DE1292838B - Process for the production of aqueous amylose solutions - Google Patents

Description

It is known from British Patent 770 089, an aqueous one Prepare amylose solution by making an aqueous amylose suspension Temperatures above 120 ° C and the resulting solution then quickly below 100 ° C cools.

To produce z. B. of films, this solution, which is up to 25 percent by weight May contain amylose, then poured onto a carrier.

The disadvantage of this method is that the solutions do not are stable and that pouring the solutions encounters many difficulties.

Furthermore, formaldehyde is known from Belgian patent specification 556192 or formaldehyde donors to the aqueous amylose solution at temperatures to be added above their setting temperature. The temperature is about 160 ° C, whereby it is stated that at concentrations of more than 25% amylose the solutions become so viscous that the addition of formaldehyde becomes difficult, so that concentrated Amylose solutions were preferably prepared by evaporation of dilute solutions.

It is also mentioned that e.g. B. when using 1 to 3 percent by weight Formaldehyde solutions with 40 percent by weight amylose the solutions up to 24 hours are stable; however, when dissolving amylose at temperatures below 100 ° C such an amount of formaldehyde does not have a solubilizing effect.

The invention relates to a process for the preparation of aqueous Amylose solutions by mixing in amylose, possibly mixed with amylopectin, in aqueous solutions containing at least 6 percent by weight formaldehyde and / or glyoxal or optionally known formaldehyde-releasing and / or glyoxal-releasing compounds contain and subsequent heating of the mixture, characterized in that the mixture is heated to temperatures of 70 to 100 ° C.

The invention makes heating an aqueous suspension of amylose to 160 ° C in an autoclave as described in the said Belgian patent its unneccessary.

With the method according to the invention, very highly concentrated Amylose solutions are produced. The concentration of amylose becomes the maximum determined by the viscosity and the dissolution time.

The viscosity increases, especially at concentrations above about 50 ° / 0, quickly and reaches very high values. The very concentrated solutions also remain however clear. The dissolution time increases rapidly as the concentration increases.

Another advantage of the method of the invention is that not a temperature above the boiling point of water, i.e. not overpressure, Must be used, A -10% amylose solution can already at about 70 to 75 ° C can be obtained in 15 minutes. However, it also takes place at room temperature to some extent dissolving instead as the change in light absorption results. For practical work, however, the rate of dissolution is at room temperature too low.

Formaldehyde or glyoxyl releasing substances are z. B. paraformaldehyde, Trioxane and polyglyoxal. Mixtures of two or more such substances can also be used be applied.

The maximum concentration of the aldehyde present in the solution becomes determined by its solubility.

As already mentioned, the solubility is largely dependent on the amylose concentration and temperature dependent. It is easier to dissolve by stirring; the stirring speed is irrelevant; however, it should not be too low.

The solutions obtained according to the invention are very stable; H., they stay clear; even after storage for several months.

The solutions obtained can be used for any desired purpose will. You are e.g. B. to carry out chemical reactions with amylose especially suitable.

Because it is not always easy to visually determine whether the amylose is present has come off completely when performing the examples below to determine whether a dispersion, a gel or a solution was present, a calorimeter and a grage ((viscometer applied. A solution absorbed namely, a considerably smaller amount of light and generally has a smaller one Viscosity as a dispersion or a gel. The change in light absorption and The viscosity is sharp enough to tell the noticeable difference between a Determine dispersion or a gel on the one hand and a solution on the other can.

Example I In one equipped with a stirrer and a reflux condenser Round bottom flask is a commercially available, aqueous formaldehyde solution, which is 36 percent by weight Contains formaldehyde, submitted. While stirring, formaldehyde solution is added per 100 cc (36 percent by weight) 25 g of amylose added. The amylose used was as analytical was found to be at least 97.5% pure. The mixture is then under steady Stir on the oil bath warmed to 95 ° C. A clear color is obtained after 10 to 15 minutes yellow-brown solution that remains clear even after cooling and prolonged storage.

In a very similar way, solutions are made from mixtures of amylose and amylopectin in weight ratios of 70:30; 50:50 and 30:70 made, with every 100 cc of formaldehyde solution used for 25 g of the mixture became. The dissolution took place a little faster than with pure amylose.

