EP4337708A1

EP4337708A1 - Flexible foams comprising flame-retardant polyurethane, a process for their production and use thereof

Info

Publication number: EP4337708A1
Application number: EP22728413.0A
Authority: EP
Inventors: Achim KRUCKENBERG; Waldemar SCHLUNDT; Oliver Hauenstein; Martin Sicken; Elke HUTMACHER; Patrick Klein
Original assignee: Clariant International Ltd
Current assignee: Clariant International Ltd
Priority date: 2021-05-11
Filing date: 2022-05-09
Publication date: 2024-03-20
Also published as: CN117222684B; CN117222684A; WO2022238293A1

Abstract

Discosed are flexible polyurethane foams comprising flame-retardant polyurethanes which comprise structural units of formula (X) and/or (XI) wherein R¹ is a monovalent organic group, R², R³, R⁴ and R⁵ independently of one another are hydrogen, alkyl groups having between one and eight carbon atoms or aryl groups having between six and eighteen carbon atoms, R⁶ and R⁷ independently of one another are hydrogen or a group of formula (XII) R⁸ is hydrogen or a group of formula (XII), n and m independently of one another are integers between 0 and 10, o, p and q independently of one another are integers between 0 and 5, with the proviso that the number of structural units of formula (a) in the structural units of formula (XI) is between 1 and 20. The flexible polyurethane foams show besides flame-retardancy low VOC emission as well as non-hydrolyzing, high compatibility and open-pore-foam-forming properties.

Description

1

Flexible foams comprising flame-retardant polyurethane, a process for their production and use thereof

The invention relates to flexible foams comprising flame-retardant polyurethanes with high aging resistance, a process for their production and to their use, e.g. for the manufacture of molded bodies.

Polyurethane foams are plastics used in many sectors, for example furniture, mattresses, transport, construction, and technical insulation applications. To comply with stringent fire-protection requirements such as those demanded for materials used, inter alia, in the interior fitting-out of automobiles, of rail vehicles, or of aircraft, or materials used to insulate buildings, polyurethane foams generally have to be provided with flame retardants. A wide variety of flame retardants are known and are commercially available for this purpose. However, their use is often inhibited by considerable technical usage problems and/or toxicological concerns.

For example, when solid flame retardants are used, e.g. melamine, ammonium polyphosphate, and ammonium sulfate, problems arise with metering techniques and often necessitate modifications to the foaming plants, i.e. complicated changes in design and modifications. Many of the liquid flame retardants used, for example tris(2-chloroethyl)phosphate and tris(2-chloroisopropyl)phosphate, are characterized by a marked tendency toward migration, which limits their usefulness in open-cell flexible polyurethane foam systems for the interior fitting- out of automobiles, in the light of requirements relating to condensable emissions (fogging).

Halogen-free flame-retardant systems are also preferred on grounds of environmental toxicology, and on grounds of improved ancillary properties in the event of a fire, in terms of smoke density and smoke toxicity. Halogen-free flame retardants can also be of particular interest for performance-related reasons. For example, when halogenated flame retardants are used severe corrosion is observed on the plant components used for the flame-lamination of polyurethane 2 foams. This can be attributed to the hydrohalic acid emissions arising during the flame-lamination of halogen-containing polyurethane foams.

Flame-lamination is the term used for a process for bonding of textiles and foams, by using a flame to melt one side of a foam sheet, and then immediately pressing a textile web onto the same.

Because increasing attention is being paid to gaseous emissions (volatile organic compounds=VOC), there is also an increase in requirements for flame retardants which resist migration.

Materials which have high resistance to migration are hydroxy-containing oligomeric phosphoric esters (DE-A 4342972) and hydroxyalkyl phosphonates (DE-A 19927548).

From the prior art phosphine oxide compounds are known exhibiting flame retardancy, but low compatibility with the polymer system, thus being technically unfeasible in such applications.

Reactions between tris-(chloromethyl)- and bis-(chloromethyl)methyl phosphine oxide with vicinal diols are disclosed by G. Borisov at al. in Phosphorus and Sulfur, 1984,Vol. 21, pp. 59-65. The products are linear or cyclic. As linear products bis- (ethylene glycol)methyl phosphine oxide and bis-(propylene glycol)methyl phosphine oxide are disclosed. These compounds are characterized by boiling point, melting point and refractive index. No mixtures of different phosphine oxides and no applications for these compounds are disclosed.

US 3,445,405 discloses flame-resistant polyurethane compositions which are produced by using condensation products of at least one alkylene oxide and tris(hydroxymethyl)phosphine oxide in the reaction involving a polyisocyanate and a polyether polymer. In this document tris-functionalized phosphine oxides are disclosed as flame retardants for polyurethanes. 3

US 5,985,965 A discloses flame-resistant poulyurethanes. These contain mixtures of oligomeric phosphoric acid esters which carry hydroxyalkoxy groups. No phosphine oxides are mentioned herein.

From CN 105801833 A1 reactive halogen-free flame-retardant polyether polyols are known. These are prepared from trimethylol phosphorus oxide by addition reaction with propylene oxide / ethylene oxide. The product is a polyvalent reactive halogen-free flame-retardant polyether which can be used in the manufacture of flame-retardant rigid foam materials. In this document tris-functionalized phosphine oxides are disclosed.

K. Zhang et al. in Journal of Applied Polymer Science, 135(5), 1-10 (2018) disclose a flame retardant polyurethane foam prepared from compatible blends of soybean oil-based polyol and phosphorus containing polyol. The phosphorus containing polyether polyol was synthesized by polymerization between tris- (hydroxymethyl) phosphine oxide and propylene oxide. A soybean oil-based polyol was synthesized from epoxidized soybean oil by ring-opening reaction with lactic acid. Polyurethane foams were prepared by mixing soybean oil-based polyol with phosphorus containing polyether polyol. Several properties of the polyurethane foams, such as their density and thermal degradation property were investigated.

One major application for flame retarded flexible polyurethane foams is seat liners and head liners in the automotive sector. However, technical demand is not limited to flame retardancy, but another very important demand from the industry - and ultimately from the end-customer - is a very low emission of volatile organic substances (VOC), which can be harmful. Typically, flame retardants are small and unreactive molecules with a tendency to migrate and evaporate, i.e. leading to leaching and emission of VOC. There are two concepts on to achieve the demand for low emission by either employing reactive or polymeric flame retardants or small reactive molecules. The latter having the advantage of being usually less viscous and thus easier to process. 4

Additionally, the molecular architecture can play a decisive role in foam production. In fact, for flexible foam a low cross-linking density is mandatory to allow a defect-free formation of an open-porous structure of the foam. The phosphine oxides disclosed in the prior art for polyurethane foam applications have one major drawback of being three-functional (i.e. each molecule carrying three hydroxy groups) thus each acting as a cross linker in the polymerization reaction (see e.g. US 3,445,405 A or CN 105801833 A or K. Zhang et al. article mentioned above).

US 6,380,273 B1 discloses a process for the production of polyurethane foams containing halogen-free flame retardants and having high oxidative thermal resistance during foaming. The process is usable for the manufacture of flexible ester and ether foams and for rigid foams and facilitates the production of polyurethane foams having low fogging values. Moreover, the process gives polyurethane foams having high aging resistance of the flame resistance, i.e. the polyurethane foam still has effective flame resistance after corresponding storage duration, even at elevated temperature. The disclosed process for the production of flame-resistant flexible polyurethane foams having a low susceptibility to core discoloration comprises employing hydroxyalkyl phosphonates as halogen-free flame retardants and as core discoloration inhibitors.

