JPH09132816A - Polyvinyl alcohol fiber having excellent hot-water resistance and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyvinyl alcohol(PVA) fiber having excellent strength and hot-water resistance and useful as a cement reinforcing material, etc., without causing the dissipation of a crosslinking agent by spinning a solution of a PVA polymer, impregnating the obtained spun fiber with a specific acetalized material and crosslinking under specific condition. SOLUTION: A PVA fiber having an inner crosslinking index (CI) and a tensile strength of fiber (DT) satisfying the formulas II to LV is produced by spinning a solution of a PVA polymer, drawing in wet state to obtain a PVA fiber, impregnating the fiber with an acetalized product of a >=6C aliphatic polyaldehyde (e.g. acetalized nonanedial), drawing under a dry hot condition to increase the fiber strength to >=10g/d and treating the fiber in a bath containing an aqueous solution of sulfuric acid and satisfying the formula I [(c) is concentration (g/L) of sulfuric acid of the bath; T is treating temperature ( deg.C)].

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyvinyl alcohol (hereinafter referred to as P) which has extremely excellent hot water resistance by being sufficiently cross-linked not only on the surface of the fiber but also inside the fiber.
Abbreviated as VA) type fiber. In particular, the fiber of the present invention has an internal fiber content when the fiber is dyed in a hot water bath at a high temperature or when steam curing is performed in a high temperature autoclave to increase the strength of a cement product added as a reinforcing fiber. The present invention relates to a PVA-based fiber in which the elution of PVA from the fiber end surface hardly occurs due to sufficient cross-linking, and the fiber has sufficient strength.

[0002]

2. Description of the Related Art PVA-based fibers have the highest strength and high modulus of elasticity among general-purpose fibers, and have excellent adhesiveness and alkali resistance, and are particularly in the spotlight as a cement reinforcing material as a substitute for asbestos. However, PVA-based fibers are poor in hot water resistance (also referred to as moist heat resistance), and their use is limited even if they are used as general industrial materials or clothing materials. For example, when PVA fiber is used as a reinforcing material for cement, there is a problem that it is impossible to cure the cement product under high temperature conditions in an autoclave. Currently, when PVA-based fibers are used as reinforcing fibers for cement products, they are forced to rely on autoclave curing under room temperature or low temperature heating conditions, and the dimensional stability and strength of cement products are not sufficient, and the curing days There is the problem of becoming longer.

When PVA-based fibers are used in a blended product of polyester-based fibers, a disperse dye which is generally used as a dyeing method for polyester fibers is used because of poor hot water resistance of PVA-based fibers. ℃ to 13
Since the method of dyeing in an aqueous solution at a high temperature of 0 ° C. cannot be used, the use of PVA-based fibers for clothing is also greatly restricted in this respect. On the other hand, although some carbon fibers are used for curing in a high temperature autoclave, carbon fibers have problems such as poor adhesion to a cement matrix, poor reinforcing effect, and high cost.

Attempts have been made for a long time to improve the hot water resistance of PVA-based fibers. For example, in JP-B-30-7360 and JP-B-36-14565, formalin is used to form hydroxyl groups of PVA into formalin. To make it hydrophobic by a crosslinking reaction (formalization) with
It is described that the fiber obtained by this method has hot water resistance that can withstand dyeing and washing. However, the PVA-based fibers obtained by these methods do not have the high level of hot water resistance required for the present invention, that is, can withstand high temperature autoclave curing, and also have low strength.

Further, Japanese Patent Laid-Open No. 63-120107 describes that high-strength PVA-based fibers are formalized, but the degree of formalization is as low as 5 to 15 mol%, and the PVA-based fibers are amorphous. Only a small part of the area is made hydrophobic by formalization, its hot water resistance is not sufficient, and it can not be used at all for industrial materials that are repeatedly exposed to humid heat for a long time and cement reinforcements that are cured by high temperature autoclave. Absent. On the other hand, JP-A-2-133605 (corresponding European patent No. 351046, corresponding US Pat. No. 5,283,281) and JP-A-1-207435 disclose that PVA-based fibers are blended with an acrylic acid-based polymer. There is described a method of increasing the hot water resistance by cross-linking the hydroxyl groups or imparting to the fiber surface with an organic peroxide, an isocyanate compound, a urethane compound, an epoxy compound or the like to cross-link the hydroxyl groups of PVA. However, since the cross-linking by acrylic acid polymer is an ester bond, it easily hydrolyzes with the alkali of cement and loses its effect.Other cross-linking agents also cross-link the fiber surface, so during autoclave curing and repeated moist heat treatment. It has problems such as swelling and dissolution from the center of the fiber when exposed to.

Other methods for improving the moist heat resistance by dehydration crosslinking using an acid are known in JP-A-2-84587, JP-A-4-100912, etc. It was found that when attempting to crosslink the inside of the fiber, the PVA fiber was severely decomposed, resulting in a significant decrease in fiber strength.

