JP2000141446A - Extrusion die and apparatus and method for extruding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a facility cost by constituting an extrusion die capable of molding a different type density resin foam formed with cavities of different land lengths from the vicinity of an extrusion inlet to outlet at an extrusion die. SOLUTION: The extrusion die 3 comprises a partition wall 3a formed to alter a land length at a position formed with a cavity therein and two land lengths formed from a slight interior near an extrusion inlet 3b toward an extrusion outlet 3c. That is, lengths of the wall 3a, an upper contact wall 3d and a lower contact wall 3e are selected to form a land length 2a of an upper part side and a land length a2 of a lower part side. Here, the length a1 is made longer than the length a2 of the lower part side, and a high density resin foam of small foaming amount is extruded, and the length a2 of the lower part side is made to extrude a low density resin foam of much foaming amount to variously manufacture different density type resin foams.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion die, an extrusion apparatus, and an extrusion method. More specifically, the present invention relates to an improved extrusion die, in which a single extrusion apparatus has a resin (mainly a thermoplastic elastomer) foam having different densities. An extrusion die, an extrusion apparatus, and an extrusion method using the same, which are capable of producing a heterogeneous density resin foam having a composite material.

[0002]

2. Description of the Related Art Conventionally, in order to manufacture a composite resin extruded product comprising a plurality of resin foams having different densities, an extruding apparatus loaded with resin foam materials having different densities is connected to one extrusion die. In addition, the resin foam material fed from each extruder is compounded with the extrusion die, and a composite resin foam is extruded.

For example, in order to extrude a composite resin foam of a high-density foaming material containing a small amount of a foaming agent and a low-density foaming material containing a large amount of a foaming agent, an apparatus as shown in FIG. 5 is used. I was going. That is, an extruding device 10 filled with a high-density foaming material (a small amount of a foaming agent) and an extruding device 11 filled with a low-density foaming material (a large amount of a foaming agent) are combined with an extrusion die 12. Then, the inside of the cylinder 13 is fed from each of the extruders 10 and 11 to the extrusion die 12 by a screw 14. Then, these are extruded from the extrusion die 12 to produce a different-density resin foam extruded product F in which the high-density resin foam 17 and the low-density resin foam 18 are combined.

[0004]

However, the extrusion molding of the composite resin foam according to the prior art as described above,
Extrusion equipment is required as many as the number of composite materials, which complicates the equipment configuration and increases equipment costs.The equipment itself becomes large-scale and requires a large space. The development of the device was desired.

Accordingly, an object of the present invention is to provide an extrusion die and an extrusion apparatus for extruding a different density resin foam which can solve the above-mentioned problems of the prior art, reduce equipment costs, and have a compact apparatus as a whole. And an extrusion method using the same.

[0006]

The above object is achieved by the invention described in each claim. That is, the characteristic configuration of the extrusion die of the present invention is from the vicinity of the extrusion inlet to the outlet,
A different density resin foam having cavities with different land lengths can be molded. With this configuration, it is not necessary to use as many extruders as the number of composite materials as in the related art to mold a different density resin foam, and the die of the present invention is attached to one extruder. A composite resin foam can be manufactured by itself. In addition, there is no need to adjust and prepare the extruded materials in advance with different densities,
By using one type of extruded material from the beginning and extruding with an extruder equipped with a die of the present invention, a resin foam of different density can be produced. As a result, in order to manufacture different density resin foam, the manufacturing process can be simplified, the equipment cost can be greatly reduced, and the equipment space can be reduced, and the compact resin resin foam for extrusion molding as a whole can be obtained. Extrusion dies could be provided.

[0007] Among the different land lengths, it is preferable that the land has at least a length such that the pressure applied to the extruded object extruded through the die is lower than the bubble formation critical pressure. In other words, when the land length is long, the pressure of the extruded object advancing in the die gradually decreases as the pressure approaches the vicinity of the outlet from the initial pressure, and there is a condition that the pressure falls below the bubble formation critical pressure in the die. The foaming starts in the die, and as a result, when the material to be extruded reaches the outside of the die, the foaming has already progressed.
Stop at. Therefore, foams having different foaming states can be reliably formed.

It is preferable that the core material or the outer cover material can be extruded into a resin foam having a different density. With this configuration, it is possible to manufacture a composite resin foam in which a high-density resin foam or a low-density resin foam is formed in a core material or a skin material, diversification of functions can be realized, and a wide range of use can be achieved. .

