US2736080A - walker etal - Google Patents

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US2736080A
US2736080A US2736080DA US2736080A US 2736080 A US2736080 A US 2736080A US 2736080D A US2736080D A US 2736080DA US 2736080 A US2736080 A US 2736080A
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/02—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances
    • H01B3/08—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of inorganic substances quartz; glass; glass wool; slag wool; vitreous enamels
    • H01B3/085—Particles bound with glass
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
    • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
    • H01B3/185—Substances or derivates of cellulose
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/002—Details
    • H01G4/018—Dielectrics
    • H01G4/20—Dielectrics using combinations of dielectrics from more than one of groups H01G4/02 - H01G4/06

Definitions

  • thin means of a thickness comparable with that of cellulose paper.
  • cellulose paper paper made from cellulose pulp, such as Wood pulp or pulp made from cotton or linen rag or natural fibres, such as cotton or manilla, or mixtures of any of these materials.
  • the first stage of the manufacture is to produce a cellulose paper loaded with the powder to a high degree, for instance to 90% or 95% by weight, and having an appropriate thickness, for instance mils (.13 mm.).
  • This stage is preferably finished by rolling or pressing so as to obtain as dense a paper as possible.
  • the paper is heated so as to burn oil the other ingredients of the paper and is continued until the powder is brought to the temperature at which it sinters to form a sheet of strongly coherent material.
  • This sheet is of substantially uniform thickness.
  • the limit of thinness is determined mainly by the capacity to produce sufiiciently thin paper.
  • the material in the final form is generally rigid so that any shaping required is preferably done while the material is still in the form of paper. In many cases flat sheets will be required.
  • the method imposes certain limitations on the choice of materials to which it can be applied, particularly as to their properties over a large range of temperature. They should be stable and unaffected by heat at the temperature at which the other ingredients of the paper are driven on and should then be capable of being softened and sintered at a substantially higher temperature. Suitable materials are, for instance, ceramic materials and glass. Small quantities of flux may be added to assist sintering.
  • the remainder of the paper is preferably substantially Wholly cellulose fibres and small quantities of binders which are commonly employed in the paper industry such as starch, dextrine or gelatine.
  • the paper may be made in known manner, preferably beating the cellulose fibres to the high degree appropriate for the making of very thin paper, such as condenser tissue. In the later stages the powdered substance is added and beaten thoroughly with the cellulose fibres. The web of paper is then taken up in the usual way, dried and preferably callendered. 1
  • the heating takes place in two stages at substantially different temperatures.
  • the conditions are oxidising so that combustion of the cellulose can take place.
  • the conditions are determined by the naturepof the material and theproperties which it is desired that the finishedproduct shall have.
  • Example I The first stage is the preparation of a paper loaded with barium titanate. This is carried out by mixing together a cellulose pulp, such as is used in paper making, with barium titanate and a small quantity of bentonite. The ingredients are used inthe following proportions by weight: 7 1
  • Cellulose pulp (solid content) 1 Bentonite l Barium titanate 98
  • the slurry so obtained is spread into sheets, dried and rolled by a normal paper making process to produce thin sheets resembling paper.
  • the final pressure applied may be of the order of 10 tons per'square inch.
  • the sheets thus obtained are arranged between flat zircon plates and fired.
  • Four sheets for-example may be stacked between one pair of zircon plates.
  • the best firing temperature is 1305 C. although this may be varied from 1280-l330 C.
  • the total firing time is three hours including a period of /2 hour during which the cellulose is burnt out, the temperature rising from 20 C. to 500 C., afurther period of /2 hour during which the temperature rises to and is held at the sintering temperature and a period of 2 hours for cooling.
  • cellulose pulp For making small quantities of the sheet material described in the example, it is possible to obtain the cellulose pulp by breaking down paper.
  • a suitable pulp can be obtained by milling 1 gm. of capacitor tissue with 100 cc. of distilled water for four hours in a plane-
  • the ingredients used, in proportions by weight are:
  • Example III In this example the ingredients used, in proportions by weight are:
  • the method of manufacture has been referred to particularly in connection with the preparation of dielectric bodies for capacitors, it is to be understood that it may also be used for the preparation of materials for other purposes.
