Method for forming cationic polymers using initiators activated only by ultraviolet light

Abstract

A method for synthesizing a polymer product is provided. The method includes combining a UV-activated polymerization initiator and a nitrogen-containing vinyl monomer to form a reaction mixture. The initiator is free-radicalized solely by exposure to UV light. The reaction mixture has a reactive component present in an amount of at least about 20% by weight of an active ingredient based on the total weight of the reaction mixture. The method further includes exposing the reaction mixture to UV light generated by a UV light source to form a polymer product. The polymer product comprises a reaction product of the initiator and the nitrogen-containing vinyl monomer. The polymer product is pulverizable to form discrete particles of the polymer product.

Description

Technical Field

[0001] This disclosure generally relates to polymer production, and more specifically to the polymerization of nitrogen-containing vinyl monomers. Background Technology

[0002] Cationic vinyl polymers are used as flocculants in a variety of applications, including wastewater treatment, ore and coal processing, and papermaking. Examples of cationic vinyl polymers formed from nitrogen-containing monomers include polyethyleneamine (PVAm) and polyacrylamide (PAM).

[0003] General methods for synthesizing cationic vinyl polymers are known in the art. In one method, a nitrogen-containing vinyl monomer is combined with a polymerization initiator to achieve a polymerization reaction. Specifically, to form polyethyleneamine, the nitrogen-containing vinyl monomer is a vinyl carboxylamide, and an acid or base is added to the resulting intermediate polymer formulation to achieve a hydrolysis reaction, thereby forming a cationic vinyl polymer dispersed in an aqueous solution. To form polyacrylamide, an amide-containing monomer (e.g., acrylamide and / or (2-acryloyloxyethyl)trimethylammonium chloride) is polymerized.

[0004] Traditionally, polymerization methods utilize dilute aqueous solutions of monomers. This method is called aqueous solution polymerization or emulsion polymerization. Emulsion polymerization forms polymers in an aqueous solution (in liquid form). Sometimes it is desirable to provide polymers in particulate form rather than liquid form. Providing polymers in particulate form is advantageous because it allows for the transport and storage of larger quantities of active polymer compared to providing polymers in liquid or gel form, and allows for a longer shelf life of the polymer composition.

[0005] Polyacrylamide polymers can be supplied in particulate form, for example, via adiabatic gel polymerization, by applying heat to activate a thermally activated azo polymerization initiator, or using a redox initiator system. In gel polymerization, the reaction mixture can have a high reactive content, for example, greater than 20% by weight of reactive components based on the total weight of the reaction mixture. The resulting polymer product can be pulverized to form polymer product particles. Gel polymerization at maximum reactive content is also advantageous because it improves sustainability by requiring less water, less energy for drying the product, lower costs, and a lower carbon footprint.

[0006] However, existing adiabatic gel polymerization methods have problems. For example, polyvinylcarboxamide, a precursor to polyvinylamine, cannot be acceptablely formed via conventional gel polymerization because controlling the reaction temperature during adiabatic gel polymerization using thermally activated azo initiators is difficult, and the monomer may decompose into byproducts at a higher rate than in emulsion polymerization. Such byproducts may inhibit the polymerization reaction or cause other undesirable effects. When polyacrylamide is formed via conventional gel polymerization using thermally activated azo initiators or redox initiator systems at higher than standard active ingredient contents, undesirable crosslinking occurs in the formed polymer. This results in polymer products of lower quality or lower purity.

[0007] Furthermore, when the active ingredient content of the reaction mixture is maximized in adiabatic gel polymerization, and / or when a polymer with a maximized weight-average molecular weight is produced by adiabatic gel polymerization, the resulting polymer product typically has minimized solubility in solution, resulting in an excess of insoluble gel in the solution of the polymer product.

[0008] Therefore, it is desirable to provide a method for synthesizing polymer products from nitrogen-containing vinyl monomers via adiabatic gel polymerization, the method minimizing byproduct formation and / or crosslinking. Furthermore, it is desirable to produce polymer products via adiabatic gel polymerization that have a minimized insoluble gel content in their solution. Other desirable features and characteristics of this disclosure will become apparent from the following detailed description and appended claims, as well as the drawings and background information. Summary of the Invention

[0009] A method for synthesizing a polymer product is provided. The method includes combining a UV-activated polymerization initiator and a nitrogen-containing vinyl monomer to form a reaction mixture. The initiator is free-radicalized solely by exposure to UV light. The reaction mixture has a reactive component present in an amount of at least about 20% by weight of an active ingredient based on the total weight of the reaction mixture. The method further includes exposing the reaction mixture to UV light generated by a UV light source to form a polymer product. The polymer product comprises a reaction product of the initiator and the nitrogen-containing vinyl monomer. The polymer product may be pulverized to form discrete particles of the polymer product. Detailed Implementation

[0010] The following specific embodiments are merely exemplary in nature and are not intended to limit this disclosure or its application and use. Furthermore, there is no intention to limit oneself to the foregoing background information or any theory presented in the following specific embodiments.

[0011] The method described herein enables the synthesis of polymer products from nitrogen-containing vinyl monomers via adiabatic gel polymerization, with minimized byproduct formation and / or minimized crosslinking compared to conventional adiabatic gel polymerization methods. The method provides an improved adiabatic gel polymerization approach using a UV initiator that is free-radiated only by UV radiation. Compared to conventional thermally activated initiators, this UV-only initiator allows for greater reaction control because the reaction can be immediately started and stopped by turning the UV light source on and off to instantly activate and deactivate the UV-only initiator. Controlling the reaction in this way minimizes initiator decomposition, thereby minimizing crosslinking. Controlling the reaction also allows for adjustment of the reaction temperature, which minimizes byproduct formation. As a result, depending on the type of nitrogen-containing vinyl monomer used, high weight-average molecular weight polymers can be produced with maximized active ingredient content without excessive byproduct formation and / or crosslinking, and with minimal amounts of insoluble gel-like material in the polymer product solution.

