WO2019043043A1

WO2019043043A1 - Process for the preparation of a polyurethane foam

Info

Publication number: WO2019043043A1
Application number: PCT/EP2018/073205
Authority: WO
Inventors: Joo-Hee KANG
Original assignee: Solvay Sa
Priority date: 2017-08-29
Filing date: 2018-08-29
Publication date: 2019-03-07
Also published as: WO2019043043A9

Abstract

The present invention relates to processes for the preparation of a polyurethane foam or a modified polyurethane foam by contacting an A-side composition comprising at least one polyol and at least one chemical compound capable of releasing a blowing agent by thermally- and/or chemically-induced decomposition with a B-side composition comprising at least one isocyanate comprising a step wherein the A-side and/or the B-side composition have a high viscosity.

Description

PROCESS FOR THE PREPARATION OF A POLYURETHANE FOAM

This application claims priority to European application No. 17188393.7 the whole content of this application being incorporated herein by reference for all purposes.

Polyurethane foams can be prepared by reacting an appropriate isocyanate with a mixture of isocyanate-reactive compounds, usually polyols, in the presence of a blowing agent. Such foams are often used as thermal insulation medium. These thermal insulating properties are dependent upon a number of factors including the cell size. Thermally insulating foams with small cell sizes have been suggested in the prior art. Theoretically, small cell sizes in the nanometer range should lead to superior insulation properties since the contribution of the gas to the thermal conductivity can be reduced ('Knudsen effect'). To this end, US9139683B2 suggests the use of supercritical or near- critical C0₂ as blowing agent. However, the handling of supercritical or near- critical is not straight-forward and could pose a risk to occupational safety.

PCT/EP2017/054302, which is incorporated by reference herein in its entirety, discloses a process for the preparation of a polyurethane foam using a chemical compound that releases a chemical and/or physical blowing agent by thermally- and/or chemically-induced decomposition wherein the chemical compound has a small particle size distribution. However, there is still a need in the industry for a process to prepare even improved polyurethane foams.

Now therefore, the invention makes available improved processes for the preparation of (modified) polyurethane foams. It is an objective of the present invention to provide a process which is safer, more economical and/or more ecological (e.g. in terms of better ozone depletion potential or global warming potential). Furthermore, it is an objective of the present invention to provide a process which leads to polyurethane foams with improved stability,

flammability, thermal insulation properties, processability, and/or cell size.

This objective and other objectives are achieved by the invention as outlined in the patent claims.

Accordingly, one aspect of the present invention concerns a process for the preparation of a polyurethane foam or a modified polyurethane foam by contacting an A-side composition comprising at least one polyol and at least one chemical compound capable of releasing a blowing agent by thermally- and/or chemically-induced decomposition with a B-side composition comprising at least one isocyanate comprising a step wherein the A-side composition has a viscosity of equal to or more than 5000 mPa-s at 25 °C and/or the B-side composition has a viscosity of equal to or more than 500 mPa-s at 25 °C.

Polyurethane foams are generally prepared by contacting two separate compositions. On the one hand, the so-called B-side, which generally consists of isocyanates or mixtures of isocyanates. On the other hand, the so-called A-side comprises all other components used in the production of the foam, notably the polyols or mixtures of polyols. This definition of the A-side and the B-side is widely followed in Europe and is also used herein. The A-side usually also comprises the blowing agents, flame retardants, catalysts, surfactants and other auxiliary agents. In a preferred embodiment the polyurethane foam is prepared by spray foaming. Spray foaming means that A-side and B-side are joined under pressure in a spray nozzle and applied directly onto the space where the insulation is required, e.g. a wall, roof or building assembly.

Blowing agents are chemical compounds which are capable of producing a cellular structure or matrix during the polyurethane foam formation.

Chemical blowing agents are known in the art. The term "chemical blowing agent" is intended to denote a blowing agent which chemically reacts with at least one of the components of the compositions used in the foam blowing process. Most specifically, water can be used as a chemical blowing agent as it forms C0₂ in the reaction with an isocyanate. The C0₂ thus formed is used to create the cellular structure in the foam. For the avoidance of doubt, the term "chemical blowing agent" as used herein is intended to mean a chemical blowing agent which is formed in the decomposition reaction of the chemical compound.

Physical blowing agents are also known in the art. The term "physical blowing agent" is intended to denote a blowing agent which generally does not react chemically with one of the components of the compositions used in the foam blowing process. Suitable physical blowing agents include carbon dioxide, carbon monoxide, nitrogen, and hydrogen. Specifically, carbon dioxide is used as a physical blowing agent. For the avoidance of doubt, the term "physical blowing agent" as used herein is intended to mean a physical blowing agent which is formed in the decomposition reaction of the chemical compound.

