The field of the present invention relates to the incorporation of functional additives, such as thermo- regulators, in sub-micron particles based on a maleimide polymer, and to the uses thereof on different surface types, such as in fabrics.

Background of the invention

Fabrics (woven, knits, non-woven,...) are an intersection of different yarns, fibers and tapes. Paper, wood, carton are also based on intersected fibers (e.g. cellulosic) . The functionality of intersected fibers can be adapted by additives, such as encapsulated additives.

The encapsulation of additives is well known in the textile industry and has been specifically developed there. For instance, melamine-formaldehyde encapsulated thermo-regulators , anti-microbial or flame retardants have been developed for improving the textile properties in textile industry. Almost all the encapsulation systems are based on melamine formaldehyde chemistry, at least for the thermo-regulator additives, allowing to encapsulate high amounts of functional additives, such as thermo-regulators .

Indeed, the encapsulation of high amounts of the functional additives is usually necessary to meet commercially-acceptable standards. For instance, in the case of thermo-regulators additives (e.g. a specific wax) for special textiles, the current market standard is set at 1000 J/m ² , and values of 2500 J/m ² are those of a top heat absorber. Thus there is a need to stably add high quantities of functional additives.

However, several disadvantages occur, such as the difficulties to apply high quantities of the functional additive, or detrimental consequences for the end- product, including increased rigidity or impaired colors, requiring further correcting additives. Moreover, depending on the functional additive to incorporate, different chemistries must be combined resulting into unstable formulations. Furthermore, melamine-formaldehyde based formulations must be quite viscous, otherwise, there is sedimentation.

In other words, to meet customer's standards, high amount of particles must be added, which is challenging. On the other hand, any blending of additives results into diluted additives and any dilution of one additive is detrimental since requiring addition of more particles. Thus, when thermo-regulators are applied on textile, usually no other functional additives can be added on the same surface, unless based on different chemistries.

Moreover, the durability of the currently marketed additives is not sufficient. Even in the case of additive incorporation inside the target structure, additives might diffuse over the time.

Processing conditions furthermore limit the possibility to choice additives to encapsulate, for instance, heat- unstable additives cannot be used for capsules having a production process requiring high temperatures (smoke release, problems with volatile components,...).

WO 2008/014903 discloses an aqueous polymer dispersion made by reacting a co-polymer of maleic anhydride and styrene with an aqueous solution of ammonia for performing an imidation reaction. This polymer has then been used as replacement of melamin-formaldehyde for encapsulation of oils or paraffin so as to impart a hydrophobic effect to paper. However, this study has not addressed the challenges of textile industry, such as the need to load high amounts of functional additives.

Summary of the invention

The present invention relates to a process for treating a substrate comprising the steps of forming particles based on a maleimide containing polymer comprising a functional additive so as to form a homogenous mixture, this homogenous mixture being applied to the substrate and being dried or cured.

Advantageously, to the homogenous mixture of maleimide- based particles comprising a functional additive, a polymer formulation (the polymer having a Tg between - 60°C and 50°C, more preferably between -55°C and 0°C) is added forming a second homogenous mixture, so that the polymer formulation once dried or cured forms a film on the substrate, wherein the maleimide-based particles are dispersed. Preferably, the mass ratio between the maleimide-based particles and the polymer added with the formulation is comprised between 1:100 and 100:1, preferably, between 1:10 and 10:1, more preferably between 1 : 3 and 3:1.

Preferred polymers having a Tg between -60°C and 50°C are selected from the group consisting of acrylics, polyurethanes , poly vinyl acetate, Polyamides (PA) , styrenebutadiene latex, natural or synthetic rubber, poly vinyl butyral, polyethylene, Ethylene Vinyl Acetate (EVA) , polyesters, natural latex, bio-based polymers (e.g. polymers and derivatives thereof from monomers from natural sources, such as poly-neoprenes , poly-isoprenes and polylactic acid), and halogenate derivatives thereof. Preferably, the maleimide-based particle (further comprising functional additives) is a reaction product of a co-polymer of maleic anhydride and styrene with an alkyl amine. Preferably at least 50% of the anhydride is transformed into the imide (e.g. between 50% and 95%, possibly between 60% and 90% or even between 60% and 80%) .

