US3503143A - Block copolymer footwear assembly - Google Patents

Description

United States Patent 3,503,143 BLOCK COPOLYMER FOOTWEAR ASSEMBLY Geofirey Holden, Los Alamitos, and William B. Luther, Long Beach, Calif., assignors to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed Jan. 16, 1968, Ser. No. 698,105

Int. Cl. A43b 1/02 US. Cl. 369 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to improvements in the wet peel strength of textile shoe foxing. More particularly it relates to a shoe assembly comprising a multiplicity of textile layers laminated with block copolymers and bearing a block copolymer foxing composition.

Textile upper footwear is designed to be used under a variety of physical conditions. More particularly, in the normal use of shoes and the like, they are subjected to a variety of stresses such as flexing, and must withstand the adverse etfects of wet weather and washing, as well as perspiration and body oils. The adhesion of foxing to textile uppers is an especially difficult matter, involving not only adhesion problems, but also such phenomena as shrinkage of uppers. While it is a reasonably easy task to design a shoe assembly which will be satisfactory under dry condition, the so-called wet peel strength of such products often leaves much to be desired. This is probably due in substantial part to the lack of true adhesion of the coating material, which is usually non-polar or substantially so, to the textile, which is often polar in character as in the case of cellulosic fibers and the like. The problem of wet peel strength is especially apparent in such functional articles as textile shoe uppers. In such articles it is not only important to maintain a high degree of flexibility, improve abrasion resistance and dry peel strength but also and perhaps more importantly to maintain a high level of peel strength when the shoes are subjected to moist or wet conditions. It is equally important that shoes or other foot-wear maintain their original assembly design when two or more textile layers are present in the laminate separated by a polymeric coating which acts as a combining composition for the two layers. Also important is the further qualification that wet peel strength should be maintained when a second polymeric coating such as foxing is present on one of the textile surfaces laminated by a polymer coating to another surface.

The impregnation and coating of textiles and the like with elastic materials normally involves a vulcanizing step in order to promote the maximum physical properties of the rubber coating. In this case, the term coating will be understood to mean either a surface coating or one which penetrates the textile or one which performs a function of combining one layer of textile with another. A case in point as referred to above where all of these aspects come into play is in the formation of textile shoe uppers such as are used for tennis shoes. In this instance it is the usual practice in the trade to laminate two or more layers of textile together with a polymeric combining paste and then to bond the textile laminate to a thermoplastic or elastomeric sole portion of the shoe. Part of this assembly is applied either simultaneously or subsequently which is known as foxing. This is a strip material which 3,503,143 Patented Mar. 31, 1970 covers the upper part of the sole edge and the lower edge of the textile upper where the upper and sole meet.

In many instances in the past, the combining paste has been made out of material such as a vulcanized elastomer. These are highly intractable materials once they have been vulcanized. Moreover, it has been found by experience that these prior art combining paste compositions lack the ability of physically combining with block polymer foxing which is a part of the footwear assemblies being considered here. This lack of proper physical coalescence or cohesion between a non-block polymeric combining paste composition and a block copolymer foxing in the case of tennis shoes is of special importance under wet conditions, since the natural physical adhesion of polymers to the usual textile drops so drastically under these conditions.

It is an object of the present invention to improve the physical properties of textile shoe assemblies. It is a particular object of the invention to construct textile footwear so as to result in superior wet peel strength of foxing to fabric. It is a special object of the invention to provide new articles of commerce showing improved wet peel strength wherein the footwear article comprises an upper made from a multiplicity of textile layer uppers and a polymeric foxing adhered thereto.

Now, in accordance with the present invention, new articles of manufacture are provided comprising footwear assemblies of laminated textile uppers wherein at least two textile sheets are bonded with a special combining composition, said composition consisting essentially of a block polymer having the general configuration wherein each A is a polymer block of a monovinyl arene and B is a polymer block of a conjugated diene, each block A having an average molecular weight between about 8,000 and 45,000 and B block having an average molecular weight between about 25,000 and 150,000, a polymeric soling and a foxing overlapping the joint of upper to soling, said foxing being of the same general type of block copolymer. While the present invention does not depend on a. particular theory, it is believed that the foxing also impregnates the textile upper and physically bonds to the block copolymer composition in the combining composition which laminates the textile layers. Under these conditions due to this physical interlocking and cohesion between the two similar types of polymeric materials on both sides of the textile upper, it has been found that surprisingly improved wet peel strengths and foxing adhesion are obtained.

More particularly, the compositions performing the function of combining composition and foxing comprise not only the block copolymer preferably modified with one or more ingredients including especially polystyrene, tackifying resins, hydrocarbon extending oils and/or mineral particulate fillers, all as more particularly described hereinafter.

