MXPA98009444A - Aqueous coating composition, with improved resistance of blo - Google Patents

Abstract

An aqueous coating composition having improved block strength is provided, which includes an emulsion polymer, a nonionic or anionic surfactant, the surfactant having a BHL value less than 11.6 or greater than 14.6, and an alkyl polyglycoside. In addition, a method is provided for improving the block strength of a dry aqueous coating composition, which comprises forming the aqueous coating composition having improved block strength, applying the aqueous coating composition to a substrate, and drying or drying. the aqueous coating composition

Description

Aqueous Composition of Resist, with Improved Block Resistance.

This invention relates to an aqueous coating composition having improved block strength. More particularly, this invention relates to an aqueous coating composition that includes an emulsion polymer, a nonionic or anionic surfactant, the surfactant having a BHL value of less than 11.6 or greater than 14.6, and an alkyl polyglycoside. In addition, the invention relates to a method for improving the block strength of a dry aqueous coating composition by forming an aqueous coating composition including an emulsion polymer, a nonionic and anionic surfactant, the surface active agent having a BHL value. less than 11.6 or greater at 14.6, and an alkyl polyglycoside; by applying the aqueous coating composition to a substrate, and drying or allowing the aqueous coating composition to dry. The present invention serves to provide a dry or partially dry coating, having an improved block strength, i.e. the strength to adhere or stick to a similar coated surface, upon partial or complete drying. Coatings are often contacted with similar coatings on painted window frames or door jambs, where it is desired that the coatings do not stick even under adverse conditions of high temperature, pressure or humidity to the extent of resisting the separation. or join the surfaces of one or both coatings in the separation. U.S. Patent No. No. 4,657,999 shows the use of alkyl polyglycosides of C8-C22 alkanols and reducing sugars, in which there is present for each alkyl group a sugar chain containing on average from 1 to 10 sugar residues bound to each other by means of bonds of glycoside, as emulsifiers alone or co-emulsifiers with other surfactants in the emulsion polymerization of the ethylenically unsaturated monomers. The use of these emulsion polymers in the coatings was not described nor is there any recognition of the criticality of the BHL value of the surfactant coagent in the block strength of a dry coating derived therefrom. U.S. Patent No. 5,340,394 shows an aqueous colored, pigmented, dispersed concentrate useful for coloring aqueous latex paints containing at least about 2% by weight of nonionic alkyl polyglycoside surfactant, based on the total weight of the pigment in the composition of colored, a polyethylene glycol polyether vehicle having a number average molecular weight between about 200 and 700, and, optionally, other surfactant coagents such as nonionic surfactants or amphoteric surfactants. No critical recognition is made of the BHL value of the surfactant coagent on the block strength of a dry coating derived therefrom. The problem faced by the inventors is to provide a suitable composition and method for improving the blogging strength of a coating, so that the surfaces having the composition exhibit a reduced tendency to the block compared to a surface containing the same polymer in the composition. emulsion without alkyl polyglycoside and the components of the surfactants selected from the composition of this invention. Now, we have found that certain surfactants that have a BHL index outside the - reported for the alkyl polyglycosides when used in conjunction with the alkyl polyglycosides are beneficial for improved block strength.

