JP2001146679A - Polyvinyl alcohol-based fiber and cured material of water-curable material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based fiber exhibiting excellent mechanical properties and a humid heat resistance even on using it under a severe condition, a water-curable material-reinforcing material, a cured material of the water curable material and a method for producing the same cured material. SOLUTION: This polyvinyl alcohol-based fiber is obtained by forming a cross-linking structure with a 2-8C aldehyde compound and its hot water extract solution shows >=4.5 pH value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol fiber suitable as a reinforcing material for hydraulic material having excellent wet heat resistance, a hydraulic hardened product using the fiber, and a method for producing the same.

[0002]

2. Description of the Related Art Polyvinyl alcohol (PVA) fibers are widely used in various applications because they have high strength and high elastic modulus among general-purpose fibers, but because of their high hydrophilicity, they are resistant to moisture. There was a problem with low thermal properties. From the above, various methods have been studied for increasing the moist heat resistance of PVA-based fibers. For example, JP-A-63-120107
In the official gazette, it is described that the fibers are formalized. However, in the formalization treatment, only a small part of the amorphous region is made hydrophobic, and industrial materials and high-temperature autoclaves that are repeatedly exposed to moist heat for a long time are repeatedly used. It is not suitable as a reinforcing material for hydraulic materials to be cured. As described above, it is possible to highly enhance the wet heat resistance of the PVA-based fiber by crosslinking the PVA-based fiber with the use of a dialdehyde compound or an acetalized compound thereof, as disclosed in JP-A-5-163309 and JP-A-5-26.
No. 3311, JP-A-9-132816, and the like.

[0003]

According to such a method, P
Although the moisture-heat resistance of the VA-based fiber can be increased to some extent and excellent moisture-heat resistance and mechanical performance can be obtained under normal use conditions, it can be stored for an extremely long time, or can be stored at 160 ° C. or higher, particularly 175 ° C. or higher. When exposed to severe moist heat conditions, there was a problem that coloring and mechanical performance of the fiber were likely to deteriorate. The purpose of the present invention is to provide excellent mechanical performance, even when used under more severe conditions,
An object of the present invention is to propose a PVA-based fiber exhibiting wet heat resistance, a hydraulic material reinforcing material using the fiber, a hydraulic cured product, and a method for producing a hydraulic cured product.

[0004]

The present invention is characterized in that (1) a crosslinked structure is formed by an aldehyde compound having 2 to 8 carbon atoms, and the pH of the hot water extract is 4.5 or more. (2) a crosslinked structure is formed by an aldehyde compound having 2 to 8 carbon atoms,
And a hydraulic material reinforcing material comprising a polyvinyl alcohol fiber having a pH of the hot water extract of 4.5 or more, (3) a crosslinked structure formed by an aldehyde compound having 2 to 8 carbon atoms, and A hydraulically cured product comprising a polyvinyl alcohol fiber having a pH of 4.5 or more.
(4) A mixture containing a polyvinyl alcohol-based fiber having a crosslinked structure formed of an aldehyde compound having 2 to 8 carbon atoms and a pH of a hot water extract of 4.5 or more and a hydraulic material is heated to 130 to 200 ° C. Autocure under temperature conditions
And a method for producing a hydraulically cured product subjected to a curing treatment.

[0005]

DETAILED DESCRIPTION OF THE INVENTION First, in the present invention, a compound having 2 carbon atoms is used.
As described above, a crosslinked structure must be formed by an aldehyde compound having preferably 3 or more carbon atoms, more preferably 4 or more carbon atoms. When the carbon number of the aldehyde compound is too small, the PVA constituting the fiber is not sufficiently hydrophobized, so that the wet heat resistance becomes insufficient. Further, as the number of carbon atoms increases, volatilization hardly occurs during the fiber production step, the crosslinking reaction, and the like, so that a desired crosslinked structure is efficiently formed. As for the fiber having the crosslinked structure, the elution rate of the fiber with respect to the hot alkaline liquid is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. Fibers with high alkali resistance can be used favorably even when used in an alkaline environment such as a reinforcing material for hydraulic materials, and those with a low elution rate to hot alkaline liquid are more fully cross-linked to the fiber interior. It can be said that the structure is formed.