The most important application of the present invention at this time, is in the manufacture of sport shoes generally referred to as tennis shoes or the like. The problem of foxing separation referred to hereinabove is substantially eliminated or largely minimized by the use of the present invention. The use of a so-called combining paste" for joining two layers of canvas and thereafter manufacturing shoes by injection molding, using a second type of polymeric material as foxing on to this laminate results in poor wet peel strength of the foxing to the outer layer of canvas. However, when the combining paste which joins at least the two layers of textile contains a block polymer and at least the foxing (and preferably the soling as well) also contains a substantial proportion of the same class of block copolymer then surprisingly the wet peel strength of the resulting article is unexpectedly improved.

While the present invention should not be made dependent upon any special theory to explain this discovery, it is believed at this time to be due to the penetration of the block copolymer foxing composition through the textile to physically join with the combining composition which joins at least two layers of canvas and results in a physically created network, locking both the combining paste composition to the foxing composition when both contain a compatible type of block copolymer. Under these circumstances high wet peel strengths are obtained.

The textile involved in the articles of the present invention may be either woven or non-woven as the case may be and the two layers of textile may be either similar or dissimilar. One or both of the layers also may be impregnated with only a superficial amount of block polymer if so desired for the purpose of improving abrasion resistance and reducing water permeability. The term combining paste is used in the shoe trade for that composition which is utilized for laminating one layer of textile to at least a second layer, resulting in a composite textile especially designed for the preparation of sport shoe uppers.

The block copolymers to be used in the assembly have the general configuration If the copolymer isanot hydrogenated, the blocks A comprise po1y(monovinyl arene) blocks while the block B is a poly(conjugated diene) block. The blocks A normally have number average molecular weights, as determined by intrinsic viscosity measurements, which have been correlated with osmometry and radiotracer measurements of tritium terminated polymer, of between about 8,000 and 45,000, while the conjugated diene polymer block has a number average molecular weight between about 25,000 and 150,000. If the copolymers are hydrogenated, the molecular weight ranges remain in about the same ranges. Two preferred species of such block copolymers include those having the block configuration polystyrene-polybutadiene-polystyrene and polystyrenepolyisoprene-polystyrene, as well as their hydrogenated counterparts. The hydrogenated counterpart of the second of the above defined block copolymers is of special interest, not only because of its high stability but because of the elastomeric nature of the hydrogenated midsection which resembles that of an ethylene-propylene rubber while the end blocks either remain as polyvinyl arene blocks or, if fully hydrogenated, become saturated blocks made up of polyvinylcyclohexane units. Thus, the fully hydrogenated preferred species has a block configuration which corresponds closely to polyvinylcyclohexane- [ethylene-propylene copolymer] polyvinylcyclohexane.

These particular block copolymers have the unique feature of attaining the stress-strain properties of an elastomer without the requirement that it be subjected to curing or vulcanization. Thus, they are sharply differentiated from other rubbers such as natural rubber, polybutadiene, SBR and the like which require vulcanization in order to attain satisfactory stress-strain properties.

The block copolymers of this invention should be the major elastomeric material utilized in the combining composition or foxing. They may, if preferred, be modified by the presence of other components such as plasticizers or other polymeric coating materials. Plasticizers such as rubber extending mineral oils may be employed and polymers such as polystyrene, polyethylene, polypropylene and the like may be incorporated in minor amounts with the block copolymers.

The compositions which are contemplated for the present purpose especially where canvas upper sport shoes are concerned include particularly combining paste and foxing which are combinations of parts by weight of the subject block copolymers with 15-150 parts by weight of polystyrene. Normally (still further modifications of such compositions are possible and are utilized for improving the flexibility and reducing the modulus of the compositions if desired as well as for reducing the over-all cost. Thus, the presence of 5-150 parts by weight of a hydrocarbon extending oil is also contemplated, as is the presence of a substantial amount of an inorganic finely divided particulate solid especially in the order of l0150 parts by weight per 100 parts of the block copolymer.

In the articles contemplated herein and especially in the case of canvas type shoe uppers, the combining paste utilized for joining two layers of textile together may be the same or different from the composition utilized for foxing around the bottom edge of a shoe upper joining the shoe upper with the shoe soling or at least masking the joint. The essential qualification according to the theory believed to be responsive for the improved wet peel strengths obtained is that the molten foxing composition containing the block polymer strikes through the porous textile to come in physical contact with and apparently coalesce with (at least superficially) the block polymer-containing combining composition on the opposite side of the intervening textile layer. Under these conditions, the adherence or lack thereof of either combining paste or foxing to the textile per se becomes of drastically less importance even under wet conditions. Thus the presence or absence of moisture becomes of little importance.

