JP2005307359A - Polylactic acid staple fiber and staple fiber nonwoven fabric using the same fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid staple fiber structure scarcely rejecting wastes and having production stability because the shrinkage is sufficiently small even when hot integral molding with a substrate, a backing material, etc., is carried out. <P>SOLUTION: The polylactic acid staple fiber is composed of polylactic acid, has 3-150 mm fiber length and is characterized in that the dry heat shrinkage percentage based on JIS L 1015:1999 under dry heat-treating conditions at 150°C for 20 min after heat shrinking the staple fiber is within the range of 0.05-5%. A nonwoven fabric is obtained by using the polylactic acid staple fiber in at least a part and has the dry heat shrinkage percentage based on JIS L 1913:1998 under dry heat-treating conditions at 150°C for 30 min is within the range of 0.05-2%. The polylactic acid staple fiber nonwoven fabric can be used as internal trim or door trim such as a ceiling material, a line carpet, an option mat or a trunk of automobiles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a short polylactic acid fiber suitable for use in automobile interior materials and a short fiber nonwoven fabric using the fiber.

  Recently, with increasing awareness of the environment on a global scale, there are concerns about global warming caused by mass consumption of petroleum resources and the depletion of petroleum resources associated with mass consumption. From such a background, a natural circulation type environmentally friendly material that is made of a plant-derived raw material (biomass) and eventually decomposes into water and carbon dioxide in the natural environment after use is eagerly desired.

  However, until now, such biodegradable polymers using biomass have problems of high production costs and low mechanical properties and heat resistance, and have not been used for general-purpose plastics. As a biodegradable polymer utilizing biomass that can solve these problems, polylactic acid, which is a kind of aliphatic polyester, is currently attracting the most attention. Polylactic acid is a polymer made from lactic acid obtained by fermenting starch extracted from plants. Among biodegradable polymers using biomass, it has the best balance of mechanical properties, heat resistance and cost. . And recently, development of resin products, fibers, films, sheets and the like using this has been carried out at a rapid pitch.

  Under such circumstances, the development of polylactic acid fibers is preceded by agricultural materials and civil engineering materials that make use of biodegradability, but the subsequent large-scale uses include clothing, hygiene, bedding and materials. Application to is expected.

  However, in these applications, it is often necessary to use short fibers because of the texture of the resulting fiber product or the nature of the form, but in the case of polylactic acid short fibers, the fibers themselves slip. Due to the extremely poor performance, various problems occur during the manufacturing process or when the product is used, and the actual situation is that the development of these applications has not progressed as expected.

  Conventionally, there is a technique for producing a short fiber of polylactic acid according to a conventional method (see Patent Document 1). However, as a result of the inventors performing a supplementary test based on the technique described in Patent Document 1, crimped spots are found. It turns out that it occurs frequently. It was also found that high-quality short fibers could not be obtained, for example, the fibers were worn at the rollers and guide portions in each step, and fluff and scraped fibers were generated. Moreover, when the polylactic acid short fiber obtained in this way was used as a spun yarn, the thickness unevenness and the variation in physical properties were large, and due to these, the stained unevenness appeared remarkably. Furthermore, when the polylactic acid short fiber obtained in this way was used for a nonwoven fabric, the dispersibility of the short fiber was extremely poor, and a nonwoven fabric having a uniform fiber density could not be obtained. In addition, the non-woven fabric has a very large thermal shrinkage when heated, and deformation, warpage, distortion, shrinkage occurs during heat molding by integral molding with a base material, backing material, etc., and a high-quality molded product can be obtained. It was extremely difficult.

