Processes for the treatment of polymer dispersions based on the use of specific organic peroxides

Abstract

The present invention relates to a process for treating a polymeric dispersion prepared by polymerizing at least one or more unsaturated monomers, said process comprising adding to said polymeric dispersion a sufficient amount of one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof. The present invention also relates to the use of an organic peroxide selected from peroxydicarbonates, diacyl peroxides and mixtures thereof for treating a polymeric dispersion prepared by polymerizing at least one or more unsaturated monomers, preferably in order to reduce the amount of volatile organic compounds present in said polymeric dispersion.

Description

[0001] The present invention relates to a process for treating a polymeric dispersion prepared by polymerizing at least one or more unsaturated monomers, said process comprising the steps of adding to said polymeric dispersion one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof.

[0002] The invention also relates to the use of one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof for treating polymeric dispersions prepared by polymerizing at least one or more unsaturated monomers, preferably in order to reduce the amount of volatile organic compounds present in said polymeric dispersions.

[0003] The preparation of dispersions of synthetic polymers is generally carried out by polymerizing unsaturated monomers in a liquid medium, especially in water or an organic solvent, in the presence of one or more free radical initiators, such as organic peroxides, azo compounds (such as azobisisobutyronitrile (AIBN)), inorganic peroxides (i.e. persulfates, such as sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8) or ammonium persulfate ((NH4)2S2O8)), or mixtures thereof.

[0004] The dispersion of the synthetic polymer obtained at the end of the polymerization process may contain volatile organic compounds resulting from incomplete conversion of the unsaturated monomers, ie unreacted unsaturated monomers, impurities of the raw materials and / or undesired by-products formed during the polymerization reaction.

[0005] However, the residual presence of these volatile organic compounds in the dispersions of synthetic polymers obtained can lead to various problems in various applications and / or technical fields, namely health problems, especially when they are present in significant amounts.

[0006] For example, in the food industry, food contact materials such as packaging, processing equipment or food-grade lubricants are generally obtained from dispersions of synthetic polymers. Therefore, monitoring the amount of volatile organic compounds is critical for mitigating potential contamination risks, health risks, and meeting industry regulatory standards, which require that these residual compounds should be determined and sometimes quantified to very low levels.

[0007] Similarly, the presence of these residual volatile organic compounds in interior paints (coatings) can also cause: hindering air quality and causing a surge in pollution, and thus affecting the health and well-being of people, especially building occupants. For example, polymer dispersions used to formulate paints, lacquers, varnishes and other coatings can trigger the release of harmful volatile organic compounds and have a negative trickle-down effect on health conditions. The adverse health effects caused by these compounds can range from minor diseases (such as irritation of the nasal and eye mucosa) to chronic complications (such as exacerbation of asthma). In addition, the resins used in these interior paints can also produce unpleasant odors caused by the aforementioned volatile organic compounds, which can have a deterrent effect on their use, especially when they are implemented to coat limited areas.

[0008] From a commercial standpoint, incomplete conversion of unsaturated monomers may also hinder the commercial development and economic value of some polymerization processes.

[0009] The presence of these residual volatile organic compounds in polymeric dispersions is therefore undesirable and, in some specific technical fields, even unacceptable for environmental and / or health reasons.

[0010] Therefore, several chemical and / or physical methods have been developed to minimize the presence of these residual volatile organic compounds in polymeric dispersions.

[0011] As an illustration of a chemical process, patent US 3,534,009 describes the implementation of a post-polymerization process aimed at reducing the amount of residual vinyl acetate monomer resulting from the primary copolymerization of vinyl acetate and ethylene by reducing the pressure to atmospheric pressure levels and providing fresh free-radical-generating materials, in particular hydrogen peroxide activated by the action of a reducing agent. In particular, this reference outlines the use of a hydrogen peroxide-zinc formaldehyde sulfoxylate redox system. According to this reference, the purpose of these fresh free-radical-generating materials is to further polymerize the residual unreacted monomeric compounds still present after the primary polymerization.

