JP3113124B2 - Method for manufacturing ultrafine fiber web - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ultrafine fiber web, and more particularly to a method for producing an ultrafine fiber web having excellent quality by dividing splittable conjugate fibers into split fibrils. .

[0002]

2. Description of the Related Art In recent years, technical development for producing ultrafine fiber webs has rapidly progressed, and these webs are used in large quantities in high-grade artificial leather and the like. There are a wide variety of methods for producing ultrafine fiber webs, starting from sea-island composite fibers or mixed sea-island spun fibers, ultrafine fibers drawn by ultra-high magnification using the superdraw phenomenon of polyester, or ultrafine fibers obtained by high-speed spinning. There is a method starting from fiber, etc.
Each has its pros and cons. The method starting from sea-island type fibers is a method in which a web is made from short fibers having relatively large fineness, and after various processings, the sea component is eluted and removed to leave island components (extra fine fibers). Since the method usually requires the use of a solvent for elution of sea components, it requires a large amount of energy because the solvent must be recovered, and the equipment for recovery is also large. In addition, it is necessary to treat the eluted and removed sea component, and in most cases, 50% or more of the starting sea-island type fiber is eluted and removed and becomes a target for treatment. is there. Also, ultra-fine short fibers utilizing the superdraw phenomenon of polyester and ultra-fine short fibers produced by the high-speed spinning method have a very low card productivity and the quality of the obtained ultra-fine fiber web tends to be inferior. Currently, almost no production is performed.

On the other hand, a technique for obtaining an ultrafine fiber web from splittable conjugate fibers, which has been developed from the conjugate spinning technique, has been rapidly progressing recently, and has begun to be used as a nonwoven fabric for high-grade artificial leather. In this method, components which are incompatible with each other are made into splittable conjugate fibers, mechanical crimping is applied after stretching, and the obtained splittable conjugate short fibers are carded into a web, and then needle punched, high-pressure liquid This is a method in which a composite short fiber is divided into fibrils by physical impact such as flow to obtain a randomly entangled nonwoven fabric (for example, Japanese Patent Publication No. 3-1426). However, in this method, due to mechanical crimping after stretching, tens of percent of the composite staple fiber is divided into fibrillated fibers, so that the card passing property is poor and the nep tends to occur frequently in the web, and There is a problem that the quality deteriorates. Conversely, if split fibrillation is less likely to occur at the time of mechanical crimping, card passability is improved, but there is a problem that split fibrillation is less likely to occur due to the impact of needle punch, high-pressure liquid flow, or the like.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional method, to improve the cardability of the splittable conjugate fiber, and to split the splittable composite fiber by physical impact such as a needle punch or a high-pressure liquid flow. An object of the present invention is to provide a method for producing an ultrafine fiber web having excellent quality by fibrillation.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method for producing a high-quality ultrafine fiber web in consideration of the balance between the card passing property and the dividing property of the splittable conjugate fiber. It has been reached.

That is, according to the present invention: In a method of manufacturing a microfiber web by applying a splittable conjugate fiber composed of mutually incompatible components to a card and then subjecting the splittable conjugate fiber to fibrillation by physical impact to produce a microfiber web, when the splittable conjugate fiber is melt spun, Compatible components are distributed unevenly with respect to the cross section of the fiber, and after stretching, a relaxation heat treatment is performed without imparting a mechanical crimp to develop a three-dimensional crimp of 5 pieces / 25 mm or more, and then applied to a card. Of producing ultrafine fiber web. 2. The number of segments of one component of the splittable conjugate fiber is 4 to
48. The method for producing a microfiber web according to the above item 1, wherein the web is 48. 3. At least one component of the splittable conjugate fiber forms split fibrillated single fibers of at least two or more types after splitting, and has a thickness ratio K (denier ratio to the finest single fiber) of 1. 3. The method for producing an ultrafine fiber web according to the above 1 or 2, which is in the range of 3 to 6. Is provided.

The combination of the polymer components constituting the splittable conjugate fiber in the present invention is typically polyester and nylon, polyester and polypropylene, polyester and polyethylene, nylon and polypropylene, and nylon and polyethylene. The combination is not limited to, and any combination of polymer components is possible as long as they are incompatible with each other.

The splittable conjugate fiber used in the method of the present invention is, specifically, as shown in FIGS.
It has a cross-sectional shape in which two or more incompatible thermoplastic polymers (first component A and second component B) or non-adhesive thermoplastic polymers having no mutual adhesion are alternately arranged. It is important that the distribution is unevenly distributed with respect to the cross section. If the distribution of each component is symmetric as shown in FIG. 1 (c), it becomes difficult to impart a three-dimensional crimp even after the relaxation heat treatment after stretching, and the card passing property is deteriorated as it is. The object of the present invention cannot be achieved because the web is easily broken.

