JP2008156789A - Polyethylene naphthalate staple fiber nonwoven fabric and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a staple fiber nonwoven fabric of a polyethylene naphthalate (PEN) having a sufficient strength even in the form of a paper sheet, and to provide a method for producing the nonwoven fabric. <P>SOLUTION: The PEN nonwoven fabric is composed of first PEN staple fibers and second PEN staple fibers having a flat cross-section. The nonwoven fabric is preferably produced by a method having a cutting step of cutting the first PEN fiber and the second PEN fiber into staple fibers, a sheeting step of forming a mixed fiber sheet composed of the first PEN staple fibers and the second PEN staple fibers, and a heating step of obtaining a nonwoven fabric by heating and pressing the mixed fiber sheet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat-resistant nonwoven fabric composed of short fibers of polyethylene naphthalate fiber and a method for producing the same.

  In nonwoven fabrics widely used in the fields of heat insulating materials, electrical insulating materials, filters, medical materials, building materials, etc., there is an increasing demand for development of nonwoven fabrics having heat resistance. As a nonwoven fabric corresponding to such a request, a nonwoven fabric using polyethylene naphthalate having high heat resistance is known (Patent Documents 1 and 2).

  Patent Document 1 discloses a nonwoven fabric obtained by heating and bonding a web obtained by mixing polyethylene naphthalate (PEN) fibers and fibers from a polymer having latent adhesiveness. In this nonwoven fabric, the fiber used as an adhesive component is typically a polyethylene terephthalate copolymer fiber, and its melting point is lower than that of PEN fiber. Therefore, the resulting nonwoven fabric is affected by the melting point of the adhesive component. The heat resistance is not high. Moreover, since the nonwoven fabric disclosed by patent document 2 is manufactured by the melt blow method, intensity | strength is not enough.

  As a non-woven fabric that solves the problems of the non-woven fabric, a long-fiber non-woven fabric that is substantially made of polyethylene naphthalate fiber and has excellent heat resistance and strength is also known (Patent Document 3).

JP 50-18773 A JP-A-4-146251 Japanese Patent Laid-Open No. 10-25651

  However, the non-woven fabric disclosed in Patent Document 3 is a non-woven fabric excellent in heat resistance because it uses PEN fibers. However, since it uses long fibers and is manufactured by the spunbond method, it is paper-like. A thin nonwoven fabric cannot be produced. It has been found that sufficient strength cannot be obtained when the PEN fiber of Patent Document 3 is cut into short fibers to produce a paper-like non-woven fabric, and this is made into a paper-like non-woven fabric.

  The present invention has been made in view of the above-mentioned problems of the known technology, and an object of the present invention is to provide a non-woven fabric composed of short fibers of PEN having sufficient strength even in the form of paper and a method for producing the same.

  The polyethylene naphthalate short fiber nonwoven fabric of the present invention comprises the first polyethylene naphthalate short fiber and the second polyethylene naphthalate short fiber having a flat cross-sectional shape.

  Such a polyethylene naphthalate short fiber non-woven fabric (hereinafter also referred to as “PEN non-woven fabric”) can produce a thin paper-like material and has sufficient strength. Moreover, since it does not use a low melting point material such as PET, it is also a non-woven fabric with excellent heat resistance. The reason why a nonwoven fabric excellent in strength can be obtained by the above configuration is not clear, but is presumed to be due to the binder effect of the second polyethylene naphthalate short fibers.

  In the above-mentioned PEN nonwoven fabric, the breaking elongation of the first polyethylene naphthalate short fibers is 5 to 50%, and the breaking elongation of the second polyethylene naphthalate short fibers is 40 to 150%. preferable. The breaking strength of polyethylene naphthalate short fibers is a value measured according to JIS L 1015 using long fibers before cutting.

  When the breaking elongation of the first PEN short fiber exceeds 50%, and when the breaking elongation of the second PEN short fiber is less than 40%, the strength of the nonwoven fabric decreases. A PEN fiber having a breaking elongation of less than 5% is difficult to produce, and a PEN fiber having a breaking elongation of more than 150% is too stretched and difficult to handle. The non-woven fabric is preferably a paper-type non-woven fabric manufactured by a paper making method using short fibers cut from long fibers. The cross-sectional shape of the first PEN short fiber is not particularly limited, but a flat shape or a circular shape having a major axis length / minor axis length ratio of less than 5 is preferable from the viewpoint of obtaining a higher strength PEN nonwoven fabric, Circular fibers and flat fibers may be mixed, and circular fibers are particularly preferable.

