JP2018090926A - Method for producing fibrous material - Google Patents

Abstract

An object of the present invention is to obtain a fiber containing a silicon material and having good shape retention under mild conditions without requiring high-temperature sintering. A spinning solution containing sodium silicate, an aliphatic amine and water is spun to form a fibrous material containing silicate ions and sodium ions, and a step of preparing an alcohol solution of polyvinyl alcohol. A method for producing a fibrous material is disclosed, comprising the steps of: contacting polyvinyl alcohol with a fibrous material in an alcohol solution of polyvinyl alcohol, and removing at least a portion of sodium ions from the fibrous material in this order. You. [Selection diagram] None

Description

  The present invention relates to a method for producing a fibrous material.

  It is known that inorganic fibers such as silicate fibers and silica fibers formed from a silicon material are produced by various methods such as an electrostatic spinning method. Examples of the electrospinning method include a method in which a precursor solution composed of a metal alkoxide and an organic polymer is fired after spinning, and a method in which a spinnable sol solution prepared from a metal alkoxide without using an organic polymer is spun. is there. Also known is a method of spinning a solution having viscosity such as water glass and neutralizing the obtained fiber with an acid (Patent Document 2).

JP 2003-73964 A Japanese Examined Patent Publication No. 60-027446

  Conventional techniques for producing inorganic fibers containing a silicon material generally require firing at a high temperature (eg, 800 ° C. or higher). Further, in the case of a method of spinning a solution such as water glass, there is a problem that when the formed fiber is insolubilized by dealkalization treatment, it becomes brittle and it is difficult to maintain the fiber form. In order to use the fibrous material as various functional materials, it is required to have a form retentivity that can be processed while maintaining the fiber form.

  Accordingly, a main object of the present invention is to obtain a fibrous material containing a silicon material and having good shape retention properties under mild conditions without requiring high-temperature firing.

  One aspect of the present invention provides a process of spinning a spinning stock solution containing sodium silicate, aliphatic amine and water to form a fibrous material containing silicate ions and sodium ions, and an alcohol solution of polyvinyl alcohol is prepared. A fibrous material comprising: a step of bringing the polyvinyl alcohol into contact with the fibrous material in an alcohol solution of polyvinyl alcohol; and a step of removing at least part of sodium ions from the fibrous material in this order. Provide a method.

  According to this method, a fibrous material containing a silicon material and having good shape retention can be obtained under mild conditions without requiring firing at a high temperature.

  According to the present invention, a fibrous material containing a silicon material and having good shape retention can be obtained under mild conditions without requiring firing at a high temperature.

  Hereinafter, some embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  One embodiment of a method for producing a fibrous material includes spinning a spinning stock solution containing sodium silicate, an aliphatic amine and water to form a fibrous material containing silicate ions and sodium ions; A step of preparing an alcohol solution of alcohol, a step of bringing polyvinyl alcohol into contact with the fibrous material in the alcohol solution of polyvinyl alcohol, and a step of removing at least a part of sodium ions from the fibrous material are provided in this order.

  The fibrous material obtained by this method contains a silicon material as a main component and is usually a porous fiber. The silicon material may comprise at least one silicon compound selected from, for example, silicon dioxide, silicic acid and silicate. Further, the fibrous material may be a porous organic-inorganic composite fiber that further contains an organic material derived from an aliphatic amine and / or polyvinyl alcohol.

  The spinning dope can be prepared, for example, by mixing an aqueous solution of sodium silicate and an aliphatic amine, and is typically a sol solution. An aqueous solution of sodium silicate and an aqueous solution of an aliphatic amine may be mixed. After mixing, the mixed solution may be stirred at room temperature or while heating.

Sodium silicate generally has a composition represented by the formula: Na ₂ O · nSiO ₂ (n represents a positive number). Sodium silicate is, for example, a single substance such as sodium orthosilicate where n is 0.5, sodium metasilicate where n is 1 or sodium disilicate where n is 2, or a hydrate thereof. May be. From the viewpoint of viscosity, sodium silicate having n of 2 or more is preferable.

An aqueous solution of sodium silicate is sometimes called water glass, and is a liquid water glass represented by the formula: Na ₂ O.nSiO ₂ .mH ₂ O (n and m are positive numbers). Examples thereof include JIS No. 1 glass (n = 2), No. 2 water glass (n = 2.5), and No. 3 water glass (n = 3).

  The aliphatic amine can be, for example, an aliphatic diamine represented by the following formula (1).

R ¹ in the formula (1) represents a divalent aliphatic group. R ¹ may be a linear, branched or cyclic alkylene group. The carbon number of R ¹ may be 2-6. When the aliphatic group becomes long, the flexibility of the fibrous material tends to be improved. Specific examples of the aliphatic diamine represented by the formula (1) include hexamethylene diamine and ethylene diamine.

