METHACRYLIC COPOLYMER, COMPOSITION, MOLDED ARTICLE, PROCESS FOR PRODUCING FILM OR SHEET, AND LAMINATE

Abstract

The present invention provides a methacrylic copolymer which comprises 40-87 mass% methyl methacrylate units, 6-30 mass% structural units (R) having at least one ring structure in the main chain and selected from the group consisting of lactone ring units, glutaric anhydride units, and N-substituted or unsubstituted glutarimide units, and 7-30 mass% α-methylstyrene units and which has a glass transition temperature of 120°C or higher. The methacrylic copolymer has a negative value of photoelasticity coefficient, and a sheet of the methacrylic copolymer having dimensions of 20 mm × 40 mm × 1.0 mm (thickness), when unidirectionally stretched 100% at a rate of 3 mm / min and a temperature higher by 10°C than the glass transition temperature, gives a stretched film which has a positive orientational birefringence.

Description

[Technical field]

[0001] The present invention relates to a methacrylic copolymer, a composition, a molded article, a method for producing a film or sheet, and a laminate. [Background technology]

[0002] (Meth)acrylic resins are widely used as materials for optical components such as lenses, prisms, retardation films, light guide plates, light diffusion films, and polarizing plate protective films, due to their excellent transparency and low optical distortion. In these applications, the birefringence of the molded products affects the performance of the devices. For example, in devices such as liquid crystal display devices, optical disk devices, and projection screens, the presence of films, lenses, etc. with birefringence in the optical path adversely affects image quality and signal reading performance. For this reason, in recent years, there has been a demand for materials with birefringence as small as possible.

[0003] The birefringence exhibited by resins includes orientation birefringence caused by the orientation of polymer molecules and photoelastic birefringence caused by stress, and the sign of each is a polymer-specific property derived from the primary structure of the polymer. One method for reducing the birefringence of a material is to blend polymers with positive and negative birefringence. In order to highly control the birefringence using this method, it is necessary to use a material with a different sign of orientation birefringence or photoelastic coefficient from the main resin and with high compatibility as an additive resin.

[0004] A polymer of 2,2,2-trifluoroethyl methacrylate is known as a polymer having a positive orientation birefringence and a negative photoelastic coefficient (Patent Document 1). However, this polymer has a low glass transition temperature and a problem with heat resistance. In addition, it has low compatibility with other resins, and it is difficult to use it as an additive resin for controlling the orientation birefringence or birefringence of other resins with the opposite sign of the photoelastic coefficient. Furthermore, the monomer itself is expensive, so there are limitations to its industrial use. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2015 / 079694 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a methacrylic copolymer which has high heat resistance, positive orientation birefringence and negative photoelastic coefficient, and excellent compatibility with other resins, and a composition, film, sheet, laminate, and molded article containing said copolymer. [Means for solving the problem]

[0007] As a result of extensive research by the present inventors in order to achieve the above object, the present invention has been completed, including the following aspects. [1] A methacrylic copolymer having a glass transition temperature of 120°C or higher, comprising 40-87% by mass of methyl methacrylate units, 6-30% by mass of structural units (R) having at least one ring structure in the main chain selected from the group consisting of lactone ring units, glutaric anhydride units, and N-substituted or unsubstituted glutarimide units, and 7-30% by mass of α-methylstyrene units, said methacrylic copolymer having a negative photoelastic coefficient and a positive orientation birefringence when a stretched film obtained by stretching a sheet of said methacrylic copolymer 20 mm x 40 mm x 1.0 mm thick to 100% in one direction at a speed of 3 mm / min at a temperature 10°C higher than the glass transition temperature is obtained. [2] The methacrylic copolymer according to [1], wherein the structural unit (R) is an N-substituted or unsubstituted glutarimide unit represented by formula (1). [ka] (In formula (1), R 1 are each independently a hydrogen atom or a methyl group, R 2is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms containing an aromatic ring.) [3] A composition obtained by melt-kneading the methacrylic copolymer described in [1] or [2] and another resin. [4] A molded article containing the methacrylic copolymer described in [1] or [2] or the composition described in [3].[[]END]] [5] The molded article according to [4], wherein the molded article is a film or a sheet. [6] A method for producing a film or a sheet, comprising a step of molding the methacrylic copolymer described in [1] or [2] or the composition described in [3] into a film or a sheet by a melt molding method. [7] A method for producing a film or a sheet, comprising a step of molding the methacrylic copolymer described in [1] or [2] or the composition described in [3] into a film or a sheet by a solution casting method. [8] A laminate having at least one layer made of a film or a sheet containing the methacrylic copolymer described in [1] or [2] or the composition described in [3].[[]END]] [Advantages of the Invention]

[0008] According to the present invention, a methacrylic copolymer having high heat resistance, a positive value of orientation birefringence and a negative value of photoelastic coefficient, and excellent compatibility with other resins, and a composition, a film, a sheet, a laminate and a molded article containing the copolymer can be obtained. [Embodiments for Carrying Out the Invention]

[0009] (Methacrylic Copolymer) The methacrylic copolymer of the present invention contains methyl methacrylate units, α-methylstyrene units, and a structural unit (R). The methacrylic copolymer of the present invention further contains copolymerizable monomer units, methacrylic acid amide units represented by the following formula (A), and 2-(hydroxyalkyl)acrylic acid ester units represented by the following formula (B).

[0010] [ka] (In the formula, R 3 R is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group having 6 to 15 carbon atoms and containing an aromatic ring, preferably a hydrogen atom, a methyl group, an n-butyl group, a cyclohexyl group, or a benzyl group, and more preferably a methyl group, an n-butyl group, or a cyclohexyl group. 4 and R 5 are each independently a hydrogen atom or an organic group having 1 to 20 carbon atoms, preferably a hydrogen atom or an organic group having 1 to 10 carbon atoms, and more preferably a hydrogen atom or an organic group having 1 to 5 carbon atoms. Here, the organic group is not particularly limited as long as it has 1 to 20 carbon atoms, and examples thereof include linear or branched alkyl groups, linear or branched aryl groups, -OCOCH 3 R may include a -CN group, an -N group, etc. The organic group may contain a heteroatom such as an oxygen atom. 4 is preferably a methyl group, R 5 is preferably a hydrogen atom. may also include

[0011] In the methacrylic copolymer of the present invention, the proportion of methyl methacrylate units is preferably 40 to 87% by mass, more preferably 50 to 85% by mass, and further preferably 65 to 80% by mass, based on the total structural units. If the proportion of methyl methacrylate units is less than this range, the total light transmittance of the resulting methacrylic copolymer is deteriorated, whereas if the proportion of methyl methacrylate units is more than this range, the heat resistance of the resulting methacrylic copolymer is reduced.

[0012] In the methacrylic copolymer of the present invention, the proportion of α-methylstyrene units is preferably 7 to 30 mass%, more preferably 8 to 27 mass%, and further preferably 11 to 25 mass% based on the total structural units. If the proportion of α-methylstyrene units is less than this range, the saturated water absorption of the resulting methacrylic copolymer is high. In addition, if the proportion of α-methylstyrene units exceeds 30 mass%, the polymerizability is low and the productivity is reduced.

[0013] The structural unit (R) is a structural unit having at least one ring structure selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, and an N-substituted or unsubstituted glutarimide unit in the main chain. The structural unit may contain a methacrylamide unit represented by the above formula (A) and / or a 2-(hydroxyalkyl)acrylic ester unit represented by the above formula (B) in the main chain. The polymer of Comparative Example 3 of the present application, which is composed of 100% methyl methacrylate units, has both negative orientation birefringence and photoelastic coefficient, so it is clear that the methyl methacrylate units contribute to making both the orientation birefringence and photoelastic coefficient negative. The polymer of Comparative Example 2, which is composed of 90% methyl methacrylate units and 10% α-methylstyrene units, has negative orientation birefringence and photoelastic coefficient, both of which are larger in absolute value than the polymer of Comparative Example 3, which is composed of 100% methyl methacrylate units. It is therefore clear that the α-methylstyrene units contribute to making both the orientation birefringence and photoelastic coefficient negative. On the other hand, the polymers of Examples 1 and 2, which contain the structural unit (R) along with the methyl methacrylate unit and the α-methylstyrene unit, have positive orientation birefringence and negative photoelastic coefficient. Furthermore, the polymer of Example 2, which has a higher imidization rate proportional to the ratio of the structural unit (R), has a larger orientation birefringence value than the polymer of Example 1. In the methacrylic copolymer of the present invention, the structural unit (R) contributes greatly to maintaining the photoelastic coefficient negative and converting the orientation birefringence to positive. Since the orientation birefringence is proportional to the structural unit (R), the orientation birefringence can be made positive by appropriately selecting the ratio of the structural unit (R). One feature of the present invention is that by further introducing a structural unit (R) into a methacrylic copolymer containing methyl methacrylate units and α-methylstyrene units, a methacrylic copolymer having high heat resistance and transparency, a positive orientation birefringence and a negative photoelastic coefficient, the birefringence of the molded article can be kept low, and excellent compatibility with other resins can be obtained. The magnitudes of the respective numerical values ​​of the orientation birefringence and the photoelastic coefficient can be adjusted by changing the ratio of the methyl methacrylate units, the α-methylstyrene units, and the structural unit (R).