The term "polyurethane foam" is intended to denote polymers resulting essentially from the reaction of polyols with isocyanates. These polymers are typically obtained from formulations exhibiting an isocyanate index number from 100 to 180. The term "modified polyurethane foam" is intended to denote polymers resulting from the reaction of polyols with isocyanates that contain, in addition to urethane functional groups, other types of functional groups, in particular triisocyanuric rings formed by trimerization of isocyanates. These modified polyurethanes are normally known as polyisocyanurates (PIR). These polymers are typically obtained from formulations exhibiting an isocyanate index number from 180 to 550.

Preferably, the polyurethane and the modified polyurethane foam is a rigid, closed-cell foam.

Any isocyanate conventionally used to manufacture such foams can be used in the process according to the invention. Mention may be made, for example, of aliphatic isocyanates, such as hexamethylene diisocyanate, and aromatic isocyanates, such as tolylene diisocyanate or diphenylmethane diisocyanate.

Any polyol conventionally used to manufacture such foams can be used in the process according to the invention. The term "polyol" is intended to denote a compound containing more than one hydroxyl group in the structure, e.g. the compound may contain 2, 3, or 4 hydroxyl groups, also preferably 5 or 6 hydroxyl groups, and is intended to comprise a polyol of a single defined chemical structure as well as a mixture of polyols of different chemical structures. Preferred are synthetic polyols. Also preferred are polymeric polyols, more preferably polyester or poly ether polyols. Suitable examples for polyester polyols include polycaprolactone diol and diethylene glycol terephthalate.

Suitable examples of polyether polyols include polyethylene glycol, e.g. PEG 400, polypropylene glycol and poly(tetramethylene ether) glycol. Also preferred are polyetherpolyols based on carbohydrates, glycerine or amines. Examples for suitable carbohydrate bases include sucrose and sorbitol. Most preferred are brominated polyether glycols, e.g. polyetherpolyol B 350 (CAS-No.: 68441-62- 3). Especially suitable is the mixture of polyetherpolyol B 350 and triethyl phosphate, which can be obtained under the brand name IXOL® B 251 from Solvay.

"Viscosity" as used in this invention is intended to denote the dynamic viscosity of a fluid, i.e. its resistance to shearing flows, and is expressed in the unit mPa-s as measured at a temperature of 25 °C. The viscosity is determined according to the standard ISO 3219:1993 "Polymers/resins in the liquid state or as emulsions or dispersions - Determination of viscosity using a rotational viscometer with defined shear rate" and can be measured on a RheolabQC from Anton Paar.

It has now been surprisingly found that using an A-side and/or a B-side composition with rather high viscosity improves the preparation of the

(modified) polyurethane foams. For example, polyurethane foams with an improved cell size can be produced. Without being bound to a theory it is believed that the high viscosities of the compositions partially suppress the coalescence of the gas bubbles formed in the preparation of the (modified) polyurethane foams. Especially when using NaHC0₃ with a small particle size distribution, which is a specifically preferred embodiment of the invention, advantageous foams with small cell sizes can be produced.

Preferably, the A-side composition has a viscosity of equal to or more than 7500 mPa^»s at 25 °C, more preferably equal to or more than 10000 mPa^»s at 25 °C, most preferably equal to or more than 20000 mPa^»s at 25 °C. The upper limit of the viscosity of the A-side composition is preferably 75,000, more preferably 50,000 mPa's.

Preferably, the B-side composition has a viscosity of equal to or more than 750 mPa^»s at 25 °C, more preferably equal to or more than 1000 mPa^»s at 25 °C, most preferably equal to or more than 2000 mPa^»s at 25 °C. The upper limit of the viscosity of the A-side composition is preferably 7500, more preferably 5000 mPa^»s.

Preferably, the A-side composition has a viscosity of equal to or more than 5000 mPa^»s at 25 °C. Such A-side compositions can be achieved using inter alia by using polyols or mixtures of polyols with a high viscosity. Examples of such high- viscosity polyols include polyester polyols like the Stepanpol® range PS 2022, 2520, 3021, 3024, 3422 and 3524 and mixtures thereof; as well as polyether polyols like the Desmophen® range 1240N, 1431, T460 and 2200B and mixtures thereof; Tercarol® 5902 and 5903; Voranol® 490, 446, 520 and 800, Specflex® NC701, Daltolac® R130, R475, R492 and R180; as well as Lupranol® 3508/1 3423 and 3504 and mixtures of the above polyols. More preferably, the A-side composition comprises a mixture of at least one polyester and at least one poly ether polyol.

