WO2021032549A1

WO2021032549A1 - A flame-retardant polyurethane foam having alternative blowing agent with improved processing

Info

Publication number: WO2021032549A1
Application number: PCT/EP2020/072564
Authority: WO
Inventors: Jian Feng XU; Sindhu Easwara MENON; Hong Bo ZHANG; Dunja Hirsemann; Lian Jiang ZHAO; Zu Bao NIE
Original assignee: Basf Se
Priority date: 2019-08-20
Filing date: 2020-08-12
Publication date: 2021-02-25
Also published as: JP2022546309A; KR20220051846A; CN114341225A

Abstract

The present invention relates to a flame-retardant polyurethane (PU) foam with improved processing property compared to conventional foams with similar flame retardant properties or better flame retardant performance at similar NCO index. The present invention also discloses a flame-retardant (FR) rigid foam produced therefrom, and to the preparation thereof, and to a composite comprising the polyurethane foam and the use of the composite as boards or panels in the application of cleanroom cold storage, reefer, roof panels, laminate and insulation boards; or as pipe insulation in the field of spray pipe applications and injection pipes.

Description

A Flame-Retardant Polyurethane Foam having alternative blowing agent with improved processing

Technical Field

The present invention relates to a polyurethane (PU) foam system with improved processing property, to a flame-retardant (FR) rigid foam produced therefrom, and to the preparation thereof, and to a composite comprising the polyurethane foam and the use of the composite as boards or panels in the application of cleanroom cold storage, reefer, roof panels, laminate and insulation boards; or as pipe insulation in the field of spray pipe applications and injection pipes.

Background

Polyurethane (PU) foams are suitable for a large number of applications, for example cushioning materials, thermal insulation materials, packaging, automobile-dashboards, or construction materials.

During the foaming process of PU foam materials physical and chemical blowing agent are used to achieve a certain material density of the foam. The difference between a physical and a chemical blowing agent is that a physical blowing agent possesses a very high vapor pressure and evaporates during the polyurethane reaction of a polyol, which is present in the A component (C-A) and polyisocyanate, which is present in the B component (C-B).

In most cases the physical blowing agent will be either dissolved in the C-A or separately dosed at the customer side. Since many physical blowing agents have a very high vapor pressure and are additionally flammable, that pre-blending of bigger amounts of blowing agent in the C-A or C-B causes a safety risk. On the other hand, some customers are not equipped to separately add flammable materials safely in the process on their lines. Therefore, only a limited number of customers can eg. handle cyclo-pentane (cP) or n-pentane (nP).

Moreover, conventional blowing agents now widely used in the market are not environmental friendly. Many blowing agents are comprised of Chloro-Fluoro-Carbons (CFC) or Hydrochlorofluorocarbons (HCFC) and these substances are already banded or might be banded in near future due to their contribution to the ozone depletion. A CFC/HCFC-free solution is therefore highly favorable.

HFC (Hydrofluorocarbones) and especially HFO (Hydrofluoroolefines) are physical blowing agents, which are more environmentally friendly. Therefore, they are not banned form the market. But blowing agents like LBA (Trans- 1-chloro-3,3,3-trifluoropropene) or 245fa (1,1, 1,3, 3 Pentafluoropropane) are not widely accepted in the market due to their price and therefore their market acceptance e.g. in the very price-driven panel market is not high.

Beside the physical blowing agents, chemical blowing agents are used in PU foam materials. Formic acid (FA) and water (H₂O) for example are the most common chemical blowing agents. FA and H₂O react with an isocyanate-group to an amine group. During this reaction carbon dioxide (CO₂) is created which will act as the actual blowing agent. The newly created amine-group can further polymerize with another isocyanate-group to a urea structure. No chain termination occurs during the blow reaction.

The acid group can react with an isocyanate group to an anhydride intermediate and will further react to an amide structure under CO₂ split off. Also in this case CO₂ will act as the actual blowing agent.

A mono-acid will stop the polymer chain, while a diacid will extent the chain. A poly-acid will lead to a further cross-linking of the PU structure.

The acid based chemical blowing agent can be added to the C-A, or if the viscosity is suitable, it can be separately added at the line. There are certain diacids and polyacids in the market, but their acceptance is not high due to the fact that they do not offer any additional benefits over the conventional blowing agents and they are also not cost-competitive. Additionally, some of the diacids and polyacids have stability issues because the compatibility with the C-A is not good.

Nevertheless, the pre-blending of flammable blowing agents with a high vapor pressure is a safety concern. The need to use alternative blowing agents which can be blended in the C-A to be more flexible to supplier also to customers which cannot handle flammable blowing agents or do not have the possibility to add the blowing agent separately at the line.

Therefore, an alternative blowing agent which is solvable in the C-A and does not have any tendency for phase separation in the C-A is therefore highly favorable. Besides a good C-A compatibility, the developed alternative blowing agent brings additional benefits to the resulting foam properties for example a better fire performance and benefits to the processability such as flow of the liquid foam.

US5527876 describes a process for the production of plastics containing amide groups with elimination of CO₂ by reaction of polyfunctional isocyanates, carboxylic acids and, optionally, alcohols in the presence of tertiary amines, more particularly heteroaromatic amines. With this technical solution, low density foams can be produced at low processing temperatures (RT) in the presence of tertiary amines.

