US2760282A - Temporary protection of narrow areas - Google Patents

Description

5 F. E. SEETON ETAL 2,760,282

TEMPORARY PROTECTION OF NARROW AREAS Filed Dec. 28, 1955 lnverii'or-s Eederzb .5. 5e ezon Payer T Perkins Kenelm W M'ns/ow Patented Aug. 28, 1956 TEMPORARY PROTECTION OF NARROW AREAS Frederic E. Seeton, Newton, Roger T. Perkins, Brockton, and Kenelm W. Winslow, Brookline, Mass., assignors to B. B. Chemical Co., Boston, Mass., a corporation of Massachusetts Application December 28, 1953, Serial No. 400,502

5 Claims. (CI. 36-72) This invention relates to a method for applying a temporary protective coat in readily strippable condition within a sharply defined area and particularly to the temporary protective covering of external stitching on the welting of a shoe.

The condition of the welt of a shoe is a factor by which prospective purchasers often evaluate the quality of shoemaking which has gone into a shoe, and protection of the welt is therefore a matter of concern to the shoemaker. Where ornamental external stitching, particularly light colored or white stitching, is featured in the welt, there is imposed on the shoemaker not only the problem of protecting the welt from mechanical damage but also the problem of insuring that the stitching does not become soiled since it is virtually impossible to clean stitching satisfactorily. It is common practice to protect such stitches during the intermediate operations upon attached soles by means of a narrow strip of pressure-sensitive adhesive tape pressed onto the welt in position to cover the stitches, the tape being stripped from the welt when shoemaking is complete. The tape is not a wholly satisfactory protection since fluids can enter into crevices between it and the welt even where the tape is pressed as firmly as possible into engagement with the welt. Also, application of the tape is time consuming and in some instances interferes with the subsequent shoemaking operations both by reason of its position and by reason of its opacity.

It is a feature of the present invention to provide a readily strippable, temporary, transparent, protective, narrow covering band which protects the important area but does not extend to adjoining surfaces where it might interfere with subsequent operations.

It is a further feature to deposit a readily strippable, temporary protective covering by a procedure which elim inates the difliculties heretofore encountered in covering with a pressure-sensitive adhesive tape and which gives more intimate engagement and better protection against contaminants than obtainable by such known protective methods.

According to the present invention, a viscous solution of a film forming resin in a highly volatile solvent is extruded in a relatively thick head in position to cover the desired area, e. g. the stitches on a shoe welt and only a very narrow adjoining area of the welt on each side of the stitches, the bead being hardened to a lightly adherent, relatively thin, transparent protective band by evaporation of the solvent. In a preferred form of the invention there is applied prior to the deposition of the protective coating a precoat of material incompatible with or not attacked by the resin or solvent of the protective covering. This precoat may serve the dual function of providing a desired additional finish to welt or bringing the welt to a better condition for treatment by such steps as stitch separating, and of forming a layer protecting surfaces, e. g. of a welt and stitching, from possible harm by the solvent component of the resin solution or excessive adhesion of the resin covering material to the strands of the stitching thread.

The invention will be described further in conjunction with the attached drawings forming part of the disclosure of the present invention, in which,

Fig. 1 is a fragmentary angular view illustrating the application of a precoat to the upper surface and stitching of the welt of a shoe;

Fig. 2 is a fragmentary angular view illustrating a preferred manner of application of a head of a viscous solution of protective material in a narrow strip to cover the stitching and only a narrow area on either side of the stitching on the welt of a shoe;

Fig. 3 is a fragmentary angular view showing the shape of the bead of protective material solution deposited over the stitching and adjacent welt areas of a shoe; and

Fig. 4 is a fragmentary angular view illustrating the step of stripping the protective material from a shoe after completion of shoemaking operations.

To simplify the description of the invention, it will be explained in connection with the protection of the surfaces of stitches and immediately adjoining areas of the welt of a shoe, but it is to be understood that the invention is applicable to the protection of other narrow surface areas.

