JP3489943B2 - Wet and heat resistant polyvinyl alcohol fiber and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to polyvinyl alcohol which is effective for general industrial materials such as fishing nets, ropes, tents and civil engineering sheets, which are required to have high humidity resistance and high strength for a long time, and reinforcing materials for cement, rubber and plastics ( (Hereinafter abbreviated as PVA)
TECHNICAL FIELD The present invention relates to a synthetic fiber and a method for producing the same, and more particularly to a PVA-based fiber that is effective in reinforcing a cement product subjected to autoclave curing.

[0002]

2. Description of the Related Art PVA-based fibers have the highest strength and elasticity among general-purpose fibers, and have good adhesiveness and alkali resistance, and thus are in the spotlight as a cement reinforcing material as a substitute for asbestos. However, PVA-based fibers have poor wet heat resistance,
Even if it is used as a general industrial material or a clothing material, its use is limited, and it is impossible to cure the autoclave at high temperature. Therefore, at present, when PVA-based fibers are used for cement reinforcements, they rely on room temperature curing. However, cement products cured at room temperature have drawbacks such as insufficient dimensional stability and strength, and long curing days.

On the other hand, although some carbon fibers are used for curing in a high temperature autoclave, there are problems such as poor adhesiveness with cement matrix, poor reinforcing effect, and high cost. Therefore, attempts have been made for a long time to improve the wet heat resistance of PVA-based fibers. For example, Japanese Patent Publication No. 30-7360 and Japanese Patent Publication No. 36-1456.
Japanese Patent Publication No. 5 discloses that PVA-based fibers that can withstand dyeing and washing can be obtained by using formalin to crosslink (formalize) a hydroxyl group of PVA to make it hydrophobic. However, since these fibers have low strength, they are not suitable for general industrial materials and cement, rubber, and plastic reinforcing materials referred to in the present invention. Further, Japanese Patent Application Laid-Open No. 63-120107 discloses that high strength PVA fiber is formalized, but the degree of formalization is as low as 5 to 15 mol%, which is very small in the amorphous region of the PVA fiber. Since the part is only hydrophobized, it does not have sufficient resistance to moist heat and is not completely satisfactory for an industrial material that is repeatedly exposed to moist heat for a long period of time or a cement reinforcement material that is cured by a high temperature autoclave.

On the other hand, in JP-A-2-133605 and JP-A-1-207435, an acrylic acid polymer is blended, or the fiber surface is treated with an organic peroxide, an isocyanate compound, a urethane compound, A method of crosslinking with an epoxy compound or the like is described. However, since the cross-linking by acrylic acid polymer is an ester bond, the cross-linking bond is easily hydrolyzed by the alkali of cement to lose its effect, and other cross-linking agents are also fiber surface cross-links. It has problems such as swelling and dissolution from the center of the fiber when it is repeatedly exposed to heat and humidity.

Another method for improving the moist heat resistance of PVA-based fibers by dehydration crosslinking using an acid is disclosed in Japanese Patent Laid-Open No. 2-84587.
As described in JP-A No. 4-100912 and the like, when the inventors of the present invention retested, when attempting to crosslink the inside of the fiber, the PVA-based fiber was severely decomposed and the fiber strength was significantly lowered. There was found. on the other hand,
Cross-linking with a dialdehyde compound is disclosed in Japanese Patent Publication No.
As disclosed in JP-B-32-5819 and JP-B-32-5819, the method is to treat the fiber after dry heat drawing in a mixed bath of a dialdehyde compound and an acid as a reaction catalyst, so that the fiber molecule is highly advanced. In the oriented high-strength fiber crystallized, it was difficult for the dialdehyde compound to penetrate into the inside of the fiber, and internal cross-linking was difficult.

Further, Japanese Patent Laid-Open No. 163609/1993 discloses that
It is described that a dialdehyde is applied to a spinning base yarn, dry-heat stretched at a high ratio, and then acid treatment is performed to cause crosslinking inside the fiber. However, since this is an aliphatic dialdehyde or aromatic dialdehyde compound having a carbon number of 6 or less, there is little cross-linking between PVA-based molecular chains (inter-molecular cross-linking) effective for moist heat resistance or steric hindrance to the inside of the fiber. It has problems that it is difficult to penetrate, and that strength is likely to decrease.
It does not fully satisfy both wet heat resistance and high strength.
Although the same publication describes the acetalization of dialdehydes, the specifically described acetalization of dialdehydes is tetramethoxypropane, and in such compounds having a small number of carbon atoms in the dialdehyde part. However, it has the same problem as described above.

