Method for producing phosphorylated 1,4-anhydroerythritols and the salts thereof and the use thereof as environmentally compatible flame retardants, and specific compounds

Abstract

The present invention relates to an efficient method for producing compounds of general formula I as specified below, and to the compounds of general formulae III, Iva and IVb, V, Via and Vlb that can be further produced therefrom, and to the use thereof as flame retardants. The present invention also relates to flame-retardant plastic compositions which contain the aforementioned compounds as flame retardants.

Description

[0001] Fraunhofer Society...e. V.

[0002] P150412PC00

[0003] Processes for the production of phosphorylated 1,4-anhydroerythritols and their salts and their use as environmentally friendly flame retardants, as well as specific compounds

[0004] The present invention relates to an efficient method for producing compounds of general formula I as specified below, as well as the compounds of general formulas III, Iva and IVb, V, Via and Vlb that can be further produced therefrom, and their use as flame retardants. Furthermore, the present invention relates to flame-retardant plastic compositions that incorporate the aforementioned compounds as flame retardants.

[0005] The high flammability of thermoset plastics such as epoxy resins, polyurethane resins, polyester resins, and thermoplastic plastics such as polyolefins, polyamides, and polyesters is a disadvantage that must be overcome or reduced for numerous applications of these materials with the help of flame retardants, for example, in the electrical and electronics sector as well as in transport and construction.

[0006] Bromine- or chlorine-containing flame retardants, which are used in large quantities for epoxy resins and polyurethane resins as well as for thermoplastic polymers, do meet the criteria regarding efficiency, processability, maintenance of material properties and moderate costs, but can cause health risks - especially due to their effect in case of fire because of the release of toxic gases - as well as environmental problems, not least in the disposal of the materials that contain them.

[0007] Nitrogen-containing additives (melamine-based), as well as organic and inorganic phosphorus compounds and boron compounds, are used as halogen-free alternatives for the flame retardancy of thermoplastics, polyurethane resins, and epoxy resins. Metal hydroxides are also used, but these usually require high concentrations to achieve effective flame retardancy. Like halogenated flame retardants, these flame retardant additives are also derived from fossil raw materials. Furthermore, some of these flame retardants—namely melamine, melamine cyanurate, and boron compounds—are now considered toxicologically problematic, while organophosphorus flame retardants are relatively expensive. Moreover, the latter are only effective in selected resin systems and thermoplastics and often impair material properties.

[0008] As an alternative to halogenated flame retardants, special organophosphorus compounds, which are less hazardous to health, have gained importance, particularly for thermoset resin systems – especially the compound 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) – which has become an important and widely used flame retardant for epoxy resins. However, the production of DOPO is based on fossil raw materials and is an unsustainable and rather complex process. The resulting relatively high price, as well as the limited flame-retardant efficiency for aromatic-rich epoxy resin systems, restrict the application of DOPO. DOPO is hardly suitable for the widely used epoxy resins with aliphatic curing amines. Another disadvantage is that DOPO worsens the glass transition temperature of the resins.To improve application properties and due to the good reactivity of the phosphorus-hydrogen bond, numerous DOPO derivatives have been synthesized and tested. This has resulted in many scientific articles and patents. Of these derivatives, only the addition products of DOPO to epoxy resins have gained significant importance. The other DOPO derivatives are either not used or only for niche applications. Combinations of organophosphorus compounds (e.g., DOPO) with mineral additives and polyphosphates have also been extensively investigated and have shown good flame-retardant properties in the epoxy resins used; however, the inorganic components significantly impair the processing properties of the resins.

[0009] Chlorinated alkyl phosphates have served as efficient and cost-effective flame retardants for polyurethane resins for decades. They provide excellent flame protection without adversely affecting resin processing or material properties. In fact, they can even improve these properties by acting as viscosity regulators and plasticizers. Tris(2-chloroisopropyl)phosphate (TCPP), in particular, is used in very large quantities, with annual global production reaching several hundred thousand tons. However, the toxicological and ecotoxicological properties of TCPP and other chlorinated alkyl phosphates are now considered highly problematic, leading to an intensive search for suitable substitutes. The use of melamine (alone or as a component of flame retardant mixtures), already mentioned in Section 1, cannot satisfactorily solve the problem, partly due to toxicological concerns.

[0010] In recent years, DOPO derivatives have been specifically developed and successfully tested for use in polyurethanes (Gaan, S.; Liang, Sh.; Mispreuve, H.; Perler, Heribert; N., Reinold; Neisius, M.: “Flame retardant flexible polyurethane foams from novel DOPO-phosphonamidate additives”; Polymer Degradation and Stability, 113 (2015), 180-188; W02013020696 A2, 06.

[0011] (August 2012). The toxicological studies also yielded positive results. However, the unsustainable and complex production of these flame retardants is a disadvantage.

[0012] Halogenated flame retardants are still used extensively in thermoplastic materials because they are efficient, cost-effective, and have a relatively minor impact on material properties. However, these can cause the aforementioned toxicological risks, particularly due to the release of toxic gases in the event of a fire. They also create problems with the disposal and recycling of the plastics. From a toxicological and ecotoxicological perspective, the combinations of halogenated flame retardants with the synergist antimony(III) oxide, which are still widely used, are particularly problematic.

[0013] As an alternative to halogenated flame retardants, organophosphorus compounds have gained importance for thermoplastic polymers, particularly the aluminum and zinc salts of diethylphosphinic acid, which, among other things, provide effective flame retardancy in polyamides and are preferably used in combination with melamine polyphosphate and melamine cyanurate (MC). However, the toxicological properties of MC, which is used in large quantities, are now viewed critically.

[0014] Macromolecular flame retardants with polyester or polyacrylate base structures, which carry DOPO groups (WO 2009109347A1 and DE 102013101487A1), are also known, but have not yet found widespread use.

[0015] Bio-based flame retardants: In addition to toxicological and ecotoxicological safety, there is an increasing demand for the highest possible bio-based structural content of flame retardants and sustainable production.

[0016] However, intensive work on the development of sustainably produced, bio-based flame retardants for plastic materials has only recently begun (Sonnier R., Taguet A., Ferry L, Lopez-Cuesta JM. (2018) "Flame Retardant Biobased Polymers. In: Towards Bio-based Flame Retardant Polymers". SpringerBriefs in Molecular Science. Springer, Cham (DOI https: / / doi.org / 10.1007 / 978-3-319-67083-6_1; Online ISBN 978-3-319-67083-6; Print ISBN 978-3-319-67082-9).

[0017] The following bicyclic phosphorus derivative of erythritol, known from the literature (Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 28, 1743-1762 (1990)), could be a suitable flame retardant for resin systems: phosphorylated anhydroerythritol (PAHE) or tetrahydrofuro[3,4-d][1,3,2]diox-aphosphol-2-oxide. This substance has already been used for the synthesis of bio-based macromolecular flame retardants for thermoplastic polymers (Kaplan M., Ciesielski M., Fuchs S., Getterle Ch., Schönberger F., Pfaffentner R.: "Novel Macromolecular and Biobased Flame Retardants Based on Cellulose Esters and Phosphorylated Sugar Alcohols", Polymers 2023, 15).

[0018] 3195-, WO 2021048335 Al, Phosphorus-containing cellulose esters, process for their production, use and flame retardants; 11.09.2020, Fraunhofer-Gesellschaft). These novel bio-based flame retardants showed

[0019] It demonstrates good efficacy in a partially bio-based polyamide processed at relatively low temperatures, as well as in synergistic flame retardant mixtures for polyolefins. However, this flame retardant is not suitable for higher melting point plastics such as PA6 and PBT.

[0020] The use of PAHE in thermoset resin systems was previously unknown. Furthermore, the two-step synthesis method described in the literature for

[0021] This organophosphate compound is neither cost-effective nor sustainable. It involves the dehydration of erythritol to anhydroerythritol, which is then reacted with the toxic and relatively expensive reagent dimethyl phosphite.

