KR20040087055A - Method of Polymer Addition for Particle Shape and Evaluation of Dispersion Stability of Precipitated Calcium Carbonate - Google Patents

Abstract

PURPOSE: A method for adding a polymer to a precipitated calcium carbonate suspension is provided, to improve the particle shape and dispersion stability of a precipitated calcium carbonate by adding a polymer surfactant during the electrical conductivity change period in the preparation process of precipitated calcium carbonate. CONSTITUTION: The method comprises the steps of adding a polymer surfactant to a calcium carbonate suspension when the calcium carbonate suspension is prepared by injecting a CO2 gas with stirring at a room temperature, to allow the polymer surfactant to be adsorbed to the surface of the precipitated carbon carbonate; and analyzing the dispersion stability of the precipitated calcium carbonate after filtering and drying. Preferably the CO2 gas is injected with a flow rate of 500 L/min and the suspension is stirred with a velocity of 300 rpm at 20 deg.C to prepare a 3.5 wt% precipitated calcium carbonate suspension. Preferably the polymer surfactant is polyoxyethylene nonylphenyl ether and is added before the carbonation of precipitated calcium carbonate or during the first increase period of electrical conductivity in carbonation, or the polymer surfactant is PMAA(polymethacrylic acid) and is added during the first increase period of electrical conductivity in carbonation.

Description

Method of Polymer Addition for Particle Shape and Evaluation of Dispersion Stability of Precipitated Calcium Carbonate}

The present invention adds PMAA (Poly (methacrylic Acid), an anionic surfactant, at each time when electrical conductivity changes during the production of precipitated calcium carbonate by carbonation, and when the molar number of ethylene oxide is large, it is a nonionic surfactant. By adding Poly (oxyethylene) Nonylphenyl Ether, the present invention relates to a method for adding a polymer for improving the shape and dispersion stability of precipitated calcium carbonate particles which improves the properties of the produced product by improving the dispersibility of the filler by improving the interfacial properties with the raw materials.

In general, in the papermaking industry, precipitated calcium carbonate is widely used in papermaking, rubber, medicine, foodstuffs, and manufacturing for two purposes, fillers and coatings. In particular, fillers form an interface between the final product and the filler surface. Since the properties of the interface directly affect the physical properties of the final material, the dispersibility and bonding strength of the final product of the filler have a great influence on the product quality, life and added value. Therefore, it can be said that improving the dispersibility of the filler in order to improve the properties of the paper.

However, in the case of powder fillers, which are widely used at present, in the post-treatment process such as filtration and drying of products, a large amount of loss occurs during transportation and processing, as well as deterioration of physical properties due to agglomeration of powder. Many problems have occurred such as deterioration.

An object of the present invention for improving this, by forming the adsorption layer at each time when the electrical conductivity is changed during the production of precipitated calcium carbonate by the carbonation method, anionic surfactant PMAA (Poly (methacrylic Acid)) to have an electrostatic repulsion If the mole number of ethylene oxide is large, water-soluble method adds Poly (oxyethylene) Nonylphenyl Ether, a nonionic surfactant that induces a new phase by the addition of this surfactant in aqueous solution. It is to improve the dispersibility of the filler by.

In addition, as the properties of the calcium carbonate is improved and the post-treatment process is omitted, the method of adding a polymer for improving the shape and dispersion stability of the precipitated calcium carbonate particles to obtain technical and economic benefits by preventing the agglomeration of the powder and simplifying the process. To provide.

1 is a manufacturing process diagram of the present invention.

2 is a graph of zeta potential according to pH of precipitated calcium carbonate synthesized by carbonation.

Figure 3 is a pH diagram over time of the precipitated calcium carbonate suspension after the end of the carbonation reaction.

4a or 4b is an electrical conductivity and electron micrograph according to the reaction time of CO ₂ after addition of Poly (oxyethylene) Nonylphenyl Ether and calcined oil before carbonation reaction.

5a or 5b is an electrical conductivity and electron micrograph after the addition of Poly (oxyethylene) Nonylphenyl Ether at the first rise in conductivity during the carbonation reaction.

Figure 6a or Figure 6b is an electrical conductivity and electron micrograph after the conductivity of the poly (oxyethylene) Nonylphenyl Ether at the time of the last drop in the carbonation reaction.

