PAINT THCCKNER

TECHNICAL FIELD The invention relates to the field of organophilic day which are capable of suspending materials and imparting thixotropic properties to aqueous coating systems such as latex paints and caulks.

RhedLogical agents are typically added to thicken aqueous systems .and to produce thixotropic flow characteristics for proper brush, roller or spray applications. Prior art tisickening agents for aqueous systems possessed various defects which have been found to be overcome by compositions and processes within the scope of the present invention. Previous thickening agents included many organic polymers such -as hydrαxyethyl cellulose, σarboxymethyl cellulose, quar gum or acid containing polyacrylates, partially hydrolyzed polyvinyl acetate, polyvinyl pyrolidone etc. Water soluble synthetic polymers known as associative thickeneis have been introduced to coating compositions for controlling application properties. These thickeners are generally polymers with water soluble backbone containing long chain hydrophobic pendants. U.S. Patents, 4,077,028 and 4,426,485 describe thickeners of such composition.

However, there are various problems associated with the use of these thickeners. In one form the prior art teaches

a high molecular weight hydroxyethyl cellulose used as the thickening agent for latex paints. Hydroxyethyl cellulose is a solid material which must be dissolved before addition to the coating system which adds additional cost. Cellulose derivatives are known to have high "low shear viscosity" and lw "high shear viscosity"; the fast viscosity recovery causes poor flow and leveling in paint application. In addition, the elastic property of cellulose derivatives gives severe roller spatter. Moreover, cellulose derivatives are subject to icrobial degradation and thus require the addition of preservatives. Preservatives are not only expensive, they are also a cause of envirαnental concern.

A second prior process teaches the use of acid containing polyacrylates as aqueous thickener. Ihis type of thickener is pH dependent, so before the agent will become sufficiently thickened to suspend the mixture, the pH must be carefully adjusted to the basic range.

The third prior process teaches h drophobicly modified polyurethane or acrylic polymers used as thickening agents. Both the polyacrylates and hydrophobicly modified polymers give improved flow, leveling and roller spatter; however they have poor sag control and poor brush pickup. They are also very expensive.

Finlayson, et al. United States Patent Number 4,208,218 teaches an organophilic clay gellant reacted with a

quaternary aπmonium, phosphonium or sulfonium cαnpσund consisting of alkyl chains and aralkyl chains or mixtures thereof; with each carbon chain consisting of 1 to 22 carbon atcms attached to the specific central element chosen for the cationic compound. However, the use of the aforementioned process is limited to non-aqueous systems, contrary to the present invention.

Mardis, et al United States Patent Number 4,391,637 teaches an organophilic clay reacted with a quaternary ammonium compound containing a first chain consisting of a beta, gamma, unsaturated alkyl group or a hydrcxalkyl group having 2 to 6 carbon atc s; a second member containing a long chain alkyl consisting of 12 to 60 carbon atcms; and a third and fourth member, each consisting of aralkyl and alkyl or combination thereof containing 1 to 22 carbon atcms for use in non-aqueous systems.

Dohman, et. al. United States Patent No. 3,298,849 describes the use of alkanolamine salt modified clay in the formulation of aqueous base paint to increase hydration rate and control rheological properties.

No prior art method or composition is known utilizing organoclay made by a polyether substituted quaternary ammonium ccmpound as a rheological additive in aqueous paint systβns.

DISCLOSURE OF THE l-NVENTION

The processes and compositions within the scope of the present invention have been unexpectedly found to produce agents which can be used to thicken aqueous coating systans, for example, latex paints and caulks.

Further, the new processes and products have many advantages over other prior art methods and compositions in that they are not subject to microbial degradation that has been found to occur in the previously described cellulose systans.

Further, components within the scope of the present invention give products in slurry form which can be easily dispersed at low shear, for example, during the "let down" stage of latex paint preparation. Processes within the scope of the present invention are not pH sensitive as are many of the other prior art thickeners, thus, eliminating the pH adjustment needed in the prior art procedures. Briefly the present invention provides a process whereby a smectite clay having a cationic exchange capacity of at least 50 meq./lOOgm of clay is reacted with a quaternary airmonium compound to yield a cationic structure suitable as a thickener for aqueous suspensions; particularly latex paints and caulks. The general structure of the quaternary ammonium compound is typically a nitrogen atom bonded to four separated carbon chains, one chain being be a methyl or alkyl group containing 10 to 22 carbons and

the second chain an alkyl group containing from 10 to 22 carbons or a polyoxyethylene chain. The third and fourth chains are polyoxyethylene chains where the total number of ethylene oxide units is from 5 to 200 moles.

