FIELD OF THE INVENTION

The present invention relates to methods to prepare an oxygen-curable composition, particularly suitable for use as a two component (2K composition) to be stored in aerosol-type pressurized cans or cannisters and particularly useful as a curable composition stored in aerosol-type pressurized cans for sprayable foam applications. The present invention further provides oxygen-curable compositions and containers comprising such compositions.

BACKGROUND

Pressurized compositions stored in portable containers, such as cans or cannisters, are used for sprayable foams useful in several applications. A known commercial example of such sprayable foam is polyurethane (PU) foam. PU foams are typically used in small bead-type applications, such as sealing windows and doors, gap and crack filling, and fixing door frames, expanded polystyrene plates, and other building materials. The foam is typically applied using a specific aerosol valve system with strawnozzle or via small dispensing gun to which the aerosol can is mounted. These products have specific safety information including guidelines for eye and skin protection on the label that should be carefully followed.

The formulations to produce a traditional PU foam upon dispensing from the pressurized container comprises a mixture of chemicals including diisocyanates which are known to be harmful. Other ingredients include polyols, liquefied gases as blowing agents and propellant, and several additives including surfactants that moderate foam formation. Once released from the pressurized container, the froth forms by evaporation of liquefied gases to give cell formation which is stabilized by the surfactant. The froth then cures by the reaction of the isocyanate functionalities with water, for example from air humidity or from prewetting of surfaces. Reaction with water causes hydrolysis of the isocyanate with formation of a free amine and release of carbon dioxide as gas, that is responsible for post expansion of the foam in the curing process. The curing process continues through the resulting amine, which is highly reactive to isocyanate groups forming strong urea crosslinks that eventually introduce rigidity to the final foam.

As in many other curing mechanisms, atmospheric humidity triggers the curing process. The difference with other curing mechanisms is the need of more water to fully cure. For every two isocyanate groups in the froth, one water molecule is needed to form a urea link. Accordingly, in PU foam curing, dependence on atmospheric humidity is high and crosslinking rates vary significantly with changing climatological conditions and different relative humidities, thereby making curing times unpredictable. In extreme cases, such as in dry, arid regions complete inhibition of curing due to lack humidity is experienced, prohibiting the use of traditional Pll foams.

In addition, the presence of unreacted isocyanates is another principal disadvantage of traditional Pll foam compositions. In standard one component foam (OCF) formulations, the reactive isocyanate groups are protected from moisture in the closed can and will not cure. The other ingredients of the formulation are contained in the can with isocyanates, including polyols, liquefied gases, and curing catalysts like tertiary amine compounds. Methylene diphenyl diisocyanate (MDI) is the isocyanate most commonly used in formulations for Pll foams. Polyether or polyester polyols in the formulation start to react with the isocyanate compound inside of the pressurized container to form urethane links that form the polyurethane prepolymers. With isocyanate to alcohol ratios of about 1 :0.4 to 1 :0.6, sufficient free isocyanate functionalities remain available for humidity curing. This stoichiometric excess of isocyanates also results in incomplete prepolymerization in the aerosol can, leaving significant residues of unreacted isocyanate monomers like MDI in final formulation. This compound is toxic, and is harmful by inhalation or ingestion, and via skin contact. 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 Ell is asking OCF manufacturers to reach < 1% w/w unreacted and free crude MDI in Pll 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 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.

In two-component (2K) Pll foam systems, known in the art, different components of the formulation for producing a Pll foam are separated from each other prior to dispensing by placing them in different compartments. In typical commercial applications, one compartment of the aerosol can is filled with the isocyanate prepolymer and the blowing agent, and another separate compartment is filled with an active species, like monoethyleneglycol. Prior to use, both components are contacted and mixed via a special valve. The crosslinking reaction between monoethyleneglycol and the isocyanate components starts immediately in the aerosol can so that it has to be emptied at once. When not emptied completely, all remaining material will cure inside the aerosol container and cannot be utilized. It is thus a disadvantage of the two-component Pll foam system in a typical commercial application to have the two components mixed in the can. In a typical professional application of a 2-component Pll foam system, the 2 components are in separate cans or cannisters so that the mixing and the curing reaction do not occur inside of the can or cannister. It is advantageous that the curing of such 2K Pll foams is fast. It is particularly disadvantageous that the component comprising the isocyanate prepolymer is difficult to blend with the component comprising the polyol crosslinker such as monoethyleneglycol.

It is further known that 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 2- component system such as, for example, a component A and a component B that are combined immediately prior to use.

There thus remains a need for polymerizable compositions, particularly free- radically polymerizable compositions, suitable for being dispensed via pressurized containers, 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. There remains a need for polymerizable compositions suitable for being dispensed via pressurized containers, which can be cured via isocyanate free curing mechanisms, such as via free-radical polymerization based curing mechanisms, that yield high quality products such as foams, preferably polyurethane foams. Also needed are compositions that can be used in existing commercial equipment including aerosol cans or cannisters. Further, there is a need for polymerizable compositions that can be cured independently from moisture and under a wide range of temperatures, and which have a sufficient stability and thus a long shelf life without implementation of extensive or costly pretreatments.

SUMMARY OF THE INVENTION

The inventors have developed viscous, oxygen-curable polymerizable foam compositions, particularly for sprayable foam applications, which address the above mentioned needs in the art. Advantageously, 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, when relative humidity is low.

More in particular, in the viscous polymerizable composition envisaged herein, reactivity of the oxygen sensitive curing initiator, in particular the organoborane radical initiator, is suppressed by formation of a stable complex compound that can be mixed in the reactive prepolymer formulation and stored without polymerization, until the composition is brought into contact with a complementary decomplexing agent and is subsequently rapidly cured by oxygen. The invention does not require rigorous deoxygenation measures, as the composition with the stabilized initiator complex, such as when contained in a pressurized container for sprayable foam applications, will not react during storage even if the precursor mixture is in contact with residual oxygen. As long as the initiator complex remains intact, a long shelf life stability is guaranteed. The compositions of the present inventions have the advantage of tolerating residues of air or oxygen. Moreover, in the context of the present invention, it is particularly beneficial to deliberately keep some oxygen dissolved in the viscous oxygen-curable polymerizable compositions, for enabling a faster and more thorough curing of the foam once the initiator compound is released from the complex. Advantageously, the viscosity of the polymerizable composition comprising the oxygen-sensitive curing initiator, in the form of a stable complex compound, particularly in the form of an amine complex, is similar or even identical to the viscosity of the polymerizable composition comprising the decomplexing agent, particularly an amine reactive substance, ensuring a uniform mixing of both compositions and, consequently, a rapid and uniform reaction between the initiator complex and decomplexing agent in the froth, resulting in an even activation of the initiator and a rapid and even polymerization and curing of the foam.

A first aspect of the present invention provides an oxygen-curable foam precursor composition, particularly a two-component oxygen-curable foam precursor composition comprising:

- a first component A, comprising a reactive precursor mixture, said reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer, and an organoborane compound as radical initiator, wherein said organoborane compound is an organoborane amine complex; and

- a second component B, comprising a reactive precursor mixture, said reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer, and an amine reactive substance; particularly wherein the first component A and the second component B are physically separated. In particular embodiments, the amine reactive substance is an acid, an aldehyde, or an anhydride. A particularly preferred organoborane amine complex is the complex of a borane compound with the formula BR3, wherein R is an alkyl or alkoxy group, with a suitable amine compound, such as in known commercial borane complexes like triethylborane-diethylenetriamine complex (TEB- DETA), triethylborane-1 ,3-diaminopropane complex (TEB-DAP) or tri-n-butylborane- methoxypropylamine complex (TnBB-MOPA).

