Aqueous polymer compositions for flexible roof coatings

Abstract

The present invention relates to the use of liquid aqueous polymer compositions containing an aqueous polymer latex and at least one inorganic particulate material for providing flexible roof coatings. The present invention also relates to a method for providing flexible roof coatings, which comprises applying said liquid aqueous polymer compositions to a flat roof. The liquid aqueous polymer composition contain, a. an aqueous polymer latex, where the polymer in the polymer latex is made of polymerized monomers M, where the polymerized ethylenically unsaturated monomers M comprise a combination of) at least two different monoethylenically unsaturated, non-ionic monomers M1, whose homopolymers have a theoretical glass transition temperature T.sub.g(th) of at least 25° C. and ii) at least two different monoethylenically unsaturated, non-ionic monomers M2, whose homopolymers have a theoretical glass transition temperature T.sub.g(th) of at less than 25° C., where each of the monomers M1 and M2 have a solubility in deionized water of at most 50 g/L and where the total amount of monomers M1 and M2 contributes with at least 90% by weight to the total amount of the monomers M, and b. at least one inorganic particulate material selected from inorganic pigments, inorganic fillers and mixtures thereof.

Claims

1. A method for providing a flexible roof coating, the method comprising obtaining a liquid aqueous polymer composition comprising: a. an aqueous polymer latex, where a polymer in the aqueous polymer latex comprises ethylenically unsaturated monomers M, where the ethylenically unsaturated monomers M comprise a combination of i) at least two different monoethylenically unsaturated, non-ionic monomers M1, whose homopolymers have a theoretical glass transition temperature T.sub.g(th) of at least 25° C. and ii) at least two different monoethylenically unsaturated, non-ionic monomers M2, whose homopolymers have a theoretical glass transition temperature T.sub.g(th) of less than 25° C., where each of the monomers M1 and M2 have a solubility in deionized water of at most 50 g/L and where a total amount of the monomers M1 and M2 contributes at least 90% by weight to a total amount of the monomers M, and where the aqueous polymer latex is prepared by free radical aqueous emulsion polymerization of the ethylenically unsaturated monomers M, which form the aqueous polymer latex, in the presence of at least one surfactant and at least one polymerization initiator and optionally in the presence of a seed latex, where an amount of seed latex, if present, is in a range from 0.1 to 10% by weight, calculated as solids and based on a total weight of the monomers M to be polymerized; and b. at least one inorganic particulate material selected from inorganic pigments, inorganic fillers and mixtures thereof, wherein the liquid aqueous polymer composition has a pigment volume concentration (PVC) of from 15% to 50%, and, wherein, when applying the liquid aqueous polymer composition to a surface of a substrate to be coated with an application rate of from 750 to 3,500 g/m.sup.2 an average coating thickness of 450 to 2,000 μm, calculated on a dry film basis is achieved.

2. The method of claim 1, where the monomers M1 have a T.sub.g(th) of at least 50° C. and where the monomers M2 have a T.sub.g(th) of at most −20° C.

3. The method of claim 1, where the monomers M1 are a combination of: at least one monomer M1a, which is selected from vinylaromatic hydrocarbon monomers and C.sub.5-C.sub.6-cycloalkyl methacrylates; and at least one monomer M1b, which is selected from C.sub.1-C.sub.4-alkyl esters of methacrylic acid and tert-butyl acrylate.

4. The method of claim 1, where the monomers M1 comprise styrene, and where styrene contributes 10 to 35% by weight to the total amount of the monomers M.

5. The method of claim 3, where a weight ratio of the at least one monomer M1a to the at least one monomer M1b is from 3:1 to 1:3.

6. The method of claim 1, where a total amount of the monomers M1 contributes 25 to 70% by weight to the total amount of the monomers M.

7. The method of claim 1, where the monomers M2 are a combination of at least two different C.sub.2-C.sub.12-alkyl acrylates, except for tert-butyl acrylate.

8. The method of claim 1, where each of the monomers M2 contributes at least 10% by weight to the total weight of the monomers M, and where a total amount of the monomers M2 contributes 20 to 75% by weight to the total amount of the monomers M.

