JPH05209001A - Manufacturing method of high strength cellulose gel - Google Patents

Abstract

PURPOSE:To obtain a cellulosic gel which is improved markedly in strength in a simple manner in the absence of any crosslinking agent by treating a gel of a cellulose derivative with heat. CONSTITUTION:A gel comprising a cellulose derivative is subjected to a heat treatment, in which the gel is preferably heated in water or an aqueous solution (e.g. an aqueous solution of urea, ethanol or sodium chloride) at 80-l30 deg.C, the gel used being in the form of fiber or granule in general.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a high strength cellulosic gel. More specifically, it relates to a method for producing a high-strength cellulose-based gel that can be used as a packing material for chromatography, a carrier for immobilizing an enzyme, a carrier for affinity chromatography, a base material of an ion exchange resin, a medical adsorbent, and the like.

[0002]

2. Description of the Related Art In recent years, cellulose gel has been actively used in the fields of medicine, food, etc. for the purpose of purification or adsorption.

As a method for producing such a cellulose gel,
A method of directly using cellulose as a starting material and a method of using a cellulose derivative as a starting material are known. In any of the methods, it is known that a cellulose gel can be usually obtained by forming a solution of cellulose or a cellulose derivative into fibers, particles or the like depending on the purpose, and then coagulating and regenerating the solution.

Cellulose is soluble only in limited special solvents such as copper ammonia solution and formaldehyde / dimethyl sulfoxide mixed solution, so that the coagulation method is also limited. Extensive control of the fine structure is not always easy (see, for example, Japanese Patent Publication No. 52-11273, Japanese Patent Publication Nos. 55-44312 and 57-159801). On the other hand, cellulose derivatives include good solvents such as dimethyl sulfoxide, N-methyl-2-pyrrodone, acetone and methylene chloride and non-solvents such as ethanol, methanol, butanol, ethylene glycol, propylene glycol, glycerin and polyethylene glycol. Since there are a wide range of solvents such as a solvent or a mixed solution with a swelling agent, and various coagulation methods, it is relatively easy to control a wide range of fine structure of the gel (for example, JP-A-52-129788, JP-A-52-129788). See JP-A-56-24429 and JP-A-63-68645.

[0005]

Generally, the structure of gel is
In addition to the fiber diameter or particle diameter, the saturated adsorption amount, exclusion limit molecular weight and the pore size and porosity of the gel surface, which are directly related to the adsorption rate, are almost determined by the microstructure such as the pore size and porosity inside the gel, Gel strength is not necessarily determined solely by these electron microscopic structural properties. However, when the cellulose gel is used in the above-mentioned applications, particularly when it is used in a packed state, its high strength is extremely important as a main factor that determines the pressure resistance of the packed column, that is, the practicality.

The gel that can be used for applications such as chromatography obtained by coagulating a cellulosic solution must have a dilute solution of cellulose according to the above-described production method, and the high crystallinity of cellulose prevents the formation of cellulose molecules. Although it is possible to form an aggregated skeleton with a relatively high density, it cannot be said that the skeleton is brittle and has high strength. Further, it is difficult to control the fine structure in a high range because the solvent of cellulose is extremely limited as well known and therefore the coagulation method is also limited.

The cellulose derivative is dissolved in various kinds of solvents to a high concentration as described above. However, the gel obtained by coagulating such a solution has a bulky skeleton due to poor crystallinity of the cellulose derivative molecule, in other words, poor cohesive force between the molecules, and its strength cannot be said to be high. . Further, if a solution having a too high concentration is used to increase the strength, it becomes difficult to control the fine structure. Therefore, in the conventional method, a gel having a wide range of practicality and high strength has not been obtained although the fine structure can be controlled in a high range by using the cellulose derivative.

As known in the art as a method for increasing the strength of these gels, it is also known to cross-link the molecules with epichlorohydrin, glutaraldehyde, etc., but not only the number of steps is increased, but the effect is not sufficient as expected. Absent.

An object of the present invention is to produce a cellulosic gel whose strength is dramatically improved by a simple method without using a cross-linking agent or the like while taking advantage of the above advantages of using a cellulose derivative. .

[0010]

The skeleton of an aqueous gel of a cellulose derivative produced by a conventional method is considered to have a structure in which many water molecules are hydrated by hydrogen bonds between the molecules. Therefore, if the water molecules can be effectively extracted while the cellulose derivative molecules are aggregated, the skeleton becomes dense and the strength of the gel can be improved. The present inventors have conducted extensive studies based on such a hypothesis, and as a result, the strength of the cellulose derivative gel is dramatically improved by simply heating it in water or an aqueous solution, and this strength is regenerated into cellulose. However, they have found that they are maintained, and have completed the present invention.

