JPS6255491B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is directed to a method for producing an oriented thermoplastic resin film that imparts orientation to a tubular thermoplastic resin film extruded from an annular die to increase the strength in the stretching direction of the resin film. The present invention relates to a method for producing a resin film. Stretched films of thermoplastic resins have traditionally been used in the field of vertically oriented binding cords for general packaging, yarns for knitting and weaving bags such as rice and wheat bags, fertilizer bags, and straw ropes and juutes. etc. is used. In addition, obliquely oriented films are being used in the field of heavy packaging bags as high-strength films by laminating them so that the orientation directions intersect. One method of obtaining such a vertically oriented film or obliquely oriented film is to use a molding device having an annular die and one or two mandrels provided downstream of the annular die, and to produce a tubular film extruded from the annular die. There are known methods in which the material is stretched as it is, or in which relative motion is applied to two mandrels. However, in the above-mentioned fields of use, the required film performance (eg, strength, elongation) differs depending on the application, and it is necessary to change the degree of stretching of the film accordingly. In the method for producing an oriented film as described above, the stretching degree (strength) of the thermoplastic resin film can be changed by changing the molding speed (stretching speed) or resin temperature from the molding side, and from the resin side there are two methods: Methods such as using raw materials with different densities or molecular weight distributions have been adopted. However, the key to changing the molding speed is molding stability (especially at high speeds).
In addition, the range of variable molding speed is narrow, and high-strength products need to be produced at high speeds, while low-speed products lack the stability of production that would be achieved if they were produced at low speeds. Regarding the method of changing the resin temperature, if the temperature is high, the bubbles become unstable, and if the temperature is low, the resin pressure increases, forcing production at low speeds, resulting in a lack of stability in molding and production. On the other hand, using different resins with different densities or molecular weights depending on the required strength makes changing the resin complicated, and the range of variation is narrow, which also requires changing the molding conditions. have. Therefore, the present inventors conducted intensive studies on a method of changing the strength of the film without frequently changing the molding speed, molding temperature, resin, etc., and as a result, completed the present invention. That is, the present invention comprises an extruder, an annular die for forming resin supplied from the extruder into a tubular resin film, a cooling mandrel (hereinafter simply referred to as mandrel) provided on the downstream side of the annular die, and A stretching disk is provided on the upstream side of the mandrel, and the running angle of the tubular resin film extruded from the annular die is changed by the peripheral portion of the stretching disk, and a tensile force is applied to the film that has passed through the mandrel to form a tubular resin film. In a method for manufacturing an oriented thermoplastic resin film by imparting orientation to the film, the peripheral part of the stretching disk is set apart from the mandrel, and the stretching disk has an angular edge on the die side, and the edge on the die side has a square edge. At least two types of stretching disks selected from the group consisting of a stretching disk with radius and a stretching disk whose peripheral surface is coated with resin are prepared, and the cooling mandrel and the stretching disk are placed inside the tube of the tubular resin film. The present invention provides a method for producing an oriented thermoplastic resin film, which comprises extruding a tubular resin film as described above, and producing resin films having different physical properties by selecting a stretching disk. According to a preferred embodiment of the present invention, at least two or more types of mandrels having different peripheral roughnesses are prepared (generally, only the peripheral surface of the mandrel needs to be replaced), and one of these mandrels and By appropriately combining one of the stretching disks described above, oriented films having different strengths can be manufactured. In the present invention, the peripheral portion of the stretching disk is placed at a distance from the mandrel, thereby creating an air pocket between the stretching disk and the mandrel,
Effects as described later can be obtained. It is preferable that the stretching disk is cooled to an appropriate temperature, and therefore it is sufficient to place it in close contact with the mandrel, leaving only the periphery apart from the mandrel, and for this purpose, the periphery of the mandrel may be cut out. Bye. FIG. 4 shows the apparatus used by the present inventors in the experiment. Annular die 1 for forming resin supplied from an extruder (not shown) into a tubular resin film F
Next, the air ring 2 blows out air to cool the tubular resin film F, and the first air ring 2 is further downstream thereof.
A mandrel 3 is provided. The first mandrel 3 is provided with a vacuum slit 3a for adsorbing the tubular resin film F, and a hard chrome satin plating is applied to the film contacting surface of the peripheral surface.
The first mandrel 3 is provided with a stretching disk 4 on the upstream side of the mandrel 3 in close contact with the mandrel 3, with an air reservoir 5 formed at a distance from the mandrel 3 only on its peripheral surface. A guide plate (width drop prevention plate) 6 is provided downstream of the mandrel 3, and further downstream thereof a second mandrel 7 having a vacuum slit 7a for adsorbing the tubular resin film F. As in the conventional method, the tubular resin film F formed by the annular die 1 is stretched using pinch rolls (not shown) to obtain a longitudinally stretched film. At this time, by relatively moving the die, the first mandrel 3, and the second mandrel, it is possible to impart oblique orientation to the tubular resin film F. When forming a film using such a device, the shape or material of the film contacting surface (die side) of the stretching disk may be an angular shape (90° or larger angle), a shape with rounded edges, or a shape with rounded edges. The effects of changing the shape to one coated with a resin (fluororesin or thermosetting resin) or one with a roughened surface in these shapes are shown below. Also, the effects of changing the roughness of the film contact surface of the mandrel and the effect of increasing the distance between the peripheral edge of the stretching disk and the mandrel will be discussed below. () Shape, material and effects of stretched disks (1) If the edges are rounded or coated with a resin with low frictional resistance such as fluororesin, the degree of stretching will be low and the strength will be low, but the elongation will be low. A large film can be obtained. A similar tendency can be observed if the film contact surface is made smaller (the land is shorter) or the peripheral surface is made rougher to reduce the frictional resistance. However, the radius of the edge of the stretched disk is preferably 5 mmR or less. 5mmR
It is difficult to stretch with a stretched disk that exceeds (2) By using a square stretching disk, a film with high strength and low elongation can be obtained. A similar effect can also be achieved by making the land longer or making the peripheral surface closer to a smooth surface. However, the land length of the stretched disk is preferably 5 mm or less; if it exceeds 5 mm, it becomes difficult to cool the disk, and the frictional resistance tends to become too large, making the molding unstable. The distance between the peripheral edge of the stretching disk and the first mandrel is absolutely necessary in order to prevent uneven frictional resistance between the first mandrel and the film from affecting the annular die surface. However, if the gap becomes too large, the width of the film will drop, so 1
A suitable length is about 1 to 10 cm, preferably about 1 to 5 cm. () Shape and effects of the first mandrel (1) The film contact surface is short. Alternatively, if the surface is rough or has low slip resistance, a film with low strength and high elongation can be obtained. (2) If the process in (1) is reversed, a film with high strength and low elongation can be obtained. (3) By increasing the cooling temperature, a film with high strength and low elongation can be obtained. (4) If the process in (3) is reversed, a film with low strength and high elongation can be obtained. The first mandrel is used to cool the film stretched by the stretching disc, prevent width loss, and obtain a stretched film that is difficult to tear. 1st
If a second mandrel is provided on the downstream side of the mandrel, the effect of preventing width loss of the stretched film will be increased,
Further, by applying relative motion between the second mandrel, the first mandrel, and the annular die, the tubular resin film is given oblique orientation, thereby obtaining an obliquely oriented thermoplastic resin film. It is preferable that the circumferential surface of the first mandrel has only a satin finish or a plating finish with a fine roughness of at least #30 mesh. A mandrel with a satin finish rougher than #30 mesh slides too well against the resin film, making it difficult to stretch the resin film. Example The stretched disks shown in FIGS. 1 to 3 were used. The stretched disk 4A shown in FIG. 1 has a matte finish with a thickness of 2 mm, an edge of 90°, and a #500 mesh on the circumference (hereinafter referred to as a stretched disk). The stretched disk 4B shown in FIG. 2 has a thickness of 1 mm and a thickness of 0.5 mm.
With mmR (hereinafter referred to as stretched disk). The stretched disk 4C shown in FIG. 3 is 2 mm thick, has a 0.5 mm radius on the edges, and has a 300 μ thick fluororesin 8 (Teflon manufactured by Mitsui Fluorochemicals) pasted on the circumferential surface (hereinafter referred to as the stretched disk). ). The three types of stretched disks and peripheral surface conditions: #30 mesh satin finish, #100 mesh satin finish, #300 mesh satin finish,
A #500 mesh mandrel with matte finish and a mandrel without matte finish were combined and tested under the conditions shown in the table below. The physical properties (strength and elongation) of the resulting resin films were measured under the conditions shown in the table below. The results are shown in the table below.

