JPH0215642B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a highly flame-retardant acrylic fiber that has excellent light resistance, transparency, and improved flame retardancy, and a method for producing the same. [Prior Art] Acrylic fibers have long been used in a wide range of applications due to their excellent texture and dyeability.In particular, acrylic fibers made of copolymers containing halogen-containing copolymer components, so-called modacrylic fibers, are flame-retardant. It is used as acrylic fiber. However, modacrylic fibers are subject to various practical limitations, particularly when chlorine is included in the copolymerization component, and the fibers tend to yellow due to light or heat. Various measures have been proposed to improve this problem (Japanese Patent Laid-Open No. 46-3444, Japanese Patent Laid-open No. 51-1982).
Publication No. 82023, Japanese Patent Publication No. 1982-29240, Japanese Patent Publication No. 1983
-134926, Japanese Patent Publication No. 53-19689, etc.), but these methods are specific to each process and cannot be widely applied to all processes, and sometimes they are used for spinning, dyeing, etc. However, there are cases where it can have a negative impact on the environment, and no definitive technology has yet been found. The effects of stabilizers for improving light resistance vary significantly depending on the target polymer composition and process conditions, and only some organotin compounds have been found to have some effect on chlorine-containing modacrylic fibers. be. On the other hand, in order to further improve the flame retardancy of modacrylic fibers, it is known to add halogen compounds, phosphorus compounds, tin compounds, and metal oxides such as antimony and zirconium as flame retardant aids. Among these, antimony oxide, which is highly effective for chlorine-containing modacrylic fibers, is insoluble in solvents, so the transparency of the fibers is significantly impaired and only products with degraded quality can be obtained. There are also problems with thread breakage during the spinning process, and it has not been possible to obtain a material that simultaneously satisfies a high degree of flame retardancy and gloss and transparency. [Problems to be Solved by the Invention] An object of the present invention is to further improve the unsatisfactory light resistance of acrylic fibers, so-called modacrylic fibers, made of copolymers containing chlorine-containing copolymer components, and to improve the manufacturing process. The object of the present invention is to provide highly flame-retardant acrylic acid fibers with good transparency and fewer problems. In line with the above objectives, the present inventors investigated light and heat resistance stabilizers and searched for flame retardant improvers, including stable productivity in the manufacturing process. To provide a chlorine-containing acrylic fiber that has excellent light stability by using a combination agent, and has excellent transparency and high flame retardancy despite the inclusion of an insoluble metal oxide, and a method for producing the same. be. [Means for Solving the Problems] That is, the gist of the present invention is as follows: (1) 50 to 70% by weight of acrylonitrile, 50 to 30% by weight of vinylidene chloride, and 0.1 to 3% by weight of sulfonic acid groups. Acrylonitrile polymer consisting of a monomer and 0 to 5.5% by weight of other unsaturated monomers, 0.5 to 4% by weight of antimony pentoxide with a particle size of 300 millimicrons or less, and a chemical structural formula ( A highly flame-retardant acrylic fiber with excellent light resistance and transparency, which is composed of 0.05 to 0.5% by weight of an ultraviolet absorber which is a benzotriazole compound represented by 1). (However, R: alkyl group) (2) 50 to 70% by weight of acrylonitrile, 50 to 30% by weight of vinylidene chloride, 0.1 to 3% by weight of a sulfonic acid group-containing monomer, and 0 to 5.5% by weight of other An acrylonitrile polymer consisting of unsaturated monomers is added to an organic solvent selected from the group of dimethylacetamide, dimethylformamide, and dimethyl sulfoxide at a low temperature of 50°C or less so that the solid content concentration is 15 to 30% by weight. After dissolving with
20 to 40% by weight of a dispersion of antimony pentoxide with a particle size of 300 millimicrons or less, and 2 to 5% by weight of an ultraviolet absorber that is a benzotriazole compound represented by the chemical structural formula (1) with a molecular weight of 500 or more. A concentrated dispersion of 0.5% of each component per polymer
The acrylonitrile polymer solution obtained by mixing to a concentration of ~4% by weight and 0.05 to 0.5% by weight is discharged into a coagulation bath consisting of a mixed solution of an acrylonitrile polymer solvent and water to form fibers. Before passing the undrawn yarn obtained by shaping into an oil bath, the drawing ratio DR/MDR (DR: drawing ratio, MDR:
A method for producing highly flame-retardant acrylic fibers with excellent light resistance and transparency, which is characterized by stretching in hot water so that the maximum stretching ratio (maximum stretching ratio) is 55% or more. (However, R is an alkyl group. Most of the antimony pentoxide used in the present invention has a particle size of 300 mμ or less, preferably 100 mμ
