HK1263231B - Flame-retardant polyamide compositions with a high heat deflection temperature and use thereof - Google Patents

Description

Flame-retardant polyamide composition with high heat deformation resistance and use thereof

Technical Field

The present invention relates to flame-retardant polyamide compositions and to molded parts produced therefrom, said molded parts being distinguished by a high heat distortion temperature (HDT).

Background Art

Flammable plastics usually have to be provided with flame retardants in order to be able to achieve the high flame retardancy requirements required by plastics processors and partly by legislators. Preferably, also for ecological reasons, non-halogenated flame retardant systems are used which form only little or no smoke.

Among these flame retardants, the salts of phosphinic acid (phosphinates) have proven to be particularly effective for thermoplastic polymers (DE 2 252 258 A and DE 2 447 727 A).

Furthermore, synergistic combinations of phosphinates with specific nitrogen-containing compounds are known which are more effective as flame retardants in a range of polymers than the phosphinates alone (WO-2002/28953 A1 and DE 197 34 437 A1 and DE 197 37727 A1).

No. 7,420,007 B2 discloses that dialkylphosphinic acid salts containing small amounts of selected telomers are suitable as flame retardants for polymers, wherein the polymers undergo only very little degradation upon incorporation of the flame retardant into the polymer matrix.

Flame retardants often have to be incorporated in high doses to ensure adequate fire resistance of plastics according to international standards. Due to their chemical reactivity, which is required for flame retardancy at high temperatures, flame retardants can impair the processing stability of plastics, especially at higher doses. This can lead to increased polymer degradation, crosslinking reactions, gas release, or discoloration.

WO 2014/135256 A1 discloses polyamide molding compounds having significantly improved thermal stability, reduced migration tendency, and good electrical and mechanical properties.

However, flame-retardant phosphinate-containing polyamide compositions which simultaneously achieve all required properties, such as good electrical values, excellent heat distortion resistance and effective flame retardancy, have been lacking to date.

Summary of the Invention

The object of the present invention was therefore to provide flame-retardant polyamide compositions based on phosphinate-containing flame retardant systems, which simultaneously possess all of the aforementioned properties and which, in particular, have good electrical values (GWFI, CTI) and excellent heat distortion resistance (HDT-A) as well as effective flame retardancy characterized by an afterflame time (UL-94, time) which is as short as possible.

The subject of the present invention is a flame retardant polyamide composition having a heat distortion temperature HDT-A of at least 280° C., comprising

a polyamide as component A having a melting point of greater than or equal to 290° C., preferably greater than or equal to 290° C. and very particularly preferably greater than or equal to 300° C.,

- as fillers and/or reinforcing materials of component B, preferably glass fibers,

- as component C a phosphinate of formula (I)

Wherein, _R1 and _R2 represent ethyl groups,

M is Al, Fe, TiO _p or Zn,

m represents 2 to 3, preferably 2 or 3, and

p＝(4–m)/2,

- as component D a compound selected from the group consisting of Al, Fe, TiO2 or Zn salts of ethylbutylphosphinic acid, dibutylphosphinic acid, ethylhexylphosphinic acid, _{butylhexylphosphinic} acid and/or dihexylphosphinic acid, and

- as component E a phosphonate of formula (II)

Wherein, R ₃ represents ethyl,

Met is Al, Fe, TiO _q or Zn,

n represents 2 to 3, preferably 2 or 3, and

q＝(4–n)/2.

In the polyamide composition according to the invention, the proportion of component A is generally 25 to 95% by weight, preferably 25 to 75% by weight.

In the polyamide composition according to the invention, the proportion of component B is generally 1 to 45% by weight, preferably 20 to 40% by weight.

In the polyamide composition according to the invention, the proportion of component C is generally 1 to 35% by weight, preferably 5 to 20% by weight.

In the polyamide composition according to the invention, the proportion of component D is generally from 0.01 to 3% by weight, preferably from 0.05 to 1.5% by weight.

In the polyamide composition according to the invention, the proportion of component E is generally from 0.001 to 1% by weight, preferably from 0.01 to 0.6% by weight.

In this case, the percentage figures for the proportions of components A to F are based on the total amount of the polyamide composition.

Preferred are flame retardant polyamide compositions wherein

- the proportion of component A is 25 to 95% by weight,

- the proportion of component B is 1 to 45% by weight,

- the proportion of component C is 1 to 35% by weight,

- the proportion of component D is from 0.01 to 3% by weight, and

- the proportion of component E is 0.001 to 1% by weight

The percentage values are based on the total amount of the polyamide composition.

