HK1260376B - Flame-retardant gray polyamide compositions and use thereof - Google Patents

Description

Flame retardant gray polyamide composition and use thereof

Technical Field

The present invention relates to flame-retardant polyamide compositions and molded parts produced therefrom.

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 act more effectively as flame retardants in a whole series of polymers than the phosphinates alone (WO-2002/28953 A1 and DE 197 34 437 A1 and DE 197 37 727 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 retardants 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 the chemical reactivity 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.

Colored polyamide compositions have also been described. WO 2010/089241 A1 discloses thermoplastic molding compounds that, in addition to gray or black colored fibrous fillers, also contain gray or black colorants. It is mentioned in this document that polyamides can also be used as thermoplastics. EP 1 121 388 B1 discloses polyamide compositions stabilized with copper complexes and organic halogen-containing compounds that can be colored with conventional pigments. DE 43 01 541 A1 describes flame-retardant, black-colored polyamide molding compounds that, in addition to polyamide, also contain red phosphorus and a colorant. Finally, WO 2014/044471 A1 discloses flame-retardant polyamides with light colors. These have a slightly reddish natural color and can be colored in an improved manner for light and gray applications.

When red phosphorus or a combination of halogen-containing aromatic compounds with antimony trioxide is used as flame retardant and the colorant mixtures conventionally used for gray coloring are used, it has been found that the gray coloring of moldings and moldings has an undesirable reddish hue.

To date, there has been a lack of flame-retardant phosphinate-containing polyamide compositions which simultaneously achieve all the required properties, such as good electrical values (GWFI, CTI), a gray color without red tints, and effective flame retardancy characterized by the shortest possible afterflame time (UL-94, afterflame time).

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 have, in particular, a grey color without red tinges and a high flame retardancy characterized by the shortest possible afterflame time.

The subject of the present invention is a flame retardant polyamide composition comprising

a polyamide as component A having a melting point of less than or equal to 290° C., preferably less than or equal to 280° C. and very particularly preferably less than or equal to 250° 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,

- 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,

- as component F, a melamine polyphosphate having an average degree of condensation greater than or equal to 20, and

- As component G, a gray colorant.

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 the polyamide composition according to the invention, the proportion of component F is generally 1 to 25% by weight, preferably 2 to 10% by weight.

In the polyamide composition according to the invention, the proportion of component G is generally from 0.01 to 20% by weight, preferably from 0.01 to 10% by weight and in particular from 0.1 to 8% by weight.

In this case, the percentage figures for the proportions of components A to G 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 0.01 to 3% by weight

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

- the proportion of component F is 1 to 25% by weight, and

- the proportion of component G is 0.01 to 20% 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 0.05 to 1.5% by weight,

- the proportion of component E is 0.01 to 0.6% by weight

- the proportion of component F is 2 to 10% by weight, and

- the proportion of component G is 0.1 to 8% by weight

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

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 H, an inorganic phosphonate.

The use of inorganic phosphonates or also salts of phosphorous acid (phosphites) used according to the invention as component H 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 H) 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 Fe, Zn or in particular Al cation, including the cation Al(OH) or Al(OH) ₂ , and p represents 1, 2, 3 or 4.

Preferably, the inorganic phosphonate (component H) 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 H) 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 H) are salts that are insoluble or poorly soluble in water.

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

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

Particularly preferred components H 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 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 H10 from Brüggemann.

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 polymer comprises as component H 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 H 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.

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.

The flame-retardant polyamide compositions according to the invention which are likewise preferred achieve a rating of VO according to UL94, 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 according to IEC-60695-2-12 of at least 960° C., in particular measured on molded parts with a thickness of 0.75 to 3 mm.

The polyamide composition according to the invention comprises as component A one or more polyamides having a melting point of less 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.

The polyamides of component A are generally aliphatic homopolyamides or copolyamides derived from (cyclo)aliphatic dicarboxylic acids or their polyamide-forming derivatives, such as their salts, and from (cyclo)aliphatic diamines or from (cyclo)aliphatic aminocarboxylic acids or their polyamide-forming derivatives, such as their salts.

