TW201527391A - Method for producing of methacrylic resin composition - Google Patents

Abstract

A methacrylic resin composition being not more than 0.3% by mass in the contented amount of dimer and trimercomposed of polymerizable monomer is obtained by the method comprising: continuously feeding the polymerizable monomer, polymerization initiator and chain transfer agent to a reactor, radical-polymerizing a part of the polymerization monomer in bulk to obtain a resin mixture comprising methacrylic resin comprising 60 to 90% by mass of structure unit derived from methyl methacrylate, 10 to 40% by mass of structure unit derived from methacrylic acid alicyclic hydrocarbon ester and 0 to 10% by mass of structure unit derived from acrylic acid ester, unreacted polymerizable monomer, and the dimer or trimer composed of the polymerizable monomer in the reactor; and continuously transferring the resin mixture from the reactor to a twin screw extruder equipped with a vent to remove the unreacted polymerizable monomer and the dimer or trimer composed of the polymerizable monomer from the resin mixture in the twin screw extruder.

Description

Method for producing methacrylic resin composition

The present invention relates to a method for producing a methacrylic resin composition. More specifically, the present invention relates to a method for producing a methacrylic resin composition or a methacrylic resin pellet, which is suitable for producing less coloration and high transparency. A thin, large-area plate-shaped molded body having a low haze value, high flushing property, low saturated water absorption, small dimensional change, and good appearance.

The methacrylic resin is excellent in transparency, light resistance, surface hardness, and the like. Various optical members such as a light guide plate and a lens can be obtained by molding a methacrylic resin composition containing the methacrylic resin.

There is a high demand for a lightweight and large-area liquid crystal display device, and accordingly, an optical member is required to be thinner and larger in area. However, when the optical member is made thinner and larger in area, it is easy to cause dimensional change due to slight moisture and heat. The optical properties will vary with this size change. Along with the high image quality of the display device, optical characteristics such as refractive index and retardation are required to be high precision. Therefore, the methacrylic resin composition as a raw material of the optical member is strongly required to have high transparency, low moisture absorption, high heat resistance, small dimensional change, high punchability, and good moldability.

As a resin material for an optical member, for example, an optical resin material obtained by polymerizing a polymerizable composition containing 5% by weight or more of tricyclodecyl (meth) acrylate is known (refer to Patent Document 1). . When the optical resin material is molded at a high molding temperature, a colored molded body is easily obtained. When the optical resin material is injection molded at a low temperature of 230 to 260 ° C, the molded body is not colored. However, when molding by low-temperature injection molding, the productivity of the molded body is low, and stress is likely to remain in the obtained molded body, so that dimensional change is likely to occur due to heat.

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open No. 61-73705

Non-patent literature

Non-Patent Document 1 Technical Information of Japan Oil & Fats Co., Ltd. "Capacity of Hydrogen Capture and Initiator Efficiency of Organic Peroxides" (produced in April 2003)

The object of the present invention is to provide a method for producing a methacrylic resin composition or a methacrylic resin pellet, which is suitable for producing less coloration, high transparency, and haze value. A thin, large-area plate-shaped molded body having a low, saturated water absorption rate, small dimensional change, and good appearance.

In order to achieve the above object, the results of the research are completed, and the invention including the following aspects is completed.

[1] A method for producing a methacrylic resin composition, which is a method for producing a methacrylic resin composition having a total content of a dimer and a trimer composed of a polymerizable monomer of 0.3% by mass or less, It has (I) continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to a reactor; (II) in the reactor, a part of the polymerizable monomer is subjected to radical block polymerization to obtain a resin mixture of a methacrylic resin, an unreacted polymerizable monomer, and a dimer or a trimer composed of a polymerizable monomer, wherein the methacrylic resin has 60 to 90% by mass of methacrylic acid a structural unit of a methyl ester, 10 to 40% by mass of a structural unit derived from an alicyclic alicyclic hydrocarbon ester, and 0 to 10% by mass of a structural unit derived from an acrylate; (III) from the resin mixture The reactor is continuously conveyed to a twin screw extruder equipped with a vent hole; (IV) in the twin screw extruder, the unreacted polymerizable monomer and the polymerizable monomer are formed from the resin mixture The dimer or trimer is removed.

[2] The method for producing a methacrylic resin composition according to [1], wherein the removal of the unreacted polymerizable monomer and the dimer or trimer composed of the polymerizable monomer is carried out at 210 Adiabatic flashing at temperatures between ° C and 300 ° C and devolatilization of the venting ports of the twin-screw extruder.

[3] The method for producing a methacrylic resin composition according to [1] or [2], wherein the amount of the methacrylate alicyclic hydrocarbon ester contained in the methacrylic resin composition is 1.0% by mass or less.

[4] The method for producing a methacrylic resin composition according to any one of [1] to [3] wherein the alicyclic methacrylate is tricyclomethacrylate [5.2.1.0 ^2,6 ]癸Dicyclopentanyl methacrylate or isodecyl methacrylate.

[5] A method for producing a methacrylic resin pellet, which is a method for producing a methacrylic resin pellet having a total content of a dimer and a trimer composed of a polymerizable monomer of 0.3% by mass or less, It has (I) continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to a reactor; (II) in the reactor, a part of the polymerizable monomer is subjected to radical block polymerization to obtain a resin mixture of a methacrylic resin, an unreacted polymerizable monomer, and a dimer or a trimer composed of a polymerizable monomer, wherein the methacrylic resin has 60 to 90% by mass of methacrylic acid a structural unit of a methyl ester, 10 to 40% by mass of a structural unit derived from an alicyclic alicyclic hydrocarbon ester, and 0 to 10% by mass of a structural unit derived from an acrylate; (III) from the resin mixture The reactor is continuously conveyed to a twin screw extruder equipped with a vent hole; (IV) in the twin screw extruder, the unreacted polymerizable monomer and the polymerizable monomer are formed from the resin mixture The dimer or trimer is removed to obtain a methacrylic resin composition, The methacrylic resin composition is extruded in a strand shape; (V) A methacrylic resin composition extruded in a strand shape was cut by a pelletizer.

[6] A method for producing a molded article, comprising: producing a methacrylic resin pellet by the production method according to the above [5]; (VI) heating and melting the methacrylic resin pellet to form a desired one The shape.

[7] A method for producing a plate-shaped formed body, which is a method for producing a plate-shaped formed body having an optical path length of 200 mm and a yellowness index of 10 or less, comprising: performing any one of [1] to [4] above; A methacrylic resin composition is obtained by the method of producing the article; the methacrylic resin composition is heated and melted and formed into a plate shape.

[8] The method for producing a plate-shaped formed body according to [7], wherein a ratio of a resin flow length of the plate-shaped formed body to the thickness thereof is 380 or more.

[9] The method for producing a plate-shaped formed body according to [7], wherein the plate-shaped molded body has a transmittance of light of a wavelength of 435 nm of 90% or more at an optical path length of 3 mm.

[10] The method for producing a plate-shaped formed body according to any one of [7] to [9] wherein the plate-shaped formed body is a light guide plate.

According to the method of the present invention, a methacrylic resin composition or a methacrylic resin pellet can be produced with high efficiency, and the methacrylic resin composition or the methacrylic resin pellet is suitable for producing less colored color, A thin and large-sized plate-shaped molded body having high transparency, low haze value, low saturated water absorption, small dimensional change, and good appearance.

1‧‧‧Note

2‧‧‧ flow path

3‧‧‧gate

4‧‧‧Resin flow length

11‧‧‧MMA slot

12‧‧‧MA slot

13‧‧‧n-OM slot

14‧‧‧Starting agent MMA solution tank

18‧‧‧Nitrogen mixer

21‧‧‧Reactor

22‧‧‧heating heat exchanger

23‧‧‧Extrusion machine with venting holes

P‧‧‧Pellet resin composition

Fig. 1 is a view showing the flow length of the resin in the injection molding die.

Fig. 2 is a view showing an example of an apparatus used in the production method of the present invention.

[Formation for implementing the invention]

The method for producing a methacrylic resin composition of the present invention comprises: (I) continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to a reactor; (II) polymerizing a part of the reactor The monomer is subjected to radical block polymerization to obtain a resin mixture containing a methacrylic resin, an unreacted polymerizable monomer, and a dimer or a trimer composed of a polymerizable monomer, wherein the methacrylic resin has 60 to 90% by mass of a structural unit derived from methyl methacrylate, 10 to 40% by mass of a structural unit derived from an alicyclic alicyclic hydrocarbon ester, and 0 to 10% by mass of an acrylate-derived structure a unit (III) continuously transporting the resin mixture from the reactor to a twin screw extruder equipped with a vent; (IV) in the twin screw extruder, removing unreacted polymerizability from the resin mixture a monomer and a dimer or a trimer composed of a polymerizable monomer.