As these causes, it is considered that the polylactic acid fiber has a larger shrinkage during dry heat than other general-purpose synthetic fibers. For example, as a method for improving the heat resistance of a polylactic acid fiber, a polylactic acid short fiber having a dry heat shrinkage rate of 110% or less at 110 ° C. by ester-bonding a hydroxyl group at the molecular end with a carboxylic acid has been proposed. (See Patent Document 2). Moreover, the nonwoven fabric whose dry heat shrinkage rate at the time of the hot-air drying of the nonwoven fabric at 100 degreeC is 5% or less is proposed by using the core-sheath composite fiber which consists of polylactic acid (refer patent document 3). However, even when the above short fibers are formed into a non-woven fabric, the heating temperature at the time of molding is 120 ° C. to 180 ° C., and there is a problem that warpage or deformation occurs due to shrinkage at the time of molding. That is, in the present situation, a technique for suppressing warpage and deformation due to shrinkage at the time of molding in a nonwoven fabric using polylactic acid fibers has not yet been established.
JP-A-6-212511 (page 2-4) JP-A-7-118922 JP-A-7-133511

  The object of the present invention is to solve the above-mentioned problems, and to reduce the dry heat shrinkage due to heating at the time of molding from the conventional 10% to about 2%, and a short polylactic acid fiber using this fiber. It is intended to provide a fiber nonwoven fabric.

  In order to solve the above problems, the present invention is a short fiber having a fiber length of 3 to 150 mm made of polylactic acid, and the short fiber is thermally shrunk to dry the subsequent short fiber at 150 ° C. for 20 minutes. Provided is a short polylactic acid fiber characterized in that a dry heat shrinkage rate based on JIS 1015-1999 in a heat treatment condition is in a range of 0.05 to 5%.

  In this case, the heat treatment is preferably a relaxation heat treatment in a temperature range of 120 to 220 ° C. The fineness is preferably in the range of 0.1 to 100 dtex, and the elongation is preferably in the range of 10 to 100%. Further, the fiber treatment oil agent is preferably attached in the range of 0.1 to 2.0% by weight.

  The short fiber nonwoven fabric of the present invention is a nonwoven fabric using at least a part of the polylactic acid short fibers described above, and is a dry nonwoven fabric based on JIS 1913-1998 under dry heat treatment conditions at 150 ° C. for 30 minutes. The heat shrinkage rate is in the range of 0.05 to 2%.

In this case, the blend ratio of the polylactic acid short fibers is preferably in the range of 10 to 100 parts by weight, and the basis weight is preferably 10 to 5000 g / m ² . Furthermore, what has resin adhered to the short fiber nonwoven fabric in 0.05-70 weight part is preferable.

  The polylactic acid short fiber nonwoven fabric described in any of the above can be used as interior materials such as automobile ceiling materials, line carpets, option mats and trunks, or door trims.

  According to the polylactic acid short fiber of the present invention, a product excellent in dimensional stability and crimp retention is obtained. In addition, according to the short fiber nonwoven fabric of the present invention, since the shrinkage is sufficiently small even when integrally molded with a base material, a backing material, etc., a nonwoven fabric with less generation of waste and production stability can be obtained. When this non-woven fabric is used, for example, in an automobile's ceiling skin, floor carpet portion, or trunk interior material, it is suitable as an automotive interior material because there is little settling and deformation during molding.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The polylactic acid referred to in the present invention refers to a polymerized lactic acid oligomer such as lactic acid or lactide, and the optical purity of the L-form or D-form is preferably 90% or higher because of its high melting point. The optical purity of the L-form or D-form is more preferably 97% or more. A blend of polylactic acid having an optical purity of 90% or higher in the L form and polylactic acid having an optical purity of 90% or higher in the D form at a ratio of 70/30 to 30/70% is preferable because the melting point is further improved. is there. In addition, in the range that does not impair the properties of polylactic acid, even if components other than lactic acid are copolymerized, polymers and particles other than polylactic acid, flame retardants, antistatic agents, matting agents, deodorants, antibacterial agents, You may contain additives, such as an antioxidant or a coloring pigment. Moreover, terminal blockers, such as a carbodiimide compound, may be contained for the purpose of suppressing hydrolysis of polylactic acid in hot water treatment for dyeing and the like and suppressing deterioration of physical properties of the product over time. When the molecular weight of the polylactic acid polymer is 50,000 to 500,000 in terms of weight average molecular weight, it is preferable that the balance between mechanical properties and moldability is good. The molecular weight of the polylactic acid polymer is more preferably 100,000 to 350,000 in terms of weight average molecular weight.