9. The method of claim 1, where the monomers M comprise at least one further monoethylenically unsaturated monomer, which is selected from the group consisting of: monomers M3, which are selected from the group consisting of monoethylenically unsaturated C.sub.3-C.sub.6-monocarboxylic acids, monoethylenically unsaturated C.sub.4-C.sub.6-dicarboxylic acids, primary amides of monoethylenically unsaturated C.sub.3-C.sub.6-monocarboxylic acids, and hydroxy-C.sub.2-C.sub.4-alkyl esters of monoethylenically unsaturated C.sub.3-C.sub.6-monocarboxylic acids and mixtures thereof, monomers M4, which are selected from the group consisting of monoethylenically unsaturated monomers having at least one keto group and monoethylenically unsaturated monomers having at least one oxirane group and mixtures thereof, and monomers M5, which are selected from the group consisting of monoethylenically unsaturated monomers having a silane group.

10. The method of claim 1, where the monomers M comprise from 25 to 70% by weight, based on a total weight of the monomers M, of a combination at least two monomers M1; from 20 to 75% by weight, based on the total weight of the monomers M, of a combination at least two monomers M2; from 0.1 to 10% by weight, based on the total weight of the monomers M, of one or more monoethylenically unsaturated monomers, selected from the group consisting of one or more monomers M3a in an amount of at most 5% by weight, based on the total amount of the monomers M, which are selected from the group consisting of monoethylenically unsaturated C.sub.3-C.sub.6-monocarboxylic acids and monoethylenically unsaturated C.sub.4-C.sub.6-dicarboxylic acids, one or more monomers M3b in an amount of at most 5% by weight, based on the total amount of the monomers M, which are selected from the group consisting of primary amides of monoethylenically unsaturated C.sub.3-C.sub.6-monocarboxylic acids, and hydroxy-C.sub.2-C.sub.4-alkyl esters of monoethylenically unsaturated C.sub.3-C.sub.6-monocarboxylic acids and mixtures thereof, one or more monomers M4 in an amount of at most 5% by weight, based on the total amount of the monomers M, which are selected from the group consisting of monoethylenically unsaturated monomers having at least one ketogroup and monoethylenically unsaturated monomers having at least one oxirane group and mixtures thereof, and one or more monomers M5 in an amount of at most 2% by weight, based on the total amount of the monomers M, which are selected from the group consisting of monoethylenically unsaturated monomers having a silane group.

11. The method of claim 1, where the polymer has a glass transition temperature T.sub.g in a range from −20° C. to +40° C., where the glass transition temperature is determined by differential scanning calorimetry using a heating rate of 20 K/min and applying a midpoint measurement in accordance with ISO 11357-2:2013-05.

12. The method of claim 1, where the liquid aqueous polymer composition comprises at least one inorganic filler selected from the group consisting of natural calcium carbonates, synthetic calcium carbonates, calcium silicates, aluminum silicates and alkalimetal silicates.

13. The method of claim 12, where the at least one inorganic filler comprises particles and at least 90% by weight of the particles of the at least one inorganic filler have a particle size in a range from 0.1 to 25 μm, as determined by laser diffraction in accordance with ISO 13320:2009.

14. The method of claim 13, where at least 50% by weight of the particles of the at least one inorganic filler have a particle size in a range from 0.1 to 2 μm, as determined by laser diffraction in accordance with ISO 13320:2009.

15. The method of claim 12, where the liquid aqueous polymer composition additionally comprises at least one inorganic white pigment.

16. The method of claim 1, where the pigment volume concentration PVC is in a range from 20 to 450.

17. A method for providing a flexible roofing, the method comprising applying the liquid aqueous polymer composition as defined in claim 1 as a coating to a flat roof having an inclination of not more than 15°.

Description

EXAMPLES

(1) Analytics 1.1 The solids contents of the aqueous polymer latexes were generally determined by drying a defined amount of the aqueous polymer dispersion (about 0.8 g) at a temperature of 130° C. to constant weight (about 2 hours) with the aid of the moisture analyzer HR73 from Mettler Toledo. Two separate measurements were conducted. The value reported in the example is the mean of the two measurements. 1.2 The particle diameter of the aqueous polymer latexes were determined by dynamic light scattering of an aqueous polymer dispersion diluted with deionized water to 0.005 to 0.01% by weight at 23° C. by means of an Autosizer IIC from Malvern Instruments, England. What is reported is the cumulant Z average diameter calculated from of the measured autocorrelation function (ISO Standard 13321). 1.3 The glass transition temperatures of the polymer latexes were determined by the DSC method (Differential Scanning calorimetry, 20 K/min, midpoint measurement, DIN 53765:1994-03) by means of a DSC instrument (Q 2000 series from TA instruments). 1.4 The pH values of the polymer latexes were determined by using a pH-meter with standard glass electrode.

