Application Of The Drainage Aid Systems In The Manufacturing Of Fiber Gasket Materials

To ensure the quality stability of fiber gasket materials and the smooth operation of the manufacturing process, control of stock drainage on the wire is critically important. Application of drainage aids is an effective way to improve the drainage, but it is also prone to cause excessive stock flocculation which may adversely impact the formation and hence the quality of the materials produced. As the result, development of drainage aid systems suitable for the manufacturing process of fiber gasket materials becomes a technical challenge because both drainage and formation must be considered. In this thesis, various evaluation methods for formation were first studied. Then, the impacts of several drainage aid systems including APAM, CPAM, Am PAM, PAE-APAM, CPAM-bentonite and PEO-Aids systems on drainage performance and formation of gasket materials was evaluated. Finally, the application technology of CPAM- bentonite micro-particulate system which was showed to have the best balanced effect was optimized.The result showed that fractal dimension could to some extent reflect the degree of stock flocculation and hence the formation. But the value difference is small so the sensitivity is low. Besides, the tightness of flocs was not reflected in.The formation of sheet materials was analyzed using computer technology through the application of different methods of calculation. It was found that the analytical results from calculation methods of histogram, standard formation index, and gradient index coincided well with the results from visual assessment. Among these methods, the method of gradient index takes into consideration both the changing rate as well as the degree of deviation of local basis weight and hence is able to reflect formation more scientifically and be more sensitive to formation differences. The method of gradient index is therefore adopted in the following studies in the screening and optimization of drainage aid systems.It was found that APAM, CPAM, Am PAM, PAE-APAM and CPAM-bentonite micro-particulate system all could to varying degrees improve the stock drainage of gasket materials, while PAE-APAM system could most significantly improve the drainage but also damaged the formation most seriously. Results also showed that CPAM-bentonite micro-particulate system had the best combined effect in term of both drainage and formation. On the other hand, it was also found that the PEO-bentonite micro-particulate system actually hurt the drainage and the PEO-calcium ligno-sulfonate system had little impact on the drainage when applied in the stock of gasket materials.The addition rate and the weight ratio between CPAM and bentonite were optimized for the application. It was found that the optimal ratio of bentonite : CPAM is 5: 1, and the dosage of CPAM should not exceed 0.03% in order to obtain the best balance between drainage and formation. With the increase of stirring speed after adding CPAM, the drainage performance of CPAM-bentonite system decreased. It was also found that for the stock system, when the p H value was between 4.5 and 9.5, the conductivity was between 750 μS/cm and 5000 μS/cm, or the cationic demand was below 30 μeq/L, the CPAM-bentonite drainage aid system had always performed well.