US2328198A - Low electrical resistance paper and method of making same - Google Patents

Description

Patented Aug. 31, 1943 UNITED STATES PATENT OFFICE. 2,328,198 a i I METHOD OF MAKING Franklyn E. Davenport, David C. Knowlton, and

Robert W.

New York No Drawing. Application McCormick, Waterto signors to Knowlton Bros.,

wn, N. Y., asa corporation of April 12, 1939,

Serial No. 267,468

18 Claims.

This invention relates to fibrous materials such as paper or the like having an extremely low electrical resistance to electricityrather than being dielectric or an insulator thereof, and more particularly pertains to the use of fibrous material of this character, when provided with suitable coating sensitive to the passage of electricity, in an apparatus for having reproduced thereon in facsimile marks. characters, designs, pictures or the like which are transmitted by wire orradio.

Finely divided mineral and inert materials and the like have heretofore been used in the manufacture of paper, these materials being used as a filler incorporated in the pulped mass from which the paper is formed or applied as a coating to one or both surfaces of the sheet fabricated from the pulped mass. Or the filling material is incorporated in the pulped mass, and the fabricated filler containing sheet may also be coated with the mineral or inert material containing compound. In whatever way the filling materials have been associated with the sheet. their purpose has been to fill the interstitial spaces within the body of the sheet or those spaces on its surfaces and/or to give color to the sheet. The "filling materials give closer'texture to the sheet, enable it to be more highly finished and color same. Kaolin, talc, clay and the like are the chief filler substances used for loading the paper. Paper made of fiber alone is more or less translucent, the degree of translucency depending on its thickness and on the nature of the fibrous material. Some kinds of fiber are more dense and opaque than others. comes translucency and gives opaqueness and color together with the other mentioned advantages.

It is the aim of the present invention to employ filling material or materials which are very highly conductive toelectricity and to disperse same thoroughly through the body of the fibrous sheet so that said filler containing or loaded fibrous sheet is also very highly conductive to electricity, thereby making said sheet useful where highly conductive sheets are employed and particularly adaptedas a base to which a coatin maybe applied to make the paper suitable for use in an apparatus on which facsimile messages or the like are to be reproduced.

Generally described, the finely divided materials of highly conductive character are intimately dispersed in water to form what may be be very highly conductive to The filling material oversuitable metallic material.

graphitic materials, metals and the like are representative of suitably highly conductive fillers. Paris black, gas-carbon and graphite are representative of carbonaceous and graphitic materials. Aluminum powder is representative of a All of the finely divided materials are electric conductive materials A sheet thus constructed is then treated on one or both sides with any suitable coating sensitive to an electric current and employed for coating sheets which are to be printed by a stylus or styli through which electrical impulses are for reproducing messages and the like on the sheet. That is. the coating has the property of changing color at selected areas where electric current is passed through, thereby contrasting these areas in color with the remaining areas ofthe coating through which the electric current is not passed and causing letters. characters and the like to be formed. The coating is usually white in color. The sheets are particularly adapted for use on what is known as the Finch machine, and other machines which print by electrical impulses on sheets sensitive to electricity. Facsimile to receive the facsimile printing.

The invention is more specifically described by giving one preferred formula which has been found satisfactory in commercial use. formula comprises about one be particularly suitable.

The Paris black is preferably very finely divided so'that same may be thoroughly dispersed called a colloidal solution. carbonaceous and 5 in water. To thoroughly disperse the Paris black I in the water,

" fibrous material,

of the finely divided material throughout the fursubsequently,

through a supercalender. A conventional superthe mixture is agitated. Dispersion may be accelerated by heating the mixture before or during agitation. Any mixer or agitator may be used which can be manipulated to thoroughly disperse the Paris black in water. While there is no limitation as to the time of mixing and agitating or the manner of mixing, 'it has been found that with a high speed motor-driven mixer the Paris black can be sufiiciently dispersed in the water in about fifteen minutes. About fifty gallons (50 gals.) of water may be used advantageously for about thirty-seven and one-half pounds (37 lbs.) of Paris black. Theseproportions are not critical but merely illustrative and may vary with a considerable wide range.

The Paris black and water mixture or colloidal solution is then mixed with the fibrous pulp mate.- rial which is then processed in. any conventional beater commonly employed in the paper industry for beating fibrous stock. The fibrous stock, if desired, may be beaten wholly or partially before the Paris black and water mixture is incorporated therein.

It is important that the Paris black be thoroughly and intimately mixed in and throughout 2.,

the pulped mass, and to obtain a sum'cient intermixture the Paris black is preferably first dispersed in water before being associated with the as more thorough distribution nish stock is obtained. The Paris black is very finely divided and of the character of fine powder or dust.

A size may be added to make the paper less absorbent or porous, to give a good surface and impart the proper degree of stiffness. It fills up the pores between the fibers and gives a finer texture. If a size is used, rosin is preferable and may be added best in the beater.

