JP2001353765A - Die for extrusion-molding sheet and method for molding sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die for extrusion molding a sheet capable of manufacturing the sheet or a film having excellent surface properties by reducing an adhesion of a resin to a lower surface of a lip of the die or preventing a contact of an adherend with a molten resin. SOLUTION: The die for extrusion molding the sheet for extrusion molding a molten resin in a sheet-like state comprises an angle between a lower surface of a lip of an opposite side to a direction for drawing the molten resin extruded from the lip of the die and a lower surface of the lip for drawing the molten resin extruded from the lip of a range of 0 to 90 degrees and an angle between the lower surface of the lip of the opposite side for drawing the molten resin extruded from the lip of the die and a surface of an inner wall of a slit in the die of a range of 15 to 45 degrees. A method for molding the sheet using the die for extrusion molding comprises the steps of installing the lower surface of the lip of the opposite side to the direction for drawing the molten resin extruded from the lip of the die so as to substantially become horizontal, and extrusion molding the molten resin in the sheet-like state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die for extruding a sheet and a method for forming the sheet, and more particularly, to a die for extruding a sheet capable of producing a sheet or a film having excellent surface properties and using the same. The present invention relates to a sheet forming method.

[0002]

2. Description of the Related Art A sheet extrusion die has conventionally been used for the production of sheets and films, and a so-called flat die having a uniform lip opening over the entire width of the die is usually used. For example, a sheet is manufactured by extruding a molten resin from a flat die into a sheet, cooling the solid with a rotary cooling drum, and solidifying the molten resin. The film is extruded from a flat die into a molten resin, cooled by a rotary cooling drum, solidified, and the resulting sheet (unstretched sheet) is further stretched in the longitudinal or transverse direction to form a uniaxially stretched film. Or by stretching a non-stretched sheet in the machine direction and the transverse direction to form a biaxially stretched film.

[0003] In the production of sheets and films by the above-mentioned method, if the deposits on the lip portion of the flat die come into contact with the molten resin, streaky defects (referred to as "die streaks") appear on the surface of the obtained sheets or films. And the surface property of the product becomes a problem.

[0004] As a method of eliminating die streaks, for example, Japanese Patent Publication No. 37-6142, Japanese Patent No. 2570453, etc., a method of casting a molten resin on the top of a cooling drum, a method of inclining a die used for extrusion, a method of forming a lip. Methods using dies with different lengths have been proposed.

However, in the method of casting on the top of the cooling drum, the angle between the flow direction of the resin in the die and the direction in which the resin coming out of the lip is taken by the cooling drum becomes large.
It is not possible to sufficiently prevent the taken-in resin from coming into contact with foreign matter attached to the lower surface of the lip. In addition, in the method of inclining the die, the resin easily adheres to the lower surface of the lip opposite to the resin take-up direction, and the problem of the die streak cannot be solved. The method using a die having a different lip length also does not solve the problem because the resin opened earlier swells and adheres to the lower surface of the lip.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and reduces the resin adhesion on the lower surface of the lip of the die, and also prevents the contact between the adhered matter and the molten resin to improve the surface property. An object of the present invention is to provide a sheet extrusion die and a sheet forming method capable of producing an excellent sheet or film.

[0007]

An object of the present invention is to provide a die used for extruding a molten resin into a sheet according to the present invention, wherein the molten resin extruded from a lip of the die is taken off. The angle between the lower surface of the lip opposite to the direction in which the molten resin is extruded and the lower surface of the lip from which the molten resin extruded from the lip is taken is in the range of 0 to 90 degrees, and the molten resin extruded from the lip of the die is taken off. Wherein the angle between the lower surface of the opposite lip and the inner wall surface of the slit portion in the die is in the range of 15 to 45 degrees, and the formation of a sheet using the extrusion die described above. A method of forming a sheet, wherein a lower surface of a lip opposite to a direction in which molten resin extruded from a lip of a die is taken is substantially horizontal, and a molten resin is extruded into a sheet. It is achieved by.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a sheet extrusion die showing one embodiment of the present invention. FIG. 2 is a sectional view of a conventional die. 1 is a die body, 2 is a manifold,
Reference numeral 3 denotes a slit, 4 denotes a die lip, 5 denotes a die lip tip (the point at which the resin separates), 6 denotes a lip lower surface in a resin take-up direction side, 7 denotes a lip lower surface in a direction opposite to the resin take-up direction, and 8 denotes a thickness unevenness adjustment. The cartridge heater 9 has an angle between the lower surface of the lip opposite to the molten resin take-up direction and the inner wall surface of the slit portion in the die (the resin flowing surface in the die), and 10 has a lower surface of the lip in the resin take-up direction and the resin take-up direction. And the angle with the lower surface of the lip on the opposite side.

The die for sheet extrusion molding according to the present invention is a die used for extruding a molten resin into a sheet, wherein a lower surface of a lip opposite to a direction in which the molten resin extruded from a lip of the die is taken. And the angle between the molten resin extruded from the lip and the lower surface of the lip on the side from which the molten resin is taken out (hereinafter, may be abbreviated as “angle A”) is in the range of 0 to 90 degrees, and is extruded from the lip of the die. The angle (hereinafter, may be abbreviated as “angle B”) between the lower surface of the lip on the opposite side from which the molten resin is drawn and the inner wall surface of the slit portion in the die is in a range of 15 to 45 degrees.

