CA1067233A - Method for producing surfactant-free water based enamels - Google Patents
Method for producing surfactant-free water based enamelsInfo
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- CA1067233A CA1067233A CA251,359A CA251359A CA1067233A CA 1067233 A CA1067233 A CA 1067233A CA 251359 A CA251359 A CA 251359A CA 1067233 A CA1067233 A CA 1067233A
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Abstract
METHOD FOR PRODUCING SURFACTANT-FREE WATER-BASED ENAMELS
ABSTRACT OF THE DISCLOSURE
The formation of surfactant-free water-based paints is described. The paint is made up of a mixture of (a) an amino resin cross-linking agent, (b) a mixture of three copolymers of acrylic monomers, one of which is a stabilizer polymer and (c) an amine. Elimination of conventional surfactants by the stabilizing polymer eliminates the prior problems of incompatibility and water sensitivity.
ABSTRACT OF THE DISCLOSURE
The formation of surfactant-free water-based paints is described. The paint is made up of a mixture of (a) an amino resin cross-linking agent, (b) a mixture of three copolymers of acrylic monomers, one of which is a stabilizer polymer and (c) an amine. Elimination of conventional surfactants by the stabilizing polymer eliminates the prior problems of incompatibility and water sensitivity.
Description
This invention relates to the formation of water-based paints. This application is a division of copending Canadian application Serial No. 228,423 filed May 30, 1975.
Water-based paints of the prior art have included "solution paints" and "emulsion (or latex) paints" with distinction being made with reference to the manner in which the sole or principal binder polymer is dispersed within the aqueous medium.
In those paints wherein the sole or principal binder polymer is soluble in the aqueous medium, the polymer is ordinarily of low molecular weight. These paints can be formulated to provide coatings of very high gloss. They tend to be slow drying and prone to sagging during application and to solvent popping during baking under high humidity conditions.
Application solids are much lower than comparable latex paints.
The emulsion or latex paints have employed as their sole or principal binder polymer a polymer of very high molecular weight, i.e., in the range of about 100,000 to about 1,000,000 or higher. Such paints have been characterized by rapid drying and comparatively low gloss relative to paints based on water-soluble polymers.
Water-soluble polymers of high molecular weight have been added to latex paints as thickeners. Characteris-tically, such thickener polymers are used in very small amounts, e.g., of the order of one percent.
It has been discovered that water-based paints having a superior combination of physical properties and application characteristics can be obtained by using certain novel combinations of solution polymers and emulsion polymers.
The coatings obtained from these hybrid compositions exhibit
Water-based paints of the prior art have included "solution paints" and "emulsion (or latex) paints" with distinction being made with reference to the manner in which the sole or principal binder polymer is dispersed within the aqueous medium.
In those paints wherein the sole or principal binder polymer is soluble in the aqueous medium, the polymer is ordinarily of low molecular weight. These paints can be formulated to provide coatings of very high gloss. They tend to be slow drying and prone to sagging during application and to solvent popping during baking under high humidity conditions.
Application solids are much lower than comparable latex paints.
The emulsion or latex paints have employed as their sole or principal binder polymer a polymer of very high molecular weight, i.e., in the range of about 100,000 to about 1,000,000 or higher. Such paints have been characterized by rapid drying and comparatively low gloss relative to paints based on water-soluble polymers.
Water-soluble polymers of high molecular weight have been added to latex paints as thickeners. Characteris-tically, such thickener polymers are used in very small amounts, e.g., of the order of one percent.
It has been discovered that water-based paints having a superior combination of physical properties and application characteristics can be obtained by using certain novel combinations of solution polymers and emulsion polymers.
The coatings obtained from these hybrid compositions exhibit
- 2 - ~
hiall gloss and generally excellent appearance.
In accordance with the present invention, there is provided an improvement in a method for producing an aqueous dispersion of paint in which a carboxy-functional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin cross-linking agent selected from melamine-formaldehyde resins and urea-formal-dehyde resins in an aqueous solution of water and water-soluble amine, wherein the carboxy functional polymer, amino resin cross-linking agent and water-soluble amine constitute about 30 to 50~ by weight of the continuous aqueous phase of the paint with the balance of the continu-. ous aqueous phase being water or a mixture of water and an organic solvent, the water soluble amine is present in an amount sufficient to provide an aqueous phase pH of about : 7.1 to about 8.5, and said water or mixture of water and organic solvent constitutes about 50 to about 65% by weight of the paint.
The improvement in this method is the aqueous dispersion being produced by intimately dispersing with the water, the amino resin cross-linking agent and the water-soluble amine: I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that: (a) is at least par-tially neutralized with water-soluble amine, (b) is soluble in the aqueous solution, (c) has average molecular weight (M ) in the range of about 3,000 to abou~ 20,000, and (d~
has Tg in the range of -15C to 50C, II. an aqueous emulsion consisting essentially of water, water-soluble amine, and about 50 to 95 parts by weight of an emulsion polymer having functionality selected from carboxy function-~ _ 3 _ B
~067Z33 ality and hydroxy f.unctlonality and is a oopoly~er of acrylic mono~ers that: (a) is essentially insoluble in the aqueous solution, (b) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (c) has Tg in the range of -15C to 50C, and III. about 0.025 to about 5 parts by weight of a stabilizer polymer which is a carboxy-functional copolymer of acrylic monomers that: (a) is soluble in the aqueous solution, (b) has average molecular weight (Mn) lower than . that of the solution polymer, and (c) has Tg of -15C to 50C, the stabilizer polymer being introduced into the dispersion intimately mixed with at least one of the solution polymer and the emulsion polymer.
- 3a -~067Z33 The term "parts" when used herein without further desi~nation shall mean "parts by weight".
The term "acrylic monomer" shall mean acrylic acid, methacrylic acid, esters of acrylic acid and a Cl - C8 monohydric alcohol, e.g., ethyl acrylate butyl acrylate, hexyl acrylate and 2-ethylhexyl acrylate, esters of methacrylic acid and a Cl - C8 monohydric alcohol, e.g., methyl methacrylate, butyl methacrylate, hexyl methacrylate and 2-ethylhexyl methacrylate, hydroxyalkYl acrylates, e.g., hydroxyethyl acrylate and hydroxypropyl acrylate, hydroxyalkyl methacrylates, e.g., hydroxyethyl methacrylate and hydroxypropyl methacrylate, acrylamide, methacrylamide, methylolacrylamides, e.g., n-methylolacrylamide, methylol-methacrylamides, e.g., N-methylolmethacrylamide, alkyl ethers of methylolacrylamides, e.g., N-isobutoxymethylolacrylamide, and alkyl ethers of methylolmethacrylamides, e.g., N-isobutoxy-methylolmethacrylamide.
The term "copolymer of acrylic monomers" shall mean a polymer of at least two different monoethylenically unsaturated monomers of which more than 50 mole percent are acrylic monomers.
The term "water-dilutable organic solvent"~means an organic solvent or mixture of organic solvents which is either miscible with water or will mix with water up to a concentration of at least one volume of solvent per three volumes of water without phase separation. Ordinarily, such solvent, when present in the paint, enters the paint through its use in the preparation of the solution resin, as herein-before described. In such embodiment, the solution polymer is, of course, soluble therein. In another embodiment, it may be added independently, if desired. In the latter case, the solution polymer may not ~e fully soluble therein.
The hybrid, water-based, paint compositions formed in accordance with this invention employ in combination a low molecular weight emulsion polymer and a low molecular weight solution polymer with the latter being present in an amount sufficient to contribute significantly to the composi-tion of the polymeric binder, i.e., at least about 5 weight percent of this polymeric combination. Thus, they differ from the conventional emulsion type paints employing a water-soluble thickener polymer in at least three compositional respects irrespective of chemical functionality, namely, (1) the emulsion polymers of the instant paints have significantly lower molecular weights, (2) the solution polymers of the instant paints have significantly lower molecular weights, and (3) the solution polymers of the instant paints are employed in significantly higher concentrations than are the water-soluble thickener polymers.
More specifically, the hybrid paint compositions formed in this invention, exclusive of optional components such as pigments, particulate fillers and catalysts, have a liquid continuous aqueous phase. About 30 to about 50% by weight of this phase, exclusive of the afore-cited optional components, is made up of a mixture of (a) an amino resin cross-linking agent; (b) a mixture of three copolymers of acrylic monomers; and (c) an amine. The balance is water or, in certain embodiments, water and an organic solvent.
The amine is a water-soluble amine and is present in an amount sufficient to solubilize the solution polymer in the aqueous phase at a pH range of about 7.1 to about 8.5. In certain embodiments, hereinafter illustrated, these hybrid compositions include organic cosolvents while in other 10~i7-33 embodim^nts such solvents are not present.
~ hen applied to the substrate to be coated by spraying, these water-based paints including pigments, particulate fillers, and catalysts, if any, contain between about 50 and about 65~ by weight water or in those embodi-ments wherein such solvents are used, water and organic cosolvents.
In one embodiment of the method of this invention, - at least one of the polymers, usually the solution polymer, is polymerized in solution in a water miscible or dilutable organic solvent while the other polymer, usually the emulsion polymer, is prepared by an emulsion polymerization in water. The resultant water-based paint will contain a conventional, essentially non-reactive, water-miscible or dilutable organic paint solvent. The concentration of organic solv~nt in such paints will be at least about 5~ by volume of the volatile phase, i.e., organic solvent an~
water, and preferably in the range of about 10 to about 20 volume percent of the volatile phase. In carrying out the emulsion polymerization the conventional surfactant, i.e., surface active agent or emulsifier, is replaced by a stabilization solution polymer hereinafter more fully described.
In another embodiment of the method of this invention, both the solution polymer and the emulsion polymer are prepared by emulsion polymerization in water as claimed in our ccpending application Serial No. 251,302 filed concurrently herewith. The paints thus prepared are prepared without organic solvents and thus employed free of same.
Organic solvents in the amounts used in the first embodiment may be added to the dispersion, if desired. In carrying out one or both, preferably both, of the emulsion polymerizations the conventional I ~ .
1~67Z33 ,lrfactant is replaced by the stabilizing solution polymer hereinafter more fully described.
The advantage provided by the invention is that elimination of the conventional surfactant eliminates the problem of incompatibility and water sensitivity associated with the use of surfactants.
The solution polymer used to form the paints in this invention has carboxy functionality and may also have hydroxy functionality and/or amide functionality. These polymers usually contain about 5 to about 30 mole percent of acrylic or methacrylic acid and 70 to 95 mole percent of olefinically unsaturated monomers copolymerizable with such acid component. Preferably, these other olefinically unsaturated monomers are monoacrylates or monomethacrylates.
In the embodiment wherein the primary solution polymer has only carboxy functionality, these are preferably esters of acrylic acid or methacrylic acid and a Cl - C8 monohydric alcohol.
