JP7298880B2 - Method for producing patterned nonwoven fabric with less fuzz - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a patterned nonwoven fabric having an arbitrary pattern formed on the surface thereof and having less fuzz.

Conventionally, a fiber web formed by accumulating thermoplastic fibers with a circular cross section is conveyed to an embossing type thermocompression bonding device, passed between a heated uneven roll and a smooth roll, and the thermoplastic fibers are interposed between the thermoplastic fibers at the convex portions of the uneven roll. are known. In such a nonwoven fabric, the fibers are strongly bonded to each other at the crimped portion, and the crimped portion is less fuzzy (Patent Document 1, paragraph 0004). However, although there is little fluffing at the crimped portion, fluffing tends to occur at the non-crimped portion or at the boundary between the non-crimped portion and the crimped portion. This is because thermoplastic fibers having a circular cross section are exposed on the front and back surfaces of the non-crimped portion, so that the non-crimped portion has an uneven, non-smooth surface with high frictional resistance. In addition, the portion pressed by the projections of the uneven roll becomes dented, and this portion becomes a pattern, but it is not possible to attach any pattern. This is because the fibers are bonded to each other at the recessed portions, so that the strength of the non-woven fabric is reduced if a striped pattern with intervals or a grid pattern with wide intervals is formed.

JP-A-2001-355176

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a patterned nonwoven fabric which has less fluffing over the entire nonwoven fabric and which allows arbitrary patterning by recesses.

The present invention solves the above problems by patterning a fibrous web made of thermoplastic fibers having a flat cross section through a specific process and then using an embossing thermocompression bonding apparatus. That is, the present invention provides a first step of randomly accumulating thermoplastic fibers having a flat cross section and a ratio of the minor axis to the major axis of 1:3 or more to produce a fibrous web, wherein the fibrous web is , between a pair of heating rolls provided with a clearance to bond the thermoplastic fibers present in the front and back layers of the fibrous web, and to bond the thermoplastic fibers present in the intermediate layer of the fibrous web. a second step of producing a fibrous fleece without stretching, a third step of producing a nonwoven fabric by applying a resin binder over the entire thickness direction of the fibrous fleece and bonding the thermoplastic fibers to each other, and A fourth step of passing the nonwoven fabric between a heated uneven roll and a non-heated smooth roll to form dents in portions of the nonwoven fabric that are in contact with the convex portions of the heated uneven roll to form a pattern by the dents. The present invention relates to a method for producing a patterned nonwoven fabric characterized by comprising:

The first step is to produce a fiber web by randomly accumulating thermoplastic fibers having a flat cross section and having a minor axis to major axis ratio of 1:3 or more. Fibers with a flattened cross-section are typically those with an elliptical cross-section. As for the degree of flattening, the ratio of the minor axis to the major axis is 1:3 or more. If the ratio of the minor axis to the major axis is less than 1:3, fluffing tends to occur over the entire nonwoven fabric. As the thermoplastic fiber, a conventionally known one is adopted, and polyethylene terephthalate fiber, polyolefin fiber, polyamide fiber, or the like is used. Further, the thermoplastic fiber may be a core-sheath type conjugate fiber or a side-by-side type conjugate fiber. The fibers may be short fibers or long fibers, but long fibers are preferably used in order to obtain a high-strength nonwoven fabric. The fineness of thermoplastic fibers is about 2.2 to 5.5 decitex. If the fineness is less than 2.2 decitex, the strength of the resulting nonwoven fabric tends to decrease. If the fineness exceeds 5.5 decitex, it is difficult to soften the fiber by simply contacting it with the heating rolls, and it tends to be difficult to bond the fibers on the front and back surfaces. As a method for randomly stacking thermoplastic fibers, in the case of long fibers, the melt-spun fibers may be opened by a known method and stacked on a moving carrier. In the case of short fibers, the fibers may be opened by a card or the like, and then accumulated on a moving carrier.