The polyamides used according to the invention as component A are thermoplastic polyamides.

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

The polyamide used as component A according to the present invention can be prepared by various methods and synthesized from a wide variety of structural units. For specific applications, the polyamide can be formulated alone or in combination with processing aids, stabilizers, or polymer alloy partners, preferably elastomers, to produce materials with a specifically tailored property profile. Also suitable are mixtures with other polymers, preferably polyethylene, polypropylene, or ABS, optionally with one or more compatibilizers. The addition of elastomers can improve the properties of the polyamide, for example, in terms of impact toughness, particularly in the case of glass-fiber-reinforced polyamides. The numerous possible combinations make it possible to create a vast array of products with a wide variety of properties.

Numerous routes are known for preparing polyamides, 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.

The polyamides to be used preferably as component A are partially crystalline aliphatic polyamides which can be prepared from aliphatic diamines and aliphatic dicarboxylic acids and/or cycloaliphatic lactams having at least 5 ring members or the corresponding amino acids.

Possible reactants include aliphatic dicarboxylic acids, preferably adipic acid, 2,2,4-trimethyladipic acid, 2,4,4-trimethyladipic acid, azelaic acid, and/or sebacic acid; aliphatic diamines, preferably tetramethylenediamine, hexamethylenediamine, 1,9-nonanediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine; the isomeric diaminodicyclohexylmethane, diaminodicyclohexylpropane, bisaminomethylcyclohexane; and aminocarboxylic acids, preferably aminocaproic acid, or the corresponding lactams. These include copolyamides formed from a plurality of these monomers. Caprolactam is particularly preferably used, and ε-caprolactam is very particularly preferred.

Preferably, the aliphatic homopolyamide or copolyamide used according to the invention is polyamide 12, polyamide 4, polyamide 4,6, polyamide 6, polyamide 6,6, polyamide 6,9, polyamide 6,10, polyamide 6,12, polyamide 6,66, polyamide 7,7, polyamide 8,8, polyamide 9,9, polyamide 10,9, polyamide 10,10, polyamide 11 or polyamide 12. These are known, for example, under the trade names K122 from DuPont, BASF, DSM, 7301 from DuPont, B 29 from Bayer and EmsChemie.

Furthermore, compounds based on PA6, PA 6,6 and other aliphatic homopolyamides or copolyamides are particularly suitable, in which the polyamide groups in the polymer chain have 3 to 11 methylene groups.

Preference is given to flame-retardant polyamide compositions in which, as component A, one or more polyamides selected from the group consisting of PA 6, PA 6,6, PA 4,6, PA 12, PA 6,10 are used.

Particular preference is given to flame-retardant polyamide compositions in which component A is polyamide 6,6 or a polymer mixture of polyamide 6,6 and polyamide 6.

Very particular preference is given to flame-retardant polyamide compositions in which component A consists of at least 75% by weight of polyamide 6,6 and at most 25% by weight of polyamide 6.

Fillers and/or preferably reinforcing materials, preferably glass fibers, are used as component B. It is also possible to use mixtures of two or more different fillers and/or reinforcing materials.

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 fabrics, for example as glass fabrics, as glass braids or as 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 provided 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 which have moieties of the phosphinic and phosphonic acid salts used according to the invention as components D and E are also known flame retardants. The preparation of these 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 likewise known as additives to diethylphosphinate in flame retardants for polymer molding compounds, for example from WO 2016/065971 A1.

The use of melamine polyphosphate derivatives having a degree of condensation of greater than or equal to 20, used as component F according to the present invention, as flame retardants is also known. For example, DE 10 2005 016 195 A1 discloses a stabilized flame retardant comprising 99 to 1% by weight of melamine polyphosphate and 1 to 99% by weight of an additive with a reserve alkalinity. This document also discloses that this flame retardant can be combined with phosphinic acid and/or phosphinic acid salts.

