JPH0482949A - Nonwoven fabric and production thereof - Google Patents

Abstract

PURPOSE:To obtain a nonwoven fabric of multilayer structure excellent in air permeability with a combination of water repellency and water proofness by hot contact bonding of the surface layer(s) of one or both of the surfaces of a nonwoven fabric consisting of special conjugate synthetic fiber into a filmy form. CONSTITUTION:Firstly, a nonwoven fabric is produced using such a kind of conjugate synthetic fiber as to be lower in the melting point of a polymer constituting the sheath than that of a second polymer constituting the core and contain a water repellent (e.g. dimethylpolysiloxane) in the former polymer. Thence, the surface layer(s) of one or both of the surfaces of said nonwoven fabric is put to hot contact bonding pref. using a hot press or hot roll into a filmy form, thus obtaining the objective product. Said conjugate fiber is made up of e.g. (A) as the sheath, polyethylene or polystyrene and (B) as the core, polypropylene or polyester.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a special nonwoven fabric that has excellent air permeability as well as water repellency and waterproof properties.

[Conventional technology and problems]

Nonwoven fabrics that are breathable, water repellent, and waterproof are often dry-processed or wet-processed nonwoven fabrics made of synthetic fibers. However, although these materials generally have sufficient air permeability, they cannot be said to have sufficient water repellency or waterproof properties, and for this reason, various improvements have been made at present. For example, ■A method of applying a water repellent to the fiber surface of a non-woven fabric, ■A method of laminating a hydrophobic film to a non-woven fabric layer and then mechanically punching fine holes in the film, ■A method of kneading a solvent-soluble substance into the film layer. Examples include a method in which holes are formed in the film layer by eluting the nonwoven fabric, and a method in which the nonwoven fabric is heat-pressed as it is to make the fibers denser.

However, in the method (■), the applied water repellent agent falls off and the performance deteriorates, and in the methods (■) and (2), the reproducibility of openings in the film layer is poor, and the cost is high. It cannot be said that it is economically advantageous. In addition, the method (2) of thermocompression bonding nonwoven fabrics is relatively superior in terms of quality and economy, but it not only impairs the unique texture of nonwoven fabrics, but also reduces tensile strength and tear strength when formed into a film. There's a problem.

[Means for solving problems]

As a result of intensive research by the present inventors to solve the above problems,
This has led to the present invention.

That is, the first aspect of the present invention is that the sheath is made of a polymeric material having a lower melting point than the core, and one side of a nonwoven fabric is made of a composite synthetic fiber in which the polymeric material of the sheath contains a water repellent and is coated with U. Alternatively, a nonwoven fabric is characterized in that the surface layer portions of both sides are thermocompression bonded to form a film to form a multilayer structure. Each content includes a method for manufacturing a nonwoven fabric, which is characterized by forming a surface layer on one or both sides of a nonwoven fabric made of a composite synthetic fiber in which a water repellent is contained in a polymeric substance into a film by thermocompression bonding. .

The composite synthetic fiber used in the present invention is a composite synthetic fiber in which the sheath part is made of a polymer material with a lower melting point than the core part, and specifically, the sheath part is made of polyethylene or polystyrene, and the core part is polypropylene or polyester. , polyamide (nylon), or combinations such as polypropylene or nylon-6 for the sheath and polyester or nylon-66 for the core.

The water repellent added to the polymer material of the sheath must have a contact angle of 90° or more, and must be well mixed with the cough polymer material. For example, dimethylpolysiloxane, which is generally referred to as silicone oil, modified silicone compounds, such as alkyl-modified silicone compounds in which the methyl group of dimethylpolysiloxane is substituted with a long-chain alkyl group, and fluorine-modified compounds, such as ethylene-4- Fluorinated ethylene copolymers, fluorosilicone compounds, and various waxes, such as low molecular weight polyethylene (
average molecular weight of about 1,500 to about 5,000), low molecular weight polypropylene (average molecular weight of about 3,000 to about 10,000)
, paraffins, etc., and these may be used alone or in combination of two or more. Modified silicone compounds are
For example, those described in JP-A-63-3076 can be suitably used. The water repellent is added in an amount of 0.5 to 20.0% by weight based on the polymer material of the sheath. If it is less than 0.5% by weight, the water repellency effect will be low, and if it exceeds 20.0% by weight, the spinnability and physical properties of the polymer material in the sheath will be significantly reduced, and the fibers will be damaged when the nonwoven fabric is further thermocompressed. This is not preferable because it hinders the fusion between the two. The compatibility between the water repellent and the sheath polymer material is also important, and it is necessary to select in advance a water repellent that will not adversely affect spinnability.

