Preparation method of nano calcium carbonate for TPR shoe material

Abstract

The application discloses a preparation method of nano calcium carbonate for TPR shoe materials, and comprises the following steps: S1, a mixed gas containing carbon dioxide is introduced into a calcium hydroxide suspension to perform a carbonation reaction, and when a downward trend of reaction conductivity appears, sodium cocoyl isethionate is added to continue the reaction; S2, when the conductivity returns to the conductivity level before the reaction, the mixed gas is stopped, and the suspension is subjected to high-speed emulsification and dispersion treatment; S3, after the emulsification is completed, the carbonation reaction is continued, and when the pH of the reaction system is less than or equal to 7.5, the nano calcium carbonate suspension is obtained; S4, the nano calcium carbonate suspension is sequentially added with an ethoxylated tallow alcohol, sodium stearate and a compound of zinc dialkyldithiophosphate to perform surface treatment; and S5, pressure filtration, drying, pulverization and sieving are performed, and the nano calcium carbonate is obtained. The nano calcium carbonate prepared by the method can be uniformly distributed in an SBS matrix, the adhesion between the calcium carbonate and the matrix is enhanced, and the processing fluidity of the SBS and the mechanical properties of the TPR shoe material are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of calcium carbonate preparation, in particular to a preparation method of nano calcium carbonate for TPR shoe materials. BACKGROUND

[0002] The TPR (Thermo Plastic Rubber) shoe material is generally a kind of high polymer material which is modified by blending a thermoplastic elastomer SBS (styrene-butadiene-styrene block copolymer) with other functional additives, and is formed into a shoe sole through processes such as extrusion, injection and mould pressing, and has the advantages of anti-skid, low-temperature resistance, strong bending property, good air permeability, small density, firm bonding strength and the like, and the waste material can be recycled, so the TPR shoe material is quickly valued and rapidly developed in the shoemaking industry. At present, the TPR shoe sole material is recognized by more and more manufacturers, merchants and consumers. The main purpose of adding fillers into the TPR shoe material is to reduce the cost and increase the hardness and wear resistance of the product. Commonly used fillers include white carbon black, calcium carbonate and talc powder. In recent years, with the continuous development of the shoemaking industry, the shoes are also developing towards diversification, functionalization and economy, and the requirements for the performance of the sole material are also continuously improved, so it is an important research direction to improve the mechanical properties of the TPR shoe sole material, reduce the cost and simplify the production process. On the basis of the existing material, the important way to realize the simplification of the production process, the reduction of the cost and the improvement of the performance of the sole material is to realize physical blending of the polymer material, filling of the inorganic filler, activation of the inorganic filler and optimization of the production process.

[0003] CaCO3 is an important inorganic chemical product which is cheap and easy to obtain, and is widely used in the rubber, plastic, papermaking, coating, sealant, ink, medicine and cosmetic industries, and has a very large demand. There are two shortcomings in the direct application of nano calcium carbonate in organic materials: one is that the particle surface energy is high and is in a thermodynamic unstable state, and is extremely easy to gather into a group, which directly affects the application effect of the nano particles; the other is that the surface of CaCO3 is hydrophilic and oleophobic, and is strongly polar, so it is difficult to uniformly disperse in the organic medium, and the bonding force between the CaCO3 and the matrix is weak, which easily causes interface defects and leads to the decline of the material performance.

[0004] Cheng Guojun et al. use a silane coupling agent (KH550) to modify the surface of superfine CaCO3, and prepare a superfine CaCO3 / SBS composite material through a direct blending method. After the surface treatment, the superfine CaCO3 can form a network structure in the SBS system, and the tensile property, hardness and heat resistance of the material are improved. When the content of CaCO3 is 10%, the composite material with excellent tensile strength, elongation at break and heat resistance can be obtained (Cheng Guojun, Yu Xiuhua, Tang Zhongfeng, Xu Chuyang; Preparation and property research of superfine CaCO3 / SBS composite material [J]. Materials Review B: Research Edition, 2011, 25: 106-109).

