Water-based stearic acid emulsion in-situ modified heavy calcium carbonate as well as preparation method and application thereof

Abstract

The invention provides water-based stearic acid emulsion in-situ modified heavy calcium carbonate as well as a preparation method and application thereof, and belongs to the technical field of fine chemical engineering. The water-based stearic acid emulsion is used as a modifier, and oleophylic-phase stearic acid is uniformly dispersed in water under the emulsification action of an emulsifier to form a stable emulsion; the calcium carbonate mineral aggregate and the water-based stearic acid emulsion are fully mixed through ball milling, so that the mixing uniformity of stearic acid and the calcium carbonate mineral aggregate is improved, the coating rate and the activation rate of the calcium carbonate mineral aggregate are improved, the grinding efficiency of the mineral aggregate of a ball mill is improved, and secondary agglomeration is prevented; meanwhile, the production process of the traditional activated calcium carbonate is simplified, and the production cost of the activated calcium carbonate is reduced. The water-based stearic acid emulsion in-situ modified heavy calcium carbonate prepared by the invention has the advantages of high activation degree, good dispersity and stability and low oil absorption value, and is suitable for being used in the field of production of plastics, coatings or adhesives.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical industry, and in particular to an aqueous stearic acid emulsion in-situ modified heavy calcium carbonate and a preparation method and application thereof. Background Art

[0002] Calcium carbonate is an inorganic metal mineral material with high whiteness, good stability, safety, environmental protection, low cost and easy processing. It is widely used in papermaking, plastics, coatings, films, rubber, adhesives and other fields. The base materials used in most downstream application systems of calcium carbonate are non-polar or weakly polar materials, so they are not compatible with calcium carbonate that has not been surface-modified. In actual production, the ground heavy calcium carbonate is often activated and modified to reduce its surface polarity and oil absorption value, thereby improving the dispersibility and stability of heavy calcium carbonate powder in the base material, so as to improve the quality of downstream products.

[0003] In the existing modification technology, the ground heavy calcium carbonate is usually transported to a modifier and modified with saturated fatty acids or coupling agents. However, this modification process has problems such as high energy consumption, high processing costs, complex procedures, and unstable product quality. Summary of the invention

[0004] The purpose of the present invention is to provide an aqueous stearic acid emulsion in-situ modified heavy calcium carbonate and a preparation method and application thereof, so as to reduce production energy consumption, simplify the modification process and improve product quality stability.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing heavy calcium carbonate by in-situ modification of an aqueous stearic acid emulsion, comprising the following steps:

[0007] The large calcite is subjected to primary crushing, ore dressing and secondary crushing in sequence to obtain calcium carbonate ore;

[0008] The calcium carbonate ore is mixed with an aqueous stearic acid emulsion, and ground and modified to obtain an active calcium carbonate powder;

[0009] Classifying the active calcium carbonate powder to obtain water-based stearic acid emulsion in-situ modified heavy calcium carbonate;

[0010] The aqueous stearic acid emulsion consists of stearic acid, an emulsifier, a defoamer and water;

[0011] The emulsifier includes sorbitan monooleate, sucrose triester stearate, sodium polyacrylate and sodium lauryl sulfate;

[0012] The defoaming agent comprises methyl silicone oil, fumed silica, polysorbate 80 and polyvinyl alcohol.

[0013] Preferably, the CaCO3 content in the macrocalcite is ≥ 98%.

[0014] Preferably, the mass of the aqueous stearic acid emulsion is 1.2-2.0% of the mass of the calcium carbonate ore.

[0015] Preferably, the mass ratio of the stearic acid, emulsifier, defoamer and water is (25-35):(1-5):(0.1-1):(59-73.9).

[0016] Preferably, the mass ratio of sorbitan monooleate, sucrose triester, sodium polyacrylate and sodium lauryl sulfate is (2-6):(1-4):(1-3):(1-3).

[0017] Preferably, the mass ratio of the methyl silicone oil, fumed silica, polysorbate 80 and polyvinyl alcohol is (25-30):(0.3-0.8):(3-9):(10-15).

[0018] Preferably, the particle size of the stearic acid is less than 0.5 mm; and the weight average molecular weight of the sodium polyacrylate is 3500-4000.

[0019] Preferably, the frequency of the classifier used for the classification is 15 to 30 Hz.

