JPH11286827A - Flame-retardant polyvinyl alcohol fiber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject flame-retardant fiber having excellent color and dry- and-wet dimensional stability and useful for protective wear, etc., by dissolving a vinyl alcohol polymer and a halogen-containing vinyl polymer in a common solvent and spinning the obtained spinning dope under a specific condition. SOLUTION: The objective flame-retardant polyvinyl alcohol fiber having a sea- island structure comprising a sea component composed of a vinyl alcohol polymer and an island component composed of a halogen-containing polymer and having a color difference of <=12 and a boiling water shrinkage of <=2% is produced by dissolving a vinyl alcohol polymer and a halogen-containing vinyl polymer such as vinyl chloride polymer in a common solvent, spinning the obtained spinning dope in a coagulation bath composed of a dope solvent and a solidifying solvent capable of solidifying the vinyl alcohol polymer by wet-spinning or dry-wet spinning, carrying out the extraction, drying and drawing of the spun fiber and subjecting the produced drawn yarn to free shrinkage treatment with hot water or steam at 85-120 deg.C. The spinning dope is preferably incorporated with 0.1-15 wt.% of a tin compound or an antimony compound based on the total weight of the polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol (hereinafter abbreviated as PVA) flame-retardant fiber having excellent dimensional stability in dry and wet conditions and good hue.
The present invention relates to a flame-retardant fiber which can be suitably used for living materials such as curtains and carpets, and industrial materials such as car seats.

[0002]

2. Description of the Related Art Among general-purpose fibers, PVA fibers have high strength, high weather resistance, high alkali resistance, and hydrophilicity. By utilizing their unique features, they are used in ropes, cold gauze, cement reinforcing materials, papermaking, etc. Many are used. PVA in it
A PVA-based flame-retardant fiber obtained by adding a halogen-containing vinyl-based polymer typified by a vinyl chloride-based polymer to the above is often used for the above-mentioned special flame-retardant applications. However, P
VA-based flame-retardant fibers have the drawback of undergoing a large dimensional change when wet because of their hydrophilicity. For application fields exposed to wet conditions, polyester-based flame-retardant fibers and the like have advanced, and PVA-based flame-retardant fibers have been developed. Flammable fibers tend to decrease.

[0003] Many attempts have been made to improve the dimensional stability of PVA-based flame retardant fibers. The most common method is to carry out intramolecular or intermolecular acetalization with formalin or the like to block and crosslink the hydroxyl groups of PVA, thereby improving the water resistance. This method can certainly increase the dissolution temperature in water, but is insufficient for reducing the shrinkage ratio (abbreviated as Wsr) when wet. Similarly, there is a method of cross-linking PVA with a divalent aldehyde such as glutaraldehyde, but it is not very effective in reducing Wsr similarly to the formalization treatment.

[0004] It is also known that a PVA-based polymer is formed into a uniform fiber cross section by gel spinning, and is highly stretched, whereby the PVA-based polymer is highly oriented and highly crystallized to obtain a high-strength PVA-based fiber. However, when the molecular chains are fully extended, molecular relaxation occurs during wetting, and the shrinkage does not decrease much. After stretching to a higher degree, by dry shrinking at or above the hot drawing temperature,
There is also known a method of reducing the shrinkage rate when wet by relaxing the extended molecular chains. Although this dry heat shrinkage treatment is effective in reducing the wet heat and the dry heat shrinkage, the polyvinyl chloride polymer (abbreviated as PVC), which is a flame retardant, is decomposed and colored yellow or brown, resulting in a commercial value. It has the disadvantage of being reduced, so that its use is limited to those areas where coloring is not a problem.

It is also known that a cut staple of PVA-based fiber having a non-circular cross-sectional structure with a skin-core structure, ie, a non-uniform cross-sectional structure, is immersed in hot water at a specific temperature to develop crimp. However, in this method, the fiber having a non-uniform cross-section structure is subjected to hydrothermal treatment under conditions near the limit at which the fiber structure is destroyed, thereby increasing the cross-sectional distortion spots, thereby aiming at the appearance of crimp, It is not an effective method for reducing the dimensional stability between wet and dry.

