JP2005264344A - Low shrinkage heat adhesive fiber and non-woven fabric by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low shrinkage heat adhesive fiber capable of easily producing a non-woven fabric without having the reduction of joined points and lack of dimensional stability caused by the shrink of the heat-adhesive fiber, and a non-woven fabric prepared by using the same. <P>SOLUTION: This low shrinkage heat adhesive fiber having a sheath/core structure consists of thermoplastic polymers, wherein, the core part has ≥60°C lower melting point than that of the sheath part, and has ≤5 & dry shrinkage at 180°C and ≤10 mm fiber length. The non-woven fabric is produced by using the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a low-shrinkable heat-bonding fiber used for bonding a base fiber in the production of a nonwoven fabric and a nonwoven fabric produced using the same.

  As a low-shrinkage heat-bonding fiber used for the production of nonwoven fabrics, particularly as a low-shrinkage heat-bonding fiber composed of a composite fiber having a core-sheath structure, for example, a low-shrinkage heat-bonding fiber manufactured at a high spinning speed is known. (Patent Document 1, Patent Document 2).

However, in such a conventional low-shrinkable heat-bonding fiber, the melting point of the adhesive component disposed in the sheath portion is low, so that when the fiber is stretched and heat-set at a high temperature, the fibers are fused with each other and shrinkage occurs. It has been difficult to produce sufficiently low thermal bonding fibers. For this reason, in the production of non-woven fabrics, when heat-bonding the base fiber and the heat-bonding fiber after mixing, the heat-bonding fiber may shrink significantly and the bonding fiber may be localized, reducing the bonding point. There was a problem that the adhesive strength was lowered and the dimensions of the nonwoven fabric were not stable.
Japanese Patent Laid-Open No. 7-3534 Japanese Patent No. 3275974

  An object of the present invention is to solve the problems in the prior art as described above, avoid a decrease in adhesion point and a decrease in adhesive strength due to shrinkage of the thermal bonding fiber, and a nonwoven fabric excellent in dimensional stability. An object of the present invention is to provide a low-shrinkage heat-bonding fiber that can be easily produced, and a nonwoven fabric produced using the same.

  In order to solve the above problems, the low shrinkable heat-bonding fiber according to the present invention is a fiber having a core-sheath structure made of a thermoplastic polymer, and the core part has a melting point of 60 ° C. or more lower than that of the sheath part, and 180 ° C. It has a dry heat shrinkage ratio of 5% or less and a fiber length of 10 mm or less.

  Moreover, the nonwoven fabric which concerns on this invention is manufactured using such a low shrinkable heat | fever adhesive fiber, and contains 3 weight% or more of this low shrinkable heat | fever adhesive fiber.

  According to the present invention, in the production of the nonwoven fabric, when the base fiber and the heat-bonding fiber are mixed and heat-bonded, only the heat-fusion component of the core component in the core-sheath structure is melted and flown to form an adhesion point. The sheath component can be left unmelted to create a network structure that connects the base fiber, and the melting point on the sheath component side can be relatively increased to enable high-temperature heat treatment, and the dry heat shrinkage rate is kept low. Therefore, it becomes possible to ensure low shrinkage as the whole heat-bonding fiber. Accordingly, it is possible to avoid a decrease in the adhesion point due to shrinkage during the production of the nonwoven fabric, and it is possible to easily produce a nonwoven fabric excellent in dimensional stability.

Hereinafter, the present invention will be described in detail together with preferred embodiments.
The low shrinkable heat-bonding fiber according to the present invention is a composite fiber having a core-sheath structure made of a thermoplastic polymer, and the melting point of the core part is 60 ° C. or more lower than the melting point of the sheath part. That is, the melting point of the sheath is relatively higher than the melting point of the core, which is 60 ° C. or higher. And the dry heat shrinkage rate in 180 degreeC of this whole composite fiber is restrained small with 5% or less, and the fiber length is cut so that it may become 10 mm or less.

Such a low shrinkable thermal bonding fiber according to the present invention is produced, for example, as follows.
For example, polyester obtained by copolymerizing 40 mol% of homopolyethylene terephthalate as a sheath component and isophthalic acid as a core component is compounded into a core-sheath type by a known composite spinning, and is spun to obtain an undrawn yarn of a composite fiber. The undrawn yarn is subjected to liquid bath drawing at a high temperature, for example, 90 ° C., which cannot be adopted when a thermal adhesive component is disposed in the sheath component, and then subjected to relaxation heat treatment at, for example, 145 ° C., and then cut into, for example, 6 mm. Since the high-temperature heat treatment can be performed on the sheath portion having a high melting point, the dry heat shrinkage at 180 ° C. can be 3%.

