BRPI0808914B1 - DIVISIBLE CONJUGATED FIBER, FIBROSAL FORM, AND PRODUCT - Google Patents

Description

Technical Field The present invention relates to a divisible conjugate fiber, including a polyacetal and having excellent divisibility. More particularly, the invention relates to a divisible conjugate fiber suitable for use, for example, in the field of industrial materials such as battery separators, pads and filters, and in the field of sanitary materials such as diapers and wipes, and to a fibrous form and each product obtained from the conjugated fiber.

BACKGROUND OF THE ART The use of sea island or split type conjugate fibers has been conventionally known as a technique for obtaining microfibers.

One method of obtaining a sea island-type conjugate fiber is to spin a combination of two or more ingredients. Removal of a component of the resulting sea island-like conjugate fiber by dissolution provides microfibres. Although this technique can produce excessively thin fibers, it is not economical because a component is removed by dissolution.

On the other hand, one method of obtaining a divisible conjugate fiber is to spin a combination of two or more resins. The obtained divisible conjugate fiber is divided into many fibers by applying a physical stress to it or by using, for example, a difference in contraction with a chemical between the resins. Thus, the microfibers are obtained.

Known divisible conjugate fibers include, for example, fibers consisting of a combination of a polyester resin and a polyolefin resin, a combination of a polyester resin and a polyamide resin, or a combination of a polyamide resin and a resin. polyolefin (see Patent Documents 1 and 2). These conjugated fibers are divided by physical tension. However, polyester and polyamide have low chemical resistance and, therefore, the microfibers obtained from them by division and the fibrous forms comprising microfibers have limited uses in the field of industrial materials required to have chemical resistance.

On the other hand, in the case of a combination of polyolefin resins having excellent chemical resistance, it was necessary to use higher physical impact to split into thinner fibers, because the combination of polyolefin resins had more compatibility than those combinations of different types. of polymers. However, for subjecting to advanced treatment of high pressure liquid jets, it is necessary to have the fiber remain in a treatment apparatus for a commensurate period of time. This has necessitated a considerable reduction in processing rate or an extension of the apparatus for treating high pressure liquid jets. Moreover, the microfibres thus obtained are not at all satisfactory, for example, because the split fibers obtained from high physical impact pressure provide a nonwoven cloth which is uneven and has an inferior texture.

A technique for alleviating this problem is described in patent document 3, wherein in the formation of a divisible conjugated fiber comprising polymers of the same species, organosiloxanes and their modifications are added to make them present at least at the interface between the constituent ingredients. the fiber, whereby this fiber can be easily divided. However, while this fiber has somewhat improved divisibility, the resulting split fibers have many problems due to the influences of organosiloxane-enhanced releaseability, for example a reduction in thermal bondability, a reduction in nonwoven cloth strength, and a failure to occur. processing in secondary processing. Patent 4 discloses a divisible conjugate fiber comprising at least two polyolefin ingredients and having a concavity. This conjugated fiber has specific values of: a proportion of a concavity; and a ratio of an average length W of the peripheral arcs of each polyolefin ingredient as a fiber component to an average thickness L extending from the concavity to the fiber periphery (W / L). There is a statement there that, because of this constitution, the conjugated fiber has excellent divisibility. However, fiber divisibility, although improved, is not yet completely satisfactory. In order to efficiently obtain microfibers using the divisible conjugate fiber while achieving a high degree of division, it is necessary to conduct a suitably advanced division operation.

Further, Patent 5 specifically describes a divisible conjugate cement reinforcing fiber comprising a polyacetal and a polymethylpentene copolymer. There is a claim therein that this conjugated fiber has excellent dispersibility in the cement sludge and is suitable for cement reinforcement. Examination of this polyacetal for crystallization temperature revealed that its crystallization temperature was 145 ° C. Although this split fiber has excellent dispersibility in the cement sludge, the fiber has poor reliability and is difficult to efficiently produce as a fiber for fibrous form production.

[Patent Citation 1] JP-A-62-133164 [Patent Citation 2] JP-A-2000-110031 [Patent Citation 3] JP-A-4-289222 [Patent Citation 4] Japanese Patent No. 3309181 [Patent Citation 5] JP-A-2002-29793 Description of the Invention Technical Problem As described above, investigations for obtaining an excellent divisible conjugate fiber in divisibility and chemical resistance are done by two ways, that is, selection of polymer types as materials and improving the sectional shape of the fiber. However, the divisible conjugate fibers obtained by existing methods are unsatisfactory in divisibility, chemical resistance or reliability. The object of the invention is to eliminate the problems described above and to provide with satisfactory productivity an excellent divisible conjugate fiber in divisibility and chemical resistance, fibrous form and each product comprising it.

Technical Solution Today's inventors have diligently made investigations to overcome the problems described above. As a result, they found that these goals are achieved with a specific divisible conjugate fiber comprising a polyacetal and a polyolefin. The invention was thus completed.

That is, the invention includes the following constitutions. (1) A divisible conjugated fiber comprising a polyacetal and a polyolefin, wherein the polyacetal satisfies the following numerical expression: Tc '<144 ° C

[wherein Tc 'represents the crystallization temperature Tc (° C) when cooling the molten polyacetal to 210 ° C at a cooling rate of 10 ° C / min]. (2) The divisible conjugate fiber as described (1) above, wherein the polyolefin is polypropylene. (3) The divisible conjugate fiber as described (1) above, wherein the polyolefin is polyethylene. (4) The divisible conjugate fiber as described in any one of (1) to (3) above having a concavity. (5) A fibrous form comprising microfibers having an average single strand fineness after splitting of less than 0.6 dtex, wherein the microfibers are obtained by dividing the splitting conjugate fiber as described in any of (1). a (4) above. (6) The fibrous form as described in (5) above, wherein 50% or more of the divisible conjugate fiber is divided. (7) A product obtained using the fibrous form as described in (5) or (6) above.

