JP2013231128A - (meth)acrylic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a (meth)acrylic resin composition capable of obtaining a molded article having high transparency, high hardness, high strength, low saturated water absorption, less dimensional change, favorable appearance, small thickness and wide area at high production efficiency.SOLUTION: A (meth)acrylic resin composition contains 100 pts.mass of a (meth)acrylic resin including 80-100 mass% of a structural unit derived from methyl methacrylate and 0-20 mass% of a structural unit derived from acrylic ester, and 1-15 pts.mass of a compound which has 2 to 4 of 5- or 6-membered ring structures composed only of carbon and hydrogen atoms in a molecule, has a boiling point of ≥250°C at normal temperatures, and has a molecular weight of <400. A melt flow rate under the conditions of 230°C and 3.8 kg load is ≥10 g/10 min.

Description

  The present invention relates to a (meth) acrylic resin composition. More specifically, the present invention provides a thin and wide-area molded product with high production efficiency with high transparency, high hardness, high strength, low saturated water absorption, small dimensional change, and good appearance. The present invention relates to a (meth) acrylic resin composition.

  The (meth) acrylic 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 (meth) acrylic resin composition containing a (meth) acrylic resin.

  In recent years, a demand for a light-weight and wide-area liquid crystal display device is high, and correspondingly, an optical member is also required to be thin and wide. Furthermore, high accuracy is required for optical characteristics such as refractive index and retardation as the image quality of display devices increases. Thin-walled and large-area molded products are prone to greatly affect optical characteristics due to dimensional changes due to moisture absorption and heat. Therefore, the (meth) acrylic resin composition that is a raw material for the optical member is strongly required to have high transparency, low moisture absorption, high heat resistance, small dimensional change, high hardness, high moldability, and the like.

  As a methacrylic resin aiming at both transparency and low water absorption, for example, Patent Document 1 discloses a copolymer of cyclohexyl methacrylate and methyl methacrylate, and Patent Document 2 discloses a copolymer of i-butyl methacrylate and methyl methacrylate. A polymer is disclosed.

Moreover, as what aimed at making hygroscopicity low, for example, in patent document 3, 5-40 mass parts of methacrylic acid ester or acrylic acid ester which has a C5-C22 alicyclic hydrocarbon group in an ester part. , 50-80 parts by weight of methyl methacrylate, 5-40 parts by weight of N-substituted maleimide, 0-30 parts by weight of benzyl methacrylate, and acrylic ester or aromatic having a hydrocarbon group having 1-5 carbon atoms in the ester moiety The absolute value of orientation birefringence of the obtained resin is less than 1 × 10 ⁻⁶ , the melt flow rate is 15 g / 10 min or more, and the bending fracture strength is 1 to 10 parts by mass of the vinyl compound, the total mass is 100 parts by mass. An optical resin composition containing a resin obtained by copolymerization at a composition ratio such that is 50 MPa or more is disclosed.

JP 58-5318 A JP 60-26014 A JP 2004-18710 A

Nippon Oil & Fats Co., Ltd. Technical Document “Organic oxide hydrogen abstraction and initiator efficiency” (prepared in April 2003) D. W. VAN KREVELEN, PROPERTIES OF POLYMERS, 3rd edition (Third Ed), Elsevier Science, 1990, p. 72-75.

However, the (meth) acrylic resin disclosed in the above prior art documents has a tendency to decrease in hardness, strength, and the like.
Accordingly, an object of the present invention is to obtain a thin-walled and wide-area molded product with high production efficiency with high transparency, high hardness, high strength, low saturated water absorption, small dimensional change, and good appearance. It is in providing the (meth) acrylic resin composition which can be carried out.

  The present inventors have intensively studied to achieve the above object. As a result, an invention including the following aspects has been completed.

[1] Consists of 100 to 100 parts by weight of a (meth) acrylic resin containing 80 to 100% by weight of structural units derived from methyl methacrylate and 0 to 20% by weight of structural units derived from an acrylate ester, and only carbon atoms and hydrogen atoms 1 to 15 parts by mass of a compound having 2 to 4 5-membered or 6-membered ring structures in the molecule, having a boiling point at room temperature of 250 ° C. or higher and a molecular weight of less than 400,
A (meth) acrylic resin composition having a melt flow rate of 10 g / 10 min or more under conditions of 230 ° C. and a load of 3.8 kg.
[2] The (meth) acrylic resin composition according to [1], wherein the compound has a molecular radius of 0.30 to 0.45 nm determined by an atomic group contribution method.
[3] The (meth) acrylic resin composition according to [1] or [2], wherein the compound is a ring assembly compound.
[4] The (meth) acrylic resin composition according to [1] or [2], wherein the compound is an aromatic ring assembly compound.
[5] The (meth) acrylic resin composition according to [1] or [2], wherein the compound has at least one selected from the group consisting of a biphenyl group, a terphenyl group, and a quaterphenyl group.
[6] The (meth) acrylic resin composition according to any one of [1] to [5], wherein the saturated water absorption is 1.7% by mass or less.

[7] A molded article comprising the (meth) acrylic resin composition according to any one of [1] to [6].
[8] The molded article according to [7], wherein the ratio of the resin flow length to the thickness is 380 or more.

