The Preparation and Application of Ring Crush Strengthening Agents for Corrugating Base Paper
|School||Tianjin University of Science and Technology|
|Course||Pulp and Paper Engineering|
|Keywords||corrugating base paper ring crush strengthening agent cationic starch cationic polyacrylamide emulsion-type strengthening agent surface sizing|
As known to all, the ring crush test (RCT) strength properties of corrugated mediums have the tendency to be decreased due to the extensive use of secondary fibers, so it is critical to improve this property effectively to meet the requirement of related paper mills.Many manufacturers try to improve ring crush strength by using physical methods, such as selecting good fiber raw materials and adjusting beating conditions, optiming process parameters, maintaining board thickness and fines content, and adjusting moisture content in the boards. Although achieved some results, it often result in a significant increase in production costs. But chemical additives can improve the ring crush strength of the papers effectively.In this study, cationic starch (CS), solution polymerized cationic polyacrylamide (CPAM) and novel emulsion-type ring crush strengthening agents (KLZ-15) were prepared in the laboratory. Their strengthening performance were compared under different additive/pulp contact time, additive dosages, wet-press pressures and conductivity, using old corrugated container recycled pulp as the raw material to be strengthened. The paper also studied the drainage capacity of agents and the effect of ring crush strength of emulsion-type strengthening by pretreating the OCC waste pulp with a polyamine fixing agent.In addition, a styrene-acrylate copolymer surface sizing agent (K-1) was also prepared in the laboratory. Then the strengthening performance and size resistance were discussed when surface sizing agent K-1, CS and CPAM were applied to the surface sizing of corrugating base paper.The result showed that:CPAM of different molecular weight and charge density can be synthesized by controlling the dosage of initiator. When the dosage of initiator was NaHSO30.50%, K2S2O80.25%(relative to the monomer), a CPAM with molecular weight of0.5million could be obtained, and its effect of ring crush strengthening was relatively good.Under different conditions of additive/pulp contact time, additive dosage, wet-press pressure and conductivity, the ring crush and other strength properties rised after adding the strengthening agents, the effects were followed by KLZ-15>CPAM>CS. The drainage improving capacity of the agents were CPAM>CS>KLZ-15. In addition, the effect of ring crush strength of the emulsion-type strengthening agent was improved by pretreating the OCC waste pulp with the polyamine fixing agent.Then cationic starches with different degrees of substitution (DS) and CPAM with different molecular weights were applied by surface sizing method with oxidized starch on the corrugated basepaper; Ring crush index and tensile index were improved and the result showed that the strength effect of CS with DS of0.03is better than those with DS of0.22and0.7, and CPAM with molecular weight of0.5million was better than CPAM with molecular weight of1million. When the CS and CPAM were compared with surface sizing agent K-1(also by surface sizing with oxidized starch), the ring crush index, tensile index and size resistance were all improved, with the ring crush index in the order of CPAM>CS> K-1when dosage of agent was less than3kg/t of paper, CS>CPAM> K-1when dosage of agent was more than3kg/t of paper, the influence of tensile index in the order of CPAM>CS> K-1, and the influence of sizing in the order of K-1>CPAM>CS.