Flame-retardant composition

Abstract

The invention relates to a flame-retardant composition, a polymeric composition, a lacquer or varnish or coating comprising the same, a system for producing the flame-retardant system and the use of the flame-retardant composition as well as a method of preparing the same.

Description

[0001] Flame-retardant composition

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a flame-retardant composition, a polymeric composition, a lacquer or varnish or coating comprising the same, a system for producing the flame-retardant composition, the use of the flame-retardant composition as well as a method of preparing the same.

[0004] BACKGROUND OF THE INVENTION

[0005] The use of ammonium polyphosphate as a halogen-free flame-retardant additive in flame-retardant compositions is known. The flame retarding quality is produced by the generation of an intumescent layer, as described in DE 19 517 499 A1. The document also discloses the production of ammonium polyphosphate starting from P2O5and ammonium orthophosphate in a NH3atmosphere.

[0006] US 2010298474 A1 relates to flame-retardant compositions comprising ammonium polyphosphate, a 1 ,3,5 triazine derivative, a zinc or aluminium phosphate compound, and a melamine foaming agent. The halogen-free flame-retardant composition can be used in a polymer matrix.

[0007] However, ammonium polyphosphates, in particular high-molecular weight representatives, exhibit a low water solubility, which drastically restricts the application range of the above-named compositions. E.g., regularly, they cannot be used in water-based coatings or varnishes.

[0008] In addition, ammonium polyphosphate has a high opacity due to its crystalline structure, so that compositions containing the same often have turbidity that is recognisable even to the naked eye. This precludes their application as coatings, in which the underlying material needs to be visible.

[0009] Further, the decomposition temperature of ammonium polyphosphates is regularly > 240 °C, whereas the decomposition of a variety of technically important polymers such as polymethyl methacrylate or polyvinyl chloride starts already at 170 °C or 200 °C. As a result, flame-retard- ant activity attributable to the decomposition of ammonium polyphosphate does not take place prior to a substantial part of the polymer to be protected being destroyed. In other words: Only a low flame-retardant effect can be achieved when ammonium polyphosphates are applied in these polymers.

[0010] WO 2017 / 183535 A1 provides a fiber treatment including a phosphorous containing unsaturated monomer, additive and a phosphorous containing flame retardant.

[0011] CN 112500757 A relates to an inkjet printing flame retardant coating comprising a modified acrylic flame retardant resin, halogen-free flame retardant and various additives.

[0012] CN 112029366 A provides intumescent fireproof coatings made of acrylic polymers, ammonium polyphosphate and additives.

[0013] CN 107603503 A describes a glue layer comprising a phosphorous containing acrylic polymer and ammonium polyphosphate as flame retardant.

[0014] KR 2010-0052657 A relates to a composition comprising phosphorous containing monomer, photo-initiators and an inorganic flame retardant.

[0015] KR 2016-0123798 A discloses a pressure sensitive adhesive comprising a phosphorous acrylic polymer and a phosphorous-based flame retardant.

[0016] TECHNICAL PROBLEM

[0017] In light of the foregoing, the object of the invention was to provide a composition comprising ammonium polyphosphate having similar or even better flame-retardant properties, and / or a higher transparency than the compositions known in the prior art with a comparable content of ammonium polyphosphate.

[0018] DESCRIPTION OF THE INVENTION

[0019] According to the present invention, this object is solved by a flame-retardant composition comprising or consisting of

[0020] A) ammonium polyphosphate and

[0021] B) a copolymer comprising two or more repeating units, wherein at least one of the two or more repeating units is a phosphorus-containing repeating unit having the following structure: wherein

[0022] R1denotes H or methyl,

[0023] Rmdenotes O' or OH,

[0024] Rndenotes O', OH, Z, X2-P(=O)Rn+1*Rm+1, n, m independently denote an integer of 2-15, X1, X2independently denote O, CH2, S, NH, and and wherein L being a hydrocarbon linker optionally comprising one or more heteroatoms and wherein optionally Z cross-links different polymer chains of the copolymer by being copolymerized via Caand Cb.

[0025] In the inventive context, "polymer" is understood to mean a chemical substance having more than 50% by weight, preferably more than 70% by weight, more preferably more than 80% by weight, even more preferably more than 90% by weight and most preferably more than 95% by weight of macromolecules. "Macromolecules" are molecules composed of one or more identical or similar structural units, the constitutional repeating units (JUPAC. Compendium of Chemical Terminology, 2nded. (the "Gold Book"), A. D. McNaught, A. Wilkinson, Blackwell Scientific Publications, Oxford (1997), S. J. Chalk. ISBN 0-9678550-9-8). Such macromolecules have more than 10 repeating units, preferably more than 15 repeating units. The molar mass is preferably at least 3,000 g / mol, preferably at least 5,000 g / mol, more preferably at least 7,000 g / mol and most preferably at least 10,000 g / mol.

[0026] A copolymer is a polymer derived from more than one species of monomer, i.e. macromolecules including two or more different types of repeating units, which may be arranged in alternation, or at random, or in other more complex patterns, such as graft or star copolymeric structures. In the copolymer of the invention, at least one of these repeating units is the phos- phorous-containing repeating unit defined in claim 1.

[0027] In the context of the invention, the term “lacquer” is to be understood as a liquid or paste or powder coating material which, when applied to a substrate, produces a covering coating with protective, decorative or specific technical properties (DIN 971-1 (09 / 1996)). The main components of coatings are binders, solvents, pigments, fillers and coating auxiliaries. In the case of the non-covering clearcoat, whose colour depends mainly only on that of the binder, the pigment is omitted, and in the case of a solid, powdery coating, the solvent is omitted.

[0028] In the context of the invention, the term “varnish” is to be understood as a collective term for non-pigmented paints containing drying oils or resins or mixtures thereof (DIN 55945 (12 / 1988)).

