Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
  • D04H1/542—Adhesive fibres
  • D04H1/549—Polyamides
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4326—Condensation or reaction polymers
  • D04H1/4334—Polyamides
  • D04H1/4342—Aromatic polyamides
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
  • D04H1/43835—Mixed fibres, e.g. at least two chemically different fibres or fibre blends
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
  • D04H1/74—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being orientated, e.g. in parallel (anisotropic fleeces)
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/249921—Web or sheet containing structurally defined element or component
  • Y10T428/249924—Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
  • Y10T428/24994—Fiber embedded in or on the surface of a polymeric matrix
  • Y10T428/249949—Two or more chemically different fibers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31725—Of polyamide
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31725—Of polyamide
  • Y10T428/31728—Next to second layer of polyamide
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
  • Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
  • Y10T442/69—Autogenously bonded nonwoven fabric
  • Y10T442/692—Containing at least two chemically different strand or fiber materials

Definitions

• the present invention relates to a new melt-bond-strengthened nonwoven based on aramid fibers, a process for its production and the use of this nonwoven as a filter material, as an insulating material or as a reinforcing material.
• Nonwovens are generally known and represent a separate category of textile fabrics.
• nonwovens are formed directly from individual fibers or filaments.
• the cohesion of such nonwovens can be produced by the fibers' inherent adhesion and / or by mechanical and / or chemical consolidation.
• DE-A-26 00 209 discloses a heat-resistant sheet material which is produced by eating or heating a woven or knitted fabric or a sheet material from a mixture of aromatic polyamide fibers. Of these fibers, one type acts as a binding agent and the other type acts as a supporting fiber. The heat-melt treatment deforms the binding fiber and forms a porous sheet material that has good paint impregnation properties. The necessary strength is only achieved through impregnation.
• a filter material which consists of glass fibers which are strengthened by means of aromatic polyamide fibers.
• the polymer fibers are deformed by heat and cause a kind of "sintering process" to strengthen the glass fleece.
• the strength of these nonwovens also leaves something to be desired.
• the object of the present invention is to provide a novel nonwoven fabric made from aromatic polyamides with improved strength.
• aramid is to be understood as meaning a polyamide which has essentially azomatic residues in the polymer chain, for example more than 80 mol% of which is composed of aromatic monomer units.
• Fusible and non-fusible aramid fibers can be used as the supporting fiber. Furthermore, the strength and the modulus of the supporting aramid fibers can be selected within wide limits.
• aramid fibers of high strength and high modulus are essentially aramids built up from p-aromatic radicals, such as poly- (p-phenylene-terephthalamide). Examples of this are the products KEVLAR® 29 and KEVLAR® 49 from Du Pont. These aramids are insoluble in organic solvents.
• medium strength and medium modulus aramid fibers are aramids which contain a substantial proportion of aromatic m compounds, such as poly (m-phenylene terephthalamide), poly (m-phenylene isophthalamide) or poly (p-phenylene) isophthalamide).
• aromatic m compounds such as poly (m-phenylene terephthalamide), poly (m-phenylene isophthalamide) or poly (p-phenylene) isophthalamide).
• examples of such aramids are the products NOMEX® from Du Pont. These aramids are insoluble in common solvents.
• supporting fibers made from aramids which are soluble in organic solvents, in particular from those aramides which are soluble in polar aprotic solvents, such as dimethylformamide or dimethyl sulfoxide.
• aromatic polyamides based on terephthalic acid and 3- (p-aminophenoxy) -4-aminobenzanilide as described in DE-A-21 44 126; or aromatic polyamides based on terephthalic acid, p-phenylenediamine and 3,4'-diaminodiphenyl ether, as described in DE-C-25 56 883 and DE-A-30 07 063, or aromatic polyamides based on terephthalic acid and selected Shares of selected diamines, as described in DE-A-35 10 655, -36 05 394 and in EP-A-199 090.
