JP6247372B2 - Methacrylic resin composition - Google Patents

Description

  The present invention relates to a methacrylic resin composition having high heat resistance, excellent optical properties such as birefringence, and capable of stably producing a stretched film excellent in quality.

  In recent years, methacrylic resins have attracted attention as optical resins for various optical materials, mainly optical films, for example, because they have excellent transparency, surface hardness, etc., and low birefringence, which is an optical property. 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 characteristics. In applications such as polarizer protective films or retardation films, the demand is rapidly expanding.

  These films for image display devices use unstretched, longitudinally uniaxially stretched, and biaxially stretched films. In particular, because of their good performance balance, biaxially stretched films using the sequential biaxial stretching method. The number of cases where is adopted is increasing.

  In recent years, when a biaxially stretched film is obtained by a continuous sequential biaxial stretching method, the equipment used for the longitudinal stretching process is inexpensive because it uses an oven type that requires a large heat-retaining furnace or heating furnace. A roll longitudinal stretching apparatus using a plurality of drive heating rolls with different peripheral speeds that can be realized is used, and then lateral stretching using a tenter is being standardized.

  However, a methacrylic resin whose heat resistance is improved by introducing various ring structures into the structural unit in the methacrylic resin becomes hard and brittle, for example, when it is processed into a film by melt molding, Only inferior flexibility film can be obtained, such as breakage and cracking of the end of the film during transportation, and the film itself breaks during the subsequent secondary processing. Many issues remain.

  As a method for solving this problem, for example, Patent Document 1 discloses a film that achieves both heat resistance and flexibility by biaxially stretching an acrylic resin film.

  At that time, as a specific example of the biaxial stretching method, only a batch type biaxial stretching method using a tenter is disclosed, and various problems at the time of secondary stretching by continuous sequential stretching have been disclosed. The content alone is not enough improvement.

  Further, in Patent Document 2, in sequential biaxial stretching by a combination of longitudinal stretching using rolls having different peripheral speeds and transverse stretching by a tenter, after performing longitudinal stretching under conditions where specific birefringence characteristics are expressed, It discloses that a stable biaxially stretched film can be produced by performing transverse stretching.

  As a method for expressing a specific birefringence characteristic, it has been proposed to use a plurality of heating means in combination while controlling the distance between rolls having different peripheral speeds to a specific interval during longitudinal stretching.

  However, it is not sufficient when there are fluctuations in the tenter clip temperature associated with continuous operation, etc., and it is not sufficient for solving the fluctuations in thickness in the width direction and longitudinal direction of the obtained stretched film.

  Moreover, in patent document 3, when extending | stretching using the film before extending | stretching which consists of a thermoplastic resin which has an acrylic resin as a main component, the edge part becomes thicker the film thickness distribution of the width direction of the film before extending | stretching. It is disclosed that stable stretching is possible by controlling.

  Looking at the evaluation results regarding the effect of improving stretchability, a simple two-stage evaluation result of “edge cracking” or “no problem” is disclosed.

  However, since it is important to form a specific thickness distribution in the width direction in the film before stretching, in order to require a special T die or to stably obtain a film having a specific thickness distribution, Not only does complicated operations increase, such as the need for advanced control when the resin is discharged, but in the longitudinal stretching using the subsequent roll stretching method, fluctuations in the stretching point during stretching and the width of the film after stretching There are concerns about variations in thickness in the direction and longitudinal direction.

  Furthermore, in Patent Document 4, when a film made of a thermoplastic resin containing an acrylic polymer is longitudinally stretched, a roll stretching apparatus including a plurality of preheating rolls and a plurality of cooling rolls in its configuration is used. It is disclosed that stable longitudinal stretching can be achieved by adopting a method of heating the infrared light emitting part capable of emitting near infrared rays having a specific wavelength in the stretched part while controlling the speed of the film to specific conditions. ing.

  However, in Patent Document 4, it is premised that a pre-stretch film having a specific film thickness distribution disclosed in Patent Document 3 is used, and it is effective even when there is no specific film thickness distribution. I'm not sure. In addition, the evaluation criteria for stretching stability are not specifically disclosed, and in longitudinal stretching by roll stretching, a shift in stretching point and accompanying film width variation, thickness in the width direction and longitudinal direction of the film. It remains unclear whether the problem can be solved only by the disclosed contents with respect to fluctuations and solutions to defects such as curling at the film edge.

  In the patent document shown above, it is an attempt to solve the problem mainly by devising the film characteristics at the time of film stretching, the film stretching apparatus and the stretching conditions.

  On the other hand, in patent document 5, the film which consists of a thermoplastic resin from which an edge part differs from a center part is used as a film for extending | stretching, and a thermoplastic resin with larger impact strength is used as resin which comprises an edge part. It is disclosed that the film can be stably stretched by adopting it.

  However, it is necessary to use an expensive T-die having a structure in which different thermoplastic resins are used and whose flow paths are controlled. Further, when the film is formed, the thickness unevenness increases or the phase difference between the thermoplastic resins used is increased. If the solubility is insufficient, there are many problems such as the film being easily broken during film formation, which is not practical.

  Furthermore, in Patent Document 6, in order to cope with further thinning of a stretched film, the movement of the thermoplastic resin used in stretching of a thermoplastic resin containing an amorphous vinyl polymer having a ring structure in the main chain is described. It is disclosed that a thin biaxially stretched film having a thickness of 35 μm or less can be produced by controlling the molecular weight between entanglement points in the rubber-like flat region of the dynamic viscoelastic spectrum and the entanglement number within a specific range.

  In general, when a methacrylic resin is used as the amorphous vinyl polymer, a rubber-like flat region in the dynamic viscoelastic spectrum is often not clearly expressed, and in particular, a methacrylic resin having a relatively high glass transition temperature. In many types of resins, parameters related to entanglement cannot be determined with high accuracy by a dynamic viscoelastic spectrum.

  In patent document 6, although the parameter regarding an entanglement is employ | adopted as a characteristic of the thermoplastic resin to be used, in the disclosed example in the Example, it is entangled using the viscoelastic property in the film before extending | stretching after melt film formation. There are many unclear points regarding the determination, such as calculating parameters related to.

  In addition, as specific examples of the biaxial stretching method, only examples in which a thin film can be formed by a batch type biaxial stretching method using a tenter are disclosed, and various problems in continuous sequential stretching composed of roll stretching and tenter stretching are disclosed. There is no mention or suggestion of whether it can be solved.

JP 2008-242426 A JP 2010-271690 A JP 2010-69731 A JP 2014-83703 A JP 2014-69437 A JP 2014-193982 A

  In recent years, with the increase in area of image display devices, there has been a strong demand for thinning and increasing the area of these films. In addition to solving problems by devising film stretching devices and stretching conditions, the resin or resin composition itself Of a methacrylic resin excellent in optical properties and heat resistance, and a composition containing the same, which can solve the above-mentioned problems at an early stage, can provide a higher quality optical film with excellent molding process stability. Offer is expected.

  Therefore, an object of the present invention is to provide a methacrylic resin composition capable of stably producing a stretched film having excellent optical properties such as birefringence and excellent quality.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a methacrylic resin having a ring structure in the main chain when a film before stretching is prepared into a stretched film through a stretching process. Are subject to various thermal histories within a temperature range from about 100 ° C. lower than the glass transition temperature to about 50 ° C. higher than the glass transition temperature, and in this temperature range, It was noticed that the methacrylic resin having a ring structure was subjected to stretching while changing its higher order structure from a glass state to a rubber state before the start of melt flow.

  As a result of further earnest studies, the present inventors have made stable viscoelasticity measurements in the above temperature range in order to stably produce a stretched film having stable quality and high optical properties. A starting material is a methacrylic resin and / or a composition thereof in which the temperature at which the loss elastic modulus and the loss tangent are maximized, and the higher order structure of the solid in the temperature range before and after the temperature, are highly controlled. It has been found that the above-mentioned problems can be solved by using it, and the present invention has been completed.

That is, the present invention is as follows.
[1] A structural unit (X) having a ring structure in the main chain, wherein the (X) structural unit is at least selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer and a lactone ring structural unit This is a methacrylic resin composition containing two or more methacrylic resins, which is a kind, and has a maximum value (T _{G ″ max} ) in the temperature dispersion spectrum of the loss modulus obtained by dynamic viscoelasticity measurement. Is 120 to 160 ° C., and the minimum value of the loss tangent in the range from the temperature (T _{tan δmax} ) showing the maximum value in the temperature dispersion spectrum of the loss tangent obtained by dynamic viscoelasticity measurement to a temperature higher by 50 ° C. is A methacrylic resin composition, which is 0.7 to 1.2.
[2] The loss tangent is 10% higher than the minimum value from the minimum value of the loss tangent in the range from the temperature (T _{tan δmax} ) showing the maximum value in the temperature dispersion spectrum of the loss tangent to the temperature 50 ° C. higher than the temperature. The methacrylic resin composition according to [1], wherein the temperature difference (ΔT) indicating the value is 12 to 24 ° C.
[3] The methacrylic resin composition according to [1] or [2], in which the weight average molecular weight (Mw) in terms of polymethyl methacrylate measured by GPC is 120,000 to 260,000.
[4] The structural unit (X) includes a structural unit derived from an N-substituted maleimide monomer, and the content of the structural unit derived from the N-substituted maleimide monomer is 100% by mass of the methacrylic resin. The methacrylic resin composition according to any one of [1] to [3], which is 5 to 40% by mass.
[5] The (X) structural unit includes a lactone ring structural unit, and the content of the lactone ring structural unit is 5 to 40% by mass with respect to 100% by mass of the methacrylic resin. [3] The methacrylic resin composition according to any one of [3].
[6] The methacrylic resin composition according to any one of [1] to [5], wherein the absolute value of the photoelastic coefficient is 2.0 × 10 ⁻¹² Pa ⁻¹ or less.
[7] The methacrylic resin composition according to [6], wherein the absolute value of the photoelastic coefficient is 1.0 × 10 ⁻¹² Pa ⁻¹ or less.

