JP2016108502A - Molded article having good hue and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded article that achieves further improvement in optical characteristics as compared with a molded article formed from the conventional thermoplastic resin and to provide a method for producing the molded article.SOLUTION: A light-irradiated molded article produced by irradiating a molded article formed from a styrene-based thermoplastic resin mainly with light including a component having a wavelength of 340 to 575 nm is brought into a molded article having good hue as compared with a molded article which is not irradiated with light. The production method can be utilized as a means for bringing a molded article formed from the conventional thermoplastic resin into a molded article having further improved good hue. The styrene-based resin is a copolymer of a styrene-based monomer and a (meth)acrylic acid ester monomer and is a styrene/(meth)acrylic acid ester copolymer containing 40.0 to 99.0 wt% of the styrene-based monomer and 60.0 to 1.0 wt% of the (meth)acrylic acid ester monomer.SELECTED DRAWING: None

Description

The present invention relates to a molded article having a good hue and a method for producing the same.

  Thermoplastic resins are used in many industrial fields such as sundries, packaging materials, automobiles, electrical equipment, and medical equipment today.

  Styrenic resins have excellent properties such as transparency, rigidity, low water absorption, and dimensional stability, and are excellent in molding processability. Therefore, various types of molding methods such as injection molding, extrusion molding, blow molding, etc. Widely used as industrial materials, food packaging containers, miscellaneous goods and the like. Moreover, it is used also for optical members, such as a light-guide plate and a diffuser plate, as an application using transparency.

  Transparency can be mentioned as a characteristic of styrene-based resins. For example, in optical applications where transparency is particularly important, there are cases where the requirements are not always satisfied, and thus the transparency is improved by various methods. Known methods for improving the transparency of styrene-based resins and preventing yellowing include a method of adding an antioxidant and a method of controlling specific components in the styrene-based resin.

JP2012-149156 JP 2014-173034 A

  An object of the present invention is to provide a molded product having further improved optical characteristics as compared with a molded product made of a conventional thermoplastic resin, and a manufacturing method for obtaining the molded product.

As a result of studies to achieve the above object, the present inventors have found that optical properties can be improved by irradiating a molded product made of a thermoplastic resin with light. The present invention is based on such knowledge and has the following gist.
1. A production method for obtaining a light-irradiated molded article by irradiating a molded article comprising a thermoplastic resin with light mainly containing a component having a wavelength of 340 nm to 575 nm, and a light-irradiated molded article obtained by the production method.
2. Preferably, the light described in the above item 1 is light mainly containing a component having a wavelength of 370 to 510 nm, and a light irradiation molded product obtained by the manufacturing method.
3. 3. A production method in which the light source of light described in 1 or 2 is an LED, and a light irradiation molded product obtained by the production method.
4). The light irradiation molded article whose thermoplastic resin of any one of said 1-3 is a styrene resin.
5. 5. A light irradiation molded article, which is a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing the styrene resin according to the above item 4 with a styrene monomer and a (meth) acrylic acid monomer.
6). 5. Light irradiation molding in which the styrene resin described in the above item 4 is a styrene- (meth) acrylate copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylate monomer. Goods.
7). The light irradiation molded article whose thermoplastic resin of any one of said 1-6 is a thermoplastic resin composition containing a thermoplastic resin and antioxidant.
8). The optical member using the light irradiation molded article of any one of said 1-7.
9. The light-guide plate using the light irradiation molded article of any one of said 1-8.

  The present inventors have found that the optical properties of a molded article made of a thermoplastic resin are improved by light irradiation, and that light in a specific wavelength range is effective for further improvement. The reason why such an effect is obtained is not necessarily clarified, but it is presumed that the colored component contained in the molded product is attributed to a colorless component due to light irradiation. Furthermore, it is assumed that this reaction is caused by light in a specific wavelength range.

  The production method of the present invention is equally applicable to thermoplastic resins and can be employed as a technique for improving optical characteristics. In addition, since the light irradiation molded product of the present invention has improved optical characteristics as compared with the conventional ones, it should be used suitably in applications where optical properties such as hue are important and optical applications where transparency is particularly important. Can do.

<< Light to irradiate molded products >>
The light irradiation molded product of the present invention refers to a product irradiated with light. In the present invention, the light irradiated to the molded product is mainly light containing a component having a wavelength of 340 nm to 575 nm. If it is 340 nm or less, physical properties such as optical properties and mechanical properties tend to deteriorate due to deterioration of the resin constituting the molded product and other various components, but this can be suppressed by setting it to 340 nm or more. The effect of improving the characteristics is increased. In addition, light of 575 nm or less is effective for improving optical characteristics. Preferably, it is 370 to 510 nm, and it has been experimentally confirmed that a higher effect can be obtained in this wavelength region.