Further, the method for producing a methacrylic resin pellet of the present invention comprises: (I) continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to a reactor; (II) a part of the reactor Polymeric monomer The radical polymerization is carried out to obtain a resin mixture containing a methacrylic resin, an unreacted polymerizable monomer, and a dimer or a trimer composed of a polymerizable monomer, wherein the methacrylic resin has 60~ 90% by mass of a structural unit derived from methyl methacrylate, 10 to 40% by mass of a structural unit derived from a methacrylate alicyclic hydrocarbon ester, and 0 to 10% by mass of an acrylate-derived structural unit; (III) continuously conveying the resin mixture from the reactor to a twin screw extruder equipped with a vent; (IV) in the twin screw extruder, unreacted polymerizable monomer from the resin mixture With a dimer or a trimer composed of a polymerizable monomer, a methacrylic resin composition is obtained, and the methacrylic resin composition is extruded in a strand shape; (V) is cut by a granulator to A strand-shaped extruded methacrylic resin composition.

In the method for producing a methacrylic resin composition or a methacrylic resin pellet of the present invention, methyl methacrylate (hereinafter also referred to as monomer (I)) or methacrylate alicyclic hydrocarbon ester (hereinafter referred to as Also referred to as a monomer (II).), and optionally an acrylate (hereinafter also referred to as a monomer (III)) and a monomer other than these are used as a polymerizable monomer.

Examples of the monomer (II) include methacrylic acid monocyclic aliphatic hydrocarbon esters such as cyclohexyl methacrylate, cyclopentyl methacrylate, and cycloheptyl methacrylate; Ester, 2-methyl-2-norbornyl methacrylate, 2-ethyl-2-norbornyl methacrylate, 2-isodecyl methacrylate, 2-methyl methacrylate -2-isodecyl ester, 2-ethyl-2-isodecyl methacrylate, -8-tricyclo [5.0.1. ^{2 2,6} ] decyl methacrylate, -8-methyl methacrylate 8-tricyclo[5.2.1.0 ^2,6 ]decyl ester, methacrylic acid-8-ethyl-8-tricyclo[5.2.1.0 ^2,6 ]decyl ester, -2-amantyl methacrylate, A 2-methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl methacrylate, 1-adamantyl methacrylate, 2-phenoxy methacrylate, A A methacrylic acid polycyclic aliphatic hydrocarbon ester such as 2-methyl-2-phenoxy acrylate or 2-ethyl-2-phenoxy methacrylate. Among these, a polycyclic aliphatic hydrocarbon methacrylate is preferred, and a tricyclo[5.2.1.0 ^2,6 ]nonyl methacrylate (alias: trimethoprim [5.2.1.0 ^{2, 6} ] dicyclopentanyl methacrylate or 2-isodecyl methacrylate (isodecyl methacrylate).

Examples of the monomer (III) include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, secondary butyl acrylate, and tertiary butyl acrylate. Amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, cyclohexyl acrylate, norbornene acrylate, isodecyl acrylate, Benzyl acrylate, phenoxyethyl acrylate, 2-hydroxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, allyl acrylate, phenyl acrylate, and the like. Among these, an alkyl acrylate having 1 to 6 carbon atoms is preferred.

In the present invention, monomers other than the monomers (I), (II) and (III) (hereinafter also referred to as monomers (IV)) can be used. Examples of the monomer (IV) include ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and dimethyl acrylate. Ester, butyl methacrylate, amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, methyl Dodecyl acrylate, An alkyl methacrylate other than methyl methacrylate such as phenyl methacrylate; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic anhydride, maleic acid or itaconic acid; ethylene, propylene, Olefins such as 1-butene, isobutylene, and 1-octene; conjugated dienes such as butadiene, isoprene, and laurel; styrene, α-methylstyrene, p-methylstyrene, and m. Aromatic vinyl compounds such as styrene; acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl pyridine, ketene, vinyl chloride, vinylidene chloride, vinylidene fluoride, etc. .

The amount of the monomer (I) to be used is usually 60 to 90% by mass, preferably 60 to 88% by mass, more preferably 70 to 86% by mass, still more preferably 74 to 86% by mass based on the total of the polymerizable monomer. quality%.

The amount of the monomer (II) to be used is usually 10 to 40% by mass, preferably 11 to 35% by mass, and more preferably 12 to 20% by mass based on the total of the polymerizable monomer.

The amount of use of the monomer (III) is usually 10% by mass or less, preferably 0.5 to 8% by mass, and more preferably 1 to 6% by mass based on the total of the polymerizable monomer.

The amount of use of the monomer (IV) is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less based on the total amount of the polymerizable monomer.

The polymerizable monomer used in the present invention, that is, the monomer (I), the monomer (II), and the monomers (III) and (IV) of any component, preferably have a yellowness index of 2 or less. More preferably 1 or less. When the yellowness index of the polymerizable monomer is small, it is easy to produce high productivity when the obtained methacrylic resin composition or methacrylic resin pellet is molded. The rate obtained a molded body which was hardly colored. In addition, the yellowness index is a value of yellowness calculated based on JIS K7373 based on a value measured in accordance with JIS Z8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

The amount of dissolved oxygen of the polymerizable monomer is preferably 10 ppm or less, more preferably 5 ppm or less, still more preferably 4 ppm or less, and particularly preferably 3 ppm or less. When the amount of dissolved oxygen is in such a range, the polymerization reaction proceeds smoothly, and a molded body free from silver streaks or coloring is easily obtained.

The polymerization initiator used in the present invention is not particularly limited as long as it generates reactive radicals. For example, peroxyisopropyl monocarbonate, hexyl peroxy-2-ethylhexanoate, peroxy-2-ethylhexanoic acid-1, 1, 3, 3-tetra Methyl butyl acrylate, tertiary butyl peroxyisobutyrate, tertiary hexyl peroxyisobutyrate, tertiary butyl peroxy neodecanoate, tertiary hexyl peroxy neodecanoate, peroxy neodecanoic acid -1,1,3,3-tetramethylbutyl ester, 1,1-bis(tri-hexylperoxy)cyclohexane, benzammonium peroxide, peroxy-3,5,5-trimethylhexyl Bismuth, dodecyl peroxide, 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azo double (methyl 2-methylpropionate) and the like. Among these, the polymerization initiator is preferably one hour half-life temperature of 60 to 140 ° C, more preferably 80 to 120 ° C. Further, the polymerization initiator preferably has a hydrogen trapping ability of 20% or less, more preferably 10% or less, still more preferably 5% or less. Specifically, preferred is trihexyl peroxy-2-ethylhexanoate, 1,1-bis(tri-hexylperoxy)cyclohexane, and 2,2'-azobis(2-methyl). Methyl propionate). These polymerization initiators may be used alone or in combination of two or more. In addition, the amount of the polymerization initiator to be used, the method of addition, and the like may be appropriately set depending on the purpose, and is not particularly limited. For example in a block The amount of the polymerization initiator to be used in the polymerization method is preferably 0.0001 to 0.02 parts by mass, more preferably 0.001 to 0.01 parts by mass, per 100 parts by mass of the total of the polymerizable monomers.

Further, the hydrogen trapping ability can be known from the technical data of the polymerization initiator manufacturer (for example, Non-Patent Document 1). Further, it can be measured by a radical trapping method using an α-methylstyrene dimer, that is, an α-methylstyrene dimer complement method. This measurement is generally carried out as follows. First, a polymerization initiator is cleaved to form radical fragments in the coexistence of an α-methylstyrene dimer as a radical scavenger and cyclohexane. Among the generated radical fragments, radical fragments having a low hydrogen capture ability are added to the double bond of the α-methylstyrene dimer to be captured. On the other hand, free radical fragments with high hydrogen capture ability capture hydrogen from cyclohexane to produce cyclohexyl radicals, which are added to the double bond of α-methylstyrene dimer and captured. The product was captured by cyclohexane. Then, the ratio of the theoretical radical fragmentation yield (mole fraction) obtained by quantifying the free radical fragment having high hydrogen capture ability to the quantitative product obtained by quantifying cyclohexane or cyclohexane is determined as Ability to catch hydrogen.

