JPWO2015064575A1 - Plate-shaped molded product - Google Patents

Abstract

A yellow index (YI) containing a methacrylic resin having 50 to 90% by mass of structural units derived from methyl methacrylate and 10 to 50% by mass of structural units derived from methacrylic acid alicyclic hydrocarbon ester and having an optical path length of 200 mm ) Is 10 or less, and a methacrylic resin composition having a methacrylic acid alicyclic hydrocarbon ester content of 1.0% by mass or less is molded to obtain a plate-shaped molded body. A light guide plate made of the plate-like molded body is obtained.

Description

  The present invention relates to a plate-like molded body. More specifically, the present invention is a thin-walled and large-area plate-shaped molded article having little coloring, high transparency, low haze, high impact resistance, low saturated water absorption, small dimensional change, and good appearance. About.

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

  There is a high demand for light-weight and large-area liquid crystal display devices, and correspondingly, optical members are also required to be thin and wide. However, when the optical member is thinned and has a large area, a dimensional change is likely to occur due to slight moisture or heat. The optical characteristics change with such dimensional changes. With higher image quality of display devices, high accuracy is required for optical characteristics such as refractive index and retardation. Therefore, a methacrylic resin composition that is a raw material for optical members is strongly required to have high transparency, low moisture absorption, high heat resistance, small dimensional change, high impact resistance, good moldability, and the like.

  As a resin material for optical members, for example, an optical resin material obtained by polymerizing a polymerizable composition containing 5% by weight or more of tricyclodecanyl (meth) acrylate is known (see Patent Document 1). . A molded product obtained by molding this optical resin material at a high molding temperature is likely to be colored. When this optical resin material is injection-molded at a low temperature of 230 to 260 ° C., the molded body is difficult to be colored. However, in low-temperature injection molding, the productivity of the molded body is low, and stress is likely to remain in the obtained molded body, so that a dimensional change is likely to occur due to heat.

JP-A-61-73705

Nippon Oil & Fats Co., Ltd. Technical document “Organic peroxide hydrogen abstraction and initiator efficiency” (created in April 2003)

  An object of the present invention is to provide a thin-walled and large-area plate-shaped molded article having little coloring, high transparency, low haze, low saturated water absorption, small dimensional change, and good appearance.

  As a result of intensive studies to achieve the above object, the present invention including the following aspects has been completed.

[1] A methacrylic resin containing 50 to 90% by mass of a structural unit derived from methyl methacrylate and 10 to 50% by mass of a structural unit derived from a methacrylic acid alicyclic hydrocarbon ester, and a methacrylic acid alicyclic ring A plate-like molded article having an optical path length of 200 mm and a yellow index (YI) of 10 or less, comprising a methacrylic resin composition having a content of a formula hydrocarbon ester of 1.0 mass% or less.

[2] The methacrylic resin composition comprises a dimer or trimer composed of methyl methacrylate, a dimer or trimer composed of acrylate ester, a dimer composed of methacrylic acid alicyclic hydrocarbon ester, or Trimer, dimer consisting of methyl methacrylate and acrylate ester, dimer consisting of methyl methacrylate and methacrylic acid alicyclic hydrocarbon ester, acrylic acid ester and methacrylic acid alicyclic hydrocarbon ester A dimer composed of two methyl methacrylates and one acrylate ester, a trimer composed of one methyl methacrylate and two acrylate esters, two methyl methacrylates and one Trimer consisting of methacrylic alicyclic hydrocarbon ester, one methyl methacrylate and two methacrylic alicyclic charcoal A trimer consisting of a hydrogen ester, a trimer consisting of two acrylic esters and one methacrylic alicyclic hydrocarbon ester, one acrylic ester and two methacrylic alicyclic hydrocarbon esters The total content of the trimer consisting of methyl methacrylate, acrylic acid ester and methacrylic acid alicyclic hydrocarbon ester is 0.3% by mass or less, and the plate shape according to [1] Molded body.
[3] The plate-like molded product according to [1] or [2], wherein the methacrylic acid alicyclic hydrocarbon ester is dicyclopentanyl methacrylate or isobornyl methacrylate.
[4] The plate-like molded body according to any one of [1] to [3], wherein the ratio of the resin flow length to the thickness is 380 or more.
[5] The plate-like molded product according to any one of [1] to [4], wherein the transmittance at a wavelength of 435 nm with an optical path length of 3 mm is 90% or more.
[6] A light guide plate comprising the plate-like molded body according to any one of [1] to [5].

[7] (I) Continuously supplying a polymerizable monomer, a polymerization initiator, and a chain transfer agent to the reactor,
(II) In the reactor, a part of the polymerizable monomer is radically bulk-polymerized, and the structure derived from 50 to 90% by mass of the structural unit derived from methyl methacrylate and the structure derived from methacrylic acid alicyclic hydrocarbon ester. A resin mixture containing a methacrylic resin having 10 to 50% by mass of a unit, an unreacted polymerizable monomer, and a dimer or trimer composed of the polymerizable monomer is obtained,
(III) The resin mixture is continuously transferred from the reactor to a twin screw extruder equipped with a vent,
(IV) In the twin-screw extruder, a methacrylic resin composition is obtained by removing a dimer or trimer composed of an unreacted polymerizable monomer and a polymerizable monomer from the resin mixture, Extruding the methacrylic resin composition into a strand,
(V) A pellet-shaped methacrylic resin composition is obtained by cutting the methacrylic resin composition extruded into a strand shape with a pelletizer,
(VI) The molten methacrylic resin composition in the form of pellets is heated and melted and molded.
[1] to [5] The method for producing a plate-like molded product according to any one of [5].

  The plate-like molded product of the present invention has little coloring, high transparency, low haze, low saturated water absorption, and small dimensional change. The plate-shaped molded body of the present invention is suitable for an optical member such as a thin-walled and wide-area light guide plate.

  The reason why the plate-like molded body of the present invention has the above-described effects is considered as follows. Most of methacrylic acid alicyclic hydrocarbon esters represented by tricyclodecanyl methacrylate have a high boiling point. In the devolatilization extrusion process employed in continuous bulk polymerization, which is a general method for producing methacrylic resins, the methacrylic acid alicyclic hydrocarbon ester cannot be sufficiently removed and tends to remain in the methacrylic resin. If a large amount of the compound remains in the methacrylic resin, it is considered that the plate-like molded product is colored or the dimensional change is increased. Further, it is considered that gas is generated at the time of injection molding, and the surfaces of the molding die and the plate-like molded body are soiled. Since the plate-shaped molded article of the present invention is composed of a methacrylic resin composition having a low content of methacrylic acid alicyclic hydrocarbon ester, it is presumed that the above-mentioned problems will not occur.

It is a figure showing the resin flow length in an injection mold. It is a figure which shows an example of the apparatus used for the manufacturing method which concerns on this invention.

The plate-shaped molded product of the present invention is made of a methacrylic resin composition.
The methacrylic resin composition comprises a structural unit derived from methyl methacrylate (hereinafter sometimes referred to as monomer (I)) and a methacrylic acid alicyclic hydrocarbon ester (hereinafter referred to as monomer (II)). And a methacrylic resin having a structural unit derived from.