Advantageous Effects The divisible conjugate fiber of the invention has the following advantages in that it is a specific divisible conjugate fiber comprising a polyacetal and a polyolefin. The divisible conjugate fiber has excellent divisibility. Even when split with low physical impact, fiber can easily be split into thinner fibers without especially requiring the addition of an additive at all to facilitate splitting. In addition, this divisible conjugate fiber has excellent chemical resistance and the raw material has excellent reliability. As a result, the divisible conjugate fiber and the fiber form and fiber product obtained have excellent productivity. Fibrous forms that are dense and have a satisfactory texture can be obtained from the splitting conjugate fiber of the invention. Products of such fibrous forms are suitable for use not only in the field of sanitary materials such as diapers and wipes but also in the field of industrial materials such as battery separators, pads and filters.

Brief Description of the Drawings [Fig. 1] Fig. 1 is a diagrammatic cross-sectional view of an embodiment of the divisible conjugate fiber for use in the invention.

[Fig. 2] Fig. 2 is a diagrammatic cross-sectional view of an embodiment of the divisible conjugate fiber for use in the invention.

[Fig. 3] Fig. 3 is a diagrammatic cross-sectional view of yet another embodiment of the divisible conjugate fiber for use in the invention.

[Fig. 4] Fig. 4 is a diagrammatic cross-sectional view of an embodiment of the divisible conjugate fiber having a concavity for use in the invention.

[Fig. 5] Fig. 5 is a diagrammatic cross-sectional view of another embodiment of the divisible conjugate fiber having a concavity for use in the invention.

[Fig. 6] Fig. 6 is a diagrammatic cross-sectional view of yet another embodiment of the divisible conjugate fiber having a concavity for use in the invention.

Reference Explanation 1 one resin component (eg polyacetal) 2 another resin component (eg polyolefin) 3 concavity d distance between fiber center and fiber surface r distance between fiber center and tip Design of a Resin Component That Is Not Exposed on the Fiber Surface Best Mode for Carrying Out the Invention The invention will be explained below in detail based on the embodiments of the invention. The divisible conjugated fiber of the invention comprises two components, that is, a polyacetal and a polyolefin, as mentioned above.

Polyacetals include two types, that is, homopolymers, generally comprising 1,000 or more oxymethylene units, and copolymers, comprising ethylene units in a polyoxymethylene backbone. Although the polyacetal used in the invention is not particularly limited, copolymers are preferred from a thermal stability standpoint. Polyacetals containing 1 to 10 mole% ethylene units therein are suitable. Particularly, a polyacetal containing 1 to 4 mole% ethylene units is preferred. The presence of 1 mol% or larger ethylene units in the polyacetal improves the thermal stability of the polyacetal, although in the presence of 10% mol or smaller ethylene units in the polyacetal, the splitting conjugate fiber has satisfactory strength. The polyacetal contained in the splitting conjugate fiber of the invention has a crystallization temperature Tc 'when cooling at a cooling rate of 10 ° C / min after melting at 210 ° C, 144 ° C or lower, preferably in the range of 136 ° C. at 144 ° C, especially preferable 138 to 142 ° C. Although polyacetals have excellent crystallinability, they have the following disadvantage in extrusion molding, in particular melt spinning. The polyacetal filament quickly solidifies in an upstream area (near the spinning nozzle). As a result, as the rate of deformation in the discharge period for solidification and the subsequent termination of thickness reduction becomes excessively high, the Skill deteriorates. However, a polyacetal having a Tc 'of 144 ° C or lower is prevented from rapidly solidifying and may retain reliability. On the other hand, when the Tc 'of this polyacetal is 136 ° C or higher, sufficient stress is applied to the resin at the solidification point to develop a fiber structure. Because of this, the excellent divisibility that is required in the fiber of the invention is apt to be obtained. Furthermore, from a reliability standpoint, a more preferred polyacetal is one that satisfies the requirement that when the crystallization temperature Tc (° C) is plotted relative to logV, that is, the logarithm of the cooling rate V (° C / min) of the polyacetal melted at 210 ° C, then the resulting graph has an A-slope of -13 to -4, especially and preferably -11a -6, and has a Tc 'of 144 ° C or more low, preferably 136 to 144 ° C, especially and preferably 138 to 142 ° C. When the slope A of the graph is -4 or lower and Tc 'is 144 ° C or lower, then this polyacetal is prevented from rapidly solidifying and is capable of satisfactory reliability. On the other hand, when the slope A of the graph is -13 or higher and Tc 'is 136 ° C or higher, then sufficient stress is applied to the resin at the solidification point to develop a fiber structure by means of that the excellent divisibility required in the fiber of the invention is apt to be obtained. In addition, a polyacetal wherein the amount of crystallization heat per 1 g of polycetal resin Qc (J / g) in a logV of 1 is 90 to 125 J / g, especially and preferably 95 to 120 J / g, can be properly used from the point of view of reliability, stretchability and divisibility. When a polyacetal having a Qc of 125 J / g or less is used, then the unstretched yarn obtained by melt spinning contains a sufficient amount of binding molecules necessary to ensure tensile strength and may therefore be stretched at a higher ratio. Thus, the required reliability of the fiber of the invention can easily be obtained. On the other hand, when a polyacetal having a Qc of 95 J / g or higher is used, then melt stress is ensured and adequate reliability is maintained. Thus high productivity is realized. Such polyacetals suitable for melt spinning may be obtained by selecting a proportion of comonomer ingredient in the resin or in a molecular structure or by selecting the type and amount of an additive. The melt flow (hereinafter abbreviated as MFR) of such polyacetals which are suitable for use is not particularly limited as long as wiring is possible. However, its MFR is preferably 1 to 90 g / 10 min, more preferably 5 to 40 g / 10 min, from the reliability point of view. Polyacetals having an MFR of 1 g / 10 min or higher are preferred from the point of view of reliability and stretchability because of the reduction in melt stress. MFR values, no higher than 90 g / 10 min, are more preferred because of the use of this polyacetal to provide a fiber in which adjoining components are regularly arranged and can be divided into thinner fibers at a desired level of physical stress. , and because the reliability can be simultaneously maintained for high productivity. A melting point of such a polyacetal is preferably 120 ° C to 200 ° C, especially and preferably 140 to 180 ° C, from the reliability point of view. Such polyacetals are commercially available from different companies under the trade names of, for example, "Tenac", "Ultraform", "Delrin", "Duracon", "Amirus", "Hostaform" and "Yubital". A polyacetal suitable for use in this invention may be selected from these.