  According to the present invention, it is possible to provide a methacrylic resin composition capable of stably producing a stretched film having excellent optical properties such as birefringence and excellent quality.

It is a figure which shows the temperature dispersion spectrum of the typical loss elastic modulus obtained when it uses for the dynamic viscoelasticity measurement of the methacrylic-type resin composition of this embodiment, and the temperature dispersion spectrum of a loss tangent. In the figure, particularly with respect to the vertical axis, the right vertical axis represents loss tangent (-), and the left vertical axis represents loss elastic modulus (Pa).

  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 the present embodiment includes a methacrylic resin and, if necessary, includes other thermoplastic resins and additives.

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

  Hereinafter, each monomer structural unit will be described.

--Methacrylate ester unit--
First, the methacrylic acid ester monomer unit will be described.
The methacrylic acid ester monomer unit is formed, for example, from 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 methacrylic acid ester single unit may contain only one kind or two or more kinds.

  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 the monomer represented by the following formula (1) and / or the 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。
また、Ｒ^１は、ハロゲン原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、ニトロ基、ベンジル基等の置換基で置換されていてもよい。

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

式（２）中、Ｒ^４は、水素原子、炭素数３〜１２のシクロアルキル基、炭素数１〜１８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 18 carbon atoms, and R ⁵ and R ⁶ are each independently a hydrogen atom. , 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-1H-pyrrole-2,5-dione, 1-cyclohexyl-3,4-dimethyl-1H-pyrrole-2,5-dione, 1-cyclohexyl-3-phenyl-1H-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 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 suspension polymerization, bulk polymerization, and solution polymerization, and more preferred is solution polymerization.
In the manufacturing method in the present embodiment, any of a batch polymerization method, a semi-batch polymerization method, and a continuous polymerization method can be used as the polymerization method.
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”), it is produced by radical polymerization using a solution polymerization method. The case where it does is demonstrated concretely.
In the present embodiment, a method in which a part of the monomer is charged into the reactor before the start of polymerization, the polymerization is started by adding a polymerization initiator, and the remainder of the monomer is supplied, so-called semi-batch weight. Legal methods can be preferably used. By adopting this method, it tends to be easy to control the molecular weight distribution and composition distribution of the polymer obtained.

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 examples of the polymerization solvent include 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 90-150 degreeC, More preferably, it is 100-140 degreeC, More preferably, it is 100-130 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.
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. is there.

These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.
In this embodiment, the type of initiator, the amount of initiator, the polymerization temperature, etc. so that the ratio of the total amount of radicals generated from the polymerization initiator to the total amount of unreacted monomers remaining in the reaction system is always below a certain value. Is preferably selected as appropriate.
In particular, in this embodiment, at least once in the first half of the time from the start of addition of the polymerization initiator to the end of the addition (polymerization initiator addition time), the addition amount per unit time of the polymerization initiator is changed to the unit at the start of addition. It is preferable to make it smaller than the addition amount per hour.
By adopting this method, it is possible to suppress the production amount of oligomers and low molecular weight substances in the later stage of polymerization, or to suppress the overheating at the time of polymerization and to achieve the stability of polymerization.

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 comprising a tubular heat exchanger and a devolatilization tank; thin film evaporators such as Wibren manufactured by Shinko Environmental Solution Co., Ltd. And a vented extruder having sufficient residence time and surface area to exhibit devolatilization performance.
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.

Moreover, as above-mentioned, as another example of the manufacturing method of the methacrylic resin which has a structural unit derived from an N-substituted maleimide monomer, it may manufacture by radical polymerization using a suspension polymerization method.
In the suspension polymerization method, a particulate (bead-shaped) methacrylic resin can be produced through a polymerization process, a washing process, a dehydration process, and a drying process.
As the suspension polymerization method, an aqueous suspension polymerization method using water as a medium is preferably used. Here, more specifically, using a stirrer, a monomer as a raw material, a suspending agent, and if necessary, a polymerization initiator and other additives are supplied into the stirrer, and a polymerization reaction is performed. I do. A slurry containing methacrylic resin particles is obtained by polymerization, and the methacrylic resin particles are separated and recovered through washing, dehydration and drying.
The polymerization temperature is preferably 40 to 90 ° C. in consideration of productivity and the amount of aggregates produced. The polymerization time effectively suppresses heat generation during polymerization, and prevents the formation of aggregates. From the viewpoint of reduction, 20 to 240 minutes is preferable.
Further, from the viewpoint of reducing the residual monomer, it is also preferable to carry out a step of raising the temperature to a temperature higher than the polymerization temperature and holding at that temperature for a certain period of time after the polymerization step. The temperature maintained at this time is not less than 5 ° C. higher than the polymerization temperature and not more than the glass transition temperature of the resulting methacrylic resin, so that resin particles having a high degree of polymerization and a small angle of repose can be easily obtained. Therefore, it is preferable.

Although details will be described later in this embodiment, from the viewpoint of obtaining suitable dynamic viscoelastic properties in the resin composition, a methacrylic resin having the same kind of ring structure in the main chain and having different weight average molecular weight and molecular weight distribution. It is preferable to use two or more of these, and appropriately select the weight average molecular weight and molecular weight distribution, and the mixing ratio thereof.
In this embodiment, before preparing the composition, at least the structure derived from the monomer represented by the above formula (1) and the simple structure represented by the above formula (2) are used as the skeleton. It is preferable to prepare by mixing two or more methacrylic resins having a structure derived from a monomer and having different weight average molecular weights and molecular weight distributions.

In the present embodiment, the range of the weight average molecular weight (Mw) of the methacrylic resin used when mixing and preparing two or more types may be arbitrarily selected from the range of 70,000 to 800,000, respectively.
When the weight average molecular weight (Mw) is low (hereinafter referred to as “low molecular weight component”), the weight average molecular weight is preferably in the range of 70,000 to 150,000, and more preferably 100,000 to More preferably, it is in the range of 150,000. The molecular weight distribution (Mw / Mn) is preferably in the range of 1.5 to 2.5.
In the case of a material having a high weight average molecular weight (Mw) (hereinafter referred to as “high molecular weight component”), the weight average molecular weight is preferably in the range of 220,000 to 800,000, particularly 220,000 to More preferably, it is in the range of 600,000. The molecular weight distribution (Mw / Mn) is preferably in the range of 2.5 to 4.0.
Although there is no restriction | limiting in particular as a mixing ratio of the low molecular weight component and high molecular weight component in this embodiment, It can select suitably from the range of 5-95 mass parts of low molecular weight components and 95-5 mass parts of high molecular weight components. .

  By mixing two or more methacrylic resins as described above, it is possible to prepare a stretched film that has excellent stretch processability, optical uniformity, and can exhibit highly controlled birefringence characteristics. become.

  In the present embodiment, the method of mixing two or more methacrylic resins having different weight average molecular weights (Mw) is not particularly limited, but 2 polymers having different weight average molecular weights obtained by the polymerization reaction described above are used. Adopting a method in which a solution containing seeds or more is mixed in a liquid phase, followed by a treatment in a devolatilization step or a precipitation treatment by addition of a poor solvent; a method in which mixing is performed using a melt-kneading apparatus such as an extruder; Can do. When using a methacrylic resin having a particularly high molecular weight, a solution containing two or more polymers obtained by the polymerization reaction is mixed in the liquid phase, and then precipitated by treatment in a devolatilization step or addition of a poor solvent. It is preferable to use a method of performing the treatment.

  Further, as described above, in this embodiment, a methacrylic resin produced by suspension polymerization such as an organic suspension polymerization method or an inorganic suspension polymerization method is added to the methacrylic resin produced by the solution polymerization method. May be used in the preparation of the composition.

--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).

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。

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.

--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-2006-171464, JP-A-2007-63541, JP-A-2007-297620, JP-A-2010-180305, and the like.

  The lactone ring structural unit constituting the methacrylic resin of this embodiment may be formed after resin polymerization.

The lactone ring structural unit in the present embodiment is preferably a 6-membered ring because it is excellent in the stability of the ring structure.
As the lactone ring structural unit which is a 6-membered ring, for example, a structure represented by the following general formula (4) is particularly preferable.

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。

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 a methyl group, an ethyl group, and a propyl group (alkyl groups and the like); 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 the range of 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 described above in the patent document.

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 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 it is preferably 50 to 200 ° C from the viewpoint of productivity, more preferably 80 to 150 ° C, and still more preferably 90 to 130 ° C. is there.

  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.

These polymerization initiators may be added at any stage as long as the polymerization reaction is in progress.
In this embodiment, the type of initiator, the amount of initiator, the polymerization temperature, etc. so that the ratio of the total amount of radicals generated from the polymerization initiator to the total amount of unreacted monomers remaining in the reaction system is always below a certain value. Is preferably selected as appropriate.
In particular, in this embodiment, at least once in the first half of the time from the start of addition of the polymerization initiator to the end of the addition (polymerization initiator addition time), the addition amount per unit time of the polymerization initiator is changed to the unit at the start of addition. It is preferable to make it smaller than the addition amount per hour.
By adopting this method, it is possible to suppress the production amount of oligomers and low molecular weight substances in the later stage of polymerization, or to suppress the overheating at the time of polymerization and to achieve the stability of polymerization.

As the chain transfer agent, a chain transfer agent used in general radical polymerization can be used. For example, the chain transfer agent disclosed in the method for preparing a methacrylic resin having a structural unit derived from the N-substituted maleimide monomer is used. it can.
These may be used alone or in combination of two or more.
These chain transfer agents may be added at any stage as long as the polymerization reaction is in progress, and are not particularly limited.
The 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, and 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 with a perforated die, and is cold-cut, aerial hot-cut, underwater strand-cut, and underwater-cut. Process into pellets.