Advantageously, the maleimide-based particle comprises one or, preferably several, functional additive (s) (embedded in the same particles or embedded in different particles) selected from the group consisting of thermo- regulating agent (e.g. a specific wax), flame retardant, anti-microbial agent, insecticide, antimite anti-acarid agent, aroma or odorant, UV or IR adsorbing agent, plasticizer and rigidity-affecting agent, preferably these particles comprise a thermo-regulating agent and possibly further comprise another functional additive of the above list.

Preferably, the thermo-regulating agent is a component or a mixture of components having a solid-liquid transition phase between 4°C and 50°C, more preferably, the transition phase temperature (from 80% solid to 80% liquid) of the thermal regulating agent is narrow (e.g. in a range of less than 10°C, preferably, less than 4°C) . Suitable thermo-regulating agents are selected from the group consisting of alkanes, paraffin, wax, mineral oils, vegetable oils or fats and modified (i.e. hydrogenanted or fractionated) vegetables oils.

Preferably, the maleimide-based particle comprises between 10 wt% and 70 wt% of the functional additive (s) : wt of the sum of the functional additive : total wt of the maleimide-based particles.

Preferred substrates are selected from the group consisting of fabrics (e.g. textiles, non-woven fabrics; any textile or fabrics are suitable) , cellulosic material (paper, carton boards) , leather (natural or artificial) , wood, paints and concrete. A most preferred substrate is a surface, such as fabrics (a textile or a non-woven fabric; for instance wovens, knits, tufted, sticht bound, carpets,...) or synthetic leather.

A fiber (cellulosic or to be used in fabrics) is also a possible surface.

Preferred polymer formulations are selected from the group consisting of a solution, an emulsion, a dispersion or a solvent-free composition (e.g. of monomers and/or of oligomers) , more preferably, the polymer is in the aqueous phase.

Preferably, the mixture added on the substrate (preferably further comprising the polymer formulation) is dried, for instance upon heating, or cured, for instance upon UV exposure.

The mixture is added to the surface by spraying, coating, printing, laminating or by impregnation (i.e. dipping so as to incorporate a known amount of the mixture) . The coating step is preferably made by the application of a foam (instable, stable or crushed), or by kiss roll. Low viscous to very high viscous pastes can be applied by this technique. A related aspect of the present invention is the substrate coated after this process. Another related aspect of the invention is a (a homogenous) composition comprising particles based on a maleimide polymer further comprising a thermo-regulating agent (e.g. a specific wax) and possibly one or several other functional additive.

Preferably this formulation comprises, further to the maleimide particles, a formulation of a polymer having a Tg between -60°C and 100°C (preferably between -55° and 50°, more preferably between -50°C and 0°C) .

Preferably, the maleimide polymer comprises a poly(styrene maleimide) polymer.

The weight ratio between the particle and the polymer added to this composition together with the formulation is advantageously comprised between 1:100 and 100:1, preferably, between 1:10 and 10:1, more preferably between 1 : 3 and 3:1.

Preferably, the maleimide-based particle (further comprising functional additives) is a reaction product of a co-polymer of maleic anhydride and styrene with ammonia or an alkyl amine. Preferably at least 50% of the anhydride is transformed into the imide (e.g. between 50% and 95%, possibly between 60% and 90% or even between 60% and 80%) . This (homogenous) composition can be in the form of a foam or of a paste: a paste or a foam comprising, consisting essentially of, or consisting of this composition . Another related aspect of the invention is the use of a (a homogenous) composition comprising particles based on a maleimide polymer for encapsulating at least two additives selected from the group consisting of thermo- regulating agent (e.g. a specific wax), flame retardant, anti-microbial agent, aroma or odorant, UV or IR adsorbing agent, and rigidity-affecting agent.

Preferably, in this use, the composition further comprises a formulation of a polymer having a Tg between -60°C and 100°C (preferably between -55° and 50°, more preferably between -50°C and 0°C).

Preferably, in this use, the maleimide polymer comprises a poly(styrene maleimide) polymer.

Brief description of the figures

Figure 1 : Diagram showing the measurement of glass transition temperature (Tg) of a polymer of the present invention .

Figure 2 shows the heat absorption properties of different compositions of the present invention.

Figure 3 shows the absorption properties in function of heating/cooling cycles.

