Patent Application
20120322936
The present invention relates to hydrophobically modified urethane polymers, which are used as rheology modifiers in waterborne coatings formulations.
Rheology modifiers are used in waterborne coatings formulations to control viscosity over a wide shear rate range. They may be associative (they associate with the dispersed phase) or non-associative (they thicken the water phase). Associative thickeners may be derived from natural products such as hydrophobically modified cellulose ethers, or prepared from synthetic polymers such as hydrophobically modified ethylene oxide urethane (HEUR) polymers. U.S. Pat. No. 4,155,892 (Emmons et al.) describes the preparation of linear as well as branched HEUR polymers in separate examples.
Rheology modifiers are typically classified as either low shear rate viscosity builders (Stormer viscosity builders, also known as KU viscosity builders) or high shear rate viscosity builders (ICI builders). It is desirable to increase ICI viscosity and the efficiency of ICI building rheology modifiers without concomitant increase in KU viscosity because an increase in KU viscosity limits the formulator's ability to add a KU building rheology modifier to the formulation. A formulation with insufficient KU building rheology modifier added can exhibit poor resistance to sagging and dripping when applied to the substrate.
The present invention addresses a need in the art by providing in a first aspect a process comprising contacting together under reaction conditions: a) a polyalkylene glycol having a weight average molecular weight in the range of from 4000-12000 Daltons; an aliphatic diisocyanate; and an alkoxylated polyol having 50 to 250 repeating alkylene oxide units to form an intermediate polymer containing residual NCO groups; then b) reacting the intermediate polymer with a capping agent which is a linear, branched, or cyclic C6-C14 alkanol or C10-C16—(OX)n—OH alkoxylated alcohol to form a hydrophobically modified alkylene oxide urethane polymer; wherein each X is independently CH2CH2 or CH2CH(CH3); n is 1 to 50; the OH group mole equivalent ratio of the polyalkylene glycol to the alkoxylated polyol in step a) is in the range of 3:1 to 12:1; the NCO to OH mole equivalent ratio in step a) is in the range of 1:0.70 to 1:0.95; the capping agent is added at or above a stoichiometric amount with respect to the residual NCO groups from step a); and the alkoxylated polyol is an alkoxylated triol or tetraol or a combination thereof.
In a second aspect, the present invention is a hydrophobically modified alkylene oxide urethane polymer comprising structural units of: a) a polyalkylene glycol having a weight average molecular weight in the range of from 4000-12000 Daltons; b) an aliphatic diiscocyanate; c) an alkoxylated polyol having 50 to 250 repeating alkylene oxide units; and d) a capping agent which is a linear, branched, or cyclic C6-C14 alkanol or C10-C16—(OX)n—OH alkoxylated alcohol; wherein each X is independently CH2CH2 or CH2CH(CH3); n is 1 to 50; the OH group mole equivalent ratio of structural units of the polyalkylene glycol to the alkoxylated polyol is in the range of 3:1 to 12:1; the OH group mole equivalent of structural units of the capping agent to the alkoxylated polyol is in the range of 0.4 to 6.5, and the alkoxylated polyol is an alkoxylated triol or tetraol.
In a first aspect, the present invention is a process comprising contacting together under reaction conditions: a) a polyalkylene glycol having a weight average molecular weight in the range of from 4000-12000 Daltons; an aliphatic diisocyanate; and an alkoxylated polyol having 50 to 250 repeating alkylene oxide units to form an intermediate polymer containing residual NCO groups; then b) reacting the intermediate polymer with a capping agent which is a linear, branched, or cyclic C6-C14 alkanol or C10-C16—(OX)n—OH alkoxylated alcohol to form a hydrophobically modified alkylene oxide urethane polymer; wherein each X is independently CH2CH2 or CH2CH(CH3); n is 1 to 50; the OH group mole equivalent ratio of the polyalkylene glycol to the alkoxylated polyol in step a) is in the range of 3:1 to 12:1; the NCO to OH mole equivalent ratio in step a) is in the range of 1:0.70 to 1:0.95; the capping agent is added at or above a stoichiometric amount with respect to the residual NCO groups from step a); and the alkoxylated polyol is an alkoxylated triol or tetraol or a combination thereof.
