Cerium hydroxycarbonate composition

Abstract

The present invention is a composition comprising water, a cerium (III) hydroxycarbonate comprising an orthorhombic cerium (III) hydroxycarbonate and optionally a hexagonal cerium (III) hydroxycarbonate, and a carboxylate functionalized dispersant. The composition of the present invention provides a high solids content additive that maintains paint retention and resists unwanted color changes.

Description

Background Technology

[0001] This invention relates to cerium hydroxycarbonate compositions that can be used to improve color retention in paint formulations and reduce undesirable color changes.

[0002] Cerium(III) carbonate is an effective additive for improving color retention and reducing color changes in paints and coatings. (See US 2021 / 1888227 A1 (Bohling), pp. 7–9.) Bohling discloses that a 20% by weight aqueous wet paste of ligand-terminated cerium(III) carbonate particles with a z-average particle size of 110 nm ± 5 nm can be prepared by blending a solution of cerium(III) nitrate ammonium with a chelating agent (EDTA) and a solution of ammonium carbonate. (p. 5, lines 1–6.) The chelating agent is considered to “promote the formation of nanodispersed particles while stabilizing the particles to prevent agglomeration.” (p. 3, lines 27–29.)

[0003] US 8,637,153 B2 (Cho) discloses (Column 10, lines 5-29) a method for preparing crystalline cerium(III) carbonate by first contacting a hydrate of Ce(NO3)3 with urea at a temperature in the range of 80°C to 100°C, followed by the addition of 10% to 30% by weight of a polymeric dispersant, such as polyethylene glycol or polyacrylic acid, to the mixture (Column 10, lines 22-24; and Column 5, lines 61-65). Water is then removed, and the temperature is raised to 140°C. After the reaction is complete, the product is washed with water to remove unreacted urea and polymeric dispersant, and then dried to separate the crystalline solid. The volume-average diameter of the experimentally prepared particles is reported to be in the range of 75 nm to 90 nm (Column 12, Table 1); generally, Cho discloses that the particle size can be controlled by varying the amount and molecular weight of the polymeric dispersant. (Column 8, lines 19-30.) Cerium(III) carbonate was then used as a precursor to prepare uniformly sized cerium oxide nanoparticles. (Column 13, lines 3-8.)

[0004] In the field of color-retaining paint additives, there is a need to design a more sustainable way to prepare additives that do not require chelating agents or non-biodegradable polymer dispersants. There is also a need to prepare additives with higher solids content to allow formulators greater flexibility in paint preparation. Summary of the Invention

[0005] This invention addresses a need in the art by providing a composition comprising 5 to 40 wt% water, 55 to 90 wt% cerium(III) hydroxycarbonate, and 0.2 to 5 wt% carboxylate-functionalized dispersant, wherein the cerium(III) hydroxycarbonate comprises orthorhombic cerium(III) hydroxycarbonate and optionally hexagonal cerium(III) hydroxycarbonate, wherein the weight percentages are based on the weight of the water, the cerium(III) hydroxycarbonate, and the dispersant. The composition of this invention provides a high-solids content additive that maintains color retention and resists unwanted color changes. Detailed Implementation

[0006] This invention relates to a composition comprising 5% to 40% by weight of water, 55% to 90% by weight of cerium(III) hydroxycarbonate, and 0.2% to 5% by weight of a carboxylate-functionalized dispersant, wherein the cerium(III) hydroxycarbonate comprises orthorhombic cerium(III) hydroxycarbonate and optionally hexagonal cerium(III) hydroxycarbonate, wherein the weight percentages are based on the weight of water, cerium(III) hydroxycarbonate, and the dispersant. The composition is advantageously prepared by blending a powder of cerium(III) hydroxycarbonate comprising orthorhombic cerium(III) hydroxycarbonate with a premix of water and a conjugate base of an acid-functionalized dispersant. As used herein, "carboxylate" refers to a conjugate base (i.e., a salt) of a carboxylic acid, wherein at least 90% or at least 95% or at least 99% of the carboxylic acid groups of the dispersant are in the form of a salt.