<< light source >>
The light source used in the present invention is not particularly limited, but the wavelength of light contributing to the improvement of optical characteristics is 340 nm to 575 nm. Therefore, from the viewpoint of energy utilization efficiency, the wavelength region is compared with the light energy in the entire wavelength region. The higher the light energy ratio, the higher the efficiency of the light source. In the present application, “mainly” means that the light energy in the wavelength region defined in the present application is 50% or more of the light energy in the entire wavelength region. As such light, for example, an LED (including an inorganic LED using an inorganic EL and an O-LED using an organic EL) can selectively use light in a specific wavelength range, and therefore satisfies the requirements of the present application. It is particularly effective as a light source. In addition, various light sources can be used.
The light energy in the wavelength region defined in the present application can be reduced by, for example, increasing the ratio of 60%, 70%, 80%, 90%, and 100% to the light energy in the entire wavelength region. It becomes a more preferable light source by setting it as the numerical value shown by.

  In addition, various light sources can be made to be a light source that satisfies the requirements of the present application in a pseudo manner by taking measures to selectively irradiate the molded product with light having a specific wavelength. Examples of such a method include a method using a filter that cuts off a specific wavelength, a method of performing spectroscopic irradiation, and the like. Although there is no restriction | limiting in a light source, For example, besides LED, it is applicable with respect to various light sources, such as a fluorescent lamp, sunlight, a mercury lamp, an incandescent lamp, a xenon lamp, a carbon arc.

  Irradiance is a physical quantity representing both the radiant flux per unit area irradiated on a planar object from a radiation source. In this application, the radiation source is a light source. The irradiance can be arbitrarily selected, but the higher the irradiance, the faster the reaction speed, so that the hue can be changed in a short time. The irradiance can be changed by the light intensity of the light source (which varies depending on the current, voltage, and light conversion efficiency) and the distance between the light source and the molded product.

  The distance between the light source and the molded product can be arbitrarily selected. However, if the distance between the light source and the molded product is increased, the light emitted from the light source may not be efficiently used due to light diffusion. Even when the distance is short, depending on the output of the light source, the molded product may be deformed or deteriorated by the heat of the light source. The distance between the light source and the molded product is from 0 mm when the light source is in close contact with the molded product to a distance (depending on the radiant intensity or energy of the light source or the external environment) that eliminates the influence of the light emitted from the light source. You can choose.

  The direction of light irradiation to the molded product is not limited, and the molded product can be irradiated from any direction. However, when using a light source that can irradiate a sufficient area (or volume) to the molded product, the shorter the distance that the light emitted from the light source passes through the molded product, the shorter the entire molded product. From the viewpoint of energy consumption, it is preferable to select an irradiation direction suitable for the shape of the molded product. For example, if it is a plate-shaped molded product (115 × 127 × 3 mm) as described in the present application example, rather than irradiating from the direction in which the light from the light source passes through the 127 mm or 115 mm portion of the molded product, Since the hue can be changed in a shorter time by irradiating from a direction that passes through the 3 mm portion, it is efficient.

The light irradiation time can be any time. Hue of the molded article by the light irradiation, but change over time, after a certain time T _s is the behavior hue is not changed. FIG. 1 shows an example of a change in the hue value YI due to light irradiation. When the irradiation is stopped within T _s , the hue can be set to an arbitrary hue until the hue does not change, and irradiation after T _s has substantially no effect on the hue change from the time point T _s . To become a waste of energy, it is preferable to stop the irradiation within T _s. T _s is the ratio of the component having a wavelength of 340 nm to 575 nm or 370 to 510 nm with respect to the entire light energy, the irradiance, the distance between the molded product and the light source, the light irradiation direction to the molded product, the light irradiation conditions, and the type of resin. The type and amount of components such as additives vary depending on the material constituting the molded product.

  The light irradiation can be performed on a molded product that does not move substantially (batch type), and can also be performed on a moving molded product (continuous type). In the case of equipment that continuously produces molded products, for example, continuous extrusion equipment or equipment that uses a belt conveyor, etc. Can be obtained continuously.

<< Thermoplastic resin >>
As the material of the molded product used in the present invention, various thermoplastic resins can be used and are not limited. Examples of the thermoplastic resin include an olefin resin, a styrene resin, an acrylic resin, a cyclic polyolefin resin, and a polycarbonate resin.
The thermoplastic resin composition is preferably composed of a thermoplastic resin and various additives, and the ratio of the thermoplastic resin in 100% by mass of the thermoplastic resin composition is, for example, 90 to 99.9% by mass. And 95-99.9 mass% is preferable. Specifically, the ratio of the thermoplastic resin is, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, 99.9% by mass, and the numerical values exemplified here It may be within the range between any two.

