US1788848A - Process of bleaching soap - Google Patents

Description

Patented Jan. 13, 1931 UNITED STATES PATENTV OFFICE CHARLES FRANK SCHUMAKER, OF SYRACUSE,

NEW YORK, ASSIGNOR TO THE MATHIE' SON ALKALI WORKS, INC-, OF NEW YORK, N. Y., A CORPORATION OF VIRGINIA PROCESS OF BLEAGHTNQ SOAP No Drawing.

This invention relates to the bleaching of soap to produce a stable bleached soap product.

It has heretofore been proposed to bleach soa by the action of hypochlorites but in sue processes chemical action other than bleaching a parently takes place and interferes with t e bleachin process. Where the soap has been bleache y the hypochlorite the bleached product has apparently been unstable and lacking in permanent whiteness. So far as I am aware the bleaching of soap with hypochlorite according to processes heretofore proposed has not been successfully carried out in a commercial manner.

The present invention provides an improved process for bleaching soap in which the bleaching is effectively carried out and a stabilized product produced which can be kept for long periods of time in a bleached I or white condition. I

I have found that soap can be readily and satisfactorily bleached by the combined action of sodium hypochlorite and formaldehyde,-which apparently gives a permanently bleached roduct. Sodium hypochlorite and formaldehyde in solution react with each other forming, among their reaction products formic acid, h pochlorus acid and sodium formate. The ringing together of solutions of sodium hypochlorite and formaldehyde in intimate admixture with soap exerts a rapid bleaching action on the soap. This bleaching action appears to be due in part to the action of hypochlorous acid formed from the reaction of sodium h pochlorite and formaldehyde. It is proba le that the formaldehyde is first in part oxidized to formic acid which reacts with sodium hypochlorite to form sodium formate and hypochlorous acid. Sodium formate is the sodium salt of the simplest of the fatt acids and is itself a desirable ingredient o the soap. Hypochlorous acid is an active bleaching agent. It is probable. that the sodium hypochlorite and the formaldehyde have other actions on the soap which contribute to the bleaching operation and to the production of a stable and preserved product. It is probable that the sodium hypochlorite acts in part to oxidize Application filed June 26,

1928. Serial No. 288,144.

acts with additional sodium hy ochlorite to set free hypochlorous acid and orm sodium formate, but it may be that the formaldehyde may otherwise react with the sodium hypochlorite or with the hyp'ochlorous acid. Formaldehyde is a valuable preservative agent, having important reducing properties because of its aldehydic character and the use of such a preservative agent appears to be important in producing a bleached soap of a stable bleached character, which resists the tendency to change from its white bleached state to a discolored state such as characterizes various soap products heretofore bleached with sodium hypochlorite.

I consider accordingly that my process in which sodium hypoc lorite andformaldehyde are employed is one in which the fatty acid, i. e., formic acid, is formed from the aldehyde, i. e., formaldehyde, and in which the fatty acid reacts with the sodium hypo chlorite to form hypochlorous acid as an ac- 3 tive bleaching agent, and also one in which the aldehyde has important properties as a stabilizing agent .or inhibitor of subsequent oxidation or deterioration. Whereas products bleached with'sodium hypochlorite alone reagent 1s added so that the reaction takes place with the reagents intimately distributed throughout the soap.

The amounts of hypochlorite and formaldehyde can be somewhat varied, but usually not more than about 2% of sodium hypochlorite and 1% of formaldehyde are required. The formaldehyde can conveniently commercial water be used in the-form of the mg and the degree solution containing around 37-40% of formaldehyde. The sodium hypochlorite can advantageously be added dissolved in water.

In the manufacture of soaps, the soap, after the boiling operation, is settled and separated from the lye and the still liquid soap. is subjected to a crutching operation where various materials, such as fillers, perfume, etc. are added and the soap thoroughly mixed. The soap from the crutcher is commonly run into frames where it is permitted to solidify, after which it is cut into slabs and bars and dried. The higher rades of soap, such as toilet soaps, are made y shaving the soap to form chips, which are then milled and formed into the final cakes. In other. methods of making toilet soaps the crutching operation is omitted and the soap on completion of the boiling operation is run to a continuous drying chamber where it is dried, after which it is chipped and subjected to a milling operation. In such case the chips may be amalgamated with perfume and other ingredients milling. p 7

'The bleaching process of the present invention can advantageously be carried out during or as a part of the milling operation, but it can also be carried out in part or in whole'during an earlier part of the soap making operation, and particularly during the crutching oramalgamating operation.

When the bleaching operation is carried out in connectionwith the milling of the soap, the soap chipsshould contain a suit able content of moisture, usually around 8 to 14%, depending upon the type of mill used. The effectiveness of the bleaching operation, however, does not appear to be debefore subjecting to pendent upon the moisture content of the chips.