[0005] Chinese patent CN104109260A discloses a preparation method of TPR shoe material special transparent filler functional calcium carbonate. In the suspension of nano calcium carbonate slurry, a certain amount of mixed solution of sodium aluminate and sodium silicate is added, and carbonization hydrolysis is continued under stirring by passing kiln gas, then water-soluble silane coupling agent is added in an amount of 2-3% based on the weight of calcium carbonate, surface coating treatment is carried out for 0.1-1 hour, and finally the slurry is filtered to a filter cake with water content less than 45%, and dried at 90-110℃ to obtain TPR transparent filler functional calcium carbonate. The principle of the invention is to uniformly coat the surface of nano calcium carbonate with silicon-aluminum sol composite, and adjust the refractive index of the powder to be similar to that of TPR resin.

[0006] Chinese patent CN112778662A discloses a process for improving the performance of PVC rain shoes using calcium carbonate whiskers, comprising the following steps: (1) calcium carbonate whisker preparation; (2) white carbon black composite bromination of 1-butyl-3-methylimidazole; (3) raw material mixing and granulation; (4) injection molding. In step (1), dolomite is added to a resistance furnace for high-temperature calcination to obtain calcined dolomite; the calcined dolomite is ground into powder, which is then added to an ammonium salt solution, stirred for 40 minutes, filtered to remove the filter residue, and the reaction liquid is obtained; the reaction liquid is heated to 70-78℃ and kept for 15 minutes, then excess carbon dioxide is introduced into the reaction liquid, and the reaction is carried out for 2 hours, followed by filtration, washing, and drying to constant weight to obtain calcium carbonate whiskers.

[0007] Chinese patent CN101037550A discloses a preparation method of SBS / calcium carbonate nanocomposite. Nano calcium carbonate and surface treatment agent are added to an organic solvent and dispersed at 10-65℃ for 1-20 minutes, then the mixed emulsion is added to SBS glue liquid and dispersed at 30-70℃ for 10-30 minutes, the glue is cooked, and the organic solvent is removed to obtain SBS / calcium carbonate nanocomposite; or nano calcium carbonate is directly added to SBS glue liquid and dispersed for 30-60 minutes, the glue is cooked, and the organic solvent is removed to obtain SBS / calcium carbonate nanocomposite; nano calcium carbonate particles are dispersed in nanoscale in the composite material, thereby playing the role of inorganic nano-particle filling and improving the performance of SBS, improving its wear resistance, and reducing the cost.

[0008] Chinese patent CN116157454A discloses a composition formed from a material comprising calcium carbonate or magnesium carbonate and a surface treatment composition comprising at least one crosslinkable compound, a dry process for preparing such a composition, a curable elastomer mixture comprising an elastomer resin and the composition, a cured elastomer product formed from the curable elastomer mixture, a process for preparing the cured elastomer product, the use of at least one crosslinkable compound comprising at least two functional groups, wherein at least one functional group is suitable for crosslinking the elastomer resin and wherein at least one functional group is suitable for reacting with the material comprising calcium carbonate or magnesium carbonate, in the compounding of an elastomer formed from an elastomer resin and at least one material comprising calcium carbonate or magnesium carbonate as a filler, and an article formed from the cured elastomer product.

[0009] In summary, it can be found that there are few studies on nano calcium carbonate specially used for TPR shoe materials at present. Nano calcium carbonate is often used as a functional filler of TPR shoe materials, which has the effects of improving reinforcement and reducing cost. At present, there are two prominent problems of nano calcium carbonate on the market, which limit the large application of nano calcium carbonate in TPR shoe materials. First, the high surface energy of nano calcium carbonate can cause poor flowability of TPR shoe materials in the processing process; second, the surface of nano calcium carbonate is hydrophilic and oleophobic, and the strong polarity can cause weak adhesion between nano calcium carbonate and the matrix SBS in TPR shoe materials, which can easily cause interface defects and reduce the performance of materials. SUMMARY

[0010] The present application aims at the problems of poor dispersibility, poor flowability and poor compatibility with the matrix of nano calcium carbonate in the filling application of TPR shoe materials, and provides a preparation method of nano calcium carbonate for TPR shoe materials. The prepared nano calcium carbonate can be uniformly distributed in the SBS matrix, enhance the adhesion between calcium carbonate and the matrix, improve the processing flowability of SBS, and improve the mechanical properties of TPR shoe materials.

