WO2022029237A1

WO2022029237A1 - Method for obtaining an oxygen curable composition using a borane compound as oxygen scavenger

Info

Publication number: WO2022029237A1
Application number: PCT/EP2021/071888
Authority: WO
Inventors: Astère DE SCHRIJVER; Kevin HUVAERE; George Georgiev
Original assignee: Greenseal Nv
Priority date: 2020-08-05
Filing date: 2021-08-05
Publication date: 2022-02-10

Abstract

The present application generally relates to the use of a borane compound as an oxygen scavenger. In particular, the present application provides a novel oxygen curable polymerizable composition for use as a foam, sealant or adhesive, particularly which can be used in 1K aerosol can systems for forming a foam, comprising a reactive precursor mixture and a borane compound as oxygen scavenger so that it will not react during storage, and an alkyl metal compound, such as an organoborane compound as initiator. Advantageously, the reactive precursor mixture is not subject to additional deoxygenation measures, such as degassing or flushing with an inert, oxygen free gas. In particular, as the initiation of the polymerization is enabled by oxygen, particularly oxygen from ambient air, the curing of the composition is not dependent on ambient moisture and proceeds even at low temperatures, below 0°C. Advantageously, the compositions of the present invention have a fast curing time when contacted with oxygen or air, and the resulting final cured product has a high quality.

Description

METHOD FOR OBTAINING AN OXYGEN CURABLE COMPOSITION USING A BORANE COMPOUND AS OXYGEN SCAVENGER

FIELD OF THE INVENTION

The present invention relates to methods to prepare an oxygen-curable composition, particularly suitable for use as a one component (1C) foam, adhesive or sealant composition. The present invention further provides one component, oxygen curable compositions and containers comprising such composition.

BACKGROUND

In single component or one component foams, sealants or adhesives, the reactive components are premixed in their final proportions. However, they are chemically blocked and they will not cure, i.e. polymerize and/or crosslink, as long as they are not subject to the specific conditions which activate the curing mechanism. Several means to initiate the curing mechanism are known.

For instance, a polyurethane (PU) foam, comprising a mixture of polyols, diisocyanates, liquefied gases as blowing agents, and several additives, are cured by the reaction of the isocyanate terminated prepolymers with ambient moisture upon spraying. A first issue with such moisture curable formulations is that curing is triggered by the moisture present in the ambient air. This means that their crosslinking rates can vary from a rainy day to a sunny day, from generally humid regions to generally dry regions, and that such PU foams can even be useless in particularly dry atmospheres as can be encountered in continental or (semi-)desert climates. A second, quite major disadvantage of PU foam compositions is that isocyanates are toxic. Methylene Diphenyl Diisocyanate (MDI) is the isocyanate most commonly used in the production of PU foams. This compound, although the least hazardous of the isocyanate groups, is still toxic, harmful by inhalation or ingestion, and also via skin contact. In addition, the compound is flammable and can also be explosive. Repeated exposure, for example by professionals, is known to trigger sensitization and respiratory conditions. This is a growing safety concern for end users and regulations have been issued including safety labelling, strict disposal of emptied cans as hazardous waste, and an upper limit on the acceptable free monomeric isocyanate level. In addition, the EU is asking OCF manufacturers to reach < 1% w/w unreacted and free crude MDI in PU formulations, with some member states imposing even stricter control of MDI levels. One alternative to meet with these regulations is the distillation of the free monomeric isocyanate from the prepolymer isocyanate, but this has a significant practical and cost impact. Another technology to control levels of monomeric isocyanates includes blocking of the free isocyanate functionalities with a protecting group that is removed prior to curing. The deprotection step requires heating to release the protective group and is less suitable for an aerosol-contained formulation.

Many compounds comprising vinyl functional groups, such as for instance acrylates and methacrylates, are polymerizable by free-radicals, wherein a polymer is formed by the successive addition of free-radical building blocks. Typically, specific initiator molecules are involved in the formation of the free radicals. Since compositions comprising free-radically polymerizable compounds and initiator compounds are typically spontaneously reactive, it is common practice to provide them as a two-part system such as, for example, a part A and a part B that are combined immediately prior to use.

There thus remains a need for methods to obtain one component free-radically polymerizable compositions, such as for foam, sealant or adhesive applications, and for the corresponding one component free-radically polymerizable compositions. In particular, there remains a need for foam compositions suitable for being dispensed via pressurized containers, which are isocyanate free, which can be cured independent from moisture and under a wide range of temperatures, and which yield high quality products upon dispensing from the pressurized container.

SUMMARY OF THE INVENTION

Surprisingly, the inventors have found that borane compounds, such as BH3 or B2H6, are very efficient oxygen scavengers, particularly in viscous, oxygen-curable polymerizable compositions, such as for use in foam, sealant or adhesive application. More in particular, the inventors have developed methods for reducing, eliminating or controlling the oxygen content of a mixture, particularly of an oxygen-curable precursor mixture, comprising adding a borane compound as an oxygen scavenger to the mixture, particularly the oxygen-curable precursor mixture. The inventors have further developed methods to obtain a viscous, one component, oxygen-curable polymerizable compositions, such as for use as a foam, sealant or adhesive, comprising a reactive precursor mixture, a borane compound as oxygen scavenger and an oxygen sensitive initiator compound, wherein the initiation of the polymerization is enabled by oxygen, particularly oxygen from ambient air. Advantageously, said composition when stored in a container, such as a pressurized container, has a long shelf-life, even in the absence of physical deoxygenation treatments (such as degassing or flushing with inert gas): the reactive precursors and the oxygen sensitive curing initiator compound may be mixed and stored without polymerization due to the borane compound as oxygen scavenger, until the composition is brought into contact with air and is subsequently rapidly cured. The polymerizable composition, such as when contained in a pressurized container for foam applications, is essentially oxygen free due to the presence of the borane compound and will not react during storage, even though the oxygen sensitive radical initiator and the reactive precursor mix are in contact with each other, as in one component foam, sealant or adhesive applications. Advantageously, the borane compound oxygen scavenger does not affect the oxygen induced initiation of the curing upon application of the composition: the compositions of the present invention have a short curing time when contacted with oxygen or air, and the resulting final cured product has a high quality. As curing is initiated by oxygen or air, curing of the composition is not dependent on ambient moisture and proceeds even at low temperatures, below 0°C.

A first aspect of the present invention thus relates to the use of a borane compound as an oxygen scavenger in a mixture, particularly in an oxygen-curable mixture as further defined herein, wherein the borane compound is BH3, B2H6 or a monoalkylborodihydride. Stated differently, the present invention provides a method for reducing, eliminating or controlling the oxygen content of a mixture, particularly of an oxygen-curable precursor mixture, comprising adding a borane compound, as an oxygen scavenger to the mixture, particularly an oxygen-curable precursor mixture as further defined herein, wherein the borane compound is BH₃, B₂H₆ or a monoalkylborodihydride.

In particular embodiments, the mixture is an oxygen-curable precursor mixture, comprising (i) at least one ethylenically unsaturated compound having at least one free- radically polymerizable carbon-carbon double bond, preferably having 1 to 10 free- radically polymerizable carbon-carbon double bonds, more preferably wherein the at least one ethylenically unsaturated compound is a vinyl compound, preferably an acrylate or methacrylate compound, an allyl ether compound or a styrene compound, and, optionally (ii) at least one reactive diluent, preferably comprising a free-radically polymerizable monomer having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bons, preferably having 1 to 4 vinyl functional groups. More in particular, the oxygen-curable precursor mixture further comprises an organometal or organoborane compound radical initiator, particularly an alkyl- or alkoxy-metal compound or an alkyl- or alkoxyborane compound. The mixture is typically stored in a container, such as a pressurized cannister.

In particular embodiments, the oxygen scavenger borane compound is added to or present in the mixture in a concentration ranging between 100 and 5000 ppm, particularly in a concentration ranging between 200 and 1000 ppm.

Another, related aspect of the present invention provides a method for preparing an oxygen-curable precursor composition, particularly a one component oxygen-curable precursor composition, comprising the steps of (i) preparing or providing a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free- radically polymerizable monomer and/or oligomer; (ii) adding a borane compound as an oxygen scavenger to the reactive precursor mixture, particularly wherein the borane compound is BH₃, B₂H₆ or a monoalkylborodihydride, and subsequently (iii) adding an organometal or organoborane compound radical initiator to reactive precursor mixture of step (ii). In particular embodiments, the borane compound is added in a concentration ranging between 100 and 5000ppm, particularly in a concentration ranging between 200 and lOOOppm.

In particular embodiments, the reactive precursor mixture is not subject to a physical deoxygenation treatment, particularly prior to step (ii). More in particular, the reactive precursor mixture is not subject to a degassing treatment and/or to purging or flushing the with an inert, oxygen-free gas.

In particular embodiments, the reactive precursor mixture, prepared or provided in step (i) comprises at least one ethylenically unsaturated compound having at least one free-radically polymerizable carbon-carbon double bond, preferably having 1 to 10 free- radically polymerizable carbon-carbon double bonds, more preferably wherein the at least one ethylenically unsaturated compound is a vinyl compound, preferably an acrylate or methacrylate compound, an allyl ether compound or a styrene compound. In particularly preferred embodiments, the reactive precursor mixture comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties.