[0012] Unlike products from conventional emulsion polymerization, gel polymerization can produce polymer products that can be pulverized or granulated. Higher active ingredient content is advantageous because it allows for higher production efficiency. Gel polymerization at high active ingredient contents is also beneficial because it leads to reduced water consumption, reduced energy consumption, a reduced carbon footprint, lower costs, and increased sustainability. However, previously, gel polymerization at high active ingredient contents yielded polymer products with insufficient weight-average molecular weight. Increasing the weight-average molecular weight of the polymer product resulted in polymer products with an excess of insoluble gel-like material in the polymer product solution (unusable for the application of the polymer product). It has been found that using a polymerization initiator activated solely by UV light in combination with a UV light source allows for the production of polymer products with maximized weight-average molecular weight via gel polymerization at higher active ingredient contents than standard, while minimizing the amount of insoluble polymer product. Without being bound by any theory, it is believed that the use of a UV-activated initiator alone reduces the amount of byproduct formation and / or crosslinking during gel polymerization compared to conventional thermally activated initiators, resulting in the aforementioned effects on polymer product quality.

[0013] Unless otherwise specified or obvious from the context, the term “about” as used herein is understood to mean within the normal tolerances in the art when measured using standard measuring equipment, such as within 2 standard deviations of the mean for a particular measuring device. “About” can be understood as within 10%, 5%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. “About” may alternatively be understood to imply the exact value stated. All numerical values ​​provided herein are modified by the term “about” unless the context clearly indicates otherwise.

[0014] As used herein, the term "active content" for reaction mixtures refers to the amount of reactive component present in the reaction mixture based on its total weight. For reaction mixtures, the term "active content" is synonymous with the terms "monomer solids" and "monomer phase concentration." For polymer products, the term "active content" refers to the amount of active polymer present in the polymer product based on its total weight.

[0015] As used herein, the term “activated” in relation to polymerization initiators refers to the radicalization or initiation of the initiator. For example, if a polymerization initiator is “activated” only by ultraviolet (UV) light, it means that the initiator is only radicalized by UV light and initiates the polymerization reaction only when exposed to UV light, but will not be radicalized when exposed to heat.

[0016] The methods provided herein are for the synthesis of polymer products. The polymerization method involves combining a UV initiator that is sensitive only to UV light and a nitrogen-containing vinyl monomer to form a reaction mixture.

[0017] The UV-activated polymerization initiator is activated solely by exposure to UV light (and not by exposure to heat or by any other method). Examples of UV-activated initiators activated solely by exposure to UV light include 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzophenone, 4'-hydroxyacetophenone, methyl benzoylformate, 2,2-dimethoxy-2-phenylacetophenone, α-ketoglutaric acid, camphorquinone, (1-hydroxycyclohexyl)-phenyl ketone, 2α-hydroxy-4-(2-hydroxyethoxy)-2α-methylphenylacetophenone, ethyl 2-oxopropionate, ethyl 3-methyl-2-oxobutyrate, 4,4-dimethyldihydrofuran-2,3-dione, ethyl benzoylformate, and combinations thereof. Alternatively, the UV-activated polymerization initiator may be an azo polymerization initiator activated solely by UV light, not by heat. The reaction mixture may contain only one polymerization initiator that is initiated solely by UV light, or the reaction mixture may contain two or more polymerization initiators that are initiated solely by UV light.

[0018] In this embodiment, in addition to a polymerization initiator activated solely by UV light, the reaction mixture also contains a co-initiator. The co-initiator is activated at least by a method other than UV light (e.g., heat). In one embodiment, the co-initiator is methyldiethanolamine. In other embodiments, the co-initiator is an azo initiator. Examples of azo initiators include 2,2'-azobis(2-methylpropanedione) dihydrochloride, 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2-methylbutanedione), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, azobisisobutanedione, azobis(2-amidinepropane) dihydrochloride, 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropanedione] tetrahydrate, and combinations thereof.

[0019] As used herein, the term "vinyl monomer" refers to a monomer having a (H₂C=C-) group in its structure. A vinyl monomer may alternatively be defined as an olefinically unsaturated monomer. The term "nitrogen-containing vinyl monomer" refers to a vinyl monomer containing at least one nitrogen atom. Examples of nitrogen-containing vinyl monomers include, but are not limited to, acrylamide, N-vinylformamide, N-vinylpyrrolidone, acrylonitrile, or combinations thereof.

[0020] In this embodiment, the nitrogen-containing vinyl monomer present in the reaction mixture is an acrylamide monomer. The acrylamide monomer may be the only nitrogen-containing vinyl monomer present in the reaction mixture. Alternatively, the reaction mixture may contain other nitrogen-containing vinyl monomers besides the acrylamide monomer. For example, the reaction mixture may also contain diallyl dimethylammonium chloride (DADMAC), acrylamide propyltrimethylammonium chloride (APTAC), methacrylamide propyltrimethylammonium chloride (MAPTAC), (3-acrylamidopropyl)trimethylammonium chloride (DIMAPA-Q), (2-acryloyloxyethyl)trimethylammonium chloride (DMA3Q), quaternary ammonium salts of dimethylaminoethyl methacrylate, quaternary ammonium salts of dimethylaminoethyl methacrylate, and combinations thereof.