  When the (meth) acrylic resin composition of the present invention is used, a thin and wide-area molded product having high transparency, high hardness, high strength, low saturated water absorption, small dimensional change, and good appearance. It can be obtained with high production efficiency.

  The (meth) acrylic resin composition of the present invention contains a (meth) acrylic resin and a compound having a ring structure.

The (meth) acrylic resin used in the present invention contains 80 to 100% by mass, preferably 80 to 96% by mass of a structural unit derived from methyl methacrylate among all monomer units. Moreover, the (meth) acrylic resin used for this invention contains 0-20 mass%, preferably 4-20 mass% of the structural unit derived from an acrylate ester in all the monomer units.
Examples of the acrylic ester include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, alkyl acrylate such as 2-ethylhexyl acrylate; aryl acrylate such as phenyl acrylate; cyclohexyl acrylate, And cycloalkyl acrylate such as norbornenyl acrylate.

  The (meth) acrylic resin used in the present invention may contain a structural unit derived from a monomer other than methyl methacrylate and acrylate ester. Such monomers include alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate and butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cycloalkyl methacrylates such as cyclohexyl methacrylate and norbornenyl methacrylate; Non-crosslinkable vinyl monomers having only one polymerizable alkenyl group in one molecule such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, etc. Can be mentioned. The amount of the structural unit derived from the monomer is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total monomer units.

  The (meth) acrylic resin has a weight average molecular weight (hereinafter sometimes abbreviated as Mw), preferably 35,000 to 100,000, more preferably 40,000 to 80,000, particularly preferably 45,000. ~ 60,000. If Mw is too small, the impact resistance and toughness of the molded product obtained from the (meth) acrylic resin composition tend to decrease. When Mw is too large, the fluidity of the (meth) acrylic resin composition is lowered and the moldability tends to be lowered.

The (meth) acrylic resin has a weight average molecular weight / number average molecular weight ratio (hereinafter, this ratio may be referred to as a molecular weight distribution), preferably 1.7 to 2.5, more preferably 1. It is 7 to 2.3, particularly preferably 1.7 to 2.0. When the molecular weight distribution is small, the molding processability of the (meth) acrylic resin composition tends to decrease. When the molecular weight distribution is large, the impact resistance of the molded product obtained from the (meth) acrylic resin composition tends to be lowered and tends to be brittle.
In addition, a weight average molecular weight and a number average molecular weight are molecular weights of standard polystyrene conversion measured by GPC (gel permeation chromatography).
The molecular weight and molecular weight distribution of the (meth) acrylic resin can be controlled by adjusting the types and amounts of the polymerization initiator and chain transfer agent described later.

  The (meth) acrylic resin is obtained by polymerizing a monomer mixture containing at least methyl methacrylate and acrylic ester having the above mass ratio.

  The methyl index, acrylic acid ester, and other monomers that are raw materials for the (meth) acrylic resin preferably have a yellow index of 2 or less, more preferably 1 or less. If the yellow index of the monomer is small, when the resulting (meth) acrylic resin composition is molded, a molded product with little coloration is easily obtained with high production efficiency. As will be described later, in the polymerization reaction of the (meth) acrylic resin, the polymerization conversion rate is not so high, so that unreacted monomers remain in the polymerization reaction solution. Unreacted monomer can be recovered from the polymerization reaction solution and used again for the polymerization reaction. The yellow index of the recovered monomer may increase due to heat applied during recovery. The recovered monomer is preferably purified by an appropriate method to reduce the yellow index. The yellow index is a value measured according to JIS Z-8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

  The polymerization reaction of the monomer mixture is preferably carried out by a bulk polymerization method or a solution polymerization method, more preferably a bulk polymerization method. The polymerization reaction is initiated by adding a polymerization initiator to the monomer mixture. Moreover, the molecular weight etc. of the polymer obtained can be adjusted by adding a chain transfer agent to a monomer mixture as needed. The monomer mixture has a dissolved oxygen content of preferably 10 ppm or less, more preferably 5 ppm or less, still more preferably 4 ppm or less, and most preferably 3 ppm or less. When the amount of dissolved oxygen is in such a range, the polymerization reaction proceeds smoothly, and it becomes easy to obtain a molded product without silver or coloring.

The polymerization initiator used in the present invention is not particularly limited as long as it generates a reactive radical. For example, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-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- Chill propionate) and the like. Of these, t-hexylperoxy 2-ethylhexanoate, 1,1-bis (t-hexylperoxy) cyclohexane, and dimethyl 2,2′-azobis (2-methylpropionate) are preferable.
Of these, the polymerization initiator preferably has a one-hour half-life temperature of 60 to 140 ° C, more preferably 80 to 120 ° C. The polymerization initiator used for bulk polymerization preferably has a hydrogen abstraction ability of 20% or less, more preferably 10% or less, and even more preferably 5% or less. These polymerization initiators can be used alone or in combination of two or more. The addition amount and addition method of the polymerization initiator are not particularly limited as long as they are appropriately set according to the purpose. For example, the amount of the polymerization initiator used for the bulk polymerization is preferably 0.0001 to 0.02 parts by mass, more preferably 0.001 to 0.01 parts by mass with respect to 100 parts by mass of the monomer mixture. is there.

