JP2009241570A - Extruder for molding hard vinyl chloride resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extruder which allows high viscosity while promoting kneading of melted resin, and increases the yield of a product without providing a breaker plate causing a linear trace stuck to the product. <P>SOLUTION: In the extruder 50, the resin which is melted and kneaded by rotation of a screw 20 installed in a cylinder 10 is extruded into a molding die 40 through a holder 30. The ratio d/D of the inner diameter d of a resin passing hole 35, which is formed between the entrance and exit of the holder 30, to the inner diameter D of the cylinder 10 is set to ≤0.170. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to an extrusion molding machine for molding a hard vinyl chloride resin , and more specifically, without providing a breaker plate, the kneading of molten resin is promoted to increase the viscosity, and the gloss of the product surface is increased . The present invention relates to an extruder for molding a hard vinyl chloride resin that does not cause unevenness .

  An extrusion molding machine is used for extrusion molding for continuously molding a product having a cross section of the same shape such as a film, a pipe, and a rod. In the extrusion molding machine, a holder is provided between a cylinder in which a screw is provided and a mold, and a breaker plate is provided between the holder and the cylinder (see Patent Documents 1 and 2). The breaker plate is a metal disc with a large number of resin passage holes concentrically arranged around its central axis, and the back pressure is applied to regulate the flow of molten resin in the cylinder, and the rotation of the screw By promoting the kneading, the viscosity of the molten resin can be increased and the shape stability of the molded product can be improved. Then, the resin with increased viscosity passes through the resin passage hole of the breaker plate, and a large number of streaky resins are bundled and pushed out to the mold through the holder.

  Some of the streak-shaped resin that has passed through the resin passage hole of the breaker plate is lined along the length direction of the streak-like resin due to passing through the resin passage hole that is extremely small compared to the inner diameter of the cylinder. In some cases, the product is molded with a metal mold, and this linear trace is also attached to the product, which may cause defective products and reduce the yield of the product. In particular, in the case of a colored resin, linear traces are conspicuous, and the yield of products may be greatly reduced.

Japanese Patent Laid-Open No. 56-150526 (figure) Japanese Patent Laid-Open No. 9-29816 (FIG. 1)

The present invention has been made in view of the above circumstances, and is not provided with a breaker plate that causes linear traces attached to the product, and the viscosity of the product can be increased by promoting kneading of the molten resin. yield can be enhanced, also an object of the present invention to provide an extruder for molding a hard vinyl chloride resin is Ru can improve the quality of the product without causing unevenness in gloss of the surface of the product.

As a result of repeated studies to solve the above-mentioned problems, the inventor made a back pressure in the cylinder and melted it by setting the ratio between the inner diameter of the resin passage hole of the holder and the inner diameter of the cylinder within a predetermined range. can regulate the flow of the resin, also by a resin passing hole in a predetermined cross-sectional shape conceive Rukoto prevents to cause unevenness in gloss of the surface of the product, and have completed the present invention.
That is, the present invention relates to a resin passage formed between an inlet and an outlet of the holder in an extruder for extruding a resin melted and kneaded by rotation of a screw provided in a cylinder to a mold through a holder. A ratio d / D between the inner diameter d of the hole and the inner diameter D of the cylinder is set to 0.170 or less, and a tapered portion that is reduced in diameter toward the resin passage hole is formed on the inlet side of the holder. A taper portion that expands toward the mold is formed on the outlet side of the resin, and the resin passage hole has a plurality of narrow region portions whose cross-sectional shape perpendicular to the resin passage direction communicates with the central portion on the outer periphery. The gist of the present invention is an extrusion molding machine for molding a hard vinyl chloride resin characterized in that a breaker plate is not provided between the cylinder and the holder. The mold includes a die.

According to the invention of the above configuration, the viscosity of the resin can be increased by promoting the kneading of the molten hard vinyl chloride resin without providing a breaker plate. In addition, the molten hard vinyl chloride resin can be smoothly pushed out from the cylinder to the holder and from the holder to the mold, and by passing a part of the hard vinyl chloride resin through multiple narrow areas, Uneven gloss on the product surface can be prevented.

The extrusion molding machine according to the first aspect of the present invention can form without causing linear traces due to the breaker plate to the product, and can increase the yield of the product. In addition, the molten resin can be smoothly extruded, and molding with a mold can be performed smoothly. Furthermore, uneven gloss occurring on the surface of the product can be prevented, and the quality of the product can be further improved.

  Hereinafter, the present invention will be described by way of embodiments with reference to the drawings.

  As shown in FIG. 1, in the extrusion molding machine 50, a screw 20 is provided in a cylinder 10, and a holder 30 is provided between the cylinder 10 and a mold 40.

  On the inlet side of the holder 30, a tapered portion 31 that decreases in diameter toward the resin passage hole 35 is formed, and on the outlet side, a tapered portion 32 that increases in diameter toward the mold 40 is formed.

