Continuous production of aqueous organic peroxide emulsion

Abstract

To provide a continuous process and a system for producing aqueous organic peroxide emulsions comprising organic peroxides that have a low self-accelerating decomposition temperature.SOLUTION: A continuous process comprises: a) a pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25°C or less, at least one protective colloid, at least one anti-freeze agent, water, and optionally at least one emulsifier, wherein the pre-emulsion mixture is fed to an inlet of an in-line emulsifier at a temperature of at least 12°C lower than the SADT of the organic peroxide; and b) transferring the emulsion from an outlet of the in-line emulsifier to a heat exchanger downstream of the outlet of the in-line emulsifier, wherein the heat exchanger reduces the temperature of the aqueous organic peroxide emulsion to a temperature of at least 12°C lower than the SADT of the organic peroxide.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a continuous process for producing aqueous organic peroxide emulsions comprising an organic peroxide having a low self-accelerating decomposition temperature, and a system for carrying out the continuous process. [Background technology]

[0002] There are many conventional methods in the art for producing aqueous organic peroxide emulsions.For example, International Patent Publication No. 99 / 31194 describes that the emulsification process can be carried out by using any conventional dispersing device, for example, by mechanical rotary stirrers of paddle, propeller, or turbine type, colloid mills, homogenizers such as ultrasonic homogenizers, high-speed shear devices, and line mixers.

[0003] While these conventional options can be used to prepare aqueous emulsions of organic peroxides that are stable over a wide range of temperatures, the currently available options are much more limited for organic peroxides with low thermal stability. In that regard, for organic peroxides with low self-accelerating decomposition temperatures (SADTs, e.g., below about 25°C), the emulsification processes used to date are batch processes. This is because the organic peroxide mixture needs to be kept at low temperatures (usually around 0°C) to prevent it from decomposing too quickly during the emulsification process, which can be extremely dangerous (e.g., resulting in an explosion). Therefore, it has been deemed too dangerous to attempt to continuously produce aqueous emulsions of these peroxides on an industrial scale.

[0004] US6350835 discloses an aqueous emulsion of peroxyester that is liquid at -20°C. US6350835 explains that the emulsification process is preferably carried out at a temperature below the SADT of the peroxyester, but does not explain how the emulsification process can be carried out in a safe and continuous manner. The processing examples in US6350835 provide only a conventional batch process for producing such aqueous emulsions of peroxyester.

[0005] US Patent No. 4,734,135 discloses aqueous emulsions of peroxydicarbonates and diacyl peroxides. As with US Patent No. 6,350,835, the processing examples in US Patent No. 4,734,135 provide only a conventional batch-type process for producing aqueous emulsions of such peroxides. US Patent No. 4,734,135 assumes that the emulsion process can be carried out continuously by an emulsifying device such as a line mixer, attached to a cooling device (i.e., a jacketed (cooling jacket) in-line mixer), but this is not exemplified in US Patent No. 4,734,135, and no further technical details are described that would allow a person skilled in the art to carry this out in a simple manner for any peroxide (and of course not one with low SADT).

[0006] Many advantages of continuous processes over batch processes are well known. For example, continuous processes increase productivity and generally require a smaller equipment footprint. However, to the inventors' knowledge, a successful industrial-scale continuous process for producing aqueous emulsions of organic peroxides with low SADT has not yet been developed.

[0007] It was therefore an object of the present disclosure to develop a continuous process for producing aqueous emulsions of organic peroxides having low SADTs. A further object was to achieve this goal without the need to develop new specialized equipment. Summary of the Invention

[0008] The inventors have found that these objectives may be accomplished using readily available equipment. In that regard, by cooling the organic peroxide-containing pre-emulsion mixture before being fed to an in-line emulsifier, followed by cooling the organic peroxide emulsion using a downstream heat exchanger, the inventors have developed a somewhat simple, yet highly effective process and equipment arrangement that solves a long-standing need for producing aqueous emulsions of organic peroxides having low SADTs.

