JP2002540056A - Method for producing discontinuous particles of calcium carbonate - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention provides a process for preparing an aqueous calcium hydroxide slurry containing a product and carbohydrates and discontinuing the aqueous calcium hydroxide slurry while maintaining a selected carbonation onset temperature. A method for producing calcium carbonate particles is provided. The products of the present invention are discontinuous particles of calcium carbonate that are particularly useful in cosmetic, pharmaceutical and food applications because of the purity level of the paints, plastics, paper coatings, paper fillers, and calcium carbonate particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of preparation and to the products obtained using said method. The product is
Discontinuous particles of calcium carbonate having a certain average particle size, specific surface area and high purity. The method of making the discontinuous calcium carbonate particles of the present invention requires varying the onset carbonation temperature and / or carbohydrate concentration to carbonate the aqueous calcium hydroxide slurry in the presence of carbohydrate. .

Calcium carbonate particles produced according to the process of the present invention are particularly useful as fillers in paper, as pigments for coated papers, as pigments for paints, as impact modifiers in polymers, and because of their high purity, Specific applications can be found in the food, nutrition, cosmetic and pharmaceutical industries.

[0003]

BACKGROUND OF THE INVENTION

Precipitated calcium carbonate (PCC) pigments are finding increasing use as fillers and coating pigments in the manufacture of paper and cardboard. This utility arises when used for papermaking due to the excellent optical and physical properties of PCC.

[0004] PCC is traditionally produced by carbonating aqueous calcium hydroxide with carbon dioxide to obtain calcium carbonate particles. Traditional methods of making PCC are quite sufficient for particles that do not require discontinuities. However, where the discontinuity of the final particles is required, there is a problem with traditional methods of manufacturing PCC. When attempting to precipitate discrete PCC particles using traditional methods that would naturally result in a clustered or agglomerated morphology, the process parameters were such that discontinuous particles of calcium carbonate could be produced consistently. Is very difficult to control. Thus, particles made according to traditional methods yield average particle size and specific surface area that are less predictable with respect to control. The present invention solves the problems of the prior art.

[0005]

[Problems to be solved by the invention]

Accordingly, it is an object of the present invention to provide a method for producing discontinuous calcium carbonate particles. Another object of the present invention is to provide a method for producing discontinuous calcium carbonate particles having a predictable average particle size and specific surface area. Another object of the present invention is to provide a reliable method for producing discontinuous calcium carbonate particles. A further object of the present invention is to produce discontinuous calcium carbonate particles having high calcium carbonate purity. Yet another object of the present invention is to produce a discontinuous calcium carbonate product from different quality quicklime sources.

[0006] These and other objects of the invention will become more apparent as further illustrated in the related art and detailed description that follows.

[0007]

[Prior art]

U.S. Pat. No. 5,332,564 discloses slaked lime in an aqueous sugar solution to form a slaked lime slurry, and the slaked lime slurry is carbonated with a carbon dioxide-containing gas until the orthorhombic calcium carbonate precipitates. A method for producing an orthorhombic or cylindrical PCC is disclosed.

[0008] US Pat. No. 4,237,147 describes a dry carbonated beverage concentrate and a process for preparing said concentrate, comprising mixing a) amorphous calcium carbonate and b) a non-toxic anhydride with water. Has been disclosed.

[0009] US Pat. No. 4,018,877 discloses an improved method for producing calcium carbonate by introducing a complexing agent to a calcium carbonate slurry during or after an initial nucleation step. are doing. The complexing agent is selected from the group including sucrose or glucose.

[0010] US Patent No. 3,443,890 discloses that PCC is prepared by carbonating an aqueous calcium hydroxide slurry in the presence of a second active ingredient selected from the group consisting of sugars and an active silicon dioxide compound. A method of manufacturing is disclosed.

[0011] US Pat. No. 2,467,082 discloses a method for producing chalk by carbonating an aqueous calcium hydroxide slurry in the presence of a sugar beet residue extract.

US Pat. No. 2,188,633 discloses the use of sugars and polyvinyl alcohol as additives to an aqueous calcium hydroxide slurry prior to carbonation to form a calcium carbonate product. I have.

