JPS5949936B2 - Manufacturing method for silicon dioxide-containing polyacrylonitrile molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silicon dioxide-containing polyacrylonitrile molded products, which has improved operability and can easily produce continuous molded products such as continuous filaments and films.

In recent years, ceramic fibers have attracted attention because of their heat resistance and high modulus, and various manufacturing methods have been developed.

Most of them are molded by melting the relevant inorganic material, but the molten material of these inorganic materials generally has low spinnability, and its molding involves various difficulties, making it virtually impossible to obtain a continuous molded product. It is technically impossible. The present inventors took advantage of the excellent spinnability of an inorganic solvent solution of a polyacrylonitrile polymer and attempted to wet-form it in the presence of silicon dioxide in the solution and then fire it. The filtration back pressure of the forming solution may increase rapidly, the thread may break frequently, especially when forming into fibers, fuzz may occur, or the thread may be brittle and have poor threading properties, resulting in poor operability. It was very inferior.

Therefore, the inventors of the present invention have conducted intensive studies to improve these problems.As a result, even if silicon oxide is finely ground, it aggregates in the inorganic solvent of polyacrylonitrile polymer and becomes large particles. It has been discovered that these large particles cause the above-mentioned problems, and the present invention has been developed. That is, in the present invention, when polymerizing acrylonitrile in an inorganic solvent, silicon dioxide is dispersed in the inorganic solvent in advance to a particle size of 5 μ or less, and then the resulting polyacrylonitrile polymer solution is used to form the polymer. This is a method for producing a silicon dioxide-containing polyacrylonitrile molded article. The silicon dioxide used in the present invention must have an average particle size of 5 μm or less in an inorganic solvent, and preferably 1 μm or less.

Examples of usable silicon dioxide include aqueous colloids such as "Snowtex" manufactured by Nissan Chemical Co., Ltd. and "Ludtux" manufactured by DuPont. In addition, even if it is not an aqueous colloid, dry silicon dioxide powder may be used as long as it can be dispersed in an inorganic solvent to a particle size of 5μ or less. For example, Aerosil MOX8Ql manufactured by Nippon Aerosil Co., Ltd. can be used. Generally white Even if silicon dioxide, which is commercially available as carbon, is a powder with a particle size of 5 μ or less, it aggregates into large particles in the solvent, causing the above-mentioned problem. The polymer preferably has an acrylonitrile residue content of 80% by weight or more.

Any other copolymerizable component may be used as long as it is copolymerizable with acrylonitrile. Preferred monomers include, for example, methyl acrylate, 2-chloroethyl acrylate, 2-chloroethyl acrylate, and 2-chloroethyl acrylate. -Hydroxy-3-chloropropyl, 2,3-dipromopropyl acrylate, tripromophenyl acrylate, 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, methoxypolyoxyethylene acrylate, N,N acrylate - Acrylic esters such as dimethylaminoethyl, methacrylic acid or methacrylic esters corresponding to the above acrylic esters, acrylic ester derivatives such as methyl 2-oxymethyl acrylate, methyl 2-oxymethyl methacrylate, itacon acid or its ester derivative, allylamine or its derivative, diallylamine or its derivative, monomethyl 2-cyan-1-methyl-allylphosphonate, dimethyl 2-cyan-allylphosphonate, dimethyl 2-ethoxycarbony-allylphosphonate, etc. Phosphorus-containing monomer, styrene or sodium p-styrene sulfonate, styrene derivatives such as chloromethylstyrene, 1-methylstyrene, vinyl acetate, acrylamide, dimethylacrylamide, diacetoacrylamide, methyl vinyl ketone, methyl isopropenyl ketone, methacrylate lonitrile, vinylidene cyanide, 1-cyanovinyl acetate, 2-oxymethylacrylonitrile, 2-acetylaminomethylacrylonitrile, 2-methoxymethylacrylonitrile, 2-(
1-oxyethyl) acrylonitrile, ? Monoethoxymetholeacrylonitrile, vinylidene chloride, vinyl bromide,
Examples include, but are not limited to, sodium allylsulfonate, sodium methacrylsulfonate, allyl alcohol, and methacrylic alcohol. The molecular weight of the polymer is preferably in the range of 30,000 to 300,000, preferably higher if the amount of silicon dioxide is large, and lower if the amount of silicon dioxide is small. As the inorganic solvent for the polyacrylonitrile polymer, industrially preferable ones include concentrated zinc chloride aqueous solution, concentrated chloride salt aqueous solution, and nitric acid.

