Olive-shaped submicron calcium carbonate and preparation method and application thereof
阅读说明：本技术 一种橄榄球形亚微米碳酸钙及其制备方法和应用 (Olive-shaped submicron calcium carbonate and preparation method and application thereof ) 是由 杜年军 颜干才 周斌 王宗民 于 2021-01-25 设计创作，主要内容包括：本发明公开了一种橄榄球形亚微米碳酸钙及其制备方法和应用。本发明的亚微米碳酸钙呈橄榄球形,长径为0.4μm～2.5μm,短径为80nm～300nm,其制备工艺简单可行,将其作为补强填料用于降解塑料具有填充量高、加工性能好等优点,不仅能够大幅降低生产成本,而且还可以显著提高制品的强度、韧性和透明度,具有较好的经济效益。(The invention discloses an olive-shaped submicron calcium carbonate and a preparation method and application thereof. The submicron calcium carbonate is in the shape of an olive ball, the major diameter is 0.4-2.5 microns, the minor diameter is 80-300 nm, the preparation process is simple and feasible, and the submicron calcium carbonate serving as a reinforcing filler for degrading plastics has the advantages of high filling amount, good processing performance and the like, not only can greatly reduce the production cost, but also can remarkably improve the strength, toughness and transparency of products, and has good economic benefit.)
1. A submicron calcium carbonate characterized by: the submicron calcium carbonate is in an olive shape, the major diameter is 0.4-2.5 mu m, and the minor diameter is 80-300 nm.
2. The submicron calcium carbonate according to claim 1, characterized in that: the BET specific surface area of the submicron calcium carbonate is 10m2/g～15m2/g。
3. Submicron calcium carbonate according to claim 1 or 2, characterized in that: the oil absorption value of the submicron calcium carbonate is 16gDOP/100 g-20 gDOP/100 g.
4. A process for the preparation of submicron calcium carbonate according to any one of claims 1 to 3, characterized in that it comprises the following steps:
1) adding water into calcium oxide for reaction, sieving and aging to obtain calcium hydroxide emulsion;
2) adding a crystal form control agent accounting for 0.5-0.8% of the dry mass of the calcium hydroxide into the calcium hydroxide emulsion in the step 1), spraying the calcium hydroxide emulsion from the top of the continuous carbonization tower, and introducing lime kiln gas from the bottom of the continuous carbonization tower to perform a first carbonation reaction until the electrical conductivity of the slurry is 3-4S/m;
3) transferring the reaction liquid obtained in the step 2) into a stirring kettle, adding a dispersing agent accounting for 0.3-0.5% of the dry basis weight of calcium carbonate, introducing lime kiln gas, and carrying out a second carbonation reaction until the electrical conductivity of the slurry is less than or equal to 1S/m;
4) adding sodium stearate or/and stearic acid-rare earth compound with 2-2.5% of the dry mass of calcium carbonate into the reaction liquid obtained in the step 3) for first modification;
5) dehydrating and drying the reaction liquid obtained in the step 4), adding the reaction liquid into a crusher for crushing, spraying a titanate coupling agent and an aluminate coupling agent which are 1-1.5% of the dry mass of calcium carbonate into the crusher during crushing, and carrying out secondary modification to obtain the rugby-shaped submicron calcium carbonate.
5. The process for the preparation of submicron calcium carbonate according to claim 4, characterized in that: the concentration of the calcium hydroxide emulsion in the step 1) is 1.0-1.2 mol/L, and the viscosity is 200-300 cP.
6. The process for the preparation of submicron calcium carbonate according to claim 4, characterized in that: the crystal form control agent in the step 2) is composed of soluble starch and L-malic acid according to the mass ratio of 5: 1-5: 3.
7. The method for preparing submicron calcium carbonate according to any one of claims 4 to 6, characterized in that: the flow rate of the calcium hydroxide emulsion in the step 2) in the continuous carbonization tower is 8m3/h～10m3H; the volume fraction of carbon dioxide in the lime kiln gas in the step 2) is 34-38%, and the flow of the lime kiln gas in the continuous carbonization tower is 1500m3/h～1800m3/h。
8. The method for preparing submicron calcium carbonate according to any one of claims 4 to 6, characterized in that: the dispersing agent in the step 3) is at least one of cellulose ether, hydroxypropyl methylcellulose and sodium carboxymethyl cellulose; the volume fraction of the carbon dioxide in the lime kiln gas in the step 3) is 34-38%, and the introduction amount of the lime kiln gas in the stirring kettle is 0.5m3/min·m3～0.6m3/min·m3。
9. The method for preparing submicron calcium carbonate according to any one of claims 4 to 6, characterized in that: and 5) the mass ratio of the titanate coupling agent to the aluminate coupling agent is 1: 2-1: 5.