<< Styrenic resin >>
The styrene resin is a resin that can be obtained by polymerizing a styrene monomer. The styrene monomer is an aromatic vinyl monomer, and examples thereof include styrene, α-methyl styrene, o-methyl styrene, p-methyl styrene, and the like. These may be used alone or as a mixture of two or more thereof. Yes, preferably styrene. Further, it may be copolymerized with a styrene monomer within the range not impairing the characteristics of the present invention, acrylic acid monomers such as acrylic acid and methacrylic acid, vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, and butyl acrylate. , Acrylic monomers such as ethyl acrylate, methyl acrylate, and methyl methacrylate; and α, β-ethylenically unsaturated carboxylic acids such as maleic anhydride and fumaric acid; and imide monomers such as phenyl maleimide and cyclohexyl maleimide. .
The styrene resin composition is preferably composed of a styrene resin and various additives, and the ratio of the styrene resin in 100% by mass of the styrene resin composition is, for example, 90 to 99.9% by mass. And 95-99.9 mass% is preferable. Specifically, the ratio of the styrene resin is, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, 99.9% by mass, and the numerical values exemplified here It may be within the range between any two.

When the styrene resin is a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylic acid monomer, the styrene resin of the styrene resin The body unit content is preferably 90.0 to 99.9% by mass, and the (meth) acrylic acid monomer unit content is preferably 0.1 to 15.0% by mass. However, the total content of styrene monomer units and (meth) acrylic acid units is 100% by mass. The (meth) acrylic acid monomer is acrylic acid, methacrylic acid or the like, and methacrylic acid is preferable. The styrene monomer unit is a structural unit derived from a styrene monomer in the molecular structure constituting the styrene- (meth) acrylic acid copolymer resin, and (meth) acrylic acid. A monomer unit is a structural unit derived from a (meth) acrylic acid monomer.

  The content of the (meth) acrylic acid monomer unit in the styrene- (meth) acrylic acid copolymer resin is measured at room temperature. 0.5 g of styrene- (meth) acrylic acid copolymer resin is weighed and dissolved in a mixed solution of toluene / ethanol = 8/2 (volume ratio), and then neutralized with a 0.1 mol / L ethanol solution of potassium hydroxide. The end point is detected, and the mass-based content of (meth) acrylic acid units is calculated from the amount of potassium hydroxide ethanol solution used. In addition, a potentiometric automatic titration apparatus can be used and it can measure by AT-510 by Kyoto Electronics Industry Co., Ltd. The content of the (meth) acrylic acid monomer unit in the styrene- (meth) acrylic acid copolymer resin is the same as that of the raw material styrene monomer at the time of polymerization of the styrene- (meth) acrylic acid copolymer resin ( It can be adjusted by the composition ratio with the (meth) acrylic acid monomer, but within a compatible range, a styrene- (meth) acrylic acid copolymer resin containing a (meth) acrylic acid monomer unit and ( It can also be adjusted by blending with a styrene resin not containing a (meth) acrylic acid monomer unit.

  When the styrene resin is a styrene- (meth) acrylate copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylate monomer, the styrene resin of the styrene resin The monomer unit content is preferably 40.0 to 99.0% by mass, and the (meth) acrylic acid ester monomer unit content is preferably 1.0 to 60.0% by mass. However, the total content of the styrene monomer unit and the (meth) acrylate monomer unit is 100% by mass. The (meth) acrylic acid ester monomer is a methacrylic acid ester such as methyl methacrylate or ethyl methacrylate, or an acrylic acid ester such as methyl acrylate or ethyl acrylate. The styrene monomer unit is a structural unit derived from a styrene monomer in the molecular structure constituting the styrene- (meth) acrylic acid ester copolymer resin, and is a (meth) acrylic. An acid ester monomer unit is a structural unit derived from a (meth) acrylic acid ester monomer.

The content of the (meth) acrylate monomer unit in the styrene- (meth) acrylate copolymer resin can be measured by pyrolysis gas chromatography under the following conditions.
Pyrolysis furnace: PYR-2A (manufactured by Shimadzu Corporation)
Pyrolysis furnace temperature setting: 525 ° C
Gas chromatograph: GC-14A (manufactured by Shimadzu Corporation)
Column: Glass 3mm diameter x 3m
Filler: FFAP Chromsorb WAW 10%
Injection, detector temperature: 250 ° C
Column temperature: 120 ° C
Carrier gas: Nitrogen

  Examples of the polymerization method of the styrene resin include known styrene polymerization methods such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. In terms of quality and productivity, bulk polymerization and solution polymerization are preferable, and continuous polymerization is preferable. Examples of the solvent include alkylbenzenes such as benzene, toluene, ethylbenzene and xylene, ketones such as acetone and methyl ethyl ketone, and aliphatic hydrocarbons such as hexane and cyclohexane.

