KR20000030999A - Method and apparatus for producing cross-linked foam - Google Patents

Abstract

PURPOSE: A method and apparatus for manufacturing a cross-linked foam is provided to enable a resin exudate to smoothly flow through a heater or mould. CONSTITUTION: The resin composition is prepared by uniformly mixing at least one cross-likable resin, at least one cross-linking agent, at least one foaming agent, and some additives. The resin composition is exuded through exuding means (2) and then forms an exudate of a predetermined shape through a die (3). A heating mould (6) receives the exudate and heats the resin to a temperature enough to cross-link and foam the resin. Then, the exudate is driven by a driving means in an exudation direction.

Description

Method and Apparatus for Producing A Crosslinked Foamed Article

The present invention relates to the production of crosslinked foamed products, and more particularly, to a method and apparatus for producing a crosslinked foamed product which allows the resin exudates to proceed smoothly through the mold during the manufacturing process of the product.

Crosslinked foam products have the advantage of being light in weight and have been widely used in insulating materials, footwear materials, cushion materials and sports goods. Raw materials for producing crosslinked foamed products include thermoplastics (eg PE, PP or EVA) and thermosetting resins (eg rubber). Methods for producing crosslinked foamed products can be classified into the following two methods.

(1) A method in which the polymer composition is mixed, exuded or molded into sheets and finally molded in a batch pressure treatment to form a crosslinked foamed product.

(2) a method in which the polymer composition is mixed, exuded or molded into an expandable sheet and finally molded in a batch crosslinking manner to form a crosslinked foam product

However, the two methods described above increase energy and manufacturing costs because a batch processing method is used. Therefore, continuous processes of simultaneous crosslinking and foaming have been developed.

For example, U.S. Patent No. 4,552,708 to Kimura et al. Uses a long die to maintain pressure to obtain the product properties of a foamed product. However, in order for the fired body to proceed smoothly through the mold, lubricant must be continuously applied to reduce friction.

Yamamoto et al., US Pat. No. 5,310,513, also uses two zones of long die. In the front zone, the fired body is heated to cause crosslinking and in the rear zone the crosslinked material is cooled. Finally, the crosslinked material is heated to freely expand and foam to obtain the final crosslinked foam product. Thus, a final crosslinked foamed product having non-uniform and large bubbles will be produced due to its free foaming.

Accordingly, it is an object of the present invention to solve the above problems, and to provide an improved method and apparatus for producing crosslinked foamed products which allows the resin exudates to proceed smoothly through the mold in the production of foamed products.

It is another object of the present invention to provide an improved method and apparatus for producing crosslinked foamed articles having uniform and smaller bubbles.

1 is a schematic view of an apparatus for producing a crosslinked foamed product according to the present invention.

2A-2C are cross-sectional views of a die in accordance with an embodiment of the present invention.

3a to 3c show a drive means according to an embodiment of the invention.

Figure 4a shows a heating mold and driving means according to a first embodiment of the present invention.

4B is a cross-sectional view cut along the line IV-IV of FIG. 4A.

Figure 5a shows a heating mold and driving means according to a second embodiment of the present invention.

5B is a cross-sectional view cut along the V-V line of FIG. 5A.

FIG. 5C illustrates another embodiment modified from FIG. 5A;

<Description of Symbols for Main Parts of Drawings>

1: pellet of crosslinkable resin composition 2: extruder

3: die 4: exudate

5: heater 6: heating mold

7: crosslinked foam product 14,24: driving pulley

15,25: Transfer belt

In order to achieve the above object, the method for producing a crosslinked foamed product according to the present invention comprises (A) uniformly mixing at least one crosslinkable resin, at least one crosslinking agent, at least one foaming agent, and some additives. Making a composition, (B) exuding the resin composition through a die to produce a desired shape of exudate, and (C) heating the exudate to a temperature sufficient to crosslink and foam the crosslinkable resin. Meanwhile, the exudates are driven by a driving device to be moved in the exudation direction, thereby obtaining a crosslinked foamed product.