A small quantity of papermaker's alum or aluminum sulphate is preferably used, particularly if a size is added to'the furnish stock. The dry alum can be put in the beater, but a solution with water is better. The function of the alum is to fix the filler material.

The pulped mass of the composition above described and beaten to the proper consistency is run into a stock chest-or a number of them or tea Jordan or other refining engine if further refining of the furnish stock is desired.

The refined stock is then felted on a conventional paper-making machine of the cylinder or Fourdrinier type and calendered, the calender compressing and ironing the sheet to provide a smooth finish. However, the conventional machine calendering alone, which comprises passing the formed sheet from the paper-making machine between a series of vertically disposed steel rolls, is-not alone sufllcient to give the very high conductivity characteristic to the sheet. The machine calendered sheet is then immediately or after being seasoned, passed calender has a number of polished rolls for giving a higher compression and more finish to the paper than can be obtained by the machine calenders. While the sheet is more highly finished by reason of the supercalendering, it appears that the higher pressure to which the sheet is subjected in the supercalender operation brings the finely divided and thoroughly distributed conductive particles into closer association if not into actual contact, thereby providing a substantially continuous medium for conducting electric current through the body or thickness of the paper.

This higher pressure of the paper beyond the mill or machine compression obtained by the conven- \tional machine calender may for convenient ref- :erence be designated super-compressed and the 3 finish resulting from same as super excellent. Without the pressure exerted by supercalenderi ing, the distributed finely divided and thoroughly 1, distributed particles are more separated from each other by the fibers. Possibly there may be l0 other factors causing or contributing to the quailties and characteristics obtained in the sheet, and thus this view is advanced as a theory rather than a fact. There is the fact that a mechanical operation, such as superoalendcring, gives a paper of the composition above described, its quality of high conductivity to electricity whatever may be the reason for it.

Supercalenders usually comprise seven to eleven rolls, more or less, in a stack, part of the rolls being chilled polished metal and part being cotton or paper rolls. The metal and cotton or paper rolls may or may not be alternately disposed.

The supercalendered sheet is manufactured and sold as an article of manufacture, and while it base sheet which is to be coated on one or both sides with any suitable coating which is sensitive to electricity, thereby being adapted to have electrically reproduced thereon messages and the like which are transmitted by wire or radio. The.

invention is not limited to any particular coating material. Any which is adapted to be changed in color by an electric current is suitable.

The base sheet is very thin, preferably from inch. The electrical resistance of a paper thus fabricated when measured on a Wheatstone bridge at six volts between contacts of weight of about '300' grams and an area *of about 3.546 40 square inches is less than one thousand (1000) ohms, although the invention i's'not thus limited. The area is that of a circle resulting from a diameter of about 2 /8 inches. A suitable sheet may be as high or higher than ten thousand (10,000) ohms.

Paris black is jet black in color, and the fabricated sheet, if Paris black is used as the filling material, is black. While Paris black is-preier able, other filling materials of the same general character, except as to color, would be suitable. Finely divided metals are suitable but are, of course, more expensive than Paris black. Finely divided material having a high carbon content is especially suitable. The finely divided materials which are suitable are those highly conductive to electricity. Thus, suitable filling materials are.

determined by their quality of being highly conductive to electricity rather than as to kind.

They should also be capable of ready dispersion in water.

While one particular formula has been described in detail for carrying out the invention, and a particular use for the sheet has been referred to, it will be understood that there may be changes in details of composition and manufacture without departing from the spirit of the invention, and that the sheet may have other uses where a sheet having a high conductivity quality is desired.

Having described our invention, we claim:

1. A paper of low resistance to electricity formed from a furnish stock composed of refined fibrous material and finely divided electrical conductive material of the first class intimately com- 75 mingled in proportions, by weight, of approxir may have other uses it is especially suitable as a three to four thousandths (.003 to .004) of an mately six and two-thirds times as much refined fibrous material as conductive material and compressed more highly and given more finish than obtained by a machine calender to render said paper highly conductive to electricity.

2. A paper of low resistance to electricity formed from a furnish stock composed of refined fibrous material and finely divided carbonaceous material intimately commingled in proportions, by weight, or approximately six and two-thirds times as much refined fibrous material as conductive material and compressed more highly and given more finish than obtained by a machine calender to render ductive to electricity.

3. A paper of low resistance to electricity formed from a furnish stock composed of refined fibrous-material and finely divided material of a high carbon content intimately commingled in proportions, by weight, of approximately six and two-thirds times as much refined fibrous material as conductive material and compressed more highly and given more finish than obtained by a machine calender to render said paper highly conductive to electricity.

4. A paper of low resistance to electricity formed from a furnish stock composed of refined fibrous material and finely divided electrical conductive material of the first class intimately commingled and supercalendered -to render said paper highly conductive to electricity.