Also preferably, a viscosity enhancer can be present in the A-side to improve its viscosity. Viscosity enhancers are preferably used in a range from 0.5 wt% to 5 wt% based on the weight of the A-side composition. Suitable examples of viscosity enhancers include natural hydrocolloids like acacia, tragacanth, alginic acid, carrageenan, locust bean gum, guar gum or gelatin, semisynthetic hydrocolloids like methylcellulose or sodium

carboxymethylcellulose, synthetic hydrocolloids like carbopol®, and clays like bentonite or Veegum®. Other suitable examples of viscosity enhancers include cross-linked polyacrylic acid copolymers, polyhydroxycarboxylic acid amides, modified ureas, and aminoplast polyethylene glycols.

Also preferably, the viscosity of the A-side is improved by using pre- polymers obtained by reacting suitable polyols with 0.5 wt% to 25 wt%, preferably 5 wt% to 15 wt%, of a suitable isocyanate. More preferably, a polyol mixture of the prior art can be reacted with 10 wt% methylene diphenyl diisocyanate (MDI) and used to prepare the complete A-side composition.

In another preferred embodiment, the B-side composition has a viscosity of equal to or more than 500 mPa-s at 25 °C. To this end, a pre-polymer is preferably used - either alone or in a mixture with other isocyanates - as the B- side compositions. "Pre-polymer" is intended to denote a monomer or system of monomers that have been reacted to an intermediate molecular mass state and still terminate with a isocyanate functionality. Such systems show a reduced percentage of NCO functionalities by weight (%NCO) as compared to non- modified isocyanates. The preferred pre-polymer according to this invention have a %NCO of 5 to 30 wt% based on the mass of the B-side composition, more preferably 10 to 25 wt%. Examples of suitable pre-polymers include

Lupranate® 5030 and MP 111/1, Suprasec® 9612, Rubinate® 1234, Echelon® MP 103, Vorastar® HB6045, Isonate® 240 and Hyper last® LP5605 as well as mixtures thereof. Optionally, at least one further component selected from a flame retardant, a foam stabilizer, a catalyst, a surfactant and a co-blowing agent can be added to the B-side or preferably, to the A-Side. The co-blowing agent can be selected from the chemical and/or physical blowing agents as described above.

"Chemical co-blowing agent" as used in this invention is intended to denote a component comprised in the A-side which can react with the isocyanate of the B-side. It is believed that the energy released from this reaction in form of heat is accelerating the further foam producing process. Preferable chemical co- blowing agents include water, NH₃, primary amines, secondary amines, alcohols, preferably difunctional or trifunctional alcohols; hydroxylamine, and

aminoalcohols. Especially preferred are bifunctional or multifunctional amines, glycols or glycerols. Suitable examples include diaminoethane, 1,3- diaminopropane and triethanolamine.

Preferable physical co-blowing agents comprise alkanes, e.g. propane or cyclopropane, fluorinated alkanes (HFCs) as well as fluorinated alkenes (HFOs). Regarding HFCs and HFOs, mention may be made, for example, of 1,1, 1,3,3- pentafluorobutane (HFC 365mfc), 1,1,1,2-tetrafluoroethane (HFC- 134a),

1,1,1,2,3,3,3-heptafluoropropane (HFC 227ea), 1,1,1,3,3-pentafluorpropane (HFC 245fa), halogenated olefins like HFO-1234yf, HFO-1234zr and HFO- 1233zd, or mixtures of said alkanes and alkenes.

In case a co-blowing agent is used, it is preferably used in a range of 1 to 20 wt%, more preferably 2 to 10 wt%, most preferably 3 to 7 wt%, based on the total weight of the A-side.

Any flame retardant conventionally used in the manufacture of such foams can be used. Mention may be made, for example, of flame retardants based on phosphorous esters. Suitable examples include triethylphosphat (TEP), tris(2- chlorisopropyl)phosphate (TCPP), dimethylpropane phosphonate (DMPP), diethylethane phosphonate (DEEP)triethyl phosphate, trischloroisopropyl phosphate . In practice, the amount of flame retardant used generally varies from approximately 0.05 to 50 parts by weight per 100 parts by weight of polyol, preferably 1 to 25, more preferably 10 to 20.

Suitable catalysts include compounds that catalyse the formation of the

-NH-CO-O- urethane bond by reaction between a polyol and an isocyanate or that activate the reaction between an isocyanate and water, such as tertiary amines and organic tin, iron, mercury or lead compounds. Mention may in particular by made, as tertiary amines, of triethylamine,

Ν,Ν-dimethylcyclohexylamine, N-methylmorpholine, N-ethylmorpholine, dimethylethanolamine, diaza[2.2.2]bicyclooctane (triethylenediamine) and substituted benzylamines, such as Ν,Ν-dimethylbenzylamine, and

N,N,N',N",N"-pentamethyldiethylenetriamine (PMDTA). Mention may in particular be made, as organic tin or lead compounds, of dibutyltin dilaurate, stannous octanoate and lead octanoate. Other suitable catalysts intended for the manufacture of modified polyurethane (polyisocyanurate) foams include compounds that catalyse the trimerization of isocyanates to triisocyanurates.

