JPH09279414A - Production of polyvinyl alcohol-based flame-retardant fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject fiber having high strength and useful as an industrial raw material in a field requiring flame retardance and strength, e.g. net or rope by fiberizing a spinning dope obtained by dissolving polyvinyl alcohol and polyvinyl chloride in dimethyl sulfoxide under specific conditions. SOLUTION: A spinning dope obtained by dissolving polyvinyl alcohol and a polyvinyl chloride into dimethyl sulfoxide is spun into a coagulating bath in which an organic solvent (a mixed solvent containing methanol and dimethylsulfoxide at a weight ratio of (35/65) to (90/10) and then, dimethyl sulfoxide in the fiber is extracted by methanol and the fiber is subjected to drying, dry heat drawing and heat treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for stably producing flame-retardant fibers of polyvinyl alcohol (hereinafter abbreviated as PVA) -based flame retardant fibers which are excellent in flame retardancy and mechanical properties such as strength.

[0002]

2. Description of the Related Art Heretofore, as flame-retardant fibers, synthetic fibers such as acrylic and polyester fibers in which a flame-retardant substance is kneaded are known, and further, natural fibers such as cotton are flame-retarded. Polymers such as aramid fibers and aramid fibers have excellent heat resistance, and as a result, fibers having flame retardancy are on the market. Among them, acrylics generate cyan gas due to thermal decomposition, and polyesters melt-drip, so when used as clothing, its use is limited to living materials such as curtains and carpets because it causes burns to the wearer. . Further, the strength of these is as low as about 4 g / d at most, and it was difficult to develop them into industrial material applications requiring high strength. On the other hand, the flame-retarded cotton has a problem that the flame retardant drops off during washing or use, and the flame retardancy decreases with time. In addition, aramid fiber is very expensive as compared with other general-purpose fibers, which hinders its quantitative expansion.

Further, PVA-based flame-retardant fibers are also known, for example, from Japanese Examined Patent Publication (Kokoku) No. 51-19494. PVA-based flame-retardant fibers generate some gas due to thermal decomposition but do not have melt drip and are used for clothing. Although it has been applied to the field of clothing such as fire fighting clothes and work clothes as well as the field of living such as carpets, there are the following two problems and it has been difficult to expand the applications.

The first problem is high cost.
Conventionally, PVA-based fibers are produced by dissolving PVA in water to form a spinning stock solution, spinning the solution into a coagulation bath composed of an aqueous solution of Glauber's salt, drying, dry heat drawing, heat treating, and optionally acetalizing. is there. In order to increase the strength of the fibers, it is industrially practiced to add boric acid to the stock solution to make the coagulating bath alkaline. Then, in order to impart flame retardancy to this, polyvinyl chloride (hereinafter abbreviated as PVC) is added to the undiluted solution, and tin or antimony compound is further added as a decomposition catalyst of PVC to produce a PVA-based flame-retardant fiber. ing.
However, in such a production method using water as a solvent, first, P
Simple commercial cheap PVC because VC does not dissolve in water
Cannot be used and expensive PVA emulsions must be used. Further, since the compatibility between PVA and PVC emulsion is very poor, it is necessary to add a surfactant or a water-soluble polymer as a stabilizer, resulting in high raw material cost and labor for preparing these raw materials. The cost is inevitable. In addition, although various stabilizers are used, PVA and PVC have essentially no affinity, so phase separation easily occurs in the stock solution and the filter of the stock solution is easily clogged. It is extremely inferior to the yarn, and the yield is low, which is also a major factor in increasing the cost.

The second problem is the low strength of the fibers. PVA-based flame-retardant fibers have a higher strength than acrylic-based and polyester-based fibers having the same flame-retardant property, but for example, LOI of 36 is 6 g / d at most and LOI of 31 is 8 g / d for industrial materials. However, it was difficult to develop into fields where flame retardancy and strength are required at the same time, such as nets and ropes.

[0006]

As described above, the conventional PVA-based flame-retardant fiber has excellent performance as compared with other flame-retardant synthetic fibers, but the cost is high and the process is stable. It lacked in properties and was insufficient in strength as an industrial material.
An object of the present invention is to provide a method for stably and inexpensively producing a high-strength PVA-based flame retardant fiber.