Since the water repellent agent is incorporated into the polymer material of the sheath, these composite synthetic fibers have a durable water repellent effect, and the effect is not reduced by washing with water or external force.

A method for obtaining a nonwoven fabric made of composite synthetic fibers with such a resin composition is to spin composite synthetic fibers using a normal composite nozzle, obtain a carded web from staple fibers using a carding machine, and use a needle punching method or an air jet method. Alternatively, when obtaining composite synthetic fibers from a composite nozzle, it may be directly made into a nonwoven fabric using a spunbond method.

The surface layer portions of one or both surfaces of the nonwoven fabric thus obtained are thermocompressed to form a film, and it is preferable to use a hot press machine or a hot roll for this purpose. For example, in the case of forming a double-sided film, it is preferable to heat both the front and back sides of the nonwoven fabric, and in the case of forming a single-sided film, it is sufficient to heat only the side to be formed into a film. The heating temperature at this time is preferably selected to be a temperature at which the polymer material in the sheath portion is melted, but the polymer material in the core portion is not melted. Therefore, the larger the difference in melting temperature between the polymeric substances used in the sheath and core, the easier it is to process. The pressure applied at this time is also related to the heating temperature, but the pressure applied is preferably 0.1 to 10 kg/afl in the case of a press plate, and 0.1 kg to 5 kg/afl in the case of a heated roll.
A linear pressure of cm is preferred. In either case, if the pressure is lower than these values, film-formed carbon is likely to come out during film formation, and if the pressure is higher than these values, the entire nonwoven fabric is likely to become a film (and it is difficult to obtain the desired physical properties). .

In this way, the surface layer of the nonwoven fabric is formed into a film by thermocompression bonding from one or both sides, and film formation here means that the fibers are thermally fused together, leaving almost no fiber form behind. Refers to a state in which most of the fill is formed. The state of this film formation can be controlled by temperature, pressure, and time. In the present invention, the optimal conditions are selected from the above according to the resin of the sheath and core, the thickness of the nonwoven fabric, etc.
It is preferable to have a multilayer structure consisting of /2 or less. By forming a multilayer structure consisting of a filmed surface layer and a nonwoven fabric layer in which fibers remain inside, it is possible to maintain the strength, elasticity, and texture of these sheet-like materials. This is because when the entire nonwoven fabric is made into a film, the fiber morphology is completely lost, and the strength that the fibers had is significantly reduced, and on the other hand, the elasticity and texture of the nonwoven fabric due to the three-dimensional structure that it had due to the intertwining of the fibers are also lost. It is from.

When making a nonwoven fabric having this multilayer structure, if a spacer is used during thermocompression bonding, the desired product can be easily obtained with good reproducibility. For example, the total thickness is 100μ
m, it is sufficient to use a spacer of about 100 μm to form a gap and perform thermocompression bonding, and when performing this using a hot roll, it is sufficient to provide a similar gap between the rolls and perform thermocompression bonding.

The spacer is not particularly limited as long as it is made of a heat-resistant material that does not melt due to heat during thermocompression bonding, and examples thereof include metals such as stainless steel, heat-resistant resins, and the like.