[0022] is converted to PAHE with the release of methanol (reaction scheme 1;

[0023] (both reactions under reduced pressure):

[0024] Reaction scheme 1

[0025] Dimethyl phosphite - 2 Methanol

[0026]

[0027] Erythritol Anhydroerythritol PAHE So far, there are no flame retardants available, especially for epoxy resins, polyurethanes, unsaturated polyester resins and other important resins, that can solve the problem described above.

[0028] The object of the present invention, in contrast to the prior art, was to provide a toxicologically safe flame retardant for plastics, which is largely bio-based, and for whose production an efficient, cost-effective and sustainable method was to be found. This flame retardant should be suitable for resin systems (thermoset plastics) and should be convertible, by means of simple reactions such as oxidation and salt formation, into substances that are also well suited for flame retardancy in thermoplastic materials.

[0029] Therefore, halogen-free, phosphorus-containing flame retardants are desirable. These should be produced cost-effectively and sustainably from renewable raw materials and provide effective flame protection in important resin systems and thermoplastic polymers. They should be manufactured from raw materials that are readily available in large quantities at low cost and whose production does not directly compete with food production. Sugar alcohols, especially erythritol, meet this requirement very well. However, they have not yet been considered in the development of phosphorus-containing flame retardants for thermoset resin systems, and for thermoplastic polymers, only in one case (WO 2021 / 048335 Al; Fraunhofer-Gesellschaft).

[0030] Furthermore, the addition of flame retardants should not significantly impair the processing properties, i.e., the curing properties of the resin systems and the processing of the thermoplastics by extrusion and injection molding. The flame retardants should also not have a detrimental effect on the application-relevant thermal and mechanical material properties of the resins and thermoplastics. For example, it is important that the flame retardants do not cause a significant reduction in the glass transition temperature of resin systems.

[0031] Furthermore, flame retardants should be effective, cost-efficient, and toxicologically and ecotoxicologically safe. In addition, there is a growing demand for the sustainable production of flame retardants, both in terms of raw materials and the production process. Environmentally friendly production from renewable resources is particularly desirable.

[0032] A bio-based, toxicologically safe substitute for melamine cyanurate, which is used in large quantities in thermoplastic materials, is also desirable.

[0033] This problem is solved using the features of the independent patent claims. The respective dependent patent claims preferably specify embodiments.

[0034] According to a first aspect, the present invention relates to a method for producing a compound according to general formula I

[0035] R

[0036] H x -rX

[0037] XT /

[0038]

[0039] R

[0040] Formula 1

[0041] where

[0042] X is the same or different in each occurrence and is O or S, R is the same or different in each occurrence and is selected from the group consisting of hydrogen or linear and branched alkyl groups with 1 to 18 carbon atoms,

[0043] in which a reaction mixture consisting of or containing

[0044] a combination of the general formula II

[0045]

[0046] R XH

[0047] Formula II

[0048] where X and R have the same meaning as in Formula I,

[0049] and phosphorous acid

[0050] is implemented. Surprisingly, it was found that the compound according to Formula I can be produced directly by reacting the compound according to Formula II in a single step. The inventive method can therefore be carried out in the simplest and most effective way.

[0051] According to a preferred embodiment, in Formula I (and thus also in Formula II) each X is oxygen and each R is hydrogen.

[0052] In particular, in the process according to the invention, the molar ratio of the compound of general formula II to the phosphorous acid is adjusted to between 2:1 and 1:2, preferably between 1.5:1 and 1:1.5, more preferably between 1.2:1 and 1:1.2, and especially preferably between 1.05:1 and 1:1.

[0053] It is further preferred that the conversion takes place at a reduced pressure compared to ambient pressure, preferably at a pressure of 0.1 to 200 mbar, more preferably from 1 to 100 mbar, and particularly preferably from 3 to 80 mbar.

[0054] For example, a decreasing pressure profile can also be selected, in which the pressure is gradually reduced.

[0055] The reaction is preferably carried out at temperatures of 80 to 220 °C, preferably 100 to 200 °C, and particularly preferably 120 to 170 °C.

[0056] During implementation, a rising temperature profile can be selected, in which the temperature is successively increased.

[0057] Furthermore, the invention also relates to the further processing of the compounds of general formula I into subsequent derivatives.

[0058] In one aspect of this, the invention also relates to a method for producing a compound of general formula III

[0059] R

[0060]

[0061] Formula III

[0062] wherein X and R have the meanings given above, wherein first a compound according to general formula I is produced according to a process according to the invention described above and then a hydrolysis of the compound of general formula I to the compound of general formula III takes place, in which the compound of general formula I is reacted with water.

[0063] Another aspect of this concerns the further processing of compounds of general formula III. After hydrolysis, the compound of general formula III becomes a compound of general formula IVa or IVb.

[0064] HX

[0065] © d ^ / X HN(R 1 )3 e oP

[0066]

[0067] Formula IVa Formula IVb where

[0068] X and R have the meanings given above,

[0069] R 1 selected from the group consisting of hydrogen and organic residues, e.g. linear and branched alkyl residues with 1 to 18 carbon atoms,

[0070] M is an n-valent, e.g. a mono-, di-, tri- or tetravalent metal cation, salted out, the compound being formed according to general formula III with a base N(R) 1 )s for combining the general formula IVa or with a base (M n+)(Y m ( n / m), where Y is an m-valent anion, e.g. a mono-, di-, tri- or tetravalent anion, is converted to the compound of the general formula IVb.

[0071] The invention relates to methods for producing a compound of the general formula V

[0072] R HO

[0073] zÄ T /

[0074]

[0075] RFormula V

[0076] from the compound according to general formula I, wherein X and R have the meanings given above, wherein first a compound according to general formula I is prepared according to a process according to the invention as described above and then the compound according to general formula I is reacted with an oxidizing agent to form a compound of general formula V, wherein the compound of general formula I is reacted with the oxidizing agent.

[0077] In particular, the oxidizing agent is selected from hydrogen peroxide, organic peroxo acids, such as m-chloroperbenzoic acid or peracetic acid, and oxygen, e.g., air, preferably in the presence of a catalyst.

[0078] After oxidation, the compound can be formed according to the general formula V to a compound according to the general formula Via or Vlb.

[0079] ©. / HN(R 1 )3O

[0080] XT /

[0081] O

[0082]

[0083] Formula Via Formula Vlb where R, X, R 1 , M and n, which have the meanings given above, are salted out, whereby the compound is salted out according to the general formula V with a base N(R) 1 )3 to combine the general formula Via or with a base (M n+ )(Y m )( n / m), where Y is an m-valent anion, e.g. a mono-, di-, tri- or tetravalent anion, is converted to the general formula Vlb.

[0084] According to a further aspect, the present use relates to a compound according to the general formula I, III, IVa, IVb, V, Via or Vlb, as defined in any of the preceding claims, as a flame retardant, preferably as a flame retardant for plastics, more preferably thermoplastic or thermoset plastics, in particular for epoxy resins and polyurethane resins.

[0085] Furthermore, the present invention relates to a plastic composition containing or consisting of

[0086] at least one plastic as well as

[0087] at least one compound according to the general formula I, III, IVa, IVb, V, Via and / or Vlb, as defined above.