10. A degradable plastic, which is characterized in that: the component of the degradable plastic comprises the submicron calcium carbonate of any one of claims 1 to 3.
Technical Field
The invention relates to the technical field of precipitated calcium carbonate, and particularly relates to rugby-shaped submicron calcium carbonate as well as a preparation method and application thereof.
Background
Statistically, over 80 million tons of plastics are produced since 1868, and 60 hundred million tons of plastics are buried or discarded in nature, which causes serious "white pollution". In 2004, thompson et al, university of princes, british, published a paper on plastic chips in marine waters and sediments in journal "science", and first proposed the concept of "micro-plastics", which is defined as plastic chips and particles with a diameter of less than 5 mm. In fact, microplastics, which range in size from a few microns to a few millimeters in diameter, are heterogeneous mixtures of plastic particles of various shapes that tend to be difficult to distinguish with the naked eye, and are figuratively referred to as "PM 2.5 in the sea". The micro plastic has tiny particle diameter, so the micro plastic has great harm to the environment, and the micro plastic is found in seawater and seabed sediments at present.
The degradable plastics are also called as environment degradable plastics, and refer to a kind of plastics whose product has various properties meeting the use requirements, and its properties are unchanged in storage period, and after use, it can be degraded into substances (carbon dioxide, methane and water, etc.) harmless to environment under the natural environment condition. At present, reinforcing fillers adopted in degradable plastics are starch, talcum powder, heavy calcium carbonate and the like generally, and the obtained product has the problems of high cost, poor toughness, insufficient rigidity, poor heat resistance and the like, and the product is difficult to popularize and apply in a large amount in a short time.
Therefore, there is a need to develop a reinforcing filler with better performance so as to promote the application of large area of degradable plastic products and effectively reduce the environmental pollution problem brought by the traditional plastic products.
The foregoing merely provides background information related to the present invention and does not necessarily constitute prior art.
Disclosure of Invention
One of the objects of the present invention is to provide a submicron calcium carbonate having a football shape.
The second object of the present invention is to provide a method for preparing the submicron calcium carbonate.
It is a further object of the present invention to provide the use of the above-described submicron calcium carbonate as a reinforcing filler in degraded plastics.
The technical scheme adopted by the invention is as follows:
the submicron calcium carbonate is in the shape of an olive ball, the major diameter of the submicron calcium carbonate is 0.4-2.5 mu m, and the minor diameter of the submicron calcium carbonate is 80-300 nm.
Preferably, the sub-micron calcium carbonate has a BET specific surface area of 10m2/g～15m2/g。
Preferably, the submicron calcium carbonate has an oil absorption value of 16gDOP/100g to 20gDOP/100 g.
The preparation method of the submicron calcium carbonate comprises the following steps:
1) adding water into calcium oxide for reaction, sieving and aging to obtain calcium hydroxide emulsion;
2) adding a crystal form control agent accounting for 0.5-0.8% of the dry mass of the calcium hydroxide into the calcium hydroxide emulsion in the step 1), spraying the calcium hydroxide emulsion from the top of the continuous carbonization tower, and introducing lime kiln gas from the bottom of the continuous carbonization tower to perform a first carbonation reaction until the electrical conductivity of the slurry is 3-4S/m;
3) transferring the reaction liquid obtained in the step 2) into a stirring kettle, adding a dispersing agent accounting for 0.3-0.5% of the dry basis weight of calcium carbonate, introducing lime kiln gas, and carrying out a second carbonation reaction until the electrical conductivity of the slurry is less than or equal to 1S/m;
4) adding sodium stearate or/and stearic acid-rare earth compound with 2-2.5% of the dry mass of calcium carbonate into the reaction liquid obtained in the step 3) for first modification;
5) dehydrating and drying the reaction liquid obtained in the step 4), adding the reaction liquid into a crusher for crushing, and spraying a titanate coupling agent and an aluminate coupling agent which are 1-1.5% of the dry mass of calcium carbonate into the crusher for secondary modification to obtain the rugby-shaped submicron calcium carbonate.
