Plastic industry, as the second largest user of Titanium Dioxide, is the fastest growing field in recent years, with an average annual growth rate of 6%. Of the more than 500 titanium dioxide brands in the world, more than 50 brands are dedicated to plastics. The application of titanium dioxide in plastic products, in addition to its high covering power, high achromatic power and other pigment properties, it can also improve the heat resistance, light resistance and weather resistance of plastic products, prevent the plastic products from the invasion of UV light, and improve the mechanical and electrical properties of plastic products.
Because plastic products are much thicker than paint and ink film, so it does not need too high pigment volume concentration. In addition, it has high covering power and strong coloring power, and the general dosage is only 3% ~ 5%. It is used in almost all thermosetting and thermoplastic plastics, such as polyolefins (mainly low-density polyethylene), polystyrene, ABS, polyvinyl chloride, etc. it can be mixed with
Resin dry powder or liquid containing
Plasticizer, and some titanium dioxide is processed into
Color Masterbatch before use.
The particle size of titanium dioxide used in most plastics is relatively small. Generally, the particle size of titanium dioxide for coating is 0.2 ~ 0.4 μ m, while the particle size of titanium dioxide for plastic is 0.15 ~ 0.3 μ M. in this way, a blue background phase can be obtained, which can shield most of the resins with yellow phase or easily yellowing.
Titanium dioxide for ordinary plastics is generally not surface treated, because the titanium dioxide coated with conventional hydrated alumina, when the relative humidity is 60%, its adsorption equilibrium water is about 1%. When the plastic is extruded at high temperature, the evaporation of water will lead to pores on the smooth plastic surface. This kind of titanium dioxide without inorganic coating generally has to go through the organic surface Surface treatment (polyol, silane or siloxane), because titanium dioxide for plastics is different from titanium dioxide for coating, the former is mixed by shearing force processing in low polarity resin, and the titanium dioxide after organic surface treatment can be well dispersed under appropriate mechanical shear force.
With the continuous expansion of the scope of application of plastic products, many external plastic products, such as plastic doors and windows, building materials and other outdoor plastic products, also have high requirements on weather resistance. In addition to the use of rutile titanium dioxide, it also needs surface treatment, which generally does not add zinc, only silicon, aluminum, zirconium, etc. Silicon has the function of hydrophilic dehumidification, which can prevent the formation of pores due to water evaporation during high temperature extrusion of plastics. However, the amount of these surface treatment agents is generally not too much.
The composition of plastics includes resins, fillers, plasticizers and other auxiliaries (such as colorants, antioxidants, flame retardants, etc.), which can be divided into extrusion blow molding process of plastic film, extrusion molding process of plastic sheet and plastic injection molding process, such as resin, filler and auxiliary masterbatch ingredients (masterbatch plus resin) blowing film Plastic film, the main equipment used in the process are double roll open mill, blowing film machine, etc.
Plastic injection molding process includes three stages: plasticizing, injection and molding cooling. The commonly used equipment includes plug type injection machine and screw type injection machine.
The quality requirements of plastic products for titanium dioxide are as follows:
Covering power: titanium dioxide with good covering power can produce lighter and thinner plastic products;
Whiteness: determine the appearance of light or white plastic products;
Dispersion: it affects the production cost of plastic products, and the poor dispersion of titanium dioxide in plastic products will affect the smoothness and brightness of the products;
Weather resistance: outdoor use of plastic products and plastic doors and windows must ensure the weatherability of titanium dioxide.
Color Masterbatch
Plastic color masterbatch is a kind of high concentration and high-efficiency color configuration product, that is, pigments are evenly distributed in the carrier resin with extraordinary concentration and form particles with certain particle size. It is mainly composed of core layer (pigment), coupling layer (coupling agent or surfactant), dispersion layer (lubricant or dispersant), and additive layer (carrier resin). It is widely used as dyeing agent in plastics and widely used in the production of plastic products such as blowing film, injection molding, hot pressing, injection molding, etc It is favored by users. The development of color masterbatch is very fast. In addition, the production process of color masterbatch is simple and the investment is low. At present, there are hundreds of Color Masterbatch factories in China, with different production scale and technical level. The annual output of small masterbatch is dozens of tons, and the large one is tens of thousands of tons. The product competition is increasingly fierce. The profit of production enterprises is on the downward trend, and the quality of most color masterbatch products is low. According to incomplete statistics, the titanium dioxide used in the production of color masterbatch is 20000-30000 tons per year. The rutile used is divided into three grades: high, middle and low grade. Imported rutile is used for high grade, domestic rutile is used for medium grade, and domestic anatase titanium dioxide is used for low grade. Huizhou taiyangshen Chemical Co., Ltd., the largest manufacturer of color granules in China, mainly uses imported titanium dioxide to produce color masterbatch for export, while the color masterbatch produced by domestic titanium dioxide meets the domestic market. Due to the fierce competition, the use of anatase titanium dioxide masterbatch is still increasing.
Color masterbatch can be used for color matching of PVC, PE, PP, PS and ABS plastics. Its main components are pigment, resin, dispersant, volume pigment, fluorescent whitening agent, antioxidant, anti ultraviolet agent, antistatic agent, toughening agent, brightener, etc. titanium dioxide used as white pigment has the advantages of non-toxic, stable chemical properties, high covering power and good dispersion.
There are several production processes of masterbatch, such as pigment, resin, dispersant, volume pigment and other additives. As an industrial raw material, the performance of color master batch is usually shown in the subsequent product application (such as film blowing or injection molding). Therefore, the performance of titanium dioxide in the color master batch is mainly reflected in the application process of color master batch. It is mainly reflected in the following aspects:
1) Coloring ability of titanium dioxide: determine the amount of titanium dioxide used in the same color of plastic products;
2) Whiteness of titanium dioxide: determine the appearance of light colored (white) plastic products with the same titanium content;
3) Dispersion of titanium dioxide: it affects the production cost of color particles and the appearance and luster of plastic products;
4) The processability of titanium dioxide affects the production cost of color masterbatch.
