JP2528577B2 - Method for producing foamed molded article - 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 producing a foamed molded product in which, for example, a leg portion gripped by a robot when it is transported by a robot is locally reinforced.

[0002]

2. Description of the Related Art Conventionally, foamed resin moldings such as polystyrene having excellent cushioning properties, light weight and moldability have been used as storage containers for transporting and storing precision parts such as gears. As the factory becomes unmanned, robots are used to transport and move the above parts inside the factory, and the robot transports the foamed resin moldings containing precision parts. Then, when the foamed resin molded body is installed at a predetermined position, the projecting portions such as legs of the foamed resin molded body are grasped by a robot arm and moved.

Such a foam-molded article is required to have a function such as high strength, and such a function may be required for the whole foam-molded article, but it is sufficient if it is partially satisfied. There are also many. Therefore, as a method of molding a foam-molded article to which a function is locally imparted as described above, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-55228, after the raw material is filled by vacuum suction, a different kind of raw material is used. A method is known in which a raw material is pressurized and filled to sequentially fractionate and fill each in a mold, and heat-foam to partially impart a desired function.

[0004]

However, in the above-mentioned conventional method, the raw material filled in the mold is floated by the air press-fitted in the vicinity of the interface in contact with the different raw material. This floating causes different raw materials to be mixed with each other in the vicinity of the interface, which is an obstacle to reliable divided filling.

Therefore, in the above method, for example, it becomes difficult to accurately fill a raw material having a low expansion ratio capable of increasing the compressive strength only in a local portion such as a leg portion required for the foamed molded product. However, there is a problem that the above-mentioned local area lacks compressive strength and is easily damaged when the local area is gripped by the robot arm or the like.

Therefore, an object of the present invention is to provide a method for producing a foam-molded article in which strengths and the like are locally increased by surely dividing and filling different raw materials.

[0007]

In order to solve the above-mentioned problems, the method for producing a foam-molded article of the present invention is a method of foam-molding pre-expanded particles obtained by pre-expanding expandable resin particles to a predetermined expansion ratio. It is characterized in that after filling the mold cavity in the mold, it is heated to roughly fuse the pre-expanded particles to each other, and then the reinforcing pre-expanded particles are further filled in the mold cavity and heated to be fused.

[0008]

According to the above-mentioned method, after the pre-expanded particles are filled in the mold, the pre-expanded particles for reinforcement are filled after the pre-expanded particles are heated and coarsely fused to each other. Mixing of the particles with the reinforcing pre-expanded particles is avoided.

Therefore, when the reinforcing pre-expanded particles having an expansion ratio lower than the predetermined expansion ratio are used as the reinforcing pre-expanded particles, for example, in order to impart a function of increasing the compressive strength, the above-mentioned method is used. The strength of the local part, which is the filled part, can be made higher than that of the part filled with the pre-expanded particles, and the above-mentioned function can be locally provided.

Thus, if the portion filled with the pre-expanded reinforcing particles is molded into a leg for gripping by the robot arm, for example, a robot in which precise control of gripping force is difficult is achieved. The gripped legs can be locally strengthened.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS. As shown in FIG. 2, the molding apparatus in the method for manufacturing a foam molded article has a male mold 1 and a female mold 2 as a mold for foam molding,
The male mold 1 and the female mold 2 are brought into contact with each other at a predetermined position to form a cavity portion (mold cavity ) 3 filled with pre-expanded particles as a raw material.

The male mold 1 and the female mold 2 are hollow inside, and the steam pipe 17 for introducing the saturated steam S of a predetermined pressure for heating and the cavity portion 3 are formed in these hollows. A cooling water pipe (not shown) for cooling is connected. Further, in the inner walls 1a and 2a of the male mold 1 and the female mold 2 on the cavity portion 3 side, a large number of male vapor holes 1b and female vapor holes 2b that respectively connect the hollow portions and the cavity portion 3 are formed. ing.

The inner wall 2a of the female mold 2 forming the cavity 3 is filled with pre-expanded particles obtained by pre-expanding expandable thermoplastic resin particles such as expanded polystyrene to a predetermined ratio. Holes 4a, 4b and 4c are formed respectively. The positions and the number of the filling holes 4 ... Are set according to the shape of the foamed molded product and the position and the number of function-added parts such as local increase in compressive strength.

The expandable thermoplastic resin particles are
It is not limited to expanded polystyrene, and it is also possible to use other expandable thermoplastic resin particles such as polyethylene and polypropylene used for foam molding.

Each of the above-mentioned filling holes 4 ... Is provided by penetrating the outer wall from the inside of the hollow of the female mold 2 at a predetermined position.
An air passage 5 for introducing air having a predetermined pressure into the filling hole 4 and a foamed grain lead-out passage 6 for introducing the raw material into the filling hole 4 are formed in the filling hole 4 penetrating the outer wall of , A feeder 8a, 8b, 8c having a built-in piston 7 capable of advancing and retreating in the direction of the cavity 3 are provided respectively, and the filling holes 4 ... Are forward movements of the piston 7 in the direction of the cavity 3. The air passage 5 and the foamed-particle leading-out passage 6 are closed by the above, and are opened by retreating.

