Aqueous organic peroxide emulsion

Abstract

To provide the use of an aqueous organic peroxide emulsion to prepare polyvinyl chloride with an increased rate of drying.SOLUTION: This disclosure provides the use of an aqueous organic peroxide emulsion comprising from 0 to 0.17 wt.% of at least one emulsifier, to prepare polyvinyl chloride with an increased rate of drying. The aqueous organic peroxide emulsion comprises: (i) from 25 to 70 wt.% of at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25°C or less; (ii) from 1.4 to 6.0 wt.% of at least one protective colloid; (iii) from 0 to 0.17 wt.% of at least one emulsifier; and (iv) at least one anti-freeze agent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to aqueous emulsions of organic peroxides containing reduced amounts of emulsifiers. The present invention further relates to the use of such emulsions in vinyl chloride monomer (VCM) polymerization to prepare polyvinyl chloride (PVC) with improved drying properties. [Background technology]

[0002] Organic peroxides are known in the art to be effective initiators for the polymerization of VCM to produce PVC. Commercially, these peroxides are available as stable aqueous emulsions that contain protective colloids, emulsifiers, and antifreeze agents.

[0003] In WO 03 / 095500, it is disclosed that a combination of di(2-ethylhexyl) peroxydicarbonate, a protective colloid, a non-ionic emulsifier, and an antifreeze agent can result in a stable aqueous emulsion with small peroxide droplet size and narrow droplet size distribution, which is advantageous when used in PVC production. In Example 1, an aqueous emulsion is made with 55% w / w di(2-ethylhexyl) peroxydicarbonate, 0.8% w / w 62-68% saponified polyvinyl acetate, 0.3% w / w ethoxylated stearyl alcohol, water, and methanol. When the ethoxylated stearyl alcohol emulsifier is omitted in Comparative Example A, the PVC polymer resulting from standard suspension polymerization of VCM is adversely affected.

[0004] Similarly, in International Patent Publication No. 2011 / 015567, an aqueous organic peroxide emulsion containing 40 wt. % diisobutyryl peroxide, 1.1 wt. % hydrolyzed polyvinyl acetate of 62-68%, 0.3 wt. % ethoxylated stearyl alcohol, water, and methanol is shown to result in a stable aqueous emulsion with small peroxide droplet sizes and a narrow droplet size distribution (99% of the dispersed phase volume well below 10 microns).

[0005] However, PVC produced using these stable aqueous organic peroxide emulsions has been found to have unsatisfactorily long drying times.

[0006] Therefore, there is a need for aqueous organic peroxide emulsions in which this problem is addressed. Summary of the Invention

[0007] Surprisingly, it has been discovered that improved aqueous emulsions of organic peroxides can be made with significantly less emulsifier. These aqueous emulsions are not only stable, but have been found to produce high quality PVC with improved drying characteristics.

[0008] Thus, in a first aspect, the present disclosure is directed to the use of an aqueous organic peroxide emulsion comprising 0 to 0.17 wt. % of at least one emulsifier to prepare polyvinyl chloride having an increased drying rate.

[0009] Advantageously, stable aqueous emulsions have been prepared with small peroxide droplet sizes and narrow droplet size distributions beneficial for PVC production, despite low (or no) concentrations of emulsifier. Furthermore, the use of these emulsions in the polymerization of VCM has been found to produce high quality PVC with unexpected improvements in drying characteristics (the drying rate of the resulting PVC polymer was substantially increased, and therefore the drying time of the polymer was reduced, which is important for industrial-scale production of PVC).

[0010] Preferably, the aqueous organic peroxide emulsion used according to the first aspect of the present invention comprises (i) 25 to 70% by weight of at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less; (ii) 1.4 to 6.0% by weight of at least one protective colloid; (iii) 0 to 0.17% by weight of at least one emulsifier; (iv) at least one antifreeze agent.

[0011] The SADT is the lowest ambient temperature at which self-accelerating decomposition occurs for a product in the packaging used for transport. The method for determining the SADT of organic peroxides is detailed in the UN Recommended Test Criteria, Revised 7th Edition (2019), Test Series H.4: Accumulated Heat Storage Tests, which criteria and test methods are incorporated herein by reference. The method determines the minimum constant ambient temperature at which a thermally unstable substance undergoes exothermic decomposition under conditions representative of the substance when packaged. The method is based on Semenov's theory of thermal explosion, where the primary resistance to heat flow is considered to be the container wall. The method is applicable to IBCs and small tanks (up to 2m 3 For the avoidance of doubt, the SADT values ​​referred to herein are determined in accordance with the methodology set out in the above referenced United Nations standard for organic peroxides in high density polyethylene (HDPE) packaging having a volume of 20-30 litres (Test Series H.4: Accumulated Heat Storage Test).

