JP7325088B2 - split type composite fiber - Google Patents

Description

The present invention relates to splittable conjugate fibers.

As a technique for improving the texture and quality of nonwoven fabrics, efforts have been made to reduce the fineness of fibers.

A splittable conjugate fiber having a composite form in which a polyalkylene terephthalate component such as polyethylene terephthalate or polybutylene terephthalate is divided into a plurality of pieces by polyolefin, polyamide, etc. incompatible with this in the cross section of the fiber, or the above conjugate fiber. A method of splitting the used fabric/nonwoven fabric by physical impact to produce ultrafine fibers is well known, and various proposals have been made for such splittable polyester conjugate fibers (for example, Patent Document 1).

Moreover, in recent years, problems such as environmental pollution and accumulation in organisms due to plastic products have arisen. Biodegradable polylactic acid is mentioned as an environmentally friendly raw material that is decomposed in the natural environment, and various proposals have been made for splittable conjugate fibers for obtaining ultrafine fibers using this polylactic acid.

In Patent Documents 2 to 4, conjugated fibers arranged so as to divide polyethylene terephthalate, polybutylene terephthalate, polyolefin, nylon, etc. with polylactic acid in the cross section of the fiber are treated with an alkaline solution to dissolve polylactic acid, and polyethylene A method for obtaining fine fineness yarn such as terephthalate has been proposed. However, since these splittable conjugate fibers contain non-biodegradable raw materials such as polyethylene terephthalate, they are insufficient as environment-friendly materials.

Patent Document 5 proposes a biodegradable splittable conjugate fiber composed of polylactic acid or the like and aliphatic polyester such as polybutylene succinate. However, for this splittable conjugate fiber, since the technology regarding the melting point and viscosity of the resin has not been established, it has not been possible to produce the splittable conjugate fiber with good operability and to obtain a fiber and a nonwoven fabric with excellent quality.

Patent Document 6 proposes a biodegradable splittable conjugate fiber composed of polylactic acid and polyalkylene succinate obtained by copolymerizing lactic acid. was difficult to split, and it was difficult to produce ultrafine fibers. In addition, polyalkylene succinate obtained by copolymerizing lactic acid is used, but since the crystallinity of the resin is low, it has not been possible to produce splittable conjugate fibers with good workability and to obtain fibers and nonwoven fabrics with excellent quality. not present.

JP-A-10-212624 JP-A-8-35121 JP-A-8-188922 JP-A-2003-119626 JP-A-9-041223 Patent No. 4624075

An object of the present invention is to provide a splittable conjugate fiber that can be produced in a biodegradable conjugate fiber with good operability and from which a fiber and a textile product with excellent quality can be obtained.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that splittable conjugate fibers made of polylactic acid and polyalkylene succinate have a specific fineness and number of splits, a melting point, and a heat shrinkage rate. The inventors have found that a splittable conjugate fiber can be obtained that has good runnability, good quality of the fiber and nonwoven fabric, and can generate polarized fine fibers by physical impact, and has arrived at the present invention.

That is, the present invention comprises polylactic acid and crystalline polyalkylene succinate,
The fiber cross section is a split type composite form in which one of the two components described above is divided into a plurality of pieces by the other component,
The cross-sectional shape of the split type composite form is a shape composed of a petal part having a plurality of petal-shaped parts radially from the center of the cross section and a split part divided into individual petal-shaped parts of the petal part,
A split-type composite form comprising a conjugate fiber having a fineness of 1 to 6 dtex, a total number of splits of 10 to 30, and a split fineness of each split component constituting at least 0.20 dtex or less. can be,
The melting point of polylactic acid is 155° C. or higher, the melting point of polyalkylene succinate is 105 to 125° C., the difference in melting point between polylactic acid and polyalkylene succinate is 30 to 60° C.,
The gist of the present invention is a biodegradable splittable conjugate fiber characterized by shrinkage of 15% or less when heat-treated at 85°C for 15 minutes.

The present invention will be described in detail below.

The splittable conjugate fiber of the present invention (hereinafter sometimes simply referred to as "conjugate fiber" or "fiber") comprises polylactic acid and polyalkylene succinate. The cross section of the fiber is a split type composite form in which one component of polylactic acid and polyalkylene succinate is split into a plurality of pieces by the other component.

