Moldable footwear

Details Moldable footwear Moldable footwear

1999-05-27

2001-05-08

Silbaugh, Jan H. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

With printing or coating of workpiece

Coating or impregnating workpiece before molding or shaping...

C264S322000, C425S002000, C008S150000, C069S021000, C427S412000

Reexamination Certificate

active

06228300

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The instant invention is broadly concerned with products molded to conform to the size and shape of a particular object and methods for producing these products. In preferred forms, the products of the invention are footwear products (such as shoes or boots) having substantially the same size and shape of the foot on which it is to be worn. Products of the invention are formed from moldable materials which stretch and shape easily, such as natural leathers, synthetic leathers, and mixtures thereof. In the methods of the invention, the moldable material is cut to a size and shape similar to that of the object around which it is to be molded. A mixture comprising a leather hardening or stiffening agent is then applied to the material. The resulting mixture-covered material is dried while remaining on the object, resulting in a form-fitting, molded product at a cost much lower than the cost of currently available custom-made products.
2. Description of the Prior Art
Animal hides or skins are preserved by a process called tanning wherein a chemical is applied to the hide or skin. This process makes the hide immune to bacterial attack, raises the shrinkage temperature of the hide, and prevents the collagen fibers from sticking together upon drying, resulting in a material that remains porous, soft, and flexible. Two widely used tanning methods include vegetable tanning and chrome tanning. With chrome tanning, the pickled hide is usually saturated with a solution of basic chrome sulfate, followed by precipitation of the chrome compound by adding a small quantity of a mild alkali. This results in a reaction of a coordination nature between the carboxyl groups of the skin collagen and the metal atoms. With vegetable tanning, heavy hides are given a series of baths in gradually increasing strengths of extracts containing tannic acid (tannins), such as quebrachro and wattle extracts. Molecular aggregates of the tannin within the hides form cross-links between the polypeptide chains of the hide proteins. Vegetable tanning produces a relatively dense leather that is pale brown in color and tends to darken upon exposure to natural light.
In the past, vegetable-tanned leather has rarely been used in footwear because it absorbs water and leather conditioner quickly, and it stretches and shapes too easily. Thus, prior art vegetable-tanned leather shoes would quickly stretch so that eventually they no longer fit the wearer's feet. This is particularly true when the vegetable-tanned leather is exposed to moisture.
Shoes, boots and other footwear have generally been made from chrome-tanned leather. While chrome-tanned leather doesn't absorb water or leather conditioners easily, it also doesn't shape easily. In the past however, chrome tanning has been the quickest and easiest way to tan leather. In the manufacturing process, shoes are built on lasts of varying sizes categorized by widths and lengths. The chrome-tanned leather is shaped over the last with heat and pressure, resulting in a shoe having a well-retained shape with little stretch remaining in the leather. If the shoe is too tight, the wearer oftentimes wears the shoe for a number of days or weeks in hopes of stretching the leather until a comfortable fit is obtained. This can be painful for the wearer as well as harmful to the wearer's feet. However, this method of manufacturing shoes is much more affordable than having shoes custom-made (which is very labor intensive) to the exact size and shape of the wearer's foot.
SUMMARY OF THE INVENTION
The instant invention overcomes the above problems by providing products (preferably leatherwear, and more particularly footwear) and methods of making leatherwear and footwear from vegetable-tanned leather or any other tanned leather (either natural or synthetic) having properties similar to vegetable-tanned leather. The methods of the invention result in footwear which is moldable to the wearer's foot, and which retains the shape of the foot even if subjected to repeated stress or exposed to water and other lubricants.
In more detail, the products and methods of the invention involve wetting a leather or leather-like material with a hardening mixture and molding the wet material into the shape of a particular object, such as a foot or some other body part. The wet material is placed on and/or around the object and dried so that the material stiffens into, and retains the shape of the object. The material to be molded is selected from the group consisting of natural leathers, synthetic leathers (as used hereinafter “synthetic leathers” refers to materials comprising a sheet of resin adhered to a piece of cloth or fabric, as well as to any other material designed to look similar to or have properties similar to those of natural leather), and mixtures thereof. Natural leathers are the preferred material, with vegetable-tanned leather or leather which contains tannin cross-linked polypeptide chains being particularly preferred.
The methods of the invention are particularly useful for forming footwear (as used hereinafter “footwear” refers to any item which can be worn on the feet, including boots, ladies' dress pumps, loafers, etc.) which molds to substantially the same size and shape of the foot around which it is dried. While the wet material can be dried simply by maintaining the material on the object (i.e., foot) until the material dries, the preferred drying process comprises subjecting the wet material (while it is molded around the particular object such as a foot) to circulating hot air having a temperature of from about 150-250° F., and more preferably from about 200-225° F. Preferably, the drying step is carried out for a time period of from about 10-30 minutes, and more preferably from about 15-20 minutes. After drying, shoes and other products in accordance with the invention will fit the individual shape of the foot or other object and will retain that shape through repeated stress and exposure to water. The final dried product should have a tensile strength (as determined by ASTM D2209-90) of at least about 1100 psi, preferably at least about 1750 psi, and more preferably at least about 2200 psi. Furthermore, the final product has a breakforce (as determined by ASTM D2209-90) of at least about 35 lbs, preferably at least about 65 lbs, and more preferably at least about 95 lbs. Finally, the final product should have a moisture absorption (as determined by ASTM D 1815-96) of at least about 62%, preferably at least about 74%, and more preferably at least about 75-86%.
The hardening mixture utilized in the instant invention comprises a leather stiffening or hardening agent and water. The hardening mixture can also include a leather conditioning agent if desired. The preferred hardening mixture will contain from about 10-40% by volume, and preferably from about 15-30% by volume, based upon the total volume of the mixture being taken as 100% by volume. Preferred leather stiffening or hardening agent are water-based acrylics.


REFERENCES:
patent: 1274837 (1918-08-01), Aschiem
patent: 2285064 (1942-06-01), Straw
patent: 2285376 (1942-06-01), Lovell
patent: 2294474 (1942-09-01), Marx
patent: 3358332 (1967-12-01), Downey

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