JP2869137B2 - Method for producing polyvinyl alcohol fiber excellent in hot water resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polyvinyl alcohol (hereinafter abbreviated as PVA) fiber having excellent hot water resistance, particularly for industrial materials and for reinforcing composite materials. An object of the present invention is to provide a method for producing a PVA-based fiber which is effective in a field of application requiring hot water such as hot water.

<Conventional technology> Conventionally, PVA-based fibers have higher strength and modulus than polyamide, polyester and polyacrylonitrile-based fibers, and are used not only as fibers for industrial materials, which are their main applications, but also as fibers for substituting asbestos in recent years. Used in

As a method for obtaining a high-strength PVA-based fiber, a high-strength fiber or a method for producing the high-strength fiber utilizing the concept of gel spinning-ultra-drawing of high molecular weight polyethylene is disclosed in JP-A-59-100710, 59-13
0314, 61-108711 and the like.

However, although PVA-based fibers obtained by these methods can realize high strength and high elastic modulus as compared with the conventional methods, they cannot satisfy the high hot water resistance required in a specific application field.

Attempts to improve the hot water resistance of PVA-based fibers have begun with water insolubilization treatment by acetalization.However, with the recent high degree of polymerization and high-strength PVA-based fibers, the molecular orientation of the amorphous part has been improved, and heat resistance to around 100 ° C has been improved. Aqueous was achieved without the insolubilization treatment described above. However, the hot water resistance under conditions exceeding 120 ° C is still inadequate, and further improvements will be made in applications such as reinforcing materials for cement moldings that require autoclave curing, and ropes that are easily affected by frictional heat. Is required.

Attempts have also been made to improve the hot water resistance by crosslinking using a peroxide compound, an isocyanate compound or boric acid (see JP-A-1-156517, JP-A-1-207435 and JP-A-1-104815). . However, in these methods, the crosslinking treatment before stretching tends to cause a decrease in strength and elastic modulus due to a decrease in stretchability, and the crosslinking treatment after stretching tends to cause decomposition and deterioration of PVA due to high-temperature heat treatment, and the effect is sufficient. The current situation is that it cannot be demonstrated.

<Problems to be Solved by the Invention> The present invention is intended to provide a method for producing a PVA-based fiber capable of producing a PVA-based fiber having excellent hot water resistance while maintaining a high strength and a high elastic modulus. It is.

<Means for Solving the Problems> That is, the present invention provides a liquid composition comprising a PVA having an average degree of polymerization of 1500 or more, an organic solvent for dissolving the PVA, and 0.5 to 20% of a surfactant based on the weight of the PVA. Spinning is performed as a spinning solution, and in the process from the spinning process to the dry heat drawing process, the surfactant in the fiber is extracted or washed and removed so that the remaining amount is less than 2% based on the weight of PVA, Thereafter, dry heat drawing is performed, and the method for producing a PVA-based fiber ".

 Hereinafter, the present invention will be described in detail.

The PVA used in the present invention has a viscosity average degree of polymerization of 1,500 or more, preferably 3,000 or more, more preferably 6,000 or more, as determined from the intrinsic viscosity of the aqueous solution at 30 ° C. Saponification degree is 98 mol% or more, preferably 99 mol% or more,
More preferably, it is 99.5 mol% or more. PVA is preferably a straight-chain PVA having a small degree of branching. When PVA having a degree of polymerization of less than 1,500 is used, the effect of the present invention is not substantially exhibited. In the present invention, other ethylenically unsaturated monomers can be contained as a copolymer as long as the content of PVA is about 2 mol% or less. The ethylenically unsaturated monomer is not particularly limited as long as it is copolymerizable with a vinyl ester represented by vinyl acetate. For example, “Poval (revised new edition)” (Polymer Publishing Association, April 1981) Issued on January 1) 281
Pp. 285 and the references cited therein can be used.

Examples of the organic solvent for dissolving PVA used in the present invention include polyhydric alcohols such as ethylene glycol, trimethylene glycol, diethylene glycol, and glycerin; aprotic polar solvents such as dimethyl sulfoxide (DMSO) and dimethylformamide; Can be exemplified as a specific example, but may contain 5% by weight or less of other solvents such as water within a range that does not hinder the practice of the present invention.

The present invention essentially requires the addition of a surfactant as a constituent factor of the liquid composition for spinning. As the surfactant, the above PVA
Dissolved in an organic solvent solution containing
It is uniformly dispersed in an organic solvent solution at a micron (μm) or less, preferably 200 μm or less, more preferably 100 μm or less, and can be extracted and removed from the yarn in a subsequent spinning and / or washing step. There is no particular limitation as long as it can exert the following, and commercially available nonionic, cationic, anionic and amphoteric surfactants or mixtures thereof can be used.

