JP3086739B2 - Manufacturing method of high strength cellulosic gel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a high-strength cellulosic gel. More specifically, the present invention relates to a method for producing a high-strength cellulosic gel that can be used as a packing material for chromatography, a carrier for immobilizing enzymes, 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 and the like for the purpose of purification or adsorption.

[0003] As a method for producing such a cellulose gel,
There are known a method using cellulose directly as a starting material and a method using cellulose derivative as a starting material. In any method, it is known that a cellulose gel is usually obtained by forming a solution of cellulose or a cellulose derivative into fibers, particles or the like according to the purpose, and then coagulating and regenerating.

[0004] Cellulose is soluble only in limited special solvents such as a cuprammonium solution and a formaldehyde / dimethylsulfoxide mixed solution, so that the coagulation method is limited. It is not always easy to control a wide range of microstructures (for example, see Japanese Patent Publication No. 52-11273, Japanese Patent Application Laid-Open Nos. 55-44312 and 57-159801). On the other hand, cellulose derivatives include good solvents such as dimethyl sulfoxide, N-methyl-2-pyridone, acetone and methylene chloride, and non-solvents such as ethanol, methanol, butanol, ethylene glycol, propylene glycol, glycerin and polyethylene glycol. There is a wide range of solvents such as a mixture with a solvent or a swelling agent, and various coagulation methods make it relatively easy to control a wide range of microstructure of the gel (for example, JP-A-52-129788, See JP-A-56-24429 and JP-A-63-68645.

[0005]

Generally, the structure of a gel is
In addition to the fiber diameter or particle diameter, it is almost determined by the fine structure such as the saturated adsorption amount, the exclusion limit molecular weight and the pore size and porosity of the gel surface directly related to the adsorption rate, 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 in a packed state, its high strength is extremely important as a main factor for determining the pressure resistance of the packed column, that is, practicability.

A gel which can be used for applications such as chromatography obtained by coagulating a cellulose solution must have a dilute cellulose solution according to the above-mentioned exemplified production method, and the cellulose molecules have high crystallinity due to the high crystallinity of the cellulose. Despite being able to form an aggregated skeleton at a relatively high density, the skeleton is not brittle and not very strong. Also, as is well known, the solvent for cellulose is very limited, and thus the coagulation method is also limited, so that it is difficult to control the microstructure in a wide range.

[0007] As described above, the cellulose derivative is dissolved in various solvents to a high concentration. However, the gel obtained by coagulating such a solution forms a bulky skeleton due to poor crystallinity of the cellulose derivative molecules, in other words, poor cohesive force between the molecules, and cannot be said to have high strength. . Also, 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 practicality and a high strength has not been obtained although the fine structure can be controlled in a wide range by using a cellulose derivative.

As a known method for increasing the strength of these gels, it is known to crosslink between molecules with epichlorohydrin, glutaraldehyde or the like. However, 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 having a remarkably improved strength by a simple method without using a cross-linking agent or the like, while keeping the above advantages of using a cellulose derivative as it is. .

[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 molecules. Therefore, if the water molecules can be effectively extracted while aggregating the cellulose derivative molecules, the skeleton becomes dense and the strength of the gel can be improved. The present inventors have made intensive studies based on such a hypothesis, and as a result, the strength of the cellulose derivative gel is dramatically improved only by heating it in water or an aqueous solution, and this strength is regenerated into cellulose. Have been found to be maintained, and the present invention has been completed.

That is, the present invention relates to cellulose fatty acid
The present invention relates to a method for producing a high-strength cellulosic gel, which comprises heat-treating a gel made of steal .

[0012]

[Action] Although the reason why the strength of a gel made of cellulose fatty acid ester is improved by heat treatment is not always clear, the hydrogen bond energy of water molecules is equivalent to the molecular kinetic energy of about 70 ° C. It is known that the energy becomes larger than the hydrogen bond energy and the water molecules are released from the bonding point. The heat treatment releases the water molecules between the cellulose fatty acid ester molecules and promotes the aggregation between the cellulose fatty acid ester molecules, thereby increasing the gel. It is considered that the strength is increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Cellulose fatty acid ester used in the present invention
The Le, such as cellulose acetate, cellulose butyrate, cellulose propionate, etc. cellulose acetate butyrate and the like. These are all dissolved in various kinds of solvents, and are easily hydrolyzed by alkali treatment to be regenerated into cellulose. Among these cellulose fatty acid ester, et al or the higher-strength gel will be obtained, particularly cellulose acetate is preferred.

As described above, since the gel strength 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 according to the purpose. For example, it can be used for medical purposes by bonding a functional group having a physiological activity, as an ion exchange resin by introducing an ion exchange group, or as a biochemical catalyst by fixing an enzyme.

The shape of the gel in the present invention is not particularly limited, but a fibrous or particulate gel is usually used in these applications. Particularly, a particulate gel is preferable because it has versatility that can be used for any purpose.

The particulate cellulose fatty acid ester gel is
Although it can be produced by the above-mentioned known method, since the particle size is extremely uniform, the method of the present applicant (for example, JP-A-63-112634, JP-A-63-117039, 275601, JP-A 1-278541, etc.).

