Recently, according to CCTV, since May, major domestic cultural paper enterprises and traders have issued several price hikes, including the general price rise of 200 yuan / ton of cultural paper, and the price rise of white paper reached 1000 yuan / ton, and the domestic paper industry also saw a three-month increase. The Jiulong paper industry, which ranked the first in packaging paper industry, started the third round of price increase in May

 

According to experts' analysis, the main reason for the price increase is the global rise of pulp, logistics, energy and other prices in the upstream of paper making, which directly increases the production cost of enterprises. Due to the rising price of pulp raw materials, the pulp price and paper price are inverted, so some paper mills have no way to stop.

 

As one of the ten pillar industries of national economy, paper industry is an important symbol of measuring the modernization level of a country. At present, the contradiction between supply and demand of fiber raw materials in domestic paper industry is increasingly prominent. On the one hand, the gap of fiber raw materials is becoming larger and larger, showing the trend of increasing year by year; On the other hand, the raw material structure is unreasonable and the proportion of wood pulp is low. In recent years, with the development of special paper and the improvement of the special performance of paper, the use of non fiber raw materials in the paper process accounts for more and more. Among them, the filler is paid more and more attention due to its low cost. At present, filler has become the second largest raw material in paper making.

 

Traditional paper filler mainly includes natural packing and artificial packing. Natural filler refers to the filler used by mining and mechanical processing of natural mineral deposits, such as talc powder, clay, titanium dioxide, gypsum, etc. artificial filler refers to the filler made by chemical reaction or used by-products of chemical plant, such as precipitation calcium carbonate, barium sulfate, paper sludge, calcium silicate filler, etc. Filling can not only save the cost of fiber raw materials, but also improve the optical properties and printing suitability of the paper sheet, and meet the requirements of some special properties of the paper sheet.

 

Characteristics and functions of various fillers

 

kaolin

 

Kaolin soil is soft and has high whiteness. In the paper industry, kaolin is chosen as filler because kaolin is not easy to react with other additives in pulp, filling the gap between wood fibers in paper, thus keeping it between fibers. In addition, kaolin has a small particle size and easy to flow, which can ensure the density and smoothness of paper.

 

Kaolin is used as filler in paper industry. Because of its low price, strong practicability and relatively good whiteness value, it is widely used. Kaolin is easy to treat and disperse. The use of kaolin makes the paper have high density and thus reduces the penetration of coating. Kaolin is often used in super calendering paper.

 

talc

 

Talc powder has high whiteness, high density, high refractive index, and stable chemical properties. It is suitable for acid paper making, and it is suitable for neutral paper making in common with CaCO3; The friction coefficient is small, the wear of the paper machine is small, the service life of the paper machine is prolonged, and the quality of the paper roll is improved; The structure of the sheet layer is helpful to keep the paper in the paper and improve the opacity, smoothness and printing performance of the paper. Talc powder is used for rotary gravure printing, rubber plate printing and special coated paper.

 

Heavy calcium carbonate

 

The choice of heavy calcium carbonate is mainly due to its low price, high brightness, large ash content, easy coloring, sizing and other advantages, and can improve the opacity, glossiness and ink absorption of paper. GCC is a common inorganic filler in medium and basic papermaking. With the gradual transformation of paper industry from acid paper to medium and alkaline paper (medium and alkaline paper making has less loss on paper machine than acid paper, it is more beneficial to environmental protection and water conservation), and the demand of GCC gradually increases.

 

Precipitated calcium carbonate

 

Precipitated calcium carbonate (PCC) is a kind of calcium carbonate prepared by chemical method. Its structure is different from that of heavy calcium carbonate. PCC can make the paper get better glossiness and opacity, reduce the use of raw fiber, reduce the loss and cost investment of paper machine equipment; Improve the whiteness, printing performance and service life of paper; At the same time, according to different needs, paper can have different characteristics.