Although details will be described later in this embodiment, from the viewpoint of obtaining suitable dynamic viscoelastic properties in the resin composition, a methacrylic resin having the same kind of ring structure in the main chain and having different weight average molecular weight and molecular weight distribution. It is preferable to use two or more of these, and appropriately select the weight average molecular weight and molecular weight distribution, and the mixing ratio thereof.
In this embodiment, before preparing the composition, at least the structure derived from the monomer represented by the above formula (1) and the simple structure represented by the above formula (2) are used as the skeleton. It is preferable to prepare by mixing two or more methacrylic resins having a structure derived from a monomer and having different weight average molecular weights and molecular weight distributions.

In the present embodiment, the range of the weight average molecular weight (Mw) of the methacrylic resin used when mixing and preparing two or more types may be arbitrarily selected from the range of 70,000 to 800,000, respectively.
When the weight average molecular weight (Mw) is low (hereinafter referred to as “low molecular weight component”), the weight average molecular weight is preferably in the range of 70,000 to 150,000, and more preferably 100,000 to More preferably, it is in the range of 150,000. The molecular weight distribution (Mw / Mn) is preferably in the range of 1.5 to 2.5.
In the case of a material having a high weight average molecular weight (Mw) (hereinafter referred to as “high molecular weight component”), the weight average molecular weight is preferably in the range of 220,000 to 800,000, particularly 220,000 to More preferably, it is in the range of 600,000. The molecular weight distribution (Mw / Mn) is preferably in the range of 2.5 to 4.0.
Although there is no restriction | limiting in particular as a mixing ratio of the low molecular weight component and high molecular weight component in this embodiment, It can select suitably from the range of 5-95 mass parts of low molecular weight components and 95-5 mass parts of high molecular weight components. .

  By mixing two or more methacrylic resins as described above, it is possible to prepare a stretched film that has excellent stretch processability, optical uniformity, and can exhibit highly controlled birefringence characteristics. become.

  In the present embodiment, the method of mixing two or more methacrylic resins having different weight average molecular weights (Mw) is not particularly limited, but polymers having different weight average molecular weights obtained by the aforementioned polymerization reaction are used. It is possible to employ a method of mixing a solution containing two or more kinds in a liquid phase, and then performing a cyclization reaction using an extruder, a devolatilization step treatment, or a precipitation treatment by addition of a poor solvent.

  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.

(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.
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 one or more of the process and the molding process, for example, a sintered filter having a filtration accuracy of 1.5 to 20 μm, a pleated filter, a leaf disk type polymer filter and the like are added to the filtration device and prepared. It is also a preferable method.

Regardless of which method is selected, it is preferable to reduce the oxygen and moisture as much as possible when producing the methacrylic resin composition.
For example, the dissolved oxygen concentration in the polymerization solution in solution polymerization is 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 less than 1% by volume. It is preferable to be less than 0.8% by volume.
It is recommended that the water content of the methacrylic resin is adjusted to preferably 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 adopting a manufacturing method using an extruder, the pelletized methacrylic resin as a raw material is heated under reduced pressure or dehumidified air and sufficiently dried in advance to remove moisture as much as possible. And preferably used. At that time, when various antioxidants and additives described later are blended, it is preferable to blend these various antioxidants and additives themselves after sufficiently reducing the amount of water contained therein.
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.
There is no particular limitation on the degree of decompression, and the degree of decompression may be selected as appropriate.

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 loss tangent change at a high temperature range is highly controlled as in the present 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 should be lowered as much as possible, the residence time from the perforated die outlet to the cooling water surface should be minimized, and the cooling water temperature should be as high as possible. It is more preferable to perform granulation.
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.

  As described above, from the viewpoint of obtaining suitable dynamic viscoelastic properties in the resin composition, two or more methacrylic resins having the same kind of ring structure in the main chain and having different weight average molecular weight and molecular weight distribution are used. It is preferable to prepare the resin composition by appropriately selecting the weight average molecular weight and molecular weight distribution, and the mixing ratio thereof.

  As described above, according to such a method, it is possible to prepare a stretched film that has excellent stretch processability, excellent optical uniformity, and can exhibit highly controlled birefringence characteristics.

  In the present embodiment, the method for preparing a resin composition by mixing two or more methacrylic resins having the same cyclic structural unit in the main chain and different weight average molecular weights (Mw) is not particularly limited. For example, a melt kneading method using an extruder can be employed.

  Also, details of the two types of methacrylic resins, and among the two types of methacrylic resins, those having a low and high weight average molecular weight (Mw), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), mixing The details of the ratio may be as described above.

  In particular, it is preferable that the molecular weight distribution of the high molecular weight component is larger than the molecular weight distribution of the low molecular weight component because the homogeneity of the resin composition is further improved and a stretched film having excellent quality can be stably produced.

  As described above, the mixing ratio of the low molecular weight component and the high molecular weight component in the present embodiment can be appropriately selected from the range of 5 to 95 parts by mass of the low molecular weight component and 95 to 5 parts by mass of the high molecular weight component. It is preferable that it is the range of 70-95 mass parts of low molecular weight components, and 30-5 mass parts of high molecular weight components. By mixing in this range, in the preparation of an unstretched film, a high-quality film can be stably obtained from the time of melt processing, and in the preparation of a stretched film, a high-quality stretched film can be stably obtained. It is done.

  As described above, the method of mixing two or more methacrylic resins is not particularly limited, and a method of performing a post-treatment by mixing a solution containing two or more polymers in a liquid phase, or after granulation A method of mixing using a melt-kneading apparatus such as an extruder can be employed. When a methacrylic resin having a particularly high molecular weight is used, a solution containing two or more kinds of polymers is mixed in the liquid phase. A method of performing post-treatment is preferred.

-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 卜 copolymer particles obtained by multistage polymerization, etc. 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 copolymer particles, and rubbery polymers, 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.

-Antioxidant-
In the methacrylic resin composition according to the present embodiment, a hindered phenolic antioxidant, a phosphorus antioxidant, and a sulfur antioxidant are exhibited in order to exhibit the original polymer characteristics of the methacrylic resin of the present embodiment. It is preferable to add an antioxidant such as an agent.
These can be used alone or in combination of two.

Specific examples of the hindered phenol antioxidant include, but are not limited to, for example, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], Thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,3 ', 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl) tri-p-cresol, 4,6 -Bis (octylthiomethyl) -o-cresol, 4,6-bis (dodecylthiomethyl) -o-cresol, ethylenebis (oxyethylene) bis [3- (5-t rt-butyl-4-hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-tris (3 5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 1,3,5-tris [(4-tert- Butyl-3-hydroxy-2,6-xylin) methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamine) phenol, acrylic acid 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl]- 4, - di -tert- pentylphenyl, acrylic acid 2-tert-butyl-4-methyl-6- (2-hydroxy -3-tert-butyl-5-methylbenzyl) phenyl and the like.
In particular, pentaerythritol terakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, Acrylic acid 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl is preferred.

The hindered phenolic antioxidant may be a commercially available phenolic antioxidant. Such a commercially available phenolic antioxidant is not limited to the following, for example: Irganox 1010 (Irganox 1010: pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], manufactured by BASF), Irganox 1076 (Irganox 1076: octadecyl-3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by BASF), Irganox 1330 (Irganox 1330: 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-t) -Butyl-a, a ', a''-(mesitylene-2,4,6-triyl) tri-p-cresol, Manufactured by ASF), Irganox 3114 (Irganox 3114: 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H , 3H, 5H) -trione (manufactured by BASF), Irganox 3125 (Irganox 3125, manufactured by BASF), Adekastab AO-60 (pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxy) Phenyl) propionate], manufactured by ADEKA), Adekastab AO-80 (3,9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxyoxy] -1,1 -Dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] undecane (manufactured by ADEKA)), Smizer BHT (Sumilizer BHT, manufactured by Sumitomo Chemical), Cyanox 1790 (Cyanox 1790, manufactured by Cytec), Sumilizer GA-80 (Sumilizer GA-80, manufactured by Sumitomo Chemical), Sumitizer GS (Sumizer GS: acrylic acid 2- [1- (2 -Hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl, manufactured by Sumitomo Chemical Co., Ltd., Sumilizer GM (2-tert-butyl-4-methyl acrylate) -6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl, manufactured by Sumitomo Chemical Co., Ltd.), vitamin E (manufactured by Eisai) and the like.
Among these commercially available phenolic antioxidants, Irganox 1010, Adekastab AO-60, Adekastab AO-80, Irganox 1076, and Sumilizer GS are preferred from the viewpoint of imparting thermal stability with the resin.
These may be used alone or in combination of two or more.

  Examples of the phosphorus antioxidant include those classified into phosphites and phosphonites.

  Specific examples of phosphorus-based antioxidants for phosphites include, but are not limited to, for example, 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, cyclic neopentane And tetraylbis (2,6-di-t-butyl-4-methylphenyl) phosphite.

  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 (A EKASTAB PEP24G: cyclic neopentanetetrayl bis (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 (Sumil zerGP: (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.).

Specific examples of phosphoric antioxidants for phosphonites include, for example, tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylenediphosphonite, tetrakis (2,4-di-tert-butyl). Examples include -5-methylphenyl) 4,4'-biphenylene diphosphonite.
It may be a commercially available phosphorus-based antioxidant, Hostanox P-EPQ (P-EPQ: tetrakis (2,4-di-tert-butylphenyl) 4,4′-biphenylene diphosphonite: manufactured by Clariant Co. Ltd) , GSY P101 (tetrakis (2,4-di-t-butyl-5methylphenyl) 4,4′-biphenylenediphosphonite: manufactured by Sakai Chemical Co., Ltd.) and the like.

