JP2681730B2 - Molding method of foam with skin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a skinned foam.

[0002]

2. Description of the Related Art As is well known, foamed plastics (also referred to simply as foams) are used in a wide range of applications such as heat insulating materials, sound absorbing materials, and floating materials. A "mold foam molding method" is known. This mold foam molding method is a method in which pre-expanded resin particles are put into a mold, and heated steam is blown into the mold to heat and fuse them (see, for example, Japanese Patent Publication No. 3-56905).

[0003] On the other hand, a foam with a skin in which the surface of a thermoplastic resin foam is made dense (for example, Japanese Patent Publication No.
No. 10752). For example, this is obtained by injecting pre-expanded resin particles into a hollow non-foamed body for foaming. With the advent of the foamed body with skin, the foamed plastic has further expanded its applications.

[0004] A method for molding such a skinned foam will be described. The non-foamable parison constituting the skin is blow-molded in a blow mold, and then solidified by cooling to form a hollow body.
Take out from the mold, put the pre-expanded resin particles (hereinafter sometimes simply referred to as expanded beads) into this hollow body, and further,
Insert a heated steam injection pipe into this, blow heated steam from this injection pipe to heat the foam beads to further foam, and remove the injection pipe before the beads are fused to each other. Is a method for producing a foam with skin (see, for example, JP-B-62-19239, JP-B-58-10217, and JP-B-62-9073).

However, in such a method of forming a foam with a skin, 1) since the hollow body and the foam in the hollow body are formed in separate steps, equipment such as a mold is separately required. Becomes complicated. In particular, since the cooling and solidifying time of the hollow body and the heating, fusing and cooling and solidifying time of the foam beads are separately required, productivity is deteriorated. 2) Foam beads are added to the cooled hollow body. Therefore, there is a problem that the fusion between the hollow body and the foam is not completely performed since the molding is performed with the addition of the heat sink.

Therefore, in order to solve the above problem, a reaction foaming liquid such as urethane is injected into the parison while the parison constituting the hollow body is sealed in a blow mold, and the parison is placed on the inner surface of the blow mold. A method has been proposed in which the parison is cooled and solidified while the mold is clamped, and the foamed material is reacted and solidified to obtain a skinned foam (for example, Japanese Patent Publication No. 58-10217, Kaihei 3-
293113).

However, in the foam molding method proposed above, since the parison is blow-molded along the inner surface of the mold by the foaming pressure of the foam material, the parison blow pressure tends to be insufficient. As a result, there has been a problem that the parison cannot sufficiently follow particularly the complicated inner surface shape, and that the expansion ratio of the parison also becomes non-uniform.

Therefore, the inventors of the present invention have combined a mold for performing ordinary blow molding and a mold for performing foam molding of a mold into one,
A method of shortening the molding cycle as much as possible by subjecting a parison to ordinary blow molding, and placing a foam bead in the molded hollow body and heating and fusing the same (Japanese Patent Application No. 3-252).
111).

The present invention has been made on the basis of the above findings, and in particular, the hollow beads which are hermetically sealed and not sufficiently cooled and solidified are pneumatically fed by an air injector or the like to efficiently generate foam beads. It was done about the point of filling well.

[0010]

The gist of the present invention is as follows: 1) In a blow molding die, a parison suspended in the die is blow molded to form a hollow molded body, Subsequently, before the hollow molded body is cooled and solidified, the hollow molded body is filled with thermoplastic pre-expanded resin particles and the particles are heated.
A method for molding a foam with a skin by fusion-bonding to form a foam, wherein the hollow foam is vacuumed when the expanded resin particles are filled. In the method, further, in order to further accelerate the molding cycle, 2) filling of the foamed resin particles into the hollow molded body is carried out by pressurized air, molding of the skinned foam body according to claim 1. On the way.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a molding apparatus that can be used in the present invention will be described below with reference to the drawings.

