A composition comprising at least two organic peroxides for the polymerization of ethylenically unsaturated monomers.

Abstract

The present invention provides a composition as an initiator that can reduce by-products for the free radical polymerization of ethylenically unsaturated monomers, particularly vinyl ester monomers, preferably vinyl acetates. [Solution] A composition comprising a first organic peroxide in an amount of 5 to 40% by weight relative to the total weight of the composition, having a half-life temperature of 1 hour that falls between 50°C and less than 85°C, wherein the first organic peroxide is of formula (I): TIFF2026071227000011.tif18169 It is a peroxyester by which, in the formula, R and R' are the same or different, and linear or branched C4-C 20 A composition is provided comprising a first organic peroxide selected from alkyl groups, and a second organic peroxide in an amount of 60-95% by weight relative to the total weight of the composition, having a 1-hour half-life temperature between 85°C and 120°C, which is intended for the radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl ester monomers, preferably vinyl acetate monomers.

Description

[Technical Field]

[0001] The present invention relates to a composition comprising a first organic peroxide having a 1-hour half-life temperature that is contained in a range of 50°C to less than 85°C, and a second organic peroxide having a 1-hour half-life temperature that is contained in a range of 85°C to 120°C.

[0002] The present invention also relates to the use of such compositions as initiators for the radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl ester monomers, preferably vinyl acetate monomers.

[0003] Finally, the present invention specifically deals with a method for preparing polyolefins, in particular polyvinyl polymers, such as polyvinyl acetate (PVA) and polyvinyl alcohol (PVOH) polymers, comprising at least one step of radical polymerization of one or more ethylenically unsaturated monomers in the presence of an effective amount of the previously defined composition. [Background technology]

[0004] Polyvinyl alcohol (PVOH) is commercially well-known and widely used as a protective colloid for the production of polymer dispersions in emulsions, as a thickener or stabilizer, as a sizing agent in the textile industry, in papermaking, and as a starting material for synthetic fibers. Polyvinyl alcohol can also be used as an adhesive, film, binder, and the like.

[0005] These polyolefins have traditionally been manufactured using a two-step process.

[0006] The first step involves the free radical polymerization of vinyl acetate (VA) carried out in an organic solvent, preferably a monohydric aliphatic alcohol having 1 to 4 carbon atoms, such as methyl alcohol, ethyl alcohol, and various isomers of propyl and butyl alcohol, in the presence of one or more initiators, such as organic peroxides, azo compounds such as azobisisobutyronitrile (AIBN), or mixtures thereof. The vinyl acetate monomer is polymerized at a temperature corresponding to the decomposition temperature of the initiator (the temperature at which the initiator generates free radicals), preferably in the range of 45°C to 130°C, until it is completely converted, or in many cases only to a certain extent, to polyvinyl acetate (PVA).

[0007] The second step involves converting the polyvinyl acetate to polyvinyl alcohol (PVOH). This conversion can be carried out by hydrolysis, alcohol decomposition, or saponification of the polyvinyl acetate. In particular, when polyvinyl acetate obtained by alkaline hydrolysis is subjected to an alcohol decomposition reaction, polyvinyl alcohol and methyl acetate are obtained.

[0008] Polyvinyl acetate (PVA) contains at least one repeating unit in its structure corresponding to the following formula: TIFF2026071227000001.tif42170

[0009] In the above formula, n represents the degree of polymerization.

[0010] When converted, polyvinyl alcohol (PVOH) contains at least one repeating unit in its structure corresponding to the following formula: TIFF2026071227000002.tif27170

[0011] In the above formula, n represents the degree of polymerization.

[0012] The degree of polymerization, molecular weight, and conversion rate achieved for both of the mentioned polymers depend primarily on the type and amount of initiator used during the polymerization of the vinyl acetate monomer.

[0013] The cumbersome aspect of the aforementioned two-step process lies in the fact that the degree of polymerization, molecular weight, and conversion rate of both polymers, polyvinyl acetate and polyvinyl alcohol, are intricately intertwined.

