JPH0129074Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a tear-resistant breathable packaging material.

Polycello, which is a cellophane film laminated with a thin layer of polyethylene, has been used for packaging moisture absorbents such as silica gel, but this has the disadvantage of being easily torn.

Also, packaging materials with holes are used for packaging quicklime. However, in order to manufacture this packaging material, not only is special equipment for heat processing required, but depending on the temperature control of the heat roll or the condition of the hole punching process, quicklime powder, which is the content, can easily come out. There is a manufacturing difficulty in that a product tends to be obtained.

In addition, a breathable packaging material made by coating paper with a vinyl acetate resin coating material has been devised, but this breathable packaging material contains residual toluene in the paper and low molecular weight resin content in the coating film. It has the drawback that it has a strong odor and is not suitable for practical use, and the coating film is thin at 3 to 10 μm and is not easily rubbed and easily torn.

In addition, a breathable packaging material has been devised in which paper is hot-melt coated with an ethylene vinyl acetate copolymer containing a high content of vinyl acetate via an anchor coat layer, but this breathable packaging material has Since the anchor coating is applied, there are disadvantages in that solvents such as toluene or alcohol remain and there is a smell of ethylene vinyl acetate copolymer. It has the disadvantage that it must be laminated with a laminate, which means that the laminate has almost no strength. Furthermore, even if the temperature of the laminating process is raised to obtain a laminated product with high strength, there are disadvantages in that thermal deterioration occurs and the vinyl acetate odor is so strong that it cannot be used for practical use.

This invention was developed as a result of research to eliminate the above-mentioned drawbacks.
A hot melt made of an ethylene acetic acid copolymer hot melt adhesive having an MI of 15 to 45 and containing 10 to 40% by weight of vinyl acetate on the surface of the paper with the lattice network reinforcing material in close contact with the paper. It has been discovered that by extrusion coating with an adhesive, it is possible to obtain a breathable packaging material that has almost no odor, is strong, and cannot be easily torn, and based on this knowledge, the present invention has been completed.

That is, the gist of the present invention is that a lattice-like reinforcing material is brought into close contact with paper, and ethylene acetate containing 10 to 40% by weight of vinyl acetate and having an MI of 15 to 45 is applied to the paper surface to which the lattice-like reinforcing material is brought into close contact. This tear-resistant, breathable packaging material is made by laminating hot melt adhesive layers formed by extrusion coating of a vinyl copolymer hot melt adhesive.

Hereinafter, the present invention will be described in detail with reference to the following sections.

Figure 1 shows tear-resistant breathable packaging material 4 according to the present invention.
shows.

A lattice network reinforcing material 2 is brought into close contact with the paper 1,
In addition, a hot melt adhesive layer 3 formed by extrusion coating is laminated on the paper surface to which the lattice network reinforcing material 2 is brought into close contact. The hot melt adhesive is bonded to the paper surface through the mesh of the grid-like reinforcing material.

Therefore, in the present invention, machine-made Japanese paper or non-fluorescent bleached shoji paper is suitable as paper 1, and those made of 100% natural pulp, or natural pulp mixed with rayon, vinylon, hemp, etc. Any mixture of polypropylene fibers, polyethylene fibers, polyester fibers, nylon fibers, etc. can be used. In particular, paper containing 3 to 30% by weight of rayon is good.

Vinylon paper can also be used, but it has the disadvantage of being expensive and is inferior to machine-made Japanese paper and shoji paper in terms of heat resistance.

Additionally, polyester-based or nylon-based nonwoven fabrics can also be used as constituent materials for the breathable packaging material of the present invention, but unlike ordinary paper, these nonwoven fabrics are easily penetrated by hot melt adhesive to the back side, and stains may occur. It has the disadvantage that it is easily bonded to the heat seal roller by the hot melt adhesive that passes through it. In particular, such adhesion accidents of paper to the heat seal roller are likely to occur in the case of nonwoven fabrics having a basis weight of 40 g/m ² or less. When using polyester-based or nylon-based nonwoven fabric, the basis weight should be 50g/m ²
However, a nonwoven fabric having such a basis weight is expensive, and it is difficult in terms of cost to employ it as a constituent material of a packaging material for a moisture absorbent.

