JPH0280231A - Manufacture of composite sheet having water-proof properties and air permeability - Google Patents

Abstract

PURPOSE:To make a film micro-porous and increase water-proof properties and air permeability by forming a film by means of an ethylene-propylene-diene copolymer of specific weight ratio and a composition of an ethylene-vinyl ace tate copolymer and a linear low density polyethylene, and hot fixing by pressure the same with a woven fabric or a non-woven fabric. CONSTITUTION:The blending proportion of an ethylene-propylene-diene copolymer(EPDM) is 50-68wt.% and the blending proportion of an ethylene-vinyl acetate copolymer(EVA) is 30-48wt.%, and further the blending proportion of linear low density polyethylene(LLDPE) is 2-20wt.%. The same is molded in a film after kneading. The film thickness is preferably 10-40mum. A hot pressure fixing device is constituted of a preheating roll 13 for preheating and heat fixing a woven fabric or a non-woven fabric 12, a first hot pressure fixing roll 14 for heat pressure fixing a film 11 and the woven fabric or non-woven fabric 12, a couple of elastic rolls 15 and 16 and a tension control roll 17 of a composite sheet after first heat pressure fixing.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a composite sheet having waterproofness and breathability. The present invention relates to a method of manufacturing a composite sheet having air permeability.

[Conventional technology]

BACKGROUND ART In recent years, waterproof and breathable sheets or films have been widely used as leak-proof sheets for disposable diapers and the like.

Such breathable films are generally made into a film by kneading inorganic fillers with polyolefin resin and melt-molding the mixture.
It is manufactured by making it porous through -axial or biaxial stretching. In such a breathable film, fine fractures occur starting from the inorganic filler due to stretching, thereby forming pores with a pore size of about 1 to 4 μm.

However, such breathable films not only do not have sufficient air permeability, but also have problems due to the rigidity peculiar to stretched films.
There is a problem in that it has a crisp paper-like feel and is not suitable for applications that require a soft feel.

In addition, a method of manufacturing a flexible porous film by adding the same kind of low melting point polymer, rubbery polymer, olefin thermoplastic elastomer, etc. to polyolefin resin along with an inorganic filler has been proposed, but the air permeability is not sufficient. In addition, there was a problem that the film strength was poor.

For this reason, various proposals have been made to impart flexibility to stretched breathable films made of polyolefin resins and inorganic fillers. For example, JP-A-60257221 discloses a mixture of 100 parts by weight of a polyolefin resin, 25 to 400 parts by weight of a filler, a liquid or waxy hydrocarbon polymer, or a mixture of the hydrocarbon polymer and an epoxy group-containing organic compound. This disclosure discloses a method for producing a porous film with excellent flexibility by melt-extruding a composition consisting of parts by weight and biaxially stretching the obtained film.

In addition, JP-A-62-10141 discloses polyolefin resin,
A method for producing a porous film or sheet is disclosed, which comprises stretching a film or sheet obtained by melt-molding a composition containing a filler and a triglyceride.

Further, JP-A No. 62-27438 discloses a method for producing a breathable film by stretching in at least one direction a film made of a composition of 42 to 87 volume % of a polyolefin resin and 58 to 13 volume % of an inorganic filler. The polyolefin resin is a mixture of 50 to 95% by weight of linear low-density polyethylene and 50 to 5% by weight of branched low-density polyethylene, and the composition includes a fatty acid having 10 to 22 carbon atoms. The aliphatic alcohol fatty acid ester, which is a compound with an aliphatic alcohol having 1 to 12 carbon atoms, is added to the composition 1.
This disclosure discloses a method for producing a breathable film, characterized in that 3 to 25 parts by weight are added to the 00 weight part of the film.

Furthermore, Japanese Patent Publication No. 63-35721 discloses a liquid-impermeable leak-proof sheet for diapers that is integrally formed by overlaying it with an absorbent material, containing 100 parts by weight of polyolefin resin and 28 parts by weight of filler
~200 parts by weight, and 10 to 70 parts by weight of a liquid or waxy polyhydroxy saturated hydrocarbon produced by hydrogenating hydroxyl-terminated liquid polybutadiene are kneaded, formed into a film, and then mixed in at least one direction. Discloses a film in which micropores are created by stretching 1.2 times or more.