[0014] The lactone ring unit is a structural unit containing a >CH-OC(=O)- group in the ring structure. The structural unit containing a >CH-OC(=O)- group in the ring structure preferably has 4 to 8 ring-constituting atoms, more preferably 5 to 6 ring-constituting atoms, and most preferably 6 ring-constituting atoms (six-membered ring). Examples of structural units containing a >CH-OC(=O)- group in the ring structure include lactone diyl structural units such as β-propiolactone diyl structural units, γ-butyrolactone diyl structural units, and δ-valerolactone diyl structural units. The structural unit containing a >CH-OC(=O)- group in the ring structure can be obtained, for example, by intramolecular cyclization of a polymer having a hydroxy group and an ester group with the hydroxy group and the ester group. In addition, ">C" in the formula means that the carbon atom C has two bonds.

[0015] For example, an example of the δ-valerolactonediyl structural unit is a structural unit represented by formula (I).

[0016] [ka]

[0017] In formula (I), R 6 , R7 and R 8 are each independently a hydrogen atom or an organic group having 1 to 20 carbon atoms, preferably a hydrogen atom or an organic group having 1 to 10 carbon atoms, and more preferably a hydrogen atom or an organic group having 1 to 5 carbon atoms. Here, the organic group is not particularly limited as long as it has 1 to 20 carbon atoms, and examples thereof include linear or branched alkyl groups, linear or branched aryl groups, -OCOCH 3 R may include a -CN group, an -N group, etc. The organic group may contain a heteroatom such as an oxygen atom. 6 and R 7 is preferably a methyl group, R 8 is preferably a hydrogen atom.

[0018] The lactone ring unit can be incorporated into the methacrylic copolymer by the method described in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, etc., for example, by intramolecular cyclization of a structural unit derived from a 2-(hydroxyalkyl)acrylic acid ester and a structural unit derived from methyl (meth)acrylate. JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084 are incorporated herein in their entirety by reference.

[0019] The glutaric anhydride unit is a unit having a 2,6-dioxodihydropyrandiyl structure. An example of the unit having a 2,6-dioxodihydropyrandiyl structure is a structural unit represented by the formula (II).

[0020] [ka] In formula (II), R 9 each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and is preferably a methyl group.

[0021] The unit having a 2,6-dioxodihydropyrandiyl structure can be incorporated into the methacrylic copolymer by the method described in JP 2007-197703 A, JP 2010-96919 A, etc., for example, intramolecular cyclization of two adjacent structural units derived from (meth)acrylic acid, intramolecular cyclization of a structural unit derived from (meth)acrylic acid and a structural unit derived from methyl (meth)acrylate, etc. JP 2007-197703 A and JP 2010-96919 A ​​are incorporated herein by reference in their entirety.

[0022] The N-substituted or unsubstituted glutarimide unit is a unit having an N-substituted or unsubstituted 2,6-dioxopiperidinediyl structure. An example of a unit having an N-substituted or unsubstituted 2,6-dioxopiperidinediyl structure is a structural unit represented by formula (1).

[0023] [ka] In formula (1), R 1 R is independently a hydrogen atom or a methyl group, and is preferably a methyl group. 2 is a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an organic group containing an aromatic ring and having 6 to 15 carbon atoms, preferably a hydrogen atom, a methyl group, an n-butyl group, a cyclohexyl group, or a benzyl group, and more preferably a methyl group, an n-butyl group, or a cyclohexyl group. The structural unit represented by formula (1) can be prepared by, for example, reacting the corresponding acid anhydride (IIa) with NH 2 R 2 It may be produced by a reaction of an imidizing agent represented by formula (1) or by an intramolecular cyclization reaction of a copolymer having a partial structure represented by formula (C). It is preferable to heat the copolymer to convert the structural unit represented by formula (A) to the structural unit represented by formula (1) by the intramolecular cyclization reaction. Scheme (i) [ka] (In the formula, R 1 , R 2 is as defined above.)

[0024] The N-substituted or unsubstituted glutarimide unit can be obtained by the method described in WO2005 / 10838A1, JP2010-254742A, JP2008-273140A, JP2008-274187A, etc., specifically, by reacting a structural unit derived from two adjacent methyl methacrylates or a glutaric anhydride unit with an imidizing agent such as ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, n-hexylamine, etc., an aromatic hydrocarbon group-containing amine such as aniline, toluidine, trichloroaniline, etc., an alicyclic hydrocarbon group-containing amine such as cyclohexylamine, etc., urea, 1,3-dimethylurea, 1,3-diethylurea, 1,3-dipropylurea, etc. Among these, methylamine is preferred. Two adjacent structural units derived from methyl methacrylate or glutaric anhydride units may be reacted with an imidizing agent, and then a dialkyl carbonate such as dimethyl carbonate may be reacted to convert a carboxylic acid such as methacrylic acid into an alkyl methacrylate ester such as methyl methacrylate. The carboxylic acid may be generated when a carboxylic acid and an amide are generated by hydrolysis of a methacrylic acid ester or a glutaric anhydride unit represented by formula (II) or by reaction of a glutaric anhydride unit represented by formula (II) with an imidizing agent. The reaction of dimethyl carbonate may be carried out in the presence of a tertiary amine such as triethylamine. WO2005 / 10838A1, JP2010-254742A, JP2008-273140A, and JP2008-274187A are incorporated herein by reference in their entirety.

[0025] The methacrylic copolymer of the present invention preferably has a ratio of the structural unit (R) of 6 to 30% by mass, more preferably 7.5 to 25% by mass, and even more preferably 8 to 25% by mass, based on the total structural units. The orientation birefringence of the methacrylic copolymer can be changed by changing the ratio of the structural unit (R) to methyl methacrylate. In addition, the higher the content of the structural unit (R), the more the heat resistance of the methacrylic copolymer improves, but the flexibility decreases, and the compatibility with other copolymers and moldability tend to decrease. If the ratio of the structural unit (R) is within the above range based on the total structural units, a methacrylic copolymer having high heat resistance and transparency, a positive orientation birefringence value and a negative photoelastic coefficient value, the birefringence of the molded product can be reduced, and excellent compatibility with other resins can be obtained, which is preferable.

[0026] In a preferred embodiment of the present invention, the methacrylic copolymer of the present invention may contain methacrylamide units represented by the above formula (A) and 2-(hydroxyalkyl)acrylic ester units represented by the above formula (B) in an amount of preferably 0 to 2 mass%, more preferably 0 to 1.5 mass%, even more preferably 0 to 1.0 mass%, and most preferably 0 to 0.5 mass% based on the total structural units. If the structural units of formula (A) and / or (B) exceed the above range, the saturated water absorption of the obtained methacrylic copolymer will be high, or crosslinked bodies will be formed during molding, resulting in foreign matter defects and a decrease in appearance quality.

[0027] The methacrylic copolymer of the present invention may contain a structural unit (O) other than the methyl methacrylate unit, the α-methylstyrene unit, and the (R). Examples of the structural unit (O) include units derived from vinyl monomers having only one polymerizable carbon-carbon double bond in one molecule, such as (meth)acrylamide, (meth)acrylonitrile, (meth)acrylic acid, and styrene, a structural unit represented by formula (A), and a structural unit represented by formula (B). In the methacrylic copolymer of the present invention, the proportion of the structural unit (O) is preferably 10 mass% or less based on the total structural units. The proportions of the methyl methacrylate unit, the α-methylstyrene unit, the structural unit (R), and the structural unit (O) are as follows: 1It can be measured by H-NMR or the like.

[0028] The methacrylic copolymer of the present invention has a weight average molecular weight (Mw) of preferably 40,000 to 200,000, more preferably 50,000 to 180,000, and further preferably 55,000 to 160,000. When Mw is 40,000 or more, the strength, toughness, etc. of the molded article of the present invention are improved. When Mw is 200,000 or less, the flowability of the methacrylic copolymer of the present invention is improved, and molding processability is improved.