EP0711799A2 describes chlorofluorocarbon-free, urethane-containing moldings having a cellular core and an integral skin with an essentially pore-free surface, ie. polyurethane (PU) integral foams, are produced by reacting the conventional starting components in the presence of blowing agents, catalysts and at least one additive selected from the group consisting of the partially or completely neutralized (1) homopolymers of monoethylenically unsaturated monocarboxylic acids, dicarboxylic acids or the internal anhydrides thereof, (2) copolymers of (2i) monoethylenically unsaturated monocarboxylic acids, dicarboxylic acids or the internal anhydrides thereof and (2ii) carboxyl-free, monoethylenically unsaturated monomers copolymerizable with (2i) and (3) copolymers or graft copolymers of (3i) monoethylenically unsaturated monocarboxylic acids and/or their salts, (3ii) monoethylenically unsaturated dicarboxylic acids, their salts and/or their internal anhydrides and (3iii) if required, carboxyl-free, monoethylenically unsaturated monomers copolymerizable with (3i) and (3ii) in a closed mold with compaction.

However, these documents fail to show any resulting benefits in term of processing and other properties of the foam, while the current innovation can clearly show an improvement in the final foam properties like fire performance and in the processing properties like flowability.

Summary of the invention

An object of this invention is to overcome the problems of the prior art discussed above and to provide a flame-retardant polyurethane foam system that shows better processing (flow of the liquid foam) compared to conventional foams with similar flame retardant properties or better flame retardant performance at similar NCO index. The flame-retardant polyurethane rigid form is of LOI index at least 26%, preferably 26% to 35%, more preferably 27% to 31% meas ured according to IS04589-2:1996.

Surprisingly, it has been found by the inventors that the above object can be achieved by a polyurethane foam system consisting of:

A. a polyol composition; and

B. an isocyanate component; wherein the polyol composition (A) comprises a) polyether polyols, polyester polyols or mixtures thereof; b) catalysts; c) at least a blowing agent, wherein the blowing agent comprising a carboxyl-terminated copolymer of diacid and alcohol; d) flame retardant; e) additives and/or auxiliaries.

For the embodiments, the polyol composition (B) includes 5 to 40 weight percent (wt. %), preferably 10 to 30 wt.%, more preferably 10 to 20 wt.% of a carboxyl-terminated copolymer of diacid and alcohol, where the wt.% values for the polyol composition are based on the total weight of the polyol composition.

In addition, the diacid component to form the carboxyl-terminated copolymer is selected from C4 to C12 aliphatic carboxylic diacids and in a preferred embodiment, the diacid component to form the carboxyl-terminated which is oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid.

Besides, the alcohol component to form the carboxyl-terminated copolymer is selected from C2 to C6 diols or triols and in a preferred embodiment, the diol component to form the carboxyl- terminated which is ethylene glycol, 1,3- propanediol, propylene glycol, 1,4-butanediol, 1,2- butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,3-pentanediol or 1 ,4-pentanediol; in another preferred embodiment, the triol component to form the carboxyl-terminated which is triethanolamine, glycerin or trimethylolpropane or modifications of the before mentioned components with a low alkoxylation degrees of up to 10.

The present disclosure also provides a method for the production of polyurethane foam from the polyurethane foam system according to the invention. The method includes providing polyol composition (A); providing isocyanate component (B); and reacting the polyol composition (A) and the isocyanate component (B) in a weight ration of such that the isocyanate (NCO) index is from 200 to 400, preferably from 220 to 330, more preferably from 230 to 300.

In a preferred embodiment, the production is a discontinuous system and in another preferred embodiment, the production is a continuous system.

In a further aspect, the present disclosure provides a flame-retardant rigid polyurethane foam produced according to the invention.

In another further aspect, the present disclosure provides a composite comprising the flame- retardant rigid polyurethane foam produced according to the invention.

The flame-retardant composite may be used as boards or panels in the application of cleanroom cold storage, reefer, roof panels, laminate and insulation boards; or as pipe insulation in the field of spray pipe applications and injection pipes.

It has been surprisingly found in this application that, by adding carboxyl-terminated copolymer of diacid and alcohol in specific amounts into the polyurethane foam system, the polyurethane foam system shows successful processing and, at the same time, good flame retardant and mechanical property.

Detailed description of the invention

Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the invention belongs. As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise.

As used herein, the articles "a" and "an" refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

Unless otherwise identified, all percentages (%) are “percent by weight". Unless otherwise identified, the temperature refers to room temperature and the pressure refers to ambient pressure.

Unless otherwise identified, the solvent refers to all organic and inorganic solvents known to the persons skilled in the art and does not include any type of monomer molecular.

In various embodiments, a polyurethane foam system is provided. In general, the system consists a polyol composition (A) and an isocyanate component (B), wherein the polyol composition comprises a) polyether polyols, polyester polyols or mixtures thereof; b) catalysts; c) at least a blowing agent, wherein the blowing agent comprising a carboxyl-terminated copolymer of diacid and alcohol; d) flame retardant; e) additives and/or auxiliaries.