[Problem to be solved by the invention]

However, since all of the above breathable films are obtained by stretching, they are thin and have poor mechanical strength.
It is often necessary to use it in conjunction with other materials. Therefore, secondary processing is required, which has the disadvantage of increasing the price.

As a result of various studies, the inventors of the present invention have found that a stretched film of a composition comprising a crystalline polyolefin, a rubbery polymer, and a filler is hot-pressed onto a mesh-like sheet at a temperature equal to or higher than the thermal contraction start temperature of the stretched film. discovered that by fixing the stretched film and heat-shrinking it, thereby making the stretched film microporous, it is possible to obtain a breathable composite film that is soft to the touch and has high mechanical strength, We have previously applied for a method for producing such a breathable composite film (patent application filed in 1983).
2-170497).

The above-mentioned breathable composite film has an excellent soft feel and also has excellent mechanical strength and air permeability. but,
Recently, in disposable diapers, sportswear, etc.
- There is a growing demand for materials that have good waterproofness, good breathability, and a soft feel. However, since the above-mentioned composite film contains crystalline polyolefin as a main component, the soft feel thereof was not necessarily satisfactory for the above-mentioned uses.

Therefore, an object of the present invention is to provide a method for manufacturing a composite sheet that has excellent soft feel, breathability, and waterproofness.

[Means to solve the problem]

As a result of intensive research in view of the above objectives, the present inventors formed a film from a composition containing an elastomer instead of a polyolefin and containing no inorganic filler,
The inventors discovered that by hot-pressing the film with a woven or non-woven fabric, the film becomes microporous and a waterproof and breathable composite sheet can be obtained, and the present invention was conceived.

That is, the method for producing a waterproof and breathable composite sheet of the present invention comprises (A) 50 to 68% by weight of an ethylene-propylene-diene copolymer and (B) 30 to 48% by weight of an ethylene-vinyl acetate copolymer. % by weight and (C) linear low-density polyethylene from 2 to 20% by weight, and the film and the woven fabric or nonwoven fabric are combined to form a film from a composition consisting of 70 to 20% by weight of (C) linear low-density polyethylene.
The film is hot-pressed at 150° C. to fix the film to the woven fabric or non-woven fabric, and is also heat-shrinked, thereby making the film microporous.

The present invention will be explained in detail below.

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

The ethylene-propylene-diene copolymer (E!PDM) 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 70 mol%. 40 mol%
The content of repeating units derived from , and diene compounds is preferably 1 to 10 mol%. More preferable ranges are 62 to 66 mol% of the ethylene derivative, 33 to 37 mol% of the propylene derivative, 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/ctl or less is preferred.

Furthermore, melt index (190℃, 2.16kg
A copolymer having a load) in the range of 0.1 to 5.0 g/10 minutes is preferable, more preferably 0.30 to 1.0 g/10 minutes.
10 minutes, more preferably 0.35 to 0.50 g
/ 10 minutes.

The ethylene-propylene-diene copolymer ([EPDM) used in the present invention basically consists of the above-mentioned repeating units, but within the range that does not impair the properties of these copolymers, for example, butene may be added. Other repeating units such as repeating units derived from alpha olefins such as -1 or 4-methylpentene-1 may also be included.

In the present invention, the blending ratio of ethylene-propylene-diene copolymer (EPDM) is 50 to 68% by weight,
In particular, it is preferably within the range of 55 to 60% by weight.

The above ethylene-propylene-diene copolymer (EPDM
) If the blending ratio is lower than 50% by weight, the elasticity of the resulting film will decrease, and if it is higher than 68% by weight, the moldability and soft feel of the resulting film will decrease.

Ethylene-vinyl acetate copolymer (EVA) used in the present invention
) has a content of vinyl acetate repeating units of 7.5% by weight.
This is a copolymer of the above. In particular, in the present invention, it is preferable to use an ethylene-vinyl acetate copolymer having a content of vinyl acetate repeating units in the range of 7.5 to 30% by weight.

Ethylene-vinyl acetate copolymer (EVA) used in the present invention
) preferably has a number average molecular weight within the range of 12,000 to 14,000. The melt index of such copolymers is usually 15-20 g/10 minutes (at 190°C
, 2.16 kg load).