  A polymerization initiator and a chain transfer agent can be used as needed during the polymerization of the styrene resin. As the polymerization initiator, a radical polymerization initiator is preferable. For example, 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (t-butylperoxy) butane, 2,2- Peroxyketals such as di (4,4-di-t-butylperoxycyclohexyl) propane, 1,1-di (t-amylperoxy) cyclohexane, cumene hydroperoxide, t-butyl hydroperoxide, etc. Alkyl peroxides such as hydroperoxides, t-butylperoxyacetate, t-amylperoxyisononanoate, t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, di-t -Dialkyl peroxides such as hexyl peroxide, t-butylperoxyacetate Peroxyesters such as t-butyl peroxybenzoate and t-butylperoxyisopropyl monocarbonate, peroxycarbonates such as t-butyl peroxyisopropyl carbonate and polyether tetrakis (t-butyl peroxycarbonate) N, N′-azobis (cyclohexane-1-carbonitrile), N, N′-azobis (2-methylbutyronitrile), N, N′-azobis (2,4-dimethylvaleronitrile), N, N '-Azobis [2- (hydroxymethyl) propionitrile] and the like can be mentioned, and these can be used alone or in combination. Examples of chain transfer agents include aliphatic mercaptans, aromatic mercaptans, pentaphenylethane, α-methylstyrene dimer, terpinolene, and the like.

  In the case of continuous polymerization, the polymerization reaction is first controlled by adjusting the polymerization temperature to achieve the target molecular weight, molecular weight distribution, and reaction conversion rate using a well-known complete mixing tank type stirring tank or tower reactor in the polymerization process. Is done. The polymerization solution containing the polymer exiting the polymerization step is transferred to the devolatilization step, and unreacted monomers and polymerization solvent are removed. The devolatilization process includes a vacuum devolatilization tank with a heater, a vented devolatilization extruder, and the like. The polymer in the molten state that has exited the devolatilization step is transferred to the granulation step. In the granulation step, the molten resin is extruded in a strand form from a porous die and processed into a pellet shape by a cold cut method, an air hot cut method, or an underwater hot cut method.

The weight average molecular weight of the styrene-based resin of the present invention is not particularly limited, but when it is 150,000 to 700,000, the properties and moldability as a molded product are improved. If it is less than 150,000, the strength of the molded product becomes insufficient, and if it exceeds 700,000, the moldability is remarkably lowered. Moreover, it is preferable that it is 180,000-500,000. The weight average molecular weight of the styrenic resin should be controlled by the reaction temperature of the polymerization process, the residence time, the type and amount of polymerization initiator, the type and amount of chain transfer agent, the type and amount of solvent used during polymerization, etc. Can do.
The weight average molecular weight (Mw), the Z average molecular weight (Mz), and the number average molecular weight (Mn) were measured using gel permeation chromatography (GPC) under the following conditions.
GPC model: Shodex GPC-101 manufactured by Showa Denko KK
Column: Polymer Laboratories PLgel 10 μm MIXED-B
Mobile phase: Tetrahydrofuran Sample concentration: 0.2% by mass
Temperature: 40 ° C oven, 35 ° C inlet, 35 ° C detector
Detector: Differential refractometer The molecular weight of the present invention is calculated as the molecular weight in terms of polystyrene by calculating the molecular weight at each elution time from the elution curve of monodisperse polystyrene.

<< Molded product >>
Although there is no restriction | limiting in particular in the shaping | molding method of the molded article described in this application, For example, a molded article can be obtained with various shaping | molding methods according to the objectives, such as injection molding, extrusion molding, blow molding, and compression molding. The shape of the molded product can be a shape according to the purpose, and is not limited. For example, if it is a plate-shaped molded article, it can be used as a light guide plate. As a method for forming a light guide plate, it is known to provide a reflection pattern such as a dot pattern on the back surface of the plate-shaped molded product (the side opposite to the light emitting surface). When processing from the resin plate to the light guide plate, it is preferable to polish the light incident surface or the entire end surface of the resin plate to make a mirror surface. In addition, in order to improve the uniformity of the emitted light, a prism pattern can be provided on the surface (surface from which light is emitted) of the plate-shaped molded product. The pattern on the front surface or the back surface of the plate-shaped molded product can be formed at the time of molding the plate-shaped molded product. For example, the pattern can be formed by a mold shape in injection molding or roll transfer in extrusion molding.