[0012] However, the subsequent polymerization process presents the disadvantage of being carried out in two steps and requires the implementation of additional equipment, which will lead to an increase in the overall cost of producing the aforementioned copolymers.

[0013] Furthermore, the addition of the hydrogen peroxide-zinc formaldehyde sulfoxylate redox system after the main polymerization is complete generates undesirable volatile organic compounds (such as formaldehyde, acetone, t-butyl alcohol and t-butyl acrylate) and results in residual monomer concentrations of between 300 and 500 ppm, which may still be unacceptable, depending on the final application of the obtained resin or polymeric dispersion. As a result, the polymerization process may generate significant amounts of volatile organic compounds overall thereafter, due to the sudden increase in the concentration of newly generated non-polymerizable volatile organic compounds.

[0014] Furthermore, in some cases, a portion of the amount of the added free radical generating material may remain at the end of the post-polymerization process and together with the residual unreacted monomers may cause the generation of an unpleasant odor in the obtained resin.

[0015] Another drawback of this process is that the use of salts as reducing agents can potentially destabilize the polymeric dispersion obtained after the polymerization process.

[0016] Alternatively, patent US 4,062,662 relates to a physical process called steam stripping, which involves injecting air and / or steam through a latex or polymer dispersion. This process is carried out in a degassing tower by passing gas and / or water vapor upward and the latex or polymer dispersion downward in countercurrent.

[0017] However, this method has the inconvenience that it cannot efficiently remove the residual unreacted monomers and requires the use of new additional equipment again for this specific operation.

[0018] Further, patent US 6,740,691 relates to a process for treating aqueous polymer latexes or dispersions of synthetic polymers, the process comprising: in a first step, by polymerization, only the unreacted unsaturated monomers are reduced, thanks to the addition of a reducing agent such as sodium formaldehyde sulfoxylate and a free radical generator such as hydrogen peroxide or a hydroperoxide, i.e. tert-butyl hydroperoxide, and in a second step, by steam stripping, all volatile organic compounds, including non-polymerizable volatile organic compounds, are removed. The purpose of the second step is to remove the non-polymerizable volatile organic compounds generated in the first step of the process and during the main polymerization.

[0019] Once again, this process has the disadvantage of implementing two sequential steps and new additional equipment to carry out the steam stripping step. Although the process comprises a second step to remove the aforementioned non-polymerizable volatile organic compounds, a portion of the added free radical generator (especially tert-butyl hydroperoxide) can remain at the end of the entire process.

[0020] Furthermore, reducing agents are generally used in the form of salts and induce a potential destabilization of the polymeric dispersion or the reaction medium. As a result, there remains a real need to develop processes capable of efficiently removing the total concentration of volatile organic compounds present in dispersions of polymers prepared by polymerization of at least one or more unsaturated monomers without encountering the aforementioned drawbacks, in order to meet the requirements set in different technical fields, in particular in the food industry and in interior coatings.

[0021] In particular, one of the objects of the present invention is to minimize the concentration of residual unsaturated monomers which have not been completely reacted during the main polymerization process without simultaneously generating new additional volatile organic compounds.

[0022] Furthermore, another object of the present invention is to minimize the total concentration of volatile organic compounds by implementing a process that is more convenient than the processes described previously, in particular a process that does not require any new additional equipment.

[0023] More specifically, one of the objectives of the present invention is to replace the use of hydroperoxides activated by the action of reducing agents, such as tert-butyl hydroperoxide and tert-amyl hydroperoxide.

[0024] The present invention relates to a process for treating a polymeric dispersion prepared by polymerizing at least one or more unsaturated monomers, said process comprising adding to said polymeric dispersion one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof, preferably selected from diacyl peroxides.

[0025] The use of the organic peroxides defined previously makes it possible to reduce the concentration of residual unsaturated monomers which have not reacted completely during the polymerization process without simultaneously generating new additional volatile organic compounds.

[0026] In other words, the process defined according to the invention is able to remove a significant portion of the volatile organic compounds, in particular the unreacted unsaturated monomers, which may be present at the end of the polymerization process, without generating non-polymerizable volatile organic compounds.