Figure 4: Dispersion of poly(styrene maleimide) -based particles.

Figure 5: Dispersion of poly(styrene maleimide) -based particles : polymer according to a preferred aspect of the present invention.

Detailed description of the invention

The inventors have found that it is possible to use the small particles based on a maleimide polymer to encapsulate functional additives in an amount sufficient to allow the additive to exert its desired function, even in the case of the additive, or of one of the additives, is a thermo-regulating agent. The addition of a polymer formulation (of a Tg between - 60°C and 100°C, preferably between -55° and 50°, more preferably between -50°C and 0°C) to the maleimide-based composition, despite of the dilutive effect caused by the polymer, that can be major, allows to more stably incorporate the maleimide particle on a substrate such as a surface and is even useful to narrow the temperature transition range to the desired temperature (e.g. corresponding to the temperature of the skin) .

Furthermore, the smooth process conditions associated to poly maleimide-based particles allow to work in one single step with several additives.

In addition, the choice of the polymer formulation allows to easily adapting the stiffness of the resulting composition, while the adaptation of its relative abundance with regard to the maleimide-based particle allows the optimization of the resulting properties.

Finally, the present mixture, which is stable and non- viscous, can be applied in different forms, such as a foam or a paste, that will in turn produce specific properties (e.g. breathability when applied as a foam vs air tight when applied as a paste) , depending on the needs . The inventors have chosen the challenging way to try to develop, for the textile industry, particles based on a poly(styrene maleimide) particles and not to select the well-established melamine-formaldehyde coating system. Indeed, a suspension of poly(styrene maleimide) particules, when dried, results into a gel full of cracks, then into a powder. This makes it challenging to use such particles as an encapsulating system to be stably applied on substrates such as surfaces, especially in textiles (exposed to weather conditions, to friction, to washings,...), at least if the goal is to have a long- lasting effect. A first aspect of the present invention is a process for treating a substrate comprising the steps of forming particles based on a maleimide containing polymer and comprising a functional additive, of obtaining an homogenous mixture, of adding this mixture on a substrate, and of allowing the mixture to dry or to cure. Advantageously, the process further comprises a step of mixing a polymer formulation to the particles based on a maleimide containing polymer and comprising a functional additive so as to form a second homogenous mixture; in this process, the drying or curing step allows the polymer to become a film on this substrate, for instance a film where the polymer forms a matrix where the maleimide containing particles are homogenously dispersed .

Advantageously, the maleimide containing particles are small, with a mean diameter between (about) 100 nm (preferably about 200 nm) and (about) 1 ym (preferably less than 300 nm) .

By "particles based on maleimide" or "particles based on a maleimide polymer", it is preferably meant a poly(styrene maleimide) copolymer stably charged with a functional additive.

The "particles based on maleimide (or on a maleimide polymer) " may also be formed from other cyclic anhydride (for instance an unsaturated organic molecule with two carboxylic groups on one molecule, so as to form a cyclic anhydride, possibly with a molecular weight of less than 300 Da, possibly less than 200 Da) . These cyclic anhydrides are co-polymersised with olefins such as styrene, ethylene, propylene, alpha-olefins . The cyclic anhydride is usually maleic anhydride, but can also be itaconic anhydride or substituted derivatives of maleic anhydride. The corresponding cyclic anhydride containing polymers (co-polymer) are then reacted with an alkyl amine to form the corresponding reaction products: imides, amides and ammonium salts. Preferably, the cyclic anhydride is for more than 50% transformed into the imide (e.g. between 50% and 95%, possibly between 60% and 90% or even between 60% and 80%) . After the transformation the maleimide containing polymer will form a particle. During the transformation of the cyclic anhydride into the maleimide containing polymer non-water soluble or slightly water soluble products can be added. These products will be encapsulated during the transformation process. The resultant particles have usually a size smaller than 1 micrometer, mostly even smaller than 300 nm. The encapsulated additive can make up till 70% of the total weight of the combination encapsulant and encapsulated product.

Due to its small size the maleimide coating particles have multiple advantages compared to the melamine formaldehyde encapsulating systems. The small size provides a much higher stability in the aqueous phase, while having the possibility to keep the viscosity low. The maleimide containing particles are more homogeneously embedded in a resulting coating. Especially in thin coating layers the particles will not stick out of the coating surface.

