JPS6317945B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a nonwoven fabric that has high tear strength, low fuzz, and good flexibility, and a method for producing the same. Nonwoven fabrics are made by providing some type of bond to the fibers within the web to secure the web. As the bonding method, a method using an adhesive, a method using mechanical fiber entanglement such as needle punching, a thermocompression bonding method using a calender roll, etc. are employed. Among these, methods for producing nonwoven fabrics from webs mainly made of thermoplastic fibers include the partial thermocompression bonding method, for example, passing the web between calendar rolls consisting of a roll with an embossed pattern and a flat roll to partially separate the web. The thermocompression bonding method is attracting attention because of its low running cost and the relatively high flexibility of the resulting nonwoven fabric. However, in order to obtain a nonwoven fabric with high strength and especially low fuzz due to friction using this method, it is necessary to increase the area ratio of partial thermocompression bonding and arrange the crimped unit units with high density. However, the flexibility of the nonwoven fabric must be greatly reduced, and on the other hand, if good flexibility is to be maintained, the increase in fluffing cannot be prevented, and the strength is even worse. As described above, reduction in fuzz and increase in flexibility of nonwoven fabrics are contradictory to each other. Furthermore, as the web becomes thicker, it becomes difficult to provide sufficient compression and heat conduction, making it difficult to perform partial thermocompression bonding itself sufficiently, and it becomes extremely difficult to suppress the occurrence of fuzz on the surface. That is, the partial thermocompression bonding method has one limitation in producing thick nonwoven fabrics. Furthermore, in the case of thick nonwoven fabrics, if partial thermocompression bonding is performed satisfactorily, the flexibility of the obtained nonwoven fabric will be extremely reduced. The purpose of the present invention is to solve the essential problems of the above-mentioned partial thermocompression bonding method, reduce fuzzing due to friction,
Moreover, it is an object of the present invention to provide a nonwoven fabric with extremely good flexibility and a method for producing the same. The object of this invention is to provide a nonwoven fabric that is partially heat-pressed and is characterized in that, on at least one side of the non-woven fabric, fused areas of single fibers in the surface layer are distributed over the entire non-pressed area. This is achieved by the nonwoven fabric of the invention. According to the present invention, the generation of fuzz on the surface of the nonwoven fabric is prevented and the strength is improved by the fusion of the single fibers in the surface layer over the entire surface of the non-partial thermocompression bonding area, so that the degree of partial thermocompression bonding can be reduced. Since the strength can be satisfied and the flexibility of the nonwoven fabric can be maintained, a nonwoven fabric with less fuzz, sufficient strength, and improved flexibility can be obtained. The present invention will be explained in detail below. 1 and 2 are schematic cross-sectional views showing one example of the nonwoven fabric of the present invention, in which 1 is the web of the non-thermo-compression bonded part, 2 is the partial thermo-compression bonded part, and 3 is the surface of the web of the non-thermo-compression bonded part. Indicates fiber fusion. The nonwoven fabric shown in FIG. 1 is flat on one side and has unevenness on only one side due to partial thermocompression bonding, and the nonwoven fabric shown in FIG. 2 has unevenness on both sides. Figures 3 and 4 show microscopic photographs of the surfaces of the nonwoven fabrics of the present invention. Figure 3 is an example of a nonwoven fabric made of polyester fibers (magnification: 80), and Figure 4 is an example of a nonwoven fabric made of nylon fibers. In the case of Figure 4, change the magnification
(B) (Magnification 80), (B) (Magnification 240), (C) (Magnification 240) 3
A photo of the seeds is shown. The state of fusion of the surface fibers in the thermocompression bonded area and the non-thermocompression bonded area can be clearly seen. The nonwoven fabric of the present invention is made from a web consisting of thermoplastic fibers or mixed fibers mainly composed of thermoplastic fibers. Thermoplastic fibers include polyamide, polyester, polyolefin, polyacrylic,
Synthetic fibers such as polyvinyl chloride or vinylidene, and composite fibers and mixed fibers thereof are used. The thickness of the fibers is usually 0.5 to 10 d, and the thinner the fibers, the softer the texture of the nonwoven fabric. The preferred range is 0.5~
It is 5d. Webs are divided into short fiber webs produced by carding methods, etc., and long fiber webs produced by spunbond methods, etc.