As used herein, the term “polyalkylene glycol” refers to polyethylene glycol, polyethylene glycol/polypropylene glycol copolymers, or polyethylene glycol/polybutylene glycol copolymers. Preferably, the polyalkylene glycol is a polyethylene glycol, more preferably a polyethylene glycol having a weight average molecular weight (Mw) in the range of from 5000 to 9000 Daltons. CARBOWAX™ 8000 Polyethylene Glycol (A Trademark of The Dow Chemical Company or its Affiliates) is an example of a commercially available polyethylene glycol.
The aliphatic diisocyanate may be saturated or partially saturated, and may be linear, branched, or cyclic, or a combination thereof. Examples of suitable diisocyanates include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-diisocyanatohexane, 1,10-decamethylene diisocyanate, 4,4′-methylenebis(isocyanatocyclohexane), 1,4-cyclohexylene diisocyanate, isophorone diisocyanate, and 1,5-tetrahydronaphthylene diisocyanate. Preferred diisocyanates include 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4′-methylenebis(isocyanatocyclohexane).
The alkoxylated polyol is preferably an ethoxylated triol having the following general formula:
wherein R is a C3-C12 alkyl group which is linear or branched or cyclic or a combination thereof;
each X is independently CH2CH2 or CH2CH(CH3);
the sum a+b+c is in the range of from 50 to 250; preferably from 60 to 220; more preferably from 90 to 200; and most preferably from 120 to 180.
Examples of RO3 groups are illustrated:
where the dotted lines represent the point of attachment to the X groups. Preferably, RO3 is
As used herein, the term “OH group mole equivalent,” as it relates to the process, is illustrated by the following example: One molecule of polyethylene glycol has two OH groups while an ethoxylated triol has three OH groups. Thus, three moles of the glycol have the same number of OH groups as two moles of the triol and a ratio of the glycol to the triol in OH equivalents of 3:1 is the same as a mole:mole ratio of 9:2. Preferably, the OH group mole equivalent ratio of the polyalkylene glycol, preferably the polyethylene glycol, to ethoxylated polyol, preferably the ethoxylated triol, is in the range of from 4:1 to 7:1.
Similarly, the mole group equivalent ratio is calculated for diisocyanates and the sum of the polyalkylene glycol and the alkoxylated polyol. The preferred NCO:OH mole equivalent ratio in step a) is 1:0.80 to 1:0.90.
In a second step, the capping agent is added to the intermediate polymer to form the hydrophobically modified alkylene oxide urethane polymer, preferably the hydrophobically modified ethylene oxide urethane polymer. Preferably, the capping reagent is added in stoichiometric excess with respect to NCO groups to ensure substantially complete conversion of the NCO groups. Preferably, the capping agent is a linear, branched, or cyclic C6-C14 alkanol, examples of which include n-hexanol, cyclohexanol, n-octanol, n-nonanol, n-decanol, and n-dodecanol. Where the capping agent is a linear, branched, or cyclic C10-C16—(OX)n—OH alkoxylated alcohol, X preferably is CH2CH2 and n is preferably 10 to 30.
In a second aspect, the present invention is a hydrophobically modified alkylene oxide urethane polymer comprising structural units of: a) a polyalkylene glycol having a weight average molecular weight in the range of from 4000-12000 Daltons; b) an aliphatic diisocyanate; c) an alkoxylated polyol having 50 to 250 repeating alkylene oxide units; and d) a capping agent which is a linear, branched, or cyclic C6-C14 alkanol or C10-C16—(OX)n—OH alkoxylated alcohol; wherein each X is independently CH2CH2 or CH2CH(CH3), preferably CH2CH2; n is 1 to 50, preferably 10 to 30; the OH group mole equivalent ratio of structural units of the polyalkylene glycol to the alkoxylated polyol is in the range of 3:1 to 12:1; and the OH group mole equivalent ratio of structural units of the capping agent to the alkoxylated polyol is in the range of 0.4 to 6.5, and wherein the alkoxylated polyol is an alkoxylated triol or tetraol.
Preferably, the OH group mole equivalent ratio of structural units of the polyalkylene glycol to the alkoxylated polyol is in the range of 4:1 to 7:1; and preferably, the OH group mole equivalent ratio of structural units of the capping agent to the alkoxylated polyol is in the range of 0.6 to 2.0.
