JPH10226958A - Production of polyvinyl alcohol base synthetic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyvinyl alcohol base synthetic fiber effective for reinforcement of cement product cured by an autoclave, comprising the first step of incorporating dialdehyde, etc., to be contained in a fiber, the second step of carrying out acetalization treatment of the fiber containing the dialdehyde and the third step of carrying out the acetalization of the treated fiber with a mixture of a monoaldehyde and an acid. SOLUTION: This method for producing a polyvinyl alcoholic synthetic fiber comprises the first step of incorporating 2-10wt.% of dialdehyde, an acetalized material thereof or both thereof in a fiber, the second step of carrying out acetalization treatment of the fiber containing the dialdehyde, etc., and the third step of carrying out the acetalization of the treated fiber with a mixture of a monoaldehyde and an acid, while adding 0.01-1wt.% thermal stabilizer to the fiber in a suitable step of the first step to the third step to provide the objective fiber having >=8g/d tenacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyvinyl alcohol (hereinafter, referred to as a "reinforcement") for general industrial materials such as fishing nets, ropes, tents, civil engineering sheets, etc., and cement, rubber, and plastic reinforcing materials which are required to have wet heat resistance and high strength. Abbreviated as PVA)
The present invention relates to a synthetic fiber and a method for producing the same, and more particularly to a PVA-based fiber which is effective for reinforcing cement products subjected to autoclave curing.

[0002]

2. Description of the Related Art PVA-based fibers have the highest strength and high elasticity among general-purpose fibers, and have good adhesiveness and alkali resistance. However, PVA fibers have poor moisture and heat resistance,
Even if it is used as a general industrial material or a garment material, its use is limited, and further, autoclaving at a high temperature, which is usually performed for a cement molded product, is impossible.
Currently, when using PVA fiber for cement reinforcement,
It is limited to room temperature cured products, and has the drawbacks that the dimensional stability and strength of cement products are not sufficient and that the curing days are long.

[0003] On the other hand, carbon fibers are partially used as a cement reinforcing material for high temperature autoclave curing, but have problems such as poor adhesion to a cement matrix, poor reinforcing effect, and high cost. . Attempts to improve the wet heat resistance of PVA-based fibers have been made for a long time. For example, in Japanese Patent Publication Nos. 30-7360 and 36-14565, formalin is used and PV
It is described that by formalizing the OH group of A to make it hydrophobic, a PVA-based fiber that can withstand dyeing and washing can be obtained. However, these fibers have low strength and are not suitable for general industrial materials and cement, rubber and plastic reinforcing materials according to the present invention. Also high strength PV
Formalization of A fiber is disclosed in JP-A-63-1201.
No. 07, the formalization degree is as low as 5 to 15 mol%, only a part of the amorphous region of the PVA-based fiber is hydrophobized, and the moist heat resistance is not sufficient. However, it has not been satisfactory at all for use in industrial materials that are repeatedly exposed to moist heat for a long period of time and cement reinforcements that are cured in a high-temperature autoclave.

On the other hand, JP-A-2-133605 and JP-A-1-207435 disclose that an acrylic acid-based polymer is blended or that the fiber surface is coated with an organic peroxide, an isocyanate compound, a urethane-based compound, or the like. A method of crosslinking with an epoxy compound or the like is described. However, since the crosslinking by the acrylic polymer is an ester bond,
Since it is easily hydrolyzed by the alkali component in the cement and loses its effect, and since other cross-linking agents are also cross-linked on the fiber surface, they swell from the center of the fiber during autoclave curing and when repeatedly exposed to moist heat, There were problems such as dissolution. Other methods for improving wet heat resistance by dehydration crosslinking using an acid are known in JP-A-2-84587 and JP-A-4-100912. However, when the present inventors conducted additional tests, the inside of the fiber was crosslinked. Attempting to do so severely decomposed the PVA fiber, resulting in a significant decrease in fiber strength.

On the other hand, the crosslinking with a dialdehyde compound is specified in Japanese Patent Publication No. 29-6145 and Japanese Patent Publication No. 32-5819, but is post-treated in a mixed bath of a dialdehyde compound and an acid which is a reaction catalyst. Therefore, in a high-strength fiber in which fiber molecules are highly oriented and crystallized, it is difficult for the dialdehyde compound to penetrate, and it is difficult to crosslink the entire fiber. JP-A-5-163609 describes that a dialdehyde or an acetal compound thereof is applied to a spun yarn, stretched by dry heat at a high magnification, and then subjected to an acid treatment to cause crosslinking within the fiber. The dialdehyde compounds specifically described are aliphatic dialdehyde compounds having 6 or less carbon atoms. However, when aliphatic dialdehydes having 6 or less carbon atoms are used, these dialdehyde compounds imparted to the original yarn are scattered from the original yarn at the time of dry heat drawing and do not sufficiently remain in the fiber. The thermal properties were not sufficient, and it was unsatisfactory for industrial materials that are repeatedly exposed to moist heat for a long period of time and cement reinforcing materials that are cured by high-temperature autoclave.

