JP2009119754A - Method for manufacturing hollow molded body with built-in foamed body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve rigidity and heat resistance of a blow molded body by uniformly expanding foamable resin beads in the hollow molded body and fusing them together in a case when the hollow molded body with a built-in foamed body is manufactured by secondarily foaming the foamable resin beads in the hollow molded body 1 in the blow molded body or the like. <P>SOLUTION: Holes 2 and 3 are formed in the hollow molded body 1, and a steam feeding pipe 4 and a vent pipe 6 in which a number of small holes 9 and 10 are formed are inserted into the hollow molded body 1 from the holes 2 and 3. Steam is fed into the inside of the hollow molded body 1 through the small holes 9 from the steam feeding pipe 4 and is vented to the outside through the small holes 10 from the vent pipe 6. After the secondary foaming is completed, the steam feeding pipe 4 and the vent pipe 6 are pulled out. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a foam-embedded hollow molded body by secondarily foaming foamable resin beads inside a hollow molded body.

  Patent Document 1 injects foamed resin beads that have undergone primary foaming (pre-foaming) into a plastic blow molded article, and supplies heated steam to the inside of the hollow molded article. A method for producing a foam-embedded hollow molded body that is heated and secondarily foamed to fill the hollow molded body is described. When supplying water vapor, holes are formed in one end and the other end of the blow molded body, a steam supply pipe in which a large number of small holes are formed is inserted in the hole formed in the one end, and the blow molded body is inserted through the small holes. Steam heated inside is supplied and exhausted through a hole (exhaust hole) formed in the other end.

Japanese Patent No. 3413257

According to the method described in Patent Document 1, the foamable resin beads secondarily foamed inside the blow molded body are filled inside the blow molded body, and the resin beads are welded to each other. Stiffness and heat insulation can be improved. Moreover, in the case of a float, there is an advantage that the foam inside has buoyancy even if the blow molded body which is the outer skin is torn and flooded.
However, a specific flow path from the steam supply pipe to the exhaust hole is formed in the blow molded body, and the steam flows preferentially through this flow path, depending on the shape of the blow molded body, but the part that is out of the flow path There is not enough steam. In such places, foaming of the resin beads becomes insufficient, the resin beads are not welded to each other (in a tattered state), and such a foam cannot sufficiently enhance the rigidity and heat insulation of the blow molded body. Also, if the resin beads are not welded together, the resin beads may spill out when the outer shell blow molded body is torn, contaminating the environment. It can be.

  On the other hand, it is conceivable to increase the flow path of the steam by forming a large number of exhaust holes and spread the steam into the blow molded body. However, forming a large number of exhaust holes increases the cost and closes the exhaust holes later. This will further increase the cost. Moreover, the closed hole is easily broken, and the strength and durability of the blow molded article are impaired, and the appearance is also deteriorated.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to foam a foamable resin bead in a hollow molded body such as a blow molded body to incorporate the foam. When manufacturing a hollow molded body, the foamable resin beads in the hollow molded body are uniformly foamed and welded together to improve the rigidity and heat resistance of the blow molded body, and this is formed into the hollow molded body The object is to achieve without increasing the number of holes to be made.

The present invention injects foamed resin beads that are primarily foamed into the hollow molded body, and supplies heated water vapor to the interior of the hollow molded body, thereby heating the foamed resin beads to cause secondary foaming. In the method of manufacturing a foam-embedded hollow molded body that fills the inside of the hollow molded body, a plurality of holes are formed in the hollow molded body, and a steam supply pipe and an exhaust pipe formed with a plurality of small holes through the holes are provided. The steam supply pipe is inserted into the hollow molded body, water vapor is supplied into the hollow molded body from the steam supply pipe through the small hole, and is exhausted to the outside through the small hole from the exhaust pipe. And the exhaust pipe is extracted.
As the hollow molded body, for example, an integrated body such as a plastic blow molded body or a rotational molded body (rotational molding is a kind of heat-melt molding method using powdered plastic as a raw material) can be used.

