US3415610A - Reaction product of alkali metal sulfide and phosphorus sulfide in an 8:1 or higher ratio, depilatories therefrom and depilation therewith - Google Patents

Description

United States Patent Oflice REACTION PRODUCT F ALKALI METAL SUL- FlDE AND PHOSPHORUS SULFIDE IN AN 8:1 OR HIGHER RATIO, DEPILATORIES THERE- FROM AND DEPILATION THEREWITH Theodore H. Dexter, Lewiston, and Alfred O. Minklei,

Kenmore, N.Y., and Thomas C. Thorstensen, Chelmsford, Mass, assignors to Hooker Chemical Corporation, Niagara Falls, N.Y., a corporation of New York No Drawing. Filed May 27, 1964, Ser. No. 370,704

27 Claims. (Cl. 8-94.16)

ABSTRACT OF THE DISCLOSURE Applicant reacts about 8 mols or more of sodium sulfide 'with one mole of phosphorous pentasulfide to produce a depilatory to which CaCl sharpener can be added. Part of the sodium sulfide is replaced by sodium hydroxide in the other examples. Other alkali sulfide such as potassium, rubidium, cesium and lithium sulfide can be used in lieu of sodium sulfide.

This invention relates to a novel composition useful for treating animal hides and skins, and more particularly relates to novel phosphorus and sulfur-containing compositions which may be used to effectively unhair animal hides and skins.

In the processing of animal hides and skins to obtain leather, one of the important steps involved is that of removing the hair from the hides or skins, prior to the actual tanning operations. Generally, the procedures involved in effecting such unhairing, include treatments of the hides and skins with a material which effects a substantial loosening. of the hair thereon and, thereafter, scraping the hides and skins, generally by passing them through an unhairing machine, to remove substantially all of the hair.

Heretofore, numerous materials have been utilized to obtain the substantial loosening of the hair on the hides and skins. Typically, these have included solutions or slurries of lime, either as such, or containing various additives, such as alkali metal sulfides, alkali metal sulfhydrates, organic compounds, such as dimethylamine sulfate, and the like. For the most part, unhairing solutions of this type are effective in loosening the hair so that it may be substantially completely removed, without appreciable damage to either the hides or the hair which is removed.

The time required to effect the loosening of the hair when using such materials has, however, frequently been undesirably long, e.g., often requiring at least about 48 hours. Although the length of time may be acceptable where it is desired to recover the hair removed as a salable product, where such hair recovery is not to be effected, the time required for unhairing may be deemed to be unduly long. In this respect, it is to be noted that in many instances recovery of the hair for resale may not be of importance, particularly during periods wherein hair prices may be low. Accordingly, at such times, the tanner may be principally concerned with effecting a rapid removal of hair from the hides, without damage to the hides, even though the hair removed may be in a pulped or badly damaged condition.

Patented Dec. 10, 1968 In the past, such rapid unhairing has been carried out using solutions of alkali metal hydroxides, such as sodium hydroxide, alkali metal sulfides, such as sodium sulfide, alkali metal sulfhydrates, such as sodium sulfhydrate, and the like. Although such compounds are effective in removing the hair from the hides in a relatively short time, some care is required with the use of these materials, particularly 'with the alkali metal hydroxides and sulfides, to avoid damage to the hide itself. Additionally, these very alkaline materials may also cause plumping or alkaline swelling of the hide which is generally undesirable in the finished leather. Moreover, these materials are generally used in conjunction with a standard lime systern, which systems have, recently, caused some difficulties in terms of disposal of the effiuent from the unhairing operation. These difiiculties have been due primarily to the amounts of solid matter in the effiuent, which solids may be detrimental when discharged into either natural waterways or municipal sewer systems. It is, therefore, desirable to provide an unhairing agent which is effective in removing the hair from animal hides or skins in a relatively short period of time without damage to the hides and which materials may be used in either a conventional lime system or in a non-lime system.

It is, therefore, an object of the present invention to provide a novel unhairing agent which is effective in rapidly removing hair from animal hides or skins without damaging the hides or resulting in plumping or swelling of the hides.

Another object of the present invention is to provide an unhairing agent as described above which may be used in either a conventional lime system or a nonlime system.

