Qian Diancun Dong Panning Ai Hong Wang Qing (Institute of Drilling and Mud Technology, Zhongyuan Oilfield, Yangshi 457001) After the chemical modification of acrylic fiber waste, the petroleum industry, water treatment industry, binder, polymer water-absorbing resin, printing and dyeing Application of agents and the like.
The material is also increasing. China's acrylic fiber waste accounts for about 2% of the total production of polyacrylonitrile (PAN). Acrylic fiber waste cannot be depolymerized. Therefore, the rational use of nitrile for waste has always been a matter of great concern. Researches have been widely carried out. Developed countries such as Europe, America, and Japan mainly use nitrile to waste materials for fabric sizing agents and water treatment agents for textile industry. Domestic research on the comprehensive utilization of acrylic fiber wastes has been carried out since the 1960s, mainly as oilfield chemical treatment agents. Industrial waste liquid flocculant, soil improver, etc. This paper describes the chemical modification methods and comprehensive utilization of domestic acrylic fiber waste in recent years.
1 The main component of chemically modified acrylic fiber waste is polyacrylonitrile (PAN). It is not feasible to directly use waste acrylic fiber as oilfield chemical agent, water quality stabilizer, binder, etc., and must be chemically processed to make corresponding products.
1.1 Hydrolysis Technology The acrylic fiber waste is converted into hydrolyzed polyacrylonitrile (HPAN) by hydrolysis reaction. At present, the hydrolysis methods of acrylic fiber include: pressurization and catalytic pressure hydrolysis, acid hydrolysis, and alkali hydrolysis.
1.1.1 Pressurization and catalytic pressure hydrolysis and hydrolysis, adding waste, water, etc. in a certain proportion in a pressure reactor, and hydrolyzing at a pressure of l.~l.5MPa and a temperature of 170~200. The hydrolyzed product of this method has a solid content and a good hydrolysis effect. However, due to the reaction temperature and pressure, the equipment is required to be flawed, which is not conducive to popularization and application. At present, a catalytic pressure hydrolysis method has been developed. For example, Wang Jie uses a suitable catalyst (transition metal oxide or alkaline earth metal oxide) and an antioxidant to hydrolyze the waste at a pressure of 0.77 MPa and a temperature of 170 for 5 hours to obtain a solid content. It is a hydrolyzate of 22.6% and its viscosity can reach 2,306 mPa-s.
1.1.2 Acid hydrolysis The acrylic acid waste is hydrolyzed by using a strong acid such as concentrated sulfuric acid as a catalyst.
The concentration of H2S04 used in this method is too large, generally more than 50%, the amount of alkali used for neutralization is also large, the cost is 篼, and a large amount of waste water is generated during the treatment process, which is easy to cause secondary pollution, and is rarely used.
1.1.3 Alkali hydrolysis of ~10% NaOH aqueous solution, under 90~100:, the nitrile waste is subjected to atmospheric pressure hydrolysis for several hours to obtain the desired product. The reaction temperature, reaction time and concentration of NaOH aqueous solution are the main factors affecting the degree of hydrolysis of acrylic fiber waste. The alkali hydrolysis reaction condition is mild, has no special requirements on equipment, is safe and reliable, and is the most commonly used method for hydrolyzing acrylic fiber waste.
Regardless of which hydrolysis process is employed, the hydrolysate: HPAN mainly contains a functional group such as a carboxyl group, an amide or an imide. From the chemical composition, it is a random copolymer of acrylamide and acrylic acid (salt). The permanent solution process makes the water-insoluble acrylic waste into a water-soluble polymer HPAN. 1.2 cross-linking reaction, etc.) A gel having a network structure formed by an ionic bond or a coordinate bond. Aici3 is one of the most commonly used cross-linking agents. HAN jelly gels can be prepared at room temperature with an appropriate amount of 10% A1C13 solution, but the gel properties are susceptible to pH (A13+ amphoteric), A13+ and hydrolysate The cross-linking reaction rate is fast, the product cross-linking density is not uniform, and the gel stability is poor.
HPAN can also be reacted with an organic crosslinking agent such as formaldehyde or glycerin epoxy. Lei Liangcai used the appropriate amount of concentration. A 5 mol/L formaldehyde solution was reacted at 100: for 2 h to obtain a viscous crosslinked polymer. The use of glycerin epoxy resin as a crosslinking agent can make up for the insufficiency of the cross-linking speed of polyvalent metal ions.
