JPH0684449B2 - Breathable film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a moisture-permeable film, and more specifically, it is a flexible film mainly composed of a polyolefin resin which is impermeable to liquid water but permeable to water vapor. It relates to a wet film.

(Prior Art) Disposable diapers have been remarkably popular as diapers used for infants and sick people. The performance required for the backside film used in such a diaper is not only water impermeable as a function of the diaper, but also water vapor permeability, that is, moisture permeability in order to prevent skin irritation. It is desired to have.

It should also be inexpensive as a disposable diaper, and thus a film of this kind should be inexpensive.

(Problems to be solved by the invention) Conventionally, a water-impermeable polyethylene film is often used as the back film used in the above-mentioned diapers. It does not evaporate and causes rashes in diapers.

However, as the conventional moisture permeable film, for example, one obtained by punching by discharge, one obtained by removing the filler after mixing the filler, one obtained by stretching the crystalline plastic, two kinds There are those obtained by blending and stretching the above resins, and none of them have sufficient performance as a disposable diaper film due to high cost or insufficient performance. .

Further, there is a moisture permeable film obtained by stretching a plastic filled with an inorganic substance, and the film can be obtained inexpensively and easily, but it sufficiently satisfies the required performance such as strength, flexibility and moisture permeability. is not.

The present inventor has conducted earnest research to solve these drawbacks, and by selecting and combining specific materials, the above-mentioned drawbacks of the prior art are sufficiently solved, and a film having high moisture permeability and flexibility is extremely The inventors have completed the present invention by finding that they can be obtained at low cost.

(Means for Solving the Problems) That is, the present invention provides 100 parts by weight of linear low-density polyethylene, 50 to 300 parts by weight of inorganic filler, and melt index 10
High-pressure low-density polyethylene and / or ethylene-α-olefin copolymer having a degree of crystallinity of less than 30% 10 to 10
It is a moisture-permeable film obtained by stretching a sheet-shaped material consisting of 0 parts by weight in at least a uniaxial direction.

Next, the present invention will be described in more detail. In order to solve various problems of the prior art as described above, the present inventor has a moisture permeability,
As a result of earnest research to obtain a moisture-permeable film satisfying the required performance such as economical efficiency, stretchability, flexibility, etc., by selecting specific materials as described above and combining them, the moisture permeability having various necessary performances can be obtained. It was found that a film can be obtained.

The linear low-density polyethylene used as the substrate in the present invention means ethylene alone or ethylene and α-such as 1-butene, 1-pentene, 1-octene, and 4-methylpentene-1.
Polymerized or copolymerized with olefin under a low pressure, and those having a density in the range of 0.90 to 0.94 are preferable.

Examples of the inorganic filler to be added to the linear low-density polyethylene include calcium carbonate, magnesium carbonate,
Calcium sulfate, calcium sulfite, magnesium sulfate, calcium phosphate, basic magnesium carbonate, sodium chloride, sodium sulfate, barium carbonate, barium sulfate, aluminum oxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, strontium oxide, barium oxide, Titanium oxide, alumina, mica, silicic acid, kaolin, talc, clay, shirasu, diatomaceous earth, glass powder, zeolite, metal powder and the like,
These are used alone or as a mixture of two or more kinds.

The particle size of such an inorganic filler is preferably 20 μm or less in powder form, and considering dispersibility in a resin,
It is also preferable to add a dispersant such as a fatty acid or a metal soap of a fatty acid to these inorganic fillers in advance or to use a surface-treated one with these dispersants. Further, when there is a risk that the film may foam due to adsorbed moisture during molding, it is preferable to use an alkaline earth metal oxide as one component of the inorganic filler.

The above-mentioned inorganic filler is the above-mentioned linear low-density polyethylene.
It is used in a ratio of 50 to 300 parts by weight per 100 parts by weight. If the amount of the inorganic filler used is less than 50 parts by weight, a moisture permeable film having sufficient moisture permeability cannot be obtained.
If the use ratio exceeds 300 parts by weight, the physical properties of the resulting moisture-permeable film will be sufficient, which is not preferable.

