Preparation of polymeric thickeners using waste acrylic fiber

Preparation of polymeric thickeners from waste acrylic fibers for chemical environmental protection Li Lizhong, Li Yonghua, Wang Min, Yan Yan, Yu Yuanzhang, Lu Xiao (Research Institute of Qilu Branch of China Petrochemical Corporation, Zibo, Shandong 255400, China) The hydrolysis temperature is 95C. The hydrolysis time of 4h hydrolysis formula is m (PAN) i (NaOH) i (H2O) =. æ°“ chain reaction temperature 95C, chain extension reaction time of about 4h thickening performance evaluation and application of different emulsion systems, using the The polymer thickener produced by the technology has excellent performance and a wide range of applications. An industrial plant with a production capacity of 1000t/a has been built.

Research has also aroused people's concern 丨3~7. However, research and development using waste acrylic fibers to make polymer thickeners have not been reported.

The research on the comprehensive utilization of waste acrylic fiber was developed, and a thick polymer thickener for polymer emulsion has been developed and a 1000t/a industrial device has been developed. The thickener product is applied in 20 factories in Jiangsu, Anhui, Shandong, and Beijing. Application, good results.

1 Test section 1.1 Main raw materials Waste Acrylic Dry Powder (drying waste) taken from Qilu Petrochemical Company Nitrile Acrylic (PAN) is one of the main varieties of synthetic fibers. By 2000, the production capacity of Chinese Acrylic Fiber had reached 600kt/a. The total amount of acrylic waste generated during the production of acrylic fiber (including waste polymer dry powder, waste plastic blocks, and waste silk, etc.) is about 1 percent of the output of acrylic fiber. In addition, at the subsequent spinning mill and product processing plant of the acrylic fiber plant, Some acrylic waste will be produced. If you add some other waste acrylic products, the total amount of acrylic waste will be very large. Because these wastes cannot be thermally decomposed and cannot be used as fuel due to their inability to degrade naturally, they are extremely detrimental to the environment. Therefore, it is necessary to carry out research on their comprehensive utilization. Since the advent of polyacrylonitrile industrial production in foreign countries, studies on the comprehensive utilization of acrylic wastes have begun. For example, developed countries such as Europe, America, and Japan mainly use acrylic waste as textile fabric sizing agents and water treatment agents. 21. Graduated from Tianjin University, China Petroleum and Chemical Corporation Qilu Branch Research Institute engineers, mainly engaged in the preparation of water-soluble polymer materials and chemical modification research.

China's research in this field since the 1960s has also made some progress. It is mainly used as an oil-field fluid loss agent, industrial waste liquid treatment agent, and soil amendments. In recent years, the use of acrylic waste to prepare polymer flocculant, high water absorbent resin, polymer antifouling agent, etc.; sodium hydroxide (industrial grade) Qilu Petrochemical Company chloralkali production; sulfuric acid (industrial grade, mass fraction 98%) Zibo City reagent factory production; chain extender and other additives (industrial grade).

1.2 Test and Analysis Method A four-necked flask equipped with a reflux condenser, a thermometer and a stirrer was charged with measured acrylic waste, sodium hydroxide, and water, respectively, to control the rate of temperature increase (gradually heating to the set hydrolysis temperature) for alkaline hydrolysis. In the reaction, ammonia gas evolves during the hydrolysis and must be absorbed. After a certain period of hydrolysis, the pH of the reaction solution is adjusted to obtain a pale yellow viscous hydrolysate solution, and then a chain extender is added to perform the molecular chain extension reaction. After reaching the prescribed reaction time, the temperature is lowered, the reaction is stopped, and after proper modulation, the material is discharged. Get polymer thickener products.

According to GB 2 Results and Discussion 2.1 Hydrolysis Process Study 2.1.1 Alkaline hydrolysis process Polyacrylonitrile fibers generally use the main monomer acrylonitrile (mass about 90%. modified monomer methyl acrylate and the third monomer itaconic acid ( Or styrene sulphonate) ternary copolymerization synthesis, is a hydrophobic polymer material, through the hydrolysis reaction can be a lot of hydrophobic cyano groups into carboxyl and amide groups and other hydrophilic groups. Hydrolysis process 131 mainly includes acid hydrolysis, pressure hydrolysis 121, catalytic hydrolysis 141 and alkali hydrolysis, because the alkali hydrolysis has no special requirements on the equipment, small investment, convenient operation, safe and reliable, and mild reaction conditions, macromolecular degradation Less, lighter colors, and thus is the most commonly used technique.

The reaction formula in the alkaline hydrolysis is as follows: When the PAN is hydrolyzed by alkali hydrolysis, the cyano group in the polymer first hydrolyzes to an amide group, and as the reaction progresses, the amide group is re-hydrolyzed to a carboxyl group.