Examples of the monomer (II) include methacrylic acid monocyclic aliphatic hydrocarbon esters such as cyclohexyl methacrylate, cyclopentyl methacrylate, and cycloheptyl methacrylate; 2-norbornyl methacrylate, 2-methyl-2-methacrylate Norbornyl, 2-ethyl-2-norbornyl methacrylate, 2-isobornyl methacrylate, 2-methyl-2-isobornyl methacrylate, 2-ethyl-2-isobornyl methacrylate, 8-tricyclomethacrylate [5.2.1. 0 ^2,6 ] decanyl, 8-methyl-8-tricyclo [5.2.1.0 ^2,6 ] decanyl, 8-ethyl-8-tricyclomethacrylate [5.2.1.0 ^2,6 ] Decanyl, 2-adamantyl methacrylate, 2-methyl-2-adamantyl methacrylate, methacrylic acid -Methacrylic acid polycyclic aliphatic hydrocarbon esters such as ethyl-2-adamantyl, 1-adamantyl methacrylate, 2-fenkyl methacrylate, 2-methyl-2-fenkyl methacrylate, 2-ethyl-2-fenkyl methacrylate; Etc. Of these, polycyclic aliphatic hydrocarbon esters of methacrylic acid are preferred, and tricyclo [5.2.1.0 ^2,6 ] decanyl methacrylate (also known as dicyclopentanyl methacrylate) or 2-isobornyl methacrylate (methacrylic acid). Isobornyl acid) is more preferred.

  The methacrylic resin used in the present invention contains structural units derived from monomers other than monomer (I) and monomer (II) (hereinafter sometimes referred to as monomer (III)). You may include in the range which does not impair the effect of invention. As the monomer (III), methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, s-butyl acrylate, t-butyl acrylate, acrylic Amyl acid, Isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, cyclohexyl acrylate, norbornenyl acrylate, isobornyl acrylate, benzyl acrylate, acrylic acid Acrylic esters such as phenoxyethyl, 2-hydroxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, allyl acrylate, phenyl acrylate;

  Ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate , Methacrylates other than methyl methacrylate such as 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate, phenyl methacrylate, etc .; unsaturateds such as acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic acid Carboxylic acid; Olefin such as ethylene, propylene, 1-butene, isobutylene and 1-octene; Conjugated dienes such as butadiene, isoprene and myrcene; Styrene, α-methylstyrene, p-methylstyrene, m-methyl Aromatic vinyl compounds such as styrene; acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl pyridine, vinyl ketones, vinyl chloride, vinylidene chloride, vinylidene fluoride is. Among these, from the viewpoint of improving transparency, an acrylic ester is preferable, and an alkyl alkyl ester having 1 to 6 carbon atoms is more preferable.

In the methacrylic resin used in the present invention, the content of the structural unit derived from the monomer (I) is usually 50 to 90% by mass, preferably 60 to 88% by mass, more preferably 70 to 86% by mass, More preferably, it is 74-86 mass%.
In the methacrylic resin used in the present invention, the content of the structural unit derived from the monomer (II) is usually 10 to 50% by mass, preferably 11 to 35% by mass, more preferably 12 to 20% by mass. is there.
In the methacrylic resin used in the present invention, the content of the structural unit derived from the monomer (III) is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 2 to 6% by mass. .

  The methacrylic resin used in the present invention has a weight average molecular weight of preferably 35,000 to 100,000, more preferably 40,000 to 90,000, still more preferably 45,000 to 80,000, most preferably. 60,000 to 80,000. If the weight average molecular weight is less than 35,000, the impact resistance and toughness of the plate-shaped molded article made of the methacrylic resin composition tend to be insufficient. If the weight average molecular weight is more than 100,000, the moldability of the methacrylic resin composition is poor. It tends to be insufficient.

  The methacrylic resin used in the present invention has a structural unit of 74 to 86% by mass derived from the monomer (I) in consideration of the balance of physical properties such as fluidity, impact resistance and glass transition temperature. What consists of 12-20 mass% of structural units derived from (II) and 2-6 mass% of structural units derived from monomer (III), and has a weight average molecular weight of 60,000-80,000 preferable.

The ratio of the weight average molecular weight to the number average molecular weight of the methacrylic resin used in the present invention (weight average molecular weight / number average molecular weight: hereinafter, this ratio may be referred to as molecular weight distribution) is preferably 1.7. It is -2.6, More preferably, it is 1.7-2.3, More preferably, it is 1.7-2.0. If the molecular weight distribution of the methacrylic resin is small, the moldability of the methacrylic resin composition tends to decrease. When the molecular weight distribution is large, the impact resistance of the plate-like molded body obtained from the 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). Further, the weight average molecular weight, number average molecular weight and molecular weight distribution of the methacrylic resin can be controlled by adjusting the types and amounts of the polymerization initiator and the chain transfer agent.

  The methacrylic resin used in the present invention has a glass transition temperature of preferably 100 to 140 ° C, more preferably 105 to 135 ° C, and still more preferably 110 to 130 ° C. When the glass transition temperature is low, the heat resistance and the like tend to decrease. When the glass transition temperature is high, moldability and the like tend to decrease.

  The amount of the methacrylic resin contained in the methacrylic resin composition used in the present invention is preferably 97% by mass or more, more preferably 98% by mass or more, and further preferably 99% by mass or more with respect to the entire methacrylic resin composition. is there.

  The methacrylic resin composition used in the present invention has a methacrylic acid alicyclic hydrocarbon ester content of 1.0% by mass or less, preferably 0.8% by mass or less, more preferably 0.6% by mass or less, More preferably, it is 0.4 mass% or less. When the content of the methacrylic alicyclic hydrocarbon ester is within the above range, the plate-shaped molded product according to the present invention has a small yellow index, hardly causes appearance defects such as silver and surface contamination, and is continuously formed. The mold is difficult to get dirty with gas, and it is difficult to generate a specific odor. The content of methacrylic acid alicyclic hydrocarbon ester can be quantified by gas chromatography.

  The methacrylic resin composition used in the present invention includes a dimer or trimer composed of methyl methacrylate, a dimer or trimer composed of acrylate ester, and a dimer composed of methacrylic acid alicyclic hydrocarbon ester. Or a trimer, a dimer composed of methyl methacrylate and an acrylate ester, a dimer composed of methyl methacrylate and an alicyclic hydrocarbon ester of methacrylate, an acrylate ester and an alicyclic hydrocarbon ester of methacrylate A dimer consisting of two methyl methacrylates and one acrylate ester, a trimer consisting of one methyl methacrylate and two acrylate esters, two methyl methacrylates and one Trimer consisting of two methacrylic alicyclic hydrocarbon esters, one methyl methacrylate and two methacrylic acids Trimers consisting of cyclic hydrocarbon esters, trimers consisting of two acrylic esters and one methacrylic alicyclic hydrocarbon ester, one acrylic ester and two methacrylic alicyclic hydrocarbons The total content of trimers composed of esters and trimers composed of methyl methacrylate, acrylic acid esters and methacrylic alicyclic hydrocarbon esters is preferably 0.3% by mass or less, more preferably 0 .25% by mass or less, more preferably 0.2% by mass or less. The smaller the total content of such a dimer or trimer, the more prominent the feature of the plate-shaped molded body according to the present invention. In addition, the above-mentioned dimer and trimer are structural units derived from the same or different two or three monomers produced by a termination reaction (recombination, disproportionation) or the like in free radical polymerization. Is a compound consisting of Such dimers and trimers can be quantified by gas chromatography.

