JP2008144299A - Short cut polyester conjugate fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a short cut polyester conjugate fiber that can solve the problems of polylactic acid inferior in strength, abrasion resistance and moist heat decomposition resistance in spite of including a polylactic acid as a constituent component, is not provided with crimps, has no pile bending and is suitably useful for wet papermaking and flocky processing of electrodeposition. <P>SOLUTION: The short cut polyester conjugate fiber is a core-sheath type conjugate fiber having a polylactic acid as a core component and an aromatic polyester as a sheath component, having a fiber length of ≤25 mm, not applied with mechanical crimps and having substantially no pile bend. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a core-sheath type composite fiber using polylactic acid as a core component, is not imparted with mechanical crimping, is substantially free of pile bending, and is used for piles of wet papermaking and electrodeposition flockeys. It is related with the shortcut polyester composite fiber suitable for.

  Synthetic fibers such as vinylon, nylon, polyester, etc. that are not crimped, use short-cut fibers with a fiber length of 5-20 mm, disperse in water, and wet in the same way as paper A method of making a paper to obtain a nonwoven fabric is well known.

  In addition, shortcut fibers called flockey piles with a fiber length of about 1 to 2 mm are used on a base material such as a woven or knitted fabric, nonwoven fabric, wood, metal, or plastic coated with an adhesive so that the shortcut fibers are perpendicular. There is a processing method to obtain a texture and feel similar to velvet by sticking the flocks so that they stand, and this is called electrodeposition flocking.

  On the other hand, most of the conventional synthetic fibers such as vinylon, nylon and polyester are made from valuable fossil resources such as petroleum. And these are hardly decomposed | disassembled in a natural environment, and disposal processing becomes a problem. In addition, carbon that was trapped in fossil resources during the disposal process is released into the air as carbon dioxide, contributing to global warming.

  Polylactic acid, on the other hand, is made from plant resources such as corn. Polylactic acid fibers made from polylactic acid are processed into various products, and finally, in natural environments such as compost or soil. It is decomposed into carbon dioxide and water, and these are the ultimate recycled materials that are taken into plants again by photosynthesis.

  However, polylactic acid fibers are inferior in strength and wear resistance to conventional synthetic fibers. Further, there is a problem that the degree of polymerization is greatly reduced by wet heat treatment such as dyeing, and this also causes a reduction in strength.

  For this reason, the use of conventional polylactic acid fibers is limited to disposable daily materials, agricultural, forestry and horticultural materials, and is not used in a wide range of fields such as clothing, civil engineering, marine materials, and automotive materials. The current situation is not.

  Therefore, when polylactic acid fibers are used for applications that require strength, a method of covering strength and wear resistance by increasing the fineness, mass, and thickness is employed. Patent Document 1 proposes a post-processed fiber using a polymer having slipperiness on the fiber surface in order to improve wear resistance. However, since it is a surface treatment, the polymer on the surface was dropped during use, and the durability was insufficient.

  Patent Document 2 proposes a composite fiber in which polylactic acid forms all or part of the surface of a single fiber, and polyester such as polyethylene terephthalate is used as another component. However, this fiber is a binder fiber that melts polylactic acid as an adhesive component and has different uses, and because polylactic acid occupies the outer periphery of the fiber, the strength that is a problem of polylactic acid fibers as described above It was not possible to eliminate the low wear resistance.

JP 2002-38378 A Japanese Patent Laid-Open No. 11-279841

  The present invention solves the above-mentioned problems and can solve the problems of polylactic acid inferior in strength, wear resistance and wet heat decomposability while using polylactic acid as a constituent component, and crimping is imparted. It is intended to provide a short-cut polyester composite fiber that can be suitably used for wet papermaking and electrodeposition flocking, and has no pile bending.

The present inventor has reached the present invention as a result of studies to solve the above-mentioned problems.
That is, the present invention is a core-sheath type composite fiber having polylactic acid as a core component and aromatic polyester as a sheath component, the fiber length is 25 mm or less, no mechanical crimp is imparted, and the pile is bent substantially. The gist of the short-cut polyester composite fiber is characterized by the absence of

  The no-crimp shortcut polyester composite fiber of the present invention is composed of a polylactic acid component, and is excellent in strength, wear resistance, and wet heat decomposability, and is friendly to the global environment. It can be used favorably for applications.

