MXPA00000826A - Emulsions of peroxyesters - Google Patents

Abstract

The invention relates to aqueous emulsions of peroxyesters comprising an anti-freeze agent, a polyvinyl acetate with a degree of hydrolysis between 45 and 68%, and a non-ionic surfactant with an HLB value greater than 16 selected from alkylene oxide block-copolymers, ethoxylated fatty alcohols, and ethoxylated fatty acids. The emulsions are safe, storage stable, and generally applicable.

Description

EMULSIONS OF PEROXIESTERES DESCRIPTIVE MEMORY The present invention relates to an aqueous emulsion of a peroxyester which is liquid at -20 ° C, which comprises a protective colloid, a nonionic surfactant and a Jteticongelant. Such peroxide emulsions are known from EP-B-0 032 757. According to this reference, a variety of peroxides, colloids and surfactants can be used in emulsions also comprising an antifreeze agent. For the surfactants and protective colloids of choice, reference is made to the patent of E.U.A. 3,988,261, which cites many such compounds. With respect to one of the types of protective colloids indicated, for example, polyvinyl acetate (PVA), it is pointed out that the degree of hydrolysis will influence the properties. It is suggested to use PVAs with a substantial degree of hydrolysis, for example, 65% or more. However, in EP-B-0 032 757, only one emulsion is present, which includes a peroxyester, for example tert-butyl peroxine-tecanoate. In this example, an ethoxylated nonylphenol is used as the surfactant, while xanthan gum is used as the protective colloid. In general, the surfactants and protective colloids mentioned in US 3,988,261 are not suitable for ^ gt ^^^ gt ^^^^ í »^ 3j É ^ guíj ß production of concentrated peroxyester emulsions, stable in storage and safe, as they are widely accepted in polymerization processes. It is known that a type of surfactant, for example the ethoxylated nonylphenols, are detrimental to the electrical properties of polyvinyl chloride (PVC) when introduced into the polymerization process of vinyl chloride monomer (VCM). It is also well known that ethoxylated nonylphenols have environmental drawbacks. With respect to the other surfactants that are cited, they are found to be generally unacceptable because they typically result in highly viscous peroxyester emulsions and / or emulsions that are not safe, particularly when emulsions with a high concentration of perester are produced. It was also found that most of the indicated protective colloids, in combination with the appropriate surfactants, are not acceptable in the formulation of peroxyesters. The mentioned protective colloids will often result in unacceptable viscosity of the peroxyester emulsion. Accordingly, there is a need for concentrated peroxy ester emulsions with a low viscosity that are storage stable, safe and generally applicable in polymerization processes, particularly those of VCM. There are several other publications that relate to water-based peroxide dispersions. However, none of them describes or suggests peroxyester emulsions that satisfy the criteria mentioned above. JP (61) 130315 (1986) suggests that peroxyester emulsions can be obtained using a protective colloid, a nonionic surfactant and an antifreeze agent. It is noted that the nonionic surfactant can be selected from a variety of materials, while the protective colloid should be a product with a high rate of dilution in water, such as modified celluloses and saponified polyvinyl acetates (PVAs). PVAs with a degree of hydrolysis greater than 60 mol% are preferred. The only exemplified formulations are peroxydicarbonate emulsions. It was found that the use of these formulations for peroxyesters results in emulsions that do not meet the requirements of safety, viscosity and / or applicability. GB 2 068 008 discloses aqueous peroxide dispersions, where protective colloid is used, such as celluloses or PVAs together with an emulsifying system with an HLB greater than 15. It is specified that the emulsifier will be non-ionic, ethoxylated, free from cyclic internal ether bonds, and suitably selected from ethoxylated alkylphenols, ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated glycol and glycerol fatty esters and alkylene oxide block copolymers. Although this reference suggests using surfactants with a very high HLB value, it does not suggest to a person skilled in the art that a specific combination of peroxyesters, antifreeze, PVAs and surfactants should be made.