[0021] In the embodiments, the nitrogen-containing vinyl monomer is selected from one or more N-vinyl carboxamide monomers having general formula I. (I) Where R 1 and R 2They are H or C1 to C6 alkyl groups, respectively. In embodiments, the N-vinylcarboxamide monomer is selected from copolymers and combinations thereof of N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide, N-vinyl-N-methylpropionamide, N-vinylbutyramide, and N-vinylformamide. For example, in some embodiments, if R 1 and R 2 If both are H, then the N-vinylcarboxamide monomer of formula I is N-vinylformamide. In other embodiments, if R 1 and R 2 If all are methyl, then the N-vinylcarboxamide monomer of Formula I is N-vinyl-N-methylacetamide. The reaction mixture may contain only one N-vinylcarboxamide monomer, or it may contain two or more N-vinylcarboxamide monomers. The N-vinylcarboxamide monomer may be the only nitrogen-containing vinyl monomer present in the reaction mixture. Alternatively, in addition to the N-vinylcarboxamide monomer, the reaction mixture may also contain other nitrogen-containing vinyl monomers having a formula different from Formula I.

[0022] In an embodiment, the nitrogen-containing vinyl monomer may include N-alkylamides selected from, for example, α,β-olefinic unsaturated monocarboxylic acids such as: N-methylacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-(n-propyl)acrylamide, N-(n-propyl)methacrylamide, N-(n-butyl)acrylamide, N-(n-butyl)methacrylamide, N-(tert-butyl)acrylamide, N-(tert-butyl)methacrylamide, N-(n-octyl)acrylamide, N-(n-octyl)methacrylamide, N-(1,1,3,3-tetramethylbutyl)acrylamide, N-(1,1,3,3-tetramethylbutyl)methacrylamide, N-(2-ethylhexyl)acrylamide, N-(2-ethylhexylmethacrylamide) and combinations thereof.

[0023] For example, the salt forms of N-alkyl-N'-vinylimidazolium can be 1-methyl-3-vinylimidazol-1-onium chloride, 1-methyl-3-vinylimidazol-1-onium methyl sulfate, or 1-ethyl-3-vinylimidazol-1-onium chloride. Similarly, the salt forms of N-alkylated vinylpyridinium are 1-methyl-4-vinylpyridin-1-onium chloride, 1-methyl-3-vinylpyridin-1-onium chloride, 1-methyl-2-vinylpyridin-1-onium chloride, or 1-ethyl-4-vinylpyridin-1-onium chloride. For example, the salt forms of acrylamidoalkyltrialkylammonium are acrylamidoethyltrimethylammonium chloride (trimethyl-[2-(prop-2-enamido)ethyl]ammonium chloride), acrylamidoethyldiethylmethylammonium chloride (diethylmethyl-[3-(prop-2-enamido)ethyl]ammonium chloride), acrylamidopropyltrimethylammonium chloride (trimethyl-[3-(prop-2-enamido)propyl]ammonium chloride), or acrylamidopropyldiethylmethylammonium chloride (diethylmethyl-[3-(prop-2-enamido)propyl]ammonium chloride). For example, the salt form of methacryloyltrialkylammonium is methacrylamidoethyltrimethylammonium chloride (trimethyl-[2-(2-methylprop-2-enamido)ethyl]ammonium chloride).

[0024] The reaction mixture has a reactive component present in an amount of at least about 20% by weight of the active ingredient based on the total weight of the reaction mixture. In an embodiment, the reaction mixture has a reactive component present in an amount of at least about 28% by weight, or at least about 35% by weight, or about 20% by weight to about 55% by weight, or about 45% by weight to about 50% by weight of the active ingredient based on the total weight of the reaction mixture.

[0025] As an example, to produce a polymer product with minimized crosslinking by the method provided herein, if the nitrogen-containing vinyl monomer present in the reaction mixture includes an acrylamide monomer, the active ingredient content of the reaction mixture can be from about 33% to about 40% by weight, while in conventional gel polymerization methods the reaction mixture can be limited to an active ingredient content of at most about 28% to about 32% by weight based on the total weight of the reaction mixture. In a specific embodiment, to produce a polymer product with minimized crosslinking containing a copolymer of acrylamide and (2-acryloyloxyethyl)trimethylammonium chloride with an active ingredient content of 75% by weight by the method provided herein, the active ingredient content of the reaction mixture can be from about 45% to about 50% by weight, while in conventional gel polymerization methods the reaction mixture can be limited to an active ingredient content of at most about 40% to about 45% by weight based on the total weight of the reaction mixture.

[0026] Gel polymerization at maximum active ingredient content is advantageous because it allows for the production of the largest volume of product per time interval compared to conventional gel polymerization, resulting in higher yields and greater production efficiency. Maximizing the active ingredient content of the reaction mixture while minimizing crosslinking and / or byproduct formation leads to maximized production efficiency without adversely affecting the quality of the polymer product. Furthermore, gel polymerization at maximum active ingredient content allows for the use of minimal amounts of water. The energy required for drying the product is also minimized, resulting in lower costs, a smaller carbon footprint, and increased sustainability compared to standard polymerization methods.

[0027] The method provided herein further includes exposing the reaction mixture to UV light generated by a UV light source to form a polymer product. In embodiments, the UV light source generates light with wavelengths of about 10 nm to about 400 nm, or about 300 nm to about 400 nm, or about 350 nm to about 370 nm, or about 360 nm to about 370 nm. In one specific embodiment, the UV light source generates light with a wavelength of about 365 nm.

