Flame-retardant polyurethane and its use

Abstract

A flame-retardant polyurethane obtained by reacting a polyol and an isocyanate in the presence of a flame retardant containing the phosphine of the following formula (I). [Formula 1] JPEG2026519763000016.jpg28170 (In the formula, R1 is C1-C 12 Alkyl and C6-C 20 A hydrocarbon group selected from aryl groups; R2 and R3 are the same or different, independently H or C1-C 12 (Represents an alkyl group.)

Description

Technical Field

[0001] The present invention relates to a flame - retardant polyurethane containing a specific type of phosphinate - based flame retardant, a method for producing the same, and its industrial use.

Background Art

[0002] To obtain the flame - retardancy desired for industrial applications, flame - modified polyurethanes usually contain at least one flame - retardant substance. In these applications, liquid flame retardants are often preferred over solid flame retardants because liquid flame retardants disperse or dissolve more easily and uniformly into the polymer in the blending process, resulting in a more consistent flame - retardant effect overall. Furthermore, liquid flame retardants can often be processed at lower temperatures than solid flame retardants, reducing the problem of polymer degradation associated with potential high temperatures. Due to their large surface area of interaction, these liquid additives can be incorporated into the polymer mixture more quickly than solid flame retardants. Additionally, liquid flame retardants are generally easier to handle in the process of mixing with polyols, so the addition amount can be accurately controlled and they can be smoothly blended with the polymer.

[0003] One common liquid flame retardant widely used in the industry is TCPP (tris(1 - chloro - 2 - propyl) phosphate), which is often included in polyurethane foams in electronic devices, consumer products, and household insulation materials. However, although it has excellent flame - retardancy, TCPP has been found to be released into the environment over time and has toxicological and ecotoxicological adverse effects as a halogen. Furthermore, due to the leaching of the TCPP flame retardant, the overall flame - retardant effect decreases over time.

[0004] US 9 631 144 B2 describes different liquid flame retardant compositions, which include one or more halogenated flame retardants, which are brominated epoxides obtained by reacting tetrabromobisphenol A with epichlorohydrin. These liquid flame retardants are said to be stable in rigid polyurethane foam and exhibit excellent flame retardancy. However, it should be noted that in the examples in US 9 631 144 B2, the brominated epoxides were obtained as resins with high softening points, requiring further treatment at high temperatures. Furthermore, the resulting liquid flame retardant compositions are characterized by a high bromine content of at least 30 wt%.

[0005] In light of growing concerns about the use of halogenated flame retardants for environmental protection, ongoing efforts have been made to find non-halogenated alternative liquid flame retardants for polymers and polymer foams.

[0006] US 4 458 035 A discloses an oligomeric phosphate flame retardant for polyurethane foam, wherein the phosphate is given by the following formula (1).

[0007] [ka]

[0008] (In the formula, n is from 0 to 10, and R is C1-C) 10 (halo)alkyl group, where R1 and R2 are hydrogen atoms or C1-C 10 It is a (halo)alkyl group.

[0009] US 7 288 577 B1 discloses two different blends of phosphate flame retardants for polyurethane, which basically consist of the following components: (a) 50 weight percent of the blend, a blend of butylated triphenyl phosphate, and (b) 50 weight percent of the blend, a blend of poly(ethylethylene oxy) phosphate.

[0010] While the aforementioned patents may disclose several effective liquid phosphorus-based flame retardants, some of them are known to be prone to hydrolysis under humid conditions, negatively impacting the polymerization process or the final polymer properties. In particular, the acids formed by hydrolysis are known to inactivate polymerization catalysts during the foaming process, further cleaving covalent bonds in the polymer foam product and thereby disrupting the intended three-dimensional foam network.

[0011] Several liquid phosphorus-based flame retardant products are commercially available, such as Antiblaze® 1045 (manufactured by Albemarle), a cyclic phosphonate compound used in polymers such as PET and PBT. The chemical structure of this cyclic phosphine is shown in the following formula (2).

[0012] [ka]

[0013] Antiblaze® 1045 typically exhibits a high viscosity of over 500,000 mPa₂s at a temperature of 25°C. Therefore, for effective use, it is necessary to carefully impregnate the carrier material and to apply it to the polymer fiber surface as an aqueous solution with utmost care. In the latter case, to obtain the desired results, it is necessary to heat the material afterward to soften the fibers and dissolve the cyclic phosphonic acid ester. [Overview of the Initiative]

[0014] The object of the present invention is to provide a novel non-halogenated flame retardant for use in polyurethanes, particularly polyurethane foams. The non-halogenated flame retardant is liquid at room temperature and under conventional polyurethane manufacturing conditions, has a suitable low viscosity for easy processing and handling, exhibits excellent hydrolysis stability even under humid conditions, and provides flame retardancy to polyurethane materials that is equivalent to or better than existing commercially available products.

