Technology . . Why can't the paint industry be separated from titanium dioxide? How can non-metallic ore powders take advantage of the opportunity to "upper position"?

Titanium white powder is known as the king of white pigments, with high refractive index, strong coloration, large cover, good dispersion, high whiteness, non-toxic and other characteristics, widely used in coatings, plastics, inks, paper, chemical fiber, ceramics and other industries. Among them, the largest amount of paint, accounting for about 57% of the total
of titanium
.
1
The application characteristics of titanium dioxide in coatings
Titanium white powder is the most used white pigment, its output accounted for more than
70% of inor
inorderable pigments, consumption accounted for
95.5% of the total consumption of white pigments
China
. At present, about

of the world's titanium dioxide is used in the manufacture of a variety of coatings, especially redstone titanium white powder, most of which is consumed by the coatings industry.
Paint made of titanium dioxide, bright colors, high cover, strong coloring force, dosage, variety, the stability of the medium to protect the role, and can enhance the mechanical strength and adhesion of the paint film, prevent cracks, prevent ultraviolet and moisture through, extend the life of the paint film, color pattern paint in almost every pattern color is inseparable from titanium dioxide.
(
1
) powder coatings
different types of coatings for different uses have different requirements for titanium dioxide, such as powder coatings require the use of highly dispersed gold-redstone titanium dioxide powder. Sharp titanium-type titanium white powder color decoloration force is low, photochemical activity is strong, used in powder coating, coating film prone to yellowing. The gold-redstone type titanium dioxide produced by sulphuric acid method has the advantages of moderate price, good dispersion, good covering force and coloration force, and is very suitable for indoor powder coatings, while outdoor powder coatings with titanium dioxide powder in addition to the requirements of dispersion, cover and coloration, but also require good weather resistance, therefore, outdoor powder coatings with titanium dioxide powder generally produced by chlorination method of gold-redstone titanium dioxide powder.
(
2
) water-based coatings
water-based coatings refers to the paint formulation of volatile substances are the vast majority of water coatings, with people's environmental awareness and environmental regulations become increasingly strict, water-based coatings have been popular. As with solvent-based coatings, titanium dioxide whiteness and dispersion are required, covering force, coloration and weather resistance are high, and impurities content is low.
Most of the titanium dioxide powder on the market is general-purpose titanium dioxide, can be used in solvent-based coatings, but also can be used in water-based coatings, but
, after all, water-based coatings and solvent-based coatings there is a fundamental difference, these general-purpose titanium dioxide in water-based coatings dispersion effect is not very good, therefore, in order to make titanium white powder in water-based coatings in a good dispersion, to choose a targeted titanium dioxide surface treatment.
(
3
) Building coatings
building coatings require acid, alkali, water and moisture resistance, regardless of rough or smooth grass surfaces have good adhesion. In addition to the above-mentioned good optical and pigment properties, the most important thing is to require titanium dioxide with high weather resistance, strong resistance to powdering, especially for exterior building coatings.
2
Titanium white powder indicators on the performance of the paint
(
1
) whiteness
titanium dioxide as a high-quality coating white pigment, its whiteness is very important, is one of the key quality indicators required by the coating, titanium white powder whiteness, will directly affect the appearance of the coating film.
The most important factor affecting the whiteness of titanium dioxide is the type and content of harmful impurities, because titanium white powder is very sensitive to impurities, especially redstone-type titanium dioxide, so even a small amount of impurities, will have a significant impact on the whiteness of titanium dioxide.
chlorination process production of titanium dioxide whiteness is often better than the production of sulfuric acid process, because the chlorination process to produce titanium dioxide used raw material titanium tetrachloride has been distilled and purified, its own impurities content is small, and sulfuric acid process used in the raw material impurity content is high,
can only be washed and bleached and other process technology to remove impurities.
the shape, size and particle size distribution of titanium dioxide particles, as well as the appearance of an undesirable crystal structure and crystal mixing of titanium dioxide can also affect its whiteness. In order to make titanium dioxide have the best whiteness, titanium white powder is required to be spherical particles, smooth and rounded surface, without angularity, do not reunite, particle size distribution control at
0.15-0.35 m
.
(
2
) cover force
the cover force is the surface area of the object being coated per square centimeter, which requires the minimum mass of the pigment when the cover is fully covered. Applying the same area of the surface, the greater the cover force of titanium dioxide used, the thinner the coating film, the less amount of paint required, then the amount of titanium dioxide required is also less, if the titanium white powder cover force is reduced, in order to achieve the same cover effect, the amount of titanium dioxide required increases, then the production cost will increase, and the amount of titanium dioxide will increase, will cause titanium white powder in the paint difficult to disperse evenly,
will also affect the coating cover effect.
The size of the titanium white powder cover force is mainly determined by its own refractive index, the refractive index of the redstone titanium dioxide is the largest of all white pigments, so its cover force is also the highest, the sharp titanium titanium white powder second. Secondly, the shape, size, particle size, particle size distribution and dispersion of titanium dioxide particles will also affect its masking force, in the range greater than the visible light half wavelength, the smoother the surface of titanium dioxide particles, the smaller the particle size, the larger the surface area, the better the dispersion, the greater its cover.
(
3
) weather resistance
coatings have high weather resistance to titanium dioxide, especially for outdoor surface coatings, requiring high weather resistance or ultra-high weather resistance type of titanium dioxide powder. Using low weather resistance of titanium dioxide, the coating film will appear fade, discoloration, powdering, cracking, peeling and other problems. The crystal structure of the gold-redstone type titanium white powder is more closely than that of the sharp titanium-type titanium white powder, the photochemical activity is low, so the weather resistance is much higher than the sharp titanium-type titanium white powder, so the coating with titanium white powder is basically all gold-redstone titanium white powder.
The main way to improve the weather resistance of titanium dioxide is to treat its inorganic surface, that is, in titanium white powder particle surface bread covered with a layer or layer of inorganic oxides or hydrated oxides, of which zirconium oxide and dense silicon oxide coating is currently recognized as the best weather resistance coating method, zirconia coating technology has been mastered in China, but dense silicon oxide coating technology is still monopolized by foreign countries, domestic has not yet been broken, to be continued research.
(
4
) dispersion
titanium dioxide is a super-fine particle, larger than the surface area, high surface energy, particles between easy to gather, difficult to stabilize dispersion in the coating. The poor dispersion of titanium dioxide will directly affect its optical properties such as color loss, cover force and surface gloss in the coating, but also affect the storage stability, mobility, leveling, coating durability, corrosion resistance and conductivity of the coating, in addition, it will also affect the production cost of the coating, because of the high energy consumption of the grinding dispersion operation, accounting for the majority of the total energy consumption of the coating manufacturing process, and the loss of equipment.
The main factors affecting the dispersion of titanium dioxide are the size of titanium dioxide particle size, surface area, surface free energy, surface charge,
pH
value, polarity, surface adsorption status and other surface properties, in addition, it is also related to the nature of the colorizer, the type and dosage of dispersants, grinding dispersion equipment and dispersion process and other factors.
In order to achieve the best dispersion effect of titanium dioxide in the coating, so that titanium dioxide particles in the coating in or close to the original particle state, fully reflect its excellent performance,
usually in the titanium dioxide production process to surface treatment, improve its dispersion
, in addition, in the paint production process should also choose the correct wetting dispersant, grinding dispersion equipment and dispersion process.
3
ore powder can replace the titanium white powder