The color of the reaction mixture first changed from milky white to yellow, then the color gradually dark reddish-brown, dark purple, and then the color of the mixture began to gradually become light reddish brown, yellow and light yellow. This is because the PAN molecule undergoes a transition state containing a C=N group during the hydrolysis process. The group is reddish-brown. Therefore, when the C=N group content of the mixture is relatively high, the color is darker and generally reddish brown. As the reaction progresses, the carboxyl content gradually increases, and the color of the mixture gradually becomes lighter, generally light yellow. At the same time, the viscosity of the mixture also appears to grow rapidly from small to large, then decreases rapidly and then increases slowly. The change in the viscosity of the hydrolysate can be explained by the fact that, as the hydrolysis proceeds, the cyano group is first hydrolyzed to an amide group. As the concentration of the water-soluble amide group increases, the viscosity of the mixture gradually increases, and the concentration of the amide group is reached. At the critical value, the water-soluble amide group and the water-insoluble cyano group in the partially hydrolyzed PAN macromolecule have a great binding effect on the water, so that the free flow is severely restricted, and the viscosity appears to be the maximum, and at this time, a large amount of release begins. Ammonia gas is evolved, and once the critical concentration is exceeded, the binding effect of the two groups on water decreases sharply; with the progress of the hydrolysis reaction, the concentration of the amide group gradually increases, the amide group is further hydrolyzed to a carboxyl group, and cyanide 2 is hydrolyzed. Effects of Conditions and Hydrolysis Formulations on Hydrolysis Products 2.1 Effects of Hydrolysis Temperature and Hydrolysis Time on Hydrolysis Products The effects of hydrolysis temperature and hydrolysis time on the hydrolysates are shown in Table 1 and Table 2. It can be seen from Table 1 and Table 2 that the hydrolysis formula can be maintained. When unchanged, the higher the hydrolysis temperature or the longer the hydrolysis time, the lighter the color of the resulting hydrolysate, the smaller the ammonia odor and the greater the viscosity. In order to obtain a completely hydrolyzed product, the hydrolysis temperature is generally selected to be 95 to 100C; however, the concentration I of the hydrolyzed antisense group becomes smaller and smaller and the viscosity increases slowly. Hydrolysis lish should go! After 3Al production, the color and viscosity of the product do not change slowly, and the hydrolysis time is too long to easily cause the polymer to maintain its hydrolysis temperature and hydrolysis time under strong alkaline conditions. Therefore, the hydrolysis time was chosen to be 3 2.2 The influence of the hydrolyzed formula on the hydrolysate The results of the hydrolysate were shown in Table 3 and Table 4. Table 1 Effect of hydrolysis temperature on the hydrolyzed product Hydrolysis temperature/°C Product properties Reaction endpoint Phenomenon Amount of ammonia evolution A small amount of ammonia evolved without ammonia gas released product color reddish brown yellow brown light yellow product state with suspended particles homogeneous solution uniform transparent product viscosity / (Pas) Note: the hydrolysis time is 4h; the hydrolysis formula is the hydrolyzed product of Table 2 hydrolysis time Hydrolysis time/h Product properties Reaction End point Phenomenon Amount of ammonia A small amount of ammonia evolved Ammonia evolved No ammonia released Product color Reddish-brown Yellow Light yellow Product State Suspended Particulate Uniform solution Uniform clear Product viscosity / (Pas) Table 3m (PAN)/m (NaOH) Effects on hydrolysates Wide-characteristics Reaction End point Phenomenon Amount of ammonia A small amount of ammonia evolved Ammonia evolved No ammonia released Product color Yellow-brown Yellow Light yellow Product State Suspended Particles Uniform Solution Uniform Clear Product Viscosity / (Pas) Table 4m (PAN)/m(H2O) Effect on Hydrolysis Product Wide-Band Properties Reaction Endpoint Phenomenon Amount of Ammonia Emission Color yellow light yellow Product state Uniform solution Uniform clear product Viscosity / (Pas) Note: The hydrolysis temperature is 95100 ° [:; The hydrolysis time is 4h; After 6, the production or m (H2) / m (PAN) is larger, the hydrolysate The lighter the color, the color and viscosity of the material no longer change; after m(H2O)/m(PAN) reaches 5, the degree of hydrolysis and product properties change little. Therefore, m(NaOHVm(PAN) is determined as 2.2 molecular chain extension reactions. Commonly used solution-type synthetic polymer thickeners are mainly aqueous solutions of medium molecular weight sodium polyacrylates. In terms of thickening of emulsions, generally speaking, The thicker the thicker solution viscosity, the better the thickening effect.According to the optimization of the hydrolysis process and formula, the prepared hydrolysate (20% solids mass fraction) viscosity of 2 ~ 4Pas can not meet the thickening requirements of the emulsion The need for thickening, low material consumption, and high stability is due to the relative molecular weight of waste acrylic fiber produced by the dry acrylic fiber plant of approximately 30,000, and the relative molecular mass of the hydrolyzed product is still less than 100,000, which is used as an emulsion thickener. The relative molecular mass of the synthetic sodium polyacrylate is generally several hundred thousand, so it is necessary to carry out the chain extension reaction on the hydrolyzate to increase its relative molecular mass.

