Application of talc powder in papermaking industry

More than 50% of talc output in China is used in the paper industry. Mainly used for paper filling, resin adsorbent, a small amount of paper coating pigment.

Talc structure and its special properties

Talc powder is hydrated magnesium silicate, and its theoretical formula is 3MgO· 4SiO2·H2O. It has a layered structure, which is divided into three layers. In the middle is an octahedral MgO layer. The two OH groups of talc powder are inside, so the surface is hydrophobic. This is the reason why talc is different from other pigments.

Application of talc powder in papermaking industry

Talc powder has its unique properties: laminar structure: the weak van der Waals force between talc layers makes it easy to crack into thin layers when grinding. Hydrophobic (hydrophilic) : low surface energy, easy adsorption of organic matter to its layered table surface, in the production of color paper, the addition of talc powder, reduces the consumption of dyes, save costs effectively, in addition, it makes the surface of the hydrophilic its control agent can be used for resin, adhesives and waste paper deinking agent; Softness: make the surface of the coating smooth and smooth, reduce the breaking of the coating, reduce the printing press, etc. Lower friction factor: it can reduce the abrasion of the equipment (forming network, scraper and printing press), thus extending its service life. Chemical inertness, and no chemical reaction, and is not influenced by any other additives, and other coatings with good compatibility, also means that is not sensitive to pH changes, the chemical inertness make it better for the environment, too.

Talc powder is used as paper filler

In the early 1990s, the main technical significance of talc in papermaking was still stuffing, accounting for 60% of the total consumption of talc in China.

Talcum powder high whiteness, high density, refractive index, as a filler in papermaking industry has its advantages: stable chemical properties, not only suitable for writing under article acid a, can also be used with calcium carbonate under neutral condition writing; Its friction coefficient is small (lower than calcium carbonate), which can extend the service life of the paper net, and is also suitable for high speed paper machine. It is a sheet particle, which is conducive to the retention and improvement of paper opacity, smoothness and printing suitability. With hydrophilic surface, can adsorption of organic compounds, as a filler with, also received from resin barrier effect, helps in waste paper deinking in ink removal, it is can't be matched by kaolin and calcium carbonate fillers; It can be well combined with the sizing agent to improve the retention of the sizing agent and reduce the absorption of the paper page, preventing printing ink from penetrating the paper page.

In the late 1990 s, the domestic papermaking industry by acidic papermaking industry art to the basic writing, high quality and low price due to calcium carbonate at the same time, make it harder to replace the talcum powder in the packing in the market dominant position. In 2002, CaCO3 consumed 1.24 million t, exceeding talc, and its market share dropped from 41.3 percent in 2001 to 23.5 percent in 2005. It is expected to decline in the next few years.

Talc powder is used as functional material

In the paper industry, low and medium grade talc powder will still be used as important filling material, while high grade talc powder is mainly used as functional material due to its high price. Such as: resin adsorbent, waste paper deinking AIDS. The us consumes the most, and its potential demand is high.

The main component of talc powder is MgO·SiO2. The special lamellar crystal structure of talc powder makes its surface hydrophobic and hydrophilic. In addition, the slippery stone powder and water, glycerin, formic acid, aniline and other larger material with surface tension contact Angle, and most of the other material contact Angle in any direction is zero, thus easy adsorption of organic matter.

The application of talc in resin control began in the 1960s. At present, talc is used in resin and adhesive control throughout the world. More than 300,000 t a year is consumed for this purpose, which is still increasing. , its principle is: talcum powder surface hydrophilic adsorption resin, can join the grout can make it a new set free has not yet been gathered thin layers of resin adsorption to its flat shape on the surface, reduce the apparent energy of resin, resin lost its peculiar viscosity, thereby inhibit the adhesion of resin, coalescence and deposition.

The purity, particle size and concentration of talc powder are closely related to the control of resin deposition. The higher the purity, the more lamellar peel, the more oil surface, the better the effect. The smaller the particle size, the bigger the surface, the greater the surface energy, the greater its adsorption capacity. When the concentration increases, the amount of talc adsorption resin increases linearly. Generally speaking, the fine talc powder used to control resin deposition (high quality talc with a fineness of no less than 800 purposes) is a lamellar thin layer structure with an adsorption resin efficiency of more than 90%.