  The hydrogen abstraction ability can be known from the technical data (for example, Non-Patent Document 1) of the polymerization initiator manufacturer. Further, it can be measured by a radical trapping method using α-methylstyrene dimer, that is, α-methylstyrene dimer trapping method. The measurement is generally performed as follows. First, the polymerization initiator is cleaved in the presence of α-methylstyrene dimer as a radical trapping agent to generate radical fragments. Among the generated radical fragments, radical fragments having a low hydrogen abstraction ability are added to and trapped by the double bond of α-methylstyrene dimer. On the other hand, a radical fragment having a high hydrogen abstraction capacity abstracts hydrogen from cyclohexane to generate a cyclohexyl radical, which is added to and trapped by the double bond of α-methylstyrene dimer to generate a cyclohexane trap product. Therefore, the ratio (mole fraction) of radical fragments having a high hydrogen abstraction capacity with respect to the theoretical radical fragment generation amount, which is obtained by quantifying cyclohexane or cyclohexane supplement product, is defined as the hydrogen abstraction capacity.

  As the chain transfer agent, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopropionate, butanediol bisthioglycolate, Alkyl mercaptans such as butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakisthiopropionate; α-methylstyrene dimer; terpinolene and the like. Of these, monofunctional alkyl mercaptans such as n-octyl mercaptan and n-dodecyl mercaptan or pentaerythritol tetrakisthiopropionate 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 0.1 to 1 part by weight, more preferably 0.2 to 0.8 part by weight, and still more preferably 0.3 to 0 part per 100 parts by weight of the monomer mixture. .6 parts by mass.

  The solvent used in the solution polymerization is not particularly limited as long as it has a solubility in the monomer mixture as a raw material and the product (meth) acrylic resin, but aromatic such as benzene, toluene, ethylbenzene and the like. Hydrocarbons are preferred. These solvents can be used alone or in combination of two or more. The amount of the solvent used is preferably 0 to 100 parts by mass, more preferably 0 to 90 parts by mass with respect to 100 parts by mass of the monomer mixture. The greater the amount of solvent used, the lower the viscosity of the reaction solution and the better the handleability but the lower the productivity.

  The polymerization conversion rate of the monomer mixture is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and still more preferably 35 to 65% by mass. When the polymerization conversion rate is in such a range, it is easy to adjust the melt flow rate to a range described later. If the polymerization conversion rate is too high, a large stirring power tends to be required for increasing the viscosity. If the polymerization conversion rate is too low, devolatilization tends to be insufficient, and when the obtained (meth) acrylic resin composition is molded, the molded product tends to have a poor appearance such as silver.

  Examples of the apparatus for performing the bulk polymerization method or the solution polymerization method include a tank reactor with a stirrer, a tube reactor with a stirrer, and a tube reactor having a static stirring ability. One or more of these apparatuses may be used, or two or more different reactors may be used in combination. The reaction apparatus may be either a batch type or a continuous flow type. The stirrer to be used can be selected according to the type of the reactor. Examples of the stirrer include a dynamic stirrer and a static stirrer. The most suitable apparatus for obtaining the (meth) acrylic resin used in the present invention is one having at least one continuous flow tank reactor. A plurality of continuous flow tank reactors may be connected in series or in parallel.

  In a tank reactor, usually, a stirring means for stirring the liquid in the reaction tank, a supply unit for supplying a monomer mixture or a polymerization auxiliary material to the reaction tank, and a reaction product is extracted from the reaction tank. And an extraction part. In the continuous flow reaction, the amount supplied to the reaction vessel and the amount withdrawn from the reaction vessel are balanced so that the amount of liquid in the reaction vessel becomes substantially constant. The amount of liquid in the reaction tank is preferably 1/4 to 3/4, more preferably 1/3 to 2/3, with respect to the volume of the reaction tank.

Examples of the agitation means include a Max blend type agitation device, an agitation device having a grid-like blade rotating around a vertical rotation shaft disposed in the center, a propeller type agitation device, and a screw type agitation device. Among these, a Max blend type stirring apparatus is preferably used from the point of uniform mixing property.
Methyl methacrylate, acrylic acid ester, polymerization initiator and chain transfer agent may be mixed and supplied to the reaction vessel before supplying them all to the reaction vessel, or they may be supplied separately to the reaction vessel. Also good. In the present invention, a method of mixing all the components before supplying them to the reaction vessel and supplying them to the reaction vessel is preferable.

  The mixing of methyl methacrylate, acrylic acid ester, polymerization initiator and chain transfer agent is preferably performed in an inert atmosphere such as nitrogen gas. In addition, in order to smoothly carry out the continuous flow type operation, from a tank storing methyl methacrylate, an acrylate ester, a polymerization initiator and a chain transfer agent, respectively, to a mixer provided in the front stage of the reaction tank through a pipe It is preferable to feed and continuously mix, and to continuously flow the mixture into the reaction vessel. The mixer can be equipped with a dynamic stirrer or a static stirrer.

The temperature during the polymerization reaction is preferably 100 to 150 ° C, more preferably 110 to 140 ° C. When the temperature during the polymerization reaction is in such a range, it is easy to adjust the melt flow rate or the like to a range described later.
The time for the polymerization reaction is preferably 0.5 to 4 hours, and more preferably 1 to 3 hours. In the case of a continuous flow reactor, the polymerization reaction time is an average residence time in the reactor. If the polymerization reaction time is too short, the required amount of polymerization initiator increases. Further, increasing the amount of the 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 polymerization reaction time is too long, it takes time for the reaction to reach a steady state, and the productivity tends to decrease. The polymerization is preferably performed in an inert gas atmosphere such as nitrogen gas.