[0027] Thus, the present invention provides improved methods for achieving a post-polymerization step in a process for polymerizing one or more unsaturated monomers.

[0028] In particular, the above-mentioned process can reduce the concentration of volatile organic compounds in a polymeric dispersion prepared by polymerizing one or more unsaturated monomers to a level below 300 ppm, and in some cases even below 100 ppm, and more preferably less than 30 ppm.

[0029] The process according to the invention thus makes it possible to provide polymeric dispersions which meet the requirements set in different technical fields, including environmental regulations, in particular in target technical fields in which consumers demand healthy and sustainable solutions, such as the food industry and interior coatings.

[0030] In particular, the polymeric dispersions obtained after implementing the process of the invention can be effectively used for formulating interior paints, since they do not present an unpleasant odor. In fact, in contrast to the use of hydrogen peroxide activated by the action of a reducing agent, such as a hydrogen peroxide-zinc formaldehyde sulfoxylate redox system, at the end of the process of the invention there are no residues of the aforementioned organic peroxides.

[0031] It also means that the process of the invention is able to recover the economic value of the classical polymerization process which is lost due to incomplete conversion of the unsaturated monomers and can even add environmental aspects to it.

[0032] Furthermore, the process of the invention is very convenient to implement, especially since the feed times can be rapid and no additional equipment is required, especially for carrying out a steam stripping step.

[0033] It also shows that the process of the present invention proves to be both environmentally friendly and environmentally competitive.

[0034] The invention also relates to the use of one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof for treating polymeric dispersions prepared by polymerizing at least one or more unsaturated monomers, preferably in order to reduce the amount of volatile organic compounds present in said polymeric dispersions.

[0035] In other words, the aforementioned organic peroxide is used to drive off the volatile organic compounds present in the polymer dispersion.

[0036] The aforementioned organic peroxides can also be used to improve the odor of the polymeric dispersion.

[0037] Another aspect of the present invention is a polymeric dispersion, especially a (meth)acrylic polymeric dispersion, obtainable by the aforementioned process.

[0038] The (meth)acrylic polymer dispersion preferably contains less than 100 ppm of volatile organic compounds, more preferably less than 50 ppm, even more preferably less than 30 ppm.

[0039] The (meth)acrylic polymer dispersion can be efficiently used in food contact materials (such as packaging, processing equipment or food-grade lubricants) and interior coatings.

[0040] Other characteristics, aspects and advantages of the invention will emerge even more clearly on reading the subsequent description and examples.

[0041] In the text hereinafter, and unless otherwise indicated, the limits of the numerical range are included in the range, especially in the expressions “between” and “ranging from … to . . . .”

[0042] In addition, the expression "at least one" used in the present specification is equivalent to the expression "one or more".

[0043] The term "polymerization" encompasses both homopolymerization and copolymerization of one or more unsaturated monomers.

[0044] The term "dispersion" encompasses both suspensions and emulsions.

[0045] According to the invention, the term "dispersion" also encompasses the term "latex".

[0046] Technology

[0047] The process for treating a polymeric dispersion prepared by polymerizing at least one or more unsaturated monomers comprises the steps of adding to the polymeric dispersion a sufficient amount of one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof.

[0048] More preferably, the organic peroxide is selected from diacyl peroxides.

[0049] The diacyl peroxide may be selected from dilauroyl peroxide, disuccinic acid peroxide, dibenzoyl peroxide, di(3,3,5-trimethylhexanoyl) peroxide, didecanoyl peroxide and mixtures thereof, especially dilauroyl peroxide.

[0050] Dilauroyl peroxide is manufactured by Arkema under the name Sold by LP.

[0051] The peroxydicarbonate may be selected from diisopropyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di(sec-butyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, bis(tert-butylcyclohexyl) peroxydicarbonate, di(3-methoxybutyl) peroxydicarbonate, dihexadecyl peroxydicarbonate, dimyristyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, and mixtures thereof.