When combined with polymeric binders the maleimide containing particles will more act as inert materials compared to melamine formaldehyde resins, meaning that the physical properties of the polymeric binders will more prevail. As such when adding low Tg polymeric binders the softness of the binder will be sensed better in combination with the maleimide containing particles than with melamine formaldehyde resins.

Such maleimide containing particles, especially the particles based on the poly(styrene maleimide) copolymer can behave as a sponge. The additive is stably incorporated (able to stay there for more than 1 month, preferably more than 2 months, even more preferably more than 1 year) in the matrix. The addition of the polymer formulation is beneficial for this aspect.

By "functional additive", it is meant any product that is able to provide a desired property and/or functionality to the target substrate. Possible additives are selected from the group consisting of thermo-regulators (e.g. a specific wax) , flame retardant, (other) hydrophobic compounds, biocides (anti-microbial such as antifungal or antibacterial, insecticide such as antimite, anti- mosquito, anti-acarid) light absorbing and/or emitting compounds, odorant, odor controlling agent, skin care agent, color pigment and probiotic material.

Advantageously, several functional additives can be applied in one step of the process of the present invention, either because they are incorporated in one maleimide-based particle, or if several maleimide-based particles, comprising different functional additives, are mixed .

Indeed the inventors have found that the maleimide-based particle is compatible with a lot of functional additives and, on the contrary to different coating systems, the mixing of differently loaded maleimide-based particles is not challenging from a chemical point of view (except for the dilutive effect that is solved thanks to the possibility offered by the present invention to apply very high amounts of particles) . The glass transition of a polymer (Tg) is the temperature at which the morphology of the polymer changes from a hard and relatively brittle state into a rubber like state. The Tg can preferably be measured by differential scanning calorimetry where the material is heated at a rate of lOK/min and the heat capacity is recorded in function of the temperature. In other words, the Tg can be measured by plotting the heat capacity as a function of temperature, then the Tg temperature is derived from the intersection of two tangents (at the start of the endotherm and at the maximal variation) .

The Tg temperature can then be defined as the middle (B) of the onset (A) and the end (C) of the increase in heat capacity (Fig. 1) .

Alternatively, the Tg temperature of a polymer is fixed at a viscosity of 10 ¹² Pa-s.

The polymer (or a mixture of polymer) usually have a Tg between -60°C and 100°C (preferably between -55° and 50°, more preferably between -50°C and 0°C) . The lowest Tg values being associated to softening effects, the highest Tg values being associated to a stiffening.

Mixtures of polymers (without taking into account the particles based on maleimide polymers) can be used in the polymer formulation, provided that the resulting Tg value (without taking into account the particles based on maleimide polymers) remains in the range as above.

The Tg value of the poly(styrene maleimide) -based particle is much higher, in the range of 180°C, which allows process conditions at relatively high temperatures, provided that the functionalities of the additive (s) are preserved.

Preferred polymers are selected from the group consisting of acrylics, polyurethanes , poly vinyl acetate, Polyamides (PA) , styrenebutadiene latex, natural or synthetic rubber, poly vinyl butyral, polyethylene, Ethylene Vinyl Acetate (EVA) , polyesters, natural latex, bio-based polymers (e.g. polymers and derivatives thereof from monomers from natural sources, such as poly- neoprenes, poly-isoprenes and polylactic acid) , and halogenate derivatives thereof.

The mass ratio between the particle based on maleimide, comprising at least one functional additive, and the polymer present within the formulation can conveniently be fixed at about 1:1 (i.e. the mass of the maleimide polymer+the mass of the other coatings + the mass of the at least one additive (s) = about the mass of the added polymer) . However, this ratio can vary. It is preferably not below 1:100 and not higher than 100:1. Usual ratios are comprised between 1:10 and 10:1, preferably between 1:5 and 5:1, more preferably between 1:3 and 3:1 or close to 1:1. The ratio may be varied according to the needs; the important aspects is to avoid a too heavy dilution of the functional additive (thus not too low ratios, yet ratios below 1:1 have been found as acceptable, even in the case of incorporation of thermo-regulators on fabrics) and to allow the resulting mixture to still form a film comprising the particles (thus not too high) .

Preferably, the formulation of the polymer is a solution or a dispersion, such as an aqueous dispersion of a polymer .

