Stable aqueous polymer dispersions
Patent Information
- Authority / Receiving Office
- ES · ES
- Patent Type
- Patents
- Current Assignee / Owner
- ARKEMA FRANCE SA
- Filing Date
- 2018-07-05
- Publication Date
- 2026-07-13
AI Technical Summary
Existing aqueous polymer dispersions destabilize and coagulate in the presence of organic solvents and under acidic conditions due to the depletion of surfactants and reduction of repulsive forces, particularly when pH drops below 2.0, leading to instability.
An aqueous polymer dispersion is stabilized by incorporating strong acid functionalities through specific monomers and initiators, ensuring anionic groups and hydroxyl groups are present in defined amounts, allowing stability in the presence of organic solvents and at low pH.
The dispersion maintains stability for at least 12 hours with high organic solvent content and pH below 2.0, preventing coagulation and maintaining particle dispersion.
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Abstract
Description
Stable aqueous polymer dispersions The present invention relates to a specific polymeric aqueous dispersion, which is stable for long periods of time, when dissolved in a large amount of organic solvents and finally acidified to a very low pH. The aqueous dispersion of the present invention is an anionic polymer dispersion, produced by emulsion polymerization of a specific mixture of monomers selected from acrylic (i.e., acrylics or methacrylics), allylic, and vinyl monomers (including the latter family of vinyl esters, vinylaromatic monomers, and maleate monomers). The main feature of this aqueous polymer dispersion is that its polymer particles contain a large number of strong acid functionalities. It is known that when a polymer with an aqueous base interacts with a large number of organic solvents, especially if these solvents are water-soluble, they can increase the solubility of surfactants in the liquid phase. This depletes the amount of surfactant bound to the surface of the particles, destabilizing them and resulting in the coagulation of the polymer dispersion. This is particularly evident when acidic substances are added to the aqueous polymer dispersion, causing the pH to drop to low values (below 2.0) and the average ionic strength to increase, compressing the repulsive ionic double layer. This leads to a significant decrease in repulsive forces, thus reducing the distance between particles, until a coagulation process begins. US patent 5910532 discloses a composition for peelable coatings, with water and other organic solvents forming the dispersion medium, propanol being the preferred solvent. However, to achieve stability, it is essential to have a functional monomer bearing a cationic group. The patent also discloses the use of acid groups, but not necessarily strong acids, and the organic solvent in the examples is added to the polymerization medium in an amount no greater than the amount of polymer dispersion with an aqueous base. EP 0357149 discloses the preparation of a pesticide formulation, where the pesticide is dissolved in an organic solvent and mixed with an aqueous copolymer in an aqueous base produced by grafting a copolymer with a copolymerizable reactive surfactant. The behavior of this grafted polymeric surfactant is independent of the pH produced by the polymerization. However, this disclosure is restricted only to a composition with pesticide dissolved in solvents and using only surfactants grafted to the copolymer; moreover, from the examples it can be deduced that water is always the main solvent of these compositions. Other aqueous-based polymer dispersions containing strong acid groups are also known in the prior art. WO 2014139074 discloses the use of a water-soluble polymer containing sulfonic groups as a co-binder in a composition useful for producing stain-resistant paints. EP 2692753 and EP 2692752 disclose the use of monomers containing sulfonic groups for the production of water-soluble polymeric dispersing agents with high dispersion efficiency on pigment particles. EP 1245240 discloses strong acid monomers used to produce water-soluble hydrogel polymer adhesives for medical use.US patent 6201048 discloses strong acid monomers used to produce aqueous-based polymer compositions stabilized against gelation due to the addition of a poly(alkyleneimine) by the subsequent addition of certain anionic surfactants. US patent 2017030015 discloses polymer compositions for, e.g., dyes comprising a core-type polymer and a shell-type polymer, both of which have structural units derived from alkenylbenzene, nitrile, sodium salt of sulfonic acid, and a methacrylate-derived structural unit. None