JPS5913548B2 - kaolin white pigment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to converting kaolin mineral, which has conventionally been used as an extender or filler without hiding power, into a pigment with hiding power comparable to ordinary white pigments. .

In general, when kaolin mineral is dispersed in a resin binder as an extender pigment, its refractive index is not much different from the refractive index of the resin binder, so it exhibits only a slight light scattering property, and kaolin mineral alone cannot hide it. The power, that is, the ability to hide the base is small.

Of course, it is possible to increase the light scattering property by increasing the amount of kaolin mineral mixed into the resin binder and increasing the volume concentration of JPVC, that is, the pigment in the coating film.
If the amount is increased to the extent that hiding power is recognized, the continuity of the coating film will be lost and the strength will decrease, so this is not actually done. For this purpose, kaolin mineral is used exclusively. It is only used as an extender, filler, or admixture for pigments with excellent hiding power and coloring power, such as titanium dioxide and zinc oxide. The present inventors researched ways to use kaolin minerals and found that kaolin minerals were treated to remove aluminum, one of the main components, and were then dispersed in a resin binder to form a coating film. , a specific PV
It has been found that when the pigment is present in excess of C, it has a hiding power comparable to that of white pigment.

In other words, when an ordinary white pigment such as titanium dioxide is dispersed in a resin binder and made into a coating film, its 10 PV
The relationship between C and hiding power (represented by reflectance in the figure) shows an almost linear relationship, for example, as shown in Figure 1A, but dealuminated kaolin white pigment has PVC30 as shown in Figure 10.
%, below which it has virtually no hiding power, whereas above 15 it shows a hiding power comparable to that of white pigment, and Figure 2 shows the case where kaolin white pigment and titanium dioxide are used together. As can be understood from this figure, it was found that the same tendency appears even when kaolin white pigment is used in combination with other pigments. It is well known that minerals whose main component is hydrated alumina-silicate, such as kaolin minerals, are treated with acid to remove the aluminum component. It was completely unknown that hiding power could be significantly improved by using PVC as a pigment in a range of 30% or more.

The present invention is a pigment obtained by calcining kaolin mineral and then dealuminizing it with a mineral acid. 0 Fees for all P
A kaolin white pigment characterized by providing improved hiding power when present in an amount of 5% or more PVC in a coating composition with 30% or more VC.

The kaolin white pigment of the present invention is obtained by dealuminating kaolin mineral '5 as follows.

That is, first, kaolin mineral is fired for a short time at 400 to 1000°C. This calcination removes most of the moisture in the mineral and further changes the crystals of the mineral into an amorphous form, making it easier for the aluminum component to dissolve into acid in the subsequent acid treatment step. If calcination is carried out at 1000°C or higher for a long time, mullite, α-alumina, etc. will be generated and difficult to be eluted by acid treatment, so calcination at 600 to 800°C for about 20 minutes to 1 hour is usually desirable.

Kaolin minerals used in the present invention include kaolinite, dateskite, and nacrite. All of these are flat plate-shaped particles of hydrated alumina silicate, and in general, particularly desirable effects can be obtained when the particle size is relatively small. For example, it is desirable that the average particle diameter is 2 μm or less, preferably 1 μm or less, as measured on the longer side of the plate-like particles. After firing, it is treated with an aqueous mineral acid solution such as hydrochloric acid, sulfuric acid, or nitric acid.

This acid treatment may be carried out by adding the fired product to an aqueous mineral acid solution and stirring as appropriate. Heating is not necessarily required at this time, but dissolution of the aluminum component is promoted if carried out at around 60°C.The amount of acid required for acid treatment is sufficient to elute most of the aluminum component, preferably 75% or more of the aluminum component. It is sufficient as long as the amount is necessary. There is no particular limit to the concentration of the acid, but it is best to set it so that the amount of liquid can make the kaolin mineral into a slurry with appropriate viscosity and concentration.
Usually, the preferred ratio of the calcined product of kaolin mineral and the mineral acid aqueous solution is 500 to 2000 ml of the mineral acid aqueous solution to 1009 of the calcined product of kaolin mineral, and the treatment time is 30 minutes to
It is 3 hours. By acid treatment in this way,
Depending on the purpose of use of the kaolin mineral, substantially all of the aluminum component contained as Al2O3 is eluted in the stage before firing, or most of it is eluted, and the content is reduced to 0 to 25%. lower. The kaolin white pigment of the present invention obtained by the dealumination treatment as described above is present in a coating composition having a total PVC of 30% or more as the kaolin white pigment alone in an amount of 30% or more of PVC, preferably 30 to 65%. In addition, by coexisting with other pigments, the kaolin white pigment is present in an amount such that the PVC is 5 (Ft) or more, preferably 5 to 60%, and the PVC of other pigments is 25 to 5%. It can provide concealing power comparable to that of