However, depending on the process, the polymer formulation can be a mixture comprising one or several monomers and/or oligomers (for instance to be polymerized at the curing step) , and this mixture can be solvent- free. Alternatively, the polymer formulation can be an emulsion or dispersion, which is advantageous if foams are to be produced.

The drying step is chosen according to the standard practice. Drying is usually performed by heating. In this case, if a polymer formulation is present, the temperature should be fixed at a temperature higher than the Tg of the polymer (the Tg of the polymer molecule present in the polymer formulation) and lower than 220°C, preferably lower than 180°C (the Tg of the particles) . An usual temperature in the textile industry is of about 120°C. Relatively higher temperatures ranging from 180°C to 220°C can be fixed for heating steps not longer than 30 seconds. Heating can also be performed by irradiation (e.g. microwave, IR) . The drying step can also be done at room temperature.

When monomers and/or oligomers are present in the formulation, the polymerization is performed in situ, and, for instance, the heating step / curing step is achieved upon UV-irradiation .

In any case, care should be taken to select drying or curing conditions that do not detrimentally affect the particle's additives, such as too high temperatures for a too long time period or too heavy irradiation. In other words, the incorporation of heat- or radiation-sensitive additives will reduce the options but, in view of the wide flexibility allowed by the present invention, there is room to select the most adapted drying/curing conditions depending on the additive (s) present. Specific processes according to the present invention are thus :

A process for treating a substrate (fabrics) where a formulation of a polymer is added to a poly(styrene maleimide) -based composition so as to obtain a homogenous mixture, this mixture being added to the substrate and being dried (preferably by heating) , wherein the formulation of the polymer is a solution, a dispersion or an emulsion, preferably an aqueous solution, an aqueous dispersion or an emulsion comprising an aqueous phase.

Another related process is a process for treating a substrate (fabrics) where a formulation of a polymer is added to a poly(styrene maleimide) -composition so as to obtain a homogenous mixture, this mixture being added to the substrate and being cured (preferably upon UV exposure) , wherein the formulation of the polymer consists of one or several monomers and/or of oligomers that will subsequently undergo polymerization. Possibly the formulation of the polymer is solvent-free.

A related aspect of the present invention is the substrate (fabrics) coated when carrying this process. In other words, the present invention further relates to substrate further comprising a film of a polymer comprising a (an homogenous) dispersion of particles of a poly(styrene maleimide) -composition comprising at least one additive (s).

Among them is a knit impregnated with a mixture of poly(styrene maleimide) -based particles (Ps) comprising a thermo-regulator and further the polymer composition made of polyurethanes (PU) and an elastomer (El) (for instance in a weight ratio of Ps:PU:El 3:0.5:0.5). This composition is transparent, and the resulting knit keeps its softness and elastic properties, together with a high cool effect level.

Other options is to impregnate a knit with a mixture of poly(styrene maleimide) -based particles comprising a phase change material, such as a thermo-regulator (Ps/Tr) and poly(styrene maleimide) -based particles comprising a flame-retardant (Ps/Fr) and further comprising the polymer composition made of acrylic polymer (PA) (Ps/Tr : Ps/Fr : PA 3:2:1) . This composition is transparent, and the resulting knit is flame-resistant, wash durable and keeps its elastic properties, in addition to have the "cool touch" effect.

Other options is to impregnate a knit with a mixture of poly(styrene maleimide) -based particles comprising a wax and poly(styrene maleimide) -based particles comprising a flame-retardant and further comprising the polymer composition made of polyurethanes and an elastomer (for instance in a weight ratio of Ps/Tr : Ps/Fr : PU : El 3:1:0.5:0.5) .

Alternatively, an instable foam made of poly(styrene maleimide) -based particles comprising thermo-regulators : acrylic polymer (Tg=-50°C) can be applied to a woven by back coating (weight ratio Ps:acrylic 3:1), or a stable foam in weight ratio Ps : acrylic 1:1 can be applied by back coating. The resulting woven remains breathable and soft and has acquired an intense "cool touch".