Preparation of the polyurethane foams has been described elsewhere, but basically involves reaction of polyether or polyester polyol and a promoting catalyst with an isocyanate in the presence of a suitable blowing agent.

The polyol composition comprises at least a compound having at least two isocyanate reactive hydrogens, a urethane promoting catalyst and at least a blowing agent comprising a carboxyl-terminated copolymer of diacid and alcohol. Preferably, polyhydroxyl compounds having a functionality of 2 to 8, more preferably 3 to 6, and a hydroxyl number of 150 to 850, more preferably 200 to 600 are examples of higher molecular weight compounds having at least two reactive hydrogen atoms.

For example, polythioether polyols, polyester amides, polyacetals containing hydroxyl groups, aliphatic polycarbonates containing hydroxyl groups, and preferably, polyester polyols and polyether polyols. In addition, mixtures of at least two of the aforesaid polyhydroxyl compounds can be used as long as these have an average hydroxyl number in the aforesaid range.

Suitable polyester polyols can be produced, for example, from organic dicarboxylic acids with 2 to 12 carbons, preferably aliphatic dicarboxylic acids with 4 to 6 carbons, and multivalent alcohols, preferably diols, with 2 to 12 carbons, preferably 2 to 6 carbons. Examples of dicarboxylic acids include succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids can be used individually or in mixtures. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives may also be used such as dicarboxylic acid mono- or di-esters of alcohols with 1 to 4 carbons, or dicarboxylic acid anhydrides. Dicarboxylic acid mixtures of succinic acid, glutaric acid and adipic acid in quantity ratios of 20-35:35-50:20-32 parts by weight are preferred, especially adipic acid. Examples of divalent and multivalent alcohols, especially diols, include ethanediol, diethylene glycol, 1,2- and 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10- decanediol, glycerine and trimethylolpropane. Ethanediol, diethylene glycol, 1,4-butanediol, 1,5- pentanediol, 1,6-hexanediol, or mixtures of at least two of these diols are preferred, especially mixtures of 1,4- butanediol, 1 ,5-pentanediol and 1,6-hexanediol.

The polyester polyols can be produced by polycondensation of organic polycarboxylic acids, e.g., aromatic or preferably aliphatic polycarboxylic acids and/or derivatives thereof and multivalent alcohols in the absence of catalysts or preferably in the presence of esterification catalysts, preferably in an atmosphere of inert gases, e.g., nitrogen, carbon dioxide, helium, argon, etc., in the melt at temperatures of 150°C to 250°C, preferably 180°C to 220°C, optionally under reduced pressure, up to the desired polymerization degree, which is preferably less than 10, especially less than 5. In a preferred embodiment, the esterification mixture is subjected to polycondensation at the temperatures mentioned above up to an acid value of 80 to 30, preferably 40 to 30, under normal pressure and then under a pressure of less than 500 mbar, preferably 50 to 150 mbar. Examples of suitable esterification catalysts include iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation may also be per formed in liquid phase in the presence of diluents and/or entraining agents such as benzene, toluene, xylene or chlorobenzene for azeotropic distillation of the water of condensation.

To produce the polyester polyols, the organic poly carboxylic acids and/or derivatives thereof and multi valent alcohols are preferably polycondensed in a mole ratio of 1:1-1.8, preferably 1:1.05-1.2.

The resulting polyester polyols preferably have a functionality of 2 to 3, and a hydroxyl number of 150 to 500, and especially 200 to 400. However, polyether polyols, which can be obtained by known methods, are especially preferred for use as the polyhydroxyl compounds. For example, polyether polyols can be produced by anionic polymerization with alkali hydroxides such as sodium hydroxide or potassium hydroxide or alkali alcoholates, such as sodium methylate, sodium ethylate or potassium ethylate or potassium isopropylate as catalysts and with the addition of at least one initiator molecule containing 2 to 8, preferably 3 to 8, reactive hydrogens or by cationic polymerization with Lewis acids such as antimony pentachloride, boron trifluoride etherate, etc., or bleaching earth as catalysts from one or more alkylene oxides with 2 to 4 carbons in the alkylene radical.

Suitable cyclic ethers and alkylene oxides include, for example, tetrahydrofuran, 1,3- propylene oxide, 1,2- and 2,3-butylene oxide, styrene oxide, and preferably ethylene oxide and 1 ,2-propylene oxide. The alkylene cyclic ethers and oxides may be used individually, in alternation, one after the other or as a mixture. Examples of suitable initiator molecules include water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, optionally N-mono-, N,N-, and N, N'-dialkyl substituted diamines with 1 to 4 carbons in the alkyl radical, such as optionally mono- and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- and 1,4-butylenediamine, 1,2-, 1,3-, 14-, 1,5-, and 1,6-hexamethylenediamine, phenylenediamines, 2,3-, 2,4- and 2,6- toluenediamine and 4,4'-, 2,4'-, and 2,2'-diaminodiphenylmethane.

Suitable initiator molecules also include alkanolamines such as ethanolamine, diethanolamine, N-methyl- and N-ethyl ethanolamine, N-methyl- and N-ethyl diethanolamine and triethanolamine plus ammonia.

