WO2001051553A1

WO2001051553A1 - Colored building materials

Info

Publication number: WO2001051553A1
Application number: PCT/US2001/001439
Authority: WO
Inventors: Edward G. Redman
Original assignee: Environmental Concrete Colorants, Llc
Priority date: 2000-01-14
Filing date: 2001-01-12
Publication date: 2001-07-19
Also published as: AU2001229519A1

Abstract

A coloned building material. The building material includes cement and a coloring agent. The coloring agent is a water/alkali soluble resin and a colorant. The colored building material may further include aggregate to produce a colored concrete. In the preferred embodiment, the cement is a hydraulic cement, such as a Portland cement and the resin is a styrenated acrylic polymer having an acid number less than about 300. The coloring agent includes about 40 wt. % of an organic colorant having a particle size of the colorant of less than about 5 microns.

Description

COLORED BUILDING MATERIALS

Background of the Invention

(1) Field of the Invention The present invention relates generally to building materials and, more particularly, to colored concrete having improved lightfastness, color stability and color fastness having a pigment preferably dispersed through shot milling in an alkali soluble acrylic resin solution.

(2) Description of the Prior Art The initial cost of cement-based building materials, such as block and panels, is significantly higher than other building materials, such as metal frame buildings. However, the long term advantages of durability and low maintenance outweigh some of the cost savings of other types of building materials. However, there is a need in the marketplace that the materials be painted or stained to meet aesthetic needs. Unfortunately, it is extremely difficult to color cement-based building materials. The colors of blue, green and black are difficult to produce using current technology that possess strong saturated color, while maintaining lightfastness, color stability and colorfastness.

Such materials would command a premium price over conventional uncolored concrete and cement products. For example, it is estimated that the market would pay up to seven dollars for an acceptable bright blue building block compared with about one dollar for an uncolored block. Even acceptable colored accent blocks would be in big demand for logos and building decorations if the colored building material was durable for use in place of plain gray or white cement. Similar opportunities exist for red, yellow and black cement-based building materials. For example, at one time, the National Highway Commission wanted to use concrete colored 'yellow' to mark entrance ramps and concrete colored 'red' for exit ramps for safety reasons but was unable to get a satisfactory product qualified. Colored waxes have been tried but these produce a slippery surface when wet. Accordingly, the Redi-Mix concrete industry is particularly interested in satisfactory red and yellow cement for safety use. Black is particularly desirable for an accent stripe and the roof tile industry also has a real interest in a black tile which is light fast, rather than the charcoal colored tiles which is the best available today. Carbon black has been tried in the past because it is so inexpensive but it fades very badly for reasons, which are not fully understood. Other pigments, which have been added, either fade quickly or react with the cement during curing. There is also the problem that there is a maximum amount of pigment, which can be added to cement without distracting from the strength of the building material. That amount appears to be between about 8 and 12 wt.% based on the amount of cement. Under ASTM 9, the maximum amount normally allowed is about 10 wt.%. Thus, some pigments which produce acceptable properties can not be loaded up high enough to produce an intense enough color without destroying the usefulness of the cement or concrete building material.

Currently, colored cement and concrete building materials are produced by adding powdered pigments or thixotropic liquids containing a pigment to the cement mix. These are difficult to use because of color variations when using prior art liquid systems, which can experience pigment sedimentation prior to use and powder handling problems in dry systems. For example, over time the viscosity of thixotropic liquids increases or becomes thicker, but when mixed returns to a lower viscosity. In the prior art, thickening agents are added to the iron oxide dispersions in order to inhibit them from settling out of solution. However, the thickening agent will cause the material to become thixotropic. Subsequently they have to be "stirred in" prior to use, both because of potential problems with sedimentation and high viscosity. Otherwise, they have to be used quickly after manufacture. Also, dry particulate systems appear to be much more abrasive during batching, thereby damaging the dispensing equipment. Even small amounts of settling may cause significant shade differences in pastel and other light colors. Since block making is such a high volume operation, the coloring must be consistent over the entire job. For example, for a typical core block production run would be about 30 thousand blocks over 3 shifts.