(2) Preparation of the Carboxylated Acrylic Polymer Latexes and Iminated Acrylic Polymer Latexes

Example 1

(3) 500.0 g deionized water and 22.73 g of polystyrene seeds, with a particle diameter of 28 nm and a solids content of 33%, were charged in a 4 l glass vessel, equipped with an anchor stirrer, heating and cooling devices, as well as various inlets, at 20 to 25° C. (room temperature) and atmospheric pressure (1 atm≙1013 bar absolute) and then heated to an internal temperature of 80° C. with stirring (140 rpm). After having reached this temperature, the initiator solution was added in one portion and the resulting mixture was stirred for 5 minutes. Subsequently, the monomer emulsion was metered in over the course of 180 minutes.

(4) Initiator Solution:

(5) TABLE-US-00001 6 g Sodium peroxodisulfate 79.71 g Deionized water

(6) Monomer Emulsion:

(7) TABLE-US-00002 445.28 g deionized water 18.75 g of a 20% by weight aqueous solution of a fatty alcohol polyethoxylate (Lutensol ® AT 18 from the company BASF SE) 50.0 g of a 15% by weight aqueous solution of sodium laurylsulfate 300 g styrene 435 g n-butyl acrylate 360 g methyl methacrylate 375 g ethylhexyl acrylate 15 g acrylic acid and 30 g of a 50 wt.- % aqueous solution of acrylamide

(8) Then, 50 g of water was added, and the reaction mixture was allowed to react for a further 30 minutes at the abovementioned temperature. Following this 30 g of a 10% aqueous solution of tert.-butyl hydroperoxide was added and the mixture was cooled to 75° C. Then, 30 g of a 10% aqueous solution of sodium hydroxymethanesulfinate was added over 60 minutes. 40 g of water was added. The resulting aqueous polymer dispersion was then adjusted to a pH of 8.2 using 58 g of a 10% by weight aqueous sodium hydroxide solution. The resulting polymer dispersion had a solids content of 53.7% by weight, a number-average particle diameter of 197 nm and a glass transition temperature of 2.3° C.

Example 2

(9) 500.0 g Deionized water and 22.21 g of polystyrene seeds, with a particle diameter of 28 nm and a solids content of 33%, were charged in a 4 l glass vessel, equipped with an anchor stirrer, heating and cooling devices, as well as various inlets, at 20 to 25° C. (room temperature) and atmospheric pressure (1 atm≙1013 bar absolute) and then heated to an internal temperature of 80° C. with stirring (140 rpm). After having reached this temperature, 22.4 g of the initiator solution was added in one portion and the resulting mixture was stirred for 5 minutes. Subsequently, the monomer emulsion was metered in over the course of 180 minutes, and the remainder of the initiator solution was simultaneously metered in, but over a period of 195 minutes.

(10) Initiator Solution:

(11) TABLE-US-00003 5.6 g Sodium peroxodisulfate 218.4 g Deionized water

(12) Monomer Emulsion:

(13) TABLE-US-00004 415.62 g deionized water 17.5 g of a 20% by weight aqueous solution of a fatty alcohol polyethoxylate (Lutensol ® AT 18 from the company BASF SE) 46.67 g of a 15% by weight aqueous solution of sodium laurylsulfate 280 g styrene 406 g n-butyl acrylate 329 g methyl methacrylate 350 g ethylhexyl acrylate 7 g vinyltriethoxysilane 14 g acrylic acid and 28 g of a 50 wt.- % aqueous solution of acrylamide

(14) Then, 50 g of water was added, and the reaction mixture was allowed to react for a further 30 minutes at the abovementioned temperature. Following this 28 g of a 10% aqueous solution of tert.-butyl hydroperoxide was added and the mixture was cooled to 75° C. Then, 28 g of a 10% aqueous solution of sodium hydroxymethanesulfinate was added over 60 minutes. 40 g of water was added. The resulting aqueous polymer dispersion was then adjusted to a pH of 8.1 using 55 g of a 10% by weight aqueous sodium hydroxide solution. The resulting polymer dispersion had a solids content of 49.9% by weight, a number-average particle diameter of 185 nm and a glass transition temperature of 2.0° C.

Example 3

(15) 500.0 g deionized water and 21.21 g of polystyrene seeds, with a particle diameter of 28 nm and a solids content of 33%, were charged in a 4 l glass vessel, equipped with an anchor stirrer, heating and cooling devices, as well as various inlets, at 20 to 25° C. (room temperature) and atmospheric pressure (1 atm≙1013 bar absolute) and then heated to an internal temperature of 80° C. with stirring (140 rpm). After having reached this temperature, 22.4 g of the initiator solution was added in one portion and the resulting mixture was stirred for 5 minutes. Subsequently, the monomer emulsion was metered in over the course of 195 minutes.