[0006]

As described above, the conventional PV
The A-based flame retardant fiber has a defect that it lacks dimensional stability in wet and dry conditions and is easy to be colored, although it has excellent performance as compared with other flame retardant fibers, and thus has a problem of practicality. was there. An object of the present invention is to provide a PVA-based flame-retardant fiber having excellent dimensional stability and good hue.

[0007]

An object of the present invention is to provide a liquid crystal display comprising a PVA and a halogen-containing vinyl polymer (abbreviated as PVX).
VA is a sea-island fiber of a sea component, PVX is a sea-island fiber of an island component, achieved by a PVA-based flame-retardant fiber characterized by having a color difference of 12 or less and a boiling shrinkage of 2% or less, and such a fiber. Dissolves PVA and PVX in a common solvent, wet-spins the resulting spinning solution into a solidification bath consisting of a solidification solvent having a solidifying ability for PVA and a stock solution solvent, and extracts, dries, stretches The drawn yarn obtained by
It is obtained by free shrinkage treatment using hot water or steam at ~ 120 ° C.

Hereinafter, the flame-retardant fiber of the present invention and the method for producing the same will be described in detail. The sea component constituting the fiber of the present invention, that is, the matrix component, must be PVA. PVA is the only general-purpose polymer that has a common solvent with PVX that imparts flame retardancy, and that can form strong intermolecular hydrogen bonds due to hydroxyl groups that high-strength sea-island fibers enable.

In the present invention, PVA means a polymer having a vinyl alcohol unit in an amount of 70 mol% or more of all the constituent units. Therefore, ethylene, vinyl acetate, itaconic acid, vinylamine, acrylamide, vinyl pivalate, and maleic anhydride are used. Monomers such as acids and sulfonic acid-containing vinyl compounds may be copolymerized in a proportion of less than 30 mol%. The saponification degree is preferably 80 mol% or more,
For oriented crystallization, PVA in which 95 mol% or more of all the constituent units are vinyl alcohol units is more preferable, more preferably 98 mol% or more, and even more preferably 99 mol% or more.
Mol% or more, most preferably 99.8 mol% or more. PVA
The degree of polymerization is not particularly limited, but the degree of polymerization is preferably 500 or more, more preferably 1500 or more in order to obtain a high-strength fiber. In order to improve the hot water resistance, acetalized PVA which is subjected to a post-reaction such as intramolecular and / or intermolecular acetalization with an aldehyde compound represented by formaldehyde or dialdehyde after fibrillation may be used.

The island component of the fibers of the present invention must be PVX. Only when PVX is used as the island component can the fiber of the present invention be a flame-retardant fiber. The PVX referred to in the present invention is a vinyl polymer having a unit containing a halogen element represented by chlorine or bromine in an amount of 50 mol% or more. For example, a vinyl chloride polymer (PVC), a vinylidene chloride polymer, a chlorinated polyolefin, a brominated polyolefin and the like are included. Among them, flame retardant,
PVC is preferred in terms of the balance between heat decomposition resistance and cost.

[0011] PVX has low crystallinity and does not have fiber-forming ability or has only low strength even if it is formed into fibers. In particular, in the wet spinning method which is a production method excellent in cost performance of staple fibers, PVX-based fibers are used. Is not manufactured. In the present invention, PVX is contained as an island component,
X makes the fiber generate a hydrogen halide gas when the fiber is exposed to a high temperature and burns, and functions as a functional component capable of capturing the radical generated at the time of burning and suppressing the burning. In order to maintain the dispersion stability of the PVX solution in the spinning solution, a monomer that improves the affinity with PVA may be copolymerized with the PVX, and a hydroxyl group may be used as such a copolymer component. Representative examples thereof include hydroxyethyl acrylate and hydroxyprolyl acrylate. Particularly preferred is hydroxyprolyl acrylate, and the copolymerization ratio is 2 to 15 with respect to the halogen-containing monomer.
% By weight.

