US1959112A - Process of manufacturing leather and products used in connection therewith - Google Patents

Description

Patented I May 15, 1934 1,959,112 'raoosss on momoronmc mum AND, PRODUCTS US WITH THERE Charles G. Shaw, Huntsville,

ED IN CONNECTION and {was Honman, Toronto, Ontario, Canada No Drawing. Application November Serial No. 496,032. Renewed January 17,193;

This invention relates to aprocess of" applyin coating materials to vegetable tanned leather and more especially to the application of such materials to sole leather suioseintently to the compacting of the leather but prior tosuch finishing operations as third rolling and/or brush- Moreparticularly, the present invention relates to a further development of the subject matter 1 disclosed in our. co-pending application Serial No.

459,103, filed June coveries set forth in the above-mentioned application and in our co-pending application Serial No. M910 filed June 3rd, 1930, in connection 1 with the application oi coating materials to vegetable tanned leather, such materials when applied to the grain of vegetable tanned leather which had previously been filled with such materials as wax, resin, oil, tanning extract, sugar, 26 and the like, for thepurpose of rectifying the unpleasant colour caused-by the filling, would lack adhesion and would be removed by subsequent operations in the shoe factory, where it is I thepractice to soak the leather in water, thus exposing the unpleasant colour beneath.

In our application Serial No. 459,103 referred to above, we havedescribed a; process which overcomes this difiiculty and provides a finish which satisfactorily adheres to the leather-throughout 30 all the subsequent operations to which it is normally submittedeither in the process of finishing the manufacture or in being worked in the shoe factory. However, the rather rough treatment to which the coating is subjected in the process of setting out, jacking, rolling, etc. makes it necessary to apply quite a substantial film'of material in order that it may withstand the simple wear of the smoothening and finishing operations and at times, if this abrasion is excessive, an additional coating of material has to be applied to bring back the freshness of appearance after the mechanical operations are completed, This-may.

have a tendency to impart to the surface of the finished leather 2. .painty appearance and the operations of rolling and pressing after'the coat-f ing material is applied may result in a darken- -ing of the colour of the leather which is ordinarily corrected in the case'of uncoated leather by the use of so-called spon ing compounds" of which there are many on the market, 'consisting mainly of a slightly alkaline aqueous solution of soaps and sulphonated oil and into which the leather after compaction is quickly dipped,

and then dried. Subsequently, when theleather 5 is thoroughly dry, it is the usual custom to sub- 3rd, N30. Prior to our dis-- unit it to the operation known as third rolling which restores the gloss without darkening the.

colour.

wine of the objects of this invenfion is the application of an adhesive film subsequent to the til compacting operations, such film being so thinthot while it is sumclent' to render the leather uniform in colour it is insuficiently thick to plug the hair holes.

Another object of this invention is the production of sole leather uniform in colour but or ex tremely rapid and uniform soamng characteristics during the tempering operations in the shoe factory. V

our application Serial No. ass-nos we showed to that if the coating materials were applied. after the-operations oi compacting and the leather, adhesion would he unsatisfactory owing to the glazing oithe hyaline layer and the'plugsing oi the hair holes. The "theory underlying .siuch results is that it is the condition of glaze or unglaze oi the surface of the leather or hyaline layer which regulates its absorptive capacity for colloidal matter and thus controls the tendency to adhesion of coating materials applied to, it. so This explanationis based upon the fact that satisfactory adhesion, so far as we have been able to ascertain has never been obtained by the simple application of the coating materials to leather which has only-been rolled, jacked, set out I or pressed and many attempts to remove the glossing effects of these operations have been made without rendering the leather in such condition that satisfactory adhesion of the coating materials would result. Simple sponging or washing with water or with the usual sponging compounds was ofno avail as, although the appear-- ance of gloss was removed, coating material applied lacked adhesion and was readily removed when the leather was resoaked. Similarly washing the leather with alternate solutions of acids and alkalies gave unsatisfactory results. On the other hand, finished leather'when bleached and oiled lightly in a drumming operation would have its surface finish removed and when dried in the, usual manner could be coated with showing satisfactory adhesion. After such treatment, however, the leather had to be once more to the complete mechanical operations of finishing in order to restore the appearance of finished leather. we have now found that the objectionable condition of thethyaline layer after the leather has beenrolledandpressedcanberemovedbywashingtheleathetflrstin a dilute alkali solution and then in a dilute acid solution such acid solution preferably containing a sulphonated oil of a type which is compatible with the acid solution used.