[0029] According to DIN 8580 (07 / 1985), a “coating” is a firmly adhering layer of formless material to a workpiece. Coatings can be differentiated by means of the process how they are applied to the workpiece, such as painting, hotmelting or spraying.

[0030] As used in the context of the present invention, the term "hydrocarbon linker" includes linker being linear and / or branched aliphatic (e.g. alkyl or alkenyl), alicyclic (e.g. cycloalkyl, cycloalkenyl), and aromatic with aromatic, aliphatic, alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g. two substituents forming one ring together).

[0031] The term "hydrocarbon linker" includes a linker with substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which do not alter the predominantly hydrocarbon nature of the linker (e.g. chloro, fluoro, bromo, iodo, hydroxy, alkoxy, mercapto, alkyl mercapto, alkylhydroxy, nitro, amino, nitroso, sulfoxy).

[0032] The term "hydrocarbon linker" also includes a linker with hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Also included are ethylene oxide (EO) and propylene oxide (PO) linkers. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, imidazolyl and other heterocycles.

[0033] The hydrocarbon linker may be a C0-60 hydrocarbon linking group having oxygen and / or nitrogen and / or sulfur atoms substituted for carbon atoms.

[0034] The linker may for instance be X1(CH2CH2O)x-P (X2= O in this case) with x = 1-20.

[0035] The inventive combination of an ammonium polyphosphate and a copolymer having a phos- phorus-containing repeating unit as defined in claim 1 results in a significant increase in transparency of the flame-retardant composition. In addition, the strong interaction of copolymer and ammonium polyphosphate leads to excellent flame-retardant properties. As a result, the application range of flame-retardant compositions containing ammonium polyphosphate can be significantly extended.

[0036] Without being bound by this theory, the inventors assume that the copolymer B) interacts with the ammonium polyphosphate, thereby disturbing the crystalline structure of the ammonium polyphosphate and creating larger amorphous regions. Because the crystalline regions of the polymer cause light refraction, the transparency is increased by the addition of the phospho- rous-containing copolymer. The water solubility and the decomposition temperature are also substantially influenced by the degree of crystallinity of the polymer.

[0037] The above effects are achieved without the necessity of influencing the molecular structure of ammonium polyphosphate with aid of metal-based components, such as heavy metal salts, which may negatively impact environmental and / or health compatibility.

[0038] Preferably, the proportion of weight of the phosphorous-containing repeating unit, preferably the phosphorous-containing repeating unit with the following structure in the copolymer B) is at least 5 wt.-%, more preferred at least 10 wt.-% and most preferred at least 15 wt.-%, but preferably also at most 90 wt.-% or at most 80 wt.-%.

[0039] Preferably, the proportion of weight of the phosphorous-containing repeating unit in the copolymer B) is within a range of 5 wt.-% to 70 wt.-% or 5 wt.-% to 50 wt or 10 wt.-% to 50 wt.-%, more preferred 5 wt.-% to 40 wt.-% or 10 wt.-% to 40 wt.-% or 15 wt.-% to 40 wt.-% most preferred 5 wt.-% to 30 wt.-% or 10 wt.-% to 30 wt.-% or15 wt.-% to 30 wt.-%.

[0040] In a preferred embodiment of the invention the phosphorus content of the copolymer B) is within the range of 0.5 wt.-% to 11 wt.-%, preferably within the range of 1 wt.-% to 8 wt.-%, and most preferred in the range of 1.5 wt.-% to 7 wt.-%.

[0041] In a preferred embodiment of the invention the weight ratio of ammonium polyphosphate to phosphorous-containing repeating unit of the copolymer B) in the inventive flame-retardant composition is in the range of 3:1 to 0.5:1 , preferably 2:1 to 0.8:1 and most preferred 2:1 to 1 :1.

[0042] In one embodiment of the present invention, the phosphorus-containing repeating unit of the copolymer B) has the following structure: wherein

[0043] R1denote H or methyl,

[0044] Rn, Rmindependently denote 0; OH, Z, O-P(=O)Rn+1Rm+1, n, m independently denote an integer of 2-15, x denotes an integer of 1-20, wherein Z optionally cross-links different polymer chains of the copolymer by being copolymerized via Caand Cb. and x' denotes an integer of 1-20.

[0045] The copolymer B) of the inventive flame-retardant composition can be obtained by copolymerizing organic phosphate-containing monomer of the general formula (I) with ethylenically unsaturated, polymerizable monomer units, such as straight-chained or branched C1-18 alkyl (meth)acrylates, preferably straight-chained or branched C1-8 alkyl (meth)acrylates, more preferably straight-chained or branched C1-4 alkyl (meth)acrylates. wherein

[0046] R1denotes H or methyl,

[0047] ORmdenotes O' or OH,

[0048] ORndenotes O', OH, Z, X2-P(=O)Rn+1Rm+1, n, m independently denote an integer of 2-15, X1, X2independently denote O, CH2, S, NH, Z=

[0049] L denotes a hydrocarbon linker optionally comprising one or more heteroatoms.

[0050] The linker moiety connects the phosphorus unit with the ethylenically unsaturated, polymerizable monomer unit.

[0051] The organic phosphate-containing monomer is preferably a 2-hydroxyalkyl (meth)acrylate phosphate, more preferably 2-hydroxyethyl methacrylate phosphate (HEMA-P).

[0052] The phosphate-containing monomer may further comprise a reactive solvent, such as an organic solvent.

[0053] As another example, the phosphate-containing monomer may contain 70 wt.% of phosphate components and 30 wt.% of a reactive solvent like methyl methacrylate. HEMA-phosphate monomers are well-known as good candidates to provide extraordinary adhesion and excellent anti-corrosion property on metal substrates, when used as coating material.