US 2001/0034388 A1 discloses a halogen-free, water-blown, flame-retardant rigid polyurethane foam which meets the necessary and prescribed requirements for flame retardancy, ease of production, low smoke density and low smoke toxicity. The polyurethane foam described in this document comprises oxalkylated alkyl- phosphonic acids as a flame retardant.

US 2004/0077741 A1 discloses flame-retardant flexible polyurethane foams with high aging resistance, and a process for their production. This document describes low-emission polyurethane foams having reduced halogen content, which when compared with a halogen-free flame-retardant polyurethane foam, has improved resistance to hydrolysis aging, and, when compared with a prior-art polyurethane foam, has lower halogen content. The flame-retardant flexible polyurethane foams 5 disclosed in this document comprise a mixture composed of hydroxyalkyl phosphonates and chlorinated phosphoric esters.

A disadvantage frequently found in the polyurethane foams known hitherto is that although the use of reactive, liquid halogen-free flame retardants achieves a high level of flame retardant action, in particular in the case of the phosphoric esters mentioned in DE-A 4342972 and the phosphonic esters mentioned in DE-A 19927548, a marked plasticizing action arises at the same time, and the resultant polyurethane foam is highly susceptible to hydrolysis, and therefore the mechanical properties of the foam have only low resistance to hydrolysis aging.

Although resistance to hydrolysis aging can be improved by using halogen- containing flame retardants, the result is then, inter alia, that the disadvantages described above for halogen-containing flame retardants have to be accepted in relation to smoke toxicity, smoke density, and formation of halogen-containing cleavage products.

Due to growing environmental and health concerns, some widely used halogenated phosphorus-based flame retardants for polyurethane applications like tris(2-chloroisopropyl)phosphate (TCPP) and tris(1 ,3-dichloroisopropyl)phosphate (TDCPP) are under regulatory scrutiny. While some of these flame retardants have already been banned in certain applications and regions, others are still being used, but alternatives are being sought after. Since most polyurethane materials are intrinsically flammable, flame retardants are needed in various applications, e.g. in upholstery and furniture, in transportation applications such as automotive, railway or aviation interior, or in building insulation.

Halogenated phosphorus-based flame retardants can be replaced with non- halogenated alternatives, e.g. various triarylphosphates like triphenylphosphate (TPP) or mixtures of alkylated aryl phosphates. While some of these avoid major problems of halogenated flame retardants - like regular scrutiny or formation of corrosive gases in the flame lamination process commonly used in the production of automotive head- and seat liner - there are still significant disadvantages. It is 6 known that additive flame retardants such as triarylphosphates can migrate and leach out of polyurethane foams, leading to significant health concerns and often to unwanted emission of organic compounds. Low-emission materials are particularly important for automotive applications, where limits are defined in standards like testing VDA-278 (emission of volatile organic compounds, VOC) and DIN 75201 B (condensable emissions, “fogging”). Other areas with low- emission requirements include consumer applications like mattresses and furniture.

There are several ways of avoiding unwanted emissions from polyurethane materials caused by flame retardants and other additives. A safe and proven way is to use reactive flame retardants, which usually bear hydroxyl groups, but might also contain other functional groups with active hydrogen atoms. These flame retardants will react with isocyanate groups present during the polyurethane manufacturing process, forming covalent bonds and thus permanently binding the flame retardant to the polymeric backbone. These covalent bonds effectively prevent migration and leaching of the flame retardant from the polyurethane material.

While very good emission properties can be achieved this way, most reactive flame retardants also pose additional challenges: Many phosphorus-based compounds are prone to hydrolysis in the presence of water, particularly at elevated temperatures. In case of reactive flame retardants, which have become part of the polymer backbone, this behavior leads to material deterioration (loss of mechanical properties), as hydrolysis leads to breakages in the polymer chains. In many key applications (e.g. automotive interior), there are increasingly stringent testing methods to guarantee long-term ageing stability of the materials under humid conditions. Hydrolytic instability also causes flame retardants to be incompatible with many polyurethane systems. This means preformulated, water- containing polyol blends containing such compounds cannot be stored for prolonged time, as decomposition products yielded by hydrolysis can deactivate catalysts usually present in most PU systems. Such flame retardants rather need to be added shortly prior to foaming, or in situ. 7

Thus, there is a strong demand for efficient non-halogenated and hydrolytically stable flame retardants that allow meeting stringent emission standards.

It is an object of the present invention to provide halogen-free flame-retardant flexible polyurethane foams having low VOC emission as well as non-hydrolyzing, high compatibility and open-pore-foam-forming properties. Said compounds shall have these different properties in one single compound.

Another object of the present invention is the provision of a flame-retardant flexible polyurethane foam having an excellent flame-retardancy combined with very low VOC emission as well as resistance against hydrolysis when subjected to high temperatures.

These objects are achieved by providing flexible polyurethane foams comprising selected phosphine oxide compounds as flame-retardants.

The present invention relates to flexible polyurethane foams which comprise at least one flame retardant polyurethane comprising structural units of formula (X) and/or (XI) wherein

R¹ is a monovalent organic group, 8

R², R³, R⁴ and R⁵ independently of one another are hydrogen, alkyl groups having between one and eight carbon atoms or aryl groups having between six and eighteen carbon atoms,

R⁶ and R⁷ independently of one another are hydrogen or a group of formula (XII)

R⁸ is hydrogen or a group of formula (XII), n and m independently of one another are integers between 0 and 10, o, p and q independently of one another are integers between 0 and 5, with the proviso that the number of structural units of formula in the the structural units of formula (XI) is between 1 and 20.

The flame retardant polyurethanes used in the flexible polyurethane foams of the present invention usually comprise besides the structural units of formula (X) and/or (XI) structural units derived from polyisocyanates and structural units derived from compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) defined below.

Structural units derived from polyisocyanates are those which are in general derived from di- or tri-isocyanates. These structural units have the formula (XV)

-0-C0-NH-PIC-(NH-C0-0)_t- (XV) 9 wherein PIC is a di- or trivalent organic residue, preferably a di- or trivalent aliphatic, cycloaliphatic or aromatic hydrocarbon residue, and t is 1 or 2.

Structural units derived from compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I),

(II) and (VI) are di- or trivalent organic residues, preferably di- or trivalent aliphatic, cycloaliphatic or aromatic hydrocarbon residues.

Preferably, structural units derived from polyisocyanates and structural units derived from compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) form recurring structural polyurethane unists of formula (XVI)

-O-CO-NH-PIC-NH-CO-O-DIOL- (XVI) wherein PIC and DIOL independently of one another are divalent organic residues, preferably divalent aliphatic, cycloaliphatic and/or aromatic hydrocarbon residues.

Preferred flexible polyurethane foams of this invention comprise a flame-retardant polyurethane comprising structural units of formula (X), preferably a flame- retardant polyurethane comprising a mixture of different structural units of formula (X).

Preferred flexible polyurethane foams of this invention comprise a flame-retardant polyurethane comprising structural units of formula (X), wherein one of R² or R³ is hydrogen and the other one of R² or R³ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms and wherein one of R⁴ or R⁵ is hydrogen and the other one of R⁴ or R⁵ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms. 10

More preferred are flexible polyurethane foams comprising a flame-retardant polyurethane comprising structural units of formula (X), wherein one of R² or R³ is hydrogen and the other one of R² or R³ is hydrogen or an alkyl group having between one and two carbon atoms, preferably methyl, and wherein one of R⁴ or R⁵ is hydrogen and the other one of R⁴ or R⁵ is hydrogen or an alkyl group having between one and two carbon atoms, preferably methyl.

