Patent GB-707292-A (GB)
Title: Improvements in or relating to the stabilization of carbohydrate ethers
Inventor: SIMON WALTER EDUARD ASMUS
IPC: C08K5/31
Filed: 1950-02-03
Abstract: A carbohydrate ether, e.g. a benzyl cellulose ether, which has a tendency to decompose and yield an aldehyde when heated, is stabilized by mixing it while in a molten or semi-molten state with urea, thiourea, a substituted urea or thiourea, a phenol, malonic ester or acetylacetone, or a mixture of two or more of these stabilizing substances, in presence of an alkaline catalyst which promotes reaction between aldehyde and the stabilizing substance, whereby any aldehyde produced is immediately converted into a compound which is stable and non-gaseous at subsequent processing temperatures.  Chemically inert materials such as plasticizers, fillers and lubricants may be incorporated with the carbohydrate ether.  The stabilized ethers form plastic masses or articles which are free from pores or bubbles and which have high resistance to the degrading effect of heat, light, weather and oxidizing agencies.  The catalyst may be caustic soda, dibenzylamine, diphenyl guanidine or piperidine.  The stabilized ethers may be used for making artificial fibres, windscreens, gramophone records, insulators, varnishes and coatings.  In an example, 1,000 grams of benzyl cellulose are stabilized by adding 3.4 grams of urea and 0.25 grams of dibenzylamine as catalyst, and mixing at 200 DEG C. for 2 hours. Tricresyl phosphate and iron oxide are then added and mixing is continued for a further half hour. The resulting mass is used for press moulding.  The proportion of stabilizer used is preferably somewhat higher than that which is equivalent to the aldehyde produced under the heating conditions to which the ether is to be subjected during processing.  This quantity of aldehyde may be determined by a preliminary test.  The Provisional Specification describes also the use of other stabilizing substances, including cyanides, aldehydes, ethylates Grignard reagents, phosphorus pentachloride and pentasulphide, hydrogen sulphide, sodium meta-bisulphite and magnesium silicide.ALSO:A carbohydrate ether, which has a tendency to decompose with production of an aldehyde when heated, is stabilized by mixing it while in a molten or semi-molten state with urea, thiourea, a substituted urea or thiourea, such as an alkyl, aryl or acyl urea, a phenol, malonic ester or acetyl acetone, or a mixture of two or more of these stabilizing substances, in presence of an alkaline catalyst which promotes reaction between aldehyde and the stabilizer, whereby any aldehyde produced is immediately converted into a stable, non-volatile compound.  Plastic masses and articles made from the stabilized ethers are resistant to the deteriorating action of heat, light, weather and oxidizing agencies and are free from pores or bubbles.  The carbohydrate may be benzylated sugar, or starch.  The catalyst may be caustic soda, dibenzylamine, diphenyl guanidine or piperidine.  The stabilized ethers may be used for making artificial fibres, windscreens, gramophone records, insulators, coatings and varnishes.  The proportion of stabilizer incorporated in the carbohydrate ether is preferably somewhat greater than that which is equivalent to the quantity of aldehyde produced under the heating conditions to which the ether is to be subjected during processing.  This quantity of aldehyde may be determined by a preliminary test.  The Provisional Specification describes also the use of other stabilizing substances, including cyanides, aldehydes, ethylates, Grignard reagents, phosphorus pentachloride and pentasulphide, hydrogen sulphide, sodium metabisulphite and magnesium silicide.