  • the applicability of the method in such cases will be recognised by a consideration of the nature of thematerials to be used and the form of the final product required. It is only necessary that the material will withstand the heat necessary to destroy the cellulose and will itself sinter to form a thin plate.
  • the method is applicable to the manufacture of thin sheets or plates from powdered glass alone or mixed with dielectric ceramic materials (particularly ceramic materials with high dielectric constants), powdered metals, for example tantalum, aluminium and titanium, silicon carbide and mixtures of carbon, silica and/ or silicates.
  • the mixtures of carbon, silica and/ or silicates are useful in the manufacture of electrical resistors.
  • the carbon itself does not sinter but becomes incorporated in the ceramic material produced by the sintering of the silicon and/or silicates present.
  • Silicon carbide is used when resistors in which resistance varies with voltage or current are required. When materials are used which are liable to oxidise at the sintering temperature precautions are taken to exclude oxygen during the latter part of the heat treatment.
  • the capacitor shown in Figure l is a stack type made up of a number of plates 1 of a material of the kind described in the examples. Each plate is formed on both S1dCS W1th metallised layers in accordance with normal practice, the layer 2 on the upper surface extending over one end of the plate and onto the lower side and the layer 3 on the lower side extending over the M 16 l fil 3 d the upper side, as shown. Metal connecting wires 4 and 5 are soldered to the ends of the stack.
  • Figure 2 shows a single plate capacitor consisting of a circular plate 6 of a material manufactured in accordance with one of the examples provided with metallised layers on its upper and lower surfaces.
  • the layer 7 on the upper surface has soldered to it a connecting wire 8.
  • a similar wire 9 is soldered to the lower metallised layer.
  • an aqueous dispersion 10 of cellulose fibres and a powdered material, formed by a heating process is contained in a vessel through which a continuous gauze 11, of the kind used in paper making, passes round a roller 12 in a clockwise direction.
  • the gauze passes from the dispersion beneath the heater 13 and over a tray 14 which is evacuated by a pump 15.
  • the gauze As the gauze rises from the surface of the dispersion 10, it picks up a layer 16 which is carried over the tray 14 and beneath the heater 13 and is dried sufiiciently to make it into a self-supporting sheet.
  • the sheet 17 is lifted continuously from the gauze 11 and passes between at least one pair of calender rolls 18, 19. During passage through these rolls it is compressed to the re-- quired thickness and density. From the rolls the sheet passes on to a conveyor 20 which carries it through a cut ting machine 21 Where it is reduced to the required shapes for example discs.
  • discs 22 are shown issuing from the machine 21. These are placed by hand into ceramic dishes 23 which are fed successively into a firing kiln: 24. In the kiln the discs are fired in the manner described in the examples. If desired, the discs, before firing, can be arranged between fiat zircon plates which are not afiected by the temperatures reached in the firing kiln.
  • Both forms of capacitor are provided with a protective layer of insulating wax or varnish.
