JPH043434B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention is formulated as an extender pigment in water-based paints and inks to provide extremely good dispersibility, good viscosity stability over time, and excellent coating properties and coating gloss. The present invention relates to a method for producing an extender pigment made of precipitated calcium carbonate powder. ``Prior art'' ``Problems to be solved by the invention'' Calcium carbonate has traditionally been used as a filler for rubber and plastics and as an extender pigment in paints, depending on its particle size and shape, and as a coating pigment in paper manufacturing. It is also widely used as a filler for paper making. This calcium carbonate originally has a strong cohesive property between particles, and in particular, precipitated calcium carbonate, which is produced by passing carbon dioxide gas through an aqueous suspension of calcium hydroxide to form a precipitate, has a remarkable cohesive property, so it is generally not used. After chemically dispersing the aggregate particles to almost primary particles, they are dehydrated and made into a slurry using a dispersant such as a polycarboxylic acid type dispersant. A surface treatment agent (anti-agglomeration agent) or an inorganic surface treatment agent is used in an aqueous suspension of calcium carbonate, followed by dehydration, drying, and pulverization, and the resulting liquid is supplied to various areas. However, even if such a surface treatment agent is adsorbed onto the surface of calcium carbonate in an aqueous system and agglomeration between particles is prevented as much as possible during the drying process, the resulting calcium carbonate powder is compared to the calcium carbonate in the aqueous suspension before the drying process. Because of the significant agglomeration of calcium carbonate, in fields where slurry can be used, such as the paper industry, which uses large amounts of calcium carbonate as a pigment for coatings and papers or as a filler in paper manufacturing, calcium carbonate is almost always used in slurry packaging. I am using it. As mentioned above, calcium carbonate slurry does not require a drying process, so it has good interparticle dispersion, and it has good physical properties, especially optical properties (such as gloss), so it is often used. Therefore, it has many disadvantages such as increased transportation costs, thickening, sedimentation, and spoilage during long-term storage. Furthermore,
Calcium carbonate, which has an even smaller particle size than the calcium carbonate currently used in the paper industry.
In particular, calcium carbonate with an average particle size of 0.1 μm or less has particularly excellent optical properties as an extender pigment for water-based paints, but because the calcium carbonate particles are fine, they have the property of retaining a large amount of adsorbed water on the particle surface. Therefore, it is difficult to form a slurry at a high concentration, and even if currently known dispersants and dispersion methods are utilized to the maximum, it is impossible to prepare a slurry with a low viscosity and long-term stability at a concentration of 60% or more. For example, it cannot be used as an extender pigment for emulsion paints, which requires a solid content concentration of 70% or more, and has the disadvantage that its field of use is extremely limited. For the reasons mentioned above, powdered calcium carbonate is currently used as an extender pigment in paints, inks, etc., but its performance, particularly the gloss of the dry coating surface, is not always fully satisfactory. for example,
In paints, there is generally an extremely strong demand for high gloss on the surface of the dried paint film for aesthetic and other reasons. Pigment-containing paints, with the exception of some paints such as clear lacquer, require Pigment Volume Concentration (hereinafter referred to as "PVC '') That is, it is normal to increase the proportion of pigments added, including extender pigments. However, when the PVC content of the paint is increased, there is a problem in that the gloss of the paint film surface decreases in most cases. For this reason, in the paint industry, the coloring property of the above-mentioned coating film,
There is currently a demand for the development of pigments that maintain various properties such as pay-hiding properties and do not reduce the surface gloss of the coating film. On the other hand, recently resource saving, pollution,
From the standpoint of occupational health, paints, inks, etc. are being converted from conventional organic solvent-based to water-based ones. However, for example, water-based paints tend to have a considerably lower surface gloss than organic solvent-based paints, and from this point of view, extender pigments that do not reduce the surface gloss of the paint film, that is, provide high gloss, are used. Development is strongly requested. In response to these demands, research is being conducted from various fields to develop extender pigments that satisfy the above requirements, and calcium carbonate, whose raw material limestone is produced in large quantities in Japan, is no exception. Japanese Patent Publication No. 55-16031,
