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
  • 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
  • D21H13/24—Polyesters
• • 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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
• • 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
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/04—Physical treatment, e.g. heating, irradiating
  • D21H25/06—Physical treatment, e.g. heating, irradiating of impregnated or coated paper
• • 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

Definitions

• the present invention relates to synthetic papers based on thermostable fibers, thermostable pulp and binder. It also relates to a process for obtaining such papers.
• paper denotes non-woven articles, in the form of sheets, films, felts and in general any coherent fibrous structure not involving any textile operation such as spinning, knitting, weaving. It more specifically designates articles based on synthetic textile fibers obtained by the wet or papermaking process.
• nonwoven articles constituted by a sheet of fibers based on an infusible material or having a melting point higher than 180 ° C., the fibers being bonded together by means a polyamide-imide binder, used in proportion from 5 to 150% of the weight of dry fibers used.
• nonwovens are obtained by the dry route, in this case by carding, which makes such a process very expensive and industrially unattractive.
• the impregnation of the resin takes place in solution in a solvent, which results in harmful effects on the characteristics of the nonwovens.
• the mixture synthetic fibers-binder based on resin does not have any cohesion to be able to be handled and in particular such a mixture does not have sufficient cohesion to be able to be prepared dynamically, for example on a commercial paper machine; such layers can be produced only on laboratory apparatus of the "Formette Franck" type, that is to say statically and discontinuously as is apparent from the examples.
• the present invention also relates to a process for obtaining reactivatable papers by introduction into water of the various constituents of the paper, the fibers, the pulp, the resin in powder form and possibly other desired fillers, and mixture of these products in any suitable device with vigorous stirring, then addition of a solution of a flocculating agent under slight stirring in the case where the chemical binder is in powder form, formation of a paper sheet containing the above elements, from which the water is gradually eliminated by gravity then under vacuum, optionally wringing until elimination of the major part of the water, drying at a temperature between room temperature and 100 ° C, densification of the sheet by any known means, and heat treatment at a temperature between 50 and 275 ° C to make the resin evolve at polycondensation desired. All the solid constituents represent a concentration of between 0.5 and 5% by weight.
• the fibers used in the invention can be chosen from the various fibers having the properties set out above. More specifically, it can be inorganic fibers such as glass fibers, carbon fibers, aluminum oxide and zirconium fibers, asbestos fibers, boron fibers, it can also act of fibers from organic polymers among the polymers which are particularly suitable for the manufacture of papers according to the invention, having to withstand for long periods temperatures of 180 ° C, preferably ⁇ 200 ° C, or higher: there may be mentioned polyamide-imides, such as polytrimellamide-imides or polyamides derived from fully aromatic reagents, or polyimides such as polyimides obtained according to European patent 0 119 185, known commercially under the trademark P84.
• polyamide-imides such as polytrimellamide-imides or polyamides derived from fully aromatic reagents
• polyimides such as polyimides obtained according to European patent 0 119 185, known commercially under the trademark P84.
• Fully aromatic polyamides can be defined as consisting of recurring units of formula: wherein the various identical or different symbols Q have the meaning given above and the symbols R3, identical or different, represent a hydrogen atom or an alkyl radical having from 1 to 4 carbon atoms.
• fibers generally have a length of between 2 and 10 mm, preferably 3 to 7 mm, and their titer, expressed in decitex, is generally between 0.5 and 20. It is theoretically possible to use fibers of length greater than 10 mm, but in practice longer fibers become entangled, requiring a greater amount of water, which makes the process heavier and more complicated.
• the fibrous binder usable according to the present invention comes from a polymer with thermal resistance greater than or equal to 180 ° C, preferably ⁇ 200 ° C, in the form of highly fibrillated pulp providing cohesion in the wet phase.