In particular embodiments, the reactive mixture, provided or prepared in step (i), further comprises at least one reactive diluent, preferably comprising a free-radically polymerizable monomer having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bons, preferably having 1 to 4 vinyl functional groups. In other preferred embodiments, the reactive precursor mixture further comprises an anaerobic radical scavenger. In certain embodiments, the reactive precursor mixture further comprises one or more additives, such as a stabilizer, a flame retardant, a surfactant, a propellant or blowing agent, a colorant, ...

In particular embodiments, the reactive precursor mixture as envisaged herein is a highly viscous, non-Newtonian fluid, with viscosities of at least 3500 cP, such as between 4000 and 5000 cP or higher, determined by rotational viscosimetry as further specified herein.

In preferred embodiments, the organometal or organoborane compound in step (iii) is an alkyl- or alkoxy-metal or an alkyl- or alkoxyborane compound. In particular embodiments, the method as envisaged herein further comprises the step (iv) filling a container with the reactive precursor mixture comprising a borane compound and, optionally, pressurizing the container by adding a blowing agent or propellant.

Another aspect of the present invention relates to a one-component, oxygen- curable precursor composition, obtainable by a method according to the present invention. In particular, the one-component, oxygen-curable precursor composition as envisaged herein, comprises (a) a reactive precursor mixture, comprising at least one ethylenically unsaturated compound having 1 to 10 free-radically polymerizable carbon-carbon double bonds, preferably wherein said at least one ethylenically unsaturated compound is a vinyl compound; (b) a borane compound as oxygen scavenger, particularly wherein the borane compound is BH3, B2H6 or a monoalkylborodihydride, or the reaction product of said borane compound with oxygen, preferably in a concentration ranging between 100 ppm and 5000 ppm; (c) an organometal or organoborane compound as radical initiator; and (d) preferably, an anaerobic radical scavenger; wherein the precursor composition comprises less than 1 ppm oxygen. In certain preferred embodiments, the oxygen-curable precursor composition is an isocyanate-free foam precursor composition, comprising a reactive precursor mixture, comprising a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties and a diluent comprising a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties; a borane compound as oxygen scavenger; an organometal or organoborane compound as radical initiator; and, preferably, an anaerobic radical scavenger, wherein the precursor composition comprises less than 1 ppm oxygen. In particular, the one-component, oxygen-curable precursor composition as envisaged herein is a highly viscous, non-Newtonian fluid, with viscosities of at least 3500 cP, such as between 4000 and 5000 cP or higher, as determined by rotational viscosimetry as further specified herein.

Another aspect of the present invention relates to a container, such as a pressurized container, comprising a composition according to the present invention.

Yet another related aspect of the present invention relates to the use of the composition according to the present invention as a one component sprayable foam composition, a one component sealant or a one component adhesive.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows the reaction between MDI and HPMA to form an NCO-terminated prepolymer of HPMA with MDI, in the preparation of an aromatic urethane methacrylate blend as envisaged in certain embodiments of the present invention. Figure 2 shows the preparation of double acrylized MDI from MDI and an excess of HPMA, in the preparation of an aromatic urethane methacrylate blend as envisaged in certain embodiments of the present invention.

Figure 3 shows the reaction between an NCO-terminated prepolymer and 2-ethyl hexanol, in the preparation of an aromatic urethane methacrylate blend as envisaged in certain embodiments of the present invention.

Figure 4 shows the reaction between IPDI and HPMA to form an NCO-terminated prepolymer of HPMA with IPDI, in the preparation of an aliphatic urethane methacrylate blend as envisaged in certain embodiments of the present invention.

Figure 5 shows the structure of double acrylized IPDI, obtained from the reaction between IPDI and an excess of HPMA, in the preparation of an aliphatic urethane methacrylate blend as envisaged in certain embodiments of the present invention.

Figure 6 shows the structure of an aliphatic urethane methacrylate with glycerol, obtained from the reaction between an NCO-terminated prepolymer and glycerol, in particular an urethane prepolymer of HPMA with IPDI, reacted with glycerol, in the preparation of an aliphatic urethane methacrylate blend as envisaged in certain embodiments of the present invention.

DETAILED DESCRIPTION

The present invention will be described with respect to particular embodiments but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope thereof.

As used herein, the singular forms “a”, “an”, and “the” include both singular and plural referents unless the context clearly dictates otherwise.

The terms “comprising”, “comprises” and “comprised of” as used herein are synonymous with “including”, “includes” or “containing”, “contains”, and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms “comprising”, “comprises” and “comprised of” when referring to recited members, elements or method steps also include embodiments which “consist of” said recited members, elements or method steps.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The term "about" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/-10% or less, preferably +/-5% or less, more preferably +/-1 % or less, and still more preferably +/-0.1 % or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

All documents cited in the present specification are hereby incorporated by reference in their entirety.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Surprisingly, the inventors have found that borane compounds are very efficient oxygen scavengers, particularly in viscous, oxygen-curable polymerizable compositions, such as for use in foam, sealant or adhesive applications. An oxygen scavenger is a reactive compound that quickly reacts or combines with oxygen to reduce or essentially completely remove oxygen in an environment, particularly an enclosed environment, thus controlling the oxygen content in the environment, particularly the enclosed environment, typically thereby avoiding reaction of oxygen with other materials in said environment, particularly said enclosed environment and maintaining the stability of the other materials in said environment. The present invention is thus generally related to the use of borane compounds as oxygen scavengers and to methods for oxygen scavenging or for reducing or eliminating the oxygen content in a mixture, comprising adding a borane compound oxygen scavenger to the mixture. In this context, the inventors have further developed novel polymerizable precursor compositions, particularly one component, oxygen-curable precursor compositions, and novel methods to prepare such compositions. The present invention concerns a system, comprising a composition containing a reactive precursor mixture and an oxygen-sensitive radical initiator, in particular an organoborane or organometal compound, wherein the curing of the reactive precursor is initiated by the generation of radicals, enabled by oxygen from the air, and wherein the chemical stability of the composition prior to its application (e.g. when stored in a container) is ensured by the addition and presence of the borane compound oxygen scavenger.

As used herein, the term “borane compound” as oxygen scavenger generally refers to a compound with formula B_xH_y or BH2X, wherein X is an alkyl group, particularly an alkyl group comprising a C1-C14 carbon chain, such as a C1-C6 carbon chain. Particular borane compounds include BH3, B2H6 and a monoalkylborodihydride.

As used herein, the term “organoborane” as radical initiator generally refers to a compound formula BR3, with R being an alkyl or alkoxy group, each independently comprising a carbon chain comprising between 1 and 14 C atoms.

Surprisingly, in the presence of a borane compound as envisaged herein, the reactive precursor compounds and the radical initiator compound may be mixed and stored together, such as in one component foam, sealant or adhesive applications, without curing, even when no other deoxygenation measures are taken, until the composition is brought into contact with air and is subsequently rapidly cured. The borane compound essentially generates an anaerobic composition by removing the oxygen. This way, a long shelf life stability is ensured. Advantageously, the compositions of the present invention have a short curing time when contacted with oxygen or air. The present invention thus also concerns oxygen-activated self-curing polymerizable compositions comprising a radical-sensitive precursor compounds, an organoborane or organometal radical initiator, and a borane compound, wherein the compositions are inert and do not polymerize during storage, but are activated and polymerize when, upon dispensing, in contact with oxygen from air. The crosslinking or curing system proposed in the present invention is a radical addition type crosslinking polymerization reaction. It can be considered as an alternative for the moisture induced curing of other systems, such as the moisture curing of isocyanate-based compositions, with the further advantage that the curing of the composition is not dependent on ambient moisture and proceeds even at low temperatures, below 0°C.

The present invention thus relates to the use of a borane compound, as envisaged herein, as an oxygen scavenger in a mixture, particularly in an oxygen-curable mixture, typically comprising an oxygen sensitive radical initiator, as further defined herein. Stated differently, the present invention provides a method for reducing, eliminating or controlling the oxygen content of a mixture, particularly of an oxygen-curable precursor mixture, comprising adding a borane compound, as envisaged herein, as an oxygen scavenger to the mixture, particularly an oxygen-curable precursor mixture as further defined herein. The present invention also provides for a method for preparing an oxygen-curable precursor composition, particularly a one component, oxygen-curable precursor composition, such as for use as a foam, sealant or adhesive, comprising the use of a borane compound as envisaged herein. In particular, the present invention provides for a method for preparing an oxygen-curable precursor composition, particularly a one component, oxygen-curable precursor composition, comprising the steps of (i) preparing or providing a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer; (ii) adding a borane compound or a borane compound precursor to the reactive precursor mixture, thereby generating an anaerobic reactive precursor mixture, and subsequently (iii) adding an oxygen-sensitive radical initiator, particularly an organometal or organoborane compound radical initiator to the reactive precursor mixture of step (ii). Particularly, step (iii) is performed after an appropriate reaction time in which the borane compound reacts with the oxygen in the reactive precursor mixture.