Multivalent alcohols, especially divalent and/or trivalent alcohols are preferred such as ethanediol, 1,2- propanediol and 1,3-propanediol, diethylene glycol, dipropylene glycol, 1,4- butanediol, 1,6-hexanediol, glycerine, trimethylolpropane, pentaerythritol, sorbitol, and sucrose.

The polyether polyols have a functionality of preferably 3 to 8 and especially 3 to 6 and have a hydroxyl number of 300 to 850, preferably 350 to 800.

Also suitable as polyether polyols are melamine polyether polyol dispersions according to U.S. Pat. No. 4,293,657; polymer polyether polyol dispersions prepared from polyepoxides and epoxide resin hardeners in the presence of polyether polyols according to U.S. Pat. No. 4,305,861; dispersions of aromatic polyesters in polyhydroxyl compounds according to U.S. Pat. No. 4,435,537; dispersion of organic and/or inorganic fillers in polyhydroxyl compounds according to U.S. Pat. No. 4,243,755; polyurea polyether polyol dispersions according to DE A 31 2 402, tris- (hydroxyalkyl)isocyanurate polyether polyol dispersions according to U.S. Pat. No. 4,514,526 and crystallite suspensions according to U.S. Pat. No. 4,560,708, whereby the details in the aforesaid patents are to be regarded as part of the patent disclosure, and are herein incorporated by reference.

Like the polyester polyols, the polyether polyols may be used either individually or in the form of mixtures. Furthermore, they can be mixed with the aforesaid dispersions, suspensions, or polyester polyols as well as the polyester amides containing hydroxyl groups, the polyacetals, and/or polycarbonates.

Examples of hydroxyl group-containing polyacetals that can be used include, for example, the compounds that can be produced from glycols such as diethylene glycol, triethylene glycol, 4,4'-dihydroxyethoxydiphenyldimethylmethane, hexanediol and formaldehyde. Suitable polyacetals can also be produced by polymerization of cyclic acetals.

Suitable hydroxyl group-containing polycarbonates include those of the known type such as those obtained by reaction of diols, e.g., 1,3-propanediol, 1,4- butanediol, and/or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol and diaryl carbonates, e.g., diphenyl carbonate, or phosgene.

The polyester amides include the mainly linear condensates obtained from multivalent saturated and/or unsaturated carboxylic acids and their anhydrides and amino alcohols, or mixtures of multivalent alcohols and amino alcohols and/or polyamines.

The polyurethane foams can be prepared with or without using chain extending agents and/or crosslinking agents. Suitable chain extenders and/or crosslinking agents include preferably alkanolamines, more preferably diols and/or triols. Typical examples are alkanolamines such as ethanolamine and/or isopropanolamine; dialkanolamines, such as diethanolamine, N-methyl-, N- ethyldiethanolamine, diisopropanolamine; trialkanolamines such as triethanolamine, triisopropanolamine; and the addition products from ethylene oxide or 1,2-propylene oxide, and alkylenediamines having 2 to 6 carbon atoms in the alkylene radical such as N,N'-tetra(2- hydroxyethyl)-ethylenediamine and N,N'-tetra(2-hydroxypropyl)ethylenediamine, aliphatic, cycloaliphatic and/or araliphatic diols having 2 to 14, more preferably 4 to 10 carbon atoms such as ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m-, p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, and preferably 1,4-butanediol, 1,6-hexanediol, and bis(2- hydroxyethyl)hydroquinone; triols such as 1 ,2,4- and 1 ,3,5-trihydroxycyclohexane, glycerine and trimethylolpropane; and lower molecular weight hydroxyl group containing polyalkylene oxides, based on ethylene oxide and/or 1,2-propylene oxide and aromatic diamines such as toluenediamines and/or diaminodiphenylmethanes as well as the aforesaid alkanolamines, diols, and/or triols as initiator molecules.

If chain extending agents, crosslinking agents, or mixtures thereof are used in the preparation of polyurethane foams, then advantageously these are used in a quantity of from up to 20 weight percent, more preferably 2 to 10 weight percent, based on the weight of the polyol composition.

Suitable catalysts (b) include especially compounds that greatly accelerate the reaction of the hydroxyl group containing compounds of components and optionally with the polyisocyanates. Examples include organic metal compounds, preferably organic tin compounds such as tin (II) salts of organic carboxylic acids, e g., tin (II) acetate, tin (II) octanoate, tin (II) ethylhexanoate and tin (II) laurate, and dialkyltin (IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate. Another preferably metal compounds e g., potassium compound is selected from a group consisting of potassium hydroxide, potassium carbonate, potassium bicarbonate, potassium benzoate, potassium formate, potassium acetate, potassium propionate, potassium butyrate, potassium valerate, potassium caproate, potassium caprylate, potassium 2-ethylhexanoate, potassium neodecanoate, potassium caprate, potassium salicylate, potassium laurate, potassium oleate, potassium maleate, potassium citrate, potassium oxalate, potassium methoxide, potassium cellulose, potassium carboxymethylcellulose, potassium hyaluronate, potassium alginate, potassium gluconate and any combination thereof.