[0088] For example, the plastic can be selected from the group consisting of thermoplastic or thermoset plastics, wherein the plastic is in particular selected from the group consisting of

[0089] a) Epoxy resins consisting of di- or polyfunctional epoxy compounds in combination with, for example, hardeners based on amines, anhydrides, dicyandiamide, mercaptans, isocyanates or catalytically acting hardeners,

[0090] b) Polyurethanes, made from hydroxy-terminated polyethers or polyesters and aromatic or aliphatic isocyanates such as 2,4- or 2,6-toluene diisocyanate or methylene diphenyl diisocyanate, in particular also linear polyurethanes (TPU), polyureas,

[0091] c) Phenolic resins such as phenol-formaldehyde resins, urea-formaldehyde resins, melamine-formaldehyde resins,

[0092] d) unsaturated polyester resins made from unsaturated dicarboxylic acids and diols with vinyl compounds, e.g. styrene, alkyd resins,

[0093] e) Polymers made from olefins or diolefins such as polyethylene (LDPE, LLDPE, VLDPE, ULDPE, MDPE, HDPE, UHMWPE), metallocene-PE (m-PE), polypropylene, polyisobutylene, poly-4-methylpentene-1, polybutadiene, polyisoprene, such as natural rubber (NR), polycyclooctene, polyalkylene-carbon monoxide copolymers, and copolymers in the form of statistical or block structures such as polypropylene-polyethylene (EP), EPM or EPDM with, for example, 5-ethylidene-2-norbornene as a comonomer, ethylene-vinyl acetate (EVA), ethylene acrylates, such as ethylene-butyl acrylate, ethylene-acrylic acid and their salts (ionomers), and terpolymers such as... B. Ethylene-acrylic acid glycidyl(meth)acrylate, graft polymers such as polypropylene-graft maleic anhydride, polypropylene-graft acrylic acid, polyethylene-graft acrylic acid, polyethylene-polybutylacrylate-graft maleic anhydride, and blends such as...LDPE / LLDPE or long-chain branched polypropylene copolymers produced with alpha-olefins as comonomers, such as 1-butene, 1-hexene, 1-octene or 1-octadecene.

[0094] f) Polystyrene, polymethylstyrene, poly-alpha-methylstyrene, polyvinylnaphthalene, polyvinylbiphenyl, polyvinyltoluene, styrene-butadiene (SB), styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene, styrene-isoprene, styrene-isoprene-styrene (SIS), styrolutadiene acrylonitrile (ABS), styrene-acrylonitrile (SAN), styrene-acrylonitrile acrylate (ASA), styrene-ethylene, styrene-maleic anhydride polymers including corresponding graft copolymers such as e.g. B. Styrene on butadiene, maleic anhydride on SBS or SEBS, as well as graft copolymers of methyl methacrylate, styrene-butadiene and ABS (MABS), as well as hydrogenated polystyrene derivatives such as polyvinylcyclohexane, g) halogen-containing polymers such as polyvinyl chloride (PVC), polychloroprene and polyvinylidene chloride (PVDC), copolymers of vinyl chloride and vinylidene chloride or of vinyl chloride and vinyl acetate, chlorinated polyethylene, polyvinylidene fluoride, epichlorohydrin homo and copolymers in particular.with ethylene oxide (ECO).

[0095] h) Polymers of unsaturated esters such as polyacrylates and polymethacrylates such as polymethyl methacrylate (PMMA), polybutyl acrylate, polylauryl acrylate, polystearyl acrylate, polyglycidyl acrylate, polyglycidyl methacrylate, polyacrylonitrile, polyacrylamides, copolymers such as polyacrylonitrile-polyalkyl acrylate,

[0096] i) Polymers made from unsaturated alcohols and derivatives, such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyallyl phthalate, polyallyl melamine,

[0097] j) Polyacetals, such as polyoxymethylene (POM) or copolymers with, for example, butanal; k) Polyphenylene oxides and blends with polystyrene or polyamides; l) Polymers of cyclic ethers, such as polyethylene glycol, polypropylene glycol, polyethylene oxide, polypropylene oxide, polytetrahydrofuran; m) Polyamides, such as polyamide-6, 6.6, 6.10, 4.6, 4.10, 6.12, 10.10, 10.12, 12.12, polyamide 11, polyamide 12, and (partially) aromatic polyamides, such as polyphthalamides, e.g., produced from terephthalic acid and / or isophthalic acid and aliphatic diamines, such as hexamethylenediamine or m-xylylenediamine, or from aliphatic dicarboxylic acids, such as... B. Adipic acid or sebacic acid and aromatic diamines such as 1,4- or 1,3-diaminobenzene, blends of different polyamides such as PA-6 and PA 6.6 or blends of polyamides and polyolefins such as PA / PP,

[0098] n) Polyimides, polyamide-imides, polyetherimides, polyesterimides, poly(ether)ketones, polysulfones, polyethersulfones, polyarylsulfones, polyphenylene sulfides, polybenzimidazoles, polyhydantoins, o) Polyesters made from aliphatic or aromatic dicarboxylic acids and diols or from hydroxycarboxylic acids such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PTI), polyethylene naphthylate (PEN), poly-1,4-dimethylolcyclohexane terephthalate, polyhydroxybenzoate, polyhydroxynaphthalate, polylactic acid (PLA), polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyethylene succinate, polytetramethylene succinate, polycaprolactone,

[0099] p) Polycarbonates, polyester carbonates, and blends such as PC / ABS, PC / PBT, PC / PET / PBT, PC / PA,

[0100] q) Cellulose derivatives such as cellulose nitrate, cellulose acetate, cellulose propionate, cellulose butyrate,

[0101] r) silicones, e.g. based on dimethylsiloxanes, methylphenylsiloxanes or diphenylsiloxanes, e.g. vinyl group terminated, s) as well as mixtures, combinations or blends of two or more of the aforementioned polymers.The plastic composition may furthermore contain at least one additive selected from the group consisting of primary and / or secondary antioxidants, in particular primary and / or secondary antioxidants selected from the group consisting of phosphites, phosphonites, thiols, phenolic antioxidants, sterically hindered amines, hydroxylamines and mixtures or combinations thereof, UV absorbers, light stabilizers, hydroxylamine-based stabilizers, benzofuranone-based stabilizers, nucleating agents, impact enhancers, plasticizers, lubricants, rheology modifiers, chain extenders, processing aids, pigments, dyes, optical brighteners, antimicrobial agents, antistatic agents, slip agents, antiblocking agents, coupling agents, dispersing agents, compatibilizers, oxygen scavengers, acid scavengers, costabilizers, marking agents and antifogging agents.This at least one additive may be added together with the at least one compound according to the general formula I, III, IVa, IVb, V, Via and / or Vlb, as defined above, or when used in the plastic, but also separately from it.

[0102] In particular, at least one additive is selected from the group consisting of primary and / or secondary antioxidants, in particular primary and / or secondary antioxidants selected from the group consisting of phosphites, phosphonites, thiols, phenolic antioxidants, sterically hindered amines, hydroxylamines and mixtures or combinations thereof, UV absorbers, light stabilizers, hydroxylamine-based stabilizers, benzofuranone-based stabilizers, nucleating agents, impact enhancers, plasticizers, lubricants, rheology modifiers, chain extenders, processing aids, pigments, dyes, optical brighteners, antimicrobial agents, antistatic agents, slip agents, antiblocking agents, coupling agents, dispersing agents, compatibilizers, oxygen scavengers, acid scavengers, costabilizers, marking agents and antifogging agents;

[0103] wherein the at least one additive is particularly preferably selected from the group consisting of phosphites, phosphonites, sulfites, polyols, acid scavengers, hindered amines, and mixtures and combinations thereof. According to a preferred aspect, the plastic composition has the following composition

[0104] 0.01 to 20.00 wt.%, preferably 0.1 to 15.0 wt.%, further preferably 0.2 to 12.00 wt.%, particularly preferably 0.5 to 10.00 wt.% of at least one compound according to the general formula I, III, IVa, IVb, V, Via and / or Vlb,

[0105] 99.99 to 10.00 wt.%, preferably 99.99 to 90.00 wt.%, preferably 99.89 to 95.00 wt.%, particularly preferably 99.90 to 98.00 wt.% of at least one plastic, as well as

[0106] 0 to 80.00 wt.%, preferably 0 to 9.99 wt.%, further preferably 0.01 to 4.98 wt.%, particularly preferably 0.02 to 2.00 wt.% of at least one additive,

[0107] the components add up to 100% by weight.