[0007] Suitable carboxylate-functionalized dispersants include salts of polyacrylic acid, such as sodium salts of polyacrylic acid, which can be used as TAMOL. ™ 963 dispersant (a trademark of Dow Chemical Company or its affiliates) is commercially available. The pH of the premix is ​​advantageously adjusted using a suitable base such as ammonium hydroxide.

[0008] Based on the weight of water, cerium hydroxycarbonate (III), and dispersant, the concentration of water is from 20 wt%, 25 wt%, or 28 wt% to 40 wt%, or 35 wt%, or 32 wt%. Based on the weight of water, cerium hydroxycarbonate (III), and dispersant, the concentrations of orthorhombic cerium hydroxycarbonate (III) and optionally hexagonal cerium hydroxycarbonate (III) are from 55 wt%, 60 wt%, or 65 wt% to 90 wt%, 80 wt%, or 75 wt%, or 72 wt%, or 70 wt%. Based on the weight of water, cerium hydroxycarbonate (III), and dispersant, the concentration of carboxylate-functionalized dispersant is typically from 0.5 wt%, 1 wt%, or 1.5 wt% to 5 wt%, or 3 wt%, or 2.5 wt%.

[0009] In one aspect, cerium hydroxycarbonate (III) is orthorhombic cerium hydroxycarbonate (III); in another aspect, cerium hydroxycarbonate (III) is a mixture of orthorhombic cerium hydroxycarbonate (III) and hexagonal cerium hydroxycarbonate (III). These mixtures of crystalline forms can be prepared by blending these crystalline forms individually or by a single synthetic method as described in the Examples section below. In one aspect, orthorhombic cerium hydroxycarbonate (III) and optionally hexagonal cerium hydroxycarbonate (III), water, and a dispersant constitute at least 90% by weight or at least 95% by weight of the composition.

[0010] The compositions of the present invention can be used as high-solids additives that promote color retention and suppress undesirable color changes in paints and coatings. These compositions are advantageously combined with components used in the preparation of paints, including preservatives, dispersants, surfactants, defoamers, opaque pigments (such as TiO2), extenders (such as CaCO3), latex, solvents, coalescing agents, rheology modifiers, and colorants.

[0011] Example

[0012] Preparation of intermediate 1-orthorhombic cerium hydroxycarbonate (III)

[0013] In a wide-mouth flask equipped with a magnetic stirrer, mix 294 g of DI water, 6.4 g of cerium nitrate hexahydrate, and 5.3 g of urea until dissolved and homogeneous. Then, distribute the mixture between two 200 mL Parr acid digestion containers (approximately 153 g in each container) and seal the containers. Place the Parr containers in an oven at 80°C for 24 hours. Remove the Parr containers from the oven and transfer them to a fume hood to cool to room temperature. Open the Parr containers and combine the contents into a glass wide-mouth flask. Rinse each Parr container with DI water to ensure removal of any solid precipitate. Aliquot the contents of the wide-mouth flasks into 50 mL centrifuge tubes. Rinse the wide-mouth flasks with DI water to ensure all precipitated solid material is transferred to the centrifuge tubes. After centrifuging at 18,500 rpm for 5 minutes, decant the supernatant from each tube. Add 50 mL of DI water to each centrifuge tube and mix thoroughly to wash away the solid product, then centrifuge again and remove the supernatant. The washing and centrifugation procedure was repeated three times. After the final washing, centrifugation, and decantation, the final solid product was dried in an oven at 60°C. The orthorhombic crystal form of the product was confirmed by X-ray powder diffraction, as described below.