However, high moisture-heat resistance cannot be obtained simply by forming a crosslinked structure with the aldehyde compound. That is, even at the beginning of fiber production, even high-strength, high-grade fibers can be stored for an extremely long period of time or exposed to severe moist heat conditions (eg, autoclave treatment) at 160 ° C. or higher, especially 175 ° C. or higher. If it is stained, there arises a problem that the fiber is easily colored or the mechanical performance of the fiber is easily impaired.

The present invention has found that the cause of the problem lies in the acid catalyst imparted during the crosslinking reaction, and solves the problem by setting the pH of the hot water extract of the PVA-based fiber to a specific range. It is. Specifically, the pH of the hot water extract of the fiber is 4.5 or more, preferably 5 or more, and more preferably 6 or more. If the pH of the hot water extract is too low, it will be stored for an extremely long time, or if it is subjected to severe moist heat conditions such as 160 ° C. or higher, especially 175 ° C. or higher, the coloring or the mechanical performance of the fiber will be impaired. The problem that becomes easy to be caused arises.

However, when a crosslinked structure is formed by an aldehyde compound having a large number of carbon atoms, it is difficult to obtain a fiber having a pH of the hot water extract in the above range. In other words, when a crosslinked structure is formed by an aldehyde compound having a large number of carbon atoms, an extremely high hydrophobic region is formed in the polymer constituting the fiber. Therefore, even if neutralization and washing are performed, the acid catalyst existing in the hydrophobic region can be sufficiently removed. Cannot be removed. From the above, it is necessary to make the number of carbon atoms of the aldehyde compound that forms a crosslinked structure in the vinyl alcohol-based polymer constituting the fiber 8 or less, preferably 7 or less, more preferably 6 or less. By forming a crosslinked structure using an aldehyde compound having a relatively small number of carbon atoms, the effects of the present invention are sufficiently exhibited.

Examples of the aldehyde compound which forms a crosslinked structure in the polymer constituting the PVA fiber include a monoaldehyde compound and / or a dialdenide compound. From the viewpoint of further improving the wet heat resistance of the fiber by introducing an intermolecular crosslink. Is preferably formed at least with a dialdehyde compound to form a crosslinked structure.

As the aldehyde compound for forming a crosslinked structure, an aromatic aldehyde compound, an aliphatic aldehyde compound and the like can be used, but the crosslinked structure is formed by the aliphatic aldehyde compound because the crosslinking agent easily penetrates into the fiber. Is preferred. Preferable examples include butanedial, pentanedial, hexanedial, heptanedial, octanedial, 2,4-dimethylhexanedial, and 5-methylheptanedial.
Of course, a crosslinked structure may be formed by two or more aldehyde compounds.

In the present invention, the aldehyde compound may be used as it is as a cross-linking agent to form a cross-linked structure in PVA, but the compound which becomes the aldehyde during the cross-linking reaction may be used as the cross-linking agent. From the viewpoint of suppressing the occurrence of volatilization and oxidation, it is preferable to use a crosslinking agent having a boiling point of 190 ° C. or higher, more preferably 230 ° C. or higher, particularly 260 ° C. or higher. In particular, it is preferable to use an acetalized product of an aldehyde compound, especially an acetalized product of a dialdehyde compound, as a cross-linking agent. preferable. When the terminal is acetalized, it is hardly oxidized even during dry heat drawing, so that the cross-linking agent is hardly decomposed or smoke or a decomposed gas is hardly generated. It is possible to perform high-magnification stretching (enhance the mechanical performance of the fiber), and then to form an aldehyde during the crosslinking reaction to efficiently form a crosslinked structure, so that a higher performance PVA-based fiber can be obtained. For example, when an acetalized aliphatic dialdehyde is used as compared with a case where an aliphatic dialdehyde is used as a cross-linking agent, the tensile strength of the obtained fiber depends on the degree of polymerization of the PVA-based polymer. dtex is improved.

Crosslinking reaction progress, progress inside fiber, P
From the viewpoint of VA crystal orientation and the like, a diacetal compound having 20 or less carbon atoms is more preferable. Of course, two or more diacetal compounds may be used in combination, or an aldehyde compound and an acetal compound may both be used as a crosslinking agent. As particularly preferred acetalized aliphatic dialdehyde, the aliphatic dialdehydes are reacted with alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol and propylene glycol, and both ends or one end is acetalized. Compounds. Among them, diacetal compounds are more preferred.

