JPH0978420A - Stretchable knit fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stretchable knit fabric having excellent surface feeling and elongation recovery by laminating a knit fabric of a thermoplastic synthetic fiber and an elastomeric nonwoven fabric and hot-bonding the fabrics keeping the form of the knit fabric. SOLUTION: A nonwoven fabric or a knit or woven fabric of a polyurethane elastomer is laminated to a circular knitted fabric gray sheet made of a thermoplastic synthetic fiber such as nylon and the laminate is pressed with a hot embossing roller to obtain a stretchable knit fabric having soft feeling and containing the elastomer melted at the joint part of the fabrics and impregnated into the knit nylon fabric to >=1/4 and <=3/4 of the thickness of the cross-section of the nylon fabric. The produced stretchable knit fabric has a soft feeling and contains the knit nylon fabric in non-melted state to keep the original form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretchable article such as a disposable paper diaper, a tape, and other stretchable parts.

[0002]

2. Description of the Related Art In order to maintain elasticity in a waist portion of a disposable diaper, a sewn piece of rubber or spandex has been put on the market. However, the number of sewing processes increased, which was economically disadvantageous.

It has been proposed to use a stretchable nonwoven fabric or knitted fabric for such purposes. For the non-woven fabric, the brand name "Espansione" is commercially available from Kanebo Co., Ltd. This is a polyurethane melt-blown non-woven fabric with 3
The elongation is 00% or more, and the 50% elongation recovery rate is 90% or more. However, since expensive polyurethane is used as a raw material, disposable applications have been limited to special applications.

Lamination with other loose nonwoven or knitted fabrics is conceivable in order to reduce costs. For example, Japanese Patent Application Laid-Open No. 6-293117 describes an example of a laminate of a nonwoven fabric similar to this nonwoven fabric and polyurethane. However, in this example, in order to improve the tensile strength, it is necessary to use a non-woven fabric having an abnormally thick basis weight of 1000 g / m ² , which is disadvantageous both economically and in texture. In addition, since a special solvent is used for adhesion, it is not environmentally preferable and economically disadvantageous.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stretchable knitted fabric having an excellent surface texture, stretchability and a large stretch recovery rate at low cost.

[0006]

[Means for Solving the Problems] In order to solve the problems, the present inventors have conducted research on a method for laminating a laminate, and have completed the present invention. The elastic knitted fabric of the present invention is a laminate composed of a thermoplastic synthetic fiber knitted fabric and an elastomer nonwoven fabric,
At the joint portion between the two, the elastomer is melted and penetrates to a thickness of at least 1/4 or more and 3/4 or less of the cross section of the thermoplastic knit, and the thermoplastic knit does not melt but is a stretchable knit that maintains its shape. is there.

The stretchable base fabric used in the present invention includes stretchable non-woven fabrics and knitted fabrics, and it is economically unfavorable if the basis weight is too large. Also, if it is too small, the required elongation stress cannot be obtained. It depends on the application, but it must be selected appropriately. A polyurethane non-woven fabric is an example of this stretchable base fabric. An example of this polyurethane nonwoven fabric is "Espancione", a trade name manufactured by Kanebo Co., Ltd. This non-woven fabric is mainly used to improve the elongation stress. If the basis weight is 15 g / m ² or more, the 50% elongation stress is 25 g / m ^2.
Can be more than cm and reach the purpose.

On the other hand, a circular knitted fabric or a warp knitted fabric having elasticity is used as the knitted fabric to be laminated on the elastic base fabric. Stretchability is only required to remain in one direction, and when a warp knitted fabric is used as the knitted fabric, the stretchable knitted fabric of the present invention having stretchability only in one direction can be manufactured. Nylon is preferable for these knitted fabric raw yarns for maintaining tear strength, but inexpensive polyethylene terephthalate may be used. As the circular knitted fabric, in addition to the above fibers, natural fibers, regenerated fibers, synthetic fibers, and spun yarns, filaments, processed yarns and the like obtained by mixing them can be used. It is more preferable to use the textured yarn because the stretchability of the knitted fabric is further increased. The basis weight of the knitted fabric should be selected according to the application, but it is approximately 30g.
If it is / m ² or more, it can be used without any trouble in operation.

Instead of the polyurethane non-woven fabric, it is also possible to use a non-woven fabric made of another elastomer, for example, a block copolymer of polybutylene terephthalate and polybutane diol and a modified product thereof as a base fabric. In this case, if the basis weight is 20 g / m ² or more, the 50% elongation stress can be 25 g / cm or more.

