CN112410882A - Whitening calcium carbonate whisker for plastic reinforcement and preparation method thereof - Google Patents
Whitening calcium carbonate whisker for plastic reinforcement and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of inorganic materials, in particular to whitening calcium carbonate whiskers for plastic reinforcement and a preparation method thereof. The invention firstly prepares calcium carbonate crystal whisker, then utilizes tetrabutyl titanate to hydrolyze under the condition of acetic acid to form titanium dioxide, so that the surface of the calcium carbonate crystal whisker is coated with a layer of titanium dioxide, and a small amount of acetic acid can lead the formed titanium dioxide to be firmly combined with the surface of the calcium carbonate crystal whisker. The calcium carbonate crystal whisker obtained by the invention is white, can be used for reinforcing plastics, can achieve the purposes of strength and whitening, and overcomes the defect that the fibrous material is difficult to cover by directly adding granular titanium dioxide. Furthermore, the calcium carbonate crystal whisker has rich interfaces, and titanium dioxide is formed on the interfaces, so that the covering and whitening effects of the interfaces of the titanium dioxide are exerted to the maximum extent; particularly, the method has huge application space in the reinforcement of plastics such as white household appliances.
Description
Technical Field
The invention relates to the technical field of inorganic materials, in particular to whitening calcium carbonate whiskers for plastic reinforcement and a preparation method thereof.
Background
With the development of plastic functionalization, plastic reinforcement becomes an indispensable link of plastic products. The plastic not only improves the service life of the plastic product through reinforcement, but also expands the use field of the plastic product. Reinforced high-performance composite plastics are developing in multiple directions, such as high specific strength, high specific modulus, high toughness, wear resistance and the like. Glass fiber is widely used as a reinforcing material in plastic reinforcement at present. However, since the glass fiber has a dark color, a large amount of titanium dioxide whitening agent is required to be added in the preparation of white home appliances such as air-conditioning cases and refrigerators, and since the glass fiber is fibrous, it is difficult to whiten the dispersion of the network.
Thus, the use of glass fiber reinforcement in white appliance housings is limited. The calcium carbonate whisker has fiber reinforcement property and white color, so that the calcium carbonate whisker becomes the first choice for reinforcing the shell of the white household appliance at present. The calcium carbonate whisker is a novel inorganic filling following the nano calcium carbonate, is non-toxic and odorless, is a white fluffy solid (needle-shaped single crystal under a microscope) serving as a new generation filling material, and has the following properties and characteristics: 1: the composite material has high mechanical strength and can reduce vibration, prevent skidding, reduce noise and absorb waves in the use process; 2: the comprehensive performance is good, the friction coefficient is high, and the wear resistance and the heat resistance are high; 3: the friction performance is stable, the heat fading and heat recovery performance is good, particularly, the friction increasing and the abrasion reducing are organically integrated in a system by filling the calcium carbonate crystal whiskers, and the high-temperature friction and abrasion performance is excellent; 4: the service life of the product can be improved by 30 percent; 5: the use amount of aramid fiber, steel fiber, red copper, potassium titanate and other high-value materials can be reduced, so that the cost of the friction material is greatly reduced; 6: the raw materials are rich in source and low in price, and the production is not influenced by the problem of the raw materials; 7: the powder produced after the product is rubbed is non-toxic and has little pollution.
The whisker is a kind of short fiber with diameter of several microns, length of several tens of microns and large length-diameter ratio, which grows in the form of single crystal and is similar to the shape of short fiber, and when it is crystallized, the atoms are arranged in high order, and can not contain the structural defects of hollow, dislocation and incomplete structure, etc. which can weaken its strength, so that it can form basically complete crystal, and its strength and modulus are nearly close to the theoretical strength of valence bond between material atoms, and far exceed the various powdered fillers used in large quantity at present. Calcium carbonate whiskers have been widely used in replacing glass fibers in paper making, plastics, rubber, and other products.
