US1597168A - Electric insulation board and method of making same - Google Patents

Description

Patented Aug. 24, 1926.

UNITED STATES ELECTRIC INSULATION BOARD AND METHOD OF MAKING SAME.

' Io Drawing.

M invention has reference to electricinsu ation boards and bodies, and is in the nature of an improvement upon or a carrying forward of that set forth and claimed in an application filed in my name on the 6th day 'of November, 1923, and designated by Serial Number 673,221 which became Patent 1,554,895.

Underrthis as under the prior invention, a board, sheet or body is formed of pulp or cellulose, combined with-gilsonite, asphaltum, mineral pitch, elaterite, resin, or other usual binder, which board or body is dried to a suitable degree, and is then given a thin coating of some substance which will prevent the board or body from adhering to the contacting surfaces of a press or mold in which it is subjected to final compression in the presence of heat. vent adherence to other sheets or surfaces after completion, such coating combining with the bodyof the sheet or board under the final pressure and heat, and ensuring a smooth, 'firm surface, devoid of tackiness and capable of being buffed, sandpapered, or otherwise finished after the manner of finishingother hard surfaces.

Under the procedure of the prior invention, cellulose acetate varnish or lacquer was used for such coating, and with very satis-' factory results in the main; but cellulose acetate is relatively expensive and adds materially to the cost of the product, and though producing a quite good surface, does not give the best obtainable results in that regard, or does not produce the kind of surface generally deemed most desirable for such insulating boards or bodies. I have found that a. varnish or lacquer of acaroid-resin dissolved in alcohol, in the proportion of about two pounds of resin to one allon of alcohol may be used in lieu of t e cellulose acetate varnish or lacquer, with excellent results as to the final product, and at materially lower cost. The present invention hence resides in the use or employment of such acaroid resin varnish or lacquer in the place of a varnish or lacquer of cellulose acetate, in the rocess of manufacture of insulation board; or bodies.

Better to identify the resin employed and above referred to as acaroid resin. it may be stated that it is also or commercial names: Gum Acroides, Red

Acaroid Resin, Yacca Gum, and Grass Tree It also serves to preknown by the trade" Application filed August 4, 1924. Serial No. 730,022.

Gum. Its botanical names are: Kan-thorrlzoea australz's, Xantiwrrhoea quadrangu- Zaris, anthom'hoea drumflwndz'i, and Xanthorrh'oea prez'sz'i. There is also another grade of acaroid resin known as Xantlzorrhoea kastz'lz's, and quite commonly called Botany Bay Gum. It is likewise sometimes known as Black-boy Gum. 'lVhile there are slight variations'in or differences between certain of-the gums known under the several names above given, they are essentially alike in character and properties, and all are found serviceable as a coating for thesheet, slab or body after formation and partial drying.

The process of manufacture of the improved board may be briefiy'stated as follows:

A pulp composition consisting essentially of cellulose of usual character combined with a suitable binder as mineral pitch, elaterite, resin, or other, is formed into a sheet, slab or body in any common'and well-known way, and 'a large percentage of the liquid or moisture is then removed therefrom, preferably through pressure applied in a mold or press of suitable form or construction.

I Preparatory to the final compression necessary to secure the requisite density, there is,applied to the sheet, slab or body by dipping, spraying, brushing, or otherwise, a thin coating or layer of varnish or lacquer composed of acaroid resin dissolved in alcohol or other known suitable solvent thereof, in the proportion of ap roximately two (2) pounds of resin to one 1) gallon of alcohol.

The alcohol may be denatured thoughthis is not necessary. The amount of resin used in the varnish or lacquer should not materially exceed two pounds per gallon of solvent, as stickiness is likely to result, and it is further apt to cause a brittleness of the film or coating and a cracking or crazing thereof.

