ACID DESTABILIZATION OF ELASTOMERIC ROOF COATING

Abstract

The present invention provides compositions for and methods of rapidly making roof coatings, wherein two-component aqueous compositions comprise a component one that has a pH of from 7.5 to 10 (i) one or more emulsion copolymers having a glass transition temperature (Tg) as determined by differential scanning calorimetry (DSC) of from 45 C. to 0 C., and (ii) one or more anionic surfactants, and, in a separate component, (iii) an aqueous acid chosen from a (poly)carboxylic acid or polymeric polyacid. The compositions have little or no ammonia, set within 10 minutes, preferably, a minute or less, and allow one to apply a film as thick as from 0.3 to 3 mm in a single application by co-spraying the two-components or applying them sequentially in one or several passes over a roofing substrate.

Claims

1. A two-component aqueous composition for coating roofing substrates comprises, in a component one that has a pH of from 7.5 to 10, (i) one or more emulsion copolymers having a glass transition temperature (Tg) as determined by differential scanning calorimetry (DSC) of from 45 C. to 0 C., (ii) one or more anionic surfactants, and, in a separate component, (iii) an aqueous acid chosen from a (poly)carboxylic acid or polymeric polyacid, wherein component one of the two-component aqueous composition comprises less than 0.09 wt % of ammonia, based on the total weight of the component one composition, and, further wherein, the solids weight ratio of the component one to the separate component ranges from 80:1 to 0.8:1.

2. The composition as claimed in claim 1, wherein each of the (i) one or more emulsion copolymers has a weight average molecular weight of from 50,000 to 2,000,000.

3. The composition as claimed in claim 1, wherein at least one of the (i) one or more emulsion copolymers comprises, in copolymerized form, a monomer mixture of (a) from 65 wt. % to 94 wt. %, of one or more soft monomer, (b) from 6.0 to 35 wt. %, of one or more hard vinyl monomers, and (c) from 0 to 3 wt. % of one or more ethylenically unsaturated carboxylic acid group containing monomer, all monomer wt. % s based on the total solids in the monomer mixture.

4. The composition as claimed in claim 1, wherein at least one of the (i) one or more emulsion copolymers comprises, in copolymerized form, from 0.1 to 2 wt. %, based on the total solids in the monomer mixture, of an adhesion promoting ethylenically unsaturated monomer (e).

5. The composition as claimed in claim 1, wherein the component one further comprises one or more pigments, extenders, fillers or mixtures thereof, and has a pigment volume concentration (% PVC) of from 20 to 55.

6. The composition as claimed in claim 1, wherein the component one further comprises one or more hydrophilic polymeric dispersants.

7. The composition as claimed in claim 1, wherein the (iii) aqueous acid of the separate component is chosen from an alkanoic acid, an alkanedioic acid, a tricarboxylic acid, and a polymeric polyacid.

8. The composition as claimed in claim 7, wherein the aqueous acid of the separate component comprises from 0.1 to 30 wt. % of total acid, all amounts based on the total weight of the aqueous acid composition.

9. A method of making roof coatings comprising: applying sequentially or by co-spraying to a roof substrate a two-component aqueous composition of a component one having a pH of from 7.5 to 10, and comprising (i) one or more emulsion copolymers having a glass transition temperature (Tg) as determined by differential scanning calorimetry (DSC) of from 45 C. to 0 C., and (ii) one or more anionic surfactants, and, a separate component comprising (iii) an aqueous acid chosen from a (poly)carboxylic acid or polymeric polyacid, wherein the solids weight ratio of the component one to the separate component ranges from 80:1 to 0.8:1, and, further wherein, the sequentially applying comprises applying component one and then the separate component and, still further wherein, the component one aqueous composition comprises less than 0.09 wt % of ammonia, all weights based on the total weight of the component one composition.

10. The method as claimed in claim 9, wherein the (iii) aqueous acid of the separate component is chosen from an alkanoic acid, an alkanedioic acid, a tricarboxylic acid and a polymeric polyacid.

Description

EXAMPLES

[0107] The following Examples illustrate the advantages of the present invention. Unless otherwise stated, all conditions are standard pressure and room temperature.