Still more preferred are flexible polyurethane foams comprising a flame-retardant polyurethane comprising structural units of formula (X), wherein R², R³, R⁴ and R⁵ independently of one another are selected from hydrogen, Ci-C₆-alkyl and phenyl, more preferred from hydrogen and Ci-Ce-alkyl, and still more preferred from hydrogen and Ci-C3-alkyl, and most preferred from hydrogen and methyl.

In these preferred flexible polyurethane foams flame-retardant polyurethanes comprising at least two different structural units of below defined formula (Xa) may be present, or at least two different structural units of below defined formula (Xb), or at least two different structural units of below defined formula (Xc), or at least two structural units of belos defined formulae (Xa) and (Xb), or at least two structural units of below defined formulae (Xa) and (Xc), or at least two structural units of below defined formulae (Xb) and (Xc).

Very preferred are flexible polyurethane foams comprising flame-retardant polyurethanes comprising structural units of formula (X), wherein R², R³, R⁴ and R⁵ independently of one another are selected from hydrogen, Ci-C₆-alkyl and phenyl, more preferred from hydrogen and Ci-Ce-alkyl, and still more preferred from hydrogen and Ci-C3-alkyl, and most preferred from hydrogen and methyl.

These preferred flame-retardant polyurethanes comprise at least two different structural units of formula (Xa), (Xb) and/or (Xc) 11 wherein

R¹, m and n are as hereinbefore defined,

R^2a and R^3a independently of one another is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon, and R^4a and R^5a independently of one another is an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon.

Other preferred flexible polyurethane foams comprise at least one flame-retardant polyurethane comprising structural units of formula (X) and/or of formula (XI), wherein R¹ is Ci-Ce-alkyl, cyclohexyl or phenyl, preferred Ci-C3-alkyl, and most preferred methyl.

Still other preferred flexible polyurethane foams comprise flame-retardant polyurethanes comprising structural units of formula (X), wherein the sum n+m is a number between 1 and 15 and most preferred between 4 and 12.

Other preferred flexible polyurethane foams comprise flame-retardant polyurethanes comprising at least one structural unit of formula (XI), preferably 12 different structural units of formula (XI), wherein R¹ is Ci-Ce-alkyl, cyclohexyl or phenyl, preferred Ci-C₃-alkyl, and most preferred methyl, and wherein the number of structural units of formula is between 1 and 10.

Unless otherwise indicated, the term "monovalent organic group" as used herein includes a monovalent organic radical derived from an organic group by removal of one hydrogen atom. Organic groups may be saturated or unsaturated straight- chain, branched-chain or mono- or multicyclic hydrocarbons or saturated or unsaturated heterocyclic groups, having - besides the ring carbon atoms - one or more ring-heteroatoms, such as oxygen, nitrogen or sulfur.

Unless otherwise indicated, the term "alkyl" as used herein includes a saturated monovalent aliphatic hydrocarbon radical with straight or branched moieties, preferably a Ci-Ci₂-alkyl radical and most preferred a Ci-C₆-alkyl radical. Examples of alkyl radicals are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl or hexyl, preferably methyl or ethyl and most preferred methyl.

Unless otherwise indicated, the term "alkylene" as used herein includes a saturated divalent aliphatic hydrocarbon radical with straight or branched moieties, preferably a C₂-Ci₂-alkylene radical and most preferred a C₂-C₆-alkylene radical. Examples of alkylene radicals are ethylene, propylene, isopropylene, butylene, isobutylene, tert-butylene, pentylen or hexylene, preferably ethylene, propylene, isopropylene or butylene and most preferred ethylene, propylene or isopropylene. 13

Unless otherwise indicated, the term "cycloalkyl" as used herein includes a cyclic saturated monovalent hydrocarbon radical with five to seven ring carbon atoms. An example of a cycloalkyl group is cyclohexyl.

Unless otherwise indicated, the term "aryl" as used herein includes an aromatic radical derived from an aromatic hydrocarbon by removal of one hydrogen, such as, but not limited to, phenyl or naphthyl.

Unless otherwise indicated, the term "aralkyl" as used herein signifies an "aryl- alkyl-" group such as, but not limited to: benzyl (C6H5-CH2-) or methylbenzyl (CH3-C6H4-CH2-).

Unless otherwise indicated, the term "alkylaryl" as used herein signifies an "alkyl- aryl-" group such as, but not limited to: methylphenyl (CH3-C6H4-), dimethylphenyl ((CH3)2-C6H3-) or isopropylphenyl ((CH3)2C-C6H4-).

R¹ is a monovalent organic group. This is preferably selected from alkyl, cycloalkyl, aryl, aralkyl or alkylaryl, more preferred selected from Ci-Ce-alkyl, cyclohexyl or phenyl. Still more preferred R¹ is Ci-C3-alkyl, most preferred methyl.

Examples of R¹ are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl or phenyl.

R², R³, R⁴ and R⁵ preferably are selected from hydrogen, C-i-Cs-alkyl and phenyl, more preferred from hydrogen and Ci-Ce-alkyl, and still more preferred from hydrogen and Ci-C3-alkyl, and most preferred from hydrogen and methyl.

Examples of R², R³, R⁴ and R⁵ as C-i-Cs-alkyl are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, heptyl and octyl. 14

Preferred examples of R² and R³ or of R⁴ and R⁵ are Ci-C₆-alkyl or phenyl. Still more preferred one of R² and R³ of R⁴ and R⁵ and one of of R⁴ and R⁵ is hydrogen and the other one is Ci-C3-alkyl, most preferred methyl.

R⁶, R⁷ and R⁸ independently of one another are hydrogen or a group of formula (XII) which is derived from glycidol.

The chain length of the alkylene oxide units in the individual groups of formulae (X) and (XII) in the flame-retardant polyurethane is characterized by integers n and m or o and p.

The chain length of the alkylene oxide units in the individual structural units of formula (X) is characterized by integers n and m.

Integers m and n independently of one another have values between 0 and 10, preferably between 1 and 10 and more preferred between 1 and 8 and still more preferred between 2 and 6.

The structural units of formula (X) in a flame-retardant polyurethane may differ in the nature of the groups R¹ to R⁵ and/or in the number of recurring units characterized by integers m and n.

Preferred flame-retardant polyurethanes comprise structural units of formula (X) with the same groups R¹ to R⁵ which differ in the values of n and/or m, more preferred in the values of (n+m).

In a flame-retardant polyurethane comprising structural units of formula (X) the sum n+m of a single structural unit in said polyurethane is a number between 0 and 20, preferably between 1 and 15 and most preferred between 4 and 12.

Preferably flame-retardant polyurethanes are used comprising at least two different structural units of formula (X). More preferred, these flame-retardant 15 polyurethanes comprise different structural units of formula (X) in a molecule, for example structural units of formulae (Xa), (Xb) and/or (Xc) mentioned above.

The alkylene oxide moieties in the single structural units of formula (X) of the flame-retardant polyurethanes may have different chain lengths (= different values of n and/or m or of the sum of m+n).

Examples of preferred flame retardant polyurethanes comprising structural units of formula (X) are polyurethanes comprising at least two different phosphine oxide structural units of formulae (Xe), (Xf) and/or (Xg) wherein

R⁸ is Ci-C₆-alkyl, preferably methyl,

R⁹ and R¹⁰ independently of one another are hydrogen, C-i-Cs-alkyl or C6-C18- aryl, preferably hydrogen, Ci-C₆-alkyl or phenyl, most preferred hydrogen or methyl, n and m independently of one another are integers between 0 and 10, preferably between 1 and 10, and wherein the sum n+m is a number between 0 and 20, preferably between 1 and

15. 16

Flame-retardant structural units of formula (XI) are derived from methylol-organyl- phosphine oxides and glycidol.