In the present invention, the above ethylene-vinyl acetate copolymer (E
The blending ratio of VA) is 30 to 48% by weight, especially 35%
The content is preferably within the range of 40% by weight.

If the blending ratio of the ethylene-vinyl acetate copolymer (EVA) is lower than 30% by weight, 1. Moldability and soft feel deteriorate, and if the content is higher than 48% by weight, the formed film becomes too sticky and difficult to handle.

Linear low density polyethylene (LLDPIl) used in the present invention
The material is a straight polyethylene with less branched structure, and preferably has a specific gravity in the range of 0.920 to 0.935. Such linear low density polyethylene (LLDPE)
The melt index of is usually within the range of 0.5 to 30 g/10 minutes (190°C, 2.16 kg load).

In the present invention, linear low density polyethylene (LLDPE)
The blending ratio is 2 to 20% by weight, particularly preferably 5 to 10% by weight. If the blending ratio of the linear low density polyethylene (LLDPB) is lower than 2% by weight, it will not be effective in improving the film formability of the resulting film, and if it exceeds 20% by weight, the resulting film will have poor elasticity and softness. feeling decreases.

Furthermore, in the present invention, in addition to the above-mentioned resin components, antioxidants, ultraviolet absorbers, antistatic agents, coloring agents, etc. can be appropriately blended. However, in the present invention, it is preferable not to add an inorganic filler because it makes it difficult to form a thin film.

Next, a method for manufacturing the waterproof and breathable composite sheet of the present invention will be explained.

The above-mentioned ethylene-propylene-diene copolymer (BPD
M), ethylene-vinyl acetate copolymer (EV^), linear low density polyethylene (LLDPB), and other components are kneaded. In the present invention, the above kneading is 150 to 175
Preferably, it is carried out at a resin temperature of °C.

After kneading, it is formed into a film. The thickness of the film is preferably 10 to 40 μm; if it is thinner than 10 μm, the film strength will decrease, and if it is thicker than 40 μm, it will be difficult to form fine through holes for providing ventilation. The film is formed by the inflation molding method (air cooling method).
It is preferable that the blowing ratio (diameter of rose pull/diameter of die slit) be in the range of 2.0 to 5.0 at a resin temperature of ~165°C.

The thickness of the film thus obtained is 10 to 40 μm.

Various woven or nonwoven fabrics can be used in the present invention, such as gauze or other plain woven fabrics, or nonwoven fabrics produced by spunbonding, melt blowing, or the like. The nonwoven fabric does not need to be made of long fibers, and may be made of short fibers intertwined or point welded. The woven or nonwoven fabric must not substantially melt or shrink during the hot pressing process described below. Therefore, the melting point or secondary transition point of woven or nonwoven fabrics is generally lower than that of the film.
Both temperatures need to be at least 20°C higher.

Hot pressure bonding between the film and woven fabric or non-woven fabric is 70 to 15
Perform at 0°C. If the temperature conditions are outside the above range, the adhesion between the film and the woven fabric or non-woven fabric and the heat shrinkage of the film will be insufficient, or the waterproofness will decrease.

The hot press bonding does not need to be carried out in one stage, but can be carried out in multiple stages to ensure the fixation of the film and the formation of microporous film. In this case, initially at a relatively low temperature,
It is preferable to gradually increase the hot pressing temperature. As a typical example, the first step at 70-90°C, 90-110°C
The second step at 110 DEG to 150 DEG C. and the third step at 110 DEG to 150 DEG C. can be carried out consecutively.

Further, the hot press bonding is preferably performed at a pressure of 0.1 to 10 kg/cI11. If it is less than 0.1 kg/cr1, the film will not have sufficient adhesion, and if it is less than 10 kg/c++
If it exceeds I, the film strength will decrease. A more preferred pressure condition is 0.5-5 kg/cJi.

The hot press bonding between the film and the woven fabric or nonwoven fabric is preferably carried out using a heat roll, as will be described in detail later. In this case, in addition to pressing the film and the woven fabric or non-woven fabric one by one, the woven fabric or non-woven fabric may be sandwiched between two films, or conversely, the film may be sandwiched between two woven fabrics or non-woven fabrics. You can also do that.

