JP2574171B2 - Method for producing composite film having waterproofness and air permeability - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a composite film having elasticity and excellent waterproofness and air permeability.

[Conventional technology]

Conventionally, as a breathable film, a film obtained by kneading a polyolefin resin with an inorganic filler, melt-molding the film, and stretching the film uniaxially or biaxially has been used. In such a breathable film, stretching causes fine breakage starting from the inorganic filler, thereby forming pores having a pore diameter of about 1 to 4 μm. At best, the ventilation volume of such a breathable film
It is about 4500 g / m ² .day. However, in uniaxial stretching, the tear strength in the stretching direction and the tensile strength in the transverse direction are extremely low due to anisotropy due to molecular orientation, and in biaxial stretching, the stretching ratio is low and the air permeability is poor. In addition, due to the inherent rigidity of the stretched film, there is a problem that it has a crisp paper-like feel and is not suitable for applications requiring a soft feeling.

In addition, a method of producing a flexible porous film by adding a low-melting polymer of the same type, a rubbery polymer, an olefin-based thermoplastic elastomer, and the like together with an inorganic filler to a polyolefin resin has been proposed, but air permeability is not sufficient. In addition, there is a problem that the film strength is inferior.

For this reason, various proposals have been made to impart flexibility to a stretched breathable film comprising a polyolefin resin and an inorganic filler. For example, JP-A-60-257221 discloses a polyolefin resin 100 parts by weight, a filler 25 to 400 parts by weight, a liquid or waxy hydrocarbon polymer, or a mixture 1 of the hydrocarbon polymer and an epoxy group-containing organic compound. Disclosed is a method for producing a porous film having excellent flexibility by melt-extrusion of a composition consisting of 部 100 parts by weight and subjecting the obtained film to biaxial stretching.

Japanese Patent Application Laid-Open No. 62-10141 discloses a method for producing a porous film or sheet, comprising stretching a film or sheet obtained by melt-molding a composition containing a polyolefin resin, a filler and triglyceride. Has been disclosed.

JP-A-62-27438 discloses a polyolefin resin 42.
To 87% by volume and 58 to 13% by volume of an inorganic filler, in a method for producing a breathable film by stretching the film in at least one direction, wherein the polyolefin-based resin is a linear low-density polyethylene 50 to 50%. A mixture of 95% by weight and 50 to 5% by weight of a branched low density polyethylene; and
An aliphatic alcohol-based fatty acid ester, which is a compound of a fatty acid having 10 to 22 carbon atoms and an aliphatic alcohol having 1 to 12 carbon atoms, is added to the composition in an amount of 3 to 25 with respect to 100 parts by weight of the composition.
It discloses a method for producing a breathable film, which is characterized by blending in parts by weight.

[Problems to be solved by the invention]

However, since any of the above-mentioned breathable films are obtained by stretching, they are thin and have poor mechanical strength, and often need to be used in combination with other materials. For this reason, secondary processing is required, and there is a disadvantage that the price is increased. Further, since it does not contain a rubber-like polymer, the flexibility is insufficient and a desired soft feeling cannot be obtained.

Therefore, the present inventors have conducted various studies, and hot-pressed a stretched film of a composition comprising a crystalline polyolefin, a rubber-like polymer, and a filler to a mesh sheet at a temperature equal to or higher than the heat shrinkage initiation temperature of the stretched film. By fixing and stretching the stretched film and heat shrinking, and thereby making the stretched film microporous, it is possible to obtain a breathable composite film having a soft feel and a large mechanical strength, We have previously filed an application for a method for producing such a breathable composite film (Japanese Patent Application
63-136733).

The breathable composite film has an excellent soft feeling and also has excellent mechanical strength and breathability. However, recently, materials such as disposable diapers, sportswear, and the like, which have great elasticity and are excellent in waterproofness and air permeability, have been required. However, since the composite film is not very stretchable, if it is forcibly pulled, the micropores may be expanded and destroyed, and the waterproof property may be lost.

Accordingly, it is an object of the present invention to provide a composite film having excellent stretchability and air permeability and waterproofness.