Beside impregnation of fibers, the mixture of the present invention (e.g. made of poly(styrene maleimide) -based particles : polyurethane ; 1:1) can be sprayed on the top surface of a foam, such as PU/latex foam, then allowed to dry at ambient temperature. The resulting foam is soft, elastic and easily applicable. Another related composition is made of poly(styrene maleimide) -based particles further comprising one functional additive (for instance a thermo-regulator additive) and a polyol that is liquid at room- temperature. This composition further comprises a blowing agent (that can be water) and a cross-linking agent (e.g. isocyanate) . This composition is then cured to form a foam where the additive is embedded. Another related aspect of the present invention is a paste or, preferably, a foam comprising (or consisting (essentially) of) the composition of the present invention . Examples.

Example 1 Encapsulation of a functional additive

The inventors have used the aqueous dispersion as in WO 2008/014903, further comprising thermo-regulators (octadecane) . After drying, this composition became a hard surface (Figure 4) risking to turn into a powder under friction. The inventors have measured the heat absorption properties of this composition (Figure 2, lines) . Example 2 coating according to the invention and suitable for textile applications

The inventors then mixed a composition comprising thermo- regulators (octadecane) as in the comparative example with an aqueous composition of an acrylic polymer with a Tg of -50°C so as to obtain an homogenous mixture.

The inventors firstly selected a 1:1 ratio (dried powder : polymer) . The inventors then dried the homogenous mixture upon heating at 120°c for 2 min (i.e. a rapid evaporation) . The inventors obtained a film with good technical properties where the poly(styrene maleimide) coat is homogeneously dispersed. Then the inventors have measured the heat absorption in function of the temperature.

Due to the dilution, the total heat absorption was reduced (Figure 2) .

However, the peak of maximal absorption was sharper, meaning that the efficacy of heat absorption at the target temperature (thus the functionality) is almost kept despite the dilutive effect.

Moreover, as shown in Figure 3, the absorption values remain constant after heating/cooling cycles.

By varying the nature or the relative amount of the polymer, the inventors have been able to displace the position of the peak, thus allowing flexibility to optimize the coating, depending on the end use of the substrate. Eg, stretchable fabrics, tight fabrics, soft fabrics, stiff fabrics,...

Example 3 Application of the coating according to the invention in a breathable textile

The inventors then mixed the polymer composition as in Example 2 (in a 1:1 mass ratio) so as to obtain an homogenous mixture in the form of a foam.

Then the inventors have applied the foam to a textile at a high concentration on the back side of the substrate by foam application technique before the drying step as in Example 2.

The inventors have noticed that the coating allows the air to pass through. As such, it is difficult to generate foams from melamine formaldehyde-based compositions. The maleimide-based capsules allow the insertion into an easy applicable coating formulation and to maintain nice foaming properties, which secures air permeability of the treated surface. Furthermore, at these very high concentrations, the color on the face of the substrate has not been affected and the "cool touch" effect is boosted by applying the encapsulated wax on one side of the fabric, meaning that the heat absorption capacity of the textile is better than in melamine-formaldehyde based compositions. This application remained stable on the textile for the time considered.

Example 4 Wash-durable flame retardant

The inventors have used the aqueous dispersion as in WO 2008/014903, further comprising a flame retardant and then mixed it with an aqueous composition of a polymer with low Tg ranges of -50 to -10°C (such as acrylic- or polyurethane-based polymers) so as to obtain an homogenous mixture in the form of a solution. Then the inventors have applied the solution to a textile by impregnating it at a high concentration in order to meet the specific flame retardant standards before the drying step as in Example 2.

The inventors have noticed that the coating allows two features: a very good flame retardant effect due to the possibility to load much higher concentrations than melamin-formaldehyde alternative, even with taking into account the dilution due to the addition of the polymer, and the development of a wash-durable barrier due to the coating itself. Interestingly, the coating is wash durable and resistant to weather conditions. Example 5 Application of particles containing two additives

The inventors have then encapsulated a thermal regulating wax in poly(styrene maleimide) particles, as well as flame retardant additives in poly(styrene maleimide) particles. These two types of particles have been mixed together with a polymer formulation ( PU : elastomer ; 1:1) and the mixture has then been applied on a textile substrate (e.g. a knit) by impregnation, and the substrate has been dried. The overall properties of the substrate, including breathability, transparency, softness, elasticity, comfort, color and design have been kept. Moreover, the two functionalities have been stably incorporated to the knit.