The application of polymer wax and polyethylene micro-powder wax in coatings is reported, the matters needing attention in application are introduced, and the coating market is prospected.
In the process of polyethylene production, a small amount of oligomer, namely low molecular weight polyethylene, is produced. It is widely used because of its excellent cold resistance, heat resistance, chemical resistance and wear resistance. In normal production, this part of wax can be directly added to polyolefin processing as an additive to improve the optical translation and processing performance of the product. Polymer wax is a good desensitizer for explosives, and can also be used as dispersion lubricant for plastics and pigments, moisture-proof agent for corrugated paper, hot melt adhesive and ground wax, and automobile beauty wax.
Polymer wax is a non-toxic, odorless, non-corrosive, white or yellowish solid with a relative molecular weight of 1800-8000. It has good chemical stability, excellent temperature resistance, drug resistance and room temperature electrical properties, and has a wide range of applications. It can be used as raw material of chlorinated polyethylene, modifier of plastics, coating agent of textiles and additive for improving viscosity of crude oil and fuel oil.
Low molecular weight polyethylene is widely used abroad and has a large demand. Japan produces about 3000t a year, and the price is about twice as high as that of ordinary resin. Although it started late in China, the demand is increasing year by year. The main manufacturers are Shanghai Jinshan, Nanjing Yangzi and beijing university of chemical technology.
Application and mechanism of polymer wax in coatings
Wax for coatings is mainly added in the form of additives. Wax additives generally exist in the form of water emulsion, which was originally used to improve the surface anti-swelling performance of coatings. It mainly includes improving the smoothness, scratch resistance and water resistance of the coating film. In addition, it can also affect the rheological properties of coatings, and its addition can make the orientation of solid particles such as aluminum powder in metal flash paint uniform. It can be used as matting agent in matte paint. According to its particle size and particle size distribution, the extinction effect of wax additives is also different. Therefore, wax additives are suitable for glossy paints and matte paint. Microcrystallization modified polyethylene wax can be used to improve the surface properties of waterborne industrial coatings. For example, Ffka-906 has enhanced smoothness, anti-blocking, scratch resistance and extinction, and can effectively inhibit pigment precipitation. The addition amount is 0.25%-2.0%.
The application mode of 1
There are four common ways to use wax:
1. melting method: the solvent is heated and melted in a closed high-pressure container, and then cooled properly.
Discharging under this condition to obtain the finished product; Disadvantages are poor quality control, high operating cost and danger, and some waxes are not suitable for this method.
2. Emulsification method: Fine and round particles can be obtained, which is suitable for water-based systems, but the added surfactant will affect the water resistance of the coating film.
3. Dispersion method: add the wax into the tree wax/solution and disperse it with a ball mill, roller or other dispersing equipment; The disadvantage is that it is difficult to obtain high-quality products and the cost is high.
4. micronization method: micronization method can be Jet-micronizer or micronizer/Classifier production process, that is, crude wax is gradually broken into particles after high-speed fierce collision with each other, and then blown out and collected by centrifugal force under weightlessness. This is the most widely used manufacturing method at present.
Although there are many ways to use wax, micronized wax is still the most, and there are many kinds of micronized wax in the market, and the production process of each manufacturer is different, which makes the particle size distribution, relative molecular weight, density, melting point, hardness and other properties of micronized wax from different manufacturers somewhat different.
The manufacture of polyethylene wax generally includes high pressure and low pressure polymerization; Among them, the polyethylene wax prepared by high pressure method has branched chain, and its density and melting temperature are low, while the wax with low specific gravity can be prepared by low pressure method. Polyethylene waxes have different densities. For example, nonpolar PE wax prepared by low pressure method is usually hard with low density (low branching and high crystallinity) and has good wear resistance and scratch resistance, but it is slightly poor in smoothness and friction coefficient reduction.
Characteristics and mechanism of wax in coatings
There are many kinds of wax, and the forms of wax in coatings can be roughly divided into the following three types:
1. frosting effect: For example, when the melting point of the selected wax is lower than the baking temperature, the wax melts during baking.