[0108] The following materials and abbreviations were used in the Examples:

[0109] BA: butyl acrylate, LMA: lauryl methacrylate; MMA: methyl methacrylate; STY: styrene; AN: acrylonitrile; MAA: methacrylic acid; Ureido: ethylene ureido functional ethyl methacrylate monomer; DDBS: sodium dodecyl benzene sulfonate; SLS; sodium laureth sulfate; ANS: ammonium nonoxynol-4 sulfate; Seed: BA-MMA seed polymer (100 nm average particle size)

[0110] emulsion copolymer 1: A 55 wt. % solids, single stage copolymer having a pH of 9, a DSC glass transition temperature (Tg) of 26.33 C., made from (by solids weight %) 85.1 BA/12.3 MMA/1.6 MAA/1 Ureido with 2.2 wt. % Seed and 0.11 wt. % DDBS, and containing 0.13 wt. % ammonia;

[0111] emulsion copolymer 2: A 55 wt. % solids, single stage copolymer having a pH of 8, a DSC Tg of 10.2 C., made from (by solids weight %) 70.3 BA/27 STY/2.7 MAA with 2.0 wt. % Seed, 0.25 wt. % SLS and 0.20 wt. % ANS, and containing 0.13 wt. % ammonia;

[0112] hydrophilic dispersant: polymethacrylic acid sodium carboxylate, 30 wt. % in water;

[0113] dispersant: Tamol 681 dispersant, (Acrylic copolymer, 37-38 wt. % solids in water and propanediol, The Dow Chemical Company, Midland, Mich. (Dow);

[0114] defoamer: DEEFO 1015 defoamer: (Petroleum distillates, solvent dewaxed heavy paraffinic CAS#64742-65-0 >50%, Munzing, Bloomfield N.J.);

[0115] extender 1: Snowhite 12 calcium carbonate (Omya, Cincinnati Ohio);

[0116] rutile titanium dioxide: Ti-Pure R-960 titanium dioxide (Chemours, Wilmington Del.);

[0117] zinc oxide: Zoco 101 (zinc oxide, Zochem Inc., Brampton, Ontario, Calif.);

[0118] KTPP: potassium tripolyphosphate (ICL Performance Products, Trenton N.J.);

[0119] coalescent 1: odorless mineral spirits or OMS;

[0120] HEC thickener: Cellosize QP-52000 hydroxyethyl cellulose (HEC thickener, Dow);

[0121] coalescent 2: UCAR Filmer (2,2,4-trimethyl-1,3-pentanediol mono(2-methylpropanoate) CAS#:25265-77-4, Dow);

[0122] propylene glycol, (99.9 wt. %, Dow);

[0123] zinc oxide: Zoco 101 ZnO, (Zochem Inc, Brampton, Ontario, Calif.);

[0124] aqueous ammonia, (28 wt. %, Fisher Scientific, St. Louis, Mo.); and,

[0125] polymeric polyacid: Polyacrylic acid with a weight average molecular weight of 2,700.

[0126] Test Methods:

[0127] The following test methods are used in the Examples.

[0128] Setting and Film Durability:

[0129] A total of 0.75 g of the indicated component one compositions in Tables 1A and 1B, below, were drawn down on a 55.9 mm by 64.8 mm coating section of a polysiloxane coated release Paper (RP-1K 219 mm286 mm (811 inch) Leneta Mahwah, N.J.) that was isolated with a 64.8 mm by 64.8 mm metal draw down square. To the thus applied coating, a spray (roughly 0.75 grams) of the indicated aqueous acid separate component compositions were then applied thereto using a plastic spray bottle (Dynalon Quick Mist HDPE Sprayer Bottle, polypropylene trigger, strainer, valve and intake, Dynalab Corp., Rochester, N.Y.). To evaluate the resulting coatings, 10 seconds after the spray was finished, a 100 gram weight with a diameter of 28.575 mm (1529.7 Pa) was applied to the surface of the coating for 10 seconds and removed. Clear fluid indicates that no part of the coating was removed under pressure and no deformation means the weight did not deform the film. It is possible to deform the film while the fluid remains clear. Deformation was considered acceptable if the fluid removed from the coating is clear; thus, deformation is acceptable if all composition solids are bound into the coating layer. Table 2, below, summarizes the results.