The invention will be further illustrated by the following specific examples, but it will be understood that the invention is not limited thereto. Soap chips having a moisture content of around 8 to 14% are mixed with the solution of sodium hypochlorite and the solu tion of formaldehyde, the precentage depending upon the color of the soap before bleachof bleaching action desired. Usually not more than 2% of hypochlorite and 1% of formaldehyde are required. After the chips have been thoroughly mixed with the hypochlorite and formaldehyde they are passed through a soap mill one or more times. The greater part of thebleaching action takes place during the'milling process, due in'all probability to the activity of the bleaching agents under mechanical pressure and the slight heat of the mill and the intimate contact brought about by the milling operation. An arrangement of, two mills in tandem appears to make the best pochlorite dissolve can be run arrangement for carrying out the process I when the bleaching ingredients are added in a single operation.

Instead of adding the bleaching ingredients in a single operation, either the sodium hypochlorite solution or the formaldehyde solution may be added in the initial milling and the other added for the second milling. For example, the sodium hypochlorite solution. may be added first and the soap. milled after which the formaldehyde is added and the soap again milled; or this process can be reversed and the formaldehyde solution added before the first milling and the sodium hypochlorite solution before the second milling.

According to another example of the invention a definite ercentage of sodium hyd in water is added to the liquid soap'properly finished as it comes from the soa kettle so that the sodium hypochlorite so ution is incorporated into the plastic mass of the soap during the crutching operation.

Subsequently the soap is dried and chipped and the soap chips with the customary moisture content for milling are mixed with a definite percentage of formaldehyde dissolved in water and subjected to the milling operation. g

When formaldehyde solution is added to soap already intimately admixed with sodium hypochlorite, or vice versa, or-where both the hypochlorite and formaldehyde solutions are added during the same operation, a decided bleaching action takes place,'which is markedly different from that obtained when sodium hypochlorite alone is added to soap. This bleaching action accordingly appears to be-due largely to reaction products produced by the interaction of the hypochlorite and formaldehyde upon each other in intimate admixture with soap, such as hypo chlorous acid and nascent oxygen.

excess of formaldehyde, in excess of its complete oxidizing and. bleaching action during the bleaching operation without leaving any residual oxidizing agent present and instead leaving more or less formaldehyde which has reducing properties and acts as a preservative'or inhibitor of oxidation.

In the carrying out of the present process the hypochlorite and formaldehyde solutions can bestored in suitable containers suspended above the mixer or mixers or otherwise arranged so that definite quantities of each into the soap chips either as a bleach the soap.

batch operation or as a continuous operation. By arranging the mixer and mills so that the operations follow each other continuously and by adding the bleaching reagents in a continuous and regulated manner, the bleaching operation as a whole can be made continuous.

An excess of one of the bleaching reagents, particularly formaldehyde, is desirable in the nal product in order to impart improved stability and I claim 2- 1. The process of bleaching soap which comprises subjecting the soap to a milling operation in intimate admixture with solutions of sodium hypochlorite and formaldehyde.

2. The process according to claim 1 in which the sodium hypochlorite and formaldehyde dissolved in water are added to the soap chips before millingand caused to act upon the soap during the subsequent milling operation.

3. The process of bleaching soap with sodium hypochlorite and formaldehyde which comprises mixing the soap before milling with one of said agents and subjecting the soap to milling, then mixing the resulting soap with the other reagent and subjecting the soap to a second milling operation.

4. The process of bleaching soap which comprises adding to the soap sodium hypochlorite dissolved in water and subjecting the soap to a crutching operation, drying and chipping the resulting soap, mixing with the soap chips a solution of formaldehyde and milling the resulting mixture.

5. The method according to claim 1 in which an excess amount of sodium hypochlorite is used over the amount required to anitseptic or other properties.

6. The process of bleaching soap which comprises subjecting the soap to the action of free hypochlorous acid, the hypochlorous acid being generated in a nascent state during the bleaching operation by the action on an alkaline hypochlorite of an acid.

7. The process of bleaching soap which comprises subjecting the soap to the action o f free hypochlorous acid, the hypochlorous acid being generated in a nascent state during the bleaching operation by the action on an alkaline hypochlorite of formic acid produced from formaldehyde during the bleaching operation.

8. The process of bleaching soap which comprises subjecting the soap to the action of an alkaline hypochlorite and formaldehyde.

9. The method of-bleaching soap which comprises subjecting the soap to the action of hypochlorous acid and formaldehyde which stabilizes the bleached soap against afterdarkening.

10. The process of bleaching soap which comprises subjecting the soap to a mechanical workin operation with addition thereto of an alka ine hypochlorite and formaldehyde, the aldehyde being in excess so as to leave some of the formaldehyde in the bleached product.

11. The method of bleaching soap which comprises incor orating with the soa an alkaline hypoc lorite and formalde yde which will react with the hy chlorite to form free hypochlorous acid, t e formaldehyde being employed in sufiicient excess to stabilize the resulting bleached product against after-darkening.

' whereof I afiix my signature.

In testimony CHARLES FRANK SCHUMAKER.