[0012] The aqueous organic peroxide emulsion used according to the first aspect of the invention preferably contains at least one organic peroxide having a low SADT (i.e., 25° C. or less), preferably below 20° C., preferably below 15° C., preferably below 10° C., preferably below 5° C., and may be below about 0° C. Preferred organic peroxides include peroxyesters, peroxydicarbonates, diacyl peroxides. Diacyl peroxides and peroxydicarbonates are preferred. Examples of preferred organic peroxides for use according to the invention are diisobutyryl peroxide (SADT 0° C.), cumyl peroxyneodecanoate (SADT 10° C.), 1,1,3,3-tetramethylbutylperoxyneodecanoate (SADT 15° C.), cumyl peroxy-neopentanoate (SADT 10° C.), tert-amyl peroxyneodecanoate (SADT 20° C.), di-sec-butyl peroxydicarbonate (SADT 0° C.), di(2-ethylhexyl)peroxy-dicarbonate (SADT 5° C.), tert-butyl peroxyneodecanoate (SADT 20° C.), 1,1,3,3-tetramethylbutylperoxypivalate (SADT 20° C.), tert-amyl peroxypivalate (SADT 25° C.), tert-butyl peroxypivalate (SADT 25° C.). 25° C.), di(3,5,5-trimethylhexanoyl)peroxide (SADT 25° C.), di-n-propyl peroxydicarbonate (SADT 0° C.), diisopropyl peroxydicarbonate (SADT 5° C.), di-n-butyl peroxydicarbonate (SADT 0° C.), di(2-ethoxyethyl)peroxydicarbonate (SADT 10° C.), 1,3-di(propa-2,2-diyl)benzenebis(neodecanoyl)peroxide (SADT 10° C.), 3-hydroxy-1,1-dimethylbutylperoxyneodecanoic acid (SADT 10° C.), di-n-butyryl peroxide (SADT 25° C.), or mixtures thereof.

[0013] The aqueous organic peroxide emulsions used according to the first aspect of the invention typically contain from 25 to 70% by weight of organic peroxide, based on the total weight of the emulsion. The amount of organic peroxide in the emulsion is preferably from 30 to 65% by weight, more preferably from 35 to 60% by weight.

[0014] The amount of water in the emulsion of the first embodiment is typically in the range of 20 to 60% by weight, preferably 25 to 50% by weight, more preferably 25 to 40% by weight, based on the total weight of the emulsion.

[0015] Preferably, the aqueous organic peroxide emulsion used according to the first aspect of the present invention contains at least one protective colloid. Any conventional protective colloid can be used. Examples of suitable protective colloids are cellulose and partially hydrolyzed (or saponified) polyvinyl acetate. Partially hydrolyzed polyvinyl acetate (PVA) is the preferred protective colloid present in the aqueous emulsion. Preferably, the PVA has a degree of hydrolysis of at least 50 mol%, more preferably at least 55 mol%, most preferably at least 60 mol%, preferably up to 90 mol%, more preferably up to 80 mol%, most preferably up to 70 mol%. Preferably, the PVA is randomly hydrolyzed as opposed to hydrolysis of a block structure.

[0016] Instead of using just one type of PVA, a blend of two or more PVAs can be used, in which case the blend can be considered simply as one PVA, and its degree of hydrolysis is the weight average of the degrees of hydrolysis of the PVAs. Preferably, such blends of PVAs do not contain more than 0.2% of PVA having a degree of hydrolysis less than 50 mol% or more than 90 mol%.

[0017] The amount of protective colloid used in the emulsion of the first aspect of the invention depends on the type and amount of organic peroxide and the desired viscosity of the final emulsion, but is typically used in an amount of 1.4 to 6.0% by weight, preferably 1.5 to 5% by weight, based on the total weight of the emulsion. For example, when the organic peroxide is di(2-ethylhexyl)peroxydicarbonate, the protective colloid is typically used in an amount of 1.4 to 3.0% by weight, preferably 1.5 to 2.0% by weight, based on the total weight of the emulsion.