  In the above-described PEN nonwoven fabric, the flat shape preferably has a major axis length / minor axis length ratio of 5 to 30.

  The PEN nonwoven fabric using the second polyethylene naphthalate short fiber having such a configuration is a nonwoven fabric having sufficient strength even when it is made into a thin paper shape. The major axis length / minor axis length ratio of the flat shape in the cross-sectional shape of the second short polyethylene naphthalate fiber is more preferably 8 or more, and even more preferably 10 or more. Although it is preferable that the ratio of the major axis length / minor axis length of the flat shape is large, it is difficult to produce ones exceeding 30 and it is preferably 25 or less because the production is easy.

  In the above-mentioned PEN nonwoven fabric, the ratio of the second polyethylene naphthalate short fibers is preferably 10 to 60% by weight.

  If the proportion of the second polyethylene naphthalate short fibers is less than 10% by weight, the strength of the resulting nonwoven fabric is not sufficient, and if it exceeds 60% by weight, the heat resistance of the fibers themselves constituting the nonwoven fabric is reduced, Unevenness due to fiber shrinkage occurs and the appearance of the nonwoven fabric deteriorates. The ratio of the second polyethylene naphthalate short fibers in the nonwoven fabric is more preferably 20 to 55% by weight.

The method for producing a PEN nonwoven fabric according to the present invention includes a cutting step of cutting the first polyethylene naphthalate fiber and the second naphthalate fiber into short fibers, the first polyethylene naphthalate short fiber and the second polyethylene naphthalate. A sheet forming step of preparing a mixed fiber sheet of short phthalate fibers, a heating step of heating the mixed fiber sheet into a nonwoven fabric,
The second polyethylene naphthalate short fiber has a flat cross-sectional shape.

  According to this production method, a paper-like thin nonwoven fabric can be produced, and a PEN nonwoven fabric having sufficient strength can be produced. The cutting of the PEN fiber may be performed while supplying the first polyethylene naphthalate fiber and the second naphthalate fiber at a predetermined ratio, and the short fibers manufactured by cutting separately are mixed at a predetermined ratio. Also good.

  In the method for producing the PEN nonwoven fabric, the breaking elongation of the first polyethylene naphthalate short fibers is 5 to 50%, and the breaking elongation of the second polyethylene naphthalate short fibers is 40 to 150%. Preferably there is.

  When the breaking elongation of the first PEN short fiber exceeds 50%, and when the breaking elongation of the second PEN short fiber is less than 40%, the strength of the resulting nonwoven fabric decreases. A PEN fiber having a breaking elongation of less than 5% is difficult to produce, and a PEN fiber having a breaking elongation of more than 150% is too stretched and difficult to handle.

  In the method for producing the PEN nonwoven fabric, the flat shape preferably has a major axis length / minor axis length ratio of 5 to 30.

  According to the manufacturing method of the structure which concerns, the paper-like thin PEN nonwoven fabric which has sufficient intensity | strength can be manufactured more reliably. The major axis length / minor axis length ratio of the flat shape in the cross-sectional shape of the second short polyethylene naphthalate fiber is more preferably 8 or more, and even more preferably 10 or more. Although it is preferable that the ratio of the major axis length / minor axis length of the flat shape is large, it is difficult to produce ones exceeding 30 and it is preferably 25 or less because the production is easy.

  In the manufacturing method of said PEN nonwoven fabric, it is preferable that the ratio of the said 2nd polyethylene naphthalate short fiber in the said mixed fiber sheet shall be 10 to 60 weight%.

  If the proportion of the second polyethylene naphthalate short fibers is less than 10% by weight, the strength of the resulting nonwoven fabric is not sufficient, and if it exceeds 60% by weight, the heat resistance of the fibers themselves constituting the nonwoven fabric is reduced, or Yankee When heated and dried with a dryer, the appearance of the nonwoven fabric (fibre uniformity) is reduced due to shrinkage of the fibers, and the appearance is deteriorated.