If the PVC of the coating composition is less than 30 (?/), the effect of the present invention will not be achieved, and the light scattering power will be too small to obtain the desired hiding power, and if it exceeds 65%, the continuity of the coating will be lost. This is not preferable because it causes the strength to deteriorate. Examples of pigments used in combination with kaolin white pigment include titanium dioxide,
Use commonly used pigments such as zinc oxide. Of course, other than these, colored pigments or dyes may also be blended. In the present invention, the kaolin white pigment exhibits improved hiding power comparable to ordinary white pigments, so that the PV
Not only does it have the advantage of being able to be used alone as a pigment with C3O% or more, but it also has the advantage of being able to significantly reduce the amount of these used when used in combination with expensive pigments such as titanium dioxide and zinc oxide. . As the resin binder as the main component of the coating composition in the present invention, for example, alkyd resin, acrylic resin, melamine resin, vinyl acetate resin, etc. can be used.

Usually, these resin binders, the above kaolin white pigment, and other pigments as necessary are kneaded together with water or an organic solvent such as xylene, toluene, kerosene, alcohol, or ketone to form the desired PVC. Used as mold paint, emulsion paint, water-soluble paint, etc. At that time, thickeners such as polyvinyl alcohol, carboxymethyl cellulose, and casein, as well as other dispersants, protective colloids, antifoaming agents, and the like can be used as auxiliaries. In addition to the various paints mentioned above, it can also be prepared into a paste and used as a coating agent for paper. Further, the present invention has the advantage that the aluminum salt can be easily recovered from the mineral acid solution in which the aluminum component is dissolved after the acid treatment by methods such as concentration and precipitation.

Next, examples according to the present invention will be shown.

Example 1 Diyodia Kaolin Hydride 10 (manufactured by Diyodia Kaolin Co., USA, trade name) having the composition shown in Table 1 below was used as a kaolin mineral.

The above kaolin mineral 589 was placed in a crucible and fired at about 800° C. for 1 hour in an electric furnace. After cooling the baked product, put it in a Yotsuro flask, add 1,000 ml of 6N hydrochloric acid, and heat at 60°C.
The acid treatment was carried out by holding the mixture for 3 hours while stirring gently. Next, the contents of the flask were filtered through a Buchna Ippuchinto filter, washed with water, dried, and ground to obtain 29.89 g of a white kaolin pigment. Analysis of the aluminum component in the kaolin white pigment revealed that the aluminum component was completely eluted. Further, the specific gravity of this product was 2.0. The kaolin white pigment 0.69, 1.39, 2.39, 2.
89 and 3.59 respectively, alkyd resin Styresol 4440 (manufactured by Dainippon Ink Co., Ltd., trade name, solid content 5)
0% by weight, specific gravity 0.95) 5f1 and xylene 2-5ml
and glass beads 259 as grinding media, approximately 50 m
1 and kneaded with a quick mill for 15 minutes to obtain pastes 1 to 4. These pastes have a reflectance of '2.6
01) on black paper, and after drying, the film thickness was 62 μm.
, pigment volume concentration 10%, 2001), 30%, respectively.
A coating film of 350/) and 40% was obtained, and the reflectance was measured: 7.4%, 11.0%, 73.50/), 7
It was 8.4 (I). FIG. 10 is a graph plotting the values of PVC and reflectance according to the above results. As is clear from this figure, PVC3O%
It can be seen that the reflectance increases rapidly near the area, indicating that the kaolin white pigment of the present invention provides high hiding power. Example 2 In Example 1, 569 of kaolin mineral was replaced with 600
A kaolin white pigment 29.69 from which aluminum was eluted was obtained by the same treatment except that it was calcined at .degree.