A further object of the present invention is to provide a novel method for unhairing animal hides and/or skins whereby the hair is quickly and easily removed from the hides with no damage thereto.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes a composition useful in unhairing animal hides and/or skins, which composition comprises an alkaline phosphorussulfur compound produced by reacting a phosphorus sulfide with a liquid alkali metal sulfide, in a mole ratio of more than about 8 moles of alkali metal sulfide to 1 mole of phosphorus sulfide, expressed as P 8 to obtain a product which is stable in aqueous solution at degrees centigrade. Aqueous solutions of these compounds, both with and without lime, have been found to be extremely effective for removing hair from animal hides and skins. Although the use of these compounds results in the substantially complete destruction of the hair, the removal is effected quickly with substantially no damage to the hides. Preferably, for ease in handling, the novel compositions of the present invention are recovered as solids.

It is to be appreciated, that in referring to a mole ratio of alkali metal sulfide to phosphorus sulfide of more than 8 to l, the amount in excess of 8:1 may be quite small, e.g., 0.1 mole or even less. Moreover, in establishing the mole ratio, the phosphorus sulfide is expressed as phosphorus pentasulfide (P 5 and the amount of alkali metal sulfide used is based on equivalents of this material present. By equivalents, it is intended to refer 3 to equivalent amounts of phosphorus in the phosphorus sulfide.

More specifically, the alkali metal sulfides used in formulating the novel phosphorus-sulfur compounds of the present invention is preferably sodium sulfide. Other alkali metal sulfides, i.e., potassium sulfide, lithium sulfide, cesium sulfide, and rubidium sulfide, may also be used with comparable results. Since it is the preferred alkali metal sulfide, primary reference will be made hereinafter to sodium sulfide. This is not, however, to be taken as a limitation on the alkali metal sulfides which may be used but merely as being exemplary of these materials. Moreover, it is to be understood that in referring to liquid alkali metal sulfides, it is intended to include both aqueous solutions as well as melts of alkali metal sulfides.

Since, as has been indicated hereinabove, the novel pl1osphorus-sulfur compounds of the present invention are preferably obtained as solids, the water content of the sodium sulfide used in their preparation is desirably maintained at a minimum. Thus, sodium sulfide solutions containing at least about 35 percent sodium sulfide are typical, with solutions of 65 percent or more sodium sulfide being preferred. Additionally, sodium sulfide solutions having a concentration below about 35 percent may also be used, as for example solutions containing 10 percent or less sodium sulfide, by weight of the solution. it will be appreciated, of course, that when such less concentrated alkali metal sulfide solutions are used, and it is still desired to obtain a solid product, appreciably larger quantities of water will have to be removed from the reaction mixture in order to obtain such desired solid product.

In this respect, with regard to the removal of water from the reaction mixture, it is important that the water be removed from the reactive mixture, e.g., by evaporation, rather than removing the solid product from the reaction mixture, e.g., by crystallization. It is to be further understood that this water removal may be effected either before, during or after the reaction of the alkali metal sulfide and the phosphorus sulfide material in the abovedescribed desirable ratio. Thus, the reaction may be carried out at a sufiiciently high temperature so that water is continuously evaporated from the reaction mixture or,

after the reaction is substantially complete, the reaction product may be heated to a sufficiently high temperature as to evaporate Water therefrom. In each instance, the amount of water removed is preferably sufficient so that upon cooling the material to substantially room temperature, a solid product is obtained. As another alternative, the removal of water may be eifected prior to the reaction, by using as the reactant, a liquid alkali metal sulfide solution which is highly concentrated. For example, when using a 60 to 65 percent solution of sodium sulfide, which material is normally solid at room temperatures, no further removal of water from the reaction product is generally necessary in order to obtain a solid product when the reaction material is cooled to room temperature.

