Preparation method of polymer additive for producing superfine ground calcium carbonate

Abstract

The invention discloses a preparation method of a polymer additive for producing superfine heavy calcium carbonate, and belongs to the field of fine chemical engineering. The preparation method comprises the following steps: (1) uniformly stirring a polyether compound and water to obtain a base material solution; (2) uniformly mixing water and the copolymerized small monomer to obtain a material A; (3) uniformly mixing a reducing agent, a chain transfer agent and water to obtain a material B; (4) adjusting the temperature of the base material solution, adding an oxidizing agent, stirring for 2-7 minutes, then adding a catalyst, stirring for 2-7 minutes, and starting to dropwise add the material A and the material B at a constant speed; and (5) after dropwise adding is finished, carrying out heat preservation and stirring, and adding a pH regulator to regulate the pH value of the solution to 5.0-6.0, so as to obtain the polymer additive. The polymer additive can promote grinding, reduce the particle size of the superfine heavy calcium carbonate, improve the dispersity of the superfine heavy calcium carbonate and increase the compatibility of the superfine heavy calcium carbonate and an organic matrix, and is beneficial to production, storage and transportation of the superfine heavy calcium carbonate.

Description

Technical Field

[0001] This invention relates to a method for preparing a polymeric additive for the production of ultrafine heavy calcium carbonate, belonging to the field of fine chemicals. Background Technology

[0002] my country possesses abundant calcium carbonate resources and has developed a relatively complete industrial chain and a large industrial scale. However, the calcium carbonate industry is mainly concentrated in the primary processing stage, with a large proportion of low- and mid-end products and a shortage of high-value-added products, resulting in low industry profits. Therefore, developing high-value-added products is currently the main development goal. Ultrafine heavy calcium carbonate is a high-value-added product produced by mechanically crushing, grinding, and classifying calcium carbonate. Due to its excellent performance, it is widely used in industries such as rubber, plastics, coatings, and papermaking.

[0003] Currently, the production processes for ultrafine heavy calcium carbonate are mainly divided into dry and wet processes. Compared to the dry process, the wet process produces ultrafine heavy calcium carbonate with a finer particle size, but the yield is lower and the energy consumption is higher. Therefore, grinding aids are usually added during the wet grinding process to reduce energy consumption and optimize the particle size of the ultrafine heavy calcium carbonate. Ultrafine heavy calcium carbonate is commonly used in rubber and plastics, requiring good compatibility with the organic matrix. Therefore, existing processes usually require modification of the ultrafine heavy calcium carbonate after grinding, which not only increases production time but also makes the process more complex. Furthermore, compatibility issues exist between some grinding aids and modifiers, further increasing production costs.

[0004] Therefore, providing a grinding aid that can both promote grinding and reduce the particle size of ultrafine heavy calcium carbonate, and improve the compatibility of ultrafine heavy calcium carbonate with organic matrices, is an urgent problem to be solved in the industrial production of ultrafine heavy calcium carbonate. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a polymeric additive for the production of ultrafine heavy calcium carbonate. This additive can reduce the particle size of ultrafine heavy calcium carbonate and improve the compatibility of ultrafine heavy calcium carbonate with organic matrix.

[0006] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: A method for preparing a polymeric additive for the production of ultrafine heavy calcium carbonate includes the following steps: (1) Add the polyether compound to a four-necked flask, add water, stir well to obtain the base solution; (2) Mix water and copolymer monomers evenly to obtain material A; (3) Mix the reducing agent, chain transfer agent and water evenly to obtain material B; (4) Adjust the temperature of the base solution, add the oxidizing agent and stir for 2-7 min, then add the catalyst and stir for 2-7 min, and then start adding A and B at a constant speed under stirring; (5) After the addition is completed, continue to heat and stir, add a pH adjuster to adjust the pH of the solution to 5.0-6.0, and then the high-molecular-weight additive is obtained.

[0007] Further, in step (1), the polyether compound is ethylene glycol monovinyl polyoxyethylene ether (EPEG) or 4-hydroxybutyl vinyl polyethylene glycol ether (VPEG).

[0008] Further, in step (1), the average molecular weight of the polyether compound is 800-1000, and the end-capping group is phosphoric acid or hydroxyl.

[0009] Further, in step (1), the mass fraction of the polyether compound in the base solution is 45-50 wt.%.