BEST M ODE FOR CARRYING OUT THE INVENTION

3h general, in accordance with the present invention, it has been found that certain organoclays can be utilized to modify the rhedogical characteristics of aqueous coating systems where the organoclays are formed by reaction of a smectite clay with a quaternary ammonium compound represented as follows :

Where R. is methyl or a C. _n to C~~ carbon chain, R» is C- _j ^-C^ carbon chain or polyoxyethylene chain, (CH ₂ -CH ₂ 0) H, with Z repeating unit where x+y+z= 5 to 200, X is a suitable anion, for example bromide, sulfate, acetate, chloride etc. The quaternary ammonium compound has been found to be effective when added to the clay at 30 to 130 meq. wt 100 gm clay. The organophiϋc clay can be prepared by admixing the clay, quaternary ammonium compound and water together, preferably at a temperature within the range of from 40° C. to 90°C, and more preferably from 60°C. to 90°C. for a p.eriod of time sufficient for the organic quaternary ammonium compound to react with the clay particLes.

Preferahly, the clay is dispersed in water at a concentration from about 5 % to 12 % by weight and, the -.lurry

is centrifuged to remove non-clay impurities. The slurry is then agitated and heated to a temperature in the range of 60°C. to 90° C. ; and the quaternary ammonium salt added in the desired milliequivalent ratio, preferably as a solution in isopropanol or dispersion in water. The agitation is continued to effect the reaction.

The amount of the quaternary ammonium compound added to the clay for purposes of this invention must be sufficient*- to impart to the clay the enhanced dispersion characteristics desired. The milliequivalent ratio is defned as the number of illiequivalents of the quaternary aπtnonium ccmpound per 100 grams of clay, 100% active basis. The organophilic clays of this invention have a milliequivalent ratios of frαn 5 to 150. At lower milliequivalent ratios the organophilic clays will cause pigment flocculation. At higher milliequivalent ratios, the organophilic clays are poor thickeners. However, the preferred milliequivalent ratio within the range of 5 to 150 will vary depending on the characteristics of the quaternary ammonium compound and the aqueous systan to be used. The organophilic clay thickener is employed in amounts sufficient to obtain the desired rheological properties for application as to control sagging of fluid films and prevent settling and hard packing of pigments present in the fluid compositions. .Mounts of the organophilic clay thickener

employed in a typical latex paint are from 41b. to 151b./100gal. depending on the particular formulation.

Ihe resulting organophilic clay is then added to the paint systaπ to provide thickening as described hereinafter.

The following examples are given to illustrate the invention, but are not deemed to be limiting thereof.

EXAMPLE 1.

One thousand grams of a 6.3% slurry of Wyoming bentonite in water which had been previously treated by centrifugation to remove all non-clay impurities was heated to about 75°C. b the clay slurry, 56.6 gm of methyl, coco-di(polyoxyethylene) quaternary ammonium chloride with an activity of 1.001 meq. wt./gm. was added under mild agitation. The mixture was stirred for 60 min while maintaining the Tanperature at 80° C. After cooling the viscosity, solids content and pH are determined. The organophilic clay product contains 90 meq. wt. of quaternary airmonium ccmpound/100 gm clay.

Examples 2 to 5 were prepared according to the procedures of Example 1, but with different quaternary ammonium compounds at different milliequivalents added as shown in Table 1. The organophilic clays prepared above were then tested as thickeners in latex paint formulations. b illustrate the effectiveness of one type of composition within the scope of this invention, various paint formulations (Formulations I to IV) were made and the thickening efficiency and application properties cαtpared with commercially available thickeners. The results are given in Tables 2 to 5.

In the preparation of latex paints, a master batch was made according to the formulation excluding the thickener solution, then divided into small portions. To each

portion, the calculated amount of thickener solution was added at low shear. The resulted paints were equilibrated and the properties determined.

11 TEST METHODS;

A. ) Sag .and leveling were done on leneta antisag bar and leneta leveling bar on leneta form 7B. b) Spatter resistance was measured by roller application of 70g paint on 4ft./4ft. pressed board, 20 strokes over an area of 10in./12in. The spatter pattern is collected on a black cardboard paper. Ihe results are rated numerically, the higher the number the better the spatter ' ^" resistance. c.) Contrast ratio is determined by ACS computer system on a film of 3.0 wet mil. thickness. The higher the contrast ratio, the better the hiding power.