Further, the present inventors have already applied for a PVA-based fiber crosslinked with an acetal compound of an aliphatic dialdehyde having 6 or more carbon atoms. surely,
By using the technology of this application, PVA-based fibers having significantly higher strength and resistance to moist heat can be obtained as compared with the conventional technology. However, even with this technology, the cross-linking to the inside of the fiber is not sufficient, and the elution of the artificial cement liquid is likely. It was difficult to control the amount sufficiently, and the bending strength and the amount of flexure of the slate plate after high temperature curing were just another step.

[0008]

Based on the above background, the present inventors have found intermolecular crosslinking (crosslinking between PVA molecular chains) that is effective for maintaining high strength and elongation and improving wet heat resistance. As a result of extensive studies on whether to sufficiently generate the inside of the fiber or to further increase the cross-linking points, a compound consisting of a long-chain aliphatic dialdehyde and a compound consisting of a short-chain aliphatic dialdehyde or formaldehyde within a certain range.
It has been found that it is effective to carry out a cross-linking reaction with the hydroxyl group of, and the present invention has been completed.

[0009]

According to the present invention, a part of the hydroxyl groups is crosslinked with the following compound (A) and the following compound (B), and the weight ratio of (A) and (B) is 9: : 1 to 5: 5
The weight ratio of the polyvinyl alcohol-based polymer is 12 g / d or more and the elongation is 5% or more.
In addition, it is a moisture-heat resistant polyvinyl alcohol fiber characterized by having an elution amount of 20% by weight or less after treatment with an artificial cement aqueous solution at 150 ° C. for 2 hours. (A) Acetal compound of aliphatic dialdehyde having 6 or more carbon atoms (B) At least one compound selected from the group consisting of aliphatic dialdehyde having 4 or less carbon atoms, acetalized product thereof and formaldehyde

Further, as a method for producing such a fiber, a spun raw yarn obtained by spinning a solution of a polyvinyl alcohol polymer is dried and subjected to dry heat drawing so that the total draw ratio becomes 14 times or more. In producing alcohol fiber, the compound of (A) and the compound of (B) are added to (A) and (B) in the spun yarn in a process until drying.
The moisture resistance is characterized in that it is contained such that the weight ratio of is from 9: 1 to 5: 5, and is subjected to dry heat drawing, and then acid treated to react (A) and (B) with a polyvinyl alcohol-based polymer. A method for producing a heat-resistant polyvinyl alcohol-based fiber, wherein a spinning raw yarn obtained by spinning a solution of a polyvinyl alcohol-based polymer is dried and subjected to dry heat drawing so that the total draw ratio is 14 times or more. In the production of fibers, in the steps up to drying, the spinning raw yarn is made to contain the compound (A), dry-heat stretched, and then treated with a liquid containing the compound (B) and an acid,
A method for producing a heat-and-moisture resistant polyvinyl alcohol fiber, comprising cross-linking the hydroxyl groups of the polyvinyl alcohol polymer so that the weight ratio of (A) and (B) is 9: 1 to 5: 5.

The contents of the present invention will be described in more detail below. The PVA-based polymer referred to in the present invention has a viscosity average polymerization degree of 1500 or more, a saponification degree of 98.5 mol% or more, preferably 99.0 mol% or more, and a linear chain having a low branching degree. It is a thing. The higher the average degree of polymerization of the PVA-based polymer, the greater the number of tie molecules that connect the crystals, and the less the number of molecular terminals, which is a defect, so that fibers with high strength, high elastic modulus, and high humidity and heat resistance can be obtained. It is easy, preferably 3,000 or more, more preferably 6000 or more.

