JP2001354799A - Method of manufacturing cellulosic porous product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing by a simple method without using the conventional cell-forming material an excellent cellulosic porous product which forms fine closed cells in the surface layer and comparatively coarse cells in the inside. SOLUTION: The method of manufacturing a cellulose porous product comprises mixing a viscose with a gas which dose not adversely affect the stability of the viscose to form a fluid having cells and solidifying the fluid to regenerate cellulose. As the gas, air or nitrogen is preferred, and further as the stabilizer of cells to be formed, a surface active agent is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulosic porous body which is formed from a natural material, cellulose, which does not adversely affect the natural environment, via viscose and forms a porous body (foam) structure. The method relates to a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a porous cellulose body (hereinafter, used as a synonym for foam or sponge), sodium sulfate (boat salt) is mixed with viscose as a foam-forming material, and then cellulose is added. It is a common practice to form interconnected or open air bubbles on the surface by coagulation / regeneration and elution of the bowl nitrate. According to this method for producing a porous cellulose body, a neutralization / washing step and, in some cases, a bleaching treatment are required as a post-treatment in order to remove bow nitrate, salts, and reaction by-products remaining after the cellulose is regenerated. It is.

As another method for obtaining a porous cellulose material, Japanese Patent Publication No. 3-231942 and Japanese Patent Publication No. 5-3
JP-A-39115 and JP-B-5-339410 disclose a method in which a mixture of viscose and an acid-decomposable foaming agent such as calcium carbonate is extruded into an acid bath to coagulate and regenerate the cellulose and to release the acid-decomposable material. A method has been proposed in which a gas generated by decomposition of a foaming agent is used as a bubble forming agent.

Further, as another method, a method of using a volatile agent together with an acid-decomposable foaming agent (Japanese Patent Publication No. 6-65412) or a method of using an alkali-soluble polysaccharide such as starch (JP-A-9-176327). Has been proposed.

[0005]

At present, the materials demanded in the world are safe and inexpensive materials.

[0006] The first problem is to produce a product in which the obtained porous cellulose material does not impair the biodegradability and non-toxicity inherent in cellulose as much as possible, that is, it is safe for the human body and the environment. It is to be. In order to manufacture a safe product, the raw materials used in the manufacturing process should not be limited to natural raw materials, but it is easy to remove in the product manufacturing process. It is important to limit to raw material chemicals that are easy to treat wastewater and waste.

[0007] The second problem is to reduce the manufacturing cost. In the conventional manufacturing technology, it is a major problem to reduce the production cost in industrial production, particularly to reduce the capital investment, the utility cost, and the productivity. In order to produce a cellulose porous body at low cost, the types of raw materials used should be reduced as much as possible,
It is to use inexpensive raw materials and to manufacture with as simple manufacturing equipment as possible.

Conventionally, a porous cellulose body having a cellulose matrix as a matrix is made of viscose as described above, to which an inorganic salt (usually using borate glass), reinforcing fibers, and, if necessary, pigments and additives. Then, the cellulose is immobilized through a coagulation / regeneration step of the cellulose by a heat treatment or an acid bath treatment, and at the same time, the glass is eluted to form bubbles, thereby producing bubbles. The biggest challenge in this manufacturing method is to use a crystal of borate. That is, it is necessary to condense and recrystallize the glass nitrate eluted from the viscose coagulation process, thereby reusing it as crystals.
Utility costs and operation management costs are a bottleneck in cost reduction. Furthermore, in this method, in order to make the size of the bubbles in the cellulose porous body uniform, it is necessary to make the particle size of the crystal of the boa glass uniform, and therefore, equipment costs for pulverizing and classifying the boa glass crystal are required. In addition, utility costs and operation management costs are required, which is also a bottleneck in cost reduction. Therefore, if a cellulose porous body can be produced without using borate, cost reduction will be achieved. In addition, the above-described method of using an inorganic or organic substance other than borate to form bubbles of cellulose also causes a complicated process including a post-treatment, which is also a factor of cost increase.

Another problem to be solved is to improve the function as a carrier. That is, the cellulose porous body manufactured by the conventional method has a structure in which the surface layer and the inside are almost the same,
Or it has a communicating structure, and as a carrier,
While there is an advantage that various bacteria and drugs can be uniformly supported, improvements in durability have been demanded, such as difficulty in surface layer strength and rapid release of the supported substance.

Accordingly, an object of the present invention is to improve the above-mentioned problems of the prior art, and a surprisingly simple means without using a conventional bubble-forming material allows a relatively dense surface layer portion. The present invention provides a method for producing an excellent porous cellulose body having fine bubbles and having relatively coarse bubbles inside.