As described above, the materials for the non-woven fabric and the knitted fabric used as the stretchable base fabric are polyurethanes composed of diisocyanates of diphenylmethane diisocyanate or tolylene diisocyanate and esters, ethers, carbonate-based polyols and chain extenders such as butanediol. Or
Ester elastomers such as block copolymers of polyethylene oxide and polyethylene terephthalate, and rubbers such as natural rubber can be selected. However, polyurethane is preferable in terms of elastic recovery. At present, the polyurethane non-woven fabric "Espansione" is industrially produced in a stable manner, and is easily available.

Polyurethane is used as a stretchable material for producing a stretchable base fabric composed of only a knitted fabric, but in general, polyurethane itself has poor smoothness and is difficult to be knitted. Threads covered with polyurethane may be used, but this is not preferable in terms of cost. On the other hand, the core-sheath type polyurethane yarn has excellent knitting and weaving properties. As a core-sheath fiber of polyurethane, there is "New Novac" manufactured by Kanebo Co., Ltd. This uses polyurethane for the core and nylon for the sheath. The core polyurethane is covered with an extremely thin nylon sheath. Since the polyurethane shrinks and the nylon does not, the thin nylon skin covers the core polyurethane in a hung state by the amount of the stretched polyurethane during the production of this yarn. Since the surface of this yarn is nylon, unlike polyurethane, the surface friction is the same as that of ordinary fibers, and the knitting property is good, which is preferable. Since this yarn itself stretches, it can be manufactured into a general woven or knitted fabric and used as a stretchable base fabric. A knitted fabric is preferable in terms of cost. If the basis weight is 15 g / m ² or more, 50% elongation stress is 25 g /
Can be more than cm.

[0012] Generally, in manufacturing a stretchable knitted fabric, an adhesive is used to bond the stretchable base fabric and the knitted fabric.
For example, a polyurethane-based or EVA-based adhesive having high flexibility is used. However, no adhesive is used in the present invention.

In the present invention, an embossing method used for embossing is used as a bonding method. Here, the processing temperature is set to a temperature at which the knitted fabric does not melt during bonding. It is at least 20 ° C or less, preferably 30 ° C or less, which is the melting temperature of the knitted fabric, and is a processing temperature above the apparent melting temperature of the stretchable base fabric. The apparent melting temperature of the stretchable base fabric depends on the polymer composition. Apparent melting temperature depends on temperature and pressure. Therefore, if the shape of the embossing is different, the pressure distribution is also different, and the melting state of the stretchable base cloth is also different. That is, the apparent melting temperature is lower than the melting point measured at normal pressure. The adhesive strength of the present invention occurs when the stretchable base fabric apparently melts and penetrates into the structure of the knitted fabric, and a part thereof becomes a film or a lump, and the knitted fabric is partially embedded.

The emboss shape may be a male-female type. It is preferable that the mold has a large clearance because the winding of the roller is small. From the same meaning, embossing of a combination of a convex roller and a flat metal roller is preferable.

The embossed pattern may be dots, stripes, or a grid. Also, a combination of these may be used. A dot pattern is preferable in terms of texture. The larger the embossed area, the greater the adhesive strength, but care must be taken because the texture becomes harder like a film. Therefore, it is preferable to select it appropriately depending on the application.

In the present invention, the elastomer at the joint portion is melted, and at least 1/4 or more of the cross section of the thermoplastic knitted fabric is used.
When the thermoplastic knitted fabric has penetrated to a thickness of 4 or less, the thermoplastic knitted fabric retains its shape without melting. This measurement was performed by a cross-section photograph by a scanning electron microscope (hereinafter referred to as SEM). When the intrusion of the elastomer was less than 1/4, the adhesive strength was weak and the film was easily peeled off. Elastomer ingress is 3/4
When it exceeded, it became a film and the texture became too hard.

The stretchable knitted fabric of the present invention can be dyed, and general dip dyeing and printing can be performed. In addition, a moped elastic stretchable fabric can also be used. Furthermore,
Antibacterial performance can also be imparted by using a stretchable base cloth or knitted fabric mixed with an antibacterial agent. Further, by using a stretchable base cloth or knitted fabric that has been subjected to water repellent treatment, deodorant treatment, etc., it is possible to impart water repellent and deodorant functions.