The steam supply pipe and the exhaust pipe are embedded in the foam after foam molding. Therefore, in order to extract this, at least a portion inserted into the hollow body of the hollow molded body is formed of a rigid tube having a shape that can be extracted along the length direction or a tube of a deformable soft resin. Things are used. Examples of the former include, for example, a straight pipe or a pipe curved in an arc shape. Note that the rigid tube is not an ideal rigid body tube in terms of rigid body dynamics, but an ordinary solid tube having a hardness that can be regarded as a rigid body in terms of engineering.
The small holes formed in the steam supply pipe and the exhaust pipe may be the same size as small-diameter vent holes (holes through which steam flows) formed in a mold used for manufacturing a plastic foam.
The steam supply pipe and the exhaust pipe need to be installed at least one by one, but two or more of either or both of them can be installed depending on the shape and size of the hollow molded body. The steam supply pipe and the exhaust pipe are installed in such a position and form that water vapor is distributed as evenly as possible inside the hollow molded body according to the shape of the hollow molded body. Whether water vapor is evenly distributed in the hollow molded body can be determined by whether secondary foaming of the expandable resin beads is performed uniformly in the hollow molded body and welded to each other.

According to the present invention, when a foam-embedded hollow molded body is produced by secondary foaming of foamable resin beads inside a hollow molded body such as a blow molded body, a large number of holes are formed from holes formed in the hollow molded body. By inserting a steam supply pipe and an exhaust pipe having small holes into the hollow molded body, supplying steam heated from the steam supply pipe and discharging it from the exhaust pipe, the steam is evenly distributed inside the hollow molded body. The foamable resin beads in the hollow molded body can be secondarily foamed uniformly. The foamed resin beads that have been secondarily uniformly foamed are filled in the hollow molded body and welded together to form a lump (this lump is referred to as a foam), and the rigidity and heat insulation of the hollow molded body can be improved. Further, the above-described effect can be obtained by devising the installation form of the steam supply pipe and the exhaust pipe without increasing the number of holes formed in the hollow molded body.
The hollow molded body with a built-in foam produced by the present invention is excellent in rigidity and heat insulation, and can be suitably used for floats, shock absorbers, heat insulation panels and the like.

Hereinafter, with reference to FIGS. 1-4, the manufacturing method of the foam-containing hollow molded object which concerns on this invention is demonstrated.
In FIG. 1, two holes 2 and 3 are formed in the vicinity of both ends of the upper wall 1a of the hollow molded body 1 made of, for example, a plastic blow molded body, and the steam supply pipe 4 is inserted from the hole 2 to the vicinity of the lower wall 1b. The hole 2 is closed with a flange 5, the exhaust pipe 6 is inserted from the hole 3 to the vicinity of the lower wall 1b, the hole 3 is closed with a flange 7, and a steam supply source (not shown) is connected to the steam supply pipe 4 via a switching valve or the like. A pipe 8 communicating with the pipe is connected. The steam supply pipe 4 and the exhaust pipe 6 are made of straight rigid pipes made of metal or plastic, sealed at the ends, and provided with a number of small holes 9, 10 in the peripheral wall of the portion inserted into the hollow molded body 1. Is formed. The formation density of the small holes 9 and 10 may be uniform over the entire peripheral wall, or may be different in the length direction or the circumferential direction. In short, it is sufficient that water vapor is evenly distributed in the hollow molded body.

  In the production of the hollow molded body with a foam, for example, the foamed resin beads that are primarily foamed are injected into the hollow molded body 1 using the holes 2 and 3, and as shown in FIG. The exhaust pipe 6 is set, and heated steam is supplied from the steam supply pipe 4 through the numerous small holes 9 into the hollow molded body 1, whereby the foamable resin beads are heated and subjected to secondary foaming. Charge inside. The water vapor ejected from the numerous small holes 9 of the steam supply pipe 4 into the hollow molded body 1 flows in the hollow molded body 1 toward the exhaust pipe 6 while heating the foamable resin beads, and passes through the numerous small holes 10. It flows into the exhaust pipe 6 and is discharged from the upper end of the exhaust pipe 6 to the outside. Conversely, water vapor can be supplied from the exhaust pipe 6 side and exhausted from the steam supply pipe 4 side. Since a large number of small holes 9 and 10 are formed in the steam supply pipe 4 and the exhaust pipe 6 that are inserted deeply into the hollow molded body 1, a large number of these small holes 9 and 10 are provided in the mold for foam production. It acts in the same manner as the small-diameter vent hole formed, and the flow of steam in the hollow molded body 1 is easy to spread throughout the hollow molded body 1. The arrows shown in FIG. 1 schematically show the flow of water vapor.

The expandable resin beads are heated and secondarily foamed by the heated water vapor, and fill the hollow molded body 1. A lump of expandable resin beads filled in the hollow molded body 1 and the beads are welded together is a foam, and this foam improves the rigidity and heat insulation of the hollow molded body 1.
When the secondary foaming of the expandable resin beads is completed, the supply of steam is stopped, and the steam supply pipe 4 and the exhaust pipe 5 are drawn straight up. After extraction, traces of the steam supply pipe 4 and the exhaust pipe 5 remain in the foam as cylindrical holes.
Next, if necessary, the holes 2 and 3 are closed to complete the production of the hollow molded body with a built-in foam.