 

titania

 

Titanium dioxide (TiO2) is a kind of pigment with high optical properties, which has high brightness, refraction and high obscurity. The obtained paper is more flat, even and has strong oil absorption ability. It can not only improve the opacity and brightness of paper, but also improve its physical and soft properties. Anatase phase TiO2 is usually used as filler TiO2 in paper making.

 

Comparison of the properties of the above packing

 

dolomite

 

Dolomite has similar crystal structure and calcite, which is cheap and has high opacity. After wet grinding, it can replace heavy calcium carbonate as paper filler or used to prepare composite materials, improve the performance of paper, make more rational and effective use of resources and reduce cost.

 

Silica

 

White carbon black is the main pigment used in ink jet printing paper in recent years. The nano or sub nano silica produced by gas phase method has higher purity, specific surface area and adsorption characteristics. With the popularization of digital image technology, the consumption of high quality white carbon black used in inkjet printing paper has increased rapidly.

 

Bentonite

 

The purification, modification and improvement of bentonite and the application of product whiteness and expansion in the paper industry are the main research fields in recent years. There are many research achievements, among which, the application of bentonite in the fields of retention and filtration aid, paper coating pigment, surface sizing agent, paper-making adhesive control agent and water treatment agent has made important progress. The consumption of bentonite in paper industry has increased rapidly in recent years, mainly used for acid (active) white soil with micro retention aid and carbon free paper, and the technology is relatively mature.

 

zeolite

 

At present, the zeolite used in paper making is mainly clinoptilolite, mordenite, rhombite and tablet zeolite. Because of its special high porosity, adsorption, ion exchange, antibacterial, special luster (glass luster, silk luster, pearl luster), etc., it is used for paper filler, special coating coating and water treatment agent. The printing paper filler can give the paper high coverage and opacity, At the same time, because of the good chemical stability of zeolite and small interference to the slurry system, it is suitable for acid or alkaline paper making, but the wear value of the fillers in high-speed paper machine is limited.

 

Wollastonite

 

Wollastonite is a fiber-like mineral with unique properties, and the ratio of length to diameter can reach 15-60 after processing. The modified wollastonite can increase the flexibility and hydrophilicity, and improve the affinity and the strength of paper formation with plant fiber. The filling capacity of modified wollastonite can increase 0.3-1.0 times than that of the same fineness talc and GCC (heavy calcium carbonate) under the same paper strength, and can significantly reduce pulp consumption. Modified wollastonite is suitable for acid and alkaline paper making, but it is limited in high speed paper machine because of its high hardness and high wear value.

 

Gypsum

 

Gypsum fiber can overcome the defects of short, fragile crack, low retention rate and high hardness of other mineral fibers, and can meet the production requirements of high-speed paper machine, and has a wide application market in printing and writing paper and paper coating. At the same time, the ratio of modified gypsum to talc and CaCO3 can improve the retention rate, strength, stiffness and opacity of the filler; The application of modified anhydrite in paint pigment can improve the paper stiffness and whiteness, and improve printing performance.

 

Vermiculite

 

With the characteristics of fluffy, low density, stable chemical properties, heat insulation, sound insulation, fire resistance, cold resistance, insulation, water absorption, antibacterial, adsorption and cation exchange, vermiculite can be used to produce a variety of functional industrial paper, military paper and decorative paper. The main application fields and paper types include: art craft packaging paper, book paper, decorative paper, agricultural seedling raising paper, frozen food preservation packaging paper, military paper, animal pad paper, advanced environmental protection wallpaper, damping pad board, building decoration board, etc.

 

sepiolite

 

Sepiolite has strong adsorption, high temperature resistance (1500-1700 ℃), good dispersion, corrosion resistance, radiation resistance, heat insulation, insulation and other properties. It is used in paper-making for liquid filter paper, deodorization paper, cigarette filter tip paper, cosmetic paper, sanitary tissue paper, diaper paper, cleaning paper, medical paper, high temperature insulation paper, firecrackers paper, flame retardant paper, industrial sealing pad paper Fresh paper, agricultural seedling paper, pet pad paper, desiccant packaging paper, precision instrument packaging paper, insulation paper, anti-oxidation and anti-corrosion packaging paper, acid alkali resistant inorganic filter paper, etc.

