JPS62164739A - moisture permeable film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a moisture permeable film, and more specifically, a flexible permeable film mainly composed of a polyolefin resin that does not allow liquid water to pass through but allows water vapor to pass through. Concerning wet films.

(Prior art) Conventionally, disposable diapers have become rapidly popular as diapers for infants, sick people, etc. The performance required of the backing film used in such diapers is that water impermeability as a function of the diaper is Needless to say, it is desired that the material has water vapor permeability, that is, moisture permeability, in order to prevent skin irritation.

It should also be inexpensive as a disposable diaper, so this type of film should be inexpensive.

(Problem to be solved by the invention) Conventionally, a water-impermeable polyethylene film has often been used as the backing film used in the above diapers, but since it is not moisture permeable, even if you sweat, it will not absorb moisture. The water is not evaporated, causing diaper rash.

However, there are two types of conventional moisture permeable films: one made by perforating by electrical discharge, one obtained by removing the filler after mixing it with a filler, and one obtained by stretching crystalline plastic. There are films that can be obtained by blending and stretching the above resins, but none of them have sufficient performance as disposable diaper films due to high cost or insufficient performance. .

There is also a moisture-permeable film obtained by stretching plastic filled with an inorganic substance, and this film is inexpensive and easy to obtain, but it satisfies the required performance such as strength, flexibility, and moisture permeability. isn't it.

As a result of intensive research in order to solve these drawbacks, the present inventors have found that by selecting and combining specific materials, the drawbacks of the above-mentioned prior art can be fully resolved, and a film with high moisture permeability and flexibility can be produced. The present invention was completed based on the finding that it can be obtained at low cost (means for solving the problem).That is, 1. The present invention consists of 100 parts by weight of linear low-density polyethylene and 50 to 300 parts by weight of an inorganic filler. Parts by weight, formed by stretching in at least one direction a sheet-like material consisting of 10 to 100 parts by weight of high-pressure low-density polyethylene with a melt index of 10 or more and/or an ethylene-α-olefin copolymer with a crystallinity of less than 30%. It is a moisture permeable film.

Next, to explain the present invention in more detail, the present inventors aimed to solve the various problems of the prior art as described above by improving moisture permeability,
As a result of extensive research in order to obtain a moisture permeable film that satisfies the required performance such as economic efficiency, stretchability, flexibility, etc., we have selected specific materials as described above and combined them to create a moisture permeable film that has various required performances. It was discovered that a film can be obtained.

The linear low-density polyethylene used as a base material in the present invention refers to ethylene alone or ethylene and α-
It is polymerized or copolymerized with olefin under low pressure, and preferably has a density in the range of 0.90 to 0.94.

Examples of inorganic fillers added to the above 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,
Examples include silicic acid, kaolin, talc, clay, shirasu, diatom, glass powder, zeolite, metal powder, etc., and these may be used alone or as a mixture of two or more.

The particle size of such inorganic fillers is preferably 20 pm or less in powder form, and considering dispersibility in the resin, these inorganic fillers may be added with a dispersant such as a fatty acid or a fatty acid metal soap in advance. Or.

It is also preferable to use a film whose surface has been treated with these dispersants.Also, if there is a risk that the film may foam due to adsorbed moisture during molding, alkaline earth metal oxides may be used as a component of the inorganic filler. It is preferable to do so.

The above-mentioned inorganic fillers are used in a proportion ranging from 50 to 300 parts by weight per 100 parts by weight of the linear low-density polyethylene. If the amount of inorganic filler used is less than 50 parts by weight, a moisture permeable film with sufficient moisture permeability cannot be obtained, while if the amount used exceeds 300 parts by weight, the physical properties of the resulting moisture permeable film may be inadequate. I don't like it because it becomes enough.

Even if the above-mentioned inorganic filler is added to the above-mentioned linear low-density polyethylene, and the film is formed and stretched, a film useful as a backside film for disposable diapers cannot be obtained.
A film with insufficient moisture permeability, stretching, flexibility, etc. was obtained. In addition to the above components, the wood invention includes the following specific components: high-pressure low-density polyethylene with a melt index of 10 or more and/or a crystallinity of 3.
By adding less than 0% of an ethylene-α-olefin copolymer and forming it into a sheet and stretching it, a moisture-permeable film with the required performance such as excellent moisture permeability and flexibility can be obtained at a low cost at a low stretching rate. This is what I found out.

High-pressure low-density polyethylene with a melt index of 10 or more is polyethylene polymerized by a high-pressure method with a melt index of 10 or more measured at 190°C under a load of 2180 g in accordance with ASTM-D-1238-65. . High-pressure low-density polyethylene with a melt index of less than 10 had insufficient stretching suitability.