1.3 Oxidative degradation In the presence of strong alkaline, strong acidic medium or oxidant (such as hydrogen peroxide, potassium hypochlorite, potassium citrate, etc.), HPAN will undergo oxidative degradation, ie carbon-carbon bond cleavage, molecular weight decreased, The viscosity of the aqueous solution becomes small, and the amide group (CONH2) is hydrolyzed to a carboxyl group (a co-) to form a low molecular weight HPAN solution containing a large amount of an oxr group. For example, the pH of the HPAN solution is adjusted to 5-6 with formic acid or hydrochloric acid, and an appropriate amount of oxidizing agent is added at 80 r100 for 1~2 h to obtain a pale yellow low molecular weight transparent solution. In addition, the hydrolysis of PAN under alkaline conditions is accompanied by the occurrence of partial thermal degradation reactions.
2 Comprehensive utilization 2.1 Oilfield chemistry In the oil drilling, HPAN has been widely used as a fluid loss reducer, viscosity reducer and shale stabilizer for drilling fluids. Hydrolyzed polyacrylonitrile sodium, hydrolyzed polyacrylonitrile calcium and hydrolyzed polyacrylonitrile ammonium are commonly used drilling fluid loss reducers. Hydrolyzed Qin acrylonitrile ammonium also has a viscosity reducing effect and is a diluent for positive electric mud. The HPAN potassium salt reduction shale stabilizer can be prepared by hydrolyzing acrylic fiber waste with KOH solution. Studies have shown that the acrylic fiber waste is only prepared by the hydrolysis method, and the performance of the product is relatively simple and not ideal. Zhongyuan Oilfield Drilling Mud Technology Research Institute. The product prepared by graft copolymerization and cross-linking of HPAN with expanded starch and lignite also has a good fluid loss reduction effect. Drilling fluid viscosity reducing agent can be prepared by alkaline hydrolysis and oxidative degradation of PAN waste. The product of oxidative degradation of HPAN is polycondensed and crosslinked with lignosulfonate and sodium sulfomethyl humate respectively to obtain chrome-free for drilling fluids. Viscosity reducer.
In the oil well production process, the use of HPAN and cross-linked HPAN for oil well chemical water shutoff and water injection well profile control can increase crude oil production. China's Jianghan Oilfield has adopted the HPAN+CaCl2 two-liquid method test and achieved satisfactory water shutoff effect. However, due to the use of CaCl2 in the formulation, the oil layer is damaged. The development of benzoic acid and formaldehyde in Shengli Oilfield has a low degree of polymerization. The HPAN gel water blocking agent with phenolic resin as cross-linking agent has the characteristics of high temperature gelation control, good temperature resistance and long effective period. Daqing Oilfield has developed a desalting HPAN low temperature water blocking agent in recent years, which is desalted HPAN. Formaldehyde, enhancer and other components, with low operating temperature (35), wide temperature range (35~50), high gel strength (indoor simulated pressure of 8.0MPa or more), no damage to the formation.
2.2 Water treatment industry The flocculant prepared by using waste acrylic fiber hydrolysate can be used for sewage treatment of papermaking waste liquid, dyeing and finishing waste liquid, leather waste liquid and food processing waste liquid. In the HPAN molecular chain, 70% to 80% of the hydrolyzate containing the acrylamide unit exhibits a better flocculation effect on the negatively charged suspended particles. HPAN high-molecular flocculant is easy to use, and its flocculation effect is stronger than that of traditional inorganic salt flocculant. It is lower than the price of bismuth molecular flocculant prepared by polymerization of water-soluble monomer in China. Wang Fengyan et al. used the acrylic fiber waste to prepare the molecular flocculant for the wastewater of the coal preparation plant. It was pointed out that the milky white liquid with a viscosity of 786 s can be obtained by appropriate hydrolysis process conditions, which is a high-molecular flocculant, which is used for the sewage of the coal preparation plant. (The sludge content of 1221 mg / L) has a good flocculation effect, and sludge dewatering efficiency is low. Yan Huaxing and others used acrylic fiber waste silk as raw material to react with diamine in alkaline solution, and successfully synthesized polymer flocculant containing various reactive groups. The polymer has a wide range of pH and can be used in conventional flocculant. The range that can not be involved, the decolorization of dye wastewater and the deoiling of the refining plant, is better than the flocculating agent such as polyaluminium chloride and polyacrylamide, and is a promising polymer flocculant.