Further, as the paper 1, a two- to four-layer paper in which a paper layer mixed with polyethylene hydrophilic pulp-like multibranched fibers is laminated on the side to which the hot melt adhesive is laminated, such as machine-made Japanese paper or shoji paper. can also be used. This paper has good adhesion to hot melt adhesives, making it possible to obtain an air-permeable packaging material with high interlaminar strength. Here, the mixing ratio of the polyethylene hydrophilic pulp-like multi-branched fibers is preferably 25 to 50% by weight. If it is less than 25% by weight, there will be little improvement in the laminate strength, which is undesirable. On the other hand, if it is more than 50% by weight, the sealed portion may melt during heat sealing, or the paper may become transparent, which may impair the appearance. Sleeping,
Furthermore, the strength of the paper will decrease. Moreover, it is not preferable because it becomes expensive.

Next, the lattice network reinforcing material layer 2 is made of polyethylene, polypropylene, etc., such as Nippon Seki Warif manufactured by Nippon Petrochemicals Co., Ltd., Krenet manufactured by Kurashiki Boseki Co., Ltd., and Soft Net and Soft Cloth manufactured by Shinnihon Sofu Co., Ltd. or a net-like material made of glass fiber.

Appropriate grid spacing is 1 to 5 mm. 1
When it is less than mm, most of the packaging material area is covered by lattice fibers, which narrows the moisture permeable area, which reduces the moisture permeability per unit area of the packaging material, making it impractical.
In addition, the price of lattice fibers is also high;
In such a case, the space between the moons becomes wider, and the granular contents may break through and come out, and the tear strength decreases, impairing the practicality of the product. The most preferred spacing is 2
It ranges from 3.5mm to 3.5mm. In particular, olefin resins such as polyethylene and polypropylene are most suitable as the material for the lattice network reinforcing material.

Next, as the hot melt adhesive for forming the hot melt adhesive 3, ethylene vinyl acetate copolymer,
Blending tackifier resins (rosin and its derivatives, terpene resins, petroleum hydrocarbon resins, phenolic resins, etc.), waxes, antioxidants, etc. in a formulation that yields a resin compound suitable for extrusion coating. An ethylene vinyl acetate copolymer hot melt adhesive containing 10 to 40% by weight of vinyl acetate and having an MI of 15 to 45 can be used. When the vinyl acetate content is 10% by weight or less, the moisture permeability is 80g/m ²
24 hours (temperature 40℃, relative humidity 90%, film thickness 20μ), which is undesirable as it has poor moisture permeability and lacks practicality.On the other hand, when the vinyl acetate content is 40% by weight or more, the lubricity of the laminate product decreases. In addition, it has a strong vinyl acetate odor, making it difficult to commercialize and therefore not preferred in practice. Also, if the MI is less than 15, it is undesirable because the lamination strength against Japanese paper etc. will decrease.On the other hand, if the MI is more than 45, it will be more permeable than the paper fibers during heat sealing, and the laminated paper will stick to the heat seal roller or become laminated. This is not preferable because it deteriorates film-forming properties and reduces hot-tack properties during heat sealing.

As described above in detail, the breathable packaging material according to the present invention has a lattice-like reinforcing material brought into close contact with paper, and a hot-melt adhesive layer formed by extrusion coating on the paper surface to which the lattice-like reinforcing material is brought into close contact. It is a laminated product that is extruded and coated with hot melt adhesive, so there is almost no odor.The hot melt adhesive layer contains a lattice-like reinforcing material, so it is strong, and the hot melt adhesive layer has a moderate amount of heat. Since it has air permeability, it has the advantage of having air permeability suitable for packaging moisture absorbents and the like.

Next, the present invention will be specifically explained with reference to examples.

Example 40 polyethylene hydrophilic pulp-like multi-branched fibers
Two-layer Japanese paper (36 g/m ^{2 )} having a mixed paper layer of 36 g/m 2 and a Warif SS type were combined and laminated with hot melt adhesive from the Warif SS side. Japanese paper 36g/m ² / Warifu SS / Hot melt adhesive (30μ) specifications with heat seal strength 700-1000g / 15mm width, moisture permeability /
50-220 g/m ² for 24 hours (temperature 40°C, relative humidity 90%) was obtained. Although the adhesion of Warif SS type fibers is weak in the areas where the paper is in close contact with the paper, delamination did not occur in the heat-sealed areas, and the adhesion of the laminate was improved by heat-sealing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the breathable packaging material of the present invention. 1...paper, 2...lattice network reinforcing material, 3...hot melt adhesive layer.

Claims (1)

[Scope of utility model registration request] A lattice-like reinforcing material is brought into close contact with the paper, and the paper surface to which the lattice-like reinforcing material is brought into close contact contains 10 to 40% by weight of vinyl acetate.
A tear-resistant breathable packaging material made by laminating hot melt adhesive layers formed by extrusion coating of an ethylene vinyl acetate copolymer hot melt adhesive with an MI of 15 to 45.