CN114716847A - Preparation method of pearlescent pigment with flaky alpha-alumina as substrate - Google Patents

Preparation method of pearlescent pigment with flaky alpha-alumina as substrate Download PDF

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CN114716847A
CN114716847A CN202210565132.3A CN202210565132A CN114716847A CN 114716847 A CN114716847 A CN 114716847A CN 202210565132 A CN202210565132 A CN 202210565132A CN 114716847 A CN114716847 A CN 114716847A
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pearlescent pigment
solution
flaky alpha
regulator
preparing
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CN114716847B (en
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刘风坤
龙开琳
姚建波
黄毅
崔博文
朱化强
何美琪
陈志豪
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Guiyang Vocational and Technical College
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
    • C09C1/0015—Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings
    • C09C1/0021—Pigments exhibiting interference colours, e.g. transparent platelets of appropriate thinness or flaky substrates, e.g. mica, bearing appropriate thin transparent coatings comprising a core coated with only one layer having a high or low refractive index
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/006—Combinations of treatments provided for in groups C09C3/04 - C09C3/12
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/04—Physical treatment, e.g. grinding, treatment with ultrasonic vibrations
    • C09C3/043—Drying, calcination
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
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    • C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
    • C09C3/06—Treatment with inorganic compounds
    • C09C3/063—Coating
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C2200/00—Compositional and structural details of pigments exhibiting interference colours
    • C09C2200/10—Interference pigments characterized by the core material
    • C09C2200/1004—Interference pigments characterized by the core material the core comprising at least one inorganic oxide, e.g. Al2O3, TiO2 or SiO2
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    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C2200/00—Compositional and structural details of pigments exhibiting interference colours
    • C09C2200/40—Interference pigments comprising an outermost surface coating
    • C09C2200/401—Inorganic protective coating
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
    • C09C2200/00—Compositional and structural details of pigments exhibiting interference colours
    • C09C2200/50—Interference pigments comprising a layer or a core consisting of or comprising discrete particles, e.g. nanometric or submicrometer-sized particles
    • C09C2200/505—Inorganic particles, e.g. oxides, nitrides or carbides

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  • Pigments, Carbon Blacks, Or Wood Stains (AREA)
  • Cosmetics (AREA)

Abstract

The invention discloses a preparation method of pearlescent pigment using flaky alpha-alumina as substrate, firstly, flaky alpha-Al is used2O3Adding adsorbent and acidic pH regulator I into the matrix solution to obtain flaky alpha-Al2O3An aqueous suspension solution with a negatively charged surface; adding a metal salt solution and an alkaline pH regulator II into the aqueous suspension solution, and performing hydrolysis coating reaction to obtain a pearlescent pigment precursor; and finally, filtering, washing, drying and calcining the pearlescent pigment precursor to obtain the pearlescent pigment. The prepared pearlescent pigment can show obvious pearlescent effect, and the pigment has higher chemical stability and mechanical stability; the application range is wide, and the coating can be applied to products which are in service outdoors for a long time and high-temperature environments.

Description

Preparation method of pearlescent pigment with flaky alpha-alumina as substrate
Technical Field
The invention relates to a preparation method of pearlescent pigment with flaky alpha-alumina as a substrate, belonging to the field of pigment preparation.
Background
With the advent of the "face-viewing" era, people gradually put higher demands on colors. The conventional common pigment can not meet the requirements of people, and the pearlescent pigment has optical characteristics of pearlescent effect, angle-dependent heterochromatic effect, metal flashing effect, color transfer effect, hyperchromic effect and the like due to different color development principles, and can be applied to the fields of cosmetics, automobile paint, coating, packaging, printing and the like with higher requirements on colors. However, since the first generation pearlescent pigment is made of natural or synthetic mica as a substrate, there are the following disadvantages: the thickness distribution range is wide. Therefore, when the metal oxide is coated, the steps and the edge thickness on the layer surface can cause the light to generate the scattering phenomenon, thereby reducing the pearlescent effect. ② containing some colored impurities. These impurities will affect the pearlescent pigment gloss, and removal of the impurities is not only time consuming but also costly. And thirdly, the surface is easy to damage in the crushing and grading processes, the surface roughness is increased, and the pearl luster of the pearlescent pigment is influenced finally. And fourthly, the heat resistance is not high (the mechanism is damaged at about 800 ℃), although some pearlescent pigments with certain weather resistance exist in the current market, the pearlescent pigments still cannot resist outdoor products such as automobiles, and the weather resistance of the pearlescent pigments is still required to be improved after long-term sunlight exposure. This greatly limits the range of applications.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing pearlescent pigment using flaky alpha-alumina as a substrate, which can overcome the defects of the prior art.
