JPS6366241A - Production of moisture-permeating water-proofing film having flexibility - Google Patents

Abstract

PURPOSE:To obtain the titled film suitable for disposable diaper, etc., by drawing a resin sheet composed of a specific thermoplastic resin containing a specific amount of an inorganic filler at a specific areal draw ratio and embossing the drawn sheet. CONSTITUTION:100pts.wt. of a thermoplastic resin composed mainly of a polyolefin resin (e.g. polyethylene) is compounded with 50-300pts.wt. of a powdery inorganic filler (e.g. calcium carbonate) having diameter of preferably <=20mu and formed to a thermoplastic sheet. The sheet is drawn at an areal draw ratio of 120-500% and embossed with an embossing roll heated at a temperature higher than the drawing temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for obtaining a waterproof and water vapor permeable film mainly used for disposable diapers and the like.

[Conventional technology]

Conventionally, water-impermeable polyolefin resin films have often been used as backing films in disposable diapers, but because they are not moisture permeable, water does not evaporate even when sweating, leading to diaper rash. was.

For this reason, there is a growing demand for resin films that have both moisture permeability and waterproof properties for various uses, including the back film of disposable diapers, and as a method for obtaining resin films that have both moisture permeability and waterproof properties, For example, (1) a method in which a resin film is subjected to electrical discharge machining to form fine holes; (2) a resin film containing an elutable filler is obtained and then the filler is eluted. and (3) a method of stretching a crystalline resin sheet to obtain a resin film with voids and fibrils inside.

[Problem that the invention seeks to solve]

By the way, among the methods for obtaining a resin film having both moisture permeability and waterproofness, the method using electric discharge machining described in item (1) requires complicated processing operations for electric discharge machining, and moreover, the perforations formed are complicated. The holes tend to be large, which is problematic in terms of waterproofness, and the larger the number of holes, the worse the physical properties. In addition, those using the elution process described in item (2) above require equipment and a drying process to recover the solvent used in the elution process, which has the disadvantage of not only poor production efficiency but also high costs. have Furthermore, those using the crystalline resin sheet described in item (3) above have drawbacks such as the resulting film lacks flexibility and lacks the good feel required for the back film of disposable diapers. have.

In contrast, the present invention has a balance between moisture permeability and waterproofness that satisfies the performance particularly required for the back film of diapers, and also provides favorable flexibility for the back film of diapers. The object of the present invention is to provide a method by which a resin film can be obtained through a simple manufacturing process and at low cost.

[Means for Solving the Problems] The method for producing a flexible moisture-permeable waterproof film of the present invention uses thermoplastic resin 1 mainly composed of polyolefin resin.
After obtaining a resin sheet containing 50 to 300 parts by weight of an inorganic filler per 00 parts by weight, the resin sheet is stretched to an area magnification of 120 to 500%, and then embossed. be.

In the first step of the method for producing a moisture-permeable waterproof film of the present invention having the above-mentioned structure, a thermoplastic resin sort containing an inorganic filler as an essential component is processed by, for example, an inflation method or T
It is obtained by extrusion molding using a die method, calender molding, or the like. The thermoplastic resin sheet is made of low density polyethylene, medium density polyethylene, high density polyethylene, cotton-like low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid (ester) copolymer, polypropylene, ionomer resin, ethylene. - A thermoplastic resin sheet mainly composed of a polyolefin resin such as a propylene copolymer or a propylene-butene copolymer, that is, a sheet made of the polyolefin resin, or a flexible sheet made of the polyolefin resin and a flexible material such as polybutadiene or styrene elastomer. It is a sheet made of a mixed resin with a small amount of a thermoplastic resin having properties, and the thermoplastic resin 10 mainly consists of the above-mentioned polyolefin resin.
It contains 50 to 300 parts by weight of inorganic filler per 0 parts by weight.

The inorganic filler added to the thermoplastic = 4-plastic resin mainly composed of the polyolefin resin is, for example,
Magnenium carbonate, Magnenium 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.

Whitebait, diatomaceous earth, glass powder, zeolite.

Gold powder, etc., and these can be used alone or as a mixture of two or more. The inorganic filler is preferably in powder form with a size of 20μ or less, and in terms of the dispersibility of the inorganic filler in the thermoplastic resin when obtaining a thermoplastic resin sheet, the inorganic filler is preliminarily mixed with a fatty acid or a metal of a fatty acid. It is preferable to use a surface treated with a dispersant such as soap or a coupling agent such as a silane coupling agent or a titanium coupling agent, or to use the above-mentioned inorganic filler together with the above-mentioned dispersant. In addition, if there is a possibility that the resulting resin sheet may become foamed due to adsorption of moisture during molding to obtain the thermoplastic resin sheet, an alkaline earth metal may be added as a component of the inorganic filler. Preference is given to using oxides. The inorganic filler is used in an amount of 50 to 300 parts by weight per 100 parts by weight of the thermoplastic resin mainly composed of the polyolefin resin. This is because a film exhibiting sufficient moisture permeability cannot be obtained, and if the amount exceeds 300 parts by weight, the resulting film will have insufficient mechanical strength.