of the previously cited techniques disclose or suggest a way to modify an aqueous acrylic polymer dispersion by using only strong acid groups attached to the polymer particles to confer stability in the presence of a large number of organic solvents, water-soluble or not, under strongly acidic conditions (pH < 2.0). Surprisingly, the aqueous polymer dispersion according to the present invention is stable in the presence of a large number of organic solvents, without the need for any polymerized surfactant grafted onto the particles or cationic groups, and without being restricted to a specific use such as the production of pesticide dispersions.Furthermore, this invention makes it possible to achieve these results using monomers containing strong acid groups copolymerized directly with the other monomers and / or by introducing the required amount of such acid groups by the alternative route of using the correct type and amount of specific initiators that introduce such acid groups. The first object of the present invention relates to an aqueous polymer dispersion with said polymer obtained by emulsion polymerization of a specific monomeric composition and initiator. A second object of the invention relates to a binding composition comprising at least one aqueous polymer dispersion as defined according to the present invention. Another object refers to the use of said binding composition for its application on specific substrates. Finally, the invention also covers the use of said aqueous polymer dispersion in two-component crosslinkable binder compositions, for example using as a crosslinking agent: aminoplastic resins, phenolic resins, urea-formaldehyde, melamine-formaldehyde, or polyisocyanates, or polyaziridines, or polycarbodiimides, with phenolic resins being particularly preferred. The objective of the present invention is an aqueous polymer dispersion that allows stability for at least 12 hours when dissolved in a large amount of organic solvents and eventually when acidified to low pH (pH < 2). This objective is achieved with an aqueous polymer dispersion comprising units (structural units) and / or groups (functional groups) derived from: a) at least one (meth)acrylic monomer that is an (meth)acrylic ester of a C1-C12 alcohol, the alcohol being linear (C1-C12) or branched (C4-C12), with no other functional group than (meth)acrylate b) at least one of monomer b1) or initiator b2) or both b1) and b2) as defined below: b1) at least one vinyl, allylic or (meth)acrylic monomer, preferably vinyl or (meth)acrylic monomer, bearing an anionic group obtained from strong acids with pKa < 3, preferably < 2 b2) at least one initiator, which carries the same anionic group as b1) c) at least one vinyl, allylic or (meth)acrylic monomer with hydroxy functionality, preferably vinyl or (meth)acrylic monomer d) at least one ethylenically unsaturated monomer with carboxy functionality e) optionally, at least one vinyl monomer, with no other functional group than the vinyl group, bearing a single vinyl group f) Optionally, at least one vinyl or (meth)acrylic monomer bearing at least one functional group selected from: nitrile, amide, acetoacetoxy, diacetone, free silane or silane blocked with alkoxy, epoxy, urea or ureide g) optionally, at least one multifunctional vinyl or (met) acrylic monomer, and where said polymer carries: • the anionic groups as defined in b) in an amount of at least 0.05 meq / g, preferably from 0.07 to 0.3 meq / g (according to the calculation, see below) with respect to said polymer and • hydroxy groups as defined in c) in an amount of at least 0.1 meq / g, preferably from 0.1 to 0.8 meq / g (according to calculation, see below) with respect to said polymer. The calculation of the amount of anionic or hydroxyl groups is based on the molar amount of said monomer b1) and / or said initiator b2) and monomer c) (vs hydroxy) used to prepare the polymer with respect to the total theoretical weight of said polymer, assuming absence of free monomer b1) oc) and absence of free initiator b2) after polymerization and that all monomers used are converted into the polymer (100% conversion). The term "at least one vinyl monomer e)," "without any functional group other than the vinyl group, which bears a single vinyl group," shall be interpreted within the meaning of the present invention as "a monovinyl monomer without any functional group such as those having monomers b1), c), d), and f) as defined above, which in particular may bear an aromatic group attached to the vinyl group or one or two ester groups attached to said vinyl group, and more particularly said monomer e) is a vinylaromatic monomer, preferably styrene or vinyl