JP2008057090A - Polyethylene naphthalate staple fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polyethylene naphthalate fiber suitable to the industrial material sector, especially as rubber-reinforcing fiber or in the form of nonwoven fabrics such as filters or cushioning materials, and uniform in the cross-section diameter on the cross section perpendicular to the fiber axis. <P>SOLUTION: The fiber is formed of polyethylene naphthalate wherein at least 90 mol% of the total recurring unit represents ethylene-2,6-naphthalate units. The fiber, polyethylene naphthalate staple fiber, meets the following requirements (a) to (d): (a) 0.45 dL/g≤intrinsic viscosity≤1.00 dL/g, (b) fiber diameter dispersion degree≤20%, (c) 1.1 dtex≤single fiber fineness≤100 dtex, and (d) 3 mm≤fiber length≤200 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a short polyethylene naphthalate fiber. More specifically, the present invention relates to a polyethylene naphthalate short fiber having a uniform cross-sectional diameter in a cross section perpendicular to the fiber axis direction of the fiber.

  Polyethylene naphthalate fibers mainly composed of ethylene-2,6-naphthalate units exhibit high strength, high elastic modulus, and excellent thermal dimensional stability, and are used in the fields of rubber reinforcement such as tire cords. It is expected to show performance superior to that of terephthalate fibers (see, for example, Patent Documents 1 to 3).

  However, in the production process of polyethylene naphthalate fiber, no explanation is given for the cross-sectional diameter in a cross section perpendicular to the fiber axis direction of the fiber, and it is difficult to say that this is a known technique. Such a fiber bundle having a large cross-sectional diameter dispersion does not sufficiently exhibit its characteristics when used as a rubber reinforcing fiber or a nonwoven fabric such as a filter or a cushion material.

JP-A-5-163612 JP-A-6-346322 JP-A-10-88422

  The present invention has been made against the background described above, and is a fiber fiber suitable for use as a reinforcing fiber for rubber materials such as tire cords, belts, hoses and the like having a uniform fiber diameter, or as a nonwoven fabric such as filters and cushion materials. An object of the present invention is to provide a polyethylene naphthalate short fiber having a uniform cross-sectional diameter in a cross section perpendicular to the axial direction.

According to the study by the present inventors, by setting the share rate for discharging the polyethylene naphthalate resin to 1200 s ⁻¹ or less, the degree of dispersion of the cross-sectional diameter in the cross section perpendicular to the fiber axis direction of the fiber is 20% or less. It has been found that a polyethylene naphthalate short fiber having a uniform cross-sectional diameter can be obtained.

Thus, a fiber formed from polyethylene naphthalate in which at least 90 mol% of all repeating units are ethylene-2,6-naphthalate units, and further a polyethylene naphthalate short fiber satisfying the following (a) to (d): .
(A) 0.45 dL / g ≦ Intrinsic viscosity ≦ 1.00 dL / g
(B) Fiber diameter dispersion ≦ 20%
(C) 1.1 dtex ≦ single fiber fineness ≦ 100 dtex
(D) 3 mm ≦ fiber length ≦ 200 mm

  The polyethylene naphthalate short fiber of the present invention has a very uniform cross-sectional diameter in a cross section perpendicular to the fiber axis direction, and is suitable for industrial materials, particularly as a rubber reinforcing fiber, or a nonwoven fabric such as a filter or cushion material. It is. Moreover, what cut | disconnected the polyethylene naphthalate fiber in this invention, without giving a crimp is a fiber suitable as uses, for example of nonwoven fabrics, such as papermaking.

  The polyethylene naphthalate referred to in the present invention is a polymer containing an ethylene-2,6-naphthalate unit in an amount of 90 mol% or more in all repeating units and containing an appropriate third component in a proportion of 10 mol% or less. There is no problem. Especially, it is more preferable that 95 mol% or more of ethylene-2,6-naphthalate units are included. If the ethylene-2,6-naphthalate unit is less than 90 mol%, the heat resistance is insufficient for the intended use, which is not preferable. In general, polyethylene-2,6-naphthalate is synthesized by polycondensation of naphthalene-2,6-dicarboxylic acid or an ester-forming derivative thereof with ethylene glycol in the presence of a catalyst under appropriate reaction conditions. At this time, if one or more appropriate third components are added before the completion of the polymerization of polyethylene-2,6-naphthalate, a copolyester is synthesized.