C8 ~ C12 monovinyl hydrocarbons such as styrene, alpha methyl styrene, t-butyl styrene, and vinyl toluene may comprise up to about 30 mole percent of such polymer. Vinyl monomers such as vinyl chloride, acrylonitrile, methacrylonitrile and vinyl acetate may be included in the copolymer as modifying monomers. However, when employed, these modifying monomers should constitute only between about 0 and about 30, preferably 0 to 15, mole percent of such polymer. In the embodiment wherein the solution polymer has both carboxy functionality and hydroxy functionality, the copolymer usually contains about 5 to about 25 mole percent of acrylic or methacrylic acid, about 5 to about 25 mole percent of a hydroxyalkylacrylate or methacrylate, e.g., hydroxylethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate or hydroxypropyl methacrylate, and a remainder of the same monofunctional monomers as set forth above for the solely carboxy-functional polymer. In still another embodiment, the polymer has amide functionality in addition to carboxy functionality. Such a polymer usually contains about 5 to about 25 mole percent acrylic acid or methacrylic acid, about 5 to about 25 mole percent of acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, or the alkyl ether or a methylolacrylamide or a methylolmethacrylamide, e.g., N-isobutoxymethylolacrylamide, with the remainder of the same monofunctional monomers as set forth above for the solely carboxy-functional polymer. A portion of the amide functional monomer may be replaced with an equimolar amount of one of the aforementioned hydroxyacrylates or hydroxymeth-acrylates.
Other monomers not heretofore mentioned may be used in these polymers if used in limited concentrations. These include 2-acrylamido-2-methylpropanesulfonic acid and methacryloyloxyethylphosphate, which may comprise up to about 3~ of such polymer.
The emsulsion polymer used to form the paints in this invention has carboxy functionality, hydroxy functionality or carboxy and hydroxy functionality. These polymers usually contain 0 to 15 mole per~ent acrylic acid or methacrylic acid, preferably 0 to 10 mole percent, and 85 to 100 mole percent of other olefinically unsaturated monomers that are copoly-merizable with each other and with the acid component when the latter is used. Such other olefinically unsaturated monomers are the same in type and of the same percentage dis-tribution range as those heretofore disclosed for the solution polymer with the exception of the acid monomer content above noted.
1~67233 In those embodiments, wherein both the solution polymer and the emulsion polymer have hydroxy functionaltiy and carboxy functionality, it is preferred to have a greater ; concentration of carboxy functionality on the solution polymer relative to the emulsion polymer and a greater con-centration of the hydroxy functionality on the emulsion polymer relative to the solution polymer.
Thus, the combinations involved include (a? a carboxy-functional solution polymer and a hydroxy-functional emulsion polymer, (b) a carboxy-functional solution polymer and a carboxy-functional emulsion polymer, (c) a carboxy-functional solution polymer and a carboxy-functional, hydroxy-functional emulsion polymer, (d) a carboxy-functional and hydroxy-functional solution polymer and a hydroxy-functional emulsion polymer, (e) a carboxy-functional, hydroxy-functional solution polymer and a carboxy-functional and hydroxy-functional emulsion polymer, (f) a carboxy-functional and amide-functional solution polymer and a hydroxy-functional emulsion polymer, (g) a carboxy-functional and amide-functional solution polymer and a carboxy-functional emulsion polymer, (h) a carboxy-functional and amide-functional solution polymer and a carboxy-functional and hydroxy-functional emulsion polymer, (i) a carboxy-functional, hydroxy-functional, and amide-functional solution polymer and a hydroxy-functional emulsion polymer, (j) a carboxy-functional, hydroxy-functional, amide-functional solution polymer and a carboxy-functional emulsion polymer, and (k) a carboxy-functional, hydroxy-functional, amide-functional solution polymer and a carboxy-functional, hydroxy-functional emulsion polymer. Amide functionality may also be incorporated into the emulsion polymer but this is more difficult to achieve efficiently than in the solution polymer, particularly in the case of modified amide functionality, e.g., N-methylol-acrylamide.
The amino resin cross-linking agent, may be and is hereafter illustrated as a conventional amino resin cross-linking agent of the type long in use as a cross-linking agent in acrylic enamels, e.g., melamine-formaldehyde resins and urea-formaldehyde resins.
In the formation of water-based paints using the first embodiment of the invention mentioned above, the following procedure may be adopted.
In preparing the water-soluble copoiymer, the functional monomers and the remaining monoethylenically unsaturated monomers are mixed and reacted by conventional free radical initiated polymerization in such proportions as to obtain the copolymer desired. A large number of free radical initiators are known to the art and are suitable for this purpose. These include benzoyl peroxide; t-butyl ` peroctoate; t-butyl perbenzoate; lauryl peroxide; t-butyl-hydroxy peroxidei acetylcyclohexane sulfonyl peroxide;
diisobutyryl peroxide; di-(2-ethylhexyl) peroxydicarbonate;
diisopropyl peroxydicarbonate; t-butylperoxypivalate; decanoyl peroxide; azobis(2-methyl propionitrile); etc. The polymer-ization is carried out in solution using a solvent which is miscible or dilutable with water. The solvent concentration at this stage is ordinarily about 30 to 60 weight percent of the polymerization solution. The polymerization is carried out at a temperature between about ~5C. and the reflux temperature of the reaction mixture. Included among the suitable solvents are n-propyl alcohol, isopropyl alcohol, dioxane, ethylene glycol monomethyl ether, ethylene glycol ~067Z33 monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, etc. The copolymer thus obtained is neutralized with amine to a pH of about 6 to 10 and diluted to desired viscosity with water or organic solvent.
In preparing the emulsion copolymer, the functional monomers are mixed and reacted by conventional free-radical initiated polymerization in aqueous emulsion to obtain the copolymer desired.
A chain transfer agent or mixture of chain transfer agents may be added to the reaction medium to limit the molecular weight of the copolymer; such chain transfer agents are generally mercaptans such as dodecanethiol, benzene-thiol, l-octanethiol, pentanethiol, and butanethiol. These are conventional materials and are employed in a conventional manner. The polymerization initiàtor is composed of one or more water-soluble, free-radical-generating species such as hydrogen peroxide or the sodium, potassium, or ammonium persulfates, perborates, peracetates, percarbonates and the like. The polymerization is carried out at a temperature between about 45C. and the reflux temperature of the reaction mixture. As is well known in the art, these initiators may be associated with activating systems such as redox systems which may incorporate mild reducing agents, such as sulfites and thiosulfites, and redox reaction promoters such as transistion metal ions, and that these allow the polymerization to be carried out at a lower temperature, e.g., 0C. or below.
As however, it is desirable to maintain a low concentration of ` 1067233 non-polymeric ionic species in the finished paint formulation in order that the cured paint film may have optimum resistance to water, it is preferred to use a minimum concentration of such optional inorganic salts as ferrous sulfate, sodium bisulfite, and the like.
As will be disclosed later herein, the solution polymer may also be prepared by emulsion polymerization. In such preparation, the resultant acid-functional copolymer latex is converted to a polymer solution by the addition of an appropriate base, usually ammonia or an organic amine.
There are, however, different needs involved in the after-preparation employment of the emulsion polymer that is used as such in formulation of paint and the solution polymer which although prepared by emulsion polymerization is subsequently converted to a solution polymer and used as such. These needs should be taken into consideration in the preparation procedure.
In the use of emulsion polymerization to produce a solution polymer, there is no need for the resulting latex to be stable under conditions different from those ensuing at the end of the polymerization process since the latex no longer exists, as such, after the polymer goes into solution upon neutralization. To facilitate such conversion to solution polymers, polymers prepared by emulsion polymerization for - use as solution polymers ordinarily contain a higher concentration of carboxyl groups and a lower concentration of decidedly hydrophobic monomers, e.g., 2-ethylhexyl acrylate, relative to the corresponding concentrations in the polymers prepared by emulsion polymerization for use as such.
In contrast, latices which are used as such in the formulation of paint are required to remain essentially :1()67Z~3 as stable latices throughout the processes of polymerization, paint formulation, and product distribution and use. This implies a requirement of stability, i.e., freedom from coagulum formation through time and under a variety of pH
conditions, solvent environment, etc. These requirements are best met, and hence it is preferred to use, an alkali metal or ammonium persulfate either as the sole polymerization init ator, or as one constituent of a mixed initiator system.
In those embodiments in which conventional surfactants are used, it is preferred to use a plurality of surfactants, more specifically a combination of anionic and nonionic surfactants, to obtain a more stable latex. Such surfactant mixtures are well known in the art.
The polymer solution and the polymer latex prepared according to the aforedescribed procedures are subsequently converted into a paint using conventional paint formulation techniques. Typically, a mill base is prepared which comprises the bulk of the pigment and/or particulate filler of the paint formulation. The mill base is "let down" i.e., blended with the remaining polymeric and liquid constituents of the final formulation. A mill base, prepared by conventional sand grinding, ball milling, or pebble milling generally comprises all or a part of the water soluble resin, pigments, organic cosolvents, and may also comprise a quantity of amine in excess of that required to solubilize the solution polymer. To complete the paint, the polymer latex which has been neutralized to a pH range of 5.0 to 10, preferably 5 to 9, is added with mild agitation to the balance of the water required in the total formulation.
The balance of the water-soluble resin, cross-linking agent, and mill ~ase are added slowly with agitation. Additional - ~uantities of pigment may be added sui~sequently as slurries in organic solvents or as separate mill bases to adjust the colour as desired. The viscosity of the finished paint is determined and adjusted as required to obtain desired application properties.
Alternately, all or a portion of the (preferably neutralized) polymer latex, water, organic cosolvent, and amine may be added to the solution polymer and pigments prior to ball milling, sand grinding, or pebble milling.
This procedure is advantageously employed to reduce the viscosity of mill bases prepared using the solution polymers of relatively high molecular weight.
Organic amines are used to neutralize carboxyl groups on the solution polymer and hence to render it soluble in the aqueous dispersion. They are also used to maintain the pH of the finished paint formulation above about 7, e.g., in the range of 7 to 10, preferably between 7 and 9.5, and with certain pigments such as aluminum flakes preferably between 7 and 9, to prevent premature reaction of the functional groups on the acrylic copolymer with the amino resin cross-linking agent. Those skilled in the art will be awaré that in certain embodiments the paint dispersion can be made up at a pH outside the pH range for application and latér adjusted to the desired pH shortly before it is applied.
A portion of the amine, e.g., preferably between about 60 and 100% of the amount chemically equivalent to the carboxyl functionality of the polymer is added to the solution polymer direct]y. Advangageously, a small additional portion of amine is used to raise the pH of the emulsion polymer to about 5 to about 10, preferably 5 to 9, prior to finishing the paint formulation so that the mill base is not subjected to the low p~I environment of the polymer latex (pH about 2.5).
Suitable amines are amines (1) which are soluble in the aqueous medium of the paint, (2) that ionize sufficiently in such aqueous medium to solubilize the solution polymer,
hiall gloss and generally excellent appearance.
In accordance with the present invention, there is provided an improvement in a method for producing an aqueous dispersion of paint in which a carboxy-functional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin cross-linking agent selected from melamine-formaldehyde resins and urea-formal-dehyde resins in an aqueous solution of water and water-soluble amine, wherein the carboxy functional polymer, amino resin cross-linking agent and water-soluble amine constitute about 30 to 50~ by weight of the continuous aqueous phase of the paint with the balance of the continu-. ous aqueous phase being water or a mixture of water and an organic solvent, the water soluble amine is present in an amount sufficient to provide an aqueous phase pH of about : 7.1 to about 8.5, and said water or mixture of water and organic solvent constitutes about 50 to about 65% by weight of the paint.