[0052] More preferably, the peroxydicarbonate is selected from di(2-ethylhexyl) peroxydicarbonate, bis(tert-butylcyclohexyl) peroxydicarbonate and mixtures thereof, in particular di(2-ethylhexyl) peroxydicarbonate and bis(tert-butylcyclohexyl) peroxydicarbonate. Di(2-ethylhexyl) peroxydicarbonate is produced by Arkema under the name 223M75 for sale.

[0053] According to a preferred embodiment, the organic peroxide is selected from dilauroyl peroxide, di(2-ethylhexyl)peroxydicarbonate, bis(tert-butylcyclohexyl)peroxydicarbonate, and mixtures thereof, especially dilauroyl peroxide.

[0054] Preferably, the organic peroxide has a half-life temperature at 10 hours ranging from 40°C to 75°C, more preferably ranging from 40°C to 70°C.

[0055] According to the present invention, the term "half-life temperature at 10 hours" refers to the temperature at which half of the aforementioned organic peroxide has decomposed in 10 hours. In other words, it is the temperature at which the loss of half of the active oxygen content of the peroxide occurs after 10 hours.

[0056] Classically, the half-life temperature of an organic peroxide at 10 hours is determined by measuring the decomposition rate in n-decane or n-dodecane. The 10-hour half-life temperature is preferably determined by differential scanning calorimetry (DSC) curve in n-dodecane at 0.1 mol / liter (mol.l -1 ) concentration measurement.

[0057] The organic peroxide may be added to the polymeric dispersion in an amount ranging from 0.2 to 5 wt%, preferably from 0.6 to 2 wt%, more preferably from 1 to 1.6 wt%, relative to the total weight of the polymeric dispersion.

[0058] Preferably, the unsaturated monomer is selected from vinyl monomers, in particular from monoethylenically unsaturated (meth) acrylic monomers, including esters, amides and nitriles of (meth) acrylic acid, for example, (meth) acrylic ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, aminoalkyl (meth) acrylates, N-alkylaminoalkyl (methacrylates), N,N-dialkylaminoalkyl (meth) acrylates. Esters; (meth)acrylonitrile and (meth)acrylamide; styrene or alkyl-substituted styrene; butadiene; vinyl acetate, vinyl propionate, or other vinyl esters; vinyl chloride, vinylidene chloride and N-vinyl pyrrolidone; allyl methacrylate, diallyl phthalate, 1,3-butanediol dimethacrylate, 1,6-hexanediol diacrylate and divinylbenzene; (meth)acrylic acid, crotonic acid, itaconic acid, sulfoethyl methacrylate, phosphoethyl methacrylate, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride; and mixtures thereof.

[0059] More preferably, the unsaturated monomer is selected from vinyl ester monomers, more preferably vinyl esters of unsaturated carboxylic acids such as vinyl acetate or vinyl propionate, (meth)acrylic acid ester monomers, styrene monomers, and mixtures thereof.

[0060] According to a preferred embodiment, the unsaturated monomers used to prepare the polymeric dispersion are formulated in an aqueous composition which may preferably contain one or more surfactants.

[0061] Preferably, the polymer dispersion is an aqueous polymer dispersion, in particular a polymer dispersion obtained by polymerizing at least one or more of the aforementioned unsaturated monomers.

[0062] More preferably, the polymeric dispersion comprises copolymerized monoethylenically unsaturated (meth)acrylic acid, in particular copolymerized monoethylenically unsaturated (meth)acrylic acid and styrene.

[0063] Even more preferably, the polymeric dispersion is an aqueous dispersion of a (meth)acrylic polymer, especially an aqueous dispersion of a styrene-acrylate polymer.

[0064] The polymeric dispersion may further comprise volatile organic compounds, including residual monomers resulting from the polymerization of unsaturated monomers.

[0065] Preferably, the polymeric dispersion comprises residual monomers selected from the group consisting of butyl acrylate, butyl methacrylate, methacrylic acid, 2-hydroxyethyl acrylate, styrene, and mixtures thereof.