[0011] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0012] A preparation method of nano calcium carbonate for TPR shoe materials, comprising the following steps:

[0013] S1: Pumping the calcium hydroxide suspension into a high-speed carbonization tower, and passing a mixed gas containing carbon dioxide to perform carbonation reaction, while monitoring the changes of conductivity and pH value in the reaction process; when the reaction conductivity shows a downward trend (i.e. about to start gelation), immediately adding sodium cocoyl isethionate into the reaction system, and continuing the reaction;

[0014] S2: When the conductivity returns to the conductivity level before the reaction, stop passing the mixed gas, and pump the suspension into a high-speed emulsifier for high-speed emulsification and dispersion treatment;

[0015] S3: the suspension after emulsification in S2 is drawn back into the carbonation tower to continue the carbonation reaction, until the pH of the reaction system is less than or equal to 7.5, the reaction is stopped, and a nano calcium carbonate suspension is obtained;

[0016] S4: the nano calcium carbonate suspension obtained in S3 is added with ethoxylated tallow alcohol, stirred uniformly, and then added with a compound of sodium stearate and zinc dialkyldithiophosphate for surface treatment, to obtain a modified nano calcium carbonate suspension;

[0017] S5: the modified nano calcium carbonate suspension is subjected to pressure filtration, drying, pulverization and sieving, to obtain a nano calcium carbonate for TPR shoe materials.

[0018] Preferably, in step S1, the specific gravity of the calcium hydroxide suspension is 1.06-1.07.

[0019] Preferably, in step S1, the carbonation reaction conditions are as follows: a mixed gas of carbon dioxide with a volume concentration of 28-32% and air is introduced at a flow rate of 2 m 3 / h, and the reaction is carried out at a temperature of less than or equal to 27°C and a stirring speed of 700-900 r / min.

[0020] Preferably, in step S1, the sodium cocoyl isethionate is added in an amount of 0.05-0.10% by weight of the dry calcium carbonate.

[0021] Preferably, in step S2, the high-speed emulsification speed is 3000-3500 r / min, and the treatment time is 15-20 min.

[0022] Preferably, in step S4, the ethoxylated tallow alcohol is added in an amount of 0.05-0.08% by weight of the dry calcium carbonate.

[0023] Preferably, in step S4, the surface modification conditions are as follows: the modification is carried out at a stirring speed of 2500-3000 r / min and a temperature of 90°C for 20-30 min.

[0024] Preferably, in step S4, the sodium stearate is added in the compound in an amount of 2.5-2.9% by weight of the dry calcium carbonate, and the zinc dialkyldithiophosphate is added in an amount of 0.1-0.3% by weight of the dry calcium carbonate.

[0025] Preferably, in step S5, the drying temperature is 160-180°C, and the time is 2-3 h.

[0026] Preferably, in step S5, the sieving mesh size is 150-200 mesh.

[0027] Compared with the prior art, the application has the following advantages and beneficial effects:

[0028] 1. The present application utilizes the gelation point of the preparation of nano calcium carbonate by carbonization, at which time a large amount of nano calcium carbonate linear intermediates are generated, which have extremely high surface energy and are prone to agglomerate together. The addition of sodium cocoyl isethionate before the gelation point reduces the surface tension of the liquid surface, reduces the generation of static electricity, prevents the aggregation of charged particles, and thus improves the dispersibility of the nano calcium carbonate linear intermediates. At the end of gelation, high-speed emulsification and dispersion of the reaction system further improves the dispersibility of the linear intermediates, laying the foundation for the preparation of nano calcium carbonate with good dispersibility.

[0029] 2. The present application adds ethoxylated tallow alcohol before the surface treatment of nano calcium carbonate, which can improve the dispersibility of nano calcium carbonate in suspension, prevent agglomeration and adhesion between particles, and at the same time impart adhesion to nano calcium carbonate particles, providing conditions for the uniform coating of treating agent on the surface of each particle during the surface treatment of nano calcium carbonate, and laying the foundation for ideal surface treatment effect.

[0030] 3. The present application uses a combination of sodium stearate and zinc dialkyldithiophosphate as a surface treatment agent for nano calcium carbonate. Sodium stearate is a commonly used surface treatment agent for nano calcium carbonate, with moderate price and easy availability. Zinc dialkyldithiophosphate has good lubricating effect, which can increase the compatibility of nano calcium carbonate with the matrix, and also has certain wear resistance and antioxidant effect, which will improve the wear resistance and antioxidant property of SBS filled with nano calcium carbonate. The combination of sodium stearate and zinc dialkyldithiophosphate can ultimately improve the compatibility and dispersibility of nano calcium carbonate with SBS matrix, enhance the adhesion between calcium carbonate and matrix, and improve the processing fluidity of SBS.

