Multi-feed multi-RAMP processes for developing acrylic emulsions with inherent high scratch resistant coating properties

Abstract

Disclosed herein are acrylic emulsion compositions with an inherent scratch resistance property and methods of synthesizing and using the emulsion compositions.

Description

MULTI-FEED MULTI-RAMP PROCESSES FOR DEVELOPING ACRYLICEMULSIONS WITH INHERENT HIGH SCRATCH RESISTANT COATINGPROPERTIESFIELD OF THE DISCLOSURE

[0001] This disclosure relates generally to acrylic emulsions, and more particularly to acrylic emulsions with an inherent scratch resistance property, and to methods of synthesizing and using the emulsion compositions.BACKGROUND OF THE DISCLOSURE

[0002] Aqueous based coatings, such as for example latex or emulsion polymer coatings, constitute a significant segment of all coatings in use today. Aqueous based coatings present advantages over conventional oil-based coatings because they contain fewer undesirable volatile organic solvents and therefore are more environmentally friendly. These polymeric products are dispersed in an aqueous medium and are stable in this condition but can form continuous dry film upon removal of the water.

[0003] The properties of aqueous based coatings, especially acrylic polymer emulsions based coatings, make them well-suited for protective coatings. Protective coatings with a high scratch resistance are essential in various applications so safeguard surfaces from damage, enhance durability, and maintain aesthetic appeal. Scratch-resistant coatings are used to create a barrier against abrasions and wear, offering extended protection to underlying materials.

[0004] A typical approach to develop acrylic emulsions with high scratch resistance is to utilize additives like wax and slip-agents that increase its surface slip or by using silica- based additives that increase the overall hardness of the coating. High Tgacrylic emulsions may also be used to produce high scratch resistance coatings. However, such polymers typically demand a higher amount of solvent and plasticizer for effective particle coalescence. This increases the overall VOC content of the coating formulations. What is needed is an improvement over the foregoing.SUMMARY OF THE DISCLOSURE

[0005] Disclosed herein are aqueous dispersions of an acrylic polymer comprising particles of the acrylic polymer dispersed in an aqueous medium, wherein the acrylic emulsion, once cured, provides a high scratch resistant property. In another aspect, providedherein are processes for making the aqueous dispersion of acrylic polymers described here. In some embodiments, the aqueous polymer dispersion is prepared using a free radical emulsion polymerization process. In some embodiments, the free radical emulsion polymerization process is performed in a dual-feed reactor.

[0006] In one form thereof, the present disclosure provides a polymer emulsion composition comprising at least one block copolymer, at least one chain transfer agent, and at least one surfactant; wherein the polymer emulsion composition, once cured, has a scratch resistance of at least 4.5 (N) as measured with a nanoscratch tester.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.

[0008] Figure 1 provides a schematic of a dual-feed polymerization reactor used in the syntheses of the acrylic emulsions of the present disclosure.

[0009] Figure 2 provides a schematic of a single-feed polymerization reactor used in the syntheses of the acrylic emulsions of the present disclosure.DETAILED DESCRIPTION

[0010] The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of’ and “consisting of’ can be used in place of “comprising” and “including” to provide for more specific embodiments and are also disclosed. As used in this disclosure and in the appended claims, the singular forms “a”, “an”, “the”, include plural referents unless the context clearly dictates otherwise. The disclosure of percentage ranges and other ranges herein includes the disclosure of the endpoints of the range and any integers provided in the range.

[0011] I, Acrylic Emulsions with an Inherent Scratch Resistance

[0012] The present disclosure provides acrylic emulsions with an inherent high scratch resistant property, as well as synthesis methods for the aforementioned emulsions. The acrylic emulsions may be prepared via a free radical emulsion polymerization in a dualfeed reactor or a single-feed reactor.

[0013] A typical formulation for the emulsions of the present disclosure may comprise a copolymer, a chain transfer agent, and a surfactant. Other ingredients may be added to harden or soften the product. Colorants may also be added. Defoamers may be added.