In addition, ethylene-α-olefin copolymers with a crystallinity of less than 30% include ethylene, propylene, 1-butene, 3
- A copolymer with one or more alpha olefins such as methylbutene-1,1-hexene and 3-methylpentene-1,4-methylpentene-1, the crystallinity of which is 30%. and the density is 0.85 to 0.9
It is in the range of 0. By adding this, flexibility and stretchability are significantly improved.

The above-mentioned high-pressure low-density polyethylene with a melt index of 10 or more and the ethylene-α-olefin copolymer with a crystallinity of less than 30% can be used individually or as a mixture, and in either case, the linear 10-100 per 100 parts by weight of density polyethylene
Use within parts by weight. If the amount used is less than 10 parts by weight, the suitability for stretching is insufficient, the flexibility is insufficient, and a moisture permeable film having sufficient moisture permeability cannot be obtained even at a low stretching ratio, which is undesirable. If the amount exceeds parts by weight, moisture permeability will be insufficient even after stretching, and the physical properties of the film will be insufficient.

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

The method of manufacturing the moisture permeable film of the present invention is not particularly limited, except that a sheet material made of the above components is stretched in at least one direction. It may be formed into a sheet by calender molding, extrusion molding, or the like. In the extrusion molding, ordinary film and sheet molding equipment and molding methods such as the inflation method and the T-die method can be used. especially.

When forming the above components into a sheet, the master patch method, in which the inorganic filler and part of the resin component are melt-kneaded to create a masterbatch and diluted with unadded resin component, is a preferred method. is melt-kneaded with high-pressure low-density polyethylene and/or ethylene-α-olefin copolymer in a twin-screw mixer, Banbury mixer, etc. to form high-pressure low-density polyethylene and/or ethylene-α- It is preferable to use the film coated with an olefin copolymer because better moisture permeability can be obtained at a low stretching ratio.

The sheet-like material obtained as described above may be stretched in at least one direction, and for example, any stretching method such as -axial roll stretching, tubular stretching, simultaneous biaxial stretching, sequential biaxial stretching, etc. may be used. By stretching the sheet material in this way, physically minute gaps are efficiently created between the inorganic filler and the resin contained in the sheet material, and water vapor permeates through these gaps. However, liquid water becomes impermeable. The stretching ratio is preferably about 120 to 500%, and the thickness of the obtained moisture permeable film is about -
Approximately 10-Jl) OJ''m is suitable.

According to the present invention as described above, a moisture permeable film having excellent required performance as a back sheet for disposable diapers, such as moisture permeability and flexibility, can be provided easily and at an extremely low cost.

Next, the present invention will be explained in more detail with reference to Examples. In the text, parts and percentages are based on weight unless otherwise specified.

Example 1 Low density polyethylene (MI=30. d=0.915
) and 130 parts of calcium carbonate (average particle size: 4 microns) were kneaded in a twin-screw kneader and then granulated.

105 parts of this granulated material was added with ethylene-1-butene copolymer (MI = 2.0, d = 0), which is linear low density polyethylene.
．． 920) was added to obtain 601 parts of a sheet using 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 JLm.

Example 2 Ethylene-4-methylpentene-1 copolymer which is linear low density polyethylene (MI=2.0, d=0°920)
100 parts, low density polyethylene (Mr=35, d=0
．． 917) and 130 parts of calcium carbonate (average particle size 2.9 ILm) were mixed in a twin-screw mixer and then granulated. This granulated material was processed using a T-die film forming machine for 60 min.
A 4 m sheet was obtained. This was uniaxially stretched in the longitudinal direction using a -axial stretching machine to obtain a moisture permeable film of the present invention having a thickness of 35 JLm.

Comparative Example 1 Ethylene-l-butene copolymer which is linear low density polyethylene (Ml engineering 2.0, d = 0.920) 135
and 130 parts of charcoal calcium (average particle size: 4 JLm) were kneaded in a twin-screw kneader and then granulated. A sheet of 60 JLm was obtained from this granulated material using a T-die film forming machine. This was uniaxially stretched in the longitudinal direction using a -axial stretching machine to obtain a comparative moisture permeable film having a thickness of 35 ILm.

Example 3 Ethylene-1-butene copolymer (Mr=2.0,
d=0.920) 100 parts, 25 parts of ethylene-propylene copolymer (MI=3.2, d=0.88), 130 parts of calcium carbonate (average particle size 2.9 pm) and 10 parts of calcium oxide. After mixing using a two-screw mixing machine, it was granulated. The granules were processed into 80IL by a T-die film forming machine.
m sheets were obtained. This was uniaxially stretched in the longitudinal direction at 70°C using a -axial stretching machine to obtain a moisture permeable film of the present invention having a thickness of 40 #Lm.

Example 4 The linear low-density polyethylene in Example 3 was converted into dihandylene-4-methylpentene-1 copolymer 011=2.0, d
= 0.920), and in the same manner as in Example 3 except that a moisture permeable film of the present invention was obtained.