• Aramid fibers made of copolyamides which are soluble in organic polyamide solvents and contain at least 95 mol%, based on the polyamide, of recurring structural units of the formulas Ia, Ib, Ic and Id are particularly preferably used -OC-Ar1-CO- (Ia), and up to 5 mol% m bonds containing structural units derived from aromatic dicarboxylic acids and / or from aromatic diamines (Ie) and / or (If), the sum of the molar proportions of the structural units (Ia) + (Ie) and the molar proportions of the structural units (Ib) + (Ic) + (Id) + (If) are essentially the same size, and the proportions of the diamine components (Ib), (Ic) and (Id) in relation to the total amount of this diamine component are within the following limits: or containing at least 95 mol%, based on the polyamide, of recurring structural units of the formulas Ia, Ig, Ib and I
• Aramides containing these structural units of the formulas (Ia) to (Ig) are known from EP-A-364 891, -364 892 and -364 893 and the content of these publications is also the content of the present description.
• thermoplastically processable aramid fibers can be used as binding fibers, as long as these fibers can be melted practically completely and the supporting aramid fibers stick together. This is usually done with the formation of so-called "tie sails". It is preferred to use thermoplastically processable aramid fibers which are soluble in organic solvents.
• Binder fibers based on thermoplastically processable aromatic polyetheramides are particularly preferably used.
• aromatic copolyetheramides which are known from DE-A-38 18 208 or from DE-A-38 18 209; aromatic polyamides known from EP-A-366,316, EP-A-384,980, EP-A-384,981 and EP-A-384,984 can also be used.
• Binding fibers based on these aramids can be processed thermoplastically and are particularly good Melting behavior and lead to nonwovens with excellent strength.
• Ar3 can be a mononuclear or condensed dinuclear aromatic divalent radical or a radical of the formula -Ar7-Q-Ar7-, in which Ar7 has the meaning defined above and Q is a direct CC bond or an -O-, -CO-, -S-, -SO- or -SO2 bridge means.
• Ar3 can be heterocyclic-aromatic or preferably carbocyclic-aromatic radicals. Heterocyclic aromatic radicals preferably have one or two oxygen and / or sulfur and / or nitrogen atoms in the nucleus.
• Ar5 and Ar6 are generally carbocyclic-aromatic arylene radicals whose free valences are in the para or meta position or in a comparable parallel or angled position to one another, preferably mononuclear aromatic radicals.
• Ar7 generally has one of the meanings defined for Ar5 or Ar6.
• residues -Ar3-, -Ar4-, -Ar5- and -Ar6- are p-phenylene, m-phenylene, biphenyl-4,4'-diyl or naphthalene-1,4-diyl.
• substituents which are optionally on the radicals -Ar1- to -Ar6- are branched or in particular straight-chain C1-C1 alkyl radicals, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, n-pentyl or n- Hexyl, as well as the corresponding perfluoro derivatives with up to six carbon atoms or the corresponding alkoxy derivatives. Methyl is preferred.
• halogen substituents are bromine or especially chlorine.
• aromatic polyetheramides of the formula II which are preferably used in accordance with the invention are produced by a targeted molecular weight control by non-stoichiometric addition of the monomer units, the sum of the mole fractions x, y and z being one, but the sum of x and z not being equal to y and x being the Can assume zero value.
• z is greater than x.
• the ends of the polymer chain are completely closed by adding reagents which react in the polymer to form groups which do not react further.
• the end groups are independent of one another and can be the same or different and are preferably selected from a group of the formulas III, IV, V and / or VI.
• the terminal nitrogen in formula (II) is an imide nitrogen.
• E represents a hydrogen or a halogen atom, in particular a chlorine, bromine or fluorine atom, or an organic radical, for example an aryl (oxy) group.
• the aromatic polyether amide of the formula II can be prepared by reacting one or more dicarboxylic acid derivatives with one or more diamines by the solution, precipitation or melt condensation process, one of the components being used in a stoichiometric deficit and a chain lock agent being added after the polycondensation has ended.
• thermoplastic aromatic polyamides of the formula II which are preferably used according to the invention are further distinguished by the fact that they have an average molecular weight in the range from 5000 to 50,000 and a low melt viscosity which does not exceed 10,000 Pas.