Especially, talc powder and glass fiber are often added to general-purpose resins represented by polypropylene to improve the elastic modulus, impact strength and dimensional stability of polypropylene. The talcum powder is a disk-shaped substance with the shape of 1-5 mu m, and the flexural modulus and the dimensional stability can not be greatly improved like fibers; long fibers, in turn, tend to affect the aesthetics and smoothness of the chemical book parts. Therefore, the novel short fiber material such as calcium carbonate whisker has unique performance: fiber reinforcement and filling capability; excellent surface smoothness, high size precision and stability, good processability, regeneration and circulation of reinforced composite material, good service performance and low cost.
However, calcium carbonate whiskers still have the problems of gray color and poor brightness when used as a reinforcing material for plastic shells of white household appliances, even if a large amount of titanium dioxide whitening agent is used, the natural color of whisker fibers is difficult to effectively cover, and the cost is increased due to the large amount of titanium dioxide.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention aims to provide a method for preparing whitening calcium carbonate whiskers for plastic reinforcement, which is used to solve the problem that the existing fibrous materials are not easy to whiten when used in plastics, and to improve the whiteness of calcium carbonate whiskers, so that the calcium carbonate whiskers are white when applied to white injection molding plastics, thereby reducing the addition amount of titanium dioxide, and at the same time, the present invention also provides whitening calcium carbonate whiskers for plastic reinforcement. The preparation method utilizes the characteristic that tetrabutyl titanate is hydrolyzed to form titanium dioxide under the condition of acetic acid, so that the surface of the calcium carbonate crystal whisker is coated with a layer of titanium dioxide, particularly, a small amount of acetic acid slightly dissolves the surface of the calcium carbonate crystal whisker while the tetrabutyl titanate is hydrolyzed under the acetic acid environment, thereby leading the specific surface of the calcium carbonate crystal whisker to be in an unstable state and leading the formed titanium dioxide to be firmly combined with the surface of the calcium carbonate crystal whisker.
In order to attain the above and other related objects,
in a first aspect of the invention, a method for preparing whitening calcium carbonate whiskers for plastic reinforcement is provided, which comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring at high speed and dispersing to obtain solution A;
wherein, Ca (OH)2The weight ratio of water to magnesium salt is 10-15:60-80: 1-2;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH of 4-5;
wherein the weight ratio of the acetic acid to the water to the ethanol is 1-3:6-8: 3-5;
step three, continuously introducing carbon dioxide into the solution A, continuously stirring, and gradually forming calcium carbonate whiskers under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate whiskers obtained in the step 3 into a stirrer, and stirring at a high speed for suspension; and adding tetrabutyl titanate into the solution B, spraying and adding into a stirrer, gradually hydrolyzing tetrabutyl titanate to coat the surface of the calcium carbonate crystal whisker, and sintering at the temperature of 400-500 ℃ to obtain the whitening calcium carbonate crystal whisker for plastic reinforcement.
The inorganic whisker is a one-dimensional single crystal material with a certain length-diameter ratio (not less than 10) and a certain sectional area (not more than 52 x 10-5cm 2), has a more complete crystal structure, less internal defects, and strength and modulus close to those of a complete crystal material, has the advantages of high strength, heat resistance, wear resistance, flame retardance and the like, and is a novel high-performance reinforcing toughening agent of a composite material.
The calcium carbonate whisker as an inorganic mineral microfiber can effectively improve the strength and modulus of plastics, but has poor whitening effect, and after the calcium carbonate fiber is used for plastic products, the fibrous calcium carbonate whisker is difficult to cover by adding granular titanium dioxide due to the fiber characteristics.
The invention is carried out by adding Ca (OH)2Introducing CO into the water charge2Gas realization, in Ca (OH)2In the slurry, is added in advance withMg facilitating growth of crystal along one-dimensional direction2+Salt, and the like. By controlling Ca (OH)2Concentration of slurry, reaction temperature and CO2The calcium carbonate crystal whisker is synthesized under gas-liquid reaction conditions such as the gas introduction speed and the like. The process flow for preparing the calcium carbonate crystal whisker by the carbonation method has the advantages of simple process, easy control of operation and easy realization of industrialization; magnesium salt can be recycled, and no by-product is generated; the raw materials are wide in source and low in cost; the product quality is stable.