  As described above, the sheath component has a substantially core-sheath structure composed of a thermoplastic polymer that is not softened by high-temperature heat treatment in order to obtain the heat-bonded fiber of the present invention, so that high-temperature heat treatment is possible. Shrinkage becomes possible. In addition, by using short fibers of 10 mm or less, the thermoplastic polymer (core component) serving as a heat-bonding component melts and flows by heating when bonded to the base fiber, and increases the number of points of bonding with the base fiber. It becomes possible.

  In the present invention, only the heat fusion component of the core component of the thermoplastic polymer is melt-flowed to form an adhesion point, the sheath component is not melted, and it is necessary to create a network structure that connects the base material fibers. The object can be achieved by setting the melting point to a melting point that is at least 60 ° C. higher than the thermoplastic polymer of the core component.

  The heating temperature for heat bonding is usually at least 20 ° C. higher than the heat bonding component, and the heat bonding component is melted and flown to form an adhesion point. Therefore, if the difference between the melting point of the core component and the melting point of the thermal bonding component is less than 60 ° C., the sheath component may be softened and deformed at the time of thermal bonding, so that it may not be possible to form a network structure that connects the base material fibers.

  In the present invention, thermoforming can be performed at a high temperature within a short time by making the melting point of the sheath component 60 ° C. or more higher than the melting point of the core component. However, if the melting point is too high, it is necessary to increase the melt spinning temperature, which may cause thermal degradation of the thermal bonding component, resulting in thermal degradation, and the durability of the bonding point may be reduced. It is 100 degreeC or more in the range of ℃

  In the low shrinkable heat-bonding fiber according to the present invention, the dry heat shrinkage rate of the fiber at 180 ° C. is 5% or less, and the fiber length is 10 mm or less. By making the fiber length 10 mm or less, the base fiber and the heat-bonding fiber are mixed, and then the heat-bonding component melts and flows from both ends of the short fiber of the heat-bonding fiber at the time of heat bonding, thereby bonding to the base fiber. The number of points can be increased and the adhesive strength can be maintained. Further, since the shrinkage rate is low, the mixed fiber state can be maintained. If the fiber length is longer than 10 mm, the base fiber and the heat-bonded fiber are mixed, and then the adhesive point decreases and the adhesive strength decreases even if the heat-bonding component melts and flows from both ends of the short fiber during heat bonding. Absent. Moreover, when the dry heat shrinkage rate of the fiber at 180 ° C. is higher than 5%, wrinkles easily enter the nonwoven fabric, which may cause a defect.

  The sheath component of the low shrinkable heat-bonding fiber according to the present invention can be formed of a thermoplastic polymer and crystallized by a high-temperature heat treatment in a stretching process to reduce the shrinkage rate. If the degree of orientation cannot be maintained sufficiently, the physical properties will deteriorate, and when the base fiber and the heat-bonded fiber are spread and laminated to form a web, the heat-bonded fiber is stretched and the shrinkage ratio is increased. This is not preferable because the adhesive fibers are localized, the adhesion point shrinks, and the adhesive strength is reduced. In the present invention, the degree of orientation is sufficiently maintained by crystallization, the physical properties are good, and the form retainability is excellent.

  The heat-bonding component of the low-shrinkable heat-bonding fiber according to the present invention is preferably composed of a low-melting thermoplastic polymer that can be configured as a core component and has a melting point of at least 160 ° C. Examples of such a low-melting point thermoplastic polymer include polyethylene, polypropylene, polybutene, and the like, and copolymers thereof with ethylene and vinyl acetate. In the case of polyester, polybutylene terephthalate or ethylene isophthalate. Polyethylene terephthalate copolymer, polybutylene terephthalate copolymer, polyethylene naphthalate copolymer, polyhexamethylene terephthalate copolymer containing 10 to 60 mol% of structural units such as butylene isophthalate and hexamethylene terephthalate. It is done.

