Nano-tech in paper

We know that paper is the most commonly used substrate in printing, and its quality is the best embodiment of print quality. As the fiber used for traditional paper such as trees, bamboo, and hemp is thick, the particles of coatings (such as calcium carbonate, etc.), fillers (such as kaolin, etc.) are relatively large, and there are some properties such as poor performance of gum and other ingredients. Reasons, make traditional papers have some defects, such as ordinary paper has shortcomings such as fear of water, fear of moisture, offset printing paper and electrostatic copy paper, although waterproof, moisture and other functions, but writing is not convenient, there are some special features can not be Implementation and so on, thus affecting the quality of the printed crystal. In recent years, with the rapid development of nanomaterials, nanotechnology has become more and more widely used in the paper industry, and new results have emerged. What is involved in pulp and papermaking is nanochemistry and nanomaterials, which has contributed to the development of the paper industry and the quality of prints.

According to the current state of the art and practical application of paper, wood fiber can only be processed to the micron (100 ~ 1000nm) level, because the wood cell diameter is relatively coarse, through the wood nanotechnology can change the cell structure of the wood and control cell growth , it may change the characteristics of wood. For most woods, when the fiber is micron-sized, the cells of the wood cells have been completely broken, and the viscous liquid in the cells can easily flow out. After mechanical pulping, it is no longer necessary to chemically extract harmful liquids and fibers from the cells. If the wood is processed to the nanometer level, the original cell structure of the wood will be destroyed, and the fibrous tissue structure will change. Cellulose and semi-fibers The lignin and lignin can be separated mechanically during processing, which can greatly increase the pulping rate and reduce the environmental pollution of the pulp and paper industry. In addition, from the general minimum specifications of the components of the papermaking furnish, with the exception of a large fiber width, the filler particles are generally in the range of 0.1 to 10 μm, and the remaining microfibres, non-fibrous fine substances, soluble polymers, etc. have a particle size of less than 1 -2 micron, as a whole colloidal state, mutual surface action and colloidal role in an important position, and papermaking wet end chemistry is essentially a surface and colloid chemistry. Due to the very small structure of many components in the furnish of the papermaking mill, the introduction of nanoscale components with special effects can exert the role of nanotechnology and improve the papermaking effect. For example, in the modern high-speed paper machine wet-end furnish, when a new generation of anionic colloidal silica (ie, ACS) and cationic polymers are applied, silicon oxide nanoparticles with a particle size of 3-5 microns can be produced in a wet-portion batching system. particle. The fine particles can flocculate the fine components in the ingredients around the fibers, thereby improving the structure of the slurry and reducing the loss of fine components. It can improve the operation of the paper machine and the formation of the paper and reduce the amount of additives in the pulp. Significant effect.

In paper coatings, the use of nano-calcium carbonate in coated white paperboard coatings can effectively improve the performance of whiteboard. Nano-calcium carbonate itself has characteristics such as high whiteness, large surface area, high surface activity, high strength and hardness. The addition of nano-calcium carbonate is beneficial to the improvement of several important performance indexes of the coating, such as IGT value, K&N ink absorption, smoothness and the like. However, the addition of nano-calcium carbonate is not directly proportional to the increase in performance. In the coating with 5% nano-calcium carbonate coating, the viscosity increased significantly when the pH and temperature were similar. However, nano-calcium carbonate has little effect on the whiteness of the coating, and it seems to be contrary to the assumption that the high whiteness of nano-calcium carbonate can improve whiteness.

There are several development directions for enhancing the dispersion of nanoparticles in the liquid phase: 1 Select a suitable solvent or solution to improve the wetting heat of the powder and allow the wetting to proceed spontaneously. 2 Design an efficient dispersing machine to make the effective volume and The energy utilization rate can be improved. I3 Select the suitable dispersant so that the produced primary particles are very stable and prevent re-flocculation. In addition, the addition of nano-silicon-based oxides to the coating can achieve the purpose of shielding the UV and greatly improve the anti-aging properties of the coating. The nano-silicon oxide (Slox) is an amorphous white powder (referring to its soft agglomerates) and is a non-toxic, odorless, non-polluting inorganic non-metallic material. Due to the small size effect of nano-SiOx, it causes the formation of silt penetration, forming a dense “nano-coating film” at the interface of the coating, greatly improving the scrub resistance of the coating and the self-cleaning properties of the coating surface. It can also produce good affinity with the coating system, thereby improving the suspension stability and rheology of the coating. At present, the use of nanotechnology in the paper industry has begun to enter practical production, it will overcome some of the defects of ordinary paper and improve the special properties of paper. For example, Henan Yinge Co., Ltd. and the Nanotechnology Research Institute of Central China Normal University have adopted the most advanced nanotechnology in the world to perform nanoscale structural layer preparation on plain paper and successfully developed a new type of waterproof nanopaper. In addition to maintaining the original writing and copying functions of the paper, the nanopaper also has special properties such as super-hydrophobicity and moisture-proofness that ordinary paper does not have, the strength of the printed surface is improved, and the rate of expansion and contraction is reduced.

In addition, in the rapid development of science and technology, people will have higher requirements for paper performance, quality, etc. In addition to conventional printing and writing paper, the demand for paper with special functions is also increasing. Nano-materials, as a special auxiliaries for special paper manufacturing, are attracting more and more attention. At present, in the papermaking industry, nanomaterials are mainly used for the development of functional papers such as water-repellent, antibacterial, antistatic, anti-aging and aromatizing, flame-retardant, and discoloration, and some products have been made available.