Examples of the chain transfer agent used in the present invention include n-octyl mercaptan, n-dodecyl mercaptan, tertiary dodecanethiol, 1,4-butanedithiol, and 1,6-hexane. Mercaptan, ethylene glycol dithiopropionate, butanediol dithioacetate, butanediol dithiopropionate, hexanediol dithioacetate, hexanediol dithiopropionate, An alkyl mercaptan such as trimethylolpropane (β-thiopropionate) or neopentyl thiopropionate; an α-methylstyrene dimer; a terpinolene. Among these, a monofunctional alkyl mercaptan such as n-octyl mercaptan or n-dodecyl mercaptan is preferred. These chain transfer agents can be used alone 1 Two or more types are used in combination. The amount of the chain transfer agent to be used is preferably 0.1 to 1 part by mass, more preferably 0.2 to 0.8 part by mass, still more preferably 0.3 to 0.6 part by mass, per 100 parts by mass of the total of the polymerizable monomer.

In the production method of the present invention, bulk polymerization is carried out in a continuous flow system. The continuous flow reaction system supplies the reaction raw material to the reactor at a constant flow rate, and the liquid containing the reaction product obtained is discharged from the reactor at a constant flow rate to balance the supply of the reaction raw material with the discharge of the liquid containing the reaction product. A method of continuously performing the reaction.

As a typical example of a reactor used in a continuous flow reaction, there are a continuous flow type tank reactor and a continuous flow type tubular type reactor. The continuous flow type tank reactor can carry out the reaction in a mixed state in which the reaction liquid is nearly completely mixed. The continuous flow type tubular reactor can carry out the reaction in a mixed state in which the reaction liquid is close to a plug flow. These reactors may be used in combination of one or more, or two or more different reactors may be used. In the present invention, for example, it is possible to carry out a continuous flow type tank reactor from the initial stage to the intermediate stage of the reaction, and to carry out the final stage of the reaction in a continuous flow type tubular reactor. The reactor may also have a stirrer which can be selected depending on the type of the reactor, but may, for example, be a Maxblend type agitator, a stirrer having a lattice-like blade rotating around a central vertical rotating shaft, a propeller type agitator, a screw A mixer, a static mixer, etc., in a continuous flow type tank reactor, a Maxblend type mixer is preferably used from the viewpoint of uniform mixing.

Suitable reaction means for use in the present invention are those having at least one continuous flow tank reactor. Multiple continuous flow tank reactors can be connected in series or in parallel. Using continuous flow tanks In the case of a type reactor, the amount supplied to the tank reactor is balanced with the amount discharged from the tank reactor, and the amount of liquid in the tank reactor is made substantially constant. The amount of liquid in the tank type reactor is preferably 1/4 to 3/4, more preferably 1/3 to 2/3, with respect to the volume of the tank type reactor.

The polymerizable monomer, the polymerization initiator, and the chain transfer agent may all be mixed, and the mixture may be continuously supplied to the reactor, or the polymerizable monomer, the polymerization initiator, and the chain transfer agent may be continuously supplied to the reaction. And then mix in the reactor. In the present invention, a method in which a polymerizable monomer, a polymerization initiator, and a chain transfer agent are all mixed, and the mixture is continuously supplied to a reactor is preferred.

The mixing of the polymerizable monomer, the polymerization initiator, and the chain transfer agent is preferably carried out in an inert gas atmosphere such as nitrogen. Further, in order to smoothly carry out the operation of the continuous flow reaction, it is preferred to store the monomer (I), the monomer (II), the polymerization initiator, the chain transfer agent, and the monomer (III) of any component and ( The tanks of IV) are continuously supplied through a pipe to a mixer disposed in the front stage of the reactor and mixed, and the mixture is continuously supplied to the reactor. The mixer is preferably provided with a mixer such as a static mixer.

Further, although the suspension polymerization method can reduce the amount of residual monomers in the resin, the yellowness index is increased by the influence of impurities such as a stabilizer and a dispersant. In the cell casting polymerization method, not only a plate-shaped molded body having a small amount of residual monomers but also a thin and large-area plate-shaped molded body is obtained, and the thickness accuracy and the yellowness index are low. It is difficult to use an optical member such as a light guide plate.

The temperature in the polymerization reactor is preferably from 100 to 160 ° C, more preferably from 110 to 150 ° C. If the temperature in the polymerization reactor is in such a range Inside, it is easy to lower the yellowness index of the obtained molded body. The average residence time in the polymerization reactor may vary depending on the scale of the reactor, but is preferably from 0.5 to 4 hours, more preferably from 1 to 3 hours. If the average residence time is too short, the necessary amount of the polymerization initiator tends to increase. On the other hand, the control of the polymerization reaction becomes difficult due to the increase in the polymerization initiator, and the control of the molecular weight tends to be difficult. On the other hand, if the average residence time is too long, it takes some time to react to a stable state, and there is a tendency for productivity to decrease. Further, the polymerization is preferably carried out in an inert gas atmosphere such as nitrogen.

By this bulk polymerization, a resin mixture containing a methacrylic resin, an unreacted polymerizable monomer, and a dimer or a trimer composed of a polymerizable monomer can be obtained.

When the resin mixture is discharged from the reactor of the last stage, the polymerization conversion ratio of the polymerizable monomer is preferably from 30 to 80% by mass, more preferably from 40 to 70% by mass, still more preferably from 50 to 65% by mass. Further, if the polymerization conversion ratio is too high, there is a tendency for a large stirring force to be required due to an increase in viscosity. When the polymerization conversion ratio is too low, the devolatilization is likely to be insufficient. When the obtained methacrylic resin composition or methacrylic resin pellet is molded, the molded article may cause appearance defects such as silver streaks. tendency.

The methacrylic resin contained in the resin mixture has 60 to 90% by mass of the structural unit derived from the monomer (I), 10 to 40% by mass of the structural unit derived from the monomer (II), and 0. ~10% by mass of the structural unit derived from the monomer (III), preferably having 74 to 86% by mass of the structural unit derived from the monomer (I), and 12 to 20% by mass derived from the monomer (II) The structural unit, and 2 to 6 mass% of the structural unit derived from the monomer (III).

The methacrylic resin contained in the above resin mixture preferably has a weight average molecular weight of from 35,000 to 100,000, more preferably from 40,000 to 90,000, still more preferably from 45,000 to 80,000, most preferably from 60,000 to 80,000. When the weight average molecular weight is less than 35,000, the impact resistance and toughness of the molded body composed of the methacrylic resin composition tend to be insufficient. When the weight average molecular weight is more than 100,000, the formability of the methacrylic resin composition may be There is a tendency to become inadequate.

The ratio of the weight average molecular weight to the number average molecular weight of the methacrylic resin contained in the resin mixture (weight average molecular weight / number average molecular weight: the ratio is also described below as molecular weight distribution) is preferably 1.7 to 2.6, more preferably Good is 1.7~2.3, and even better is 1.7~2.0. When the molecular weight distribution of the methacrylic resin is small, the formability of the methacrylic resin composition tends to be lowered. When the molecular weight distribution is large, the impact resistance of the molded article obtained from the resin composition tends to be lowered, and it tends to be brittle. Further, the weight average molecular weight and the number average molecular weight are molecular weights in terms of standard polystyrene measured by GPC (gel permeation chromatography). Further, the weight average molecular weight, the number average molecular weight, and the molecular weight distribution of the methacrylic resin can be controlled by adjusting the type and amount of the polymerization initiator and the chain transfer agent.

The methacrylic resin contained in the resin mixture preferably has a glass transition temperature of from 100 to 140 ° C, more preferably from 105 to 135 ° C, still more preferably from 110 to 130 ° C. When the glass transition temperature is low, heat resistance and the like tend to be lowered. When the glass transition temperature is high, moldability and the like tend to be lowered.

The dimer or trimer contained in the resin mixture is a structure derived from the same or different 2 or 3 polymerizable monomers by a polymerization step and/or a heating step after polymerization or the like. a compound composed of units. Specific examples of the dimer or the trimer include a dimer or a trimer composed of methyl methacrylate, a dimer or a trimer composed of an acrylate, and a methyl group. a dimer or a trimer composed of an acrylate cyclic hydrocarbon ester, a dimer composed of methyl methacrylate and an acrylate, and a methyl methacrylate and a methacrylate alicyclic hydrocarbon ester. a dimer, a dimer composed of an acrylate and a methacrylate alicyclic hydrocarbon ester, a terpolymer composed of two methyl methacrylates and an acrylate, and a methyl methacrylate a terpolymer composed of two acrylates, a terpolymer composed of two methyl methacrylates and one alicyclic methacrylate, one methyl methacrylate and two methacrylic acid a terpolymer composed of an alicyclic hydrocarbon ester, a terpolymer composed of two acrylates and one alicyclic methacrylate, and an acrylate and two alicyclic hydrocarbon esters. a terpolymer composed of methyl methacrylate, acrylate and Methacrylic acid alicyclic hydrocarbon ester trimer composed of.