On the other hand, crosslinking by a dialdehyde compound is specified in Japanese Patent Publication No. 29-6145 and Japanese Patent Publication No. 32-5819, but it is post-treated in a mixed bath of a dialdehyde compound and an acid as a reaction catalyst. Therefore, in a high-strength PVA-based fiber in which the fiber molecules are highly oriented and crystallized, it is difficult for the dialdehyde compound to penetrate into the fiber, and thus it is difficult to crosslink the fiber. Further, JP-A-5-163609 describes that a dialdehyde compound is applied to a spun raw yarn, dry heat drawn at a high ratio, and then acid treatment is carried out to cause cross-linking inside the fiber. The dialdehyde compound described in 1 is an aliphatic dialdehyde compound having 6 or less carbon atoms or an aromatic dialdehyde compound. However, in the case of an aliphatic dialdehyde having a small number of carbon atoms, these dialdehyde compounds applied to the raw yarn are diffused from the raw yarn during dry heat drawing and do not sufficiently remain in the fiber, which is effective for hot water resistance. There is a problem that there is little crosslinking between PVA-based molecules (intermolecular crosslinking). On the other hand, when an aromatic dialdehyde compound is used, there are problems that the dialdehyde compound is sterically hindered due to its aromaticity, internal penetration is difficult, and strength is likely to decrease. Therefore, even the above method does not sufficiently satisfy both hot water resistance and high strength. In this publication, in the case of a highly reactive dialdehyde compound, the dialdehyde compound may be acetalized with alcohol, and as a representative example thereof, malondialdehyde (having 3 carbon atoms) is described. A compound obtained by acetalizing (aliphatic dialdehyde) in methanol with methanol, that is, tetramethoxypropane is described. However, the highly reactive dialdehyde compound is generally a dialdehyde compound having a small number of carbon atoms, such as malondialdehyde, and in the case of an acetalized product of such a dialdehyde compound, the above-mentioned aliphatic dialdehyde compound In the same manner as in the case, the acetalized product of the dialdehyde compound is easily radiated during the dry heat drawing, and thus a sufficient crosslinking reaction is not formed, and in the case of the dialdehyde compound having a smaller number of carbons, the intramolecular crosslinking is Easy to happen,
There is also a problem that intermolecular crosslinking, which is necessary for improving heat resistance, is unlikely to occur.

Further, the applicant of the present invention impregnated the dry heat-stretched PVA fiber with the dialdehyde compound described in the above-mentioned JP-A-5-163609 to the inside of the fiber and then added it to a bath containing a monoaldehyde and a crosslinking catalyst. By dipping and causing a crosslinking reaction, a PVA-based fiber excellent in hot water and crosslinked to the inside of the fiber was obtained, and it was found that this crosslinked PVA-based fiber is a fiber that can withstand autoclave curing at 160 ° C. Filed a patent application, and the application was published as Japanese Patent Application Laid-Open No. 5-263331 (corresponding European Patent No. 520297, US Pat. No. 5,380,58).
No. 8). Certainly, when this method is used, it is possible to obtain a PVA-based fiber which is crosslinked to the inside of the fiber and has excellent hot water resistance. However, in this method, PVA after completion of so-called crystal orientation after completion of dry heat drawing is obtained. Since the dialdehyde compound is added to the base fiber, the dialdehyde compound does not sufficiently penetrate to the inside of the fiber, and therefore, when the obtained fiber is subjected to autoclave curing at 170 ° C. or more, the problem that the fiber melts out Occurs.

In summary, in order to permeate the cross-linking agent into the inside of the fiber, which is conventionally known, in the case of applying the cross-linking agent to the fiber before the dry heat drawing in which the fiber is not crystal-oriented, the cross-linking agent is impregnated. The cross-linking agent is scattered or oxidized from the fiber during the subsequent dry hot drawing, and as a result, a sufficient cross-linking reaction does not occur, while the cross-linking agent is added to the fiber after dry hot drawing. In this case, it is difficult for the crosslinking agent to penetrate into the inside of the fiber, and there is a problem that sufficient crosslinking is not formed inside the fiber.

[0010]

DISCLOSURE OF THE INVENTION According to the present invention, high strength is maintained and intermolecular crosslinking effective for improving hot water resistance is generated inside the fiber, and the crosslinking agent is oxidized by heat during dry drawing. The present invention relates to a method in which the cross-linking agent hardly scatters during stretching and a PVA-based fiber having high strength and high hot water resistance obtained by the method. The present inventors, by using a specific dialdehyde compound as a crosslinking agent, by crosslinking in a specific method,
The inventors have found that a PVA-based fiber having hot water resistance and high strength, which has not been obtained by the conventional technique, can be obtained, and thus reached the present invention.

[0011]

Means for Solving the Problems In the present invention, an acetalized product of an aliphatic polyaldehyde having 6 or more carbon atoms is crosslinked, and the internal crosslinking index (CI) and the tensile strength (DT) of the fiber are expressed by the following formula ( PV satisfying 1) to (3)
It is an A-based fiber. CI ≧ 86.5-2 × 10 ⁻⁶ × (DT) ^5.8 (1) CI ≧ 75 (2) DT ≧ 5 g / d (3) The present invention also provides a solution of PVA-based polymer. A PVA-based fiber obtained by spinning and wet drawing was made to contain an acetalized product of an aliphatic polyaldehyde having 6 or more carbon atoms and then dry-heat drawn to obtain a tensile strength of 10 g / d or more, and then the following formula A method for producing a PVA fiber, which comprises treating with a sulfuric acid aqueous solution bath satisfying (4). ^{137 / C 0.05 -52 ≦ T ≦} 137 / C 0.05 -32 (4) [ where, C is meant the concentration of sulfuric acid aqueous sulfuric acid solution bath (g / l), T is the treatment temperature (° C.). ]

FIG. 1 is a diagram showing the relationship between the internal cross-linking index (CI) and the tensile strength (DT) of the fiber defined in the present invention. In the figure, the hatched portion is the scope of the present invention. FIG. 1 also shows Japanese Patent Laid-Open No. 5-263331 (corresponding European Patent No. 520297, US Pat. No. 5380).
588) and the value of the crosslinked PVA-based fiber obtained by the method of JP-A-2-133605 (corresponding European Patent No. 351046, corresponding US Patent No. 528328).
The value of the crosslinked PVA-based fiber obtained in No. 1) is also shown. From this result, it can be understood that the fiber of the present invention has much higher internal cross-linking than the known cross-linked PVA-based fiber and is excellent in hot water resistance.