Preferably, the concentration of the calcium hydroxide emulsion in the step 1) is 1.0-1.2 mol/L, and the viscosity is 200-300 cP.
Preferably, the temperature of the calcium hydroxide emulsion in the step 1) is 50-60 ℃.
Preferably, the crystal form control agent in the step 2) is composed of soluble starch and L-malic acid according to a mass ratio of 5: 1-5: 3.
Preferably, the flow rate of the calcium hydroxide emulsion in the step 2) in the continuous carbonization tower is 8m3/h～10m3/h。
Preferably, the volume fraction of the carbon dioxide in the lime kiln gas in the step 2) is 34-38%, and the flow rate of the lime kiln gas in the continuous carbonization tower is 1500m3/h～1800m3/h。
Preferably, the dispersant in step 3) is at least one of cellulose ether, hydroxypropyl methylcellulose and sodium carboxymethyl cellulose.
Preferably, the volume fraction of the carbon dioxide in the lime kiln gas in the step 3) is 34-38%, and the introduction amount of the lime kiln gas in the stirring kettle is 0.5m3/min·m3～0.6m3/min·m3。
Preferably, the time for the first modification in the step 4) is 30min to 60 min.
Preferably, the mass ratio of the titanate coupling agent to the aluminate coupling agent in the step 5) is 1: 2-1: 5.
The degradable plastic comprises the submicron calcium carbonate.
The invention has the beneficial effects that: the submicron calcium carbonate is in the shape of an olive ball, the major diameter is 0.4-2.5 microns, the minor diameter is 80-300 nm, the preparation process is simple and feasible, the submicron calcium carbonate serving as a reinforcing filler for degrading plastics has the advantages of high filling amount, good processing performance and the like, the production cost can be greatly reduced, the strength, toughness and transparency of products can be remarkably improved, and the submicron calcium carbonate has good economic benefits.
Specifically, the method comprises the following steps:
1) in the first carbonation reaction, the generation of small-particle-size strip crystals is promoted by adding a crystal form control agent, adjusting the raw material ratio, the process parameters and other means, and the agglomeration of the crystals is avoided by adding a dispersing agent, so that the crystals are ensured to grow and shape gradually in a stirring kettle in the second carbonation reaction, and finally the rugby-shaped submicron calcium carbonate is obtained;
2) the invention carries out two-time modification on calcium carbonate, and carries out complete coating modification on the calcium carbonate, so that the filling amount of the football-shaped submicron calcium carbonate in the degradable plastic is obviously improved;
3) the submicron calcium carbonate has moderate particle size, is monodisperse, has low oil absorption value and simple and feasible preparation process, can obviously improve the toughness, strength and transparency of a product when used for degrading plastics, can greatly reduce the production cost of the degraded plastic product, and has better economic benefit.
Drawings
Fig. 1 is an SEM image of rugby-shaped submicron calcium carbonate of example 1.
Fig. 2 is an SEM image of rugby-shaped submicron calcium carbonate of example 2.
Fig. 3 is an SEM image of rugby-shaped submicron calcium carbonate of example 3.
Detailed Description
The invention will be further explained and illustrated with reference to specific examples.