Preferably, each component constituting the splittable conjugate fiber is divided into 4 to 48 segments, and at least one component has at least two or more different thicknesses after splitting. It is preferable that the split fibrillated single fiber is formed and that the thickness ratio K (denier ratio with respect to the finest single fiber) is in the range of 1.3 to 6.0 in order to develop a sufficient three-dimensional crimp. . When the thickness ratio is less than 1.3, it is difficult to impart a bias to the distribution of each component in the cross section of the fiber, the three-dimensional crimping ability is reduced, and the frequency of occurrence of web breakage during the carding process is increased. Tend. On the other hand, when it exceeds 6.0, the balance of viscosity is lost during melt spinning, so that kneeling is liable to occur, and it becomes difficult to perform stable spinning.

In addition to the above requirements, it is important that the splittable conjugate fiber used in the present invention has substantially no mechanical crimp and has only three-dimensional crimp. When mechanical crimping is applied, it is not preferable because fibrillation is partially divided due to mechanical stress acting during the processing, and NEP frequently occurs in a web obtained by reducing card passing property. The number of three-dimensional crimps is required to be 5 pieces / 25 mm or more, and if it is less than 5 pieces / 25 mm, the card passing property is reduced and the web is liable to be cut.

The fineness of the splittable conjugate fiber is about 1 to 30 denier, preferably about 1 to 5 denier. When the denier is less than 1 denier, the spinnability is remarkably deteriorated. Spots such as cloudy tend to occur. On the other hand, when it exceeds 30 denier, the spinnability is good, but the fiber diameter is too large, so that cotton loss in the carding process increases and spots such as cloudy tend to occur.

The denier of the split fibrillated single fiber formed by split fibrillation is preferably as thin as possible within a range satisfying the requirement of the thickness ratio (area ratio) between the segments. .8 denier or less,
Preferably, it is 0.5 denier or less. If it exceeds 0.8, the feel tends to be hard.

In order to produce a splittable conjugate fiber having such a three-dimensional crimp, for example, as shown in FIG. 2, two or more different hole diameters are formed in a cap upper plate through which one component A flows into the other component B. Using a spinneret for splittable conjugate fibers arranged asymmetrically, melt-spinning is performed according to a conventional method, and the obtained undrawn yarn is usually 100 ° C or lower, preferably 60 to 90 ° C.
At a temperature of 70% or more of the maximum stretching ratio. Next, when the stretched yarn is subjected to a relaxation heat treatment at a temperature of 90 ° C. or more without substantially imparting mechanical crimp, a three-dimensional crimp is developed. The upper limit of the heat treatment temperature is preferably set to the melting point of the polymer component on the low melting point side of the splittable conjugate fiber minus 10 ° C.

By the relaxation heat treatment, a three-dimensional crimp based on the cross-sectional anisotropy (component distribution anisotropy) is developed, and 5 pieces / 25 mm
A splittable conjugate fiber having the above three-dimensional crimp number is obtained.
After a three-dimensional crimp is developed by relaxation heat treatment, it is cut into short fibers. The short fiber preferably has a fiber length of usually 20 to 80 mm. If the fiber length is too short, the card passing property is inferior and the web tends to break. Conversely, if the fiber length is too long, quality problems such as cutting of some fibril fibers divided by the card or occurrence of neps are likely to occur.

It is to be noted that, prior to the relaxation heat treatment, the fiber can be opened by pressurization or the like or cut into short fibers to enhance the crimp development.

The physical impact imparting means used for dividing fibrillated split conjugate short fibers formed into a card web may include a needle punch, a high-pressure liquid flow, and the like. Water or hot water is suitable as the liquid in the case of using a high-pressure liquid stream because it is easy to handle.

If the basis weight at the time of needle punching is too high, needle breakage occurs frequently. On the other hand, if the basis weight is too low, split fibrillation or entanglement hardly occurs.
It is preferably in the range of g / m ² . The number of punch needles is not particularly limited, but may be 200 due to the strength of the obtained nonwoven fabric.
It is desirable to punch more than book / cm ² .

On the other hand, the pressure applied to the high-pressure liquid flow (injection pressure)
Depends on the structure of the web, the ease with which the splittable conjugate fiber is divided into fibrils, the fineness, etc.
00 kg / cm ² , preferably 50 to 150 kg / cm
² Further, by increasing the number of treatments, the degree of split fibrillation and confounding can be increased.

The injection nozzle has a hole diameter of 0.01 to 0.5 m.
It is preferable that ones having a length of about m are arranged in one row or several rows in a horizontally long manner. The interval between the holes is arbitrary as long as the divided fibrillation and entanglement of the fibers can be performed.
Usually, a range of 0.2 to 5.0 mm is adopted.

