Cerium hydroxy carbonate composition

Abstract

The present invention is a composition comprising water, cerium (III) hydroxy carbonate that comprises orthorhombic and optionally hexagonal cerium (III) hydroxy carbonate, and a carboxylate functionalized dispersant. The composition of the present invention provides a high solids content additive that preserves paint retention and resists unwanted color change.

Description

[0001] Cerium Hydroxy Carbonate Composition

[0002] Background of the Invention

[0003] The present invention relates to a cerium hydroxy carbonate composition, which is useful for improving tint retention and attenuating undesirable color change in paint formulations.

[0004] Cerium (III) carbonate has recently been reported to be an effective additive for improving tint retention and reducing color change in paint coatings. (See US 2021 / 1888227 Al (Bohling), pp. 7-9.) Bohling discloses that a 20 wt.% aqueous wet paste of ligand-capped cerium (III) carbonate particles having a z-average particle size of 110 + 5 nm can be prepared by admixing a solution of ammonium cerium (III) nitrate and a solution of a chelating agent (EDTA) and ammonium carbonate. (Pg. 5, lines 1-6.) The chelating agent is believed to “promote the formation of the nanodisperse particles while stabilizing the particles against agglomeration.” (Pg. 3, lines 27-29.)

[0005] US 8,637,153 B2 (Cho) discloses (col. 10, lines 5-29) a method for preparing a crystalline cerium (III) carbonate by first contacting a hydrate of CeiNChh with urea at a temperature in the range of from 80 °C to 100 °C, then adding 10 to 30 weight percent of a polymer dispersant such as polyethylene glycol or polyacrylic acid to the admixture. (Col. 10, lines 22-24; and col. 5, lines 61-65.) Water is then removed, and the temperature is raised to 140 °C. After completion of the reaction, the product may be washed with water to remove unreacted urea and the polymer dispersant, then dried to isolate a crystalline solid. The volume mean diameter of experimentally prepared particles are reported to be in the range of from 75 nm to 90 nm (Col. 12, Table 1); in general, Cho discloses that particle sizes are controllable by varying the amounts and molecular weights of the polymer dispersants. (Col. 8, lines 19-30.) The cerium (III) carbonate is then used as a precursor to prepare uniform sized cerium oxide nanoparticles. (Col. 13, lines 3-8.)

[0006] There is a need in the field of tint retention paint additives to design a more sustainable way of preparing an additive that does not require chelating agents or non-biodegradable polymer dispersants. There is also a need to prepare the additive at a higher solids content to allow formulators greater flexibility in the preparation of paints. Summary of the Invention

[0007] The present invention addresses a need in the art by providing a composition comprising from 5 to 40 weight percent water, from 55 to 90 weight percent of a cerium (III) hydroxy carbonate that comprises orthorhombic and optionally hexagonal cerium (III) hydroxy carbonate, and from 0.2 to 5 weight percent of a carboxylate functionalized dispersant, wherein the weight percentages are based on the weight of the water, the cerium (III) hydroxycarbonate and the dispersant. The composition of the present invention provides a high solids content additive that preserves color retention and resists unwanted color change.

[0008] Detailed Description of the Invention

[0009] The present invention is a composition comprising from 5 to 40 weight percent water, from 55 to 90 weight percent of a cerium (III) hydroxy carbonate that comprises orthorhombic and optionally hexagonal cerium (III) hydroxy carbonate, and from 0.2 to 5 weight percent of a carboxylate functionalized dispersant, wherein the weight percentages are based on the weight of the water, the cerium (III) hydroxycarbonate and the dispersant. The composition is advantageously prepared by admixing cerium (III) hydroxy carbonate powder comprising an orthorhombic cerium (III) hydroxy carbonate with a premix of water and the conjugate base of an acid functionalized dispersant. As used herein “a carboxylate” refers to a conjugate base (i.e., salt) of a carboxylic acid, wherein at least 90 percent or at least 95 or at least 99 percent of the carboxylic acid groups of the dispersant are in the form of the salt.

[0010] Suitable carboxylate functionalized dispersants include salts of polyacrylic acid, such as the sodium salt of polyacrylic acid, commercially available as TAMOL™ 963 Dispersant (A trademark of The Dow Chemical Company or its Affiliates). The pH of the premix is advantageously adjusted using a suitable base such as ammonium hydroxide.