[0018] The emulsion used according to the first aspect of the present invention contains from 0 to 0.17% by weight, preferably from 0 to 0.15% by weight, preferably from 0 to 0.10% by weight, preferably from 0 to 0.05% by weight, more preferably 0% by weight, of at least one conventional emulsifier, based on the total weight of the emulsion.

[0019] Conventional emulsifiers are known to those skilled in the art and include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and mixtures thereof.Examples of surfactants typically used in aqueous organic peroxide emulsions include alkylene oxide block copolymers, alkoxylated fatty alcohols (including ethoxylated and / or propoxylated C6-C22 fatty alcohols, such as ethoxylated stearyl alcohol, ethoxylated cetyl alcohol, and mixtures thereof), and alkoxylated fatty acids (including ethoxylated and / or propoxylated C6-C22 fatty acids).Additional examples include sorbitan fatty acid esters, ethoxylated sorbitan fatty acid esters, ethoxylated castor oil, oxyalkylated vegetable oils and animal oils (hydrogenated or non-hydrogenated).

[0020] If an emulsifier is added to the emulsion used according to the first aspect of the invention, preferably a non-ionic surfactant is used, more preferably a non-ionic surfactant having an HLB value of 8 or more, preferably 10 or more, even more preferably 14 or more. The HLB value represents the hydrophilic-lipophilic balance as described in "The Atlas HLB-System, a time saving guide to emulsifier selection" (publisher: Atlas Chemical Industry Inc., 1963). However, it is preferred that the emulsifier is omitted from the emulsion, i.e. the emulsion used according to the first aspect of the invention is preferably substantially free of emulsifier.

[0021] The emulsion used according to the first aspect of the invention also preferably contains at least one cryoprotectant, and may contain a combination of two or more cryoprotectants. Any conventional cryoprotectant can be used. Preferably, the use is made from methanol, ethanol, propanol, isopropanol, (ethylene) glycol, propanediol, glycerol, and mixtures thereof, more preferably methanol, ethanol, propanediol, and mixtures thereof. These compounds are known to have little effect on the polymerization process in which the peroxide emulsion is used. Most preferably, methanol is used as the cryoprotectant.

[0022] The amount of cryoprotectant is typically selected so that the emulsion does not freeze at a temperature of -10°C, preferably -15°C, most preferably -20°C or -25°C. The amount of freezing point depressant used depends on the type of cryoprotectant used, or mixture of cryoprotectants. It is appropriate to first make a mixture of cryoprotectant and water, containing a sufficient amount of cryoprotectant to be pourable at the indicated temperature. This mixture can then be used in further processes to make the emulsion. Those skilled in the art will have no difficulty in balancing the ratio of water to cryoprotectant. Typically, the amount of cryoprotectant used in the emulsion according to the present invention is less than the amount of water.

[0023] In a second aspect, the present disclosure is directed to an aqueous organic peroxide emulsion, the aqueous organic peroxide emulsion comprising: (i) 30 to 45% by weight of diisobutyryl peroxide; (ii) 2.0 to 6.0% by weight of at least one protective colloid; (iii) 0 to 0.17% by weight of at least one emulsifier; (iv) at least one antifreeze agent.

[0024] By combining high concentrations of diisobutyryl peroxide (SADT 0°C) with low concentrations of emulsifiers, stable aqueous emulsions have been prepared that are surprisingly beneficial for the production of PVC. In particular, low or no emulsifier content in the resulting PVC polymer has been found to result in faster drying characteristics, which when combined with the possible continuous and / or intermittent dosing of the peroxide emulsion, saves considerable time in the production process.

[0025] The aqueous organic peroxide emulsion of the second aspect of the present invention contains 30 to 45% by weight of diisobutyryl peroxide (CAS No. 3437-84-1) based on the total weight of the emulsion. The amount of diisobutyryl peroxide in the aqueous emulsion is preferably 35 to 42% by weight.

[0026] The amount of water in the aqueous organic peroxide emulsion of the second embodiment typically ranges from 20 to 60% by weight, preferably from 25 to 50% by weight, and more preferably from 25 to 40% by weight, based on the total weight of the emulsion.