  After the completion of polymerization, unreacted monomers and solvent are removed as necessary. The removal method is not particularly limited, but heating devolatilization is preferable. Examples of the devolatilization method include an equilibrium flash method and an adiabatic flash method. In particular, in the adiabatic flash method, devolatilization is preferably performed at a temperature of 200 to 300 ° C, more preferably 220 to 270 ° C. Below 200 ° C., it takes time for devolatilization, and devolatilization tends to be insufficient. When devolatilization is insufficient, appearance defects such as silver may occur in the molded product. On the other hand, if it exceeds 300 ° C., the (meth) acrylic resin composition tends to be colored due to oxidation, burning, or the like.

The compound having a ring structure used in the present invention is a compound having 2 to 4 5-membered or 6-membered ring structures composed only of carbon atoms and hydrogen atoms in the molecule. The compound is preferably a ring assembly compound, and more preferably an aromatic ring assembly compound. The ring assembly compound is a compound having a structure in which two or more aromatic rings or alicyclic rings do not have a shared atom and are linked through a single bond or a double bond. An aromatic ring assembly compound is a compound having a structure in which two or more aromatic rings do not have a shared atom and are linked via a single bond or a double bond.
The compound has a boiling point at room temperature of 250 ° C. or more, preferably 300 to 400 ° C., and the compound has a molecular weight of less than 400, preferably 150 to 300. The molecular radius of the compound determined by theoretical calculation using an atomic group contribution method is preferably 0.30 to 0.45 nm, more preferably 0.32 to 0.40 nm. In the atomic group contribution method, first, a molecule is regarded as a set of functional groups and is divided for convenience. For example, biphenyl is divided into two phenyl groups. The van der Waals volume V _{W, i} of each divided functional group was added together to calculate the van der Waals volume of the molecule. From the volume, the molecular radius was calculated by assuming that the molecule was spherical. In addition, the numerical value described in TABLE4.2 of the nonpatent literature 2 was used for van der Waals volume VW _{, i} of each functional group. The specific calculation is based on the following formula. R is the molecular radius and N _A is Avogadro's number.

  Specific examples of the compound include a compound having a biphenyl group such as biphenyl; a compound having a terphenyl group such as m-terphenyl, p-terphenyl, 5′-phenyl-m-terphenyl; 1,1 ′: Compounds having a quaterphenyl group, such as 3 ′, 1 ″: 3 ″, 1 ″ -quaterphenyl, 1,1 ′: 3 ′, 1 ″: 4 ″, 1 ″ ′-quaterphenyl; bicyclohexyl, Bicyclopentyl, bi (cyclohex-2-en-1-yl), bi (bicyclo [2.2.1] hept-5-en-2-yl, bi (cyclopenta-2,4-dien-1-ylden) 1,1 ′: 3 ′, 1 ″ -tercyclohexane, quatercyclopentene, 1,4-di (cyclohexyl) benzene, etc. Among these, biphenyl group, terphenyl group and A compound having at least one selected from the group consisting of an terphenyl group is preferable, and m-terphenyl, biphenyl, or 1,4-di (cyclohexyl) benzene is preferable, and the amount of the compound is 100 mass of (meth) acrylic resin. 1 to 15 parts by mass, preferably 1 to 10 parts by mass, and more preferably 2 to 7 parts by mass, when the compound having a ring structure is added to the (meth) acrylic resin in such an amount, It is easy to obtain a molded article having high transparency, high hardness, high strength, low saturated water absorption, small dimensional change, and good appearance.

  The (meth) acrylic resin composition according to the present invention is obtained by melt-kneading a (meth) acrylic resin and the compound having the ring structure at the above-described mass ratio. Examples of the melt kneading means include known kneaders such as a single screw extruder, a twin screw extruder, a Banbury mixer, a brabender, an open roll, and a kneader. Among these, a twin screw extruder is preferable because of excellent productivity and efficient melt kneading. The resin temperature at the time of melt kneading is preferably 170 ° C. or higher, more preferably 180 to 280 ° C., and further preferably 200 to 260 ° C. After melt-kneading, it is cooled to a temperature of 120 ° C. or lower. Cooling can be performed by a method such as immersing the melted strand in a tank in which cold water is stored.

The (meth) acrylic resin composition of the present invention may contain various additives at 0.5% by mass or less, preferably 0.2% by mass or less, if necessary.
Additives include antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, dyes and pigments, light diffusing agents, organic dyes , Matting agents, impact resistance modifiers, phosphors and the like.

The antioxidant alone has an effect of preventing oxidative deterioration of the resin in the presence of oxygen. Examples thereof include phosphorus antioxidants, hindered phenol antioxidants, and thioether antioxidants. These antioxidants can be used alone or in combination of two or more. Among these, from the viewpoint of preventing the deterioration of optical properties due to coloring, phosphorus-based antioxidants and hindered phenol-based antioxidants are preferable, and the combined use of phosphorus-based antioxidants and hindered phenol-based antioxidants is more preferable. preferable.
In the case where a phosphorus antioxidant and a hindered phenol antioxidant are used in combination, the ratio is not particularly limited, but is preferably a mass ratio of phosphorus antioxidant / hindered phenol antioxidant, preferably 1/5. ˜2 / 1, more preferably ½ to 1/1.

