| 摘要 |
<p>1462651 Reducing the HCN content of nitrile polymers during extrusion MONSANTO CO 15 Jan 1974 [15 Jan 1973] 1884/74 Heading B5A [Also in Division C3] In the production of shaped packaging materials from nitrile polymers containing 55- 85 wt. per cent of nitrile monomer units selected from acrylonitrile and acrylonitrile/methacrylonitrile mixtures containing up to 16 wt. per cent acrylonitrile based on total polymer weight by processes involving at least one forming operation comprising melting and shaping of the polymer, there is present during at least one forming operation either formaldehyde or a compound which releases formaldehyde, in an amount sufficient to reduce the extractable HCN content of the resulting material, preferably to below 50 parts per billion. Numerous formaldehyde donors are mentioned, including formaldehyde itself, paraformaldehyde, trioxane, tetraoxane, hexamethylene tetramine, sodium formaldehyde sulphoxylate or bisulphate, ptoluene sulphonamide-formaldehyde, dimethylol urea, and condensates of formaldehyde with an alcohol, and urea, melamine or phenol. The packaging material, especially intended for food or drink, may take the form of film, sheet, bottle, can or jar; and the forming operation may be pelletizing, extrusion, blow moulding, injection moulding, parison forming, vacuum forming or thermoforming. In examples, the polymers used are acrylonitrile/styrene, acrylonitrile/methyl methacrylate and acrylonitrile/ methacrylonitrile/styrene copolymers. Rubber impact modifiers are present in some cases, and the compositions may also contain other conventional additives.</p> |