  • a method of manufacturing a thin, strongly co-- herent electrically insulating sheet from a ceramic powder which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least by weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, consolidating said sheet by the application of pressure and heating said sheet under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
  • a method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, selected from the group consisting of titanium dioxide and metallic titanate powders with or without small quantities of additives which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a heating process, taking up a thin layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least 95% by Weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, self supporting, removing said layer as a sheet from said support, consolidating said sheet by the application of pressure and heating said sheet under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
  • a method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, selected from the group consisting of titanium dioxide drying said layer until it is and metallic titanate powders with or without small quantities of additives which comprises preparing a suspension of cellulose fibers, bentonite and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than about mils thickness on a pervious support, the relative proportions of said ingredients of said suspension being such that the solid content by weight of said layer is cellulose /2-2%, bentonite /2--1% and ceramic powder 99-97%, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, consolidating said sheet by the application of pressure and heating said sheet under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
  • a method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least 95% by Weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, stacking a plurality of said sheets, consolidating said stacked sheets by the application of pressure and heating under oxidising conditions first to burn 01f the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
  • a method of manufacturing a thin, strongly coherent electrically insulating sheet made from a ceramic powder, selected from the group consisting of titanium dioxide and metallic titanate powders with or without small quantities of additives which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least 95% by weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support,
  • a method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, selected from the group consisting of titanium dioxide and metallic titanate powders with or without small quantities of additives which comprises preparing a suspension of cellulose fibers, bentonite and said powder in an aqueous liquid by a heating process, taking up a layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of said ingredients of said suspension being such that the solid content of weight of said layer is cellulose /z--2%, bentonite /21% and ceramic powder 99-97%, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, stacking a plurality of said sheets, consolidating said stacked sheets by the application of pressure and heating under oxidising conditions first to burn oil? the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
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Description

Feb. 28, 1956 H. WALKER ET AL 7 2,736,080
MANUFACTURE OF THIN SHEETS OR PLATES OF HEAT-TREATED MATERIAL SUITABLE FOR THE DIELECTRICS OF CAPACITORS AND FOR OTHER PURPOSES Filed Feb. 28, 1951 2 Sheets-Sheet 1 Inuenlor: l/erer-f Waller 4;"! 7' F Ste/r y JIM; MvM
Attorney;
Feb. 28, 1956 H, WALKER ET AL 2,736,080
MANUFACTURE OF THIN SHEETS 0R PLATES 0F HEAT-TREATED MATERIAL SUITABLE FOR THE DIELECTRICS OF CAPACITORS AND FOR OTHER PURPOSES Filed Feb. 28, 1951 2 Sheets-Sheet 2 I nventors HM wallhw A ttorney United States Patent ice ,gented flifilfifl MANUFACTURE OF THIN SHEETS OR PLATES OF HEAT-TREATED MATERIAL SUITABLE FOR THE DIELECTRICS OF CAPACITORS ALJD FOR OTHER PURPOSES Herbert Walker and Tzu En Sheri, London, England, assignors to British Dielectric Research Limited, Loan, don, England, a British company Application February 28, 1951, Serial No. 213,107 Claims priority, application Great Britain March 9, 1950 6 Claims. ((331.25-156} In the manufacture of sheets or plates of material suitable for the dielectrics of capacitors the attainment of small thickness is obviously important. It is also difficult of attainment with materials which in the early stages of manufacture are in the form of powder given cohesion by appropriate means. Such materials are not readily made to flow into thin layers by moulding, pressing, or rolling unless excessive quantities of other materials are added. These additions have disadvantageous results, either in later stages of manufacture or in the final product. Such materials if they can be formed into thin plates are usually very fragile and difiicult to handle in later stages of the manufacture. Materials to which these comments apply are ceramic bodies, such as titanium dioxide (rutile) and titanates of barium and strontium and of other elements. The present invention provides a new method of manufacturing thin sheets or plates from such materials in which the limitations indicated above are not present.
The term thin as used herein means of a thickness comparable with that of cellulose paper.
By cellulose paper is meant paper made from cellulose pulp, such as Wood pulp or pulp made from cotton or linen rag or natural fibres, such as cotton or manilla, or mixtures of any of these materials.
The first stage of the manufacture is to produce a cellulose paper loaded with the powder to a high degree, for instance to 90% or 95% by weight, and having an appropriate thickness, for instance mils (.13 mm.). This stage is preferably finished by rolling or pressing so as to obtain as dense a paper as possible. In the next stage the paper is heated so as to burn oil the other ingredients of the paper and is continued until the powder is brought to the temperature at which it sinters to form a sheet of strongly coherent material.
This sheet is of substantially uniform thickness. The limit of thinness is determined mainly by the capacity to produce sufiiciently thin paper. The material in the final form is generally rigid so that any shaping required is preferably done while the material is still in the form of paper. In many cases flat sheets will be required.
