Qian Diancun, Dong Panning, Ai Hong, Wang Qing (Zhongyuan Oilfield Drilling Mud Technology Institute, Yangcheng 457001) Acrylic waste after chemical modification in the petroleum industry, water treatment industry, adhesives, polymer absorbent resin, printing and dyeing Agent applications.
The material is also increasing, China's acrylic waste accounts for about 2% of the total production of polyacrylonitrile (PAN). Acrylic waste can not be depolymerized, so rational use of nitrile to waste has always been a matter of great concern, related to the comprehensive utilization of acrylic waste Research has been widely carried out. Developed countries such as Europe and the United States and Japan mainly use nitriles as waste sizing agents and water treatment agents for textile industrial fabrics. Domestic research on the comprehensive utilization of acrylic wastes since the 1960s is mainly used as an oilfield chemical treatment agent. Industrial waste liquid flocculants, soil conditioners, etc. This article describes the recent domestic chemical modification methods and comprehensive utilization of acrylic waste.
1 The main component of chemically modified acrylic waste is polyacrylonitrile (PAN). Direct use of waste acrylic fiber as an oil field chemical, water stabilizer, adhesive, etc. is not acceptable and must be chemically processed to produce the corresponding product.
1.1 Hydrolysis Technology Through the hydrolysis reaction, acrylic waste is converted to hydrolyzed polyacrylonitrile (HPAN). Acrylic hydrolysis methods are currently: pressure and catalytic pressure hydrolysis, acid hydrolysis, alkali hydrolysis.
1.1.1 Pressurization and Catalytic Pressurization Hydrolysis and Pressurization Hydrolysis is performed by adding a certain proportion of waste materials, water, etc. in a pressure-reacting reaction vessel, and hydrolyzing at a pressure of 1 to 1.5 MPa and a temperature of 170 to 200. In this method, the hydrolyzed product has a very poor solid content and a good hydrolysis effect. However, due to the reaction temperature and pressure, the equipment requirements are poor, which is not conducive to popularization and application. At present, a catalytic pressurization hydrolysis method has been developed. For example, Wang Jie et al. used solid catalysts (transition metal oxides or alkaline earth metal oxides) and antioxidants to hydrolyze the waste at a pressure of 0.77 MPa and a temperature of 170 for 5 h to obtain a solid content. It is 22.6% of the hydrolyzed product and its viscosity can reach 2306 mPa-s (built).
1.1.2 Acid hydrolysis Acrylic waste is hydrolyzed using a strong acid such as concentrated sulfuric acid as a catalyst.
The concentration of H2SO4 used in this method is too large, generally more than 50%, the amount of alkali used in neutralization is also more, the cost is low, and a large amount of waste water is generated in the treatment process, which easily causes secondary pollution, and is rarely used.
1.1.3 Alkaline hydrolysis ~10% NaOH aqueous solution, in the 90 ~ 100: nitrile pounds of waste at atmospheric pressure hydrolysis for several hours, you can get the ideal product. The reaction temperature, reaction time, and concentration of NaOH aqueous solution are the main factors affecting the degree of hydrolysis of acrylic waste. This alkaline hydrolysis reaction conditions are mild, no special requirements for equipment, safe and reliable, is the most common method of hydrolysis of acrylic waste.
Regardless of which hydrolysis process is used, the hydrolysate thereof: HPAN mainly contains functional groups such as carboxyl groups, amides, and imides. In terms of chemical composition, it is a random copolymer of peracetamide and acrylic acid (salt). The permanent solution process converts water-insoluble acrylic waste into a water-soluble polymer HPAN. 1.2 Cross-linking reaction, etc.) A network-forming gel is formed by ionic or coordination bonds. Aici3 is one of the most commonly used cross-linking agents. HAN gel-like hydrogel can be prepared with a suitable amount of 10% A1C13 solution at room temperature, but its gel property is easily affected by pH (A13+ amphoteric), A13+ and hydrolyzate. The cross-linking reaction speed is faster, the cross-linking density of the product is not uniform, and the gel stability is poor.
HPAN can also react with organic cross-linkers such as formaldehyde and glycerol epoxy resins. Lei Liangcai et al. 5mol/L formaldehyde solution was reacted at 100:2 for 2 hours to obtain a viscous cross-linked polymer. Using glycerol epoxy resin as a cross-linking agent can compensate for the excessively fast cross-linking of polyvalent metal ions.