[0011]

The above object of the present invention can be achieved as follows.

That is, according to the method for producing a porous cellulose material of the present invention, a gas which does not impair the stability of the viscose is mixed into viscose to form a fluid containing many microbubbles, and the fluid is coagulated. And regenerating the cellulose.

In the method for producing a porous cellulose material of the present invention, the gas is air or nitrogen, a surfactant is used as a stabilizer for generated bubbles, and the cellulose used as a raw material of viscose has a degree of polymerization. Is 300
It is included as a particularly preferable embodiment that the natural fiber is mixed as a reinforcing fiber.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the method for producing a porous cellulose material of the present invention will be described in detail.

The porous cellulose body of the present invention is preferably prepared by mixing and dispersing reinforcing fibers such as cotton and flax in viscose, if necessary, and adding water to form a uniform dispersion. Add a surfactant as an agent, mix it vigorously with agitation, etc. to form a fluid containing many bubbles, and need a fluid containing bubbles obtained in this way. Then, the cellulose is regenerated by solidifying by a conventional method after the desired shape is formed, and in particular, a cellulose porous body containing a myriad of independent air bubbles in the surface layer can be produced.

In the present invention, the cellulose porous body can be obtained as a spherical or particulate cellulose porous body. The particulate cellulose porous body can be obtained by supplying or dropping a fluid containing bubbles in an acidic bath in a droplet form. The particle diameter can be changed according to the purpose of use, but it is usually easy to produce a particle having a particle diameter of about 0.5 to 10 mm when swollen in water, and it is easy to handle.

As the viscose used in the production of the porous cellulose material in the present invention, a viscose having a polymerization degree of about 600 is usually used. From the viewpoint of physical properties such as mechanical strength, it is preferable that the degree of polymerization is large, and it is also possible to use viscose made of cellulose having a degree of polymerization of about 1,000. The preferred range of the degree of polymerization in the present invention is 300
１1,300, more preferably 400-800.

As the viscose used in the present invention, viscose used in the production of regenerated cellulose fibers can be used. The cellulose concentration of viscose used in the production of regenerated cellulose fibers is usually about 8 to 15%. In the present invention, a viscose having the same cellulose concentration can be used, but a more preferred cellulose concentration is 8%. 〜１０10%.

As a measure of the coagulability of the viscose used, a hotten-roth value (20 g of viscose) is used.
Was diluted with 30 cc of water, a 10% ammonium chloride solution was added dropwise while stirring, and the number of ml required for viscose to start coagulation was determined. Here, the salt point was simply evaluated by the simple saline method. . The salt point in the simple salt solution method is represented by a salt concentration at which 1 g of viscose is added to 100 to 250 g / l salt solution while stirring and solidified. The viscose used in the present invention has a salt point (by the simple salt solution method) of 150 g / or less and does not coagulate, and preferably has an alkali concentration of 6 to 7.5%.

In order to improve the mechanical strength of the product, natural fibers such as cotton, flax and ground pulp are preferably mixed with the viscose as reinforcing fibers. Polyester fiber, nylon fiber, acrylic fiber or other synthetic fibers may be mixed for the purpose of reinforcement, but maintain the original biodegradability of cellulose, which is the object of the present invention, and harmlessness in waste treatment. To do so, it is preferable to use only natural fibers. The amount of the reinforcing fiber to be added is preferably 1 to 30 parts by weight, more preferably 3 to 15 parts by weight based on 100 parts by weight of viscose.

In the present invention, the mixture of the viscose and the reinforcing fibers is diluted with water to form a uniform dispersion, and then is vigorously stirred to generate innumerable air bubbles. Make a high fluid. The apparent viscosity of a fluid containing innumerable air bubbles varies greatly depending on conditions such as the degree of polymerization of cellulose and the dilution ratio of viscose, but is in the range of several poises to several hundred poises, more specifically, 2 poises.
When the range is about 0 to 200 poise, the shape can be easily regulated. The apparent specific gravity of the fluid at this time is preferably 0.4 to 1.0, and more preferably 0.5 to 0.9.

The size and shape of the bubbles are governed by the shape and size of the stirring vessel / agitating blade, the speed during stirring, the temperature, the viscosity, the type and amount of the surfactant, and the like. By selecting a combination of these controlling factors, it is possible to obtain a bubble having a desired size and the stability of the bubble. The bubble in the fluid in the bubble formation stage has a spherical shape due to interfacial tension, and the size of the bubble formed by a mixer such as a whisk is 0.1 mm.
It is about 02 to 1 mm. The viscose diluent before mixing the gas is dark yellow, but the fluid containing countless bubbles becomes pale yellowish white, so it is desirable to mix and disperse the gas up to this stage.