In addition, specific examples of the sulfur-based antioxidant are not limited to the following. For example, 2,4-bis (dodecylthiomethyl) -6-methylphenol (Irganox 1726, manufactured by BASF), Irganox 1520L, manufactured by BASF), 2,2-bis {[3- (dodecylthio) -1-oxopolopoxy] methyl} propane-1,3-diylbis [3-dodecylthio] propionate] (ADK STAB AO-412S, ADEKA 2,2-bis {[3- (dodecylthio) -1-oxopolopoxy] methyl} propane-1,3-diylbis [3-dodecylthio] propionate] (cheminox PLS, manufactured by Chemipro Kasei Co., Ltd.), di (tridecyl) ) 3,3′-thiodipropionate (AO-503, manufactured by ADEKA) and the like. It is.
Among these commercially available sulfur antioxidants, Adeka Stab AO-412S and Cheminox PLS are preferable from the viewpoints of the effect of imparting thermal stability with the resin, the effect of combined use with various antioxidants, and the handleability.
These sulfur-based antioxidants may be used alone or in combination of two or more.

  The content of the antioxidant may be an amount that can achieve the effect of improving the thermal stability, and if the content is excessive, there is a possibility that problems such as bleeding out during processing may occur. The amount is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, still more preferably 0.8 parts by mass or less, more preferably 100 parts by mass or less based on methacrylic resin. More preferably, it is 0.01-0.8 mass part, Most preferably, it is 0.01-0.5 mass part.

-Other additives-
The methacrylic resin composition according to this embodiment may contain other additives as long as the effects of this embodiment are not significantly impaired.
Other additives are not particularly limited, but include, for example, inorganic fillers; pigments such as iron oxides; lubricants such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bisstearamide.・ Mold release agent: Softeners / plasticizers such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, mineral oil, etc .; hindered amine light stabilizer; benzotriazole ultraviolet absorber; Higher alcohols such as cetyl alcohol and stearyl alcohol; Release agents such as higher fatty acid esters of glycerin such as stearic acid monoglyceride and stearic acid diglyceride; Flame retardants; Antistatic agents; Reinforcing organic fibers, glass fibers, carbon fibers, metal whiskers, etc. Agent; coloring agent; Other additives; or mixtures thereof.

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

The methacrylic resin composition of the present embodiment preferably has a polymethyl methacrylate equivalent weight average molecular weight (Mw) measured by GPC measurement method of 120,000 to 260,000, more preferably 120,000 to 240,000, more preferably 120,000 to 230,000.
When the weight average molecular weight (Mw) is in this range, the balance between mechanical strength and moldability is excellent, which is preferable.
Specifically, the weight average molecular weight (Mw) of the methacrylic resin composition can be measured by the method described in Examples below.

-Dynamic viscoelastic properties-
The methacrylic resin composition containing the structural unit (X) having a ring structure in the main chain of the present embodiment has a maximum temperature (T) in the temperature dispersion spectrum of the loss elastic modulus when subjected to dynamic viscoelasticity measurement. _{G "max),} the temperature showing the maximum value at a temperature variance spectrum of the loss tangent _{(T tanδmax),} in the range from a temperature _{(T tanδmax)} showing a maximum in the temperature variance spectrum of the loss tangent to 50 ° C. higher temperature than the said temperature The temperature (T _{tan δmin} ) showing the minimum value of the loss tangent is shown.
FIG. 1 shows a typical temperature dispersion spectrum of loss elastic modulus and temperature dispersion spectrum of loss tangent obtained when the methacrylic resin composition of this embodiment is subjected to dynamic viscoelasticity measurement. In FIG. 1, particularly with respect to the vertical axis, the right vertical axis represents the loss tangent (−), and the left vertical axis represents the loss elastic modulus (Pa).
In this embodiment, the loss tangent is in the range from the above temperature (T _{tan δmax} ), temperature (T _{tan δmax} ), temperature (T _{tan δmin} ), and further from the above temperature (T _{tan δmax} ) to a temperature 50 ° C. higher than the temperature. The temperature difference (ΔT) indicating from the local minimum value to the loss tangent value 10% higher than the local minimum value satisfies the following conditions, and preferably satisfies the following conditions.

First, in the present embodiment, the temperature (T _{G ″ max} ) exhibiting the maximum value in the temperature dispersion spectrum of the loss elastic modulus is in the range of 120 to 160 ° C., and preferably in the range of 120 to 155 ° C. More preferably, it is the range of 120-150 degreeC.
It is preferable that the temperature at which the maximum value of the loss elastic modulus is within this range since sufficient heat resistance as a film can be exhibited.

Second, the loss tangent minimum value (tan δmin) in the range from the temperature (T _{tan δmax} ) showing the maximum value in the temperature dispersion spectrum of the loss tangent to a temperature 50 ° C. higher than the temperature is 0.7 to 1.2. The range is preferably in the range of 0.7 to 1.1, more preferably 0.8 to 1.1.
It is preferable that the minimum value (tan δmin) in the range from the temperature at which the loss tangent has a maximum value (T _{tan δmax} ) to a temperature higher by 50 ° C. is in this range, since a high-quality stretched film can be produced stably.

Third, in the range from the temperature (T _{tan δmax} ) showing the maximum value in the temperature dispersion spectrum of the loss tangent to a temperature 50 ° C. higher than the temperature, the loss tangent value is 10% higher than the minimum value from the minimum value of the loss tangent. The temperature difference (ΔT) indicating the above is preferably in the range of 12 to 24 ° C, more preferably in the range of 13 to 23 ° C, and still more preferably in the range of 14 to 22 ° C.
If the temperature difference (ΔT) showing a loss tangent value 10% higher than the minimum value in the range from the temperature (T _{tan δmax} ) showing the maximum value of the loss tangent to the temperature higher by 50 ° C. is within this range, high quality The range of selection of the stretching temperature at which a stretched film can be obtained can be expanded, and further, it is not affected by subtle fluctuations in temperature and environment during stretching, so that a high-quality stretched film can be stably produced.

By the way, when preparing a stretched film using a resin composition containing a methacrylic resin having a ring structure in the main chain, the two maximum values appearing in the temperature dispersion spectrum obtained by the dynamic viscoelasticity measurement described above are obtained. In general, the stretching operation is performed in a high temperature range including the indicated temperatures (T _{G ″ max} and T _tanδmax ), and the inventors have determined that the temperature dispersion spectrum of the loss tangent Since it represents the ratio with the elastic property, it has been found that the above-mentioned various problems can be solved by providing a material in which the loss tangent change in the above temperature range is highly controlled.

The method for controlling the loss tangent behavior in the above temperature range of the methacrylic resin composition having a ring structure in the main chain is not particularly limited as long as a composition satisfying the above characteristics can be prepared. , When preparing the resin composition, using two or more methacrylic resins having the same type of cyclic structural unit in the main chain and having different weight average molecular weight and molecular weight distribution, the respective weight average molecular weight and molecular weight distribution, Moreover, the method of selecting those mixing ratios suitably is mentioned.
The reason why the high-order structure of the solid in the above-mentioned temperature range can be controlled by such a method is not clear, but the molecular weight, molecular weight distribution, component weight of weight average molecular weight less than 10,000, composition distribution, solid It is estimated that the regularity distribution etc. acted in a complex manner.
According to the above method, since a resin composition is prepared by mixing methacrylic resins having the same kind of ring structural unit in the main chain, it can be obtained by mixing methacrylic resins having relatively large weight average molecular weights. Even if it is a resin composition, it is possible to prepare a stretched film that is excellent in stretch processability, excellent in optical uniformity, and can exhibit highly controlled birefringence characteristics. When a stretched film is produced using a methacrylic resin composition in which the high temperature range in the temperature dispersion spectrum is highly controlled, the various problems described above during stretching can be solved, and various temperature fluctuations during stretching It was found that it can cope with.

Here, the dynamic viscoelasticity measurement is performed by applying a periodic minute strain to the sample and measuring the response thereto, thereby storing the storage elastic modulus (may be referred to as “E ′” or “G ′”), Loss modulus (may be written as “E” ”or“ G ””) and loss tangent (“E” / E ′ ”,“ G ”/ G ′”, or “tan δ”) ).
The storage elastic modulus indicates the degree to which the energy generated by external force and strain is stored as an elastic index, and the loss elastic modulus is the viscous index that dissipates energy generated by external force and strain as heat. The loss tangent (tan δ), which expresses the degree and is represented by the ratio of the loss elastic modulus to the storage elastic modulus, is used as an index indicating whether the state of the sample is viscous or elastic.

In the dynamic viscoelasticity measurement, a temperature dispersion spectrum of each index can be obtained by using a method of changing the measurement temperature at a constant speed.
For example, when the sample to be measured is an amorphous polymer such as an acrylic resin, it is generally derived from γ dispersion derived from the movement of the side chain of the polymer and local movement of the main chain from the low temperature side. A relaxation mechanism called α dispersion (also called main dispersion) derived from β dispersion and micro-Brownian motion of the main chain is observed.

