JPS6115904B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to extender pigments used in water-based paints, water-based inks, etc., and more specifically, extender pigments and extender pigments whose main component is calcium carbonate coated with a phosphoric acid surfactant and which can be advantageously used in water-based paints, water-based inks, etc. It pertains to its manufacturing method. Traditionally, calcium carbonate has been used in paints, inks,
It is also widely used as an extender pigment. However, its performance, particularly the gloss of the surface of the dried coating film, was not always fully satisfactory.
For example, in the case of paint, for aesthetic and other reasons,
Generally, there is an extremely strong demand for high gloss on the surface of a dried coating film. With the exception of some paints such as clear lacquer, pigment-containing paints have a pigment volume ratio (Pigment Volume
Concentration (hereinafter abbreviated as "PVC"), that is, the proportion of pigments added, including extender pigments, is usually increased. However, increasing the PVC content of the paint had the disadvantage that the gloss of the paint film surface decreased in most cases. For this reason, in the paint industry,
There is a demand for the development of pigments that maintain the above-mentioned properties such as coloring properties and hiding properties of the coating film, and which do not reduce the surface gloss of the coating film.In particular, from the viewpoint of economy, it is preferable to use extender pigments rather than coloring pigments. The current situation is that there is an even stronger demand for this. On the other hand, recently, from the viewpoint of resource saving, pollution, occupational health, etc., paints, inks, etc. are being changed from conventional organic solvent type to water-based or aqueous type. However, for example, water-based paints tend to have a considerably lower surface gloss than organic solvent-based paints. From this point of view as well, there is a strong demand for the development of extender pigments for aqueous compositions that do not reduce the surface gloss of the coating film, that is, provide high gloss. In view of the current situation, the present inventor has conducted intensive research on extender pigments that can be used in water-based paints, inks, etc. to obtain high-gloss coatings or ink films. As a result, calcium carbonate coated with a phosphoric acid-based surfactant that has an appropriate balance of hydrophilic groups and lipophilic groups and is thought to have a large interaction with calcium carbonate particles is used as an extender pigment. It has been found that by using this method, a high-gloss coating film that cannot be obtained with conventional extender pigments can be obtained.
The present invention was completed based on this new knowledge. That is, in the present invention, particles with a particle size of 10 μm or more measured by a water suspension light transmission method account for 5% or less of the weight of calcium carbonate, and 90.0-99.95% by weight of precipitated calcium carbonate with an average particle size of 0.02-2 μm is added to HLB6. ~18
coated with 10.0 to 0.05% by weight of a phosphoric acid surfactant, and the sedimentation volume in 98.1ml butyl cellosolve after standing for 1 hour is 90ml/5g or more after standing for 120 hours
The present invention relates to an extender pigment for an aqueous composition, characterized in that the amount is 10 ml/5 g or less, and a method for producing the same. In this specification, the "average particle size" refers to the particle size as the median diameter (D50) based on cumulative distribution. In addition, the sedimentation volume is determined by adding 5 g of calcium carbonate to 98.1 ml of butyl cellosolve, stirring for 5 minutes to uniformly disperse the calcium carbonate, and then storing it in a 100 ml measuring cylinder. ) is indicated by the volume. For example, "90
ml/5g" means the suspended part (opaque part)
indicates that the volume of is 90ml. The use of the extender pigment of the present invention in water-based paints significantly improves the surface gloss of the paint film. for example,
When the extender pigment of the present invention is added to acrylic emulsion at PVC = 20%, the coating film gloss is
It actually shows a high value of over 70% at 60° specular gloss. On the other hand, when conventional extender pigments are used, the value is only about 60% at most. Moreover, the extender pigment of the present invention imparts the above-mentioned excellent coating gloss to a wide range of conventionally known paints, regardless of the water-based paint to which it is added. Furthermore, when used in water-based ink, it also improves the gloss of the coated surface. The above-mentioned excellent effects of the present invention are due to the average particle size
Particles with a particle size of 0.02 to 2 μm and a particle size of 10 μm or more measured by water suspension light transmission method are made by coating 5% by weight or less of calcium carbonate with a phosphoric acid surfactant having an HLB of 6 to 18 in the above prescribed ratio, and It is expressed only when the sedimentation volume in 98.1 ml of butyl cellosolve is the above-mentioned specific value. For example, when the average particle size of the calcium carbonate exceeds 2 μm, when the coating ratio of the phosphoric acid surfactant on the calcium carbonate is outside the predetermined ratio, when the sedimentation volume is outside the specific value, etc. In both cases, the initial effect is not achieved. The reason why the above-mentioned excellent effects of the present invention are achieved is as follows.