The metal compounds are used alone or preferably in combination with strong basic amines. Examples include amines such as 2,3- dimethyl-3, 4, 5, 6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methylmorpholine, N- ethylmorpholine, N-cyclohexylmorpholine, N,N,N'N'-tetramethylethylenediamine, N,N,N',N'- tetraymethylbutanediamine, or -hexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2- dimethylimidazole, 1-azabicyclo[3.3.0]octane and preferably 1,4-diaza-bicyclo[2.2.-2]octane and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N- ethyldiethanolamine and dimethylethanolamine.

Suitable catalysts include tris-(dialkylamino-s-hexahydrotriazines, especially tris(N,N- dimethylaminopropyl)-s-hexahydrotriazine, tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, alkali hydroxides such as sodium hydroxide and alkali alcoholates such as sodium methylate and potassium isopropylate as well as alkali salts of long chain fatty acids with 10 to 20 carbons and optionally OH dependent groups. A particular catalyst or combination of catalysts may be chosen by one skilled in the art.

The blowing agents (c) disclosed in this invention comprises a carboxyl-terminated copolymer of diacid and alcohol wherein the diacid is preferably selected form a C4 to C12 aliphatic carboxylic diacid and the alcohol is preferably selected form a C2 to C6 diol or triol.

Suitable diacids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid, in which preferably diacid is adipic acid.

Suitable diols include ethylene glycol, 1,3- propanediol, propylene glycol, 1,4-butanediol, 1,2- butanediol, 1,3-butanediol, 1 ,5-pentanediol, 1,2-pentanediol, 1,3-pentanediol, and 1,4- pentanediol; and, suitable triols include triethanolamine, glycerin or trimethylolpropane or modifications of the before mentioned components with a low alkoxylation digress of up to 10. Preferably, the alcohol is selected from diethylene glycol and trimethylolpropane.

In various embodiments, the molecular weight of carboxyl-terminated copolymer is from 200 to 2000, preferably from 150 to 1300; and the acid number is from 50-600, preferably from 90- 600.

Acid number is determined by titration and is calculated as below,

F_n is defined as the functionality

M_n is defined as the number average of the molecular weight

The polymerization process is a conventional esterification in an excess of diacid monomers.

In further embodiments, the carboxyl-terminated copolymer could be used solo or combined with other blowing agents. The other blowing agents including physical blowing agents such as alkane (for example pentane), fluorocarbons, hydrofluoro-carbons, chlorocarbons, chlorofluorocarbons, hydrochlorofluorocarbons and chemical blowing agents such as water.

Suitable flame retardants (d) for the purposes of this invention are preferably liquid organic phosphorus compounds such as halogen-free organic phosphates such as triethyl phosphate (TEP), halogenated phosphates, for example tris (1-chloro-2-propyl) phosphate (TCPP) and tris (2-chloroethyl) phosphate (TCEP), and organic phosphonates such as dimethyl methylphosphonate (DMMP), dimethyl propane (DMPP), or solids such as ammonium polyphosphate (APP) and red phosphorus. Furthermore, as flame retardant, halogenated compounds, for example, halogenated polyols, as well as solids, such as expanded graphite and melamine are suitable.

Optionally other additives and/or auxiliaries (e) may be incorporated into the reaction mixture to produce the polyurethane foam. Examples include surface active substrates, foam stabilizers, cell regulators, fillers, dyes, pigments, hydrolysis preventing agents, fungistatic and bacteriostatic agents.

Examples of suitable surfactants are compounds which serve to support homogenization of the starting materials and may also regulate the cell structure of the plastics. Specific examples are salts of sulfonic acids, e.g., alkali metal salts or ammonium salts of fatty acids such as oleic or stearic acid, of dodecylbenzene- or dinaphthylmethanedisulfonic acid, and ricinoleic acid; foam stabilizers, such as siloxane-oxyalkylene copolymers and other organopolysiloxanes, oxyethylated alkyl-phenols, oxyethylated fatty alcohols, paraffin oils, castor oil esters, ricinoleic acid esters, Turkey red oil and groundnut oil, and cell regulators, such as paraffins, fatty alcohols, and dimethylpolysiloxanes. The surfactants are usually used in amounts of 0.01 to 5 parts by weight, based on 100 parts by weight of the polyol composition. Furthermore, the oligomeric acrylates with polyoxyalkylene and fluoroalkane side groups are also suitable for improving the emulsifying effect, the cell structure and/or for stabilizing the foam. These surface active substances are generally used in amounts of 0.01 to 5 weight percent based on the weight of the polyol composition. For the purposes of the invention, fillers are conventional organic and inorganic fillers and reinforcing agents. Specific examples are inorganic fillers, such as silicate minerals, for example, phyllosilicates such as antigorite, serpentine, hornblendes, amphiboles, chrysotile, and talc; metal oxides, such as kaolin, aluminum oxides, titanium oxides and iron oxides; metal salts, such as chalk, baryte and inorganic pigments, such as cadmium sulfide, zinc sulfide and glass, inter alia; kaolin (china clay), aluminum silicate and coprecipitates of barium sulfate and aluminum silicate, and natural and synthetic fibrous minerals, such as wollastonite, metal, and glass fibers of various lengths. Examples of suitable organic fillers are carbon black, melamine, colophony, cyclopentadienyl resins, cellulose fibers, polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, and polyester fibers based on aromatic and/or aliphatic dicarboxylic acid esters, and in particular, carbon fibers. The inorganic and organic fillers may be used individually or as mixtures and may be introduced into the polyol composition or isocyanate side in amounts of from 0.5 to 40 percent by weight, based on the weight of components (the polyols and the isocyanate).

