EP0496313B1 - Non-woven reinforced with a meltbinder - Google Patents

Abstract

A nonwoven reinforced with a melt binder is described, based on load-bearing aramid fibres and binder fibres of thermoplastic aramids, the melting point of which is below the melting or decomposition point of the said load-bearing aramid fibres. The nonwoven is characterised in that the binder fibres are virtually completely melted. The nonwoven are distinguished by a high strength.

Description

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. In contrast to conventional textile fabrics, such as fabrics, knitted fabrics or knitted 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 pressing 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 binder and the other type acts as a supporting fiber. As a result of the heat-melt treatment, the binding fiber is deformed and a porous sheet material is formed which has good paint impregnability. The necessary strength is only achieved through impregnation. Fibers which consist of more than 80 mol% of m-phenylene isophthalamide units are proposed as binding fibers.

From US-A-3,920,428 a filter material is known which consists of glass fibers which are strengthened by means of aromatic polyamide fibers. Here, too, 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.

This object is achieved by the nonwoven fabric according to claim 1.

As a result of the practically complete melting of the binding fibers and the convergence of the material forming these fibers at the crossing points of the supporting aramid fibers, usually with the formation of so-called "binder blessings", a considerable increase in the strength of the nonwovens is found.

In the context of the present description, the term “aramide” is understood to mean a polyamide which has essentially aromatic residues in the polymer chain, for example more than 80 mol% of which is composed of aromatic monomer units.

Practically all combinations of aramid fibers can be used to produce the nonwoven fabric according to the invention, as long as the binding fiber consists of thermoplastic aromatic polyether amide and the supporting fiber has a melting or decomposition point which is higher than the melting point of the binding fiber, so that the binding fiber can be melted practically completely without that the load-bearing fiber is changed significantly.

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.

Examples of 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.

• Poly-(m-phenylen-isophthalamid) oder
• Poly-(p-phenylen-isophthalamid). Beispiele für solche Aramide die Produkte NOMEX® der Fa. Du Pont. Diese Aramide sind in gängigen Lösungsmitteln unlöslich.

Examples of 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). Examples of such aramids are the products NOMEX® from Du Pont. These aramids are insoluble in common solvents.

It is preferred to use 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.

These include, for example, soluble 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.

und

und bis zu 5 Mol-% m-Bindungen enthaltende, von aromatischen Dicarbonsäuren und/oder von aromatischen Diaminen abgeleitete Struktureinheiten (Ie) und/oder (If), wobei die Summe der Molanteile der Struktureinheiten (Ia)+(Ie) und der Molanteile der Struktureinheiten (Ib)+(Ic)+(Id)+(If) im wesentlichen gleich groß sind, und die Anteile der Diaminkomponenten (Ib), (Ic) und (Id) im Verhältnis zur Gesamtmenge dieser Diaminkomponente innerhalb folgender Grenzen liegen: Struktureinheit (Ib): 30-50 Mol-%, Struktureinheit (Ic): 15-35 Mol-%, Struktureinheit (Id): 20-40 Mol-%; oder enthaltend mindestens 95 Mol-%, bezogen auf das Polyamid, an wiederkehrenden Struktureinheiten der Formeln Ia, Ig, Ib und Id

        - OC- Ar¹- CO-     (Ia),



        - HN- Ar²- NH-     (Ig),

und

und bis zu 5 Mol% m-Bindungen enthaltende, von aromatischen Dicarbonsäuren und/oder von aromatischen Diaminen abgeleitete Struktureinheiten (Ie) und/oder (If), wobei die Summen der Molanteile der Struktureinheiten (Ia)+(Ie) und der Molanteile der Struktureinheiten (Ig)+(Ib)+(Id)+(If) im wesentlichen gleichgroß sind, und die Anteile der Diaminkomponenten (Ig), (Ib) und (Id) im Verhältnis zur Gesamtmenge dieser Diaminkomponenten innerhalb folgender Grenzen liegen: Struktureinheiten (Ig): 15-25 Mol-%, Struktureinheiten (Ib): 45-65 Mol-%, Struktureinheiten (Id): 15-35 Mol-%; oder enthaltend mindestens 95 Mol-%, bezogen auf das Polyamid, an wiederkehrenden Struktureinheiten der Formeln Ia, Ig, Ib und Ic