The improvement in this method is the aqueous dispersion being produced by intimately dispersing with the water, the amino resin cross-linking agent and the water-soluble amine: I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that: (a) is at least par-tially neutralized with water-soluble amine, (b) is soluble in the aqueous solution, (c) has average molecular weight (M ) in the range of about 3,000 to abou~ 20,000, and (d~
has Tg in the range of -15C to 50C, II. an aqueous emulsion consisting essentially of water, water-soluble amine, and about 50 to 95 parts by weight of an emulsion polymer having functionality selected from carboxy function-~ _ 3 _ B
~067Z33 ality and hydroxy f.unctlonality and is a oopoly~er of acrylic mono~ers that: (a) is essentially insoluble in the aqueous solution, (b) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (c) has Tg in the range of -15C to 50C, and III. about 0.025 to about 5 parts by weight of a stabilizer polymer which is a carboxy-functional copolymer of acrylic monomers that: (a) is soluble in the aqueous solution, (b) has average molecular weight (Mn) lower than . that of the solution polymer, and (c) has Tg of -15C to 50C, the stabilizer polymer being introduced into the dispersion intimately mixed with at least one of the solution polymer and the emulsion polymer.
- 3a -~067Z33 The term "parts" when used herein without further desi~nation shall mean "parts by weight".
The term "acrylic monomer" shall mean acrylic acid, methacrylic acid, esters of acrylic acid and a Cl - C8 monohydric alcohol, e.g., ethyl acrylate butyl acrylate, hexyl acrylate and 2-ethylhexyl acrylate, esters of methacrylic acid and a Cl - C8 monohydric alcohol, e.g., methyl methacrylate, butyl methacrylate, hexyl methacrylate and 2-ethylhexyl methacrylate, hydroxyalkYl acrylates, e.g., hydroxyethyl acrylate and hydroxypropyl acrylate, hydroxyalkyl methacrylates, e.g., hydroxyethyl methacrylate and hydroxypropyl methacrylate, acrylamide, methacrylamide, methylolacrylamides, e.g., n-methylolacrylamide, methylol-methacrylamides, e.g., N-methylolmethacrylamide, alkyl ethers of methylolacrylamides, e.g., N-isobutoxymethylolacrylamide, and alkyl ethers of methylolmethacrylamides, e.g., N-isobutoxy-methylolmethacrylamide.
The term "copolymer of acrylic monomers" shall mean a polymer of at least two different monoethylenically unsaturated monomers of which more than 50 mole percent are acrylic monomers.
The term "water-dilutable organic solvent"~means an organic solvent or mixture of organic solvents which is either miscible with water or will mix with water up to a concentration of at least one volume of solvent per three volumes of water without phase separation. Ordinarily, such solvent, when present in the paint, enters the paint through its use in the preparation of the solution resin, as herein-before described. In such embodiment, the solution polymer is, of course, soluble therein. In another embodiment, it may be added independently, if desired. In the latter case, the solution polymer may not ~e fully soluble therein.
The hybrid, water-based, paint compositions formed in accordance with this invention employ in combination a low molecular weight emulsion polymer and a low molecular weight solution polymer with the latter being present in an amount sufficient to contribute significantly to the composi-tion of the polymeric binder, i.e., at least about 5 weight percent of this polymeric combination. Thus, they differ from the conventional emulsion type paints employing a water-soluble thickener polymer in at least three compositional respects irrespective of chemical functionality, namely, (1) the emulsion polymers of the instant paints have significantly lower molecular weights, (2) the solution polymers of the instant paints have significantly lower molecular weights, and (3) the solution polymers of the instant paints are employed in significantly higher concentrations than are the water-soluble thickener polymers.
More specifically, the hybrid paint compositions formed in this invention, exclusive of optional components such as pigments, particulate fillers and catalysts, have a liquid continuous aqueous phase. About 30 to about 50% by weight of this phase, exclusive of the afore-cited optional components, is made up of a mixture of (a) an amino resin cross-linking agent; (b) a mixture of three copolymers of acrylic monomers; and (c) an amine. The balance is water or, in certain embodiments, water and an organic solvent.
The amine is a water-soluble amine and is present in an amount sufficient to solubilize the solution polymer in the aqueous phase at a pH range of about 7.1 to about 8.5. In certain embodiments, hereinafter illustrated, these hybrid compositions include organic cosolvents while in other 10~i7-33 embodim^nts such solvents are not present.
~ hen applied to the substrate to be coated by spraying, these water-based paints including pigments, particulate fillers, and catalysts, if any, contain between about 50 and about 65~ by weight water or in those embodi-ments wherein such solvents are used, water and organic cosolvents.
In one embodiment of the method of this invention, - at least one of the polymers, usually the solution polymer, is polymerized in solution in a water miscible or dilutable organic solvent while the other polymer, usually the emulsion polymer, is prepared by an emulsion polymerization in water. The resultant water-based paint will contain a conventional, essentially non-reactive, water-miscible or dilutable organic paint solvent. The concentration of organic solv~nt in such paints will be at least about 5~ by volume of the volatile phase, i.e., organic solvent an~
water, and preferably in the range of about 10 to about 20 volume percent of the volatile phase. In carrying out the emulsion polymerization the conventional surfactant, i.e., surface active agent or emulsifier, is replaced by a stabilization solution polymer hereinafter more fully described.
In another embodiment of the method of this invention, both the solution polymer and the emulsion polymer are prepared by emulsion polymerization in water as claimed in our ccpending application Serial No. 251,302 filed concurrently herewith. The paints thus prepared are prepared without organic solvents and thus employed free of same.
Organic solvents in the amounts used in the first embodiment may be added to the dispersion, if desired. In carrying out one or both, preferably both, of the emulsion polymerizations the conventional I ~ .
1~67Z33 ,lrfactant is replaced by the stabilizing solution polymer hereinafter more fully described.
The advantage provided by the invention is that elimination of the conventional surfactant eliminates the problem of incompatibility and water sensitivity associated with the use of surfactants.
The solution polymer used to form the paints in this invention has carboxy functionality and may also have hydroxy functionality and/or amide functionality. These polymers usually contain about 5 to about 30 mole percent of acrylic or methacrylic acid and 70 to 95 mole percent of olefinically unsaturated monomers copolymerizable with such acid component. Preferably, these other olefinically unsaturated monomers are monoacrylates or monomethacrylates.
In the embodiment wherein the primary solution polymer has only carboxy functionality, these are preferably esters of acrylic acid or methacrylic acid and a Cl - C8 monohydric alcohol.
C8 ~ C12 monovinyl hydrocarbons such as styrene, alpha methyl styrene, t-butyl styrene, and vinyl toluene may comprise up to about 30 mole percent of such polymer. Vinyl monomers such as vinyl chloride, acrylonitrile, methacrylonitrile and vinyl acetate may be included in the copolymer as modifying monomers. However, when employed, these modifying monomers should constitute only between about 0 and about 30, preferably 0 to 15, mole percent of such polymer. In the embodiment wherein the solution polymer has both carboxy functionality and hydroxy functionality, the copolymer usually contains about 5 to about 25 mole percent of acrylic or methacrylic acid, about 5 to about 25 mole percent of a hydroxyalkylacrylate or methacrylate, e.g., hydroxylethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate or hydroxypropyl methacrylate, and a remainder of the same monofunctional monomers as set forth above for the solely carboxy-functional polymer. In still another embodiment, the polymer has amide functionality in addition to carboxy functionality. Such a polymer usually contains about 5 to about 25 mole percent acrylic acid or methacrylic acid, about 5 to about 25 mole percent of acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, or the alkyl ether or a methylolacrylamide or a methylolmethacrylamide, e.g., N-isobutoxymethylolacrylamide, with the remainder of the same monofunctional monomers as set forth above for the solely carboxy-functional polymer. A portion of the amide functional monomer may be replaced with an equimolar amount of one of the aforementioned hydroxyacrylates or hydroxymeth-acrylates.
Other monomers not heretofore mentioned may be used in these polymers if used in limited concentrations. These include 2-acrylamido-2-methylpropanesulfonic acid and methacryloyloxyethylphosphate, which may comprise up to about 3~ of such polymer.
The emsulsion polymer used to form the paints in this invention has carboxy functionality, hydroxy functionality or carboxy and hydroxy functionality. These polymers usually contain 0 to 15 mole per~ent acrylic acid or methacrylic acid, preferably 0 to 10 mole percent, and 85 to 100 mole percent of other olefinically unsaturated monomers that are copoly-merizable with each other and with the acid component when the latter is used. Such other olefinically unsaturated monomers are the same in type and of the same percentage dis-tribution range as those heretofore disclosed for the solution polymer with the exception of the acid monomer content above noted.
1~67233 In those embodiments, wherein both the solution polymer and the emulsion polymer have hydroxy functionaltiy and carboxy functionality, it is preferred to have a greater ; concentration of carboxy functionality on the solution polymer relative to the emulsion polymer and a greater con-centration of the hydroxy functionality on the emulsion polymer relative to the solution polymer.
Thus, the combinations involved include (a? a carboxy-functional solution polymer and a hydroxy-functional emulsion polymer, (b) a carboxy-functional solution polymer and a carboxy-functional emulsion polymer, (c) a carboxy-functional solution polymer and a carboxy-functional, hydroxy-functional emulsion polymer, (d) a carboxy-functional and hydroxy-functional solution polymer and a hydroxy-functional emulsion polymer, (e) a carboxy-functional, hydroxy-functional solution polymer and a carboxy-functional and hydroxy-functional emulsion polymer, (f) a carboxy-functional and amide-functional solution polymer and a hydroxy-functional emulsion polymer, (g) a carboxy-functional and amide-functional solution polymer and a carboxy-functional emulsion polymer, (h) a carboxy-functional and amide-functional solution polymer and a carboxy-functional and hydroxy-functional emulsion polymer, (i) a carboxy-functional, hydroxy-functional, and amide-functional solution polymer and a hydroxy-functional emulsion polymer, (j) a carboxy-functional, hydroxy-functional, amide-functional solution polymer and a carboxy-functional emulsion polymer, and (k) a carboxy-functional, hydroxy-functional, amide-functional solution polymer and a carboxy-functional, hydroxy-functional emulsion polymer. Amide functionality may also be incorporated into the emulsion polymer but this is more difficult to achieve efficiently than in the solution polymer, particularly in the case of modified amide functionality, e.g., N-methylol-acrylamide.
The amino resin cross-linking agent, may be and is hereafter illustrated as a conventional amino resin cross-linking agent of the type long in use as a cross-linking agent in acrylic enamels, e.g., melamine-formaldehyde resins and urea-formaldehyde resins.
In the formation of water-based paints using the first embodiment of the invention mentioned above, the following procedure may be adopted.