[0009] Thus, in a first aspect, the present invention relates to a continuous process for producing an organic peroxide emulsion, the process comprising: a) feeding a pre-emulsion mixture to an inlet of an in-line emulsifier, the pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, at least one protective colloid, at least one cryoprotectant, water, and optionally at least one emulsifier, the pre-emulsion mixture being fed to the inlet at a temperature at least 12° C. lower than the SADT of the organic peroxide, preferably at least 14° C. lower than the SADT of the organic peroxide, more preferably at a temperature between about 15° C. and about 35° C. lower than the SADT of the organic peroxide, and most preferably at a temperature between about 15° C. and about 25° C. lower than the SADT of the organic peroxide, for example, at a temperature between about 15° C. and about 20° C. lower than the SADT of the organic peroxide; b) transferring the aqueous organic peroxide emulsion from the outlet of the in-line emulsifier to a heat exchanger located downstream of the outlet of the in-line emulsifier, where the heat exchanger reduces the temperature of the aqueous organic peroxide emulsion to a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably about 15° C. to about 25° C. below the SADT of the organic peroxide, for example, about 15° C. to about 20° C. below the SADT of the organic peroxide.

[0010] In a second aspect, the present invention relates to a system for continuously producing an organic peroxide emulsion, the system comprising: at least one container for preparing and / or receiving a pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, at least one protective colloid, at least one cryoprotectant, water, and optionally at least one emulsifier, said at least one container comprising a means for cooling and / or maintaining the pre-emulsion mixture at a temperature at least 12° C. below the SADT of the organic peroxide, preferably at a temperature at least 14° C. below the SADT of the organic peroxide, more preferably at a temperature between about 15° C. and about 35° C. below the SADT of the organic peroxide, and most preferably at a temperature between about 15° C. and about 25° C. below the SADT of the organic peroxide, for example at a temperature between about 15° C. and about 20° C. below the SADT of the organic peroxide; an in-line emulsifier having at least one inlet and at least one outlet, the in-line emulsifier being in fluid communication with and positioned downstream of the at least one vessel and configured to receive the pre-emulsion mixture at the at least one inlet at a temperature that is at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably at a temperature between about 15° C. and about 35° C. below the SADT of the organic peroxide, and most preferably at a temperature between about 15° C. and about 25° C. below the SADT of the organic peroxide, e.g., at a temperature between about 15° C. and about 20° C. below the SADT of the organic peroxide; a heat exchanger in fluid communication with and positioned downstream of the in-line emulsifier, the heat exchanger configured to reduce the temperature of the aqueous organic peroxide emulsion obtained from at least one outlet of the in-line emulsifier to a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably from about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably from about 15° C. to about 25° C. below the SADT of the organic peroxide, e.g., from about 15° C. to about 20° C. below the SADT of the organic peroxide; and Optionally, a packout unit in fluid communication with and positioned downstream of the heat exchanger.

[0011] By using a specific feed temperature combined with the introduction of a heat exchanger downstream of the outlet of the in-line emulsifier, the safety profile of the emulsification process is significantly improved to the extent that it can now be safely carried out in a continuous and highly scalable manner (i.e., carried out continuously on an industrial scale).

[0012] For the avoidance of doubt, a "pre-emulsion mixture" is a mixture of components that has not been subjected to emulsifying conditions (and therefore is not yet in the form of a stable emulsion).

[0013] The cooled aqueous organic peroxide emulsion obtained in step b) can be used directly (i.e., produced and used on-site) or can be transferred (packaged and shipped) to a pack-out unit located downstream of the heat exchanger. In that regard, the present invention provides a small equipment footprint, easily installable system for on-site continuous production of aqueous organic peroxide emulsions, where the organic peroxide has a low SADT. This is a significant improvement in terms of ease of production, cost, safety, and environmental impact (less amount of raw material to transport).

[0014] 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 described in detail in the UN Manual of Tests and Criteria, Revised Seventh Edition (2019), Test Series H.4: Heat Accumulation Storage Test, which manual and test method are incorporated herein by reference. The method determines the lowest constant environmental air temperature at which a thermally unstable substance undergoes exothermic decomposition under conditions representative of the substance when packaged. The method is based on the Semionov theory of thermal explosion, i.e. the main resistance to heat flow is considered to be in the walls of the container. 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 method described in the above referenced United Nations manual (Test Series H.4: Thermal Accumulation Storage Test) for organic peroxides in high density polyethylene (HDPE) packages having a volume of 20-30 litres.

