US2402437A - Lacquer - Google Patents

Description

lated electric wires and, cables.

Patented June 18, 1946 ton, England, assignor to British Insulated Cables Limited, Prescot, Lancashire, England,

a. British company No Drawing. Application December 8, 1944, Se-

rial No. 567,328. In Great Britain January 22, 1944 This invention relates "to lacquers and is more particularly concerned with the production of a lacquer that is suitable for application to insu- For such purposes it is desirable that the lacquer should yield a lacquer film thatmaintains its flexibility over 1 can. (011. 106--171) a wide temperature range, for instance, a range extending from 2 C. to 150 C. The lacquer film should be both hard and tough and should not fuse to adjacent lacquer films under'high operating temperatures. It should also be resistant to hot oil, petrol and water and should have a low co-efllcient of friction that will permit a lacquer co'ated insulated wire or cable to slide easily over similar wires or cables with which I it is in contact. It is the object of my invention to produce an improved lacquer'that will yield lacquer films p s g the aforesaid characteristics to a high degree.

In accordance with the invention my improved lacquer comprises a solution containing ethyl cellulose having an ethoxy content of-from 43.5%

to 46.5% and a viscosity of from 100 to 250 centiing zero to a value approaching 55%, corres ond-L ing to an average value of from nearly 0 to 3 ethyl radicals per glucose unit. The selected range which I employ with the specified proportions of particular plasticisers in order to obtain my' improved heat-resistant lacquers is comparatively narrow, being from 43.5% to 46.5%.

corresponding to an average value of 2.15 to'2.35 ethyl radicals per glucose unit.

As a solvent for the ethyl cellulose and the plasticisers I prefer a mixture of benzene and alcohol (methylated spirit) in which the benzene predominates, the optimum proportion of benzene to alcohol being of the. order of 2 to l.

' If desired acetone may be substituted for a part of the benzene, but this will entail a slight increase in the viscosity of the lacquer.

Examples of compositions of my improved lac-- quers are given in Table I below:

Table I I 11 111. IV

Ethyl cellulose having ethoxy content of I Ki-46.5% .and viscosity of 150 one -.grams-. 10.0 10.0 10.0 10.0 Castor oil (raw or bodied) .do.... 4. 0 6.0 4. 5 5. 0 TransformeroiL do 2.0 2.0 2.2 Y 2.2 Petroleum jelly -do 2. 0 '2. 0 2. 2 2. 2 enzene "cubic centimeters.. 42 42 42 42 Alcohol (methylated spirit) .do 18 18 l8 18 If desired my improved lacquer may incorporate a spirit-soluble dye. The amount of dye used ,is of the order of 0.5% by weight on they ethyl cellulose content of the lacquer. Conveniently it is added as a 1% solution in alcohol, in which.

case the proportion to be used with each of the compositions specified in Table I above is 5 cos.

the lacquers given in Table I, and for purposes of comparison, from a lacquer, designated V, which prior to my invention has been regarded as the most satisfactory for the purpose in view.

Table II Test on fllm I II III IV V Tensile strength .lbs. per sq. in. 2,050 2, 475 2, 650 2, 450 1,050 Percentage elongation at break 55 70 60 Product of tensile strength and elongation X 10-4.... 11. 2 l8. 6 14. 6 l7. 2 6. 3 Shore hardness at 20 C. -93 8886 95-93 93-90 87-85 Shore hardness at C... 45 20 45 42 45 low test pounds 0.25 0.2 0. 3 0. 2 0. 2

Friction test do. l. 0 1.5 l. 5 l. 6 Over 6 The Shore hardness at 20 C. wa measured, applying the durometer by hand, initially and after 30 seconds application. The fiow test consistd in pressing together two films under a pressure of l lb. per square inch for two hours at 150 C. and in measuring the weight necessary o p r e the fi s after cooling to room temperature for one hour. The value recorded is in pounds per One inch width of film. The frictionai properties of the film were assessed byfixing it to a cylindrical metal disc having a diameter of 2.5 inches and a thickness of 0.5 inch I placing the film covered disc on to another film 0t lacquer so that the two films were in contact, and measuring the horizontally applied force in pounds required Just to keep the one film slidin over the other when a 7 lb. weight had been placed on the disc.

Tests on the heat resisting ,cores of 7 mms. diameter lacquered with my improved lacquer showed the lacquer to be very flexible at normal temperatures and to possess ample flexibility at temperatures as low as :35? C., and also after being heated for 100 hours at a temperature of 43.5% to 46.5% and a viscosity of from 100 to 250 centipoises,andtoeachten parts by weight of ethyl cellulose, from 2 to 4 parts by weight of transformer oil, from 2 to 4 parts by weight of petroleum jelly and from 3 to 6 parts by weight of castor oil.

HERBERT STUART N OR'I'I-IWAY.