  Further, the methacrylic resin composition used in the present invention has a melt flow rate of preferably 5 to 35 g / 10 minutes, more preferably 8 to 30 g / 10 minutes, and still more preferably 230 ° C. and a load of 3.8 kg. 10-25 g / 10 min. The melt flow rate is a value of a melt mass flow rate measured according to JIS K7210.

  The methacrylic resin composition used in the present invention preferably has a saturated water absorption rate of 1.6% by mass or less from the viewpoint of suppressing dimensional changes of the plate-shaped molded product of the present invention obtained from this, It is more preferable that the amount is not more than mass%. In the present specification, the saturated water absorption is the mass after leaving the plate-like molded body for 300 hours at a temperature of 60 ° C. and a humidity of 90% with respect to the mass of the plate-shaped molded body vacuum-dried for 3 days or more. It is a value measured as the rate of increase of.

  The methacrylic resin composition used in the present invention is composed of monomer (I), monomer (II) and optional monomer (III) (hereinafter collectively referred to as “polymerizable monomer”). ) By polymerization to form a methacrylic resin, and then adjusting the content of the methacrylic alicyclic hydrocarbon ester and, if necessary, the content of the aforementioned dimer or trimer can get. The amount of monomer (I) used during polymerization is preferably 50 to 90% by mass, and the amount of monomer (II) used during polymerization is preferably 10 to 50% by mass.

  The monomer (I), the monomer (II) and the optional monomer (III), which are raw materials for methacrylic resins, have a yellow index of preferably 2 or less, more preferably 1 or less. is there. If the yellow index of the polymerizable monomer is small, when the resulting methacrylic resin composition is molded, it is easy to obtain a plate-shaped molded body with little coloration with high production efficiency. The yellow index is a yellowness value calculated according to JIS K7373 based on a value measured according to JIS Z8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. .

  Polymerization of the polymerizable monomer is preferably performed by a bulk polymerization method, and more preferably by a radical bulk polymerization method. The bulk polymerization method is preferably a continuous bulk polymerization method from the viewpoint of productivity. The suspension polymerization method can reduce the amount of residual monomer in the resin, but the yellow index increases due to the influence of impurities such as stabilizers and dispersants. In the cell cast polymerization method, it is not only difficult to obtain a plate-like molded product with a small amount of residual monomer, but it is also difficult to obtain a thin-walled and large-area plate-like molded product. The quality is low and it is difficult to use for optical members such as a light guide plate.

  The polymerization reaction is started by adding a polymerization initiator to the polymerizable monomer at a predetermined temperature. Moreover, the weight average molecular weight, number average molecular weight, molecular weight distribution, etc. of the methacryl resin obtained can be adjusted by adding a chain transfer agent to a polymerizable monomer as needed.

  The amount of dissolved oxygen in the polymerizable monomer is preferably 10 ppm or less, more preferably 5 ppm or less, still more preferably 4 ppm or less, and particularly preferably 3 ppm or less. When the amount of dissolved oxygen is in such a range, the polymerization reaction proceeds smoothly, and it becomes easy to obtain a plate-like molded body without silver or coloring.

  The polymerization initiator used in the polymerization of the polymerizable monomer 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-methyl Tilpropionate) and the like. Among these, the polymerization initiator preferably has a one-hour half-life temperature of 60 to 140 ° C, and more preferably 80 to 120 ° C. When the polymerization reaction is carried out by a bulk polymerization method, the polymerization initiator has a hydrogen abstraction ability of preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. Specifically, t-hexylperoxy 2-ethylhexanoate, 1,1-bis (t-hexylperoxy) cyclohexane, and dimethyl 2,2'-azobis (2-methylpropionate) are preferable. These polymerization initiators can be used alone or in combination of two or more. Moreover, the usage-amount of a polymerization initiator, the addition method, etc. should just be set suitably according to the objective, and are not specifically limited. For example, the amount of the polymerization initiator used in the bulk polymerization method 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 polymerizable monomer. Part.

  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, a radical initiator is generated by cleaving the polymerization initiator in the presence of α-methylstyrene dimer and cyclohexane as a radical trapping agent. 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.

  Chain transfer agents used in the polymerization of polymerizable monomers include n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, 1,4-butanedithiol, 1,6-hexanedithiol, ethylene glycol bisthiopro. Pionate, butanediol bisthioglycolate, butanediol bisthiopropionate, hexanediol bisthioglycolate, hexanediol bisthiopropionate, trimethylolpropane tris- (β-thiopropionate), pentaerythritol tetrakis Alkyl mercaptans such as thiopropionate; α-methylstyrene dimer; terpinolene and the like. Of these, monofunctional alkyl mercaptans such as n-octyl mercaptan and n-dodecyl mercaptan are preferred. These chain transfer agents can be used alone or in combination of two or more. The amount of the chain transfer agent used in the polymerization is preferably 0.1 to 1 part by mass, more preferably 0.2 to 0.8 part by mass, and still more preferably 0 with respect to 100 parts by mass of the polymerizable monomer. .3 to 0.6 parts by mass.

  Bulk polymerization of the polymerizable monomer can be performed in a batch reactor, but it is preferably performed in a continuous flow reactor. A continuous flow reactor is a device that supplies reaction raw materials to a reactor at a constant flow rate, draws out a liquid containing reaction products obtained in the reactor at a constant flow rate, and supplies a reaction raw material and liquid containing reaction products. This is a device for continuously advancing the reaction while balancing the extraction of the water. As a reactor used for a continuous flow reactor, there are a tank reactor capable of performing a reaction in a state close to complete mixing and a tubular reactor capable of performing a reaction in a state close to plug flow. is there. One or more of these reactors may be used, or two or more different reactors may be used in combination. For example, in order to obtain the methacrylic resin used in the present invention, the initial reaction stage to the intermediate stage can be carried out in a continuous flow tank reactor, and the final reaction stage can be carried out in a continuous flow tube reactor. The reactor may have a stirrer, and the stirrer can be selected according to the type of the reactor. For example, a max blend type stirrer, a lattice rotating around a vertical rotation shaft arranged in the center And a stirrer having a blade shape, a propeller stirrer, a screw stirrer, a static mixer and the like. In a continuous flow tank reactor, a max blend type stirrer is preferable from the viewpoint of uniform mixing.