Examples of the solvent for the PVA polymer include polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, dimethyl sulfoxide, dimethylformamide, diethylenetriamine, water, and a mixed solvent of two or more thereof. Is mentioned. However, when the compound (A) or the compound (B) is mixed and added to the solvent, a solvent for aggregating or separating the compound is not preferable, and the compound (A) or the compound (B) is uniformly dispersed or Solvents that dissolve are preferred. In this respect, the above-mentioned polyhydric alcohols such as dimethyl sulfoxide, elene glycol and glycerin are preferable. Further, when dissolving the PVA-based polymer in a solvent, it is possible to add boric acid, a surfactant, a decomposition inhibitor, a dye, and a pigment, but it is not preferable to add spunability or stretchability.

The spinning dope thus obtained is discharged from the nozzle and solidified by any of a wet method, a dry method, and a dry-wet method by a conventional method. In the wet and dry wet spinning methods, the discharge liquid is solidified in a coagulation bath to form fibers, and as the coagulant, alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone, and methyl butyl ketone, an alkaline aqueous solution, Any one of alkali metal salt aqueous solution or a mixed solution of two or more thereof is used. It is preferable to mix 10% by weight or more of the solvent with the coagulant in order to slow the solvent extraction in the coagulation to form a uniform gel structure and to obtain higher strength and resistance to moist heat. Particularly, a mixed solution of an alcohol represented by methanol and a stock solution solvent is preferable. In the case of the dry-wet spinning method, there is a gas layer represented by air between the spinning nozzle and the liquid surface of the coagulation bath.

Further, rapid cooling of the discharge liquid by setting the coagulation bath temperature to 20 ° C. or lower can obtain gel fibers having a uniform microcrystalline structure, which is convenient for obtaining high-strength fibers. Further, in order to reduce the sticking between fibers and facilitate the subsequent dry heat drawing, it is desirable that the spun raw yarn taken out from the coagulation bath is wet drawn twice or more in a state containing a solvent. In the case of alkali coagulation, it is preferable to perform neutralization under tension before wet heat stretching.

Next, solvent extraction from the spun yarn is carried out.
As the extractant, primary alcohols such as methanol, ethanol and propanol, ketones such as acetone, methyl ethyl ketone, methyl procyroketone and methyl butyl ketone, and ethers such as dimethyl ether and methyl ethyl ether can be used. Subsequently, if necessary, an oil agent or the like is added to dry the extractant, or in the case of a dry method, the solvent of the spinning dope is evaporated and dried at the time of spinning and after spinning without using a coagulant or an extractant.

The features of the present invention are, as described above, (A)
An acetal compound of an aliphatic dialdehyde having 6 or more carbon atoms, and (B) at least one compound selected from the group consisting of an aliphatic dialdehyde having 4 or less carbon atoms, an acetalized product thereof and formaldehyde, from a spinning dope to immediately before drying. In any one of the steps 1) to 2), the inside of the spun raw yarn is contained and treated with an acid after the drawing, or in the process until drying, the spun raw yarn is made to contain the above compound (A), and dry heat drawing is performed. Treatment with a liquid containing the compound (B) and an acid. When the above-mentioned compound (A) is applied after drying and just before the dry heat drawing, the compound (A) is difficult to penetrate into the fiber due to the large molecular weight of the compound (A), and the moist heat resistance by surface cross-linking is high. It's hard to get enough satisfaction. A preferred application method is a method in which the compound is dissolved in alcohol or ketones in the extraction bath, and a swollen yarn, that is, a wet yarn is passed through the compound to be contained inside the fiber.

The acetal compound (A) of an aliphatic dialdehyde having 6 or more carbon atoms referred to in the present invention is, for example, hexanediar, heptanedial, octanedial, nonanedial, decandiar or 2,4-dimethylhexanediearl. Dialdehydes such as 5-methylheptanedial and 4-methyloctanedial and methanol,
It is a compound obtained by reacting alcohols such as ethanol, propanol, butanol, ethylene glycol and propylene glycol to acetalize both terminals or one terminal. From the viewpoint of odor and volatility, acetal compounds of aliphatic dialdehydes having 7 or more carbon atoms are preferable, for example,
Nonanedial and methanol reacted 1,1,9,9
Examples include 1,1,9,9-bisethylenedioxynonane obtained by reacting tetramethoxynonane and nonanedial with ethylene glycol. An acetal compound of an aliphatic dialdehyde having more than 13 carbon atoms is industrially difficult to obtain in terms of production.