Advantageously, complexation of the organoborane compound by an amine compound results in a stable, inactivated or passivated oxygen initiator complex, which, when present in the reactive precursor mixture of component A, results in an inactive reactive precursor mixture, which will not polymerize despite the presence of low amounts of oxygen present in the reactive precursor mixture. A deoxygenation treatment of said reactive precursor mixture is thus not needed to avoid polymerization or curing before applying the composition according to the present invention. Furthermore, the amine reactive compound, also referred to herein as a decomplexing agent, of component B is a compound that, upon contact, destabilizes or provokes disintegration of the organoborane amine complex, present in component A to release the active organoborane initiator molecule. Accordingly, upon contacting or mixing component A and component B of the oxygen-curable foam precursor composition, particularly the two-component oxygen- curable foam precursor composition according to the present invention, such as upon application, dispensing or spraying of the foam precursor composition, the decomplexing agent is contacted with the inactive initiator complex, thereby activating the organoborane initiator. The activated organoborane will in its turn generate radicals in the presence of oxygen, thus initiating the curing reaction of the foam composition of the present invention.

It was surprisingly found that upon spraying and mixing of a polymerizable foam precursor composition comprising an inactivated organoborane initiator, in the form of an organoborane amine complex, (component A) with a polymerizable foam precursor composition comprising a decomplexing agent (component B), the resulting froth can be cured to a high quality foam, with a satisfactory foam cell structure and a high dimensional stability and good adhesion. Although the initiation of the curing requires the extra step of the activation of the inactivated initiator by liberating the organoborane from its amine complex, and despite the highly viscous nature of the compositions which is typically considered as hindering the reaction between complex and decomplexing agent, curing time was fast and curing proceeded uniformly both at the surface and at the centre of the froth, thus minimizing foam cell coalescence and foam collapse. In particular embodiments, the reactive mixture of component A and/or component B comprises at least one ethylenically unsaturated compound having 1 to 10 free-radically polymerizable carbon-carbon double bonds. Preferably, the reactive mixture of component A and/or B comprises at least one vinyl compound. More preferably, the reactive mixture of component A and/or B comprises an acrylate or methacrylate compound, an allyl ether compound or a styrene compound. In particularly preferred embodiments, the reactive mixture of component A and/or B comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties

In particular embodiments, the reactive mixture of component A and/or component B further comprises at least one reactive diluent, said diluent preferably comprising a free- radically polymerizable monomer having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bonds. More in particular, said at least one reactive diluent comprises a free-radically polymerizable monomer having 1 to 4 vinyl functional groups. A particularly preferred reactive diluent comprises a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties.

In particular embodiments, the reactive precursor mixture as envisaged herein is a highly viscous, non-Newtonian fluid. In particular, the viscosity of component A and/or component B, particularly the viscosity of the reactive precursor mixture of component A and/or component B, is at least 3500 cP, such as between 4000 and 5000 cP, as measured by rotational viscosimetry at a temperature of about 23 °C and a relative humidity of 50%. In particular embodiments, the difference in viscosity of component A and component B is less than 10%, particularly less than 8%, 6%, 5% or 3%. In particular embodiments the viscosity of component A and component B are essentially the same. Advantageously, the reactive precursor mixture of component A is the same as the reactive precursor mixture of component B, thus ensuring a superior mixing efficiency due to the almost identical rheology of component A and component B, which in its turn results in the suitable amine reactive substance being contacted with the organoboron-amine complex in an optimal way to trigger the selective decomplexing reaction that releases the active organoboron initiator, thereby obtaining a fast and homogeneous cure of the foam composition.

In particular embodiments, the reactive precursor mixture of component A and/or component B further comprises a radical scavenger or radical inhibitor.

In particular embodiments, the reactive precursor mixture of component A and/or component B further comprises one or more additives, including but not limited to a stabilizer; a flame retardant, a surfactant, a propellant or blowing agent, and/or a colorant. Another aspect of the present invention provides a container system comprising the oxygen-curable foam precursor composition according to the present invention. More in particular, the container system is a pressurized container system. More in particular, in the container system according to the present invention, component A and component B as envisaged herein are physically separated from each other.

In a particular embodiment, the container system comprises a container, particularly an aerosol can, containing a first compartment comprising component A as envisaged herein and a second compartment comprising component B as envisaged herein, preferably wherein the first and second compartment are pressurized with a blowing agent or propellant.

In another particular embodiment, the container system comprises a first container comprising component A as envisaged herein and a second container comprising component B as envisaged herein, preferably wherein the first and second container are pressurized with a blowing agent or propellant.

In particular embodiments, the container system further comprises a mixing chamber with a static mixer for mixing component A and component B upon dispensing the oxygen-curable foam precursor composition from the container system.

Another aspect of the present invention provides a method for preparing an oxygen-curable polymerizable foam precursor composition, particularly a two component oxygen curable polymerizable composition according to the present invention, comprising the steps of:

(i) preparing a first component A by mixing an organoborane compound as radical initiator with a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer, wherein said organoborane compound is an organoborane amine complex;

(ii) preparing a second component B by mixing an amine reactive substance with a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer.

In particular embodiments, said amine reactive substance is an acid, an aldehyde or an anhydride.

In particular embodiments, the reactive mixture of component A and/or component B comprises at least one ethylenically unsaturated compound having 1 to 10 free-radically polymerizable carbon-carbon double bonds. Preferably, the reactive mixture of component A and/or B comprises at least one vinyl compound. More preferably, the reactive mixture of component A and/or B comprises an acrylate or methacrylate compound, an allyl ether compound or a styrene compound. In particularly preferred embodiments, the reactive mixture of component A and/or B comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties.

In particular embodiments, the reactive mixture of component A and/or component B further comprises at least one reactive diluent, said diluent preferably comprising a free- radically polymerizable monomer having 1 to 4 unsaturated free-radically polymerizable groups or carbon-carbon double bonds. More in particular, said at least one reactive diluent comprises a free-radically polymerizable monomer having 1 to 4 vinyl functional groups. A particularly preferred reactive diluent comprises a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties.

In particular embodiments, the reactive precursor mixture of component A and/or component B further comprises a radical scavenger or radical inhibitor.

In particular embodiments, the reactive precursor mixture of component A and/or component B further comprises one or more additives, including but not limited to a stabilizer; a flame retardant, a surfactant, a propellant or blowing agent, and/or a colorant.

In particular embodiments, the method according to the present invention further comprises the step of filling a container system with component A and component B, wherein component A and component B are physically separated from each other and, optionally, pressurizing the container system by adding a blowing agent or propellant, wherein said container system comprises a container comprising at first compartment for holding component A and a second compartment for holding component B, respectively, or wherein said container system comprises a first container for holding component A and a second compartment for holding component B.