[0108] The invention also relates to a connection according to the general formula Via or Vlb

[0109] ©. / HN(R 1 )3O

[0110] XT /

[0111] O

[0112]

[0113] Formula Via Formula Vlb where R, X, R 1 and have the meaning given above and

[0114] M is an n-valent, e.g. a mono-, di-, tri- or tetravalent metal cation, excluding Li and Na as metal cations.

[0115] The invention also relates to a compound of general formula VII.

[0116]

[0117] R

[0118] Formula VII

[0119] where

[0120] X and R are defined as above and R 2an organic residue, preferably an organic residue with at least one polymerizable functionality, which is further preferably an epoxy group, wherein the residue R is particularly preferably 2 the following structure according to Formula VIII

[0121]

[0122] Formula VIII

[0123] The present invention will be explained in more detail below using an exemplary embodiment, without limiting the invention to specific details.

[0124] According to a particularly preferred aspect, the present invention relates to an efficient method for the production of the phosphorylated anhydroerythritols PAHE and oxPAHE from erythritol, as well as the production of salt-like substances from these phosphorus compounds. The invention also relates in particular to the use of PAHE, oxPAHE, and their salts as environmentally friendly flame retardants for thermoset resin systems and thermoplastic polymers.

[0125] The invention preferably relates to an efficient manufacturing method for phosphorylated anhydroerythritol (PAHE), its oxidation to oxPAHE, the conversion of both compounds to salt-like substances, and the use of the aforementioned substances as environmentally friendly flame retardants for resin systems and thermoplastic polymers.

[0126] The production of PAHE from erythritol and phosphorous acid by direct esterification and dehydration under reduced pressure is described as an example. This production method requires no solvent, yields the product with good purity and almost quantitative yield, and can be carried out on a large scale. Furthermore, the oxidation of PAHE to oxPAHE using peracids and hydrogen peroxide is described. In addition, the invention includes the production of salt-like compounds from PAHE and oxPAHE by reaction with ammonia, amine bases, and metal salts. The invention also preferably relates to the use of PAHE, oxPAHE, and their salts as efficient, environmentally friendly, and cost-effective flame retardants for epoxy resins, polyurethanes, unsaturated polyester resins, and other thermoset resin systems, as well as for polyamides, polyolefins, and other thermoplastic polymers.

[0127] It has been found that the bicyclic phosphorus compound PAHE, in particular, is an effective flame retardant for thermoset plastics, including technically important epoxy resins and polyurethanes. This organophosphorus compound can be successfully used both as a standalone flame retardant and as a component of flame retardant mixtures. Furthermore, it has been found that PAHE can be converted by simple derivatization (oxidation, salt formation) into compounds that possess the thermal stability required for use as a flame retardant in important thermoplastic materials.

[0128] In particular, the use of the compounds of formulas I, III, Iva, IVb, V, Via, Vlb and VII and their salts as a new, efficient flame retardant for important resins such as epoxy resins and polyurethanes and thermoplastic polymers has the following advantages:

[0129] • High flame retardancy

[0130] • Organic structural component entirely bio-based

[0131] • High phosphorus content

[0132] • Environmentally friendly and toxicologically safe

[0133] The new method according to the invention for the production of, for example, PAHE from phosphorous acid and, for example, erythritol has the following advantages:

[0134] • Both starting materials are cost-effective and toxicologically advantageous

[0135] • The new synthesis method is sustainable because no solvent is required and only water is produced in addition to the product. • The new synthesis method can be carried out cost-effectively with high space-time yield.

[0136] • No product cleaning required

[0137] Furthermore, PAHE can be efficiently oxidized to oxPAHE. Additionally, salt-like flame retardants can be easily produced from PAHE and oxPAHE.

[0138] The most important advantage of the invention is the new, efficient, and sustainable production of PAHE from the cost-effective, toxicologically advantageous, and / or bio-based starting materials phosphorous acid and erythritol. Almost equally important, however, is the suitability of PAHE and its derivatives as highly effective flame retardants for resin systems and thermoplastic polymers.

[0139] The present invention is particularly suitable for the production of flame-retardant epoxy resins, polyurethane resins, and UP resins, which can be used in large quantities in construction, vehicle manufacturing, electronic and electrical devices, furniture, and for many other applications. The new flame retardant represents a good alternative to the flame retardants established for these resins, as it offers the advantages mentioned above.

[0140] Compounds of general formula I and their derivatives, i.e., the oxidized and salt-like derivatives, can also be used in resin systems, even for flame retardancy in thermoplastics. Flame-retardant thermoplastics are also widely used. It is particularly noteworthy that, for example, the easily produced ammonium and zinc salts have thermal resistance up to approximately 280°C and 300°C, respectively. Thus, they can serve as an alternative to melamine cyanurate, which is used in large quantities for flame retardancy in thermoplastic materials but is problematic from a toxicological perspective.

[0141] Surprisingly, it was found that PAHE can be synthesized directly from phosphorous acid and erythritol (reaction scheme 2). The new PAHE synthesis is preferably carried out under reduced pressure. Reaction scheme 2: New PAHE from

[0142]

[0143] acid and

[0144] Erythritol

[0145]

[0146] OH Erythritol Phosphorous acid

[0147] The reaction of the components can be carried out in a simple distillation apparatus, whereby the pressure is gradually reduced and the temperature is increased. In this reaction, only water is formed in addition to PAHE, which is continuously distilled off. The product is obtained as a melt, which is removed from the apparatus after the reaction and then...

[0148] Upon cooling, it solidifies into a white solid. This solid contains > 96%

[0149] PAHE is sufficient for the applications according to the invention, so that no product cleaning is necessary. The PAHE production according to the invention can be carried out very well on a large scale.

[0150] Conversion of PAHE by oxidation: It has been found that the PH functionality of PAHE can be oxidized by peracids, hydrogen peroxide and other oxidizing agents, yielding the previously unknown compound oxPAHE, see reaction scheme 3.

[0151] Reaction scheme 3: Oxidation of PAHE with hydrogen peroxide (above) and

[0152] per acid

[0153]

[0154] PAHE axPAHE

[0155] Examples of peracids that can be used include m-chloroperbenzoic acid or peracetic acid.

[0156] Salt-like phosphorylated anhydroerythritols: It was found that PAHE reacts with aqueous ammonia solution and with amine bases according to Scheme 4, with ring opening and salt formation.

[0157] Reaction scheme 4: Ring opening of PAHE and reaction with ammonia or amine bases to form salt-like compounds (R = H or organic residue)

[0158] NRJ

[0159] H2O

[0160]

[0161] PAKE

[0162] Furthermore, salts of the ring-opened PAHE are formed by reaction with metal salts and metal hydroxides according to Scheme 5.

[0163] Reaction scheme 5: Ring opening of PAHE and reaction with metal salts or metal hydroxides to form salt-like compounds (X = OH or acid anion)

[0164]

[0165] oxPAHE reacts with aqueous ammonia solution and with amine bases according to scheme 6 to form salts:

[0166] Reaction scheme 6: Reaction of oxPAHE with ammonia or amine bases to form salt-like compounds (R = H or organic residue)

[0167]

[0168] oxPAHE ammonium salt of oxPAHE

[0169] Furthermore, salts of oxPAHE are formed by reaction with metal salts and metal hydroxides according to Scheme 7:Reaction Scheme 7:

[0170]

[0171] from oxPAHE with metal salts or

[0172]

[0173] roxiden to salt-like

[0174]

[0175] = OH or

[0176]

[0177] MX n

[0178] -nHX

[0179]

[0180] oxPAHE metal salt of oxPAHE

[0181] It was found that the salt formation from oxPAHE can be carried out well in aqueous solution according to Schemes 6 and 7. Thermogravimetric investigations of the salt-like compounds showed good thermal stability. For example, the decomposition of the zinc salt of oxPAHE begins at approximately 300°C.