It will be seen that the method imposes certain limitations on the choice of materials to which it can be applied, particularly as to their properties over a large range of temperature. They should be stable and unaffected by heat at the temperature at which the other ingredients of the paper are driven on and should then be capable of being softened and sintered at a substantially higher temperature. Suitable materials are, for instance, ceramic materials and glass. Small quantities of flux may be added to assist sintering.
The remainder of the paper is preferably substantially Wholly cellulose fibres and small quantities of binders which are commonly employed in the paper industry such as starch, dextrine or gelatine. The paper may be made in known manner, preferably beating the cellulose fibres to the high degree appropriate for the making of very thin paper, such as condenser tissue. In the later stages the powdered substance is added and beaten thoroughly with the cellulose fibres. The web of paper is then taken up in the usual way, dried and preferably callendered. 1
As already indicated the heating takes place in two stages at substantially different temperatures. In the first the conditions are oxidising so that combustion of the cellulose can take place. In the latter stage the conditions are determined by the naturepof the material and theproperties which it is desired that the finishedproduct shall have.
In order to give the finished plates or sheets the desired form, it may be necessary or advantageous to hold the paper between' shaping surfaces during the heat treatment. The attainment of a flat sheet can be assisted by ensuring uniformity of the thickness and structure of the paper and of the heat treatment as far as possible. It may be further ensured by placing the paper between flat plates for the heat treatment.
The following are examples of methods of manufacture in accordance with the invention. These ex-- amples describe the manufacture of sheet materials of high dielectric constant, suitable for use as capacitor dielectrics.
Example I The first stage is the preparation of a paper loaded with barium titanate. This is carried out by mixing together a cellulose pulp, such as is used in paper making, with barium titanate and a small quantity of bentonite. The ingredients are used inthe following proportions by weight: 7 1
Cellulose pulp (solid content) 1 Bentonite l Barium titanate 98 The slurry so obtained is spread into sheets, dried and rolled by a normal paper making process to produce thin sheets resembling paper. The final pressure applied may be of the order of 10 tons per'square inch.
The sheets thus obtained are arranged between flat zircon plates and fired. Four sheets for-example may be stacked between one pair of zircon plates. The best firing temperature is 1305 C. although this may be varied from 1280-l330 C.
The total firing time is three hours including a period of /2 hour during which the cellulose is burnt out, the temperature rising from 20 C. to 500 C., afurther period of /2 hour during which the temperature rises to and is held at the sintering temperature and a period of 2 hours for cooling. l i
The proportion of ingredients given above can be varied between the following limits:
- Percent Cellulose /2*-2- Bentonite /z--l Barium titanate 99.97
In all cases a strongly coherent sheet having a dielectric constant between 1,000 and 2,000 at room temperature is obtained. If higher proportions of cellulose are used the sheet-obtained is liable to be too porous for use as a capacitor dielectric. If less than /2 of celluloseis used the loaded paper is too weak to handle. It is preferred to use 1% of cellulose.
For making small quantities of the sheet material described in the example, it is possible to obtain the cellulose pulp by breaking down paper. For example, a suitable pulp can be obtained by milling 1 gm. of capacitor tissue with 100 cc. of distilled water for four hours in a plane- In this example the ingredients used, in proportions by weight are:
Cellulose pulp (solid content) 1 Bentonite 1 Titanium dioxide 98 the same process as described in Example I is used but the firing temperature is 1450 C. The firing times are the same.
Example III In this example the ingredients used, in proportions by weight are:
Cellulose pulp (solid content) l Bentonite 1 Magnesium titanate 98 the same process as described in-Example I is used but the firing temperature is 1400 C. The firing times are the same.