1. Antibacterial Nano Paper

Many organic antibacterial agents have the disadvantages of poor heat resistance, high volatility, easy decomposition and generation of harmful substances, and poor safety performance. For this reason, people actively develop and research inorganic antibacterial agents, and the use of ultra-fine technology to produce submicron and nanoscale inorganic antibacterial agents, can be a good solution to the shortcomings of organic antibacterial agents. The inorganic inorganic antibacterial agent mixed paper pulp and surface sizing liquid, paper can be anti-bacterial industrialization, such as physical antibacterial composite fiber nonwovens, medical food packaging paper, senior living paper.

2. Anti-static, wear-resistant nano-paper

In diversified industrial product packaging, especially high-precision instrument appliances, stainless steel materials with high finish requirements, and various alloy material packaging liners, not only require that the packaging paper be waterproof, oil-proof, and rust-proof, but also required With high strength, abrasion resistance, anti-static, anti-aging characteristics, and ordinary paper are difficult to have these characteristics. However, if the special paper made of 0.1%-0.3% of nano titanium dioxide, chromium oxide, zinc oxide, iron oxide, tin dioxide and other powders is mixed into the papermaking pulp, it can have Excellent wear resistance, water resistance, corrosion resistance and other effects, but it will also produce a good electrostatic shielding performance, greatly reducing its electrostatic effects, which can greatly improve the safety factor of the packaging products.

3. Dyeing function nano paper

Colorants for paper coloring can be divided into two major categories of dyes and pigments. Most of the dyeing pigments are natural inorganic pigments, and some are organically synthesized. Pigments are insoluble in water, have no affinity with fibers, and have dyeing properties that are not as good as dyes. However, pigments have strong light resistance and are resistant to acid, alkali and other chemical agents. Although dyes are easy to be colored, they are easily hydrolyzed, have a large loss in the wet part, are highly polluting, have poor color fastness to paper, and are not resistant to acids, alkalis, and other chemical agents. If nano-scale pigments are used, the color fastness of colored paper can be solved. Recent studies have found that the addition of nano titanium dioxide, chrome yellow, iron oxide red and other powders to chemical fibers can shield the ultraviolet radiation from overexposure. The use of electronic computer simulations and design found that titanium dioxide particles with a particle size of 50-120 lm, the best absorption of ultraviolet light, this particle size range of shielding powder particles added to the fiber, can be made into light-resistant matt high white paper, And colorful colored paper, and can achieve anti-ultraviolet effect.

4. Inorganic fiber nano paper

The paper industry mainly uses plant fibers as raw materials and now also uses inorganic compounds to produce special papers. Since these inorganic materials have excellent dimensional stability, heat resistance, chemical resistance, flame retardancy, and electrical insulation due to the inorganic fibers produced by processing, these properties are beyond the reach of plant fibers. The representative inorganic fiber-glass fiber, because it can not afford to be beaten, there is a lack of adhesion between the glass fibers, and the copied paper sheet is very fragile, but if the glass fiber diameter is controlled below 100 nm, then it can be solved. The phenomenon of paper formation caused by the small shrinkage and poor flexibility of the glass filaments is conducive to the intertwined formation of fibers.

5. Colored flavored nano paper

With the development of science and technology, people's living standards have been continuously improved, and the quality requirements for paper have become higher and higher. Nowadays, various types of papers such as offset printing papers and writing papers of various flavors and colors have been developed and produced. This flavoring paper is not only soft and delicate, but also contains a hint of fragrance. The application of nanotechnology to the application of fragrant paper will greatly improve the quality and printability of fragrant paper, and the image of high-grade printed crystals printed will be more exquisite and realistic. Using colored fragrant paper for printed books, primary and secondary school textbooks, exercise books, notebooks, and various children's books, etc., people do not feel dazzling because of the high whiteness of the paper when reading, which can reduce long-term reading fatigue. , It has a certain effect on protecting eyesight and preventing myopia. Therefore, after the introduction of this flavoring paper, it was well received by the users.

6. Nano flame retardant paper

It is a paper that can stop the burning of fire. For it, no matter how much firepower, it will not cause burning. It is the nemesis of any kind of fire. It can only scorch, and often have to deal with the clothes of the personnel to prevent the clothing from burning. Plays a flame retardant effect. In addition, fire-retardant paper is applied to dry-type transformers. It is safe, non-toxic and resistant to carbonization, but it does not catch fire. After the paper is used, it can be treated as waste paper without any harmful substances in natural degradation. Fire-retardant paper can be used for fireworks, fireworks, color fireworks, Christmas toys, and travel bedding. It is the ideal green product in today's holiday products. Some people even suggested using this kind of paper to make firefighters play a special role. Such as color paper, energy storage paper and other high-performance specialty paper product development and research. In addition, due to its excellent chemical activity, nanomaterials also have broad application prospects as catalysts in papermaking chemical crystals and wastewater treatment. In addition to the application of nanotechnology on paper, there are many applications in the packaging and printing industry, such as nano-adhesives and sealants in packaging and printing, nano-magnetic materials, nano-substrate packaging materials, nano-catalysts and water purifying agents. , nano-luminescent materials and security printing and so on. In short, nanotechnology, as a rapidly developing new technology in recent years, will be applied in the printing field as well as other fields and will continue to develop in depth and breadth.

Although nano-materials and nano-composites have good performance and wide applications in the papermaking field, the current research and development of nano-materials is not yet mature, and it still has some problems that need to be further solved, such as crushing, agglomeration, and dispersion technologies. It is not ideal enough to be further improved. For the performance testing of nano products, the product standards have yet to be further improved. However, it can be predicted that with the reduction of nanoparticle production costs and the increase of functional nanoparticle varieties, nanotechnology will play a greater role in the printing industry and the paper industry, bringing infinite vitality and vitality to printing and related industries.



Source: Greater China Graphic Arts