• More specifically, peroxyesters and / or antifreeze agents are not mentioned. Surprisingly, it has now been found that improved aqueous peroxy ester emulsions can be produced, which can be applied by a suitable combination of peroxyester, nonionic surfactant and protective colloid. The invention is characterized in that the protective colloid is a polyvinyl acetate with a degree of hydrolysis between 45 and 68%, and the nonionic surfactant has an HLB value of 16 or more, and is selected from block copolymers of sodium oxide. alkylene, ethoxylated fatty alcohols and ethoxylated fatty acids. In this specification, the term "surfactant" refers to the surfactant chemical compound that will be used in the peroxyester formulations according to the present invention and which influences the interfacial surface tension between the water and the peroxyester phase. Said compounds are also known as "emulsifiers". Preferably, the aqueous peroxy ester emulsion according to the invention contains only a surfactant with an HLB value of 16 or more. More preferred are surfactants with an HLB value of 17 or more, since such surfactants tend to result in less viscous emulsions. If desired, a mixture of surfactants can be used. In that case, the combined surfactants must have an HLB value of 16 or more, although it is preferred that all surfactants used have tenghter HLB lalor greater than 10, preferably greater than 12.5, and mt &prefectly 16 or more, because surfactants with a lower HLB value may have an adverse effect on the viscosity of the final emulsifier. The HLB value refers to the hydrophilic-lipophilic balance as described in "The Atlas HLB-System, a time-saving guide to emulsifier selection", published by Atlas Chemical Industries Inc., 1963. For mixtures of surfactants, the value of HLB is calculated from the weight ratio of the components, as also mentioned in this publication. The nonionic surfactants which can be used in the aqueous emulsions according to the invention are block copolymers of alkylene oxide, ethoxylated fatty alcohols and ethoxylated fatty acids. Preferred surfactants are ethoxylated fatty alcohols and ethoxylated fatty acids with an HLB value greater than 16. Ethoxylated fatty alcohols are more preferred. It was found that these products are preeminently suitable for obtaining emulsions with good stability, safety and viscosity properties at high concentrations of peroxyester. The amount of surfactant or the combination of surfactants in the final emulsion is 0.05-5 weight percent (% w / w). Preferably, 0.1 to 2% w / w of surfactant is used, although an amount between 0.1 and 1% w / w is more preferred. yi &ig The protective colloid to be used in the aqueous emulsions according to the invention must be a PVA with a degree of hydrolysis between 45 and 68%. Preferably, the degree of hydrolysis is between 45 and 62.5%. More preferred is a PVA with a degree of hydrolysis between 50 and 60%. A PVA with a degree of hydrolysis of less than 45% can not be used, because said PVA is not soluble in the mixture of water and antifreeze. A PVA with a degree of hydrolysis greater than 68% resulted in emulsions with a very high viscosity. Instead of using only one type of PVA, a mixture of two or more PVAs can also be used. In that case, the mixture can be observed as only a PVA of which the degree of hydrolysis is the degree of average hydrolysis by weight of the PVAs. Preferably, said PVA mixture does not comprise a PVA with a degree of hydrolysis of less than 45% or more than 68%, due to the reasons mentioned above. The amount of PVA used in the emulsions according to the invention, will depend on the concentration and types of peroxyester, the surfactant used and the desired viscosity of the final emulsion. Typically, the amount of PVA in the final emulsion will be between 0.5 and 10% w / w. The use of these protective colloids in combination with the aforementioned surfactants allows the production of concentrated, storage stable and safe peroxyester emulsions. The antifreeze used in the emulsions according to the invention will be used in an amount sufficient to keep the emulsion pourable and / or pumpable at -20 ° C, although it is preferred that the emulsions are still fluid at temperatures of -25 ° C and less. The amount of freezing point suppressor that will be used will depend on the type of antifreeze, or mixture of antifreeze, that is used. Conveniently, a mixture of antifreeze and water containing a sufficient amount of antifreeze is first obtained to be pourable at the indicated temperatures. This mixture can then be used in the additional process to obtain emulsions. Although most antifreeze agents such as salts and organic compounds can be used, it is preferred to use organic compounds selected from methanol, ethanol, isopropanol, glycol, propanediol and glycerol, since it is known that said compounds will hardly have any effect on the processes of polymerization in which peroxyester emulsions are used. According to the invention, combinations of two or more antifreeze agents in the emulsions can also be used. It is considered that the peroxyester emulsions will be concentrated when the amount of the ester in them exceeds 30% in w / w. Preferably, the peroxy ester concentration in the emulsions according to the invention is greater than 40% w / w. Even more preferred are emulsions containing 45-65% w / w peroxy ester. More preferred are emulsions wherein the peroxy ester concentration is 50 to 60% w / w, because such emulsions will allow substantially reduced transportation and handling costs compared to those emulsions containing 40% w / w or less of peroxyester. The safety aspects of the final emulsion predominantly determine the upper end of the peroxy ester concentration scale. More specifically, the water / antifreeze content of the formulation must be high enough to dissipate the heat of peroxy ester decomposition. The peroxyester emulsions according to the invention are suitable for most peroxyesters which are liquid at -20 ° C, but are particularly relevant for peroxyesters having a recommended storage temperature of 15 ° C or less. Typically, the recommended storage temperature is specified by the producer of the peroxyesters, for example, by Akzo Nobel Chemical B.V. in the brochure "Initiators for high polymers" with the code 10737. Peroxyesters which are preferably used in the aqueous emulsions according to the invention include: a-cumyl peroxineodecanoate, 2,2,4-trimethylpentyl peroxydecanoate, peroxyphenolate -amyl, tert-butyl peroxineodecanoate, 2,4,4-thomethylpentyl peroxypivalate, ter-amyl peroxypivalate, tert-butyl peroxypivalate, tert-butyl peroxyheptanoate, 2,5-bis (2-ethylhexanoylperoxy) - 2,5-dimethylhexane, It is also preferred to use the ter-butyl peroxy-2-ethylhexanoate and tert-butyl peroxy-2-ethexanoate. The emulsions according to the invention may comprise, if desired, one or more thickeners at a concentration of up to 2% by weight to control the viscosity of the composition. If used, the thickener preferably constitutes less than 1% by weight of the emulsion. Non-limiting examples of thickeners useful in the formulation are xanthan gum, gum arabic and alginates. In addition to the compounds mentioned above, the compositions according to the invention may also comprise other "standard" additives, including pH adjusting agents such as phosphate or calcium oxide pH regulators, sequestering agents and, if so, you want, biocides, for example, fungicides. The concentration of these additives will depend on the desired effect and the other ingredients in the emulsion. Given the information presented herein, the person skilled in the art will have no problem to select the appropriate concentrations of the individual ingredients in the emulsions of choice. What is meant by stable emulsions in storage, is that the products do not freeze at storage temperatures of -20 ° C, preferably -25 ° C, and have an average peroxy ester drop size (d50) and 99 percentiles of the drop size distribution (d99) that does not change by more than 20μm during 3 months of storage. Preferably, the change in d50 is less than 10 μm, more preferably less than 5 μm, since changes in droplet size will influence the viscosity and stability in additional storage of the emulsion, but also the polymerization procedure. can be adversely affected when larger peroxy ester droplets are introduced, for example, by an increased number of fish eyes It is also for this reason that the d50 of the droplet size distribution should be less than 20μm, although a d50 less than 10μm is preferred, particularly less than 5μm. The particle size is determined by means of a technique of light scattering, using an Easy Malvern® sizer.