  Aliphatic amines can react with sodium silicate in the spinning dope to form salts with structures composed of silicon and oxygen atoms. For example, the diamine of the formula (1) may form a partial structure in which two silicon atoms are represented by the following formula (2). However, such a partial structure is an example, and the fibrous material does not necessarily include this.

  The ratio of the aliphatic amine in the spinning dope may be 0.1 to 15% by mass, or 2 to 10% by mass with respect to the total amount of sodium silicate and aliphatic amine. When the ratio of the aliphatic amine is within these ranges, the spinning dope tends to have a viscosity suitable for spinning. From the same viewpoint, the concentration of sodium silicate in the spinning dope may be 50 to 54% by mass based on the mass of the spinning dope.

  By spinning the spinning dope, a gel-like fibrous material is formed. The spinning method of the spinning dope is not particularly limited, and for example, methods such as centrifugal spinning and electrostatic spinning can be applied. Centrifugal spinning can be performed with a simple apparatus. The electrostatic spinning method is particularly suitable for forming a fibrous material having a fiber diameter of several nm to several tens of nm.

  A part of water is usually removed by drying from the fibrous material formed by spinning. The fiber diameter of the fibrous material formed by spinning can be controlled mainly based on the size of the discharge port of the spinning container and the viscosity of the spinning dope. The fiber diameter of the fibrous material may be about 1 to 50 μm.

  The fibrous material formed by spinning can be brought into contact with polyvinyl alcohol in an alcohol solution of polyvinyl alcohol, for example, by immersing it in an alcohol solution of polyvinyl alcohol prepared separately. By this step, it is considered that polyvinyl alcohol adheres to the surface of the fibrous material, which contributes to prevention of weakening of the fibrous material.

  Polyvinyl alcohol can be bonded to a structure composed of silicon atoms and oxygen atoms by the reaction of a hydroxyl group and silicic acid. By this reaction, for example, when polyvinyl alcohol which is a saponified product of polyvinyl acetate is used, it is considered that a partial structure represented by the following formula (3) is formed. In the formula, p and q each independently represent a positive integer, and may be, for example, 1 to 100.

  Highly saponified polyvinyl alcohol is highly reactive with silicic acid. However, if the degree of saponification is too high, the reaction with silicic acid may proceed excessively, making it difficult to maintain the fiber shape. From such a viewpoint, the saponification degree of polyvinyl alcohol may be 10 to 90 mol%, or 30 to 60 mol%. Here, the saponification degree means a value measured according to the test method for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponified product of chemical products described in JISK0072-1992.

  The alcohol solution of polyvinyl alcohol can be prepared by, for example, dissolving polyvinyl alcohol in alcohol. Although the density | concentration in particular of the polyvinyl alcohol in the alcohol solution of polyvinyl alcohol is not restrict | limited, For example, 1-10 mass% may be sufficient on the basis of the mass of a solution. The alcohol used here may be methanol, for example.

  The contact time (immersion time) between the fibrous material and the alcohol solution of polyvinyl alcohol may be, for example, 1 to 100 minutes. Meanwhile, the solution may be heated if necessary.

  After treatment with polyvinyl alcohol, at least some of the sodium ions are removed from the fibrous material. This step can be rephrased as dealkalization treatment, thereby imparting water resistance to the fibrous material. It is sufficient that sodium ions are removed to such an extent that the fibrous material has sufficient water resistance, and a certain amount of sodium ions often remains in the fibrous material after this step.

  In order to remove sodium ions, for example, a fibrous solution can be contacted with an acid solution. In this case, sodium ions are usually exchanged for hydrogen ions. Both may be brought into contact by immersing the fibrous material in an acid solution. The solvent of the acid solution may be, for example, water, alcohol, or a mixed solvent thereof. In particular, by using only the alcohol or a mixed solvent containing alcohol, the fibrous solution is added before water resistance is imparted. There exists a tendency which can suppress that a thing melt | dissolves. The alcohol may be, for example, methanol. The contact time (immersion time) between the fibrous material and the alcohol solution of the weak acid may be about 0.1 to 12 hours.

  The acid can be arbitrarily selected from those that can be dissolved in a solvent, and can be a weak acid or a strong acid. The weak acid may be at least one selected from, for example, acetic acid and ammonium (such as ammonium chloride). Examples of strong acids include hydrochloric acid. In particular, in the case of a strong acid, there is a tendency that a fibrous material having a good shape can be easily obtained by using a low-concentration solution. Specifically, the concentration of the strong acid solution may be 5% by mass or less based on the mass of the solution. A low-concentration solution of strong acid can be prepared, for example, by diluting a high-concentration strong acid aqueous solution (such as 1M HCl) with alcohol.

  After contact with the acid solution, the fibrous material may be dried with heating if necessary.