The present invention will be described in detail below. First, the PVA-based polymer referred to in the present invention is one having a viscosity average polymerization degree of 1500 or more and a saponification degree of 98.5 mol% or more, preferably a saponification degree of 99.0 mol% or more. As the average degree of polymerization of the PVA-based polymer is higher, the number of tie molecules connecting the crystals is larger, and the number of molecular terminals as a defect is smaller, so that high strength, high elastic modulus, and high hot water resistance are easily obtained, which is preferable. In particular, the degree of polymerization is preferably 1700 or more, more preferably 2000 or more. However, a PVA-based polymer having a degree of polymerization of more than 30,000 is generally difficult to manufacture, and is not necessarily suitable from the viewpoint of industrial production. In addition, ethylene, allyl alcohol, itaconic acid, acrylic acid, maleic anhydride and ring-opened products thereof, arylsulfonic acid, fatty acid vinyl esters such as vinyl pivalate, vinylpyrrolidone and neutralized products of some or all of the above ionic groups. Also included are PVA-based polymers modified by the modifying unit of. The amount of the denaturing unit is preferably 2 mol% or less, more preferably 1
Mol% or less.

In order to spin the PVA-based polymer, first the PVA-based polymer is dissolved in a solvent and defoamed to obtain a spinning dope. Examples of the solvent at this time 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. In particular, dimethylsulfoxide and polyhydric alcohols such as glycerin and ethylene glycol generate a uniform gel structure when charged into a coagulation bath, and as a result, high strength fibers are obtained, which is preferable. In addition, boric acid, a surfactant, a decomposition inhibitor, various stabilizers, dyes, pigments and the like may be added to the spinning dope prepared by dissolving the PVA polymer in a solvent. However, those that deteriorate the spinnability and stretchability are not preferred.

The concentration of the PVA-based polymer in the spinning dope is preferably 5 to 50% by weight, particularly 5 to 20% by weight when the wet spinning method or the dry-wet spinning method is used, and when the dry spinning method is used. Is preferably 10 to 50% by weight. The temperature of the spinning dope is generally 100 to 230 ° C.

The spinning dope thus obtained is wet,
It is spun and solidified by either a dry method or a dry method. In the wet or dry-wet spinning method, the coagulation bath is solidified to form fibers, and the coagulation bath liquid at that time includes alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, and an alkaline aqueous solution. , An alkali metal salt aqueous solution, or a mixed solution thereof is used. In order to slowly perform solvent extraction in coagulation to generate a uniform gel structure and to obtain higher strength and hot water resistance, it is preferable to mix 10% by weight or more of a solvent constituting the spinning dope with the coagulation bath solution. . In particular, a mixed solvent in which the weight ratio of the alcohol represented by methanol and the stock solution solvent is 9/1 to 6/4 is preferable. Furthermore, it is also preferable to rapidly cool the discharged spinning dope by setting the coagulation bath liquid to 20 ° C. or lower in order to obtain a gel having a uniform microcrystalline structure, that is, high-strength fibers. Furthermore, the coagulation bath temperature is 10
It is preferable that the temperature is not higher than 0 ° C. because the coagulated yarn becomes more homogeneous.

The fibers thus solidified are preferably wet-stretched twice or more in a solvent-containing state in order to reduce sticking between the fibers and to facilitate dry heat stretching thereafter. When the coagulation bath solution is an aqueous alkali solution or a solution containing an alkali, it is preferable to perform neutralization under tension before wet drawing. Next, solvent extraction is carried out. As the extractant, primary alcohols such as methanol, ethanol, propanol, acetone, methyl ethyl ketone,
Ketones such as methyl propyl ketone and methyl isobutyl ketone, ethers such as dimethyl ether and methyl ethyl ether, and water are used. Subsequently, if necessary, an oil agent or the like is added to dry the extracted fiber. In the case of the dry spinning method, the solvent is evaporated during and after spinning without using an extractant to obtain a dry yarn.

One of the greatest features of the present invention is that an acetalized product of an aliphatic dialdehyde having 6 or more carbon atoms is used as a crosslinking agent. Then, such an acetalized product is applied to the spinning raw yarn in any step from spinning to drying, and the acetalized product is permeated into the spinning raw yarn. An acetalized product of an aliphatic dialdehyde having 6 or more carbon atoms does not easily scatter from the inside of the fiber due to heat during dry heat drawing of the fiber, and remains in the inside of the fiber even after drawing, and is used for autoclave curing at 170 to 180 ° C. It provides sufficient cross-linking to achieve hot water resistance that can be tolerated. Furthermore, even if such an acetalized product is applied after drying the fiber, the acetal compound has a large molecular weight, so that it hardly penetrates into the fiber,
Since the fiber surface is unidirectionally cross-linked, it is difficult to obtain a fiber having sufficient hot water resistance.

From the above, in the present invention, as the cross-linking agent, an acetalized product of an aliphatic dialdehyde having 6 or more carbon atoms, which has a larger molecular weight than the cross-linking agents used conventionally, is used. It is applied to the spun raw yarn in any step from spinning to drying, and as a result, it cannot be obtained by conventional autoclave curing at 170 to 180 ° C. in combination with the specific crosslinking treatment condition described later. A PVA-based fiber that can withstand the above is obtained.