1 to 5, reference numeral 5 denotes a blow molding die (one split die shown in a state in which the other of the blow molding die consisting of a pair of split dies is removed), Is blow
FIG. 2 is a cross-sectional view of the molding die 5 taken along a parting line. Reference numeral 4 denotes a parison extruder installed above the blow molding die 5. The parison extruder 4
The desired resin is heated and melted and blown as parison 2.
It can be supplied to the molding die 5.

Below the blow molding die 5, pipes 8 and 9 and a filling feeder 7 are provided on the parting line of the blow molding die 5 in the guide grooves 8a and 9a. , And 7a are installed so that their tips can slide in and out of the blow molding die 5, respectively. The other ends of the pipes 8 and 9 and the filling feeder 7 are fixed to a vertically movable mount 6 with the filling feeder 7 at the center. The mounting base 6 is provided with an elevating device 11 or the like on its leg 10 so as to be able to move up and down, and the pipes 8 and 9 and the filling feeder 7 are provided.
Is configured to be able to enter and exit the blow molding die 5.
As the elevating device 11, a rack and pinion mechanism, a servomotor mechanism, an air or hydraulic cylinder elevating mechanism, or the like is used.

When the mount 6 is moved forward, the pipes 8 and 9 penetrate deeply into the blow molding die 5 to some degree so that air or the like can be uniformly blown, and the filling feeder 7 is inserted.
Is in contact with or close to the inner wall surface of the blow mold 5;
Alternatively, a difference is provided between the lengths of the pipes 8 and 9 and the length of the filling feeder 7 so as to be slightly protruded.

Although FIG. 2 shows an example in which two pipes are provided, one pipe may be provided, or a larger number may be used when a large product is formed.

Each of the pipes 8 and 9 has a tip smaller than the diameter of the foam bead 3 and has an open tip, and a plurality of pores or slits 8 "and 9" having the same size on the side walls thereof. A perforated pipe or a pipe having its tip closed 8 ', 9', etc. is used. Further, these pipes are configured to be expandable and contractible to control the vertical positions of the pores or slits 8 ", 9". You may do it.

These pipes 8 and 9 are blown with blow molding air, vacuum in the hollow molded body before and / or during filling of the foam beads 3 and heated steam of the foam beads 3. And the function of the exhaust during the supply of heated steam, which will be described later, the function of the vacuum during the cooling and the function of the vacuum at the time of cooling. , The vacuum device 21, and the drain pipe 25 are valves 22, 22, 2 respectively.
Although they communicate with each other via 2,..., Of course, separate pipes may be provided according to the respective applications.

The filling feeder 7 communicates with an inlet 12 for introducing the foam beads 3 and an air source 18, and the foam beads
Air inlet 13 for filling the blow mold 3 into the blow molding die 5 by air pressure, and their inlets 12
And a piston valve 14 for opening and closing the air injector port 13. And this inlet 12
Is connected to a bead storage box 15 through a flexible pipe 16. In this bead storage box 15,
Pressurizing device 17 for effectively filling foam beads 3
Is provided.

Reference numeral 24a is a needle pin having a hole smaller than the diameter of the foam bead 3 provided in the upper corner portion of the blow molding die 5 and connected to the vacuum device 24. There is.

Further, in FIG. 5, a needle pin 24a having a hole smaller than the diameter of the foam bead 3 provided in the upper corner portion of the blow molding die 5 is referred to as an inner pin 24a '. Outside pin 24
It is a partial cross-sectional view showing another mold structure constituted by a "and is shown along the parting line of the blow molding mold 5.

A method for molding the foam with skin of the present invention using the above apparatus will be described below with reference to FIGS.

The parison 2 (for example, 180 to 220 ° C. for polypropylene resin and 160 to 200 ° C. for polyethylene resin) heated and melted was released from the extruder 4 arranged above the blow molding die 5. It is extruded and supplied to the mold 5. At this time, the temperature of the mold 5 is set at 40 to 80 ° C. (see FIG. 2).

