JPS6127177B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a molded article made of a uniaxially oriented thin film. More specifically, the present invention relates to a method of laminating uniaxially oriented thermoplastic resin thin films by roll rolling to form a tubular body, a special pipe, a hollow container, or the like. Conventionally, it is well known that thin films made by stretching and orienting thermoplastic resin sheets have excellent mechanical properties such as strength and rigidity, and are widely used as binding materials, packaging materials, etc. . However, the use of these thin films is mostly limited to the film field, and in order to use them for so-called molded objects such as general hollow containers and pipes, they must be combined with other special molding methods. For example, as a method of molding the above-mentioned mold with a stretched thin film with excellent mechanical properties, the stretched thin film is stretched many times under pressure.
A method of obtaining molded products such as pipes by winding and laminating under heating and then applying heat shrinkage to bring the layers into close contact is in operation. However, in the case of laminated winding using stretched thin films, industrial implementation is not easy. In other words, the thin film produced by tensile stretching becomes thicker at both ends, and the thickness unevenness must be removed, resulting in a large amount of loss. Also, due to the minute irregularities on the surface, it is difficult to completely ensure the adhesion between the layers after lamination shrinkage. It is difficult to do this uniformly, and if the stretching ratio is too high when obtaining a stretched thin film to increase the rigidity of the laminate, tearing along the stretching direction is likely to occur. Since it tends to tear easily, the molding operation must be performed carefully, resulting in low productivity. The inventors of the present invention have carried out intensive research to solve these problems in the laminated winding method, and have found that when a thin film obtained by roll rolling is used instead of the previously proposed tensile stretched thin film, the above-mentioned problem occurs. It has been found that all of the problems have been solved, and in addition, a laminate can be obtained that has a high level of transparency that could not be obtained when using a tensile stretched thin film, leading to the present invention. i.e. 1.5 in the longitudinal direction by roll rolling.
A thermoplastic resin sheet that has been stretched ~10 times and has molecules oriented in this direction is held at a temperature lower than its melting point or below its softening point and above the temperature during roll rolling, and then rolled into a predetermined core. After wrapping and laminating the materials and compressing the inside of each laminated surface using shrinkage force, the core material is removed to make tubular molded products with high rigidity and good transparency, as well as special pipes, hollow containers, etc. That is, in the rolled thin film whose thickness was reduced by such roll rolling, no thickening phenomenon was observed at both ends, the surface of the thin film was extremely smooth, and the tearability along the stretching direction was low. This is significantly lower than that of the tensile-stretched oriented material. Further, the high transparency of the rolled film laminate is maintained due to the complete adhesion between the layers resulting from the smoothness of the thin film surface and the high transparency of the rolled film itself. Further, the rigidity of the laminate obtained due to the uniform adhesion between the layers and the high rigidity of the rolled thin film itself combine to significantly increase the rigidity of the laminate. As mentioned above, the requirements of the present invention are that the thermoplastic resin sheet is roll-rolled in a solid state, and that the thermoplastic resin sheet is rolled at a temperature lower than the melting point or below the softening point of the obtained thermoplastic resin thin film, and at a temperature at the time of roll-rolling. By keeping the thin film above the temperature, tension is applied to the thin film, and the core material is used to wind and laminate the thin film, and the adhesiveness between the layers is obtained by the shrinkage force of the thin film itself. Further, if necessary, by heating with an appropriate heating device after lamination, a stronger shrinkage force can be obtained, and as a result, better adhesion can be obtained. The thermoplastic resin used in the present invention includes polyethylene, polypropylene, polyamide, polyester, polystyrene, polyvinyl chloride, polycarbonate, etc., and there are no particular limitations on the thermoplastic resin. Also included are copolymers and mixtures of these. Also, commonly used additives may be added. The roll rolling method used in the present invention may be any conventionally known method. In other words, the commonly used roll rolling method is so-called constant circumferential speed rolling, in which the rolls are rotated in opposite directions at a constant circumferential speed and passed between a pair of rolls adjusted to have a gap smaller than the thickness of the sheet to be rolled. However, in this case, it is difficult to obtain a large rolling ratio with a viscoelastic body such as a thermoplastic resin thin film because of elastic recovery after rolling. In order to further increase the rolling ratio, there is a liquid rolling method such as that proposed in Japanese Patent Publication No. 14199/1982, but it is necessary to completely wash away the liquid film adhering to the surface of the rolled thin film during lamination. On the other hand, the so-called non-uniform circumferential speed rolling method, in which the peripheral speeds of a pair of rolls are made different from each other, gives the most favorable results. That is, in the above-mentioned constant circumferential speed rolling, the constant circumferential speed settings of each roll are changed to non-uniform circumferential speeds. In this case, either the thin film discharged from the rolling roll is directly brought along the surface of the high-speed rolling roll in close contact with 1/8 or more of the entire circumference of the roll, or the thin film discharged from the rolling roll is taken off. If the material is forcibly removed at the same speed as the peripheral surface speed of a high peripheral speed roll, the rolling ratio can be easily increased (Japanese Patent Application Laid-Open No. 16360-1971). The thermoplastic sheet is rolled by the roll rolling method described above, and the rolling ratio (thickness of the sheet before rolling/thickness of the thin film formed after rolling) varies depending on the intended molded product, but usually The rolling ratio is 1.5 to 10 times, and the rolling effect (orientation effect) of the sheet is particularly remarkable at 3 to 7 times, and the larger the rolling ratio is, the
The stiffness and clarity of rolled thin films tend to increase. Additionally, as a rolling condition, the gap between the pair of rolls must naturally be smaller than the thickness of the sheet before rolling, but the gap is set depending on the thickness of the sheet before rolling and the desired rolling ratio. be done. Furthermore, the temperature of the sheet during rolling is below the melting point or below the softening point of the sheet, and the sheet is rolled in a solid state. If it is introduced into rolls at a temperature above the melting point or softening point, almost no orientation effect is imparted and rolling is no longer possible.