In preparing the water-soluble copoiymer, the functional monomers and the remaining monoethylenically unsaturated monomers are mixed and reacted by conventional free radical initiated polymerization in such proportions as to obtain the copolymer desired. A large number of free radical initiators are known to the art and are suitable for this purpose. These include benzoyl peroxide; t-butyl ` peroctoate; t-butyl perbenzoate; lauryl peroxide; t-butyl-hydroxy peroxidei acetylcyclohexane sulfonyl peroxide;
diisobutyryl peroxide; di-(2-ethylhexyl) peroxydicarbonate;
diisopropyl peroxydicarbonate; t-butylperoxypivalate; decanoyl peroxide; azobis(2-methyl propionitrile); etc. The polymer-ization is carried out in solution using a solvent which is miscible or dilutable with water. The solvent concentration at this stage is ordinarily about 30 to 60 weight percent of the polymerization solution. The polymerization is carried out at a temperature between about ~5C. and the reflux temperature of the reaction mixture. Included among the suitable solvents are n-propyl alcohol, isopropyl alcohol, dioxane, ethylene glycol monomethyl ether, ethylene glycol ~067Z33 monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, etc. The copolymer thus obtained is neutralized with amine to a pH of about 6 to 10 and diluted to desired viscosity with water or organic solvent.
In preparing the emulsion copolymer, the functional monomers are mixed and reacted by conventional free-radical initiated polymerization in aqueous emulsion to obtain the copolymer desired.
A chain transfer agent or mixture of chain transfer agents may be added to the reaction medium to limit the molecular weight of the copolymer; such chain transfer agents are generally mercaptans such as dodecanethiol, benzene-thiol, l-octanethiol, pentanethiol, and butanethiol. These are conventional materials and are employed in a conventional manner. The polymerization initiàtor is composed of one or more water-soluble, free-radical-generating species such as hydrogen peroxide or the sodium, potassium, or ammonium persulfates, perborates, peracetates, percarbonates and the like. The polymerization is carried out at a temperature between about 45C. and the reflux temperature of the reaction mixture. As is well known in the art, these initiators may be associated with activating systems such as redox systems which may incorporate mild reducing agents, such as sulfites and thiosulfites, and redox reaction promoters such as transistion metal ions, and that these allow the polymerization to be carried out at a lower temperature, e.g., 0C. or below.
As however, it is desirable to maintain a low concentration of ` 1067233 non-polymeric ionic species in the finished paint formulation in order that the cured paint film may have optimum resistance to water, it is preferred to use a minimum concentration of such optional inorganic salts as ferrous sulfate, sodium bisulfite, and the like.
As will be disclosed later herein, the solution polymer may also be prepared by emulsion polymerization. In such preparation, the resultant acid-functional copolymer latex is converted to a polymer solution by the addition of an appropriate base, usually ammonia or an organic amine.
There are, however, different needs involved in the after-preparation employment of the emulsion polymer that is used as such in formulation of paint and the solution polymer which although prepared by emulsion polymerization is subsequently converted to a solution polymer and used as such. These needs should be taken into consideration in the preparation procedure.
In the use of emulsion polymerization to produce a solution polymer, there is no need for the resulting latex to be stable under conditions different from those ensuing at the end of the polymerization process since the latex no longer exists, as such, after the polymer goes into solution upon neutralization. To facilitate such conversion to solution polymers, polymers prepared by emulsion polymerization for - use as solution polymers ordinarily contain a higher concentration of carboxyl groups and a lower concentration of decidedly hydrophobic monomers, e.g., 2-ethylhexyl acrylate, relative to the corresponding concentrations in the polymers prepared by emulsion polymerization for use as such.
In contrast, latices which are used as such in the formulation of paint are required to remain essentially :1()67Z~3 as stable latices throughout the processes of polymerization, paint formulation, and product distribution and use. This implies a requirement of stability, i.e., freedom from coagulum formation through time and under a variety of pH
conditions, solvent environment, etc. These requirements are best met, and hence it is preferred to use, an alkali metal or ammonium persulfate either as the sole polymerization init ator, or as one constituent of a mixed initiator system.
In those embodiments in which conventional surfactants are used, it is preferred to use a plurality of surfactants, more specifically a combination of anionic and nonionic surfactants, to obtain a more stable latex. Such surfactant mixtures are well known in the art.
The polymer solution and the polymer latex prepared according to the aforedescribed procedures are subsequently converted into a paint using conventional paint formulation techniques. Typically, a mill base is prepared which comprises the bulk of the pigment and/or particulate filler of the paint formulation. The mill base is "let down" i.e., blended with the remaining polymeric and liquid constituents of the final formulation. A mill base, prepared by conventional sand grinding, ball milling, or pebble milling generally comprises all or a part of the water soluble resin, pigments, organic cosolvents, and may also comprise a quantity of amine in excess of that required to solubilize the solution polymer. To complete the paint, the polymer latex which has been neutralized to a pH range of 5.0 to 10, preferably 5 to 9, is added with mild agitation to the balance of the water required in the total formulation.
The balance of the water-soluble resin, cross-linking agent, and mill ~ase are added slowly with agitation. Additional - ~uantities of pigment may be added sui~sequently as slurries in organic solvents or as separate mill bases to adjust the colour as desired. The viscosity of the finished paint is determined and adjusted as required to obtain desired application properties.
Alternately, all or a portion of the (preferably neutralized) polymer latex, water, organic cosolvent, and amine may be added to the solution polymer and pigments prior to ball milling, sand grinding, or pebble milling.
This procedure is advantageously employed to reduce the viscosity of mill bases prepared using the solution polymers of relatively high molecular weight.
Organic amines are used to neutralize carboxyl groups on the solution polymer and hence to render it soluble in the aqueous dispersion. They are also used to maintain the pH of the finished paint formulation above about 7, e.g., in the range of 7 to 10, preferably between 7 and 9.5, and with certain pigments such as aluminum flakes preferably between 7 and 9, to prevent premature reaction of the functional groups on the acrylic copolymer with the amino resin cross-linking agent. Those skilled in the art will be awaré that in certain embodiments the paint dispersion can be made up at a pH outside the pH range for application and latér adjusted to the desired pH shortly before it is applied.
A portion of the amine, e.g., preferably between about 60 and 100% of the amount chemically equivalent to the carboxyl functionality of the polymer is added to the solution polymer direct]y. Advangageously, a small additional portion of amine is used to raise the pH of the emulsion polymer to about 5 to about 10, preferably 5 to 9, prior to finishing the paint formulation so that the mill base is not subjected to the low p~I environment of the polymer latex (pH about 2.5).
Suitable amines are amines (1) which are soluble in the aqueous medium of the paint, (2) that ionize sufficiently in such aqueous medium to solubilize the solution polymer,
(3) that ionize sufficiently in such aqueous medium when employed in suitable amounts to provide the paint dispersion with a pH of at least about 7, preferably 7.2 or higher, and thereby keep the rate of reaction between reactive groups of the amino resin (cross-linking agent) negligible prior to curing, and (4) that allow for rapid curing of the enamel upon heating. Suitable amines include alkyl, alkanol and aryl primary, secondary and tertiary amines. Preferred are secon-dary and tertiaryalkyl and alkanol amines having a boiling point within the range of 80 to 200C. By way of example, these include N,N-dimethyl ethanolamine, N,N-diethylethanol-amine, isopropanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine, N-methylethanolamine, 2,6-dimethylmorpholine, methoxypropylamine, and 2-amino-2-methyl-1-propanol.
Catalysts for the curing of resins described herein are not normally required to obtain satisfactory film properties. If desired, however, for purposes of lowering the film baking temperature or of further improving cured film properties, strong acid catalysts can be employed in an amount not in excess of 3~ by weight of the total finished paint formulation. Said strong acid catalysts may be introduced either as copolymerizable species incorporated in one or both acrylic copolymers, e.g., 2-acrylamide-2-methylpropanesulfonic acid, or as a non-polymerizable additive, e.g., p-toluenesulfonic acid. It is generally preferred not to add such catalysts, however, as they may tend to increase the water sensitivity of the cured film and 1~)67Z33 may deleteriously affect storage stability of the liquid paint.
In those embodiments wherein a volatile organic solvent is employed as a cosolvent, i.e., solution of the solution polymer also being effected by the use of a water-soluble amine, the following solvents are suitable for this use include: n-propyl alcohol, isopropyl alcohol, butanol, 2-butoxyethanol, 2t2-butoxy)ethoxyethanol, n-octyl alcohol, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, etc.
In the second embodiment of the invention mentioned above, the water-soluble copolymer is produced by emulsion polymerization. The functional monomers are mixed and reacted by conventional free-radical initiated polymerization in aqueous emulsion to obtain the copolymer desired. The resulting acid-functional copolymer latex is converted to a polymer solution by the addition of an appropriate base, usually ammonia or an organic amine.
Conventional surfactants, chain transfer agents, and initiators are employed in the emulsion polymerization. The monomer charge is usually emulsified by one or more micelle-forming compounds composed of a hydrophobic part, such as a hydrocarbon group containing six or more carbon atoms, and a hydrophilic part, such as hydroxyl group, alkali metal or ammonium carboxylate groups, phosphate or sulfate partial ester groups, sulfonate groups, or a polyether chain.
Exemplary emulsifying agents include al~ali metal sulfonates of styrene, naphthalene, decyl benzene and dodecyl benzene;
!
;` ,odium dodecyl sulfate; sodium stearate; sodium oleate, the sodium alkyl aryl polyether or sulfates and phosphates; the ethylene oxide condensates of long chain fatty acids, alcohols, and mercaptans, and the alkali metal salts of rosin acids.
These materials and the techniques of their employment in emulsion formation and maintenance are well known in the art.
As previously pointed out, however, when emulsion polymeriza-tion is used to produce a solution polymer, there is no need for the resulting latex to be stable under conditions different from those ensuing at the end of the polymerization process since the latex no longer exists as such after the polymer goes into solution upon neutralization. To facilitate such conversion to solution polymers, polymers prepared by emulsion polymerization for use as a solution polymer ordinarily contain a higher concentration of carboxyl groups and a lower concentration of decidedly hydrophobic monomers, e.g., 2-ethylllexyl acrylate, relative to the corresponding concentrations in the polymers prepared for use as emulsion polymers. Further, the teaching hereinbefore set forth with respect to the choice of initiators when preparing the latter, i.e., using an alkali metal or ammonium persulfate either as the sole polymerization initiator or as one constituent of a mixed initiator system to avoid coagulum formation through time and under a variety of pH conditions, solvent environment, etc., is applicable where the polymer is to be converted to a solution polymer. Such initiators may be used when preparing the solution polymer by emulsion polymerization but conventional peroxide initiators are quite suitable for this. Hence, this method offers an advantage, in this respect, in that the concentration of ionic inorganic contaminants, e.g., sufate ions, in the paint formulation is reduced. A chain transfer agent or mixture of chain transfer agents may be a~ded to the reaction medium to limit the molecular weight of the polymer, such chain transfer agents are generally mercapta~s such as dodecanethiol, benzenethiol, l-octanethiol, pentanethiol and butanethiol. These are conventional materials employed in a conventional manner. The polymerization initiator is composed of one or more water-soluble, free-radical-generating species such as hydrogen peroxide or the sodium, potassium or ammonium persulfates, perborates, peracetates, percarbonates and the like. As is well known in the art, these initiators may be associated with activating systems such as redox systems which may incorporate mild reducing agents, such as sulfites and thiosulfites and redox reaction promoters such as transition metal ions. As hereinbefore mentioned, however, -it is desirable to maintain a low concentration of non-poly-meric ionic species in the finished paint formulation in order that the cured paint film may have optimum resistance to water. Hence, it is preferred to use a minimum concentra-tion of such optional inorganic salts as ferrous sulfate, sodium bisulfite, and the like. Those skilled in the art will be aware that other emulsifying agents, polymerization initiators and chain transfer agents may be used which are compatible with the polymerization system herein required and with the attainment of acceptable cured paint film properties.