        -OC-Ar¹-CO-     (Ia),



        -HN-Ar²-NH-     (Ig),

und

und bis zu 5 Mol-% m-Bindungen enthaltende, von aromatischen Dicarbonsäuren und/oder von aromatischen Diaminen abgeleitete Struktureinheiten (Ie) und/oder (If), wobei die Summe der Molanteile der Struktureinheiten (Ia)+(Ie) und der Molanteile der Struktureinheiten (Ig)+(Ib)+(Ic)+(If) im wesentlichen gleich groß sind, und die Anteile der Diaminkomponenten (Ig), (Ib) und (Ic) im Verhältnis zur Gesamtmenge dieser Diaminkomponenten innerhalb folgender Grenzen liegen: Struktureinheiten (Ig): 20-30 Mol-%, Struktureinheiten (Ib): 35-55 Mol-%, Struktureinheiten (Ic): 15-40 Mol-%; dabei bedeuten in diesen Formeln (Ia) bis (Ig)

• -Ar¹- und -Ar²- zweiwertige aromatische Reste, deren Valenzbindungen in para- oder vergleichbarer koaxialer oder paralleler Stellung stehen und die durch einen oder zwei inerte Reste, wie Alkyl, Alkoxy oder Halogen substituiert sein können, und
• -R¹ und -R² sind voneinander verschiedene niedere Alkylreste oder niedere Alkoxyreste oder Halogenatome. Beispiele für -Ar¹- und -Ar²- sind Naphthalin-1,4-diyl und bevorzugt p-Phenylen.

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-Ar ¹ -CO- (Ia),

and

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: Structural unit (Ib): 30-50 mol%, Structural unit (Ic): 15-35 mol%, Structural unit (Id): 20-40 mole%; or containing at least 95 mol%, based on the polyamide, of recurring structural units of the formulas Ia, Ig, Ib and Id

- OC- Ar ¹ - CO- (Ia),



- HN- Ar ² - NH- (Ig),

and

and up to 5 mol% containing m bonds, of aromatic dicarboxylic acids and / or of aromatic diamines derived structural units (Ie) and / or (If), the sums of the molar proportions of the structural units (Ia) + (Ie) and the molar proportions of the structural units (Ig) + (Ib) + (Id) + (If) being essentially the same size , and the proportions of the diamine components (Ig), (Ib) and (Id) in relation to the total amount of these diamine components are within the following limits: Structural units (Ig): 15-25 mol%, Structural units (Ib): 45-65 mol%, Structural units (Id): 15-35 mole%; or containing at least 95 mol%, based on the polyamide, of recurring structural units of the formulas Ia, Ig, Ib and Ic

-OC-Ar ¹ -CO- (Ia),



-HN-Ar ² -NH- (Ig),

and

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 (Ig) + (Ib) + (Ic) + (If) are essentially the same size, and the proportions of the diamine components (Ig), (Ib) and (Ic) in relation to the total amount of these diamine components are within the following limits: Structural units (Ig): 20-30 mol%, Structural units (Ib): 35-55 mol%, Structural units (Ic): 15-40 mole%; in these formulas mean (Ia) to (Ig)

• -Ar ¹ - and -Ar ² - divalent aromatic radicals, the valence bonds of which are in a para- or comparable coaxial or parallel position and which can be substituted by one or two inert radicals, such as alkyl, alkoxy or halogen, and
• -R ¹ and -R ² are different lower alkyl radicals or lower alkoxy radicals or halogen atoms. Examples of -Ar ¹ - and -Ar ² - are naphthalene-1,4-diyl and preferably p-phenylene.

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.

All known thermoplastically processable aromatic polyetheramide fibers can be used as binding fibers, as long as these fibers can be melted practically completely and the supporting aramid fibers are glued. This is usually done with the formation of so-called "tie sails". It is preferred to use thermoplastically processable aromatic polyetheramide fibers which are soluble in organic solvents.

