Defoaming wetting agents for aqueous coating systems

Abstract

The disclosure relates to the use of compounds of specific structure as defoaming wetting agents for aqueous coating systems, for example paints and varnishes. The disclosure is more particularly related to methods of reducing the surface tension and/or increasing the density of an aqueous coating system, which methods include adding alcohol propoxylates to an aqueous coating system. The alcohol propoxylates have the general structure RO(PO).sub.xH, in which R is a saturated alkyl radical having 7 to 10 C atoms, PO is a propylene oxide unit, and x is a number in the range from 4 to 6. The resulting aqueous coating composition has good wetting properties, but is low in foam, so it does not disrupt processing operations of the coating system.

Claims

1. A method of reducing the surface tension of an aqueous coating system, the method comprising adding a compound of the structure (I)
RO(PO).sub.xH(I) in which R is a saturated alkyl radical having 7 to 10 C atoms, PO is a propylene oxide unit, and x is a number in the range from 4 to 6, to an aqueous coating system.

2. The method of claim 1, wherein the aqueous coating system comprises a paint or varnish.

3. The method of claim 2, wherein the aqueous coating system comprises a transparent varnish.

4. The method of claim 1, wherein R is a saturated alkyl radical having 8 C atoms and x is the number 6.

5. The method of claim 1, wherein (I) is an adduct of 6 mol of PO with 1 mol of n-octanol.

6. The method of claim 1, wherein the surface tension is decreased by at least 5%.

7. A method of increasing the density of an aqueous coating system, the method comprising adding a compound of the structure (I)
RO(PO).sub.xH(I) in which R is a saturated alkyl radical having 7 to 10 C atoms, PO is a propylene oxide unit, and x is a number in the range from 4 to 6, to an aqueous coating system.

8. The method of claim 7, wherein the aqueous coating system comprises a paint or varnish.

9. The method of claim 7, wherein the aqueous coating system comprises a transparent varnish.

10. The method of claim 7, wherein R is a saturated alkyl radical having 8 C atoms and x is the number 6.

11. The method of claim 7, wherein (I) is an adduct of 6 mol of PO with 1 mol of n-octanol.

12. The method of claim 7, wherein the density is increased by at least 5%.

13. The method of claim 7, wherein the density is increased by at least 5%, and the surface tension is decreased by at least 5%.

14. The method of claim 7, wherein the density is increased by an amount in a range from 5% to 73%, and the surface tension is decreased by an amount in a range from 5% to 26%.

Description

EXAMPLES

(1) Substances Used:

(2) All wetting agents were prepared by addition reaction of ethylene oxide and/or propylene oxide with alcohols. The meaning of the designations is as follows: C10-3EO: Adduct of 3 mol of ethylene oxide with 1 mol of n-decanol. i-C8-3EO: Adduct of 3 mol of ethylene oxide with 1 mol of 2-ethylhexanol. i-C8-3PO-b-3EO: Adduct of 3 mol of propylene oxide and 3 mol of ethylene oxide with 1 mol of 2-ethylhexanol. PO and EO here were added on in blocks, with the alcohol being reacted first with PO and the resultant propoxylate subsequently with EO. i-C9-3PO-b-3EO: Adduct of 3 mol of propylene oxide and 3 mol of ethylene oxide with 1 mol of isononanol. PO and EO here were added on in blocks, with the alcohol being reacted first with PO and the resultant propoxylate subsequently with EO. C8-5PO-b-1EO: Adduct of 5 mol of propylene oxide and 3 mol of ethylene oxide with 1 mol of n-octanol. PO and EO here were added on in blocks, with the alcohol being reacted first with PO and the resultant propoxylate subsequently with EO. C8-6PO: Adduct of 6 mol of propylene oxide with 1 mol of n-octanol. C8-5PO: Adduct of 5 mol of propylene oxide with 1 mol of n-octanol. C8-4PO: Adduct of 4 mol of propylene oxide with 1 mol of n-octanol. C8-6PO: Adduct of 6 mol of propylene oxide with 1 mol of n-octanol.

(3) These compounds are set out once again in tables 1 and 2 below, and are classed as inventive or noninventive (for comparison).

(4) TABLE-US-00001 TABLE 1 Noninventive alkoxylated wetting agent structures Compound Structure V1 C10-3EO V2 i-C8-3EO V3 i-C8-3PO-b-3EO V4 i-C9-3PO-b-3EO V5 i-C9-3EO-b-3PO V6 C8-5PO-b-1EO

(5) TABLE-US-00002 TABLE 2 Inventive defoaming wetting agent structures Compound Structure V7 C8-6PO V8 C8-5PO V9 C8-4PO
Methods of Investigation:

(6) The surface tension was determined in accordance with test 1 described above. The foam test took place in accordance with test 2 described above.

(7) The test results can be found in tables 3 and 4 below.

(8) TABLE-US-00003 TABLE 3 Surface tensions according to test (1) Surface Reduction in surface tension at tension relative to No. Structure 1 Hz (mN/m) reference (%) Reference 56.7 0 V1 C10-3EO 41.8 26 V2 i-C8-3EO 44.2 22 V3 i-C8-3PO-b-3EO 42.4 25 V4 i-C9-3PO-b-3EO 42.4 25 V5 i-C9-3EO-b-3PO 42.3 25 V6 C8-5PO-b-1EO 42.1 26 V7 C8-6PO 42.2 26 V8 C8-5PO 43.7 23 V9 C8-4PO 44.4 22

(9) TABLE-US-00004 TABLE 4 Densities according to test (2) Increase in density Density relative to reference No. Structure (g/mL) (%) Reference / 0.497 0 V1 C10-3EO 0.39 22 V2 i-C8-3EO 0.482 3 V3 i-C8-3PO-b-3EO 0.435 12 V4 i-C9-3PO-b-3EO 0.474 5 V5 i-C9-3EO-b-3PO 0.501 1 V6 C8-5PO-b-1EO 0.438 12 V7 C8-6PO 0.861 73 V8 C8-5PO 0.802 61 V9 C8-4PO 0.812 63

(10) From tables 3 and 4 it is evident that the defoaming wetting agents of the invention reduce the surface tension of the binder dispersion (as per test 1) by at least 22% and also raise the densities as per the foam test (test 2) by at least 61%. In contrast, the noninventive wetting agent structures in some cases show a marked reduction in the densities according to the foam test (unwanted foam development) or raise the densities only by a maximum of 1% (and can therefore be classed, at best, as low-foam or foam-neutral, but not as defoaming).