[0014] The acrylic emulsions of the present invention may be acrylic or styrene- acrylic copolymers. Suitable monomers employed in the preparation of the emulsion include, but are not limited to, acrylic acid in an amount of from about 0% - 2.0% by weight, methacrylic acid in an amount of from about 0% - 2.0% by weight, styrene in an amount of from about 0% - 55% by weight, hydroxy ethylmethacrylate in an amount of from about 0% - 5% by weight, butyl acrylate in an amount of from about 0% - 48% by weight, butyl methacrylate in an amount of from about 0% - 25% by weight, methyl methacrylate in an amount of from about 0% - 55% by weight, diacetone acrylamide in an amount of from about 0% - 5% by weight, methacrylate in an amount of from about 0% - 15% by weight, ethyl acrylate in an amount of from about 0% - 15% by weight, glycidyl methacrylate in an amount of from about 0% - 5% by weight, 2-ethylhexyl acrylate in an amount of from about 0% - 40% by weight, isobutyl acrylate in an amount of from about 0% - 10% by weight, and isobutyl methacrylate in an amount of from about 0% - 10% by weight, based on the total weight of the composition.

[0015] In some embodiments, the copolymer may be a carboxylic acid-functional resin. In some embodiments, the carboxylic acid-functional resin may be an alkali soluble resin. In other words, the carboxylic acid-functional resin may react with alkali materials to form ion salts at the carboxylate groups of the polymer, thereby enhancing the water solubility characteristics of the resin. Suitable monomers for preparation of the carboxylic acid-functional resin and the low molecular weight copolymer include monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, acrylic anhydride, methacrylic anhydride, itaconic anhydride, maleic anhydride, fumaric anhydride, crotonic anhydride, styrene, methyl styrene, alpha-methyl styrene, ethyl styrene, isopropyl styrene, tertiary -butyl styrene, ethyl methacrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, ethyl acrylate, vinyl acetate, methyl acrylate, openchain conjugated dienes, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, methylol acrylamide, glycidyl acrylate, glycidyl methacrylate, vinyl esters, vinyl chloride, or mixtures of any two or more such monomers. In some embodiments, the carboxylic acidfunctional support resin includes polymerized monomers of one or more of ethyl methacrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate,ethyl acrylate, vinyl acetate, methyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, or mixtures of any two or more such monomers. In one embodiment, the carboxylic acid-functional resin includes polymerized monomers of one or more acrylic acid, ethyl methacrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, ethyl acrylate, vinyl acetate, methyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, styrene, methyl styrene, alpha-methyl styrene, diacetone acrylamide, ureido methacrylate, or a mixture of any two or more such monomers. In some embodiments, the carboxylic acid-functional resin may include a co-polymer including two or more of styrene, methyl methacrylate, and acrylic acid. In some embodiments, the carboxylic acidfunctional support resin may include a copolymer of acrylic acid and styrene.

[0016] The polymer or polymers used within the emulsions may have a glass transition temperature (Tg) for the individual polymer from -60 °C to 130 °C or any subrange or value within this range. For example, any given polymer within an emulsion may have a Tg from -60 °C to 100 °C, from -60 °C to 75 °C, from -60 °C to 50 °C, from - 15 °C to 50 °C, from -15 °C to 45 °C, from -15 °C to 40 °C, from -15 °C to 35 °C, from - 15 °C to 30 °C, from -15 °C to 25 °C, from -15 °C to 20 °C, from -15 °C to 15 °C, from - 15 °C to 10 °C, from -15 °C to 5 °C, from -15 °C to 0 °C, from 0 °C to 50 °C, from 0 °C to 45 °C, from 0 °C to 40 °C, from 0 °C to 35 °C, from 0 °C to 30 °C, from 0 °C to 20 °C, from 0 °C to 15 °C, from 0 °C to 10 °C, from 10 °C to 50 °C, from 10 °C to 45 °C, from 10 °C to 40 °C, from 10 °C to 35 °C, from 10 °C to 30 °C, from 10 °C to 25 °C, from 10 °C to 20 °C, or any range including any two of these values as endpoints.