The dilution water used for diluting the viscose is
Of course, ion-exchanged water and distilled water can be used without any problem, and ordinary drinking water can also be used unless there is a special reason such as regulation of impurities mixed in the product.

Further, the amount of the dilution water added affects the viscosity of the fluid after foaming, and also affects the shrinkage rate when forming a sponge. For this reason, the dilution water is usually added about 1 to 6 times, more preferably about 2 to 5 times the viscose from the viewpoint of workability and ease of defining the shape of the sponge to be produced.

In the present invention, it is preferable to use a surfactant as a foam stabilizer in order to stably produce bubbles generated by stirring. Since the viscose diluent diluted with diluting water is alkaline, the surfactant used must exhibit its function under alkaline conditions. Commercially available anionic surfactants have a sufficient function. Suitable surfactants include alkyl allyl sulfonates, sulfates, fatty acids and the like.

The surfactant may be added in an amount of about 0.1 to 0.5 part by weight based on 100 parts by weight of viscose. The surfactant may be added at the time of diluting the viscose with the diluting water, but since foaming is large, it is better to add the surfactant after the dilution. In any case, it is important to stir a viscose diluent or a dispersion mixed with reinforcing fibers in the presence of a surfactant to form countless bubbles. The diameter of the bubble can be set to a size of about 0.02 mm to 1 mm. The bubbles can be formed by a mixing means capable of uniformly dispersing the gas throughout the liquid, but a mixing method capable of dispersing a gas such as air or (and / or) nitrogen uniformly and small enough, for example, VIBROMIXER
A gas-liquid disperser such as (manufactured by Reika Kogyo Co., Ltd.) is preferable.

Next, the thus obtained fluid containing a large number of air bubbles is poured into an acidic aqueous solution to coagulate the viscose fluid containing the air bubbles, thereby regenerating the cellulose.
The acid used here is preferably an inorganic acid such as sulfuric acid or hydrochloric acid, and particularly preferably sulfuric acid. Organic acids can be used,
Post-treatment and wastewater treatment measures are cumbersome. At this time, the fluid is supplied to the coagulating liquid in the form of droplets (spherical shape) or a shape close thereto, and the coagulation progresses from the surface, and the inside is coagulated and regenerated by the acid that gradually penetrates, and the particulate cellulose is formed. A porous body is obtained. The air bubbles in the surface layer are similar to the shape and size at the time of foaming (diameter of about 0.02 mm to 1 mm) and are mostly closed cells, but the air bubbles in the center have many irregular shapes and air bubbles in the surface layer Are several times to several tens of times larger, and some are mutually connected. When the surface layer solidifies, the resulting particulate cellulose porous bodies do not adhere to each other, so that the regeneration of cellulose can be completed by treatment in an acidic bath or heating in a bowl glass bath. I can do it. Thereafter, if necessary, through steps such as neutralization and washing with water, it is possible to obtain a porous cellulose body in a state in which 90% or more of the bubbles are closed from the surface.

In the present invention, the fluid containing air bubbles is extruded into an acidic bath in the form of a gut having a diameter of about 2 to 6 mm to form a porous cellulose material.
To obtain a pellet-shaped porous cellulose body.

The porous cellulose obtained as described above is further subjected to post-treatments such as washing with water, bleaching and drying, if necessary. During these steps, a coloring agent such as a dye or a pigment can be added for coloring.

The maximum water absorption of the porous cellulose of the present invention is preferably 2 to 33 g / g (dry), more preferably 5 to 30 g / g (dry).

The cellulosic porous body of the present invention is a closed cell in which the majority of the bubbles in the surface layer are minute closed cells, and various biocarriers such as a carrier for nitrifying bacteria and denitrifying bacteria in wastewater treatment, or an insect repellent. Useful as a carrier for drugs such as fragrances.

[0032]

The present invention will be specifically described below with reference to examples.

Example 1 Polymerization degree: about 700, cellulose concentration: 9.7%, alkali concentration: 7%, salt point: 170 g / l ·
To 25 g of NaCl viscose, 1.25 g of crumb (pulverized product of alkali cellulose) having an average fiber length of 3 mm was added as a reinforcing fiber and uniformly dispersed. Further, 75 g of distilled water was added thereto to obtain a uniform dispersion having a viscosity of 220 ps (25 ° C.). Then, as a surfactant, a household detergent “Mama Lemon” (manufactured by Kao, main component: 27% linear alkylbenzene, alkyl 0.03 g of ether sulfate (Na)
In addition, air was mixed by vigorously stirring with a home whisk for 30 minutes to obtain a pale yellow-white fluid containing countless bubbles. The apparent specific gravity was 0.88.

