JPS634771B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a double-sided matte film or sheet. Currently, thermoplastic resin films are used for general packaging,
Sheets are widely used for food packaging, agricultural materials, etc., and sheets are widely used for civil engineering and construction, food container trays, agricultural materials, etc. In recent years, the quality of these films or sheets has improved,
The trend towards higher functionality and specialization has become stronger, and the need for double-sided matte coating has increased as a way to achieve this goal. A thermoplastic resin film or sheet that has been matted on both sides can prevent blocking, surface crazing, etc., and has the function of improving its texture compared to non-matting. There is. Conventionally, as a method for manufacturing double-sided matte sheets that meet these demands, a method of blending additives has been used. For example, to prevent blocking and impart slipperiness, higher fatty acid metal salts such as calcium stearate and zinc stearate, oleic acid amide,
In addition to higher fatty acid amides such as erucic acid amide and stearic acid amide, phosphoric acid esters, glycerin esters, and waxes were blended as additives. Furthermore, in order to prevent surface crazing, a method of flattening the surface by adding a large amount of an inorganic filler, a different type of thermoplastic resin, a crosslinking substance of the same type or a different type, etc. is used. However, in order to exhibit sufficient effects, a large amount of additives must be blended, resulting in a decrease in compatibility with the resin. Further, these additives only exhibit their effects when they are present in the surface layer, but conversely, their presence in the surface layer has caused problems such as a decrease in suitability for secondary processing. Furthermore, the type and amount of additives must be changed depending on the resin and its intended use, resulting in complicated manufacturing. As another example, a method has been proposed in which the surface of molten resin is treated with steam, but this method has problems such as complicated manufacturing and adhesion of moisture to the resin surface, making it unsuitable for some applications. . Furthermore, there is also a method in which both sides are matted by pressing with a metal grain roll that has been completely matt-plated. However, rolls with completely matte plating are expensive to manufacture, and the plating parts are subject to severe wear and damage due to use.Not only can they not withstand long-term use, but the plating may peel off in some areas. Even if re-plating was performed, there were drawbacks such as problems with the thickness and thickness accuracy of the entire plating. In order to improve this, a method has been adopted in which the surface of the pressure roll is coated with rubber and pressed. Alternatively, the sheet may become wrapped around the pressure roll, resulting in loosening of the film or sheet feed, incomplete matting, and other problems that prevent the work from proceeding smoothly. As a result of intensive research to solve these problems, the present inventors have found that the quality can be improved by pressing the roll surface with a pair of rolls coated with rubber or filler-containing rubber. The present invention was completed based on the discovery that it is possible to produce a uniform, low-cost, double-sided matte film or sheet with good productivity. That is, a thermoplastic resin film or sheet melt-extruded from an extruder is coated with a cooling roll and a pressure roll, which are coated with rubber or filler-containing rubber, and at least one of the rolls is heated. The present invention provides a method for producing a double-sided matte film or sheet, which is characterized by pressing using a roll coated with rubber containing a filler. In the present invention, the rubber or filler-containing rubber may be synthetic rubber such as styrene-butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber, silicone rubber, or natural rubber, but silicone rubber, Chloroprene rubber or chlorosulfonated polyethylene rubber is preferred. The filler to be added to the rubber is preferably one having sufficient heat resistance and strength, and preferably silica or a compound containing silica as a main component, such as silica, talc, clay, silica sand, glass fiber, and glass beads. The average particle diameter of the filler can be appropriately selected depending on the purpose of matting both sides as long as it is in the range of 1.5 to 150 μm, but an average particle diameter of 5 to 100 μm is particularly preferred.
If the average particle diameter is less than 1.5 μm, a sufficient matting effect cannot be obtained, and if it exceeds 150 μm, although a matting effect can be obtained, problems such as holes in the film or sheet may occur. The blending ratio of the filler to the rubber may be in the range of 5 to 50% by weight, and is particularly preferably 5 to 20% by weight. If it exceeds 50% by weight, the compatibility between the rubber and the filler will be poor and the processability will be poor, so when coated on a roll, the unevenness will become severe and the film will break. Furthermore, the rubber or filler-blended rubber in the present invention preferably has a rubber hardness of 50 to 70 degrees (JIS K-6301). If the hardness exceeds 70 degrees, it is too hard and may cause holes or not be sufficiently matte. If the hardness is less than 50 degrees, it is too soft and cannot be matted. Regarding the thickness of the rubber layer coated on the roll,
0.5 to 5 mm for cooling rolls, 0.5 mm for press rolls
~60mm is preferred. If the thickness is less than 0.5 mm, sufficient matteness cannot be obtained. A cooling roll thickness exceeding 5 mm is not preferable because sufficient cooling cannot be achieved. The combination of the rubber coating the roll or the filler-containing rubber and the cooling roll or press roll can be freely selected depending on the intended use. Further, the pressure roll may be coated either directly on the metal surface of the roll or additionally coated on the surface of a known rubber coating. The resin applicable to the method for producing the double-sided matte film or sheet of the present invention may be a homopolymer, a copolymer, a graft polymer, or a blend thereof as long as it is a thermoplastic resin. This method can also be applied to the production of single-layer films or to the production of coated films by coextrusion. Depending on the use, these thermoplastic resins may contain conventional compounding agents such as colorants, fillers, and antioxidants. Further, the thickness of the film or sheet can be used in a wide range of 20 to 300 μm. As described above, according to the present invention, it is possible to obtain a film or sheet that has excellent matte properties on both sides and is uniform in quality. The present invention will be further explained below with reference to Examples.
It is not limited to this. Examples 1 to 12, Comparative Examples 1 to 5 Rubber compounds were prepared using the fillers and amounts shown in Table 1 based on 100 parts by weight of silicone rubber, 3 mm for the cooling roll and 400 mm for the press roll.
The coating was applied to a thickness of . The thermoplastic resin was produced using an extruder with a cylinder diameter of 90 mm (L/D=29, C/R=
4.6), a double-sided matte film or sheet was produced by melt extrusion at a T-die temperature of 250 to 290°C. The evaluation of the double-sided matte property is also shown in Table 1. The evaluation criteria are as follows. ◎...Very good matte finish on both sides〇...Good matte finish on both sides△...Not matte on both sides ×...Perforations etc. occur