  The single fiber fineness of the polylactic acid short fiber of the present invention is preferably 0.1 to 100 dtex, more preferably 0.3 to 50 dtex. Moreover, as a fiber length of the polylactic acid short fiber of this invention, it is required to be the range of 3-150 mm. When the thickness is less than 3 mm, the card passing property is extremely poor and the productivity is inferior. When the thickness exceeds 150 mm, the card passing property is deteriorated and, at the same time, the texture of the spun yarn and the nonwoven fabric is deteriorated. These fineness and length are appropriately selected according to the application as described later.

  Further, the elongation of the polylactic acid short fibers is preferably in the range of 10 to 100% from the viewpoint of card passing property.

  The polylactic acid short fiber of the present invention preferably has a strength of 2.0 cN / dtex or more in order to keep the process passability and the mechanical strength of the product sufficiently high. Moreover, it is preferable that the elongation of the polylactic acid short fiber of the present invention is in the range of 10 to 80% with good passability in the card process and production stability at the production of the nonwoven fabric.

  As the cross-sectional shape, a round cross-section, a multi-leaf cross-section such as a hollow cross-section or a trilobal cross-section, and other irregular cross-sections can be freely selected. In particular, polylactic acid short fibers having a hollow cross-sectional shape are preferred for uses in which lightweightness, softness, and heat retention are regarded as important, such as filling cotton. The hollowness in this case is preferably 15 to 45%. By setting the hollow ratio to 15% or more, lightness, softness, and heat retention can be achieved, and by setting the hollow ratio to 45% or less, the hollow can be crushed or the fiber can be cracked during crimping. It is suppressed and the physical properties and quality of the fiber can be maintained. The hollow ratio here refers to the area ratio of the hollow portion to the area obtained from the outer shape of the fiber cross section, expressed as a percentage.

  The polylactic acid short fiber of the present invention is a composite of a type that elutes one component such as a core-sheath type, an eccentric core-sheath type, a side-by-side type, a split fiber split type, or a sea-island type containing at least polylactic acid as a component. It is good also as a form of a fiber.

  The polylactic acid short fiber of the present invention is preferably provided with a spinning oil containing a smoothing agent. Examples of the smoothing agent include fatty acid esters, polyhydric alcohol esters, ether esters, polyethers, silicones, and mineral oils. These smoothing agents may be used as a single component, or a plurality of components may be mixed and used. By adding an oil agent containing a smoothing agent as described above to polylactic acid short fibers, the slipping property of the polylactic acid short fibers is further improved, including spinning and drawing, processability in carding and spinning, and In addition to improving the quality of crimped fluff and fluff of the obtained short fiber itself, it is possible to further improve the opening property of the short fiber and the dispersibility of the short fiber in the fiber structure. Moreover, it is preferable that the adhesion amount is 0.1 to 2.0% by weight because the card passing property and the productivity at the time of producing the nonwoven fabric are good. More preferably, it is preferably 0.2 to 0.7% by weight.

  In the present invention, in addition to the smoothing agent, the component constituting the oil agent is an emulsifier that emulsifies the oil agent in water, lowers the viscosity and improves adhesion to the yarn and penetration, and if necessary, an antistatic agent, an ion A surfactant, a sizing agent, a rust inhibitor, a preservative, or an antioxidant can be appropriately used.

  The polylactic acid short fiber of the present invention is characterized in that the heat shrinkage of the short fiber by heat setting reduces the dry heat shrinkage ratio of the heat-treated short fiber at 150 ° C. for 20 minutes. It is. The treatment temperature is preferably a temperature within the range of 120 to 220 ° C., and relaxation heat treatment is performed on the short fibers within this temperature range. When the relaxation heat treatment temperature is less than 120 ° C., thermal shrinkage increases, and the dimensional stability and crimp retention of short fibers deteriorate. When the temperature exceeds 200 ° C., fusion of short fibers increases, resulting in poor productivity. Result. This temperature is more preferably 140 to 160 ° C., and in this range, short fibers with little fusion and a low dry heat shrinkage ratio can be obtained, so that productivity is improved. When the number of crimps of the polylactic acid short fiber of the present invention is 6 peaks / 25 mm or more and the crimp rate is 10% or more, a good texture with a bulky and light feeling can be achieved. In addition, if the number of crimps is too large or the crimp rate is too large, the bulkiness may decrease, so the number of crimps and the crimp rate are 20 peaks / 25 mm or less and 50% or less, respectively. It is preferable that The number of crimps is more preferably 8-15 peaks / 25 mm, and the crimp rate is more preferably 15-30%.