Figure 7 is a graph showing the dispersion characteristics according to the amount of PMAA added to the precipitated calcium carbonate suspension after the carbonation reaction is finished at 20 ℃.

Figure 8 is a graph showing the dispersion characteristics when the carbonation reaction while injecting PMAA into the Ca (OH) ₂ suspension and blowing the CO ₂ .

9 is a graph showing dispersion characteristics according to the amount of PMAA added at the first rise in conductivity.

10 is a graph showing the dispersion characteristics according to the amount of PMAA added at the last drop in electrical conductivity during carbonation reaction.

The present invention for achieving the object as described above, when preparing a precipitated calcium carbonate suspension by injecting CO ₂ gas while stirring the calcium hydroxide suspension at room temperature, the polymer surfactant according to the point of change in the electrical conductivity of the precipitated calcium carbonate suspension Provided is a method for adding a polymer for improving the shape and dispersion stability of precipitated calcium carbonate particles which are charged, sample collected, filtered and dried to analyze dispersion stability.

In addition, the precipitated calcium carbonate suspension according to the present invention is prepared by injecting CO ₂ gas at 500 ml / min while stirring at a rate of 300 rpm at a reaction temperature of 20 ° C. to prepare a precipitated calcium carbonate suspension having a concentration of 3.5 wt.%. It is characterized by.

In addition, the addition of the polymer surfactant according to the present invention, the crystal growth interval of the chain type calsite is shortened by the delay of the first falling step of the electrical conductivity is made to produce a colloidal calsite of 50 nm or less with good dispersibility Poly (oxyethylene) Nonylphenyl Ether, which is a nonionic surfactant, is added before the carbonation reaction of precipitated calcium carbonate and during the first rise of electrical conductivity.

In addition, the addition of the polymer surfactant according to the present invention, during the first rise of the electrical conductivity during the precipitated calcium carbonate carbonation reaction to suppress the transition of the intermediate phase chain-calcite to the colloidal calsite to form a needle-like calsite PMAA, an anionic surfactant having a concentration of 0.6wt.% To 0.8wt.%, Is added thereto.

Referring to the configuration of the present invention and its operation in detail with reference to the accompanying drawings as follows.

As shown in FIG. 1, first, 16.281 g of calcium hydroxide and 600 ml of distilled water were prepared in a beaker at 1 ° C. to prepare a calcium hydroxide suspension, and then stirred at a speed of 300 rpm at room temperature with 500 ml / min of CO _2. Prepare a precipitated calcium carbonate suspension by injecting gas, add surfactant, a polymer dispersant, and collect, filter, and dry at the time when the electrical conductivity changes during the reaction, and then zeta potential, particle size, and viscosity. Dispersion stability is investigated by means of precipitation boundary height, X-ray diffraction analysis and transmission electron microscope analysis.

At this time, the surfactant used is water-soluble, stable in aqueous solution to form an adsorption layer, and when the molar number of PMAA (Poly methacrylic Acid) and Ethylene Oxide, which is an anionic surfactant that can have electrostatic repulsion, is water soluble In the aqueous solution method, by using the poly (oxyethylene) Nonylphenyl Ether, a nonionic surfactant in which the addition of the surfactant induces a new phase, the prepared calcium carbonate was a colloidal calsite of about 80 nm, Try to have an isoelectric point.

Example 1

2 is a zeta potential measured according to the pH of the precipitated calcium carbonate synthesized by the carbonation method. Indicates that

FIG. 3 shows the pH of the precipitated calcium carbonate suspension after the completion of the carbonation reaction. As a result, the pH was 6.3 after the completion of the reaction, but the pH was increased over time, and the pH was maintained at 8.3 after about 4 hours. ..

FIG. 4a or FIG. 4b shows the change in the electrical conductivity and the change of particle shape at each time by transmission electron microscope in the process of reacting CO (Poly (oxyethylene) Nonylphenyl Ether with CO ₂ after adding slaked oil before carbonation reaction. As a result, if surfactant is added before carbonation reaction, the first falling step of electrical conductivity is slightly delayed, and 2) and 3) sections are shortened, so that the chain type calsite in the final falling step (4 in FIG. 4) is colloidal. The particle size of precipitated calcium carbonate is reduced to about 50 nm by being present as a type calsite and adding a surfactant to Ca (OH) ₂ particles.