<< Additives / Antioxidants >>
The molded article shown in the present application may contain various additives such as a lubricant and an antioxidant. For example, internal lubricants such as mineral oil, stearic acid, ethylenebisstearic acid amide, hindered phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, lactone antioxidants, hindered amine stabilizers, Examples thereof include additives such as ultraviolet absorbers and antistatic agents. As the external lubricant, ethylene bis stearamide is preferable, and the content is preferably 30 to 200 ppm in the resin composition.

  In particular, in a molded article containing an antioxidant, the production method of the present application was confirmed because the result of the assumption that the coloring component derived from the antioxidant in the molded article was changed to a colorless component by light irradiation was experimentally confirmed. Or as a molded product to be used.

  Phosphorous antioxidants are phosphites that are trivalent phosphorus compounds, and various substances can be used. Phosphorus antioxidants include, for example, tris (2,4-di-tert-butylphenyl) phosphite, 2,2′-methylenebis (4,6-di-tert-butyl-1-phenyloxy) (2- Ethylhexyloxy) phosphorus, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, 4,4′-biphenylenediphosphinic acid tetrakis (2,4-di-tert-butylphenyl), 3,9-bis (2 , 6-Di-tert-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane, cyclic neopentanetetraylbis (2,4-di -T-butylphenyl phosphite), distearyl pentaerythritol diphosphite, bis (nonylphenyl) Intererythritol diphosphite, bis- [2-methyl-4,6-bis- (1,1-dimethylethyl) phenyl] ethyl phosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 -Oxide, tetrakis (2,4-di-tert-butyl-5-methylphenyl) -4,4'-biphenylenediphosphonite and the like. As the phosphorus-based antioxidant, those excellent in hydrolysis resistance are preferred, such as tris (2,4-di-tert-butylphenyl) phosphite, 2,2′-methylenebis (4,6-di-tert-). Butyl-1-phenyloxy) (2-ethylhexyloxy) phosphorus, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, 3,9-bis (2,6-di-tert-butyl-4-methyl) Phenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane is preferred. Particularly preferred is tris (2,4-di-tert-butylphenyl) phosphite. Phosphorous antioxidants may be used alone or in combination of two or more.

  The hindered phenol-based antioxidant is an antioxidant having a phenolic hydroxyl group in the basic skeleton, and various products can be used. Examples of the hindered phenol antioxidant include octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,9-bis [2- [3- (3-tert-butyl). -4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate], 4,6-bis (octylthiomethyl) -o-cresol, 4,6-bis [(dodecylthio) methyl] -o-cresol, 2, , 4-Dimethyl-6- (1-methylpentadecyl) phenol, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphene) L) propionate] methane, DL-α-tocopherol, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2 -Hydroxy-3,5-di-t-pentylphenyl) ethyl] -4,6-di-t-pentylphenyl acrylate, 4,4'-thiobis (6-t-butyl-3-methylphenol), 1, 1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), bis- [3,3-bis- (4′-hydroxy-3′-tert-butylphenyl) -butanoic acid] -glycol ester and the like. Preferably, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,9-bis] 2- [3- (3-tert-butyl-4-hydroxy-5-methyl) Phenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4 -Hydroxy-m-tolyl) propionate]. Hindered phenolic antioxidants may be used alone or in combination of two or more.

  The method for adding various additives is not particularly limited. For example, a method of adding and mixing in the polymerization step, devolatilization step, and granulating step of a styrene resin, or a method of adding and mixing in an extruder or an injection molding machine at the time of molding. And a method of diluting and mixing a resin composition prepared by adjusting these additives to a high concentration to a target content with a styrene-based resin having no addition or a low concentration.

  The ultraviolet absorber has a function of suppressing deterioration and coloring caused by ultraviolet rays. UV absorbers such as those of formaldehyde and formamidine. These can be used alone or in combination of two or more thereof, and a light stabilizer such as hindered amine may be used in combination.

  Since the light irradiation molded product of the present invention is superior in transparency compared to conventional molded products, it can be suitably used for optical applications where hue and transparency are particularly important in addition to miscellaneous goods. . Examples of the optical member include a light guide plate, a light diffusion plate, a lens, and a cover. In addition, a light guide plate, a diffuser plate, and the like refer to not only plate-shaped molded products but also light guides and diffusers in a broad sense having various shapes such as a rod shape and a cylindrical shape.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.