[0015] The present invention aims to provide a flame-retardant polyurethane. In particular, it aims to provide a polyurethane foam that achieves excellent flame-retardant efficiency by containing the aforementioned non-halogenated flame retardant.

[0016] The present invention provides the use of a phosphinate of the following formula (I) as a flame retardant for polyurethanes.

[0017] [Chemical formula]

[0018] (In the formula, R1 is a hydrocarbon group selected from a C1-C 12 alkyl group and a C6-C 20 aryl group; R2 and R3 are the same or different and independently represent H or C1-C 12 alkyl.)

[0019] The present invention provides a flame-retardant polyurethane obtained by reacting a polyol and an isocyanate in the presence of a flame retardant containing the phosphinate of formula (I).

Embodiments for Carrying Out the Invention

[0020] Detailed Description Unless otherwise specified, the term "hydrocarbon group" used in this specification refers to an aliphatic group, an aromatic group, or an alicyclic group, which is saturated or unsaturated, straight-chain or branched-chain, and optionally substituted with heteroatoms (e.g., O, N, S).

[0021] R1 is preferably selected from C1-C6 alkyl, more preferably selected from C2-C4 alkyl. Also, preferably, R2 and R3 are not both H at the same time.

[0022] In a preferred embodiment of the present invention, one of R2 and R3 is H or ethyl, and the other is C1-C6 alkyl.

[0023] In another preferred embodiment of the present invention, either R2 or R3 is methyl, and the other is H or C1-C4 alkyl.

[0024] In a preferred embodiment, R1 is ethyl, either R2 or R3 is methyl, and the other is ethyl.

[0025] In another particularly preferred embodiment, R1 is butyl, either R2 or R3 is methyl, and the other is H.

[0026] In yet another particularly preferred embodiment, either R2 or R3 is methyl, and the other is butyl.

[0027] Due to its chemical properties, the phosphinate-based flame retardant according to the present invention is liquid at room temperature and under conventional polyurethane production conditions. Advantageously, the liquid phosphinate-based flame retardant is characterized by a low viscosity of less than 100 mPa s, preferably less than 50 mPa s, and more preferably less than 10 mPa s at a temperature of 25°C. This viscosity can be measured according to DIN 51398. As described above, the advantageous property of low viscosity plays an important role when actually using the liquid flame retardant in the production of flame-retardant polyurethanes. The use of viscous liquid flame retardants usually has the difficulty that it is necessary to heat the containers, feeds, and discharge pipes during the storage or transportation of the liquid. Furthermore, in order to uniformly incorporate a high-viscosity liquid flame retardant into a polymer composition, additional effort is often required, especially in industrial processes for large-scale chemical production.

[0028] The phosphinate of the following formula (I) can be prepared in different ways. One approach is to react an α-monoolefin and an (alkyl)phosphinate in the presence of a free radical generator, as described in US 39 14 345 A, EP 23 73 666 A1, US 87 35 477 B2, and EP 23 67 834 A1.

[0029]

Chemical formula

[0030] The phosphinate of formula (I) can also be prepared from the corresponding phosphite by a catalytic rearrangement reaction. For example, one of the corresponding phosphites is shown in the following structural formula (II).

[0031] [ka]

[0032] As shown in Synthesis Example 1, this preparation method may include two steps. In the first step, a phosphite corresponding to the desired phosphinate product is generated as an intermediate product, and in the second step, the phosphinate of formula (I) is obtained from this intermediate product by a catalytic rearrangement reaction. Alternatively, if the corresponding phosphite is readily available from the market, the preparation method can be streamlined to a single step.

[0033] The rearrangement catalyst in this preparation method may be an iodine-containing catalyst such as iodine, alkyl iodine, and alkali metal iodate salts (especially potassium iodide), or a Lewis acid catalyst, as described in CN104693238A. Alternatively, the rearrangement catalyst may be sodium iodide, as described in CN109400643A.

[0034] The rearrangement catalyst may be, more preferably, a low molecular weight organic sulfonate, and more preferably, selected from the group consisting of diethyl sulfate, ethyl ethanesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, methyl p-chlorobenzenesulfonate, and ethyl p-chlorobenzenesulfonate. Advantages of using a low molecular weight organic sulfonate rearrangement catalyst in this preparation method include cost-effectiveness and simplified catalyst recovery.

[0035] If either R2 or R3 is H, the phosphinate of formula (I) may be prepared by reacting an alkyldichlorophosphine and an alcohol at a suitable temperature, as shown in Synthesis Example 2. This reaction, known as alcohol decomposition, partially oxidizes the phosphine, generating one pH bond, while forming the corresponding alkylphosphinate ester.