Considering the expression of the effect on the present invention, and further the solubility and dispersibility in the organic solvent solution containing PVA and the extraction and removal of the surfactant in the subsequent spinning and / or washing step in the organic solvent system, the nonionic type is considered. Use of a surfactant is recommended, and examples thereof include nonionic surfactants such as polyoxyethylene, polyoxypropylene, polyhydric alcohol, and alkylolamide.

A suitable amount of the surfactant is 0.5% or more, preferably 1% or more, and more preferably 3% or more based on the weight of PVA. It is not preferable because defoaming of the composition is difficult and extraction and removal in a subsequent step are complicated. The method of adding the surfactant may be simultaneous dissolution with PVA or post-addition to the PVA solution. When a dispersion type surfactant is used in a PVA solution, an addition method in which uniform dispersion during spinning is taken into consideration is preferable.

In the method of the present invention, a liquid composition (a stock solution for spinning) comprising an organic solvent solution of PVA and a surfactant is extruded from a nozzle into a fibrous form. The method includes a conventionally known dry method, wet method, and wet / dry method. Any method of the formula method can be adopted, but PVA which is superior in the hot water resistance intended for the present invention.
In order to obtain a system fiber, a wet method and a dry-wet method are preferred.

Incidentally, in the specification of the present application, the dry-wet method includes, in the case where the first spinning bath into which the yarn extruded from the nozzle enters is a coagulation bath having a coagulation action on the discharged yarn,
The meaning includes the case where the first bath serves as a cooling bath having a cooling action on the discharge yarn, and the case where the first bath serves as a bath having both of the above.

When the first spinning bath in the wet method and the dry-wet method is a coagulation bath, the coagulation bath is a non-solvent for PVA;
The organic solvent in the spinning solution is arbitrarily mixed, and the organic solvent that dissolves the surfactant is constituted as one component. Specific examples of the organic solvent include alcohols such as methanol, ethanol and n-propanol; ketones such as acetone, diethyl ketone and methyl iso-butyl ketone; esters of lower carboxylic acids such as methyl acetate and ethyl acetate; Examples thereof include ethers such as glycol dimethyl ether, diethylene glycol dimethyl ether, and dioxane. Further, other solvents typified by water and salts such as sodium acetate can be contained within a range that does not hinder the practice of the present invention.

The composition of the coagulation bath has a weight ratio of an organic solvent that dissolves PVA and an organic solvent that does not substantially dissolve PVA from the viewpoint of improving fiber performance in a weight ratio of 0/10 to 7/3, preferably 1/9 to 6/4. And more preferably 2/8 to 5/5. The temperature of the coagulation bath cannot be unambiguously defined depending on the solvent system used, but -30 ° C to -60 ° C, and more preferably 0 ° C to 30 ° C can be recommended as a suitable temperature range.

In the present invention, the surfactant added to the spinning stock solution after the spinning process, in the process up to the dry heat drawing process,
PV, which is to be removed from the yarn by extraction or washing, etc.
In order to make A fiber, and at the same time to make high strength and high modulus PVA fiber at the same time, the residual amount of surfactant in the yarn is P
It has been found necessary to remove to less than 2%, preferably less than 1%, by weight of VA. Still more preferably, the amount of the surfactant to be added to the spinning solution is 1 to 15% by weight based on PVA, and the removal of the surfactant after spinning is less than 1% by weight based on PVA. It was found that extraction or washing and removal were carried out to the remaining amount.

The surfactant remaining in the yarn at a level higher than the above level unfavorably affects hot water, such as increasing the affinity of the PVA fiber for water and promoting the penetration of water into the fiber.

The reason why the hot water resistance is improved by the action of adding a surfactant to the spinning solution and coagulating or extracting after spinning, or extracting and removing the surfactant during washing is not clear, but the orientation of PVA molecular chains, PVA It is presumed that it contributes to the promotion of the crystallization of, for example.

Fibers that have gone through the coagulation step or fibers that have gone through the cooling gel step are generally washed or extracted, wet stretched, dried, and dried and hot stretched to complete fiberization. In order to obtain a high-performance fiber having a tensile strength of 16 g / d or more and an elastic modulus of 350 g / d or more, a polymerization degree of 3000 or more is required.
Using PVA, wet drawing of the yarn in a state containing a solvent after spinning is taken to 2 to 6 times, and the total drawing ratio of dry heat drawing including the wet drawing ratio is 16 times or more, preferably 18 times or more. It is desirable that the ratio be at least 20 times, more preferably at least 20 times. The stretching temperature in the dry heat stretching is 200 ° C. or higher, preferably 230 ° C. or higher.