<< Test 1 >>
(Production of styrene resins A-1 to A-3)
The polymerization reactor is configured by connecting a first reactor, which is a complete mixing tank, a second reactor, and a third reactor, which is a plug flow reactor with a static mixer. The styrene resin was manufactured by the above. The capacity of each reactor was 39 liters for the first reactor, 39 liters for the second reactor, and 16 liters for the third reactor. A raw material solution was prepared with the raw material composition described in Table 1, and the raw material solution was continuously supplied to the first reactor at a flow rate described in Table 1. The polymerization initiator is added to the raw material solution at the inlet of the first reactor so as to have the addition concentration shown in Table 1 (concentration based on mass relative to the total amount of raw material styrene, methacrylic acid, and methyl methacrylate). did. The polymerization initiators listed in Table 1 are as follows.
Polymerization initiator-1: 2,2-di (4,4-t-butylperoxycyclohexyl) propane (Pertetra A manufactured by NOF Corporation was used.)
Polymerization initiator-2: 1,1-di (t-butylperoxy) cyclohexane (Perhexa C manufactured by NOF Corporation was used.)
In the third reactor, a temperature gradient was provided along the flow direction, and the temperature was adjusted so that the temperature shown in Table 1 was obtained at the intermediate part and the outlet part.
Subsequently, the solution containing the polymer continuously taken out from the third reactor was introduced into a vacuum devolatilization tank with a preheater constituted by two stages in series, and the preheater was adjusted to the resin temperature shown in Table 1. By adjusting the temperature and adjusting to the pressure shown in Table 1, unreacted styrene and ethylbenzene are separated and then extruded into a strand form from a perforated die, and the strand is cooled and cut by a cold cut method. Pelletized.
The PMAA content shown in Table 1 represents the content of methacrylic acid monomer units, and the PMMA content represents the content of methyl methacrylate monomer units.

<MFR>
The MFR (melt mass flow rate) of the styrene resin composition was measured based on JIS K 7210 under the conditions of 200 ° C. and 49 N load.

<Vicat softening temperature>
The Vicat softening temperature was determined according to JIS K-7206 at a heating rate of 50 ° C / hr and a test load of 50N.

Using the obtained pellets, injection molding was performed at a cylinder temperature of 230 ° C. and a mold temperature of 50 ° C. to form a plate-shaped molded article having a thickness of 127 × 127 × 3 mm.

Commercially available PMMA and PC resins shown below were used as the resins A-4 and A-5. Resin A-4 is injection molded at a cylinder temperature of 230 ° C. and a mold temperature of 50 ° C., and resin A-5 is injection molded at a cylinder temperature of 250 ° C. and a mold temperature of 50 ° C., 127 × 127 ×. A plate-shaped molded product having a thickness of 3 mm was molded.
Resin name A-4: PMMA resin manufactured by Mitsubishi Rayon Co., Ltd., VH5-000
Resin name A-5: Mitsubishi engineering plastic PC resin, HL-4000

<Hue evaluation>
The obtained plate-like molded product was cut and polished to 115 × 127 × 3 mm using a gate processing machine GCPB-500 manufactured by Megaro Technica Co., Ltd. to obtain a plate-shaped molded product having a mirror surface on the end face. About the obtained plate-shaped molded article, using an ultraviolet-visible spectrophotometer V-670 manufactured by JASCO Corporation, the incident light having a size of 20 × 1.6 mm and a spread angle of 0 ° has a wavelength at an optical path length of 115 mm. Spectral transmittances from 350 nm to 800 nm were measured, and the YI value at a visual field of 2 ° with a C light source was calculated according to JIS K7105. The obtained value is YI in Table 2. Moreover, the transmittance | permeability shown in Table 2 represents the average transmittance | permeability with a wavelength of 380 nm-780 nm.
ΔYI represents the difference between the YI of the molded product before irradiation with light and the YI of the molded product after irradiation with light (Formula 1).
ΔYI = (YI of molded product after light irradiation) − (YI of molded product before light irradiation) (Formula 1)
Taking Example 1-1 as an example, YI = 3.1, and YI before irradiation is YI = 3.5 in Comparative Example 1-1, so ΔYI = −0.4. The hue improvement effect is greater when ΔYI is negatively larger.

