HU198219B - Process for producing starch-solution - Google Patents

Abstract

A modified soluble starch soln. is prepd. by oxidising granular starch or starch contg. milled prods. dispersed and homogenised in water with 2-20 wt.% (based on starch) of conc. sodium-hypochlorite soln. contg. 12.5% active chlorine, at 0-50 deg.C pref. 15-30 deg.C.. The oxidised starch is mixed with 4-25 wt.% (based on starch) of solid NaOH or KOH dissolved in water, at 0-50 deg.C.. The alkaline soln. is used directly or following neutralisation. - The prod. is used as an adhesive thickening agent, paper coating, textile size, printing means and as films.

Description

BACKGROUND OF THE INVENTION The present invention relates to a starch solution from powdered starch or flour meal of plant seeds, tubers, roots, wherein the solid particulate starch is subjected to oxidation and alkaline treatment without heat treatment, which results in a wide range of viscosity aqueous starch solution. win. The starch solution thus prepared is a versatile starting material, from which glue, thickener, paper treating agent, textile interpreting material, starch film, printing paste, etc. can be produced.

It is known that vegetable seeds and tubers, e.g. wheat, rye, rice, maize or potatoes, which can be isolated by a simple washing process, are comprised of two main components, amylose consisting of spiral but unbranched molecules and amylopectin containing a large number of branched molecules. The starch-forming molecules are composed of D-glucose units and contain only less than 0.1% other substances, mainly ester-bound phosphoric acid.

The starch is insoluble in cold water but swells in hot water and is soluble colloidally. The aqueous solution of the starch obtained by heating hardens into a gel upon cooling, so that it is no longer liquid when cold; starch germ. Of the two components of starch, amylopectin consisting of branched molecules causes germination, while amylose re-precipitates from solution during cooling and causes opacity of the germ.

The starch chain molecules are gradually degraded by boiling with water, the final result of hydrolysis being D-glucose solution. When cooked in pure water, the rate of cleavage of the glycoside bond is very low, when cooked under pressure at temperatures above 180 ° C, only the reaction is believed to be sufficiently rapid. Hot water hydrolysis can be greatly accelerated by the use of dilute mineral acids, e.g. When cooked with 2% hydrochloric acid, decomposition takes place in one hour. The starch can be degraded cold by the enzyme amylose. Partial degradation of starch yields various dextrins. Starch gives a characteristic color reaction with iodine, amylose has a blue color reaction, amylopectin has a violet color reaction, which is a very sensitive and characteristic reaction for the detection of starch (eg Bruckner: Organic Chemistry 1-2, Budapest, 1961,

1081).

By heat treating an aqueous suspension of starch, a so-called. starch germ is more or less suitable for simple paper bonding purposes, but the ready-to-use adhesive can only be used freshly, is prone to irreversible coagulation during storage and easily molds, so it is not suitable for general industrial use. For industrial users, a paste-like mixture known as .Stein-Hall glue is prepared from hot-melted starch by blending unexcavated granular starch in a boiled starch solution by cooking near the boiling point of water. This is because the starch content of the mixture is high enough because at low starch concentrations below 20%, the coagulating film is not strong, but on the other hand, hot-digested aqueous starch compositions containing more than 20% starch are so viscous and tend to gel that they are unsuitable for technical use or that they can only be processed by special high shear machines.

The above drawbacks of the conventional .stein-Hall glue starch pastes are overcome by the English Patent No. 2,061,307, which has been subjected to high shear treatment at a temperature of 95-160 ° C with a disintegrated starch mass containing non-gelatinized starch granules. treatment with water-soluble oxidizing agent, which produces a nascent oxygen at a reaction temperature of at least 95 ° C using inlet stirring. Such oxidizing agents include inorganic peroxy compounds such as ammonium persulfate, percarbonates, perborates.

The prior art processes, which have resulted in a commercially available aqueous starch pulp containing at least 2C% starch, could only be carried out using sophisticated machine and heat treatment equipment technology. Such devices are very costly in themselves, as they usually employ devices for indirect heating and high shear, and the operating costs are also high due to the demand for heat energy. A further disadvantage is the need to employ control equipment and qualified operating personnel to manage the process safely.

In our attempts to reduce the above-mentioned technological disadvantages, by attempting to develop a starch solution in a simple manner, it has been found that the purified granular starch can be completely optically homogeneous in a clear aqueous solution without the use of heat. an aqueous suspension of starch is treated with hypochlorite and diluted, e.g. A 5% solution of NaOH or KOH was added. The reaction then proceeds rapidly at ambient temperature, resulting in a viscous but homogeneous clear solution which can be diluted with water indefinitely. This solution can also be used directly e.g. for bonding purposes. The true nature of the solution is clearly demonstrated by the total lack of scattering effect.

