JP7300920B2 - resin sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin sheet, and more particularly to a resin sheet having translucency and light diffusing properties.

BACKGROUND ART A so-called matte resin sheet having translucency and light diffusing properties is used in various applications such as indoor building materials such as indoor partitions and front panels of cupboards, display materials, and the like.

As a method for imparting light diffusion performance to a resin sheet, generally, a method of transferring the surface unevenness of a roll having fine unevenness on the surface to the surface of the resin sheet (for example, Patent Document 1), and a method of sandblasting the resin sheet. There are a method of forming fine unevenness on the surface (for example, Patent Document 2), a method of adding a light diffusing agent to the inner layer, the surface layer, or both of the resin sheet (for example, Patent Document 3). Alternatively, a resin sheet having translucency and light diffusing properties can be obtained by combining them.

Japanese Patent Application Laid-Open No. 2004-155101 JP-A-11-245293 JP 2006-195218 A

However, there is a limit to transferring the surface unevenness of a roll having fine unevenness on the surface to the surface of the resin sheet or forming fine unevenness on the surface of the resin sheet by sandblasting. In some cases, it was difficult to form fine unevenness. In particular, in the case of a thick resin sheet having a thickness of 1 mm or more, the heat of the resin sheet melted during production is difficult to decrease, and this tendency is remarkable.
In addition, when adding a light diffusing agent to make a resin sheet having light diffusing properties, there is a problem that the amount of the light diffusing agent added increases the cost. was required.

The present invention has been made in view of the above-described problems of the background art, and provides a resin sheet that is translucent and does not contain a light diffusing agent in the surface layer portion and exhibits good light diffusing performance. for the purpose.

In order to achieve the above object, the present invention provides a resin sheet described in [1] to [ 3 ] below.
[1] A resin sheet formed by extrusion molding,
The resin sheet is a multi-layer sheet comprising a core layer and surface layers laminated on both sides of the core layer to form a surface layer portion . The fine unevenness of
The surface layer has a melt flow rate (temperature of 200° C., load of 5.00 kg) of 3 g/10 minutes or less, is made of a branched polystyrene resin having a branched structure, and does not contain a light diffusing agent,
The resin sheet has a thickness of 1 to 10 mm, a total light transmittance of 80% or more, and a haze of 10% or more.
[ 2 ] The resin sheet according to [1] above, wherein the fine unevenness has an average length of roughness curve elements of 300 μm or less.
[ 3 ] The resin sheet as described in [1] or [2] above, wherein the resin sheet has a thickness of 2 to 8 mm and a haze of 30% or more.

The resin sheet according to the present invention does not use a light diffusing agent in the surface layer portion, forms a specific fine unevenness on the surface, is a resin sheet with a specific total light transmittance and haze, and can be manufactured at a low cost. In addition, it becomes a resin sheet having good light diffusion performance.

1 is a conceptual side view of a typical forming apparatus used for manufacturing the resin sheet of the present invention; FIG.

Hereinafter, the resin sheet according to the present invention will be described in detail.

The resin sheet according to the present invention is a single-layer or multilayer resin sheet formed by extrusion molding, and fine unevenness having an arithmetic mean roughness of 0.2 to 1.0 μm is formed on at least one side of the resin sheet. The surface layer portion of the resin sheet on the side where the fine unevenness is formed is made of polystyrene resin, the resin sheet does not contain a light diffusing agent in the surface layer portion, has a thickness of 1 to 10 mm, and a total light transmittance. The resin sheet has a haze of 80% or more and a haze of 10% or more.

In the present invention, it is important that fine irregularities having an arithmetic mean roughness of 0.2 to 1.0 μm are formed on at least one surface of the resin sheet. By forming fine unevenness with an arithmetic mean roughness of 0.2 to 1.0 μm on the surface of the resin sheet, it is possible to obtain a resin sheet having good light diffusion performance, and the unevenness is less than 0.2 μm. In the case of , the haze is low and the light diffusibility is poor. On the other hand, when the irregularities exceeding 1.0 μm are formed, the resin sheet has an inferior appearance because the irregularities on the surface are too large. From this point of view, it is preferable that fine unevenness having an arithmetic mean roughness of 0.2 to 0.8 μm is formed, and it is preferable that fine unevenness having an arithmetic mean roughness of 0.2 to 0.7 μm is formed. more preferred.
The "arithmetic mean roughness" is defined in JIS B0601 (2013) and is a value measured according to the JIS. For the above "arithmetic mean roughness", the arithmetic mean value obtained by measuring 10 points shall be adopted.

The fine unevenness formed on the surface of the resin sheet is very dense and has a relatively sharp mountain-like shape, and a large number of extremely fine unevennesses are uniformly present. Due to the presence of a large number of fine irregularities uniformly, it can be suitably used as an indoor building material such as a partition plate in a room or a front plate of a cupboard, a display material, or the like. From the above point of view, it is preferable to measure the arithmetic mean roughness Ra of 10 points on the surface of the resin sheet, determine the standard deviation of them, and find the value to be low. The value of the standard deviation is preferably 0.1 or less, more preferably 0.06 or less. The value of the standard deviation is a value given by the square root of the unbiased variance.