<Light source used for testing>
In the test, the following light sources were used. Each light source has a specific spectral radiation distribution, and the maximum wavelength is a wavelength at which the graph of the spectral radiation distribution has a maximum value, and the wavelength range is a wavelength having a radiation energy> 0. The region from the shortest wavelength to the longest wavelength is shown.
Green LED: manufactured by Nichido Kogyo Co., Ltd., LED lighting, LEN-30D-DB-G, maximum wavelength 520 nm, wavelength range 465 nm to 605 nm
Blue LED: manufactured by Nichido Kogyo Co., Ltd., LED lighting, LEN-30D-DB-B, maximum wavelength 450 nm, wavelength range 415 nm to 505 nm
White LED: manufactured by Nichido Kogyo Co., Ltd., LED lighting, LEN-30D-ES-W, maximum wavelength 450 nm, 565 nm, wavelength range 415 nm to 760 nm
Purple LED: manufactured by Eye Graphics Co., Ltd., LED illumination, maximum wavelength 405 nm, wavelength range 385 nm to 430 nm
Ultraviolet LED (1): manufactured by Eye Graphics Co., Ltd., LED illumination, maximum wavelength 395 nm, wavelength range 375 nm to 420 nm
Ultraviolet LED (2): manufactured by Eye Graphics Co., Ltd., LED illumination, maximum wavelength 385 nm wavelength range 365 nm to 410 nm
UV LED (3): manufactured by Eye Graphics Co., Ltd., LED illumination, maximum wavelength 365 nm wavelength range 345 nm to 390 nm
Red LED: manufactured by Nichido Kogyo Co., Ltd., LED lighting, LEN-30D-DB-R, maximum wavelength 630 nm, wavelength range 575 nm to 670 nm
Here, the white LED used in this test is a pseudo white LED using a blue LED and a yellow phosphor, and has two maximum wavelengths derived from each.
Further, the spectral radiation distribution takes values every 5 nm, such as 340 nm, 345 nm,..., All light energy is E _A , light energy of 340 nm to 575 nm is E ₁ , 370 to 510 nm. light energy as _{E 2,} it was determined _E 1 / _{E a} and _E 2 / _{E a} is the respective ratios. Mathematically, E _A , E ₁ and E ₂ are integrated values of energy in the respective ranges for each light source. As an example, an example of E _A and E ₁ is shown in FIG.
For fluorescent lamps, sunlight, and high-pressure mercury lamps, molded products were installed indoors or outdoors.

<Measurement of irradiance>
Irradiance is measured with Hioki Denki Co., Ltd.'s illuminance meter Lux HiTESTER 3423, or Eye Graphics Co., Ltd. UV METER UVPF-A1 PD-405 (purple LED, ultraviolet LED (1) to ultraviolet LED (3) only). The irradiance was calculated from the visible relative spectral response characteristics of the illuminometer or the spectral sensitivity characteristics of UV METER and the spectral radiation distribution of the light source.

<Example 1>
The resin A-1 molded product was irradiated with a light source having optical characteristics shown in Table 2 for 120 minutes to obtain a light irradiated molded product. Since the irradiation was performed on a 115 × 127 mm surface, the distance that light passes through the molded product is 3 mm. The irradiance at this time was 100 W / m ² . Moreover, the transmittance | permeability and YI of the light irradiation molded product were implemented.

<Examples 1-2 to 1-19>
In the same manner as in Example 1-1, the molded product made of the resins A-1 to A-5 was irradiated with light with the optical characteristics shown in Table 2, the irradiation time, and the irradiance to obtain a light irradiated molded product. Moreover, the transmittance | permeability and YI of the light irradiation molded product were implemented.

<Comparative Examples 1-1 to 1-5>
Comparative Example 1-2 measured the transmittance and YI without irradiating the light source having the optical characteristics shown in Table 2 and the other comparative examples without irradiating the molded product made of Resin A-1 to A-5.

<Reference Examples 1-1 to 1-3>
The molded article made of the resin A-1 was irradiated with sunlight, fluorescent light, high-pressure mercury lamp, and incandescent light for a predetermined time. Further, the transmittance and YI of the molded product after irradiation were measured.

As in Reference Examples 1-1 and 1-2, the energy of each wavelength is not uniform, YI changes negatively in so-called white light, and the behavior in which the hue is improved was observed, but the wavelength of 340 nm to 575 nm It was found that ΔYI is negatively large in light having a high ratio of light energy, and the effect of improving the hue is large. Referring to Comparative Example 1-2, the effect of improving the hue was not observed with light of 575 nm or more. In particular, those having a high ratio of light energy having a wavelength of 370 to 510 nm were more effective. In Reference Example 1-3, ΔYI has a positive value. This is considered to be because the ultraviolet rays contained in the light from the mercury lamp had an adverse effect and the molded product was deteriorated.
Referring to Example 1-7 and Examples 1-13 to 1-15, a high effect is obtained even with light whose ratio of light energy of 340 nm to 575 nm is not relatively high. It is a pseudo-white LED using a blue LED and a yellow phosphor, and is considered to be due to the large influence of light having a wavelength of 415 nm to 505 nm, which is light derived from the blue LED.

