JP2009299209A - Sheath-core conjugate filament - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermobondable filament having a high strength and alkali resistance sufficiently usable for industrial materials used in an alkali environment by forming the filament into a sheath-core conjugate filament using a polyester at the core part and a polyethylene at the sheath part. <P>SOLUTION: The sheath-core conjugate filament is formed of the core part comprising a polyethylene terephthalate and the sheath part comprising the polyethylene having a melting point lower than that of the core part, the sheath-core conjugate filament has a breaking strength of not less than 3.5 cN/dtex, and a strength retention after subjected to alkali treatment in 10% sodium hydroxide solution at 70°C for 100 min of 80%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a long fiber of a composite fiber in which polyethylene terephthalate is disposed in the core and polyethylene is disposed in the sheath, and the sheath becomes an adhesive component by heat treatment and can be used for mesh sheets and nets that require alkali resistance. The present invention relates to a suitable core-sheath type composite continuous fiber.

  2. Description of the Related Art Conventionally, processing is performed using a resin such as a vinyl chloride resin in applications in which fixing of intersections such as mesh sheets and water permeability such as tarpaulin fabrics are important. However, in recent years, vinyl chloride resins and the like have been considered to have a problem of influence on the environment, and processing methods that do not perform resin processing have been studied.

  As one of them, core-sheath type heat-bondable long fibers whose sheath part is a low melting point component are used for knitting and weaving, and then heat treatment is performed to melt or soften the low melting point component to fix the intersection part. A mesh sheet, a net with a fixed mesh shape, and a molded rod made of fibers have been proposed (see, for example, Patent Documents 1, 2, and 3).

  And as for such heat-bondable long fibers, polyester-based heat-bondable long fibers using polyester as a core component and a sheath component are generally used in terms of dimensional stability, weather resistance, and price. . However, polyester fibers have the disadvantage of poor alkali resistance.

  Therefore, when a mesh sheet or net using polyester-based heat-bondable long fibers is used in an alkaline environment, degradation due to hydrolysis is rapid and there is a problem in long-term use.

For these reasons, there has been a growing demand for heat-bondable long fibers having excellent alkali resistance while being polyester fibers having excellent dimensional stability and weather resistance.
JP 2001-271245 A JP 2001-271270 A JP 2001-214388 A

  The present invention solves the above-described problems, and can be sufficiently used for industrial materials used in an alkaline environment by using a core-sheath type composite fiber using polyester for the core and polyethylene for the sheath. It is a technical problem to provide a heat-bondable long fiber having high strength and alkali resistance.

The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems.
That is, the present invention is a long fiber of a core-sheath type composite fiber having a core part made of polyethylene terephthalate and a sheath part made of polyethylene having a melting point lower than that of the core part, and the cutting strength is 3.5 cN / dtex or more, 10% The gist is a core-sheath type composite continuous fiber characterized by having a strength retention of 80% or more after an alkali treatment at 70 ° C. for 100 minutes in a sodium hydroxide solution.

  The core-sheath type composite continuous fiber of the present invention uses polyester having excellent dimensional stability and weather resistance as a core part, and polyethylene having a melting point lower than that of the core part is arranged in the sheath part. Melts to become an adhesive component. When polyethylene is melted by the heat treatment, the surface of the fiber made of polyester in the core is coated, and since polyethylene is excellent in alkali resistance, hydrolysis of polyester can be suppressed. Therefore, the core-sheath type composite continuous fiber of the present invention can be suitably used for industrial materials used in an alkaline environment, such as mesh sheets and nets.

Hereinafter, the present invention will be described in detail.
The core-sheath type composite continuous fiber of the present invention may be multifilament or monofilament, but exhibits a core-sheath type composite shape in a cross-sectional shape obtained by cutting a single yarn perpendicularly to the yarn length direction. Is. There may be one core part or a multi-core type having about 2 to 5 cores. The core-sheath shape may be concentric or eccentric. Furthermore, as long as the cross-sectional shape is a core-sheath type, it may be not only a round cross-sectional shape but also an irregular shape such as a polygon.