Hereinafter, the present invention will be described in detail.
The shortcut polyester conjugate fiber of the present invention needs to be substantially free from pile bending. Here, “substantially no pile bending” means that the value measured by the following method for measuring the degree of pile bending is 10% or less.
[Measurement of degree of pile bending]
A single fiber is taken out and the fiber length is cut to 10 mm to obtain a sample. This sample is placed on paper and left for 1 week in an atmosphere of temperature 20 ° C. and humidity 60%. And the ratio of the perpendicular (length) to the point on the sample furthest away from this line segment to the line segment (length) connecting both ends of the sample is measured. Ten samples are measured and the average value is taken.
When the fiber length is less than 10 mm, a sample of 10 mm is obtained from the fiber bundle and measured before the fiber bundle is cut into shortcut fibers.

  If the value measured by the method of measuring the degree of pile bending exceeds 10%, pile bending occurs, and it is difficult to disperse in water during wet paper making, and uniform paper making cannot be performed. In this case, the flocking process cannot be performed uniformly, and a product with good quality and texture cannot be obtained.

  Since the shortcut polyester conjugate fiber of the present invention is used for wet papermaking and electrodeposition flocking, the fiber length is 25 mm or less, and no mechanical crimp is imparted. The fiber length is preferably 5 to 25 mm for wet papermaking, and preferably 0.5 to 2 mm for electrodeposition flocking.

  The fact that mechanical crimps are not applied usually means that when a shortcut fiber is obtained, the fibers are focused, subjected to drawing or heat treatment, and then applied to a stuffing box or push-type crimp. A crimp is imparted by the crimping device, but such crimp is not imparted.

The following are mentioned as polylactic acid used as the core component of the polyester composite fiber of this invention.
Poly D-lactic acid, poly L-lactic acid, poly DL-lactic acid which is a copolymer of poly D-lactic acid and poly L-lactic acid, a mixture of poly D-lactic acid and poly L-lactic acid (stereo complex), poly D -Copolymer of lactic acid and hydroxycarboxylic acid, copolymer of poly L-lactic acid and hydroxycarboxylic acid, copolymer of poly D-lactic acid or poly L-lactic acid, aliphatic dicarboxylic acid and aliphatic diol, Or it is preferable to use these blends.

  The polylactic acid is one in which L-lactic acid and D-lactic acid are used alone or in combination as described above. Among them, the melting point is 120 ° C. or more, and the heat of fusion is 10 J / g or more. It is preferable that

  In other words, the melting point of L-lactic acid and D-lactic acid, which are homopolymers of polylactic acid, is about 180 ° C., but in the case of a copolymer of D-lactic acid and L-lactic acid, the ratio of either component is 10 mol. When it is about%, the melting point is about 130 ° C. Furthermore, when the proportion of any of the components is 18 mol% or more, the melting point is less than 120 ° C. and the heat of fusion is less than 10 J / g, which is almost completely amorphous. When such an amorphous polymer is used, it becomes difficult to heat-stretch particularly in the production process, and it becomes difficult to obtain high-strength fibers. Even if fibers are obtained, heat resistance and wear resistance It is not preferable because it becomes inferior to the above.

  Therefore, as polylactic acid, L / D or D / which is the content ratio (molar ratio) of L-lactic acid and D-lactic acid indicated by the content ratio of L-lactic acid or D-lactic acid when polymerizing using lactide as a raw material. L is preferably 82/18 or more, more preferably 90/10 or more, and even more preferably 95/5 or more.

  Among polylactic acids, the mixture of poly D-lactic acid and poly L-lactic acid (stereo complex) as described above has a high melting point of 200-230 ° C, and can be dyed at high temperatures and ironed after being made into a fabric. It is particularly preferable.

  In the case of a copolymer of polylactic acid and hydroxycarboxylic acid, specific examples of hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxypentanoic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, etc. Can be mentioned. Of these, the use of hydroxycaproic acid or glycolic acid is preferable from the viewpoint of cost.