The fiber of the present invention is in a state of being a fiber alone, or is split by giving a physical impact to a yarn, non-woven fabric, woven or knitted fabric, etc., made of this fiber, and is obtained as an ultrafine fiber or polyalkylene sax made of polylactic acid component. It is a fiber that can produce ultrafine fibers composed of a nitrate component.

The physical impact for splitting the fibers of the present invention includes the impact of blended cotton and carding in web production, the impact of needle punching and high-pressure water jet treatment when making a web into a nonwoven fabric, and the impact of the present invention. Examples include impact such as high-pressure water flow treatment, liquid flow treatment, and air flow treatment when processing fibrous threads, non-woven fabrics, woven or knitted fabrics, and the like.

The polyalkylene succinate constituting the fiber of the present invention has crystallinity. Here, the crystallinity means that the glass transition temperature, crystallization temperature, and melting temperature are clearly shown in thermal analysis methods such as differential scanning calorimetry (DSC).

If the polyalkylene succinate does not have crystallinity, the resin is likely to soften and hard to solidify, so the single yarns are likely to adhere to each other during the spinning and drawing processes, and operability deteriorates due to the yarn being cut due to adhesion. Otherwise, adhesion becomes a lump-like defect, and the quality of the fiber and the nonwoven fabric is deteriorated. In addition, during the heat treatment for producing the nonwoven fabric, heat shrinkage due to softening or melting increases, and the quality of the nonwoven fabric deteriorates, which is not preferable.

A polyalkylene succinate is a product obtained by copolymerizing an alkylenediol such as ethylene glycol or butanediol with succinic acid, such as polyethylene succinate, polybutylene succinate or polypropylene succinate. Among them, it is preferable to use polybutylene succinate from the viewpoint of crystallinity and melting point. In addition, to the extent that the effects of the present invention are not impaired, the polyalkylene succinate may be added with lactic acid, cyclic lactones such as ε-caprolactone, α-hydroxybutyric acid such as α-hydroxybutyric acid, α-hydroxyisobutyric acid and α-hydroxyvaleric acid. Acids, glycols such as ethylene glycol and 1,4-butanediol, dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and malic acid may be copolymerized. The copolymerization amount is preferably 5 mol % or less, more preferably 3 mol % or less. A large amount of copolymerization is not preferable because the crystallinity is lowered, and the workability and the quality of fibers and nonwoven fabrics are deteriorated.

Polylactic acid constituting the fiber of the present invention is poly-L-lactic acid, poly-D-lactic acid, poly-DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or poly-L-lactic acid and poly-D-lactic acid. Any mixture (stereocomplex) may be used.

In the present invention, when polylactic acid is polyDL-lactic acid, the copolymerization ratio of D-lactic acid and L-lactic acid (D-lactic acid/L-lactic acid) is 100/0 to 95/5, 5/95 to 0/100 is preferred. If the ratio is out of this range, the crystallinity is lowered, so that the workability and the quality of the fiber and nonwoven fabric are deteriorated, which is not preferable.

In addition, the polylactic acid component may contain a small amount of a chain extender such as an organic peroxide, a bisoxazoline compound, a diisocyanate compound, an epoxy compound, an acid anhydride, etc., as long as the effect of the present invention is not impaired. .

The cross-section of the fibers of the present invention is a split composite cross-section in which one component is divided into multiple pieces by the other component. That is, it is a split type composite form in which the polylactic acid component is divided into a plurality of pieces by the polyalkylene succinate component, or the polyalkylene succinate component is divided into a plurality of pieces by the polylactic acid component.

FIG. 1 shows a cross-sectional view of a split type composite form, which is an example of the cross section of the composite fiber of the present invention. FIG. 1 is composed of a petal portion (1) having a plurality of petal-like portions radially from the central portion of the cross section and a divided portion (2) divided into individual petal-like portions of the petal portion. In FIG. 1, the outer tip portion of the petal-shaped part of the petal part is not exposed to the fiber surface and is slightly covered with the dividing part, but it is not completely covered and is exposed to the fiber surface. good too.