Although it has not yet been completely elucidated, it can be thought of as follows. That is, a suspension of 5 g of the coated calcium carbonate of the present invention (approximately 1.9 ml with a specific gravity of 2.7 to 2.6) dispersed in 98.1 ml of butyl cellosolve, which is used as a water-soluble organic solvent or a film-forming agent in water-based paints. Sedimentation volume is 90ml or more after 1 hour,
It shows a specific value of 10ml or less after 120 hours. In other words, the sedimentation rate is slow and the sedimentation volume that reaches equilibrium is small. Therefore, the coated calcium carbonate of the present invention has extremely excellent affinity with butyl cellosolve and has good dispersion and suspension stability in the butyl cellosolve. Therefore, when this is applied to water-based paint, even in the water system before the paint dries,
It is also believed that the coating resin system produced by drying the coating material is maintained in a well-dispersed state with few secondary agglomerated particles, thereby providing a coating film with high gloss. The calcium carbonate used in the present invention is precipitated calcium carbonate having an average particle size of 0.02 to 2 μm and containing 5% by weight or less of coarse particles with a particle size of 10 μm or more measured by a water suspension light transmission method. Calcium carbonate with an average particle size exceeding 2 μm has poor dispersion and suspension stability in butyl cellosolve, and it is difficult to obtain a high-gloss coating or ink film even when applied to water-based paints and inks. Calcium carbonate with an average particle size of less than 0.02 μm is difficult to produce industrially. Furthermore, even if the average particle size of calcium carbonate is within the above range, if the content of particles with a particle size of 10 μm or more as measured by the water suspension light transmission method exceeds 5% by weight, it tends to be difficult to achieve the desired effect. . The phosphoric surfactant used in the present invention includes:
Various types can be used as long as their HLB (Hydrophile-Lypophile Balance) is 6 to 18. For example, the general formula () or () RO-(CH ₂ CH ₂ O) _o -PO(OH) ₂ () {RO-(CH ₂ CH ₂ O)n} ₂ -PO(OH) () [in the formula , R represents a higher alkyl group or a higher alkylaryl group, and n represents an integer of 1 to 50], an alkali metal salt, ammonium salt or amine salt thereof, or a mixture thereof, HLB6~ 18 examples can be given. When using a phosphoric acid surfactant with a highly lipophilic HLB of 6 or less or a highly hydrophilic HLB of 18 or more, the dispersion and suspension stability of the resulting coated calcium carbonate in butyl cellosolve is poor, and it is difficult to use this as a water-based paint. Even if applied, high-gloss coatings cannot be obtained. The coated calcium carbonate of the present invention is 90.0 to 99.95% by weight of the above calcium carbonate, preferably 95.0 to 99.95% by weight.
99.5% by weight of the above phosphoric surfactant 10.0~0.05
% by weight, preferably 5.0 to 0.5% by weight. The coverage ratio of phosphoric acid surfactant is
If it exceeds 10.0% by weight, the sedimentation volume after standing for 120 hours in butyl cellosolve will be 10ml/5g or more, and the coating ratio of the phosphoric surfactant will be
If it is less than 0.05% by weight, the sedimentation volume after standing for 1 hour and 120 hours in butyl cellosolve is 90%, respectively.
ml/5g or less, 10ml/5g or more, and in either case, the dispersion and suspension stability in butyl cellosolve is not good. The coated calcium carbonate of the present invention can be industrially advantageously produced, for example, as follows. That is, calcium carbonate with an average particle size of 2 μm or less suspended in water.