[0014] Preparation of intermediate 2-hexagonal cerium hydroxycarbonate (III)

[0015] Ce(III) nitric acid hexahydrate (30.0 g, 69.1 mmol) and urea (25.0 g, 416 mmol) were added to a round-bottom flask equipped with a stir bar, condenser, and Dean-Stark separator. The thermocouple was then set to 150 °C, and the mixture was heated at 750 rpm with stirring. The reaction was maintained at this temperature with stirring for 5 hours, after which the reaction was cooled to below 100 °C, and the reaction mixture was washed with DI water (80 g). The mixture was collected in centrifuge tubes and centrifuged at 18,500 rpm for 5 minutes. The supernatant was decanted, and the solid particles were washed again with water (80 g). The solid was washed and centrifuged a total of 4 times. After the final wash, the solid was collected as particles and dried at room temperature to give 13.7 g of white solid, a yield of 91.3%. The hexagonal crystal form of the product was confirmed by X-ray powder diffraction, as described below.

[0016] Preparation of intermediates 3-orthorhombic cerium hydroxycarbonate (III) and hexagonal cerium hydroxycarbonate (III)

[0017] The following synthesis was performed using a semi-batch process. Cerium(III) nitrate hexahydrate (461 g) and urea (384 g) were charged into a round-bottom reactor equipped with a mechanical overhead stirrer, an overhead condenser, a condensate collection vessel, and a heating mantle for controlling the temperature of the reactor jacket and the reactor contents. The reactor contents were mixed and heated to an internal temperature of 115 °C and held for 1 hour. The temperature was then increased to 130 °C over 75 minutes and held at that temperature for approximately 3 hours, after which the reactor was cooled to below 80 °C. Water was then added to the reactor, and the contents were mixed for several minutes, then drained into a wide-mouth flask and allowed to undergo phase separation overnight. The separated aqueous layer was decanted, and the product was washed three more times using a centrifuge to further promote phase separation. X-ray powder diffraction (XRPD) confirmed a mixture of orthorhombic and crystalline forms of cerium(III) hydroxycarbonate.

[0018] XRPD parameters

[0019] Diffraction patterns were collected using a Rigaku SmartLab 3kW X-ray diffractometer equipped with a Hypix3000 detector. Samples were detected using copper Kα radiation (α = 1.5406 Å) from a sealed source tube operating at 40 kV and 44 mA. XRPD data were collected from 5° to 90°2θ, with a step size of 0.02° and a collection time of 5° / min. The resulting XRPD patterns were analyzed using MDI JADE2010 X-ray pattern analysis software.

[0020] Figure 1X-ray powder diffraction patterns of a mixture of orthorhombic and crystalline forms of cerium(III) hydroxycarbonate are illustrated. A search-match analysis of the diffraction patterns was performed against the PDF4+ database available from the International Data Center for Diffraction (ICDD). Matches were found with hexagonal cerium carbonate hydroxide (PDF# 04-018-6741) and orthorhombic cerium carbonate hydroxide (PDF# 00-041-0013). The principal reflectances (in 2θ°) of orthorhombic cerium(III) hydroxycarbonate are as follows: 15.8, 20.5, 23.9, 26.4, 33.7, and 38.1. The principal reflectances of hexagonal cerium(III) hydroxycarbonate are 17.7, 24.6, 30.5, 35.9, 43.3, 44.0, and 47.1. The w / w ratio of the orthorhombic to hexagonal forms was measured to be 13.7:86.3.

[0021] Procedure for measuring color retention

[0022] Natural external weathering from sunlight and typical moisture cycles for external coatings were simulated using ASTM D4587-11. Cycle #4 in Table 1 of the ASTM method describes the conditions used. The weathering test was accelerated using a QUV Accelerated Weathering Tester, Model QUV / se. A chrome-treated aluminum panel (AL-36 3" × 6") was used as the substrate for the coating application. A vacuum plate was used to hold the aluminum panel during the application of the test paint. Apply a wet film thickness of approximately 5 mil using a 10-mil edge of a 2" wide multi-gap film applicator. Allow the coated panels to dry for 7 days in a controlled temperature laboratory (72℉ (22℃) / 50% RH) before exposure to accelerated weathering. Record L*, a*, and b* color values ​​using a BYK Specto-guide 45 / 0 spectrophotometer (approx. 6801). Color values ​​were recorded before exposure in the QUV unit (time = 0) and in approximate increments of 500 hours of total QUV unit operating time. Test increments of 500 hours were continued until a color change was observed sufficient to reveal differential degradation between test samples, typically from 1000 to 4000 hours. ΔE values ​​were measured using L*, a*, and b* color values.

