JPS59178221A - Preparation of packaging bag - Google Patents

Abstract

PURPOSE:To prepare a packaging bag of strong heat seal strength by mixing a specific quantity of specific resin to specific linear low density polyethylene and making blown film extrusion under a specific condition. CONSTITUTION:A mixture wherein 5-70wt% of low density polyethylene having melt indexes 0.1-2g/10min, fluidities 30-70, densities 0.915-0.940g/cm<3> is mixed with linear low density polyethylene having melt indexes 0.2-2g/10min, fluidities 18-35, densities 0.915-0.935g/cm<3> is blown under conditions of blow-up ratios 0.9-1.5 and draft ratios 10-40. Then, the obtained cylindrical film is heat-sealed at 230-280 deg.C making the longitudinal direction intersect the take-up direction and then the heat-sealed portion is liberated to cause shrinkage to the heat- sealed portion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a packaging bag. Specifically, the present invention relates to a method of manufacturing a packaging bag with high heat-sealing strength using linear low-density polyethylene.

Normally, when manufacturing bags for packaging by inflation molding and heat sealing using linear low-strength polyethylene, the body of the bag has strong strength, but the strength of the heat sealing part is extremely low9. There was a problem.

This is due to the molecular structure of linear low-density polyethylene, which will be explained later.
Even if linear low-density polyethylene is tried to have heat shrinkability by imparting molecular alignment through bath melt stretching, etc., it is not possible to make the linear low-density polyethylene have 5Ji shrinkability. This results in a decrease in film thickness and lack of heat roll strength.

The inventors of the present invention have made various efforts to obtain packaging bags with excellent heat sealing strength using linear low-density polyethylene, and as a result, the inventors have developed a special method using a specific linear low-density polyethylene with a special resin. The purpose of the present invention was achieved by blending sufficient amounts and conducting an injection molding session under specific conditions.That is, the gist of the present invention is to achieve the object of the present invention by blending a sufficient amount and conducting an injection molding session under specific conditions. 29/
/ 0 minutes, flow ratio / g ~ 35 nominal density polyethylene, melt index 0.7 ~ 29 / 10 minutes, flow ratio 3
0-70 low density polyethylene
゛ A mixture containing 70% by weight of S-9 was prepared with a blow-up ratio of 0.9-/, and a draft rate of 10-'t.
Inflation molding under '00 conditions, heat sealing and cutting 1>r with the longitudinal direction of the obtained cylindrical film transverse to the take-up direction'f:4+¥:
The characteristic lies in the manufacturing method of the packaging bag.

The present invention is hereby falsely congratulated.

The linear low-density polyethylene resin used in the present invention is a copolymer of ethylene and other α-olefins, and is different from low-density polyethylene resins produced by conventional high-pressure methods. Linear low density polyethylene is, for example, ethylene,
Other α-olefins such as butene, hexene, octene, decene, gmethylpentene, etc. are copolymerized to a large extent by weight, preferably S to 77% by weight, and are copolymerized with medium-low pressure low-density polyethylene. It is manufactured using a Ziegler-type catalyst or a Phillips-type catalyst, which is used for manufacturing, and the conventional high-density polyethylene is made into a short branched structure by a copolymer component, and the density is appropriately lowered using this short chain branching. 0.9/~0.9!
The polyethylene has a linearity of about r I /ca, and has a structure that is more linear than conventional low-density polyethylene and more branched than high-density polyethylene.

When such linear low-density polyethylene is heat-sealed, the shrinkage of the heat-sealed portion is small because the horizontal molecules of linear low-density polyethylene are short-chain branched as described above. It is considered that thermal relaxation does not occur at 0.0 The linear low density polyethylene mentioned above has a melt indica- tion range of 0.2~. 211 for 10 minutes and a flow ratio of /g to 3S is used. If the melt index and flow ratio are out of this range, the strength of the body will decrease when used as a packaging bag, making it undesirable.

Low density polyethylene 1Jff blended into linear low density polyethylene
4-lene includes ethylene homopolymers and copolymers of ethylene and other co-components.

Copolymerization components include vinyl acetate, ethyl acrylate,
Vinyl compounds such as methyl acrylate, hexene, propylene, octene, l-methylpentene/Chiang olefins having 3 or more carbon atoms, and the like. The copolymerization amount of the copolymerization component is θ, 5~/g weight%, preferably 1~/g/wt%.
It is about the same as the θM quantity coefficient. These low-density polyethylenes are produced using the normal high-pressure method (7000~, ?000 Kg/atl
), it is preferable that it be obtained by radical combination using a radical generating agent such as oxygen or a spiritual peroxide.
It is also possible to substitute linear low-density polyethylene with a fluidity ratio of 35 to 70 (3!). Among these low-density polyethylenes, vinyl acetate content O, S~/g
Particularly preferred is an ethylene-vinyl acetate copolymer having a weight ratio of 10 mm or less.