[Means for solving the problem]

In view of the above objects, as a result of intensive studies, the present inventor has determined that a foamed film having a specific composition and a stretchable woven or nonwoven fabric are thermocompressed and then stretched in a uniaxial or biaxial stretching direction to form a fine film on the foamed film. The present inventors have discovered that an important communication hole is formed, and arrived at the present invention.

That is, the method for producing the waterproof and breathable composite film of the present invention comprises (A) 40 to 70% by weight of an ethylene-propylene-diene copolymer and (B) 30 to 60% of an ethylene-vinyl acetate copolymer. % By weight and the above (A) + (B) 100
A foamed film is formed from a composition comprising 0.1 to 1.0 parts by weight of the foaming agent (C) with respect to parts by weight, and the foamed film and the stretchable woven or nonwoven fabric are hot-pressed to form the foamed film. After being fixed to the stretchable woven or nonwoven fabric, the stretchable woven or nonwoven fabric is stretched in the direction of expansion and contraction to form fine communication holes in the foamed film.

Another method for producing a waterproof and breathable composite film according to the present invention comprises the steps of (A) 35 to 65% by weight of an ethylene-propylene-diene copolymer and (B) 30 to 30% by weight of an ethylene-vinyl acetate copolymer. 55% by weight, (C) 1 to 10% by weight of linear low density polyethylene, and (A) + (B) + (C) 10
A foamed film is formed from a composition comprising 0.1 to 1.0 parts by weight of (D) a foaming agent with respect to 0 parts by weight, and the foamed film and an elastic woven or nonwoven fabric are hot-pressed to form the foamed film. After being fixed to the stretchable woven fabric or nonwoven fabric, the stretchable woven fabric or nonwoven fabric is stretched in the expansion and contraction direction to form fine communication holes in the foamed film.

 The present invention will be described in detail below.

In the present invention, ethylene-propylene-diene copolymer (EPDM) is a repeating unit derived from ethylene,
It is a copolymer containing a repeating unit derived from propylene and a repeating unit derived from a diene compound. Examples of the diene compound include ethylidene norbornene, 1,4-hexadiene, and dicyclopentadiene.

The ethylene-propylene-diene copolymer (EPDM) used in the present invention has a content of repeating units derived from ethylene of 60 to 70 mol% and a content of repeating units derived from propylene of 30 to 40 mol. % And the content of the repeating unit derived from the diene compound is from 1 to 10
Preferably it is mol%. A more preferred range is that the ethylene derivative is 62 to 66 mol% and the propylene derivative is 33 to 66 mol%.
37 mol%, and 3 to 6 mol% of the diene compound derivative.

The number average molecular weight is preferably 400,000 to 600,000, and the density is 0.87 g /
cm ³ or less is preferred.

In addition, melt index (190 ° C, 2.16kg load)
Is preferably in the range of 0.1 to 5.0 g / 10 minutes,
The copolymer is more preferably in the range of 0.30 to 1.0 g / 10 minutes, and still more preferably in the range of 0.35 to 0.50 g / 10 minutes.

The ethylene-propylene-diene copolymer (EPDM) used in the present invention is basically composed of the above-mentioned repeating units. However, as long as the properties of these copolymers are not impaired, for example, butene- Other repeating units such as repeating units derived from α-olefins such as 1 or 4-methylpentene-1 may be included.

The blending ratio of the ethylene-propylene-diene copolymer (EPDM) in the composition of the present invention is 70 to 40% by weight, and particularly in the range of 65 to 45% by weight, based on the resin component (100% by weight). Is preferable. When the blending ratio of the ethylene-propylene-diene copolymer (EPDM) is lower than 40% by weight, the elasticity of the obtained foamed film is reduced, and
If the amount is higher than 70% by weight, the moldability and softness of the obtained foamed film are reduced.

Ethylene-vinyl acetate copolymer (EV used in the present invention)
A) is a copolymer having a vinyl acetate repeating unit content of 7.5% by weight or more. In particular, in the present invention, it is preferable to use an ethylene-vinyl acetate copolymer having a vinyl acetate repeating unit content in the range of 7.5 to 30% by weight.