5A or 5B is a result of analyzing the change in the electrical conductivity and the particle shape of each time by the transmission electron microscope after the addition of Poly (oxyethylene) Nonylphenyl Ether when the electrical conductivity is first increased during the carbonation reaction, the surfactant is carbonated It can be seen that the electrical conductivity decreases more rapidly, without causing a transition from the first falling step to the first rising step of the electrical conductivity in the reaction. The descending of the conductivity curve rapidly rises after a little more time, and immediately passes through the final descending step to form a colloidal calsite, and in the particle size, the chain type calsite at the final descending step 3). 2) has a very thin needle-like shape with no significant difference from the nucleated chained calcitic at the time, which has a very small particle size as the reaction ends because the chained calcitic hardly undergoes crystal growth. Ultrafine particles of approximately 20 nm are formed.

Figure 6a or 6b is when the poly (oxyethylene) Nonylphenyl Ether when the final drop in the electrical conductivity during the carbonation reaction, the change in the conductivity and particle shape according to the reaction time observed by transmission electron microscope to add a surfactant Compared with the case of not, the change in the shape and size of the electrical conductivity and the termination phase does not show a large change. Since the timing of the surfactant is transferred from the chain type calsite to the colloid type calsite, the chain type calsite is colloid type. It did not inhibit the transition to Calsite.

That is, in the present invention, when the precipitated calcium carbonate is prepared by carbonation, the total amount of the reaction suspension is 600 ml, the concentration of the precipitated calcium carbonate is 3.5wt.%, The reaction temperature is 20, the CO ₂ gas flow rate is 500ml / min, Stirring speed is 300rpm, and crystal growth of the chain type calsite is caused by delay of the first falling step of electrical conductivity when poly (oxyethylene) Nonylphenyl Ether, a nonionic surfactant, is added before the carbonation reaction and at the first rise of electrical conductivity. The interval is shortened to produce a colloidal calsite of 50 nm or less with good dispersibility.

Example 2

Figure 7 shows the dispersion characteristics of precipitated calcium carbonate when the amount of PMAA is added to the precipitated calcium carbonate suspension after the carbonation reaction is finished at 20 ° C. Change to wt.% and adjust pH to 9. At this time, the pH was adjusted to 9 because the aggregation of particles occurred near pH 8.3, which is the isoelectric point of precipitated calcium carbonate, and the particles became negatively charged and dispersed by the electrostatic effect. First, the zeta potential is -10.5 mV, but the zeta potential is increased to negative value by adding PMAA, but when 0.8 wt.% Or more of PMAA is added, it is almost constant at -17 mV, and the viscosity is clearly different. And the precipitation boundary surface is slightly lowered from 14 cm to 12 cm.

8 is Ca (OH) Loading blowing CO ₂ gas to the _second before the Ca (OH) after injection of PMAA to the _second suspension a dispersion property of the product when the carbonation reaction while blowing a CO ₂ gas zeta potential, particle size, As measured by viscosity and precipitation boundary height, the zeta potential decreases from -10.5mV to -16.5mV as the concentration of PMAA increases from 0wt.% To 1wt.%, And the particle size is 150nm regardless of the amount of PMAA added. It is constant and the viscosity does not change according to the shear rate, but the precipitation boundary height is lowered from 14cm to 3cm.

9 shows that the zeta potential decreases from -10.5 mV to -22 mV as the concentration of PMAA increases from 0 wt.% To 1 wt.% As a result of dispersion characteristics depending on the amount of PMAA added at the first rise in electrical conductivity. It becomes small from 550 nm to 200 nm. In case of the precipitation boundary height, the boundary height of PMAA concentration of 0.6wt.% Or less is about 2cm, and it is maintained at 12.5cm at 0.6wt.%. PMAA concentration suddenly drops at 0.6 wt.%. Therefore, it is confirmed that the precipitated calcium carbonate is stably dispersed at the concentration of 0.6 wt.% PMAA as opposed to the case where the surfactant is added before the carbonation reaction.

10 shows that the zeta potential decreases from -10.5mV to -15mV as the concentration of PMAA increases from 0wt.% To 1wt.% As a result of the dispersion characteristics according to the amount of PMAA added during the final drop in electrical conductivity during the carbonation reaction. Regardless of the PMAA concentration, the particle size and precipitation boundary height of the precipitated calcium carbonate were constant at 500 nm and 3 cm, respectively, and the viscosity measured according to the shear rate was also almost constant.