  A particularly suitable apparatus used for bulk polymerization of a polymerizable monomer 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. When a continuous flow tank reactor is used, the amount supplied to the reactor and the amount withdrawn from the reactor are balanced so that the amount of liquid in the reactor becomes substantially constant. The amount of liquid in the reactor is preferably 1/4 to 3/4, more preferably 1/3 to 2/3, with respect to the volume of the reactor.

  In the continuous flow reaction, the monomer (I), the monomer (II), the optional monomer (III), the polymerization initiator, and the chain transfer agent are all mixed and the mixture is reacted in a reactor. The monomer (I), the monomer (II) and the optional monomer (III), the polymerization initiator and the chain transfer agent may be separately supplied to the reactor. Good. In the present invention, a method in which all are mixed and the mixture is supplied to the reactor is preferred.

  Mixing of the monomer (I), the monomer (II), the optional monomer (III), the polymerization initiator and the chain transfer agent is preferably performed in an inert atmosphere such as nitrogen gas. Further, in order to smoothly operate the continuous flow reaction, for example, from a tank storing methyl methacrylate, methacrylic acid alicyclic hydrocarbon ester, a polymerization initiator and a chain transfer agent, respectively, a reactor is connected through a tube. It is preferable to continuously feed and mix in the mixer provided in the preceding stage, and to continuously flow the mixture to the reactor. The mixer is preferably equipped with a stirrer such as a static mixer.

The temperature during the polymerization reaction is preferably 100 to 160 ° C, more preferably 110 to 150 ° C. When the temperature during the polymerization reaction is in such a range, it is easy to adjust the yellow index and the melt flow rate of the plate-shaped molded body to the above-described ranges.
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.

  The polymerization conversion rate of the polymerizable monomer is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and still more preferably 50 to 65% by mass. When the polymerization conversion ratio is in such a range, it is easy to adjust the yellow index and the melt flow rate of the plate-shaped molded body to preferable ranges. 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 is likely to be insufficient, and when the obtained methacrylic resin composition is molded, there is a tendency to cause appearance defects such as silver in the plate-shaped molded body.

  By the polymerization, a resin mixture containing a methacrylic resin, an unreacted polymerizable monomer, and a dimer or trimer composed of the polymerizable monomer can be obtained. After completion of the polymerization, the unreacted polymerizable monomer, the dimer or trimer comprising the polymerizable monomer, and the solvent are removed as necessary. The removal method is not particularly limited, but heating devolatilization is preferable. Examples of the devolatilization method include equilibrium flash and adiabatic flash. In particular, the adiabatic flash is preferably performed at a temperature of 210 to 300 ° C, more preferably 220 to 280 ° C, and further preferably 230 to 260 ° C. If it is less than 210 degreeC, time will be required for devolatilization, and devolatilization will be insufficient. When devolatilization is insufficient, the plate-like molded product may have a poor appearance such as silver. On the other hand, when the temperature exceeds 300 ° C., not only the production of the dimer and trimer described above increases, but also the amount of terminal double bonds increases, making it difficult to ensure thermal stability.

  In the heat insulating flash, the pressure of the resin melt immediately before the flash is preferably 1.5 to 3.0 MPa, more preferably 2.0 to 2.5 MPa. If it is less than 1.5 MPa, the flash is insufficient and the residual monomer tends to increase. Conversely, if it exceeds 3.0 MPa, it tends to be difficult to obtain stable production.

  After the adiabatic flush, the resin composition is obtained by extruding the polymer with a screw extruder. The screw extruder preferably has at least one vacuum vent or open vent downstream from the polymer inlet. The pressure in the vacuum vent is preferably 30 Torr or less, more preferably 15 Torr or less, further preferably 9 Torr or less, and most preferably 6 Torr or less. When the pressure in the vacuum vent is in the above range, the deaeration efficiency is good and the residual monomer can be reduced.

  The screw of the screw extruder is preferably a biaxial screw in the same direction. Compared to the uniaxial case, the shear energy applied to the resin is large and the degree of surface renewal is large, so that deaeration can be performed efficiently, so that the residual monomer can be reduced. Moreover, it is preferable that the screw structure has a kneading segment part of 5% or more with respect to the total length of the screw. Examples of the kneading segment include a rotor segment, a forward feed kneading disc, a reverse feed kneading disc, and a mixing gear.

  The cylinder heating temperature of the screw extruder is preferably 220 to 300 ° C, more preferably 230 to 290 ° C, and further preferably 240 to 280 ° C. Below 220 ° C., devolatilization tends to be insufficient and the residual monomer tends to increase. Conversely, if the temperature exceeds 300 ° C., the residual monomer increases due to the main chain depolymerization of the methacrylic resin, or other impurities other than the residual monomer increase due to side chain elimination, and the methacrylic resin may be oxidized or burned. The composition tends to be colored.

  Volatiles can be removed with a vented extruder. In order to take advantage of the continuous flow reaction, it is preferable that the resin mixture continuously extracted from the polymerization reactor is continuously transferred to a vented extruder. In general, an extruder with a vent generally includes a reaction product supply port capable of supplying a reaction product containing a polymer and a volatile matter, a polymer discharge port capable of discharging a polymer separated from the reaction product, and a reaction It has at least one vent capable of discharging volatile matter separated from the product, and a screw for transferring the reaction product while kneading from the reaction product supply port to the polymer discharge port. The vent 27 located on the side closer to the polymer discharge port than the reaction product supply port is called a front vent, and the vent 26 located on the side farther from the polymer discharge port than the reaction product supply port is called a rear vent. In the extruder with a vent preferably used in the present invention, the additive inlet is provided at a position closer to the polymer outlet than the front vent located at the position closest to the polymer outlet. The pressure inside the extruder is preferably reduced, and the supplied reaction product is preferably flash evaporated at the reaction product supply port. The volatile components are evaporated while being transferred by the screw. The evaporated volatile matter is discharged from the vent. Examples of the extruder include a single screw extruder and a twin screw extruder, and a twin screw extruder is preferable. The extruder is usually divided into a feed zone, a compression zone, a metering zone, and a mixing zone. Screws suitable for these zones can be selected as appropriate. In the mixing zone, screws having various shapes such as dull image type, rotor type, flute mixing type, etc., grooves, and pins can be used in appropriate combination.

  The methacrylic resin composition of the present invention may contain various additives as necessary. An additive can be added from the additive inlet of the above-mentioned extruder, for example. Additives include heat stabilizers, antioxidants, heat deterioration inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, inorganic fillers, inorganic or organic fibers, mineral oil softeners, polymer processing Auxiliaries, antistatic agents, flame retardants, dyes and pigments, colorants, matting agents, light diffusing agents, impact resistance modifiers, phosphors, adhesives, tackifiers, plasticizers, foaming agents, etc. . The content of the additive is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less. When there is too much content of an additive, external appearance defects, such as silver, may be caused to a plate-shaped molded object.

  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 the effect of preventing deterioration of optical properties due to coloring, the combined use of a phosphorus-based antioxidant and a hindered phenol-based antioxidant or the combined use of a thioether-based antioxidant and a hindered phenol-based antioxidant More preferred.