The purpose of the invention is realized by the following technical scheme:
a preparation method of pearlescent pigment using flaky alpha-alumina as a substrate comprises the following steps:
s1 flaky alpha-Al2O3Adding adsorbent and acidic pH regulator I into the matrix solution to obtain flaky alpha-Al2O3An aqueous suspension solution with a negatively charged surface;
s2, adding a metal salt solution and an alkaline pH regulator II into the aqueous suspension solution, and carrying out hydrolysis coating reaction to obtain a pearlescent pigment precursor;
s3, filtering, washing and drying the pearlescent pigment precursor, and calcining the dried precursor to obtain the pearlescent pigment.
In the preparation method described above, the raw materials,
firstly, continuously heating the matrix liquid, adding an adsorbent and an acidic pH regulator I, and carrying out ultrasonic dispersion and strong stirring;
secondly, slowly adding a metal salt solution and an alkaline pH regulator II while continuously heating, slowly stirring to gradually weaken the acidity of the solution, driving the metal salt solution to hydrolyze and coat on the surface of alumina, and preparing a pearlescent pigment precursor;
and finally, filtering, washing and drying the pearlescent pigment precursor, and calcining at the calcining temperature of 750-900 ℃ to obtain the pearlescent pigment.
In the preparation method described above, the raw materials,
when preparing the aqueous suspension solution, continuously heating to 60-90 ℃, ultrasonically dispersing for 15-20min, and then strongly stirring for 20-30 min;
continuously heating and keeping at 60-90 ℃, simultaneously adding the metal salt solution at the dropping speed of 0.5-1.5ml/min, slowly adding the alkaline pH regulator II, and continuously stirring at the stirring speed of 200-350r/min to perform hydrolysis coating reaction.
The preparation method comprises preparing flaky alpha-Al2O3Adding deionized water as matrix to obtain matrix solution, wherein the deionized water is added in flaky alpha-Al2O31500-2500% by weight.
In the preparation method, the adding amount of the adsorbent is flaky alpha-Al2O30.5-2% by weight;
the adsorbent is an anionic polyelectrolyte adsorbent; comprises at least one of sodium polyacrylate, polyacrylic acid, acrylic acid/acrylate copolymer and sodium hexametaphosphate.
In the preparation method described above, the raw materials,
the adding amount of the acidic pH regulator I is 10 percent of the weight of the aqueous suspension or the pH value of the solution is not more than 2;
the acidic pH regulator I comprises one or a mixture of more of dilute hydrochloric acid, dilute sulfuric acid and dilute nitric acid, and the mixing amount is not limited.
In the preparation method described above, the raw materials,
the addition amount of the metal salt solution is 10 percent of the weight of the aqueous suspension solution;
the metal salt solution is any soluble metal salt solution.
In the preparation method described above, the raw materials,
the addition amount of the alkaline pH regulator II is 10 percent of the weight of the aqueous suspension solution or the pH value of the solution is not less than 2.5;
the alkaline pH regulator II is one or a mixture of more of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonia water, ammonia gas, potassium hydroxide, potassium carbonate and potassium bicarbonate, and the mixing amount is not limited.
The pearlescent pigment prepared by the preparation method is flaky alpha-Al2O3Is a substrate, and the coating layer on the outer surface of the substrate is one or more layers of metal oxides; and the thicknesses of the coating layers are the same or different.
In the preparation method, the metal salt solution is added in sequence, and the matrix is coated by adopting the following sequence:
α-Al2O3+Fe2O3
α-Al2O3+TiO2
α-Al2O3+Fe2O3+TiO2
α-Al2O3+TiO2+Fe2O3。
compared with the prior art, the invention discloses a method for preparing pearlescent pigment by using flaky alpha-alumina as a substrate, which firstly uses flaky alpha-Al2O3Adding adsorbent and acidic pH regulator I into the matrix solution to obtain flaky alpha-Al2O3An aqueous suspension solution with a negatively charged surface; adding a metal salt solution and an alkaline pH regulator II into the aqueous suspension solution, and performing hydrolysis coating reaction to obtain a pearlescent pigment precursor; and finally, filtering, washing, drying and calcining the pearlescent pigment precursor to obtain the pearlescent pigment.
