Studies On A New Nonionic Microparticle Retention System And Its Retention Mechanism

In current papermaking industry, for saving fiber materials and fresh-water, a great deal of high-yield pulps, deinking pulps and coating brakes were used, and the close degree of white water circulation was enhanced. Which made more and more dissolved and colloidal substances (DCS) accumulate in wet end of paper machine and these substances will damage stability of wet end operation system. Therefore, not only the applicable areas and effects of cationic microparticle retention system were restricted, but also its drainage and retention efficiencies cannot be exerted fully. In addition, the efficiencies of other additives will be likely affected in the wet end. In order to solve these questiones, it is planed to be developed that a new nonionic microparticle retention system to make up the shortages of the existing retention system. And the flocculation mechanism was investigated too.Nonionic microparticle retention system of PEO/silicate was investigated in this paper, including: (1) Study of PEO/silicate microparticle retention system; (2) Influencing factors of PEO/attapulgite microparticle retention system; (3) Research of attapulgite modification; (4) Research of flocculation mechanism of PEO/silicate microparticle retention system.Many results are obtained through analysis and discussing of test data. The main results are as follows:1 .Attapulgite and Li-bentonite are more suitable for building retention system with PEO than other inorganic clays. When the dosage of attapulgite was 4% and PEO was 0.01%, they had better drainage efficiency. PEO/attapulgite retention system had good retention efficiencies on Kaolin clay, grounded calcium carbonate (GCC) and talc. And talc is best of all. When its dosage was 0.5%, Li-bentonite could be built better retention system with PEO, increasing paper's brightness somewhat.2.The effects of PEO/attapulgite retention system on physical performances are: tensile strength of paper sheets declined; brightness decreased 1-2%; when talc dosage was 25%, opacity was increased about 5%; And there is no effect of PEO dosage on formation.3.The PEO/attapulgite retention system is superior to the PEO/Li-bentonite retention system, and is superior to the Hydrocol retention system too, compared from the same drainage and retention effect, and product cost etc.4.The effects of many factors in the wet end on drainage and retention of PEO/attapulgitesystem: During the scope of 2-12, pH has no effect on drainage, and retention ratio lower in acidic conditions and higher in neutral or alkaline conditions. There were some improvement on slurry's drainage and some impairment on retention efficiency for the existence of inorganic salts. Lignosulphonate had no effect on drainage and made retention ratio decrease 5-8%; lignosulphonate and xylan had no effect on drainage and made retention ratio decrease a little.5 .Attapulgite could be modified by intercalation. And modified attapulgite dosage was decreased from 4% to 1.5%. Slurry's drainage was improved by PEO and modified attapulgite. Furthermore, the clay intercalated with formaldehyde first is better than that intercalated with phenol first. But the modified attapulgite had strongly effect on paper's brightness.6.The retention mechanism of PEO, attapulgite or Li-bentonite and fibers is that PEO and intercalary ions of clay, e.g. Li+, Na+, Ca2+, intercalated and formed association complex. This complex has gel property and better shear-resistance. And it adsorbed onto the surfaces of fibers and fines to form floes. These floes had good shear-resistance too. Therefore, the PEO/attapulgite, PEO/Li-bentonite retention system had good performances of drainage and retention aid. Summing up all conclusions above, this nonionic retention system belongs to microparticle retention system.