[0028] In this implementation, the UV light source is a UV light-emitting diode (LED). The implementation using a UV LED as the UV light source is advantageous because, unlike UV tube lamps and other conventional UV light sources, UV LEDs can be tailored to emit a narrow band of UV light wavelengths. Specifically, the narrow band of UV light emitted by the UV LED can be tailored to match the activation wavelength of the polymerization initiator, which is activated only by UV light. This wavelength matching allows for increased control over initiator decomposition and extended polymerization time. This is important because the decomposition of the polymerization initiator can trigger polymer chain growth and crosslinking. Furthermore, UV LEDs provide sufficient irradiance to reduce the amount of residual monomer after polymerization. UV LEDs are significantly more efficient than standard UV light sources. Compared to standard UV light sources, UV LEDs have a longer lifespan and lower energy consumption, resulting in reduced costs, a smaller carbon footprint, and increased sustainability.

[0029] In this embodiment, the UV light source is selectively modulated during the exposure of the reaction mixture to UV light generated by the UV light source. As used herein, the term "modulation" means turning the UV light source on or off, or adjusting the intensity of the UV light generated by the UV light source. Modulating the UV light source is advantageous because it allows for reaction control. Turning the UV light source on and off allows for immediate initiation or cessation of the reaction. Adjusting the intensity of the UV light source allows for control of reaction conditions such as the reaction rate, the temperature of the reaction mixture, and the reaction time. The initial intensity of the UV light source can be from about 10 μW / cm² to about 2000 μW / cm², or from about 70 μW / cm² to about 600 μW / cm², from about 50 μW / cm² to about 200 μW / cm², or from about 100 μW / cm² to about 200 μW / cm², or from about 130 μW / cm² to about 150 μW / cm². The final intensity of the UV light source can be from about 5000 μW / cm² to about 40,000 μW / cm², or from about 8000 μW / cm² to about 12000 μW / cm², or from about 8000 μW / cm² to about 9000 μW / cm². In an embodiment, the intensity of the UV light source is increased at a certain point in the reaction based on the observed temperature of the reaction mixture, the elapsed time, or the degree of polymerization in the reaction mixture. In an embodiment, the intensity is increased when the reaction mixture reaches its maximum temperature. In an embodiment, the intensity is increased when the temperature of the reaction mixture reaches at least 10°C below the maximum temperature, or from about 10°C to about 30°C below the maximum temperature. The reaction mixture may be exposed to the increased intensity for a period of time after reaching the maximum temperature, for example, about 30 minutes after reaching the maximum temperature. In one specific embodiment, the initial intensity is about 140 μW / cm², and the intensity is adjusted to a final intensity of about 8500 μW / cm² when the temperature of the reaction mixture reaches about 60°C.

[0030] In some embodiments, modulating the UV light source can reduce crosslinking in the resulting polymer. Polymerization occurs during the time the reaction mixture is exposed to UV light. Prolonged exposure to UV light during polymerization can cause the polymerization initiator to decompose, which can trigger polymer chain growth and crosslinking. The ability to modulate the UV light source during polymerization allows for control of initiator decomposition, thereby minimizing crosslinking.

[0031] In embodiments, reaction temperature can be critical, and modulating the UV light source allows for control of the reaction mixture temperature. Gel polymerization using conventional thermally activated initiators makes temperature control difficult, while gel polymerization using initiators as described herein enables excellent temperature control because the reaction temperature begins to decrease almost immediately upon modulation of the UV light source. For example, the UV light source can be modulated to maintain the temperature of the reaction mixture below about 70°C, or below about 80°C, or from about 70°C to about 80°C. In embodiments, the reaction mixture can be controlled between about -5°C and about 100°C during the reaction. Controlling the temperature of the reaction mixture reduces the formation of byproducts from unreacted monomers. For example, in the synthesis of polyvinyl carboxylamide, byproducts such as acetaldehyde may begin to form at reaction temperatures of about 70°C, with excessive byproduct formation observed at reaction temperatures of 80°C and higher. Such byproducts can introduce undesirable properties into the resulting polymer and polymer product.

[0032] In this embodiment, the reaction mixture may change from an aqueous solution to a gel during the time the reaction mixture is exposed to UV light. As used herein, the term "gel" refers to a gel-like material having the consistency of a gelling agent or a gummy candy. The point at which the reaction mixture changes from an aqueous solution to a gel during a polymerization reaction (measured based on the molar percentage of the reactive component in the reaction mixture compared to the amount of reactive component in the reaction mixture before the start of the reaction) is called the "gel point". If the reaction mixture changes from an aqueous solution to a gel during polymerization, the polymerization process is considered a gel polymerization process. In this embodiment, during gel polymerization, the reaction mixture may have a reactive component content of at least 20% by weight based on the total weight of the reaction mixture.

[0033] Gel polymerization offers advantages because it allows for maximized active ingredient content in the reaction mixture and the resulting polymer product, leading to maximized product yield at each time interval, which is beneficial for production efficiency. Gel polymerization also produces polymer products that can be pulverized and formed into distinct product particles, which will be discussed in more detail below. However, conventional gel polymerization methods typically produce polymer products with lower average weight-average molecular weights than polymers produced via emulsion polymerization. Furthermore, polymer products produced by conventional gel polymerization may exhibit higher insolubility in the final product than those produced via emulsion polymerization, rendering the product unusable. These disadvantages of gel polymerization are mitigated by using UV-only initiators (optionally in combination with a UV LED) in methods such as those described herein.

[0034] As used herein, the term "polymer product" refers to a formulation produced by combining a UV-activated polymerization initiator and a nitrogen-containing vinyl monomer to form a reaction mixture, and by exposing the reaction mixture to UV light generated by a UV light source. The polymer product comprises the reaction product of the initiator and the nitrogen-containing monomer. The polymer product may also contain other components such as water, residual polymerization initiator, unreacted nitrogen-containing vinyl monomer, byproducts, and other impurities. The polymer product is a pulverizable discrete particle to form the polymer product. The polymer product can be produced in gel form.