[0014] In fact, when attempting to produce high molecular weight polyvinyl alcohol, polyvinyl acetate having the corresponding degree of polymerization must be used, and therefore must be obtained in the first step of the process. Consequently, if the conversion rate or degree of polymerization of polyvinyl acetate is unsatisfactory during the first step of the process, it may become difficult to produce high molecular weight polyvinyl alcohol.

[0015] In particular, AIBN is classically used to generate 2-cyanopropyl free radicals to initiate the free radical polymerization of vinyl acetate monomers. AIBN has the advantage of being soluble in organic solvents, especially monohydric aliphatic alcohols.

[0016] However, the presence of unreacted AIBN in the final product can lead to discoloration of the resulting polymer, particularly yellowing of the resulting polyvinyl alcohol.

[0017] Furthermore, tetramethylsuccinonitrile (TMSN), a by-product of AIBN degradation, is highly toxic and remains in the final product, interfering with the properties of the resulting polyvinyl alcohol.

[0018] Several attempts are already underway to develop new, environmentally friendly organic peroxides that can replace AIBN, or more commonly, azo compounds, used as initiators.

[0019] Therefore, to achieve this objective, peroxides, particularly peroxyesters such as tert-butylperoxypivalate, marketed by Arkema under the name Luperox® 11M75, have been used to initiate the free radical polymerization of vinyl acetate monomers instead of AIBN, and especially to produce low molecular weight polyvinyl alcohols.

[0020] This type of peroxide exhibits the advantage of being more reactive than AIBN, allowing for the consideration of using this compound in a smaller amount, for example, about 50 to 70% less than AIBN. Further, tert-butyl peroxypivalate tends to decompose into smaller molecules than AIBN, which is easier to remove from the final product.

[0021] However, the main drawback of tert-butyl peroxypivalate is that the energy of the generated free radicals is high, which may lead to branched non-linear polyvinyl acetate during polymerization. More specifically, during polymerization, hydrogen atoms from the alpha, beta positions or methyl carbon of the acetate group may react with another vinyl acetate monomer, resulting in some branched formations.

[0022] Such branched polyvinyl acetate contains at least one repeating unit corresponding to the following formula. TIFF2026071227000003.tif65170

[0023] In the above formula, a, n, and x represent integers, where n ≥ 1, x ≥ 1, and a ≥ 0, and a < n.

[0024] Therefore, if the polyvinyl acetate obtained at the end of the first step is branched and non-linear, it also hinders the degree of polymerization of polyvinyl alcohol during the conversion reaction in the second step of the process. Due to these side reactions, the degree of polymerization of PVOH decreases and is even lower than that obtained with AIBN.

[0025] This means that tert-butyl peroxypivalate is less satisfactory than AIBN in terms of the degree of polymerization, conversion rate, and thus the resulting molecular weight.

[0026] Furthermore, additional attempts have been developed using other peroxy esters, particularly tert-butyl peroxy-2-ethylhexanoate sold under the name Luperox® 26 and tert-amyl peroxy-2-ethylhexanoate sold under the name Luperox® 575.

[0027] However, the conversion rate of vinyl acetate monomer to polyvinyl acetate is lower with these compounds.

[0028] As a result, it remains very difficult to replace AIBN as an initiator with a peroxy ester such as Luperox® 11M75, Luperox® 26 or Luperox® 575 in order to produce polyolefins, particularly polyvinyl acetate and polyvinyl alcohol, having a high degree of polymerization and high molecular weight.

[0029] Furthermore, it is noteworthy that the above-mentioned drawbacks encountered in the polymerization of vinyl acetate monomer also occur more extensively in the radical polymerization of ethylenically unsaturated monomers, particularly vinyl monomers such as vinyl ester monomers and (meth)acrylate ester monomers.