It has been reported in Japanese Patent Application Laid-Open No. 57-184430. However, when it comes to current water-based paints, such as emulsion paints, most of them use calcium carbonate as an extender, with the exception of emulsion paints that use particularly cheap heavy calcium carbonate with an average particle size of 5 μm or more simply as an extender. It is not used in emulsion paints that aim for high gloss, because it has a high hiding rate as an extender pigment, and because it reduces the surface gloss of the paint film less than calcium carbonate etc. Although it is very expensive, large amounts of titanium dioxide are used, and no calcium carbonate is used. "Means for Solving the Problems" In order to cope with the current situation, the inventors of the present invention have developed a method that can be used in water-based paints, inks, etc. to obtain coatings and ink films with extremely good dispersibility and high gloss. As a result of extensive research into calcium carbonate powder, which is an extender pigment with good viscosity stability over time for paints, we have developed a continuous wet dispersion machine that slurries calcium carbonate using a polycarboxylic acid dispersant with a specific composition. It was discovered that by wet grinding and then dry grinding, a high gloss coating film that could not be obtained even with calcium carbonate slurry, let alone with conventional calcium carbonate powder, could be obtained, and the present invention was developed. Completed. That is, the present invention provides a calcium carbonate water-containing cake obtained by dehydrating an aqueous suspension containing precipitated calcium carbonate having an average particle diameter of 0.01 to 0.5 μm, and at least one selected from () acrylic acid, methacrylic acid, and crotonic acid. One α,β unsaturated monocarboxylic acid
100 parts by weight, () 1 to 100 parts by weight of at least one α, β unsaturated dicarboxylic acid selected from itaconic acid, maleic acid, and fumaric acid, and () (a) acrylic acid alkyl ester and methacrylic acid alkyl ester, (b) acrylate and methacrylate having an alkoxy group, (c) acrylate and methacrylate having a cyclohexyl group, (d) α,
β monoethylenically unsaturated hydroxy ester, (e)
Polyalkylene glycol monoacrylate and monomethacrylate, (f) vinyl ester, (g) vinyl aromatic, (h) unsaturated nitrile, (i) unsaturated dicarboxylic acid ester, (j) vinyl ether, (k) conjugated diene, At least one polymerizable monomer selected from chain olefins and cyclic olefins 5-
Sodium salt, ammonium salt, and/or amine of a copolymer obtained by copolymerizing 90 to 100% by weight of a mixture consisting of 300 parts by weight and 10 to 0% by weight of at least one other polymerizable monomer. 0.01 to 10 parts by weight of salt is added to 100 parts by weight of calcium carbonate solid content, stirred or kneaded to prepare a calcium carbonate slurry, and then wet-milled, and the resulting milled slurry is then dried and ground. The content is a method for producing an extender pigment made of precipitated calcium carbonate powder, which is characterized by: In this specification, the term "average particle diameter" refers to the length of one side of a cubic crystal obtained from the specific surface area measured by the so-called BET method, assuming that calcium carbonate particles are cubic particles. '' includes the case where the carboxyl group in the copolymer and the calcium atom of the calcium carbonate particles form a salt or are physically adsorbed. The present invention will be described in detail based on steps showing embodiments. Manufacturing process A: A dough of precipitated calcium carbonate, which is the extender pigment of the present invention, is manufactured, and after the carbonation reaction is completed, secondary particles (aggregates of primary particles) are formed by controlling the pH of the calcium carbonate aqueous suspension. ) is destroyed and dispersed. The production of precipitated calcium carbonate in this process can be carried out, for example, by passing a carbon dioxide gas-containing gas (hereinafter referred to as carbon dioxide gas) through an aqueous suspension of calcium hydroxide, or by introducing an aqueous suspension of calcium hydroxide or This may be carried out by a known method such as a method of spraying a mixture of calcium and precipitated calcium carbonate. Regarding the method of dispersing aggregated particles of precipitated calcium carbonate obtained by such a method, for example, the carbonation reaction is stopped at a pH of 6.5 to 10.0, and the alkali remaining in the calcium carbonate is eluted by stirring. This can be easily achieved by adding or introducing milk of lime and carbon dioxide into the system as necessary to control the pH of the system at 9.0 to 12.0 for 5 hours or more. Manufacturing step B: This is a step in which the aqueous suspension of precipitated calcium carbonate produced in step A is dehydrated using a filter press or other known dehydrator to obtain a press cake of precipitated calcium carbonate. Manufacturing process C: This is a process in which a dispersant necessary for slurrying the press cake manufactured in process B in process D is added. The dispersant used in this process is required to have the following characteristics and functions; In the slurry process of Step D, the amount of dispersant used is small, the amount is 2000 cps or less, and the solid content concentration is 30