Particularly preferred are flame retardant polyamide compositions wherein

- the proportion of component A is 25 to 75% by weight,

- the proportion of component B is 20 to 40% by weight,

- the proportion of component C is 5 to 20% by weight,

- the proportion of component D is from 0.05 to 1.5% by weight, and

The proportion of component E is 0.01 to 0.6% by weight.

Salts of component C which are preferably used are those in which M ^m+ denotes Zn ²⁺ , Fe ³⁺ or, in particular, Al ³⁺ .

Salts of component D which are preferably used are zinc salts, iron salts or in particular aluminum salts.

Salts of component E which are preferably used are those in which Met ⁿ⁺ represents Zn ²⁺ , Fe ³⁺ or, in particular, Al ³⁺ .

Very particular preference is given to flame-retardant polyamide compositions in which M and Met denote Al, m and n are 3 and in which the compound of component D is present as an aluminum salt.

In a preferred embodiment, the flame-retardant polyamide composition described above comprises as further component F an inorganic phosphonate.

The use of inorganic phosphonates or also salts of phosphorous acid (phosphites) used according to the invention as component F as flame retardants is known. Thus, WO 2012/045414 A1 discloses flame retardant combinations which, in addition to phosphinates, also contain salts of phosphorous acid (=phosphites).

Preferably, the inorganic phosphonate (component F) corresponds to the general formula (IV) or (V)

[(HO)PO ₂ ] ^2- _p/2 Kat ^p+ (IV)

[(HO) ₂ PO] ^- _p Kat ^p+ (V)

Kat is a p-valent cation, in particular an alkali metal, alkaline earth metal, ammonium cation and/or a Fe, Zn or in particular Al cation, including the cations Al(OH) or Al(OH) ₂ , and p represents 1, 2, 3 or 4.

Preferably, the inorganic phosphonate (component F) is aluminum phosphite [Al(H ₂ PO ₃ ) ₃ ], aluminum hypophosphite [Al ₂ (HPO ₃ ) ₃ ], basic aluminum phosphite [Al(OH)(H ₂ PO ₃ ) ₂ *2aq], aluminum phosphite tetrahydrate [Al ₂ (HPO ₃ ) ₃ *4aq], aluminum phosphonate, Al ₇ (HPO ₃ ) ₉ (OH) ₆ (1,6-hexanediamine) _1.5 *12H ₂ O, Al ₂ (HPO ₃ ) ³ *xAl ₂ O ₃ *nH ₂ O where x=2.27-1 and/or Al ₄ H ₆ P ₁₆ O ₁₈ .

The inorganic phosphonate (component F) is preferably also an aluminum phosphite of the formula (VI), (VII) and/or (VIII)

Al ₂ (HPO ₃ ) ₃ x(H ₂ O) _q (VI)

Where q represents 0 to 4,

Al _2.00 M _z (HPO ₃ ) _y (OH) _v x (H ₂ O) _w (VII)

wherein M represents an alkali metal cation, z represents 0.01 to 1.5, y represents 2.63 to 3.5, v represents 0 to 2, and w represents 0 to 4;

Al _2.00 (HPO ₃ ) _u (H ₂ PO ₃ ) _t x(H ₂ O) _s (VIII)

wherein u represents 2 to 2.99 and t represents 2 to 0.01 and s represents 0 to 4, and/or

is aluminum phosphite [Al(H ₂ PO ₃ ) ₃ ], is aluminum hypophosphite [Al ₂ (HPO ₃ ) ₃ ], is basic aluminum phosphite [Al(OH)(H ₂ PO ₃ ) ₂ *2aq], is aluminum phosphite tetrahydrate [Al ₂ (HPO ₃ ) ₃ *4aq], is aluminum phosphonate, is Al ₇ (HPO ₃ ) ₉ (OH) ₆ (1,6-hexanediamine) _1.5 *12H ₂ O, is Al ₂ (HPO ₃ ) ³ *xAl ₂ O ₃ *nH ₂ O where x=2.27-1, and/or Al ₄ H ₆ P ₁₆ O ₁₈ .

Preferred inorganic phosphonates (component F) are salts that are insoluble or poorly soluble in water.

Particularly preferred inorganic phosphonates are the aluminum, calcium and zinc salts.

Particularly preferably, component F is a reaction product of phosphorous acid and an aluminum compound.

Particularly preferred components F are aluminum phosphites having the CAS numbers 15099-32-8, 119103-85-4, 220689-59-8, 56287-23-1, 156024-71-4, 71449-76-8 and 15099-32-8.

The aluminum phosphite used is preferably prepared by reacting an aluminum source with a phosphorus source and optionally a template in a solvent at 20 to 200° C. over a period of up to 4 days. For this purpose, the aluminum source and the phosphorus source are mixed for 1 to 4 hours, heated hydrothermally or under reflux, filtered, washed and dried, for example at 110° C.