The second step is a step of passing the fibrous web obtained in the first step between a pair of heating rolls provided with a clearance to produce a fibrous fleece. In the second step, the thermoplastic fibers existing only in the front and back layers of the fibrous web are bonded to each other, and the thermoplastic fibers existing in the intermediate layer of the fibrous web are substantially not bonded to each other. By this method, a flexible fiber fleece is obtained in which thermoplastic fibers having a flat cross section are lodged in the plane direction on the front and back surfaces of the fiber fleece. That is, a fiber fleece having front and back surfaces formed by the thermoplastic fibers lodged in the direction perpendicular to the fiber axis can be obtained. A clearance (gap) between the pair of heating rolls is about 0.05 to 0.2 mm. If the clearance is less than 0.05 mm, not only the front and back layers of the fibrous web but also the thermoplastic fibers existing in the intermediate layer of the fibrous web may be bonded. If the clearance exceeds 0.2 mm, the thickness of the fibrous web is about 0.2 to 0.4 mm. It becomes difficult to bond between plastic fibers. As the pair of heating rolls, for example, a combination of smooth rolls or a combination of an uneven roll and a smooth roll is adopted. The surface temperature of the heating roll is appropriately determined according to the type of thermoplastic fiber used. Specifically, the temperature is set to such an extent that only the thermoplastic fibers present in the front and back layers are bonded to each other, and the thermoplastic fibers present in the intermediate layer are not substantially bonded to each other. For example, in the case of polyethylene terephthalate fiber, it is preferable to set the surface temperature of the heating roll to about 230 to 240.degree. If the surface temperature is less than 230°C, the polyethylene terephthalate fibers are less likely to soften, and the fibers present in the front and back layers are less likely to bond with each other. Moreover, if the surface temperature exceeds 240° C., not only the front and back layers of the fibrous web but also the polyethylene terephthalate fibers existing in the intermediate layer of the fibrous web may be bonded together, resulting in a decrease in flexibility of the fibrous fleece.

The third step is a step of applying a resin binder over the entire thickness direction of the fiber fleece obtained in the second step, and bonding the thermoplastic fibers with the resin binder to produce a nonwoven fabric. . As the resin binder, a known resin binder such as an acrylic binder, a urethane binder, an NBR binder or an SBR binder is used. Among these binders, it is preferable to employ an acrylic binder that is soft and has excellent elasticity. This is to maintain the flexibility of the fiber fleece. As a method of applying the resin binder over the entire thickness direction of the fiber fleece, a method of immersing the fiber fleece in a dispersion liquid in which the resin binder is dispersed is generally used. Further, by spraying the dispersion liquid toward the surface of the fiber fleece and sucking it from the back surface, the resin binder can be applied over the entire thickness direction of the fiber fleece. Furthermore, the resin binder can be applied over the entire thickness of the fiber fleece by allowing the dispersion to remain between a pair of rolls and passing the fiber fleece between these rolls. As described above, the fiber fleece is impregnated with the dispersion liquid, and then dried and/or cured to bond the thermoplastic fibers with the resin binder to obtain a nonwoven fabric.

The fourth step is a step of passing the nonwoven fabric obtained in the third step between a heated uneven roll and a non-heated smooth roll to form a pattern with depressions in the nonwoven fabric to produce a patterned nonwoven fabric. This process also promotes lodging of the thermoplastic fibers having flat cross sections. It is preferable that no clearance is provided between the heated uneven roll and the non-heated smooth roll. When a clearance is provided, there is a tendency that it becomes difficult to form a handle due to the depression. The recessed portion of the handle has a higher fiber density than the other portions due to the recessed portion. Therefore, the pattern is formed by the recesses and the high fiber density. In addition, the bonding between the thermoplastic fibers by thermal adhesion is progressing at the recessed portions, so that a high-strength patterned nonwoven fabric can be obtained. The surface temperature of the uneven heating roll is preferably slightly lower than the surface temperature of the heating roll used in the second step. Therefore, when polyethylene terephthalate fiber is used as the thermoplastic fiber, it is about 225 to 235°C. If the surface temperature of the heated uneven roll is too low, it tends to be difficult to form a pattern with depressions. On the other hand, if the surface temperature of the heated uneven roll is too high, the thermal adhesion between the thermoplastic fibers of the front and back layers will progress, and the resulting patterned nonwoven fabric will tend to be rigid. Although the shape of the protrusions on the surface of the uneven heating roll is arbitrary, linear shapes are preferred. For example, the convex portions on the surface of the uneven heating roll are provided in a spiral shape, a plurality of convex portions are provided in a ring shape in parallel, or a plurality of linear convex portions are provided in parallel in the axial direction. You can adopt what you have. In this case, the obtained patterned nonwoven fabric has linear recesses, and has a diagonal stripe pattern, a vertical stripe pattern, or a horizontal stripe pattern. The uneven heated roll is generally made of metal, and the non-heated smooth roll is generally made of rubber, fiber or resin.