[0054] Because of the phosphate functional groups in monomer structure, HEMA-phosphate monomers can endow resins or coatings with fireproofing performance as well. Nowadays, more and more attentions are attracted to flame retardancy in many applications, such as construction coatings, wood coatings, composites, etc., since a large multitude of lives and properties sacrifices were witnessed during last many years. According to lots of reports and research, the content of phosphor in polymer B) should be necessarily above at least 0.5 wt%, preferably at least 1 wt.% and most preferably at least 1 .5 wt.%, if an excellent flame-retardant performance is expected. In terms of HEMA-phosphate containing emulsion technology, the dosage of HEMA-phosphate in an ideal emulsion polymer for flame resistance need to be as high as 15 wt.%.

[0055] Preferably, the copolymer B) of the inventive composition is obtained via the polymerization, in particular via emulsion polymerization, of a monomer composition, comprising:

[0056] (a1 ) 5 wt.% to 70 wt.%, preferably 10 wt.-% to 50 wt.-%, of a phosphorus-containing monomer;

[0057] (a2) a base selected from the group consisting of ammonia and 2-amino-2-methyl-1 -propanol being present in the composition in a molar ration of (a1 ) to (a2) = 1 :1 .1 to 1 :1 .2, preferably 1 :1.1;

[0058] (b) 30 wt.% to 95 wt.%, preferably 50 wt.-% to 90 wt.-%, of straight-chained or branched C1-18 alkyl (meth)acrylates; and

[0059] (c) 0 wt.% to 15 wt.% of one or more further ethylenically unsaturated comonomers different than monomers (a1 ) and (b).

[0060] The content of each component (a1 ), (b) and (c) is based on the total weight of the monomer composition. In a particular embodiment, the proportions of components (a1), (b) and (c) add up to 100% by weight.

[0061] The content of component (a2) is dependent on the content of component (a1 ). The molar ratio of (a1 ) to (a2) is 1 : 1 .1 to 1 : 1.2, preferably 1 :1.1. The monomers (b) can be selected from the group consisting of straight-chained or branched C1-18 alkyl (meth)acrylates, preferably straight-chained or branched C1-8 alkyl (methacrylates, more preferably straight-chained or branched C1-4 alkyl (meth)acrylates.

[0062] [C1-18 alkyl (meth)acrylates]

[0063] The C1-18 alkyl (meth)acrylates for use in accordance with the present invention are esters of (meth)acrylic acid and straight chain or branched alcohols having 1 to 18 carbon atoms. The term "C1 -18 alkyl methacrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths.

[0064] Suitable C1-18 alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tertbutyl (meth)acrylate and pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (methacrylate, heptyl (meth)acrylate, 2-tert-butylheptyl (meth)acrylate, octyl (meth)acrylate, 3-iso- propylheptyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acry- late, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate, 5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, 2-m ethyl hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, 5-isopropyl heptad ecyl (meth)acrylate, 4-tert-butyloctadecyl (meth)acrylate, 5- ethyl octadecyl (meth)acrylate, 3-isopropyloctadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, cetyleicosyl (meth)acrylate, stearyl eicosyl (meth)acrylate, docosyl (meth)acrylate, and eicosyltetratriacontyl (meth)acrylate.

[0065] [C1-8 alkyl (meth)acrylates]

[0066] The C1-8 alkyl (meth)acrylates for use in accordance with the present invention are esters of (meth)acrylic acid and straight chain or branched alcohols having 1 to 8 carbon atoms. The term "C1-8 alkyl methacrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths.

[0067] Suitable C1-8 alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tertbutyl (meth)acrylate and pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (methacrylate, heptyl (meth)acrylate, 2and octyl (meth)acrylate.

[0068] [C1-4 alkyl (meth)acrylates] The C1-4 alkyl (meth)acrylates for use in accordance with the present invention are esters of (meth)acrylic acid and straight chain or branched alcohols having 1 to 4 carbon atoms. The term "C1-4 alkyl methacrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths.

[0069] Suitable C1-4 alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and tert-butyl (meth)acrylate.

[0070] The one or more further ethylenically unsaturated comonomers (c), which are different than monomers (a1) and (b), can be selected from the group consisting of cycloalkyl (methacrylates, (meth)acrylates derived from unsaturated alcohols, heterocyclic (meth)acrylates, nitriles of (meth)acrylic acid and other nitrogenous methacrylates, (meth )acrylam ides, aryl (meth)acry- lates, (meth)acrylates which have two or more (meth)acryloyl groups, (meth)acrylates having three or more double bonds, ethylenically unsaturated carbocylic acid(s), hydroxyalkyl (meth)acrylates, styrene monomers and vinyl esters.

[0071] [cycloalkyl (meth)acrylates]

[0072] The cycloalkyl (meth)acrylates for use in accordance with the present invention are esters of (meth)acrylic acid and cyclic alcohols. Suitable cycloalkyl (meth)acrylates include, for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, 3-vinylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, cycloalkyl (meth)acrylates, such as 2,4,5-tri-tert-butyl-3-vinylcyclo- hexyl (meth)acrylate, and 2,3,4,5-tetra-tert-butylcyclohexyl (meth)acrylate.

[0073] The (meth)acrylates which are derived from unsaturated alcohols for use in accordance with the present invention include, for example, 2-propynyl (meth)acrylate, allyl (meth)acrylate and vinyl (meth)acrylate.

[0074] The heterocyclic (meth)acrylates for use in accordance with the present invention include, for example, 2-(1-imidazolyl)ethyl (meth)acrylate, 2-(4-morpholinyl)ethyl (meth)acrylate and 1-(2- methacryloyloxyethyl)-2-pyrrolidone.

[0075] The nitriles of (meth)acrylic acid and other nitrogenous methacrylates for use in accordance with the present invention include, for example, N-(methacryloyloxyethyl)diisobutyl ketimine, N-(methacryloyloxyethyl)dihexadecyl ketimine, methacryloylamidoacetonitrile, 2-methacrylo- yloxyethylmethyl cyanamide, and cyanomethyl methacrylate. The (meth)acrylamides for use in accordance with the present invention include, for example, (meth )acrylam ide and N-isopropyl (meth )acrylam ide.