[0015] The emulsion contains at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, preferably 20° C. or less, preferably 15° C. or less, preferably 10° C. or less, preferably 5° C. or less, which may be about 0° C. or less. Preferred organic peroxides include peroxyesters, peroxydicarbonates, and diacyl peroxides. Peroxyesters and diacyl peroxides are preferred. Examples of preferred organic peroxides for use according to the invention are diisobutyryl peroxide (SADT 0° C.), di-n-propyl peroxydicarbonate (SADT 0° C.), diisopropyl peroxydicarbonate (SADT 5° C.), di-n-butyl peroxydicarbonate (SADT 0° C.), di-sec-butyl peroxydicarbonate (SADT 0° C.), di(2-ethoxyethyl) peroxydicarbonate (SADT 10° C.), di(2-ethylhexyl) peroxydicarbonate (SADT 5° C.), 1,3-di(prop-2,2-diyl)benzene bis(neodecanoyl)peroxide (SADT 10° C.), 1,1,3,3-tetramethylbutyl peroxyneodecanoate (SADT 15° C.), 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate (SADT 10° C.), tert-amyl peroxyneodecanoate (SADT 20° C.), cumyl peroxyneodecanoate (SADT 10° C.), di-n-butyryl peroxide (SADT 25° C.), tert-butyl peroxyneodecanoate (SADT 20° C.), 1,1,3,3-tetramethylbutyl peroxypivalate (SADT 20° C.); tert-amyl peroxypivalate (SADT 25° C.), tert-butyl peroxypivalate (SADT 25° C.), di(3,5,5-trimethylhexanoyl)peroxide (SADT 25° C.), or mixtures thereof.

[0016] The organic peroxide emulsion typically contains 25-70% by weight of organic peroxide, based on the total weight of the emulsion. The amount of organic peroxide in the emulsion is preferably 30-65% by weight, more preferably 35-60% by weight, and most preferably 40-60% by weight. The organic peroxide may be introduced into the emulsification process disclosed herein in the form of a phosphorylated 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 diluted form from Nouryon® as a 75% solution in odorless mineral spirits ("Trigonox® 193-CH75").

[0017] The amount of water in the emulsion is usually in the range of 20 to 70% by weight, more preferably 25 to 50% by weight, and most preferably 25 to 40% by weight, based on the total weight of the emulsion.

[0018] The emulsion 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, isopropanol, (ethylene) glycol, propanediol, glycerol, and mixtures thereof, more preferably methanol, ethanol, propanediol, and mixtures thereof. These agents are known to have little effect on the polymerization process. It is not difficult for a person skilled in the art to balance 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.

[0019] The emulsion also contains at least one protective colloid. Any conventional protective colloid can be used. Suitable protective colloids include partially hydrolyzed (or saponified) polyvinyl acetate, polyvinylpyrrolidone, polyacrylates, cellulose, cellulose derivatives, starch, and starch derivatives. Particularly useful are partially hydrolyzed / saponified polyvinyl acetate, cellulose, cellulose derivatives, starch, and starch derivatives. Typically, a polyvinyl acetate (PVA) component is used, preferably a PVA having a degree of hydrolysis of 50-90 mol%, more preferably 55-80 mol%, and most preferably 60-70 mol%. The amount of protective colloid used in the emulsion according to the present invention depends on the type and amount of organic peroxide, as well as the desired viscosity of the final emulsion, but is typically used in an amount of about 0.1 to about 5 wt.%, based on the total weight of the emulsion.

[0020] The emulsion according to the invention may contain at least one conventional emulsifier. Suitable emulsifiers are known to those skilled in the art and include nonionic, anionic, cationic and amphoteric surfactants, as well as mixtures thereof. They may be incorporated in conventional amounts, such as from about 0.05 to about 4% by weight, based on the total weight of the emulsion. Preferably, nonionic surfactants are used having an HLB (hydrophilic lipophilic balance) value of 7 or more, even more preferably 16 or more. Alternatively, the emulsion according to the invention may contain very low amounts of emulsifiers or no emulsifiers at all. Substantially or completely removing emulsifiers, especially those in the form of nonionic, anionic, cationic and amphoteric surfactants, from peroxide emulsions has been found to be highly beneficial in the manufacture of polyvinyl chloride (PVC). In that respect, such "emulsifier-free" emulsions of low SADT peroxides (especially diisobutyryl peroxide, SADT 0°C) have been found to produce high quality PVC from vinyl chloride monomer (VCM) with an unexpected improvement in the drying properties of the polymer (the drying rate of the resulting PVC polymer is substantially increased, thus shortening the drying time of the polymer, which is important for industrial-scale production of PVC). Thus, in a preferred embodiment, the emulsion according to the invention may contain emulsifiers in a total amount of 0% to 0.17% by weight, based on the total weight of the emulsion. Even more preferably, the emulsion according to the invention may contain 0% to 0.17% by weight, more preferably 0% by weight, of a (non-ionic) surfactant having an HLB (hydrophilic-lipophilic balance) value of 7 or more (% by weight, based on the total weight of the emulsion). Thus, the emulsion according to the invention may contain emulsifiers in a total amount of 0% to about 4% by weight, based on the total weight of the emulsion.