Particularly in the present invention, the preferred method of applying the acetal compound is to add and dissolve the acetal compound in alcohols and ketones of the extraction bath, and to dissolve the acetal compound in the swollen yarn while passing through the extraction bath. Is a method of infiltrating into the fiber, and when this method is used, the acetalized product easily penetrates into the inside of the fiber. Therefore, in the present invention, as a spinning method, it is preferable to use a wet spinning method using an extraction bath or a dry wet spinning method.

Examples of acetalized aliphatic dialdehydes having 6 or more carbon atoms in the present invention include, for example, hexanediar, heptanedial, octanedial, nonanedial, decanedial, 2,4-dimethylhexanedial, 5 -A dialdehyde having 6 or more carbon atoms such as methylheptanedial and 4-methyloctanedial is reacted with an alcohol such as methanol, ethanol, propanol, butanol, ethylene glycol, and propylene glycol to prepare both terminals or one end. It is a compound in which the terminal is acetalized, and preferably has a boiling point of 230 ° C. or higher, more preferably 260 ° C. or higher. In the case of an aliphatic dialdehyde having more than 14 carbon atoms, a crosslinking reaction is difficult to occur and molecular orientation is hindered, and high strength is difficult to obtain, which is not preferable. On the other hand, in the case of an aliphatic dialdehyde having a carbon number of 5 or less, the acetalized product is scattered during dry heat drawing and a sufficient amount of the acetalized product does not remain inside the fiber, and as a result, a PVA system having sufficient hot water resistance is obtained. Fiber is not obtained, and further, the acetalized product is oxidized during dry drawing to become an acid, which decomposes PVA, or it acts as a catalyst for the cross-linking reaction to cause a cross-linking reaction during the dry-heat drawing, which makes it difficult to draw. As a result, sufficient strength cannot be obtained and the object of the present invention cannot be achieved.

In the case of a non-aliphatic dialdehyde compound, for example, an acetal compound of an aromatic dialdehyde, the acetal compound is less likely to penetrate into the fiber due to steric hindrance, and the strength is likely to decrease. I cannot achieve my purpose. Furthermore, if it is not an acetal compound,
That is, when the dialdehyde itself is used, as in the above case, the dialdehyde is oxidized into a carboxylic acid during hot stretching, which decomposes PVA or causes a cross-linking reaction during stretching to perform high-strength stretching. It is difficult to obtain high strength fiber. Further, during dry heat drawing, the dialdehyde tends to scatter and has a problem of odor.

As described above, in the case of an aliphatic dialdehyde, it is oxidized by heat and oxygen under dry heat stretching conditions to be converted into a carboxylic acid, and some cross-linking occurs during stretching to fix the PVA molecules to each other. No stretch ratio can be obtained, high-strength fiber cannot be obtained, and there is a problem that the working environment is contaminated by smoke and decomposition gas caused by decomposition during dry heat drawing, but the end is acetalized. In this case, it is hardly oxidized even during the dry heat drawing, and the above problems do not occur. Particularly, in the case of an acetalized product of an aliphatic dialdehyde having 6 or more carbon atoms, it is particularly thermally stable, and as described above, it hardly scatters during dry heat drawing. When the acetalized product is used as compared with the case where an aliphatic dialdehyde having 6 or more carbon atoms is used as the cross-linking agent, the tensile strength of the obtained fiber depends on the degree of polymerization of the PVA-based polymer. A high strength fiber having a high strength of 1 g / d or more is obtained. Specific examples of particularly preferable acetalized products of aliphatic dialdehyde having 6 or more carbon atoms include:
1,9,9-Tetramethoxynonane obtained by reacting 1,9-nonanediol with methanol 1,1,9-nonanediol obtained by reacting ethylene glycol
9-nonanediar-bisethylene acetal and the like are mentioned, and these acetalized products are extremely excellent in suppressing reduction in strength of the fiber and generating intermolecular crosslinks effective for hot water resistance. Further, among these compounds, compounds in which both terminals are acetalized are extremely stable to heat, and are particularly preferable.

The amount of the acetalized product in the present invention is 0.3 to 10% by weight, preferably 0.7 to 6% by weight, based on the dry heat drawn yarn. Adhesion amount is 0.3
If it is less than 10% by weight, the hot water resistance is insufficient, and if it exceeds 10% by weight, the molecular orientation is disturbed or P
The decomposition of the VA-based polymer is promoted, and the strength is likely to be reduced.

Next, when it is used as a reinforcing fiber for high temperature curing FRC, in order to maintain high strength, the spun raw yarn containing the acetalized product after the drying treatment has a temperature of 220 ° C. or higher 26
Dry heat stretching is performed at 0 ° C or lower, preferably at 240 ° C or higher and 255 ° C or lower at a total stretching ratio of 15 times or more, preferably 17 times or more. The total draw ratio referred to here is a value represented by the product of the draw ratio of wet drawing performed before the drying treatment and the draw ratio of dry heat drawing. If the total draw ratio is less than 15 times, the high tenacity fiber aimed at by the present invention cannot be obtained. Preferable is a wet draw ratio of 2 to 5 times and a dry heat draw ratio of 3 to 10 times.

The dry heat drawing temperature is preferably higher as the degree of polymerization of the PVA polymer is higher.
If it exceeds 60 ° C, the PVA-based polymer is unfavorably melted or decomposed. When used for clothing, it does not require as high a strength as FRC, but it requires a higher degree of crosslinking and hot water resistance to withstand high temperature dyeing in a free state (that is, a state in which fibers can freely shrink). become. In this case, the stretching temperature is lowered by 5 to 10 ° C. from the above, the total stretching ratio is accordingly lowered, and crosslinking is easily promoted by suppressing the orientation and crystallization of molecules, and the hot water resistance is extremely high. Become.