[0020] The invention provides water-based stearic acid emulsion in-situ modified heavy calcium carbonate prepared by the preparation method, wherein the mesh number of the water-based stearic acid emulsion in-situ modified heavy calcium carbonate is 400-2500 meshes.

[0021] The present invention also provides the use of the above-mentioned aqueous stearic acid emulsion in-situ modified heavy calcium carbonate in the fields of plastics, coatings or adhesives.

[0022] Beneficial effects of the present invention:

[0023] The invention selects sorbitan monooleate, sucrose triester stearate, sodium polyacrylate and sodium lauryl sulfate as emulsifiers, and adjusts the HLB value of the emulsifier to between 14 and 16 through the compounding of the four, and uniformly disperses the stearic acid of the oil phase in water through the emulsifying effect of the emulsifier to form a uniform and stable aqueous stearic acid emulsion; because the stearic acid emulsion exists in the form of a liquid phase, it is beneficial for the effective components (stearic acid, sucrose triester stearate and sodium polyacrylate) in the emulsion to be uniformly dispersed on the surface of the calcium carbonate mineral material and to form an effective coating, thereby improving the coating rate and activation rate of the calcium carbonate mineral material.

[0024] In addition, the four components in the emulsifier are also surfactants. Their molecules contain a large number of hydrophilic and lipophilic groups, which can strengthen the binding force between the surfactant and the surface of the calcium carbonate mineral. Through the synergistic effect of stearic acid, sorbitan monooleate, sucrose triester stearate, sodium polyacrylate, and sodium lauryl sulfate, the surface coverage and activation quality of the calcium carbonate mineral are greatly improved.

[0025] The aqueous stearic acid emulsion of the present invention can not only coat and modify the calcium carbonate particles, but also effectively promote the grinding efficiency of the calcium carbonate ore in the ball mill. As the calcium carbonate ore is continuously ground and crushed in the ball mill, its particle size will gradually decrease, and more and more unsaturated valence bonds and structural units with positive and negative charges will form on the surface of the microparticles, making the particles in an unstable high-energy state, and the interaction force between the calcium carbonate microparticles will increase accordingly. When the interaction force between the microparticles is large to a certain extent, agglomeration will occur between the particles. When the crushing and agglomeration of calcium carbonate reach a dynamic equilibrium, the apparent particle size of the calcium carbonate ore will no longer decrease. When the calcium carbonate ore is ground and crushed, the aqueous stearic acid emulsion having a large amount of RCOO is added. - and Na + It can form a strong bond with the exposed particles of calcium carbonate particles, thereby reducing the surface energy of calcium carbonate ore, making the surface of calcium carbonate ore hydrophobic, and completely eliminating the source of power for secondary agglomeration. The sodium polyacrylate and sodium silyl sulfate in the emulsifier are also dispersants. Through their unique long-chain structure, they can form a steric hindrance effect on calcium powder microparticles, improve the dispersibility of calcium powder during grinding and modification, and synergistically promote the activation effect of calcium powder.

[0026] The invention blends and grinds aqueous stearic acid emulsion with calcium carbonate mineral raw materials for in-situ modification, simplifies the existing calcium carbonate powder modification process, and effectively reduces the energy loss and production cost of calcium carbonate mineral modification. The aqueous stearic acid in-situ modified heavy calcium carbonate prepared by the invention has the advantages of high activation, good dispersibility and stability, low oil absorption value, etc. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing heavy calcium carbonate by in-situ modification of an aqueous stearic acid emulsion, comprising the following steps:

[0028] The large calcite is subjected to primary crushing, ore dressing and secondary crushing in sequence to obtain calcium carbonate ore;

[0029] The calcium carbonate ore is mixed with an aqueous stearic acid emulsion, and ground and modified to obtain an active calcium carbonate powder;

[0030] Classifying the active calcium carbonate powder to obtain water-based stearic acid emulsion in-situ modified heavy calcium carbonate;

[0031] The aqueous stearic acid emulsion consists of stearic acid, an emulsifier, a defoamer and water;

[0032] The emulsifier includes sorbitan monooleate, sucrose triester stearate, sodium polyacrylate and sodium lauryl sulfate;

[0033] The defoaming agent comprises methyl silicone oil, fumed silica, polysorbate 80 and polyvinyl alcohol.