  The core-sheath composite long fiber of the present invention is composed of polyethylene terephthalate at the core and polyethylene having a melting point lower than that of the core. By constituting the core portion with polyethylene terephthalate (hereinafter sometimes abbreviated as PET), good yarn-making properties can be obtained, and weather resistance, dimensional stability, and strength are excellent.

  The PET in the core may contain other components as long as the intended performance of the present invention is not impaired. For example, various additives or colored pigments for making the original fibers, or others The copolymer component may be contained.

  The intrinsic viscosity [η] of the PET at the core is preferably 0.6 to 1.1. If the intrinsic viscosity [η] is lower than 0.6, the cutting strength tends to decrease, which is not preferable. On the other hand, when the intrinsic viscosity is higher than 1.1, since the sheath portion has a low melting point, sufficient heat treatment cannot be performed at the time of stretching, and heat shrinkage at the time of heat bonding processing increases, and the workability tends to be lowered. It is not preferable.

  Further, the sheath part is composed of polyethylene having a lower melting point than the core part, and it is preferable to use medium density or high density polyethylene. Among them, the melt fluidity and cooling are excellent, and the yarn production is good. Therefore, it is preferable to use high-density polyethylene (hereinafter sometimes abbreviated as HDPE).

  The melting point of polyethylene is preferably 100 to 150 ° C. lower than that of the sheath PET, and more preferably 110 to 140 ° C. among them.

  The density of HDPE is preferably 0.945 to 0.965. The density of HDPE is measured by the method D (density density tube) for measuring the density and specific gravity of JISK7112 plastic-non-foamed plastic.

  Further, the melt index value of HDPE (hereinafter sometimes abbreviated as MI value) is preferably in the range of 5 to 30 g / 10 min as measured by the method of ASTM D-1238 (E). If this range is exceeded, strength may be reduced. On the other hand, if the MI value is less than 5 g / 10 min, the melt viscosity becomes high, resulting in poor melt fluidity during thermal bonding processing, resulting in adhesion spots. Therefore, it is not preferable.

  In addition, a color pigment and various additives may be added to the polyethylene of the sheath within a range that does not impair the target performance of the present invention.

  Next, the core-sheath type composite continuous fiber of the present invention is required to have a cutting strength of 3.5 cN / dtex or more, and preferably 3.8 dtex or more. When the cutting strength is less than 3.5 cN / dtex, the strength is insufficient for use as a general industrial material application, and the use application is limited.

  And the core-sheath composite ratio (core: sheath mass ratio) in the core-sheath-type composite long fiber of the present invention is preferably 1: 1 to 5: 1. When the core part is larger than this range, the composite form is obtained. This is not preferable because the yarn tends to be nonuniform between the single yarns and the drawability becomes poor. On the other hand, if the core is smaller than this range, the cutting strength is lowered, which is not preferable.

  Furthermore, the core-sheath type composite continuous fiber of the present invention is excellent in alkali resistance, and its index is 80% strength retention after being subjected to alkali treatment in 10% sodium hydroxide solution at 70 ° C. for 100 minutes. % Or more, and more preferably 85% or more.

The strength retention in the present invention is that the cutting strength before alkali treatment is A, and the sample is fixed to a frame of 25 cm in length, and subjected to alkali treatment in 10% sodium hydroxide solution at 70 ° C. for 100 minutes, After natural drying, the strength retention is calculated by the following equation, where B is the cutting strength measured by removing it from the frame.
Strength retention (%) = (B / A) × 100

  When the strength retention is 80% or more, it can be used for a long period of time in applications requiring alkali resistance. On the other hand, if the strength retention is lower than this, the mesh sheet or net breaks before use for a long period of time, resulting in poor durability.

  Further, the core-sheath type composite fiber of the present invention preferably has a cutting elongation of 15 to 30% in order to improve dimensional stability and orientation crystallization.

  The cutting strength, cutting strength, and cutting elongation in the present invention were measured according to JIS L-1013 tensile strength and elongation test using an autograph DSS-500 manufactured by Shimadzu Corporation, with a grip interval of 25 cm and a pulling speed of 30 cm / It is measured in minutes.

