JP3065787B2 - Method and apparatus for producing a textured sheet - Google Patents

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 melt-extruded crystalline thermoplastic resin sheet, and more particularly to a method and an apparatus for improving the texture 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 production method and a production apparatus are widely known in which a roll with a texture is arranged on one or both of the rolls (3), and the sheet is pressed with these rolls to obtain a textured sheet having a grain pattern on one or both sides of the sheet. Have been.

[0003]

In the method described above,
Crystalline thermoplastic resins such as polyethylene and polypropylene are less likely to transfer the grain pattern than amorphous thermoplastic resins such as polystyrene, and depending on the molding conditions, the transfer of the grain pattern may worsen, especially if the molding speed is increased. There is a problem that the graining property is extremely deteriorated and the productivity cannot be increased. In particular, the lower surface of the sheet has a problem that it is difficult to produce a textured sheet having a textured pattern on both sides because the textured pattern is less likely to be formed than the upper surface. The molding conditions under which the transfer of the grain pattern deteriorates include a case where the molding speed is high, a case where the sheet thickness is large, a case where the extrusion temperature is high, and a case where the roll temperature is high. The present invention solves the problem that the transfer of the grain pattern is deteriorated by the molding conditions, and that the grained sheet can be molded only under very limited molding conditions, and enables the molding of the grained sheet under wider molding conditions. It is an object of the present invention to provide a manufacturing method and a manufacturing apparatus that greatly improve productivity.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for producing a textured sheet of a crystalline thermoplastic resin.
Cooling is performed by injecting a gas having a melting point or lower than the melting point of the resin using an air knife or / and an air chamber on at least one sheet surface before the section where the first roll and the second roll are nipped. A method for producing a textured sheet, in particular, a method for producing a textured sheet, wherein the surface temperature of the sheet after passing through a section where the sheet is nipped by the first roll and the second roll is equal to or lower than the melting point of the thermoplastic resin. A method and a sheet manufacturing apparatus characterized in that after the die, an air knife or / and / or an air chamber is provided on at least one side of a section nipped by the first roll and the second roll.

[0005] The crystalline thermoplastic resin used as a raw material in the present invention may be any plastic that has the property of crystallizing and is softened by heating, and the most typical one is polypropylene. As other raw materials, all crystalline thermoplastic resins that can be formed into a sheet, such as high-density polyethylene, low-density polyethylene, ethylene copolymer, and polyamide, can be used.

The present inventor has studied in detail the relationship between the sheet surface temperature and the graining property, and has found that the sheet surface temperature has a close relationship with the graining property, and that the sheet from the die to the first roll or the second roll has a good relationship. The inventors have found that the sheet surface temperature can be easily lowered by injecting a gas having a temperature lower than the melting point of the crystalline thermoplastic resin onto the surface, thereby completing the present invention.

[0007]

The disappearance of the grain pattern is caused by insufficient cooling of the sheet surface by the first roll and the second roll. That is, in the case of manufacturing a double-sided grained sheet using the conventional grained sheet manufacturing apparatus (FIG. 1), the upper surface of the sheet (A)
When the sheet comes into contact with the first roll, the upper surface temperature of the sheet decreases, but when the sheet leaves the first roll, the surface temperature rises again due to heat inside the sheet. At this time, depending on the molding conditions, due to insufficient cooling of the first roll, the temperature of the upper surface of the sheet becomes higher than the melting point of the resin, so that the grain pattern disappears. Further, when the lower surface (a) of the sheet comes into contact with the second roll, the temperature of the lower surface of the sheet decreases, and the resin on the lower surface of the sheet crystallizes.

[0008] Due to insufficient cooling of the second roll, this crystallization does not occur in the section II (FIG. 1), and when it occurs in the section III (FIG. 1), the sheet shrinks with the crystallization. In the case of, the lower surface of the sheet in the semi-molten state moves on the second roll, and it is considered that the grain pattern disappears. In addition, by injecting low-temperature air onto the resin surface, the sheet temperature can be sufficiently reduced, and in a sheet manufacturing apparatus with a crystalline thermoplastic resin grain, preventing the disappearance of the grain pattern due to insufficient cooling, improving the graining property. Thus, the productivity of the textured sheet could be greatly improved. That is, using an air knife and / or an air chamber on the sheet surface from the die to the first roll and / or the second roll, the crystallization temperature of the resin or less,
The sheet surface can be sufficiently cooled by the first and second rolls by injecting a gas having a temperature of preferably 50 ° C. or less, more preferably 30 ° C. or less, and lowering the resin temperature before the sheet is nipped. .