[0034] The present invention preferably crushes the large calcite into ore materials with a size of less than 200 mm after washing, selects and removes ore materials with hues other than white mixed in the ore materials, and crushes the qualified large calcite into calcium carbonate ore materials with a size of less than 2 mm for secondary crushing; in the present invention, the CaCO3 content in the large calcite is preferably ≥98%.

[0035] The present invention preferably transports the calcium carbonate ore to a ball mill for grinding, and at the same time, uniformly sprays the prepared aqueous stearic acid emulsion on the surface of the calcium carbonate ore through a wet spray device to coat the surface of the calcium carbonate ore, and obtains an activated calcium carbonate powder after grinding and modification; in the present invention, the specification of the ball mill is a 2200×7500mm wet ball mill, the grinding and modification time is preferably 15 to 25 minutes, more preferably 20 minutes, the rotation speed is preferably 45 to 55 rpm, more preferably 50 rpm; the mass of the aqueous stearic acid emulsion is preferably 0.5 to 2.0% of the mass of the calcium carbonate ore, more preferably 1.0 to 1.5%, and more preferably 1 .2~1.3%; The aqueous stearic acid emulsion is preferably composed of stearic acid, an emulsifier, a defoamer and water. The preparation process of the aqueous stearic acid emulsion is specifically as follows: first, the emulsifier, the defoamer and 5% of water (the total amount of water added is 100%) are added into a reactor together, heated to 75°C, and then stirred for 20 minutes, with the rotation speed maintained at 600rpm, so that the emulsifier and the defoamer are completely dissolved in water; stearic acid is added, and stirring is continued for 30 minutes to completely melt the stearic acid into a liquid state and fully mix with the emulsifier; then 25% of water is added, and stirring is performed for 20 minutes to form an oil-in-water emulsion; finally, the remaining 70% of water is added, and stirring is performed for 30 minutes, and then heating is stopped, and stirring is cooled to room temperature.

[0036] In the present invention, the mass ratio of stearic acid, emulsifier, defoamer and water is preferably (25-35):(1-5):(0.1-1):(59-73.9), and more preferably (30-35):(1.5-5):(0.1-0.5):(59.5-68.4); the mass ratio of sorbitan monooleate, sucrose triester, sodium polyacrylate and sodium lauryl sulfate is preferably (2-6):(1-4):(1-3):(1-3), and more preferably (3-6):(1-2):(1-2):(1-2).

[0037] In the present invention, the stearic acid is preferably a primary acid, and its appearance is white spherical particles with a particle size of <0.5 mm; the weight average molecular weight of the sodium polyacrylate is preferably 3500-4000, more preferably 3500-3800, and more preferably 3700-3800.

[0038] In the present invention, the mass ratio of sorbitan monooleate, sucrose triester, sodium polyacrylate and sodium lauryl sulfate is preferably (2-6):(1-4):(1-3):(1-3), and more preferably (3-6):(1-2):(1-2):(1-2).

[0039] In the present invention, the mass ratio of the methyl silicone oil, fumed silica, polysorbate 80 and polyvinyl alcohol is preferably (25-30):(0.3-0.8):(3-9):(10-15), and more preferably (28-30):(0.4-0.6):(5-8):(9-13).

[0040] The present invention preferably classifies the activated calcium carbonate powder, collects the classified powder particles through a bag dust collector, and obtains an aqueous stearic acid emulsion in-situ modified heavy calcium carbonate; in the present invention, the frequency of the classifier used for the classification is preferably 15 to 30 Hz, more preferably 18 to 26 Hz, and more preferably 19 to 22 Hz.

[0041] The present invention provides an aqueous stearic acid emulsion in-situ modified heavy calcium carbonate prepared by the above preparation method, wherein the mesh number of the aqueous stearic acid emulsion in-situ modified heavy calcium carbonate is preferably 400-2500 meshes, further preferably 500-2000 meshes, and more preferably 1000-1250 meshes.

[0042] The present invention also provides the use of the above-mentioned aqueous stearic acid emulsion in-situ modified heavy calcium carbonate in the fields of plastics, coatings or adhesives.

[0043] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0044] The ball mill used in Examples 1 to 3 and Comparative Examples 1 to 4 is a 2200×7500mm wet ball mill;

[0045] The stearic acid used was primary acid with a particle size of <0.5 mm;

[0046] The weight average molecular weight of the sodium polyacrylate used is 3800.