The obtained product is a thin film with low rigidity and poor transparency, which is not preferable because the desired molded product cannot be obtained. On the other hand, the lower limit of the rolling temperature must be at most 80°C below the melting point or softening point, preferably at most 60°C below, and at a temperature at which the sheet remains in a solid state. The rolled thin film produced under the above-mentioned rolling equipment and rolling conditions is wound around the core material. For this laminated winding, the rolled thin film may be unrolled once rolled, or it may be unrolled from the rolling machine. It may also be directly applied to lamination and winding. Further, when winding around the core material, the winding shaft (core material) and the thin film length direction may be perpendicular to each other, or may be wound diagonally. This should be determined by the desired molded product; for example, in the manufacture of hollow containers, it is preferable to have a relationship at right angles to the winding axis (core material), while in the manufacture of tubular bodies, etc., the molded product When the length of is large, it is preferable to wind it diagonally to the winding shaft. In the present invention, the thin film obtained by roll rolling is not simply wound around a core material, but the thin film is heated during winding to generate a contraction force in the thin film itself, and as a result, the thin film is put under tension. It is wound around the core material at the bottom, and the respective laminated surfaces are compressed by the shrinkage force caused by the heating to form an integrally molded product. It is important to heat the thin film to a temperature higher than the rolling temperature of the thin film and lower than the melting point or softening point of the thin film. This is because the thermal contraction is small at the temperature during rolling, and as a result, it is impossible to wrap it around the core material under tension, and on the other hand, at temperatures above the melting point or softening point, the thin film melts and cannot be put to practical use. No. By wrapping it around the core material under these conditions and heating it with an appropriate heating device as necessary, a stronger shrinkage force can be obtained, resulting in better adhesion between the laminated surfaces. can. Although the winding of a single rolled thin film has been described above, the present invention is not limited to just a single thin film, but two or more thin films obtained by rolling may be used to wrap around a core material. Further, in that case, the case where different types of resin films are used together is also included in the scope of the present invention. Furthermore, when wrapping two or more thin films around a core material, as long as there is no problem with the adhesion between the laminated surfaces, the thin films used do not necessarily all need to be rolled thin films; Only one rolled thin film may be used, and the other thin films may be mere thin films. After the core material is laminated and wound in this way, by removing the core material, a molded article such as a tubular body or a hollow container made of thermoplastic resin with high rigidity and good transparency can be obtained. Note that the core material in the present invention may be cylindrical, prismatic, or various other materials.
There is also no particular limitation on the length. The material is also not particularly limited, but metal or hard plastic is preferred. After wrapping and laminating a rolled thin film around such a core material, the core material is removed, but to make the operation easier, a release material such as paraffin wax or the like is coated on the core material in advance, or a material with a low melting point is applied to the core material. It is possible to apply a substance on the core material and heat it slightly to dissolve it after wrapping and laminating it, or to make the core material from water-soluble polyvinyl alcohol and immerse it in water after lamination to dissolve it. It is also possible to use a core material that can be broken after lamination, or a structure in which the core material itself can be disassembled or deformed as necessary and can be easily separated from the laminate. In addition, the molded product from which the core material has been removed is strong because the laminated surfaces are tightly bonded due to shrinkage due to heat treatment.
Each end of the film may be fixed by heat-sealing or using an adhesive, if necessary.
The heat fusion bonding may be carried out by any commonly used method. The present invention will be explained below with reference to the accompanying drawings, but the drawings show one embodiment of the present invention and do not limit the present invention. In FIG. 1, 1 is a sheet of thermoplastic resin before rolling, and this sheet is rolled by a pair of constant circumferential speed rolling rolls 4, 4' to reduce the thickness and form a rolled thin film 2 with high rigidity and good transparency. can get. Next, the thin film is heated by a suitable heating device 5 to generate tension due to thermal contraction, and is wound around the core material 3 and laminated under this tension. FIG. 2 shows another embodiment of the invention,
In the figure, rolling rolls 4 and 4' have non-uniform circumferential speeds, 4 is a high circumferential speed roll, and 4' is a low circumferential speed roll. After passing through a rear presser roll 6 that follows the length of 1/8 or more of A tubular molded product can be obtained by removing the core material from the wound and laminated product by the above-mentioned means, but in order to obtain a molded product with a bottom such as a hollow container, it is necessary to As shown in the figure, a circular sheet 7 made of thermoplastic resin is attached to the circular part of the core material in advance with double-sided adhesive tape or the like on one end face of the core material, and then a rolled thin film is wrapped and laminated, and then the circular sheet 7 made of thermoplastic resin is After heat-sealing the joint between the sheet 7 and the wrapped laminate using a plastic welder or the like, or after adhering the joint with a polyolefin adhesive, the core material is removed by the above-mentioned method to form a hollow. A container is obtained. The present invention will be explained in more detail below using Examples and Comparative Examples. Example 1 High-density polyethylene with a density of 0.957 and MI4, 5 was melt-molded to obtain a thin film with a width of 480 mm and a thickness of 200 μm, and this was rolled with non-uniform circumferential speed rolls as shown in Fig. 2 under the conditions described below. After forming a 5x rolled thin film with a thickness of 40μ, a decomposable core material of 100 mmφ as shown in Fig. 1 and a polypropylene disk 7 with a thickness of 0.5 mm and a diameter of -100 mmφ were attached to the tip of the core material. hand,
A thin film maintained at a temperature of 130°C is wrapped 25 times around this, and the joint between the polyethylene wrapped laminate and the circular sheet 7 is heat-sealed, and the core material is disassembled and pulled out. A cylindrical container with a thickness of 0.5 mm was obtained. The characteristics of this container are shown in Table 1. Rolling conditions Roll shape Width 500mm, diameter 200mmφ Roll circumferential speed 60m/min (high speed side) Roll circumferential speed 20m/min (low speed side) Roll surface temperature (roll rolling temperature) 110℃±1
C. Comparative Example 1 Using the high density polyethylene used in Example 1, a cylindrical container having the same shape as Example 1 was made using an injection molding device, and the properties are shown in Table 1. Comparative Example 2 In Example 1, a thin film obtained by a non-uniform circumferential speed rolling method was used, but in place of this, a 40μ thin film obtained by a 5 times tension stretching method was used. The same operations as above were carried out, and the properties of the obtained products are shown in Table 1.