An apparatus for producing a crosslinked foamed product according to the present invention is a molten resin composition by heating a crosslinkable resin composition comprising at least one crosslinkable resin, at least one crosslinker, at least one foaming agent and some additives. An extruder for making a furnace, a die connected to the extruder to allow the molten resin composition to exudate into a extrude of a predetermined shape, and a temperature sufficient to crosslink and foam the crosslinkable resin by accommodating the exudate. And a heating means for heating and driving means for driving the exudate in the heating mold to move in the ejecting direction.

The above objects and features of the present invention will be more clearly understood from the following detailed description with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described.

The crosslinkable resin, crosslinking agent, blowing agent and other additives are mixed and then purified into pellets of the crosslinkable resin composition. Formation of the crosslinkable resin composition will be known from the following tables.

ingredient Composition water 1 Composition water 2 Composition water 3 EVA 100 g 100 g 100 g ADCA 3 g 3 g 3 g DCP 0.15 g 0.3 g 0 BPO 0.15 g 0.3 g 0 CaCO₃ 30 g 30 g 30 g ZnO 0.3 g 0.3 g 0.3 g ZnSt 0.3 g 0.3 g 0.3 g

ingredient Composition water 4 Composition water 5 Composition water 6 LDPE 100 g 100 g 100 g ADCA 3 g 3 g 3 g DCP 0.15 g 0.3 g 0 BPO 0.15 g 0.3 g 0 CaCO₃ 30 g 30 g 30 g ZnO 0.3 g 0.3 g 0.3 g ZnSt 0.3 g 0.3 g 0.3 g

ingredient Composition water 7 Composition water 8 SBR-Rubber 100 g 100 g Sulfur 2 g 2 g ADCA 3 g 3 g CaCO₃ 30 g 30 g ZnO 0.3 g 0.3 g ZnSt 0.3 g 0.3 g BPO 0 0.1

In these tables, EVA represents poly (ethyl-co-vinylacetate), LDPE represents low concentration polyethylene, and SBR-rubber represents styrene butadiene rubber, respectively. ADCA (azodicarbonamide) is used as a blowing agent and DCP (dicumyl peroxide) and BPO (benzoyl peroxide) are used as crosslinking agents.

Referring to FIG. 1, the pellet 1 of the crosslinkable resin composition is extruded by the extruder 2 through the die 3 to form an extruded material 4 of a predetermined shape. The exudates 4 then pass through the heater 5 (only as needed) and the heating mold 6 to allow the crosslinkable resin to crosslink and foam to obtain a crosslinked foam product 7.

The extruder 2 is used to heat the pellets of the crosslinkable resin composition 1 into a melt and to extrude the melt into an exudate. The die 3 is used to cause the exudates to be formed into a predetermined shape. The cross section of the die 3 can take a rectangle (FIG. 2A), a circle (FIG. 2B) or another shape (FIG. 2C).

The heater 5 is used to heat the exudate 4 to a temperature sufficient to crosslink some or a minor amount of the crosslinkable resin. The heater 5 may also be provided with means for driving the exudate to move in the exudation direction. This movement can be made by a conveying belt and a pair of pulleys (FIG. 3A). The conveying belt is transmitted and driven by the pair of pulleys. The conveying belt drives the exudate by contacting the exudate to move in the exudation direction. Movement in the heater 5 may be made by two conveying belts and two pairs of pulleys (FIG. 3B). Each of the two transfer belts is transmitted and driven by each pair of pulleys. The conveying belts come in contact with the exudate to drive the exudate between the two conveying belts so that they move in the exuding direction. Referring to FIG. 3C, the drive may alternatively be performed by multiple rollers. In this case, the exudate is moved in the exudation direction as the roller moves.

Next, the exudate 4 flows into the heating mold 6. 4A and 4B, the heating mold 6 consists of two half molds 17, 17 ', which have a U-shaped cross section. Adjacent positions of the heating mold 6 are provided with drive means having a drive pulley 14 and a transfer belt 15. Each conveying belt 15 is transmitted and driven by a pair of pulleys 14 and in contact with the exudate 4 to drive the exudate 4 in the heating mold 6 to move in the exudation direction. The exudates 4 in the heating mold 6 are heated at the positions indicated at 16 for crosslinking and foaming of the resin, thereby exudating the exudates into crosslinked foamed products 7.