[Action/Effect]

The nonwoven fabric of the present invention thus obtained has remarkable water clarity and waterproofness due to the filmed surface layer, and only the surface layer of the nonwoven fabric, that is, the sheath of the composite synthetic fiber is fused, and the core Because it maintains its fiber form, it has micropores and has good air permeability and moisture permeability. Moreover, since it is a composite with a fibrous nonwoven fabric layer, the obtained nonwoven fabric has strong tensile strength and tear strength, and also has a soft texture.

Therefore, the nonwoven fabric of the present invention can be used as a material for wrapping breathable waterproof sheets used as wall materials or roofing materials, as packaging materials for desiccant materials, as sanitary materials such as medical pad materials, and diaper covers, or as materials with a smooth surface. Therefore, it can be applied as a recording material such as tack paper or slip paper, and moreover, these can be supplied economically.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by these.

Synthesis example: Synthesis of water repellent (modified silicone compound) Polymethylhydrodiene siloxane (P-300, MW=2
2000) 45.6 parts, α-olefin (“Dialen-30”, manufactured by Mitsubishi Chemical Industries, Ltd., MW=650) 54.
4 parts of a 0.1% H2PtCl6.6H20 tetrahydrofuran solution were charged into a reactor, and the addition reaction was carried out at 80'C for 8 hours, and further reacted at 130°C for 8 hours. The reaction was stopped when the viscosity of the reaction product reached approximately 10,000 cps.

The reaction product was washed three times with acetone to remove unreacted parts, and purified and dried. The silicone content of the obtained modified silicone compound was 45.6%.

Example 1 The modified silicone compound obtained in the above synthesis example (Gonyo Paper Co., Ltd. NR-B) was added to high-density polyethylene (melting point 132'C).
) is mixed with polyethylene in an amount of 3% by weight to form the polymer material of the sheath, and the core is made of crystalline polypropylene (melting point: 167
°C) with a composite ratio of 1/1 and a single fineness of 3 using the usual method.
A denier composite synthetic fiber was obtained. This composite synthetic fiber was cut to a fiber length of 51 mm, and made into cotton using a synthetic fiber card.
Preliminary pressure bonding was performed using an air jet at 120°C, and the web weight was 40 g/rrf and the length was 21. A nonwoven fabric measuring cm x width 30 cm was obtained.

This web was heat-pressed on both sides using a hydraulic heat press machine.

The thermocompression bonding method is to set a spacer with a thickness of 150 μm on a press plate, then set the above web and preheat it to 120 μm.
°C for 3 minutes, and at the same temperature the main press was applied to a pressure of 5 kg.
/ cf for 3 minutes to obtain a nonwoven fabric with a thickness of 180 μm. The thickness of the film layers on both the front and back sides of this nonwoven fabric was 80 μm when both the front and back layers were combined.

The physical properties of the obtained nonwoven fabric are shown in Table 1.

Example 2 A nonwoven fabric having a total thickness of 110 μm and having both the front and back layers formed into films was obtained in the same manner as in Example 1 except that no spacer was used. In addition, the thickness of the film layer is 5 in total for both the front and back layers.
It was 0 μm.

The physical properties of the obtained nonwoven fabric are shown in Table 1.

Example 3 Using the composite synthetic fiber of Example 1, a web-like nonwoven fabric with a basis weight of 70 g/I was obtained in the same manner as in Example 1. When this material is heat-pressed using a hydraulic heat press machine, the thickness is 200 mm.
Using a μm spacer, 120"C only for the lower press plate
Preheating was performed for 3 minutes, and at the same temperature, the press was heated and pressed at a pressure of 5 kg/cA.

The product obtained in this way has only one surface layer formed into a film, and the thickness of the filmed layer is 30 μm, and the other surface has a fiber layer remaining and has a soft texture, and has a total thickness of 30 μm. The nonwoven fabric had a length of 480 μm.

The physical properties of the obtained nonwoven fabric are shown in Table 1.

Comparative Example 1 A polypropylene fiber (Mitsubishi Rayon's Vilene) with a single denier of 3 denier and a fiber length of 51 mm was produced using a synthetic fiber card, and was pre-pressed with an air jet at 140°C to give a web weight of 40 g/r+ (of Vertical 2Ic+nX Width 30c
Although an attempt was made to obtain a +n nonwoven fabric, sufficient adhesion between the fibers could not be obtained. Moreover, when the temperature of the air jet was further increased to 160° C., the fiber morphology collapsed and a nonwoven fabric could not be obtained.

