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Process for preparing cellulose ether with low degree of polymerization and cellulose ether prepared therefrom

A cellulose ether, low degree of polymerization technology, applied in the field of cellulose ether, can solve problems such as discoloration and yellowing

Active Publication Date: 2017-04-12
SHIN ETSU CHEM IND CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0002] Common problems with cellulose ethers with a low degree of polymerization are yellowing and discoloration

Method used

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  • Process for preparing cellulose ether with low degree of polymerization and cellulose ether prepared therefrom

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preparation example Construction

[0025] It is preferable to carry out the preparation of alkali cellulose and the depolymerization reaction while sufficiently stirring. This makes it possible to distribute the alkali metal hydroxide solution, oxygen or oxygen-containing gas and heat evenly into the slurry, thereby obtaining the advantageous results of the invention.

[0026] The reaction temperature of the first depolymerization of alkali cellulose with oxygen is preferably 20 to 100°C, more preferably 30 to 90°C, still more preferably 40 to 90°C. The reaction time for the depolymerization of alkali cellulose with oxygen is generally 5 minutes to 2 hours, but depends on the temperature.

[0027] The percent viscosity reduction in the depolymerization reaction of alkali cellulose with oxygen is preferably from 10 to 95%. The term "percent viscosity reduction" as used herein can be determined by the following equation:

[0028] Viscosity reduction percentage (%)={1-(V 1 / V 0 )}×100

[0029] where V 0 (mPa...

Embodiment 1

[0058] (a) Preparation of hydroxypropylmethylcellulose (HPMC) without depolymerization

[0059] Wood pulp in the form of chips (degree of polymerization Dpw=2100) was immersed in 44% by weight aqueous sodium hydroxide solution, followed by centrifugation to obtain alkali cellulose. The weight ratio of the alkali metal hydroxide in the alkali cellulose to the solid component in the slurry was determined by titration and was found to be 1.25. The resulting alkali cellulose (5.5 kg, as a solid component in the slurry) was placed in a 100 L pressure-resistant reactor. After vacuum treatment, 11 kg of methyl chloride and 2.7 kg of propylene oxide were added thereto and reacted with alkali cellulose. The reaction product was washed with hot water and then dried in a drier using a combination of jacket heating and hot air heating until the weight loss on drying reached 2% by weight. Subsequently, impact crushing was performed to obtain HPMC. Regarding the degree of substitution of...

Embodiment 2

[0066] Prepare HPMC in the same manner as in Example 1, the difference is that the weight ratio of the alkali metal hydroxide in the alkali cellulose and the solid component in the slurry is 1.05, and the gained alkali cellulose (5.5kg, as the solid component in the slurry points) were placed in a 100L pressure-resistant reactor, and after vacuum treatment, 10 kg of methyl chloride and 1.3 kg of propylene oxide were added. Regarding the degree of substitution of the HPMC thus obtained measured using the method of the Japanese Pharmacopoeia, DS was 1.80 and MS was 0.15. The results are shown in Table 1.

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Abstract

Provided are a method for preparing a cellulose ether having a low degree of polymerization and undergoing less yellowing and a cellulose ether prepared thereby. More specifically, provided is a method for preparing a cellulose ether having a low degree of polymerization, the method comprising a step of bringing pulp and an alkali metal hydroxide solution into contact with each other or mixing them to obtain a corresponding alkali cellulose, a first depolymerization step of reacting the alkali cellulose with oxygen to adjust a viscosity reduction percentage of the alkali cellulose to from 10 to 95%, a step of reacting the depolymerized alkali cellulose with an etherifying agent, a step of washing and drying the reaction product to obtain a cellulose ether, and a second depolymerization step of bringing the cellulose ether into contact with hydrochloric acid to adjust a viscosity reduction percentage of the cellulose ether to from 40 to 99.9%.

Description

technical field [0001] The present invention relates to a process for the production of cellulose ethers having a low degree of polymerization for coating tablets and the like, and to cellulose ethers produced by the process. Background technique [0002] A common problem with cellulose ethers with a low degree of polymerization is yellowing and discoloration. Such yellowing or discoloration is also seen in compositions containing cellulose ethers. Yellowing or discoloration can be easily observed in transparent pharmaceutical capsules and white food compositions. [0003] There is a need for a process for the preparation of cellulose ethers with a low degree of polymerization, which have low or no degree of yellowing or discoloration. There is also a need to use such cellulose ether pharmaceutical capsules and foods with a low degree of polymerization. [0004] As a method of reducing the degree of polymerization of cellulose ether and as shown in Japanese Phase Publicat...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08B11/08A61K47/38
CPCC08B11/08C08B1/06C08B1/08C08B11/02C08B11/20
Inventor 成田光男西山裕一
Owner SHIN ETSU CHEM IND CO LTD
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