[0036] An example of this chemistry is shown in CN 113493478A, in which methyldichlorophosphine reacts with n-butanol at room temperature. This reaction produces the desired n-butylmethylphosphinate, with hydrogen chloride and n-butyl chloride formed as byproducts. The present invention also provides flame-retardant polymers obtained by polymerizing monomers in the presence of a flame retardant containing the phosphinate of formula (I).

[0037] The flame-retardant polyurethane (PUR) of the present invention is a polyurethane composition comprising a phosphine of formula (I) as a flame retardant. In one embodiment of the polyurethane composition, the phosphine of formula (I) is present in an amount ranging from 0.5% to 30% by weight relative to the weight of the polyurethane. Preferably, the phosphine of formula (I) is present in an amount ranging from 0.5% to 20% by weight relative to the weight of the polyurethane.

[0038] The flame-retardant polyurethane of the present invention is preferably obtained by reacting a polyol and an isocyanate in the presence of a flame retardant containing a phosphinate of formula (I), and optionally in the presence of a polymerization catalyst. Polymerization catalysts suitable for the production of flame-retardant polyurethanes can be selected from aliphatic tertiary amines (e.g., triethylamine, tetramethylbutanediamine), alicyclic tertiary amines (e.g., 1,4-diaza(2,2,2)bicyclooctane), aliphatic amino ethers (e.g., dimethylaminoethyl ether and N,N,N-trimethyl-N-hydroxyethylbisaminoethyl ether), alicyclic amino ethers (e.g., N-ethylmorpholine), aliphatic amidines, alicyclic amidines, urea, urea derivatives (such as aminoalkylureas, see e.g., EP-A 0 176 013, particularly (3-dimethylaminopropylamine)urea), and tin catalysts (such as dibutyltin oxide, dibutyltin dilaurate, and tin octoate).

[0039] One notable advantage of using the phosphinate of formula (I) as a flame retardant for polyurethanes is its high compatibility with polyols, one of the essential starting materials for polyurethanes. The phosphinate of formula (I) readily dissolves in polyols, forming a homogeneous solution that remains stable for extended periods during storage or transport. This homogeneous solution serves as a valuable starting material for polymerization, ensuring that the resulting polyurethane product is flame-retardant overall.

[0040] The present invention provides a method for producing flame-retardant polyurethane, comprising the steps of preparing a mixture containing a polyol containing a phosphine of formula (I) and a flame retardant, and adding an isocyanate compound to the mixture.

[0041] For the purposes of this invention, the term "polyol" refers to a compound having at least two hydrogen atoms that can react with isocyanate. These are compounds having an amino group, a thio group, or a carboxyl group, preferably a hydroxyl group, and more particularly a compound having 2 to 8 hydroxyl groups.

[0042] Polyols suitable for the purposes of the present invention include those with a molecular weight (Mw) of 400 to 10,000, particularly 1,000 to 6,000, preferably 2,000 to 6,000, and are generally divalent to octavalent, preferably divalent to hexavalent, polyethers or polyesters, or polycarbonates or polyesteramides, which are known for the production of homogeneous or porous polyurethanes, for example, those described in DE-A 28 32 253.

[0043] Preferred polyester polyols are obtained by polycondensation of polyalcohols 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 dibasic acids 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.

[0044] For the production of thermosetting flame-retardant polyurethanes, a more preferred group of polyester polyols includes ethylene glycol, propylene glycol, trimethylolpropane, and pentaerythritol, having two, three, or four hydroxyl groups. Preferred polyether polyols are not particularly limited, but include triols such as glycerol, trimethylolethane (i.e., 1,1,1-tris(hydroxymethyl)ethane), and trimethylolpropane (i.e., 1,1,1-tris(hydroxymethyl)propane); tetraols such as pentaerythritol; pentaols such as glucose; hexaols such as dipentaerythritol and sorbitol; or alkoxylated derivatives of all these polyalcohols, preferably their ethoxylated and propoxylated derivatives.

[0045] A particularly preferred polyether polyol is polyoxypropylenetriol.

[0046] Other polyols suitable for the purposes of the present invention include those having a low molecular weight of 30 to 400, preferably compounds having a hydroxyl group and / or an amino group, and functioning as a chain extender or crosslinking agent. These compounds generally have 2 to 8, preferably 2 to 4, hydrogen atoms that can react with isocyanates.

[0047] Suitable isocyanates used in the production of the flame-retardant polyurethane of the present invention can be selected from, for example, aliphatic, alicyclic, aromatic aliphatic, aromatic, or heterocyclic polyisocyanates (see, for example, W. Siefken, Justus Liebigs Annalen der Chemie, 562, pp. 75-136), for example, represented by the formula Q(NCO)r, where r is 2 to 4, preferably 2 to 3, and Q is an aliphatic hydrocarbon group having 2 to 18 carbon atoms, preferably 6 to 10; an alicyclic hydrocarbon group having 4 to 15 carbon atoms, preferably 5 to 10; an aromatic hydrocarbon group having 6 to 15 carbon atoms, preferably 6 to 13; or an aromatic aliphatic hydrocarbon group having 8 to 15 carbon atoms, preferably 8 to 13.

