JPH1044177A - Molding method and molding die for thermoplastic resin foamed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the generation of recesses (notches) on the corners of step sections by uniformizing the heating to foaming synthetic resin on the step section when a foamed body with step sections is molded. SOLUTION: In a molding method for a thermoplastic resin foamed body in which foaming synthetic resin is filled into a molding space 14 formed by setting a male mold 1 with a female mold 2 of a male and female setting mold 3 and then the foaming synthetic resin is heat fusion bonded to form a foamed body 17 with step sections 19, 20 and 21, a heating medium is sprayed through a slit 13 formed in the mold peripheral edge direction of corners 20C of the above-said step sections 20 and the like of the male and female setting mold 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for filling a molding space formed by fitting a male mold and a female mold of a male-female fitting mold with a foaming synthetic resin and then heating the molding space with steam or the like. The present invention relates to a thermoplastic resin foam molding method for molding a foam by heating and fusing a medium to the foamable synthetic resin, and a mold for molding a thermoplastic resin foam.

[0002]

2. Description of the Related Art In a conventional molding method, a plurality of circular steam holes for spraying steam as a heating medium to a foamable synthetic resin filled in a molding space are formed in a mold. By blowing steam directly to the foamable synthetic resin from the steam holes, good heat fusion is performed. By the way, when molding a foam having a complicated shape having a stepped portion, by blowing steam to a portion corresponding to a corner of the stepped portion, the elongation of the foamable synthetic resin in the blown portion is good. To be able to. However, since a circular steam hole having a size larger than the corner of the step cannot be formed at the corner as described above, conventionally, as shown in FIG. 10, the hole corresponds to the corner of the step. A steam outlet for blowing steam to the portion was constituted by a plurality of small holes 30 having small diameters. The numbers other than the drill holes 30 shown in the figure are the same as those given the same numbers as described below, and therefore, the description will be omitted.

[0003] By blowing steam from a plurality of small-diameter drill holes 30 formed along the peripheral direction of the mold 1 to a portion corresponding to the stepped portion, foaming of the blown portion is performed. Although it is possible to improve the elongation of the conductive synthetic resin, at the corner of the step portion of the peripheral portion deviated from the drill hole 30, that is, at the corner of the step portion located between the drill hole 30 and the drill hole 30, Good expansion of the expandable synthetic resin cannot be achieved. For this reason, the expansion of the entire foamable synthetic resin at the corners of the step portion cannot be made uniform in the peripheral direction, and a part of the corner portion of the step portion to which steam is not blown is recessed, and the step portion In some cases, dents (chips) may occur at some of the corners. In particular, when the foamable synthetic resin is polypropylene or polyethylene, since the holding power of the blowing agent gas is weak, the dents (chips) are easily generated, and there is room for improvement.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present invention aims to solve the problem by uniformly heating a foamable synthetic resin in a step portion when molding a foam having a step portion. Thus, it is possible to prevent the occurrence of a dent (chipping) at the corner of the step portion.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a foamable synthetic resin in a molding space formed by fitting a male mold and a female mold of a male-female fitting mold. A method for molding a thermoplastic resin foam, wherein the foam obtained by heating and fusing the foamable synthetic resin after filling the resin is a thermoplastic resin foam having a stepped portion, wherein a corner of the stepped portion of the male and female fitting mold is provided. It is characterized in that a heating medium is blown through a slit formed in the peripheral direction of the mold of the portion. Therefore, by blowing steam as a heating medium to the foamable synthetic resin filled in the molding space through a long slit in the peripheral direction of the male and female fitting mold, the foamable synthetic resin filled in the molding space Steam heating can be performed uniformly over substantially the entire area in the peripheral direction.

[0006] After filling a foamable synthetic resin into a molding space formed by fitting a male mold and a female mold of a male and female fitting mold, the foamable synthetic resin is heated and fused. A mold for molding a foam to be molded, wherein at least one of the male mold and the female mold has a stepped portion for molding a thermoplastic resin foam, A blowing port for blowing a heating medium to the foamable synthetic resin filled in the molding space is formed in a slit shape in a peripheral direction of a corner portion in the step portion of the male and female fitting mold, and the thermoplastic resin foam is formed. A mold for molding the body was constructed. Thus, as described above, the steam as the heating medium was filled in the molding space by spraying the foamable synthetic resin filled in the molding space through a long slit in the peripheral direction of the male and female fitting mold. Steam heating can be performed uniformly over substantially the entire peripheral direction of the expandable synthetic resin.

The step portion is formed by forming a surface along the fitting direction of the male and female fitting dies and a vertical surface orthogonal to the surface, and forming the outlet on the vertical surface. Chipping can be effectively prevented from occurring in a part of the vertical surface of the foam. On the other hand, conventionally, a projecting portion in which a part or the whole of a portion where steam as a heating medium is blown is raised, that is, a burr is formed,
In the present invention, since the burr is formed on a surface perpendicular to the fitting direction, when the step portion of the foam is viewed from the fitting direction, when the burr is formed on a surface along the fitting direction, It is inconspicuous and has high commercial value.