• Examples of compounds of the formula (VII) are: Terephthalic acid Terephthalic acid dichloride Diphenyl terephthalate Isophthalic acid Diphenyl isophthalate Isophthaloyl chloride Phenoxy terephthalic acid Phenoxytherephthalic acid dichloride Phenoxyterephthalic acid diphenyl ester Di (n-hexyloxy) terephthalic acid Bis (n-hexyloxy) terephthalic acid dichloride Bis- (n-hexyloxy) terephthalic acid diphenyl ester 2,5-furanedicarboxylic acid 2,5-furandicarboxylic acid chloride 2,5-furan diphenyl ester Thiophene dicarboxylic acid Naphthalene-2,6-dicarboxylic acid Diphenyl ether 4,4'-dicarboxylic acid Benzophenone 4,4'-dicarboxylic acid Isopropylidene-4,4'-di
• Aromatic diamines of the formula (IX) are: 2,2-bis- [4- (3-trifluoromethyl-4-aminophenoxy) phenyl] propane Bis- [4- (4-aminophenoxy) phenyl] sulfide Bis- [4- (3-aminophenoxy) phenyl] sulfide Bis- [4- (3-aminophenoxy) phenyl] sulfone Bis- [4- (4-aminophenoxy) phenyl] sulfone 2,2-bis- [4- (4-aminophenoxy) phenyl] propane 2,2-bis [4- (3-aminophenoxy) phenyl] propane 2,2-bis- [4- [4- (2-aminophenoxy) phenyl] propane 1,1,1,3,3,3-hexafluoro-2,2-bis- [4- (4-aminophenoxy) phenyl] propane,
• the polyetheramides used according to the invention are preferably prepared via solution condensation
• the solution condensation of the aromatic dicarboxylic acid dichloride with the aromatic diamines takes place in aprotic, polar solvents of the amide type, e.g. in N, N-dimethyl-acetamide, preferably in N-methyl-2-pyrrolidone.
• these solvents can be added in a known manner to increase the solvency or to stabilize the polyether amide solutions, halide salts of the first and / or second group of the periodic system.
• Preferred additives are calcium chloride and / or lithium chloride.
• the condensation is carried out without the addition of salt, since the aromatic polyetheramides described above are notable for high solubility in the amide-type solvents mentioned above.
• a monofunctional aromatic acid chloride or acid anhydride is added, for example, at the end of the polymerization reaction as a chain lock Benzoyl chloride, fluorobenzoyl chloride, diphenylcarboxylic acid chloride, phenoxybenzoyl chloride or else phthalic anhydride, naphthalic anhydride, chloronaphthalic anhydride.
• Such chain locking agents can optionally be substituted, preferably with fluorine or chlorine atoms.
• Benzoyl chloride or phthalic anhydride is preferably used, particularly preferably benzoyl chloride.
• a monofunctional, preferably aromatic amine for example fluoraniline, chloroaniline, 4-aminodiphenylamine, aminobiphenylamine, aminodiphenyl ether, aminobenzophenone or aminoquinoline, is used as chain closing agent after the end of the polycondensation.
• diacid chloride is polycondensed in a deficit with diamine and then the remaining reactive amino groups are deactivated with a monofunctional acid chloride or diacid anhydride.
• the diacid chloride is used in a deficit and polycondensed with a diamine.
• the remaining reactive amino end groups are then deactivated with a monofunctional, preferably aromatic, optionally substituted acid chloride or acid anhydride.
• the chain locking agent ie the monofunctional amine or acid chloride or acid anhydride, is preferably used in a stoichiometric or superstoichiometric amount, based on the diacid or diamine component.
• the molar ratio is particularly preferably in the range from 0.90 to 0.99 and 1.01 to 1.10, particularly preferably in the range from 0.93 to 0.98 and 1.02 to 1.07, in particular in the range from 0.95 to 0.97 and 1.03 to 1.05.
• the polycondensation temperatures are usually between -20 and +120 ° C, preferably between +10 and +100 ° C. Particularly good results are achieved at reaction temperatures between +10 and + 80 ° C.
• the polycondensation reactions are preferably carried out such that 2 to 40, preferably 5 to 30,% by weight of polycondensate are present in the solution after the reaction has ended.
• the solution can be diluted with N-methyl-2-pyrrolidone or other solvents, e.g. DMF, DMAC or butyl cellosolve, if necessary, or concentrated under reduced pressure (thin film evaporator).
• the hydrogen chloride formed, loosely bound to the amide solvent is removed by adding acid-binding auxiliaries.
• acid-binding auxiliaries lithium hydroxide, calcium hydroxide, but in particular calcium oxide, propylene oxide, ethylene oxide or ammonia are suitable.
