Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
  • D21H13/10—Organic non-cellulose fibres
  • D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H13/26—Polyamides; Polyimides
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/30—Multi-ply
  • D21H27/38—Multi-ply at least one of the sheets having a fibrous composition differing from that of other sheets
• • 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
  • H01B3/48—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances fibrous materials
  • H01B3/52—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances fibrous materials wood; paper; press board
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/36—Polyalkenyalcohols; Polyalkenylethers; Polyalkenylesters

Definitions

• the present invention relates to high temperature papers, and in particular to high temperature papers comprising an aramid component.
• Such high temperature papers can comprise a single layer or multiple layers.
• High temperature E-board is used in transformers and performs two functions.
• the E-board provides electrical insulation. This keeps the coils in the transformer from short circuiting.
• the board provides mechanical strength. When there is a large passage of current through the transformer, there is force on the layers of the coil to move the board, which is glued to the coils. The glueing of the board to the coil keeps the various coils from telescoping. Each coil acts like a solenoid and tries to move. It is the E-board which prevents this telescoping.
• Yet another object of the present invention is to provide a paper structure which exhibits enhanced mechanical strength.
• Still another object of the present invention is to provide a high temperature paper suitable for use in transformers.
• a paper structure comprised of an aramid component.
• the paper structure comprises an aramid fiber and/or fibrid, a polymeric binder, such as polyvinyl alcohol, and cellulosic pulp fiber.
• the paper structure is comprised of two outside layers and at least one inside layer.
• the two outside layers are preferably comprised of substantially cellulosic (wood) pulp fiber.
• the inside layer is comprised of cellulosic pulp fiber, the aramid fiber and/or fibrid and a polymeric binder.
• the structure comprises at least three inside layers, all comprised of cellulosic pulp fiber, the aramid component and a polymeric binder.
• the resulting paper structure provides a paper quite useful as E-board in transformers due to its enhanced thermal resistance. Moreover, the aramid fiber also helps to reinforce the paper to avoid the problems in telescoping coils.
• the paper structure of the present invention is quite useful as a high temperature E-board.
• the paper exhibits enhanced thermal resistance as well as good mechanical strength.
• the good thermal resistance would allow the use of the paper in a transformer with coils of smaller size as it would allow the coils to run hotter.
• the paper is also reinforced so that when glued to the coils, it would keep the various coils from telescoping.
• the paper is coated with an adhesive, such as an epoxy adhesive, and heat bonded to the wire coil surface. It is this bonding to the coils that permits the board to keep the various coils from telescoping.
• the mechanical strength of the paper structure of the present invention including its aramid component in combination with the polymeric binder, permits the E-board to act efficiently and effectively while preventing the coils from telescoping.
• the paper structure of the present invention comprises a polymeric binder, an aramid component which can be an aramid fiber, a fibrid, or a combination thereof, together with cellulosic pulp fiber.
• the aramid fiber can be any commercially available polyaramid fiber, such as that under the trademark NOMEX®. Generally, the fiber is about 1 ⁇ 4 inch in length and has about a 2 denier.
• the fibrid is a small irregularly shaped piece of aramid polymer that is much larger in two dimensions than it is in the third dimension. It is like a microscopic corn flake in shape. The large dimensions are on the order of 5 to 25 micrometers while the third and smaller dimension is about 0.01 to 1 micrometer.
• the amount of cellulosic wood pulp fiber generally ranges from 50 to 80 wt %, while the amount of aramid component generally ranges from about 5 to 25 wt %.
• the amount of polymeric binder, preferably polyvinyl alcohol generally ranges from about 10 to 25 wt %.
• the aramid component from 5 to 25 wt %, can be comprised of solely aramid fiber, aramid fibrid, or preferably a combination of the two. When a combination is used, it is preferred that about a 60/40 wt % ratio of fiber/fibrid is employed.
• the amount of polymeric binder can be reduced as the fibrid can also function as binder for the web. For this reason, it is preferred that some aramid fibrid is present. It performs a dual role and can reduce the amount of aramid fiber and binder needed.
• Such synthetic fiber can be, for example, polyester or nylon fiber.
• the paper structure of the present invention can comprise a single layer or multiple layers.
• the paper structure contains the cellulosic pulp fiber, aramid component and polymeric binder as discussed above. Multiple layers of such combinations can also be employed, wherein the amounts of each component of a particular layer may change.
• a veiled structure can also be used.
• the two outside layers are comprised of substantially wood pulp fiber, preferably without any polymeric binder, while the inside layers, whether one or more, comprise the components of cellulosic wood pulp fiber, aramid component and polymeric binder.
• a minor amount of synthetic fiber, such as polyester or nylon fiber, can be present in the outside cellulosic pulp fiber layers.
• the paper structure is comprised of five different layers.