Preferred flame-retardant polyamide compositions according to the invention comprise, as component F, melamine polyphosphates having an average degree of condensation of 20 to 200, in particular 40 to 150.

A further preferred flame-retardant polyamide composition according to the invention comprises as component F a melamine polyphosphate having a decomposition temperature of greater than or equal to 320° C., in particular greater than or equal to 360° C. and very particularly preferably greater than or equal to 400° C.

Preferably, as component F, melamine polyphosphates are used, which are known from WO 2006/027340 A1 (corresponding to EP 1 789 475 B1) and WO 2000/002869 A1 (corresponding to EP 1 095 030 B1).

Preference is given to using melamine polyphosphates whose average degree of condensation is between 20 and 200, in particular between 40 and 150, and whose melamine content is from 1.1 to 2.0 mol, in particular from 1.2 to 1.8 mol, per mole of phosphorus atom.

Preference is likewise given to using melamine polyphosphates whose average degree of condensation (number average) is >20, whose decomposition temperature is greater than 320° C., whose molar ratio of 1,3,5-triazine compound to phosphorus is less than 1.1, in particular from 0.8 to 1.0, and whose pH value of a 10% suspension in water at 25° C. is above 5, preferably from 5.1 to 6.9.

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

The polyamide composition according to the invention comprises as component G a grey colorant.

Colorants are generally understood to be all coloring substances according to DIN ISO 18451, which can be divided into inorganic and organic colorants and natural and synthetic (see Chemie Lexikon, 1981, 8th edition, page 1237).

According to DIN ISO 18451, a distinction is made between dyes and pigments, the latter being insoluble in plastics, whereas dyes are soluble.

The gray colorants used according to the invention as component G generally consist of a mixture of black and white pigments or dyes.

White pigments or dyes produce different matte shades of the color of the black pigment or black dye, thus producing a gray color. Suitable white pigments are generally known; see, for example, R. and H. Müller, Taschenbuch der Kunststoffadditive, Carl Hanser Verlag, 1983, pp. 494-510. Preferred pigment groups include white pigments such as zinc oxide, zinc sulfide, lead white ( _2PbCO₃ ·Pb(OH) _₂ ), lithopone, antimony white, barium sulfate, and titanium dioxide. Of the two most common crystal modifications of titanium dioxide (rutile and anatase), rutile is particularly useful for fine-tuning the molding compounds according to the invention.

Furthermore, it is possible to achieve the grey color of the polyamide composition using pigments or dyes of complementary colors.

Among the dyes and pigments which can preferably be used for preparing component G are carbon black, graphite, graphene, aniline black, bone char, black coloring pigments, or combinations of red to yellow pigments with complementary colors of green, blue or violet pigments, or mixtures of one or more of these compounds, each of which is mixed with a white pigment or white dye to produce gray colors.

Suitable carbon blacks for preparing component G include, in particular, carbon blacks having a pore volume (DBP dibutyl phthalate adsorption) according to DIN ISO 18451 of at least 30 ml/100 g, preferably at least 50 ml/100 g.

The carbon blacks further preferably used for preparing component G have a specific surface area according to BET (according to ISO 4652) of at least 20 to 1000 ^{m 2} /g, preferably 30 to 300 m ² /g.

Further carbon blacks preferably used for preparing component G have an average primary particle size of 5 to 50 nm, in particular 10 to 35 nm. Such carbon black types are available, for example, under the designations XE2 (Evonik GmbH) or EC600JD (Akzo) and as furnace blacks such as 90, 75, 80, 85, 95 and 60-A.

Graphite can also be used to prepare component G. It can be ground by grinding. The particle size is generally in the range of 0.01 μm to 1 mm, preferably in the range of 1 to 250 μm. Graphite is very soft (Mohs hardness 1) and has a slightly grey to black natural color.

