GB2073767A - Method of Purifying Wool Grease - Google Patents

Abstract

A method of purifying wool grease comprises mixing a colloidal dispersion of wool grease in a hydrocarbon solvent with an alcohol in a ratio of dispersion to alcohol of from 10:1 to 10:4, dispersing the mixture so obtained in an aqueous alkali/alcohol mixture having a ratio of water to alkali to alcohol of 60 to 75: 2 to 5:20 to 35, and then separating the phases obtained.

Description

SPECIFICATION Method of Purifying Wool Grease The present invention relates to a method of purifying wool grease and, more specifically, wool grease recovered by washing wool with a hydrocarbon solvent or recovered from waste waters obtained by washing wool with an aqueous solution of a surfactant so as to obtain lanolin suitable for use in the pharmaceutical industry and cosmetics.

It is known to purify wool grease by neutralizing a colloidal dispersion of the wool grease in a hydrocarbon solvent, for example hexane, with an aqueous solution of an alkali in the presence of an alcohol, for example isopropanol.

This process is typically carried out by supplying the colloidal dispersion having a wool grease content of 25% by weight to a mixer into which a 20% aqueous solution of an alkali and an aqueous solutiop of the alcohol are also introduced. After thorough mixing, the mixture is allowed to stratify into two layers: the upper layer comprising the neutralized colloidal dispersion and the lower layer comprising an aqueous alcoholic soap solution (soap stock). The neutralized colloidal dispersion containing a considerable amount of soap is subjected to multiple washing with an aqueous alcoholic solution. The layer of aqueous alcoholic soap solution is washed with a hydrocarbon solvent to recover the grease (N.V. Rogachev, "Wool Washing with Solvents", Moscow, CNIITElegprom, 1971, p. 29).

This process contemplates the use of a considerable excess of a highly concentrated alkali which contributes to saponification of the grease and reduces the solubility of the soap formed in the neutralizing solution. The composition of the reacting phases is theoretically determined by the phase equilibrium diagram for the pure solvents, for example, hexane, isopropanol and water. The reaction mixture contains the colloidal dispersion, isopropanol, the aqueous soap solution, and the alkali, but the detailed composition of the reaction system is more complicated and the composition of the phases obtained with particular ratios of the components is substantially different from the composition theoretically given by the phase diagram.The intensive contact of the phases during mixing and, as a result, the mutual dissolution of the components contributes to an increased dissolution of soap in the colloidal dispersion. In this connection, the neutralized dispersion contains a considerable amount of the soap and for the production of a high quality lanolin, repeated washing of the dispersion with the aqueous alcoholic solution is required and at the same time in order to reduce losses of the grease, repeated washing of the soap stock with a hydrocarbon solvent is needed.

The above-described prior art process, characterized by the use of a considerable excess of alkali, leads to saponification of'the neutral wool grease and, hence, a reduced yield of the desired product and, furthermore, in carrying out this known process, a wrong selection of the ratio of the starting materials, the order of their addition to the mixer, and the intensive phase contact which takes place in the latter all enhance migration of the soap into the neutralized dispersion and an increased content of lanolin in the neutralizing solution, with the consequential necessity of repeated washings of the grease dispersion to reduce its soap content and extraction of the neutralizing solution to reduce losses of lanolin. These latter steps complicate the process technology and increase the equipment employed.

We have now developed an improved method of purifying wool grease which improves the quality and the yield of the desired product.

According to the present invention, we provide a method of purifying wool grease, which comprises mixing a colloidal dispersion of wool grease in a hydrocarbon solvent with an alcohol in a ratio of dispersion to alcohol of from 10:1 to 10:4, dispersing the mixture so obtained in an aqueous alkali/alcohol mixture having a ratio of water to alkali to alcohol of 60 to 75: 2 to 5: 20 to 35, and then separating the phases obtained.

It is preferred to use hexane as the hydrocarbon solvent and isopropanol as the alcohol; it is further preferred to treat a colloidal dispersion of wool grease which contains from 10 to 40% by weight of the latter.

The process according to the invention is based upon the selection of conditions for the neutralization step which reduce the water-absorbing capacity of the grease and increase the solubility of the resulting soaps. The neutralization is conducted under mild conditions and with minimal agitation; that is just sufficient agitation is used on initially bringing together the colloidal dispersion/alcohol mixture and the aqueous alcoholic alkali to form a homogeneous mixture. Agitation is not continued and the phases are allowed to separate. In this way saponification of the neutral grease is avoided and emulsification of the grease and migration thereof to the neutralizing solution is reduced.

The method according to the invention is carried out in the following manner.