[0076] The aryl (meth)acrylates for use in accordance with the present invention include, for example, benzyl (meth)acrylate and phenyl (meth)acrylate, wherein the aryl radicals can in each case be unsubstituted or up to quadruply substituted.

[0077] The (meth)acrylates which have two or more (meth)acryloyl groups for use in accordance with the present invention include, for example, glycol di(meth)acrylates, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetra- and polyethylene glycol di(meth)acrylate, 1 ,3-butanediol (meth)acrylate, 1 ,4-butanediol (meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, glycerol di(meth)acrylate; dimethacrylates of ethoxylated bisphenol A.

[0078] The (meth)acrylates having three or more double bonds for use in accordance with the present invention include, for example, glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and di pentaerythritol penta(meth)acrylate.

[0079] The ethylenically unsaturated carboxylic acid(s) for use in accordance with the invention include acrylic acid and methacrylic acid.

[0080] The hydroxyalkyl (meth)acrylates for use in accordance with the present invention include, for example, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl(meth)acrylate, 3,4-dihydroxy- butyl(meth)acrylate and 2-hydroxyethyl (methacrylate).

[0081] The styrene monomers for use in accordance with the present invention include, for example, styrene, substituted styrenes having an alkyl substituent in the side chain, for example a-me- thylstyrene and a-ethylstyrene, substituted styrenes having an alkyl substituent on the ring, such as vinyltoluene and p-methylstyrene.

[0082] Suitable vinyl esters for use in accordance with the present invention include, for example, vinyl acetate.

[0083] Suitable self-cross-linking monomers like diacetone-acrylamide (DAAM) or acetoacetoxyethyl methacrylate (AAEMA) can also be used as comonomers in accordance with the present invention. Crosslinking or curing occurs in the presence of diamines and dihydrazides at ambient temperatures during the drying process of the coating.

[0084] The term "(meth)acrylate" refers to both, esters of acrylic acid and esters of methacrylic acid.

[0085] In accordance with the present invention, particular preference is given to using monomer mixtures which comprise methacrylates and acrylates. Thus, use may especially be made of mixtures of methyl methacrylate and acrylates having 2 to 4 carbon atoms, such as ethyl acrylate and butyl acrylate.

[0086] A dispersion containing the copolymer B) of the inventive composition is preferably obtained via emulsion polymerization. Methods of emulsion polymerization are inter alia described in Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition. In general, for this purpose an aqueous phase is prepared which, as well as water, can comprise customary additives, especially emulsifiers and protective colloids for the stabilization of the emulsion.

[0087] Further information regarding the emulsion polymerization may be found in the specialist literature, especially H. Rauch-Puntigam, Th. Volker, "Acryl- und Methacrylverbindungen” [acrylic and methacrylic compounds], Springer, Heidelberg, 1967 or Kirk-Othmer, Encyclopedia of Chemical Technology, vol. 1 , pages 386ff, J. Wiley, New York, 1978.

[0088] In a preferred embodiment of the invention, the weight ratio of the weight of the ammonium polyphosphate A) to the weight of the copolymer B) is in the range of 1 :1 to 1 :20, preferably 1 :1 to 1 :10, more preferably 1 :1 to 1 :5, even more preferably 1 :1 to 1 :3, and most preferably 1 :1 to 1 :2.

[0089] Preferably, ammonium polyphosphate A) and copolymer B) constitute the lion’s share of the flame-retardant composition. Hence, the sum of weights of the two components is preferably within a range of 50 wt.-% to 99 wt.-% of the weight of the flame-retardant composition, preferably 60 wt.-% to 99 wt.-%, more preferred 70 wt.-% to 95 wt.-% and most preferred 70 wt.- % to 90 wt.-%.

[0090] It goes without saying that the flame-retardant composition may comprise more than one copolymer B). In this case, the above ratios relate to the summed weights of the copolymers.

[0091] Ammonium polyphosphate has 6 kinds of different crystalline structures, wherein type I and II are the most widely used and with type II having the best thermal stability. In a preferred embodiment of the invention, the ammonium polyphosphate A) is a crystalline type II ammonium polyphosphate

[0092] Because the effects according to the invention are attributable to the interaction of copolymer B) with ammonium polyphosphate on a molecular level, these interactions are enhanced by increasing the potential interaction surface of copolymer B) with ammonium polyphosphate.

[0093] Therefore, preferably, the copolymer B) and / or the ammonium polyphosphate have a low particle size. In a preferred embodiment of the invention, the copolymer B) and / or the ammonium polyphosphate have a particle size of 100 pm, preferably 50 pm, more preferably 20 pm, and most preferably < 10 pm, but preferably also 1 pm, as determined by light scattering in accordance with DIN-ISO-ISO 13320.

[0094] The effects resulting from the addition of copolymer B) to ammonium polyphosphate can be observed even in ammonium polyphosphates of very high chain length, which typically have very low water solubility, moderate transparency, and a high decomposition temperature and therefore regularly necessitate sophisticated methods for homogeneous incorporation in or coating on the structure to be protected.

[0095] In a preferred embodiment of the invention, the number-average degree of polymerization of the ammonium polyphosphate is therefore 100, preferably 200, more preferably 400, even more preferably 600, still more preferably 1000, and most preferably 1500. The number-average degree of polymerization of the ammonium polyphosphate indicates the number of building blocks per polymer molecule and can be determined from the number-average molar mass of the polymer molecule. In the case of ammonium polyphosphate, for example, the number-average molar mass can be determined by31P-NMR spectroscopy, size exclusion chromatography (SEC), and / or light scattering.

[0096] In the decomposition of flame retardants, halogens contained therein are released as corrosive and harmful gases. Such corrosive combustion gases pose a high risk, in particular in the field of electronics. Because of this, despite the highly flame-retardant effect of halogens, halogen- free flame retardants are nowadays preferred.