Hereinafter, the temperature dispersion spectrum of the resin composition will be described with reference to FIG.
At a low temperature, a small part of the energy given to the sample in the glass state is dissipated as energy accompanying local movement of the molecular chain, but most of it is stored inside.
When the temperature gradually rises from this point to near the glass transition temperature, the entire molecular chain in the sample suddenly starts active movement, and the energy dissipated as the temperature rises also increases.
Then, gradually, the entanglement of molecular chains in the solid begins to be solved, and when the unit of motion spreads over the entire sample, a maximum value appears in the temperature dispersion spectrum of the loss elastic modulus. It is known that the temperature (T _{G ″ max} ) indicating the maximum value of the loss elastic modulus usually appears in a temperature range lower than the temperature (T _{tan δmax} ) indicating the maximum value of the loss tangent (tan δ). .
When the temperature further rises, the molecular chain is further entangled, and both the storage elastic modulus and the loss elastic modulus decrease. However, a maximum value appears in the temperature dispersion spectrum of the loss tangent at a temperature at which the magnitude of the slope is switched. The temperature (T _{tan δmax} ) showing the maximum value of the loss tangent may be used as a dynamic glass transition temperature (this notation is used in this embodiment to distinguish it from a generally used glass transition temperature). In general, the larger the tan δ value at the dynamic glass transition temperature, the easier the plastic composition undergoes plastic deformation, and the smaller the value, the greater the repulsive force. Therefore, the magnitude of this value may be used to evaluate the impact absorbability of rubber and elastomer products.
As the temperature rises further, the entanglement between the molecular chains is further released, the resin starts to flow, and the storage elastic modulus is significantly reduced. Therefore, in both temperature dispersion profiles of the storage elastic modulus and the loss elastic modulus, the slope again and again changes in magnitude, and as a result, the loss tangent represented by the ratio of the loss elastic modulus to the storage elastic modulus starts to increase. Thus, the minimum value of the loss tangent (tan δmin) appears in a temperature range higher than the temperature (T _{tan δmax} ) temperature at which the maximum value of the loss tangent is shown. In the temperature range higher than the temperature showing the minimum value (T _{tan δmin} ), it is suggested that the resin composition is substantially changed from a solid state to a molten state having fluidity.
In the present embodiment, in view of the circumstances described above, the value of the loss tangent at the temperature (T _{tan δmin} ) indicating the minimum value of the loss tangent and the change in the loss tangent in the temperature range before and after the temperature are precisely controlled, thereby stretching. The state of entanglement of molecular chains at the time can be optimized, and as a result, a stretched film having excellent quality can be stably produced.

Conventionally, a glass transition temperature based on a specific heat change using DSC, which is widely used as a method for measuring a glass transition temperature, and a temperature (T _{G ″ max} ) indicating a maximum value of a loss elastic modulus obtained by this dynamic viscoelasticity Many studies have been made on the relationship with the dynamic glass transition temperature based on the maximum value of the loss tangent (T _{tan δmax} ), but no clear conclusion has been reached at this time.
In general, the information obtained by DSC measurement used as a means for measuring the glass transition temperature includes only the temperature of the specific heat change point, whereas the information obtained by dynamic viscoelasticity measurement is a change in viscoelasticity. Since it includes not only the temperature of the point but also changes in polymer properties such as the modulus of elasticity in the vicinity of the change point temperature, it can be used effectively for optimizing resins used in film stretching processing that performs thermal processing in a solid state. It will be a thing.

As a method for measuring the temperature dispersion spectrum of dynamic viscoelasticity, the following method can be used.
Sample preparation: A test piece having a length of 50 mm, a width of 10 mm, and a thickness of 1 mm was subjected to a desired treatment and placed in a predetermined environment. Measuring apparatus: PHYSICA MCR301: manufactured by Anton Paar. Temperature control system: CTD450: Anton Paar's analysis software: RheoPlus Anton Paar's measurement mode: Torsion measurement system (SRF)
・ Measurement frequency: 1Hz
-Strain amount: 0.2%
Normal force: -0.3N
・ Distance between clamps: 38mm
・ Measurement temperature range: 30 ~ 190 ℃
Temperature rising rate: 2 ° C./min A more specific method for measuring the temperature dispersion spectrum of dynamic viscoelasticity is as described in the examples.

-Photoelastic coefficient-
The absolute value of the photoelastic coefficient C _R of the methacrylic resin composition containing a structural unit (X) in the main chain of the present embodiment having a ring structure is preferably at 3.0 × 10 ^-12 Pa ^-1 or less, It is more preferably 2.0 × 10 ⁻¹² Pa ⁻¹ or less, and 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 a direction perpendicular to the extension direction in the plane. The refractive index of each is shown.)
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 It is possible to suppress or prevent the contrast at the periphery of the display screen from decreasing or the occurrence of light leakage.
Photoelastic coefficient C _R, specifically, can be determined by the method described in Examples described later.

-Manufacturing method of molded body-
The methacrylic resin composition of this embodiment is a known method such as injection molding, sheet molding, blow molding, injection blow molding, inflation film molding, T-die film molding, press molding, extrusion molding, foam molding, cast molding, Furthermore, it can be set as a molded object by applying secondary processing shaping | molding methods, such as pressure forming and vacuum forming.

As a method for producing a pre-stretched film (unstretched film) and a stretched film using the methacrylic resin composition of the present embodiment, a known method can be used.
As such a method, for example, a raw material resin is supplied to a single-screw or twin-screw extruder, melted and kneaded, and then a sheet extruded from a T die is guided onto a cast roll and solidified. Subsequently, uniaxial stretching that performs longitudinal uniaxial stretching that extends in the mechanical flow direction using a pair of rolls having different peripheral speeds or that performs lateral uniaxial stretching that extends in a direction orthogonal to the mechanical flow direction (TD direction). Stretching; sequential biaxial stretching using roll stretching and tenter stretching, simultaneous biaxial stretching by tenter stretching, biaxial stretching by tubular stretching, inflation stretching, biaxial stretching by tenter method sequential biaxial stretching, etc. can be exemplified . Among these, since the characteristics of the methacrylic resin composition of the present embodiment can be expressed most, sequential biaxial stretching composed of roll stretching and tenter stretching is preferable.
With respect to tenter stretching, the tenter is a film in the width direction (also referred to as a transverse direction) by widening the gap between the clips while running in the transport direction a clip that holds both ends of the film in the width direction. This is a stretching device.
Inside the tenter, a preheating part, a lateral stretching part, a heat fixing part, and a heat relaxation part as necessary are provided.
Tenter clips are often combined with drive chains and placed on endless tracks. As this drive chain, a type that travels in the tenter device for both reciprocations and a type that travels outside the tenter device are known for the return path. In general, since the entire apparatus can be made compact, there is a situation where a type that travels in the tenter apparatus for both reciprocations is widely used.
The clip in the tenter device grips the film at the inlet of the tenter device, receives the thermal history of preheating temperature, stretching temperature, and heat treatment temperature, then turns while being cooled by the cooling mechanism, and returns to the inlet of the tenter device again. Grab the film again.

Here, the interior of the tenter is composed of a plurality of compartments controlled at different temperatures, and a temperature difference occurs between the clip temperature and the environmental temperature of each compartment, or the stretching operation by the tenter is continued for a long time. The tenter device again due to insufficient cooling due to the fact that the clip has returned to the inlet of the tenter device and the cooling has become insufficient as the clip travels through the tenter device. The clip temperature may not be stable when returning to the entrance. For this reason, the film may break near the clip, the uniformity of the gripping force of the clip may decrease, and the film thickness distribution may increase. The proposal of the resin which can respond flexibly is expected.
The methacrylic resin composition of the present embodiment is also useful in the sense of solving troubles such as film breakage at the time of stretching accompanying the fluctuation of the clip temperature in the stretching process, and according to the present embodiment, mechanical A stretched film having an excellent balance of optical properties and mechanical properties in the flow direction (MD direction) and the direction orthogonal to the mechanical flow direction (TD direction) can be obtained.

  The final draw ratio can be determined from the heat shrinkage rate of the obtained molded / stretched body. The draw ratio is preferably 0.1 to 400%, more preferably 10 to 400%, and still more preferably 50 to 350% in at least one direction. When it is less than the lower limit, the bending strength tends to be insufficient, and when it exceeds the upper limit, breakage and tear frequently occur in the film production process, and the film cannot be produced continuously and stably. By designing in this range, a stretched molded article that is preferable from the viewpoint of birefringence, heat resistance, and strength can be obtained.

The stretching temperature is preferably _{(T G''max) ℃ ~ (T} G "max +50) ℃.
Here, _{TG ″ max} refers to a temperature showing a maximum value in a temperature dispersion spectrum of a loss elastic modulus obtained by dynamic viscoelasticity measurement for a methacrylic resin composition used for preparing a film.
By setting the stretching temperature in the above range, a stretched film having excellent balance of optical characteristics and mechanical characteristics in the mechanical flow direction (MD direction) and the direction perpendicular to the mechanical flow direction (TD direction) can be obtained.
In order to obtain good film thickness uniformity, the lower limit of the stretching temperature is more preferably ( _{TG "max} + 5 ° C) or more, and more preferably _{TG" max} + 10 ° C) or more. More preferably, it is ( _{TG "max} + 15 ° C) or more, particularly preferably ( _{TG" max} + 20 ° C) or more, and the upper limit of the stretching temperature is more preferably ( _{TG "max} + 45 ° C). Hereinafter, it is more preferably (T _{G ″ max} + 40 ° C.) or less.

  In addition, when using the film of this embodiment as an optical film, in order to stabilize the optical isotropy and mechanical characteristic, it is preferable to perform heat processing (annealing) etc. after an extending | stretching process. The conditions for the heat treatment may be appropriately selected similarly to the conditions for the heat treatment performed on a conventionally known stretched film, and are not particularly limited.

  Applications of molded products include, for example, household goods, OA equipment, AV equipment, battery electrical equipment, lighting equipment, tail lamps, meter covers, headlamps, light guide bars, lenses, and other automotive parts, housings, sanitary ware replacement Light guide plate, diffuser plate, polarizing plate protective film, 1/4 wavelength plate, 1/2 wavelength used in sanitary applications such as liquid crystal display, plasma display, organic EL display, field emission display, rear projection TV, etc. Examples thereof include a retardation film such as a plate, a viewing angle control film, and a liquid crystal optical compensation film, a display front plate, a display substrate, a lens, a touch panel, and the like, and can be suitably used for a transparent substrate used for a solar cell. In addition, in the fields of optical communication systems, optical switching systems, and optical measurement systems, they can also be used for waveguides, lenses, optical fibers, optical fiber coating materials, LED lenses, lens covers, and the like. It can also be used as a modifier for other resins.