[0017] The emulsion or combination of polymers may have a glass transition temperature (Tg) for the individual polymer from -60 °C to 130 °C or any subrange or value within this range. For example, any given polymer within an emulsion may have a Tg from -60 °C to 100 °C, from -60 °C to 75 °C, from -60 °C to 50 °C, from -15 °C to 50 °C, from - 15 °C to 45 °C, from -15 °C to 40 °C, from -15 °C to 35 °C, from -15 °C to 30 °C, from - 15 °C to 25 °C, from -15 °C to 20 °C, from -15 °C to 15 °C, from -15 °C to 10 °C, from - 15 °C to 5 °C, from -15 °C to 0 °C, from 0 °C to 50 °C, from 0 °C to 45 °C, from 0 °C to 40 °C, from 0 °C to 35 °C, from 0 °C to 30 °C, from 0 °C to 20 °C, from 0 °C to 15 °C, from 0 °C to 10 °C, from 10 °C to 50 °C, from 10 °C to 45 °C, from 10 °C to 40 °C, from 10 °C to 35 °C, from 10 °C to 30 °C, from 10 °C to 25 °C, from 10 °C to 20 °C, or any range including any two of these values as endpoints.

[0018] The polymers may be formed from emulsion-polymerizable monomers. Emulsion-polymerizable monomers are known in the art, see e.g. U.S. Patents Nos. 4,820,762; 7,253,218; 7,893,149; and U.S. Patent Publication No. 2015 / 0166803, each of which are incorporated herein by reference. The emulsion polymerizable monomer may include an ethylenically unsaturated monomer. In some embodiments, emulsion polymerizable monomer may include at least one ethylenically unsaturated nonionic monomer. By "nonionic monomer" herein is meant that the copolymerized monomer residue does not bear an ionic charge between pH 1 and 14. Suitable ethylenically unsaturated nonionic monomers include, but are not limited to, (meth)acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; (meth)acrylonitrile; (meth)acrylamide; ureido-functional monomers; monomers bearing acetoacetate-functional groups; styrene and substituted styrenes; butadiene; ethylene, propylene, .alpha. -olefins such as 1-decene; vinyl acetate, vinyl butyrate and other vinyl esters; and vinyl monomers such as vinyl chloride, vinylidene chloride.

[0019] The emulsion-polymerizable monomer may include acrylate monomers, methacrylate monomers, styrene monomers, or a mixture of any two or more thereof. In some embodiments, the emulsion polymerizable monomer does not include styrene monomers.

[0020] In some embodiments, the at least one emulsion polymerizable monomer may be a C1-C4 acrylate, a C1-C4 (meth)acrylate, or a mixture of any two or more thereof. In some embodiments, the emulsion-polymerizable monomer may be n-butyl acrylate, 2- ethylhexyl acrylate, methyl acrylate, methyl methacrylate, styrene, ethyl acrylate, or a mixture of any two or more thereof.

[0021] In some embodiments, the emulsion polymerizable polymer may include one or more keto-functional monomers. Examples of keto-functional monomers include diacetone acrylamide, diacetone methacrylamide, diacetone acrylate, diacetone methacrylate, acetoacetoxymethyl (meth)acrylate, 2-(acetoacetoxy)ethyl (meth) acrylate, 2- acetoacetoxypropyl(meth)acrylate, butanediol-l,4-acrylate-acetylacetate, vinyl methyl ketone, vinyl ethyl ketone, and vinyl isobutyl ketone, allyl acetoacetate, vinyl acetoacetate, 1,4 butane diol diacrylate or vinyl acetoacetamide. In one embodiment, the emulsion polymerizable polymer includes a repeat unit derived from diacetone acrylamide.

[0022] The emulsions may be formed thorough an emulsion polymerization reaction, which may involve at least one emulsion polymerizable monomer, a low molecular weight copolymer, and other ingredients and / or reagents, such as an initiator. In some embodiments, the emulsion polymerization occurs in a dual-feed reactor and in some embodiments the emulsion polymerization occurs in a single-feed reactor.

