Paint dispersion

Abstract

The invention relates to a method of providing an aqueous paint dispersion comprising silanized colloidal silica particles and an acrylate-based binder wherein the weight ratio of SiO.sub.2 to acrylate-based binder on a dry basis ranges from 0.02 to 0.2, and wherein the content of SiO.sub.2, measured by XRF, in said dispersion ranges from 1.05 to 7.5 wt %, wherein silane groups present in the silanized colloidal silica particles are derived from silanes containing an epoxy group, glycidoxy group, glycidoxypropyl group, ureido-based silanes, methacrylamido silanes, mercapto silanes, and combinations thereof. The invention also relates to the use thereof.

Claims

1. Aqueous paint dispersion comprising silanized colloidal silica particles, an acrylate-based binder, and polysiloxane; wherein the weight ratio of SiO.sub.2 to acrylate-based binder on a dry basis ranges from 0.02 to 0.2; wherein the content of SiO.sub.2, measured by XRF, in said dispersion ranges from 1.05 to 7.5 wt %; wherein silane groups present in the silanized colloidal silica particles are derived from silanes containing an epoxy group, glycidoxy group, glycidoxypropyl group, ureido-based silanes, methacrylamido silanes, mercapto silanes, and combinations thereof; wherein the polysiloxane is present in an amount of 0.05 to 2 wt %; and wherein the colloidal silica particles are prepared by polymerization of polysilicic acid originating from water glass.

2. The dispersion of claim 1 wherein the dispersion remains stable for at least 12 months at a temperature from 15 to 25 C.

3. The dispersion of claim 1, wherein the SiO.sub.2 content in the dispersion ranges from 1.3 to 5 wt %.

4. The dispersion of claim 3, wherein the SiO.sub.2 content in the dispersion ranges from 1.3 to 4.5 wt %.

5. The dispersion of claim 4, wherein the SiO.sub.2 content in the dispersion ranges from 2 to 3 wt %.

6. The dispersion of claim 1, wherein the total dry content in the dispersion ranges from 45 to 75 wt %.

7. The dispersion of claim 1, wherein the silane group of the silanized colloidal silica particles is derived from an epoxy silane.

8. The dispersion of claim 6, wherein the total dry content in the dispersion ranges from 50 to 65 wt %.

9. The dispersion of claim 1, wherein the content of SiO.sub.2 is measured by XRF using a Philips Magix PW2424 spectrometer.

10. A method for painting of bricks, minerals, wood, metal surfaces, plastics, ceramics, cementitious materials, glass, or porcelain comprising the step of applying the paint dispersion of claim 1 to bricks, minerals, wood, metal surfaces, plastics, ceramics, cementitious materials, glass, or porcelain.

11. Method of preparing an aqueous paint dispersion comprising mixing silanized colloidal silica particles, an acrylate-based binder and a polysiloxane; wherein the weight ratio of SiO.sub.2 to acrylate-based binder on a dry basis ranges from 0.02 to 0.2; wherein silanized colloidal silica particles is mixed in such amount that the content of SiO.sub.2, measured by XRF, in said dispersion ranges from 1.05 to 7.5 wt %; wherein silane groups present in the silanized colloidal silica particles are derived from silanes containing an epoxy group, glycidoxy group, glycidoxypropyl group, ureido-based silanes, methacrylamido silanes, mercapto silanes, and combinations thereof; wherein the polysiloxane is present in an amount of 0.05 to 2 wt %; and wherein the colloidal silica particles are prepared by polymerization of polysilicic acid originating from water glass.

12. The method of claim 11, wherein the SiO.sub.2 content in the dispersion ranges from 1.3 to 5 wt %.

13. The method of claim 11, wherein the total dry content of the dispersion ranges from 45 to 75 wt %.

14. The method of claim 11, wherein the silane groups present in the silanized colloidal silica particles are derived from silanes containing an epoxy group.

Description

EXAMPLES

Paint Preparation

(1) Aqueous paint formulations Ref.Paint and Paint A-H as set out in Table 1 were prepared at room temperature by first providing a mill base of components 1 to 7 which have been ground and dispersed by means of a high speed Kreis-dissolver (Niemann) type KDV 30-3.0 (2240 rpm for 30 minutes). Explanations of the components used can be found in table 2. A letdown comprising components 8 to 14 was subsequently added to the mill base after dispersing and moderate agitation at 1000 rpm for 15 minutes. As can be noted from table 1 below, Ref. Paint contains no silanized colloidal silica (Bindzil CC301) whereas the further paints A-H comprise Bindzil CC301 added to the letdown or the millbase (addition to mill base only for Paint B bis). Table 3 below shows characteristics of the prepared paint compositions.