Further, in the present invention, it is preferable that the fine irregularities formed on the surface of the resin sheet have an average length of roughness curve elements of 300 μm or less. By forming unevenness in which the average length of the roughness curve element is 300 μm or less on the surface of the resin sheet, the resin sheet has a high haze and excellent light diffusion properties. From this point of view, it is more preferable to form unevenness with an average length of roughness curve elements of 250 μm or less, and it is even more preferable to form unevenness with an average length of roughness curve elements of 200 μm or less. Since the average length of the roughness curve element means the average length of peaks and valleys in the reference length, if the value of the average length of the roughness curve element is small, fine irregularities are densely present. means
The above "average length of roughness curve elements" is a value measured according to JIS B0601:2013. For the "average length of the roughness curve element", an arithmetic mean value obtained by measuring 10 points is adopted.

It is important that the resin sheet of the present invention has a thickness of 1 to 10 mm, preferably 2 to 8 mm, more preferably 3 to 6 mm. By setting the thickness to the above, the light from the back side is appropriately diffused, and the translucency and light diffusing properties are moderate. will be excellent. If the thickness is less than 1 mm, it becomes difficult to obtain strength such as flexural rigidity and impact resistance required for interior building materials, display materials, and the like. Conversely, if the thickness exceeds 10 mm, the resin sheet tends to sag under its own weight during production, making it difficult to mold into a resin sheet shape, or it may be heavy and difficult to handle. Moreover, the secondary processing after obtaining a resin sheet becomes difficult.

In addition, the resin sheet of the present invention has a length of 50 to 300 cm and a width of 20 to 200 cm, which is suitable for indoor building materials, display materials, etc. The length is 80 to 250 cm and the width is 25 to 180 cm. More preferably, the length is 100 to 200 cm and the width is 30 to 160 cm.

The resin sheet of the present invention has a total light transmittance of 80% or more. By setting the total light transmittance to 80% or more, the amount of light transmitted can be made preferable. From this point of view, the total light transmittance is preferably 82% or more, more preferably 85% or more. Although the upper limit of the total light transmittance is not particularly limited, it is preferably approximately 98% or less.
The "total light transmittance" referred to in the present invention is a value measured according to JIS K7361-1:1997. For the above "total light transmittance", an arithmetic mean value obtained by measuring 10 points shall be adopted.

Further, it is important that the resin sheet of the present invention has a haze of 10% or more, preferably 20% or more, and more preferably 30% or more. By setting the haze of the resin sheet to the above range, the diffusion of light can be made preferable, and the resin sheet can be suitably used as an indoor building material such as an indoor partition plate exhibiting a matte tone or a front panel of a cupboard, a display material, or the like. becomes possible.
In addition, "haze" as used in the field of this invention is the value measured based on JISK7136:2000. For the above "haze", an arithmetic mean value obtained by measuring 10 points shall be adopted.

In the resin sheet of the present invention, the surface layer portion of the resin sheet on which fine irregularities are formed is made of polystyrene resin. Polystyrene resin has low water absorption and excellent rigidity. Therefore, a resin sheet whose surface layer portion is made of polystyrene resin is preferable because it can suppress warpage and deformation.
Examples of the polystyrene resin include polystyrene, styrene-α-methylstyrene copolymer, styrene-p-methylstyrene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid copolymer. Polymer, styrene-methacrylic acid copolymer, styrene-maleic anhydride copolymer, styrene-polyphenylene ether copolymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer , acrylonitrile-styrene acrylate copolymer, styrene-methylstyrene copolymer, styrene-dimethylstyrene copolymer, styrene-ethylstyrene copolymer, styrene-diethylstyrene copolymer, high-impact polystyrene (high-impact polystyrene resin ) and the like, and these may be used alone or in combination of two or more. The above polystyrene resin has a styrene-based unit or styrene component content of more than 50 mol %, preferably 80 mol % or more, more preferably 90 mol % or more.

The above polystyrene resin is a resin having a total light transmittance of 80% or more as determined by JIS K7361-1:1997 by preparing a test piece with a thickness of 2 mm.

Moreover, the polystyrene resin is preferably a branched polystyrene resin having a branched structure. The branched polystyrene resin may be a single branched polystyrene resin, or a mixed resin of a linear polystyrene resin and a branched polystyrene resin.

The branched polystyrene resin generally has a branched structure such as a random branched structure, a star structure, or a pompom structure. Methods for introducing branches into a styrenic resin include a method using an organic peroxide, a method using a polyfunctional monomer, a method using ionic crosslinking, and a method using a multibranched macromonomer. The present invention may have any of the above-described branched structures, and may be produced by any of the above-described methods.

Branched polystyrene resins tend to have less fluidity and higher melt viscosity and melt tension than other resins under the same conditions. easy to do The fine unevenness is preferable because the unevenness is very dense and has a relatively sharp mountain shape, and a large number of extremely fine unevenness are uniformly present.
In general, a branched resin tends to have a smaller molecular size than a linear resin having the same absolute molecular weight. The shrinkage factor of the present invention is a measure of the size ratio of a molecule to a linear polymer of presumably the same absolute molecular weight. That is, the shrinkage factor tends to decrease as the degree of branching of the resin increases. From this, it can be seen that a polystyrene resin having a shrinkage factor of less than 1.0 is a branched polystyrene resin.

