2022-06-14 Pageview：652
Fischer-Tropsch (F-T) synthetic wax is a kind of product obtained by Fischer-Tropsch synthesis technology, using syngas (CO and H2) as raw materials, reacting in a Fischer-Tropsch reactor under certain conditions, and then by hydrorefining. There are many Fischer-Tropsch waxes in foreign countries. Sasol Company of South Africa and Shell Company of Holland have developed a series of Fischer-Tropsch wax products. In recent years, the Fischer-Tropsch synthesis industrial demonstration units of Guoneng Group, Lu’an Group, Yitai Group and Yankuang Group have achieved long-term full-load operation successively. Relying on the coal-based Fischer-Tropsch synthesis technology with independent intellectual property rights, domestic enterprises are A lot of work has been done in the development, production and deep processing of coal-based synthetic oils, among which Fischer-Tropsch wax has attracted more and more attention due to its excellent properties [1]. However, with the large amount of Fischer-Tropsch wax being put into the market at the same time, the price of the product has continued to fall. In order to improve economic benefits, major coal-to-liquids companies have turned their attention to the special wax market. The production of special wax has the following characteristics: high production technology, many varieties, low output, high added value, diversified market demand, no one company can monopolize the market, and it is easy to find opportunities in the market. In general, the output and variety of special wax products in my country are far from foreign countries. Therefore, taking Fischer-Tropsch wax as the center, producing high value-added special wax through modification and blending, continuously expanding and extending to Fischer-Tropsch wax series products, and taking the road of fine chemical industry, is the future development direction of my country’s Fischer-Tropsch wax industry. The only way for coal-to-liquid enterprises to make the leap from producing primary products to high value-added fine chemicals.
1. Features of fischer trops wax
Fischer-Tropsch wax is composed of a small amount of methyl branched straight-chain saturated high-carbon alkanes, the relative molecular mass is 500~1000, the carbon number is distributed in C20~C80, the chemical properties are stable at room temperature, and almost no sulfur, nitrogen, aromatics are contained. and other impurities, the chemical composition can meet the food-grade requirements. Compared with petroleum wax, it has the characteristics of high melting point, narrow melting point range, low penetration, low oil content, low melt viscosity, low mobility, hardness, wear resistance and high stability [2]. According to the melting point or freezing point, the domestic Fischer-Tropsch wax products mainly include 60#, 70#, 85#, 95#, 100#, 105#, 110#. The melting point of the products of foreign South African company Sasol can reach up to 120 ℃. Fischer-Tropsch waxes are much more valuable than ordinary petroleum waxes and have replaced petroleum waxes in many high-end applications.
The molecular structure and properties of Fischer-Tropsch wax with melting point below 70 °C are similar to paraffin wax, which can be used as a substitute for some paraffin wax, and can also be used as a modifier of paraffin wax to improve dropping point, hardness, etc.; After proper isomerization, Fischer-Tropsch wax can be used as a substitute for microcrystalline wax in some fields; the molecular weight of Fischer-Tropsch wax with a melting point higher than 100 °C is between petroleum wax and plastic, and in principle it can no longer be called wax but belongs to synthetic materials. Substances are basically not related to the application field of petroleum wax. At present, Fischer-Tropsch wax with high melting point mainly relies on imports, and its application field is more extensive. Based on the many advantages of Fischer-Tropsch wax, it can be widely used in rubber protection, hot melt adhesive, investment casting, polishing agent, electrical, food, cosmetics and agriculture.
2 Application of Fischer-Tropsch wax
2.1 Waxes for Industry
In the rubber industry, Fischer-Tropsch wax can be used as an antioxidant and toughening agent for rubber. In the process of processing, storage and use, rubber products are easily damaged by oxygen and ozone in the air, and at the same time, they are subject to the combined effects of light, heat, radiation, and mechanical force, which can easily cause rubber products to become sticky, hardened, and cracked. and other aging phenomena. Adding a certain amount of protective wax to rubber products can effectively enhance the anti-oxidation performance of rubber, inhibit the occurrence of aging, and prolong the service life. The working principle of rubber protective wax is that the rubber protective wax added to the rubber compound can migrate from the inside of the rubber to the surface, and “bloom” on the surface to form a layer of inert, dense structure, strong adhesion, non-crystalline, and tough. The wax film reacts with ozone first, thus hindering the invasion of ozone, light and heat to rubber [3]. The properties of rubber protective wax depend on carbon number distribution and n-isoparaffin content. Traditional rubber protective wax is compounded by ordinary paraffin and microcrystalline paraffin. It can reduce the regularity of paraffin wax and destroy the dense crystalline structure, thereby forming an amorphous film with good barrier properties and flexibility. Fischer-Tropsch wax is mainly based on n-alkane, which needs to be properly isomerized when it is used as the raw material of rubber protective wax.