In the method of the present invention, the melt index is JiS
It is a value measured at 790°C in accordance with KA71.0, and the flow ratio is a value measured using the above-mentioned melt index measuring device, with a shear force of 10' dynes/clr (load///3g) and 70
Extrusion amount (1
7710 minutes) and is billed at .

The fluidity ratio is a measure of the molecular weight distribution of the resin used; the smaller the fluidity ratio, the narrower the molecular weight distribution; the higher the fluidity ratio, the wider the molecular weight distribution. It has a major feature in that it contains polyethylene.

As mentioned above, when trying to manufacture a bag with sufficient strength in the body, it is necessary to use linear low-density polyethylene with a flow ratio of /g to 3S, but linear low-density polyethylene alone cannot As mentioned above, the strength of the seal portion is significantly reduced. In the present invention, low density polyethylene having a wide molecular weight distribution is blended in order to improve the heat sealing strength of the linear low density polyethylene.

Low-density polyethylene, which has a wide molecular weight distribution, has long chain branches and has low melt elasticity, so molecular orientation easily occurs during inflation molding, and the strength of the heat barrel of a film covered with such a resin is improved.

By blending low-density polyethylene with the powdered low-density polyethylene described above, it is possible to impart the above-mentioned four effects to the linear low-density polyethylene, or to add the shrinkage effect of the low-density polyethylene to the linear low-density polyethylene. Whether low-density polyethylene can be canceled out or not can be determined by various studies after molding, but by inflation molding the mixture of the present invention under specific conditions, it has good heat-sealability. It was found that the thickness of the part increases due to shrinkage.

The molding conditions are inflation molding with a blow-up ratio of o, q to /, 5 and a draft rate of /θ to qo.

Here, the draft rate is 0 obtained by the following formula. In the formula, the symbols are as follows.

At the time of packaging, the heat foil shrinks in the longitudinal direction, causing distortion in the direction opposite to the orientation of the bag body, which reduces the strength of the heat-sealed end of the resulting bag, causing the bag to break.

If the draft rate is less than 10, good shrinkage will not occur during heat sealing, and if it is greater than tio, the molecular orientation of the body of the bag will become too large in one direction, causing tearing of the body.

EXAMPLES The present invention will be explained in more detail by way of examples below, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

Example/ Linear low density polyethylene (melt index (M process)
: 19710 minutes, flow ratio:, 2o, density: 0, 9.20
9/cJ % Copolymerization component Nibutene-/, Copolymerization amount:
1ON amount%) and gravitational process low-density polyethylene (M process: 0.
ri/10 minutes, flow ratio 2 da 5, density 0.92'lJ1/
ctd, manufactured by Mitsubishi Chemical Industries @, Tsubachik-L vloo
) (Tsubachik is a registered trademark of Mitsubishi Chemical Corporation) at 30'
Blend the amount of N, and install an annular slit diameter -〇01 ring clearance 3 ring clearance inflation die and cooling air ring to a Delsa 45' extruder manufactured by Modern Machinery Co., Ltd. Under the condition of a straight rate of 2y, film thickness / 30μ inflation was carried out. film f
−3/ζ.

The length of the obtained blown film is &70crn
, cut into a cylindrical film with a width of 0.0 cm, and heat sealer manufactured by New Long Co., Ltd. H82, 2B-, 2 type heat sealer = (heating part length / 30 ran, heating part clearance 0.3 tan, cooling part length: /!; 0ttan, cooling clearance/body)
Heat seal temperature (heated part thorn surface temperature) 2 left 0℃ using
, cooling part temperature 30℃, film feeding speed f/km
One of the openings of the cylindrical film was heat-sealed at a position of Cn1 from the end under the condition of It was thicker than it was.

The resulting bag was filled with 20'Kf of fertilizer, and the opening was heat-sealed under the same conditions as described above to obtain a packaging bag for the drop bag test.

In the drop bag test, the bags filled with 20 Kq of fertilizer were heat-sealed and left to accumulate for 2F, then the body of the packaging bag was parallel to the floor and the heat-sealed part was approximately perpendicular to the floor. A test was conducted by dropping 20 bags (lateral drop) in such a manner that the bag breakage rate was determined.

The drop conditions are room temperature -5℃ and Rakushu height/,! ;m.

/ The number of times the bag was dropped was set to S times. The bag tear rate was 01, which was calculated from the rate of bags that were torn in the packaging bags used in the test.The heat shrinkage rate of the blown film was measured to understand the condition of the heat seal part.

To measure the heat shrinkage rate, cut out a circular test piece with a diameter of 6 mm from an arbitrary position on the film, place it on a hot plate with a light surface temperature of 200°C for 5 seconds, and then The change in length (in the film width direction) was determined by the proportion of the original length. It is recognized that if the shrinkage rate in the longitudinal direction is large, the shrinkage rate in the film take-off direction during heat sealing will be higher, and the strength of the heat-sealed portion will be improved.

