JP2600764B2 - Method of manufacturing air-permeable bag - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a bag having air permeability. More specifically, the present invention relates to a method for manufacturing a breathable bag that contains a moisture absorbent, a deodorant, and the like therein, and that is used for forming an absorber that absorbs moisture and odor.

[Prior art and its problems] There has been known an absorbent body in which a moisture absorbent, a deodorant, and the like are accommodated in a bag made of a film having air permeability and absorb moisture and odor.

Various types of air-permeable films constituting such an absorber are considered, but moisture absorbed due to the material and the degree of opening of the holes may leak in reverse, or the strength of the film may be weak, and the film may be transported. There was a problem that the bag was broken by the impact at the time of etc. and the contents leaked.

The present inventors have conducted various studies in order to obtain a bag having air permeability and excellent air permeability in terms of strength, and as a result, made a porous film obtained by a specific manufacturing method by a specific method. As a result, it has been found that the object can be achieved, and the present invention has been completed.

[Means for solving the problem]

The gist of the present invention is to manufacture a bag by heat-sealing a porous film or sheet formed by stretching a film or sheet obtained by melt-molding a composition obtained by blending a filler with a polyolefin resin. The present invention resides in a method for producing a breathable bag, which comprises heat-sealing a nonwoven fabric made of a fiber whose inside (core) is made of polyester and whose outer periphery (sheath) is made of polyethylene as a back sheet.

The porous film or sheet used in the present invention is formed by subjecting a film or sheet obtained by melt-molding a composition obtained by blending a filler to a polyolefin resin to a stretching treatment.

Examples of the polyolefin resin include polyethylene, polypropylene, and copolymers thereof with other α-olefins, and may be used alone or as a mixture of two or more.

As the filler, inorganic and organic fillers are used,
Inorganic fillers include calcium carbonate, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, and oxide. Magnesium, titanium oxide, alumina, mica, asbestos powder, glass powder, shirasu balloon, zeolite, silicate clay, etc. are used, particularly calcium carbonate, talc, clay, silica, diatomaceous earth,
Barium sulfate and the like are preferred.

Cellulose-based powders such as wood powder and pulp powder are used as the organic filler. These are used alone or in combination.

The average particle size of the filler is preferably 30 μm or less, more preferably 10 μm or less, and most preferably 1 to 5 μm.

If the particle size is too large, the denseness of the pores of the stretched product will be poor. If the particle size is too small, dispersibility in the resin will be poor and moldability will be poor.

The surface treatment of the filler is preferably carried out from the viewpoint of dispersibility in a resin and further extensibility, and treatment with a fatty acid or a metal salt thereof gives preferable results.

A liquid or waxy hydrocarbon polymer may be blended with the polyolefin resin in addition to the filler. The addition of the liquid or waxy hydrocarbon polymer helps to form fine pores.

Examples of the liquid or waxy hydrocarbon polymer include liquid polybutadiene and liquid polybutene, and hydrogenated products of liquid polybutadiene. Among them, polyhydroxy saturated hydrocarbons obtained by hydrogenating hydroxyl group-terminated liquid polybutadiene show good results.

The polyhydroxy saturated hydrocarbon is a hydrocarbon polymer in which the main chain having at least 1.5 hydroxyl groups per molecule is saturated or mostly saturated, and
Those having a number average molecular weight of 0, preferably in the range of 500 to 20,000 (by vapor pressure method) are suitably used. If the number average molecular weight is too small, the weather resistance is not sufficient, and if the number average molecular weight is too large, the fluidity is reduced and handling becomes difficult. The average number of hydroxyl groups per molecule is 1.5 or more, preferably 1.8 or more, particularly preferably 2.0 to 5.0. The hydroxyl group is preferably at the end of the main chain or at the end of the long chain branch.

Thus, such polyhydroxy saturated hydrocarbons
Known methods, for example, using hydrogen peroxide or the like as a polymerization initiator,
It is obtained by hydrogenating a butadiene-based liquid polymer obtained by radical polymerization of butadiene alone or a copolymerizable monomer. Examples of the copolymerizable monomer include isoprene, chloroprene, styrene, methyl (meth) acrylate, and methyl vinyl ether.

The hydrogenation is carried out by a conventional method using a nickel-based catalyst (for example, reduced nickel, Raney nickel), a cobalt-based catalyst, a platinum catalyst, a palladium catalyst, a rhodium catalyst, a ruthenium catalyst, a mixture thereof, or an alloy-based catalyst.