The beneficial effects of the invention are:
in order to meet the higher pursuit of pearlescent pigments, the pearlescent pigments using flaky alpha-alumina as a substrate have the following advantages: compared with the traditional natural mica, the flaky alumina has the characteristics of high refractive index, uniform and controllable thickness, flat and smooth surface, pure and transparent appearance, high temperature resistance and the like, and can be effectively combined with active functional groups of other materials, so that the product has design freedom and physicochemical properties which cannot be obtained by the natural mica, has narrower particle size distribution and large thickness-diameter ratio, is almost completely colorless and has a smooth and flat surface, and is an ideal pearlescent pigment substrate for replacing the mica; adding adsorbent and acidic pH regulator I into flaky alpha-alumina matrix to obtain flaky alpha-Al2O3An aqueous suspension solution with a negatively charged surface; the aqueous suspension solution is acidic, after the metal salt solution is added, the hydrolysis speed of the metal salt solution can be well controlled by controlling the adding speed of the alkaline pH regulator II, and metal cations hydrolyzed by the metal salt solution can be well coated on the flaky alpha-Al according to the principle of opposite attraction2O3The surface of the pearlescent pigment enables the pearlescent pigment prepared subsequently to show obvious pearlescent effect, and the pearlescent pigment prepared after the coating rate is improved has higher chemical stability and mechanical stability.
The pearlescent pigment disclosed by the invention is wide in application range, can be applied to products which are used outdoors for a long time, such as the automotive industry, can enable the appearance of a vehicle to be more cool and individual, can also enable the vehicle to still keep the original color under the condition that the vehicle is subjected to wind, wind and sun for a long time, and greatly prolongs the service life of the automotive paint; can be used in high-temperature environment: the pearlescent pigments of the invention can be used for products with color requirements during the sintering of ceramics.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings, in which:
FIG. 1 is a schematic view of the preparation process of the present invention.
FIG. 2 shows flaky alpha-Al2O3Zeta potential of an aqueous suspension solution is plotted against pH.
FIG. 3 shows flaky alpha-Al after sodium polyacrylate is added2O3Zeta potential change curve of water suspension solution.
Detailed Description
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the preferred embodiments are illustrative of the invention only and are not limiting upon the scope of the invention.
As shown in fig. 1, a method for preparing pearlescent pigment using flaky alpha-alumina as a substrate comprises the following steps:
s1 flaky alpha-Al2O3Adding adsorbent and acidic pH regulator I into the matrix solution to obtain flaky alpha-Al2O3An aqueous suspension solution with a negatively charged surface;
s2, adding a metal salt solution and an alkaline pH regulator II into the aqueous suspension solution, and carrying out hydrolysis coating reaction to obtain a pearlescent pigment precursor;
and s3, filtering, washing and drying the pearlescent pigment precursor, and calcining the dried precursor to obtain the pearlescent pigment.
In particular, the amount of the solvent to be used,
firstly, continuously heating the matrix liquid, adding an adsorbent and an acidic pH regulator I, and carrying out ultrasonic dispersion and strong stirring; preferably, the continuous heating temperature is kept at 60-90 ℃, and ultrasonic dispersion is firstly carried out for 15-20min and then strong stirring is carried out for 20-30 min when the aqueous suspension solution is prepared;
secondly, slowly adding a metal salt solution and an alkaline pH regulator II while continuously heating, slowly stirring to gradually weaken the acidity of the solution, driving the metal salt solution to hydrolyze and coat on the surface of alumina, and preparing a pearlescent pigment precursor; preferably, the continuous heating temperature is kept between 60 and 90 ℃, the metal salt solution is added at the dropping speed of 0.5 to 1.5ml/min, meanwhile, the alkaline pH regulator II is slowly added, and the continuous stirring is carried out at the stirring speed of 200-350r/min, so as to carry out the hydrolysis coating reaction;
and finally, filtering, washing and drying the pearlescent pigment precursor, and calcining at the calcining temperature of 750-900 ℃ to obtain the pearlescent pigment.
In a step s1, the method is carried out,
in the form of flaky alpha-Al2O3Adding deionized water as matrix to obtain matrix solution, wherein the deionized water is added in flaky alpha-Al2O31500-2500% by weight. Flaky alpha-Al2O3May be made by oneself or purchased, and the flaky alpha-Al2O3D50, MIU value and thickness range of the alloy meet the use requirements; preferably, the flaky alpha-Al2O3D of (A)50Greater than 10 μm, an MIU value (measured by KES Friction tester) of less than 0.8 and a thickness of less than 0.5 μm.
The addition amount of the adsorbent is flaky alpha-Al2O30.5-2% by weight.