In an embodiment of the invention, in the first step, the magnesium salt is at least one of magnesium chloride, magnesium hydroxide, magnesium sulfate, magnesium borate, magnesium oxide, and magnesium nitrate. Calcium carbonate belongs to a multi-type crystal, and various crystal forms such as a cubic crystal, a spindle crystal, a plate crystal, a needle crystal, a spherical crystal, a rose crystal and the like are prepared successfully at present. Introducing carbon dioxide gas into Ca (OH) at a certain rate2The method for preparing calcium carbonate whiskers in suspension has the characteristics of simple specific process, low cost and the like, but the thermodynamics of calcite is more stable, and CO is generated2And Ca (OH)2The reaction tends to form a calcite phase, and therefore a crystal form control agent needs to be added to the system before the carbonization reaction is started.
The crystal form control agent changes the arrangement mode of molecules when calcium carbonate is crystallized according to the difference of properties such as electrical property, dipole moment and the like, so as to complete the control of different crystal shapes and obtain various products with different crystal forms. The crystal form control agent can be magnesium salt, sylvite, sodium polyphosphate and the like. The invention takes magnesium salt as a crystal form control agent, can prepare spherical calcium carbonate powder with the particle size of 40-50nm, and the calcium carbonate whisker has large length-diameter ratio and high purity.
In one embodiment of the present invention, the magnesium salt in the first step is preferably magnesium chloride.
In one embodiment of the present invention, the Ca (OH) in step one2The weight ratio of water to magnesium salt is 12:70: 1.5.
The invention is stirred at high speed to ensure that Ca (OH)2Can be fully and uniformly mixed with a crystal form control agent magnesium salt, so that the magnesium salt can be uniformly dispersed into a calcium hydroxide suspension to prepare calcium carbonate crystals for next carbonizationConditions must be provided. In an embodiment of the invention, the high-speed stirring speed in the first step is 500-600r/min, and the stirring time is 1-3 h.
In an embodiment of the invention, the weight ratio of the acetic acid, the water and the ethanol in the second step is 3:7: 4.
In an embodiment of the invention, the carbon dioxide is continuously introduced into the solution A in the third step at an introduction rate of 30-60mL/min and a stirring rate of 100-200 r/min.
In an embodiment of the invention, the stirring speed of the high-speed stirring in the fourth step is 800-1200r/min, and the stirring time is 3-5 h.
The whiteness of the calcium carbonate product is reduced by the influence of impurities therein, wherein the metal ions mainly influence the whiteness. These ions are dark in color themselves, thereby reducing the whiteness of the product. In the early Japanese patent, sodium bisulfite or zinc, tetrahydroborane ring, sodium sulfite, sodium bisulfite, thiourea dioxide or sodium chloride powder and the like are adopted to stop the recovery and bleaching of impurity ions in calcium carbonate in an alkaline medium, but thiourea has potential carcinogenic effect and is not used any more. The calcium carbonate product bleached by other substances has low-valence metal ions due to incomplete removal of impurity ions, is not only incompletely whitened, but also is very easy to have oxidation and color reversion in applied downstream products, and the application of the calcium carbonate is limited at a certain level. Some products can improve the whiteness only by adding brightening agents to change the absorption of the products to light with specific wavelength, but the phenomenon of oxidation color reversion also exists.
Therefore, the invention firstly prepares the calcium carbonate whisker, then utilizes the characteristic that tetrabutyl titanate is hydrolyzed to form titanium dioxide under the condition of acetic acid to coat a layer of titanium dioxide on the surface of the calcium carbonate whisker, particularly, when tetrabutyl titanate is hydrolyzed under the acetic acid environment, a small amount of acetic acid can slightly dissolve the surface of the calcium carbonate whisker, thereby leading the specific surface of the calcium carbonate whisker to be in an unstable state, leading the formed titanium dioxide to be firmly combined with the surface of the calcium carbonate whisker, and basically improving the whiteness of the calcium carbonate product.
In an embodiment of the invention, in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 2-4; and the spraying amount of the tetrabutyl titanate added with the solution B is 15-18% of the mass of the calcium carbonate crystal whisker.