[0048] Polyisocyanates suitable for the purposes of the present invention are aromatic, alicyclic and / or aliphatic polyisocyanates having at least two isocyanate groups and mixtures thereof. Preferably, aromatic polyisocyanates, such as tol diisocyanate, methylenediphenyl diisocyanate, naphthylene diisocyanate, xylylene diisocyanate, tris(4-isocyanatophenyl)methane and polymethylene polyphenylene diisocyanate; alicyclic polyisocyanates, such as methylenediphenyl diisocyanate and tol diisocyanate; aliphatic polyisocyanates and hexamethylene diisocyanate, isophorene diisocyanate, dimethyl diisocyanate, 1,1-methylenebis(4-isocyanatocyclohexane-4,4'-diisocyanatodicyclohexylmethane-isomer mixture, 1,4-cyclohexyl diisocyanate and lysine diisocyanate and mixtures thereof.

[0049] Particularly preferred are polyisocyanates that are generally readily available industrially, such as 2,4- and 2,6-toluenediisocyanates, methylenediphenyl isocyanates (MDI), or their polymeric forms (pMDI).

[0050] For the purposes of the present invention, the flame-retardant polyurethane may be linear PUR (e.g., produced from a diol and a diisocyanate) or crosslinked PUR (e.g., produced by converting a triisocyanate-diisocyanate mixture with a triol-diol mixture). The properties of the flame-retardant polyurethane can be varied over a wide range. Depending on the degree of crosslinking and / or the use of isocyanate or OH components, thermosetting, thermoplastic, or elastomer properties can be obtained.

[0051] The flame-retardant polyurethane of the present invention may be used as a soft or rigid foam, a molding compound for molding, a casting resin (isocyanate resin), a (textile) elastic fiber, a polyurethane coating, and a polyurethane adhesive.

[0052] The present invention also provides a flame-retardant polyurethane foam obtained by reacting a polyol and an isocyanate in the presence of a flame retardant containing a phosphine of formula (I), and further in the presence of a blowing agent, a blowing catalyst, a blowing stabilizer, and optionally other additives.

[0053] In a preferred embodiment of the present invention, the flame-retardant polyurethane foam is a flexible foam.

[0054] In another preferred embodiment of the present invention, the flame-retardant polyurethane foam invented is a rigid foam.

[0055] For the purposes of this invention, the term "foaming agent" refers to a substance that can supply gas in the polyol-isocyanate reaction and produce a porous foam. Conventional foaming agents used in the manufacture of polyurethane foam are suitable for this use and include both physical and chemical foaming agents. Examples of physical foaming agents include low-boiling liquids such as butane and carbon dioxide, which expand under reduced pressure, as well as short-chain (C5-C6) aliphatic molecules such as pentane and cyclopentane, and various hydrofluoroolefins such as 1,3,3,3-tetrafluoropropene. Examples of chemical foaming agents include water and carboxylic acids, which release gas when reacting with isocyanates. Water is a particularly preferred foaming agent.

[0056] For the purposes of the present invention, the foaming catalyst suitable for the production of the invented flame-retardant polyurethane foam is preferably selected from amine catalysts (e.g., tertiary amines) and organometallic compounds (e.g., tin octoate, tin acetate, dibutyltin diacetate, etc.).

[0057] For the purposes of the present invention, the foam stabilizer suitable for the production of flame-retardant polyurethane foam may be any conventional stabilizer for controlling and stabilizing polyurethane foam. As a preferred example, the stabilizer may be selected from silicone surfactants.

[0058] In the production of flame-retardant polyurethane foam according to the present invention, other additives, including fillers, pigments, light stabilizers, and processing aids, may be added to the reaction mixture.

[0059] The present invention further relates to the use of the aforementioned flame-retardant polyurethane or flame-retardant polyurethane foam for the manufacture of door liners, headliners, seat covers, high-rebound foam sheets, high-rebound foam mattresses, rigid foam insulation panels, viscoelastic foam mattresses, potting foams for batteries, seals and gaskets of micro-porous foams, wheels and tires of durable elastomers, automotive suspension bushings, potting compounds for electrics, high-performance adhesives, surface coatings and sealants, synthetic fibers, underlays for carpets, rigid plastic parts and hoses.

[0060] The present invention also relates to the use of flame-retardant polyurethane or flame-retardant polyurethane foam for the manufacture of electrical switch parts, automotive structures, parts used in electrical engineering or electronics engineering, printed circuit boards, prepregs, potting compounds for electronic parts, outdoor GFRP applications in boat and rotor blade structures, household and sanitary applications, and engineering materials.