More specifically, 2-methyl-1,1,1,
3,3-tetramethoxypropane, 2-methyl-1,
1,3,3-tetraethoxypropane, 2-methyl-1,1,3,3-tetrapropoxypropane, 2-methyl-1,1,3,3-tetrabutoxypropane, 1,
1,4,4-tetramethoxybutane, 1,1,4,4-
Tetraethoxybutane, 1,1,4,4-tetrapropoxybutane, 1,1,4,4-tetrabutoxybutane,
1,1,5,5-tetramethoxypentane, 1,1,
It is preferable to use at least one selected from 5,5-tetraethoxypentane, 1,1,5,5-tetrapropoxypentane and 1,1,5,5-tetrabutoxypentane.

Hereinafter, a preferred example of the method for producing a PVA-based fiber of the present invention will be described in detail. First, the PVA-based fiber of the present invention is a fiber containing a vinyl alcohol-based polymer, and does not need to be composed of only the vinyl alcohol-based polymer. For example, it may contain other components, and may be a composite fiber with another polymer or the like, a sea-island structure fiber, or the like. However, from the viewpoint of sufficiently obtaining the effects of the present invention, the content of the vinyl alcohol-based polymer should be 30% by mass or more, and
It is preferable that the fiber contains 0% by mass or more, more preferably 80% by mass or more.

[0015] The vinyl alcohol-based polymer constituting the PVA-based fiber is not particularly limited.
500 or more, more preferably 1700 or more, particularly preferably 2000 or more. 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 become defects, so that high strength, high elastic modulus,
It is preferable because high hot water resistance is easily obtained. However, the degree of polymerization is 30
A PVA-based polymer having a molecular weight exceeding 000 is generally difficult to produce, and is not necessarily suitable from the viewpoint of industrial production. The saponification degree is preferably 98.5 mol% or more, particularly preferably 99.0 mol% or more, from the viewpoints of wet heat resistance and fiber strength. Further, it may be modified or copolymerized with other components as long as the effects of the present invention are not impaired.

The method of spinning the vinyl alcohol polymer is not particularly limited, and examples thereof include dry spinning, wet spinning, and dry-wet spinning using a PVA solution as a spinning solution. From the viewpoint of fiber performance and the like, it is preferable to dissolve the vinyl alcohol-based polymer in an organic solvent and defoam it to obtain a spinning stock solution. As the organic solvent at this time, for example, glycerin, ethylene glycol, diethylene glycol,
Examples include polyhydric alcohols such as triethylene glycol and butanediol, dimethyl sulfoxide, dimethylformamide, diethylene triamine and the like. These two
A mixed solvent of at least one kind may be used, and a mixture of an organic solvent and water may be used. Among them, dimethyl sulfoxide,
Polyhydric alcohols such as glycerin and ethylene glycol are preferable because they form a uniform gel structure when poured into a coagulation bath, and as a result, high-strength fibers are obtained. Further, boric acid, a surfactant, a decomposition inhibitor, various stabilizers, a dye, a pigment, and the like may be added to the spinning dope.

The polymer concentration in the spinning dope is 5 to 5
The amount is preferably 0% by mass, particularly preferably 5 to 30% by mass when using a wet spinning method or a dry-wet spinning method, and 10 to 50% by mass when using a dry spinning method. The temperature of the spinning dope is generally 40 to 230 ° C, and particularly preferably 100 ° C or higher in the case of a spinning dope using an organic solvent.

The spinning solution thus obtained is wet-processed,
It is spun and solidified by any of a dry spinning method and a dry and wet spinning method. It is preferable to employ a wet or dry-wet spinning method from the viewpoints of manufacturing processability, cost, and the like, and a solidified yam can be obtained by discharging a spinning stock solution into a solidifying bath. For example, when a PVA aqueous solution is used as the spinning solution, the solution may be discharged into a conventionally known solidifying solution such as a saturated sodium sulfate solution. When a spinning solution using an organic solvent is used, alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, an aqueous alkali solution and an aqueous alkali metal salt solution, or a mixed solution thereof Can be suitably used as a solidification liquid. At this time, in order to form a uniform gel structure by slowly performing solvent extraction in coagulation and to obtain higher strength and hot water resistance, the coagulation bath solution is mixed with a solvent constituting a spinning solution at 10% by mass or more. Is preferred.
In particular, a mixed solvent in which the mass ratio of an alcohol represented by methanol and a stock solution solvent is 9/1 to 6/4 is preferable. It is also preferable to set the coagulation bath solution to 20 ° C. or lower and rapidly cool the discharged spinning dope to form a gel having a uniform microcrystalline structure in order to obtain a high-strength fiber. Further, it is preferable to set the coagulation bath temperature to 10 ° C. or lower because the coagulated yarn becomes more homogeneous.