In the case of the cross-sectional shape as shown in FIG. 1, when polylactic acid is placed in the petals, since polylactic acid has a higher melting point than polyalkylene succinate, it tends to have a high viscosity during melt extrusion. The shape of the petal-shaped part of the fiber becomes uniform, and along with this, the individual shapes of the divided parts (2) in which the polyalkylene succinate is arranged also become uniform, and the shape of the ultrafine fibers expressed by the split fiber is uniform. It will be excellent in quality. On the other hand, when polylactic acid is placed in the dividing portion, polylactic acid has a higher melting point than polyalkylene succinate and solidifies quickly by cooling after melt spinning. By arranging it in the part, sticking of the single yarns in the spinning and drawing process is suppressed, and the workability is improved.

The number of petal-shaped parts of the dividing part and the petal part is 5 to 15 respectively. If the number of divided parts and petal-shaped parts is less than 5, the number of ultrafine fibers generated by splitting is relatively small. The fineness of the fibers tends to be not small. On the other hand, when the number of divided parts and petal-like parts exceeds 15, there is an advantage that the fineness of the ultrafine fibers produced by the split fiber is reduced, but a complicated spinneret is required, which reduces the production cost. Disadvantageously, it is difficult to obtain a fiber product of excellent quality because it is difficult to obtain a uniform shape of each piece after splitting. In the present invention, the total number of divided parts in the petal-shaped cross-sectional shape is the total number of divided parts and the number of petal-shaped parts, and the total number of divided parts is 10 to 30 for the reason described above. , The number of divisions is obtained by cutting the fiber in the cross-sectional direction, observing it under a microscope at an arbitrary magnification, and counting each number.

In the cross-sectional shape of the conjugate fiber, the split fineness of individual split components may be at least 0.20 dtex or less. This split fineness is the fineness of the ultrafine fibers developed by the splitting, and by setting it to 0.20 dtex or less, excellent ultrafine fibers are developed. For example, in the case of the split type composite form consisting of the petal-shaped part and the split part shown in FIG. 1, since the split component is at least the split part, the fineness of each split part is the split fineness. The petals shown in FIG. 1 are integrated at the center, but the area of the center is slightly smaller, and the petal-shaped parts and divided parts are alternately arranged without being integrated at the center. If so, the fineness of the individual petals is also called split fineness.

In the present invention, the cross-sectional shape composed of the petals and the divided portions as shown in FIG. 1 is preferable from the viewpoint of the large number of divisions, the easy production of ultrafine fibers, and the workability.

The cross-sectional shape of the fiber is preferably circular from the viewpoint of operability, but is not limited to this, and may be selected from triangular, flat, hollow, etc. within the range that does not impair the effects of the present invention.

The composite fiber of the present invention has a fineness of 1 to 6 dtex, preferably 1.5 to 5 dtex, more preferably 2 to 4 dtex. If the fineness is less than 1 dtex, the fiber diameter becomes too small, resulting in a large number of cut yarns during spinning and drawing, resulting in poor workability. On the other hand, when it exceeds 6 dtex, the fiber diameter becomes large, so that splitting becomes difficult when a physical impact is applied. In addition, since the fibers have a large fineness, the fibers produced by splitting tend not to be extremely fine. The fineness is measured by the method of JIS L-1015 7-5-1-1A.

The mass ratio of polylactic acid and polyalkylene succinate constituting the conjugate fiber is preferably polylactic acid/polyalkylene succinate=1/3 to 3/1, more preferably 1/2 to 2/1.

The melting point of polylactic acid is 155° C. or higher, preferably 160° C. or higher, more preferably 165° C. or higher. By setting the melting point of polylactic acid to 155°C or higher, the crystallinity of polylactic acid is increased, the workability is good, the thermal shrinkage rate of the fiber is easily suppressed, and a difference in melting point from that of polyalkylene succinate is provided. When making fiber products, polylactic acid is less likely to soften or melt under the influence of heat during the heat treatment that functions as a thermal adhesive component, and is less likely to shrink due to heat, resulting in high-quality fibers. you can get the product.