In an embodiment of the present invention, in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 3; and the spraying amount of the tetrabutyl titanate added with the solution B is 16 percent of the mass of the calcium carbonate crystal whisker.
The whitening calcium carbonate whisker for plastic reinforcement is prepared by the preparation method.
As described above, the whitening calcium carbonate whisker for plastic reinforcement and the preparation method thereof of the invention have the following beneficial effects:
1. the invention leads carbon dioxide gas into Ca (OH) containing crystal form control agent magnesium salt at a certain speed2Preparing calcium carbonate whiskers in suspension by mixing magnesium salt with Ca (OH)2The turbid liquid is mixed uniformly, so that the dispersity of the magnesium salt can be greatly increased, and the crystal form, uniformity and purity of the calcium carbonate crystal whisker can be greatly controlled.
2. The invention firstly prepares calcium carbonate crystal whisker, then utilizes the characteristic that tetrabutyl titanate is hydrolyzed to form titanium dioxide under the condition of acetic acid to coat a layer of titanium dioxide on the surface of the calcium carbonate crystal whisker, particularly, when tetrabutyl titanate is hydrolyzed under the acetic acid environment, a small amount of acetic acid can slightly dissolve the surface of the calcium carbonate crystal whisker, thereby leading the specific surface of the calcium carbonate crystal whisker to be in an unstable state and leading the formed titanium dioxide to be firmly combined with the surface of the calcium carbonate crystal whisker.
3. The calcium carbonate crystal whisker obtained by the invention is white, can be used for reinforcing plastics, can achieve the purposes of strength and whitening, and overcomes the defect that the fibrous material is difficult to cover by directly adding granular titanium dioxide. Furthermore, the calcium carbonate crystal whisker has rich interfaces, and titanium dioxide is formed on the interfaces, so that the covering and whitening effects of the interfaces of the titanium dioxide are exerted to the maximum extent; particularly, the method has huge application space in the reinforcement of plastics such as white household appliances.
Drawings
FIG. 1: the preparation process flow diagram is provided.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
A preparation method of whitening calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring at a high speed of 550r/min, and dispersing for 2h to obtain solution A; the magnesium salt is magnesium chloride;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 12:70: 1.5;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH value of 5;
specifically, the raw materials are respectively as follows by weight: the weight ratio of acetic acid, water and ethanol is 3:7: 4;
step three, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 40mL/min, the stirring speed is 150r/min, and stirring is continuously carried out, so that calcium carbonate whiskers are gradually formed under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate crystal whiskers obtained in the step three into a stirrer, stirring at a high speed for suspension, wherein the stirring speed is 1000r/min, and the stirring time is 4 hours; adding tetrabutyl titanate into the solution B, spraying and adding into a stirrer, gradually hydrolyzing tetrabutyl titanate and coating on the surface of the calcium carbonate crystal whisker, and sintering at 450 ℃ to obtain the whitening calcium carbonate crystal whisker for reinforcing plastics; in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 3; and the spraying amount of the tetrabutyl titanate added with the solution B is 16 percent of the mass of the calcium carbonate crystal whisker.
Example 2
A preparation method of whitening calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring and dispersing at a high speed of 500r/min for 1h to obtain solution A; the magnesium salt is magnesium hydroxide;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 10: 80: 2;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH value of 4;
specifically, the raw materials are respectively as follows by weight: the weight ratio of acetic acid, water and ethanol is 1: 8: 3;
step three, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 60mL/min, the stirring speed is 100r/min, and stirring is continuously carried out, so that calcium carbonate whiskers are gradually formed under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate crystal whiskers obtained in the step three into a stirrer, stirring at a high speed of 800r/min, and stirring for 3 hours; adding tetrabutyl titanate into the solution B, spraying and adding into a stirrer, gradually hydrolyzing tetrabutyl titanate and coating on the surface of the calcium carbonate crystal whisker, and sintering at 400 ℃ to obtain the whitening calcium carbonate crystal whisker for reinforcing plastics; in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 2; and the spraying amount of the tetrabutyl titanate added with the solution B is 15 percent of the mass of the calcium carbonate crystal whisker.