The foregoing resin mixture was continuously transferred from the aforementioned polymerization reactor to a twin screw extruder equipped with a vent. The resin mixture to be conveyed is preferably equilibrated or adiabatic flashed at the inlet of the twin screw extruder, more preferably adiabatic flash. The adiabatic flash is preferably carried out at a temperature of 210 to 300 ° C, more preferably 220 to 280 ° C, and still more preferably 230 to 260 ° C. The pressure of the current resin mixture to be flashed is preferably from 1.5 to 3.0 MPa, more preferably from 2.0 to 2.5 MPa. If it is less than 1.5MPa, the flash will be insufficient and there will be residual The tendency of the monomer to increase. On the contrary, if it is more than 3.0 MPa, there is a tendency that it is difficult to stabilize production. The volatile component (unreacted polymerizable monomer and dimer or trimer composed of polymerizable monomer) evaporated by flashing is usually discharged from the rear vent hole, but may be discharged from other rows. The stomata are discharged.

Next, the resin mixture which has been introduced into the twin-screw extruder is removed by evaporation by a screw kneading. The removed volatile component is discharged from the vent hole. The vent hole provided in the twin screw extruder used in the present invention is preferably a vacuum vent or an open vent. The vent hole is provided at least one downstream of the polymer inflow portion. Further, the pressure in the vacuum vent hole is preferably 30 Torr or less, more preferably 15 Torr or less, still more preferably 9 Torr or less, and most preferably 6 Torr or less. When the pressure of the vacuum vent hole is within the above range, the devolatilization efficiency is good, and the residual monomer can be reduced.

The screw of the aforementioned twin screw extruder is preferably a co-directional twin screw. Compared with the case of the uniaxial phase, since the shear energy is large and the degree of surface renewal is large, the devolatilization can be efficiently performed, and the residual monomer can be reduced. The screw structure preferably has a mixing section of 5% or more with respect to the entire length of the screw. Examples of the kneading section include a rotor segment, a kneading disk, a reverse feed kneading disk, a mixing gear, and the like.

The cylindrical heating temperature of the above-mentioned twin-screw extruder is preferably 210 to 300 ° C, more preferably 220 to 280 ° C, still more preferably 230 to 260 ° C. When the temperature is less than 210 ° C, it takes some time for the devolatilization, and the devolatilization is not easy. When the devolatilization is insufficient, an appearance defect such as silver streaks is caused on the formed body. On the other hand, if it is more than 300 ° C, not only the formation of the dimer and the trimer will increase, but also the amount of the terminal double bond will increase, and it will be difficult to ensure thermal stability.

The methacrylic resin composition can be obtained by flashing in any step and devolatilization using a twin-screw extruder equipped with a vent hole in the subsequent step. The obtained methacrylic resin composition can be formed into pellets or powders by a well-known method.

In the present invention, the obtained methacrylic resin composition is preferably extruded from the twin-screw extruder in a strand shape, and then cut into a granulator to prepare a methacrylic resin pellet. In order to form a strand, a template is usually used at the front end of the extrusion molding machine. The cross section of the strand may be a circle, an ellipse, a quadrangle or the like. The thickness of the strand is not particularly limited as long as it can be a desired resin pellet size.

The polymer filter is preferably filtered before the molten methacrylic resin composition is supplied to the template. By arranging the polymer filter at the front end portion of the extrusion molding machine, foreign matter can be effectively removed. The filtration accuracy of the polymer filter is preferably 1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less, and still more preferably 2 μm or more and 3 μm or less.

The shape of the methacrylic resin pellet obtained by the method of the present invention is not particularly limited. For example, a cylindrical shape, a prismatic shape, or the like can be cited. The size of the methacrylic resin pellets varies depending on the application, and examples thereof include those having a width of 4 mm or less, a thickness of 4 mm or less, and a length of 5 mm or less, a width of 3 mm or less, a thickness of 3 mm or less, and a length of 4 mm or less. The strands are preferably cut at a temperature which does not cause cutting defective products (long resin sheets), cutting chips (resin powder), and the like as much as possible. This temperature is appropriately set in consideration of the glass transition temperature of the methacrylic resin. Examples of the method of cooling the strand include an air cooling method, a water cooling method, a refrigerant cooling method, and a spray cooling method.

The amount of the methacrylic resin composition or the methacrylic resin contained in the methacrylic resin pellet obtained by the method of the present invention is relatively larger than that of the methacrylic resin composition or the methacrylic resin pellet. The content is preferably 97% by mass or more, more preferably 98% by mass or more, and still more preferably 99% by mass or more.

The methacrylic resin composition obtained by the method of the present invention or the methacrylic resin contained in the methacrylic resin pellet has 60 to 90% by mass of the structural unit derived from the monomer (I), 10~ 40% by mass of the structural unit derived from the monomer (II), and 0 to 10% by mass of the structural unit derived from the monomer (III), preferably having 74 to 86% by mass of the monomer derived (I) The structural unit, 12 to 20% by mass of the structural unit derived from the monomer (II), and 2 to 6% by mass of the structural unit derived from the monomer (III).

The methacrylic resin composition obtained by the method of the present invention or the methacrylic resin contained in the methacrylic resin pellet preferably has a weight average molecular weight of 35,000 to 100,000, more preferably 40,000 to 90,000, and still more The best is 45,000~80,000, and the best is 60,000~80,000. When the weight average molecular weight is less than 35,000, the impact resistance and toughness of the molded body composed of the methacrylic resin composition tend to be insufficient. When the weight average molecular weight is more than 100,000, the formability of the methacrylic resin composition may be There is a tendency to become inadequate.

The ratio of the weight average molecular weight to the number average molecular weight of the methacrylic resin composition or the methacrylic resin contained in the methacrylic resin pellet obtained by the method of the present invention (weight average molecular weight / number average molecular weight: below) This ratio is also described as a molecular weight distribution.) It is preferably from 1.7 to 2.6, more preferably from 1.7 to 2.3, still more preferably from 1.7 to 2.0. When the molecular weight distribution of the methacrylic resin is small, the formability of the methacrylic resin composition tends to be lowered. When the molecular weight distribution is large, the impact resistance of the molded article obtained from the resin composition tends to be lowered, and it tends to be brittle. Further, the weight average molecular weight and the number average molecular weight are molecular weights in terms of standard polystyrene measured by GPC (gel permeation chromatography). Further, the weight average molecular weight, the number average molecular weight, and the molecular weight distribution of the methacrylic resin can be controlled by adjusting the type and amount of the polymerization initiator and the chain transfer agent.

The methacrylic resin composition obtained by the method of the present invention or the methacrylic resin contained in the methacrylic resin pellet preferably has a glass transition temperature of 100 to 140 ° C, more preferably 105 to 135 ° C. More preferably, it is 110~130 °C. When the glass transition temperature is low, heat resistance and the like tend to be lowered. When the glass transition temperature is high, moldability and the like tend to be lowered.

The methacrylic resin composition or the methacrylic resin pellet obtained by the method of the present invention has a total content of the dimer and the trimer of 0.3% by mass or less, preferably 0.25 mass% or less, more preferably It is 0.2% by mass or less. The smaller the total content of the dimer and the trimer, the easier it is to obtain a molded article having a small yellowness index and being transparent. Among them, such dimers and trimers can be quantified by gas chromatography.

Further, the melt flow rate of the methacrylic resin composition or the methacrylic resin pellet obtained by the method of the present invention at 230 ° C and a load of 3.8 kg is preferably 5 to 35 g/10 min, more preferably 8~30g/10 minutes, and more preferably 10~25g/10 minutes. Among them, the melt flow rate is a value of a melt mass flow rate measured in accordance with JIS K7210.

The methacrylic resin composition or the methacrylic resin pellet obtained by the method of the present invention preferably has a content of the methacrylate alicyclic hydrocarbon ester of 1.0% by mass or less, more preferably 0.8% by mass or less. More preferably, it is 0.6 mass% or less, and it is more preferably 0.4 mass% or less. When the content of the methacrylate alicyclic hydrocarbon ester is in the above range, it is easy to obtain a molded article having a small yellowness index and no appearance defects such as silver streaks and surface stains. Further, the content of the alicyclic alicyclic hydrocarbon ester can be quantified by gas chromatography.