The adsorbent is an anionic polyelectrolyte adsorbent; comprises at least one of sodium polyacrylate, polyacrylic acid, acrylic acid/acrylate copolymer and sodium hexametaphosphate. Preferably the adsorbent is sodium polyacrylate and acrylic acid/acrylate copolymer.
The addition amount of the acidic pH regulator I is 10 percent of the weight of the aqueous suspension or the pH value of the solution is not more than 2.
The acidic pH regulator I comprises one or a mixture of more of dilute hydrochloric acid, dilute sulfuric acid and dilute nitric acid, and the mixing amount is not limited.
In a step s2, the method is carried out,
the metal salt solution is added in an amount of 10% by weight of the aqueous suspension solution.
The metal salt solution is any soluble metal salt solution, such as ferric trichloride, ferric nitrate, titanium tetrachloride, titanyl sulfate and the like.
The addition amount of the alkaline pH regulator II is 10 percent of the weight of the aqueous suspension solution or the pH value of the solution is not less than 2.5.
The alkaline pH regulator II is one or a mixture of more of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonia water, ammonia gas, potassium hydroxide, potassium carbonate and potassium bicarbonate, and the mixing amount is not limited.
Step s3, the pearlescent pigment is prepared as flaky alpha-Al2O3Is a substrate, and the coating layer on the outer surface of the substrate is one or more layers of metal oxides; and the thicknesses of the clad layers are the same or different.
Preferably, the metal salt solutions are added sequentially, coating the substrate in the following order:
α-Al2O3+Fe2O3
α-Al2O3+TiO2
α-Al2O3+Fe2O3+TiO2
α-Al2O3+TiO2+Fe2O3
the pearlescent pigment can be applied to the fields of cosmetics, automobile paint, coating, packaging, printing and the like with higher requirements on colors.
In the embodiment of example 1, the following procedure was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate is added to 100ml of deionized water, and the pH of the solution is adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 80 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 2, the following example was carried out,
no adsorbent is added;
5g of flaky alpha-Al was taken2O3The solution was added to 100ml of deionized water, and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 80 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace, and calcining at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 3, the following example was carried out,
5g of flaky alpha-Al was taken2O30.1g of sodium polyacrylate, addThe solution was added to 100ml of deionized water and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 80 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the example of the implementation of the process according to example 4,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate was added to 100ml of deionized water, and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 80 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 2.5. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace, and calcining at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 5, the following example was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate is added to 100ml of deionized water, and the pH of the solution is adjusted to 2. Stirring strongly with magnetic stirrer for 60min, and ultrasonic dispersing for 15 minThe temperature of the solution was maintained at 85 ℃. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.5. Stirring slowly for 5min, stopping stirring, filtering out suspended solid while the suspended solid is hot, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 6, the following example was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate is added to 100ml of deionized water, and the pH of the solution is adjusted to 2. The solution is stirred vigorously by a magnetic stirrer for 60min, and then dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 70 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace, and calcining at 830 ℃ for 60 min. Taking out the calcined product, namely Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 7, the following example was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate was added to 100ml of deionized water, and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 90 ℃ in the process. While keeping the suspension slowly stirred by a magnetic stirrer, adding 10% of tris (hydroxymethyl) phosphonium chloride slowlyDissolving 50ml of ferric chloride, and adding 10 percent sodium hydroxide solution by mass to adjust the pH value so as to slowly increase the pH value from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 8, the following example was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate was added to 100ml of deionized water, and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 80 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 35ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 2.5. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine at 830 ℃ for 60 min. Taking out the calcined product, namely Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the example of the embodiment 9, the following example was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate was added to 100ml of deionized water, and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 80 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 75ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Continuously slowly stirringStirring for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine at 830 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the embodiment of example 10, the following example was carried out,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate was added to 100ml of deionized water, and the pH of the solution was adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 90 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace, and calcining at 700 ℃ for 60 min. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
In the example of the implementation of the process of example 11,
5g of flaky alpha-Al was taken2O30.03g of sodium polyacrylate is added to 100ml of deionized water, and the pH of the solution is adjusted to 2. The solution is stirred strongly by a magnetic stirrer for 60min, and then is dispersed by ultrasonic for 15 min, and the temperature of the solution is kept at 90 ℃ in the process. While keeping the suspension being slowly stirred by a magnetic stirrer, 50ml of 10% by mass ferric chloride solution was slowly added, and 10% by mass sodium hydroxide solution was added to adjust the pH value so that the pH value was slowly increased from 2.0 to 3.0. Stirring slowly for 5min, filtering to obtain suspended solid, washing with water, and drying to obtain Fe2O3/Al2O3A precursor of an iron-based pearlescent pigment.