  As the phosphorus-based antioxidant, 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite (manufactured by Asahi Denka Co., Ltd .; trade name: ADK STAB HP-10), Tris (2,4-dit -Butylphenyl) phosphite (manufactured by Ciba Specialty Chemicals; trade name: IRUGAFOS168) is preferred.

  As the hindered phenol-based antioxidant, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Specialty Chemicals; trade name IRGANOX 1010), Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by Ciba Specialty Chemicals; trade name IRGANOX 1076) is preferred.

The thermal degradation inhibitor can prevent thermal degradation of the resin by scavenging polymer radicals generated when exposed to high heat in a substantially oxygen-free state.
As the thermal degradation inhibitor, 2-t-butyl-6- (3′-t-butyl-5′-methyl-hydroxybenzyl) -4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumilizer GM), 2,4-di-t-amyl-6- (3 ′, 5′-di-t-amyl-2′-hydroxy-α-methylbenzyl) phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumitizer GS) preferable.

The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays. The ultraviolet absorber is a compound that is said to have a function of mainly converting light energy into heat energy.
Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, succinic anilides, malonic esters, formamidines, and the like. These can be used alone or in combination of two or more.
Among these, benzotriazoles or ultraviolet absorbers having a maximum molar extinction coefficient ε _{max at a} wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less are preferable.

  Since benzotriazoles have a high effect of suppressing deterioration of optical properties such as coloring due to ultraviolet irradiation, they are used when the (meth) acrylic resin composition of the present invention is applied to applications requiring the above properties. Preferred as a UV absorber.

  As benzotriazoles, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (manufactured by Ciba Specialty Chemicals; trade name TINUVIN329), 2 -(2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (manufactured by Ciba Specialty Chemicals; trade name TINUVIN234) is preferred.

Further, the maximum value ε _max of the molar extinction coefficient at a wavelength of 380 to 450 nm is 1200 dm ³ ·
The ultraviolet absorber having a mol ⁻¹ cm ⁻¹ or less can suppress the yellowness of the obtained molded product. The ultraviolet absorber is preferable as an ultraviolet absorber used when the (meth) acrylic resin composition of the present invention is applied to applications requiring such characteristics.

In addition, the maximum value ε _max of the molar extinction coefficient of the ultraviolet absorber is measured as follows. Add 10.00 mg of UV absorber to 1 L of cyclohexane and dissolve it so that there is no undissolved material by visual observation. This solution is poured into a 1 cm × 1 cm × 3 cm quartz glass cell, and the absorbance at a wavelength of 380 to 450 nm is measured using a U-3410 spectrophotometer manufactured by Hitachi, Ltd. The maximum value ε _max of the molar extinction coefficient is calculated from the molecular weight (Mw) of the ultraviolet absorber and the maximum value (A _max ) of the measured absorbance by the following formula.

ε _max = [A _max / (10 × 10 ⁻³ )] × Mw

As an ultraviolet absorber having a maximum extinction coefficient ε _{max at a} wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less, 2-ethyl-2′-ethoxy-oxalanilide (manufactured by Clariant Japan, Inc .; Trade name Sundeyuboa VSU).
Of these ultraviolet absorbers, benzotriazoles are preferably used from the viewpoint of suppressing resin degradation due to ultraviolet irradiation.

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

  A mold release agent is a compound having a function of facilitating release of a molded product from a mold. Examples of the release agent include higher alcohols such as cetyl alcohol and stearyl alcohol; glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride. In the present invention, it is preferable to use a higher alcohol and a glycerin fatty acid monoester in combination as a release agent. When higher alcohols and glycerin fatty acid monoester are used in combination, the ratio is not particularly limited, but the mass ratio of higher alcohols / glycerin fatty acid monoester is preferably 2.5 / 1 to 3.5 / 1. Preferably it is 2.8 / 1 to 3.2 / 1.

The polymer processing aid is a compound that exhibits an effect on thickness accuracy and thinning when a (meth) acrylic resin composition is molded. The polymer processing aid is polymer particles having a particle diameter of 0.05 to 0.5 μm, which can be usually produced by an emulsion polymerization method.
The polymer particles may be single layer particles composed of polymers having a single composition ratio and single intrinsic viscosity, or multilayer particles composed of two or more kinds of polymers having different composition ratios or intrinsic viscosities. May be. Among these, particles having a two-layer structure having a polymer layer having a low intrinsic viscosity in the inner layer and a polymer layer having a high intrinsic viscosity of 5 dl / g or more in the outer layer are preferable.

The polymer processing aid preferably has an intrinsic viscosity of 3 to 6 dl / g as a whole.
If the intrinsic viscosity is too small, the effect of improving moldability is low. If the intrinsic viscosity is too large, the melt fluidity of the (meth) acrylic resin composition tends to be lowered.