• the fibrous binder is in the form of very short fibers, of length which can vary for example between 0.1 and 5 mm, generally from 0.1 to 2 mm.
• the polymers which can be used for the preparation of the pulp are fibrillable polymers based on polyamides or fully aromatic polyesters.
• Aromatic polyamides of the polyparaphenyleneterephthalamide type are particularly suitable, for example that known in the trade under the brand "Twaron®”; totally aromatic, crystallized polyesters also fibrillate very well and can be used in the form of pulp.
• the fibrous binder can be in the form of flock or felt still containing a certain proportion of water from their preparation.
• the pulp was generally obtained from fibers of usual length, beaten or thrown, in known manner, to give it a large number of attachment points and thus increase its specific surface.
• synthetic fibers only highly crystallized fibers can be fibrillated, this is the case of totally aromatic polyamides and polyesters, but other highly crystallized polymers can be split along the axis of the fibers or fibrillable.
• the symbols A and B may be the same or different and represent a linear or branched alkylene radical, having less than 13 carbon atoms, a cycloalkylene radical with 5 or 6 carbon atoms in the ring, a heterocyclic radical containing at least one of the atoms O, N and S, a benzene or polycyclic aromatic radical; these various radicals can also carry substituents which do not give side reactions under the operating conditions.
• N, N'-bis imide and diamine are chosen so that the ratio: nb. of moles of N, N'-bis-imide (I) nb. of moles of diamine (II) is at least equal to 1; moreover, it is generally preferred that it be less than 50.
• a polyimide resin is preferably used resulting from the reaction between a bis-maleimide such as N, N'-4,4'-diphenylmethane bis-maleimide and a primary diamine such as diamino-4,4 'diphenylmethane.
• It is generally used in the form of a dry powder or dispersion in an aqueous medium.
• the polyimide resin is advantageously combined with an epoxy resin of bisphenol A type, in a proportion of 0 to 100% and preferably 25 to 75% of polyimide resin, ie 0 to 75% of epoxy resin, preferably 25 to 75% by weight.
• reactivatable paper implies a product in which the resin is incompletely polymerized while having sufficient cohesion for obtaining the actual paper.
• the chemical binder is a polyether imide or a aromatic polyester
• it is preferably used in the form of fibers to promote bonding with other fibers and the pulp, thus avoiding the flocculation step.
• Polyether imides are high performance polymers. Among these, it is possible to use, for example, the product sold under the brand ULTEM 1010 by the General Electric Plastics Company, which is in the form of fibers.
• aromatic polyester means fully aromatic polyesters which are liquid crystal polymers characterized by straight polymer chains generally obtained from at least one aromatic diacid such as terephthalic acid and from at least one diphenol. They have excellent unidirectional mechanical properties.
• aromatic diacid such as terephthalic acid
• diphenol diphenol
• the polyimide resin is used
• Such paper can enter into the composition of many composite articles and in particular be associated with other constituent elements for example for the purpose of insulation and reactivated "in situ" until complete polymerization.
• the reactivity of the paper depends on the progress of the polymeric binder, this advancement can also be achieved at the outlet of the paper machine by heat treatment to the level desired for use.
• the reactivatable paper according to the invention can be used for numerous applications, which depend on certain essential elements such as, the formulation, the rate of advancement of the resin.
• a paper containing only the quantity of resin necessary to fill the porosity of the fibers will have the function of "spacer paper” to be inserted between two parts to be electrically insulated; a paper very rich in resin and therefore susceptible to hot creep will have a "reservoir paper” function, the excess resin of which will fill the gaps between the elements to be insulated.
• This type of paper could have a role of "reactive paper” playing the role of hardener (because of the secondary and tertiary amine functions which it contains with respect to an "in situ” contribution of epoxy resin in the case of an additional isolation technique called “drop”).
• the prepolymer used in the paper phase will essentially be a polyimide prepolymer.
• Very advanced paper will be relatively rigid and usable as insulation for closing notches.
• a moderately advanced paper will have a slight creep under pressure and will therefore be usable for the production of complexes (for example paper + film) without additional resin supply.