Preferred aluminum sources are aluminum isopropoxide, aluminum nitrate, aluminum chloride, aluminum hydroxide (eg pseudo-boehmite).

Preferred phosphorus sources are phosphorous acid, (acidic) aluminum phosphite, alkali metal phosphites or alkaline earth metal phosphites.

Preferred alkali metal phosphites are disodium phosphite, disodium phosphite hydrate, trisodium phosphite, and potassium hydrogen phosphite.

A preferred disodium phosphite hydrate is Brüggemann's H10.

Preferred templates are 1,6-hexanediamine, guanidine carbonate, or ammonia.

The preferred alkaline earth metal phosphite is calcium phosphite.

The preferred ratio of aluminum to phosphorus to solvent in this case is 1:1:3.7 to 1:2.2:100 mol. The ratio of aluminum to template is 1:0 to 1:17 mol. The preferred pH value of the reaction solution is 3 to 9. The preferred solvent is water.

Particularly preferably, the salts of the same phosphinic acids as the phosphorous acid are used, ie, for example, aluminum diethylphosphinate together with aluminum phosphite or zinc diethylphosphinate together with zinc phosphite.

In a preferred embodiment, the flame retardant polyester composition comprises as component F a compound of formula (III)

wherein Me is Fe, TiO _r , Zn or especially Al,

o represents 2 to 3, preferably 2 or 3, and

r＝(4–o)/2.

Compounds of the formula (III) which are preferably used are those in which Me ^o+ represents Zn ²⁺ , Fe ³⁺ or, in particular, Al ³⁺ .

Component F is preferably present in an amount of 0.005 to 10% by weight, in particular in an amount of 0.02 to 5% by weight, based on the total amount of the polyamide composition.

The flame-retardant polyamide composition according to the invention has a high heat distortion temperature (HDT-A) to DIN EN ISO 75-3 of at least 280° C., preferably at least 290° C. and particularly preferably at least 300° C.

Preferred are flame retardant polyamide compositions according to the invention having a comparative tracking index, measured according to International Electrotechnical Commission standard IEC-60112/3, greater than or equal to 500 Volts.

Likewise preferred flame-retardant polyamide compositions according to the invention achieve a rating of VO according to UL-94, in particular measured on moldings having a thickness of 3.2 mm to 0.4 mm.

Further preferred flame-retardant polyamide compositions according to the invention have a glow-wire flammability index to IEC-60695-2-12 of at least 960° C., in particular measured on mouldings with a thickness of 0.75 to 3 mm.

The polyamide composition according to the invention comprises as component A one or more thermoplastic polyamides having a melting point greater than or equal to 290° C. The melting point is determined in this case by means of differential scanning calorimetry (DSC) at a heating rate of 10 K/s.

Thermoplastic polyamides are understood to be polyamides whose molecular chains have no or more or less long and varying numbers of side chain branches, according to Hans Domininghaus in "Die Kunststoffe und ihre Eigenschaften", 5th edition (1998), p. 14, which soften on heating and are almost arbitrarily shapeable.

The polyamides preferred according to the invention can be prepared by various methods and synthesized from a wide variety of structural units. For specific applications, they can be formulated into materials with a specifically tailored combination of properties, either alone or in combination with processing aids, stabilizers, or polymer-based alloy partners, preferably elastomers. Also suitable are blends with other polymers, preferably polyethylene, polypropylene, or ABS, optionally with one or more compatibilizers. The properties of polyamides can be improved, for example, in terms of impact toughness, by adding elastomers, especially in the case of reinforced polyamides. The numerous possible combinations make it possible to produce a vast array of products with a wide variety of properties.

For the preparation of polyamides, numerous routes are known in which, depending on the desired end product, different monomer building blocks, various chain regulators for adjusting the desired molecular weight or also monomers having reactive groups for the desired subsequent post-processing are used.

Industrially relevant processes for preparing polyamides are mostly carried out by polycondensation in the melt. In this context, hydrolytic polymerization of lactams is also understood as polycondensation.

Preferably, the polyamide to be used as component A is a partially crystalline and aromatic or partially aromatic polyamide which can be prepared from diamines and dicarboxylic acids and/or lactams having at least 5 ring members or the corresponding amino acids.