[0035] In embodiments, if the nitrogen-containing vinyl monomer present in the reaction mixture is an acrylamide monomer, then the polymer product comprises a polymer containing an amide functional group derived from the acrylamide monomer. For example, the polymer product may comprise a polyacrylamide homopolymer or a polyacrylamide copolymer. If other nitrogen-containing vinyl monomers are present in the reaction mixture besides the acrylamide monomer, then the polymer product comprises a polyacrylamide copolymer. For example, in one specific embodiment, if the reaction mixture comprises an acrylamide monomer and a (2-acryloyloxyethyl)trimethylammonium chloride monomer, then the polymer product comprises a polymer having both an acrylamide functional group and a (2-acryloyloxyethyl)trimethylammonium chloride functional group.

[0036] In other embodiments, if the nitrogen-containing vinyl monomer present in the reaction mixture is an N-vinylcarboxamide monomer having Formula I, then the polymer product comprises a polymer containing a carboxamide functional group. The polymer can be a homopolymer or a copolymer, particularly if other nitrogen-containing vinyl monomers are present in the reaction mixture besides the N-vinylcarboxamide monomer. For example, if an N-vinylformamide monomer is present in the reaction mixture, then the polymer product comprises a polyvinylformamide homopolymer or copolymer.

[0037] In the embodiment, a 1% by weight solution of the polymer product, containing 10% by weight sodium chloride (based on the total weight of the solution), has a dynamic viscosity of approximately 200 mPas to approximately 2500 mPas, or approximately 400 mPas to approximately 1500 mPas, measured using a Brookfield viscometer at 10 rpm and LV rotor 2 at 20°C. It is noteworthy that the dynamic viscosity of the polymer product is higher than that of polymer products produced by conventional gel polymerization methods without using only UV initiators and UV light sources. The increased dynamic viscosity is beneficial because it is associated with an increased weight-average molecular weight.

[0038] In some embodiments, the polymer product undergoes further processing. For example, if the polymer product contains a polyvinyl carboxylamide polymer, the functional groups in the polyvinyl carboxylamide polymer can be hydrolyzed to form ethyleneamine groups. Such hydrolysis can be carried out at a location far from where the polyvinyl carboxylamide polymer is produced, particularly where the polymer product is pulverized or granulated, as described in further detail below.

[0039] The polymer product is a pulverizable discrete particle to form the polymer product. Therefore, in some embodiments, the polymer is pulverized and dried to form discrete particles of the polymer product. For example, in one embodiment, the polymer product may be cut and then dried by heating in an environment at 120°C for 10 minutes, followed by heating in an environment at 100°C for 30 minutes, and then heating in an environment at 90°C for 40 minutes. The dried polymer product can then be ground to form particles of the dried polymer product. In embodiments, the particles have a particle size of about 100 micrometers to about 1000 micrometers, as measured by filtering the particles through a sieve with different pore sizes.

[0040] Crushing and granulating polymer products is advantageous for transporting and storing polymer products with a higher content of active ingredients compared to when the polymer product is not in particulate form. Producing polymer products in particulate form also allows the polymer product to contain a higher weight-average molecular weight than other forms of polymer products, resulting in improved polymer performance in its applications, such as flocculants in papermaking processes.

[0041] In one embodiment, the polymer product contains a vinyl carboxylamide-containing polymer with a weight-average molecular weight of about 5,000 Daltons to about 5,000,000 Daltons, or about 100,000 Daltons to about 2,000,000 Daltons, or about 250,000 Daltons to about 750,000 Daltons. In one embodiment, the polymer product contains an acrylamide-containing polymer with a weight-average molecular weight of about 500,000 Daltons to about 1,500,000 Daltons, or about 500,000 Daltons to about 1,000,000 Daltons, or about 750,000 Daltons to about 1,250,000 Daltons. It is noteworthy that the weight-average molecular weight of the polymer product is higher than that of polymer products produced by conventional gel polymerization methods that do not use only UV initiators and UV light sources. A higher weight-average molecular weight is advantageous for improving the performance of the polymer product in its applications, such as flocculants in papermaking processes.

[0042] Although polymer products can be produced in gel form, they can be subsequently cut and dried to obtain particulate polymer products soluble in aqueous solutions. Any amount of particulate polymer product that remains as a gel without dissolving in an aqueous solution is referred to as a "polymer solution gel." As used herein, the term "polymer solution gel" refers to the amount of undissolved gel-like particles present in a solution of particulate polymer product. In an embodiment, a 0.5% by weight solution of particulate polymer product has a polymer solution gel of less than about 0.5 g, or less than about 0.3 g, or about 0.0 g to about 1.0 g based on 9.0 g of polymer product, as determined by filtration through a 150 μm Schopper-Riegler sieve using a water jet pump. Notably, the polymer solution gel of the particulate polymer product is lower than that of the particulate polymer product with comparable active ingredient content and weight-average molecular weight produced by conventional gel polymerization methods without the use of only UV initiators and UV light sources. The lower polymer solution gel is advantageous because any particles present in solution in a gel state are insoluble and therefore ineffective in the application of the polymer product. Lower polymer solution gelation is equivalent to higher usable product yield and higher production efficiency.

[0043] It should be understood that any or all of the above components (e.g., monomers, modifiers, etc.) can be prepared or otherwise obtained (e.g., from commercial sources). Furthermore, these components and / or the reagents used to prepare them can be derived from conventional (e.g., fossil-based) sources, or can be bio-based, i.e., prepared using biological methods and / or products derived from such methods. In some embodiments, the method uses all bio-based components in the preparation of the ethyleneamine-containing polymer. In other embodiments, at least a portion of the components is bio-based.

