JP2737236B2 - Method for producing breathable film - Google Patents

Description

The present invention relates to a method for producing a breathable film. More specifically, the present invention relates to a method for producing a breathable film that allows air and water vapor to pass therethrough but does not allow water to pass through, and relates to a method for producing a breathable film for supplying a breathable film having high strength and high water pressure resistance.

<Conventional Technology> Conventionally, a breathable film that is impermeable to water and that is permeable to a substrate such as aeration and water vapor has been used for a back sheet of a disposable diaper, packaging of a moisture absorbent and a deoxidizer, and the like. As a method for producing the composition, a composition comprising a resin and a filler as described in JP-A-60-229731 or, in some cases, a composition obtained by adding a waxy hydrocarbon polymer to the composition. In some cases, a film is formed and stretched to generate microvoids inside the film to exhibit air permeability. However, a film comprising a resin and a filler has limitations in both tensile strength and tear strength. In addition, there is a problem that the water pressure resistance is reduced due to the increase in elongation for small stress, and large and small portions of microvoids are generated due to physical generation of microvoids between the filler and the resin. There is a problem that hinders uniformity.

As a method for solving these problems, there is a method of arranging a reinforcing material such as a nonwoven fabric on a breathable film. For example, as described in JP-A-63-286330, a nonwoven fabric is partially bonded to a breathable film, or an adhesive layer is selected as in JP-A-63-116849 or JP-A-63-136926. The technique of laminating the breathable film and the nonwoven fabric on the entire surface is already known.

However, when the air-permeable film and the nonwoven fabric are partially bonded, a difference in air permeability may occur between the bonded portion and the non-bonded portion, or the water pressure may be reduced due to stress concentration in the non-bonded portion. Also, the method of selecting an adhesive layer and laminating the air permeable film and the nonwoven fabric over the entire surface is problematic in that the air permeability changes or the adhesive strength is not uniform unless the thickness of the adhesive layer is controlled to be thin and uniform. was there.

<Means for Solving the Problems> The present inventors have intensively studied a method for obtaining a uniform breathable film having high air permeability and high strength. As a result, after laminating a resin composition comprising a resin and a filler on a specific non-woven fabric, and stretching the resin at the same time as the non-woven fabric, it was found that a uniform breathable film having high air permeability and high strength was obtained. Reached.

That is, the present invention, after melt-laminating a resin composition comprising 100 parts by weight of a thermoplastic resin and 50 to 400 parts by weight of a filler on a nonwoven fabric having a thickness of 10 μm to 400 μm, uniaxially or biaxially simultaneously with the nonwoven fabric.
In the method of stretching at a magnification of 1.1 to 3.0 times, the nonwoven fabric is
Higher than 40 ° C and higher than the melt lamination temperature of the resin composition
A method for producing a breathable film, comprising a resin composition having a melting point lower by at least ° C.

As a thermoplastic resin for a breathable film, for example,
Α-olefin homopolymers such as low-density polyethylene, high-density polyethylene, polypropylene, and polybutene, copolymers of ethylene and at least one α-olefin having 3 to 18 carbon atoms, propylene and ethylene and / or butene-1 Copolymers, and copolymers of ethylene with an organic carboxylic acid derivative having an ethylenically unsaturated bond such as vinyl acetate and / or acrylates / methacrylates, and the like can be given.

In particular, ethylene and at least one kind of α-
Copolymers with olefins are preferred from the viewpoint of the strength at the time of compounding the filler, and blends of low-density polyethylene, a copolymer of ethylene and at least one α-olefin having 3 to 8 carbon atoms form a film having processability, It is not preferable from the viewpoint of stretchability. Further, in the present invention, in order to express high air permeability at a low draw ratio of 1.1 to 3.0 times, the thermoplastic resin,
It is preferable to contain 40% by weight or more of a resin having a density of 0.920 g / cm ³ or more.

In the present invention, if the amount of the filler is less than 50 parts by weight based on 100 parts by weight of the thermoplastic resin, it is difficult to develop air permeability after stretching, and if it exceeds 400 parts by weight, processability is deteriorated. Not preferred. Particularly, from the viewpoint of processing stability, the amount of the filler is preferably 70 to 200 parts by weight.

Examples of the filler include carbonates such as calcium carbonate, magnesium carbonate and barium carbonate, sulfates such as barium sulfate, magnesium sulfate and calcium sulfate, phosphates such as magnesium phosphate and calcium phosphate, magnesium hydroxide, and aluminum hydroxide. Hydroxides, oxides such as alumina, silica, magnesium oxide, calcium oxide, zinc oxide, titanium oxide, zinc chloride, iron chloride, etc.
Chlorides such as sodium chloride, aluminum powder, zeolite, shirasu, clay, diatomaceous earth, talc, carbon black, inorganic fillers such as volcanic ash, wood powder, cellulose powder such as pulp powder, nylon powder, polycarbonate powder, polypropylene powder, Poly-4-methylbenthene-
Organic powders such as synthetic resin-based powders such as No. 1 powder and starch, and these can be used alone or in combination. Calcium carbonate is particularly preferred from the viewpoint of air permeability, flexibility and appearance of the film. The average particle size of the filler is preferably from the viewpoint of uniformity of the film due to dispersion of the filler of 0.1 to 20 μm, and particularly preferably from 0.8 to 5.0 μm from the viewpoint of processability.