収縮因子の重量平均値ｇｗは、ＧＰＣ－ＭＡＬＳ法を用いて次のように特定できる。ＧＰＣによりポリスチレン系樹脂の試料液の溶出クロマトグラムを得る。そして、溶出クロマトグラムの任意の区間ｉにおいて、ＭＡＬＳにより区間ｉにおけるポリスチレン系樹脂の収縮因子ｇｉが特定される。区間ｉにおけるポリスチレン系樹脂の濃度ｃｉは、市販の濃度検出器等を適宜用いて特定される。
これらの値から収縮因子の重量平均値ｇｗは、下記式（２）により求められる。

ＧＰＣ－ＭＡＬＳ法の測定機器は、島津製作所社製Ｐｒｏｍｉｎｅｎｃｅ ＬＣ－２０ＡＤ（２ＨＧＥ）／ＷＳシステム、Ｗｙａｔｔ Ｔｅｃｈｎｏｌｏｇｙ社製の多角度光散乱検出器 ＤＡＷＮ ＨＥＬＥＯＳ II等を用いて、溶離液：テトラヒドロフラン（ＴＨＦ）、流量１．０ｍｌ／ｍｉｎという条件で測定できる。カラムとしては、例えば、東ソー社製ＴＳＫｇｅｌ ＨＨＲ－Ｈ×１本、ＴＳＫｇｅｌ ＧＭＨＨＲ×２本を直列に接続して用いることができる。測定の解析は、Ｗｙａｔｔ社の解析ソフト ＡＳＴＲＡ等により行い、スチレン系樹脂の収縮因子の重量平均値が求められる。 As a method for obtaining the contraction factor, for example, it is measured by the GPC-MALS method as follows. As shown in the following formula (1), the shrinkage factor g is the root-mean-square radius of gyration of a styrene resin having a branched structure <Rg ² > _B and the root-mean-square radius of gyration of a straight-chain styrene resin <Rg It is calculated as a ratio of ² > _L.

The weight average value gw of the contraction factor can be determined as follows using the GPC-MALS method. An elution chromatogram of a polystyrene resin sample liquid is obtained by GPC. Then, in an arbitrary interval i of the elution chromatogram, MALS specifies the shrinkage factor gi of the polystyrene resin in the interval i. The concentration ci of the polystyrene-based resin in the section i is specified by appropriately using a commercially available concentration detector or the like.
From these values, the weight average value gw of the shrinkage factor is obtained by the following formula (2).

The GPC-MALS method is measured using a Prominence LC-20AD (2HGE)/WS system manufactured by Shimadzu Corporation, a multi-angle light scattering detector DAWN HELEOS II manufactured by Wyatt Technology, etc., and an eluent: tetrahydrofuran (THF). , and a flow rate of 1.0 ml/min. As the column, for example, TSKgel HHR-H×1 column and TSKgel GMHHR×2 columns manufactured by Tosoh Corporation can be used by connecting them in series. The analysis of the measurement is performed by Wyatt's analysis software ASTRA or the like, and the weight average value of the shrinkage factor of the styrene resin is obtained.

In addition, from the viewpoint of low fluidity and easy formation of fine unevenness, the polystyrene resin constituting the surface layer portion is preferably made of a branched polystyrene resin having a melt flow rate of 3 g/10 minutes or less. It is more preferable to use a branched polystyrene resin having a flow rate of 2 g/10 minutes or less.
The "melt flow rate" (hereinafter also referred to as "MFR") of the present invention is a value measured under conditions of a temperature of 200 ° C. and a load of 5.00 kg according to the test method specified in JIS K7210-1:2014. be.

In the present invention, the “surface layer portion” refers to a portion extending from the surface of the resin sheet to the center in the thickness direction up to 100 μm when the resin sheet is a single layer, and when the resin sheet is a multilayer, the core layer. It refers to the thickness of the surface layer laminated to

The polystyrene resin forming the surface layer portion preferably has a relative weight average molecular weight of 400,000 or more, more preferably 450,000 or more. On the other hand, the upper limit of the relative weight average molecular weight of the polystyrene resin forming the surface layer portion is approximately 1,000,000. When the relative weight-average molecular weight of the polystyrene resin constituting the surface layer portion is within the above range, fine irregularities are easily formed.
The "relative weight average molecular weight" used in the present invention is a value obtained by dissolving 10 mg of a sample in 10 ml of tetrahydrofuran (THF), measuring by gel permeation chromatography (GPC) analysis, and calibrating with standard polystyrene.

Further, from the viewpoint that the fine unevenness is easily formed, the melt viscosity of the resin sheet under the conditions of 200 ° C. and a shear rate of 100 sec ^-1 is preferably 1200 to 3000 Pa s, preferably 1500 to 2500 Pa s. It is more preferable to have
From the same point of view, the melt tension at 200° C. is preferably 300-1000 mN, more preferably 400-600 mN.
The above-mentioned "melt viscosity" and "melt tension" can be measured using a measuring instrument such as Capilograph Model 1D manufactured by Toyo Seiki Seisakusho Co., Ltd., which will be described later in the [Examples] section.

