Study On Modification Technology And Performance Of Used Paper

In recent years,with the supply and demand of paper in many industries,used paper recycling has become a topic that can not be ignored.As of 2021,China’s waste paper recycling rate is still far lower than that of developed countries,so it is urgent to improve the recycling rate of waste paper,one way to improve the recycling rate of waste paper is to increase the added value of waste paper.In this paper,superhydrophilic waste paper and superhydrophobic waste paper were prepared by using waste non-deinked A4 printing paper as raw material and surface modification of waste paper by impregnation method which is easy to realize and low cost.In addition,a multifunctional recycled paper was prepared by fiber modification of waste paper by suction filtration method and freeze-drying method which are also low cost and green environmental protection:（1）The process of preparing super-hydrophilic paper from waste paper was studied,which was mainly realized by orthogonal test.ZnO emulsion and nano-SiO₂-anhydrous ethanol solution were compounded,and super-hydrophilic paper was prepared by impregnation method.Different factors of L₉（3⁴）orthogonal test were set to regulate and control,and the optimal scheme was obtained after analyzing the orthogonal test data.Subsequently,different instruments were used to characterize the surface properties of superhydrophilic paper under the optimal process of orthogonal test.The results showed that ZnO and nano-SiO₂ could adhere to the paper surface stably.The surface roughness of the modified paper is larger.The superhydrophilic surface was tested by oil,and the results showed that the surface had superoleophilic properties.（2）The process of preparing superhydrophobic paper from waste paper was studied.The secondary impregnation method was used to make the surface of the paper undergo a metathesis reaction to form a layer of precipitation,and then the low surface energy substance stearic acid（SA）was used for superhydrophobic modification to obtain superhydrophobic paper.The superhydrophobic properties of paper were determined by orthogonal test,and the superhydrophobic modification process of paper was optimized by range analysis to obtain the best process.The performance of the modified superhydrophobic paper was characterized by instruments.The results show that the rough structure is stably attached to the surface of the paper;the treated paper surface has good roughness;experiments show that the modified superhydrophobic paper has good self-cleaning and antifouling properties.Different oils were used to test the lipophilicity of the paper surface,and it was concluded that the superhydrophobic paper had excellent lipophilicity and could achieve superoleophilic effect.（3）The waste A4 paper is broken,and the drugs which are beneficial to forming and flame retardant are added to the fiber to reorganize the waste paper by suction filtration method,and then freeze-dried.The strength of the formed paper is better than that of the unmodified waste paper.Subsequently,the single factor test was used to optimize the strength and flame retardancy of the molding,and the optimal performance of the recycled paper was obtained.Then the superhydrophobic modification was carried out by the method in（2）,and the performance of the fiber modified paper was compared with the superhydrophobic paper after surface modification under the same conditions.The results showed that the recycled paper after fiber modification was superior to the surface modified paper in terms of mechanical properties,surface structure stability and roughness.At the same time,the recycled paper also has flame retardancy,which can prevent the spread of flame for a period of time.It has great application prospects and improves the added value of the paper.