One aspect of the present invention involves the modification of the basic system with polymer extender oils both for the purpose of reducing the cost of the compositions and more particularly for imparting better processing and physical properties thereto. This is especially important as the average molecular weights of the block copolymer increase. In some instances, in the higher molecular weight ranges processing becomes extremely difiicult at ordinary processing temperatures short of decomposition temperatures in the absence of extender oils. It is preferred that the extender oils be those utilized for extending other polymers and particularly rubbers and that these have no more than about 50% aromatics and greater than about 45% of saturates, usually naphthenic types of hydrocarbons.

The extender oils should be utilized in amounts between about 2 and 300 parts (preferably 5-100 parts) by weight per 100 parts by weight of the block copolymer.

Another component which not only alters hardness and other properties but also reduces or prevents the combining composition from striking through the textile is a particulate solid, including fillers, which are mineral extenders, and inorganic or organic pigments. These include the various carbon blacks, titanium dioxide, calcium carbonate, silica, clays and ammonium clays, as well as mineral pigments such as the earth colors, including the iron oxides and the like. Pigments are normally utilized in as large amounts as possible while still maintaining desired physical properties. Usualiy this will be an amount between about 25 and 400 parts by weight per 100 parts by weight of the block copolymer. The presence of polystyrene in compositions of this invention comes into play in the incorporation of these particulate solids in that the presence of the polystyrene unaccountably and substantially raises the retention of the particulate solids which otherwise may be loosely held by the block copolymers.

The incorporation of these materials together may take place on the usual polymer processing mills and internal mixers or in an extrusion type of apparatus or may be composited by means of other masterbatching processes, particularly a solution masterbatch. In this process a solution of the block copolymer is formed in a solvent which is preferably not a good solvent for polystyrene. Specifically, such a solvent will comprise 21-85% by volume of an open-chain hydrocarbon having from 4-8 carbon atoms per molecule and 79-15% by volume of a cyclic hydrocarbon having from 5-8 carbon atoms per molecule. The polymer solution (cement) so formed is then combined with 5-200 parts by weight of polystyrene and 25-400 parts by weight of the finely divided particulate solids per 100 parts by weight of the block copolymer. The mixture is then subjected to coagulating procedures so as to isolate the solid materials from the solvents. This is best effected by forcing the mixture into a vessel containing steam and hot water under such conditions that the solvent is flashed off and the composition becomes suspended in a bath of water in the form of crumbs. These are then separated from the water by screening or decantation and subjected to grinding if necessary to effect relatively uniform particle size after which the particles are subjected to drying procedures as in moving belt drier, expander drier or the like. The use of this particular type of solvent accentuates the effectiveness of the polystyrene in retaining the finely divided particulate solids. Apparently, the polystyrene exists under these conditions as a gummy highly swollen material which aids in the incorporation of the particulate solids within the body of the block copolymer.

Again referring to sport shoe upper canvases, the term will include those textiles well known in the art for this purpose. While they often are cotton canvases exclusively, they may be combinations of cotton with synthetic materials or regenerated cellulose such as rayon or may comprise at least in part textiles such as polyesters, polyamides and the like.

In the preparation of canvas or other textile uppers for footwear, it is particularly contemplated to utilize a combining composition which is used in the form of either a latex, a cement, or a calendered film and in such consistency that the combining composition when deposited on one surface of the canvas essentially remains on that surface and does not cause any appreciable amount of strikethrough. This is for appearance purposes since the outer surface of the canvas or of the canvas laminate should preferably appear to be unmodified canvas. The consistency specifically employed for this purpose will depend upon the equipment and working conditions encountered in such application and will be easily adjusted by experts in the art. If solvent compositions are utilized, e.g., cements, then readily volatilized hydrocarbon solvents such as cyclohexane or toluene are especially contemplated.

It is especially contemplated to apply the combining composition to one surface of a first textile sheet such as by a blade application, then applying a second layer of the block copolymer utilized in the sole composition, space also being provided in the same machine for the simultaneous formation of a foxing strip around the area of joining the lower part of the canvas upper to the edge of the shoe sole. The conditions, e.g., temperature, pressure, etc., are then adjusted such that the shoe soling and foxing composition is injected in a sufliciently thermoplastic condition to allow flow throughout the cavity provided in the machine for the shoe sole and foxing, not only to form in the proper shape but also in the case of the foxing to be sufficiently fluid that it penetrates as described in the present theory through the canvas upper to physically contact and coalesce with the block polymer-containing combining composition. Under these circumstances, sport shoes are prepared having superior wearing property and also superior resistance to foxing separation.

