| 摘要 |
<p>1363039 Particulate UF/silica flatting agents; coating compositions CABOT CORP 11 Oct 1972 [12 Oct 1971] 46743/72 Headings C3R and C3P A flatting additive for coating compositions consists of 20-80 wt. per cent of a non-porous, infusible, insoluble urea-formaldehyde powder of U : F ratio 1 : 1-2 and BET specific surface area 5-100 m.<SP>2</SP>/g. and 80-20 wt. per cent of non- porous fume silica of specific surface area of 30-100 m.<SP>2</SP>/g., silica content at least 99À8% and having spherical particles. The UF powder is prepared in a known manner and may contain a protective colloid. The additive may be used in amount 5-30 wt. per cent of the film-forming material, and the two solids may form 20-60 wt. per cent of the total coating composition. In Examples A-C UF powders are prepared with and without Na carboxymethylcellulose using NH 2 SO 3 H or H 2 SO 4 as the acid to give products of surface 53, 31À8 and 28À1 m.<SP>2</SP>/g., U : F ratio 1 : 1À5, specific gravity 1-4 and bulk density 60 g./l. These are mixed with fume silica in ratios 47 : 53 or 25 : 75 by weight and added in amounts of 5-30 phr to an acrylic resin in isopropanol.</p> |