In the thus obtained composite sheet, the film has become microporous due to heat shrinkage due to hot pressing. The micropores in the film vary slightly depending on the hot press bonding conditions, but are generally 5μ.
Since it has a pore diameter of less than m, it has excellent air permeability and is also excellent in waterproofness.

[For production]

In the hot pressing step of the production method of the present invention, vinyl acetate in the ethylene-vinyl acetate copolymer (εVA) dispersed in the film becomes sticky by heating to 70°C or higher. The force causes the film to stick to the woven or non-woven fabric. At the same time, the film is heat-shrinked, so that the film is stretched by the fibers of the woven or non-woven fabric.

Looking at this microscopically, as shown in Figure 1, film 1
It can be seen that the film is fixed to the fibers 2 of the woven or non-woven fabric, and the periphery of the film portion 3 in the gap between the fibers is fixed by the fibers 2.

If heat shrinkage occurs in the film portion 3, the frame of the fibers 2 hardly changes, so the film portion 3 ends up in a stretched state due to the heat shrinkage. In this way, a large number of micropores of 5 μm or less can be formed in the film 1.

〔Example〕

FIG. 2 is a schematic diagram showing an example of an apparatus suitable for performing hot press bonding according to the present invention. This hot press bonding device includes a preheating roll 13 for preheating and heat setting the woven or nonwoven fabric 12;
A first hot press roll 14 and a pair of elastic rolls 15 for hot press bonding the film 11 and the woven fabric or nonwoven fabric 12.
16, a tension control roll 17 for the composite sheet after the first hot pressing, and a roll 17 for controlling the tension of the composite sheet after the first hot pressing.
- second hot pressing roll 1 for hot pressing the sheet again;
8, a pair of elastic rolls 19 and 20, a tension control roll 21 for the composite sheet after the second hot compression bonding, and a third heat roller for again thermocompression bonding the composite sheet after the second hot compression bonding. A pressure bonding roll 22 and a pair of elastic rolls 23.
24.

The temperature of each hot press roll is as follows.

The temperature of the first hot pressure bonding roll 14... 70-90℃ Second hot pressure bonding roll 18... 90-110℃ Third hot bonding roll 22... 110-150℃ The temperature of the preheating roll 13 depends on the woven fabric or nonwoven fabric used. It varies depending on the type and thickness, but it is about 12
0°C is preferred.

Gap between first hot crimping roll 14 and elastic roll 15.16, second hot crimping roll 18 and elastic roll 19.2
0 and the gap between the third hot press roll 22 and the elastic rolls 23 and 24 can be adjusted as appropriate so as to apply the desired pressure. Further, the tension of the composite sheet can be adjusted by moving the tension control roll 17.21 up and down as shown by %r'.

One woven or nonwoven fabric 12 on one side of one film 11
In the case of hot pressing, each elastic roll 15.1
6.19.20.23.24 is preferably cooled to maintain a temperature of 30°C or less. On the other hand, when using two pieces of wire cloth or nonwoven fabric, it is sufficient to insert the second woven or nonwoven fabric 12' from the position indicated by the dotted line. In that case, the elastic rolls 15, 16, 19, 20, 23, 24 do not need to be cooled.

Conversely, in order to obtain a structure in which a woven fabric or non-woven fabric is sandwiched between films, a film 11 and a woven fabric or non-woven fabric 12.
12' can be simply replaced.

The method of the present invention will be explained in more detail by the following specific examples.

Example 1 55.5% by weight of ethylene-bropyrene-diene copolymer (Vistaron 3708, manufactured by Exxon Chemical Co., Ltd.), 37% by weight of ethylene-vinyl acetate copolymer (DQDJ-3269, manufactured by Nippon Unicar), shaped low density polyny
Shi:/ (TUF-2060, made by Japan Yu=h-@)7.
A composition consisting of 5% by weight is melt-kneaded using an extruder,
A film was formed by the inflation method under the following conditions.

Die diameter: 150 IIlffi Temperature: 145-165°C Extrusion rate: 40-60 kg/hour Take-up speed: 10-20 m/min The obtained film has a thickness of 15-30 μm and a blow ratio of 3.
It was 0 to 4.0.

This film and a polyester elastic nonwoven fabric are
Hot pressing was carried out under the following conditions using an apparatus having two hot pressing rolls.