Comparative Example 2 Ethylene-1-butene copolymer (MI=2.0, d=0
．． 1l120) and 104 parts of dust key calcium (average particle size 2.9 ILm) were mixed in a twin-screw mixer and then granulated. A sheet of 80 gm was obtained from this granulated material using a T-die film forming machine. This is processed by an axial stretching machine for 7
A comparative moisture permeable film having a thickness of 401 parts m was obtained by uniaxially stretching in the longitudinal direction at 0°C.

Example 5 Ethylene-1-butene copolymer (XI = :1O1d
= 0.920) 100 parts, high pressure low density polyethylene (MI = 30. d = 0.915) 35 parts, ethylene-propylene copolymer (Ml = 3.2, d
= 0.88) and 150 parts of calcium carbonate (average particle size 2.9 ILm, fatty acid treatment) were mixed in a twin-screw kneader and then granulated. A 704 m sheet was obtained from this granulated material using a T-die film forming machine. This was uniaxially stretched in the longitudinal direction at 50° C. using a -axial stretching machine to obtain a moisture permeable film of the present invention having a thickness of 401 parts m.

Examples 6 to 10 Moisture-permeable films of the present invention were obtained using the same materials, processing method, and processing conditions as in Example 5, but varying the blending ratio as shown below.

Disaster A Yuu J Linear low density polyethylene IOO part High pressure process low density polyethylene 35 parts Amorphous resin
35 parts inorganic filler
Thickness of 150 parts stretched film
35 end meter support 1 Linear low density polyethylene 100 parts High pressure process low density polyethylene 35 parts Amorphous resin
35 parts inorganic filler
180 parts stretched film thickness
50 parts mX treatment J linear low density polyethylene 100 parts high pressure low density polyethylene 35 parts amorphous resin
35 parts inorganic filler
180 parts stretched film thickness
45JLm Bunshiyong Linear low density polyethylene 10 parts High pressure low density polyethylene 35 parts Amorphous resin
35 parts inorganic filler
180 parts stretched film thickness
40ILm supporting structure and linear low density polyethylene 100 parts high pressure process low density polyethylene 30 parts amorphous resin
40 parts inorganic filler
190 parts stretched film thickness
50 lm Examples 11-12 Using the same materials as in Example 5 in the following formulation, first, calcium carbonate and high-pressure low-density polyethylene were kneaded and granulated using a twin-screw kneader, and the resulting granules were The product and other materials were further kneaded and granulated using a twin-screw kneader, and then formed into a film using a T-die method to obtain a moisture-permeable film of the present invention.

Fruit 1" 1u Linear low density polyethylene 100 parts High pressure low density polyethylene 35 parts Amorphous resin
35 parts inorganic filler
Thickness of 150 parts stretched film
45 parts linear low density polyethylene 100 parts high pressure low density polyethylene 35 parts amorphous resin
35 parts inorganic filler
180 parts stretched film thickness
55ILm Comparative Examples 3 to 5 Moisture permeable films of comparative examples were obtained in the same manner as in Example 5 with the following composition.

Comparative Thoughts] Linear low-density polyethylene ・100 parts high-pressure low-density polyethylene Non-crystalline resin
Inorganic filler
90 parts stretched film thickness
40ILm Comparative Yu” Linear low density polyethylene 100 parts High pressure low density polyethylene 35 parts Amorphous resin
Inorganic filler
140 parts stretched film thickness
40JLm soil-squeezed linear low-density polyethylene 100 parts high-pressure low-density polyethylene non-crystalline resin
35 parts inorganic filler
140 parts stretched film thickness
Table 1 shows the results of measuring the physical properties of the moisture permeable films of the above Examples and Comparative Examples using the following criteria.

(I) Moisture permeability (g/m' 24hrg,): JI
Measurement was performed at 40°C and 90% RH according to S Z-0208.

(II) Breaking strength (j'/15 pair length/width): Width 15
Cut into the intestinal layer and use a tensile tester to test 300 dragons/■in,
The strength at break was determined by pulling at a speed of .

(DI) Elongation at break (%, length/width); The elongation at break was determined in the same manner as the breaking strength.

(IT) Flexibility; measured as a sense of touch by hand.

l (good) --5 (bad) Self (''−)≧− engineering mrv

Claims (3)

[Claims] (1) 100 parts by weight of linear low-density polyethylene, 50 to 300 parts by weight of inorganic filler, high-pressure low-density polyethylene with melt index of 10 or more and/or crystallinity of 30
less than 10% to 10% ethylene-α-olefin copolymer
A moisture-permeable film obtained by stretching a sheet-like material containing 0 parts by weight in at least one axis. (2) Claim 1, wherein the inorganic filler is melt-kneaded in advance with high-pressure low-density polyethylene and/or an ethylene-α-olefin copolymer with a crystallinity of less than 30%. Moisture-permeable film. (3) The moisture permeable film according to claim (1), wherein the inorganic filler contains an alkaline earth metal oxide.