• pure water is used as the "acid-binding" agent, which dilutes the hydrochloric acid and at the same time serves to precipitate the polymer.
• the copolyamide solutions according to the invention described above are filtered, degassed and further processed in a manner known per se to give aramid fibers or threads.
• additives can also be added to the solutions.
• suitable amounts of additives can also be added to the solutions.
• a precipitant can be added to the solution and the coagulated product can be filtered off.
• Typical precipitants are, for example, water, methanol, acetone, which may also contain pH-controlling additives such as May contain ammonia or acetic acid.
• the isolation is preferably carried out by comminuting the polymer solution with an excess of water in a cutting mill.
• the finely crushed coagulated polymer particles facilitate the subsequent washing steps (removal of the secondary products formed from the hydrochloric acid) and drying of the polymer (avoiding inclusions) after filtration. Subsequent shredding is also unnecessary, since a free-flowing product is created directly.
• the aromatic polyamides of the formula II which are preferably used according to the invention have surprisingly good mechanical properties and high glass transition temperatures.
• the Staudinger index [ ⁇ ] o is in the range from 0.4 to 1.5 dl / g, preferably in the range from 0.5 to 1.3 dl / g, particularly preferably in the range from 0.6 to 1.1 dl / g G.
• the glass transition temperatures are generally above 180 ° C., preferably above 200 ° C., the processing temperatures in the range from 320 to 380 ° C., preferably in the range from 330 to 370 ° C., particularly preferably in the range from 340 to 360 ° C.
• polyamides can be processed using extrusion processes since the melt viscosity does not exceed 10,000 Pas.
• the extrusion can be carried out on conventional single or twin screw extruders.
• the nonwovens according to the invention can be produced in any of the ways known per se. Staple fibers or short fibers or also continuous filaments from the two types of aramid can be used. The formation of the fleece can take place via dry or wet processing.
• At least one type of fiber is an aramide that is not soluble in organic solvents, processing with staple or short fibers is preferred.
• carded nonwovens In such a case, it is preferred to produce carded nonwovens.
• the two types of fibers are preferably mixed before carding.
• nonwovens according to the invention can, however, also be produced by other conventional nonwoven formation techniques, for example by wet nonwoven technology (in particular for producing paper-like nonwovens) or aerodynamic or hydrodynamic nonwoven formation (in particular for producing bulky nonwovens).
• the invention relates in particular to papers based on the nonwovens according to the invention, which are characterized by a content of approximately 70 to 98% by weight, in particular 80 to 90% by weight, of load-bearing aramid fibers in the form of staple fibers which are fibrillated and a content from about 2 to 30% by weight, in particular 10 to 20% by weight, of binding fibers made of thermoplastic aramides, which are solidified by melting the carrier fibers onto the binding fibers or by practically completely melting the binding fibers.
• the stack lengths of the supporting aramid fibers are generally 2 to 6 mm.
• the fibers can be made by cutting or tearing. These fibers are preferably fibrillated by mechanical processing, for example by treating an aqueous suspension of the aramid staple fibers in a dissolver.
• the aramid binding fibers are preferably used in the form of staple fibers.
• the staple length of the binding fibers preferably corresponds approximately to the staple length of the carrier fibers.
• the binder fibers can be used as such, i.e. prior fibrillation is not absolutely necessary.
• the two types of fibers which in turn can be in the form of mixtures, are mixed together. This is generally done in an aqueous medium.
• the suspension produced in this way is applied to a sieve pad, the aqueous medium being separated off and the fibers which have been felted together remaining on the pad.
• the fabric obtained in this way is stabilized and / or solidified by heat treatment. If necessary, the heat treatment is carried out under pressure.
• Typical temperatures for the consolidation step depend on the fiber types selected in the individual case and can be determined by a person skilled in the art using simple test series.
• the papers produced in this way - depending on the consolidation conditions used - either have practically no binding fibers, i.e. the binding fibers have melted so completely through the consolidation step that their fiber shape has been lost, or some of the melting fibers have been preserved, and only the carrier fibers have melted onto the binding fibers.
• the papers according to the invention can be used in particular for the production of laminates, for example as top layers in the reinforcement of "honeycomb laminates", as described in WO-A-84/04727 or in the reinforcement of network materials, as in EP-A- 158,234.