JP 9-156,923 discloses a method at 250 ° C. using an aqueous calcium hydroxide slurry inoculated with polysaccharides and calcium carbonate to produce 25 m ² / g calcium carbonate particles. are doing.

JP-A-9-271,313 discloses a method for producing spindle-shaped precipitated calcium carbonate at 50 to 65 ° C. using an inexpensive low-grade furnace gas (CO ₂ ). The method relies on quicklime mesh size to control particle size and no additives are used.

[0015] In view of the related art, a new method for producing discontinuous calcium carbonate is continuously desired.

[0016]

[Means for Solving the Problems]

The present invention provides discontinuous calcium carbonate particles and a method for producing the same. The method comprises:
Production of an aqueous calcium hydroxide slurry, adjustment of the slurry to a selected carbonation onset temperature, addition of carbohydrate to the slurry, and carbon dioxide gas of the aqueous calcium hydroxide slurry to produce discontinuous calcium carbonate particles Requires carbonation.

The present invention also provides discontinuous calcium carbonate particles. It is more economical to manufacture because it requires less additives and processing, as opposed to traditionally formed clustered particles, resulting in predictable and discontinuous 98%
% Yields calcium carbonate particles.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Accordingly, the present invention provides a method for producing discontinuous calcium carbonate particles. The method comprises:
By varying the selected onset carbonation temperature and keeping the carbohydrate concentration level constant, or in another aspect, changing the carbohydrate concentration in the calcium hydroxide slurry while maintaining the carbonate start temperature constant. It requires the introduction of gaseous carbon dioxide into an aqueous calcium hydroxide slurry containing carbohydrates. In yet another aspect, the onset carbonation temperature and the carbohydrate concentration in the calcium hydroxide slurry are varied together.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

All percentages used herein are weight percentages, and when used to describe the amount of additive introduced into the process, the percentages are weight percentages relative to calcium carbonate equivalent to available quicklime.

As used herein, discontinuity means that the particles are generally clearly identified and separated. Preferred particles are rhomboidal and have an average arpect ratio (compare length / width (l / w)) of about 2.0 or greater.

As used herein, average particle size refers to the equivalent sphere diameter of an individual particle or as part of a cluster or aggregate, as opposed to the equivalent sphere diameter of the cluster or aggregate itself. means. Aggregates are spherical clumps or clusters of particles.
As used herein, a cluster or cluster formation refers to a bunch (bunch).
) Or assemblage growth or formation.

[0022] The aqueous calcium hydroxide slurry of the present invention has about 5% to about 30% by weight calcium hydroxide. Preferably, the calcium hydroxide concentration in the slurry is about 1
0% to about 20% by weight.

An important aspect of the present invention is that the aqueous calcium hydroxide slurry contains carbohydrates. Such carbohydrates can be added to the slurry by any conventionally known method, for example, stirring, mixing or stirring. Carbohydrates are added all at once to the aqueous calcium hydroxide slurry, as opposed to being performed intermittently or continuously during the carbonation process. Carbohydrates that are preferably useful in the present invention include, but are not limited to, those monosaccharides, disaccharides, and polysaccharides. Monosaccharides include, but are not limited to, simple saccharides such as fructose and glucose. Disaccharides include sucrose, maltose, lactose and cellobiose, while polysaccharides generally include nine or more monosaccharides linked together by glycosidic bonds. Non-limiting examples include starch, cellulose and glycogen.

[0024] Carbohydrates useful in the present invention are preferably selected from the group consisting of sucrose, glucose, fructose, crude sugar, molasses, gums, starch and other organic compounds and the like. The carbohydrates present in the aqueous calcium hydroxide slurry are generally present at a concentration level of from about 0.05% to about 3.0% by weight, based on calcium carbonate equivalent to available quicklime. The preferred carbohydrate is sucrose. The concentration of sucrose present in the aqueous calcium hydroxide slurry is preferably from about 0.1% to about 0.1% by weight.
5% by weight.