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

<1. Analysis of structural units>
Unless otherwise specified in each production example described below, 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 Blue Car Co., Ltd.
Measurement solvent: CDCl3 or d6-DMSO
・ Measurement temperature: 40 ℃
When the ring structure of the methacrylic resin is a lactone ring structure, it is confirmed by the method described in JP 2001-151814 A. When the ring structure of the methacrylic resin is a glutarimide ring structure, This was confirmed by the method described in the republished patent WO2012 / 114718.

<2. Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn)>
The weight average molecular weights (Mw) of the methacrylic resins produced in the production examples described later and the methacrylic resin compositions produced in the examples and comparative examples described later were measured using the following apparatuses and conditions.
-Measuring apparatus: Tosoh Corporation gel permeation chromatography (HLC-8320GPC)
·Measurement condition:
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 Sensitivity: 3.0 mV / min Sample: 0.02 g of methacrylic resin or methacrylic resin composition in 20 mL of tetrahydrofuran. Injection volume: 10 μL
Standard sample for calibration curve: The following 10 polymethyl methacrylates (manufactured by Polymer Laboratories; PMMAC calibration Kit M-M-10) having different molecular weights but known monodisperse weight peak molecular weights were used.
Weight peak molecular weight (Mp)
Standard sample 1 1,916,000
Standard sample 2 625,500
Standard sample 3 298,900
Standard sample 4 138,600
Standard sample 5 60,150
Standard sample 6 27,600
Standard sample 7 10,290
Standard sample 85,000
Standard sample 9 2,810
Standard sample 10 850
Under the above conditions, the RI detection intensity with respect to the elution time of the methacrylic resin or methacrylic resin composition was measured.
Based on the calibration curve obtained by the measurement of the standard sample for the calibration curve, the weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the methacrylic resin and the weight average molecular weight (Mw) of the methacrylic resin composition. )

<3. Dynamic viscoelastic properties>
The following method was used as a method for measuring the temperature dispersion spectrum of dynamic viscoelasticity.
-Preparation of test piece used for measurement A test piece having a length of 50 mm, a width of 10 mm, and a thickness of 1 mm was prepared by a press molding method using the methacrylic resin compositions obtained in Examples and Comparative Examples. And the same thermal history was given to the test piece by heat-processing to the obtained test piece at the temperature of 100 degreeC for 20 hours. Then, after leaving for 48 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 50 RH%, the width and thickness dimensions were measured, and the temperature dispersion spectrum of dynamic viscoelasticity was measured.
Measurement device: PHYSICA MCR301: manufactured by Anton PaarTemperature control system: CTD450: manufactured by Anton PaarAnalysis software: manufactured by RheoPlus Anton Paar
・ Measurement frequency: 1Hz
-Strain amount: 0.2%
Normal force: -0.3N
・ Distance between clamps: 38mm
・ Measurement temperature range: 30 ~ 190 ℃
Temperature rising rate: 2 ° C./min Then, from the obtained temperature dispersion spectrum, _{TG ″ max} , T _{tan δmax} , T _{tan δmin} , T _{tan δmin} -T _{tan δmax} , tan δmin, ΔT were obtained.

<4. 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, using a vacuum compression molding machine (SFV-30 manufactured by Shinfuji Metal Industry Co., Ltd.), preheating at 260 ° C. under reduced pressure (about 10 kPa) for 10 minutes, the resin composition was heated to 260 ° C. Then, after compressing at about 10 MPa for 5 minutes and releasing the reduced pressure and the press pressure, it was transferred to a cooling compression molding machine and solidified by cooling. The obtained press film was cured for 24 hours or more in a constant temperature and humidity chamber adjusted to 23 ° C. and a humidity of 60%, and then a test specimen (thickness: about 150 μm, width: 6 mm) was cut out.
The photoelastic coefficient C _R (Pa ⁻¹ ) was measured using a birefringence measuring apparatus described in detail in Polymer Engineering and Science 1999, 39, 2349-2357.
The film-shaped test piece was similarly arrange | positioned so that it might become 50 mm between chuck | zippers on the film tension apparatus (made by Imoto Seisakusho) installed in the constant temperature and humidity chamber. Next, the apparatus was arranged so that the laser beam path of the birefringence measuring apparatus (manufactured by Otsuka Electronics, RETS-100) was positioned at the center of the film, and the strain rate was 50% / min (between chucks: 50 mm, chuck moving speed: The birefringence of the test piece was measured while applying an extensional stress at 5 mm / min.
From the relationship between the absolute value of birefringence (| Δn |) and the tensile stress (σ _R ) obtained from the measurement, the slope of the straight line is obtained by least square approximation, and the photoelastic coefficient (C _R ) (Pa ⁻¹ ) is obtained. Calculated. For the calculation, data with an extensional stress between 2.5 MPa ≦ σ _R ≦ 10 MPa was used.
C _R = | Δn | / σ _R
Here, the absolute value (| Δn |) of birefringence is a value shown below.
| Δn | = | nx−ny |
(Nx: refractive index in the stretching direction, ny: refractive index in the direction perpendicular to the stretching direction in the plane)

<5. Evaluation of stretchability of methacrylic resin composition>
From the methacrylic resin compositions obtained in Examples and Comparative Examples described later, a 50 mmφ single unit in which a filter for resin filtration (leaf filter, manufactured by Nagase Sangyo Co., Ltd.) and a T-die having a width of 480 mm was installed at the tip of the extruder. Films were prepared using a screw extruder.
As film forming conditions at that time, extruder set temperature: (T _{G ″ max} +130) ° C., T die set temperature: (T _{G ″ max} +125) ° C., discharge rate: 8 kg / hour, drawdown ratio: 2.7 Double, cast roll set temperature: (T _{G ″ max} ) ° C. was adopted to obtain an unstretched film with a film thickness of 210 μm. As the cast roll, a ceramic surface coated product excellent in peelability was used.

Continuously after the preparation of the unstretched film, a preheating roll, a pair of stretching rolls, an infrared heater (4.2 KW, 230 V) installed between the stretching rolls (installed at a distance of 20 mm to the film), and a transport roll Were stretched longitudinally with respect to the unstretched film using a roll stretching apparatus provided in this order.
At that time, as the temperature of each roll, based on _{TG ″ max} (° C.) of the resin composition used for evaluation, preheating roll temperature: (T _{G ″ max} + 20) ° C., low-speed-side stretching roll temperature: (T _{G ″ max} + 40) ° C., infrared heater output: 60 to 80%, high-speed stretching roll temperature: (T _{G ″ max} +20) ° C., transport roll temperature: (T _{G ″ max} ) ° C. The distance between the stretching rolls was 200 mm, and the peripheral speed difference between the high-speed and low-speed stretching rolls was 2.5 times under this temperature condition.

Continuously with the above-described longitudinal stretching, the longitudinally stretched film was subjected to lateral stretching using a tenter-type lateral stretching machine having an inner return clip.
Here, the inner return clip means that the clip fixed to the drive chain finishes a series of transverse stretching operations, releases the stretched film, circulates through the inside of the tenter device, and turns while being cooled by the cooling device. It means a clip for the tenter device that returns to the entrance of the tenter device and grips the film after longitudinal stretching.
Moreover, what was comprised from the entrance side of the film as a tenter apparatus from the preheating part, the transverse stretch part, and the heat fixing part was used.
The temperature of each part inside the tenter device is preheated part: (T _{G "max} +20) ° C. and stretched part: (T _{G" max, based on TG "max} (° C) of the resin composition used for evaluation. +30) ° C., heat fixing portion: (T _{G ″ max} +10) ° C.
Under the above conditions, the film was stretched 2.5 times by transverse stretching to obtain a biaxially stretched film having an average thickness of 40 microns.

  In order to obtain a biaxially stretched film by subjecting an unstretched film to longitudinal stretching and lateral stretching, the following evaluation (5-1) and the following evaluation (5-2) were performed as film stretchability evaluation.

<Evaluation (5-1)>
The longitudinally stretched film that had undergone the longitudinal stretching step in the stage before preparing the biaxially stretched film by lateral stretching was sampled for a length of 1000 mm, and the variation in thickness in the longitudinal direction was evaluated.
Specifically, with respect to the sampled longitudinally stretched film, first, a 50 mm portion is trimmed from both ends in the width direction, and the strip-shaped film having a length in the width direction of 50 mm and a length in the length direction of 1000 mm is obtained from the trimmed film. The thickness in the longitudinal direction of the strip-like film was continuously measured using a continuous thickness meter (manufactured by Anritsu). And the average (micrometer) of the thickness measured continuously was calculated | required.
And the ratio (Dmax / Dmin) with respect to the minimum thickness (Dmin) of the largest thickness (Dmax) of the measured thickness was calculated, and the dispersion | variation in the thickness of the longitudinal direction of a longitudinally stretched film was evaluated. The larger the ratio (Dmax / Dmin), the greater the variation.