[0027] The aqueous organic peroxide emulsion of the second aspect of the invention typically contains at least one protective colloid in an amount of 2.0-6.0 wt.%, preferably 2.5-4.0 wt.%, more preferably 2.7-3.5 wt.%, based on the total weight of the emulsion. As in the first aspect of the invention, any conventional protective colloid can be used. Examples of suitable protective colloids are cellulose and partially hydrolyzed (or saponified) polyvinyl acetate. Partially hydrolyzed polyvinyl acetate (PVA) is the preferred protective colloid present in the aqueous emulsion. Preferably, the PVA has a degree of hydrolysis of at least 50 mol.%, more preferably at least 55 mol.%, most preferably at least 60 mol.%, preferably up to 90 mol.%, more preferably up to 80 mol.%, most preferably up to 70 mol.%. Preferably, the PVA is randomly hydrolyzed as opposed to hydrolysis of a blocky structure.

[0028] Instead of using just one type of PVA, a blend of two or more PVAs can be used, in which case the blend can be considered simply as one PVA, and its degree of hydrolysis is the weight average of the degrees of hydrolysis of the PVAs. Preferably, such blends of PVAs do not contain more than 0.2% of PVA having a degree of hydrolysis less than 50 mol% or more than 90 mol%.

[0029] The aqueous organic peroxide emulsion according to the second aspect of the present invention contains from 0 to 0.17% by weight, preferably from 0 to 0.15% by weight, preferably from 0 to 0.10% by weight, preferably from 0 to 0.05% by weight, more preferably 0% by weight, of at least one conventional emulsifier, based on the total weight of the emulsion.

[0030] Conventional emulsifiers are known to those skilled in the art and include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and mixtures thereof. Examples of surfactants typically used in aqueous organic peroxide emulsions include alkylene oxide block copolymers, alkoxylated fatty alcohols (including ethoxylated and / or propoxylated fatty alcohols), and alkoxylated fatty acids (including ethoxylated and / or propoxylated fatty acids).

[0031] As in the first aspect of the invention, if an emulsifier is added to the emulsion according to the second aspect of the invention, preferably a non-ionic surfactant is used, more preferably a non-ionic surfactant having an HLB value of at least 10, even more preferably at least 14. However, it is preferred that the emulsifier is omitted from the emulsion, i.e. the emulsion of the second aspect of the invention is preferably substantially free of emulsifier.

[0032] The aqueous organic peroxide emulsion according to the second aspect of the present invention also contains at least one antifreeze agent and may include a combination of two or more antifreeze agents. Any conventional antifreeze agent can be used. Preferably, the antifreeze agent is made from methanol, ethanol, propanol, isopropanol, (ethylene) glycol, propanediol, glycerol, and mixtures thereof, more preferably methanol, ethanol, propanediol, and mixtures thereof. These compounds are known to have little effect on the polymerization process in which the peroxide emulsion is used. Most preferably, methanol is used as the antifreeze agent.

[0033] The amount of cryoprotectant is typically selected so that the emulsion does not freeze at a temperature of -10°C, preferably -15°C, preferably -20°C, or most preferably -25°C. The amount of freezing point depressant used depends on the type of cryoprotectant used, or mixture of cryoprotectants. It is appropriate to first make a mixture of cryoprotectant and water, containing a sufficient amount of cryoprotectant to be pourable at the indicated temperature. This mixture can then be used in further processes to make the emulsion. Those skilled in the art will have no difficulty in balancing the ratio of water to cryoprotectant. Typically, the amount of cryoprotectant used in the emulsion according to the present invention is less than the amount of water.

[0034] The aqueous organic peroxide emulsions of the first and second aspects of the present invention may also optionally contain other additives including phosphate and citrate buffers, sequestrants, biocides such as bactericides, antiozonants, antioxidants, antidegradants, UV stabilizers, co-agents, comonomers, antistatic agents, foaming agents, mold release agents, process oils, etc. These additives may be added in conventional amounts.

[0035] The aqueous organic peroxide emulsions of the first and second aspects of the present invention can be produced by conventional methods. Typically, the components of the emulsion are mixed and / or homogenized using well-known equipment such as high speed mixers, colloid mills, pearl mills, pressure homogenizers, fluidizers, ultrasonic homogenizers, etc. The mixing and / or homogenization should be performed significantly below the SADT of the organic peroxide, since the peroxide may not be stable at higher temperatures.