  The manufacturing method described above is used, for example, as a method for manufacturing a float. Even if the outer shell of the float (hollow molded body 1) is torn, the function of the float is not lost because the foam has buoyancy, and the foamed resin beads are welded together. There is no environmental pollution. Further, in the method of Patent Document 1, the holes for supplying and exhausting the steam are formed in the wall portion at one end and the other end where the distance between them is the largest, but in the present invention, for example, both holes are formed in the upper wall 1a. Since it is possible to form the hole and it is not necessary to form a hole in the side wall that is most likely to break in the float, safety is high.

FIG. 2 shows another embodiment of the present invention. In FIG. 2, the same reference numerals are assigned to substantially the same parts as in FIG.
The hollow molded body 1 is made of a plastic blow molded body, has a step on the upper wall 1a, and one side wall is greatly curved. Two holes 2 and 3 are formed near both ends of the upper wall 1 a of the hollow molded body 1, the steam supply pipe 4 is inserted from the hole 2, the hole 2 is closed by the flange 5, and the exhaust pipe 6 is inserted from the hole 3. The hole 3 is closed with a flange 7, and a pipe 8 communicating with a steam supply source (not shown) is connected to the steam supply pipe 4 via a switching valve or the like.
The steam supply pipe 4 is formed of a metal or plastic rigid pipe, and a portion inserted into the hollow molded body 1 is curved in an arc shape substantially along the curvature of the side wall, and a plurality of small holes 9 are formed in the peripheral wall. Is formed and the tip is sealed. The exhaust pipe 6 is made of a soft resin tube that can be freely deformed. The exhaust pipe 6 is inserted to the back of the hollow molded body 1, and a plurality of small holes 10 are formed in the peripheral wall, and the tip is sealed.

The foam-embedded hollow molded body is manufactured in the same manner as shown in FIG. Due to the steam supply pipe 4 along the curve of the side wall of the hollow molded body 1 and the exhaust pipe 6 inserted deeply into the hollow molded body 1, the flow of the vapor in the hollow molded body 1 Easy to get around. Conversely, water vapor can be supplied from the exhaust pipe 6 side and exhausted from the steam supply pipe 4 side.
When the secondary foaming of the expandable resin beads is completed, the supply of steam is stopped, and the steam supply pipe 4 and the exhaust pipe 6 are extracted. Although the steam supply pipe 4 and the exhaust pipe 6 are buried in a foam, the steam supply pipe 4 is curved in an arc shape, so that it can be extracted along the curve, and the exhaust pipe 6 is flexible and deformable. Therefore, it can be extracted in the length direction, and after the extraction, traces of the steam supply pipe 4 and the exhaust pipe 6 remain in the foam as cylindrical holes.
Next, if necessary, the holes 2 and 3 are closed to complete the production of the hollow molded body with a built-in foam.

FIG. 3 shows another embodiment of the present invention. In FIG. 3, the same reference numerals are assigned to substantially the same parts as in FIG.
The hollow molded body 1 is made of a plastic blow molded body, and a recess 12 is formed in the upper wall 1a. Two holes 2 and 3 are formed near both ends of the upper wall 1 a of the hollow molded body 1, the steam supply pipe 4 is inserted from the hole 2, the hole 2 is closed by the flange 5, and the exhaust pipe 6 is inserted from the hole 3. The hole 3 is closed with a flange 7, and a pipe 8 communicating with a steam supply source (not shown) is connected to the steam supply pipe 4 via a switching valve or the like.
The steam supply pipe 4 is made of a straight rigid pipe made of metal or plastic, and a plurality of small holes 9 are formed in the peripheral wall, and the tip is sealed. The exhaust pipe 6 is made of a metal or plastic rigid pipe, and a portion to be inserted into the hollow molded body 1 is curved in an arc shape, and is inserted into the hollow molded body 1 beyond the concave portion 12. A large number of small holes 10 are formed in the top and sealed at the tip.