The chain length of the glycidol units in the individual structural units of formula (XI) is characterized by integers o, p and q.

Integers o, p and q independently of one another have values between 0 and 5, preferably between 1 and 5 and more preferred between 1 and 3 and still more preferred between 2 and 3.

The single structural units of formula (XI) in a flame-retardant polyurethane may differ in the nature of the groups R¹ and R⁶ to R⁸ and/or in the number of recurring units characterized by integers o, p and q.

Preferred flame-retardant polyurethanes comprise different structural units of formula (XI) with the same groups R¹ which differ in the values of o, p and/or q.

In a preferred flame-retardant polyurethane comprising structural units of formula (XI) the sum o+p+q of a single structural unit in said polyurethane is a number between 2 and 20, preferably between 3 and 15 and most preferred between 4 and 12.

In another preferred embodiment of the present invention the flame-retardant polyurethane used in the flexible polyurethane foams comprises besides structural units of formula (X) or (XI) as hereinbefore described, at least one structural unit of formula (Via) 17 wherein

R², R³, R⁴, R⁵, m and n are defined as above,

R¹⁴ and R¹⁵ independently of one another are hydrogen, alkyl groups having between one and eight carbon atoms or aryl groups having between six and eighteen carbon atoms, and r independently of n and m is an integer between 0 and 10, preferably between 1 and 10.

Very preferred flame-retardant polyurethanes comprise at least one structural unit of formula (Via) besides at least one structural unit of formula (X), wherein one of R² or R³ is hydrogen and the other one of R² or R³ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms and wherein one of R⁴ or R⁵ is hydrogen and the other one of R⁴ or R⁵ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms and wherein one of R¹⁴ or R¹⁵ is hydrogen and the other one of R¹⁴ or R¹⁵ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms.

Still more preferred flame-retardant polyurethanes comprise at least two different structural units of formula (X) and at least one structural unit of formula (Via). 18

Structural units of formula (Via) are similar to structural units of formula (X), but the former carries a group -0-(CHR¹⁴-CHR¹⁵-0)_r-H instead of a group R¹ (= trifunctional compounds carrying three alkylene oxide groups).

Preferably, the content of bifunctional structural units of formulae (X) and/or of formula (XI) is from 50 to 100, more preferred from 90 to 100 and still more preferred from 90 to 99.5 mol %, referring to the total content of structural units of formulae (X), (XI and (Via) in a molecule.

Preferably, the content of trifunctional structural units of formula (Via) is from 50 to 0, more preferred from 10 to 0 and still more preferred from 10 to 0.5 mol %, referring to the total content of structural units of formulae (X), (XI) and (Via) in a molecule.

Flame-retardant polyurethanes comprising structural units of formula (X) and/or (XI) and optionally (Via) may be prepared by standard reactions known to the skilled artisan.

Thus, organic polyisocyanates are reacted with compounds of formula (I) and/or (II) and optionally (VI) together with compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds from formulae (I), (II) and (VI) 19 wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R¹⁴, R¹⁵, m, n, o, p and r are defined as above.

The compounds of formula (I), (II) or (VI) may be prepared by standard reactions known to the skilled artisan.

Alkylene oxides of formula (I) may be produced by reacting bis-methylol- phosphine oxide of formula (VII) with one or more epoxides of formula (VIII) wherein R¹, R² and R³ are as defined hereinbefore.

Phosphine oxide glycidol compounds of formula (II) may be produced by reacting bis-methylol-phosphine oxide of formula (VII) with glycidol of formula (IX) wherein R¹ is as defined hereinbefore. 20

Alkylene oxides of formula (VI) may be produced by reacting tris-methylol- phosphine oxide with one or more epoxides of formula (VIII).

The amounts of bis- or tris-methylol-phosphine oxide and epoxides or glycidol are selected in a manner so that the desired number of recurring alkylene oxide units or glycidol units is obtained.

The reaction between bis- or tris-methylol-phosphine oxide and epoxides or glycidol may be initiated by mixing said compounds and by heating these compounds in the presence of a basic compound, for example an alkali hydroxide, such as sodium hydroxide or potassium hydroxide. The reaction temperature may be varied in a broad range, for example between 50 and 200°C. During reaction the reaction mixture is preferably agitated, e.g. by using a stirrer.

The reaction may be carried out at atmospheric pressure, preferably at reduced pressure, for example in the pressure range between 1 and 10⁵ Pa, preferably between 10 and 10⁴ Pa.

The reaction may also be carried out in solution using an organic solvent which is inert under reaction conditions. Examples of solvents are aprotic organic solvents, such as dimethyl sulfoxide, dimethyl formamide or dimethyl acetamide, or aromatic hydrocarbons, such as benzene, toluene or xylene.

Phosphine oxide starting materials of formula (VII) or tris-methylol-phosphine oxide starting materials are known compounds or can be produced using standard procedures of phosphorus-organic chemistry.

Epoxy starting materials of formulae (VIII) and (IX) are known compounds or can be produced using standard procedures of organic chemistry.

Examples of preferred epoxy starting materials are ethylene oxide, propylene oxide, styrene oxide or glycidol. 21

Surprisingly, it has been found that flexible polyurethane foams can be manufactured from flame-retardant polyurethanes comprising structural units of formula (X) and/or (XI) and optionally (Via) derived from alkoxylated phosphine oxide compounds of formula (I) and/or (II) and optionally (VI). Single compounds of formula (I) or (II) or mixtures of different compounds of formula (I) or of formula (II) or mixtures of compounds of formulae (I) and (II) or mixtures of compounds of formulae (I) and (VI) or mixtures of compounds of formulae (II) and (VI) or mixtures of compounds of formulae (I), (II) and (VI) may be used in the manufacture of flame-retardant polyurethanes used in the flexible foams of this invention.

The invention also relates to a kit-of-parts comprising a container A containing an organic polyisocyanate or a mixture of organic polyisocyanates, and comprising a container B containing a mixture of compounds of formula (I) and/or (II) and optionally (VI) together with compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I),

(II) and (VI) 22 wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R¹⁴, R¹⁵, m, n, o, p and r are as defined above.

In a preferred embodiment of the kit-of-parts the compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) are selected from the group consisting of polyalkylene ether polyols, polyester polyols and hydroxyl-terminated elastomers.

In another preferred embodiment of the kit-of-parts the compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) are low-molecular weight polyols.

Surprisingly, a compound of formula (I) and/or (II) optionally together with a compound of formula (VI) when incorporated into a polyurethane molecule provides excellent flame-retardancy combined with very low VOC emission as well as resistance against hydrolysis when subjected to high temperatures. Furthermore, flexible polyurethane foams comprising flame-retardant polyurethanes comprising structural units derived from compounds of formula (I) and/or (II) and optionally (Via) show an excellent extrudability and moldability in different plastic articles.

The amount of structural units of formula (X) and/or of formula (XI) and optionally of formula (Via) in a flame-retardant polyurethane used in the flexible foams of this invention may vary in a broad range. Typically, the amount of structural units of 23 formula (X) and/or of formula (XI) and optionally of formula (Via) is from 0.5 to 30 mol.-%, preferably from 0.5 to 20 mol.-% and most preferred from 1 to 10 mol.-%, referring to the total amount of the polyurethane.

The amount of structural units derived from polyisocyanates and from compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) in a flame-retardant polyurethane used in the flexible foams of this invention may also vary in a broad range. Typically, the amount of structural units derived from polyisocyanates and from compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) is from 70 to 99.5 mol.-%, preferably from 80 to 99.5 mol.-% and most preferred from 90 to 99 mol.-%, referring to the total amount of the polyurethane.

