JPH04189769A - Synthetic resin made inner container for use in bag-in-box - Google Patents

Abstract

PURPOSE:To obtain a soft, thin-wall container good in folding characteristic and free from pinhole and break even in a long distance transportation with the contents filled in an inner container by mixing a straight chain polyethylene and a low-density polyethylene in a specific proportion. CONSTITUTION:An inner container for use in a bag-in-box is synthetically manufactured from the resin wherein 55-65 parts of a straight-chain polyethylene and 35-45 parts of a low-density polyethylene are blended. The straight-chain polyethylene has a M.F.R. of 0.5-1.5 and a density of 0.910-0.915 and the low- density polyethylene has a M.F.R. of 1.0-2.0 and a density of 0.917-0.921.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an inner container for a bag-in-box made of soft thin-walled synthetic resin and housed in an outer container known as a bag-in-box. In particular, the present invention relates to an inner container for a bag-in-box made of synthetic resin that extremely suppresses the occurrence of pinholes and does not cause peeling at the fused portion.

(Prior Art and Problems to be Solved) Conventionally, containers such as cardboard boxes or other outer boxes containing soft, thin-walled synthetic resin are called bag-in-boxes.
Because they are convenient and economical, they are widely used as containers for storing various liquids, including alcoholic beverages, vinegar, and developing solutions.

The soft, thin-walled synthetic resin inner container (hereinafter referred to as the inner container) used in such hang-in boxes is made so that it can be joined on diagonal sides of the container immediately after the synthetic resin is melted and extruded. The container is manufactured by molding the container halves by air pressure molding or blow molding using a mold having a similar shape, and then joining these halves together.

Before use, the inner container is in a folded state for transportation efficiency, ease of handling, etc., that is, one container half is folded and inserted into the other container half so that it is overlapped with the inner container.

By the way, as a synthetic resin for manufacturing such a container, a synthetic resin having the following primary characteristics is required.

(i) Using a synthetic resin with a high melting point to prevent cracking (peeling) at the fusion weld; (ii) Using a synthetic resin with high bending strength to prevent pinholes and cuts caused by wrinkles. To prevent the occurrence of

However, using a synthetic resin with a high melting point poses a problem with resin extrusion suitability during molding, making it difficult to process the container, and using a synthetic resin with high bending strength lacks flexibility and makes it difficult to fold. So, bag in bag
It becomes impossible to maintain the container's original function as a box.

For this reason, back-in-box inner containers have traditionally been made of ethylene-vinyl acetate copolymer (EVA) or linear polyethylene to maintain folding properties.
A highly flexible synthetic resin composition containing A is used.

However, since EVA has a low melting point, the fused portion is weakly fused during molding, and after the contents are filled into the inner container, repeated vibrations may cause peeling at the fused portion.

(Problems to be Solved) The present inventor has improved the above-mentioned drawbacks, and has created a product that has good folding characteristics and that does not cause any pinholes or cuts even when the inner container is filled with contents and transported over long distances. We investigated various types of soft and thin-walled containers.

As a result, the present invention has been completed, and an object of the present invention is to provide a soft, thin-walled container that is easy to fold without producing pinholes.

(Means for Solving the Problem) That is, the gist of the present invention is that 55 parts to 65 parts of linear polyethylene and 35 parts to 45 parts of low-density polyethylene, that is, 55 parts of linear polyethylene in the present invention. Below, if a resin composition containing 45 parts or more of low-density polyethylene is used, pinholes are likely to occur, and
If a resin composition containing 65 parts or more of linear polyethylene and 35 parts or less of low-density polyethylene is used, the resin extrusion aptitude is unfavorable.

A preferred resin composition in the present invention is a resin composition comprising about 60 parts of linear polyethylene and about 40 parts of low-density polyethylene.

The linear polyethylenes used in the present invention are M and F.

Ro is 0.5 to 1.5, density is 0.910 to 0.915, and low density polyethylene has A, F, R, 1
．． 0 to 2.0, and density 0.917 to 0.921.

In the present invention, other conventional resin compounding agents such as antioxidants, processing stabilizers, etc. may be added.

Next, the present invention will be explained in more detail with reference to Examples.

(Example) A 200 Å back-in-box inner container was molded using the following resin composition. The minimum thickness of the container at this time was 0.13+a. Further, for comparison, an inner container was similarly molded using a resin composition using conventionally used EVA.

In order to investigate the performance of these obtained containers, the following actual test was conducted.

(1) Add a 30% aqueous solution of surfactant and
, a pressure of 1 kg/cxn 2 was applied, the product was stored at 50°C, and peeling from the welded part was measured.

(2) Fill with water and store at 20°C, top and bottom 5 mml0) 12, I
A vibration test was conducted under G(7) conditions.

Example 1 Linear low density polyethylene (M, F, R, 0,8), 6
t) part and low density polyethylene (M, F, R, 1,5) 4
Immediately after melt extrusion, an inner container was formed by vacuum forming using a mold having a shape that allows the diagonal surfaces of the container to be joined.

The resulting container was tested according to the test method described above.

The results are shown in Table 1.

Example 2 By the same method as in Example 1, 65 parts of linear low density polyethylene (M, F, R, 0,8) and 35 parts of low density polyethylene (M, F, R, 1,5) were prepared. An inner container was molded using the resin composition.

The resulting container was tested according to the test method described above.

The results are shown in Table 1.

Example 3 55 parts of linear low density polyethylene (MFR0,8) and low density polyethylene (MF
An inner container was molded using a resin composition consisting of 45 parts of R1,5).

The resulting container was tested according to the test method described above.

The results are shown in Table 1.

Comparative Example I EVA (VA content 6.5tit%, M, F, R, 1,
2) was used to mold an inner container in the same manner as in Example 1, and the resulting container was tested according to the test method described above. The results are shown in Table 1.

Comparative Example 2 EVA (VA content 4, 0 wt%, M, F, R, 0,
5) 50 parts and linear low density polyethylene (MFR1,2
) An inner container was molded using a resin composition consisting of 50 parts. The resulting container was tested according to the test method described above.

The results are shown in Table 1.

Table 1 Test (1) Test (2) Example 1゜ No peeling for 10 hours No breaking for 2 hours 2
, Same as above Same as above 3, Same as above As is clear from the results in Table 1, in all comparative examples (conventional products), peeling occurred at the fused part and breakage occurred in about one and a half hours. The products of the examples according to the present invention did not cause peeling at the fused portion, and the products of the examples according to the present invention did not break in the vibration test.

(Effects) As described above, the resin composition for soft, thin-walled containers according to the present invention is firmly fused at the fused portion, so no peeling phenomenon occurs, and it is also resistant to breakage. It has extremely good properties as a resin composition for soft, thin-walled containers.

Claims (1)

[Claims] 1. Inner container for bag-in-box made of synthetic resin made of resin blended with 55-65 parts of linear polyethylene and 35-45 parts of low-density polyethylene.