[0023] The initiator may be a water-soluble compound for ready mixing and blending with the emulsions. Non-limiting examples of water-soluble initiators for the emulsion polymerization include ammonium salts and alkali metal salts of peroxydisulfuric acid, e.g., sodium peroxodi sulfate, hydrogen peroxide or organic peroxides, e.g., tert-butyl hydroperoxide. The initiator may be a thermal initiator. Suitable initiators include, but are not limited to 2,2'-azobis(2-methylpropionamidine)dihydrochloride, ammonium persulfate, sodium persulfate, and potassium persulfate. Also suitable are reduction-oxidation (redox) initiator systems. The redox initiator systems consist of at least one, usually inorganic, reducing agent and an organic or inorganic oxidizing agent. The oxidizing component comprises, for example, the emulsion polymerization initiators already identified above. The reducing components comprise, for example, alkali metal salts of sulfurous acid, such as, for example sodium sulfite, sodium hydrogensulfite, alkali metal salts of disulfurous acid such as sodium disulfite, bisulfite addition compounds with aliphatic aldehydes and ketones, such as acetone bisulfite, or reducing agents such as hydroxymethanesulfinic acid and its salts, or ascorbic acid. The redox initiator systems can be used along with soluble metal compounds whose metallic component is able to exist in a plurality of valence states. Typical redox initiator systems are, for example, ascorbic acid / iron(II) sulfate / sodium peroxy di sulfate, tert-butyl hydroperoxide / sodium disulfite, tert-butyl hydroperoxide / Na hydroxymethanesulfinic acid. The individual components, the reducing component for example, may also be mixtures, an example being a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium disulfite. The stated compounds are used usually in the form of aqueous solutions, with the lower concentration being determined by the amount of water that is acceptable in the dispersion, and the upper concentration by the solubility of the respective compound in water. Generally speaking, the concentration is 0.1% to 30% by weight, preferably 0.5% to 20% by weight, more preferably 1.0% to 10% by weight, based on the solution. The amount of the initiators is generally 0.1% to 10% by weight, preferably 0.5% to 5% by weight, based on the monomers to be polymerized. It is also possible for two or more different initiators to be used in the emulsion polymerization.

[0024] In some embodiments, an initiator may be ammonium persulfate and an oxidizer may be t-butyl hydroperoxide. In such case, a weight ratio between ammonium persulfate and t-butyl hydroperoxide may range from 40: 1 to 2: 1 or from 30: 1 to 4: 1 or any subrange or value within these ranges.

[0025] In some embodiments, the emulsion includes one or more chain transfer agents or diacrylate or triacrylate monomers to control molecular weight, branching and / or gel formation. Such monomers include, but are not limited to, isooctyl mercaptopropionate (IOMPA), butylmercaptopropionate, 1,6 hexane diol diacrylate and trimethylolpropane triacrylate, 2-ethyl hexylmercaptopropionate, tertiary dodecylmercaptan, and thioglycerol.

[0026] As described herein, incorporation of crosslinker into the polymer emulsion may help to improve the scratch resistance properties of the resulting cured coatings. In general, the amounts of the chain transfer agents employed can as low as 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, or as high as 8 wt.%, 9 wt.%, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, or within any range encompassed by any two of the foregoing values as endpoints, based on the total weight of the polymer emulsion. For example, the amount of chain transfer agent may be from 0.5 wt.% to 15 wt.%, from 0.1 wt.% to 10 wt.%, or from 0.5 wt.% to 10 wt.%.

[0027] The polymer emulsions described herein may also contain a surfactant. In some embodiments, the surfactant is anionic or non-ionic. In some embodiments, the surfactant contains one or more fatty alcohol alkoxylates. In further embodiments, the one or more fatty alcohol alkoxylates are fatty alcohol ethoxylates, fatty alcohol propoxylates, or any combination thereof. In some embodiments, the surfactant contains one or more ethylene oxide / propylene oxide block copolymers. In some embodiments, the surfactant contains one or more fatty alcohol ethoxylates. In some embodiments, the surfactant contains one or more alkyl sulfosuccinate ethoxylates. In some embodiments, the surfactant contains one or more fatty alcohols having an alkyl chain length of about 12 to about 18 carbons; and a degree of ethoxylation of about 10 to about 80 molar ethylene oxide units. In some embodiments, the surfactant includes non-ionic surfactants. In some embodiments, the surfactant includes anionic surfactants. In some embodiments, the anionic surfactant includes one or more alkyl sulfonates, alkyl benzene sulfonates, alkyl sulfates, alkyl benzene sulfates, phosphates, phosphinates, fatty carboxylates, or any combination of two or more thereof.

[0028] In general, the amounts of the surfactants employed can be varied from 0.3% to 1% by weight, based on the total amount of the monomers to be polymerized.

[0029] The polymer emulsion compositions of the present disclosure, once cured may have a scratch resistance of at least 3 (N), at least 3.5 (N), at least 4 (N), at least 4.5 (N), at least 5 (N), at least 5.5 (N), at least 6 (N), at least 6.5 (N), or at least 7 (N).