[0182] Thus, a production method for PAHE was successfully developed that meets all criteria for sustainable and cost-effective manufacturing. Furthermore, it was possible to oxidize PAHE to the corresponding acid, oxPAHE, efficiently using aqueous hydrogen peroxide, among other methods. Salt-like compounds were also produced from PAHE and oxPAHE, some of which exhibit high thermal stability. This provided potential flame retardants for a wide range of applications, i.e., for various resin systems and thermoplastic polymers. Of particular note is the different oxidation state of the phosphorus in PAHE and oxPAHE. The former is a phosphonate, while the latter is a phosphate. This expands the application range of phosphorylated anhydroerythritols, as phosphonates are more effective in some polymers, while phosphates perform better in others.

[0183] PAHE demonstrated excellent flame-retardant properties in epoxy resin systems, as tested using the established UL94 V flame retardant test according to DIN EN 60695-11-10. Very short burn times were observed, achieving the highest possible UL94 V classification of V0. Surprisingly, a high level of flame retardancy was also achieved with epoxy resins known for their intense combustion and difficulty in flame retardancy, such as combinations of the diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamines (e.g., isophorone diamine). Particularly good results were obtained when PAHE was first bound to the DGEBA by opening the epoxy resin ring, as shown in reaction scheme 8 (an analogous reaction is already known for DOPO). This reaction is catalyzed, for example, with triphenylphosphine.

[0184] Reaction scheme 8: Implementation of PAHE with DGEBA in the presence of the Kata-

[0185]

[0186] When such a reaction was carried out according to reaction scheme 8, better flame retardancy test results were achieved than without such a connection of the PAHE to the DGEBA, or a UL94V classification could be achieved with a lower amount of PAHE.

[0187] Furthermore, very good flame-retardant properties were observed in polyurethane resins. Tests of polyurethane samples using the established UL94 V flame retardancy test according to DIN EN 60695-11-10 resulted in the highest possible UL94 V classification (V0) being achieved with the addition of 7.5% PAHE.

[0188] Examples:

[0189] Example 1: Synthesis of PAHE from erythritol and phosphorous acid according to reaction scheme 2:

[0190] The synthesis was carried out in a distillation apparatus consisting of a three-liter, three-necked flask, a mechanical stirrer with a Teflon stir bar and vacuum seal, a water-cooled Liebig condenser, a thermometer, and a one-liter flask as the distillation receiver. The distillation apparatus was connected to a pressure-controlled vacuum pump (diaphragm pump). The distillation receiver was cooled to approximately -20°C using a cooling mixture. 843 g (6.9 mol) of erythritol and 549 g (6.7 mol) of phosphorous acid were added to the three-liter flask. The target oil bath temperature was set to 130°C. The pressure in the apparatus was then adjusted to 80 mbar. Once the mixture of starting materials had partially melted, the stirrer was carefully started.

[0191] The pressure was reduced to 40 mbar and the oil bath temperature increased to 137°C over the course of one hour. Over the next two hours, the pressure was reduced to 35 mbar and the temperature slightly increased to 138°C. The distillation of the water proceeded at a sufficient rate. After another half hour, the pressure was reduced to 33 mbar and the oil bath temperature increased to 140°C. After a further 20 minutes, the pressure was reduced to 30 mbar and 20 minutes later to 27 mbar. Over the next 6 hours, the oil bath temperature was gradually increased to 160°C and the pressure in the apparatus was reduced to 7 mbar. The apparatus was then filled with nitrogen. An NMR sample was taken from the product melt and dissolved in dry deutero-dimethyl sulfoxide. The NMR spectra show that the product contains approximately 96% PAHE, which was obtained as a stereoisomeric mixture (see Figs. 1a and 1b). 1 H-NMR spectrum (Fig. ala) and 31P-NMR spectrum (Fig. 1b) of PAHE (stereoisomeric mixture) obtained from the reaction of erythritol and phosphorous acid (PAHE content approximately 96%), product signals in the 31 P-NMR spectrum at 23.8 ppm and 25.8 ppm).

[0192] After the reaction, the colorless product melt was poured into a sealable stainless steel tray, where it solidified into a white crystalline mass. The solidified product was then crushed and transferred to a tightly sealed screw-top bottle. The yield was approximately 96%.

[0193] Example 2 - Synthesis of the ammonium salt of the ring-opened PAHE

[0194] 25 g of PAHE were dissolved in 200 ml of acetonitrile under heat. After cooling to room temperature, 20 ml of a 28% aqueous ammonia solution were added while stirring. A white solid precipitated and was isolated by suction filtration. The product was dried for approximately one hour in a Schlenk flask using a diaphragm pump (heating bath temperature: 50°C) while stirring. The drying process was then interrupted to crush the resulting lumps. Subsequently, the mixture was stirred for approximately 30 minutes under diaphragm pump vacuum at an oil bath temperature of 70°C. 22.5 g of white powder were obtained. The NMR spectra clearly show the formation of the ammonium salt of the ring-opened PAHE (Figs. 2a and 2b). 1 H-NMR spectrum (Fig. 2a) and 31 P-NMR spectrum (Fig. 2b) of the ammonium salt of ring-opened PAHE obtained from the reaction of PAHE with aqueous ammonium solution.

[0195] Example 3a - Oxidation of PAHE to oxPAHE using m-chloroperbenzoic acid (mCPBA)

[0196] 12 g of mCPBA (75%, aqueous) were dissolved in 200 ml of toluene at room temperature with stirring. The solution was then decanted from the water that had separated at the bottom.

[0197] 7.5 g of PAHE were dissolved in acetonitrile under nitrogen (Schlenk flask). The mCPBA solution was then added portionwise while stirring. As heating occurred, the mixture was cooled in a water bath. The addition took approximately 20 minutes. The water bath was then removed. Stirring continued for about 20 minutes, and then the stirrer was stopped. The reaction mixture was stored overnight at room temperature. The solid was isolated by suction filtration. The crude product was stirred into approximately 75 ml of chloroform while heating. After cooling, a further suction filtration was performed. Some solid precipitated in the filtrate, which was also isolated. The combined solid was dried under vacuum while heating. Approximately 7.8 g of the substance were obtained. It was stirred a second time into approximately 50 ml of chloroform while heating. After cooling, the mixture was filtered. After heating the product under vacuum, 6.2 g of white powder were obtained. The substance is completely water-soluble.The yield was approximately 75%. Figures 3a and 3b show the NMR spectra of the oxPAHE prepared in this way.

[0198] Fig. 3a and 3b: 1 H-NMR spectrum (Fig. 3a) and 31 P-NMR spectrum (Fig. 3b) of oxPAHE obtained from the reaction of PAHE with m-chloroperbenzoic acid (oxPAHE content approximately 94%). 3b - Oxidation of PAHE to oxPAHE by means of

[0199]

[0200] PAHE was dissolved in acetonitrile under warming conditions, then an approximately equivalent amount of 35% H₂O₂ solution was added and mixed. The solution was allowed to stand for 7 days. The volatile components were then removed by vacuum distillation. The mixture was heated to approximately 130°C. The residue was stirred with acetonitrile at 50°C. After cooling, the oxPAHE was isolated by filtration. The yield of oxPAHE was 30%.

[0201]

[0202] of the ammonium salt of oxPAHE

[0203] In a 250 ml Schlenk flask, 8 g of oxPAHE were placed under nitrogen. Then, 12 g of 28% aqueous ammonia solution were added while stirring, resulting in rapid dissolution and heating. After a few minutes, a vacuum was applied (diaphragm pump, starting at approximately 80 mbar). The mixture was then heated quite vigorously using a hairdryer, while stirring continued and the pressure was reduced to approximately 30 mbar. Once no further release of volatile substances occurred (no bubble formation) and the liquid had become significantly more viscous, the heating was stopped and the flask was filled with nitrogen.