The liquid dispersion system shown below should be used, and a benzotriazole compound should be used as the ultraviolet absorber. In particular, its chemical structure is formula (1) Compounds having a molecular weight of 500 or more are preferred from the viewpoint of stability in producing high molecular weight products and improving light resistance. The acrylic fiber of the present invention will be described in detail later, but
After preparing a stock solution with a polymer concentration in the range of 15 to 30% by weight at a low temperature of 50°C or less, a dispersion solution of antimony pentoxide of 20% by weight or less and a highly concentrated dispersion solution of an ultraviolet absorber of 2 to 5% by weight are added. It is formed by mixing in a predetermined ratio to form a spinning dope, discharging the spinning dope through a thin nozzle into a coagulation bath consisting of a dope solvent and water, and subjecting it to washing and stretching and relaxation heat treatment. Regarding polymer design, containing 20 to 37% by weight of chlorine can be achieved by copolymerizing unsaturated monomers containing chlorine as a constituent atom with acrylonitrile; can select vinyl chloride and vinylidene chloride, which are inexpensively supplied on an industrial scale. Vinylidene chloride in particular has a slightly high boiling point and is easy to handle in the polymerization process, while the characteristics of fibers made from vinylidene chloride copolymer are superior to those of general acrylic in terms of flame retardant performance. It can be used advantageously because it has excellent mechanical and thermal properties similar to those of fibers. The content of chlorine must be 20% by weight or more in order to have effective flame retardancy as a flame retardant fiber. In addition, if it is contained in an amount not exceeding 37% by weight, it can be used in most products in current practical applications, and including combinations with flame retardant additives described later. , this fiber can be applied to almost all applications. On the other hand, as the amount of the copolymerized component increases, the mechanical and thermal properties of the fiber deteriorate, so it is desirable to avoid copolymerizing an unnecessarily large amount of the second component. In that sense, the content of chlorine atoms is
It is preferable to keep it to 37% by weight or less. Here, it is desirable that the liquid in which antimony pentoxide is dispersed has as a main component the solvent used for preparing the polymer stock solution. Generally, this type of product is provided on the market as an aqueous dispersion containing a surfactant, but if this is added directly to the stock solution, partial precipitation may occur or the transparency of the resulting fiber may decrease. ,
The clarity of the dyed product will be poor. To solve this problem, increase the water content in the dispersion liquid to 10
It is necessary to reduce the amount to below 7% by weight, preferably below 7% by weight, and replace it with a solvent that dissolves the polymer. In particular, it is most rational to replace it with the solvent for preparing the stock solution used in the fiber manufacturing process. In the case of organic solvents, water is preferentially evaporated and removed by adding a predetermined amount of solvent to an aqueous dispersion and then heating and distilling it, or by pressurizing it and blowing it out from a nozzle to a low-pressure area. Furthermore, it is also possible to selectively adsorb and remove with a water-absorbing substance. When an aqueous solution of an inorganic salt such as Rodan salt or zinc chloride is used as a solvent, the purpose can be achieved by adding a predetermined amount of these salts to the aqueous sol. Furthermore, as an addition method in the fiber manufacturing process, there is a method of mixing with the polymer and adding a solvent, but the most rational method is to press a predetermined amount of a concentrated dispersion of 20 to 40% by weight into the polymer stock solution. . Antimony oxide, especially antimony trioxide, is originally known as a flame retardant improver, but the antimony pentoxide used in the present invention has a flame retardant improvement equal to or higher than that of antimony trioxide, despite its high oxygen content. It showed the effect. Although the detailed mechanism is unknown, it is thought that the effect of antimony pentoxide's crystal water and its fine and uniform dispersion in the fibers also contribute. In addition, antimony pentoxide, which has water of crystallization, has a refractive index similar to that of the polymer having the chemical composition set in the present invention, and the selection of its particle size also makes it possible to mix it in at a high concentration of about 4% by weight. The special effect of hardly lowering the transparency of the fibers has been recognized. On the other hand, antimony pentoxide, which was known as a flame retardant improver after a series of studies, has the property of improving the light resistance of copolymerized acrylic fibers containing chlorine, but surprisingly, it was used in combination with a UV absorber. As a result, the light resistance is significantly improved, and the light resistance is even better than that of the conventionally known tin-based stabilizer. However, it is possible to speculate that there is some kind of interaction, such as whether this effect is due to the uniform dispersion effect