None of the prior art methods of coloring cement-based building materials appears to be able to strongly bond the pigment to the cement. For example, U.S. Patent No. 3,068, 109, issued to Rodeffer discloses a method for coloring Portland cement concrete by mixing with the usual plastic Portland cement, sand, aggregate, and water mixture, a pozzolanic material premixed with small quantities of suitable mineral pigments and preferably also premixed with a small amount of a dispersing agent. U.S. Patent No. 3,720,548, issued to Jordon discloses a colored cement having improved color prepared by adhering to a portion of the surface of the unset cement particles a surface tension reducing agent or dispersant wherein the organic matter is adhered to the cement particles by impinging a stream of particles on a stream of the cement. U.S. Patent No. 5,322,563, issued to van Bonn et al. discloses a method for coloring building materials wherein a pigment suspension is added to the building materials. The pigment suspension based on pigment granules contains at least one pigment such as iron oxide, and a soluble phosphate salt. The soluble phosphate salt has a number ratio of monofunctional metal ions to phosphorus of 2:1 to 1:1, and is exemplified by sodium pyrophosphate, sodium polyphosphate and sodium hexametaphosphate.

U. S. Patent No. 5,951,752, issued to Johansen, Jr. et al. discloses an aqueous composition for coloring cement based compositions comprising water, pigment, a suspension enhancing agent and latex polymer solids. While these products appear to have acceptable light fastness, color stability and color fastness for use as building materials, the color intensity is weak, and the products have a tendency to settle out due to the use of heavy iron oxide pigments. Another problem is that these products have to use much more expensive dispensers and have to be under agitation for them to work. A comprehensive review of coloring techniques is set forth in: Cyril Lynsdale & Joe Cabrera, Coloured Concrete, A State of the Art Review, Concrete, Aug. 1989, at 29-34, the entire disclosure hereby incorporated by reference in its entirety. It does not however, seem to disclose colorants similar to the present invention. Specifically, the prior art, as set forth by Lynsdale et al. seems to be grounded in the idea that colorants are aqueous suspensions, which usually refers to a pigment which is dispersed in water. Although carbon black and the phthalocyanine are mentioned, it does so in reviewing the limitations, almost to the point of saying that they should not be used. As examples, the article teaches that carbon black leaches out of the concrete. It also teaches that the phthalocyanine pigments have low color stability in an alkaline environment. In addition, it teaches that pigments should be of the same size for colorates. .This appears to indicate that the current art has problems in obtaining uniform pigment sizes in the products. This can be a particular problem for color matching since few real colors are of only one pigment. Finally, it appears that much of the problems associated with the prior art colorants are the effect they have on the water equihbrium in the concrete product.

Thus, there remains a need for a new and improved colored building material which is light fast, color stable and color fast while, at the same time, avoids the prior art problems associated with thixotropic liquids and powdered particulates.

Summary of the Invention

The present invention is directed to a colored building material. The building material includes cement and a coloring agent. The coloring agent is a water/alkali soluble resin and a colorant.

The colored building material may further include aggregate to produce colored concrete. Preferably, the aggregate is between about 55 and 75 wt.% of the colored building material. The aggregate may be a heavy weight aggregate having a weight of greater than about 145 lbs. per cubic foot; a light weight aggregate having a weight of less than about 105 lbs. per cubic foot; a normal weight aggregate having a weight of about 135 lbs. per cubic foot. The aggregate may also be sand for stucco use.

In the preferred embodiment, the cement is a hydraulic cement, such as a Portland cement. The Portland cement may be gray or white Portland cement. In another embodiment, the hydraulic cement is a gypsum hydration product.

In the preferred embodiment, the resin is a styrenated acrylic polymer possessing carboxylic acid functional groups having an acid number between about 200-300.

Preferably, the acid number of the styrenated acrylic resin is between about 40 and 300. The aqueous resin solution may be prepared from a styrenated acrylic resin, an amine, such as ammonia, and water.

In the preferred embodiment, the coloring agent includes less than 2.5 wt.% ammonia, between about 20 and 70 wt.% of colorant (pigment), less than 2 wt.% of a surfactant, about less than 15 wt.% styrenated acrylic resin, and the balance water. Preferably the solids portion of the colorant is about 42 wt.% solid materials, between about 30 and 35 wt.% pigment, about 7 wt.% acrylic styrene resin, about 1 wt.% surfactants, and the liquid component including about 1 wt.% ammonia and between about 58 to 64 wt.% water. Preferably, the colorant has a particle size of less than about 5 microns.

Accordingly, one aspect of the present invention is to provide a colored building material including cement; a water/alkali soluble resin; and a colorant. Another aspect of the present invention is to provide a coloring agent for coloring building materials including a water/alkali soluble resin wherein said resin is a styrenated acrylic polymer having an acid number less than about 300; and a colorant.

Still another aspect of the present invention is to provide a colored building material including cement; a water/alkali soluble resin wherein said resin is a styrenated acrylic polymer having an acid number less than about 300; and a colorant. These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment.