The spinning stock solution can also be prepared by suspending and dissolving silicon dioxide and the monomer in the above-mentioned inorganic solvent and polymerizing with stirring, but a more preferable method is to use a zinc chloride aqueous solution with a concentration of 40% or more. Suspend silicon dioxide in
It is easy to polymerize by adding each monomer and a polymerization initiator, and the dispersion stability of silicon dioxide is also good.

The ratio of silicon dioxide to the polymer can be freely selected depending on the purpose within the range of 1 to 90% by weight of silicon dioxide based on the total of both. - The concentration of the stock solution is preferably 5 to 50%, and the viscosity of the solution is preferably about 150 to about 10,000 poise. For molding, the stock solution is coagulated by extruding it into a water bath at 10 DEG C. or lower, in which the inorganic solvent is diluted with water to a concentration of 15 to 30%, followed by washing with water, stretching if necessary, and further drying.

The molding process is no different from that of conventional acrylonitrile polymers. According to the present invention, a silicon dioxide-containing polyacrylonitrile molded product having sufficient strength can be produced as a continuous body such as a filament, film, or sheet.
They can be obtained with good operability, and these molded products can be used as they are as absorbent materials by taking advantage of the absorbent properties of silicon dioxide, and can also be made into silicon dioxide molded products and silicon dioxide-containing carbon molded products by the method described below. , silicon carbide molded product, and silicon nitride molded product.

When obtaining a silicon dioxide molded product from the silicon dioxide-containing polyacrylonitrile molded product obtained according to the present invention, the molded product obtained as described above is heated at about 150 to 400°C in an oxidizing atmosphere. It becomes nonflammable by processing,
Continuing (1) Approximately 500 to 2,000 in an inert atmosphere
It is preferable to heat the material to a temperature of 500° C. and further to sinter it in an oxidizing atmosphere, or (2) to sinter it at a temperature of 500° C. or higher in an oxidizing atmosphere. By selecting the processing conditions, it is possible to obtain a variety of silicon dioxide moldings, from porous to dense. In addition, when trying to obtain absorbent molded products,
The silicon dioxide-containing polyacrylonitrile molded product obtained by the above method was heated at about 150 to 400°C in an oxidizing atmosphere.
The material is made incombustible by treatment with water and then heat treated at a temperature of about 500 to 1,500°C in an inert atmosphere.

The five molded products obtained are useful absorbent molded products that have both activated carbon and silicon dioxide adsorption properties. In addition, when trying to obtain a molded product made of silica and silicon carbide, silicon carbide and carbon, or only silicon carbide, the acrylonitrile molded product containing silicon dioxide may be oxidized depending on the purpose. It is rendered inflammable at about 150 to 400°C in an atmosphere, and then fired at about 500 to 2,500°C in an inert atmosphere.

Here, the inert atmosphere refers to a gas that does not react in the system, such as nitrogen or argon, but of course a vacuum may also be used. The presence of water vapor is preferred when producing breathable fibers. Further, the oxidizing atmosphere refers to a gas containing oxygen or ozone, and may also contain hydrogen chloride gas. If nitrogen is used instead of the oxidizing atmosphere during firing, the resulting molded product may contain silicon nitride depending on the conditions. In addition, it is preferable to apply a slight tension to the molded product during the nonflammability process from the viewpoint of the physical properties of the molded product obtained. In the case of fibers, this tension is suitably 0.001 to 3 g/d. Additionally, there are also catalysts for producing silicon nitride, such as FesCO.
SN. Simple substances such as Mn, Mi, MOlA2 or compounds thereof, preferably halides of these metals,
In particular, fluorides may be added to the spinning dope or introduced into the moldings during the molding or after-treatment steps. The molded product or fired product obtained by the present invention can be used in a wide range of applications, including various adsorbents, heat-resistant materials, reinforcing materials for metals and plastics, abrasive materials, sliding materials, heaters, and electrical applications such as luminescent materials. can.