Another aspect of the present invention provides a method for preparing a foam comprising the steps of

(a) preparing or providing oxygen-curable foam precursor composition as further specified herein, or preparing or providing a container system comprising the oxygen-curable foam precursor composition as further specified herein, particularly wherein component A and component B are pressurized with a propellant or blowing agent; and

(b) mixing and dispensing, particularly spraying, component A and component B in an oxygen containing environment or atmosphere, thereby forming a foam. 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.

The present invention provides novel polymerizable foam precursor compositions, particularly oxygen-curable foam precursor compositions, more particularly two component oxygen curable foam precursor composition, container systems comprising such polymerizable foam precursor compositions and novel methods to obtain and use such compositions.

In general, the present invention concerns a system comprising a composition containing a reactive precursor mixture and a stabilized, inactive oxygen-sensitive radical initiator compound. The curing of the reactive precursor mixture is initiated by the generation of radicals, enabled by oxygen from the 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. The system of the present invention further comprises implementing specific measures to ensure the chemical stability of the composition prior to its application, such as when stored in a container, i.e. to protect the stabilized inactive radical initiator compound from premature activation, and to ensure the proper activation and radical generation functionality of the system upon its application and the concomitant activation by oxygen from air. In particular, in the context of the present invention, the oxygen-sensitive radical initiator compound is stabilized and inactivated as a chemical complex, and as such can be mixed with a reactive precursor, even in the presence of oxygen or air, in particular the residual air or oxygen present in the reactive precursor mixture, and can be stored together without premature and unwanted curing, thus ensuring a stable shelf life. The inactivated state of the oxygen-sensitive radical initiator complex remains until the complex, or the composition comprising the complex, is brought into contact with a suitable compound, also referred herein as a “decomplexing agent” that selectively releases the active initiator from the complex, thus enabling a rapid curing. Prior to its application, typically, a reactive precursor composition comprising the inactive oxygen-sensitive radical initiator complex is thus physically separated from the decomplexing agent. Preferably, the stabilized and inactivated oxygen initiator compound is the complex of a borane compound, particularly with the formula BR3 as further defined herein, with a suitable amine compound. A preferred chemical decomplexing agent is an amine reactive substance, i.e. a chemical reagent that reacts with an amine functionality, preferably with the amine functionality in the stabilized and inactivated organoborane amine complex, particularly in such way that the amine functionality is chemically transformed so that it no longer serves as Lewis base for the boron compound.

In this context, the compositions as envisaged herein are highly viscous, nonNewtonian fluids, with viscosities of at least 3500 cP, such as between 4000 and 5000 cP or even higher, with the viscosity determined by rotational viscosimetry as further specified herein. It is a particular object of the invention to ensure in these high viscosity compositions an efficient contact between an amine reactive substance that acts as decomplexing agent with the organoboron-amine initiator complex to trigger the selective decomplexing reaction that releases the active initiator. An inefficient release of the initiator from its inactive complex may result in incomplete, slow, and inhomogeneous curing reactions that affect the quality of the final foam.

Advantageously, as during storage the radical initiator complex is physically separated from the decomplexing agent, the organoboron radical initiator is not released from its complex during storage in the container, thus ensuring that the reactive precursor mixture has a long shelf life. When the organoboron radical initiator is released, the compositions of the present invention have a short curing time when contacted with oxygen or air from the atmosphere or with oxygen or air dissolved in the compositions.

A first aspect of the present invention thus concerns oxygen-activated curing polymerizable foam compositions comprising radical-sensitive precursor compounds and a radical initiator, wherein the compositions are inert and do not polymerize during storage due the radical initiator being present in the composition as an inactive and stable complex. The compositions are activated and polymerize (or cure) upon their application, such as upon dispensing or spraying from a container containing the oxygen activated polymerizable foam compositions, when the inactive complex is contacted with a suitable decomplexing agent as to disintegrate the complex to release the active radical initiator, which will be contacted with oxygen from the air, thereby initiating the curing process. A first aspect of the present invention thus provides an oxygen curable, polymerizable foam precursor composition, particularly a two-component (2K) oxygen- curable, polymerizable foam precursor composition, said foam precursor composition comprising a first component A and a second component B, which are particularly separated from each other during storage, wherein component A comprises a reactive precursor mixture and an inactivated oxygen-sensitive radical initiator in complex with a suitable ligand, wherein the reactive precursor mixture comprises at least one free- radically polymerizable monomer and/or oligomer; and wherein component B comprises a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer, and a decomplexing agent, i.e. a chemical compound that destabilizes or provokes disintegration of the radical initiator complex to release the active radical initiator molecule from its complex. Advantageously, the reactive precursor mixture of component A is the same as the reactive precursor mixture of component B, thereby ensuring an optimal mixing efficiency of both components A and B, and an optimal contact between complex and decomplexing agent.

As the oxygen-sensitive radical initiator complex is inert, it will not react and generate radicals in the presence of oxygen. Advantageously, the radical initiator can be provided in the same composition comprising the reactive precursor mixture, thereby obtaining an inactive reactive precursor mixture, without implementing additional measures to remove the oxygen from the composition, such as by degassing, flushing with an inert gas or by using oxygen scavengers.

In the context of the present invention, the reactive precursor mixture of component A and component B comprises reactive oligomers and monomers, which are transformed upon curing in the final product. The curing process is defined as the hardening of the liquid precursor mixture through the event of cross-linking of the reactive prepolymer chains to produce a solidified final foam. Chemically, the process involves a series of addition reactions of simple monomers and oligomers and monomer-terminated prepolymers to results in a tri-dimensional polymer network. The molecular structure growth is macroscopically translated into reduced solubility and steep viscosity increase that continues until the majority of reactive molecules are chemically integrated in the network which defines the end of the chemical reaction. Considering the entire process is exotherm in nature, at this point heat release ceases and curing is complete. The monomers and oligomers envisaged in the present invention are curable by radical reactions or polymerizations. In particular, the monomers and oligomers suitable for this invention have unsaturated backbones with reactive groups and different functionalities i.e. they are monofunctional, difunctional, trifunctional, multifunctional or they comprise of mixtures of several types of monomers and oligomers and have different molecular weight.

In the context of the present invention, the reactive precursor mixture of component A and component B generally contains monomeric and oligomeric compounds, particularly unsaturated monomeric and oligomeric compounds, which are able to polymerize and crosslink via radical addition. 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 those skilled in the art. Preferable 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 particular embodiments, the ethylenically-unsaturated compounds, particularly ethylenically-unsaturated monomers and/or oligomers, are suitable substrates in radical addition reactions and may be selected from the series of acrylates, methacrylates, acrylonitrile, acrylamides, methacrylamides, styrene, maleate esters, fumarate esters, unsaturated polyester resins, alkyd resins, and/or acrylate, methacrylate or vinyl terminated resins, including acrylate, methacrylate or vinyl terminated silicones, urethanes, epoxies, polyethers, polyesters, and/or acrylate, methacrylate or vinyl terminated renewable derivatives including but not limited to (meth)acrylated vegetable oils, meth)acrylated fatty acids, (meth)acrylated terpenes and the like. It can be further explained that the prefix "(meth)acryl" refers to acryl and/or methacryl. For example, (meth)acrylate refers to acrylate and/or methacrylate.

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 a free-radical mechanism. 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.