[0029] The weight average molecular weight (Mw) is a value calculated by converting a chromatogram measured by gel permeation chromatography into the molecular weight of standard polystyrene.

[0030] The methacrylic copolymer of the present invention has an acid value of preferably 0.01 to 0.30 mmol / g, more preferably 0.05 to 0.28 mmol / g. The acid value is a value proportional to the content of carboxylic acid units and carboxylic anhydride units in the methacrylic copolymer. The acid value can be calculated, for example, by the method described in JP-A-2005-23272. When the acid value is within the above range, the balance of heat resistance, mechanical properties, and moldability is excellent.

[0031] The methacrylic copolymer of the present invention has a glass transition temperature of preferably 120° C. as a lower limit, more preferably 121° C., and further preferably 122° C. as an upper limit, although not particularly limited, preferably 160° C. The higher the glass transition temperature of the methacrylic copolymer, the less likely a molded article containing the methacrylic copolymer is to deform or shrink due to heat, i.e., the higher the heat resistance. In this specification, the "glass transition temperature (Tg)" is measured in accordance with JIS K7121. Specifically, the temperature is raised once to 230°C, then cooled to room temperature, and then the DSC curve is measured under conditions of raising the temperature from room temperature to 230°C at a rate of 10°C / min. The midpoint determined from the DSC curve measured during the second heating is determined as the "glass transition temperature (Tg)".

[0032] The methacrylic copolymer of the present invention preferably has a negative photoelastic coefficient measured by the method described below and a positive orientation birefringence measured by the method described below. When such a methacrylic copolymer is contained in a molded article, it is easy to provide a molded article with small birefringence. The lower limit of the orientation birefringence is preferably 0.1×10 -4 , more preferably 0.5 × 10 -4 , and more preferably 1.0×10 -4 The upper limit is not particularly limited, but is preferably 2.0×10 -3 It is. The upper limit of the photoelastic coefficient is preferably −0.1×10 -12 / Pa, more preferably -0.2×10 -12 / Pa, and more preferably -0.5×10 -12 / Pa, and the lower limit is not particularly limited, but is preferably −2.0×10 -11 / Pa. The present inventor regards the reduction of orientation birefringence and the reduction of stress birefringence as separate issues. When the methacrylic copolymer of the present invention is alloyed with another resin having a different sign of birefringence, it contributes to suppressing the orientation birefringence and the photoelastic coefficient (or stress birefringence) of the resin composition to zero or low.

[0033] The photoelastic coefficient was measured by applying tension to a press-molded sheet of methacrylic copolymer, 15 mm wide x 60 mm long x 1.0 mm thick, at a chuck distance of 45 mm and a temperature of 23°C, increasing the tension from 0 N to 100 N in increments of 10 N. Each time the tension was increased, the birefringence of the central part of the sheet was measured at a temperature of 23°C and the D-line wavelength of Na, and the slope was calculated by approximating the relationship between the measured stress and birefringence to a linear function using the least squares method. The stress is the value obtained by dividing the tension by the cross-sectional area of ​​the sheet. The cross-sectional area of ​​the sheet was calculated as the product of the sheet width of 15 mm and the thickness at the measurement point in the central part of the sheet. Birefringence is the refractive index n of light with a polarization plane parallel to the tensile direction. p and the refractive index n of light with a polarization plane perpendicular to the tensile direction o Difference from (Δn=n p -no )

[0034] The orientation birefringence is the birefringence measured at the center of a stretched film obtained by stretching a press-molded sheet of methacrylic copolymer, 20 mm wide x 40 mm long x 1.0 mm thick, in one direction at a speed of 3 mm / min at a temperature 10°C higher than the glass transition temperature, at a temperature of 23°C and a D-line wavelength of Na without tension. The methacrylic copolymer of the present invention has positive orientation birefringence and negative photoelastic coefficient, and the magnitudes of the orientation birefringence and photoelastic coefficient can be adjusted. Therefore, by blending it in any ratio with other resins having different signs of orientation birefringence or photoelastic coefficient, such as styrene-acrylonitrile copolymer (orientation birefringence: negative, photoelastic coefficient: positive), polymethyl methacrylate (orientation birefringence: negative, photoelastic coefficient: negative), polybenzyl methacrylate (orientation birefringence: positive, photoelastic coefficient: positive), etc., the orientation birefringence and photoelastic birefringence of the resulting molded product can be reduced.

[0035] The methacrylic copolymer of the present invention can be obtained by a method including subjecting a copolymer of methyl methacrylate and α-methylstyrene (hereinafter sometimes referred to as a precursor polymer) to a ring structure-forming reaction. That is, the methacrylic copolymer of the present invention can be produced by the following steps: continuously supplying a monomer mixture containing 70 to 93 mass % of methyl methacrylate, 30 to 7 mass % of α-methylstyrene, and 0 to 10 mass % of a copolymerizable monomer, a radical polymerization initiator, and optionally a chain transfer agent, to a tank-type reactor; a step of bulk polymerizing the monomer mixture in a tank reactor to a polymerization conversion rate of 30 to 60 mass% to obtain a reaction product; removing the monomer mixture in the reaction product; and The polyimide can be obtained by a production method including a step of subjecting the obtained precursor polymer to a ring structure-forming reaction.

[0036] The precursor polymer is polymerized from reaction raw materials including a monomer mixture, a radical polymerization initiator, and optionally a chain transfer agent, and the monomer mixture contains 70 to 93 mass %, preferably 75 to 90 mass %, of methyl methacrylate, and 30 to 7 mass %, preferably 25 to 10 mass % of α-methylstyrene. The content of the copolymerizable monomer is 0 to 10% by mass, preferably 0 to 5% by mass. The monomer mixture may contain a monomer other than methyl methacrylate and α-methylstyrene. Examples of such monomers include alkyl methacrylate esters other than methyl methacrylate, such as ethyl methacrylate and butyl methacrylate; aryl methacrylate esters such as phenyl methacrylate; cycloalkyl methacrylate esters such as cyclohexyl methacrylate and norbornyl methacrylate; aryl acrylate esters such as phenyl acrylate; cycloalkyl acrylate esters such as cyclohexyl acrylate and norbornyl acrylate; aromatic vinyl monomers such as styrene; acrylamide; methacrylamide; acrylonitrile; and vinyl monomers having only one polymerizable alkenyl group in one molecule, such as methacrylonitrile. The content of monomers other than methyl methacrylate and alkyl acrylate esters in the monomer mixture is preferably 10% by mass or less, more preferably 5% by mass or less.

[0037] The monomer mixture may contain a monomer other than methyl methacrylate and α-methylstyrene. Examples of such monomers include alkyl methacrylate esters other than methyl methacrylate, such as ethyl methacrylate and butyl methacrylate; aryl methacrylate esters such as phenyl methacrylate; cycloalkyl methacrylate esters such as cyclohexyl methacrylate and norbornyl methacrylate; aryl acrylate esters such as phenyl acrylate; cycloalkyl acrylate esters such as cyclohexyl acrylate and norbornyl acrylate; aromatic vinyl monomers such as styrene; acrylamide; methacrylamide; acrylonitrile; and vinyl monomers having only one polymerizable alkenyl group in one molecule, such as methacrylonitrile. The content of monomers other than methyl methacrylate and alkyl acrylate esters in the monomer mixture is preferably 10% by mass or less, more preferably 5% by mass or less.

[0038] The monomer mixture preferably has b* of -1 to 2, more preferably -0.5 to 1.5. When b* is within this range, it is advantageous for obtaining molded products with almost no coloring at high production efficiency when the resulting methacrylic copolymer is molded. Note that b* is a value measured in accordance with the International Commission on Illumination (CIE) standard (1976) or JIS Z-8722. The monomer mixture removed from the reaction product by the step of removing the monomer mixture in the reaction product can be recovered and reused in the present invention. If the b* of the recovered monomer mixture becomes high due to heat applied during recovery, it is preferable to purify the monomer mixture by an appropriate method to make the b* within the above range.

[0039] The polymerization initiator used in the present invention is not particularly limited as long as it generates reactive radicals. For example, t-hexylperoxyisopropylmonocarbonate, t-hexylperoxy2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy2-ethylhexanoate, t-butylperoxypivalate, t-hexylperoxypivalate, t-butylperoxyneodecanoate, t-hexylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1,1-bis(t-hexylperoxy)cyclohexane, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), dimethyl 2,2'-azobis(2-methylpropionate) are preferred; Examples include t-hexylperoxy 2-ethylhexanoate, 1,1-bis(t-hexylperoxy)cyclohexane, and dimethyl 2,2'-azobis(2-methylpropionate).