Examples

[0061] Hereinafter, the present invention will be described in more detail with reference to examples, but these examples do not limit the present invention.

[0062] 1. Components used: Flame retardant: FR-1: Product ethyl ethyl (methyl) phosphinate (MEPE) of Synthesis Example 1 FR-2: Product butyl methyl phosphinate of Synthesis Example 2 FR-3: Product butyl butyl (methyl) phosphinate (MUPU) of Synthesis Example 3 Ref-1: Fyrol® PCF (ICL Industrial Products), TCPP (tris(1-chloro-2-propyl) phosphate), halogenated phosphate ester Ref-2: Exolit® OP 550 (Clariant International), a non-halogenated polymeric phosphate polyol with a hydroxyalkyl group, specifically designed for flexible polyurethane foam.

[0063] polyol : Polyether polyol (P1): Arcol® 1104 or 1108 (Covestro), a medium molecular weight polyoxypropylene triol with an OH value of 56 mg KOH / g. Polyester polyol (P2): Terate® HT 5510 (Stepan), aromatic polyester polyol (hydroxyl value, 257 mg KOH / g)

[0064] polymerization catalyst : Cat 1: Kosmos® EF (Evonik Industries), tin catalyst Cat 2: Kosmos® 29 (Evonik Industries), tin octoate catalyst Cat 3: Niax® A1 (Momentive Performance Materials), a bis(2-dimethylaminoethyl) ether-based amine catalyst. Cat 4: Tegoamin® 33 (Evonik Industries), a triethylenediamine-based amine catalyst. Cat 5: JEFFCAT® ZF-10 (Huntsman), an amine catalyst based on N,N,N'-trimethyl-N'-hydroxyethylbisaminoethyl ether. Cat 6: Polycat 5 E10 (Evonik Industries), an amine catalyst based on bis(2-dimethylaminoethyl)methylamine. Cat 7: Kosmos 75 MEG (Evonik Industries), a foaming catalyst based on low-viscosity potassium octate.

[0065] Foam stabilizer: S1: Tegostab (registered trademark) B 8232 (Evonik Industries), silicone surfactant S2: Tegostab® B 8522 (Evonik Industries), silicone surfactant

[0066] TDI (Diisocyanate totril): TDI (Trilled Diisocyanate): T80: Desmodur® T80 (Covestro), 2,4- and 2,6-toluene diisocyanate, 80 / 20 isomer mixture

[0067] MDI (Methylenediphenyl diisocyanate): MDI1: Desmodur® 44 V 70 L (Covestro) is a mixture of diphenylmethane-4,4'-diisocyanate (MDI) and its isomers and highly functional homologs (PMDI).

[0068] 2. Synthesis examples of flame retardants FR-1, FR-2, and FR-3 according to the present invention 2.1. Synthesis Example 1: Manufacturing of FR-1 Step 1: Production of diethylmethylphosphonite A mixture of 5280 g of petroleum ether, 413 g of anhydrous ethanol, and 1100 g of triethylamine was added to a 25 L autoclave equipped with a thermometer and condenser. The reaction system was purged three times with nitrogen, and then 501 g of methyldichlorophosphan solution was added dropwise at 25°C. After all additions were made, the system was maintained at 25°C for 30 minutes.

[0069] Next, the resulting reaction mixture was subjected to pressure filtration to remove the generated NEt3·HCl. The resulting filter cake was washed with 1000 mL of petroleum ether. Subsequently, 6590 g of the filtrate was distilled to recover the petroleum ether, yielding the crude product of diethylmethylphosphonite.

[0070] Finally, 557.8 g of diethylmethylphosphonite was obtained by rectification. The purity, as measured by gas chromatography (GC), was 98.5%, and the yield was 96.1%.

[0071] Step 2: Production of ethyl ethyl (methyl) phosphinate (FR-1) A mixture of 557.0 g of diethylmethylphosphonite and 27.50 g of p-toluenesulfonate was added to a 1 L three-neck flask equipped with a thermometer and condenser. The flask was then purged with N2. The temperature was gradually increased, and the reaction mixture was thoroughly stirred and refluxed. Before insulation, the oil temperature slowly rose from 120°C to 170°C. After 9 hours, reflux was almost completely eliminated (less than 0.5% of the starting material was detected by GC), and the reaction was complete.

[0072] Finally, 535.0 g of the FR-1 product (viscosity 3.5 mPa s) was obtained by vacuum distillation (2-3 kPa, 101°C). The purity of the product, as measured by GC, was 98%, and the yield was 98%.

[0073] 2.2. Synthesis Example 2: Manufacturing of FR-2 Methyldichlorophosphan was continuously supplied to the vaporizer at a flow rate of 119.39 g / h. The vaporized methyldichlorophosphan was transferred to a column-type continuous reactor at a rate of 80 ml / min using a nitrogen stream.