The melting point of the polyalkylene succinate is 105-125°C, preferably 108-122°C, more preferably 110-120°C. When the melting point of the polyalkylene succinate is 105° C. or higher, the crystallinity of the polyalkylene succinate is maintained, the heat shrinkage is not excessively increased, and the quality is excellent. On the other hand, by setting the melting point of the polyalkylene succinate to less than 125°C, it is possible to provide a difference in melting point from that of polylactic acid, and when making fiber products, during heat treatment to function the polyalkylene succinate as a heat bonding component. In addition, polylactic acid is resistant to softening or melting under the influence of heat, and is resistant to heat shrinkage, so that high-quality textile products can be obtained.

The difference in melting point between polylactic acid and polyalkylene succinate is 30 to 60°C, preferably 35 to 55°C, more preferably 40 to 50°C. By setting the melting point difference to 30° C. or more, the polylactic acid is less likely to soften or melt under the influence of heat during the heat treatment that causes the polyalkylene succinate to function as a thermal adhesive component, and is less likely to be thermally shrunk. High quality textiles can be obtained. On the other hand, by setting the melting point difference to be less than 60°C, any polymer having good crystallinity can be selected, resulting in good workability and good quality of fibers and fiber products. .

The melting point of each of the polymers described above was measured using a composite fiber as a sample, using a PerkinElmer differential scanning calorimeter (Diamond DSC), in a nitrogen stream, a temperature range of -50°C to 200°C, and a heating rate of 20. It is obtained from the value of the melting temperature peak measured by measuring the fiber at ° C./min. Composite fibers in which each polymer has the melting point described above can be obtained by using polylactic acid having a melting point of 155° C. or higher and polyalkylene succinate resin having a melting point of 105 to 125° C. as raw materials.

The conjugate fiber of the present invention has a shrinkage rate of 15% or less when heat-treated at 85° C. for 15 minutes. It is preferably 12% or less, more preferably 10% or less. By setting the shrinkage rate to 15% or less, shrinkage due to the influence of heat is less likely to occur during the heat treatment that causes the polyalkylene succinate to function as a thermal adhesive component, and a high-quality textile product can be obtained. The shrinkage rate after heat treatment is measured by the method of JIS L1015 8.15 b) when the conjugate fiber is mechanically crimped. In addition, when the fiber is not mechanically crimped, the shrinkage rate is determined by the following method when heat-treated. That is, the fiber length (N) is obtained by observing with a microscope at an arbitrary magnification, then the fiber is placed in a dryer with an internal temperature of 85 ° C. and heat-treated for 15 minutes. The fiber length (M) after the treatment is measured, and the value calculated by [1−(M/N)]×100 is taken as the shrinkage rate when heat treated.

The intrinsic viscosity of the polylactic acid constituting the composite fiber is preferably 1.25 or higher, more preferably 1.30 or higher. By setting the intrinsic viscosity to 1.25 or more, the mechanical strength of the fiber can be improved. Also, the intrinsic viscosity of the polyalkylene succinate is preferably 1.35 to 1.55, more preferably 1.40 to 1.50. By setting the intrinsic viscosity to 1.35 or more, the mechanical strength of the fiber can be improved, and when the composite fiber or the fiber product made of the composite fiber is stored for a long period of time, the fibers are less likely to adhere to each other. is easily maintained over a long period of time, and since it has the cohesive strength of a polyalkylene succinate resin, it functions well as a heat-adhesive component, and the adhesive strength is less likely to decrease. On the other hand, when it is less than 1.50, the melt fluidity is maintained, the heat bonding component functions well, and the adhesive strength is less likely to decrease.

The difference in intrinsic viscosity between polylactic acid and polyalkylene succinate is preferably 0.15 or less, more preferably 0.10 or less. By setting the difference in intrinsic viscosity to 0.15 or less, the difference in melt viscosity can be reduced, and the spinning tension can be uniformly applied to both components in the cooling process and the winding process in spinning. Yarn breakage due to uneven tension does not occur, and since sufficient spinning tension is applied to polyalkylene succinate having a low intrinsic viscosity, adhesion is less likely to occur, resulting in good runnability.

In addition, the intrinsic viscosity is measured at 20° C. according to a conventional method using an equal weight mixture of phenol and tetrachloroethane as a solvent, dissolving 0.5% by mass of the raw material resin in the solvent, and measuring the relative viscosity: [ηr]. is calculated by the conversion formula of 1.451×[ηr]−1.369.