And (3) putting the pearlescent pigment precursor into a muffle furnace to calcine for 60min at 900 ℃. Taking out the calcined product to obtain Fe2O3/Al2O3Iron-based pearlescent pigment samples.
The invention has the advantages that:
(1) from the pearlescent pigments prepared in the embodiments 1 to 11, the addition of the adsorbent can significantly improve the coating rate, the pigment can exhibit strong pearlescent effect, the pigment still has high chemical stability and mechanical stability at high temperature,
the preparation parameters of the examples 1 to 11 are summarized in the following table:
Figure BDA0003657771320000121
(2) the hydrolysis coating effect is good;
the charging of the aqueous suspension of flaky alpha-alumina is shown in figure 2,
in the flaky alpha-alumina aqueous suspension solution, the surface of alumina has different charges due to the adsorption of different ions and has different Zeta potentials, the Zeta potential in the flaky alumina serving as amphoteric oxide in the suspension solution is related to the pH value of the solution, the Zeta potential in the suspension solution is a positive potential under the condition of not adding an adsorbent, namely in an environment with the pH value less than 6, and the Zeta potential in the suspension solution is a weak negative potential only in the environment with the pH value less than 6; however, the hydrolysis of the metal salt solution can be inhibited to a certain extent only in an acidic solution environment, the hydrolysis reaction speed is controlled, if the hydrolysis speed is too high, a large amount of ferric hydroxide particles are generated in a short time, and the large amount of generated particles can not be completely adsorbed by the surface of aluminum hydroxide, so that the particles grow into flocculent precipitates, which affects the coating rate on one hand and affects the pearl effect of the product on the other hand.
Therefore, the flaky alpha-alumina aqueous suspension solution can only be acidic, so that the Zeta potential in the suspension aqueous solution is positive potential, the metal cation generated by hydrolysis of the metal salt solution is also positive potential, the potentials of the two are the same, and the adsorption effect is poor.
When a certain amount of sodium polyacrylate is added into the flaky alumina suspension aqueous solution and the pH value is adjusted at the same time, the relation between the Zeta potential and the pH value is shown in figure 2, and the added sodium polyacrylate enables the Zeta potential of the flaky alumina suspension aqueous solution to be changed from the original positive potential to a strong negative potential in an acidic environment, for example, when the pH value is equal to 3, the Zeta potential is changed from +40mV to-35 mV.
The flaky alpha-alumina with negative charges on the surface can absorb ions with opposite electric property and equal charges in the solution, so as to form an electric double layer structure. Thus, when a solution of an iron salt is added to an aqueous suspension of flaky alpha-alumina, [ Fe (H) is present in the solution2O)6]3+Is tightly bound on the surface of alumina in the form of counter particles in an 'electric double layer structure', and under the action of hydrolysis driving force such as pH value or temperature, the Fe (H) is bound on the surface of alumina2O)6]3+Since the concentration is higher than that of other parts in the solution, hydrolysis occurs first to generate iron hydroxide fine particles, and these iron hydroxide fine particles formed on the surface of alumina are the first formed crystal nuclei. As the driving force for hydrolysis increases, on the one hand, these first-formed nuclei start to grow in a different manner, and on the other hand, iron hydroxide particles start to form in solution, in which they are suspended, at other locations in the solution, and can adsorb FeO in the solution+The ions become positively charged. In the hydrolysis system of the sheet-shaped alumina-ferric salt, the particle size of the sheet-shaped alumina particles is 10 μm, the sheet-shaped alumina particles have large specific surface area, the sheet-shaped alumina particles are thermodynamically unstable systems, the surface energy of the systems needs to be reduced through agglomeration, and the average particle size of the positively charged ferric hydroxide colloid particles suspended in the solution is not more than 0.1 μm, so that strong mutual agglomeration is generated between the sheet-shaped alumina particles and the ferric hydroxide colloid particles, and strong electrostatic adsorption is also generated due to opposite charges between the sheet-shaped alumina particles and the ferric hydroxide colloid particles. Thus, under the simultaneous action of mutual condensation and electrostatic adsorption, liquid phase deposition is completedAnd reacting to prepare the pearlescent pigment precursor.