Even if the inorganic filler as described above is added to the linear low-density polyethylene as described above and formed into a film and stretched, a useful one as the backside film of the disposable diaper cannot be obtained,
It was unavoidable to obtain a film having insufficient moisture permeability, stretching and flexibility. In the present invention, in addition to the above-mentioned components, the following specific components, that is, a high-pressure low density polyethylene having a melt index of 10 or more and / or a crystallinity of 30%
By adding an ethylene-α-olefin copolymer of less than less than the sheet-forming and stretching treatment, it is possible to obtain a moisture-permeable film having a required performance such as excellent moisture permeability and flexibility at a low stretching rate at a low cost. It is a finding.

The high-pressure low-density polyethylene having a melt index of 10 or more is polyethylene polymerized by a high-pressure method having a melt index of 10 or more measured at 190 ° C. under a load of 2160 g according to ASTM-D-1238-65. In high-pressure low density polyethylene with a melt index of less than 10,
The stretchability was insufficient.

The ethylene-α-olefin copolymer having a crystallinity of less than 30% means ethylene and propylene, 1-butene, 3-
A copolymer with one or more kinds of alpha-olefins such as methylbutene-1,1-hexene, 3-methylpentene-1,4-methylpentene-1, etc., the crystallinity of which is less than 30%. , The density is in the range of 0.85-0.90. By adding this, flexibility and stretchability are remarkably improved.

The high-pressure low density polyethylene having a melt index of 10 or more and the ethylene-α-olefin copolymer having a crystallinity of less than 30% can be used alone or as a mixture, and in any case, the linear low Used in the range of 10 to 100 parts by weight per 100 parts by weight of density polyethylene. If the amount used is less than 10 parts by weight, stretchability is insufficient, flexibility is insufficient, and a moisture-permeable film having sufficient moisture permeability at a low stretch ratio cannot be obtained, which is not preferable. On the other hand, if the amount used exceeds 100 parts by weight, moisture permeability will be insufficient even when stretched, and the physical properties of the film will be insufficient.

The moisture-permeable film of the present invention contains the above-mentioned components as essential components, but various other additives such as pigments, lubricants, dispersants, stabilizers, flame retardants, antistatic agents, and plasticizers may be added as necessary. Of course, it can be included arbitrarily.

The moisture-permeable film of the present invention is not particularly limited in its production method except that a sheet-like material comprising the above components is stretched in at least one direction, and for example, a resin component and an inorganic filler are mixed in a conventional manner, It may be formed into a sheet by calender molding or extrusion molding. In extrusion molding, a normal film such as an inflation method or a T-die method, a sheet molding apparatus and a molding method can be used. In particular, when forming the above-mentioned components into a sheet, a masterbatch method in which an inorganic filler and a part of a resin component are melt-kneaded, a masterbatch is prepared, and the masterbatch is diluted with a resin component not added is a preferred method, particularly an inorganic material. The filler is melt-kneaded together with the high-pressure low-density polyethylene and / or the ethylene-α-olefin copolymer in a twin-screw kneader, a Banbury mixer or the like to surround the inorganic filler with the high-pressure low-density polyethylene and / or
Alternatively, it is preferable to use it in a state of being coated with an ethylene-α-olefin copolymer, since it is possible to obtain better moisture permeability at a low draw ratio.

The sheet obtained as described above may be stretched in at least a uniaxial direction, and for example, any stretching method such as uniaxial roll stretching, tuber stretching, simultaneous biaxial stretching, and sequential biaxial stretching may be used. By stretching the sheet-like material by such a method, physically minute gaps are efficiently generated between the inorganic filler and the resin contained in the sheet-like substance, and water vapor permeates through these gaps. However, liquid water becomes impermeable. The draw ratio is preferably about 120 to 500%, and the thickness of the moisture-permeable film obtained is about 10 to 100.
About μm is preferable.