toluene, or is a vinyl alcohol ester, preferably vinyl acetate or vinyl versatate, or a monoalkyl ester or dialkyl ester maleate or fumarate. Said alkyl in the fumarate or maleate monoesters or diesters is an alkyl selected from C1 to Cs, preferably C2 to C6." More preferably, said vinyl monomers e) are selected from: vinyl acetate, vinyl versatate and di- or mono-alkyl maleates or di- or mono-alkyl fumarates or styrene. According to a specific option of the invention, said monomer d) is present in said polymer in a weight content with respect to said polymer of 0.05% to 6%. Such anionic groups as defined in b) are preferably an acid group containing sulfur and salts or an acid group containing phosphorus and salts. In particular, such anionic groups as defined in b) are selected from the group consisting of: • a sulfonic acid group (-SO3H) (I, see below) or a sulfuric acid half-ester group (II) and its corresponding salts or a phosphonic acid group (III) or a phosphoric acid partial ester group (IV or V) and its corresponding salts as presented in the following formulas (I) to (V) below with said groups supported by the polymeric moiety represented by R: More specifically, such anionic groups as defined in b) can come from: b1) monomers selected from the group consisting of the following acids and their salts, preferably sodium, ammonium or other cation salts, of: • 2-acrylamido-2-methylpropane-sulfonic acid (VI, as shown below), styrene sulfonic acid (VII), 1-allyloxy-2-hydroxypropane sulfonic acids (VIII), vinyl sulfonic acid (IX), 3-sulfopropyl acrylic acid (X) • monomeric partial esters of phosphoric acid and derivatives, such as bis(methacryloxyethyl) hydrogen phosphate (XI) or 2-(phosphonooxy)ethyl methacrylate (XII), vinylphosphonic acid (XIII), b2) Selected initiators from the group consisting of: sodium persulfate, ammonium persulfate, and potassium persulfate. The aqueous polymer dispersion polymer according to the invention may additionally contain h) at least one anionic polymerizable surfactant and / or at least one non-ionic polymerizable surfactant in an amount of 0.1 to 5%, preferably 0.1 to 2% by weight with respect to the total monomers, more preferably said polymerizable surfactant being selected as follows: • for polymerizable anionic surfactants between: Polyoxyethylene 9-octadecenyl ether phosphate (XIV, Maxemul® 6106), unsaturated phosphate ester (XV, as Maxemul® 6112) or ethoxylated allyl nonyl phenol sulfate (XVI) (XVII) as respectively Hytenol® AR, BC or polyoxyalkylene alkenyl ether sulfate (XVIII) as Hytenol® KH-Reasop® SR SE and Latemul® PD, all as shown according to the following formulas below: (C18 H36OHC 2H4OVPO 3 H2 (XIV) RO-PO3H2 (XV) Where R is an alkyl group containing more than 10 carbon atoms and one unsaturation for polymerizable non-ionic surfactants, such as alkyl allyl ethoxylate (IXX) (Reasop® ER, Maxemul® 5011) or allylnonyl phenol ethoxylate (XX) (Reasop® NE), respectively with the following structures: The appropriate monomers c) can be selected from: • (meth) C2-C4 hydroxyl alkyl acrylates, in particular (meth) hydroxyethyl acrylate, (meth) hydroxypropyl acrylate or (meth) hydroxybutyl acrylate or • allyl alcohol, monomer c) being preferably selected from C2-C4 hydroxyl acrylates. According to a specific option, said monomer e) is present and is selected from: vinyl acetate, vinyl versatate and maleates, di- or mono-alkyl fumarates or styrene. According to another option, said monomer f) is present and is selected from: acetoacetoxy (meth) acrylate, diacetone acrylamide, alkoxysilane monomers such as vinyl triethoxy ethyl silane or gamma-methacryloxypropyl trimethoxysilane, monomers containing ureido groups such as N-(2-methacryloyloxyethyl)-ethyleneurea. According to another option, said multifunctional monomer g) is present and is selected from ethylene glycol di(meth) acrylate, trimethylolpropane tri(meth) acrylate, or divinylbenzenes. Suitable monomers a) may be selected from: (meth) methyl acrylate, (meth) ethyl acrylate, (meth) propyl acrylate, (meth) n-butyl acrylate, (meth) 2-ethylhexyl acrylate, (meth) 2-octyl acrylate, (meth) isooctyl acrylate, (meth) nonyl acrylate or (meth) decyl acrylate, (meth) dodecyl acrylate, preferably n-butyl acrylate and preferably monomer e) is selected from styrene and monomer f) is selected from acrylonitrile. More particularly, the aqueous polymer dispersion as defined by the present invention is stable for at least 12 hours when diluted with a large quantity of organic solvent, meaning a dilution with more than 30% w / w of organic solvent with respect to the total weight of the aqueous polymer dispersion (including the solvent). More