| 摘要 |
1513125 Seaming non-metallic sheet material TEMCA CHEMISCHE UNION GmbH 7 April 1977 [9 April 1976] 14944/77 Heading B5K A web 21 of acetalized polyvinyl alcohol foam is joined to another web 22 of the same material or of a textile fabric by bringing the lengths thereof to be joined into contact and hotpressing, in the presence of moisture, at a temperature of 100-300�C, preferably 200-250�C, and a pressure of 1-10 kp. per sq. cm., preferably 4-6 kp per sq. cm. Prior to joining, the or each web of acetalized polyvinyl alcohol foam is saturated with water to its expansive limit. Preferably, the or each acetalized polyvinyl alcohol foam web comprises polyvinyl alcohol acetalized with formaldehyde and having an acetalization level of approximately 200% by weight. Of the second web is a textile fabric, it may comprise cotton, rayon, polyacrylonitrile or polyester fibres. Joining may be effected continuously by a heated wheel or intermittently by the device shown. The device comprises an elongate copper plunger 2 heated by an electric heating coil 6 and having an internal temperature sensor 7 connected to an external indicator 8. The plunger 2 is provided on a piston rod 10 of a fixed hydraulic cylinder 3 connected by pipes 15, 16 and valves 17, 18 to a supply of liquid under pressure. The webs 21, 22 are overlapped and laid on a fixed stainless steel anvil 1 and the plunger 2 is lowered when the desired temperature of the working face 5 thereof is reached to effect joining. |
