Porous Silicon Oxide Beads for Use As Drying Agents for Waterborne Latex Paint Compositions

Abstract

A highway marking paint is provided formed from a waterborne latex paint and porous silica beads having a pore volume in the range of 0.3 cc/g to 3.0 cc/g. The silica beads enable the paint to achieve sufficient viscosity to permit the application of a highway marking of at least 40 mil and preferably at least 120 mil. The highway marking paint can also include retroreflective glass beads. Optionally, the highway marking paint further includes an acrylic polymer emulsion. The porous silica in bead form enhances the flowability of the porous silica beads and retroreflective beads.

Claims

1. A highway marking paint comprising: a. waterborne latex paint; and b. porous silica beads having a pore volume in the range of 0.3 cc/g to 3.0 cc/g, a particle size ranging from 10 US Mesh to 150 US Mesh, and a pore volume in the range of 200 m.sup.2/g to 500 m.sup.2/g, said beads comprising silica and a binder.

2. The highway marking paint of claim 1 wherein said binder is polyvinylpyrrolidone

3. The highway marking paint of claim 1 wherein said binder is sodium silicate.

4. The highway marking paint of claim 3 wherein said porous silica beads further comprise glass dust.

5. The highway marking paint of claim 1 wherein the porous silica has a pore volume in the range of 0.5 cc/g to 1.5 cc/g.

6. The highway marking paint of claim 1 wherein the porous silica has a surface area in the range of pore volume in the range of 250 m.sup.2/g to 450 m.sup.2/g.

7. The highway marking paint of claim 1 wherein the porous silica constitutes from 1% to 20% by weight of the paint.

8. The highway marking paint of claim 1 further comprising retroreflective glass beads.

9. A highway marking having a thickness of at least 40 mil comprising: a. waterborne latex paint; b. porous silica beads having a pore volume in the range of 0.3 cc/g to 3.0 cc/g, a particle size ranging from 10 US Mesh to 150 US Mesh, and a pore volume in the range of 200 m.sup.2/g to 500 m.sup.2/g, said beads comprising silica and a binder.

10. The highway marking paint of claim 9 wherein said binder is polyvinylpyrrolidone

11. The highway marking paint of claim 9 wherein said binder is sodium silicate.

12. The highway marking paint of claim 11 wherein said porous silica beads further comprise glass dust.

13. The highway marking of claim 9 further comprising retroreflective glass beads.

14. The highway marking of claim 9 having a thickness of at least 60 mil.

15. The highway marking of claim 15 having a thickness of at least 90 mil.

16. The highway marking of claim 16 having a thickness of at least 120 mil.

17. A method of applying a highway marking comprising the steps of: a. dispensing a stream of a waterborne latex paint; b. forming a paint composition by directing into said stream of a waterborne latex paint a stream of porous silica beads having a pore volume in the range of 0.3 cc/g to 3.0 cc/g, a particle size ranging from 10 US Mesh to 150 US Mesh, and a pore volume in the range of 200 m.sup.2/g to 500 m.sup.2/g, said beads comprising silica and a binder; and c. applying said paint composition to a transportation corridor at a thickness of at least 40 mil.

18. The method of claim 17 wherein retroreflective glass beads are directed into said stream of a waterborne latex paint together with said porous silica beads.

19. The method claim 17 wherein said porous silica beads further comprise glass dust.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Porous silicon dioxide beads used in this invention can have a pore volume of 0.3 cc/g to 3.0 cc/g. The preferred material has a pore volume of 0.5 cc/g to 1.5 cc/g. The amount of porous silica which can be added to the paint can be from 5% to 20% wt/wt to the paint. The preferred amount is 10% to 18%. This amount can be adjusted depending on the pore volume of silicon oxide.

[0025] The surface area of porous silicon oxide beads can be from 200 m.sup.2/g to 500 m.sup.2/g, preferably from 250 m.sup.2/g to 450 m.sup.2/g.

[0026] Porous silicon dioxide beads used in this invention can be used as intermix with latex paints by injecting the drying agent into the paint stream, or can be added on the top of paint layer.

[0027] Porous silicon oxide beads used in this invention range in size from 10 US Mesh to 150 US Mesh. Preferred particles are 16 US Mesh to 100 US Mesh, and the optional product is from 18 US Mesh to 80 US Mesh.

[0028] Porous silicon oxide particles can be blended with retro reflective glass beads of refractive index 1.5 to 2.2, preferably 1.5 to 1.9. Retroreflective glass beads particle size can be from 16 US Mesh to 100 US Mesh.