[0040] The polymerization initiator used in the present invention has an average uncleaved initiator concentration (I) of 5.1×10 at the polymerization temperature in a tank reactor described below. -5 ~2.4×10 -4 (mol / L) range is desirable. The amount of the polymerization initiator used is adjusted to the polymerization temperature and added to the monomer mixture so as to obtain the above initiator concentration (I).

[0041] Examples of the chain transfer agent used in the present invention include alkyl mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris-(β-thiopropionate), and pentaerythritol tetrakisthiopropionate; and terpinolene. Among these, monofunctional alkyl mercaptans such as n-octyl mercaptan and n-dodecyl mercaptan are preferred. These chain transfer agents can be used alone or in combination of two or more. The amount of the chain transfer agent used is preferably 0 to 1 part by mass, more preferably 0.01 to 0.8 parts by mass, and even more preferably 0.02 to 0.6 parts by mass, based on 100 parts by mass of the monomer mixture.

[0042] In principle, no solvent is used in bulk polymerization, but when it is necessary to adjust the viscosity of the reaction liquid, a solvent can be included in the monomer mixture. As the solvent, aromatic hydrocarbons such as benzene, toluene, and ethylbenzene are preferable. These solvents can be used alone or in combination of two or more. The amount of such a solvent to be used is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the monomer mixture.

[0043] The reaction raw material used in the present invention has a dissolved oxygen content of preferably 10 ppm or less, more preferably 5 ppm or less, further preferably 4 ppm or less, and most preferably 3 ppm or less. If the dissolved oxygen content is within such a range, the polymerization reaction proceeds smoothly, and molded products without silver streaks or coloring can be easily obtained.

[0044] The temperature inside the tank reactor, i.e., the temperature of the liquid inside the reaction tank, is preferably 110 to 140° C., more preferably 114 to 135° C. If the temperature is higher than this range, it becomes difficult to produce high molecular weight compounds containing α-methylstyrene, which causes a decrease in heat resistance.

[0045] In the method for producing a methacrylic copolymer of the present invention, the water content in the reaction liquid in the tank reactor is preferably 1000 ppm or less, more preferably 700 ppm or less, and even more preferably 280 ppm or less. By keeping the water content at 1000 ppm or less, it is possible to suppress the generation of resin foreign matter of several μm to several tens of μm during the polymerization reaction, and when the obtained methacrylic copolymer is formed into a film or sheet by melt molding, it is possible to significantly reduce the occurrence of defects having an outer diameter of several tens of μm caused by the resin foreign matter.

[0046] In a tank reactor, bulk polymerization is preferably carried out until the polymerization conversion rate reaches 30 to 65% by mass, and more preferably 35 to 60% by mass.

[0047] The average residence time (θ) of the reaction raw materials in the tank reactor is preferably 1.5 to 5 hours, more preferably 2 to 4.5 hours, and even more preferably 2.5 to 4 hours. If the average residence time is too short, the amount of polymerization initiator required increases. Furthermore, an increase in the amount of polymerization initiator makes it difficult to control the polymerization reaction and tends to make it difficult to control the molecular weight. On the other hand, if the average residence time is too long, it takes time for the reaction to reach a steady state, and productivity tends to decrease. The average residence time can be adjusted by the capacity of the tank reactor and the amount of reaction raw materials supplied.

[0048] The bulk polymerization is preferably carried out in an atmosphere of an inert gas such as nitrogen gas.

[0049] The manufacturing method of the present invention has a step of removing the monomer mixture in the reaction product. Here, the reaction product is not limited to the reaction product obtained by bulk polymerization in a tank reactor, and may be a reaction product obtained in another reactor connected after the tank reactor as necessary, that is, a reaction product in which the unreacted monomer mixture in the reaction product obtained by bulk polymerization in a tank reactor is further polymerized in another reactor to increase the polymerization conversion rate. In addition, in this step, the solvent is also removed at the same time as necessary. Although the removal method is not particularly limited, a thermal devolatilization method is preferred. Examples of the thermal devolatilization method include an equilibrium flash evaporation method and an adiabatic flash evaporation method, and the adiabatic flash evaporation method is preferred. The temperature at which the adiabatic flash evaporation method is performed is preferably 200 to 280°C, more preferably 220 to 280°C, and even more preferably 220 to 270°C. If the temperature at which the adiabatic flash evaporation method is performed is less than 200°C, it takes a long time to devolatilize, and the devolatilization becomes insufficient, which may cause poor appearance such as silver streaks on the molded product. On the other hand, when the temperature at which the adiabatic flash evaporation method is carried out exceeds 280°C, the methacrylic copolymer tends to be colored and depolymerized due to oxidation, burning, decomposition, etc. The adiabatic flash evaporation method may be carried out in multiple stages. In this case, the reaction product flowing through the heat transfer tube is heated with the vapor of the flash-evaporated monomer mixture, and the heated reaction product can be supplied to a low-pressure flash tank for flash evaporation. The reaction product can be pressurized by a pump or the like. After removing the monomer mixture, the methacrylic copolymer can be made into pellets or powder particles according to a known method to facilitate ease of handling as a molding material. The content of the monomer mixture in the methacrylic copolymer obtained by the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less.

[0050] The glass transition temperature of the precursor polymer is preferably 114°C as a lower limit, more preferably 115°C, and even more preferably 117°C as an upper limit, and is preferably 150°C. The glass transition temperature can be changed by adjusting the molecular weight, the amount of α-methylstyrene copolymerized, etc. The higher the glass transition temperature of the precursor polymer, the more improved the heat resistance. A methacrylic copolymer obtained by using a precursor polymer having a high glass transition temperature has high heat resistance even if the amount of structural unit (R) is small, and is therefore unlikely to cause deterioration of saturated water absorption, etc.

[0051] The precursor polymer is not particularly limited as long as the total content of structural units derived from methyl methacrylate is 70 to 93% by mass and the total content of structural units derived from α-methylstyrene is 30 to 7% by mass. From the viewpoints of polymerizability, transparency, etc., the total content of structural units derived from methyl methacrylate in the precursor polymer is preferably 73% by mass or more and 93% by mass or less, more preferably 75% by mass or more and 92% by mass or less, and most preferably 80% by mass or more and 92% by mass or less.

[0052] From the viewpoints of heat resistance, polymerizability, water absorption, etc., the total content of structural units derived from α-methylstyrene in the precursor polymer is preferably 7% by mass or more and 27% by mass or less, more preferably 8% by mass or more and 25% by mass or less. If the structural units derived from α-methylstyrene are less than this range, sufficient heat resistance cannot be obtained, and if they are more than this range, polymerizability is significantly reduced.

[0053] The precursor polymer has a polystyrene-equivalent weight average molecular weight Mw of preferably 30,000 to 200,000, more preferably 40,000 to 180,000, and even more preferably 50,000 to 160,000 in a chromatogram obtained by gel permeation chromatography. If the weight average molecular weight Mw is smaller than this range, the resulting molded article becomes brittle, and if it is higher than this range, the productivity deteriorates. Mw can be controlled by adjusting the type, amount, and addition timing of the polymerization initiator and chain transfer agent (optional components) used in the production of the precursor polymer.

[0054] The ring structure forming reaction can be carried out, for example, using an extruder. Examples of the extruder include a single screw extruder, a twin screw extruder, and a multi-screw extruder. From the viewpoint of mixing performance, a twin screw extruder is preferred. Twin screw extruders include non-intermeshing co-rotating type, intermeshing co-rotating type, non-intermeshing counter-rotating type, and intermeshing counter-rotating type. The intermeshing co-rotating type is preferred because it can rotate at high speed and efficiently promote mixing. These extruders may be used alone or connected in series.

[0055] In the ring structure forming reaction using an extruder, for example, a precursor polymer as a raw material is fed from the raw material inlet of the extruder, the precursor polymer is melted, and the cylinder is filled with the precursor polymer. Then, an imidizing agent (optional component) and the like are injected into the extruder using an addition pump, whereby the ring structure forming reaction can proceed in the extruder. When an imidizing agent is used, the structural unit (R) is formed as an N-substituted or unsubstituted glutarimide unit, and may be formed as a lactone ring unit and / or a glutaric anhydride unit as necessary. When an imidizing agent is not used, the structural unit (R) is formed as a lactone ring unit and / or a glutaric anhydride unit. A preferred imidizing agent is R 2 -NH 2 (R 2 is as defined above). The imidizing agent is used in an amount of 1.6 to 12 parts by mass per 100 parts by mass of the methacrylic copolymer. When the amount of the imidizing agent used is within the above range, the by-production of methacrylic acid amide units can be suppressed.