Polylactic acid preferably has a melt flow rate (hereinafter abbreviated as “MFR”) at 190° C. of 5 to 20 g/10 minutes, more preferably 7.5 to 15 g/10 minutes. When the MFR is 5 g/10 minutes or more, the melt extrusion during spinning is good, the elongation of the undrawn yarn is less likely to decrease, the fiber can be drawn at a predetermined ratio, and the fiber has good strength. Obtainable. On the other hand, by setting it to 20 g/10 minutes or less, it is possible to perform good melt extrusion without the melt viscosity being too low. The quality of textile products is improved.

The polyalkylene succinate preferably has an MFR at 190° C. of 15 to 30 g/10 minutes, more preferably 20 to 25 g/10 minutes. When the MFR is 15 g/10 minutes or more, the elongation of the undrawn yarn is less likely to decrease, the fiber can be drawn at a predetermined ratio, and the fiber having good strength can be obtained. On the other hand, by setting it to 30 g/10 minutes or less, the melt viscosity is not too low and good melt extrusion is possible, the single yarns are less likely to adhere to each other in the cooling process of spinning, the workability is good, and the fibers and The quality of textile products is improved.

The difference between the MFR at 190° C. of polylactic acid and the MFR at 190° C. of polyalkylene succinate is preferably 15 g/10 min or less, more preferably 10 g/10 min or less. By setting the MFR difference to 15 g/10 minutes or less, the difference in melt viscosity does not become too large, so the spinning tension can be uniformly applied to both components, and the fiber can be crossed without causing broken yarn due to uneven spinning tension. A split shape with two components in the plane can form the desired shape. MFR is a measurement of the raw material resin according to the method described in ASTM D 1238 at a temperature of 190° C. for 10 minutes and a load of 20.2 N.

The polyalkylene succinate preferably has a b/a value of 0.20 mW/(mg.°C) or more, more preferably 0.25 mW/(mg.°C.) or more, of a peak showing temperature-cooling crystallization in DSC. . When b/a is 0.20 mW/(mg·°C) or more, the polymer has good crystallinity, is easily solidified after being extruded from the spinneret, and adheres between single filaments in the cooling process of spinning. It is difficult to wash, the workability is good, and the quality of fibers and textile products is good. In the present invention, using a differential scanning calorimeter (Diamond DSC) manufactured by PerkinElmer, a temperature range of -50 ° C. to 200 ° C. and a heating rate of -50 ° C. to 200 ° C. in a nitrogen stream It is determined from the peak of crystallization at a temperature range of 200° C. to −50° C. at a rate of 20° C./min after melting the raw material resin at 20° C./min. The value of b/a is, as shown in FIG. 2, in the DSC curve of the resin, a is the temperature A1 (° C.) , is the difference (A1-A2) between the temperature A2 (° C.) at the intersection of the tangent line with the minimum slope and the baseline, and b is the baseline heat quantity B1 (mW) at the peak top temperature and the peak top heat quantity It is a value obtained by dividing the difference (B1-B2) from B2 (mW) by the sample amount (mg), and the larger the b/a, the better the crystallinity when the temperature is lowered.

In the composite fiber of the present invention, for the purpose of increasing durability, either or both of polylactic acid and polyalkylene succinate are added with a terminal blocker such as an aliphatic alcohol, a carbodiimide compound, an oxazoline compound, an oxazine compound, an epoxy compound, or the like. can do. Among these end blocking agents, carbodiimide compounds are the best in terms of effect and cost. Examples of the carbodiimide compound include N,N'-di-2,6-diisopropylphenylcarbodiimide, N,N'-di-2,6-di-tert.-butylphenylcarbodiimide, N,N'-di-2, 6-diethylphenylcarbodiimide, N,N'-di-2-ethyl-6-isopropylphenylcarbodiimide, N,N'-di-2-isobutyl-6-isopropylphenylcarbodiimide, N,N'-di-2,4 ,6-trimethylphenylcarbodiimide, N,N'-di-2,4,6-triisopropylphenylcarbodiimide and the like.