The leather is then dried and the finishing mate- 5 rials applied.

As an example of the manner in which we carry out our invention, the leather is finished and dried and brought to a condition ready for the application of the sponging compound as already described earlier in this specification. It is, however, not treated with the sponging compound but instead is washed on the grain side by applying a solution containing 2% of borax in water at a temperature of about 160 F; to 180 F. This application is conveniently carried out by means of a harness leather. blacking machine. The leather is then passed quickly through a solution of a weak organic acid, such as acetic or lactic acid, the strength of the solution being such as to neutralize the efiect of the alkali treatment which has darkened the leather, and thus rectify and lighten the colour in much the same 'manner. as is done in the ordinary opera- 1 tion for bleaching the leather. To the acid solution is-added about 2% of a sulphonated oil of such a nature that it is not 'readily thrown out of solution by the acid. sulphonated but not neutralized, are examples of the sulphonated oils which we may employ. The

: leather after being dfied is now ready for coating.

The materials we prefer are first a priming coat containing pyroxalin and a heavy bodied China woodoil in the proportions of about one part of the former to three parts of the latter made up in the usual lacquer solvents to contain about 12% of solids. This primer is mixed with an equal volume of thinner consisting of the same solvents and is very lightly sprayed on the grain surface of the leather, one gallon of the mixture covering about 300 to 500 sq. feet of surface. After the primer has dried a short time the pigmented coating is applied. This coating composition has the general composition:-

- Per cent 5 Pigment 12.8

. Pyroxyl I 6.0 Dibutyl phthalate 2.5 Neats-foot nil 1.4 Butyl acetate 20.3

Ethyl acetat 24.0 Tnlnnl 27.0

the nature of the pigment being varied in ac- 5 cordance with the colour required.

This material is reduced with thinner and a very'fine or mist 'coat is applied just suflicient to impart a uniform appearance to the surface of the leather. After the coatedmaterial has dried a fine coating of a wax emulsion is sprayed upon the top of the coating composition. This wax emulsion is prepared by melting together two parts of carnauba wax and one part of ceresine wax and slowly stirring in one part of sul- C5 phonated castor oil. The mixture is then diluted with water, run through a colloid mill and again diluted with water to the desired spraying consistency. After the wax coating has dried, the

leather is third rolled and brushed. As the 73 customary brass rolling ball and bed have a tendency to mark the coating, a steel ball or one chromium plated is preferably used and over comes this difficulty.

We wish it to be understood that we do not con- 7 fine ourselves to the exact details as outlined in Acidopole fish oil the'above example, as many modifications can be made without departing from the spirit of this invention. For instance, the temperatures of the alkali and acid solutions .used can be varied considerably. The alkali solution can be used at room temperature orlat any temperature up to that at which it might damagejhe leather or down to that at which its action upon the leather would be so slow as to demand a prolonged soaking. Similarly the acid solution may be used at any convenient temperature up to that at which the oil will not stay properly in solution or the leather be harmed by the hot water.

Again we may introduce into the alkali solution a small percentage (about 1%) of an ordinary sponging compound into which the leather may be clipped and subsequently treated with an acid solution from which the sulphonated oil has been omitted, subsequently spraying or swabbing on about a 5% solution of sulphonated oil'or such emulsifiable mineral oils as are obtained by the addition of triethanolamine soap. We have found that the action of such oil is to prevent the hyaline layer from becoming harsh or tinny and aids in securing satisfactory adhesion.

We also wish to point out other alkalies may be used in place of the borax referred to. For instance, sodium or potassium hydrates, carbonates or bicarbonates may be used although we prefer borax on account of its less vigorous action on the leather.

