JPH05287001A - Production of high-viscosity alkylcellulose ether - Google Patents

Abstract

PURPOSE:To produce a water-soluble alkylcellulose ether having a high viscosity from cellulose having a relatively low degree of polymerization. CONSTITUTION:Cellulose is reacted with an etherifying agent in the presence of a base. The etherification is conducted in the presence of a polyhalogenated alkane in an amount of 0.01-1.5 pts.wt. per pt.wt. cellulose to produce an alkylcellulose ether having a high viscosity. When this ether is used as, e.g. an additive for a cement paste to be extruded, it enables the extrusion even when added in a smaller amount than conventional ones.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a highly viscous alkyl cellulose ether suitable as an admixture for extrusion molding of concrete and cementitious moldings.

[0002]

2. Description of the Related Art Water-soluble alkyl cellulose ethers are used in a wide range of fields such as building materials and foods as thickeners and binders because they exhibit thickening effects with a relatively small amount added. The degree of polymerization of industrially produced cellulose ethers is broad, ranging from several centipoises to 100,000 centipoises, as expressed by the viscosity of its 2% aqueous solution.
A material having an appropriate amount and viscosity is selected according to the purpose of use.

In recent years, in particular, it has been widely used in the field of building materials centering on extruded cementitious moldings containing no asbestos as a reinforcing agent and concrete to which viscosity is imparted. It is known that the higher the degree of polymerization of the admixture, that is, the higher the viscosity of the aqueous solution thereof, the smaller the addition amount, the more effective the
The supply of cheaper and more viscous alkyl cellulose ethers is strongly desired. This alkyl cellulose ether is generally obtained by a method of etherifying cellulose with an alkyl monohalide, and has many problems such as harsh reaction conditions, restriction of the degree of raw material polymerization, depolymerization, and difficulty in controlling production conditions. Met.

By the way, in order to obtain an alkyl cellulose ether having a high aqueous solution viscosity, it is necessary to use cellulose having a high degree of polymerization as a raw material and further perform etherification under the condition of suppressing a decrease in the degree of polymerization. Various studies have been made. For example, according to JP-A-3-146501, a crude linter having a high degree of polymerization, which has not been purified, is used as a cellulose source, and etherification is carried out by a known method for producing an alkyl cellulose ether to obtain an alkyl cellulose ether having a high aqueous solution viscosity. A method is disclosed. However, the viscosity of the alkyl cellulose ether obtained by using natural cellulose is limited. In other words, even if a natural cellulose having a high degree of polymerization is used, the estimated degree of polymerization is about 5000, and since a cellulose having a degree of polymerization higher than this does not exist in nature, the aqueous solution viscosity of the obtained alkyl cellulose ether is limited. There is. Even if the alkyl cellulose ether obtained by using these conventional techniques has a high viscosity, the measured viscosity of a 1% aqueous solution at 20 ° C. is about 30,000 centipoise. On the other hand, a method of introducing a long-chain alkyl group to achieve high viscosity is disclosed in JP-A-55-110103.
Nos. 56-801, JP-A-3-12401, etc., these long-chain alkylating agents are expensive, and they are not suitable for washing and removing long-chain alkylating agents during production. It has a drawback that an organic solvent has to be used, which is industrially problematic.

[0005]

DISCLOSURE OF THE INVENTION The present invention eliminates the difficulty of manufacturing process control such as careful selection of raw materials, prevention of depolymerization during the purification process, etc. Moreover, it is intended to facilitate the production of the high-viscosity alkyl cellulose ether by using a raw material having a relatively low degree of polymerization that is easily available.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of such problems, and as a result, when the etherification is proceeded, a polyhalogenated alkyl is allowed to coexist with the etherification reaction to proceed in the conventional method. It was found that an alkyl cellulose ether having a high aqueous solution viscosity which could not be obtained by the method described above can be produced, and the present invention has been achieved.

That is, the method for producing a high-viscosity alkyl cellulose ether of the present invention is a method of producing an alkyl cellulose ether by reacting cellulose with an etherifying agent in the presence of a base, wherein 1 part by weight of cellulose is polyhalogenated. It is characterized in that 0.01 to 1.5 parts by weight of alkyl is coexistent and etherification is performed. Explaining this in more detail, the cellulose used as a raw material in the present invention may be either natural cellulose such as cotton, cotton linter, or wood pulp, or regenerated cellulose, and is not particularly limited.