of antimony pentoxide, or whether its surface properties promote the action of the ultraviolet absorber. The mechanism has not been elucidated. The amount of antimony pentoxide added should be determined by taking into account factors such as the effect of improving fiber transparency and light resistance, flame retardancy, and manufacturing cost, but in terms of the effect of improving light resistance, it should be at least 0.5% by weight per polymer. It is necessary to contain the above amount. The limit on the high concentration side should be set at 4% by weight or less. If the amount exceeds this, the rate of improvement in flame retardancy will be saturated, so adding more than this will be disadvantageous in terms of cost, and process stability will begin to deteriorate somewhat in terms of manufacturing. As the ultraviolet absorber used in combination, benzotriazole stabilizers are particularly effective. Various types of this type of ultraviolet absorber are known, such as the "Sumisorb" series manufactured by Sumitomo Chemical Co., Ltd., the "Tomisorb" series manufactured by Yoshitomi Pharmaceutical Co., Ltd.,
"Tinuvin" series manufactured by Ciba Geigy Japan, and "Mark LA-" manufactured by Adeka Argus Chemical Co., Ltd.
32, 34, 36'' series.
Others include hindered phenols, anilides,
There are UV absorbers such as benzophenone type, but the type that exhibits high light resistance is benzotriazole type stabilizer. However, it should be noted that in the wet spinning method, if these ultraviolet absorbers are added in the stock solution process, some of the stabilizer may fall off during the coagulation or washing process and the desired target may not be achieved. Regarding this point, as shown in the chemical structural formula shown in formula (1) above, if improvements are made such as having a high molecular weight and increasing the molecular length of the alkyl group (R), it will be possible to prevent it from falling into the coagulation bath during the spinning process. This is advantageous in terms of improving the stability of the manufacturing process and recovering and re-preparing the coagulating liquid.Also, since the added stabilizer remains effectively in the fiber, the cost for improving light resistance and heat resistance is reduced. can be kept low. The amount of ultraviolet absorber added must be at least 0.05% by weight, and in order to ensure a high effect not found in conventional products, it is desirable to add 0.1% by weight or more. Even if a large amount of ultraviolet absorber is added, shedding during the fiber manufacturing process increases, but the improvement effect ratio is low compared to the amount added, and it is disadvantageous in terms of cost. Therefore, it is recommended that the amount added be less than 0.5% by weight. preferable. As mentioned earlier, the acrylic polymer used in the present invention contains chlorine atoms within a specified range, and among them, so-called modacrylic fibers copolymerized with vinylidene chloride are used for quality and ease of production. Polymers can be preferably used, and in the case of a vinylidene chloride copolymerized acrylic polymer, the amount of vinylidene chloride copolymerized is 30 to 50% by weight. In order to ensure the flame retardant performance required in the market, the amount of vinylidene chloride must be 30% by weight or more, but on the other hand, if a large amount is copolymerized, a great deal of effort is required to ensure stability during polymerization. The other reason is that acrylic fibers have inferior feel, stiffness, etc., so the upper limit of the amount of copolymerization is set at 50% by weight. In this composition range, the refractive index of the polymer is approximately at the same level as the refractive index of the antimony pentoxide/crystalline water system, resulting in good transparency of the mixture. In addition to acrylonitrile and vinylidene chloride, other copolymerization components to be copolymerized include monomers containing sulfonic acid groups. This copolymerized component is
It is highly effective in suppressing the occurrence of devitrification in the dyeing process, and the polymer contains 0.1% by weight or more, preferably 0.5% by weight.
or more. Examples of the sulfonic acid group-containing vinyl monomer include methallylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, vinylbenzylsulfonic acids, and salts thereof. Various other unsaturated monomers can be used as copolymerization components, but these are monomers that can be introduced depending on the purpose to improve the properties of the fibers, such as acrylic acid, methacrylic acid, vinyl acetate, methacrylic acid, etc. Amides and the like can be mentioned. However, the amount of copolymerization is limited to at most 5.5% by weight. Introducing more than this will significantly reduce the properties of the fiber, including its heat resistance. Preferably, the solvent for the acrylic polymer is dimethylformamide, dimethylacetamide,
Examples include organic solvents such as dimethyl sulfoxide. Incidentally, inorganic salts, strong acid salts, acetone, and other inorganic solvents can also be used as the solvent, but it is necessary to carefully consider each in setting appropriate conditions. In addition to those listed above, quality improvers to improve heat resistance, rust prevention, and color resistance, as well as other additives such as pigments and dyes, may be mixed into the mixture of the acrylic polymer and its solvent. I can't hold back in any way. When preparing the stock solution, the concentration of the polymer is set at 15 to 30% by weight to ensure process passability, and the solution is melted at a low temperature, preferably below 50°C, to avoid coloring due to heat.
