JPH0140673Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a packaging base material for protecting various products, for example, electronic equipment such as broadcasting equipment.

(Prior Art) Conventionally, this type of packaging base material has often been made of polystyrene or polyethylene that has been foamed with beads alone, or a mixture of the former two that has been foamed with beads. All of these use a cushioning layer made of a hard foam material as a packaging base material, and have the disadvantage that products are easily damaged when used. In particular, when packaging electronic equipment such as computers and video equipment, cameras, and other high-end products, if the product is damaged due to contact with the packaging material, the value of the product will be significantly reduced. It will end up being put away.

Therefore, ABS or
Packaging base materials to which a flexible film such as PVC is attached have been proposed. When this material is used, the buffer layer made of a hard foam material does not come into direct contact with the product, which prevents damage to the product. Not only does the weight increase due to the amount of pasting, but also the process of manufacturing the packaging base material includes the process of pasting the soft film, which leads to an increase in manufacturing man-hours, leading to an increase in costs. Further, there are disadvantages in that dimensional stability is reduced and wrinkles are likely to occur due to the difference in thermal shrinkage between the buffer layer and the soft film. others,
When PVC is used as a soft film, the plasticizer naturally contained in the soft film may migrate into the product and have an adverse effect.

(Problems to be solved by this invention) The problems to be solved by this invention are that it does not damage the product, the manufacturing process is simple and can reduce costs, the dimensional stability is good, and the plasticizer The purpose of the present invention is to provide a packaging base material that is free from the risk of migration to other products.

(Means for solving the problem) The means for solving the above problem consists of a buffer layer made of a foamed synthetic resin containing 1,2-polybutadiene, and an unfoamed buffer layer made of a synthetic resin having the same composition as the buffer layer. The 1.2-polybutadiene has a 1.2 bond of about 70% or more, a molecular weight of 100,000 or more, a crystallinity of 10 to 50%, and a syndiotactic stereoregularity of 20% or more. .

(Function) The properties of 1.2-polybutadiene are the ratio of 1.2 bonds,
It depends slightly on the molecular weight size, crystallinity, and stereoregularity of side chains, and if these are within the above range, the synthetic resin foam containing 1,2-polybutadiene will be highly flexible and elastic. Moreover, it is lightweight and leaves no bending marks. Therefore, 1.2−
Synthetic resin foams containing polybutadiene are formed into thin layers and are used in floor mats for exercise that require a good treading feeling and appropriate elasticity, as well as clothing for special purposes.

As is clear from this, in the packaging base material according to the present invention, the buffer layer made of foamed synthetic resin containing 1,2-polybutadiene exhibits great flexibility and elasticity and protects the product from impact.

Further, since the unfoamed skin layer made of a synthetic resin containing 1.2 polybutadiene is harder than the above-mentioned buffer layer, it is useful for improving the shape retention of a packaging base material having unevenness. Although this skin layer is said to be hard, it is softer than the foam that forms the buffer layer of the conventional packaging base material explained at the beginning, and only has a certain degree of "firmness". Even if this skin layer rubs against the product, the product will not be damaged. Moreover, since the skin layer 2 is difficult to tear even during deep drawing, it helps to prevent the buffer layer 1 from breaking.

Furthermore, since the packaging base material according to the present invention has the same composition as the buffer layer and the skin layer, there is no difference in heat shrinkage between the two layers, and therefore dimensional stability is impaired and wrinkles are likely to occur. Not only does it not have a layer, but it also allows both layers to be formed in the same continuous process, making it easy to reduce costs. Furthermore, since there is no need to use a plasticizer, there is no adverse effect on the product due to migration of the plasticizer.

(Example) The basic structure of the packaging base material according to the present invention is as follows:
As shown in the figure, the buffer layer 1 is made of a foamed synthetic resin, and the unfoamed skin layer 2 is made of a synthetic resin having the same composition as the buffer layer 1. The resin has a 1.2 bond of approximately 70% or more, a molecular weight of 100,000 or more, and a crystallinity of 10 to 50%.
% or more of syndiotactic stereoregularity
Contains 1.2-polybutadiene.

Such packaging base materials are made by continuously extruding synthetic resin raw materials into sheets using an extrusion molding method, continuously irradiating the sheets with ultraviolet rays, and heating them in a foaming tank to completely foam the unfoamed skin layer 2. The buffer layer 1 is simultaneously formed.

In other words, the sheet extruded from the extrusion molding machine contains 240
After photocrosslinking to a gel fraction of 30 to 80% by irradiating ultraviolet light with a wavelength of ~400 mμ in a short period of time within 10 minutes, it is heated to about 100 to 230°C in a foaming tank to foam.

When heating, the temperature is controlled so as to create a temperature difference between the upper and lower surfaces of the sheet to be foamed, so that an unfoamed skin layer 2 and a completely foamed buffer layer 1 are formed at the same time. Further, various conditions such as the wavelength of ultraviolet rays, irradiation time, gel fraction, foaming temperature, etc. in the above method should be appropriately determined in consideration of the properties of the buffer layer 1 such as flexibility and elasticity.

The synthetic resin used in this invention is as described above.
1.2-Polybutadiene is suitably determined depending on the desired properties, but is 5 to 100%, particularly 30 to 100%.
It is desirable that the content be within the range of %. The flexibility and elasticity of the buffer layer 1 increases as the amount of 1,2-polybutadiene contained therein increases, which is preferable for improving the impact resistance of products. If the 1.2-polybutadiene content is less than 5%, the packaging material tends to lack flexibility and elasticity. If the amount is less than 100% of 1,2-polybutadiene, it is preferable to use a synthetic resin that is a blend of 1,2-polybutadiene and one or both of EVA and PE.

FIG. 2 shows the packaging base material described in connection with FIG. 1, which has been press-molded to form recesses 3 and protrusions 4, so that it can be used for packaging video equipment. When video equipment was actually packaged using packaging material A shown in Figure 2 and handled as specified, the video equipment was completely protected from impact despite the thin wall thickness of packaging material A. It was also confirmed that neither the outer surface of the video equipment nor the skin layer of packaging material A was damaged.

(Effects of the invention) The packaging base material according to the invention includes a buffer layer made of a foamed synthetic resin containing the above-mentioned 1,2-polybutadiene, and an unfoamed skin layer made of a synthetic resin having the same composition as this buffer layer. Therefore, the buffer layer and the skin layer can be formed in parallel in the same synthetic resin raw material extrusion process, and by doing so, the dimensional stability is good and there is no heat shrinkage between the skin layer and the buffer layer. Wrinkles due to differences do not occur, and both layers are highly integrated. Further, since the cushioning layer has the excellent flexibility and elasticity characteristic of the above-mentioned 1,2-polybutadiene foam, the product can be sufficiently protected from impact even if the cushioning layer is made relatively thin. Even if the buffer layer is highly flexible, its shape retention is ensured by the skin layer, making it suitable as a base material that can easily provide packaging materials with unevenness.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a packaging base material according to an embodiment of the present invention, and FIG. 2 is a schematic perspective view showing a packaging material made from the packaging base material. 1...Buffer layer, 2...Skin layer.

Claims (1)

[Scope of utility model registration request] 1.2-A buffer layer formed by foaming a synthetic resin containing polybutadiene, and an unfoamed skin layer formed from a synthetic resin having the same composition as the buffer layer;
1.2-polybutadiene is a packaging base material having about 70% or more 1.2 bonds, a molecular weight of 100,000 or more, a crystallinity of 10 to 50%, and a syndiotactic stereoregularity of 20% or more.