In the context of the present invention, the borane compound is preferably a monoalkylboradihydride (BH₂X, wherein X is an alkyl group, particularly an alkyl group comprising a C1-C14 carbon chain, such as a C1-C6 carbon chain), borane or trihydroboron (BH₃), or diborane (B₂H₆). Advantageously, the borane compounds as envisaged herein have been found to be highly efficient oxygen scavengers in the present composition. As used herein, the term “oxygen scavenger” particularly refers to a compound capable of reacting with oxygen which has at least substantially the same, preferably a higher, efficiency of accepting oxygen than the organometal or organoborane radical initiator as envisaged herein. In particular, the borane compounds as envisaged herein are very sensitive to oxygen, more so than the oxygen-sensitive radical initiators, but they do not generate radicals upon reaction with oxygen, and will thus not initiate the curing reaction. Advantageously, the presence of a borane compound as oxygen scavenger ensures that, during storage, the composition remains anaerobic or oxygen- free, i.e. that the oxygen content of the composition remains below 1 ppm or even below 0.5 or 0.1 ppm and thus remains too low to react with the radical initiator compound, thus preventing the generation of radicals and the polymerization or curing of the reactive precursor mixture. Advantageously, the borane compounds as envisaged herein are soluble in the reactive precursor mixture, particularly in the reactive diluent (as further defined below).

Particularly preferred are borane or diborane. In borane (BHs), the boron atom carries 6 valence electrons and thus does not meet the octet rule. Hence, it behaves as a strong Lewis acid that instantly reacts with a Lewis base, thus explaining its reactivity with water and oxygen. The parent compound, diborane BaHe is an inflammable gas with similar high reactivity to air and moisture.

In certain embodiments, a borane compound precursor, in particular sodium borohydride may be added to the precursor mixture. In the presence of an acid or by mild oxidation, the borane compound precursor may be in situ converted into a borane compound oxygen scavenger, as envisaged herein.

In certain embodiments, the borane oxygen scavenger may be added to the precursor mixture as a stabilized complex, which may be safer to handle. It is particularly understood that, in this embodiment, the borane is liberated from the borane complex when introduced in the reactive precursor mixture by low levels or residues of acid or acidic compounds typically present in the reactive precursor mixture. Such borane complex may comprise a borane compound as envisaged herein complexed with THF, dimethylsulfide, or an amine. The amine used to complex the borane can be any amine or mixture of amines which complex the borane. Preferred amines include primary or secondary amines or polyamines containing primary or secondary amine groups, or ammonia; ethanolamine, secondary dialkyl diamines or polyoxyalkylenepolyamines; and amine terminated reaction products of diamines and compounds having two or more groups reactive with amines, n-octylamine, 1 ,6-diaminohexane (1 ,6-hexane diamine), diethylamine, dibutyl amine, diethylene triamine, dipropylene diamine, 1 ,3-propylene diamine (1 ,3-propane diamine), 1 ,2-propylene diamine, 1 , 2-ethane diamine, 1 ,5-pentane diamine, 1 ,12-dodecanediamine, 2-methyl-1 ,5-pentane diamine, 3-methyl-1 ,5-pentane diamine, triethylene tetraamine, diethylene triamine. Particularly preferred amines are diethylenetriamine, diaminopropane and methoxypropylamine. In particular embodiments, the borane compound oxygen scavenger as envisaged herein is present or added in an amount which is sufficient to prevent the curing of the composition during storage, i.e. by reacting with oxygen, thereby removing it from the reactive precursor mixture, to prevent the oxygen-mediated generation of radicals by the initiator compound, and which, at the same time, does not affect the curing of the composition after dispensing. In preferred embodiments, the amount of borane compound is added in a sufficient excess to ensure that the organometal or organoborane initiator remains inactive during storage, without affecting the curing upon dispensing. In general, the amount of oxygen scavenger present in the composition is in accordance with its oxygen content, with some excess to block accidental, unwanted traces of oxygen, which may penetrate into the container, particularly during longer storage times. If a too large excess of oxygen scavenger is present, it will delay the solidification of the composition after dispensing, which will reflex unfavorably on the foam, sealant or adhesive characteristics and quality.

Advantageously, the optimum content of the borane compound may be determined experimentally, such as by preparing several series of containers comprising the composition according to the present invention with varying borane compound concentrations but with the same amount of the same radical initiator, and subsequently assessing the shelf life of the closed containers and the quality and curing time of the composition (e.g. foam) when the composition is dispensed in the air.

In particular embodiments, the borane compound is typically added to or present in the reactive precursor mixture as envisaged herein in the range of 100 ppm to 5000 ppm, particularly in the range of 200 ppm to 2500 ppm or in the range of 200 ppm to 2000 ppm, more particularly in the range of 250 ppm to 1000 ppm, such as in the range of 250 ppm to 500 ppm or in the range of 500 ppm to 1000 ppm.

Advantageously, the invention does not require other deoxygenation measures: no extensive or costly deoxygenation pretreatment of the reactive precursor mixture, in particular prior to the addition of the radical initiator, needs to be implemented. The composition comprising a borane compound as envisaged herein as oxygen scavenger, such as when contained in a pressurized container for foam applications, will not react during storage, as the borane compound will ensure that the oxygen is removed from the composition, or, stated differently, that the composition is essentially anaerobic, with the oxygen content in the composition according to the present invention limited/controlled to below 1 ppm, preferably below 0.5 or 0.1 pm. Accordingly, in preferred embodiments, the method as envisaged herein does not include the step of subjecting the reactive precursor mixture or the composition as envisaged herein to an additional deoxygenation treatment, particularly does not include the step of subjecting the reactive precursor mixture or the composition as envisaged herein to a physical deoxygenation treatment. As envisaged herein, a physical deoxygenation treatment generally refers to subjecting a mixture to a degassing treatment, particularly a degassing treatment by vacuum, and/or subjecting a mixture to a saturation treatment with an inert gas, such as by purging or flushing the mixture with an inert gas (CO2, N2). In addition, a physical deoxygenation may comprise subjecting the mixture to alternating degassing treatments and saturation treatments by an inert gas.

In the context of the present invention, the radical initiator compound envisaged in the present application is an oxygen-activated free-radical generating compound. In particular, the radical initiator compound envisaged in the present application is an organometal or organoborane compound which generates organic radicals when exposed to oxygen, preferably oxygen from the ambient air, thus initiating the curing of the reactive precursor mixture blend via a direct radical addition type curing mechanism. In preferred embodiments, the organometal or organoborane compound radical initiator is an alkyl- or alkoxy-metal or an alkyl- or alkoxyborane compound.

Preferably, the radical initiator is an organoborane compound according to the formula BR3, with R being an alkyl or alkoxy group, each independently comprising a carbon chain comprising between 1 and 14 C atoms. Stated differently, the organoborane radical initiator may be an alkyl- or alkoxy-borane according to formula (alkoxy)3-n - B - (alkyl)n, with n = 0, 1 , 2 or 3, and wherein alkyl and alkoxy each independently comprise a carbon chain comprising between 1 and 14 C atoms. In particular, the organoborane compound radical initiator is a trialkylborane, and may be selected among the group of trimethylborane, triethylborane, tripropylborane, tributylborane, tri-sec-butylborane, trihexylborane, trioctylborane, tridecylborane, tritridecylborane, triethylborane, methoxydiethylborane, and tributylborane are preferred organoborane compounds. More preferably, the organoborane initiator compound is a trialkyl borane like triethylborane or tri-n-butylborane.

The organoborane radical initiator is generally present in an amount effective for initiating/activating the polymerisation of the composition upon exposure to atmospheric oxygen. More in particular, the organometal or organoborane compound radical initiator is present in an amount comprised between 0.1 and 10 wt.%, with respect to the total weight of reactive precursor mixture, preferably between 0.1 and 6 wt.%, more preferably between 0.1 and 2 wt%. In preferred embodiments, in addition to the organometal or organoborane radical initiator described herein, a small amount of acid is added to the reactive precursor mixture, in particular between 1 and 200 ppm, preferably between 1 and 100 ppm or between 1 and 50 ppm) of phenylphosphonic acid, pyrogallol or a suitable Lewis acid.

Advantageously, with an organometal radical initiator or an organoborane radical initiator, the curing kinetics of the reactive precursor mixture are not dependent on the weather and climate of the place of application and is constant regardless of the moisture content of the atmosphere. Another great advantage is that the product can also cure at temperatures below freezing point.

It is understood that the initiating or curing activating system comprising an organometal or organoborane radical generating compound as described herein, particularly in combination with a borane oxygen scavenger as described herein, occurs in two modes, i.e. a passive mode and an active mode.

The passive mode corresponds to the situation during storage of the oxygen- curable precursor composition prior to its application, such as when stored in a container, such as in a pressurized container for foam applications. In this mode, polymerization and curing of the composition is unwanted and the initiating system needs to be inactive. This is ensured by the use of a borane compound oxygen scavenger as envisaged herein, which ensures that the oxygen-curable precursor composition as envisaged herein is essentially anaerobic, containing only traces of oxygen, below a maximum permissible concentration, lower than the sensitivity of the reaction of the radical initiator and oxygen. Accordingly, a one component composition can be obtained wherein the initiator is not encapsulated or separated from the reactive precursor mixture, but is freely mixed within the reactive precursor mixture.

The active mode corresponds to the situation after dispensing the oxygen-curable precursor composition from the container wherein it is stored, wherein the initiating system is activated by the oxygen from the air. Upon contact with ambient oxygen, the oxygen will quickly eliminate the remaining borane oxygen scavenger and the radical initiator compound will quickly release free organic radicals, independent of the ambient temperature or humidity, thus resulting in the curing of the dispensed foam precursor mixture.