After the parison 2 is supplied to the die 5, or before the parison 2 is supplied, the mounting table 6 is raised to insert the filling feeder 7 and the pipes 8 and 9 into the parison 2. When the supply of the parison 2 is completed, the mold 5 is closed and the parison 2 is sealed. Next, the valves 22 of the blow air pipes 19, 19 are opened, and air having a pressure of ^{2 to} 7 kg / cm ² (gage pressure) is supplied from the air source 18 through the pressure reducing valve 23 to the pipes 8, 9 to 10 to 10. The parison 2 is blown for 20 seconds to blow the parison 2 to form the hollow molded body 2a.

Thereafter, the valves 22 of the blow air pipes 19 and 19 are closed, the piston type valve 14 is opened during the cooling of the hollow molded body 2a, and air is supplied from the air source 18 to the air injector port 13. Then, the foam beads 3 are pneumatically fed to the hollow molding 2a through the inlet 12 (see FIG. 3).

When the foam beads 3 are filled, before and during the filling of the foam beads 3 into the hollow molded body 2a,
The valves 22 leading to the vacuum devices 21 and 21 are opened and / or needle pins 24a and 24a are inserted into the molded hollow molded body 2a to vacuum the hollow molded body 2a. The vacuum force at this time is 300 to 760 mm
The Hg is preferably 600 to 760 mmHg.

Furthermore, when filling the foam beads 3,
In order to improve the filling efficiency, bead storage box 15
Using a pressurizing device 17 attached to the above, pressure of 0.5 to 3 kg / cm ² , preferably 1.0 to 1.2 kg / cm ² (gate It may be filled by pressurizing the foam bead 3 or by sucking the foam bead 3 into the hollow molded body 2a by the force of the vacuum without applying a fluid pressure such as air to the foam bead side. You may fill so that it may do.

When the inside of the hollow molded body 2a is vacuumed,
Depending on the degree of cooling of the hollow molded body 2a, the size, the shape, etc., the hollow molded body 2a may tend to be recessed inward. In that case, although not shown, it is normally provided through the inner wall surface of the mold. The hollow molded body 2a is attracted to the mold side by vacuuming from the exhaust hole formed therein, or the inner pin 24a 'of the needle pin having a double structure is pierced into the hollow molded body as shown in FIG. At the same time as vacuuming, the hollow molded body 2a is also vacuumed by vacuuming the outer pin 24a "whose tip is located on the contact surface between the hollow molded body 2a and the mold 5.
It is good to pull the to the mold side.

The needle pin 24a can be provided at an appropriate position in addition to the upper corner portion of the blow molding die 5 described above, and particularly faces the filling feeder 7 in the filling direction. It is effective to install it in the position.

Then, each valve is closed and the heated steam source 2
Each of the valves 0, 20 is opened, and pipes 8, 9 are used to fill the foamed beads 3 with 0.1 to 1.2 kg / cm.
² , preferably 0.8 to 1.0 kg / cm ² (gage pressure);
That is, heated steam at 115 to 120 ° C. is blown in for 2 to 20 seconds. As a result, the pre-foamed bead 3 is
Further, they are foamed and fused to each other to form a foam molded article. At this time, heated steam is caused to flow from one of the two pipes 8 and 9, and the other pipe is opened to the atmosphere or vacuumed so that the heated steam in the filled foam beads 3 is heated. The flow of may be smooth. Further, depending on the shape of the skinned foam to be molded, the pipes 8 and 9 may alternately communicate with the vacuum device 21 and the heated steam source 20 at regular intervals.

After that, the molded skinned foam is cooled. As the cooling method, cooling from a conventional mold is used, but in addition, the condensed water may be sucked out by vacuuming from the pipes 8 and 9 through the vacuuming devices 21 and 21.

Finally, the mounting table 6 is lowered, and the filling
The blower 7, the pipes 8 and 9 are pulled out, the blow molding die 5 is opened, and the skinned foam 1 as a product is taken out (see FIG. 4).