In a first aspect of the present invention there is provided an aqueous coating composition having improved block strength, including an emulsion polymer, a nonionic and anionic surfactant, wherein the surface active agent has a BHL value of less than 11.6 or greater. at 14.6, and an alkyl polyglycoside. In a second aspect of the invention, there is provided a method for improving the block strength of a dry aqueous coating composition by forming an aqueous coating composition including an emulsion polymer, a nonionic or anionic surfactant, wherein the surfactant has a BHL value of less than 11.6 or greater than 14.6, and an alkyl polyglycoside; applying the aqueous coating composition to a substrate, and drying or allowing the aqueous coating composition to dry. The aqueous coating composition contains an emulsion polymer made of water. The emulsion polymer contains at least one ethylenically unsaturated copolymerized monomer such as a (meth) acrylic ester monomer which includes methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, aminoalkyl (meth) acrylate; styrene or substituted styrenes; butadiene; vinyl acetate or other vinyl esters; vinyl monomers such as vinyl chloride, vinylidene chloride, N-vinyl pyrolidone; (meth) acrylonitrile and (meth) acrylamide. The use of the term "(met)" followed by another term such as acrylate or acrylamide, as used throughout the description, refers to both acrylates and acrylamides as well as methacrylates and methacrylamides, respectively. The emulsion polymer may also contain from 0% to 15%, preferably from 1% to 5%, of a monoethylenically unsaturated copolymerized acid monomer, based on the dry weight of the polymer, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, sulfoethyl methacrylate, phosphorus ethyl methacrylate, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate and maleic anhydride. The emulsion polymer used in this invention is substantially thermoplastic or substantially non-crosslinked when applied to the substrate, although low levels of deliberate or adventitious crosslinking may be present. When low levels of pre-crosslinked or gel content are desired, low levels of multiethylenically unsaturated monomers such as 0.1% -5% by weight based on the weight of the emulsion polymerized polymer, 1,6-hexanedioldiacrylate and divinyl benzene can be used. However, it is important that the quality of the film formation is not materially damaged. Chain transfer agents, such as alkyl mercaptans, can be used to moderate the molecular weight of the polymer. The polymerization techniques used to prepare the emulsion polymers are well known in the art. In the preparation of the emulsion polymers, conventional surfactants such as anionic and / or nonionic emulsifiers such as alkali or alkyl ammonium sulfates, alkyl sulfonic acids, fatty acids and oxyethylated alkyl phenols can be used. The amount of surfactant that is usually used is up to 6% by weight, based on the weight of the total monomer. The processes of initiation by reduction or thermal can be used. Conventional free radical initiators such as hydrogen peroxide, t-butyl hydroperoxide and ammonium and / or alkali persulfates can be used, typically at a level of 0.05% to 3.0% by weight, based on the weight of the total monomer. Redox systems using the same primers coupled with a suitable reductant, such as sodium bisulfite, can be used at similar levels. In another aspect of the present invention, the emulsion polymer can be prepared by means of a multistage emulsion polymerization process, in which at least two steps differing in the composition are sequentially polymerized. Said process usually results in the formation of at least two mutually incompatible polymer compositions, thereby resulting in the formation of at least two phases within the polymer particles. Said particles are composed of two or more phases of diverse geometry such as core / shell or core / shell particles, core / shell particles with shell phases that incompletely encapsulate the core, core / shell particles with a multiplicity of nuclei, and interpenetrating network particles. In all these cases, most of the surface area of the particle will be occupied by at least one interior phase. Each of the steps of the multistage emulsion polymer can contain the same monomers, surfactants, chain transfer agents, etc., as shown above for the emulsion polymer. The polymerization techniques used to prepare such multi-stage emulsion polymers are well known in the art, for example in US Pat. 4,325,856, 4,654,397 7 4,814,373. The emulsion polymer typically has an average particle diameter of 30 nanometers to 500 nanometers. Processes that produce polymodal particle size distributions such as those disclosed in US Pat. Nos. 4,384, 056 and 4,539,361, for example. The glass transition temperature ("Tg") of the emulsion polymer is preferably -10 ° C. at 70 ° C, according to the differential scanning calorimetry (CED) measurement, using the midpoint in the heat flux against the temperature transition as the Tg value. The aqueous coating composition contains a nonionic or anionic surfactant, the surfactant having a BHL value of less than 11.6 or greater than 14.6. The BHL (hydrophilic / lipophilic balance) is a value that characterizes the relative proportions of the hydrophilic and lipophilic (ie, hydrophobic) portions of the molecules, such as the surfactants of the present invention. The highest BHL values (those approaching 40 to 40) represent relatively higher hydrophilic molecules, and the lower BHL values (about 6 to 10) represent relatively more hydrophobic molecules. The BHL values can be calculated or experimentally determined by a variety of known procedures, such as those described in "Surfactants and Interf acial Phenomena" (Surface active agents and dihedral phenomena), Milton J. Rose, John Wiley and Son, New York, NY, page 242-244 (1978) and "Interfacial Phenomena" (Dihedral Phenomena), JT Davies and E.k. Ridel, Academic Press, 2a. Edition, page 373-383 (1963). The BHL values used here were provided by the surfactant agent provider. If the BHL value is not provided by the manufacturer, the 1949 calculation method by Griffin described in "Surfactants and Interf cial Phenomena" can be used. The anionic surfactants which contain - the salts of strong acids such as sulfates and phosphates, therefore contain a very hydrophilic group and have a high value of BHL.; the BHL for said surfactants not published by the supplier here has been assigned as a value of 20. A composition containing 0.1% to 10% surfactant by weight, based on the weight of the polymer, is preferred. Even more preferred is a composition containing 0.5% to 3% surfactant by weight, based on the weight of the polymer. The aqueous coating composition contains an alkyl polyglycoside, by which is meant here an alkyl polyglycoside of C 1 -C 8 alcohols and reducing sugars, in which a sugar chain containing an average of 1 to 10 residues of sugar is present. sugar, linked to each other by glycoside bonds, for each alkyl group. The alkyl polyglycosides can be prepared by the process described in U.S. Pat. 3,839,318, starting with glucose or oligosaccharides and C8-C18 alcohols that can be reacted at 80-130 ° C. in the presence of an acid catalyst, for example sulfuric acid. The alkyl polyglycosides are surfactants having BHL values of 11.6 to 14.6, and can be used as surfactant coagents or surfactants alone in the preparation of the emulsion polymer or added later during or after the formation of the emulsion polymer. Preferred alkyl polyglycosides are GLUCOPON ™ 225 (GLUCOPON ™ is a trademark of Henkel Corporation) with an average alkyl chain length reported as 9.1, and GLUCOPON ™ 625 with an average alkyl chain length reported as 12.8. A composition containing from 0.1% to 10% alkyl polyglycoside by weight, based on the weight of the polymer, is preferred. Even more preferred is a composition containing from 1% to 7% alkyl polyglycoside by weight, based on the weight of the polymer. The amount of pigment in the aqueous coating composition can vary from a pigment volume concentration (CVP) of from 0 to 75, and thus include otherwise described coatings, for example, light coatings, gloss or semi-gloss coatings, uniform coatings. and primers. The aqueous coating composition is prepared by techniques that are well known in the art of coatings. First, if the coating composition is to be pigmented, at least one pigment is dispersed either in an aqueous medium under high shear conditions such as that provided with a COWLES® mixer or, alternatively, at least one predispersing pigment can be used. Next, the emulsion polymer, the selected surfactant and the alkyl polyglycoside are added with light cutting agitation together with other coating auxiliaries, as desired. Alternatively, one or both of the selected alkyl polyglycoside and surfactant may be pre-added to the emulsion polymer, before, during or subsequent to the preparation of the emulsion polymer. Alternatively, the emulsion polymer may be present during the pigment dispersion step. The aqueous coating composition may contain conventional coating aids, such as emulsifiers, regulators, neutralizers, coalescers, thickeners or rheology modifiers, thawing additives, wet margin auxiliaries, humectants, wetting agents, biocides, antifoaming agents, dyes, waxes and antioxidants. The solids content of the aqueous coating composition can be from 25% to 60% by volume. The viscosity of the aqueous polymer composition can be from 50 UK (Krebs Units) to 120 UK, which is measured using a Brookfield Digital Viscometer KU-1; The appropriate viscosity for the different methods of application varies considerably. Conventional coating application methods, such as by brush, roller, and spray methods such as atomized air spraying, air assisted spraying, airless spraying, can be used., spray of low pressure and high volume, and airless spraying assisted by air. The aqueous coating composition can be applied to substrates such as wood, metal, plastics, and cement substrates such as concrete, stucco and mortar, previously painted or primed surfaces, and surfaces exposed to the weather. Typically it is allowed to dry to proceed under ambient conditions such as 0 ° C. at 35 ° C. The following examples are presented to illustrate the invention and the results obtained by the test procedures.