Similarly other acids than acetic or lactic may be employed, such as oxalic, sulphurous, sulphuric, and other common organic or inorganic acids but, as some of these harm the leather unless used with caution, we prefer to. use acetic or lactic as they are more normal to the tannage of leather.

Further, third rolling or brushing" are not essential to the successful carrying out of our invention although the waxing and brushing greatly improve the quality of the finished surface.

We have found that treatment such as that described above is essential if satisfactory adhesion of the coating materials to leather which has already been compacted is to be obtained. It is necessary that the hyaline layer or surface of the leather should be cleansed and held open until the coating materials are applied and we ,have found that the ordinary sponging compounds applied as such do not accomplish this I end. They leave a heavy residue which it has been proven does not function. Borax and the like satisfactorily prepare. thehyaline layer but darken and stain the surface, whose colour is only properly restored by the subsequent action of the acid which, however, without the treatment with sulphonated or similar oil assumes a harsh character which it is necessary to overcome if the natural appearance andcharacter of the leather is to be fully restored. This is accomasagna Vegetable tanned leather, such as harness leather or sole leather, finished in accordance with the present invention does not bruise or change colour on scufling or rubbing. It has a very high degree of uniformity of -colour and an excellently natural appearance due to the fact that the alkali-acid treatment produces a light and uniform colour which enables a minimum of coating materials to be applied and thus does not detract from the natural appearance of the leather itself.

This minimum of coating materials also-means that the leather has excellent soaking properties and in this respect is superior to that produced by either of the processes described in our copending applications. In fact we have produced by this process leather which will soak satisfactorily for working in the shoe factory in from 3 to 10 seconds immersion in water which is of considerable importance in connection with some of the or more coatings of waterproof material to the leather in such amanner as not to plug the hair holes.

3. A process of manufacturing leather which includes the steps of treating the grain surface of the leather as in claim 1, and then applying a priming composition containing a pyroxylin and heavy bodied China wood oil dissolved in suitable solvents, and a second coating of a composition containing pyroxylin, neats-foot oil and a pigment or colouring matter. I

4. A process of manufacturing leather which includes the steps of treating the grain surface of the leather as in claim 1, then applying one or more fine coats of waterproof material in such a manner as not to plug the hair holes, and then applying a coating of a wax emulsion and subsequently third rolling" and/or brushing the leather.

5. A process of manufacturing leather which includes the steps of treating the grain surface of vegetable tanned leather, subsequent to the com-.

pacting operation, with a solution of alkali folhated oil.

lowed. by treatment wit an acid and a sulpho- 6. The herein described process of applying coating materials to vegetable tanned leather fol lowing compacting of the leather but prior to such finishing operations'as third rolling and/or brushing, said process comprising the following steps 1) washing the leather in a dilute alkaline solution (2) subjecting the washed leather to the action of a solution of a weak organic acid containing a small percentage of a sulphonated oil which is compatible with the particular acid solution used, the strength of said acid solution being suflicient to offset the darkening effect exerted on the leather by the alkaline treatment (3) spraying onto the grain surface of the leather a priming coat containing pyroxylin and a heavy bodied Chinawood oil dissolved in suitable solvents (4) permitting the priming coat to dry and (5) applying to the previously coated surface a second coating of a composition containing pyroxylin and coloring matter.

7. The herein described process of applying coating materials to vegetable tanned leather following compacting of the leather but prior to such finishing operations as third rolling and/or brushing, said process comprising the following steps 1) subjecting the leather to the action of a dilute alkaline solution containing a small percentage of an ordinary sponging compound (2) treating the leather with a solution of a weak organic acid of suflicient strength to neutralize the darkening effect of the alkaline treatment (3) treating the leather with sulphonated oil to prevent the hyaline layer becoming harsh and to promote adhesion of subsequently applied coating materials (4) then applying to the leather one .or more coating compositions containing pyroxylin dissolved in suitable solvents.

8. Vegetable tanned leather, to the grain surface of which has been applied one or more adhesive layers of a composition comprising a cellucharacterized by being uniform in color and ca.-

pable of being satisfactorily and uniformly soaked in water in from.3 to 10 seconds. 4

, CHARLES G. SHAW.

JACQUES HOFFMAN.