  Next, the manufacturing method of the polylactic acid short fiber of this invention is demonstrated.

  Although this manufacturing method is not specifically limited, For example, the manufacturing method currently disclosed by Unexamined-Japanese-Patent No. 6-65360 is mentioned. That is, a direct dehydration condensation method in which lactic acid is dehydrated and condensed as it is in the presence of an organic solvent and a catalyst. Further, there is a method of copolymerizing and transesterifying at least two kinds of homopolymers disclosed in JP-A-7-173266 in the presence of a polymerization catalyst. Furthermore, there is a method disclosed in US Pat. No. 2,703,316. That is, an indirect polymerization method in which lactic acid is once dehydrated to form a cyclic dimer and then subjected to ring-opening polymerization.

  The spinning temperature varies depending on the copolymerization ratio and molecular weight of the polylactic acid used, but is preferably 180 to 280 ° C. When the spinning temperature is less than 180 ° C., melt extrusion is difficult, and when it exceeds 280 ° C., the degradation of polylactic acid becomes remarkable, making it difficult to obtain high-strength polylactic acid short fibers having excellent crimp characteristics.

  The melt-spun yarn is subjected to cooling, application of oil, take-up, drawing, drawing, and heat setting. The oil agent can be applied after cooling the yarn spun from the die. Further, when the take-up speed is 400 to 2,000 m / min and the draw ratio is 1.5 to 6 times, a polylactic acid short fiber having appropriate strength is obtained when the polylactic acid short fiber is used as a fiber structure. It is done. The drawing may be performed by combining a plurality of wound yarns so that the final fineness becomes a tow with a total fineness of 5 to 1 million dtex. Moreover, in order to extend | stretch a tow | bowl uniformly, it is preferable to perform the liquid bath extending | stretching using 60-100 degreeC warm water.

  Next, crimp is applied to the drawn yarn, and the fiber length is cut within a range of 3 to 150 mm by a cutting device such as a rotary cutter. The crimping method is not particularly limited, and examples thereof include a stuffing box method, an indentation heating gear method, and a high-speed air jet indentation method. Further, if necessary, an oil agent may be applied as a finishing agent after stretching or after crimping.

  The fiber structure using the polylactic acid short fiber of the present invention is not particularly limited as long as the polylactic acid short fiber is used for at least a part thereof, and examples thereof include spun yarn, nonwoven fabric, insert cotton, and binder fiber. Can be mentioned. These are fibers other than polylactic acid short fibers, for example, biodegradable fibers such as polyglycolic acid, polyhydroxybutyrate, polybutylene succinate, and polycaprolactone, and natural fibers such as cotton, silk, hemp, and wool. Further, it may be a recycled fiber such as rayon or acetate, a mixed article with synthetic fibers such as polyethylene terephthalate, nylon, acrylic, vinylon, polyolefin or polyurethane.

  Since the polylactic acid short fiber of the present invention is excellent in the spreadability in a spreader or a card machine, a uniform web can be produced.

  Next, the short fiber nonwoven fabric of the present invention will be described.

  The short fiber nonwoven fabric of the present invention is a nonwoven fabric obtained by mixing the above-described polylactic acid short fibers and other fibers, and the polylactic acid short fibers may be used at least in part. Binder fibers are preferably used as the fibers other than the polylactic acid short fibers, the entanglement points between the fibers can be fixed, and the wearability and heat shrinkability can be improved. As the binder fiber, various thermoplastic fibers are used. For example, polyethylene terephthalate and nylon fiber can be used as well as polyolefin fibers such as polyethylene and polypropylene. Especially, the polyethylene terephthalate short fiber is from the viewpoint of cost performance and strength. It can be preferably used. The fiber to be used may be a total-melt type or a core-sheath type fiber in which only the sheath part is unwound, and any of them can be preferably used. The blending rate is preferably 10 to 100 parts by weight from the viewpoint of biodegradability and durability.