The invention also provides a process for preparing flexible polyurethane foams, which comprises reacting organic polyisocyanates with compounds having at least two hydrogen atoms reactive toward isocyanates and being different from compounds of formulae (I), (I) and (VI), with conventional blowing agents, stabilizers, activators, and/or other conventional auxiliaries and additives, in the presence of flame retardants of formula (I) and/or (II) and optionally (VI) defined hereinbefore.

Preferably organic polyisocyanates are reacted with compounds having at least two hydrogen atoms reactive toward isocyanates and being different from compounds of formulae (I), (II) and (VI), with conventional blowing agents, stabilizers, activators, and/or other conventional auxiliaries and additives, in the presence of a flame retardant of formula (I) or of a mixture of of at least two structurally different flame retardants of formula (I), very preferred of formulae (la), (lb) and/or (lc) 24 wherein

R¹, m and n are as hereinbefore defined, R^2a and R^3a independently of one another is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon, and

R^4a and R^5a independently of one another is an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon.

The flame retardants of formula (I) or (II) or (VI) are compounds reactive toward isocyanates and are incorporated into the polyurethane when reacted with the polyurethane-forming monomers.

The production of flexible foams based on isocyanate is known per se, and is described in DE-A 1694 142, DE-A 1694215, and DE-A 1720768, for example. 25

These are mainly flexible foams containing urethane groups and optionally a lower amount ofallophanate groups and/or urea groups.

Polyurethanes are polymers comprising organic units joined by carbamate (urethane) links. Polyurethanes may be thermosetting polymers that do not melt when heated; but thermoplastic polyurethanes are also available.

Polyurethanes are commonly formed by reacting a di- or triisocyanate with a polyol. Both the isocyanates and polyols used to make polyurethanes contain, on average, two or more functional groups per molecule. Diols and diisocyanates lead to linear polyurethanes, crosslinked polyurethanes can be produced e.g. by converting triisocyanate diisocyanate mixtures with triol-diol mixtures. The properties of polyurethanes can be varied in a wide range. Depending on the degree of cross-linking and/or isocyanate or OH component used, thermosets, thermoplastics or elastomers are obtained. In terms of quantity, polyurethane foams are most important. This invention concerns flexible polyurethane foams. The polyurethanes forming flexible foams are characterized by having soft portions in the molecule. These are derived from a reaction between polyisocyanate and polyalkylene ether polyols, polyester polyols or hydroxyl-terminated elastomers, such as hydroxyl-terminated polybutadienes. Preferably, the polyurethanes forming flexible foams besides soft and flexible portions contain hard and rigid portions in the molecule. These are derived from a reaction between polyisocyanate and low-molecular weight polyols, such as ethylene glycol or propylene glycol.

Starting components for the manufacture of the polyurethanes used for preparing the flexible foams of this invention are, for example, aliphatic, cycloaliphatic, araliphatic, aromatic, or heterocyclic polyisocyanates (e.g. W. Siefken in Justus Liebigs Annalen der Chemie, 562, pp. 75-136), for example those of the formula Q(NCO)s, where s is from 2 to 4, preferably from 2 to 3, and Q is an aliphatic hydrocarbon radical having from 2 to 18, preferably from 6 to 10, carbon atoms, a cycloaliphatic hydrocarbon radical having from 4 to 15, preferably from 5 to 10, carbon atoms, an aromatic hydrocarbon radical having from 6 to 15, preferably 26 from 6 to 13, carbon atoms, or an araliphatic hydrocarbon radical having from 8 to 15, preferably from 8 to 13, carbon atoms.

Suitable polyisocyanates are aromatic, alicyclic and/or aliphatic polyisocyanates having at least two isocyanate groups and mixtures thereof. Preference is given to aromatic polyisocyanates such as tolyl diisocyanate, methylene diphenyl diiso cyanate, naphthylene diisocyanate, xylylene diisocyanate, tris(4- isocyanatophenyl)-methane and polymethylene-polyphenylene diisocyanates; alicyclic polyisocyanates such as methylenediphenyl diisocyanate, tolyl diisocyanate; aliphatic polyisocyanates and hexamethylene diisocyanate, isophorone diisocyanate, dimeryl diisocyanate, 1 ,1-methylenebis(4- isocyanatocyclohexane-4,4'-diisocyanatodicyclohexylmet hane isomer mixture,

1 ,4-cyclohexyl diisocyanate, Desmodur products (Covestro) and lysine diisocyanate and mixtures thereof.

Particular preference is generally given to the polyisocyanates readily available industrially and derived from tolylene 2,4- and/or 2, 6-di isocyanate or from diphenylmethane 4,4'- and/or 2,4'-diisocyanate.

Suitable polyisocyanates are modified products which are obtained by reaction of polyisocyanate with polyol, urea, carbodiimide and/or biuret.

Other starting components for the manufacture of the polyurethanes used for preparing the flexible foams of this invention are compounds having at least two hydroxy groups which starting materials are different from compounds of formulae (I), (II) and (VI). These other starting components preferably have a molecular weight of from 400 to 10,000 ("flexible or soft polyol component"). These have preferably from 2 to 8 hydroxy groups, and specifically those of molecular weight from 1000 to 6000, preferably from 200 to 6000, generally compounds having from 2 to 8, but preferably from 2 to 6, hydroxy groups, these compounds being polyethers and polyesters, or else polycarbonates and polyesteramides, as are known per se for the production of cellular polyurethanes, and as are described in 27

DE-A 2832253, for example. The polyesters and polyethers having at least two hydroxy groups are preferred according to the invention.

Preferred polyesters are polyester polyols which are obtained by polycondensation of a polyalcohol such as ethylene glycol, diethylene glycol, propylene glycol,

1 ,4-butanediol, 1 ,5-pentanediol, methylpentanediol, 1 ,6-hexanediol, trimethylolpropane, glycerol, pentaerythritol, diglycerol, glucose and/or sorbitol, with a dibasic acid such as oxalic acid, malonic acid, succinic acid, tartaric acid, adipic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid and/or terephthalic acid. These polyester polyols can be used alone or in combination.

Other optional starting components for the manufacture of the polyurethanes used for preparing the flexible foams of this invention are compounds having at least two hydroxyl groups and having a molecular weight of from 32 to 399 (“hard polyol component”) which are different from compounds of formulae (I), (II) and (VI). In this case, too, these are compounds having preferably 2 to 8 hydroxyl groups, these compounds serving as chainextenders or crosslinking agents. These compounds generally have from 2 to 8, preferably from 2 to 4, hydroxyl groups reactive toward isocyanates.

The flame-retardant flexible polyurethane foams of the present invention may contain one or more additives.

The amount of additive(s) may vary in a broad range. Typical amounts of additive(s) are between 0 and 60 % by weight, preferably between 0.5 and 50 % by weight, more preferred between 0.5 and 30 % by weight, and most preferred between 0.5 and 5 % by weight, referring to the total amount of the flame-retardant flexible polyurethane foam.

Examples of additives are antioxidants, blowing agents, further flame retardants, light stabilizers, heat stabilizers, impact modifiers, processing aids, glidants, processing aids, nucleating agents and clarifiers, antistatic agents, lubricants, such as calcium stearate and zinc stearate, viscosity and impact modifiers, 28 compatibilizers and dispersing agents, dyes or pigments, antidripping agents, additives for laser marking, hydrolysis stabilizers, chain extenders, softeners, plasticizers, fillers, reinforcing agents, surface-active additives, foam stabilizers, cell regulators, retarders, further flame-retardant substances, or else substances with fungistatic or bacteriostatic action. Examples of additives are described in Kunststoff-Handbuch [Plastics Handbook], Volume VII, Carl Hanser Verlag,

Munich, 1993, pp.104-123 as are details of the method of use and the mode of action of these additives.