[0007]

That is, the present invention provides a PV
A solution in which A and PVC are dissolved in dimethylsulfoxide is used as a spinning stock solution and is spun in a coagulation bath made of an organic solvent to extract dimethylsulfoxide in the fiber, followed by drying, dry heat drawing and heat treatment. Further, the present invention has a polymerization degree of 1500 or more and 4000 or less and a saponification degree of 9 or less.
PVC with a PVA of 8 mol% or more and a polymerization degree of 5000 or less
However, the spinning dope was prepared by dissolving in dimethylsulfoxide at a weight ratio of 95: 5 to 60:40, and the weight ratio of methanol to dimethylsulfoxide was 35:65 to 9.
A method for producing a PVA-based flame-retardant fiber, which comprises spinning in a coagulation bath of 0:10, extracting dimethyl sulfoxide with methanol, and then performing drying, dry heat drawing, and heat treatment.

[0008] The present inventors first of all, the raw materials PVA and P
With the aim of improving the mixing stability of the undiluted solution of VC, add PVC or PVC and PVA to an aqueous solution of PVA,
In addition, it was tried to add various stabilizers such as block copolymers and graft copolymers of PVC and vinyl acetate. However, almost no improvement effect was recognized as compared with the method using the conventional PVC emulsion.

Therefore, the idea was fundamentally changed, and PVA and P
A method for preparing a stock solution in which VC is compatible was examined.
In order to make PVA and PVC compatible with each other, it is effective means to use a common solvent for both, and as such a common solvent, there are various solvents such as aqueous solution of rhodanese, glycerin, ethylene glycol and dimethyl sulfoxide. However, as a result of examining the relationship between these solvents and PVA and PVC, only when dimethyl sulfoxide (hereinafter abbreviated as DMSO) was used as the solvent,
The inventors have found that a stock solution in which PVA and PVC are compatible with each other can be prepared, and have reached the present invention. In particular, when PVA having a polymerization degree of 1500 or more and 4000 or less and PVC having a polymerization degree of 5000 or less is used, the compatibility becomes remarkably excellent.

The PVA used in the present invention is a component that determines the mechanical properties of the fiber, and its polymerization degree is preferably 1500 or more and the saponification degree is 98 mol% or more in order to obtain sufficient physical properties. However, to satisfy compatibility with PVC, P
The polymerization degree of VA and PVC is 4000 or less and 500, respectively.
It is preferably 0 or less. If either PVA or PVC having a degree of polymerization exceeding the above range is used, phase separation is likely to occur in the stock solution, and spinning may be difficult. It should be noted that those obtained by copolymerizing PVA or PVC with a copolymerizable vinyl monomer such as ethylene, styrene, vinyl acetate, or an acrylic ester at a ratio of 20 mol% or less are stable without compromising compatibility. Stock solutions can be prepared. PVA and P
The mixing ratio of VC is set to the target degree of flame retardancy (flame retardancy index LO
It depends on I) and may be set appropriately.
The weight ratio of PVA and PVC is 60:40 due to the fiber forming property.
PVA-rich is more preferable than PVA-rich. Even so, it is possible to obtain a LOI having a sufficient flame retardancy of about 40. Further, LOI of 25 or more is required to be in the flame retardant category, and for this purpose, the mixing ratio of PVC is 5% by weight.
The above is preferable.

On the other hand, if the solvent is not mainly DMSO, a stable stock solution cannot be prepared. DM
In addition to water, it is also possible to mix, in addition to water, glycols such as ethylene glycol and glycerin, alcohols such as methanol and ethanol, and ketones such as acetone and methyl ethyl ketone, which are easily miscible with DMSO. Since all of these reduce the performance of DMSO as a solvent, the mixing ratio is preferably 20% by weight or less, more preferably 15% by weight or less,
More preferably, it is 10% by weight or less.

