Patent GB-417177-A (GB)
Title: Improvements in or relating to flexible abrasive articles, sandpaper or the like, and processes for making same
IPC: B24D11/00
Filed: 1932-12-22
Abstract: 417,177. Flexible abrasive articles. STEVENS, A. H., 5, Quality Court, Chancery Lane, London.-(Minnesota Mining & Manufacturing Co. ; 791, Forest Street, St. Paul, Minnesota, U.S.A.) Dec. 22, 1932, No. 36331. [Class 60.] In a flexible abrasive article comprising a layer of abrasive particles on one side of a flexible base or sheet, such as sandpaper, the base or sheet is treated by impregnating or saturating it, or alternatively or additionally by coating it on the back with a composition including a protein and a flexibility augmenting agent. The same composition is preferably used as a binding medium for the abrasive particles. Examples of suitable proteins are glue, casein, and albumen, whilst the flexibility augmenting agents may be hygroscopic materials such as calcium chloride, or organic hydroscopic materials such as glycerine, ethylene glycol, or diethylene glycol. Rubber or pigments, or both, may be added to the protein composition. To render the protein resistant to liquids employed with the abrasive article when in use, it is preferably insolubilized by suitable agents added to the composition, or by treatment after it has been applied to the backing material. An example is given of a solution containing casein, calcium hydroxide, and sodium hydroxide, to which the flexibility augmenting agent is added either before or after it is applied to the backing, the protein being virtually insoluble after drying. Agents employed for tanning or waterproofing the protein after application to the backing include aldehydes, chrome alum, ferric chloride, and tannic acid. Alternatively, tanning agents may be embodied in the protein solution, examples being aldehydes with ammonia, sodium bisulphite, or hydrogen cyanide ; polymers of an aldehyde, such as paraformaldehyde ; compounds capable of liberating an aldehyde, such as methyleneparatoluidine ; and carriers with adsorbed aldehydes, such as silica gel or charcoal, these forming the subject-matter of Specification 417,173. The aldehydes may be liberated by heat, preferably in the presence of moisture. In one example, a water-solution of glue with hexamethyltetramine, and with a flexibility augmenting agent, is used to saturate the backing, which preferably consists of an unsized paper, and is subjected after drying to steam at about fifty pounds per square inch. Alternatively, the waterproofing may be performed by subjecting the sheet after treatment with the protein solution and drying to the simultaneous action of live steam and formaldehyde fumes. The abrasive may be bonded by a layer of the protein composition, or of varnishes formed of resins or cellulose derivatives. Similar varnish coatings may be employed for water-proofing the sheet, in which case the protein is not necessarily insolubilized. A number of alternative arrangements of coatings formed of the protein composition and of waterproofing material on backing impregnated with the protein composition are described. Fig. 7 shows one arrangement, in which a backing sheet 1 is impregnated with a protein composition including a flexibility augment agent, and is provided on the back with a layer 3 of the protein composition, which is insolubilized. On the front of the sheet are a layer 2, which may be of the insolubilized protein composition, an adhesive layer 4 for the abrasive particles 5, and a waterproofing layer 6, which may also be of insolubilized protein composition. In cases where the protein material is used only in the form of a coating, the backing may consist of a flexible sheet of waterproof or oilproof material. Specification 417,243 also is referred to. Reference has been directed by the Comptroller to Specification 302,430, [Class 60].