As used herein, the term “structural units” is used to refer to the repeating groups that are formed in the polymer by reaction of the materials. Thus, a structural unit of diisocyanate OCN—R′—NCO is as follows:
where R′ is an linear, branched or cyclic aliphatic group.
The term “OH group mole equivalent ratio,” as it relates to the composition of the present invention, refers to the structural units of the glycol, the alkoxylated polyol, or the capping agent in the polymer. Thus, for example, a structural unit of glycerin has three OH group mole equivalents while a structural unit of n-decanol has one OH group mole equivalents.
The coating composition according to the present invention may further include one or more of the following additives: Solvents; fillers; pigments, such as titanium dioxide, mica, calcium carbonate, silica, zinc oxide, milled glass, aluminum trihydrate, talc, antimony trioxide, fly ash, and clay; polymer encapsulated pigments, such as polymer-encapsulated or partially encapsulated opacifying pigment particles including titanium dioxide, zinc oxide, or lithopone polymers; polymers or polymer emulsions adsorbing or bonding to the surface of pigments such as titanium dioxide; hollow pigments, including pigments having one or more voids; dispersants, such as aminoalcohols and polycarboxylates; surfactants; defoamers; preservatives, such as biocides, mildewcides, fungicides, algaecides, and combinations thereof; flow agents; leveling agents; and additional neutralizing agents, such as hydroxides, amines, ammonia, and carbonates.
For example, the coatings composition may include polymer-encapsulated opacifying pigment particles comprising i) opacifying pigment particles, such as titanium dioxide particles, having a diameter in the range of 100 nm to 500 nm and an index of refraction of at least 1.8; ii) an encapsulating polymer, and iii) a polymeric dispersant for the encapsulated opacifying pigment particles and the polymer. Such polymer-encapsulated opacifying pigment particles are described, for example, in U.S. Patent Publication US 2010/0298483 A1. In another example, the coating composition may include polymer-encapsulated opacifying pigment particles as described in WO 2007/112503A1.
The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.
Comparative Examples 1 and 2 and Examples 1-5 are all illustrative of HEURs prepared using 1,6-hexamethylene diisocyanate (HDI), a polyethylene glycol (PEG) with Mw=8200, and n-decanol as a capping reagent. The triol ethylene oxide (EO) length was varied from 0 to 200 EO units.
The ratios in each of the following examples and comparative examples was 0.75 PEG/0.15 triol/1.1 diisocyanate//0.25 capping agent based on OH and NCO group equivalents.
A mixture of CARBOWAX™ 8000 Polyethylene Glycol (150.0 g Mw=8200, 18.29 mmol, 36.58 OH mmol equivalents), 1,1,1-tris(hydroxymethyl)propane (0.33 g, 2.46 mmol, 7.39 OH mmol equivalents), and toluene (400.0 g) was dried by azeotropic distillation for 2 h. The mixture was cooled to 90° C., whereupon HDI (4.51 g, 26.84 mmol, 52.69 NCO mmol equivalents) and bismuth octoate solution (0.16 g, 28% by weight) were added with stiffing. After 1 h, n-decanol (1.93 g, 12.2 mmol) was added and the mixture was maintained at 80° C. for another 1 h. Toluene was removed in vacuo and the resulting solid polymer was isolated.
The procedure for Comparative Example 2 and Examples 1-5 was substantially the same as that for Comparative Example 1, the difference being the nature of the triol. Table 1 illustrates the triols used and their corresponding molecular weights and further illustrates the effect on ICI and ICI/KU viscosity ratios on EO length. 1,1,1-THMP refers to 1,1,1-tris(hydroxymethyl)propane.
The performance obtained by the use of associative thickeners was demonstrated in a latex paint composition. A latex paint composition, Pre-paint #1, was prepared by combining the following components in the order listed:
RHOPLEX™ VSR-2015 Binder was made using VERSAIR™ Technology (TAMOL™, RHOPLEX™ and VERSAIR are all Trademarks of The Dow Chemcial Company or its Affiliates.) The formulated paint was obtained by slowly adding with stirring thickener and water (combined weight 158.9 g) to Pre-paint #1 (905.4 g). Stirring was continued for 10 min. The density of the fully formulated paint was 1064 lb/100 gal (1.3 Kg/L). The pH values of the fully formulated paints were in the range of 8.5 to 9.0.
