US1161967A - Method of producing vulcanized plastic articles. - Google Patents

Description

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ran snares rad ans? orrrcn RAYMOND LB. PRICE, OF YORK, N. Y., ASSIGNOR T0 RUBBER REGENERATING COMPANY, A CORPORATION OF INDIANA.

METHOD OF PRODUCING VUILCANIZED PLASTIC ARTICLES.

To all whom it may concern Be it known that I, RAYMOND B. PRICE, a citizen of the-United States, residing at New York, county and State of New York, have invented certain new and useful Improvements in Methods of Producing Vulcanized Plastic Articles, of which the following is a full, clear, and exact description.

This invention relates to the method of producing vulcanized plastic articles, and more particularly to the manner-of drying the plastic on the form after each submersion in the plastic solution.

In the manufacture of dipped vulcanized plastic articles, the practice heretofore has been to accumulate the vulcanizable plastic upon a form by repeatedly dipping the form in a solution of the plastic, and subjecting the form and the plastic thereon after each dipping to atmospheric air for a sufficient interval of time to remove the slvent from the plastic solution by evaporation. This old and Well known practice has certain disadvantages both as to the time consumed in, drying, and as to defects in and lack of uniformity in the thickness or gage of different portions of the same article, or. diiferent articles which have undergone exactly the same treatment. in part from the presence of moisture and dust particles in atmospheric air and the variances in the quantity of both moisture and dust from time to time.

The evaporation of the solvent contained in the plastic upon a form has the effect of chilling the form with a resultant condensation of moisture contained in the air upon the plastic. The presence of this moisture reduces the area of the article fromwhich the volatilization of the solvent may be eflected, with a resultant prolongation of the time required to properly condition the plastic for another dip or for subjection to a vulcanizing medium. Furthermore, if I .this condensate is not entirely removed before the form is againdipped in the solution, there is likelihood of blisters being formed. When the article is vulcanized by the'cold cure process, the presence of moisture in the body of the articlemay result in the formation of hydrochloric acid in the article thus causing rapid deterioration and poor aging properties.

With the old and well known method above referred to the recovery of the .sol-

Specification of Letters Patent.

These conditions arise Patented Nov. 30, 1915.

Application filed January 16, 1915. Serial No. 2,733.

' from the plastic deposited upon the form at each dipping under conditions which preclude allpossibility of moisture being de posited on thesurface of the article during drying with a resultant elimination of possibility ofthose defects in the completed article arising fromcondensation of the mois ture of the air upon the article.

The drying of the article within an inclosed space and in the presence of a subatmospheric pressure or vacuum, also has the advantage that the solvent removed by evaporation or volatilization from the plastic may be readily recovered and danger of gas intoxication is avoided without the expense of, or Waste incidental to the apparatus" heretofore used to protect the workmen. Furthermore, the dangers of the formation of an explosive mixture of the volatile solvent and air is reduced to a minimum.

The invention consists primarily in the method of producing vulcanized plastic articles including therein the steps of dipping a form in a solution of vulcanizable plastic and thereafter removing the solvent by exposing the form and the plastic thereon in an inclosed space to a sub-atmospheric pressure; and in such other novel steps and practice as are hereinafter set forth and described and more particularly pointed out in the claims hereto appended.

In the-practice of my invention, I submerge a form. of the desired contour in a solution of a vulcanizable plastic. The composition of this plastic may either be such as space, and a vacuum or partial vacuum is created and maintained within said space for a sufficient interval to insure the com-- plete evaporation or volatilization of the solvent in the plastic. To prepare the article for vulcanization, the form is repeatedly and alternately dipped and subjected to sub-atmospheric pressure or a vacuum as described.

If desired, the plastic on the form may be subjected to heat which may if desired be supplied directly to the form itself, which being subjected to sub-atmospheric pressure or a vacuum accelerates the evaporation of the solvent. lVhen heat is used it may be applied at any time during any drying step and in various ways.

By maintaining a sub-atmospheric or reduced pressure about the form while the plastic thereon is drying, I not only reduce the time required to dry the plastic after each dip, but avoid the presence about the form of atmospheric air containing sufficient moisture to cause the deposition of moisture upon the plastic as a result of the evaporation of the solvent. As a conse- ,quence those defects in the completed article resulting from such moisture are avoided and no time and attention is required to remove any such moisture prior to again dipping the form. My improved method also admits of the drying of large numbers of articles under substantially identical conditions, irrespective of changeable atmosphericconditions.

As the solvent volatilizes, it is withdrawn from the drying chamber unmixed with any substantial quantity of air, and hence a large percentage thereof may be quickly and cheaply recovered. The withdrawal of the solvent, also prevents waste of the solvent and gas intoxication of the workmen through the. escape of thesolvent into the dryingroom.

Thelow pressure maintained about the form while within an inclosed space,- and the short time required to effect a satisfactory drying of the plastic, avoids possibility of dust settling upon the plastic while dryin Y 4 articles made by my improved method seem to have uniform thickness, to be compact throughout and tougher, which I attribute to conditions of surface tension resulting from the action of the reduced pressure.

vent by exposing the form and the plastic thereon in an inclosed space to a sub-atmospheric pressure.

2. The method of producing vulcanized plastic articles including therein the steps of repeatedly and alternately dipping a form in a solution of vulcaniz'able plastic and exposing the form and the plastic thereon in an inclosed space to a sub-atmospheric pressure whereby the solvent is removed after each dip, the deposit of moisture and dust particles upon the plastic are prevented, and the escape of the volatile solvent is prevented.

Signed at New York, N. Y., January 14, 1915.

RAYMOND B. PRICE.

Witnesses:

.DANIEL A. WILCOX, VERQNICA BRAUN.