[0066] Preferably, the process of the present invention comprises adding one or more organic peroxides as previously described at a temperature ranging from 75 to 90°C, preferably at a temperature ranging from 80 to 85°C, preferably for a period of time ranging from 1.5 to 4 hours, more preferably for a period of time ranging from 2 to 3.5 hours.

[0067] Advantageously, the addition of the aforementioned organic peroxide is done in one step.

[0068] In particular, the process of the present invention may be one of the steps carried out after the polymerization of one or more unsaturated monomers as described hereinbefore.

[0069] Preferably, the process of the present invention is a post-polymerization step of a polymerization process of at least one or more unsaturated monomers.

[0070] According to a preferred embodiment, the polymer dispersion is an aqueous dispersion of a (meth)acrylic polymer, in particular an acrylic polymer, and the organic peroxide is selected from peroxydicarbonates, diacyl peroxides and mixtures thereof.

[0071] According to this embodiment, the organic peroxide is preferably selected from dilauroyl peroxide, di(2-ethylhexyl)peroxydicarbonate, bis(tert-butylcyclohexyl)peroxydicarbonate and mixtures thereof, especially dilauroyl peroxide.

[0072] According to a preferred embodiment, the present invention aims to provide a process, which comprises:

[0073] - polymerizing one or more unsaturated monomers in the presence of one or more free radical initiators, preferably selected from organic peroxides, inorganic peroxides and mixtures thereof, to obtain a polymeric dispersion, especially an aqueous polymeric dispersion, as defined hereinbefore,

[0074] - adding to the polymeric dispersion one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof as defined hereinbefore.

[0075] use

[0076] The invention also relates to the use of one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof as defined above for treating the aforementioned polymeric dispersions prepared by polymerizing at least one or more unsaturated monomers.

[0077] Preferably, an organic peroxide as defined hereinbefore is used to reduce the amount of volatile organic compounds present in the polymeric dispersion.

[0078] More preferably, the organic peroxide defined hereinbefore is used to reduce the amount of residual monomers resulting from the polymerization of unsaturated monomers.

[0079] The volatile organic compounds preferably contain residual monomers resulting from the polymerization of unsaturated monomers.

[0080] The aforementioned organic peroxides can also be used to improve the odor of the polymeric dispersions, especially those used in interior paints.

[0081] In other words, the aforementioned organic peroxides can also be used to improve the odor of interior paints.

[0082] According to the present invention, the term "improving odor" means that the organic peroxide as defined hereinbefore is able to reduce the amount of volatile organic compounds in the polymeric dispersion to a very low level, so that their evaporation will be minimized.

[0083] In particular, the organic peroxide as defined previously is capable of reducing the amount of volatile organic compounds in the polymeric dispersion to less than 300 ppm, preferably to less than 100 ppm, more preferably less than 50 ppm, even more preferably less than 30 ppm, relative to the total weight of the dispersion.

[0084] Polymer dispersion

[0085] Another aspect of the invention consists in the polymeric dispersion obtainable by the process defined hereinbefore.

[0086] The polymeric dispersion preferably contains less than 300 ppm of volatile organic compounds, in particular less than 100 ppm, more preferably less than 50 ppm, even more preferably less than 30 ppm.

[0087] Preferably, the present invention relates to a (meth)acrylic polymer dispersion obtainable by the aforementioned process.

[0088] The organic peroxide is selected from the aforementioned organic peroxides.

[0089] The (meth)acrylic polymer dispersion contains less than 300 ppm, preferably less than 100 ppm, more preferably less than 50 ppm, even more preferably less than 30 ppm of volatile organic compounds, relative to the total weight of the dispersion.

[0090] Preferably, the (meth)acrylic dispersion is an aqueous (meth)acrylic dispersion, even more preferably an aqueous acrylic dispersion.

[0091] The (meth)acrylic polymer dispersion can be efficiently used in food contact materials (such as packaging, processing equipment or food-grade lubricants) and interior coatings.

[0092] In particular, the (meth)acrylic polymer dispersion can be used in interior paints.

[0093] The following examples are provided as illustrations of the present invention. Example

[0094] I. Preparation of the polymer dispersion

[0095] The following detailed description of aqueous acrylic resins is provided in Table 1 ( 5181CS, produced by ACR, CHINA).