EXAMPLE 1. Preparation of the emulsion polymers. Sample 1. A five-liter round bottom flask with four necks, equipped with a paddle stirrer, heating blanket and temperature controller, condenser and a nitrogen atmosphere, was charged with 1200 gr. of water and 2 gr. of sodium lauryl sulfate. The ingredients were heated to 85 ° C. A 700 g monomer emulsion was prepared. of water, 20 gr. of sodium lauryl sulfate, 920 gr. of butyl acrylate, 1040 gr. of methyl methacrylate and 40 gr. of methacrylic acid. Then, a solution of 3 gr. of sodium carbonate and 20 gr. of water, 25 gr. of the charge of the monomer emulsion, and a solution of 6 gr. of ammonium persulfate and 20 gr. of water were added to the flask. The ingredients were stirred for 10 minutes at 85 ° C. The remaining monomer emulsion and a solution of 1 gr. of ammonium persulfate and 100 gr. of water were added continuously for 180 minutes. At the end of the feeding, 216.2 gr. of Glucopon® 625 (37% active ingredient in water) for 20 minutes, and stirred for an additional 20 minutes. The whole mixture was cooled to 60 ° C, and 5 gr. (0.15% by weight) of a ferrous sulfate heptahydrate, 1 gr. of t-butyl hydroperoxide and 10 gr. of water, and 0.5 gr. of sodium sulfoxylate in 20 gr. of water were added to the mixture, and stirred for 30 minutes. While it was getting hot, 11 gr. of ammonium hydroxide (28% by weight). The consignment was cooled and filtered. Sample 2 was prepared according to the method of sample 1 above, with the exception that Glucopon® 625 was not added.