Another example of a black agent suitable for preparing component G is graphene. Commercially available graphene is, for example, the product Vorbeck Materials. Graphene typically has a thickness of 1 to 5 nm, a diameter of 20 to 1000 nm and a specific surface area according to BET of 500 to 1000 m ² /g(N ₂ ).

The preferred black coloring agent for preparing component G is nigrosine. This is generally understood in various embodiments to be a group of black or gray phenazine dyes (azine dyes) that are related to para-nitroanthracene blue. Nigrosine can be water-soluble, fat-soluble, or gasoline-soluble. Nigrosine is obtained industrially by heating nitrobenzene, aniline, and aniline hydrochloride with metallic iron and _FeCl₃ .

Nigrosine can be used as the free base or else as a salt (for example as the hydrochloride).

Bone char or bone black can also be used to prepare component G. Bone char can be prepared by heating defatted bone chips to approximately 700°C in the absence of air. A mixture of bone char and sugar or molasses, carbonized with concentrated sulfuric acid, produces so-called bone black or Cologne black. Finely ground bone char is suitable for coloring thermoplastic molding compounds. Modified bone char can also be used as component G. Extracting the mineral components from bone char, for example with hydrochloric acid, leaves a darker bone char that, when mixed with some Berlin blue, can be obtained as Lackschwarz or Paris Black.

Suitable colorants which can be used as component G are generally classified according to the Colour Index (C.I.), wherein, in addition to the systematic or common name, a C.I. designation is added which enables an unambiguous assignment.

Black coating pigments which can be combined according to the invention as component G with white pigments such as titanium dioxide, barium sulfate or zinc sulfide are, for example, iron oxide black (Fe ₃ O ₄ ), spinel black (Cu,(Cr,Fe) ₂ O ₄ ), manganese black (a mixture of manganese dioxide, silicon dioxide and iron oxide), cobalt black or antimony black.

Furthermore, it is possible to achieve the grey color of the polyamide composition according to the invention using pigments of complementary colors.

For this purpose, red to yellow pigments are used together with corresponding complementary green, blue or violet pigments or mixtures thereof in order to achieve the desired grey color of the polyamide composition.

As preferred pigments, mention may be made of copper phthalocyanine pigments, which have a green or blue color. The green color is usually achieved by replacing hydrogen with chlorine atoms on macrocyclic tetramines.

Further suitable pigments are manganese violet pigments (manganese(III) and ammonium pyrophosphates _{of the formula MnNH4P2O7 ,} which, by varying the stoichiometric composition, produce bluer or redder shades), ultramarine pigments (sodium silicates, aluminum silicates), blue and green pigments with a spinel structure based on, for example, chromium oxide or cobalt oxide. Such pigments are commercially available under the trade names -Blue, -Green, -Green, -Blue (trademarks of BASF SE) and as ultramarine, chromium oxide pigments or manganese violet pigments.

Preferred pigments are Pigment Blue 15, Pigment Blue 15:2, Pigment Blue 15:4, Pigment Blue 16, Pigment Blue 28, Pigment Blue 29, Pigment Blue 36, Pigment Green 17, Pigment Green 24, Pigment Green 50, Pigment Violet 15 and Pigment Violet 16 according to C.I. Part 1, of which Pigment Blue 15:1 and 15:3 and Pigment Green 7 and 36 are particularly preferred.

Preferably used as component G is a mixture of a white pigment and a black pigment or dye, wherein the white pigment is selected from zinc oxide, zinc sulfide, lead white, lithopone, antimony white, barium sulfate and/or titanium dioxide and wherein the black pigment or dye is selected from carbon black, graphite, graphene, aniline black, bone char, black coloring pigments, or a combination of a red to yellow pigment with a complementary color of a green, blue or violet pigment, or a mixture of one or more of these compounds.

The polyamide composition according to the invention preferably has a grey color, which is characterized by the numbers 7000 to 7048, in particular by RAL 7035, of the RAL color chart.

Particularly preferred as component G are mixtures of titanium dioxide with black pigments, in particular carbon black, which are used in particular in polyamide compositions used in the electronics sector (so-called “electrograin”).