  Suitable third components include: (a) compounds having two ester-forming functional groups: for example, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid; cyclopropanedicarboxylic acid, Cycloaliphatic dicarboxylic acids such as cyclobutanedicarboxylic acid, hexahydroterephthalic acid, decalin dicarboxylic acid; phthalic acid, isophthalic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-1,8- Aromatic dicarboxylic acids such as dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 3,4′-diphenyldicarboxylic acid; diphenyl ether dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid 3,5-dicarboxybenzenesulfo Carboxylic acid such as sodium acid; oxycarboxylic acid such as glycolic acid, p-oxybenzoic acid, p-oxyethoxybenzoic acid; propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, triethylene glycol, neo Pentylene glycol, tetraethylene glycol, dibutylene glycol, p-xylylene glycol, 1,4-cyclohexanedimethanol, bisphenol A, p, p'-dihydroxydiphenyl sulfone, 1,4-bis (β-hydroxyethoxy) benzene , 2,2-bis (p-β-hydroxyethoxyphenyl) propane, polyalkylene glycol and other dihydroxy compounds; functional derivatives thereof; carboxylic acids, oxycarboxylic acids Compounds having a high degree of polymerization derived from dihydroxy compounds or functional derivatives thereof, and (b) compounds having one ester-forming functional group such as benzoic acid, benzyloxybenzoic acid, methoxypolyalkylene glycol, etc. . Here, the functional derivative represents a derivative having a functional group capable of forming an ester group by reacting with a compound having another functional group.

Furthermore, (c) compounds having three or more ester-forming functional groups such as glycerin, pentaerythritol, trimethylolpropane, trimesic acid, trimellitic acid, pyromellitic acid are substantially linear in polymer. It can be used within a certain range.
Further, it goes without saying that the polyester may contain a matting agent such as titanium dioxide and a stabilizer such as phosphoric acid, phosphorous acid and esters thereof.

  The intrinsic viscosity (IV) of the polyethylene naphthalate that forms the fiber of the present invention needs to be 0.45 dL / g or more and 1.00 dL / g or less. More preferably, it is 0.49-0.80 dL / g. The intrinsic viscosity as used in the present invention is a value obtained from the viscosity measured at 35 ° C. by dissolving the fiber in a mixed solvent of phenol and orthodichlorobenzene (volume ratio 6: 4). When the intrinsic viscosity is less than 0.45 dL / g, the strength and toughness of the polyethylene naphthalate short fiber are lowered. On the other hand, polyethylene naphthalate having an intrinsic viscosity exceeding 1.00 dL / g has an extremely high melt viscosity, and a thermal decomposition reaction that excessively raises the spinning (melting) temperature proceeds, so that the spinning process tends to be poor. Manufacture of phthalate short fibers may be difficult. When the polyethylene naphthalate is polymerized, it can be made to be within the range of this intrinsic viscosity by appropriately adjusting the polymerization mode such as melt polymerization or solid phase polymerization, polymerization temperature, pressure, polymerization time and the like. Furthermore, it can be realized by suppressing a decrease in the intrinsic viscosity by a technique such as sufficient drying when the fiber is formed.

The polyethylene naphthalate short fibers in the present invention can be melt-spun using a generally known melt-spinning apparatus. However, it is preferable that melt spinning is performed using a nozzle having a spinneret hole diameter of 0.60 to 0.80 mm, and the shear rate from the nozzle hole at the time of melt spinning is 1200 s ⁻¹ or less. More preferably, it is 1000 s ⁻¹ or less. When the shear rate exceeds 1200 s ⁻¹ , the cross-sectional diameter in the cross section perpendicular to the fiber axis direction of the fiber is not preferable. The shear rate of 1200 s ^-1 or less can be achieved by increasing the diameter of the die hole used for spinning within the above range. As will be described later, it can also be set by a balance with the discharge amount, which is one of the spinning conditions.