In the practice of the present invention for the temporary protective coating of a surface, it is necessary that the surface be in condition or be brought into condition for such protection. That is, the surface must be smooth and substantially free from projecting fibers and wide open pores. Ordinarily, and particularly in the protection of the stitches and the welt of a shoe, precoating of the surface, for example, the exposed stitching and welt surface of a shoe, to provide a desirable surface character for cooperation with the cover material to be applied is an important part of the method. The precoating step for conditioning the surface to be protected involves the spreading of a thin layer 10 (see Fig. 1) of material on the welt 12 and stitches 14 of a shoe 16 prior to the protective coating step shown in Figs. 2 and 3. The precoating step may immediately precede the application of the stitch protector or may be applied after stitch separation or at some other point preceding the application of the temporary protecive coating. This precoat layer 10 may be any of numerous materials generally applied from solution which deposit a substance tending to seal off the pores of porous welting and to form a surface substantially unaffected by the components of the protective coating material. Thus, there have been applied with satisfactory results such materials as solutions of a cellulose derivative, e. g. cellulose acetate, cellulose nitrate and cellulose acetate-butyrate, or, a high styrene-butadiene copolymer resin in a volatile organic solvent. Solutions containing from about 5% to about 20% solids have been found most desirable. Aqueous coating materials such as solutions of ammonia-cut casei nor ammonia-cut shellac or hydrolyzed polyvinyl esters (du Pont Elvanol 725 1) or even such materials as a thin wax dispersion in a soap solution may also be used. These materials may deposit a luster-improving agent and, in the case of the water base precoatings, the water content may serve to bring leather welting into temper suitable for such operations as stitch separating or the like. The nature of the precoat material is not particularly critical so long as it does not attack the finish on the welt and is incompatible with the protective coating material, i. e. is not softened unduly by the protective coating material and does not develop a bond to the protective coating material. The precoat may be applied by such simple means as brushing with a hand brush 18 as shown in Fig. l or application by a sponge, a nozzle or other applicator such as a perforated wheel (not shown). The precoat layer 10 should be permitted to air dry for a period of about 5 minutes or more prior to applying the protective coating material.

A continuous bead 20 of a special solution of protective plastic is deposited on the prepared, preferably precoated surface 12 of the welt and the stitching 14 of a shoe. This special solution comprises a film forming plastic dissolved or finely dispersed in a highly volatile liquid vehicle possessing physical characteristics such that the solution will cover the desired portions of the stitching 14 and welt surface but will not spread into areas, e. g. over the edge 22 of the welt 12 or into the crevice 24 between the welt 12 and the upper 26 of the shoe 16, in which it might interfere in shoemaking or be difficult to remove. Also the consistency of the solution must be such as to enter into intimate engagement with the welt surface 12 to afiord the necessary protection and ability to remain in place while at the same time being readily strippable as a continuous ribbon or band 28 (see Fig. 4) by simple pulling otf when no longer needed. Even the application of a precoat 10 does not entirely eliminate the importance of close control of the condition of the protective cover material. In order that the coating material may remain in proper physical condition and be laid on in elfective position and quantity, the coating material is led through a closed conduit 31) to a nozzle 32 which applies it directly, i. e. without opportunity for loss of solvent, to the narrow strip on the welt 12 which is to be protected.

As shown in Figs. 2 and 3, conduit 30 which leads from a supply of protective coating solution (not shown) terminates in nozzle 32 which extends angularly inward to be capable of reaching under the overhanging edge portions of a shoe upper 26. The nozzle 32 is provided with a groove 34 in its lower portion for engagement with the upper face of welting to be protected. The groove 34 in the lower portion of the nozzle 32 has a width at its base sufiicient to extend slightly beyond the stitching 14 on each side and has a height sufiicient to deposit a head 20 of viscous protective coating material of a thickness which on drying will provide a transparent guard ribbon of plastic material over the stitching and adjacent portions of the welting.

As explained above, the quantity of coating material deposited is important in order to provide a satisfactory readily removable guard ribbon or band 28, and since the amount deposited is dependent not only on the rate of pumping of coating material to the nozzle but on the rate of movement of the welt 12 with respect to the nozzle 30, there is ordinarily provided a driven rubber supporting roll 36 and a driven rotary rubber edge gage 38 which move the welt 12 and stitches 14 beneath the nozzle 32 at a rate proportional to the rate at which the coating material is delivered so that the desired uniform quantity of coating material is deposited. The driven rubber edge gage 38 also insures that the groove 34 of the nozzle 32 is positioned accurately with respect to the stitching 14 and welt surface 12 to be covered.