[0011] The concentration of water is from 20 or from 25 or from 28 weight percent, to 40 or to 35 or to 32 weight percent, based on the weight of the water, the cerium (III) hydroxycarbonate and the dispersant. The concentration of the orthorhombic and optionally hexagonal cerium (III) hydroxy carbonate is in the range of from 55 or from 60 or from 65 weight percent, to 90 or 80 or to 75 or to 72 or to 70 weight percent, based on the weight of the water, the cerium (III) hydroxycarbonate and the dispersant. The concentration of the carboxylate functionalized dispersant is in the range of from 0.5 or from 1 or from 1.5 weight percent, to 5 or to 3 or to 2.5 weight percent, based on the weight of the water, the cerium (III) hydroxycarbonate and the dispersant.

[0012] In one aspect, the cerium (III) hydroxy carbonate is orthorhombic cerium (III) hydroxy carbonate; in another aspect, the cerium (III) hydroxy carbonate is a mixture of orthorhombic cerium (III) hydroxy carbonate and hexagonal cerium (III) hydroxy carbonate. The mixture of these crystalline forms can be prepared either by blending the forms separately, or in a single synthetic method as described in the example section below. In one aspect, the orthorhombic and optionally hexagonal cerium (III) hydroxy carbonate, the water, and the dispersant comprise at least 90 weight percent, or at least 95 weight percent of the composition.

[0013] The composition of the present invention is useful as a high solids content additive that promotes color retention and inhibits undesirable color change in paint coatings. The composition is advantageously combined with ingredients that are used to make paints including preservatives, dispersants, surfactants, defoamers, opacifying pigments such as TiCb, extenders such as CaCCh, latexes, solvents, coalescents, rheology modifiers, and colorants.

[0014] Examples

[0015] Intermediate 1 - Preparation of Orthorhombic Cerium (III) Hydroxy Carbonate

[0016] DI water (294 g), cerium nitrate hexahydrate (6.4 g) and urea (5.3 g) were mixed in ajar with a magnetic stirrer until dissolved and homogeneous. This mixture was then divided between two 200-mL Parr acid digestion vessels (about 153 g in each vessel) and the vessels sealed. The Parr vessels were placed in an oven at 80 °C and held for 24 h. The Parr vessels were then removed from the oven and transferred to a hood and allowed to cool to room temperature. The Parr vessels were then opened, and the contents combined into a glass jar. Each Parr vessel was rinsed with DI water to ensure removal of the solid, precipitated product. The contents of the jar were divided equally into 50- mL centrifuge tubes. The jar was rinsed with DI water to ensure transfer of all precipitated solid material to the centrifuge tubes. After centrifuging for 5 min at 18,500 rpm, the supernatant in each tube was decanted off. DI water (50 mL) was added to each centrifuge tube and mixed well to wash the solid product, followed by centrifuging again and removal of supernatant. This wash and centrifuge procedure was repeated three times. After the final wash, centrifuge and decanting, the final solid product was dried in a 60 °C oven. The orthorhombic form of the product was confirmed by x-ray powder diffraction, as described below. Intermediate 2 - Preparation of Hexagonal Cerium (III) Hydroxy Carbonate

[0017] Ce(III) nitrate 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 trap. The thermocouple was then set to 150 °C and the mixture was allowed to heat with stirring at 750 rpms. The reaction was held at this temperature with stirring for 5 h, after which time the reaction was allowed to cool to below 100 °C whereupon the reaction mixture was then washed with DI water (80 g). The mixture was collected in centrifuge tubes, then centrifuged at 18,500 rpms for 5 min. The supernatant was decanted, and the solid pellet was washed again with water (80 g). The solid was washed and centrifuged a total of 4 times. After the last wash, the solids were collected as a pellet and allowed to dry at room temperature to afford 13.7 g of a white solid in 91.3% yield. The hexagonal form of the product was confirmed by x-ray powder diffraction, as described below.

[0018] Intermediate 3 - Preparation of Orthorhombic and Hexagonal Cerium (III) Hydroxy Carbonate

[0019] The following synthesis was carried out using a semi-batch process. Cerium (III) nitrate hexahydrate (461 g) and urea (384 g) were charged into a round bottom reactor equipped with mechanical overhead agitation, an overhead condenser, a condensate collection container, and a heating mantle to control the temperature of the reactor jacket and contents of the reactor. The reactor contents were mixed and heated to an internal temperature of 115 °C and held for 1 h. The temperature was then increased to 130 °C over 75 min, then held at this temperature for ~3 h, after which time the reactor was cooled to below 80 °C. Water was then added to the reactor and the contents were mixed for few minutes, then discharged into ajar and allowed to phase separate overnight. The separated aqueous layer was decanted and the product was washed three additional times, using a centrifuge to facilitate phase separation. The mixture of orthorhombic and crystalline forms of cerium (III) hydroxy carbonate were confirmed by x-ray powder diffraction (XRPD).