• the two outside layers are comprised substantially of cellulosic, preferably wood, pulp fiber.
• the three internal layers are all comprised of cellulosic pulp fiber, aramid component and a polymeric binder.
• the internal layers can be of different compositions. For example, they can contain different relative amounts of the cellulosic pulp fiber, aramid component and polymeric binder, since different stock compositions can be fed to the various corresponding cylinders to make the various layers.
• the paper structure comprises two outer layers comprised substantially of cellulosic pulp fiber, and the inner layer is comprised of the aramid component and polymeric binder.
• the presence of the aramid component and polymeric binder together is important, in at least one inner layer of the paper structure.
• the remaining layers may differ in composition, as long as the two outside layers do not contain the polymeric binder.
• the preferred polymeric binder is polyvinyl alcohol, but other polymeric binders such as acrylics can also be used. It can be added in the form of a synthetic fiber or as a dry powder. If the binder is added as a fiber, it is important that the fiber has the proper chemical characteristics.
• Polyvinyl alcohol fiber is available with a wide range of water solubilization temperatures. The temperature at which the polymer becomes soluble depends on the properties of the polymer like the degree of polymerization, degree of hydrolysis, and crystallinity. This solubilization temperature can range from about 60° C. to over 100° C. It is important to match this solubilization temperature to the paper making process.
• the polyvinyl alcohol fiber should behave as a binder while it is in the fiber form. It should not be allowed to fully dissolve. The strongest binding occurs when the surface of the fiber just starts to dissolve. Then upon drying, the polyvinyl alcohol fiber will bond to all of the other fibers, both synthetic and natural, that it contacts.
• a polyvinyl alcohol fiber with a low solubilization temperature should be used with a low to medium basis weight paper (roughly 25 to 120 pounds per 3000 square feet) that is typically run at high machine speeds. Because of the higher machine speed and low sheet mass, evaporation will cool the paper. It will dry before it gets very hot. The maximum temperature that the paper will reach is likely to be less than 70° C.
• the polymer When the powder form of the polyvinyl alcohol binder is used, the polymer should be fully hydrolyzed (99% or higher) and the polymer should be ground to a particle size of 100 mesh or smaller.
• the powder can be added to the wood fiber prior to refining or it can be added to the system after refining. It is important that the powdered polymer be allowed to swell after it is added to the paper making system. Swelling time depends on the water temperature. Cold water (0-14° C.) requires a swelling period of about one hour. Warm water (40-50° C.) will swell the particles in about 20 minutes. It is essential that the process water used with either polyvinyl alcohol fibers or powder not be over 60° C., as hot water will dissolve the polymer and most of the bonding characteristics will be lost.
• a cylinder machine in preparing the “veiled” embodiment of the present invention, can be and is preferably employed.
• the cylinder machine allows for the creation of different layers using different stock compositions, as discussed above, thus allowing the paper structure to be tailored as needed within the present invention.
• the process for making a veiled paper structure comprises feeding a stock composition comprised substantially of wood pulp fiber to the cylinders corresponding to the outer layers.
• the two outside layers of the resulting paper structure comprises substantially cellulosic, preferably wood, pulp fibers.
• a minor amount of synthetic fibers can be included in the stock compositions.
• a cylinder corresponding to the inner layer is then fed with a stock solution comprised of cellulosic pulp fiber, the chosen aramid component, whether fiber, fibrid or a mixture thereof, and a polymeric binder.
• the inner layer of the paper structure is comprised of the cellulosic pulp fiber, aramid component and polymeric binder.
• the resulting paper structure is such that only the inner layer contains the polymeric binder, whereas the outside layers do not, and thus potential sticking problems are avoided when the paper structure is dried, preferably on drier cans, and the polymeric binder is activated due to the high temperature.
• the binder Upon activation of the polymeric binder, the binder acts to bind the aramid component together with the wood pulp fiber, and since it is on the inside layer it will not cause sticking problems.
• the paper structure of the present invention provides one with a paper quite useful as a high temperature paper for transformers.
• the paper exhibits enhanced thermal resistance, as well as excellent mechanical strength to perform all of the necessary functions of a transformer E-board.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)

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Citations (22)

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• 2003
  • 2003-09-09 US US10/657,183 patent/US20040140072A1/en not_active Abandoned
  • 2003-09-10 WO PCT/US2003/028386 patent/WO2004025024A1/fr active Application Filing
  • 2003-09-10 EP EP03752201A patent/EP1558808A4/fr not_active Withdrawn
  • 2003-09-10 AU AU2003270503A patent/AU2003270503A1/en not_active Abandoned
  • 2003-09-10 CA CA002498579A patent/CA2498579A1/fr not_active Abandoned
  • 2003-09-10 MX MXPA05002636A patent/MXPA05002636A/es not_active Application Discontinuation
  • 2003-09-10 JP JP2004571976A patent/JP2006519318A/ja active Pending

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