After the fourth step, optional steps can be added as desired. For example, a process of dyeing, textile printing or printing, a lamination process of laminating other layers such as paper or film, or a coating process of forming a resin layer by applying a resin to the front or back surface can be added. The obtained patterned nonwoven fabric can be used for any purpose. For example, it can be used as wallpaper, filter material, packaging material, light shielding material for agriculture, curtain, blind, car ceiling material, car sunshade, and the like.

In the patterned nonwoven fabric obtained by the method according to the present invention, in the second step, the thermoplastic fibers having a flat cross section in the fiber web are lodged in the plane direction, and in the third step, the resin binder is is imparted, and the flat surfaces of the thermoplastic fibers are closely bonded to each other. That is, since the thermoplastic fibers are surface-bonded to each other, the bonding between the fibers is stronger than when the thermoplastic fibers having a circular cross section are point-bonded or line-bonded to each other. Therefore, even if the obtained patterned nonwoven fabric has a high basis weight or bulkiness, the effect is that peeling in the thickness direction is less likely to occur. In addition, the lodging state of the thermoplastic fibers with a flat cross section progresses in the subsequent fourth step, and the front and back surfaces of the obtained patterned nonwoven fabric are smooth and have low frictional resistance, and the effect that fluffing does not easily occur. play. Furthermore, in the method according to the present invention, after obtaining a strong nonwoven fabric in which the thermoplastic fibers that are the constituent fibers are bonded, in the fourth step, the nonwoven fabric is passed between the heated uneven roll and the non-heated smooth roll to form dents. be. That is, since the fourth step is mainly to apply the pattern by denting, there is an effect that arbitrary patterning is possible.

Example 1
Using a spinneret with flat spinning holes, polyethylene terephthalate having a melting point of 255° C. is melt-spun to obtain filaments having a fineness of 3.3 decitex and an elliptical cross-section (short diameter:long diameter=1:4). At the same time, long fibers were randomly accumulated on a conveyor to obtain a fiber web with a basis weight of 90 g/m ² . This fiber web was passed between a pair of steel heating rolls heated to a surface temperature of 235° C. (clearance of about 0.1 mm) to obtain a fiber fleece. This fiber fleece is immersed in an acrylic emulsion (manufactured by DIC, trade name "Boncoat"), squeezed with a mangle roll, dried at about 100°C, and then heat-treated at about 150°C to harden the acrylic binder. to obtain a nonwoven fabric having a basis weight of 100 g/m ² . This nonwoven fabric was passed between a heated uneven steel roll heated to a surface temperature of 230° C. and an unheated resin roll to obtain a patterned nonwoven fabric. The projections of the uneven heating roll are provided in a spiral shape, and no clearance is provided between the uneven heating roll and the resin roll. The obtained patterned nonwoven fabric had a clear oblique stripe pattern.

Example 2
A patterned nonwoven fabric was obtained in the same manner as in Example 1, except that a heated uneven roll having a plurality of linear projections provided on the peripheral surface of the roll perpendicular to the axial direction was used. This patterned nonwoven fabric had a clear vertical stripe pattern.

Example 3
A patterned nonwoven fabric was obtained in the same manner as in Example 1, except that the basis weight of the fibrous web was 70 g/m ² .

Example 4
A patterned nonwoven fabric was obtained in the same manner as in Example 3, except that a heated uneven roll having leather-like protrusions on the peripheral surface of the roll was used.

Example 5
A patterned nonwoven fabric was obtained in the same manner as in Example 1, except that the basis weight of the fibrous web was 50 g/m ² .