  The number of single yarns and single yarn fineness constituting the core-sheath type composite continuous fiber of the present invention are not particularly limited, but in the case of multifilament, the number of single yarns is 20 to 300, and the single yarn fineness is in the range of 5 to 30 dtex. In the case of a monofilament, the fineness is preferably in the range of 200 to 2000 dtex.

  Next, the manufacturing method of the core-sheath-type composite long fiber (multifilament) of this invention is demonstrated. First, the core and sheath chips are respectively supplied and melt-spun using a conventional compound spinning apparatus. Further, a two-step method in which the undrawn yarn is wound once and then drawn may be used, but the spin draw method in which drawing is performed continuously without winding is preferable in terms of productivity and cost. As the stretching method, it is possible to employ a roller stretching performed only with a heating roller or a method performed by providing a steam heat treatment apparatus between the heating rollers. The winding speed is preferably about 2000 to 4000 m / min. If the winding speed is slower than this range, the productivity is inferior.

Next, the present invention will be specifically described with reference to examples. In addition, each physical-property value in an Example was measured with the following method.
(A) Intrinsic Viscosity of Polyester Measured at a concentration of 0.5 g / dl and a temperature of 20 ° C. using a mixture of equal weight of phenol and ethane tetrachloride as a solvent.
(B) Cutting strength, cutting strength, cutting elongation, strength retention rate Measured and calculated by the method described above.
(C) Melting point It measured using the differential scanning calorimeter DSC-7 type | mold by Perkin Elmer, Inc., and the temperature increase rate was 20 degree-C / min.

Example 1
As the PET constituting the core, PET having an intrinsic viscosity [η] of 0.70 and a melting point of 255 ° C. was used. As the polyethylene constituting the sheath, HDPE having a density of 0.951 g / cm ³ , an MI value (measured by the method of ASTM D-1238 (E)) of 10 g / 10 min, and a melting point of 130 ° C. was used.
A conventional compound melt spinning apparatus is equipped with a core-sheath type compound spinneret having a hole diameter of 0.5 mm and 48 holes, and is spun at a base temperature of 280 ° C. and a core-sheath mass ratio (core: sheath) of 1: 1. did. After passing through a heating cylinder having a temperature of 200 ° C. and a length of 15 cm provided immediately below the spinneret, it was cooled at a cooling air temperature of 15 ° C. and a speed of 0.7 m / sec with an annular spraying device having a length of 40 cm.
Next, the oil agent is applied and taken up by one unheated roller, continuously aligned by 1.02 times with two rollers at a temperature of 90 ° C., and then 4.8 times with three rollers at a temperature of 110 ° C. Stretching, performing 2% relaxation heat treatment with 4 rollers at a temperature of 100 ° C, winding 1% with a winder with a speed of 3000m / min, circular cross-sectional shape (core and sheath are arranged concentrically) Of 550 dtex / 48 filament core-sheath type composite continuous fiber.

Example 2
Core-sheath mass ratio (core: sheath) The same as Example 1 except that the core-sheath mass ratio was changed to 3: 1.

Comparative Example 1
Core-sheath mass ratio (core: sheath) The same as Example 1 except that the core-sheath mass ratio was changed to 1: 2.

Comparative Example 2
The same procedure as in Example 1 was performed except that the polyethylene of the sheath was changed to PET using the core.

  Table 1 shows the results of measuring the characteristic values of the fibers obtained in Examples 1-2 and Comparative Examples 1-2.

As is apparent from Table 1, the core-sheath type composite continuous fibers of Examples 1 and 2 were excellent in cutting strength, cutting elongation, and strength retention after alkali treatment.
On the other hand, the core-sheath type composite continuous fiber of Comparative Example 1 was inferior in cutting strength because the mass ratio of the core part was small. Moreover, since the core-sheath-type composite long fiber of the comparative example 2 used PET instead of polyethylene for the sheath part, it was inferior in the strong retention after alkali treatment.

Claims (1)

A core-sheath-type composite fiber composed of polyethylene terephthalate in the core and polyethylene having a lower melting point than the core, and having a cutting strength of 3.5 cN / dtex or more in a 10% sodium hydroxide solution A core-sheath type composite continuous fiber characterized by having a strength retention of 80% or more after being subjected to an alkali treatment at 70 ° C. for 100 minutes.