Example II An attempt was made to limit the concentration of To determine amylose in a 36% (weight percent) formaldehyde solution. It the same device as indicated in Example I was used, with the piston was provided with a thermometer. In the manner described in Example I was a 30% solution of amylose in formaldehyde solution was produced at 95 ° C. the Dissolving time was approximately 30 minutes. After that, the amylose concentration was below Maintaining the above-mentioned temperature and the same stirring speed in stages increased by 5 ° / 0. The dissolution time of the amount of amylose added in each stage varied from 30 to 60 minutes.

In this way stable, clear solutions with amylose concentrations were obtained received up to 75 ° / 0. Another increase in concentration was done in this way Not easy to carry out because of the extremely high viscosity. It then became the solutions with amylose concentrations of 70 to 75 ° / 0 slowly and carefully on the water bath evaporated. the Solutions, which an ever increasing concentration did not become cloudy. Eventually they became almost dry, thick, clear Movies received.

In Fig. 1 is the course of the viscosity of the solutions with increasing Concentration indicated. The viscosity was at 65 ° C and a shear stress of 5000 dyn / sqcm measured.

Example III For various amylose concentrations, the minimum concentration was determined on formaldehyde, which resulted in a solution. This was based on viscosity and the light absorption and light absorbance performed. The results are in the F i g. 2a, 2b and 2c. The amylose concentrations were 20.1 and 10 percent by weight.

The dissolving temperature was always 100 ° C. As can be seen from these figures, the minimum concentration of formaldehyde is 7 to 10.2 percent by weight.

Example IV In this example the dissolving temperature was steady Treatment time and concentration determined.

The extent to which 10 g of amylose per 100 ccm of 35.7 percent by weight was determined Formaldehyde solution dissolved over the course of 15 minutes at various temperatures. The results are from FIG. 3, in addition to the viscosity, the Absorbance and extinction, nor the visual observation values are given. Of course, it cannot be seen from this figure that amylose would not dissolve in the formaldehyde solution at temperatures below 70 ° C. In other experiments, the type of dissolution was determined by determining the light absorption After the invention .............................

According to the known procedure .................

From this table it can be seen that the process according to the invention results in less chain degradation of amylose than the known method.

Example VII In a very similar manner to that described in Example I, 25% solutions of amylose and mixtures of amylose and amylopectin were added in 36% aqueous solutions of glyoxal, paraformaldehyde, trioxane and polyglyoxal manufactured. The results were completely analogous to those obtained with formaldehyde were obtained; the minimum concentration of glyoxal also corresponds to that of formaldehyde.

It was worked at 95 ° C in each case. found that at room temperature there is some loosening after standing for a long time. The entire release time is here presumably in the order of a few hundred hours.

Example V Two comparative tests were carried out, wherein a 25% amylose solution in each case in a 36% amylose solution, with a 25% amylose solution in each case in a 36 weight percent formaldehyde solution under otherwise similar conditions was prepared, once with rapid stirring, and the other time under slow stirring at 55 ° C.

No difference in the dissolution times was found during the The course of the viscosity and the light absorption was identical.

Example VI One according to the invention by heating the components at 95 ° C obtained solution with a according to the brochure of A v e b e from the Components in the same amounts prepared solution compared.

The loosening according to the manner described in the brochure was as follows carried out: 25 g of Amylsoe, 15 g of a 36% (percent by weight) formaldehyde solution and 60 g of water (based on the dry amylose) were placed in an autoclave and this was heated in an oil bath. After heating for 10 minutes the solution was removed from the autoclave under a pressure of 6 atm.

The viscosity of the two solutions was determined in the Grage viscometer at 20 ° C. The result is shown in the table below: Viscosity in poises Amylose content content at 20 ° C and one Shear stress of Weight percent Weight percent 15,000 dynes / sq cm 25 7.3 880 25 7.2 120

Claims (1)

Claim: Process for the production of aqueous amylose solutions by mixing amylose, optionally mixed with amylopectin, into aqueous Solutions containing at least 6 percent by weight formaldehyde and / or glyoxal, or optionally known formaldehyde and / or glyoxal-releasing compounds contain, and subsequent Heating the mixture, characterized in that the mixture is heated to temperatures is heated from 70 to 100 ° C.