LIQUID APPLIED MEMBRANE WITH IMPROVED INTERCOAT ADHESION

Abstract

A method for coating a surface, including the steps: a) applying a first layer of a moisture-curable composition onto a surface, b) optionally letting the applied moisture-curable composition cure into a dried first layer, c) applying a second layer of the moisture-curable composition onto the optionally dried first layer, wherein the moisture-curable composition includes: between 20 and 50 wt.-%, preferably between 25 and 45 wt.-%, based on the total weight of the composition, of at least one organic polymer which is liquid at room temperature and contains reactive silane groups, and between 10 and 30 wt.-%, preferably between 15 and 25 wt.-%, based on the total weight of the composition, of at least one polyether PE having between 2 and 6 ether oxygen atoms and is free of hydroxyl groups; and at least one curing catalyst for reactive silane groups. The method yields a multilayer coating with high intercoat adhesion.

Claims

1. A method for coating a surface, comprising the steps: a) applying a first layer of a moisture-curable composition onto a surface, b) optionally letting the applied moisture-curable composition cure into a dried first layer, c) applying a second layer of the moisture-curable composition onto the optionally dried first layer, wherein the moisture-curable composition comprises between 20 and 50 wt. %, based on the total weight of the composition, of at least one organic polymer which is liquid at room temperature and contains reactive silane groups, and between 10 and 30 wt. %, based on the total weight of the composition, of at least one polyether PE having between 2 and 6 ether oxygen atoms and is free of hydroxyl groups; and at least one curing catalyst for reactive silane groups.

2. The method as claimed in claim 1, wherein the polymer containing silane groups is a polyether containing silane groups.

3. The method as claimed in claim 2, wherein the polyether containing silane groups contains urethane groups and/or urea groups additionally to the silane groups.

4. The method as claimed in claim 1, wherein in the first layer is letting to be cured into a dried first layer before the second layer is applied, with a drying time after step a) of at least 48 hours before step c) is performed.

5. The method as claimed in claim 1, wherein the moisture-curable composition additionally comprises between 10 wt.-% and 50 wt.-% of at least one filler.

6. The method as claimed in claim 1, wherein the polyether PE contains between 4 and 12 carbon atoms and the ether oxygen atoms are bridged by 1 or 2 carbon atoms.

7. The method as claimed in claim 6, wherein the polyether PE is selected from dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol dibutyl ether, dipropylene glycol dipropyl ether, and 2,5,7,10-tetraoxaundecane.

8. The method as claimed in claim 1, wherein the moisture-curable composition contains less than 5 wt.-%, based on the total composition, of aliphatic or aromatic alkylalkoxysilanes.

9. The method as claimed in claim 1, wherein the curing catalyst is a combination of a primary aminosilane and a metal complex, said metal complex in particular being a tin complex.

10. The method as claimed in claim 9, wherein the composition comprises between 0.5 and 1.0 wt.-% of the primary aminosilane and between 0.01 and 0.1 wt.-% of the metal complex.

11. The method as claimed in claim 1, wherein the composition additionally comprises at least one further constituent selected from moisture scavengers, UV absorbers and stabilizers, pigments, and rheology modifiers.

12. The method as claimed in any claim 1, wherein the surface to be coated is a roof of a building.

13. The moisture-curable composition to be used in the method as claimed in claim 1.

14. A cured multilayer coating obtained from the method as claimed in claim 1.

15. A roof sealing system comprising optionally a primer and/or a base coat and/or a repair or levelling compound, at least two layers of the composition as described in claim 1 in a thickness of each layer of 0.5 to 3 mm, optionally in combination with a mechanical reinforcement, optionally a topcoat and/or seal coat.

Description

EXAMPLES

[0161] Adduced hereinafter are working examples which are intended to elucidate the invention described in detail. It will be appreciated that the invention is not restricted to these described working examples.

[0162] Standard climatic conditions refer to a temperature of 231 C. and a relative air humidity of 505%. SCC stands for standard climatic conditions.