Component G used with particular preference is the pigment paste Elektrograu RAL 7032 from Brohl Chemie.

Component G used with further preference is a combination of titanium dioxide with yellow, red and black pigments, which gives a color shade according to RAL 7032. Combinations of this type are described, for example, in DE 41 04 681 A1.

The polyamide composition according to the invention may also contain further additives as component I. Preferred components I in the sense 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 other than component G, pigments other than component G and/or further flame retardants other than components C, D, E, F and H.

Further additives 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, F, G, and optionally H and/or I can be processed in various combinations to form the flame-retardant polyamide composition according to the present invention. It is therefore possible to mix the components into the polyamide melt at the beginning of the polycondensation, at its end, 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 a possibly hot polymer pellet by 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 produce a further 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, E, F and G and optionally components H and/or I.

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 molding method. 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 fields.

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: connectors, energized parts in distributors (FI protection), circuit boards, potting materials, power plugs, safety switches, lampshades, LED housings, capacitor housings, coil tubes and fans, protective contacts, plugs, in/on circuit boards, plug housings, 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, 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 6,6 (PA 6,6-GV; melting range 255-260°C): A27 (BASF)

Polyamide 6 (melting range 217-222°C): B29 (Lanxess)

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

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, containing 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 ethylbutylphosphinic acid 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 H):

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

Flame retardant FM 8 (component F):

Melamine polyphosphate, prepared according to the example of WO 2000/002869 A1

Flame retardant FM 9 (not according to the invention):

Melamine polyphosphate with an average degree of condensation of 18, prepared analogously to WO 2000/002869 A1

Flame retardant FM 10 (not according to the invention):

Red phosphorus (RP 607, Clariant)

Flame retardant FM 11 (not according to the invention):

Brominated polystyrene (HP 3010, Albemarle), 75%:25% masterbatch mixed with antimony trioxide in PA 6 80% (Campine)

Gray colorant (component G)

Pigment granules in polyamide, Elektrograu RAL 7032 (Lifocolor, Lichtenfels, D)

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

The flame retardant components were mixed with the colorant in the proportions given in the table and added to PA 6,6 at a temperature of 260 to 310°C, PA 6 at 250 to 275°C, or PA 6T/6,6 at 310 to 330°C via a side feed of a twin-screw extruder (model: Leistritz ZSE 27/44D). 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 CAllrounder) at a material temperature of 250 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 color of the moldings was assessed visually, in this case by: 1 = gray without a red tint, 2 = gray with a slight red tint, and 3 = gray with a pronounced red tint.

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, 1a, 1b, 5a and comparative examples V1-V3, using PA 6,6

The results of the tests with PA 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, additives and reinforcements.

The polyamide compositions according to the invention of Examples 1 to 5, 1a, 1b, and 5a are molding compounds that achieve the UL94 V-0 flame retardancy class at 0.4 mm, have a CTI of 600 volts and a GWFI of 960°C, and exhibit a continuous gray solid color without any red tint. The addition of component H to Examples 5 and 5a further improves 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 a reduction in the CTI value compared with examples 1 to 4.

The replacement of component F by a component having a lower degree of condensation in comparative example V2 resulted in foaming of the polyamide strands during production and no measurement was possible.

The use of red phosphorus instead of components C, D and E in comparative example V3 leads to a pronounced red hue in the color of the molding.

The use of a brominated polystyrene/antimony trioxide masterbatch in PA6 in comparative example V4 instead of components C, D and E likewise resulted in a distinct red tint in the color of the moldings and a significant reduction in the CTI value.

The omission of components D and E in comparative example V5 leads, in addition to a prolonged afterflame time, to a reduction in the CTI value compared with examples 1 to 4.

Examples 6-10 and comparative examples V6-V10, using PA 6,6/PA 6

The results of the tests with PA6/PA 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, additives and reinforcements.