The head surface of the filling hole 4b facing the cavity 3 of the piston 7 in the central portion is formed into a flat surface, while the head surface of the piston 7 of each filling hole 4a, 4c at the end portion is formed on the head top surface. As shown in FIG. 1, a protrusion 18 having a substantially columnar shape from the center of the head top surface in the advancing / retracting direction of the piston 7 forms a leg having a substantially cylindrical shape as a portion for adding a function such as increasing compression strength. Has been set up for. The shape of the protruding portion 18 is not particularly limited as long as it does not hinder the die cutting.

Further, as shown in FIG. 2, each of the above-mentioned expanded granule outlet paths 6 is provided with a granulation hose 9, and among these granulation hoses 9 ..., Upper and lower filling holes 4a.
Granule feeding hose 9 provided in 4c via foamed grain lead-out path 6
Are respectively connected to one side and the other side of a branch nozzle 10. The branch nozzle 10 is a pre-expanded reinforcing particle which is, for example, expanded polystyrene particles pre-expanded five times through a shutter valve 11 which can be opened and closed. (Not shown)
Is connected to the first hopper 12 stored as a raw material.

On the other hand, the foamed grain lead-out path 6 formed in the filling hole 4b in the central portion is provided with the second hopper arranged in parallel with the first hopper 12 through the grain feeding hose 9, the nozzle 13 and the shutter valve 11. It is connected to 14. Also, this second
In the hopper 14, pre-expanded particles (not shown), which are expanded polystyrene particles pre-expanded 20 times, are stored as a raw material. Thus, in the above device, 2
Two systems of filling means are provided so that the seed materials can be filled.

Next, using the apparatus having the above structure, as shown in FIGS. 3 and 4, the wall thickness is 15 mm, the length is 200 mm, and the width is
An approximately box-shaped foamed body 19 having an upper surface opening of 300 mm and a rising portion of 40 mm is molded, and the required portion is formed of pre-expanded particles having a foaming ratio of 20 times, and a substantially cylindrical leg portion extending downward at the four corners of the bottom surface. A method of forming 20 by using pre-expanded particles for strengthening having a foaming ratio of 5 times and strengthening the strength of the leg portions 20 will be described below.

First of all, as shown in FIG.
The piston 7b corresponding to b is retracted, the filling hole 4b is opened, and the shutter valve 11 of the second hopper 14 is opened. As a result, the pre-expanded particles 15 having the expansion ratio of 20 times are sucked by the airflow flowing from the air passage 5 to the cavity portion 3 and filled in the cavity portion 3. At this time, the other filling holes 4a, 4c are closed by the pistons 7a, 7c, as shown in FIG.

Thereafter, the female steam hole 2b is changed to the male steam hole 1
Pressurized steam (0.3 to 0.35 kg / cm ² G) is caused to flow toward b for about 15 seconds to cause the pre-expanded particles 15 filled in the cavity 3 to be coarsely fused to each other and roughly formed. At this time, a mark of the filling hole 4b is formed on the surface of the rough-molded product which is in contact with the female mold 2, as shown in FIG.

Subsequently, the pistons 7a and 7c of the filling holes 4a and 4c in FIG. 2 are retracted to open the foamed particle lead-out passages 6 and the air passages 5 in the filling holes 4a and 4c, and the first hopper 12 of the first hopper 12 is opened. The shutter valve 11 is opened.
At this time, since the pre-expanded particles 15 in the cavity portion 3 are roughly fused to each other, the shape of the contact surface with the pistons 7a and 7c can be maintained.

Next, the pressurized air is sent from the air passages 5 and 5 into the filling holes 4a and 4c, and the blowing force of this air flow causes the expansion ratio of 5 times stored in the first hopper 12 to be increased. Each of the filling holes 4a
Fill 4c.

Thereafter, as shown in FIG. 5, the piston 7a in the filling hole 4a is advanced to close the air passages 5 and the foamed-particle lead-out paths 6, and the reinforcing pre-expanded particles 16 are pushed in to top the head. It is formed into a shape corresponding to the shape of the protruding portion 18 of the surface, that is, a substantially cylindrical leg portion. In the figure,
Although the filling hole 4a has been described as an example, the same applies to the other filling holes 4c.

Next, one-side heating, that is, the female steam hole 2
Pre-expanded particles 15 filled in the cavity 3 are heated by flowing pressurized steam (0.9 to 0.95 kg / cm ² G) into the cavity 3 from b toward the male-type steam hole 1b for about 20 seconds.
The reinforcing pre-expanded particles 16 of the filling holes 4a and 4c are made to adapt to each other and fused. Pressurized steam (0.9 to 0.95 kg / cm ²
The pressure of G), that is, the heating temperature is for forming and fusing pre-expanded particles for reinforcement having a low expansion ratio of about 5 times.