Example 3
A preparation method of whitening calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring at a high speed of 600r/min, and dispersing for 3h to obtain solution A; the magnesium salt is magnesium borate;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 15: 80: 1;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH value of 5;
specifically, the raw materials are respectively as follows by weight: the weight ratio of acetic acid, water and ethanol is 3:7: 5;
step three, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 60mL/min, the stirring speed is 200r/min, and stirring is continuously carried out, so that calcium carbonate whiskers are gradually formed under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate crystal whiskers obtained in the step three into a stirrer, stirring at a high speed for suspension, wherein the stirring speed is 1000r/min, and the stirring time is 3 hours; adding tetrabutyl titanate into the solution B, spraying and adding the solution B into a stirrer, gradually hydrolyzing tetrabutyl titanate and coating the tetrabutyl titanate on the surface of the calcium carbonate crystal whisker, and sintering at 500 ℃ to obtain the whitening calcium carbonate crystal whisker for reinforcing plastics; in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 4; and the spraying amount of the tetrabutyl titanate added with the solution B is 18 percent of the mass of the calcium carbonate crystal whisker.
Example 4
A preparation method of whitening calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt to the suspension to be stirred and dispersed at a high speed of 600r/min for 2 hours to obtain solution A; the magnesium salt is magnesium nitrate;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 14:70: 2;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH value of 5;
specifically, the raw materials are respectively as follows by weight: the weight ratio of acetic acid, water and ethanol is 3:6: 4;
step three, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 40mL/min, the stirring speed is 140r/min, and stirring is continuously carried out, so that calcium carbonate whiskers are gradually formed under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate crystal whiskers obtained in the step three into a stirrer, stirring at a high speed of 900r/min, and stirring for 3 hours; adding tetrabutyl titanate into the solution B, spraying and adding into a stirrer, gradually hydrolyzing tetrabutyl titanate and coating on the surface of the calcium carbonate crystal whisker, and sintering at 440 ℃ to obtain the whitening calcium carbonate crystal whisker for reinforcing plastics; in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 3; and the spraying amount of the tetrabutyl titanate added with the solution B is 16 percent of the mass of the calcium carbonate crystal whisker.
Example 5
A preparation method of whitening calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring at a high speed of 580r/min, and dispersing for 3h to obtain solution A; the magnesium salt is magnesium sulfate;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 13:75: 2;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH value of 5;
specifically, the raw materials are respectively as follows by weight: the weight ratio of acetic acid, water and ethanol is 2:7: 3;
step three, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 45mL/min, the stirring speed is 180r/min, and stirring is continuously carried out, so that calcium carbonate whiskers are gradually formed under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate crystal whisker obtained in the step three into a stirrer, stirring at a high speed of 1100r/min for 3 hours, and suspending; adding tetrabutyl titanate into the solution B, spraying and adding into a stirrer, gradually hydrolyzing tetrabutyl titanate and coating on the surface of the calcium carbonate crystal whisker, and sintering at 490 ℃ to obtain the whitening calcium carbonate crystal whisker for reinforcing plastics; in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 2; and the spraying amount of the tetrabutyl titanate added with the solution B is 18 percent of the mass of the calcium carbonate crystal whisker.
Example 6
A preparation method of whitening calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring and dispersing at a high speed of 570r/min for 3 hours to obtain solution A; the magnesium salt is magnesium chloride;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 14:60: 1;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH value of 4;
specifically, the raw materials are respectively as follows by weight: the weight ratio of acetic acid, water and ethanol is 2:7: 5;
step three, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 55mL/min, the stirring speed is 110r/min, and stirring is continuously carried out, so that calcium carbonate whiskers are gradually formed under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate crystal whiskers obtained in the step three into a stirrer, stirring at a high speed of 950r/min, and stirring for 4 hours; adding tetrabutyl titanate into the solution B, spraying and adding the solution B into a stirrer, gradually hydrolyzing tetrabutyl titanate and coating the tetrabutyl titanate on the surface of the calcium carbonate crystal whisker, and sintering at 410 ℃ to obtain the whitening calcium carbonate crystal whisker for reinforcing plastics; in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 2; and the spraying amount of the tetrabutyl titanate added with the solution B is 15 percent of the mass of the calcium carbonate crystal whisker.
