JPS6030367B2 - Method for manufacturing flame-resistant fibers or flame-resistant fiber structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing flame-resistant fibers or flame-resistant fiber structures.

Flame-resistant fibers and flame-resistant fiber structures have superior heat resistance and chemical resistance compared to natural fibers, synthetic fibers, or man-made fibers, so they can be used as industrial materials for aircraft, industrial machinery, automobiles, and packing materials. It is being considered as

In addition, the flame-resistant fibers and flame-resistant fiber structures have no electrical conductivity compared to carbon fibers and carbon fiber structures, and are inferior in heat resistance, chemical resistance, and tensile strength of the single fibers as a whole.
It has an extremely flexible texture and exhibits excellent strength when made into fibrous structures, and can be heat treated at low temperatures. It has the advantage that it can be manufactured at low cost. Conventional flame-resistant fibers and flame-resistant fiber structures are made of polyacrylonitrile fibers or cellulose in an oxidizing atmosphere of 200 C~
Examples include those heat-treated at a temperature of 350 degrees Celsius,
The material thus obtained is extremely brittle and thermally unstable, decomposing or melting when exposed to flame, making it impractical.

For this purpose, the above-mentioned heat-treated product must be further heat-treated at a temperature of 400 to 80,000 ℃ in a non-oxidizing atmosphere and under tension. Therefore, it is necessary to spin flame-resistant fibers to produce a flame-resistant fiber structure, and even the products obtained in this way tend to shrink due to heat and are not sufficient in terms of heat resistance and chemical resistance. The present inventors focused on the above problem and as a result of intensive research,
The invention has been completed. An object of the present invention is to provide flame-resistant fibers or flame-resistant fiber structures with excellent heat resistance.

Another object of the present invention is to provide a method for manufacturing flame-resistant fibers or flame-resistant fiber structures having excellent heat resistance industrially and easily at low cost. The method of the present invention is characterized in that hardened novolac fibers obtained by melt-weaving novolac resin are cured with aldehydes or hardened/borac fibers are at least 7
It is characterized by heat treating a cured/borac fiber structure consisting of % by weight of 280° C. to 400 qo in a non-oxidizing atmosphere under no tension.

Applied to the method of the present invention/borac resin is a thermoplastic resin obtained by adding phenols in excess of aldehydes and polycondensing the mixture in the presence of an acidic catalyst.
It has a molecular weight of 0.00. Furthermore, the cured/volatile fiber applied to the present invention is produced by melting the novolac resin into paper yarn and then curing it with aldehydes. may be melt-mixed and used in a proportion of 3% by weight or less.

In the present invention, the curing treatment involves treating uncured novolac fibers in a mixed aqueous solution of an acidic catalyst and an aldehyde, or pre-curing the outer portion of the fiber with a mixed aqueous solution of an acidic catalyst and aldehydes, and then further curing the outer part of the fiber with a mixed aqueous solution of an acidic catalyst and aldehydes. A method of curing the inside of the fiber in a mixed aqueous solution of
In this case, hydrochloric acid is usually used as the acidic catalyst, but inorganic acids and organic acids such as sulfuric acid, phosphoric acid, and P-toluenesulfonic acid are also applicable.

Ammonia is usually used as the basic catalyst, but examples include hexamethylenetetramine, urea, potassium hydroxide, and the like. As the aldehyde, formaldehyde is usually used, but other examples include paraformaldehyde, trioxane, tetraoxane, benzaldehyde, hexamethylenetetramine, and glyoxal. The thus obtained cured/volatile fibers may be treated with an aqueous solution of lower alcohols such as methanol or ethanol or an aqueous ammonia solution in order to remove hybrids, military condensates of aldehydes, and acidic catalysts contained in or attached to the fibers. good.