In the following data, thickener concentrations in the paint are described in terms of dry grams of thickener added even though the aqueous thickener composition was admixed into the paint. For example, 5 grams (dry) of a thickener can be obtained in the paint by adding 25 grams of 20% active solids thickener solution. Following a 24-hour equilibration at room temperature, the thickened paint was stirred for one minute on a lab mixer before measuring viscosity values.
KU viscosity is a measure of the mid-shear viscosity as measured by a Krebs viscometer. The Krebs viscometer is a rotating paddle viscometer that is compliant with ASTM-D562. KU viscosity was measured on a Brookfield Krebs Unit Viscometer KU-1+ available from Brookfield Engineering Labs (Middleboro, Mass., USA). KU refers to Krebs unit.
ICI viscosity is the viscosity, expressed in units of poise, measured on a high shear rate, cone and plate viscometer known as an ICI viscometer, which is described in ASTM D4287. The viscometer measures the viscosity of a paint at approximately 10,000 sec−1. ICI viscosities of paints were measured on a viscometer manufactured by Research Equipment London, Ltd (London, UK). An equivalent ICI viscometer is the Elcometer 2205 manufactured by Elcometer, Incorporated (Rochester Hills, Mich., USA). The ICI viscosity of a paint typically correlates with the amount of drag force experienced during brush application of the paint.
Table 1 illustrates the surprising effect of Triol EO length on ICI viscosity and ICI/KU: As the data show, ICI values advantageously rise without a corresponding increase in KU viscosity.
For Comparative Example 3 and Example 6n-nonanol was used as the capping agent. Poe(26) glycerine was used as the triol for the Comparative Example 3 and Poe(200) glycerine was used as the triol for Example 6.
A mixture of CARBOWAX™ 8000 Polyethylene Glycol (200.0 g Mw=8200), Poe(26) Glycerine (4.02 g), and toluene (400.0 g) was dried by azeotropic distillation for 2 h. The mixture was cooled to 90° C., whereupon HDI (6.01 g) and bismuth octoate solution (0.21 g, 28% by weight) were added with stirring. After 1 h, n-nonanol (2.35 g) was added and the mixture was maintained at 80° C. for another 1 h. Toluene was removed in vacuo and the resulting solid polymer was isolated. After formulating in Pre-paint #1, KU was found to be 73; ICI was found to be 1.20; and 100*ICI/KU was found to be 1.65.
A mixture of CARBOWAX™ 8000 Polyethylene Glycol (120.0 g Mw=8200), Poe(200) Glycerine (16.84 g), and toluene (400.0 g) was dried by azeotropic distillation for 2 h. The mixture was cooled to 90° C., whereupon HDI (3.61 g) and bismuth octoate solution (0.16 g, 28% by weight) were added with stirring. After 1 h, n-nonanol (1.41 g) was added and the mixture was maintained at 80° C. for another 1 h. Toluene was removed in vacuo and the resulting solid polymer was isolated. After formulating in Pre-paint#1, KU was found to be 83; ICI was found to be 1.55; and 100*ICI/KU was found to be 1.87.
A mixture of CARBOWAX™ 8000 Polyethylene Glycol (120.0 g Mw=8200), Poe(200) Glycerine (16.84 g), and toluene (400.0 g) was dried by azeotropic distillation for 2 h. The mixture was cooled to 90° C., whereupon 4,4′-methylenebis(isocyanatocyclohexane) (HDMI, 5.62 g) and bismuth octoate solution (0.16 g, 28% by weight) were added with stiffing. After 1 h, n-hexanol (1.00 g) was added and the mixture was maintained at 80° C. for another 1 h. Toluene was removed in vacuo and the resulting solid polymer was isolated. After formulating in Pre-paint#1, KU was found to be 107; ICI was found to be 1.90; and 100*ICI/KU was found to be 1.77.
The polymer was prepared essentially as described for Example 7 except that isophorone diisocyanate (IPDI, 4.77 g) was used as the diisocyanate and n-nonanol (1.41 g) was used as the capping reagent. After formulating in Pre-paint#1, KU was found to be 115; ICI was found to be 2.30; and 100*ICI/KU was found to be 2.00.
| Number | Date | Country | |
|---|---|---|---|
| 61498135 | Jun 2011 | US |
