 3.0 × 10 ⁻¹² Pa ⁻¹ .
Injection molding evaluation was performed using the obtained composition. The results are shown in Table 1.

  The methacrylic resin composition of the present invention is excellent in transparency, heat resistance, weather resistance, and birefringence is highly controlled. As an optical material, for example, liquid crystal Polarizing plate protective films used for displays such as displays, plasma displays, organic EL displays, field emission displays, rear projection televisions, retardation plates such as quarter-wave plates and half-wave plates, viewing angle control films, etc. In the field of liquid crystal optical compensation film, display front plate, display substrate, lens, etc., transparent substrate used for solar cells, transparent conductive substrate such as touch panel, and further optical communication system, optical switching system, optical measurement system, Waveguide, lens, lens array, optical fiber, optical fiber coating material, ED lens, to the lens cover and the like can be suitably used.

Claims (6)

The structural unit (X) includes a structural unit (X) having a ring structure in the main chain, and the structural unit (X) is composed of a structural unit derived from an N-substituted maleimide monomer, a glutarimide-based structural unit, and a lactone ring structural unit. Including at least one selected methacrylic resin and an organophosphorus compound,
The glass transition temperature is over 120 ° C. and below 160 ° C.,
The phosphorus element content is 143 to 1000 ppm by mass,
The content of a hindered phenol compound having a molecular weight of less than 300 is 5 to 120 mass ppm or less, and a methacrylic resin composition.   The methacrylic resin composition according to claim 1, wherein the organic phosphorus compound includes an organic phosphorus compound having a trivalent phosphorus element.   The methacrylic resin composition of Claim 1 or 2 whose weight average molecular weight (Mw) of polymethylmethacrylate measured by GPC measurement method is 80,000-170,000. The R value of the following formula derived from the weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) in terms of polymethyl methacrylate measured by GPC is 1.0 to 1.5. The methacrylic resin composition according to any one of claims 1 to 3, which is a range.
R value = [Mw / Mn] / [Mz / Mw] The methacrylic resin composition according to any one of claims 1 to 4, wherein the absolute value of the photoelastic coefficient is 3.0 × 10 ^-12 Pa ^-1 or less. The methacrylic resin composition according to claim 5, wherein the absolute value of the photoelastic coefficient is 1.0 × 10 ⁻¹² Pa ⁻¹ or less.