JPS635497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In manufacturing a nonwoven fabric, the present invention involves fusing the individual filaments constituting the nonwoven fabric with heat or a solvent, or using an adhesive to maintain the shape and strength of the nonwoven fabric. Long-fiber nonwoven fabrics are produced by bonding them together by hand, by mechanically intertwining them by needle punching, or by using a combination of these methods, especially nonwoven fabrics produced by the spunbond method in which spinning, drawing, and web formation are continuous, and pressure bonded with heated rolls. This relates to improvements in methods for In the production of nonwoven fabrics, when unbonded raw webs are heat pressure welded using heated rolls, high temperatures close to the melting point of the filament and high linear pressure are necessary to improve the welding effect and obtain a nonwoven fabric with high strength and no surface fuzz. For example, for polyester, 200
It requires high temperatures of 220 to 220 degrees Celsius, sometimes 300 degrees Celsius, and high linear pressure. However, at such high temperatures, the material of the roll is naturally limited to metal and has no elasticity, so the higher the pressure welding effect, the harder the texture of the resulting nonwoven fabric becomes, paper-like. I had a flaw that I got used to it. In addition, the heating roll is likely to be damaged due to fiber lumps due to poor opening during web formation, that is, when depositing filament groups, or wrinkles in the raw web that occur during the process, resulting in severe damage to the equipment. There were some unavoidable drawbacks. Therefore, one way to obtain a flexible nonwoven fabric without impairing the texture of the nonwoven fabric is to use a so-called embossing roll, which has various patterns such as regular patterns on the surface of the heating roll, to dot the nonwoven fabric. There is a method of partial pressure contact in a shape or a line, and embossing rolls with various patterns are being considered. However, with this method, if the flexibility of the nonwoven fabric is emphasized, and the pattern of the embossing roll is made to have a large non-pressure contact area, the filaments that make up the nonwoven fabric will not be sufficiently bonded, resulting in fluffing and insufficient strength. However, high temperature and linear pressure were required, and the problem remained that the rolls were easily damaged by fiber lumps and wrinkles. Increasing the roll hardness can be considered to make the heating roll less prone to scratches, but in the case of embossing rolls, it is necessary to engrave a pattern on the roll surface, so there is a constraint that the hardness of the roll surface cannot be increased very much. It also didn't rise. Furthermore, in order to increase the pressure welding effect without increasing the linear pressure of the heating roll, there is a method of mixing low-melting substances into the web to increase adhesiveness. In the case of manufacturing using the spunbond method, mixed fibers, core-sheath or dorsal-ventral composite methods are adopted, but using composite spinning equipment increases equipment costs and requires less raw material. It is necessary to prepare two types of chips, which imposes a heavy burden on inventory management, and furthermore, the low melting point polymer itself is generally expensive. Furthermore, a method of uniformly mixing fibrous or powdered material made of a low melting point polymer into the web to improve adhesion without using the composite spinning method has many difficulties in terms of equipment and technology. Other methods include bonding by dissolving or swelling with a solvent, such as dimethylformamide for acrylic fibers, cyclohexane for polyolefin fibers, methanol solution of calcium chloride for polyamide fibers, and phenol for polyester fibers. - There is a method using a mixture of tetrachloroethane, etc., but most of these solvents volatilize quickly, so there are many problems in terms of process and health and safety. Additionally, if the core of the fiber swells or dissolves, the strength will drop drastically, so only the surface layer of the fiber will dissolve or swell, so it is necessary to control the solvent effect, but it is very important to maintain this balance. It was difficult and it was necessary to remove these solvents after the adhesive treatment. In view of the current situation, the present invention aims at producing a long-fiber nonwoven fabric by applying water to a raw web that has not been bonded between fibers so that microscopic differences in the wet state occur over the entire web, and applying the water to a heated roll. By press-welding, it is possible to increase the pressure-welding effect with low linear pressure and to obtain a nonwoven fabric with high strength and no surface fuzz without damaging the texture.Moreover, it does not damage heating rolls etc. during manufacturing. It is possible to provide a method for press-welding long fiber nonwoven fabrics that can be easily produced with low material and equipment costs, and the present invention will be described in detail below. The raw web used in the present invention is a raw web in which end-fiber bonding is not applied in the production of long-fiber nonwoven fabrics, and unbonded raw webs are particularly suitable in the production of spunbond nonwoven fabrics in which spinning, stretching, and web formation are continuous. It is. It is desirable that the material of the filaments constituting the raw web be hydrophobic fibers, and in particular, highly hydrophobic fibers such as polyester fibers and polyolefin fibers will prevent the applied water from penetrating the entire web. This is suitable because it can maintain a state of non-uniform adhesion. Water is applied to the raw web by spraying or other means such that microscopic differences in wetting occur throughout the web, but in particular by dispersing water droplets in spots, it is possible to separate wet and non-wet areas. It is desirable to apply the water in such a way that the parts are scattered throughout.