[0031] 4. The nano calcium carbonate prepared by the present application can improve the mechanical properties of TPR shoe material, and the preparation method is simple and easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Scanning electron microscope picture of nano calcium carbonate prepared in Example 1;

[0033] Figure 2 Scanning electron microscope picture of nano calcium carbonate prepared in Example 2;

[0034] Figure 3 Scanning electron microscope picture of nano calcium carbonate prepared in Example 3;

[0035] Figure 4 Scanning electron microscope picture of nano calcium carbonate prepared in Example 4;

[0036] Figure 5 Scanning electron microscope picture of nano calcium carbonate prepared in Example 5;

[0037] Figure 6 Scanning electron microscope picture of nano calcium carbonate prepared for Comparative Example 1;

[0038] Figure 7 Scanning electron microscope picture of nano calcium carbonate prepared for Comparative Example 2;

[0039] Figure 8 Scanning electron microscope picture of nano calcium carbonate prepared for Comparative Example 3;

[0040] Figure 9 Scanning electron microscope picture of nano calcium carbonate prepared for Comparative Example 4;

[0041] Figure 10 Scanning electron microscope picture of nano calcium carbonate prepared for Comparative Example 5;

[0042] Figure 11 Scanning electron microscope picture of nano calcium carbonate prepared for Comparative Example 6. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0044] Embodiment 1

[0045] A preparation method of nano calcium carbonate for TPR shoe material, comprising the following steps:

[0046] S1: Pump the calcium hydroxide suspension with a specific gravity of 1.06 into a high-speed carbonation tower, control the temperature of the calcium hydroxide suspension to be 27℃, start stirring with a stirring speed of 700r / min, and introduce carbon dioxide mixed gas with a concentration of 28% and a flow rate of 2m 3 / h for reaction, and simultaneously monitor the conductivity and pH value of the reaction process. When the reaction conductivity first shows a downward trend (i.e. gelation is about to start), immediately add 0.05% of sodium cocoyl hydroxyethyl sulfonate based on the weight of calcium carbonate dry base to the reaction system, and continue the reaction;

[0047] S2: When the conductivity returns to the conductivity level before the reaction (i.e. gelation is over), stop introducing the carbon dioxide mixed gas, and pump the suspension into a high-speed emulsifier for high-speed emulsification and dispersion treatment at a speed of 3000r / min for 15min;

[0048] S3: the suspension after S2 emulsification is pumped back to the carbonation tower to continue the carbonation reaction, until the pH of the reaction system is ≤7.5, the reaction is stopped, and a nano calcium carbonate suspension with good dispersibility is obtained;

[0049] S4: the suspension obtained in S3 is subjected to surface treatment, the suspension is heated to 90℃, 0.08% of ethoxylated tallow alcohol based on the dry weight of calcium carbonate is first added to the suspension, stirred at 2800 r / min for 10 min, then a compound of 2.5% of sodium stearate and 0.3% of zinc dialkyldithiophosphate based on the dry weight of calcium carbonate is added to the nano calcium carbonate for surface treatment, and stirring is continued at 2800 r / min for 30 min, to obtain a modified nano calcium carbonate suspension;

[0050] S5: the nano calcium carbonate is subjected to pressure filtration, dried at 180℃ for 2h, pulverized, and sieved through a 150 mesh sieve, to obtain a nano calcium carbonate product for TPR shoe materials.