On the other hand, (B) at least one compound selected from the group consisting of an aliphatic dialdehyde having 4 or less carbon atoms, its acetalized product and formaldehyde means dialdehydes such as glyoxal, malondialdehyde and succindialdehyde. Alternatively, it means a compound obtained by reacting them with alcohols such as methanol, ethanol, and ethylene glycol to acetalize both ends or one end, or formalin, and these compounds having a small molecular weight are particularly permeated into the PVA fiber. Well, many crosslinking points are formed inside the fiber. Further, when used in combination with the compound (A), intermolecular cross-linking is sufficiently carried out to the inside of the fiber due to the synergistic effect of both, as compared with the case where each is used alone.

The weight ratio of the compound (A) to the compound (B) in the present invention is 9: 1 to 5: 5. Compound (A)
When it exceeds 90% by weight, the resistance to moist heat due to intermolecular cross-linking is improved, but it is difficult to cross-link evenly inside the fiber and there are few cross-linking points. Therefore, the amount eluted after treatment for 2 hours in an artificial cement liquid at 150 ° C As a result, the bending strength of the slate plate after high-temperature autoclaving and the amount of flexure are reduced, and a problem tends to occur in the durability when used as an outer wall material or roof tile. On the other hand, when the compound (A) is less than 50% by weight, there are few effective intermolecular crosslinks, the resistance to moist heat is insufficient, the elution amount of the artificial cement liquid is very large, and since the compound (B) is large, there are many crosslinking points. Since the elongation of the fiber becomes too low, a high value-added cement reinforcing material cannot be obtained.

Further, in order to increase the bending strength and the amount of flexure of the slate plate, the single fiber strength after cross-linking must be 12 g / d or more and the elongation must be 5% or more. Therefore, the compound (A) and the compound (B) are required. It is preferable that the total adhesion amount of 1 to 10% by weight with respect to the PVA fiber. If the adhered amount is less than 1% by weight, the desired moist heat resistance, that is, the amount of the artificial cement liquid eluted is large, and thus the high temperature autoclave resistance is insufficient, and if the adhered amount exceeds 10% by weight, the orientation of the PVA molecular chain is disturbed or the PVA Degradation occurs and the fiber strength and elongation decrease, so the bending strength of the slate plate and the amount of bending are small, and it is difficult to obtain a durable product.

Then, after the dried raw yarn containing the compound is spun into 2
At 20 ° C or higher, the total draw ratio is 14 times or higher, preferably 16
Dry heat drawing is performed so as to be double or more. The total draw ratio here means a value obtained by multiplying the wet draw ratio and the dry heat draw ratio. If it is less than 14 times, the orientation of PVA molecular chains is insufficient and it is difficult to obtain a single fiber strength of 12 g / d or more after crosslinking. It is preferable that the stretching temperature is increased as the degree of polymerization of PVA is higher to maintain a high stretching ratio, but if it exceeds 260 ° C., melting or decomposition of PVA is likely to occur, which is not preferable. On the other hand, if the temperature is less than 220 ° C., it is difficult to stretch at a high ratio and it is difficult to crystallize, so that the fiber tends to shrink during the crosslinking treatment and the autoclave treatment, and it is difficult to obtain a high strength material.

The above compound (A) thus obtained
A high-strength drawn yarn containing the compound (B) and an inorganic acid such as sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, chromic acid or an organic acid such as carboxylic acid, sulfonic acid, etc. By immersing at 90 ° C. for 5 to 120 minutes, the compound (A) and the compound (B) are acetalized with the OH group of PVA to cause crosslinking. Moreover, only the compound (A) is contained in the spun raw yarn, and the acid and the compound (B) are added after dry heat drawing.
It is also possible to use a method in which the compound (A) and the compound (B) are crosslinked at a weight ratio of 9: 1 to 5: 5 by treating with a liquid containing When the compound (B) is not soluble in water, it may be treated with an emulsifier to prepare an aqueous emulsion.