<Evaluation (5-2)>
The stretching stability in the transverse stretching step at the stage of preparing a biaxially stretched film by transverse stretching was evaluated.
Specifically, the clip temperature before running in the tenter at the time of transverse stretching by the tenter is used from the (T _{G ″ max} −40) ° C. of the resin composition used for the evaluation by using a cooling device attached to the tenter device. Transverse stretching was continued for 3 hours at the four temperatures, varying in increments of 20 ° C. until (T _{G ″ max} +20) ° C.
And, according to the quality of the obtained film, the case where the stable transverse stretching can be continued at any of the four temperatures without causing a defective phenomenon that the film breaks is `` ◎ '' Only when the film breakage occurred in the vicinity of the clip only at the temperature of (T <sub>G ″ max</sub> −40) ° C. among the four temperatures, and stable transverse stretching could be continued at other temperatures. `` O ~ ◎ '' and only when one of the four temperatures, film breakage in the vicinity of the clip, when the stable transverse stretching can be continued at other temperatures, "○", The case where film breakage in the vicinity of the clip occurred at two or more of the four temperatures was evaluated as “x”.
The clip temperature during running was measured using a radiation thermometer. At that time, the radiation thermometer was used for temperature measurement after the emissivity was made fair so as to coincide with the temperature measured by the contact thermometer in the state where the clip provided with the radiation thermometer was stopped. In order to improve the measurement accuracy, temperature measurement was performed after applying black spray or black heat-resistant tape on the clip surface.

[material]
It shows below about the raw material used in the Example and comparative example which are mentioned later.
[[Monomer]]
・ Methyl methacrylate: Asahi Kasei Chemicals Corporation ・ N-phenylmaleimide (phMI): Nippon Shokubai Co., Ltd. ・ N-cyclohexylmaleimide (chMI): Nippon Shokubai Co., Ltd. ・ 2- (hydroxymethyl) methyl acrylate (MHMA) : Combi Blocks [[other thermoplastic resin]]
・ Stylac AS783 (AS resin (acrylonitrile-styrene resin), manufactured by Asahi Kasei Chemicals Corporation)
[[Antioxidant]]
・ Irganox 1010 (manufactured by BASF)
・ ADK STAB PEP36 (manufactured by ADEKA)
・ ADK STAB AO-412S (manufactured by ADEKA)
Tris (2,4-di-t-butylphenyl) phosphite (Wako Pure Chemical Industries, Ltd.)

[Production Example 1-1]
450.7 kg of methyl methacrylate (hereinafter referred to as “MMA”), 39.8 kg of N-phenylmaleimide (hereinafter referred to as “phMI”), 59.7 kg of N-cyclohexylmaleimide (hereinafter referred to as “chMI”), chain A transfer agent, n-octyl mercaptan (0.41 kg) and meta-xylene (450 kg) were 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 carried out by adding a polymerization initiator solution in which 0.30 kg of t-butylperoxyisopropyl monocarbonate as a polymerization initiator was dissolved in 3.85 kg of metaxylene at a rate of 1 kg / hour. During the polymerization, the solution temperature in the reactor was controlled in the range of 122 to 126 ° C.
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 concentrating device comprising a tubular heat exchanger and a vaporization tank preheated to 170 ° C., and the concentration of the polymer contained in the solution was increased to 70% by mass.
The obtained polymerization solution was supplied to a thin film evaporator having a heat transfer area of 0.2 m ² to perform devolatilization.
At this time, the temperature in 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. The polymer after devolatilization was pressurized with a gear pump, pushed from a strand die, cooled with water, and pelletized. .
When the composition of the obtained pellet-shaped methacrylic resin polymer (1-1) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass and 7.9% by mass, respectively. % And 10.8% by mass. Moreover, the weight average molecular weight was 145,000 and molecular weight distribution (Mw / Mn) was 2.3.

[Production Example 1-2]
In Production Example 1-1, the polymerization solvent used was changed from meta-xylene to methyl isobutyl ketone, and the polymerization initiator was changed from t-butyl peroxyisopropyl monocarbonate to 1,1-di (t-butylperoxy) cyclohexane. Further, polymerization was carried out in the same manner as in Production Example 1-1 except that the amount of n-octyl mercaptan added was changed to 0.35 kg, and a polymer (1-2) was recovered.
When the composition of the obtained methacrylic resin polymer (1-2) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.9% by mass, 10%, respectively. It was 8 mass%. Moreover, the weight average molecular weight was 287,000, and molecular weight distribution (Mw / Mn) was 2.9.

[Production Example 1-3]
Polymerization was carried out in the same manner as in Production Example 1-1 except that the amount of n-octyl mercaptan (chain transfer agent) added was changed to 0.80 kg in Production Example 1-1. ) Was recovered.
The obtained methacrylic resin polymer (1-3) had a weight average molecular weight of 95,000 and a molecular weight distribution (Mw / Mn) of 1.7.

[Production Example 1-4]
In Production Example 1-1, the amount of MMA used was changed to 503.5 kg, the amount of phMI used was changed to 17.2 kg, the amount of chMI used was changed to 29.5 kg, and t-butylperoxyisopropyl monocarbonate ( Polymerization was carried out in the same manner as in Production Example 1-1, except that the amount of polymerization initiator) was changed to 0.49 kg and the amount of n-octyl mercaptan (chain transfer agent) added was changed to 0.85 kg. And the polymer (1-4) was recovered.
When the composition of the obtained methacrylic resin 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%, respectively. 0.7% by mass. Moreover, the weight average molecular weight was 88,000, and molecular weight distribution (Mw / Mn) was 1.7.

[Production Example 1-5]
In Production Example 1-3, the same method as in Production Example 1-3, except that the amount of MMA used was changed to 351.2 kg, the amount of phMI used was changed to 79.6 kg, and the amount of chMI used was changed to 119.4 kg. The polymer (1-5) was recovered.
When the composition of the obtained methacrylic resin polymer (1-5) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 63.3 mass%, 15.8 mass%, and 20 respectively. It was 9 mass%. The weight average molecular weight of the obtained polymer was 85,000, and the molecular weight distribution (Mw / Mn) was 1.8.

[Production Example 1-6]
In Production Example 1-4, the polymerization solvent used was changed from metaxylene to methyl isobutyl ketone, and the polymerization initiator was changed from t-butylperoxyisopropyl monocarbonate to 1,1-di (t-butylperoxy) cyclohexane. Further, the polymerization was carried out in the same manner as in Production Example 1-4, except that the amount of n-octyl mercaptan (chain transfer agent) added was changed to 0.27 kg, and the polymer (1-6) was recovered. did.
When the composition of the obtained methacrylic resin polymer (1-6) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 90.3% by mass, 4.0% by mass, and 5%, respectively. 0.7% by mass. Moreover, the weight average molecular weight was 281,000 and molecular weight distribution (Mw / Mn) was 2.9.

[Production Example 1-7]
In Production Example 1-5, the polymerization solvent used was changed from meta-xylene to methyl isobutyl ketone, and the polymerization initiator was changed from t-butyl peroxyisopropyl monocarbonate to 1,1-di (t-butylperoxy) cyclohexane. Further, the polymerization was carried out in the same manner as in Production Example 1-5 except that the amount of n-octyl mercaptan (chain transfer agent) added was changed to 0.21 kg, and the polymer (1-7) was recovered. did.
When the composition of the obtained methacrylic resin polymer (1-7) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 63.3 mass%, 15.8 mass%, and 20 respectively. It was 9 mass%. The weight average molecular weight of the obtained polymer was 253,000, and the molecular weight distribution (Mw / Mn) was 2.8.

[Production Example 2]
2 kg of water, 65 g of tricalcium phosphate, 39 g of calcium carbonate, and 0.39 g of sodium lauryl sulfate were charged into a container having a stirrer equipped with four inclined paddle blades, and a mixed solution was obtained.
Next, 26 kg of water was charged into a 60 L reactor equipped with a stirrer equipped with three receding blades, and the temperature was raised to 40 ° C., MMA: 18.6 kg, phMI: 1.8 kg, chMI: 2.5 kg, Lauroyl peroxide: 0.04 kg as a polymerization initiator, n-octyl mercaptan: 0.012 kg as a chain transfer agent, and the previously prepared mixed solution were charged into a reactor and mixed with stirring.
Next, the mixture was heated to 75 ° C. at a rate of about 1 ° C./min, and suspension polymerization was carried out while maintaining the temperature at about 75 ° C. About 150 minutes after the starting material mixture was added, an exothermic peak was observed in the mixture. Was observed.
Thereafter, the mixture was heated to about 96 ° C. at a rate of about 1 ° C./min, and then aged for 120 minutes to substantially complete the polymerization reaction.
Here, in order to cool to 50 ° C. and dissolve the suspending agent, 20 mass% sulfuric acid was added.
Next, the polymerization reaction solution was passed through a sieve having a mesh of 1.68 mm to remove the aggregates, and water was filtered off. The obtained aggregate slurry was dehydrated to obtain a bead polymer. The obtained bead polymer is washed with water, then dehydrated by the same operation as described above, and further washed and dehydrated with ion-exchanged water, and a methacrylic resin having a ring structure in the particulate main chain A polymer (2) was obtained.
When the composition of the obtained methacrylic resin polymer (2) was confirmed, the structural units derived from MMA, phMI, and chMI monomers were 81.3% by mass, 7.9% by mass, and 10.8%, respectively. It was mass%. Moreover, the weight average molecular weight was 249,000 and molecular weight distribution (Mw / Mn) was 2.5.