The methacrylic resin composition or the methacrylic resin pellet obtained by the method of the present invention has a saturated water absorption ratio of preferably 1.6% by mass or less from the viewpoint of suppressing dimensional change of the molded body obtained therefrom. More preferably, it is 1.4% by mass or less. In the present specification, the saturated water absorption rate is a measure of the mass of the plate-shaped formed body which has been vacuum-dried for more than 3 days, and the quality of the molded body after being placed at a temperature of 60 ° C and a humidity of 90% for 300 hours. The value of the increase rate.

In the methacrylic resin composition or the methacrylic resin pellet obtained by the method of the present invention, various other additives as needed may be blended. The amount of the additive is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.3% by mass or less based on the methacrylic resin. If the amount of the additive is too large, appearance defects such as silver streaks may occur on the plate-shaped formed body.

Examples of the additives include heat stabilizers, antioxidants, thermal deterioration inhibitors, ultraviolet absorbers, light stabilizers, lubricants, mold release agents, inorganic fillers, inorganic fibers or organic fibers, mineral oil softeners, and polymers. Processing aids, antistatic agents, flame retardants, dyes, colorants, matting agents, light diffusing agents, impact-resistant modifiers, phosphors, adhesives, tackifiers, plasticizers, foaming agents Wait.

The antioxidant is one which has an effect of preventing oxidative degradation of the resin in the presence of oxygen. For example, a phosphorus-based antioxidant, a hindered phenol-based antioxidant, a thioether-based antioxidant, and the like can be given. These antioxidants may be used alone or in combination of two or more. In particular, from the viewpoint of preventing the deterioration of the optical properties due to coloring, it is more preferably used in combination with a phosphorus-based antioxidant and a hindered phenol-based antioxidant, or a combination of a thioether-based antioxidant and a hindered phenol-based antioxidant.

In the case where a phosphorus-based antioxidant (or a thioether-based antioxidant) and a hindered phenol-based antioxidant are used in combination, the ratio thereof is not particularly limited, but the quality of the phosphorus-based antioxidant (or thioether-based antioxidant)/hindered phenol-based antioxidant The comparison is preferably 1/5~2/1, more preferably 1/2~1/1.

Examples of the phosphorus-based antioxidant include 2,2-methylenebis(4,6-di(tributyl)phenyl)octyl phosphite (manufactured by ADEKA, trade name: ADK STAB HP-10) ), phosphite ginseng (2,4-di(tributyl)phenyl ester) (manufactured by Ciba Specialty Chemicals, trade name: IRUGAFOS 168), 3,9-bis (2,6-di (tri-butyl) -4-Methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphole[5.5]undecane (made by Adeka Co., Ltd., trade name: ADK STAB PEP-36), etc. .

Examples of the hindered phenol-based antioxidant include pentaerythritol oxime [3-(3,5-di(tri-butyl)-4-hydroxyphenyl)propionate] (manufactured by Ciba Specialty Chemicals Co., Ltd., Name: IRGANOX 1010), octadecyl 3-(3,5-di(tributyl)-4-hydroxyphenyl)propionate (manufactured by Ciba Specialty Chemicals, trade name: IRGANOX 1076).

Examples of the thioether-based antioxidant include 2,2-bis[(3-dodecyl-1-oxopropoxy)methyl]propyl-1,3-diylbis(3-dodecanesulfuric acid). C Acid ester (manufactured by Adeka Co., Ltd., trade name: ADK STAB AO-412S), 3,3'-thiodipropionic acid di(tridecyl) ester (trade name: ADK STAB AO-503, manufactured by ADEKA Corporation) .

The thermal deterioration inhibitor is a compound capable of preventing thermal deterioration of the resin by capturing polymer radicals generated when exposed to high heat in a state of substantially no oxygen. For example, acrylic acid-2-tert-butyl-6-(3'-tris-butyl-5'-methylhydroxybenzyl)-4-methylphenyl ester (manufactured by Sumitomo Chemical Co., Ltd., trade name) Sumilizer GM), 2,4-di(trisylpentyl)-6-[3',5'-di(tripentyl)-2'-hydroxy-α-methylbenzyl]phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumilizer GS).

The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays. For example, benzophenones, benzotriazoles, and tri Classes, benzoates, salicylates, cyanoacrylates, oxalic acid anilines, malonic esters, formazan and the like. These may be used alone or in combination of two or more. Among these, benzotriazoles and anilines are preferable.

Examples of the benzotriazoles include 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (manufactured by Ciba Specialty Chemicals Co., Ltd.). , trade name TINUVIN329), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (manufactured by Ciba Specialty Chemicals, trade name TINUVIN234 )Wait.

Examples of the aniline include 2-ethyl-2'-ethoxyxantanilide (trade name: Sanduvor VSU, manufactured by Clariant Japan Co., Ltd.).

Among these ultraviolet absorbers, benzotriazoles are particularly preferred from the viewpoint of suppressing deterioration of the resin which is caused by irradiation of ultraviolet rays.

A light stabilizer refers to a compound having a function of capturing a radical generated mainly by photoinitiated oxidation. For example, a hindered amine such as a compound having a 2,2,6,6-tetraalkylpiperidine skeleton may be mentioned.

The release agent is a compound having a function of easily releasing the molded body from the mold. For example, higher alcohols such as cetyl alcohol and stearyl alcohol; higher fatty acid glycerides such as octadecanoic acid glyceride and octadecanoic acid glyceride may be mentioned. Among these, higher alcohols and mono-fatty acid glycerides are preferably used in combination. In the case where a higher alcohol and a monoglyceride are used in combination, the ratio thereof is not particularly limited, but the quality of the higher alcohol/monoglyceride is preferably from 2.5/1 to 3.5/1, more preferably from 2.8/1 to 3.2/. 1.

The polymer processing aid is a compound which exhibits an effect on thickness precision and thinning when a methacrylic resin composition or a methacrylic resin pellet is molded. Polymer processing aids can usually be produced by emulsion polymerization. The polymer processing aid is preferably a polymer particle having a particle diameter of 0.05 to 0.5 μm. The polymer particles may be a single layer particle composed of a polymer having a single composition ratio and a single ultimate viscosity, or may be a multilayer particle composed of two or more kinds of polymers having different composition ratios or ultimate viscosity. Among them, a polymer layer having a low ultimate viscosity in the inner layer and a two-layer structure having a polymer layer having a high ultimate viscosity of 5 dl/g or more in the outer layer are preferable. The ultimate viscosity of the polymer processing aid is preferably from 3 to 6 dl/g. If the ultimate viscosity is too small, the effect of improving the formability is low. If the ultimate viscosity is too large, it is easy to cause a decrease in the melt fluidity of the methacrylic resin composition or the methacrylic resin pellet.

Examples of the impact-resistant modifier include a core-shell type modifier containing an acrylic rubber or a diene rubber as a core component, and a modifier including a plurality of rubber particles.

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

Examples of the light diffusing agent and the matting agent include glass fine particles, polyoxyalkylene-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, and barium sulfate.

Examples of the phosphor include a fluorescent pigment, a fluorescent dye, a fluorescent white dye, a fluorescent whitening agent, and a fluorescent bleaching agent.

Mineral oil softeners are used to improve fluidity during forming. For example, a paraffinic oil, a naphthenic oil, etc. are mentioned.

Examples of the inorganic filler include calcium carbonate, talc, carbon black, titanium oxide, cerium oxide, clay, barium sulfate, and magnesium carbonate. Examples of the fibrous filler include glass fibers and carbon fibers.

Further, the methacrylic resin composition or the methacrylic resin pellet obtained by the production method of the present invention can be used in combination with other polymers within a range not impairing the effects of the present invention. Examples of such other polymers include polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polydecene; ethylene-based ionic polymers; and poly Styrene, styrene-maleic anhydride copolymer, high impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, MBS resin, etc. styrene resin; methyl methacrylate - Styrene copolymer; polyethylene terephthalate, polybutylene terephthalate and other polyester resins; nylon 6, nylon 66, polyamide amines and other polyamines; polycarbonate, poly Vinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, polyurethane, modified polyphenylene ether, polyphenylene sulfide, polyfluorene Oxygen modified resin; Acrylic rubber, polyoxyethylene rubber; styrene-based thermoplastic elastomers such as SEPS, SEBS, and SIS; olefin-based rubbers such as IR, EPR, and EPDM.

The methacrylic resin composition or the methacrylic resin pellet obtained by the production method of the present invention is injection molded (embedded molding method, two-color molding method, pressure molding method, core expansion molding method, and interlayer injection). Various methods, such as a molding method, compression molding, extrusion molding, vacuum molding, air blowing molding, blow molding, and calender molding, are carried out by heating and melt molding.