[0021] The aqueous organic peroxide emulsions 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, coagents, comonomers, antistatic agents, foaming agents, mold release agents, and pH adjusters such as process oils. These additives may be added in conventional amounts.

[0022] The process and system of the present disclosure require an in-line emulsifier. In-line emulsifiers suitable for use in the present process are very well known in the art, such as (but not limited to) those discussed in WO 99 / 31194 and those described in US 2004 / 223407, and suitable in-line emulsifiers are widely available, such as (but not limited to) Process Pilot 2000, DRS 2000, and their various configurations and scaled-up equivalents, available commercially from IKA®-WERKE GmbH & Co KG. Although these well-known in-line emulsifiers are not typically used at low (e.g., sub-zero) operating temperatures, it is easy to make routine modifications to them to accommodate low temperatures (e.g., by changing the material of replaceable components such as O-rings to one known to be mechanically stable at very low temperatures). Such routine modifications are within the routine capabilities of those skilled in the art.

[0023] The residence time of the organic peroxide mixture in the in-line emulsifier is preferably from about 1 to about 10 seconds, preferably from about 2 to about 8 seconds, and more preferably from about 3 to about 6 seconds, such as from about 3.8 to about 5.5 seconds.

[0024] The in-line emulsifier preferably comprises at least one mill head, preferably at least two mill heads, and may comprise at least three mill heads. The in-line emulsifier may comprise mill heads in a rotor-stator arrangement, may be configured as a single stage rotor-stator system, or may be configured as a multiple (e.g., two or three) stage rotor-stator system. The mill heads may be of a coarse type, a medium type, a fine type, or a combination thereof. In a preferred embodiment, the tip speed of the or each mill head is from about 15 meters per second (m / s) to about 50 m / s, preferably from about 20 m / s to about 45 m / s, and more preferably from about 25 m / s to about 40 m / s.

[0025] It is within the routine capabilities of one of ordinary skill in the art to configure in-line emulsifiers known in the art to operate within these operating parameters.

[0026] Thus, in a preferred embodiment, the continuous process for producing an organic peroxide emulsion comprises: a) feeding a pre-emulsion mixture to an inlet of an in-line emulsifier, the in-line emulsifier having at least one mill head, preferably at least two mill heads, the tip speed of the or each mill head being 15 m / s to 50 m / s, preferably about 20 m / s to about 45 m / s, more preferably about 25 m / s to about 40 m / s, the pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, at least one protective colloid, and at least providing a pre-emulsion mixture comprising at least one cryoprotectant, water, and optionally at least one emulsifier, the pre-emulsion mixture being provided to the inlet at a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably at about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably at about 15° C. to about 25° C. below the SADT of the organic peroxide, e.g., at about 15° C. to about 20° C. below the SADT of the organic peroxide; and b) transferring the aqueous organic peroxide emulsion from the outlet of the in-line emulsifier to a heat exchanger located downstream of the outlet of the in-line emulsifier, the heat exchanger reducing the temperature of the aqueous organic peroxide emulsion to a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably from about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably from about 15° C. to about 25° C. below the SADT of the organic peroxide, e.g., from about 15° C. to about 20° C. below the SADT of the organic peroxide; The residence time of the pre-emulsion mixture in the in-line emulsifier is about 1 to about 10 seconds, preferably about 2 to about 8 seconds, more preferably about 3 to about 6 seconds, for example, about 3.8 to about 5.5 seconds.