[0036] The aqueous organic peroxide emulsions of the first and second aspects of the invention can also be produced continuously using an in-line emulsifier by first cooling a pre-emulsion mixture containing the organic peroxide to a temperature at least 12° C. below the SADT of the organic peroxide before being fed to the in-line emulsifier, and then cooling the organic peroxide emulsion using a downstream heat exchanger to a temperature at least 12° C. below the SADT of the organic peroxide.

[0037] The organic peroxide may be introduced into the emulsification process in the form of a desensitized organic peroxide. In that regard, any suitable desensitizing agent may be used to dilute and / or dissolve the peroxide, such as an inert desensitizing solvent. Such inert desensitizing solvents are well known in the art and include, for example, isododecane and mineral oil. For example, 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate (SADT 10° C.) is commercially available in desensitized form from Nouryon® as a 75% solution in odorless mineral spirits ("Trigonox® 193-CH75").

[0038] The present disclosure also relates to the use of the above-mentioned aqueous diisobutyryl peroxide emulsion of the second aspect in other reactions involving free radicals, such as polymerization processes, crosslinking reactions, curing of unsaturated polyester resins, polymer modification processes, and the synthesis of certain chemicals.

[0039] The diisobutyryl peroxide emulsion of the second aspect of the invention is preferably used in a polymerization process, more preferably in the polymerization of vinyl chloride monomer (VCM) and the copolymerization of VCM with styrene or (meth)acrylates. Most preferred is the use of the emulsion according to the invention in a suspension polymerization process for preparing PVC. The polymerization process preferably comprises a step of continuously and / or intermittently dosing the emulsion into a polymerization reactor at the polymerization temperature. Such a process is described in WO 2000 / 017245.

[0040] The resulting improved drying properties of the PVC polymer, i.e., increased drying rate, are quantified in the examples below and are intended to include a normalized drying rate of greater than 0.840 at a time t* of 0.5, as determined by the methods described in the article "Dehydration and drying poly(vinyl) chloride (PVC) porous grains: 2. Thermogravimetric analysis and numerical simulations," P. Agaciak et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 470 (2015) 120-129, the article and test methods of which are incorporated herein by reference.

[0041] The present disclosure therefore also relates to a process for preparing a polyvinyl chloride (PVC) polymer having a normalized drying rate of greater than 0.840 at a time t* of 0.5 (as determined by the method described in "Dehydration and drying poly(vinyl) chloride (PVC) porous grains: 2. Thermogravimetric analysis and numerical simulations", P. Agaciak et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 470(2015)120-129), the process comprising polymerizing monovinyl chloride monomer (VCM) using an aqueous organic peroxide emulsion, the aqueous organic peroxide emulsion comprising 0-0.17 wt. % of an emulsifier.

[0042] In this process, the aqueous organic peroxide emulsion may be as defined above in the first aspect.

[0043] It should be noted that various elements of the invention, including but not limited to the preferred ranges of the various parameters, can be combined unless they are mutually exclusive.

[0044] The present invention is illustrated by the following figures and examples but is not limited thereto or by them. [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 shows the dimensionless drying rate of water inside the pores of the PVC samples prepared in Example 2 and Comparative Example 2A. EXAMPLES

[0046] Example 1 and Comparative Example 1A Two emulsions were made according to the following procedure to have the final amounts of components (i)-(iv) shown in Table 1.1 below.

[0047] 1. Methanol and water were introduced into a double jacketed vessel. 2. PVA (polyvinyl acetate, hydrolysis degree 65-70%) and optionally emulsifier (C16 / C18 ethoxylated alcohol, HLB=18) were added to the water / methanol mixture at room temperature and dissolved for 30 minutes with a stirring speed of about 250 rpm. 3. The aqueous mixture was cooled to below -10°C with stirring. 4. An oil phase containing 70 wt% diisobutyryl peroxide in isododecane was added at a slow rate to the aqueous mixture with Ultra Turrax type S25N-25GM. 5. The oil phase was dispersed at Ultra Turrax speed (2.5 min / kg of emulsion) while keeping the temperature below 0° C. If it was necessary to go below this temperature, the action of the Ultra Turrax was temporarily discontinued. 6. The emulsion was stored at -25°C.

[0048] [Table 1.1]

[0049] The storage stability of the emulsions was determined by measuring the droplet volume distribution by light scattering technique using a Malvern type 3000 instrument.