[0047] Example 1

[0048] The large calcite is washed and crushed into ore materials with a size of less than 200 mm, the ore materials with other colors other than white mixed in the ore materials are selected and removed, and the qualified ore materials are crushed for the second time to obtain calcium carbonate ore materials with a size of less than 2 mm;

[0049] Emulsifier (225g sorbitan monooleate, 75g sucrose triester stearate, 75g sodium polyacrylate, 75g sodium lauryl sulfate), defoamer (184.62g methyl silicone oil, 3.3g fumed silica, 39.56g polysorbate 80 and 72.52g polyvinyl alcohol) and 1.026kg water were added to a reactor, heated to 75°C, and stirred for 20min, with the rotation speed maintained at 600rpm, so that the emulsifier and defoamer were completely dissolved in water; 9kg stearic acid was added, and stirring was continued for 30min, so that the stearic acid was completely melted into a liquid state and fully mixed with the emulsifier; 5.13kg water was added, and stirred for 20min to form a water-in-oil emulsion; finally, the remaining 14.364kg water was added, and after stirring for 30min, heating was stopped, and stirring was cooled to room temperature to obtain an aqueous stearic acid emulsion;

[0050] The calcium carbonate ore is transported to a ball mill for grinding, and at the same time, 30 kg of aqueous stearic acid emulsion (the mass of which is 1.5% of the mass of the calcium carbonate ore) is evenly sprayed onto the surface of the calcium carbonate ore in the ball mill through a wet spray device, and the surface of the calcium carbonate ore is coated and then ground and modified (the rotation speed is 50 rpm, and the time is 20 min) to obtain an activated calcium carbonate powder;

[0051] The modified powder was classified with a frequency of a classifying wheel of 20 Hz. After classification, the powder was collected by a bag filter and cooled to room temperature to obtain the aqueous stearic acid emulsion in-situ modified heavy calcium carbonate of Example 1 with a fineness of 1250 mesh.

[0052] Example 2

[0053] The large calcite is washed and crushed into ore materials with a size of less than 200 mm, the ore materials with other colors other than white mixed in the ore materials are selected and removed, and the qualified ore materials are crushed for the second time to obtain calcium carbonate ore materials with a size of less than 2 mm;

[0054] Emulsifier (225g sorbitan monooleate, 112.5g sucrose triester stearate, 60g sodium polyacrylate, 52.5g sodium lauryl sulfate), defoamer (184.62g methyl silicone oil, 3.3g fumed silica, 39.56g polysorbate 80 and 72.52g polyvinyl alcohol) and 1.026kg water were added to a reactor, heated to 75°C, and stirred for 20min, with the rotation speed maintained at 600rpm, so that the emulsifier and defoamer were completely dissolved in water; 9kg stearic acid was added, and stirring was continued for 30min, so that the stearic acid was completely melted into a liquid state and fully mixed with the emulsifier; 5.13kg water was added, and stirred for 20min to form a water-in-oil emulsion; finally, the remaining 14.364kg water was added, and after stirring for 30min, heating was stopped, and stirring was cooled to room temperature to obtain an aqueous stearic acid emulsion;

[0055] The calcium carbonate ore is transported to a ball mill for grinding, and at the same time, 30 kg of aqueous stearic acid emulsion (the mass of which is 1.5% of the mass of the calcium carbonate ore) is evenly sprayed onto the surface of the calcium carbonate ore in the ball mill through a wet spray device, and the surface of the calcium carbonate ore is coated and then ground and modified (the rotation speed is 50 rpm, and the time is 20 min) to obtain an activated calcium carbonate powder;

[0056] The modified powder was classified with a frequency of a classifying wheel of 20 Hz. After classification, the powder was collected by a bag filter and cooled to room temperature to obtain the aqueous stearic acid emulsion in-situ modified heavy calcium carbonate of Example 2 with a fineness of 1250 mesh.