As reactants, aromatic dicarboxylic acids, preferably isophthalic acid and/or terephthalic acid, or their polyamide-forming derivatives, such as salts, come into consideration, alone or in combination with aliphatic dicarboxylic acids or their polyamide-forming derivatives, preferably adipic acid, 2,2,4-trimethyladipic acid and 2,4,4-trimethyladipic acid, azelaic acid and/or sebacic acid, together with aliphatic and/or aromatic diamines, preferably tetramethylenediamine, hexamethylenediamine, 1,9-nonanediamine, 2,2,4-trimethylhexamethylenediamine and 2,4,4-trimethylhexamethylenediamine, the isomeric diaminodicyclohexylmethane, diaminodicyclohexylpropane, bis(aminomethyl)cyclohexane, phenylenediamine and/or xylenediamine, and/or with aminocarboxylic acids, preferably aminocaproic acid, or the corresponding lactams. Copolyamides composed of a plurality of the aforementioned monomers are also included.

Furthermore, aromatic and partially aromatic polyamides are particularly suitable, i.e. compounds in which at least a portion of the repeating units consists of aromatic structural units. If these polymers are optionally used in combination with smaller amounts, e.g. up to 20% by weight, based on the amount of polyamide, of aliphatic polyamides, in particular PA6 and/or PA 6,6, heat distortion temperatures of the molding materials or moldings produced therefrom are achieved of at least 290°C.

Suitable are preferably aromatic polyamides derived from xylene diamine and adipic acid; or polyamides prepared from hexamethylene diamine and isophthalic acid and/or terephthalic acid and optionally elastomers as modifiers, such as poly-2,4,4-trimethylhexamethylene terephthalamide or poly-m-phenylene isophthalamide; block copolymers of the aforementioned polyamides with polyolefins, olefin copolymers, ionomers or chemically bound or grafted elastomers; or with polyethers, such as polyethylene glycol, polypropylene glycol or polytetramethylene glycol. Furthermore, polyamides or copolyamides modified with EPDM or ABS; and polyamides condensed during processing ("RIM-polyamide systems").

In a preferred embodiment, component A is an aromatic or partially aromatic polyamide or a mixture of a plurality of aromatic or partially aromatic polyamides or a mixture of polyamide 6,6 with one or more aromatic or partially aromatic polyamides.

In addition to the thermoplastic polyamide, conventional additives, in particular release agents, stabilizers and/or flow aids, can be mixed into the melt or applied to the surface of the polymers used in the preferred embodiment. The starting materials of the thermoplastic polyamide of component A can be derived synthetically, for example from petrochemical raw materials and/or from renewable raw materials by chemical or biochemical processes.

Fillers and/or preferably reinforcing materials, preferably glass fibers, are used as component B. Mixtures of two or more different fillers and/or reinforcing materials can also be used.

Preferred fillers are mineral microgranular fillers based on talc, mica, silicates, quartz, titanium dioxide, wollastonite, kaolin, amorphous silicon dioxide, nanoscale minerals, particularly preferably montmorillonite or nanoboehmite, magnesium carbonate, chalk, feldspar, glass beads and/or barium sulfate. Particularly preferred are mineral microgranular fillers based on talc, wollastonite and/or kaolin.

Particularly preferably, acicular mineral fillers are also used. According to the present invention, acicular mineral fillers are understood to be mineral fillers with very pronounced acicular characteristics. Preference is given to acicular wollastonite. Preferably, the mineral has an aspect ratio of 2:1 to 35:1, particularly preferably 3:1 to 19:1, and especially preferably 4:1 to 12:1. The average particle size of the acicular mineral filler used according to the invention as component B is preferably less than 20 μm, particularly preferably less than 15 μm, and even more preferably less than 10 μm, as determined using a CILAS particle size analyzer.

Component B preferably used according to the invention is a reinforcing material. This can be, for example, a reinforcing material based on carbon fibers and/or glass fibers.

In a preferred embodiment, the fillers and/or reinforcements can be surface-modified, preferably using adhesion promoters or adhesion promoter systems, particularly preferably based on silanes. In particular, when using glass fibers, polymer dispersions, film formers, branching agents, and/or glass fiber processing aids can also be used in addition to silanes.

The glass fibers preferably used as component B according to the present invention may be short glass fibers and/or long glass fibers. Chopped strands may be used as short or long glass fibers. Short glass fibers may also be used in the form of ground glass fibers. Furthermore, the glass fibers may also be used in the form of continuous fibers, for example in the form of rovings, monofilaments, filament yarns or twisted yarns, or in the form of textile webs, for example as glass fabrics, braided glass fabrics or glass mats.

The typical fiber length of the short glass fibers before incorporation into the polyamide matrix ranges from 0.05 to 10 mm, preferably from 0.1 to 5 mm. After incorporation into the polyamide matrix, the length of the glass fibers decreases. The typical fiber length of the short glass fibers after incorporation into the polyamide matrix ranges from 0.01 to 2 mm, preferably from 0.02 to 1 mm.