In particular, fibers treated with an aqueous solution of a lower alcohol such as methanol or ethanol greatly improve the elongation of the fibers, and are therefore optimal for producing hardened novolak fiber structures. The cured novolac fiber applied to the present invention has a weight increase rate of 5 to 20% by weight, preferably 8% by weight, relative to the uncured novolac fiber.
~15% by weight. In the curing reaction of the present invention, a methylene cross-linking reaction progresses between the molecules of the novolac resin, and methylol groups and dimethylene ether groups are generated, so that the curing process produces a larger amount of cured/volac fibers than uncured novolak fibers. In some cases, the amount is increased by 4% by weight. In this case, the curing of the fiber progresses from the surface to the inside, so the inside of the cured novolac fiber with a low degree of hardening is uncured novolac resin, while if the weight increase rate, that is, the degree of hardening is too high, methylol Many groups are generated.
Therefore, the weight increase rate of the above-mentioned cured novolac fiber is 5.
If it is less than % by weight, the novolak resin will melt or decompose during the heat treatment of the present invention, and the desired product will not be obtained. Moreover, even if the weight increase rate exceeds 2% by weight, a large amount of decomposed gas is generated during heat treatment, the carbonization yield is low, and the fiber strength is not practical. Examples of cured novolac fiber structures that can be applied to the method of the present invention include knitted/woven fabrics, nonwoven fabrics, braids, and papers made of cured/borac fibers. , preferably at a ratio of 15% by weight or less, or may be used by drying, but as the mixing ratio with the other fibers mentioned above increases, the flame-resistant fiber structure obtained by heat treatment becomes harder and brittle. .

In the present invention, the cured novolac fibers or cured novolac fiber structures are heated in a non-oxidizing atmosphere to give a
Although the heat treatment is performed at a temperature of 0.000000, the moisture contained in the cured novolac fibers or the cured novolac fiber structure may damage the flame-resistant fibers or the flame-resistant fiber structure, so they are dried in advance to reduce the moisture content to 7% by weight. Hereinafter, it is preferable to use the amount at 3% by weight or less.

Also, the cured/pollac fibers or the cured/pollac fiber structure are easily oxidized and turn brown if left for a long time. When heat-treated, this product generates a large amount of oxidizing gas and damages the fibers, so cured novolac fiber structures that are left for a long period of time should be treated with at least 3% by weight methanol or ethanol aqueous solution before use. and the effect is great.
Furthermore, in the present invention, in order to improve the heat treatment survival rate and tensile strength of the flame-resistant fiber or flame-resistant fiber structure, for example, zinc chloride, ammonium phosphate, boric acid, etc. may be used after pretreatment. The heat treatment of the present invention is carried out batchwise or continuously in a non-oxidizing atmosphere with the cured novolac fibers or cured novolac fiber structure in an untensioned state. As the non-oxidizing atmosphere in the present invention, nitrogen is usually used, but in addition, helium, hydrogen, trichloroethylene, tetrachloroethylene,
Examples include cracked gas during firing, methane, coke, or a mixed atmosphere of two or more thereof.

In this case, the presence of oxygen lowers the overall weaving performance, so care must be taken to prevent oxygen from being mixed in as much as possible. Normally, when polyacrylonitrile or bisroll is used as a precursor fiber, the fiber shrinks due to heat, so heat treatment must be performed under tension such as constant tension or stretching in order to maintain fiber strength. Since the cured nopolac fibers or cured nopolac fiber structures are infusible, they are extremely advantageous in that they can be heat treated without any tension.

This is because the productivity is extremely low if the process is carried out under tension, the fiber structure cannot actually be heat treated, and furthermore, the strength of the obtained fibers varies widely and tends to be hard and brittle. be. The heat treatment start temperature of the present invention is usually 20
Although the temperature is below 0 qC, it is best to avoid subjecting cured/borac fibers or cured novolac fiber structures to higher temperatures because the fibers may be oxidized or rapidly decomposed. The temperature increase rate during heat treatment in the present invention is usually 20
0 qo/hour to 2000 pm ○/hour, but considering fiber strength, fiber flexibility, and production department, 600 pm ○
/hour to 120 ○/hour is preferable. The heat treatment temperature in the present invention is 280 to 400 degrees Celsius, preferably 0 degrees Celsius to total temperature. When the cured/borac fiber or the cured/borac fiber structure used in the present invention is heat-treated in a nitrogen atmosphere, for example, at 150 to 250 oo, the methylol groups and dimethylene ether groups contained in the fiber decompose or polycondense. Formation of formaldehyde and water is observed, and when the temperature approaches 300°C, further decomposition of phenolic hydroxyl groups is observed. When the heat treatment temperature becomes higher, most methylene groups disappear, resulting in conductive carbon fibers or carbon fiber structures. The hardened novolac fiber itself is “Bakelite”
Therefore, it is easily colored by oxidation and does not have sufficient heat resistance in an oxidizing atmosphere. However, the products in which the methylol group, dimethylene ether group, or phenolic hydroxyl group is thermally decomposed by the present invention exhibit excellent heat resistance, and the tertiary Since a large amount of methylene groups, which are original crosslinking groups, are present, the flexibility remains unchanged before and after heat treatment.