Example 1:
a preparation method of rugby-shaped submicron calcium carbonate comprises the following steps:
1) adding water into calcium oxide for reaction, and then sieving and aging to obtain calcium hydroxide emulsion with the concentration of 1.0mol/L and the viscosity of 215 cP;
2) adding a crystal form control agent accounting for 0.5 percent of the dry mass of the calcium hydroxide into the calcium hydroxide emulsion obtained in the step 1)The crystal form control agent consists of soluble starch and L-malic acid according to the mass ratio of 5:1, the temperature of the calcium hydroxide emulsion is adjusted to 55 ℃, then the calcium hydroxide emulsion is sprayed from the top of the continuous carbonization tower by an emulsification pump, and the flow rate of the calcium hydroxide emulsion is 10m3Blowing lime kiln gas with the volume fraction of carbon dioxide of 35% from the bottom of a continuous carbonization tower at the same time, wherein the flow rate of the lime kiln gas is 1700m3Performing a first carbonation reaction until the electrical conductivity of the slurry is 3.5S/m;
3) transferring the reaction liquid obtained in the step 2) into a stirring kettle, adding cellulose ether accounting for 0.3 percent of the dry basis weight of calcium carbonate, introducing lime kiln gas accounting for 35 percent of the volume fraction of carbon dioxide, wherein the introduction amount of the lime kiln gas in the stirring kettle is 0.5m3/min·m3Carrying out a second carbonation reaction until the electrical conductivity of the slurry is reduced to 0.5S/m;
4) adding a modifier accounting for 2.0 percent of the dry mass of the calcium carbonate into the reaction liquid obtained in the step 3), wherein the modifier consists of sodium stearate and a stearic acid-rare earth compound according to the mass ratio of 1:2, stirring for 30min, and carrying out primary modification;
5) and (3) carrying out filter pressing, dehydration and drying on the reaction liquid obtained in the step (4), adding the reaction liquid into a crusher for crushing, spraying a modifier which is 1.0% of the dry mass of calcium carbonate into the crusher during crushing, wherein the modifier consists of a titanate coupling agent and an aluminate coupling agent according to the mass ratio of 1:2, and carrying out secondary modification to obtain the rugby-shaped submicron calcium carbonate (shown in an SEM (scanning electron microscope) figure in figure 1).
The tests show that the average major diameter of the rugby-ball submicron calcium carbonate is 1.25 mu m, the average minor diameter is 120nm, and the BET specific surface area is 11.57m2(ii)/g, oil absorption number 16.39gDOP/100 g.
Example 2:
a preparation method of rugby-shaped submicron calcium carbonate comprises the following steps:
1) adding water into calcium oxide for reaction, and then sieving and aging to obtain calcium hydroxide emulsion with the concentration of 1.2mol/L and the viscosity of 296 cP;
2) adding a crystal form control agent accounting for 0.7 percent of the dry mass of the calcium hydroxide into the calcium hydroxide emulsion obtained in the step 1), wherein the crystal form control agent is solubleStarch and L-malic acid are mixed according to the mass ratio of 5:3, the temperature of the calcium hydroxide emulsion is adjusted to 60 ℃, then the calcium hydroxide emulsion is sprayed from the top of a continuous carbonization tower by an emulsification pump, and the flow rate of the calcium hydroxide emulsion is 9m3Blowing lime kiln gas with the volume fraction of carbon dioxide of 35% from the bottom of the continuous carbonization tower at the same time, wherein the flow rate of the lime kiln gas is 1800m3Performing a first carbonation reaction until the electrical conductivity of the slurry is 3.0S/m;
3) transferring the reaction liquid obtained in the step 2) into a stirring kettle, adding cellulose ether accounting for 0.4 percent of the dry basis weight of calcium carbonate, introducing lime kiln gas accounting for 35 percent of the volume fraction of carbon dioxide, wherein the introduction amount of the lime kiln gas in the stirring kettle is 0.55m3/min·m3Carrying out a second carbonation reaction until the electrical conductivity of the slurry is reduced to 0.5S/m;
4) adding a modifier accounting for 2.3 percent of the dry mass of the calcium carbonate into the reaction liquid obtained in the step 3), wherein the modifier consists of sodium stearate and a stearic acid-rare earth compound according to the mass ratio of 1:4, stirring for 30min, and carrying out primary modification;
5) and (3) performing filter pressing dehydration and drying on the reaction liquid obtained in the step (4), adding the reaction liquid into a crusher for crushing, spraying a modifier which is 1.3% of the dry mass of calcium carbonate into the crusher during crushing, wherein the modifier consists of a titanate coupling agent and an aluminate coupling agent according to the mass ratio of 1:4, and performing secondary modification to obtain the rugby-shape submicron calcium carbonate (shown in an SEM (scanning electron microscope) picture as figure 2).
The tests show that the average major diameter of the rugby-ball submicron calcium carbonate is 1.6 mu m, the average minor diameter is 145nm, and the BET specific surface area is 13.39m2(ii)/g, oil absorption number 17.25gDOP/100 g.