[0204] Upon cooling, the melt solidified into a solid adhering to the glass wall, which was removed using a spatula. After grinding, 7 g of white powder were obtained. The NMR spectra confirm the structure of the ammonium salt of oxPAHE, see Figs. 4a and 4b: 1 H-NMR spectrum (Fig.

[0205] 4a) and 31P-NMR spectrum (Fig. 4b) of the ammonium salt of oxPAHE obtained from the reaction of oxPAHE with aqueous ammonia solution.

[0206] Thermal analysis (TGA) shows that decomposition begins at approximately 280°C.

[0207]

[0208] of the zinc salt of oxPAHE

[0209] 3.44 g of zinc acetate were dissolved in approximately 12 ml of water. The mixture was warmed slightly (it did not dissolve completely). The zinc acetate suspension was transferred at room temperature to a nitrogen-filled apparatus consisting of a 250 ml Schlenk flask and a distillation bridge with a liquid nitrogen-cooled receiver, connected to a rotary vane pump. The oxPAHE was dissolved in 10 ml of water (a clear solution was obtained after a few minutes). The oxPAHE solution was added to the zinc acetate suspension in the 250 ml flask, and the mixture was stirred at room temperature, resulting in a clear solution very quickly. After approximately 2 minutes, a vacuum was applied and the mixture was stirred. The target oil bath temperature was then set to 33°C. Since the temperature in the flask dropped significantly, the oil bath was warmed to approximately 40°C and, once the distillation had progressed, to 52°C and then approximately 65°C. Heating was then continued.When the liquid had concentrated significantly and become so viscous that stirring was no longer possible (after a total of approximately 25 minutes), an oil bath temperature of approximately 183°C had been reached. This temperature was maintained for approximately 30 minutes. The mixture was then allowed to cool, and an NMR sample was analyzed, which showed that the zinc salt was obtained with approximately 95% purity (see figure).

[0210] 5a and 5b: 1 H-NMR spectrum (Fig. 5a) and 31 P-NMR spectrum (Fig. 5b) of the zinc salt of oxPAHE obtained from the reaction of oxPAHE with aqueous ammonia solution.

[0211] Thermal analysis (TGA) shows that decomposition begins at approximately 300°C.

[0212] PAHE-containing samples of the epoxy resin DGEBA / Iso-

[0213]

[0214] and flame retardancy tests using UL94V

[0215] DGEBA (Leuna Resins, Epilox A 19-02, epoxy equivalent weight 185-200 g / mol) and IPDA were used in a 2:1 molar ratio to produce the test specimens. A speed mixer was used to mix and dissolve the resin components. UL94 test bars with a thickness of 3 mm were produced using a silicone mold. The following conditions were applied for curing the specimens: 80°C (0.5 h), 120°C (0.5 h), 160°C (1.0 h), and post-curing at 200°C (1.0 or 2.0 h). The results of the UL94 V tests, as well as key results from the thermal analyses performed by TGA and DSC, are summarized in Table 1a: Table 1a: UL94V, TGA and DSC results of DGEBA / IPDA epoxy resin samples

[0216] PAHE P Ge- Post-curing- Through- Burn times (s) Drip-off UL94V Tg T 2% Return (Wt.%) halt tung schnittli- (DSC) (TGA) STAND (Wt.%) che (°C) (TGA) fire times (°C) times

[0217] (s)

[0218] 0 0 200°C / 2h ti = 261 ti = 231, 294, 259 Burning nk 147°C 331 8.6

[0219] t2= - t2= -

[0220]

[0221] 10.0 2.06 200°C / lh ti = 154 Burning n.k

[0222] t2= 207

[0223] 12.5 2.58 200°C / 2h ti = 33 ti = 9.9, 55.6, 69.4, 8.8, One sample nk 200°C 258 14.5 t2= 27 20 -' 7 (not burning t2= 92.7, 4.6, nend) < 0.5, 36.8, < 0.5

[0224]

[0225] 15.0 3.10 200°C / 2h ti = 1.6 ti = 1.0, 2.4, 0.7, 2.7, no VI 195°C 257 15.4

[0226] t2= 13.4 i 2

[0227] t2 = 22.9, 41.8, < 0.5,

[0228] 0.9, 0.7

[0229] nk: not classified Example 6b - Production of PAHE-containing samples of the epoxy resin DGEBA / IPDA with prior chemical bonding of the PAHE to the DGEBA and flame retardancy tests using UL94V

[0230] Further UL94V specimens were prepared by chemically bonding PAHE to DGEBA prior to the addition of IPDA, according to reaction scheme 8. For this chemical bonding, PAHE was stirred with DGEBA in the presence of 3 wt% triphenylphosphine in a Schlenk flask under nitrogen for 2.5–3.5 h at 130°C. NMR studies unambiguously confirmed the reaction of PAHE with DGEBA. The resulting reaction product was mixed with the amine hardener IPDA using a speed mixer. The preparation of the UL94V specimens was carried out according to Example 6a. The results of the UL94V tests, as well as important results of the thermal analyses performed by TGA and DSC, are summarized in Table 1b: Table 1b: UL94V, TGA, and DSC results of DGEBA / IPDA epoxy resin samples (PAHE chemically bonded to DGEBA)

[0231] PAHE P After-burn times (s) Average- Off- UL94V Tg T 2%Return (Wt content hardening borrowed drops (DSC) (TGA stand ■-%) (Wt%) Burn times n (°C) ) (TGA)

[0232] (s) (°C) (°C) 10.5 2.17 200°C / ti = 4., 2, < 0.5, 6.6, ti = 4.5 No 170°C 331° 8.8

[0233] lh 5.9, 5.1 t2= 22.5 C

[0234] t2= 34.6, 31.5,

[0235] 38.3, 7.3, 0.8

[0236]

[0237] 10.5 2.17 200°C / ti = < 0.5, 7.6, 6.9, ti = 6.8 No VI 170°C 257 16.1

[0238] 2h 5.9, 12.9 t2 = 34

[0239] t2= 4.2, 4.5, 3.5,

[0240] 2.3, 2.3

[0241] 11.5 2.37 200°C / ti = < 0.5, < 0.5, ti = 2.0 No VI 2h 6.0, < 0.5, 3.0 t2 = 5.4 (V0) t2= (20.0), 3.3, 1.4, 0.8, 1.6

[0242]

[0243]

[0244] PAH E-containing samples of the rzez n-diamide (DICY) / fenuron with prior chemical analysis

[0245]

[0246] of the PAHE to the DGEBA and flame protection tests using UL94V

[0247] The following resin components were used: DGEBA (Leuna Resins, Epi-lox A 19-02; epoxy equivalent weight EEW = 185-200 g / mol); DICY (dicyandiamide, DYHARD 100SF, ALZCHEM AG); Fenuron (1,1-dimethyl-3-phenylurea, DYHARD UR 300, ALZCHEM AG).

[0248] The chemical bonding of PAHE to DGEBA was carried out as described in Example 6b. A speed mixer was used to mix and dissolve the resin components and to degas them.

[0249] For the production of the test specimens, DGEBA and DICY were used in a ratio of 5 mol epoxy groups to 1 mol DiCY. The mass of the accelerator Fenuron was one-third that of the DICY. A speed mixer was used to mix and dissolve the resin components. UL94 test rods with a thickness of 3 mm were produced using a silicone mold. The following conditions were applied for curing the specimens: 1 hour at 110 °C, 1 hour at 130 °C, and 2 hours at 200 °C. The heating rate was 1 °C / min.