Since the present invention is to stretch simultaneously with the nonwoven fabric after laminating the resin composition that expresses air permeability by stretching on the nonwoven fabric, the thickness of the nonwoven fabric is 10 to 400 μm
Is preferred. If it is less than 10 μm, the strength after stretching cannot be expected. On the other hand, if it exceeds 400 μm, the stretchability becomes poor, which is not preferable.

In the present invention, since the resin composition and the non-woven fabric are stretched simultaneously with the non-woven fabric after being melt-laminated on the non-woven fabric, if the adhesive strength between the resin composition and the non-woven fabric is not high, the resin composition will peel off during stretching. A material containing at least one or more low-melting resin components having a melting point lower by at least 50 ° C. than the melt lamination temperature of the product is used. As such a nonwoven fabric, for example, a nonwoven fabric composed of a single resin component, the low-melting-point resin component adhered by solution immersion, or a mixture obtained by mixing two or more resin components into fibers, fibers, Nonwoven fabrics formed by mixing two or more resin components are exemplified. Examples of a fiber obtained by mixing fibers with two or more resin components include a concentric multilayer type including a core layer and a sheath layer, and a multilayer type in which each resin is eccentric and a part or all of the sheath layer is formed of the low melting point resin. And a fiber in which at least a part of the fiber is at least the low-melting resin, which is continuously or intermittently appeared on the fiber surface. In particular, from the viewpoint of the strength of the nonwoven fabric, a nonwoven fabric made of a fiber having a core layer and a sheath layer, and at least the outermost sheath layer made of a low-melting resin component is preferable. If the difference between the melt lamination temperature and the melting point of the resin component constituting part or all of the nonwoven fabric is less than 50 ° C., it is not preferable because the adhesive strength is not at the time of melt lamination, and the melting point of the resin component is low.
If the temperature is lower than 40 ° C., particularly during film processing in summer, the tackiness of the film is extremely increased, the roll separation becomes poor, and it is not preferable because it causes trouble.

Examples of the resin component constituting part or all of the nonwoven fabric include polyester, nylon, and α-olefin homopolymers such as polyethylene, polypropylene, and polybutene; ethylene and at least one α-olefin having 3 to 18 carbon atoms.
Organic carboxylic acid derivatives having an ethylenically unsaturated bond such as copolymers with olefins, copolymers with propylene and ethylene and / or butene-1, ethylene and vinyl acetate and / or acrylates and methacrylates And the like.

In particular, the core layer is preferably polyester and the sheath layer is preferably polyethylene from the viewpoint of workability, strength, and adhesion,
For example, Elbes manufactured by Unitika Ltd., Daiwa Spinning Co., Ltd.
NBF manufactured by Kuraray Co., Ltd., and the like.

In the present invention, the breathable film is prepared by mixing a thermoplastic resin and a filler, and if necessary, a dispersant and a stabilizer by a usual method using a roll-type or Banbury-type kneader or a single- or twin-screw extruder. Alternatively, the composition is obtained by kneading. This composition is then placed on a nonwoven fabric for 5-150μ.
The laminated product is stretched in the range of m so as to exhibit air permeability, but the stretching is performed uniaxially or biaxially. In the case of uniaxial stretching, roll stretching is usually preferred. In the case of biaxial stretching, simultaneous biaxial stretching is also possible, or sequential biaxial stretching in which stretching in the longitudinal direction is performed and then stretching in the transverse direction is also possible. The appropriate stretching ratio varies depending on the type of the resin component and the nonwoven fabric, but a stretching ratio of 1.1 to 3.0 times is preferable. If it is less than 1.1 times, breathability cannot be expected, and 3.0
Exceeding the number of times is undesirable because the material may be broken or the tear strength in the longitudinal direction may be reduced. A more preferred stretching ratio is 1.2 to 2.0 times. The stretching temperature varies depending on the resin composition, but is usually preferably in the range of 30 to 140 ° C. 30 ℃
If it is less than 1, the stability at the time of stretching is not preferable, and if it exceeds 140 ° C., microvoids are not easily generated, which is not preferable. In particular, after stretching in the range of 30 to 140 ° C, 8
Heat setting in the range of 0 ° C. to 170 ° C. is preferable from the viewpoint of preventing film wrinkles.