[Table] Comparing Example 1 and Comparative Examples 1 and 2,
From containers made by injection molding or tensile stretching,
It is clear that the container using the thin film obtained by rolling according to the present invention has significantly better transparency, the rigidity of the side wall of the container is greater, and the buckling strength of the container is also greater. Example 2 Rolling was carried out in the same manner as in Example 1 except that 0.2% of carbon black was kneaded into high-density polyethylene with a density of 0.951 and MI of 0.3 and the rolling roll temperature was 115°C, and this was rolled into a 25 mmφ core material at 120°C. At a film temperature of 95
After wrapping, heat in a hot air oven at 125℃ for 3 minutes.
After complete interlayer adhesion, the core material was removed and a tubular body (pipe) was created. Table 2 shows the properties of the various tubular bodies. Comparative Example 3 Using the high-density polyethylene used in Example 2 and 0.2% carbon black added as raw materials, a pipe having the same shape as Example 2 was made by extrusion molding, and the properties are shown in Table 2. Comparative Example 4 In Example 2, a thin film obtained by a non-uniform circumferential speed rolling method was used, but in place of this, a 40μ thin film obtained by a 7-fold tensile stretching method was used. The same operations as above were performed, and the properties are shown in Table 2.

【table】

[Table] Comparing Example 2 and Comparative Examples 3 and 4, the strength of the pipe using the thin film obtained by rolling according to the present invention is greater than that of the pipe made by extrusion molding or tensile stretching. is obvious.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the present invention, and FIG. 2 shows one using the non-uniform circumferential speed rolling method according to the present invention. 1... Thermoplastic resin sheet, 2... Rolled thin film, 3...
Core material, 4, 4'... Roll, 5... Heating device, 6
...Press roll, 7...Container bottom material.

Claims (1)

[Scope of Claims] 1 A thermoplastic resin sheet is longitudinally rolled between a pair of rolls at a temperature below its melting point or below its softening point in a solid state, and the resulting rolled sheet is rolled at a temperature below its melting point or below its softening point. or heated to a temperature below the softening point and higher than that during roll rolling, wrapped around a predetermined core material and laminated, the laminated surfaces are crimped by the shrinkage force of the heating sheet, and then the core material is removed. A method for producing a thermoplastic resin molded product, characterized by: 2 The sheet is rolled in the longitudinal direction
The manufacturing method according to claim 1, wherein the film is stretched 1.5 to 10 times. 3. The manufacturing method according to claim 1, wherein the pair of rolls rotates at a constant circumferential speed. 4 The rolling was carried out by a non-uniform circumferential speed rolling method, and the sheet passed through the non-uniform circumferential speed roll gap was directly attached to the surface of a high-peripheral speed rolling roll over 1/8 or more of the entire circumference of the roll. The manufacturing method according to claim 1, wherein the manufacturing method is carried out after being collected. 5. The manufacturing method according to claim 1, wherein a container bottom forming material is arranged on one end surface of the core material.