In practice, the amount of catalyst used generally varies from

approximately 0.05 to 10 parts by weight per 100 parts by weight of polyol. In general, the amount of the composition according to the invention is from 1 to 80 parts by weight per 100 parts by weight of polyol. It is preferably from 10 to 60 parts by weight per 100 parts by weight of polyol.

Any foam stabilizer conventionally used in the manufacture of such foams can be used. Mention may be made, for example, of siloxane polyether copolymers. In practice, the amount of foam stabilizer used generally varies from approximately 0.05 to 10 parts by weight per 100 parts by weight of polyol, preferably 0.5 to 3.0, more preferably 1 to 2.

The term "thermally-induced decomposition" is intended to denote the decomposition of the chemical compound which is mainly affected by exposing the chemical compound to an elevated temperature. Preferably, the elevated temperature is a result of the exothermic chemical reactions involved in the formation of the foam, e.g. a result of the reaction of an isocyanate with a polyol. Also preferably, the elevated temperature is supplied by an external energy source, more preferably by pre-heating any or all of the components of the A- or B-side or of the equipment used in the foaming process. "Elevated temperature" is intended to denote a temperature which is above ambient temperature. Suitable temperatures are from 30 to 100 °C, preferably from 40 to 90 °C, more preferably from 50 to 80 °C. A specific example of a thermally-induced decomposition is the decomposition of sodium bicarbonate (NaHC03). In this case, the elevated temperature is above the decomposition temperature of sodium bicarbonate, which is 50 °C.

Preferably, the chemical compound releases the chemical and/or physical blowing agent by thermally- induced decomposition. More preferably the chemical compound releases the chemical and/or physical blowing agent by thermally- induced decomposition in the absence of an acidic activator. In a preferred embodiment, the A-side or the B-side or both A-side and B-side may be pre-heated before the production of the foam. They may be pre-heated to a temperature of from 25 °C to about 80 °C, preferably from 30 °C to 60 °C, more preferably from 40 to 50 °C. Said pre-heating step may be conducted in the storage tank containing the A- and/or B-side. It may also be conducted in the lines from the storage tank to the point of mixing the A- and B-side. Said mixing is conventionally conducted using a mixing head. Alternatively, the mixing head itself may be heated to pre-heat the A and/or B-side immediately before the mixing step. If the foam production is performed by a spray foaming process the spray nozzle itself may be heated.

The term "chemically-induced decomposition" is intended to denote a decomposition of the chemical compound which is mainly affected by the chemical reaction of the chemical compound with an activator, preferably with a basic or acidic activator. Suitable acidic activators include Bronsted acids, for example carboxylic acids, specifically phosphoric acid, citric acid, acidic acid and formic acid. Also preferably, the acidic activator can be formed in situ during the foaming process. A suitable example is acetic acid which can be formed in situ from acidic anhydride by reaction with water. In a more preferred embodiment, NaHC0₃ is used in combination with phosphoric acid.

Preferably, the chemical compound releases the chemical and/or physical blowing agent by chemically- induced decomposition, more preferably in the presence of an acidic activator, most preferably in the presence of citric acid, acetic acid, polyphosphoric acid, phosphoric acid and/or formic acid. Also preferably, the acid activator is a dicarboxylic acid, e.g. oxalic acid, malonic acid, succinic acid, glutaric acid or adipic acid. The acid activator is preferably comprised in the A- side. In another preferred embodiment for spray foaming, the acid activator is added via a third line to the spraying nozzle simultaneously during the spray foaming process.

Also preferably, the chemical compound releases both a chemical and a physical blowing agent. More preferably, the chemical compound releases both a chemical and a physical blowing agent by thermally- induced decomposition.

Preferably, the chemical compound is an inorganic carbonate. Suitable inorganic carbonates include NaHC0₃, Na₂C0₃, CaC0₃, (NH₄)₂C0₃, NH₄HC0₃, MgC0₃ and trona. In a specific embodiment of this invention, the chemical compound is NaHC0₃.

Also preferably, the chemical compound is a hydrate of an inorganic salt, more preferably the hydrate of a salt of an alkaline metal or an alkaline earth metal, most preferably the chemical compound is a hydrate of sodium sulphate, specifically Na₂S0₄- 10 H₂0.

Preferably, the chemical compound, specifically the NaHC0₃, has a particle size distribution expressed as a D50 of equal to or less than 1000 nm, preferably equal or below 500 nm, more preferably equal to or below 250 nm, specifically equal to or below 100 nm. Also preferably, the chemical compound has a particle size distribution expressed as a D50 of equal to or above 10 nm, preferably equal to or above 50 nm, more preferably equal to or above 100 nm. Also preferably, the particle size distribution expressed as a D50 is equal to or higher than 1 nm, preferably equal to or higher than 10 nm. More preferable is from 25 to 250 nm, most preferably from 100 to and 200 nm. Specifically, from 60 to 100 nm. In a specific embodiment, the chemical compound is NaHC0₃ with a particle size distribution expressed as a D50 between 10 and 100 nm.