On the other hand, examples of polyolefin include polyethylene, polypropylene, polybutene-1, polyoctene-1, ethylene / propylene copolymers and polymethylpentene copolymers. Of these, polypropylene is preferred from the point of view of production cost and thermal properties. From the point of view of production cost, reliability and stretchability, polyethylene is preferred. In addition, from a reliability point of view, the polypropylene for use in the invention preferably has a Q value (weight average molecular weight / number average molecular weight) of 2 to 5, and the polyethylene used in the invention preferably has a value Q from 3 to 6. The MFR of such polyolefin resin suitable for use is not particularly limited as long as spinning is possible. However, its MFR is preferably 1 to 100 g / 10 min, more preferably 5 to 70 g / 10 min, from the reliability point of view. Polyolefins having an MFR of 1 g / 10 min or higher are preferred from the point of view of reliability and stretchability because of the reduction in melt stress. MFR values no higher than 100 g / 10 min are more preferred because such polyolefin ingredients have improved peeling property and the fiber obtained can be split into microfibres at a desired level of physical strain and because of reliability can be simultaneously maintained for high productivity. From the reliability point of view, a melting point of such a polypropylene is preferably 100 to 190 ° C, more preferably 120 to 170 ° C, and a melting point of such a polyethylene is preferably 80 to 170 ° C, especially; preferably 90 to 140 ° C.

In the production of polyacetal and polyolefin, another ingredient may be copolymerized for modification purposes, for example to improve divisibility or chemical resistance. In addition, various other types of polymers may be mixed or various types of additives may be incorporated therein. For example, an inorganic pigment, such as fiery black, chrome yellow, cadmium yellow or iron oxide, or an organic pigment such as a diazo pigment, anthracene pigment or phthalocyanine pigment, may be incorporated to staining purposes.

The sections of the divisible conjugate fiber of the invention will be explained below. Figs. 1 to 6 are sectional views showing examples of divisible conjugate fibers usable in the invention. From the point of view of reducing area where a component is in contact with the adjoining component to thereby improve divisibility, it is preferred that the fiber section, in a direction perpendicular to the direction of the splitting conjugate fiber extension, is a direction. wherein the polyacetal and polyolefin are highly disposed in the peripheral direction. Regarding the degree of exposure of the polyacetal to the fiber surface, it is preferred that the polyacetal is responsible for 10 to 90% of the periphery of the fiber section perpendicular to the geometric axis of the fiber. When the polyacetal is responsible for 10 to 90% of the fiber section periphery, resin interfaces where splitting begins to occur are exposed on the fiber surface, whereby this fiber shows the excellent divisibility that is characteristic of the invention. The end portions of the resin interfaces of one component (1) may be at least partially coated with the other component (2) (Fig. 3). Fibers having such a section may constitute at least a part of all fibers. From the point of view of divisibility, provided that each component must be responsible for at least 10% of the periphery of the fiber section with respect to the resin interface end portions extending towards the surface of each fiber and with respect to At the average value of the resin interface end portions extending toward the fiber surfaces of ten arbitrarily selected fibers, it is desirable that the ratio (r / d) of the distance (r) between the fiber center and the fiber portion end of each resin interface extending towards the fiber surface to the distance (d) between the fiber center and the fiber surface, being 0.7 to 1.0, especially in the range of 0.8 at 1.0. Such sectional shape and the mixed ratios of fibers having the sectional shape differing in r / d ratio can be adjusted by changing the shape of the nozzle and the MFRs of the resin ingredients constituting the fibers. Specifically, fibers having a shape in which the polyacetal is exposed to the periphery of the fiber section in a relatively larger proportion can be produced, for example, by placing a polyacetal resin passing into a nozzle disposed near the periphery of the hole of the fiber. nozzle, employing a combination wherein the polyolefin has a relatively lower MFR than the polyacetal, with a relatively high spinning temperature set for the polyacetal or the like. The ratio of the MFR of the polyolefin used in the divisible conjugate fiber of the invention to that of the polyacetal is preferably 0.2 to 5.0, especially 0.2 to 0.8. When the ratio of the MFR of the polyolefin used in the divisible conjugate fiber of the invention to that of the polyacetal is 0.8 to 1.25, a fiber having a sectional shape such as that shown in Fig. 1 can be advantageously obtained. When the ratio is less than 0.8, then a fiber having a sectional shape wherein the polyacetal is exposed at the periphery of the fiber section in a relatively larger proportion, such as the sectional shape shown in Fig 2 or 3 wherein White segments are polyacetal, can be advantageously obtained. When the ratio is higher than 1.25, then a fiber having a sectional shape where the polyolefin is exposed at the periphery of the fiber section in a relatively large proportion, such as the sectional shape shown in Fig. 2 or 3 in that the white segments are polyolefin, can be advantageously obtained. From the point of view of efficiently producing a fiber wherein the polyacetal is exposed to the periphery of the fiber section to a large extent, it is preferred that the spinning be performed at 190 ° C or higher. The components are connected and joined together at the central side of the fiber and are present independently of each other. The number of resin interface end portions of each component extending toward the fiber surface may be 2 or greater. However, this number for each component is preferably 4 to 18, more preferably 5 to 12, from the point of view of reliability and thinner microfibres by division. When the number of resin interface end portions of each component extending toward the fiber surface is 4 or greater, it is preferred from the point of view that finer microfibres are obtained by division. Setting its number to 18 or lower is preferred from the viewpoint that the flowability of the resin in the spinning nozzle is optimized for stable spinning. The fiber periphery may be a true circle or may have an elliptical shape or other sectional shape such as polygon, e.g. triangle to octagon, such shapes present no problem at all.