Comparative Example 2 A nonwoven fabric having a thickness of 170 μm and having a thickness of 170 μm was obtained in the same manner as in Example 1 except that the modified silicone compound was not added to the sheath portion. The thickness of the film layer on both the front and back layers of this nonwoven fabric is 80μ in total.
It was m.

The physical properties of the obtained nonwoven fabric are shown in Table 1.

A comparison between Example 1 and Comparative Example 1 shows that a nonwoven fabric that does not use composite synthetic fibers can only provide a nonwoven fabric with poor interfiber adhesion. Also, from the comparison between Example 1 and Example 2,
By using a spacer during thermocompression bonding, the thickness of the film layer can be easily controlled, especially the tensile strength and
It is understood that a nonwoven fabric with high tear strength is obtained.

Furthermore, a large difference was observed in the contact angles θ and Δθ between Example 1 and Comparative Example 2 without evaluation of water clarity, and the effect of using the water repellent in combination with the sheath was observed.

Example 4 The sheath was made of polyethylene mixed with 10% by weight of Sunwax 15]-P (average molecular weight 2000, manufactured by Sanyo Kasei), and the core was made of polyester with a composite ratio of 1/1. Spun using the spunpond method according to the law,
At the same time, a nonwoven fabric with a basis weight of 50 g/bo was obtained. This material was further heat-pressed using a hydraulic heat press machine in the same manner as in Example 1, using a 50 μm spacer, preheating at 140°C for 3 minutes, and main pressing at the same temperature at 5 kg/ci for 3 minutes. As a result, a nonwoven fabric having a thickness of I 601t m was obtained. This nonwoven fabric was made into a film with both front and back layers, and the total thickness of both the front and back layers was 70 μm. The physical properties are shown in Table 2.

Comparative Example 3 In Example 4, Suwanwa Nox 151P was added to the sheath part.
A sheet-like product with a thickness of 80 μm was obtained in the same manner as in Example 4, except that no . This sheet-like material was almost entirely formed into a film. The physical properties are shown in Table 2.

Both Example 4 and Comparative Example 3 in Table 1 have air permeability and water repellency, but Example 3, which has a multilayer structure, has better air permeability and has the same basis weight. Despite this, the tensile strength and tear strength were excellent. Furthermore, it can be seen that Example 4, in which wax was mixed in the sheath portion, had better water repellency.

Claims (7)

[Claims] 1. The sheath is made of a polymer material with a lower melting point than the core, and the surface layer of one or both sides of a nonwoven fabric is made of a composite synthetic fiber in which the polymer material of the sheath contains a water repellent. A nonwoven fabric characterized by having a multilayer structure. 2. 2. The nonwoven fabric according to claim 1, wherein the sheath portion of the composite synthetic fiber is polyethylene, and the core portion is polypropylene, polyester, or polyamide. 3. The nonwoven fabric according to claim 1 or 2, wherein the surface layer portion formed into a film on one or both sides of the nonwoven fabric is 1/2 or less of the thickness of the entire nonwoven fabric. 4. 4. The nonwoven fabric according to claim 1, wherein the water repellent is at least one selected from silicone oil, modified silicone compounds, fluorine modified compounds, fluorine silicone compounds, and waxes. 5. The nonwoven fabric according to any one of claims 1 to 4, wherein the content of the water repellent is 0.5 to 20.0% by weight. 6. The surface layer of one or both sides of a nonwoven fabric made of composite synthetic fibers, the sheath of which is made of a polymeric material with a lower melting point than the core, and the polymeric material of the sheath contains a water repellent, is formed into a film by thermocompression bonding. A method for producing a nonwoven fabric characterized by: 7. 7. The manufacturing method according to claim 6, wherein the thermocompression bonding is performed using a spacer.