[0020] XRPD Parameters

[0021] A Rigaku SmartLab 3kW X-ray diffractometer equipped with a Hypix3000 detector was used to collect diffraction patterns. The samples were examined with copper K„ radiation a = 1.5406 A) from a sealed-source tube operated at 40 kV and 44 mA. XRPD data were collected from 5° to 90° 20, with a step size of 0.02° and 5 min collection time. Analysis of the resulting XRPD patterns was performed using MDI JADE2010 X-ray pattern analysis software.

[0022] FIG. 1 illustrates the x-ray powder diffraction patterns for the mixture of orthorhombic and crystalline forms of cerium (III) hydroxy carbonate. Search-match analysis of the diffraction patterns was performed against the PDF4+ database available from the International Centre for Diffraction Data (ICDD). Matches were found with a hexagonal phase cerium carbonate hydroxide (PDF# 04-018-6741) and an orthorhombic phase cerium carbonate hydroxide (PDF# 00-041-0013). The major reflections for orthorhombic cerium (III) hydroxy carbonate (in units of 200are as follows: 15.8, 20.5, 23.9, 26.4, 33.7, and 38.1. The major reflections for hexagonal cerium (III) hydroxy carbonate 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.

[0023] Procedure for Measuring Color Retention

[0024] ASTM D4587-11 was used to simulate natural exterior weathering from sunlight and moisture cycles that are typical for exterior coatings. Cycle #4 from Table 1 of the ASTM method describes the conditions used. QUV Accelerated Weathering Tester model QUV / se was used for the accelerated weathering experiments. Q-Panel (AL-36 3” x 6”) chrome treated aluminum panels were used as the substrates for the coating applications. A vacuum plate was used to hold the aluminum panels during application of the test paint. A 10-mil edge of a 2” width multiple clearance film applicator was used to apply the coatings with an approximate wet film thickness of 5 mil. Coated panels were allowed to dry over 7 d in a controlled temperature lab (72 °F (-22 °C) / 50% relative humidity) before exposure to accelerated weathering. A BYK Specto-guide 45 / 0 spectrophotometer (cat: 6801) was used to record L*, a*, b* color values. Color values were recorded prior to exposure in the QUV unit (Time = 0) and at approximate increments of 500 h total QUV unit operation time. The 500-h testing increments until color change was found sufficient to observe differentiated degradation between experimental samples, generally 1000 to 4000 h. AE values were measured from L*, a*, b* color values. Examples 1-3 - Preparation of a Paint with Cerium (HI) Hydroxy Carbonate

[0025] A liquid premix of TAMOL™ 963 Dispersant (5.2 g, 35 wt% active), ammonium hydroxide (1.5 g, 28 wt.% aq.), and water (25 g) was added to a vessel a wet paste of washed cerium (III) hydroxy carbonate as prepared in the Intermediate Example 3 (175 g). The mixture was pre-dispersed with a glass rod until a smooth textured slurry was obtained. The slurry was blended using a Flacktec dual axis mixer at 2900 rpm for 3 to 5 min. The solid content of this mixture was measured gravimetrically with room temperature dry for 16 h (69.2%). ColorTrend 808-0836 Organic Red (Red Colorant, 4 oz / gal, 30 g / L) was used to prepare Example 1; ColorTrend 808-9907 Lamp Black (Black Colorant, 4 oz / gal, 30 g / L) was used to prepare Example 2; and ColorTrend 808-7214 Phthalo Blue (Blue Colorant, 4 oz / gal, 30 g / L) was used to prepared Example 3.

[0026] Comparative Examples 1-3 - Preparation of Paint without Cerium (III) Hydroxy Carbonate

[0027] The comparative examples (CE1 - CE3) were prepared as described for Examples 1-3 except that no cerium (III) hydroxy carbonate was included in the formulation.