(16) Initiator Solution:

(17) TABLE-US-00005 5.6 g sodium peroxodisulfate 218.4 g deionized water

(18) Monomer Emulsion:

(19) TABLE-US-00006 415.62 g deionized water 17.5 g of a 20% by weight aqueous solution of a fatty alcohol polyethoxylate (Lutensol ® AT 18 from the company BASF SE) 46.67 g of a 15% by weight aqueous solution of sodium laurylsulfate 280 g styrene 406 g n-butyl acrylate 326 g methyl methacrylate 350 g ethylhexyl acrylate 7 g acrylic acid and 28 g of a 50 wt.- % aqueous solution of acrylamide

(20) Then, 50 g of water was added, and the reaction mixture was allowed to react for a further 30 minutes at the abovementioned temperature. Following this, 28 g of a 10% aqueous solution of tert.-butyl hydroperoxide was added and the mixture was cooled to 75° C. Then, 28 g of a 10% aqueous solution of sodium hydroxymethanesulfinate was added over 60 minutes. 40 g of water was added. The resulting aqueous polymer dispersion was then adjusted to a pH of 7.9 using 55 g of a 10% by weight aqueous sodium hydroxide solution. The resulting polymer dispersion had a solids content of 50% by weight, a number-average particle diameter of 186 nm and a glass transition temperature of 2.0° C.

Example 4

(21) 500.0 g deionized water and 22.73 g of polystyrene seeds, with a particle diameter of 28 nm and a solids content of 33%, were charged in a 4 l glass vessel, equipped with an anchor stirrer, heating and cooling devices, as well as various inlets, at 20 to 25° C. (room temperature) and atmospheric pressure (1 atm≙1013 bar absolute) and then heated to an internal temperature of 80° C. with stirring (140 rpm). After having reached this temperature, 8.57 g of the initiator solution was added in one portion and the resulting mixture was stirred for 5 minutes. Subsequently, the monomer emulsion was metered in over the course of 195 minutes.

(22) Initiator Solution:

(23) TABLE-US-00007 6 g sodium peroxodisulfate 79.71 g deionized water

(24) Monomer Emulsion:

(25) TABLE-US-00008 457.53 g deionized water 18.75 g of a 20% by weight aqueous solution of a fatty alcohol polyethoxylate (Lutensol ® AT 18 from the company BASF SE) 50 g of a 15% by weight aqueous solution of sodium laurylsulfate 225 g styrene 465 g n-butyl acrylate 341.25 g methyl methacrylate 420 g ethylhexyl acrylate 9 g acetoacetoxyethyl methacrylate 3.75 g vinyltriethoxysilane 15 g acrylic acid and 12 g of a 50 wt.- % aqueous solution of acrylamide

(26) Then, 50 g of water was added, and the reaction mixture was allowed to react for a further 30 minutes at the abovementioned temperature. Following this, 30 g of a 10% aqueous solution of tert.-butyl hydroperoxide was added and the mixture was cooled to 75° C. Then, 30 g of a 10% aqueous solution of sodium hydroxymethanesulfinate was added over 60 minutes. 40 g of water was added. The resulting aqueous polymer dispersion was then adjusted to a pH of 7.9 using 54 g of a 10% by weight aqueous sodium hydroxide solution. The resulting polymer dispersion had a solids content of 53.2% by weight, a number-average particle diameter of 181 nm and a glass transition temperature of −6.6° C.

Reference Example 5

(27) 500.0 g deionized water and 22.73 g of polystyrene seeds, with a particle diameter of 28 nm and a solids content of 33%, were charged in a 4 l glass vessel, equipped with an anchor stirrer, heating and cooling devices, as well as various inlets, at 20 to 25° C. (room temperature) and atmospheric pressure (1 atm≙1013 bar absolute) and then heated to an internal temperature of 80° C. with stirring (140 rpm). After having reached this temperature, 5.84 g of the initiator solution was added in one portion and the resulting mixture was stirred for 5 minutes. Subsequently, the monomer emulsion was metered in over the course of 180 minutes, and the remainder of the initiator solution was simultaneously metered in, but over a period of 195 minutes.