The particularly preferred binder fibers based on thermoplastically processable aromatic polyetheramides include, for example, the 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.

worin

• Ar³ einen zweiwertigen substituierten oder unsubstituierten aromatischen Rest bedeutet, dessen freie Valenzen sich in para- oder meta-Stellung oder in vergleichbarer paralleler oder gewinkelter Stellung zueinander befinden,
• Ar⁴ eine der für Ar³ angegebenen Bedeutungen haben kann oder eine Gruppe -Ar⁷-Z-Ar⁷- darstellt,
• wobei Z eine -C(CH₃)₂- oder -O-Ar⁷-O- Brücke ist und
• Ar⁷ für einen zweiwertigen aromatischen Rest steht,
• Ar⁵ und Ar⁶ gleich oder verschieden voneinander sind und für einen substituierten oder unsubstituierten para- oder meta-Arylenrest stehen,
• Y eine -C(CH₃)₂-, SO₂-, -S- oder -C(CF₃)₂-Brücke darstellt,

wobei

• a) das Polyetheramid ein mittleres Molekulargewicht (Zahlenmittel) im Bereich von 5000 bis 50000 aufweist,
• b) die Molekulargewichtskontrolle gezielt durch nicht-stöchiometrische Zugabe der Monomereinheiten erfolgt, wobei die Summe der Molenbrüche x, y und z eins ist, die Summe von x und z nicht gleich y ist und x den Wert null annehmen kann, und
• c) die Enden der Polymerkette praktisch vollständig mit monofunktionellen, im Polymer nicht weiterreagierenden Resten R³ verschlossen sind, die unabhängig voneinander gleich oder verschieden sein können.

It is particularly preferred to use binder fibers made from thermoplastically processable aromatic copolyetheramides of the formula II

wherein

• Ar ³ denotes a divalent substituted or unsubstituted aromatic radical, the free valences of which are in the para or meta position or in a comparable parallel or angled position to one another,
• Ar ^{4 can have} one of the meanings given for Ar ³ or represents a group -Ar ⁷ -Z-Ar ⁷ -,
• where Z is a -C (CH ₃ ) ₂ - or -O-Ar ⁷ -O- bridge and
• Ar ^{7 represents} a divalent aromatic radical,
• Ar ⁵ and Ar ^{6 are} identical or different from one another and represent a substituted or unsubstituted para or meta-arylene radical,
• Y represents a -C (CH ₃ ) ₂ -, SO ₂ -, -S- or -C (CF ₃ ) ₂ bridge,

in which

• a) the polyether amide has an average molecular weight (number average) in the range from 5000 to 50,000,
• b) the molecular weight control is carried out specifically by non-stoichiometric addition of the monomer units, the sum of the mole fractions x, y and z being one, the sum of x and z not being y and x being able to assume the value zero, and
• c) the ends of the polymer chain are almost completely closed with monofunctional radicals R ³ which do not react further in the polymer and which, independently of one another, can be the same or different.

Binding fibers based on these aramids can be processed thermoplastically and are particularly good Melting behavior and lead to nonwovens with excellent strength.

• Bei Ar³ kann es sich um heterocyclisch-aromatische oder bevorzugt um carbocyclisch-aromatische Reste handeln. Heterocyclisch-aromatische Reste weisen vorzugsweise ein oder zwei Sauerstoff- und/oder Schwefel- und/oder Stickstoffatome in Kern auf.
• Bei Ar⁵ und Ar⁶ handelt es sich im allgemeinen um carbocyclisch-aromatische Arylenreste, deren freie Valenzen sich in para- oder meta-Stellung oder in vergleichbarer paralleler oder gewinkelter Stellung zueinander befinden, vorzugsweise handelt es sich um einkernige aromatische Reste.
• Ar⁷ hat im allgemeinen eine der für Ar⁵ bzw. Ar⁶ definierten Bedeutungen .

