JPH05301270A - Method and apparatus for manufacturing textured sheet - Google Patents

Abstract

(57) [Summary] (Corrected) [Purpose] In the production of textured sheets, the objective is to enable the formation of textured sheets under a wider range of molding conditions than before, and to greatly improve productivity. In the method for producing a textured sheet of a crystalline thermoplastic resin, an air knife or / and an air chamber is used on the sheet surface immediately after passing a section nipped by the first roll 2 and the second roll 3, A method for producing a textured sheet and an apparatus therefor, which comprises cooling by injecting a gas having a melting point of the resin or lower. [Effect] The graininess was good, and the production amount could be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing a crystalline thermoplastic resin sheet to be melt extruded, and more particularly to a method and an apparatus for enhancing the graininess of the resin sheet.

[0002]

2. Description of the Related Art As shown in FIG. 1, when a conventional thermoplastic resin is melt-extruded by an extruder through a die (1) to produce a textured sheet, a first roll (2) and a second roll (2) are used.
A manufacturing method and a manufacturing apparatus for obtaining a textured sheet having a textured pattern on one side or both sides of the sheet by arranging a textured roll on one or both of the rolls (3) and pressing the sheet with these rolls are widely known. Has been.

[0003]

SUMMARY OF THE INVENTION In the above method,
Compared to amorphous thermoplastics such as polystyrene, crystalline thermoplastics such as polyethylene and polypropylene are less likely to transfer the embossed pattern, and depending on the molding conditions, the transfer of the embossed pattern worsens, especially when the molding speed is increased. There is a problem that the graininess is extremely deteriorated and the productivity cannot be increased. The molding conditions under which the transfer of the embossed pattern is deteriorated include a high molding speed, a thick sheet thickness, a high extrusion temperature, and a high roll temperature. The present invention solves the problem that the transfer of the embossed pattern is deteriorated by the molding conditions, and the textured sheet can be molded only under extremely limited molding conditions, and enables the molding of the textured sheet under a wider molding condition, It is an object of the present invention to provide a manufacturing method and a manufacturing apparatus that significantly improve productivity.

[0004]

SUMMARY OF THE INVENTION In the above-mentioned method for producing a textured sheet of crystalline thermoplastic resin, an air knife or an air knife is formed on the sheet surface immediately after passing through a section where the first roll and the second roll are nipped. And / or an air chamber is used to cool the resin by injecting a gas having a temperature not higher than the melting point of the resin, in particular, a surface temperature of the sheet after passing through a section where the sheet is nipped. To a melting point of the thermoplastic resin or less, and a sheet manufacturing apparatus characterized in that an air knife or / and an air chamber is provided immediately after the first roll and the second roll. To be done.

The crystalline thermoplastic resin used as a raw material in the present invention may be any plastic which has the property of crystallizing and is softened by heating, and the most typical one is polypropylene. As other raw materials, it is possible to use all crystalline thermoplastic resins that can be formed into sheets, such as high-density polyethylene, low-density polyethylene, ethylene copolymer, and polyamide.

As a result of a detailed study of the relationship between the sheet surface temperature and the wrinkle property, the present inventor has found that the sheet surface temperature and the melting point of the crystalline thermoplastic resin have a close relationship with the wrinkle property. The present invention has been completed by finding that the sheet surface temperature can be easily lowered by injecting a gas having a melting point of the crystalline thermoplastic resin or less onto the sheet surface immediately after passing through the section nipped by the first roll and the second roll. It has come to do.

[0007]

FIG. 2 is a conventional grained sheet manufacturing apparatus (FIG. 1).
It is a temperature state figure of the upper surface (a) of a sheet in the case of. The sheet extruded from the die is wound around the second roll and conveyed after passing through a section where the first roll and the second roll, both of which are the textured rolls, are nipped. The temperature of the upper surface of the sheet cooled by the first roll after passing through the section nipped by the first roll and the second roll again rises due to the heat inside the sheet (A). When the take-up speed is increased (B), the time during which the upper surface of the sheet is in contact with the first roll is shortened and the cooling is insufficient, so that the temperature of the upper surface is greatly increased. When the thickness of the sheet is increased (C), the heat from the inside of the sheet becomes large, and the temperature rise of the upper surface becomes large. In addition, when the upper surface temperature reaches or exceeds the melting point of the resin under molding conditions such that the upper surface temperature becomes high, the resin melts and the viscosity decreases again, so that the grain pattern transferred by the first roll disappears. It was found that they would end up. In particular, the crystalline thermoplastic resin has a large rise in the surface temperature due to the heat generated by crystallization, and the viscosity sharply decreases during melting, so that the wrinkle pattern tends to disappear.

Further, it has been found that the temperature rise on the sheet surface can be sufficiently suppressed by injecting low-temperature air onto the resin surface, so that in the sheet manufacturing apparatus with a grain of crystalline thermoplastic resin, the grain surface due to the melting of the sheet surface is used. It was possible to prevent the disappearance of the pattern, improve the texture, and significantly improve the productivity of the textured sheet. That is,
An air knife or / and an air chamber is used on the sheet surface immediately after passing through the section nipped by the first roll and the second roll, and the temperature is below the crystallization temperature of the resin, preferably below 50 ° C, more preferably below 30 ° C. By injecting the above gas, it is possible to suppress an increase in the upper surface temperature of the sheet.