The protective coating material is a volatile solvent solution of a film forming plastic having a viscosity of at least 1500 centipoises and not more than about 3600 centipoises. Where the viscosity is less than the minimum value the deposited head 20 of material tends to run from the desired area either into the crevice 24 between the shoe upper 26 and the welt 12 or over onto the welt edge 22 and likewise tends to adhere too strongly to the surface to be protected. Viscosities higher than the maximum introduce dilficulties of insufiicient adhesion and dilficulties in machine application. The preferred viscosity range is from 3000 to 3600 centipoises and in this range the deposited head 20 of coating material retains essentially the form in which it is extruded from the groove 34 of the nozzle 32, i. e. does not run appreciably under the influence of gravity, and conforms closely to the surface of the welt 12 and stitching 14 so that it provides eflicient protection and adheres with the desired tenacity to the stitching 14 and adjacent areas of the welt 12. The preferred film forming plastic is a vinyl resin such as a copolymer vinyl chloride and vinyl acetate containing at least of vinyl chloride, but vinyl chloride-vinylidene chloride copolymers and other commercial vinyl resins may be used. It has been found that vinyl resin solutions containing from about 20% to about 40% of vinyl resin and having Viscosities of from 3000 to 3600 centipoises give most satisfactory protection. The resins will generally be plasticized with a relatively small amount of a conventional plasticizer desirably a plasticizer which does not attack the precoat 10 or tend to increase the bond between the temporary protective coat 2%; and the precoat material. It is important to use a solvent of extremely high vapor pressure such as propylene oxide or comparable organic solvents for the coating resin such as the ketones including acetone, methyl ethyl ketone or mixtures of these with other volatile liquids such as diethyl ether, in order that coating compositions having a desired solids content of 20% to 40% resin may have a viscosity useful for application, and that solvent may escape rapidly from the coating material. Rapid evaporation of the solvent is important in order that excessive bond may not develop between the temporary protective cover 20 and the welt surface 12 and that the temporary protective cover material 20 may dry to a condition such that it does not interfere with further operations within a period which can be fitted into the operation schedule of a shoe factory. It should be noted that an entirely different set of conditions is involved in the application of a bead of viscous solvent-rich resin according to the present invention and the spray application of resin solution as has heretofore been used in the covering of entire shoes. For example, in the spray application, the surface of each droplet is dried in passing through the air to an only slightly tacky condition in which it can knit itself together with other particles into an opaque film, and there is a reduced tendency for strong adhesion to the surface protected. On the other hand, where a continuous bead 20 of resin solution is applied the solution contains its full solvent content at the time of application to the welt so that special conditions must be observed to avoid excessive adhesive bond, and the deposited material dries to a transparent ribbon.

After the deposited ribbon 28 of plastic coating material has been deposited on the stitches 14 and welt 12 and permitted to dry, the shoe 16 may be passed through other shoemaking steps such as sole leveling, heeling, heel scouring, jointing, and so on, depending on the stage selected for applying the protective coating band.

I The thickness of protector ribbon or band 28 which 1t is desirable to form depends to some extent upon the stage at which the material is applied. For example, if the protective band is applied before edge trimming, it may be desirable to use a thinner coating because of the possibility of interference between the protective band and the shield of the edge trimming machine. A generally useful thickness of protective coating may be provided by the deposition of a layer of coating solution from 1 to 4 mm. in wet thickness and preferably from 3 to 4 mm. in width. A protective coating bead 20 of this thickness shrinks and flattens out on drying and is dry to the touch in about 3 minutes.

As shown in Fig. 4, the protective ribbon or band 28 s removed from the shoe by lifting one end and graspmg it between the fingers and merely pulling it ofi, the protective strip or band 28 having sufiicient strength that it can he pulled olf in a single strand.

The following example is given as of possible assistance to aid in understanding the invention and it is to be understood that the invention is not restricted to the particular materials, conditions or procedural details given in the example:

Example.A solvent precoat solution was prepared by dissolving 75 lbs. of cellulose acetate in 70 gal. of acetone and thereafter adding approximately 2 gal. of

tributyl phosphate, 9.4 gal. of diacetone alcohol and 14.5 gal. of toluol and mixing the materials. A thin layer of this precoat material was applied to the welt and white stitching on the edge of a shoe and the precoat was permitted to dry for about minutes.

