FIELD OF THE DISCLOSURE

This disclosure relates to formed leather products and their method of manufacture. Particularly, the disclosure relates to a leather substrate material formed from waste leather having improved strength and tear-resistance characteristics. De-wetting and dispersion aids that assist in de-wetting steps to remove desired amounts of moisture from interim wet lap products are described. The interim wet lap products realize improved fiber and fibril dispersion which results in improved formation and resultant physical properties in formed leather substrates.

The disclosure further relates to the formation of a composite leather substrate formed from multiple leather substrates having different compositions. Creation of a composite leather substrate from two or more component sheets of leather material allows for the use of source scrap leather that would otherwise be undesirable in a finished leather product.

BACKGROUND OF THE DISCLOSURE

Conventional leather is formed by tanning animal hides. The tanning process treats an animal hide with a variety of substances to improve and maintain leather's desirable physical characteristics for use in clothing, upholstery, luggage and like applications. The most desirable physical characteristics of tanned leather include appearance, feel, resilience to stretching, longevity, treatability with a variety of surface conditioning finishes and natural drape.

Leather's desirable characteristics are attributed in part to it being a fibrous, semi-porous material made up of an entangled, open matrix of resistant collagen fibers. Collagen fibers make up the majority of leather's composition. Collagen fibers are made up of constituent collagen fibril bundles made up in turn by smaller elongated strands of collagen protein known as collagen fibrils.

Generally, the tanning process is directed toward collagen fibers to fix chemically reactive sites on collagen fibers and to increase intramolecular salt links between adjacent collagen molecules. This links the matrix of resistant collagen fiber bundles, leaving tanned leather pliable, and occupies reactive sites that otherwise would allow leather to degrade and rot. The tanning process likewise removes other compounds from the hide that may be susceptible to degradation and/or perform other functions in the hide. Such compounds may be replaced with other materials.

Obtaining natural leather is problematic due to supply hide having varying qualities, tanning process costs, varying hide costs over time and other challenges.

The leather harvesting, tanning and preparation process produces waste leather byproducts in leather scraps and shavings. If not otherwise used, the waste leather is disposed of by landfill or incineration, creating a negative environmental impact.

Artificial leather products containing waste leather, such as bonded leather, attempt to emulate natural leather. Bonded leather is synthetic leather formed by embedding shredded leather particles into various binding materials. The shredded leather and binding material substance may be applied onto a fabric backing carrier.

Bonded leather type synthetic leathers lack the above-noted desirable characteristics of natural leather. This is due to synthetic leathers lacking the continuous matrix of resistant collagen fiber bundles found in natural leather.

The failure of known artificial and synthetic leathers that contain shredded leather particles is that the individual particles do not physically interact to reproduce or emulate the characteristics of a continuous piece of natural leather having an entangled matrix of resistant collagen fibers. Most notably, artificial and synthetic leathers suffer as lacking desirable tear resistance, drape, flexibility and other esthetic attributes.

In tests applied by a conventional tensometer, artificial and synthetic leather samples of 0.010 to 0.080 inch thickness were subjected to pulling stresses under tension to failure. Measurement of maximum applied force before failure was recorded and calculated as maximum tensile strength PSI measurements ranging generally from about 790 PSI to about 1750 PSI.

Likewise, given the inherently variable makeup of organic animal hides and tanning treatments, the tensile strength qualities of tanned natural leather can vary widely. The tensile strength of representative natural tanned leathers have been found to vary from about 2000 to 3200 PSI depending on leather quality, mechanical treatments and coatings applied to the leather.

Processes for forming other types of formed leather substrates containing shredded and fibrillated collagen leather fibers derived from waste derived leather are known. A challenge with these processes is the inability to achieve acceptable levels of fibril dispersion so that subsequently formed leather substrates have the potential for fibril-to-fibril entanglement.

Another challenge is that wet lap products that are formed mid-process are difficult to dewater and represent a limit to the degree of fibril dispersion which can be achieved in a final leather substrate product. Wet lap may refer to a sheet containing the dispersed fibrils, where particles or fibers are suspended in a fluid (such as a slurry), and the wet lap may be pressed or otherwise manipulated to eliminate or remove at least a portion of that fluid.

The interim wet lap products of these processes also tend to have low wet lap strengths. This presents processing challenges with manipulating interim wet lap products in large-scale production processes using known paper-type processing machines. During transition of the interim wet lap from wire mesh sections of paper-type processing machines, the wet lap tends to break reducing process efficiency and making it very difficult or impossible to produce the end product on a large scale.

Another challenge with prior art processes for forming leather substrates is that required leather particles must be shredded or ground to small sizes and passed through screens having likewise small apertures of approximately 3/32 (0.09375) of an inch in diameter in order to attain desired fibril dispersion and interaction between leather particles. These small grind sizes can slow processing times which reduce process productivity and also limits the ability to achieve some desired physical properties.

Yet another challenge with known processes for forming leather substrates derived from waste leather is the inability to obtain an end product having desired qualities in the outer, presentation surface of an end leather product.

Waste leather that is used in methods of producing a leather substrate may be obtained from different sources including strip waste, cuttings and scraps from the processing of source leather of various grades. Source waste leather may be higher quality full grain or top grain leather obtained from surface or top cuts of animal hide. Alternatively, source waste leather may be lower quality split grain or genuine leather obtained from inner split or bottom cuts of animal hide.