After the adsorbent is added, in the flaky alpha-alumina aqueous suspension solution, when the pH value is 2-3, the zeta potential of the surface of the alumina changes from positive to negative, which is just opposite to the electric property of the adsorbed metal cation, so that the coating effect can be improved.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention without departing from the technical spirit of the present invention are within the scope of the present invention.

Claims (10)

1. A method for preparing pearlescent pigment with flaky alpha-alumina as a substrate is characterized by comprising the following steps:
s1 flaky alpha-Al2O3Adding adsorbent and acidic pH regulator I into the matrix solution to obtain flaky alpha-Al2O3An aqueous suspension solution with a negatively charged surface;
s2, adding a metal salt solution and an alkaline pH regulator II into the aqueous suspension solution, and carrying out hydrolysis coating reaction to obtain a pearlescent pigment precursor;
and s3, filtering, washing and drying the pearlescent pigment precursor, and calcining the dried precursor to obtain the pearlescent pigment.
2. The method for preparing pearlescent pigment based on flaky alpha-alumina according to claim 1, characterized in that:
firstly, continuously heating the matrix liquid, adding an adsorbent and an acidic pH regulator I, and carrying out ultrasonic dispersion and strong stirring;
secondly, slowly adding a metal salt solution and an alkaline pH regulator II while continuously heating, slowly stirring to gradually weaken the acidity of the solution, driving the metal salt solution to hydrolyze and coat on the surface of alumina, and preparing a pearlescent pigment precursor;
and finally, filtering, washing and drying the pearlescent pigment precursor, and calcining at the calcining temperature of 750-900 ℃ to obtain the pearlescent pigment.
3. The method for preparing a pearlescent pigment based on flaky alpha-alumina according to claim 2, characterized in that:
when preparing the aqueous suspension solution, continuously heating to 60-90 ℃, ultrasonically dispersing for 15-20min, and then strongly stirring for 20-30 min;
continuously heating and keeping at 60-90 ℃, simultaneously adding the metal salt solution at the dropping speed of 0.5-1.5ml/min, slowly adding the alkaline pH regulator II, and continuously stirring at the stirring speed of 200-350r/min to carry out hydrolysis coating reaction.
4. A method for preparing a pearlescent pigment based on flaky alpha-alumina according to claim 3, characterized in that: in the form of flake alpha-Al2O3Adding deionized water as matrix to obtain matrix solution, wherein the deionized water is added in flaky alpha-Al2O31500-2500% by weight.
5. The method for preparing pearlescent pigment based on flaky alpha-alumina according to claim 3, characterized in that: the addition amount of the adsorbent is flaky alpha-Al2O30.5-2% by weight;
the adsorbent is an anionic polyelectrolyte adsorbent; comprises at least one of sodium polyacrylate, polyacrylic acid, acrylic acid/acrylate copolymer and sodium hexametaphosphate.
6. A method for preparing a pearlescent pigment based on flaky alpha-alumina according to claim 3, characterized in that:
the addition amount of the acidic pH regulator I is 10 percent of the weight of the aqueous suspension or the pH value of the solution is not more than 2;
the acidic pH regulator I comprises one or a mixture of more of dilute hydrochloric acid, dilute sulfuric acid and dilute nitric acid, and the mixing amount is not limited.
7. A method for preparing a pearlescent pigment based on flaky alpha-alumina according to claim 3, characterized in that:
the addition amount of the metal salt solution is 10 percent of the weight of the aqueous suspension solution;
the metal salt solution is any soluble metal salt solution.
8. The method for preparing pearlescent pigment based on flaky alpha-alumina according to claim 3, characterized in that:
the addition amount of the alkaline pH regulator II is 10 percent of the weight of the aqueous suspension solution or the pH value of the solution is not less than 2.5;
the alkaline pH regulator II is one or a mixture of more of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonia water, ammonia gas, potassium hydroxide, potassium carbonate and potassium bicarbonate, and the mixing amount is not limited.
9. A process for preparing pearlescent pigments based on flaky alpha-alumina according to any one of claims 1 to 8, characterized in that: the prepared pearlescent pigment is flaky alpha-Al2O3Is a substrate, and the coating layer on the outer surface of the substrate is one or more layers of metal oxides; and the thicknesses of the clad layers are the same or different.
10. The method for preparing a pearlescent pigment based on flaky alpha-alumina according to claim 9, characterized in that: the metal salt solution was added sequentially, and the matrix was coated in the following order:
α-Al2O3+Fe2O3
α-Al2O3+TiO2
α-Al2O3+Fe2O3+TiO2
α-Al2O3+TiO2+Fe2O3。
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