Although the method of manufacture has been referred to particularly in connection with the preparation of dielectric bodies for capacitors, it is to be understood that it may also be used for the preparation of materials for other purposes. The applicability of the method in such cases will be recognised by a consideration of the nature of thematerials to be used and the form of the final product required. It is only necessary that the material will withstand the heat necessary to destroy the cellulose and will itself sinter to form a thin plate. The method is applicable to the manufacture of thin sheets or plates from powdered glass alone or mixed with dielectric ceramic materials (particularly ceramic materials with high dielectric constants), powdered metals, for example tantalum, aluminium and titanium, silicon carbide and mixtures of carbon, silica and/ or silicates. The mixtures of carbon, silica and/ or silicates are useful in the manufacture of electrical resistors. In such mixtures the carbon itself does not sinter but becomes incorporated in the ceramic material produced by the sintering of the silicon and/or silicates present. Silicon carbide is used when resistors in which resistance varies with voltage or current are required. When materials are used which are liable to oxidise at the sintering temperature precautions are taken to exclude oxygen during the latter part of the heat treatment.
While the upper limits of the thickness of the sheets or plates which can be made by the method of the invention from a single sheet of loaded paper is controlled only by the thickness of the loaded paper sheet there would be little advantage in using the method for the manufacture of sheets or plates thicker than about mils (.25 mm.) since such plates or sheets would probably be more easily made by known dry pressing processes.
In the accompanying drawing Figures 1 and 2 show two alternative forms of capacitor manufactured in accordance with the invention and Figure 3 shows a process in accordance with the invention.
The capacitor shown in Figure l is a stack type made up of a number of plates 1 of a material of the kind described in the examples. Each plate is formed on both S1dCS W1th metallised layers in accordance with normal practice, the layer 2 on the upper surface extending over one end of the plate and onto the lower side and the layer 3 on the lower side extending over the M 16 l fil 3 d the upper side, as shown. Metal connecting wires 4 and 5 are soldered to the ends of the stack.
Figure 2 shows a single plate capacitor consisting of a circular plate 6 of a material manufactured in accordance with one of the examples provided with metallised layers on its upper and lower surfaces. The layer 7 on the upper surface has soldered to it a connecting wire 8. A similar wire 9 is soldered to the lower metallised layer.
Referring to Figure 3 of the drawings an aqueous dispersion 10 of cellulose fibres and a powdered material, formed by a heating process, is contained in a vessel through which a continuous gauze 11, of the kind used in paper making, passes round a roller 12 in a clockwise direction. The gauze passes from the dispersion beneath the heater 13 and over a tray 14 which is evacuated by a pump 15.
As the gauze rises from the surface of the dispersion 10, it picks up a layer 16 which is carried over the tray 14 and beneath the heater 13 and is dried sufiiciently to make it into a self-supporting sheet. The sheet 17 is lifted continuously from the gauze 11 and passes between at least one pair of calender rolls 18, 19. During passage through these rolls it is compressed to the re-- quired thickness and density. From the rolls the sheet passes on to a conveyor 20 which carries it through a cut ting machine 21 Where it is reduced to the required shapes for example discs.
In the drawing, discs 22 are shown issuing from the machine 21. These are placed by hand into ceramic dishes 23 which are fed successively into a firing kiln: 24. In the kiln the discs are fired in the manner described in the examples. If desired, the discs, before firing, can be arranged between fiat zircon plates which are not afiected by the temperatures reached in the firing kiln.
Both forms of capacitor are provided with a protective layer of insulating wax or varnish.