In order to make PVA a sea component and PVX an island component, the PVA content is preferably 55% by weight or more and PVX is 45% or less. If the PVA content is less than 55% by weight, some of the PVX may become a sea component, which is not preferable in terms of performance and process passability due to reduced strength and elution of PVX into the extraction bath. PVA exceeds 95% by weight and PVX is 5%
If the amount is less than% by weight, the amount of halogen in the fiber is so small that flammability becomes insufficient, which is not preferable. From the balance of flame retardancy, strength, etc., the mixed weight ratio of PVA / PVX is 90/10
More preferably, it is 55/45. In the present invention, PVA or PVX is used as long as the object of the present invention is not impaired.
Polymers other than the above may be added. Further, various stabilizers, coloring agents and the like may be added.

[0013] In the present invention, in order to use inexpensive commercial PVX powder as a component of the PVA-based flame-retardant fiber, a conventional PVX powder is used.
As a result of changing the concept of A-based flame-retardant fiber and conducting intensive studies,
VA and PVX are dissolved in a common organic solvent typified by dimethyl sulfoxide, dimethylacetamide, dimethylformamide, etc., and the resulting sea-island phase separation solution containing PVA as a sea component and PVX as an island component is used as a spinning stock solution. Is spun in a solidification bath, extracted, dried, and stretched by dry heat, and then subjected to wet heat-free shrinkage treatment under specific conditions to produce an inexpensive PVX powder. An excellent fiber of the present invention can be obtained.

Further, it is preferred that the fiber of the present invention contains a tin compound or an antimony compound in an amount of 0.1 to 15% by weight based on the total weight of the polymer, because the flame retardancy is greatly improved. Of course, a tin compound and an antimony compound may be used in combination. The tin compound referred to in the present invention is not particularly limited as long as it is a compound containing a tin element, but in view of the effect of enhancing flame retardancy as a flame retardant auxiliary and cost performance, inorganic oxides such as tin oxide and metastannic acid. Is preferred. The antimony compound referred to in the present invention is not particularly limited as long as it is a compound containing an antimony element. However, inorganic compounds such as antimony pentoxide and antimony trioxide in terms of a flame retardant enhancing effect as a flame retardant aid and cost performance. Oxides are preferred. If the content of the tin compound or the antimony compound is less than 0.1% based on the total weight of the polymer, the effect of addition cannot be obtained, and the flame retardancy becomes insufficient. Even if the content exceeds 10%, the flame retardant effect reaches a plateau, which is disadvantageous in cost performance. Tin or antimony compound content
It is preferably from 0.5 to 8% by weight, more preferably from 1 to 6% by weight.

In the production method of the present invention, the stock solution for spinning is P
It is obtained by dissolving VA and PVX in a common organic solvent of PVA and PVX represented by dimethyl sulfoxide, dimethylacetamide, dimethylformamide and the like. The polymer concentration in the spinning solution is 1
0-30% by weight is preferred. In the spinning dope stage,
PVX exists in a state of being dissolved in an organic solvent and being dispersed in a PVA solution. The temperature of the spinning dope is preferably 50 to 100 ° C., and the viscosity of the spinning dope is preferably 10 to 400 poise when using wet spinning, and 50 to 2000 poise when using the dry-wet spinning method. Such a spinning stock solution is passed through a nozzle and PV
The wet or dry-wet spinning is performed in a solidifying bath having a solidifying ability for A. The wet spinning method, in which the solidification bath is brought into direct contact with the spinning nozzle, is suitable for spinning using a multi-hole nozzle because the fibers can be spun without sticking together even if the nozzle pitch is narrowed. The dry-wet spinning method in which an air gap is provided therebetween is suitable for high-speed spinning because the elongation at the air gap is large. In the present invention, the wet type or the dry-wet type can be appropriately selected depending on the purpose and application.

Examples of the solidification bath having a solidifying ability for PVA include alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and aqueous solutions containing coagulable salts. Alcohols are preferred in terms of solidification and the like, and methanol is particularly preferred. In addition, in order to suppress the solidification property of the solidification bath and to consider the cost of recovering the solidification bath, a mixed solution of methanol and a stock solution solvent is preferable as the solidification bath, and the mixing weight ratio of methanol: stock solution solvent is 25:75.
A mixture of 混合 85:15 is most preferred. The solidification bath temperature is preferably 30 ° C. or less, and 20 ° C. for uniform cooling gelation.
C. or lower, more preferably 15 C. or lower.

