JP3605231B2 - Heat resistant nonwoven - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-resistant nonwoven fabric. More specifically, the present invention relates to a heat-resistant nonwoven fabric composed of long fibers made of polyethylene naphthalate and an electrical insulating paper using the same.
[0002]
[Prior art]
Conventionally, there has been a demand in various fields for the development of nonwoven fabrics having heat resistance. For example, non-woven fabrics are widely used in the fields of heat insulating materials, electric insulating materials, filters, medical materials, building materials, etc., but heat resistance is required in some of these fields, and thus non-woven fabrics having heat resistance are required. The demand for development is increasing.
One direction for obtaining a heat-resistant nonwoven is to use a heat-resistant polymer as its material. Nonwoven fabrics using polyethylene naphthalate, one of the heat-resistant polymers, have already been proposed. Japanese Patent Application Laid-Open No. 50-18773 proposes a nonwoven fabric obtained by heating and bonding a web in which polyethylene naphthalate fibers and fibers of a polymer having latent adhesive properties are mixed. In this nonwoven fabric, the fibers used as the adhesive component are typically fibers from a polyethylene terephthalate copolymer, and have a considerably low melting point. Therefore, this nonwoven fabric is affected by the melting point of the adhesive component and does not make use of the inherent heat resistance of polyethylene naphthalate.
[0003]
Japanese Unexamined Patent Publication (Kokai) No. 4-146251 proposes a nonwoven fabric which is substantially made of polyethylene naphthalate fiber, has an average fiber diameter of 0.1 μm to 10 μm, and has excellent vertical and horizontal tensile strength. However, this non-woven fabric is specifically manufactured by a jet spinning (melt blow) method, and although the fiber diameter is non-uniform and fine and ultra-fine, the strength of the fiber cannot be said to be sufficiently high. It also affects the strength of the nonwoven fabric. In addition, this nonwoven fabric has a problem that it is difficult to provide nonwoven fabrics having various types of characteristics because of jet spinning.
[0004]
[Problems to be solved by the invention]
Therefore, a first object of the present invention is to provide a heat-resistant long-fiber nonwoven fabric substantially formed from polyethylene naphthalate fibers.
A second object of the present invention is to provide a long-fiber nonwoven fabric having excellent heat resistance and strength.
Another object of the present invention is to provide an electrical insulating paper having class F heat resistance.
[0005]
[Means for Solving the Problems]
According to the study of the present inventors, the object of the present invention is to provide a polyethylene naphthalate long fiber having a melting point of 270 ° C. or more and a birefringence (Δn) of 0.22 or more, and a birefringence ( It has been found that a low-oriented polyethylene naphthalate long fiber having Δn) of 0.01 or less is mixed and thermocompression-bonded, and is achieved by a heat-resistant nonwoven fabric and an electric insulating paper made of the nonwoven fabric.
[0006]
In the nonwoven fabric of the present invention, two types of polyethylene naphthalate long fibers are used. One is a long fiber having a high orientation and the other is a long fiber having a low orientation. This low-oriented polyethylene naphthalate long fiber substantially acts as an adhesive component, and the obtained nonwoven fabric has strength and excellent heat resistance.
[0007]
The polymer constituting the nonwoven fabric of the present invention is polyethylene naphthalate, specifically, polyethylene-2,6-naphthalate or copolymerized polyethylene-2,6-naphthalate containing 5 mol% or less of the third component. In general, polyethylene-2,6-naphthalate is prepared by combining naphthalene-2,6-dicarboxylic acid or a functional derivative thereof with ethylene glycol or a functional derivative thereof under appropriate reaction conditions in the presence of a catalyst. Synthesized. In this case, if one or more suitable third components are added before the completion of the polymerization of polyethylene-2,6-naphthalate, a copolymer or a mixed polyester is synthesized. 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, cyclobutanedicarboxylic acid, hexahydroterephthalic acid, etc. Alicyclic dicarboxylic acid; aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, naphthalene-2,7-dicarboxylic acid, diphenyldicarboxylic acid; diphenylether dicarboxylic acid, diphenylsulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, 3 , 5-Dicarboxybenzenesulfonic acid sodium salt Carboxylic acids; oxycarboxylic acids such as glycolic acid and p-oxyethoxybenzoic acid; propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentylene glycol, p-xylene glycol, 1,4-cyclohexane Dimethanol, bisphenol A, p, p-diphenoxysulfone 1,4-bis (β-hydroxyethoxy) benzene, 2,2-bis (p-β-hydroxyethoxyphenyl) propane, polyalkylene glycol, p-phenylenebis An oxy compound such as (dimethylsiloxane) or a functional derivative thereof; a high-polymerization degree compound derived from the carboxylic acid, oxycarboxylic acid, oxy compound or a functional derivative thereof, and (b) one compound. (C) compounds having three or more ester-forming functional groups, such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyalkylene glycol, etc., such as glycerin, pentaerythritol, and trimethylol Propane and the like are also exemplified as compounds which are substantially linear and can be used to some extent.