The stretched fiber containing the acetalized aliphatic dialdehyde having 6 or more carbon atoms has a tensile strength of 10 g / d or more. When the tensile strength is less than 10 g / d, the tensile strength of the fiber is greatly reduced by the subsequent crosslinking treatment, which is not preferable.
More preferably, it has a tensile strength of 12 g / d or more.

As a specific cross-linking treatment, there is used a method of immersing the drawn fiber containing the acetalized product of the aliphatic dialdehyde having 6 or more carbon atoms for 5 to 120 minutes in an aqueous solution containing sulfuric acid. Depending on the method, a reaction occurs between the hydroxyl group of the PVA-based polymer and the acetal compound, resulting in intermolecular crosslinking. In addition, at this time,
The relationship between the sulfuric acid concentration (g / l) in the bath and the treatment temperature (bath temperature) must satisfy the following formula (4). 137 / C ^0.05 −52 ≦ T ≦ 137 / C ^0.05 −32 (4) [where C means the sulfuric acid concentration (g / l) in the sulfuric acid aqueous solution bath, and T means the treatment temperature (° C.). ]

When the treatment temperature (T) is lower than 137 / C ^0.05 -52, crosslinking does not proceed sufficiently, while 137 / C.
Strength reduction is increased to higher than ^0.05 -32. More preferably, the following formula (5) is satisfied. ^{137 / C 0.05 -48 ≦ T ≦} 137 / C 0.05 -35 ‥‥ (5)

The relational expression between the sulfuric acid concentration and the treatment temperature defined in the above (4) shows that the sulfuric acid concentration is lower or the treatment temperature is lower than the general conditions conventionally used for acetalization of PVA fibers in the industry. . In the method of the present invention, such conditions that are different from the conditions conventionally used are adopted,
By adopting such conditions and using the above-mentioned special cross-linking agent, the cross-linking reaction sufficiently progresses to the inside of the fiber, and the surprisingly hot water resistance that can withstand autoclave curing at 170 ° C or higher is obtained. Be done. Further, by treatment with high temperature and low concentration sulfuric acid in the range of (4), a fiber which can withstand dyeing at 120 ° C. in a free state can be obtained. During the cross-linking treatment, formalin may be added together with sulfuric acid to cause formalization at the same time. Further, a small amount of zinc chloride or a surfactant may be added to promote crosslinking.

In the present invention, the above-mentioned cross-linking treatment is carried out when the fibers have a predetermined length, for example, a length of 15 to 100 mm when the fibers are used as staples, and a short-cut fiber such as a fiber for cement reinforcement. Is
It is preferable to carry out after cutting to a length of 2 to 15 mm in order to improve the hot water resistance of the fiber. When the fiber is cut after cross-linking, the cut cross-section has a lower degree of cross-linking than the fiber peripheral surface, and PVA elutes from the cut cross-section under severe wet heat conditions, but the cross-linking treatment is performed after cutting. Since the cut cross section is sufficiently cross-linked like the fiber peripheral surface, PVA does not elute from the cut cross section even under severe wet heat conditions.

The PVA fiber obtained by such a method simultaneously satisfies the following expressions (1) to (3). CI ≧ 86.5-2 × 10 ⁻⁶ × (DT) ^5.8 (1) CI ≧ 75 (2) DT ≧ 5 g / d (3) In the above formula, CI is the internal crosslinking index, DT Represents the tensile strength of the fiber.

When the above equations (1) and (2) cannot be satisfied, autoclave curing at 170 ° C. or higher or 120 ° C.
When it is difficult to withstand the dyeing treatment in the free state, and when the above formula (3) is not satisfied, not only the cement reinforcement that requires strength but also the characteristics of PVA fiber for clothing are reduced, It becomes useless. More preferably, the following formulas (6) to (8) are satisfied. CI ≧ 90-2 × 10 ⁻⁶ × (DT) ^5.8 (6) CI ≧ 80 (7) DT ≧ 5 g / d (8)

Particularly, PVA-based fibers are likely to shrink or dissolve in the dyeing treatment in a free state, and CI ≧ 90 is preferable. On the other hand, when the fibers are fixed in cement as in an autoclave, it is preferable that CI ≧ 80 and DT ≧ 14 g / d, which are high in strength. However, CI> 99 and DT> 2
Fibers satisfying 5 g / d are difficult to manufacture industrially. The PVA-based fiber obtained in the present invention is a high temperature curing FRC.
It is used for general industrial materials that require water resistance and clothing that can be dyed at high temperatures.

[0035]

EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples. In Examples and Comparative Examples,% and parts mean values based on weight unless otherwise specified. In addition, various physical property values in the present invention are values measured by the following methods.

1. Viscosity average degree of polymerization (P) of PVA-based polymer Based on JISK-6726, the specific viscosity (ηsp) of a dilute aqueous solution of PVA-based polymer at 30 ° C was measured at 5 points, and the intrinsic viscosity [η] was calculated by the following formula (9). The viscosity average polymerization degree P was calculated by the following equation (10). The uncrosslinked stretched fiber of the sample was dissolved in water at 140 ° C or higher under pressure so that the concentration of the uncrosslinked stretched fiber was 1 to 10 g / l.
It was filtered with a m glass filter and the viscosity of the filtrate was measured. Further, the concentration of the aqueous solution at that time was calculated using a correction value obtained by subtracting the weight of the gel substance of the residue from the weight of the sample. [Η] = lim (c → 0) ηsp / c (9) P = ([η] × 10 ⁴ /8.29) ^1.613 (10)