If the heat treatment temperature is less than 280qo, no improvement in heat resistance, flame resistance or chemical resistance will be seen compared to cured novola fibers or cured novolac fiber structures;
Those heat treated with 00oo are flexible and heat resistant.
Improved chemical and flame resistance.

On the other hand, even if the heat treatment temperature becomes higher than 400°C, the productivity of the present invention will only decrease; at higher temperatures, carbon fibers or carbon fiber structures will be produced, and the flame-resistant fibers or flame-resistant fiber structures of the present invention will not be obtained. do not have. The holding time of the heat treatment is usually longer at low temperatures, but preferably 350-3703
The heat treatment time is 30 to 120 minutes at a temperature of do not have. In the present invention, the high density of the cured novolac fiber structure upon heat treatment is 0.6 cc or less, preferably 0.4 tan/cc or less.

If the density is higher than 0.6 mm/cc, it will be difficult to remove the air inside the fiber structure, and gases and low boiling point substances generated during heat treatment will be encapsulated in the fiber structure, causing fusion between the fibers. This is not desirable as it may be visible or damage the fibers. - Since the flame-resistant fibers and flame-resistant fiber structures thus obtained by the present invention have excellent heat resistance, chemical resistance, and flame resistance, they can be widely used as various industrial materials. Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 Phenol 65k9, 44% by weight formalin 3.4[9] and oxalic acid 20ml were placed in a parable flask and the temperature was raised from 0 to 100qo over 6 hours while holding a light. . Next, after holding at this temperature for 1 hour, the two materials were heated under reduced pressure on a day and night until the temperature reached 180℃ in 3 hours.
The temperature was raised to 0.degree. C. to remove water, unreacted substances, and low-boiling compounds. The thus obtained Borac resin had a value of 0.071 when dissolved in 20 qo of acetone, and a melt softening temperature of 125°C. Using the above / Borac resin with a thread cap with a diameter of 120 and a diameter of 0.20 ◇,
Melt-spun at C and wound at a winding speed of 700 m/rib to obtain a weave of 1.8, a strength of 0.25 k9/rail, and an elongation of 1.7.
% uncured/Pollack fibers were obtained.

10.0 mm of each of the uncured/borac fibers was immersed in a mixed aqueous solution consisting of 17.5% by weight of hydrochloric acid and 145% by weight of formaldehyde at 28°C, and the temperature was gradually increased to 9% over a period of 2 hours. It was warm.

Next, 1 to 9 scales were placed in the mixed aqueous solution for 5 minutes, then 30 minutes. Samples cured for 3 hours, 5 hours, 1q hours, and 3q hours were respectively sample-, sample-'B}, sample-1, sample-nagi, sample-1 field, sample-1 field, and sample-.
(G). Each of the materials thus obtained was washed with hot water at a temperature of 4 degrees and then dried at a temperature of 8 degrees and 0 for 60 minutes. Next, each of the above sample-~sample-(G) was divided into two equal parts, each having an inner diameter of 52
Inside the quartz tube of Hawk◇, one was kept calm without tension, and the other was charged with 20k9/negative. 30 from the bottom of the quartz tube
36°C from room temperature while flowing nitrogen at 0'/min.
It took 20 minutes to reach a temperature of 0, and then it was held at 36 pi for 60 minutes, then cooled to 20 and 0, and then probed. 1st
The table shows the weight increase rate due to hardening treatment of cured novolac fibers, Samples - Samples - (G), tensile strength after heat treatment, and each fiber was cut into a length of 1 meter and dispersed in water. The average fiber length after preparing a .2% by weight slurry and stirring for 30 minutes is shown.