The sheet, slab or body having been thus coated on its several faces, or on any face or faces desired, is next subjected to heavy compression, preferably in a hydraulic press, and at the same time subjected to heat. For this purpose it is customary to employ presses having a hollow bed, hollow platen, or both, and to supply the chambered memberor members with steam or other heating medium. After compression as reached the gilsonite, asphaltum,

proper point or degree, and as been con tinned for a time sufiicientto givethe required density and set the sheet, slab or body permanently, the temperature is lowered,

and the body treated isccooled. This gradual cooling serves to prevent cracking, checking or crazing of the finished surface, and leaves it smooth and unbroken throughout. Under the pressure andheat the var- I nish or lacquer coating enters into and unites or combines with the-cellulose body, and be- I comes an integral part thereof.

Any desired color may be imparted to the varnishor lacquer prior to its application toY-thesh'eet, slab or body, by incorporating therein and thoroughly distributing through the same, a suitable pigment or pigments.

If it be desired to render the sheet, slab or body more or less pliable or flexible, a suitable softening agent or agents such as methyl ester of paratoluelsulphoneamide, triphenyl phosphate, triacetin, or the like, may be added to the varnish or lacquer employed. Care should be taken to avoid excess of such agent, since an undue quantity begets efliorescence on the surface of the product.

Except as herein described theprocess may be the same as that set forth in my application above mentioned, with the single highly polished surface, a flat finish, or what is commonly termed an egg shell finish.

The di-electric properties of the'finished product are in no manner or degree impaired through the utilization of the varnish or lacquer having the acaroid resin base, and said roduct may be safely used as a panel board or base for electrical appliances requiring a high degree of electric insulation. It can be drilled, cut, and machined with the facility of and in practically the same manner as indurated fiber, hard rubber, and other like bodies.

The foregoing sets forth the preferred mode of procedure, but the acaroid; resin may be incorporated in the cellulose or pulp composition by dissolving it in caustic soda and precipitating it with alum in conjunction with gum resin, oil soaps, asphalt, and other well-known binders, but 'in all, other respects the rocedure will be as first above described. oatin with the lacquer or varnish as .contradistmguished from incorporating the acaroid resin in the pulp mass is, however, the. preferred procedure.

What is claimed is 1 The herein described method of producing an electro-insulation sheet, slab or body, which consists in forming the same of a pulp composed of cellulose and a suitable binder; removing a large percentage of the liquid or moisture contents therefrom; coating the same on its exterior with a lacquer or varnish of acaroid resin dissolved in alcohol; subjecting said body'to high compression in the presence of heat and maintaining such pressure and heat until the acaroid resin combines with the binder of the cellulose body and the body becomes dense and set; and finally cooling the same while still under pressure.

2. As a step in the manufacture of electrio-insulation boards or bodies, the application to the surface thereof and prior to complete drying of the board or body, ofa lacquer or varnish consisting of acaroid resin and a suitable solvent, preparatory to final compression in the presence of heat, the resin so supplied serving to prevent adhesion of the finished product to the surfaces of the mold or press in which such final compression takes place, or to bodies with which it may subsequently come into contact.

3. The method of finishing electric-insulation sheets, boards and bodies formed of pulp composed of cellulose and a suitable binder, which consists in incorporating in the surfacethereof after the same is'shaped and deprived of the bulk' of its moisture content, acaroid resin; subjecting the body so prepared to heavy compression in the presence of heat; and finally cooling the body while still held under com ression.

4. As a new article of manu acture, an electric-insulation sheet, board or body having a smooth even surface produced by incorporating therein and uniting or combining therewith, acaroid resin.

5..As a new article of manufacture, an

electric-insulation sheet, board or body hav-- ing a surface impregnated with acaroid resin united or combined with the cellulose base and its binder through high compression in the presence of heat.

6. As a new article of manufacture, an electric-insulation board, sheet or body composed of cellulose and a binder such as described, and having its surface impregnated .with acaroid resin, combined with said binder and deprived of stickiness or tackiness through compression and heat.

7. An electric-insulation sheet, slab, or body formed of cellulose and a suitable binder, and having acaroid resin incorporated and bound in its surface.

In testimony whereof I have signed my f