Considering now the phosphorus sulfide which is reacted with the liquid alkali metal sulfide, in forming the novel compounds of the present invention, various phos phorus sulfide materials are found to be suitable. Generally, it is preferable that the molar ratio of sulfur to phosphorus in the phosphorus sulfide material used is not appreciably less than about to 2. It is known that in some instances, phosphorus sulfide materials having lower sulfur to phosphorus ratios, e.g., P 8 may hydrolyze to form phosphine. In view of the poisonous nature of this material, its formation is desirably avoided and for this reason, the use of phosphorus sulfide materials which have a sufficiently high sulfur to phosphorus ratio so as not normally to hydrolyze and form phosphine are preferred. Exemplary of typical phosphorus sulfide materials which may be used are those materials falling within the range of about P 8 to about P 5 Of the various phosphorus and sulfide materials falling within this range, the preferred material is phosphorus pentasulfide, P 3 Accordingly, although primary reference will be made thereinafter to phosphorus pentasulfide as being the preferred phosphorus sulfide material, this is not to be taken as a limitation on such materials which may be used but merely as being exemplary thereof.

As has been noted hcreinabove, the sodium sulfide and the phosphorus pentasulfide, i.e. P 5 are reacted in amounts so as to provide a molar ratio of more than about 8 moles of sodium sulfide to 1 mole of phosphorus pentasulfide. It will be appreciated, that in forming the novel phosphorus sulfur compounds of the present invention, a portion of the sodium sulfide used in the reaction mixture may be replaced by an alkali metal hydroxide, such as sodium hydroxide. Other alkali metal hydroxides which may be used include potassium hydroxide, lithium hydroxide, and the like. By replacing the sodium sulfide with an equivalent amount of sodium hydroxide, it is meant that the amount of sodium hydroxide used will provide in the reaction mixture sodium in the amount equal to that in the sodium sulfide which is replaced. Thus, for example, since there are 2 moles of sodium in each mole of sodium sulfide, in the reaction mixture containing 8 moles of sodium sulfide to 1 mole of phosphorus pentasulfide, 2 moles of sodium sulfide will be replaced by 4 moles of sodium hydroxide to give a reaction mixture containing 6 moles of sodium sulfide, 4 moles of sodium hydroxide, and 1 mole of phosphorus pentasulfide.

Since, as has been indicated in our co-pending application, compositions formed by the reaction of alkali metal hydroxides, alkali metal sulfides, and phosphorus sulfides, may be used to effect the unhairing of animal hides or skins without substantial damage to either the hides or the hair removed, it is important in the compounds of the present invention that the amount of alkali metal hydroxide present is not sufiiciently large to prevent the normal hair destruction action of these compounds. Accordingly in compounds of the present invention, it is desired that at least half of the total alkali metal ions in the composition be provided by the alkali metal sulfides, rather than the alkali metal hydroxides. In general, in the compositions of the present invention, it is preferred that there be at least half as many moles of sodium sulfide present as sodium hydroxide.

In preparing the novel phosphorus-sulfur compositions of the present invention, the mole ratio of alkali metal sulfide to phosphorus sulfide material is more than about 8 to 1. Where these materials are to be used in a conventional lime system for unhairing animal hides or skins, it is preferred that the mole ratio of sodium sulfide to phosphorus pentasulfide used in preparing the compounds is not greater than about 14 to 1, with mole ratios of about 10 to 1 to about 12 to 1 specifically preferred. Although compounds having appreciably higher ratios of alkali metal sulfide to phosphorus sulfide material, such as ratios of 25 to 30 to 1 or even higher, may be used to effect a rapid and complete unhairing of the hides, such higher ratio materials may, in some instances, result in undesirable swelling or plurnping of the hides, which may have an adverse effect on the leather ultimately produced, or their use may require more careful controls in order to avoid damage to the hides. Accordingly, the lower ratio materials, such as those having a sodium sulfide phosphorus pentasulfide ratio of from about 8 to 1 to about 14 to 1 are preferred.

In referring to a conventional lime system for unhairing, it is believed that those in the art will understand this to mean a system wherein a solution or slurry of lime is used. Frequently, the lime slurry used may contain about 6 percent of lime, based on the total weight of the hides to be unhaired. This amount of lime, of course, includes both the lime which is in solution and that which remains in the solid state, suspended in the solution. Obviously, as is known to those in the art, lime slurries or solutions containing greater or lesser amounts of lime may also be used.