Comparative example 1
A preparation method of unbleached calcium carbonate whiskers for plastic reinforcement comprises the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt, stirring at a high speed of 550r/min, and dispersing for 2h to obtain solution A; the magnesium salt is magnesium chloride;
specifically, the raw materials are respectively as follows by weight: ca (OH)2The weight ratio of water to magnesium salt is 12:70: 1.5;
step two, continuously introducing carbon dioxide into the solution A, wherein the introduction speed is 40mL/min, the stirring speed is 150r/min, and stirring is continuously carried out to gradually form calcium carbonate whiskers under the induction of magnesium salts; soaking, cleaning and drying to obtain the calcium carbonate crystal whisker.
Comparative example 1 is a comparative example of example 1, and in comparative example 1, the surface of calcium carbonate whiskers was not subjected to titanium dioxide whitening treatment.
Sample preparation and whiteness measurement
The performance tests of examples 1 to 6 and comparative example 1 were performed, and the test results are shown in table 1:
1. 1Kg of the calcium carbonate whiskers obtained in examples 1 to 6 and comparative example 1 of the present invention were weighed, mixed with 5Kg of polypropylene, extruded and calendered into sheets (which were respectively referred to as sample 1, sample 2, sample 3, sample 4, sample 5, sample 6, and sample 7 in this order), and the whiteness of the sheets was measured.
2. 1Kg of the unbleached calcium carbonate whiskers of comparative example 1 were weighed, mixed with 0.1Kg of titanium dioxide and 5Kg of polypropylene, extrusion-calendered to form a sheet (designated as sample 8), and the whiteness of the sheet was measured.
Test standards and methods:
samples 1 to 8 prepared by the above method were subjected to the whiteness test as specified in the test method for whiteness of plastics (GB 2913-1982), and the results are shown in Table 1:
table form
As can be seen from the data in Table 1, the polypropylene sheets prepared in examples 1 to 6 all have higher whiteness values, and the whiteness is more than 90%. However, the whiteness of the polypropylene sheet obtained in the comparative example 1 is lower than 60% because the surface is not coated and whitened by titanium dioxide, and the polypropylene sheet is darker in color; the calcium carbonate whiskers prepared in comparative example 1 had low whiteness of the final polypropylene sheet because the surface titanium dioxide whitening treatment was not performed, and even when the polypropylene sheet (sample 8) was prepared by adding a certain amount of finished titanium dioxide at a later stage, the whiteness of the final polypropylene sheet was still lower than that of the polypropylene sheets prepared in examples 1 to 6. Therefore, after the calcium carbonate fiber is used for plastic products, the natural color of the fibrous calcium carbonate whisker is difficult to cover by adding the granular titanium dioxide due to the fiber characteristics, the whiteness of the calcium carbonate whisker prepared by coating titanium dioxide on the surface in the preparation process cannot be achieved, the whitening effect is poor, and more powdery titanium dioxide needs to be wasted in order to achieve the almost whiteness; the titanium dioxide powder added in the process of preparing the plastic by the calcium carbonate whiskers at the later stage is very easy to agglomerate in the plastic, is unevenly distributed, even leads to different whiteness values of all parts of the plastic, and can lead to the falling of the titanium dioxide powder in the preparation and use processes of the plastic, thereby seriously influencing the normal use of the plastic.