Example 6
A patterned nonwoven fabric was obtained in the same manner as in Example 5, except that the fineness of the polyethylene terephthalate long fibers was 4.4 decitex.

Comparative example 1
Polyethylene terephthalate with a melting point of 255°C is melt-spun using a spinneret with circular spinning holes to obtain long fibers with a fineness of 3.3 decitex, and the long fibers are randomly accumulated on a conveyor to A fibrous web of 50 g/m ² with a thickness of about 0.2 mm under no load was obtained. This fiber web is passed between a heated embossing roll (a roll engraved with a lattice pattern on the surface) heated to a surface temperature of 230 ° C. and a heated smooth steel roll heated to a surface temperature of 230 ° C. (without clearance), A nonwoven fabric was obtained in which the long fibers were thermally bonded to each other over the entire thickness direction of the fibrous web. This nonwoven fabric was passed between a heated uneven steel roll heated to a surface temperature of 230° C. and an unheated resin roll to obtain a patterned nonwoven fabric. The projections of the uneven heating roll are provided in a spiral shape, and no clearance is provided between the uneven heating roll and the resin roll.

Comparative example 2
Polyethylene terephthalate with a melting point of 255°C is used as a core component, polyester copolymer with a melting point of 230°C is used as a sheath component, and composite melt spinning is performed using a spinneret with a circular spinning hole to obtain a core-sheath composite type with a fineness of 3.3 decitex. Long fibers were obtained and randomly accumulated on a conveyor to obtain a fiber web having a basis weight of 50 g/m ² (thickness under no load of about 0.2 mm). This fiber web is passed between a heated embossing roll (a roll engraved with a lattice pattern on the surface) heated to a surface temperature of 205 ° C. and a heated smooth steel roll heated to a surface temperature of 205 ° C. (without clearance), A nonwoven fabric was obtained in which the long fibers were thermally bonded to each other by fusion bonding of the sheath component over the entire thickness direction of the fiber web. This nonwoven fabric was passed between a heated uneven steel roll heated to a surface temperature of 230° C. and an unheated resin roll to obtain a patterned nonwoven fabric. The projections of the uneven heating roll are provided in a spiral shape, and no clearance is provided between the uneven heating roll and the resin roll.

The patterned nonwoven fabrics obtained in Examples 1 to 6 had less fluffing throughout and had excellent mechanical properties such as tensile strength as compared to the patterned nonwoven fabrics obtained in Comparative Examples 1 and 2. Met.

Claims (6)

A first step of randomly accumulating thermoplastic fibers having a flat cross section and a minor axis to major axis ratio of 1:3 or more to produce a fiber web;
The fibrous web is passed between a pair of heating rolls provided with a clearance to bond the thermoplastic fibers present in the front and back layers of the fibrous web, and the thermoplastic fibers present in the intermediate layer of the fibrous web. A second step of producing a fiber fleece without bonding between each other,
a third step of applying a resin binder over the entire thickness direction of the fiber fleece to bind the thermoplastic fibers together to produce a nonwoven fabric;
A fourth step of passing the nonwoven fabric between a heated uneven roll and a non-heated smooth roll to form dents in portions of the nonwoven fabric that are in contact with the convex portions of the heated uneven roll to form a pattern by the dents. A method for producing a patterned nonwoven fabric with less fluffing, characterized by comprising: The method for producing a patterned nonwoven fabric with less fuzz according to claim 1, wherein the clearance is 0.05 to 0.2 mm. 2. The method for producing a patterned nonwoven fabric with less fuzz according to claim 1, wherein the resin binder is an acrylic binder. 4. The patterned non-woven fabric with less fluffing according to claim 3, wherein the fiber fleece is immersed in a dispersion containing an acrylic binder, and then the acrylic binder is cured to bond the thermoplastic fibers to each other to obtain a nonwoven fabric. A method for manufacturing a nonwoven fabric. 2. The method for producing a patterned nonwoven fabric with less fuzz according to claim 1, wherein the recessed portions have a higher fiber density than other portions. 2. The method for producing a patterned nonwoven fabric with less fluffing according to claim 1, wherein the dents are linearly formed.