Generally, source waste leather obtained from the surface of animal hide contains leather fibers which provide higher strength and tear-resistance qualities over source leather obtained from the inner portions of animal hide. However, source waste leather derived from full grain or top grain leather often contains the residue of protective coatings and other processing agents which can interfere with the steps of properly processing leather particles, resulting in lumps or non-uniform formation of interim wet lap products as well as lumps on the surface of formed leather substrates. These imperfections can limit the use of source waste leather derived from full grain or top grain leather for the disclosed method.

Thus, there is a need for an improved formed leather product that is created from available waste leather byproducts that reproduces desirable physical characteristics of natural leather. The improved leather product should emulate the collagen fiber matrix that is found in natural leather, have predictable physical characteristics including high tear resistance, desired elastic properties for a range of end applications, and treatability by conventional leather conditioning substances. The process of creating the improved leather product should allow improved de-watering of interim wet lap products and have good wet lap strength to facilitate physically manipulating interim wet lap products. The improved leather product should also have desired qualities in its outer, presentation surface.

SUMMARY OF THE DISCLOSURE

Disclosed is a formed leather material created from commonly available waste leather byproducts and its method of manufacture. The formed leather material reliably reproduces desirable physical characteristics of natural leather, including high tear resistance, high tensile strength, desired elastic properties for end applications and treatability by conventional leather conditioning substances.

The improved leather material includes a formed leather substrate containing a matrix formed by collagen fibrils. The collagen fibril matrix is formed from entangled collagen fibrils derived from collagen fibril bundles and collagen fibers found in naturally occurring leather.

The formed leather substrate is formed by obtaining leather waste and physically processing the waste by shredding or grinding to create leather particles of desired size. The leather particles are combined with water to form a particle/water mixture. The mixture is processed to allow collagen fibril bundles within the particles to absorb a quantity of water. The water absorption swells and partially distresses the collagen fibril bundles. The partially distressed bundles are particularly susceptible to mechanical dispersion. Appropriate treatment of mechanical dispersion of the swollen, partially distressed fibril bundles extracts a high yield of constituent collagen fibrils from the bundles to the particle/water mixture. Water is then removed from the mixture through a series of de-watering steps to form a leather substrate product containing a matrix of collagen fibrils, bundles and fibers.

In embodiments, the formed leather substrate may be formed by the treatment of leather waste to obtain appropriately partially distressed collagen fibril bundles which are additionally treated to form a desirable leather substrate product.

In disclosed process steps, the particle/water mixture is treated with various materials to facilitate manufacturing steps and the formation of a leather substrate having desired physical properties.

In particular, disclosed are process steps including the use of specific de-wetting and dispersion aids. These aids assist in the formation of interim wet lap products having improved qualities and improved moisture drainage rates. Improved moisture drainage rates allow for the formation of thicker interim wet lap products during process steps. This allows for formation of a thicker and more resilient leather substrate. The improved moisture drainage rates also allow for use of higher wet pressing pressures through process steps, which allow for improved fibril-to-fibril interactions to form an improved collagen fibril matrix. The improved fiber and fibril dispersion significantly contribute to the necessary fiber-to-fiber and fibril interactions to achieve improved physical properties in formed leather substrates.

In alternative process embodiments, the interim wet lap products may be treated directly with various processing aids to allow the formation of a leather substrate having desired physical properties.

Disclosed de-wetting and dispersion aids also allow the use of larger leather particles over old art methods. In disclosed process steps, source leather material may be shredded/ground and screened through apertures of up to 0.75 inches in diameter. These larger grind sizes allow accelerated processing times as well as preserve naturally occurring fiber-to-fiber interactions within leather material, allowing for formation of leather substrates having better tear resistance.

Leather products containing the collagen fibril matrix substrate have improved tensile strength qualities over known artificial and synthetic leathers. In tests by conventional tensometer, samples of leather substrate products are subjected to pulling stresses under tension to failure to determine maximum applied force measurements before failure. Measurements recorded and calculated as maximum tensile strength PSI ranged up to and over 6632 PSI, well above known artificial and synthetic leathers and many natural tanned leather samples.

Leather products containing the collagen fibril matrix substrate share the desirable physical characteristics of conventional leather and may be treated by mechanical enhancement techniques such as embossing, calendaring, staking, tumbling and so forth.

The disclosed processes allow for the formation of improved leather substrates having improved physical properties, including improved strength and tear resistance characteristics over prior-art leather substrates. In particular, a leather substrate formed according to the method disclosed herein may exhibit a tear resistance of greater than about 40 Newtons when tested in accordance with ASTM D 4704.

The disclosed processes also allow for improved processing of interim products mid-process over prior-art processes.

The disclosure also relates to the formation of a composite leather substrate that is formed from multiple leather substrates having different compositions. Creation of a composite leather substrate from two or more component sheets of leather material allows the use of source scrap leather that would otherwise be undesirable in a finished leather product. The composite leather substrate includes an outer, presentation surface having desired elastic properties for end applications including treatability with surface conditioning finishes and a high degree of smoothness.

The present disclosure further relates to the formation of a high-strength, tear-resistant multilayer composite leather substrate formed from multiple leather substrates.

The multilayer composite leather substrate incorporates leather substrate layers that do not contain process-interfering protective coating or agent residues in outer, presentation surfaces. Leather substrate layers formed from waste leather containing interfering residues are positioned as internal middle layers of the composite leather substrate.

Other features of the leather substrate will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing sheets illustrating embodiments of the leather substrate and related method of manufacture.