[0027] In a preferred embodiment, a system for continuously producing an organic peroxide emulsion comprises: at least one vessel (e.g., at least one (continuous) stirred tank reactor) for preparing and / or receiving a pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, at least one protective colloid, at least one cryoprotectant, water, and optionally at least one emulsifier, said at least one vessel comprising means (e.g., internal and / or external cooling coils, external cooling jacket, etc.) for cooling and / or maintaining the pre-emulsion mixture at a temperature of at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably at a temperature of about 15° C. to about 35° C. below the SADT of the organic peroxide, most preferably at a temperature of about 15° C. to about 25° C. below the SADT of the organic peroxide, for example at a temperature of about 15° C. to about 20° C. below the SADT of the organic peroxide; an in-line emulsifier comprising at least one inlet and at least one outlet, the in-line emulsifier comprising at least one mill head, preferably at least two mill heads, the or each mill head having a tip speed of from 15 m / s to 50 m / s, preferably from about 20 m / s to about 45 m / s, more preferably from about 25 m / s to about 40 m / s, the in-line emulsifier being in fluid communication with and positioned downstream of the at least one vessel, and configured to receive the pre-emulsion mixture at the at least one inlet at a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably at a temperature of from about 15° C. to about 35° C. below the SADT of the organic peroxide, most preferably at a temperature of from about 15° C. to about 25° C. below the SADT of the organic peroxide, for example at a temperature of from about 15° C. to about 20° C. below the SADT of the organic peroxide; a heat exchanger in fluid communication with and positioned downstream of the in-line emulsifier, the heat exchanger configured to reduce the temperature of the aqueous organic peroxide emulsion obtained from at least one outlet of the in-line emulsifier to a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably from about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably from about 15° C. to about 25° C. below the SADT of the organic peroxide, e.g., from about 15° C. to about 20° C. below the SADT of the organic peroxide; and Optionally, a packout unit located downstream of the heat exchanger; The system is configured such that the residence time of the pre-emulsion mixture in the in-line emulsifier is from about 1 to about 10 seconds, preferably from about 2 to about 8 seconds, more preferably from about 3.8 to about 5.5 seconds, for example, from about 3 to about 6 seconds.

[0028] In a preferred embodiment, the system further comprises at least one mixing device in fluid communication with and positioned upstream of the at least one vessel for preparing and / or receiving a pre-emulsion mixture. In the aforementioned embodiment, the at least one mixing device prepares a mixture including a protective colloid, a cryoprotectant, water, and optionally an emulsifier. The mixture is then transferred to the at least one vessel where it is mixed with at least one organic peroxide having a SADT of 25° C. or less to form the pre-emulsion mixture. In one embodiment, the mixing device may be a continuous stirred tank reactor (CSTR). In another embodiment, the mixing device may be an in-line static mixer including one or more static mixer elements. Such mixers are well known to those skilled in the art.

[0029] Thus, in a preferred embodiment, the present invention relates to a system for continuously producing an organic peroxide emulsion, the system comprising: at least one mixing device for preparing a mixture comprising at least one protective colloid, at least one antifreeze agent, water, and optionally at least one emulsifier; at least one container in fluid communication with and positioned downstream of the at least one mixing device and configured to receive a mixture including at least one protective colloid, at least one cryoprotectant, water, and optionally at least one emulsifier, the at least one container separately receiving at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, the at least one protective colloid, the at least one cryoprotectant, water, and optionally at least one emulsifier; and optionally at least one emulsifier, wherein the at least one container is equipped with means for cooling and / or maintaining the pre-emulsion mixture at a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably at about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably at about 15° C. to about 25° C. below the SADT of the organic peroxide, e.g., at about 15° C. to about 20° C. below the SADT of the organic peroxide; an in-line emulsifier having at least one inlet and at least one outlet, the in-line emulsifier being in fluid communication with and positioned downstream of the at least one vessel and configured to receive the pre-emulsion mixture at the at least one inlet at a temperature that is at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably at a temperature between about 15° C. and about 35° C. below the SADT of the organic peroxide, and most preferably at a temperature between about 15° C. and about 25° C. below the SADT of the organic peroxide, e.g., at a temperature between about 15° C. and about 20° C. below the SADT of the organic peroxide; a heat exchanger in fluid communication with and positioned downstream of the in-line emulsifier, the heat exchanger configured to reduce the temperature of the aqueous organic peroxide emulsion obtained from at least one outlet of the in-line emulsifier to a temperature at least 12° C. below the SADT of the organic peroxide, preferably at least 14° C. below the SADT of the organic peroxide, more preferably from about 15° C. to about 35° C. below the SADT of the organic peroxide, and most preferably from about 15° C. to about 25° C. below the SADT of the organic peroxide, e.g., from about 15° C. to about 20° C. below the SADT of the organic peroxide; and Optionally, a packout unit in fluid communication with and positioned downstream of the heat exchanger.