[0051] Example 2

[0052] A method for preparing a nano calcium carbonate for TPR shoe materials, comprising the following steps:

[0053] S1: a calcium hydroxide suspension with a specific gravity of 1.07 is pumped into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25℃, stirring is started, the stirring speed is 900 r / min, a carbon dioxide mixed gas with a concentration of 32% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time, when the conductivity of the reaction first shows a downward trend (i.e. gelation is about to start), 0.10% of sodium cocoyl isethionate based on the dry weight of calcium carbonate is immediately added to the reaction system, and the reaction continues;

[0054] S2: when the conductivity returns to the conductivity level before the reaction (i.e. gelation is over), the introduction of the carbon dioxide mixed gas is stopped, and the suspension is pumped to a high-speed emulsifier for high-speed emulsification and dispersion treatment at a speed of 3500 r / min for 20 min;

[0055] S3: the suspension after S2 emulsification is pumped back to the carbonation tower to continue the carbonation reaction, until the pH of the reaction system is ≤7.5, the reaction is stopped, and a nano calcium carbonate suspension with good dispersibility is obtained;

[0056] S4: Surface treatment of the suspension obtained in S3. The suspension was heated to 90°C, and 0.05% of ethoxylated tallow alcohol by dry weight of calcium carbonate was added to the suspension, and stirred at a speed of 2900 r / min for 10 min, then a compound of 2.7% of sodium stearate and 0.2% of zinc dialkyldithiophosphate by dry weight of calcium carbonate was added to the suspension for surface treatment of the nano calcium carbonate, and the stirring was continued at a speed of 2900 r / min for 28 min, to obtain the modified nano calcium carbonate suspension;

[0057] S5: The nano calcium carbonate was subjected to pressure filtration, dried at 160°C for 3 h, pulverized, and sieved through a 200-mesh screen, to obtain the nano calcium carbonate product for TPR shoe materials.

[0058] Example 3

[0059] A method for preparing nano calcium carbonate for TPR shoe materials, comprising the following steps:

[0060] S1: A calcium hydroxide suspension with a specific gravity of 1.06 was pumped into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension was 25°C, the stirring was started with a stirring speed of 800 r / min, a carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h was introduced for reaction, and the conductivity and pH value of the reaction process were monitored, when the conductivity of the reaction first showed a downward trend (i.e. gelation was about to start), 0.08% of sodium cocoyl isethionate by dry weight of calcium carbonate was immediately added to the reaction system, and the reaction was continued;

[0061] S2: When the conductivity returned to the conductivity level before the reaction (i.e. the gelation was over), the introduction of the carbon dioxide mixed gas was stopped, and the suspension was pumped into a high-speed emulsifier for high-speed emulsification and dispersion treatment at a speed of 3200 r / min for 15 min;

[0062] S3: The suspension after the emulsification in S2 was pumped back into the carbonation tower for further carbonation reaction, and the reaction was stopped when the pH value of the reaction system was ≤7.5, to obtain a nano calcium carbonate suspension with good dispersibility;

[0063] S4: Surface treatment of the suspension obtained in S3. The suspension was heated to 90°C, and 0.05% of ethoxylated tallow alcohol by dry weight of calcium carbonate was added to the suspension, and stirred at a speed of 2900 r / min for 10 min, then a compound of 2.7% of sodium stearate and 0.2% of zinc dialkyldithiophosphate by dry weight of calcium carbonate was added to the suspension for surface treatment of the nano calcium carbonate, and the stirring was continued at a speed of 2900 r / min for 28 min, to obtain the modified nano calcium carbonate suspension;

[0064] S5: The nano calcium carbonate is pressure filtered, dried at 180℃ for 2h, pulverized, and sieved through a 150 mesh sieve to obtain the nano calcium carbonate product for TPR shoe materials.

[0065] Example 4

[0066] A preparation method of a nano calcium carbonate for TPR shoe materials includes the following steps:

[0067] S1: A calcium hydroxide suspension with a specific gravity of 1.07 is pumped into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 24℃, stirring is started with a stirring speed of 900r / min, a carbon dioxide mixed gas with a concentration of 31% and a flow rate of 2m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time. When the conductivity of the reaction first shows a downward trend (i.e., gelation is about to start), 0.05% of sodium cocoyl isethionate based on the dry weight of calcium carbonate is immediately added to the reaction system, and the reaction continues;

[0068] S2: When the conductivity returns to the conductivity level before the reaction (i.e., gelation is over), stop introducing the carbon dioxide mixed gas, and the suspension is pumped into a high-speed emulsifier for high-speed emulsification and dispersion treatment at a speed of 3000r / min for 20min;

[0069] S3: The suspension after emulsification in S2 is pumped back into the carbonation tower for further carbonation reaction, and the reaction is stopped when the pH of the reaction system is ≤7.5, to obtain a nano calcium carbonate suspension with good dispersibility;