It is preferable that the fiber thus solidified be subjected to wet drawing at least twice in a state containing a solvent in order to reduce sticking between the fibers and facilitate subsequent dry heat drawing. 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 stretching. Next, when a solution obtained by dissolving PVA in an organic solvent is used as a spinning solution, solvent extraction is performed.
As the extractant, primary alcohols such as methanol, ethanol and propanol, ketones such as acetone, methyl ethyl ketone, methyl propyl ketone and methyl isobutyl ketone, ethers such as dimethyl ether and methyl ethyl ether, and water are used. You.
Subsequently, an oil agent or the like is applied as necessary, and the extracted fiber is dried. 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.

At this time, it is preferable to add the cross-linking agent before the PVA is highly oriented and crystallized by dry drawing, from the viewpoint of sufficiently penetrating the cross-linking agent into the interior of the fiber. Spinning solution,
A cross-linking agent may be added to the solidification liquid or a cross-linking agent may be added to the fiber after dry heat drawing.However, in the former method, the cross-linking agent may flow out of Itoshino during the solidification reaction, and In the method, the polymer constituting the fiber is highly crystallographically oriented, so that it becomes difficult for the crosslinking agent to penetrate into the fiber. Therefore, it is preferable to add a crosslinking agent in the steps from the solidifying bath to the dry heat stretching step after the bathing. By employing such a method, the crosslinking agent can be sufficiently penetrated into the interior of the fiber.

When a spinning solution containing an organic solvent is used, it is preferable that a crosslinking agent is added to an extract for extracting the organic solvent, and the crosslinking agent is applied by passing the solution through the extraction bath. . In such an extraction bath, since the PVA fibers are swollen, the cross-linking agent can easily penetrate into the interior of the fibers, and is also preferable from the viewpoint of processability. In the case of dry spinning, this method cannot be adopted because such an extract is not used. From the above points, it is preferable to use an undiluted spinning solution containing an organic solvent, and it is particularly preferable to employ a wet spinning method or a dry-wet spinning method.

The amount of the cross-linking agent attached to the fibers should be 0.3% by mass or more / fiber, in order to sufficiently form a cross-linked structure.
Further, the content is preferably 0.7% by mass or more / fiber, particularly preferably 2% by mass or more. From the addition of suppressing the molecular orientation and decomposition of PVA, 10% by mass or less / fiber, and further 6% by mass / fiber Is preferred.

A cross-linked structure can be formed by applying an acid catalyst after the cross-linking agent is applied, but it is preferable to form the cross-linked structure after performing dry heat drawing from the viewpoint of improving the mechanical performance of the fiber. . If a crosslinked structure is formed before dry heat drawing, it is difficult to draw at a high magnification, and it becomes difficult to obtain a fiber having high strength. The temperature of dry heat stretching is 200 ° C or more,
The temperature is preferably 220 ° C. or higher, and more preferably 260 ° C. or lower, and further preferably 240 ° C. or lower from the viewpoint of not impairing the fiber performance. The stretching ratio may be changed depending on the application, desired mechanical performance, etc., but when high strength is desired, the total stretching ratio is preferably at least 14 times, particularly preferably at least 15 times, more preferably 2% or more. It is preferable that the draw ratio is 3 to 10 times and the dry heat stretching ratio is 3 to 10 times. Note that the total stretching ratio here is a value represented by the product of the stretching ratio of the wet stretching performed before the drying treatment and the stretching ratio of the dry stretching. The strength of the fiber in which the crosslinked structure is formed is 9 cN / dtex or more, further 10 cN / dtex or more, and further 11 cN / d.
tex or more is preferable. In addition, as for the fiber before the crosslinked structure is formed, it is preferable that the strength is as high as possible because the fiber strength is reduced when the crosslinked structure is formed.
Specifically, 10 cN / dtex or more, and further 11 cN / dtex
It is preferably at least dtex, more preferably at least 12 cN / dtex, particularly preferably at least 13 cN / dtex.