That is, the present invention, the total amount of the suspension when preparing precipitated calcium carbonate by carbonation method is 600ml, the concentration of precipitated calcium carbonate 3.5wt.%, Reaction temperature 20 ℃, CO ₂ flow rate 500ml / min, stirring speed 300rpm The first increase of the electrical conductivity during the carbonation reaction was added PMAA, an anionic surfactant, and the surfactant added at the beginning of the reaction breaks the primary particles of Ca (OH) _2, the final phase is a colloidal calsite with small particles By synthesizing, the surfactant added during the reaction inhibits the transition from the intermediate phase chainsite to colloidal calsite, thereby producing needle-like calsite.

As described above, when the poly (oxyethylene) Nonylphenyl Ether, which is a nonionic surfactant, is added during the carbonation reaction, since the surfactant is adsorbed on the surface of the precipitated calcium carbonate, the growth of calcium carbonate is suppressed. In the case where PMAA, an anionic surfactant, is added during the carbonation reaction, PMAA changes the shape of the calcium carbonate-terminated phase from colloidal to needle-shaped, so that the specific surface area of calcium carbonate is reduced, thereby making the dispersion optimum interval different. Therefore, when PMAA was added during the first rise in electrical conductivity, the specific surface area of calcium carbonate was relatively smaller than that without adding a surfactant, so that the addition amount of PMAA was decreased so that the optimum dispersion condition was 0.8wt.% To 0.6wt. Will be%.

While the invention has been shown and described with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit or scope of the invention as provided by the following claims. I would like to know that those who have knowledge of this can easily know.

In the present invention, poly (oxyethylene) Nonylphenyl Ether and PMAA are added during the carbonation reaction in the preparation of precipitated calcium carbonate, thereby improving the fluidity and dispersibility, and thus preventing the agglomeration of powder as the post-treatment process is omitted. Of course, economic and technical benefits are increased by the process simplification.

Claims (5)

When preparing a precipitated calcium carbonate suspension by injecting CO ₂ gas while stirring the calcium hydroxide suspension at room temperature, a polymer surfactant was added according to the point of change in the electrical conductivity of the precipitated calcium carbonate suspension so that the polymer surfactant was adsorbed on the precipitated calcium carbonate surface. A method of adding a polymer for improving the shape and dispersion stability of precipitated calcium carbonate particles characterized by analyzing the dispersion stability after filtration and drying by taking a sample of precipitated calcium carbonate adsorbed with a surfactant. The method of claim 1, wherein the precipitated calcium carbonate suspension is prepared by injecting CO ₂ gas at 500 ml / min while stirring at a rate of 300 rpm at a reaction temperature of 20 ° C. to prepare a precipitated calcium carbonate suspension having a concentration of 3.5 wt.%. Method for adding a polymer for improving the shape and dispersion stability of precipitated calcium carbonate particles, characterized in that. The method of claim 1, wherein the addition of the polymer surfactant is such that the crystal growth section of the chain type calsite is shortened by the delay of the first falling step of the electrical conductivity, so that the colloidal calsite of 50 nm or less having good dispersibility is produced. A method for adding a polymer for improving the shape and dispersion stability of precipitated calcium carbonate particles, wherein the ionic surfactant Poly (oxyethylene) Nonylphenyl Ether is added before the carbonation reaction of precipitated calcium carbonate. The method of claim 1, wherein the addition of the polymer surfactant is such that the crystal growth section of the chain type calsite is shortened by the delay of the first falling step of the electrical conductivity, so that the colloidal calsite of 50 nm or less having good dispersibility is produced. A method for adding a polymer for improving the shape and dispersion stability of precipitated calcium carbonate, characterized in that the poly (oxyethylene) Nonylphenyl Ether, an ionic surfactant, is added during the first rise in electrical conductivity during the carbonation reaction of precipitated calcium carbonate. The method according to claim 1, wherein the addition of the polymer surfactant is to increase the electrical conductivity during the precipitated calcium carbonate carbonation reaction to suppress the transition of the intermediate-type chain-calcite to the colloidal calsite to form a needle-like calsite A method of adding a polymer for improving precipitate shape and dispersion stability by adding PMAA, an anionic surfactant having a concentration of 0.6 wt.% To 0.8 wt.