[0070] S4: The suspension obtained in S3 is surface treated by heating the suspension to 90℃, first adding 0.06% of ethoxylated tallow alcohol based on the dry weight of calcium carbonate to the suspension, stirring at a speed of 3000r / min for 10min, then adding a compound of 2.6% of sodium stearate and 0.2% of zinc dialkyldithiophosphate based on the dry weight of calcium carbonate to the suspension for surface treatment of the nano calcium carbonate, and continuing to stir at a speed of 3000r / min for 20min, to obtain a modified nano calcium carbonate suspension;

[0071] S5: The nano calcium carbonate is pressure filtered, dried at 170℃ for 2.5h, pulverized, and sieved through a 150 mesh sieve to obtain the nano calcium carbonate product for TPR shoe materials.

[0072] Example 5

[0073] A preparation method of a nano calcium carbonate for TPR shoe materials includes the following steps:

[0074] S1: Pump the calcium hydroxide suspension with a specific gravity of 1.06 into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 26℃, start stirring, the stirring speed is 800 r / min, and a carbon dioxide mixed gas with a concentration of 29% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time. When the reaction conductivity first shows a downward trend (i.e., gelation is about to start), 0.07% of sodium cocoyl isethionate based on the dry weight of calcium carbonate is immediately added to the reaction system, and the reaction continues;

[0075] S2: When the conductivity returns to the conductivity level before the reaction (i.e., gelation is over), stop introducing the carbon dioxide mixed gas, and pump the suspension into a high-speed emulsifier for high-speed emulsification and dispersion treatment at a speed of 3000 r / min for 15 min;

[0076] S3: Pump the suspension after S2 emulsification into the carbonation tower to continue the carbonation reaction, and stop the reaction when the pH of the reaction system is ≤7.5, to obtain a nano calcium carbonate suspension with good dispersibility;

[0077] S4: Perform surface treatment on the suspension obtained in S3 by heating the suspension to 90℃, first adding 0.08% of ethoxylated tallow alcohol based on the dry weight of calcium carbonate to the suspension, stirring at a speed of 3000 r / min for 10 min, then adding a compound of 2.9% sodium stearate and 0.1% zinc dialkyldithiophosphate based on the dry weight of calcium carbonate to the nano calcium carbonate for surface treatment, and continuing to stir at a speed of 2500 r / min for 30 min, to obtain a modified nano calcium carbonate suspension;

[0078] S5: Perform pressure filtration, drying at 180℃ for 2h, pulverization, and sieving through a 150-mesh sieve on the nano calcium carbonate, to obtain a TPR shoe material-specific nano calcium carbonate product.

[0079] Comparative Example 1

[0080] S1: Pump the calcium hydroxide suspension with a specific gravity of 1.06 into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25℃, start stirring, the stirring speed is 800 r / min, and a carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time. When the reaction conductivity first shows a downward trend (i.e., gelation is about to start), 0.07% of sodium cocoyl isethionate based on the dry weight of calcium carbonate is immediately added to the reaction system, and the reaction continues;

[0081] S2: Perform pressure filtration, drying at 180℃ for 2h, pulverization, and sieving through a 150-mesh sieve on the nano calcium carbonate, to obtain a TPR shoe material-specific nano calcium carbonate product.

[0082] Comparative Example 2

[0083] S1: Pump the calcium hydroxide suspension with a specific gravity of 1.06 into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25℃, start stirring, the stirring speed is 800 r / min, and a carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time;

[0084] S2: When the conductivity first decreases (i.e., the gelation starts) and returns to the conductivity level before the reaction (i.e., the gelation ends), stop introducing the carbon dioxide mixed gas, and pump the suspension into a high-speed emulsifier for high-speed emulsification and dispersion treatment at a speed of 3000 r / min for 15 min;

[0085] S3: Pump the suspension after the emulsification in S2 back into the carbonation tower to continue the carbonation reaction, and stop the reaction until the pH of the reaction system is ≤7.5, to obtain a nano calcium carbonate suspension;

[0086] S4: The obtained nano calcium carbonate suspension is subjected to pressure filtration, drying at 180℃ for 2 h, pulverization, and sieving through a 150-mesh sieve to obtain a nano calcium carbonate product.