The methacrylic resin composition or the methacrylic resin pellets are preferably dried before forming. Examples of the drying method include a hot air drying method, a dehumidifying drying method, a reduced pressure drying method, and a low oxygen drying method. If the water content is reduced by drying before forming, molding defects such as crazing can be reduced.

Further, it is preferred to remove the cut defective product and the resin powder from the methacrylic resin pellets before molding. The long resin sheet obtained after the cutting of the defective product is the result of the mistake of the cutting stock. The resin powder is a powder obtained by cutting chips or pellets generated when the strands are cut, and the like. The method of removing the defective product and the resin powder is not particularly limited. For example, a centrifugal separation method, a sieving method, etc. are mentioned.

Further, in the case where the methacrylic resin composition or the methacrylic resin pellet is transferred to the hopper of the molding machine, it is preferred to maintain the temperature of the methacrylic resin composition or the methacrylic resin pellet at, for example, 70 ° C or higher. . When the temperature is raised and transported, it is possible to suppress the generation of the resin powder caused by the moisture absorption during the conveyance and the rubbing of the pellets.

According to the method of the present invention, a plate-shaped formed body can be obtained efficiently. The resin flow length of the plate-shaped formed body is preferably 380 or more in comparison with the thickness. Moreover, the thickness of the plate-shaped formed body is preferably 1 mm or less. Further, the resin flow length is the distance between the gate of the injection mold and the inner wall of the mold which is the farthest from the gate. The resin flow length of the film gate is the foot of the perpendicular line extending from the mounting portion of the injection molding die with respect to the gate (the intersection with the gate) and the inner wall of the mold farthest from the intersection. The distance between them (refer to Figure 1). The gate of the mold for obtaining the plate-shaped formed body is preferably a film gate. The film gate is cut by a cutter, and subjected to surface treatment with a trimmer or the like. In the mold for obtaining the light guide plate for the liquid crystal display device, it is preferable to provide a gate on the end surface where the light source is not disposed.

The sheet-like formed body obtained by the method of the present invention preferably has a yellowness index (YI) of an optical path length of 200 mm, preferably 10 or less, more preferably 8 or less, still more preferably 6 or less. In addition, the yellowness index is a value calculated based on JIS K7373 based on a value measured in accordance with JIS Z8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

The plate-shaped formed body obtained by the present invention preferably has a transmittance at a wavelength of 435 nm of an optical path length of 3 mm of 90% or more, more preferably 90.5% or more, still more preferably 91% or more.

Examples of the use of the plate-shaped formed body include: advertising towers, booth signboards, wall pillar signs, signboards on doors and windows, roof signboards, and the like; display items such as shop windows, partitions, and shop displays; fluorescent lampshades, moods Lighting fixtures, lampshades, ceiling lamps, wall lamps, chandeliers, etc.; interior decorations for hangings, mirrors, etc.; doors, vaults, Construction parts for safety window glass, compartments, stair panels, balcony panels, roofs for leisure buildings, aircraft windshields, driver sun visors, locomotives, water motorized windshields, bus shading Transportation machine-related parts such as panels, automotive sun visors, rear sun visors, head wings, headlight covers, etc.; electronic machine parts for acoustic image display boards, stereo housings, TV protective covers, vending machine display covers, etc.; Medical machine parts such as X-ray machine parts; machine-related parts such as mechanical casings, instrument covers, experimental devices, scales, keyboards, observation windows, etc.; liquid crystal protection plates, light guide plates, light guide films, Fresnel lenses, lenticular lenses Optical related parts such as front panel and diffuser of various displays; transportation related articles such as road signs, navigation boards, curved mirrors, and soundproof walls; surface materials for automobile interiors, surface materials of mobile phones, and film members such as marking films; Parts for home appliances such as cover materials for washing machines and control panels, top panels for electric cookers; other greenhouses, large sinks, aquariums, and time Clock panels, bathtubs, public toilets, table mats, game accessories, toys, face protection covers when welding. Among them, the plate-shaped formed body is suitable for a light guide plate.

In the case where the plate-shaped molded body is used as a light guide plate which is one of the planar light source elements, it can also be used in a known method using welding, bonding, coating, printing, injection molding, and processing using laser light. The back surface is formed with a concave-convex shape for guiding light. The light incident from the end surface of the plate is reflected, refracted, or the like in the uneven shape, and can be emitted to the front surface of the panel. Examples of the uneven shape include a dot pattern having a perfect circle or an elliptical shape, a linear pattern such as a rectangular shape or a V-shaped groove, a concave-convex shape of a hemispherical lens shape, and a particle pattern. These irregularities cannot be absolutely specified due to the optimum structure depending on the size and thickness of the light guide plate, but are preferably wide. 1 to 600 μm, length 2 to 1200 μm, height or depth 1 to 500 μm, and the interval between adjacent concavo-convex shapes is 2 to 10000 μm. If the uneven shape is too large, it will be visually recognized, and the quality of the display will be low. If it is too small, the processing will be difficult, resulting in low productivity. Moreover, when the interval between the adjacent uneven shapes is narrower than 2 μm, it becomes difficult to independently form adjacent unevenness, and molding failure is likely to occur. If it is wider than 10000 μm, the number of the uneven portions cannot be increased. Since the uneven portion has a function of emitting light, the limitation of the number of the uneven portions limits the ratio of light that is efficiently emitted from the light incident from the end surface of the light guide plate, that is, limits the utilization of light. These concavo-convex shapes may have the same shape in one of the light guide plates, or may be combined to form different shapes, or may be arranged in the same shape but different in size. Further, the interval and size of the concavities and convexities may be adjusted in accordance with the distance of the light source disposed adjacent to the end surface of the light guide plate.

Further, the white reflective material can be printed on the back surface of the light guide plate instead of the formation of the uneven shape. The size of the white reflective material is preferably from 500 μm to 5000 μm. When it is smaller than 500 μm, it is difficult to print a white reflective material by conventional screen printing or the like. If it is larger than 5000 μm, even when viewed through a diffusion sheet or the like, the white reflective material is recognized, resulting in a low quality of the display. Further, the interval of the reflective material is preferably from 1,000 to 5,000 μm. If the interval is narrower than 1000 μm, the adjacent white reflective material may overlap in screen printing or the like. When it is wider than 5000 μm, even when viewed through a diffusion sheet or the like, the dark portion between the white reflective materials is recognized, resulting in a deterioration in display quality. In addition, the interval and size of the white reflective material may be adjusted according to the distance of the light source disposed adjacent to the end surface of the light guide plate. again The light-emitting surface (front surface of the light guide plate) of the light guide plate can also form a linear convex portion of a meandering or arc shape in the same manner. In the case of being used as a backlight, the reflection sheet may be appropriately disposed on the back side of the light guide plate, and the diffusion sheet and/or the sheet may be appropriately disposed on the front side of the light guide plate.

The molded article of the present invention can be used as a front panel of various displays. Such a front panel can be obtained by a general molding method such as heating, melt extrusion molding, and injection molding of a resin composition.

The display device using the front panel is not particularly limited, and examples thereof include large-sized display devices such as large-screen televisions and advertisement displays, and small-sized display devices such as mobile phones and smart phones.

Further, the front panel is not limited to a flat shape, and may have a curved shape. The shape of the curved surface may be a shape that is curved in one direction or a shape that is curved in a plurality of directions. In order to allow the front panel to have a curved shape, the plate-shaped formed body may have a flexible property or may be formed into a desired curved shape in advance.

Further, the molded article of the present invention can be used in the above various applications in a state where the surface is hard-coated by a method such as spraying or dip coating. Since the hard coating makes the pencil hardness of the surface high, it is not easily damaged. In addition to the hard coating, an anti-glare layer, an anti-reflection layer, and a functional layer such as a layer that blocks electromagnetic waves, ultraviolet rays, and near-infrared rays may be provided.

The molded article of the present invention can be laminated with other functional films or functional sheets through an adhesive layer or an adhesive layer, or can be laminated by film insertion molding. Examples of the functional film and the functional sheet include a light guide plate, a diffusion plate, an explosion-proof film, and a transparent conductive film.

[Examples]

The invention will be more specifically described below by way of examples and comparative examples. However, the invention is not limited to the following embodiments.

The physical properties of the methacrylic resin composition obtained in the examples and the comparative examples and the properties of the plate-shaped molded body were measured by the following methods.

(polymerization conversion rate, containing volatile components)

INERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m) manufactured by GL Sciences Inc., which is a column, was attached to a gas chromatograph GC-14A manufactured by Shimadzu Corporation, and analyzed based on the following analysis conditions. Calculated.