Melting into liquid, film forming and cooling, that is, forming a frosty thin layer on the coating.
2. Spherical axis effect: This effect is that the wax is exposed through its own particle size close to or even greater than the thickness of the coating film, thus showing the scratch resistance and scratch resistance of the wax.
3. Floating effect: No matter what the particle shape of wax is, in the process of film formation, the wax drifts to the surface of the coating film and spreads evenly, so that the top layer of the coating film is protected by wax, showing the characteristics of wax.
3 Characteristics provided by wax in coating film
1, wear resistance, scratch resistance, scratch resistance: wax is distributed in the coating to protect the coating and prevent scratches.
Scratch and provide wear resistance; Such as container coatings, wood coatings, decorative coatings, etc. Everyone needs this function.
2. Control of friction coefficient: Usually, its low friction coefficient is used to provide excellent smoothness of the coating, and at the same time, it has the soft touch of special silk due to different types of wax.
3. Chemical resistance: Due to the stability of wax, the coating film can be given better water resistance, salt water spray resistance and other properties.
4. Prevention of adhesion: avoid adhesion and adhesion of coating or printed matter.
5. Control the glossiness: Choose a suitable wax, and different amounts of wax will have different extinction effects.
6. Prevent the deposition of silicon dioxide and other hard knots, and increase the storage stability of the coating.
7. Anti-metal marking: Especially in the paint for printing cans, it can not only provide good processability, but also protect the storage stability of printing cans.
2. Study on polyethylene micropowder wax
Micro-powder technology is a high-tech developed in recent years. Generally, particles with a particle size less than 0.5μm are called ultrafine particles, those with a particle size less than 20μm are called microparticles, and aggregates of ultrafine particles are called ultrafine powder.
There are three main methods to prepare polymer particles: one is to start with coarse particles and adopt physical methods such as mechanical crushing, evaporation, condensation and melting; Secondly, with the action of chemical reagents, molecules in various dispersed states gradually grow into particles with the required size, which can be divided into two types: dissolution and emulsification. Third, directly adjust the polymerization or degradation preparation. Such as PMMA micropowder, controllable molecular weight PP, dispersion polymerization to prepare PS microparticles, thermal cracking to radiation cracking to prepare PTF micropowder. At first, we prepared PWEax micropowder in China, and it reached the advanced level of similar products abroad through the test in Shanghai powder engineering pilot base. The main technological process is physical method.
Application of (1) polyethylene glycol micropowder
Polyethylene wax for coatings can be used to prepare high gloss solvent coatings, water-based coatings and powder uncoated coatings.
Can coating, UV curing, metal decorative coatings, etc. It can also be used as a daily moisture-proof coating for cardboard.
(2) Ink, overprinter varnish and printing ink. PEWax can be used to prepare letterpress water-based ink, solvent gravure ink, lithographic/offset printing ink, ink, overprint varnish and so on.
(3) Cosmetics and personal care products. Beeswax can be used as raw material for powder cake and antiperspirant/deodorant.
(4) Micro-powder wax for coiled materials. Wax for coil has two requirements: that is, when improving the surface smoothness and hardness of the coating, the leveling and water sensitivity of the coating should not be affected.
(5) Hot melt adhesive. PEWax micropowder can be used to prepare hot melt adhesive for hot stamping.
(6) Other applications. PEWax can also be used as an isolation agent for cast-pressed metal parts and foam parts, an additive for rubber-plastic sheets and pipes, a modifier and an electrorheological agent for purple oil, a carrier and a lubricant for masterbatch.
2.2 Development of Modified Polyethylene Wax
In the early 1990s, we modified low molecular weight polyethylene wax, and there were many reports about carboxylation and grafting. Abroad, Germany, France, Poland and Japan applied for patents. China also applied for related patents in two stages.
According to literature research and market analysis, polyethylene wax and modified polyethylene wax, especially after micronization, will have greater development.