In the context of the present invention, the reactive precursor mixture as envisaged herein comprises reactive oligomers and monomers, which are transformed upon curing in the final product. The oligomers used in the present invention preferably have unsaturated backbones with reactive groups and different functionalities i.e. they are monofunctional, difunctional, trifunctional, multifunctional or mixtures of several types and different molecular weight. The reactive precursor mixture as envisaged herein generally contains monomeric and oligomeric compounds, particularly unsaturated monomeric and oligomeric compounds, which are able to polymerize and crosslink via a radical addition reaction. Stated differently, the reactive precursor mixture comprises at least one free- radically polymerizable monomer and/or oligomer. Free-radically polymerizable compounds, in particular monomers and oligomers that can polymerize and/or crosslink by free radical polymerization, are known to the skilled person. Suitable compounds include ethylenically-unsaturated compounds having at least one free-radically polymerizable carbon-carbon double bond per molecule, preferably having 1 to 10 free- radically polymerizable carbon-carbon double bonds per molecule, such as 2 to 10 or 3 to 10 free-radically polymerizable carbon-carbon double bonds per molecule. In addition, the reactive precursor mixture as envisaged herein is a highly viscous fluid, particularly a highly viscous, non-Newtonian fluid. More in particular, the viscosity of the reactive precursor mixture is at least 3500 cP, such as between 4000 and 5000 cP or even higher. Any technique known to the skilled person may be used to determine the viscosity, for instance using a viscometer comprising rotating spindles, such as produced by Brookfield. The viscosity is typically determined by rotational viscosimetry, particularly at a temperature between 20°C and 30°C, in particular about 23°C or 25°C, at a relative humidity of about 50% and with a standard spindle at a speed between 20-50 rpm, such as 20 rpm or 50 rpm.

In particular embodiments, the ethylenically-unsaturated compounds, particularly ethylenically-unsaturated monomers and/or oligomers, may be selected from the acrylates, methacrylates, styrene, maleate esters, fumarate esters, unsaturated polyester resins, alkyd resins, thiolene compositions, and/or acrylate, methacrylate or vinyl terminated resins, including acrylate, methacrylate or vinyl terminated silicones and urethanes.

In particular embodiments, the at least one ethylenically-unsaturated compound present in the reactive precursor mixture is a vinyl compound. Vinyl compounds, such as acrylates and methacrylates, acrylamides and methacrylamides, allyl ethers, and styrenes, are polymerizable by free radicals. As used herein, the prefix "(meth)acryl" refers to acryl and/or methacryl. For example, (meth)acrylate refers to acrylate and/or methacrylate. Examples of suitable free-radically polymerizable vinyl compounds include vinyl esters such as diallyl phthalate, diallyl maleate, diallyl succinate, diallyl adipate, diallyl azelate, diallyl suberate, and other divinyl derivatives thereof. Other suitable free-radically polymerizable compounds include siloxane-functional (meth)acrylates.

The free-radically polymerizable double bonds are particularly preferably present in the form of (meth)acryloyl groups. Examples of prepolymers or oligomers include (meth)acryloyl-functional poly(meth) acrylates, urethane (meth) acrylates, polyester (meth)acrylates, unsaturated polyesters, polyether (meth) acrylates, silicone (meth)acrylates, epoxy (meth) acrylates, amino (meth)acrylates and melamine (meth)acrylates.

In particular embodiments, the reactive precursor mixture comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties.

In certain embodiments, the reactive precursor mixture further comprises an unsaturated polyester resin (USPER). In foam applications, LISPER compounds contribute to the foaming properties of the composition after dispensing, such as foam resilience, and also allow to reduce the price of the foam. Unsaturated polymers include polyesters like polyethylene terephtalate and polyethers like polyethylene glycol. Any polymer with a (poly)ester backbone and possessing some amount of double bonds may be utilized to some extend and is therefore included in the broad definition of an unsaturated polyester resin. In preferred embodiments, the unsaturated polyester resin (USPER) comprises an unsaturated polyester resin, obtained by polyesterification of a glycol and an anhydride, as known in the art, and diluted or dissolved in a blend of reactive diluents as taught herein. Particularly, said glycol is i-propylene glycol. Particularly, the anhydride is a blend of anhydrides, preferably a blend of maleic and o-phthalic anhydrides. In general, the so prepared USPER is used for diluting the more expensive components of the reactive precursor mixture, without affecting the consistence and quality of the resulting product (foam).

The free-radically polymerizable monomers and/or oligomers as envisaged herein may be used in combination with reactive diluents having one or more unsaturated free- radically polymerizable groups, such as having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bonds. Accordingly, the reactive mixture as envisaged herein preferably further comprises a reactive diluent.

Reactive diluent is used herein according to the definition of DIN 55945:1996-09, which defines such substances as diluents which react chemically during curing to become a constituent of the product. Reactive diluents may be mono-, di- or polyfunctional free- radically polymerizable monomeric compounds, preferably, having (meth)acryloyl groups. The reactive diluents are of low molecular weight and have, for example, a molar mass of below 500 g/mol.

The reactive diluent typically controls the viscosity of the reactive precursor mixture and to a proper functioning of the composition during application. In foam application, the diluents may advantageously also increase the solubility of a propellant or blowing agent in the reactive precursor mixture, resulting in an improved physical structure of the foam after the composition according to the present application is dispensed from a pressurized container. The reactive diluent also contributes to the foam resilience, with, for instance, iBoMA contributing to a more rigid foam, and 2-EHMA to a more soft foam. Also, reactive diluents with vinyl functionality of 2 or higher contribute to an increased cross-linking density. Exemplary reactive diluents include (meth-)acrylic esters of polyols, such as a blend of 1 ,6 hexanediol diacrylate (1 ,6 HDDA), tripropyleneglycol diacrylate (TPGDA), isobornyl methacrylate (iBoMA) and/or 2-ethyl hexyl methacrylate (2-EHMA), most preferably a blend of TPGDA and 2-EHMA. In certain embodiments, an unsaturated polyester resin may be dissolved in a reactive diluent, such as in 1 ,6 hexanediol diacrylate (1 ,6 HDDA) and/or tripropyleneglycol diacrylate (TPGDA), most preferably TPGDA.

In certain embodiments, the methods according to the present invention further comprise the step of preparing the ethylenically-unsaturated monomers and/or oligomers having at least one free-radically polymerizable carbon-carbon double bond per molecule, such as by preparing a vinyl derivative, preferably a (meth)acryl derivative of a suitable compound.

In particular embodiments, the method further comprises adding an anaerobic radical scavenger to the reactive precursor mixture as envisaged herein. An anaerobic radical scavenger as envisaged herein is a compound capable of capturing accidently occurring free radicals during storage, before application, for preventing the curing of the foam precursor composition under anaerobic conditions. Although the use of radical scavengers in compositions containing compounds with vinyl functional groups to prevent unwanted polymerization or curing of such composition is known, many of such radical scavengers require some oxygen to be efficient, and are thus not suitable in the anaerobic composition envisaged herein. A preferred anaerobic radical scavenger is phenothiazine. Preferably, the anaerobic radical scavenger is present in the reactive precursor mixture in an amount comprised between 50 and 700 ppm, preferably between 100 and 500 ppm, more preferably between 150 and 350 ppm, or between 250 and 350 ppm.

In particular embodiments, the method further comprises adding one or more other additives to the reactive precursor mixture, including but not limited to rheology modifiers, plasticizers, flame retardants, crosslinkers, surfactants, tackifiers, colorants and the like. These compounds are added in a concentration between 0.01 to 10 % by weight of the total mixture, more preferably between 1 and 8 wt%. Preferred additives include one or more of the following:

* a flame retardant, such as tris(2-chloroisopropyl)phosphate (TCPP);

* a surfactant, preferably a non-ionic surfactant, more preferably a silicone surfactant, such as Tegostab ® available from Evonik Industries or Vorasurf available from Dow Chemicals. * a diluent for the organometal or organoborane initiator compound, such as monoethylene glycol (MEG).

In the context of the present invention, it is understood that all operations on the anaerobic reactive precursor mixture (i.e. the reactive precursor mixture after addition of the borane compound oxygen scavenger) are performed in inert (anaerobic) atmosphere. In certain embodiments, the methods for preparing a one component, oxygen-curable precursor composition as envisaged herein further comprises the step of filling a container with the anaerobic oxygen-curable precursor composition, optionally comprising one or more additives, such as an anaerobic radical inhibitor, surfactant, flame retardant and the like. In particular embodiments, the composition or container may further comprise a blowing agent or propellant to create a pressurized system, such as a pressurized container or aerosol can, which allows spraying of the precursor composition into a curing froth, resulting in a stable foam. Several blowing agents, typical liquefied petroleum gases like butane, propane, isobutane, dimethylether, isobutene and halogenated compounds can be used. Preferably, the blowing agent or propellant comprises i-butane and DME. These gases have some typical characteristics such as the amount of dissolution of the resins in the liquid phase, boiling temperature and vapour pressure in the can in order to create an ideal mixture for the foam formulation. Typically, the propellants or blowing agents are introduced in the range of 50 to 60vol%, based on the volume of the reactive precursor mixture.

