CA2123615A1 - Use of diluents to incorporate thickeners in latex paints - Google Patents

Abstract

ABSTRACT

The present invention relates to a thickening composition that is made by preblending a diluent and a thickener. The diluent-thickener blend is used to incorporate urethane thickeners having branched and terminal hydrophobes which contain a total of at least 36 carbon atoms into aqueous systems, including latex paints. By preblending the thickener with a diluent, properties such as viscosity, sag resistance and thickening efficiency are realized.

Description

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FI~Lp OF THE rNVENTION

The present invention relates to a thickening composition that ' is made by preblending a diluent and a thickener. The diluent-; thickener blend is used to incorporate urethane thickeners having : branched and terminal hydrophobes which contain a total of at least 36 carbon atoms into aqueous systems, including latex paints. By preblending the thickener with a diluent, properties such as viscosity, sag resistance and thickening efficiency are realized.
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':' BACKGROUND OF TE~E INVEN~IO~J
~' , Among the many well-known thickeners are natural products ,~ sudh as the alginates, casein, gum karaya, locust bean gum and gum tragacanth and modified natural products such as the cellulosics, induding methyl cellulose, hydroxyethyl cellulose and hydroxypropylmethyl cellulose. Totally synthetic thickeners are also available, such as carboxyl vinyl ether copolymers, acrylic polymers and `~ maleic and anhydride styrene copolymers.

Thidkeners are useful in well drilling and flooding fluids, fire-fighting foams and fluids, detergents, leather pastes and finishes, adhesives, pharmaceuticals, agricultural formulations, latex paints, printing inlcs, cosmetics, paper coatings and emulsions of all kinds.

It is generally known in the art that the iengths of the capping hydrophobes are useful in controlling the balance of low shear and -high shear thickening efficiency. Capping meaning it reacts with (i.e., "caps") the terminal functional groups of the reaction product of reactants (a) and (b), hereinafter further discussed under "Urethane Polymer". However, as the hydrophobe size increases, incorporation of thickener into latex paints and into other aqueous systems becomes ~
;: more difficult, especially with large particle size hydrophilic lattices :
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such as PVA (polyvinyl acetates). Additionally, the design of the high viscosity thickeners has been limited to choosing as large a hydrophobe (or a blend of hydrophobes) as can be incorporated into most latex paints. The present invention solves the problems of prior art thickening systems.

What has been found to be novel and non-obvious is a thickening system comprising a diluent-thickener blend that is useful for incorporating urethane thickeners into aqueous systems, such as PVA paints. The diluent-thickener blend allows urethane thickeners having branched and terminal hydrophobes, which contain a total of at least 36 carbon atoms, to be incorporated into aqueous systems to develop viscosity, sag resistance and thickening efficiency. Also, the thickening efficiency of the diluent-thickener blend of the present invention permits the use of less thickener, thus reducing cost of the thickening system.
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' PRIOR RELATED ART
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Although several polymeric agents useful for thickening aqueous systems, including latex paints and other aqueous coating compositions, are known, none neither use, nor suggest the use of, diluent-thickener blends as a method of incorporating long hydrophobe urethane thickeners into aqueous systems. For example, U.S. Pat. No. 4,079,028 discloses a low molecular weight polyurethane thickener characterized by at least three hydrophobic groups interconnected by hydrophilic polyether groups. The urethane thickeners are non-ionic, hydrophobically stable and resistant to biodegradation, and are useful in thickening aqueous systems.

U.S. Pat. No. 4,327,008 discloses rheology modifiers useful in ;
water-based and organic solvent-based compositions which are derived from the reaction product of polyalkylene oxide, polyfunctional ':
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material, diisocyanate, water and mono-functional active hydrogen-containing compounds or mono-isocyanates.

U.S. Pat. No. 4,507,426 discloses a thickening composition comprising (a) a syneresis-reducing amount of a liquid emulsion polymer comprising (i) an addition polymerizable acid monomer, (ii) an addition polymerizable non-ionic vinyl monomer, (iii) a non-ionic vinyl surfactant ester; and (b) a thickening amount of a urethane polymer having at least three hydrophobic groups, at least two of b which are terminal hydrophobic groups, said hydrophobic groups being linked by a hydrophilic group.