The particle size distribution according to the present invention is given as a D50 value meaning that 50% of a sample's mass is comprised of particles smaller than the given value. The particle size distribution can be measured using a Laser Diffraction Particle Size Analyser (Beckmann Coulter® LS 230). The sample is added to the instrument where it is added to an isopropanol medium at room temperature.

Chemical compounds with a particle size distribution in the inventive range are commercially available. Alternatively, they can be prepared, for example by controlled precipitation from suitable starting materials. For example, NaHC0₃ with a suitable particle size distribution can be precipitated from a saturated solution of sodium chloride by addition of ammonium bicarbonate, filtrated and collected.

Chemical compounds with a particle size distribution in the inventive range can also be prepared by reducing the particle size of the chemical compound. Preferably, this reduction in particle size is performed in a mill. A particularly suitable mill is a ball mill, also called planetary mill, bead mill or pearl mill. Thus, a loose solid grinding medium is agitated together with the chemical compound to achieve a milling and/or grinding effect. Suitably, the solid grinding medium comprises hard objects made for example of flint, steel, glass or ceramic, e.g. zirconia. The shape of the grinding medium may vary and can be selected for example from a sphere, an ovoid, a polyhedron, or a torus. A sphere is especially suitable. In case of a sphere, the size of the grinding medium is from 0.01 to 1.00 mm, preferably between 0.03 to 0.10 mm, more preferably around 0.05 mm.

The particle size of the chemical compound can also be reduced by co- milling. Thus, the chemical compound is subjected to a milling step in the presence of co-grinding agent, preferably a co-grinding agent having a greater hardness than the chemical compound. The term "hardness" refers to the hardness according to the Mohs scale. Suitable examples for co-grinding agents include silica, sand, zeolithes, and oxides of metals, preferably alkaline metals or alkaline earth metals, such as Ce0₂, Zr0₂, MgO or ZnO. The co-milling can be performed according to the procedures as disclosed in US5466470. The co- milling agent can preferably also be a chemical compound capable of releasing a chemical and/or physical blowing agent. In a suitable example, a mixture of NaHC0₃ and NaS0₄ - 10H₂O can be co-milled. The co-milling step is most preferably conducted in a ball mill.

Also preferably, the particle size of the chemical compound can be reduced after suspending it in either the B-side or in at least one component of the B-side, e.g. in an isocyanate or a mixture of isocyanates used in the foam blowing process. More preferably, the particle size of the chemical compound can be reduced after suspending it in either the A-side or in at least one component of the A-side, e.g. in at least one polyol used in the foam blowing process. Also preferably, the particle size of the chemical compound can be reduced after suspending it in at least one flame retardant, e.g. in triethyl phosphate and/or trischloroisopropyl phosphate. Accordingly, this more preferred embodiment is a process comprising the steps of

al) preparing a suspension comprising the chemical compound and at least one polyol or at least one flame retardant or a mixture thereof,

a2) subjecting the suspension formed in step al) to a treatment to reduce the particle size distribution of the chemical compound, and

b) contacting the suspension formed in step a2) with a composition comprising at least one isocyanate to prepare a polyurethane foam wherein a chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μιη.

Preferably, the treatment to reduce the particle size distribution comprises a milling step, more preferably a milling step using a ball mill. Also preferably, the treatment to reduce the particle size distribution comprises a sonication treatment step.

Also preferably, the treatment to reduce the particle size distribution comprises a simultaneous milling and sonication treatment step.

In a further preferred embodiment of the process according to the invention, the particle size of the chemical compound, specifically of the NaHCC"3, is reduced by milling in a milling solvent. The term "milling solvent" is intended to denote a solvent in which the chemical compound is subjected to a milling step and which is removed before the chemical compound is used for the foam production. The boiling point of said milling solvent is preferably between 50 and 150 °C, more preferably between 60 and 120 °C. Examples of suitable milling solvents include alcohols, water, hydrocarbons, hydro fluorocarbons, and chlorinated hydrocarbons. Preferably, the alcohol is ethanol, propanol, isopropanol, isobutanol. Also preferred milling solvents are perfluoropolyethers, especially the Galden® product range from Solvay Fluor GmbH, specifically Galden® HT55.

The concentration of the chemical compound, specifically the NaHCC"3, in the milling solvent is between 10 and 70 wt%, preferably, 20 to 50 wt%, and more preferably between 30 and 40 wt%.