Besides, tin compounds (stannic acid, metastannic acid, etc.) or antimony compounds (antimony trioxide, antimony pentoxide, etc.) which accelerate the decomposition of PVC, which are well known in the art, are used.
The same can be preferably used in the present invention as well, and a heat stabilizer typified by tin, various additives, and a coloring agent can also be used. Further, in the present invention, since PVA and PVC are compatible with each other, it is not necessary to use a mixing stabilizer originally. However, for example, when a pigment, a substance having antibacterial property or deodorant property is added to the stock solution, ethylene is used. The stability can also be improved by adding 0.1 to 5% of vinyl acetate copolymer, ethylene-vinyl alcohol copolymer and the like to PVA.

The method for preparing the stock solution is not particularly limited, but when the polymers of PVA and PVC are mixed and dissolved in DMSO, spinning of the stock solution for a long period of time tends to cause clogging of the filter of the stock solution. Particularly when good stability is required for a long period of time, one of PVA and PVC is first dissolved in DMSO, and then the other is added when necessary, and dissolved and mixed, or PVA is added to a DMSO solution of PVA.
A method in which a DMSO solution of C is added and mixed in a pipeline is preferable. Probably, due to the difference in the dissolution rate of both of them with respect to DMSO, it is presumed that phase separation proceeds with time even if they are compatible at the beginning of dissolution. For the addition and mixing in the pipeline, specifically, PVA and PVC are separately DMSO.
A DMSO solution of PVC is similarly measured and extruded into a pipe in which a DMSO solution of PVA is measured and sent by a gear pump or the like, and after addition, the DMSO solution of PVC is added and stirred and mixed by a mixer.

The coagulation bath is preferably composed mainly of methanol. However, since DMSO is inevitably brought from the stock solution, it is preferable to use a mixed composition of methanol and DMSO, and the mixing weight ratio is methanol: DMSO = 3.
The range of 5:65 to 90:10 is preferable. If the methanol ratio is lower than 35:65, fiber formation is difficult due to insufficient coagulation or sticking occurs. Conversely, if the methanol ratio is higher than 9: 1,
It is easily affected by the carry-in of DMSO from the stock solution, and it is necessary to supplement a large amount of methanol in order to maintain its composition, which is not practical as a production process. Further, it is possible to add a substance such as water or ketones which promotes the coagulation property to the coagulation bath without any trouble. Alcohols and ketones other than methanol can also be used. The coagulation bath consisting of an organic solvent referred to in the present invention is a bath containing an organic solvent which is compatible with DMSO but is not compatible with PVA or PVC, such as methanol and ketones. It means that, of course, the polymer component in the spinning stock solution discharged into the bath is solidified to give a fibrous form.

The spinning method may be either a wet spinning method or a dry / wet spinning method in which an air layer is provided between the nozzle and the coagulating bath. The yarn formed in the coagulation bath is subsequently subjected to DMSO or water extraction with methanol while being drawn 1.5 to 5 times, and an oil agent is applied as necessary to dry. After that,
Dry heat stretching and heat treatment may be performed, and if necessary, chemical treatment such as acetalization may be performed according to a standard method. The fiber thus obtained has a characteristic that it has a LOI equivalent to that of a conventional flame-retardant PVA-based fiber but has a strength of 10% or more. The reason for this is not clear, but basically, the fact that PVA and PVC were made compatible with each other in the undiluted solution and that the addition of various stabilizers was unnecessary as a ripple effect thereof contributed to the improvement in strength. I think that the.

[0016]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. The strength and elongation in the examples are measured according to JIS L-1013. The flame retardancy index (LOI) is JIS
It measured based on K7201.

Example 1 PVA having a polymerization degree of 1750 and a saponification degree of 99.7 mol% was added to a dispersion liquid in which tin oxide having a particle diameter of 0.4 μ was dispersed in DMSO so that the addition ratio was 4% by weight with respect to PVA. Was dissolved at 70 ° C. to a concentration of 18% by weight (solution A). on the other hand,
Using another dissolving machine, 2% of tin-based heat stabilizer for PVC (MARK BT-18 manufactured by Asahi Denka Co., Ltd.) and PVC having a degree of polymerization of 400 were dissolved in DMSO at a concentration of 20% (B
liquid). 189 g of liquid A is measured by a gear pump per minute and sent to the spinning machine. During the process, liquid B is supplied by a gear pump at 7 per minute.
3 g was weighed, extruded and added, and was added by T.K. K. Pipeline homomixer 2SL6 type 3 per minute
The mixture was stirred and mixed at 000 rpm (the weight ratio of PVA and PVC was 7: 3). The spinning dope thus prepared was passed through a nozzle with a hole size of 0.08 mm and 2000 holes and methanol / D.
Wet spinning was performed in a coagulation bath at 5 ° C with a weight ratio of MSO of 70/30. Subsequently, it was stretched 3.5 times while extracting DMSO with methanol at 10 ° C., dried with hot air at 120 ° C., further stretched 4.0 times at 228 ° C. and wound up. The above manufacturing process is stable and the obtained fiber is 4000
Denier, strength 9.2g / d, elongation 13.5%, LOI
The value was 34, which was excellent.