[0018]

The stretchable knitted fabric of the present invention is excellent in stretchability, particularly stretch recovery rate due to the elastomer, and excellent in mechanical properties such as tearing and tensioning due to the knitted fabric and the like. Also, no adhesive is used when laminating. Therefore, the manufacturing process is simple, and the initial capital investment and operating cost are low.

[0019]

EXAMPLES Further details will be described in Examples. The stretchability and the like of the stretchable nonwoven fabric and the like were measured in accordance with the standards of JIS knitted fabrics and interlining nonwoven fabrics. Example 1 Nylon SD30d / 4f manufactured by Kanebo Co., Ltd. was knitted into a Tenjiku circular knitted fabric and lightly heat-set into 18 warp and 19 weft / inch. The longitudinal and lateral tear strength of this knitted fabric is 0.55k each
g, 0.52 kg, and basis weight was 50 g / m ² . The tensile elongations were 141% and 135% in the length and width, respectively.

On this knitted fabric, a polyurethane nonwoven fabric manufactured by Kanebo Co., Ltd., with a trade name of "Espancione", has a weight of 50 g / m ^2.
The width of the heat-sealed part is 0.3 mm, and the size of the orthogonal grid is 4 mm.
The corners were stacked by pressing with a metal heating embossing roller having a depth of 0.5 mm and a flat chrome-plated metal roller. The temperature of the heating roller is 170 ° C, and the nylon is laminated so that it is in contact with the heating roller, and the gauge pressure is 20 kg /
It was crimped at cm ² .

The tear strength of the stretchable knitted fabric of the present invention was 0.85 kg and 0.78 kg in the longitudinal and transverse directions, respectively. Also, 50%
The tensile elongation recovery rates were 89% and 90% in the longitudinal and lateral directions, respectively. When the cross section was photographed by SEM, polyurethane entered the knitted fabric to a thickness of 1/2 to 2/3 at the joint portion. Even after repeating 50% expansion and contraction 100 times, the knitted fabric and the nonwoven fabric did not separate. A part of the polyurethane was formed into a film at the joint portion, but most of them had a fiber shape. The texture was soft and I liked it.

When the heating temperature of the metal roller was raised to 200 ° C., the fusion of the polyurethane proceeded, and the cross section photograph exceeded 3/4 of the knitted fabric, and part of the polyurethane had entered the thickness of the knitted fabric. In this reference example, the texture became film-like and became too hard.

The heating temperature of the metal roller is 170 ° C.
However, when polyurethane and nylon were laminated in reverse so that the polyurethane was in contact with the heating roller, the polyurethane rolled up on the metal embossing roller and the operation could not be performed.

Example 2 Nylon SD5 manufactured by Kanebo Co., Ltd. was used instead of Tenjiku circular knitted fabric using Nylon SD30d / 4f manufactured by Kanebo Co., Ltd. of Example 1.
Knitted tricot using 0d / 16f, 20 lengths, 1 width
9 pieces / inch was tensioned in the vertical direction and heat set. A widthwise width was applied to create a knitted fabric with elongation. The basis weight of this knitted fabric was 82 g / m ² , and the tensile strengths in the longitudinal and transverse directions were 0.89 kg / cm and 0.78 kg / cm, respectively.
The tensile elongations were 13% and 123% in the length and width, respectively.

After that, the present invention was advanced according to Example 1.
Polyurethane had penetrated to a thickness of ⅓ to ½ in the cross section of the joined portion of the obtained stretchable knit.
Even after repeating 50% expansion and contraction 100 times, the knitted fabric and the nonwoven fabric did not separate. The tensile strength of the stretchable knitted fabric of the present invention was 1.35 kg / cm and 1.28 kg / cm in the longitudinal and transverse directions, respectively. The 50% tensile elongation recovery in the transverse direction was 90%.

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Claims (3)

[Claims] 1. A laminate comprising a thermoplastic synthetic fiber knitted fabric and an elastomeric nonwoven fabric or a knitted woven fabric, wherein an elastomer is melted at a joint portion between the two and the thermoplastic knitted fabric has a cross section of at least 1/4 or more and 3/4 or less. A stretchable knit that has penetrated to the thickness and retains its shape without melting the thermoplastic knit. 2. The stretchable knitted fabric according to claim 1, wherein the elastomer is polyurethane. 3. The bonding method is embossing.
A method for producing the elastic knitted fabric described.