<Function> In the present invention, stretching after melt-laminating a resin composition comprising 100 parts by weight of a thermoplastic resin and 50 to 400 parts by weight of a filler to a nonwoven fabric involves expanding the adhesion surface between the nonwoven fabric and the porous film. The purpose is to make uniform air permeability and strength by forming uniform microvoids during stretching.

In the present invention, a stretching start point is widely dispersed by stretching after melt-laminating the resin composition on a specific nonwoven fabric, whereby uniform porosity of a breathable film, that is, uniform air permeability and uniform strength are obtained. Is to be expressed.

Further, since there is no treatment such as adhesion or fusion after stretching, air permeability and strength are not impaired.

<Effect of the Invention> The breathable film obtained by the method for producing a breathable film of the present invention has excellent strength and breathability, and the physical properties thereof are uniform and stable regardless of the portion of the film. It is extremely useful for applications that require uniform air permeability, such as packaging materials such as moisture absorbers and oxygen absorbers, and applications that require high strength and moisture permeability, such as wallpaper and clothes covers.

<Example> Hereinafter, an example will be described in detail, but the present invention is not limited thereto. The moisture permeability, water pressure resistance, strength, stretching unevenness, and adhesion between the nonwoven fabric and the resin composition shown in Examples and Comparative Examples were determined according to the following criteria.

Air permeability: Water vapor permeability was measured under the conditions of 40 ° C. and 90% RH in accordance with JIS Z0208.

Water pressure: The water level when water came out from three places on the back side of the test piece was measured by the JIS L1092-A method.

Stretch unevenness: The state of stretch unevenness was visually determined, and x to ○ were determined based on the following criteria.

：: Uniform stretching was observed without any stretching unevenness.

Δ: Stretch unevenness is observed in part, but the distance from the unstretched part is 5 m
Most are within m.

×: Stretching unevenness is clearly seen, and there are many unstretched portions exceeding 5 mm.

Adhesion: The state of adhesion between the nonwoven fabric and the film made of the thermoplastic resin composition after stretching is determined visually and by resin,
× to ○ were determined based on the following criteria.

：: No separation between the nonwoven fabric and the film was seen at all, and the film was uniformly adhered.

Δ: The nonwoven fabric and the film have partially peeled portions, and the film can be peeled from the nonwoven fabric by hand.

X: The nonwoven fabric and the film are almost peeled off.

Example 1 75% by weight of linear low-density polyethylene (Sumikasen α CS3003 manufactured by Sumitomo Chemical Co., Ltd., density: 0.932 g / cm ³ ) and high-pressure low-density polyethylene (Sumikasen F208-0 manufactured by Sumitomo Chemical Co., Ltd., density: 0.922 g / cm ³ ) A composition consisting of 100 parts by weight of a thermoplastic resin consisting of 25% by weight and 150 parts by weight of calcium carbonate (whiten SSB (red) manufactured by Shiraishi Calcium Co., Ltd.) was mixed with a Banbury-type kneader. After kneading, the core layer is made of polyester (melting point 257 ° C), and the sheath layer is made of polyethylene (melting point 1).
24 ° C) Concentric fiber thickness 100μm, basis weight 30g
/ m ² non-woven fabric (Unitika (product) Elves S0303WD0) 270
Lamination was performed at a resin temperature of 30 ° C. and a basis weight of 30 g / m ² . This laminate film is uniaxially stretched by a roll-type stretching machine.
The film was stretched 1.3 times at 50 ° C. to obtain a breathable film. As shown in Table 1, the obtained air-permeable film has high air permeability, water resistance, temperature, and uniform stretchability (without unevenness).
And good adhesion.

Example 2 As a nonwoven fabric, the core layer was made of polypropylene (melting point 165).
° C), and the sheath layer is made of polyethylene (melting point: 130 ° C) eccentric type fiber (ES fiber manufactured by Chisso Corp., the core layer is partially exposed on the surface), the thickness is 150 µm, and the basis weight is 20 g / m ^2. (A nonwoven fabric was prepared by a usual dry method), and a breathable film was obtained in the same manner as in Example 1. The obtained breathable film showed the same good physical properties as in Example 1.

Example 3 As a nonwoven fabric, a polypropylene (melting point: 165 ° C.) nonwoven fabric (PolyProspan Bond P1015 manufactured by Asahi Kasei Corporation) was used as an ethylene-butene-1 copolymer (melting point: 115 ° C., density: 0.900 g / cm).
³ ) The surface was coated with 5% by weight of an ethylene-butene-1 copolymer by dipping in the xylene solution. Thickness 200
A breathable film was obtained in the same manner as in Example 1, except that a film having a thickness of 20 μm and a basis weight of 20 g / m ² was used. The obtained breathable film showed good physical properties as shown in Table 1.