Examples 2 to 3 The same method as in Example 1 except that the polymerization degree of PVA was 5000 (Example 2) or the polymerization degree of PVC was 8000 (Example 3). I tried to manufacture it. In the performance of the obtained fiber, Example 1
Although it was not inferior to that obtained in step 1, in both cases, phase separation of the undiluted solution occurred and stable spinning was difficult.

Example 4 PVA85 having a polymerization degree of 2400 and a saponification degree of 99.8 mol%
0 g and 17 g of tin oxide were dissolved in 4 kg of DMSO at 80 ° C., and then 213 g of PVC having a polymerization degree of 2000 and a tin-based heat stabilizer (MARK BT-1 manufactured by Asahi Denka Co., Ltd.).
8) 3 g, and 1.56 Kg of DMSO were added and dissolved to prepare a spinning dope (PVA: PVC = 8:
2). Then, as in Example 1, spinning, extraction, drying, stretching and winding were performed. The process is stable and the fibers obtained are 4000 denier, strength 12.5 g / d, elongation 15.
It had a strength of 3% and a LOI value of 30, and had sufficient strength and flame retardancy as an industrial material.

Examples 5 to 6 In Example 4, the coagulation bath composition was changed to methanol / DMSO.
= 45/55 (Example 5) and 30/70 (Example 6)
Fibers were produced in the same manner as in Example 4 except that In Example 5, fibers having stable and equivalent performances were obtained without any problems in production, almost as in Example 4. In Example 6 also, although equivalent fibers were obtained, it was not possible to form fibers having no interfiber gluing.

[0021]

Industrial Applicability According to the method of the present invention, it is possible to inexpensively and stably produce a PVA-based flame-retardant fiber having high strength and excellent flame retardancy that can be easily developed for both clothing and industrial materials. became.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Sato, 1621 Sakazu, Kurashiki, Okayama Prefecture, Kuraray Co., Ltd. (72) Inventor Akio Omori, 1621, Satsuki, Kurashiki, Okayama, Kuraray, Inc.

Claims (4)

[Claims] 1. A polyvinyl chloride solution in which polyvinyl alcohol and polyvinyl chloride are dissolved in dimethylsulfoxide to spin a spinning solution in a coagulation bath containing an organic solvent to extract dimethylsulfoxide in the fiber, followed by drying, dry heat drawing and heat treatment. Method for producing alcohol-based flame-retardant fiber. 2. A weight ratio of polyvinyl alcohol having a degree of polymerization of 1500 to 4000 and saponification degree of 98 mol% or more to polyvinyl chloride having a degree of polymerization of 5000 or less of 95: 5 to 60:40. Was dissolved in dimethylsulfoxide to form a spinning solution, and the mixture was spun into a coagulation bath in which the weight ratio of methanol and dimethylsulfoxide was 35:65 to 90:10, and dimethylsulfoxide was extracted with methanol, followed by drying, dry heat stretching, A method for producing a polyvinyl alcohol-based flame-retardant fiber, which comprises performing heat treatment. 3. The method according to claim 1, wherein one of polyvinyl alcohol and polyvinyl chloride is first dissolved in dimethyl sulfoxide, and then the other is added and dissolved and mixed. 4. The method according to claim 1, wherein a dimethyl sulfoxide solution of polyvinyl chloride is added to and mixed with a dimethyl sulfoxide solution of polyvinyl alcohol in a pipeline.