Further, Japanese Unexamined Patent Publication No. Hei 5-263331 (corresponding European Patent No. 520297, US Pat. No. 5,380)
No. 588), a dialdehyde compound described in JP-A-5-163609 is penetrated into the dry-heat drawn PVA fiber to the inside of the fiber, and then immersed in a bath containing monoaldehyde and a cross-linking catalyst to perform cross-linking. By causing the reaction, a PVA-based fiber having excellent hot water resistance is obtained,
It is reported that this crosslinked PVA-based fiber is a fiber that can withstand autoclaving at 160 ° C.

This method comprises a crosslinking reaction with a dialdehyde compound and a crosslinking reaction with a monoaldehyde compound or
It is said that the combined use of the VA fiber hydrophobizing reaction is superior in that fibers having higher moist heat resistance can be obtained as compared with the case of using a dialdehyde compound alone or a monoaldehyde compound alone. However, in this method, since the amount of the monoaldehyde compound in the reaction bath is larger than the amount of the dialdehyde compound in the PVA fiber,
The monoaldehyde compound reacts preferentially, or an exchange reaction occurs between the dialdehyde compound reacted with the PVA fiber and the monoaldehyde compound. Therefore, the degree of crosslinking expected from the dialdehyde compound is low, and as a result, under severe moist heat conditions such as autoclave curing at 170 ° C. or higher, the moist heat resistance was insufficient.

On the other hand, attempts have been made for a long time to suppress the coloring and the decrease in the strength of the PVA fiber during the dry heat drawing or the dry heat standing, for example, Japanese Patent Publication No. 35-1669 and Japanese Patent Publication No. 45
No. 7691, Japanese Patent Publication No. 47-29048,
No. 82815 and the like. However, these methods do not have sufficient heat and moisture resistance, and are not completely satisfactory for industrial materials that are repeatedly exposed to moist heat for a long period of time and cement reinforcing materials that are cured by high-temperature autoclave.

JP-A-5-78907 reports that a PVA-based fiber having excellent wet heat resistance can be obtained by adding an antioxidant and using a crosslinking agent together. However, when phosphorus compounds, sulfur compounds, zirconium-based compounds, etc. which are mentioned as cross-linking agents in this report are used, when exposed to extremely intense high temperature and high humidity conditions such as cement reinforcing agents cured in a high temperature autoclave. It has been found that the wet heat resistance is not sufficient. JP-A-5-106109 reports that a PVA-based fiber having excellent wet heat resistance can be obtained by using a decomposition inhibitor in combination with acetalization. This method is superior in that it gives PVA-based fibers having better wet heat resistance as compared with the production method using only the acetalization reaction or adding only the decomposition inhibitor. However, in this method, the PVA-based fiber after the completion of the so-called crystal orientation after the completion of the dry heat drawing is acetalized, so that the aldehyde compound does not sufficiently penetrate into the inside of the fiber, and therefore, is repeatedly exposed to moist heat for a long time. Moisture and heat resistance was not enough for industrial materials to be used and cement reinforcements cured by high-temperature autoclave.

[0010]

SUMMARY OF THE INVENTION In view of the above background, the inventors of the present invention have developed excellent properties such as high strength, high elasticity and excellent properties even under severe high temperature and high humidity conditions such as high temperature autoclave curing. As a result of diligent studies on a method for producing PVA-based fibers having high moisture-heat resistance without impairing the adhesiveness and alkali resistance, the diacetal-type compound or its acetal compound is dispersed in the fibers, and then the diacetal-type cross-linking is performed by cross-linking. Is completed once, and then a two-stage acetalization in which an acetalization reaction is added with a monoaldehyde compound, or the addition of a heat stabilizer thereto, is used to produce a desired PVA-based fiber having excellent wet heat resistance. This has led to the present invention.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to a PVA which is crosslinked by acetalization using a dialdehyde compound or an acetal compound thereof, and has improved moist heat resistance by acetalization treatment using a monoaldehyde compound.
The present invention relates to a method for producing a PVA-based fiber having high moist heat resistance, which cannot be obtained by the conventional technique, by using the effect of adding a stabilizer in combination.

That is, in the present invention, after the dialdehyde and / or acetalized product thereof are contained in the first stage in an amount of 2 to 10% by weight based on the fiber, the second stage is subjected to an acetalization treatment, and then the third stage. A polyvinyl alcohol-based synthetic fiber having a strength of 8 g / d or more, characterized in that it is treated with a mixed solution of monoaldehyde and an acid to form an acetal. A process for producing a polyvinyl alcohol-based synthetic fiber, characterized in that the heat-resistant stabilizer is contained at 0.01 to 1% by weight with respect to the fiber in an appropriate process up to the step (a).