[0010] Further, in step (2), the copolymerization small monomer is composed of monomer A and monomer B, monomer A is one or both of acrylic acid and maleic anhydride, and monomer B is one or both of vinyl triethoxysilane and p-styrene sulfonic acid sodium.

[0011] Further, the mass ratio of monomer A to monomer B is (4-5):(0-1).

[0012] Further, in step (2), the molar ratio of the copolymerization small monomer to the polyether compound is (3.0-5.0):1.

[0013] Further, in step (3), the reducing agent is vitamin C or chalk powder; and the chain transfer agent is one or both of mercaptopropionic acid, mercaptoethanol, and sodium hypophosphite.

[0014] Further, in step (3), the amount of the reducing agent added is 0.05-0.5% of the total mass of the polyether compound and the copolymerization small monomer; and the amount of the chain transfer agent added is 0.2-0.7% of the total mass of the polyether compound and the copolymerization small monomer.

[0015] Further, in step (4), the temperature of the base solution is heated to 15-25°C.

[0016] Further, in step (4), the oxidizing agent is one of hydrogen peroxide, ammonium persulfate, and potassium persulfate; and the catalyst is ferrous sulfate.

[0017] Further, in step (4), the amount of the oxidizing agent added is 0.1-1.0% of the total mass of the polyether compound and the co-polymerized monomer; the amount of the catalyst added is 0-0.2% of the oxidizing agent. The amount of the catalyst depends on the initial reaction temperature, and when the initial reaction temperature is high, the catalyst can not be added.

[0018] Further, in step (4), the dropping time of the A material is 50-75 min, and the dropping time of the B material is 60-90 min.

[0019] Further, the temperature increase range of the process of dropping the A and B materials in step (4) and the process of heat preservation and stirring in step (5) is controlled within 10-15℃.

[0020] Further, in step (5), the heat preservation and stirring time is 45-75 min.

[0021] Further, in step (5), the pH regulator is sodium hydroxide or potassium hydroxide.

[0022] Since the surface energy of calcium carbonate particles is high, the particles are prone to spontaneous agglomeration to reduce the surface energy. The additive in the present application covers the surface of the calcium carbonate particles by adsorption, significantly reduces the surface energy of the particles, reduces the agglomeration driving force, and at the same time enables the particles to be more uniformly contacted with the grinding medium, improves the grinding efficiency, and reduces the particle size. Among them, acrylic acid and maleic anhydride provide carboxyl groups, and sodium p-styrene sulfonate provides sulfonic acid groups. These strong polar groups can be firmly adsorbed on the surface of the calcium carbonate particles through ionic bonds or hydrogen bonds, and through electrostatic repulsion, the particles are prevented from agglomerating due to van der Waals force, ensuring the grinding effect; the polyether segment in the polyether compound is a flexible long chain with large steric hindrance, which can avoid the secondary agglomeration of the particles, thereby effectively reducing the particle size and improving the dispersion effect of the particles. The steric hindrance of the polyether segment and the electrostatic repulsion of the polar groups synergistically act, significantly reducing the amount of grinding medium and energy consumption, improving the efficiency of the grinding process, promoting grinding, and reducing the particle size of the superfine heavy calcium carbonate, while improving the uniform dispersion of the particles.

[0023] In addition, the high molecular additive forms a "polarity gradient" through multiple functional groups; the strong polar carboxyl groups, sulfonic acid groups, and silicon hydroxyl groups can be combined with the hydroxyl groups on the surface of the inorganic phase calcium carbonate; the polyether segment has moderate polarity and certain "amphiphilicity", which can reduce the interfacial tension between the calcium carbonate and the organic phase; the non-polar groups such as vinyl and alkyl groups can be combined with the organic phase. This gradient structure eliminates the polarity mutation between the inorganic phase (high polarity) and the organic phase (low polarity), disperses the interfacial stress, significantly improves the compatibility, and realizes the uniform dispersion of the superfine heavy calcium carbonate in the organic material and the performance improvement.

[0024] Compared with the prior art, the present application has the following advantages: (1) The polymer additive prepared by the application contains groups such as carboxyl, silane and sulfonic acid in the molecular chain, can be combined with calcium carbonate, has a modifying effect in the production process of superfine heavy calcium carbonate, effectively reduces particle collision and agglomeration, and ensures the dispersion stability of superfine heavy calcium carbonate.