It is essential to be able to prepare a calcium carbonate slurry with a relatively low viscosity of at least 50%, and if this is not met, the precipitated calcium carbonate slurry due to its high viscosity is sent to the wet dispersion machine in Step E. development of difficulty, an increase in power consumption in the slurry process due to high viscosity, and a decrease in grinding efficiency in the wet dispersion machine in step E and power consumption in process F due to a decrease in solid content concentration. Therefore, the drying energy consumption rate increases, making it impossible to effectively achieve the present invention. In the wet dispersion process of process E, it is necessary for the calcium carbonate slurry injected from process D to be efficiently dispersed and discharged with low viscosity and transferred to process F. If this is not met, the power consumption rate will decrease. Not only does this increase, but the calcium carbonate slurry thickens in the vessel of the mill and cannot be discharged, and the wet disperser (mill) stops, making it impossible to produce the extender pigment of the present invention. Adsorbs uniformly onto the surface of precipitated calcium carbonate,
This calcium carbonate is used as an extender pigment to impart good optical properties. Adsorbs uniformly onto the surface of precipitated calcium carbonate,
When this calcium carbonate is used as an extender pigment, paints and the like have good viscosity stability over time. Dispersants with the above properties and functions include () 100 parts by weight of at least one α, β unsaturated monocarboxylic acid selected from acrylic acid, methacrylic acid, and crotonic acid, () maleic acid, and itaconic acid. acid, 1 to 100 parts by weight of at least one α,β unsaturated dicarboxylic acid selected from fumaric acid, and (a) methyl acrylate, ethyl, propyl, isobutyl, 2-ethylhexyl, methyl methacrylate, ethyl, propyl, isobutyl, 2
- Acrylic acid alkyl esters and methacrylic acid alkyl esters such as ethylhexyl, (b) acrylates and methacrylates having alkoxy groups such as methoxyethyl acrylate, metaxyethyl methacrylate, ethoxyethyl acrylate, ethoxyethyl acrylate, and ethoxyethyl methacrylate; (c) Acrylates and methacrylates having a cyclohexyl group such as cyclohexyl acrylate and cyclohexyl methacrylate, (d) 2-hydroxyethyl acrylate, 2-
αβ-monoethylenically unsaturated hydroxy esters such as hydroxyethyl methacrylate, (e) polyalkylene glycol monoacrylates and monomethacrylates such as polyethylene glycol monomethacrylate, polyethylene glycol monoacrylate, polypropylene glycol monomethacrylate, polypropylene glycol monoacrylate, (f ) Vinyl esters such as vinyl acetate and vinyl stearate, (g) Vinyl aromatics such as styrene vinyl toluene, (h) Unsaturated nitriles such as acrylonitrile and methacrylonitrile, (i) Monomethyl maleate and itaconic acid. Unsaturated dicarboxylic acid esters such as dibutyl, (j) vinyl ethers such as methyl vinyl ether and butyl vinyl ether, (k) conjugated dienes and chains such as butadiene, isobutene, ethylene, propylene, n-butene, n-pentene, and cyclobutene. 90 to 100% by weight of a mixture consisting of 5 to 300 parts by weight of at least one polymerizable monomer selected from olefins and cyclic olefins, and other monomers with polymerizability other than the above, such as acrylamide. , αβ-monoethylenically unsaturated carboxylic acid amide such as methacrylamide,
A copolymer obtained by copolymerizing 10 to 0% by weight of at least one selected from sulfo group-containing monomers such as vinyl sulfonic acid, styrene sulfonic acid, 2-acrylic 2-methylpropanesulfonic acid, and methacryl sulfonic acid. Preferred are polycarboxylic acid type dispersants which are sodium, ammonium and/or amine salts of. On the other hand, even if a polycarboxylic acid type dispersant having a composition different from that of the above-mentioned dispersant is used in the present invention, the object of the present invention cannot be achieved for the reasons shown below. In addition, the above α, β−
Monoethylenically unsaturated carboxylic acid amide and sulfo group-containing monomer have resistance to calcium ions and other polyvalent metal ions, so these should be used in an amount of 10% by weight.