[0097] Proportions of heavy metals, i.e. metals having a density of > 5 g / cm3, must also be avoided out of environmental and health considerations. Therefore, in a preferred embodiment of the invention, the composition has a halogen content and / or a content of metals having a density > 5 g / cm3of < 1.0 wt.-%, preferably 0.5 wt.-%, particularly preferably 0.2 wt.-%, and most preferably < 0.1 wt.-%. The halogen content can be determined by analytical methods commonly known by the skilled person, such as combustion ion chromatography (CIC).

[0098] In a preferred embodiment of the invention, the flame-retardant composition further comprises at least one additive selected from the group consisting of fillers, inhibitors, nitrogen-based synergistic flame retardants such as urea or melamine, UV-absorbers, and mixtures thereof. The weight proportion of the one or more additives in the flame-retardant composition is preferably within a range of 1 wt.-% to 50 wt.-%, preferably 5 wt.-% to 40 wt.-%, more preferred 5 wt.-% to 30 wt.-% and most preferred 10 wt.-% to 20 wt.-%.

[0099] Ammonium polyphosphate can be employed advantageously in combination with other flame retardants, e.g., those that cause flame retardation by another mechanism. Due to the interaction of ammonium polyphosphate with other flame retardants, a synergistic effect, i.e. an effect that goes beyond the mere sum of the flame-retardant effect of the individual components, can be achieved.

[0100] In a preferred embodiment, the composition thus contains at least one further flame-retardant component, which is preferably selected among nitrogen bases, melamine derivatives, phosphates, pyrophosphates, polyphosphates, organic and inorganic phosphinates, organic and inorganic phosphonates, and derivatives of the aforementioned compounds, preferably selected under ammonium polyphosphate, ammonium polyphosphate particles coated and / or coated and cross-linked with melamine, melamine resin, melamine derivatives, urea and urea derivates, silanes, siloxanes, polysiloxanes, silicones, or polystyrenes, as well as 1 ,3,5-triazine compounds, including melamine, melam, melem, melon, ammeline, ammelide, 2- ureidomelamine, acetoguanamine, benzoguanamine, diaminephenyl triazine, melamine salts and adducts, melamine cyan urate, melamine borate, melamine orthophosphate, melamine pyrophosphate, dimelamine pyrophosphate, aluminium diethyl phosphinate, melamine polyphosphate, oligomeric and polymeric 1 ,3,5-triazine compounds, and polyphosphates of 1 ,3,5-tria- zine compounds, guanine, piperazine phosphate, piperazine polyphosphate, ethylenediamine phosphate, pentaerythritol, di pentaerythritol, borophosphate, 1 , 3, 5-tri hydroxy ethyl isocyanu- rate, 1 ,3,5-triglycidyl isocyanurate, triallyl isocyanurate, and derivatives of the aforementioned compounds. In a preferred embodiment, the polymeric material contains waxes, silicones, siloxanes, fats, or mineral oils for better dispersibility of the further flame-retardant component. The present invention also relates to a polymeric composition comprising a polymer and a flame-retardant composition according to the present invention. It goes without saying that the “polymer” of this polymeric composition is different from the inventive copolymer B), i.e. the “polymer” is an additional component, which is distinct from the flame-retardant composition and its ammonium polyphosphate and its copolymer B). The polymeric composition is a matrix material and contains the inventive flame-retardant composition to ensure adequate fire resistance.

[0101] In order to achieve this goal, the proportion of the inventive flame-retardant composition in the polymeric composition should not be too low. On the other hand, too much flame retardant can adversely affect the mechanical properties of the polymer.

[0102] Hence, preferably, the weight fraction of the flame-retardant composition in the total weight of the polymeric composition is therefore from 0.5 to 30 wt.-%, particularly preferably from 1.0 to 20 wt.-%, more preferably from 2.0 to 20 wt.-%, and most preferably from 3 to 15 wt.-%.

[0103] The weight fraction of the polymeric material of the polymeric composition is from 50 to 99.5 wt.%, particularly preferably from 70 to 95 wt.-%, and most preferably from 75 to 95 wt.- %.

[0104] The polymer of the polymeric composition is preferably a thermoplastic, more preferably selected from polyolefins such as polyethylene, polypropylene, polybutylene, polym ethyl pentene and block, graft and copolymers thereof; styrene polymers such as standard polystyrene; impact-resistant polystyrene, styrene acrylonitrile, acrylonitrile butadiene styrene, acrylonitrile styrene; acrylic rubber, halogen-bearing vinyl polymer such as polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, tetrafluoromethylene hexafluoromethylene copolymer, ethylene tetrafluoroethylene copolymer, polychlorotrifluoroethylene, ethylene chlorotrifluoroethylene copolymer; acrylic polymers, such as polyacrylates or polymethacrylates; polyacetate such as polyoxymethylene; linear polycondensates such as polyamides (PA-6, PA-6,6, PA- 6,10, PA-6,12, PA-11 , PA-12 and so forth), polycarbonates, polyesters (for example polyethyleneterephthalate, polybutylene terephthalate and so forth), polyimides, polyaryl ketones, polysulfones, polyurethanes, polyphenylenes, polymers of unsaturated alcohols and amines or acyl derivatives or acetals thereof such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl benzoate, cross-linked polycondensates and polyadducts such as phenoplasts, ami- noplasts, epoxy resins, unsaturated polyesters, polyurethane; modified natural substances such as cellulose ester, including copolymers or mixtures of the aforementioned polymers. The inventive flame-retardant composition can be introduced into the polymeric composition by various methods. The inventive flame-retardant composition can be incorporated into the polymer during the moulding process. If the polymer is processed by extrusion, for example, the inventive flame-retardant composition can be added during the extrusion process, e.g. by means of a masterbatch. A masterbatch within the meaning of the present invention is a polymeric material, in the form of granules or powder, containing the inventive flame-retardant composition and the optional further additives in concentrations that are higher than in the final application.