Hereinafter, the contents of the present invention will be described in more detail. The PVA-based polymer referred to in the present invention is a polymer having 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 low linearity. Things. The higher the average degree of polymerization of the PVA-based polymer, the greater the number of tie molecules connecting the crystals, and the smaller the number of molecular terminals that are disadvantageous, so that high strength, high elastic modulus, and high resistance to moist heat are easily obtained, and therefore, it is preferable. Is a PVA-based polymer having a polymerization degree of 1700 or more, and more preferably a PVA-based polymer having a polymerization degree of 2000 or more. However, it is generally difficult to produce a PVA-based polymer having a degree of polymerization of more than 30,000, and is not necessarily suitable from the viewpoint of industrial production.

Examples of the solvent for the PVA polymer include polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol and butanediol, dimethyl sulfoxide, dimethylformamide, diethylene triamine, water, and a mixed solvent of two or more of these. Is mentioned. However, when the dialdehyde of the present invention and / or an acetalized product thereof are mixed and added to the solvent, a solvent for coagulating or separating the compound is not desirable, and a solvent capable of uniformly dispersing or dissolving is preferable. In this respect, dimethyl sulfoxide and glycerin described above are preferable, and dimethyl sulfoxide is particularly preferable. Further, when dissolving the PVA-based polymer with a solvent, addition of boric acid, a surfactant, a decomposition inhibitor, a dye, a pigment, or the like does not cause any problem, but those which deteriorate spinnability and stretchability are not preferred. The concentration of the PVA-based polymer in the stock solution is preferably 5 to 50% by weight, particularly 5 to 20% by weight when using a wet spinning method or dry-wet spinning method, and 10 to 10% when using a dry spinning method. 50% by weight is preferred. The temperature of the spinning solution is generally from 100 to 230 ° C.

The spinning solution thus obtained is discharged from a nozzle by a conventional method such as a wet method, a dry method or a dry-wet method and solidified. In wet and dry-wet spinning, the fibers are solidified in a coagulation bath to form fibers. As the coagulant, any of alcohol, acetone, methyl ethyl ketone, an aqueous alkali solution, an aqueous alkali metal salt solution and the like may be used. In addition,
In order to form a uniform gel structure by slowing the solvent extraction in coagulation and obtain higher strength and wet heat resistance, it is preferable to mix the coagulant with the spinning stock solution solvent in an amount of 10% by weight or more. Particularly, a mixed solution of an alcohol represented by methanol and a stock solution solvent is preferable. Further, rapid cooling at a solidification temperature of 20 ° C. or less is also convenient for obtaining a uniform microcrystalline structure. Further, in order to reduce sticking between fibers and to facilitate subsequent dry drawing, a solvent containing 2 to 10 wt.
It is desirable to perform double stretching. The wet stretching temperature is 2
A range from 0 to 60 ° C. is preferred. In the case of alkali coagulation (coagulation in which the coagulant contains an alkali), it is preferable to perform neutralization under tension before wet stretching. Next, the fiber is immersed in an extraction bath to extract a solvent. As the extractant, alcohols such as methanol, ethanol, and propanol, acetone, methyl ethyl ketone, ether, and water can be used. Subsequently, the extractant is dried by applying an oil agent or the like as necessary. In the case of a dry method, the solvent is evaporated and dried at the time of spinning and after the spinning without using the extractant.

In order to develop the strength of the PVA-based fiber, the dried spun yarn is dry-heat drawn at 200 ° C. or higher, preferably 230 ° C. or higher, so that the total draw ratio is 14 times or higher, preferably 16 times or higher. . The stretching temperature is preferably increased as the degree of polymerization increases to maintain a high magnification.
It is not preferable because VA is easily decomposed. The dry heat drawing step may be performed before the first step described later, or at any step between the first to third steps, but the dialdehyde compound is sufficiently contained in the fiber. For this reason, it is preferable that the step be a step after the first step. In order to achieve a high draw ratio, it is preferable that the step be a step before the second step of acetalizing the dialdehyde compound and the PVA-based fiber. The total draw ratio is represented by the product of the wet draw ratio and the dry heat draw ratio.

A feature of the present invention is that a dialdehyde and / or an acetalized product thereof are penetrated into the interior of the fiber (first stage), and a crosslinking reaction is performed by causing the compound to undergo an acetalization reaction with a hydroxyl group contained in PVA. Separating from the step (step 2)
As a post-step of the step, a step of treating with a mixed solution of monoaldehyde and an acid to form an acetal (third step) is added, and preferably, an appropriate process from the first step to the third step is performed. In the above, a heat stabilizer is added.