  When fibers other than the polylactic acid short fibers are mixed, a web in which different types of short fibers are uniformly mixed can be produced due to the slipperiness of the polylactic acid short fibers. Moreover, when using a polylactic acid short fiber as a heat bonding fiber, you may use a polylactic acid short fiber with low optical purity and a low melting point.

In the present invention, the polylactic acid short fibers constituting the nonwoven fabric can be applied to various uses as long as the single fiber fineness is in the range of 0.3 to 100 dtex and the fiber length is in the range of 10 to 100 mm. preferable. Moreover, as the fabric weight of the whole nonwoven fabric, Preferably it is the range of 10-5000 g / m < ² >, and application to various uses is possible.

  The polylactic acid short fiber nonwoven fabric in the present invention can fix the entanglement point of the fiber by using a resin or a binder fiber, and this has an effect of making the thermal shrinkage of the nonwoven fabric smaller than that without using it, Abrasion and texture can also be improved. The adhesion amount of the resin to the nonwoven fabric is in the range of 0.1 to 70% by weight, and if it is 1 to 10% by weight, the dry heat shrinkage rate and cost performance are excellent. The resin to be used is not particularly limited as long as the fiber entanglement point can be fixed, and acrylic resin, urethane resin, and polyethylene terephthalate resin are preferably used. If these resins are plant-derived resins, all of them, including the polylactic acid short fibers of the present invention, are plant-derived substances, and therefore, the appeal of the effects of the invention is increased, which is more preferable.

  The polylactic acid short fiber nonwoven fabric according to the present invention has a small heat shrinkage at the time of molding, and has less settling and deformation than conventional polylactic acid short fibers, so that it can be used for automobile ceiling materials, line carpets, option mats, trunk interior materials, door trims, etc. It is suitable for automotive interior material applications using these fibers.

  Examples of the polylactic acid short fibers of the present invention will be described below.

  In addition, the following method was used as a measuring method of the characteristic in an Example.

A. Strength, elongation, number of crimps and crimp rate Conforms to JIS L 1015-1999.

B. Dry heat shrinkage rate JIS L 1015-1999 was followed except that the fiber was heat treated at 150 ° C. for 20 minutes.

C. Dry heat shrinkage rate of nonwoven fabric It conformed to JIS L 1913-1998.

Example 1
A polylactic acid chip (6201D manufactured by Cargill Dow) was charged into a spinning machine hopper, melted at 220 ° C. with an extruder type spinning machine, spun at a discharge rate of 505 g / min from a die having 600 holes, and a spinning speed of 1000 m / min. I took it. Similarly, a plurality of spun yarns were combined and received in a can. The undrawn yarn was further combined into a 27.7 ktex tow, drawn to 3.1 times in an 80 ° C. water bath, and then crimped by a stuffing box. Next, relaxation heat treatment was performed at 130 ° C., and after applying an oil agent, cutting was performed to obtain a polylactic acid short fiber SF1 of the present invention having a single fiber fineness of 3.1 dtex and a fiber length of 51 mm.

  As shown in Table 1, the properties of this polylactic acid short fiber are as follows: strength 2.9 cN / dtex, elongation 67%, dry heat shrinkage 2.5%, and good yarn physical properties. A good crimping characteristic of 25 mm and a crimping ratio of 11% was shown.

Example 2
In the present Example, it aimed at reducing the heat shrinkage rate of a short fiber more. The manufacturing conditions are the same as in Example 1 except that the relaxation heat treatment temperature is 150 ° C. As a result, as shown in Table 1, the dry heat shrinkage ratio was 0.2%, indicating good characteristics.