If a copolymerized dispersant is used, Step D
The calcium carbonate slurry produced in this method has good viscosity stability during long-term storage, which is advantageous in producing the extender pigment of the present invention. However, water-based paint
As a processing agent for extender pigments such as water-based inks, it cannot improve physical properties such as optical properties, pigment viscosity, and stability, so calcium carbonate slurry must be produced in large quantities and stored for long periods of time for process reasons. If it is not present, there is no particular problem even if it is not added as a component of the copolymer. In the copolymer, if the total amount of α, β unsaturated monocarboxylic acid, unsaturated dicarboxylic acid, and monomer having polymerizability selected from (a) to (k) is less than 90% by weight, dispersion of calcium carbonate is Because it is easily inhibited,
When calcium carbonate prepared from this composition as a dispersant is used as an extender, sufficient optical properties cannot be imparted and viscosity stability over time tends to deteriorate. The α,β unsaturated dicarboxylic acid used in the present invention is
If it exceeds 100 parts by weight, although the above-mentioned properties and functions are met, the viscosity increases significantly during the wet dispersion process, and the wet dispersion machine stops due to overtorque, making it impossible to meet the above requirements. On the other hand, α,
When the β-unsaturated dicarboxylic acid is less than 1 part by weight, the wet dispersion step in Step E is satisfactory, but the amount of dispersant used in the slurry forming step in Step D increases, which is not only uneconomical, but also In particular, regarding extremely fine precipitated calcium carbonate of less than 0.1 μm, even if this dispersant is used in large quantities, it is not possible to prepare a slurry with a solid content concentration of 30% or more and a viscosity of 2000 cps or less, and the requirements cannot be met. . In addition, when calcium carbonate prepared using this dispersant is used as an extender pigment, the viscosity stability of paints and the like over time is poor, and the viscosity tends to increase and become pudding-like, so that the above requirements are not met. When the amount of the polymerizable monomers (a) to (k) used in the present invention is less than 5 parts by weight, calcium carbonate prepared using this dispersant will not exhibit good results when used as an extender pigment. It is not possible to impart optical properties and the requirements cannot be met. On the other hand, if the monomer exceeds 300 parts by weight, not only will the foaming in step D significantly deteriorate the workability, but also the solubility of the copolymer in water will significantly decrease, resulting in a uniform distribution on the surface of each calcium carbonate. It becomes difficult to adsorb to the calcium carbonate, and the viscosity increases easily in the wet dispersion step of step E. Furthermore, when calcium carbonate prepared using this dispersant is used as an extender pigment, the viscosity stability of paints etc. over time is poor. , the foaming property also increases, and the above conditions (1) and (2) are not satisfied, making it impossible to achieve the object of the present invention. The number average molecular weight (measured by gel osmotic pressure chromatography (GPC)) of the dispersant (copolymer) used in the present invention varies depending on the type and composition ratio of the constituent components, but is usually 500 to 50,000, more preferably 2,000. ~
It is best to set it to around 30,000. If the molecular weight is less than 500, the adsorption rate tends to decrease, and if it exceeds 50,000, it is difficult to produce the dispersant, and the viscosity of the calcium carbonate slurry increases significantly. Furthermore, when added to a calcium carbonate suspension, its agglomerative effect may make it difficult to uniformly adsorb onto the particle surface. To obtain a copolymer consisting of the unsaturated monocarboxylic acid (), unsaturated dicarboxylic acid (), and a polymerizable monomer () selected from (a) to (k), a conventionally known method can be used. I can do it. for example,
Polymerization can be carried out in a solvent such as water, an organic solvent, or a mixed solvent of a water-soluble organic solvent and water. Hydrogen or the like is used, and an accelerator such as sodium bisulfite or ascorbic acid can be used in combination. For polymerization in organic solvents,
An azo compound, an organic peroxide, etc. are used as an initiator, and an accelerator such as an amine compound can be used in combination. For polymerization in a mixed solvent of a water-soluble organic solvent and water, an appropriate polymerization initiator or a combination of a polymerization initiator and an accelerator can be selected from among the various polymerization initiators described above. By neutralizing the copolymer thus obtained with an alkaline substance such as a sodium compound, an ammonium compound, or an organic amine, the desired sodium salt, ammonium salt, or amine salt of the copolymer can be obtained. It will be done. The amount of the dispersant added to calcium carbonate is 0.01 to 10.0 parts by weight, more preferably 0.1 to 5.0 parts by weight, per 100 parts by weight of calcium carbonate solid content. If the amount added is less than 0.01 part by weight, the difference in treatment effect from the untreated product will not be significant. On the other hand, if the amount exceeds 10.0 parts by weight, the amount of adsorption decreases, a more significant effect of the dispersant cannot be expected, and it is often not economically advantageous. Manufacturing process D: This is a process of forming a press cake of precipitated calcium carbonate and a dispersant into a slurry by vigorous stirring and kneading. As the equipment used for this slurry formation, known equipment is sufficient, such as a kneader, a Keddy mill, a Coles mixer, and the like. The solid content concentration of the calcium carbonate slurry produced in this step varies depending on the average particle size of calcium carbonate, but it is preferably at least 30% or more, more preferably 40% or more. solids concentration
If it is less than 30%, the pulverization efficiency in the wet dispersion machine in step E will decrease, the power consumption rate will increase, and the media,
Damage to the dispersion equipment such as Betucel becomes significant, and the drying energy consumption rate in Step F increases, which is economically disadvantageous. Manufacturing process E: This is a process in which the precipitated calcium carbonate slurry produced in process D is ground and dispersed using a continuous wet disperser. The wet grinder used in this process is a sand grinder type that uses glass beads, zirconia beads, etc. as media, and has a high shear rate.
