Patent GB-739384-A (GB)
Title: Process for the production of cold water dispersible, cold water soluble starch products suitable for use as textile sizes
IPC: C08B30/12
Filed: 1953-01-05
Abstract: A cold water dispersible, cold water soluble textile size is obtained by treating starch with an oxidizing agent to a level below that at which extensive breakdown of the starch into low molecular weight bodies occurs, the starch being substantially completely gelatinized and dispersed before, during, or after oxidation, and dehydrating the starch paste in the presence of about 3 to about 7 per cent of boric acid based on the weight of the starch (dry basis).  The oxidation of the starch is preferably carried out to paste viscosities within the range of Scott test of about 45 seconds per 100 ml. using 100 grains of starch in 280 ml. of water to about 35 seconds per 100 ml. using 28.35 grams of starch in 280 ml. of water, and particularly from about 80 to 125 seconds using 100 grams of starch in 280. ml of water.  Any native starch such as corn, grain sorghum, or wheat starch, or mixtures thereof, may be employed.  The preferred oxidizing agent is sodium hypochlorite, but other reagents such as per compounds, e.g. sodium, calcium, and hydrogen peroxides; persulphates, perborates, chromates and dichromates, usually in the form of their sodium salts; nitrogen dioxide, and sodium p-toluene sulphonechloramide may be used.  The starch is preferably treated with the oxidant in the granule stage as an aqueous dispersion at temperatures below its gelatinization point, but the oxidation may also be performed on gelatinized starch.  The dispersion and gelatinization of the starch is preferably effected in a "Votator" (Registered Trade Mark) operated at 90-95 DEG  C. although other equipment and higher temperatures may be used, e.g. a heated mixture of the starch and water may be pumped under pressure through the feed orifice of a conventional spray drier.  The starch sol is finally dehydrated preferably by using a set of heated double rolls although spray driers may also be used.  The starch may be substantially completely gelatinized almost simultaneously with the dehydration by feeding a slurry of the starch to heated rollers provided it has been oxidized to a paste viscosity by Scott test of about 45 to 55 seconds per 100 ml. for 100 grams of starch in 280 ml. of water.  In examples: (1) corn starch is suspended in water and treated at 25 DEG C. with a solution of sodium hypochlorite until a sample, after washing, showed a paste viscosity by Scott test of 50 seconds per 100 ml. using 100 grams of starch in 280 ml. of water.  After filtering and washing with water, the starch is suspended in fresh water and 5 per cent boric acid based on the starch (dry basis) is added.  This slurry is fed to steam heated rolls on which the starch is dried and gelatinized and the resulting flake ground; (2) and (3) as in (1) except that 3 per cent and 7 per cent boric acid respectively is added to the starch fed to the rolls; (4) as in (1) except that wheat starch is used; (5) a blend of wheat starch and corn starch is oxidized as in (1) to a paste viscosity by Scott test of 45 seconds per 100 ml. using 100 grams of starch in 280 ml. of water; (6) as in (1) except that the oxidization is carried out to a paste viscosity of 90 seconds per 100 ml. using 100 grams of starch in 280 ml. of water; (8) corn starch is oxidized as in (1) and after washing it is suspended in fresh water, 5 per cent boric acid added and the liquors passed through a "Votator" heated with steam, the completely gelatinized paste being then fed through a heated pipe to the valley between two steam heated rolls and the resulting flake is ground; (9) as in (8) except that the oxidation is limited to the value shown in (6); (10) as in (8) except that the oxidation is restricted to a paste viscosity of 53 seconds per 100 ml. using 40 grams of starch per 280 ml. or 35 seconds per 100 ml. using 28.35 grams of starch per 280 ml. of water.  In a comparative example (7), the procedure of (1) is repeated using less available chlorine in the oxidation step so as to give a paste viscosity of 125 seconds per 100 ml. using 100 grams of starch in 280 ml. of water, the product in this case being generally unacceptable.  The cold water solubility, dispersibility ratings in cold water, water spotting tendencies and flexometer sizing values of the products are referred to and the methods used to determine these values are described.  Specification 658,525 is referred to.