It is presumed that introduction of a polar group at the terminal into a polyolefin resin or filler system gives a favorable result in improving the compatibility between the two.

The polyolefin resin may be added with a heat and ultraviolet stabilizer, a pigment, an antistatic agent, a fluorescent agent, and the like according to a conventional method.

The compounding ratio of this composition is preferably 25 to 400 parts by weight of a filler with respect to 100 parts by weight of a polyolefin resin, and 1 to 100 parts by weight of a liquid or waxy hydrocarbon polymer as required.

The compounding of the polyolefin resin, the filler, and the liquid or waxy hydrocarbon polymer added as necessary may be performed by mixing the three components into a common blender or mixer.

Next, kneading of the mixture is appropriately performed by a conventionally known device, for example, a usual screw extruder, a twin-screw extruder, a mixing roll, a Banbury mixer, a twin-screw kneader, or the like.

The molding of the film or sheet may be performed according to a usual film or sheet molding apparatus and molding method, and any suitable method such as isoflation molding with a circular die and T-die molding with a T die may be employed.

The stretching treatment may be uniaxial stretching or biaxial stretching, but is preferably at least 1.1 times the stretching ratio in order to achieve porosity.

Such a porous film or sheet has air permeability and moisture permeability, and has fine openings that do not allow water to permeate. Therefore, since the bag having the film or sheet as a component has air permeability and moisture permeability, for example, if a bag contains a desiccant or the like as an absorbent, the bag absorbs moisture outside the bag, and also has a deodorant, for example. Absorb the odor outside the bag. In particular, in the former case, that is, when the absorbed moisture becomes water and accumulates in the bag when the hygroscopic agent is placed in the bag, the porous film or sheet has excellent water impermeability. It never penetrates outside the bag. Although it has already been described that a number of fine holes are formed in this porous film or sheet, the diameter of the holes is 0.
1 to 10 μm, the film or sheet has a moisture permeability of 1000 to 4
500g · H ₂ O / cm ² · 24hr, air permeability is 300-2000sec / 100cc. When this film or sheet is used as a bag for an absorber, the hole diameter is 0.1 to 3 μm, and the moisture permeability is 2,000.
~ 3000g ・ H ₂ O / cm ²・ 24hr, air permeability 600 ~ 1000sec / 10
It is preferable to use a 0 cc one.

Thus, the porous film or sheet described above,
Usually, it has a thickness of 10 to 200 μm and has a specific effect on air permeability and the like, but there is a problem that the strength of the film, particularly the strength of the heat seal portion formed at the time of bag making is weak.

In the present invention, when heat-sealing the porous film or sheet, a specific heat-sealing method is used.

The heat-sealing method is a method of heat-sealing using a nonwoven fabric made of a fiber whose inside (core) is made of polyester and whose outer periphery (sheath) is made of polyethylene as a back sheet of a porous film.

That is, the configuration of the bag after heat sealing generally has a configuration of nonwoven fabric / porous film / porous film / nonwoven fabric.

The nonwoven fabric of the present invention is a nonwoven fabric in which the inside (core) is made of polyester and the outer periphery (sheath) is made of polyethylene.

It is preferable to use polyethylene having a melting point of about 80 to 170 ° C. in the nonwoven fabric. Usually, it is better to select a film having a melting point approximately equal to or lower than the melting point of the porous film.

The nonwoven fabric made of a fiber whose inner (core) is made of polyester and whose outer periphery (sheath) is made of polyethylene is about 5 to 100 μm thick,
Those having a weighing of about 5 to 100 g / m ² can be suitably used.

When a non-woven fabric made of a fiber whose inner (core) is made of polyester and whose outer periphery (sheath) is made of polyethylene is used as the back sheet of the porous film, they are used simply by being overlapped or bonded by using an adhesive. You can also. In this case, if the adhesive is applied to the entire surface of the porous film, the air permeability may be impaired. Therefore, it is preferable to apply the adhesive in a dotted or linear shape and partially bond the adhesive.

The lamination of the nonwoven fabric made of a fiber whose inner side (core) is made of polyester and whose outer side (sheath) is made of polyethylene is preferably on the side opposite to the side to be heat-sealed in order to make use of the effect of the net.