[0096] [Table 1]

[0097] Characteristics of acrylic resin

[0098] Solid content% Viscosity, cps 55～57 800

[0099] Butyl acrylate (hereinafter indicated as BA) was added to the aqueous acrylic resin described in detail in Table 1 to obtain a total amount of 2000 ppm. Subsequently, the mixture was stirred and dispersed for one and a half hours to obtain an aqueous acrylic dispersion.

[0100] II. Tested Organic Peroxides

[0101] The organic peroxides implemented in the experimental protocols described hereinafter are listed below:

[0102] - By Name 10M75 tert-butyl peroxyneodecanoate (denoted as 10M75) is sold with a half-life temperature of 48°C at 10 hours.

[0103] - By Name 554M75 tert-amyl peroxypivalate (denoted as 554M75) is sold with a half-life temperature of 55°C at 10 hours.

[0104] - tert-butyl hydroperoxide and sodium metabisulfite (expressed as TBHP from Arkema + SBS from Enox)

[0105] - bis(tert-butylcyclohexyl)peroxydicarbonate having a half-life temperature at 10 hours of 48° C.,

[0106] - By Name 223M75 Di(2-ethylhexyl)peroxydicarbonate (denoted as 223M75) sold as having a half-life temperature of 49°C at 10 hours

[0107] - By Name A75 dibenzoyl peroxide (denoted as A75) sold with a half-life temperature of 73°C at 10 hours,

[0108] - By Name Dilauroyl peroxide (indicated as LP) is sold by LP and has a half-life temperature of 64°C at 10 hours.

[0109] III. Experimental plan

[0110] At a temperature of 80° C., 2.4 g of a prepolymer obtained by Arkema under the name Dilauroyl peroxide sold by LP. After 3 hours, the residual concentration of volatile organic compounds in the dispersion was recorded.

[0111] This protocol was the same for all organic peroxides described in Part II, except for the redox system tert-butyl hydroperoxide and sodium metabisulfite (TBHP+SBS), where the addition of tert-butyl hydroperoxide was continued for 3 hours at 60°C.

[0112] IV. Results

[0113] The results are provided in Table 2 below:

[0114] [Table 2]

[0115] Evaluation of Volatile Organic Compounds in Aqueous Acrylic Dispersions

[0116]

[0117]

[0118] The results show that the redox system TBHP+SBS generates a significant amount of new volatile organic compounds, while the organic peroxides LP, 223M75 and bis(tert-butylcyclohexyl)peroxydicarbonate used according to the present invention can significantly reduce the amount of residual butyl acrylate (BA) without generating new additional components.

[0119] The results also show that the peroxyesters 554M75 and 10M75 are not as effective as the organic peroxides of the present invention in reducing the amount of residual butyl acrylate.

[0120] Furthermore, the peroxyesters tested also generate new additional volatile organic compounds such as acetone, tert-amyl alcohol and tert-butyl alcohol, both non-polymerizable and polymerizable volatile organic compounds.

[0121] Finally, the results also demonstrated that the half-life temperature of 73 °C at 10 hours A75 (dibenzoyl peroxide) can reduce the residual amount of butyl acrylate.

Claims

1. A process for treating an aqueous (meth)acrylic polymer dispersion prepared by polymerizing at least one or more ethylenically unsaturated monomers, the process comprising adding to the (meth)acrylic polymer dispersion one or more organic peroxides selected from peroxydicarbonates, diacyl peroxides and mixtures thereof, wherein the organic peroxide is added to the (meth)acrylic polymer dispersion in an amount ranging from 0.6% by weight to 5% by weight, relative to the total weight of the (meth)acrylic polymer dispersion.

2. The process according to claim 1, characterized in that The aqueous (meth)acrylic polymer dispersion is an aqueous (meth)acrylic polymer emulsion.

3. The process according to claim 1, characterized in that The one or more organic peroxides are selected from diacyl peroxides.

