DE663004C - Process for clarifying glue and gelatin solutions - Google Patents

Description

A method for clarifying glue and gelatin solutions solutions of gelatin or glue of bone glue leather, skin or like animal raw materials usually 'contain 2 aleringe amounts of haze substances which can not be filtered out by ordinary methods. A known method of removing these substances is that the glue and gelatin solutions are treated with aluminum sulphate and then with phosphoric acid Very precise control of the conditions is necessary in order to obtain the optimum results in terms of clarity, color and gelling power.

According to the invention, glue and gelatin solutions are clarified by adding a preferably 3 to 60 "oi" c glue and gelatin solution at elevated temperature with a water-soluble aluminate, in particular sodium aluminate, to pii = 8-5 to 10 ( measured adjusts at 2o'C) and the solution filtered after neutralization or de- decanted.

-The better results obtained with this way of working are probably due to this. that. while when working with common Ahiminitimsalzen, I for example aluminum sulfate, a colloidal solution of aluminum hydroxide is formed, the hydroxyl ions of which are positively charged, when using an aluminate, for example sodium aluminate, a negatively charged sol is formed. Wähi # end in the former case, an effective when working with aluminum salts of Trübuncrsstoffe and thus improved clarity of the glue and the gelling Gelatinelösun Koa ulierun- simultaneously with a low-9 Z> sten loss only in a medium can be obtained, whose PBI Value is approximately between 4.2 and 4.9, in the latter case, when working with an aluminate, these results can only be achieved if the pFi value is above 3.5 dear-t, and preferably between 8.5 and 10 ° C (, -measured at 20'C). Here goes. lost when operating in this range of pii-word, the gelling is much slower, and this has the consequence that the solution whose clarity has been in these working conditions are improved, ierkraft a higher gel has' as if they themselves -having by application of an aluminum salt optimum Conditions would be clarified. Furthermore, II - was -efunden that the clarification * r Lö-ZD dc solution with the Altiminat Koacrulierung the l # r> ZD turbidity substances much faster proceeds more than in your first case, and atis this reason also. the loss of gel strength that occurs when working with aluminates is lower.

The application of an alliminate instead of an aluminum salt to clarify glue and gelatin solutions makes it possible under these circumstances to obtain products of greater clarity and less color than would otherwise be possible. The concentration of the solution to be processed does not play a special role in the clarification. However, it has been found that with solutions containing more than - about 8011 ° gelatin or glue - difficulties arise in separating the precipitate. Therefore, concentrations are applied io 3-6 # preferably, and the Klärun- is eführt by-at temperatures of 5 to 7 ungeti ferry ioo '.

The amount of aluminate required for clarification depends of course in -e-I ZD to a certain extent on the degree of cloudiness of the material to be processed away. However, it should be noted that the addition of an aluminate reduces the alkalinity the solution grows, and it has been found that as the pH increases, the pH -the gelling power decreases with the specified treatment method. If the pri value rises above io, and #it becomes a high treatment temperature on the one hand and on the other hand If a long sitting time is used, this will reduce the gelling force quite considerable. It is therefore advisable to gradually reduce the aluminate under constant Stir to avoid these adverse conditions local or specific Times come.

By adding small amounts of acids, for example hydrochloric acid or phosphoric acid. or of alkali, such as ether soda, immediately before or during the gradual addition of the aluminate, the pH number during the The clarification process must be set correctly.

In a preferred embodiment of the invention, the pi-i value of the gelatin or glue solution is, if necessary, adjusted between 5 and 6 (measured at 2JC) by adding acid or alkali, depending on the case at hand, before the treatment with the aluminate then-Crenü-end aluminate is added. in order to bring the endpil value of the solution within the specified limits. For this purpose, an amount of alumina of about 1 to 3 percent of the dry weight of the gelatin or glue is necessary Separation is complete after about 11.2 hours. The clear solution can then be decanted and / or filtered off, preferably after neutralization with hydrochloric acid or another acid.

Some embodiments of the invention are given in the following examples: 1. 315ol of a 4% cloudy gelatin solution are brought to a pri value of 6.0 (measured at 20 ° C.) by adding hydrochloric acid, and then 3.121 , -g sodium aluminate slowly stirred in at 100 ', the pii value of the liquid after the addition of all the Altiminate is approximately above 8.5, but below 9.5 (measured at 26 ° C). Coagulation takes place in a few minutes, and after standing for one hour the liquid is brought to a pH of 7 (measured at 20 ° C.) by adding hydrochloric acid, and the precipitate which has formed is then allowed to settle. When draining and filtering, a crystal clear filtrate with a pale yellow color results. The gelling power of the clarified gelatin (measured with a diving instrument) is: ityt e 75010 of the unclarified material.

2. 72001 of a 4.5Üi'oi, -, el- 'cloudy gelatin solution are brought to a pii value of 6.0 (measured at 2o'C) by adding hydrochloric acid. Then 4.54 kg of sodium aluminate are gradually stirred in at go`, and the pii value of the liquid after the addition of the entire amount of aluminate is above 8.5 and below 9.5 ( measured at 2o`C). Coagulation takes place in a few minutes, and after standing for one hour, the liquid is brought to a pH value of 7 (measured at 20 ° C.) by adding hydrochloric acid and then left to stand. After draining and filtering, a crystal-clear filtrate is disfigured , which has a pale yellow color. The gelling power of the clarified gelatin (measured with a diving instrument) is about% of that of the unclarified material.

3. 45001 of a 40% solution of cloudy C Z> hide glue with a pH value of 4.75 (-measure at 2o ' C) are stirred at 90' with 7.26'1, ZD sodium aluminate, and the pii- After the whole amount of aluminate has been added, the value of the liquid is approximately 9 (measured at 20 ° C.). The Koa ulierung is completely in a few minutes, and after standing, the liquid is istündigem (measured at 20 'C.) by addition of hydrochloric acid to a value of 6 Pii and allowed to settle. C When filtering, a clear filtrate of yellow color results, which has a gelling power of 77% of the uncleared solution.

Instead of the aforementioned addition of the aluminate in solid form you can also achieve satisfactory results with a solution of the Alummate. solutions of alkali aluminate are subject to -, hydrolysis, whereby free 'alkali is formed, and for this reason it is preferred to use it in solid form.

Claims (1)

PATENTANSPRUCII. Process for clarifying glue and gelatin solutions using aluminum compounds at elevated temperature, characterized in that a preferably 3- to 60/10-liter glue and gelatin solution with a water-soluble aluminate, in particular sodium aluminate, is measured to pH 8.5 to 10 ( at 26 ° C) and the solution is filtered or decanted after neutralization.