[0163] Silane Group-Containing Polymer Used:

[0164] STP Polymer-1:

[0165] In the absence of moisture, 1000 g of Acclaim 12200 polyol (from Covestro; low monool polyoxypropylenediol, OH number 11.0 mg KOH/g, water content around 0.02 wt %), 62.5 g of isophorone diisocyanate (Vestanat IPDI from Evonik Industries), 131.2 g of triethylene glycol bis(2-ethylhexanoate) (TEG-EH from Eastman) and 0.3 g of Coscat 83 (from Vertellus) were heated to 90 C. with continuous stirring and left at this temperature until the free isocyanate group content as determined by titrimetry had reached a value of 1.32 wt %. Subsequently, 144.9 g of diethyl N-(3-trimethoxysilylpropyl)aminosuccinate were mixed in and the mixture was stirred at 90 C. until it was no longer possible to detect any free isocyanate by means of FT-IR spectroscopy. The silane-functional polymer was cooled to room temperature and stored in the absence of moisture. It was liquid at room temperature and had a viscosity at C. of 3.5 Pa.Math.s

[0166] STP Polymer-1 contains 11% by weight of plasticizer (triethylene glycol bis(2-ethylhexanoate)).

[0167] Further Substances Used:

TABLE-US-00001 OCTMO Octyltrimethoxysilane; Dynasylan OCTMO (Evonik) DMM Dipropylene glycol dimethyl ether; PROGLYDE DMM (Dow) PGDA Propylene glycol diacetate; DOWANOL PGDA (Dow) DPM Dipropylene glycol monomethyl ether; DOWANOL DPM (Dow) DPnP Dipropylene glycol monopropyl ether; DOWANOL DPnP (Dow) TOU 2,5,7,10-Tetraoxaundecane; Tetraoxaundecan SOLVAGREEN (Carl Roth) PC Propylene carbonate; Propylene carbonate (Sigma Aldrich) TEG-EH Triethylene glycol bis(2-ethylhexanoate); Eastman TEG-EH (Eastman) VTMO Vinyltrimethoxysilane; Geniosil XL 10 (Wacker); (moisture scavenger) UV-A UV absorber (organic) UV-S UV stabilizer (Hindered Amine Light Stabilizer) TiO.sub.2 Titanium dioxide (white pigment) Pigment Black pigment ATH Aluminium trihydroxide Al(OH).sub.3 (filler) CaCO.sub.3 Calcium carbonate (chalk) (filler) SiO.sub.2 Pyrogenic silica (reinforcement/rheology modifier) AMMO 3-Aminopropyltrimethoxysilane; Dynasylan AMMO (Evonik) (catalyst) DBTDL Dibutyltin dilaurate (catalyst) D-400 Polyetherdiamine based on polypropylene glycol with terminal primary amino groups (average molecular weight 430 g/mol); Jeffamine D-400 (Huntsman) D-230 Polyetherdiamine based on polypropylene glycol with terminal primary amino groups (average molecular weight 230 g/mol); Jeffamine D-230 (Huntsman)

[0168] Production of Sealing Membranes:

[0169] For each sealing membrane, the ingredients specified in tables 1 and 2 were mixed in the specified amounts (in parts by weight) by means of a centrifugal mixer (SpeedMixer DAC 150, FlackTek Inc.) or by means of a high speed disperser into a homogeneous liquid and stored with exclusion of moisture.

[0170] The following test protocol was applied:

[0171] 24 hours after mixing, the viscosity of each composition was determined at on a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 25 mm, cone angle 1, cone tip-plate distance 0.05 mm, shear rate 10 rpm) or on a Rotothinner (according to principles outlined in BS 3900-A7).

[0172] The full through-cure was determined by applying the composition as described in a first reinforced layer followed by a second layer onto a wet first layer under SCC. Films that exhibited full though cure after 24 hours were given a pass result, while incomplete through-cure in sample films led to a fail result.

[0173] To measure the time until the composition became free from tack, or tack-free time abbreviated to TFT, a small portion of the mixed composition at room temperature was applied in a layer thickness of around 3 mm to cardboard and, under standard conditions, a determination was made of the time which elapsed until an LDPE pipette used to gently touch the surface of the composition for the first time no longer had any residues left on it.

[0174] To determine the intercoat adhesion, the composition was applied in a first reinforced layer and a wet-on-wet second layer. The sample was left to cure and condition for hours/days respective to the overcoat time to be tested. Once the desired conditioning period was reached, the first reinforced layer was applied directly on top of the conditioned sample (with a bond-break) and the wet-on-wet second layer was subsequently applied. The combined sample was left to cure and condition for seven days from the time overcoating was carried out. Samples were cut to a width of 50 mm and a minimum length of 120 mm.

[0175] Testing was conducted in accordance with the principles outlined in ISO 8510-2:2006 AdhesivesPeel test for a flexible-bonded-to-rigid test specimen assemblyPart 2:180 Peel).