The amount of these terminal blocking agents to be added is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, based on the fiber mass. If it is less than 0.01% by mass, the terminal blocking effect is not sufficient, and if it exceeds 5% by mass, cut threads are likely to occur, which is not preferable.

Various pigments, dyes, water repellents, water absorbing agents, flame retardants, antioxidants, ultraviolet absorbers, metal particles, crystal nucleating agents, lubricants, plasticizers, and agents, antibacterial agents, and other additives can be mixed.

In order to obtain the conjugate fiber of the present invention, the polylactic acid and polyalkylene succinate described above are prepared and conjugate-spun by a conventional method so as to form the splittable conjugate form described above. That is, first, the above polylactic acid and polyalkylene succinate are prepared, spun by a known melt composite spinning method, and cooled by blowing air using a conventionally known cooling device such as horizontal blowing or annular blowing, An oil agent is applied to the yarn, and the yarn is wound up on a winder as an undrawn yarn through a take-up roller. The wound undrawn yarn is drawn by a known drawing machine between rollers with different peripheral speeds, oil is applied as necessary, and mechanical crimping is applied with a crimper or the like as desired to form short fibers. In that case, it can be cut to the desired length with a cutter such as an EC cutter or a guillotine cutter.

The resulting conjugate fiber may be twisted or spun into a thread, and the obtained thread may be knitted to form a woven or knitted fabric, thereby producing a textile product.

In the case of obtaining a nonwoven fabric as a textile product, the conjugate fiber of the present invention is used to form a web by a method such as a wet papermaking method, a carding method, an airlaid method, etc., and then a known nonwoven fabric forming means is applied. A non-woven fabric may be used. In addition, when a means for entangling fibers by a needle punching method, a high-pressure water entanglement method, or the like is selected as a non-woven fabric forming means, a physical impact is applied to the fibers, and the conjugate fibers are divided and split by the impact. , polylactic acid component or polyalkylene terephthalate component. The high-pressure water entanglement method is preferable because high-pressure water jets are applied uniformly over the entire web, so that splitting can be performed uniformly over the entire nonwoven fabric obtained and also over the entire fibers. In addition, it is preferable that the filaments and the woven or knitted fabrics, which are the above-mentioned textile products, are subjected to a physical impact so that the conjugate fibers are divided and split to develop ultrafine fibers. Examples of the splitting method include a high-pressure hydroentanglement method, a method of applying impact through a jet dyeing machine, a buckling method, and the like.

A textile product in which ultrafine fibers are developed by splitting fibers is subjected to heat treatment to melt and soften the polyalkylene succinate, and the melt-softened polyalkylene succinate component is melted and fixed to form a heat adhesive component. It functions as a heat bond between the constituent fibers.

The heat treatment temperature and treatment time for heat bonding may be set so as to melt and soften the polyalkylene succinate, which is a heat bonding component. The temperature is preferably 90 to 150°C, more preferably 100 to 140°C. . When the treatment temperature is lower than 90°C, the polyalkylene succinate component is difficult to melt and function as a heat-bonding component. On the other hand, if the temperature exceeds 150°C, the polylactic acid component may undergo heat shrinkage and may be melted and softened, which may deteriorate the quality of fibers and textile products.

A textile product using the conjugate fiber of the present invention may consist of only the conjugate fiber of the present invention, or may be mixed with other fibers depending on the purpose and application. When mixed, in order to exhibit the effect of the conjugate fiber well, the fiber product preferably contains 20% by mass or more of the conjugate fiber, more preferably 30% by mass or more. Other fibers when mixed with other fibers include, for example, regenerated fibers such as rayon, semi-synthetic fibers such as acetate fibers, nylon fibers, vinylon fibers, vinylidene fibers, polyvinyl chloride fibers, polyester fibers, acrylic fibers, Synthetic fibers such as polyethylene fibers, polypropylene fibers, and polyurethane fibers, vegetable fibers such as cotton, and animal fibers such as wool. is preferred because it is biodegradable.

According to the present invention, it is possible to obtain a splittable conjugate fiber that can be produced with good operability and that can yield high-quality fibers and fiber products.

1 is a cross-sectional view of a split type composite form, which is an example of the cross section of the composite fiber of the present invention. FIG. FIG. 2 is a DSC curve of cooling crystallization in DSC, and is a schematic diagram showing b/a of a peak indicating cooling crystallization.