[0030] Therefore, there is a real need to provide a composition that can reduce by-products while maintaining the degree of polymerization, molecular weight and / or conversion rate of polyolefins obtained by free radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl monomers, more preferably vinyl ester monomers and (meth)acrylate ester monomers, compared to prior art azo initiators. SUMMARY OF THE INVENTION

[0031] The present invention relates to a composition, A first organic peroxide, present in an amount of 5 to 40% by weight of the total weight of the composition, having a 1-hour half-life temperature between -50°C and less than 85°C, more preferably between 54°C and 77°C, and even more preferably between 60°C and 70°C, wherein the first organic peroxide is of formula (I): It is a peroxyester according to TIFF2026071227000004.tif18169, In the formula, R and R' are the same or different, and are linear or branched from C4 to C 20 A first organic peroxide selected from alkyl groups, and A second organic peroxide in an amount of 60 to 95% by weight relative to the total weight of the composition, having a half-life temperature of 1 hour between -85°C and 120°C, more preferably between 88°C and 120°C, and even more preferably between 90°C and 95°C. This relates to a composition containing the following:

[0032] The previously defined compositions enable the conversion kinetics of polyolefins, particularly vinyl polymers, obtained by free radical polymerization of one or more ethylenically unsaturated monomers, comparable to those obtained using AIBN, without the drawbacks associated with their use.

[0033] Furthermore, unlike the use of AIBN, the compositions of the present invention do not cause discoloration of vinyl polymers, particularly polyvinyl alcohols, and especially their yellowing. In fact, the decomposition of the peroxyesters of the present invention yields small molecules that can be easily removed.

[0034] In particular, the decomposition of peroxyesters used in the composition generates smaller molecules that are less toxic than TMSNs during the free radical polymerization of ethylenically unsaturated monomers.

[0035] Preferably, the compositions according to the present invention are liquid at room temperature and highly soluble in organic solvents used in the free radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl monomers, more preferably vinyl ester monomers. In particular, the compositions are more soluble in organic solvents than AIBN, which facilitates their removal from the final product.

[0036] Another object of the present invention relates to the use of the previously defined compositions as initiators for the radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl monomers, preferably vinyl ester monomers, and more preferably vinyl acetate.

[0037] The ethylenically unsaturated monomers suitable for radical polymerization may be the same or different for the production of polyolefins.

[0038] This means that the term "polymerization" encompasses both homopolymerization and copolymerization of one or more ethylenically unsaturated monomers.

[0039] The present invention also deals with a method for preparing polyolefins, particularly polyvinyl polymers, such as polyvinyl acetate (PVA) and polyvinyl alcohol (PVOH), comprising at least one step of radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl monomers, in the presence of an effective amount of the previously defined composition.

[0040] The process according to the present invention makes it possible to obtain polyolefins having either low molecular weight or high molecular weight, particularly polyvinyl acetate (PVA) and polyvinyl alcohol (PVOH).

[0041] In particular, this process can efficiently produce high molecular weight polyolefins, polyvinyl acetate (PVA), and polyvinyl alcohol (PVOH) as azo compounds such as AIBN.

[0042] This process can also efficiently yield low molecular weight polyolefins, particularly polyvinyl acetate (PVA) and polyvinyl alcohol (PVOH), as azo compounds such as AIBN.

[0043] Other subjects, characteristics, embodiments, and advantages of the present invention will become clearer upon reading the following description and examples. [Modes for carrying out the invention]

[0044] In the following text of this specification, unless otherwise indicated, the limits of a range of values ​​are included in that range, in particular in expressions such as “between” and “range of ~”.

[0045] Furthermore, the expression "at least one" as used herein is synonymous with the expression "one or more."

[0046] In the following text of this specification, the terms "perester" and "peroxyester" are equivalent.

[0047] composition The composition of the present invention, A 1-hour half-life temperature that falls between -50°C and less than 85°C, more preferably between 54°C and 77°C, and even more preferably between 60°C and 70°C, The 1-hour half-life temperatures are contained within the range of -85°C to 120°C, more preferably between 88°C and 120°C, and even more preferably between 90°C and 95°C. It comprises at least two organic peroxides having [a specific characteristic].