The amount of water applied varies somewhat depending on the weight per unit area of the nonwoven fabric to be manufactured, that is, the basis weight, but since the optimum basis weight for obtaining a highly strong and flexible nonwoven fabric is in the range of 10 to 70 g/ ^m2 , 50 to 100 c.c. per unit area (m ² ) of the web is optimal. This is because if the amount of water applied is too large, the above-mentioned differences in wetting, particularly spot-like wetting, will not be formed, and if the amount is too small, the effect of moist heat pressure welding will not be enhanced. In this way, by bringing the heating roll into pressure contact with a raw web that has microscopic differences in wetness, especially a raw web that is dotted with wet and non-wet areas, the pressure welding effect can be achieved with a low linear pressure. In addition, since only small wetted portions of the web are selectively subjected to the pressure contact effect, it has become possible to partially adhere the web in dots and produce a flexible and highly strong nonwoven fabric. It is possible to use an embossing roll, especially an embossing roll engraved with a regular dotted or linear pattern, as at least one of the pair of heating rolls, and the synergistic effect with the partial adhesion effect allows the desired A nonwoven fabric having excellent flexibility etc. can be produced. Example 1 60 c.c. of water was applied by spraying to an unbonded green web made of polyester having a weight per unit area, that is, a basis weight of 50 g/m ² to form wet areas and non-wet areas, and then the temperature was increased. 220℃, linear pressure 10, 20, 30,
A flexible and highly strong nonwoven fabric was obtained by heat-pressure welding at 40 kg/cm using an embossing roll with a square dotted pattern (area ratio of non-pressure-welded parts, 62%). The tensile strength (Kg/3cm) of the obtained nonwoven fabric is shown in Table 1 together with the tensile strength of a nonwoven fabric similarly obtained without adding water for comparison. It is clear from Table 1 that the nonwoven fabric of this example exhibited higher tensile strength than the nonwoven fabric of the comparative example. Furthermore, the texture of the nonwoven fabric according to this example was much softer than that of a paper-like fabric such as a sheet pressed by a flat roll. 【table】

Claims (1)

[Scope of Claims] 1. In producing a long fiber nonwoven fabric, water is applied to a raw web without interfiber bonding so that microscopic differences in the wet state occur over the entire web, and then heated rolls are applied. A method for thermo-pressure welding long-fiber nonwoven fabrics, characterized by pressure-welding them at . 2 50 to 100 c.c. per unit area (m ² ) of web.
2. A method for thermo-pressure welding long fiber nonwoven fabrics according to claim 1, wherein the water is applied by spraying. 3. The method of thermocompression welding of long fiber nonwoven fabrics according to claim 1, wherein at least one of the heating rolls is an emboss roll engraved with a regular dotted or linear pattern. 4 Claim 1, characterized in that the filament constituting the nonwoven fabric is made of polyester.
Long fiber nonwoven fabric as described in Section 1.