The resin sheet of the present invention may be single-layered or multi-layered. The resin constituting the core layer in the multilayer resin sheet is a resin having a total light transmittance of 80% or more as determined by JIS K7361-1:1997 by preparing a test piece with a thickness of 2 mm. A plastic resin can be used. From the viewpoint of satisfying that the total light transmittance of the resin sheet is 80% or more, the thermoplastic resin is preferably a resin that corresponds to "transparent plastic" known in JIS K 7361 (1997). . Specific examples of such thermoplastic resins include polystyrene resins, polypropylene resins, polycarbonate resins, thermoplastic polyester resins, cyclic olefin resins, and the like. Among them, polystyrene or methyl methacrylate-styrene copolymer can be preferably used from the viewpoint of being easily laminated with the surface layer by co-extrusion. When a resin comprising a methyl methacrylate-styrene copolymer is used as the thermoplastic resin, the content of units based on styrene or a styrene component is preferably 30 mol% or more, more preferably 50 mol% or more. , more preferably 70 mol % or more. The above thermoplastic resins may be used alone or in combination of two or more, but from the viewpoint of satisfying the total light transmittance of 80% or more, it is preferable to use them alone. The resin sheet of the present invention preferably contains 90% by mass or more of the thermoplastic resin, and more preferably contains only the thermoplastic resin.

The resin sheet of the present invention may be a multi-layered structure comprising a core layer and a surface layer laminated on one side of the core layer and forming the surface layer portion. It may be a multi-layer consisting of a surface layer forming a surface layer portion. In the case of a multilayer resin sheet, the thickness of the surface layer is preferably 50-500 μm, more preferably 100-300 μm. In the case of a multilayer resin sheet, the ratio of the thickness of the surface layer per side to the thickness of the core layer is preferably 2 to 10%, more preferably 3 to 6%.

When the resin sheet is a single-layer sheet, the surface layer portion of the resin sheet on which the fine unevenness is formed has a melt flow rate (temperature of 200° C., load of 5.00 kg) of 3 g/10 minutes or less, Moreover, it is preferably made of a branched polystyrene resin having a branched structure. On the other hand, when the resin sheet is a multilayer sheet comprising a core layer and surface layers laminated on both sides of the core layer and forming the surface layer portion, the surface layer has a melt flow rate (temperature of 200°C, load 5.00 kg) is 3 g/10 min or less, is made of a branched polystyrene resin having a branched structure, and is preferably formed with the above-described fine irregularities on both sides of the resin sheet.

In addition, the resin used in the resin sheet of the present invention may optionally contain additives such as antioxidants, coloring agents, fillers, slip agents (lubricants), anti-blocking agents, ultraviolet absorbers, and light stabilizers. can be contained within a range that does not impair its purpose and performance. From the viewpoint of facilitating the formation of fine unevenness, it is preferable that the additive is not contained in the surface layer portion of the resin sheet and is contained in a portion other than the surface layer portion.
However, it is important that the surface layer portion of the resin sheet of the present invention does not contain a light diffusing agent. In the present invention, without using a light diffusing agent in the surface layer of the resin sheet, fine unevenness having the above-mentioned specific arithmetic mean roughness is formed on the surface of the resin sheet immediately after extrusion, and the specific total light transmission It is made into a resin sheet exhibiting a modulus and a haze. Any part other than the surface layer of the resin sheet may contain a light diffusing agent. Since a resin sheet having a total light transmittance and a haze can be obtained, there is no need to use a light diffusing agent. From the above viewpoint, the amount of the light diffusing agent contained in the portion other than the surface layer portion of the resin sheet is preferably 3% by mass or less, more preferably 1% by mass or less, and 0.5% in the portion of the resin sheet other than the surface layer portion. % by mass or less is more preferable, and it is particularly preferable not to contain a light diffusing agent.

A method for producing the resin sheet according to the present invention includes an extrusion molding method such as a T-die molding method. For example, it can be produced by the apparatus conceptually shown in FIG.

In FIG. 1, a molten thermoplastic resin is extruded from an extruder 1 into a sheet, and after being taken out under pressure by a pinching roll 2, the sheet is slowly cooled on a plurality of linearly arranged transfer rolls 3, and cut by a cutting machine 4. Cut the sheet to the desired length.

A commonly used T-die can be used as the die of the extruder 1 to extrude the sheet. When molding a single-layer resin sheet, molten resin is extruded through a manifold through a lip outlet, which is a discharge port, to form a single-layer resin sheet. Multi-layered resin sheets can be molded by "co-extrusion" in which multiple resins are extruded at the same time. As a method, the "feed block method" that merges the resin in front of the T-die, and the "multi-manifold method" that spreads each single layer in the manifold and merges near the lip outlet, which is the discharge port of the T-die, etc. However, the manufacturing method is not limited in the present invention.

In the present invention, by adjusting the extrusion temperature and extrusion speed of the molten resin extruded from the extruder 1, a large number of fine irregularities are formed on the surface of the resin sheet immediately after being extruded from the die. These numerous fine irregularities are formed on both sides or one side of the resin sheet. Since these numerous fine irregularities are formed on the surface of the resin sheet immediately after being extruded from the die, it is considered to be a phenomenon due to melt fracture.