The first stage is, as described above, a step of infiltrating the dialdehyde and / or its acetalized compound into the interior of the fiber. Examples of dialdehyde compounds that can be used in the present invention include glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, hexane 1,6 dial, octane dial, nonandial, decandial, dodecandial,
Compounds such as 2,4-dimethylhexanedial, 5-methylheptanedial, 4-methyloctanedial, 2,5-dimethyloctanedial, 3,6-dimethyldecandial, or orthophthalaldehyde;
Aromatic compounds such as isophthalaldehyde, terephthalaldehyde, and phenylmalondialdehyde, and alicyclic compounds such as 1,4-cyclohexanedialdehyde are exemplified. Among these, compounds which are highly reactive and polymerize even when they do not coexist with an acid, such as malondialdehyde, can be acetalized with an alcohol and used as an acetalized product. A typical example is tetramethoxypropane obtained by acetalizing malondialdehyde with methanol, which is stable if no acid coexists, but can be converted back to dialdehyde by the acid to react with PVA. These compounds may be used alone or in combination of two or more, but glutaraldehyde, malondialdehyde, succinaldehyde, nonandial, or an acetalized product thereof is used in view of permeability and reactivity into the fiber. Glutaraldehyde, nonandial, or an acetalized product thereof are particularly preferred.

The first step is a step for infiltrating the dialdehyde compound into the interior of the fiber, and it is necessary to prevent the dialdehyde compound from undergoing an acetalization reaction with PVA in the first step. It is important that the dialdehyde compound-containing liquid used in the first stage does not substantially contain an acid or the like which serves as an acetalization catalyst.

The application of the dialdehyde compound or the acetalized product thereof used in the present invention may be performed in any step after the dry spinning from the spinning stock solution, as long as it is a step of performing the acetalization reaction, that is, a step prior to the second step. Although there is no problem, a preferable method for imparting high moist heat resistance is to dissolve the compound in alcohol or ketones in the extraction bath and pass the swollen yarn into the compound, thereby allowing the compound to enter the inside of the fiber. This is a method of allowing sufficient content to be contained. In this case, the temperature of the bath containing the dialdehyde compound or the acetalized compound thereof is preferably from -10 ° C to 50 ° C, and the content of the compound in the bath is preferably from 0.3 to 20% by weight. The immersion time of the fiber in the bath is preferably 5 seconds or more, and if the immersion time is less than 5 seconds, the amount of the compound adhering to the fiber is insufficient and sufficient hot water resistance cannot be obtained.

In the present invention, the amount of the attached dialdehyde compound is 2 to 15% by weight, more preferably 3 to 12% by weight, based on the dry heat drawn yarn. If the amount is less than 0.5% by weight, the crosslink density is low, so that the wet heat resistance is insufficient. If the amount exceeds 10% by weight, the molecular orientation is disturbed or PVA is disturbed.
Decomposition is promoted, and the strength tends to decrease. The adhesion amount can be controlled by changing the content of the dialdehyde compound or the acetalized product in the bath containing the dialdehyde compound or the acetalized product.

The PVA fiber containing the dialdehyde compound thus obtained is acetalized in the second step. The production conditions in this step are not particularly limited as long as the conditions are such that the dialdehyde compound and the hydroxyl group of PVA undergo an acetal reaction, but the treatment is generally carried out with an acid. As a specific example, the dialdehyde compound-containing PVA-based fiber obtained through the first step is
Inorganic acids such as phosphoric acid, hydrochloric acid, nitric acid or carboxylic acids,
Immerse in an aqueous solution having a concentration of 0.1 N or more with an organic acid such as sulfonic acid at 60 ° C. to 100 ° C. for 10 to 120 minutes, or heat treat at 200 ° C. or higher by attaching the acid aqueous solution and / or alcohol solution. Causes an acetalization reaction. Here, in order to prevent deterioration of the PVA-based fiber, treatment in an aqueous solution is more preferable. The degree of acetalization by a dialdehyde compound is 2.0 to 10
Mol% is preferred, and more preferably 2.5 mol% to 8.0 mol%. The processing time is preferably between 30 minutes and 60 minutes.

Next, the third step in the present invention, that is, the step of treating with a mixed solution of a monoaldehyde and an acid to form an acetal as a post-step of the second step will be described.
The method of crosslinking PVA fibers with a dialdehyde compound is an effective method for improving the moist heat resistance of PVA fibers.
Since the original excellent properties of VA fiber, such as high strength and high elasticity, are impaired, the amount of dialdehyde compound that can be actually used is actually limited. On the other hand, the combined use of cross-linking and hydrophobization of PVA fibers with monoaldehyde can achieve further improvement in wet heat resistance. However, in the method of acetalizing a dialdehyde compound and a monoaldehyde compound at the same time as conventionally reported, since the amount of the monoaldehyde compound in the reaction bath is large, the monoaldehyde compound preferentially reacts, or An exchange reaction occurs between the dialdehyde compound reacted with the PVA fiber and the monoaldehyde compound. Therefore, the degree of crosslinking expected from the dialdehyde compound is low. Therefore,
The diacetal-type crosslinking is once completed in the second step described above, and then a two-stage acetalization in which an acetalization reaction is added with a monoaldehyde compound is performed. Unreacted hydroxyl groups can be further crosslinked and hydrophobized with a monoaldehyde compound.

Examples of the type of monoaldehyde used here include known ones such as formaldehyde and benzaldehyde, and formaldehyde is suitable from the viewpoint of permeability and minimizing a decrease in strength of PVA-based fiber as a raw yarn.

