Process for preparation of cerium (iii) hydroxycarbonate
By contacting cerium (III) nitrate with urea at high temperature to form hydroxycerium (III) carbonate, the problem of using non-biodegradable materials in the prior art is solved without or very small amounts of polymer dispersants and chelators. , achieving efficient and sustainable nanoparticle preparation and improved coating color retention.
Patent Information
- Application Number
- CN202380040396.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-05-23
- Filing Date
- 2023-05-15
- Publication Date
- 2024-12-27
AI Technical Summary
The prior art requires the use of non-biodegradable chelating agents or polymer dispersants in the preparation of cerium (III) carbonate, which affects its sustainability and environmental friendliness.
The reaction conditions are controlled to prepare nanoparticles by contacting cerium (III) nitrate with urea, and the reaction conditions are controlled in the range of 110°C to 200°C.
The efficient preparation of biodegradable cerium (III) hydroxycarbonate nanoparticles is achieved, reducing color changes in the coating, and providing a high solids content of aqueous slurry, improving the color retention of paint preparation.
Abstract
Description
Background Art
[0001] The present invention relates to a method for preparing cerium (III) hydroxy carbonate, which can be used to improve the color retention of coatings prepared from paint formulations and reduce undesirable color changes. Cerium (III) carbonate is an effective additive for improving color retention and reducing color changes in paint coatings. (See US2021 / 1888227 A1 (Bohling).) Bohling discloses that cerium (III) hydroxy carbonate has 110 nm + A 20 wt% aqueous dispersion of ligand-terminated cerium (III) carbonate particles having a z-average particle size of 5 nm can be prepared by mixing a solution of ammonium cerium (III) nitrate with a solution of a chelating agent (EDTA) and ammonium carbonate, followed by centrifugation and removal of the supernatant. (Page 4, lines 4 to 6 and page 5, lines 1 to 6). The chelating agent is believed to "promote the formation of nano-dispersed particles while stabilizing the particles to prevent agglomeration." (Page 3, lines 27 to 29).
[0002] US 8,637,153 B2 (Cho) discloses (column 10, lines 5 to 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 and then adding 10 to 30% by weight of a polymer dispersant, such as polyethylene glycol or polyacrylic acid, to the mixture. (column 10, lines 22 to 24 and column 5, lines 61 to 65.) The water is then removed and the temperature is raised to 140°C. After the reaction is complete, the product can be washed with water to remove unreacted urea and polymer dispersant and then dried to isolate the crystalline solid. The volume average diameter of the experimentally prepared particles is reported to be in the range of 75nm to 90nm (column 12, Table 1); in general, Cho discloses that the particle size can be controlled by varying the amount and molecular weight of the polymer dispersant. (column 8, lines 19 to 30). Cerium (III) carbonate is then used as a precursor to prepare cerium oxide nanoparticles of uniform size. (Column 13, lines 3 to 8).
[0003] There is a need in the field of cerium(III) carbonate chemistry to devise a more sustainable method for preparing cerium(III) carbonate that does not require chelating agents or non-biodegradable polymeric dispersants. Summary of the invention
[0004] The present invention solves the need in the art by providing a method comprising the steps of contacting cerium (III) nitrate and urea at a temperature in the range of 110°C to 200°C and in the substantial absence of a polymeric dispersant to form cerium (III) hydroxycarbonate. The method of the present invention can be used to prepare an additive that reduces fading and attenuates unwanted color changes in coatings caused by paint. DETAILED DESCRIPTION
[0005] The present invention is a process comprising the steps of contacting cerium (III) nitrate and urea at a temperature in the range of 110°C to 200°C and in the substantial absence of a polymeric dispersant to form cerium (III) hydroxycarbonate.
[0006] As used herein, the term "substantially absent polymer dispersant" refers to less than 5 wt%, preferably less than 1 wt%, more preferably less than 0.1 wt%, and most preferably 0 wt% of polymer dispersant in the polymer melt of cerium (III) nitrate and urea, based on the weight of cerium (III) nitrate. More specifically, the polymer dispersant refers to polyethylene glycol; polymers functionalized with carboxylic acid groups, such as polyacrylic acid and polymethacrylic acid; polyvinyl alcohol; or polyvinyl pyrrolidone; or combinations thereof.
[0007] Preferably, the reaction is also carried out in the substantial absence of a chelating agent capable of forming a capping ligand with cerium (III) hydroxycarbonate. The term "substantially absent a chelating agent capable of forming a capping ligand with cerium (III) hydroxycarbonate" refers to less than 1 wt%, preferably less than 0.5 wt%, more preferably less than 0.1 wt%, and most preferably 0 wt% of a chelating agent based on the weight of cerium (III) nitrate, the chelating agent being a) an amine carboxylic acid or a salt thereof, such as ethylenediaminetetraacetic acid (EDTA), ethylenediaminediacetic acid (EDDA), and nitrilotriacetic acid (NTA); and b) an amine phosphonic acid or a salt thereof, such as aminotrimethylphosphonic acid (ATMP), 6-amino-2-[bis(carboxymethyl)amino]hexanoic acid, and N-(phosphonomethyl)iminodiacetic acid (PIDA).
[0008] As used herein, "cerium (III) nitrate" refers to anhydrous or hydrated cerium (III) nitrate. Cerium (III) nitrate is preferably used as a hydrate, more particularly as a hexahydrate. The reaction of cerium (III) nitrate and urea is most preferably carried out under a net condition (i.e., solvent-free and anhydrous) except the water produced by the hydrate. It is also preferred that the combination of cerium (III) nitrate and urea accounts for at least 95% by weight, or at least 98% by weight, or at least 99% by weight or 100% by weight of the components in the initial reaction mixture.