The fine fibrous web thus divided into fibrillated fibers has a random entanglement, a small amount of neps and a high quality, and can be used for applications such as high-grade artificial leather and wiping cloth.

[0021]

According to the method of the present invention, since the splittable conjugate staple fiber has not been subjected to the mechanical crimping step, the degree of split fibrillation is low, and therefore, it can easily pass through the card by a conventional method, and can be formed with a low nep. A high quality web is obtained. Also,
Since partial fibrillation of some fibers is promoted when passing through the card, the resulting web can be relatively easily fibrillated by applying a physical impact such as a needle punch or a high-pressure liquid flow.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Polyethylene terephthalate having an intrinsic viscosity of 0.64 measured in o-chlorophenol at 35 ° C. was used as component A, and nylon-6 having an intrinsic viscosity of 1.34 measured in m-cresol at 35 ° C. was used. On the other hand, as the component B, at a spinning temperature of 280 ° C. and a spinning speed of 1100 m / min, a splittable conjugate fiber having a cross-sectional shape shown in FIG. 1 was obtained. At this time, the composite ratio of both components was 50/50 (weight ratio), the number of each segment was 8 (16 in total), and the thickness ratio of the segments was as shown in Table 1. The obtained undrawn yarn is 70
After stretching 3.0 times in hot water at a temperature of 140 ° C., it was subjected to relaxation heat treatment in an atmosphere at 140 ° C., and then cut into a fiber length of 51 mm.
Table 1 shows the physical properties of the obtained short fibers.

The obtained short fiber is put on a card and put on a web.
None, card web 300g / m ^TwoLaminated so that
And with the 40th needle, 700 needles / cm^TwoNeedle in proportion
Punched for fibrillation and entanglement
Was.

The card passing property when each short fiber is put on a card, the ratio of raw fibres, the split fibrillation of the ultrafine fiber web after passing the card and after the needle punching, and the number of neps in the web are as shown in Table 1. there were. The ratio of split fibrillation is the ratio of complete or partial fibrillation determined by an optical microscope.

For comparison, Table 1 shows the results obtained in the same manner as described above for the case where each component had a segment thickness ratio of 1, the case where each component had a symmetric distribution, and the case where a mechanical crimp was applied.
Shown along with.

[0027]

[Table 1]

The evaluation in the table was based on the following criteria. Spinning condition ○: Good △: Slightly unstable ×: Spinning frequently occurs and spinning is not possible Card passability ○: Almost no cotton or nep △: Some cotton or nep ×: Many cotton or nep

[0029]

The ultrafine fiber web obtained by the method of the present invention uses a splittable conjugate short fiber having a three-dimensional crimp that has not progressed to split fibrillation. The number of NEPs contained in the fiber web is small, and the quality is high. Therefore, a nonwoven fabric suitable for high-grade artificial leather, wiping cloth, and the like can be provided.

[Brief description of the drawings]

1 (a) and 1 (b) show examples of a cross section of a splittable conjugate fiber used in the present invention. (C) is the components A and B
Fig. 1 shows an example of a splittable conjugate fiber having no uneven distribution.

FIG. 2 is a schematic view showing an example of a spinneret for producing a splittable conjugate fiber used in the present invention.

[Explanation of symbols]

 1 Largest segment of A component 2 Minimum segment of A component 3 B component 4 Spinneret upper plate 5 Spinneret lower plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-213553 (JP, A) JP-A-4-257357 (JP, A) JP-A-5-156557 (JP, A) 116467 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) D04H 1/00-18/00 D01D 5/30-5/36 D01F 8/00-8/18

Claims (3)

(57) [Claims] 1. A method for producing an ultrafine fiber web, comprising applying a splittable conjugate fiber composed of mutually incompatible components to a card and then subjecting the splittable conjugate fiber to fibrillation by physical impact to produce a fine fiber web.
In melt-spinning the splittable conjugate fiber, the mutually incompatible components are distributed unevenly with respect to the cross section of the fiber, and after stretching, heat-relaxed without imparting mechanical crimping to 5/2.
A method for producing an ultrafine fiber web, which comprises applying a three-dimensional crimp of 5 mm or more to a card after developing it. 2. The method according to claim 1, wherein the number of segments of one component of the splittable conjugate fiber is from 4 to 48. 3. At least one component of the splittable conjugate fiber forms split fibrillated single fibers having at least two or more types of thickness after splitting, and has a thickness ratio K (denier to finest single fiber). 3. The method for producing an ultrafine fiber web according to claim 1, wherein the ratio is in the range of 1.3 to 6.