• variable state of advancement also allows heat sealing, in particular in the case of insulation by covering.
• the mechanical characteristics of the paper are dependent on the rate of advancement of the resin. The closer it is to its final crosslinking rate, the better the characteristics.
• adjuvants or fillers can also be used in various proportions depending on the desired properties; for example mica can be introduced to further increase the dielectric properties of such papers; the papers according to the invention have, in addition to good dielectric properties, good mechanical properties depending on the rate advancement of the resin, in particular a high tensile strength.
• the good characteristics exhibited by the papers according to the invention largely come from a very regular and homogeneous fine structure attesting to the very good distribution of the various constituents.
• This good homogeneity comes from a set of selected elements, such as the proportion of the different raw materials, the nature and length of the fibers used as well as the fibrous binder, the particle size of the resin, as well as the method of preparation, such as we will see it later.
• the preparation of the papers according to the invention is carried out by wet or papermaking. According to this technique, all of the starting materials, including the fillers, are directly incorporated into an appropriate device called "pile" by the paper manufacturers.
• the raw materials present in the proportions and in the form indicated above, are introduced in the divided state to promote the obtaining of a good dispersion. They are mixed in the presence of water with vigorous stirring. It is also possible at this stage to add aluminum sulphate in solution to promote dispersion.
• the dry product rate is around 1.5%; when the mixture has become homogeneous, it is generally transferred to a storage device called a "vat" in which the paste obtained is stored with gentle agitation; then in the case where the chemical binder is in the form of a powder, the paste is added with a flocculating system, always with gentle agitation.
• a flocculating system This comprises on the one hand alumina sulfate and on the other hand a flocculant.
• a cationic flocculant based on acrylamide known commercially under the trademark PRAESTOL 611 BC from STOCKHAUSEN, which has good efficacy.
• the flocculating system ensures physical fixation of the resin particles on the fibers, which allows, if desired, to use a very small particle size of resin particles and thus obtain very homogeneous papers.
• the particle size of the resin particles can be as low as 15 ⁇ m or less, but can also be higher (up to 50 or 10 ⁇ m). But until then it was difficult to use resin particles as small as 15 ⁇ or less because the particles resin was retained very little by the fibers, even with a much larger particle size, so that a large proportion of the resin was removed with water. This was the case with the process according to FR 2 156 452.
• the pulp is then taken up by any known means to feed the distribution table of a traditional paper machine. On its arrival on the distribution table, the homogeneous paste, containing a high water content spreads out regularly while the water is gradually removed by gravity first then by force, by suction, for example by means of '' a device producing vacuum.
• the felt thus obtained is wrung until the elimination of most of the water, then after having been peeled off from the endless cloth, dried at a temperature between the atmosphere and 110 ° C., then densified by all known means for example by cold or hot calendering, at a temperature between room temperature and 150 ° C or by hot pressing. It is possible to make several passes on the densification device so as to obtain the desired density, generally between 0.5 and 1 or even more depending on the desired mechanical characteristics.
• the papers thus obtained are then subjected to a heat treatment at a temperature between 50 and 275 ° C to make the resin evolve to the desired polycondensation level, which is a function of their subsequent use.
• the heat treatment is carried out at a temperature close to the melting point to ensure the cohesion of the fibers.
• the rate of dryness in the stack is of the order of 1.5%.
• the dough is transferred to an endless canvas which constitutes the shaping machine.
• the dry matter carried by a high rate of water is distributed homogeneously while the water, by gravity escapes through the fabric.
• the drained dough then passes over vacuum boxes which improve the elimination of water, and finally under a cylinder, which by light pressure densifies the wet dough.
