JPS5839944B2 - Thai netseifushiyokufuoyobi Shijiyoubutsuno Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing nonwoven fabrics and paper-like materials with excellent heat resistance and suitable as electrical insulating materials.

Conventionally, when nonwoven fabrics made of heat-resistant fibers such as wholly aromatic polyamide fibers and polyimide fibers are manufactured by thermocompression bonding, fibers with a lower melting point than the heat-resistant fibers, such as polyester fibers and 6-nylon fibers, are used as adhesives. However, such a method had the disadvantage that the heat resistance of the heat-resistant fiber itself was not fully demonstrated.

On the other hand, it is conceivable to utilize the self-adhesive properties of the heat-resistant fibers, but such a method requires high heat-pressure treatment temperatures and is extremely disadvantageous from an industrial perspective.

The present invention solves the problems of such conventional methods at once and provides a method for producing nonwoven fabrics and paper-like materials with excellent heat resistance at low heat-pressure treatment temperatures, and is the gist of the invention. However, when manufacturing nonwoven fabrics or paper-like materials from heat-resistant fibers or fibrils by thermocompression bonding, a dry crystalline complex consisting of a polymetaphenylene isophthalamide polymer and its polar solvent is used as an adhesive component, and , a method for producing heat-resistant nonwoven fabrics and paper-like materials, characterized in that the polar solvent is removed after the thermocompression bonding process.

The heat-resistant fibers in the present invention may be selected depending on the purpose and are not particularly limited, but preferred examples include wholly aromatic polyamide fibers such as polyparaphenylene terephthalamide and polymetaphenylene isophthalamide. , polyimide fibers, polyamide/imide fibers, aromatic polyether fibers, polyphenol fibers, and polysulfone fibers.

The polymetaphenylene isophthalamide polymer referred to in the present invention is a polymer in which 75 or more repeating units are composed of metaphenylene isophthalamide, and the relative viscosity is about 1.
．． 5-5.5 (in a solution of concentrated sulfuric acid at 25°C, 100
(value measured at a concentration of 1.0 g of polymer per cc)
consisting of or containing an entirely aromatic linear polymer.

Copolymers include, for example, poly(metaphenylene isophthalamide/terephthalamide) copolymer, poly(metaphenylene 5-carboxy-1,3-phenylene isophthalamide) copolymer, poly(4,4' methylene diphenylene isophthalamide) copolymer, amide), poly(5-methyl-1,3-phenylene isophthalamide), and the like.

Furthermore, as a polar solvent, N-methyl-2-pyrrolidone (
NMP), hexamethylphosphoramide (HMPA)
A polar solvent having a dielectric constant of 40 Debye (in benzene) or more is preferable.

A complex compound consisting of a polymetaphenylene isophthalamide polymer and its solvent can be manufactured using raw materials in the form of powder, undrawn thread, drawn thread, or drawn heat-treated material, depending on the process or purpose of the product. Possible, immersion in a solvent of 20 liters or more per weight of polymer or placing in solvent vapor, at least 5.0 liters or more, preferably 20 liters or more per weight of polymer.
% or more of weight increase.

Solvent absorption occurs when the solvent dissolves at a temperature below its boiling point, and this
You can concentrate by keeping it below 30℃, or you can concentrate it at room temperature to 130℃.
It may be absorbed at a temperature of

If the morphology of the complex is important, it is desirable to carry out the solvent absorption at a temperature of 130° C. or lower.

When a complex is formed in this manner, a clear crystal diffraction pattern of the complex can be seen in the X-ray diffraction pattern, which is clearly different from polymetaphenylene isophthalamide.

It also shows a clear melting point, and the HMPA complex is heated to 120°C with N
MP has a melting point at 90°C.

When using a fibrous complex compound, the sheet-like material made of the complex compound and heat-resistant fibers is formed by mixing the side fibers through a combing machine to form a web, and then heating and pressing with a roller, etc. urge

On the other hand, when using a powdered complex compound, a method can be used in which the powder is uniformly added using a roller or the like to a sheet-like material that has been formed in advance by a known method, and the mixture is heated and pressed using a roller or the like.

The amount of the complex compound added varies depending on the use and performance of the product, but it is usually 1.0 to 10φ by weight for thin products and 10mm for thick products.
~50%, preferably 501% or more for paper-like materials.

It is desirable that the web be heat-pressed at a temperature equal to or higher than the melting point of the complex compound, such as 120° C. or higher for a complex compound with hexamethylene phosphoramide, and 90° C. or higher for N-methyl-2.pyrrolidone.

The upper limit of temperature is substantially the glass transition temperature (3
00 to 330℃) or less, but from an industrial perspective
A temperature of 00°C or higher is economically unfavorable, and a temperature of 250°C or lower is preferred.

Nonwoven fabrics treated with heat and pressure have sufficient strength and uniform appearance as they are, and have excellent dimensional stability and shape retention, but they contain a small amount of solvent.

For this reason, it is desirable to remove the solvent, which can be done with cold water,
This is easily achieved by passing it through hot water or steam.

Thereafter, it is passed through a drying process, but in this process the complex compound has already been transformed into polymetaphenylene isophthalamide, which has excellent heat resistance, so it is in a strong and heat-resistant state.