In the above-described procedures all or part of the conventional surfactant, i.e., surface active agent or emulsifier, employed in preparing the emulsion polymer, the solution polymer, when the emulsion polymerization procedure is used, or preferably both, is replaced with a stabilizer polymer, that is identical with or similar to, the solution polymer heretofore described and employed as a primary constituent of the paints described herein.
he stabilizer polymer used in accordance with this invention is carboxy-functional and soluble in the aqueous phase of these paint dispersions and is either the same as the primary solution polymer, heretofore discussed, or similar to such solution polymer and compatible with the system. The average molecular weight (Mn) of the stabilizer polymer may be the same as that of the primary solution polymer, i.e., between 3,000 and 20,000 but essentially is of lower molecular weight than the primary solution polymer.
Preferably, the average molecular weight of this third copolymer is in the range of about 3,000 to about 8,000.
Its Tg is in the range of -15C to 50C. The stabilizer polymer is used in a concentration in the range of about 0.025 to about 5 parts by weight.
The stabilizer polymer may be prepared by any of several methods, including (1) the method used to prepare the solution polymer mentioned above, i.e., polymerization in solution in a water miscible or dilutable organic solvent;
(2) emulsion polymerization using an emulsifier or surfactant;
(3) emulsion polymerization using in lieu of a surfactant a small amount of the intended polymer from a previous prepar-ation; and (4) a method of emulsion polymerization described hereinafter which employs neither surfactant nor a water soluble polymer in lieu thereof. In the latter, conventional chain transfer agents and polymerization initiators are used as described hereinbefore for the preparation of a solution polymer by emulsion polymerization. A mixture of monomers 1C)67Z33 including carboxyl functic,nal monomers and a chain transfer agent is added slowly to a stirred mixture of initiator and water maintained at a suitable reaction temperature, e.g., between 45 and 95C. It is preferred to add simultaneously with the monomer mixture an additional quantity of polymer-ization initiator to sustain a sufficient initiator concen-tration throughout the polymerization. The polymer latex so obtained is filtered and neutralized with ammonia or water-soluble amine to render it water soluble.
This invention will be more fully understood from the following illustrative examples:
EXAMPLE I
A water-based paint is prepared from the following materials:
Step I Preparation of Stabilizer Polymer There is charged to a reactor 200 parts of water.
The reactor charge is heated to boiling and then cooled to 95C. To the reactor charge is added Solution A, a solution of 0.1 parts af ammonium persulfate in 0.8 parts of water.
A solution, hereinafter termed 5O1ution B, is prepared from 0.4 parts of ammonium persulfate in 2.5 parts water. A
reactant monomer and chain transfer agent mixture is formed from the following materials:
Materials Parts by Weight methyl methacrylate 35 methacrylic acid 15 butyl acrylate 50 l-octanethiol 2 The monomer mixture and Solution B are simultaneously charged to the reactor by incremental addition over a two-hour period. The temperature of the reaction mixture is 1~)67Z33 maintained fc~r 3 hours after-addition of the last of the reactants. The latex so obtained is cooled to room tempera-ture and filtered. The polymer thus obtained, hereinafter termed stabilizer polymer I, is then neutralized with 2-(dimethylamino)ethanol in an amount equivalent to the acid monomer content of the polymer. A clear solution is obtained.
Step II Preparation of Emulsion Polymer An emulsion polymer is produced by first preparing the following: (1) there is charged to the reactor 200 parts of water and 4.25 parts of the stabilizer polymer from step I; (2) the following materials are thoroughly mixed:
Materials Parts b~7eight styrene 20.0 methacrylic acid 15.0 butyl acrylate 55.0 butyl methacrylate 10.0 l-octanethiol 0.6 (3) there are dissolved in 0.5 parts of ammonium persulfate and one part of 2-acrylamide-2-methylpropanesulfonic acid in 2.5 parts of water; and (4) there is dissolved 0.2 parts of ammonium persulfate in 5 parts of water. After these are prepared the emulsion polymer is prepared using the procedure and conditions used to prepare the stabilizer polymer of Step I. In such, the order of addition of the four above listed components is as follows: (4) is added to (1) in the reactor and (2) and (3) are added simultaneously to the mixture of (1) and (4).
Step III Preparation of the Solution Polymer The procedures and steps of Step II of this example are repeated with thefollowing employment of reactant monomers:
Materials Parts_by Wei~ht methyl methacrylate 35 methacrylic acid 15 butyl acrylate 50 l-octanethiol After this latex is cooled and filtered, it is , neutralized with 2-(dimethylamino)ethanol to the amount ; equivalent to the methacrylic acid constituent of the polymer.
; Step IV Preparation of the Organic Solvent-Free, Surfactant-Free Hybrid Water-Based Enamel Materials Parts_~y Weight solution polymer from 14.1 -Step III
"CYMEL" (Trademark) 300 6.5 titanium dioxide16.1 water 6.4 The above materials are ball milled for 16 hours and mixed (let down) with the following materials:
Materials Parts by Weight latex from Step II (includes 47.3 both emulsion polymer and stabilizer polymer I
10% aqueous 2-(dimethylamino) 9.6 ethanol The enamel thus prepared is adjusted to a viscosity of 17 to 20 seconds (No. 4 Ford Cup) by adding water. It is sprayed on primed steel panels and baked for 25 minutes at 160C. The coatings thus obtained exhibit good appearance, gloss and solvent resistance.
EXAMPLE II
. .
A water-based enamel is prepared in from the following materials:
B
Step I Preparation of Latex (includes stabilizer polymer and emulsion polymer) (1) There is charged to a reactor 127 parts of water and two parts of the stabilizer polymer prepared in Step I of Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
Materials Parts by Weight styrene 20.0 hydroxypropyl methacrylate 14.0 methacrylic acid 6.0 butyl acrylate 30.0 butyl methacrylate30.0 l-octanethiol 0.6 (3) There is dissolved 0.5 parts of ammonium persulfate in 16.7 parts of water.
Catalysts for the curing of resins described herein are not normally required to obtain satisfactory film properties. If desired, however, for purposes of lowering the film baking temperature or of further improving cured film properties, strong acid catalysts can be employed in an amount not in excess of 3~ by weight of the total finished paint formulation. Said strong acid catalysts may be introduced either as copolymerizable species incorporated in one or both acrylic copolymers, e.g., 2-acrylamide-2-methylpropanesulfonic acid, or as a non-polymerizable additive, e.g., p-toluenesulfonic acid. It is generally preferred not to add such catalysts, however, as they may tend to increase the water sensitivity of the cured film and 1~)67Z33 may deleteriously affect storage stability of the liquid paint.
In those embodiments wherein a volatile organic solvent is employed as a cosolvent, i.e., solution of the solution polymer also being effected by the use of a water-soluble amine, the following solvents are suitable for this use include: n-propyl alcohol, isopropyl alcohol, butanol, 2-butoxyethanol, 2t2-butoxy)ethoxyethanol, n-octyl alcohol, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, etc.
In the second embodiment of the invention mentioned above, the water-soluble copolymer is produced by emulsion polymerization. The functional monomers are mixed and reacted by conventional free-radical initiated polymerization in aqueous emulsion to obtain the copolymer desired. The resulting acid-functional copolymer latex is converted to a polymer solution by the addition of an appropriate base, usually ammonia or an organic amine.
Conventional surfactants, chain transfer agents, and initiators are employed in the emulsion polymerization. The monomer charge is usually emulsified by one or more micelle-forming compounds composed of a hydrophobic part, such as a hydrocarbon group containing six or more carbon atoms, and a hydrophilic part, such as hydroxyl group, alkali metal or ammonium carboxylate groups, phosphate or sulfate partial ester groups, sulfonate groups, or a polyether chain.
Exemplary emulsifying agents include al~ali metal sulfonates of styrene, naphthalene, decyl benzene and dodecyl benzene;
!
;` ,odium dodecyl sulfate; sodium stearate; sodium oleate, the sodium alkyl aryl polyether or sulfates and phosphates; the ethylene oxide condensates of long chain fatty acids, alcohols, and mercaptans, and the alkali metal salts of rosin acids.
These materials and the techniques of their employment in emulsion formation and maintenance are well known in the art.
As previously pointed out, however, when emulsion polymeriza-tion is used to produce a solution polymer, there is no need for the resulting latex to be stable under conditions different from those ensuing at the end of the polymerization process since the latex no longer exists as such after the polymer goes into solution upon neutralization. To facilitate such conversion to solution polymers, polymers prepared by emulsion polymerization for use as a solution polymer ordinarily contain a higher concentration of carboxyl groups and a lower concentration of decidedly hydrophobic monomers, e.g., 2-ethylllexyl acrylate, relative to the corresponding concentrations in the polymers prepared for use as emulsion polymers. Further, the teaching hereinbefore set forth with respect to the choice of initiators when preparing the latter, i.e., using an alkali metal or ammonium persulfate either as the sole polymerization initiator or as one constituent of a mixed initiator system to avoid coagulum formation through time and under a variety of pH conditions, solvent environment, etc., is applicable where the polymer is to be converted to a solution polymer. Such initiators may be used when preparing the solution polymer by emulsion polymerization but conventional peroxide initiators are quite suitable for this. Hence, this method offers an advantage, in this respect, in that the concentration of ionic inorganic contaminants, e.g., sufate ions, in the paint formulation is reduced. A chain transfer agent or mixture of chain transfer agents may be a~ded to the reaction medium to limit the molecular weight of the polymer, such chain transfer agents are generally mercapta~s such as dodecanethiol, benzenethiol, l-octanethiol, pentanethiol and butanethiol. These are conventional materials employed in a conventional manner. The polymerization initiator is composed of one or more water-soluble, free-radical-generating species such as hydrogen peroxide or the sodium, potassium or ammonium persulfates, perborates, peracetates, percarbonates and the like. As is well known in the art, these initiators may be associated with activating systems such as redox systems which may incorporate mild reducing agents, such as sulfites and thiosulfites and redox reaction promoters such as transition metal ions. As hereinbefore mentioned, however, -it is desirable to maintain a low concentration of non-poly-meric ionic species in the finished paint formulation in order that the cured paint film may have optimum resistance to water. Hence, it is preferred to use a minimum concentra-tion of such optional inorganic salts as ferrous sulfate, sodium bisulfite, and the like. Those skilled in the art will be aware that other emulsifying agents, polymerization initiators and chain transfer agents may be used which are compatible with the polymerization system herein required and with the attainment of acceptable cured paint film properties.