  The fibers constituting the PEN nonwoven fabric of the present invention are polyethylene naphthalate (PEN) fibers, specifically, polyethylene-2,6-naphthalate fibers. PEN may be copolymer polyethylene-2,6-naphthalate containing 5 mol% or less of the third component. Polyethylene-2,6-naphthalate is synthesized by polymerizing naphthalene-2,6-dicarboxylic acid or a derivative thereof and ethylene glycol in the presence of a catalyst. Examples of naphthalene-2,6-dicarboxylic acid derivatives include methyl esters, acid halides, bishydroxyethyl-2,6-naphthalate and the like.

  Examples of components copolymerizable with polyethylene-2,6-naphthalate at 5 mol% or less include dicarboxylic acids, glycols or bisphenols, oxycarboxylic acids or derivatives thereof. Examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as naphthalene-2,6-dicarboxylic acid oxalic acid, succinic acid, adipic acid, sebacic acid, and dimer acid, cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, and hexahydroterephthalic acid. Aromatic dicarboxylic acids such as cyclic dicarboxylic acid, phthalic acid, terephthalic acid, isophthalic acid, naphthalene-2,7-dicarboxylic acid, diphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, 3, Examples include dicarboxylic acids such as sodium 5-dicarboxybenzenesulfonate.

  Examples of copolymerizable glycols or bisphenols include propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentylene glycol, p-xylene glycol, 1,4-cyclohexanedimethanol, bisphenol A, p. -Diphenoxysulfone 1,4-bis (β-hydroxyethoxy) benzene, 2,2-bis (p-β-hydroxyethoxyphenyl) propane, polyalkylene glycol, p-phenylenebis (dimethylsiloxane), etc. . Examples of oxycarboxylic acid and its derivatives include glycolic acid, hydroxybenzoic acid and alkyl esters thereof.

  The polyethylene naphthalate having an intrinsic viscosity [η] of 0.45 to 1.0 is used. The intrinsic viscosity [η] is a value obtained from a viscosity measured at 35 ° C. by dissolving PEN or a copolymer in a mixed solvent of phenol and orthodichlorobenzene (weight ratio 6: 4). When the intrinsic viscosity [η] exceeds 1.0, the melt viscosity becomes abnormally high and melt spinning becomes difficult, and when [η] is less than 0.45, a fiber having a desired high melting point and good physical properties is obtained. I can't get it.

  In the PEN nonwoven fabric of the present invention and the manufacturing method thereof, the first polyethylene naphthalate (PEN) fiber and the second PEN fiber are used. The first PEN fiber is a method in which a drawn yarn is spun directly at a spinning speed of 2500 to 6000 m / min, preferably 3000 to 5000 m / min, or less than 2000 m / min, preferably 400 to 1500 m / min. It can be produced by a method in which a drawn yarn is spun and then drawn. The fineness of the first PEN fiber is not particularly limited, but a range of 0.5 dtex to 10 dtex, preferably 1 dtex to 8 dtex is advantageous. When a PEN fiber having a small fineness is used, a thin paper-like nonwoven fabric can be produced.

  The second PEN fiber has a low degree of orientation of PEN molecules in the fiber that can be obtained by spinning with a spinning chain of 2000 m / min or less, preferably 500 to 1500 m / min. The fineness of the second PEN fiber is not particularly limited, but is in the range of 1 dtex to 15 dtex, preferably 2 dtex to 12 dtex.

  The cross-sectional shape of the 2nd PEN fiber which comprises the nonwoven fabric of this invention is a flat shape, and the flat shape which has an unevenness | corrugation may be sufficient. As a flat shape, convex polygons, such as an ellipse, an ellipse, a rhombus, and a rectangle, are preferable. A rhombus or a rectangle has a chamfered corner. FIG. 1 illustrates an elliptical example (FIG. 1A) and an oval shape (FIG. 1B). x is the major axis length and y is the minor axis length.

  The PEN nonwoven fabric of the present invention includes a cutting step of cutting the first polyethylene naphthalate fiber and the second naphthalate fiber into short fibers, the first polyethylene naphthalate short fibers and the second naphthalate short fibers. It is preferable to manufacture by the manufacturing method which has the heating process which produces the mixed fiber sheet which becomes the sheet forming process, and pressurizes and heats the said mixed fiber sheet. The first polyethylene naphthalate fiber and the second naphthalate fiber are produced by spinning by a general production method of long fibers. Although the sheeting step is not particularly limited, it is based on a wet method, that is, a method in which the first PEN fiber and the second PEN fiber are dispersed in water at a predetermined ratio, and a mixed fiber sheet is obtained using a paper machine. preferable. In the sheet forming step for producing the mixed fiber sheet, no adhesive is used. The mixed fiber sheet is dried (drying step), subjected to a heating step, and pressurized and heated by a known means such as a heat roll and a hot press to obtain a nonwoven fabric. The sheet forming step, the drying step, and the heating step are preferably performed continuously.