U.S. Pat. No. 4,598,120 discloses a process for the production of ; aqueous dispersion compositions containing aqueous dispersions of polyurethanes and optionally poly(meth) acrylates, carboxyl group-containing, aqueous polymeric thickeners, self-crosslinkable polyorganosiloxanes and crosslinking agents. Polymers made according to the process of this invention may be used for coating and for printing substrates to form hydrophobic coatings which are crosslinked after drying at elevated temperatures.

U.S. Pat. No. 4,703,080 discloses an aqueous emulsion copolymer -prepared by copolymerization in aqueous emulsion of monoethylenically unsaturated monomers which provide a copolymer having a glass temperature below 20 degrees C, preferably below 5 -degrees C and which include from about 0.3% to about 10% of a monoethylenically unsaturated copolymerizable polyether containing ` a chain of from about 6 to about 150 C2-C4 oxyalkylene groups, the `~ terminal hydroxy group provided by said chain of oxyalkylene groups -being capped with a monofunctional hydrophobic group.
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SUMM~RY OF THE rWENTION
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In one aspect of the present invention is provided a thickening composition comprising a diluent and a urethane thickener, wherein the urethane thickener and diluent is preblended and used as a - thickening composition for aqueous systems.

. In another aspect of the present invention is provided a methodfor incorporating thickeners into aqueous systems which comprises preblending a diluent with a urethane thickener, adding the diluent-!' thickener blend to an aqueous system.
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' DETAILED DESCRIPTION OF THE INVENTION
The thickening composition of the present invention has several advantages such as, for example, the development of viscosit,v, sag resishnce, thickening efficiency and reduced syneresis (separation of solid and liquid components).

The present invention discloses a thickening composition made ;
by blending a diluent with a thickener and a method of using the compositional blend. The diluent permits the use of urethane thickeners having branched and terminal hydrophobes, which contain a total of at least 36 carbon atoms, to be incorporated into aqueous systems to develop viscosity, sag resistance and thickening efflciency.
By preblending a urethane thickener with a diluent, properties such as viscosity, sag resistance and thickening efficiency are realized.
R~ -~he Diluent The first component of the present invention is a diluent that is used for blending with urethane Wckeners. When employing the ~ --present invention consisting of the diluent-thickener blend ~ ~ 5 ,j~, ~ ~ .
r' composition and the method of using same, the problem of incorporating urethane thickeners having branched and terminal hydrophobes, which contain a total of at least 36 carbon atoms, into aqueous systems is solved. Additionally, the problem of designing urethane thickener is no longer limited to choosing as large a hydrophobe as can be incorporated into aqueous systems.

Diluents useful in the present invention consist of naturally occurring C4 to C20 fatty acids selected from the group consisting of Pamonyl 380 (an air-curing Clg surfactant from Hercules) and Pentalyn 255 (a rosin acid ester from Hercules), butyric (Butanoic), caproic (Hexanoic), caprylic (Octanoic), capric (Decanoic), lauric (Dodecanoic), lauroleic (cis-9-Dodecenoic), myristic (Tetradecanoic), -myristoleic (Hexadecanoic), palmitic (cis-9-Hexadecenoic), stearic (Ochdecanoic), oleic (cis-9-Octadecenoic), ricinoleic (12-Hydroxyl-cis-9-Octadecenoic), linoleic (cis-9-, cis-12-Octadecadienoic), linolenic (cis-9, cis-12, cis-15~chdecatrienoic), linoleic (cis-9-, cis-12-Octadecadienoic), linolenic (cis-9, cis-12, cis-15-Octadecatrienoic), eleostearic (cis-9, trans-11, trans-13-Ochdecatrienoic). Preferred diluents are Pamonyl 380, Pentalyn255, andoleic acid.