Furthermore, the fiber diameter dispersion of the obtained polyethylene naphthalate fiber needs to be 20% or less. The fiber diameter dispersity is a value obtained by actually measuring a cross-sectional diameter in a cross section perpendicular to the fiber axis direction of 50 or more single yarns and dividing the standard deviation by an average value. A more preferable fiber diameter dispersion is 10% or less. When the fiber diameter dispersity exceeds 20%, it is not preferable because physical properties such as strength are not uniform when used for industrial applications such as nonwoven fabric. In order to reduce the fiber diameter dispersion to 20% or less, it can be achieved by setting the share rate of the polymer discharged from the die to 1200 s ⁻¹ or less.

  Furthermore, the single fiber fineness of the obtained polyethylene naphthalate fiber is 1.1 to 100 dtex, and the fiber length needs to be 3 to 200 mm. A fiber having a single fiber fineness of less than 1.1 dtex is not preferable from the viewpoint that it is difficult to obtain a discharge amount capable of stably continuing spinning, or a poor spinning property due to an increase in the number of holes in the die. . On the other hand, when the single fiber fineness is 100 dtex or more, it becomes hard when molded into a nonwoven fabric or the like, and the texture of the nonwoven fabric is not excellent. The single fiber fineness is preferably 1.1 to 20 dtex, more preferably 1.1 to 15 dtex, even more preferably 1.1 to 13 dtex, even more preferably 1.1 to 12 dtex, and most preferably 1.1. ~ 11 dtex. The single fiber fineness can be appropriately adjusted depending on conditions such as the size of the hole in the die in the spinning process, the discharge rate, the draft and the shear rate, and the setting conditions of the draw ratio in the drawing process. If the fiber length is less than 3 mm, it may be slightly removed from the end of the fiber in the process of high-order processing in the subsequent process of the fiber, and this rate of removal will be higher, which is not preferable. When the fiber length exceeds 200 mm, the process passability is poor including the spinning process, which is not preferable. The fiber length is preferably 4 to 100 mm, more preferably 4 to 70 mm, and most preferably 5 to 55 mm.

  Furthermore, when producing the polyethylene naphthalate fiber of the present application, it is preferable to melt-spin using a die having a spinneret hole diameter of 0.30 to 0.80 mm. If the spinneret hole diameter exceeds the range of 0.30 to 0.80 mm, the fiber diameter dispersion degree of the fibers is not preferable because it is 20% or more.

  Further, the cross-sectional shape of the polyethylene naphthalate fiber of the present invention is not particularly limited. For example, a round shape, an oval shape, a polygon shape such as a triangle, a square, a hexagon, a star shape, a tens (cross shape), and a Y shape. -An irregular cross section such as an H shape, a petal shape, a hat shape, and a hollow shape can be mentioned, and a partially modified shape or a synthesized shape may be used. Moreover, you may combine these various cross-sectional shapes.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, each physical property value is measured by the following method.

(1) Fiber elongation and fineness, fiber length Using a tensile load measuring instrument (Shimadzu Autograph), the fiber was measured according to the method described in JIS L-1015.

Ｘｉ：繊維断面の面積、 ｘ：ΣＸｉ／ｎ、 ｎ：測定したサンプル数
以下の実施例、比較例においてはサンプル数１０で測定を行った。 (2) Fiber diameter dispersion degree: V
The fiber diameter dispersion degree was calculated by the following calculation formula by taking a section photograph in a cross section perpendicular to the fiber axis direction of the fiber, measuring the cross section diameter, and calculating the area of the fiber cross section.

Xi: Fiber cross-sectional area, x: ΣXi / n, n: Measurement was carried out with 10 samples in Examples and Comparative Examples below the number of measured samples.

(3) Intrinsic viscosity: IV
The intrinsic viscosity is a value obtained by dissolving a fiber sample in a mixed solvent of phenol and orthodichlorobenzene (volume ratio 6: 4) and measuring the viscosity at 35 ° C. using an Ubbelohde viscometer.

