JP3527582B2 - Cellulose porous body and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous cellulose material having minute spherical independent pores which are not communicated with each other and a method for producing the same.

[0002]

2. Description of the Related Art Cellulose porous material is a perfume,
Carriers of functional materials such as agricultural chemicals and pharmaceuticals, or bacterial cells,
It is used as an immobilization carrier for yeasts, adsorbents, raw materials for ion exchangers, and the like.

By the way, conventionally, the following method has been known as a method for producing a cellulose porous body.

First, one of them is Japanese Patent Publication No. 6-62781.
The method is disclosed in Japanese Patent Laid-Open Publication No. 2004-242242, in which viscose and a water-soluble polymer are mixed and the mixture is added to an aqueous solution of anionic polymer to form fine particles containing viscose and the water-soluble polymer. It is a method in which a porous cellulose material is obtained by forming it, coagulating and regenerating it, and removing the water-soluble polymer by washing with water.

This method is a method in which a water-soluble polymer compound serves as a porosifying agent to make cellulose porous, and polyethylene glycol and its derivatives are used as the water-soluble polymer compound. These water-soluble synthetic polymers phase-separate into a net-like shape as the cellulose coagulates.
Traces of synthetic polymer remain in the cellulose as pores, and the pores become communication pores penetrating the surface. Therefore, in this method, it is not possible to form minute spherical independent pores that do not communicate with each other inside the cellulose, and there is also a risk that the synthetic polymer trapped inside will remain if the washing is not sufficient.

Another method is disclosed in Japanese Patent Laid-Open No. 63-92.
There is a method disclosed in Japanese Patent No. 602, which is a method in which viscose, calcium carbonate and a water-soluble anionic polymer compound are mixed to prepare a viscose fine particle dispersion liquid containing calcium carbonate. This is a method in which fine particles are prepared by coagulation and neutralization, and then calcium carbonate is removed by acid decomposition to obtain spherical spherical cellulose particles.

However, in this method, since calcium carbonate, which is a porosifying agent, is decomposed after coagulation, the pores obtained largely depend on the particle size and shape. Although calcium carbonate having a diameter of 0.1 μm to several mm is manufactured, it is extremely difficult to uniformly disperse fine calcium carbonate having a particle size of 0.1 to 2 μm in a highly viscous solution such as viscose. However, since calcium carbonate having a particle size larger than that is often manufactured by crushing and classifying, there is a problem that the pores formed are indefinite and there is a high possibility that the pores communicate with each other. .

Another method is disclosed in Japanese Patent Laid-Open No. 64-43.
There is a method disclosed in Japanese Patent No. 530, which is a method in which a cellulose solution is made into droplets, cooled and frozen, and then the solvent separated by extraction or the dissolution ability is lost so that the diameters separated by a membrane can be reduced. It is a method of obtaining particles of a porous cellulose body having a large number of pores larger than about 2 μm.

However, since the pores formed in the particles of the cellulose porous body obtained by this method are continuous pores from the inside to the surface, they are disadvantageous in terms of mechanical strength. Moreover, it requires a very expensive process of cooling, which is economically disadvantageous.

Still another method is disclosed in JP-A-6-15.
There is a method disclosed in Japanese Patent No. 772, in which viscose and calcium carbonate are mixed and extruded from a nozzle, and coagulation and regeneration of cellulose as droplets and acid decomposition of calcium carbonate are simultaneously performed to obtain a particle size of 0. 2.5 at 5-10 mm
This is a method of obtaining particles of a porous cellulose body having pores of ˜250 μm.

In this method, however, it is difficult to obtain an independent small pore structure because the carbon dioxide gas generated by the acid decomposition of calcium carbonate forms voids, and large communicating pores are formed, resulting in a cross section. When observed with an electron microscope, it was normally possible to generate only a few tens of holes in terms of a cross-sectional area of 1 mm ² .

As described above, in the conventional method for producing a porous cellulose material, when it is used as a sustained-release carrier for various drugs, those having a small pore diameter have a too small pore volume and cannot sufficiently carry the drug. On the contrary, if the pore size is large, the drug release rate becomes too high, or the mechanical strength is weak.
In addition, if the pores are not independent pores but communicate with each other or are continuous so as to reach the surface from the inside, the release rate of the retained drug is high, and especially for the drug that easily volatilizes, it should be stored before use. It releases the drug during the period.

Therefore, the present invention provides a porous cellulose material which is excellent in liquid absorption and liquid retention and has high mechanical strength, and is particularly useful as a sustained release carrier for various drugs and functional agents, and a method for producing the same. It is the one we are trying to provide.