  The sheath component constituting the low-shrinkage thermobonding fiber according to the present invention is preferably a thermoplastic polymer having a melting point of at least 220 ° C. and capable of orientational crystallization by high-temperature heat treatment. Such thermoplastic polymers include olefins, nylons, polyesters, and the like, and are not particularly limited as long as they can be combined with the core component, but when the core component is a polyester, the sheath component is also preferably polyester. Examples thereof include polyesters having at least 90 mol% of repeating units such as polybutylene terephthalate, polyethylene terephthalate, and polyethylene naphthalate.

  Therefore, as a preferable form of the low shrinkable heat-bonding fiber according to the present invention, for example, 10 to 60 mol% of the acid component of the polyester contained in the core is isophthalic acid, and the polyester contained in the sheath is polyethylene terephthalate. The form which is can be mentioned. Moreover, as shown in the below-mentioned Example, it is preferable that the weight ratio of a core component and a sheath component exists in the range of core / sheath = 5 / 5-8 / 2.

  As a method for producing the nonwoven fabric, any conventionally known method may be used. However, since the low shrinkable heat-bonding fiber according to the present invention has a short fiber length, a papermaking method is particularly preferable.

  For example, in manufacturing by papermaking, it is necessary to first disaggregate the fibers. It is preferable to uniformly disperse the dispersant in the aqueous solution before the disaggregation in advance to promote the disaggregation, and it is effective to prevent the entanglement after the disaggregation. Then, stirring is performed.

  As for stirring, it is preferable to perform stirring for disaggregation promptly in order to prevent the fibers from being tangled. Next, when the disaggregated fibers are dispersed, in order to prevent the fibers from being entangled, the dispersion of the fibers is maintained and the stirring is performed as gently as possible. If a slurry that has been disaggregated in advance is necessary, water is further added to lower the concentration, and then a viscosity is quickly added to maintain dispersion. In this way, a uniformly dispersed slurry is prepared. The slurry thus prepared can be made into a preferred form of web. This web may be continuously three-dimensionally entangled with a high-pressure water stream. Web bonding is performed by applying heat to bond the fibers of the web and increase the strength of the nonwoven fabric. As the dryer for applying heat, a Yankee dryer, an air dryer, a multi-cylinder cylinder dryer, or the like can be used. Then, a nonwoven fabric is wound up with a winder.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the measurement and evaluation of each physical property value in the examples were performed by the following methods.
(1) Melting point (softening point)
A differential scanning calorimeter DSC-7 manufactured by Perkin Elmer was used, and the temperature was increased at a rate of 20 ° C./min. The softening point of the isophthalic acid copolyester having no clear melting point was measured.

(2) Fiber length and dry heat shrinkage rate A single fiber is affixed to a lubricant paper, and the original length (A) is measured with a prescribed weight of 2 g. Then, after performing heat processing for 20 minutes at 180 degreeC with a hot air dryer, processing length (B) is measured. The dry heat shrinkage is obtained by the following equation.
Dry heat shrinkage (%) = [((A) − (B)) / (A)] × 100
(A): Fiber length (B): Treatment length (fiber length after heat treatment)
(3) Adhesive strength 40% heat bonded fiber and single-fiber fineness of 6.6 decitex obtained by conventional methods, hollow cross-section yarn (polyethylene terephthalate) with a fiber length of 51 mm is mixed by air opening to heat-treat the web Then, it was cut into strips having a thickness of 5 mm, a width of 5 cm, and a length of 15 cm, and the strength was measured with a Tensilon tensile tester.

Example 1
A composite fiber having a core-sheath structure by a known composite spinning, in which a polyester having a softening point of 110 ° C. copolymerized with isophthalic acid in the core and a homopolyethylene terephthalate having a melting point of 220 ° C. in the sheath are arranged in a weight ratio of 60/40 Was spun into. The obtained undrawn yarn was drawn at 95 ° C. by liquid bath drawing and then subjected to relaxation heat treatment at 145 ° C. and cut into a fiber length of 8 mm. The short fiber was used to make a nonwoven fabric by the above method, and the adhesive strength was measured. The results are shown in Table 1. The nonwoven fabric had no wrinkles and the surface finish was beautiful.