In the hot melt adhesive industry, wax is an important component. As a special kind of adhesive, hot sol is generally composed of polymers, tackifiers, plasticizers, antioxidants and fillers. On the surface, when the temperature is lowered, the hot melt adhesive wax cools and solidifies, bonding the bonded substances together. According to different materials, hot melt adhesives are divided into EVA type hot melt adhesives, polyolefin hot melt adhesives and rubber type hot melt adhesives (commonly known as self-adhesives), which are widely used in packaging, textiles, furniture edge sealing, book binding, automobiles and household appliances. assembly and other industries. The properties of hot melt adhesives at high temperatures are mainly determined by the melting temperature range and the type of wax added. The freezing point and crystallinity of the wax control the initial solidification temperature and curing time of the hot melt adhesive, and at the same time affect the plasticity of the hot melt adhesive. and tensile properties. By adding an appropriate proportion of Fischer-Tropsch wax, the softening point, shear strength and peel strength of hot melt adhesives can be improved, melting temperature can be reduced, operational performance can be improved, and costs can be reduced [4].
In the investment (precision) casting industry, wax is the most commonly used mold material. In ancient my country, it was called the lost wax casting process. This process does not require much cutting after molding, and can be used directly after fine processing. The process flow of investment casting is as follows: the melted wax is pressed into a wax mold according to the size and quality required by the design, and several layers of refractory materials are coated on the surface. The molten metal flows out, and finally the molten metal liquid is poured into the mold shell. The metal liquid is cooled and solidified in the mold shell, and becomes a precise and smooth casting after shelling and cleaning. Wax for investment casting requires melting point in the range of 60℃~100℃, good fluidity, softening point not lower than 35℃~40℃, shrinkage rate less than 1%, sufficient strength and surface hardness in solid state, easy to recycle, Good reusability, pollution-free and abundant sources, low price, etc. [5]. The lost wax casting process is suitable for the casting of various types of alloy parts. It has the characteristics of high dimensional precision, accurate shape, low surface roughness and wide application range. This method can be taken.
In the plastics processing industry, waxes can be used as lubricants for polyvinyl chloride resins (PVC). In the process of PVC processing, friction will occur between PVC and between the PVC melt and the metal surface of the processing machine. The main purpose of adding PVC lubricant is to reduce the viscous flow resistance of the melt. Since wax is a non-polar substance, it is difficult for small molecular compounds to penetrate into each layer of PVC resin molecules uniformly, resulting in poor compatibility between wax lubricants and PVC. According to the lubrication mechanism of PVC, wax as a lubricant mainly exhibits external lubrication, and the external lubricity is very strong. It also has good lubricity in the middle and late stages of molding and is non-toxic. After PVC plasticization, the wax forms a thin film on the surface of the PVC, which reduces the adhesion and friction between the PVC and the metal surface of the processing machinery, thereby preventing the decomposition of the resin caused by local overheating and improving the thermal stability and fluidity. . Wax lubricants should not be used in excess. Excessive use will cause “blooming” on the surface of PVC. The melting point of wax as a lubricant is generally 60 ° C ~ 95 ° C, and the molecular chain is long, because the wax with long carbon chain can make the two friction surfaces farther away, and the lubrication effect is better.
In the textile industry, emulsified waxes are often used in sizing, printing, glazing, waterproofing and other processes. In the sizing process, it can be used as a softener and a sizing aid, which can significantly improve the softness and lubricity of the fiber, reduce the breakage rate, improve the efficiency of the loom and the quality of the fabric, but the selected wax should be considered in the post-treatment. Easy to remove in the process. In the printing process, a large number of bleached cotton fabrics are irregularly coated with a layer of wax according to the designed pattern, and dyed with vat dyes. The dyes only penetrate into the fibers in the places covered by the wax layer that are not thick. Wax removal can be repeated depending on the number of patterns and colors used. In the varnishing process, the emulsified wax liquid can give the fabric a soft silky high gloss. In the waterproof process, the waxy water-repellent finishing agent is coated on the fabric to block the pores on the fabric and prevent water from passing through it, so that the fabric can be made waterproof. Raincoats and umbrellas are made by this process. [7].