Ethylene-vinyl acetate copolymer (EV used in the present invention)
A) preferably has a number average molecular weight in the range of 12,000 to 14000. The melt index of such a copolymer is usually in the range of 15 to 20 g / 10 minutes (190 ° C., 2.16 kg load).

The mixing ratio of the ethylene-vinyl acetate copolymer (EVA) in producing the composition of the present invention is based on the resin component (1
(00% by weight) is 30 to 60% by weight, particularly preferably in the range of 35 to 55% by weight. If the content of the ethylene-vinyl acetate copolymer (EVA) is less than 30% by weight, the moldability and softness are reduced. Becomes difficult.

The foaming agent used in the present invention is a compound that is liquid or solid at room temperature, but decomposes or evaporates when heated to the film forming temperature of the composition, and does not substantially hinder molding such as film formation. Anything can be used as long as it is used. Examples of such foaming agents include azodicarbonamide. The product name is Celtect's foaming agent 5001, 50
06, NC-100 and the like. The addition amount of the foaming agent is 0.1 to 1.0 part by weight based on the resin component (100 parts by weight).

Further, in the present invention, by adding linear low density polyethylene (LLDPE) to the composition, the film formability of the composition is improved, and the composition can be formed into a thin film.

When the linear low density polyethylene (LLDPE) is added, EPDM is 35 to 65% by weight, EVA is 30 to 55% by weight, and LLD
PE is 1 to 10% by weight. If LLDPE is less than 1% by weight, there is no effect on improving film formability, and if it exceeds 10% by weight, the stretchability, softness, etc. of the obtained foamed film are reduced. Also in this case, the content of the foaming agent is 0.1 to 1.0 part by weight based on 100 parts by weight of the resin component.

In the present invention, in addition to the linear low-density polyethylene (LLDPE), an antioxidant, an ultraviolet absorber, an antistatic agent, a coloring agent, and the like can be appropriately compounded.

The above ethylene-propylene-diene copolymer (EPD
M), ethylene-vinyl acetate copolymer (EVA), a blowing agent, and optionally blended linear low density polyethylene (LL
DPE) and other ingredients.

In the present invention, kneading of the ethylene-propylene-diene copolymer (EPDM) and the foaming agent is performed at 140 to 170 ° C.
At a resin temperature of

After kneading as described above, it is formed into a film while foaming. The film formation temperature is generally from 120 to 170 ° C. By performing film formation at such a low temperature, thermal degradation of the resin can be effectively prevented. In particular, in the present invention, it is preferable that the film formation temperature is in the range of 140 to 175 ° C. The low-temperature film formation as described above can be performed by a known method such as an inflation method using a circular die or a T-die method using a T-die, using a full flight screw having a deep groove for preventing heat generation.

Further, the film forming speed is preferably 15 m / min or less.
When the film forming speed is higher than 15 m / min, foaming is not sufficiently performed, and foam film forming cannot be performed. A more preferred film forming speed is 5 to 10 m / min.

By performing foam film formation under the above conditions, the expansion ratio becomes 1.1 to 2.0 times. Furthermore, the size of the foam cell
Although it varies slightly depending on the type and amount of the foaming agent, generally 10
It is about 0 to 5 μm.

As the stretchable woven fabric or nonwoven fabric used in the present invention, various stretchable woven fabrics or stretchable nonwoven fabrics such as stretch woven fabrics, knitted fabrics, and knitted fabrics can be used. It is necessary that the stretchable woven or nonwoven fabric does not substantially melt or shrink in the following hot pressing process. Therefore, in general, the melting point or the second transition point of a stretchable woven or nonwoven fabric needs to be at least 20 ° C. higher than that of a foamed film.