In a preferable embodiment, the free-radical polymerizable double bonds are in the form of (meth)acryloyl groups. Acrylic and methacrylic esters can be polymerized by free radical and anionic polymerization, but the free-radical polymerization is most evident. Relevant and non-limiting 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 a particularly preferred embodiment of the current invention, the reactive precursor mixture comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 (meth)acryloyl-functional groups.

In certain embodiments, the reactive precursor mixture may further comprise an unsaturated polyester resin (USPER). In foam applications, LISPER compounds are known to contribute to the foaming properties of the composition after dispensing and introduce foam resilience. A major advantage for including LISPER in reactive precursor mixtures is their use as bulk chemical materials such as to reduce final price of the foam. Accordingly, in general, the LISPER is used for diluting the more expensive components of the reactive precursor mixture, without affecting the consistency and quality of the resulting product (for example a foam).

Unsaturated polyesters are typically produced by a combined addition and condensation reaction between a diol and a mixture of different anhydrides with saturated and unsaturated functionality. Non-limiting examples of such unsaturated polymers include polyesters like poly(ethylene terephtalate), poly(ethylene tetrahydroterephtalate), polypropylene maleate), polypropylene fumarate) and mixed polymers thereof. Essentially 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 isopropylene glycol, n-propylene glycol or ethylene glycol. Particularly, the anhydride is a blend of anhydrides, preferably a blend of maleic and o-phthalic anhydrides. The condensation product is a durable, resin-like material that can be further cross-linked with reactive monomers, oligomers, or prepolymers such as acrylates, methacrylates, acrylonitrile, acrylamides, methacrylamides, styrene, maleate esters, fumarate esters, other unsaturated polyester resins, alkyd resins, and/or acrylate, methacrylate or vinyl terminated resins, including acrylate, methacrylate or vinyl terminated silicones, urethanes, epoxies, polyethers, polyesters, and/or acrylate, methacrylate or vinyl terminated renewable derivatives including (meth)acrylated vegetable oils, (meth)acrylated fatty acids, (meth)acrylated terpenes and the like. In particularly preferred embodiments of the invention, the properties of the unsaturated polyester resin are used to implement specific characteristics in the final foam. In a relevant application of such embodiment, LISPER applied in a specified proportion introduces better thermal and chemical resistance or gives better flexibility in the cured final product. In a more preferred embodiment, residual carboxyl groups in the unsaturated polyester resin are terminated as (meth)acryloyl moieties, for example by reaction with glycidyl (meth)acrylates. Alternatively, the residual carboxyl groups in the unsaturated polyester resin are neutralized with a base such as an organic nitrogen base like triethylamine.

In certain embodiments, the reactive precursor mixture further comprises a (meth)acrylated vegetable oil derivative.

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. Advantageously, the viscosity of component A is about the same as the viscosity of component B, thereby ensuring an optimal mixing efficiency of both components A and B, and an optimal contact between complex and decomplexing agent. In particular, the difference in viscosity of component A and the viscosity of component B is less than 10% of the viscosity of component A or B, particularly is less than 8%, 6%, 5%, 4% or even less than 1%. 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.

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. In view of the free radical mechanism for polymerization and cross-linking, the 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 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.

In the context of the present invention, the reactive diluent typically controls the viscosity of the reactive precursor mixture and to a proper functioning of the composition during application. In foam applications, 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, iso-bornyl methacrylate (iBoMA) contributing to a more rigid foam, and 2-ethylhexyl methacrylate (2-EHMA) resulting in a softer 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), iso-bornyl methacrylate (iBoMA) and/or 2-ethylhexyl 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 the context of the present invention, the oxygen sensitive radical initiator is an organoborane compound. The reactive precursor mixture as envisaged herein, particular component A of the oxygen-curable composition as envisaged herein, thus comprises a non-metal based initiator system. In the context of the present invention, the organoborane radical initiator compound is added to or present in the reactive precursor mixture in a form that the composition remains unreactive prior to application, such as when stored in a closed container, and that polymerisation and crosslinking is only initiated upon application of the composition, such as upon spraying or dispensing the composition from the closed container. In the context of the present invention, the organoborane radical initiator compound is added to or present in the reactive precursor mixture as a stabilized, inactive complex. Advantageously, the organoborane complex remains stable and inactive despite the presence of residual oxygen from the atmosphere or air in the reactive precursor mixture. Advantageously, the use of stabilized organoborane complex as envisaged herein avoids additional measures to remove the oxygen from the composition in an attempt to critically control or limit the oxygen content in a similar reactive precursor composition below 1 ppm, or preferably below 0.1 ppm. Such deoxygenation measures would be necessary when a highly oxygen-sensitive but unstabilized organoborane compound is used as the initiating system to avoid premature curing of the composition, such as during storage in a closed container.

In organoboranes, the boron atom carries 6 valence electrons, thus failing to meet the octet rule. It thus behaves as a strong Lewis acid that instantly reacts with a Lewis base like water and oxygen. Without being bound by theory, the inventors believe that amino compounds have a higher Lewis basicity and thus bind stronger to the boron atom via the empty p orbital, resulting in a strong complex formation. Oxygen and water are unable to eliminate the amino group from the boron center, thus the organoborane amine initiator complex remains insensitive to oxygen.

In preferred embodiments, the organoborane amine complex comprises an organoborane compound according to the formula BR3, in complex with an amine compound, with R being an alkyl or alkoxy group, each independently comprising a carbon chain comprising between 1 and 14 C atoms, preferably comprising a carbon chain comprising between 1 and 6 C or between 1 and 8 C atoms. In particular, the organoborane radical initiator may be an alkyl- or alkoxy-borane according to formula (alkoxy)s-n - B - (alkyl) _n , with n = 0 to 3, and wherein alkyl and alkoxy each independently comprise a carbon chain comprising between 1 and 14 C atoms, preferably between 1 and 8 C or between 1 and 6 C atoms. In particular, the borane compound is a trialkyl borane, and may be selected among the group of tri methyl borane, triethylborane, tripropyl borane, tributylborane, tri-sec-butylborane, tri hexyl borane, trioctylborane, tridecylborane, tritridecylborane, triethylborane, methoxydiethylborane, and tributylborane are preferred borane compounds. More preferably, the organoborane initiator compound is a trialkyl borane like triethyl borane 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. In particular, the organoborane compound with the formula BR3 has reacted with an amine compound to form a stable organoborane amine complex that is not sensitive to oxygen.

The amines used to complex the organoborane compound can be any amine or mixture of amines which complex the organoborane and which can be decomplexed when exposed to a decomplexing agent. The desirability of the use of a given amine in an amine/organoborane complex can be calculated from the energy difference between the Lewis acid-base complex and the sum of energies of the isolated Lewis acid (organoborane) and base (amine) known as binding energy. The more negative the binding energy the more stable the complex. It is within the ordinary skill of the skilled person to calculate such binding energies, particularly using theoretical ab initio methods. Suitable organoborane complexing amine compounds are particularly disclosed in US6762260B2, which is incorporated herein by reference. They have particularly binding energies of at least 10 kcal/mol, such as between 10 kcal/mol and 50 kcal/mol, preferably at least 15 kcal/mol or between 15 kcal/mol and 30 kcal/mol, more preferably as at least 20 kcal/mol or between 20 kcal/mol and 30 kcal/mol. 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.