The isocyanate component (B) in this invention includes all essentially known aliphatic, cycloaliphatic, araliphatic and preferably aromatic multivalent isocyanates. Specific examples include alkylene diisocyanates with 4 to 12 carbons in the alkylene radical such as 1,12-dodecane diisocyanate, 2-ethyl-1,4-tetramethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 1 ,4-tetramethylene diisocyanate and preferably 1,6-hexamethylene diisocyanate; cycloaliphatic diisocyanates such as 1,3- and 1,4- cyclohexane diisocyanate as well as any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate as well as the corresponding isomeric mixtures, 4,4'-2,2'-, and 2,4'-dicyclohexylmethane diisocyanate as well as the corresponding isomeric mixtures and preferably aromatic diisocyanates and polyisocyanates such as 2,4- and 2,6-toluene diisocyanate and the corresponding isomeric mixtures 4,4'-, 2,4'-, and 2,2'-diphenylmethane diisocyanate and the corresponding isomeric mixtures, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates and polyphenylenepolymethylene polyisocyanates (polymeric MDI), as well as mixtures of polymeric MDI and toluene diisocyanates. The organic di and polyisocyanates can be used individually or in the form of mixtures.

The polyurethane foams of this invention can be prepared batch wise (discontinuously) or continuously according to the prepolymer process or more preferably according to the one-shot process with the help of conventional mixing equipment. The method includes providing polyol composition (A); providing isocyanate component (B); and reacting the polyol composition (A) and the isocyanate component (B) in a weight ration of such that the isocyanate (NCO) index is from 200 to 400, preferably from 220 to 330, more preferably from 230 to 300.

In the context of the present invention the following terms have the following meaning:

1) isocyanate index or NCO index or index: the ratio of NCO-groups over isocyanate-reactive hydrogen atoms present in a formulation, given as a percentage:

[NCO] x 100 (%)/ [active hydrogen]

In other words, the NCO-index expresses the percentage of isocyanate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive hydrogen used in a formulation.

It should be observed that the isocyanate index as used herein is considered from the point of view of the actual foaming process involving the isocyanate ingredients and the isocyanate- reactive ingredients. Any isocyanate groups consumed in a preliminary step to produce modified polyisocyanates (including such isocyanate-derivatives referred to in the art as prepolymers) or any active hydrogens consumed in a preliminary step (e.g. reacted with isocyanate to produce modified polyols or polyamines) are not taken into account in the calculation of the isocyanate index. Only the free isocyanate groups and the free isocyanate-reactive hydrogens (including those of the water) present at the actual foaming stage are taken into account.

In a further aspect, the present disclosure provides a flame-retardant rigid polyurethane foam produced according to the above process. Discontinuous system will be produced in a discontinuous process with a one point or a two-point injection method and be used in applications eg. reefer container, roof panels, etc. The liquid foam needs to fill the whole mold before the gelling starts. Therefore, a system with long gel time is needed. Continuous system will be produced in a continuous process on a double conveyor belt line. The produced panel will be used eg. cold storage applications. The reactivity of this continuous process is compared with the discontinuous process much faster, because the panels need to be processed and cut in a short time.

In another further aspect, the present disclosure provides a composite comprising the flame- retardant rigid polyurethane foam produced according to the invention. The flame-retardant composite may be used as boards or panels in the application of cleanroom cold storage, reefer, roof panels, laminate and insulation boards; or as pipe insulation in the field of spray pipe applications and injection pipes.

Examples

Measuring and test methods

The measuring and test methods are shown in Table 1.

Table 1 Measuring and test standards

Moreover, the Flow property is measured as follows: Liquid foam was applied in a flow mold with the size 100cm*15cm*3cm. The liquid foam was placed at one end of the flow mold. During the reaction, the temperature in the mold was kept constantly at 57 °C for 30min. After keeping the foam in the mold for 30 min, the cured foam was removed from the mold. The average length expansion of the foam and weight of the foam is measured. Afterwards the ratio between length and weight is calculated to determine the flow in cm/g of each foam composition. Therefore, the bigger the calculated ratio the better the flowability of the liquid foam.

Materials The materials used in the examples are as follows.