[0014]

In the cellulose porous body provided by the present invention, fine spherical independent pores having a pore diameter of 0.1 to 50 μm and not communicating with each other are converted into a cross-sectional area of 1 mm ² and a volume of 1000 to 100. It is composed of regenerated cellulose scattered at a ratio of 1,000, and can be produced by the following method.

The method is to regenerate the cellulose while coagulating an alkaline cellulose solution mixed with an alkali-soluble polysaccharide and then hydrolyzing the polysaccharide in an acid bath, or a mixed solution thereof. Is directly added to the acid bath to coagulate and regenerate the cellulose and hydrolyze the polysaccharide at the same time. This method does not allow the production of small independent pores having a pore size of 0.1 to 50 μm and which cannot be communicated with each other. A cellulosic porous material in which pores are uniformly scattered is obtained.

That is, when the cellulose in the cellulose solution coagulates, the polysaccharide dissolved in the cellulose solution is concentrated and separated, and the cellulose becomes porous due to a phase separation phenomenon in which minute regions are formed.

The shape of the cellulose porous body obtained by the present invention is not particularly limited, and various shapes such as spherical, oblong or oblate spherical particles, cylindrical, cylindrical, fibrous, and film shapes can be used according to the purpose of use. It can be shaped,
The spherical shape is advantageous in terms of mechanical strength and ease of handling.

For example, the shape and particle size of the particulate cellulose porous material can be adjusted by the cellulose concentration and viscosity of the cellulose solution, or the kind and addition amount of the polysaccharide. When regenerating cellulose, if a cellulose solution is dropped from a nozzle toward a coagulation bath, particles with a relatively large particle size of about several mm can be obtained, and if sprayed from a spray nozzle, particles with a particle size of several tens of μm can be obtained. Porous cellulose particles are obtained.

Examples of the alkali type cellulose solution used in the present invention include viscose and cellulose copper ammonia solution. For example, in viscose, the cellulose concentration is 3 to 15 wt% (preferably 4 to 10 wt%).
%) And the ammonium chloride value is 3 to 12 (preferably 4 to 4).
9), alkali concentration is 2 to 15 wt% as caustic soda
(Preferably 5 to 13 wt%), viscosity at 20 ℃ 5
Those having a range of 0 to 10,000 centipoise (preferably 100 to 7,000 centipoise) can be used, and viscose which is usually used for cellophane production is preferably used.

The polysaccharide used in the present invention may be any one as long as it is soluble in alkali and easily acid-hydrolyzed, and examples thereof include starch or its derivatives, vullan, dextran and gum arabic. Is mentioned. In particular, starch and its derivatives are mentioned as easily available and inexpensive ones, and their origins are wheat, potato,
It may be corn, tapioca, or the like, or may be modified starch modified by chemical, physical, or biological means. Examples of the modified starch include starch decomposition products such as dextrin, acid-treated starch, oxidized starch and dialdehyde starch, starch ethers such as carboxymethyl starch and hydroxyethyl starch, starch esters such as phosphoric acid starch and acetic acid starch, or α. Physically modified starch such as modified starch, heat-moisture treated starch and the like, enzyme modified starch such as amylose and the like can be mentioned.

In particular, in the present invention, the viscosity when the polysaccharide is dissolved in the cellulose solution is important. When the polysaccharide is dissolved in a 6 wt% alkaline aqueous solution at a concentration of 10 wt%, the viscosity at 20 ° C. is 10 centipoise to 100.
It is preferably in the range of 00 centipoise, particularly 10 centipoise to 5000 centipoise. When a high-viscosity polysaccharide is used, the viscosity of the mixed solution when mixed with a cellulose solution is extremely increased, which makes it difficult to prepare particles.
Moreover, when a monosaccharide or a low molecular weight oligosaccharide which is a structural unit of a polysaccharide is used, a porous structure cannot be formed.

Next, the addition amount of the polysaccharide is preferably 0.1 to 17 wt% in the polysaccharide mixture of the cellulose solution.
If the amount added is too low, the effect as a porosifying agent will not be obtained, and if it is too high, the amount of polysaccharides to be removed will increase and the mechanical strength of the obtained cellulose porous material will significantly decrease.

For coagulating the cellulose in the cellulose solution, a method using a coagulant is generally used. As the coagulant, an organic solvent such as ethanol or acetone, a salt solution such as calcium salt, an inorganic acid such as hydrochloric acid or sulfuric acid, an organic acid such as acetic acid, or the like can be used. It is possible. In addition, strong acids such as hydrochloric acid and sulfuric acid are usually used to regenerate cellulose, but weak acids such as acetic acid can also be regenerated.