<Analysis conditions>

Injection temperature: 250 ° C

Detector temperature: 250 ° C

Column temperature conditions:

Initial temperature: 60 ° C

Initial temperature hold time: 5 minutes

Heating rate: 10 ° C / min

Maximum temperature: 250 ° C

Maximum temperature retention time: 10 minutes

(weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn))

The weight average molecular weight (Mw) and the molecular weight distribution were determined by GPC (gel permeation chromatography) to obtain a molecular weight in terms of polystyrene.

. Device: GPC device "HLC-8320" manufactured by Tosoh Co., Ltd.

. Separation column: "TSKgel GMHXL" and "G4000HXL" manufactured by Tosoh Co., Ltd.

. Lysate: tetrahydrofuran

. Dissolution flow: 0.35ml/min

. Column temperature: 40 ° C

. Detection method: differential refractive index (RI)

(melt flow rate)

The melt flow rate of the methacrylic resin compositions obtained in the examples and the comparative examples was measured in accordance with JIS K7210 at 230 ° C under a load of 3.8 kg for 10 minutes.

(saturated water absorption rate)

A pellet-shaped methacrylic resin was formed using an injection molding machine (SE-180DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.) at a cylinder temperature of 280 ° C, a mold temperature of 75 ° C, and a molding cycle of 1 minute. The object was injection molded to obtain a test piece having a length of 290 mm, a width of 100 mm, and a thickness of 2 mm. The test piece was vacuum dried for 3 days under the conditions of a temperature of 50 ° C and 5 mmHg, and the mass W ₀ of the test piece at the time of complete drying was measured. Thereafter, the completely dried test piece was allowed to stand at a temperature of 60 ° C and a humidity of 90% for 300 hours. Thereafter, the mass W _{1 of the} test piece was measured. The saturated water absorption ratio (%) was calculated by the following formula.

Saturated water absorption rate (%)={W ₁ -W ₀ }/W ₀ ×100

(appearance of the plate-shaped formed body)

The appearance of the plate-shaped formed body produced in the examples and the comparative examples was visually observed. It was evaluated by the presence or absence of appearance defects such as surface stains and breakage.

A: Good

B: There are stains on the surface

C: There is damage

(yellowness index)

The yellowness index of the monomer mixture used in the examples and the comparative examples was calculated in accordance with JIS K7373 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. based on the value measured in accordance with JIS Z-8722.

Test pieces having a length of 200 mm were cut out from the plate-shaped molded bodies produced in the examples and the comparative examples, and measured by a colorimeter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. based on JIS Z-8722. The value of the yellowness index of the optical path length of 200 mm of these test pieces was calculated in accordance with JIS K7373.

(Transmittance)

A test piece having an optical path length of 200 mm and a test piece having an optical path length of 3 mm were cut out from the plate-shaped formed bodies prepared in the examples and the comparative examples, respectively, and the light having a wavelength of 435 nm was measured at an optical path length of 200 mm and an optical path length of 3 mm. Transmittance.

(dimension change rate)

The plate-shaped formed bodies prepared in the examples and the comparative examples were placed in a thermostat at 60 ° C for 4 hours in the atmosphere. The plate-shaped formed body was taken out from the thermostat, and the dimension in the longitudinal direction was measured. The dimensional change rate was calculated from the dimension (205 mm) in the longitudinal direction before being placed in the thermostat.

(The punching resistance of the plate-shaped formed body)

Using Examples 1 to 3 and Comparative Example 1 using an injection molding machine (SE-180DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.) at a cylinder temperature of 230 ° C, a mold temperature of 65 ° C, and a molding cycle of 0.5 minutes. ~6 The obtained pelletized methacrylic resin composition was injection-molded, or the plate-shaped formed body obtained in Comparative Example 8 was cut, and a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was produced, according to ISO179-1. The intensity of the incision-free skin was measured.

Hereinafter, methacrylic acid tricyclo [5.2.1.0 ^2,6] dec-8-yl ester (dicyclopentanyl methacrylate) labeled TCDMA, methacrylate, isobornyl acrylate IBXMA labeled, marked as methyl methacrylate MMA, acrylic The methyl ester is labeled as MA, the n-octyl thiol is labeled as n-OM, and the 2,2'-azobis(2-methylpropionitrile) is designated as AIBN.

Example 1

Into the autoclave equipped with a stirrer and a tube, 78 parts by mass of MMA purified, 20 parts by mass of TCDMA, and 2 parts by mass of MA were added to prepare a monomer mixture. The yellowness index of the monomer mixture was 0.9. 0.006 parts by mass of a polymerization initiator (AIBN, hydrogen capture ability: 1%, 1 hour half-life temperature: 83 ° C) and 0.37 parts by mass of a chain transfer agent (n-OM) were added to the monomer mixture to dissolve it. The raw material liquid was obtained. The oxygen in the manufacturing unit was expelled with nitrogen.

The raw material liquid was supplied from the autoclave to the continuous flow type tank reactor controlled at a temperature of 140 ° C at a constant flow rate, and the average residence time was 120 minutes to carry out bulk polymerization. The reaction liquid was separated and taken out in a take-up tube of a reactor, and when measured by gas chromatography, the polymerization conversion ratio was 57% by mass.

The liquid discharged from the reactor was warmed to 250 ° C, supplied at a constant flow rate to a twin-screw extruder controlled at 260 ° C, and adiabatic flashing was carried out at the extruder inlet. Volatile components (monomers, dimers, trimers, etc.) which are evaporated by adiabatic flashing are discharged from the open vent. Use snail The rod is introduced into the liquid kneading of the twin screw extruder by adiabatic flashing, whereby the volatile component is evaporated from the liquid, and the evaporated volatile component is discharged from the vent hole of the twin screw extruder. The methacrylic resin composition in a molten state obtained by the above-described adiabatic flashing and devolatilization of the vent hole of the twin-screw extruder is extruded in a strand shape from the outlet of the twin-screw extruder. The strand was cut with a granulator to obtain a pelletized methacrylic resin composition. The content of TCDMA was 0.4% by mass. The physical properties of the obtained pelletized methacrylic resin composition were measured.

The pelletized methacrylic resin was composed of an injection molding machine (SE-180DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.) at a cylinder temperature of 280 ° C, a mold temperature of 75 ° C, and a molding cycle of 1 minute. The object was injection molded to form a plate-shaped formed body having a length of 205 mm, a width of 160 mm, and a thickness of 0.5 mm. The resin flow length (190 mm) to thickness ratio was 380.

The properties of the obtained plate-shaped formed body were evaluated. These results are shown in Table 1.

Example 2

In addition to changing the amount of MMA to 73 parts by mass, the amount of TCDMA to 23 parts by mass, the amount of MA to 4 parts by mass, the amount of n-OM to 0.33 parts by mass, and the resin production conditions to values shown in Table 1, In the same manner as in Example 1, a pelletized methacrylic resin composition was obtained. The physical properties of the obtained pelletized methacrylic resin composition were measured in the same manner as in Example 1. Then, a plate-shaped formed body was produced in the same manner as in Example 1, and the properties were evaluated. These results are shown in Table 1.

Example 3

Pellets were obtained in the same manner as in Example 1 except that the amount of MMA was changed to 83 parts by mass, the amount of TCDMA was changed to 15 parts by mass, the amount of MA was changed to 2 parts by mass, and the amount of n-OM was changed to 0.38 parts by mass. A methacrylic resin composition. The physical properties of the obtained pelletized methacrylic resin composition were measured in the same manner as in Example 1. Then, a plate-shaped formed body was produced in the same manner as in Example 1, and the properties were evaluated. These results are shown in Table 1.

Example 4

A pelletized methacrylic resin composition was obtained in the same manner as in Example 1 except that the amount of TCDMA was changed to IBXMA and n-OM was changed to 0.36 parts by mass. The physical properties of the obtained pelletized methacrylic resin composition were measured in the same manner as in Example 1. Then, a plate-shaped formed body was produced in the same manner as in Example 1, and the properties were evaluated. These results are shown in Table 1.

Comparative example 1~4

A pelletized methacrylic resin composition was obtained in the same manner as in Example 1 except that the synthesis conditions and resin production conditions shown in Tables 1 and 2 were changed. The physical properties of the pelletized methacrylic resin compositions were measured in the same manner as in Example 1. Then, it was molded in the same manner as in Example 1, and the properties were measured. These results are shown in Tables 1 and 2.

Comparative Example 5

A pelletized methacrylic resin composition was obtained in the same manner as in Example 1 except that the synthesis conditions and the resin production conditions shown in Table 2 were changed.