2. Content of acetalization product of aliphatic dialdehyde Dissolving uncrosslinked drawn yarn in deuterated dimethylsulfoxide at 140 ° C or higher, and calculating peak area ratio of acetalization product to CH ₂ group peak of PVA polymer by NMR The amount was calculated. 3. Internal cross-linking index (CI) About 1 g / sample was cut into 6 mm and the weight W ₁ was precisely weighed.
Artificial cement aqueous solution (KOH 3.5g / l and NaOH
0.9 g / l and an aqueous solution (0.4 g / l of Ca (OH) ₂ dissolved in 100 cc) were placed in a pressure-resistant stainless steel pot and sealed, and then treated at 150 ° C. for 2 hours. The residue is then filtered through filter paper, dried and the residue weight W ₂ is measured,
CI is calculated by the following formula. CI = W ₂ / W ₁ × 100

4. Heat of fusion of crystal: ΔH (joule / g) About 10 mg of a sample was precisely weighed and placed in an open container in a free state, and using DSC-2C type manufactured by Perkin Elmer Co., Ltd., a heating rate of 10 ° C./in a nitrogen gas atmosphere. 28 minutes from room temperature
Measured up to 0 ° C and calculated from the area of the crystal melting endotherm ΔH
(Joule / sample 1 g) was determined. 5. Tensile strength of fiber (gram / denier: g / d) According to JISL-1015, pre-conditioned humidity monofilament is pasted on a mount so that the test length is 10 cm, and 25 ° C x 60% R
Leave in H for 12 hours or more, then Instron 1122
Using a 2 kg chuck, the breaking strength (that is, the tensile strength) was determined at an initial load of 1/20 g / d and a tensile speed of 50% / min, and an average value of n ≧ 10 was adopted. Denier (d)
Is 1/20 g / d, cut into a length of 30 cm under load,
The average value of n ≧ 10 was shown by the gravimetric method. The tensile strength was measured using the single fiber after the denier measurement, and one fiber was made to correspond to the denier. Also, the fiber length is short and the test length is 10 cm.
When it was not possible to measure, the maximum length was used as the sample length, and measurement was performed according to the above measurement conditions.

6. Autoclave resistance (wet bending strength of slate plate WBS) PVA-based synthetic fibers cut to a length of 4 to 8 mm are 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 with a Hascheck machine. Wet papermaking with 1 part blending, and curing at 50 ℃ for 12 hours, then 150 ℃ × 2
0 hours, 160 ° C x 15 hours, 170 ° C x 15 hours, 1
After autoclaving at 80 ° C for 10 hours to prepare a slate plate, JISK-6911
After soaking in water for 1 day, the bending strength was measured in a wet state. 7. Hot water stability temperature (° C) About 1 g of crosslinked fiber or cloth and about 200 cc of water are put into a mini color dyeing machine (made by Texum Giken) without tension, heated to 110 ° C in 30 minutes, and up to 110 to 130 ° C. 5 ° C
After processing for 40 minutes each at intervals, the fiber condition is visually judged,
The maximum temperature without shrinkage or sticking was defined as the hot water stable temperature.

Examples 1 and 2 and Comparative Examples 1 and 2 PV having a viscosity average degree of polymerization of 1700 (Example 1) and 3500 (Example 2) and a saponification degree of 99.5 mol%.
A of 15% by weight (Example 1) and 11% by weight, respectively
(Example 2) Dimethyl sulfoxide (DM
SO) at 110 ° C. and the resulting solutions were added to 1000
It was discharged from the nozzle of the hole and wet-spun in a coagulation bath of methanol / dimethyl sulfoxide = 6/4 (weight ratio) at 7 ° C. Further, the film was wet stretched 4 times in a methanol bath at 40 ° C., and then the solvent was almost completely removed with methanol. In the final methanol extraction bath, the boiling point of methoxylated both terminal aldehydes of 1,9-nonanedial was about 3
After adding 1,1,9,9-tetramethoxynonane at 00 ° C. so as to contain 4% by weight to form a uniform solution, the fibers were allowed to stay for 1.5 minutes and the acetal was formed inside and on the surface of the methanol-containing fiber. The compound was included and dried at 120 ° C. In Example 1, the obtained fiber raw yarn was 170 ° C. and 2
Dry hot drawing with a total draw ratio of 17.2 was carried out in a hot-air stove consisting of three sections of 00 ° C. and 230 ° C. In Example 2, the total drawing was carried out in a hot-air stove consisting of three sections of 170 ° C., 210 ° C. and 240 ° C. Dry drawing was performed at a magnification of 17.5 times to obtain a multifilament of about 1800 denier / 1000 filaments. Next, both drawn yarns were mixed with sulfuric acid 20 g /
1 was immersed in an aqueous solution of 70 ° C. for 30 minutes to cause a cross-linking reaction (137 / C ^0.05 when C = 20 g / l and T = 70 ° C.).
= 117.9 ° C). In Examples 1 and 2, smoke and odor were hardly felt during dry heat stretching, and there was no problem in working environment.

As Comparative Example 1, 1,9-nonanedial having a boiling point of about 240 ° C. was used in place of 1,1,9,9-tetramethoxynonane in the method of Example 1, and was stretched. The total draw ratio was reduced to 16.5 times, probably because part of 9-nonanedial was oxidized to carboxylic acid and became acidic. In addition, there was smoke and odor during stretching, which was a problem in the working environment. Also, as Comparative Example 2, a drawn yarn containing no 1,1,9,9-tetramethoxynonane in the method of Example 2 (total draw ratio: 17.
5 times) formalin 100 g / l + sulfuric acid 80 g / l
The solution was immersed in the aqueous solution of 80 ° C. for 60 minutes to cause a formalization reaction. In case of slate board evaluation, each cross-linked yarn is 6m
It was cut into m and used. Table 1 shows the average degree of polymerization and physical properties of the fibers obtained in the above Examples and Comparative Examples.