According to the present invention as described above, it is possible to provide a moisture permeable film having excellent performances such as moisture permeability and flexibility as a back sheet for disposable diapers at extremely low cost and easily.

Next, the present invention will be described more specifically with reference to examples.
In the text, “part” and “%” are based on weight unless otherwise specified.

Example 1 35 parts of low-density polyethylene (MI = 30, d = 0.915) and 130 parts of calcium carbonate (average particle size 4 μm) were kneaded by a biaxial kneader and then granulated. 100 parts of an ethylene-1-butene copolymer (MI = 2.0, d = 0.920) which is a linear low density polyethylene was added to 165 parts of this granulated product, and a 60 μm sheet was obtained by a T-die film forming machine. This was uniaxially stretched in the longitudinal direction at 50 ° C. to obtain a moisture-permeable film of the present invention having a thickness of 35 μm.

Example 2 100 parts of ethylene-4-methylpentene-1 copolymer (MI = 2.0, d = 0.920) which is a linear low density polyethylene, 35 parts of low density polyethylene (MI = 35, d = 0.917) and calcium carbonate 130 parts (average particle size 2.9 μm) were kneaded with a biaxial kneader and then granulated. A 60 μm sheet was obtained from this granulated product using a T-die film forming machine. This was uniaxially stretched in the machine direction with a uniaxial stretching machine to obtain a moisture-permeable film of the present invention having a thickness of 35 μm.

Comparative Example 1 135 parts of an ethylene-1-butene copolymer (MI = 2.0, d = 0.920), which is a linear low density polyethylene, and 130 parts of calcium carbonate (average particle size 4 μm) were kneaded with a biaxial kneader,
Granulated. This granulated product is 60 by a T-die film forming machine.
A sheet of μm was obtained. This was uniaxially stretched in the machine direction with a uniaxial stretching machine to obtain a moisture-permeable film of Comparative Example having a thickness of 35 μm.

Example 3 Ethylene-1-butene copolymer (MI = 2.0, d = 0.920)
100 parts, ethylene-propylene copolymer (MI = 3.2, d =
0.88) 25 parts, calcium carbonate (average particle size 2.9 μm) 130 parts and calcium oxide 10 parts were kneaded by a biaxial kneader and then granulated. 80 μm of this granulated product with a T-die film forming machine
Got a sheet of. This was uniaxially stretched in the longitudinal direction at 70 ° C. by a uniaxial stretching machine to obtain a moisture-permeable film of the present invention having a thickness of 40 μm.

Example 4 The linear low-density polyethylene in Example 3 was changed to ethylene-
4-methylpentene-1 copolymer (MI = 2.0, d = 0.92)
Instead of (0), the moisture permeable film of the present invention was obtained in the same manner as in Example 3.

Comparative Example 2 Ethylene-1-butene copolymer (MI = 2.0, d = 0.920)
100 parts and 104 parts of calcium carbonate (average particle size: 2.9 μm) were kneaded with a biaxial kneader and then granulated. A 80 μm sheet was obtained from this granulated product using a T-die film forming machine. This was uniaxially stretched in the longitudinal direction at 70 ° C. by a uniaxial stretching machine to obtain a moisture-permeable film of Comparative Example having a thickness of 40 μm.

Example 5 Ethylene-1-butene copolymer (MI = 2.0, d = 0.920)
100 parts, high-pressure direction low-density polyethylene (MI = 30, d = 0.9
15) 35 parts, ethylene-propylene copolymer (MI = 3.2,
d = 0.88) 35 parts by weight and calcium carbonate (average particle size 2.
150 parts (9 μm, treated with fatty acid) were kneaded with a biaxial kneader and then granulated. 70 μm of this granulated product by T-die film forming machine
Got a sheet of. This was uniaxially stretched in the longitudinal direction at 50 ° C. by a uniaxial stretching machine to obtain a moisture-permeable film of the present invention having a thickness of 40 μm.