[0176] The results are reported in table 3. Examples 1-1 to 1-4 are compositions according to the invention, while examples R-1 to R-8 are reference example compositions not according to the invention.

TABLE-US-00002 TABLE 1 Composition of examples R-1, R-2, and R-8 and I-1 to I-3. All numbers are in weight parts. (weight parts) R-1 I-1 I-2 I-3 R-2 R-8 STP Polymer-1 35.4 35.4 35.4 35.4 35.4 35.4 OCTMO 20 DMM 15 20 25 PGDA 20 D-230 20 VTMO 1 1 1 1 1 1 UV-A 0.9 0.9 0.9 0.9 0.9 0.9 UV-S 0.1 0.1 0.1 0.1 0.1 0.1 TiO.sub.2 6.2 6.2 6.2 6.2 6.2 6.2 Pigment 0.6 0.6 0.6 0.6 0.6 0.6 ATH 15.7 15.7 15.7 15.7 15.7 15.7 CaCO.sub.3 12.5 12.5 12.5 12.5 12.5 12.5 SiO.sub.2 3 3 3 3 3 3 AMMO 1 1 1 1 1 1 DBTDL 0.06 0.06 0.06 0.06 0.06 0.06

TABLE-US-00003 TABLE 2 Composition of examples R-3 to R-7 and I-4. All numbers are in weight parts. (weight parts) R-3 R-4 I-4 R-5 R-6 R-7 STP Polymer-1 35.4 35.4 35.4 35.4 35.4 35.4 DPM 20 DPnP 20 TOU 20 PC 20 TEG-EH 20 D-400 20 VTMO 1 1 1 1 1 1 UV-A 0.9 0.9 0.9 0.9 0.9 0.9 UV-S 0.1 0.1 0.1 0.1 0.1 0.1 TiO.sub.2 6.2 6.2 6.2 6.2 6.2 6.2 Pigment 0.6 0.6 0.6 0.6 0.6 0.6 ATH 15.7 15.7 15.7 15.7 15.7 15.7 CaCO.sub.3 12.5 12.5 12.5 12.5 12.5 12.5 SiO.sub.2 3 3 3 3 3 3 AMMO 1 1 1 1 1 1 DBTDL 0.06 0.06 0.06 0.06 0.06 0.06

TABLE-US-00004 TABLE 3 Test data (full through-cure test, viscosity, and intercoat adhesion) of examples I-1 to I-4 and R-1 to R-8. Full Intercoat Intercoat Intercoat Intercoat through- Viscosity adhesion adhesion adhesion adhesion Example cure (Pa .Math. s) (N/50 mm) (N/50 mm) (N/50 mm) (N/50 mm) composition 24 h 24 h 1 d 3 d 6 d 7 d R-1 Pass 2.4 47 10 9 9 I-1 Pass 5.9 52 51 38 17 I-2 Pass 2.7 32 31 31 32 I-3 Pass 1.5 n/m n/m n/m 22 R-2 Fail >6.5 56 33 44 44 R-3 Fail >6.5 50 30 27 19 R-4 Fail >6.5 41 41 34 29 I-4 Pass 3.0 n/m n/m n/m 28 R-5 Fail >6.5 n/m n/m n/m n/m R-6 Pass >6.5 n/m n/m n/m n/m R-7 Pass >6.5 n/p n/p n/p n/p R-8 Pass >6.5 n/p n/p n/p n/p n/m. stands for not measured. n/p means that the measurement was not possible due to severe migration of liquids to surface of first coating layer after 24 h.

[0177] Table 3 shows that reference examples R-2, R-3, R-4, and R-5 did not show sufficient through-cure in the test layer after 24h.

[0178] Viscosity was excellent in examples R-1, 1-2, 1-3, and 1-4, and it was sufficient in example 1-1. Examples R-2, R-3, R-4, R-5, R-6, R-7, and R-8 all did show too high viscosity for ideal application as liquid-applied membrane.

[0179] R-1 already after 3 days did not provide a suitable intercoat adhesion anymore. Examples R-7 and R-8 were not possible to properly assess for intercoat adhesion properties. In both cases, especially in R-8, there was a strong formation of a greasy liquid layer on the surface of the first applied layer after 24h, possibly a surface migration of the polyetherdiamine, which made further analysis of the intercoat adhesion impossible.

[0180] Only the examples according to the present invention within this test series exhibited a good or excellent intercoat adhesion even after 7 days, together with excellent through-cure and a sufficiently low viscosity for use as a liquid applied membrane.