1.3 Oxidative degradation HPAN undergoes oxidative degradation in strongly alkaline, strongly acidic media, or in the presence of oxidizing agents (such as hydrogen peroxide, potassium hypo-potassium, potassium osmium manganate, etc.), that is, carbon-carbon bonds break, and the molecular weight decreases. The viscosity of the aqueous solution becomes smaller, while the amide group (CONH2) is hydrolyzed to a carboxyl group (co-), resulting in a low molecular weight HPAN solution containing a large amount of an oxr group. If the pH of HPAN solution is adjusted to 5 ~ 6 with formic acid or hydrochloric acid, and a suitable amount of oxidizing agent is added to react under 80r100 for 1~2h, a light yellow low molecular weight transparent solution can be obtained. In addition, PAN hydrolysis in alkaline conditions is accompanied by the occurrence of partial thermal degradation reactions.
2 Comprehensive utilization 2.1 Field of oil chemistry In oil drilling, HPAN has been widely used as a fluid loss reducer, viscosity reducer, and shale stabilizer. Hydrolyzed sodium polyacrylonitrile, hydrolyzed polyacrylonitrile calcium, and hydrolyzed polyacrylonitrile ammonium are commonly used as fluid loss control agents for the drilling fluid. Hydrolysis of ammonium acrylonitrile also has a viscosity-reducing effect and is a diluent for positive-charged mud. KPAN solution was used to hydrolyze the waste of acrylic fiber to prepare HPAN potash shale drop shale stabilizer. Studies have shown that the acrylic waste is prepared only by hydrolyzing the drilling fluid material, and the product performance is still relatively simple and unsatisfactory. Zhongyuan Oilfield Drilling Mud Technology Research Institute. The products prepared by HPAN grafted copolymerization and cross-linking with expanded starch and lignite also have better filtration loss effect. Drilling fluid viscosity reducing agent can be prepared by alkaline hydrolysis and oxidative degradation of PAN wastes, and the products degraded by HPAN oxidation are crosslinked with lignosulfonate and sulfomethyl humate to obtain a series of drilling fluids. Viscosity reducer.
In oil well production, the use of HPAN and cross-linked HPAN for chemical plugging of oil wells and profile adjustment of injection wells can increase crude oil production. The Jianghan Oilfield in China adopts the HPAN+CaCl2 dual-liquid technique test and has achieved satisfactory water shutoff. However, due to the use of CaCl2 in the formulation, the damage to the oil layer is greater; the low polymerization degree developed by Shengli Oilfield using benzoic acid and formaldehyde The HPAN gel water shutoff agent with a phenolic resin as a cross-linking agent has the characteristics of controllable high-temperature gelation, good anti-warm temperature performance and long effective period; Daqing Oilfield has developed a desalination HPAN low temperature water shutoff agent in recent years, which consists of desalinated HPAN. , formaldehyde, enhancer and other components, with the use of low temperature (35), to adapt to a wide temperature range (35 to 50), a large gel strength (indoor simulation pressure of 8.0MPa or more), does not harm the characteristics of the formation.
2.2 Water treatment industry The flocculant produced by using waste acrylic fiber hydrolyzate can be used for the waste water treatment of papermaking waste liquid, dyeing and finishing waste liquid, tanning leather waste liquid and food processing waste liquid. In the HPAN molecular chain, hydrolysates containing 70% to 80% of acrylamide units show better flocculation effects on negatively charged suspended particles. HPAN polymer flocculant is easy to use, and its flocculation efficiency is higher than that of traditional inorganic salt flocculants. It is lower than that of domestic flocculant molecular flocculants obtained by polymerization of water-soluble monomers. Wang Fengyan et al. used acrylic fiber waste to prepare flocculant flocculants for wastewater from coal preparation plants. He pointed out that the milky white liquid with a viscosity of 786 s can be obtained by adopting proper hydrolysis process conditions. This is a high-molecular flocculant, and the product is used to treat the wastewater from coal preparation plants. (The sludge content of 1221 mg/L) has a good flocculation effect and the sludge dehydration efficiency is low. Hao Huaxing and others used acrylic waste fiber as raw material to react with diamines in alkaline solution to successfully synthesize polymer flocculants containing various active groups. The polymer has a wide range of pH values ​​and can be used in conventional flocculants. The range that can not be involved is the decolorization of dye wastewater and the deoiling of the refining plant. The effect of removing phenol is better than polyaluminum chloride, polyacrylamide and other flocculants, and it is a promising polymer flocculant.