[0023] Examples 1 to 3 - Preparation of paints containing cerium(III) hydroxycarbonate

[0024] TAMOL ™A liquid premix of 963 dispersant (5.2 g, 35 wt% active material), ammonium hydroxide (1.5 g, 28 wt% aqueous solution), and water (25 g) was added to a container of a wet paste (175 g) of washed cerium(III) hydroxycarbonate prepared as in Intermediate Example 3. The mixture was pre-dispersed using a glass rod until a smooth slurry was obtained. The slurry was blended for 3 to 5 minutes at 2900 rpm using a Flacktec biaxial mixer. After drying at room temperature for 16 hours, the solids content of the mixture was measured by gravimetric analysis (69.2%).

[0025] Example 1 was prepared using ColorTrend 808-0836 Organic Red (red colorant, 4 oz / gal, 30 g / L); Example 2 was prepared using ColorTrend 808-9907 Light Black (black colorant, 4 oz / gal, 30 g / L); and Example 3 was prepared using ColorTrend 808-7214 Phthalocyanine Blue (blue colorant, 4 oz / gal, 30 g / L).

[0026] Comparative Examples 1 to 3 - Preparation of paints without cerium(III) hydroxycarbonate

[0027] Comparative examples (CE1 to CE3) were prepared as described in Examples 1 to 3, except that cerium(III) hydroxycarbonate was not contained in the formulation.

[0028] Table 1 shows semi-gloss paint formulations for black, blue, and red paints with and without cerium(III) hydroxycarbonate. All values ​​(except PVC%) are reported in parts by weight. In-can preservative refers to Kathon LX in-can preservative (1.5% by weight of active ingredient); dry film preservative refers to Bioban dry film preservative; dispersant refers to TAMOL. ™ 165A dispersant; HW-1000 surfactant refers to TRITON. ™ HW-1000 surfactant; defoamer refers to DOWSIL. ™ 8590 is the defoamer; TiO2 refers to Ti-Pure R-706 TiO2; CaCO3 refers to Omycarb 8 CaCO3; 15-S-12 is the surfactant TERGITOL. ™ 15-S-12 surfactant; latex refers to RHOPLEX. ™ 101 acrylic emulsion; the coalescing agent refers to Optifilm Enhancer 400 coalescing agent; RM-3030 refers to ACRYSOL. ™ RM-3030 is a rheology modifier; RM-8W refers to ACRYSOL. ™RM-8W rheology modifier. All amounts listed in Table 1 are parts by weight. (TAMOL, TRITON, DOWSIL, TERGITOL, RHOPLEX, and ACRYSOL are trademarks of Dow Chemical Company or its affiliates.)

[0029]

[0030] Table 2 illustrates the ΔE values ​​from exposure tests after 3500 hours or QUV exposure.

[0031]

[0032] The ΔE values ​​of the sample containing a mixture of hexagonal cerium hydroxycarbonate (III) and orthorhombic cerium hydroxycarbonate (III) showed a significant improvement in color retention compared to the control sample.