TABLE-US-00001 TABLE 1A Coating Example 1 Level (wt. % s/s or Material Name Grams % PVC) Grind Water 125.00 hydrophilic dispersant 5.00 0.27 (30 wt. % solids) dispersant 4.50 0.29 KTPP, 100% solids 1.50 0.27 emulsion copolymer 2 275.00 defoamer 2.00 extender 1 425.00 36.24% PVC rutile titanium dioxide 100.00 5.95% PVC zinc oxide 25.00 1.04% PVC subtotal 43.23% PVC Let Down emulsion copolymer 2 200.00 defoamer 2.00 Aqueous Ammonia, 28% 2.00 Premix OMS, HEC and Water. coalescent 1 7.00 2.68 HEC thickener 3.00 Water 30.00 Water, final solids adjustment 2.80 TOTAL 1211.80

TABLE-US-00002 TABLE 1B Coating Example 2 Level Material Name Grams (wt. % s/s or % PVC) Grind Water 152.00 hydrophilic dispersant 5.00 0.28 KTPP dispersant 1.50 0.28 Defoamer 1.50 extender 1 425.00 36.85% PVC rutile titanium dioxide 75.00 4.54% PVC zinc oxide 45.00 1.91% PVC Sub-total 706.50 43.29% PVC Let Down emulsion copolymer 1 475.00 Defoamer 1.50 coalescent 2 6.00 2.30 aqueous ammonia, 1.00 28 wt. % propylene glycol 14.00 HEC thickener 4.50 Water 2.48 Total 1216.48

TABLE-US-00003 TABLE 2 Setting and Film Durability for Examples 1 and 2 Concentration Acid (wt. % of acid in Runoff Comp comp) Fluid Deformation Acetic 1 Clear Yes Acetic 2 Clear No Acetic 2.5 Clear No Acetic 5 Clear No Citric 2.5 Milky Yes Citric 5 Clear No polymeric 2.5 Milky Yes polyacid polymeric 5 Milky Yes polyacid polymeric 7.5 Milky Yes polyacid polymeric 10 Milky Yes polyacid polymeric 12.5 Clear Yes polyacid polymeric 15 Clear Yes polyacid polymeric 20 Clear No polyacid

[0130] Both of the coatings in Examples 1 and 2 gave the same results in Table 2, above. Without the acid (results not shown), the coating materials adhered completely to the applied weight, thereby evidencing a lack of setting or hardness development in the applied coating layer. As shown in Table 2, organic (poly)carboxylic acids, and particularly alkanoic (mono) acids are more effective in enabling an instant (10 second) set at a low acid concentration. A larger amount of polymeric polyacid (>10 wt. %) in the separate component is needed to insure that the coating solids are bound or cured into the coating layer (clear liquid). Coating hardness after the 10 second setting period in the test is improved more by using the preferred aqueous (poly)carboxylic acid separate component than by the aqueous polymeric polyacid. Ammonia was not involved in the setting of the coatings because less than 0.06 wt. % of the coating compositions contain ammonia.

[0131] Film Formation and Film Build (Co-Spray Method):

[0132] A Graco Truecoat Plus li Airless Handheld Paint Sprayer (Graco Inc., Minneapolis, Minn., equipped with a XWD 515 (20 to 25.4 cm (10-12) width, 0.038 cm (0.015) tip) was used along with a Devilbliss Type HB siphon Sprayer (Model F-97, 0.076 cm (0.030) BU Tip, Illinois Tool Works, Glenview. Ill.) to apply the roof coating formulation and the acid. A 25 wt. % aqueous solution of polyacrylic acid with a weight average molecular weight of 2,700 was co-sprayed with coating Example 2 making 3 passes on a piece of polysiloxane coated release paper (Leneta Release Paper RP-1K 219 mm286 mm (811 inch)) Mahwah, N.J.).

[0133] When the coating was touched by hand, only a clear fluid was removed; the coating did not deform. The dry film thickness of the coating was 540 m.

[0134] The setting and film durability, as measured and reported in Table 2 above, was tested using the co-spray method and applying the 100 g weight 30 seconds after spraying. The following acid concentrations were successfully used as the separate acid component in the co-spraying of the two components to make a film having clear fluid running off and, therefore, acceptable deformation:

[0135] Acetic acid at 2.5 wt. %, Citric acid at 5 wt. %, and the 2,700 Mw polyacrylic at 10 wt. %.

[0136] It was found that co-spraying rather than sequential application of the two components allowed for polyacrylic acid to be used at lower levels, also meaning that less overall water was used in application.