The extrusion temperature of the molten resin when it is extruded from the die is preferably 200-250°C.

The nipping roll 2 that nips the extruded resin sheet, adjusts the thickness, and picks up the resin sheet is a mirror-finished roll having an arithmetic average roughness of 0.1 μm or less. By adjusting the surface temperature of each of the pressure rollers, three pressure rollers 2a, 2b, and 2c in the illustrated embodiment, the fine irregularities formed on the surface of the resin sheet are not crushed. , its thickness is adjusted. In addition, when the resin sheet is pressed between the first roll 2a and the second roll 2b, the resin sheet is pressed between the first roll 2a and the second roll 2b so as not to crush the numerous fine irregularities formed on the surface of the resin sheet. The linear pressure when pressing with the second roll 2b is preferably 10 N/cm or less, more preferably 3 N/cm or less. The linear pressure means the force (N) per 1 cm in the length direction of the rolls when a pair of rolls are pressed against each other. Determined.

Any or all of the pinch rolls 2 are preferably cooled rolls. Further, when rolls are used after the resin sheet is sandwiched between the first roll 2a and the second roll 2b, these rolls are also preferably cooled rolls. Although the cooling mechanism of each roll is not particularly limited, for example, the roll has a double structure of an inner cylinder and an outer cylinder, and a cooling solvent is circulated between them to cool the roll surface. The temperature of the first roll 2a is preferably 50 to 70.degree. The temperature of the second roll 2b is preferably 80-100.degree. When the surface temperature of the roll is within the above range, the thickness of the resin sheet can be easily adjusted without crushing the numerous fine irregularities formed on the surface of the resin sheet.

In the present invention, after the resin sheet is pinched between the first roll 2a and the second roll 2b, the second roll 2b can hold the resin sheet to pick it up. The resin sheet can be cooled by letting the second roll 2b embrace the resin sheet and taking it over. Next, the resin sheet is taken off from the second roll 2b by the third roll 2c.

The resin sheet separated from the third roll 2c is then cooled on a plurality of transfer rolls 3 arranged linearly. Here, by slowly cooling the resin sheet in a flat state, a flat resin sheet having no optical distortion over the entire surface of the resin sheet can be obtained. At this time, if excessive take-up tension is applied in the flow direction of the resin sheet, optical distortion occurs in the flow direction of the resin sheet. Tension is adjusted.

The cooled resin sheet is cut into a desired size by the cutting machine 4 . A method such as scissors, a cutter, or a laser can be used for cutting. If necessary, a protective film made of polyethylene or the like can be attached to the surface of the resin sheet that has been cut into a product.

The resin sheet according to the present invention has the structure described above, does not use a light diffusing agent in the surface layer portion, forms specific fine unevenness on the surface, and is a resin sheet having a specific total light transmittance and haze. Therefore, the resin sheet can be manufactured at low cost and has good light diffusion performance.

Next, the resin sheet of the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is by no means limited to the following examples.

An extrusion apparatus conceptually shown in FIG. 1 was used.
In this device, a T-die (lip width: 130 mm, lip gap: 1.0 mm) is attached to the extruder 1, and three mirror-finished rolls (diameter: 160 mm, width: 350 mm) are used as the pressure rolls 2 with the same rotation axis. It is arranged so as to be high, and a transfer roll 3 and a cutting machine 4 are arranged on the downstream side thereof.
In the multi-layer device, a T-die (lip width: 300 mm, lip gap: 2.5 mm) is attached to the extruder 1, and three mirror-finished rolls (diameter: 195 mm, width: 700 mm) are used as the pinching rolls 2. They are arranged at the same height, and a transfer roll 3 and a cutter 4 are arranged on the downstream side.