It is preferred that the divisible conjugate fiber of the invention has an especially preferable concavity in a central part of the fiber. Figs. 4, 5 and 6 show sectional views illustrating embodiments of the divisible conjugate fiber having a concavity. The shape of the concavity can be any of: circular, elliptical, triangular, quadrangular and other shapes. The proportion of the concavity is desirably in the range of 1 to 50%, especially 5 to 40%, in terms of its surface proportion in the fiber section perpendicular to the geometric axis of the fiber. When its ratio is 1% or higher, the contact between adjoining resin components on the central side of the fiber and the contact area is reduced and this enables the undivided fiber to be readily ground when split into thinner fibers by physical stress. In this case, low energy is sufficient to separate the two components at the contact interface between them. That is, the presence of a concavity is able to produce the divisibility enhancing effect. Concavity ratios of 40% or lower are more preferred because Skill is maintained and high productivity can be achieved while maintaining reduced contact and a reduced contact area between contiguous resin components, and maintaining a desired level of divisibility in the thinner fibers by physical stress. In addition, the concavity being formed in a central part of the fiber, the concavity can be formed as follows. A swelling agent is incorporated into a polyacetal or polyolefin and these polymers are spun. As a result, a concavity can be formed in polyacetal and polyolefin by the action of the swelling agent. This concavity is present at the interface between the polyacetal components and the polyolefin to reduce the contact area between the adjoining components. Consequently, the low impact energy is sufficient to split the fiber and the property of being readily split can be greatly improved. Examples of swelling agent include azodicarbonamide, barium azodicarboxylates, N, N-dinitrosopentamethylenetetramine, p-toluenesulfonylsemicarbazide and trihydrazinotriazine. The divisible conjugate fiber of the invention preferably has a single strand fineness of 1 to 15 dtex (decitexes). Single-wire fineness is determined by controlling the amount of resins being discharged from the single hole of a spinning nozzle. When the amount of resin discharge is adjusted to result in a single strand fineness of 1 dtex or greater, the cited target section is fit. Furthermore, the amount of resins being discharged from the single orifice of the spinning nozzle during melt spinning is stable and therefore the reliability and stretchability are maintained satisfactory.

In addition, by adjusting the amount of resin discharge to result in a single strand fineness of 15 dtex or less, the filament may be sufficiently cooled. As a result, tensile resonance, which is attributable to insufficient cooling, does not occur and sufficiently stable reliability / stretchability can be maintained. The average fineness of single strand after splitting is preferably less than 0.6 dtex, more preferably 0.5 dtex or less, from the point of view of obtaining a flexible fibrous shape that is uniform throughout the fiber division. and has a satisfactory texture, which is the most notable feature of conjugated fibers.

A process for producing a divisible conjugate fiber comprising a combination of a polyacetal resin and a polypropylene resin as an embodiment of the divisible conjugate fiber of the invention is shown below as an example. In the production of this divisible conjugate fiber, the known melt conjugate spinning process is used to spin the resins. The resulting filament is cooled by blowing air through a known cooler, such as lateral or circular blowing. Then a surfactant is applied to the cooled filament to obtain an undrawn yarn through an extraction roller.

A known split split fiber spinning nozzle may be used. A spinning temperature is especially important from the point of view of optimizing fiber reliability and sectional shape. Specifically, the spinning of the polyacetal resin is preferably conducted in the range of 170 to 250 ° C, especially and preferably 190 to 250 ° C. With respect to polyacetal resin, spinning at 250 ° C or lower is preferred from the pyrolysis inhibition point of view, and spinning at 190 ° C or higher is preferred from the point of view of reliability. The spinning of the polypropylene resin is preferably conducted in the range of 190 to 330 ° C, especially and preferably 210 to 260 ° C, in order to ensure reliability. An extraction roller speed is preferably 500 to 2,000 m / min. Two or more of such undrawn yarns thus obtained are bundled and stretched with a known roll-stretching machine differing in peripheral velocity. Multistage stretching can be conducted as needed. The draw ratio may be in the range of generally about 2 to 5. Subsequently, the stretched tow (fiber bundle) was pleated with a push type pleat as needed and then cut to a given fiber length to short fibers are obtained. The process steps shown above are for short fiber production. However, without being cut, the long fiber tow can be treated, for example, with a yarn dividing guide to obtain a cloth. The fibers are then subjected to the highest order processing steps as required, and then formed to a fibrous shape according to any of several applications. It is also possible to use a method in which the filament obtained through reliability and stretch is wound like a filament yarn and this yarn is knitted or woven to obtain a fibrous shape, such as a knitted article or woven. Alternatively, use may be made of a method in which short fibers are formed into a woven yarn and this yarn is knitted or woven to obtain a fibrous shape as a knitted article or woven.

That is, the term fibrous form herein means any product consisting of fibers joined together. Examples include woven cloths, knitted cloths, continuous fiber bundles, nonwoven cloths and nonwoven fiber aggregates. In addition, the fibers may be formed into a cloth by a technique such as fiber blending, mixed spinning, filament combining, co-twisting, knitting, joining or the like. Examples of nonwoven fiber aggregates include continuous sheet form up to products obtained by a carding process, air braiding process, a papermaking process or the like, and multi-layer products obtained by one or more cloth laminations. woven, knitted and non-woven fabrics, for such a continuous sheet product. Examples of them even include wool or cotton fibers. The fibrous form of the invention may be a mixture of the divisible conjugated fiber of the invention and other fibers and powders as required, provided that they do not reduce the effects of the invention. Examples of such optional fibers include synthetic fibers such as polyamide, polyester, polyolefin and acrylic, fibers obtained by imparting a function such as, for example, biodegradability or deodorising properties to such synthetic fibers, natural fibers such as cotton, wool and hemp, regenerated fibers such as rayon, cupra and acetate and semi-synthetic fibers. Examples of powders include natural derived substances such as pulverized pulp, leather powder, bamboo charcoal powder, wood charcoal powder and agar powder, synthetic polymers such as water absorption polymers and inorganic substances, such as iron powder and titanium oxide.

After the divisible conjugate fiber of the invention is obtained by spinning in a manner described above, a surfactant may be adhered to it for purposes of, for example, static fiber protection or surface softening to improve processing property. The type and concentration of surfactant can be appropriately regulated according to the applications. For the adhesion method, use may be made of a roll method, dipping method, padding-drying method or the like. Adhesion is not limited in the spinning step described above, and adhesion can be performed in the stretching or crimping step. In addition, regardless of whether the fiber is a short fiber or a long fiber, a surfactant may be adhered to it at a stage other than the spinning step, stretching step and crimping step, such as after formation of a fibrous form. The fiber length of the divisible conjugate fiber of the invention is not particularly limited. However, in the case of production of a continuous sheet using a carding machine, fibers of 20 to 76 mm are generally used. In the case of the papermaking process or air braiding process, it is generally preferred to use fibers of 20 mm or shorter. When fibers having a length set at 76 mm or shorter are used, a continuous sheet forming with a carding machine or the like may be uniformly conducted and a continuous sheet having a uniform texture can be readily obtained. The divisible conjugate fiber of the invention is applicable to various processes for producing the fibrous form, including the air braiding process. The processes for producing a nonwoven cloth are shown as examples. For example, short fibers obtained from the divisible conjugate fiber described above are used to produce a continuous web having a required basis weight, by carding, air braiding or by the papermaking process. Alternatively, a continuous sheet may be directly produced by a melt blowing process, spinning joint process or the like. The web produced by the above methods may be subjected to fiber separation by a known method, such as, for example, the needle punch method or high pressure liquid jet treatment, whereby a fibrous shape may be formed. be obtained. It is also possible to treat this fibrous form by a known processing technique with hot air or a heated roller.