Example 3:
a preparation method of rugby-shaped submicron calcium carbonate comprises the following steps:
1) adding water into calcium oxide for reaction, and then sieving and aging to obtain calcium hydroxide emulsion with the concentration of 1.1mol/L and the viscosity of 262 cP;
2) adding a crystal form control agent accounting for 0.6 percent of the dry mass of the calcium hydroxide into the calcium hydroxide emulsion obtained in the step 1), wherein the crystal form control agent is prepared from soluble starch and L-malic acid according to the mass ratio5:2, regulating the temperature of the calcium hydroxide emulsion to 58 ℃, and spraying the calcium hydroxide emulsion from the top of the continuous carbonization tower by using an emulsification pump, wherein the flow rate of the calcium hydroxide emulsion is 8m3At the same time, blowing lime kiln gas with the volume fraction of carbon dioxide of 35 percent from the bottom of the continuous carbonization tower, wherein the flow rate of the lime kiln gas is 1600m3Performing a first carbonation reaction until the electrical conductivity of the slurry is 3.8S/m;
3) transferring the reaction liquid obtained in the step 2) into a stirring kettle, adding sodium carboxymethylcellulose accounting for 0.5 percent of the dry basis weight of calcium carbonate, introducing lime kiln gas accounting for 35 percent of the volume fraction of carbon dioxide, wherein the introduction amount of the lime kiln gas in the stirring kettle is 0.5m3/min·m3Carrying out a second carbonation reaction until the electrical conductivity of the slurry is reduced to 1.0S/m;
4) adding a modifier accounting for 2.5 percent of the dry mass of the calcium carbonate into the reaction liquid obtained in the step 3), wherein the modifier consists of sodium stearate and a stearic acid-rare earth compound according to the mass ratio of 1:5, stirring for 30min, and carrying out primary modification;
5) and (3) carrying out filter pressing, dehydration and drying on the reaction liquid obtained in the step (4), adding the reaction liquid into a crusher for crushing, spraying a modifier which is 1.5% of the dry mass of calcium carbonate into the crusher during crushing, wherein the modifier consists of a titanate coupling agent and an aluminate coupling agent according to the mass ratio of 1:5, and carrying out secondary modification to obtain the rugby-shaped submicron calcium carbonate (shown in an SEM (scanning electron microscope) picture as figure 3).
The tests show that the average major diameter of the rugby-ball submicron calcium carbonate is 0.8 mu m, the average minor diameter is 98nm, and the BET specific surface area is 14.01m2The oil absorption number is 16.86gDOP/100 g.
Comparative example 1:
ground calcium carbonate (1250 mesh).
Comparative example 2:
starch.
And (3) performance testing:
the rugby-shaped submicron calcium carbonate of examples 1-3, the heavy calcium carbonate of comparative example 1 and the starch of comparative example 2 are respectively used as reinforcing fillers to prepare the degradable plastics, and the degradable plastics comprise the following components: the properties of the degraded plastics were tested with 57 parts by mass of PBAT (poly (adipic acid)/butylene terephthalate), 20 parts by mass of PLA (polylactic acid), 20 parts by mass of reinforcing filler and 3 parts by mass of maleic anhydride functionalized polyester elastomer (compatibilizer), the test results are shown in the following table:
TABLE 1 Performance test results for degradable plastics
Note:
specific gravity: the test is carried out according to the test method of GB 1033-1986 for the density and relative density of the plastic;
shrinkage rate: the test was carried out with reference to "determination of the shrinkage in injection moulding of thermoplastic plastics in GB/T15585 & 1995";
notched izod impact strength: the test is carried out according to the GB/T1843-2008 plastic cantilever beam impact strength test;
heat distortion temperature: the test is carried out according to GB/T8802-2001 plastic pipe softening temperature measurement;
vicat softening point: the test is carried out according to GB/T8802-2001 plastic pipe softening temperature measurement;
melt index: the test is carried out by referring to the determination of the melt mass flow rate and the melt volume flow rate of the GB/T3682.1-2018 plastic thermoplastic plastics;
tensile strength: the test is carried out according to the test method for the tensile property of the plastics of GB/T1040-;
elongation percentage: the test is carried out according to the test method for the tensile property of the plastics of GB/T1040-;
flexural modulus: the test is carried out according to the' GB/T9341-;
bending strength: the test was carried out with reference to "determination of the bending Properties of GB/T9341-.
As can be seen from Table 1: the rugby-shaped submicron calcium carbonate is used as a reinforcing filler, not only can obviously improve the shock resistance, tensile property and bending property of the degradable plastic, but also can improve the processing property of the degradable plastic, and is a very effective reinforcing and toughening modifier.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
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