All of them are according to the present invention, but the effects of the present invention are particularly effectively exhibited in nonwoven fabrics made of long fiber webs. The reason for this is that in the case of short fiber webs, the fluff easily falls off, but in the case of long fiber webs, long fluffs tend to remain due to the cutting of the single fibers, and the high tensile strength of the nonwoven fabric is reduced by relatively low partial thermocompression bonding. Because you can get it. The pattern of the partial thermocompression bonded part of the web can be arbitrarily selected, but it may be a pattern in which short lines are arranged in parallel or orthogonally in a zigzag pattern, a discontinuous pattern such as a polka dot pattern, a hexagonal pattern, a textured pattern, a lattice pattern, etc. Any continuous pattern may be used. Various other types of patterns may be considered for these two types. The area ratio of the partial thermocompression bonded part of the nonwoven fabric to the entire web surface is 5.
~50% is normal. The smaller the area ratio, the wider the interval between the thermocompression bonded parts, and the greater the height of the non-thermocompression bonded parts (projections), the better the flexibility of the resulting nonwoven fabric.
It becomes easy to fluff. The fibers at the thermocompression bonding part must be firmly bonded and fixed. Partial thermocompression bonding can be carried out by sandwiching the web between an embossing roll with an uneven surface and a metal roll with a smooth surface, between metal rolls with uneven surfaces on both sides, or between hot plates with uneven surfaces. Further, it can also be carried out using ultrasonic waves, high frequency welders, etc. The heating temperature of the rolls is preferably set to 10 to 50°C below the melting point of the web fibers in order to perform firm thermocompression bonding. For a mixed web of different types of fibers, it is better to set the heating temperature based on the lower melting point. In the present invention, fusion of single fibers means that the surface of the single fibers is softened due to temperature rise, and the single fibers are bonded at the contact intersection between the single fibers, or that the softened surface single fibers are attached to the next layer that has not been softened. This refers to the state in which the fiber is bonded in point or full contact with the single fiber layer. A single layer on the outer surface, which is fused by softening, has a sufficient fuzz-preventing effect. Although it is possible that the second and third layers are fused, the more fused layers there are, the more the flexibility decreases. Macroscopically, the fused portions of the single fibers in the surface layer cover the entire surface of the non-thermocompression bonded area, but microscopically, they do not need to cover the entire surface layer, and the fused portions are randomly (or systematically) bonded. It is sufficient if it is distributed in the surface layer to the extent that it can exhibit the effect of preventing the generation of fuzz. Although this does not necessarily exclude fusion in the entire surface layer, the situation of this surface layer fusion is very clearly shown in FIGS. 3 and 4. This is particularly visible in the enlarged photographs B and C of Figure 4. Although fluffing can be prevented by softening and fusing the single fibers in the outermost layer, the fusing of the present invention is not limited to fusing the single fibers in the outermost layer. Although the single fibers of the surface layer can be fused together by spraying high-temperature fluid, it can be simply and thermally efficiently carried out by applying flame directly to the web surface. FIG. 5 is a simplified diagram showing one example of a flame treatment device. The partially thermocompressed nonwoven fabric 5 is exposed to flame 8 from a burner 7 installed at an appropriate distance while being placed along a roll 6 to prevent shaking during flame treatment. The shape of the burner, and therefore the shape of the flame, may be appropriately determined in consideration of the shape of the welding surface. In general, it may be a slit or a collection of small holes arranged in one or multiple rows. The roll 9 and burner 10 are used for fusing both sides of the web. It is not necessary if only one side is processed. Reference numeral 11 denotes a cooling roll, which is provided as necessary. The illustration of the feed roll and take-up roll of the nonwoven fabric is omitted. It is best to make the flame extinguisher automatically when the movement of the nonwoven fabric stops. Next, examples will be shown. Example 1 A web made of 2.5 d long polyester fibers (basis weight 50 g/m ² ) was partially thermocompressed at 230°C between an uneven roll having an embossed pattern and a smooth roll, and then the uneven surface was Flame treatment was performed using the apparatus shown in Figure 5. The treatment conditions were propane gas as the gas source, a burner (effective width 2 m) with 7 rows of small holes (5 mm φ) arranged at 6 mm pitch, a distance from the cloth of 20 mm, and flame treatment at a speed of 30 m/min. The obtained nonwoven fabric consists of a partial thermocompression bonded part and a non-thermocompression bonded part where some of the fibers on the surface are fused, as shown in the photograph in Figure 3, and exhibits web characteristics as shown in Table 1, and is resistant to wind. The nonwoven fabric had improved abrasion resistance without impairing the bonding properties.