The methods for dividing the divisible conjugate fiber of the invention are not particularly limited. Examples include methods such as a needle puncture method and high pressure liquid jet treatment. The method of splitting by high pressure liquid jet treatment is explained here as an example. As an apparatus for treating high pressure liquid jet, use may be made of an apparatus having many ejection holes with a diameter of, for example, 0.05 to 1.5 mm, especially 0.1 to 0.5. mm, arranged within a range of 0,1 to 1,5 mm in one or more rows. High pressure liquid jets, obtained by ejecting a liquid through the eject holes at a high water pressure, are made to collide with the continuous sheet or non-woven cloth placed on a porous support member. Thus, the undivided divisible conjugate fiber of the invention is tangled and simultaneously divided into finer fibers by the high pressure liquid jets. The rows of eject holes are arranged in a row perpendicular to the direction of travel of the continuous sheet. Like high pressure liquid jets, use can be made of ordinary temperature liquid jets or hot water jets or any other desired liquid. The distance between the order of the ejection holes and the continuous sheet or nonwoven cloth is preferably 10 to 150 mm. When this distance is less than 10 mm, there are cases where this treatment produces a fibrous shape having a disordered texture. On the other hand, when this distance exceeds 150 mm, there are cases when the physical impact of the liquid jets on the web or nonwoven cloth is weak and the tangling and splitting of the fiber into thinner fibers is not sufficiently supported. The pressure in this high pressure liquid jet treatment is regulated according to the production process and the required performances of the fibrous form. However, it is generally preferred to eject high pressure liquid jets at a pressure of 20 to 200 kg / cm. A method may be used wherein the continuous sheet or nonwoven cloth is treated in such a way that the pressure from the high pressure liquid jets successively increases from low water pressure to high water pressure within the range. treatment pressure above, although this range depends on the base weight being treated, etc. This method is less apt to clutter the texture of the web or nonwoven cloth and can achieve tangling and splitting into thinner fibers. The porous support member, wherein the web or non-woven cloth is placed in the treatment with high pressure liquid jets, is not particularly limited as long as it enables the high pressure liquid jets to pass through the web or non woven cloth. For example, a 50 to 200 mesh synthetic or resin mesh screen or perforated plate may be used. Incidentally, use may be made of a method comprising subjecting the web or nonwoven cloth to a high pressure liquid jet treatment on one side, subsequently reversing the web or matted nonwoven cloth and subjecting it to high pressure liquid jet treatment. This method can produce a fibrous shape in which both the front and back sides are dense and have a satisfactory texture. After high pressure liquid jet treatment, water is removed from the fibrous form obtained after treatment. For this water removal known methods can be employed. For example, a juicer, such as a calender, is used to remove water to some degree and a drying apparatus such as a circulating hot air dryer is then used to completely remove water, whereby a The fibrous form of the invention can be obtained. The basic weight of the fibrous form of the invention is not particularly limited. However, the fibrous form having a basis weight of 10 to 200 g / m 2 can be suitably used. When the fibrous form has a basis weight of 10 g / m 2 or higher, the texture of the woven cloth may be kept satisfactory, when the divisible conjugate fiber is divided into thinner fibers by the physical stress obtained by, for example, a fiber treatment. high pressure liquid jet. Where the fibrous form has a basis weight of 200 g / m 2 or less, even division may be conducted with a satisfactory texture without excessively conducting the high pressure liquid jet treatment.

Compared to conventional polyolefin-based split fibers, the split conjugate fiber of the invention can be easily split. Even though the physical impact obtained by the high pressure liquid jets is low, the conjugated fiber of the invention can be divided into thinner fibers. When the divisible conjugate fiber of the invention is used, a fibrous form can be readily obtained wherein 50% or more of the conjugate fiber is divided. In particular, a fibrous form in which 60% or more, especially 70% or more, of the conjugated fiber is divided can be readily obtained. Because of this, an increase in the rate of a high pressure liquid jet treatment, which is a rate determination step in braided lace, and a texture improvement by reducing the pressure of high pressure liquid jets, can be obtained. In the case of a continuous sheet comprising short fibers, such as, for example, a fiber produced by the papermaking process, the pressure of the high pressure liquid jets may be reduced, whereby problems such as a paper disorder. texture in the fibrous form and formation through hole can be attenuated.

Furthermore, the divisible conjugate fiber of the invention has excellent resistance to chemicals, especially alkalis, because it is a divisible conjugate fiber comprising a polyacetal and a polyolefin, each having excellent chemical resistance.

As described above, the divisible conjugate fiber of the invention can be easily split and a dense fibrous shape having a satisfactory texture can be obtained from it. Conjugated fiber still has excellent chemical resistance. Nonwoven fabrics that are highly dense and have a satisfactory texture can be obtained from the splitting conjugate fiber of the invention. The products of such nonwoven cloths are not only suitable for use in the field of sanitary materials such as diapers and wipes, but are also suitable for use in the field of industrial materials such as battery separators, pads and filters. The divisible conjugate fiber of the invention may be used as fibrous aggregates containing the conjugate fiber in an amount of 10% by weight or greater. Other fibers that may be used in combination with the divisible conjugate fiber of the invention are not particularly limited. Examples include the divisible conjugate fibers outside the scope of the invention, high density polypropylene based heat-bindable conjugate fibers, polypropylene based heat-bindable conjugate fibers and an ethylene copolymerized polypropylene, heat-bindable conjugate fibers with polypropylene base and an ethylene-butene-1 copolymerized polypropylene, heat-bindable composite fibers based on a high density polyester and polyethylene, polyester fibers, polyolefin fibers and rayon.