A known dispersing machine having a dispersion efficiency of about 10 ³ sec ^-1 or more may be used, such as an attriter, a grain mill, a modular grinding mill, a pearl mill, a Molinex mill, a Dyno mill, an agitator mill, a bead mill, an annular mill, a Kobo mill, and the like. By going through this step, the unadsorbed dispersant will stick to the calcium carbonate surface and the adsorption rate will be greatly improved. Therefore, in step F after this step, the calcium carbonate powder obtained by drying and pulverizing is redispersed in water. However, it can have the same dispersibility as the calcium carbonate slurry produced in Step D. In order to achieve the purpose of this step, the residence time of the calcium carbonate slurry produced in step D in this step is preferably 0.5 minutes or more, more preferably 1 minute or more. If the residence time is less than 0.5 minutes, there is no big difference from not passing through this step, and even if the calcium carbonate powder obtained by dry powdering in Step F is redispersed in water, it will not be the same as the calcium carbonate slurry produced in Step D. In comparison, aggregation is observed, making it difficult to exhibit excellent optical properties even when used as an extender pigment. Manufacturing process F: This process is a process of drying and pulverizing the precipitated calcium carbonate slurry that has been subjected to the grinding and dispersion treatment in process E. The drying method may be carried out by a conventional method, but since the object to be dried is a slurry, it is necessary to use a dryer that can directly dry the slurry, such as a spray dryer, sludge dryer, drum dryer, etc. After drying, It may be crushed and powdered by a known method depending on the purpose. The thus obtained coated calcium carbonate powder of the present invention can be used in water-based paints, etc. because the dispersion state (particle size distribution state) obtained by redispersing it in water is similar to the dispersion state in the slurry before drying. When used as an extender pigment, it has good optical properties and good viscosity stability over time. Usable resins for water-based paints include emulsion resins for paints on the general market, such as polyacrylic, polyvinyl acetate, polystyrene, epoxy, alkyd, melamine, and urethane resins;
General market water-soluble resins for paints such as alkyd type, amine type, styrene-allylic alcohol type, amino alkyd type, and polybutadiene type, dispersion resin for paints that is a blend of emulsion resin and water-soluble resin, and cross-linked water-soluble resin as an emulsifier. It can be widely used as dispersion resin, acrylic hydrosol, etc. In addition, when making water-based paints, paint coloring and other extender pigments, antifoaming agents, non-adhesive agents, wetting agents, dispersants, curing accelerators, corrosion inhibitors, dryers, antifungal agents, film forming aids, Additives commonly used in this field, such as antifreeze agents, may be used in combination with the coated calcium carbonate of the present invention, if necessary. "Action" and "Effects of the Invention" The calcium carbonate powder of the present invention has extremely good redispersibility in water and is restored to almost the same degree as the dispersion state of the slurry before the drying process. When used as a pigment, it very significantly improves the surface gloss of the coating. For example, the extender pigment of the present invention may be applied to an acrylic emulsion.
When 20% PVC is added, the coating film gloss is as high as 75% or more at a specular gloss level of 60. On the other hand, when conventional extender pigment powders other than titanium dioxide are used, the value is only about 60% at most. Furthermore, the extender pigment of the present invention can impart excellent coating gloss as described above to a wide range of conventionally known coatings, regardless of the aqueous coating to which it is added. Furthermore, when used in water-based ink, it also improves the gloss of the coated surface. "Examples" The present invention will be described in more detail below with reference to Examples, Comparative Examples, Applied Examples, and Applied Comparative Examples, but the present invention is not limited in any way by these. Precipitated calcium carbonate used in Examples and Comparative Examples was prepared in the following manner. Precipitated calcium carbonate A: Milk of lime with a specific gravity of 1.060 [Ca(OH) ₂ content 10%] was prepared at 8°C, and 30
The carbonation reaction was carried out by introducing carbon dioxide gas (including 25% CO ₂ ) for 1 minute, and the carbonation reaction was stopped at the system pH of 8.0.