[0074] Simultaneously, 99.5% n-butanol was introduced into another vaporizer at a rate of 243 g / h. The vaporized butanol, using a nitrogen stream, was purged into the column reactor at a rate of 80 ml / min. Subsequently, the vaporized methyldichlorophosphane and n-butanol were rapidly reacted in the column reactor.

[0075] The light fraction of chlorobutane produced by the rapid reaction was concentrated and collected in a low-boiling point substance receiving bottle. The heavy fraction of crude butylmethylphosphine produced during the reaction process was collected in a separate receiving bottle and neutralized with triethylamine.

[0076] After neutralization, n-butanol was removed by vacuum distillation. This process yielded 96.0% butyl methylphosphinate with a viscosity of 3.4 mPa s and a purity of 98.5% through rectification.

[0077] 2.3. Synthesis Example 3: Manufacturing of FR-3 Step 1: Production of dibutylmethylphosphonite A mixture of 6200 g of petroleum ether, 674 g of anhydrous n-butanol, and 910 g of triethylamine was added to a 25 L autoclave equipped with a thermometer and condenser. The reaction system was purged three times with nitrogen, and 507 g of methyldichlorophosphan solution was added dropwise at -10°C. After all additions were made, the system was maintained at 0°C for 30 minutes.

[0078] Next, the resulting reaction mixture was subjected to pressure filtration to remove the generated NEt3·HCl. The resulting filter cake was washed with 1000 mL of petroleum ether. Subsequently, 7506 g of the filtrate was distilled to recover the petroleum ether, yielding the crude product of dibutylmethylphosphonite.

[0079] Finally, 756.7 g of dibutylmethylphosphonite was obtained by rectification. The purity, as measured by gas chromatography (GC), was 95%, and the yield was 88%.

[0080] Step 2: Production of butylbutyl(methyl)phosphinate (FR-3) A mixture of 600 g of dibutylmethylphosphonite and 30 g of p-toluenesulfonate was added to a 1 L three-neck flask equipped with a thermometer and condenser. The flask was then purged with N2. The temperature was gradually increased, and the reaction mixture was stirred well under slight reflux. Before insulation, the oil temperature slowly rose from 150°C to 180°C. After 6 hours, the amount of starting material detected by GC was less than 0.5%, indicating that the reaction was complete.

[0081] Finally, 571 g of the FR-3 product (viscosity 6.4 mPa s) was obtained by vacuum distillation (0.2-0.3 kPa, 86°C). The purity of the product, as measured by GC, was 98%, and the yield was 98.0%.

[0082] 3. Hydrolysis stability comparison test The hydrolysis stability of different flame retardants was compared by measuring the acid value of polyol mixtures containing flame retardants and water over time during storage at high temperatures. For this purpose, 90 g of polyol, 9 g of flame retardant, and 4.5 g of water were homogenized by stirring at 1500 rpm for 2 minutes. The acid value was measured using a 3:1 (v / v) isopropanol / water mixture as the solvent and a 0.1 N NaOH (water) solution as the titrator. The samples were stored at 40°C, and the acid value was measured after 11, 17, and 28 days. Before measurement, the samples were homogenized by stirring at 1500 rpm for 2 minutes. The change in acid value over time for polyol-water blends without flame retardant was also measured after 11 and 28 days, respectively, and is shown in Table 1.

[0083] [Table 1]

[0084] Compared to the reference example without a flame retardant, Example FR-1 of the present invention did not cause a significant increase in the acid value of its polyol mixture during and after a 28-day storage period at 40°C. This demonstrates the high hydrolysis stability of FR-1 during storage in the polyol mixture, i.e., indicating that hydrolysis of FR-1 is zero or negligible. For comparison, the acid value of the polyol mixture containing Ref-2 increased significantly after only 11 days under the same storage conditions, which can be explained solely by the hydrolysis of Ref-2.

[0085] 4. Viscosity comparison of polyols and flame retardant mixtures As mentioned above, the viscosity of the liquid flame retardant of the present invention is advantageously low, making it easy to process and handle in industrial applications. In the above synthesis example, the viscosity of both FR-1 and FR-2 was less than 5 mPa s, and the viscosity of FR-3 was less than 7 mPa s. On the other hand, the viscosity of TCPP (Ref-1), when measured using DIN 51398, is typically 10 times (60-70 mPa s) at room temperature.

[0086] Table 2 compares the viscosity of a single polyol (P2) and a mixture of polyol (P2) containing a flame retardant (FR-1, FR-2, FR-3, or Ref-1). The polyol-flame retardant mixture was prepared by combining polyol P2 with a specific flame retardant (FR-1, FR-2, FR-3, or Ref-1) in a weight ratio of 89.5:10.5 at room temperature. The mixture was thoroughly mixed using a mechanical stirrer at 1000 rpm for 1 minute to ensure uniformity. The viscosity of the single polyol and the polyol-flame retardant mixture was then measured according to DIN 51398.

