| 摘要 |
<p>An abrasive sheet is made from paper or cloth impregnated with a polyurethane which is chemically bonded to the cellulose of the sheet material (see Divisions D1 and D2). In Example VII, kraft paper is impregnated with the polyurethane and then coated on one side with a butadiene-acrylonitrile latex. It is then coated on the same side with a conventional alkyd varnish and silicon carbide applied. It is finally coated with a conventional alkyd resin. In Example VIII, jeans-cloth is impregnated with the polyurethane and then coated successively with a phenol-formaldehyde make coat, aluminium oxide and a phenol-formaldehyde size.ALSO:Compositions for impregnating paper or cloth to form a polyurethane in situ and to bond it chemically to the cellulose of the sheet material comprise a secondary hydroxyl-terminated polyether polyol and a polyisocyanate. A catalyst for the reaction may be included in the composition or may be incorporated into the sheet before the composition is applied. In the examples: (I) the composition comprises polypropylene glycol, a secondary hydroxyl-terminated triol formed by reacting 1,2,6-hexanetriol with propylene oxide, toluene - 2,4 - diisocyanate, xylene, a polyallyl - polyphenol antioxidant and lead isooctoate; (II) the composition omits the triol but otherwise comprises the same ingredients as in Example (I); (III) the composition comprises a polypropylene glycol, a poly-propylene ether triol and toluene-2,4-diisocyanate, but no solvent or catalyst, paper is first impregnated with a solution of lead octoate, and then with the composition; (IV) the composition comprises polypropylene glycol, polypropylene ether triol, xylene, toluene-2,4-diisocyanate, calcined clay, phenyl mercuric acetate and lead octoate; (V) the composition comprises a polyether triol, toluene-2,4-diisocyanate, xylene and bismuth naphthenate; (VI) the composition comprises a polypropylene glycol, an ethyl acetate solution of the product of reaction of one mole of trimethylol-propane and three moles of toluene diisocyanate, xylene and lead octoate; (VII) the composition comprises a blend of two poly-propylene glycols of different molecular weight, three polyether triols of different molecular weight, toluene-2,4-diisocyanate, TiO2, green pigment, carbon black, xylene and lead octoate; and (VIII) the composition comprises a polyether triol, xylene, toluene-2,4-diisocyanate, and lead octoate.ALSO:A pressure sensitive adhesive tape is made from paper impregnated with a polyurethane which is chemically bonded to the cellulose of the sheet material (see Division D2). In an example, a creped kraft paper is impregnated with the polyurethane and then coated on one side with a butyurea-aldehyde, and on the other with a neoprenephenolic resin containing magnesium and zinc oxide as curing agents. The second side is then again coated with a conventional rubber-resin adhesive.ALSO:Fibrous cellulosic sheet material is impregnated with a polyurethane which is chemically bonded to the cellulose of the sheet material, and is formed by reaction between the hydroxyl groups of the cellulose and of a secondary hydroxyl-terminated polyether polyol with a polyisocyanate sufficient to provide at least one NCO group for each OH group of the polyether. The cellulosic sheet may be paper, e.g. creped kraft, or jeans-cloth. The impregnation may be carried out using a liquid composition containing the secondary hydroxyl-terminated polyol, the polyisocyanate and a catalyst for the reaction, e.g. lead iso-octoate or bismuth naphthamate. Alternatively the sheet may be impregnated first with a solution of the catalyst, dried and p then impregnated with the polyol and polyisocyanate. The polyol and the polyisocyanate may each be bifunctional, e.g. polypropylene glycol and toluene-2,4-diisocyanate, or trifunctional, or contain more than three functional groups. Several examples are given. The impregnating composition may contain a filled e.g. clay, and by suitable choice of filler, the product may be made transparent, e.g. for tracing paper, or opaque. The product may be coated with pressure-sensitive adhesive and used as a pressure-sensitive adhesive tape, or may be coated with adhesive and abrasive to make an abrasive sheet.</p> |