Preferably, the organoborane amine complex is present in an amount comprised between 0.1 and 10 wt.%, with respect to the total weight of the reactive precursor mixture of the composition according to the invention, particularly with respect to the weight of the reactive precursor mixture of component A, preferably between 0.1 and 6 wt.%, more preferably between 0.1 and 2 wt%. In particular embodiments, the organoborane amine complex may be a commercially available borane complex like triethylboranediethylenetriamine complex (TEB-DETA), triethylborane-1 ,3-diaminopropane complex (TEB-DAP) or tri-n-butylborane-methoxypropylamine complex (TnBB-MOPA) available from Callery, now part of Ascensus Specialties Callery LLC.

In particular embodiments, component B comprises an amine reactive substance, that is able to disintegrate the organoborane amine complexes as envisaged herein. Said amine reactive substances are known in the art and include acids, aldehydes, or anhydrides. Non limiting examples of suitable amine reactive substances provided herein are acetic acid, propionic acid, butyric acid, and longer chain fatty acids, acetaldehyde, propionaldehyde, butyraldehyde, and longer chain aldehydes, aromatic aldehydes like benzaldehyde and vanillin, acetic anhydride, succinic anhydride, and other anhydrides. Particularly preferred amine reactive substances include acetic acid or propionic acid, benzaldehyde, acetic anhydride or succinic anhydride. More in particular, the amine reactive substances are present in an amount comprised between 0.1 and 10 wt.%, with respect to the total weight of the reactive precursor mixture of the composition according to the invention, particularly with respect to the weight of the reactive precursor mixture component B, preferably between 0.1 and 6 wt.%, more preferably between 0.1 and 2 wt%.

In the context of the present invention, it is understood that the initiating or curing activating system comprising an organoborane radical generating compound as described herein occurs in two modes, i.e. a passive or inactive mode and an active or radical generating mode.

The passive mode corresponds to the situation during storage of the oxygen- curable precursor composition according to the present invention, particularly wherein component A of the oxygen-curable precursor composition according to the present invention is physically separated from component B, 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 stable complex of the organoborane with an amine, which is physically separated from the decomplexing agent and does not react with oxygen.

As long as the complex is intact, the oxygen-curable precursor composition cannot cure despite the presence of oxygen in the precursor composition, as for example from contact with the air before filling the canister. To ensure the passivation of the system, controllable measures are implemented to avoid the presence of amine reactive substances including mineral acids, organic acids, Lewis acids, aldehydes, ketones, and the like. A known methodology to monitor the stability of the complex in the reactive precursor mixture is electron paramagnetic resonance spectroscopy. If the complex disintegrates, radical formation is eminent and detectable as paramagnetic species.

The active mode corresponds to the situation upon application of the oxygen- curable composition of the present invention, such as during and after dispensing, particularly upon mixing of component A and component B, when the organoborane complex is disintegrated to release the oxygen reactive organoborane that starts oxygen initiated free radical formation and subsequent curing of the oxygen-curable precursor composition. The organoborane complex may be disintegrated thermally with instability starting at 50°C and becoming more prominent at higher temperature. However, a more controlled way is to disintegrate the complex by contacting the complex with a substance, such as an amine reactive substance, that selectively reacts with the complex and causes disintegration of the complex with release of the organoborane initiator compound. When the organoborane amine complex is contacted with an amine reactive substance, such as by mixing component A and component B, the amine complex disintegrates and the organoborane is released and the initiating system is activated. The reaction of the organoborane with the oxygen from the air or with the oxygen present in the reactive precursor mixture leads to quick release of free organic radicals, independent of the ambient temperature, thus resulting in the curing of the dispensed foam precursor mixture. Advantageously, the curing kinetics of the reactive precursor mixture are not dependent on the weather and climate of the place of application: the curing rate is not controlled by humidity and is constant regardless of the moisture content of the atmosphere. In addition, the product can also cure at temperatures below freezing point.

In the context of the present invention, physical deoxygenation of the compositions and mixtures used in the present invention is not needed. Moreover, the presence of residual oxygen or air in the reactive precursor mixture is particularly advantageous for ensuring an optimal curing of the composition according to the present invention. Oxygen or air dissolved in or present in the reactive precursor mixture makes the curing mechanism less dependent on the migration of oxygen from the atmosphere into the mixture during curing. In general, the curing reaction via a radical addition reaction is fast at the interface between the reactive mixture and the atmosphere, where the concentration of oxygen is high, resulting in a fast skin formation, which reduces permeability and oxygen migration inwards the curing mixture. In its turn, this may lead to inhomogeneous distribution, and a disfavoured curing direction from the outward to the bulk of the mixture. The presence of oxygen inside the precursor mixture may thus counter the reduced oxygen migration and contributes to a more homogenous curing.

In particular embodiments, component A and/or component B may comprise an aerobic radical scavenger. The radical scavenger as envisaged herein is a compound capable of capturing accidently occurring free radicals during storage, before application, for preventing the premature curing of the foam precursor composition under the conditions whereunder the reactive precursor mixture is stored. It is known to those skilled in the art to use radical scavengers in compositions containing compounds with vinyl functional groups to prevent unwanted polymerization or curing of such composition. It is also known that these radical scavengers typically require some oxygen to be efficient, and thus are effective in the reactive precursor mixture that contains residual oxygen. A preferred radical scavenger is mequinol, also known as methylhydroquinone or 4- methoxyphenol. Preferably, the 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 reactive precursor mixture of component A and/or component B further comprises one or more other additives, including but not limited to rheology modifiers, plasticizers, flame retardants, crosslinkers, blowing agents, 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 organoborane initiator amine complex.

In particular embodiments, the present invention relates to an oxygen-curable polymerizable foam precursor composition, particularly stored in a pressurized container system, comprising:

(i) a component A comprising a first reactive precursor mixture and a reversibly inactivated radical initiator, wherein said first reactive precursor mixture comprises a urethane and/or polyester (meth)acrylate and/or polyether (meth)acrylate compound with 1 to 6 vinyl moieties, a reactive diluent comprising a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties as defined herein and, optionally, further comprising an unsaturated polyester resin, and wherein said radical initiator is particularly an organoborane amine complex radical initiator as described herein, and

(ii) a component B comprising a second reactive precursor mixture and an amine reactive substance, wherein said second reactive precursor mixture is as described for the first reactive precursor mixture ofcomponent A, preferably wherein the first and second reactive precursor mixtures are the same, wherein the composition becomes curable upon mixing the component A with the component B.

In more particular embodiments, component A and component B of the oxygen- curable polymerizable foam precursor composition, particularly stored in a pressurized container system, 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-)acrylate with 3 to 6 vinyl functional groups, preferably 3 to 5, most preferably 3 to 4 vinyl functional groups, optionally (c) an unsaturated polyester resin, and (d) a reactive diluent, comprising (meth)acrylated monomers with 1 to 4 vinyl functional groups. Advantageously, the acrylate or methacrylate functional groups permanently block the generally toxic and harmful diisocyanates groups in the backbone of the (urethane) prepolymers. Typically, the aromatic urethane (meth-)acrylates as described herein contribute to a higher reactivity of the precursor mixture and contribute to the resilience and rigidity of the final foam product. Aliphatic urethane (meth-)acrylates contribute to a high cure speed at low temperatures, to the flexibility 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 certain embodiments, component A and component B of the oxygen-curable polymerizable foam precursor composition, particularly stored in a pressurized container system, 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 di-isocyanate; (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 di-isocyanate; (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) optionally, an unsaturated polyester resin (LISPER); (v) a radical scavenger or inhibitor; and (vi) preferably, one or more additives, such as a surfactant, a flame retardant, and the like.

