| 摘要 |
Condensation products are manufactured by causing a polyvinyl ester to react with two aldehydes in an aqueous solution of hydrochloric acid, all the primary materials being added at the commencement of the reaction and the operation being carried out from start to finish at ordinary temperature without isolating any intermediate product. The reaction may be accelerated by the addition of a small quantity of ethyl alcohol to the hydrochloric acid solution. The products may be employed for the manufacture of photographic and cinematographic films, for rendering fabrics impermeable to very diffusible gases, particularly for balloon envelopes, and for the manufacture of plastic masses in blocks, sheets, tubes and artificial fibres. In examples: (1) polyvinyl acetate is agitated with formaldehyde, paracetaldehyde, hydrochloric acid and denatured alcohol, the mixture then being allowed to stand at ordinary temperature and the product precipitated with water, washed and dried; flexible sheets may be formed from the product with the addition of plasticizers such as benzyl alcohol or p-toluenesulphonamide; (2) as in (1) but using more formaldehyde and less paracetaldehyde; films may be prepared from a solution of the product in methanol and benzene; (3) to (5) a less highly polymerized vinyl acetate is employed, with various proportions of formaldehyde and paracetaldehyde; a film, formed from a solution of the product of (5) in methyl or ethyl acetate or a mixture of ethanol or methanol and benzene, if desired with the addition of plasticizers, is placed between two sheets of fabric, e.g. flax, cotton or silk and united thereto to produce a fabric impermeable to diffusible gases and suitable for the manufacture of balloon envelopes; the impermeability may be obtained by direct coating of fabrics, e.g. single fabrics or multiple fabrics in which the warps may be crossed at 45 DEG , by means of a suitably plasticized solution of the product; (6) as in (1) but using different proportions of the two aldehydes; a support for a photographic or kinematographic film may be prepared from a suitably plasticized solution of the product in methyl acetate and ethanol. Specification 409,507 is referred to. |