[0008]

FIG. 1 shows a molding die for molding a thermoplastic resin foam using the extrusion molding method of the present invention. This mold is a male mold (core mold) 1 on the movable side.
A male-female fitting mold 3 is composed of a fixed female mold (cavity mold) 2 fitted to the male mold 1. As a material to be filled in such a male-female fitting mold 3, a molding material made of a bead-like foamable synthetic resin foamed with a foaming agent such as propane, butane, or pentane is used. By filling the pre-foamed one into the male and female mating mold 3 and heating,
I try to get a foam. The molding material to be filled in the male and female fitting mold 3 is referred to as an expandable synthetic resin, and the molded product obtained by filling the male and female fitting mold 3 and heating is referred to as a foam. The mold is pre-foamed (primarily foamed) as described above, and is then heated to a temperature required for secondary foaming or to a temperature required for good fusion between the foams. A heating mechanism for blowing steam as a medium to the foamable synthetic resin and a water cooling mechanism for lowering the temperature to a temperature required for mold release are provided. The description of the water cooling mechanism is omitted. As the molding material, besides polystyrene resin, various synthetic resin materials such as polyolefin resin such as polypropylene and polyethylene can be used, and the molding material is not limited to these.

Referring to the male mold (core mold) 1, as shown in FIGS. 1 and 3, a male mold (core mold) having three steps 4, 5, 6 in the fitting direction. 1 is fixed to a fixing plate 7 with screws 8... A frame 10 for forming a steam chamber 9 is fixed to the fixing plate 7, and a back plate 11 for closing the upper opening of the frame 10 is formed on the frame 10. Is fixed. Accordingly, the steam in the steam chamber 9 supplied with steam from a steam generator (not shown) is filled into the male mold (core mold) 1 through the opening 7A formed in the center of the fixed plate 7. This constitutes a heating mechanism that can perform heating.

The step portion 4 or 5 or 6 is composed of a surface 4A or 5A or 6A along the fitting direction of the male and female fitting mold 3, and a vertical surface 4B or 5B or 6B orthogonal to this surface. ing.

The steam filled in the male mold (core mold) 1 is guided downward through a plurality of vertical holes 12 formed in the male mold (core mold) 1. Through a long slit-shaped peripheral groove 13 extending in the peripheral direction of the mold communicating with the vertical holes 12, a space 14 defined by the male mold (core mold) 1 and the female mold (cavity mold) 2 is formed. The foamed synthetic resin is sprayed. This prevents a dent (chip) from being generated at any position of the peripheral corner 20C of the blown foamable synthetic resin. In order to form the circumferential groove 13,
The male mold (core mold) 1 is composed of a first mold part 1A located at an upper part and a second mold part 1B located at a lower part which is fixed to a center part of a lower end of the first mold part 1A by a bolt 25. It is composed of The end of the peripheral groove 13 on the foamable synthetic resin side is
The steam outlet 13A for blowing steam to the foamable synthetic resin is referred to as a face 4A or 5A or 6A along the fitting direction of the male and female fitting die 3.
A is formed at the corner 5C of the surface 5A located at the middle in the vertical direction of A. The first mold part 1A and the second mold part 1B may be integrally formed.

The female mold (cavity mold) 2 is fixed to a fixing plate 15 with screws 16.

The male mold (core mold) may be configured as shown in FIGS. That is, in FIG. 1, the steam outlet 13A is formed at the corner 5C of the surface 5A along the fitting direction of the male-female fitting die 3, but instead, in FIG. Vertical surface 4B orthogonal to surface 4A or 5A or 6A along the fitting direction of female fitting mold 3
Alternatively, an example is shown in which the vertical surface 5B is formed at the corner 5C of the vertical surface 5B located at the middle in the vertical direction of 5B or 6B. With this configuration, the foam 17 formed by blowing the steam from the steam outlet 13A onto the foamable synthetic resin has a part of the portion where the steam is blown, as shown in FIG. Or, the raised portion that is all raised, that is, burr 18
Is formed. However, when viewed from the fitting direction of the male and female fitting mold 3, that is, the arrow K direction in the figure, the burr 18 is in the case illustrated in FIG. In the case where the product is formed, the protrusion (burr) is clear, but it is hard to stand out from the direction in which the product is observed, so that the aesthetic appearance of the product is increased and a favorable result is obtained. Although the case where the steam outlet 13A is formed at the corner of the vertical surface 5B located in the middle in the vertical direction or the corner of the surface 5A along the fitting direction of the male and female fitting mold 3 is shown, the other surface 4A is shown. , 4B, 6A, 6B may be formed at the corners,
The position and number of the steam outlets 13A are not limited to those shown in the drawing.