TABLE I RAW MATERIALS AND COMPOSITIONS OF ORGANOCLAYS Product Cone of Activity Structure Meq wt Wt or Cone of of Inv. Clay of Quaternary of Quater Organo- Slurry Quater Ammonium Quater gm Clay

% by wt Meq/g % by wt

Esc 1 6.3 1.001 R- _j ^Methyl 90

R =coco 56.6 11.4

X*Y=15

Ex 2 6.8 0.303 R^ethyl 30 67.3 11.0

^2=H-Tallow X+Y=50

Ex 3 7.2 1.001 R-^methyl 90 64.8 12.8

R„=COCO

Xl=Y=15

Ex 4 6.7 0.303 R^ethyl 30 66.5 11.9

^R 2=H-Tallow X+Y=50

Ex 5 6.8 1.001 R^ethyl 90 61.0 12.2

R ₂ =coco X+Y=15

FORMULATION I VINYL ACETATE LATEX PAINT

PIGMENT POUNDS GALLONS water 83.3 10.00

Tamol 731 (25%) 9.0 0.98

Dcwicil 75 2.0 0.16

Ebamaster NEW 2.0 0.28

Propylene Glycol 50.0 5.81

Ethylene Glycol 15.0 1.61

Butyl Carbitol 18.0 2.11

Triton 100 2.0 0.22

Ti-Pure R-900 200.0 6.08.

ASP - 200 60.0 2.79

LET DOWN water 125.0 15.00 ϋCAR 131 Vinyl Acetate Eftiulsion (60%) 376.0 41.32

Ebamaster NEW Defoamer 2.0 0.27

Rheological Additive Soln 103.7 12.39

Total 1048.0 99.02

Volume Sold 32.6% PVC 27.3%

TABLE II PROPERTIES OF VINYL ACETATE LATEX PAINT OF FORMULATION

USE LEVEL STORMER RVT LENETA LB/100 GAL KU BROOKFIED SAG cps 0.5 rp

HEC .(ER - 4400) ^" 3.0 87 38,000 13

HBC (ER - 4400) 5.0 107 48,000 20

RM-5 16.0 87 2,800 8

QR-708 8.0 96 14,960 10

Organoclay Exp II 7.0 74 42,200 20

Organoclay Exp I 12.0 85 90,000 30

Paint Formulation I was used as an example, where Table II gives the application properties. This example demonstrates that organoclays of this invention can be made to equal the thickening efficiency of associative thickener.

ORMULATION II VINYL ACRYLIC INTERIOR LATEX FLAT PAINT

PIGMENT WEIGHT VOLUME

LB GALLON

Water 120.0 14.40

Tamol 960 (40%) 10.0 0.94 Ethylene Glycol 25.0 2.69 Dowicil 75 1.0 0.08 PAG-188 2.0 0.25 Attagel 50 5.0 0.25 Ti-Pure R-900 200.0 5.84 Optiwhite 100.0 5.45 -Qπsil A-15 75.0 3.40

LET DCWN

Butyl Carbitol 20.0 2.50

Vinyl Acrylic Copolymer

(55%) (JCAR 367 350.0 38.68

PAG-188 4.0 0.50

Thickner Solution 208.0 24.94

Total 1120.0 99.92

Volume Solid 35% PVC 43%

TABLE III PROPERTIES OF VINYL ACRYLIC INTERIOR LATEX FLAT OF

FORMULATION II

Stormer RVT Leneta Leneta No. Description Use Level Ku Brookfield SAG Level lb./lOOgal cps, 0.5 rrm

A HEC- (ER-4400) 4.4 91 58,000 20 7

B RM-5 12.0 85 47,000 16 8

C QR-708 6.8 101 12,480 10 10

D Organoclay Exp I 12 95 72,000 18 5

E Organoclay ExpII 6 92 79,000 11 8

F Organoclay Exp I 6 89 32,000 13 10 QR-708 ^• 3

In paint Formulation II, the thickening efficiency of organoclay frcm Experiment I is equivalent to Acrysol RM-5 whereas organoclay frcm Experiment II is .equivalent to QR-708 but scmewhat less effective than HEC (ER-4400) . It is generally accepted that associative thickeners offer excellent flow out properties but are relatively poor in sag

control. It is shown here that the combined use of associative thickener QR-708 and organoclay can iπprove paint flow out and at the same time, maintain proper sag control.