particularly, it is stable for at least 12 hours at strongly acidic pH, i.e., pH < 2.0, particularly when diluted with an organic solvent in an amount greater than 30% w / w with respect to the aqueous polymer dispersion. Said initiator b2) is preferably selected from ammonium persulfate, sodium persulfate or potassium persulfate. The aqueous polymer dispersion of the invention preferably has polymer particles with an average particle size measured by dynamic light scattering of 20 to 3000 nm, preferably 20 to 500 nm, with a particle size distribution that is monomodal or polymodal, being more preferably monomodal with an average particle size of 20 to 500 nm. The aqueous polymer dispersion of the present invention is prepared by a current emulsion polymerization method. The aqueous dispersions of the present invention are prepared by a conventional emulsion polymerization process with continuous addition of the preemulsified monomer composition to an aqueous solution of an emulsion initiator system, such as an initiator based on ammonium, sodium, or potassium persulfate. Redox initiator systems can also be used for low polymerization temperatures, for example, using ammonium or sodium persulfate combined with metabisulfite as a reducing agent. This procedure may comprise seed polymerization with a portion of the monomer preemulsion ranging from 1 to 10% or without seed polymerization. The polymerization process can be a multi-phase emulsion polymerization process with at least two polymerization stages of two different monomeric compositions successively. For this purpose (emulsion polymerization), a conventional surfactant or a combination of surfactants may be used as a stabilizer in the emulsion polymerization of the invention. Generally, the surfactant is at least one selected from the group consisting of anionic and / or nonionic surfactants. Examples of preferred surfactants include, but are not limited to, alkaline or ammonium salts of alkyl sulfate, alkylaryl sulfate, alkyl ether sulfate, alkylsulfonic acid, fatty acid (which may be an ethoxylated fatty acid), C10-C18 ethoxylated alcohol, sulfosuccinates and derivatives, or any combination thereof. A list of suitable surfactants is available in the book "Surfactants and Polymers in Aqueous Solutions" (Holmberg et al., 2002, John Wiley & Sons). More specifically, polymerizable surfactants can be used to produce the aqueous polymer dispersion of the present invention, which may contain anionic or nonionic polymerizable surfactants, such as the Maxemul® range (Croda) or the Reasop® range from ADEKA or the Latemul® PD range (KAO Chemicals), Noigen®, and Hitenol® (Dai-Ichi Kogyo), in an amount between 0.1 and 5% as presented above. The initiators may preferably be selected from ammonium persulfate, sodium persulfate, or potassium persulfate as defined above in b2). The solids content (% w / w polymer versus aqueous polymer dispersion) may range from 30 to 65%, preferably from 40 to 60%. The second object of the present invention relates to a binding composition, which is a two-component composition comprising at least one aqueous polymer dispersion as defined above according to the invention, and further comprising a crosslinking agent. The crosslinking agent reacts with the hydroxyl groups provided by comonomer c), and preferably is selected from aminoplastic resins, phenolic resins, urea-formaldehyde resins, melamine-formaldehyde resins, or polyisocyanates, phenolic resins being the most preferred. According to another option, said crosslinking agent reacts with the carboxyl group provided by the comonomer d), and in particular, said crosslinking agent is selected from polyaziridines or polycarbodiimides, "poly-" meaning a multifunctional compound that carries aziridine or carbodiimide. According to another option, this two-component crosslinkable binder composition is suitable for the treatment of textile articles or non-woven fabrics. Another object of the invention relates to the use of said binding composition by applying it to a substrate selected from: cellulose fibers, glass fibers, composite materials, textile fibers, woven and non-woven fabrics, paper, cardboard, wood including plywood and particleboard, metals, in particular aluminum, glass, plastics, including plastic films. Another and final object of the invention relates to the use of said aqueous polymer dispersion according to the invention in a two-component crosslinkable binder composition. A more specific use of this aqueous dispersion relates to the treatment of textile articles or non-woven fabrics. Regarding a particularly stable aqueous polymer dispersion in an organic solvent (with respect to the addition