That is, the present invention relates to a method for producing a high-strength cellulosic gel characterized by heat treating a gel of a cellulose derivative.

[0012]

[Function] Although the reason why the strength of a cellulose derivative gel is improved by heat treatment is not always clear, the hydrogen bond energy of water molecule is equivalent to the molecular kinetic energy of about 70 ° C. It is known that the water molecule becomes larger than the hydrogen bond energy and desorbs from the bonding point. When the heat treatment causes the desorption of water molecules between the cellulose derivative molecules and the progress of aggregation between the cellulose derivative molecules, the strength of the gel increases. Conceivable.

[0013]

Examples As the cellulose derivative used in the present invention, in addition to cellulose fatty acid esters such as cellulose acetate, cellulose butyrate, cellulose propionate and cellulose acetate butyrate,
Examples include cellulose organic acid esters such as cellulose carbamate and cellulose benzoate. All of them are dissolved in many kinds of solvents and easily hydrolyzed by alkali treatment to be regenerated into cellulose. Among these cellulose derivatives, a cellulose fatty acid ester, particularly cellulose acetate is preferable because it gives a gel having higher strength.

As described above, since the strength of the gel improved by the heat treatment is maintained even when regenerated into cellulose, it can be used as it is as a packing material for chromatography. Various known chemical modifications may be added depending on the purpose. For example, it can be used for medical purposes by binding a functional group having physiological activity, as an ion exchange resin by introducing an ion exchange group, or as a biochemical catalyst by immobilizing an enzyme.

The shape of the gel in the present invention is not particularly limited, but a fiber-like or particle-like gel is usually used in these applications. In particular, a particulate gel is preferable because it has versatility and can be used for any purpose.

The particulate cellulose derivative gel can be produced by the above-mentioned known method, but since the particle diameter is extremely uniform, the method by the applicants (for example, JP-A 63-112634 and JP-A 63-112634). 63-117039, Japanese Patent Laid-Open No.
The method described in JP-A 1-275601 and JP-A 1-278541) is particularly preferable.

The function of the heat treatment in the present invention is to make the thermal kinetic energy of water molecules larger than the hydrogen bond energy so as to separate them from the cellulose derivative molecules and promote the aggregation between the cellulose derivative molecules. . This thermal kinetic energy is provided by heating to a temperature of at least 70 ° C, preferably above 80 ° C, when the heat treatment is carried out in water. Naturally, the higher the heat treatment temperature is, the more effectively the desorption of water molecules is promoted as the temperature rises, but economically, it is recommended to keep the vapor pressure of water below a few atmospheres at about 130 ° C or lower. preferable. Therefore, when the heat treatment is carried out in water, the temperature may be 80 to 130 ° C., and the treatment time may be shorter as the temperature is higher, but it is usually 10 to 60 minutes unless the gel is large.

As is well known, lower alcohols such as urea and ethanol and metal salts such as sodium chloride and calcium chloride have the effect of weakening the hydrogen bonding force. Therefore, the heat treatment effect is further promoted by using an aqueous solution containing these substances in appropriate amounts as the gel heating medium. It is also possible to increase the heating temperature without increasing the vapor pressure by adding a high boiling point polyhydric alcohol such as ethylene glycol, propylene glycol, or glycerin, which is a nonsolvent for the cellulose derivative.

The strength of the cellulose derivative gel dramatically improved by the above heat treatment as described above is maintained even when regenerated into a cellulose gel by hydrolysis. Also,
The strength of the gel is still maintained even if various chemical modifications are added to the gel according to the purpose of use as described above. Therefore, in order to have versatility in such applications, the cellulose derivative gel is usually treated with an alkali. Is regenerated into a cellulose gel by. The method of alkali treatment is well known, and these known methods can also be used in the present invention.

Since the heat treatment in the present invention does not involve the dissolution of the cellulose derivative gel, the original microstructure is basically maintained as it is, but the heat treatment causes a similar shrinkage due to the elimination of hydration water and the aggregation of the cellulose derivative molecules. Is inevitable. However, the alkali treatment hardly changes. Furthermore, biochemical modification of the regenerated cellulose gel as described above hardly changes the microstructure. Therefore, it can be said that the use of the cellulose gel of the present invention makes it easy to design gel properties in various applications.