At this time, the higher the boiling point of the cross-linking agent, the less the volatilization or the cross-linking reaction proceeds even during the dry stretching, and the effect is further enhanced particularly when the acetal compound described above is used. . Therefore, even if a cross-linking agent is applied before the dry heat drawing, problems such as the cross-linking reaction progressing and the drawability being impaired hardly occur, and a fiber having high strength and excellent wet heat resistance can be obtained.

In order to introduce a crosslinked structure into the PVA fiber to which the crosslinking agent has been added, an acid catalyst may be added. The method of applying the acid catalyst is not particularly limited, but a method of dipping in an acid catalyst bath can be suitably used. Among them, a sulfuric acid aqueous solution bath can be used, and the sulfuric acid concentration is 0.2 to 30% by mass, particularly 0.5 to 1% by mass.
It is preferably 0% by mass, more preferably 1 to 5% by mass. The bath temperature is preferably 55 to 80 ° C. By adopting such a method, a reaction occurs between the hydroxyl group of PVA and the aldehyde compound to cause cross-linking, and particularly when a reaction occurs between a dialdehyde compound, intermolecular cross-linking occurs, resulting in an excellent effect. Is obtained. At the time of the cross-linking treatment, formalin may be added together with sulfuric acid to simultaneously cause formalization. Further, a small amount of a metal halide such as zinc chloride or magnesium chloride, a surfactant or the like may be added to promote crosslinking.

Next, the desired fiber is obtained by neutralizing, washing and drying the fiber. The neutralization method is not particularly limited, but can be neutralized by immersion in a desired alkaline bath or spraying an alkaline solution. As the neutralized alkali solution, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, an aqueous solution of lithium hydroxide, or the like can be used, and the alkali concentration is preferably about 2 to 15% by mass. At this time, the form of the fiber may be fixed length or non-fixed length,
The treatment time is preferably 1 to 240 minutes, particularly preferably 3 to 70 minutes.

Next, washing may be performed. As the washing with water, for example, a method of immersing the fiber in a washing bath at a fixed length or an emergency fixed length or spraying a washing liquid is preferably mentioned. From the viewpoint of sufficiently removing the acid catalyst, it is preferable to adopt a method of immersion in a washing bath, and the form of the fiber may be fixed length or non-fixed length. For the same reason, the processing time is 1 to 240 minutes, especially 3 to 7 minutes.
It is preferably 0 minutes. At this time, in order to sufficiently remove the remaining acid catalyst, the temperature of the neutralizing solution and / or the washing solution needs to be 30 ° C., preferably 40 ° C. or more, and more preferably 45 ° C. or more. If the temperature of the treatment liquid is too low, the desired catalyst cannot be obtained because the acid catalyst cannot be sufficiently removed even when the crosslinked structure is formed by an aldehyde compound having a small number of carbon atoms. By treating in a high temperature bath, the polymer that composes the fiber is relaxed, and as a result,
The acid catalyst retained in the hydrophobic region can be sufficiently removed. In order to efficiently remove the acid catalyst, it is preferable that both the neutralization bath and the washing bath have the above-mentioned temperatures. Further, from the viewpoints of efficiency, fiber performance, etc., it is preferable that the temperature of the neutralizing solution and the washing bath is 90 ° C. or lower, particularly 75 ° C. or lower. Drying the fibers gives the desired fibers.

According to the present invention, it is possible to obtain a fiber which exhibits not only high performance at the beginning of production but also high performance even after a long period of time or when left under severe conditions. Specifically, even after the dry heat test described in Examples, fibers having a tensile strength of 10 cN / dtex or more were obtained, and 85% or more, particularly 88% of the tensile strength before the dry heat test.
As described above, the strength of 90% or more can be maintained. In addition, since the fibers and the like do not deteriorate even when the dry heat treatment is performed, even when the dry heat test is performed, the fibers do not exhibit a color such as yellow or brownish color, and the fibers are high-quality white fibers.