of organic solvent), for the present invention, this is an aqueous polymer dispersion in which, after 12 h from dilution with more than 30% organic solvent, it is not possible to recognize coagulated polymer at the bottom of the flask where the mixture has been prepared or particles floating in the mixture. Regarding a particularly stable aqueous polymer dispersion according to the present invention, at low acidic pH, this is an aqueous polymer dispersion in which, after 12 hours from acidification of the mixture to pH < 2.0 with strong acids, it is not possible to recognize coagulated polymer at the bottom of the flask where the mixture was prepared or particles floating in the mixture. This could be alone or combined with organic solvents. The aqueous polymer dispersion of the present invention may be used as a sole binder in a composition or in combination with other binders. This composition may be a one-component composition, meaning that no crosslinking agent needs to be added before use, or a two-component composition, meaning that a crosslinking agent must be added before use. This crosslinking agent may also be intended to be a reactive co-binder. In this latter case, the crosslinking agents could react with the hydroxyl groups provided by the comonomer c). Suitable crosslinking agents can be aminoplastic resins (phenolic resins, urea-formaldehyde resins, melamine-formaldehyde resins) or polyisocyanates; in particular, phenolic resins are preferred. Furthermore, the crosslinking agents can react with the carboxyl group provided by the comonomer d), and suitable crosslinking agents in this case can be polyaziridines or polycarbodiimides. These crosslinkable compositions can be used for textile articles or non-woven cellulose fibers, glass fibers, composite materials, textile fibers, woven and non-woven fabrics, paper, cardboard, wood including plywood and particleboard, metals, glass, plastics including plastic films. The following examples are provided solely to illustrate the present invention and its results and, accordingly, do not limit the scope and extent of the present invention. The following examples are presented to illustrate the invention and its results, and consequently, the scope of the invention is not limited to these examples. Experimental section Table 1: Table of raw materials used Preparation of aqueous polymer dispersions Example 1 (comparative) Production of an aqueous polymer dispersion: 1480 g of deionized water and 12 g of Disponil® FES32 are added to a glass reactor equipped with a condenser, a stirrer, a temperature control system, and inlets for nitrogen, the initiator solutions, and the preemulsion feed, respectively. A monomer preemulsion composed of 1087 g of deionized water, 141 g of Disponil® FES32, 48 g of Disponil® A1065, 1658 g of butyl acrylate, 2028 g of styrene, 79 g of methacrylic acid, and 231 g of hydroxyethyl methacrylate is prepared in another container equipped with a stirrer (pre-emulsifier). When the reactor contents have reached a temperature of 80°C, 286 g of the monomer preemulsion and 16 g of 10% aqueous sodium persulfate solution are added to the reactor.Approximately one minute after the initiator is added, the remaining portion of the monomer pre-emulsion and 300 g of 5% aqueous sodium persulfate solution are added over a period of 2 hours, taking care to maintain the reactor contents at 80°C throughout the introduction. The reaction medium is then maintained at 80°C for a further 45 minutes, after which it is cooled to 70°C. Separately, 53 g of 13% tert-butyl hydroperoxide and 143 g of 6% Bruggolite® FF6 solution are fed into the reactor at 60°C for a period of 90 minutes at a constant rate. Half an hour after the end of the previous addition, the resulting product is cooled to 35°C. Finally, the mixture is filtered through a 36 mesh sieve. The pH and solids content are adjusted respectively with ammonia between 5.0 and 6.0 and demineralized water at approximately 50%. The dispersion obtained has a pH of 5.6, a viscosity (Brookfield RVT at 20 rpm and 23°C) of 300 mPa.s, a dry residue (solids content) of 49.9% by weight (1 ha 105°C) and a pre-coagulated product content on a 275 mesh sieve of approximately 170 ppm and a particle size of 130 nm. This dispersion is comparative because its quantity of sulfo groups from the initiator is 0.03 meq / g (less than 0.05 meq / g which is the minimum required for the dispersion of the invention) calculating the quantity of hydroxyl groups of 0.42 meq / g against the total weight of monomers (corresponding to the total weight of polymer). Example 2 The authors of the present invention proceed as in Example 1 disclosed above, with