A suitable excess amount of phosphoric acid surfactant is added to cover 90.0 to 99.95% by weight (in terms of solid content) so as to cover 10.00 to 0.05% by weight, and the mixture is stirred and mixed uniformly. In this case, the aqueous suspension of calcium carbonate is usually adjusted to a solid content concentration of 1 to 70% by weight, preferably 5 to 50% by weight, and the phosphoric acid surfactant is preferably added as is or in the form of an aqueous solution. . and,
The coating efficiency is better when the coating ratio of the phosphoric acid surfactant is reduced, so the amount of surfactant added is as follows:
Generally, a slight excess of the amount to be coated on the calcium carbonate will be sufficient. On the other hand, when increasing the coating ratio of surfactant, the coating efficiency decreases, so the amount of surfactant added is usually about 20 to 40% excess of the amount that should be coated on calcium carbonate. Bye. Furthermore, when mixing the surfactant aqueous solution and the calcium carbonate suspension, it is necessary to perform an operation to lower the PH of the system in which both are mixed than the PH of the aqueous suspension. Such operations involve adjusting the pH of the surfactant aqueous solution.
A method in which the pH of calcium carbonate is adjusted to be lower than the pH of the aqueous suspension of calcium carbonate and then mixed, or a system in which both are mixed is mixed with CO ₂
There is a method of blowing gas or a method of using these two methods together. Such an operation of lowering the pH of the mixed system promotes the adhesion of the phosphoric acid surfactant molecules to the surface of the solid basic calcium carbonate particles, forming a strong coating layer of the phosphoric acid surfactant. If the coating treatment is performed without performing the PH reduction operation of the above mixed system, molecules of the phosphoric surfactant are liberated from the surface of the calcium carbonate particles, and secondary aggregates of calcium carbonate are formed.
It is not possible to obtain a high-gloss coating film when applied to water-based paints. Furthermore, it is necessary to maintain the temperature at 5 to 80°C, preferably 15 to 50°C when mixing the calcium carbonate aqueous suspension and the phosphoric acid surfactant. At temperatures below 5°C, the phosphoric acid surfactant has low solubility in water, making it difficult to coat calcium carbonate, while at temperatures above 80°C, foaming occurs significantly during stirring, interfering with subsequent processes, and It is also economically disadvantageous. The mixture obtained as described above is usually press-dehydrated, dried, and ground into a powder.
Depending on the concentration and other conditions of the calcium carbonate aqueous suspension, it can be applied to water-based paints and inks even if it is an aqueous system without press dehydration or drying. The thus obtained coated calcium carbonate of the present invention is used by adding 1 to 50%, preferably 5 to 30%, of PVC to a water-based paint, and provides a coating film with significantly higher gloss than conventional extender pigments. . The addition ratio of coated calcium carbonate to water-based paint is 1 for PVC.
If it is less than 50%, no difference in gloss will be observed compared to conventional extender pigments, and if it is more than 50%, a coating film that can be said to be practically high gloss cannot be obtained. Examples of usable resins for water-based paints include:
Polyacrylic, polyvinyl acetate, polystyrene, epoxy, alkyd, melamine,
Emulsion resins for paints on the market such as urethane resins, water-soluble resins for paints on the market such as alkyd-based, amine-based, styrene-allyl alcohol-based, aminoalkyd-based, polybutadiene-based, paint-based resins that are blends of emulsion resins and water-soluble resins. Spurge resins, dispersion resins using crosslinked water-soluble resins as emulsifiers, acrylic hydrosols, and the like can be widely used. In addition, when making water-based paints, additives include coloring and other extender pigments, antifoaming agents, non-adhesives, wetting agents, dispersants, curing accelerators, corrosion inhibitors, dryers, antifungal agents, and additives. Film aids, antifreeze agents, and other agents commonly used in this field may be used in combination with the coated calcium carbonate of the present invention, if necessary. Examples are given below to further clarify the characteristics of the present invention. Examples 1 and 2 A volume of 1.2 kg of precipitated calcium carbonate (-1) with an average particle size of 0.4 μm and 1% by weight or less of particles with a particle size of 10 μm or more in the particle size distribution determined by water suspension light transmission method.