The hot pressing of the foamed film and the stretchable woven or nonwoven fabric is generally performed at a temperature of 70 to 140 ° C. and a pressure of 0.1 to 10 kg / cm ² . Depending on the composition of the foamed film and the type of stretchable woven or nonwoven fabric, etc., if it is out of the range of the above-mentioned hot pressing conditions, the fixation between the foamed film and the stretchable woven or nonwoven fabric is not sufficient, Or the air permeability decreases. That is, when the temperature is lower than 70 ° C., the adhesion of the foamed film is not sufficient,
When the temperature exceeds 0 ° C., fine cells are broken by foaming, and the air permeability is reduced. If it is less than 0.1 kg / cm ² , the adhesion of the foamed film is not sufficient, and if it exceeds 10 kg / cm ² , the film strength decreases. Preferred hot pressing conditions are 95-120 ° C and 0.5-5.
It is 0 kg / cm ² .

As will be described later in detail in Examples, hot pressing of the foamed film and the stretchable woven or nonwoven fabric is preferably performed by performing hot pressing multiple times using a plurality of heat rolls.

At this time, besides pressing the foamed film and the stretchable woven fabric or nonwoven fabric one by one, the stretchable woven fabric or nonwoven fabric may be sandwiched between two foamed films.
It is also possible to adopt a configuration in which a foamed film is sandwiched between two stretchable woven or nonwoven fabrics.

Next, a stretched woven or nonwoven fabric obtained by thermocompression bonding the foamed film is stretched in the stretching direction (vertical axis direction and / or horizontal axis direction) to form fine communication holes in the foamed film.

The uniaxial or biaxial stretching magnification is 1.
It is preferably about 2 to 2 times, more preferably about 1.5 times. Stretching can generally be performed at room temperature,
The temperature may be 35 ° C or less.

If the stretching magnification is less than 1.2 times, the cells inside the foamed film will not be broken because the cells inside the foamed film will not become communication holes, and if it is more than 2 times, the breakage inside the foamed film will be large. The waterproofness of the foamed film decreases.

When the tension is released after stretching the composite film, the composite film returns to its original state. Thereby, a composite film having air permeability and waterproofness can be obtained. In addition, since both the foamed film and the woven or nonwoven fabric have sufficient elasticity, even if the obtained composite film is expanded or contracted, the air permeability and waterproofness are not lost.

(Operation)

As shown in FIG. 1 (a), the foamed film contains many fine cells 3. Therefore, after fixing to stretchable woven or non-woven fabric, 1.
When the stretching is performed in the range of 2 to 2 times, the wall between the fine cells 3 breaks, and the cells 3 are interconnected as shown in FIG. 1 (b), and the fine communication holes 4 are formed. Is done. Air flows through the communication holes 4 as shown by F, and air permeability is imparted to the foamed film. However, since the diameter of the fine cell 3 is extremely small, the communication hole 4 can prevent the flow of water. Therefore, the composite film of the present invention has air permeability and is excellent in waterproofness.

〔Example〕

FIG. 2 is a schematic view showing an example of an apparatus suitable for performing hot pressing by the method of the present invention. The hot pressing device includes a roll 13 for cooling and thermally fixing the foamed film 11, a heat roll 14 for guiding and heating the stretchable woven or nonwoven fabric 12, a foamed film 11, and a stretchable woven fabric. Or non-woven fabric 12
A pair of elastic rolls 16 and 17 controlled at a temperature of 40 ° C. or less, a roll 18 for cooling the thermocompressed composite film, and a heat roll 19 for heating the composite film. A metal roll 20 for thermocompressing the composite film again, and a pair of elastic rolls 21 and 22 controlled at 40 ° C. or lower. The gap between the metal roll 15 and the elastic rolls 16 and 17, and the metal roll 20
The gap between the elastic rolls 21 and 22 can be appropriately adjusted so as to apply a desired pressing pressure. In a preferred example, the temperature of each roll is as follows.