[0042]

[Table 1]

Example 3 and Comparative Example 3 Viscosity average degree of polymerization is 8000 and saponification degree is 99.9 mol%.
170% of PVA-based polymer to a concentration of 8% by weight
Dissolved in ethylene glycol at ° C. The resulting solution is
It is discharged from a nozzle of 00 hole and is composed of methanol / ethylene glycol = 7/3 by dry-wet spinning method.
Quenched and gelled in a coagulation bath at ℃. Further, the film was wet-stretched 4 times in a 40 ° C. methanol bath, and then almost all of the solvent was removed with methanol. The final methanol extraction bath is 1,9-
Boiling point of about 330 ℃ obtained by acetalizing nonanedial both terminal aldehyde with ethylene glycol, 1.
After adding 9-nonanediar-bisethylene acetal so as to be 8% by weight / bath to form a uniform solution, the fibers are allowed to stay for 2 minutes to contain the acetal compound inside and on the surface of the fibers and dried at 130 ° C. did. 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 19.4 times, the viscosity average degree of polymerization was 8200, and the acetal compound content was 3.7%.
A multifilament consisting of 1000d / 400 filaments was obtained. Then, the drawn yarn was cut into 6 mm, and then in a 75 ° C. aqueous solution containing sulfuric acid at a concentration of 10 g / l (13
7 / C ^0.05 = 122.1) for 30 minutes to proceed the crosslinking reaction. The obtained crosslinked fiber has an internal crosslinking index of 85.6,
Tensile strength 19.5 g / d [(DT) ^5.8 = 30.4 × 1
0 ⁶ ] and WBS even at 180 ° C autoclave
Had a very excellent performance of 295 kg / cm ² . Further, even during the hot stretching treatment, there were no problems such as smoking or odor, and the working environment was never contaminated.

As Comparative Example 3, phosphoric acid was added to 0.0 instead of 1,9-nonanedial-bisethylene acetal.
5% by weight / bath was added and dry heat drawing was carried out in the same manner as in Example 3 to obtain a fiber having only acid crosslinking. The internal crosslinking index was 47.8 and the fiber tensile strength was 16.9 g / d. Was considerably inferior to the result.

Example 4 Comparative Examples 4 to 5 Obtained by acetalizing both terminal aldehydes of 1,6-hexanedial with methanol in place of 1,1,9,9-tetramethoxynonane in Example 2 above. 1,1,6,6-tetramethoxyhexane (boiling point about 350
Cross-linked P by the same method except that 5% by weight) is used.
VA fiber was obtained (Example 4). In this example as well, smoke and odor were hardly felt during dry heat drawing, and there was no problem in working environment. In Example 2 above, instead of 1,1,9,9-tetramethoxynonane,
A crosslinked PVA fiber was obtained by the same method except that 5% by weight of 1,1,3,3-tetramethoxypropane (boiling point: about 185 ° C.) obtained by acetalizing both terminal aldehydes of malonaldehyde with methanol was obtained ( Comparative example 4).

In the second embodiment, 1,1,9,9
-Instead of tetramethoxynonane, 1,1,5,5-tetramethoxypentane obtained by acetalizing both ends of glutaraldehyde with methanol (boiling point about 250
Cross-linked P by the same method except that 5% by weight) is used.
A VA fiber was obtained (Comparative Example 5). The physical properties of the fibers obtained in these Examples and Comparative Examples are shown in Table 2 below.

[0047]

[Table 2]

Example 5 A completely saponified PVA having a viscosity average degree of polymerization of 4000 was concentrated to 1
Dissolve the resulting solution in DMSO to 2% and add 4
Discharge from the 00 hole nozzle and methanol / DMSO
= 7/3 (weight ratio) wet spinning was performed in a coagulation bath at 7 ° C. Further, the film was wet-stretched 4 times in a methanol bath, and then the solvent was almost completely removed with methanol. Add 1,1,9,9-tetramethoxynonane to the final methanol extraction bath.
The content of the acetalized product was added to the inside and the surface of the fiber, and the product was dried at 120 ° C. The obtained spun raw yarn was subjected to dry heat drawing with a total draw ratio of 16.0 times in a hot air oven consisting of three sections of 170 ° C., 200 ° C. and 235 ° C. to obtain a multifilament consisting of 1500 denier / 400 filaments. Tensile strength of drawn yarn is 1
7.2 g / d, tetramethoxynonane content 3.9% by weight
Met. Then, the drawn yarn was cut into 8 mm, and sulfuric acid 8
70g x 20 at 0g / l [(80) ^0.05 = 1.245]
It was subjected to a minute treatment to cause a crosslinking reaction. The crosslinked yarn obtained is
It has an internal cross-linking index of 88.4, a tensile strength of 14.1 g / d [(DT) ^5.8 = 4.63 × 10 ⁶ ], and has a WBS of 256 kg / cm ² after 180 ° C. autoclave treatment, which is heat and moisture resistant. It became a high-strength PVA fiber. In this example as well, smoke and odor were hardly felt during dry heat drawing, and there was no problem in working environment.