[0030] The polymer compositions described herein may contain other materials such as, but not limited to, other aqueous resin solutions, rheology modifiers, wetting agents, defoamers, thickeners, stabilizers, buffering agents, salts, preservatives, fire retardants, biocides, corrosion inhibitors, cross-linkers, lubricants, colorants, dyes, waxes, perfumes, and fillers.II. Methods of Making Emulsions

[0031] The emulsions of the present disclosure may be formed through an emulsion polymerization, which relies on the use of small molecule surfactants containing a polar / hydrophilic group and a nonpolar / hydrophobic group. The amphiphilic nature of these materials allows them to effectively stabilize heterogenous solutions (i.e., polymer particles in water). The emulsion polymerization reactions of the present disclosure may be performed in a dual-feed reactor such as the one depicted in FIG. 1. As shown therein, the reactor 14 is fed with two tanks 12 and 16. Pumps 18 and 22 help convey the contents of tanks 12 and 16 into the reactor 14. Tank 10 typically contains the initiator solution and is fed into tank 14 via pump 20.

[0032] The reactor 14 may be equipped with a water bath, mechanical stirrer, temperature control probes, feeding tubes for monomer addition, feeding tubes for initiator addition, and reflux condensers.

[0033] For a dual-feed reactor, in general, each tank may be charged with the contents listed below in Table 1.Table 1. Charges for different vessels in dual-feed reactor depicted in FIG. 1.

[0034] Three different methods may be employed for the synthesis process: a single pre-emulsion feed method, a two pre-emulsion ramp and constant feed method, and a two- pre-emulsion multi-ramp method.

[0035] In the single pre-emulsion feed method the reactor may first be charged with the required amount of de-ionized water, surfactant and seed. Then the reactor may be heated to a temperature of 50°C to 100°C, preferably around 85°C. Once the desired temperature is reached, an initial initiator short may be added instantly, followed by the start of a pre-emulsion feed. The pre-emulsion feed may last from 5 minutes to 60 minutes, preferably around 15 minutes. Next, the second charge of initiator feed may be started. The total feeding time may be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. At the end of the pre-emulsion feed, the reactor may be held at a temperature of 50°C to 100°C, preferably around 85°C for around 30 minutes before flush water is added to reduce the reactor’s temperature to around 70°C. At this point, delayed oxidizer and reducer feeds may be started to reduce the amount of residual monomers. Once the chemical strip process is completed, the reaction is cooled to around room temperature. Finally, post-addition solutions may be added to the reactor and mixed for around 15 minutes before the completed polymer is filtered into a storage container.

[0036] In the two pre-emulsion ramp and constant feed process, the reactor setup is similar to the single-emulsion process described above, except two separate pre-emulsion feeds are pumped into the reactor. Initially, the reactor may be charged with a required amount of de-ionized water, surfactant, and seed. Then the reactor may be heated to a temperature of 50°C to 100°C, preferably around 85°C. Once the desired temperature is reached, an initial initiator short may be added instantly, followed by the start of a first pre- emulsion feed. After about 15 minutes of feeding the first pre-emulsion feed, the second charge of initiator feed may be started. The total feeding time for the first pre-emulsion feed and the second charge of the initiator feed may be about 1 hour, about 2 hours, about 3 hours, about 4 hours, or about 5 hours. Following the feeding of the first pre-emulsion feed and the second charge of initiator feed, the reactor may be held for about 15 minutes before the third charge of initiator feed and the second pre-emulsion feed is added. The third charge of initiator feed and second pre-emulsion feed may have a feeding time of about 30 minutes, about 45 minutes, or about 1 hours. At the end of the feeding time, the reactor maybe held at 85°C for about 30 minutes before flush water is added to reduce the reactor temperature to about 70°C. At this point, delayed oxidizer and reducer feeds may be started to reduce the amount of residual monomers. Once the chemical strip process is completed, the reaction is cooled to around room temperature. Finally, post-addition solutions may be added to the reactor and mixed for around 15 minutes before the completed polymer is filtered into a storage container.