[Table] The hardness of the rubbers of Examples 1 to 12 and Comparative Examples 1 to 5 is 61, 60, 59, 65, 65, 65, 65, 65, 65, respectively.
They were 65, 61, 61, 63, 64, 64, 77, 77. Examples 13-14 The coating rubber for the cooling roll and press roll is 3 mm for the cooling roll and 30 mm for the press roll using the combinations shown in Table 2.
A double-sided matte film was produced using a low density polyethylene film coated with a thickness of 50 μm.
Table 2 shows the evaluation of the matte property on both sides.

[Table] Examples 15, 16 100 parts by weight of chloroprene rubber (Example 15) or chlorosulfonated polyethylene rubber (Example 16) is mixed with 10 parts by weight of silica sand with an average particle size of 50 μm, and the rubber hardness is 60 degrees. The cooling roll is coated with 2mm, the pressure roll is coated with 20mm, and the thickness is 50μm.
A double-sided matte film was obtained using a low-density polyethylene film. The resulting film had good matte properties on both sides.

Claims (1)

[Scope of Claims] 1. A thermoplastic resin film or sheet melt-extruded from an extruder is processed using a pair of cooling rolls and pressure rolls coated with rubber or filler-containing rubber. 1. A method for producing a double-sided matte film or sheet, characterized in that at least one of the rolls is coated with a rubber coated with 5 to 50% by weight of a filler having an average particle diameter of 1.5 to 150 μm. 2. The manufacturing method according to claim 1, wherein the filler is selected from silica or a compound containing silica as a main component.