Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1988-11-23
1990-04-17
Kight, III, John
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536 61, 536 80, 536 91, 536126, C08B 3700, C08B 306, C08B 11193, C08B 1108
Patent
active
049181807
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improved method of preparing cellulose ethers. In particular, the present invention relates to a method of producing cellulose ethers having a reduced dust content relative to prior art products.
The manufacture of cellulose ethers from natural sources of cellulose (known in the art as cellulose furnishes) are known industrial processes. In such processes the cellulose furnish is first contacted with alkali to produce alkali cellulose and then contacted with an etherifying agent to convert the alkali cellulose into the cellulose ether. The crude cellulose ether product is then washed, separated from the washing and finally dried to form a solid product.
A disadvantage of these processes is that the solid product tends to have a wide particle size distribution. In particular such solid products tend to contain large amounts of dust (<45 .mu.m particles) which are difficult to handle and hence of limited commercial value.
An improvement has now been developed which produces cellulose ethers having a reduced dust content relative to those processes employed previously. The improvement is achieved by treating the cellulose ether with a novel aggregating agent.
Accordingly the present invention provides a process for preparing a modified cellulose ether which comprises reacting a cellulose ether with an effective amount of an aggregating agent comprising (1) a polypropylene glycol or a propoxylated alcohol and (2) an ethylene oxide/propylene oxide copolymer.
The first component of the aggregating agent is a polypropylene glycol, a propoxylated alcohol or mixture thereof. Preferably the first component is a molecule having the formula and n is an integer from 1 to 30.
The second component, which is an ethylene oxide/propylene oxide copolymer, is suitably a polyfunctional alcohol, amine or the like which has been alkoxylated with ethylene oxide and propylene oxide. The alkoxylation can be carried out to produce either a random or a block ethylene oxide/propylene oxide copolymer. Examples of such materials include alkylene oxide adducts of ethylene glycol, propylene glycol, glycerol, the isomeric butanediols, hexanediols, octanediols, pentaerythritol, sorbitol, arabitol, mannitol, alkyl glucoside, alkylene glycol glucosides and glycerol glucosides. Adducts of alkylene diamines and hydrazine can also be used. The hydroxyl number of the ethylene oxide/propylene oxide copolymer is preferably in the range 25 to 180.
As regards the ratio of the two components (component 1:component 2) this suitably lies in the weight ratio range 10:1 to 1:10 preferably 3:1 to 1:3. The weight ratio of cellulose ether to aggregating agent preferably lies in the range 100,000:1 to 100:1.
Although the process described above is applicable to the production of any cellulose ether, it is particularly applicable where the cellulose ether is a C.sub.2 -C.sub.4 hydroxyalkyl cellulose (e.g. HEC), carboxymethyl cellulose, methyl cellulose or ethyl hydroxyethyl cellulose.
Although treatment with the aggregating agent can take place at any time, it is preferable that aggregation is carried out during the manufacture of the cellulose ether, e.g. immediately after washing and centrifuging the crude product of the etherification process. In such a case it is convenient to mix the wet centrifuge cake and the aggregating agent and thereafter dry the cake in the usual way.
The invention is now illustrated by the following Examples.
EXPERIMENTAL PROCEDURE
To the wet centrifuge cake of the chosen grade of hydroxyethyl cellulose (HEC) was added an appropriate amount of the aggregating agent comprising a mixture of the two specified components. The weights of each component are expressed in the table as a percentage of the wet cake used. The centrifuge cake and the aggregating agent were mixed together and then the cake was dried to produce a final product for testing. The dust content of the final product was measured by studying the % retained when passed through sieves of various mesh size in the range 850.mu. to
REFERENCES:
patent: 2839526 (1958-06-01), Miller
Azpuru C.
Gibson Henry H.
Kight III John
Union Carbide Chemicals and Plastics Company Inc.
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