Ar ³ can be a mononuclear or condensed dinuclear aromatic divalent radical or a radical of the formula -Ar ⁷ -Q-Ar ⁷ -, in which Ar ^{7 has} the meaning defined above and Q is a direct CC bond or a -O-, -CO-, -S-, -SO- or -SO ₂ bridge means.

• Ar ³ 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.
• Ar ⁵ and Ar ⁶ 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, and are preferably mononuclear aromatic radicals.
• Ar ⁷ generally has one of the meanings defined for Ar ⁵ or Ar ⁶ .

Examples of residues -Ar ³ -, -Ar ⁴ -, -Ar ⁵ - and -Ar ⁶ - are p-phenylene, m-phenylene, biphenyl-4,4'-diyl or naphthalene-1,4-diyl.

Examples of substituents which are optionally located on the radicals -Ar ¹ - to -Ar ⁶ - are branched or in particular straight-chain C ₁ -C ₆ 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.

Examples of halogen substituents are bromine or especially chlorine.

The aromatic polyetheramides of the formula II which are preferably used in accordance with the invention are produced by a targeted molecular weight control by adding the monomer units in a non-stoichiometric manner, 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 same Can assume zero value. In a preferred embodiment, z is greater than x.

After the polycondensation reaction has ended, 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.

In the case of end groups V and / or VI, the terminal nitrogen in formula (II) is an imide nitrogen.

In the formulas given above, 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.

• a) das Molekulargewicht durch Verwendung nicht stöchiometrischer Mengen der Monomeren gezielt kontrolliert wird,
• b) die Enden der Polymerkette durch monofunktionelle, im Polymer nicht weiter reagierende Verbindungen vollständig verschlossen werden, und vorzugsweise
• c) der Gehalt an anorganischen Verunreinigungen im Polymer nach der Aufarbeitung und Isolierung 500 ppm nicht übersteigt.

It has been found that thermoplastic aromatic polyetheramides which have very good mechanical properties can be produced using conventional techniques, if

• a) the molecular weight is specifically controlled by using non-stoichiometric amounts of the monomers,
• b) the ends of the polymer chain are completely closed by monofunctional compounds which do not react further in the polymer, and preferably
• c) the content of inorganic impurities in the polymer after processing and isolation does not exceed 500 ppm.

The 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.

The following compounds are suitable for the preparation of these preferred polyetheramides:

Dicarboxylic acid derivatives of the formula (VII)

W - CO - Ar ³ - CO - W (VII)

where Ar ^{3 has} the meaning given above, and W represents a fluorine, chlorine, bromine or iodine atom, preferably a chlorine atom, or a —OH or OR ⁴ group, where R ^{4 is} a branched or unbranched aliphatic or aromatic radical can.

• Terephthalsäure
• Terephthalsäuredichlorid
• Terephthalsäurediphenylester
• Isophthalsäure
• Isophthalsäurediphenylester
• Isophthalsäurechlorid
• Phenoxyterephthalsäure
• Phenoxytherephthalsäuredichlorid
• Phenoxyterephthalsäurediphenylester
• Di(n-Hexyloxy)terephthalsäure
• Bis-(n-Hexyloxy)terepthalsäuredichlorid
• Bis-(n-Hexyloxy)terephthalsäurediphenylester
• 2,5-Furandicarbonsäure
• 2,5-Furandicarbonsäurechlorid
• 2,5-Furandiphenylester
• Thiophendicarbonsäure
• Naphthalin-2,6-dicarbonsäure
• Diphenylether-4,4'-dicarbonsäure
• Benzophenon-4,4'-dicarbonsäure
• Isopropyliden-4,4'-dibenzoesäure
• Diphenylsulfon-4,4'-dicarbonsäure
• Tetraphenylthiophen-dicarbonsäure
• Diphenylsulfoxid-4,4'-dicarbonsäure
• Diphenylthioether-4,4'-dicarbonsäure
• Trimethylphenylindandicarbonsäure

