Re pulping of the hottest wet strong paper I

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Re pulping of wet strength paper (I)

for paper mills, waste paper fiber is an important source of raw materials, which has economic advantages. Paper mills can make use of the mixing of raw fiber and secondary fiber, as well as the reuse of damaged paper and cut edges, so as to reduce the cost of raw materials

due to the increased demand for secondary fibers, paper made from permanent wet strength resins such as polyamide polyamine epichlorohydrin has become an important fiber raw material. However, these papers, especially unbleached paper and waste corrugated box (OCC), are difficult to pulping

sodium hypochlorite is generally used in the re pulping of bleached wet strength paper. Because it cannot completely re pulping unbleached wet strength paper and environmental regulations require paper mills to reduce the emission of Absorbable Organic Halogen (AOX) wastewater, the use of sodium hypochlorite is limited

it is reported that persulfate (m2s2o8) and potassium persulfate (the active ingredient in trimer salt so4.k2so4 is KHSO5) are effective reagents for bleaching wet strength paper for pulping. However, under the conventional neutral or alkaline pulping process conditions, the effect of this reagent on OCC wet strength paper and unbleached paper is worse

we do not expect the side reaction between oxidant and lignin to make unbleached paper difficult to pulping. The oxidant decomposed into free radicals can extract hydrogen from lignin, form inactive free radicals, and leave the wet strong resin that has not been oxidized to the greatest extent. Excessive oxidant can overcome the side reaction. However, it is expensive, inefficient and harmful to fibers

after further study on the chemical properties of organic and inorganic peroxides, it is found that they are very important in the oxidation-reduction and polymerization processes. Under appropriate reaction conditions, oxidants are activated by metals or form free radicals through thermal decomposition

a large number of reactivated free radicals can extract hydrogen or other atoms from saturated and unsaturated reactants, add them to unsaturated reactants, combine or polymerize with other free radicals to form dimers, or carry out redox reactions, including electron and ligand transfer processes. Reactants such as polyhexylidene diamide (nylon 6.6), a linear polyamide similar to the main chain of PAE, are oxidized by H2O2 ions

it is reported that the oxidant catalyzed by metal ligands has a nucleophilic reaction with amine on the oxidized reactant through oxidation reaction, and has formed a long-term friendly cooperative relationship with well-known domestic universities, enterprises and quality inspection centers to split the polypeptide. The reaction between hydroxyl groups in hydrogen peroxide and model compounds representing phenol and non phenol nuclei in lignin was found to depend on the pH value of the reaction

the above research shows that under the conditions conducive to free radical wet strength resin reaction rather than free radical lignin reaction, free radicals can effectively re pulping unbleached wet strength paper. In this study, the re pulping of wet strength paper was tested with inorganic oxidants. PH value, time, temperature, re wetting agent, shear force and reagent concentration all have effects on re pulping

the re pulped pulp is screened with a vibrating screen with a gap of 0.15mm, and its re pulping degree is quantitatively determined. In this study, the dry tensile strength of the hand-made sheet made by re pulping was compared with that of the base paper. In addition, the performance of the new re pulping process was compared with that of alkaline unbleached vermicelli board in different paper mills. High availability

1 experiment

1.1 re pulping process

1.1.1 alkaline process

cut the industrial paper into 1-inch fragments, dilute it to a concentration of 2% with tap water containing less than 0.15ppm iron and 0.30ppm copper respectively, and adjust phcfrp to more than 80% to 11 with NaOH solution before heating to the required reaction temperature (70 ~ 90 ℃), while gently stirring the pulp. If it is necessary to add oxidant, then add NaOH to adjust the pH value to 11. Then, mix the pulp at the reaction temperature for 60min, send it to the fiber separator, and shear it at 3000r/min for several minutes. Use a vibrating screen with a gap of 0.15mm to screen for 20min, and the screen residue (non digested component) is dried at 105 ℃

1.1.2 two stage pH process

cut the industrial paper into 1-inch fragments, and dilute it to 2% with tap water with iron and copper ion contents less than 0.15ppm and 0.30ppm respectively. Re wetting agent can be selectively added. Before heating the required reaction temperature (i.e. 70 ~ 90 ℃), adjust the pH value with inorganic acid in the range of 3 ~ 7, and gently stir at the same time

add oxidant and mix at least 30min at the reaction temperature. Then adjust the pH value to 11 with NaOH solution, and mix at least 30min at the reaction temperature. The pulp mixture is sent to the rod fiber shredder and sheared at 3000r/min for several minutes. Use a vibrating screen with a gap of 0.15mm to screen for 20min, obtain a paper sample, and dry the screen residue at 105 ℃. (to be continued)

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