JPH0665681B2 - Method for producing cellulose acetate without rumor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing cellulose acetate having no hot water rubbing property, which is used for medical materials and the like.

(Prior Art) A general industrial production method of cellulose acetate uses pulp or linter as a raw material, acetic acid as a solvent, and sulfuric acid as a catalyst,
It is manufactured by using acetic anhydride as an acetylating agent and taking steps of pretreatment, acetylation, aging, precipitation, washing, dehydration and drying.

The cellulose acetate thus obtained is used in various industrial fields such as tobacco filters, clothing, plastics, photographic films and semipermeable membranes.

(Problems to be Solved by the Invention) Recently, a unique function of cellulose acetate, which is a semi-synthetic product from a natural product, has been reconsidered, and a lot of researches have been conducted for application to a special field.

In the case of application to such special fields, for example, medical materials, hot water bubbling property of cellulose acetate is a problem.

However, the cellulose acetate obtained by the above-mentioned general production has a drawback that it has hot water bubbling property.

The hot-water astringency is specified based on the dissolution test of the Japanese Pharmacopoeia, and the method is as follows.

After 0.5 g of the sample and 100 ml of water are sealed and heated at 121 ° C for 1 hour and allowed to stand at room temperature, 5 ml of the test solution is placed in a test tube with a ground stopper and shaken vigorously for 3 minutes to measure the height of foam in the test tube.

(Means for Solving Problems) The present inventors have completed the present invention by finding out that the cause of rudder is based on the low polymerization degree component.

That is, the present invention is a process for producing cellulose acetate without rubbing, which comprises extracting and removing a low-polymerization degree component of cellulose acetate having a polymerization degree of 80 or less using an aqueous solution of an organic solvent.

Cellulose acetate used in the present invention is a cellulose acetate obtained by a general industrial production method using pulp or linter as a raw material and acetic anhydride as an acetylating agent, and having an acetylation degree of 40% to 60%. used.

The solvent used in the present invention may be acetone, which is a solvent for cellulose acetate, and acetic acid, and alcohols such as methanol and ethanol, which are non-solvents.

As an extraction condition, in the case of a non-solvent, it is not always necessary to make an aqueous solution, but in the case of a solvent, it is used as an aqueous solution so that a high degree of polymerization of cellulose acetate does not dissolve and a low degree of polymerization component dissolves. It will be.

The concentration of the aqueous solution is solvent / water = 30 to 70 by weight ratio, preferably
40 to 60, liquid temperature during extraction is room temperature to 50 ° C, extraction time is
The extraction efficiency is improved when the extraction is performed in two steps for 10 to 120 minutes.

The amount of low polymer to be removed is about 5%, and it is appropriate to remove components having a polymerization degree of 80 or less.

(Effects of the Invention) The cellulose acetate produced according to the present invention is useful as a medical material because it does not cause rumors in the eluate test of the Japanese Pharmacopoeia, which is imposed when used as a medical or pharmaceutical material.

(Example) Into a stainless steel autoclave, 4 kg of cellulose acetate, 24 kg of acetic acid as an extraction solvent, and 36 kg of pure water were charged, and the temperature was 35 ° C.
After conducting the first extraction under stirring for 12 hours, filter and then acetic acid 12kg
After extraction with 18 kg of pure water at a temperature of 35 ° C for 15 minutes twice, washing with 60 kg of pure water at a temperature of 40 ° C for 15 minutes was repeated 8 times. The properties and bubble height of the obtained cellulose acetate are shown.
(According to the above-mentioned Japanese Pharmacopoeia test) Before extraction After extraction Acetification degree 54.06% 54.12% Degree of polymerization 183 190 Awadashi test Immediately after shaking Bubble height 6mm 0mm After shaking 3 minutes Bubble height 4mm 0mm On the other hand, extracted and removed Regarding cellulose acetate, the extraction waste liquid obtained twice was poured into a large amount of water to be reprecipitated and recovered, then filtered and dried to measure the degree of polymerization. As a result, the degree of polymerization was 72.

Example 2 100 g cellulose acetate and 750 g acetone in a glass flask.
And 750 g of pure water were charged and extracted at 40 ° C for 1 hour under stirring, then filtered and 550 g of new acetone and 550 g of pure water were charged and stirred under 40
After extraction at 20 ° C. for 20 minutes, 1100 g of pure water was washed at 40 ° C. for 20 minutes.

The properties and bubble height of the obtained cellulose acetate are shown.

Before extraction After extraction 55.06 55.13 Degree of polymerization 175 187 Rudder test Immediately after shaking Bubble height 6mm 0mm 3 minutes after shaking Bubble height 6mm 0mm On the other hand, for cellulose acetate that was extracted and removed, extraction waste liquid was extracted twice. Was poured into a large amount of water to reprecipitate and collect, and then filtered and dried to measure the degree of polymerization. As a result, the degree of polymerization was 76.

Claims (1)

[Claims] 1. A process for producing cellulose acetate free from rubbing, which comprises extracting low-polymerization degree components of cellulose acetate having a polymerization degree of 80 or less with an aqueous solution of an organic solvent.