[0056] The resin temperature in the reaction zone in the extruder is preferably in the range of 180 to 280°C, more preferably in the range of 200 to 280°C. If the resin temperature in the reaction zone is less than 180°C, the heat resistance of the methacrylic copolymer tends to decrease due to a decrease in the reaction efficiency of the ring structure formation reaction, the by-production of methacrylamide units, etc. If the resin temperature in the reaction zone exceeds 280°C, the resin decomposition becomes significant, and the mechanical strength, such as the tensile breaking strength, of the molded body and film made of the obtained methacrylic copolymer tends to decrease. The reaction zone in the extruder refers to the region between the injection position of the imidizing agent, etc., in the cylinder of the extruder to the resin discharge port (die part).

[0057] By increasing the reaction time in the reaction zone of the extruder, the ring structure forming reaction can be promoted. The reaction time in the reaction zone of the extruder is preferably longer than 10 seconds, and more preferably longer than 30 seconds. If the reaction time is less than 10 seconds, the ring structure forming reaction may hardly proceed.

[0058] The resin pressure in the extruder is preferably in the range of atmospheric pressure to 50 MPa, and more preferably in the range of 1 to 30 MPa. If it exceeds 50 MPa, it exceeds the limit of the mechanical pressure resistance of a normal extruder, and a special device is required, which is not preferable from the viewpoint of cost.

[0059] It is preferable to use an extruder having a vent hole that can reduce the pressure to below atmospheric pressure. With such a configuration, unreacted materials, by-products such as methanol, and monomers can be removed, and the breaking strength of a molded article containing the methacrylic copolymer of the present invention tends to be improved.

[0060] For the ring structure-forming reaction, a horizontal twin-screw reactor such as Bivolac manufactured by Sumitomo Heavy Industries, Ltd. or a vertical twin-screw stirring tank such as Superblend, which is suitable for high viscosity reaction, can be suitably used instead of an extruder.

[0061] During the ring structure formation reaction, carboxy groups may be by-produced in the methacrylic copolymer. Such carboxy groups may be converted into ester groups with an esterifying agent, a catalyst, etc. as needed. Thereby, foaming of the resin during the production of the optical film can be reduced. Such ester groups vary depending on the esterifying agent and catalyst used, but from the viewpoints of reducing the resin melt viscosity during melt molding, the reactivity of esterification, and the heat resistance of the resin after esterification, it is preferable to contain methyl methacrylate units, and it is more preferable to contain both methyl methacrylate units and ethyl methacrylate units. As the esterifying agent, dimethyl carbonate is preferable from the viewpoints of cost, reactivity, etc.

[0062] The addition amount of the esterifying agent can be set, for example, so that the acid value of the methacrylic copolymer becomes a desired value.

[0063] In addition to the above esterifying agent, a catalyst can also be used in combination. The type of the catalyst is not particularly limited, and examples thereof include amine compounds such as trimethylamine, triethylamine, monomethyldiethylamine, and dimethylmonoethylamine. Among these, triethylamine is preferable from the viewpoints of cost, reactivity, etc.

[0064] Additives generally used in resin compositions may be contained within a range not impairing the object of the present invention. Examples of the additives include fillers, antioxidants, heat deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, colorants, dyes, pigments, light diffusing agents, organic dyes, matting agents, impact resistance modifiers, phosphors, etc. The total amount of such additives other than fillers is preferably 7% by mass or less, more preferably 5% by mass or less, and still more preferably 4% by mass or less.

[0065] The antioxidant is effective in preventing the oxidative deterioration of the resin by itself in the presence of oxygen. Examples of the antioxidant include phosphorus-based antioxidants, hindered phenol-based antioxidants, and thioether-based antioxidants. These antioxidants may be used alone or in combination of two or more.

[0066] The heat deterioration inhibitor is capable of preventing the thermal deterioration of a resin by capturing polymer radicals that are generated when the resin is exposed to high heat in a substantially oxygen-free state. Examples of the heat deterioration inhibitor include 2-tert-butyl-6-(3'-tert-butyl-5'-methyl-hydroxybenzyl)-4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd.; product name: Sumilizer GM), 2,4-di-tert-amyl-6-(3',5'-di-tert-amyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd.; product name: Sumilizer GS), and the like.

[0067] An ultraviolet absorber is a compound that has the ability to absorb ultraviolet rays. An ultraviolet absorber is a compound that is said to have the function of converting light energy into heat energy. Examples of ultraviolet absorbents include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, oxalic anilides, malonic acid esters, and formamidines. These may be used alone or in combination of two or more. Among these, benzotriazoles, triazines, or compounds having a maximum molar absorption coefficient ε at a wavelength of 380 to 450 nm are preferred. max 1200dm 3 mol -1 cm -1 Preferred are UV absorbers which are:

[0068] Benzotriazoles are highly effective in suppressing the deterioration of optical properties such as coloring caused by ultraviolet rays, and are therefore preferred as ultraviolet absorbing agents when the molded article of the present invention is applied to optical applications. As benzotriazoles, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (manufactured by BASF; product name TINUVIN329), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (manufactured by BASF; product name TINUVIN234), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol] (manufactured by ADEKA; product name LA-31), 2-(5-octylthio-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol, etc. are preferred.

[0069] In addition, the maximum molar absorption coefficient ε max 1200dm 3 mol -1 cm -1 The following ultraviolet absorbents can suppress the yellowing of the resulting molded product. Examples of such ultraviolet absorbents include 2-ethyl-2'-ethoxy-oxalanilide (manufactured by Clariant Japan; product name: Sandubor VSU). Among these ultraviolet absorbents, benzotriazoles are preferably used from the viewpoint of suppressing resin deterioration due to ultraviolet rays.

[0070] In addition, when it is desired to efficiently absorb short wavelengths of 380 nm or less, triazine ultraviolet absorbers are preferably used. Examples of such ultraviolet absorbers include 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine (manufactured by ADEKA; product name LA-F70), its analogues, hydroxyphenyltriazine ultraviolet absorbers (manufactured by BASF; product names TINUVIN477, TINUVIN460, and TINUVIN479), and 2,4-diphenyl-6-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine.

[0071] Furthermore, when it is desired to particularly effectively absorb light with a wavelength of 380 to 400 nm, it is preferable to use a metal complex having a ligand with a heterocyclic structure as disclosed in WO2011 / 089794A1, WO2012 / 124395A1, JP2012-012476A, JP2013-023461A, JP2013-112790A, JP2013-194037A, JP2014-62228A, JP2014-88542A, JP2014-88543A, or the like, as an ultraviolet absorber. The entire disclosures of WO2011 / 089794A1, WO2012 / 124395A1, JP 2012-012476 A, JP 2013-023461 A, JP 2013-112790 A, JP 2013-194037 A, JP 2014-62228 A, JP 2014-88542 A, and JP 2014-88543 A are incorporated herein by reference.

[0072] Examples of the ligand of the heterocyclic structure include 2,2'-iminobisbenzothiazole, 2-(2-benzothiazolylamino)benzoxazole, 2-(2-benzothiazolylamino)benzimidazole, (2-benzothiazolyl)(2-benzimidazolyl)methane, bis(2-benzoxazolyl)methane, bis(2-benzothiazolyl)methane, bis[2-(N-substituted)benzimidazolyl]methane, and derivatives thereof. Copper, nickel, cobalt, and zinc are preferably used as the central metal of such metal complexes. In addition, in order to use these metal complexes as ultraviolet absorbents, it is preferable to disperse the metal complexes in a medium such as a low molecular weight compound or a polymer. The amount of the metal complex added is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the molded product of the present invention. Since the molar extinction coefficient of the metal complex at a wavelength of 380 to 400 nm is large, a small amount of the metal complex added is sufficient to obtain a sufficient ultraviolet absorbing effect. If the amount of the metal complex is small, deterioration of the appearance of the molded product due to bleeding out can be suppressed. In addition, since the metal complex has high heat resistance, deterioration and decomposition during molding are small. Furthermore, since the metal complex has high light resistance, the ultraviolet absorbing performance can be maintained for a long period of time.