The length of the short fibers of PEN is preferably 1 to 10 mm for both the first PEN fiber and the second PEN fiber, and more preferably 2 to 8 mm. The short fibers of the first PEN fiber and the second PEN fiber may have the same length or different lengths. The heating temperature in a heating process is 180-250 degreeC, More preferably, it is 190-240 degreeC, and the linear pressure in pressurization is 0.5-4 kN / cm. The basis weight of the nonwoven fabric of the present invention is preferably 10 to 70 g / m ² , more preferably 20 to 60 g / m ² .

<Evaluation method>
The measuring method of the characteristic of the fiber in an Example is as follows.
(1) Elongation at break According to JISL 1015, measured at room temperature (20 ° C.) with a constant-speed elongation type tensile tester.
(2) Nonwoven fabric strong elongation According to JISL 1096, measured at room temperature (20 ° C.) with a constant-speed elongation type tensile tester.

<Production example of nonwoven fabric>
(Example of production of first PEN fiber)
A PEN resin is spun at a spinning speed of 600 m / min using a die having a circular cross section by a spinning device, and then stretched 5 times by a conventional method to obtain a first fineness of 2.0 dtex and a breaking elongation of 26%. PEN fiber (1A) was produced. A first PEN fiber (1B) having a fineness of 4.4 dtex and a breaking elongation of 122% was produced by changing the draw ratio.

(Example of production of second PEN fiber)
The PEN resin was spun at a spinning speed of 900 m / min by using a die having an oval cross section with a spinning device to produce a second PEN fiber having a fineness of 7.6 dtex. A die having a major axis length / minor axis length ratio of 15 in the fiber cross section is used, the second PEN fiber (2A) (breaking elongation: 66%), and the major axis length / minor axis length of the fiber. An oval die having a thickness ratio of 9 was used to produce a second PEN fiber (2B) (breaking elongation: 141%) having a fineness of 11.1 dtex at a spinning speed of 900 m / min.

(Example of production of third PEN fiber)
The PEN resin was spun at a spinning speed of 900 m / min using a die having a circular cross section by a spinning device to produce a second PEN fiber (breaking elongation: 105%) having a fineness of 7.2 dtex.

  Attempts were made to produce a second PEN fiber having a major axis length / minor axis length ratio of 5 at a spinning speed of 400 m / min and a breaking elongation of 200% or more. It was difficult and no nonwoven fabric was produced.

<Examples of non-woven fabric production>
(Experimental example 1)
The first PEN fiber (1A) and the second PEN fiber (2A) having a major axis length / minor axis length ratio of 15 in the fiber cross section are each cut into a length of 5 mm by a cutter to form a short fiber. The PEN fiber (1A) short fiber and the second PEN fiber (2A) short fiber were mixed so that the ratio of the second PEN fiber (2A) was 50% by weight and dispersed in water to make paper. A mixed fiber sheet was prepared using a machine. The mixed fiber sheet after drying was pressed and heated at a linear pressure of 1.2 kN / cm using an embossed calendar at a temperature of 230 ° C. to obtain a PEN nonwoven fabric having a basis weight of 57.9 g / m ² . The strength was measured using this PEN nonwoven fabric (1). Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength, elongation, and visual texture (uniformity of the fiber distribution) of the nonwoven fabric.

(Experimental example 2)
A PEN nonwoven fabric having a basis weight of 56.5 g / m ² was obtained in the same manner as in Experimental Example 1 except that the second PEN fiber (2B) having a major axis length / minor axis length ratio of 9 was used as the ^second PEN fiber. Obtained. Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength and elongation of the nonwoven fabric.

(Experimental example 3)
A PEN nonwoven fabric having a basis weight of 57.6 g / m ² was obtained in the same manner as in Experimental Example 1 except that the second PEN fiber (2A) and the second PEN fiber (2C) were used in combination as the ^second PEN fiber. Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength and elongation of the nonwoven fabric.