The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

Example 1 The method described in JP-A 1-278541, that is, 8 parts by weight of cellulose diacetate and propylene glycol
A solution consisting of 64 parts by weight and 28 parts by weight of dimethylsulfoxide was heated to 95 ° C and discharged from a 50-micron pore at 15 m / s, and mechanical vibration of 17 kHz was applied to form uniform droplets. After flying in 1.5 m of air,
It is trapped in a 40% by weight dimethylsulfoxide aqueous solution and coagulated. After standing for 24 hours, the gel obtained is washed with water to have pores of approximately 0.5 microns from the surface to the inside, and the skeleton has a network structure. A nearly uniform cellulose diacetate gel with a particle size of 130 microns was prepared. This gel is called A.

Next, while the gel is moistened with water,
It was heated at 121 ° C. for 1 hour. By this heat treatment, the particle size
Shrinked to 100 microns. This gel is called B.

Furthermore, the gel after this heat treatment is 1.5% by weight.
The regenerated cellulose gel was obtained by immersing in a sodium hydroxide aqueous solution at 40 ° C. for 2 hours and then washing with water. The particle size was hardly changed by this treatment. This gel is called C.

For comparison, an alkali treatment was carried out in the same manner as above without heat treatment to obtain a regenerated cellulose gel. This treatment caused the particle size to shrink to 110 microns. This is called gel D.

Further, this gel was heat-treated in the same manner as above. The particle size was hardly changed by this treatment. This gel is called E.

These gels were evenly packed in an acrylic resin transparent column having an inner diameter of 14 mm and a length of 50 mm, and the pressure loss when water was flown through this column 2 by a pump 1 using the circuit shown in FIG. It was measured with a pressure gauge 3. Reference numeral 4 is a graduated cylinder for flow rate measurement. As a result, the pressure loss (critical pressure) and the flow rate at that time when the proportional relationship between the flow rate of water and the pressure loss is lost and the pressure loss starts to rise rapidly are as shown in Table 1 below for each gel. It was

[0028]

[Table 1]

From these results, it can be seen that the heat resistance of the cellulose derivative gel dramatically improves the pressure resistance.

Example 2 The method described in JP-A-63-117039, that is,
A solution consisting of 8 parts by weight of cellulose diacetate, 46 parts by weight of propylene glycol, and 46 parts by weight of dimethylsulfoxide was heated to 90 ° C. and discharged at a rate of 15 m / s through 50 micron pores, and mechanical vibration of 17 kHz was applied. A uniform droplet was made to fly in the air of 1.5 m, and then at 20 ℃
By capturing in an aqueous solution of 30% by weight of ethanol and coagulating, and leaving the gel for 2 hours and washing it with water, a dense layer having a thickness of about 1 micron is formed on the surface, and the inside has a thickness of about 1 micron. Almost uniform cellulose triacetate gel having a network structure of pores and a particle size of 130 microns was prepared. The exclusion limit molecular weight of this gel was about 80,000.

This gel was heat treated in the same manner as in Example 1 and then treated with alkali to obtain a regenerated cellulose gel. By these treatments, the particle size of the gel shrank to 100 μm, and its exclusion limit molecular weight became about 20,000.

As a result of measuring the limit pressure of each gel in the same manner as in Example 1, the limit pressure of the gel not heat-treated was 16
0 mmHg, heat treated gel has a critical pressure of 300 mmH
It was g.

Example 3 The regenerated cellulose produced in Example 1 according to the present invention was epoxidized by a known method using epichlorohydrin, and then dextran sulfate was fixed. The particle size of the gel did not change after these reactions. The limit pressure of this gel was 280 mmHg.

From these examples, the strength of the cellulose derivative gel was dramatically improved by the method of the present invention regardless of its microstructure, and the regenerated cellulose gel obtained by the method of the present invention was further biochemically. It can be seen that high strength is maintained even after modification.

[0035]

According to the present invention, a packing material for chromatography, a carrier for immobilizing an enzyme, a carrier for affinity chromatography, a base material of an ion exchange resin, and a medical adsorbent by a very simple method of heat treatment. It is possible to obtain a high-strength cellulosic gel that can be used over a wide range.

[Brief description of drawings]

FIG. 1 is an explanatory view of an apparatus for measuring pressure loss of gel used in an example of the present invention.

Claims (4)

[Claims] 1. A method for producing a high-strength cellulose-based gel, which comprises heat-treating a gel comprising a cellulose derivative. 2. The method according to claim 1, wherein the cellulose derivative is a cellulose fatty acid ester. 3. The method according to claim 1, wherein the heat treatment is heating the gel in water or an aqueous solution at 80 to 130 ° C. 4. The method according to claim 1, wherein the gel is in the form of fibers or particles.