To a lime solution or slurry, as described above, the novel phosphorus-sulfur compositions of the present invention are added. Preferably, such compositions are prepared by the reaction of an alkali metal sulfide and a phosphorus sulfide material in a mole ratio of at least about 8 to 1 and includes also those compositions wherein a portion of the sodium sulfide has been replaced by sodium hydroxide in the reaction mixture, as has been described above. The phosphorus and sulfur compositions of the present invention are added to the lime solution or slurry in an unhairing amount, i.e., an amount which is effective in promoting the unhairing of the animal hides and skins in a relatively short time, by destroying the hair, without excessive damage to the hides. Typically, the amounts of the composition added will be within the range of about 0.1 to about 10 percent by weight of the hides or skins being treated. It will be appreciated, however, that depending upon the total. alkalinity of the phosphorus-sulfur composition added, its sulfur content and the like, greater and lesser amounts of this material may be used to obtain rapid unhairing of the hides. In many instances, it has been found that ex cellent results are produced by using the novel phosphorus and sulfur compositions in amounts within the range of about 1 to about 4 percent by weight of the hides being treated.

In addition to conventional lime systems for unhairing animal hides and skins, considerable attention has been given recently to the use of so-called non-lime systems. Such systems have become increasingly important in view of more stringent governmental regulations relating to the disposal of tannery eflluent materials, since with such non-lime systems there are no substantial amounts of suspended solids in the effluent. As has been indicated hereinabove, the novel phosphorus-sulfur compositions of the present invention have also been found to be extremely effective in unhairing animal hides or skins in non-lime systems without substantial damage to the hides.

In these non-lime systems, the necessary alkalinity, i.e., alkalinity sufficient to effect unhairing, is provided by a compound which, in aqueous solution, produces suificient hydroxyl ions to provide the needed alkalinity. Suitable compounds for this purpose include the alkali metal hydroxides, e.g., sodium, potassium, lithium, cesium, and rubidium hydroxides, as Well as ammonium hydroxide amines, urea, ammonia, and the like. Additionally, the non-lime systems may contain a source of calcium ions as a sharpening agent, the amount of such calcium ion source being such that the amount of calcium ions provided is not sufficient to form a substantial amount of a calcium-containing precipitate in solution. Suitable materials which may be used include the more soluble calcium salts such as calcium chloride, calcium nitrate, and the like. Other sharpening agents which may be used include alkali metal sulfhydrates, alkali metal carbonates, hydrosulfites, such as zinc hydrosulfite, as well as compounds of alkaline earths other than calcium, such as barium, strontium, and the like. As with the calcium materials, the more soluble salts, such as halides, nitrates, sulfates and the like are preferred. These and other sharpening agents which may be used are known to those in the art.

Additionally, it may also be desirable to include in the composition an inert salt which, in solution, provides a moderating or buffering action on the system. Suitable inert salts include the alkali metal chlorides, e.g., sodium chloride, alkali metal nitrates, alkali metal sulfates, and the like. In general, it is desirable that unhairing solutions, both lime and non-lime, have sufiicient alkalinity so as to have a pH of at least about 12 and preferably within the range of about 12.2 to about 12.8. Desirably, the pH of the unhairing solution is not substantially in excess of about 13, since at such higher pH values, undue swelling and burning of the hides may occur.