The following materials were used as raw materials (thermoplastic resins).
(A) HIMETREN (=29% by weight): G9305 (=71% by weight)
・Shrinkage factor: 0.96
・Relative weight average molecular weight: 469,000 ・MFR (temperature 200°C, load 5.00 kg): 0.9 g/10 minutes ・Melt viscosity (temperature 200°C, shear rate 100 s ^-1 ): 1930 Pa s
・ Melt tension (200 ° C.): 540 mN
"HIMETREN" is branched polystyrene manufactured by JSP Co., Ltd. (shrinkage factor: 0.72, relative weight average molecular weight: 1,200,000, melt viscosity (temperature: 200°C, shear rate: 100 s ^-1 ): 1900 Pa s, Melt tension (200° C.): 1100 mN), “G9305” is a linear polystyrene manufactured by PS Japan. The raw material (A) is a mixed resin obtained by kneading and extruding "HIMETREN" and "G9305" in the above weight ratio with a single-screw extruder at 200°C. Using the mixed resin as the raw material (A), the physical properties were measured.
(B) HP780AN (branched polystyrene manufactured by DIC)
・Shrinkage factor: 0.71
・Relative weight average molecular weight: 479,000 ・MFR (temperature 200°C, load 5.00 kg): 1.2 g/10 minutes ・Melt viscosity (temperature 200°C, shear rate 100 s ^-1 ): 1840 Pa s
・ Melt tension (200 ° C.): 430 mN
(C) GX156 (branched polystyrene manufactured by PS Japan)
・Shrinkage factor: 0.90
・Relative weight average molecular weight: 433,000 ・MFR (temperature 200°C, load 5.00 kg): 1.8 g/10 minutes ・Melt viscosity (temperature 200°C, shear rate 100 s ^-1 ): 1650 Pa s
・Melt tension (200°C): 470 mN
(D) HP600ANJ (branched polystyrene manufactured by DIC)
・Shrinkage factor: 0.85
- Relative weight average molecular weight: 322,000 - MFR (temperature of 200°C, load of 5.00 kg): 5.0 g/10 minutes - Melt viscosity (temperature of 200°C, shear rate of 100 s ^-1 ): 1130 Pa·s
・Melt tension (200°C): 190 mN
(E) G9305 (linear polystyrene manufactured by PS Japan)
・Shrinkage factor: 1.0
・Relative weight average molecular weight: 356,000 ・MFR (temperature 200°C, load 5.00 kg): 1.5 g/10 minutes ・Melt viscosity (temperature 200°C, shear rate 100 s ^-1 ): 1510 Pa s
・Melt tension (200°C): 310 mN
(F) 680 (linear polystyrene manufactured by PS Japan)
・Shrinkage factor: 1.0
- Relative weight average molecular weight: 209,000 - MFR (temperature of 200°C, load of 5.00 kg): 7.0 g/10 minutes - Melt viscosity (temperature of 200°C, shear rate of 100 s ^-1 ): 960 Pa·s
・ Melt tension (200 ° C.): 70 mN

The "shrinkage factor" of each raw material was measured by the following methods.

収縮因子の重量平均値ｇｗは、ＧＰＣ－ＭＡＬＳ法を用いて次のように特定した。
ＧＰＣによりポリスチレン系樹脂の試料液の溶出クロマトグラムを得る。そして、溶出クロマトグラムの任意の区間ｉにおいて、ＭＡＬＳにより区間ｉにおけるポリスチレン系樹脂の収縮因子ｇｉが特定される。区間ｉにおけるポリスチレン系樹脂の濃度ｃｉは、市販の濃度検出器等を適宜用いて特定される。
これらの値から収縮因子の重量平均値ｇｗは、下記式（２）により求めた。

ＧＰＣ－ＭＡＬＳ法の測定機器は、島津製作所社製Ｐｒｏｍｉｎｅｎｃｅ ＬＣ－２０ＡＤ（２ＨＧＥ）／ＷＳシステム、Ｗｙａｔｔ Ｔｅｃｈｎｏｌｏｇｙ社製の多角度光散乱検出器 ＤＡＷＮ ＨＥＬＥＯＳ IIを用いて、溶離液：テトラヒドロフラン（ＴＨＦ）、流量１．０ｍｌ／ｍｉｎという条件で測定した。カラムとしては、東ソー社製ＴＳＫｇｅｌ ＨＨＲ－Ｈ×１本、ＴＳＫｇｅｌ ＧＭＨＨＲ×２本、を直列に接続して用いた。測定の解析は、Ｗｙａｔｔ社の解析ソフト ＡＳＴＲＡにより行い、スチレン系樹脂の収縮因子の重量平均値が求められた。 [Contraction factor]
As the contraction factor, the value measured by the GPC-MALS (multi-angle light scattering detector) method was used.
As shown in the following formula (1), the shrinkage factor g is the root-mean-square radius of gyration of a styrene resin having a branched structure <Rg ² > _B and the root-mean-square radius of gyration of a straight-chain styrene resin <Rg It is calculated as a ratio of ² > _L.

The weight average value gw of the contraction factor was determined using the GPC-MALS method as follows.
An elution chromatogram of a polystyrene resin sample liquid is obtained by GPC. Then, in an arbitrary interval i of the elution chromatogram, MALS specifies the shrinkage factor gi of the polystyrene resin in the interval i. The concentration ci of the polystyrene-based resin in the section i is specified by appropriately using a commercially available concentration detector or the like.
From these values, the weight average value gw of the shrinkage factor was determined by the following formula (2).

The GPC-MALS method is measured using a Prominence LC-20AD (2HGE)/WS system manufactured by Shimadzu Corporation, a multi-angle light scattering detector DAWN HELEOS II manufactured by Wyatt Technology, and an eluent: tetrahydrofuran (THF). Measurement was performed under the condition of a flow rate of 1.0 ml/min. As a column, TSKgel HHR-H (manufactured by Tosoh Corporation)×1 and TSKgel GMHHR×2 were connected in series and used. Analysis of the measurement was performed using Wyatt's analysis software ASTRA, and the weight average value of the shrinkage factor of the styrene-based resin was obtained.

