The amount of Oxidized Polyethylene in the domestic paper industry has reached 5,000 tons per year, and it is mainly high molecular weight products with a molecular weight of 3 million to 6 million. There are a large number of ether-oxygen bonds with lone pair electrons in the polyethylene oxide molecule, which is easy for water to form hydrogen bonds, which can increase the solubility of polyethylene oxide on the one hand, but lead to polyethylene oxide on the other hand. Diffusion in aqueous solution is difficult, and the dissolution rate is slow. With the increase in the molecular weight of Oxidized Polyethylene, this trend is more obvious, and it is more and more difficult to meet the requirements of high-speed paper machines and other equipment for the dissolution rate of polyethylene oxide.
At present, there are few reports in the literature on improving the dissolution rate of Oxidized Polyethylene. The Dow Company of the United States once designed a special stirring device suitable for the dissolving process of polyethylene oxide to improve the dispersion of polyethylene oxide in water, but the dissolution time of polyethylene oxide is still more than 2 hours . U.S. Patents US4029622 and US435861 have reported a method for promoting the dissolution of polyethylene oxide by using water-soluble sizing agents such as mineral oil or compounds such as potassium salts. For the dissolution process, the above method not only requires a large amount of solvent to achieve slurrying, but also leads to a decrease in the stability of the slurried polyethylene oxide, so the slurried polyethylene oxide is not suitable for long-term storage, and needs to be stored by downstream manufacturers. Completing the slurrying process increases the dissolution time and application difficulty of Oxidized Polyethylene in disguise.
In China, Zhou Weiping and others have proposed in the invention patent ZL001365537.1 a method of spraying surfactants, such as alkylphenol polyoxyethylene ether, sodium disec-octyl maleate sulfonate and other compounds. The method of mixing with polyethylene oxide to improve the dissolution rate of polyethylene oxide, but the accelerant is mostly a viscous liquid with a pungent odor and is not resistant to acid, alkali and heavy metal salts, which affects to a certain extent. Scope of application of Oxidized Polyethylene.
CN201510043867 provides a method for improving the dissolution rate of high molecular weight polyethylene oxide in order to overcome the above-mentioned defects in the prior art. The object of the present invention can be realized through the following technical solutions: adopt the following steps:
(1) adding the accelerant and polyethylene oxide to the oscillator in proportion to mix;
(2) adding the polyethylene oxide after mixing into the water by the feeder and stirring at high speed;
(3) After the polyethylene oxide is added, the stirring speed is lowered;
(4) Stop stirring when there are no obvious Oxidized Polyethylene particles in the solution, and use a rotational viscometer to test the real-time viscosity of the solution;
(5) When the fluctuation of the rotational viscometer reading within 5 minutes is less than 5% as the dissolution end point, the time when the viscosity first reaches a stable value is the dissolution time. Described accelerant is one or more of inorganic salt accelerant, alkali accelerant, hydrophilic anionic polymer surfactant or hydrophilic nonionic polymer dispersant.
Preferably, the inorganic salt accelerator is CaCl2, Ca(NO3)2, NaCl or NaNO3, the alkali accelerator is NaOH, and the hydrophilic anionic polymer surfactant has a molecular weight of 10 million ~18 million polyacrylamide, and the hydrophilic nonionic polymer dispersant is polyethylene glycol with a molecular weight of 6000-20000. The particle size of the accelerator is 100-200 meshes, and the added amount is 1wt%-10wt% of the polyethylene oxide consumption. The polyethylene oxide has a viscosity-average molecular weight of 3 million to 6 million, a particle size of 20 to 40 meshes, and a dissolution temperature of 20 to 50°C. In step (1), the oscillation frequency of the oscillator is 2-5 Hz, and the closing time is 30-120 min. The speed of high-speed stirring in step (2) is 400-600 rpm. The dissolution of polyethylene oxide can be divided into two processes: water molecules diffuse into the polyethylene oxide to form water-soluble micelles (swelling), and the micelles diffuse into the water phase to form a uniform solution. There are a large number of ether-oxygen bonds with lone pair electrons in polyethylene oxide molecules, and the ether-oxygen bonds are easy for water molecules to form hydrogen bonds during the dissolution process, which increases the solubility of polyethylene oxide on the one hand, but on the other hand. On the one hand, it reduces its diffusion rate into the water phase. Especially high molecular weight polyethylene oxide, its hydrogen bond is strong, the diffusion speed is slow, so the dissolution speed is slow.
The present invention adopts the method of improving the dissolving speed of Oxidized Polyethylene by using solid powder substances. The solid accelerant is uniformly dispersed in the polyethylene oxide powder. During the dissolving process, the accelerant can reduce the surface tension of water and weaken the polyethylene oxide. The role of hydrogen bonds between alkane and water promotes the penetration of water into polyethylene oxide particles and the diffusion of micelles into the water phase after swelling, thereby achieving the effect of improving the dissolution rate of polyethylene oxide, which is consistent with the prior art. Compared with the following advantages:
(1) The used accelerator has low chemical toxicity and no irritating odor, and has no obvious impact on the later quality of polyethylene oxide products;
(2) The accelerant used is a common papermaking additive, and the dosage is small, which has no obvious influence on the quality of papermaking products;
(3) The mixing method is a mechanical mixing method, the process is simple, and it can also be completed in one step in the drying and screening process of polyethylene oxide before leaving the factory, and there is no need to adjust the existing polyethylene oxide production process on a large scale.
(4) The adopted method can directly provide polyethylene oxide with high dissolution rate for downstream manufacturers, which is suitable for the existing dissolution process of downstream manufacturers. In step (3), the mass concentration of Oxidized Polyethylene is 0.1‰-1‰, and the stirring speed is 100-200rpm. After adding the solubilizer, the dissolution time of high molecular weight polyethylene oxide can be shortened by 20% to 50%; compared with the solution viscosity without adding the solubilizer, the viscosity change range of adding the solubilizer is within 15%.