The usual treatment method is to disperse (dissolve) antimony pentoxide dispersion and ultraviolet absorber in a solvent before dissolving the polymer. A rational process can be used for assembly by preparing a dispersion of an ultraviolet absorber of up to 8% by weight and pressurizing it into the stock solution piping. The stock solution prepared in this way is discharged from a thin nozzle into a coagulating liquid consisting of a solvent and water mixture, and is formed into an undrawn yarn. The obtained undrawn yarn is drawn while washing away the solvent in the washing-drawing process, but it is better to set the drawing ratio in hot water as high as possible in order to prevent devitrification from occurring again in the dyeing process. . Usually, the material is stretched in hot water to a maximum stretching ratio of 55% or more, then an oil agent is applied, and the material is dried and densified. If necessary, it is also possible to perform stretching under dry heat after completion of drying. The stretched fibers are subjected to a relaxation heat treatment under moist heat to create mechanically balanced fibers, which are then cut to the required length to become raw cotton for spinning. The fibers obtained in this way have superior light resistance, good transparency, and high flame retardant performance compared to chlorine-containing modacrylic fibers, which have traditionally been known as flame-retardant fibers. It is. [Example] The present invention will be explained in more detail with reference to Examples below. The evaluation method for fibers in this example is as follows. Flame retardancy is evaluated using the oxygen index method (JISK720-1A1
issue). Light resistance was evaluated using fade meter irradiation.
Judgment was made based on JISL-1044. Transparency was evaluated by the light transmittance method shown below. In general, when fibers copolymerized with a large amount of flame-retardant halogen-containing monomers are boiled or dyed in hot water, fine cavities are created in the fibers, but the fibers become transparent due to light scattering. Sexuality is significantly reduced. Therefore, the transparency of the fiber can be quantified by measuring the light transmittance of the boiling water treated yarn. Therefore, in the present invention, in order to reduce the measurement error and quantify the transparency required for the product, measurements were performed using the following method. The fibers were treated with boiling water for 1 hour and then cut into 30 mm lengths.
5 g of this was collected and a felt with a length of 100 mm x width of 200 mm and a thickness of 1 mm was produced by the needle punch method. A 10 mm x 20 mm felt piece weighing 50 mg is taken and placed in a 1 mm thick glass cell containing 5 ml of benzyl alcohol, and the transmittance at this time is measured using a spectrophotometer at a wavelength of 490.5 μm. According to this method, determination can be made with high accuracy using a small amount of sample. Also, although the absolute value of the numerical value displayed as transmittance% is small, the transmittance of the boiling water treatment system is 40%.
% or more, it can be said that the fiber has extremely good transparency. The whiteness was determined by the L value (whiteness) and b value (yellowness index) using an electronic color difference meter (Model 1500). The larger the L value, the better the whiteness, and the smaller the b value, the less yellowish tinge. Therefore, the larger the L value and the smaller the b value, the higher the commercial value. Further, the degree of coloring of the spinning dope was measured by a light transmittance method. A higher transmission value indicates a lower degree of coloring of the stock solution. Example 1 Acrylonitrile 58.5% by weight, vinylidene chloride
An acrylonitrile polymer consisting of 40% by weight and 1.5% by weight of sodium methacrylsulfonate was mixed with 3% by weight of antimony pentoxide in a micronized liquid dispersion system and 0.1% of a benzotriazole ultraviolet absorber (MARK LA-31 manufactured by Adeka Argus). A spinning stock solution was prepared by dissolving it at 40°C to a concentration of 23.0% by weight in dimethylacetamide in which % by weight had been dispersed. Next, this stock solution was spun into a 53% by weight dimethylacetamide-water coagulation bath (temperature 30°C) using a nozzle with a nozzle diameter of 0.1mmφ, subjected to solvent removal treatment, and then stretched 6 times in hot water. (DR/MDR=0.667)
A fiber of 10 denier was obtained by applying an oil agent, drying, and moist heat relaxation treatment. This fiber was evaluated by the oxygen index method (LOI) and transparency method described above. In addition, this fiber was subjected to a scouring treatment under boiling water for 60 minutes with a 0.2% by weight aqueous solution of Scoreroll (a detergent manufactured by Kao Soap Co., Ltd.), dried, and then irradiated with a fade meter at 60°C for 80 hours for evaluation. The results are shown in Table 1.
Both flame retardancy and light resistance were superior to additive-free systems, and transparency was also good.