(4) Discharge amount per hole: Q ₁
The discharge amount per hole was calculated by actually measuring the discharge amount per minute of the polyethylene naphthalate polymer from the base and dividing it by the number of the base holes. The share rate can also be controlled to a predetermined value by adjusting this value.

γ：シェアレート、 Ｑ_２：１孔当たりの１秒間の吐出量、 Ｄ：口金の孔径、 ρ：溶融ポリマー密度 (5) Share rate: γ
The discharge linear velocity was calculated by the following formula.

γ: shear rate, Q ₂ : discharge amount per second per hole, D: hole diameter of the die, ρ: molten polymer density

[Example 1]
An ethylene-2,6-naphthalate chip having a melt viscosity of 0.62 dL / g was melted at a temperature of 310 ° C. and then discharged from a spinneret having 250 holes having a hole diameter of 0.65 mm at a rate of 2.0 g / min · hole. . The discharged yarn was solidified by blowing cooling air, applied with an oil agent with an oiling roller, and then wound up at a speed of 500 m / min. Subsequently, the undrawn yarn is heated to 110 to 140 ° C. between the first drawing roller and the second drawing roller to perform the first stage drawing (drawing ratio: 2.0 to 4.0 times), and then the second drawing roller. The second stage stretching (stretching ratio: 1.00 to 1.50 times) was performed by heating between 110 and 140 ° C. between the first and third stretching rollers, and then heat setting was performed with a 200 ° C. heat setting roller. . The drawn yarn was preheated to 70 to 120 ° C., and crimped by a push-in crimper. Thereafter, the fibers were cut to a predetermined length. The conditions at the time of fiber production and the physical properties of the obtained short fibers are shown in Table 1.

[Example 2]
Fibers were obtained in the same manner as in Example 1 except that the spinneret hole diameter was 0.60 mm and 1.3 g / min · hole. The conditions at the time of fiber production and the physical properties of the obtained fiber are shown in Table 1.

[Example 3]
Fibers were obtained in the same manner as in Example 1 except that the spinneret hole diameter was 0.60 mm and 0.94 g / min · hole. The conditions at the time of fiber production and the physical properties of the obtained fiber are shown in Table 1.

[Example 4]
Fibers were obtained in the same manner as in Example 1 except that the spinneret hole diameter was 0.40 mm and 0.94 g / min · hole. The conditions at the time of fiber production and the physical properties of the obtained fiber are shown in Table 1.

[Comparative Example 1]
Fibers were obtained in the same manner as in Example 1 except that the spinneret hole diameter was 0.26 mm and 1.3 g / min · hole. The conditions at the time of fiber production and the physical properties of the obtained fiber are shown in Table 1.

[Comparative Example 2]
Fibers were obtained in the same manner as in Example 1, except that the spinneret hole diameter was 0.26 mm, 0.23 g / min · hole, and the spinning speed was 800 m / min. The conditions at the time of fiber production and the physical properties of the obtained fiber are shown in Table 1.

  The polyethylene naphthalate fiber of the present invention has a very uniform cross-sectional diameter in a cross section perpendicular to the fiber axis direction, and is a fiber suitable for industrial materials, particularly rubber reinforcing fibers, or non-woven fabrics such as filters and cushion materials. is there. Moreover, what cut | disconnected the polyethylene naphthalate fiber in this invention, without providing a crimp is a short fiber suitable for nonwoven fabric uses, such as papermaking, for example. Such a fiber is very significant industrially in that it is a suitable fiber for the above-mentioned applications.

Claims (2)

Polyethylene naphthalate short fibers which are fibers formed from polyethylene naphthalate in which at least 90 mol% of all repeating units are ethylene-2,6-naphthalate units, and satisfy the following (a) to (d).
(A) 0.45 dL / g ≦ Intrinsic viscosity ≦ 1.00 dL / g
(B) Fiber diameter dispersion ≦ 20%
(C) 1.1 dtex ≦ single fiber fineness ≦ 100 dtex
(D) 3 mm ≦ fiber length ≦ 200 mm   The polyethylene naphthalate short fiber according to claim 1, wherein the single fiber fineness is 1.1 to 15 dtex.