[0057] Example 3

[0058] The large calcite is washed and crushed into ore materials with a size of less than 200 mm, the ore materials with other colors other than white mixed in the ore materials are selected and removed, and the qualified ore materials are crushed for the second time to obtain calcium carbonate ore materials with a size of less than 2 mm;

[0059] Emulsifier (180g sorbitan monooleate, 120g sucrose triester stearate, 60g sodium polyacrylate, 60g sodium lauryl sulfate), defoamer (147.69g methyl silicone oil, 2.64g fumed silica, 31.65g polysorbate 80 and 58.02g polyvinyl alcohol) and 757.8g water were added to a reactor, heated to 75°C, and stirred for 20min, with the rotation speed maintained at 600rpm, so that the emulsifier and defoamer were completely dissolved in water; 8.4kg stearic acid was added, and stirring was continued for 30min, so that the stearic acid was completely melted into a liquid state and fully mixed with the emulsifier; 3.789kg of water was added, and stirred for 20min to form a water-in-oil emulsion; finally, the remaining 10.6092kg of water was added, and after stirring for 30min, heating was stopped, and stirring was cooled to room temperature to obtain an aqueous stearic acid emulsion;

[0060] The calcium carbonate material is transported to a ball mill for grinding, and at the same time, 24 kg of aqueous stearic acid emulsion (the mass of which is 1.2% of the mass of the calcium carbonate material) is uniformly sprayed onto the surface of the calcium carbonate material in the ball mill through a wet spray device, and the surface of the calcium carbonate material is coated and then ground and modified (the rotation speed is 50 rpm, and the modification time is 20 min) to obtain an activated calcium carbonate powder;

[0061] The modified powder was classified with a frequency of a classifying wheel of 20 Hz. After classification, the powder was collected by a bag filter to obtain the aqueous stearic acid emulsion in-situ modified heavy calcium carbonate of Example 3 with a fineness of 1250 mesh.

[0062] Comparative Example 1

[0063] The only difference from Example 1 is:

[0064] The mass of the aqueous stearic acid emulsion is 1.0% of the mass of the calcium carbonate ore;

[0065] The water-based stearic acid emulsion in-situ modified heavy calcium carbonate of Comparative Example 1 was obtained, with a moisture content of 0.18%, an activation degree of 87.7%, and an oil absorption value of 15 mL / 100 g; because the oil absorption value was >14 mL / 100 g, the product was unqualified and was returned for reprocessing.

[0066] Comparative Example 2

[0067] The only difference from Example 1 is:

[0068] Based on 100% of the mass of the aqueous stearic acid emulsion, the mass of the stearic acid is 25%;

[0069] The water-based stearic acid emulsion in-situ modified heavy calcium carbonate of Comparative Example 2 was obtained, with a moisture content of 0.42%, an activation degree of 83.4%, and an oil absorption value of 16 mL / 100 g; because the moisture content was > 0.3% and the oil absorption value was > 14 mL / 100 g, the product was unqualified and was returned for reprocessing.

[0070] Comparative Example 3

[0071] The only difference from Example 1 is:

[0072] Sodium polyacrylate is not added to the aqueous stearic acid emulsion;

[0073] The water-based stearic acid emulsion in-situ modified heavy calcium carbonate of Comparative Example 3 was obtained, with a water content of 0.23%, an activation degree of 80.6%, and an oil absorption value of 18 mL / 100 g; because the oil absorption value was >14 mL / 100 g, the product was unqualified and was returned for reprocessing.

[0074] Comparative Example 4

[0075] The only difference from Example 1 is:

[0076] No sucrose triester stearate was added to the aqueous stearic acid emulsion;

[0077] The water-based stearic acid emulsion in-situ modified heavy calcium carbonate of Comparative Example 4 was obtained, with a moisture content of 0.21%, an activation degree of 84.0%, and an oil absorption value of 16 mL / 100 g; because the oil absorption value was >14 mL / 100 g, the product was unqualified and was returned for reprocessing.

[0078] Performance measurement

[0079] 1. The water content, activation degree and oil absorption value of the in-situ modified heavy calcium carbonate obtained by the aqueous stearic acid emulsion obtained in the above Examples 1 to 3 and Comparative Examples 1 to 4 were measured by the following method. The measurement results are shown in Table 1.

[0080] Moisture (%): Refer to the 105℃ determination method in "GB_T19281-2014 Calcium Carbonate Analysis Method". The product factory acceptance standard is moisture ≤ 0.3%.

[0081] Activation degree (%): Refer to the activation degree determination method in "GB_T19281-2014 Calcium Carbonate Analysis Method", the product factory acceptance standard is activation degree ≤ 85%.

[0082] Oil absorption value (mL / 100g): Refer to the oil absorption value determination method in "GB_T19281-2014 Calcium Carbonate Analysis Method". The product factory acceptance standard is oil absorption value ≤14mL / 100g.