[Relative weight average molecular weight]
The relative weight average molecular weight was measured by gel permeation chromatography analysis.
10 mg of resin sample was dissolved in 10 ml of tetrahydrofuran (THF), measured by gel permeation chromatography (GPC) analysis, and corrected with standard polystyrene.
The details of the GPC analysis conditions are as follows.
・Equipment used: GPC high-performance liquid chromatograph manufactured by GL Sciences Co., Ltd. ・Column: Column manufactured by Showa Denko K.K., trade names Shodex GPC KF-806, KF-805, and KF-803 are connected in series in this order and used.・Column temperature: 40°C
・Solvent: THF
・Flow rate: 1.0 mL/min ・Concentration: 0.15 w/v%
・Injection volume: 0.2 ml
・ Detector: UV-visible detector manufactured by GL Sciences Co., Ltd., trade name UV702 type (measurement wavelength 254 nm)
・Molecular weight range of calibration curve used for calculation of molecular weight distribution: 1.2×10 ⁷ to 5.2×10 ³

[MFR (melt flow rate)]
MFR was measured under conditions of a temperature of 200°C and a load of 5.00 kg according to the test method specified in JIS K7210 (2014).

[Melt viscosity]
The melt viscosity is a value obtained by measuring with a capilograph model 1D manufactured by Toyo Seiki Seisakusho.
Specifically, using a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice with a nozzle diameter of 1.0 mm and a length of 10.0 mm, the set temperature of the cylinder and orifice was set to 200 ° C., and a measurement sample was placed in the cylinder. (resin pellet) was filled. After filling, the piston was filled in the cylinder and melted by preheating for 4 minutes. During the preheating, the piston was temporarily pushed down to sufficiently remove air bubbles from the molten measurement sample. In addition, the amount of the measurement sample to be filled was set to a sufficient amount to secure 15 cc or more of the measurement sample after removing the air bubbles. After preheating, the sample was extruded from the cylinder with a piston so that the shear rate of the capillary portion was 100 s ^-1 , and the melt viscosity at that time was measured. Melt viscosities were measured for five measurement samples randomly collected from the raw material, and the arithmetic mean value of the measured values was taken as the melt viscosity of the raw material.

[Melt tension]
The melt tension is a value obtained by measuring with a capillograph model 1D manufactured by Toyo Seiki Seisakusho.
Specifically, using a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice with a nozzle diameter of 2.095 mm and a length of 8.0 mm, the set temperature of the cylinder and orifice is 200 ° C., and the required amount of the sample is After being placed in the cylinder and left for 4 minutes, the molten resin was extruded from the orifice at a piston speed of 10 mm/min in the form of a string. While increasing the take-up speed at a constant rate so that the speed reaches 200 m/min from 0 m/min, take the string-like material with the take-up roller, and measure the maximum tension immediately before the string-like material breaks. obtain. Here, the reason why the time required for the take-up speed to reach 200 m/min from 0 m/min is set to 4 minutes is to suppress thermal deterioration of the resin and improve the reproducibility of the obtained values.

Using the extrusion molding apparatus and raw materials described above, the resin sheets described in Examples 1 to 7, Comparative Examples 1 to 3, and Reference Example were produced.

Example 1: Using the mixed raw material of (A) above, extruding the resin temperature at 210 ° C. (melt viscosity: 1500 Pa s, melt tension: 320 mN), extruder 1 T die at a discharge rate of 20.4 kg / h More molten resin is extruded into a sheet, the extruded sheet is pinched by pinching rolls 2 to adjust the thickness, slowly cooled on transfer rolls 3, and cut by cutting machine 4 to obtain a thickness of 1.0 mm. , a resin sheet having a length of 600 mm and a width of 120 mm was obtained.
Example 2: A resin sheet was produced in the same manner as in Example 1, except that the branched polystyrene of (B) above was used and the extrusion resin temperature was 210°C (melt viscosity: 1500 Pa s, melt tension: 300 mN). Obtained.
Example 3: A resin sheet was produced in the same manner as in Example 1, except that the branched polystyrene (B) above was used and the extrusion resin temperature was 220°C (melt viscosity: 1200 Pa s, melt tension: 200 mN). Obtained.
Example 4: A resin sheet was produced in the same manner as in Example 1, except that the branched polystyrene of (B) above was used and the extrusion resin temperature was 250°C (melt viscosity: 600 Pa s, melt tension: 50 mN). Obtained.
Example 5: A resin sheet was produced in the same manner as in Example 1 except that the branched polystyrene of (C) above was used and the extrusion resin temperature was 205 ° C. (melt viscosity: 1500 Pa s, melt tension: 350 mN). Obtained.
Example 6: A resin sheet was produced in the same manner as in Example 1 except that the branched polystyrene of (B) above was used and the extrusion resin temperature was 210°C (melt viscosity: 1500 Pa s, melt tension: 300 mN). Obtained.
Example 7: Using the above (B) branched polystyrene as a surface layer (thickness: 0.2 mm), using the above (E) linear polystyrene as a core layer (thickness: 3.6 mm), extruding The resin temperature is 210 ° C. (melt viscosity: 1500 Pa s, melt tension: 300 mN), the molten resin is extruded into a sheet from the T die of extruder 1 at a discharge rate of 42.5 kg / h, and the extruded sheet is The resin sheet was nipped with a nipping roll 2 to adjust its thickness, slowly cooled on a transfer roll 3, and then cut by a cutter 4 to obtain a resin sheet having a thickness of 4.0 mm, a length of 900 mm and a width of 290 mm.
Comparative Example 1: A resin sheet was produced in the same manner as in Example 1 except that the branched polystyrene (D) was used and the extrusion resin temperature was 193°C (melt viscosity: 1500 Pa s, melt tension: 400 mN). Obtained.
Comparative Example 2: A resin sheet was prepared in the same manner as in Example 1 except that the linear polystyrene of (E) was used and the extrusion resin temperature was 200 ° C. (melt viscosity: 1500 Pa s, melt tension: 300 mN). got
Comparative Example 3: A resin sheet was prepared in the same manner as in Example 1, except that the linear polystyrene of (F) was used and the extrusion resin temperature was 185 ° C. (melt viscosity: 1500 Pa s, melt tension: 200 mN). got
Reference Example 1: The above (F) linear polystyrene was used as the surface layer (thickness: 0.2 mm), and the surface layer contained a light diffusing agent (Aica Kogyo Co., Ltd. Staphyloid (registered trademark) GSM-1261: weight average particle size 12 μm) is added so that the concentration is 10% by weight, and the above (E) linear polystyrene is used as the core layer (thickness: 3.6 mm). The extruded resin temperature is 250 ° C., the molten resin is extruded into a sheet from the T die of the extruder 1 at a discharge rate of 42.5 kg / h, and the extruded sheet is pinched by a pinching roll 2 to obtain a thickness. After being annealed on transfer rolls 3, it was cut by cutting machine 4 to obtain a resin sheet having a thickness of 4.0 mm, a length of 900 mm and a width of 290 mm.