In the above-described procedures all or part of the conventional surfactant, i.e., surface active agent or emulsifier, employed in preparing the emulsion polymer, the solution polymer, when the emulsion polymerization procedure is used, or preferably both, is replaced with a stabilizer polymer, that is identical with or similar to, the solution polymer heretofore described and employed as a primary constituent of the paints described herein.
he stabilizer polymer used in accordance with this invention is carboxy-functional and soluble in the aqueous phase of these paint dispersions and is either the same as the primary solution polymer, heretofore discussed, or similar to such solution polymer and compatible with the system. The average molecular weight (Mn) of the stabilizer polymer may be the same as that of the primary solution polymer, i.e., between 3,000 and 20,000 but essentially is of lower molecular weight than the primary solution polymer.
Preferably, the average molecular weight of this third copolymer is in the range of about 3,000 to about 8,000.
Its Tg is in the range of -15C to 50C. The stabilizer polymer is used in a concentration in the range of about 0.025 to about 5 parts by weight.
The stabilizer polymer may be prepared by any of several methods, including (1) the method used to prepare the solution polymer mentioned above, i.e., polymerization in solution in a water miscible or dilutable organic solvent;
(2) emulsion polymerization using an emulsifier or surfactant;
(3) emulsion polymerization using in lieu of a surfactant a small amount of the intended polymer from a previous prepar-ation; and (4) a method of emulsion polymerization described hereinafter which employs neither surfactant nor a water soluble polymer in lieu thereof. In the latter, conventional chain transfer agents and polymerization initiators are used as described hereinbefore for the preparation of a solution polymer by emulsion polymerization. A mixture of monomers 1C)67Z33 including carboxyl functic,nal monomers and a chain transfer agent is added slowly to a stirred mixture of initiator and water maintained at a suitable reaction temperature, e.g., between 45 and 95C. It is preferred to add simultaneously with the monomer mixture an additional quantity of polymer-ization initiator to sustain a sufficient initiator concen-tration throughout the polymerization. The polymer latex so obtained is filtered and neutralized with ammonia or water-soluble amine to render it water soluble.
This invention will be more fully understood from the following illustrative examples:
EXAMPLE I
A water-based paint is prepared from the following materials:
Step I Preparation of Stabilizer Polymer There is charged to a reactor 200 parts of water.
The reactor charge is heated to boiling and then cooled to 95C. To the reactor charge is added Solution A, a solution of 0.1 parts af ammonium persulfate in 0.8 parts of water.
A solution, hereinafter termed 5O1ution B, is prepared from 0.4 parts of ammonium persulfate in 2.5 parts water. A
reactant monomer and chain transfer agent mixture is formed from the following materials:
Materials Parts by Weight methyl methacrylate 35 methacrylic acid 15 butyl acrylate 50 l-octanethiol 2 The monomer mixture and Solution B are simultaneously charged to the reactor by incremental addition over a two-hour period. The temperature of the reaction mixture is 1~)67Z33 maintained fc~r 3 hours after-addition of the last of the reactants. The latex so obtained is cooled to room tempera-ture and filtered. The polymer thus obtained, hereinafter termed stabilizer polymer I, is then neutralized with 2-(dimethylamino)ethanol in an amount equivalent to the acid monomer content of the polymer. A clear solution is obtained.
Step II Preparation of Emulsion Polymer An emulsion polymer is produced by first preparing the following: (1) there is charged to the reactor 200 parts of water and 4.25 parts of the stabilizer polymer from step I; (2) the following materials are thoroughly mixed:
Materials Parts b~7eight styrene 20.0 methacrylic acid 15.0 butyl acrylate 55.0 butyl methacrylate 10.0 l-octanethiol 0.6 (3) there are dissolved in 0.5 parts of ammonium persulfate and one part of 2-acrylamide-2-methylpropanesulfonic acid in 2.5 parts of water; and (4) there is dissolved 0.2 parts of ammonium persulfate in 5 parts of water. After these are prepared the emulsion polymer is prepared using the procedure and conditions used to prepare the stabilizer polymer of Step I. In such, the order of addition of the four above listed components is as follows: (4) is added to (1) in the reactor and (2) and (3) are added simultaneously to the mixture of (1) and (4).
Step III Preparation of the Solution Polymer The procedures and steps of Step II of this example are repeated with thefollowing employment of reactant monomers:
Materials Parts_by Wei~ht methyl methacrylate 35 methacrylic acid 15 butyl acrylate 50 l-octanethiol After this latex is cooled and filtered, it is , neutralized with 2-(dimethylamino)ethanol to the amount ; equivalent to the methacrylic acid constituent of the polymer.
; Step IV Preparation of the Organic Solvent-Free, Surfactant-Free Hybrid Water-Based Enamel Materials Parts_~y Weight solution polymer from 14.1 -Step III
"CYMEL" (Trademark) 300 6.5 titanium dioxide16.1 water 6.4 The above materials are ball milled for 16 hours and mixed (let down) with the following materials:
Materials Parts by Weight latex from Step II (includes 47.3 both emulsion polymer and stabilizer polymer I
10% aqueous 2-(dimethylamino) 9.6 ethanol The enamel thus prepared is adjusted to a viscosity of 17 to 20 seconds (No. 4 Ford Cup) by adding water. It is sprayed on primed steel panels and baked for 25 minutes at 160C. The coatings thus obtained exhibit good appearance, gloss and solvent resistance.
EXAMPLE II
. .
A water-based enamel is prepared in from the following materials:
B
Step I Preparation of Latex (includes stabilizer polymer and emulsion polymer) (1) There is charged to a reactor 127 parts of water and two parts of the stabilizer polymer prepared in Step I of Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
Materials Parts by Weight styrene 20.0 hydroxypropyl methacrylate 14.0 methacrylic acid 6.0 butyl acrylate 30.0 butyl methacrylate30.0 l-octanethiol 0.6 (3) There is dissolved 0.5 parts of ammonium persulfate in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 16.7 parts of water.
The reactor charge is heated to boiling and cooled to 95C. After the solution of (4) is charged to the reactor, there is added to the reaction medium 0.45 parts of the monomer mixture of (2) and the temperature is held at 95C without further addition of reactants for 15 minutes.
The remaining portion of the monomer mixture is added simultaneously and incrementally with the solution of (3) over a two to three hour period, while the temperature is maintained. The temperature is maintained at 95~C for two hours after the addition of monomers is complete. The latex so obtained is cooled and filtered.
Step II Coating Formulation The latex obtained in Step I of this example is ~ 1067233 substituted for the latex of Step II of Example I and a water~based enamel is prepared using the procedures and other ingredients used to prepare the water-based enamel in Example 1.
Example III
The procedures of Example I are repeated with the difference that the solution resin (Step III) is prepared from the following materials:
(1) There is charged to the reactor 119 parts of water and 1.8 parts of the stabilizer polymer prepared in Step I of Example 1.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
Materials Parts by Weight butyl methacrylate10.0 methyl methacrylate35.0 methacrylic acid 15.0 butyl acrylate 40.0 l-octanethiol 1.3 (3) There is dissolved 0.5 parts of ammonium persulfate in 25 parts of water.
(4) There is dissolved 0.2 parts of ammonium persulfate in 5 parts of water.
After the latex preparation procedures of Example I are carried out and the resultant latex is cooled and filtered, the polymer is neutralized with water-soluble amine.
Example IV
A surfactant-free hybrid water-based enamel containing organic solvent is prepared using the formulation procedures of Step IV of Example I with the following differences:
Materials Parts by Weight solution polymer prepared as 7.6 described below Cymel 301tl) 7,0 titanium dioxide 17.4 isopropanol 2.8 n-butanol 3.5 latex from Example I, Step Il 51.3 (emulsion polymer plus stabilizer polymer I) 10% aqueous 2-(dimethylamino) 10.4 ethanol (1) a commercial grade of hexamethoxymethylmelamine sold by American Cyanimid Company.
The enamel when adjusted by water to a viscosity of 20 seconds (Ford Cup No. 4) is sprayed in a conventional manner upon primed steel panels and baked for 30 minutes.
The initial baking temperature is 80C. This temperature is gradually raised to 180C and held there for at least 10 of the 30 minutes.
Step II Preparation of Solution Polymer Monomer Mixture and IniatorParts by Weight methacrylic acid 15.0 methylmethacrylate 15.0 styrene 20.0 butyl acrylate 40,0 butyl methacrylate 10.0 t-butylperoctoate 3.5 Reactor Charge isopropyl alcohol 45 A mixture of the monomers and iniator listed is added to refluxing isopropyl alcohol over a 90-minute period.
An additional initiator change - 0.2 parts t-butylperoctoate in 5 parts isopropyl alcohol is added 30 minutes after completion of the monomer addition. The reaction mixture is maintained at reflux an additional 2 hours, cooled to room temperature, neutralized with 90~ of the calculated equivalent weight (based on acid functional comonomer) of dimethyleth-anolamine, and reduced to 60% by weight solids with water.
The polymer thus prepared has molecular weight (Mn) of about 9,20n. The glass transition temperature of this polymer is about 18C.
EXAMPLE V
Step I Preparation of Latex A latex is prepared according to the procedures of Step II of Example I using the following mixture of reactant monomers and chain transfer agent:
MaterialsParts by Wei~ht styrene 2.0 hydroxypropylmethacrylate 18.0 acrylic acid 2.0 butyl acrylate 50.0 butyl methacrylate10.0 l-octanethiol 0.6 Step II Preparation of Enamel There is prepared a surfactant-free, solvent-free, hybrid water-based enamel. The procedures used are those of Step IV of Example I, but with the following materials:
1(~67233 Materials Parts by Weight solution polymer from Step III 15.2 of Example I
Cymel 300(1) 6.9 titanium dioxide 17.3 water 5.5 latex from Step I of this Example 50.9 10~ aqueous 2-(dimethylamino) 4.2 ethanol (1) a commercial grade of hexamethoxymethylmelamine sold by American Cyanamid Company.
This enamel is sprayed on primed steel panels and baked for 25 minutes at 160C.
EXAMPLE VI
Step I Preparation of Latex _ __ _ A latex is prepared in the followiNg manner:
(1) There is charged to a reactor 127 parts of water and 2.57 parts of stabilizer polymer prepared as in Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed:
Materials Parts by ~ei~ht styrene 20.0 hydroxypropylmethacrylate 18.0 acrylic acid 2.0 butyl acrylate 50.0 butyl methacrylate 10.0 l-octanethiol 0.6 1~)67233 (3) There is dissolved 0.5 parts of a~nonium persulfate and one part of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 4.17 parts of water.
The procedures of Example II are repeated using the materials above listed to prepare the latex.
Step II Formulation of Coating Material The process of Step IV of Example I are repeated substituting the latex prepared in Step I of the example for the latex prepared in Step II of Example I.
EXAMPLE VII
The procedures of Example VI are repeated with the difference that the latex (let down) is prepared as follows:
(1) There is charged to a reactor 127 parts of water and 2.84 parts of stabilizer polymer prepared from the materials and according to the procedures used in Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
MaterialsParts by Weight styrene 20.0 methacrylic acid 15.0 butyl acrylate 55.0 butyl methacrylate10.0 l-octanethiol 0.6 (3) There is dissolved 0.4 parts of ammonium persulfate and 1.0 parts of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium :1067Z33 persulfate in 4.17 parts of water.