The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. In addition, parts in the examples are parts by weight. Example 1 159 parts of a 67.92% zinc chloride aqueous solution has a particle size of 10~
20 mμ silicon oxide content 30 weight? 30 parts of colloidal silica liquid and 11 parts of acrylonitrile were added, and as catalysts, 1% by weight of ammonium persulfate based on the acrylonitrile and 1.5% by weight of sodium sulfite based on the acrylonitrile were added, and the mixture was stirred at 20°C for 2 hours. Polymerization was carried out while

The viscosity of the obtained solution was about 300 voids at 30°C,
The total concentration of silica and polymer was 1 to 9.98%.
This solution was degassed and filtered, but it turned out to be smooth. Furthermore, this solution was spun into a 30% zinc chloride aqueous solution at 0°C,
After washing with water, it was stretched approximately 3 times in hot water and dried to obtain a silica-containing polyacrylonitrile fiber. The final winding speed is 350.
The operation was carried out at m/min, and stable operation was possible for more than one day.
The dry strength of the obtained fiber is 2.5f! /d1 dry elongation is 1Z
It was 5%. This fiber has adsorption properties even as it is, and its iodine adsorption properties are approximately 500~/f! It was hot. Note that when silica was not included, it was about 10η/9. Further, this fiber was treated in air at 200 to 300°C for 1 hour, then gradually heated in a nitrogen atmosphere, and fired at 1,100°C for 1 hour.

As a result, silica-containing carbon fibers were obtained. The strength of this fiber was 5t/CfLl, and the elastic modulus was 1,000t/Clli. In Comparative Example 1 and Example 1, silica with a primary particle size of 12 mμ (Aerosil 2) was used instead of the colloidal silica solution.
00; Nippon Aerosil Co., Ltd. product) 9 parts and 21 parts of water added,
Furthermore, 159 parts of a 67.92% zinc chloride aqueous solution and 11 parts of polyacrylonitrile were added to prepare a silica dispersion polymer solution. The obtained polymerization stock solution contained a transparent gel, and the spinneret was clogged, making it impossible to perform satisfactory spinning. Example 2 2 parts of silica with the particle size shown in Table 1, 8 parts of polyacrylonitrile with a molecular weight of about 150,000, 6
0? A solution consisting of 90 parts of an aqueous zinc chloride solution was prepared in the same manner as in Example 1.

The filterability of this stock solution was determined by the state of filtration and discharge using a 400-mesh stainless wire mesh. ◎ If the discharge amount does not change for more than one day, it will not become completely clogged within 1 hour to 1 day, but the discharge amount will gradually decrease ○
, those that were completely clogged within 1 hour were marked with an x.

Regarding spinnability, spinning was performed using a spinneret with a diameter of 0.30 Tnm in a 30% zinc chloride aqueous solution at 0°C by the air gap method, and after washing with water, it was stretched to 2 times in hot water, and then stretched to 2 times in pressurized steam. It was stretched twice, dried, and its spinnability was examined. 1
The spinnability is shown as ◎ for those that could be spun smoothly for more than an hour without yarn breakage or generation of fuzz, 0 for those that could be spun for more than 1 hour with some fluff, and X for those that could not be spun. A comparison is made in Table 1.

The quality of the yarn that could be spun is also shown. The spun fibers were treated in air at about 200 to 300°C for 1 hour while applying a tension of 0.2 y/d, and then gradually heated to 1,100°C under the tension in a nitrogen atmosphere. After treatment for 30 minutes, silicon dioxide-containing fibers as shown in Table 2 were obtained.

Further, this fiber was reacted at 1,300° C. for about 3 hours to obtain silicon carbide-containing carbon fiber. The yarn quality of this fiber is also shown in Table 2. Further, Table 3 shows the physical properties when the heat treatment after spinning was performed under substantially no tension.

Example 3 The fiber obtained by spinning, washing with water, stretching, and drying in Example 1 was heated at 200 to 300°C for 1 hour in air, then heated to 850°C for 5 minutes in nitrogen containing water vapor, and the fiber containing silica was heated to 850°C for 5 minutes in nitrogen containing water vapor. An absorbent fiber was obtained.

The iodine absorbability of this fiber was approximately 800Tn9/y. Example 4 The fiber obtained by spinning, washing with water, stretching, and drying in Example 1 was immersed in a 2% ferric chloride aqueous solution and then dried to introduce ferric chloride into the fiber,
The mixture was heated in air to 200 to 300°C for about 1 hour, then gradually raised in a nitrogen stream, and maintained at 1,500°C for 20 minutes to obtain a silicon nitride-containing fibrous material.

Claims (1)

[Claims] 1 When polymerizing acrylonitrile in an inorganic solvent, silicon dioxide is dispersed in the inorganic solvent in advance to a particle size of 5 μ or less, and the resulting polyacrylonitrile polymer solution is used to form a molded product. 1. A method for producing a silicon dioxide-containing polyacrylonitrile molded article.