The conditions to be applied, that is, the concentration and humidity may be appropriately adjusted so as not to cause excessive swelling, but the monoaldehyde concentration is approximately 0.5 to 20% by weight, preferably 1 to 15% by weight, Preferably it is 2 to 10% by weight. The acid used as the reaction catalyst is not particularly limited, but is 1 to 50% by weight, and preferably 3 to 20% by weight in the case of the most common sulfuric acid. The temperature of the bath may be appropriately adjusted based on the reaction rate, the swelling state of the fibers, and the like.
To 95 ° C, preferably 70 to 90 ° C, and the treatment time is preferably 0.5 to 8 hours. Glauber's salt can also be used in the bath to suppress swelling. The degree of acetalization by monoaldehyde is not particularly limited,
It is good to be 5 mol% or more, preferably 10 to 30 mol%. Acetalization degree by monoaldehyde is 5 mol%
If it is less than 3, the heat and humidity resistance is not sufficient, and if the degree of acetalization by monoaldehyde exceeds 30 mol%, the decrease in fiber strength is extremely undesirable.

Next, the heat stabilizer used in the present invention will be described. The heat stabilizer is added or / and deposited in a suitable step between the first to third steps described above.

The heat stabilizer referred to in the present invention includes phenol-based, phosphite-based, thioester-based, benzotriazole-based and hindered amine-based organic antioxidants;
Alternatively, sulfate, nitrate, halide inorganic metal salts such as Cu, Mn, Ti, Sn, Pb, Zn, and Cr, and nitrogen-containing surfactants classified into the following three are mentioned. One or more of these can be used.

(1) An ammonium compound having an amide bond or a urea bond in the molecule. For example, a cationic surfactant represented by the following structural formula 1

[0029]

Embedded image In the above formula, R represents an alkyl group, an alkoxyl group, a phenyl group, a phenol group, a hydroxyl group, a hydrogen atom, or the like;
^- is a group having a negative ion, for example, NO ₃ ^{-,
_{Cl -, OH -, CH 3}} SO 4 - represents the like, but not limited to.

(2) Sulfonate compounds having an amide bond or a urea bond in the molecule. For example, an anionic surfactant represented by the following chemical formula 2.

[0031]

Embedded image In the above formula, R represents an alkyl group, an alkoxyl group, a phenyl group, a phenol group, a hydroxyl group, a hydrogen atom, or the like, and M represents an alkali metal such as Na or K, but is not limited thereto.

(3) Amine compounds of sulfonates. For example, an anionic activator represented by the following chemical formula 3.

[0033]

Embedded image In the above formula, R represents an alkyl group, an alkoxyl group, a phenyl group, a phenol group, a hydroxyl group, a hydrogen atom, or the like, and M represents an alkali metal such as Na or K, but is not limited thereto.

The content of the heat stabilizer varies depending on the type.
% By weight, preferably 0.001 to 0.1% for inorganic metal salts.
01% by weight, and 0.1% for nitrogen-containing surfactants.
1 to 1% by weight is preferred. When the amount is less than the above amount, the effect of expressing wet heat resistance is small, and when the amount exceeds the above amount, the yarn breakage during spinning or the draw ratio at the time of dry heat drawing is reduced, or conversely the decomposition may be promoted, which is preferable. Absent. The content when two or more heat stabilizers are used means the total amount.

The single fiber strength of the fiber obtained by the present invention is at least 8 g / d, more preferably at least 10 g / d. When the single fiber strength is less than 8 g / d, the effectiveness as a reinforcing material for general industrial materials such as fishing nets, ropes, tents, civil engineering sheets and the like, cement, rubber, and plastic, which are required to have wet heat resistance and high strength, In particular, it cannot be used as a reinforcing material for cement products subjected to autoclave curing.

[0036]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the examples.
The various physical properties in the present invention are defined by the following methods. 1) Viscosity average degree of polymerization PA of PVA The specific viscosity ηSP of the PVA dilute aqueous solution at 30 ° C. was measured at 5 points based on JIS K-6726, and the intrinsic viscosity [η] was obtained from the following equation (1). ) Was used to calculate the viscosity average degree of polymerization PA. [Η] = lim (C → O) ηSP / C (1) PA = ([η] × 10 ⁴ /8.29) ^1.613 (2)

2) Content of Aliphatic Dialdehyde The fiber containing the dialdehyde compound after the first step is 100
The dialdehyde was dissolved in dimethyl sulfoxide at ~ 140 ° C, the peak area ratio of the dialdehyde to the CH ₂ group peak of PVA was calculated by proton NMR, and the content was determined from a previously prepared calibration curve.