The latex is then prepared from the above materials using the procedures of Step II of Example I.
EXAMPLE VIII
A water-based enamel is produced in the following manner:
Step I Preparation of (let down) latex (1) There is charged to a reactor 128 parts of water and 2.67 parts of stabilizer polymer prepared from the materials and using the procedures of Step I of Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
MaterialsParts by Weight styrene 20.0 hydroxypropylmethacrylate 18.0 acrylic acid 2.0 butyl acrylate 25.0 butyl methacrylate35.0 l-octanethiol 0.6 (3) There is dissolved 0.5 parts of ammonium persulfate and 1.0 parts of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 4.17 parts of water.
The latex is prepared using the above materials and the procedures of Step II of Example I.
Step II Preparation of the Solution Polymer (1) There is charged to a reactor 200 parts of water and 4 parts of stabilizer polymer prepared from the same materials and procedures used to prepare the stabilizer polymer in Example I.
-~067Z33 (2) The following reactant monomers and chain transfer agent are thoroughly mixed.
~aterials Parts by Weight methyl methacrylate 35 methacrylic acid 15 butyl acrylate 50 l-octanethiol Thè solution polymer is then prepared from the above materials using the procedures used in Step II of Example I.
The latex so obtained is neutralized with 2-(dimethylamino)ethanol to an amount equivalent to the methacrylic acid constituent of the polymer.
Step III Formulation of Coating Material A coating formulation is prepared from the following materials:
Materials Parts by Weight sQlution polymer from the Example 17.5 Step II
Cymel 301(1) 8.7 titanium dioxide 19.8 water 7 9 latex from this Example Step I43.5 20% aqueous 2-(dimethylamine)ethanol 2~4 (1) defined in Example IV~
The coating material is formulated from the above materials using the procedures of Step IV of Example I.
The resultant enamel adjusted to a viscosity of 20 seconds (Ford Cup No. 4) is sprayed on prime steel panels and baked for 25 minutes. The initial baking temperature is 100C.
This temperature is gradually raised to 180C and maintained at 180C for at least 10 of the 25 minutes. The resultant ~067Z33 coatings demonstrate good gloss and physical properties.
The resistance of these coatings to soaking in water at 32C for 240 hours is excellent.
EXAMPLE IX
A water-based enamel is produced in the following manner:
Step I Preparation of (let down) Latex (1) There is charged to a reactor 127 parts of water and 2 parts of stabilizer polymer prepared from the materials and using the procedures used to prepare the stabilizer polymer of Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
Materials Parts by Weight styrene 20.0 hydroxypropylmethacrylate 14.0 methacrylic acid 6.0 butyl acrylate 25.0 butyl methacrylate 35.0 l-octanethiol 0,7 (3) There is dissolved 0.5 parts of ammonium persulfate in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 4.66 parts of water.
The latex is prepared from the above materials following the procedures of Step II of Example I.
The resultant latex polymer, i.e., the emulsion polymer, has average molecular weight (Mn) of about 8,000 and a Tg of 20C.
Step II Formulation of Coating Material A coating material is prepared from the following materials:
Materials Parts_by Weight solution resin from Step II, 12.6 Example VIII
Cymel 300(1) 7.6 titanium dioxide 21.0 latex 'rom Step I of this 46.2 Example (includes emulsion polymer and stabilizer polymer) 10% aqueous 2~(dimethylamino) 4.2 ethanol Water 8.4 (1) defined in Example V
The coating formulation is prepared from the above materials using the procedures of Step IV of Example I.
EXAMPLE X
The procedures of Example I are repeated with the difference that in preparing the soluble stabilizer polymer of Step I there is used with the reactant monomers 3.5 parts by weight of l-octanethiol. The average molecular weight (Mn) of the resultant stabilizer polymer is about 3,000. It has a Tg of about -8C.
EXAMPLE XI
_ _ _ _ .
The procedures of Example I are repeated with the difference that in preparing the soluble stabilizer polymer of Step I there is used with the reactant monomers 0.5 parts by weight of l-octanethiol. The average molecular weight (Mn) of the resultant stabilizer polymer is about 10,000. It has a Tg of about -8C.
EXAMPLE XII
The procedures of Example I are rep~ated with the difference that in preparing the soluble stabilizer polymer of Step I the following reactant monomers and chain transfer agent are used:
Materials Parts by Weight methacrylic acid 15 methyl methacrylate30 styrene 5 butyl acrylate 40 butyl methacrylate 10 l-octanethiol 2 - The average molecular weight (Mn) of the resultant soluble stabilizer polymer is about 4,000. Its Tg is about 18C.
EXAMPLE XIII
The procedure of Example I is repeated with the single difference that in lieu of the commercially available amino resin (Cymel 300) cross-linking agent there is used a chemically equivalent amount of a melamine resin prepared from the following materials and in the following manner:
Water (400 parts by weight), sodium hydroxide (3.5 parts by weight), and paraformaldehyde (326 parts by weight) are heated to reflux and refluxed 15 minutes. The solution is cooled to 85C, and the pH is adjusted to 8.5 with aqueous sodium hydroxide. Melamine (126 parts) is added, and the mixture is maintained at 80 to 90C for 10 minutes. Methanol (992 parts) and concentrated sulfuric acid (36 parts) are added and the mixture is stirred for about one hour. Upon addition of 320 parts 25~ aqueous sodium hydroxide, a white precipitate is formed which is removed by filtration.
Approximately 300 parts of a semi-solid methylated melamine are isolated from the filtrate by vacuum distillation and used in the formulation of water-based enamels.
EXAMPLE XIV
The procedure of Example I is repeated with the single difference that in lieu of the commercially available amino resin (Cymel 300) cross-linking agent there is used a chemically equivalent amount of a urea-formaldehyde resin prepared from the following materials and in the following manner:
In a one liter three-necked flask equipped with reflux condenser, thermometer, and stirrer are placed 243 g.
of 37% aqueous formaldehyde and 4 to 6 g. of concentrated ammonium hydroxide to bring the pH to 7.5 to 8.5. Sixty g.
urea is added with stirring and the mixture heated to 100C
over a one-hour period by means of a heating mantle. This temperature is maintained 10 1/2 hours. 64 g. methanol is added, followed by enough phosphoric acid to bring the pH
to 5.5. The reaction is stirred for one hour. Water can be removed by heating 60 to 70C under a water aspirator pressure of 100 to 200 mm. The resin can be dissolved in isopropyl alcohol to give a 60~ solution.
The reactor charge is heated to boiling and cooled to 95C. After the solution of (4) is charged to the reactor, there is added to the reaction medium 0.45 parts of the monomer mixture of (2) and the temperature is held at 95C without further addition of reactants for 15 minutes.
The remaining portion of the monomer mixture is added simultaneously and incrementally with the solution of (3) over a two to three hour period, while the temperature is maintained. The temperature is maintained at 95~C for two hours after the addition of monomers is complete. The latex so obtained is cooled and filtered.
Step II Coating Formulation The latex obtained in Step I of this example is ~ 1067233 substituted for the latex of Step II of Example I and a water~based enamel is prepared using the procedures and other ingredients used to prepare the water-based enamel in Example 1.
Example III
The procedures of Example I are repeated with the difference that the solution resin (Step III) is prepared from the following materials:
(1) There is charged to the reactor 119 parts of water and 1.8 parts of the stabilizer polymer prepared in Step I of Example 1.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
Materials Parts by Weight butyl methacrylate10.0 methyl methacrylate35.0 methacrylic acid 15.0 butyl acrylate 40.0 l-octanethiol 1.3 (3) There is dissolved 0.5 parts of ammonium persulfate in 25 parts of water.
(4) There is dissolved 0.2 parts of ammonium persulfate in 5 parts of water.
After the latex preparation procedures of Example I are carried out and the resultant latex is cooled and filtered, the polymer is neutralized with water-soluble amine.
Example IV
A surfactant-free hybrid water-based enamel containing organic solvent is prepared using the formulation procedures of Step IV of Example I with the following differences:
Materials Parts by Weight solution polymer prepared as 7.6 described below Cymel 301tl) 7,0 titanium dioxide 17.4 isopropanol 2.8 n-butanol 3.5 latex from Example I, Step Il 51.3 (emulsion polymer plus stabilizer polymer I) 10% aqueous 2-(dimethylamino) 10.4 ethanol (1) a commercial grade of hexamethoxymethylmelamine sold by American Cyanimid Company.
The enamel when adjusted by water to a viscosity of 20 seconds (Ford Cup No. 4) is sprayed in a conventional manner upon primed steel panels and baked for 30 minutes.
The initial baking temperature is 80C. This temperature is gradually raised to 180C and held there for at least 10 of the 30 minutes.
Step II Preparation of Solution Polymer Monomer Mixture and IniatorParts by Weight methacrylic acid 15.0 methylmethacrylate 15.0 styrene 20.0 butyl acrylate 40,0 butyl methacrylate 10.0 t-butylperoctoate 3.5 Reactor Charge isopropyl alcohol 45 A mixture of the monomers and iniator listed is added to refluxing isopropyl alcohol over a 90-minute period.
An additional initiator change - 0.2 parts t-butylperoctoate in 5 parts isopropyl alcohol is added 30 minutes after completion of the monomer addition. The reaction mixture is maintained at reflux an additional 2 hours, cooled to room temperature, neutralized with 90~ of the calculated equivalent weight (based on acid functional comonomer) of dimethyleth-anolamine, and reduced to 60% by weight solids with water.
The polymer thus prepared has molecular weight (Mn) of about 9,20n. The glass transition temperature of this polymer is about 18C.
EXAMPLE V
Step I Preparation of Latex A latex is prepared according to the procedures of Step II of Example I using the following mixture of reactant monomers and chain transfer agent:
MaterialsParts by Wei~ht styrene 2.0 hydroxypropylmethacrylate 18.0 acrylic acid 2.0 butyl acrylate 50.0 butyl methacrylate10.0 l-octanethiol 0.6 Step II Preparation of Enamel There is prepared a surfactant-free, solvent-free, hybrid water-based enamel. The procedures used are those of Step IV of Example I, but with the following materials:
1(~67233 Materials Parts by Weight solution polymer from Step III 15.2 of Example I
Cymel 300(1) 6.9 titanium dioxide 17.3 water 5.5 latex from Step I of this Example 50.9 10~ aqueous 2-(dimethylamino) 4.2 ethanol (1) a commercial grade of hexamethoxymethylmelamine sold by American Cyanamid Company.
This enamel is sprayed on primed steel panels and baked for 25 minutes at 160C.
EXAMPLE VI
Step I Preparation of Latex _ __ _ A latex is prepared in the followiNg manner:
(1) There is charged to a reactor 127 parts of water and 2.57 parts of stabilizer polymer prepared as in Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed:
Materials Parts by ~ei~ht styrene 20.0 hydroxypropylmethacrylate 18.0 acrylic acid 2.0 butyl acrylate 50.0 butyl methacrylate 10.0 l-octanethiol 0.6 1~)67233 (3) There is dissolved 0.5 parts of a~nonium persulfate and one part of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 4.17 parts of water.
The procedures of Example II are repeated using the materials above listed to prepare the latex.
