USRE22893E - Manufacture of an improved - Google Patents

Description

Reissued June 24, 1947 MENHFKC'BURE OF AN IMPROVED VITREQUS MATERIAL Albert. William. Henry Wedlock,.Cinencester, Eng-- land, assignor, by mesne assignments, to Mycalex Corporation of America, New York,

Ni Y:, a corporation of NewYorl'r' No. Drawing. Original N 0. 2,032,239, dated February 25, 1936, Serial No. 25,964, June 10, 1935.

Application. for reissue May 4", 1944, Serial No.

534,1fi8.. In Great Britain ctolier26; 1933 4 Claims.

'I'hi'szinvention relates to: animproved vitreous material and a. method of? manufacturing; the

same,.the' objectof the inventiombeing toeproduce I a vitreous material. which. apart from having: high dl -e'lectrict properties possessesin an unusual degree the. quality of. adhesionto metal, especially those metals that are largely'usediin the-mechane ical arts such as inter alia steel and cast iron, aluminium, bronze -an'dgunmetal. Moreover the materiallis capable of being moulded, pressed and rolled; and accordingly has the. widest possible fi'eld of application for electrical, mechanical" and physical apparatuse.

Amongst the many applications to which the material lends itself is the manufacture of high pressure gas seals,.for the leading-in insulators for high electric frequency mercury converters and allied purposes wherein high quality insulation and fluid tightness is possible between a central metal electrode, the vitreous material itself and an outer retaining metal part.

According to the invention an improved vitreous material capable of adhesion to metallic surfaces is provided consisting of an admixture of mica and/or asbestos with dried and finely ground ceramic materials including a proportion of cryolite and alkaline carbonates.

The invention also consists in a method of manufacturing an improved vitreous material capable of adhesion to metallic surfaces comprising the step of admixing mica and/or asbestos with dried and finely ground ceramic materials including a proportion of cryolite and alkaline carbonates.

The preferred manner of practicing the invention utilizes ceramic materials which consist of the following ingredients, the proportions thereof being by weight:

Per cent Cryolite (3NaF,AlF3) Barium carbonate (BaCOa) 10 Potassium carbonate (K2003) 13 Soda ash (NazCOa) 9 Boric acid (H3303) 48 These materials are ground to a fine powder and then carefully admixed and then passed through a drying furnace at 500 C. until the moisture of crystallization has been driven off, without producing fusion or vitrification leaving a white glass frit with a gravity loss of approximately The frit, thus produced is then ground to a fine powder to pass 120 x 120 mesh per square inch.

This forms a partial reaction product containin 320: (boron oxide) combined with the oxides 2 andifiuorides ofi the? metals involved in. the reaction; The partialmea'ctionaproduct-is now: incondition for incorporation with. the other constituents; of. the; final: composition;

The mica product is ground: to: an: e'qual'fineness and then. 410% by weight of. frit: is. addedi to by weight of mica the whole" being: compounded in;atmixingtmachine,.8:% of water being added to the mixture: as at spray: ormist:

The: damped? admixture is. then: subjected to cold. pressing, the moisture. present being just sufiicient to causeabin'ding' without adhesion to the; mold, and ifsthe mica priorito mixing be not sufliciently dry a slightly less: addition of' water is employecla- In this connection itis: preferable notrto dry: the mica or asbestosunless under temperature control to avoid crystal degradation. As micas vary in this respect, the point of breakdown should be found empirically arid the furnace drying levels set below this figure. The pressure employed is approximately 1% tons per square inch and this pressure is maintained for at least ten minutes. The billets produced from pressing require no intermediate drying, but are inserted as blocks, scales or thick plates into the furnace within which they are progressively heated to 620 C. or thereabouts, the period of heat soak depending upon the thickness of the billet used, and the heat level being such that plasticity shall have set in. The material from the furnace is then used for molding, the parts or molds to receive the material being treated and the material fed from the furnace to the press, with the least possible delay. Pressings should remain in the mold under pressure, as the material in cooling tends to swell, this feature enabling a hermetic seal to be produced between metal parts and the material itself.

The property of metallic adhesion of the finished material even when made in slabs or blocks is very pronounced. Thus a block of finished material made according to this invention may have a layer of metal such as aluminum cast upon its surface, and the metal and materials upon cooling are inseparable and can be tooled, sawn or otherwise worked together without the one material becoming detached from the other.

The di-electric properties of the vitreous material hereunder produced are good, and it also possesses in high degree resistance to shock; to a is to be broadly construed and not to be limited except by the character of the claims appended hereto. i

What is claimed is:

1. An insulating material consisting of a mixture of mica with a frit which is a product resulting from heating a mixture of finely powdered boric acid and alkaline carbonates to a sufficiently high temperature to drive off the water of crystallization to produce a frit, said heated mixture containing cryolite.

2. A method of making molded compositions which consists in providing a mixture of mica with a frit which is a product resulting from heating a mixture of finely powdered boric acid and alkaline carbonates to a sufficiently high temperature to drive off the water of crystallization to produce a frit, said heated mixture containing cryolite, subjecting the same to a temperature at which plasticity sets in, placing the same in a mold, and pressing said mixture.

3; A method of making molded compositions which consists in providing a mixture of mica with a frit which is a product resulting from heating a mixture of finely powdered boric acid and alkaline carbonates to a sufiiciently high temperature to drive ofi the water of crystallization to produce a irit, said heated mixture containing cryolite, subjecting the same to a temperature at which plasticity sets in, placing the same in a mold, and pressing said mixture, and cooling said molded composition while maintaining pressure thereon.

4. A method of making molded compositions which consists in providing a mixture of mica with a frit which is a reaction product resulting from heating a. mixture of finely powdered boric acid and alkaline carbonates with cryolite to a sufliciently high temperature to drive off the water of crystallization to produce a frit, heating the same to render said mixture plastic, then placing the same in a mold, subjecting the same to pressure to form said mixture into the desired shape, and cooling the same under pressure.

1 ALBERT WILLIAM HENRY WEDLOCK.

REFERENCES CITED The following references are of record in the ,file of this patent:

UNITED STATES PATENTS Number Name Date 2,136,877 Delpech Nov. 15, 1938 2,303,244 Wedlock Nov. 24, 1942 Re. 15,727 Crossley Dec. 4, 1923 1,394,973 Crossley Oct. 25, 1921 1,795,200 Crossley Mar. 3, 1931 2,032,239 Wedlock Feb. 25, 1936 FOREIGN PATENTS Number Country Date 113,397 Australia 1941 OTHER REFERENCES Andrews: Enamels (1935), page 206. Shaw: The Chemistry of Pottery (1900), page 470.