[0048] The "1-hour half-life temperature" is the temperature at which half of the peroxide decomposes in one hour. In other words, it is the temperature at which half of the reactive oxygen species content of the peroxide is lost after one hour.

[0049] Classically, the half-life temperature of an organic peroxide at 1 hour is determined by measuring the decomposition rate in n-decane or n-dodecane.

[0050] The first organic peroxide having a 1-hour half-life temperature found between 50°C and less than 85°C is given by formula (I): It is a peroxyester according to TIFF2026071227000005.tif18169, In the formula, R and R' are the same or different, and the linear or branched C4 to C 20 Selected from alkyl groups.

[0051] In other words, R and R' are independent of each other, and are linear or branched from C4 to C 20 It can represent an alkyl group.

[0052] In particular, R and R' are independent of each other, and R is a linear or branched C4 to C4 chain containing more carbon atoms than R'. 20 It can represent an alkyl group.

[0053] Preferably, R and R' are independent of each other, branching from C4 to C 20 Represents an alkyl group.

[0054] To the advantage, R is at branch C4 to C 10 R' represents an alkyl group, preferably a C7 to C9 alkyl group, and R' represents a branched C4 to C9 alkyl group, preferably a C4 to C5 alkyl group.

[0055] More preferably, R represents a branched C6 to C8 alkyl group, more preferably a C7 alkyl group, and R' represents a branched C4 to C5 alkyl group.

[0056] In a preferred embodiment, R represents a branched C9 alkyl group, and R' represents a branched C4 alkyl group.

[0057] Preferably, the first organic peroxide is selected from the group consisting of 1,1,3,3-tetramethylbutyl peroxypivalate, tert-butyl peroxypivalate (sold under the name Luperox® 11), 1,1,3,3-tetramethylbutyl peroxyneodecanoate (sold under the name Luperox® 810), tert-amyl peroxyneodecanoate (sold under the name Luperox® 546), tert-butyl peroxyneodecanoate (sold under the name Luperox® 10), 1,1,3,3-tetramethylbutyl peroxypivalate, tert-butyl peroxyneoheptanoate (sold under the name Luperox® 701), tert-amyl peroxypivalate (sold under the name Luperox® 554), and mixtures thereof; more preferably, the first organic peroxide is at least one tert-butyl peroxyneodecanoate.

[0058] The first organic peroxide is present in an amount in the range of 5 to 40% by weight, preferably 10 to 30% by weight, more preferably 15 to 25% by weight, based on the total weight of the composition.

[0059] Preferably, the second organic peroxide having a one-hour half-life temperature included between 85°C and 120°C is a peroxyester, preferably of the formula (II): is a peroxyester according to TIFF2026071227000006.tif23167, wherein R1 and R2 are the same or different and are selected from linear or branched C4 to C 20 alkyl groups.

[0060] In other words, R1 and R2 can each independently represent a linear or branched C4 to C 20 alkyl group.

[0061] In particular, R1 and R2 can each independently represent a straight-chain or branched C4 to C 20 alkyl group in which R contains more carbon atoms than R2.

[0062] Preferably, R1 and R2 are independent of each other, branching from C4 to C 20 Represents an alkyl group.

[0063] To gain an advantage, R1 branches off from C4 to C 10 R2 represents an alkyl group, preferably a C6 to C8 alkyl group, and R2 represents a branched C4 to C9 alkyl group, preferably a branched C4 to C5 alkyl group, and more preferably a branched C5 alkyl group.

[0064] More preferably, R1 represents a branched C6 to C8 alkyl group, more preferably a C7 alkyl group, and R2 represents a branched C4 to C5 alkyl group.

[0065] In a preferred embodiment, R1 represents a branched C7 alkyl group, and R2 represents a branched C5 alkyl group.