[0050] In Table 1.2, d99 (expressed in μm) is the 99th percentile of the droplet volume distribution of the organic peroxide in the emulsion, and d50 (expressed in μm) is the 50th percentile of the droplet volume distribution of the organic peroxide in the emulsion. The emulsion samples were stored at -25°C and the data were collected at room temperature.

[0051] [Table 1.2]

[0052] The above data shows that both emulsions were highly stable for at least 12 weeks (a 12 week droplet size d99 value of <10 μm indicates a highly stable aqueous organic peroxide emulsion). Hence, in contrast to expectations, the inventors have succeeded in producing a highly stable and well-dispersed aqueous emulsion of diisobutyryl peroxide without an emulsifier. Furthermore, despite the absence of an emulsifier during emulsification, the aqueous organic peroxide emulsion of Example 1 is formed with an advantageously small peroxide droplet size and narrow droplet size distribution.

[0053] PVC suspension polymerization process Vinyl chloride (VCM) polymerizations were carried out according to a standard suspension polymerization process using a 10 liter Buchi reactor equipped with baffles, one flat blade agitator, a pressure transducer, a VCM feed line, a nitrogen purge line, a peroxide feed line, and a peroxide injection point.

[0054] The reactor was charged with 75.4 g of a 2% (w / w) solution of Alcotex® B72 (polyvinyl acetate / alcohol) and 3480 g of demineralized water containing 11.6 g of a 2% (w / w) solution of Gohsenol GH23 (polyvinyl acetate / alcohol). The reactor was then pressurized to 12 bar with nitrogen. When no leaks were observed, the reactor was depressurized (with stirring) to 75 mbar to remove air and nitrogen. The reactor was then charged with 2900 g of VCM. While charging with VCM, the reactor was heated to 52° C. in 30 minutes. At 52° C., continuous dosing of the organic peroxide emulsion was started, reaching a maximum polymerization rate of 30% / h in 40 minutes, after which the exotherm caused the temperature at 52° C. to rise further to 57° C., the polymerization temperature of the emulsion. The polymerization was stopped when 83% conversion was reached (calculated by temperature and pressure using CiD software). The reactor was then cooled and degassed, and after removal of residual VCM by venting, the reactor contents were sampled for analysis.

[0055] Example 2 and Comparative Example 2A The PVC samples were produced according to the polymerization process described above.

[0056] Example 2: The aqueous organic peroxide emulsion of Example 1 was used to prepare PVC (diluted to 0.5% diisobutyryl peroxide with cold water for a relatively small polymerization (10 liters) and kept in an ice bath with stirring during polymerization).

[0057] Comparative Example 2A: A PVC was prepared using the aqueous organic peroxide emulsion of Comparative Example 1A (diluted to 0.5% diisobutyryl peroxide with cold water for a smaller polymerization (10 liters) and kept in an ice bath with stirring during polymerization).

[0058] Experiments were carried out to investigate the drying kinetics of two PVC samples by thermogravimetric analysis under a dry nitrogen gas flow, as described in detail in the article “Dehydration and drying poly(vinyl) chloride (PVC) porous grains: 2. Thermogravimetric analysis and numerical simulations”, P. Agaciak et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 470(2015)120-129.

[0059] As explained in the article, the overall duration of drying of a PVC sample depends on the free water, interstitial water, and internal water content. To establish a comparison between the two PVC samples, the drying rate was normalized for the internal water content as described on page 123 of the article, as follows:

[0060] - v* is the normalized drying rate, - t* is the dimensionless time normalized by the time required to dry the same mass of pure water, - When t<0, water is evaporating between the PVC particles, - For t>0, water is evaporating from (or out of) the PVC particle.

[0061] The normalized drying rates are shown in Figure 1, where it can be seen that the PVC of Example 2 (v* is 0.861 at t* of 0.5 and 0.694 at t* of 1) dries quickly, while the PVC of Comparative Example 2A dries more slowly (v* is 0.837 at t* of 0.5 and 0.673 at t* of 1). In particular, the PVC of Example 2 is almost completely dry at t* = 1.6, while the PVC of Comparative Example 2A requires a longer time to reach the same dry state.

[0062] These results indicate that the inclusion of less (or no) emulsifier in the resulting PVC polymer results in faster drying characteristics, resulting in time savings in the PVC production process.

