KR20070058739A - Method for preparing cellulose ethers - Google Patents

Abstract

Provided is a method for preparing cellulose ether, which reduces the production of byproducts including salts to shorten the time required for purification, and is eco-friendly by virtue of a decreased amount of waste water. The method for preparing cellulose ether comprises the steps of: softening cellulose and reacting the resultant cellulose with an etherifying agent. In the method, the softening treatment is carried out by using an amidine derivative represented by a formula 1. In the formula 1, A is -(CH2)n-, wherein n is an integer of 2-4; B is -(CH2)m-, wherein m is an integer of 2-5; and X is CH2, O, NH or NR', wherein R' is a C1-C4 alkyl or acyl.

Description

Method for preparing cellulose ether {Method for preparing Cellulose ethers}

The present invention relates to a method for producing cellulose ether, and more particularly, to a method for producing cellulose ether using an amidine derivative.

Cellulose ethers include alkyl celluloses such as methyl cellulose, ethyl cellulose, propyl cellulose; Hydroxyalkyl celluloses such as hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; Hydroxyalkyl alkyl celluloses such as hydroxyethyl methyl cellulose.

Due to their excellent properties and physiological safety, these cellulose ethers are not only used as thickeners, adhesives, binders, dispersants, humectants, protective colloids and stabilizers in medicine, construction, paints, etc., but also in numerous applications such as suspensions, emulsifiers and film-forming agents. Has

In particular, cationic cellulose derivatives comprising 2-hydroxypropyl trialkyl ammonium chloride groups are widely used as conditioning agents in hair care and skin care products and are mentioned in this regard in a number of documents. Bernard Ldson, Cosme. Sci. Technol. Ser. (1999), 21, 251-279; Korean Patent Publication No. 2003-0086252]

In general, a method for preparing cellulose ether (US Pat. No. 4,477,657) is treated with caustic soda and then added with an etherification agent, followed by filtration and pulverization with a pulverizer, followed by drying to remove residual water. The process gives a cellulose ether.

The reason for treating cellulose with caustic soda is that caustic soda combines with cellulose to expand and weaken the crystal structure, thereby increasing the accessibility of the hydroxyl group, and on the other hand, nucleophilic substitution reaction or epoxide of halogen in etherification agent. In order to polarize the hydroxyl group so that the addition reaction is possible after ring opening.

As a result, a large amount of side reactants, such as sodium chloride, are present in the etherified cellulose ether slurry. The greater the amount of caustic soda or the amount of etherification agent used in the reaction, the greater the absolute amount of salt that is produced, and the greater the amount of salt remaining when purified by the same method.

When these salts are contained in a large amount in the final product has a great effect on the intrinsic physical properties, it is very important to remove the salt of the side reactions during the purification, filtration of the prepared cellulose ether.

Therefore, a conventional desalting technique for removing salts, which are side reactions generated in the preparation of cellulose ether, is a method of washing the salts contained in the cellulose ether slurry while stirring by adding a large amount of hot water or an isopropyl alcohol aqueous solution to the filter. However, despite repeated washing several times, not only the removal efficiency of the salt is very low, but also the drawback of the wasteful process time and the large amount of waste water has been pointed out as a problem. Therefore, how to reduce the amount of salt produced is more important.

Accordingly, the present inventors have been searching for a method for preparing a new cellulose ether that can solve the problems in the generation of by-products when manufacturing cellulose ethers using caustic soda and the processes required for removing such by-products. Patent WO 2003/000652 discloses examples of catalytic amounts of amidine and guanidine bases to replace conventional organometallic bases for the production of intermediates of the antidepressant venlafaxine. As a result of confirming that the catalytic amount of the amidine derivative can replace the conventional metal hydroxide, the possibility was proved and completed the present invention.

Accordingly, an object of the present invention is to provide a method for preparing cellulose ethers by reducing the absolute amount of salts which are reactants by treating cellulose with an amidine derivative and reacting with an etherifying agent.

The manufacturing method of the cellulose ether of the present invention as described above is characterized by using an amidine derivative represented by the following formula (1) in the method for producing a cellulose ether.

Wherein A is-(CH ₂ ) _n -wherein n is an integer from 2 to 4; B is-(CH ₂ ) _m- , where m is an integer from 2 to 5; X is CH _2, O, NH, NR 'wherein R' is a C ₁ -C ₄ alkyl group or an acyl group.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention relates to a process for the preparation of cellulose ethers which can reduce the absolute amount of salt produced as side reactants by reacting cellulose with a catalytic amount of amidine derivatives and reacting with etherification agents.

Referring to the step of preparing the cellulose ether according to the present invention step by step.

The first step is to soften the base cellulose. The present invention is a step of treating cellulose with a catalytic amount of amidine (amidine) derivative in a step different from the prior art. That is, the amidine derivative is bound to cellulose to expand and weaken the crystal structure to help various chemicals bind or react.