[0025] (2) The polymer additive prepared by the application has strong electrostatic repulsion and steric hindrance, and the two synergistically promote the grinding efficiency and reduce the energy consumption, can effectively reduce the particle size of superfine heavy calcium carbonate, ensure the dispersibility of superfine heavy calcium carbonate in the slurry solution, and reduce the sedimentation volume, which is beneficial to the production, storage and transportation of superfine heavy calcium carbonate.

[0026] (3) The polymer additive is prepared by water-based free radical polymerization reaction of polyether compounds and copolymerized small monomers in an oxidation-reduction system, and the multi-functional groups in the additive eliminate the polarity mutation between heavy calcium carbonate and the organic matrix, disperse the interface stress, and improve the compatibility of superfine heavy calcium carbonate and the organic matrix.

[0027] (4) The application selects water as the solvent, the selected raw materials have good water solubility, the preparation method is simple, is more environmentally friendly and safe compared with the use of organic solvents, is also beneficial to reduce the production cost and increase the economic benefit, and the prepared polymer additive can be directly used for wet grinding of superfine heavy calcium carbonate without additional emulsification or dispersion steps, and the operation is simple. DETAILED DESCRIPTION

[0028] Example 1 A preparation method of a polymer additive for superfine heavy calcium carbonate production, comprising the following steps: (1) EPEG is added to a four-necked flask, water is added, and stirring is uniform to obtain a base solution; (2) Water, acrylic acid and vinyl triethoxysilane are uniformly mixed to obtain A material; (3) Vitamin C, mercaptoethanol and water are uniformly mixed to obtain B material; (4) The temperature of the base solution is adjusted to 25 DEG C, hydrogen peroxide is added and stirred for 5 min, then A and B materials are uniformly added at a constant speed under stirring, the dropping time of A material is 75 min, the dropping time of B material is 90 min, and the temperature increasing range during the dropping process is controlled within 10-15 DEG C; (5) After the dropping is completed, the temperature is kept stirring for 50 min, the temperature increasing range is controlled within 10-15 DEG C, sodium hydroxide is added to adjust the pH of the solution to 5.0-6.0, and the polymer additive is obtained; The high polymer additive, each component is as follows: by mass fraction, EPEG 30.5%, acrylic acid 8.3%, vinyl triethoxysilane 0.5%, hydrogen peroxide 0.22%, vitamin C 0.07%, mercaptoethanol 0.15%, sodium hydroxide 1.0%, and the rest is deionized water.

[0029] Example 2 A preparation method of a high polymer additive for superfine heavy calcium carbonate production, comprising the following steps: (1) EPEG is added to a four-necked flask, and water is added, and stirred uniformly to obtain a base solution; (2) Water, acrylic acid and sodium p-styrenesulfonate are mixed uniformly to obtain A material; (3) Vitamin C, sodium hypophosphite and water are mixed uniformly to obtain B material; (4) The temperature of the base solution is adjusted to 15 DEG C, hydrogen peroxide is added and stirred for 5 min, then ferrous sulfate is added and stirred for 5 min, and then A and B materials are added at a uniform speed under stirring, the adding time of A material is 50 min, the adding time of B material is 60 min, and the temperature increasing range during the adding process is controlled within 10-15 DEG C; (5) After the adding is completed, the temperature is kept for 50 min under stirring, the temperature increasing range is controlled within 10-15 DEG C, and potassium hydroxide is added to adjust the pH of the solution to 5.0-6.0, thereby obtaining the high polymer additive; The high polymer additive, each component is as follows: by mass fraction, EPEG 30.5%, acrylic acid 8.0%, sodium p-styrenesulfonate 1%, hydrogen peroxide 0.22%, ferrous sulfate 0.0002%, vitamin C 0.07%, sodium hypophosphite 0.25%, potassium hydroxide 1.0%, and the rest is deionized water.

[0030] Example 3 A preparation method of a high polymer additive for superfine heavy calcium carbonate production, comprising the following steps: (1) EPEG is added to a four-necked flask, and water is added, and stirred uniformly to obtain a base solution; (2) Water, maleic anhydride and vinyl triethoxysilane are mixed uniformly to obtain A material; (3) Vitamin C, mercaptoethanol and water are mixed uniformly to obtain B material; (4) The temperature of the base solution is adjusted to 20 DEG C, ammonium persulfate is added and stirred for 5 min, and then A and B materials are added at a uniform speed under stirring, the adding time of A material is 60 min, the adding time of B material is 75 min, and the temperature increasing range during the adding process is controlled within 10-15 DEG C; (5) After the end of the drop, keep stirring for 50 min, control the temperature growth range within 10-15℃, and add sodium hydroxide to adjust the solution pH to 5.0-6.0, and the high molecular additive is obtained; The high molecular additive comprises the following components by mass fraction: EPEG 30.5%, maleic anhydride 9.5%, vinyl triethoxysilane 0.5%, ammonium persulfate 0.25%, vitamin C 0.1%, mercaptoethanol 0.15%, sodium hydroxide 1.0%, and the rest is deionized water.