Table 1 In Table 1, when the weight increase rate of the cured novolac fibers relative to the uncured novolac fibers is 2.1% by weight, the tensile strength of the fibers obtained by heat treatment is low, and furthermore, they are hard and brittle.

The same applies to the case of 24% by weight. Furthermore, when heat treated under tension, the product became brittle and had a lower tensile strength than the non-stressed heat-treated product of the present invention. Example 2 16.0% by weight of uncured novolac fiber obtained in Example 1
of hydrochloric acid, 4% by weight of sulfuric acid, and 17.5% by weight of formaldehyde for 60 minutes, then soaked in the mixed aqueous solution of 65q0 for 60 minutes, and further soaked in the mixed aqueous solution at 90°C for 6 nights. After soaking for a while, the weight increase rate is 5.5% compared to the uncured Nopolac fiber. Partially cured fibers with a weight percentage of 1.5% were obtained.

After washing the thus obtained fibers with water, they were treated at 6°C in a mixed aqueous solution of 25% by weight ammonia and 25% by weight formaldehyde.
Those treated for 0 minutes had a weight increase rate of 14.1% by weight with respect to the uncured novolac fiber, a strength of 1.73 m/d,
The elongation was 18%. Next, the cured novolak fiber obtained by the above method was washed with water, and then treated with 50 qo of 5% methanol aqueous solution for 60 minutes, and the strength was 1.76.
The elongation was 55%. The cured novolac fiber obtained by the above method was placed in an alumina combustion tube with an inner diameter of 48 mm inserted into a horizontal silicone heating furnace, and the temperature inside the furnace was lowered to 2.
From room temperature of 5q0 to 200℃, 28 pi○, 330q○, 3
The temperature was raised to 7000°C, 400°C, 500°C, and 650°C at a rate of 700qC/hour, and then held at each of the above temperatures for 90 minutes.

Table 2 shows the heat treatment residual rate, tensile strength,
T. ○． The temperature at which weight loss starts in A and the average fiber length of each cut into 1-meter lengths and mixed with slurry according to Example 1 are shown. Table 2 Example 3 The cured novolac fibers, polyacrylonitrile fibers and piscose fibers obtained in Example 2 were prepared in the same manner as in Example 2.
Heat treatment was performed at 0qC for 90 minutes.

Table 3 shows the tensile strength of the cured novolac fibers and the various heat-treated fibers mentioned above, and the tensile strength after burning these fibers in a 1M sand spacing in a gas burner flame of 800 to 900 qo. Table 3 Example 4 The cured/borac fiber obtained in Example 2 was washed with water and then dehydrated, and the dehydrated and dried fibers were dried at 40o0, 6pi0, and 80qo for 30 minutes each.

Another portion was dried at a temperature of 60 qC for 3 hours using a vacuum dryer. Next, these fibers were processed according to Example 2.
Heat treatment was carried out at 70 o'clock for 60 minutes. Table 4 shows the moisture content of the cured novolac fibers before heat treatment and the tensile strength after heat treatment. Table 4 Example 5 The hardening treatment was carried out according to Example 1, and the material was treated with Satoshi~9 bait ○ for 5 hours, then soaked in an aqueous solution of ethanol containing 5% by weight and treated at 60°C for 30 minutes, washed with water and dried. did.

The cured novolac fibers prepared by the above method were spun to obtain a spun yarn having a flea count of 2. Six months had passed since the production of the cured novolac fiber, and this spun yarn was colored brown. Next, a part of the above-mentioned spun yarn was left as it was, and a part was soaked in a 59% by weight methanol aqueous solution to give 60%
After treatment with qo for 30 minutes, 80q with the untreated spun yarn
Dry for 60 minutes at a temperature of 350 ml according to Example 1.
Heat treatment was performed for 120 minutes at midnight. Table 5 shows the tensile strengths of untreated and treated spun yarns and the tensile strengths after heat treatment. Table 5 Example 6 The cured novolac fiber of Example 2 was cut into 6 lengths and mixed with kraft paper woven with water to obtain a dense yarn with a basis weight of 100 mm/strength.