[Table] Example 2 Fibers were formed in the same manner as in Example 1 except that the amount of antimony pentoxide added was changed from 0 to 4% by weight. Table 2 shows the relationship between the amount of antimony pentoxide added, flame retardancy, and light resistance. Flame retardancy (LOI) was improved depending on the amount of antimony pentoxide added, but no further effect was observed even when the concentration of antimony pentoxide exceeded 4% by weight.

[Table] Example 3 Antimony pentoxide is 1% by weight, and the amount of benzotriazole ultraviolet absorber added is 0 to 5% by weight.
Fibers were formed in the same manner as in Example 1 except that the following was changed. As shown in Table 3, the effect of the combination of antimony pentoxide and ultraviolet absorber on light resistance was observed.

[Table] Example 4 Fibers were formed in the same manner as in Example 1 except that benzotriazole ultraviolet absorbers having different molecular weights were added to the stock solution. As shown in Table 4, when the molecular weight was less than 500, a lot of the particles fell off in the coagulation bath, resulting in poor light resistance and spinning stability.

[Table] Example 5 Fibers were formed in the same manner as in Example 1 except that the melting temperature of the acrylic polymer in Example 1 was changed to 40 to 60°C. Table 5 shows the retention time and light transmittance of the dissolved substance, and Table 6 shows the whiteness of the yarn obtained using the spinning dope after standing for 12 hours. At a dissolution temperature of 40°C, the change in coloring of the spinning dope and yarn was small, and at 60°C, the change in coloring of the spinning dope and yarn was greatly inferior.

【table】

[Table] Example 6 When stretching the undrawn yarn obtained by wet spinning the spinning stock solution of Example 1 in hot water, the drawing ratio (DR/MDR) in hot water was changed to the maximum drawing ratio (MDR). ) of 45~
After the fiber was changed to 67% and an oil agent was added, dry heat stretching was performed so that the total stretching ratio was constant, and a moist heat relaxation treatment was performed, a fiber was formed in the same manner as in Example 1. This fiber was evaluated using the light transmittance method described above. The results are shown in Table 7, and the drawing ratio (DR/MDR) in hot water is 55, which is the maximum drawing ratio (MDR).
%, the devitrification property after boiling water treatment was poor.

〔Effect of the invention〕

The present invention provides an acrylic fiber that significantly improves the light resistance of chlorine-containing modacrylic fibers, which have been a problem in the past, has enhanced flame retardant performance, and has excellent transparency. It expands the uses of fibers and can meet the demands of various markets related to improving the safety of the social environment.

Claims (1)

[Claims] 1. 50-70% by weight of acrylonitrile, 50-30% by weight of vinylidene chloride, 0.1-3% by weight of a sulfonic acid group-containing monomer and 0-5.5% by weight of other unsaturated monomers. Acrylonitrile polymer consisting of
Antimony pentoxide 0.5 with particle size less than 300 millimicrons
-4% by weight and 0.05-0.5% by weight of an ultraviolet absorber which is a benzotriazole compound represented by the chemical structure (1) with a molecular weight of 500 or more. Highly flame retardant with excellent light resistance and transparency. treated acrylic fiber. (However, R: alkyl group) 2 50-70% by weight of acrylonitrile, 50-30% by weight of vinylidene chloride, 0.1-3% by weight of a sulfonic acid group-containing monomer, and 0-5.5% by weight of other unsaturation An acrylonitrile polymer consisting of monomers is dissolved in an organic solvent selected from the group of dimethylacetamide, dimethylformamide, and dimethyl sulfoxide at a solid concentration of 15 to 30% by weight.
20-40% by weight after melting under low temperature below ℃
A dispersion of antimony pentoxide with a particle size of 300 millimicrons or less and 2 to 5% by weight of its molecular weight 500
A concentrated dispersion of an ultraviolet absorber, which is a benzotriazole compound represented by the chemical structural formula (1) below, is prepared in such a manner that each component is 0.5 to 4% by weight and 0.05 to 0.5% by weight based on the polymer.
An acrylonitrile-based polymer solution obtained by mixing the acrylonitrile-based polymer solution to a concentration of Before passing the drawn yarn through an oil bath, the drawing ratio DR/MDR (DR: drawing ratio,
A method for producing highly flame-retardant acrylic fibers with excellent light resistance and transparency, which is characterized by stretching in hot water so that MDR (maximum stretching ratio) is 55% or more. (However, R: alkyl group)