[0037] In the 2 pre-emulsion multi-ramp synthesis method, both the pre-emulsion feeds are fed into the reactor simultaneously. Initially, the reactor may be charged with a required amount of de-ionized water, surfactant, and seed. Then the reactor may be heated to a temperature of 50°C to 100°C, preferably around 85°C. Once the desired temperature is reached, an initial initiator short may be added instantly, followed by the start of the first and second pre-emulsion feeds simultaneously. After about 15 minutes, the second charge of initiator feed may be started. The total feeding time may be about 1 hour, about 2 hours, about 3 hours, about 4 hours, or about 5 hours. At the end of the feeding time, the reactor may be held at 85°C for about 30 minutes before flush water is added to reduce the reactor temperature to about 70°C. At this point, delayed oxidizer and reducer feeds may be started to reduce the amount of residual monomers. Once the chemical strip process is completed, the reaction is cooled to around room temperature. Finally, post-addition solutions may be added to the reactor and mixed for around 15 minutes before the completed polymer is filtered into a storage container.

[0038] As described herein, the free radical initiators can be water-soluble initiators. Examples of such water-soluble initiators can include but are not limited to, persulfates such as sodium persulfate (Na2S20s), ammonium persulfate and potassium persulfate; peroxides such as hydrogen peroxide and tert-butyl hydroperoxide (t-BHP); and azo compounds such as VAZO™ initiators, commercially available from The Chemours Company. They can be used alone or in combination with one or more reducing agents or activators, for example, bisulfites, metabisulfites, ascorbic acid, erythorbic acid, sodium formaldehyde sulfoxylate, ferrous sulfate, ferrous ammonium sulfate, and ferric ethylenediamine tetraacetic acid.

[0039] In general, the amounts of the free-radical initiators employed can be varied from 0.1% to 1% by weight, based on the total amount of the monomers to be polymerized.

[0040] For a single-feed reactor, in general, each tank may be charged with the contents listed below in Table 2.Table 2. Charges for different vessels in single-feed reactor depicted in FIG. 2.

[0041] Referring to FIG. 2, for example reactor 44 is charged with Dl-water which is then heated to 85°C. Acid monomer at 80°C is added to reactor 44 at one shot followed by an initial initiator shot from tank 40 which is pumped into reactor 44 via pump 30. Then, the pre-emulsion feed in tank 42 comprising Dl-water, surfactant, Monomer A, Monomer B, and optionally a chain transfer reagent is pumped through pump 32 to feed into reactor 44 . After 15 minutes of pre-emulsion, a second charge of initiator feed from tank 40 is pumped into reactor 44. The total feeding time is three hours. At the end of pre-emulsion, the neat monomer and initiator feeds hold the reactor at 85°C for 30 minutes and then flush water is added to reduce the temperature to 70°C. After completion of the chemical stripping process, reactor 44 is cooled to room temperature before the polymer finished polymer is filtered into a storage container.

[0042] The Examples below are intended to further illustrate certain aspects of the methods and compositions described herein and are not intended to limit the scope of the claims.EXAMPLES

[0043] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compositions and / or methods claimed herein are made and evaluated and are intended to be purely exemplary and are not intended to limit the scope of the disclosure. Unless indicated otherwise, partsare parts by weight, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric.I. Synthesis of Acrylic Emulsions

[0044] Initially, the polymerization reactor was charged with a required amount of Dl-water, surfactant amount and seed polymer. The reactor was heated to 85°C and at 80°C acid monomer was added at one shot. Then at 85°C an initial initiator shot was instantly added. After the initiator shot, pre-emulsion-1 and pre-emulsion-2 / neat monomer feeds were started simultaneously (for the dual-feed processes) or the single pre-emulsion feed was started (for the single-feed process). After 15 minutes of pre-emulsion and neat monomer feeds, the second charge of initiator feed was started. The total feeding (Neat Monomer + Pre-emulsion + Initiator) time was 3 hours. At the end of pre-emulsion, the neat monomer and initiator feed held the reactor at 85°C for 30 minutes and then flush water was added to reduce the reactor temperature to 70°C. At 70°C, delayed oxidizer and reducer feeds were started to reduce the residual monomers. After the completion of chemical strip process, the reaction was cooled to room temperature. Finally post addition solution was added and the reactor mixed the contents for 15 minutes before filtering the polymer in storage container.Table 3. List of acrylic emulsion formulations

[0045] The acrylic emulsions 1-5 from Table 3 were incorporated into coating formulations with the ingredients provided in Table 4 below.Table 4. Mass balance for coating formulations 1-5

[0046] Coating Formulations 1-5 were cured on a substrate and subsequently tested for their scratch resistance using a Fischerscope ST30 Nanoscratch Tester.Table 5. Scratch resistance for Coating Formulations 1-5

[0047] The results from the scratch resistance test demonstrate that coating formulation 4 which was prepared using a single-feed reactor setup with no ramping up from a second tank had the highest scratch resistance.