[0087] [Table 2]

[0088] From the measurement results in Table 2, it was observed that the liquid flame retardant according to the present invention has an additional advantage over conventional liquid flame retardants such as TCPP (Ref-1) in that it effectively reduces the viscosity of the polyol-flame retardant mixture during mixing. This advantageous property can further improve the overall processability in polymer manufacturing.

[0089] 5. Performance testing of flexible polyurethane (PUR) foam formulations Tin catalyst, polyol, flame retardant, water, foam stabilizer, and amine catalyst were weighed and placed in a dry beaker in that order. The polyether polyol mixture was pre-mixed at 500 rpm for 60 seconds, and the polyester polyol mixture at 1000 rpm for 60 seconds. After adding TDI, the mixture was stirred at 2500 rpm for 7 seconds. The resulting mixture was quickly poured into a box-shaped mold (25 × 26 × 26 cm) lined with paper. The foaming time and other observations during the foaming process were recorded. After the foam was cured at room temperature for approximately 16 hours, it was cut and collected for further evaluation for each comparative example (C1-C3) or inventive example (I1-I2).

[0090] The polymerization catalyst, foam stabilizer, and TDI in each foam example were selected based on existing empirical guidelines for optimal foaming in each case. Details are shown in Table 2 below.

[0091] [Table 3]

[0092] Flame retardancy evaluation of flexible foam (FMVSS 302) Sample of flexible polyurethane foam containing flame retardant (target density 30 kg / m³) 3 The effectiveness of the flame retardant was evaluated by testing the combustion behavior of the foam using the horizontal combustion test described in Federal Motor Vehicle Safety Standard 302 (FMVSS 302). The foam density in each case was measured according to DIN 53420. According to this standard, a sample is classified as the highest category (SE, "self-extinguishing") if the flame does not spread beyond the 38 mm mark on the test specimen and extinguishes within this distance. Lower categories include SE / NBR (self-extinguishing / no combustion rate), SE / B (self-extinguishing / with combustion rate), and B (combustion rate). Five test specimens were cut from each foam and subjected to testing. The lowest-rated test specimen determined the overall classification of the foam.

[0093] The flame retardancy of the tested flexible foam examples is compared in Table 4.

[0094] [Table 4]

[0095] As the performance data shown in Table 4 indicates, Comparative Example C1 (polyether polyurethane foam without flame retardant) does not meet the required flame retardancy standards. Comparative Example C2, which contains 12 php of the reference halogenated flame retardant TCPP (Ref-1), shows that the polyether polyurethane foam meets the required flame retardancy standards. As shown in Comparative Example C3, when the amount of flame retardant TCPP was reduced to 8 php, the amount of flame retardant was insufficient, and the resulting foam did not achieve optimal flame retardancy (SE).

[0096] Example I1 of the present invention demonstrates that polyether polyurethane foam can achieve the best flame retardancy standards by adding only 4 php of the non-halogenated flame retardant (FR-1) according to the present invention.

[0097] Example I2 according to the present invention is a polyether polyurethane foam in which the non-halogenated flame retardant (FR-2) according to the present invention is 4 php, and exhibits flame retardancy evaluation as excellent as that of I1.

[0098] 6. Performance testing of rigid polyisocyanurate (PIR) foam formulations Octanoic acid catalyst, polyol, flame retardant, water, foam stabilizer, and amine catalyst were weighed and sequentially placed in a dry beaker and pre-mixed at 1000 rpm for 50 seconds. After adding n-pentane, the mixture was stirred at 1000 rpm for 10 seconds to incorporate it into the mixture. Then, MDI was added to the mixture and the liquid was stirred at 2500 rpm for 7 seconds. The resulting mixture was quickly poured into a box-shaped mold (25 × 26 × 26 cm) lined with paper. The foaming time and other observations during the foaming process were recorded. The foam was cured at room temperature for approximately 16 hours before cutting, and each was collected and further evaluated as comparative examples (C4-C6) or examples according to the present invention (I3-I4).

[0099] The polymerization catalyst, foam stabilizer, and MDI for each cured foam example were selected based on existing empirical guidelines for optimal foaming properties in each case. Details are shown in Table 5 below.

[0100] [Table 5]

[0101] Method for evaluating the flame retardancy of rigid foam (DIN4102-1) DIN 4102-1 classifies building materials according to their flammability. The standard is divided into two fire resistance classes: "A" indicates non-combustible materials, and "B" indicates flammable materials. Class B relates to polyurethane foam, such as PIR insulation panels. This is further subdivided into the following levels: B1 = low flammability; B2 = normal flammability; B3 = high flammability. For reference, most construction foams sold in spray cans in Germany fall under the B2 building material class. The main criterion for classification as flammability class B2 is the flame height in a vertical combustion test, which must remain below 150 mm, and this is an ideal guideline for benchmarking the flame retardancy of building materials.