[0031] Example 4 A preparation method of a high molecular additive for superfine heavy calcium carbonate production comprises the following steps: (1) VPEG is added to a four-necked flask, and water is added, and stirred uniformly to obtain a base solution; (2) Water, acrylic acid, maleic anhydride, and vinyl triethoxysilane are mixed uniformly to obtain A material; (3) Calcined white powder, sodium hypophosphite, and water are mixed uniformly to obtain B material; (4) The temperature of the base solution is adjusted to 25℃, potassium persulfate is added and stirred for 5 min, and then A and B materials are added at a uniform speed under stirring, the dropping time of A material is 60 min, the dropping time of B material is 70 min, and the temperature growth range during the dropping process is controlled within 10-15℃; (5) After the end of the drop, keep stirring for 50 min, control the temperature growth range within 10-15℃, and add sodium hydroxide to adjust the solution pH to 5.0-6.0, and the high molecular additive is obtained; The high molecular additive comprises the following components by mass fraction: VPEG 30.5%, acrylic acid 4.0%, maleic anhydride 4.5%, vinyl triethoxysilane 1.0%, potassium persulfate 0.25%, calcined white powder 0.1%, sodium hypophosphite 0.15%, sodium hydroxide 1.0%, and the rest is deionized water.

[0032] Example 5 A preparation method of a high molecular additive for superfine heavy calcium carbonate production comprises the following steps: (1) VPEG is added to a four-necked flask, and water is added, and stirred uniformly to obtain a base solution; (2) Water, acrylic acid, maleic anhydride, vinyl triethoxysilane, and sodium p-styrenesulfonate are mixed uniformly to obtain A material; (3) Calcined white powder, mercaptopropionic acid, and water are mixed uniformly to obtain B material; (4) Adjust the temperature of the base solution to 20℃, add potassium persulfate and stir for 5 minutes. Then, start to add A and B materials at a constant rate while stirring. The addition time of A material is 60 minutes and the addition time of B material is 70 minutes. The temperature increase during the addition process is controlled within 10-15℃. (5) After the addition is completed, keep warm and stir for 50 minutes, and control the temperature increase within 10-15℃. Add sodium hydroxide to adjust the pH of the solution to 5.0-6.0 to obtain the polymer additive. The polymeric additives consist of the following components by mass fraction: VPEG 30.5%, acrylic acid 3.0%, maleic anhydride 5.0%, vinyltriethoxysilane 1.0%, sodium p-styrene sulfonate 0.5%, potassium persulfate 0.25%, sodium bicarbonate 0.1%, mercaptopropionic acid 0.15%, sodium hydroxide 1.0%, and the remainder is deionized water.

[0033] Experimental Example 1 Ultrafine heavy calcium carbonate was prepared using a horizontal planetary ball mill with different additives. The addition of the polymeric additives from Examples 1-3 resulted in ultrafine heavy calcium carbonate preparations, designated as groups A, B, and C. Ultrafine heavy calcium carbonate was prepared without additives, designated as group D. Ultrafine heavy calcium carbonate was prepared with sodium polyacrylate (average molecular weight approximately 3500), designated as group E. The raw material was 500-mesh calcium carbonate powder, prepared into a slurry with a solid content of 70-80 wt.%. The additive dosage was 1% of the dry weight of the raw calcium carbonate. After grinding and drying, the ultrafine heavy calcium carbonate product was tested according to GB / T19281-2014 for particle size, oil absorption value, viscosity, and sedimentation volume. Viscosity was measured using an NDJ-5S viscometer. The test results are shown in Table 1.