The mechanism of talc in deinking of waste paper is that when the waste paper deinking, it can use talc to absorb ink and other organic materials. In the process of flotation deinking, talc can concentrate on the circumference of foam and ink, and then separate the ink and organic matter from the fiber together with talc through screening and purification.

Talc is used as coating paint

Talc has a long history in the paper industry and was first used as a filler in the early 20th century. With the development of papermaking technology, talc was introduced into industry as coating pigment in Finland and France in 1982. Since then, talc has been used as an ingredient in gravure LWC paper, coated paper without mechanical wood pulp (matt and matt coated paper) and special coated paper (wallpaper and label paper).

Application of talc powder in papermaking industry

As can be seen from FIG. 2 and FIG. 3, kaolin and talc particles are patchy. Sheet pigments can endow the coating with good fiber coverage and high smoothness. Due to the orderly arrangement of pigment particles in the coating, the coating structure is dense and solid, which can improve the gloss of printing and reduce the permeability of coating.

Because the talc has larger its particularity, than have a close study abroad, the quality of the talc processed products can replace water concentration kaolin used in large scale or all of the coating pigment, in producing medium and high-grade coated paper.

4.1 main advantages of talc as coating pigment [3]

Talc powder can improve the whiteness, opacity, smoothness and gloss of coated paper.

As a coating pigment with high morphological ratio, talc powder has excellent fiber dimensional covering ability and good printing effect, and can also improve the quality of gravure printing.

When mixed with kaolin, the rheological property of coating can be changed, and the pseudoplastic flow is sheared and diluted. High solid content coatings can be prepared, which have good rheology and stability.

Talcum powder particles with a soft, multi-layer and low friction coefficient, sex, thereby reducing the friction effect and improve the abrasion resistance, it can improve the ink wear and tear of the matte jersey coated paper (in the process of printing processing, paper weight and the mutual friction between the surface causes with stress, which would abrasion of printed ink layer surface), so as to improve the quality of printing products; The low friction factor of talc makes it easier to slide between the paper layers and reduces the fracture of the paper core.

Talc powder has special lubricity, and the coated paper made from it can obtain high finishing degree and reduce the amount of lubricant in the coating.

Low hardness, low abrasion consumption, conducive to scraper coating.

4.2 main disadvantages of talc

Because of its hydrophobicity, talc powder is difficult to be wetted and dispersed in the preparation of coating, and the coating is also shear and expansion.

The application of talc powder in offset printing coated paper is easy to cause ink accumulation and paper hair removal and powder removal.

4.3 the indirect reason why talc has not been widely used as coating pigment in China is that gravure printing has not been popularized in China.

Since the ninety s, the development and utilization of talc mainly made rough machining, a few enterprises engaged in the ultrafine powder processing, surface modification and modification after deep processing is still not started, basically overall processing technology behind [4]. Therefore, coating grade talc powder quality is poor.

In recent years, due to the extension of talc application, the price of high-grade talc has been increasing.

Domestic high-quality kaolin resources are few, and most of them are rod shaped (not suitable for coating), most of the flake kaolin for coating is imported from abroad, the price is high. And talcum powder domestic resources are rich, although talcum powder and kaolin soil in difficulty and effects of their use, there are differences, but their use is basically can substitute, if use talcum powder part of domestic instead of imported kaolin production of coated paper, can not only save resources, and can meet the different needs of coating cloth printing paper performance.

The development trend of talc powder in papermaking industry

The unique performance of talc determines its unique position in papermaking.

From the prospect of future paper USES analysis, low-grade packing use talcum powder will be as important, and the high quality talc will play its proper function, the most economic and technical value in the specialty paper, is the purpose of the adsorbent resins and adhesives and paper coating pigment in the application. Application of modified talc powder: the surface treatment of talc powder to make it cation can improve its adsorption, such as better adsorption of anionic garbage produced in papermaking process. Development and application of talc with high calcium content: over 95% whiteness, it can be used in SC paper, newsprint paper and paper coating. The relevant data show that it has better opacity, whiteness and packing retention rate when used for filling than GCC alone, and also reduces anionic deposits. It can also be used in paper coatings to improve the whiteness, smoothness, printability and water retention of paper coatings.

Research on the development of black talc: after calcining ultra-fine, the whiteness can reach more than 94%, which changes its original hydrophobicity and makes pigment have better compatibility. It can be used for paper filling and coating instead of partial TiO2 and calcined kaolin.

Talcum powder