[0009] The molar ratio of cerium nitrate (III) and urea is preferably in the range of 1:3 or 1:4 or 1:5 to 1:20 or to 1:10 or to 1:8. The reaction is carried out at a temperature in the range of 110°C or 125°C or 140°C to 200°C or to 180°C or to 160°C, continuing the time for a satisfactory conversion rate sufficient to produce the desired product, usually in the range of 1 to 10 hours. It has been found that the particle size of the product can be controlled by adjusting the relative amount of cerium nitrate (III) and urea and by changing the temperature. Generally, it is found that higher temperatures and higher urea: cerium nitrate (III) ratio provide smaller particle size.
[0010] The cerium (III) hydroxycarbonate solid prepared using the method of the present invention is advantageously washed with water to remove unwanted by-products and starting materials. The washed product is then dried and separated into a crystalline white powder. The product has a z-average particle size in the range of 100nm to 1000nm measured using dynamic light scattering.
[0011] The process of the present invention provides high solids aqueous slurries (about 70 wt %) of cerium (III) hydroxycarbonate nanoparticles in greater than 90% yield using inexpensive and biodegradable starting materials. Higher solids contents are particularly valuable because dilute solutions limit the ability of paint formulators to control water addition.
[0012] Small particle size is achieved by reacting at a sustained reaction temperature of 110°C or above, preferably above 140°C, using excess urea in the absence of polymeric dispersants or chelating agents.
[0013] Example 1 - Preparation of cerium (III) hydroxycarbonate
[0014] Cerium (III) nitrate hexahydrate (30.0 g, 69.1 mmol, 1 eq) and urea (25.0 g, 416 mmol, 6 eq) were added to a round-bottom flask equipped with a stirring bar, a condenser, and a Dean-Stark trap. The solid mixture was heated to 150 ° C and stirred for 5 h. The mixture was cooled to less than 100 ° C, and then water (80 g) was added to wash the material. The aqueous slurry was centrifuged at 18,500 rpm for 5 minutes to separate the solids, followed by three more rounds of washing and centrifugation. The solids were collected and dried at room temperature to produce 13.7 g (91.3% yield) of white powder, which was identified as hexagonal cerium (III) hydroxycarbonate by X-ray powder diffraction. The material exhibited the same powder XRD pattern observed in Figure 7 of Cho.
[0015] Additional Examples 2-5 were prepared substantially as described in Example 1, except that the molar ratio of cerium (III) nitrate hexahydrate: urea (Ce: urea) and the reaction temperature were varied. Comparative Example 1 was prepared substantially as described in Example 1, except that the reaction temperature was maintained at 140°C and PEG 600 polyethylene glycol (PEG600, 4.0 g) was mixed with cerium (III) nitrate hexahydrate (20.0 g, 46.1 mmol, 1 equivalent) and urea (8.33.0 g, 208 mmol, 3 equivalents). Samples for particle size measurement were prepared by diluting dried cerium (III) hydroxycarbonate powder (10 mg) with deionized water (5 mL). The mixture was sonicated for 2 minutes, after which a drop of the mixture was diluted with 0.01 M NaCl solution (1 mL) and then placed in a cuvette for analysis using a Malvern Zetasizer Nano-S90 instrument. The Z-average particle size was obtained after the 6-minute method (three measurements, 2 minutes each). Table 1 illustrates the effect of temperature and starting material ratio on particle size (PS nm).
[0016] Table 1 - Particle size of cerium (III) hydroxycarbonate
[0017] Example No. Ce:Urea Temperature ℃ Dispersant? PS (in nm) Standard Deviation Comparative Example 1 1:3 140 PEG 600 590 115 Ex.1 1:3 150 no 978 56 Ex.2 1:6 130 no 307 2 Ex.3 1:6 150 no 208 4 Ex.4 1:6 170 no 146 2
[0018] This data shows that the particle size can be significantly reduced by increasing the urea concentration relative to the cerium (III) carbonate concentration and by increasing the reaction temperature.
Claims
1. A method comprising the following steps: Cerium (III) nitrate and urea are contacted at a temperature in the range of 110°C to 200°C and in the substantial absence of a polymeric dispersant to form cerium (III) hydroxycarbonate.
2. The method according to claim 1, which is carried out using less than 1 wt% of a polymer dispersant based on the weight of the cerium (III) nitrate, wherein the molar ratio of the cerium (III) nitrate to the urea is in the range of 1:3 to 1:
20.
3. The method according to claim 2, which is carried out at a temperature in the range of 130°C to 180°C, wherein the cerium (III) nitrate is a hydrate of cerium (III) nitrate, and wherein the polymer dispersant is any one or all of polyethylene glycol, a polymer functionalized with a carboxylic acid group, polyvinyl alcohol or polyvinyl pyrrolidone.
4. The method according to claim 3, which is carried out at a temperature in the range of 140°C to 180°C, wherein the molar ratio of the hydrate of cerium (III) nitrate to the urea is in the range of 1:5 to 1:
10.
5. The method according to claim 4, which is carried out using less than 0.1 wt% of the polymer dispersant based on the weight of the hydrate of cerium (III) nitrate.
6. The method of claim 1, which is carried out in the substantial absence of a chelating agent capable of forming a capping ligand with the cerium (III) hydroxycarbonate.
7. The method according to claim 5, which is carried out using less than 0.1 wt% of a chelating agent based on the weight of the cerium (III) nitrate hydrate, the chelating agent being an amine carboxylic acid or a salt thereof, or an amine phosphonic acid or a salt thereof.
8. The process of claim 1, which is carried out under neat conditions.