In the method of the present invention, the polysaccharide used as the porosifying agent is hydrolyzed to have a low molecular weight by the acid used for regenerating the cellulose from the cellulose solution, and the regenerated cellulose thus obtained is very easily converted into the polysaccharide. To be removed.
At this time, in order to sufficiently proceed the hydrolysis of the polysaccharide, an inorganic acid such as hydrochloric acid or sulfuric acid which is a strong acid is used in the acid bath,
When the concentration is 0.5 to 2.0 N, it is preferable to react for 1 hour or more.

If an acid is used in the coagulation / regeneration bath,
Coagulation / regeneration of cellulose in the cellulose solution and acid hydrolysis of the polysaccharide can be simultaneously performed. Therefore, if the desired porous structure can be formed, the use of an acid in the coagulation / regeneration bath is very advantageous in terms of cost.

If necessary, a foaming agent such as calcium carbonate is mixed with a polysaccharide in an alkaline type cellulose solution, and phase separation of cellulose and polysaccharide and foaming of the foaming agent are carried out at the same time. It is also possible to form a cellulosic porous body in which desired microscopic independent pores and various pores coexist.

[0027]

【Example】

Example 1 As a polysaccharide, the viscosity at 20 ° C. when dissolved in a 6 wt% alkaline aqueous solution at a concentration of 10 wt% was 2
Soluble starch (manufactured by Nacalai Tesque Co., Ltd.) having a density of 2.5 centipoise (500 g) was mixed with cold water (2900 g). (6, alkali concentration 6%) was mixed with 5000 g to prepare a soluble starch mixed solution of viscose.

A viscose liquid containing the soluble starch is sucked and pressurized by a tube pump to have a diameter of 1.2 mm.
The liquid was extruded in the form of droplets from the nozzle at a speed of 1 cc / min and dropped into a 2N concentration hydrochloric acid bath which is a coagulation and regeneration bath.

Then, it was washed with a large excess of water and desulfurized at 70 ° C. for 30 minutes in a desulfurization bath containing 5 g / 1 of sodium sulfide. Then, wash with a large excess of water, then 2.6 g
/ 2 in a bleaching bath containing 1/1 sodium hypochlorite
Bleaching was carried out for 0 minutes, and the particles were washed again with a large excess of water to obtain water-swollen cellulose porous particles.

Thereafter, the particles in a water swollen state were dried to obtain dried particles. At the time of drying, water in the water-swelled particles was replaced with ethanol and then with tert-butanol, and then freeze-vacuum drying was performed so that the independent pores of the porous body were not blocked by shrinkage.

The particles thus obtained were spherical with an average particle size of 2.3 mm in a water swollen state, and the inside was observed with a scanning electron microscope. As a result, as shown in FIG. The spherical independent pores were uniformly formed.

(Example 2) 6 wt% instead of soluble starch
20 when dissolved at 10 wt% concentration in
Carbamic acid esterified and phosphoric acid esterified starch derivative having a viscosity of 16.0 centipoise (SK-3000 manufactured by Nippon Corn Starch Co., Ltd.) was used in the same manner as in Example 1 except that the cellulose porosity was used. Got body particles.

The obtained particles have a spherical shape with an average particle size of 2.0 mm in a water swollen state, and when observed by a scanning electron microscope, spherical independent pores of about 3 μm have a uniform cross-sectional area of 1 mm ²
There were 9500 converted.

(Example 3) 6 wt% instead of soluble starch
20 when dissolved at 10 wt% concentration in
The same procedure as in Example 1 was carried out except that the raw material having a viscosity at 1 ° C. of 11.0 centipoise was used (manufactured by Nacalai Tesque, Inc.) to obtain particles of a porous cellulose material.

The obtained particles are spherical particles having an average particle size of 2.0 mm in a water swollen state, and are 3 according to a scanning electron microscope.
It was a porous particle having spherical independent pores of about μm.

Example 4 A soluble starch mixed solution of viscose obtained in the same manner as in Example 1 was sucked and pressurized by a high-pressure electric pump and sprayed from a nozzle having a diameter of 0.4 mm toward a hydrochloric acid bath. Except for this, the same procedure as in Example 1 was carried out to obtain fine cellulose porous particles.

The obtained particles have an average particle size of 2 when swollen in water.
When observed with a scanning electron microscope, the spherical particles of 90 μm showed that spherical independent pores of about 4 μm were uniformly formed as shown in FIG.