(Experimental example 4)
A nonwoven fabric having a basis weight of 57.4 g / m ² was obtained in the same manner as in Experimental Example 1 except that the mixing was performed so that the ratio of the second PEN fiber (2A) was 20% by weight. Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength and elongation of the nonwoven fabric.

(Experimental example 5)
A nonwoven fabric having a basis weight of 58.4 g / m ² was obtained in the same manner as in Experimental Example 1 except that mixing was performed so that the ratio of the second PEN fiber (2A) was 65% by weight. Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength and elongation of the nonwoven fabric.

(Experimental example 6)
A nonwoven fabric having a basis weight of 58.1 g / m ² was obtained in the same manner as in Experimental Example 1 except that the first PEN fiber (1B) having a breaking elongation of 122% was used as the first PEN fiber. Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength and elongation of the nonwoven fabric.

(Experimental example 7)
The first PEN fiber (1B) and the third PEN fiber having a circular elongation having a breaking elongation corresponding to the second PEN fiber were cut into a length of 5 mm and used in the same manner as in Experimental Example 1. A nonwoven fabric having a basis weight of 58.4 g / m ² was obtained. Table 1 shows the measurement results of the mixing ratio (weight ratio) of the short fibers and the strength and elongation of the nonwoven fabric.

  From the result of the said Table 1, the PEN nonwoven fabric (Experimental Examples 1-3) of this invention has the outstanding strong elongation. On the other hand, the nonwoven fabric of Experimental Example 7 using the third PEN fiber having a circular cross section, although having a breaking elongation corresponding to the second PEN fiber, had a weak high elongation. The nonwoven fabrics of Experimental Examples 4, 5, and 6 use the second PEN fiber having an oval cross section, and both the first PEN fiber (1A) and the second PEN fiber having a breaking elongation within a preferable range. Of PEN fibers (2A), the composition of which is outside the preferred range, and the nonwoven fabrics of Experimental Examples 4 and 5, and the PEN fiber (1B) having a breaking elongation exceeding the preferred range as the first PEN fiber The nonwoven fabric of No. 6 had lower strength than Experimental Examples 1 to 3.

The figure which showed the example of the cross-sectional shape of the 2nd PEN fiber which comprises the PEN nonwoven fabric of this invention

Claims (8)

  A polyethylene naphthalate short fiber nonwoven fabric comprising a first polyethylene naphthalate short fiber and a second polyethylene naphthalate short fiber having a flat cross-sectional shape.   The breaking elongation of the first polyethylene naphthalate short fiber is 5 to 50%, and the breaking elongation of the second polyethylene naphthalate short fiber is 40 to 150%. The polyethylene naphthalate short fiber nonwoven fabric described.   The polyethylene naphthalate short fiber nonwoven fabric according to claim 1 or 2, wherein the flat shape has a major axis length / minor axis length ratio of 5 to 30.   The ratio of said 2nd polyethylene naphthalate short fiber is 10 to 60 weight%, The polyethylene naphthalate short fiber nonwoven fabric in any one of Claims 1-3 characterized by the above-mentioned. A cutting step of cutting the first polyethylene naphthalate fiber and the second naphthalate fiber into short fibers, and a mixed fiber sheet comprising the first polyethylene naphthalate short fibers and the second polyethylene naphthalate short fibers. A sheeting step to be prepared, and a heating step to press and heat the mixed fiber sheet to form a nonwoven fabric;
The method for producing a polyethylene naphthalate short fiber nonwoven fabric, wherein the second polyethylene naphthalate short fiber has a flat cross-sectional shape.   6. The breaking elongation of the first polyethylene naphthalate short fiber is 5 to 50%, and the breaking elongation of the second polyethylene naphthalate short fiber is 40 to 150%. The manufacturing method of the polyethylene naphthalate short fiber nonwoven fabric of description.   The method for producing a polyethylene naphthalate short fiber nonwoven fabric according to claim 5 or 6, wherein the flat shape has a major axis length / minor axis length ratio of 5 to 30.   The method for producing a polyethylene naphthalate short fiber nonwoven fabric according to any one of claims 5 to 7, wherein a ratio of the second polyethylene naphthalate short fibers in the mixed fiber sheet is 10 to 60% by weight.

Images