For each resin sheet obtained in Examples 1 to 7, Comparative Examples 1 to 3, and Reference Example, "arithmetic mean roughness", "average length of roughness curve element", "total light transmittance" and "Haze" was measured respectively.
The measurement results are shown in Table 1.
The "arithmetic mean roughness", "average length of roughness curve element" and the like were measured by the following methods.

[Arithmetic mean roughness (Ra), mean length of roughness curve element (RSm)]
The arithmetic average roughness (Ra) and the average length (RSm) of the roughness curve element on the surface of the resin sheet are based on JIS B0601 (2013), with a cutoff λc = 0.8 and a measurement length = 8 mm. It was measured using a surface roughness measuring machine (Surfcorder SE1700α, surface roughness measuring machine manufactured by Kosaka Laboratory Co., Ltd.).
Specifically, the resin sheet obtained (the length in the width direction is the width of the obtained sheet) is randomly selected from the surface, and the full width in the width direction is divided into 5 equal parts, and each of the 5 equal parts Measurements were taken at the center of the position, and 5 measurements were obtained. The above operation was performed in the same manner at positions separated by 100 mm in the length direction of the resin sheet, and further measured values were obtained at five positions. The arithmetic average value of the values obtained at 10 locations was defined as the arithmetic average roughness (Ra) on the surface of the resin sheet and the average length (RSm) of the roughness curve elements. Also, the standard deviation of the values measured at 10 points to obtain the arithmetic mean roughness (Ra) was obtained. The standard deviation value was obtained from the square root of the unbiased variance.

[Total light transmittance, haze]
Randomly select from the surface of the obtained resin sheet (the length in the width direction is the width of the obtained sheet), divide the total width in the width direction into 5 equal parts, and about the center part of each position divided into 5 equal parts , total light transmittance in accordance with JIS K7361-1:1997, and haze in accordance with JIS K7136:2000, and five measurement values were obtained. The above operation was performed in the same manner at positions separated by 100 mm in the length direction of the resin sheet, and further measured values were obtained at five positions. The arithmetic mean value of the values obtained at 10 points was taken as the total light transmittance and the haze. A haze meter (NDH7000SP manufactured by Nippon Denshoku Industries Co., Ltd.) was used for the measurement.

In addition, the resin sheets obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated for their appearance according to the following criteria.
Good: total light transmittance is 80% or more and haze is 10% or more. x: haze is less than 10%.

The resin sheet according to the present invention does not use a light diffusing agent, forms specific fine irregularities on the surface, and is a resin sheet having a specific total light transmittance and haze. Since it becomes a resin sheet having good light diffusion performance, it can be suitably used as an indoor building material such as an indoor partition plate and a front plate of a cupboard, a display material, and the like.

REFERENCE SIGNS LIST 1 extruder 2 pinching roll 2a first roll 2b second roll 2c third roll 3 transfer roll 4 cutting machine

Claims (3)

A resin sheet formed by extrusion molding,
The resin sheet is a multi-layer sheet comprising a core layer and surface layers laminated on both sides of the core layer to form a surface layer portion . The fine unevenness of
The surface layer has a melt flow rate (temperature of 200° C., load of 5.00 kg) of 3 g/10 minutes or less, is made of a branched polystyrene resin having a branched structure, and does not contain a light diffusing agent,
The resin sheet has a thickness of 1 to 10 mm, a total light transmittance of 80% or more, and a haze of 10% or more. 2. The resin sheet according to claim 1 , wherein the fine irregularities have an average length of roughness curve elements of 300 [mu]m or less . 3. The resin sheet according to claim 1 , wherein the resin sheet has a thickness of 2 to 8 mm and a haze of 30% or more .

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