Examples 6 to 10 The moisture permeable film of the present invention was obtained by changing the compounding ratio as described below with the same materials, processing methods and processing conditions as in Example 5.

Example 6 Linear low-density polyethylene 100 parts High-pressure method low-density polyethylene 35 parts Amorphous resin 35 parts Inorganic filler 150 parts Stretched film thickness 35 μm Example 7 Linear low-density polyethylene 100 parts High-pressure method low-density polyethylene 35 Part amorphous resin 35 parts inorganic filler 180 parts stretched film thickness 50 μm Example 8 linear low density polyethylene 100 parts high pressure low density polyethylene 35 parts amorphous resin 35 parts inorganic filler 180 parts stretched film thickness 45 μm Example 9 Linear low density polyethylene 100 parts High pressure low density polyethylene 35 parts Amorphous resin 35 parts Inorganic filler 180 parts Stretched film thickness 40 μm Example 10 Linear low density polyethylene 100 parts High pressure method low density Polyethylene 30 parts Amorphous resin 40 parts Inorganic filler 190 parts Stretched film thickness 50 μm Examples 11 to 12 The same materials as in Example 5 were used in the following formulation, and firstly, Sium and high-pressure low-density polyethylene are kneaded and granulated by a biaxial kneader, and the obtained granules and other materials are further kneaded and granulated by a biaxial kneader, and then formed into a film by a T-die method, The breathable film of the present invention was obtained.

Example 11 Linear low-density polyethylene 100 parts High-pressure method low-density polyethylene 35 parts Amorphous resin 35 parts Inorganic filler 150 parts Stretched film thickness 45 μm Example 12 Linear low-density polyethylene 100 parts High-pressure method low-density polyethylene 35 Part Amorphous resin 35 parts Inorganic filler 180 parts Stretched film thickness 55 μm Comparative Examples 3 to 5 In the same manner as in Example 5, a moisture permeable film of Comparative Example was obtained with the following composition.

Comparative Example 3 Linear low-density polyethylene 100 parts High-pressure low-density polyethylene Non-crystalline resin Non-inorganic filler 90 parts Stretched film thickness 40 μm Comparative example 4 Linear low-density polyethylene 100 parts High-pressure low-density polyethylene 35 parts Non Crystalline resin No inorganic filler 140 parts Stretched film thickness 40 μm Comparative example 5 Linear low density polyethylene 100 parts High pressure low density polyethylene amorphous resin 35 parts Inorganic filler 140 parts Stretched film thickness 40 μm Table 1 shows the results of measuring the physical properties of the moisture-permeable films of Examples and Comparative Examples according to the following criteria.

(I) Water vapor transmission rate (g / m ² 24 hrs.); Measured according to JIS Z-0208 at 40 ° C. 90% RH.

(II) Breaking strength (g / 15 mm, length / width): Cut to a width of 15 mm and pulled at a speed of 300 mm / min. By a tensile tester to determine the strength at break.

(III) Elongation at break (%, vertical / horizontal); The elongation at break was determined in the same manner as the breaking strength.

(IV) Flexibility: It was touched by the hand and sensually determined.

1 (good)-5 (bad)

Claims (3)

[Claims] 1. A linear low-density polyethylene 100 parts by weight, an inorganic filler 50 to 300 parts by weight, a high-pressure low-density polyethylene having a melt index of 10 or more and / or an ethylene-α-olefin copolymer copolymer having a crystallinity of less than 30%. A moisture-permeable film obtained by stretching a sheet-like material composed of 10 to 100 parts by weight of a united body in at least a uniaxial direction. 2. The inorganic filler is a high-pressure low-density polyethylene and / or ethylene-α-having a crystallinity of less than 30% in advance.
The moisture-permeable film according to claim (1), which is melt-kneaded together with the olefin copolymer. 3. The moisture permeable film according to claim 1, wherein the inorganic filler contains an alkaline earth metal oxide.