Examples The invention will be explained below in detail with reference to the Examples. However, the invention should not be limited to them. The methods used to determine the property values shown in the Examples or the property definitions are given below. (1) Single-wire fineness Measurement was made according to JIS-L-1015. (2) Tensile Strength and Elongation Measurement was made with Autograph AGS 500D, produced by Shimadzu Corp., according to JIS-L-1017 under the conditions of a sample length of 100 mm and a tensile rate of 100 mm. / min (3) Fusion Flow (MFR) Measurement was made according to JIS-K-7210.

Raw Material Polyacetal Resin: 4 conditions Raw Material Polypropylene Resin: 14 conditions Raw Material Polyethylene Resin: 4 conditions Raw Material Polymethylpentene Resin: 20 conditions (4) Determination Method (r / dl Os The following values were calculated from cross-sectional photographs of ten arbitrarily selected undivided fibers.The value of r / d was calculated from their averages.r: Average distance between the peripheral end of the coated component and the center of fiber d: Average distance between the center of the fiber and the fiber surface (5) Method of Determining the Concavity Ratio The concavity ratio was calculated from ten arbitrarily selected undivided fibers in a cross-sectional photograph of undivided fibers using the following equation: Concave ratio (%) = [(cavity sectional area) / (total fiber sectional area including cavity)] x (6) Method for Determining the Degree of Fiber Surface Polyacetal Exposure The following values were calculated from ten arbitrarily undivided fibers selected from a cross-sectional photograph of undivided fibers. The degree of polyacetal exposure on the fiber surface was calculated from their means. c: Length of the periphery of the fiber section perpendicular to the geometric axis of the fiber. w: Length of the polyacetal arches at the periphery of the fiber section perpendicular to the geometric axis of the fiber.

Degree of polyacetal exposure on fiber surface (%) = (w / c) x 100 (7) Reliability The melt-spinning ability of the yarn was evaluated at the following three degrees in terms of the number of filaments broken that occurred. A: No filament breakage occurs and operation is satisfactory. B: One or two filament breaks occur per hour. C: Four or more filament breaks occur per hour and this is problematic in operation. (8) Stretch Ratio The stretch ratio was calculated using the following equation.

Stretch Ratio = [Extraction Roll Speed (m / min)] / [Feed Roll Speed (m / min)] (9) Divisibility Rating Divisibility was assessed by a split operation with a mixer (Mixer Osterizer) as a surrogate assessment for high pressure liquid jet treatment. A stream of water in the blender provides the same physical stimulation to the fibers when being supplied by the high pressure liquid jet treatment, thereby dividing the fibers. (Method of Producing Split Fiber Continuous Sheet) 500 ml of deionized water and 1.0 g (weight of fiber) of a divisible conjugate fiber of the invention were introduced into the mixer. The contents were stirred at 7,900 rpm for 3 minutes. The resulting mixture was filtered through a Buchner funnel having a diameter of 12 cm and dried at 80 ° C. (Air Permeability Measurement Method) The split fiber continuous sheet was interleaved between 150 mesh wire mesh and an air permeability was measured according to the method JIS L 1096 6.27 A.

The higher the divisibility is, the denser the continuous sheet will be. In the case of fibers having the same diameter before splitting, an index for divisibility is obtained by comparing the air permeability of the split fiber continuous sheets. That is, with respect to fibers having the same fiber diameter before splitting, the following judgment can be formed. The lower the air permeability of the split fiber continuous sheet, the higher the divisibility of the divisible conjugate fiber and the easier the division of this fiber will be. (10) Texture Volunteers examined a non-woven (1m square) cloth that had supported fiber splitting into thinner fibers. The cloth was visually examined for uneven fiber distribution and the results were evaluated based on the following criteria: A: At least seven volunteers felt that the cloth had slight unevenness and no through hole. B: Four to six volunteers felt that the cloth had slight unevenness and no through hole. C: The number of volunteers who felt that the cloth had slight unevenness was 3 or less. (11) Chemical Resistance A fiber was immersed in 100 mL of ethanol or aqueous sodium hydroxide solution and allowed to stand in this state at 20 ° C for 3 months. The fiber was examined for the degree of weight change through positioning. Results were evaluated based on the following criteria. A: A decrease in fiber weight is less than 0.3%. B: A decrease in fiber weight is 0.3% or more and less than 2.0%. C: A decrease in fiber weight is 2.0% or more.

(12) Tc and Oc Measurement at Various V-Values The DSC Q10 (commercial name) differential scanning calorimeter produced by TA Instruments. Inc., was used to measure a crystallization temperature Tc (° C) when cooling a fused polyacetal resin to 210 ° C at various rates. Specifically, 4.0 to 4.5 mg of a polyacetal resin sample was heated from room temperature to 210 ° C, at a heating rate of 10 ° C / min, kept at this temperature for 10 minutes and then cooled. at a rate of 5, 10, 20, 30 or 65 ° C / min. The crystallization temperature Tc (° C) was determined from the resulting peak heat flux. In addition, the amount of crystallization heat Qc in a logV of 1 was determined from a value obtained by integrating the heat flux based on a baseline extraction at 130 to 150 ° C.

Example 1 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 9 and where the graph obtained by plotting Tc relative to logV had an A slope of -9.0 and Tc, when measured at a logV of 1 (Tc '), and Qc were 141 ° C and 106 J / g, respectively. As a polyolefin polypropylene having a melting point of 160 ° C, MFR of 16 and Q value of 4.9 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a polyacetal / polyolefin ratio of 50/50 by volume and a fineness of 8.9 dtex and mainly had a shape of cross-sectional areas such as that shown in Fig. 5 and still partially had cross-sectional shapes such as those shown in Figs. 4 and 6. In these fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 16. The fibers included a fiber having a structure in which part of the terminal parts of the polyacetal copolymer resin interface was coated with polypropylene. The r / d value with reference to the polyacetal copolymer was 0.97. The fibers had a concavity ratio of 20.3%. The degree of polyacetal exposure on the fiber surface was 28.9%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was drawn at 80 ° C in a ratio of 4.7 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 6 mm.

