Analysis of the application performance of titanium dioxide in plastics

Since plastic products are much thicker than paints and inks, they do not require too much pigment volume concentration, and their high hiding power and coloring power are generally only 3% to 5%. It is used in almost all thermosetting and thermoplastic plastics, such as polyolefins (mainly low-density polyethylene), polystyrene, ABS, polyvinyl chloride, etc., which can be mixed with resin dry powder or The liquid phase of the plasticizer is mixed, and some are used to process the titanium dioxide powder into a masterbatch.

Specific application analysis of titanium dioxide in plastic industry and color masterbatch industry

Most of the plastic titanium dioxide has a fine particle size. Usually, the titanium dioxide powder for coating has a particle size of 0.2-0.4 μm, and the titanium dioxide powder for plastic has a particle size of 0.15-0.3 μm, so that a blue base phase can be obtained. Most yellow-colored resins or yellow-yellow resins have a shielding effect.

Titanium dioxide for ordinary plastics generally does not undergo surface treatment, because the inorganic coated titanium dioxide such as conventional hydrated alumina, when the relative humidity is 60%, its adsorption equilibrium water is about 1%, when the plastic is extruded at high temperature. When processed, water evaporation causes pores on the smooth plastic surface. This inorganic coated titanium dioxide is usually subjected to organic surface treatment (polyol, silane or siloxane) because titanium dioxide for plastics Unlike titanium dioxide used in coatings, the former is processed by shearing force in a low-polarity resin, and the organic surface-treated titanium dioxide can be dispersed well under appropriate mechanical shearing force.

With the continuous application of plastic products, many external plastic products, such as plastic doors and windows, building materials and other outdoor plastic products, have high requirements on weather resistance. In addition to the use of rutile titanium dioxide, surface treatment is required. This surface treatment is generally free of zinc, and only silicon, aluminum, zirconium, etc. are added. Silicon has a hydrophilic dehumidification effect, which prevents pores from being generated by evaporation of water when the plastic is extruded at a high temperature, but 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, anti-aging agents, flame retardants, etc.), which can be divided into plastic film extrusion blow molding process and plastic sheet extrusion according to product processing methods. Out of the molding process and plastic injection molding process, for example:

Extrusion blow molding process for plastic film:

Resin, filler, auxiliary masterbatch (masterbatch plus resin) blown film plastic film

The main equipment used in this process is a two-roll mill, a blown film machine, and the like.

The plastic injection molding process includes plasticizing, injection and molding cooling. The common equipments include embolic injection machines and screw injection machines.

The quality requirements for titanium dioxide in plastic products are:

Covering power: Titanium white with good hiding power, and the produced plastic products are lighter and thinner;

Whiteness: determines the appearance of light or white plastic products;

Dispersibility: affecting the production cost of plastic products. Titanium white with poor dispersion will affect the smoothness and brightness of the products in plastic products;

Weather resistance: Plastic products for outdoor use, plastic doors and windows, etc. must ensure the weather resistance of titanium dioxide.

Masterbatch

The plastic masterbatch is a highly concentrated, high-performance color formulation in which the pigment is uniformly distributed in the carrier resin at an extraordinary concentration and forms particles of a certain particle size. It is mainly composed of a core layer (pigment), a coupling layer (coupling agent or surfactant), a dispersion layer (lubricant or dispersant), a compounding layer (carrier resin), etc., and is used as a coloring agent in plastics. It is widely used in the production of plastic products such as blown film, injection molding, hot pressing, injection molding, etc. The color masterbatch has superior coloring effect, convenient use, energy saving, no dust and sewage when used, so it is favored by users. The development of color masterbatch is very fast, and the production process of masterbatch is simple, and the investment is small. At present, there are hundreds of masterbatch factories in China, the scale of production and technical level are uneven, and the small annual output is several tens of tons. With 10,000 tons, the competition for products is becoming increasingly fierce, the profits of production enterprises are declining, and the quality of most masterbatch products is low. According to incomplete statistics, the titanium dioxide used for masterbatch production is 2-3 million tons per year. The rutile used is divided into high, medium and low grades. The high grade uses imported rutile, the medium grade uses domestic rutile, and the low grade uses domestic anatase. Type titanium white.

Masterbatch can be used to color match polyvinyl chloride, polyethylene, polypropylene, polystyrene and ABS plastics. The main components are pigments, resins, dispersants, volume pigments, fluorescent whitening agents, antioxidants, anti-UV agents, antistatic agents, toughening agents, brighteners, etc. Titanium dioxide is used as a white pigment in it, with or without Poisonous, chemically stable, high hiding power, good dispersion and so on.

There are several production processes for masterbatch, such as: pigments, resins, dispersants, volume pigments, other additives, high-speed mixers, twin-screw extruder masterbatch.

Masterbatch is used as an industrial raw material. The performance is usually manifested in subsequent product applications (such as blown film or injection molding). Therefore, the performance of titanium dioxide in color particles is mainly reflected in the application of masterbatch. Mainly reflected in the following aspects:

1) The coloring ability of titanium white: the amount of titanium white used to determine the color of the same plastic product;

2) Whiteness of titanium white: the appearance of light (white) plastic products having the same titanium white content;

3) Dispersibility of titanium dioxide: affecting the production cost of color particles and the appearance and gloss of plastic products;

4) Processing properties of titanium dioxide: affecting the production cost of masterbatch.