  In the (meth) acrylic resin composition of the present invention, an impact modifier may be used. Examples of the impact modifier include a core-shell type modifier containing acrylic rubber or diene rubber as a core layer component; a modifier containing a plurality of rubber particles, and the like.

As the organic dye, a compound having a function of converting ultraviolet rays that are harmful to the resin into visible light is preferably used.
Examples of the light diffusing agent and matting agent include glass fine particles, polysiloxane-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 brightener, and a fluorescent bleach.

  These additives may be added to the polymerization reaction solution for producing the (meth) acrylic resin, or when the compound having the ring structure is added to the (meth) acrylic resin produced by the polymerization reaction. May be added together, or may be added to the (meth) acrylic resin composition of the present invention.

  The (meth) acrylic resin composition of the present invention has a melt flow rate of 10 g / 10 min or more, preferably 10 to 35 g / 10 min, more preferably 10 to 32 g / 10 min under the conditions of 230 ° C. and 3.8 kg load. It is. The melt flow rate is a value measured under conditions of 230 ° C., 3.8 kg load, and 10 minutes in accordance with JIS K7210.

  The preferred (meth) acrylic resin composition of the present invention has a saturated water absorption rate of preferably 1.7% by mass or less, more preferably 1.6% by mass or less.

  Various molded products can be obtained by subjecting such a (meth) acrylic resin composition of the present invention to conventionally known melt-heat molding such as injection molding, compression molding, extrusion molding, and vacuum molding. In particular, the (meth) acrylic resin composition of the present invention provides a thin and wide-area molded product with high production efficiency with high transparency, high hardness, low saturated water absorption, small dimensional change, and good appearance. can do.

  Examples of molded products made of the (meth) acrylic resin composition of the present invention include billboard parts such as advertising towers, stand signs, sleeve signs, column signs, and rooftop signs; display parts such as showcases, dividers, and store displays. Fluorescent lamp cover, mood lighting cover, lamp shade, lighting parts such as light ceiling, light wall, chandelier; interior parts such as pendant and mirror; door, dome, safety window glass, partition, stair lumbar, balcony lumbar, for leisure Building parts such as roofs of buildings; aircraft windshields, pilot visors, motorcycles, motorboat windshields, bus shading plates, automotive side visors, rear visors, head wings, headlight covers, and other transportation equipment related parts; Nameplates, stereo covers, TV protection masks, vending machines, etc. Child equipment parts; Medical equipment parts such as incubators and X-ray parts; Machine-related parts such as machine covers, instrument covers, experimental devices, rulers, dials, observation windows; LCD protective plates, light guide plates, light guide films, Fresnel lenses , Lenticular lenses, optical display parts such as front panels and diffusers for various displays; traffic-related parts such as road signs, guide boards, curved mirrors, sound barriers; automobile interior surface materials, mobile phone surface materials, marking films, etc. Film materials: Household appliances such as washing machine canopies and control panels, rice cooker top panels; other greenhouses, large aquariums, box aquariums, clock panels, bathtubs, sanitary, desk mats, game parts, toys And a mask for protecting the face during welding. Of these, a thin injection molded product having a thickness of 1 mm or less is preferable, and is particularly suitable for a thin injection molding product having a resin flow length to thickness ratio of 380 or more. A light guide plate is a good example of a thin-walled and large-area injection molded product.

The resin flow length is the distance between the gate of the injection mold and the inner wall of the mold farthest from the gate. The resin flow length in the film gate is the distance between the runner and sprue attachment part of the injection mold and the inner wall of the mold farthest from the attachment part.
The gate of the mold for obtaining a molded product having a thin wall and a large area according to the present invention is preferably a film gate. The film gate is cut with a cutting machine and finished with a router or the like. In a mold for obtaining a light guide plate used in a liquid crystal display device, it is preferable to provide a gate on an end face on which no light source is scheduled. Further, a pinpoint gate (also called a center gate or a pin gate) can be used as a gate of a mold for obtaining a molded product according to the present invention. The pinpoint gate is automatically cut off from the runner, and there is little work such as finishing.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, this invention is not restrict | limited by a following example. The invention of the present application includes all modes that are obtained by arbitrarily combining the items representing the technical features such as characteristic values, forms, manufacturing methods, and uses described above.

  The measurement of physical property values in Examples and Comparative Examples was performed by the following method.

(Polymerization conversion)
The gas chromatograph GC-14A manufactured by Shimadzu Corporation was used as a column for GL Sciences Inc. INTERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m) is connected, injection temperature is 250 ° C., detector temperature is 250 ° C., column temperature is 60 ° C. (held for 5 minutes) → temperature rise The speed was set to 10 ° C./min→250° C. (10 minutes hold), the analysis was performed, and the calculation was performed based on the analysis.

(Yellow Index)
The yellow index was measured according to JIS Z-8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

(Melt flow rate)
According to JIS K7210, it measured on 230 degreeC, the 3.8kg load, and the conditions for 10 minutes.