The diameter of the individual fibers can vary within a wide range. Typical diameters of individual fibers range from 5 to 20 μm.

The glass fibers may have any cross-sectional shape, such as circular, oval, polygonal (n-eckig) or irregular cross-sections. Glass fibers having a unilobal or multilobal cross-section may be used.

The glass fibers can be used as continuous fibers or as chopped or milled glass fibers.

The glass fibers themselves, independently of their cross-sectional area and their length, can in this case be selected, for example, from E-glass fibers, A-glass fibers, C-glass fibers, D-glass fibers, M-glass fibers, S-glass fibers, R-glass fibers and/or ECR-glass fibers, with E-glass fibers, R-glass fibers, S-glass fibers and ECR-glass fibers being particularly preferred. The glass fibers are preferably provided with a sizing material, which preferably comprises a polyurethane as a film former and an aminosilane as an adhesion promoter.

E-glass fibers used with particular preference have the following chemical composition: _SiO2 50-56%; _{Al2O3 12-16} %; CaO 16-25%; MgO≤6%; _{B2O3 6-13} %; F≤0.7%; _Na2O 0.3-2%; _K2O 0.2-0.5%; _{Fe2O3 0.3} %.

Particularly preferably used R-glass fibers have _the following chemical composition: SiO2 _50-65 %; _{Al2O3 20-30} %; CaO 6-16%; MgO 5-20%; _Na2O 0.3-0.5%; _K2O 0.05-0.2%; _Fe2O3 0.2-0.4%; _TiO2 0.1-0.3%.

Particularly preferably used ECR glass fibers have the following chemical composition: SiO ₂ 57.5-58.5%; Al ₂ O ₃ 17.5-19.0%; CaO 11.5-13.0%; MgO 9.5-11.5%.

The salts of diethylphosphinic acid used according to the invention as component C are known flame retardants for polymer molding compounds.

Salts of diethylphosphinic acid containing proportions of the phosphinic and phosphonic acid salts used according to the invention as components D and E are likewise known flame retardants. The preparation of such substance combinations is described, for example, in US Pat. No. 7,420,007 B2.

The salt of diethylphosphinic acid of component C used according to the invention may contain small amounts of salts of component D and salts of component E, for example up to 10% by weight of component D, preferably 0.01 to 6% by weight and in particular 0.2 to 2.5% by weight, and up to 10% by weight of component E, preferably 0.01 to 6% by weight and in particular 0.2 to 2.5% by weight, based on the amount of components C, D and E.

The salts of ethylphosphonic acid used according to the invention as component E are also known as additives to diethylphosphinate in flame retardants for polymer molding compounds, for example from WO 2016/065971 A1.

In a further preferred embodiment, components C, D and E are present in microparticulate form, with an average particle size (d ₅₀ ) of 1 to 100 μm.

The polyamide compositions according to the invention may also contain further additives as component G. Preferred components G within the meaning of the present invention are antioxidants, UV stabilizers, gamma stabilizers, hydrolysis stabilizers, costabilizers for antioxidants, antistatic agents, emulsifiers, nucleating agents, plasticizers, processing aids, impact modifiers, dyes, pigments and/or further flame retardants different from components C, D, E and F.

The further additives mentioned are known per se as additions to polyamide compositions and can be used individually or in the form of mixtures or masterbatches.

The aforementioned components A, B, C, D, E, and optionally F and/or G, can be processed in various combinations to form the flame-retardant polyamide composition according to the present invention. It is thus possible to mix the components into the polyamide melt at the beginning or at the end of the polycondensation process, or during a subsequent compounding process. Furthermore, there are processes in which the individual components are added only later. This is particularly practical when using pigment or additive masterbatches. Furthermore, there is the possibility of drum processing the powdered components into polymer pellets, which may be hot, after a drying process.

It is also possible to combine two or more components of the polyamide composition according to the invention by mixing before incorporation into the polyamide matrix. In this case, conventional mixing equipment can be used, wherein the components are mixed in a suitable mixer, for example at 0 to 300° C. for 0.01 to 10 hours.

It is also possible to prepare pellets from two or more components of the polyamide composition according to the invention, which pellets can subsequently be incorporated into a polyamide matrix.

For this purpose, two or more components of the polyamide composition according to the invention can be processed with granulation aids and/or binders in suitable mixers or pan granulators to give granules.

The crude product initially produced can be dried in a suitable dryer or temperature-controlled to give a different particle structure.

The polyamide composition according to the invention or two or more components thereof can in one embodiment be prepared by roller compaction.