The effect of heat treatment in the present invention, cellulose fatty acid ester with disengaging from between the cellulose fatty acid ester <br/> molecule by greater than the hydrogen bonding energy thermal kinetic energy of water molecules as
It is to promote the cohesion between Le molecules. This thermal kinetic energy is provided by heating to a temperature of at least 70 ° C, preferably at least 80 ° C if the heat treatment is performed in water. The higher the temperature, the more effective the heat treatment temperature is. Therefore, it is more effective to increase the heat treatment temperature.However, economically, the temperature should be about 130 ° C or less so that the vapor pressure of water is several atmospheres or less. preferable. Therefore, if the heat treatment is performed in water, the temperature will be
The treatment time is 80 to 130 ° C and the treatment time is shorter as the temperature is higher, but it is usually 10 to 60 minutes unless the gel is particularly large.

As is known, lower alcohols such as urea and ethanol and metal salts such as sodium chloride and calcium chloride have an effect of weakening the hydrogen bonding force. Therefore, if an aqueous solution to which these substances are added in an appropriate amount is used as a heating medium for the gel, the heat treatment effect is further promoted. The heating temperature can be increased without increasing the vapor pressure by adding a high-boiling polyhydric alcohol such as ethylene glycol, propylene glycol, or glycerin which is a non-solvent for the cellulose fatty acid ester .

As described above, the strength of the cellulose fatty acid ester gel dramatically improved by the above heat treatment is maintained even when the cellulose gel is regenerated by hydrolysis. Further, since the strength thereof be added to various chemical modifications used depending on the purpose such as a gel on the still is maintained, in order to provide versatility on such applications, typically cellulose fatty acid ester gel The cellulose gel is regenerated by alkali treatment. The method of alkali treatment is well known, and these known methods can be used in the present invention.

[0020] The heat treatment in the present invention, cellulose fat
Since the acid ester gel is not dissolved, the original microstructure is basically maintained as it is, but the similar shrinkage cannot be avoided due to detachment of hydration water and aggregation of cellulose fatty acid ester molecules. However, the alkali treatment hardly changes. Furthermore, even if the cellulose gel regenerated as described above is biochemically modified, the microstructure hardly changes. Therefore, it can be said that the use of the cellulose gel of the present invention makes it easy to design gel characteristics in various applications.

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

Example 1 The method described in Japanese Patent Application Laid-Open No. 1-278541, namely, 8 parts by weight of cellulose diacetate, propylene glycol
A solution consisting of 64 parts by weight of dimethyl sulfoxide and 28 parts by weight of dimethyl sulfoxide was heated to 95 ° C. and discharged at a rate of 15 m / sec from a 50-micron pore, and subjected to 17 kHz mechanical vibration to form uniform droplets. After flying in 1.5m of air,
It is trapped in a 40% by weight aqueous solution of dimethyl sulfoxide, coagulated, and after standing for 24 hours, the obtained gel is washed with water to have pores of about 0.5 micron from the surface to the inside, and the skeleton has a network structure. An almost uniform cellulose diacetate gel having a particle size of 130 microns was prepared. This gel is referred to as A.

Next, this gel is wetted with water.
Heated at 121 ° C for 1 hour. By this heat treatment, the particle size becomes
Shrink to 100 microns. This gel is called B.

Furthermore, 1.5% by weight of the gel after the heat treatment was used.
After being immersed in an aqueous sodium hydroxide solution at 40 ° C. for 2 hours, it was washed with water to obtain a regenerated cellulose gel. This treatment did not substantially change the particle size. This gel is called C.

For comparison, a regenerated cellulose gel was obtained by alkali treatment in the same manner as described above without heat treatment. This treatment reduced the particle size to 110 microns. This is called Gel D.

Further, this gel was heat-treated in the same manner as described above. This treatment did not substantially change the particle size. This gel is called E.

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

[0028]

[Table 1]

From these results, the cellulose fatty acid ester
Pressure resistance by heat treating the Le gel it can be seen that remarkably improved.

Example 2 The method described in JP-A-63-117039, ie,
A solution consisting of 8 parts by weight of cellulose diacetate, 46 parts by weight of propylene glycol, and 46 parts by weight of dimethyl sulfoxide was heated to 90 ° C. and discharged at a rate of 15 m / sec from a 50-micron pore, and subjected to a mechanical vibration of 17 kHz. After flying a uniform droplet in 1.5 m air,
By capturing and coagulating in a 30% by weight aqueous ethanol solution and washing the gel obtained after standing for 2 hours with water, a dense layer having a thickness of about 1 micron on the surface and an inside of about 1 micron was obtained. An almost uniform cellulose triacetate gel having a network structure of pores and a particle diameter of 130 microns was produced. 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. These treatments reduced the particle size of the gel to 100 microns and its exclusion limit molecular weight to about 20,000.

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

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

From these examples, it can be seen that the strength of the cellulose fatty acid ester gel is significantly improved by the method of the present invention irrespective of its microstructure, and the regenerated cellulose gel obtained by the method of the present invention is further biochemically treated. It can be seen that high strength is maintained even when the objective modification is added.

[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 can be obtained by a very simple method called heat treatment. Thus, it is possible to obtain a high-strength cellulosic gel that can be widely used.

[Brief description of the drawings]

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

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08B 15/00 CA (STN)

Claims (3)

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