[0008]
The polyethylene naphthalate used has an intrinsic viscosity [η] of 0.45 to 1.0. The intrinsic viscosity [η] referred to in the present specification is a value obtained by dissolving a polymer in a mixed solvent of phenol and orthodichlorobenzene (mixing ratio 6: 4) and measuring the viscosity at 35 ° C. When the intrinsic viscosity [η] exceeds 1.0, the melt viscosity becomes abnormally high and melt spinning becomes difficult. When the [η] is less than 0.45, a fiber having a desired high melting point and good physical properties is obtained. It is not suitable because it cannot be obtained.
[0009]
The nonwoven fabric of the present invention has the polymer composition of the polyethylene naphthalate described above, but is formed of the following two types of oriented long fibers A and B.
(A) Polyethylene naphthalate filaments having a melting point of 270 ° C. or higher, preferably 275 ° C. or higher, and a birefringence (Δn) of 0.22 or higher (hereinafter abbreviated as “highly oriented PEN filaments”) Sometimes).
(B) Low-oriented polyethylene terephthalate long fibers having a birefringence (Δn) of 0.01 or less (hereinafter sometimes abbreviated as “low-oriented PEN long fibers”).
Highly oriented PEN long fibers can be obtained by spinning at a spinning speed of usually 2500 to 6000 m, preferably 3000 to 5000 m. Highly oriented PEN filaments have a melting point of 270 ° C. or higher, preferably 275 ° C. or higher, and particularly those having a melting point of 280 to 285 ° C. are suitable. Further, the birefringence (Δn) has a value of 0.22 or more, preferably 0.24 to 0.28. Advantageously, the finely oriented PEN filament has a fineness of 0.5 to 5 de, preferably 1 to 4 de.
[0010]
On the other hand, the low-oriented PEN long fiber can be obtained by spinning at a spinning speed of 800 m or less, preferably 300 to 700 m. The birefringence (Δn) of this low-oriented PEN long fiber is 0.01 or less, preferably 0.005 or less. The fineness of the low-oriented PEN long fiber is preferably in the range of 1 to 10 de, and more preferably in the range of 2 to 8 de. In the nonwoven fabric of the present invention, the highly oriented PEN long fiber and the low oriented PEN long fiber are mixed by weight in a range of preferably 90:10 to 60:40, more preferably 85:15 to 65:35. As the means for producing the nonwoven fabric, means and conditions generally known as a method for producing a spunbonded nonwoven fabric are employed.
[0011]
The mixed web can be nonwoven by compression bonding by either full-surface compression bonding or partial thermocompression bonding. The temperature at this time is suitably from 200 to 250 ° C., and the linear pressure is preferably from 10 to 50 kg / cm.
The nonwoven fabric of the present invention has a basis weight of 10 to 70 g / m ² , preferably 20 to 60 g / m ² , and more preferably 30 to 50 g / m ² , depending on the use.
Since the nonwoven fabric of the present invention has high strength and excellent heat resistance, it is used as a type F grade as an electrical insulating paper.
[0012]
【The invention's effect】
A long-fiber nonwoven fabric having Class F heat resistance and high strength is provided. Therefore, it can be advantageously used for non-woven fabrics requiring heat resistance, such as electric insulating paper.
Further, since the nonwoven fabric of the present invention has excellent strength and heat resistance, it can be used for asphalt roofing base cloth, carpet base cloth and various filters, and is particularly effective in terms of weight reduction.
[0013]
【Example】
The measuring method in the example is as follows.
(1) Melting point The melting point is measured at a heating rate of 20 ° C./min with a differential calorimeter manufactured by Perkin-Elmer.
(2) Fiber birefringence Measured using a polarizing microscope Rebex compensator under white light.
(3) Nonwoven fabric strength and elongation Measured with a constant-speed elongation type tensile tester according to JIS L 1096.
(4) The long-term heat-resistant nonwoven fabric is heat-treated in an oven at a temperature of 180 ° C, 200 ° C, or 230 ° C, and the time required for the elongation in the vertical direction to become 50% of the elongation before the heat treatment is measured. From the half-life of the three-point temperature, the temperature at which the elongation is expected to be 50% of that before the heat treatment in 40,000 hours is obtained from an Arrhenius plot.
[0014]
Example 1
(Spinning of highly oriented fibers)
A polyethylene naphthalate resin having an intrinsic viscosity of 0.65 was melted at 300 ° C., and discharged from a spinning head having 10 spinnerets having 100 holes at a spinning temperature of 290 ° C. The discharge rate was 100 g / min per mouthpiece. After the discharge, while being cooled by cooling air, it was taken out at a speed of 4000 m / min by ten ejectors arranged at a position of 1500 mm below the base.