The crosslinked PVA-based fiber obtained in the present invention has a single fiber strength of 12 g / d or more and an elongation of 5% or more,
The amount of elution after treatment for 2 hours in the artificial cement aqueous solution is 20
The content is less than 10% by weight, and the fiber is crosslinked to the inside of the fiber, and it is used as a cement reinforcing material with high strength and durability, which is used as an exterior wall material of a house sighting or a building or a new roof tile. It is also effective for general industrial materials such as fishing nets, ropes and civil engineering sheets that are exposed to water and heat for a long period of time, as well as rubber and plastic reinforcement materials.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
Various physical property values in the present invention are defined by the following methods. 1) Viscosity-average degree of polymerization (PA) of PVA To make the concentration of uncrosslinked drawn fiber 1 to 10 g / l,
Specific viscosity η of the solution obtained by pressure dissolution with water at 40 ° C or higher
sp was measured at 30 ° C. according to JIS K-6726, the intrinsic viscosity [η] was calculated from the following formula, and the viscosity average polymerization degree PA was calculated from the following formula. [Η] = lim (C → 0) ηsp / c ...... PA = ([η] × 10 ⁴ /8.29) ^1.613 ......

2) Content of aliphatic dialdehyde or its acetal compound The uncrosslinked drawn yarn was dissolved in deuterated dimethyl sulfoxide at 120 ° C. or higher and the peak area ratio of the compound to the CH ₂ group peak of PVA was calculated by NMR. Then, the content was obtained. When the solution was cross-linked with a solution containing an acid and a cross-linking agent after stretching, the content was determined from the weight increase rate. 3) Dissolution amount (CS) in artificial cement liquid About 1 g of a sample was cut into 4 to 8 mm, and an artificial cement aqueous solution ((KOH 3.5 g / l + NaOH 0.9 g / l + C
After immersing in a (OH) ₂ 0.4 g / l, pH≅13) at 150 ° C. for 2 hours, washing with water and drying, the elution amount (CS) was determined from the reduction rate of the sample weight.

4) Tensile strength / elongation of single fiber In accordance with JIS L = 1015, single fiber preliminarily conditioned to humidity is attached to a mount so that the test length is 10 cm, and 25 ° C. × 65% R
Leave in H for 12 hours or more. Next, using a 2 kg chuck with Instron 1122, the breaking strength and elongation were determined at an initial load of 1/20 g / d and a pulling speed of 50% / min, and an average value of n ≧ 10 was adopted. Denier was cut into a length of 30 cm under a load of 1/20 g / d, and shown by an average value of n ≧ 10 by a gravimetric method. The tenacity was measured using the single fibers after the denier measurement, and each fiber was made to correspond to the denier. 5) Autoclave resistance (wet bending strength W of slate plate)
BS and amount of deflection) PVA-based synthetic fiber is cut into a length of 4 to 8 mm, and wet-paper-making is carried out by using a Hatek machine in a combination of 2 parts by weight of the fiber, 3 parts by weight of pulp, 38 parts by weight of silica, and 57 parts by weight of cement. ,
After primary curing for 12 hours at 50 ℃, 160 ℃ × 15hr
Alternatively, autoclave curing is performed at 180 ° C. for 10 hours, a slate plate is created, and a 25 × 70 × 4 mm test piece is cut out and immersed in water for 3 days in accordance with JIS K-6911, and the span length is determined using an autograph. The bending strength (kg / cm ² ) and the amount of deflection (mm) were measured at 5 cm and a compression rate of 2 mm / min.

Examples 1 and 2 and Comparative Examples 1 and 2 PVA having a viscosity average degree of polymerization of 1700 (Example 1) and 4000 (Example 2) and a saponification degree of 99.5 mol%.
16% by weight (Example 1) and 10% by weight, respectively.
(Example 2) Dimethyl sulfoxide (DM
SO) at 110 ° C., and each of the resulting solutions was discharged from a nozzle with 400 holes, and methanol / DMSO = 7
Wet spinning was carried out in a coagulation bath of 8/3 (weight ratio) at 8 ° C.
Further, the film was wet-stretched 4 times in a 40 ° C. methanol bath, and then almost all the solvent was removed with methanol.