<< Test 2 >>
Resin A-1 was obtained in the same manner as in Test 1. Next, using a single screw extruder having a screw diameter of 40 mm as an additive, pellets of the styrenic resin obtained above and an additive as an additive so that the contents shown in Table 3 were used, a cylinder temperature of 230 ° C., and a screw rotation speed Pellets were obtained by melting and kneading at 100 rpm. The additives used are shown below. In addition, the resin used in Example 2-1 and Comparative Example 2-1 was melt-kneaded without adding an additive.
Additive 1: Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (Irganox 1076, manufactured by BASF Japan Ltd.)
Additive 2: Tris (2,4-di-tert-butylphenyl) phosphite (Irgafos 168 manufactured by BASF Japan Ltd.)
The obtained pellets were injection-molded, cut and polished under the same conditions as in Test 1 to obtain a plate-like molded product having a mirror surface on the end surface. Hue evaluation, irradiance measurement, and the like were performed in the same manner as in Test 1.

<Examples 2-1 to 2-4>
The molded product of each resin composition consisting of the resin A-1, the additive 1 and the additive 2 described in Table 3 is irradiated with light from a light source having the optical characteristics described in Table X, and the light irradiated molded product is obtained. Obtained. Since the irradiation was performed on a 115 × 127 mm surface, the distance that light passes through the molded product is 3 mm. The irradiation time was 60 minutes, and the irradiance was 630 W / m ² . Further, the transmittance and YI of the molded product after irradiation were measured.

<Comparative Examples 2-1 to 2-4>
The transmittance and YI were measured without irradiating the molded product of each resin composition comprising the resin A-1, the additive 1 and the additive 2 shown in Table 3 with light.

  As shown in Table 3, even when the antioxidant was included, the decrease in YI was confirmed by light irradiation as in Test 1. In Example 2-1, compared to the case where melt kneading is not performed (Example 1-1), ΔYI is negatively increased. This is because a colored component due to thermal oxidative degradation is generated in the resin composition by melt kneading. However, this is thought to be due to the change to a colorless component by light irradiation. In addition, ΔYI is negatively larger than when no antioxidant is included, but this is because there is a colored component derived from the antioxidant in the molded product, and this has changed to a colorless component by light irradiation. It is thought that.

The light irradiation molded article of the present invention has an improved colorless transparency compared to conventional molded articles, and is excellent in transparency and hue. It can be suitably used also for applications. For example, the optical member can be applied to applications such as a lens, a diffusion plate, a cover, and a light guide plate.
Further, the production method of the present invention can be used as a means for making a molded product made of a conventional thermoplastic resin into a molded product having a better hue.

Claims (12)

A light irradiation molded product obtained by irradiating a molded product made of a thermoplastic resin with light mainly containing a component having a wavelength of 340 nm to 575 nm. The light irradiation molded article according to claim 1, wherein the light to be irradiated is light mainly containing a component having a wavelength of 370 to 510 nm. The light irradiation molded article of Claim 1 or Claim 2 whose light source of the light to irradiate is LED. The light irradiation molded product of any one of Claims 1-3 whose thermoplastic resin is a styrene resin. A styrene resin is a styrene- (meth) acrylic acid copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylic acid monomer, wherein the styrene resin is a styrene resin. The light irradiation molding according to claim 4, wherein the content of the body unit is 90.0 to 99.9% by mass, and the content of the (meth) acrylic acid monomer unit is 0.1 to 15.0% by mass. Goods. However, the total content of styrene monomer units and (meth) acrylic acid monomer units in the styrene resin is 100% by mass. A styrene resin is a styrene- (meth) acrylate copolymer resin obtained by copolymerizing a styrene monomer and a (meth) acrylate monomer, and the styrene resin is a styrene resin The content of the monomer unit is 40.0 to 99.0 mass%, and the content of the (meth) acrylic acid ester monomer unit is 1.0 to 60.0 mass%. Light irradiation molded product. However, the total content of styrene monomer units and (meth) acrylate monomer units in the styrene resin is 100% by mass. The light irradiation molded article of any one of Claims 1-6 whose said thermoplastic resin is a thermoplastic resin composition containing a thermoplastic resin and antioxidant. The optical member using the light irradiation molded article of any one of Claims 1-7. The light-guide plate using the light irradiation molded article of any one of Claims 1-8. A production method for obtaining a light-irradiated molded article by irradiating a molded article comprising a thermoplastic resin with light mainly containing a component having a wavelength of 340 nm to 575 nm. The manufacturing method of Claim 10 whose light to irradiate is a light mainly containing the component of wavelength 370-510 nm. The manufacturing method of Claim 10 or Claim 11 whose light source of the light to irradiate is LED.