The specific gravity of this product was 2.0. This kaolin white pigment 0.1f110.89, 1.89, 3.19 and 5.
19 respectively titanium dioxide (rutile type, specific gravity 4.2)
1.79, 1.99, 2.2f112.69 and 3.3
9. 44,405 g of the above alkyd resin styresol, 3 to 7.2 ml of xylene and 259 glass beads and about 5
Pastes 1 to 5 were prepared in the same manner as in Example 1, and the film thickness after coating and drying was 17μ and the pigment volume concentration was 15(f), 25(f), 35%, and 4, respectively.
5% and 56% coatings (PVC of titanium dioxide in each coating)
13%). When the reflectance was measured, the results were as shown in Table 2 below, which is illustrated in FIG. 2. Example 3 In Example 1, 3/4N hydrochloric acid 1,000ml
Kaolin white pigment (39.4%
I got a 9.

When the aluminum component of this pigment was measured, it was found that 65% of the aluminum component was eluted. Further, the specific gravity of this product was 2.2. A paste was prepared by using this kaolin white pigment in combination with titanium dioxide in the same manner as in Example 2, and after coating and drying, the film thickness was 19μ and the pigment volume concentration was 50 (:Ft) (45% of kaolin white pigment, 5% of titanium dioxide). %) coating film was obtained. When the reflectance was measured, it was 81.1%. For comparison, pigment volume concentration 20% (kaolin white pigment 150%
A coating film with a dry film thickness of 20 μm was obtained, and the reflectance was measured to be 61.3%.

Example 4 The kaolin white pigment 89 obtained in Example 1 was mixed with 0.1 m of antifoaming agent Bulb (manufactured by Rohm and Haas, trade name).
11 Glass beads 259 and mixed solution 35ml with the following composition
1 and a pin of about 50 m1, 30 at Kuitsuku Mill.
Mill base was obtained by grinding for a minute.

Composition of mixed solution: 0R0TAN731SD (dispersant), acrylic emulsion (Primal AC
3444 Rohm & Haas Solids content 46% by weight
, specific gravity 1.15) 109, a small amount of 2% zero size and antifoaming agent isoamyl alcohol were added and mixed to obtain a paste.

This paste was applied on black paper with a reflectance of 2.6%, and after drying, the film thickness was 35μ and the pigment volume concentration was 50! ) was obtained, and the reflectance was measured and found to be 83.2%. For comparison, the amount of acrylic emulsion added was slightly increased in the above method to obtain a coating film with a pigment volume concentration of 20% and a dry film thickness of 42 μm, and the reflectance was measured to be 15.4%.

Example 5 An aluminum-eluting olefin white pigment was obtained in the same manner as in Example 1 except that the calcined product of kaolin mineral was acid-treated with 6N sulfuric acid below the boiling point.

The specific gravity of this product was 2.0. This kaolin white pigment was treated in the same manner as in Example 1 to prepare a paste, and after coating and drying, a coating film having a thickness of 53 μm and a PVC of 40% was obtained. In addition, a paste was prepared by using kaolin white pigment in combination with titanium dioxide in the same manner as in Example 2, and after coating and drying, the film thickness was 20 μm.
PVC43% (Kaolin white pigment 23%, TiO22O
%) coating film was obtained.

For comparison, we conducted an untreated kaolin mineral (specific gravity 2.59) that had not been calcined or acid-treated, and a fired product that had been calcined at 800°C for one hour but had not been acid-treated (specific gravity 2.53). According to Example 1, PVC was prepared to have a content of 40%, and a coating film was obtained. Table 3 shows the results of measuring the reflectance of these coatings.

[Brief explanation of drawings]

FIG. 1 shows the relationship between PVC and reflectance of the kaolin J white pigment of the present invention obtained in Example 1 and titanium dioxide,
Part A shows the relationship between PVC and reflectance of the kaolin white pigment of the present invention.

Claims (1)

[Claims] 1 A pigment obtained by calcining kaolin mineral and then dealuminizing it with mineral acid, which has a total PVC of 30%.
A kaolin white pigment characterized in that it provides improved hiding power when present in the above coating composition in an amount of 5% or more of PVC.