5A and 5B showing the heating mold and the driving means according to the second embodiment of the present invention, the driving means includes a driving pulley 24 and a conveying belt 25. Each conveyance belt 25 is transmitted and driven by a pair of pulleys 24. The heating mold 8 is driven by being connected to the conveying belt 25 so that the exudate 4 moves in the ejecting direction in accordance with the movement of the heating mold 8. Each heating mold 8 consists of two half molds 27 and 27 'and has a U-shaped cross section. The exudates 4 in the heating mold 6 are heated at the positions indicated at 26 for crosslinking and foaming of the resin so that the exudates expand into a crosslinked foam product 7.

Referring to FIG. 5C, which shows another embodiment modified from FIG. 5B, the heating mold consists of two half molds, each of which has an L-shaped cross section.

In the above embodiments, the heating mold may be a full hermetic, half hermetic or a combination of hermetic and semi hermetic.

As described above, according to one aspect of the present invention, since the resin exudates can proceed smoothly through a heater or mold, no lubricant is required.

According to another feature of the invention, the resin exudates are foamed under pressure rather than freely foamed, resulting in a uniform crosslinked foam product as well as being smaller.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (13)

(A) uniformly mixing at least one crosslinkable resin, at least one crosslinker, at least one blowing agent, and some additives to form a resin composition, (B) exuding the resin composition through a die to produce exudates of a predetermined shape; (C) obtaining the crosslinked foamed product by heating the exudate to a temperature sufficient to crosslink and foam the crosslinkable resin while driving the exudate with a drive to move in the exudation direction; A process for producing a crosslinked foam product, characterized in that The method of claim 1, After step (B) and before step (C) (B1) further comprising heating the exudate to a temperature sufficient to crosslink a portion of the crosslinkable resin. The method of claim 2, Carried out simultaneously with the step (B1) (B2) further comprising the step of driving the exudate by the drive means to move in the exudation direction. An extruder for heating the crosslinkable resin composition comprising at least one crosslinkable resin, at least one crosslinker, at least one blowing agent and some additives to make the molten resin composition, A die connected to the extruder so that the molten resin composition can be extruded into an extruder having a predetermined shape; A heating mold for receiving the exudates and heating the crosslinkable resin to a temperature sufficient to crosslink and foam the resin; And driving means for driving the exudates in the heating mold to move in the exudation direction. The method of claim 4, wherein Apparatus for producing a cross-linked foamed product, characterized in that the heating mold has two half molds each having a U-shaped cross section. The method of claim 4, wherein Apparatus for producing a cross-linked foamed product, characterized in that the heating mold has two half molds each having an L-shaped cross section. The method of claim 4, wherein The driving means includes a plurality of driving pulleys and a plurality of conveying belts, and transfers and drives each conveying belt by a pair of pulleys, and drives the exudate in the heating mold by contacting the exudates to move in the exuding direction. Apparatus for producing a crosslinked foam product, characterized in that. The method of claim 4, wherein The driving means includes a plurality of drive pulleys and a plurality of transfer belts, and transfers and drives each transfer belt by a pair of pulleys, and drives the heating mold connected to the transfer belt by a transfer belt. Apparatus for producing a cross-linked foamed product, characterized in that the exudates are moved in the exudation direction in accordance with the movement of the heating mold. The method of claim 4, wherein And a heater provided between said die and said heating mold for heating said exudates to crosslink a portion of said crosslinkable resin. The method of claim 9, And said heater comprises means for driving said exudate to move in the exudation direction. The method of claim 10, The driving means has a conveying belt and a pair of pulleys, and the conveying belt is transferred and driven by a pair of pulleys, and in contact with the exudate to drive the exudate to move in the exuding direction. Apparatus for producing a cross-linked foam product. The method of claim 10, The drive means has two conveying belts and two pairs of pulleys, and the exudates between the two conveying belts are moved in the exuding direction by transmitting and driving each conveying belt by a pair of pulleys and contacting the exudates. Apparatus for producing a crosslinked foam product, characterized in that. The method of claim 10, And said drive means comprises a plurality of rollers, said exudates being moved in the outflow direction in accordance with the movement of said rollers.