  When a phosphorus antioxidant (or thioether antioxidant) and a hindered phenol antioxidant are used in combination, the ratio is not particularly limited, but a phosphorus antioxidant (or thioether antioxidant) / hinder The mass ratio of the dophenol antioxidant is preferably 1/5 to 2/1, more preferably 1/2 to 1/1.

  Examples of phosphorus antioxidants include 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite (manufactured by ADEKA; trade name: ADK STAB HP-10), tris (2,4-di-t- (Butylphenyl) phosphite (manufactured by Ciba Specialty Chemicals; trade name: IRUGAFOS168), 3,9-bis (2,6-di-tert-butyl-4-methylphenoxy) -2,4,8,10- Tetraoxa-3,9-diphosphaspiro [5.5] undecane (manufactured by ADEKA; trade name: ADK STAB PEP-36) and the like.

  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), And octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by Ciba Specialty Chemicals; trade name IRGANOX1076).

  As the thioether-based antioxidant, 2,2-bis {(3-dodecylthio-1-oxopropoxy) methyl} propane-1,3-diylbis (3-dodecylthiopropionate) (manufactured by ADEKA; trade name: Adekastab AO-412S), ditridecyl 3,3′-thiodipropionate (manufactured by ADEKA; trade name: Adekastab AO-503) and the like.

  A thermal degradation inhibitor is a compound that can prevent thermal degradation of a resin by scavenging polymer radicals generated when exposed to high heat in a substantially oxygen-free state. For example, 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- and t-amyl-6- (3 ′, 5′-di-t-amyl-2′-hydroxy-α-methylbenzyl) phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumitizer GS).

  The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays. Examples 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 and anilides are preferable.

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) and the like.
Examples of the anilides include 2-ethyl-2′-ethoxy-oxalanilide (manufactured by Clariant Japan; trade name Sundebore VSU).
Among these ultraviolet absorbers, benzotriazoles are particularly preferable from the viewpoint that resin deterioration due to ultraviolet irradiation can be suppressed.

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

  The mold release agent is a compound having a function of facilitating release of the plate-shaped molded body from the mold. Examples thereof include higher alcohols such as cetyl alcohol and stearyl alcohol; glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride. Of these, higher alcohols and glycerin fatty acid monoester are preferably used in combination. 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 methacrylic resin composition is molded. The polymer processing aid can usually be produced by an emulsion polymerization method. The polymer processing aid is preferably polymer particles having a particle size of 0.05 to 0.5 μm. 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. If the intrinsic viscosity is too small, the effect of improving moldability is low. When the intrinsic viscosity is too large, the melt fluidity of the methacrylic resin composition is likely to be lowered.

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 fluorescent pigments, fluorescent dyes, fluorescent white dyes, fluorescent brighteners, and fluorescent bleaching agents.
Mineral oil softeners are used to improve fluidity during molding. Examples thereof include paraffinic oil and naphthenic oil.
Examples of the inorganic filler include calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, and magnesium carbonate. Examples of the fibrous filler include glass fiber and carbon fiber.

  Moreover, the methacrylic resin composition used for this invention can be mixed and used with polymers other than the said methacrylic resin used for this invention in the range which does not impair the effect of this invention. Examples of such other polymers include polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene ionomers; polystyrene, styrene-maleic anhydride copolymer, and high impact polystyrene. Styrene resin such as AS resin, ABS resin, AES resin, AAS resin, ACS resin, MBS resin; methyl methacrylate-styrene copolymer; polyester resin such as polyethylene terephthalate and polybutylene terephthalate; nylon 6, nylon 66, Polyamide such as polyamide elastomer; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, Polyurethane, modified polyphenylene ether, polyphenylene sulfide, silicone-modified resins; acrylic rubber, silicone rubber; SEPS, SEBS, styrene-based thermoplastic elastomers such as SIS, IR, EPR, and olefin-based rubber such as EPDM and the like.

  The methacrylic resin composition from which the unreacted polymerizable monomer and the dimer or trimer composed of the polymerizable monomer have been removed is formed into pellets, granules to improve convenience of storage, transfer, molding, etc. Can be powder, etc. The pellet can be obtained, for example, by extruding the methacrylic resin composition in a strand shape in the above-described extruder and cutting the methacrylic resin composition extruded in the strand shape with a pelletizer.

  The plate-shaped molded product according to the present invention is obtained by subjecting the methacrylic resin composition to injection molding (insert method, two-color method, press method, core back method, sandwich method, etc.), compression molding, extrusion molding, vacuum molding, blow molding. It can be obtained by heat-melt molding by a method such as inflation molding or calendar molding. In the heat-melt molding, a methacrylic resin composition is preferably used in a pellet form.

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

  Further, it is preferable to remove defective cut products and resin powder from the methacrylic resin pellets before molding. The defective cut is a long resin piece obtained as a result of failing to cut the strand. The resin powder is a powder that can be produced by rubbing chips and pellets generated when a strand is cut. A method for removing defective products and resin powder is not particularly limited. Examples thereof include a centrifugal separation method and a sieving method.

  Furthermore, when transferring a methacrylic resin composition to the hopper of a molding machine, it is preferable to maintain the temperature of a methacrylic resin composition or a methacrylic resin pellet at 70 degreeC or more, for example. When the transfer is performed at a high temperature, it may be possible to suppress the generation of resin powder due to moisture absorption during transfer or rubbing between pellets.

  The plate-shaped molded body according to the present invention preferably has a resin flow length to thickness ratio of 380 or more. Moreover, it is preferable that the plate-shaped molded object which concerns on this invention is 1 mm or less in thickness.

The resin flow length is a 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 vertical leg (intersection with the gate) drawn from the sprue attachment part of the injection mold and the inner wall of the mold farthest from the intersection. (See FIG. 1).
The gate of the mold for obtaining the plate-shaped molded body 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.

  The plate-like molded product of the present invention has a yellow index (YI) with an optical path length of 200 mm of 10 or less, preferably 8 or less, more preferably 6 or less. The yellow index is a value calculated according to JIS K7373 based on a value measured according to JIS Z8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

  The plate-like molded product of the present invention has a transmittance at an optical path length of 3 mm at a wavelength of 435 nm of preferably 90% or more, more preferably 90.5% or more, and still more preferably 91% or more.

  Examples of the use of the plate-shaped molded article 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, partition plates, and store displays; fluorescent lamp covers, Lighting parts such as mood lighting covers, lamp shades, light ceilings, light walls, chandeliers; interior parts such as pendants and mirrors; doors, domes, safety window glass, partitions, staircases, balconies, roofs of leisure buildings, etc. Building parts; aircraft windshield, pilot visor, motorcycle, motorboat windshield, bus shading plate, automotive side visor, rear visor, head wing, headlight cover, etc. transportation equipment related parts; acoustic image nameplate, stereo cover, Electronics such as TV protection masks and vending machine display covers Parts: Medical equipment parts such as incubators and X-ray parts; equipment-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, lenticulars Optical parts such as lenses, front plates and diffusers for various displays; traffic-related parts such as road signs, guide boards, curve mirrors, and sound barriers; surface materials for automobile interiors, surface materials for mobile phones, films such as marking films Components: Household appliances such as washing machine canopy and control panels, rice cooker top panels; other greenhouses, large aquariums, box aquariums, clock panels, bathtubs, sanitary, desk mats, game parts, toys, welding For example, a face protection mask. Among these, the plate-shaped molded body of the present invention is suitable for a light guide plate and a front plate of various displays.