In a preferred embodiment, the milling step is performed in the presence of a surfactant. Not to be bound by a theory, it is believed that the surfactant avoids the agglomeration and/or aggregation of the chemical compound.

"Surfactant" shall denote organic compounds that are amphiphilic, meaning they contain both a hydrophobic group and a hydrophilic group.

Examples of suitable non-ionic surfactants include without limitation linear alcohol ethoxylates, polyoxy ethylene alkylphenol ethoxylates, polyoxy ethylene alcohol ethoxylates, polyoxy ethylene esters of fatty acids, polyoxy ethylene alkylamines, alkyl polyglucosides, ethylene oxide-propylene oxide copolymers or a combination thereof.

Examples of suitable cationic surfactants include without limitation quaternary ammonium salts, ethoxylated quaternary ammonium salts, or a combination thereof. A preferred cationic surfactant may have a carbon chain length of 8-20 carbon atoms.

Surfactants having phosphate, carboxylate, sulphonate or sulphate groups as hydrophilic groups are preferred. Also preferred are surfactants having polyether or polyester based side chains as hydrophobic groups are preferred. Preferred polyether based side chains have 3 to 50, preferably 3 to 40, in particular 3 to 30 alkyleneoxygroups. The alkyleneoxygroups are preferably selected from the group consisting of methyleneoxy, ehtyleneoxy, propyleneoxy and butyleneoxy groups. The length of the polyether based side chains is generally from 3 to 100, preferably from 10 to 80 nm.

Suitable examples of such surfactants are represented by phosphoric acid derivatives in which one oxygen atom of the P(O) group is substituted by a C3- C10 alkyl or alkenyl radical.

The surfactant may be, for example, a phosphoric diester having a polyether or polyester based side chain and an alkenyl group moieties. Alkenyl groups with 4 to 12, in particular 4 to 6 carbon atoms are highly suitable.

Especially preferred are phosphoric esters with polyether/polyester side chains, phosphoric ester salts with polyether/alkyl side chains and surfactants having a deflocculating effect, based for example on high molecular mass copolymers with groups processing pigment affinity.

The milling solvent is removed after the milling step and a suspension of the chemical compound in the A-side or at least one component of the A-side is prepared, i.e. an exchange of the suspension medium is performed. This exchange can be performed by conventional means, e.g. using a rotary evaporator.

According to this preferred embodiment, the treatment to reduce the particle size distribution comprises the following steps:

ml) preparing a suspension of the chemical compound, specifically NaHCC"3, in a milling solvent,

m2) subjecting the suspension formed in step ml) to a treatment to reduce the particle size distribution of the chemical compound, specifically a milling step,

m3) removing the milling solvent by evaporation and/or filtration m4) preparing a suspension of the chemical compound, specifically NaHCC"3, formed in step m3) in the A-side or in one or several components of the A-side, and

m5) contacting the suspension formed in step m4) with a composition comprising at least one isocyanate to prepare a polyurethane foam wherein a chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μιη. Another aspect of the present invention concerns a (modified) polyurethane foam obtainable by the inventive process as outlined above. Preferably, said foam comprises cells with an average cell size measured according to ASTM D 3576 from 10 nm to 1 μιη, preferably from 50 nm to 500 nm, more preferably from 100 nm to 250 nm. The polyurethane or modified polyurethane foam according to the invention is preferably a rigid closed-cell foam. The

polyurethane or modified polyurethane foam can also be selected from a flexible or semi-flexible foam, e.g. for the production of show soles or for padding of saddles, or integral skin foam.

A further aspect of the present invention is an A-side composition with a viscosity of equal to or more than 5000 mPa^»s at 25 °C comprising at least one polyol and at least one chemical compound capable of releasing a blowing agent by thermally- and/or chemically-induced decomposition. Preferably, the chemical compound is NaHC0₃, and more preferably, the NaHC0₃ has a particle size distribution expressed as a D50 of equal to or less than 250 nm, specifically between 100 and 200 nm.

Preferably, the polyurethane foam or modified polyurethane foam is produced by spray foaming. Also preferably, the inventive process is used to produce discontinuous or continuous panels, tubes for pipe insulation, sandwich panels, laminates and block foams. Also preferably, the inventive foam is used for noise cancellation. Still another aspect of the present invention concerns a composition comprising at least one polyol and a chemical compound capable of releasing a chemical and/or physical blowing agent by thermally- and/or chemically- induced degradation wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μιη as well as the use of such compositions in the preparation of a polyurethane or modified polyurethane foam.

The improved process for the preparation of (modified) polyurethane foams according to the present is a process which can be safer, more economical and/or more ecological (e.g. in terms of better ozone depletion potential or global warming potential). Without wanting to be bound to a particular theory, it is assumed that making (modified) polyurethane foams departing from A- and B- side according to the present invention the polymeric matrix exhibits less flexibility and a low surface tension in the foam matrix during the foaming step which can prevent cell coalescence and can lead to a better control of the action of the blowing agent, for example the steepness of the decomposition of the inorganic carbonate, preferably NaHC0₃. The obtained polyurethane foams show improved stability, flammability, thermal insulation properties, processability, and/or cell size.