As the base used in the production of the alkyl cellulose ether of the present invention, sodium hydroxide,
Alkali metal bases such as potassium hydroxide or organic bases such as quaternary ammonium hydroxide and sulfonium salts can be used. It is said that this base also has an action of destroying the crystallinity of cellulose in order to accelerate the reaction,
Further, in order to reduce the decrease in the polymerization degree due to the depolymerization due to the base and the remaining oxygen, it is preferable that the base is almost consumed at the end of the reaction. Therefore, normally, the amount of the base used may be selected in the range of 0.3 to 1.3 parts by weight with respect to 1 part by weight of cellulose. If the amount of the base used is less than 0.3 parts by weight, the amount of the base is too small, so that the progress of the reaction between the cellulose and the etherifying agent is reduced, and the solubility of the resulting alkyl cellulose ether in water tends to be poor. Not preferable. On the other hand, if the amount of the base exceeds 1.3 parts by weight, depolymerization due to an excess of the base will reduce the degree of polymerization of cellulose, which is not preferable. In the present invention, it is particularly preferable to react the cellulose with the alkyl halide which is an etherifying agent in the presence of an approximately equimolar base.

The etherifying agent used in the present invention includes
Alkyl halides such as methyl chloride, ethyl chloride, propyl chloride, epoxy, etc. can be used. Alkyl monohalides are particularly preferably used. Moreover, it is also possible to mix and use these. The amount of the etherifying agent used in the present invention is 0.5-1.
It is preferable to use 5 parts by weight. This is because the resulting alkyl cellulose ether has sufficient water solubility,
This is a preferable range for expressing high viscosity. This is 0.
If it is less than 5 parts by weight, the water-solubility of the alkyl cellulose ether to be produced is insufficient and the tendency to become difficult to dissolve in water increases, which is not preferable. On the other hand, if the amount exceeds 1.5 parts by weight, the alkyl cellulose ether becomes hydrophobic and becomes difficult to dissolve in water, and in any case, the expression of viscosity tends to decrease, which is not preferable.

In the present invention, in order to enhance the solubility of the alkyl cellulose ether in water and to raise the gelling temperature of the aqueous solution of the alkyl cellulose ether, the alkylene oxide is added to the alkyl halide to effect the etherification reaction. You can do it. Propylene oxide, ethylene oxide and the like are generally used as the alkylene oxide. The amount of the alkylene oxide added may be within a range in which the effect of increasing the water solubility of the etherified alkyl cellulose ether and increasing the gelling temperature of the aqueous solution is large, and is 0 to 0.5 part by weight per 1.0 part by weight of cellulose. It is sufficient if any more alkylene oxide is added, and the gelation temperature is not improved even more, and the hot water washing tends to become more difficult.

In the present invention, the reaction is further carried out by adding a polyhalogenated alkyl. By adding a polyhalogenated alkyl and reacting it, it became possible to produce an alkyl cellulose ether having a high aqueous solution viscosity which could not be obtained by the conventional method. The polyhalogenated alkyl referred to in the present invention is one in which two or more halogen atoms are substituted at arbitrary positions in the chain hydrocarbon chain. Examples of these include compounds such as dichloromethane, 1,2-dichloroethane, 1,3-dichloropropane, 1,2-dichloropropane, 1,4-dichlorobutane, and 1,3-dichlorobutane. The amount of the polyhalogenated alkyl added was 1.
It may be in the range of 0.01 to 1.5 parts by weight with respect to 0 parts by weight, and may be appropriately selected according to the application conditions. If the amount of the polyhalogenated alkyl is less than 0.01 parts by weight, the amount of the alkyl halide is too small to obtain the effect of increasing the viscosity of the aqueous solution of alkyl cellulose ether, which is not preferable. On the other hand, when the amount of the polyhalogenated alkyl added exceeds 1.5 parts by weight, when the product is dissolved in water, a water-insoluble gelled product is likely to be formed, which is not preferable. Generally, it is difficult to control the cross-linking reaction by a method of thickening with a cross-linking agent, and the cross-linked alkyl cellulose ether is in a gel state or has insufficient water solubility, and may not exhibit satisfactory flow characteristics. Is generally known.

In the present invention, by reacting in the presence of a polyhalogenated alkyl, the product after completion of the reaction can be an alkyl cellulose ether having a high aqueous solution viscosity without gelation. It is considered that the alkyl cellulose ether obtained by the method of the present invention shows a high viscosity due to the formation of a cross-linked product in a small part of the cellulose chain and has a pseudo-high molecular weight, and has a satisfactory fluidity. .. The action of the polyhalogenated alkyl of the present invention is considered to be a remarkable thickening action due to an increase in apparent molecular weight due to partial cross-linking of the cellulose molecular chain, but such a cross-linking reaction causes a marked decrease in solubility as the degree of cross-linking increases. It is well known that it becomes a so-called gel substance. The present invention aims to obtain a thickening effect without causing gelation by adjusting the degree of crosslinking to an extremely small value, and the degree of crosslinking cannot be measured at present. Ideally, the reaction will occur at a ratio of 1 to 2 molecules of cellulose, and the apparent molecular weight will almost double.
It is considered that the thickening effect can be obtained without significantly impairing the dissolution behavior in water.