Example 4 As a nonwoven fabric, polyethylene (Sumitomo Chemical Co., Ltd.)
35% by weight of Sumikasen-L FA202-0, melting point 124 ° C), nylon (Nylon 6 A1030B, manufactured by Unitika Ltd.)
RT, melting point 215 ° C) 60% by weight and ethylene / acrylic acid ester / maleic anhydride terpolymer (sold by Sumika CDF Chemical Co., Ltd., Bondine FX8000) 5% by weight
Using a composition obtained by melt-kneading
The thickness described in the method described in the example of Japanese Patent Publication No. 4 (except for the entanglement and drying, followed by pressing with a roll under the condition of a linear pressure of 40 kg / cm and a temperature of 130 ° C.), a thickness of 200 μm, and a grammage of 25 g / m ²
A non-woven fabric (fiber fineness: 2 deniers) was used in the same manner as in Example 1 to obtain a breathable film. The obtained breathable film showed good physical properties as shown in Table 1.

Example 5 As a thermoplastic resin, a linear low-density polyethylene (Sumikacene α CS3003 manufactured by Sumitomo Chemical Co., Ltd., density 0.932 g / c)
m ³ ), titanium dioxide (R10 manufactured by DuPont)
An air-permeable film was obtained in the same manner as in Example 1 except that the processing conditions shown in Table 1 were used using 1). The obtained breathable film showed good physical properties as shown in Table 1.

Comparative Example 1 A breathable film was obtained in the same manner as in Example 1, except that processing was performed under the stretching conditions shown in Table 1 without using a nonwoven fabric. The obtained breathable film had remarkably low tensile strength and water resistance, and also had many stretching irregularities.

Comparative Example 2 Calcium carbonate (Shiroishi Calcium Co., Ltd.)
Except that 40 parts by weight of Whiten SSB (red) manufactured by Tokyo Gas Co., Ltd.) was used, a breathable film was obtained in the same manner as in Example 1. As shown in Table 1, the obtained air-permeable film had extremely low air permeability.

Comparative Example 3 As a thermoplastic resin, a high-pressure method low-density polyethylene (Sumikasen F208-0, manufactured by Sumitomo Chemical Co., Ltd., density 0.922 g / c)
m ³ ) A film was processed in the same manner as in Example 1 except that 100 parts by weight and 500 parts by weight of calcium carbonate (Whiten SSB (red) manufactured by Shiraishi Calcium Co., Ltd.) were used as a filler, but stretching was performed. Sometimes, the resin composition side was broken, and a breathable film could not be obtained.

Comparative Example 4 A breathable film was obtained in the same manner as in Example 1 except that a nonwoven fabric made of polyester (melting point 257 ° C.) fiber was used. As shown in Table 1, the obtained breathable film had remarkably low adhesion between the nonwoven fabric and the film.

Comparative Example 5 A breathable film was obtained in the same manner as in Example 1 except that the temperature at the time of laminating the resin composition was 160 ° C. As shown in Table 1, the obtained breathable film had remarkably low adhesiveness between the nonwoven fabric and the resin composition.

Comparative Example 6 Linear low density polyethylene (Excellen VL VL200 manufactured by Sumitomo Chemical Co., Ltd., density 0.900 g / c) was used as the thermoplastic resin.
m ³ ) A breathable film was obtained in the same manner as in Example 1 except that 75% by weight was used. As shown in Table 1, the obtained air-permeable film had considerably low air-permeability, and also had many stretching irregularities.

Claims (4)

(57) [Claims] 1. A resin composition comprising 100 parts by weight of a thermoplastic resin and 50 to 400 parts by weight of a filler is melt-laminated on a nonwoven fabric having a thickness of 10 μm to 400 μm. In the method of stretching at a magnification of 3.0 times,
A method for producing a breathable film, characterized in that the nonwoven fabric contains a resin component having a melting point higher than 40 ° C and lower than the melting lamination temperature of the resin composition by 50 ° C or more. 2. The nonwoven fabric comprises two or more resin components,
The resin component contains at least one resin component having a melting point higher than 40 ° C. and lower than the melting lamination temperature of the resin composition by 50 ° C. or more, and at least a part or all of the surface of the nonwoven fabric is the resin component. The method for producing a breathable film according to claim 1, wherein: 3. A nonwoven fabric comprising a fiber having a core layer and a sheath layer,
The method for producing a breathable film according to claim 1, wherein at least the outermost sheath layer is made of a resin having a melting point higher than 40 ° C and lower than the melting lamination temperature of the resin composition by 50 ° C or more. 4. The method according to claim 1, wherein the thermoplastic resin comprises one or more resins and has a density of 0.920 g / cm ³ or more by 40% by weight.
The method for producing a breathable film according to claim 1, wherein the method includes the above.