"
"
?
is by far the best performance of white inorder pigments, widely used in coatings, plastics, inks, paper, rubber, chemical fibers and cosmetics and other fields. But its high prices and the sharp rise in prices in recent years have made some downstream users miserable! If titanium dioxide can be replaced or partially replaced with relatively inexpensive non-metallic minerals, production costs will be significantly reduced.
The pigment properties of titanium dioxide powder are reflected in optical properties, which mainly depend on the surface properties of titanium dioxide particles, the core is almost non-functional, so researchers and enterprises are committed to the development of mineral
/
titanium dioxide composite particle materials to prepare high-performance, low-priced titanium dioxide alternatives.
In recent years, China has developed calcium carbonate, kaolin, talc, mica, silica ash and other minerals
-TiO 2
composite pigments, to replace or partially replace titanium dioxide, for cosmetics, coatings, paper, plastics and other industries.
(
1
) calcium carbonate
calcium carbonate is rich in sources, low price, its own high whiteness, larger than the surface area, strong cover, but also important white pigments. Sandalwood and other mechanically active method to prepare calcium carbonate
-
titanium dioxide composite material, the calcium carbonate
-
titanium dioxide composite pigment cover force
22.8g/m

2
, oil absorption
22.5g/100g
, whiteness
95.50%
, obviously has the pigment properties of titanium-like white powder.
(
2
) kaolin paint with white pigments is intended to produce white color and cover, kaolin can not replace titanium dioxide, but can produce synergies, improve the effective utilization rate of titanium dioxide, reduce the amount, when the whiteness and fineness of kaolin requirements are very strict.

Inge porcelain
PVC
decoration with paint in kaolin part of the replacement titanium dioxide scheme
2018

3
, Inge porcelain (
Imerys
) proposed a partial replacement of titanium dioxide with kaolin, reducing the amount of
20%
titanium dioxide, which can effectively solve the problem of titanium dioxide in the field of coatings and inks.
, BASF also said its
Ultrex
pigment additives also have good coloring and masking power and are cost-effective alternatives to titanium dioxide. The product is an ultra-fine calcination of kaolin as the main component of pigments, widely used in flat light, eggshell light, low light and special coatings;
(
3
) silica ash
silica ash is a silicate mineral with a refrengation index (
1.63
) higher than many white minerals and a surface prone to

active groups such as OH
-
, which help to create synergies in the preparation of composite pigments based on silica ash, covered with table bread
TiO
2
.
chen Wanxuan and other water medium wet ultra-fine grinding method prepared silica ash
-TiO
2
composite pigment, its performance is comparable to titanium dioxide
TiO
2
ratio
45%
's composite pigment cover is
17.97g/m
2
, an increase of
36.08% over
TiO
2
's
. The particles of the
-TiO
2
composite pigment are characterized by
TiO
2
particles evenly encased on the surface of the silica ashstone.
At present, non-metallic mineral powder material can not be replaced by titanium dioxide, but by preparing similar performance with titanium dioxide mineral
-TiO
2
composite pigment, can significantly alleviate the production and application of titanium dioxide resources, environment and cost prices, but also conducive to the efficient use of non-metallic mineral resources.
to
source: titanium white powder in the application of paint overview, Xiao Yongli, mechanically active preparation of calcium carbonate / TiO2 composite particle materials and characterization, sandalwood, etc. , mechanical grinding method preparation of silica ash -TiO2 composite pigment experimental research, Chen Wanyu, Ding Hao, etc.
editing and finishing: powder technology network