The PVA-based fiber of the present invention can be used in various forms, for example, filament yarn, cut fiber, bundled yarn, crimped fiber, spun yarn, string, cloth (woven or knitted, non-woven fabric, etc.). No. What is necessary is just to process suitably according to the objective.

The fiber of the present invention has hot water resistance, heat aging resistance,
It is highly excellent in various properties such as storage stability and can be used for all applications, but it is particularly suitable as a hydraulic material reinforcing material because it has excellent alkali resistance and high adhesiveness to the matrix. is there. The form of the reinforcing material may be appropriately selected, such as a fiber shape or a sheet shape. From the viewpoint of uniformly reinforcing the hydraulic hardened material, it is preferable to use cut fibers, and the cut fiber may be added to the hydraulic material to obtain a fiber-reinforced hydraulic hardened material. in this case,
From the viewpoint of dispersibility and reinforcing effect, the aspect ratio (the ratio of the fiber length to the average diameter of the fibers) is 150 to 1500, particularly 3
Desirably, the fiber addition ratio in the hydraulically cured product is set to 0.1 from the viewpoint of dispersibility, reinforcing property, and the like.
It is preferably from 1 to 10% by mass, especially from 0.5 to 5% by mass.

The hydraulic material used in the present invention is not particularly limited, but cement is typical. Portland cement and other various cements, gypsum, gypsum slag, magnesia, and the like can be used. Raw materials can be mixed and used. Mortar or concrete may be obtained by mixing a hydraulic substance with sand or gravel. In the present invention, additives other than the PVA fiber and the hydraulic substance may be blended. Examples of the additive include fibers other than the fibers specified in the present invention, and wood pulp. It is preferable that the additives other than the PVA fiber and the hydraulic substance be 1 to 50% by mass based on the total mass of the molded product. The method for producing the molded article is not particularly limited,
Conventionally used wet papermaking method, fourdrinier method, vibration molding method,
A centrifugal molding method, an extrusion molding method, or the like can be employed.

Further, in the present invention, even when autoclave curing (steam curing) is performed at a high temperature, the fiber performance is not deteriorated, so that a more excellent effect can be obtained. In general, PVA-based fibers are poor in hot water resistance, so it is difficult to perform autoclave curing at a high temperature, and currently rely on autoclave curing under room temperature or low temperature heating conditions. Therefore, there is a problem that the dimensional stability and strength of the hydraulic molded product tend to be insufficient, because the curing time is longer than that of the high-temperature autoclave curing, which is not efficient.
Since the fiber of the present invention has a high moisture and heat resistance,
Autoclave curing can be performed at high temperature. For example, by using the fiber of the present invention, an autoclave treatment at 160 ° C. or higher, more preferably 170 ° C. or higher, particularly 172 ° C. or higher can be performed. The autoclave curing temperature in the present invention indicates the temperature of the atmosphere, not the temperature of the cured product. From the point of fiber performance, the autoclave curing temperature is 200 ° C or less, especially 1 ° C.
The temperature is preferably 80 ° C. or lower, and the curing time is preferably 2 to 15 hours.

The hydraulic molded product obtained according to the present invention can be used for various purposes, for example, slats, pipes, and the like.
Examples include cement / concrete moldings such as blocks, wall panels, floor panels, roofing materials, and partitions, and secondary products.

[0034]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. [Viscosity average polymerization degree (P) of PVA-based polymer] JIS
Based on K-6726, the specific viscosity (ηsp) of the diluted aqueous solution of the PVA polymer at 30 ° C. was measured at five points, the intrinsic viscosity [η] was determined by the following equation (1), and the viscosity was further determined by the following equation (2). The average degree of polymerization P was calculated. The uncrosslinked stretched fiber of the sample is dissolved in water at 140 ° C. or more under pressure so as to have a concentration of 1 to 10 g / liter.
The solution was filtered through a m glass filter, and the viscosity of the filtrate was measured. The concentration of the aqueous solution at that time was calculated using a correction value obtained by subtracting the amount of the residual gel substance from the mass of the sample. [Η] = lim (c → 0) ηsp / c (1) P = ([η] × 10 4 /8.29) 1.613 (2)