A protective coating solution was made by mixing in a churn 101 fl. oz. of propylene oxide, 8.9 11. oz. of triethylene glycol di-2-ethyl-butyrate, a plasticizer and 1 lb. 12 /2 oz. of a vinyl chloride-vinyl acetate copolymer resin comprising from about 88.5 to 90.5 percent of vinyl chloride (Vinylite VYNS). This coating solution was pumped to a nozzle and extruded onto the precoated welting in position to cover the stitch threads and at a thickness of about 3 mm. wet thickness, the band of material deposited being from 3 to 4 mm. in width. The deposited stitch protection solution was permitted to dry for three minutes and at that time was found to be dry to the touch. The dried protective ribbon was transparent so that the stitching and surface of the welting could readily be seen through it. The shoe with the protective ribbon on the stitch and welting was then subjected to further shoemaking operations includ ing the steps of edge trimming, edge inking, and edge setting. On completion of shoemaking, the end of the protective ribbon was lifted and the protective ribbon was readily pulled olf in a continuous band.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

l. A shoemaking method for providing on a shoe a stitched welt portion having improved appearance which includes the steps of applying to the upper surface of the welt portion and to exposed stitching on said surface a coating of material incompatible with temporary protective coating material to be applied later, extruding directly on the coated stitching and adjacent areas of the coated welt surface substantially without loss of solvent a relatively thick bead of a viscous solution of a film forming resin in a highly volatile solvent to cover said stitching and only those areas of said welt surface immediately adjoining said stitching, thereafter evaporating solvent from said solution to harden said bead to a tough, resin band lightly adherent to said stitching and welt surface, carrying out further shoemaking operations on said shoe and pulling said resin band from said coated stitching and coated welt surface as a continuous strip leaving said first-mentioned coating on said welting and stitching.

2. A shoemaking method for providing on a shoe 8. stitched welt portion having improved appearance which includes the steps of applying to the upper surface of the welt portion and to exposed stitching on said surface a coating of material incompatible with a temporary protective coating material to be applied later, extruding directly on the coated stitching and adjacent areas of the welt surface substantially without loss of solvent a relatively thick bead of a 3000 to 3600 centipoise viscosity solution of a vinyl resin in a highly volatile organic solvent to cover said stitching and only those areas of said welt surface immediately adjoining said stitching, thereafter evaporating solvent from said solution to harden said bead to a tough, resin band lightly adherent to said stitching and Welt surface, carrying out further shoemaking operations on said shoe and thereafter pulling said hardened resin band from said coated stitching and coated welting surface as a continuous strip leaving said first-mentioned coating on said welting and stitching.

3. A shoe comprising a welt with exposed stitching on a surface of said welt, a thin layer of material permanently adherent to the surface of the welt and exposed stitching, a tough transparent vinyl resin band in temporary protective covering relationship and lightly adherent to the coated surface of said welt and stitching, the material of said coating being incompatible with the resin of said resin band, said resin band being removable as a continuous strip from said coated welt and stitching by pulling the band from said stitching and welt.

4. A shoemaking method for providing on a shoe a stitched welt portion having improved appearance which includes the steps of extruding on the stitching and adjacent areas of the upper surface of the welt portion substantially without loss of solvent, a relatively thick head of a viscous solution of a film forming resin in a highly volatile solvent to cover said stitching and only those areas of said welt surface immediately adjoining said stitching, thereafter evaporating solvent from said solustitched welt portion having improved appearance which includes the steps of extruding on the stitching and adjacent areas of the welt surface substantially without loss of solvent a relatively thick bead of a 3,000 to 3,600 centipoises viscosity solution of a vinyl resin in a highly volatile organic solvent to cover said stitching and only those areas of said welt surface immediately adjoining said stitching, thereafter evaporating solvent fromsaid solution to harden said head to a tough resin band lightly adherent to said stitching and welt surface, carrying out further shoemaking operations on said shoe and pulling said resin band from said stitching and welt surface as a continuous strip leaving said stitching and welt surface unmarred by said further shoemaking operations.

References Cited in the file of this patent UNITED STATES PATENTS 2,396,313 Brophy Mar. 12, 1946

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