3) Degree of acetalization of PVA-based fiber The degree of acetalization referred to herein is a ratio (%) of hydroxyl groups consumed as a result of acetalization reaction of the dialdehyde or the monoaldehyde with hydroxyl groups of PVA. . Regarding the degree of acetalization, the degree of acetalization by the dialdehyde was determined from the ratio of the peak area derived from the acetal bond between the dialdehyde and PVA to the methine carbon peak area of PVA by solid carbon NMR.
The degree of acetalization by the monoaldehyde was determined from the ratio of the peak area derived from the acetal bond between the monoaldehyde and PVA to the methine carbon peak area of PVA.

4) Tensile strength of single fiber According to JIS L-1015, a previously conditioned single fiber is stuck on a backing so as to have a test length of 10 cm at 25 ° C. × 60% R.
Leave at H for 12 hours or more. Next, using an Instron 1122 using a chuck for 2 kg, the breaking strength was determined at an initial load of 1/20 g / d and a tensile speed of 50% / min, and the average value of n ≧ 10 was adopted. Denier is 30cm under 1 / 10g / d load
It was cut to length and determined by the gravimetric method. In addition, the strength and elongation and the elastic modulus were measured using the single fiber after the denier measurement, and each fiber was made to correspond to the denier.

5) Amount of heat-resistant stabilizer in fiber The antioxidant was used to remove the yarn before acetalization treatment from 100 to 13
It was dissolved in dimethyl sulfoxide at 0 ° C., the peak ratio of the antioxidant to the CH ₂ group peak of PVA was calculated by NMR, and the amount of adhesion was determined from a previously prepared calibration curve.
In addition, the inorganic metal salt can be used for the yarn before the acetalization treatment by 100%.
It was dissolved in dimethyl sulfoxide at ~ 130 ° C, the peak of a specific element was measured by X-ray fluorescence, and the peak was determined from a calibration curve.

6) Autoclave resistance (wet bending strength of slate plate WBS) PVA-based synthetic fiber is cut into a length of 6 mm, and 2 parts by weight of the fiber, 3 parts by weight of pulp, silica 38
Parts by weight, wet papermaking with a blending of 57 parts by weight of cement, 50 parts by weight
After primary curing at 12 ℃ for 12 hours, 150 ℃ × 20hr or 160 ℃ × 15hr or 170 ℃ × 15hr or 180
Autoclave curing was carried out at a temperature of 10 ° C. × 10 hours, a slate plate was prepared, and then immersed in water for 1 day according to JIS K-6911, and the bending strength was measured in a wet state.

Example 1 A viscosity average degree of polymerization was 1700 and a saponification degree was 99.5 mol%.
Of PVA was dissolved in dimethyl sulfoxide (DMSO) at 100 ° C. so as to have a concentration of 20% by weight, and the resulting solution was discharged from a 1000-hole nozzle.
DMSO was wet-spun in a coagulation bath at 5 ° C with a weight ratio of 7/3. Further, after performing a 3.5-fold wet drawing in a 40 ° C. methanol bath, the fibers were sequentially passed through a two-stage methanol extraction bath to remove all dimethyl sulfoxide. After adding 5% by weight of tetramethoxynonane to the final methanol extraction bath to make a uniform solution, the fiber is retained for 1.5 minutes to contain the dialdehyde compound inside and on the surface of the methanol-containing fiber. And then dried at 120 ° C. The adhesion amount of tetramethoxynonane in the fiber is 5
% By weight. The obtained spun yarn is heated at 175 ° C and 175 ° C.
The film was stretched in a hot-air furnace consisting of three sections at a temperature of 230 ° C. and a temperature of 230 ° C. so that the total stretching ratio was 16.1 times. Next, the drawn yarn was immersed in an aqueous solution of 8% by weight of sulfuric acid at 75 ° C. for 30 minutes to cause an acetalization reaction. At this stage, the degree of acetalization with tetramethoxynonane was 3.5 mol%. Furthermore, formaldehyde 10% by weight, sulfuric acid 8% by weight
Was immersed in an aqueous solution at 80 ° C. for 4 hours to cause an additional acetalization reaction. The finally obtained fiber had a degree of acetalization with tetramethoxynonane of 3.3 mol%, a degree of acetalization with formaldehyde of 15 mol%, a single fiber thickness of 1.8 denier, and a single fiber strength of 1 mol.
3.1 g / d, in autoclave curing, slate plate wet bending strength WBS is 251 k
g / cm ² , 170 ° C. × 15 hr, 200 kg / cm ²
cm ² .

Example 2 A spun yarn obtained by spinning in the same manner as in Example 1 was heated at 175 ° C., 175 ° C. and 230 ° C. in a hot-air furnace having three sections so that the total draw ratio was 16.1 times. Stretched.
Next, the drawn yarn is placed in an aqueous solution of 8% by weight of sulfuric acid at 75 ° C. × 30.
It was immersed for a minute to cause an acetalization reaction. Furthermore, it was immersed in an aqueous solution containing 10% by weight of formaldehyde and 8% by weight of sulfuric acid at 80 ° C. for 8 hours to cause an additional acetalization reaction. The degree of acetalization of the finally obtained fiber with tetramethoxynonane is 2.9 mol%, the degree of acetalization with formaldehyde is 23 mol%, the thickness of the single fiber is 1.8 denier, and the single fiber strength is 11 In the autoclave curing of 0.5 g / d, the wet bending strength WBS of the slate plate was 203 kg / cm ² after the treatment at 170 ° C. for 15 hours.

