US2138751A - Process for the production of elastic objects from polyvinyl alcohol - Google Patents

Description

able in the art Patented Nov. 29, 1938 PROCESS Fort THE; PRODUCTION or Lass-f no onmc'rs mom roLYvnwL Loonoi...

erb ert Vohrer, Berlin, Germany,- assignor to the Germany firms Techno Ohemie Kom'mandltgesellv schai't Kessler & 00., Berlin, Germany, and Dr. Schnabel & Co. Komm-Ges.,.

lierlin-Neukolln, I

No Drawing. Application November 12, 1935, Sei'igasl No. 49,439. Ink Germany November-.19, V 4 i x s Claims.

My invention relates to the production "of elasticarticles from polyvinyl alcohol. Elastic objects made from polyvinyl alcohol have various advantages as compared with those made from rubber, for exai iple extremely high resistance to tearing, resistance to organic solvents and oils and lack of ageing in appearance, which make themappear to be eminently suitas a substitute for rubber articles. In order to render objects made from polyvinyl alcohol elastic,- there must be added thereto socalled softening-or plasticizing agents", that is to say, substances retaining a certain amount of water inthe finished article, or substances which themselves constitute a high-boiling solvent for the polyvinyl alcohol. Such articles may be produced by using aqueous solutions to start with and producing any desired moulded pieces by immersion according to known processes, or by extruding threads, tubes or bands from concentrated solutions through nozzles. As initial substance, use must be made of solutions of a relatively low percentage and it is necessary to apply a very high pressure during pressing. The additions of softening agents, and if necessary, filling materials consisting of organic colloidal substances are bound down to very narrow limits, because the softening agents, such as, glycerine or'ethylene glycol easily give rise to sweating in the finished articlepand the filling materials mix well with polyvinyl alcohol only in a limited degree; 1

The present process is based on the property of certain polyvinyl alcohols of not, or only to a certain extent, dissolving in cold water. If such a polyvinyl alcohol be worked up to a paste in the cold state with water and softening agents in the weight ratio of 1:1 or 1:15, pressed into the desired form, and heated to -100, articles are obtained which may be taken from the press in the hot state without losing shape. A completely homogeneous clear mass arises and the polyvinyl alcohol absorbs the small quantity of water and softening medium and. sinters together, forming a soft and elastic body of constant shape. In this respect, the present process difi'ers fundamentally from known processes intended to produce hard articles under very highipressure andat a temperature of over 200. The paste-like mass may be directly hot-pressed or even cold-pressed and the mould subsequently heated.

'Iheadvantag'of the process as'compared with the known methods used .with solutions resides not only in that the tedious dissolving process rand the frequently complicated working up method are replaced by simple pressing, but also in that there may be added to the mass before the pressing large quantities of different substances in the dissolved or undissolved state which serve as filling bodies or impart particularly valuable properties to the article. For example, there -is obtained from polyvinylalcohol,- water, a high percentage of glue, gelatine; starch and-the like with tanning substances,- a body which is insoluble in water. By the tanning substance, for example formaldehyde, glue, gelatine and starch areconverted into the form in which they are insoluble in water." The mixed product thus produced is also insoluble in boiling water. However, it is not'possible to produce an object of the same composition from a solution, because only a limited quantity of glue or gelatine, about 10-15%, can be dissolved .in a [polyvinyl alcohol solution, and because the tanning agents would immediately precipitate the gluten from this solution.

When filling substances are added, the weightratio between polyvinyl and filling substances on the one hand and water and softening agents on the other hand must .be about 1: 1 tolz'lj In the case of the addition of large quanti s-"'5 of organic colloidal-substances, such for .example as glue, starch, dextrin and the like, the glycerine content may be increased up to and more, without the object sweating in damp atmosphere. only 40% softening agent at the most.

' Numerous articles can be manufactured according to the process, such for example as slabs .with and without insertions of fabric, thin films,

packings, articles of complicated shape, tubes and the like. Tubes may, for example, be continuously produced either by means of a worm press or a stamping press having an extrusion nozzle. The extrusion nozzle must be such that it may be heated and so long that the polyvinyl alcohol is able to combine with the water.

- Example 1 Example 2 100 parts by weight polyvinyl alcohol are worked up to a paste with a solution of 50 parts in; g

Polyvinyl alcohol alone mixes with by weight of gelatine or glue and 5 parts by weight of potassium bichromate in 150 parts by weight of water and 75 parts by weight of glycerine. There is formed a plastic mass, to which mineral dyestuffs and filling agents may be added. The mass may be worked up to tubes by means of a worm press.

Example 3 The same procedure is followed as in Example 2 and 100 parts by weight of starch is also kneaded in, which starch has preferably first been emulsionized with water. After the pressing, a clear uniform mass arises, which may be spread over a textile fabric and pressed-at a raised temperature.

Having now particularly described and ascertained the nature of my invention and in what manner the same is to be performed, I declare that what I claim is:

1. A process for the production of elastic objects from polyvinyl alcohol comprising working up polyvinyl alcohol insoluble in cold water to a paste with water and softening agents in the cold state, pressing said paste into the desired form and heating it to 80-100 c.

2. Process according to claim 1, wherein the weight ratio between the polyvinyl alcohol on the one hand and water and softening agents on the other hand is about 1:1 to 1:15.

3. A process for the production of elastic objects from polyvinyl alcohol comprising, working up polyvinyl alcohol insoluble in cold water to a paste with water, softening agents and organic colloidal filling materials in the cold state, pressing said paste into the desired form and heating itto ISO-100 C.

4. A process according to claim 3 comprising in addition converting the filling materials contained in the parts into a state in which they are insoluble in water.

5. A process according to claim 3 comprising in addition, adding tanning substances to the parts to convert the filling materials into a state in which they are insoluble in water.

6. Process according to claim 3, wherein the weight ratio between the polyvinyl alcohol and the filling substances on the one hand, and water and softening agents on the other hand is about 1:1 to 1:15.

'7. Process according to claim 1', wherein ethylene glycol is added as softening agent.

8, Process according to claim 1, wherein glycerine is added as softening agent.

9. Process according to claim 3, wherein gelatine is added as filling substance.

10. Process according to claim 3, wherein glue is added as filling substance.

11. Process according to claim 3, wherein dextrin is added as filling substance.

12. Process according to claim 1, wherein the paste is pressed and heated simultaneously.

13. Process according to claim 1, wherein the paste is heated after the pressing operation.

14. Elastic objects of polyvinyl alcohol containing more than 20 parts by weight of polyvinyl alcohol and more than parts by weight of organic colloidal filling substances.

15. Elastic objects of polyvinyl alcohol containing more than parts by weight of polyvinyl alcohol, more than 15 parts by weight of organic colloidal filling substances, and tanning substances in such quantities as necessary for making the said filling substances insoluble in boiling water.

16. Elastic objects of polyvinyl alcohol containing more than 20 parts by weight of polyvinyl alcohol, more than 15 parts by weight of organic colloidal filling substances, and more than 40 parts by weight of softening agents.

HERBERT VOHRER.