After stirring at pH 10.0 for 10 hours, when the viscosity of the system reached 3000 cps, carbon dioxide gas was introduced again to bring the pH of the system to 6.9. As a result, calcium carbonate (BET specific surface area 71 m ² /g) with an average particle diameter of 0.03 μm and significantly less aggregate particles was obtained. Precipitated calcium carbonate B: Milk of lime with a specific gravity of 1.070 [Ca(OH) ₂ content 11.8%]
The carbonation reaction and particle dispersion were carried out in the same manner as precipitated calcium carbonate A, except that the temperature was adjusted to 15℃, and the viscosity of the system was 2500 cps and the average particle size was 0.07μ.
m of calcium carbonate (BET specific surface area 30m ² /g)
I got it. Precipitated calcium carbonate C: Three types of lime milk (hereinafter referred to as primary carbonated lime milk) obtained by partially carbonating lime milk by passing carbon dioxide gas through it in the following manner were prepared; (a) lime with a specific gravity of 1.060; Milk [Ca(OH) ₂ content 10%]
Calcium hydroxide per 1 kg
Primary carbonation was carried out by passing carbon dioxide gas (including 25% CO ₂ ) for 27 minutes, and the carbonation reaction was stopped at a carbonation rate of 20%. (b) Milk of lime with a specific gravity of 1.060 [Ca(OH) ₂ content 10%]
Calcium hydroxide per 1 kg
Primary carbonation was carried out by passing carbon dioxide gas (including 25% CO ₂ ) for 27 minutes, and the carbonation reaction was stopped at a carbonation rate of 10%. (c) Milk of lime with a specific gravity of 1.090 [Ca(OH) ₂ content 14.9%]
was heated to 30°C, and a carbon dioxide-containing gas (including 25% CO ₂ ) was introduced at a rate of 8/min per 1 kg of calcium hydroxide to carry out the primary carbonation reaction, resulting in a carbonation rate of 2%.
The carbonation reaction was stopped. After mixing the above primary carbonated lime milk (A) 60 and (C) 60 to make 120, carbon dioxide gas (including CO ₂ 25%)
The carbonation reaction was carried out under stirring at a rate of 15/min, and the carbonation reaction was stopped when the pH of the reaction system was 8.0.Then, stirring was carried out at a system temperature of 55°C and a pH of 10.0, and after 12 hours. Calcium carbonate with an average particle diameter of 0.08 μm was obtained at 2000 cps. Primary carbonated lime milk (b) is fed into this high viscosity calcium carbonate at 150c.c./min,
At the same time, carbon dioxide gas (including 25% CO ₂ ) was introduced at a rate of 25/min to carry out the carbonation reaction at a reaction diameter of 10.5 under stirring, and 13 hours after the start of supply, the supply and conduction were stopped, and then the pH was 10. After stirring was continued for 5 hours at a temperature of .5, carbon dioxide gas was introduced again to complete the carbonation reaction, thereby obtaining a significantly smaller average particle diameter of aggregate particles of 0.15 μm (BET specific surface area: 13.4 m ² /g). Precipitated calcium carbonate D: Except for supplying primary carbonated lime milk (b) at a rate of 450 c.c./min and at the same time passing carbon dioxide gas (including CO ₂ 25%) at a rate of 75/min. Carbonation reaction and particle dispersion were carried out in the same manner as for precipitated calcium carbonate C, thereby obtaining a significantly smaller average particle diameter of 0.30 μm (BET specific surface area 7.0 m ² /g). Precipitated calcium carbonate E: Other methods except that primary carbonated lime milk (b) is supplied at a rate of 900 c.c./min, and at the same time carbon dioxide gas (including CO ₂ 25%) is conducted at a rate of 150/min. Carbonation reaction and particle dispersion are performed in the same manner as precipitated calcium carbonate C, which results in an average particle size with less aggregates.
0.8 μm (BET specific surface area 3.8 m ² /g) was obtained. Examples 1 to 4 After dehydrating the aqueous suspension of precipitated calcium carbonate A to D using a filter press to obtain a press cake, 100 parts by weight of acrylic acid and itaconic acid were added.