The colloidal dispersion obtained by washing wool with a hydrocarbon solvent, such as hexane, or by dispersing the grease recovered by aqueous washings in a hydrocarbon solvent is mixed with an alcohol, such as isopropanol, in a volume ratio of from 10:1 to 10:4. An aqueous solution of an alkali is mixed with an alcohol, preferably isopropanol, in a volume ratio of water to the alkali to the alcohol of 60-75:2-5:20-35. These ratios ensure a minimal mutual dissolution of the components upon mixing of the phases. As already stated, it is preferred to use a colloidal dispersion having a grease content of from 10 to 40% by weight.

The dispersion/alcohol mixture is dispersed in aqueous alcoholic alkali solution with minimal agitation and the phases are then allowed to stratify and are separated.

The method according to the invention has the following advantages over the prior art:- lanolin of improved quality is obtained due to its reduced soap content which is attained by the addition of the alcohol to the colloidal dispersion and the neutralizing solution having the abovespecified proportions ensuring the maximum stratification of phases and a reduced migration of the soap to the neutralized colloidal dispersion; increased yield of the final product due to the use of alkali solutions having a low concentration; elimination of repeated washings of the dispersion and the neutralizing solution due to a reduced migration of the soap to the neutralized wool grease and losses of lanolin with the neutralizing solution; simplified process technology and equipment.

In order that the invention may be more fully understood, the following examples are given by way of illustration only. All proportions and percentages are by weight.

Example I 1 5 Kg of a colloidal dispersion of wool grease in hexane containing 10% of wool grease having an acid number of 12.5 mg KOH and 10% of isopropanol, were neutralized with an aqueous isopropanol solution of caustic soda having a ratio of water, alcohol and alkali of 73.5:24:2.5.

The neutralization was carried out in a laboratory unit comprising a glass column surrounded by a thermostatting jacket. The process was carried out at a temperature of 50+50C.

The aqueous alcoholic alkali solution was placed in the column and the prepared colloidal dispersion was dispersed in the alkali solution. The mixture was then allowed to stratify into separate phases and samples of the separated phases were taken to determine the characteristics of the neutralized wool grease.

As a control, a sample of a colloidal dispersion of wool grease containing 25% of wool grease, was neutralized by the prior art method. The dispersion was mixed in a beaker with a 20% aqueous solution of caustic soda and isopropanol was added to the mixture at the rate of 40% based on the amount of the aqueous phase. The neutralized wool grease was washed 5 times with a 40% aqueous isopropanol solution.

The aqueous soap alkali solution obtained from the neutralization step was washed with hexane and the resulting wool grease dispersion was combined with the major portion of the dispersion and samples of the mixed product were taken to determine the characteristics of the neutralized wool grease.

The comparative data obtained in the experiments are given in Table 1 below. From the data of this Table it can be seen that neutralization of wool grease by the process of the invention gives a product of improved quality as its soap content is some 10 times less than that of the product obtained by the prior art method.

Example 2 1 5 Kg of a colloidal dispersion of wool grease in hexane containing 27% of wool grease having an acid number of 14.1 mg KOH and 20% of isopropanol, were neutralized with an aqueous isopropanol solution of caustic soda having a ratio of water, alcohol and alkali of 62:35:3. The process was carried out under the same conditions and in the same apparatus as described in Example 1.

The results obtained are given in Table 1 below.

Example 3 1 5 Kg of a colloidal dispersion of wool grease in hexane containing 27% of wool grease having an acid number of 14.1 mg KOH and 10% of isopropanol, were neutralized with an aqueous isopropnaol solution of caustic soda having a ratio of water, alcohol and alkali of 73.5:24:2.5.

The process was carried out under the same conditions and in the same apparatus as described in Example 1. The results obtained are given in Table 1 below.

Table 1

By the process of the invention By the Characteristic known process Ex. 1 2 3 1. Acid number of the neutralized wool grease, mg KOH 0.36 0.32 0.34 0.35 2. Soap content of neutralized grease, % 0.62 0.03 0.08 0.05 3. Ash content, 9/0 0.06 0.03 0.04 0.03 4. Yield of neutralized grease, % 90.0 94.0 93.0 92.5 5. Saving of neutralized grease, % 4.0 3.0 2.5

Claims (5)

Claims

1. A method of purifying wool grease, which comprises mixing a colloidal dispersion of wool grease in a hydrocarbon solvent with an alcohol in a ratio of dispersion to alcohol of from 10:1 to 10:4, dispersing the mixture so obtained in an aqueous alkali/alcohol mixture having a ratio of water to alkali to alcohol of 60 to 75:2 to 5:20 to 35, and then separating the phases obtained.

2. A method according to claim 1, in which the hydrocarbon solvent is hexane.

3. A method according to claim 1 or 2, in which the initial colloidal dispersion of wool grease contains 10 to 40% by weight of the latter.

4. A method according to any of claims 1 to 3, in which the alcohol is isopropanol.

5. A method of purifying wool grease substantially as herein described in any of the Examples.