[0033] Examples 4 and 5 - Preparation of colored paints containing orthorhombic cerium(III) hydroxycarbonate

[0034] TAMOL ™ A premix of 963 dispersant (0.56 g), 28% wt% NH4OH aqueous solution (0.16 g), and water (5.65 g) was added to a container containing dry powder (13.28 g) from intermediate 1. The contents of the container were pre-dispersed using a glass rod to obtain a smooth, textured slurry, and then mixed at 2900 rpm for approximately 4 minutes using a Flacktec biaxial mixer. An orthorhombic cerium hydroxycarbonate (III) dispersion was added to a container containing a conventional pigment dispersion prepared on a uniaxial high-speed dissolver. The contents were then mixed again at 2900 rpm for approximately 4 minutes using a Flacktec biaxial mixer. The final paint was prepared using a conventional thinning technique, in which each of the remaining paint components was added one at a time to a container containing an inorganic solid dispersion using continuous low-speed mixing with an overhead agitator. Finally, while stirring with a Flacktec biaxial mixer (2900 rpm, 3 minutes), organic red (Example 4) or phthalocyanine blue colorant (Example 5) was added to the paint at a concentration of 4 oz / gal.

[0035] Examples 6 and 7 - Preparation of colored paints containing hexagonal cerium(III) hydroxycarbonate

[0036] Paints were prepared as described in Examples 5 and 6, except that dry powder derived from hexagonal cerium hydroxycarbonate (III) (intermediate 2) was used. Example 6 was prepared using organic red, and Example 7 was prepared using phthalocyanine blue.

[0037] Preparation of paints without cerium(III) hydroxycarbonate (Comparative Examples 4 and 5)

[0038] The formulations were prepared as described in Examples 4 and 5, respectively, except that the paint did not contain cerium(III) hydroxycarbonate.

[0039] Table 3 illustrates the paint formulations of Examples 4 to 7 and Comparative Examples 4 and 5.

[0040]

[0041] Table 4 illustrates the ΔE values ​​from exposure tests after 2000 hours of QUV exposure.

[0042]

[0043] Data show that orthorhombic cerium hydroxycarbonate (III) exhibits the strongest resistance to fading in accelerated weathering tests. Both sets of examples demonstrate excellent resistance to fading compared to comparative examples without any cerium hydroxycarbonate (III).

Claims

1. A composition comprising 5% to 40% by weight of water, 55% to 90% by weight of cerium hydroxycarbonate (III) and 0.2% to 5% by weight of a carboxylate-functionalized dispersant, wherein the cerium hydroxycarbonate (III) comprises orthorhombic cerium hydroxycarbonate (III) and optionally hexagonal cerium hydroxycarbonate (III), wherein the weight percentages are based on the weight of the water, the cerium hydroxycarbonate (III) and the dispersant.

2. The composition according to claim 1, wherein the cerium(III) hydroxycarbonate, the water, and the dispersant constitute at least 90% by weight of the composition.

3. The composition according to claim 1, wherein the composition comprises 20% to 40% by weight of water, 55% to 75% by weight of cerium(III) hydroxycarbonate and 0.5% to 5% by weight of a carboxylate-functionalized dispersant.

4. The composition according to claim 2, wherein the composition comprises 25% to 35% by weight of water; and 60% to 72% by weight of the cerium(III) hydroxycarbonate.

5. The composition according to claim 3, wherein the carboxylate-functionalized dispersant is in a salt of polyacrylic acid, wherein the cerium(III) carbonate, the water, and the dispersant constitute at least 95% by weight of the composition.

6. The composition of claim 3, wherein the carboxylate-functionalized dispersant is a salt of polyacrylic acid, and wherein at least 90% of the carboxylic acid groups of the dispersant are in the form of a salt.

7. The composition according to claim 1, wherein the cerium hydroxycarbonate (III) is orthorhombic cerium hydroxycarbonate (III).

8. The composition according to claim 1, wherein the cerium hydroxycarbonate (III) is a mixture of orthorhombic cerium hydroxycarbonate (III) and hexagonal cerium hydroxycarbonate (III).

9. The composition according to any one of claims 7 or 8, wherein the composition further comprises a dispersant, a surfactant, a defoamer, an opaque pigment, a extender, a latex, a rheology modifier, and a colorant.

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