In the electrical industry, waxes are mainly used for insulation and moisture-proofing of electrical equipment at room temperature. Due to the extremely strict requirements of the electrical industry for conditions such as temperature, humidity and voltage, the melting point of different types of waxes selected should generally be higher than 55°C, with low oil content, high relative permittivity, low dielectric loss and high resistance. In addition, it must have good flexibility, ductility and a low coefficient of thermal expansion. In the electrical industry, wires, cables or irregularly shaped metal surfaces are often directly coated with a wax layer for insulation. Capacitors, cable terminations and couplers are often filled with wax in the space around their interior [8]. The zinc shell of the dry battery can be sealed with wax or wax-impregnated paper, which can effectively reduce the drying shrinkage of the battery.
2.2 Waxes for Food, Cosmetics and Agriculture
In food processing, wax can be used as a coating material for wrapping paper to keep food fresh. It can make disposable paper cups and instant noodle boxes, and coat a layer of high-melting Fischer-Tropsch wax on the surface of the paper. Melt and cause harm to the human body. The use of wax as an emulsifier, whipping agent and softener is common in the making of bread and pastries. Waxes are also used as anti-sticking agents for candies, retainers for the luster and flavor of chocolate candies, emulsifiers and whipping agents for ice cream, and emulsifiers for margarines. From the perspective of food safety, adding a certain amount of food-specific wax according to the national standard limit will not cause harm to the human body due to the intake of a large amount of edible wax at one time.
Fischer-Tropsch wax can be used as a preservative for fruit and vegetable coatings. Due to the high water content of fruits and vegetables, if the fruits and vegetables are not kept fresh after picking, they will easily lose moisture and lead to quality degradation. Fruits and other agricultural products that do not need to eat the skin and need to be transported long distances are waxed to block the pores on the epidermis, reduce shrinkage and weight loss caused by water evaporation, and slow down nutrient loss and after-ripening due to the inhibition of respiration rate Aging helps maintain freshness. After waxing, the appearance quality of fruits and vegetables is bright and shiny, which improves the commodity value to a certain extent. High-quality fruit and vegetable wax has the following requirements: after the wax liquid is processed, it is closely combined with the surface of the fruit and vegetable, easy to wash off, no peculiar smell, fast drying, non-toxic to the human body, and low price. High-end Fischer-Tropsch wax is oxidatively modified and dissolved in water to obtain emulsified wax. If it is used for fruit and vegetable preservation, it can not only meet the needs of long-distance transportation, but also play a role in preventing insects. Fischer-Tropsch wax is used as an additive for chewing gum base material, which can adjust the hardness and dispersion of chewing gum, increase the solubility of sugar, make it taste better and chew better, and not easy to break. After the sugar coating process in the production process, the surface of the chewing gum is relatively dull, and it is easy to absorb moisture, which has a great impact on the later storage. After polishing with Fischer-Tropsch wax with high melting point and high hardness, it can not only prevent the chewing gum from being damp and absorb water, but also can Improve appearance and enhance aesthetics.
In the field of cosmetics, wax is one of the most important raw materials for the production of cosmetics, which can be used to make makeup dispersions, mascara, eyeliner, lipstick and hair wax. Waxes can be used in cosmetics because they form a water-repellent film, act as an emulsifier or co-emulsifier, and act as a thickener to improve the structure and smoothness of emulsions. Waxes are oil soluble, so they improve the emolliency of the film left on the skin and give a good shine. The wax used in cosmetics has the following requirements: good stability, no darkening of color during storage, odorless and tasteless, no color body, no carcinogenic polycyclic aromatic hydrocarbon compounds. Unrefined waxes contain a certain amount of oil, sulfur, nitrogen and oxygen, so the refining of cosmetic waxes is very important. Based on the above requirements, Fischer-Tropsch wax is particularly suitable as a raw material for the production of cosmetics.
In the agricultural field, the emulsion of Fischer-Tropsch wax can be used as an anti-transpiration agent for flowers and plants. After the flowers are picked, they are treated with fresh-keeping wax to prevent the opening of the stomata of flowers and plants, effectively control the water loss of flowers, and prevent their wilting and loss. Extend flower life [12]. In addition, after the saplings and shrubs are sprayed with fresh-keeping wax, they can also withstand the severe drought environment well, and their survival rate is significantly improved.