The polyamide compositions according to the invention of Examples 6 to 10 are molding compounds that achieve the UL94 V-0 flame retardancy rating at 0.4 mm, have a CTI of 600 volts and a GWFI of 960°C, and exhibit a continuous gray solid color without any red tint. The addition of component H in Example 10 further improves the flame retardancy, as evidenced by a shortened afterflame time.

The omission of component D in comparative example V6 leads, in addition to a prolonged afterflame time, to a reduction in the CTI value compared with examples 6 to 9.

The replacement of component F in comparative example V7 by a component having a lower degree of condensation resulted in foaming of the polyamide strands during production and no measurement was possible.

The use of red phosphorus instead of components C, D and E in comparative example V8 leads to a pronounced red tint in the color of the molding.

The use of a brominated polystyrene/antimony trioxide masterbatch in PA6 in comparative example V9 instead of components C, D, and E likewise resulted in a distinct red tint in the color of the moldings and a significant reduction in the CTI value.

The omission of components D and E in comparative example V10 leads, in addition to a prolonged afterflame time, to a reduction in the CTI value compared with examples 6 to 9.

Comparative Examples V11-V17, using PA 6T/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, additives and reinforcements.

Table 3: PA 6T/6, 6GF 30 test results (n.b. = not determined)

Example No. V11 V12 V13 V14 V15 V16 V17 A: Polyamide 6T/6,6 51 51 51 51 51 51 51 B: Glass fiber HP3610 30 30 30 30 30 30 30 C+D+E:FM 1 12 - - - - - - C+D+E:FM 2 - 12 - - 10 - - C+D+E:FM 3 - - 12 - - - - C+D+E:FM 4 - - - 12 - - - C: FM 5 - - - - - - 12 H:FM 7 - - - - 2 - - F:FM 8 5 5 5 5 5 5 5 Comparison: FM 10 - - - - - 12 - G: 2 2 2 2 2 2 2 UL940.4mm/time [seconds] n.b. n.b. n.b. n.b. n.b. n.b. n.b. GWFI[℃] n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. n.b. color n.b. n.b. n.b. n.b. n.b. n.b. n.b. CTI[volts] n.b. n.b. n.b. n.b. n.b. n.b. n.b.

No test pieces could be produced from the PA molding compounds of comparative examples V11 to V17, since they proved to be unprocessable. The polyamide strands foamed during production and no test pieces suitable for measurement could be produced.

Comparative Examples V18-V22, using PA 6,6

Table 4 shows that using only the flame retardant combination according to the present invention, a polyamide composition having V-0, GWFI 960, CTI 600, and a gray color without a red tint can be prepared. While V-0 can be achieved using only melamine polyphosphate or brominated polystyrene with antimony trioxide, a dark gray solid color cannot be achieved.

Table 4: Comparative Example Polyamide 6,6GF Results (n.k. = not classifiable)

Example No. V18 V19 V20 V21 V22 A: Polyamide 6,6 43 51 43 51 43 B: Glass fiber HP3610 30 30 30 30 30 Comparison: FM 8 25 17 5 5 5 Comparison: FM 9 - - 25 17 - Comparison: FM 11 25 G: 2 2 2 2 2 UL940.4mm/time [seconds] V-0/45 n.k. V-0/43 n.k. V-0/23 GWFI[℃] 960 750 960 700 960 color 2 2 2 2 2 CTI[volts] 500 500 350 500 350

Claims (21)