In particular embodiments, the reactive precursor mixture of component A and/or B comprises about 60-95 wt%, such as 70-95 wt%, of a urethane and/or polyester (meth)acrylate compound with 1 to 6 (meth)acryloyl functional groups; 0-25 wt%, such as 0-10 wt%, of a reactive diluent and 0-10 wt% of other additives, with wt% expressed on the total weight of the reactive precursor mixture.

Particularly high quality foams were obtained with reactive precursor mixtures, wherein the ratio between polyfunctional (>4) : tri- + difunctional : monofunctional vinyl functional groups, particularly (meth)acrylates, present in the reactive precursor mixture of component A and/or B is 10-20 : 70-80 : 5-15, preferably is 12-18 : 72-78 : 7-12, such as 15:75:10 (for polyfunctional, tri+difunctional and monofunctional respectively).

It is understood that the reactive compounds of the foam precursor composition are designed, prepared and combined, in order to (a) be able to undergo cross-linking 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 non-toxic 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 two component (2K) foam system, wherein the inactive initiator complex is dissolved in a first compartment with a reactive precursor mixture, and referred to as component A, is physically separated from the decomplexing substance dissolved in a second compartment with the same reactive precursor mixture, and referred to as component B. Advantageously, as the reactive precursor mixture compositions in both compartments are nearly or essentially completely identical, and thus have nearly identical rheology, mixing of the two components A and B is very efficient.

Another aspect of the present invention provides a container system, preferably a pressurized container system, comprising the oxygen-curable foam precursor composition according to the present invention, particularly wherein component A, comprising the stable and inactive organoborane amine complex, and component B, comprising the decomplexing agent, are physically separated from each other. In particular embodiments, the container system comprises a container, such as an aerosol can, containing a first compartment comprising component A and a second compartment comprising component B, preferably wherein the first and second compartment are pressurized with a blowing agent or propellant. In other particular embodiments, the container system comprises a first container comprising component A and a second container comprising component B, preferably wherein the first and second container are pressurized with a blowing agent or propellant.

In the context of the present invention, the composition or container system may further comprise a blowing agent or propellant to create a pressurized system, such as a pressurized container system or aerosol system, 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. In particular embodiments, the container system comprises a means adapted to dispense and mix component A and component B upon dispensing. Particularly, the container system further comprises a dispenser with a static mixer.

Another aspect of the present invention provides a method for preparing an oxygen-curable foam precursor composition, which contains a passivated, i.e. inactivated radical initiator complex as envisaged herein. Said method for preparing an oxygen- curable precursor composition comprises the steps of

(i) preparing a first component A by mixing an organoborane compound as radical initiator with a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer as envisaged herein, wherein said organoborane compound is an organoborane amine complex as envisaged herein;

(ii) preparing a second component B by mixing an amine reactive substance as envisaged herein with a reactive precursor mixture, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer.

In particular, said reactive precursor mixture comprises at least one ethylenically unsaturated compound having 1 to 10 free-radically polymerizable carbon-carbon double bonds, more preferably comprises at least one vinyl compound, such as an acrylate or methacrylate compound, an allyl ether compound or a styrene compound, even more preferably comprises a urethane and/or polyester (meth)acrylate compound with 1 to 6 vinyl moieties.

In certain embodiments, said method comprises the steps of (a) preparing or providing a reactive precursor mixture as envisaged herein, wherein the reactive precursor mixture comprises at least one free-radically polymerizable monomer and/or oligomer; (b) adding to this reactive precursor mixture a stable, passivated and inactive organoborane amine complex, preferably without subjecting the reactive precursor mixture to a prior deoxygenation treatment, thus obtaining component A, comprising an inactive reactive precursor mixture; (c) preparing or providing a reactive precursor mixture similar as described in step (a); (d) adding to this reactive precursor mixture an amine reactive substance, thus obtaining component B. Advantageously, although the reactive precursor mixture cures with oxygen, residual oxygen or air in component A or component B does not need to be removed, nor does component A or B need to be stored under an inert, oxygen free atmosphere, because the organoborane initiator is present in the mixture in an inactive form, as an amine complex. In certain embodiments, the reactive precursor mixture is prepared by mixing the individual components, in particular the free-radically polymerizable monomers and/or oligomers as envisaged herein, and any other components needed to obtain a specific composition, such as optionally LISPER, a reactive diluent, and/or other additives, such as a flame retardant or a surfactant, as described above.

In certain embodiments, the methods according to the present invention further comprises the step of filling at least one container with the oxygen-curable reactive precursor composition according to the present invention. In particular embodiments, the method comprises filling a first compartment of the at least one container with component A as described herein, and a second compartment of the at least one container with component B as described herein. In another embodiment, the method comprises filing a first container with component A as described herein, and a second container with component B as described herein.

Particular embodiments of the present application provide a method to prepare a foam precursor composition, 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, optionally an unsaturated polyester resin, and a diluent comprising a (meth)acrylate functionalized monomer with 1 to 4 vinyl moieties,

(ii) adding an organoborane amine complex as described herein to the reactive precursor mixture of step (i), thereby obtaining component A,

(iii) preparing or providing a reactive precursor mixture similar as described in step (i),

(iv) adding to the reactive precursor mixture of step (iii) an amine reactive substance for destabilizing or disintegrating the organoborane amine complexes, thereby obtaining component B.

In particular, the method further comprising adding a blowing agent or propellant to component A and component B, to create a pressurized system, such as a pressurized container system or aerosol system. Pressurizing the container allows spraying of the foam precursor composition into a curing froth, resulting in 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. Another aspect of the present invention relates to the use of an oxygen curable foam precursor composition as described herein as a two component (2K) sprayable foam composition. Stated differently, the present invention also provides A method for preparing a foam comprising the steps of:

(a) preparing or providing oxygen-curable foam precursor composition as envisaged herein, or preparing or providing a container system comprising an oxygen-curable foam precursor composition as envisaged herein, particularly wherein component A and component B are pressurized with a propellant or blowing agent; and

(b) mixing and dispensing, particularly spraying, component A and component B in an oxygen containing environment or atmosphere, and allowing the mixed components A and B to cure, thereby forming a cured foam.

More in particular, component A and component B of the polymerizable compositions according to the present invention are blended in an operation as one skilled in the art would perform when working with such materials. Indeed, component B comprising the amine reactive substance, also referred to as the decomplexing agent to react with the organoborane amine complex so to release the free organoborane initiator, is included with part of the reactive precursor and separate from component A, comprising the organoborane amine complex, which is preferably included in an identical or similar reactive precursor composition as in component B.