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-furandicarboxylic 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'-dibenzoic acid
• Diphenylsulfone-4,4'-dicarboxylic acid
• Tetraphenylthiophene dicarboxylic acid
• Diphenyl sulfoxide-4,4'-dicarboxylic acid
• Diphenylthioether-4,4'-dicarboxylic acid
• Trimethylphenylindane dicarboxylic acid

As aromatic diamines of the formula (VIII)

• m-Phenylendiamin
• p-Phenylendiamin
• 2,4-Dichlor-p-phenylendiamin
• Diaminopyridin
• Bis(aminophenoxy)benzol
• 2,6-Bis(aminophenoxy)pyridin
• 3,3'-Dimethylbenzidin
• 4,4'- und 3,4'-Diaminodiphenylether
• Isopropyliden-4,4'-dianilin
• p,p'- und m,m'-Bis(4-aminophenylisopropyliden)benzol
• 4,4'- und 3,3'-Diaminobenzophenon
• 4,4'- und 3,3'-Diaminodiphenylsulfon
• Bis(2-amino-3-methylbenzo)thiophen-S,S-dioxid

H ₂ N - Ar ⁴ - NH ₂ (VIII)

in Ar ⁴ - has the meaning given above, the following compounds are preferably suitable:

• m-phenylenediamine
• p-phenylenediamine
• 2,4-dichloro-p-phenylenediamine
• Diaminopyridine
• Bis (aminophenoxy) benzene
• 2,6-bis (aminophenoxy) pyridine
• 3,3'-dimethylbenzidine
• 4,4'- and 3,4'-diaminodiphenyl ether
• Isopropylidene-4,4'-dianiline
• p, p'- and m, m'-bis (4-aminophenylisopropylidene) benzene
• 4,4'- and 3,3'-diaminobenzophenone
• 4,4'- and 3,3'-diaminodiphenyl sulfone
• Bis (2-amino-3-methylbenzo) thiophene-S, S-dioxide

Aromatic diamines which may also be used are those of the formula (IX)

H ₂ N - Ar ⁵ - O - Ar ⁶ - Y - Ar ⁶ - O - Ar ⁵ - NH ₂ (IX)

where Ar ⁵ , Ar ⁶ and Y have the meaning given above.

• 2,2-Bis-[4-(3-trifluormethyl-4-aminophenoxy)phenyl]propan
• Bis-[4-(4-aminophenoxy)phenyl]sulfid
• Bis-[4-(3-aminophenoxy)phenyl]sulfid
• Bis-[4-(3-aminophenoxy)phenyl]sulfon
• Bis-[4-(4-aminophenoxy)phenyl]sulfon
• 2,2-Bis-[4-(4-aminophenoxy)phenyl]propan
• 2,2-Bis-[4-(3-aminophenoxy)phenyl]propan
• 2,2-Bis-[4-(2-aminophenoxy)phenyl]propan
• 1,1,1,3,3,3-Hexafluor-2,2-bis-[4-(4-aminophenoxy)phenyl] propan,

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- (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 processes.

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. Optionally, halide salts of the first and / or second group of the periodic system can be added to these solvents in a known manner to increase the solvency or to stabilize the polyether amide solutions. Preferred additives are calcium chloride and / or lithium chloride. In a preferred embodiment, the condensation is carried out without the addition of salt, since the aromatic polyetheramides described above are distinguished by a high solubility in the abovementioned amide-type solvents.

wobei

1 und gleichzeitig q = y/x+z ist.

• $\overline{\text{P}}$
  
  _n = Polymerisationsgrad
• q = Molverhältnis der Disäurekomponenten zu Aminkomponenten

The polyamides of the formula II which are preferably used according to the invention permit thermoplastic processing by standard methods. They can be produced if at least one of the starting components is used in the stoichiometric deficit. In this way it is possible to limit the molecular weight according to the well-known Carothers equation: $${\overline{\text{P}}}_{\text{n}}\text{=}\frac{\text{1 + q}}{\text{1 - q}}$$

in which

1 and at the same time q = y / x + z.

• $\overline{\text{P}}$
  
  _n = degree of polymerization
• q = molar ratio of the diacid components to amine components

When working with a deficit of acid dichloride, 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.