It will be appreciated that in effecting unhairing of hides and skins in a n0n-lime system, the novel phosphorus-sulfur composition of the present invention, prepared from a reaction mixture containing the preferred sodium sulfide to phosphorus pentasulfide ratios of from about 8 to l to about 14 to 1, may be added to an alkaline solution containing sufficient alkaline matreial, such as sodium hydroxide, to provide the requisite alkalinity. Such alkaline solution will also, generally, contain the sharpening agents, such as calcium chloride, and the inert salts such as sodium chloride, in the amounts as have been indicated hereinabove. Alternatively, the alkaline material needed to provide the alkalinity for carrying out the unhairing may be incorporated in the novel phosphorussulfur compositions of the present invention by including alkali metal hydroxides, such as sodium hydroxide in the reaction mixture with the sodium. sulfide and the phosphorus pentasulfide. For unhairing, such composi tions may then be formed into an aqueous solution to which is added the sharpening material and the inert salt in the amounts desired. Compositions containing all of these components may be prepared by adding calcium chloride and sodium chloride to the alkali metal sulfide, sodium hydroxide, phosphorus sulfide reaction mixture or by adding calcium chloride and/ or sodium chloride to the reaction product after it has been formed. In each instance, of course, the amounts of these materials combined will be such that when the resulting composition is dissolved in water, the resulting aqueous solution will contain the requisite amounts of sharpening agent, inert salt, phosphorus-sulfur composition and have sufiicient alkalinity to effect rapid and substantially complete unhairing of the animal hides or skins. In general it is preferred that the Sharpening agent is dry blended with the phosphoru sulfur composition of the present invention after its preparation. In this manner, there is obtained a product which is relatively easily handled and formulated into an aqueous unhairing solution. Typical of compositions which may be formulated in this manner is one formed by the reaction of sodium sulfide, sodium hydroxide, and phosphorus pentasulfide, in a molar ratio of 24 moles of caustic soda to 12 moles of sodium sulfide to 1 mole of P 8 The thus-obtained solid reaction product is then dry blended with 7.8 moles of calcium chloride.

In general, in formulating non-lime systems, these will preferably contain the hydroxyl ion source in an amount within the range of about 0.5 to about 50 percent by weight, the sharpening agent in an amount within the range of about 0.1 to about 10 percent by weight, the novel phosphorus-sulfur composition of the present invention in an amount within the range of about 0.1 to about 10 percent by weight, and the inert salt in an amount within the range of about 0.5 to about 50 percent by weight, all of the above amounts being percent by weight of the hides to be unhaired. Preferably, such nonlime unhairing system will contain the hydroxyl ion source, such as sodium hydroxide, in an amount within the range of about 3 to about 20 percent by weight, the sharpening agent, such as calcium chloride in an amount within the range of about 1 to about 4 percent by weight, the novel phosphorus-sulfur composition, such as one prepared by reacting 8 moles of sodium sulfide with 1 mole of phosphorus pentasulfide, in an amount within the range of about 1 to about 4 percent by weight and the inert salts such as sodium chloride in an amount within the range of about 3 to about 20 percent by Weight. It will be appreciated that where the non-lime system is prepared by forming an aqueous solution of a composition containing all of the above materials, such compositions are typically dissolved in water in amounts within the range of about 0.3 to about 40 percent by weight of the hides to be unhaired, and preferably in amounts within the range of about 3 to about 12 percent by weight of the hides.

In effecting the unhairing of animal hides or skins utilizing the compositions of the present invention, a conventional lime system is formulated with a solution or slurry of lime and the novel phosphorus-sulfur composition of the present invention as described hereinabove, or a nonlime system is used, formulated in the manner which has heretofore been described. Preferably, prior to contacting the hides with the unhairing solutions, the hides are subjected to a soaking operation, as is known in the art. Typically, such soaking operations are carried out utilizing water as the soaking medium, although, if desired, small amounts of alkali metal sulfides, tetrasulfides, sulfhydrates, and the like, may be added to the soaking solution. Where such materials are added in amounts up to about 2 percent by weight of the hides being treated they have been found to have a beneficial effect in providing a preliminary loosening of the hair prior to the actual unhairing operation. The use of such sulfur-containing additives in the soaking operation, is, however, not essential to the operation of the present process.

The hides are maintained in the soaking medium for a period of time sufficient to provide a thorough wetting of the hide, times of up to 24 hours being typical. Generally, sufficient quantities of soaking solution will be provided so as to float the hides, weight ratios of soaking solution to hides of about 4 to 1 being typical of those which may be used. The temperatures utilized in the soaking operation are, in general, not critical although at higher temperatures the soaking may proceed more rapidly. For convenience, however, the soaking operation is usually carried out at about room temperature, e.g., about to 27 degrees centrigrade, although higher or lower temperatures may be used. During the soaking, the hides or skins may be agitated or paddled, the frequency and amount of such agitation or paddling being determined by the practice normally followed in ordinary soaking procedures.