[Production Example 3-1]
In a 30 liter reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen gas introduction pipe, the inside of which was previously replaced with nitrogen, 8 kg of methyl methacrylate, 2 kg of methyl 2- (hydroxymethyl) acrylate, 10 kg of toluene, As a phosphorus antioxidant, 2.0 g of tris (2,4-di-t-butylphenyl) phosphite was charged.
Thereafter, the temperature was raised to 100 ° C. while introducing nitrogen gas, and 2 g of a toluene solution containing 10 g of t-amylperoxyisonononanoate was added while adding 5 g of t-amylperoxyisonononanoate as a polymerization initiator. While dropping over time, 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, 30 g of a stearyl phosphate / distearyl phosphate mixture, which is an organic phosphorus compound, was added as a cyclization catalyst, and a cyclization condensation reaction was performed at about 90 to 102 ° C. for 2 hours under reflux. .
Next, the solution containing the obtained copolymer is heated to 240 ° C. with a heater composed of a multitubular heat exchanger, and equipped with a plurality of vent ports and a plurality of side feed ports downstream for devolatilization. By introducing it into the twin screw extruder, the cyclization reaction was allowed to proceed while performing devolatilization.
In the twin screw extruder, the obtained copolymer solution was supplied so as to be 2 kg / hour in terms of resin, and the conditions were a barrel temperature of 260 ° C., a rotation speed of 100 rpm, and a degree of vacuum of 10 Torr to 300 Torr.
At that time, an antioxidant (BASF, Irganox 1010) and a catalyst deactivator (2-ethylhexylate zinc; manufactured by Nippon Chemical Industry Co., Ltd.) were obtained from two side feeds provided in the latter half of the twin-screw extruder. : Product name Nikka Octix Zinc 18%) and AS resin (Asahi Kasei Chemicals Co., Ltd., acrylonitrile-styrene resin, product name: Stylac AS783) were added.
Both the antioxidant and the catalyst deactivator were added to the polymer at a feed rate of 4 g / hour. AS resin was added at a feed rate of 0.22 kg / hr.
It melt-kneaded, extruded from the strand die, pelletized after water cooling to obtain a resin composition (3-1).
When the composition of the obtained methacrylic 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. Further, the obtained composition had a weight average molecular weight of 129,000 and a molecular weight distribution (Mw / Mn) of 2.3.

[Production Example 3-2]
A resin composition (3-2) was obtained in the same manner as in Production Example 3-1, except that the polymerization solvent used was changed to methyl isobutyl ketone.
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 259,000, and molecular weight distribution (Mw / Mn) was 2.8.

[Example 1]
(Preparation of methacrylic resin composition)
The methacrylic resin (1-2) obtained in Production Example 1-2 and the methacrylic resin (1-3) obtained in Production Example 1-3 were vacuum-dried at 90 ° C. for 5 hours under a nitrogen atmosphere. The mixture was cooled to 30 ° C. and used for the preparation of the composition.
Using a tumbler mixer previously substituted with nitrogen, 30 parts by mass of methacrylic resin (1-2), 70 parts by mass of methacrylic resin (1-3), 0.1 part by mass of ADK STAB PEP36, Irganox 1010 Was mixed with 0.05 part by mass, and 0.05 part by mass of ADK STAB AO-412S 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 20 kg / hour.
The melt-kneaded resin composition is extruded into a strand shape 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.
The weight average molecular weight was 133,000, T _{tan δmax} was 145 ° C., _{TG ″ max} was 132 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the evaluation results of the film stretchability.

[Example 2]
The same composition as in Example 1 except that the methacrylic resin used was changed to 70 parts by mass of the polymer obtained in Production Example 1-4 and 30 parts by mass of the polymer obtained in Production Example 1-6. A product was prepared.
The weight average molecular weight was 124,000, T _{tan δmax} was 133 ° C., _{TG ″ max} was 120 ° C., and the photoelastic coefficient was 0.4 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the evaluation results of the film stretchability.

[Example 3]
The same composition as in Example 1 except that the methacrylic resin used was changed to 70 parts by mass of the polymer obtained in Production Example 1-5 and 30 parts by mass of the polymer obtained in Production Example 1-7. A product was prepared.
The weight average molecular weight was 118,000, T _{tan δmax} was 162 ° C., _{TG ″ max} was 150 ° C., and the photoelastic coefficient was 0.4 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the evaluation results of the film stretchability.

[Example 4]
The same composition as in Example 1 except that the methacrylic resin used was changed to 90 parts by mass of the polymer obtained in Production Example 1-3 and 10 parts by mass of the polymer obtained in Production Example 1-2. A product was prepared.
The weight average molecular weight was 107,000, T _{tan δmax} was 145 ° C., _{TG ″ max} was 132 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the evaluation results of the film stretchability.

[Example 5]
The same procedure as in Example 1 was conducted except that the methacrylic resin used was changed to 70 parts by mass of the resin composition obtained in Production Example 3-1, and 30 parts by mass of the resin composition obtained in Production Example 3-2. A composition was prepared.
The weight average molecular weight was 153,000, T _{tan δmax} was 136 ° C., _{TG ″ max} was 122 ° C., and the photoelastic coefficient was 1.5 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the evaluation results of the film stretchability.

[Example 6]
The same composition as in Example 1 except that the methacrylic resin used was changed to 80 parts by mass of the polymer obtained in Production Example 1-1 and 20 parts by mass of the polymer obtained in Production Example 2. A product was prepared.
The weight average molecular weight was 159,000, T _{tan δmax} was 146 ° C., _{TG ″ max} was 133 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the film stretchability evaluation results.

[Example 7]
  The same composition as in Example 1 except that the methacrylic resin used was changed to 50 parts by mass of the polymer obtained in Production Example 1-2 and 50 parts by mass of the polymer obtained in Production Example 1-3. A product was prepared.
  The weight average molecular weight is 162,000, T _tanδmax Is 145 ° C, T _{G "max} Is 132 ° C. and the photoelastic coefficient is 0.2 × 10 ^-12 Pa ^-1 Met. Table 1 shows evaluation results of other dynamic viscoelastic properties and evaluation results of film stretchability.

[Comparative Example 1]
  A composition was prepared in the same manner as in Example 1, except that the methacrylic resin used was changed to 100 parts by mass of the polymer obtained in Production Example 1-1.
  The weight average molecular weight is 141,000, T _tanδmax Is 139 ° C, T _{G "max} Is 130 ° C. and the photoelastic coefficient is 0.2 × 10 ^-12 Pa ^-1 Met. The results of evaluating other dynamic viscoelastic properties and the results of evaluating film stretchability are shown in Table 1.

[Comparative Example 2 ]
The composition was the same as in Example 1 except that the methacrylic resin used was changed to 70 parts by mass of the polymer obtained in Production Example 1-2 and 30 parts by mass of the polymer obtained in Production Example 1-3. A product was prepared.
The weight average molecular weight was 204,000, T _{tan δmax} was 144 ° C., _{TG ″ max} was 133 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the film stretchability evaluation results.

[Comparative Example 3 ]
The composition was the same as in Example 1 except that the methacrylic resin used was changed to 90 parts by mass of the polymer obtained in Production Example 1-2 and 10 parts by mass of the polymer obtained in Production Example 1-3. A product was prepared.
The weight average molecular weight was 258,000, T _{tan δmax} was 144 ° C., _{TG ″ max} was 133 ° C., and the photoelastic coefficient was 0.2 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the evaluation results of the film stretchability.

[Comparative Example 4 ]
A composition was prepared in the same manner as in Example 1 except that the methacrylic resin used was changed to 100 parts by mass of the resin composition obtained in Production Example 3-1.
The weight average molecular weight was 121,000, T _{tan δmax} was 135 ° C., _{TG ″ max} was 122 ° C., and the photoelastic coefficient was 1.5 × 10 ⁻¹² Pa ⁻¹ . Other dynamic viscoelastic properties Table 1 shows the evaluation results and the film stretchability evaluation results.

[Reference Example 1]
Properties were evaluated using Delpet 80N manufactured by Asahi Kasei Corporation as it was.
T _{tan δmax} was 128 ° C., _{TG ″ max} was 115 ° C., and the photoelastic coefficient was 5.0 × 10 ⁻¹² Pa ⁻¹ . Evaluation results of other dynamic viscoelastic properties and evaluation of film stretchability The results are shown in Table 1.

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

Claims (7)

The main unit includes a structural unit (X) having a ring structure, and the (X) structural unit is at least one selected from the group consisting of a structural unit derived from an N-substituted maleimide monomer and a lactone ring structural unit. A methacrylic resin composition containing two or more methacrylic resins in its composition,
The temperature (T _{G ″ max} ) showing the maximum value in the temperature dispersion spectrum of the loss modulus obtained by dynamic viscoelasticity measurement is 120 to 160 ° C.,
The minimum value of the loss tangent in the range from the temperature (T _tanδmax ) showing the maximum value in the temperature dispersion spectrum of the loss tangent obtained by dynamic viscoelasticity measurement to a temperature 50 ° C. higher than the temperature is 0.7 to 1.2. A methacrylic resin composition characterized by being. In the range from the temperature (T _{tan δmax} ) showing the maximum value in the temperature dispersion spectrum of the loss tangent to a temperature 50 ° C. higher than the temperature, the minimum value of the loss tangent to the loss tangent value 10% higher than the minimum value. The temperature difference (ΔT) shown is 12-24 ° C.
The methacrylic resin composition according to claim 1.   The methacrylic resin composition according to claim 1 or 2, wherein the weight average molecular weight (Mw) in terms of polymethyl methacrylate measured by GPC is 120,000 to 260,000.   The (X) structural unit includes a structural unit derived from an N-substituted maleimide monomer, and the content of the structural unit derived from the N-substituted maleimide monomer is 5% based on 100% by mass of the methacrylic resin. The methacrylic resin composition according to any one of claims 1 to 3, which is -40% by mass.   The said (X) structural unit contains a lactone ring structural unit, Content of the said lactone ring structural unit is 5-40 mass% by making the said methacrylic resin 100 mass%, Any one of Claims 1-3 The methacrylic resin composition according to claim 1. The methacrylic resin composition according to any one of claims 1 to 5, wherein the absolute value of the photoelastic coefficient is 2.0 × 10 ^-12 Pa ^-1 or less. The methacrylic resin composition according to claim 6, wherein the absolute value of the photoelastic coefficient is 1.0 × 10 ⁻¹² Pa ⁻¹ or less.

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