In the poultry processing industry, Fischer-Tropsch wax can be used for the plucking of poultry, that is, after the feathers are plucked, the poultry is first immersed in the molten wax, and then when the covering wax layer is solidified, the wax is removed with a slap machine, This buries the quills and small feathers left after plucking in the wax and removes them at the same time as the wax.
2.3 Waxes in the field of polishes
The main component of the polishing agent is wax, which is applied to the surface of the paint film of leather goods, leather shoes, furniture, floors, automobiles, and equipment, mainly for decontamination, glazing and protection. Variety. Polishing agents usually need to mix together several suitable waxes and other additives in suitable proportions to achieve the desired effect. Soft waxes with low melting point in glazing agents have poor oil absorption and brightness, and cannot be used as the main raw materials of glazing agent waxes, but they have excellent adhesion, and adding a certain amount can change the flexibility and spreading effect. Hard wax with high melting point and high gloss is the key ingredient for glazing agent and plays a brightening role in glazing agent. High melting point Fischer-Tropsch wax has high hardness, good brightness and small penetration, and is suitable as a refined hard wax for glazing products.
Leather shoe polish is a leather polish and protective agent applied to the surface of leather shoes and leather goods. It can not only clean the leather and increase the luster on the surface, but also protect the leather from wear and tear [14]. The types of shoe polish include solvent-based plaster, emulsified ointment and liquid. The first two are traditional products. Liquid shoe polish is currently more popular in the market due to its characteristics of not rubbing on itself and being easy to carry.
Wooden floors are favored by many home decorations because of their natural beauty, easy processing, and good thermal insulation. However, wooden floors have defects such as easy corrosion and moth-eaten. Therefore, many businesses have introduced floor polish protectants, which can be divided into solid floor polish and liquid floor polish according to different forms. Solid floor varnishes are paste or solvent-free varnishes, and liquid varnishes can be dried directly to form a glossy surface layer. The main function of the floor polish protectant is to prevent the penetration of water, water vapor and air into the floor, protect the floor, and reduce wear and tear. After wiping on the floor, the film left behind can produce luster.
Car polish is mainly used as a “beauty” for cars. The main components of the exterior surface paint of automobiles are acrylic or polyurethane coatings. The pollution of sulfides in the air, acid mist, acid rain, salt mist hydrocarbons, and dust has a great influence on the surface paint, so it needs to be cleaned, varnished and cleaned regularly. Protect. The traditional process is cleaning first, then waxing and glazing, which has the disadvantages of a large amount of wax, high labor intensity, slow glazing speed and poor gloss. The current market demand is a multi-functional cleaning and glazing agent that combines cleaning, glazing and protection. The active ingredients of cleaning and polishing agents are composed of abrasives, linear and branched aliphatic hydrocarbon solvents, waxes, silicones, water, surfactants, stabilizers, etc. [15].
2.4 Waxes for Paper Packaging Industry
The moisture barrier, water barrier and gas barrier properties of paper product packaging have always been the focus of attention in the industry. After the paper packaging product is damp, the strength will be reduced, resulting in the rupture or collapse of the packaging, which not only loses the protective function of the packaging, but also affects the appearance of the packaging, and directly destroys the quality of the packaged items in severe cases. Using Fischer-Tropsch wax as raw material, adding various auxiliary raw materials and additives can prepare paper product packaging protective wax, which is mainly used to improve the moisture-proof and waterproof performance of paper product packaging, protect the packaged objects and enhance the safety and hygiene performance. After the packaging material is impregnated with packaging protective wax, a continuous water- and oil-repellent film can be formed on the surface, which plays a protective role, and can also improve the printing effect on the packaging material, and improve its smoothness and toughness [16]. Compared with Fischer-Tropsch wax, packaging raw materials such as salicylates, alkenyl succinates, arabinoxylanase-hydrogenated palm kernel oil are expensive, complicated to operate, inconvenient to use, and even very few products are toxic and odorous , flammable, pollute the environment, endanger the body. According to the characteristics of paper product packaging boxes, paper product billboards and food packaging, Fischer-Tropsch wax as a raw material for packaging has the advantages of low price, convenient use, non-toxicity and good quality.