  When the plate-shaped molded body of the present invention is used as a light guide plate which is one of planar light source elements, the light guide can be guided by a known method such as fusion, adhesion, coating, printing, injection molding, or processing by laser light. An uneven shape may be formed on the back surface of the plate. Light incident from the end face of the plate can be reflected and refracted by the uneven shape and emitted to the front of the plate. Examples of the concavo-convex shape include a perfect circle or elliptical dot pattern, a line pattern such as a rectangle or a V-groove, a hemispherical lens concavo-convex pattern, and a wrinkle pattern. These uneven shapes cannot be defined unconditionally because the optimum structure varies depending on the size and thickness of the light guide plate, but the width is 1 to 600 μm, the length is 2 to 1200 μm, the height or depth is 1 to 500 μm, and the adjacent unevenness The shape interval is preferably 2 to 10,000 μm. If the concavo-convex shape is too large, it is visually recognized and the quality of the display is lowered, and if it is too small, the processing is difficult and the productivity is lowered. Further, if the interval between adjacent uneven shapes is narrower than 2 μm, it becomes difficult to form adjacent uneven portions independently, and molding defects tend to occur. If the width is larger than 10,000 μm, the number of uneven portions cannot be increased. Since the concavo-convex portion has a function of emitting light, the limitation on the number of the concavo-convex portions causes a utilization rate limitation that is a ratio of light that is effectively emitted from the light incident from the end face of the light guide plate. These uneven shapes may be the same shape in one light guide plate, may be formed by combining different shapes, or patterns having the same shape and different sizes may be arranged. Furthermore, the interval and size of the unevenness may be modulated according to the distance from the light source arranged adjacent to the end face of the light guide plate.

  Moreover, it may replace with formation of uneven | corrugated shape and may print a white reflector on the back surface of a light-guide plate. The size of the white reflector is preferably 500 μm to 5000 μm. If the thickness is smaller than 500 μm, it is difficult to print the white reflective material by the existing screen printing or the like. If it is larger than 5000 μm, the white reflective material is visually recognized even when viewed through a diffusion sheet or the like, and the quality of the display deteriorates. The spacing between the reflecting materials is preferably 1000 to 5000 μm. If the interval is smaller than 1000 μm, adjacent white reflectors overlap with each other by screen printing or the like, resulting in a defect. When it is larger than 5000 μm, even when viewed through a diffusion sheet or the like, the dark part between the white reflectors is visually recognized, and the display quality is deteriorated. Further, the interval and size of the white reflecting material may be modulated in accordance with the distance from the light source arranged adjacent to the end face of the light guide plate. In addition, prisms and arcuate line-shaped convex portions may be formed on the surface of the light guide plate from which light is emitted (front of the plate) by the same means. When used as a backlight, a reflection sheet may be appropriately disposed on the back side of the light guide plate, and a diffusion sheet and / or a prism sheet may be appropriately disposed on the front side of the light guide plate.

The molded product of the present invention can be used as a front plate for various displays. Such a front plate can be obtained by a general molding method such as extrusion molding or injection molding by heating and melting the resin composition.
The display device in which the front plate is used is not particularly limited, and examples thereof include large display devices such as large-screen televisions and advertising displays; small and medium display devices such as mobile phones and smartphones.
Further, the front plate is not limited to a planar shape, and may have a curved shape. The curved surface shape may be a shape curved in one direction or a shape curved in a plurality of directions. In order to make the front plate have a curved shape, the plate-like molded body may have a flexible characteristic, or may be previously molded into a desired curved shape.

Moreover, you may use the molded article of this invention for the above-mentioned various uses in the state hard-coated by methods, such as spray coating and dip coating, on the surface. Hard coating increases the pencil hardness of the surface and makes it difficult to scratch. In addition to the hard coat, a functional layer such as an antiglare layer, an antireflection layer, a layer that cuts electromagnetic waves, ultraviolet rays, near infrared rays, or the like may be provided.
The molded article of the present invention may be laminated with another functional film or functional sheet via an adhesive layer or an adhesive layer, or may be laminated by film insert molding. Examples of the functional film and functional sheet include a light guide plate, a diffusion plate, a scattering prevention film, and a transparent conductive film.

  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 polymer physical properties of the methacrylic resin compositions obtained in the examples and comparative examples and the properties of the plate-shaped molded bodies were implemented by the following methods.

(Polymerization conversion rate, residual volatile content)
The gas chromatograph GC-14A manufactured by Shimadzu Corporation was used as a column for GL Sciences Inc. Made by INERT CAP 1 (df = 0.4 μm, 0.25 mm ID × 60 m), analysis was performed under the following analysis conditions, and calculation was performed based on the analysis conditions.
<Analysis conditions>
Injection temperature: 250 ° C
Detector temperature: 250 ° C
Column temperature conditions:
Initial temperature: 60 ° C
Initial temperature holding time: 5 minutes Temperature rising rate: 10 ° C / min Maximum temperature: 250 ° C
Maximum temperature holding time: 10 minutes

(Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn))
The weight average molecular weight (Mw) and molecular weight distribution were determined by polystyrene-equivalent molecular weight by GPC (gel permeation chromatography).
・ Equipment: GPC equipment “HLC-8320” manufactured by Tosoh Corporation
-Separation column: "TSKgel GMHXL" and "G4000HXL" manufactured by Tosoh Corporation are connected in series.-Eluent: Tetrahydrofuran-Eluent flow rate: 0.35 ml / min-Column temperature: 40 ° C
・ Detection method: Differential refractive index (RI)

(Melt flow rate)
The melt flow rate of the methacrylic resin compositions obtained in Examples and Comparative Examples was measured under conditions of 230 ° C., 3.8 kg load, and 10 minutes in accordance with JIS K7210.