【table】

【table】

Figure 5 shows another apparatus for carrying out the method of the invention, in which a stretching disk is also provided upstream of the second mandrel for high-axial stretching. That is, in the figure, 1 is an annular die, 2 is an air ring, 3 is a first mandrel, 4 is a stretching disk, 6 is a guide plate, 9 is a second mandrel, 10 is a heating device, and 11 is a pinch roll. As explained above, in the past, resin temperature and
The molding speed was controlled, but this control was quite troublesome, and the product obtained was uneven and not necessarily satisfactory. However, according to the present invention, it is possible to easily obtain a resin film with predetermined physical properties. can.

[Brief explanation of the drawing]

The drawings show an apparatus for carrying out the method of the invention, and FIGS. 1, 2 and 3 are side views of various stretching disks. FIGS. 4 and 5 are diagrams showing the overall outline of the apparatus. 1... Annular die, 2... Air ring, 3...
First mandrel, 4,4A to 4C...stretching disk,
5...Air reservoir portion, 6...Guide plate, 7, 9...Second mandrel, F...Resin film.

Claims (1)

[Claims] 1. An extruder, an annular die for forming resin supplied from the extruder into a tubular resin film,
A cooling mandrel provided on the downstream side of the annular die and a stretching disk provided on the upstream side of the cooling mandrel are provided, and the annular resin film extruded from the annular die is In a method for manufacturing an oriented thermoplastic resin film by changing the running angle and applying a pulling force to the film that has passed through a cooling mandrel to impart orientation to the tubular resin film, the surrounding area of the stretched disk is attached to the cooling mandrel. At least a stretched disk selected from the group consisting of a drawn disk with a square edge on the die side, a drawn disk with a rounded edge on the die side, and a drawn disk whose peripheral surface is coated with a resin. Two types of stretching disks are prepared, and the tubular resin film is extruded so that the cooling mandrel and the stretching disk are arranged inside the tube of the tubular resin film, and resin films with different physical properties are manufactured depending on the selection of the stretching disks. A method for producing an oriented thermoplastic resin film characterized by: 2. Production of an oriented film according to claim 1, characterized in that at least two types of mandrels with different peripheral roughness are prepared, and one of the mandrels and one of the stretching disks are appropriately combined. Method.