(28) Initiator Solution:

(29) TABLE-US-00009 6 g sodium peroxodisulfate 114 g deionized water

(30) Monomer Emulsion:

(31) TABLE-US-00010 417.24 g deionized water 18.75 g of a 20% by weight aqueous solution of a fatty alcohol polyethoxylate (Lutensol ® AT 18 from the company BASF SE) 50 g of a 15% by weight aqueous solution of sodium laurylsulfate 627 g styrene 840 g n-butyl acrylate 30.43 g methyl methacrylate 15 g acrylic acid 30 g of a 50% by weight aqueous solution of acrylamide

(32) Then, 28.33 g of water was added, and the reaction mixture was allowed to react for a further 30 minutes at the abovementioned temperature. Following this, 30 g of a 10% aqueous solution of tert.-butyl hydroperoxide was added and the mixture was cooled to 75° C. Then, 30 g of a 10% aqueous solution of sodium hydroxymethanesulfinate was added over 60 minutes. 40 g of water was added. The resulting aqueous polymer dispersion was then adjusted to a pH of 7.2 using 43.5 g of a 10% by weight aqueous sodium hydroxide solution. The resulting polymer dispersion had a solids content of 54.0% by weight, a number-average particle diameter of 178 nm and a glass transition temperature of 5.1° C.

(33) Determination of the Mechanical Properties

(34) a) Preparation of the Aqueous Polymer Compositions

(35) Based on the aqueous polymer dispersions of examples 1 to 5, roof skin formulations were prepared by mixing the constituents indicated in Table 1 (amounts in g) at room temperature in the order shown from top to bottom using a disk stirrer at 400 to 2500 rpm.

(36) TABLE-US-00011 TABLE 1 Roof skin formulation F1 F2 F3 F4 F5 .sup.6) Dispersion/amount 1/55 2/53 3/55 4/54 5/56 Wetting agent .sup.1) 0.4 0.4 0.4 0.4 0.4 Defoamer .sup.2) 0.5 0.5 0.5 0.5 0.5 Dispersant .sup.3) 1.2 1.2 1.2 1.2 1.2 Filler .sup.4) 42.5 42.5 42.5 42.5 42.5 Thickener .sup.5) 0.35 0.35 0.65 0.35 0.3 Defoamer .sup.2) 0.4 0.4 0.4 0.4 0.4 .sup.1) Lutensol TO 82, BASF SE, Ludwigshafen .sup.2) Agitan 282, Münzing Chemie GmbH, Heilbronn .sup.3) Dispex CX 4320, BASF SE, Ludwigshafen .sup.4) Hydrocarb 95 ME, Omya, Oftringen, Switzerland .sup.5) Rheovis PU 1270, BASF SE, Ludwigshafen .sup.6) Comparative example

(37) After the addition of the last component, stirring was continued until everything was mixed homogeneously (about 10 min) and then the resulting roof skin formulation was added to a Speed Mixer DAC 400 FVZ from Hauschild and mixed for 0.5 min at 2000 rpm.

(38) The roof skin formulation has a solids content of about 63-67%, a pigment volume concentration of about 29 and a viscosity of 8000-10000 mPas (Brookfield, spindle 6, 20 rpm).

(39) b) Preparation of Coatings and Test Specimens

(40) The aforesaid roof skin formulation was applied to a Teflon coated substrate with a doctors blade in a layer having a thickness of 1.2 mm. Subsequently, the thus obtained coatings were dried for 7 days at 23° C. and 50% relative humidity in a climatic chamber. The resulting dry film thickness is about 0.60 mm. After the coating had been peeled off from the substrate, the required test specimens were punched out with an appropriate punching iron.

(41) c) Determination of Tensile Strength, Breaking Strength and Elongation at Break

(42) From the above-described coatings, dumbbell test specimens of size S1 were punched out with the aid of a punching iron. The test was carried out in accordance with DIN 53504. The dumbbell test specimens are clamped in a tensile/strain testing machine from the company Zwick and subsequently pulled apart at a rate of 200 mm/min until tearing.

(43) d) Determination of the Water Absorption

(44) A piece of the coating of about 5*5 cm in size is stored for 24 hours under water; then the water on the surface is wiped off and the thus treated coating is weighed back. The difference in weight before and after the water storage corresponds to the water absorption of the coating.

(45) TABLE-US-00012 TABLE 2 Roof skin formulation 1 2 3 4 5 Tensile strength N/mm.sup.2 3.0 4.74 5.0 4.18 2.4 Elongation at break % 703 492 341 696 324 Water absorption (24 h) % 23.8 20.0 14.9 11.8 23.5

(46) The tested coatings according to the invention have large tensile strength of 3 to 5 N/mm.sup.2 and simultaneously a large elongation at break of 341 to 703%. The water absorption of the coatings 2 to 5 is only 10 to 20%.