FORMULATION III VINYL ACRYLIC LATEX PAINT

INGREDIENTS POUNDS GALLONS

PIGMENT water 174.0 20.85

Propylene Glycol 46.4 53.63

Filming Aid, Texanol 12.0 1.45

Antifoam, colloid 643 2.3 0.31

Preservative, dowicil 1.0 0.14

TERGITOL Nonionic Surfactant NP-10 2.3 0.27

Dispersant, Tamol 731 10.0 1.12

Titanium Dioxide, Ti-pure R-901 225.0 7.84

Calcium Carbonate 46.0 2.06

Clay, ASP 170 69.5 3.20

LET DOWN

UCAR Latex 367 385.4 42.49 Antifoam, Colloid 643 2.3 0.31 Thickener Solution 120.0 14.45 TERGITOL NP-10 1.0 0.13 TOTAL 1126.8 99.98

PAINT PROPERTIES

Pigment Volume Concentration (PVC) 37. .5% Solids by Volume 34. .7%

TABLE IV PROPERTIES OF VINYL ACRYLIC LATEX PAINT OF FORMULATION III

Rheological Use Stor er Brook- Sag Spatter Contrast Additive Level KU field leneta resistance Ratio lb/100 §0.5 gal rpm

HEC 4 95 62,000 25 1 0.908

SCT-270 4.2 108 50,000 18 6 0.881

QR-708 5.0 111 8,000 13 6 0.899

RM-5 11.0 89 27,000 18 3 0.882

ORGANOCLAY EXP. Ill

12.0 98 81,000 14 2 0.912

ORGANOCLAY EXP. IV

7.0 115 100,000 30 2 0.898

ORGANOCLAY EXP. IV

3.2 101 21,600 20 0,906

QR-708 2.0

ORGANOCLAY EXP IV

3.4 91 43,000 25 4 0,916

•SCT-270 2.0

Formulation III is a vinyl acrylic latex flat paint. In this formulation, organoclay from Experiment TV is much more efficient than Acrysol RM-5 but somewhat less efficient than other associative thickeners and HEC as shown in Table IV. When used alone, organoclay gives excellent sag control. Compared to HEC, organoclay improves spatter resistance and gives good hiding. However, it should be mentioned that the hiding power of organoclay is superior' ^" to that of associative thickeners. Ihe advantages of the combined use of organoclay and associative thickeners are further illustrated in this formulation- excellent sag control, improv-ed spatter resistance and leveling while maintaining higher hiding power.

FORMULATION IV INTERIOR FLAT WALL PAINT BASED ON A VTNYL ACRYLIC COPOLYMER

MATERIALS WEIGHT PARTS PER HUNDRED

RATIO (VOLUME BASIS)

Water 120.0 14.40

Tamol 960 (40%) 10.0 0.94

Ethylene Clycol 25.0 2.69

Dowicil 75 1.0 0.08

Colloid 643 2.0 0.25

Add the following at low spe-ad:

Attagel 50 5.0 0.25

Ti-Pure R-900 200.0 5.84

Optiwhite 100.0 5.45

Min-u-sil 30 55.0 3.40

20.0 Grind the above on a high speed impeller mill at 3800-4500 RPM for 20 minutes. At a slower speed let down as follows:

Butyl Carbitol - 20.0 2.50

Vinyl Acrylic Copolymer(55%) 350.0 38.68 Walpol 40-136

Colloid 643 4.0 0.50

Thickener Solution 208.0 24.94

1120.0 99.92

FORMULATION CONSTANTS

PVC 43%

Volume Solids 35%

TABLE V PROPERTIES OF VINYL ACRYLIC INTERIOR FLAT LATEX PAINT OF

FORMULATION TV

Rheological Use Stor er Brook- Sag Level- Spatter Contrast Additive Level KU field leneta ing resistance Ratio lb/100 (§0.5 leneta

Gal. RIM

HEC 4.4 99 91,000 60 1 1 0.8.63

SCT-270 6.8 106 53,000 50 4 3 0.845

QP.-708 6.8 111 40 9 4 0.842

BM-5 13.0 87 46,800 50 7 4 0.863

10

ORGANOCLAY EXP. IV

7 100 175,000 60 2 2 0.863

ORGANOCLAY EXP. V

12 100 142,000 60 2 3 0.877

ORGANOCLAY EXP. IV

SCT-270 5 90 101,000 60 4 0.871

2

15

Formulation IV and Table V give additional data to demonstrate the usefulness of organoclay as a rheological additive. Hie formulation is different from formulation II, yet similar application properties were obtained and the synergistic effects-of organoclay with associative

20 thickeners were again observed.

The present invention has been described in seme detail by way of examples, it is understood that certain changes and modifications may be practiced within the scope of the invention, and such variations are not to be regarded as _{j c} departure from the scope of the invention and all such

modifications are intended to be included within the scope of the following claims.