As described above, the higher the amount of caustic soda or the higher amount of etherification agent, the more the amount of salt is consequently higher. However, when preparing cellulose ether using caustic soda as in the prior art, the minimum amount of caustic soda needed was 0.4 to 0.5 compared to the cellulose equivalent. Since no reaction takes place below this equivalent, at least 0.4 equivalent or more must be added.

However, in the present invention, since the catalyst amount of the amidine derivative is used, there is an advantage of minimizing the amount of salt produced. The content of the amidine derivative of the present invention is preferably 0.01 to 0.5 equivalent ratio relative to the cellulose.

Specific examples of the amidine derivative represented by Formula 1 include 1,8-diazabicyclo [5,4,0] undec-7-ene (1,8-diazabicyclo [5,4,0] undec- 7-ene, DBU) and 1,5-diazabicyclo [4,3,0] non-5-ene (1,5-diazabicyclo [4,3,0] non-5-ene (DBN)). .

Step 2 is a step of preparing a cellulose ether slurry by adding an etherifying agent to the softened activated alkaline cellulose. As the etherification agent, alkylene oxide, alkyl halides, and the like are used, for example, ethylene oxide, propylene oxide, methyl chloride, ethyl chloride is not particularly limited.

The activated alkaline cellulose treated with the amidine derivative is reacted with vigorous stirring in the presence of an etherification agent to prepare cellulose ether, followed by neutralization of the reaction solution with hydrochloric acid and filtration using a filter.

In addition, the cellulose ethers of the present invention may be prepared as necessary to prepare the cellulose ethers, including cation epoxides such as glycidyl trimethyl ammonium chloride; Or quaternary ammonium cellulose ethers can be prepared by further addition of at least one quaternary ammonium compound selected from halohydrins such as 3-chloro-2-hydroxypropyltrimethyl ammonium chloride.

Step 3 is a step of washing the prepared slurry to remove salt, pulverization and drying. The aqueous solution of isopropyl alcohol is added to the prepared slurry with a filter to wash the salts contained in the cellulose ether slurry with stirring, followed by grinding and drying.

The salt content of the cellulose ether prepared by the same method as the present invention is 1.0% or less with respect to the dry product weight, and even when using a conventional caustic soda, it is impossible to remove the salt content by 1% or less. Compared to the excellent effect can be said.

The present invention is explained in more detail in the following examples. However, the scope of the present invention is not limited to these embodiments.

Example 1: Preparation of hydroxyethylcellulose ether using amidine

90 g of ground cotton linter (cellulose) was charged to a 2 L pressure reactor and the air in the reactor was replaced with nitrogen. After exhaust, 35.8 g (0.42 eq) of 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) was sprayed onto cellulose. After the reactor was heated to 85 ° C. for 1 hour, 90 g of ethylene oxide was added dropwise for 1 hour. After stirring for 1 hour at that temperature, the reactor was cooled and vented. After neutralization, the crude product was washed with hot water to remove residual salt and dried at 65 ℃.

The yield of the resulting hydroxyethyl cellulose ether was 87%, and the resultant product was 2.4% when the organic matter was burned and the remaining salt content (ignition residue) was calculated.

Example 2: Preparation of hydroxyethylcellulose ether using catalytic amount of amidine

90 g of ground cotton linter (cellulose) was charged to a 2 L pressure reactor, and the air in the reactor was replaced with nitrogen. 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) after exhaust 4.3 g (0.05 equiv) was sprayed onto cellulose. After the reactor was heated to 85 ° C. for 1 hour, 90 g of ethylene oxide was added dropwise for 1 hour. After stirring for 1 hour at that temperature, the reactor was cooled and vented. After neutralization the crude product was washed with hot water to remove residual salts and dried at 65 ° C.

The yield of the produced hydroxyethyl cellulose ether was 87%, and the resultant product was burned with organic matter and the remaining salt content (ignition residue) was calculated to be 0.8%.

Example 3: Preparation of Quaternary Ammonium Cellulose Ether Using Amidine

60.0 g of hydroxyethyl cellulose and 320.0 g of IPA were added to a 3-neck-1L round bottom flask reactor, and the mixture was stirred at room temperature. The used hydroxyethyl cellulose had an average MS _EO of 2.0 (MW _saccharide = 250). 15.3 g (0.42 eq) of 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) After dissolving in g, the mixture was stirred for 1 hour.

32.4 g of 65% 2,3-epoxypropyltrimethyl ammonium chloride was added dropwise to the reaction for 1 hour, followed by further stirring at room temperature for 4 hours. 8.6 ml of concentrated hydrochloric acid was added, and the reaction solution was filtered to confirm that the pH was changed to 1.0 to 2.0. The filtrate was placed in a 2 L beaker and 500 ml of 80% isopropyl alcohol was added to make a slurry, which was then washed with stirring. After washing twice, the filtrate was dried under reduced pressure in a vacuum dryer (50 ° C). The viscosity of the resulting quaternary ammonium cellulose ether was measured using a Brookfield viscometer (2% aqueous solution, 25 ° C, SP2), The drying loss was measured after intensive drying for 2 hours in a vacuum oven at 105 ℃. After burning the organic material in the final product was measured the content of salt content (ignition residue) and the content of N and the results are shown in Table 1 below.