Step II Formulation of Coating Material The process of Step IV of Example I are repeated substituting the latex prepared in Step I of the example for the latex prepared in Step II of Example I.
EXAMPLE VII
The procedures of Example VI are repeated with the difference that the latex (let down) is prepared as follows:
(1) There is charged to a reactor 127 parts of water and 2.84 parts of stabilizer polymer prepared from the materials and according to the procedures used in Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
MaterialsParts by Weight styrene 20.0 methacrylic acid 15.0 butyl acrylate 55.0 butyl methacrylate10.0 l-octanethiol 0.6 (3) There is dissolved 0.4 parts of ammonium persulfate and 1.0 parts of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium :1067Z33 persulfate in 4.17 parts of water.
The latex is then prepared from the above materials using the procedures of Step II of Example I.
EXAMPLE VIII
A water-based enamel is produced in the following manner:
Step I Preparation of (let down) latex (1) There is charged to a reactor 128 parts of water and 2.67 parts of stabilizer polymer prepared from the materials and using the procedures of Step I of Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
MaterialsParts by Weight styrene 20.0 hydroxypropylmethacrylate 18.0 acrylic acid 2.0 butyl acrylate 25.0 butyl methacrylate35.0 l-octanethiol 0.6 (3) There is dissolved 0.5 parts of ammonium persulfate and 1.0 parts of 2-acrylamide-2-methylpropane sulfonic acid in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 4.17 parts of water.
The latex is prepared using the above materials and the procedures of Step II of Example I.
Step II Preparation of the Solution Polymer (1) There is charged to a reactor 200 parts of water and 4 parts of stabilizer polymer prepared from the same materials and procedures used to prepare the stabilizer polymer in Example I.
-~067Z33 (2) The following reactant monomers and chain transfer agent are thoroughly mixed.
~aterials Parts by Weight methyl methacrylate 35 methacrylic acid 15 butyl acrylate 50 l-octanethiol Thè solution polymer is then prepared from the above materials using the procedures used in Step II of Example I.
The latex so obtained is neutralized with 2-(dimethylamino)ethanol to an amount equivalent to the methacrylic acid constituent of the polymer.
Step III Formulation of Coating Material A coating formulation is prepared from the following materials:
Materials Parts by Weight sQlution polymer from the Example 17.5 Step II
Cymel 301(1) 8.7 titanium dioxide 19.8 water 7 9 latex from this Example Step I43.5 20% aqueous 2-(dimethylamine)ethanol 2~4 (1) defined in Example IV~
The coating material is formulated from the above materials using the procedures of Step IV of Example I.
The resultant enamel adjusted to a viscosity of 20 seconds (Ford Cup No. 4) is sprayed on prime steel panels and baked for 25 minutes. The initial baking temperature is 100C.
This temperature is gradually raised to 180C and maintained at 180C for at least 10 of the 25 minutes. The resultant ~067Z33 coatings demonstrate good gloss and physical properties.
The resistance of these coatings to soaking in water at 32C for 240 hours is excellent.
EXAMPLE IX
A water-based enamel is produced in the following manner:
Step I Preparation of (let down) Latex (1) There is charged to a reactor 127 parts of water and 2 parts of stabilizer polymer prepared from the materials and using the procedures used to prepare the stabilizer polymer of Example I.
(2) The following reactant monomers and chain transfer agent are thoroughly mixed.
Materials Parts by Weight styrene 20.0 hydroxypropylmethacrylate 14.0 methacrylic acid 6.0 butyl acrylate 25.0 butyl methacrylate 35.0 l-octanethiol 0,7 (3) There is dissolved 0.5 parts of ammonium persulfate in 16.7 parts of water.
(4) There is dissolved 0.1 parts of ammonium persulfate in 4.66 parts of water.
The latex is prepared from the above materials following the procedures of Step II of Example I.
The resultant latex polymer, i.e., the emulsion polymer, has average molecular weight (Mn) of about 8,000 and a Tg of 20C.
Step II Formulation of Coating Material A coating material is prepared from the following materials:
Materials Parts_by Weight solution resin from Step II, 12.6 Example VIII
Cymel 300(1) 7.6 titanium dioxide 21.0 latex 'rom Step I of this 46.2 Example (includes emulsion polymer and stabilizer polymer) 10% aqueous 2~(dimethylamino) 4.2 ethanol Water 8.4 (1) defined in Example V
The coating formulation is prepared from the above materials using the procedures of Step IV of Example I.
EXAMPLE X
The procedures of Example I are repeated with the difference that in preparing the soluble stabilizer polymer of Step I there is used with the reactant monomers 3.5 parts by weight of l-octanethiol. The average molecular weight (Mn) of the resultant stabilizer polymer is about 3,000. It has a Tg of about -8C.
EXAMPLE XI
_ _ _ _ .
The procedures of Example I are repeated with the difference that in preparing the soluble stabilizer polymer of Step I there is used with the reactant monomers 0.5 parts by weight of l-octanethiol. The average molecular weight (Mn) of the resultant stabilizer polymer is about 10,000. It has a Tg of about -8C.
EXAMPLE XII
The procedures of Example I are rep~ated with the difference that in preparing the soluble stabilizer polymer of Step I the following reactant monomers and chain transfer agent are used:
Materials Parts by Weight methacrylic acid 15 methyl methacrylate30 styrene 5 butyl acrylate 40 butyl methacrylate 10 l-octanethiol 2 - The average molecular weight (Mn) of the resultant soluble stabilizer polymer is about 4,000. Its Tg is about 18C.
EXAMPLE XIII
The procedure of Example I is repeated with the single difference that in lieu of the commercially available amino resin (Cymel 300) cross-linking agent there is used a chemically equivalent amount of a melamine resin prepared from the following materials and in the following manner:
Water (400 parts by weight), sodium hydroxide (3.5 parts by weight), and paraformaldehyde (326 parts by weight) are heated to reflux and refluxed 15 minutes. The solution is cooled to 85C, and the pH is adjusted to 8.5 with aqueous sodium hydroxide. Melamine (126 parts) is added, and the mixture is maintained at 80 to 90C for 10 minutes. Methanol (992 parts) and concentrated sulfuric acid (36 parts) are added and the mixture is stirred for about one hour. Upon addition of 320 parts 25~ aqueous sodium hydroxide, a white precipitate is formed which is removed by filtration.
Approximately 300 parts of a semi-solid methylated melamine are isolated from the filtrate by vacuum distillation and used in the formulation of water-based enamels.
EXAMPLE XIV
The procedure of Example I is repeated with the single difference that in lieu of the commercially available amino resin (Cymel 300) cross-linking agent there is used a chemically equivalent amount of a urea-formaldehyde resin prepared from the following materials and in the following manner:
In a one liter three-necked flask equipped with reflux condenser, thermometer, and stirrer are placed 243 g.
of 37% aqueous formaldehyde and 4 to 6 g. of concentrated ammonium hydroxide to bring the pH to 7.5 to 8.5. Sixty g.
urea is added with stirring and the mixture heated to 100C
over a one-hour period by means of a heating mantle. This temperature is maintained 10 1/2 hours. 64 g. methanol is added, followed by enough phosphoric acid to bring the pH
to 5.5. The reaction is stirred for one hour. Water can be removed by heating 60 to 70C under a water aspirator pressure of 100 to 200 mm. The resin can be dissolved in isopropyl alcohol to give a 60~ solution.
Claims (2)
1. In a method for producing an aqueous dispersion of paint in which a carboxy-functional polymer is at least partially neutralized with a water-soluble amine and dispersed with an amino resin cross-linking agent selected from melamine-formaldehyde resins and urea-formaldehyde resins in an aqueous solution of water and water-soluble amine, wherein said carboxy functional polymer, amino resin cross-linking agent and water-soluble amine constitutes about 30 to 50% by weight of the continuous aqueous phase of the paint with the balance of the continuous aqueous phase being water or a mixture of water and an organic solvent, said water-soluble amine is present in an amount sufficient to provide an aqueous phase pH of about 7.1 to about 8.5 and said water or mixture of water and organic solvent constitute about 50 to about 65% by weight of the paint, the improvement wherein the aqueous dispersion is produced by intimately dispersing with said water, said amino resin cross-linking agent and said water-soluble amine:
I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that:
(a) is at least partially neutralized with water-soluble amine, (b) is soluble in said aqueous solution, (c) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (d) has Tg in the range of -15°C. to 50°C., II. an aqueous emulsion consisting essentially of water, water-soluble amine, and about 50 to about 95 parts by weight of an emulsion polymer having functionality selected from carboxy functionality and hydroxy functionality and is a copolymer of acrylic monomers that:
(a) is essentially insoluble in said aqueous solution, (b) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (c) has Tg in the range of -15°C., to 50°C., and III. about 0.025 to about 5 parts by weight of a stabilizer polymer which is a carboxy-functional copolymer of acrylic monomers that:
(a) is soluble in said aqueous solution, (b) has average molecular weight (Mn) lower than that of said solution polymer and (c) has a Tg in the range of -15°C to 50°C, said stabilizer polymer being introduced into said dispersion intimately mixed with at least one of said solution polymer and said emulsion polymer.
I. about 5 to about 50 parts by weight of a solution polymer which is a carboxy-functional copolymer of acrylic monomers that:
(a) is at least partially neutralized with water-soluble amine, (b) is soluble in said aqueous solution, (c) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (d) has Tg in the range of -15°C. to 50°C., II. an aqueous emulsion consisting essentially of water, water-soluble amine, and about 50 to about 95 parts by weight of an emulsion polymer having functionality selected from carboxy functionality and hydroxy functionality and is a copolymer of acrylic monomers that:
(a) is essentially insoluble in said aqueous solution, (b) has average molecular weight (Mn) in the range of about 3,000 to about 20,000, and (c) has Tg in the range of -15°C., to 50°C., and III. about 0.025 to about 5 parts by weight of a stabilizer polymer which is a carboxy-functional copolymer of acrylic monomers that:
(a) is soluble in said aqueous solution, (b) has average molecular weight (Mn) lower than that of said solution polymer and (c) has a Tg in the range of -15°C to 50°C, said stabilizer polymer being introduced into said dispersion intimately mixed with at least one of said solution polymer and said emulsion polymer.
2. The method of claim 1 wherein the average molecular weight (Mn) of said stabilizer polymer is between about 3,000 and about 8,000.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA251,359A CA1067233A (en) | 1974-06-03 | 1976-04-28 | Method for producing surfactant-free water based enamels |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US476115A US3926888A (en) | 1974-06-03 | 1974-06-03 | Method of making aqueous coating compositions of acrylic polymer latex, acrylic polymer solution, aminoplast and acrylic stabilizer polymer |
| CA228,423A CA1071789A (en) | 1974-06-03 | 1975-05-30 | Method for producing solvent free water based enamels |
| CA251,359A CA1067233A (en) | 1974-06-03 | 1976-04-28 | Method for producing surfactant-free water based enamels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1067233A true CA1067233A (en) | 1979-11-27 |
Family
ID=27163984
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,359A Expired CA1067233A (en) | 1974-06-03 | 1976-04-28 | Method for producing surfactant-free water based enamels |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1067233A (en) |
-
1976
- 1976-04-28 CA CA251,359A patent/CA1067233A/en not_active Expired
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