This pelletized methacrylic resin composition was supplied at a constant rate to a twin screw extruder controlled at 270 °C. In the twin-screw extruder, a volatile component containing an unreacted monomer as a main component was separated and removed, and the resin component was extruded in a strand shape. The strand was cut with a granulator to obtain a pelletized methacrylic resin composition (regranulation). The content of TCDMA was 0.7% by mass. The physical properties of the re-granulated methacrylic resin composition were measured in the same manner as in Example 1. Then, a plate-shaped formed body was produced in the same manner as in Example 1, and the properties were measured. These results are shown in Table 2.

Comparative Example 6

A pelletized methacrylic resin composition was obtained in the same manner as in Example 1 except that the synthesis conditions and the resin production conditions shown in Table 2 were changed.

20 parts by mass of this pelletized methacrylic resin composition and 80 parts by mass of a toluene solution were prepared, and this solution was poured into a large amount of methanol to be reprecipitated to obtain a powdery methacrylic resin composition.

The powdery methacrylic resin composition was supplied to a uniaxial extruder controlled at 230 ° C at a constant rate, and the extruded strand was cut by a granulator to obtain a pelletized methacrylic resin composition ( Regranulation). The content of TCDMA was 0.2% by mass. The physical properties of the re-granulated methacrylic resin composition were measured in the same manner as in Example 1. Then, a plate-shaped formed body was produced in the same manner as in Example 1, and the properties were measured. These results are shown in Table 2.

Comparative Example 7

83 parts by mass of MMA, 15 parts by mass of TCDMA, and 2 parts by mass of MA were added to prepare a monomer mixture. The yellowness index of the monomer mixture was 0.9. 0.1 part by mass of a polymerization initiator (AIBN, hydrogen capture ability: 1%, 1 hour half-life temperature: 83 ° C), and 0.4 parts by mass of a chain transfer agent (n-OM) were added to the monomer mixture to dissolve it. , to obtain a raw material liquid.

100 parts by mass of ion-exchanged water, 0.03 parts by mass of sodium sulfate, and 0.46 parts by mass of a suspension dispersant were mixed to obtain a mixed solution. 420 parts by mass of the mixed solution and 210 parts by mass of the raw material liquid were placed in a pressure-resistant polymerization tank, and the temperature was adjusted to 70 ° C while stirring under a nitrogen atmosphere to start a polymerization reaction. After the start of the polymerization reaction, the temperature was raised to 90 ° C over 3 hours, and stirring was continued for 1 hour to obtain a dispersion in which bead fine particles were dispersed.

The obtained dispersion liquid was filtered, and the fine particles were washed with ion-exchanged water, and then dried at 80 ° C under reduced pressure of 100 Pa for 4 hours to obtain a bead copolymer.

The obtained copolymer was supplied to a uniaxial extruder controlled at 230 ° C, and volatile components such as unreacted monomers were separated and removed, and then the resin component was extruded to form strands. The strand was cut with a granulator to obtain a pelletized methacrylic resin composition. Then, a plate-shaped formed body was produced in the same manner as in Example 1, and the properties were measured. These results are shown in Table 2.

Comparative Example 8

73 parts by mass of MMA, 25 parts by mass of TCDMA, and 2 parts by mass of MA were added to prepare a monomer mixture. The yellowness index of the monomer mixture was 0.9. 0.1 parts by mass of a polymerization initiator added to the monomer mixture (AIBN, hydrogen capture capacity: 1%, 1 hour half-life temperature: 83 ° C), which was dissolved to obtain a raw material liquid.

This raw material liquid was poured into a glass tank composed of two water-repellent glass plates (thickness 10 mm, 30 cm x 30 cm) and a gasket made of vinyl chloride resin, and degassed at 760 mmHg for 3 minutes. The glass vessel was polymerized at 70 ° C for 2 hours, and then polymerized at 120 ° C for 2 hours. After removing the glass plate to form a plate-shaped formed body having a thickness of 0.5 mm, the plate-shaped formed body was broken at the time of take-out, and the plate was broken. Low thickness accuracy.

A plate-shaped molded body having a thickness of 2 mm and 4 mm was produced under the same polymerization conditions as above, and the obtained plate-shaped molded body was cut into test pieces having a length of 290 mm, a width of 100 mm, and a thickness of 2 mm for evaluation of light transmittance, and a punching resistance. For the evaluation, a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was used to evaluate the physical properties of the resin composition and the properties of the plate-shaped molded body. The obtained plate-shaped formed body was not dissolved in the solvent because it was a very high molecular weight body, and only swelled. Therefore, the molecular weight cannot be determined. The weight average molecular weight is estimated to be 1,000,000 g/mol or more. These results are shown in Table 2.

As shown by the above results, the plate-shaped formed body of the present invention has less coloration, high transparency, low haze value, low saturated water absorption, small dimensional change, and good appearance.

Claims (10)

A method for producing a methacrylic resin composition, which is a method for producing a methacrylic resin composition having a total content of a dimer and a trimer composed of a polymerizable monomer of 0.3% by mass or less, and comprising: (I) continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to the reactor; (II) subjecting a part of the polymerizable monomer to a radical block polymerization to obtain a methacrylic acid a resin mixture of a resin, an unreacted polymerizable monomer and a dimer or a trimer composed of a polymerizable monomer, wherein the methacrylic resin has 60 to 90% by mass of methyl methacrylate-derived a structural unit, 10 to 40% by mass of a structural unit derived from a methacrylate alicyclic hydrocarbon ester, and 0 to 10% by mass of an acrylate-derived structural unit; (III) the resin mixture is continuously continuous from the reactor Transfer to a twin-screw extruder equipped with a vent hole; (IV) in the twin-screw extruder, unreacted polymerizable monomer and a dimer composed of a polymerizable monomer from the resin mixture Or trimer removal. The method for producing a methacrylic resin composition according to claim 1, wherein the removal of the unreacted polymerizable monomer from the dimer or trimer composed of the polymerizable monomer is carried out at 210 ° C to 300 The adiabatic flash at a temperature of °C and the devolatilization of the vent hole of the twin screw extruder. The method for producing a methacrylic resin composition according to claim 1, wherein the amount of the methacrylate alicyclic hydrocarbon ester contained in the methacrylic resin composition is 1.0% by mass or less. The method of manufacturing a composition of a requested item of methyl acrylic resin, wherein the alicyclic hydrocarbon methacrylate methacrylic acid ester is tricyclo [5.2.1.0 ^2,6] dec-8-yl ester (dicyclopentanyl methacrylate), or A Isodecyl acrylate. A method for producing a methacrylic resin pellet, which is a method for producing a methacrylic resin pellet having a total content of a dimer and a trimer composed of a polymerizable monomer of 0.3% by mass or less, comprising: (I) continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to the reactor; (II) subjecting a part of the polymerizable monomer to a radical block polymerization to obtain a methacrylic acid a resin mixture of a resin, an unreacted polymerizable monomer and a dimer or a trimer composed of a polymerizable monomer, wherein the methacrylic resin has 60 to 90% by mass of methyl methacrylate-derived a structural unit, 10 to 40% by mass of a structural unit derived from a methacrylate alicyclic hydrocarbon ester, and 0 to 10% by mass of an acrylate-derived structural unit; (III) the resin mixture is continuously continuous from the reactor Transfer to a twin-screw extruder equipped with a vent hole; (IV) in the twin-screw extruder, unreacted polymerizable monomer and a dimer composed of a polymerizable monomer from the resin mixture Or the trimer is removed to obtain a methacrylic resin composition, which will The methacrylic resin composition was extruded in a strand shape; (V) a methacrylic resin composition extruded in a strand shape was cut by a pelletizer. A method for producing a molded body comprising: carrying out the production method according to claim 5 to obtain a methacrylic resin pellet; and (VI) heating and melting the methacrylic resin pellet into a desired shape. A method for producing a plate-shaped formed body, which is a method for producing a plate-shaped formed body having an optical path length of 200 mm and a yellowness index of 10 or less, which is obtained by performing the production method according to any one of claims 1 to 4. a methacrylic resin composition; the methacrylic resin composition is heated and melted and formed into a plate shape. The method for producing a plate-shaped formed body according to claim 7, wherein the ratio of the resin flow length of the plate-shaped formed body to the thickness thereof is 380 or more. The method for producing a plate-shaped formed body according to claim 7, wherein the plate-shaped molded body has a light transmittance of 90% or more with respect to light having a wavelength of 435 nm at an optical path length of 3 mm. A method of producing a plate-shaped formed body according to claim 7, wherein the plate-shaped formed body is a light guide plate.