The diluent-thidkener blend ratios, based on the percent weight ratio of solids, ranged from about 9:91 to about 34:66, preferably from :
about 9:91 to about 26:74, i.e., 26 percent diluent solids and 74 percent urethane thickener solids.

Other components such propylene glycol and ammonia may also be included in the diluent blend. A typical diluent blend, based on - - -total weight, indudes from about 25 percent to about 100 percent fatty acid, from about 0 percent to abaut 65 percent propylene glycol, and from about 0 percent to about 10 percent ammonia. ~ -~ ,' ;~
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The diluent blend is mixed with the urethane thickener, by any means known in the art such as, for example, manual or mechanical stirring. The amount of diluent-thickener composition required to thicken an aqueous system depends on the particular paint ~,~ formulation, latex type and other additives present. Therefore, various diluent-thickener blend ratios should be tested for ease of incorporation and thickening efaciency in the aqueous system. This ~.
allows the formulator to determine the diluent-thickener ratio necessary to optimize thickener incorporation and thickening efficiency.

,1 Urethane Polymer "
~; As a second component, the practice of the present invention contemplates the use of a thickening amount of urethane polymers 4 having at least three hydrophobic groups at least two of which are terminal (external) hydrophobic groups. Many of the polymers also contain one or more intemal hydrophobic groups. The hydrophobic groups together desirably contain a total of at least 36 carbon atoms and ` desirably are linked through hydrophilic (water-soluble) groups containing polyether segments of at least about 1,500, preferably at least ;~` about 3,000 molecular weight each so that the polymers readily solubilize in water, either by self-solubilization or through interaction with a known solubilizing agent such as a water-miscible alcohol or ~ :
surfactant. The molecular weight of the polyurethane is desirably of the order of about 10,000 to 200,000.

The urethane polymers are advantageously prepared in non-~` aqueous media and are preferably the reaction products of at least reactants (a) and (c) of the following reactants:
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(a) a water-soluble polyether polyol, ; (b) a water-insolubleorganic polyisocyanate, ~ .
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tc) a monofunctional hydrophobic organic compound selected from monofunctional active hydrogen compounds and organic monoisocyanates, and (d) a polyhydric alcohol or polyhydric alcohol ether.

The products formed include the following:

1. Reaction products of a reactant (a) containing at least three hydroxyl groups and the foregoing organic monoisocyanates;

2. Reaction products of reactant (a), reactant (b) containing two isocyanate groups, and the foregoing active hydrogen containing compounds. Such compounds wherein the ratio of equivalents of (a) to(b)isO.5:1tol:1a;

3. Reaction products of reactant (a), reactant (b) containing at least three isocyanate groups, and the active hydrogen containing compounds;

4. Reaction products of reactant (a), reactant (b) and the organic monoisocyanates; and, 5. Reaction products of reactants (a), (b), (d) and the organic monoisocyanates.

The reactants are normally employed in substantially stoichiometric proportions, that is, the ratio of total equivalents of active hydrogen containing reactants (whether mono- or polyfunctional) to isocyanate reactants is at least 1:1. A slight stoichiometric excess (e.g., about 5-10 percent) of monofunctional-active hydrogen-containing compound may be used to eliminate any unreacted isocyanate functionality, thus avoiding toxicity from this source. Greater excesses, particularly of capping hydroxyl compound, may be used to increase thickening efflciency. A slight excess of !~ :

2l23S~5 monoisocyanate is sometimes desirable in cases where such isocyanate is a capping hydrophobe, to ensure capping of all available active hydrogen functionality.