As mentioned above, it is important that the concentrated peroxy ester emulsions according to the invention have a viscosity that allows easy handling and use. In practice, this means that the product must have a viscosity lower than 500 mPa.s when measured at 0 ° C using an Ehchsen viscometer, model 332 (0-500 mPa.s). Preferably, the Erichsen viscosity is less than 300 mPa.s, although viscosity lower than 200 mPa.s is more preferred. In alternative form, suitable emulsions were found to have a viscosity of less than 2000 mPa.s when measured at 0 ° C, using a Brookfield LVT with sp3 spindle at 12 rmp. Preferably, the emulsions will have a Brookfield viscosity less than 1500 mPa.s. As is well known, peroxyesters are thermally labile organic compounds. Since the decomposition of the peroxyesters is exothermic, it is dangerous when the heat of decomposition can not be dissipated, for example, by loss of heat to the surrounding area. When heat buildup occurs, the decomposition reaction eventually becomes uncontrollable and potentially dangerous. To avoid such undesirable situations, the peroxide is typically formulated with one or more phlegmatizing agents, such as inert organic materials including water. It is generally considered that aqueous peroxide emulsions are safe products because the peroxide is dispersed in the aqueous phase, which is very suitable for the removal of heat from the decomposition of the peroxide molecules, for example, by convection and / or evaporation. However, it was observed that many peroxyester emulsions according to the prior art formulations suffer from the disadvantage that they show phase separation during heating, in particular at temperatures where water evaporation becomes noticeable. If so, the peroxyester is separated and forms a highly concentrated peroxy ester phase, whose heat of decomposition is not dissipated. As a result, said aqueous peroxy ester emulsions can be as dangerous as the pure peroxyester. One of the objectives of the emulsions according to the invention was therefore to develop formulations that do not form a significant amount of a dangerous phase after heating. More specifically, it is considered that an emulsion will be safe if less than 10% by volume of one or more other phases is formed or, if more than 10% by volume of phase separation occurred, none of the phases has a peroxyester content such that the active oxygen content is greater than 1% w / w. For safety purposes, the emulsions as described herein were evaluated by maintaining them, for 8 hours, at a temperature which is 30 ° C higher than the well-known autocatalyst decomposition temperature (SADT) of the peroxide. The emulsions of the invention can be produced in conventional manner. Typically, the emulsion compounds are mixed and / or homogenized using well-known equipment, such as colloid mills, bead mills, pressure homogenizers, fluidizers, ultrasonic homogenizers, etc. Since many of the peroxyesters are not stable at higher temperatures, mixing and / or homogenization must be carried out below a temperature of 15 ° C, preferably well below the SADT. The emulsions of the invention are preferably used in suspension or emulsion polymerization processes. However, they can also be used in other processes, such as polymer modification processes, crosslinking reactions, mass polymerization processes and curing processes, for example, of unsaturated polyester resins. In these processes, various monomers and / or polymers can be reacted including, for example, acrylates, vinyl esters, vinyl halides, vinyl ethers, aromatic vinyl compounds such as styrene, lower alkenes, polybutadiene, methacrylate-butadiene copolymers, styrene, and the like. Therefore, the emulsions can be used, for example, in the polymerization 3e. masses of vinyl chloride monomer (VCM). However, emulsions are more preferably used in a suspension or emulsion polymerization process, wherein at least VCM, styrene or a (meth) acrylate is reacted. More preferred is the use of the emulsions in the suspension polymerization process, predominantly of VCM. Emulsions are used only in these processes when they do not affect the properties of the resulting polymer, or they do so only to a very limited extent. In the preferred VCM polymerization process, this means that hardly any clogging is observed, and that the particle size, porosity, number of fish eyes and electrical properties of PVC are hardly affected. The peroxyester emulsions according to the invention and their uses are better illustrated in the following examples.