In conclusion, the calcium carbonate whisker is prepared firstly, then the characteristic that tetrabutyl titanate is hydrolyzed to form titanium dioxide under the condition of acetic acid is utilized, so that the surface of the calcium carbonate whisker is coated with a layer of titanium dioxide, particularly, a small amount of acetic acid slightly dissolves the surface of the calcium carbonate whisker while tetrabutyl titanate is hydrolyzed under the environment of acetic acid, and thus the specific surface of the calcium carbonate whisker is in an unstable state, and the formed titanium dioxide is firmly combined with the surface of the calcium carbonate whisker. The calcium carbonate crystal whisker obtained by the invention is white, can be used for reinforcing plastics, can achieve the purposes of strength and whitening, and overcomes the defect that the fibrous material is difficult to cover by directly adding granular titanium dioxide. Furthermore, the calcium carbonate crystal whisker has rich interfaces, and titanium dioxide is formed on the interfaces, so that the covering and whitening effects of the interfaces of the titanium dioxide are exerted to the maximum extent; particularly, the method has huge application space in the reinforcement of plastics such as white household appliances.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A preparation method of whitening calcium carbonate whiskers for plastic reinforcement is characterized by comprising the following steps:
step one, Ca (OH)2Adding water to prepare suspension, and then adding magnesium salt to the solution A, stirring and dispersing at a high speed of 600r/min for 1-3 h;
wherein, Ca (OH)2The weight ratio of water to magnesium salt is 10-15:60-80: 1-2;
step two, mixing acetic acid, water and ethanol to prepare a solution B with the pH of 4-5;
wherein the weight ratio of the acetic acid to the water to the ethanol is 1-3:6-8: 3-5;
step three, continuously introducing carbon dioxide into the solution A, continuously stirring, and gradually forming calcium carbonate whiskers under the induction of magnesium salts; soaking, cleaning and drying to obtain calcium carbonate whiskers;
step four, adding the calcium carbonate whiskers obtained in the step 3 into a stirrer, and stirring at a high speed for suspension; and adding tetrabutyl titanate into the solution B, spraying and adding into a stirrer, gradually hydrolyzing tetrabutyl titanate to coat the surface of the calcium carbonate crystal whisker, and sintering at the temperature of 400-500 ℃ to obtain the whitening calcium carbonate crystal whisker for plastic reinforcement.
2. The method of claim 1, wherein the whitening calcium carbonate whiskers are prepared by the following steps: in the step one, the magnesium salt is at least one of magnesium chloride, magnesium hydroxide, magnesium sulfate, magnesium borate, magnesium oxide and magnesium nitrate.
3. The method for preparing whitening calcium carbonate whiskers for plastic reinforcement according to claim 2, characterized in that: in the step one, the magnesium salt is magnesium chloride.
4. A method for preparing whitening calcium carbonate whiskers for plastic reinforcement according to any one of claims 1-3, characterized in that: step oneCa (OH) described in (1)2The weight ratio of water to magnesium salt is 12:70: 1.5.
5. The method of claim 1, wherein the whitening calcium carbonate whiskers are prepared by the following steps: in the second step, the weight ratio of the acetic acid to the water to the ethanol is 3:7: 4.
6. The method of claim 1, wherein the whitening calcium carbonate whiskers are prepared by the following steps: in the third step, the carbon dioxide is continuously introduced into the liquid A at the introduction rate of 30-60mL/min and the stirring rate of 100-200 r/min.
7. The method of claim 1, wherein the whitening calcium carbonate whiskers are prepared by the following steps: in the fourth step, the stirring speed of the high-speed stirring is 800-1200r/min, and the stirring time is 3-5 h.
8. The method of claim 1, wherein the whitening calcium carbonate whiskers are prepared by the following steps: in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 2-4; and the spraying amount of the tetrabutyl titanate added with the solution B is 15-18% of the mass of the calcium carbonate crystal whisker.
9. The method of claim 8, wherein the whitening calcium carbonate whiskers are prepared by the following steps: in the fourth step, the mixing mass ratio of the tetrabutyl titanate to the liquid B is 1: 3; and the spraying amount of the tetrabutyl titanate added with the solution B is 16 percent of the mass of the calcium carbonate crystal whisker.
10. The whitening calcium carbonate whisker for plastic reinforcement is characterized by being prepared by the preparation method of any one of claims 1 to 9.
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| CN113564688A (en) * | 2021-07-09 | 2021-10-29 | 沈阳化工大学 | Preparation method of calcium carbonate whisker |
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