• the paper thus formed is peeled from the endless canvas, and directed to a drying oven, ventilated with air at 100-110 ° C.
• the paper formed After drying, the paper formed has a basis weight of 136 g / m2.
• This paper can be hot calendered up to 280 ° C. For example at 270 ° C. its thickness after calendering is 175 ⁇ m, its density of 0.750 g / cm3 and its tensile strength of 66 N / cm. In the case of calendering at room temperature, the same product has a thickness of 199 ⁇ m and a density of 0.66 g / cm3; the tensile strength is then 7.5 N / cm.
• Example 2 As indicated in Example 1, the following compositions are used: 2 3 4 KERMEL% fibers 86.4 75 65.4 TWARON®% pulp 4.5 8.3 11.5 KERIMID 613 resin 9.1 16.7 23.1
• the characteristics of hot pressed papers are as follows: 2 3 4 Weight g / m2 119 122 130 Thickness ⁇ m 191 173 174 Density kg / m3 623 705 749 Resistance N / cm 42.3 57.3 66.1 Elongation% 3.9 4.6 4.4
• composition tests 5 6 7 KERMEL% fibers 62 54.5 46.5 TWARON®% pulp 13 15.5 18.5 KERIMID 613 resin 25 30 35 was pressed at 270 ° C for 1 minute, but with a pressure of 60 bars.
• the mechanical characteristics of the reactivatable papers obtained according to Examples 1 to 10 are not the final characteristics liable to be reached, they will be increased by any subsequent heat treatment, when the paper is used in a hot environment.
• the rate of dryness in the pile is of the order of 1.5%, reduced to 0.5% by adding water when the dispersion is deemed sufficient.
• the dough is transferred to an endless canvas which constitutes the shaping machine.
• the dry matter carried by a high rate of water is distributes evenly while water, by gravity escapes through the fabric.
• the drained dough then passes over vacuum boxes which improve the elimination of water, and finally under a cylinder, which by light pressure densifies the wet dough.
• the paper thus formed is peeled from the endless canvas, and dried on cylinders at 100 ° C - 140 ° C.
• the paper formed After drying the paper formed has a density of 0.640 g / m3.
• This paper can be hot calendered. For example at 270 ° C. its thickness after calendering is 138 ⁇ m, its density of 0.970 g / cm3 and its tensile strength of 105 N / cm for a paper weight 134 g / m2. In the case of calendering at 295 ° C the same product (grammage 132 g / m2) has a thickness of 137 ⁇ m and a density of 0.962 g / cm3; the tensile strength is then 104 N / cm.
• the rate of dryness in the stack is of the order of 1.5%. It is reduced to 0.5% by adding water when the dispersion is deemed sufficient.
• the slightly agitated pulp flows by gravity to feed the distribution table of a paper machine.
• the dough is transferred to an endless canvas which constitutes the shaping machine.
• the dry matter carried by a high rate of water is distributed homogeneously while the water, by gravity escapes through the fabric.
• the drained dough then passes over vacuum boxes which improve the elimination of water, and finally under a cylinder, which by light pressure densifies the wet dough.
• the paper thus formed is peeled from the endless canvas, and dried on 2 cylinders with a diameter of 2.5 m at 100 ° C - 140 ° C.
• the paper formed After drying the paper formed has a density of 125 g / m3.
• This paper can be hot calendered. For example at 270 ° C. its thickness after calendering is 186 ⁇ m, its density of 0.665 g / cm3 and its tensile strength of 90 N / cm. In the case of calendering at 295 ° C the same product has a thickness of 154 ⁇ m and a density of 0.812 g / cm3; the tensile strength is then 97.5 N / cm.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Paper (AREA)
• Cell Separators (AREA)
• Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
• Reinforced Plastic Materials (AREA)
• Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9420662

Family Applications (1)

Country Status (10)

Cited By (3)

Families Citing this family (10)

Citations (2)

Family Cites Families (7)

• 1991
  • 1991-12-24 FR FR9116340A patent/FR2685363B1/fr not_active Expired - Fee Related
• 1992
  • 1992-12-21 AT AT92420476T patent/ATE173310T1/de not_active IP Right Cessation
  • 1992-12-21 DE DE69227576T patent/DE69227576T2/de not_active Expired - Fee Related
  • 1992-12-21 EP EP92420476A patent/EP0550355B1/de not_active Expired - Lifetime
  • 1992-12-22 NO NO92924977A patent/NO924977L/no unknown
  • 1992-12-23 FI FI925868A patent/FI925868A7/fi not_active Application Discontinuation
  • 1992-12-23 MX MX9207512A patent/MX9207512A/es unknown
  • 1992-12-23 CA CA002086144A patent/CA2086144C/fr not_active Expired - Fee Related
  • 1992-12-24 JP JP4344753A patent/JP2740098B2/ja not_active Expired - Fee Related
• 1993
  • 1993-12-14 US US08/165,864 patent/US5431782A/en not_active Expired - Lifetime

Patent Citations (2)

Also Published As

Similar Documents

Legal Events