Another important aspect of the products and methods of the present invention is the selected carbonation onset temperature. Carbonation onset temperature is the temperature of the aqueous calcium hydroxide slurry just prior to adding gaseous carbon dioxide to initiate carbonation without the need for a means to control the temperature during the carbonation process. It has been found that the selected carbonation onset temperature varies from about 20 ° C. to about 85 ° C. and the carbohydrate concentration in the calcium hydroxide slurry ranges from about 0.05% to about 3.0% by weight. By changing with
Having an average particle size of about 0.1 micron to about 3.0 microns and about 2 m ² / g to about 6
That is, discontinuous calcium carbonate particles having a specific surface area of 0 m ² / g are produced. Throughout the specification, control of the temperature after the onset of carbonation can be performed as long as it does not substantially inhibit the formation of discrete particles.

In a preferred embodiment of the present invention, about 10% to about 20% by weight of calcium hydroxide, about 0.1% to about 1.0% by weight of carbohydrate, and about 30 ° C. to about 75 ° C. the aqueous calcium hydroxide slurry having a selected carbonated initiation temperature, average particle from about 0.1 microns to about 3.0 microns diameter and about 2m ² / g to about 25 m ² /
Discontinuous calcium carbonate particles having a specific surface area of g are produced.

The nature of the gas containing carbon dioxide is not a particularly important aspect of the present invention. In the process of the present invention, pure carbon dioxide gas can be used, or a standard mixture of carbon dioxide in air or nitrogen can be used. It should be noted that during the carbonation process step, by introducing liquid carbon dioxide in its gaseous state, liquid carbon dioxide can also be used in accordance with the products and methods of the present invention.

[0028] Discontinuous calcium carbonate particles and methods for making them can be obtained using various quicklimes and quicklime concentrations and quicklime qualities, but the slurry produced therefrom has a calcium hydroxide concentration of about 5% by weight. It has been found to be particularly suitable to use a high quicklime concentration.

In another embodiment for producing the discontinuous calcium carbonate particles of the present invention, while maintaining the selected onset carbonation temperature and maintaining a constant level of carbohydrates, a process for preparing calcium carbonate from various quicklimes. It has been found that continuous calcium carbonate particles are produced. The particles have an average particle size of about 0.1 micron to about 3.0 microns and about 2 m ² / g
It is characterized by having a specific surface area of up to about 60 m ² / g. Carbonation of the aqueous quicklime slurry by the introduction of carbon dioxide is continued until the precipitation of calcite is substantially complete. The carbonation process is preferably carried out at the pH of the carbonated slurry.
Is almost neutral (7) and is complete when the calcium carbonate particles have a purity of about 98% calcium carbonate.

[0030] Even after the carbonation process is complete, there may still be some unreacted calcium hydroxide in the carbonated slurry. Various techniques known to those skilled in the art can be used to achieve complete neutralization of the remaining calcium hydroxide (in the present invention, no more than about 2%). Such techniques include, for example, monitoring the slurry pH by introducing additional carbon dioxide gas when unreacted calcium hydroxide needs to be treated. The carbonated slurry may also be treated with a sufficient amount of an organic or inorganic polybasic acid, such as citric acid, maleic acid, malic acid, malonic acid, phthalic acid, tartaric acid, boric acid, phosphoric acid, sulfurous acid or sulfuric acid. it can.

The average particle size of the discontinuous particles of calcium carbonate produced according to the method of the present invention is about 0
. It can range from 1 micron to about 3.0 microns. The average particle size of the particles produced in accordance with the present invention is measured by Microm
eritics Determined using a Sedigraph 5100.

To determine the specific surface area of the calcium carbonate particles of the present invention, the surface area can be determined using a Micromeritics FLOWSORB II 2300 using BET theory with nitrogen as the adsorption gas.

[0033]

【Example】

By changing the selected carbonation onset temperature and changing the carbohydrate concentration,
Although discontinuous particles of various shapes and sizes are produced, it is noted that the present invention should not be so limited in scope. Furthermore, the following examples are merely illustrative of the products and methods of the present invention, and should not be construed in any way limiting the scope of the invention, which is more clearly defined by the claims.

Example 1 A high speed stirrer having a hemispherical bottom and driven by a 1/15 hp variable speed motor and a curved stainless steel tube below the center of the bottom wing for the introduction of carbon dioxide / air flow. The invention was carried out using a cylindrical stainless steel reactor for the preparation and reaction of calcium hydroxide (slaked lime).

