Patent GB-629268-A (GB)
Title: Products to be used for painting or impregnation
IPC: D06M13/224
Filed: 1946-08-13
Abstract: Linseed oil for use in admixture with nitro-cellulose in paints, varnishes, and impregnating compositions, is purified by treatment with 2-3 per cent of dilute sulphuric acid (35-80 per cent) followed by air blowing at room temperature or temperatures up to 150 DEG  C. The blown linseed oil is miscible with nitro-cellulose in any proportion.  In an example, cold-pressed linseed oil is stirred at room temperature with 72 per cent sulphuric acid and allowed to stand over night.  The oil is drawn off from the acid pitch and washed several times with water.  It is then air-blown for 24 hours with air at 100 DEG  C. U.S.A. Specification 2,059,259 is referred to. According to the Specification as open to inspection under Sect. 91, the process is applicable to vegetable or animal drying or semi-drying oils or fats generally.  The strength of the sulphuric acid to be used depends upon the mucin content of the oil, oils with high mucin content requiring acid of about 40 per cent strength and oils of lower mucin content requiring stronger acid. After blowing such acid-treated linseed oil with air to a viscosity of about twice that of ordinary linseed oil, an oil is obtained of light colour and of superior wetting capacity for pigments such as zinc white.  This subject-matter does not appear in the Specification as accepted.ALSO:A composition for use in lacquers or varnishes, and for impregnating and finishing textiles consists of a mixture of nitrocellulose and linseed oil, the latter having been refined by treatment with 2-3 per cent of dilute sulphuric acid (35-80 per cent) and then with air or oxygen at room temperature or temperatures up to 150 DEG  C.  A diluent such as ethyl acetate, ethyl alcohol, or turpentine may be added and siccatives such as lead or cobalt compounds.  The blown linseed oil is miscible with nitrocellulose in any proportion.  In an example, cold-pressed linseed oil is stirred at room temperature with 72 per cent sulphuric acid and allowed to stand overnight.  The oil is drawn off from the acid pitch and washed several times with water.  It is then blown for 24 hours with air at 100 DEG  C.  A solution of Bofors VF2 nitrocellulose paste (12 per cent nitrogen content) in an equal quantity of such oil may be diluted with alcohol or with Swedish sulphate turpentine and a small quantity of ethyl acetate added to make the mixture clear.  In another example, a varnish is made by mixing 35 per cent of the treated oil with 40 per cent of the VF2 paste and 25 per cent ethyl acetate together with a small quantity of cobalt or lead compounds. U.S.A. Specification 2,059,259 is referred to.  According to the Specification as open to inspection under Sect. 91, the strength of the sulphuric acid to be used for purifying linseed or other oils or fats depends upon the mucin content thereof, oil with high mucin content requiring acid of about 40 per cent strength and oils of lower mucin content requiring stronger acid.  After blowing with air to a viscosity about twice that of ordinary linseed oil, an oil is obtained of light colour and of superior wetting capacity for pigments such as zinc white. The refined oil is stated to be suitable for use in the production of alkyd resin and if heated with dibasic acids, such as phthalic anhydride, maleic acid, azelaic acid or sebacic acid, a resin is formed having light colour and quick setting properties.  This subject-matter does not appear in the Specification as accepted.