• the nonwovens produced in a first step can optionally be pre-consolidated before final consolidation. This can be done for example by needles.
• the final consolidation to the nonwovens according to the invention is carried out by heating the initially obtained nonwoven to a temperature at which the binding fibers melt and / or deform thermoplastic, whereby they usually form so-called "binding sails" at the crossing points of the supporting aramid fibers while losing their fiber structure.
• the heating can be carried out by treatment with a hot carrier medium, for example with air, or by treatment with hot rollers or calenders, which may have a surface structure, and impart an embossed structure to the nonwoven fabric.
• the duration of the heat treatment depends, for example, on the desired end properties, on the dimensions of the Fleece and the nature of the types of fibers forming the fleece.
• the melting point of the binding fibers is usually at least 10 ° C. below the melting or decomposition point of the supporting fibers, in particular more than 30 ° C. below the melting or decomposition point of the supporting fibers.
• the melting point of the binding fibers below the melting or decomposition point of the supporting fibers so that they do not experience any significant changes in properties during the heat treatment.
• the character of the nonwovens according to the invention is also influenced by the proportion of melt binders. Depending on the area of application, a voluminous nonwoven with only a few bonding points is preferred or an almost flat connection, e.g. for laminates.
• Typical values for the proportion of melt binder are in the range of 20-80% by weight of binder fiber, based on the amounts of binder fiber and load-bearing fiber.
• the basis weights of the nonwovens according to the invention and the individual titer and stack lengths of both types of fibers can be varied within wide limits and adapted to the requirements of the further processing processes and the area of use.
• Typical values for the grammages are 30 to 500 g / m2.
• Typical values for the individual titer of the fibers are in the range from 0.5 to 5 dtex.
• the filaments or staple fibers making up the nonwovens according to the invention can have a practically round cross section or can also have other shapes, such as dumbbell, kidney-shaped, triangular or tri or multilobal cross sections. Hollow fibers can be used. Furthermore, the two types of fibers can be combined in the form of bicomponent or multicomponent fibers, the binding component filling at least part of the fiber surface.
• the supporting aramid fibers are spun from solvents in a known manner, and the thermoplastic aramids can be spun from the solution or from the melt.
• the nonwovens according to the invention consist practically exclusively of aromatic polyamides and thus have all the advantages of these polymers, such as chemical and thermal stability, extremely good flame resistance and good compatibility with one another. They also have all the advantages of melt-bonded nonwovens, i.e. good tear and tear behavior.
• the nonwovens according to the invention can be finished in a conventional manner, for example by adding antistatic agents, dyes or biocidal additives.
• the nonwovens according to the invention can be used in particular in areas where high stability (chemical, thermal and mechanical) is required.
• examples include the use as filter materials, as insulating materials (thermal and electrical) and as reinforcing materials for different substrates (e.g. plastics or as geotextiles).
• the suspension obtained is dewatered by filtration and the filter cake obtained is applied to a hot plate at about 300 ° C. and dried at this temperature; the drying process is supported by treating the side of the filter cake facing away from the heating plate with an iron of approximately 300 ° C.
• the papers produced in this way can then be further consolidated by treatment in a heating press.
• Table 1 shows the production conditions of different aramid papers and their strengths. The strength values were determined by recording force-expansion diagrams on 1.5 cm wide test strips of the papers. The measurements were carried out with an Instron tester. The clamping length was 50 mm. The strength values are based on the basis weight of the paper.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Polyamides (AREA)
• Nonwoven Fabrics (AREA)
• Paper (AREA)
• Laminated Bodies (AREA)
• Reinforced Plastic Materials (AREA)
• Artificial Filaments (AREA)
• Materials For Medical Uses (AREA)

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• 1992
  • 1992-01-18 DE DE59206760T patent/DE59206760D1/de not_active Expired - Fee Related
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  • 1992-01-18 AT AT92100815T patent/ATE140493T1/de not_active IP Right Cessation
  • 1992-01-18 EP EP92100815A patent/EP0496313B1/fr not_active Expired - Lifetime
  • 1992-01-21 US US07/823,376 patent/US5393601A/en not_active Expired - Fee Related
  • 1992-01-21 IE IE920180A patent/IE74904B1/en not_active IP Right Cessation
  • 1992-01-22 JP JP4009174A patent/JPH04352860A/ja active Pending

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