Titanium dioxide is the most widely used and most used white pigment in the field of application, but high prices and industrial pollution seriously restrict the application level of White Titanium Dioxide Pigment. The use of non-metallic minerals as a matrix to prepare composite pigments by coating titanium dioxide on its surface is considered to have good prospects and Titanium Dioxide In Bath Bombs is of positive significance for the development of new white pigments that are inexpensive and environmentally friendly.
Talc is a layered magnesium silicate mineral with good slipperiness and flaky cleavage, Lomon Tio2 chemical resistance, good dry lubricity, easy grinding and high whiteness. Then, what is the effect of preparing a white pigment by combining talc with titanium dioxide?
1. Preparation of talc-titanium dioxide composite pigment: talc powder: purity of 94.88% (mass fraction), whiteness of 98.01%, containing a small amount of dolomite, particle diameter d50 of 7.37 μm;
Titanium dioxide: Rutile titanium dioxide having a particle diameter d50 of 0.40 μm, a hiding power of 10.25 g/m 2 , an oil absorption mass of 27.88 g per 100 g, a specific surface area of 6.13 m 2 /g, and a whiteness of 95%.
Grinding equipment: wet stirring mill, grinding medium is ceramic microbeads.
Preparation process: using talc and titanium dioxide powder as raw materials, the talc-titanium dioxide composite white pigment is prepared by mechanical grinding composite method in aqueous medium, including talc matrix grinding and talc-titanium dioxide blending grinding.
Talc-titanium dioxide composite white pigment: Two kinds of talc-titanium dioxide composite white pigments were prepared, and the composite ratio of titanium dioxide was 60% and 70%, respectively.
2. Preparation of exterior wall coating The talc-titanium dioxide composite white pigment or rutile titanium dioxide (mass fractions of 5%, 10%, 15%, 20%, respectively) and other fillers are mixed with water to form a slurry, which is then added to the emulsion. Mixing with other additives to produce building exterior paint.
Table 1 Coating composition formula
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raw material name
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Add amount
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Water (as solvent)
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230g
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X-405 wetting agent
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1g
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731A dispersant
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6g
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C-12 filming aid
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14g
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CF-754 defoamer
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2g
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CF-254 defoamer
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1g
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Thickener water
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Moderate amount
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AC-261 acrylic emulsion
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270g
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FSN leveling agent
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1g
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Ethylene glycol solvent
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15g
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Rutile titanium dioxide or talc-titanium dioxide composite white pigment
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Add by quality score
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Heavy calcium carbonate
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205g
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Kaolin
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150g
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2020 leveling agent
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5g
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total
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1000g
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3, talc-titanium dioxide composite white pigment properties
● Titanium dioxide composite ratio 70% and 60% composite pigment hiding power is equivalent to rutile titanium dioxide powder hiding power;
● The hiding power of talc-titanium dioxide composite white pigment exceeds and is close to that of pure rutile titanium dioxide, and the oil absorption is equivalent;
● The talc-titanium dioxide composite white pigment has good pigment properties comparable to titanium dioxide, and it is expected to be used instead of titanium dioxide in coatings and other products.
4. Microscopic morphology of talc-titanium dioxide composite white pigment.
The degree of coating of titanium dioxide is an important factor affecting the performance of composite particle pigments. It can be seen from the above figure that titanium dioxide particles are uniformly and firmly coated on the surface of talc particles, which is significantly different from the smooth layered surface of talc raw materials. There are large pores between them and the dispersion is good.
5, the coating film contrast ratio will be added talc-titania composite white pigment (titanium dioxide ratio 70% and 60%) and rutile titanium dioxide prepared by three coatings on black and white card paper to obtain a coating thickness of 100μm, and The reflectance of the coating film in the black and white areas was measured, and the contrast ratio was calculated.
● The coating ratio of the added talc-titania composite white pigment continues to increase with the increase of the added amount;
● When the proportion of titanium dioxide 60% composite pigment is 5%, the paint contrast ratio meets the requirements of the national standard GB/T 9755-2014 for the conformity of the top coat (≥0.87); the added amount reaches 10% to meet the requirements of the first grade (≥0.90) The addition amount of 15% reaches the requirement of superior product (≥0.93), indicating that the talc-titania composite white pigment exerts strong hiding performance in the coating.
● Adding TiO2 ratio 70% composite pigment 5%, the coating contrast ratio meets the requirements of the first grade; the addition amount of 10% reaches the requirement of superior products; when the pigment addition amount is 15%, the pair of talc-titania composite white pigment coating is used. The ratio is slightly smaller than that of the rutile titanium white paint, but it reaches the standard grade; when the addition amount is 20%, the ratio is the same, so it is considered that the talc-titanium dioxide composite white pigment and the rutile titanium dioxide have comparable application properties in the coating.
6. Anti-UV aging performance of the coating By comparing the color difference (ΔE*ab) of the coating film after ultraviolet irradiation with the unirradiated coating film, the anti-UV aging performance of the coating film is judged, thereby reflecting the performance of the added pigment.
As can be seen from the above figure:
● With the increase of ultraviolet irradiation time, the △E*ab value of the coating prepared by adding talc-titanium dioxide composite pigment gradually increased, and the irradiation time was smaller in the range of 100-400h, and the irradiation time increased over 400h. , indicating that the long-term exposure to ultraviolet light has a certain degradation effect on the coating film;
● Within the effective range of UV irradiation for 500 hours, only the coating ΔE*ab using titanium oxide composite ratio 70% composite pigment (addition amount 15%) is larger than the same amount of rutile titanium dioxide coating, and the coating prepared by the other conditions △E *ab is less than the addition of rutile titanium dioxide, which means that the color difference is mostly smaller than the color difference of the coating film with rutile pigment added, that is, the UV anti-aging performance is better than the rutile added coating;
●When the UV light is irradiated for less than 600 hours, the color difference ΔE*ab of the coating film prepared by the composite pigment is less than 1.8, which fully meets the requirements of coating application. The results show that the talc-titanium dioxide composite pigment has better UV aging resistance than titanium dioxide.
7. Conclusions (1) The talc-titanium dioxide composite white pigment prepared by the mechanical force grinding method has pigment properties comparable to titanium white powder;
(2) The talc-titanium dioxide composite white pigment particles are characterized by tight and firm coating of titanium dioxide particles on the surface of the talc, and the diameter distribution is uniform;
(3) The coating ratio of the coating film with talc-titanium dioxide composite white pigment is close to or equivalent to that of rutile-type titanium dioxide coating, and the addition amount can reach the national standard (GB/T 9755-2014) level in the range of 10%-20%. Product or superior product requirements;
(4) The talc-titanium dioxide composite white pigment has better UV resistance and aging resistance than rutile titanium dioxide, and can be used in the coating instead of titanium dioxide.
(5) The use of talc as a matrix for the preparation of titanium dioxide composite pigments has a positive effect on effectively exerting its performance advantages and increasing the added value, and the cost is low. In practical applications, the amount of titanium dioxide can be reduced and the cost of the product can be reduced, which is expected to be excellent overall cost performance. The new white pigment.