Particular embodiments of the present application provide a method to prepare a

, particularly a method to prepare a container, preferably a pressurized container, containing the foam precursor composition, wherein the method comprises the steps of (i) providing a reactive precursor mixture, comprising a urethane (meth)acrylate with 1 to 6 vinyl moieties, preferably an unsaturated poly-ester resin, and a diluent comprising a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties, and, (ii) adding a borane compound as described herein, particularly BH₃, B₂H₆ or a monoalkylborodihydride, as oxygen scavenger to the reactive precursor mixture, particularly without subjecting the reactive precursor mixture to a physical deoxygenation treatment, thereby generating an anaerobic reactive precursor mixture and (iii) adding an organometal or organoborane radical initiator compound as described herein to the anaerobic reactive precursor mixture, particularly after allowing the reaction between the borane compound and the oxygen dissolved in the reactive precursor mixture to conclude. In particular, a blowing agent or propellant is further added to the reactive precursor mixture to create a pressurized system, such as a pressurized container system or aerosol system, which allows spraying of the foam precursor composition.

In certain embodiments, the methods for preparing a foam precursor composition as envisaged herein, further comprises the step of filling a container with the anaerobic foam precursor mixture, optionally comprising one or more additives, such as an anaerobic radical inhibitor, surfactant, flame retardant and the like. In particular embodiments, the methods comprise the step of filling a container with the anaerobic reactive precursor mixture comprising the borane compound oxygen scavenger (i.e. wherein the borane compound is added to the anaerobic reactive precursor mixture prior to the step of filling the container), and subsequently closing the container, adding a propellant or blowing agent to the container, such as by injection, and finally adding the organometal or organoborane radical initiator. In particular embodiments, the methods comprise the step of filling a container with the reactive precursor mixture, adding the borane compound oxygen scavenger and allowing the oxygen present in the closed container to react with the borane compound, adding a propellant or blowing agent to the closed container, such as by injection, and finally adding the organometal or organoborane radical initiator.

Another aspect of the present invention provides a novel one-component, oxygen curable, polymerizable precursor composition, comprising a reactive precursor mixture as described herein, a borane compound as described herein as oxygen scavenger, and/or the reaction product between the borane compound and oxygen, and an organometal or organoborane compound as radical initiator, wherein the reactive precursor mixture comprises at least one monomeric and oligomeric free-radically polymerizable compounds, particularly at least one unsaturated monomeric and oligomeric compounds, which are able to polymerize and crosslink via a radical addition reaction. Particularly, the novel one- component, oxygen curable composition is obtainable by an embodiment of the method according to the present invention.

Advantageously, the incorporation of a borane compound as oxygen scavenger in the composition according to the present invention ensures that unwanted polymerization before application, such as when it is stored in a container, is avoided, since the composition is essentially anaerobic, having an oxygen content of less than 1 ppm, preferably less than 0.5 or 0.1 ppm, because the borane compound is more sensitive to oxygen than the organometal or organoborane radical initiator. This ensures that the initiator compound cannot generate radicals during storage, even though they are in contact with each other during storage. This further ensures that the polymerization reaction is not initiated prior to application resulting in a prolonged shelf life stability. In addition, despite the presence of an oxygen scavenger in the mixture, upon application, the curing of the composition by oxygen is not affected.

In particular embodiments, the present invention relates to an oxygen-curable precursor composition, particularly stored in a container, such as a pressurized container or aerosol can, comprising (i) a reactive precursor mixture as described herein, (ii) a borane compound as described herein and/or the reaction product of said borane compound and oxygen, and (iii) a radical initiator, particularly an organometal or organoborane radical initiator as further described herein, wherein the composition has an oxygen content of less than 1 ppm, preferably less than 0.5 or 0.1 ppm, and wherein the composition preferably further comprises (iv) an anaerobic radical scavenger as described herein. Preferably, the oxygen-curable precursor composition further comprises one or more additives, such as (v) a flame retardant, (vi) a surfactant, and/or (vii) a propellant.

As described above, a borane compound, in particular a monoalkylboranedihydride, BH3 or B2H6, is particularly dissolved in the reactive precursor mixture. As the borane compound has reacted with the oxygen dissolved in the precursor mixture, thus creating an anaerobic composition, at least part of the borane compound present in the composition according to the present invention has been converted in its borinate ester. Advantageously, the presence of an oxygen scavenger ensures that, during storage, the composition remains anaerobic, i.e. that the oxygen content of the composition remains below 1 ppm, particularly or below 0.5 or 0.1 ppm and thus remains too low to react with the radical initiator compound, thus preventing the generation of radicals and the polymerization of the reactive precursor mixture. In particular embodiments, the borane compound, more particularly the borane compound and/or the reaction product between the diborane compound and oxygen, is typically present in the reactive precursor mixture as envisaged herein in the range of 100 ppm to 5000 ppm, particularly in the range of 200 ppm to 2500 ppm or in the range of 200 ppm to 2000 ppm, more particularly in the range of 250 ppm to 1000 ppm, such as in the range of 250 ppm to 500 ppm or in the range of 500 ppm to 1000 ppm.

As described above, preferred radical initiator compounds included organometal or organoborane compounds. For example, triethylborane, methoxydiethylborane, tributylborane, and tri-sec-butylborane are preferred borane compounds. The organometal or organoborane initiator is preferably present in an amount comprised between 0.1 and 10 wt.%, with respect to the total weight of reactive precursor mixture, preferably between 0.1 and 6 wt.%, more preferably between 0.1 and 2 wt%.

As described above, in preferred embodiments, the reactive precursor mixture further comprises an unsaturated polyester resin (LISPER) as described above, for instance dissolved in a reactive diluent, such as in 1 ,6 hexanediol diacrylate (1 ,6 HDDA) and/or tripropyleneglycol diacrylate (TPGDA). In foam applications, LISPER compounds contribute to the foaming properties of the composition after dispensing, such as foam resilience, and also allow to reduce the price of the foam.

As described above, the precursor composition may comprise further additives, including but not limited to rheology modifiers, plasticizers, flame retardants, crosslinkers, blowing agents, surfactants, tackifiers, colorants and the like.

In particular embodiments, the present invention relates to the use of a borane compound as envisaged herein, particularly BH₃, B₂H₆, or a monoalkylborodihyride, as an oxygen scavenger, in an oxygen-curable polymerizable foam precursor mixture, particular comprising an oxygen sensitive organoborane radical initiator, as further defined herein.

Stated differently, the present invention provides a method for reducing, eliminating or controlling the oxygen content of a mixture^ particularly stored in a pressurized container, comprising adding a borane compound, as envisaged herein, as an oxygen scavenger to the mixture. The present invention thus also relates to an oxygen-curable polymerizable foam :ion, particularly stored in a pressurized container, comprising (i) a reactive precursor mixture comprising a urethane and/or polyester (meth)acrylate and/or polyether (meth)acrylate compound with 1 to 6 vinyl moieties, preferably also an unsaturated polyester resin, and a diluent comprising a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties as further defined herein, (ii) a borane or diborane, and/or the corresponding reaction product of borane or diborane with oxygen; (iii) a radical initiator, particularly an organometal or organoborane radical initiator as described herein, and, optionally (iv) an anaerobic radical scavenger, wherein the composition has an oxygen content of less than 1 ppm, preferably less than 0.5 or 0.1 ppm. In more particular embodiments, the oxygen-curable polymerizable foam precursor composition, particularly stored in a pressurized container, comprises a reactive precursor mixture comprising (a) an aromatic urethane (meth-)acrylates with 1 to 4 vinyl functional groups, preferably 1 to 3 vinyl functional groups, most preferably 1 to 2 vinyl functional groups; (b) an aliphatic urethane (meth-)acrylates with 3 to 6 vinyl functional groups, preferably 3 to 5, most preferably 3 to 4 vinyl functional groups, preferably (c) an unsaturated polyester resin and (d) a reactive diluent, comprising (meth)acrylated monomers with 1 to 4 vinyl functional groups. Advantageously, the acrylates or methacrylates functional groups block the generally toxic and harmful diisocyanates groups in the backbone of the (urethane) prepolymers. In certain embodiments, the oxygen-curable polymerizable foam precursor composition, particularly stored in a pressurized container, comprises a reactive precursor mixture comprising (i) an aliphatic urethane (meth-)acrylate blend comprising an aliphatic (meth)acrylate with 3 to 6 vinyl functional groups, preferably 3 to 5, most preferably 3 to 4 vinyl functional groups; and a fully (meth)acrylized monomeric aliphatic poly- or diisocyanate; (ii) an aromatic urethane (meth-) acrylate blend, comprising an aromatic (meth)acrylate with 1 to 4 vinyl functional groups, preferably 1 to 3, most preferably 1 to 2 vinyl functional groups; and a fully (meth)acrylized monomeric aromatic poly- or diisocyanate; (iii) a blend of reactive diluents, comprising monomers with 1 to 4 vinyl functional groups, preferably 1 to 3, most preferably 1 to 2 vinyl functional groups; (iv) an unsaturated polyester resin (LISPER); (v) a borane compound oxygen scavenger; and (vi) preferably, one or more additives, such as an anaerobic radical scavenger, a surfactant, a flame retardant, and the like.

Specifically, the reactive compounds of the foam precursor composition are designed, prepared and combined, in order to inter alia (a) be able to undergo crosslinking polymerization to yield a final foam product resilience (upon oxygen mediated curing) with the necessary toughness, adhesion, mechanical and other properties for its respective field of application; (b) enable curing with sufficiently high speed and at sufficiently low temperatures to yield a final foam product with assigned quality; (c) not change physically and/or chemically during storage; (d) not release toxic products upon curing; and (e) enable high uniformity of the cell structure of the final foam product. Advantageously, the foam precursor compositions of the present application are a nontoxic alternative to the one component isocyanate - moisture curable polyurethane foams, with better design and enlarged area of potential use.