In particular, when manufacturing a sheet with a double-sided embossed surface, although the side A in FIG. 1 is easy to be cooled, it is hard to be embossed. However, as shown in FIG. 2, when the sheet surface from the die to the second roll is cooled. Great effect. Further, the upper surface of the sheet immediately after passing through the section nipped by the first roll and the second roll may be cooled by an air knife or / and an air chamber.

[0010]

The present invention will be described in more detail with reference to the following examples. (Embodiments 1 to 3) FIG. 3 is a side view of a sheet manufacturing apparatus showing an embodiment of the present invention. In the apparatus shown in FIG. 3, an extruder manufactured by Tanabe Plastics Machine Co., Ltd. (40 mmφ, L / D
= 32), die (400 mm width), first to third rolls (2
(00 mmφ). As the first roll and the second roll, a roll with a grain (a mat roll having a grain depth of 70 μm, manufactured by Miyamori Metals, Ltd.) was used. Also,
The molding conditions were a die temperature of 230 ° C, a first roll temperature of 60 ° C,
At a second roll temperature of 60 ° C. and a third roll temperature of 30 ° C., the resin is polypropylene (Mn = 8.00 ×) manufactured by Showa Denko KK
10 ⁴ , Mw = 52.33 × 10 ⁴ , Mw / Mn = 6.
54, ρ = 0.90 g / cm ³ , melting point 160 ° C., crystallization temperature 110 ° C.). In this example, the air knife was mounted 10 cm below the die, connected to a friction blower (3.7 KW, maximum air flow 4.0 m ³ / min), and the air temperature was 30 ° C. The air outlet of the air knife was directed to the lower surface of the sheet from the die to the second roll.

Table 1 shows the surface roughness and surface condition of the sheet obtained by changing the material discharge amount and the take-off speed under the above conditions. For the surface roughness in the table, a ten-point average roughness Rz was determined according to JIS B0601-1982. The ten-point average roughness is the average of the altitudes of the top to fifth peaks measured in the direction of the vertical magnification from a straight line that is parallel to the average line and does not intersect the cross-sectional curve at the portion extracted by the reference length from the cross-sectional curve. The difference between the value and the average of the altitude of the valley bottom from the deepest to the fifth is expressed in μm. Therefore, when the graining property is poor, the ten-point average roughness is small because the sheet surface becomes almost flat. As is clear from Table 1, the surface condition of the sheet was good even when the take-up speed was high by jetting air from the air knife and hitting the sheet surface.

(Comparative Examples 1 to 3) The same operation as in Examples 1 to 3 was performed except that air was not injected from the air knife, but the surface condition of the sheet was not good.

[0013]

[Table 1]

[0014]

According to the manufacturing method using the manufacturing apparatus according to the present invention, a rise in the temperature of the sheet surface on the second roll can be suppressed, and the grain can be formed at a higher take-up speed than the conventional method. . The seat with the grain is a desk mat,
It can be used for stationery, VTR cases, bags, food containers and the like.

[Brief description of the drawings]

FIG. 1 is a side view of a conventional sheet production apparatus with a grain.

FIG. 2 is a side view of an embossed sheet manufacturing apparatus showing an embodiment of the present invention.

[Explanation of symbols]

1 Die 2 1st roll (roll with a grain) 3 2nd roll (roll with a grain or gloss) a Upper surface of the sheet a Lower surface of the sheet I Section of the sheet until the sheet is nipped from the die II Sheet Nipped section III Sheet section from immediately after the sheet is passed through the nip section until it leaves the second roll

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-203019 (JP, A) JP-A-58-153630 (JP, A) JP-A-62-267132 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B29C 59/00-59/18 B29C 47/00-47/96

Claims (3)

(57) [Claims] 1. A method for producing a textured sheet of a crystalline thermoplastic resin, comprising: at least one sheet surface after a die and before a section nipped by a first roll and a second roll;
A method for producing a textured sheet, comprising cooling the resin by injecting a gas having a temperature equal to or lower than the melting point of the resin using an air knife or / and an air chamber. 2. The embossed sheet according to claim 1, wherein the surface temperature of the sheet after passing the section where the sheet is nipped by the first roll and the second roll is lower than the melting point of the thermoplastic resin. Production method. 3. The sheet manufacturing apparatus according to claim 1, wherein an air knife and / or an air chamber is provided on at least one side of a section that is nipped by the first roll and the second roll after the die.