Example 2
A composite fiber having a core-sheath structure by a known composite spinning, in which a polyester having a softening point of 150 ° C. copolymerized with isophthalic acid is disposed in the core and homopolyethylene terephthalate having a melting point of 230 ° C. is disposed in the sheath at a weight ratio of 70/30 Was spun into. The obtained undrawn yarn was drawn at 90 ° C. by liquid bath drawing and then subjected to relaxation heat treatment at 150 ° C. to cut the fiber length to 5 mm. The short fiber was used to make a nonwoven fabric by the above method, and the adhesive strength was measured. The results are shown in Table 1. The nonwoven fabric had no wrinkles and the surface finish was beautiful.

Example 3
A composite fiber having a core-sheath structure by a known composite spinning, in which a polyester having a softening point of 160 ° C. copolymerized with isophthalic acid in the core and a homopolyethylene terephthalate having a melting point of 230 ° C. in the sheath are arranged at a weight ratio of 50/50 Was spun into. The obtained undrawn yarn was drawn at 95 ° C. by liquid bath drawing and then subjected to relaxation heat treatment at 160 ° C. and cut into a fiber length of 4 mm. The short fiber was used to make a nonwoven fabric by the above method, and the adhesive strength was measured. The results are shown in Table 1. The nonwoven fabric had no wrinkles and the surface finish was beautiful.

Comparative Example 1
A composite fiber having a core-sheath structure by a known composite spinning, in which a polyester having a softening point of 110 ° C. obtained by copolymerizing isophthalic acid in a sheath portion and homopolyethylene terephthalate having a melting point of 220 ° C. in a core portion is arranged at a weight ratio of 50/50 Was spun into. When the obtained undrawn yarn was drawn at 90 ° C. by liquid bath drawing and then subjected to relaxation heat treatment at 145 ° C., the single fibers were bonded to each other and the tow became hard and could not be cut.

Comparative Example 2
A composite fiber having a core-sheath structure by a known composite spinning, in which a polyester having a softening point of 110 ° C. copolymerized with isophthalic acid in the core and a homopolyethylene terephthalate having a melting point of 230 ° C. in the sheath are arranged in a weight ratio of 50/50 Was spun into. The obtained undrawn yarn was drawn at 60 ° C. by liquid bath drawing and then subjected to relaxation heat treatment at 55 ° C. to cut the fiber length to 8 mm. The short fiber was used to make a nonwoven fabric by the above method, and the adhesive strength was measured. The results are shown in Table 1. The shrinkage ratio was higher than that of Example 1, and the adhesive strength was low. The nonwoven fabric was wrinkled and uneven on the surface. Neither the adhesive strength nor the surface finish of the nonwoven fabric was satisfactory.

Comparative Example 3
A composite fiber having a core-sheath structure by a known composite spinning, in which a polyester having a softening point of 110 ° C. copolymerized with isophthalic acid in the core and a homopolyethylene terephthalate having a melting point of 230 ° C. in the sheath are arranged in a weight ratio of 50/50 Was spun into. The obtained undrawn yarn was drawn at 90 ° C. by liquid bath drawing and then subjected to relaxation heat treatment at 145 ° C. and cut into a fiber length of 24 mm. The short fiber was used to make a nonwoven fabric by the above method, and the adhesive strength was measured. The results are shown in Table 1. The adhesive strength was lower than in Example 1 and was not satisfactory. However, the surface of the nonwoven fabric was clean.

  The low shrinkable heat-bonded fiber of the present invention can be used to avoid the reduction of the adhesion point due to shrinkage of the heat-bonded fiber and to easily produce a nonwoven fabric excellent in dimensional stability. It is not limited to.

Claims (5)

  It is a fiber having a core-sheath structure made of a thermoplastic polymer, the core has a melting point of 60 ° C. or more lower than that of the sheath, the dry heat shrinkage at 180 ° C. is 5% or less, and the fiber length is 10 mm or less. A low shrinkable heat-bonding fiber.   The low shrinkable heat-bonding fiber according to claim 1, comprising a polyester polymer.   The low shrinkable heat-bonding fiber according to claim 2, wherein 10 to 60 mol% of the acid component of the polyester contained in the core is isophthalic acid, and the polyester contained in the sheath is polyethylene terephthalate.   The low shrinkable heat-bonding fiber according to any one of claims 1 to 3, wherein a weight ratio of the core component to the sheath component is core / sheath = 5/5 to 8/2.   A non-woven fabric comprising 3% by weight or more of the low shrinkable heat-bonding fiber according to any one of claims 1 to 4.