Example 3 The viscosity-average degree of polymerization was 1700 and the degree of saponification was 99.5 mol%.
Of PVA was dissolved in dimethyl sulfoxide (DMSO) at 100 ° C. so as to have a concentration of 20% by weight, and the resulting solution was discharged from a 1000-hole nozzle.
DMSO was wet-spun in a coagulation bath at 5 ° C with a weight ratio of 7/3. Further, after performing a 3.5-fold wet drawing in a 40 ° C. methanol bath, the fibers were sequentially passed through a two-stage methanol extraction bath to remove all dimethyl sulfoxide. After adding 5% by weight of bisethylenedioxynonane to the final methanol extraction bath and 1% by weight of a phenolic antioxidant Irganox 1098 manufactured by Ciba Geigy as a heat resistant stabilizer to the bath to form a uniform solution, The fiber was kept for 1.5 minutes to contain the dialdehyde compound and the heat stabilizer inside and on the surface of the methanol-containing fiber, and dried at 120 ° C. The deposition amount of tetramethoxynonane in the fiber was 5% by weight, and Irganox1
098 was 1% by weight. The obtained spun yarn was drawn in a hot-air furnace consisting of three sections at 175 ° C, 175 ° C, and 230 ° C so that the total draw ratio was 16.1 times. Next, the drawn yarn is placed in an aqueous solution of 8% by weight of sulfuric acid at 75 ° C. ×
It was immersed for 30 minutes to cause a crosslinking reaction. Further, 80% by weight of an aqueous solution containing 10% by weight of formaldehyde and 8% by weight of sulfuric acid.
It was immersed at 4 ° C. for 4 hours to cause an additional acetalization reaction. The degree of acetalization of the finally obtained fiber with tetramethoxynonane is 3.2 mol%, the degree of acetalization with formaldehyde is 16 mol%, the amount of the heat stabilizer in the fiber is 1% by weight, and the thickness of the single fiber is large. 1.8 denier,
The single fiber strength was 9.2 g / d, and in the autoclave curing, the slate plate wet bending strength WBS was 227 kg / cm ² after treatment at 170 ° C. for 15 hours.

Example 4 MnCl2 as a heat stabilizer was added to the bath at 0.0025.
A fiber was produced in exactly the same manner as in Example 3 except that the amount was added by weight. The degree of acetalization of the finally obtained fiber with tetramethoxynonane is 3.3 mol%, the degree of acetalization with formaldehyde is 15 mol%, the amount of heat stabilizer in the fiber is 0.014% by weight, Has a thickness of 1.8 denier, a single fiber strength of 9.2 g / d and a slate plate wet bending strength WBS of 170 in autoclave curing.
After treatment at 150 ° C. for 15 hours, the pressure was 209 kg / cm ² .

Example 5 The viscosity average degree of polymerization was 4000 and the degree of saponification was 99.5 mol%.
Of PVA was dissolved in dimethyl sulfoxide (DMSO) at 100 ° C. so as to have a concentration of 14% by weight, and the obtained solution was discharged from a 1000-hole nozzle.
DMSO was wet-spun in a coagulation bath at 5 ° C with a weight ratio of 7/3. Further, after performing a 3.5-fold wet drawing in a 40 ° C. methanol bath, the fibers were sequentially passed through a two-stage methanol extraction bath to remove all dimethyl sulfoxide. After adding 5% by weight of tetramethoxynonane to the final methanol extraction bath to make a uniform solution, the fiber is retained for 1.5 minutes to contain the dialdehyde compound inside and on the surface of the methanol-containing fiber. And then dried at 120 ° C. The adhesion amount of tetramethoxynonane in the fiber is 5
% By weight. The obtained spun yarn is heated at 175 ° C and 178 ° C.
The film was stretched in a hot-air stove consisting of three sections at a temperature of 240 ° C. and a total stretching ratio of 16.0 times. Next, the drawn yarn was immersed in an aqueous solution of 8% by weight of sulfuric acid at 75 ° C. for 30 minutes to cause an acetalization reaction. At this stage, the degree of acetalization with tetramethoxynonane was 3.5 mol%. Furthermore, it was immersed in an aqueous solution of 10% by weight of formaldehyde and 8% by weight of sulfuric acid at 80 ° C. for 4 hours to cause an additional acetalization reaction. The degree of acetalization of the finally obtained fiber with tetramethoxynonane is 3.2 mol%, the degree of acetalization with formaldehyde is 15 mol%, the thickness of the single fiber is 1.8 denier, and the single fiber strength is 1
4.0 g / d, in autoclave curing, slate plate wet bending strength WBS is 298 k after processing at 150 ° C. × 20 hr.
g / cm ² , 170 ° C. × 15 hr, 271 kg / cm ²
cm ² .