2.5 Waxes for Pharmaceutical Industry
In the pharmaceutical industry, most waxes are used in the production of wax creams and ointments, and a small part is used in the production of enteric sugar coatings for suppositories and pills. Ointments are softer than waxes and have a buttery consistency, so they can be easily applied to the skin. Suppositories can be put into the human body and they melt or soften at a body temperature of 37°C. Pills and tablets are often coated with several layers of sugar to prevent unpleasant taste in the mouth when swallowed. After the icing is colored, a thin layer of wax is applied to give the drug a nice appearance.
In the process of dental treatment, wax materials are often used, because wax has plasticity, low melting point, non-toxicity, low hardness, and easy molding and casting. Therefore, it is often used for high-precision work such as dental inlays, braces, and dentures. go in.
In histopathology, in order to improve the strength of the sample tissue to withstand thinning, wax materials are often used for embedding, by infiltrating the sample tissue into the wax, and then thinning the tissue and paraffin to 1 μm~ 2 μm for microscopy [17].
2.6 Waxes used in other fields
Fischer-Tropsch wax can be used in the field of printing inks. Ink is a uniform and stable dispersion system composed of colorants, binders and various additives. The colorant is the main body of the ink, which makes the printed matter have colorful tones, and can also make the ink have certain rheological properties. The binder is the carrier of the pigment particles, which makes the pigment particles evenly dispersed, and at the same time plays the role of transferring the colorant to the surface of the printed matter and fixing it, so that the ink has the ability to flow and print. It is also a film-forming substance, which affects the ink. dryness and quality. The addition of auxiliaries improves the ink properties and enables it to meet various printing conditions. Special waxes for inks include polyethylene wax, polytetrafluoroethylene wax and Fischer-Tropsch wax. Waxes usually play the role of anti-friction additives in inks, which can change the working properties of inks and improve the anti-slip and anti-wear properties of inks. Sex [18]. The friction resistance of wax mainly depends on its particle size and hardness. Waxes used in the ink field are mainly spherical particles and micropowder products with low surface tension. The size of the wax particles should be as small as possible to ensure that there will be no adverse effects during production and no problems during printing. After the wax is printed on the substrate, it must be able to float on the ink film layer, which can increase the friction resistance. Once the printed matter is rubbed and heated under the action of external pressure, the wax particles will roll to improve its friction resistance. The addition of wax in the ink must be moderate. Excessive amount may affect the fluidity, transfer and gloss of the ink.
Fischer-Tropsch wax can be used to prepare special wax for bottle-made handicraft sealing. Bottle handicrafts are a class of handicrafts made of glass bottles with flowers, fruits, transparent liquids and other decorations. In order to prevent the leakage of liquid inside the bottled handicrafts, special sealing wax is usually used to seal the bottled handicrafts. In the process of handicraft production, the special sealing wax is required to have strong adhesion, smooth surface, no cracks, and not easy to break under the action of external force. In view of the above requirements, the special wax for bottle-made handicraft sealing must meet the following indicators, the melting point is lower than 70 ℃, no smoke is generated during use, the wax can condense quickly, which is convenient for continuous and automatic high-speed operation, good film-forming performance, strong adhesion, It has certain hardness and toughness, and the price is low [19]. sasol ft technology In order to reduce the cracks of the special wax for bottle-making crafts and improve the brittle and hard defects, a small amount of low-melting wax with high isomerous hydrocarbon content, high penetration, high toughness and flexibility, and good low temperature resistance is usually added.
Fischer-Tropsch wax can be used as a thermostatic valve thermosensitive wax. The temperature control valve is widely used in the temperature and flow of automatic control equipment. Its core component is a temperature-sensitive wax-type thermal element, which determines the temperature control range and temperature control accuracy of the temperature control valve. Wax is used as a temperature-sensing filling medium. , the selection of the melting point range should be appropriate. Its principle is to use wax to increase the intermolecular distance and volume expansion in the phase transition temperature range, which will drive the components to change the flow of hot and cold fluids, and ensure that the temperature of the fluid at the outlet of the pipeline remains within a constant range [20]. The temperature-controlled temperature-sensing wax requires strict temperature control before and after the phase change, rapid response to temperature changes, large volume changes, and precise control of the valve stem stroke. The most important factors affecting the expansion rate of temperature-sensitive wax in application are the melting point and melting range. In addition, the expansion rate of isoparaffin is generally lower than that of n-paraffin with the same carbon number, and the main component of temperature-sensitive wax is required to be mainly n-paraffin.
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