[Table] Note that tensile strength and elongation were measured using the JIS-L-1068 strip method, tear strength was measured using the JIS-L-1085 pendulum method, and bending strength was measured using the 45° cantilever method. Friction resistance was measured using a Gakushin type friction tester with a load of 500g and #320 sandpaper as a friction element, and after rubbing 100 times, a limit sample (grade 5: no fluff (good), grade 3: moderate (Almost good), Grade 1:
(poor (too much fuzz)) and ranked in 5 levels. As described above, it is clear that the nonwoven fabric of the present invention has the strength necessary for use by partial thermocompression bonding, and has further improved abrasion resistance without changing the feel (flexibility). Example 2 1.5D nylon 6 long fiber web (fabric weight 150g/m ² )
was partially heat-pressed at 190°C between an uneven roll having a texture pattern as shown in Figure 4A and a smooth roll, and then the uneven surface was flame-treated on both sides using the apparatus shown in Figure 5. . The processing conditions are natural gas as the gas source, 2.5mm
Using a burner (effective width 3m) with 10 rows of slit-shaped spout nozzles arranged at 5mm pitch, the distance from the fabric was 40mm.
mm and processed at 20 m/min. The obtained nonwoven fabric had a form as shown in FIG. 4, and surprisingly, as shown in Table 2, the longitudinal tensile strength was significantly improved, and it was also a nonwoven fabric with excellent abrasion resistance.

[Table] Example 3 An example of a long fiber web (fabric weight 100 g/m ² ) consisting of a 3D single yarn polyester composite fiber (sheath: polyethylene terephthalate-isophthalate copolymer (mp210°C), core: polyethylene terephthalate) Similar to 2, partial thermocompression bonding was performed and flame treatment was performed. A soft nonwoven fabric with excellent abrasion resistance was obtained. As shown in the above examples, the non-woven fabric of the present invention is able to significantly reduce fuzzing due to surface friction without substantially reducing flexibility due to the fusion of single fibers in the surface layer distributed over the entire surface of the non-thermo-bonded area. A decrease is seen. In some cases, a significant improvement in tensile strength is also observed at the same time. Therefore, by combining the partial heat-compression bonding with a moderate degree of reduction commensurate with the required strength of the nonwoven fabric with the fusion of the single fibers in the surface layer, it is possible to create a fabric with high strength, less fuzz, and greater flexibility than before. A nonwoven fabric with improved properties is obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic cross-sectional views of the nonwoven fabric of the present invention, and FIGS. 3 and 4 are microscopic photographs showing the fiber shape on the surface of the nonwoven fabric of the present invention. FIG. 5 is a diagram showing the mechanism of a flame treatment machine for producing the nonwoven fabric of the present invention.

Claims (1)

[Scope of Claims] 1. A nonwoven fabric that has been partially thermocompression bonded, in which, on at least one side, fused portions of single fibers in the surface layer are distributed over the entire non-thermocompression bonded portion. Characteristic non-woven fabric. 2. Production of a nonwoven fabric characterized by applying flame or high-temperature fluid to at least one surface of a partially thermocompressed nonwoven fabric to fuse the single fibers of the surface layer over the entire non-thermocompression bonded part. Law.