[0044] The following examples are intended to illustrate a method for producing ethyleneamine-containing polymer solutions as described herein and should not be considered limiting. Example Examples 1-3

[0045] Add 2.5 g of Trilon to a standard polymerization container in the order listed. ®C (10 wt% diethylenetriaminepentaacetic acid solution), 455.2 g 50 wt% acrylamide aqueous solution, 120 g 80 wt% (2-acryloyloxyethyl)trimethylammonium chloride (DMA3Q) solution, and 416.1 g water. These amounts resulted in a reaction mixture containing 32 wt% active ingredient. A 50 wt% sulfuric acid solution was added to the reaction mixture until the pH reached 5.0. The amounts of initiator and formic acid added are shown in Table 1, where V50 is 2,2'-azobis(2-methylpropanediamine) dihydrochloride. The reaction mixture was then cooled to -5°C, and oxygen was removed by purging the polymerization vessel with nitrogen.

[0046] Polymerization was initiated by applying UV light from a UV lamp source (Philips Cleo Performance 40W). The distance between the UV lamp source and the reaction mixture resulted in an intensity measurement of approximately 1200 μW / cm² at the reaction mixture location (measured using a UV meter). The temperature of the reaction mixture was monitored, and when the temperature reached 60°C, the distance between the UV lamp source and the reaction mixture was decreased until the UV lamp source intensity at the reaction mixture location, measured using a UV meter, was approximately 6000 μW / cm².

[0047] Within minutes, the temperature of the reaction mixture rose from approximately -5°C to approximately 80°C. The resulting polymer product was in gel form. The gelled polymer product was cut using a meat grinder. The cut polymer product was then dried at 120°C for 10 minutes, then at 100°C for 30 minutes, and then at 90°C for 40 minutes. The dried polymer product was then ground using an ultracentrifuge to a particle size of approximately 100 micrometers to approximately 1000 micrometers, as measured by filtering the particles through a sieve with different pore sizes.

[0048] The embodiments obtained by the above procedure are designated as Embodiments 1-3. The embodiments designated as "Comp. Ex" are comparative examples that do not conform to this disclosure. Example 4

[0049] The polymerization process followed the procedures of Examples 1-3 above, except that a UV LED module (with 3-5 365nm diodes, 3.5W) was used instead of a UV lamp light source to initiate the polymerization. The intensity also differed from that of Examples 1-3. The initial intensity was approximately 140 μW / cm², and the intensity was adjusted to approximately 8500 μW / cm² when the temperature of the reaction mixture reached approximately 60°C.

[0050] The polymer product was formed into granular form following the drying and milling procedures described in Examples 1-3, and the resulting example is designated as Example 4. The example designated as "Comp. Ex" is a comparative example not conforming to this disclosure. Examples 5-9

[0051] The polymerization process follows the procedures described in Examples 1-3 above, except that for Examples 6-9, a UV LED module (with 3-5 365nm diodes, 3.5W) is used instead of a UV lamp light source to initiate polymerization, as described in Example 4 above. For Examples 6-9, the intensity described in Example 4 above is used.

[0052] The amounts of each component added to the reaction mixture as described in Examples 1-3 above produced a reaction mixture with an active ingredient content of 32% by weight, as shown in Examples 5-7. To prepare Examples 8-9, the amounts of acrylamide solution and DMA3Q solution added were increased, and the amount of water added was reduced as needed to achieve the active ingredient content listed in Table 1.

[0053] In addition, for Examples 5-7 and Example 9, 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) was added to the reaction mixture instead of V50. HMPP was added to the reaction mixture in an amount of 0.6 g.

[0054] The polymer product was formed into granular form following the drying and milling procedures described in Examples 1-3, and the resulting examples are designated as Examples 5-9. Examples designated as "Comp. Ex" are comparative examples not conforming to this disclosure. Examples 10-14

[0055] The polymerization process follows the procedures of Examples 1-3 above, except that for Examples 12 and 14, a UV LED module (with 3-5 365nm diodes, 3.5W) is used instead of a UV lamp light source to initiate polymerization, as described in Example 4 above. For Examples 12 and 14, the intensity described in Example 4 above is used.

[0056] In addition, for Examples 13-14, 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) was added to the reaction mixture instead of V50. HMPP was added to the reaction mixture in an amount of 0.6 g. The amount of water added to the reaction mixture was increased or decreased as needed to achieve the active ingredient content listed in Table 1.

[0057] The polymer product was formed into granules following the drying and grinding procedures of Examples 1-3 described above, and the resulting examples are designated as Examples 10-14. Examples designated as "Comp. Ex" are comparative examples not conforming to this disclosure.

[0058] The results of Examples 1-13 are shown in Table 1 below.

[0059] Table 1: Effect of UV initiator only on viscosity and polymer solution gelation

[0060] The gel value of the polymer solution was determined by dissolving and mixing 9 g of dried, granulated polymer product in water to produce a 0.5 wt% aqueous solution of the polymer product. The solution was then poured onto a 150 μm Schopper-Riegler sieve under vacuum. After passing through the sieve, the sieve was rinsed with water, excess water was blotted with paper towels, and the net weight of the material remaining on the sieve was measured. The dynamic viscosity was determined by dissolving the dried, granulated polymer product in water to produce a 1 wt% aqueous solution of the polymer product (containing 10 wt% sodium chloride, based on the total weight of the solution). The dynamic viscosity was then measured at 10 rpm using a Brookfield viscometer with LV rotor 2 at 20°C. The UL viscosity was determined by producing a 0.1 wt% solution of the polymer product in 1M NaCl (based on the total weight of the solution). The UL viscosity was then measured at 60 rpm using a Brookfield viscometer (model LVT) with a UL adapter with LV rotor 2 at 25°C.