(Saturated water absorption)
A flat plate having a thickness of 2 mm was cut into a length of 100 mm and a width of 290 mm to obtain a test piece. The test piece was vacuum-dried for 3 days under conditions of a temperature of 50 ° C. and 5 mmHg, and the mass of the test piece W0 at the time of absolute drying was measured. Then, the absolutely dry test piece was left for 200 hours under conditions of a temperature of 60 ° C. and a humidity of 90%. Thereafter, the mass W1 of the test piece was measured. Hereinafter, the saturated water absorption (%) expressed as a percentage (%) was calculated according to the following formula.
Saturated water absorption = {W1-W0} / W0 × 100

(Rockwell hardness)
According to JIS K7202-2, it measured on the M scale using the flat plate of 500 mm x 500 mm x thickness 4mm obtained by injection molding.

(Bending strength)
It measured based on JISK7203 using the 80 mmx10mmx4mm molded article produced from the pellet-shaped (meth) acrylic resin obtained by the Example and the comparative example.

(Appearance evaluation)
The appearance of the flat plate T produced by the method described later was observed with the naked eye. The quality of the moldability was judged with and without molding defects such as sink marks.
○: There are no defects such as sink marks, cloudiness, and silver.
×: Sink, cloudiness or silver occurs

(Dimensional change rate)
The flat plate was placed in a thermostat having a temperature of 60 ° C. and a relative humidity of 90% and left in the atmosphere for 500 hours. The flat plate was taken out from the thermostat and the length dimension was measured. The dimensional change rate from the dimension in the length direction before putting in the thermostat was calculated.

Production Example 1
A monomer mixture was prepared by putting 95.5 parts by mass of purified methyl methacrylate and 4.5 parts by mass of methyl acrylate into an autoclave with a stirrer and a sampling tube. The yellow index of the monomer mixture was 0.9. Into the monomer mixture, a polymerization initiator (2,2′-azobis (2-methylpropionitrile (AIBN), hydrogen abstraction capacity: 1%, 1 hour half-life temperature: 83 ° C.) 0.006 and a chain transfer agent ( n7-octyl mercaptan) 0.37 parts by mass was added and dissolved to obtain a raw material liquid, and oxygen in the production apparatus was purged with nitrogen.
The raw material liquid was discharged from the autoclave in a constant amount, and supplied to a continuous flow tank reactor controlled at a temperature of 140 ° C. at a constant flow rate so as to have an average residence time of 120 minutes, and bulk polymerization was performed. . When the reaction solution was collected from the collection tube of the reactor and measured by gas chromatography, the polymerization conversion rate was 55% by mass.

  The liquid discharged from the reactor was heated to 230 ° C. and supplied to a twin screw extruder controlled at 260 ° C. at a constant flow rate. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the resin component was extruded in a strand shape. The strand was cut with a pelletizer to obtain a pellet-like (meth) acrylic resin.

Production Example 2
A pellet-shaped MS resin was obtained in the same manner as in Example 1 except that the monomer mixture was changed to one consisting of 45 parts by mass of methyl methacrylate and 55 parts by mass of styrene.

Production Example 3
A monomer mixture was prepared by putting 95.5 parts by mass of purified methyl methacrylate and 4.5 parts by mass of methyl acrylate into an autoclave with a stirrer and a sampling tube. The yellow index of the monomer mixture was 0.9. Into the monomer mixture, a polymerization initiator (2,2′-azobis (2-methylpropionitrile (AIBN), hydrogen abstraction capacity: 1%, 1 hour half-life temperature: 83 ° C.) 0.005 and a chain transfer agent ( n-octyl mercaptan) 0.17 parts by mass was added and dissolved to obtain a raw material liquid, and oxygen in the production apparatus was purged with nitrogen.
The raw material liquid was discharged from the autoclave in a constant amount, and supplied to a continuous flow tank reactor controlled at a temperature of 140 ° C. at a constant flow rate so as to have an average residence time of 120 minutes, and bulk polymerization was performed. . When the reaction solution was collected from the sampling tube of the reactor and measured by gas chromatography, the polymerization conversion was 50% by mass.

  The liquid discharged from the reactor was heated to 230 ° C. and supplied to a twin screw extruder controlled at 260 ° C. at a constant flow rate. In the twin-screw extruder, volatile components mainly composed of unreacted monomers were separated and removed, and the resin component was extruded in a strand shape. The strand was cut with a pelletizer to obtain a pellet-like (meth) acrylic resin.

Example 1
Using 100 parts by mass of the (meth) acrylic resin obtained in Production Example 1 and 5 parts by mass of m-terphenyl, a twin-screw kneading extruder (TEX-44α, L / D = 40, manufactured by Nippon Steel Works) was used. The mixture was kneaded and extruded at a cylinder temperature of 240 ° C. and a screw speed of 200 rpm to obtain a pellet-like (meth) acrylic resin composition. The melt flow rate was measured. m-Terphenyl has a boiling point of 379 ° C., a molecular weight of 230, and a molecular radius of 0.38 nm.

The pellet-shaped (meth) acrylic resin composition was injection-molded 10 times at a cylinder temperature of 280 ° C., a mold temperature of 75 ° C., and a molding cycle of 1 minute to produce a flat plate of a predetermined size. Saturated water absorption, Rockwell hardness, bending strength and dimensional change were measured.
Injection molding machine manufactured by Sumitomo Heavy Industries, Ltd .: Using SE-180DU-HP, pellet-shaped (meth) acrylic resin composition is injection molded at a cylinder temperature of 280 ° C, a mold temperature of 75 ° C, and a molding cycle of 1 minute. Thus, a flat plate T having a length of 205 mm, a width of 160 mm, and a thickness of 0.5 mm was manufactured. The ratio of the resin flow length (190 mm) to the thickness is 380. Appearance evaluation was performed. The results are shown in Table 1.