The obtained short fibers were subjected to split treatment with a mixer described above to obtain a fibrous form of the invention. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Example 2 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 31 and in which the graph obtained by plotting Tc with respect to logV had an A slope of -9.4 and Tc, when measured at a logV of 1 (Tc '), and Qc were 141 ° C and 119 J / g, respectively. As a polyolefin polypropylene having a melting point of 160 ° C, MFR of 16 and Q value of 4.9 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a polyacetal / polyolefin ratio of 50/50 by volume and a fineness of 8.9 dtex and mainly had a shape of cross-sectional areas such as that shown in Fig. 4 and still partly had a cross-sectional shape such as that shown in Fig. 5. In these fibers the number of resin interface end portions extending across The fiber surface direction was 8 with respect to each component. That is, these fibers were divided into 16. The r / d value with reference to the polyacetal copolymer was 1.00. The fibers had a concave proportion of 9.2%. The degree of polyacetal exposure on the fiber surface was 60.2%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was drawn at 80 ° C in a ratio of 4.7 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 6 mm.

The obtained short fibers were subjected to the same split treatment as in Example 1 to obtain a fibrous form of the invention. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Example 3 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 9 and where the graph obtained by plotting Tc with logV had an A slope of -9.0 and Tc, when measured at a logV of 1 (Tc '), and Qc were 141 ° C and 106 J / g, respectively. As a polyolefin polypropylene having a melting point of 160 ° C, MFR of 11 and Q value of 4.9 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a polyacetal / polyolefin ratio of 50/50 by volume and a fineness of 8.9 dtex and mainly had a shape of cross-sectional areas such as that shown in Fig. 5 and still partially had cross-sectional shapes such as those shown in Figs. 4 and 6. In these fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 16. The fibers included a fiber having a structure in which part of the terminal parts of the polyacetal copolymer resin interface was coated with polypropylene. The r / d value with reference to the polyacetal copolymer was 0.97. The fibers had a concavity ratio of 24.7%. The degree of polyacetal exposure on the fiber surface was 28.9%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was drawn at 80 ° C in a ratio of 4.7 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 6 mm.

The obtained short fibers were subjected to the same split treatment as in Example 1 to obtain a fibrous form of the invention. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Example 4 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 9 and where the graph obtained by plotting Tc relative to logV had an A slope of -9.0 and Tc, when measured at a logV of 1 (Tc '), and Qc were 141 ° C and 106 J / g, respectively. As a polyolefin, polypropylene having a melting point of 160 ° C, MFR of 30 and Q value of 2.9 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a polyacetal / polyolefin ratio of 50/50 by volume and a fineness of 8.9 dtex and mainly had a shape of cross-sectional areas such as that shown in Fig. 5 and still partially had cross-sectional shapes such as those shown in Figs. 4 and 6. In these fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 16. The fibers included a fiber having a structure in which part of the terminal parts of the polyacetal copolymer resin interface was coated with polypropylene. The r / d value with reference to the polyacetal copolymer was 0.97. The fibers had a concavity ratio of 16.9%. The degree of polyacetal exposure on the fiber surface was 25.1%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was drawn at 80 ° C in a ratio of 4.7 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 6 mm.

The obtained short fibers were subjected to the same split treatment as in Example 1 to obtain a fibrous form of the invention. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Example 5 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 9 and where the graph obtained by plotting Tc relative to logV had an A slope of -9.0 and Tc, when measured at a logV of 1 (Tc '), and Qc were 141 ° C and 106 J / g, respectively. As a polyolefin high density polyethylene having a melting point of 130 ° C, MFR of 16.5 and Q value of 5.1 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a polyacetal / polyolefin ratio of 50/50 by volume and a fineness of 8.9 dtex and mainly had a shape of cross-sectional areas such as that shown in Fig. 5 and still partially had cross-sectional shapes such as those shown in Figs. 4 and 6. In these fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 16. The fibers included a fiber having a structure in which part of the end portions of the resin interface of the polyacetal copolymer was coated with high pressure polyethylene. The r / d value with reference to the polyacetal copolymer was 0.97. The fibers had a concave proportion of 14.3%. The degree of polyacetal exposure on the fiber surface was 25.8%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was drawn at 80 ° C in a ratio of 4.7 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 6 mm.

The obtained short fibers were subjected to the same split treatment as in Example 1 to obtain a fibrous form of the invention. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Comparative Example 1 Polypropylene having a melting point of 160 ° C and high density polyethylene having a melting point of 130 ° C were used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a 50/50 volume polypropylene / polyethylene ratio and a fineness of 6.5 dtex and had a cross-sectional shape. , as shown in Fig. 4. Polypropylene had an MFR of 11 and a Q value of 4.9, while high density polyethylene had an MFR of 16.5 and a Q value of 5.1. In fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 16. The r / d value with reference to polypropylene was 1.00. The fibers had a concavity ratio of 18.7%. The degree of polypropylene exposure on the fiber surface was 26.8%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was stretched at 95 ° C in a ratio of 4.4 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 5 mm. The divisible conjugate fibers thus obtained had the same fiber diameter as in Examples 1 to 5.

The short fibers obtained were subjected to split treatment with a mixer to obtain a fibrous form of the invention. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Comparative Example 2 Polyethylene terephthalate having a melting point of 260 ° C and polypropylene having a melting point of 160 ° C were used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a 50/50 volume polyethylene / polypropylene terephthalate ratio and a fineness of 5.4 dtex and which were mainly shaped to cross-section, such as that shown in Fig. 5, and still had cross-section shapes, such as those shown in Figs. 4 and 6. Polyethylene terephthalate had an intrinsic viscosity of 0.64, while polypropylene had an MFR of 30 and a Q value of 2.9. In these fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 16. The fibers included a fiber having a structure in which part of the end portions of the polyethylene terephthalate resin interface were coated with polypropylene. The r / d value with reference to polyethylene terephthalate was 0.97. The fibers had a concavity ratio of 14.5%. The degree of exposure of polyethylene terephthalate to the fiber surface was 35.0%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained unstretched yarn was stretched at 90 ° C in a ratio of 1.8 and a papermaking dispersant was adhered to it. The yarn was then cut to a length of 6 mm. The short fibers obtained were subjected to the same split treatment as in Example 1 to obtain a fibrous shape. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Comparative Example 3 A polyacetal copolymer having a melting point of 160 ° C and an MFR of 9 was used as a polyacetal and the graph obtained by plotting Tc relative to logV had an A-slope of -10.1 ° C. and Tc, when measured at a logV of 1 (Tc '), and Qc were 145 ° C and 148 J / g, respectively. As a polyolefin, polypropylene having a melting point of 160 ° C, MFR of 11 and Q value of 4.9 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber, which had a polyacetal / polyolefin ratio of 50/50 by volume and a fineness of 8.3 dtex, and mainly had a shape of cross-sectional areas such as that shown in Fig. 5 and still partially had cross-sectional shapes such as those shown in Figs. 4 and 6. These fibers had poor reliability and a sufficient sample to examine various fiber properties could not be obtained.