[0063] Example 3 and Comparative Example 3A Two emulsions were made according to the following procedure to have the final amounts of components (i)-(iv) shown in Table 3.1 below.

[0064] 1. Methanol and water were introduced into a double jacketed vessel. 2. PVA (polyvinyl acetate, hydrolysis degree 65-70%) and optionally emulsifier (C16 / C18 ethoxylated alcohol, HLB=18) were added to the water / methanol mixture at room temperature and dissolved for 30 minutes with a stirring speed of about 250 rpm. 3. The aqueous mixture was cooled to below -10°C with stirring. An organic peroxide composition containing 4.98 wt. % di(2-ethylhexyl) peroxydicarbonate was added slowly to the aqueous mixture with Ultra Turrax type S25N-25GM. 5. The organic peroxide composition was dispersed at Ultra Turrax speed (2.5 min / kg of emulsion) while maintaining the temperature below 0° C. If it was necessary to go below this temperature, the Ultra Turrax was temporarily discontinued. 6. The emulsion was stored at -20°C.

[0065] [Table 3.1]

[0066] The storage stability of the emulsions was determined by measuring the droplet volume distribution by light scattering technique using a Malvern type 3000 instrument.

[0067] In Table 3.2, d99 (expressed in μm) is the 99th percentile of the droplet volume distribution of the organic peroxide in the emulsion, and d50 (expressed in μm) is the 50th percentile of the droplet volume distribution of the organic peroxide in the emulsion. The emulsion samples were stored at -20°C and the data were collected at room temperature.

[0068] [Table 3.2]

[0069] The above data show that both emulsions were highly stable for at least 12 weeks (a 12 week droplet size d99 value of <10 μm indicates a highly stable aqueous organic peroxide emulsion). Hence, in contrast to expectations, the inventors have succeeded in producing a highly stable and well-dispersed aqueous emulsion of di(2-ethylhexyl) peroxydicarbonate without an emulsifier. Furthermore, despite the absence of an emulsifier during emulsification, the aqueous organic peroxide emulsion of Example 3 is formed with an advantageously small peroxide droplet size and narrow droplet size distribution.

[0070] Although the invention has been described with reference to an exemplary embodiment, it will be understood that various modifications are possible within the scope of the invention.

[0071] In this specification, unless expressly indicated otherwise, the word "or" is used in the sense of an operator that returns a true value when either or both of the stated conditions are met, as opposed to the operator "exclusive or," which requires that only one of the stated conditions be met. The word "comprising" is used in the sense of "including," not "consisting of." All prior teachings acknowledged above are incorporated herein by reference. Acknowledgement herein of any previously published document should not be construed as an admission or representation that the teachings were general knowledge in Europe or elsewhere as of the date hereof.

Claims

1. Use of an aqueous organic peroxide emulsion containing 0 to 0.17 weight percent of at least one emulsifier to prepare polyvinyl chloride with increased drying rate.

2. The aqueous organic peroxide emulsion comprises: (i) 25 to 70% by weight of at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less; (ii) 1.4 to 6.0 wt. % of at least one protective colloid; (iii) 0 to 0.17 wt. % of at least one emulsifier; (iv) at least one antifreeze agent; 2. Use according to claim 1, wherein the SADT value is determined according to the method described in the United Nations Recommended Test Criteria, Revised Seventh Edition (2019), Test Series H.4: Accumulated Heat Storage Test for Organic Peroxides in High Density Polyethylene (HDPE) Packaging with a volume of 20 to 30 liters.

3. 3. Use according to claim 1 or claim 2, wherein the organic peroxide has a self-accelerating decomposition temperature (SADT) of 20°C or less, preferably 15°C or less, preferably 10°C or less, preferably 5°C or less, preferably 0°C or less, the SADT value being determined according to the method described in the United Nations Recommended Test Criteria, Revised Seventh Edition (2019), Test Series H.4: Accumulated Heat Storage Test, for organic peroxides in high density polyethylene (HDPE) packaging having a volume of 20 to 30 litres.

