| 摘要 |
Compositions for use as adhesive cements comprise a cement and a urea-formaldehyde resin of limited water tolerance which on the addition of water give an aqueous alkaline adhesive that is tacky until it sets. The cement may be Portland cement, Ciment Fondu or "417" (Registered Trade Mark) Super Fast Setting. The compositions may also contain neutral fillers such as china clay, sand, silica flour, chalk plaster of Paris, wood flour and asbestos and may additionally contain a water-soluble alkali such as sodium hydroxide or calcium hydroxide. Examples are given. The Provisional Specification also refers to the use of a resorcinol-formaldehyde resin in place of the urea-formalde resin.ALSO:Compositions for use as adhesive cements comprising a mixture of a resin which is ureaformaldehyde condensation product of limited water tolerance and a filler which provides when water is added thereto an aqueous alkaline adhesive that is tacky until it sets. "Limited water tolerance" is defined as meaning that the dry resin forms an opalescent solution in the presence of not less than 2 parts by weight of water, but in the presence of more than 10 parts by weight of water exhibits incompatibility and incipient precipitation with concomitant formation of an opaque system. An alkaline filler may be used, e.g. cement or lime, or a neutral filler may be used in conjunction with an alkaline filler and/or a water soluble alkali such as sodium hydroxide or calcium hydroxide. Neutral fillers specified are china clay, sand, silica flour, chalk, plaster of Paris, wood flour and asbestos fibres. Water soluble cellulose derivatives, e.g. sodium carboxymethylcellulose may also be present. Examples are given. The Provisional Specification also refers to the use of a resorcinol-formaldehyde resin in place of the urea-formaldehyde resin. |