  In the case of a copolymer of polylactic acid, aliphatic dicarboxylic acid and aliphatic diol, the aliphatic dicarboxylic acid and aliphatic diol include sebacic acid, adipic acid, dodecanedioic acid, trimethylene glycol, 1,4-butane. Diol, 1,6-hexanediol, etc. are mentioned.

  As described above, when polylactic acid is copolymerized with other components, the polylactic acid is preferably 80 mol% or more. If it is less than 80 mol%, the crystallinity of the copolymerized polylactic acid tends to be low, and the melting point is less than 120 ° C. and the heat of fusion is less than 10 J / g.

  The molecular weight of polylactic acid is preferably 1 to 100 (g / 10 min), as measured by ASTM D-1238 method used as an index of molecular weight at a temperature of 210 ° C. and a load of 2160 g. More preferably, it is 5-50 (g / 10min). By setting the melt flow rate within this range, strength, wet heat decomposability, and wear resistance are improved.

  Furthermore, for the purpose of improving the hydrolysis resistance of polylactic acid, a terminal blocking agent such as a carbodiimide compound, an oxazoline compound, an oxazine compound, or an epoxy compound may be added to polylactic acid.

  As long as it does not impair the purpose of the present invention, a heat stabilizer, a crystal nucleating agent, a matting agent, a pigment, a light resistance agent, a weather resistance agent, a lubricant, an antioxidant, an antibacterial agent, A fragrance, a plasticizer, a dye, a surfactant, a flame retardant, a surface modifier, various inorganic and organic electrolytes, and other similar additives may be added.

  On the other hand, the aromatic polyester used as the sheath component of the polyester composite fiber of the present invention has fiber-forming properties, mainly composed of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, Examples include those obtained by copolymerizing other components such as acid, 5-sulfoisophthalic acid, 1,4-butanediol, and diethylene glycol.

  As the aromatic polyester, if the melting point difference from the polylactic acid of the core component is too large, the spinning operability is hindered during composite spinning or the polylactic acid is thermally decomposed. Preferably, the temperature difference between the two is preferably 0 to 60 ° C.

  As the aromatic polyester having such a melting point, polyethylene terephthalate copolymerized with isophthalic acid, polytrimethylene terephthalate (homopolyester), polybutylene terephthalate (homopolyester), and copolymerized polyester of polyethylene terephthalate and polybutylene terephthalate are preferable.

  In the case where polyethylene terephthalate is used as the aromatic polyester, it is preferable to use a polyester having a degree of polymerization as low as possible within a range that does not impair the physical properties because the spinning temperature can be lowered.

  Also, in the aromatic polyester, as long as the purpose of the present invention is not impaired, a thermal stabilizer, a crystal nucleating agent, a matting agent, a pigment, a light-resistant agent, a weathering agent, a lubricant, an antioxidant, if necessary. Agents, antibacterial agents, fragrances, plasticizers, dyes, surfactants, flame retardants, surface modifiers, various inorganic and organic electrolytes, and other similar additives may be added.

  The polyester composite fiber of the present invention is a core-sheath type composite fiber having the above-described aromatic polyester as a sheath component and polylactic acid as a core component, and having a core-sheath type in the cross-sectional shape of a single yarn. And if it arrange | positions so that a sheath component may cover the whole fiber surface, even if a core part is one thing, a core part may be a thing of several sea island shape.

  In the case of a core-sheath type composite fiber having a single core part, it is preferable that the core part has a shape (concentric core-sheath type) that exists substantially at the center of the fiber cross section. In the case where the core portion has a plurality of sea-island shapes, it is preferable that the plurality of island portions be arranged substantially uniformly without being biased in the fiber cross section. By using such a shape, pile bending can be suppressed.

  Furthermore, by setting it as such a composite form, since aromatic polyester can cover the strength and abrasion resistance which are the performances which polylactic acid is inferior, the whole fiber is excellent in strength and abrasion resistance.

  The composite ratio of the core component (polylactic acid) and the sheath component (aromatic polyester) is 20 in terms of mass ratio (core / sheath) in consideration of operability and for the aromatic polyester to cover the entire fiber surface. / 80 to 80/20, preferably 30/70 to 70/30.