Polyol 1, polyester polyol (PO based) with glycerin-EO as starter, OHv 240 Polyol 2, polyether polyol (PO based) with glycerin as starter, OHv 230 Polyol 3, polyether polyol (PO based) with sorbitol as starter, OHv 490 Polyol 4, polyether polyol (PO based) with DEG as starter, OHv 215 Acid A1 , carboxyl-terminated copolymer (esterification) of adipic acid and diethylene glycol, Acid Number 188, Mn 896

Acid A2, carboxyl-terminated copolymer (esterification) of adipic acid and trimethylolpropane (TMP550), Acid Number 240, Mn 701

PMDI, 4,4'-diphenylmethane diisocyanate (MDI) containing oligomers of high functionality and isomers, Lupranat® M 20 S from BASF

Synthesis of the Acid A1 (Two-functionality)

The chemical pathway to create this chemical is a copolymer/esterification of adipic acid and diethylene glycol. Both monomers were copolymerized in a weight ratio of adipic acid : DEG as 2:1 to make sure that all chain ends are end-capped with adipic acid. The reaction was catalyzed with 0.0025wt% of titanium butoxide (TTB). The reaction mixture was heated in a reactor slowly up to 200 °C under water separator. Afterward the temperature was maintained at 200 °C and the water separation was continued. After approximately 5 hours in total (heating and maintaining the temp at 200 °C) and after the right acid number was achieved the vacuum was released and the reaction mixture was cool down to room temperature.

Synthesis of the Acid A2 (Three-functionality)

The chemical pathway to create this chemical is a copolymer/esterification of adipic acid and trimethylolpropane (TMP550). Both monomers were copolymerized in a weight ratio of 1.433 parts of TM P550 to 1 weight part of adipic acid. The reaction was catalyzed with 0.03wt% of TTB. The reactor was fitted with a Vigreux column and a Dean-Stark type condenser to collect the condensation product. During the first half of the synthesis, the setup was continuously flushed with Nitrogen gas to limit oxidation and facilitate transport of water vapor. While stirring, the mixture was heated to 120 °C using a heating mantle. The catalyst was added when the temperature of the mixture reached 120 °C. The reaction temperature was increased stepwise to maintain distillation of the formed by-products. After 8 h at 230 °C the polymer was left to cool and discharged from the reactor.

Discontinuous system

The compositions of the discontinuous system with the ester-version of the invented blowing agent Acid A1 is show in Table 2 in the column Ex.1 and Ex. 2. In the column in Table 2 with the name Control.1 the composition of a reference system is shown.

These three compositions were used to prepare a box mold foam with the size of 40cm*40cm*9cm. During the reaction, the temperature in the mold was controlled at 60 °C for Control 1 and at 55 °C for Ex.1 and Ex. 2. 30 minutes after injecting the foam into the mold the cured foam was demolded. Table 2 Recipes and properties of discontinuous system

The NCO index is one of the major factors for a foam system to improve the fire performance of a PU foam. For the composition of Control. 1, an index of 300 was chosen to achieve a B2 value of 13 cm and a LOI value of 26.6 %. In the composition of Ex. 1 in Table 1 besides other minor changes the polymeric Acid A1 was used with 20 parts. The overall index was also 300. Therefore, the B2 value could be reduced to 8 cm and the LOI value was increased to 29.2 %. In Ex. 2 the index was reduced to 240. The resulting B2 was with 12 cm similar to the benchmark system and the LOI was with 27.4% slightly better. But for Ex. 2 the flow with a value of 0.528 cm/g could be drastically increased in comparison to the benchmark system (0.498 g/cm). In summary, with the same NCO index, the fire performance can be improved if the Acid A1 is used (Ex. 1). Furthermore, the results of Ex. 2 showed that the fire performance can be remained similar or even better while the index can be drastically decreased. Additionally, the flowability of the system (Ex. 2) shows superior performance. Moreover, the processing temperature can be reduced by 5 °C without having any drawback in terms of flow or curing of the foam.

The polyol composition (A) is stable in absence of water, if the polymeric acid is present in a range of 0 wt% to 30 wt% based on the total weight of polyol composition (A). In table 3 the mixing ratio was adjusted and additionally the NCO index was kept between 240 and 300. With increasing polymeric acid content, the index was designed to be lower. The compositions of the formulation and the related properties are summarized in Table 3.

Table 3 Recipes and properties of different Acid A1 concentrations in discontinuous system

In Ex.3 only 5 parts of Acid A1 were used. Nevertheless, the fire performance could be already improved. Furthermore, an improvement of the flow was detected.

The NCO index of the formulation Ex.3, Ex.4 and Ex5 could be gradually reduced from 273 to 240, compared to Control.1 which was 300. Even the index was dramatically reduced, the fire performance still showed a big improvement. Moreover, the flow was also improved. Continuous system

These two compositions were foamed in individual box molds with the size of 40cm*40cm*9cm. The mold temperature was 60°C. After 30min the block foams were demolded and used to test all mechanical properties. The compositions and properties of the continuous system are shown in Table 4.

Table 4: Recipes and properties of continuous system: comparison of the system with and without alternative blowing agent

Similar to the discontinuous system, the index in the continuous system could be lowered from 380 in Control.2 to 330 in Ex.6. Even the index was reduced, the fire properties remained similar. On the other hand, the flowability of the reference system was increase. Overall, the benefits in the discontinuous system are more obvious, but also in continuous system benefits like the improvement in the flow and the possibility to reach a very good fire performance at lower index can be detected. Three-functionality blowing agent Acid A2

After evaluating the two-functional blowing agent Acid A1 , three-functional Acid A2 was also evaluated. The compositions and properties are shown in Table 5. In the column Control.1 shows the composition of reference system, and the system with the three-functional blowing agent Acid A2 is shown in column Ex. 7. Both two systems are foamed in one box mold (40cm*40cm*9cm) under the mold temperature 60 °C, and the demold time is 30min. The blocks will be used to test all the mechanical properties.