  The fibrous material obtained by the above process has moderate flexibility and easily maintains the fiber form. Moreover, it can also have high heat resistance by a silicon material, for example, can endure the high temperature of 500 degreeC. The porous fibrous material can be used, for example, as an ion exchange material that captures metal ions and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
Powdered sodium silicate (manufactured by Kishida Chemical Co., Ltd.) was dissolved in distilled water to a concentration of 52% by mass to obtain a sodium silicate aqueous solution. To 40 g of this sodium silicate aqueous solution, 2.0 g of a hexamethylenediamine aqueous solution having a concentration of 90% by mass was added, and the vacuum defoaming mixer (Awatori Rentaro ARV-310, manufactured by Shinkey Co., Ltd.) in the atmosphere at 2000 rpm. The mixture was stirred for 10 minutes to obtain a spinning dope. This spinning dope was transferred to a spinning vessel, and a gel-like fibrous material was formed by centrifugal spinning at a rotational speed of 4000 rpm. The formed fibrous material was immersed in a methanol solution (concentration 5 mass%) of polyvinyl alcohol (PVA) for 10 minutes. Next, the fibrous material was immersed in a 5% acetic acid methanol solution for 1 hour for dealkalization treatment to remove sodium ions. The fibrous material after immersion was dried by vacuum drying at room temperature for 24 hours to obtain a porous fiber that was a cotton-like fibrous material.

(Example 2)
A porous fiber was produced in the same manner as in Example 1 except that the amount of the hexamethylenediamine aqueous solution having a concentration of 90% by mass was changed to 1.44 g.

(Example 3)
Porous fibers were produced in the same manner as in Example 1 except that the amount of the 90% by weight hexamethylenediamine aqueous solution was changed to 0.88 g.

Example 4
Porous fibers were produced in the same manner as in Example 1 except that an ammonium chloride aqueous solution (concentration 5 mass%) was used as the acid solution for dealkalization treatment instead of the acetic acid methanol solution.

(Example 5)
The amount of the hexamethylenediamine aqueous solution having a concentration of 90% by mass was changed to 1.44 g, and the porous material was porous in the same manner as in Example 1 except that it was immersed in an aqueous solution of ammonium chloride (concentration 5% by mass) instead of the acetic acid methanol solution. Fiber was produced.

(Example 6)
Example 1 except that the amount of the hexamethylenediamine aqueous solution having a concentration of 90% by mass was 0.88 g and was immersed in an aqueous solution of ammonium chloride (concentration of 5% by mass) instead of the acetic acid methanol solution for dealkalization treatment. A porous fiber was produced in the same manner.

(Comparative Example 1)
Porous fibers were produced in the same manner as in Example 2 except that the fibrous material was not immersed in a methanolic solution of polyvinyl alcohol.

(Comparative Example 2)
A porous fiber was produced in the same manner as in Example 2 except that the hexamethylenediamine aqueous solution was not added to the sodium silicate aqueous solution.

(Comparative Example 3)
Porous fibers were produced in the same manner as in Example 1 except that the hexamethylenediamine aqueous solution was not added to the sodium silicate aqueous solution and the fibrous material was not immersed in the methanolic polyvinyl alcohol solution.

<Evaluation of fibrous material>
Shape retention property It was confirmed whether or not the shape of the fiber was retained when the obtained fibrous material was touched by hand. “A” indicates that the shape of the fiber can be maintained, “B” indicates that it breaks into powder, and “C” indicates that it breaks into a mass.

Flexibility The cotton-like fibrous material that was able to maintain the fiber shape in the evaluation of shape retention was placed in a glass cylindrical container having an inner diameter of 30.5 mm and a depth of 54.5 mm. On top of that, a plastic weight having an outer diameter of 18.5 mm, a thickness of 2 mm and a weight of 131 g was placed to compress the fibrous material. The difference between the height of the fibrous material on which the weight was placed and the height of the fibrous material when the weight was removed was measured to evaluate the flexibility. A large difference means that the flexibility of the fibrous material is high.

  Table 1 shows the production conditions of the porous fibers in each Example and Comparative Example, and the evaluation results of the formed fibers. In an example in which a spinning solution containing sodium silicate and an aliphatic amine was used, and the fibrous material after spinning was immersed in an alcohol solution of PVA, a fibrous material having an appropriate flexibility while maintaining a good fiber shape. I was able to get things.

Claims (3)

Spinning a spinning dope containing sodium silicate, aliphatic amine and water to form a fibrous material containing silicate ions and sodium ions;
Preparing an alcohol solution of polyvinyl alcohol;
Contacting the polyvinyl alcohol with the fibrous material in an alcohol solution of the polyvinyl alcohol;
Removing at least a portion of the sodium ions from the fibrous material;
Are provided in this order, and the manufacturing method of a fibrous material.   The method according to claim 1, wherein, in the step of removing at least a part of the sodium ions from the fibrous material, the sodium ions are removed by contacting the fibrous material with an acid solution.   The method according to claim 1 or 2, wherein a proportion of the aliphatic amine in the spinning dope is 0.1 to 15% by mass with respect to a total amount of the sodium silicate and the aliphatic amine.