[0030] It should be noted that various elements of the invention, including but not limited to the preferred ranges of the various parameters, may be combined unless they are mutually exclusive.

[0031] The present invention is illustrated by, but not limited to, the following examples. [Brief description of the drawings]

[0032] [Figure 1] 1 is a schematic diagram of a system according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Referring to FIG. 1, a continuous process for the continuous production of an aqueous emulsion of diisobutyryl peroxide (SADT 0° C.) was developed.

[0034] A pre-emulsion mixture containing methanol (15 wt%), polyvinyl acetate having a degree of hydrolysis of 50 to 75 mol% (1.5 wt%), a nonionic surfactant (1 wt%), diisobutyryl peroxide (40 wt%), and water is placed in a container. 1 The mixture was cooled to -15°C while stirring.

[0035] container 1 The cooled pre-emulsion mixture from the in-line emulsifier was mixed at a temperature of -15°C. 2 The in-line emulsifier applied shear force to the pre-emulsion mixture to form a stable emulsion of diisobutyryl peroxide. The emulsified product was discharged from the outlet of the in-line emulsifier and passed through a heat exchanger. 3 The emulsified product was then cooled to -15°C. The product was then transferred to a pack-out buffer tank. 4 and packed out from the downstream packing line.

[0036] No safety concerns were observed at any point during the continuous emulsification process.

[0037] Device feature description: 1. A vessel equipped with an agitator and an external cooling coil configured to cool the pre-emulsion mixture contained therein to -15°C. 2. A DISPAX-REACTOR® Type DRS 2000 / 10 equipped with at least two mill heads, each operating at a tip speed of approximately 40 m / s and having a peroxide residence time of 3.8 seconds to 5.5 seconds. 3. A heat exchanger configured to reduce the temperature of the organic peroxide emulsion to -15°C 4. Packaging unit (buffer tank and downstream packaging container)

[0038] In this specification, unless expressly indicated otherwise, the term "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 conditions be met. The word "comprising" is used in the sense of "including," not "consisting of." All prior teachings identified above are incorporated herein by reference. Admission of any prior-published document herein should not be construed as an admission or representation that the teachings were general knowledge in Europe or anywhere else as of the date hereof.

Claims

1. 1. A continuous process for producing an organic peroxide emulsion comprising: a) feeding a pre-emulsion mixture to an inlet of an in-line emulsifier, said pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, at least one protective colloid, at least one cryoprotectant, water, and optionally at least one emulsifier, said pre-emulsion mixture being fed to said inlet at a temperature at least 12° C. below the SADT of said organic peroxide; b) transferring an aqueous organic peroxide emulsion from an outlet of the in-line emulsifier to a heat exchanger downstream of the outlet of the in-line emulsifier, wherein the heat exchanger reduces the temperature of the aqueous organic peroxide emulsion to at least 12° C. below the SADT of the organic peroxide.

2. 2. The process of claim 1, wherein the pre-emulsion mixture of step a) is fed to the inlet at a temperature of at least 14° C. lower than the SADT of the organic peroxide, preferably from about 15° C. to about 35° C. lower than the SADT of the organic peroxide, most preferably from about 15° C. to about 25° C. lower than the SADT of the organic peroxide, such as from about 15° C. to about 20° C. lower than the SADT of the organic peroxide.

3. 3. The method according to any one of claims 1 to 2, wherein in step b) the heat exchanger reduces the temperature of the organic peroxide emulsion to at least 14°C below the SADT of the organic peroxide, preferably to about 15°C to about 35°C below the SADT of the organic peroxide, most preferably to about 15°C to about 25°C below the SADT of the organic peroxide, such as about 15°C to about 20°C below the SADT of the organic peroxide.

4. 4. The method according to any one of claims 1 to 3, further comprising: c) transferring the cooled aqueous organic peroxide emulsion of step b) to a pack-out unit located downstream of the heat exchanger.

5. 5. The method according to any one of claims 1 to 4, wherein said 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.