1: Petal part 2: Divided part

EXAMPLES Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these.

Incidentally, the method for measuring the characteristic values, etc. in the examples is as follows. The fineness, heat shrinkage, melting point of the fiber, intrinsic viscosity, MFR and b/a were measured by the methods described above. The heat shrinkage rate was measured using 51 mm cut cotton described in (3) below.
(1) Workability Under the conditions described in the examples below, spinning was carried out for 7 days with 20 spindles, and the number of yarn cuts was counted. △ indicates less than 11 times/day, and x indicates more than 11 times/day.
(2) Adhesion of Fibers The resulting fibers were cut into 5 mm lengths to form short-cut cotton, and 10 g of short-cut cotton was added to 1 liter of water. After stirring for 1 minute, the mixture was spread in a water tank and visually confirmed. If there are fibers stuck together by the above-mentioned method, put 10 g of shortcut cotton in 1 liter of water, use a pulp disintegrator (manufactured by Tester Sangyo Co., Ltd.), stir at 3000 rpm for 1 minute, and then put in a water tank. It was spread out and visually confirmed, and the case where there were no fibers in close contact was rated as Δ, and the case where there were fibers in close contact was rated as x.
(3) Quality of nonwoven fabric 1
The resulting fiber was cut into 51 mm lengths to form long-cut cotton, which was opened by a carding machine to prepare a web having a basis weight of 50 g/m ² . Next, this web is placed on a net conveyor consisting of a 100-mesh screen, and injection nozzles having a plurality of injection holes with a hole diameter of 0.12 mm and a hole interval of 1.0 mm are provided in three stages, 1960 kPa in the front stage, 2940 kPa in the middle stage, and 2940 kPa in the rear stage. The front and back surfaces of the web were subjected to a high-pressure water stream treatment at a water pressure of 100 rpm to entangle the constituent fibers and develop ultrafine fibers, followed by drying with hot air at 60°C to produce an entangled nonwoven fabric. Then, the nonwoven fabric was heat-treated at 110° C. for 10 minutes using a continuous heat treatment machine, and the polyalkylene succinate was melted by the heat treatment to obtain a non-woven fabric. This nonwoven fabric was cut into 10 pieces of 20 cm × 50 cm, and the lump defects were visually counted, and the average number of defects possessed by each of the 10 cut nonwoven fabrics was calculated. Those with no defects were evaluated as ◯, those with defects with an average value of 3 or less were evaluated as Δ, and those with defects with an average value of more than 3 were evaluated as ×.
(4) Quality of nonwoven fabric 2
Visually check the texture of the nonwoven fabric produced in the above (3) item, ◯ if the texture is uniform, △ if the unevenness of the texture due to shrinkage is slightly noticeable, and x if the texture due to shrinkage is noticeable. evaluated.

Example 1
Polylactic acid with melting point = 166°C, intrinsic viscosity = 1.34, MFR = 9 g/10 min, L-lactic acid/D-lactic acid = 98.6/1.4 mol%, melting point = 115°C, intrinsic viscosity = 1.45, MFR = 20 g/10 min, and b/a = 0.37 mW/(mg·°C) using polybutylene succinate as a raw material. Using a spinneret that serves as a surface (split composite type with 10 petal-shaped parts in the petal part and 10 split parts), polylactic acid is placed in the petal part and polybutylene succinate is placed in the split part, and polylactic acid is and polybutylene succinate in a mass ratio of 50/50, melt spinning was carried out at a spinning temperature of 230°C and a spinning speed of 1100 m/min to obtain an undrawn splittable conjugate fiber.

Next, the obtained undrawn yarn was drawn at a drawing temperature of 60° C. and a drawing ratio of 3.50 times, then a finishing oil was applied and cut to obtain a splittable conjugate fiber having a fineness of 2.0 dtex.

Example 2, Comparative Example 1
The procedure was the same as in Example 1, except that the discharge amount was changed so that the fineness was the value shown in Table 1.

Example 3
The same procedure as in Example 1 was carried out, except that the spinneret was changed so that the number of petal-shaped parts of the petal part and the number of divided parts of the split type cross section were the values shown in Table 1.