1. A flame-retardant polyamide composition comprising - As component A, a polyamide having a melting point of less than or equal to 290°C, said polyamide being polyamide 6,6 or a polymer mixture of polyamide 6 and polyamide 6,6. - As a filler and/or reinforcing material for component B, - Phosphinate of formula (I) as component C Where _R1 and _R2 represent ethyl groups, M can be Al, Fe, TiO2, _p , or Zn. m represents 2 or 3, and p = (4–m)/2, - Component D is selected from the following compounds: Al, Fe, TiO2, or Zn salts of ethyl butyl phosphine, dibutyl phosphine, ethyl hexyl phosphine, butyl hexyl _phosphine , and/or dihexyl phosphine. - Phosphate of formula II as component E Wherein, _R3 represents ethyl, Met can be Al, Fe, _TiO2 , or Zn. n represents 2 or 3, and q = (4 – n) / 2, - As component F, melamine polyphosphate has an average degree of condensation greater than or equal to 20, and - As a gray coloring agent for component G, - Component A accounts for 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 0.01% to 3% by weight. - The proportion of component E is 0.001 to 1% by weight. - The proportion of component F is 1 to 25% by weight, and - The proportion of component G is 0.01 to 20% by weight. The percentage values are based on the total amount of the polyamide composition, and wherein... Component G is a mixture of white pigment and black pigment or dye, wherein the white pigment is selected from zinc oxide, zinc sulfide, lead white, zinc barium white, antimony white, barium sulfate and/or titanium dioxide, and wherein the black pigment or dye is selected from black coloring pigments. 2. The flame-retardant polyamide composition according to claim 1, wherein the black pigment or dye is selected from carbon black, graphite, graphene, aniline black, and bone char. 3. 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. 4. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that, - Component A accounts for 25 to 75% by weight. - Component B accounts for 20 to 40% by weight. - The proportion of component C is 5 to 20% by weight. - The proportion of component D is 0.05 to 1.5% by weight. - The proportion of component E is 0.01 to 0.6% by weight. - The proportion of component F is 2 to 10% by weight, and - The proportion of component G is 0.1% to 8% by weight. The percentage values are based on the total amount of the polyamide composition. 5. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that the polyamide composition comprises an inorganic phosphonate as an additional component H. 6. The flame-retardant polyamide composition according to claim 5, characterized in that the inorganic phosphonate is a compound of formula (III). Where Me is Fe, _TiO₂ , Zn, or Al. o represents 2 or 3, and r = (4–o)/2, The compound of formula III is present in an amount of 0.005 to 10% by weight, based on the total amount of the polyamide composition. 7. The flame-retardant polyamide composition according to claim 6, characterized in that the compound of formula III is present in an amount of 0.02 to 5% by weight, based on the total amount of the polyamide composition. 8. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that it has a relative tracking index of 500 volts or greater, as measured according to the International Electrotechnical Commission standard IEC-60112/3. 9. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that it achieves a thickness of 3.2 mm to 0.4 mm according to the UL94 V0 rating. 10. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that it 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. 11. The flame-retardant polyamide composition according to claim 1, characterized in that component A comprises at least 75% by weight of polyamide 6,6 and at most 25% by weight of polyamide 6. 12. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that glass fiber is used as component B. 13. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that components C, D, E and F are present in particulate form, wherein the average particle size _d50 of these components is 1 to 100 μm. 14. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that the average degree of condensation of the melamine polyphosphate is 20 to 200. 15. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that the melamine polyphosphate has a decomposition temperature greater than or equal to 320°C. 16. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that it comprises an additional additive as component I, wherein the additional additive is selected from emulsifiers, nucleating agents, processing aids, and impact modifiers. 17. The flame-retardant polyamide composition according to claim 16, characterized in that the processing aids include antioxidants, UV stabilizers, gamma-ray stabilizers, hydrolytic stabilizers, co-stabilizers of antioxidants, antistatic agents, dyes different from component G, pigments different from component G, and/or additional flame retardants different from components C, D, E, F, and H. 18. The flame-retardant polyamide composition according to any one of claims 1 to 3, characterized in that it comprises additional additives as component I, 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, impact modifiers, dyes different from component G, pigments different from component G, and/or additional flame retardants different from components C, D, E, F, and H. 19. Use of the polyamide composition according to any one of claims 1 to 18 for the preparation of fibers and molding articles. 20. Use of the polyamide composition according to any one of claims 1 to 18 for the preparation of films. 21. Use of the polyamide composition according to claim 19 or 20, for application in the electrical and electronic fields.