” >1. What is titanium dioxide?
” >Titanium dioxide is a non-toxic inorganic pigment with excellent whiteness, brightness and strong covering ability. It is currently the world’s most powerful pigment One of the best white pigments, it is widely used in industrial fields such as coatings, plastics, rubber, papermaking, chemical fiber inks, and cosmetics.
” >2. The importance of dispersants to titanium dioxide
” >Because titanium dioxide has good photochemical activity, when it is exposed to visible light or ultraviolet light, it can oxidize the organic compounds in contact with it, resulting in Organic compounds degrade, causing brittleness and pulverization. Therefore, in the industrial production of titanium dioxide, surface treatment is generally carried out, that is, it is coated with a layer of inorganic oxide to make up for this defect of titanium dioxide. Before surface treatment, titanium dioxide is first dispersed and slurried. The dispersion of the prepared slurry directly affects the surface treatment effect of titanium dioxide. If the titanium dioxide particles cannot be well dispersed, not only will it not be possible to achieve continuous and uniform coating, but it will also affect the scattering of light by the pigment particles, thereby reducing the optical properties and performance of the pigment, and may even cause damage during the subsequent airflow crushing process. The coating will be damaged, thereby affecting the weather resistance of the pigment. Therefore, it is particularly important to choose the dispersant used before surface treatment of titanium dioxide.
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” >3. How to choose the correct dispersant
” >1. Selection method of dispersant:
” >（1) Determined by the polarity of the dispersion system and the composition of the resin: select the range of the solvation chain
” >（2) The composition of the dispersion (pigment and filler) determines: which anchoring group to choose
” >2. The choice of dispersant needs to be considered based on the different pigments
” >（1) Inorganic pigments such as calcium carbonate, talc, titanium dioxide, iron red, iron yellow, etc., these extremely The organic molecular structure is very easy to interact with acidic groups such as carboxylic acid, phosphoric acid or sulfuric acid functional groups. Generally, anionic types such as carboxylates, phosphates, sulfonates, etc. are used. For example, polyacrylic acid sodium salt is usually used as a dispersant for inorganic pigments and fillers. For most inorganic pigments and fillers, this type of dispersant can provide quite satisfactory aqueous phase dispersion effect and is cheap.
” >（2) For organic pigments, aromatic groups will be very effective, containing the dispersion of aromatic groups (such as phenyl, naphthyl) agent, which is particularly helpful for the long-term stability of the dispersion.
” >It should be pointed out that transparent iron oxide and carbon black are relatively difficult to disperse pigments, and the industry will consider them together with organic pigments.
” >In dispersant screening experiments, it is often found that This phenomenon: dispersants that have good dispersion effects on carbon black and phthalocyanine series cannot disperse wellDPP red, organic violet and other organic pigments. In turn, dispersant can disperse and stabilize DPP red, organic violet and other pigments well, but it is usually used to disperse carbon black to obtain the ideal The hue and viscosity-reducing effect on phthalocyanine pigments are not obvious.
” >There are very few dispersants that can simultaneously show extremely good performance for the above two categories of difficult-to-disperse pigments. There is an explanation for this: the number and strength of the hydrogen bonding structures of different pigments will be different.
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” >For pigments such as carbon black and phthalocyanine blue, the most important interaction force between pigments is not dominated by hydrogen bonds, but other forces, such as carbon black Coupling between layered molecules, coupling of phthalocyanine structure, and the effect of halogen. The polar groups contained in their surface treatments are independent of the structure of the pigment itself.
” >WithDPP represents organic red and permanent purple pigments. The pigments themselves have strong hydrogen bonds in their design. This hydrogen bonding effect It improves the performance of the pigment and also directly affects the effect of the dispersant on the pigment. The polar groups on its interface participate in the hydrogen bonding of the pigment itself. This is confirmed after post-pigmentation processing.
” >According to this, it can be explained why a single structure is used It is not easy for dispersants to obtain the best dispersion effect in two major types of pigments with different intrinsic functions at the same time. Therefore, the choice of dispersant needs to be considered based on the pigment.
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” >For pigments such as carbon black and phthalocyanine blue, the most important interaction force between pigments is not dominated by hydrogen bonds, but other forces, such as carbon black Coupling between layered molecules, coupling of phthalocyanine structure, and the effect of halogen. The polar groups contained in their surface treatments are independent of the structure of the pigment itself.
” >WithDPP represents organic red and permanent purple pigments. The pigments themselves have strong hydrogen bonds in their design. This hydrogen bonding effect It improves the performance of the pigment and also directly affects the effect of the dispersant on the pigment. The polar groups on its interface participate in the hydrogen bonding of the pigment itself. This is confirmed after post-pigmentation processing.
” >According to this, it can be explained why a single structure is used It is not easy for dispersants to obtain the best dispersion effect in two major types of pigments with different intrinsic functions at the same time. Therefore, the choice of dispersant needs to be considered based on the pigment.
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