(Spinning of low oriented fiber)
A polyethylene naphthalate resin having an intrinsic viscosity of 0.65 was melted at 300 ° C., and discharged from a spinning head having 10 spinnerets having 200 holes at a spinning temperature of 290 ° C. The discharge rate was 40 g / min per mouthpiece. After the ejection, while being cooled by cooling air, it was taken out by a godet roll at a speed of 500 m / min, and supplied to 10 opening fiber ejectors installed near an ejector for taking out highly oriented fibers.
(Mixed fiber)
The yarn spouted from each ejector is made into a pair of high-orientation fiber and low-orientation fiber and collides with one collision plate to perform fiber mixing and fiber opening. Ten collision plates are installed.
(Nonwoven fabric manufacturing)
The mixed yarn is collected on a moving conveyor net to form a web, and then pressed at a temperature of 240 ° C. using an embossing calender having a pressing area ratio of 24% to form a nonwoven fabric having a basis weight of 50 g / m ² . Obtained.
[0015]
Example 2
A nonwoven fabric was obtained in the same manner as in Example 1, except that the spinning speed during production of the highly oriented fiber was 5000 m / min and the spinning speed of the low oriented fiber was 700 m / min.
Example 3
A nonwoven fabric was obtained in the same manner as in Example 1, except that the spinning speed during production of the highly oriented fiber was 3000 m / min and the spinning speed of the low oriented fiber was 700 m / min.
[0016]
Comparative Example 1
A non-woven fabric was obtained in the same manner as in Example 1, except that the spinning speed during production of the highly oriented fiber was 2000 m / min and the spinning speed of the low oriented fiber was 500 m / min.
[0017]
Comparative Example 2
A nonwoven fabric was obtained in the same manner as in Example 1, except that the spinning speed during production of the highly oriented fiber was 4000 m / min, and the spinning speed of the low orientation fiber was 1000 m / min.
[0018]
Comparative Example 3
A polyethylene terephthalate resin having an intrinsic viscosity of 0.70 is melted at 290 ° C. and discharged from a spinning head having 10 holes with 200 holes at a spinning temperature of 285 ° C. at a rate of 40 g / min per spinner and 800 m / min by a godet roll. A web was prepared in the same manner as in Example 1 except that a low-orientation fiber was prepared by drawing at a speed, and pressed at 220 ° C. using an embossing calender having a pressing area ratio of 24% to obtain a nonwoven fabric having a basis weight of 50 g / m 2. Obtained.
[0019]
Comparative Example 4
A polyethylene terephthalate resin having an intrinsic viscosity of 0.70 is melted at 290 ° C., and discharged from a spinning head having 100 holes with 10 spinnerets at a spinning temperature of 285 ° C. at a rate of 100 g / min per spinneret. A web was produced in the same manner as in Comparative Example 3 except that the ten ejectors were pulled at a speed of 4000 m / min to prepare highly oriented fibers. C. to obtain a nonwoven fabric with a basis weight of 50 g / m ² .
[0020]
Table 1 shows the characteristics of the fibers constituting the nonwoven fabrics of the examples and the comparative examples, and the characteristics of the nonwoven fabrics. The nonwoven fabrics of Example 1, Comparative Examples 3 and 4 were evaluated for long-term heat resistance, and the results are shown in Table 1. Since the nonwoven fabric of the present invention is composed entirely of a heat-resistant resin called polyethylene naphthalate, it has good long-term heat resistance. In contrast, when only the adhesive component is made of polyethylene terephthalate, the heat resistance of the nonwoven fabric composed entirely of polyethylene terephthalate is attained. In addition, even in a nonwoven fabric composed entirely of polyethylene naphthalate, if the orientation of the low-orientation fiber, which is an adhesive component, proceeds, the nonwoven fabric does not fulfill a sufficient adhesive function and becomes brittle. Alternatively, when the degree of orientation of the highly oriented fiber decreases, the fiber shrinks during thermocompression bonding increases, and the strength of the nonwoven fabric also decreases. Since the nonwoven fabric of the present invention also retains excellent strength, the weight of the nonwoven fabric can be reduced, and when used as an insulating material such as an electric wire holding tape, the weight of the insulating material can be reduced.
[0021]
[Table 1]

Claims (2)

Polyethylene naphthalate long fibers having a melting point of 270 ° C. or more and a birefringence (Δn) of 0.22 or more and low-oriented polyethylene naphthalate long fibers having a birefringence (Δn) of 0.01 or less Is a heat-resistant non-woven fabric that is mixed and thermo-compressed. An electrically insulating paper comprising the heat-resistant nonwoven fabric according to claim 1.