The skinned foam 1 according to this embodiment is a hollow molded body 2a made of a polyolefin resin such as polyethylene or polypropylene, a polystyrene resin, a polyvinyl chloride resin, an ABS resin or the like and having a diameter of about 1 ^{mm to} 3 ^mm . The foamed molded article is obtained by heating and fusing pre-expanded resin particles 3 of polystyrene type, polyethylene type, or the like.

[0033]

According to the present invention, the following effects are listed. 1) Since the mold for blow molding and the mold for foam molding are combined into one mold, the molding process becomes one step, the molding equipment is simplified, the equipment cost is reduced, and eventually the production of foam with skin The cost can be reduced. 2) When the foamed beads were filled into the bag-shaped hollow molded body with the mold closed, the hollow molded body was filled while vacuuming, so that the entire molding cycle was extremely shortened and the foamed beads were densely packed. Can be filled. 3) If the expanded beads are filled into the hollow molded body under pressure, the expanded beads can be packed more densely. 4) Since the hollow molded body and the foamed beads are made of the same polyolefin resin, the fusion between the hollow molded body and the foamed body according to 1) is improved, and the foamed beads according to 2) and 3) above. Combined with the improvement of the filling efficiency of (1), a foam with skin having improved overall adhesive strength can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along a parting line of a mold in an example of an apparatus used in the first step of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the skinned foam of the present invention.

FIG. 3 is a cross-sectional view illustrating a production process of the skinned foam of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of the skinned foam of the present invention.

FIG. 5 is a partial cross-sectional view of another embodiment of the device used in the present invention.

[Explanation of symbols]

1 ... foam with skin, 2 ... parison, 2a ... hollow molded body,
3 ... Thermoplastic pre-expanded resin particles, 5 ... Blow molding die, 7 ... Filling feeder, 8, 9 ... Pipe, 22 ... Valve, 21, 24 ... Vacuum device, 24a ... Needle pin

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hiroyuki Yamaji, Inventor Hiroyuki Yamaji, 1000, Kawajiri-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Verdische Co., Ltd. (72) Inventor Yoshikazu Hatakeyama 4-chome, Minami-Yokkamachi, Sanjo City, Niigata Prefecture No. 6-1 Sanko Sogyo Co., Ltd. (72) Inventor Yoshiyuki Shida No. 86-1, Minami-Yokkamachi, Sanjo City, Niigata Sanko Sogyo Co., Ltd. (72) Inventor Atsushi Tamura East, Shinagawa-ku, Tokyo 1-14, Gotanda, Aron Kasei Co., Ltd. (72) Inventor, Kitaoka Takumi, 1-14, Higashi-Gotanda, Shinagawa-ku, Tokyo 1-chome, Aron Kasei (72) Inventor, Takashi Obama 1, Higashi-Gotanda, Shinagawa-ku, Tokyo Chome 14 Aron Kasei Co., Ltd. (56) Reference JP 59-145125 (JP, A) JP 3-293113 (JP, A) JP 5-138722 (JP, A) Open flat 1-184108 (JP, A) JP flat 6-166112 (JP, A) JP flat 6-166113 (JP, A)

Claims (3)

(57) [Claims] 1. A blow molding die is blow-molded into a parison hung in the die to form a hollow molding body, and subsequently, the hollow molding body is cooled and solidified. A method for molding a foam with skin, comprising molding thermoplastic pre-foamed resin particles in a molded body, heating and fusing the particles to mold a foamed molded body, wherein the hollow is used when filling the foamed resin particles. A method for molding a foam with skin, comprising vacuuming a molded body. 2. The method for molding a foam with a skin according to claim 1, wherein the foamed resin particles are filled in the hollow molded body with pressurized air. 3. Inside a blow molding die, depending on the die.
The parison was blow molded to form a hollow molded body and
Then, before the hollow molded body is cooled and solidified, the hollow molded body is
Fill the body with thermoplastic pre-expanded resin particles and add the particles.
Forming a foamed body with skin that heats and fuses to form a foamed body
Forming the hollow molded body and the particles
Of a foam with a skin characterized by using the same resin
Molding method.