The additive(s) can impart other desired properties to the flexible polyurethane foam of the invention.

The flexible polyurethane foams are prepared by methods known by the artisan. Often blowing agents are used for foam manufacture. Examples of blowing agents are water and/or highly volatile organic hydrocarbons, such as n-pentane, isopentane or cyclopentane, hydrofluoroolefins (HFO) and CO2.

Optionally concomitant use is made of auxiliaries and additives, for example catalysts of the type known per se, surface-active additives, such as emulsifiers and foam stabilizers, retarders, e.g. acidic substances, such as hydrochloric acid or organic acid halides, or else cell regulators of the type known per se, for example paraffins or fatty alcohols, and dimethylpolysiloxanes, or else pigments or dyes, and other flame retardants of the type known per se, or else stabilizers to protect from the effects of aging and weather, plasticizers, and substances with fungistatic or bacteriostatic action, or else fillers, such as barium sulfate, Kieselguhr, carbon black, or precipitated chalk (DE-A 2732292).

A further overview of the raw materials, auxiliaries, and additives used for producing polyurethane foams, and the process technology for their production, is given in Kunststoff-Handbuch [Plastics Handbook], Volume VII, Carl Hanser Verlag, Munich, 1993, pp.104-123. 29

The methods for the production of the flexible polyurethane foams of the invention are known per se. The components for the reaction may be reacted by the single- stage process known per se, the prepolymer process, or the semi-prepolymer process. Details of foam manufacture are found, for example, in Kunststoff- Handbuch [Plastics Handbook], Volume VI, Carl Hanser Verlag, Munich, 1993.

According to the invention, it is also possible to produce cold-curing foams.

However, it is also possible, to produce foams by slab foaming process known per se.

The flame retardant flexible polyurethane foams according to the invention may be produced by a continuous or batchwise method, or as foamed moldings. Preference is given to flexible foams produced by a slab foaming process.

Examples of applications of the flame retardant flexible polyurethane foam of the invention are: furniture padding, textile inserts, mattresses, automobile seats, armrests, headrests, and construction components, and also automotive seat coverings (seat liners), headliners and dashboard coverings. These uses form also part of the invention.

Examples

The following examples serve to illustrate the invention.

Raw Materials 30

Flame retardants 31

¹⁾ sum of indices of main component in I

²⁾ calculated

Hydrolytic stability test

Hydrolytic stability of the flame retardants was determined by measuring the development over time of the acid number of blends of polyols with the flame retardants and water during storage at increased temperature. For this purpose, 90 g of polyol, 9 g of FR (10 wt.-%) and 4,5 g of water (5 wt.-%) were homogenized by stirring at 1500 rpm for 2 min. The acid number was determined using a 3:1 (v/v) isopropanol / water mixture as solvent and 0.1 N NaOH (aq) solution as titration agent. The samples were then stored at 40 °C and the acid numbers were determined after given periods of time. Samples were homogenized before analysis by stirring at 1500 rpm for 2 min. As a reference, the acid number development of polyol-water blends without added FR was determined (Comp. Example 1 and Comp. Example 3). 32

Table 1 : Hydrolytic stability test: Development of the acid number of mixtures of polyols with 10 wt.-% of flame retardant and 5 wt.-% of water during storage at 40°C.

¹⁾ after 7 d; ²⁾ after 14 d

Table 1 shows that the acid number increase of water-containing polyol blends with FR3 (Example 1 and Example 2) is not significantly higher than for the water- containing polyols without flame retardant (Comp. Example 1 and Comp.

Example 3), demonstrating high hydrolytic stability of BMPO-based flame retardants like FR3 during storage in the polyols. After 28 d of storage, an acid value of 0.1 mg KOFI/g was found for the water-containing polyol Arcol^® 1104 (polyether polyol, Comp. Example 1 ), and of 0.5 mg KOFI/g with added FR3 (Example 1 ). These results show only a negligible degree of hydrolysis of FR3. In comparison, the Arcol^® 1104 blend containing Exolit OP 550 (Ref-2) shows a significantly increased acid value of > 40 mg KOFI/g after 11 d already, which can be explained by hydrolysis of the flame retardant (Comp. Example 2). The same experiments in Desmophen^® 60WB01 (polyester polyol) show comparable observations. The acid number of pure water-containing polyol (Comp. Example 3) and the system with added FR3 (Example 2) show the same acid numbers of 1 .9 mg KOFI/g after 28 d. This proves that hydrolysis of FR3 does not considerably contribute to the increase of acid value of the polyol systems. This property of BMPO-based flame-retardants as FR3 is beneficial for typical applications of reactive flame retardants like automotive flexible polyurethane foam, because pre blends of polyols and other polyurethane foam ingredients including flame 33 retardants and water are required not to undergo hydrolysis before the foam production step (mixing with isocyanates) for as long as possible. In contrast, Ref-2 shows a marked rise of acid number at same conditions (94.7 mg KOH/g after 28 d) indicating fast hydrolysis of this material in water-containing systems. These results demonstrate that the flame retardants according to the invention, in contrast to Ref-2, are also suitable for the use in storable, ready-to-use polyol pre blends as parts of so-called polyurethane systems.

Flexible polyurethane foam formulations with performance testing

Polyol, additives, catalysts, stabilizer and blowing agent are weighed into a dry beaker and premixed for 60 s at 500 rpm (for polyether polyol formulations) and 1000 rpm (for polyester polyol formulations), respectively. After addition of TDI (tolyl diisocyanate), the mixtures are homogenized for 7 s at 2500 rpm. The resulting mass is rapidly poured into a paper-wrapped box mould (25*26*26 cm). Rise time and further observations are noted during the foaming process. The foams are cured at room temperature for approx. 16 h before cutting and further evaluation.

Table 2: Flexible polyurethane foam formulations. Amounts of all components are given in parts per 100 parts of polyol (php)

35 36

Evaluation of flame retardancy

The efficiency of the flame retardants was evaluated by testing the burning behavior of flexible polyurethane foam samples with a target density of 30 kg/m³, containing the flame retardants in the horizontal burn test, as described in the Federal Motor Vehicle Safety Standard 302 (FMVSS 302). According to this standard, samples are given the highest classification (SE, “self-extinguishing”) if the flame does not travel beyond a 38 mm mark on the specimen but extinguishes within this distance. Lower classifications include SE/NBR (self-extinguishing/no burn rate), SE/B (self-extinguishing/burn rate) and B (burn rate). Five sample specimens were cut from each foam and submitted to the test. The lowest-rated specimen determined the overall classification for the foam.

Evaluation of compression set and humid ageing performance Compression set is the relative ratio of sample thickness after recovery from compression and initial sample thickness under defined parameters. The test is carried out with untreated and humid-aged samples. It is an important quality parameter for flexible polyurethane foam, e.g. for automotive or furniture applications, ensuring stable mechanical properties during prolonged storage under compression under adverse climate conditions.