The foam precursor composition according to an embodiment of the present invention is preferably stored in a container, such as an aerosol can. The foam precursor composition is particularly in the form of a one component (1C) foam system, wherein the initiator and the reactive precursor mixture are not physically separated but in the same compartment in the container. Advantageously, as the composition only comprises traces of oxygen due to the presence of the borane compound oxygen scavenger, the radical initiator can remain in contact with the reactive precursor mixture without enabling curing in the can. There is thus no need to microencapsulate the initiator compound, as it is inert in the absence of oxygen. Only upon spraying the composition out of the can through an aerosol nozzle, the organometal or organoborane initiator is activated by contact with oxygen and curing starts. Another aspect of the present invention provides a container, optionally a pressurized container comprising a one component, oxygen curable precursor composition as described herein.

Another aspect of the present invention relates to the use of an oxygen curable precursor composition as described herein as a one component sprayable foam composition, a one component sealant composition or a one component adhesive composition.

The present invention is further illustrated with the following non-limiting illustrative embodiments.

EXAMPLES

Example 1: experimental determination of the required amount of diborane B₂H₆

In an exemplary embodiment of the present invention, the amount of diborane as oxygen scavenger in the reactive precursor mixture, which ensures a sufficient reduction in oxygen content to obtain a good shelf life of the foam precursor composition, particularly when stored in a (pressurized) container, while, at the same time does not affect the curing rate of the foam precursor composition after dispensing, may be determined experimentally.

To this end, a series of containers comprising the same precursor compositions but a different amount of the oxygen scavenger are prepared. After filling the containers with the reactive precursor mixture and the oxygen scavenger, the containers are (temporarily) closed by valves, under an oxygen-free atmosphere (e.g. via an Anaerobic Glove Box). The prepared containers are then shaken for a time, sufficient for the reaction between the remaining oxygen in the reactive precursor mixture and the oxygen scavenger to be completed. Next, the same amount of an organoborane initiator compound is added to each container. Finally, the containers are closed by the valves and a propellant is added under inert atmosphere. Typically, two identical series of containers are prepared, wherein a first series is used for assessing the curing rate and foam properties (cell structure, shrinkage & adhesion) of the foam after dispensing, and a second series is used to assess the shelf life of the containers. The containers which provide a good curing of the foam upon dispensing and have an optimal shelf life define the amount of diborane needed to be added to the reactive precursor mixture. Example 2: Preparation of an aerosol container comprising a foaming composition

In another exemplary embodiment of the present invention, the preparation of an aerosol container comprising a foaming composition according to the present invention is considered, comprising the following steps.

1. Initial preparation of the reactive precursor mixture by mixing the following components:

Urethane (Meth-)acrylates from all foreseen types; dissolved in the reactive diluents of the reactive precursor mixture; reactive diluents, for dissolving the Urethane (Meth-)acrylates and USPER. The reactive diluent may comprise a blend of monomers with 1 to 4 vinyl functional groups, preferably 1 to 3, most preferably 1 to 2 vinyl functional groups. Preferably, the reactive diluent blend comprises (meth-)acrylic esters of polyols, particularly a blend of 1 ,6 hexanediol diacrylate (1 ,6 HDDA), tripropyleneglycol diacrylate (TPGDA), iso-bornyl methacrylate (iBoMA) and/or 2-ethylhexyl methacrylate (2-EHMA), most preferably a blend of TPGDA and 2-EHMA. The urethane (mhet)acrylates may be separately prepared, as further illustrated below;

- providing or preparing an unsaturated polyester resin (USPER), particularly comprising the synthesis of USPER via methods known in the art, and further dilution of the obtained USPER in the reactive monomeric diluents (instead of the usual styrene); additives in the required amounts, including an anaerobic radical scavenger; a flame retardant, preferably TCPP; a surfactant, preferably a silicone type surfactant, such as Tegostab 8870.

2. Transferring the reactive precursor mixture and silicone surfactant into an inert atmosphere, with oxygen content of max. 5 ppm, preferably max 1 ppm, most preferably below 1 ppm. In lab conditions, an inert atmosphere can be created in an Anaerobic Glove Box in Lab condition. In commercial production conditions, the fluids are kept in containers under inert atmosphere.

3. Providing the required amounts of organoborane initiator and diborane oxygen scavenger. The preparation of the aerosol cans is completed under inert atmosphere. Particularly, in a commercial production facility, the filling of the aerosol cans is essentially similar to a filling line for filling traditional PU aerosol containers, but adapted to work in an anaerobic regime. In particular, three anaerobic operating systems are implemented, connected by anaerobic tunnels to transport the filling can (from one system to another): system 1 : empty containers are flushed by an inert gas to less than 5 ppm oxygen, preferably 1 ppm, most preferably less than 1 ppm; system 2, where the flushed cans are filled with the reactive precursor mixture plus any additions, including the required amount of the diborane oxygen scavenger, as well as with the silicone surfactant. In the same system, the containers are closed by valves and filled with the blowing agent(s). Preferably, after system 2, the filled cans are typically stored (in normal atmosphere) for a period of about 4 hours, preferably 3 hours, most preferably less than 2 hours, so that the diborane compound can react with the available oxygen in order to obtain fully anaerobic conditions in the can; - system 3, where the organoborane compound is introduced in the aerosol can by injecting it through a gas burette under pressure of inert gas (similar to the burette filling of the blowing agent). It is understood that a producer of non-isocyanate foams does not have to implement drastic changes in its production facilities, particularly in the final steps thereof, in comparison to filling PU foams. Advantageously, there are no reactions taking place in the aerosol can, unlike as in the case of PU foams, except for the reaction of the oxygen scavenger with the oxygen traces, but this reaction has an ignorable thermal effect. Example 3: Preparation of a reactive precursor mixture for an isocyanate-free foaming composition. In certain embodiments, Example 2, pt 1 comprises the step of preparing the reactive precursor mixture. (a) The reactive precursor mixture may comprise an aromatic urethane (meth-)acrylate blend comprising a blend of reaction products of an aromatic polyisocyanate, particularly an aromatic diisocyanate, particularly a partially meth(acrylized) aromatic polyisocyanate, and an alcohol or polyol, wherein all isocyanate groups are blocked by a (meth)acrylate moiety. Particularly, said aromatic urethane (meth-)acrylate blend comprises a blend of an aromatic urethane (meth)acrylate, a fully acrylized aromatic polyisocyanate, such as a double acrylized monomeric aromatic diisocyanate, e.g. monomeric MDI, and a suitable reactive monomeric diluent. Advantageously, the aromatic urethane (meth-)acrylates as described herein contribute to a higher reactivity of the precursor mixture and contribute to the resilience of the final foam product. In particular, the reactive precursor mixture comprises an aromatic urethane acrylate and/or urethane methacrylate blend, which is configured for use in an isocyanate-free foamable composition. In particular, the aromatic urethane acrylates and/or methacrylates blend comprises a blend of (i) fully (meth)acrylized NCO-terminated prepolymers or oligomers, which are the reaction products of an aromatic diisocyanate, preferably monomeric MDI, and suitable alcohol(s) with 1 to 2 hydroxyl groups, preferably one hydroxyl group, and (ii) a double (meth)acrylized aromatic diisocyanate, wherein all isocyanate groups are blocked by a (meth)acrylate moiety, particularly a hydroxyl(meth)acrylate moiety. In particular embodiments, the aromatic urethane(meth)acrylate blend comprises a blend of (i) fully (meth)acrylized NCO- terminated prepolymers or oligomers, which are the reaction products of an aromatic diisocyanate, preferably monomeric MDI, with a mono-functional alcohol with a branched aliphatic chain, preferably 2-ethyl hexanol, which is (meth)acrylized by a hydroxyalkyl(meth)acrylate, such as hydroxypropyl methacrylate (HPMA), or 2- hydroxyethyl acrylate (2-HEA), and (ii) a double acrylized monomeric diisocyanate, preferably double acrylized monomeric MDI. Preferably, the double acrylized monomeric MDI comprises the same (meth)acrylate moieties as the monofunctional alcohol. Advantageously, this urethane metacrylate blend composition has a low viscosity, a prolonged shelf life and is not expensive to produce.

The preparation of an aromatic urethane (meth)acrylate may thus comprise two steps (i) the reaction between a NCO-bifunctional aromatic isocyanate and a hydroxy(meth)acrylate to obtain a NCO-monofunctional aromatic isocyanate derivative and a double (meth)acrylized aromatic isocyanate; (ii) reacting the reaction product of step (i) with an alcohol or polyol, particularly an alcohol with 1 or 2 hydroxyl groups.