[0073] The maximum molar absorption coefficient ε of the ultraviolet absorber max The molecular weight (M) of the ultraviolet absorber is measured as follows. 10.00 mg of the ultraviolet absorber is added to 1 L of cyclohexane, and dissolved until no undissolved matter is found by visual observation. The solution is poured into a quartz glass cell measuring 1 cm x 1 cm x 3 cm, and the absorbance at wavelengths of 380 to 450 nm is measured using a spectrophotometer (Hitachi, Ltd.; product name U-3410). UV ) and the maximum absorbance measured (A max ) and the maximum molar absorption coefficient ε max Calculate. ε max =[A max / (10×10 -3 )]×M UV

[0074] A light stabilizer is a compound that is said to have the function of capturing radicals generated mainly by oxidation due to light. Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

[0075] Examples of the lubricant include stearic acid, behenic acid, stearamide acid, methylene bisstearamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, and hardened oil.

[0076] Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; and higher fatty acid esters of glycerin such as monoglyceride stearate and diglyceride stearate. In the present invention, it is preferable to use higher alcohols and glycerin fatty acid monoesters in combination as the release agent. When higher alcohols and glycerin fatty acid monoesters are used in combination, the ratio is not particularly limited, but the amount of higher alcohols used: the amount of glycerin fatty acid monoester used is preferably 2.5:1 to 3.5:1, more preferably 2.8:1 to 3.2:1, by mass ratio.

[0077] As the polymer processing aid, polymer particles (non-crosslinked rubber particles) having a particle size of 0.05 to 0.5 μm, which can be produced by emulsion polymerization, are usually used. The polymer particles may be single-layer particles made of a polymer with a single composition ratio and a single intrinsic viscosity, or may be multi-layer particles made of two or more polymers with different composition ratios or intrinsic viscosities. Examples of the antistatic agent include alkylsulfonates such as sodium heptyl sulfonate, sodium octyl sulfonate, sodium nonyl sulfonate, sodium decyl sulfonate, sodium dodecyl sulfonate, sodium cetyl sulfonate, sodium octadecyl sulfonate, sodium diheptyl sulfonate, potassium heptyl sulfonate, potassium octyl sulfonate, potassium nonyl sulfonate, potassium decyl sulfonate, potassium dodecyl sulfonate, potassium cetyl sulfonate, potassium octadecyl sulfonate, potassium diheptyl sulfonate, lithium heptyl sulfonate, lithium octyl sulfonate, lithium nonyl sulfonate, lithium decyl sulfonate, lithium dodecyl sulfonate, lithium cetyl sulfonate, lithium octadecyl sulfonate, and lithium diheptyl sulfonate. Examples of the flame retardant include metal hydrates having a hydroxyl group or crystal water, such as magnesium hydroxide, aluminum hydroxide, hydrated aluminum silicate, hydrated magnesium silicate, and hydrotalcite; phosphate compounds, such as polyamine phosphoric acid esters; and silicon compounds. Of these, preferred are phosphate ester-based flame retardants, such as trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, tricyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, dimethylethyl phosphate, methyl dibutyl phosphate, ethyl dipropyl phosphate, and hydroxyphenyl diphenyl phosphate. Examples of dyes and pigments include red organic pigments such as Para Red, Fire Red, Pyrazolone Red, Thioindigo Red, and Perylene Red; blue organic pigments such as Cyanine Blue and Indanthrene Blue; and green organic pigments such as Cyanine Green and Naphthol Green. One or more of these can be used.

[0078] As the organic dye, a compound having a function of converting ultraviolet light into visible light is preferably used. Examples of the light diffusing agent and the matting agent include glass particles, polysiloxane-based crosslinked particles, crosslinked polymer particles, talc, calcium carbonate, and barium sulfate. Examples of fluorescent materials include fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent brighteners, and fluorescent bleaches.

[0079] The methacrylic copolymer composition of the present invention is not particularly limited by its production method, and can be produced, for example, by melt-kneading the methacrylic copolymer of the present invention, additives such as an ultraviolet absorber, and other polymers selected as necessary that have different signs of orientation birefringence or photoelastic coefficient. The melt-kneading can be carried out using a melt-kneading device such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer. The temperature during kneading can be appropriately set according to the softening temperatures of the methacrylic copolymer and the other polymers, and can be set, for example, to 150 to 300°C. The shear rate during kneading can be, for example, 10 to 5000 sec -1 can be set to.

[0080] The methacrylic copolymer composition of the present invention can be made into a form such as pellets in order to enhance convenience in storage, transportation, or molding.

[0081] The molded article of the present invention includes the methacrylic copolymer or methacrylic copolymer composition of the present invention. The manufacturing method of the molded article of the present invention is not particularly limited. For example, melt molding methods such as the T-die method (lamination method, coextrusion method, etc.), inflation method (coextrusion method, etc.), compression molding method, blow molding method, calendar molding method, vacuum molding method, injection molding method (insert method, two-color method, press method, core-back method, sandwich method, etc.), and solution casting method can be mentioned. Among these, the T-die method, inflation method, injection molding method, and solution casting method are preferred in terms of high productivity, cost, etc. The type of molded article is not limited, but a film (a planar molded article having a thickness of 5 μm to 250 μm) and a sheet (a planar molded article having a thickness of more than 250 μm) are preferred. The molded article of the present invention has an average absolute value of the in-plane retardation (retardation; Re) of preferably 10.0 nm or less, more preferably 6.0 nm or less, even more preferably 5.0 nm or less, and still more preferably 3.0 nm or less, expressed as a value per mm of thickness.

[0082] The film, which is one form of the molded article of the present invention, can be produced by a solution casting method, a melt casting method, an extrusion molding method, an inflation molding method, a blow molding method, or the like. Among these, the extrusion molding method or the solution casting method is preferred from the viewpoint of obtaining a film having excellent transparency, improved toughness, excellent handling properties, and an excellent balance between toughness, surface hardness, and rigidity. The temperature of the molten resin discharged from the extruder is preferably set to 160 to 270°C, more preferably 220 to 260°C.

[0083] Among the extrusion molding methods, the T-die method is preferred from the viewpoint of obtaining a film with good surface smoothness, good mirror gloss, and low haze. In this T-die method, it is preferable to sandwich the molten resin discharged from the T-die through an extruder, a gear pump, a polymer filter, and a mixer between two or more mirror-finished rolls or mirror-finished belts to form a film. When sandwiching between the mirror-finished rolls or mirror-finished belts, a bank may or may not be formed. The die has an automatic lip opening adjustment function, and the air gap is preferably 100 mm or less. The mirror-finished roll or mirror-finished belt is preferably made of metal. As the mirror-finished roll, a metal rigid roll, a metal elastic roll, etc. can be used, and it is preferable to use a combination of a metal elastic roll and a metal rigid roll. In addition, the surface temperatures of both the mirror-finished roll or the mirror-finished belt are preferably 130°C or less. In addition, it is preferable that at least one of the pair of mirror-finished rolls or mirror-finished belts has a surface temperature of 60°C or more. By setting the surface temperature at such a level, the molten resin discharged from the extruder can be cooled at a rate faster than natural cooling, and a film with excellent surface smoothness and low haze can be easily produced. The linear pressure between the pair of rolls or belts is preferably 10 N / mm or more, more preferably 30 N / mm or more. The thickness of the unstretched film obtained by extrusion molding is preferably 10 to 300 μm. The haze of the film at a thickness of 100 μm is preferably 0.7% or less, more preferably 0.5% or less, and even more preferably 0.3% or less.

[0084] The unstretched film obtained as described above may be subjected to a stretching treatment. The stretching treatment increases the mechanical strength, and a film that is less likely to crack can be obtained. The stretching method is not particularly limited, and examples thereof include simultaneous biaxial stretching, sequential biaxial stretching, and tubular stretching. From the viewpoint of obtaining a film that can be uniformly stretched and has high strength, the lower limit of the temperature during stretching is a temperature 10°C higher than the glass transition temperature of the methacrylic copolymer or methacrylic copolymer composition, and the upper limit of the temperature during stretching is a temperature 40°C higher than the glass transition temperature of the methacrylic copolymer or methacrylic copolymer composition. The stretching is usually performed at 100 to 5000% / min. After stretching, a film with little thermal shrinkage can be obtained by performing heat setting. The thickness of the film after stretching is preferably 10 to 200 μm.

[0085] A functional layer may be provided on the surface of the film, which is one embodiment of the molded article of the present invention. Examples of the functional layer include a hard coat layer, an antiglare layer, an antireflection layer, an antisticking layer, a diffusion layer, an antiglare layer, an antistatic layer, an antifouling layer, and a slippery layer such as a fine particle layer.