EXAMPLES In the examples, the following products and abbreviations were used: LL02 = Gohsenol® LL02, a PVA, for example, from Nippon Gohsei 55-2H = Alcotex® 55-2H, a PVA, for example, from Revertex UMR10M = Unitika® UMR10M , a PVA, for example, from Unitika 552P = Alcotex 55 P (as 100% active material), a PVA, for example, from Revertex. KP08 = Gohsenol KP08, a PVA, for example, from Nippon Gohsei KH17 = Gohsenol KH17, a PVA, for example, from Nippon Gohsei M05 / 190 = Polyviol® M05 / 190, a PVA, for example, from Wacker GH20 = Gohsenol GH20, a PVA, for example, from Nippon Gohsei Berol®08 = ethoxylated stearyl alcohol, for example, from Akzo Nobel (HLB = 18.7) Myrj®53 = ethoxylated stearic acid, for example, from ICI (HLB = 17. 9) Softigen® 767 = ethoxylated caprylic glyceride, for example, from Hüls (HLB = 18.0) Tween® 20 = ethoxylated sorbitan monolaurate, for example, from ICI (HLB = 16.7) Remcopal® 20 = ethoxylated lauryl alcohol, for example, of Ceca (HLB = 16.0) Ethylan® R = ethoxylated cetyl / oleyl alcohol for example, from Akcros (HLB = 15.4). Typically, the peroxyesters used in the examples were industrial grade (raw reactor products). However, purified peroxyesters can also be used to obtain emulsions that meet the criteria of the emulsions according to the invention.