In a 4 liter reactor, at 50 ° C., a granular Bell having an available calcium oxide content of 94% by weight or more (determined by ASTM procedure C-25-72).
By adding 250 g of efonte quicklime to 2000 ml of water, an aqueous calcium hydroxide slurry of 14.2% by weight (0.154 g / cc) was prepared.
Stirred at RPM for 10 minutes. The slurry was sieved through a 60 mesh screen to remove sand and heated to a carbonation onset temperature of 55 ° C. The stirrer was adjusted to 1250 RPM and 0.5% Domino Sugar (from Domino Sugar Corporation) (hereinafter referred to as sucrose (by weight based on calcium carbonate equivalent to available quicklime)) was added to the slurry. The slurry was carbonated to precipitate calcium carbonate by introducing a gaseous mixture of 10% carbon dioxide in air at 0.45 SLM into the slurry. Carbonation was continued for 263 minutes until the pH value was less than 8.0. The slurry was prepared according to US Standard No. The sand was removed by passing through a 325 (44 micron) sieve. The particle size of the slurried product was evaluated and found to have an average particle size of 0.88 microns. The product was well dispersed and completely discontinuous by SEM. A portion was vacuum filtered and the filter cake was dried at about 165 ° C. for at least 1 hour to obtain a PCC product having a specific surface area of 13.5 m ² / g. This experiment is shown in Table 1.
In Example 1.

Examples 2, 3 and 4 Three additional samples were synthesized at various carbonation onset temperatures, namely 60 ° C, 65 ° C and 70 ° C. The data of Examples 1-4 are compared in Table 1.

Example 5 Example 5 was prepared according to the procedure of Example 1 using the same quicklime but with the following changes. The concentration of the calcium hydroxide slurry was 10.7% (0.114 g / cc) instead of 14.2% by weight. Again, the addition of sucrose is 0.
It was 5%, but the gas consisted of 18% CO _2, rather than 10% CO _2. C
The O ₂ rate was 1.75 SLM, giving a reaction time of 63 minutes to a pH of 8.0. The initial reaction temperature was 60 ° C. The product was prepared according to US Standard No. The sand was removed by passing through a 325 (44 micron) sieve. The product had an average particle size of 1.30 microns and a specific surface area (SSA) of 10.4 m ² / g. This experiment is identified in Table 1 as Example 5.

[0038]

[Table 1]

The data show that the calcium hydroxide slurry concentration has an effect on the resulting particle size of the product. The magnitude of the change will likely vary for different quicklimes, but higher concentrations tend to result in finer particle sizes (compare Examples 2 and 5). Examples 1-4 show the effect of temperature on particle size, while keeping sucrose levels constant. As the temperature increases, the particle size increases and the specific surface area decreases.

EXAMPLES 6, 7, 8 Three samples were synthesized according to the procedure of Example 1 using Bellefonte quicklime, but with 0.4% sucrose at 70 ° C and 0.15% at 50 ° C. 0.1% sucrose was used. These samples were compared to Example 4 of the previous sample in Table 2 below.

[0041]

[Table 2]

The data in Table 2 show that by controlling both temperature and sucrose levels, at a given carbonation onset temperature, the average particle size can generally be retained.

Example 9 Calcium hydroxide was prepared for large scale carbonation using a 70 gallon modified motor mixer. Carbonation was performed in a 30 liter jacketed, baffled, cylindrical stainless steel reactor having an inner diameter of 11.5 inches, a height of 20 inches, and a hemispherical bottom. The reactor had about 4 inches and 8 inches from the bottom.
With two 4.5 inch diameter flat wing turbine impellers at 5 inches
It was equipped with a high speed stirrer driven by a P variable speed motor. In addition, carbon dioxide /
A 0.25 inch ID stainless steel tube curved below the center of the bottom of the wing was also provided for the introduction of airflow. In the 70 gallon motor mixer described above,
At 50 ° C., 15.7% by weight (0.1692 g / cc) aqueous calcium hydroxide slurry was prepared by adding 3000 g of Bellefonte quicklime to 18.0 liters of water and stirred for 10 minutes. The slurry was passed through a 60 mesh sieve to remove sand and heated in the reactor to a carbonation onset temperature of 45 ° C. 6 stirrers
Adjust to 15 RPM, 0.1% for calcium carbonate equivalent to available quicklime
5% by weight of sucrose was added to the slurry. The calcium hydroxide slurry was carbonated by introducing a gas mixture of 10% by volume carbon dioxide in air at 4.4 standard liters / minute (SLM) to precipitate calcium carbonate. Carbonation was continued until the pH was less than 7.4. The slurry was prepared according to US Standard No. 32
The sand was removed by passing it through a 5 (44 micron) sieve. This experiment is described in Table 3.
In Example 9.