4. The process according to claim 1, characterized in that The organic peroxide has a half-life temperature ranging from 40°C to 75°C in 10 hours.

5. The process according to claim 4, characterized in that The organic peroxide has a half-life temperature ranging from 40°C to 70°C in 10 hours.

6. The process according to any one of claims 1 to 5, characterized in that The organic peroxide is a diacyl peroxide selected from the group consisting of dilauroyl peroxide, disuccinic acid peroxide, dibenzoyl peroxide, di(3,3,5-trimethylhexanoyl) peroxide, didecanoyl peroxide, and mixtures thereof.

7. A process according to claim 6, characterised in that The organic peroxide is selected from dilauroyl peroxide.

8. The process according to any one of claims 1 to 5, characterized in that The organic peroxide is a peroxydicarbonate selected from the group consisting of diisopropyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di(sec-butyl) peroxydicarbonate, di(n-propyl) peroxydicarbonate, bis(tert-butylcyclohexyl) peroxydicarbonate, di(3-methoxybutyl) peroxydicarbonate, dihexadecyl peroxydicarbonate, dimyristyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, and mixtures thereof.

9. A process according to claim 8, characterised in that The organic peroxide is selected from di(2-ethylhexyl)peroxydicarbonate or di(sec-butyl)peroxydicarbonate.

10. The process according to claim 1, characterized in that The organic peroxide is added to the (meth)acrylic polymer dispersion in an amount ranging from 0.6% by weight to 2% by weight relative to the total weight of the (meth)acrylic polymer dispersion.

11. The process according to claim 10, characterized in that The organic peroxide is added to the (meth)acrylic polymer dispersion in an amount ranging from 1% by weight to 1.6% by weight relative to the total weight of the (meth)acrylic polymer dispersion.

12. The process according to any one of claims 1 to 5, characterized in that The unsaturated monomers include (meth)acrylic monomers and are selected from monoethylenically unsaturated (meth)acrylic monomers, including esters, amides and nitriles of (meth)acrylic acid; styrene or alkyl-substituted styrene; butadiene; vinyl acetate, vinyl propionate, or other vinyl esters; vinyl chloride, vinylidene chloride and N-vinyl pyrrolidone; allyl methacrylate, diallyl phthalate, 1,3-butanediol dimethacrylate, 1,6-hexanediol diacrylate and divinylbenzene; (meth)acrylic acid, crotonic acid, itaconic acid, sulfoethyl methacrylate, phosphoethyl methacrylate, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride; and mixtures thereof.

13. A process according to claim 12, characterised in that The esters, amides and nitriles of (meth)acrylic acid are selected from (meth)acrylic ester monomers, including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, aminoalkyl (meth)acrylate, N-alkylaminoalkyl (methacrylate), or N,N-dialkylaminoalkyl (meth)acrylate; (meth)acrylonitrile and (meth)acrylamide.

14. The process according to any one of claims 1 to 5, characterized in that The (meth)acrylic polymer dispersion further comprises one or more residual monomers resulting from the polymerization of unsaturated monomers.

15. The process according to any one of claims 1 to 5, characterized in that The treatment is a post-polymerization step of a polymerization process of at least one or more unsaturated monomers.

16. The process according to any one of claims 1 to 5, wherein the (meth)acrylic polymer dispersion is an aqueous dispersion of a styrene-acrylate polymer.

17. Use of an organic peroxide as defined in any one of claims 1 and 3 to 11 for treating a (meth)acrylic polymer dispersion as defined in any one of claims 1 to 2, 12 to 14 and 16 prepared by polymerizing at least one or more unsaturated monomers as defined in any one of claims 1 and 12 to 14.

18. Use according to claim 17 for reducing the amount of volatile organic compounds present in the (meth)acrylic polymer dispersion.

19. The use according to claim 17 or 18 for improving the odor of the (meth)acrylic polymer dispersion.

20. The use according to claim 19 for improving the odor of the (meth)acrylic polymer dispersion used in interior paints.

21. (Meth)acrylic polymer dispersion obtainable by a process as defined in any one of claims 1 to 16.

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