Table 5 Recipes and properties of the three-functionality Acid A2

Similar with Acid A1, three-functional blowing agent Acid A2 also shows benefit on fire performance and flow.

Claims

What is claimed:

1. A polyurethane foam system consisting of:

A. a polyol composition; and

B. an isocyanate component; wherein the polyol composition (A) comprises a) polyether polyols, polyester polyols or mixtures thereof; b) catalysts; c) at least a blowing agent, wherein the blowing agent comprising a carboxyl-terminated copolymer of diacid and alcohol; d) flame retardant; e) additives and/or auxiliaries

2. The polyurethane foam system according to claim 1, wherein the polyol composition (A) includes 5 to 40 weight percent (wt. %), preferably 10 to 30 wt.%, more preferably 10 to 20 wt.% of a carboxyl-terminated copolymer of diacid and alcohol, where the wt.% values for the polyol composition are based on the total weight of the polyol composition.

3. The polyurethane foam system according to claim 1 or claim 2, wherein the diacid is a C4 to C12 aliphatic carboxylic diacid and the alcohol is a C2 to C6 diol or triol.

4. The polyurethane foam system according to any of claim 1 to claim 3, wherein the diacid is selected from oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid.

5. The polyurethane foam system according to any of claim 1 to claim 4, wherein the alcohol is selected from diols including ethylene glycol, 1 ,3- propanediol, propylene glycol, 1 ,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,3-pentanediol, and 1,4- pentanediol.

6. The polyurethane foam system according to any of claim 1 to claim 4, wherein the alcohol is selected from triols including triethanolamine, glycerin or trimethylolpropane or modifications of the before mentioned components with a low alkoxylation digress of up to 10.

7. The polyurethane foam system according to any of claim 1 to claim 6, the molecular weight of the carboxyl-terminated copolymer is from 200 to 2000, preferably from 150 to 1300.

8. The polyurethane foam system according to any of claim 1 to claim 6, the acid number of the carboxyl-terminated copolymer is from 50-600, preferably from 90-600.

9. The polyurethane foam system according to claim 1, wherein the isocyanate component

(B) is selected the group consisting of aliphatic, cycloaliphatic, araliphatic and/or aromatic isocyanates, such as tri-, tetra-, penta-, hexa-, hepta- and/or octamethylene diisocyanate, 2- methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene 1,4-diisocyanate, pentamethylene 1,5- diisocyanate, butylene 1 ,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5- isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and/or 1,3- bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and/or 2,6-diisocyanate and/or dicyclohexylmethane 4,4’-, 2,4’- and 2,2’-diisocyanate, diphenylmethane 2,2'-, 2,4‘- and/or 4,4‘-diisocyanate (MDI), polymeric MDI, naphthylene 1,5- diisocyanate (NDI), tolylene 2,4- and/or 2,6-diisocyanate (TDI), 3,3‘-dimethyl diphenyl diisocyanate, 1,2-diphenylethane diisocyanate and/or phenylene diisocyanate.

10. The polyurethane foam system according to claim 1, wherein the catalysts (b) comprises amine-based catalysts and catalysts based on organic metal compounds.

11. The polyurethane foam system according to claim 1 , wherein the blowing agent (c) further comprises other chemical blowing agents and/or physical blowing agents.

12. The polyurethane foam system according to claim 11, wherein the chemical blowing agents include water, formic acid and the physical blowing agents include pentane, HFC.

13. The polyurethane foam system according to claim 1 , wherein the flame retardant (d) comprises at least one phosphorus-containing flame retardant which is a derivative of phosphoric acid, phosphonic acid, and/or phosphinic acid.

14. The polyurethane foam system according to claim 1, wherein the component (e) comprises organosilicone surfactant.

15. A method for the production of polyurethane foam from the polyurethane foam system according to any one of claims 1-14, comprising the following steps:

- providing polyol composition (A);

- providing isocyanate component (B); and

- reacting polyol composition (A) and isocyanate component (B) in a weight ration of such that the isocyanate (NCO) index is from 200 to 400, preferably from 220 to 330, more preferably from 230 to 300

16. The method according to claim 15, wherein the production is a discontinuous system or a continuous system.

17. A flame-retardant rigid polyurethane foam produced according to claims 15 or 16.

18. The flame-retardant rigid polyurethane foam according to claim 17, wherein the foam has a LOI value of at least 26%, preferably 26% to 35%, more preferably 27% to 31% meas ured according to IS04589-2:1996.

19. The flame-retardant rigid polyurethane foam according to claim 17, wherein the foam has a flow value (cm/g) of at least 0.4 cm/g, preferably at least 0.5 cm/g.

20. A composite comprising the flame-retardant rigid polyurethane foam according to any one of claims 17-19.

21. Use of the composite of claim 20 as boards or panels in the application of cleanroom cold storage, reefer, roof panels, laminate and insulation boards; or as pipe insulation in the field of spray pipe applications and injection pipes.