More in particular, in step (i), the aromatic diisocyanate, preferably MDI, is reacted with a hydroxy(meth)acrylate, preferably HEMA or HPMA, in particular using a suitable catalyst such as dibutyltin dilaurate. The amount of (meth)acrylate added is sufficient to react with at least half of the isocyanate groups of the aromatic diisocyanate, so that they are blocked with a (meth)acrylate moiety. It is thus understood that in step (i) also a certain amount of a double (meth)acrylized aromatic diisocyanate (MDI) is formed. For instance, after step (i), between 10 and 80%, such as between 20 and 60%, or between 20 and 50% of the MDI is converted to double (meth)acrylized MDI. To avoid allophanates formation, the reaction temperature is below 55°C, such as about 50 °C. To this end, preferably, the required amount of hydroxyl(meth)acrylate, preferably HPMA is added stepwise. Additionally, an inert gas atmosphere is preferably maintained over the reaction mixture to prevent accidental contamination of the reaction medium with water. Step (i) continues up to the full exhaustion of the hydroxy(meth-)acrylate, such as HPMA, in the reaction.

In step (ii), the reaction product of step (i), i.e. a mono-NCO terminated prepolymer reaction product between the aromatic diisocyanate and the hydroxyl(meth)acrylate, is further reacted with an alcohol compound comprising 1 or 2 hydroxylgroups, preferably 1 hydroxyl group, such as 2-ethyl hexanol. Preferably, to avoid that non-reacted NCO groups remain after step (ii), the alcohol is added in excess. The reaction of step (ii) should continue until no free NCO groups can be detected in the reaction medium. In the second step, the fully acrylized diisocyanate from the first step, is present as inert component An illustrative example of the preparation of an aromatic urethane (meth-)acrylate blend as envisaged in this section (a) of example 3 is as follows.

In a well stirred, hermetically closable, jacketed glass laboratory reactor with bottom valve, with a capacity of 2 I and equipped with a controllable heating/cooling system, 275.19 g of MDI (Suprasec 2004) is added and diluted with a blend of 78.75 g of 2-ethyl hexyl methacrylate, 78.75 g of iso-bornyl methacrylate and 157.5 g of tripropylene glycol diacrylate. An inert gas is passed in bubbles (2 - 3 per second) through the mixture under stirring. A triphenyl phosphite stabilizer (3.6 g) and di-butyltin laurate catalyst (0.27 g) are additionally added to the mixed medium. The reactor is warmed up to a temperature of 40 °C and then, via a dividing funnel, 230.53 g of hydroxypropyl methacrylate are added dropwise (for about 15 min), taking care that the temperature of the reactor does not increase to over 50 °C. After all HPMA is introduced, the reaction continues under the created thermodynamic and mass - exchange conditions up to full reaction of HPMA (according to the reaction scheme shown in Figures 1 and 2), which at a temperature of about 50 °C takes about 3 hours. Next, at the same temperature, 79.28 g of 2-ethylhexanol are added to the reaction medium at once and the process continues under the same conditions (the temperature is kept at ±1 °C) until no NCO-groups remain in the reaction medium (at a temperature of about 55 °C this takes about 3 hours) (see reaction scheme presented in Figure 3). Next, the reactor is emptied without cooling. The obtained blend of aromatic urethane methacrylate (about 900 g), contains about 45% double methacrylized MDI and the remainder comprises an aromatic urethane acrylate of 2-ethylhexanol. The blend is a slightly yellow, transparent liquid, which is able to cure by radical initiation, for example when contacted with 1% benzoyl peroxide and 0.2% di-methyl p-toluidine, in about 20 min at a maximum temperature of about 65°C.

(b) The reactive precursor mixture may comprise an aliphatic urethane (meth-)acrylate blend comprising a blend of reaction products of an aliphatic polyisocyanate, particularly an aliphatic diisocyanate, particularly a partially meth(acrylized) aliphatic polyisocyanate, and an alcohol or polyol, particularly an alcohol with between one or two and six hydroxyl groups, preferably three or four hydroxyl groups, wherein all isocyanate groups are blocked by a (meth)acrylate moiety. Particularly, said aliphatic urethane (meth-)acrylate blend comprises a blend of an aliphatic urethane (meth)acrylate, a fully acrylized aliphatic polyisocyanate, such as a double acrylized monomeric aliphatic diisocyanate, e.g. monomeric IPDI, and a suitable reactive monomeric diluent. Aliphatic urethane (methacrylates contribute to a high cure speed at low temperatures, to the resilience of the final foam product, to the toughness and dimensional stability of the foam body and to the adhesion of the final foam product to various substrates.

In particular, the reactive precursor mixture comprises an aliphatic urethane acrylate and/or urethane methacrylate blend, which is configured for use in an isocyanate- free foamable composition. In particular, the aliphatic urethane acrylates and/or methacrylates blend comprises a blend of (i) fully (meth)acrylized NCO-terminated prepolymers or oligomers, which are the reaction products of an aliphatic diisocyanate, preferably Isophorone Diisocyanate or IPDI, and suitable polyols with 3 to 6 hydroxyl groups, preferably 3 to 5, most preferably 3 to 4 hydroxyl groups, and (ii) a double (meth)acrylized aliphatic diisocyanate, wherein all isocyanate groups are blocked by a (meth)acrylate moiety, particularly a hydroxyl(meth)acrylate moiety. In particular embodiments, the aromatic urethane(meth)acrylate blend comprises a blend of (i) fully (meth)acrylized NCO-terminated prepolymers or oligomers, which are the reaction products of an aliphatic diisocyanate, preferably IPDI, with a polyol, particularly a blend of glycerol and penta-erythritol, such as a blend of 60-70% glycerol and 30-40% pentaerythritol, which are (meth)acrylized by hydroxy(meth-)acrylate, hydroxypropyl methacrylate (HPMA), or 2-hydroxyethyl acrylate (2-HEA); and (ii) a double acrylized aliphatic diisocyanate, preferably double acrylized IPDI. Preferably, the double acrylized aliphatic diisocyanate comprises the same (meth)acrylate moieties as the polyols.

The preparation of an aliphatic urethane (meth)acrylate thus comprises two steps (i) the reaction between a NCO-bifunctional aliphatic isocyanate and a hydroxy(meth)acrylate to obtain a NCO-monofunctional aliphatic isocyanate derivative and a double (meth)acrylized aliphatic isocyanate; (ii) reacting the reaction product of step (i) with a polyol, particularly a polyol comprising between 3 to 6 hydroxyl groups, preferably 3 to 5, most preferably 3 to 4 hydroxyl groups. Preferably, the hydroxy(meth-)acrylate, as well as polyols have branched hydrocarbon chains in their chemical structure.

More in particular, in step (i), an aliphatic diisocyanate, preferably IPDI, is reacted with a hydroxy(meth)acrylate, preferably HEMA or HPMA, in particular using a suitable catalyst such as dibutyltin dilaurate. The amount of (meth)acrylate added is sufficient to react with at least half of the isocyanate groups of the aliphatic diisocyanate, so that they are blocked with a (meth)acrylate moiety. It is thus understood that in step (i) also a certain amount of a double (meth)acrylized aliphatic diisocyanate (IPDI) is formed. For instance, after step (i), between 10 and 80%, such as between 20 and 60%, or between 20 and 50% of the IPDI is converted to double (meth)acrylized IPDI. To avoid allophanate formation, the reaction temperature is below 60 °C, such as about 55 °C or about 50 °C. To this end, preferably, the required amount of hydroxyl(meth)acrylate, preferably HPMA is added stepwise. Additionally, an inert gas atmosphere is preferably maintained over the reaction mixture to prevent accidental contamination of the reaction medium with water. Step (i) continues up to the full exhaustion of the hydroxy(meth-)acrylate, such as HPMA, in the reaction.

In step (ii), the reaction product of step (i), i.e. a mono-NCO terminated prepolymer reaction product between the aliphatic diisocyanate and the hydroxyl(meth)acrylate, is further reacted with a polyol, particularly a glycerol/ pentaerythritol mixture comprising about 30-40% pentaerythritol, such as about 35% pentaerythritol. Preferably, to avoid that non-reacted NCO groups remain after step (ii), the polyol or polyol mixture is added in excess. The reaction of step (ii) should continue until no free NCO groups can be detected in the reaction medium. In the second step, the fully acrylized diisocyanate from the first step, is present as inert component.

An illustrative example of the preparation of an aliphatic urethane (meth-)acrylate blend as envisaged in this section (b) of example 3 is as follows.