A feature of the extrusion apparatus of the present invention resides in that any one of the extrusion dies described above is provided. With this configuration, it is not necessary to use the same number of extruders as the number of materials to be composited as in the prior art to form a different density resin foam, and a single extruder is used to produce a composite resin foam. it can. In addition, it is not necessary to prepare the materials to be extruded in different densities in advance, and a different density resin foam can be manufactured by extruding one type of extruded material from the beginning with the extrusion apparatus of the present invention. As a result, it is possible to simplify the manufacturing process and significantly reduce equipment costs for manufacturing different density resin foams, and also to provide a compact composite resin foam extruder as a whole, which requires less equipment space. did it.

It is preferable that a foaming agent capable of foaming the object to be extruded is supplied to an intermediate position of an extrusion cylinder for extruding the object to be extruded. With this configuration, when extruding the extruded object, water,
Various foaming agents such as carbon dioxide gas and nitrogen gas can be surely mixed into the extruded material, which is convenient. In other words, when the resin raw material in the form of pellets is put into a cylinder from a hopper or the like and the resin is extruded through a screw, when a foaming agent is introduced in the vicinity of the hopper, the resin remains in a solid state in this portion, so that the foaming agent is This is because it is easy to escape to the hopper side, which is not preferable. However, even if a foaming agent is introduced near the rear end of the extrusion, mixing cannot be sufficiently performed. Therefore, it is preferable to introduce the foaming agent after the pellet-shaped raw material is heated and melted while being extruded, and at a cylinder position not near the rear end of the extrusion.

Furthermore, a characteristic configuration of the extrusion method of the present invention is that an object to be extruded is extruded by using the above-described extrusion apparatus. With this configuration, it is not necessary to use as many extruders as the number of materials to be composited as in the prior art to form composite resin foams having different densities. Can be manufactured. Moreover, there is no need to prepare the materials to be extruded at different densities in advance, and a different density resin foam can be produced by extruding the same extruded material by the extrusion method of the present invention from the beginning. As a result, to produce different density resin foam,
By using a composite resin foam extruder that can simplify the production process and reduce the equipment cost and is compact as a whole, an extrusion method with reduced production cost can be provided.

[0012]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic partial structure of an extruder A for feeding a resin foam base material such as a thermoplastic elastomer in a cylinder 1 to an extrusion die 3 side by a screw 2. On the way, a pipe 4 for supplying water as a foaming agent for foaming the resin foam base material into the cylinder 1 is connected, and a water tank 5 and a predetermined amount of water Is connected to a pump 6 which feeds the pump 6. Then, while a pellet-shaped resin foam base material is supplied into the cylinder 1 from a hopper (not shown) provided on the upper side of the extruder A, it is kneaded and fed by the screw 2 to the extrusion die 3 side. The resin foam base material is kneaded and fed by the screw 2 and is heated and melted by a heater (not shown) arranged around the cylinder 1. At a position where the melting of the resin foam base material has progressed to some extent, water as a foaming agent is mixed and stirred into the resin foam base material via the pump 6, and as a result, the water is heated and becomes fine particles in the resin. Spread. However, at this stage, large bubbles are not formed by the action of the compressive force in the cylinder 1.
The mixture of the resin foam base material and the steam is fed to the extrusion die 3, where it is separated into two directions having different land lengths and foams when extruded from the extrusion die outlet.

Next, the configuration of the extrusion die 3 will be described with reference to FIG.
This will be described in detail with reference to FIG. The extrusion die 3 is capable of manufacturing a different-density resin foam product F in which two types of resin foams having different densities (high-density resin foam 7 and low-density resin foam 8) are combined. A partition wall 3 for changing the land length is formed at the location where the internal cavity is formed.
a is formed, and two land lengths are formed toward the extrusion outlet 3c from a position slightly inside the extrusion inlet 3b near the die. That is, the lengths of the partition wall 3a, the upper contact wall 3d, and the lower contact wall 3e are selected so that the upper land length a1 and the lower land length a2 shown in FIG. 2 can be formed. Here, the land length a1 is longer than the lower land length a2, and a high density resin foam having a small foaming amount is extruded. The lower land length a2 is a low density resin foam having a large foaming amount. Extrude the body. When the land length is long, the pressure of the resin traveling in the die gradually decreases as the pressure approaches the extrusion outlet 3c from the initial pressure P, and a condition that the pressure falls below the bubble formation critical pressure P0 in the die occurs. Start foaming inside. As a result, when the resin reaches the outside of the die, the foaming has already progressed, so that the foaming does not largely foam, but stops at a small foaming (low foaming). However, when the land length is short, the pressure of the resin traveling in the die is maintained at a high level, and while the resin travels in the short land, the resin pressure decreases. Therefore, foaming does not start in the resin inside the die, and sudden foaming occurs only after the resin reaches the outside of the die, so that the resin foams largely (high foaming). As described above, by changing the land length in the die, composite resin foams having different foaming degrees can be obtained. FIG. 3 schematically shows the relationship between the resin pressure in the die and the die position. FIG. 3 corresponds to the type of resin, extrusion conditions such as extrusion speed, type and amount of foaming agent, die cross-sectional shape, land length and cross-sectional shape, etc.
By preparing the data shown in (1), it becomes possible to manufacture various types of different density resin foams in which resin foams having different degrees of foaming are combined.