(Saturated water absorption)
Using an injection molding machine (SE-180DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.), a pellet-shaped methacrylic resin composition was injection molded at a cylinder temperature of 280 ° C, a mold temperature of 75 ° C, and a molding cycle of 1 minute. Thus, a test piece having a length of 290 mm, a width of 100 mm, and a thickness of 2 mm was obtained. The test piece was vacuum-dried for 3 days under conditions of a temperature of 50 ° C. and 5 mmHg, and the mass W ₀ of the test piece when completely dried was measured. Then, the absolutely dry test piece was left for 300 hours under the conditions of a temperature of 60 ° C. and a humidity of 90%. Thereafter, the mass W _{1 of the} test piece was measured. The saturated water absorption (%) was calculated from the following formula.
Saturated water absorption (%) = {W ₁ −W ₀ } / W ₀ × 100

(Appearance of plate-shaped molded product)
The appearance of the plate-like molded bodies produced in the examples and comparative examples was observed with the naked eye. Evaluation was made based on the appearance defects such as surface contamination and cracks.
A: Good B: Dirt on the surface C: With cracks

(Yellow Index)
The yellow index of the polymerizable monomer used in Examples and Comparative Examples was measured based on a value measured according to JIS Z-8722 using a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. It calculated based on JISK7373.
Test pieces having a length of 200 mm were cut out from the plate-shaped molded bodies produced in Examples and Comparative Examples, and a yellow index having an optical path length of 200 mm was used as a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. Was calculated according to JIS K7373 based on the value measured according to JIS Z-8722.

(Light transmittance)
A test piece with an optical path length of 200 mm and a test piece with an optical path length of 3 mm were cut out from the plate-shaped molded bodies produced in Examples and Comparative Examples, respectively, and the transmittance of light having a wavelength of 435 nm at an optical path length of 200 mm and an optical path length of 3 mm was measured.

(Dimensional change rate)
The plate-like molded bodies produced in Examples and Comparative Examples were placed in a 60 ° C. thermostat and left in the atmosphere for 4 hours. The plate-like molded body was taken out from the thermostat and the length dimension was measured. The rate of dimensional change from the dimension in the length direction (205 mm) before putting in the thermostat was calculated.

(Impact resistance of plate-shaped molded products)
Using an injection molding machine (SE-180DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.), the pellet-shaped methacrylic resin compositions obtained in Examples and Comparative Examples 1 to 7 were used at a cylinder temperature of 230 ° C. and a mold temperature. A test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was prepared by injection molding at 65 ° C. with a molding cycle of 0.5 minutes or cut out from the plate-like molded body obtained in Comparative Example 8, and ISO 179- According to No. 1, Charpy impact strength without notch was measured.

  In the following, dicyclopentanyl methacrylate is TCDMA, isobornyl methacrylate is IBXMA, methyl methacrylate is MMA, methyl acrylate is MA, n-octyl mercaptan is n-OM, 2,2'-azobis (2-methylpropio) Nitrile) is denoted AIBN.

Example 1
A monomer mixture was prepared by putting 78 parts by mass of purified MMA, 20 parts by mass of TCDMA, and 2 parts by mass of MA in an autoclave with a stirrer and a sampling tube. The yellow index of the monomer mixture was 0.9. To the monomer mixture, 0.006 parts by mass of a polymerization initiator (AIBN, hydrogen abstraction ability: 1%, 1 hour half-life temperature: 83 ° C.) and 0.37 parts by mass of a chain transfer agent (n-OM) are added and dissolved. The raw material liquid was obtained. The oxygen gas in the production apparatus was purged with nitrogen gas.
The raw material liquid was supplied from an autoclave 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 was 57% by mass.

The liquid discharged from the reactor was heated to 250 ° 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-shaped methacrylic resin composition. The residual TCDMA was 0.4% by mass. The polymer physical property of the obtained pellet-shaped methacrylic resin composition was measured.
It was.

The pellet-like methacrylic resin composition is injection molded using an injection molding machine (SE-180DU-HP, manufactured by Sumitomo Heavy Industries, Ltd.) with a cylinder temperature of 280 ° C., a mold temperature of 75 ° C., and a molding cycle of 1 minute. Thus, a plate-like molded body having a length of 205 mm, a width of 160 mm, and a thickness of 0.5 mm was produced. The ratio of the resin flow length (190 mm) to the thickness is 380.
The properties of the obtained plate-like molded body were evaluated. The results are shown in Table 1.

Example 2
The amount of MMA was changed to 73 parts by mass, the amount of TCDMA was changed to 23 parts by mass, the amount of MA was changed to 4 parts by mass, and the amount of n-OM was changed to 0.33 parts by mass. A pellet-like methacrylic resin composition was obtained in the same manner as in Example 1 except that the value was changed. The polymer physical properties of the obtained pellet-like methacrylic resin composition were measured by the same method as in Example 1. Moreover, the plate-shaped molded object was produced similarly to Example 1, and the characteristic was evaluated. These results are shown in Table 1.

Example 3
Except for changing the amount of MMA to 83 parts by mass, the amount of TCDMA to 15 parts by mass, the amount of MA to 2 parts by mass, and the amount of n-OM to 0.38 parts by mass, the same procedure as in Example 1 was used. A pellet-like methacrylic resin composition was obtained. The polymer physical properties of the obtained pellet-like methacrylic resin composition were measured by the same method as in Example 1. Moreover, the plate-shaped molded object was produced similarly to Example 1, and the characteristic was evaluated. These results are shown in Table 1.

Example 4
A pellet-like methacrylic resin composition was obtained in the same manner as in Example 1 except that TCDMA was changed to IBXMA and the amount of n-OM was changed to 0.36 parts by mass. The polymer physical properties of the obtained pellet-like methacrylic resin composition were measured by the same method as in Example 1. Moreover, the plate-shaped molded object was produced similarly to Example 1, and the characteristic was evaluated. These results are shown in Table 1.

Comparative Examples 1-4
A pellet-shaped methacrylic resin composition was obtained in the same manner as in Example 1 except that the synthesis conditions and the resin production conditions shown in Tables 1 and 2 were changed. The polymer physical properties of these pellet-like methacrylic resin compositions were measured in the same manner as in Example 1. Moreover, it shape | molded similarly to Example 1 and measured the characteristic. These results are shown in Tables 1 and 2.

Comparative Example 5
A pellet-like methacrylic resin composition was obtained in the same manner as in Example 1 except that the synthesis conditions and the resin production conditions shown in Table 2 were changed.
This pellet-shaped methacrylic resin composition was supplied to a twin screw extruder controlled at 270 ° C. at a constant speed. 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-shaped methacrylic resin composition (repellet). The residual TCDMA was 0.7% by mass. The polymer physical properties of the re-pelletized methacrylic resin composition were measured in the same manner as in Example 1. Moreover, the plate-shaped molded object was produced similarly to Example 1, and the characteristic was measured. These results are shown in Table 2.

Comparative Example 6
A pellet-like methacrylic resin composition was obtained in the same manner as in Example 1 except that the synthesis conditions and the resin production conditions shown in Table 2 were changed.
A solution of 20 parts by mass of the pellet-shaped methacrylic resin composition and 80 parts by mass of toluene was prepared, and the solution was poured into a large amount of methanol and reprecipitated to obtain a powdery methacrylic resin composition.
The powdery methacrylic resin composition was supplied to a single screw extruder controlled at 230 ° C. at a constant speed, and the extruded strand was cut with a pelletizer to obtain a pellet-like methacrylic resin composition (repellet). The residual TCDMA was 0.2% by mass. The polymer physical properties of the re-pelletized methacrylic resin composition were measured in the same manner as in Example 1. Moreover, the plate-shaped molded object was produced similarly to Example 1, and the characteristic was measured. These results are shown in Table 2.