The solidified fiber is immersed in a substitution bath represented by methanol to extract and remove the solvent contained in the fiber. At that time, it is preferable to perform wet stretching, and the stretching ratio at that time is in the range of 1.5 to 8 times. The fiber removed from the displacement bath is then dry-drawn.
The dry heat stretch ratio is preferably 2 to 8 times, and it is preferable to perform the draw ratio so that the product of the wet stretch ratio and the dry heat stretch ratio is 6 or more. As a temperature condition for the dry heat stretching, a range of 200 to 240 ° C. is used.

[0018] Since flame retardant fibers containing PVX are easily decomposed by PVX, they are easily colored when exposed to high temperatures. Especially Ws
In the case where the drawn yarn is heat-treated in order to reduce r and improve dimensional stability, if the dry heat treatment is performed at a temperature equal to or higher than the drawing temperature, coloring becomes large and the commercial value is reduced. However, the fibers of the present invention are subjected to shrinkage treatment in a free state (ie, a state in which substantially no tension is applied to the fibers) under low-temperature hot water or steam at a temperature of 80 to 120 ° C., so that coloring is suppressed, and the difference in color difference and Wsr is reduced. Low suitable fibers are obtained.

In the fiber of the present invention, Ws of the obtained fiber
r is 2% or less. Wsr referred to in the present invention means that a load of 2 mg / dr is suspended on a sample fiber and a predetermined length L0
(For example, 1.00 m) is accurately collected, boiled in a free state at 100 ° C. for 30 minutes, then air-dried, and a 2 mg / dr load is again suspended on the air-dried sample, and the yarn length is measured accurately in the same manner. (L1), and Wsr is calculated by the following equation. Wsr = [(L0−L1) / L0] × 100 (%)

The fiber of the present invention has a color difference of 12 or less.
The color difference referred to in the present invention is defined as L * a * b by measuring the color of a fiber with a color analyzer (C-2000S type) manufactured by HITACHI.
* Value obtained by the system color difference formula.

In the above production method, the fiber according to the present invention is characterized in that the PVA flame-retardant fiber obtained by dry drawing is shrunk by 2% or more in hot water at a temperature of 85 to 120 ° C. or in a steam atmosphere. This is a point in the manufacturing method.
The shrinking atmosphere must be moist and hot. Even if free shrinkage is applied at a temperature of 200 to 250 ° C. in a dry heat state, Wsr and Dsr are greatly improved, but they are colored yellow to brown and the commercial value is reduced. Shrinkage by 2% or more in a hot and humid atmosphere at 85 to 120 ° C can provide flame retardant fibers having a color difference of 12 or less and Wsr of 2% or less and excellent in hue of dry and wet and excellent in dimensional stability. If the wet heat temperature is lower than 85 ° C., the shrinkage is not sufficiently performed, and Wsr is 2%.
Not less. On the other hand, when the temperature exceeds 120 ° C., the decrease in Wsr reaches a plateau, and there is no effect in spite of large energy consumption, and the production cost is increased. The degree of flame retardancy of the fiber obtained in the present invention is preferably 35 or more in LOI value.

[0022]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In Examples,% and ratio are values based on weight unless otherwise specified.