  Specifically, a polylactic acid chip (Cargildau's 6201D) was charged into a spinning machine hopper, melted at 220 ° C. with an extruder-type spinning machine, spun from a die having 600 holes at a discharge rate of 505 g / min, and a spinning speed of 1000 m / I took it in minutes. Similarly, a plurality of spun yarns were combined and received in a can. The undrawn yarn was further combined into a 27.7 ktex tow, drawn to 3.1 times in an 80 ° C. water bath, and then crimped by a stuffing box. Next, relaxation heat treatment was performed at 150 ° C., and after applying an oil agent, cutting was performed to obtain a polylactic acid short fiber SF2 having a single fiber fineness of 3.2 dtex and a fiber length of 51 mm. As shown in Table 1, the properties of this polylactic acid short fiber are as follows: strength 2.4 cN / dtex, elongation 73%, dry heat shrinkage 0.2%, and good yarn physical properties. A good crimping characteristic of 25 mm and a crimping ratio of 11% was shown.

Example 3
In this example, in order to improve the wearability of the short fibers, the fineness is increased, and a lubricant (ethylene bis stearamide, hereinafter abbreviated as EBA) is added to the dry heat shrinkage. We went to confirm that there was no change. The production conditions were the same as in Example 1 except that 1% by weight of a lubricant was added to the polymer, except for the draw ratio. A polylactic acid chip (6201D manufactured by Cargill Dow), a black master chip and a smoothing agent (6.5: 1: 2.5) Charged into a spinning machine hopper, melted at 220 ° C. with an extruder type spinning machine, spun from a die having 200 holes at a discharge rate of 484 g / min, and taken up at a spinning speed of 1000 m / min. Similarly, a plurality of spun yarns were combined and received in a can. The undrawn yarn was further combined into a 28.8 ktex tow, drawn in a water bath at 80 ° C. by 3.6 times, and then crimped by a stuffing box. Next, relaxation heat treatment was performed at 110 ° C., and after applying an oil agent, cutting was performed to obtain a polylactic acid short fiber SF3 having a single fiber fineness of 9 dtex and a fiber length of 64 mm. As shown in Table 1, the properties of this polylactic acid short fiber are as follows: strength 2.2 cN / dtex, elongation 75%, dry heat shrinkage ratio 0.7%, and good yarn physical properties. Good crimp characteristics of 25 mm and a crimp rate of 17% were shown.

Example 4
Using the polylactic acid short fiber SF1 obtained in Example 1 as raw cotton, a web having a basis weight of 91.5 g / m ² was prepared through a fiber opening machine and a parallel card machine. Subsequently, the web was entangled with a fiber using a needle punch machine (number of needles 50 / cm 2) to obtain a nonwoven fabric. Thereafter, two sheets of this nonwoven fabric were further stacked, and further passed through a needle punch machine twice to obtain a polylactic acid short fiber nonwoven fabric 1 having a basis weight of 183 g / cm 2. The obtained non-woven fabric showed a dry heat shrinkage rate as low as 150% at a temperature of 30 ° C. and a heat shrinkage rate as low as 1.0% and 1.0% in width.

Example 5
In the present Example, it performed in order to confirm that the dry heat shrinkage rate of a short fiber nonwoven fabric changes with the relaxation heat treatment temperature of raw cotton. The production conditions are the same as in Example 4 except that SF2 obtained in Example 2 is used for the raw cotton.

Using a polylactic acid short fiber SF2 as raw cotton, a web having a basis weight of 89.5 g / m ² was prepared through a fiber opening machine and a parallel card machine. Subsequently, the web was entangled with a fiber using a needle punch machine (number of needles 50 / cm 2) to obtain a nonwoven fabric. Thereafter, two sheets of this nonwoven fabric were further stacked, and further passed through a needle punch machine twice to obtain a polylactic acid short fiber nonwoven fabric 2 having a basis weight of 179 g / cm 2. The obtained non-woven fabric exhibited a dry heat shrinkage rate as low as 150% at a temperature of 30 ° C. and a heat shrinkage rate as low as 0.7% and 0.5% in width.

Example 6
In the present Example, it performed in order to confirm that the dry heat shrinkage rate of a short fiber nonwoven fabric does not change with the fineness of raw cotton, and lubricant addition. The production conditions are the same as in Example 4 except that SF3 is used for the raw cotton.