  The cross-sectional shape of the polyester conjugate fiber of the present invention is not particularly limited. Besides the round cross-section, it may be oval, rhombus, flat, T-shaped, well-shaped, or polygonal shape such as triangle or six-leaf, You may have.

  The single yarn fineness of the polyester composite fiber of the present invention is not particularly limited, but when used as a non-woven fabric for living materials or industrial materials, it is preferably 1 to 100 dtex.

Next, the manufacturing method of the polyester composite fiber of this invention is demonstrated using an example.
Spinning using a conventional compound melt spinning apparatus. Polylactic acid is melt-spun so that the core portion and aromatic polyester become the sheath portion, and the spun yarn is cooled and solidified and then temporarily stored in a container. A plurality of these yarns are converged to form a yarn bundle, which is stretched between rollers at a stretch ratio of about 2 to 4 times. Subsequently, heat treatment is performed at 120 to 150 ° C., and after applying a finishing oil agent, a shortcut polyester composite fiber is obtained by cutting into a target fiber length without applying mechanical crimping with a stuffing box or the like.

  For wet papermaking, the fiber obtained as described above is packed and shipped as it is, and when it is used for electrodeposition flockey processing, it is once dispersed in water or 100 ° C in a dyeing solution. It is processed at a low temperature of less than or equal to dyeing it to a desired color, and at the same time, each pile is separated, dried, packed and shipped.

Hereinafter, the present invention will be described specifically by way of examples. In addition, the measuring method and evaluation method of each physical property value in an Example are as follows.
(1) Melt flow rate value of polylactic acid (g / 10 min): Measured by the method described above.
(2) Relative viscosity of aromatic polyester: Measured under the conditions of a sample concentration of 0.5 g / 100 ml and a temperature of 20 ° C. using an Ubbelohde viscometer with an equal mass mixture of phenol and ethane tetrachloride as a solvent.
(3) Melting point (° C.) and heat of fusion (J / g) of polylactic acid: A differential scanning calorimeter DSC-2 manufactured by Perkin Elmer was used and measured under the condition of a temperature rising rate of 20 ° C./min.
(4) Content ratio (molar ratio) of L-lactic acid and D-lactic acid in polylactic acid: high-performance liquid chromatography (HPLC) method using an equal mass mixed solution of ultrapure water and 1N sodium hydroxide in methanol as a solvent. It was measured by. The column used was sumichiral OA6100, and was detected by a UV absorption measuring device.
(5) Fineness: JIS L1015 8.5.1 Measured by the A method of the positive fineness.
(6) Strength: JIS L1015 8.7 It was measured at a grip interval of 20 mm using a constant speed extension type tensile tester according to the standard test method of tensile strength and elongation rate.
(7) Degree of pile bending: measured by the method described above.
(8) Humidity and thermal decomposition resistance: The obtained fiber was treated (left) for 1000 hours under conditions of 50 ° C. and 95% relative humidity, and the ratio of the strength after treatment to the strength before treatment was calculated by the following equation. did. In addition, these intensity | strengths were measured according to said (6).
Moisture and heat resistance (%) = (strength after treatment / strength before treatment) × 100
(9) Abrasion resistance: Using the obtained non-woven fabric, it was measured by A method of JIS L1018 8.18.1 abrasion strength.