OS 1 to 4 An aqueous emulsion of 2-peroxineodecanoate of 2,4,4-t methylpentyl was obtained by addition to a vessel cooled to -5 ° C: - 50% by weight (% w / w) of 2-peroxineodecanoate 2.4 , 4- trimethylpentyl (100% active material), supplied as Trigonox® 151 from industrial grade with a purity higher than 85%, - 3.0% in w / w PVA (see table), - 0.3% w / w in Berol 08 (an ethoxylated fatty alcohol, HLB = 18.7), - the rest being one 76/24 mixture of water / methanol which is not frozen at -20 ° C. Then, the initiator was dispersed with an UltraTurrax® type S25N-25GM (4 minutes / kg of emulsion) at total energy, during which the temperature of the solution / dispersion was maintained at 0 to 5 ° C below the SADT of the initiator. In example 4, the amount of Berol 08 was reduced up to 0.2% in w / w. TABLE 1 Example 1 PVA LL02 55-2H UMR10M 552P Hydrolysis (%) 45-51 54-57 62.6-67.5 54-57 After production Erichsen (mPa.s) 385 345 Boundary line 250 Brookfield (mPa.s) 790 610 1600 360 d50 / d99 (μm) 1.1 / 15.4 0.8 / 2.8 0.7 / 2.0 0.9 / 2.5 After 12 weeks storage Erichsen (mPa.s) 315 265 420 No data Brookfield (mPa.s) 1970 460 1080 No data d50 / d99 (μm) 5.2 / 36.3 2.9 / 4.3 2.5 / 3.4 No data All these emulsions are acceptable. Emulsions are preferred according to examples 2 and 4.

COMPARATIVE EXAMPLES A A D Example 1 was repeated using other types of PVA, with the following result: TABLE 2 Example A B D PVA KP08 KH17 M05 / 190 GH20 Hydrolysis (%) 72-75 78-82 81-84 87-89 After production Erichsen (mPa.s) > 500 > 500 > 500 > 500 Brookfield (mPa.s) 5990 > 10000 > 10000 3030 d50 / d99 (μm) 2.1 / 12.8 2.2 / 15.2 2.0 / 14.2 1.4 / 6.4 From the examples 1 to 3 and the comparative examples A-D, it follows that only a PVA with a limited degree of hydrolysis can be used in the emulsions according to the invention. & In the emulsion of Example 1, the 2,4-dimethylpentyl 2-peroxineodecanoate was replaced by a-cumyl pggagliredecanoate, which It was supplied as industrial grade Trigonox 99 with at least 80% purity.

TABLE 3 Example PVA 552P KP08 Hydrolysis (%) 54-57 71-75 After Erichsen production (mPa.s) 390 Decomposed during Brookfield (mPa.s) 2000 preparation d50 / d99 (μm) 1.9 / 4.4 These examples confirm that only stable and safe emulsions can be obtained according to the invention, using PVAs with a degree of hydrolysis on a specific scale.