[0105] To produce the polymeric composition, the masterbatch or different masterbatches are combined with additional polymer without the inventive flame-retardant composition (or with lower concentrations thereof) contained in the masterbatch in quantities or ratios so that the desired concentrations of the composition in the end product, the polymeric composition, are reached.

[0106] Compared to the addition of various substances in the form of pastes, powders or liquids, masterbatches have the advantage that they ensure a high level of process reliability and are very easy to process and meter. Through extrusion, the flame retardant is evenly distributed in the polymeric material.

[0107] The introduction of the composition into the polymeric composition can be demonstrated by suitable analysis techniques, in particular31P-NMR spectroscopy.

[0108] The present invention also relates to a lacquer or varnish comprising a preferably water-based solvent and the flame-retardant composition according to the present invention. In this context, “water-based” is to be understood that water constitutes 50 wt.-% of the solvent, thereby forming an “aqueous solution” or “aqueous dispersion”.

[0109] The inventive flame-retardant compositions exhibit a good dispersity / solubility in aqueous solvents, which predestines them for the application in water-based lacquer or varnish system, in particular at high concentrations. Preferably, the mass concentration of the composition in the preferably aqueous solution or aqueous dispersion is at least 10 g / L, preferably at least 200 g / L, more preferably at least 400 g / L, even more preferably at least 600 g / L, and most preferably at least 800 g / L, but preferably also not more than 950 g / L.

[0110] The present invention is also directed to a coating comprising or consisting of the flame-retard- ant composition as well as a workpiece with a coating adhered thereon. Because the composition according to the invention has a high transparency, it is particularly suitable for coating applications in which the structure of the coated material is to remain visible even after the coating process, such as coating for wood, glass, paper, textile, polymeric materials or metal. Hence, the present invention also relates to wood or metal comprising an inventive coating. Particularly preferred is the use of the inventive composition in coating application for E-mobility applications. Therefore, the present invention also relates to fuel cells, batteries, fuel cells or battery cases or fuel cells or battery assemblies comprising an inventive coating.

[0111] The present invention is also directed to a system, i.e. a set of chemicals for producing the inventive flame-retardant composition. According to the invention, the term "set of chemicals" is understood to mean a predetermined arrangement of individual chemicals which are either present as separate but functionally interacting individual components (kits-of-parts) or as partially premixed components.

[0112] The system comprises

[0113] I) ammonium polyphosphate A),

[0114] II) the copolymer B)

[0115] The composition may further comprise one or more of the following components:

[0116] III) at least one solvent, wherein the solvent is preferably selected from water and / or alcohols.

[0117] IV) additives preferably selected from the group consisting of fillers, colorants, antiaging stabilizers, inhibitors, nitrogen-based synergistic flame retardants such as urea or melamine, LIV absorbers, or mixtures thereof. A nitrogen-based synergistic flame-retardant urea is particularly preferred.

[0118] The invention also relates to the use of the flame-retardant composition or a lacquer or varnish comprising the same for producing a coating, in particular for wood, glass, polymeric materials or metal. Particularly preferred is the use for so-called natural-fibre-reinforced plastics, preferably wood-plastic composites.

[0119] There are various approaches to produce varnishes, printing inks or coating materials in general. Two common procedures are: (1) the step-by-step production of a recipe comprising a "regrind" step and a "coating" step; and

[0120] (2) the production from intermediates, in particular liquid preparations, which is particularly common in the case of preparations of particles to receive efficient dispersion and avoid damage to the binders due to high shear forces, such as coagulation of polymer dispersions.

[0121] Coating compositions often contain particles, such as pigments as colouring substances and / or fillers.

[0122] In order to facilitate and to improve the dispersion of particles in liquid media it is common to employ dispersants and wetting additives, which as surfactants promote wetting of the particulate solids to be dispersed, and aid in the disruption of agglomerates. These dispersants also have a stabilizing effect on the resultant dispersions and prevent re-agglomeration or flocculation of the particles.

[0123] Examples of wetting and dispersing additives comprise:

[0124] • poly(meth)acrylates and their derivates;

[0125] • styrene-maleic anhydride copolymers;

[0126] • alkoxylates, produced by using various starting alcohols and monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, as well as products from subsequent reactions such as esterification;

[0127] • tetramethyldecindiol and its derivates;

[0128] • copolymers of vinyl group-containing monomers and oligomers; and

[0129] • hyperdispersants.

[0130] For the use in coatings and / or printing inks, in another embodiment, it is desirable to produce highly concentrated preparations of the ammonium polyphosphate first for blending with conventional dye and binder systems respectively coating components in a subsequent and separate step. Particle preparations typically have good meterability and are often used for efficient and reliable production of coatings and inks. Examples are pigment preparations used for colouring both aqueous and solvent-borne paints.

[0131] In this embodiment, it is advantageous for the production of particle preparations, that

[0132] (i) ammonium polyphosphate A) is added into the particle preparations containing wetting and dispersing additives and

[0133] (ii) the copolymer B) is added when blending the particle preparations with other coating components. In such an embodiment, the particle preparations facilitate the introduction of ammonium polyphosphate A) into the coating or printing ink without flocculation or reaggregation of the ammonium polyphosphate A).

[0134] The invention also relates to the use of the copolymer B) for increasing the transparency of ammonium polyphosphate in the visible spectral range of electromagnetic radiation and / or increasing water solubility and / or for decreasing the decomposition temperature of ammonium polyphosphate.

[0135] The invention also relates to a method of preparing the inventive flame-retardant composition, the method comprising the steps of

[0136] (a) providing the copolymer B),

[0137] (b) providing ammonium polyphosphate A),

[0138] (c) optionally providing at least one additive preferably selected from the group consisting of fillers, colorants, anti-aging stabilizers, inhibitors, nitrogen-based synergistic flame retardants such as urea or melamine, UV absorbers, or mixtures thereof, and

[0139] (d) contacting (a), (b) and the optional component (c), preferably by mixing.