[0034] Table 1. Performance Indicators of Ultrafine Heavy Calcium Carbonate As shown in Table 1, compared with the preparation of ultrafine heavy calcium carbonate without the addition of additives, the D of ultrafine heavy calcium carbonate prepared after adding the polymeric additives of Examples 1-3 is significantly higher. 90 With a particle size ≤2.2μm, smaller particle size, lower oil absorption value and viscosity, and a significantly increased sedimentation volume, it is evident that the ultrafine heavy calcium carbonate prepared by adding the polymeric additive of this invention has smaller particle size, better dispersibility, and no agglomeration. Currently, sodium polyacrylate is a commonly used grinding aid in existing technologies. Compared with ultrafine heavy calcium carbonate prepared without additives, the particle size, oil absorption value, and viscosity decrease, and the sedimentation volume increases in the addition of sodium polyacrylate as an additive, but all its properties are significantly inferior to those prepared by the polymeric additive of this invention. This indicates that the polymeric additive prepared by this invention has excellent grinding and dispersing properties, good compatibility with organic matrices, and is beneficial for the production, storage, and transportation of ultrafine heavy calcium carbonate.

Claims

1. A method for preparing a high molecular additive for the production of ultrafine ground calcium carbonate, characterized in that: The method comprises the following steps: (1) adding a polyether compound into a four-necked flask, adding water, and stirring to obtain a base solution; (2) mixing water and a copolymerization monomer to obtain A material; (3) mixing a reducing agent, a chain transfer agent and water to obtain B material; (4) adjusting the temperature of the base solution, adding an oxidizing agent and stirring for 2-7 min, then adding a catalyst and stirring for 2-7 min, and then starting to add A material and B material at a constant speed under stirring; (5) continuing to heat and stir after the addition is completed, adding a pH regulator to adjust the pH of the solution to 5.0-6.0, thereby obtaining a high-molecular-weight additive.

2. The method for preparing the high molecular additive for the production of ultrafine heavy calcium carbonate according to claim 1, characterized in that: In step (1), the polyether compound is ethylene glycol monovinyl polyoxyethylene ether or 4-hydroxybutyl vinyl polyethylene glycol ether.

3. The method for preparing the high molecular additive for the production of ultrafine heavy calcium carbonate according to claim 2, characterized in that: In step (1), the mass fraction of the polyether compound in the base solution is 45-50 wt.%.

4. The method for preparing the high molecular additive for the production of ultrafine heavy calcium carbonate according to claim 3, characterized in that: In step (2), the copolymerization monomer is composed of monomer A and monomer B, monomer A is one or both of acrylic acid and maleic anhydride, and monomer B is one or both of vinyl triethoxysilane and p-styrene sulfonic acid sodium.

5. The method for preparing the high molecular additive for the production of ultrafine heavy calcium carbonate according to claim 4, characterized in that: In step (2), the molar ratio of the copolymerization monomer to the polyether compound is (3.0-5.0):

1.

6. The method for preparing the high molecular additive for the production of ultrafine heavy calcium carbonate according to claim 5, characterized in that: In step (3), the reducing agent is vitamin C or chalk powder; the chain transfer agent is one or both of mercaptopropionic acid, mercaptoethanol and sodium hypophosphite; the adding amount of the reducing agent is 0.05-0.5% of the total mass of the polyether compound and the copolymerization monomer; and the adding amount of the chain transfer agent is 0.2-0.7% of the total mass of the polyether compound and the copolymerization monomer.

7. The method for preparing the high molecular additive for the production of ultrafine ground calcium carbonate according to claim 6, characterized in that: In step (4), the temperature of the base solution is adjusted to 15-25°C.

8. The method for preparing a high molecular additive for the production of ultrafine ground calcium carbonate according to claim 7, characterized in that: In step (4), the oxidizing agent is one of hydrogen peroxide, ammonium persulfate and potassium persulfate; the catalyst is ferrous sulfate; the adding amount of the oxidizing agent is 0.1-1.0% of the total mass of the polyether compound and the copolymerization monomer; and the adding amount of the catalyst is 0-0.2% of the oxidizing agent.

9. The method for preparing the high molecular additive for the production of ultrafine heavy calcium carbonate according to claim 8, characterized in that: In step (4), the adding time of the A material is 50-75 min, and the adding time of the B material is 60-90 min; and the temperature increase range during the whole adding process is controlled to be 10-15°C.

10. The method for preparing a high molecular additive for the production of ultrafine ground calcium carbonate according to claim 9, characterized in that: In step (5), the heat preservation and stirring time is 45-75 min; and the pH regulator is sodium hydroxide or potassium hydroxide.

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