Description of the Preferred Embodiments The building material of the present invention is produced by combining

Portland cement and a coloring agent. The coloring agent of the present invention is a water/alkali soluble resin and a colorant. Preferably, the coloring agent is an alkali/water soluble resin and a pigment that is produced through milling on a shot mill. It is believed that the shot milling process provides the encapsulation of the pigment by the acrylic styrene resin. While, in the prior art, there has been some milling, it does not appear from examination of such products, that the pigment was sufficiently encapsulated, as in the present invention by acrylic styrene resins which are alkali/water soluble, to provide acceptable properties as discussed above. Apparently, simply dispersing (as in mixing) a pigment and an alkali/water soluble resin is not sufficient to provide the improved characteristics of the present invention. In the preferred embodiment, the resin is a styrenated acrylic polymer possessing carboxylic acid functional groups having an acid number between about 200-300. Preferably, the acid number of the styrenated acrylic resin is between about 40 and 300. The aqueous resin solution may be prepared from a styrenated acrylic resin, an amine, such as ammonia, and water. One acrylic resin, which is particularly suitable, is Joncryl 67, available from SC Johnson of Racine, WI. This styrenated acrylic- polymer is a styrenated acrylic, co-polymer resin. A co-polymer resin is preferred because of the improved drying and resin compatibility properties of such resins.

In the preferred embodiment, the coloring agent includes less than 2.5 wt.% ammonia, between about 20 and 70 wt.% of colorant (pigment), less than 2 wt.% of a surfactant, about less than 15 wt.% styrenated acrylic resin, and the balance water.

Preferably the solids portion of the colorant is about 42 wt.% solid materials, between about 30 and 35 wt.% pigment, about 7 wt.% acrylic styrene resin, about 1 wt.% surfactants, and the liquid component including about 1 wt.% ammonia and between about 58 to 64 wt.% water. Preferably, the colorant has a particle size of less than about 5 microns.

However, different pigment groups and sizes can be used. For example, the black product is a carbon black pigment, while the green and blue are phthalocyanine pigments. Pigment groups are often defined by the chemistry that produces them and their chemical structure. There are several different groups that may be used to make one color. For instance, there are several different chemical groups for yellow, red and orange. It is not possible to simply rule out an entire chemical group, because some of the pigments in the groups will work while others will not.

In the preferred embodiment, the cement is hydraulic cement, such as a Portland cement. The Portland cement may be gray or white Portland cement. In another embodiment, the hydraulic cement is a gypsum hydration product, which is prepared under pressure and temperature to reduce curing time, thereby improving plant production.

The colored building material may further include aggregate to produce a colored concrete. Preferably, the aggregate is between about 55 and 75 wt.%. of the colored building material. The aggregate may be a heavy weight aggregate having a weight of greater than about 145 lbs. per cubic foot; a light weight aggregate having a weight of less than about 105 lbs. per cubic foot; a normal weight aggregate having a weight of about 135 lbs. per cubic foot. The aggregate may also be sand for stucco use. Since the thixotropic and powdered color systems have so many drawbacks, it was thought that one way to add colorant to cement would be to use a conventional printing, water dispersed pigment to color the concrete. However, these color agents have not previously been considered for building materials because the application is so different from printing. Specifically, these coloring agents were not known to be sufficiently water soluble while, at the same time, able to still disperse a sufficient amount of colorant to provide an intense color.

The term "water-dispersed pigment" as often used may be overly vague and not descriptive of the present invention. It is also something that does not really exist er se. If it is attempted to disperse a pigment into water, a heterogeneous mixture would be produced in which the pigment would simply be suspended in the water for awhile. It would eventually either float to the top or sink to the bottom of the container depending on the specific gravity of the pigment according to Stokes' Law. If this type of material was used in printing inks, the printed ink would be random pigment particles on the substrate upon which the printing took place. In the water-based ink industry, resin is added and mixed with water, and then ammonia is added and mixed, whereby the resin becomes solubilized in the water. The printing pigment is then added on a mixer to produce a mixture of resin and pigment. This mixture is then passed through a shot mill, which breaks the conglomerated pigment into much smaller pigment particles, which enable the resin to encapsulate the smaller particles. When this material is used in ink and printed, the resulting ink film is a continuous film of pigment that appears to be a solid color. The film is created by the evaporation of the ammonia from the ink, causing the acrylic resins to form polymer chains in which the pigment is encapsulated.

These types of materials have not previously been used for coloring concrete. While, they are sufficiently water soluble since they are used in water based printing inks, and are used in water based inks to provide intense colors, the lightfastness requirements for concrete appears to have discouraged investigating their utility in coloring concrete. For example, while blue, green, and black are relatively fade resistant, other colors used in printing inks are not. Additionally, the concrete coloring industry traditionally has used iron oxides. Very few ink companies use iron oxide pigments due to the difficulty in keeping such pigments in suspension and the weak colors that such pigments produce.