FIG. 3 is a side view of a sheet manufacturing apparatus showing an embodiment of the present invention. In FIG. 3, (4) is an air knife, which is directed to the sheet surface immediately after the section where the first roll and the second roll are nipped. FIG. 4 compares the temperature state diagrams of the upper surface of the sheet when the manufacturing apparatus of FIG. 3 is used (D) and when the conventional manufacturing apparatus (FIG. 2) is used (E). The sheet extruded from the die (1) is
Only the first roll or both pass through a section where the first and second rolls are wrinkled rolls and move to the second roll, whereby the wrinkles on the wrinkled roll are transferred at the same time as being cooled. .. At this time, the upper surface of the sheet is cooled by the first roll, passes through the section where the sheet is nipped, and then leaves the first roll. At this point, the temperature of the upper surface of the sheet rises due to the heat from the inside of the sheet, but by injecting cold gas with an air knife onto the upper surface of the sheet immediately after leaving the first roll, the upper surface temperature is Since the rise is suppressed and the cooling rate is increased, it is possible to prevent disappearance of the grain pattern due to remelting of the upper surface.

[0010]

EXAMPLES The present invention will be described in more detail below with reference to examples. (Examples 1 to 3) In the apparatus shown in FIG. 3, an extruder manufactured by Tanabe Plastics Co., Ltd. (40 mmφ, L / D = 3) was used.
2), die (width 400 mm), first to third rolls (radius 1
The sheet was formed by using (00 mm). The first roll has a textured roll (matte roll with a texture depth of 70 μm,
(Miyamori Metal Works, Ltd.) was used. The molding conditions are a die temperature of 230 ° C and a first roll temperature of 60 ° C or 30.
° C., the second roll temperature 60 ° C. or 30 ° C., at a third roll temperature 30 ° C., the resin Showa Denko KK polypropylene ^{(Mn = 8.00 × 10 4,} Mw = 52.33 × 10
⁴ , Mw / Mn = 6.54, ρ = 0.90 g / cm ³ ,
Mp 160 ° C.) was used. In this example, the air outlet of the air knife is attached at a position 10 cm from the point where the sheet separates from the first roll, and is connected to a friction blower (3.7 KW, maximum air volume 4.0 m ³ / min), The air temperature was 30 ° C. Table 1 shows the surface roughness and surface condition of the sheets obtained by changing the raw material discharge rate and the take-up speed under the above conditions. For the surface roughness in the table, the ten-point average roughness Rz was determined according to JIS B0601-1982. Ten-point average roughness is the average of the elevations from the highest to the fifth summit measured in the direction of longitudinal magnification from a straight line that does not cross the cross-section curve and is parallel to the average line in the part where the reference length is extracted from the cross-section curve. The difference between the value and the average value of the valley bottom elevations from the deepest to the fifth is expressed in μm. Therefore, when the graininess is poor, the sheet surface approaches a flat surface, and the ten-point average roughness becomes small. As is clear from Table 1, the surface condition of the sheet was good even when the take-up speed was high by injecting air from the air knife to hit the surface of the sheet.

(Comparative Examples 1 to 3) The same operations as in Examples 1 to 3 were carried out except that the air was not jetted from the air knife, but the surface condition of the sheet was not good.

[0012]

[Table 1]

[0013]

By the manufacturing method using the manufacturing apparatus according to the present invention, the rise of the temperature of the sheet surface on the second roll is suppressed, and it becomes possible to form the grain at a higher take-up speed than the conventional method. .. Desk mat with textured sheet,
It can be used for stationery, VTR cases, bags, food containers, etc.

[Brief description of drawings]

FIG. 1 is a side view of a conventional textured sheet manufacturing apparatus.

FIG. 2 is a temperature state diagram of an upper surface of a sheet when a conventional sheet manufacturing apparatus with a texture is used.

FIG. 3 is a side view of a wrinkled sheet manufacturing apparatus showing an embodiment of the present invention.

FIG. 4 is a temperature state diagram of the upper surface of the sheet when using the textured sheet manufacturing apparatus showing the embodiment of the present invention.

[Explanation of symbols]

1 Die 2 1st roll (texture roll) 3 2nd roll (texture roll or glossy roll) a Sheet top surface I Sheet section from die to sheet nip Section II Sheet nip section III A section of the sheet from immediately after passing the section where the sheet is nipped until it is separated from the second roll A In the normal case B When the take-up speed is increased C When the thickness of the sheet is increased D With the wrinkled sheet manufacturing apparatus of the present invention When using E When using the conventional sheet manufacturing device with a texture

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nao Takeuchi 3-2 Chidori-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Akira Kawasaki Plastic Research Laboratory

Claims (3)

[Claims] 1. A method for producing a textured sheet of a crystalline thermoplastic resin, wherein an air knife or / and an air chamber is used on the sheet surface immediately after passing a section nipped by the first roll and the second roll, A method for producing a textured sheet, which comprises cooling by injecting a gas having a melting point of the resin or lower. 2. The method for producing a textured sheet according to claim 1, wherein the surface temperature of the sheet after passing through the section where the sheet is nipped is set to be equal to or lower than the melting point of the thermoplastic resin. 3. A sheet manufacturing apparatus comprising an air knife and / or an air chamber immediately after the first roll and the second roll.