If a deficit of diamine component is used, 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.

In a particularly preferred embodiment of the polycondensation process, diacid chloride is polycondensed in deficit with diamine and the remaining reactive amino groups are then deactivated with a monofunctional acid chloride or diacid anhydride.

In a further preferred embodiment, 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.

To produce the aromatic polyamides preferably used according to the invention, the molar ratio q (acid components to diamine components) can be varied in the range from 0.90 to 1.10, exact stoichiometry (q = 1) of the bifunctional components being excluded. 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. For special applications, the solution can be diluted with N-methyl-2-pyrrolidone or other solvents, e.g. DMF, DMAC or butyl cellosolve, or concentrated under reduced pressure (thin-film evaporator).

After the polycondensation has ended, the hydrogen chloride formed, loosely bound to the amide solvent, is removed by adding acid-binding auxiliaries. For example, lithium hydroxide, calcium hydroxide, but in particular calcium oxide, propylene oxide, ethylene oxide or ammonia are suitable. In a particular embodiment, pure water is used as the "acid-binding" agent, which dilutes the hydrochloric acid and at the same time serves to precipitate the polymer. To produce shaped structures in accordance with the present invention, 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.

If necessary, suitable amounts of additives can also be added to the solutions. Examples are light stabilizers, antioxidants, flame retardants, antistatic agents, dyes, color pigments or fillers.

To isolate the polyether amide, 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 comminuted coagulated polymer particles facilitate the subsequent washing steps (removal of the secondary products formed from the hydrochloric acid) and the drying of the polymer (avoiding inclusions) after filtration. Subsequent shredding is also unnecessary, since a free-flowing product is created directly.

In addition to the solution condensation described, which is considered to be an easily accessible process, as already mentioned, other customary processes for producing polyamides, such as melt or solid condensation, can also be used. In addition to condensation with regulation of the molar mass, these processes also include cleaning or washing steps and the addition of suitable additives. The additives can also be added to the isolated polymer during thermoplastic processing.

The aromatic polyamides of the formula II preferably used according to the invention have surprisingly good mechanical properties and high glass transition temperatures.

The Staudinger index [η] _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.

These 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.

If at least one type of fiber is an aramide that is not soluble in organic solvents, the preferred choice is processing using staple or short fibers.

In such a case, it is preferred to produce carded nonwovens. The two types of fibers are preferably mixed before carding.

Likewise, the 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 about 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 aromatic polyetheramides, which are solidified 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. Fibrillation of these fibers is preferably carried out 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 stack length of the binding fibers preferably corresponds approximately to the stack length of the carrier fibers. The binder fibers can be used as such, i.e. prior fibrillation is not absolutely necessary.

To produce the paper, 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 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.

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 the 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.

It is preferred to choose 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 staple 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 / m ² . 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.

While high values for strength and modulus are generally taken into account in the load-bearing reinforcing fibers, largely unoriented fibers can also be used as the melting matrix fibers.

For the production of nonwovens, 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 following examples describe the invention without limiting it. Quantities refer to the weight, unless otherwise stated.

Examples 1 to 10

General working instructions regarding the production of aramid paper from fiber pulp Staple fibers with a single fiber titer of 1.8 dtex from aramids based on terephthalic acid, p-phenylenediamine, dimethylbenzidine and bis- (4-aminophenoxy) benzene with a cutting length of 6 mm are suspended to about 1% in water and about 1.5 to 2 Treated for hours in a dissolver at about 1200 revolutions / min so that the staple fibers fibrillate. Excess water is suctioned off and the fiber pulp obtained is slurried in water in the moist state and mixed with different proportions (see Table 1) of staple fibers with a cutting length of 6 mm made of fusible aramid. The fusible aramide is a copolymer based on terephthalic acid, isophthalic acid and 2,2'-bis (4-aminophenoxyphenyl) propane, the end groups of which are sealed with benzoyl chloride.