For the determination of compression set, 5 specimens with a dimension of 50^*50^*25 mm are prepared. The initial thickness ho is determined using sliding calipers in at least five positions without squeezing the foam. The specimens are then placed between two plates and are compressed to 50 % +1-2 % of their initial thickness, or to 75 % +1-2% of their initial thickness, for polyether and polyester polyurethane foams, respectively. The compressed specimens are stored for 72 h in a standardized climate chamber (according to DIN 50014-23/50-2) or at for 22 h at 70 °C in a heat chamber. The compression plates are then removed, and the specimens left to decompress in a standardized climate chamber (according to DIN 50014-23/50-2) for 30 min. The sample thickness after decompression IIR is measured directly thereafter. 37

Compression set is calculated as follows:

CS (%, °C, h) = [(ho - h_R) / ho] ^* 100 Evaluation of emission performance

Low emissions from materials are particularly important in interior automotive applications. They can be classified into two types: semi-volatile condensable emissions (FOG) and volatile organic compounds (VOC). The name FOG emissions stems from the fogging effect they can have on cold surfaces such as car windshields. They can be quantified according to DIN 75201 B: A sample is heated to 100 °C for 16 h in a specialized device, while semi-volatile components of the emissions are condensed on a cooled surface and quantified gravimetrically. VOC emissions can be quantified by thermodesorption analysis according to the automotive standard VDA 278. A sample in a thermodesorption tube is heated to 90 °C for 30 min, and condensates are collected in a cooling trap before being identified and quantified via GC/MS against an external standard like toluene. The emission performance of the new flame retardant described herein was evaluated by determining both FOG and VOC emissions according to these procedures.

Table 3: Foam properties

Shrinkage; ²⁾strong sagging

39

Flexible polyether polyurethane foam formulations with performance testing

As can be seen from the results in table 3, stable and defect-free polyurethane foams based on an industry-typical polyether polyol could be obtained using reference flame retardants TCPP (Comp. Example 5) and reactive flame retardant Exolit OP 550 (Comp. Example 6), as well as using the flame retardants according to the invention FR3, FR6, FR2 and FR5 (Example 3, Example 4, Example 6 and Example 8). When using trifunctional polyol TMPO-PO (Ref-3), no stable polyurethane foam formulation could be found (Comp. Example 7). Instead, strong shrinkage of the foam was observed, which can be attributed to more pronounced cross-linking due to the higher functionality of TMPO-PO compared to the flame retardants according to the invention. This finding indicates that trifunctional TMPO-PO is not a suitable flame retardant for the flexible polyether foam system used in these trials. Also, it was not possible to obtain defect-free polyurethane foams when using FR1 and FR4. Formulations containing these flame retardants (Example 5 and Example 7) led to foams that showed strong sagging and inferior flame retardancy ratings (class B), presumably as a result of limited compatibility of FR1 and FR 4 with the polyol.

Table 3 also shows that SE-ratings in the FMVSS 302 test can be achieved with significantly lower dosages of 4 php with the reactive flame retardants Ref-2, FR2 and FR3 (Comp. Example 6, Example 6 and Example 3), compared to the reference foam in Comp. Example 5, which needed 12 php of TCPP as flame retardant to achieve an SE rating. A lower flame retardant efficiency compared to FR3 was found for FR6. As shown in Example 4, a dosage 7 php was required to obtain a foam with an SE rating in the FMVSS 302 test. This inferior flame retardancy performance compared to the foams in Comp. Example 6 and Example 3 can be explained with lower solubility of FR6 in the polyol system, leading to partial demixing and an inhomogenous phosphorus distribution in the foam. This trend can also be seen for FR5, for which formulations with an FR dosage of 4 php only achieved an SE/NBR rating (Example 8). 40

Flame retardants FR2, FR3 and FR6, as well as reference reactive flame retardant Ref-2 allow the production of open-cell foams, which can be seen from good air permeability results in Example 6, Example 3, Example 4 and Comp. Example 6. Low air permeability values indicate that low pressure is required for air to pass through the foam samples, as a result of a highly open-cell foam structure. The air permeability for the foams in Example 6, Example 3 and Example 4 (containing FR2, FR3 and FR6) are in the range of the TCPP-containing reference foam Comp. Example 5, demonstrating that the cell-closing property often associated with reactive flame retardants is low for flame retardants according to the invention. This property of the flame retardants according to the invention is beneficial in the industrial production of flexible polyurethane foam, as it facilitates formulation of open-cell foams with reactive flame retardants.

Table 3 futhermore shows that very low values of compression set can be achieved when flame retardants according to the invention are used, e.g. FR2,

FR3 or FR6. Low compression set values are beneficial for typical applications like automotive headliner foam, which is usually compressed during storage and transport, and which needs to fully decompress according to OEM requirements. The compression set found for foams in Example 3, Example 4 and Example 6 (containing FR3, FR6 or FR2) are similarly low as the value found for the TCPP- containing reference foam in Comp. Example 5. Compression set is negatively influenced by ageing under humid conditions, due to hydrolytic cleavage of polymer chains. This is particularly the case for foams containing reactive flame retardants, that can act as breaking points in the polymer backbone if they are not hydrolytically stable. The good compression set values observed for the foams in Example 3, Example 4 and Example 6 can be explained with the high hydrolytic resistance of the phosphine oxide group as also demonstrated for FR3 in Example 1.

Finally, table 3 illustrates that foams containing flame retardants according to the invention are clearly advantageous in applications requiring low emissions of volatile compounds from the final material, e.g. automotive interior materials like polyurethane foam for head- and seatliners. Foams containing flame retardants 41 according to the invention FR1-F6 showed very low fogging values ranging between 0,1 and 0,3 mg. For the polyurethane foams containing FR3 (Example 3), FR6 (Example 4), FR2 (Example 6) and FR5 (Example 8), VDA-278 emission values were dramatically lower than for the TCPP-containing reference foam Comp. Example 5, and significantly lower than for the reference foam in Comp. Example 6.

In summary, these examples demonstrate that the flame retardants according to the invention provide a clear benefit over existing alternatives like reference flame retardants Ref-1 and Ref-2, as they allow polyurethane foam manufacturers to produce flame retarded foams with an open-cell structure, low compression set and very low emission values all at the same time, without using halogenated flame retardants.

Flexible polyester polyurethane foam formulations with performance testing

In additional examples, the use of the flame retardants according to the invention was demonstrated in flexible polyester polyurethane foam. The foam in Example 9, containing flame retardant FR3 was compared with reference foams using TDCPP and Exolit OP 550 as flame retardants (Comp. Example 8 and Comp. Example 9). The foams were produced according to the procedure described above for polyether-based polyurethane foams. The detailed compositions of these formulations are provided in table 2, the performance data is summarized in table 3.

As can be seen from the performance testing results (table 3), stable and defect- free foams could be made with both reference flame retardants Ref-2 and Ref-4, and with the flame retardant of the invention FR3. FR3 showed very good flame retardant efficiency in polyester-based flexible polyurethane foam (Example 9), passing the FMVSS 302 test with an SE rating at a dosage of only 6 php. The reference foams in Comp. Example 8 and Comp. Example 9, containing Ref-4 and the reactive Ref-2 as flame retardants, required significantly higher flame retardant dosages (8 and 9 php, respectively) to achieve the same rating. 42

Example 9, Comp. Example 8 and Comp. Example 9 also demonstrate the benefit of the reactive properties of the flame retardants according to the invention. As can be seen from the fogging values in table 3, the foams containing reactive flame retardants Ref-2 and FR3 lead to significantly lower condensable emissions, compared to the additive flame retardant Ref-4 in Comp. Example 8.

Example 9 also shows the advantage of the flame retardants according to the invention over other reactive flame retardants like Ref-2 in Comp. Example 9, in terms to the resistance against hydrolysis. The results for compression set after ageing are considerably better for Example 9 (containing FR3) and Comp.

Example 8 (containing Ref-4), than Comp. Example 9 (containing Ref-2). This is in line with the higher resistance to hydrolysis in water-containing polyol blends, demonstrated for FR3 in Example 2. In summary, these examples demonstrate that flame retardants according to the invention can be used for the production of flexible polyester-based flame retardant polyurethane foams which show beneficial emission characteristics and have improved resistance against hydrolysis compared to foams using other reactive flame retardants, at the same time avoiding halogenated flame retardants.