[Content of Acetalized Aliphatic Aldehyde (mass% / fiber)] An uncrosslinked drawn yarn is dissolved in deuterated dimethyl sulfoxide at 140 ° C. or higher, and NM
The peak area ratio of the acetalized compound to the peak of the CH ₂ group of the PVA-based polymer was calculated from R to determine the content. [Tensile strength of fiber (cN / dtex)] JIS L-1
In accordance with 015, a single fiber conditioned in advance was attached to a backing so as to have a test length of 10 cm, allowed to stand at 25 ° C. × 60% RH for 12 hours or more, and then instron 1122 (2 × 0.98 ) Using a cN chuck, initial load 1/2
The breaking strength (tensile strength) was determined at 2 cN / dtex and a tensile strength of 50% / min, and the average value of n ≧ 10 was adopted. The fineness (dtex) was 1/22 cN / dtex, cut to a length of 30 cm under a load, and indicated by an average value of n ≧ 10 by a gravimetric method. In addition, the tensile strength was measured using the single fibers after the fineness measurement, and each fiber was corresponded to the fineness. When the fiber length was too short to obtain a test length of 10 cm, the maximum length was used as the sample length and measured according to the above measurement conditions.

[Elution rate to hot alkaline solution (mass% /
Fiber)] A fiber having a fiber length of 8 mm was prepared by using NaOH 0.9 g / liter, KOH 3.5 g / liter, and Ca (OH) ₂ 0.
The elution ratio of the PVA-based fiber after immersion in a 150 ° C. alkaline aqueous solution having a composition of 4 g / liter at a bath ratio of 1: 100 for 4 hours was calculated. For fibers having a fiber length of 8 mm or less, the elution rate is determined under the same conditions by using the fibers without cutting them. [PH of hot water extract] The pH of a liquid obtained by immersing a fiber having a fiber length of 8 mm in ion-exchanged water at 150 ° C for 4 hours at a bath ratio of 1: 100 was determined. In addition, about the fiber whose fiber length is 8 mm or less, pH is calculated | required by the same method using a fiber without cutting it.

[Dry Heat Acceleration Test] The sample fiber was put in a hot air circulation type drier, subjected to dry heat treatment at 105 ° C. for 24 hours in the presence of air, and the color of the fiber after the treatment was observed. Further, the tensile strength after the dry heat treatment was measured, and the ratio (strength retention%) to the tensile strength before the dry heat treatment was calculated.

[Autoclave resistance WBS (MP
a)] 2 parts by mass of sample fiber cut to a fiber length of 4 to 8 mm, 3 parts by mass of wood pulp (100 ml of beating degree CSF manufactured by NUKP Paltech Co., Ltd.), silica (blur value 4)
000 Keiwa Furnace Materials Co., Ltd.) 38 parts by mass, cement (Normal Portland Cement Chichio Onoda Cement)
After wet papermaking at a mixing ratio of 57 parts by mass and primary curing at 50 ° C for 24 hours, 160 ° C, 170 ° C, 175 ° C,
Autoclave curing was performed for 15 hours at each temperature condition of 180 ° C. to produce a slate plate having a specific gravity of about 1.6. Thereafter, a test piece of 25 mm × 70 mm × 4 mm was cut out, and J
After immersing in water for 3 days according to IS K-6911,
The bending strength (MPa) of the wet test piece was measured using an autograph, and the autoclave resistance was evaluated by converting it to a bending strength of specific gravity 1.6. At this time, the span length was 50 mm, and the compression speed was 2 mm / min. [Specific gravity of slates (g / cm3)]
The mass of the molded slates after curing was dried at 100 ° C. for 24 hours, and the mass was measured. The mass was calculated from the mass of the slates and the apparent volume.