Example 1 PVA having a polymerization degree of 1740 and a saponification degree of 99.8 mol%, PVC powder having a polymerization degree of 400 and metastannic acid were stirred in dimethyl sulfoxide (DMSO) at 80 ° C. for 5 hours under a nitrogen stream. Dissolve, PVA / PVC = 65/35, polymer (P
A stock solution for spinning having a composition of (VA + PVC) 18%, metastannic acid 5% / polymer was obtained. This spinning stock solution is used for a pore size of 0.
Through a nozzle having a diameter of 08 mm and a number of holes of 1000, wet spinning was carried out in a solidification bath at 5 ° C. comprising a mixture of methanol and DMSO at a mixing ratio of methanol / DMSO = 7/3. Next, while extracting methanol and DMSO from the fiber, the film was wet-drawn by a factor of 2.0, and the methanol was dried with hot air at 100 ° C. to obtain a spun yarn. Subsequently, it was subjected to 3.0 times dry heat drawing at 227 ° C. to obtain a drawn yarn having a single yarn thickness of 1.9 dr. The obtained drawn yarn is immersed in hot water at 95 ° C. for 1 minute and dried in a free state for 4 minutes.
% Heat-shrink and dried at 100 ° C. at constant length. When the cross section of the obtained heat-shrinkable fiber was observed with a transmission electron microscope photograph at a magnification of 20,000, PVC was found to be about 0.9 μm.
It was an islands-in-the-sea fiber in which PVA was the sea component, forming islands of size m. This fiber had a color difference of 10.5, little coloring, and a boiling shrinkage (Wsr) of 1.5%. The strength is 7.3 g / d, the elongation is 10.2%, and the LOI value is 3
9 and a fiber having high strength, high flame retardancy and excellent dimensional stability.

Comparative Example 1 In Example 1, the fiber performance of the drawn yarn before the wet heat shrinkage treatment was evaluated. Although the color difference was almost the same at 10.8, the dimensional stability was poor when Wsr was 5.2%. The strength is 8.0 g
/ D, elongation was 6.5%, and the fiber was a low elongation.

Comparative Example 2 The drawn yarn obtained in Example 1 was subjected to a dry heat shrinkage treatment at 110 ° C. and 6.55%, but the Wsr was 5.5% and the dimensional stability was poor. Therefore, the temperature of the dry heat shrinkage treatment was increased to 230 ° C., and the dry heat shrinkage treatment of 7.5% was performed. The obtained fiber is W
Although the sr was 1.6% and the dimensional stability was good, the color difference was 22.4 and the product was colored yellow-brown, which was inferior as a commercial product.

Example 2 The drawn yarn obtained in Example 1 was continuously subjected to a 5% free shrinkage heat treatment with pressure steam. The Wsr of the obtained fiber was 1.8%, and the dimensional stability was good. The color difference is 11.0
And less hue and good hue. Strong elongation is dT = 7.
5 g / d, dE = 11.5%, LOI value was 38 and the fiber was excellent in high strength and high flame retardancy.

[0027]

The present invention is a fiber having a circular cross section having a sea-island structure comprising a PVA polymer as a sea component and a PVC polymer as an island component, having a color difference of 12 or less and a Wsr of 2 or less.
% Or less flame-retardant fiber. The production method of the present invention is characterized in that a PVA-based flame-retardant fiber is obtained by spin-drawing and then performing a wet heat treatment at 80 to 120 ° C. A flame retardant fiber having good Wsr, low color difference hue, and excellent dimensional stability can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akio Omori 1621 Sazu, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd.

Claims (4)

[Claims] 1. A fiber comprising a vinyl alcohol polymer and a halogen-containing vinyl polymer as main components, wherein the vinyl alcohol polymer has a sea-island structure and the halogen-containing vinyl polymer has an islands-in-sea structure. A polyvinyl alcohol-based flame retardant fiber having a color difference of 12 or less and a boiling shrinkage of 2% or less. 2. The fiber according to claim 1, wherein the tin compound or the antimony compound is contained in an amount of 0.1 to 15% by weight based on the total weight of the polymer. 3. A solidification bath comprising a solidification solvent having a solidifying ability for a vinyl alcohol-based polymer and a stock solution, wherein a vinyl alcohol-based polymer and a halogen-containing vinyl-based polymer are dissolved in a common solvent. Producing a polyvinyl alcohol-based flame-retardant fiber, comprising subjecting a drawn yarn obtained by wet or dry-wet spinning to extraction, drying and drawing to free shrinkage treatment using hot water or steam at 85 to 120 ° C. Method. 4. The production method according to claim 3, wherein a tin compound or an antimony compound is mixed in the spinning solution at 0.1 to 15% by weight based on the total weight of the polymer.