The foam-embedded hollow molded body is manufactured in the same manner as shown in FIG. The steam flow in the hollow molded body 1 is hollow molded by the steam supply pipe 4 inserted deep inside the hollow molded body 1 and the exhaust pipe 6 inserted into the hollow molded body 1 beyond the recess 12. Easy to spread throughout the body 1. Conversely, water vapor can be supplied from the exhaust pipe 6 side and exhausted from the steam supply pipe 4 side.
When the secondary foaming of the expandable resin beads is completed, the supply of steam is stopped, and the steam supply pipe 4 and the exhaust pipe 6 are extracted. The steam supply pipe 4 and the exhaust pipe 6 are buried in a foam, but since the steam supply pipe 4 is a straight pipe, the steam supply pipe 4 and the exhaust pipe 6 can be drawn straight up, and the exhaust pipe 6 is curved in an arc shape. It can be extracted along the curve, and after the extraction, traces of the steam supply pipe 4 and the exhaust pipe 6 remain in the foam as cylindrical holes.
Next, if necessary, the holes 2 and 3 are closed to complete the production of the hollow molded body with a built-in foam.

FIG. 4 shows another embodiment of the present invention. In FIG. 4, the same reference numerals are assigned to substantially the same parts as in FIG.
The hollow molded body 1 is made of a plastic blow molded body, and is a thin plate-shaped hollow body having a double wall. Three holes are formed near the center and both ends of the side wall 1c of the hollow molded body 1, the steam supply pipe 4 is inserted from the center hole, the hole is closed with a flange 5, and a hole near both ends (the one hole is indicated by a symbol). 3), the exhaust pipe 6 is inserted, the hole is closed with a flange 7, and a pipe 8 communicating with a steam supply source (not shown) is connected to the steam supply pipe 4 via a switching valve or the like.
The steam supply pipe 4 and the exhaust pipe 6 are made of a metal or plastic straight rigid pipe, extend to the vicinity of the other side wall 1d, and a plurality of small holes (only the small holes 10 of the exhaust pipe 6 are shown) are formed on the peripheral wall. The tip is sealed.

The foam-embedded hollow molded body is manufactured in the same manner as shown in FIG. Even in a narrow hollow interior, the steam flow in the hollow molded body 1 is hollow molded by the steam supply pipe 4 deeply inserted in the center of the hollow molded body 1 and the exhaust pipe 6 inserted deep in the vicinity of both ends. Easy to spread throughout the body 1. Conversely, water vapor can be supplied from the exhaust pipe 6 side and exhausted from the steam supply pipe 4 side.
When the secondary foaming of the expandable resin beads is completed, the supply of steam is stopped, and the steam supply pipe 4 and the exhaust pipe 6 are extracted. Although the steam supply pipe 4 and the exhaust pipe 6 are buried in the foam, since both are straight pipes, the steam supply pipe 4 and the exhaust pipe 6 can be drawn straight out to the side. Traces remain as cylindrical holes.
Then, if necessary, the hole formed in the side wall is closed to complete the production of the foam-embedded hollow molded body. This foam-embedded hollow molded body is suitable as a heat insulating wall, for example.

It is sectional drawing of the hollow molded object which set the steam supply pipe and the exhaust pipe. It is sectional drawing of the other hollow molded object which set the steam supply pipe and the exhaust pipe. It is sectional drawing of the other hollow molded object which set the steam supply pipe and the exhaust pipe. It is sectional drawing of the other hollow molded object which set the steam supply pipe and the exhaust pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hollow molded object 2,3 Hole 4 opened in hollow molded object 4 Steam supply pipe 6 Exhaust pipe 9 Small hole opened in the peripheral wall of the steam supply pipe 10 Small hole opened in the peripheral wall of the exhaust pipe

Claims (3)

The foamed resin beads that are primarily foamed are injected into the hollow molded body, and heated water vapor is supplied into the hollow molded body, whereby the foamable resin beads are heated and subjected to secondary foaming to form the hollow molded body. In the method of manufacturing a foam-embedded hollow molded body that fills the inside of the body, a plurality of holes are formed in the hollow molded body, and a steam supply pipe and an exhaust pipe formed with a plurality of small holes through the holes are provided in the hollow molded body. The steam supply pipe supplies water vapor to the inside of the hollow molded body through the small hole, and exhausts from the exhaust pipe to the outside through the small hole. After the secondary foaming, the steam supply pipe and the exhaust pipe are connected to each other. A method for producing a hollow molded article with a foam, wherein the molded article is extracted. At least a portion inserted into the hollow body of the steam supply pipe and the exhaust pipe is composed of a rigid pipe having a shape that can be extracted along the length direction or a deformable soft resin pipe. The manufacturing method of the foaming body hollow molded object described in Claim 1. A foam-embedded hollow molded body produced by the production method according to claim 1 or 2.

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