25 parts by weight of methyl acrylate and 42 parts by weight of methyl acrylate were added as an ammonium salt of a copolymer with a weight average molecular weight of 10,000. A slurry was prepared. Thereafter, the slurry was wet-milled using a wet milling-dispersing machine (Dynomil Pilot, manufactured by WAB, Vessel capacity: 1400 c.c.), and then dry-milled to obtain an extender pigment made of precipitated calcium carbonate powder. . Type of precipitated calcium carbonate used,
Table 1 shows the dispersant composition, the amount of dispersant used, and the solid content concentration of the calcium carbonate slurry. The operating conditions of the Dyno Mill pilot are as follows; Disk rotation speed: 3350 rpm Media: Glass beads with a diameter of 0.59 to 0.84 mm Media filling rate: 80% (effective grinding volume 700 c.c.) Calcium carbonate slurry feed Amount: 350c.c./
min (calcium carbonate slurry residence time: 2 minutes) Comparative Examples 1 to 4 Constitution made of precipitated calcium carbonate powder in the same manner as Examples 1 to 4, except that wet grinding and dispersion using Dyno Mill pilot was not performed. I got the pigment. Table 1 shows the type of precipitated calcium carbonate used, the composition of the dispersant, the amount used of the dispersant, and the solid content concentration of the calcium carbonate slurry. Comparative Examples 5 to 8 A dispersant was added to the aqueous suspension of the precipitated calcium carbonate A to D, and after stirring for 1 hour, dehydration was performed using a filter press to obtain a press cake, which was then dried and pulverized to obtain a precipitated calcium carbonate. An extender pigment consisting of calcium carbonate powder was obtained. Table 1 shows the type of precipitated calcium carbonate used, the composition of the dispersant, and the amount of dispersant used. Comparative Example 9 An extender pigment made of precipitated calcium carbonate powder was obtained in the same manner as in Examples 1 to 4 except for using the aqueous suspension of precipitated calcium carbonate E. Type of precipitated calcium carbonate used,
Table 1 shows the dispersant composition, the amount of dispersant used, and the solid content concentration of the calcium carbonate slurry. Examples 5 to 28, Comparative Examples 10 to 17 After dehydrating the aqueous suspension of the precipitated calcium carbonate B using a filter press to obtain a press cake, dispersants of various compositions were added and a high speed laboratory disper [special machine] A calcium carbonate slurry was prepared using the following product (manufactured by Kakogyo Co., Ltd.). Thereafter, the slurry was dynomilled under the same conditions as the wet milling dispersion in Examples 1 to 4.
Wet milling was performed using a pilot, followed by drying and pulverization to obtain an extender pigment consisting of precipitated calcium carbonate powder. Table 2 shows the type of precipitated calcium carbonate used, the dispersion composition, the amount of dispersant used, the solid content concentration of the calcium carbonate slurry, the viscosity of the calcium carbonate slurry, and the state of pulverization and dispersion using the Dyno Mill pilot. Comparative Example 18 The aqueous suspension of the precipitated calcium carbonate B was dehydrated using a filter press to obtain a press cake, which was then dried and pulverized to obtain an extender pigment consisting of precipitated calcium carbonate powder. Application Examples 1 to 28, Application Comparative Examples 1 to 15 Of the extender pigments made of calcium carbonate obtained in Examples 1 to 28 and Comparative Examples 1 to 18, the Dynomill stopped due to significant thickening during the grinding and dispersion process. Extender pigments made of calcium carbonate were used, except for Comparative Example 13, in which feed could not be collected, and Comparative Example 10, in which it was impossible to send the liquid to the grinding and dispersion process due to extremely high viscosity in the calcium carbonate slurry process. Table 3 shows the specular gloss and viscosity change over time of the coating film when applied to an acrylic emulsion using the following proportions and methods. "Paint formulation (PVC 27%, NV = 39)" [MILL BASE] Weight part dispersant A (Daiichi Kogyo Seiyaku Co., Ltd., Neugen EA-120)
2 Dispersant B (Sympathy, Discoat N-14) 8 Propylene glycol 50 Titanium white (Ishihara Sangyo, R-630) 194 Calcium carbonate powder (when using slurry,
(as calcium carbonate solid content in slurry) 65 Water (including water in slurry if slurry is used)
52 [LET DOWN] MILL BASE 186 Emulsion (Dainippon Ink, Boncourt EC
-821) 222 Butyl Cellsolve 35 "Blending method" Add 297 parts by weight of glass beads (manufactured by Toshiba Balloteini, GB-503B) to the above millbase blend,
Grinding was performed for 20 minutes using a simple sand mill. The above-mentioned emulsion and butyl cellosolve were added to the mill base thus obtained, and the mixture was stirred for 5 minutes at 1000 rpm using Labo Disper (manufactured by Tokushu Kika Kogyo Co., Ltd.). Reference Examples 1 to 3 Calcium carbonate slurry before the wet dispersion process (Reference Example 1) and calcium carbonate slurry after the wet dispersion process (Reference Example 2) produced during the manufacturing process of Example 2, and further calcium carbonate slurry with an average particle size of 0.07 μm. Extender pigment made by surface-treating precipitated calcium carbonate with fatty acid ester and dodecylbenzenesulfonic acid (manufactured by Maruo Calcium)
Table 3 shows the specular gloss and viscosity change over time of the coating film when MC-S) (Reference Example 3) was applied to an acrylic emulsion using the same formulation and method as the Application Example and Application Comparative Example. Reference Examples 4 to 9 The measurement results of the particle distribution of the calcium carbonate powders obtained in Example 2, Comparative Example 2, Comparative Example 6, and Comparative Example 18 and the calcium carbonate slurry used in Reference Example 1 and Reference Example 2 are Shown in the table. The method for measuring viscosity distribution is to put a sample into a 0.2% Na hexametaphosphate aqueous solution, disperse it using an ultrasonic disperser for 10 minutes, and then use a SA-CP-2 viscosity distribution type (manufactured by Shimadzu Corporation).