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 below shows the production conditions for 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. Table 1: Manufacturing conditions and area-related strengths Example No. Proportion of fusible aramid fiber (% by weight) Press conditions hot press (bar, ° C) Tear resistance / comments Basis weight (cN / mg / cm ² ) 1 5 no hot press 22 2nd 10th no hot press 13 3rd 15 no hot press 12th 4th 20th no hot press 12th 5 30th no hot press 14 6 5 50, 290 26 parchment-like 7 10th 50, 290 22 parchment-like 8th 15 50, 290 31 parchment-like 9 20th 50, 290 22 parchment-like 10th 30th 50, 290 23 parchment-like

Examples 11 to 28 Production of aramid papers from fiber pulp

The general procedure is as described in Examples 1 to 10. In deviation from this, staple fibers made from aramids based on terephthalic acid, p-phenylenediamine, dimethylbenzidine and bis- (4-aminophenoxy) benzene with a cutting length of 2 mm are used. The cutting length of the aramid binding fibers is 6 mm, as in the examples above.

Details of the manufacture and properties of the papers are shown in Table 2 below. Table 2: Manufacturing conditions and area-related strengths Example No. Proportion of fusible aramid fiber (% by weight) Press conditions hot press (bar, ° C) Tear resistance / comments Basis weight (cN / mg / cm ² ) 11 5 no hot press 60 12th 10th no hot press 58 13 15 no hot press 37 14 20th no hot press 32 15 30th no hot press 34 16 5 50, 290 42 parchment-like 17th 10th 50, 290 49 parchment-like 18th 15 50, 290 57 parchment-like 19th 20th 50, 290 74 parchment-like 20th 30th 50, 290 60 parchment-like 21 5 100.350 320 22 10th 100.350 260 23 15 100.350 340 24th 30th 100.350 160 25th 5 400.350 560 26 10th 400.350 590 27 15 400.350 820 28 20th 400.350 200

Claims (11)

1. A non-woven consolidated by means of a melt-fusible binder and based on loadbearing aramid fibers and on binding fibers made of thermoplastic aromatic polyether amides whose melting point is below the melting or decomposition point of said loadbearing aramid fibers, the non-woven being obtainable by the virtually complete melting of the binding fibers.
2. A non-woven as claimed in claim 1, wherein the loabearing fibers and the binding fibers comprise aramids which are soluble in organic solvents.
3. A non-woven as claimed in claim 2, wherein the loadbearing fibers used are aramids (copolyamides) soluble in organic solvents and containing at least 95 mol%, relative to the polyamide, of recurring structural units of the formulae Ia, Ib, Ic and Id,
   
           -OC-Ar¹-CO-     (Ia),
   
   

   

   

   and

   

   and containing up to 5 mol% of structural units (Ie) and/or (If) containing m-bonds and derived from aromatic dicarboxylic acids and/or from aromatic diamines, the sums of the molar proportions of structural units (Ia)+(Ie) and of the molar proportions of structural units (Ib)+(Ic)+(Id)+(If) being substantially identical,
   and the proportions of diamine components (Ib), (Ic) and (Id) being within the following limits, relative to the total amount of this diamine component: structural unit (Ib): 30-55 mol%, structural unit (Ic): 15-35 mol%, structural unit (Id): 20-40 mol%, in which

   -Ar¹- and -Ar²- are divalent aromatic radicals whose valence bonds are in the para or comparable coaxial or parallel position and which can be substituted by one or two inert radicals, such as alkyl, alkoxy or halogen, and in which

   -R¹ and -R², independently of one another, are lower alkyl radicals or lower alkoxy radicals or halogen atoms.
4. A non-woven as claimed in claim 2, wherein the loadbearing fibers used are aramids (copolyamides) soluble in organic solvents and containing at least 95 mol%, relative to the polyamide, of recurring structural units of the formulae Ia, Ig, Ib and Id
   
           -OC-Ar¹-CO-      (Ia),
   
   
   
           -HN-Ar²-NH-     (Ig),
   
   