[0087] Comparative Example 3

[0088] S1: Pump the calcium hydroxide suspension with a specific gravity of 1.06 into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25℃, start stirring, the stirring speed is 800 r / min, and a carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time, when the conductivity of the reaction first decreases (i.e., the gelation starts), immediately add 0.08% of sodium cocoyl isethionate based on the weight of calcium carbonate dry basis to the reaction system, continue the reaction, and stop the reaction until the pH of the reaction system is ≤7.5, to obtain a nano calcium carbonate suspension;

[0089] S2: The obtained nano calcium carbonate suspension is subjected to pressure filtration, drying at 180℃ for 2 h, pulverization, and sieving through a 150-mesh sieve to obtain a nano calcium carbonate product.

[0090] Comparative Example 4

[0091] S1: Pump the calcium hydroxide suspension with a specific gravity of 1.06 into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25℃, start stirring, the stirring speed is 800 r / min, and a carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time, when the conductivity of the reaction first decreases (i.e., the gelation starts), immediately add 0.08% of sodium cocoyl isethionate based on the weight of calcium carbonate dry basis to the reaction system, continue the reaction, and stop the reaction until the pH of the reaction system is ≤7.5, to obtain a nano calcium carbonate suspension;

[0092] S2: The nano calcium carbonate suspension is heated to 90°C, 0.05% of the dry weight of calcium carbonate of ethoxylated tallow alcohol is added to the suspension, stirred at 3000 r / min for 10 min, and then stirred at 2500 r / min for 30 min to obtain the modified nano calcium carbonate suspension;

[0093] S3: The modified nano calcium carbonate suspension is filtered, dried at 180°C for 2h, pulverized, and sieved through a 150 mesh sieve to obtain the calcium carbonate product.

[0094] Comparative Example 5

[0095] S1: The calcium hydroxide suspension with a specific gravity of 1.06 is pumped into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25°C, the stirring is started, the stirring speed is 800 r / min, the carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h is introduced for reaction, and the pH value of the reaction process is monitored at the same time, until the pH of the reaction system is ≤7.5, the reaction is stopped, and the nano calcium carbonate suspension is obtained;

[0096] S2: The nano calcium carbonate suspension is heated to 90°C, stirred at 3000 r / min for 10 min, then 3.0% of the dry weight of calcium carbonate of sodium stearate is added to the nano calcium carbonate for surface treatment, and stirred at 2500 r / min for 30 min to obtain the modified nano calcium carbonate suspension;

[0097] S3: The modified nano calcium carbonate suspension is filtered, dried at 180°C for 2h, pulverized, and sieved through a 150 mesh sieve to obtain the calcium carbonate product.

[0098] Comparative Example 6

[0099] S1: The calcium hydroxide suspension with a specific gravity of 1.06 is pumped into a high-speed carbonation tower, the temperature of the calcium hydroxide suspension is 25°C, the stirring is started, the stirring speed is 800 r / min, the carbon dioxide mixed gas with a concentration of 30% and a flow rate of 2 m 3 / h is introduced for reaction, and the conductivity and pH value of the reaction process are monitored at the same time, until the pH of the reaction system is ≤7.5, the reaction is stopped, and the nano calcium carbonate suspension is obtained;

[0100] S2: The nano calcium carbonate suspension is heated to 90°C, stirred at 3000 r / min for 10 min, then 3.0% of the dry weight of calcium carbonate of zinc dialkyldithiophosphate is added to the nano calcium carbonate for surface treatment, and stirred at 2500 r / min for 30 min to obtain the modified nano calcium carbonate suspension;

[0101] S3: The modified nano calcium carbonate suspension was filtered, dried at 180℃ for 2h, pulverized, and sieved through a 150 mesh screen to obtain nano calcium carbonate product.

[0102] Performance test experiment

[0103] The nano calcium carbonate prepared in the above examples and comparative examples was mixed, extruded, and molded to prepare TPR according to the formulation in Table 1. The Shore A hardness was tested according to standard GB / T 531.1-2008, and the tensile strength, breaking strength, and tear strength were tested according to standard GB / T 528-2009. The test results of the examples and comparative examples are shown in Table 2.