Comparative Example 1 The viscosity average degree of polymerization was 1700 and the saponification degree was 99.5 mol%.
Of PVA was dissolved in dimethyl sulfoxide (DMSO) at 100 ° C. so as to have a concentration of 20% by weight, and the resulting solution was discharged from a 1000-hole nozzle.
DMSO was wet-spun in a coagulation bath at 5 ° C with a weight ratio of 7/3. Further, after performing a 3.5-fold wet drawing in a 40 ° C. methanol bath, the fibers were sequentially passed through a two-stage methanol extraction bath to remove all dimethyl sulfoxide. After adding 5% by weight of tetramethoxynonane to the final methanol extraction bath to make a uniform solution, the fiber is retained for 1.5 minutes to contain the dialdehyde compound inside and on the surface of the methanol-containing fiber. And dried at 120 ° C. 5% by weight of tetramethoxynonane in fiber
Met. The obtained spun yarn is heated at 170 ° C, 200 ° C,
A total stretching ratio of 1 in a hot blast stove consisting of three sections at 35 ° C.
It was stretched to 6.1 times. Next, the drawn yarn is immersed in an aqueous solution of formaldehyde 10% by weight and sulfuric acid 8% by weight.
It was immersed at 8 ° C. for 8 hours to cause an acetalization reaction. The degree of acetalization of the finally obtained fiber with tetramethoxynonane was 1.5 mol%, the degree of acetalization with formaldehyde was 22 mol%, and the thickness of the single fiber was 1.
8 denier, single fiber strength 11.5 g / d, slate plate wet bending strength WBS of 150 ° C in autoclave curing
246 kg / cm ² at 170 ° C. × 1 after × 20 hr treatment
After treatment for 5 hours, the pressure was 181 kg / cm ² .

Comparative Example 2 The viscosity average degree of polymerization was 4000 and the saponification degree was 99.5 mol%.
Of PVA was dissolved in dimethyl sulfoxide (DMSO) at 100 ° C. so as to have a concentration of 14% by weight, and the obtained solution was discharged from a 1000-hole nozzle.
DMSO was wet-spun in a coagulation bath at 5 ° C with a weight ratio of 7/3. Further, after performing a 3.5-fold wet drawing in a 40 ° C. methanol bath, the fibers were sequentially passed through a two-stage methanol extraction bath to remove all dimethyl sulfoxide. After adding 5% by weight of tetramethoxynonane to the final methanol extraction bath to make a uniform solution, the fiber is retained for 1.5 minutes to contain the dialdehyde compound inside and on the surface of the methanol-containing fiber. And then dried at 120 ° C. The adhesion amount of tetramethoxynonane in the fiber is 5
% By weight. The obtained spun yarn is heated at 175 ° C and 178 ° C.
The film was stretched in a hot-air stove consisting of three sections at a temperature of 240 ° C. and a total stretching ratio of 16.0 times. Next, the drawn yarn was immersed in an aqueous solution containing 10% by weight of formaldehyde and 8% by weight of sulfuric acid at 80 ° C. for 4 hours to cause an acetalization reaction. The degree of acetalization of the finally obtained fiber with tetramethoxynonane was 1.8 mol%, the degree of acetalization with formaldehyde was 14 mol%, the thickness of the single fiber was 1.8 denier, and the single fiber strength was 13%. 0.9g / d, slate plate wet bending strength WBS is 1 in autoclave curing
274 kg / cm ² , 170 after treatment at 50 ° C. × 20 hours
It was 249 kg / cm ² after treatment at 15 ° C. for 15 hours.

[0049]

According to the present invention, even under severe high temperature and high humidity conditions such as high temperature autoclave curing, high moisture and heat resistance which does not impair the original excellent properties of high strength, high elasticity, excellent adhesion and alkali resistance. And can be used for a wide range of applications such as ropes, fishing nets, tents, civil engineering sheets and other general industrial materials, as well as cement reinforcements capable of high-temperature autoclaving.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshinori Ando 2045-1, Sazu, Kurashiki-shi, Okayama Prefecture Within Kuraray Co., Ltd. (72) Inventor Masahiro Sato 1621, Sakurazu, Kurashiki-shi, Okayama Prefecture Kuraray Co., Ltd.

Claims (2)

[Claims] (1) a first stage containing 2 to 10% by weight of dialdehyde and / or an acetalized product thereof based on the fiber, followed by an acetalization treatment in a second stage;
Further, in the third step, a method for producing a polyvinyl alcohol-based synthetic fiber having a strength of 8 g / d or more, characterized in that it is treated with a mixed solution of a monoaldehyde and an acid to form an acetal. 2. The method for producing a polyvinyl alcohol-based synthetic fiber according to claim 1, wherein the heat-resistant stabilizer is contained in an amount of 0.01 to 1% by weight with respect to the fiber in an appropriate process from the first stage to the third stage. .