 

diatomite

 

Domestic paper industry mainly uses its high porosity, strong adsorption, small bulk density, heat insulation, sound absorption, chemical stability, non-toxic and other technological characteristics to produce liquid drinks, sugar making, brewing filter paper and board, and also used for building decoration board, battery partition, high water absorption domestic paper, flame retardant paper, pet pad paper, waste water purification agent, coagulant aid, etc.

 

Eclosite

 

It is in the stage of industrial development and application. Low abrasion, can be used in high speed paper machine, low production cost. The results showed that the tensile strength (30% ～ 60%), opacity and ash content of cationic products modified by PVA, APM and modified starch were improved. It has better softness and smoothness than wollastonite filler.

 

Tremolite

 

Translucent fiber. The contribution of filler to paper properties is similar to that of wollastonite and complex. It has special technical quality contribution to extrusion hot melt coating and paper plastic laminated resin filler.

 

Maifan stone

 

The related research shows that Maifanshi has a certain antibacterial effect, which can be used to make health care medical insole board, food packaging paper and fresh-keeping paper. The modified Maifanshi composite products will be used as filler for medical paper and daily paper or board by the Chinese Academy of military medicine and Beijing University of traditional Chinese medicine.

 

High temperature calcination of alumina, silica powder, garnet, mullite and other high hardness powders

 

At present, it is mainly used for wear-resistant paper filler and dressing of abrasive tape paper for polishing industry. In recent years, the consumption of composite floor, furniture decoration and decorative paper for building materials has increased. The manufacturing technology of high hardness inorganic powder materials and the development and application of paper filler need to be further deepened.

 

Properties of packing

 

The reflection index, particle shape, particle size and distribution, specific surface area, particle charge, pH, solubility and abrasivity of filler are important properties, which have great influence on the opacity and physical properties of paper.

 

Reflection index: a basic property determined by the chemical composition and molecular structure of the filler. Atomic structure has a direct effect on light scattering (opacity). This is because the light enters the packing and reflects more than once inside it, rather than directly through it. The larger the reflection index of the filler, the more the reflected light, the higher the opacity of the paper. The reflectance index of anatase and rutile TiO2 is 2.55 and 2.76 respectively, and the reflection index of other commonly used fillers is much lower than that of TiO2.

 

Particle morphology: it is an important property of filler. It affects the light scattering mode, and thus affects the optical properties of the filler in the paper. It is found that the different forms of CaCO3 precipitate, which makes the light scattering ability different. The best value of light scattering of different shapes of particles is different.

 

Particle size and distribution: the size, size and aggregation of filler particles strongly affect the optical properties of the filler. It is found that when the size of the filler is narrow, especially when the filler is evenly distributed in paper, it can improve the light scattering rate. The narrower the distribution range of the particle size centered on the optimum particle size, the more conducive to increase the opacity of the paper.

 

Specific surface area: the surface area of the particles, particle size distribution and particle shape have direct influence on the surface area. The specific surface area of particles affects light scattering, and also affects the paper strength and printing performance. Generally, the packing with high specific surface area will increase the printability of the paper page, but it will weaken the strength of the paper sheet and increase the difficulty of sizing.

 

Particle charge: the surface charge of the filler particles plays an important role in the dispersion of the filler. There are three kinds of forces that affect the filling state: van der Waals force (usually gravity), static power and space resistance. These three forces vary with the distance between particles. The balance between them determines whether the filler particles are in suspension or flocculent.

 

Abrasivity: it is an important index of filler. The high abrasive filler will cause excessive wear on the web and printing plate of paper machine. The abrasivity of the filler is mainly caused by two factors: the crystal property or the hardness of the filler (the bonding strength between atoms, spatial arrangement and impurities), the physical properties of the filler (particle size, particle size distribution, shape, surface area, etc.). A small amount of impurities, such as silica, are the main causes of abrasion. The abrasive resistance of the large particle filler is high when the same crystalline form is used.