[0250] The results of the UL94V tests and key results of the thermal analyses performed using TGA and DSC are summarized in Table 2: Table 2: UL94V, TGA and DSC results of DGEBA / DICY / Fenuron epoxy resin samples (PAHE chemically bonded to DGEBA)

[0251] PAHE P Burn times Average dripping UL94V Tg (DSC) T 2% Residue (wt.%) Content ( s ) che(°C) (TGA) (TGA) (% by weight) Fire times (°c) (°C) (s)

[0252] 0 ti = 167, 183 ti = 175 Ja nk 126 316 11.9

[0253] t2= - t2= -

[0254]

[0255] 10.0 2.06 ti = 3.3, 3.2, < ti = 2.4 No V0 141 257 19.8

[0256] 1.0, 1.6, 2.7 t2 = 3.3

[0257] t2= 1.8, 3.7,

[0258] 4.1, 4.5, 2.5

[0259] 7.5 1.55 ti = < 0.5, ti = 6.7 No VI 144

[0260] 12.8, 10.0, < t2= 5.5 0.5, 10.4 t2= 4.7, 14.8, 6.3, 1.2, < 0.5

[0261]

[0262] nk: not classified Example 8 - Production of PAHE-containing samples of the polyurethane resin Iso-phorone diisocyanate (IPDI) / Lupranol® 2095 and flame retardancy tests using UL94V

[0263] The polyurethane resin samples were produced from isophorone diisocyanurate (isomer mixture) and Lupranol® 2095, using 1,4-diazabicyclo[2.2.2]octane (DA-BCO) as a catalyst. Lupranol® 2095 is an oligomeric polyether polyol containing primary hydroxyl groups and has an OH number of 35 mg KOH / g.

[0264] Lupranol® 2095 (21 g), DABCO (0.45 g), and PAHE (2.43 g) were heated to approximately 130 °C in a beaker with a magnetic stir bar. After the components had dissolved, the temperature was reduced to 100 °C, and IPDI (9.0 g) was added. This mixture was stirred for approximately 5 minutes at 100 °C. It was then poured into preheated aluminum molds. The aluminum molds were placed in an oven preheated to 100 °C. After 1 hour, the oven was switched off. Further curing took place at room temperature.

[0265] Finally, the PU sheets were cut, yielding flexible UL94V specimens approximately 4 mm thick. The results of the UL94V tests are shown in Table 3: Table 3: UL94V Results of Lupranol® 2095 / IPDI Polyurethane Resin Samples

[0266] PAHE P Burn times Average dripping Burning to UL94V Remarks (wt%) Content ( s ) Burn times to bracket (wt.%) (s) mer

[0267] 0 ti = 93, 50, 6, 40 ti = 47 Yes Yes nk Completely burned t2= -, -, 30, - t2= - strong burning dripping

[0268]

[0269] 7.5 1.55 ti = 0, 0, 0, 0 ti = 0 No No V0

[0270] t2= 0, 0, 0, 0 t2= 0

[0271] nk: unclassified

Claims

Fraunhofer Society...e. V. P150412PC00 Patent claims 1. Method for producing a compound according to general formula I R R Formula 1 where X is the same or different in each occurrence and is O or S, R is the same or different in each occurrence and is selected from the group consisting of hydrogen or linear and branched alkyl groups with 1 to 18 carbon atoms, in which a reaction mixture consisting of or containing a compound of general formula II XH R R XH Formula II where X and R have the same meaning as in formula I, and phosphorous acid is being implemented.

2. The method according to claim 1, characterized in that in formula I each X is oxygen and each residue R is hydrogen.

3. Method according to one of the preceding claims, characterized in that the molar ratio of the compound of general formula II to the phosphorous acid is adjusted between 2:1 and 1:2, preferably between 1.5:1 and 1:1.5, more preferably 1.2:1 and 1:1.2, and particularly preferably from 1.05:1 to 1:

1.

4. Method according to one of the preceding claims, characterized in that the conversion takes place at a pressure reduced compared to an ambient pressure, preferably at a pressure of 0.1 to 200 mbar, more preferably from 1 to 100 mbar, and particularly preferably from 3 to 80 mbar.

5. Method according to one of the preceding claims, characterized in that a decreasing pressure profile is selected during the implementation.

6. Method according to one of the preceding claims, characterized in that the reaction is carried out at temperatures of 80 to 220 °C, preferably 100 to 200 °C, particularly preferably 120 to 170 °C.

7. Method according to one of the preceding claims, characterized in that an increasing temperature profile is selected during the conversion.

8. Method for the preparation of a compound of general formula III Formula III wherein X and R have the meanings specified in claim 1, wherein a compound according to general formula I is first prepared according to a method according to one of the preceding claims, and subsequently a hydrolysis of the compound according to general formula I to the compound according to general formula III takes place, in which the compound according to general formula I is reacted with water.

9. Method according to the preceding claim, characterized in that, after hydrolysis, the compound according to general formula III is formed to a compound according to general formula IVa or IVb R HX '-rX T x M n+ ® d z X ^( HN(R1 )3 e oP R H Formula IVa Formula IVb where X and R have the meaning specified in claim 1, R 1 selected from the group consisting of hydrogen and organic residues, e.g. linear and branched alkyl residues with 1 to 18 carbon atoms, M is an n-valent, e.g., a mono-, di-, tri- or tetravalent metal cation, The compound is salted out according to general formula III with a base N(R) 1 )3 to combine the general formula IVa or with a base (M n+ )(Y m ( n / m), where Y is an m-valent anion, e.g. a mono-, di-, tri- or tetravalent anion, is converted to the compound of the general formula IVb.

10. Method for producing a compound of general formula V Formula V wherein X and R have the meaning specified in claim 1, wherein first a compound according to general formula I is prepared according to a method according to one of claims 1 to 7 and subsequently the compound according to general formula I is reacted with an oxidizing agent to form a compound of general formula V, wherein the compound of general formula I is reacted with the oxidizing agent.

11. Method according to the preceding claim, characterized in that the oxidizing agent is selected from hydrogen peroxide, organic peroxo acids, such as m-chloroperbenzoic acid or peracetic acid and oxygen, e.g. air, preferably in the presence of a catalyst.

12. Method according to one of the two preceding claims, characterized in that, after oxidation, the compound according to general formula V is formed into a compound according to general formula Via or Vlb. © 1 A HN(R 1)3O OX / Formula Via Formula Vlb where R, X, R 1 , M and n have the meanings given above, is salted out, the compound being salted out according to the general formula V with a base N(R 1 )3 to combine the general formula Via or with a base (M n+ )(Y m ( n / m), where Y is an m-valent anion, e.g. a mono-, di-, tri- or tetravalent anion, is converted to the general formula Vlb.

13. Use of a compound according to the general formula I, III, IVa, IVb, V, Via or Vlb, as defined in any of the preceding claims, as a flame retardant, preferably as a flame retardant for plastics, more preferably thermoplastic or thermoset plastics, in particular for epoxy resins and polyurethane resins.

14. Plastic composition, containing at least one plastic and at least one compound according to the general formula I, III, IVa, IVb, V, Via and / or Vlb, as defined in any of the preceding claims.