By "monofunctional active hydrogen compound" is meant an organic compound having only one group which is reactive with isocyanate, such group therefore containing an active hydrogen atom, any other functional groups, if present, being substantially unreactive to isocyanate. Such compounds include monohydroxy compounds such as alcohols, alcohol ethers and monoamine, as well as polyfunctional compounds providing the compound is only monofunctional to isocyanates. For example, the primary amines, although difunctional in many reactions, are only monofunctional towards isocyanates, the hydrogen atom in the resulting urea group being relatively unreactive to isocyanate as compared with the hydrogen atom of the amino group or of unhindered alcohols.
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Reactant (c) is a "capping" compound, meaning it reacts with (i.e., "caps") the terminal functional groups of the reaction product of reactants (a) and (b).
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The polyether polyol reactant (a) is desirably an adduct of an aIkylene oxide and a polyhydric alcohol or polyhydric alcohol ether, a hydroxy-terminated pre-polymer of such adduct and an organic polyisocyanate, or a mixture of such adducts with such pre-polymers.

Reachnt (d) may be employed to terminate isocyanate functionality or to link isocyanate-terminated reaction intermediates.
Reachnt (d) may be a polyhydric alcohol or polyhydric alcohol ether of the same type as used to form the adducts of reactant (a). The polyhydric alcohols or alcohol ethers may be aliphatic, cycloaliphatic or aromatic and may be used singly or in mixtures of either type or mixtures of the two types.

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~ The organic polyisocyanates include simple di- and '~ triisocyanates, isocyanate-terminated adducts of such polyhydric ~:r~ alcohols and organic di- or triisocyanates, as well as isocyanate-' term~nated pre-polymers of polyalkylene ether glycols and organic di-or triisocyanates.

The hydrophobic groups of the polyurethanes occur in the residues of reactants (b) and (c) and may also occur in the residue of reactant (d) if present. The terminal (external) hydrophobes are the residues of the monofunctional active hydrogen compounds, organic --monoisocyanates, or combinations of the residues of such compounds.

~x By appropriate selection of reactants and reaction conditions, ~f including proportions and molecular weights of reactants, a variety of polymeric urethane products may be obtained.

Further details concerning the description and manufacture of the urethane polymers useful in the invention may be found in U.S.
Pat. No. 4,079,028, which is incorporated herein by reference.
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The diluent and the urethane thickener are preblended to ;~ produce a thickening system useful in aqueous systems, including coating compositions for paper, leather and textiles, latex paints, oil well flooding compositions and drilling muds, detergents, adhesives, waxes, polishes, cosmetics and toiletries, topical pharmaceuticals, and pesticidal and agricultural compositions. Additionally, the diluent-thickener blend is useful for thickening water alone, the resulting mixture itself then being useful as a thickener for other systems.
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l~tex Paint Compositions : :
The invention includes latex paint compositions containing an emulsion or dispersion of a water-insoluble polymer and a diluent that has been preblended with the diluent-thickener composition of the 1 0 , ' ~ - ~

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foregoing polymer groups prior to its use as a thickening system. The water-insoluble polymers may be any of the types conventionally utilized in latex paint compositions and include natural rubber latex ingredients and synthetic lattices wherein the water-insoluble polymer is an emulsion polymer of mono- or polyethylenically unsaturated olefinic, vinyl or acrylic monomer types, including homopolymers and copolymers of such monomers. Specifically, the water-insoluble emulsion polymer may indude poly (vinyl acetate) and copolymers of vinyl acetate (preferably at least 50% by weight) with one or more of vinyl chloride, vinylidene chloride, styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, maleic acid and esters thereof, or one or more of the acrylic and methyl acrylic acid esters mentioned in U.S. Pat. No. 2,795,564 and 3,356,627, which polymers are well-known as the film-forming component of aqueous base paints; homopolymers of C2-40 alpha olefins such as ethylene, isobutylene, octene, nonene, and styrene, and the like; copolymers of one or more of these hydrocarbons with one or more esters, nitriles or amides of acrylic acid or of methacrylic acid or with vinyl esters, such as vinyl acetate and vinyl chloride, or with vinylidene chloride; and diene polymers, such as copolymers of butadiene with one or more of styrene, vinyl toluene, acrylonitrile, methacrylonitrile, and esters of acrylic acid or methacrylic acid.