A feature of the method of the present invention is that the obtained fiber has a WTb of 5 to 30 ° C. higher in hot water than that of a conventional fiber without a surfactant. Here, WTb represents the hot water melting temperature, and after applying a load of 200 mg per denier to 25 single fibers and suspending them in water, heating at a heating rate of 1 to 2 ° C./min. Means temperature. According to the present inventors' detailed studies, WTb also shows a tendency to increase with an increase in the average degree of polymerization of PVA used in the surfactant-free fiber, but the surfactant-added fiber is It was found that WTb was always higher than that of the non-added fiber at the same degree of polymerization. It was also found that the relationship between the amount of surfactant added and the effect of improving WTb showed a tendency to increase as the amount of addition increased up to about 10%.

By the production method of the present invention, it can not be obtained by a conventionally known method, and can highly excel in hot water resistance, and has high strength,
High elastic modulus PVA fibers can be obtained. The PVA-based fiber is expected to have a wide range of application fields such as ropes, canvas and other industrial materials, asbestos substitute cement reinforcing material, tire reinforcing material, hose reinforcing material for high temperature and high pressure, reinforcing material for FRP, and autoclave curing cement reinforcing material. The ripple effect is great.

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited by the examples.

Example 1 PVA having a viscosity average degree of polymerization of 18,000 and a saponification degree of 99.8 mol% was mixed with glycerin so as to form a 5% by weight solution, and at the same time, a mixture of sucrose stearic acid mono / diester was used as a surfactant in an amount of 5% by weight based on PVA. The mixture was added and dissolved by heating at 180 ° C. under a nitrogen atmosphere to obtain a transparent homogeneous solution.

This solution was used as a spinning dope and discharged into the air from a spinning nozzle having 150 holes and a hole diameter of 0.17 mm by a dry-wet method to obtain a spinning solution.
It was dropped into a coagulation bath below mm. The composition of the coagulation bath was methanol / glycerin = 7/3 (weight ratio), and the bath temperature was 0 ° C.
Held. The spun yarn that has exited the coagulation bath is wet-drawn four times in a 40 ° C methanol bath, and the solvent and surfactant are extracted in the subsequent methanol bath, dried with hot air at 80 ° C, and dried. Yarn was obtained. The residual amount of the surfactant was 0.15% by weight based on quantitative analysis by NMR spectrum. Next, the spun yarn was drawn in a hot air oven at 256 ° C. so that the total draw ratio became 18.5 times. Yarn performance of drawn yarn is 420 denier, strength 22.4 g
/ dr, modulus of elasticity 537g / dr, hot water melting temperature (WTb) 178
° C.

Comparative Example 1 The same operation as in Example 1 was performed except that the surfactant was not added in Example 1, and a drawn yarn was obtained. The yarn performance of the drawn yarn was 410 denier, the strength was 22.1 g / dr, the elastic modulus was 530 g / dr, and the hot water dissolution temperature was 151 ° C.

Example 2 to Example 5, Comparative Example 2 to Comparative Example 4 Average polymerization degree of charged PVA, solvent for dissolving PVA, PVA concentration, type of surfactant, addition concentration, spinning solution temperature, solvent for coagulation, coagulation bath The operation was carried out according to the method of Example 1 while changing the temperature variously to obtain a drawn yarn. Table 1 shows the results of the residual amount of the surfactant, the yarn performance of the drawn yarn, and the hot water dissolution temperature in the spun yarn.

────────────────────────────────────────────────── (5) References JP-A-62-289606 (JP, A) JP-A-64-85312 (JP, A) JP-B-43-7429 (JP, B1) (58) Field (Int.Cl. ⁶ , DB name) D01F 6/14 D01F 6/50 D01F 11/06

Claims (2)

(57) [Claims] 1. A spinning solution comprising a liquid composition comprising polyvinyl alcohol having an average degree of polymerization of 1500 or more, an organic solvent for dissolving the polyvinyl alcohol and a surfactant of 0.5 to 20% by weight based on the weight of the polyvinyl alcohol. In the steps from the spinning step to the dry heat drawing step, the surfactant in the fiber is extracted or washed and removed so that the remaining amount is less than 2% based on the weight of polyvinyl alcohol, and then the dry heat drawing For producing polyvinyl alcohol-based fibers 2. The amount of the surfactant to be added to the spinning solution is from 1 to 15% based on the weight of polyvinyl alcohol, and the amount of the surfactant in the fiber after spinning is based on the weight of polyvinyl alcohol. 2. The method for producing a polyvinyl alcohol-based fiber according to claim 1, wherein the extraction or washing is performed so as to be less than 1%.