In addition, when obtaining a thermoplastic resin sheet mainly composed of the polyolefin resin, various components other than the above-mentioned inorganic filler, such as lubricant 9.
Dispersant, stabilizer.

Of course, flame retardants, antistatic agents, plasticizers, organic pigments, dyes, etc. may be added as appropriate.

The second step of the method for producing a moisture-permeable waterproof film of the present invention is as follows:
The thermoplastic resin sheet obtained in the first step is stretched to an area ratio of 120 to 500%, and preferably a stretched film having a thickness of about 10 to 100 μm is obtained. The stretching treatment of the thermoplastic resin sheet may be carried out in at least one direction, and may be any stretching method such as -axial roll stretching, tubular stretching, simultaneous biaxial stretching, or sequential biaxial stretching.

The third step of the method for producing a moisture-permeable waterproof film of the present invention is as follows:
Embossing is applied to the stretched film obtained through the stretching process, which is the second step, and is generally composed of an engraved iron roll, a paper roll, a cotton roll, and a rubber roll. This is carried out by supplying the stretched film between embossing rolls and pressing them together. The embossing process is carried out in a heated state if necessary, but it is carried out by replacing the heating roll in the annealing process that follows the stretching process in the second stretching process described above with an embossing roll. That is, the annealing device in the stretching device is composed of an embossed roll consisting of an engraved iron roll and a paper roll, cotton roll, aluminum roll, or rubber roll, and between the embossed rolls that are heated to a higher temperature than the stretching temperature. By passing the film that has come out of the stretching process, the annealing process and the embossing process can be carried out at the same time, allowing for efficient emporation and processing.

〔Example〕

The specific structure of the method for producing a flexible moisture-permeable waterproof film of the present invention will be described below with reference to Examples.

Example 1 Ethylene-4/methylpentene-1 copolymer [linear low density polyethylene: MI2. O, d=o, 920) 1
00 parts by weight and 100 parts of calcium carbonate with an average particle size of 2.9μ
parts by weight were kneaded in a twin-screw kneader and then granulated in a granulation molding machine.

The obtained granules were used as a film-forming raw material to obtain an extruded sheet of thermoplastic resin with a thickness of 55 μm using a T-die film-forming machine, and then the sheet was uniaxially stretched at a stretching temperature of 50'C. A uniaxially stretched film with an area magnification of 200% was obtained.

Next, the -axially stretched film was stretched so that the size of the convex portion was 1.
mm
kg/cA at a running speed of 20 m/min to emboss the -axially stretched film.

The moisture permeability of the obtained embossed film is 3000y.
/ m', 24 hrs (40°C190%RH
), and the water pressure resistance is 0.4 kg / ca (JIS
L1092), and was flexible and had a good texture.

Example 2 An extruded sheet of thermoplastic resin with a thickness of 55 μm, which is the same as that used in Example 1, was uniaxially stretched at a stretching temperature of 50°C to an area magnification of 220%. embossing roll, that is, the size of the convex part is 0
．． An embossing roll consisting of a combination of a metal engraving roll (heating temperature 90°C) and a paper roll, which is 5mm x 0.5mm and 0.5mm in height,
Roll pressure 70kg/Ca, running speed 20m/m
An embossed film was obtained by simultaneously carrying out an annealing process and an embossing process after the stretching process.

The moisture permeability of the obtained embossed film is 3sooy
/rr? , 24 hrs (40'C, 90%RH
), the water pressure resistance was 0.3 kg/crl, and it was flexible and had a good texture.

[Operation and effect of the invention]

The method for producing a flexible, moisture-permeable and waterproof film of the present invention uses thermoplastic resin 1 mainly composed of polyolefin resin.
After obtaining a resin sheet containing 50 to 300 parts by weight of an inorganic filler per 00 parts by weight, the resin sheet is stretched to an area magnification of 120 to 500%, and then embossed. By stretching a thermoplastic resin sheet mainly composed of a polyolefin resin containing an inorganic filler, physical fine voids are efficiently generated between the inorganic filler and the resin in the resin sheet, It provides so-called moisture-permeable waterproof properties that allow water vapor to pass through but not liquid water, and also introduces flexibility through embossing.

Therefore, the present invention provides a thermoplastic resin that has a well-balanced moisture permeability, waterproofness, and mechanical strength that are particularly required for a backing film in disposable diapers, and also has flexibility that is advantageous for disposable diapers. This provides the effect that the film can be mass-produced at low cost by combining simple manufacturing processes.

Claims (2)

[Claims] (1) Stretching a resin sheet containing 50 to 300 parts by weight of an inorganic filler to 100 parts by weight of a thermoplastic resin mainly composed of polyolefin resin to an area magnification of 120 to 500%, and then subjecting it to embossing. A method for producing a flexible moisture-permeable waterproof film characterized by: (2) A method for producing a flexible, moisture-permeable and waterproof film as claimed in claim 1, wherein embossing is performed using an embossing roll heated to a higher temperature than the stretching temperature immediately after the stretching process.