The polyamide composition according to the invention or two or more of its components can in one embodiment be prepared by mixing the ingredients, strand extruding, pelletizing (or optionally crushing and classifying) and drying (and optionally coating).

The polyamide composition according to the invention or two or more components thereof can in one embodiment be prepared by spray granulation.

The flame-retardant polymer molding compound according to the invention is preferably in the form of pellets, for example as extrudates or as compounds. The pellets are preferably cylindrical with a round, oval or irregular base, spherical, pillow-shaped, cubic, rectangular, prismatic.

Typical aspect ratios of the pellets are 1 to 50 to 50 to 1, preferably 1 to 5 to 5 to 1.

The granules preferably have a diameter of 0.5 to 15 mm, particularly preferably 2 to 3 mm, and a length of preferably 0.5 to 15 mm, particularly preferably 2 to 5 mm.

The present invention also provides a molded part produced from the flame-retardant polyamide composition described above, which comprises components A, B, C, D and E and optionally components F and/or G.

The molded parts according to the invention may be of any desired form. Examples of these are fibers, films or moldings, which can be obtained from the flame-retardant polyamide molding compound according to the invention by any molding method, in particular by injection molding or extrusion.

The flame-retardant polyamide moldings according to the invention can be produced by any desired molding methods. Examples include injection molding, pressing, foam injection molding, gas internal pressure injection molding, blow molding, film casting, calendering, lamination, or coating using flame-retardant polyamide molding compounds at elevated temperatures.

The molded part is preferably an injection-molded part or an extruded part.

The flame-retardant polyamide composition according to the invention is suitable for producing fibers, films and moldings, in particular for applications in the electrical and electronics sectors.

The present invention preferably relates to the use of the flame-retardant polyamide composition according to the invention in the following items or in the following items: plug connectors, energized parts in distributors (FI protection), circuit boards, potting materials, power plugs, safety switches, lamp covers, LED housings, capacitor housings, coil formers and fans, protective contacts, plugs, in/on circuit boards, housings of plugs, cables, flexible printed circuit boards, charger cables for mobile phones, engine covers or textile coatings.

The present invention likewise preferably relates to the use of the flame-retardant polyamide composition according to the invention for producing moldings in the form of components in the electrical/electronic sector, in particular components of printed circuit boards, housings, films, conductors, switches, distributors, relays, resistors, capacitors, coils, lamps, diodes, LEDs, transistors, connectors, regulators, memories and sensors, in the form of large-area components, in particular housing components for switch cabinets, and in the form of components of complex design with demanding geometries.

The wall thickness of the moldings according to the invention can typically be up to 10 mm. Particularly suitable are moldings having a wall thickness of less than 1.5 mm, more preferably less than 1 mm and particularly preferably less than 0.5 mm.

DETAILED DESCRIPTION

The following examples illustrate the invention without limiting it.

1. Components used

Commercially available polyamide (component A):

Polyamide 6T/6,6 (melting range 310-320°C): HAT plus 1000 (Evonik)

Polyamide 6T/6I (amorphous): G21, (EMS)

Glass fiber (component B):

Glass fiber PPG HP 3610, 10 μm diameter, 4.5 mm length (PPG, NL),

Flame retardant FM 1 (components C, D and E):

Aluminum salt of diethylphosphinic acid, comprising 0.9 mol % of aluminum ethylbutylphosphinic acid and 0.5 mol % of aluminum ethylphosphonate, prepared according to Example 3 of US 7,420,007 B2

Flame retardant FM 2 (components C, D and E):

Aluminum salt of diethylphosphinic acid, containing 2.7 mol% of aluminum ethylbutylphosphinate and 0.8 mol% of aluminum ethylphosphonate, prepared according to Example 4 of US 7,420,007 B2

Flame retardant FM 3 (components C, D and E):

Aluminum salt of diethylphosphinic acid, containing 0.5 mol% of aluminum ethylbutylphosphinate and 0.05 mol% of aluminum ethylphosphonate, prepared according to the method of US 7,420,007 B2

Flame retardant FM 4 (components C, D and E):

Aluminum salt of diethylphosphinic acid, containing 10 mol% of aluminum ethylbutylphosphinic acid and 5 mol% of aluminum ethylphosphonate, prepared according to the method of US 7,420,007 B2

Flame retardant FM 5 (component C):

Aluminum salt of diethylphosphinic acid, prepared analogously to Example 1 of DE 196 07 635 A1

Flame retardant FM 6 (components C and E):

Aluminum salt of diethylphosphinic acid, containing 8.8 mol % of aluminum ethylphosphonate

Flame retardant FM 7 (component F):

Aluminum salt of phosphonic acid, prepared according to Example 1 of DE 10 2011 120 218 A1

2. Preparation, processing and testing of flame retardant polyamide molding compounds

The flame retardant components were mixed with one another in the proportions given in the table and introduced via a side feed into a twin-screw extruder (model: Leistritz ZSE 27/44D) at a temperature of 310 to 330° C. Glass fibers were added via a second side feed. The homogenized polymer strands were withdrawn, cooled in a water bath, and subsequently pelletized.

