JPH0369788B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the production of foamed plastic cushioning material for packaging packed in small bags, in which unfoamed material is packed into bags, and then the contents are placed inside the bags. The present invention relates to a method for producing a foamed plastic cushioning material packaged in small bags, which improves the various drawbacks associated with packaging lightweight and bulky foams in bags.

[Conventional technology]

Traditionally, natural products such as wood wool and sawdust, which have been used as cushioning materials to prevent damage to the contents in the wrapping and packing of various products, have been gradually replaced by plastic foam. These foams include those that have a unique shape that matches the shape of the product, and those that fill a predetermined space with multiple pieces of foam. The small pieces of foam are entangled in a unique twist, and the synergistic effect of the cushioning properties of the foam itself and the cushioning properties based on the entanglement makes it an extremely excellent cushioning material.

Although these cushioning materials made of small piece-like foams allow the space to be filled to be freely shaped, they have the disadvantage that the filling material scatters when the contents are taken out. For this reason, a method has also been adopted in which the above-mentioned foam pieces are filled in a small bag in advance and the bag is inserted into a predetermined filling space.

Although the filling material in the form of small pieces packed in sachets is convenient to handle, it is accompanied by various difficulties during filling. First, the material itself is extremely lightweight, making it susceptible to air resistance.
It takes time to fall, and falling is hindered by small obstacles such as contact with protrusions, entanglement of small pieces, static electricity, etc., and in order to reliably fill a certain amount, it is necessary to force the filling material such as a push rod. A compression mechanism was required.

Therefore, although a large-scale filling machine was required, the working efficiency was low. Even with the use of such a device, due to the characteristics of the filler itself, namely its low bulk density and compressive strain recovery, the expanded filler will still be able to seal the seal at the entrance of the pouch. This tends to cause incomplete sealing and machine failure, and further reduces the commercial value of the product.

Japanese Utility Model Application Publication No. 51-84875 discloses a method in which an unfoamed foamed fibrous material is packed into a plastic bag having a large number of small holes, and then heated and foamed.

[Problem to be solved by the invention]

However, despite attempts to implement the above method, in the case of foamable polystyrene, there is a limit to the amount of steam that can be supplied to the unfoamed material through the perforations provided in the film that makes up the bag, resulting in incomplete foaming such as uneven foaming. Due to this, it was not possible to obtain a satisfactory product.

[Means of problem solving]

The present invention aims to solve the above problems,
The structure is as follows: (1) Foaming is performed in a manufacturing method in which small bags of foamable plastic are filled into small bags, sealed, and then the small bags of foamable plastic are heated and foamed to obtain a small bag of foamed plastic cushioning material. The material of the plastic flakes is polystyrene resin; (2) the bag uses a plastic net; and (3) the heating during foaming is performed by passing through a steam tunnel. shall be.

The material used for the small pieces of foamed plastic cushioning material used in the present invention is made by kneading a resin commonly called polystyrene and a foaming agent such as propane in an extruder, and extruding it into a string shape in an unfoamed state. This is cut to a regular length into small pieces. These foamable unfoamed pieces can be foamed when subjected to a suitable heat treatment to form a piece-like foam that can be used as a cushioning material.

The small pieces of foamed plastic cushioning material used in the present invention include non-linear string-like pieces, rod-like pieces, cubic pieces,
Although the shape is not limited to cut pieces or small pieces that are prismatic, irregularly shaped, etc., it does not include those that are shaped to fit the space formed by the container to be packed and the packaging container. In particular, curved, elongated, non-linear string-like pieces that are bent or looped exhibit excellent cushioning properties due to the intertwining of the string-like pieces and the compressive strain of the material.

The heating method used for foaming differs depending on the type of plastic and the type of foaming agent. For example, if polyethylene is foamed with a known chemical foaming agent such as azodicarbonamide, which can be sufficiently foamed by dry heat alone, vent holes should be drilled to the extent that it does not interfere with the exhaust of the expanded gas. It is sufficient to use the plastic sheet provided. However, when using a gaseous heat medium, polystyrene is used as a material resin, and a low boiling point hydrocarbon such as propane is added to this as a foaming agent to form foamable pieces. When heating, a bag material is required that has sufficient space to allow free supply of heat medium. In such cases, if you use net as the material for the bag, the moist heat transfer medium will freely pass through the holes of the net, softening the surface of the unfoamed material, and allowing heat to be quickly transmitted to the center. The surrounding area can also be foamed uniformly at the same magnification.

Furthermore, if the net is diamond-shaped, if there is no filling or there is only a small amount of filling, pulling it in the vertical direction will make it narrower and longer like a string, reducing the apparent space and preventing the unfoamed material from falling. After foaming, the width expands and the space expands as the contents expand, but at the same time, the contents also become larger and can still prevent the contents from falling. That is, a bag with a mesh that is large enough to prevent the foamed cushioning material from falling can be used.