What we claim as our invention is:
l. A method of manufacturing a thin, strongly co-- herent electrically insulating sheet from a ceramic powder which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least by weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, consolidating said sheet by the application of pressure and heating said sheet under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
2. A method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, selected from the group consisting of titanium dioxide and metallic titanate powders with or without small quantities of additives, which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a heating process, taking up a thin layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least 95% by Weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, self supporting, removing said layer as a sheet from said support, consolidating said sheet by the application of pressure and heating said sheet under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
3. A method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, selected from the group consisting of titanium dioxide drying said layer until it is and metallic titanate powders with or without small quantities of additives which comprises preparing a suspension of cellulose fibers, bentonite and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than about mils thickness on a pervious support, the relative proportions of said ingredients of said suspension being such that the solid content by weight of said layer is cellulose /2-2%, bentonite /2--1% and ceramic powder 99-97%, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, consolidating said sheet by the application of pressure and heating said sheet under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
4. A method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least 95% by Weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, stacking a plurality of said sheets, consolidating said stacked sheets by the application of pressure and heating under oxidising conditions first to burn 01f the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
5. A method of manufacturing a thin, strongly coherent electrically insulating sheet made from a ceramic powder, selected from the group consisting of titanium dioxide and metallic titanate powders with or without small quantities of additives, which comprises preparing a suspension of cellulose fibers and said powder in an aqueous liquid by a beating process, taking up a layer of said suspension of not more than 10 mils thickness on a pervious support, the relative proportions of cellulose and ceramic powder in said suspension being such that at least 95% by weight of the solid content of said layer consists of said powder, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support,
stacking a plurality of said sheets, consolidating said stacked sheets by the application of pressure and heating under oxidising conditions first to burn off the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
6. A method of manufacturing a thin, strongly coherent electrically insulating sheet from a ceramic powder, selected from the group consisting of titanium dioxide and metallic titanate powders with or without small quantities of additives which comprises preparing a suspension of cellulose fibers, bentonite and said powder in an aqueous liquid by a heating process, taking up a layer of said suspension of not more than about 10 mils thickness on a pervious support, the relative proportions of said ingredients of said suspension being such that the solid content of weight of said layer is cellulose /z--2%, bentonite /21% and ceramic powder 99-97%, draining liquid contained in said layer through said support, drying said layer until it is self supporting, removing said layer as a sheet from said support, stacking a plurality of said sheets, consolidating said stacked sheets by the application of pressure and heating under oxidising conditions first to burn oil? the cellulose and then at a higher temperature to sinter said powder and form a sheet of strongly coherent material.
References Cited in the file of this patent UNITED STATES PATENTS 1,152,060 Sturm et a1. Aug. 31, 1915 1,447,347 Kirschbraum Mar. 6, 1923 2,063,102 Jones Dec. 8, 1936 2,145,151 Braunstein Ian. 24, 1939 2,330,106 Bernstein Sept. 21, 1943 2,391,376 Monack Dec. 18, 1945 2,486,410 Howatt Nov. 1, 1949 2,499,229 Rankine Feb. 28, 1950 2,539,446 Lies Jan. 30, 1951 2,616,813 Klasens Nov. 4, 1952 2,643,192 Ionkers et a1 June 23, 1953 FOREIGN PATENTS 574,577 Great Britain Jan. 11, 1946 OTHER REFERENCES The Bible, Exodus, ch. 5, verses 6-8, (King James Version); Collins Clear Type Press, London, Eng. (1949).

Claims (1)

1. A METHOD OF MANUFACTURING A THIN, STRONGLY COHERENT ELECTRICALLY INSULATING SHEET FROM A CERAMIC POWDER WHICH COMPRISES PREPARING A SUSPENSION OF CELLULOSE FIBERS AND SAID POWDER IS AN AQUEOUS LIQUID BY A BEATING PROCESS, TAKING UP A LAYER OF SAID SUSPENSION OF NOT MORE THAN ABOUT 10 MILS THICKNESS ON A PERVIOUS SUPPORT, THE RELATIVE PROPORTIONS OF CELLULOSE AND CERAMIC POWDER IN SAID SUSPENSION BEING SUCH THAT AT LEAST 95% BY WEIGHT OF THE SOLID CONTENT OF SAID LAYER CONSISTS OF SAID POWDER
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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2924540A (en) * 1958-05-23 1960-02-09 Du Pont Ceramic composition and article
US2946937A (en) * 1956-05-07 1960-07-26 Plessey Co Ltd Ceramic material and method of producing the same
US2966719A (en) * 1954-06-15 1961-01-03 American Lava Corp Manufacture of ceramics
DE1117765B (en) * 1957-09-04 1961-11-23 Telefunken Patent Ceramic stack capacitor
US3187242A (en) * 1960-10-07 1965-06-01 Schick Walter Stacked electrical capacitors
US3192086A (en) * 1960-06-16 1965-06-29 Rca Corp Methods for manufacturing multilayered monolithic ceramic bodies
US3235939A (en) * 1962-09-06 1966-02-22 Aerovox Corp Process for manufacturing multilayer ceramic capacitors
US3649891A (en) * 1970-06-18 1972-03-14 Corning Glass Works Capacitive cryogenic thermometer
US3962389A (en) * 1972-12-27 1976-06-08 Toppan Printing Co., Ltd. Method for producing ceramics from particle sheet material using cationic pulp
AT376517B (en) * 1981-06-30 1984-11-26 Siemens Bauelemente Ohg METHOD FOR THE PRODUCTION OF AREA-LIMITED, SOLDERABLE METAL LAYERS ON ELECTRICAL COMPONENTS
US4641221A (en) * 1985-08-02 1987-02-03 The Dow Chemical Company Thin tape for dielectric materials
US4675644A (en) * 1985-01-17 1987-06-23 Siemens Aktiengesellschaft Voltage-dependent resistor

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US2539446A (en) * 1947-07-12 1951-01-30 Sprague Electric Co Process for producing dielectric sheets
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US1152060A (en) * 1914-05-06 1915-08-31 Conrad Sturm Manufacture of colored foil, bronze foil, and metal foil.