(2) TABLE-US-00001 TABLE 1 Paint formulations (amounts given in parts by weight) Ref. Paint Paint Paint Paint Paint Paint Paint Paint Paint Component Paint A B B bis C D E F G H Millbase 1. Water 5.34 5.34 5.34 5.34 5.34 5.34 5.34 5.34 5.34 5.34 2. Disperbyk 1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15 1.15 190 3. Envirogem 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 AD01 4. Acticide 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 MBS 5. Kronos 24.00 24.00 24.00 24.00 24.00 24.00 24.00 24.00 24.00 24.00 2310 6. Coapur XS 0.66 0.66 0.66 0.66 0.66 0.66 0.66 0.66 0.66 0.66 52 7. Bindzil 0.00 0.00 0.00 2.40 0.00 0.00 0.00 0.00 0.00 0.00 CC301 Letdown 8. Primal HG 57.01 57.01 57.01 57.01 57.01 57.01 57.01 57.01 57.01 57.01 1000 9. Texanol 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 10. Coapur XS 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 0.44 52 11. Aquaflow 1.44 1.44 1.44 1.44 1.44 1.44 1.44 1.44 1.44 1.44 NHS 300 12. Acticide 0.29 0.29 0.29 0.29 0.29 0.29 0.29 0.29 0.29 0.29 MBS 13. Water 4.90 3.65 2.50 2.50 1.15 0.00 0.00 0.00 0.00 0.00 14. Bindzil 0.00 1.25 2.40 0.00 3.75 5.00 7.5 10.00 12.5 15.00 CC301 TOTAL 97.97 97.97 97.97 97.97 97.97 98.07 100.57 103.07 105.57 108.07

(3) TABLE-US-00002 TABLE 2 Description of components Component Description/function of components Millbase Disperbyk 190 Dispersant and wetting agent Envirogem AD01 De-foamer Acticide MBS Biocide Kronos 2310 Titanium dioxide pigment of rutile type Coapur XS 52 Polyurethane thickener Bindzil CC301 Silane modified colloidal silica dispersion, silane modified silica content of 28%-wt SiO.sub.2 (based on XRF measurement) Letdown Primal HG 1000 Acrylic resin, TS: 46% Texanol Coalescing agent Coapur XS 52 Polyurethane thickener AquaFlow NHS 300 Rheology modifier for flow and leveling properties Acticide MBS Biocide (5 wt-% active product; 2.5% MIT + 2.5% BIT) Bindzil CC301 Silane modified colloidal silica dispersion, silane modified silica content of 28%-wt SiO.sub.2 (based on XRF measurement)

(4) TABLE-US-00003 TABLE 3 Characteristics of paint formulations of table 1 (percentages in wt %) Ref. Paint Paint Paint Paint Paint Paint Paint Paint Paint Component Paint A B B bis C D E F G H Bindzil CC301 0 1.28 2.45 2.45 3.82 5.10 7.46 9.70 11.84 13.88 product (wt %) SiO.sub.2 content of 0 0.36 0.69 0.69 1.07 1.43 2.09 2.72 3.32 3.89 silane modified colloidal silica in total formulation wt % Amount dry silane 0 1.3 2.6 2.6 4.0 5.3 8.0 10.7 13.3 16.0 modified silica, SiO.sub.2, based on dry resin (wt %) Dry content of 51.3 51.6 52.0 52.0 52.3 52.6 52.0 51.4 50.9 50.4 resin pigment and silanized colloidal silica (wt %)

(5) As can be noted in table 4 below, a too high addition of silane modified colloidal silica (Bindzil CC 301) will not result in a prolonged open time but will lower the solid content of the paint which is not desirable. For example, addition of 20 weight parts of Bindzil CC301 (on a product basis) to the formulations as indicated in Table 1 will result in a solid content of 49.3 wt % which means an additional portion of water needs to evaporate. In addition, a high dosage of silane modified silica may be uneconomical from a cost perspective. The SiO.sub.2 content was measured and quantified by XRF. The method for measuring the silica content of the present invention is as follows: sample preparation was done by fusing the sample with Li.sub.2B.sub.4O.sub.7 to a glass bead. If the carbon content is high, the sample is heated in air before fusion. Reference samples were prepared by using certified standards in the same way. Quantification of SiO.sub.2 using XRF was performed by radiating the sample with gamma radiation generated by a Rh-tube and then measuring the amount of fluorescence radiation emitted by the sample by a Philips Magix PW2424 Spectrometer. The best sample preparation to reduce the spread is fusing the sample to a glass bead using for example Li.sub.2B.sub.4O.sub.7. The amount of fluorescence is measured by using a calibration built on 16 different certified standards from, among others, British Chemical Standards (BCS) and National Bureau of Standards (NBS).

(6) TABLE-US-00004 TABLE 4 ASTM D7488 - Test method for open time of latex (wet open time) Elapsed Time (minutes) before paint surface reworking Open Time with Open Time without Open Time with well visible Open Time without surface defects, well visible surface defects, surface defects relative increase surface defects relative increase (minutes) in % (minutes) in % Ref. Paint 4 6 Paint A 5 25% 6 0% Paint B 6 50% 7 17% Paint B bis 5 25% 7 17% Paint C 6 50% 8 33% Paint D 8 100% 9 50% Paint E 9 125% 10 67% Paint F 9 125% 10 67% Paint G 9 125% 11 83% Paint H 9 125% 11 83%

(7) This method of measuring the open time covers a procedure to determine the length of time a paint remains wet or open enough to allow for brush-in and repair. The method involves reworking of the paint surface by means of a brush as paint is being loaded (10 brush strikes backward and forward) over time intervals (interval=1 minute) until this is no longer possible. From Table 4 it can be noted that the addition point of silane-modified silica to the mill base and the letdown does not appear to be of any importance (cf. Paint B and Paint B bis). A significant enhancement in view of open time is achieved for paints C-H both when it comes to i) open time during which period of time the paint can be reworked without any visible defects and ii) open time until paint had clear well visible defects.