Next, reverse heating is performed, that is, pressurized steam (0.9 to 0.95 kg / cm ² G) is flowed into the cavity 3 from the male steam hole 1b toward the female steam hole 2b for about 8 to 10 seconds. After heating by heating both sides, that is, pressurizing steam (0.9 steam) from the male steam hole 1b and the female steam hole 2b into the cavity 3
~ 0.95 kg / cm ² G) for about 15 seconds.

Next, water is flowed through the hollow portions of the male mold 1 and the female mold 2 for about 20 seconds to cool the foamed molded product in the cavity 3, and then the surface pressure is allowed to cool to 0.1 kg / cm ^2. By taking out the obtained foamed molded product from the cavity portion 3, the production of the foamed molded product which is strengthened in a plurality of local parts such as the leg portions and which is excellent in lightness and cushioning property is completed.

As described above, in the method of the above-described embodiment, the mixing between raw materials having different expansion ratios is extremely small. That is, as shown in FIG. 1, the reinforcing pre-expanded particles 16 filled in the filling holes 4a and 4c are
Since the pre-expanded particles 15 in the cavity portion 3 have already been roughly fused, they do not mix with the reinforcing pre-expanded particles 16, and then the pre-expanded particles 15 and the reinforcing pre-expanded particles 16 are heated and fused. As a result, they are fused at their contact surfaces, and mixing is prevented.

Therefore, according to this method, the pre-expanded reinforcing particles as a raw material for imparting the function can be accurately provided only in a necessary portion of the foam-molded article by setting the filling hole in the portion where the function is to be imparted. It is possible to fill separately.

[0030] As described above, the method capable of performing accurate divided filling does not require excessive filling of the reinforcing pre-expanded particles, which causes an increase in cost, so that the cost of the foam-molded article can be reduced. In addition, since it is possible to easily and locally express the property of high compressive strength of the pre-expanded particles for reinforcement, it is possible to transport a robot or the like in which it is difficult to control the high-precision gripping force. Also, it is possible to stably obtain a foam-molded article having a locally reinforced gripped portion so that it can also be suitably used.

Further, the apparatus in the above-mentioned method only needs to consider the filling order of each raw material and the head shape of each piston 7, and does not require, for example, a conventional apparatus for sorting, so that the structure is simple. It is possible to make it relatively inexpensive.

Moreover, conventionally, the pre-expanded particles as the raw material previously filled are not roughly fused but are almost fixed by using an air flow or the like, and the different raw materials are sequentially laminated and then heat-fused. Therefore, filling of different raw materials was possible only in one local area.

However, in the above method, if the number and positions of the filling holes 4 are set according to the required local portions, it is possible to impart a function of increasing the compressive strength to a plurality of local portions.

In this embodiment, two kinds of raw materials having different functions are respectively filled,
The present invention is not limited to this, and it is possible to locally fill three or more kinds of raw materials having different functions, respectively.

Further, in the method of the above-mentioned embodiment, the example in which the expanded polystyrene having a low expansion ratio is used as the reinforcing pre-expanded particles for increasing the compressive strength as the function to be imparted has been described. In order to impart the function of improving the properties and chemical resistance, polyethylene-based pre-expanded particles, styrene-modified polyethylene-based pre-expanded particles and the like may be used as the reinforcing pre-expanded particles.

[0036]

As described above, according to the method for producing a foamed molded article of the present invention, after the pre-expanded particles obtained by pre-expanding the expandable resin particles to a predetermined expansion ratio are filled in the mold cavity in the mold for foam molding. After heating and pre-expanding the pre-expanded particles to each other, the pre-expanded reinforcing particles are further filled in the mold cavity and heated to be fused.

Therefore, the above method is locally strengthened when, for example, preexpanded particles having a lower expansion ratio than the predetermined expansion ratio are used as the reinforcing preexpanded particles in order to impart the function of increasing the compressive strength. The foamed molded product can be easily and stably manufactured.

From this, for example, the robot can be used for transportation in which it is difficult to control the high-precision gripping force,
This has the effect of stably obtaining a foamed molded product having a strengthened local portion to be gripped.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a main part of an apparatus used in a method for producing a foamed molded product of the present invention.

FIG. 2 is a schematic sectional view of the device.

FIG. 3 is a front view showing a partially broken view of a foam molded article obtained by the above apparatus.

FIG. 4 is a bottom view of the foam molded article.

FIG. 5 is a cross-sectional view of the main parts of the device.

[Explanation of symbols]

3 Cavity (mold cavity ) 15 Pre-expanded particles for reinforcement 16 Pre-expanded particles

Claims (1)

(57) [Claims] 1. A pre-expanded particle obtained by pre-expanding expandable resin particles to a predetermined expansion ratio is filled in a mold cavity of a mold for foam molding and then heated to coarsely fuse the pre-expanded particles to each other. A method for producing a foamed molded product, further comprising filling pre-expanded reinforcing particles in the mold cavity and heating and fusing.