After completion of the soaking operation, the hides or skins are brought into contact with the unhairing solution. Generally, the contact of the hides in the unhairing solution is effected in a paddle, although if desired, batch or still pits may be used. The temperature of the unhairing solution, i.e., the temperature at which the unhairing operation is carried out, is generally not critical although the use of higher temperatures may shorten the time of the unhairing operation. Typically, the unhairing is carried out at about room temperature, e.g., about 20 to 27 degrees Centigrade, although higher or lower temperatures may be used. As in the soaking operation, sufficient unhairing solution is utilized to effectively float the hides, weight ratio of solution to hides of about 4 to 1 again being typical. The time required to effect substantial loosening of the hair on the hides will, of course, vary depending upon the nature of the hides, solution strength, temperature, and the like. Although times of 48 hours or more are not uncommon, in some instances periods of 18 to 24 hours may be sufiicient to effect substantially complete unhairing of the hides. During the time the hides are in contact with the unhairing solution, they may be agitated or paddled so as to effect a more intimate contact between the hides and the solution. The extent and nature of such paddling may vary in each instance and will generally conform to the normal practices in the art.

Upon removal of the hides or skins from the unhairing solution, they are passed through conventional unhairing equipment wherein substantially all of the hair including the very fine hair is removed. Frequently, after contact with the unhairing solution, the hair removed will be quite matted and pulped, with substantially complete destruction of the hair not being uncommon. It has been found that by the use of the procedure of the present invention, substantially all of the hair is removed from the hides, generally in periods of times appreciably shorter than that which has been heretofore possible, with substantially no damage or excessive swelling of the hides.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. In these examples, unless otherwise indicated, the temperatures are given in degrees centigrade, quantities are expressed in grams, and percentages are percent by weight of the soaked hides being treated.

Example 1 One hundred and fifty-two grams of phosphorus pentasulfide was added to 356 grams of a 60 percent sodium sulfide dissolved in 350 grams of water. The rate of addition of the phosphorus pentasulfide was controlled only to the extent that violent boiling of the solution by the exothermic reaction taking place was avoided. After the addition of the phosphorus pentasulfide was completed, heating of the reaction was continued to evaporate about percent of the water from the reaction mixture. The reaction mixture was then permitted to cool, hardening to a solid having a mole composition of 8 moles Na S to 1 mole P S This composition was found to contain 9 percent phosphorus and 41.46 percent sulfur.

Example 2 The procedure of Example 1 was repeated with the exception that the amount of 60 percent sodium sulfide used was 445 grams. The product obtained after evaporation and cooling of the reaction mixture had a mole composition of about 10 moles of sodium sulfide to 1 mole of phosphorus pentasulfide.

Example 3 152 grams of phosphorus pentasulfide and 530 grams of 60 percent sodium sulfide was added to 655 grams of sodium hydroxide. The sodium hydroxide which was present as about a 70 percent solution was at an elevated temperature of about 60 degrees centigrade. After the addition of the sodium sulfide and phosphorus pentasulfide was complete, the reaction product was cooled to obtain a solid product. This material was then ground and 309 grams of calcium chloride was dry blended into the mixture. The resulting product had a mole composition of 24 moles sodium hydroxide, 12 moles sodium sulfide, 7.8 moles calcium chloride, and 1 mole phosphorus pentasulfide.

Example 4 To illustrate the effectiveness of the compositions prepared as described hereinabove in unhairing animal hides and skins, a quantity of hide pieces were soaked in water overnight at a temperature of about 21 degrees centigrade. The soaked hides were then divided into 500 gram sample quantities and each sample quantity was placed into 2,000 milliliters of a lime slurry, containing about 6 percent lime based on the weight of the soaked hides. To each of the lime slurries was then added varying amounts of the composition prepared as in Example 1, the amount of the composition added being percent by weight of the hides to be treated. The hide samples remained in the lime slurry for a period of 24 hours, with periodic agitation to ensure thorough wetting of the hides. The initial pH of the unhairing slurry was within the range of about 12.4 to 12.5 and there was substantially no change in pH over the 24 hour period. At the end of 24 hours, the hides samples were removed from the unhairing solution and evaluated as to unhairing and hair condition, with the following results being obtained.

The procedure of Example 4 was repeated with the exception that the compositions prepared in the manner set forth in Example 3 were used. Using this procedure, the results obtained were as follows:

Concentration Hair Condition (Percent) Unhairing xcellent Hair pulped. .d Do.