Claims

43 Patent Claims

1. A flexible polyurethane foam which comprises at least one flame retardant polyurethane comprising structural units of formula (X) and/or (XI) wherein R¹ is a monovalent organic group,

R⁸ is hydrogen or a group of formula (XII), n and m independently of one another are integers between 0 and 10, o, p and q independently of one another are integers between 0 and 5, with the proviso that the number of structural units of formula 44 in the the structural units of formula (XI) is between 1 and 20, characterized in that the flame-retardant polyurethane comprises at least two different structural units of formula (X).

2. The flexible polyurethane foam according to claim 1 , wherein one of R² or R³ is hydrogen and the other one of R² or R³ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms and wherein one of R⁴ or R⁵ is hydrogen and the other one of R⁴ or R⁵ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms.

3. The flexible polyurethane foam according to claim 2, wherein one of R² or R³ is hydrogen and the other one of R² or R³ is hydrogen or an alkyl group having between one and two carbon atoms, preferably methyl, and wherein one of R⁴ or R⁵ is hydrogen and the other one of R⁴ or R⁵ is hydrogen or an alkyl group having between one and two carbon atoms, preferably methyl.

4. The flexible polyurethane foam according to at least one of claims 1 to 3, wherein R², R³, R⁴ and R⁵ independently of one another are selected from hydrogen, Ci-C₆-alkyl and phenyl, more preferred from hydrogen and Ci-Ce-alkyl, and still more preferred from hydrogen and Ci-C3-alkyl, and most preferred from hydrogen and methyl.

5. The flexible polyurethane foam according to at least one of claims 1 to 4, wherein R¹ is Ci-Ce-alkyl, cyclohexyl or phenyl, preferred Ci-C3-alkyl, and most preferred methyl. 45

6. The flexible polyurethane foam according to at least one of claims 1 to 5, wherein the sum n+m in each of the phosphine oxide of formula (I) is a number between 1 and 15 and most preferred between 4 and 12.

7. The flexible polyurethane foam according to at least one of claims 1 to 6, wherein the flame-retardant polyurethanes comprise at least two different structural units of formula (Xa), (Xb) and/or (Xc) wherein

R¹, m and n are as defined in claim 1 , R^2a and R^3a independently of one another is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon, and

8. The flexible polyurethane foam according to claim 1 , wherein the flame- retardant polyurethane comprises at least one structural unit of formula (XI), preferably different structural units of formula (XI), R¹ is Ci-Ce-alkyl, cyclohexyl or 46 phenyl, preferred Ci-C3-alkyl, and most preferred methyl, and wherein the number of structural units of formula is between 1 and 10.

9. The flexible polyurethane foam according to at least one of claims 1 to 6, wherein the flame-retardant polyurethane comprises at least two different phosphine oxide structural units of formulae (Xe), (Xf) and/or (Xg) wherein

R⁸ is Ci-C₆-alkyl, preferably methyl,

R⁹ and R¹⁰ independently of one another are hydrogen, C-i-Cs-alkyl or C6-C18- aryl, preferably hydrogen, Ci-C₆-alkyl or phenyl, most preferred hydrogen or methyl, n and m independently of one another are integers between 0 and 10, preferably between 1 and 10, and 47 wherein the sum n+m is a number between 0 and 20, preferably between 1 and 15.

10. The flexible polyurethane foam according to at least one of claims 1 to 9, wherein the flame-retardant polyurethane comprises besides structural units of formula (X) or (XI) at least one structural unit of formula (Via) wherein

R², R³, R⁴, R⁵, m and n are defined as in claim 1 ,

11 . The flexible polyurethane foam according to claim 10, wherein one of R² or R³ is hydrogen and the other one of R² or R³ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms and wherein one of R⁴ or R⁵ is hydrogen and the other one of R⁴ or R⁵ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms and wherein one of R¹⁴ or R¹⁵ is hydrogen and the other one of R¹⁴ or R¹⁵ is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon atoms. 48

12. The flexible polyurethane foam according to at least one of claims 10 to 11 , wherein the flame-retardant polyurethane comprises at least two different structural units of formula (X) and at least one structural unit of formula (Via).

13. The flexible polyurethane foam as claimed in at least one of claims 1 to 12, wherein the amount of structural units of formula (X) and/or of formula (XI) and optionally of formula (Via) in the flame-retardant polyurethane used in the flexible foam is from 0.5 to 30 mol.-%, preferably from 0.5 to 20 mol.-% and most preferred from 1 to 10 mol.-%, referring to the total amount of the polyurethane.

14. The flexible polyurethane foam as claimed in at least one of claims 1 to 13, wherein the flame-retardant polyurethane is prepared by reacting organic polyisocyanates with compounds of formula (I) and/or (II) and optionally (VI) together with compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI)

49 wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, m, n, o and p are defined as in claim 1, and R¹⁴, R¹⁵ and r are defined as in claim 11.

15. The flexible polyurethane foam as claimed in claim 14, wherein the flame- retardant polyurethane is characterized by having soft portions in the molecule which are derived from a reaction between polyisocyanate and a compound having at least two hydrogen atoms reactive toward isocyanates which is different from compounds of formulae (I), (II) and (VI), said compound being selected from the group consisting of polyalkylene ether polyol, polyester polyol and hydroxyl- terminated elastomer.

16. The flexible polyurethane foam as claimed in claim 15, wherein the flame- retardant polyurethane is characterized by having besides soft portions also hard portions in the molecule which hard portions are derived from a reaction between polyisocyanate a compound having at least two hydrogen atoms reactive toward isocyanates which is different from compounds of formulae (I), (II) and (VI), said compound being a low-molecular weight polyol.

17. The flexible polyurethane foam as claimed in at least one of the claims 1 to 16, wherein the flexible polyurethane foam contains one or more additives which are present in an amount between 0 and 60 % by weight, preferably between 0.5 and 50 % by weight, more preferred between 0.5 and 30 % by weight, and most 50 preferred between 0.5 and 5 % by weight, referring to the total amount of the flexible polyurethane foam.

18. Use of the flame retardant flexible polyurethane foam as claimed in at least one of claims 1 to 17 as furniture padding, textile inserts, mattresses, automobile seats, armrests, headrests, construction components, automotive seat coverings, headliners and dashboard coverings.

19. A kit-of-parts comprising - a container A containing an organic polyisocyanate or a mixture of organic polyisocyanates, and comprising a container B containing a mixture of compounds of formula (I) and/or (II) and optionally (VI) together with compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) 51 wherein

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, m, n, o and p are defined as in claim 1, and R¹⁴, R¹⁵ and r are defined as in claim 11 , characterized in that the mixture in the container B comprises a mixture of at least two structurally different compounds of formula (I), preferred of formulae (la), (lb) and/or (lc) wherein R^2a and R^3a independently of one another is hydrogen, an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon, and R^4a and R^5a independently of one another is an alkyl group having between one and eight carbon atoms or an aryl group having between six and eighteen carbon.

20. The kit-of-parts as claimed in claim 19, wherein the compounds having at least two hydrogen atoms reactive toward isocyanates which are different from 52 compounds of formulae (I), (II) and (VI) are selected from the group consisting of polyalkylene ether polyols, polyester polyols and hydroxyl-terminated elastomers.

21. The kit-of-parts as claimed in claim 19, wherein the compounds having at least two hydrogen atoms reactive toward isocyanates which are different from compounds of formulae (I), (II) and (VI) are low-molecular weight polyols.