It was measured with Application Examples 29 to 32, Application Comparative Examples 16 to 21 Using the extender pigments made of calcium carbonate obtained in Examples 1 to 4 and Comparative Examples 1 to 4, 14, and 18, a water-based ink with the following formulation was prepared. The specular gloss and viscosity were measured and shown in Table 5. "Composition" [MILL BASE] Part by weight Melting varnish (styrene-maleic acid type) 60 Extender pigment 40 Glass beads (1.5mmφ) 112 [LET DOWN] Part by weight MILL BASE 100 Emulsion varnish (styrene-acrylic acid type)
20 Wax emulsion (manufactured by Sanyo Kasei) 2 Antifoaming agent (manufactured by Sanno Pco) 0.5 Water 20 "Blending method" MILL as in the above emulsion paint preparation
Create BASE and LET after glass bead separation
I went DOWN. "Test Method" The water-based ink prepared by the above method was applied onto general art paper (manufactured by Mitsubishi Paper Industries) using a 4 mill blade coater, and after drying, the 60°-60° specular gloss was measured. Regarding the viscosity of water-based ink, type B viscosity (6 rpm and 60 rpm) immediately after preparation and after 7 days at 25°C.
Measured at

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Claims (1)

[Claims] 1. A calcium carbonate-containing cake obtained by dehydrating an aqueous suspension containing precipitated calcium carbonate with an average particle size of 0.01 to 0.5 μm () selected from acrylic acid, methacrylic acid, and crotonic acid. at least 1
100 parts by weight of alpha, beta unsaturated monocarboxylic acid of seeds,
() 1 to 100 parts by weight of at least one α, β unsaturated dicarboxylic acid selected from itaconic acid, maleic acid, and fumaric acid, and () (a) acrylic acid alkyl ester and methacrylic acid alkyl ester, (b) alkoxy (c) acrylates and methacrylates having a cyclohexyl group, (d) α, β monoethylenically unsaturated hydroxy esters, (e) polyalkylene glycol monoacrylates and monomethacrylates, (f) vinyl esters, At least one polymerizable species selected from (g) vinyl aromatic, (h) unsaturated nitrile, (i) unsaturated dicarboxylic acid ester, (j) vinyl ether, (k) conjugated diene, chain olefin, and cyclic olefin. Sodium salt, ammonium copolymer obtained by copolymerizing 90 to 100% by weight of a mixture consisting of 5 to 300 parts by weight of a monomer having the above and 10 to 0% by weight of at least one other polymerizable monomer. A salt and/or amine salt is added in an amount of 0.01 to 10 parts by weight per 100 parts by weight of calcium carbonate solid content, stirred or kneaded to prepare a calcium carbonate slurry, and then wet-milled. A method for producing an extender pigment consisting of precipitated calcium carbonate powder, characterized by drying and pulverizing the finished slurry. 2. The manufacturing method according to claim 1, wherein wet grinding is carried out for 0.5 minutes or more using a continuous wet disperser. 3. The manufacturing method according to claim 1, wherein the other polymerizable monomer is at least one selected from α, β-monoethylenically unsaturated carboxylic acid amide and a sulfo group-containing monomer. 4. The production method according to claim 1, wherein the copolymer added to the calcium carbonate hydrated cake has a weight average molecular weight of 500 to 50,000. 5. The manufacturing method according to claim 1 or 2, wherein the solid content concentration of the calcium carbonate slurry wet-milled by a continuous wet disperser is 30% by weight or more.