Here again, it was noted that in none of the above runs was there any evidence of damage to the hides which were treated.

The procedures of the preceding Examples 1 through 3 are repeated using varying mole ratios of alkali metal sulfides to phosphorus sulfides, e.g., from 14 to 1, 20 to 1; using other alkali metal sulfides such as potassium sulfide, lithium sulfide, and other phosphorus sulfides such as P 5 to prepare compounds similar to those prepared in Examples 1 through 3. Thereafter, these compositions are tested for unhairing elfectiveness in the manner as set forth in Examples 4 and 5 to obtain comparable results.

While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. An alkaline phosphorus-sulfur composition produced by reacting a phosphorus sulfide with a liquid alkali metal sulfide in a mole ratio of more than about 8 moles of alkali metal sulfide to 1 mole of phosphorus sulfide, expressed as P S to obtain a product which is stable in aqueous solution at 100 degrees centigrade.

2. The composition as claimed in claim 1 wherein the alkali metal sulfide is sodium sulfide and the phosphorus sulfide is a material from P 8 to P 8 3. The composition as claimed in claim 2 wherein the phosphorus sulfide is phosphorus pentasulfide.

4. The composition as claimed in claim 1 wherein a portion of the alkali metal sulfide is replaced by an alkali metal hydroxide, the amount of alkali metal sulfide remaining in the product being sufiicient to provide at least half of the alkali metal ions in the product.

5. The composition as claimed in claim 4 wherein the alkali metal hydroxide is sodium hydroxide.

6. The alkaline phosphorus-sulfur composition as claimed in claim 1 having a mole composition of from about 8 to about 12 moles of sodium sulfide to 1 mole of phosphorus pentasulfide.

7. The composition as claimed in claim 4 wherein in addition to the reaction product of the alkali metal sulfide, alkali metal hydroxide, and phosphorus sulfide there is also contained a sharpening agent.

8. The composition as claimed in claim 7 wherein the sharpening agent is calcium chloride.

9. The composition as claimed in claim 8 having a mole composition of 24 moles of sodium hydroxide, 12 moles of sodium sulfide, 7.8 moles of calcium chloride, 1 mole of phosphorus pentasulfide.

10. A method of preparing an alkaline phosphorussulfur composition which comprises reacting a phosphorus sulfide with a liquid in a mole ratio of more than about 8 moles of alkali metal sulfide to 1 mole of phosphorus sulfide, expressed as P S and obtaining a product which is stable in aqueous solution at degrees centigrade.

11. The method as claimed in claim 10 wherein the liquid alkali metal sulfide is an aqueous solution of sodium sulfide and the phosphorus sulfide is within the range Of P4810 P4824.

12. The method as claimed in claim 11 wherein the phosphorus sulfide is phosphorus pentasulfide.

13. A method of preparing an alkaline phosphorussulfur composition which comprises reacting an aqueous solution of sodium sulfide with phosphorus pentasulfide in a mole ratio of more than about 8 moles of sodium sulfide to 1 mole of phosphorus pentasulfide, removing sutficient water from the reaction mixture so that a solid product is obtained upon cooling the mixture and cooling the reaction mixture to obtain a solid product which is stable in aqueous solution at 100 degrees centigrade.

14. The method as claimed in claim 10 wherein a portion of the alkali metal sulfide in the reaction mixture is replaced with an alkali metal hydroxide, the amount of alkali metal sulfide remaining in the reaction mixture being sufiicient to provide at least half of the alkali metal ions in the mixture.

15. The method as claimed in claim '13 wherein a portion of the sodium sulfide in the reaction mixture is replaced with sodium hydroxide, the amount of sodium sulfide remaining in the reaction mixture being sufilcient to provide at least half of the sodium ions in the reaction mixture.

16. A composition for unhairing animal hides and skins which comprises an aqueous solution having a pH of at least 12 and containing an unhairing amount of an alkaline phosphorus sulfur composition produced by reacting a phosphorus sulfide with a liquid alkali metal sulfide in a mole ratio of more than about 8 moles of alkali metal sulfide to 1 mole of phosphorus sulfide expressed as P S to obtain a product which is stable in aqueous solution at 100 degrees centigrade.