A random copolymer of various functional groups such as a chain extender is selected, and thus the chain extender may be a plurality of low-molecular or high-molecular compounds having a bi- or multi-functionality capable of undergoing a bonding reaction with the above groups. It should be said that divalent or polyvalent metal ions can also be used, but it is not suitable to form ion pairs because the double polyvalent metal ions react with the negative charges on the polymer chains to form ion pairs at a very high speed and are not uniform and easy to form insoluble gels. Used as a chain extender. Organic polyols, however, cannot undergo esterification condensation reactions with carboxyl groups in aqueous solutions, nor can they be used as chain extenders for hydrolysates. After a lot of experimental research, the chain extender suitable for chain extension reaction of aqueous solution of hydrolysate was screened out. During the molecular chain extension reaction, the chain extender reacts with the functional group in the hydrolysate to couple two or more macromolecules to each other, resulting in an increase in the relative molecular mass of the product and an increase in the viscosity of the hydrolysate solution. With a suitable chain extender, the relative molecular mass and chain extension rate after product chain extension can be controlled and adjusted very easily to obtain a series of polymer thickener products suitable for different applications.

2 Effect of Chain Extension Reaction Time on Product Viscosity The effect of reaction time on product viscosity is shown in the table below. It can be seen that as the reaction time is extended, the chain extension reaction proceeds at a substantially constant rate, and the viscosity of the product gradually increases. After the reaction time reaches about 4 to 5 hours, the reaction rate gradually decreases or even completely stops. The viscosity remains essentially unchanged. This is because the relationship between the viscosity of the hydrolyzed product at the reaction temperature and the reaction time varies with the effect of the temperature of the chain extender and 2.2.3 chain extension reaction on the product viscosity. It can be seen that the reaction temperature has a significant effect on the increase of the viscosity of the product, the higher the reaction temperature, the faster the viscosity growth; and the lower the reaction temperature, the slower the viscosity growth. Therefore, increasing the reaction temperature helps to speed up the reaction, shorten the reaction cycle, and increase production efficiency.

A thickening effect evaluation test was conducted using commercially available thickeners of sodium polyacrylate aqueous solution, QHT-01 and QHT-02, respectively. The main technical indicators of self-made thickeners and commercial thickeners are basically the same. The solids mass fraction in the four thickeners is (20±1)%, and the pH is 7~8, among which QHT-01 and commodity general type. The viscosity of the thickeners are all 8-02 and the sizing reaction in the commercial hydrolysate (relative splitting of the product solution, high-efficiency thickening agent viscosity, several sodium thickeners compared to the styrene-acrylic emulsion The effect of thickening is obviously better than that of the latter (including normal type and high efficiency type) QHT-02 thickener, and it shows that two kinds of homemade thickeners are also good for ethylene vinyl acetate emulsion and styrene-butadiene emulsion. Thickening effect Therefore, the thickener synthesized by this process can thicken a variety of emulsions and is an excellent thickener for a wide range of applications.

At present, the two brand products produced by the 1000t/a industrial device built using this process have been widely used in more than two dozen carpet adhesives and building material adhesives in Jiangsu, Anhui, Henan, and Shandong, with good results.

3 Conclusion The waste hydrolyzate of waste acrylic fiber is an aqueous solution of a random copolymer containing various hydrophilic groups such as sodium carboxylate groups and amide groups. Polymer macromolecular thickeners with excellent properties can be obtained through molecular chain extension reaction. The hydrolysis process conditions were as follows: hydrolysis temperature 95C, hydrolysis time 4h, and hydrolysis formula m (PAN)m (NaOHM (H2O) = D: 65: The molecular hydrolysis of 95 C in the hydrolysis product obtained under the above conditions. 4h can be polymer thickeners that meet the thickening requirements of emulsions.Adopting selected chain extenders and controlling the reaction temperature and time for molecular chain extension reaction, can adjust the viscosity of thickener products to obtain series suitable for different application fields. Thickener: The use of waste acrylic fiber to prepare high-value polymer thickeners is worth promoting.