Heat roll 14 ・ ・ 100-150 ℃ Heat roll 19 ・ ・ 100-200 ℃ Metal roll 15 ・ ・ 70-110 ℃ Metal roll 20 ・ ・ 100-200 ℃ Elastic roll 16,17,21,22 ・ ・ 40 ℃ or less Cooling roll 18 ・ ・ 30 ℃ or less In this embodiment, one foam film 11 has one side
Although the stretchable woven or nonwoven fabric 12 is hot-pressed, if two stretchable woven or nonwoven fabrics are used, the stretchable woven or nonwoven fabric 12 'should be inserted from the position indicated by the dotted line. Good. Further, in that case, the elastic rolls 16, 17, 21, 22 need not be cooled.

Further, in order to form a structure in which a stretchable woven fabric or nonwoven fabric is sandwiched by a foamed film, the foamed film 11 and the stretchable woven fabric or nonwoven fabric 12, 12 'may be simply replaced.

FIG. 3 is a plan view showing an example of a state in which a stretchable woven or nonwoven fabric obtained by pressing a foam film is stretched. 31
Indicates a full size portion, and 32 indicates a stretched state.

The method of the present invention is described in more detail by the following specific examples.

Example 1 Ethylene-vinyl acetate copolymer (vinyl acetate content 28
% By weight), 40% by weight of an ethylene-propylene-diene copolymer (Vistalon 3708, manufactured by Nippon Unicar Co., Ltd.) and 100 parts by weight of a resin component, and a blowing agent (NC-100)
(0, manufactured by Cell Techno Co.) was melt-kneaded with an extruder, and foaming and film formation were simultaneously performed by an inflation method at a resin temperature of 120 ° C. and a film formation speed of 5 m / min. The thickness of the obtained foam film is 120 μm,
The expansion ratio was about 1.2 times.

This foamed film was overlapped with a stretchable woven fabric (vertical and horizontal stretch woven fabric, manufactured by Toyobo Co., Ltd.), pressed at a pressing temperature of 90 ° C., for a pressing time of 20 seconds, at a pressure of 5 kg / cm ² , and thermocompressed.

The obtained composite film was stretched 1.5 times in the biaxial direction, and then the stretching was released.

The waterproofness and air permeability of the obtained composite film were measured. The results are shown in Table 1.

Example 2 The ethylene-propylene-diene copolymer 57 of Example 1
% By weight and 38% by weight of ethylene-vinyl acetate copolymer,
A foaming agent (5001, manufactured by Cell Techno Co., Ltd.) is used for 100 parts by weight of a resin component containing 5% by weight of a linear low-density polyethylene (TUF-2060, manufactured by Nihon Yunika Co., Ltd., density 0.920, melt index 2.2). The composition consisting of 0.8 parts by weight was melt-kneaded in the same manner as in Example 1, foaming and film formation were carried out to obtain a foamed film having a thickness of 60 μm and an expansion ratio of 15 times.

This foamed film is overlapped with an elastic woven fabric (vertical stretch woven fabric, manufactured by Toyobo Co., Ltd.) and thermocompression-bonded under the same conditions as in Example 1, and the resulting composite film is uniaxially machined in the machine direction (MD direction).
The film was stretched 1.5 times, and then the stretching was released. The measurement results of waterproofness and air permeability of the obtained composite film are shown in Table 1.

Example 3 A foamed film was obtained in the same manner as in Example 1, except that the content of the foaming agent was changed to 1.0 part by weight. The thickness of the obtained foamed film was 160 μm, and the expansion ratio was 1.8 times. A composite film was obtained in the same manner as in Example 1 except that the foamed film and the stretchable polyester-based nonwoven fabric were stretched 1.5 times uniaxially in the transverse direction (TD direction). The measurement results of waterproofness and air permeability of the obtained composite film are shown in Table 1.

Comparative Examples 1-3 Except for not performing the stretching step in Examples 1, 2, and 3,
A composite film was obtained in the same manner as in each example. The measurement was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4 A composite film (1.5 times stretched and then released) was prepared in the same manner as in Example 1 except that no foaming agent was added. The same measurement as in Example 1 was performed on the obtained composite film. The results are shown in Table 1.

As is clear from the results in Table 1, in the method of the present invention, by expanding and contracting the film after foaming,
Breathability can be imparted while maintaining waterproofness.
In addition, when expansion and contraction are performed without foaming, the unfoamed film is locally broken, and the waterproofness is significantly reduced (Comparative Example 4).