17. The composition as claimed in claim 16 wherein the phosphorus-sulfur composition has a mole composition of from about 8 to about 12 moles of alkali metal sulfide to 1 mole of phosphorus pentasulfide.

18. A composition for unhairing animal hides and skins which comprises an aqueous slurry of lime and an unhairing amount of an alkaline phosphorus-sulfur composition produced by reacting phosphorus sulfide with a liquid alkali metal sulfide in a mole ratio of more than about 8 moles of alkali metal sulfide to 1 mole of phosphorus sulfide, expressed as P 8 to obtain a product which is stable in aqueous solution at 100 degrees centigrade, which composition has a pH within the range of about 12 to about 13.

19. A composition for unhairing animal hides and skins which comprises an aqueous solution containing an unhairing amount of an alkaline phosphorus-sulfur composition produced by reacting phosphorus sulfide and a liquid alkali metal sulfide in a mole ratio of more than about 8 moles of alkali metal sulfide to 1 mole of phosphorus sulfide, expressed as P 5 to obtain a product which is stable in aqueous solution at 100 degrees centigrade, a source of hydroxyl ions and a sharpening agent, with the hydroxyl ion source being present in an amount to provide sufiicient alkalinity to maintain the solution at a pH within the range of about 12 to about 13.

20. A composition as claimed in claim 19 wherein the hydroxyl ion source and the sharpening agent are combined with the alkaline phosphorus composition, and the resulting composition is dissolved in water to form the aqueous unhairing composition.

21. The composition as claimed in claim 20 wherein the alkaline phosphorus-sulfur composition has a mole composition of about 24 moles of sodium hydroxide, 12 moles of sodium sulfide, 7.8 moles of calcium chloride, and 1 mole of phosphorus pentasulfide.

22. A method for unhairing animal hides and skins which comprises contacting the hides and skins to be unhaired with the unhairing compositions of claim 16 for a suflicient period of time to ellect substantial loosening of the hair thereon.

23. A method of unhairing animal hides and skins which comprises contacting the hides and skins to be unhaired with the unhairing composition of claim 17 for a sufficient period of time to effect substantially complete loosening of the hair thereon.

24. A method for unhairing animal hides and skins which comprises contacting the hides and skins to be unhaired with the unhairing composition of claim 19 for a sufiicient period of time to effect substantially complete loosening of the hair thereon.

25. A method for unhairing animal hides and skins which comprises contacting the hides and skins to be unhaired with the unhairing composition of claim 20 for a suflicient period of time to effect substantially complete loosening of the hair thereon.

26. A method of unhairing animal hides and skins which compirses contacting the hides and skins to be unhaired with the unhairing composition of claim 21 for a sufiicient period of time to efiect substantially complete loosening of the hair thereon.

27. A method for unhairing animal hides and skins which comprises contacting the hides and skins to be unhaired with the unhairing composition of claim 18 for a sufficient period of time to effect substantially complete loosening of the hair thereon.

References Cited UNITED STATES PATENTS 2,033,913 3/1926 Fiske et a1. 894 2,067,628 1/1937 Fiske et a1. 894 2,229,420 1/1941 Neugebauer 8-94.16

FOREIGN PATENTS 378,425 8/1907 France.

29,989 1910 Great Britain.

OTHER REFERENCES NORMAN G. TORCHIN, Primary Examiner.

DONALD LEVY, Assistant Examiner.

7% UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO- 3, +l5,610 Dat d De gember 10, 1968 Inventor(s) Theodore H. Dexter and Alfred 0. Minklei and Thomas C. Thorstens It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 lines 53 (page I line 25), "the length" should read ----this length---;

Column 6, line 9 (page 8, line 33), "matreial should read--- material---; 4

Column 9, l ine 75 (Claim l0, l ine 2), "a liquid in" should read------ A l iquid alkali metal sulfide in----.

SIGNED ANL SEALED JAN 6 --l970 (SEAL) Attest:

Edward M. Fletc ,1- WILLIAM E. SCadUYLER, JR. Anesfing Officer Commissioner of Patents