EXAMPLES

Example 1: Porous Silica Beads Using Polyvinylpyrrolidone Binder

[0029] Dried silica press cake (1.51 Kg., 16.08% wt/wt water) is weighed into the pan of a Model RV02E Eirich Laboratory Mixer fitted with a pin type rotor tool. The pan is then mounted onto the mixer. The rotor is spun at a tip speed of 15 m/s, and the pan is rotated at 37.5 RPM in a counter-rotational direction. After 0.5 minute of mixing, 0.7978 kg water is rapidly poured into the pan. After a total of 3 minutes of mixing, 0.16 kg PVP solution (containing 0.0264 kg polyvinylpyrrolidone K-30 completely dissolved in water) is gradually sprayed into the pan over 10 to 45 seconds. After a total of 3.75 minutes of mixing, the rotor speed is increased to 30 m/s. After 9.75 minutes total of mixing, the rotor speed is reduced to 20 m/s. After 11 minutes total of mixing, the rotor speed is reduced to 3 m/s, and 0.010 kg of dried silica press cake is added to the pan. After 1.5 more minutes of mixing, the rotor and pan are stopped, the pan is removed from the mixer, and the beads are poured out into a large pan. The beads are then dried with air between 120 C. and 160 C. to 7% moisture, and sieved to the desired particle size range. The beads have a bulk density of 0.44 g/cc.

Example 2: Porous Silica Beads Using Sodium Silicate Binder

[0030] Silica press cake (0.755 Kg., 23.80% wt/wt water) is weighed into the pan of a Model RV02E Eirich Laboratory Mixer fitted with a pin type rotor tool. The pan is then mounted onto the mixer. The rotor is started at 15 m/s, and the pan is started at 37.5 RPM in a counter-rotational direction. After 1 minute of mixing 0.61040 kg water is poured into the pan. After another 2 minutes of mixing, 0.08255 kg diluted sodium silicate (25% wt/wt N silicate in water) is sprayed into the pan over 10 to 90 seconds. After a total of 3.75 minutes of mixing, the rotor speed is increased to 30 m/s. After 14 minutes total of mixing, the rotor speed is reduced to 20 m/s. After 15 minutes total of mixing, the rotor speed is reduced to 3 m/s, and 0.020 kg of dried silica press cake is added to the pan. After 1 more minute of mixing, the rotor and pan are stopped, the pan is removed from the mixer, and the beads are poured out into a large pan. The beads are then dried to 7% moisture with air between room temperature and 160 C., and sieved to the desired particle size range. The beads have a bulk density of 0.42 g/cc.

Example 3: Porous Silica Beads Using Sodium Silicate Binder and Glass Dust

[0031] The process set forth in Example 2 was repeated except, instead of silica press cake alone, a 3/1 mixture of silica press cake and glass dust (Potters C-dust, less than 212 microns) was used. The beads from this experiment have a bulk density of 0.59 g/cc, higher than those of Examples 1 and 2.

Example 4: Dry Time of Silica Beads

[0032] The following experiment was conducted to determine the drying efficiency of porous silicon oxides. Twenty g of waterborne latex paint (Sherwin Williams yellow paint) was placed in a 4 oz. plastic cup with 10 g of a 2/1 mixture of type I AASHTO M247 glass beads and drying agent. The mixture was added to the paint and stirred by hand using a wood spatula (wood applicator). The time that elapsed from the beginning until the paint could not be stirred any more (completely solidified) was determined and is shown in Table 1.

TABLE-US-00001 TABLE 1 Time for the paint to Products solidify completely Paint without any drying agent >80 min Silica granules 10-15 sec 2/1 mixture with glass beads Silica beads Example 1 10-15 sec 2/1 mixture with glass beads Silica beads Example 2 10-15 sec 2/1 mixture with glass beads Silica beads Example 3 40-45 sec 2/1 mixture with glass beads Silica beads Example 3 10-15 sec 1/1 mixture with glass beads

[0033] The above results show the drying efficiency of porous silica beads are similar to that of porous silica granules. Mixing with glass dust does not affect the drying effect.

Example 5: Flow Properties of Porous Silica Beads Vs. Granules

[0034] The following experiment measures the flow properties of different porous silica based materials. A glass funnel (80 mm diameter, 75 mm stem height, and 5 mm stem diameter) was placed vertically in a clamp. Porous silica (50 g) was poured into the funnel while holding the bottom of the stem closed. When the stem was opened the time for all silica to flow out into a beaker placed under the funnel was measured. The data presented in Table 2 shows that the porous beads flow much faster than the granules. This difference can be significant when large quantities are used while striping highway marking lanes.

TABLE-US-00002 TABLE 2 Time for silica drying agent to Products flow out of the funnel Silica granules 46 sec Silica beads Example 1 22 sec Silica beads Example 2 25 sec Silica beads Example 3 20 sec

[0035] Any documents referenced above are incorporated by reference herein. Their inclusion is not an admission that they are material or that they are otherwise prior art for any purpose.

[0036] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

[0037] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein.

[0038] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. Use of the term about should be construed as providing support for embodiments directed to the exact listed amount. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0039] Although the present invention has been described with respect to its application in highway marking paint compositions, it is to be distinctly understood that the present invention can be used in connection with other waterborne paints.

[0040] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.