[0014]

Next, an example in which a polyolefin-based thermoplastic resin is used as the material to be extruded using the extrusion die and extrusion-molded using water as a foaming agent will be described. Die entrance diameter 40mm
In contrast, two types of land lengths a1 = 8 mm and a2 = 2
mm and a die exit size of 2 × 2.2 mm and 1 × 2.0 for each cavity of each land length.
mm and extruded at an extrusion speed of 400 g / min. As a result, two layers of different density resin foam sheets having a density of 0.9 g / cc as a high density resin foam and a density of 0.5 g / cc as a low density resin foam were obtained.

[Other Embodiments] (1) In the production of a different density resin foam according to the present invention, as shown in FIG. 4, a different density resin foam consisting of a cylindrical core material and a shell material covering the peripheral surface thereof is used. The present invention is also applicable to a case where a body product F ′ is manufactured. FIG.
(A) shows a hollow material extrusion die 3 ′ for simplification.
And only the different-density resin foam product F ′ extruded by the die 3 ′. The land length a2 for foaming the high-density resin constituting the core material is short, and the land length a1 for foaming the low-density resin constituting the skin material is formed long. The partition 3a 'located at the center may be supported by a column connected to the outer wall of the die, or may be formed of a combination die similar to a hollow extrusion die or the like. Here, details are omitted for simplicity. FIG. 4 shows a cross section of a different-density resin foam product F ′ extruded by an extruder A having such a die.
(B). The appearance of such a composite resin foam is coated with a material having a small amount of foaming, so that it can have some gloss and rigidity, and since the inside is highly foamed, the weight can be reduced as a whole, and the appearance can be reduced. It can be used for products that are valued and want to reduce weight.

Contrary to what is shown in FIG. 4, a product in which a low-density resin foam is disposed in a core material and a high-density resin foam is disposed in a skin material can be obtained by changing the land length. Can be easily manufactured. Such a product is foamed in appearance, but has a structure resistant to bending or buckling due to the presence of the bottom density resin foam of the core material, and can be used for applications requiring such strength.

(2) In the above embodiment, an example was described in which two types of resin foams were manufactured as extrusion dies, but three or more different types of resin foams could be formed. This is possible by providing partition walls inside the die so as to form different lands.

(3) Although water is used as the foaming agent in the above embodiment, the present invention is not limited to this, and a gas foaming agent such as carbon dioxide or nitrogen gas may be used as the foaming agent. It can be changed appropriately according to the application.

(4) The present invention can be applied to various thermoplastic elastomers, for example, extrusion molding of polystyrene-based, polyolefin-based, polydiolefin-based, chlorine-based and engineering plastic-based thermoplastic resins.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view when extrusion molding is performed using the extrusion apparatus of the present invention.

FIG. 2 is a schematic cross-sectional view of an extrusion die used in the extrusion apparatus of FIG.

FIG. 3 is a diagram for explaining a relationship between a position in a die and a resin pressure.

FIG. 4A is a schematic cross-sectional view when extrusion molding is performed using an extrusion die according to another embodiment, and FIGS.
-B sectional view

FIG. 5 is a schematic partial cross-sectional view when extrusion molding is performed using a conventional composite resin foam extrusion molding apparatus.

[Explanation of symbols]

 Reference Signs List 1 cylinder 3, 3 'die 3b extrusion inlet 3c extrusion outlet a1, a2 land length

Claims (6)

[Claims] 1. An extrusion die capable of molding a different density resin foam having cavities having different land lengths from the vicinity of an extrusion inlet to an outlet. 2. The extrusion die according to claim 1, wherein, among the different land lengths, at least a pressure applied to an extruded object extruded through the die is lower than a bubble formation critical pressure. 3. The extrusion die according to claim 1, which can be extrusion-molded into a resin foam having a different density with a core material or a skin material. 4. An extrusion apparatus provided with the extrusion die according to claim 1. 5. The extruder according to claim 4, wherein a foaming agent capable of foaming the object to be extruded is supplied to an intermediate position of an extrusion cylinder for extruding the object to be extruded. 6. An extrusion method for extruding an object to be extruded using the extrusion apparatus according to claim 4.