Comparative Example 7
A monomer mixture was prepared by adding 83 parts by mass of MMA, 15 parts by mass of TCDMA, and 2 parts by mass of MA. The yellow index of the monomer mixture was 0.9. 0.1 parts by mass of a polymerization initiator (AIBN, hydrogen abstraction capacity: 1%, 1 hour half-life temperature: 83 ° C.) and 0.4 parts by mass of a chain transfer agent (n-OM) are added to the monomer mixture. To obtain a raw material solution.
100 parts by mass of ion-exchanged water, 0.03 parts by mass of sodium sulfate, and 0.46 parts by mass of a suspension dispersant were mixed to obtain a mixed solution. 420 parts by mass of the mixed solution and 210 parts by mass of the raw material liquid were charged into a pressure-resistant polymerization tank, and the polymerization reaction was started at a temperature of 70 ° C. while stirring in a nitrogen atmosphere. After 3 hours from the start of the polymerization reaction, the temperature was raised to 90 ° C. and stirring was continued for 1 hour to obtain a dispersion in which bead-shaped fine particles were dispersed.
The obtained dispersion was filtered, and the fine particles were washed with ion-exchanged water, and then dried under reduced pressure at 100 Pa for 4 hours at 80 ° C. to obtain a bead-shaped copolymer.
The obtained copolymer was supplied to a single screw extruder controlled at 230 ° C. to separate and remove volatile components such as unreacted monomers, and then the resin component was extruded into a strand. The strand was cut with a pelletizer to obtain a pellet-shaped methacrylic resin composition. Moreover, the plate-shaped molded object was produced similarly to Example 1, and the characteristic was measured. These results are shown in Table 2.

Comparative Example 8
A monomer mixture was prepared by adding 73 parts by mass of MMA, 25 parts by mass of TCDMA, and 2 parts by mass of MA. The yellow index of the monomer mixture was 0.9. 0.1 parts by mass of a polymerization initiator (AIBN, hydrogen abstraction ability: 1%, 1 hour half-life temperature: 83 ° C.) was added to the monomer mixture and dissolved to obtain a raw material solution.
This raw material solution was poured into a glass cell composed of two glass plates (thickness 10 mm, 30 cm square) treated with water repellency and a vinyl chloride resin gasket, and deaerated at 760 mmHg for 3 minutes. The glass cell was polymerized at 70 ° C. for 2 hours and then at 120 ° C. for 2 hours, and the glass plate was removed to produce a plate-like molded product having a thickness of 0.5 mm. Was cracked and the thickness accuracy was low.
A plate-like molded body having a thickness of 2 mm and 4 mm was prepared under the same polymerization conditions as above, and a test piece having a length of 290 mm, a width of 100 mm, and a thickness of 2 mm was used for evaluating light transmittance from the obtained plate-shaped molded body. For the impact resistance evaluation, a test piece having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm was cut out to evaluate the polymer physical properties and the properties of the plate-shaped molded body. The obtained plate-like molded body was a very high molecular weight body and therefore did not dissolve in the solvent, but only swelled. Therefore, the molecular weight could not be measured. The estimated weight average molecular weight is 1 million g / mol or more. These results are shown in Table 2.

  As the above results show, the plate-shaped molded body according to the present invention has little coloring, high transparency, low haze, low saturated water absorption, small dimensional change, and good appearance.

1 sprue; 2 runners; 3 gates;
4 resin flow length;

21 reactor; 11 MMA tank; 12 MA tank;
13 n-OM tank; 14 initiator MMA solution tank;
18 nitrogen gas mixer; 23 vented extruder;
22 Heat exchanger for heating; P Pellet resin composition

Claims (7)

  A methacrylic resin containing 50 to 90% by mass of a structural unit derived from methyl methacrylate and 10 to 50% by mass of a structural unit derived from a methacrylic acid alicyclic hydrocarbon ester, and containing a methacrylic acid alicyclic hydrocarbon A plate-shaped molded article having an optical path length of 200 mm and a yellow index (YI) of 10 or less, comprising a methacrylic resin composition having an ester content of 1.0 mass% or less.   The methacrylic resin composition is a dimer or trimer composed of methyl methacrylate, a dimer or trimer composed of acrylate ester, a dimer or trimer composed of methacrylic acid alicyclic hydrocarbon ester. , Dimer consisting of methyl methacrylate and acrylate ester, dimer consisting of methyl methacrylate and methacrylic acid alicyclic hydrocarbon ester, dimer consisting of acrylic acid ester and methacrylic acid alicyclic hydrocarbon ester A trimer consisting of two methyl methacrylates and one acrylate ester, a trimer consisting of one methyl methacrylate and two acrylate esters, two methyl methacrylates and one methacrylic fat. Trimers consisting of cyclic hydrocarbon esters, one methyl methacrylate and two methacrylate cycloaliphatic hydrocarbons A trimer composed of steal, a trimer composed of two acrylic esters and one methacrylic alicyclic hydrocarbon ester, a single acrylic ester and two methacrylic alicyclic hydrocarbon esters The plate-shaped molding according to claim 1, wherein the total content of the trimer and the trimer composed of methyl methacrylate, acrylic ester and methacrylic alicyclic hydrocarbon ester is 0.3% by mass or less. body.   The plate-shaped molded article according to claim 1 or 2, wherein the methacrylic acid alicyclic hydrocarbon ester is dicyclopentanyl methacrylate or isobornyl methacrylate.   The plate-shaped molded product according to any one of claims 1 to 3, wherein a ratio of a resin flow length to a thickness is 380 or more.   The plate-shaped molded article according to any one of claims 1 to 4, wherein the transmittance at an optical path length of 3 mm at a wavelength of 435 nm is 90% or more.   The light-guide plate which consists of a plate-shaped molded object as described in any one of Claims 1-5. (I) A polymerizable monomer, a polymerization initiator, and a chain transfer agent are continuously supplied to the reactor,
(II) In the reactor, a part of the polymerizable monomer is radically bulk-polymerized, and the structure derived from 50 to 90% by mass of the structural unit derived from methyl methacrylate and the structure derived from methacrylic acid alicyclic hydrocarbon ester. A resin mixture containing a methacrylic resin having 10 to 50% by mass of a unit, an unreacted polymerizable monomer, and a dimer or trimer composed of the polymerizable monomer is obtained,
(III) The resin mixture is continuously transferred from the reactor to a twin screw extruder equipped with a vent,
(IV) In the twin-screw extruder, a methacrylic resin composition is obtained by removing a dimer or trimer composed of an unreacted polymerizable monomer and a polymerizable monomer from the resin mixture, Extruding the methacrylic resin composition into a strand,
(V) A pellet-shaped methacrylic resin composition is obtained by cutting the methacrylic resin composition extruded into a strand shape with a pelletizer,
(VI) The molten methacrylic resin composition in the form of pellets is heated and melted and molded.
The manufacturing method of the plate-shaped molded object as described in any one of Claims 1-5.

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