CN-122029025-A - Method and apparatus for stretching resin sheet

Abstract

The application provides a method and a device for stretching a resin sheet, which can obtain a resin film with uniform thickness more efficiently. A stretching device for a resin sheet according to an embodiment of the present application includes a roller disposed in a stretching region for stretching a polyethylene resin sheet in a conveying direction, a roller disposed in a relaxation region for relaxing the stretched resin sheet in a direction opposite to the conveying direction, and a control unit for controlling a speed difference between a peripheral speed of an adjacent roller and a peripheral speed of the roller so as to relax the resin sheet.

Inventors

• KUSHISAKI YOSHIYUKI
• Zhenjin Cheping
• NAKAMURA SO

Assignees

• 株式会社日本制钢所

Dates

Publication Date

20260512

Application Date

20241003

Priority Date

20231017

Claims (10)

1. 1. A method for stretching a resin sheet, comprising the steps of: a step of stretching the polyethylene resin sheet in a first direction by a first roller disposed in a stretching region, and And a step b of relaxing the stretched resin sheet in a direction opposite to the first direction by a second roller disposed in a relaxation area after the step a.
2. 2. The method for stretching a resin sheet according to claim 1, wherein, In the step b, the relaxation is performed by making the peripheral speed of the second roller of the adjacent first roller and second roller slower than the peripheral speed of the first roller.
3. 3. The method for stretching a resin sheet according to claim 2, wherein, The relaxation is performed at a ratio of 3 to 12% relative to the resin sheet after the stretching.
4. 4. The method for stretching a resin sheet according to claim 1, wherein, The relaxation is performed by maintaining the temperature of the second roll at a temperature that is capable of alpha-relaxation of the polyethylene.
5. 5. The method for stretching a resin sheet according to claim 4, wherein, And maintaining the temperature of the second roller at 45-100 ℃.
6. 6. A stretching apparatus for a resin sheet, comprising: a first roller disposed in a stretching region for stretching the polyethylene resin sheet in a first direction; A second roller disposed in a relaxation region for relaxing the resin sheet stretched in the stretching region in a direction opposite to the first direction, and A control portion that controls a circumferential speed of the first roller and a circumferential speed of the second roller to relax the resin sheet.
7. 7. The stretching device for a resin sheet as claimed in claim 6, wherein, The control section controls such that the peripheral speed of the second roller of the adjacent first roller and second roller is slower than the peripheral speed of the first roller.
8. 8. The stretching device for a resin sheet as claimed in claim 7, wherein, The control unit controls the circumferential speeds of the first roller and the second roller so as to relax at a ratio of 3 to 12% relative to the stretched resin sheet.
9. 9. The stretching device for a resin sheet as claimed in claim 6, wherein, The control section controls to maintain the temperature of the second roller at a temperature at which alpha relaxation can be performed on the polyethylene.
10. 10. The stretching device for a resin sheet as claimed in claim 9, wherein, The control part controls to keep the temperature of the second roller at 45-100 ℃.

Description

Method and apparatus for stretching resin sheet Technical Field The present invention relates to a method and an apparatus for stretching a polyethylene resin sheet. Background As a method for producing a resin film, a method is known in which a pellet as a raw material is melted by an extruder, and the obtained molten resin is extruded into a sheet form from an extrusion molding die (T die) to produce a resin film. Further, in order to form a desired thickness, shape, or the like as needed, a sheet-like resin sheet is stretched by sequential biaxial stretching in which longitudinal stretching in the longitudinal direction (traveling direction) of the resin sheet and transverse stretching in the transverse direction (direction orthogonal to the traveling direction) after the longitudinal stretching are performed via a plurality of rollers (for example, refer to patent document 1 (japanese patent application laid-open No. 2021-54030)). Here, the longitudinal stretching device for longitudinal stretching uses a plurality of heated rollers and stretches the resin sheet in the longitudinal direction (traveling direction) by using the difference in circumferential speeds of the rollers. After this longitudinal stretching, the transverse stretching is performed as the next step while maintaining the stretched state. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2021-54030 Disclosure of Invention Problems to be solved by the invention Here, when a crystalline resin such as polyethylene is used as a raw material, a strain may be generated by orienting molecules in a specific direction during stretching (elongation) due to a characteristic that a shrinkage ratio during molding tends to be large. If the strain is directly cooled and fixed, the strain becomes a stress and remains in the resin sheet (residual stress), and when the resin sheet is stretched in the transverse direction thereafter, the initial load becomes large, and there is a possibility that defects such as a decrease in the thickness uniformity of the resin film and deterioration in physical properties may occur, and the resin sheet cannot be efficiently produced. Accordingly, a stretching method and a stretching apparatus for a resin sheet capable of obtaining a resin film having a uniform thickness more efficiently have been desired. Other problems and novel features will become apparent from the description and drawings of the specification. Means for solving the technical problems According to one embodiment, the method for stretching a resin sheet includes a step of stretching a polyethylene resin sheet in a conveying direction by a roller disposed in a stretching region, and a step of relaxing the stretched resin sheet in a direction opposite to the conveying direction by a roller disposed in a relaxing region. Here, it is preferable that the relaxation is performed by making the circumferential speed of the roll in the relaxation region slower than the circumferential speed of the roll in the stretching region at the adjacent roll in the stretching region and roll in the relaxation region. Effects of the invention According to one embodiment, a method and an apparatus for stretching a resin sheet, which can more efficiently obtain a resin film having a uniform thickness, can be provided. Drawings Fig. 1 is a schematic view showing the structure of an extrusion molding system having a stretching apparatus according to an embodiment. Fig. 2 is a schematic diagram showing the structure of the stretching apparatus according to the embodiment. Fig. 3 is a graph showing the processing conditions (roller temperatures) at the time of stretching in examples and comparative examples of the present embodiment. Detailed Description An embodiment will be described in detail below with reference to the drawings. In all the drawings referred to for the purpose of describing the embodiments, the same reference numerals are given to the same or substantially the same functional components and the like. In addition, the description of the components and the like described once is not repeated in principle. < Extrusion System > Before explaining the stretching method and the stretching apparatus according to the present embodiment, a schematic configuration of an extrusion molding system including the stretching apparatus will be described first. Fig. 1 is a schematic diagram showing an example of a configuration of a system for producing a resin film including a stretching apparatus. Wherein S1 is a double-shaft mixing extruder, S2 is a T die, S3 is a material roll cooling device (CAST device), S4 is a longitudinal stretching device (MD device), S5 is a transverse stretching device (TD device), and S6 is a winding device. For example, a resin material (pellets) is added to the raw material supply portion Ta of the twin-screw kneading extruder S1 of fig. 1, and the mixture (molten resin) is extruded from the sli