When the sheet extrusion molding die of the present invention is used for sheet extrusion molding, the flow direction (flow surface) of the molten resin in the die and the time until the sheet-shaped molten resin exiting the lip is taken up by the cooling drum. The angle with the surface of the sheet can be reduced. As a result, the molten resin can be extruded smoothly, and since the lower surface 7 of the lip opposite to the resin take-up direction is substantially horizontal, it is possible to prevent the resin from adhering to this portion. Lip lower surface 6
Is substantially vertical, it is possible to prevent the attached matter at this portion from coming into contact with the sheet-like molten resin.

The sheet extrusion molding die of the present invention preferably has a die lip tip cross-sectional shape on the side opposite to the direction in which the molten resin is drawn, including a curved shape having a radius of curvature of 5 to 50 μm. This radius of curvature is 5 to 15 μm
Is particularly preferred. By setting the cross-sectional shape of the tip portion of the die lip within the above range, the portion where the molten resin separates from the lip is stabilized, and a film having more excellent surface properties can be manufactured.

In the die for sheet extrusion molding of the present invention, a film with good uniformity of the thickness in the width direction can be produced by further providing the means 8 for adjusting unevenness in the width direction of the product. As a means for adjusting the thickness unevenness, a means for adjusting the temperature by changing the flow rate by raising or lowering the temperature of the thermoplastic resin by a plurality of cartridge heaters provided in the die width direction is preferable, or adjustment by a motor drive method. Bolts, piezo actuators, heat bolts, hydraulic or electric actuators that deform the lip are also possible.

When a sheet is extruded using the sheet extrusion die of the present invention, the lower surface 7 of the lip opposite to the direction in which the molten resin extruded from the lip of the die is taken is substantially horizontal. It is preferable to extrude the sheet by setting it.

The die is preferably installed such that the lower surface 7 of the lip is at an angle of not more than 15 degrees with respect to the horizontal plane.
It is particularly preferred to install at an angle within degrees.

[0015]

The present invention will be further described with reference to the following examples.

Example 1 A sheet extrusion die having a width of 1.8 m shown in FIG. 1 (an angle 10 between a lower surface of a lip opposite to a direction in which molten resin is taken off and a lower surface of a lip on a side where molten resin is taken out). (Angle A) is 15 degrees, and polyethylene terephthalate is formed into a film using an angle 9 (angle B) of 30 degrees between the lower surface of the lip on the opposite side from which the molten resin is taken off and the inner wall surface of the slit in the die. The film was extruded, quenched and solidified by a rotating cooling drum to obtain an unstretched film, and the unstretched film was biaxially stretched to produce a biaxially stretched film. As a result of continuous production of the film for six days, adhesion of sublimates and the like was observed on the lower surface of the lip, but production was possible without generation of streaks.

Example 2 A biaxially stretched film was produced in the same manner as in Example 1 except that a die having an angle of 10 (angle A) of 0 degree was used. No muscle development was observed during 4.5 days of continuous production.

[Comparative Example 1] An angle 9 (angle B) between the lower surface of the lip on the opposite side from which the molten resin is drawn and the inner wall surface of the slit portion in the die is 90 as shown in FIG.
A) A biaxially stretched film was produced in the same manner as in Example 1 except that the film was used. As a result, the die streaks became noticeable after two days of continuous production, so production was stopped.

[Comparative Example 2] An example was used except that the die had an angle 9 (angle B) of 60 degrees between the lower surface of the lip on the opposite side from which the molten resin was taken off and the inner wall surface of the slit in the die. A biaxially stretched film was produced in the same manner as in Example 1. As a result, die streaks occurred after 2.5 days of continuous production, and no effect was exhibited.

[0020]

According to the die for sheet extrusion molding of the present invention,
It is possible to produce a sheet or film having excellent surface properties and small thickness unevenness, which can greatly contribute to improvement in productivity.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a sheet extrusion die according to the present invention.

FIG. 2 is a sectional view showing a conventional die.

[Explanation of symbols]

 1: Die body 2: Manifold 3: Slit 4: Die lip 5: Die lip tip (separation point) 6: Lower surface of lip in resin take-up direction side 7: Lower surface of lip opposite to resin take-up direction 8: Thickness adjustment Cartridge heater 9: Angle of resin flow 10: Angle of lower surface of lip in resin take-off direction

Claims (5)

[Claims] 1. A die used for extruding a sheet, wherein the lower surface of the lip is opposite to the direction in which the molten resin extruded into a sheet from the lip of the die is taken, and the lower surface of the lip is a side from which the molten resin is taken. Is in the range of 0 to 90 degrees, and the angle between the lower surface of the lip opposite to the direction in which the molten resin is drawn and the inner wall surface of the slit in the die is 15 degrees.
From 45 to 45 degrees. 2. A vertical cross-sectional shape of a tip portion of a die lip opposite to a direction in which a molten resin is drawn has a radius of curvature of 5 to 50 μm.
The sheet extrusion die according to claim 1, wherein the die has a curved shape in the range of m. 3. The sheet extrusion molding die according to claim 1, wherein a plurality of sheet thickness unevenness adjusting means are provided on the lip block of the die in a width direction of the die. 4. The sheet extrusion molding die according to claim 3, wherein the thickness unevenness adjusting means is a heating means for adjusting the temperature of the molten resin of the lip land. 5. A method for forming a sheet using the sheet extrusion die according to claim 1, wherein the lower surface of the lip opposite to the direction in which the molten resin extruded from the lip of the die is taken off. A sheet forming method in which a molten resin is extruded into a sheet by being installed horizontally.