For a 2-component sprayable foam such as described in the present invention to be most easily used in commercial and industrial applications, the volume ratio at which the 2 components are dispensed and mixed is preferably constant. This type of application is facilitated by using commercially available dispensers in combination with a static mixer. In a typical application of the invention, these dispensers are aerosol cans or cannisters arranged side-by-side connected by tubes with each tube transferring one component of the 2-component system to a mixing valve. By pressurizing the two cans or cannisters each containing a component of the 2-component system to similar pressure, a constant volume ratio at which the 2 components are dispensed upon opening the valve is obtained. It is particularly advantageous that the viscosities of component A and component B are similar. The similarity in viscosity is preferably equal or greater than 90%, more preferably equal or greater than 95%, and most preferably equal or greater than 98%. Upon opening the valve, the two components are thus simultaneously advanced with similar velocity to release the reactive precursor mixtures from the cans or cannisters via the tubes through the valve into a static mixer, for instance a tube-shaped mixing chamber that contains a static mixer to enhance the mixing of the two components. The blended reactive precursor mixtures are extruded from the mixing chamber as a curable froth that blows by expansion of the gaseous propellant and by the evaporation of liquified propellant. The curing process commences instantly and the blown froth cures to a solid foam. As the tube-shaped mixing chamber with static mixer remains filled with curing mixture after use, the chamber thus needs to be replaced before the process of spraying can be continued at a later stage. Alternatively, the spraying chamber can be reused after mechanically removing the cured foam.

In an alternative application of the invention, the dispenser is an aerosol can or cannister that contains two compartments that separates one component from the other component of the 2-component system by a physical barrier. Without being bound by a specific technological setup, such compartments can be formed by a bag in a can, two bags in a can, a can in a can, and the like. By pressurizing the two compartments of the can or cannister, the reactive precursor mixtures can be dispensed by operating a single valve connected to the two compartments. The ratio at which the two components are combined is dependent of the volume of the two compartments. If the volume of the two compartments is equal, the preferable mixing ratios are between 2:1 and 1 :2 and more preferably, 1 :1. If the volume ratio of the two compartments is 2:1 , the preferable mixing ratios is between 4:1 and 1 :1 , and more preferably 2:1. It is obvious that other volume ratios of the two compartments proportional other preferable mixing ratios.

Advantageously, the foam obtained by the methods and composition according to the present invention have excellent curing properties, both at the surface and within the foam. In particular embodiments, a tack-free foam, expressed as the Tack Free Time and measured according to FEICA test method 1014:2013 and representing the surface curing, is obtained within 150 s, particularly within 120 s after dispensing. In particular embodiments, the foam curing, expressed as the cutting time measured according to FEICA test method 1005:2013 and representing the internal curing, is complete in less than 10 min, preferably in less than 8 min or even less than 6 min.

EXAMPLES

The following examples explain in more detail the present invention. They are not under any circumstances exclusive and do not intend to limit the scope of the present invention.

The following examples provide a polymeric foam precursor blend, further called “blend”, essentially composed of urethane acrylate or polyester acrylate, reactive diluent, cross-linking agent, fire retardant, and surfactant. This blend was divided over two cans which are referred to as “compartment A” and “compartment B”, respectively. An alkyl borane amine complex, in particular TEB-DAP, was added to compartment A and the resulting blend comprising the alkyl borane amine complex is further referred to as “component A”, as is described in more detail below. An amine reactive substance, in particular acetic acid, was added to compartment B and the resulting blend is further referred to as “component B”. The viscosity and density of the blend were determined before filling the compartments.

After spraying the froth by blending components A and B, Tack Free Time (TFT) and Cutting Time (CT) were monitored. After full curing, Brittleness (B), Density on Paper (DP), Density in Mould (DM), Compression (% Comp.), Adhesion (Adh.), and Elongation at Fmax (EF) were determined, as reported in Tables 1 and 2. The parameters of the blends according to the present application are compared to those obtained for commercial isocyanate-curing formulas (from Rectavit) and against a proprietary isocyanate-curing formula (referred to as Greenseal 2).

Example 1. Formulation based on combination of urethane acrylate, urethane methacrylate and epoxy acrylate

A polymeric foam precursor blend was prepared by mixing 24 parts CN9196, 24 parts CN1963CG, 32.4 parts CN104A80, 11.84 parts iBOMA, 4.16 parts TPGDA, 3.6 parts 2- EHMA, 8 parts TCPP and 3 parts Tegostab B8870. CN9196 is a hexafunctional aromatic urethane acrylate, CN1963CG is a difunctional aliphatic urethane methacrylate and CN104A80 is a difunctional epoxy acrylate (diluted with TPGDA). All are commercially available products from the company Sartomer. Tegostab B8870 is a commercially available surfactant from the company Evonik.

Compartment A was filled with 51.15 g blend and 1 mL TEB-DAP. Compartment B was filled with 51.15 g blend and 2 mL acetic acid.

The cans were capped and each was pressurized by addition of 18.2 mL DME. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. Viscosity of blend and density of blend were determined before filling the compartments.

Example 1 is a fast-curing foam without shrinking, but with high brittleness and high density.

Example 2. Formulation with flexible urethane acrylates and a combination of DME and isobutane as propellants.

A polymeric foam precursor blend was prepared by mixing 12.4 parts CN9196, 30 parts Ebecryl4101 , 40 parts Ebecryl210, 11.84 parts iBOMA, 4.16 parts TPGDA, 3.6 parts 2- EHMA, 8 parts TCPP and 3 parts Tegostab B8870. CN9196 and Tegostab B8870 are as in example 1. Ebecryl4101 is a trifunctional aliphatic urethane acrylate and Ebecryl210 is a difunctional aromatic urethane acrylate. Both are commercially available products from the company Allnex.

Compartment A was filled with 50.19 g blend and 1 mL TEB-DAP. Compartment B was filled with 50.19 g blend and 2 mL acetic acid.

The cans were capped and each was pressurized by addition of 8.13 mL DME and 10.1 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. A fast-curing foam without shrinking, with high density was produced. Compared to example 1 , the flexible urethane acrylates backbone reduces the brittleness of the foam.

Example 3. Formulation with increased volume of propellant mixture.

A polymeric foam precursor blend was prepared by mixing 24 parts CN9210, 25 parts CN1963CG, 32.40 parts CN104A80, 11.84 parts iBOMA, 4.16 parts TPGDA, 3.6 parts 2- EHMA, 8 parts TCPP and 2 parts Tegostab B8485. CN1963CG, CN104A80 and Tegostab B8485 are as in example 1. CN9210 is a hexafunctional aliphatic urethane acrylate and is commercially available from the company Sartomer.

Compartment A was filled with 44.77 g blend and 0.9 mL TEB-DAP. Compartment B was filled with 44.77 g blend and 1 .8 mL acetic acid.

The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. Some foam shrinkage was observed but the higher propellant ratio gives foam that has lower density.

Example 4. Formulation with a reactive diluent.

A polymeric foam precursor blend was prepared composed of 17 parts CN9196, 66 parts Ebecryl4101 , 10 parts Ebecryl210, 10.6 parts iBOMA, 8 parts TCPP and 2 parts Tegostab B8485. CN9196, Ebecryl4101 , Ebecryl210 and Tegostab B8485 are as in the preceding examples.

Compartment A was filled with 44.77 g blend and 0.9 mL TEB-DAP. Compartment B was filled with 44.77 g blend and 1 .8 mL acetic acid.