the same quantities of reactants and the same overall duration of feeding the monomer pre-emulsion at a constant rate, but the amount of 5% sodium persulfate solution, fed together with the pre-emulsion, is increased to 895 g. The pH and solids content are adjusted with ammonia between 5.0 and 6.0 and demineralized water at approximately 50%. The resulting dispersion has a pH of 5.8, a viscosity (Brookfield RVT at 20 rpm and 23°C) of 160 mPa·s, a dry residue (solids content) of 50.7% by weight (1 ha at 105°C), and a precoagulated product content (passing through a 275 mesh sieve) of approximately 80 ppm with a particle size of 125 nm. Sulfo group content: 0.102 meq / g; OH group content: 0.42 meq / g. Example 3 (comparative) Production of an aqueous polymer dispersion: 1480 g of deionized water and 12 g of Disponil® FES32 are added to a glass reactor equipped with a condenser, a stirrer, a temperature control system, and inlets for nitrogen, the initiator solutions, and the preemulsion feed, respectively. A monomer preemulsion composed of 1087 g of deionized water, 141 g of Disponil® FES32, 48 g of Disponil® A1065, 1658 g of butyl acrylate, 2028 g of styrene, 79 g of methacrylic acid, and 231 g of hydroxyethyl methacrylate is prepared in another container equipped with a stirrer (pre-emulsifier). When the reactor contents have reached a temperature of 50°C, 286 g of the monomer pre-emulsion are added to the reactor, followed by 4.8 g of 13% tert-butyl hydroperoxide solution, 60 mg of ferrous sulfate dissolved in 2 g of deionized water, and 10.5 g of 6% Bruggolite® FF6 solution. Approximately one minute after the initiator addition, the remaining portion of the monomer pre-emulsion, 89 g of tert-butyl hydroperoxide, and 192 g of 6% Bruggolite® FF6 solution in deionized water are fed into the reactor at a constant feed rate for a period of 2 hours, taking care to maintain the reactor contents at a temperature of 65°C throughout the introduction.Next, the reaction medium is maintained at 65°C for a further 45 minutes, then cooled to 70°C and 53 g of 13% tert-butyl hydroperoxide and 143 g of 6% Bruggolite® FF6 solution are fed separately into the reactor at 60°C for a period of 90 minutes at a constant rate. Half an hour after the end of the previous addition, the resulting product is cooled to 35°C. Finally, the mixture is filtered through a 36 mesh sieve. The solids content is adjusted with demineralized water to approximately 50%. The resulting dispersion has a pH of 5.9, a viscosity (Brookfield RVT at 20 rpm and 23°C) of 1085 mPa.s, a dry residue (solids content) of 49.7% by weight (1 ha 105°C), and a precoagulated product content on a 275 mesh sieve of approximately 110 ppm and a particle size of 110 nm. Sulfo groups = 0 meq / g and OH = 0.42 meq / g. Example 4 (invention, with monomers having sulfonate functionality) The authors of the present invention proceed as in example 1 disclosed above, with the same reactants, but add to the pre-emulsion, after having transferred the quantities for the start of polymerization, 130 g more of NaAMPS 2405. After final treatment, the product is cooled, and the mixture is then filtered through a 36-mesh sieve. The pH and solids content are adjusted with ammonia to between 5.0 and 6.0, and demineralized water to approximately 50%. The resulting dispersion has a pH of 5.4, a viscosity (Brookfield RVT at 20 rpm and 23°C) of 2200 mPa·s, a dry residue (solids content) of 50.3% by weight (1 ha at 105°C), and a precoagulated product content on a 275-mesh sieve of approximately 151 ppm and a particle size of 126 nm. Sulfo groups = 0.104 meq / g and OH groups = 0.41 meq / g. The summary of the monomeric and initiator composition of the polymeric dispersions of examples 1 to 4 and their characteristics are reported respectively in Table 2 and Table 3: Table 2: Monomeric composition and starters used during feeding, for examples 1 to 4 (% of total monomers) Table 3: Characteristics of the polymeric dispersions of examples 1 to 4 Zeta potential The zeta potential is an indicator of the stability of colloidal dispersions. Its magnitude indicates the degree of electrostatic repulsion between similarly charged adjacent particles in a dispersion. When the potential is small, attractive forces can overcome this repulsion, and the dispersion can break down and flocculate. Therefore, colloids with a high zeta potential (negative or positive) are electrically stabilized, while colloids with a low zeta potential tend to coagulate. Using a Malvern Nanosizer ZS90, the inventors of the present invention measured the zeta potential of the polymer dispersion of the present invention at different pH values to assess