In the case of using an absorbent stored in the bag as a moisture absorbent, for example, calcium chloride, silica gel,
There are zeolites and ion exchange resins. Insect repellents or fragrances may be added together with such a hygroscopic agent to use in combination. This insect repellent or fragrance may be used by impregnating the above-mentioned porous film or sheet.

Further, in the case where the absorbent is used as a deodorant, there are, for example, activated carbon, molecular sieves, deodorant substances (phthalocyanine, ferrous iron / ascorbic acid, etc.). When this is used as an ethylene absorbent, there are activated carbon or activated carbon or a synthetic adsorbent to which bromine or a bromine compound is added. Further, an insect repellent may be added together with such a deodorant and ethylene deodorant to be used in combination.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

Example 1 Melt index: 1.0 g / 10 min, density: 0.918 g / cm
³ is a linear low-density polyethylene resin (NOVATEC-U, FW
20G, Mitsubishi Kasei Kogyo Co., Ltd.] 3.4 kg and calcium carbonate (average particle size 0.9 μm, fatty acid treatment) 5.8 kg were first stirred and mixed in a Henschel mixer, and then a mixture of 0.8 kg of polyhydroxy saturated hydrocarbon was added thereto. Obtained.

The compounding operation was performed 10 times, and finally 100 kg of a mixture was obtained.

The melt index indicates the amount of resin extruded at 190 ° C. and a load of 2.16 kg according to ASTM D1238-70, and the density is determined at 20 ° C. by a density gradient tube method according to ASTM D1505.

The mixture thus obtained was kneaded with a twin-screw kneader DSM-65 (manufactured by Nippon Steel Works, Ltd.) and granulated. This is 50
Inflation molding by mmφ extruder, thickness 120μ
Was formed into a film.

 Here, the film forming conditions are as follows.

Extruder cylinder temperature: 170-190-190 ° C Head, die temperature: 190-190 ° C Blow ratio: 2.7 The film thus obtained is uniaxially stretched by a roll stretching machine, and then further subjected to a heat relaxation treatment. A porous film having a thickness of 95 μ was obtained.

 The stretching and thermal relaxation conditions are as follows.

Stretching temperature 70 ° C Stretching ratio 2.3 times Thermal relaxation temperature 100 ° C Thermal relaxation rate 13% Inner (core) of the porous film thus obtained
Is a polyester, and the outer periphery (sheath) is a non-woven fabric made of polyethylene fiber (ELVES S0403WD manufactured by Unitika Ltd.)
O) was bonded with a urethane adhesive. The adhesive was applied to the porous film by a transfer method using a gravure roll, and then the porous film and the nonwoven fabric were bonded together by a pressure roll.

The two obtained laminates were faced to each other with the porous film side, and heat-sealed with a heat bar type heat sealer.
The heat sealing was performed at a temperature of 180 ° C., a pressure of 2.4 kg / cm ² and a pressurization time of 1 second.

When the peel strength of the heat-sealed portion was measured by a T-type peel tester (peeling speed 300 mm / min), it was 1,700 g / 15 mm.

Comparative Example 1 When only the porous film used in Example 1 was heat-sealed under the same conditions as in Example 1, the peel strength was 390 g / 15 mm.
Met.

Comparative Example 2 A laminate of the porous film used in Example 1 and a nonwoven fabric (grade name 323, manufactured by Honey Fiber Co., Ltd.) composed of a blend of polyethylene fibers and polypropylene fibers in a ratio of 50:50 was prepared. When heat sealing was carried out under the same conditions as those described above, an edge was cut off at the sealing portion, and a hole was formed, making it impossible to use as a bag.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the method of this invention, it becomes possible to manufacture easily the bag which is excellent in the strength of a heat seal part and has air permeability, and is very useful practically.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B29L 9:00 22:00 (56) References JP-A-62-212752 (JP, A) JP-A JP-A-59-54558 (JP, A) JP-A-55-42638 (JP, A) JP-A-1-176041 (JP, U) JP-A-58-22733 (JP, Y2)

Claims (1)

(57) [Claims] 1. A method for producing a bag by heat-sealing a porous film or sheet formed by subjecting a film or sheet obtained by melt-molding a composition obtained by blending a filler to a polyolefin resin to a bag. And a heat-sealing method, wherein a non-woven fabric made of a fiber whose inner side (core) is made of polyester and whose outer side (sheath) is made of polyethylene is interposed as a back sheet and heat-sealed.