Next, the above-mentioned Takasho papers with different mixing ratios of cured novolac fibers and kraft paper were placed in a rectangular coke oven and heated from room temperature to 370°C in 30 minutes, and further heated to 370°C for 60 minutes.
Hold for minutes. Table 6 shows the mixing ratio of cured novolac fibers and kraft paper, the heat treatment residual rate, and the form of the paper.

Table 6 Example 7 Phenol 0.94kg, m-cresol 1.08k9
A novolac resin having a melt softening temperature of 0.6 & 0.0 and a pore size of 0.25 was obtained by polymerizing according to Example 1 using 2.8% by weight of formalin (1.72k9) and oxalic acid (10%). The uncured yarn was melt-spun at 14 mm using a paper thread cap of Kazuhiro and wound at 1000 mm/min.
Borac fibers were cut with an average fiber length of 7 meters.

The thus obtained uncured novolak fiber was dissolved in a mixed aqueous solution of 2% by weight of hydrochloric acid and 2% by weight of formaldehyde at 250% by weight.
It took 3 hours to rise to 98q0, and then
After holding for another 5 hours, it was washed with water, and then treated in a 55% by weight methanol aqueous solution at a temperature of 55q○ for 60 minutes, resulting in a weave of 2.21d, a tensile strength of 1.82/d, and an elongation of H%.
A cured novolak fiber was obtained. The above cured novolac fibers were spun to obtain a spun yarn with a cotton count of 2.5 mm, and the high density was 0.21 when stacked by changing the number of threads (2, 4, and 8) and the weaving structure. , 0.32, 0.38, 0.4&0
．． Fabrics of 56 and 0.67 m/cc were obtained.

These various fabrics were cut into 20 strips in width and 50 strips in length and rolled into a cylindrical shape, each of which was made of SUS-42 with an inner diameter of 50 strips.
After heating up the internal temperature from 50 qo to 360 qo in 15 minutes while lighting a static light in the center of the cylindrical tube and flowing nitrogen from one side of the cylindrical tube at a rate of 100 qo, the temperature was further increased to 350 qo It was held for 9 powders at 370q0. Table 7 shows the heat treatment residual rate of each fabric thus obtained, the tensile strength and apparent morphology of the spun yarn after loosening each fabric after heat treatment.

Claims (1)

[Scope of Claims] 1. A cured novolac fiber obtained by melt-spinning a novolac resin and cured with an aldehyde, or a cured novolac fiber structure consisting of at least 70% by weight of the cured novolac fiber, in a non-oxidized manner. 1. A method for producing flame-resistant fibers or flame-resistant fiber structures, which comprises heat-treating them at a temperature of 280°C to 400°C in a neutral atmosphere without tension. 2. The manufacturing method according to claim 1, wherein the curing treatment is performed using a mixed aqueous solution of an acidic catalyst and aldehydes. 3. The manufacturing method according to claim 1, wherein the curing treatment is performed in a mixed aqueous solution of an acidic catalyst and an aldehyde, and then further in a mixed aqueous solution of a basic catalyst and an aldehyde. 4. The manufacturing method according to claim 1, wherein the curing treatment is carried out at a weight increase rate of 8 to 15% by weight of the cured novolac fibers relative to the uncured novolac fibers. 5. The manufacturing method according to claim 1, wherein the cured novolac fiber or the cured novolac fiber structure has a moisture content of 3% by weight or less. 6. The method of claim 1, wherein the fibrous structure is a yarn, tow, knit, woven, non-woven fabric or paper comprising at least 85% by weight of cured noporak fibers. 7. The manufacturing method according to claim 1 or 4, wherein the fiber structure has a bulk density of 0.4 g/cc or less. 8. The manufacturing method according to claim 1, wherein the heat treatment is performed at a temperature of 330 to 370°C for 30 to 120 minutes.