its stability under severe conditions, i.e., very low pH (< 2.0). The zeta potential of the aqueous polymer dispersion of the examples of the present invention, measured at different pH values, is shown in the following graph 1. Using this graph, it is possible to recognize that examples 2 and 4, which show the best stability in methanol and under acidic conditions, also exhibit a lower zeta potential at pH < 2.0 than the comparative examples 1 and 3, which is a clear sign of greater stability at this lower pH. Stability test in methanol In a sealed glass flask with a magnetic stirrer, 950 g of methanol are slowly added to 100 g of polymer dispersion with 50% solids, while stirring. After the addition is complete, the mixture is stirred for an additional 60 minutes. The product is then considered stable if, after 12 hours, no coagulated polymer is visually visible at the bottom or any particles are floating in the mixture. Stability test in methanol and acid After preparing the mixture as described above in the methanol stability test, a few drops of 98% sulfuric acid are slowly added to the mixture under stirring to achieve a pH of < 2.0, as measured with indicator paper. Once the addition is complete, the mixture is stirred for another 60 minutes. The product is then considered stable if, after 12 hours, no coagulated polymer is visually visible at the bottom or any particles are floating in the mixture. The results of the stability test are shown in Table 4 below. Table 4: Stability test results (in hours) in methanol alone and with acidic pH of the polymer dispersions of examples 1 to 4
Claims
1. An aqueous polymer dispersion, characterized in that said polymer comprises units and / or groups derived from: a) at least one (meth)acrylic monomer which is an (meth)acrylic ester of a C1-C12 alcohol, the alcohol being linear (C1-C12) or branched (C4-C12), with no functional group other than (meth)acrylate; b) at least one monomer b1) or initiator b2), or both b1) and b2), as defined below: b1) at least one vinyl, allylic, or (meth)acrylic monomer, preferably vinyl or (meth)acrylic monomer, bearing an anionic group obtained from strong acids with pKa < 3, preferably < 2; b2) at least one initiator, bearing the same anionic group as b1); c) at least one vinyl, allylic, or (meth)acrylic monomer with hydroxy functionality, preferably vinyl or (meth)acrylic monomer; d) at least one monomer ethylenically unsaturated with carboxy functionality e) optionally, at least one vinyl monomer, bearing a single vinyl group,without any other functional group than the vinyl group, (f) optionally, at least one vinyl or (meth)acrylic monomer bearing at least one functional group selected from: nitrile, amide, acetoacetoxy, diacetone, free silane or alkoxy-blocked silane, epoxy, urea or ureide; (g) optionally, at least one multifunctional vinyl or (meth)acrylic monomer, wherein said polymer bears: • the anionic groups as defined in (b) in an amount of at least 0.05 meq / g, preferably from 0.07 to 0.3 meq / g (as calculated) with respect to said polymer and • hydroxy groups as defined in (c) in an amount of at least 0.1 meq / g, preferably from 0.1 to 0.8 meq / g (as calculated, see below) with respect to said polymer.
2. The aqueous dispersion according to claim 1, characterized in that said monomer d) is present in said polymer at a weight content with respect to said polymer of 0,0.5% to 6%.
3. The aqueous polymer dispersion according to claim 1 or 2, characterized in that said anionic groups as defined in b) are selected from the group consisting of: - a sulfonic acid group (-SO3H) (I) or a sulfuric acid half-ester group (II) and its corresponding salts or a phosphonic acid group (III) or a phosphoric acid partial ester group (IV and V) and its corresponding salts as presented in the following formulas (I) to (V) below and carried by the polymer moiety represented by R:
4. The aqueous polymer dispersion according to any one of claims 1 to 3, characterized in that said anionic groups defined in b) are derived from: b1) monomers selected from the group consisting of the following acids and their salts, preferably sodium, ammonium, or other cation salts, of: - 2-acrylamido-2-methylpropanesulfonic acid (VI), styrenesulfonic acid (VII), acids 1-allyloxy-2-hydroxypropanesulfonic acids (VIII),vinylsulfonic acid (IX), 3-sulfopropylacrylic acid (X), - monomeric partial esters of phosphoric acid and derivatives, such as bis(methacryloyloxyethyl) hydrogen phosphate (XI) or 2-(phosphonooxy)ethyl methacrylate (XII), vinylphosphonic acid (XIII). b2) initiators selected from the group consisting of: sodium persulfate, ammonium persulfate and potassium persulfate.