- ~ It is also quite common to include a small amount such as 0.5 to 2.5%, or more, of an acid monomer in the monomer mixture used for making the copolymers mentioned above by emulsion polymerization.
Acids used indude acrylic, methacrylic, itaconic, aconitic, citraconic, crotonic, maleic, fumaric, the dimer of methacrylic acid, and so on. ~-:

The vinyl acetate copolymers are well-known and include copolymers such as vinyl acetate/butyl acrylate/2-ethylhexyl acrylate, vinyl acetate/butyl maleate, vinyl acetate/ethylene, vinyl acetate/vinyl chloride/butyl acrylate and vinyl acetate/vinyl chloride/ethylene. ~ ~

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- Throughout this specification, the term "acrylic polymer" means any polymer wherein at least 50% by weight is an acrylic or methacrylic acid or ester, including mixtures of such acids and esters individually and together. The term "vinyl acetate polymer" means any polymer containing at least 50% by weight of vinyl acetate.

y Even small particle size (about 0.1-0.15 micron) acrylic and other lattices are thickened effectively by the diluent-Wckener blend of this . invention.
,~, The aqueous polymer dispersions may be prepared according to well-known procedures using one or more emulsifiers or an anionic, cationic or nonionic type. Mixtures of two or more emulsifiers regardless of type may be used, except that it is generally undesirable to mix a cationic with an anionic type in any appreciable amounts since they tend to neutralize each other. The amount of emulsifier may range from about 0.1% to 6% by weight, or sometimes even more, based on ~e weight of the total monomer charge. When using a persulfate type of initiator, the addition of emulsifiers is often unnecessary. This omission or the use of only a small amount, e.g., less than about 0.5%, of emulsifier, may sometimes be desirable from a cost standpoint, and less sensitivity of the dried coating or impregnation to moisture, and hence less liability of the coated substrate to be affected by moisture. In general, the molecular weight of these emulsion polymers is high, e.g., from about 100,000 to 10,000,000 viscosity average, most commonly above 500,000.

The foregoing and other emulsion polymer systems which may be thickened with the diluent-thickener blend of the present invention :
are set forth in the extensive literature on the subject, such as U.S. Pat.
Nos. 3,035,004; 2,795,564; 2,875,166 and 3,037,952, for example. The diluent-thickener blend is also suitable as substitutes for the polymeric thickeners disclosed in U.S. Pat. Nos. 2,875,166 and 3,035,004 and in Canadian Pat. No. 623,617.

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~- An example of this diluent-thickener blend approach in preparing an interior flat paint formulation at 66% pigment volume concentration (PVC) and 33% volume solids (VS) is as follows. These ingredients are added to an open stainless steel beaker which, depending upon its size, may require that the tohl weight of ingredients shown here be scaled accordingly to provide a half-full . container to insure good mixing during this dispersion step.

Ingredient Parts by Weight Add the following into an appropriately sized steel beaker:
Water 47.07 Ethylene Glycol, Cosolvent 6.97 Colloid 643, Defoamer 0.25 Tamol 850 (30%), Dispersant 2.63 Triton CF-10, Wetting Aid 1.00 Add the following pigments, via Cowles Dissolver at low speed:
TiO2 R-902, Primary Pig~ent 31.25 Icecap K, Extender Pigment 43.75 Snowflake, Extender Pigment 56.25 ;