Example 2
A pellet-like (meth) acrylic resin composition of the present invention was obtained in the same manner as in Example 1 except that m-terphenyl was changed to biphenyl. Various physical properties of these pellet-like (meth) acrylic resin compositions were measured in the same manner as in Example 1. The results are shown in Table 1. Biphenyl has a boiling point of 256 ° C., a molecular weight of 154, and a molecular radius of 0.33 nm.

Example 3
A pellet-like (meth) acrylic resin composition of the present invention was obtained in the same manner as in Example 1 except that m-terphenyl was changed to 1,4-di (cyclohexyl) benzene. Various physical properties of these pellet-like (meth) acrylic resin compositions were measured in the same manner as in Example 1. The results are shown in Table 1. 1,4-di (cyclohexyl) benzene has a boiling point of 195 ° C./13 mmHg, a molecular weight of 242 and a molecular radius of 0.40 nm.

Comparative Example 1
A pellet-like (meth) acrylic resin composition was obtained in the same manner as in Example 1 except that m-terphenyl was not added. Various physical properties of these pellet-like (meth) acrylic resin compositions were measured in the same manner as in Example 1. The results are shown in Table 1. This (meth) acrylic resin composition had a high water absorption rate, and the injection molded product obtained thereby had a high dimensional change rate.

Comparative Example 2
A pellet-like (meth) acrylic resin composition was obtained by the same method as in Comparative Example 1 except that the (meth) acrylic resin was changed to the MS resin obtained in Production Example 2. Various physical properties of these pellet-like (meth) acrylic resin compositions were measured in the same manner as in Example 1. The results are shown in Table 1. This (meth) acrylic resin composition had low hardness.

Comparative Example 3
A pellet-like (meth) acrylic resin composition was obtained in the same manner as in Example 1 except that the (meth) acrylic resin was changed to the resin obtained in Production Example 3. Various physical properties of these pellet-like (meth) acrylic resin compositions were measured in the same manner as in Example 1. The results are shown in Table 1. In this (meth) acrylic resin composition, sink marks were generated during injection molding, and a flat plate T having a good appearance could not be obtained. Therefore, the dimensional change was not measured.

Comparative Example 4
A pellet-like (meth) acrylic resin composition was obtained in the same manner as in Example 1 except that the amount of m-terphenyl was changed to 0.5 parts by mass. Various physical properties of these pellet-like (meth) acrylic resin compositions were measured in the same manner as in Example 1. The results are shown in Table 1. This (meth) acrylic resin composition had a high water absorption, and the injection molded product obtained thereby had a high dimensional change rate.

Comparative Example 5
Except that m-terphenyl was changed to naphthalene, an attempt was made to produce a pellet-like (meth) acrylic resin composition by the same method as in Example 1, but foaming occurred and a good pellet could not be obtained. Therefore, various physical properties were not measured. Naphthalene has a boiling point of 218 ° C., a molecular weight of 128.18, and a molecular radius of 0.31 nm.

Comparative Example 6
Except that m-terphenyl was changed to hexaphenylbenzene, an attempt was made to produce a pellet-like (meth) acrylic resin composition by the same method as in Example 1. However, since white turbidity was seen in the pellet, various physical property measurements were performed. Not implemented. Hexaphenylbenzene has a boiling point of 450 ° C. or higher, a molecular weight of 535, and a molecular radius of 0.50 nm.

  As shown in Table 1, when the (meth) acrylic resin composition of the present invention is used, it is thin with high transparency, high hardness, high strength, low saturated water absorption, small dimensional change, and good appearance. In addition, a large-area molded product can be obtained with high production efficiency.

Claims (8)

100 mass parts of (meth) acrylic resin containing 80 to 100 mass% of structural units derived from methyl methacrylate and 0 to 20 mass% of structural units derived from acrylic acid ester, and 5 composed of only carbon atoms and hydrogen atoms 1 to 15 parts by mass of a compound having 2 to 4 membered or 6-membered ring structures in the molecule, having a boiling point at room temperature of 250 ° C. or higher and a molecular weight of less than 400,
A (meth) acrylic resin composition having a melt flow rate of 10 g / 10 min or more under conditions of 230 ° C. and a load of 3.8 kg.   The (meth) acrylic resin composition according to claim 1, wherein the compound has a molecular radius of 0.30 to 0.45 nm determined by an atomic group contribution method.   The (meth) acrylic resin composition according to claim 1 or 2, wherein the compound is a ring assembly compound.   The (meth) acrylic resin composition according to claim 1 or 2, wherein the compound is an aromatic ring assembly compound.   The (meth) acrylic resin composition according to claim 1 or 2, wherein the compound is a compound having at least one selected from the group consisting of a biphenyl group, a terphenyl group, and a quaterphenyl group.   The (meth) acrylic resin composition according to any one of claims 1 to 5, wherein the saturated water absorption is 1.7% or less.   The molded article which consists of a (meth) acrylic resin composition as described in any one of Claims 1-6.   The molded article according to claim 7, wherein the ratio of the resin flow length to the thickness is 380 or more.