US1447347A (en) * 1920-12-31 1923-03-06 Raybestos Co Process in making clutch rings
US2063102A (en) * 1933-07-24 1936-12-08 Illinois Clay Products Co Porous refractory insulating cement
US2145151A (en) * 1935-02-11 1939-01-24 Anciens Ets Braunstein Method of manufacturing cigarette paper
US2330106A (en) * 1941-03-14 1943-09-21 Victor Mfg & Gasket Co Gasket material
GB574577A (en) * 1942-12-08 1946-01-11 Dubilier Condenser Co 1925 Ltd Improvements in or relating to ceramic compositions
US2391376A (en) * 1943-09-30 1945-12-18 Mycalex Corp Machinable insulating composition
US2486410A (en) * 1944-09-15 1949-11-01 Glenn N Howatt Continuous process for forming high dielectric ceramic plates
US2539446A (en) * 1947-07-12 1951-01-30 Sprague Electric Co Process for producing dielectric sheets
US2499229A (en) * 1947-10-04 1950-02-28 Johns Manville Refractory insulating brick and method of manufacture
US2643192A (en) * 1948-06-25 1953-06-23 Hartford Nat Bank & Trust Co Electrical insulator
US2616813A (en) * 1948-11-10 1952-11-04 Hartford Nat Bank & Trust Co Condenser

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US2966719A (en) * 1954-06-15 1961-01-03 American Lava Corp Manufacture of ceramics
US2946937A (en) * 1956-05-07 1960-07-26 Plessey Co Ltd Ceramic material and method of producing the same
DE1117765B (en) * 1957-09-04 1961-11-23 Telefunken Patent Ceramic stack capacitor
US2924540A (en) * 1958-05-23 1960-02-09 Du Pont Ceramic composition and article
US3192086A (en) * 1960-06-16 1965-06-29 Rca Corp Methods for manufacturing multilayered monolithic ceramic bodies
US3187242A (en) * 1960-10-07 1965-06-01 Schick Walter Stacked electrical capacitors
US3235939A (en) * 1962-09-06 1966-02-22 Aerovox Corp Process for manufacturing multilayer ceramic capacitors
US3649891A (en) * 1970-06-18 1972-03-14 Corning Glass Works Capacitive cryogenic thermometer
US3962389A (en) * 1972-12-27 1976-06-08 Toppan Printing Co., Ltd. Method for producing ceramics from particle sheet material using cationic pulp
AT376517B (en) * 1981-06-30 1984-11-26 Siemens Bauelemente Ohg METHOD FOR THE PRODUCTION OF AREA-LIMITED, SOLDERABLE METAL LAYERS ON ELECTRICAL COMPONENTS
US4675644A (en) * 1985-01-17 1987-06-23 Siemens Aktiengesellschaft Voltage-dependent resistor
US4641221A (en) * 1985-08-02 1987-02-03 The Dow Chemical Company Thin tape for dielectric materials

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