A known automatic packaging and filling machine can be used to pack and seal the sachets.

〔Effect of the invention〕

According to the present invention, work efficiency is significantly improved and products are completely sealed, increasing commercial value. Furthermore, even when it is necessary to supply sufficient steam and heat to the inside of the bag, such as when foaming polystyrene using a low-boiling point hydrocarbon as a foaming agent, it is not possible to make the mesh ratio of the net sufficiently large. This made it possible to foam uniformly.

〔Example〕

Embodiment 1 FIG. 1 is a perspective view of an automatic filling and packaging machine in which a net made of plastic thread is used as the bag material. 1 is a plasticnate having a large number of meshes 2. 3 is a hopper that supplies an unfoamed material 4 made of foamable pieces, and a supply valve 5
A fixed amount of the unfoamed material 4 is intermittently applied to the core shaft 6 through the
drop it inside. The net 1 is wound into a roll and is unwound through a supply roll 7 while adjusting its position and angle, so as to surround the core shaft 6. Both ends of the net 1 which surround the mandrel 6 and are in contact with each other are connected to the mandrel 6.
vertical heat sealer 8 provided almost in contact with
is fused into a cylindrical shape. Reference numeral 9 denotes a welding cutter that performs longitudinal welding and cutting at the same time, and is provided below the core shaft 6.

By moving in the direction of the arrow in the figure, the lower end of the cylindrical net is fused and cut at the same time to form a bag. The unfoamed material that has fallen into the mandrel 6 is supplied from the hopper 3 through the supply valve 5 into this bag. After the cylindrical net is further moved downward, the fusing cutter 9 closes again in the direction of the arrow to perform fusing and cutting at the same time, yielding a pouched unfoamed product. Since the amount of unfoamed material 4 to be filled was small compared to the internal volume of the pouch 10, a flat pouch with almost no bulge was formed.

Furthermore, in this embodiment, a net woven from synthetic resin fibers may be used instead of the plastic net.

In addition, as another embodiment, if a plastic rhombus net formed in a cylindrical shape from the beginning is stretched and wound into a string shape and used as the material for the pouch, the vertical heat sealer 8 is not required, and as shown in FIG. A sachet unfoamed material as shown in is obtained. Reference numeral 11 is a fused portion, and the unfoamed material 4 is a long and thin curved string-like piece.

Propane was added as a foaming agent to polystyrene in an extruder and kneaded, then extruded into a string shape, rapidly cooled, and cut to create bent string-like foamable unfoamed pieces with an actual length of about 6 cm. This string-like small piece is
A large number of plastic net sachets were manufactured using the method shown in the figure. When these many small bags were placed on a belt conveyor and passed through a heat tunnel that heated them while supplying water vapor,
It was possible to continuously obtain sachet foamed plastic cushioning materials having a low bulk density and sufficient cushioning properties.

Comparative example 1 In place of the net bag in Example 1, about 1 mm
An experiment was conducted in the same manner as in Example 1, except that a polypropylene pouch was used, which had small holes per ^cm2 distributed over the entire surface of the bag.

As a result, when comparing the heating (tunnel passage) time, the heating was completed in 30 seconds in the case of Example 1, which was packaged in a net bag, but in Comparative Example 1, there were significant bubbling spots in each small piece inside the bag, and heating was completed in 30 seconds. Although the time was extended to 60 to 90 seconds, it was not possible to completely prevent bubbling spots. Furthermore, when the heating time was extended to 120 seconds, a phenomenon in which small pieces in a state of shrinkage were noticeable after foaming was observed.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; FIG. 1 is a perspective view of an automatic packaging and filling machine, and FIG. 2 is a perspective view of an unfoamed material packed into sachets. In the drawings, 1 is a net, 2 is a mesh, 3 is a hopper, 4 is an unfoamed material, 5 is a supply valve, 6 is a mandrel,
7 is a supply roll, 8 is a longitudinal heat sealer, 9
10 is a welding cutter, 10 is a pouch, and 11 is a welding portion.

Claims (1)

[Claims] 1. Filling a small bag with foamable plastic pieces,
In the manufacturing method for obtaining a sachet foam plastic cushioning material by heating and foaming the foamable plastic flakes in the sachet after sealing, (1) the material of the foamable plastic flakes is polystyrene resin; (2) ) A method for producing a foamed plastic cushioning material packaged in a sachet, characterized in that a plastic net is used for the sachet; (3) heating during heating and foaming is performed by passing the material through a steam tunnel.