[0028] Table 1 illustrates semi-gloss paint formulations for black, red, and blue paints with and without the mixture of cerium (III) hydroxy carbonates. All numbers (except PVC%) are reported as parts by weight. In-can Preservative refers to Kathon LX In-can Preservative (1.5 wt.% active); 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 Defoamer; T1O2 refers to Ti-Pure R-706 TiO2; CaCOi refers to Omycarb 8 CaCXL; 15-S-12 Surfactant refers to TERGITOL™ 15-S-12 Surfactant; Latex refers to RHOPLEX™ 101 Acrylic Emulsion; Coalescent refers to Optifilm Enhancer 400 Coalescent; RM-3030 refers to ACRYSOL™ RM-3030 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 The Dow Chemical Company or its Affiliates.) Table 1 - Paint formulations with and without Mixture of Hexagonal and Orthorhombic

[0029] Cerium (III) Hydroxy Carbonates

[0030] Table 2 illustrates the AE values from the exposure tests after 3500 h or QU V exposure.

[0031] Table 2 - Exposure Test Results

[0032] The AE values for the samples containing the mixture of hexagonal and orthorhombic cerium (III) hydroxy carbonate show marked improvement in color retention over the control samples.

[0033] Examples 4 and 5 - Preparation of a Colored Paint with Orthorhombic Cerium (III) Hydroxy Carbonate

[0034] A premix of TAMOL™ 963 Dispersant (0.56 g), NH4OH 28 wt% aq. (0.16), and water (5.65 g) mixed were added to a vessel containing the dry powder from Intermediate 1 (13.28 g). The contents of the vessel were pre-dispersed with a glass rod to achieve a smooth textured slurry, which was mixed using a Flacktec dual axis mixer at 2900 rpm for ~ 4 min. The orthorhombic cerium (III) hydroxy carbonate dispersion was added to a vessel containing a conventional pigment dispersion that was prepared on a single shaft high speed dissolver. The contents were mixed again using a Flacktec dual axis mixer at 2900 rpm for ~ 4 min. The final paint was prepared by a traditional letdown technique wherein each of the remaining paint components were added one at a time to the vessel containing inorganic solids dispersion using continuous low speed mixing with an overhead stirrer. Finally, organic red (Example 4) or phthalo blue colorant (Example 5) was added to the paint at a concentration of 4 oz / gal with stirring by a Flacktec dual axis mixer (2900 rpm, 3 min). Examples 6 and 7 - Preparation of a Colored Paint with Hexagonal Cerium (III) Hydroxy

[0035] Carbonate

[0036] The paints were prepared as described in Examples 5 and 6 except that dry powder from hexagonal cerium (III) hydroxy carbonate (Intermediate 2) was used. Example 6 was prepared with organic red, and Example 7 was prepared with phthalo blue.

[0037] Comparative Examples 4 and 5 - Preparation of a Paint without Cerium (III) Hydroxy Carbonate

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

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

[0040] Table 3 - Unextended Paint Formulations with Hexagonal and Orthorhombic Cerium (III) Hydroxy Carbonate

[0041] Table 4 illustrates the AE values from the exposure tests after 2000 h of QUV exposure.

[0042] Table 4 - Exposure Test Results

[0043] The data demonstrate that orthorhombic cerium (III) hydroxy carbonate shows the most robust resistance to fading in accelerated weathering tests. Both sets of examples show superior resistance to fading as compared to the comparative examples without any cerium (III) hydroxy carbonate.

Claims

Claims:

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

2. The composition of Claim 1 wherein the cerium (III) hydroxy carbonate, the water, and the dispersant comprise at least 90 weight percent of the composition.

3. The composition of Claim 1 which comprises 20 to 40 weight percent water, from 55 to 75 weight percent of a cerium (III) hydroxy carbonate and from 0.5 to 5 weight percent of a carboxylate functionalized dispersant.

4. The composition of Claim 2 which comprises from 25 to 35 weight percent water; from 60 to 72 weight percent of the cerium (III) hydroxy carbonate.

5. The composition of Claim 3 wherein the carboxylate functionalized dispersant in a salt of a polyacrylic acid, wherein the cerium (III) carbonate, the water, and the dispersant comprise at least 95 weight percent of the composition.

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

7. The composition of Claim 1 wherein the cerium (III) hydroxy carbonate is orthorhombic cerium (III) hydroxy carbonate.

8. The composition of Claim 1 wherein the cerium (III) hydroxy carbonate is a mixture of orthorhombic and hexagonal cerium (III) hydroxy carbonate.

9. The composition of either of Claims 7 or 8 which further comprises a dispersant, a surfactant, a defoamer, an opacifying pigment, an extender, a latex, a rheology modifier, and a colorant.

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