To produce the alkyl cellulose ether according to the present invention, so-called alkali cellulose generally used in the viscose industry or the like can be used. As a method for adjusting the alkali cellulose, there are a dipping pressing method, a spray method, a slurry method, a continuous dipping method, and the like.
Either adjustment method may be used. In these methods, it is more desirable to carry out under the condition that air or oxygen is substantially absent for the purpose of reducing oxidative deterioration of cellulose. Alkaline cellulose prepared by such a method is charged in a pressure resistant container and made into a high vacuum. Then, with stirring, an etherifying agent such as an alkyl halide, an alkylene oxide or the like and a polyhalogenated alkyl are charged under vacuum, and the reaction proceeds at room temperature to 100 ° C. for several hours.
During this reaction, a solvent inert to the reaction such as dimethyl ether, toluene, benzene, etc. may be added to the reaction.

The reaction product after the completion of the reaction is treated in order to prevent the formed alkyl cellulose ether from being dissolved.
After washing with hot water at 80 ° C. or higher, it can be dried and pulverized with an appropriate pulverizing device, or it can be dissolved in water as it is for use.

[0015]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The composition used in the examples is expressed in parts by weight.

[0016]

[Example 1] Degree of polymerization (DP) = 930 as cellulose
Using a purified linter of No. 3, a 35% NaOH aqueous solution was impregnated and then pressed to prepare alkali cellulose. This was charged into an autoclave, the inside was evacuated so that air (oxygen) did not enter, and then a toluene suspension slurry was formed while stirring, and methyl chloride, propylene oxide and dichloromethane were charged. The composition ratio at this time is
The ratio of 0.8 of cellulose, 1.0 of methyl chloride, 0.2 of propylene oxide and 0.2 of dichloromethane was relative to 1.0 of cellulose. Then, the temperature was raised from room temperature to 80 ° C. over 2 hours, and then the reaction was further performed at 80 ° C. for 2 hours. The obtained reaction product was filtered to separate the product from toluene. The product was filtered after washing with hot water at 80 ° C. or higher. After repeating this several times, it was dried and pulverized. A 1% aqueous solution of the obtained product was prepared and the viscosity was measured at 20 ° C. As a result, the viscosity of the 1% aqueous solution was 31,000 centipoise.

[0017]

Comparative Example 1 Alkyl cellulose ether was obtained by carrying out the reaction in the same manner as in Example 1 except that the dichloromethane of Example 1 was not used. As a result of measuring the viscosity of the obtained alkyl cellulose ether, the viscosity of a 1% aqueous solution was 9000 centipoise.

[0018]

Example 2 The procedure of Example 1 was repeated except that the composition ratio was 1.0 for cellulose and 0.6 for dichloromethane. As a result of measuring the viscosity of the obtained alkyl cellulose ether, the viscosity of a 1% aqueous solution was 35,000 centipoise.

[0019]

Example 3 The procedure of Example 1 was repeated except that 1,2-dichloroethane was used instead of dichloromethane. As a result of measuring the viscosity of the obtained alkyl cellulose ether, the viscosity of a 1% aqueous solution was 32000 centipoise.

[0020]

[Example 4] The reaction was carried out in the same manner as in Example-1 except that crude linter that was not purified was used as the cellulose. The composition ratio at this time was NaO to 1.0 for cellulose.
The proportions were H 0.9, methyl chloride 1.4, propylene oxide 0.3, and dichloromethane 0.2. As a result of measuring the viscosity of the obtained alkyl cellulose ether, the viscosity of a 1% aqueous solution was 52,000 centipoise.

[0021]

[Comparative Example 2] The reaction was carried out in the same manner as in Example 4 except that dichloromethane was not used in Example 4. As a result of measuring the viscosity of the obtained alkyl cellulose ether, the viscosity of a 1% aqueous solution was 28,000 centipoise.

[0022]

INDUSTRIAL APPLICABILITY The method for producing a high-viscosity alkyl cellulose ether according to the present invention does not use an expensive high-polymerization-degree cellulose raw material which is expensive to purify, but uses a low-cost and easily available polymerization-degree cellulose raw material, It has achieved cellulose etherification. Further, by using a cellulose raw material having a higher degree of polymerization, for example, a crude linter which has not been purified, it has become possible to produce a high viscosity cellulose ether which has never been obtained.

That is, the method of the present invention makes it possible to produce an inexpensive high-viscosity alkyl cellulose ether. Therefore, in the field of cementitious extrusion molding, which requires a high-viscosity cellulose ether as an admixture, by using the alkyl cellulose ether of the present invention, extrusion molding of cement mortar with a smaller addition amount than a conventional cellulose ether-based admixture is used. Became possible. Further, since the addition amount thereof is small, it becomes possible to obtain a high-quality cement molded product without inhibiting the hardening of cement, and it is very useful as an admixture for extrusion molding.

Claims (1)

[Claims] 1. A method for producing an alkyl cellulose ether by reacting cellulose with an etherifying agent in the presence of a base, wherein 0.01 to 1.5 parts by weight of a polyhalogenated alkyl coexists with 1 part by weight of cellulose. A method for producing a high-viscosity water-soluble alkyl cellulose ether, which is characterized in that it is subjected to etherification.