A polylactic acid short fiber SF3 was used as raw cotton, and a web having a basis weight of 89.5 g / m ² was produced through a fiber opening machine and a parallel card machine. Subsequently, the web was entangled with a fiber using a needle punch machine (number of needles 50 / cm 2) to obtain a nonwoven fabric. Thereafter, two sheets of this non-woven fabric were further stacked, and further passed through a needle punch machine twice to obtain a polylactic acid short fiber non-woven fabric 2 having a basis weight of 187 g / cm 2. The obtained nonwoven fabric exhibited a dry heat shrinkage rate as low as 150% at a temperature of 30 ° C. and a heat shrinkage rate as low as 0.8% and 0.7% in width.

Comparative Example 1
Influence of relaxation heat treatment temperature on the above Examples 1 to 6 This time, the temperature of relaxation heat treatment was set to 90 degrees and 110 degrees. As a result, the dry heat shrinkage ratio of the raw cotton SF4 to 6 was 6.0 to 9.3%. In addition, the non-woven fabrics 4 to 6 made using the same also had a dry heat shrinkage rate of 2.7 to 6.2%, which was insufficient in terms of the dry heat shrinkage rate.

Comparative Example 2
A polylactic acid chip (Cargildau 6201D) was charged into a spinning machine hopper, melted at 220 ° C. with an extruder-type spinning machine, spun at a discharge rate of 390 g / min from a base having 600 holes, and a spinning speed of 1000 m / min. I took it. Similarly, a plurality of spun yarns were combined and received in a can. The undrawn yarn was further combined into a 28 ktex tow, drawn 6.6 times in a water bath at 80 ° C., and then crimped by a stuffing box. Next, relaxation heat treatment was performed at 90 ° C., and after applying an oil agent, cutting was performed to obtain a polylactic acid short fiber SF5 having a single fiber fineness of 6.6 dtex and a fiber length of 51 mm. The properties of this polylactic acid short fiber are as shown in Table 1. The strength is 2.8 cN / dtex, the elongation is 60%, the dry heat shrinkage is 9.3%, the number of crimps is 11 peaks / 25 mm, and the crimp is 20%. It showed the crimp characteristics.

Comparative Example 3
Polylactic acid chips (Cargildau 6201D), black master chips and smoothing agent (6.5: 1: 2.5) were charged into a spinning machine hopper, melted at 220 ° C. with an extruder spinning machine, and 200 holes were formed. Spinning was carried out from the die having a discharge rate of 484 g / min and taken up at a spinning speed of 1000 m / min. Similarly, a plurality of spun yarns were combined and received in a can. The undrawn yarn was further combined into a 28.8 ktex tow, drawn in a water bath at 80 ° C. by 3.6 times, and then crimped by a stuffing box. Next, relaxation heat treatment was performed at 110 ° C., and after applying an oil agent, cutting was performed to obtain a polylactic acid short fiber SF6 having a single fiber fineness of 9 dtex and a fiber length of 64 mm. As shown in Table 1, the properties of this polylactic acid short fiber are as follows: strength 2.6 cN / dtex, elongation 64%, dry heat shrinkage 7.5%, and good yarn physical properties. Good crimp characteristics of 25 mm and a crimp rate of 19% were exhibited.

Comparative Example 4
Using a polylactic acid short fiber SF4 as raw cotton, a web having a basis weight of 93.5 g / m ² was produced through a fiber opening machine and a parallel card machine. Subsequently, the web was entangled with a fiber using a needle punch machine (number of needles 50 / cm 2) to obtain a nonwoven fabric 3. Thereafter, two sheets of this nonwoven fabric were further stacked, and further passed through a needle punching machine twice to obtain a polylactic acid short fiber nonwoven fabric 4 having a basis weight of 187 g / cm 2. The obtained non-woven fabric exhibited dry heat shrinkage of 2.7% vertically and 3.3% horizontally at 150 ° C. for 30 minutes.