In the present invention, an acrylic resin is added and mixed with water and then ammonia is added and mixed, whereby the resin becomes solubilized in the water. The pigment is then added on a mixer to produce a first mixture of resin and pigment. Since the desired effect of the present invention is to have the pigment chemically bind to the solublized resin, this is not a very efficient way of joining the pigment and resin since the pigment conglomerates, leaving resin encapsulating large groups of pigment particles. Ideally, each particle of pigment should be encapsulated by resin.

To achieve encapsulation of smaller or individual pigment particles, in the preferred embodiment of the present invention, the mixture is then passed through a shot mill, which breaks the conglomerated pigment into much smaller pigment particles which enable the resin to encapsulate the smaller particles. In a perfectly efficient system the smallest possible pigment particle will be encapsulated by the acrylic resin. The resinated shot mill dispersion can then be added to the concrete as it is being mixed. The present invention can best be understood after a review of the following examples:

An phthalocyanine blue dispersion was prepared consisting of styrenated acrylic polymer resin, which was first neutralized with ammonia and combined with the phthalocyanine blue press cake. The coloring agent was then shot milled to break the pigment into very small particles. This appears to cause the resin to surround the individual colorant particles to keep the colorant particles from reagglomerating. The resulting coloring agent was very stable and homogeneous even though the colorant was about 32 wt.%. The present invention was compared to conventional coloring system as shown below.

Examples 1-3 The present invention was prepared and compared against two colors prepared using a typical 'unbonded' coloring system. The samples were subjected to a standard CTL/ASTM test to determine color retention. Color retention was measured on a scale of 1-5 with 5 being best.

Table 1

Color Retention Test Results

Example Description Color Retention

1 Present Invention 5 Prior Art System

2 Harcross Green 2

3 Harcross Blue 1

These results clearly show that the present invention provides superior color retention to the prior art.

Examples 4-11 Various organic colorants were used in the present invention and tested for color fastness and lightfastness. Suitability was measured on a scale of 1-5 with 5 being best. Table 2

Colorant Test Results

Example Colorant Family Color Fastness Lightfastness

4 Black 7 Carbon Black 5 5

5 Green 7 Phthalocyanine 5 5 6 Blue 15:3 Phthalocyanine 5 5

7 Red 122 Quinacridone 2 1 8 Red 22 Monoazo 2 2

9 Violet 19 Quinacridone 2 . 1

10 Yellow 74 Monoazo: 4 4 ^'

Acetoacetyl

11 Yellow 95 Disazo 2 1 Condensation 5

These results show that while there are numerous chemical classes, because one pigment in a chemical class does not work, it does not mean that they all will not.

Interestedly, Hansa Yellow changed color from yellow to gold. This could be due to reaction with trace metals in the concrete or, heat stability problems due to the cement curing temperature of about 170F, which can destroy heat sensitive organic colors. Also, the pigment particle size in the above examples were on the range of less than about 5 microns. There may be a point where the particle size of the pigment could too small, in some cases, to be effective colorants. However, this lower limit has not been detected to date.

In addition, when prepared according to the present invention, the carbon black did not leach out. This improvement is expected to be due to being encapsulated in the acrylic resin, which is attached to the concrete matrix unlike the prior art taught by Lynsdale et al. Also, in the prior art, phthalocyanine pigments have low color stability in an alkaline environment. To the contrary, the present invention exhibits exceptional stability in an alkaline environment. Similarly, in the prior art, it is taught that pigments should be of the same size. This indicates that the current art has problems in obtaining uniform pigment sizes in their products. The present invention has uniform pigment sizes and are readily mixed together. For example, in conventional printing, very few of the many thousands or so colors that are used commercially are of one pigment. Finally, the present invention preferably includes acrylic styrene resins that exhibit both hydrophobic and hydrophilic characteristics. This characteristic enables the present invention to maintain water equilibrium contrary to the problems associated with the prior art suspensions.

Furthermore, a petrographical analysis of the product produced according to the present invention appears to withstand a higher pigment loading without affecting the integrity of the concrete. While not known, it is believed that this may be due to -the pigments in the present invention being smaller in size than prior art pigments and the effect of the acrylic resins in attaching to various parts of the cured concrete. It is suspected that smaller pigments provide less of a barrier to the forming of the structure of concrete than larger pigments (i.e. iron oxides). Thus, by taking up less space, the concrete may be able to structure around the pigments. In combination with the acrylic resins becoming part of the structure, potentially providing bonds around the pigment, integrity of the concrete is not only maintained, but it is suspected actually may be increased due to the interaction of the resin and the concrete matrix.

Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. By way of example, other water/alkali soluble dispersing resins may work. This would include, for example, fumaric anhydride resins; maliec anhydride resins; and styrenated maliec anhydrides. Also, others that may work based on the success of the present invention would include: water emulsified urethanes; epoxy resins; polyester resins; and polyvinyl alcohol resins. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.

Claims

We Claim:

1. A colored building material comprising: (a) cement;

(b) a water/alkali soluble resin; and

(c) a colorant.

2. The colored building material according to Claim 1 further including aggregate.

3. The colored building material according to Claim 2, wherein the aggregate is between about 55 and 75 wt.%.

4. The colored building material according to Claim 2, wherein the aggregate is a heavy weight aggregate having a weight of greater than about 145 lbs. per cubic foot.

5. The colored building material according to Claim 2, wherein the aggregate is a light weight aggregate having a weight of less than about 105 lbs. per cubic foot.

6. The colored building material according to Claim 2, wherein the aggregate is a normal weight aggregate having a weight of about 135 lbs. per cubic foot.

7. The colored building material according to Claim 2, wherein the aggregate is sand.

8. The colored building material according to Claim 1, wherein the cement is hydraulic cement.

9. The colored building material according to Claim 8, wherein said hydraulic cement is a Portland cement.

10. The colored building material according to Claim 9, wherein said

Portland cement is gray Portland cement.

11. The colored building material according to Claim 8, wherein said hydraulic cement is a gypsum hydration product.

12. A coloring agent for coloring building materials comprising:

(a) a water/alkali soluble resin, wherein said resin is a styrenated acrylic polymer having an acid number less than about 300; and

(b) a colorant.

13. The coloring agent according to Claim 12, wherein the acid number of the styrenated acrylic polymer is between about 40 and 300.

14. The coloring agent according to Claim 12, wherein said styrenated acrylic polymer is a styrenated acrylic, co-polymer resin and an amine.

15. The coloring agent according to Claim 14, wherein said amine is ammonia.

16. The coloring agent according to Claim 15, wherein said ammonia is less than about 2 wt.%.

17. The coloring agent according to Claim 12, wherein said colorant is between about 30 and 70 wt.%.

18. The coloring agent according to Claim 17, wherein said colorant is about 40 wt.%.

19. The coloring agent according to Claim 12, wherein the particle size of said colorant is less than about 5 microns.

20. The coloring agent according to Claim 12, wherein said colorant is organic.

21. The coloring agent according to Claim 12, wherein said colorant is inorganic.

22. A colored building material comprising:

(a) cement;

(b) a coloring agent including a water/alkali soluble resin, wherein said resin is a styrenated acrylic polymer having an acid number less than about 300; and a colorant; and

(c) aggregate.

23. The colored building material according to Claim 22, wherein the aggregate is between about 55 and 75 wt.%.

24. The colored building material according to Claim 22, wherein the aggregate is a heavy weight aggregate having a weight of greater than about 145 lbs. per cubic foot.

25. The colored building material according to Claim 22, wherein the aggregate is a light weight aggregate having a weight of less than about 105 lbs. per cubic foot.

26. The colored building material according to Claim 22, wherein the aggregate is a normal weight aggregate having a weight of about 135 lbs. per cubic foot.

27. The colored building material according to Claim 22, wherein the aggregate is sand.

28. The colored building material according to Claim 22, wherein the cement is hydraulic cement.

29. The colored building material according to Claim 28, wherein said hydraulic cement is a Portland cement.

30. The colored building material according to Claim 29, wherein said Portland cement is gray Portland cement.

31. The colored building material according to Claim 28, wherein said hydraulic cement is a gypsum hydration product.

32. The colored building material according to Claim 22, wherein the acid number of the styrenated acrylic polymer is between about 40 and 300.

33. The colored building material according to Claim 22, wherein said styrenated acrylic polymer is a styrenated acrylic, co-polymer resin and an amine.

34. The colored building material according to Claim 33, wherein said amine is ammonia.

35. The colored building material according to Claim 34, wherein said ammonia is less than about 2 wt.%.

36. The colored building material according to Claim 22, wherein said colorant is between about 30 and 70 wt.%.

37. The colored building material according to Claim 36, wherein said colorant is about 40 wt.%.

38. The colored building material according to Claim 22, wherein the particle size of said colorant is less than about 5 microns.

39. The colored building material according to Claim 22, wherein said colorant is organic.

40. The colored building material according to Claim 22, wherein said colorant is inorganic.