The alkaline solution obtained as described above is very characteristic during neutralization3

HU 198219 Β tea shows changes. If, for example, Neutralization with a 1: 1 dilution of hydrochloric acid results in a sharp increase in the viscosity of the solution as a result of the initial small doses of acid. The initially strongly alkaline solution does not give a color reaction with iodine, but nearing the neutral pH range, a characteristic bluish-violet color reaction occurs, demonstrating the presence of starch in dissolved form.

x It is noted that oxidative hypochlorite has an interesting effect on starch even without solution pretreatment: the alkaline solution causes the starch to swell suddenly, producing an extremely viscous, gelatinous, difficult to knead mass which can only be moved under very high shear forces. and is very prone to puncture.

Examining the possible mechanism of action of hypochlorite solution pretreatment, it can be assumed that solubility in solution is related to the oxidative effect of hypochlorite; oxidation can be effected by carboxylic oxidation of the hidden end-oxo group and possibly by shortening the chain length. Amylopectin is known to have a large number of end-groups. The decrease in the size of the starch molecules indicates that the viscosity of the homogeneous alkaline solution prepared according to the invention gradually decreases initially and then stabilizes at a limit. The large ρκ dependence of the viscosity of the solution suggests that the alkaline solvation of the primary and secondary OH groups capable of association may play a role in keeping the macromolecules in solution.

The present invention therefore relates to a process for the preparation of a starch solution by oxidation and alkaline digestion, gluing, thickening, papermaking, textile interpretation, printing paste and film making, characterized in that solid granular starch or starch-containing flour at 0-50 ° C. Homogenized at 15-30 ° C in an aqueous medium containing 2-20% by weight of starch, i.e. 12.5% active chlorine, in an aqueous medium, and the substance is known per se to an alkaline solution, suitably with a solution of 4-25% solid NaOH and / or KOH at 0-50 ° C, and optionally neutralizing the resulting solution with acid.

The invention is illustrated in more detail by the following representative examples:

Example 1

100 parts by weight of potato starch are suspended in 200 parts by weight of water and 10 parts by weight of a commercial concentrated HYPO solution are added. Stirring is continued for 1 hour and then mixed with 180 parts by weight of 5% NaOH. The mixture is initially a viscous, jelly-like substance which, after stirring for 15-20 minutes, turns into a clear, viscous but water-dilutable homogeneous solution which can be used directly for paper bonding, glass labeling, etc. The solution does not react with iodine.

After stirring for 1 hour, the solution is added to a 1: 1 dilute hydrochloric acid solution with continuous stirring until neutral. Already at pH = 8 the solution shows an intense color reaction with iodine solution. The neutralized solution can be stored without any other preservative, excellent for general paper bonding purposes.

Example 2

100 parts by weight of corn (marine) starch are mixed with 150 parts by weight of water and 4 parts by weight of concentrated HYPO solution. Stir occasionally for 4 hours and then mix with 120 parts by weight of 5% KOH. A thick mass is obtained which, after standing for 1 day, is diluted with 200 parts by weight of water and neutralized with 85% phosphoric acid. The solution is a homogeneous, clear liquid. 4 parts by weight of anhydrous (so-called dynamite) glycerol are added and, after homogenization, a solution is obtained which adheres well to the paper labels on the glass and the metal and which can be washed off with warm water without any residue. By spreading the solution as a thin film, a translucent flexible film is obtained which is soluble in water.

Example 3

100 parts by weight of rye flour are diluted with 300 parts by weight of water, 8 parts by weight of concentrated HYPO solution are added and stirred continuously for 2 hours. 60 parts by weight of a 40% NaOH solution are added in small portions under continuous stirring to give a fiber-like, film-forming mass. 50 parts by weight of a 1: 1 dilute hydrochloric acid are added with stirring while the material's consistency is substantially altered, its fiber pulling ability is lost and it becomes a pulpy-jelly consistency. The still alkaline solution is made neutral by addition of solid boric acid. The pulp thus obtained is very suitable for use as a thickener, for finishing and for general paper bonding purposes.

Example 4 To a mixture of parts by weight of wheat flour and 50 parts by weight of rye flour, 150 parts by weight of water and 3 parts by weight of a concentrated commercial HYPO solution are added, pulped and allowed to rest for 24 hours. While stirring, 220 parts by weight of 10% NaOH solution are added and homogenized. A thick, yellowish ointment is obtained, which exhibits a very good initial adhesion and is therefore well suited for hand-lettering, cardboard boxing, corrugating.

Claims (3)

CLAIMS 1. A process for producing a starch solution by oxidation and alkaline digestion, bonding, thickening, papermaking, textile interpreting, printing and film making, characterized in that a solid granular structure opener or starch-containing flour is 0-50 ° C. homogenized in an aqueous medium containing 2 to 20% by weight of starch, preferably 12,5% by weight of active chlorine, preferably at 15 to 30 ° C, and the substance is made alkaline in a manner known per se, preferably mixed with a solution of 4-25% solid NaOH and / or KOH, based on the weight of starch, at 0-50 ° C, and optionally neutralizing the resulting solution with acid. 2. The process according to claim 1, wherein the solid particulate starch is potato starch and / or corn starch. 3. The process according to claim 1, wherein the starch-containing flour is wheat and / or rye and / or corn and / or rice flour.