The fluid obtained in this way is supplied with an inner diameter of 7 m.
The solution was extruded from a discharge hole of m, dropped as a droplet in a 5% sulfuric acid bath to solidify the surface, and left as it was in an acidic bath overnight at room temperature to complete the regeneration reaction of cellulose. The obtained spherical particles were sufficiently washed with water until the particles became neutral, and a particulate foam having a diameter of about 7 mm was obtained in a wet state. As a result of observing the inside of these particles with a 50 × microscope, a large number of bubbles having an average diameter of about 0.2 mm (0.1 to 0.4 mm) were present in the surface layer, and the inside was 0.3 to 1 It had a foam structure with 0.3 mm circular or irregular cells. FIG. 1 shows a cross-sectional shape of the obtained porous cellulose material. As a result of measuring the particles wetted with water by hot air drying, the maximum water absorption was 8.42 g / g (dry).

Here, the maximum water absorption is represented by maximum water absorption = water absorption (g) / dry product weight (g), which is measured specifically as follows. That is, after leaving it in a container filled with water for 2 hours or more, it is drained on a wire mesh for 3 minutes, and about 10 g of a wet sample is precisely weighed (B). Then, this sample is dried with a hot air dryer at 100 ° C. for 2 hours. The weight (A) after drying for hours is measured and expressed as (BA) / Ag / g (dry).

Example 2 A degree of polymerization of about 600, a cellulose concentration of 8.7%, an alkali concentration of 7%, and a salt point of 210 g / L ·
100 g of viscose of NaCl is placed in a 1 L round-bottomed flask, and the inside is filled with nitrogen gas. Then, while a small amount of nitrogen gas is passed, 4.7 g of crumb (ground alkali cellulose) is added as a reinforcing fiber and stirred. Then, 400 g of ion-exchanged water was added to obtain a uniform dispersion. Furthermore, a household detergent "Mama Lemon" (manufactured by Kao, main component: 27% alkyl benzene, alkyl ether sulfate Na) was used as an air bubble stabilizer.
g, and the mixture was vigorously stirred for about 90 minutes under a nitrogen atmosphere using a household whisk to mix nitrogen to obtain a fluid containing a large number of apparently uniform microbubbles.

The obtained fluid is dropped from a nozzle having an inner diameter of 5 mm into a 7% sulfuric acid bath to coagulate the surface, and coagulation / regeneration of viscose is completed in an acid bath. With this, a particulate cellulose porous body having a diameter of about 5 mm was obtained. The cellulose porous body obtained by sufficiently washing this with water was observed under a microscope of 50 times magnification to find that the surface layer had a diameter of 0.1 mm.
There are many bubbles of about 1 mm to 0.5 mm.
0% or more does not communicate with the surface and the inside has a diameter of 0.3 to
The porous body had circular or irregular bubbles of about 1.5 mm. The porous body swollen with water was dried with a hot air drier in the same manner as in Example 1 and the maximum water absorption was measured. The result was 9.5 g / g (dry). FIG. 2 shows a cross-sectional shape of the obtained cellulose porous body.

[0038]

According to the present invention, it is possible to obtain an excellent cellulosic porous body having a surface layer portion having independent fine cells and relatively coarse cells inside by a simple method without using a conventional cell forming material. Obtainable. In particular, by using an extremely inexpensive and easy-to-handle raw material such as air or nitrogen as a cell forming material, it is possible to produce a cellulose porous body safely and at low cost.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional view showing a state of a porous cellulose body of the present invention by a photograph as a substitute for a drawing.

FIG. 2 is a cross-sectional view showing a state of another porous cellulose body of the present invention, using a photograph as a substitute for a drawing.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yuji Oishi 3-360 Ogaga, Matsuyama-shi, Ehime Toray Fine Chemical Co., Ltd. Matsuyama Plant F-term (reference) 4F074 AA02 AE04 BA31 BA33 BC01 BC03 CA22 CB51 CC22X CC22Y CC30Z

Claims (5)

[Claims] 1. A method for producing a porous cellulose material, comprising mixing a gas into viscose to form a fluid containing bubbles, and coagulating the fluid to regenerate cellulose. 2. The gas according to claim 1, wherein the gas is air or nitrogen.
The method for producing a porous cellulose body according to the above. 3. The method for producing a porous cellulose material according to claim 1, wherein a surfactant is used as a cell stabilizer. 4. The polymerization degree of cellulose used as a raw material for viscose is 300 to 1,300.
4. The method for producing a porous cellulose body according to any one of items 1 to 3. 5. The method for producing a porous cellulose material according to claim 1, wherein natural fibers are mixed as reinforcing fibers.