The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. The cured foam is not brittle and has a low density.

Example 5. Formulation without a reactive diluent.

A polymeric foam precursor blend was prepared by mixing 29 parts CN9196, 59 parts Ebecryl4101 , 12 parts Ebecryl210, 8 parts TCPP, 2 parts Tegostab B8485 and 2 parts NX-7214. NX-7214 is a trifunctional, branched acrylate commercially available from the company Cardolite. CN9196, Ebecryl4101 , Ebecryl210 and Tegostab B8485 are as in the preceding examples.

Compartment A was filled with 45.37 g blend and 1.2 mL TEB-DAP. Compartment B was filled with 45.37 g blend and 2.4 mL acetic acid.

The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. The higher amount of initiator complex and decomplexing agent shortens curing time.

Example 6. Formulation with a reactive diluent and less compatibilizer.

A polymeric foam precursor blend was prepared by mixing 26 parts CN9196, 56 parts Ebecryl4501 , 9 parts Ebecryl210, 9 parts iBOMA, 8 parts TCPP, 2 parts Tegostab B8485 and 1 part NX-7214. Ebecryl4501 is an aromatic urethane acrylate with a functionality of 3.9 and is commercially available from the company Allnex. CN9196, Ebecryl210, Tegostab B8485 and NX-7214 are as in the preceding examples.

Compartment A was filled with 45.28 g blend and 0.9 mL TEB-DAP. Compartment B was filled with 45.28 g blend and 1.8 mL acetic acid. The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions.

Example 7. Formulation with alternative crosslinker.

A polymeric foam precursor blend was prepared by mixing 26 parts Ebecryl221 , 56 parts Ebecryl4501 , 9 parts Ebecryl210, 9 parts iBOMA, 8 parts TCPP, 2 parts Tegostab B8485 and 1 part NX-7214. Ebecryl221 is a hexafunctional aromatic urethane acrylate commercially available from the company Allnex. Ebecryl4501 , Ebecryl210, Tegostab B8485 and NX-7214 are as in the preceding examples. Compartment A was filled with 45.80 g blend and 0.9 mL TEB-DAP. Compartment B was filled with 45.80 g blend and 1.8 mL acetic acid. The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. The high functionality urethane acrylates with crosslinking properties resulted in desirable foam characteristics.

Example 8. Formulation based on a polyester acrylate.

A polymeric foam precursor blend was prepared by mixing of 100 parts CN2303EU, 8 parts TCPP and 2 parts Tegostab B8485. CN2303EU is a hexafunctional hyperbranched polyester acrylate commercially available from the company Sartomer.

Compartment A was filled with 44.26 g blend and 1 mL TEB-DAP. Compartment B was filled with 44.26 g blend and 2 mL acetic acid. The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions.

Example 9. Formulation based on an acrylic oligomer combined with a urethane acrylate crosslinker.

A polymeric foam precursor blend was prepared by mixing of 50 parts Ebecryl221 , 50parts CN2912, 8 parts TCPP and 2 parts Tegostab B8485. CN2912 is a trifunctional acrylic oligomer commercially available from the company Sartomer. Ebecryl221 and Tegostab B8485 are as in the preceding examples.

Compartment A was filled with 46.18 g blend and 1 mL TEB-DAP. Compartment B was filled with 46.18 mL blend and 2 mL acetic acid. The cans were capped and each was pressurized by addition of 5.07 mL DME and 18.8 mL isobutane. The cans were shaken for about 5 minutes and fixed to a 2K gun with a disposable static mixing nozzle. The cans were sprayed out on a paper surface under ambient conditions. Replacing the urethane acrylate content by alternative polyester acrylates (as in examples 8 and 9), the foam is not tough and has high brittleness.

The characteristics of the different blends and foams prepared in examples 1-9 are summarized in Tables 1 and 2, and compared with comparative examples RectaPUR, Multifoam and Greenseal2. The parameters are measured according to FEICA test methods, in particular: FEICA TM 1005:2013: Measurement of cutting time, used for determination of the cutting time of an OCF1 canister foam;

FEICA TM 1014:2013: Measurement of tack free time, used for determination of the tack free time of an OCF1 canister foam;

FEICA TM 1008:2013: Measurement of brittleness, used for determination of the brittleness of an OCF1 canister foam. Integers 1 to 4 represent brittleness assessment in following order: 1 : The foam is flexible and makes no noise at all, 2: The foam creaks but does not break, 3: The foam breaks, 4: The foam pulverizes. Tests were carried out at ambient temperature and relative humidity, 1 day after foam was sprayed.

FEICA TM 1002:2014: Density mould, used for determination of the density of foam in a joint to calculate the joint yield of an OCF1 canister foam;

FEICA TM 1019:2014: Density paper, used for determination of the free foamed density of an OCF1 canister foam;

FEICA TM 1011 :2015: Compression strength, used for determination of the compression strength of an OCF1 canister foam. Wooden boards were used as such and not immersed in water. The reported value is the result of one measurement.

Adhesion strength and elongation at Fmax: All test specimens are prepared by foaming between two wooden plates. The foam dimensions between the two substrates are 50 +/- 2 mm x 50 +1-2 mm x 30 +1-2 mm. After 24h, the specimen is stretched by a tensile testing machine (Instron), gradually increasing the distance at a set speed of 2mm/min until the sample fractures. The adhesion strength is the maximum force withstood by the specimen, expressed in Newton per unit area. The elongation at this maximum force is also reported. The reported values are the result of one measurement.

Density of the blend: The density of the blend is measured by first weighing a volume of it in a recipient and marking the blend level. Next the recipient is emptied, filled with water till the level mark and the water volume is determined by its weight.

Viscosity of the blend: Blend is acclimatised overnight at 23°C and 50% relative humidity. The viscosity is measured with a rotational viscosimeter (I KA) with a standard spindle at a speed of 20 or 50rpm.

TABLE 1

(foam);

* Rectavit Multifoam; ** GreenSeal benchmark isocyanate curing foam; NA: not assessed

TABLE 2 B: Brittleness; DP: Density Paper; DM: Density Mould; Comp.: Compression; Adh.: Adhesion; EF: Elon. Fmax. * Rectavit Multifoam. ** GreenSeal benchmark isocyanate curing foam; NA: not assessed; SHR: Shrinkage of foam; SF: Sample failed, no adhesion to wood test specimen. The experimental data indicate that the methods and compositions of the present invention effectively result in the fast curing of a polymeric foam precursor blend. Borane initiator, TEB-DAP as used in examples, leads to a fast surface curing at the interface between froth and atmosphere where oxygen concentration is high and radical production from the borane initiator is high. The excellent surface curing gives a tack-free foam within minutes. The efficient mixing of the high viscosity blends gives an extensive contact between the 2 components of the formula which is ideal for an efficient initiation reaction, and which is aided by the similar, particularly identical, viscosities of component A and component B. The internal curing is homogeneous and instant to result in full curing time in shorter than 10 min.

A person skilled in the art will understand that the foam examples described above are merely illustrative. In accordance with the present invention, and not limiting the intended scope of the invention, other borane initiator complexes including TnBB-MOPA, TEB- DETA, and the like produce foams with comparable characteristics. Other formula compositions in application of the present invention may also be considered.