Comparative Example 4 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 9 and where the graph obtained by plotting Tc relative to logV had an A slope of -10.1 ° C. and Tc, when measured at a logV of 1 (Tc '), and Qc were 145 ° C and 148 J / g, respectively. As a polyolefin polymethylpentene having a melting point of 238 ° C and an MFR of 85 was used. A split fiber nozzle was used to spin these polymers to obtain hollow split fiber having a polyacetal / polyolefin ratio of 50. / 50 by volume and a 9.1 dtex fmure which mainly had a cross-sectional shape such as that shown in Fig. 5 and partly had cross-sectional shapes such as those shown in the Figs. 4 and 6. These fibers had poor reliability and a sufficient sample to examine various fiber properties could not be obtained.

Comparative Example 5 As a polyacetal a polyacetal copolymer was used which had a melting point of 160 ° C and an MFR of 9 and where the graph obtained by plotting Tc relative to logV had an A slope of -10.1 ° C. and Tc, when measured at a logV of 1 (Tc '), and Qc were 145 ° C and 148 J / g, respectively. As a polyolefin, polymethylpentene having a melting point of 238 ° C and an MFR of 85 was used. A split split nozzle was used to spin these polymers to obtain solid split split conjugate fibers, which had a polyacetal / polyolefin ratio of 50. / 50 by volume and a pitch of 9.1. In these fibers, the number of resin interface end portions extending toward the fiber surface was 8 with respect to each component. That is, these fibers were divided into 8. The fibers included a fiber having a structure in which part of the terminal portions of the polyacetal copolymer resin interface was coated with polymethylpentene. The r / d value with reference to the polyacetal copolymer was 0.97. The degree of polyacetal exposure on the fiber surface was 27.3%.

A potassium alkyl phosphate salt was adhered to the fibers in one extraction step. The obtained undrawn yarn was drawn at 90 ° C in a ratio of 4.0 and a papermaking dispersant was adhered to it. The wire was then cut to a length of 6 mm.

The obtained short fibers were subjected to the same split treatment as in Example 1 to obtain a fibrous form. The obtained fiber properties and air permeability and other properties of the fibrous form are shown in Table 1.

Those fibers had poor reliability and the sample obtained had many yarn ends attributable to yarn breakage. Because of this, the texture of the fibrous form was not satisfactory.

Table 1 * In terms of fiber diameter, corresponding to 2.3 dtex polyacetal / polyolefin fiber. * Degree of PP or PET exposure on fiber surface.

As is clear from Table 1, the divisible conjugate fibers of Examples 1 to 5 according to the invention, comprising a polyacetal and a polyolefin, obtain lower air permeability and excellent divisibility compared to those of Comparative Examples 1 and 2. and were also divided to a higher degree, even under the same conditions. That is, the conjugate fibers of the Examples readily support division into thinner fibers without requiring a split treatment conducted under severe conditions, as in conventional techniques. Because of this, even a nonwoven cloth having a relatively low base weight can be treated by fiber splitting without texture clutter. Accordingly, the time required for the split treatment (e.g., a high pressure liquid jet treatment) and its cost can be considerably reduced.

In addition, the divisible conjugate fibers of Examples 1 to 5 according to the invention comprising a polyacetal and a polyolefin show the same chemical resistance as the divisible conjugate fiber made of a combination of polyolefin resins (Comparative Example 1). Accordingly, the conjugated fibers of the Examples may be advantageously used also in the field of industrial materials, especially required to have chemical resistance, such as, for example, battery separators, pads and filters. In addition, the divisible conjugate fibers of Examples 1 to 5 according to the invention, each of which the polyacetal Tc 'is 144 ° C or lower, has better reliability than the conjugate fibers of Comparative Examples 3 and 4. , which have the same section, but have a Tc 'exceeding 144 ° C, and than the conjugate fibers of Comparative Example 5, which have a simpler section, but have a Tc' exceeding 144 ° C. Thus, divisible conjugate fibers capable of efficiently producing split fiber can be produced with satisfactory productivity. The present application is based on Japanese Patent Application No. 2007-73221 filed March 20, 2007 and Japanese Patent Application No. 2007-332295 filed December 25, 2007, the contents of which are incorporated herein by reference. .

Industrial Applicability The invention provides with satisfactory productivity a divisible conjugate fiber, excellent in divisibility and chemical resistance, the fibrous form and each product comprising it. More particularly, the invention provides a divisible conjugate fiber suitable for use, for example, in the field of industrial materials, such as battery separators, pads and filters, and in the field of sanitary materials, such as diapers and wipes, and in a form. fibrous is a product each obtained from the conjugated fiber.

Claims (7)

1. A divisible conjugated fiber, characterized in that it comprises a polyacetal and a polyolefin, wherein the polyacetal satisfies the following numerical expression Tc '<144 ° C [where Tc' represents a crystallization temperature Tc (° C) when it cools polyacetal melted at 210 ° C at a cooling rate of 10 ° C / min). Divisible conjugated fiber according to Claim 1, characterized in that the polyolefin is polypropylene. Divisible conjugated fiber according to Claim 1, characterized in that the polyolefin is polyethylene. Divisible conjugate fiber according to any one of Claims 1 to 3, characterized in that it has a concavity. Fibrous form, characterized in that it comprises microfibers having an average single strand fineness after splitting of less than 0.6 dtex, wherein the microfibers are obtained by dividing the splitting conjugate fiber as defined in any one of claims 1. to 4. Fibrous form according to claim 5, characterized in that 50% or more of the divisible conjugate fiber is divided. Product, characterized in that it is obtained using the fibrous form as defined in claim 5 or 6.