[0086] In addition, it is preferable to provide an undercoat layer on at least one side of the film of the present invention in order to improve the adhesive strength with the functional layer or to improve the adhesive strength when laminated with other films via an adhesive or pressure-sensitive adhesive.

[0087] A laminate can be obtained by laminating a layer containing the methacrylic copolymer or methacrylic copolymer composition of the present invention with another material (e.g., a layer containing another thermoplastic copolymer). Examples of other materials used in the laminate include plastics (e.g., thermoplastic resins), glass, etc. The laminate obtained by the present invention can be suitably used for the surface of automobile interior parts; the surface of mobile phones; the surface of personal computers; the surface of vending machines; etc.

[0088] The film, which is one embodiment of the molded article of the present invention, is highly transparent and heat resistant, and therefore suitable for optical applications, and is particularly suitable for polarizer protection films, liquid crystal protection plates, surface materials for portable information terminals, display window protection films for portable information terminals, light guiding films, transparent conductive films with silver nanowires or carbon nanotubes applied to the surface, and front panels for various displays. The film of the present invention has high transparency and heat resistance, and can be used for applications other than optical applications, such as infrared cut films, crime prevention films, shatterproof films, decorative films, metal decorative films, shrink films, and in-mold label films.

[0089] When the film, which is one embodiment of the molded article of the present invention, is used as a polarizer protective film or a retardation film, it may be laminated on only one side of the polarizer film or on both sides. When laminating with the polarizer film, it can be laminated via an adhesive layer or a pressure-sensitive adhesive layer. As the polarizer film, a stretched film made of a polyvinyl alcohol resin and iodine can be used, and its thickness is preferably 1 to 100 μm. EXAMPLES

[0090] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0091] Measurements of physical properties were carried out by the following methods.

[0092] (Polymerization conversion rate) A gas chromatograph GC-14A manufactured by Shimadzu Corporation was connected to an INERTCAP1 (df=0.4 μm, 0.25 mm I.D.×60 m) manufactured by GL Sciences Inc. as a column, and analysis was performed under the following conditions, and calculations were made based on the results. injection temperature=250℃ detector temperature=250℃ Temperature conditions: Hold at 60°C for 5 minutes → Raise temperature to 250°C at 10°C / min → Hold at 250°C for 10 minutes

[0093] (Molecular weight distribution Mw / Mn) The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the resin were determined by GPC (gel permeation chromatography). A sample solution was prepared by dissolving 4 mg of the resin to be measured in 5 ml of tetrahydrofuran. The temperature of the column oven was set to 40°C, and 20 μl of the sample solution was injected into the device at an eluent flow rate of 0.35 ml / min to measure the chromatogram. Ten standard polystyrene points with molecular weights in the range of 400 to 5,000,000 were measured by GPC, and a calibration curve showing the relationship between retention time and molecular weight was created. The Mw and Mw / Mn of the resin to be measured were determined based on this calibration curve. Equipment: Tosoh GPC equipment HLC-8320 Separation column: Tosoh Corporation's TSKguardcolum SuperHZ-H, TSKgel HZM-M, and TSKgel SuperHZ4000 connected in series Eluent: Tetrahydrofuran Eluent flow rate: 0.35 ml / min Column temperature: 40℃ Detection method: Refractive index (RI)

[0094] (Composition of each unit in the copolymer) 1 The proton ratio of the phenyl group of the α-methylstyrene unit or the styrene unit to the methoxy group of the methyl methacrylate unit was determined by H-NMR, and the content of the α-methylstyrene unit or the styrene unit was calculated from this.

[0095] (glass transition temperature Tg) The methacrylic copolymers obtained in the examples were measured for their DSC curves in accordance with JIS K7121 using a differential scanning calorimeter (Shimadzu Corporation, DSC-50 (product number)) by heating them once to 250° C., then cooling them to room temperature, and then heating them from room temperature to 200° C. at a rate of 10° C. / min. The midpoint glass transition temperature determined from the DSC curve measured during the second heating was taken as the glass transition temperature in the present invention.

[0096] (Imidization rate) 1 The copolymer was analyzed using H-NMR (Bruker Corporation; product name ULTRA SHIELD 400 PLUS). 1 H-NMR measurement was performed, and the O-CH 3 The area A of the peak due to the N-CH group of glutarimide at around 3.0 to 3.3 ppm 3 The value calculated from the area B of the peak derived from the group using the following formula was taken as the imidization rate (mol %). (Imidization rate (mol %)) = [B / (A + B)] × 100 The imidization rate (wt %) was calculated from the imidization rate (mol %).

[0097] (Photoelastic Coefficient) A 1.0 mm sheet was obtained by press molding a methacrylic copolymer. A 15 mm x 60 mm test piece was cut out from the center of the obtained press molded sheet. Both ends of the long side direction of the cut out sheet were fixed so that the distance between the chucks was 45 mm, and tension was applied to the sheet in steps of 10 N from 0 N to 100 N using an X-axis dovetail stage B05-11BM manufactured by Suruga Seiki. The tension T was monitored by a sensor separate type digital force gauge ZPS-DPU-50N manufactured by Imada Co., Ltd. The phase difference PD at each tension was measured at the D line wavelength of Na using KOBRA-WR manufactured by Oji Scientific Instruments. After the phase difference measurement, the sheet was removed from the jig and the thickness d of the phase difference measurement part was measured. From the measured values, the cross-sectional area S of the sheet (S = 15 mm × d), stress σ (= T / S), and birefringence Δn (= PD / d) were calculated, and the stress σ was plotted on the horizontal axis and the birefringence Δn on the vertical axis. The slope of the straight line obtained by the least squares method was taken as the photoelastic coefficient.

[0098] (Orientation birefringence) A 1.0 mm sheet was obtained by press molding the methacrylic copolymer. A 20 mm x 40 mm test piece was cut out from the center of the obtained press molded sheet, and the test piece was placed in an autograph with a heating chamber (manufactured by SHIMADZU). The grip distance in the autograph was set to 20 mm, and the sheet was held at the glass transition temperature + 10 ° C for 3 minutes. Then, the sheet was stretched 100% in one direction at a speed of 3 mm / min (grip distance became 40 mm). The obtained stretched film was cooled to 23 ° C, removed from the autograph, and the retardation PD of the central part of the stretched film was measured at the D line wavelength of Na using KOBRA-WR manufactured by Oji Scientific Instruments. The thickness d of the retardation measurement part was measured. From the measured value, the birefringence Δn (= PD / d) was calculated, and this was taken as the orientation birefringence.

[0099] Manufacturing Example 1 Purified methyl methacrylate (MMA), α-methylstyrene (αMS), 2,2'-azobis(2-methylpropionitrile) (AIBN) and n-octyl mercaptan (n-OM) were charged in the ratios shown in Table 1 into autoclave A equipped with a stirrer and dissolved uniformly to obtain polymerization raw materials. The polymerization raw materials were continuously supplied from the autoclave A at 1.5 kg / hr to a tank reactor controlled at the polymerization temperature shown in Table 1, and polymerization reaction was carried out by the bulk polymerization method at the average residence time shown in Table 1, and a liquid containing a methacrylic copolymer was continuously discharged from the tank reactor. The polymerization conversion rate was the value shown in Table 1. Next, the liquid discharged from the reactor was heated to 230°C and supplied to a twin-screw extruder controlled at 240°C. In the twin-screw extruder, volatile matters mainly composed of unreacted monomers were separated and removed, and the methacrylic copolymer was extruded into strands. The strands were cut with a pelletizer to obtain pellets of the methacrylic copolymer Aa.

[0100] Manufacturing Example 2 Pellets of methacrylic polymer Ab were obtained in the same manner as in Production Example 1, except that the composition of the raw material solution and the polymerization conditions were changed as shown in Table 1.

[0101] Production Example 3 According to the method for producing copolymer (A) described in the section [Examples] of JP 2003-231785 A, an MS resin (a copolymer of methyl methacrylate (MMA) and styrene (St)) was produced. The mass ratio of MMA, St, and t-dodecyl mercaptan (t-DM) charged in an autoclave was changed to obtain a liquid containing a methacrylic copolymer Ac. Next, the liquid containing the methacrylic copolymer was heated to 230°C and fed to a twin-screw extruder controlled at 240°C. In the twin-screw extruder, volatile matters mainly composed of unreacted monomers were separated and removed, and the methacrylic copolymer was extruded into strands. The strands were cut with a pelletizer to obtain pellets of the methacrylic copolymer Ac.