[0083] Table 1 Performance measurement results of modified heavy calcium obtained from Examples 1 to 3 and Comparative Examples 1 to 4

[0084] Detection indicators Moisture (%) Activation degree (%) Oil absorption value (mL / 100g) Example 1 0.16 93.6 11 Example 2 0.19 93.2 11 Example 3 0.15 91.1 12 Comparative Example 1 0.18 87.7 15 Comparative Example 2 0.42 83.4 16 Comparative Example 3 0.23 80.6 18 Comparative Example 4 0.21 84.0 16

[0085] As can be seen from Table 1, the activation degree of the in-situ modified heavy calcium carbonate prepared by the aqueous stearic acid emulsion of the present invention is above 80%, especially the heavy calcium carbonate prepared in Examples 1 to 3, the activation degree is above 90%, the oil absorption value is below 12 mL / 100 g, and the water content is below 0.25%, which has excellent activation performance; the calcium carbonate powder products prepared in Comparative Examples 1 to 4 have unqualified oil absorption values, and some of them have excessive water content, and need to be downgraded or sent back for reprocessing.

[0086] Comparing Example 1 and Comparative Example 1, it can be seen that the addition amount of the aqueous stearic acid emulsion is reduced by 0.5%, the corresponding water content of the modified heavy calcium carbonate obtained is reduced by 0.02%, the activation degree is reduced by 5.9%, and the oil absorption value is increased by 4mL / 100g; this is because the addition amount of the aqueous stearic acid emulsion is reduced, and the effective ingredients coated on the surface of the calcium carbonate ore are reduced accordingly, resulting in a reduction in the coverage rate of the calcium carbonate ore and a reduction in the activation degree of the modified heavy calcium carbonate obtained.

[0087] Comparative Example 1 and Comparative Example 2 show that the stearic acid content in the aqueous stearic acid emulsion is reduced by 5%, the corresponding modified heavy calcium carbonate moisture content is increased by 0.26%, the activation degree is reduced by 10.2%, and the oil absorption value is increased by 5 ml / 100 g; this is because stearic acid in the aqueous stearic acid emulsion is the main effective ingredient for surface modification of calcium carbonate ore, and a reduction in stearic acid content means that the concentration of the emulsion is reduced and the moisture content is increased, which results in the moisture content and oil absorption value of the modified heavy calcium carbonate exceeding the standard and the activation degree being reduced.

[0088] Comparative Example 1 and Comparative Example 3 show that sodium polyacrylate is not added to the aqueous stearic acid emulsion, and the moisture content of the corresponding modified heavy calcium carbonate increases by 0.07%, the activation degree decreases by 13.0%, and the oil absorption value increases by 7 mL / 100 g; this is because sodium polyacrylate is a good dispersant and surfactant, which can evenly disperse the micelles in the aqueous stearic acid emulsion to form a uniform and stable colloid, which is conducive to the full mixing and coating modification of the emulsion and the calcium carbonate ore; on the other hand, the long-chain molecular structure of sodium polyacrylate itself and a large number of positive and negative charge units can effectively reduce the surface energy of the calcium carbonate ore, prevent the agglomeration of the heavy calcium carbonate powder microparticles, and play a role in grinding aid and modification during the grinding process of the calcium carbonate ore, thereby improving the uniformity, stability and dispersibility of the modified heavy calcium carbonate obtained.

[0089] Comparative Example 1 and Comparative Example 4 show that, without adding sucrose stearate to the aqueous stearic acid emulsion, the moisture content of the corresponding modified heavy calcium carbonate increased by 0.05%, the activation decreased by 9.6%, and the oil absorption value increased by 5 mL / 100 g; this is because sucrose stearate is a surfactant containing a large number of hydroxyls, which are combined with the surface hydroxyls of calcium powder through hydrogen bonds, and then a water molecule is removed to form a stable covalent bond so that sucrose stearate is firmly coated on the surface of calcium carbonate microparticles, which can effectively improve the coating rate of the additive on calcium carbonate, thereby improving the activation and stability of the modified heavy calcium carbonate obtained.