The thermal conductivity of the inventive foams can be measured using the norm "EN 12667: Thermal performance of building materials and products" by means of a guarded hot plate and a heat flow meter.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The examples hereafter are intended to illustrate the invention in a non- limitative manner.

Examples:

Example 1: Preparation of polyol mixture

12 wt% NaHC0₃ (Bicar® from Solvay) is dispersed in a polyol mixture comprising 50.0 g Stepanol® 3524 and 50.0 g Deltolac® R130 by using a PENDRAULIK overhead dissolver at 10000 rpm for 30 min. Subsequently, the resulting mixture was subjected to a milling step in a bead mill DISPERMAT® SL-C 25 (manufacturer: VMA-Getzmann GmbH) using Zr02 beads (diameter: 0.5 mm) at 200 rpm for 12.5 h. Subsequently, the mixture was subjected to a sonication step for 1 h.

The particle size distribution of the NaHC0₃ in the resulting suspension was measured as described above and showed a D50 of 0.85 μιη.

Table 1 shows the D50 values achieved with various milling times and optional sonication (1 h). This mixture can be used to prepare the A- side composition by adding the other components of the A-side as required and mixing by

conventional means. Conditions D50 (μηι)

Bicar®, initial 10.5

Milling 5.5 h 4.1

Milling 5.5 h

2.4

& sonication

Milling 12.5 h 1.8

Milling 12.5 h

0.85

& sonication

Table 1

Example lb: Preparation of the Aside with milling solvent

NaHC0₃ (Bicar® from Solvay) is dispersed in Galden® HT55 by using a PENDRAULIK overhead dissolver at 3000 rpm for 1 hour to give 10 kg of a slurry containing 40 wt% NaHC0₃. The suspension is grinded by ball milling (Netzsch Zeta® RS) with Zr0₂ beads (diameter around 0.1 mm). The particle size distribution expressed as a D50 achieved in this step is from 50 to 150 nm depending on the total milling energy. The slurry is then evaporated on a rotary evaporator and the solid obtained is re-dispersed in a polyol mixture comprising 50.0 g Stepanol® 3524 and 50.0 g Deltolac® R130 by using a PENDRAULIK overhead dissolver at 10000 rpm for 30 min. Afterwards other components of the A-side are added to this polyol/NaHC0₃ mixture.

Example 2: Manufacture of polyurethane foams (PU panel)

The polyol suspension from Example lb is used to prepare a polyurethane foam using the components as shown in the table below:

^represents as parts per hundred of polyols by weight 100 g of the polyol/NaHC03 mixture prepared in example lb and the flame retardant are stirred using a PENDRAULIK overhead dissolver in a 500 mL paper cup. Subsequently, MDI is added and stirring continued at 2500 rpm for 10 s after which the mixture looks uniform and bubbles start to appear. After the stirrer is stopped, the mixture is poured into a 1 L paper cup to allow the foam to expand and cure for at least one day. The foam obtained can be used to prepare discontinuous panels.

In an alternative inventive example, 5.5 pbw of phosphoric acid is added simultaneously from a separate line to the paper cup.

Example 3: Spray foaming

A polyurethane foam (spray foam) was prepared by conventional means using the components as shown in the table below.

^represents as parts per hundred of polyols by weight

Polyol, chemical compound and flame retardant are blended to form the A- side composition. Preparation of the spray- foam is achieved by contacting this with the B-side composition in a conventional spray-foaming gun.

In an alternative inventive example, 5.5 pbw of phosphoric acid is added simultaneously from a separate line using a three-way spraying gun. Example 4: Use of pre-polymers (polyols terminate with isocyanate

functionality) with 5-25% of%NCO

Example 4a:

Polyurethane foam was prepared using the components as shown in

below:

* optional

Polyol, blowing agent and flame retardant were stirred using a PENDRAULIK overhead dissolver in a 500 mL paper cup. Subsequently, optionally additive 1 or 2 and pre-polymer heated at 60-90 °C were added and stirring continued at 25000 rpm for <5 s after which the mixture looked uniform and bubbles started to appear. After the stirrer was stopped, the mixture was poured into a 1 L paper cup to allow the foam to expand and cure for at least one day. The foam obtained can be used to prepare panels and spray foams.

For closed cell content (80-90%) and average cell size (10-50 micron), the trend showed a clear improved value by using pre-polymer.