[0102] The copolymer pellets were used to measure the weight average molecular weight Mw, molecular weight distribution Mw / Mn, the proportion of α-methylstyrene units or styrene units, and the glass transition temperature Tg. The results are shown in Table 1. In this production example, the amount of units derived from MMA is the amount of units other than α-methylstyrene units or styrene units, so it is not shown in the table.

[0103] [Table 1]

[0104] <Example 1> The copolymer [Aa] shown in Production Example 1 was fed at 2 kg / hr to the feed section of a twin-screw extruder (manufactured by Technobel Co., Ltd.; product name KZW20TW-45MG-NH-600) consisting of a feed section, a melt-kneading section, a devolatilizing section, and a discharge section, and set at a screw speed of 120 rpm and a temperature of 250° C., and monomethylamine was injected at 0.10 kg / hr from the additive supply port of the twin-screw extruder in the melt-kneading section equipped with a kneading block, to react the precursor polymer [Aa] with monomethylamine. A reverse flight was installed on the screw at the end of the reaction zone. In the volatilizing section set at 20 Torr (about 2.7 kPa), by-products and excess monomethylamine were volatilized from the molten resin that had passed through the melt-kneading section, and discharged through a vent. The molten resin extruded as a strand from a die provided at the end of the discharge section of the twin-screw extruder was cooled in a water tank and then cut with a pelletizer to obtain a pellet-shaped methacrylic copolymer (Aa-1).

[0105] The copolymer (Aa-1) was fed at 1 kg / hr to the transport section of a twin-screw extruder (manufactured by Technobel Co., Ltd.; product name KZW20TW-45MG-NH-600) consisting of a transport section, a melt-kneading section, a devolatilizing section and a discharge section, and set at a screw speed of 100 rpm and a temperature of 230 ° C. In the melt-kneading section in which the kneading block was installed, a liquid consisting of 0.8 parts by mass of dimethyl carbonate and 0.2 parts by mass of triethylamine was injected at 0.024 kg / hr, and the dimethyl carbonate was reacted with the carboxyl group in the methacrylic copolymer (Aa-1). A reverse flight was installed on the screw at the end of the reaction zone. In the volatilizing section set at 20 Torr (about 2.7 kPa), by-products and excess dimethyl carbonate were volatilized from the molten resin that had passed through the melt-kneading section, and were discharged through a vent. The molten resin extruded as a strand from a die provided at the end of the discharge part of the twin-screw extruder was cooled in a water tank and then cut with a pelletizer to obtain a pellet-shaped methacrylic copolymer (Aa-2).

[0106] The methacrylic copolymer (Aa-2) was supplied at 1 kg / hr to the transport section of a twin-screw extruder (manufactured by Technobel Co., Ltd.; product name KZW20TW-45MG-NH-600), which consisted of a transport section, a melt-kneading section, a devolatilization section, and a discharge section, and was set at a screw rotation speed of 100 rpm and a temperature of 230°C. In the volatilizing section set at 20 Torr (approximately 2.7 kPa), volatile matters such as unreacted substances were volatilized from the molten resin that had passed through the melt-kneading section, and discharged through a vent. The molten resin extruded as a strand from the die at the end of the discharge section of the twin-screw extruder was cooled in a water tank and then cut with a pelletizer to obtain a pellet-shaped methacrylic copolymer [1]. The methacrylic copolymer [1] had an imidization rate of 8.6 mol%, a glass transition temperature of 130°C, and an orientation birefringence of 8.4×10 -4 , photoelastic coefficient is -5.5×10 -12 Pa -1 The physical properties of the methacrylic copolymer [1] are shown in Table 2.

[0107] <Example 2> A methacrylic copolymer [2] was obtained in the same manner as in Example 1, except that the amount of monomethylamine added was 0.15 kg / hr and a solution consisting of 0.8 parts by mass of dimethyl carbonate and 0.2 parts by mass of triethylamine was injected at 0.036 kg / hr. The physical properties of the methacrylic copolymer [2] are shown in Table 2.

[0108] <Comparative Example 1> Except for using the methacrylic copolymer Ac as the precursor resin, a methacrylic copolymer [3] was obtained in the same manner as in Example 1. The physical properties of the methacrylic copolymer [3] are shown in Table 2.

[0109] <Example 3> 50 parts by mass of the methacrylic copolymer [2] synthesized in Example 1 and 50 parts by mass of the methacrylic resin synthesized in Production Example 2 were kneaded in a small melt kneader at a temperature of 230°C to obtain a methacrylic copolymer composition. The physical properties of the methacrylic copolymer composition [4] are shown in Table 3.

[0110] <Comparative Examples 2, 3, and 4> The physical properties were evaluated in the same manner as in Example 1, except that the copolymers [Aa], [Ab], and [Ac] shown in Production Example 1 were used instead of the methacrylic copolymer [1]. The results are shown in Table 3.

[0111] <Comparative Example 5 (3FMA)> Into the autoclave, 100 parts by mass of 2,2,2-trifluoroethyl methacrylate (3 FMA), 0.06 parts by mass of azobisisobutyronitrile, 0.2 parts by mass of octyl mercaptan, 231 parts by mass of water, 1.4 parts by mass of dispersant and 17.5 parts by mass of pH adjuster were placed. While stirring inside the autoclave, the liquid temperature was raised from room temperature to 70°C, held at 70°C for 120 minutes, and then held at 120°C for 60 minutes to perform suspension polymerization. The liquid temperature was lowered to room temperature, and the polymerization reaction liquid was extracted from the autoclave. The solid content was removed from the polymerization reaction liquid by filtration, washed with water, and dried with hot air at 80°C for 24 hours. The obtained solid content was fed to the hopper of a twin-screw extruder and melt-kneaded at a cylinder temperature of 230°C. The molten resin was then extruded to obtain a pellet-shaped fluoromethacrylate polymer. The subsequent operations were the same as those in Example 1, and the physical properties were evaluated. The evaluation results are shown in Table 3. <Comparative Example 6> 50 parts by mass of the fluoromethacrylate polymer synthesized in Comparative Example 3 and 50 parts by mass of the methacrylic resin synthesized in Production Example 2 were kneaded in a small melt kneader at a temperature of 230°C to obtain a methacrylic copolymer composition. The methacrylic copolymer composition had two glass transition points, 72°C and 120°C, and was an incompatible system. The appearance was cloudy, and the orientation birefringence and photoelastic coefficient were unmeasurable.

[0112] [Table 2]

[0113] [Table 3]

[0114] The methacrylic copolymers obtained in Examples 1 and 2 and the methacrylic copolymer composition obtained in Example 3 have high heat resistance, positive orientation birefringence and negative photoelastic coefficient, and excellent compatibility with other resins, and therefore can be suitably used as materials for constituting optical members. In particular, by blending with other resins having different signs of orientation birefringence or photoelastic coefficient (for example, styrene-acrylonitrile copolymer (orientation birefringence: negative, photoelastic coefficient: positive), polymethyl methacrylate (orientation birefringence: negative, photoelastic coefficient: negative), polybenzyl methacrylate (orientation birefringence: positive, photoelastic coefficient: positive)), it is useful in that the birefringence of the phase difference of the obtained molded product can be reduced. On the other hand, the methacrylic copolymers obtained in Comparative Examples 1 to 5 are not within the scope of the present invention, so they have low heat resistance and negative orientation birefringence, and the methacrylic copolymer composition obtained in Comparative Example 6 is an incompatible system, and all of them are inferior to the present invention.

Claims

1. A film comprising: a methacrylic copolymer having a glass transition temperature of 120°C or higher, the methacrylic copolymer comprising 40 to 87% by mass of methyl methacrylate units, 6 to 30% by mass of structural units (R) which are N-substituted glutarimide units represented by formula (1), and 7 to 30% by mass of α-methylstyrene units, the methacrylic copolymer having a negative photoelastic coefficient, and a stretched film obtained by stretching a press-molded sheet of the methacrylic copolymer, measuring 20 mm x 40 mm x 1.0 mm in thickness, in one direction at a temperature 10°C higher than the glass transition temperature and at a speed of 3 mm / min, the stretched film having a positive orientation birefringence. 【Chemistry 1】 (In formula (1), each R 1 is independently a hydrogen atom or a methyl group, and each R 2 is an alkyl group having 1 to 18 carbon atoms.)

2. A method for producing the film described in claim 1, comprising a step of forming the methacrylic copolymer into a film by a melt molding method.

3. A method for producing the film described in claim 1, comprising a step of forming the methacrylic copolymer into a film by a solution casting method.

4. A laminate comprising at least one layer of the film according to claim 1.

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