5. A facsimile recording paper through which electricity is adapted to be passed and which is of low resistance to electricity formed from a furnish stock composed of refined fibrous mate rial and finely divided electrical conductive material oi' the first class intimately commingled in proportions, by weight, of approximately six and two-thirds times as much refined fibrous material as conductive material and compressed more highly and given more finish than obtained by a machine calender to render; said paper highly conductive to electricity, and a coating on the paper which is sensitive to electric current for being changed in color when electricity is passed through the paper.

6. A facsimile recording paper throughwhich electricity is adapted to be passed and which is of low resistance to electricity formed from a' furnish stock composed of refined fibrous material and finely divided carbonaceous material intimately commingled in proportions, by weight, of approximately six and two-thirds times as much refined fibrous material as conductive material and compressed more highly and given more finish than obtained by a machine calender to render said paper highly conductive to electricity, and a coating on the paper which is sensitive to electric current for being changed in color when electricity is passed through the paper.

LA facsimile recording paper through which electricity is adapted to be passed and which is of low resistance to electricity formed from a furnish stock composed of refined fibrous material and finely divided material of a high carbon content intimately commingled in proportions, by weight, of approximately six and two-thirds times as much refined fibrous material as conductive material and compressed more highly and given more finish than obtained by a machine calender to render said paper highly conductive to electricity, and a coating on'the paper which is sensitive to electric current for being changed said paper highly con-' commingling the solution 1 material of the first class, intimately commingling in color when electricity is passed through the paper. 1

8. A facsimile recording paper through which electricity is adapted to be passed and which is of low resistance to electricity formed from a furnish stock composed of refined fibrous mate- ,rial and finely divided electrical conductive material of the first class intimately commingled and supercalendered to render said paper highly conductive to electricity, and a coating on the paper to electric current for being when electricity is passed area of a circle resulting from a diameter-of about two'and one-eighth (2%) inches.-

10. A facsimile recording paper through which electricity is adapted to be passed and which is of low resistance to electricity formed in thickness from about three to four thousandths of an inch from a furnish stock comprising about one thousand (1000) pounds of refined fibrous material and about one hundred and fifty pounds of Paris black intimately commingled and supercalendered to provide an electrical resistance not substantially exceeding ten thousand (10,000) ohms measured over the area of a circle resulting from a diameter or about two and one-eight (2%) inches, and a coating on the paper which is sensitive to electric current for being changed in color when electricity is passed through the paper.

- 11. A method of fabricating a paper of low resistance to electricity comprising forming a colloidal solution of water and finely divided electrically conductive material of the first class, intimately commingling the solution with a furnish stock of fibrous pulp, felting the furnish stock into a sheet, calendering and supercalendering the felted sheet.

12. A method of fabricating a paper of low resistance to electricity comprising forming a colloidal solution of water and finely divided material having a high carbon content, intimately with a furnish stock of fibrous pulp, felting the furnish stock into a sheet, calendering 1 and supercalendering the felted sheet.

13. A method of fabricating a facsimile recording paper throughwhich electricity is adapted to be passed and which is of low resistance .to electricity comprising forming a colloidal solution of water and finely divided electrically conductive the solution with a furnish stock of fibrous pulp, felting the furnish stock into a sheet, calendering and supercalendering the felted sheet, and coating the supercalendered sheet with a coating whichis sensitive to electric current for being changed in color when electricity is passed through the sheet.

14. A method of fabricating a facsimile recording paper through which electricity is adapted to be passed and which is of low resistance to electricity comprising forming a colloidal solution of water and finely divided material having a high carbon content, intimately commingling the solu-- 15. A'method of fabricating a paper of low resistance to electricity comprising rapidly agitating finely divided particles of electricity conducting material of the first class with water to inti mately commingle same, mixing the aqueous mixture with a refined furnish stock of fibrous material, felting a sheet from the furnish stock, calendering and supercalendering the sheet to compress same and bring the conductive particles in close association.

16. A method of fabricating a paper of low resistance to electricity comprising rapidly agitat ing finely divided particles of electricity conduct-r ing material of the first class with water, in pro portions of about thirty-seven (37) pounds of the finely divided material to fifty (50) gallons of water, to intimately commingle same, mixing the aqueous mixture with a refined furnish stock or fibrous material, felting a sheet from the furnish stock, calendering and supercalendering the sheet to compress same and bring the conductive particles in close association.

17. A paper 01 low resistance to electricity formed irom a furnish stock composed of refined fibrous material and an aqueous colloidal solution 01 finely divided electrical conductive material o! the first class intimately commingled and supercalendered to render said paper highly conductive to electricity.

18. A paper of low resistance to electricity formed Irom a furnish stock composed of refined fibrous material and an aqueous colloidal solution of finely divided electrical conductive material of the first class intimately commingled and supercalendered to render said paper highly conductive to electricity, and a coating on the paper which is sensitive to electrical current for bein changed in color when electricity is passed through the paper.

RioBmT W. MCCORMICK. DAVID C. mtown'rou. mamim s. DAVENPORT.