   

   and

   

   and up to 5 mol% of structural units (Ie) and/or (If) containing m-bonds and derived from aromatic dicarboxylic acids and/or from aromatic diamines, the sums of the molar proportions of structural units (Ia)+(Ie) and of the molar proportion of structural units (Ig)+(Ib)+(Id)+(If) being substantially identical,
   and the proportions of diamine components (Ig), (Ib) and (Id) being within the following limits, relative to the total amount of these diamine components: structural units (Ig): 15-25 mol%, structural units (Ib): 45-65 mol%, structural units (Id): 15-35 mol%, in which -Ar¹-, -Ar²- and -R¹ have the meaning defined in claim 3.
5. A non-woven as claimed in claim 2, wherein the loadbearing fibers used are aramids (copolyamides) soluble in organic solvents and containing at least 95 mol%, relative to the polyamide, of recurring structural units of the formulae Ia, Ig, Ib and Ic
   
           -OC-Ar¹-CO-     (Ia),
   
   
   
           -HN-Ar²-NH-     (Ig),
   
   

   

   and

   

   and containing up to 5 mol% of structural units (Ie) and/or (If) containing m-bonds and derived from aromatic dicarboxylic acids and/or from aromatic diamines, the sums of the molar proportions of structural units (Ia)+(Ie) and of the molar proportions of structural units (Ig)+(Ib)+(Ic)+(If) being substantially identical, and the proportions of diamine components (Ig), (Ib) and (Ic) being within the following limits, relative to the total amount of these diamine components: structural units (Ig): 20-30 mol%, structural units (Ib): 35-55 mol%, structural units (Id): 15-40 mol%, in which -Ar¹, -Ar², -R¹ and -R² have the meaning defined in claim 3.
6. A non-woven as claimed in claim 1, wherein the aromatic polyether amides are compounds of the formula II

   

   in which

   Ar³ is a divalent substituted or unsubstituted aromatic radical whose free valences are in the para or meta position or in a comparable parallel or angled position relative to one another,

   Ar⁴ can have one of the meanings given for Ar³ or is a group -Ar⁷-Z-Ar⁷-,

   in which Z is a -C(CH₃)₂- or -O-Ar⁷-O- bridge and Ar⁷ is a divalent aromatic radical,

   Ar⁵ and Ar⁶ are identical to or different from one another and are a substituted or unsubstituted para-or meta-arylene radical,

   Y is a -C(CH₃)₂-, -SO₂-, -S- or -C(CF₃)₂- bridge, in which

   a) the polyether amide has an average molecular weight (number average) in the range from 5,000 to 50,000,

   b) molecular weight control takes place selectively by non-stoichiometric addition of the monomer units, in which the sum of the molar fractions x, y and z is one, the sum of x and z is not y and x can adopt the value zero, and

   c) the ends of the polymer chain are virtually completely capped by monofunctional radicals R³ which do not further react in the polymer and which, independently of one another, can be identical or different.
7. A paper based on aramid fibers, which contains about 70 to 98% by weight, in particular 80 to 90% by weight, of loadbearing aramid fibers in the form of fibrillated staple fibers and contains about 2 to 30% by weight, in particular 10 to 20% by weight, of binding fibers made of thermoplastic aromatic polyether amides which have been solidified by virtually complete melting of the binding fibers.
8. A paper as claimed in claim 7, wherein the staple lengths of the loadbearing aramid fibers are 2 to 6 mm and the staple length of the binding fibers is about the same as the staple length of the loadbearing fibers.
9. A process for the production of the paper of claim 7, which comprises:

   i) preparing an aqueous suspension of aramid loadbearing fibers and mechanically processing this suspension, resulting in the formation of fibrillated aramid loadbearing fibers,

   ii) mixing the fibrillated aramid loadbearing fibers with about 2 to 30% by weight, relative to the total amount of fibers, of binding fibers made of thermoplastic aramids,

   iii) removing the suspension medium and forming a filter cake, and

   iv) drying and heating the filter cake to a temperature, leading to its consolidation by virtually complete melting of the binding fibers.
10. Use of the non-woven of claim 1 as filter material, as insulating material or as reinforcing material.
11. Use of a paper as claimed in claim 7 for the production of laminates.