Example 4b:

Polyurethane foam was prepared using the components as shown in the table below:

Compound Type Part by weight (pbw)

Stepanpol PS2352 poly ether polyol 60

Daltolac R130 Polyether polyol 40

Nano-sized NaHC0₃ blowing agent 4

TCPP flame retardant 11

PMDETA catalyst 0.4 Silstab 2100 surfactant 2

Water Co-blowing agent 2

Desmodur PF pre-polymer 210

Polyol, blowing agent, catalyst, surfactant and flame retardant were stirred using a PENDRAULIK overhead dissolver in a 500 mL paper cup. Subsequently, pre- polymer heated at 60-90 °C was added and stirring continued at 25000 rpm for <5 s after which the mixture looked uniform and bubbles start to appear. After the stirrer was stopped, the mixture was poured into a 1 L paper cup to allow the foam to expand and cure for at least one day. The foam density of the foam obtained was 49.5 kg/m3, which is comparable to the theoretical density (54 kg/m3). The closed cell content was 85 %. The cell size was estimated to 10-50 micron (A), which is much smaller and thus more advantageous than the cell size (-300 micron) for the foam prepared by using Lupranat® M 20 S instead of Desmodur PF (B).

Claims

C L A I M S

1. A process for the preparation of a polyurethane foam or a modified polyurethane foam by contacting an A-side composition comprising at least one polyol and at least one chemical compound capable of releasing a blowing agent by thermally- and/or chemically-induced decomposition with a B-side composition comprising at least one isocyanate comprising a step wherein the A- side composition has a viscosity of equal to or more than 5000 mPa-s at 25 °C and/or the B-side composition has a viscosity of equal to or more than 500 mPa-s at 25 °C.

2. The process according to claim 1 wherein the chemical compound is an inorganic carbonate, preferably the chemical compound is NaHC0₃.

3. The process according to claim 1 or 2 wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μιη, preferably equal or below 500 nm, more preferably equal to or below 250 nm, specifically between 100 and 200 nm.

4. The process according to any one of claims 1 to 3 wherein the chemical compound releases the chemical and/or physical blowing agent by thermally- induced decomposition, preferably in the absence of an acidic activator.

5. The process according to any one of claims 1 to 3 wherein the chemical compound releases the chemical and/or physical blowing agent by chemically- induced decomposition, preferably in the presence of an acidic activator, more preferably in the presence of citric acid, formic acid, phosphoric acid or a mixture thereof.

6. The process according to any one of claims 1 to 5 wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or above 10 nm, preferably equal to or above 50 nm, more preferably equal to or above 100 nm.

7. The process according to any one of claims 1 to 6 wherein the A-side composition has a viscosity of equal to or more than 7500 mPa-s at 25 °C, preferably equal to or more than 10000 mPa-s at 25 °C, more preferably equal to or more than 20000 mPa-s at 25 °C.

8. The process according to any one of claims 1 to 7 wherein the B-side composition has a viscosity of equal to or more than 750 mPa-s at 25 °C, preferably equal to or more than 1000 mPa-s at 25 °C, more preferably equal to or more than 2000 mPa-s at 25 °C.

9. The process according to any one of claims 1 to 8 wherein the B-side comprises a prepolymer formed by a reaction of an isocyanate with a polyol with a %NCO of equal to or less than 25%, preferably from 5% to 20%.

10. The process according to any one of claims 1 to 9 comprising the steps of

a) preparing the A-side composition by suspending the chemical compound in at least one polyol, and

b) contacting the A side composition formed in step a) with the B- side composition comprising at least one isocyanate to prepare a polyurethane foam wherein the chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μιη.

11. The process according to any one of claims 1 to 9 comprising the steps of

ml) preparing a suspension comprising the chemical compound, specifically NaHC0₃, and a milling solvent, m2) subjecting the suspension formed in step ml) to a treatment to reduce the particle size distribution of the chemical compound, specifically a milling step, m3) separating the chemical compound from the milling solvent m4) preparing the A-side composition by suspension of the chemical compound, specifically NaHC0₃, formed in step m3) in the at least one polyol and/in in at least one other component of the A-side, and m5) contacting the A-side composition formed in step m4) with the B- side composition comprising at least one isocyanate to prepare a polyurethane foam wherein the chemical compound releases a chemical and/or physical blowing agent under thermal and/or chemical activation and wherein the chemical compound has a particle size distribution expressed as a D50 of equal to or less than 1 μιη.

12. The process according to claim 11 wherein the treatment to reduce the particle size distribution comprises a milling step, preferably a ball milling step.

13. A polyurethane foam or a modified polyurethane foam obtainable by the process of any one of claims 1 to 12.

14. An A-side composition with a viscosity of equal to or more than 5000 mPa-s at 25 °C comprising at least one polyol and at least one chemical compound capable of releasing a blowing agent by thermally- and/or chemically- induced decomposition.

15. The A-side composition of claim 14 wherein the chemical compound is NaHC03.