[0140] The mixing step can for example be performed with aid of an intensive mixer / disperser.

[0141] The invention also relates to a product obtainable by the above method.

[0142] EXAMPLES

[0143] The invention will now be explained in more detail with the aid of specific examples describing the synthesis of polymer B) and the process for obtaining and characterizing the flame-retard- ant compositions in accordance with the invention.

[0144] Measurement methods

[0145] The Brookfield viscosity was determined at 23°C using a Brookfield rotational viscometer LVT DV II with safety bar using spindle I at different speeds.

[0146] The solid content was measured using a moisture analyzer HB43-S (Mettler-Toledo). The pH measurements were performed using a pH meter Climatic 761 (Knick) using a pH / Pt-1000 single-rod measuring cell (glass with ceramic diaphragm) and 3-molar KCI solution.

[0147] The particle size was measured using a Delsa Nanosizer (Beckmann Coulter).

[0148] Table 1: Starting materials

[0149] 1. Synthesis of copolymer B)

[0150] Example 1 : Emulsion comprising 15 wt.% of HEMA-P

[0151] Example 2: Emulsion comprising 10 wt.% of HEMA-P

[0152] Example 3: Emulsion comprising 5 wt.% of HEMA-P

[0153] Apparatus set-up:

[0154] 2L-Rettberg-reactor (double-wall), blade agitator (metal, 150 rpm), thermostat (filling: water), reflux condenser, two metering pumps, thermo couple

[0155] Preparation of aqueous dispersion:

[0156] 1) The components A1-A3 (see table 2) were weighed into the reactor and heated up to 80 °C (internal temperature). The stirring rate was adjusted to 150 rpm.

[0157] 2) The components B1 -B4 (see table 2) were premixed and were added into a solution of C1-C3 to complete the monomer pre-emulsion. This mixture was emulsified with an Ultra-Turrax homogenizer at 10,000 rpm for 3 minutes.

[0158] 3) D1 -D2 (see T able 2) were weighed and mixed. 10% of this solution was added into the reactor at 80°C and stirred for 5 minutes.

[0159] 4) After 5 min, the feed of the prepared monomer pre-emulsion (B+C) was started for 15 minutes (= addition of 10% of the pre-emulsion). Afterwards, the reaction was kept for another 30 minutes without further additions.

[0160] 5) The rest of the pre-emulsion (B+C) was added within 4 hours, the rest of the initiator solution D within 4.25 hours via two different feeds. After end of the feeds, the reaction was kept at 80°C for 1 hour.

[0161] 6) The internal temperature of the reactor was decreased to 60°C.

[0162] 7) The components E1 and E2 (see table 2) were weighed separately and added via two different feeding lines within 30 minutes.

[0163] 8) The reaction was kept at 60°C for another 30 minutes to remove the residual monomers.

[0164] 9) The reactor was cooled down to room temperature. All aqueous dispersions (Examples 1-3 and reference) were prepared according to the previous described procedure except that the ratio of monomers and the neutralizing agent were varied according to Table 2. Table 2: Composition of prepared emulsion polymers (examples and reference)

[0165] Table 3: Basic dispersion properties

[0166] 2. Preparation and use of inventive flame-retardant composition

[0167] Preparation of flame-retardant compositions

[0168] A HEMA-P resin polymer dispersion with 30% HEMA-P weight proportion ( Acrilem® FR30, commercially available from leap Sira) is introduced in a Oliver+Batlle VF-1 .5 high speed disperser together with urea - and in case of example F-ref together with water to ensure mixability. The proportions of weight of the components are depicted in the below table. The components are intensively mixed via stirring at 500 rpm. Subsequently, FR Cros® 584 (APP II) is added and the stirring rate is increased to 1000 rpm to obtain a homogeneous, ready to use dispersion. Flame retardant tests

[0169] Epiradiateur NF P 92501 flame-retardant tests have been conducted with wooden board specimens (standard Okume wood of following dimension: 30 cm x40 cm x1 cm (HxWxD)), which have been coated with the above dispersions. The coated boards are obtained by painting a specimen with one of the above defined dispersions F-ref and F-1 with aid of a brush and drying at 23 °C for 7 days. The coat weight is 600 g / m2.

[0170] During the flame retardant test, the specimens are burned. For this sake, the specimens are mounted to the test equipment at an angle of 45° to the horizontal and are exposed to thermal radiation (heat source: 500W radiation). The heat source starts to burn the specimen and if the material is flammable, pilot flames ignite the gases released due to decomposition. If the flame last more than 5 seconds, the flame is considered as effective flame. The test duration is 20 minutes and during this time the length of the flames are evaluated. The materials are classified M1 to M4 according to the q index.

[0171] M1 - Non-flammable 0 < q < 2.5

[0172] M2 - Low flammability 2.5 < q < 15

[0173] M3 - Moderately flammable 15 < q < 50

[0174] M4 - flammable q >50

[0175] Following results are obtained for samples F-ref and F-1.

[0176] Pictures from the tests are shown in Fig. 1 (F-1) and Fig. 2 (F-ref).

[0177] Transparency tests - preparation of polymer films

[0178] 23.8 g urea and HEMA-P resin 10% dispersion (example 2, tables 2, 3) are introduced in a Oliver+Batlle VF-1.5 high speed disperser and mixed via stirring at 500 rpm. Subsequently, 142.9 g FR Cros 584 (APP II) are added and the stirring rate is increased to 1000 rpm to obtain a homogeneous, ready to use resin dispersion. A specimen is painted with a brush to obtain a coating of 600 g / m2, which is then dried at 23 °C for 7 days.

[0179] A coating on a black-white chart after the drying process is shown in Fig. 3. In comparison, Fig. 4 depicts a black-white chart, which has been painted with a conventional acrylic binder with FR CROS 584 contained in the binder. As can be seen, the inventive coatings are transparent in contrast to the ones known from the state-of-the-art, which yield an opaque coating.