EXAMPLES 6 TO 7 Example 5 was repeated, except that a mixture of 50:50 (by weight) of Alco552P (as 100% active material) and Unitika UMR10M as a protective colloid was used [therefore Alcocontains 40% active material, 125 parts by weight of PVA (as supplied) were combined with 50 parts by weight of Unitika. It is noted that, for easy reference, the amount of the ingredients used is presented as 100% pure materials throughout this specification. Accordingly, in the following examples, the amount of PVA is the total amount of 100% active material that is used. In Example 6, the amount of Berol 08 was reduced to 0.15% in w / w.

TABLE 4 Example Quantity of PVAs 1% in w / w 1.5% in w / w Average hydrolysis (%) 58.3-62.3 58.3-62.3 After production Erichsen (mPa.s) 275 395 Brookfield (mPa.s) 950 Boundary line d50 / d99 (μm) 1.2 / 4.0 2.7 / 4.0 After 12 weeks of storage Erichsen (mPa.s) No data 140 Brookfield (mPa.s) No data 750 d50 / d99 (μm) No data 5.1 / 11.7 Both emulsified were safe. From these examples, it follows that the PVA combinations can also be used as a protective colloid in the emulsions according to the invention.

EXAMPLE 8 AND COMPARATIVE EXAMPLES F AND G In the emulsion of example 1, Alco552P was used as the PVA, while Berol 08 was replaced with the surfactants according to the table, with the following results: TABLE 5 Example 8 Surfactant Myrj 53 Softigen 767 Tween 20 Value of HLB 17.9 18.0 16.7 After production Erichsen (mPa.s) 440 > 500 495 Brookfield (mPa.s) 840 4260 3750 d50 / d99 (μm) 7.1 / 28.2 25.7 / 92.3 24.4 / 98.9 The emulsion of example 8 was safe. From these examples, it follows that the ethoxylated glyceryl esters of fatty acids (such as Softigen 767) and ethoxylated sorbitan esters (such as Tween 20), although they may have the desired HLB value, can not be used in the emulsions according to the invention.

EXAMPLE 9 AND COMPARATIVE BJgMPLQS H AND I Example 1 was repeated, using the following components: - 50% w / w of tert-butyl peroxineodecanoate (as 100%), supplied as Trigonox 23 of industrial grade, - 3.5% w / w of a mixture of 50 : 50 of Alcotex 552P (as 100%) and Unitika UMR10M with an average degree of hydrolysis of 58.3-62.3%, - for comparative example H, 0.5% w / w of the nonionic surfactant mentioned in the table, although in the comparative example I no surfactant was used, and - the rest being a 74/26 mixture of water / methanol.

TABLE 6 Example H Surface active agent Remcopal 20 Ethylan R None Value of HLB 16.0 15.4 n.r.

After production Erichsen (mPa.s) 480 > 500 > 500 Brookfield (mPa.s) 1440 > 2000 1550 d50 / d99 (μm) 1.2 / 6.0 0.7 / 5.0 0.7 / 5.9 The emulsion of example 9 was safe, while the emulsion of comparative example I was not. These examples show that surfactants of the appropriate type (an ethoxylated fatty alcohol) can not be used if the HLB value is 6.0, and that the use of a surfactant is required.

EXAMPLE 10 AND COMPARATIVE EXAMPLE J An emulsion of 2,4-trimetilpentyl 2-peroxineodecanoate in the polymerization of VCM was used in a Büchi stainless steel one liter autoclave with 3-blade agitator, baffle and temperature sensor. The polymerization components were the following: VCM 260g H2O 520g KP-08 0.39g Peroxyester emulsion 0.26g (0.05% w / w pure peroxide over VCM) Na2HPO4 0.1g NaH2PO4 0.1g The PVA was dissolved in the water, and the phosphate pH regulator was added. The reactor was evacuated, and refluxed four times with N2 (at room temperature). While stirring at 735 rpm, VCM was added. Subsequently, the reactor was heated to 53.5 ° C in 25 minutes. Then, the initiator emulsion was added by injection through a septum. Polymerization was stopped after 480 minutes by unreacted VCM ventilation and cooling. The PVC that formed was filtered, washed with H2 and dried overnight at 30 ° C in an air oven, and analyzed. The conversion was determined gra \ | etherically, the average particle size per medium of a Counter Multisizer Coulter®, the global density with a Din Cup 243 / 11.8 Erichsen, the dry flow with the same Din Cup, the plasticizer absorption according to DIN 53417, and the number of fish eyes as described by O. Leachs in Kunststoffe, Band 50 (4), 1960, pp. 227-234. In Example 10, the emulsion of 2,4-trimetilpentyl 2-peroxineodecanoate was the emulsion according to Example 4, while in Comparative Example J, the emulsion was prepared by dispersing 50% w / w peroxy ester and 3% w / w of Unitika UMR10M in 47% w / w of a 74/26 mixture of water / methanol. The viscosity of the last emulsion was not in accordance with the invention. The results are shown below.