In a well stirred, hermetically closable, jacketed glass Laboratory reactor with a bottom valve, with a capacity of 2 I and equipped with a controllable heating/cooling system, 307.07 g Isophorone Diisocyanate (IPDI) is added and diluted with a blend of 78.75 g of 2-ethyl hexyl methacrylate, 78.75 g of iso-bornyl methacrylate and 157.5 g of tripropylene glycol diacrylate. An inert gas is passed in bubles (2-3 per second) through the mixture under stirring. A triphenyl phosphite stabilizer (3.6 g) and di-butyltin laurate catalyst (0.54 g) are additionally added to the mixture. The reactor is warmed up to a temperature of 45 °C and then, via a dividing funnel, 242.72 g of HPMA is added dropwise (for about 15 min), taking care that the temperature of the mixture does not increase to over 55 °C. After all HPMA is introduced, the reaction continues under the created thermodynamic and mass - exchange conditions up to full reaction of HPMA (according to the reaction scheme presented in Figure 4 and obtaining a double methacrylized IPDI as shown in Figure 5) (at a temperature of about 55°C this takes about 3.5 hours). Next, at the same temperature, 24.64 g of glycerol (minimum moisture content) and 10.56 g. of pentaerythritol are added to the reaction medium at once and the process continues under the same conditions (the temperature is kept ±1 °C) until no NCO-groups remain in the reaction medium (at a temperature of 55 °C (this takes about 3 h) (with glycerol, the structure shown in Figure 6 is obtained). Next, the reactor is emptied without cooling. The obtained blend of aliphatic urethane acrylate (about 900 g) contains about 25% double methacrylized IPDI and the remainder comprises an aliphatic urethane acrylate prepolymer of a pentaerythritol/glycerol mixture with 30% pentaerythritol. The blend is a colourless, transparent liquid, which is able to cure by radical initiation, for example, when contacted with 1% benzoyl peroxide and 0.2% di-methyl p-toluidine, in about 12 min. at a maximum temperature of about 65 °C. Example 4: Further examples of reactive precursor compositions for an isocyanate- free foaming composition. A/ An example of a formulation according to the present invention is shown in the following table 1 (expressed as part by weight (PBW) or wt% (expressed vs the total weight of the composition). Table 1

A first illustrative example of an urethane methacrylate (UMA) is synthesized from isophorone diisocyanate (IPDI), pentaerythritol and glycerol, acrylized by hydroxyethylmethacrylate with functional distribution 3 to 4 of 65% and 35%. Double acrylized IPDI makes 25% of all UMA, reactive diluent is 35% of total product, Tegostab B8870 is a silicone surfactant with MW 2600 and an average hydroxyl number of 60. Diethylamine condensed coconut oil (DEA/Coconut Oil or cocamide diethanolamine) is a surfactant partly composed of renewable resources. Tripropylene glycol diacrylate monomer (TPGDA) is a typical cross-linking agent with functionality 2. Tris(chloroisopropyl)phosphate (TCPP) is added as a flame retardant. The formulation was not subjected to a physical deoxygenation treatment, comprising alternating vacuum degassing and flushing with inert gas. To this formulation is added diborane as an oxygen scavenger and triethylborane and tributylborane as initiator. LPG 4.7 is used as the propellant. B/ Another illustrative example is shown in Table 2. The composition is composed of an urethane methacrylate (UMA), aliphatic TMP, which is composed of a blend of 75% UMA and 25% double methacrylized I PDI. The UMA consists of 60% UMA synthesized from the reaction of trimethylol with diisocyanate (I PDI) and acrylized by hydroxypropylmethacrylate (functional acrylate distribution 3) and 40% UMA synthesized from diisocyanate (I PDI) reacted with trimethylol propane, subsequent reaction with I PDI, then acrylized by hydroxypropylmethacrylate (functional acrylate distribution 4). The Urea- Urethane (MA), Aromatic H, NPG/DEA is a blend of 75% Urea-Urethane MA aromatic and 25% double methacrylized mMDI. Urea MA, aromatic, D 2-EHA is a blend of 75% Urea

MA aromatic and 25% double methacrylized mMDI. Cross-linking occurs by polypropylene glycol diacrylate, monomer, f = 2 (Mw 700).

Table 3.

The structure/composition of these components is shown below.

* UMA TMP, aliphatic

Double methacrylized mMDI (25% of Urea/Urethane MA)

* UMA NPG/GLY, aromatic H

Aromatic UMA, f = 3 (70% of f3 + f2, GLY = Glycerol, PPM5 LI = Bisomer®

Polypropyleneglycol Monomethacrylate)

Aromatic UMA, f = 2 (30% of f3 + f2 , NPG = Neopentyl Glycol)

Double acrylized mMDI (25% of all amount of UMA in the blend)

* UMA, Aromatic, 2-EH L

Aromatic UMA, f = 1, 75% of UMA

Double methacrylized mMDI (25%) The formulation was not subjected to a physical deoxygenation treatment, comprising alternating vacuum degassing and flushing with inert gas. To this formulation is added diborane as an oxygen scavenger and triethylborane and tributylborane as initiator. LPG 4.7 is used as the propellant. Example 5: Foaming performance. As a comparative example, to a typical formulation according to the above examples in an aerosol can, triethylborane was added without preceding addition of the borane oxygen scavenger. Immediate reaction was observed by heating of the can typical of the exothermic curing reaction and foam spraying was not possible. A similar test with preceding addition of a borane (BH₃)-THF mixture gives an aerosol can that is still shakeable 3 h after filling. Foam spraying is possible and gives a fast curing foam. Therefore, borane acts as a suitable oxygen scavenger and radical cure control agent, even when the precursor mixture was not subject to a prior physical deoxygenation treatment.

Claims

1. A method for reducing, eliminating or controlling the oxygen content of a mixture, particularly of an oxygen-curable precursor mixture, comprising adding a borane compound selected from the group consisting of BH₃, B₂H₆ and a monoalkylborodihydride, as an oxygen scavenger to the mixture, particularly the oxygen-curable precursor mixture.

2. The method according to claim 1 , wherein the mixture is an oxygen-curable precursor mixture, comprising (i) at least one ethylenically unsaturated compound having at least one free-radically polymerizable carbon-carbon double bond, preferably having 1 to 10 free-radically polymerizable carbon-carbon double bonds, and, optionally (ii) at least one reactive diluent, preferably comprising a free-radically polymerizable monomer having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bonds.

3. The method according to claim 2, wherein the at least one ethylenically unsaturated compound is a vinyl compound, preferably an acrylate or methacrylate compound, an allyl ether compound or a styrene compound, and/or wherein the reactive diluent comprises a free-radically polymerizable monomer having 1 to 4 vinyl functional groups.

4. The method according to claim 2 or claim 3, wherein the mixture further comprises an organometal or organoborane compound radical initiator.

5. The method according to claim 4, wherein the organometal or organoborane compound is an alkyl- or alkoxy-metal compound or an alkyl- or alkoxyborane compound.

6. The method according to any one of claims 1 to 5, wherein the oxygen scavenger borane compound is added in a concentration ranging between 100 and 5000 ppm, particularly in a concentration ranging between 200 and 1000 ppm.

7. The method according to any one of claims 1 to 6, wherein the mixture, particularly the oxygen-curable precursor mixure, is stored in a container.

8. Use of a borane compound selected from the group consisting of BH₃, B₂He and a monoalkylborodihydride as an oxygen scavenger, particularly in an oxygen-curable precursor mixture.

9. A method for preparing an oxygen-curable precursor composition, particularly a one component oxygen-curable precursor composition, comprising the steps of:

(i) preparing or providing a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer;

(ii) adding a borane compound as an oxygen scavenger to the reactive precursor mixture, particularly wherein the borane compound is BH3, B2H6 or a monoalkylborodihydride, and subsequently

(iii) adding an organometal or organoborane compound radical initiator to reactive precursor mixture of step (ii).

10. The method according to claim 8, wherein the borane compound oxygen scavenger is added in a concentration ranging between 100 and 5000 ppm.

11 . The method according to claim 9 or 10, wherein the reactive precursor mixture is not subject to a physical deoxygenation treatment, such as degassing the reactive precursor mixture and/or by purging or flushing the degassed reactive precursor mixture with an inert gas, particularly prior to step (ii).

12. The method according to any one of claims 9 to 11 , wherein the reactive precursor mixture comprises at least one ethylenically unsaturated compound having at least one free-radically polymerizable carbon-carbon double bond, preferably having 1 to 10 free- radically polymerizable carbon-carbon double bonds, more preferably wherein the at least one ethylenically unsaturated compound is a vinyl compound, preferably an acrylate or methacrylate compound, an allyl ether compound or a styrene compound.

13. The method according to claim 12, wherein the reactive precursor mixture comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties.

14. The method according to any one of claims 9 to 13, wherein the reactive mixture further comprises at least one reactive diluent, preferably comprising a free-radically polymerizable monomer having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bons, preferably having 1 to 4 vinyl functional groups.

15. The method according to any one of claims 9 to 14, wherein the organometal or organoborane compound is an alkyl- or alkoxy-metal compound or an alkyl- or alkoxyborane compound.

16. The method according to any one of claims 9 to 15, wherein the reactive precursor mixture further comprises an anaerobic radical scavenger and/or one or more additives, such as a stabilizer, a flame retardant, a surfactant, a propellant or blowing agent, a colorant, ...

17. The method according to any one of claims 9 to 16, wherein the method further comprises filling a container with the reactive precursor mixture comprising a borane compound as oxygen scavenger and, optionally, pressurizing the container by adding a blowing agent or propellant.

18. A one component, oxygen-curable precursor composition, obtainable by the method according to any one of claims 9 to 17.

19. The oxygen-curable precursor composition according to claim 18, comprising

- a reactive precursor mixture, comprising at least one ethylenically unsaturated compound having 1 to 10 free-radically polymerizable carbon-carbon double bonds, preferably wherein said at least one ethylenically unsaturated compound is a vinyl compound, more preferably wherein the reactive precursor mixture comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties and a diluent comprising a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties;

- a borane compound as oxygen scavenger, selected from the group consisting of BH₃, B2H6 and a monoalkylborodihydride, or the reaction product of the borane compound with oxygen, particularly in a concentration between 100 ppm and 5000 ppm;

- an organometal or organoborane compound as radical initiator; and

- preferably, an anaerobic radical scavenger, wherein the precursor composition comprises less than 1 ppm oxygen.

20. A container, optionally a pressurized container, comprising a composition according to claim 18 or 19.

21 . Use of the composition according to claim 18 or 19 as a one component sprayable foam composition, a one component sealant or a one component adhesive.