The compound (A) was added to the final methanol extraction bath.
As 1,1,9,9-tetramethoxynonane (TM
N) 4% by weight / bath and 1,1 as compound (B)
2% by weight of 3,3-tetramethoxypropane (TMP)
/ Bath is added to form a homogeneous solution, and the fibers are allowed to stay in this bath for 1.5 minutes to contain the acetal compound of the dialdehyde in the inside and the surface of the methanol-containing fibers and dried at 120 ° C. did. The obtained spun raw yarn was made to have a total draw ratio of 16.5 times in a hot air stove consisting of three sections of 170 ° C., 200 ° C. and 230 ° C. in Example 1, and 170 ° C., 210 ° C. and 240 ° C. in Example 2. Draw in a hot blast stove consisting of sections so that the total draw ratio is 17.2 times,
A multifilament of about 1500d / 400f was obtained.
Then, both of the drawn yarns at 75 ° C. in an aqueous solution of sulfuric acid 80 g / l.
It was immersed for 30 minutes to cause a crosslinking reaction. As Comparative Example 1, only TMN in Example 1 was added in an amount of 6% by weight / bath and the same stretching and acid treatment were performed. In Comparative Example 2,
2% TMN / bath and 4% TMP in Example 2
/ Bath was added so as to form a bath and the same stretching and acid treatment were performed. Table 1 shows the content of the crosslinking agent in the obtained fibers and the physical properties of the crosslinked fibers.

The crosslinker content of the uncrosslinked drawn yarn of Example 1 is T
It was 3.5% by weight in terms of MN and 1.8% by weight in terms of TMP. The single fiber strength of the crosslinked fiber was 13.2 g / d, the elongation was 5.4%, and the elution amount (CS) after treatment for 2 hours in the artificial cement liquid at 150 ° C. was 15.9% by weight. It was
The CS of the uncrosslinked drawn yarn was 96.7% by weight, and the wet heat resistance was remarkably improved as compared with the case where almost all was eluted. Also, the slate plate bending strength WBS after 160 ° C autoclave
Is 242 kg / cm ² , and the amount of deflection is 1.0 mm,
It became an excellent wall material for residential siding.
The crosslinker content of the uncrosslinked drawn yarn of Example 2 was TMN 3.1.
% By weight and TMP was 1.3% by weight. The single fiber strength after cross-linking was 15.9 g / d and the elongation was 5.8%.
= 9.7 wt%, it was found that most of the fibers were crosslinked. WB after autoclaving at 160 ℃
S is 338 kg / cm ² , deflection is 1.4 mm, 18
WBS after autoclaving at 0 ° C is 271 kg / cm ² ,
The amount of deflection was 0.6 mm, which made it a valuable fiber as a reinforcing material for new tiles that can withstand high temperature curing. It was also found that it can be applied to general industrial materials and clothing materials that are associated with heat and humidity.

In Comparative Example 1, only TMN was contained, but the amount was 5.4% by weight, and the strength and elongation of the obtained crosslinked fiber was the same as in Example 1, but the elution amount of the artificial cement liquid was Is as high as 28.0% by weight, which does not sufficiently crosslink inside the fiber,
It was inferior in moist heat resistance. Further, the WBS and the amount of deflection of the slate plate were also lower than those in Example 1. In Comparative Example 2, the content of TMP is larger than that of TMN in Example 2, but the elongation of the fiber is low and the CS is high. Therefore, WBS of the slate plate is used.
The amount of flexure was reduced, and both were inferior to Example 2.

[0031]

[Table 1]