[0061] The results in Table 1 demonstrate the effectiveness of using an initiator activated solely by UV light. For example, when HMPP initiator was used instead of V50 initiator, at 35% wt% active ingredient content and under UV LED conditions, the HMPP initiator resulted in polymer products with lower polymer solution gel values, higher dynamic viscosity, and lower residual monomer content compared to polymer products produced by the same method but using V50 initiator. Example 15

[0062] Add 2.5g of Trilon to a standard polymerization container in the order listed. ® C. 506.7 g of 50 wt% acrylamide aqueous solution, 132 g of 60 wt% (3-acrylamidopropyl)trimethylammonium chloride (DIMAPA-Q) solution, and 530.3 g of water. Add 50 wt% sulfuric acid solution to the reaction mixture until the pH reaches 4.5. Add the amounts of V50 and formic acid shown in Table 2 to the reaction mixture. Then, cool the reaction mixture to -5°C and remove oxygen by purging the polymerization vessel with nitrogen. Polymerization was initiated by applying UV light from a UV tube lamp source (Philips Cleo Performance 40W) with an intensity of approximately 6000 μW / cm².

[0063] Within minutes, the temperature of the reaction mixture rose from approximately -5°C to approximately 80°C. The resulting polymer product was in gel form. The gelled polymer product was cut using a meat grinder. The cut polymer product was then dried at 120°C for 10 minutes, then at 100°C for 30 minutes, and then at 90°C for 40 minutes. The dried polymer product was then ground using an ultracentrifuge to a particle size fraction of approximately 100 micrometers to approximately 1400 micrometers, as measured using sieve analysis. Examples 16 and 17

[0064] Add 2.5g of Trilon to a standard polymerization container in the order listed. ® C. 583.4 g of 50 wt% acrylamide aqueous solution, 152 g of 60 wt% (3-acrylamidopropyl)trimethylammonium chloride (DIMAPA-Q) solution, and 254.1 g of water. Add 50 wt% sulfuric acid solution to the reaction mixture until the pH reaches 4.5. Add the amounts of V50 and formic acid shown in Table 2 to the reaction mixture. Then, cool the reaction mixture to -5°C and remove oxygen by purging the polymerization vessel with nitrogen. Initiate polymerization by applying UV light from a UV LED module (with 3-5 365nm diodes, 3.5W). The initial intensity is approximately 1200 μW / cm². When the temperature of the reaction mixture reaches approximately 70°C, adjust the intensity to approximately 5700 μW / cm². After the reaction mixture reaches its maximum temperature (monitored by a temperature probe in the reaction mixture), adjust the intensity to approximately 9000 μW / cm² and apply UV light at this final intensity for approximately 30 minutes.

[0065] Within minutes, the temperature of the reaction mixture rose from approximately -5°C to approximately 99°C. The resulting polymer product was in gel form. The gelled polymer product was cut using a meat grinder. The cut polymer product was then dried at 120°C for 10 minutes, then at 100°C for 30 minutes, and then at 90°C for 40 minutes. The dried polymer product was then ground using an ultracentrifuge to a particle size fraction of approximately 100 micrometers to approximately 1400 micrometers, as measured using sieve analysis.

[0066] The results of Examples 15-17 are shown in Table 2 below.

[0067] Table 2: Acrylamide copolymers using DIMPA-Q

[0068] The gel value and dynamic viscosity of the polymer solution were measured using the same methods described in Examples 1-14 above. Examples 18-19

[0069] For Example 18, 2.5 g of Trilon was added to a standard polymerization container in the order listed. ® C (10 wt% diethylenetriaminepentaacetic acid solution), 227.3 g 50 wt% acrylamide aqueous solution, 421.9 g 80 wt% (2-acryloyloxyethyl)trimethylammonium chloride (DMA3Q) solution, and 347 g water. Add 50 wt% sulfuric acid solution to the reaction mixture until the pH of the reaction mixture reaches 5.

[0070] For Example 19, 2.5 g of Trilon was added to a standard polymerization container in the order listed. ® C (10 wt% diethylenetriaminepentaacetic acid solution), 252.5 g 50 wt% acrylamide aqueous solution, 468.8 g 80 wt% (2-acryloyloxyethyl)trimethylammonium chloride (DMA3Q) solution, and 275.4 g water. Add 50 wt% sulfuric acid solution to the reaction mixture until the pH of the reaction mixture reaches 5.

[0071] Then, for Examples 18 and 19, formic acid and initiator in the amounts shown in Table 3 were added, wherein V50 was 2,2'-azobis(2-methylpropanediamine) dihydrochloride. The reaction mixture was cooled to -5°C and oxygen was removed by purging the polymerization vessel with nitrogen.

[0072] Polymerization was initiated by applying UV light from a UV LED module (with a 365nm LED, 3.5W) at an intensity of approximately 140 μW / cm². The temperature of the reaction mixture was monitored, and when the temperature of the reaction mixture reached 60°C, the intensity of the UV lamp source was increased to approximately 8500 μW / cm².

[0073] The polymer product was formed into granular form following the drying and milling procedures described in Examples 1-3, and the resulting examples are designated as Examples 18-19. Examples designated as "Comp. Ex" are comparative examples not conforming to this disclosure. Examples 20 and 21

[0074] Example 20 followed the polymerization procedure of Example 18 described above, and Example 21 followed the polymerization procedure of Example 19 described above, except that 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) was added to the reaction mixture instead of V50. The amounts of HMPP added to the reaction mixture are shown in Table 3 below.