Example 10 This sample was prepared from Bellefonte quicklime on plant equipment according to the procedure of Example 9. Batch times, temperatures and sucrose levels of the reaction conditions were generally the same. This experiment is identified in Table 3 as Example 10.

[0045]

[Table 3]

Examples 11, 12, 13 These three products were made according to the procedure of Example 1 using three quicklime sources, namely Greer quicklime, Frey quicklime and Western quicklime. All products were carbonated at 0.1% sucrose and a carbonation onset temperature of 45 ° C.
Table 4 shows the results of the average particle size and the specific surface area.

[0047]

[Table 4]

[0048]

[Brief description of the drawings]

FIG. 1 shows a conventional scalenohedral form of calcite.

FIG. 2 shows a conventional rhombohedral calcite.

FIG. 3 shows a conventional aragonite.

FIG. 4 shows conventional short and thick prismatic (stubby-prismatic form) calcite.

FIG. 5 is an SEM (scanning electron micrograph) of a novel discontinuous calcite crystal of the present invention.
Is shown.

FIG. 6 shows a further enlarged photograph of the novel discontinuous calcite crystals of the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZA, ZWF term (reference) 4G076 AA12 AB06 BA11 BB08 BD02 BD06 CA01 DA02 DA15

Claims (15)

[Claims] An aqueous calcium hydroxide slurry is prepared, one or more carbohydrates are added to the aqueous calcium hydroxide slurry, and the aqueous calcium hydroxide slurry is carbonated at a selected carbonation onset temperature to form a discontinuous mixture. A method for producing discontinuous particles of calcium carbonate, comprising producing calcium carbonate particles. 2. The concentration of calcium hydroxide in the calcium hydroxide slurry is from about 5% to about 30% by weight, preferably from about 10% to about 20% by weight.
The described method. 3. The method of claim 2, wherein the concentration of calcium hydroxide in the calcium hydroxide slurry is preferably from about 10% to about 20% by weight. 4. The method of claim 1 wherein the selected onset carbonation temperature is from about 30 ° C. to about 85 ° C. 5. The carbonation initiation temperature selected is preferably from about 40 ° C. to about 75 ° C.
5. The method of claim 4, wherein 6. The method of claim 1, wherein the carbohydrate is selected from the group consisting of sucrose, glucose, fructose, crude sugar, molasses, gum, starch, maltose, lactose, cellobiose, cellulose and glycogen. 7. The method of claim 6, wherein the carbohydrate concentration is from about 0.05% to about 3.0% by weight. 8. The method of claim 7, wherein the concentration of carbohydrate is preferably from about 0.01% to about 1.0% by weight. 9. The method according to claim 6, wherein the carbohydrate is sucrose. 10. The method of claim 1, wherein the concentration of carbon dioxide gas during carbonation is from about 1% to about 100%. 11. The concentration of carbon dioxide gas during carbonation is preferably about 10%.
11. The method of claim 10, wherein the method is about 30%. 12. The method of claim 1, wherein the discontinuous particles of calcium carbonate have an average particle size of from about 0.1 microns to about 3.0 microns. The specific surface area of 13. discrete particles of calcium carbonate is about 2m ² / g to about 25 m ² / g, The method of claim 12, wherein. 14. The method of claim 1, wherein the discontinuous calcium carbonate particles are 98% calcium carbonate. Containing 15. 2m ² / g to the specific surface area of about 25 m ² / g, discrete calcium carbonate particles having a purity of average particle diameter and 98% of calcium carbonate of from about 0.1 microns to about 3.0 microns Composition.