[0066] In particular, the second organic peroxide is 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (sold under the name Luperox® 826), tert-amylperoxy-2-ethylhexanoate (sold under the name Luperox® 575), tert-butylperoxy-2-ethylhexanoate (sold under the name Luperox 26®), tert-butylperoxydiethylacetate The second organic peroxide may be selected from the group consisting of tert-butylperoxyisobutyrate (marketed under the name Luperox® 80), tert-amylperoxy-3,5,5-trimethylhexanoate (marketed under the name Luperox® 570), and mixtures thereof, and is preferably selected from tert-amylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, and mixtures thereof. More preferably, the second organic peroxide is at least one tert-amylperoxy-2-ethylhexanoate.

[0067] The second organic peroxide is present in an amount ranging from 60 to 95% by weight, preferably 70 to 90% by weight, and more preferably 75 to 85% by weight, relative to the total weight of the composition.

[0068] Preferably, the weight ratio between the first organic peroxide and the second organic peroxide, particularly between tert-butylperoxyneodecanoate and tert-amylperoxy-2-ethylhexanoate, is in the range of 5:95 to 40:60, preferably 10:90 to 30:70, and more preferably 15:85 to 20:80.

[0069] Preferably, the first organic peroxide is tert-butylperoxyneodecanoate, and the second organic peroxide is tert-amylperoxy-2-ethylhexanoate.

[0070] The compositions of the present invention may also contain at least one additive, particularly mineral oil.

[0071] Preferably, the composition contains less than 20% of the additive relative to the weight of the composition.

[0072] Preferably, the composition contains less than 10% of the additive relative to the weight of the composition.

[0073] According to the embodiment, the composition does not contain any additional additives, which means that it consists of two organic peroxides as defined above.

[0074] process Another object of the present invention relates to a step of preparing a polyolefin comprising at least one step a) of radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl monomers, in the presence of an effective amount of the composition defined above.

[0075] The radical polymerization process can be carried out under classically known conditions, depending on the monomers involved.

[0076] This means that the radical polymerization process can be carried out in an emulsion, suspension, bulk, or solution.

[0077] In particular, when polyolefins are selected from among (meth)acrylic polymers, their corresponding radical polymerization may be carried out in emulsion, suspension, bulk, or solution.

[0078] The previously defined compositions can be added to ethylenically unsaturated monomers in batches or sequentially.

[0079] The radical polymerization step can be carried out at a temperature in the range of 45°C to 130°C, preferably 50°C to 90°C, preferably 60°C to 80°C, and more preferably 65°C to 75°C.

[0080] The radical polymerization step may be carried out in the presence of at least one organic solvent, which can be selected from the group consisting of monohydric aliphatic alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, acetone, isopropyl alcohol, methyl acetate, ethyl acetate, and mixtures thereof.

[0081] Preferably, the organic solvent contains methanol, and more preferably consists of methanol.

[0082] The radical polymerization step may preferably be carried out in the presence of at least one additive selected from the group consisting of aldehydes, particularly acetaldehyde, butyraldehyde, and valeraldehyde; mercaptans, particularly dodecyl mercaptan, methyl mercaptan, and ethyl mercaptan; alcohols, particularly ethanol, n-butyl alcohol, isopropyl alcohol, and vinyl ethers, particularly vinyl ether and vinyl polyoxyethylene ether.

[0083] Preferably, the amount of at least the additive is less than 20% by weight, more preferably less than 10% by weight, relative to the total weight of the ethylenically unsaturated monomer.

[0084] The amount of composition introduced to initiate radical polymerization is preferably 0.001 to 5% by weight, preferably 0.01 to 2.5% by weight, more preferably 0.01 to 0.8% by weight, and even more preferably 0.015 to 0.5% by weight, relative to the total weight of the ethylenically unsaturated monomer.