According to the present invention configured as described above, since a special crystalline complex compound with a low melting point is used as an adhesive component, a nonwoven fabric or paper-like material can be easily formed at a low heat-pressure treatment temperature.
In addition, since the complex compound is crystalline and has a clear melting point, the heat-pressure treatment temperature can be kept constant, quality control and handling are extremely easy. Since the complex compound is converted into polymetaphenylene isophthalamide which has good heat resistance, it has great industrial effects such as being able to obtain nonwoven fabrics and paper-like materials that have far superior heat resistance than conventional products. It is something.

Example 1 A drawn fiber (fineness 2 de
, strength 5. O,! 9/d, elongation 28) was cut into 51 pieces, and a web was formed using a card in the ridge line process.

On the other hand, the powder consisting of the polymetaphenylene isophthalamide was immersed in hexamethylphosphoramide (HMPA) at a weight ratio of 200% at 50°C for 1 hour, and then separated on a daily basis.
By drying under reduced pressure at 80° C. for 5 hours, a complex powder of the polymetaphenylene isophthalamide and HMPA was obtained.

The complex powder was confirmed to be a highly crystalline substance clearly different from polymetaphenylene isophthalamide crystals by X-ray diffraction, and its melting point was 120°C by differential thermal analysis.
The average particle size was 0.2 mm.

After uniformly mixing the complex powder into the web, the mixture was heated to 140°C.
The material was calendered under the conditions of 100 kg/CIIL, then treated with 1 kg of steam at 10 tG for 3 minutes, and then dried.

The obtained nonwoven fabric exhibited physical properties as shown in Table 1, was at normal temperature, and exhibited self-extinguishing properties without changing its strength and elongation even after being treated at 250°C for 5 hours.

Example 2 After dry spinning the same polymer as in Example 1, undrawn fibers (sample A) that were washed under water and drawn fibers (sample B) that were stretched 40 times under water were obtained.

Samples A and B were immersed in 100% hexamethylphosphoramide at 50°C for 1 hour, separated, and then heated at 80°C for 5 hours.
A fibrous complex was obtained by drying under reduced pressure for hours.

Also, sample B was added to 100 wt. HMPA at 30°C for 20 min.
Partially complexed fibers were obtained by soaking for a minute, separating and drying under reduced pressure at 80° C. for 5 hours.

In the X-ray diffraction pattern of this product, both complex crystals and polymetaphenylene isophthalamide crystals were present.

These three types of fibrous complexes were uniformly mixed at 20% with the same short fibers as in Example 1, and three types of webs were obtained by carding.

The three types of webs were calendered at 140°C and 100kg/CrfL, and then calendered with 1kg/dG steam.
After processing for a minute, it was dried.

The physical properties of the obtained nonwoven fabric are shown in Table 2.
Even after treatment at ℃ for 5 hours, the strength and elongation did not change and self-extinguishing properties were exhibited.

Example 3 Powder made of the same polymer as in Example 1 was heated to 30'C N-
Soak in methylpyrrolidone (NMP) for 5 hours, portion out,
By drying under reduced pressure at 0° C. for 5 hours, a complex powder of polymetaphenylene isophthalamide and NMP was obtained.

The complex powder is a crystalline substance clearly different from polymetaphenylene isophthalamide crystals by X-ray diffraction,
The melting point was 90°C.

The same web as in Example 1 was uniformly sprinkled with 20% of the complex powder, calendered at 100° C. and 100 ky/crrL, treated with steam at 1 kg/cyyfG for 3 minutes, and then dried.

The obtained nonwoven fabric had a tensile strength of 4.8 kg150 and an elongation of 15. Even after being treated at 250° C. for 5 hours, the elongation remained unchanged and exhibited self-extinguishing properties.

Example 4 Drawn fiber (fineness 1.5 de1 strength 25 g/d1 elongation 4 man) made by dry-wet spinning polyparaphenylene terephthalamide with an intrinsic viscosity of 6.0 in sulfuric acid and then heat-treated at 360° C. for 1.5 seconds. A web was obtained by wet paper making from short fibers cut into 50 mm pieces.

In addition, the intrinsic viscosity at 30°C in dimethylacetamide is 0.
A polyimide copolymer made of toluene diisocyanate and benzophenone tetracarboxylic anhydride (No. 7) was dry-spun and then stretched 28 times in water (fineness 2).
de1 strength 3.5g/d.

A web was obtained from short fibers cut with an elongation of 25 threads) to 50 mm1 by carding in the combing process.

20% of the same complex powder as in Example 1 was added to each of the above two types of webs.
100kg/Crr at 140℃ after evenly mixing
It was calendered under L conditions, then treated with steam at 1 kg/iG for 3 minutes, and then dried.

The physical properties of the obtained nonwoven fabric are as shown in Table 3.
Even after treatment at ℃ for 5 hours, the strength and elongation did not change, indicating self-extinguishing properties.

Claims (1)

[Claims] 1. When producing nonwoven fabrics or paper-like products from heat-resistant fibers or fibrils by thermocompression bonding, a dry crystalline complex consisting of a polymetaphenylene isophthalamide polymer and its polar solvent is used as an adhesive component, and thermocompression bonding is also carried out. A method for producing heat-resistant nonwoven fabrics and paper-like materials, which comprises removing the polar solvent after the treatment.