Method for the production of transparent soap

Description

[0001] The present invention refers to a method of production of transparent solid soap starting from common fatty materials (glycerides, fatty acids) and classical additives (multivalent alcohols).The appearance and transparency of the soap are improved and in parallel the moulding process is also facilitated through the addition of hydroxy polycarbonic or polyhydroxy carbonic or polyhydroxy polycarbonic acid esters at a 1 to 5 % on the soap mass. At the same time the tendency of the transparent soap for rancidity is reduced through the addition of stilbene, hydroxy benzophenone derivatives or 4- alkoxy cinnamates.

[0002] By the term "solid transparent soap" is characterized as to composition, colour and gloss a wide range of products which under the shape and size of the usual toilet soap show a relative transparency, that is, allow the passage of light through their mass.

[0003] Up to date, several techniques for the production of transparent soap are known, like the addition of multivalent alcohols; for example glycerol, sorbitol, sugars and the like that are used for the preparation of classical transparent soap . (i.e. sodium soaps of fatty acids made by boiling simmering or cold saponification).

[0004] Transparent soaps are also prepared by the dissolution of usual soap in alcohol in order to remove the electrolytes and other unsaponifiables followed by the distillation or evaporation of the alcohol.

[0005] The production of transparent soap by the combination of soap, polyhydroxy alcohols and alkylphenol polyalkoxy ethers is described in the 3562167 US Patent. Respectively, in the 3903008 US Patent the transparent soap results from the combination of multivalent alcohols and an amphoteric imidazole derivative as surfactant. In the 3793214 and 3926808 US Patents several soaps obtained from branched fatty acids are described and in the 3864272 US Patent tedious processes for transparency are dealt with. The 2820768 US Patent refers to sodium soap of tallow, coconut oil and castor oil mixed with triethanolamine, oleic and stearic acid soaps, while in the 42909041 US Patent tetrakis-(hydroxy alkyl) ethylenodiamine is applied instead of triethanolamine.

[0006] The forementioned approaches either constitute difficult elaboration methods or presume the use of chemical additives that are unusual to the classical and already applied raw materials of the soap industry.

[0007] I. The soapmass for the production of transparent soap according to our invention consists of a mixture of fatty acid sodium soaps ranging from 12 to 18 carbon chains. Coconut oil, palmist oil and more seldom babassu oil are used as the 12 to 14 carbon chain sources. II. For the 16 to 18 carbon chains the main raw material used is tallow as well as various seeds oils like palm oil, kernel oils etc.

[0008] For the production of transparent soap mixtures of (I) and (II) are used at the proportions of 15-30% of I and 85-70 % of II. In many cases small quantities of hydroxyacid soaps are added, like ricinoleic acid salts (from castor oil, 1-10%) or potassium soaps in order to avoid undesired forms of crystallization of the soap, thus preventing the consequent loss of transparency. Often, multivalent alcohols like propylene glycol, sorbitol, glycerol, sugars etc. and superfatting agents like fatty acids, fatty alcohols and their alkoxy derivatives are added at the same time to the soapmass. Of course, besides the composition of the starting materials, the basic requirements for the preparation of transparent soap remains the least possible alkalinity as well as the least elecrolyte and unsaponifiables' concentration of the soapmass. Moreover, the final product should lather well, be soft, be neutral in odour as possible and it should not crack or become muddy. At the same time it should keep its transparency during use and the pH should remain as low as possible. The keeping of the above mentioned classical requirements does not always lead to products of homogenous transparency. On the other hand these products might suffer important alterations due to the mechanical difficulties during the moulding process in the plodders.

[0009] As well known, local overheating of the soap in the plodders tends to rancidity and alteration of the crystallization form, hence loss of transparency and homogeneity. At the same time production is delayed with inevitable increase in cost because of the mechanical resistance within the plodders as indicated by an increase in power consumption.

[0010] If small quantities of hydroxy polycarbonic or polyhydroxy carbonic or polyhydroxy polycarbonic acid esters (i.e. citric, tartaric, aldonic, uronic sugar acids etc at a 1-5% content and at best 1,5-3%) were added to soapmass during production according to the above specifications and materials, we surprisingly observed the following:

i) The production of the transparent soap is improved as indicated by the decrease in power consumption of the plodders (from 42 Amperes to 30-32 Amperes). Subsequently, all the drawbacks mentioned in page 3 (lines 1-8) are removed.

ii) The so produced soap is more transparent and better in appearance and stability. At the same time, either stilbene or hydroxy benzophenone derivatives or alkoxy cinnamates (10-100 ppm) are added. They slow down eventual photochemical oxidations acting as synergetic agents of the usually incorporated antioxidants to the soap.

EXAMPLE

[0011] A soapmass "made by the usual methods or the automatic saponification procedure from 760 kg of distilled tallow fatty acids, 220 kg of distilled palmist oil fatty acids and 30 kg of sodium ricinoleat with the following specifications:

Humidity

: 35-38%

Alkalinity (Na₂O)

: 0.03

Nacl

: 0.25-0.45

Unsaponifiables

: <0.01%

is dried in a continuous vertical vacuum drier, while a mixture of 70 kg glycerol, 50 kg sorbitol and 20 kg tributyl acetyl citric acid is introduced per ton of soap together with a mixture of antioxidants and alkyl stilbene derivatives (i.e. stilbene, -4,4'-diamino-2,2' disulphonic acid sodium salt or 4-hydroxy benzophenone or 2-ethyl hexyl, 4-methoxy cinnamic ester, tocopherol (0.02-0.03%), ascorbic palmitate (0.02-0.03%)). Then the mixture is elaborated in the plodders and moulded.

Final product specifications:

[0012] 

Humidity

: 12-14 %

Fatty acids

: 66-68%

Alkalinity (Na₂O)

: 0.03%

Nacl

: <0.03%

Unsaponifiables

: <0.1%

[0013] The final product is moulded easier (32A instead of 43A for the same product and without the present invention additives), it has a sensibly better transparency and its resistance to rancidity is improved.

Claims

1. Method for the production of transparent soap from usual starting materials (glycerides, fatty acids) and additives (multivalent alcohols) the transparency and appearance of which are improved. The mechanical moulding procedure is also improved by the addition of hydroxy polycarbonic or polyhydroxic carbonic or polyhydroxy polycarbonic acid esters (1-5% ). Also the tendency for rancidity of the soap is decreased by the addition of stilbene and hydroxy benzophenone derivatives and hydroxy cinnamates.

2. Method according to claim 1, characterized by the fact that the fatty materials may be :

a. Coconut oil, palmest oil and babassu oil.

b. Tallow or palm or seed oils' fatty acids.

c. Castor oil.

3. Method according to claim 1, characterized by the fact that the usual additives are: Polyhydroxy alcohols (glycerol, propylene glycol, sorbitol, sugars etc) and superfatting agents like fatty acids, fatty alcohols and their alkoxy derivatives.

4. Method according to claim 1, characterized by the fact that the polyhydroxy polycarbonic esters may be citrates, tartrates, saccharates, aldonates and glucuronates of 3 to 5 carbon chain alcohols.

5. Method according to claim 1, characterized by the fact that the additives that diminish the tendency for rancidity may be stilbene and hydroxy benzophenone derivatives or alkoxy cinnamates like :

- Sodium, stilbene-4,4' diamino-2,2' disulphonate

- 4-hydroxy benzophenone

- 2-ethyl hexyl, 4-methoxy cinnamate