5. The aqueous polymer dispersion according to any one of claims 1 to 4, characterized in that said polymer further contains h) at least one polymerizable anionic and / or non-ionic surfactant in an amount of 0.1 to 5%, said polymerizable surfactant preferably being selected from: - for polymerizable anionic surfactants, polyoxyethylene 9-octadecenyl ether phosphate (XIV) unsaturated phosphate ester (XV) or allyl nonyl phenol ethoxylated sulfate (XVI,XVII) or polyoxyalkylene alkenyl ether sulfate (XVIII) as shown below in the following formulas: (C18 H36O HC 2H4O VPO 3H2 (XIV) RO-PO3 H2 (XV) where R is an alkyl group containing more than 10 carbon atoms and an unsaturation CH 3{ CH 2 ) 9 ( 11 chch 2º ch 2 ch = ch 2 Ó (EO) n SO3NH4 (XVIII) - for non-ionic polymerizable surfactants from: alkyl allyl ethoxylated (IXX) , allylnonyl phenol ethoxylated (XX) , respectively with the following structures: .. (XX) 6. The aqueous polymeric dispersion according to any one of claims 1 to 5, characterized in that the monomer c) is selected from: - (meth) hydroxyl alkyl acrylates C2-C4, in particular (meth)hydroxyethyl acrylate, (meth)hydroxypropyl acrylate or (meth)hydroxybutyl acrylate or - preferably allyl alcohol, the monomer c) being selected from C2-C4 (meth)hydroxyalkyl acrylates.
7. The aqueous polymer dispersion according to any one of claims 1 to 6,characterized in that said monomer f) is present and is selected from: acetoacetoxy(meth) acrylate, diacetone acrylamide, alkoxy silane monomers such as vinyl triethoxy ethyl silane or gamma-methacryloxypropyltrimethoxysilane, monomers containing ureido groups such as N-(2-methacryloyloxyethyl)-ethylene urea.
8. The aqueous polymer dispersion according to any one of claims 1 to 7, characterized in that said multifunctional monomer g) is present and is selected from ethylene glycol di(meth) acrylate, trimethylolpropane tri(meth) acrylate, or divinylbenzenes.
9. The aqueous dispersion according to any one of claims 1 to 8, characterized in that the monomer a) is selected from: (meth) methyl acrylate, (meth) ethyl acrylate, (meth) propyl acrylate, (meth) n-butyl acrylate, (meth) 2-ethylhexyl acrylate, (meth) 2-octyl acrylate, (meth) isooctyl acrylate, (meth) nonyl acrylate, (meth) decyl acrylate or (meth) dodecyl acrylate,preferably n-butyl acrylate and preferably in that monomer e) is selected from styrene and monomer f) is selected from acrylonitrile.
10. The aqueous dispersion according to any one of claims 1 to 9, characterized in that it is stable for at least 12 h when diluted with a large amount of organic solvent, i.e., a dilution with more than 30% w / w of organic solvent, with respect to the total weight of said aqueous polymer dispersion (including said solvent). The dispersion is considered stable if, after 12 h from dilution with more than 30% organic solvent, it is not possible to recognize coagulated polymer at the bottom of the flask in which the mixture was prepared or particles floating in the mixture.
11. The aqueous dispersion according to any one of claims 1 to 10, characterized in that it is stable for at least 12 h at a strongly acidic pH, i.e., pH < 2.0.in particular when diluted with an organic solvent to more than 30% w / w as defined in claim 10, the dispersion being considered stable if, after 12 hours from acidification of the mixture to pH < 2.0 with strong acids, no coagulated polymer can be recognized at the bottom of the flask in which the mixture was prepared, or particles floating in the mixture.
12. A binding composition, characterized in that it is a two-component composition, comprising at least an aqueous polymer dispersion as defined according to any one of claims 1 to 11, and said two-component composition further comprising a crosslinking agent.
13. A binding composition according to claim 12, characterized in that said crosslinking agent reacts with the hydroxyl groups contributed by the comonomer c), said crosslinking agent being preferably selected from: aminoplastic, phenolic, or urea-formaldehyde resins,Melamine-formaldehyde resins, polyisocyanates, polyaziridines, or polycarbodiimides, phenolic resins being particularly preferred.
14. A binding composition according to claim 12 or 13, characterized in that said crosslinking agent reacts with the carboxyl group provided by comonomer d), and in particular, said crosslinking agent is selected from polyaziridines or polycarbodiimides.
15. The use of a binding composition according to any one of claims 12 to 14, characterized in that it is applied to a substrate selected from: cellulose fibers, glass fibers, composite materials, textile fibers, woven and non-woven fabrics, paper, cardboard, wood, including plywood and particleboard, metals, particularly aluminum, glass, plastics, including plastic films.
16. The use of an aqueous polymer dispersion according to any one of claims 1 to 11,in a two-component crosslinkable binding composition for the treatment of textile articles or non-woven fabrics.