[0102] The flame retardancy of various rigid PIR foam samples was evaluated using DIN4102-6, and the results are shown in Table 6 below.

[0103] [Table 6]

[0104] As the performance data shown in Table 6 indicates, Comparative Example C4 (PIR foam without flame retardant additives) does not meet the desired flame retardancy standard evaluation B2. By including 15 php of the reference halogenated flame retardant TCPP (Ref-1), the rigid PIR foam in Comparative Example C5 achieves the desired flame retardancy evaluation. However, when the amount of this halogenated flame retardant is reduced to 12 php TCPP, as shown in Comparative Example C6, the flame retardant level is insufficient, and as a result, the foam fails to achieve the desired flame retardancy evaluation.

[0105] Example I3 according to the present invention exhibits excellent flame retardancy by containing a rigid PIR foam at the same level as 12 php of the non-halogenated flame retardant FR-1 according to the present invention, thus meeting the optimal flame retardancy criteria.

[0106] Similarly, Examples I4 and I5 according to the present invention achieve excellent flame retardancy evaluations even when FR-1 is replaced with FR-2 or FR-3, respectively, at the same level as in I3. This further emphasizes the effectiveness of the non-halogenated flame retardants according to the present invention in achieving desired flame retardancy evaluations in rigid foam.

Claims

1. A flame-retardant polyurethane obtained by reacting a polyol and an isocyanate in the presence of a flame retardant containing the phosphine of the following formula (I). 【Chemistry 1】 (In the formula, R1 is C 1 -C 12 Alkyl and C 6 -C 20 It is a hydrocarbon group selected from aryl groups; R2 and R3 are the same or different, independently H or C 1 -C 12 (Represents alkyl.)

2. R1 is C 1 -C 6 from an alkyl group, preferably C 1 -C 4 The flame-retardant polyurethane according to claim 1, selected from alkyls.

3. The flame-retardant polyurethane according to claim 1 or 2, wherein R2 and R3 cannot be H at the same time.

4. One of R2 and R3 is H or ethyl, and the other is C 1 -C 6 The flame-retardant polyurethane according to claim 3, wherein the polyurethane is alkyl.

5. Either R2 or R3 is methyl, and the other is H or C. 1 -C 4 The flame-retardant polyurethane according to claim 3, wherein the polyurethane is alkyl.

6. The flame-retardant polyurethane according to claim 1, wherein R1 is an ethyl group, and either R2 or R3 is methyl or the other is ethyl.

7. The flame-retardant polyurethane according to claim 1, wherein R1 is a butyl group, and either R2 or R3 is methyl and the other is H.

8. The flame-retardant polyurethane according to claim 1, wherein R1 is butyl, and either R2 or R3 is methyl and the other is butyl.

9. A flame-retardant polyurethane foam obtained by reacting a polyol and an isocyanate in the presence of a flame retardant as defined in any one of claims 1 to 8, and further in the presence of a blowing agent, a foaming catalyst and a foam stabilizer.

10. The flame-retardant polyurethane foam according to claim 9, wherein the polyurethane foam is a flexible foam.

11. The flame-retardant polyurethane foam according to claim 9, wherein the polyurethane foam is a rigid foam.

12. Use of flame-retardant polyurethane according to any one of claims 1 to 8 or flame-retardant polyurethane foam according to any one of claims 9 to 11 for the manufacture of door liners, head liners, seat covers, high-rebound foam sheets, high-rebound foam mattresses, rigid foam insulation panels, viscoelastic foam mattresses, potting foam for batteries, microporous foam seals or gaskets, durable elastomer wheels or tires, automotive suspension bushings, electrical potting compounds, high-performance adhesives, surface coatings or sealants, synthetic fibers, carpet underlays, or rigid plastic parts or hoses.

13. A method for producing a flame-retardant polyurethane according to any one of claims 1 to 8, comprising the steps of preparing a mixture containing a polyol and a flame retardant, and adding an isocyanate compound to the mixture.

14. Use of the phosphinate of the following formula (I) as a flame retardant for polyurethane. 【Chemistry 2】 (In the formula, R1 is C 1 -C 12 Alkyl and C 6 -C 20 It is a hydrocarbon group selected from aryl groups; R2 and R3 are the same or different, independently H or C 1 -C 12 (Represents alkyl.)

15. A flame-retardant polyurethane composition containing the phosphine of the following formula (I) as a flame retardant. 【Transformation 3】 (In the formula, R1 is C 1 -C 12 Alkyl and C 6 -C 20 It is a hydrocarbon group selected from aryl groups; R2 and R3 are the same or different, independently H or C 1 -C 12 (Represents alkyl.)

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