〔The invention's effect〕

The method of the present invention is performed by hot-pressing a foam film and a stretchable woven or non-woven fabric and then stretching,
The wall between the fine cells formed by the foaming is broken, and the communication hole can be formed. Therefore, the obtained composite film has excellent breathability and waterproofness, and is generally reinforced by a fixed elastic woven or nonwoven fabric, and has high mechanical strength. Further, since the foamed film used in the present invention only causes breakage of the foam cell due to expansion and contraction and does not cause local breakage of the film, the obtained composite film does not deteriorate in waterproofness even when expanded and contracted. That is, the composite film according to the present invention has elasticity, and also has waterproofness and air permeability without any functional change due to expansion and contraction.

In the method of the present invention, desired air permeability and waterproofness can be obtained by appropriately adjusting the conditions of the expansion ratio of the film and the stretching ratio of the pressure-bonded woven fabric. Also, thickness unevenness, which has been difficult with the conventional stretching method, can be substantially eliminated. Furthermore, since it can be manufactured in-line, it helps to reduce the manufacturing cost.

Such a composite film of the present invention is particularly suitable for use in disposable diapers, sportswear and the like.

[Brief description of the drawings]

FIG. 1 is a partially enlarged cross-sectional view showing a microstructure of a waterproof and breathable composite film obtained by the method of the present invention, wherein (a) shows a state before a stretching step,
(B) shows a state after expansion and contraction, FIG. 2 is a schematic view showing an example of a hot pressing apparatus for carrying out the method of the present invention, and FIG. 3 is drawn by a stretching step of the present invention. FIG. 2 is a plan view showing an example of a composite film. DESCRIPTION OF SYMBOLS 1 ... Foam film 2 ... Stretchable woven or non-woven fabric fiber 3 ... Foam cell 4 ... Communication hole 11 ... Foam film 12, 12 '... Stretchable woven or non-woven fabric 14, 19 ... Heat rolls 15, 20 Metal rolls 16, 17, 21, 22 Elastic rolls 18 Cooling rolls

Claims (5)

(57) [Claims] (1) 40 to 70% by weight of an ethylene-propylene-diene copolymer (A), 30 to 60% by weight of an ethylene-vinyl acetate copolymer (B), and 100% by weight of the above (A) + (B) A foamed film is formed from a composition comprising 0.1 to 1.0 parts by weight of the foaming agent (C) with respect to the part, and the foamed film and the stretchable woven or nonwoven fabric are hot-pressed to expand and contract the foamed film. After being fixed to a woven or non-woven fabric, the stretchable woven or non-woven fabric is stretched in the direction of expansion and contraction to form fine communication holes in the foam film. A method for producing a composite film. 2. An ethylene-propylene-diene copolymer (A) 35-65% by weight, (B) an ethylene-vinyl acetate copolymer 30-55% by weight, and (C) a linear low-density polyethylene 1.
To form a foamed film from a composition comprising 0.1 to 1.0 parts by weight of (D) a foaming agent with respect to 100 parts by weight of (A) + (B) + (C). After fixing the foam film to the stretchable woven fabric or nonwoven fabric by hot pressing the stretchable woven fabric or nonwoven fabric, by stretching in the stretch direction of the stretchable woven fabric or nonwoven fabric,
A method for producing a waterproof and breathable composite film, characterized by forming fine communication holes in the foamed film. 3. The method according to claim 1, wherein foaming of the composition is carried out under conditions of a resin temperature of 120 to 170 ° C. and a film forming speed of 15 m / min or less, and then the hot pressing is performed. 70 ~
A method characterized in that it is carried out at a temperature of 140 ° C. and a pressure of 0.1 to 10 kg / cm ² . 4. The method according to claim 1, wherein said hot pressing is performed by a plurality of hot pressing. 5. The method according to claim 1, wherein the stretchable woven or nonwoven fabric to which the foam film is fixed is stretched about 1.2 to 2.0 times to form fine communication holes. Features method.