Acrylic waste silk hydrolysis degradation products can effectively prevent boilers, pipes, heat exchanger surfaces and oil field water injection fouling. It has been reported that M, polyacrylic acid-based water-based scale inhibitors obtained by hydrolysis, oxidative degradation, and washing of acrylic wastes, is correct! : aC03, BaS04 scale ratio is close to 100% and greater than 80%. 2.3 Other chemical fields 2.3.1 Casting binder Acrylic hydrolysate has been widely used in the casting core. The adhesive has the characteristics of tensile strength, good collapsibility, small air volume, no transmutation and the like, and is therefore an adhesive with excellent casting properties, but the main component is a highly hygroscopic sodium polyacrylate. Therefore, the sand core has a sharp drop in strength due to moisture absorption during the placement process. According to reports, acrylic fiber wastes are catalytically hydrolyzed and then crosslinked to prepare casting binders. This problem can be better resolved. Acrylic waste hydrolysate is also an ideal material for the preparation of lead foil composite adhesives and polymer emulsion protective adhesives. Zhang Guangyan's research shows that the acrylic waste hydrolysate is used as a protective glue for the synthesis of polyvinyl acetate (PVAc) emulsions. In addition to the advantages of general emulsions, it also has a unique freeze-thaw stability and low viscosity characteristics. In addition, HPAN has a large initial adhesion and can also be used as a quick-stick label.
2.3.2 Preparation of polymer water absorbent resin Acrylic waste after hydrolysis under alkaline conditions, and then add the cross-linking agent, the resulting cross-linked polymer by precipitation, drying, crushing, sifting, to obtain water-absorbing resin molecules. Since the carboxylic acid group and amide group converted into the nitrile group in the polymer are hydrophilic groups, the water absorbing resin has a high water absorption capacity. Studies have shown that: in the acrylic waste hydrolyzate by adding cross-linking agent formaldehyde, cross-linked nitrile to the waste hydrolysate prepared by absorbing water can absorb distilled water 500g / g, physiological saline (0.9% NaCl) 60g / g. Li Yong, etc. with A1C13 The cross-linking agent prepared a water-absorbing material that can absorb 477 g/g of pure water and 55 g/g of physiological saline. However, A1C13 is used as a cross-linking agent, and the cross-linking speed is too fast and the stability of the gel is poor. Ding Lunhan uses glycerin epoxy resin as a cross-linking agent to better solve this problem. The resulting water-absorbent resin has a higher water absorption capacity, and its water absorption rate can reach 600 ~ 800 g/g (pure water), and the saline solution absorbs water. The rate reached 90g/g.
The water-absorbing resin obtained by hydrolysis and re-crosslinking of the nitrile waste is excellent in performance and lower in cost than the water-absorbent resin prepared by polymerization of monomers such as acrylic acid and acrylonitrile.
2.3.3 As a dispersant for paints and pigments, 40% HPAN solution is used as a wetting and dispersing agent for waterborne coatings. It has a good dispersion effect for white powder, calcium carbonate, talcum powder and lithopone etc. 0.5% to 1.5% of the amount of pigment. HPAN dispersant dispersion effect is better than sodium pyrophosphate and sodium hexametaphosphate.
2.3.4 Preparation of dyeing auxiliaries The non-ionic polar group-CONH2 in the hydrolysate of acrylic fiber has a strong ability to adsorb dye particles. The ionic hydrophilic group-COO can bind to free water molecules and reduce the free water content. Difficulty in dye migration. Adding an inorganic salt electrolyte to the acrylic hydrolysate can destroy the dispersed protection of the dye particles and cause the dye particles to have a slightly loose self-polymerization. Therefore, the acrylic hydrolyzate is used for hot melt dyeing of lacquer, polyester-cotton, and polyester-viscose fabrics, and has good anti-migration effect, so that the leveling and deepening effects of the fabrics after processing are significantly improved, and disperse dyes, vat dyes and sulfur dyes can be saved.
The acrylic rubber obtained by the alkali hydrolysis of acrylic was crosslinked to obtain a modified acrylic rubber. Acrylic rubber and modified acrylic rubber are ideal raw materials for reactive dyes and can completely replace sodium alginate. Because of its low reactivity with reactive dyes, its color yield is 10%~15% higher than that of sodium alginate, except for a few dyes. The economic and social benefits are particularly remarkable, especially the denaturalized acrylic rubber 2.4 agricultural HPAN aqueous solution and gelatinization. The starch is mixed and stirred, dried at 150 to prepare a highly water-absorbing, water-retaining agricultural seed coating agent and soil improver, which can make the crop sprout early, the seedling rate is low, and the agricultural production increase. HPAN is used as a clay soil conditioner and cross-linked with clay to form pellets
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