After sufficient drying, the molding compound was processed into test pieces on an injection molding machine (type: Arburg 320 C Allrounder) at a material temperature of 300 to 320° C. and tested for fire resistance using the UL94 test (Underwriter Laboratories) and classified. In addition to the classification, the afterflame time is also reported.

The comparative tracking index of molded parts is determined according to the International Electrotechnical Commission standard IEC-60112/3.

The glow wire flammability index (GWIT index) is determined according to standard IEC-60695-2-12.

The heat deflection temperature (HDT) is determined according to DIN EN ISO 75-3.

To determine the HDT, standard specimens with a rectangular cross-section are subjected to three-point bending under constant load. Depending on the specimen height, weights and/or springs are used to apply a force in order to achieve a so-called edge fiber stress σ _f of 1.80 N/mm ² (Method A), 0.45 N/mm ² (Method B), or 8.00 N/mm ² (Method C). The loaded specimen is then heated at a constant heating rate of 120 K/h (or 50 K/h). If the bending of the specimen reaches an edge fiber elongation of 0.2%, the corresponding temperature corresponds to the HDT value.

Unless otherwise stated, all tests within each series were performed under identical conditions (such as temperature program, screw geometry and injection molding parameters) for comparability.

Examples 1-5 and Comparative Examples V1-V3 use PA 6,6

The results of tests with PA 6T/6,6 moulding materials are listed in the examples cited in the table below. All amounts are given in % by weight and are based on the polyamide moulding material including flame retardant and reinforcement.

Table 1: PA 6T/6,6 GF 30 test results (1-5 are according to the present invention; V1-V3 are comparative)

Example No. 1 2 3 4 5 V1 V2 V3 A: PA 6T/6,6 55 55 55 55 55 55 50 55 B: Glass fiber HP3610 30 30 30 30 30 30 30 30 C+D+E:FM 1 15 - - - - - - - C+D+E:FM 2 - 15 - - 13 - - - C+D+E:FM 3 - - 15 - - - - - C+D+E:FM 4 - - - 15 - - - - C: FM 5 - - - - - - - 15 C+E:FM 6 - - - - - 15 20 - F:FM 7 - - - - 2 - - - HDT-A[℃] 295 295 295 295 295 285 295 285 UL 940.4mm/time [seconds] V-0/23 V-0/17 V-0/37 V-0/23 V-0/08 V-0/41 V-0/35 V-0/47 GWFI[℃] 960 960 960 960 960 900 900 900 CTI[volts] 600 600 600 600 600 500 600 500

The polyamide compositions according to the invention of Examples 1 to 5 are molding compounds that achieve the flame retardancy class UL-94 V-0 at 0.4 mm while having a CTI of 600 V, a GWFI of 960° C., and an HDT-A of 295° C. The addition of component F in Example 5 leads to a further improvement in the flame retardancy, as evidenced by a shortened afterflame time.

The omission of component D in comparative example V1 leads, in addition to a prolonged afterflame time, to reduced CTI, GWFI and HDT/A values compared to examples 1 to 4.

In comparative example V2, an improvement in the afterflame time compared to example V2 is achieved by increasing the concentration of components C and E. However, the polyamide composition still always exhibits lower GWFI values compared to example 2.

The omission of components D and E in comparative example V3 leads, in addition to a prolonged afterflame time, to reduced CTI, GWFI and HDT/A values compared to examples 1 to 4.

Examples 6-10 and Comparative Examples V4-V6, using PA 6T/6I

The results of the tests with PA 6T/6I moulding materials are listed in the examples cited in the table below. All amounts are given in % by weight and are based on the polyamide moulding material including flame retardant and reinforcement.