20, added 13.8 g of water, and mixed well with a disper type stirrer to make calcium carbonate suspension water (PH9.2). This suspended water was kept at 35 to 40°C, and a phosphoric acid surfactant (product name: GAFAC RD-510, Manufactured by Toho Chemical Industry Co., Ltd.)
Add 10g of the solution in the form of an aqueous solution with a concentration of 10% and pH 6.0 dropwise while stirring, and mix uniformly. This was press-dehydrated, dried at 100°C, and ground to obtain 1.1 kg of coated calcium carbonate (-1) powder (Example 1).
The coating percentage of surfactant is 0.80% by weight. The coated carbonate of the present invention was prepared in the same manner as above except that precipitated calcium carbonate (-2) was used with an average particle size of 1.0 μm and a particle size of 10 μm or more in the particle size distribution determined by water suspension light transmission method was 1% by weight or less. Calcium (-2) powder was obtained (Example 2). The surfactant coverage is approximately 0.75% by weight. These coated calcium carbonate (-1) and (
Table 2 shows the sedimentation volume of 2) in butyl cellosolve and the specular gloss of the paint film when applied to acrylic emulsion at the ratios listed in Table 1. PVC made by Dainippon Ink & Chemicals Co., Ltd.
Table 3 shows the gloss of the printing ink film when 20% of the ink was added. Coated calcium carbonate of the present invention (
It is clear that -1) and (-2) have high gloss values. Comparative Example 1 Instead of precipitated calcium carbonate (-1), precipitated calcium carbonate with an average particle size of 3.0 μm, average particle size 5
Microscopic calcium carbonate in μm and average particle size 4.5μ
Except for using m heavy calcium carbonate,
Coated calcium carbonate (), () and () were obtained in the same manner as in Example 1, respectively. Table 2 shows the precipitation volumes of the obtained coated calcium carbonates (), () and () in butyl cellosolve and the specular gloss of the coatings when applied to acrylic emulsions in the proportions listed in Table 1. still,
Table 2 shows calcium carbonate coated with fatty acid (trade name "Hakuenka CCR", manufactured by Shiroishi Kogyo Co., Ltd.) and calcium carbonate coated with resin acid (trade name "Homocal D", made by Shiroishi Kogyo Co., Ltd.). In addition, the sedimentation volume in butyl cellosolve for precipitated calcium carbonate (-1) and the specular gloss of the coating film when applied to an acrylic emulsion at the ratio shown in Table 1 are also listed.

[Table] Manufactured by Co., Ltd.)

【table】

[Table] Composition Weight%

Claims (1)

[Claims] 1. Particles with a particle size of 10 μm or more measured by water suspension light transmission method account for 5% or less of the weight of calcium carbonate, and 90.0-99.95% by weight of precipitated calcium carbonate with an average particle size of 0.02-2 μm. 98.1ml coated with 10.0-0.05% by weight of phosphoric surfactant with HLB6-18
Sedimentation volume in butyl cellosolve after standing for 1 hour
An extender pigment for an aqueous composition, characterized in that the amount is 90 ml/5 g or more and 10 ml/5 g or less after standing for 120 hours. 2. An aqueous suspension of precipitated calcium carbonate in which particles with a particle size of 10 μm or more measured by a water suspension light transmission method account for 5% or less of the weight of calcium carbonate and an average particle size of 0.02 to 2 μm, and a phosphoric acid system with an HLB of 6 to 18. and a surfactant, and during this mixing, the PH of the phosphoric acid surfactant is lower than the PH of the aqueous suspension of calcium carbonate, or instead of this operation or this operation. In addition, as a post-treatment after mixing, the pH of the aqueous suspension of calcium carbonate is
1. A method for producing an extender pigment for an aqueous composition, characterized by blowing CO ₂ gas in an amount that is lower than or equal to .