4. The organic peroxide is selected from peroxyesters, peroxydicarbonates, diacyl peroxides, or mixtures thereof, preferably diisobutyryl peroxide (SADT 0°C), cumyl peroxyneodecanoate (SADT 10°C), 1,1,3,3-tetramethylbutylperoxyneodecanoate (SADT 15°C), cumyl peroxy-neopentanoate (SADT 10°C), tert-amylperoxyneodecanoate (SADT 20°C), di-sec-butylperoxydicarbonate (SADT 0°C), di(2-ethylhexyl)peroxydicarbonate (SADT 5°C), tert-butylperoxyneodecanoate (SADT 20°C), 1,1,3,3-tetramethylbutylperoxypival ... 20°C), tert-amyl peroxypivalic acid (SADT 25°C), tert-butyl peroxypivalic acid (SADT 25°C), di(3,5,5-trimethylhexanoyl)peroxide (SADT 25°C), di-n-propyl-peroxy-dicarbonate (SADT 0°C), diisopropyl peroxydicarbonate (SADT 5°C), di-n-butyl peroxydicarbonate (SADT 0°C), di(2-ethoxyethyl)peroxydicarbonate (SADT 10°C), 1,3-di(propa-2,2-diyl)benzenebis(neodecanoyl)peroxide (SADT 10°C), 3-hydroxy-1,1-dimethylbutylperoxyneodecanoic acid (SADT 10°C), di-n-butyryl peroxide (SADT 25°C), or mixtures thereof, and the SADT value is determined according to the method described in the United Nations Recommended Test Criteria, Revised Seventh Edition (2019), Test Series H.4: Accumulated Heat Storage Test, for organic peroxides in high density polyethylene (HDPE) packaging having a volume of 20 to 30 liters.

5. 5. Use according to any one of claims 1 to 4, wherein the protective colloid is polyvinyl acetate having a degree of hydrolysis of 60 to 75% and / or the at least one emulsifier is a compound selected from the group consisting of alkylene oxide block copolymers, ethoxylated fatty alcohols, ethoxylated fatty acids, and combinations thereof, having an HLB (hydrophilic-lipophilic balance) value of 8 or more, preferably 10 or more, more preferably 14 or more.

6. The use according to any one of claims 1 to 5, wherein no emulsifier is added to the aqueous emulsion.

7. 7. Use according to any one of claims 1 to 6, wherein the at least one antifreeze agent is a compound selected from the group consisting of methanol, ethanol, propanol, isopropanol, (ethylene) glycol, propanediol, glycerol, and combinations thereof, preferably methanol, used in an amount such that the emulsion does not freeze at a temperature of -10°C.

8. 1. An aqueous organic peroxide emulsion comprising: (i) 30 to 45% by weight of diisobutyryl peroxide; (ii) 2.0 to 6.0 wt. % of at least one protective colloid; (iii) 0 to 0.17 wt. % of at least one emulsifier; (iv) at least one antifreeze agent.

9. 9. The aqueous emulsion of claim 8 comprising 35 to 42 weight percent diisobutyryl peroxide.

10. 10. Aqueous emulsion according to claim 8 or claim 9, comprising from 2.5 to 4.0% by weight of at least one protective colloid, preferably from 2.7 to 3.5% by weight.

11. 11. Aqueous emulsion according to any one of claims 8 to 10, wherein the protective colloid is polyvinyl acetate having a degree of hydrolysis of 60 to 75%.

12. 12. The aqueous emulsion according to any one of claims 8 to 11, wherein the at least one emulsifier is a compound selected from the group consisting of alkylene oxide block copolymers, ethoxylated fatty alcohols, ethoxylated fatty acids, and combinations thereof, having an HLB (hydrophilic-lipophilic balance) value of 10 or more, preferably 14 or more.

13. The aqueous emulsion according to any one of claims 8 to 12, wherein no emulsifier is added to the aqueous emulsion.

14. 14. The aqueous emulsion according to any one of claims 8 to 13, wherein the at least one antifreeze agent is a compound selected from the group consisting of methanol, ethanol, propanol, isopropanol, (ethylene) glycol, propanediol, glycerol, and combinations thereof, preferably methanol, used in an amount such that the emulsion does not freeze at a temperature of -10°C.

15. A process for preparing polyvinyl chloride polymers having a normalized drying rate of more than 0.840 at a time t* of 0.5 ("Dehydration and drying poly(vinyl) chloride (PVC) porous grains:

2. Thermogravimetric analysis and numerical simulations", P. Agacia et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 470 (2015) 120-129, said process comprising polymerizing monovinyl chloride monomer using an aqueous organic peroxide emulsion, said aqueous organic peroxide emulsion comprising 0 to 0.17 weight percent emulsifier.

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