The degree of wetting which shoes are subjected to will vary, for example, this may be due to rainy weather, to washing the shoes for the purpose of removing soil or dirt and perspiration or body oils may also create a condition similar to other types of moisture and the like which cause the general condition encountered in wet peel.

The wet peel strength is usually determined by an Instron tester at 180 angle pulled at 0.2 inch per minute at 23 C.

The following examples illustrate the results obtained by the use of the present invention and also illustrate the less than satisfactory results obtained by the use of polymers other than block copolymers for the coating or combining of canvas.

EXAMPLE I A series of comparative articles were prepared by depositing from a toluene solution 6 dry ounces per square yard of compositions representing a combining paste on one side of enameling duck weighing 1.35 pounds per running yard of 51 inch-wide material, and coating the opposite side of the cloth under pressure with the composition described as Composition I in Table A. A combining composition is that which would be used when combining a first canvas layer with a second canvas layer. In the present instance, in order to simplify the interpretation of the results obtained, the second canvas layer was omitted. Thus, in effect, the present compositions represent a laminate of three layers, the first layer being the combining composition, the middle layer being a single canvas layer and the third layer being a composition representing a material which would be used for the formation of foxing. The articles so prepared were dried and tested for 180 Instron peel strength at a speed of 0.2 inch per minute at 23 C. Other peel strengths were determined after wetting the sample by dipping. into 1% detergent in distilled Water, soaking in the same solution for /z-hour, rinsing the samples in distilled water and redrying the soaked samples and also after redipping the textile on the top side of the combining composition, 55 redried samples.

TABLE A C0mpo Block Polysrtion polymer styrene Oil Filler Remarks I 100 110 90 Block polymer moLwts.

23,000-4I,00023,000. II 100 20 Block polymer mol. \vts.

14,000 64,00014,000. III 100 25 25 15 Block polymer m0l.wts.

passing the laminate so formed between heated rolls or at least over a heated surface to compress the laminate and volatilize any solvent or water which may be present therein to result in a laminate of the two textiles, e.g., canvas sheets. These sheets are then cut by any desired means and the edges stitched to prevent ravelling. In the instances where molded shoe soles are then to be attached to these uppers, the latter are fitted onto suitable forms in an injection molding shoe making machine which is pro- Table B below shows the results obtained under these varying conditions. The combining composition referred to as vulcanized SBR is a latex composition which is used widely throughout the industry for making tennis shoe uppers. It will be noted, that its wet strength either after initial dipping and especially after soaking and after redipping is especially poor. Contrasted to this, it will be seen that the wet peel strengths of the several types of block polymer compositions are substantially better in all vided with proper spaces and inlets for the injection of respects.

TABLE B 180 peel strength (pounds per linear inch) Wet by Soaked 4 4 Combining composition Dry dipping hour Rodi-led Rte-dipped Vulcanized SB R 22 7 *1 13 4 Block polymer Composition I..- 15 8 8 14 12 Block polymer Composition IL. 18 12 11 9 Block polymer Composition III- 14 13 14 14 14 EXAMPLE II 10 2. A shoe assembly according to claim 1 wherein the combining composition comprises 100 parts by weight of block copolymer and 15-150 parts by weight of polystyrene.

3. A shoe assembly according to claim 2 wherein the foxing comprises 100 parts by weight of block copolymer and 15-100 parts by weight of polystyrene.

4. A shoe assembly according to claim 1 consisting essentially of a block copolymer as claimed in section (a).

5. A shoe assembly according to claim 1 wherein the combining composition and the foxing composition comprise 100 parts by weight of block copolymer, 15-150 We claim as our invention:

1. A footwear assembly comprising (a) a multi-layer textile upper having at least two layers of textile combined with a composition comprising essentially of an unvulcanized block polymer, said polymer having the general configuration wherein each A is a polymer block of a monovinyl arene and B is a polymer block of a conjugated diene; (b) a polymeric sole and (c) as a foxing covering the bottom of the textile upper and the circumference of the sole a composition consisting essentially of an unvulcanized copolymer as claimed in section (a).

parts by weight of polystyrene and 30-150 parts by weight of hydrocarbon extending oil.

6. A shoe assembly according to claim 5 wherein the combining composition and foxing composition contain in addition 10-150 parts by weight of inorganic filler.

References Cited UNITED STATES PATENTS 2,995,839 8/1961 Cronin 36-9 3,238,173 3/1966 Bailey et al. 260-876 3,242,038 3/1966 Dallas et al. 260-876 3,299,174 1/1967 Kuhre et al 260-876 PATRICK D. LAWSON, Primary Examiner