Example 3 Viscosity average degree of polymerization is 8000 and degree of saponification is 99.9 mol%.
Was dissolved in ethylene glycol (EG) at 170 ° C. to a concentration of 8% by weight. The resulting solution is 40
The mixture was discharged from a 0-hole nozzle, and was rapidly cooled and gelated by dry-wet spinning in a 0 ° C. coagulation bath consisting of methanol / EG = 7/3 (weight ratio). Further, the film was wet-stretched 4 times in a 40 ° C. methanol bath, and then almost all the solvent was removed with methanol. 1,1,9,9-Bisethylenedioxynonane (BEN) was added to the final methanol extraction bath at 8 wt% / bath to form a uniform solution, and the fibers were allowed to stay for 1.2 minutes to obtain fibers. The acetal compound was added to the inside and the surface of the and dried at 130 ° C. The obtained spun raw yarn was drawn in a radiant furnace consisting of two sections at 180 ° C. and 248 ° C. so that the total draw ratio was 18.5 times, and a 1000d / 400f multifilament having a BEN content of 4.9% by weight. Got Then, with an aqueous solution containing 60 g / l of sulfuric acid and 30 g / l of malondialdehyde, 80 ° C. × 60
A cross-linking treatment was performed. From the weight increase rate, the content was 2.2% by weight in terms of malondialdehyde.

The single fiber strength of the obtained crosslinked fiber is 17.7 g.
/ D, the elongation was 6.0% and the CS was as low as 5.9% by weight, and it was found that the wet heat resistance was very excellent. 180 ° C
The WBS after autoclaving was as high as 305 kg / cm ² , and the amount of deflection was 0.8 mm, which was a high-value-added fiber that has never existed as a FRC for high temperature curing.

[0034]

As described above, according to the present invention, two kinds of aldehyde compounds are added in a specific ratio to crosslink PVA fibers, and the PVA fibers are crosslinked sufficiently while maintaining high strength and high elongation. An unprecedented autoclave resistant PVA-based fiber for FRC is obtained. The fiber of the present invention can be widely used for general industrial materials such as ropes, fishing nets, tents, and civil engineering sheets, which are required to have moist heat resistance and durability, as well as clothing materials, in addition to cement reinforcing materials.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-263311 (JP, A) JP-A-5-163609 (JP, A) JP-A-6-184810 (JP, A) JP-A-5- 321020 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D06M 13/137 D01F 6/14

Claims (3)

(57) [Claims] 1. A part of the hydroxyl groups is crosslinked with the compound of the following (A) and the compound of the following (B), and the weight ratio of (A) and (B) is 9: 1 to 5: 5. It is made of polyvinyl alcohol-based polymer, which has a ratio of 12 per fiber.
A moist-heat-resistant polyvinyl alcohol fiber, which has a g / d or more, an elongation of 5% or more, and an elution amount of 20% by weight or less after treatment with an artificial cement aqueous solution at 150 ° C. for 2 hours. (A) Acetal compound of aliphatic dialdehyde having 6 or more carbon atoms (B) At least one compound selected from the group consisting of aliphatic dialdehyde having 4 or less carbon atoms, acetalized product thereof and formaldehyde 2. A spinning raw yarn obtained by spinning a solution of a polyvinyl alcohol-based polymer is dried to give a total draw ratio of 1
When a polyvinyl alcohol fiber is produced by carrying out dry heat drawing so as to have a draw ratio of 4 times or more, the compound of the following (A) and the compound of the following (B) are added to the (A) ( B) is contained in a weight ratio of 9: 1 to 5: 5, subjected to dry heat drawing, and then acid-treated to react (A) and (B) with a polyvinyl alcohol-based polymer. A method for producing a heat and moisture resistant polyvinyl alcohol fiber. (A) Acetal compound of aliphatic dialdehyde having 6 or more carbon atoms (B) At least one compound selected from the group consisting of aliphatic dialdehyde having 4 or less carbon atoms, acetalized product thereof and formaldehyde 3. A spinning yarn obtained by spinning a solution of a polyvinyl alcohol-based polymer is dried to give a total draw ratio of 1
When a polyvinyl alcohol fiber is produced by dry heat drawing so as to have a draw ratio of 4 times or more, the following compound (A) is added to the spun raw yarn in the steps up to drying, and after dry heat drawing, A treatment with a liquid containing the compound (B) and an acid to crosslink the hydroxyl groups of the polyvinyl alcohol-based polymer so that the weight ratio of (A) and (B) is 9: 1 to 5: 5. A method for producing a heat and moisture resistant polyvinyl alcohol fiber. (A) Acetal compound of aliphatic dialdehyde having 6 or more carbon atoms (B) At least one compound selected from the group consisting of aliphatic dialdehyde having 4 or less carbon atoms, acetalized product thereof and formaldehyde