[0075] The polymer product was formed into granular form following the drying and grinding procedures described in Examples 1-3, and the resulting examples are designated as Examples 20-21. Examples designated as "Comp. Ex" are comparative examples not conforming to this disclosure.

[0076] Table 3: Effect of UV-activated initiators on high-charge cationic polyacrylamide

[0077] The results in Table 3 show that when a UV-activated initiator is used instead of a thermally activated azo initiator at an active content of 45-50% by weight, the resulting polymer product has a higher dynamic viscosity.

[0078] While at least one exemplary embodiment has been presented in the foregoing detailed descriptions, it should be understood that numerous variations exist. It should also be understood that one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of this disclosure in any way. Rather, the foregoing detailed descriptions will provide those skilled in the art with a convenient roadmap for implementing exemplary embodiments of this disclosure. It should be understood that various changes can be made to the function and arrangement of the elements described in the exemplary embodiments without departing from the scope of this disclosure as set forth in the appended claims.

Claims

1. A method for synthesizing a polymer product, the method comprising the following steps: (a) Combining a UV-activated polymerization initiator and a nitrogen-containing vinyl monomer to form a reaction mixture, wherein the initiator is free radicalized only by exposure to UV light, and wherein the reaction mixture has a reactive component present in an amount of at least about 20% by weight of an active ingredient based on the total weight of the reaction mixture; (b) Exposing the reaction mixture to ultraviolet light generated by an ultraviolet light source to form a polymer product comprising the reaction product of the initiator and the nitrogen-containing vinyl monomer, wherein the polymer product is pulverizable to form discrete particles of the polymer product.

2. The method of claim 1, wherein the UV-activated polymerization initiator and the nitrogen-containing vinyl monomer are combined to form the reaction mixture, the reaction mixture having a reactive component present in an amount of at least about 28% by weight of active ingredient based on the total weight of the reaction mixture.

3. The method according to any one of claims 1 or 2, wherein the reaction mixture is exposed to ultraviolet light of about 350 nm to about 370 nm, or about 360 nm to about 370 nm, generated by the ultraviolet light source.

4. The method according to any one of claims 1-3, wherein the ultraviolet light source is an ultraviolet light-emitting diode, and wherein the reaction mixture is exposed to ultraviolet light generated by the ultraviolet light-emitting diode.

5. The method according to any one of claims 1-4, wherein the nitrogen-containing vinyl monomer is combined with the UV-activated polymerization initiator, wherein the UV-activated polymerization initiator is selected from 2-hydroxy-2-methyl-1-phenyl-1-propanone, benzophenone, 4'-hydroxyacetophenone, methyl benzoylformate, 2,2-dimethoxy-2-phenylacetophenone, α-ketoglutaric acid, camphorquinone, (1-hydroxycyclohexyl)-phenyl ketone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylphenylpropanone, ethyl 2-oxopropionate, ethyl 3-methyl-2-oxobutyrate, 4,4-dimethyldihydrofuran-2,3-dione, ethyl benzoylformate, and combinations thereof.

6. The method according to any one of claims 1-5, wherein the reaction mixture is exposed to ultraviolet light generated by the ultraviolet light source at least up to the gel point.

7. The method according to any one of claims 1-6, further comprising pulverizing the polymer product to form discrete particles of the polymer product.

8. The method according to any one of claims 1-7, wherein the ultraviolet light-activated polymerization initiator is combined with a nitrogen-containing vinyl monomer comprising an acrylamide monomer.

9. The method of claim 8, wherein the UV-activated polymerization initiator and the acrylamide monomer are combined with an additional nitrogen-containing vinyl monomer selected from diallyl dimethylammonium chloride, acrylamide propyltrimethylammonium chloride, methacrylamide propyltrimethylammonium chloride, a quaternary ammonium salt of dimethylaminoethyl acrylate, a quaternary ammonium salt of dimethylaminoethyl methacrylate, and combinations thereof.

10. The method according to any one of claims 8 or 9, wherein the reaction mixture is exposed to ultraviolet light generated by the ultraviolet light source to form a polymer product with a weight-average molecular weight of at least about 1,000,000 Daltons.

11. The method according to any one of claims 8-10, further comprising selectively modulating the ultraviolet light source.

12. The method of claim 11, wherein modulating the ultraviolet light source comprises increasing the intensity of the ultraviolet light source once the temperature of the reaction mixture reaches a temperature about 10°C to about 30°C below the highest temperature of the reaction mixture.

13. The method according to any one of claims 1-12, wherein the ultraviolet-activated polymerization initiator is combined with a nitrogen-containing vinyl monomer selected from one or more N-vinylcarboxamide monomers having general formula I. (I) Where R 1 and R 2 They are independently H or C1 to C6 alkyl groups.

14. The method of claim 13, further comprising maintaining the temperature of the reaction mixture at less than about 80°C or at less than about 70°C to about 80°C during the duration of the reaction.

15. The method of claim 14, wherein maintaining the temperature of the reaction mixture comprises selectively modulating the ultraviolet light source.

16. The method according to any one of claims 13-15, wherein the reaction mixture is exposed to ultraviolet light generated by the ultraviolet light source, and further comprises pulverizing the polymer product to form discrete particles of the polymer product, wherein the functional groups in the polymer product are hydrolyzed to form primary amine functional groups present in the hydrolyzed polymer product, the hydrolyzed polymer product having a weight-average molecular weight of at least about 250,000 Daltons.

17. The method of claim 1, wherein the reaction mixture is exposed to ultraviolet light of a wavelength of about 350 nm to about 370 nm generated by the ultraviolet light-emitting diode light source at least up to the gel point, the reaction mixture having a reactive component present in an amount of at least about 28% by weight of active ingredient based on the total weight of the reaction mixture.

Images