[0085] The ethylenically unsaturated monomer used in the process of the present invention is selected from the group consisting of vinyl monomers, particularly (meth)acrylic acid ester monomers such as methyl acrylate and methyl methacrylate, styrene monomers, vinyl ester monomers, and mixtures thereof, more preferably selected from the group consisting of vinyl esters of carboxylic acid saturated monomers such as vinyl acetate or vinyl propionate, and even more preferably vinyl acetate.

[0086] Preferably, the ethylenically unsaturated monomer corresponds to a vinyl monomer, particularly a vinyl ester monomer, and preferably a vinyl acetate monomer.

[0087] The vinyl monomer can be selected from the group consisting of vinyl formate, vinyl acetate, vinyl propionate, butyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl acetate, vinyl caprylate, vinyl laurate, vinyl stearate, benzyl acetate, vinyl acetate, and mixtures thereof, more preferably vinyl acetate or vinyl propionate, and even more preferably vinyl acetate.

[0088] Therefore, the polyolefin obtained in the process of the present invention is selected from the group consisting of polyvinyl polymers, more preferably (meth)acrylic polymers, such as (meth)acrylic homopolymers, acrylic / methacrylic styrene copolymers, (meth)acrylic / vinyl acetate and (meth)acrylic / vinyl acetate / styrene copolymers, polyvinyl acetate, and polyvinyl alcohol.

[0089] More preferably, the polyolefin obtained in the process of the present invention is selected from the group consisting of polyvinyl acetate and polyvinyl alcohol.

[0090] More specifically, this process yields polyvinyl acetate and polyvinyl alcohol having a degree of polymerization higher than 500, preferably between 500 and 3000, and more preferably between 1100 and 2000.

[0091] More specifically, this process yields polyvinyl alcohol having a degree of hydrolysis of 60% to 99.9%, more preferably 90% to 99.9%, and even more preferably 96% to 99.9%.

[0092] The degree of polymerization and the degree of hydrolysis can be evaluated according to the standard ISO 15023-2:2003.

[0093] According to a preferred embodiment, the process according to the present invention is a process for preparing a polyvinyl polymer, comprising at least one step a) of radical polymerization of one or more vinyl monomers, preferably vinyl ester monomers, and particularly vinyl acetate.

[0094] The present invention also relates to a process for preparing polyvinyl alcohol, comprising step b) the conversion of the polymeric vinyl ester to polyvinyl alcohol obtained after step a).

[0095] In other words, the process for obtaining polyvinyl alcohol consists of at least two steps: the first step is the radical polymerization of one or more vinyl ester monomers as described above, and the second step is the conversion of the polymeric vinyl ester obtained in the first step into polyvinyl alcohol.

[0096] In this embodiment, the polymeric vinyl ester obtained in the first step is preferably polyvinyl acetate.

[0097] At the end of step a) of radical polymerization, step a') can be performed before step b) of transformation to remove any remaining residue and organic solvent.

[0098] The conversion step b) can be carried out by hydrolysis, alcohol decomposition, or saponification of the high-molecular-weight vinyl ester.

[0099] Preferably, the conversion step is carried out by performing an alcohol decomposition reaction of the polymer vinyl ester.

[0100] The alcohol decomposition reaction is preferably carried out in the presence of methanol to obtain the polyvinyl alcohol and methyl acetate.

[0101] The alcohol decomposition reaction may be carried out in the presence of an alkaline catalyst or an acid catalyst.

[0102] The alkaline catalyst is preferably selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methylate, potassium methylate, and the like.

[0103] The acid catalyst is preferably selected from the group consisting of organic and inorganic sulfonic acids, and is preferably an organic sulfonic acid.

[0104] Preferably, the organic sulfonic acid is selected from the group consisting of benzenesulfonic acid, p-toluenesulfonic acid, alkylsulfonic acid, 2-methyl-5-propylbenzenesulfonic acid, 1,5-naphthalenesulfonic acid, 2,7-benzenedisulfonic acid, methanesulfonic acid, ethanesulfonic acid, butylsulfonic acid, and octylsulfonic acid.

[0105] The conversion step b) may be carried out at a temperature between 20°C and 50°C, preferably between 30°C and 40°C.