EXAMPLE 2. Preparation of the coating bases.

The coating base 1 (BR-1) was prepared according to Table 2-1, and the coating base 2 (BR-2) according to Table 2-2.

Table 2-1. Coating base BR-1 MATERIAL Grams CRUSHED Methyl Carbitol 6.3 Tego FOAMEX® 800 1.0 Propylene Glycol 33.8 TAMOL® 731 (25%) 8.2 TiPure® R700 205.4 Grind the above for 15 to 20 minutes, and then add at low speed Water 20.00 DECREASE Emulsion polymer-Sample 1 566.5 Methyl Carbitol 5.0 TEXANOL® 32.3 ACRYSOL.®RM-2020 90.0 Water 58.5 PVC "17.9 Solid volume 34.4% Notes: Tipure® is a trademark of The DuPont of Nemours Co., TEXANOL® is a trademark of Eastman Chemical Co., FOAMEX® is a trademark of Tego Chemie Service USA, a division of Goldschmidt Chemical Corporation. TAMOL® and ACRYSOL® are trademarks of Rohm and Haas Company.

Table 2-2. Preparation of the BR-2 coating base. MATERIAL Grams CRUSHED Methyl Carbitol 6.3 Tego FOAMEX® 800 1.0 Propylene Glycol 33.8 TAMOL® 731 (25%) 8.2 TiPure® R700. 205.4 Grind the above for 15 to 20 minutes, and then add at low speed Water 20.00 DECREASE Polymer emulsion-Display 2 552.4 Carbitol Methyl 5.0 TEXANOL® 32.0 ACRYSOLTRM-2020 90.0 Water 71.6 PVC 17.9 Volume solids 34.4% EXAMPLE 3. Evaluation of the coating compositions. To a sample of the coating base surfactant was added, if appropriate, with stirring to obtain the coating compositions identified in Tables 3-1. To determine block strength, the coating composition was poured into a Leneta WB ("panel") test table (from The Leneta Company, Mahwah, New Jersey) using a 3 mil Bird applicator. The covered panels were kept at constant ambient temperature ("TAC") (25 ° C, 50% RH) for one day or seven hours. Four sections of 3.8 cm. x 3.8 cm (1-1 / 2 inches x 1-1 / 2 inches) (for duplicates) were cut from the white area of each conditioning panel. The cut sections were placed with the surfaces covered face to face. The face-to-face sample was placed on the top of the platform at TAC ("Block at room temperature"). Each individual sample was covered with a solid plug of rubber number 8, and a weight of 1000 gr. It was placed on each stopper. After 16 hours, the plugs and weights were removed. The samples were separated slowly and uniformly at an angle of approximately 180 ° while the noise produced by the separation of the blocked surfaces was being voided. Alternatively, for the "baked block" test the changes made to the previous procedure were that the face-to-face sample was placed in an oven at 50 ° C. (120 ° F.) On a flat metal plate. Each sample was covered with a rubber plug number 8, solid and heated, and a weight of 1000 gr was placed. hot on each stopper. After exactly 30 minutes, the plugs and weights were removed, and the samples were taken out of the oven. The test samples were allowed to cool for 30 minutes at room temperature, before separating them as indicated above.

The samples were rated for block resistance on a scale of 0 to 10, which corresponded to a sealing index and subjective separation noise (the seal is physical damage to a covered surface, caused by the separation of the blocked surfaces). as listed below in descriptive terms. 10. no noise, perfect 9. pinch of noise, excellent 8. light noise, very good 7. light noise, good 6. moderate noise, good 5. moderate noise, regular 4. severe noise, if seal, regular 3. 5 -25% seal, bad 2. 25-50% seal, bad 1. 50-75% seal, bad 2. full seal, very bad Differences of the block resistance of ± 1 unit are considered significant.