TABLE 7 Example 10 J Performance on VCM (%) 81.2 76 Null clogging Some PVC particles > 800μm (g) 0.12 2.85 Overall PVC density (g / l) 374 404 Dry PVC flow 3.02 3.36 Average PVC particle size (μm) 126.7 139.0 Number of fish eyes (approx.) 50 100 Absorption of DOP ( %) 29.5 26 These examples show that the emulsions according to the invention are very suitable for the production of PVC.

Claims (14)

NOVELTY OF THE INVENTION CLAIMS

1. - An aqueous emulsion of a peroxyester which is liquid at -20 ° C and which comprises a protective colloid, a nonionic surfactant and an antifreeze agent, characterized in that the protective colloid is a polyvinyl acetate with a degree of hydrolysis between 45 and 68%, and the nonionic surfactant has an HLB value of 16 or more and is selected from alkylene oxide block copolymers, ethoxylated fatty alcohols and ethoxylated fatty acids.

2. The aqueous emulsion according to claim 1, further characterized in that the peroxy ester is present in an amount between 45 and 65% by weight.

3. The aqueous emulsion according to the claims 1 or 2, further characterized in that the polyvinyl acetate has a degree of hydrolysis between 45 and 62.5%, preferably between 50 and 60%.

4. The aqueous emulsion according to any of the preceding claims, further characterized in that the polyvinyl acetate is present in an amount between 0.5 and 10% by weight.

5. The aqueous emulsion according to any of the preceding claims, further characterized in that the surfactant is an ethoxylated fatty alcohol or an ethoxylated fatty acid.

6. The aqueous emulsi fi ed according to any of the preceding claims, further characterized in that the surfactant is present in an amount of 0.05 to 5% by weight, preferably 0.1 to 2% by weight.

7. The aqueous emulsion according to any of the preceding claims, further characterized in that the surfactant has an HLB value of 17 or more.

8. The aqueous emulsion according to any of the preceding claims, further characterized in that the antifreeze is a compound selected from the group consisting of methanol, ethanol, isopropanol, glycol, propanediol, glycerol, and combinations thereof, and use in such an amount that the emulsion does not freeze at a temperature of -20 ° C.

9. The aqueous emulsion according to any of the preceding claims, further characterized in that the average droplet size of the peroxy ester in the emulsion is less than 20 μm.

10. The aqueous emulsion according to any of the preceding claims, further characterized in that the viscosity of the emulsion is less than 500 mPa.s when analyzed with an Erichsen viscometer.

11. The aqueous emulsion according to any of the preceding claims, further characterized in that the viscosity of the ^^ MA ^^^^^^^^^^^^^ emulsion is less than 2000 mPa, s when analyzed with a Brookfield LVT and spindle sp3 at 12 rpm.

12. The use of an emulsion according to any of claims 1 to 11 as a f? Etote of free radicals.

13. The use according to claim 12, wherein the free radicals are used in a polymerization process.

14. The use according to claim 13, wherein the vinyl chloride is polymerized, optionally together with other monomers and / or in the presence of a polymer. Toi »rtW¿a < Atheb? ^ g g ¡i j ^^