[0090] 2. Product stability performance determination: The water-based stearic acid emulsion in-situ modified heavy calcium carbonate obtained in Examples 1 to 3 above was sealed and stored in a dry environment at room temperature for 100 days. The moisture, activation degree and oil absorption value of the product after storage were measured, and the range of change was calculated. The results are shown in Table 2.

[0091] Judgment criteria: Moisture content variation range ≤ ±0.1%, activation degree variation range ≤ ±3%, oil absorption value variation range ≤ ±1, indicating that the product has good stability.

[0092] Table 2 Index measurement results of modified heavy calcium obtained in Examples 1 to 3 before and after storage

[0093] Detection indicators Moisture (%) Activation degree (%) Oil absorption value (mL / 100g) Example 1 Before storage 0.16 93.6 11 Example 1 After storage 0.18 93.3 11 Range of variation +0.02 -0.3 0 Example 2 Before storage 0.19 93.2 11 Example 2 After storage 0.19 93.1 11 Range of variation 0 -0.1 0 Example 3 Before storage 0.15 91.1 12 Example 3 After storage 0.18 91.5 12 Range of variation +0.03 +0.4 0

[0094] As can be seen from Table 2, after the aqueous stearic acid emulsion in-situ modified heavy calcium carbonate obtained in Examples 1 to 3 was sealed and stored in a dry environment at room temperature for 100 days, the moisture change range was less than 0.03%, the activation degree change range was less than ±0.4%, and the oil absorption value change range was 0, indicating that the aqueous stearic acid emulsion in-situ modified heavy calcium carbonate obtained in Examples 1 to 3 has good stability.

[0095] It can be seen from the above embodiments that the present invention provides an aqueous stearic acid emulsion in-situ modified heavy calcium carbonate, by scientifically compounding the aqueous stearic acid emulsion, stearic acid, sorbitan monooleate, stearic acid sucrose triester, sodium polyacrylate, sodium lauryl sulfate and the defoamer in the aqueous stearic acid emulsion produce a synergistic effect, thereby improving the activation modification effect of the heavy calcium carbonate product; the obtained modified heavy calcium carbonate has high activation degree, good dispersibility and stability, and low oil absorption value.

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing heavy calcium carbonate modified in situ by aqueous stearic acid emulsion, characterized in that: The following steps are involved: The large calcite is subjected to primary crushing, ore dressing and secondary crushing in sequence to obtain calcium carbonate ore; The calcium carbonate ore is mixed with an aqueous stearic acid emulsion, and ground and modified to obtain an active calcium carbonate powder; Classifying the active calcium carbonate powder to obtain water-based stearic acid emulsion in-situ modified heavy calcium carbonate; The aqueous stearic acid emulsion consists of stearic acid, an emulsifier, a defoamer and water; The emulsifier includes sorbitan monooleate, sucrose triester stearate, sodium polyacrylate and sodium lauryl sulfate; The defoaming agent comprises methyl silicone oil, fumed silica, polysorbate 80 and polyvinyl alcohol.

2. The preparation method according to claim 1, characterized in that: The CaCO3 content in the macrocalcite is ≥98%.

3. The preparation method according to claim 1, characterized in that: The mass of the aqueous stearic acid emulsion is 1.2-2.0% of the mass of the calcium carbonate ore.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the stearic acid, emulsifier, defoamer and water is (25-35):(1-5):(0.1-1):(59-73.9).

5. The preparation method according to claim 1, characterized in that: The mass ratio of sorbitan monooleate, sucrose triester, sodium polyacrylate and sodium lauryl sulfate is (2-6):(1-4):(1-3):(1-3).

6. The preparation method according to claim 1, characterized in that: The mass ratio of the methyl silicone oil, fumed silica, polysorbate 80 and polyvinyl alcohol is (25-30):(0.3-0.8):(3-9):(10-15).

7. The preparation method according to claim 1, characterized in that: The particle size of the stearic acid is less than 0.5 mm; the weight average molecular weight of the sodium polyacrylate is 3500-4000.

8. The preparation method according to claim 1, characterized in that: The frequency of the classifier used in the classification is 15 to 30 Hz.

9. The aqueous stearic acid emulsion in-situ modified heavy calcium carbonate prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The mesh number of the water-based stearic acid emulsion in-situ modified heavy calcium carbonate is 400 to 2500 meshes.

10. Use of the water-based stearic acid emulsion in-situ modified heavy calcium carbonate according to claim 9 in the fields of plastics, coatings or adhesives.