[0106] use The present invention also deals with the use of compositions previously defined as initiators for the radical polymerization of one or more ethylenically unsaturated monomers, particularly vinyl monomers selected from vinyl ester monomers, and more preferably vinyl acetate.

[0107] Product-specific processes The present invention also relates to polyolefins, particularly polyvinyl acetate or polyvinyl alcohol, obtained by the previously defined process.

[0108] Preferably, the polyolefin has a degree of polymerization higher than 500, preferably 500 to 3000, and more preferably 1100 to 2000.

[0109] Preferably, the polyolefin has a degree of hydrolysis of 60% to 99.9%, more preferably 90% to 99.9%, and even more preferably 96% to 99.9%.

[0110] The following examples are given as illustrations of the present invention. [Examples]

[0111] F The protocol described below for obtaining polyvinyl alcohol (see Part II) was performed using the following initiators: [Table 1] TIFF2026071227000007.tif186170

[0112] II. Synthesis of polyvinyl acetate and conversion to polyvinyl alcohol 210 grams of Celanese-derived vinyl acetate monomer and 90 grams of methanol are introduced into a 2 L glass reactor. The reactor temperature is then raised to 70°C.

[0113] To initiate radical polymerization, a fixed amount of each initiator (see Part I) is introduced into the reactor. The reaction is maintained at a temperature of 70°C for 4 hours.

[0114] After 4 hours, collect a 5-gram sample and weigh it precisely for conversion calculations.

[0115] The sample is placed in a 90°C vacuum oven for 12 hours to remove residue and methyl alcohol. Then, the polymerization conversion rate is calculated.

[0116] After the calculation, 100 grams of polyvinyl acetate are left in the reactor.

[0117] The molecular weight of polyvinyl acetate is analyzed by gel permeation chromatography (GPC) using THF as the solvent. Polystyrene is used as the time reference.

[0118] Next, in order to convert the polyvinyl acetate into polyvinyl alcohol, an alcohol decomposition step is carried out at 35°C by first dissolving the polyvinyl acetate in methanol and sodium hydroxide.

[0119] Next, the polyvinyl alcohol is extracted with methanol to remove salt residue, and then dried under reduced pressure at a temperature of approximately 45°C for 8 hours.

[0120] The molecular weight of polyvinyl alcohol is analyzed by gel permeation chromatography (GPC) using water as the fluid. PEG is the standard.

[0121] III. Conversion rate of polyvinyl acetate Table 2 shows the conversion rates of polyvinyl acetate at 120, 180, 240, and 300 minutes for the initiators listed in Table 1, expressed in percentage. [Table 2] TIFF2026071227000008.tif44170

[0122] The compositions of the present invention enable the achievement of very good conversion of polyvinyl acetate in a time similar to that of azo initiators, with significantly lower initiator usage levels. Such kinetics are not observed with peroxyesters used alone.

[0123] Furthermore, it is found that the conversion of polyvinyl acetate using such compositions proceeds much more linearly than with tert-butyl peroxypivalate alone (see Comparative Example 3). This can be advantageous in avoiding runaway conditions and the need for more steady-state cooling capacity. Thus, this enables potentially higher reactor loads or higher polymerization temperatures, and therefore faster kinetics.

Claims

1. A composition, A first organic peroxide in an amount of 5 to 40% by weight of the total weight of the composition, having a 1-hour half-life temperature between -50°C and less than 85°C, more preferably between 54°C and 77°C, and even more preferably between 60°C and 70°C, wherein the first organic peroxide is of formula (I): It is a peroxyester produced by In the formula, R and R' are the same or different, and C is linear or branched. ４ ~C ２０ A first organic peroxide selected from alkyl groups, and A second organic peroxide in an amount of 60 to 95% by weight relative to the total weight of the composition, having a half-life temperature of 1 hour between -85°C and 120°C, more preferably between 88°C and 120°C, and even more preferably between 90°C and 95°C. A composition containing the following:

2. R is a branched C ４ -C １０ alkyl group, preferably C ７ -C ９ alkyl group, and R' is a branched C ４ -C ９ alkyl group, preferably C ４ -C ５ alkyl group, and the composition according to claim 1.