Example 5 As a polysaccharide, 3.0 g of soluble starch (manufactured by Nacalai Tesque, Inc.) having a viscosity of 22.5 centipoise at 20 ° C. when dissolved in a 6 wt% alkaline aqueous solution at a concentration of 10 wt% , 0.3 g of sodium hydroxide was dissolved in 5.0 g of distilled water.

Separately, cotton linter as a cellulose raw material was dissolved in a copper ammonia solution to give a copper concentration of 4.
0 wt%, ammonia concentration 9.8%, cellulose concentration 5.
A 7% solution was prepared. The starch solution was mixed with 50 g of this cellulose solution to prepare a mixed solution having a cellulose and starch concentration of 4.9% each.

This mixed solution was treated in the same manner as in Example 1 to obtain porous cellulose particles. The obtained particles were 3 mm in the major axis direction and 1.5 mm in the minor axis direction, and spherical independent pores having a pore diameter of about 2 μm were converted into a cross-sectional area of 1 mm ² of 58200.
Had formed individually.

Comparative Example 1 Example 1 was repeated except that sucrose (having a viscosity of 6 centipoise when dissolved in a 6 wt% alkaline aqueous solution) as a constitutional unit of the polysaccharide was used instead of the soluble starch. When spherical cellulose particles were prepared in the same manner as above, flat spherical particles having an average particle diameter of 2.1 mm were obtained in a water swollen state. However, when the section was observed with an electron microscope, no pore structure was found inside.

Comparative Example 2 Calcium carbonate (SS # 30 manufactured by Nitto Koka Kogyo KK) 142 was used instead of soluble starch.
Porous cellulose particles were prepared in the same manner as in Example 1 except that 5 g of viscose was added to prepare a calcium carbonate mixed solution of viscose.

The obtained particles are spherical particles having an average particle size of 3.1 mm in a water swollen state, and when observing the cross section with an electron microscope, they are porous particles having radial pores with a pore diameter of about 60 μm. there were. The number of holes in terms of cross-sectional area 1 mm ^{2 of} this product was 60.

Table 1 shows the results of a water absorption test and a water retention test performed on the porous cellulose particles obtained in each of these Examples and Comparative Examples.

The methods of the water absorption test and the water retention test are as follows. (Water Absorption Test) A 10 ml sample was sampled in a ground-in stopper Erlenmeyer flask and shaken while dripping distilled water. The maximum amount of water absorption was defined as the amount of distilled water at which the wall surface of the flask began to get wet.

(Water retention test) 3 ml of sample was made to absorb distilled water corresponding to 80% of the maximum water absorption amount, and 5 cm which was impermeable to water.
Heat sealed in a corner plastic bag. It was left at room temperature, and the number of days when the inner surface of the plastic bag started to be wet was defined as the number of days of water retention.

[0047]

[Table 1] As shown in Table 1, the materials of Examples 1 to 5 are very excellent in water absorption and have sufficient water retention. On the other hand, although some of Comparative Examples have good water retention like Comparative Example 1, the water absorption and water retention are inferior in balance.

[0048]

Industrial Applicability As described above, the porous cellulose material according to the present invention is excellent in liquid absorption and liquid retention and has high mechanical strength, so that various chemicals and functional agents, particularly volatilization or outflow, are easy. It is useful as a sustained release carrier for substances.

Further, in the method for producing a porous cellulose material according to the present invention, an alkali-soluble cellulose solution is mixed with an alkali-soluble polysaccharide, and the mixed solution is coagulated or directly in an acid bath. Since the addition is performed, it is possible to easily and inexpensively obtain the above-mentioned cellulose porous body having excellent liquid absorbing properties and liquid retaining properties.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph (× 500) of a cellulose porous body of Example 1.

FIG. 2 is a scanning electron micrograph (× 500) of the cellulose porous body of Example 2.

Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 9/26

Claims (3)

(57) [Claims] 1. After coagulating a cellulose solution in which an alkali-soluble polysaccharide is dissolved in an alkaline type cellulose solution,
Either regenerate the cellulose while hydrolyzing the polysaccharide in an acid bath, or add the cellulose solution in which the polysaccharide is dissolved directly to the acid bath to coagulate and regenerate the cellulose and simultaneously hydrolyze the polysaccharide. A method for producing a cellulose porous body, comprising: 2. The method for producing a cellulose porous body according to claim 1 , wherein the alkaline type cellulose solution is viscose. 3. A polysaccharide which is dissolved in an alkaline type cellulose solution has a viscosity at 20 ° C. when dissolved in an aqueous 6% by weight alkali solution at a concentration of 10% by weight.
Claim 1 using those 0-10000 centipoise
Or the method for producing a cellulose porous body according to item 2 .