Example 6 and Comparative Examples 6 to 7 Viscosity average degree of polymerization is 1700 and degree of saponification is 99.5 mol%.
10% PVA in DMSO to a concentration of 17% by weight.
Dissolve at 0 ° C., discharge the obtained solution from a nozzle having 0.12φ × 60 holes, and methanol / DMSO = 7/3
Wet spinning was performed in a coagulation bath with a weight ratio of 10 ° C. 40 ° C
After 3.5 times wet drawing in a methanol bath, 1,2,9,9-tetramethoxynonane was added to the final methanol extraction bath.
It was added so that it would be wt%, and dried at 120 ° C. The obtained spun raw yarn was drawn in a radiation furnace consisting of two sections at 170 ° C. and 200 ° C. so that the total draw ratio was 10 times,
A multifilament of 195 denier / 60 filaments was obtained. The drawn yarn had a tensile strength of 12.6 g / d and a tetramethoxynonane content of 1.3% by weight. Next, the drawn yarn is twisted at 80 T / m to form a pellicle shape, and a bath ratio of 1:50 is added to an aqueous dispersion of tetramethoxynonane 5 g / l + sulfuric acid 1.5 g / l + sodium dodecylbenzenesulfonate 0.5 g / l. It was put in a mini color dyeing machine [(1.5) ^0.05 = 1.02]. The temperature was raised from 60 ° C. to 98 ° C. over 1 hour, crosslinked at this temperature for 30 minutes, washed with water, and dried at 60 ° C. The CI of the crosslinked yarn was 91.8, indicating that the crosslinking had proceeded to the inside of the fiber. Fiber tensile strength is 9.1 g / d [(DT) ^5.8 = 0.365 × 10 ⁶ ].
However, the stable temperature of hot water without tension is 120 ° C,
It has been found that it can be used as a fiber for clothing. In this example as well, smoke and odor were hardly felt during dry heat drawing, and there was no problem in working environment.

In Comparative Examples 6 to 7, the sulfuric acid concentration was 20 g / l (137/20 ^0.05) as the crosslinking treatment condition in Example 5.
= 117.9) and the treatment bath temperature was changed to 98 ° C (Comparative Example 6), and the sulfuric acid concentration was 10 g / l (137/10).
^0.05 = 122.1) and the treatment bath temperature was changed to 110 ° C. (Comparative Example 7). In the case of Comparative Example 6, since the sulfuric acid concentration is high relative to the treatment bath temperature, the fiber physical properties are
The CI was 94.1 and the tensile strength (DT) was 4.5 g / d. On the other hand, in the case of the fiber of Comparative Example 7, the fiber physical property obtained was CI 9 because the treatment bath temperature was high for the sulfuric acid concentration.
The tensile strength (DT) was 5.2 and was 3.8 g / d.

[0051]

INDUSTRIAL APPLICABILITY In the present invention, since the acetalization product of the aliphatic dialdehyde having 6 or more carbon atoms, which is used as the acetalizing agent, has a high boiling point, there is no scattering, odor, or thermal decomposition during hot stretching, The PVA-based fiber, which has not been hitherto high strength and is excellent in moist heat resistance, is obtained by infiltrating the acetalizing agent to the inside of the fiber before the inside of the fiber and causing intermolecular crosslinking under a relatively mild crosslinking treatment condition after hot drawing. Is obtained. The fiber of the present invention is used in general industrial materials such as ropes, fishing nets, tents, and civil engineering sheets, as well as in the field of autoclave curing cement reinforcements where high temperature autoclave curing is performed, and further, it is mixed with polyester fiber to disperse dyes and the like. It can be widely used in fields such as clothing materials where high temperature dyeing is performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an internal cross-linking index (CI) and a tensile strength (DT) of a fiber defined in the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinori Hitomi 1-2-1, Kaigandori, Okayama-shi, Kuraray Co., Ltd. (72) Inventor Shimizu Akira, 2045 Sakata, Kurashiki-shi, Okayama, Kuraray Co., Ltd. (72) Inventor, Yoshinori Ando, Kuraray Co., Ltd., 2045, Satsuki, Kurashiki, Okayama Prefecture (72) Inventor, Hiroshi Sumura, 145, 2045, Satsuki, Kurashiki, Okayama, Kuraray Co., Ltd.

Claims (5)

[Claims] 1. Crosslinked with an acetalized product of an aliphatic polyaldehyde having 6 or more carbon atoms, and the internal crosslinking index (CI) and the tensile strength (DT) of the fiber are expressed by the following formulas (1) to (1).
Polyvinyl alcohol fiber satisfying (3). CI ≥ 86.5-2 x 10 ^-6 x (DT) ^5.8 ... (1) CI ≥ 75 ... (2) DT ≥ 5 g / d ... (3) 2. The polyvinyl alcohol fiber according to claim 1, wherein the acetalized product of an aliphatic polyaldehyde having 6 or more carbon atoms is a nonanedial acetalized product. 3. A polyvinyl alcohol fiber obtained by spinning a solution of a polyvinyl alcohol polymer and wet drawing, containing an acetalized product of an aliphatic polyaldehyde having 6 or more carbon atoms, and then dry-heat drawing the fiber. And a tensile strength of 10 g / d or more, followed by treatment with a sulfuric acid aqueous solution bath satisfying the following formula (4). 137 / C ^0.05 −52 ≦ T ≦ 137 / C ^0.05 −32 (4) [where C means the sulfuric acid concentration (g / l) in the sulfuric acid aqueous solution bath, and T means the treatment temperature (° C.). ] 4. The method for producing a polyvinyl alcohol fiber according to claim 3, wherein the acetalized product of an aliphatic polyaldehyde having 6 or more carbon atoms is a nonanediacetalized product. 5. The method for producing a polyvinyl alcohol fiber according to claim 3, wherein the dry-heat drawn fiber is used as a cut fiber and then treated with a sulfuric acid-containing bath.