3. The composition according to claim 1 or 2, wherein the first organic peroxide is selected from the group consisting of 1,1,3,3-tetramethylbutylperoxyneodecanoate, tert-amylperoxyneodecanoate, tert-butylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxypivalate, tert-butylperoxyneoheptanoate, tert-amylperoxypivalate, tert-butylperoxypivalate, and mixtures thereof, and preferably the first organic peroxide is at least one tert-butylperoxyneodecanoate.

4. The composition according to any one of claims 1 to 3, characterized in that the first organic peroxide is present in an amount of 10 to 30% by weight, more preferably 15 to 25% by weight, based on the total weight of the composition.

5. The second organic peroxide having a 1-hour half-life temperature between 85°C and 120°C is a peroxyester, preferably of formula (II): It is a peroxyester produced by In the formula, R １ and R ２ C is the same or different, linear or branched. ４ ~C ２０ A composition according to any one of claims 1 to 4, selected from alkyl groups.

6. R １ Branch C ４ ~C １０ Alkyl alkyl group, preferably C ６ ~C ８ Represents an alkyl group, R ２ Branch C ４ ~C ９ Alkyl alkyl groups, preferably branched C ４ ~C ５ Alkyl alkyl groups, more preferably branched C ５ The composition according to any one of claims 1 to 5, characterized in that it represents an alkyl group.

7. The composition according to any one of claims 1 to 6, characterized in that the second organic peroxide is present in an amount of 70 to 90% by weight, more preferably 75 to 85% by weight, based on the total weight of the composition.

8. The composition according to any one of claims 1 to 7, characterized in that the second organic peroxide is selected from the group consisting of 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxydiethyl acetate, tert-butylperoxyisobutyrate, tert-amylperoxy-3,5,5-trimethylhexanoate and mixtures thereof, preferably selected from the group consisting of tert-amylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate and mixtures thereof, and more preferably at least one tert-amylperoxy-2-ethylhexanoate.

9. A method for preparing a polyvinyl polymer comprising at least one step a) of radical polymerization of one or more vinyl monomers in the presence of an effective amount of the composition according to any one of claims 1 to 8.

10. The method according to claim 9, characterized in that the radical polymerization step is carried out at a temperature in the range of 45°C to 130°C, preferably 50°C to 90°C, preferably 60°C to 80°C, and more preferably 65°C to 75°C.

11. The method according to claim 9 or 10, characterized in that the radical polymerization step is carried out in the presence of at least one organic solvent which can be selected from the group consisting of monohydric aliphatic alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, acetone, isopropyl alcohol, methyl acetate, ethyl acetate, and mixtures thereof.

12. The method according to any one of claims 9 to 11, characterized in that the vinyl monomer is a vinyl ester monomer, preferably a vinyl acetate monomer.

13. A method according to any one of claims 9 to 12 for preparing polyvinyl alcohol, comprising step b) the conversion of the polymer vinyl ester to polyvinyl alcohol obtained after step a).

14. The method according to claim 13, wherein step b) of the conversion is carried out by hydrolysis, alcohol decomposition, or saponification of the polymer vinyl ester.

15. Use of the composition according to any one of claims 1 to 8 as an initiator for the radical polymerization of one or more vinyl monomers, more preferably vinyl ester monomers, and even more preferably vinyl acetate monomer.

16. A polyvinyl polymer obtained by the method described in any one of claims 9 to 14, having a degree of polymerization preferably higher than 500, preferably 500 to 3000, and more preferably 1100 to 2000.

17. The polyvinyl polymer according to claim 16, having a degree of hydrolysis of 60% to 99.9%, more preferably 90% to 99.9%, and even more preferably 96% to 99.9%.

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