Example 4
The procedure was the same as in Example 1, except that polybutylene succinate was applied to the petals and polylactic acid was applied to the dividing parts.

Examples 5-6
In Example 1, the procedure was the same as in Example 1, except that the discharge amount was changed so that the mass ratio of polylactic acid to polybutylene succinate was the value shown in Table 1.

Examples 7-8
In Example 4, the procedure was the same as in Example 4, except that the discharge rate was changed so that the mass ratio of polylactic acid to polybutylene succinate was the value shown in Table 1.

Comparative example 2
Melting point = 130°C, intrinsic viscosity = 1.48, MFR = 11 g/10 min, and polylactic acid having a L-lactic acid/D-lactic acid ratio of 90.1/9.9 mol% was used, except that polylactic acid was used. I did the same.

Comparative example 3
As the polyalkylene succinate, polybutylene succinate (melting point = 90°C, intrinsic viscosity = 1.38, MFR = 35 g/10 min, b/a = 0.12 mW/(mg· °C)) was used as in Example 1.

Table 1 shows the runnability of the fibers obtained in Examples 1 to 6 and Comparative Examples 1 to 3, and the quality of the fibers and nonwoven fabrics.

As is clear from Table 1, in Examples 1 to 8, the runnability and the quality of fibers and nonwoven fabrics were good.

On the other hand, since Comparative Example 1 had a small fineness, the workability was deteriorated, and a fiber sample could not be collected.

In Comparative Example 2, the melting point of the polylactic acid was low and the crystallinity was low, so the workability and the quality of the fiber were deteriorated. In addition, the difference in melting point between polylactic acid and polybutylene succinate was small, and the shrinkage rate of the fiber was high, so the quality of the nonwoven fabric was also inferior.

In Comparative Example 3, the melting point of the polybutylene succinate was low and the crystallinity was low, so the workability and the quality of the fiber were deteriorated. Moreover, since the shrinkage rate of the fiber was high, the quality of the nonwoven fabric deteriorated.

Claims (6)

Consisting of polylactic acid and crystalline polyalkylene succinate,
The fiber cross section is a split type composite form in which one of the two components described above is divided into a plurality of pieces by the other component,
The cross-sectional shape of the split type composite form is a shape composed of a petal part having a plurality of petal-shaped parts radially from the center of the cross section and a split part divided into individual petal-shaped parts of the petal part,
A split-type composite form comprising a conjugate fiber having a fineness of 1 to 6 dtex, a total number of splits of 10 to 30, and a split fineness of each split component constituting at least 0.20 dtex or less. can be,
The melting point of polylactic acid is 155° C. or higher, the melting point of polyalkylene succinate is 105 to 125° C., the difference in melting point between polylactic acid and polyalkylene succinate is 30 to 60° C.,
A biodegradable splittable conjugate fiber having a shrinkage of 15% or less when heat-treated at 85°C for 15 minutes.
2. The splittable conjugate fiber according to claim 1, wherein the crystalline polyalkylene succinate is polybutylene succinate. The intrinsic viscosity of the polylactic acid is 1.25 or more, the intrinsic viscosity of the polyalkylene succinate is 1.35 to 1.55, and the difference in intrinsic viscosity between the polylactic acid and the polyalkylene succinate is 0.15 or less. The splittable conjugate fiber according to claim 1 or 2, characterized in that Polylactic acid has a melt flow rate at 190° C. of 5 to 20 g/10 minutes, polyalkylene succinate has a melt flow rate of 15 to 30 g/10 minutes at 190° C., and polylactic acid and polyalkylene succinate 4. The splittable conjugate fiber according to any one of claims 1 to 3, characterized in that the difference in melt flow rate from that of the splittable conjugate fiber is 15 g/10 minutes or less. 5. The resolution according to any one of claims 1 to 4, comprising a polyalkylene succinate having a peak b/a of 0.20 mW/(mg·° C.) or more indicating temperature-lowering crystallization obtained by DSC. type composite fiber. A nonwoven fabric comprising the splittable conjugate fiber according to any one of claims 1 to 5, wherein the constituent fibers are thermally bonded to each other by a thermal bonding component formed by melting and fixing polyalkylene succinate.