Comparative Example 5
A polylactic acid short fiber SF5 was used as raw cotton, and a web having a basis weight of 96.0 g / m ² was produced through a fiber opening machine and a parallel card machine. Subsequently, the web was entangled with a fiber using a needle punch machine (number of needles 50 / cm 2) to obtain a nonwoven fabric. Thereafter, two sheets of this nonwoven fabric were further stacked, and further passed through a needle punching machine twice to obtain a polylactic acid short fiber nonwoven fabric 5 having a basis weight of 192 g / cm 2. The obtained non-woven fabric had values of a dry heat shrinkage of 150% at 30 ° C. for 30 minutes, and a length of 6.2% and a width of 5.5%.

Comparative Example 6
A polylactic acid short fiber SF6 was used as raw cotton, and a web having a basis weight of 75.0 g / m ² was produced through a fiber opening machine and a parallel card machine. Subsequently, the web was entangled with a fiber using a needle punch machine (number of needles 50 / cm 2) to obtain a nonwoven fabric. Thereafter, two sheets of this non-woven fabric were further stacked, and further passed through a needle punch machine twice to obtain a polylactic acid short fiber non-woven fabric 6 having a basis weight of 150 g / cm 2. The obtained non-woven fabric exhibited values of dry heat shrinkage at 150 ° C. for 30 minutes of 4.0% vertical and 3.4% horizontal.

  Table 1 below summarizes the above Examples 1 to 3 and Comparative Examples 1 to 3.

  As is clear from Table 1, the polylactic acid short fiber of the present invention provides a low-shrinkage raw cotton having a very low dry heat shrinkage rate.

  On the other hand, Table 2 below summarizes the above Examples 4 to 6 and Comparative Examples 4 to 6.

  As is apparent from Table 2, the nonwoven fabrics 1 to 3 using the low shrinkage raw cotton obtained from Examples 1 to 3 have a very low dry heat shrinkage rate when heat-treated at 150 ° C. for 30 minutes. It can be said that this is a non-woven fabric with small shrinkage and excellent moldability.

  On the other hand, the nonwoven fabrics 4 to 6 using the raw cotton obtained from Comparative Examples 4 to 6 have a high dry heat shrinkage rate during heat treatment, and deformation, warpage, and the like due to shrinkage of the nonwoven fabric during molding are expected. Is unsuitable.

Claims (10)

It is a short fiber having a fiber length of 3 to 150 mm made of polylactic acid, and the short fiber is thermally shrunk so that the short fiber is dried according to JIS 1015-1999 in a dry heat treatment condition at 150 ° C. for 20 minutes. A polylactic acid short fiber having a thermal shrinkage in the range of 0.05 to 5%. The polylactic acid short fiber according to claim 1, wherein the heat treatment is a relaxation heat treatment in a temperature range of 120 to 220 ° C. The polylactic acid short fiber according to claim 1 or 2, wherein the fineness is in a range of 0.1 to 100 dtex. The polylactic acid short fiber according to any one of claims 1 to 3, wherein the elongation is in the range of 10 to 100%. The polylactic acid short fiber according to any one of claims 1 to 4, wherein the fiber treatment oil is adhered within a range of 0.1 to 2.0% by weight. A non-woven fabric using at least a part of the polylactic acid short fibers according to any one of claims 1 to 5, wherein the dry heat shrinkage of the non-woven fabric is based on JIS 1913-1998 in a dry heat treatment condition at 150 ° C for 30 minutes. Is in the range of 0.05 to 2%. The short fiber nonwoven fabric according to claim 6, wherein the blend ratio of the polylactic acid short fibers is in the range of 10 to 100 parts by weight. Staple fiber nonwoven fabric according to claim 6 or 7 basis weight is characterized by a 10~5000g / m ^2. The short fiber nonwoven fabric according to claim 8 or 9, wherein the resin is adhered to the short fiber nonwoven fabric in a range of 0.05 to 70 parts by weight. An automobile interior material, wherein the polylactic acid short fiber nonwoven fabric according to any one of claims 6 to 9 is used as an automobile ceiling material, line carpet, option mat, trunk interior material or door trim.