US2262970A - Thermoplastic box toes - Google Patents

Description

Patented Nov. 18, 1941 THERMOlfLASTIC BOX TOES Hymen Shrager and Barney Shinberg, Lawrence,

Mass., asslgnors to Atlas Shoe Products Corporation, Lowell, Mass., a corporation of Massachusetts No Drawing. Application February 12, 1938,

Serial No. 190,325.

7 Claims.

' This invention relates to thermoplastic compositions foruse in the manufacture of box toes for shoes. v

Inthe manufacture of thermoplastic box toes,

a sheet of 1 suitable fibrous material such as steamed felt or water-laid felt is saturated with, in a hot bath, a thermoplastic composition, cooled, and then cut into blanks which are incorporated in the shoe structure, and the present invention is concerned primarily withthe preparation of the thermoplastic composition.

The present invention has for its primary object to provide a thermoplastic composition which, when used as a saturant for fibrous material from which the shoe box toes are cut, will give a box toe blank having stiffness which will maintain the finished box toe in the desired shaped form with a suiiicient flexibility to prevent distortion without cracking or breaking, and acquiring a tackiness when subjected to the steam of the lasting operation which causes a fusion of the toe cap to the lining and upper of the shoe without bleeding through and discoloring the lining orthe shoe upper.

In the preparation of the composition embodying the present invention, rubber and copal are mixed together in a rubber mill with about five parts by weight of copal to four parts of rubber. Although there is in this mixture more copal than rubber, no difliculty of sticking is encountered on the rolls and the mixture can be milled and sheeted with very little trouble.

We prefer to use the grades of copal known as Manila CBB and Manila DBB, which grades consist of mixtures of. Boea and Loba copals. These consist of small chips and nubs containing bark and other foreign material. The copal is given a preparatory treatment by grinding it and screening it through a 40 mesh screen. The copal-rubber mixture is then readily and uniformly blended.

The rubber-copal mixture is then dissolved in hot rosin "or a mixture of rosin and Montan wax, or other suitable hard wax, asumcient amount of the rubber-copal mixture being'used to make the rubber in the total or final mixture amount to approximately 7%. Rubber added to the rosin or rosin wax mixture in this manner dissolves readily. The temperature required is not excessive and will not cause thermal decomposition of the rosin or the depolymerization of the rubber.

After preparing the composition in this manher, the fibrous material is then saturated therewith by dipping the material in a hot solution of the composition, and after the stock sheet thus Renewed January 16, 1940 prepared has cooled, it may be cut into the desired box toe blanks.

The blanks prepared with the composition herein set forth are characterized by having a stiifness which causes them to maintain their proper shape when incorporated in a shoe structurevbut they are sufiiciently resilient or flexible to permit slight deformation without becoming cracked or broken, and they are characterized further by becoming slightly tacky when subjected to the steam of the lasting operation so that the toe cap becomes fused to the lining and upper of the shoe without bleeding through depolymerization of the rubber. By rosin mixture" we refer to rosin and asphalt, or rosin along with thewaxes or plasticizers commonly used in the manufacture of box toes. An alternative method of preparing this composition is by dissolving vulcanized rubber in a volatile solvent or by using a vulcanized latex and adding these to the rosin mixture, resulting in compositions of inferior quality to the composition embodying the present invention. In the procedure set forth in this application, the rubbercopal mixture swells immediately on being added to the rosin and dissolves readily without depolymerization.

In another process known to us, rubber is milled with a protective colloid. When this is added to the rosin bath, a two-phase mixture is formed, the particles of rubber bei g protected by a hydrophilic colloid, the rosin mixture forming the continuous phase of the dispersion. The

prepared with rosin alone or with a mixture of rosin and Montan wax, it ispossible to use other cheap resins with the rubber-copal mixture. For

'of which we are mixture with I example, cumar resin may be used or there may be used a mixture of wood rosin and Vinsol and the rubber-copal mixture dissolved in these resins. Vinsol is a hard, brittle thermoplastic material of resinous nature produced from the Southern long leaf pine. While a thoroughly satisfactory mixture is obtainable by mixing the rubber-copal mixture with these other resins, the best results are obtained with rosin alone or a mixture of rosin and Montan wax. Carnauba wax may also be, employed in place of the Montan wax. 1

As an example of a composition using rosin and wax, a mixture of six parts wood rosin and one part Montan wax may be made, and in this may be dissolved the previously referred rubber-copal mixture made up in the proportions respectively of 4 to 5. In this mixture the rubber-copal combination will be employed in a quantity sufilcient to make the rubber. content approximate 7% of the entire mass.

What we claim is:

v 1. The improved thermoplastic'box toe having a body of fibrous material permeated with a composition comprising essentially rosin, and a minor quantity of a mixture-of copal and rubber, in which the rubber constitutes approximately seven percent of the composition and the box toe being characterized in that it acquires a tackiness when subjected to the steam of a lasting operation which eflfeots its fusion to adjacent elements of the shoe structure into which it is built.

2. The improved shoe box toe stock consisting of a body of sheet material impregnated with a mixture of rosin and hard wax combined in the proportions, respectively, of six to one, and a mixture of rubber and copal which are in the proportions. respectively, of four to five, the said rubber copal mixture being incorporated in the stock in an amount suflicient to make the rubber content approximately 7% of the entire impregnated material.

3. The improved box toe stock having abase orv carrier body of fibrous material impregnated with a composition comprising essentially rosin having a minor quantity of a milled mixture of rubber and copal dissolved therein, in which the rubber content of the mixture is approximately 7%.

4. The improved box toe stock having a base impregnated with a composition comprising essentially rosin and aminor quantity ofa milled mixtureof rubber and copal dispersed in the rosin,-in which the rosin content of the mixture is approximately 73%.

5. The improved box toe stock consisting of a base impregnated with a composition consisting of a rosin and wax mixture combined with and having dissolved therein a milled mixture of rubber and copal, the rosin and wax being in the proportions respectively of six to one.

6. The improved box toe stock consisting of a base impregnated with a composition consisting of a rosin and wax mixture combined with and having dissolved therein a milled mixture of rubber and copal, the rosin and wax being in the proportions respectively of six to one and the rubber and copal being in the proportions respectively of four to five. r

'7. The improved box toe stock consisting of a base impregnated with a composition consisting of a rosin and wax-mixture combined with and.

having dissolved therein a milled mixture of rubber and, copal, and the two mixtures being proportioned in the composition to give o the box toe a rubber content of approximately 7%.

HYMEN SHRAGER. BARNEY SHINBERG.