The surface effect and volume effect of polyethylene micro-powder wax provide excellent physical and chemical properties for the development of new products, and more series of ultra-fine powders will be available to meet the requirements of various fields such as ink, coatings and finishing agents.
3. Study on the application of polyethylene wax in coating industry.
3. 1 Present situation of coating industry in China
With the growth of China, especially the reform and opening up, the coating industry in China has gone through an extraordinary 50 years.
Since the reform and opening up 20 years ago, with the rapid development of economic construction and chemical industry, the coating industry has made great progress. 1992 China's coating output broke through for the first time 1058400 t, 1995 China's coating output increased to 169 10000 t, the highest in history. 1999 coating output was110.5 million t, and the total demand for coatings in the domestic market in 2000 was about10.9 million t.
There are many kinds of coatings, which are divided into eighteen categories according to the main film-forming substances in the components; According to whether there is pigment or not, it can be divided into varnish and color paint. The basic varieties are primer, topcoat and putty. China's coating production can basically meet the needs of the development of various industries in the national economy, and its output has ranked fourth in the world.
At present, there are 18 categories of coating products produced in China, with nearly 1000 varieties. During the Sixth Five-Year Plan and the Seventh Five-Year Plan, the product structure was adjusted, the production of oil-based paint was restricted, and the synthetic resin paint was developed vigorously, which made the coating structure change fundamentally. The proportion of synthetic resin paint in the total paint output increased from 48% in 1980 to 57% in 1990, and further increased to more than 72% in 1998.
After the reform and opening up, with the development of national economy and the improvement of people's living standards, the consumption of coatings in China has been growing steadily. But also gradually develop to high-grade and pollution-free coatings.
As an additive, polyethylene wax is mainly used in high-grade coatings such as matte paint, and the general addition amount is 5%~6%. It is added in the form of micropowder and emulsion through high-speed stirring. The addition of wax in other coatings is 0.25~2.0%, and the price is between 30,000 ~ 50,000 yuan per ton.
3.2 Polyethylene Wax Market
Due to the limitation of technical level, there is still a certain gap in quality between domestic polyethylene wax and similar products abroad. Therefore, despite the high price, foreign products still occupy a large part of the market share, about 48%. This is because manufacturers pay more and more attention to quality, no longer simply pursue efficiency, and put product quality and customer satisfaction first.
With the improvement of people's living standards, people's requirements for coatings have also changed. More and more low-grade coatings have been eliminated, and beautiful and practical high-grade and medium-grade coatings occupy most of the market. The market for wax additives is also expanding.
Only by speeding up technical transformation and strictly controlling quality can China's polyethylene wax production enterprises face WTO entry, occupy a larger market share and push our products to the world. It is estimated that the polyethylene wax market in China will be around 2,200 tons to 2,500 tons in 200 1 year. At present, foreign research and manufacturers of synthetic wax include allied and chemicakl in the United States, hoechst, basf, beba, chen and Pora Thornton in Germany, Sanhua Chemical Co., Ltd. in Japan, Petrochemical Industry Co., Ltd. in Japan, Mitsubishi Chemical in Japan, Anyuan Grease and Deqian in Taiwan Province Province. There are mainly Jinshan Petrochemical Company in Shanghai and Jinfude Company in Guangzhou. Among them, the main synthetic wax products that have been successfully studied and applied are fatty wax, amide wax and polyethylene fatty acid mixed wax. However, its emulsification is not ideal, and the research and production of high-quality synthetic wax in China has broad market prospects.
4. Concluding remarks
Polymer wax has developed into a new functional material, and the functionalization of organic polymer micropowder is also becoming a research hotspot. With the preparation, application and in-depth development of polymer micropowder, it will open up more new properties and applications, and form a new field of functional polymers and intelligent materials.
The excellent properties of polymer wax provide good physical and chemical properties for the development of new products, and more series of waxes will be available to meet the needs of ink, coatings, finishing agents and other fields. China's polymer wax industry will also go global.
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