Example 1
Polylactic acid has a melting point of 1700C, L / D, which is a content ratio of L-lactic acid and D-lactic acid, of 98.5 / 1.5, and a melt flow rate value (hereinafter referred to as MFR) of 23 g / 10 minutes. Poly DLlactic acid was used, and 15 mol% copolymerized polyethylene terephthalate (hereinafter referred to as copolymerized PET) having a relative viscosity of 1.37 and a melting point of 217 ° C. was used as an aromatic polyester. Each chip was dried under reduced pressure and then melt-spun using a composite melt spinning apparatus so that the single yarn had a round cross-section and a concentric core-sheath type. At this time, the copolymer PET was arranged so as to be a sheath part and polylactic acid was a core part, and the composite ratio (mass ratio) was 50/50, and the spinning temperature was 240 ° C. After cooling the spun yarn, it was drawn at a take-up speed of 1000 m / min to obtain an undrawn yarn.
The obtained yarn is converged to form a 330,000 dtex yarn bundle, drawn at a draw ratio of 3.2 times, heat treated with a 140 ° C. heat drum, and 10 mm long without being crimped. Disconnected.
The obtained shortcut polyester composite fiber had a single yarn fineness of 2.4 denier and a degree of pile bending of 3.0%.
80% by mass of this shortcut polyester composite fiber and a polyester binder fiber for wet papermaking (Melty <4080> 2.2 dtex × 5 mm) manufactured by Unitika Fiber Co., Ltd. are mixed so as to be 20% by mass, and the stock concentration is 0.1%. When dispersed in water with a surfactant concentration of 0.02%, it was uniformly dispersed. When this was subjected to wet papermaking using a square sheet machine of 25 cm square, a nonwoven fabric with good texture was obtained. Thereafter, it was dried through a Yankee dryer at 110 ° C., and further subjected to thermocompression treatment in a hot roller at 140 ° C. to obtain a nonwoven fabric.

Examples 2-3, Comparative Example 1, Reference Example 1
A shortcut polyester composite fiber was obtained in the same manner as in Example 1 except that the composite ratio of copolymerized PET and polylactic acid was changed as shown in Table 1. Furthermore, using this fiber, a nonwoven fabric was obtained in the same manner as in Example 1.

Example 4
A shortcut polyester composite fiber was obtained in the same manner as in Example 1 except that polytrimethylene terephthalate (relative viscosity 1.44, melting point 215 ° C.) was used instead of copolymerized PET. Furthermore, using this fiber, a nonwoven fabric was obtained in the same manner as in Example 1.

Example 5
A shortcut polyester composite fiber was obtained in the same manner as in Example 1 except that polybutylene terephthalate (relative viscosity 1.46, melting point 218 ° C.) was used instead of copolymerized PET. Furthermore, using this fiber, a nonwoven fabric was obtained in the same manner as in Example 1.

  Table 1 shows the characteristic values of the shortcut polyester composite fibers obtained in Examples 1 to 5, Comparative Example 1 and Reference Example 1, and the abrasion resistance evaluation when used as nonwoven fabrics.

As is apparent from Table 1, the shortcut polyester conjugate fibers of Examples 1 to 5 are substantially free of pile bending, have excellent strength and moist heat resistance, and the obtained nonwoven fabric has excellent wear resistance. Met.
On the other hand, since the fiber of Comparative Example 1 was a fiber composed only of polylactic acid, the strength was low, and when the wet heat decomposition resistance was measured, the fiber after the wet heat treatment was tattered, and the strength could not be measured. It was impossible to calculate sex. Moreover, the obtained nonwoven fabric was inferior to abrasion resistance.

Example 6
Manufactured in the same manner as in Example 1 and cut with a fiber length of 1 mm to obtain a shortcut polyester composite fiber.
The obtained fibers were put in water with a small amount of colloidal silica, stirred and dispersed, and then dried to separate each one into powdery fibers. The powdered fiber was charged by supplying it to one of the electric fields applied with a high voltage.
A taffeta fabric using 83dtex / 36f polyester yarn coated with polyurethane adhesive was placed on the other side of the electric field, and the powdered fibers were accelerated and thrown toward the taffeta fabric.

  When the obtained electrodeposited flocky product was heat-treated at 150 ° C. for 2 minutes, a soft leather-like texture product was obtained.

Claims (3)

A core-sheath type composite fiber having polylactic acid as a core component and aromatic polyester as a sheath component, characterized in that the fiber length is 25 mm or less, no mechanical crimp is imparted, and there is substantially no pile bending. Shortcut polyester composite fiber. The shortcut polyester composite fiber according to claim 1, wherein the polylactic acid has a melting point of 120 ° C or higher and a heat of fusion of 10 J / g or higher. The shortcut polyester composite fiber according to claim 1 or 2, wherein the aromatic polyester is polyethylene terephthalate copolymerized with isophthalic acid, polytrimethylene terephthalate, or polybutylene terephthalate.