GB464688A - Improvements in or relating to electrical resistances and to their manufacture - Google Patents

Abstract

464,688. Moulding synthetic resins. ROHM, O. Oct. 21, 1935, No. 29034. Convention date, April 5. [Class 87 (ii)] [Also in Groups XXXVI and XI] In an electric resistance the conductor or conductors is or are embedded in a material comprising one or more solid polymerization products of one or more vinyl, acrylic or homologous compounds. Examples of such compounds are methacrylic acid methyl or ethyl ester, acrylic acid ethyl ester, cynnamic acid esters, vinyl acetate or vinyl chloride and styrene. Resistances may be made for heating or measuring purposes and may be hard and tough or soft and flexible. They may be in the form of sheets, blocks or rods and may be transparent or opaque. The resistance wire 1 may be wound to form a visible pattern if desired. The resistance wire 1 may be wound around spaced porcelain rods 2 and placed in a narrow chamber into which the polymerizable material 3 is poured. The compound is then polymerized and a resistor of plate form having the resistance completely embedded is obtained. Examples of resistances and their manufacture are as follows : (1) a heating filament of nickelin is wound as a plate composed of mica sheets stuck together. and is placed in a chamber into which is introduced a de-aerated solution of 90 parts methacrylic acid methyl ester and 0À02 parts benzoyl peroxide. The vessel is heated for 20-30 hours at a temperature rising from 50-120‹ C. A glass like mass enclosing the resistance is obtained. The solution may however consist of methacrylic acid methyl ester, acrylic acid, butyl ester and ground asbestos with benzoyl peroxide ; (2) Maganin wire is wound on a plate or frame of polymethacrylic acid methyl ester having 10 per cent dibutyl phothalate and is immersed in a solution of polymethacrylic acid methyl ester in the monomeric form. The solution is polymerized as in example (1) and a resistor is obtained in which artificial ageing of the manganin has been effected ; (3) A film of polyacrylic acid methyl ester is wound in narrow coils with a heating wire and then poured over in a bag of viscose foil with a de-aerated partially polymerized solution of aerylic acid methyl ester having a small percentage of turpentine oil and benzoyl peroxide. The mass is heated for 10-20 hours at 50-70‹ C. and a rubber like transparent mass is obtained giving a flexible heater ; (4) A helical wire is stretched centrally through a tube of metal or glass and the tube is filled with a mixture of methacrylic acid methyl ester, acrylic acid ethyl ester, kaolin, and benzoyl peroxide. The mass polymerizes when raised slowly from 50-120‹ C. The product is then removed from the tube. Instead of kaolin, slate powder, soot, &c. may be used. The polymerizible material may be a mixture of methyl methacrylate and butyl acrylate. The esters may also be made by compressing the heating elements with the finished polymerization products in the form of plates, films, powder &c. Specification 436,084, [Group IV], is referred to.