Table 3-1: Block resistance of the compositions of coating.

Agent BHL Oven level Drying Temperature Drying surfactant agent ten. 7 days block environment block 1 day kg./l. Base rev. Base rev. Base rev. Base BR -2 BR-1 BR-2 rev. BR-1 None "~ 0 0 0 5 TRITON®GR-7M 20 0.24 0 5 0 7 TRITON © H-66 20 0.24 0 6 0 7 TRITON®CF-10 14.0 0.24 0 2 0 5 TRITON®X-15 3.S 0.24 0 0 0 5 TRITON®X-45 10.4 0.24 0 3 0 5 TRITON®X-102 14.6 0.24 0 0 0 5 TRITON®X-405 17.9 0.24 0 8 0 5 TRITON®N-I7 4.S 0.24 0 0 0 5 TRITON ®N-57 10.0 0.24 0 6 0 5 TRITON®N-128 14.4 0.24 0 0 0 2 TRITON®N-401 17.8 0.24 0 2 0 6 None - - 0 0 0 4 Igepal®C0-630 13.0 0.24 0 0 0 4 Tergitol®NP-9 12.9 0.24 0 0 0 2 Tergitol®NP-lC 13.6 0.24 0 0 0 2 TRITON®N-101 13.4 0.24 0 0 0 0 TRITON®GR-7M 20 0.48 0 6 0 6 TRITON®H-66 20 0.48 0 0 0 5 TRITON®CF-10 14.0 0.48 0 5 0 5 TRITON®X-15 3.S 0.48 0 5 0 5 TRITON®X- 45 10.4 0.48 0 5 0 5 TRITON®X-102 14.6 0.48 0 0 0 2 TRITON®X-405 17.9 0.48 0 6 0 6 TRITON®N-17 4.6 0.48 0 3 0 5 TRITON®N-57 10.0 0.48 0 2 0 5 TRITON®N-128 14.4 0.48 0 0 0 5 TRITON®N-401 17.8 0.48 0 6 0 6 None 0.48 0 0 0 4 Igepal®C0-630 13.0 0.48 0 0 0 0 Tergitol®NP-9 12.9 0.48 0 0 0 0 Tergitol®NP-10 13.6 0.48 0 0 0 0 TRITON®N-101 13.4 0.48 0 0 0 0 Note: TRITON® and TERGITOL® are trademarks of Union Carbide Chemical & Plastics co .; IGEPAL® is a brand of Rhone-Poulenc Surfactants and Specialties.

Examples of the invention containing an alkyl polyglycoside (Coating Base-1) and an anionic or nonionic surfactant, the surfactant having a BHL value less than 11.6 or greater than 14.6, exhibit a block strength higher than the examples comparatives which do not have alkyl polyglucoside (Coating Base 2) and / or which contain an anionic or nonionic surfactant having a BHL value of 11.6 to 14.6, particularly at higher levels of surfactants or under the most extreme test conditions of block in oven.

Claims (8)

Claims

1. An aqueous coating composition having improved block strength, comprising an emulsion polymer; a nonionic or anionic surfactant, said surfactant having a BHL value of less than 11.6 or greater than 14.6; and an alkyl polyglycoside.

2. The aqueous coating composition according to claim 1, wherein said polymer has a glass transition temperature of -10 ° C. at 70 ° C ..

3. The aqueous coating composition according to claim 1, wherein the amount of said surfactant is from 0.1 to 10% by weight, based on the weight of the dry polymer.

4. The aqueous coating composition according to claim 1, wherein the amount of said alkyl polyglycoside is from 0.1 to 10% by weight, based on the weight of the dry polymer.

5. A method for improving the block strength of a dry aqueous coating composition, comprising: forming an aqueous coating composition comprising an emulsion polymer, a nonionic or anionic surfactant, said surfactant having a BHL value of less than 11.6 or greater than 14. 6, and an alkyl polyglycoside; applying said aqueous coating composition to a substrate; and drying or allowing said aqueous coating composition to dry.

6. The method according to claim 5, wherein said polymer has a glass transition temperature of -10 ° C. at 70 ° C ..

7. The method according to claim 5, wherein the amount of said surfactant is from 0.1 to 10% by weight, based on the weight of the dry polymer.

8. The method according to claim 5, wherein the amount of said alkyl polyglycoside is from 0.1 to 10% by weight, based on the weight of the dried polymer.