  The ratio d / D between the inner diameter d of the resin passage hole 35 of the holder 30 and the inner diameter D of the cylinder 10 is set to 0.170 or less. This is because when d / D is greater than 0.170, the back pressure is lowered, the kneading degree of the molten resin is lowered, and the shape stability of the molded product cannot be maintained. The lower limit of d / D is not particularly limited, but is preferably 0.050 in view of the efficiency of resin extrusion.

  The cross-sectional shape orthogonal to the resin passage direction of the resin passage hole 35 may have a plurality of narrow region portions 37 communicating with the central portion 36 on the outer periphery. In order to knead and extrude the molten resin, the screw 20 is formed with a helical screw flight 21. The resin extruded into the holder 30 by the screw 20 in a donut shape has a thin portion corresponding to the screw flight 21 of the screw 20 and a thick portion corresponding to the screw groove 22 between the screw flights 21. There may be a difference in the reflectance of light on the surface of the product molded from the resin extruded through the holder 30 into the mold 40, and this may cause unevenness in the gloss of the surface of the product. The uneven gloss on the surface of the product is not a problem that reduces the yield of the product like the linear trace generated by the breaker plate, but it solves this problem from the viewpoint of further improving the quality of the product. It is preferable. In the conventional extrusion molding machine provided with the breaker plate, since there was no such problem, the resin can be solved by passing the outer periphery of the doughnut-shaped resin extruded by the screw 20 through a narrow place. When the cross-sectional shape of the passage hole 35 was configured as described above, this problem could be solved. Of course, even if the resin is allowed to pass through the narrow region portion 37, there is no linear trace that reduces the product yield that may have been caused by the breaker plate.

  The shape of the narrow region portion 37 formed in the resin passage hole 35 is not particularly limited as long as it communicates with the central portion 36. For example, the narrow region portion 37 may have a substantially triangular shape as shown in FIG. It may be circular.

  A thermoplastic resin is put into a hopper (not shown), heated and melted by a band heater (not shown), and the melted resin is kneaded by the rotation of the screw 20. By setting the ratio d / D between the inner diameter d of the resin passage hole 35 of the holder 30 and the inner diameter D of the cylinder 10 as described above, back pressure is generated, the flow of the molten resin is restricted, and the resin is screwed The rotation of 20 promotes kneading and increases the viscosity. The resin with increased viscosity passes through the resin passage hole 35 of the holder 30 and is extruded from the outlet to the mold 40, and is molded into a predetermined product by the mold 40. And since the breaker plate is not provided in the obtained product, a linear trace is not attached.

  The thermoplastic resin of the material resin used is not particularly limited, and examples thereof include polyethylene, polypropylene, hard vinyl chloride resin, polyvinyl acetate resin, polystyrene resin, and ABS resin.

  EXAMPLES Next, although an Example is given and this invention is demonstrated, this invention is not limited to a following example.

  Prototype extrusion machine with cylinder inner diameter of 90.0 mm was manufactured, holders with resin passage holes set to the inner diameter shown in Table 1 were prepared, attached to each of the above extrusion machines, and extruded using hard vinyl chloride resin Molding was performed. The degree of kneading in Table 1 is determined based on whether or not the molding by the mold has shape stability. The case where the melted resin is sufficiently kneaded to increase the viscosity and has shape stability. Was evaluated as x.

  In Test Example 1, the back pressure in the cylinder was insufficient and the melted resin was not sufficiently kneaded, so the viscosity was low and a molded product with a stable shape could not be obtained. In Test Examples 2 to 4, the degree of kneading was good and, of course, no linear trace was attached to the molded product.

A prototype of the same extruder as described above was produced. A holder having a substantially triangular shape on the outer periphery shown in FIG. 2 and having an inner diameter similar to those of Test Examples 2 to 4 above is prepared, and each of the holders is attached to the extruder and extruded as described above. Went. As a result, a product having shape stability was obtained, and the surface gloss of the product was not uneven.

Sectional drawing of the extrusion molding machine which concerns on embodiment. The figure which shows the expanded cross-sectional shape of the resin passage hole of the extrusion molding machine which concerns on embodiment.

Explanation of symbols

10 cylinder 20 screw 21 screw flight 22 screw groove 30 holder 31, 32 taper part 35 resin passage hole
36 Central part 37 Narrow area part 40 Mold 50 Extruder

Claims (3)

  In an extruder for extruding a resin melted and kneaded by rotation of a screw provided in a cylinder into a mold through a holder, an inner diameter d of a resin passage hole formed between an inlet and an outlet of the holder An extrusion molding machine characterized in that the ratio d / D to the inner diameter D of the cylinder is set to 0.170 or less.   The taper part which diameter-reduces toward the resin passage hole is formed in the inlet side of a holder, and the taper part which diameter-expands toward a metal mold | die is formed in the exit side. The extrusion machine described.   The extrusion molding machine according to claim 1 or 2, wherein a cross-sectional shape perpendicular to the resin passage direction of the resin passage hole has a plurality of narrow region portions communicating with the central portion on the outer periphery.

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