Hydrolyzed degradation products of acrylic fiber waste silk can effectively prevent scaling of boilers, pipes, heat exchanger surfaces and oilfield water injection. It is reported that M, a polyacrylate water-based scale inhibitor prepared by hydrolysis, oxidative degradation and washing of acrylic fiber waste, right! The scale inhibition rates of aC03 and BaS04 are close to 100% and more than 80%, respectively. 2.3 Other chemical fields 2.3.1 Foundry binders Acrylic hydrolysates have been widely used as casting binders in casting cores. The adhesive has the characteristics of good tensile strength, good collapsibility, small gas generation and no enthalpy change, and thus is an adhesive with excellent casting properties, but the main component is hygroscopic sodium polyacrylate. Therefore, the sand core has a sharp drop in strength due to moisture absorption during the placement process. It has been reported that the acrylic binder waste can be solved by catalytic pressure hydrolysis and then cross-linking to prepare a casting binder. Acrylic fiber waste hydrolysate is also an ideal material for preparing lead foil paper composite adhesive and polymer emulsion protective rubber. Zhang Guangyan's research shows that the acrylic hydrolysate is used as a protective rubber for the synthesis of polyvinyl acetate (PVAc) emulsion. In addition to the advantages of general emulsion, it also has unique freeze-thaw stability and low viscosity. In addition, HPAN has a high initial adhesion and can also be used as a quick-stick trademark.
2.3.2 Preparation of polymer water-absorbing resin Acrylic fiber waste After hydrolysis under alkaline conditions, a cross-linking agent is added, and the obtained cross-linked polymer is precipitated, dried, pulverized and sieved to obtain a hydrazine molecular water-absorbent resin. Since the carboxylic acid group and the amide group converted into a nitrile group in the polymer are hydrophilic groups, the water absorbing resin has a high water absorption capacity. The research shows that the cross-linking formaldehyde is added to the acrylic fiber waste hydrolyzate, and the water-absorbent resin prepared by the cross-linked nitrile to the waste hydrolyzate can absorb 500g/g of distilled water, 60g/g of normal saline (0.9% NaCl), and A1C13. The cross-linking agent prepared a water-absorbing material capable of absorbing 477 g/g of pure water and 55 g/g of physiological saline, but A1C13 was used as a cross-linking agent, and the cross-linking speed was too fast, and the gel stability was poor. Ding Lunhan uses glycerin epoxy resin as a crosslinking agent to solve this problem better. The obtained water absorbing resin has high water absorption capacity, and its water absorption rate can reach 600 ~ 800g / g (pure water), physiological saline absorbs water. The rate is about 90g/g.
The water-absorbent resin prepared by hydrolyzing and re-crosslinking the waste material by the nitrile has excellent performance, and the cost is lower than that of the water-absorbent resin prepared by polymerization of monomers such as acrylic acid and acrylonitrile.
2.3.3 Dispersing agent used as coating and pigment 40% of HPAN solution is used as a wetting and dispersing agent for waterborne coatings. It has good dispersing effect on white powder, calcium carbonate, talcum powder and lithopone. The amount of pigment is 0.5%~1.5%. The dispersion effect of HPAN as dispersant is better than that of sodium pyrophosphate and sodium hexametaphosphate.
2.3.4 Preparation of printing and dyeing auxiliary acrylic fiber hydrolysate non-ionic polar group-CONH2 has strong ability to adsorb dye particles, ionic hydrophilic group-COO can combine free water molecules to reduce free water content It causes difficulty in dye migration. An inorganic salt electrolyte is added to the acrylic acid hydrolyzate, which can destroy the dispersion protection of the dye particles, and the dye particles are slightly loosely self-polymerized. Therefore, the acrylic hydrolysate is used for hot-melt dyeing of lacquer, polyester-cotton and polyester-bonded fabrics, and has good anti-migration effect, so that the uniform dyeing and deepening effect of the fabric after processing is obviously improved, and the disperse dye, vat dye and sulphur dye can be saved.
The acrylic fiber obtained by alkaline hydrolysis of acrylic fiber is cross-linked to obtain a modified acrylic fiber. Acrylic rubber and modacrylic 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% to 15% higher than that of sodium alginate except for a small number of dyes. The economic and social benefits are particularly significant, especially the denatured acrylic rubber 2.4 agricultural HPAN aqueous solution and gelatinization. The starch is mixed and stirred. After drying at 150, a seed coating agent with high water absorption and water retention can be prepared, and a soil improving agent can be used to make the crops sprout early, the emergence rate is high, and the agricultural production and income increase are promoted. HPAN is used as a clay soil improver to form agglomeration by cross-linking with clay
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