The results are shown in Table 1.

Using only the linear low density polyethylene used in Comparative Example/Example/,
That is, a packaging bag was obtained by performing inflation molding and heat sealing in the same manner as in Example 1, except that low density polyethylene was not mixed.

The obtained packaging bags were subjected to a drop bag test and the heat shrinkage rate was measured.

The results are shown in Table 1.

*This shows how many parts of the knee have expanded to their original length without shrinking.

In place of the high-pressure low-density polyethylene used in Example 1, high-pressure low-density polyethylene (manufactured by Mitsubishi Chemical Corporation, Tubatic-LTO/10.M work = 0.7 hiroy/70 minutes, fluidity ratio = A packaging bag was obtained in the same manner as in Example/, except that 5S1 densities o, q, 2q) were mixed in /θ weight ratio.

The obtained packaging bag was subjected to a drop bag test and a heat shrinkage rate measurement in the same manner as described in Example.

The results are shown in Table 1.

In place of the high-pressure low-density polyethylene used in Example 3 and Example 3, an ethylene-vinyl acetate co-combined vehicle (manufactured by Sanen Yuka, product name: Yucalon HERO0, a'1.Acid vinyl) was used. 1. if
%, MI: 0. 'l ji/10 minutes, flow ratio/
Io, vt degree: 0.9279/crtt j to qO#
(Example J), enalene-vinyl acetate copolymer (manufactured by Mitsubishi Yuka ■, trade name: Yucalon X-3')
l/, vinyl acetate content 71%, Ii', I: 0.2
9/10 minutes, flow ratio so, density: o, 3ss/cd'
A packaging bag was obtained in the same manner as in Example 1, except that a bag containing 25% by weight of t (Example 1) was used.

The resulting packaging bag was subjected to a drop bag test and heat shrinkage rate measurement in the same manner as described in Example.

The results are shown in Table 2.

Table 2 Examples j, 6 Ethylene-vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., trade name: Mirason AQθ3θN) was used in place of the high-pressure low-density folded polyethylene used in Examples.

Vinyl acetate content angle A weight %, M I ” = 0.59/
10 minutes, flow ratio 0, density: 0.92g 11/cJ
'J in yo* amount (example), ethylene-vinyl acetate copolymer [manufactured by Mitsui Polychemicals ■, part name: Mirason 1 (12,S-ri, vinyl acetate content s
, qz quantity, M:r, = 0. ．． 2'l 9710
minute, flow ratio 15, density 20.9.331//cd) A
Using the same sample (Example 6) containing 0% by weight, the extrusion amount was set to ? ! A packaging bag was obtained in the same manner as in Example except that fX9/br was used.

The obtained packaging bag was subjected to a υ drop bag test in the same manner as shown in Example except that the room temperature of the drop condition was 1/θ℃.
Thermal shrinkage rate was measured.

The results are shown in Table 3.

Table 3 Procedural Amendment (Voluntary) Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, January 2nd, 2017 1 Case Description Showa JK Patent Application No. J3/7g No. 2 Title of Invention Process for Manufacturing Packaging Bags 3 Amendment Related applicants (!; 9t) Mitsubishi Chemical Industries, Ltd. 4 agents 〒10
0 Reversal (1 other person) 5 Subject of amendment Contents of amendment in Column 6 of 1 Detailed explanation of the invention in the specification (1) Specification 7. From the λth line to the last line from the bottom of page 2, "Example/ ``Used only...'' was replaced with ``Linear low-density polyethylene (MT: 2'; l-710 min, flow ratio: 20, density: 0 tgg-/crd, copolymer component Using only nibten-/゛, copolymerization amount: 10 weight ratio),
” he corrected.

2.

Claims (4)

[Claims] (1) Melt index O0-~29/10 minutes,
Linear low density polyethylene with flow ratio/g~33 and melt index 0. /~211//θ min, flow ratio 30~70
Blow-up ratio o, q~/, S1 draft rate 10~
1. A method for producing a packaging bag, which comprises inflation-molding the film under conditions of 0.0 and 1.0, and then heat-sealing and cutting the obtained cylindrical film with its longitudinal direction being in the direction of insertion with respect to the take-up direction. (2) Linear low density polyethylene has a density of 0.97! r～0
．． 93! ;II/d. (3) Low density polyethylene @ summer 0.9 / jT ~ 0
, 9 da Og/cr/I. (4) Low density polyethylene has vinyl acetate content of 0, S~
The method 0(5) according to any one of claims 1 to 3, characterized in that the ethylene-vinyl acetate copolymer has an ethylene-vinyl acetate copolymer with an Claims 1 to 2 are characterized in that the heat-sealed portion is caused to shrink by heating at a temperature of ~2gθ°C until the films are fused together, and then leaving the heat-knolled portion in a free state. The method described in any of Item 9.