[0180] A coating on a cardboard after the drying process is shown in Fig. 5. Fig. 6 right half, depicts a cardboard, which has been painted with a conventional acrylic binder with FR CROS 584 contained in the binder. As can be seen, the inventive coatings are transparent in contrast to the ones known from the state-of-the-art, which yield an opaque coating.

Claims

C l a i m s1. Flame-retardant composition comprisingA) ammonium polyphosphate with a number-average degree of polymerization of 100 andB) a copolymer comprising two or more repeating units, wherein one or more of the two or more repeating units is a phosphorous-containing repeating unit, wherein the phosphorous-containing repeating unit has the following structure:whereinR1denotes H or methyl,Rmdenotes O' or OH,Rndenotes O', OH, Z, X2-P(=O)Rn+1Rm+1, n, m independently denote an integer of 2-15, X1, X2independently denote O, CH2, S, NH, andwherein L being a hydrocarbon linker optionally comprising one or more heteroatoms and wherein optionally Z cross-links different polymer chains of the copolymer by being copolymerized via Caand Cb, wherein the weight proportion of the phosphorous-containing repeating unit in the copolymer B) is within a range of 5 wt.-% to 40 wt.-%, preferably 10 wt.-% to 40 wt.-%, more preferably 10 wt.-% to 30 wt.-%, and most preferred 15 wt.-% to 30 wt.-%, and wherein the weight ratio of A) to B) in the flame-retardant composition is in the range of 1 :1 to 1 :20.

2. Flame-retardant composition as defined in any of the precedent claims, wherein the flame-retardant composition comprises or consists of particles with a size determined by light scattering in accordance with DIN ISO 13320 of < 100 pm, preferably < 50 pm, more preferably 25 pm.

3. Flame-retardant composition as defined in any of the precedent claims, wherein the flame-retardant composition has a halogen content and / or a content of metals having a density > 5 g / cm3of < 1.0 wt.-%, preferably < 0.1 wt.-%.

4. Flame-retardant composition as defined in any of the precedent claims, wherein the flame-retardant composition further comprises at least one additive selected from the group consisting of fillers, inhibitors, nitrogen-based synergistic flame retardants such as urea or melamine, UV absorbers, and mixtures thereof.

5. Flame-retardant composition as defined in any of the precedent claims, wherein the phosphorous-containing repeating unit in component B) is a 2-hydroxyalkyl (meth)acrylate phosphate, preferably 2-hydroxyethyl methacrylate phosphate (HEMA- P).

6. Polymeric composition comprising a polymeric material and a flame-retardant composition according to any of the claims 1-5 contained therein, wherein the weight fraction of the flame-retardant composition is from 0.5 to 30 wt.-% of the polymeric composition.

7. Lacquer or varnish comprising a preferably water-based solvent and a flame-retard- ant composition according to any of the claims 1-5 contained therein or a polymeric composition according to claim 6 contained therein, wherein the mass concentrationof the flame-retardant composition in the solvent is preferably at least 500 g / L, preferably 800 g / L.

8. Coating comprising a flame-retardant composition according to any of the claims 1-5 or a polymeric composition according to claim 6.

9. Set of chemicals for producing a flame-retardant composition according to any of the claims 1-5 comprising at least the following components:I) ammonium polyphosphate with a number-average degree of polymerization of > 100, andII) a copolymer as defined in any of the claims 1-5, optionally one or more of the following:III) at least one solvent,IV) additives preferably selected from the group consisting of fillers, colorants, antiaging stabilizers, inhibitors, nitrogen-based synergistic flame retardants such as urea or melamine, UV absorbers, or mixtures thereof.

10. Use of a flame-retardant composition according to any of the claims 1-5, a polymeric composition according to claim 6 or a lacquer or varnish according to claim 7 for producing a coating, preferably for producing a coating for wood, glass, paper, textile, polymeric materials or metal.11 . Use of a copolymer comprising two or more repeating units, wherein one or more of the repeating units is a phosphorous-containing repeating unit, wherein the phosphorous-containing repeating unit has the following structure:whereinR1denotes H or methyl,Rmdenotes O' or OH,Rndenotes O', OH, Z, X2-P(=O)Rn+1Rm+1, n, m independently denote an integer of 2-15, X1, X2independently denote O, CH2, S, NH, andZ=wherein L being a hydrocarbon linker optionally comprising one or more heteroatoms and wherein optionally Z cross-links different polymer chains of the copolymer by being copolymerized via Caand Cb, wherein the weight proportion of the phosphorous-containing repeating unit in the copolymer B) is within a range of 5 wt.-% to 40 wt.-%, preferably 10 wt-% to 40 wt.-%, more preferably 10 wt.-% to 30 wt.-%, and most preferred 15 wt.- % to 30 wt.-%, and wherein the weight ratio of A) to B) in the flame-retardant composition is in the range of 1:1 to 1:20.to increase the transparency of ammonium polyphosphate with a number-average degree of polymerization of the ammonium polyphosphate of 100, in the visible spectral range of electromagnetic radiation and / or to decrease the decomposition temperature of ammonium polyphosphate.

12. Use as defined in claim 11 , wherein the phosphorous-containing repeating unit is a 2- hydroxyalkyl (meth)acrylate phosphate, preferably 2-hydroxyethyl methacrylate phosphate (HEMA-P).

13. Method of preparing a flame-retardant composition according to any of the claims 1- 5, the method comprising the steps of(a) providing a copolymer as defined in any of the claims 1-5,(b) providing ammonium polyphosphate with a number-average degree of polymerization of > 100,(c) optionally providing at least one additive preferably selected from the group consisting of fillers, colorants, anti-aging stabilizers, inhibitors, nitrogen-based synergistic flame retardants such as urea or melamine, UV absorbers, or mixtures thereof, and(d) contacting (a), (b) and the optional component (c), preferably by mixing.

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