6. The method of any one of claims 1 to 5, wherein the organic peroxide is selected from a peroxyester, a peroxydicarbonate, a diacyl peroxide, or a mixture thereof.

7. The organic peroxide is selected from the group consisting of diisobutyryl peroxide (SADT 0°C), di-n-propyl peroxydicarbonate (SADT 0°C), diisopropyl peroxydicarbonate (SADT 5°C), di-n-butyl peroxydicarbonate (SADT 0°C), di-sec-butyl peroxydicarbonate (SADT 0°C), di(2-ethoxyethyl)peroxydicarbonate (SADT 10°C), di(2-ethylhexyl)peroxydicarbonate (SADT 5°C), 1,3-di(prop-2,2-diyl)benzene bis(neodecanoyl)peroxide (SADT 10°C), 1,1,3,3-tetramethylbutyl peroxyneodecanoate (SADT 15°C), 3-hydroxy-1,1-dimethylbutyl peroxyneodecanoate (SADT 15°C), and 1,2-dimethylbutyl peroxyneodecanoate (SADT 15°C). 10°C), tert-amyl peroxyneodecanoate (SADT 20°C), cumyl peroxyneodecanoate (SADT 10°C), di-n-butyryl peroxide (SADT 25°C), tert-butyl peroxyneodecanoate (SADT 20°C), 1,1,3,3-tetramethylbutyl peroxypivalate (SADT 20°C); tert-amyl peroxypivalate (SADT 25°C), tert-butyl peroxypivalate (SADT 25°C), di(3,5,5-trimethylhexanoyl) peroxide (SADT 25°C), or mixtures thereof.

8. 8. The method according to claim 1, wherein the pre-emulsion mixture comprises from 25 to 70% by weight of organic peroxide, based on the total weight of the pre-emulsion mixture.

9. 9. The method according to any one of claims 1 to 8, wherein the at least one protective colloid is selected from partially hydrolyzed (or saponified) polyvinyl acetate, polyvinylpyrrolidone, polyacrylates, cellulose, cellulose derivatives, starch and starch derivatives, preferably partially hydrolyzed (or saponified) polyvinyl acetate.

10. 10. The method according to any one of claims 1 to 9, wherein the at least one emulsifier is omitted from the pre-emulsion mixture or is selected from nonionic, anionic, cationic and amphoteric surfactants, and mixtures thereof, preferably nonionic surfactants.

11. The method according to any one of claims 1 to 10, wherein the at least one antifreeze agent is selected from methanol, ethanol, isopropanol, (ethylene) glycol, propanediol, glycerol, and mixtures thereof.

12. 12. The method of any one of claims 1 to 11, wherein the in-line emulsifier comprises at least one mill head, preferably at least two mill heads, and the tip speed of the or each mill head is from about 15 meters per second (m / s) to about 50 m / s, preferably from about 20 m / s to about 45 m / s, more preferably from about 25 m / s to about 40 m / s.

13. 13. The method according to any one of claims 1 to 12, wherein the residence time of the pre-emulsion mixture in the in-line emulsifier is from about 1 to about 10 seconds, preferably from about 2 to about 8 seconds, more preferably from about 3 to about 6 seconds, for example from about 3.8 to about 5.5 seconds.

14. 1. A system for continuously producing an organic peroxide emulsion, comprising: at least one vessel for preparing and / or receiving a pre-emulsion mixture comprising at least one organic peroxide having a self-accelerating decomposition temperature (SADT) of 25° C. or less, at least one protective colloid, at least one cryoprotectant, water, and optionally at least one emulsifier, said at least one vessel comprising means for cooling and / or maintaining said pre-emulsion mixture at a temperature at least 12° C. below the SADT of said organic peroxide; an in-line emulsifier including at least one inlet and at least one outlet, the in-line emulsifier in fluid communication with and positioned downstream of the at least one vessel and configured to receive the pre-emulsion mixture at a temperature at least 12° C. below the SADT of the organic peroxide; and a heat exchanger in fluid communication with and positioned downstream of the in-line emulsifier, the heat exchanger configured to reduce a temperature of the aqueous organic peroxide emulsion obtained from the at least one outlet of the in-line emulsifier to a temperature at least 12° C. below the SADT of the organic peroxide.

15. The system of claim 14 further comprising a packout unit located downstream of the heat exchanger.

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