The foam 17 molded by the male and female fitting die 3 has three steps 19, 20, 21 corresponding to the steps 4, 5, 6 as shown in FIG. Hole 22
Is formed into a frame shape in which a plurality (actually four) are formed, the frame-shaped foams 17 are arranged on the left and right, and these two right and left are set as one set, and both ends of the medical tube are set on the left and right It is intended to be inserted into the holes 22 and 22 and used as a sealing jig. The step 19, 20 or 21 is composed of a surface 19A or 20A or 21A along the fitting direction of the male and female fitting mold 3, and a vertical surface 19B or 20B or 21B orthogonal to this surface. I have.

The shape of each of the steps 4, 5 and 6 of the male and female fitting mold 3 may be a curve, in addition to the linear shape shown in the drawings, or a surface forming the steps 4 or 5 or 6. 4A,
The angle between 4B or 5A, 5B or 6A, 6B may be set to 90 degrees or may be set to any other angle.

The steam outlet 13A is formed so as to be continuous over the entire peripheral direction of the male and female fitting die 3, but as shown in FIG. Alternatively, it may be configured as a slit-shaped hole that is continuous for a certain length.

Steps 19 and 2 are formed on the inner surface of the foam 17.
The male-female fitting mold 3 is configured so that the molds 0 and 21 are formed. However, as shown in FIG.
The steam outlet 13A may be formed in the female mold 2 of the male-female fitting mold 3 so that 9, 20, 21 are formed. In this case, the steam chamber 9 is formed in the female mold 2.

[0018]

According to the first and second aspects of the present invention, steam as a heating medium is blown onto the foamable synthetic resin through a long outlet in the peripheral direction. In the case where the structure of the present invention is used to blow steam to the foamable synthetic resin through a plurality of drill holes in the related art, the steam in the circumferential direction is larger than that in the case where steam is not often blown in the circumferential direction. Can increase the spray area of
A molding method and a molding method for a thermoplastic resin foam capable of avoiding the occurrence of a dent (chipping) at a corner of a step portion and capable of favorably molding a foam having a complicated shape having a step portion. Mold can be provided. In particular, even with a foaming synthetic resin such as polypropylene or polyethylene having a low holding power for a foaming agent gas, no dents (cracks) are generated at the corners of the step portion, and good foam molding can be achieved. It can be carried out.

According to the third aspect, by forming the outlet at a vertical surface, the protrusion, that is, the burr can be made less noticeable than when the outlet is formed at the surface along the fitting direction. Is advantageous.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a male and female fitting mold.

FIG. 2 is a cross-sectional view of a foam formed using the male-female fitting mold of FIG. 1;

FIG. 3 is a partially omitted perspective view of an example of a male-female fitting mold.

FIG. 4 is a cross-sectional view showing an example of a male and female fitting mold.

FIG. 5 is a cross-sectional view of a foam formed using the male-female fitting mold of FIG. 4;

FIG. 6 is a perspective view of an example of a male-female fitting mold with a part omitted.

FIG. 7 is a partially omitted perspective view of a foam.

FIG. 8 is a plan view of an example of a male-female fitting die cut in a horizontal direction with a part omitted.

FIG. 9 is a sectional view showing an example of a male-female fitting mold.

FIG. 10 is a sectional view showing a conventional example of a male and female fitting mold.

[Explanation of symbols]

 1 Male mold 1A First mold part 1B Second mold part 2 Female mold 3 Male and female mating mold 4 Step part 4A surface 4B Vertical surface 5 Step part 5A surface 5B Vertical surface 6 Step part 6A surface 6B Vertical surface 7 Fixing plate 7A Opening 8 Screw 9 Steam room 10 Frame 11 Back plate 12 Vertical hole 13 Peripheral groove 13A Steam outlet 14 Space 15 Fixing plate 16 Screw 17 Foam 18 Burr 19 Step 19A surface 19B Vertical surface 20 Step 20A surface 20B Vertical surface 21 Stepped part 21A surface 21B Vertical surface 25 Bolt 5C, 20C Corner 30 Drill hole K Arrow

Claims (3)

[Claims] 1. A foamable synthetic resin is filled in a molding space formed by fitting a male mold and a female mold of a male-female fitting mold, and then the foamable synthetic resin is heated and fused. The foam obtained is a method for molding a thermoplastic resin foam having a stepped portion, wherein steam is transmitted through a slit formed in a peripheral direction of a corner of the stepped portion of the male and female fitting die. A method for molding a thermoplastic resin foam, characterized by spraying. 2. A foamable synthetic resin is filled in a molding space formed by fitting a male mold and a female mold of a male-female fitting mold, and then the foamable synthetic resin is heated and fused. A mold for molding a foam obtained by the above method, wherein at least one of the male mold and the female mold is provided with a stepped portion, and the mold for molding a thermoplastic resin foam is provided. An outlet for blowing a heating medium onto the expandable synthetic resin filled in the molding space is formed in a slit shape in a peripheral direction of a corner of the step portion of the male and female fitting die. For molding thermoplastic resin foam. 3. The step portion comprises a surface along the fitting direction of the male and female fitting die and a vertical surface orthogonal to the surface, and the outlet is formed on the vertical surface. 2. A mold for molding the thermoplastic resin foam according to 2.