First hot crimping roll... 80~90℃ Second hot crimping roll... 110~130℃ crimping speed...
When the adhesive strength of the composite sheet obtained for 10 to 25 m7 was examined, there was no problem with peeling. Furthermore, the elongation at break (tear strength) in the longitudinal direction was also sufficient. The waterproofness, air permeability, moisture permeability and soft feel of the obtained composite sheet were measured. The results are shown in Table 1.

Comparative Example 1 Regarding the waterproof sheet used in commercially available disposable diapers,
Waterproofness, air permeability, moisture permeability and soft feel were measured in the same manner as in Example 1. The results are also shown in Table 1.

No. table did.

Note) 2 (1) Waterproofness... Permiagraph (Toyo Seiki @
The pressure is expressed as the pressure when the air permeability changes significantly by increasing the differential pressure applied to the sample using a vent hole (manufactured by the company), that is, when the air hole is damaged or destroyed.

(2) Air permeability: Using a permia graph, find the point where the differential pressure applied to the sample and the amount of air passing through the sample become constant, and calculate the amount of air permeating per unit area, unit time, and unit pressure at that point. represent.

(3) Moisture permeability: expressed as a value measured according to JIS-X-0208.

(4) Soft feel: Evaluated by the feel of direct touch ○
. . . Good △ . . . Normal As is clear from the results in Table 1, the composite sheet obtained by the method of the present invention is excellent in waterproofness, air permeability, moisture permeability, and soft feel.

〔Effect of the invention〕

The composite sheet of the present invention is produced by hot-pressing a film composed of EPDM as a main component and blending BVA and LLDPE with a woven fabric or non-woven fabric, thereby fixing the film to the woven fabric or non-woven fabric. The film is heat-shrinked to make it microporous, so it has excellent waterproofness and breathability, as well as an excellent soft feel, and does not make a rustling sound or feel uncomfortable when worn. There is no. Furthermore, it is strongly reinforced with a woven fabric or non-woven fabric that is firmly attached to the body, and has high mechanical strength.

Furthermore, since no adhesive is used to integrate the film and the woven fabric or non-woven fabric, there is no adverse effect on the human body such as rash even when the film is directly attached to the human body.

In the method of the present invention, a desired air permeability can be achieved by appropriately adjusting conditions such as hot pressing temperature and pressure between the film and the woven or nonwoven fabric. Moreover, since thickness unevenness, which is difficult with conventional stretching methods, can be minimized, the quality of a waterproof and breathable composite sheet can be improved. Furthermore, a waterproof and breathable composite sheet can be manufactured in-line, which helps reduce manufacturing costs.

Such a composite sheet according to the present invention is particularly suitable for paper diapers, disposable sheets, and the like.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged view showing the fine structure of a waterproof and breathable composite sheet of the present invention, and FIG. 2 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention. 12, 12'...Woven fabric or nonwoven fabric 13...Preheat roll 14...First hot pressure bonding roll 18...Second hot pressure bonding roll 22... Third hot pressure bonding rolls 15, 16, 19, 20, 23, 24... Elastic rolls 17, 21... Tension control rolls Applicant Tonen Petrochemical Co., Ltd. Agent Patent attorney Taka Ishibashi
Horse 1... Film 2... Woven or non-woven fibers 11... Film

Claims (3)

[Claims] (1) (A) Ethylene-propylene-diene copolymer 5
0 to 68% by weight, and (B) 30 to 48% by weight of ethylene-vinyl acetate copolymer.
and (C) 2 to 20% by weight of linear low-density polyethylene to form a film, and the film and a woven fabric or nonwoven fabric are hot-pressed at 70 to 150°C, and the film is A method for producing a waterproof and breathable composite sheet, which comprises adhering to a woven or nonwoven fabric and heat-shrinking the film, thereby making the film microporous. (2) In the method according to claim 1, the hot pressing of the film and the woven fabric or nonwoven fabric is performed in a first step at 70 to 90°C, a second step at 90 to 110°C, and a second step at 110 to 150°C.
A method characterized by carrying out the third step at ℃. (3) The method according to claim 1 or 2, characterized in that the thickness of the film is 10 to 40 μm.