[0104] Table 1: TPR formulation

[0105] Name Parts SBS 100 Polystyrene 20 Calcium carbonate 20 Zinc oxide 5 Accelerator 1 Wear resistance agent 5 Antioxidant 1 Flame retardant 3

[0106] Table 2: Performance test of the nano calcium carbonate filled base material prepared in the examples and comparative examples

[0107]

[0108] As can be seen from the table, the TPR prepared in Examples 1-5 and Comparative Examples 1-6 has no significant difference in Shore A hardness, but is significantly superior to Comparative Examples 1-6 in tensile strength, elongation at break, and tear strength. This shows that the nano calcium carbonate prepared in the examples has good compatibility and dispersion with the SBS matrix, and can significantly improve the mechanical properties. Comparative Examples 2-6 respectively added sodium cocoyl isethionate, high-speed emulsification, ethoxylated tallow alcohol, sodium stearate, and zinc dialkyldithiophosphate on the basis of Comparative Example 1, and the TPR prepared has no change or an increase in Shore A hardness, and a certain increase in tensile strength, elongation at break, and tear strength, but the change is not significant. Comparative Example 1 is based on Example 3, and no sodium cocoyl isethionate is added during carbonation, and no high-speed emulsification and surface modification are performed, and the TPR prepared has a significant increase in Shore A hardness, and a significant decrease in tensile strength, elongation at break, and tear strength. Therefore, under the combined action of adding sodium cocoyl isethionate, high-speed emulsification, and surface modification during carbonation in Example 3, the effect is better than that of each surface treatment agent and high-speed emulsification alone.

[0109] The above content is a further detailed description of the present application in combination with specific / preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, they can make several alternatives or modifications to the described embodiments without departing from the concept of the present application, and these alternatives or modifications shall be considered as falling within the protection scope of the present application.

Claims

1. A method for preparing nano calcium carbonate for TPR shoe material, characterized in that, The method comprises the following steps: S1: carbonation reaction is carried out by introducing mixed gas containing carbon dioxide into calcium hydroxide suspension, and when the reaction conductivity shows a downward trend, sodium cocoyl isethionate is added into the reaction system, and the reaction is continued; S2: when the conductivity returns to the conductivity level before the reaction, the introduction of the mixed gas is stopped, and the suspension is subjected to high-speed emulsification and dispersion treatment; the high-speed emulsification speed is 3000-3500 r / min, and the treatment time is 15-20 min; S3: the suspension after emulsification is continuously subjected to carbonation reaction, and when the pH of the reaction system is less than or equal to 7.5, the reaction is stopped, and a nano calcium carbonate suspension is obtained; S4: the nano calcium carbonate suspension is added with ethoxylated tallow alcohol, stirred uniformly, and then added with a compound of sodium stearate and zinc dialkyldithiophosphate for surface treatment, so that a modified nano calcium carbonate suspension is obtained; S5: the modified nano calcium carbonate suspension is subjected to pressure filtration, drying, pulverization and sieving, so that a nano calcium carbonate for TPR shoe material is obtained.

2. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S1, the specific gravity of the calcium hydroxide suspension is 1.06-1.

07.

3. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S1, the carbonation reaction conditions are as follows: the mixed gas of carbon dioxide and air with a volume concentration of 28-32% and a flow rate of 2 m 2 / h is introduced, and the reaction is carried out at a temperature of ≤27°C and a stirring speed of 700-900 r / min.

4. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S1, the addition amount of the sodium cocoyl isethionate is 0.05-0.10% of the dry weight of calcium carbonate.

5. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S4, the addition amount of the ethoxylated tallow alcohol is 0.05-0.08% of the dry weight of calcium carbonate.

6. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S4, the surface treatment conditions are as follows: the stirring speed is 2800-3000 r / min, the temperature is 90°C, and the modification time is 20-30 min.

7. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S4, the addition amount of the sodium stearate in the compound is 2.5-2.9% of the dry weight of calcium carbonate, and the addition amount of the zinc dialkyldithiophosphate is 0.1-0.3% of the dry weight of calcium carbonate.

8. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S5, the drying temperature is 160-180°C, and the time is 2-3 h.

9. The method for preparing nano-calcium carbonate for TPR shoe materials according to claim 1, characterized in that: In step S5, the sieving mesh number is 150-200 meshes.

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