Example 1 PVA having a viscosity average degree of polymerization of 2400 and a saponification degree of 99.9 mol% was added to dimethyl sulfoxide (DMSO) at 110 ° C. so that the concentration became 12% by mass.
To prepare a spinning stock solution. The obtained spinning dope was added to 4
Methanol / DMS
The wet spinning was performed in a 5 ° C. solidification bath having O = 7/3 (mass ratio). Further, after performing 3.5 times wet stretching in a 40 ° C. methanol bath, almost all of the solvent was removed with methanol. By adding 3.5% by mass of the high-boiling diacetal compound 2-methyl-1,1,3,3-tetramethoxypropane to the final methanol extraction bath, and allowing the fibers to remain in the extraction bath for 1.5 minutes. The crosslinker was allowed to penetrate into the fibers and then dried at 150 ° C. The obtained dry raw yarn is subjected to dry heat drawing at a total draw ratio of 15 times in a hot air furnace consisting of three sections at 175 ° C, 200 ° C and 230 ° C,
A multifilament of about 1980 dtex / 400 filament was obtained. Next, the drawn yarn is cut into 8 mm and immersed in an aqueous solution having a sulfuric acid concentration of 80 g / liter and a temperature of 75 ° C. for 30 minutes to cause a crosslinking reaction.
Neutralization was performed with a 0 g / liter aqueous sodium hydroxide solution for 60 minutes, and the fiber was washed with warm water at 50 ° C. for 60 minutes and then dried to obtain a fiber. Table 1 shows the results.

Example 2 1,1,4,4 as a crosslinking agent
-Same as Example 1 except that tetramethoxybutane was added to the 3.6% by weight final extraction bath. Table 1 shows the results. Example 3 Example 1 was repeated except that 1,1,5,5-tetramethoxypentane was added as a crosslinking agent to a 4.0% by mass final extraction bath. Table 1 shows the results. Example 4 2-Methyl-1,1,3,3 as crosslinking agent
1.8% by weight of tetramethoxypropane and 1,1,
The procedure was as in Example 1, except that 4,4-tetramethoxybutane was added to the 1.8% by weight final extraction bath. Table 1 shows the results.

[Comparative Example 1] The procedure was carried out except that 1,9-nonandial-bisethylene acetal was added as a cross-linking agent to a 5.1% by mass final extraction bath, and the neutralization and washing temperatures were changed as shown in Table 1. It carried out like Example 1. Table 1 shows the results. [Comparative Example 2] The same operation as in Example 1 was carried out except that 1,9-nonandial-bisethylene acetal was added as a cross-linking agent to a 5.1% by mass final extraction bath. Table 1 shows the results. Comparative Example 3 2-Methyl-1,1,3,3 as a crosslinking agent
1.8% by weight of tetramethoxypropane and 1,1,
The procedure was as in Example 1, except that 4,4-tetramethoxybutane was added to the 1.8% by weight final extraction bath and the neutralization and washing temperatures were changed as shown in Table 1. Table 1 shows the results.

[0042]

[Table 1]

According to the present invention, high strength at the beginning of fiber production,
In addition to being excellent in alkali resistance, even after performing a dry heat test, it had high tensile strength and strength retention, and white and high-quality fibers were obtained (Examples 1 to 4). On the other hand, in Comparative Examples 1 to 3, although the acid catalyst has not been sufficiently removed, although it has high performance at the beginning of fiber production,
When a dry heat test was performed, the fiber was colored yellow to brown, and the tensile strength was reduced, resulting in a fiber having a low strength retention. In addition, with regard to the hydraulic hardened body using these fibers, the mechanical performance of the hardened body of the comparative example is significantly deteriorated particularly when the temperature is exceeded 170 ° C., and only the hardened body having a lower performance than the embodiment is obtained. Could not be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 BE061 DM006 FA041 GL00 4L033 AA05 AB01 AC05 AC15 BA08 BA09 BA99 4L035 BB03 BB07 BB15 BB85 BB89 BB91 CC02 EE20 FF01

Claims (4)

[Claims] 1. A polyvinyl alcohol-based fiber, wherein a crosslinked structure is formed by an aldehyde compound having 2 to 8 carbon atoms, and the pH of the hot water extract is 4.5 or more. 2. A hydraulic material reinforcing material comprising a polyvinyl alcohol-based fiber having a crosslinked structure formed of an aldehyde compound having 2 to 8 carbon atoms and having a pH of a hot water extract of 4.5 or more. 3. A hydraulically hardened product comprising a polyvinyl alcohol fiber having a crosslinked structure formed of an aldehyde compound having 2 to 8 carbon atoms and having a pH of a hot water extract of 4.5 or more. 4. A mixture containing a polyvinyl alcohol-based fiber having a crosslinked structure formed of an aldehyde compound having 2 to 8 carbon atoms and a pH of a hot water extract of 4.5 or more and a hydraulic material is mixed with 130 to 200. A method for producing a hydraulically cured product which is subjected to an autoclave curing treatment at a temperature of ℃.