15. Plastic composition according to the preceding claim, characterized in that the plastic is selected from the group consisting of thermoplastic or thermoset plastics, wherein the plastic is in particular selected from the group consisting of a) Epoxy resins consisting of di- or polyfunctional epoxy compounds in combination with, for example, hardeners based on amines, anhydrides, dicyandiamide, mercaptans, isocyanates, or catalytically acting hardeners, b) Polyurethanes, made from hydroxy-terminated polyethers or polyesters and aromatic or aliphatic isocyanates such as 2,4- or 2,6-toluene diisocyanate or methylenediphenyl diisocyanate, in particular also linear polyurethanes (TPU), polyureas, c) Phenolic resins such as phenol-formaldehyde resins, urea-formaldehyde resins, melamine-formaldehyde resins, d) unsaturated polyester resins made from unsaturated dicarboxylic acids and diols with vinyl compounds, e.g., styrene, alkyd resins; e) polymers made from olefins or diolefins, e.g., polyethylene (LDPE, LLDPE, VLDPE, ULDPE, MDPE, HDPE, UHMWPE), metallocene-PE (m-PE), polypropylene, polyisobutylene, poly-4-methylpentene-1, polybutadiene, polyisoprene, e.g., natural rubber (NR), polycyclooctene, polyalkylene-carbon monoxide copolymers, and copolymers in the form of statistical or block structures, e.g., polypropylene-polyethylene (EP), EPM, or EPDM with e.g., 5-ethylidene-2-norbornene as a comonomer, ethylene vinyl acetate (EVA), ethylene acrylate, e.g., B. Ethylene butylacrylate, ethylene acrylic acid and their salts (ionomers), as well as terpolymers such as ethylene acrylic acid glycidyl (meth)acrylate, graft polymers such as e.g.Polypropylene graft-maleic anhydride, polypropylene graft-acrylic acid, polyethylene graft-acrylic acid, polyethylene-polybutylacrylate graft-maleic anhydride, and blends such as LDPE / LLDPE or long-chain branched polypropylene copolymers produced with alpha-olefins as comonomers, such as 1-butene, 1-hexene, 1-octene, or 1-octadecene. f) Polystyrene, polymethylstyrene, poly-alpha-methylstyrene, polyvinylnaphthalene, polyvinylbiphenyl, polyvinyltoluene, styrene-butadiene (SB), styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene, styrene-isoprene, styrene-isoprene-styrene (SIS), styrolutadiene acrylonitrile (ABS), styrene-acrylonitrile (SAN), styrene-acrylonitrile acrylate (ASA), styrene-ethylene, styrene-malei anhydride polymers including corresponding graft copolymers such as e.g. B. Styrene on butadiene, maleic anhydride on SBS or SEBS, as well as graft copolymers of methyl methacrylate, styrene-butadiene and ABS (MABS), and hydrogenated polystyrene derivatives such as polyvinylcyclohexane, g) halogen-containing polymers such as polyvinyl chloride (PVC), polychloroprene and polyvinylidene chloride (PVDC), copolymers of vinyl chloride and vinylidene chloride or of vinyl chloride and vinyl acetate, chlorinated polyethylene, polyvinylidene fluoride, epichlorohydrin homo and copolymers, especially with ethylene oxide (ECO); h) polymers of unsaturated esters such as polyacrylates and polymethacrylates such as polymethyl methacrylate (PMMA), polybutyl acrylate, polylauryl acrylate, polystearyl acrylate, polyglycidyl acrylate, polyglycidyl methacrylate, polyacrylonitrile, polyacrylamides, copolymers such as polyacrylonitrile-polyalkyl acrylate. i) Polymers made from unsaturated alcohols and derivatives, such as: Polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyallyl phthalate, polyallyl melamine, j) Polyacetals, such as polyoxymethylene (POM) or copolymers with, for example, butanal; k) Polyphenylene oxides and blends with polystyrene or polyamides; l) Polymers of cyclic ethers, such as polyethylene glycol, polypropylene glycol, polyethylene oxide, polypropylene oxide, polytetrahydrofuran. m) Polyamides such as polyamide-6, 6.6, 6.10, 4.6, 4.10, 6.12, 10.10, 10.12, 12.12, polyamide 11, polyamide 12, and (partially) aromatic polyamides such as polyphthalamides, e.g., produced from terephthalic acid and / or isophthalic acid and aliphatic diamines such as hexamethylenediamine or m-xylylenediamine, or from aliphatic dicarboxylic acids such as adipic acid or sebacic acid and aromatic diamines such as 1,4- or 1,3-diaminobenzene, blends of different polyamides such as PA-6 and PA 6.6, or blends of polyamides and polyolefins such as PA / PP. n) polyimides, polyamidimides, polyetherimides, polyesterimides, poly(ether) ketones, polysulfones, polyethersulfones, polyarylsulfones, polyphenylene sulfides, polybenzimidazoles, polyhydantoinenes, o) Polyesters made from aliphatic or aromatic dicarboxylic acids and diols or from hydroxycarboxylic acids such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PTI), polyethylene naphthylate (PEN), poly-1,4-dimethyl cyclohexane terephthalate, polyhydroxybenzoate, polyhydroxy naphthalate, polylactic acid (PLA), polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), polyethylene succinate, polytetramethylene succinate, polycaprolactone, p) Polycarbonates, polyester carbonates, and blends such as e.g. PC / ABS, PC / PBT, PC / PET / PBT, PC / PA, q) Cellulose derivatives such as cellulose nitrate, cellulose acetate, cellulose propionate, cellulose butyrate, r) silicones, e.g. based on dimethylsiloxanes, methylphenylsiloxanes or diphenylsiloxanes, e.g. vinyl group terminated, s) as well as mixtures, combinations or blends of two or more of the aforementioned polymers.

16. Plastic composition according to one of claims 14 to 15, characterized in that at least one further additive, selected from the group consisting of primary and / or secondary antioxidants, in particular primary and / or secondary antioxidants selected from the group consisting of phosphites, phosphonites, thiols, phenolic antioxidants, sterically hindered amines, hydroxylamines and mixtures or combinations thereof, UV absorbers, light stabilizers, hydroxylamine-based stabilizers, benzofuranone-based stabilizers, nucleating agents, impact enhancers, plasticizers, lubricants, rheology modifiers, chain extenders, processing aids, pigments, dyes, optical brighteners, antimicrobial agents, antistatic agents, slip agents, antiblocking agents, coupling agents, dispersing agents, compatibilizers, oxygen scavengers, acid scavengers, costabilizers, marking agents, and Antifogging agentscontains and / or is added to the plastic during use.

17. Plastic composition according to the preceding claim, characterized in that the at least one additive is selected from the group consisting of primary and / or secondary antioxidants, in particular primary and / or secondary antioxidants selected from the group consisting of phosphites, phosphonites, thiols, phenolic antioxidants, sterically hindered amines, hydroxylamines and mixtures or combinations thereof, UV absorbers, light stabilizers, hydroxylamine-based stabilizers, benzofuranone-based stabilizers, nucleating agents, impact enhancers, plasticizers, lubricants, rheology modifiers, chain extenders, processing aids, pigments, dyes, optical brighteners, antimicrobial agents, antistatic agents, slip agents, antiblocking agents, coupling agents, dispersing agents, compatibilizers, oxygen scavengers, acid scavengers, co-stabilizers, marking agents and antifogging agents;wherein the at least one additive is preferably selected from the group consisting of phosphites, phosphonites, sulfites, polyols, acid scavengers, hindered amines and mixtures and combinations thereof.

18. Plastic composition according to one of the two preceding claims, comprising the following composition 0.01 to 20.00 wt.%, preferably 0.1 to 15.0 wt.%, further preferably 0.2 to 12.00 wt.%, particularly preferably 0.5 to 10.00 wt.% of at least one compound according to the general formula I, III, IVa, IVb, V, Via and / or Vlb, 99.99 to 10.00 wt.%, preferably 99.99 to 90.00 wt.%, preferably 99.89 to 95.00 wt.%, particularly preferably 99.90 to 98.00 wt.% of at least one plastic, as well as 0 to 80.00 wt.%, preferably 0 to 9.99 wt.%, further preferably 0.01 to 4.98 wt.%, particularly preferably 0.02 to 2.00 wt.% of at least one additive, the components add up to 100% by weight.

19. Connection according to general formula Via or Vlb ©. a HN(R 1 )3O X x R Formula Via Formula Vlb where R, X, R 1 and n have the meaning given above and M is an n-valent, e.g. a mono-, di-, tri- or tetravalent metal cation, excluding Li and Na as metal cations.

20. Combination of the general formula VII R Formula VII where X and R as defined in claim 1 and R 2 an organic residue, preferably an organic residue with at least one polymerizable functionality, which is further preferably an epoxy group, wherein the residue R is particularly preferably 2 the following structure according to Formula VIII Formula VIII

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