[0048] The compositions and methods of the appended claims are not limited in scope by the specific compositions and methods described herein, which are intended as illustrations of a few aspects of the claims and any compositions and methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compositions and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative compositions and method steps disclosed herein are specifically described, other combinations of the compositions and method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of’ and “consisting of’ can be used in place of “comprising” and “including” to provide for more specific embodiments of the invention and are also disclosed. Other than in the examples, or where otherwise noted, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood at the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, to be construed in light of the number of significant digits and ordinary rounding approaches.

Claims

WHAT IS CLAIMED IS1. A polymer emulsion composition comprising at least one block copolymer, at least one chain transfer agent, and at least one surfactant; wherein the polymer emulsion composition, once cured, has a scratch resistance of at least 4.5 (N) as measured with a nanoscratch tester.

2. The polymer emulsion of claim 1, wherein the emulsion composition has a glass transition temperature from -60°C to 130°C.

3. The polymer emulsion of claim 1, wherein the copolymer is an acrylic or styrene- acrylic copolymer.

4. The polymer emulsion composition of claim 1 wherein the polymer comprises the functional monomers acrylic acid, methacrylic acid, styrene, alpha-methylstyrene, hydroxyethylmethacrylate, esters of acrylic acid, or methacrylic acid, diacetone acrylamide, 1,4 butane diol di acrylate and 1,6 Hexane diol di acrylate.

5. The polymer emulsion of claim 1, wherein the chain transfer agent is present in an amount of from 0.1 wt. % to 10 wt. % based on the total weight of the composition.

6. The polymer emulsion of claim 1, wherein the chain transfer agent is selected from the group consisting of isooctyl mercaptopropionate (IOMPA), butylmercaptopropionate, 2- ethyl hexylmercaptopropionate, tertiary dodecylmercaptan, and thioglycerol.

7. The polymer emulsion of claim 1, wherein the surfactant or reactive surfactant is present in an amount of from 0.3 wt. % to 1 wt. % based on the total weight of the composition8. The polymer emulsion of claim 1, wherein the surfactant is selected from the group consisting of fatty alcohol alkoxylates, fatty alcohol ethoxylates, ethylene oxide block copolymers, propylene oxide block copolymers, alkyl sulfonates, alkyl benzene sulfonates, alkyl sulfates, alkyl benzene sulfates, phosphates, phosphinates, or fatty carboxylates.

9. The polymer emulsion of claim 1, wherein the emulsion further comprises an aqueous resin solution, rheology modifier, wetting agent, defoamer, thickener, stabilizer, buffering agent, salt, preservative, fire retardant, biocide, corrosion inhibitor, cross-linker, lubricant, colorant, dye, wax, perfume, or filler.

10. A method for producing the polymer emulsion of claim 1 in a reactor comprising(i) charging a polymerization reactor with Dl-water, surfactant, and seed polymer;(ii) adding an initiator to the reactor;(iii) feeding monomers into the reactor to form a polymer composition;(iv) adding flush water to the reactor;(v) chemically stripping the polymer composition; and(vi) filtering the polymer composition into a storage container.

11. The method of claim 10, wherein the polymer composition comprises gradient molecular weight polymeric chains.

12. The method of claim 10, wherein the monomers are fed into the reactor from two separate tanks.

13. The method of claim 12, wherein the amount of monomers from each tank is ramped-up or ramped-down during the feed.

14. The method of claim 12, wherein the amount of monomers from first tank is ramped up while the amount of monomers from the second tank is ramped down during the feed.

15. The method of claim 12, wherein the amount of monomers from first tank is ramped up while the amount of monomers from the second tank is kept constant during the feed.

16. The method of claim 10, wherein the monomers are fed into the reactor from a single tank.

17. The method of claim 16, wherein the amount of monomers from the single tank is ramped-up or ramped-down during the feed.

18. The method of claim 10, wherein the dual power feed synthesis process produces a gradient Tg.

19. A substrate coated with the composition of claim 1.

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