Yield (%) 86 Loss on Drying (%) 2.4 Viscosity (cps) 500 Ignition residue (%) 2.5 N content (%) 1.6

Example 4 Preparation of Quaternary Ammonium Cellulose Ethers Using Catalytic Amidine

60.0 g of hydroxyethyl cellulose and 320.0 g of IPA were added to a 3-neck-1L round bottom flask reactor, and the mixture was stirred at room temperature. The hydroxyethyl cellulose used had an average MS _EO of 2.0 (MW _saccharides = 250). 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) 1.82 g (0.05 equiv) of water 58.0 After dissolving in g, the mixture was stirred for 1 hour.

32.4 g of 65% 2,3-epoxypropyltrimethyl ammonium chloride was added dropwise to the reaction for 1 hour, followed by further stirring at room temperature for 4 hours. After adding 8.6 ml of concentrated hydrochloric acid, the pH of the reaction solution was changed to 1.0-2.0, and then filtered. The filtrate was placed in a 2 L beaker and 500 ml of 80% isopropyl alcohol was added to make a slurry, followed by washing with stirring. After washing twice, the filtrate was dried under reduced pressure in a vacuum dryer (50 ° C.). The analysis of the resulting quaternary ammonium cellulose ether was performed in the same manner as in Example 3 , and the results are shown in Table 2 below.

Yield (%) 87 Loss on Drying (%) 2.5 Viscosity (cps) 496 Ignition residue (%) 0.7 N content (%) 1.5

Comparative Example 1: Preparation of hydroxyethylcellulose ether using NaOH

90 g of ground cotton linter (cellulose) was charged to a 2 L pressure reactor and the air in the reactor was replaced with nitrogen. After evacuation, 35.8 g of a 50% caustic soda aqueous solution was sprayed onto the cellulose. After the reactor was heated to 85 ° C. for 1 hour, 90 g of ethylene oxide was added dropwise for 1 hour. After stirring for 1 hour at that temperature, the reactor was cooled and vented. After neutralization the crude product was washed with hot water to remove residual salts and dried at 65 ° C.

The yield of the resulting hydroxyethyl cellulose ether was 87%, and the resultant product was 2.7% when the organic matter was burned and the remaining salt content (ignition residue) was calculated.

Comparative Example 2: Preparation of Quaternary Ammonium Cellulose Ether Using NaOH

60.0 g of hydroxyethyl cellulose was added to a 3-neck-1L round bottom flask reactor, and 320.0 g of IPA was added thereto and stirred at room temperature. The used hydroxyethyl cellulose had an average MS _EO of 2.0 (MW _saccharide = 250), and 50 g of NaOH (0.42 equiv) was dissolved in 52.6 g of water, and then stirred for 1 hour.

32.4 g of 65% 2,3-epoxypropyltrimethyl ammonium chloride was added dropwise to the reaction for 1 hour, followed by further stirring at room temperature for 4 hours. After adding 8.6 ml of concentrated hydrochloric acid, it was confirmed that the pH of the reaction solution was changed to 1.0 to 2.0 and filtered. The filtrate was placed in a 2 L beaker and 500 ml of 80% isopropyl alcohol was added to make a slurry, followed by washing with stirring. After washing twice, the filtrate was dried under reduced pressure in a vacuum dryer (50 ° C.). The resulting quaternary ammonium cellulose ether analysis was performed in the same manner as in Example 3 , and the results are shown in Table 3 below.

Yield (%) 86 Loss on Drying (%) 2.3 Viscosity (cps) 503 Ignition residue (%) 2.8 N content (%) 1.6

As can be seen from the results of the examples and comparative examples, it can be seen that the use of amidine derivatives in the preparation of cellulose ethers as in the present invention significantly reduced the production of side reactions compared to the use of conventional NaOH.

As described in detail above, the preparation time of the cellulose ether can be reduced by the treatment with a catalyst amount of amidine (amidine) derivative to react with the etherifying agent, thereby reducing the amount of salt produced as a side reactant, thereby reducing the purification time, and the waste water amount. By reducing the cellulose ether can be produced in an environmentally friendly process.

Claims (3)

In a method of softening cellulose and reacting with an etherifying agent to produce cellulose ether, The softening treatment of the cellulose is a method for producing a cellulose ether, characterized in that using the amidine derivative represented by the following formula (1). Formula 1

Wherein A is-(CH ₂ ) _n- , where n is an integer from 2 to 4; B _is- (CH ₂ ) _m- , where m is an integer from 2 to 5; X is CH _2, O, NH, NR 'wherein R' is a C ₁ -C ₄ alkyl group or an acyl group. The method of claim 1, wherein the amidine derivative is used in an amount of 0.01 to 0.5 equivalents based on the cellulose. The method of claim 1, wherein the amidine derivatives are 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) and 1,5-diazabicyclo [4,3,0] non A process for producing cellulose ethers, characterized in that selected from -5-ene (DBN).