Table 2: PA 6T/6I GF 30 test results (6-10 are according to the present invention; V4-V6 are for comparison)

Example No. 6 7 8 9 10 V4 V5 V6 A: PA 6T/6I 55 55 55 55 55 55 50 55 B: Glass fiber HP3610 30 30 30 30 30 30 30 30 C+D+E:FM 1 15 - - - - - - - C+D+E:FM 2 - 15 - - 13 - - - C+D+E:FM 3 - - 15 - - - - - C+D+E:FM 4 - - - 15 - - - - C: FM 5 - - - - - - - 15 C+E:FM 6 - - - - - 15 20 - F:FM 7 - - - - 2 - - - HDT-A[℃] 305 305 305 305 305 295 300 295 UL 940.4mm/time [seconds] V-0/21 V-0/15 V-0/35 V-0/21 V-0/06 V-0/39 V-0/33 V-0/43 GWFI[℃] 960 960 960 960 960 900 950 900 CTI[volts] 600 600 600 600 600 500 600 500

The polyamide compositions according to the invention of Examples 6 to 10 are molding compounds that achieve the UL-94 V-0 flame retardancy class at 0.4 mm while having a CTI of 600 V, a GWFI of 960° C., and an HDT-A of 305° C. The addition of component F in Example 10 leads to a further improvement in the flame retardancy, as evidenced by a shortened afterflame time.

The omission of component D in comparative example V4 leads, in addition to a prolonged afterflame time, to reduced HDT-A, GWFI and CTI values compared to examples 6 to 9.

In comparative example V5, an improvement in the afterflame time compared to example V4 is achieved by increasing the concentration of components C and E. However, the polyamide composition still exhibits lower HDT-A and GWFI values compared to example 7.

The omission of components D and E in comparative example V6 leads, in addition to a prolonged afterflame time, to reduced HDT-A, GWFI and CTI values compared to examples 6 to 9.

Claims (15)

1. A flame-retardant polyamide composition having a heat distortion temperature (HDT-A) of at least 280°C, comprising... -25 to 75% by weight of a polyamide as component A, having a melting point greater than or equal to 290°C, wherein component A is polyamide 6T/6.6 or polyamide 6T/6I. -20 to 40% by weight of fillers and/or reinforcing materials as component B, -5 to 20% by weight of phosphinate of formula (I) as component C Where _R1 and _R2 represent ethyl groups, M can be Al, Fe, _TiO2 , or Zn. m represents 2 to 3, and p = (4–m)/2, -0.05 to 1.5% by weight of a compound selected from the group consisting of: Al, Fe, _TiO2 , or Zn salts of ethylbutylphosphonic acid, dibutylphosphonic acid, ethylhexylphosphonic acid, butylhexylphosphonic acid, and/or dihexylphosphonic acid; and -0.01 to 0.6% by weight of phosphonates of formula (II) as component E Wherein, _R3 represents ethyl, Met can be Al, Fe, _TiO2 , or Zn. n represents 2 to 3, and q = (4 – n) / 2, The total of all components is less than or equal to 100 wt%. 2. The flame-retardant polyamide composition according to claim 1, characterized in that M and Met represent Al, m and n are 3, and component D is an aluminum salt. 3. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that the polyamide composition contains an inorganic phosphonate as an additional component F. 4. The flame-retardant polyamide composition according to claim 3, characterized in that the inorganic phosphonate is a compound of formula (III). Where Me represents Fe, _TiO₂ , and Zn. o represents 2 to 3, and r = (4–o)/2, where The amount of the compound of formula (III) is from 0.005 to 10% by weight, based on the total amount of the polyamide composition. 5. The flame-retardant polyamide composition according to claim 4, wherein Me is Al. 6. The flame-retardant polyamide composition according to claim 4, characterized in that the amount of the compound of formula (III) is 0.02 to 5% by weight, based on the total amount of the polyamide composition. 7. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that the composition has a relative tracking index of 500 volts or greater, as measured according to the International Electrotechnical Commission standard IEC-60112/3. 8. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that the composition achieves a thickness of 3.2 mm to 0.4 mm according to the UL-94 V0 rating. 9. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that the composition has a glow wire flammability index of at least 960°C according to IEC-60695-2-12 when the thickness is 0.75-3 mm. 10. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that the composition has an HDT-A temperature of at least 300°C according to DIN EN ISO 75-3. 11. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that glass fiber is used as component B. 12. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that components C, D, E and optional F are present in particulate form, wherein the average particle size _d50 of these components is 1 to 100 μm. 13. The flame-retardant polyamide composition according to claim 1 or 2, characterized in that it comprises additional additives as component G, wherein the additional additives are selected from antioxidants, UV stabilizers, gamma-ray stabilizers, hydrolytic stabilizers, co-stabilizers of antioxidants, antistatic agents, emulsifiers, nucleating agents, plasticizers, processing aids, impact modifiers, dyes, pigments and/or additional flame retardants different from components C, D, E and F. 14. Use of the polyamide composition according to any one of claims 1 to 13, for the preparation of fibers, films and molding articles. 15. The use according to claim 14, for application in the electrical and electronic fields.