~; This mixture is dispersed for 20 minutes via Cowles Dissolver at -high speed, or other suitable dispersing device. Then the following are added stepwise with stirring over a period of approximately 15 minutes:
Texanol, Coalescent 3.30 Amsco-Res 3077 (55%) 50.00 ~ -Diluent-Thickener Blend~ 7.15 `\ ~ Water 49.92 Total Weight 299.54 ~;~ 13 :,:
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~ Diluent-Thickener Blend ratio as percent weight solids is 26:74, i.e., 26% diluent solids (using Pamolyn 380 at 31% solids) and 74% urethane thickener at 29.1% solids. The diluent composition consists of 31%
Pamolyn 380 plus 61% propylene glycol and 8% concentrated ammonium hydroxide.
Colloid 6~i3, Defoamer is sold by Collids, Inc.
Tamol 850 (30%), Dispersant is sold by Rohm and Haas Company Triton CF-10, Wetting Aid is sold by Union Carbide TiO2 R-902, Primary Pigment is sold by E. I. Du Pont de Nemours & Co.
Icecap K, Extender Pigment is sold by Burgess Pigments, Corporation Snowflake, Extender Pigment is sold by ECC America Texanol, Coalescent is sold by Eastman Amsco-Res 3077 (55%) is sold by Rohm and Haas Company Table 1 Comparision of Paint Applications Properties for Various ''UT/Pamolyn 380 Blends versus UT Control PVA Interior Flat Paint From Example 1 `i _ Sample 1 2 3 4 5 UT/Pamolyn 380 Blend Ratios 66/34 74/2683/1791/9 100/0 UTdry ~;~ lbs/lOO gal. 7.86 6.886.08 5.76 Pamolyn 380 ~1 lbs/lOO gal. 4.13 2.411.28 0.56 Base of UT/Diluent Incorporation inPaint ok ok ok ok did not ~ incorporate ¦ Equil ICI 1.3 1.2 1.1 0.8 Equil KU 108 102 103 102 l ~ Leneta sag 12 10 9 7 l~ 1 4 ~ ---`- 212361~

*UT is a urethane thickener having branched and terminal hydrophobes of at least 36 carbon atoms.

Table 1 illustrates that by preblending UT urethane thickener with a diluent, UT can be easily incorporated into PVA paints for improved sag resistance while maintaining viscosity and thickening ef9ciency.

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Claims (10)

1. A thickening composition comprising a diluent and a urethane thickener, wherein the urethane thickener and diluent are preblended prior to their use as a thickening composition for aqueous systems and wherein the urethane thickener having branched and terminal hydrophobes which contain a total of at least 36 carbon atoms.

2. The composition of Claim 1 wherein the diluent is selected from the group consisting of Pamonyl 380, Pentalyn 255, butyric (Butanoic), caproic (Hexanoic), caprylic (Octanoic), capric (Decanoic), lauric (Dodecanoic), lauroleic (cis-9-Dodecenoic), myristic (Tetradecanoic), myristoleic (Hexadecanoic), palmitic (cis-9-Hexadecenoic), stearic (Octadecanoic), oleic (cis-9-ctadecenoic), ricinoleic (12-Hydroxyl-cis-9-Octadecenoic), linoleic (cis-9-, cis-12-Octadecadienoic), linolenic (cis-9, cis-12, cis-15-Octadecatrienoic), linoleic (cis-9-, cis-12-ctadecadienoic), linolenic (cis-9, cis-12, cis-15-Octadecatrienoic), eleostearic (cis-9, trans-11, trans-13-Octadecatrienoic).

3. The composition of Claim 2 wherein the diluent is selected from the group consisting of Pamonyl 380, Penhlyn 255 and oleic acid.

4. The composition of Claim 1 wherein the urethane polymer having at least three hydrophobic groups, at least two of which are terminal groups, the hydrophobic groups being linked by hydrophilic groups.

5. The composition of Claim 4 wherein the hydrophobic groups of the urethane polymer contain at least 36 carbon atoms, and they are linked together by water soluble polyether segments each having a molecular weight of about 1500.

6. The composition of Claim 1 wherein the diluent-urethane thickener blend ratio is from about 9:91 to about 34:66, based on the percent weight ratio of solids.

7. The composition of Claim 1 wherein the diluent-urethane thickener blend ratio is from about 9:91 to about 26:74, based on the percent weight ratio of solids.

8. A method for incorporating urethane thickeners having branched and terminal hydrophobes which contain a total of at least 36 carbon atoms, which comprises preblending a diluent with a urethane thickener, and adding the diluent-thickener blend to an aqueous system.

9. The diluent-thickener blend of Claim 1 or Claim 8 employed as a thickening system for aqueous systems.

10. The diluent-thickener blend of Claim 1 or Claim 8 employed as a thickening system for latex paints.