cDNA encoding caffeoyl CoA O-methyltransferase (CCoAOMT) from Chinese white poplar ( Populus tomentosa Carr.) was cloned by RT-PCR and sequenced. Northern analysis displayed that the CCoAOMT was expressed specifically...cDNA encoding caffeoyl CoA O-methyltransferase (CCoAOMT) from Chinese white poplar ( Populus tomentosa Carr.) was cloned by RT-PCR and sequenced. Northern analysis displayed that the CCoAOMT was expressed specifically in the developing secondary xylem and its expression was coincident with lignification. The antisense CCoAOMT cDNA was transformed into P. tremula x P. alba mediated by Agrobacterium tumefaciens ( Smith et Townsend) Conn. Transgenic plants were identified with PCR, PCR-Southern and Southern analysis. Lignin content in 5- to 6-month-old transgenic plants was measured. One of the transgenic lines had significant reduction of 17.9% in Klason lignin content as compared with that of untransformed poplar. The results demonstrate that antisense repression of CCoAOMT is an efficient way to reduce lignin content for improving pulping property in engineered trees.展开更多
Substituting bleached CTMP (BCTMP) for chemical pulps, such as bleached hardwood kraft pulp in many paper grades is in rising demand for reducing cost and improving product performance. In this paper we investigated t...Substituting bleached CTMP (BCTMP) for chemical pulps, such as bleached hardwood kraft pulp in many paper grades is in rising demand for reducing cost and improving product performance. In this paper we investigated the effect of substituting aspen BCTMP for hardwood kraft pulp (varying from 10% to 30%) on product performance of light weight coated paper. The results show that the tensile index increases and other strength properties are essentially unchanged as the substitution level increases. With the increased BCTMP substitution level, the surface roughness of base sheets increases slightly, while coating coverage of base sheets is not affected significantly. The increased BCTMP substitution results in an increase in porosity of the base sheets, but does not change the average pore diameter. Increasing BCTMP substitution level leads to a slight decrease in gloss and an increase in surface roughness of the coated paper, however the latter can be compensated by a higher nip load calendering.展开更多
In this investigation, two different grades of birch chemical mechanical (P-RC APMP) pulps and aspen market bleached kraft pulp were compared by low consistency refining of the pulps separately and in different combin...In this investigation, two different grades of birch chemical mechanical (P-RC APMP) pulps and aspen market bleached kraft pulp were compared by low consistency refining of the pulps separately and in different combinations. In addition, the separately refined pulps were also combined to compare with the pulps from the co-refined pulp blend. The results showed that in both cases there were synergistic effects between the two types of pulps: adding the birch P-RC APMP pulp to the aspen kraft pulp improved pulp properties, and the resultant pulp blends had a higher fiber bonding strength (tensile and tensile energy absorption) than the sum of weighted contributions from the individual components. Understanding this synergistic effect between chemical mechanical (P-RC APMP) and kraft pulps can help to improve their applications and performances in various papermaking processes.The results also showed that introducing, at least up to certain percentage of, the birch P-RC APMP pulp into the aspen bleached kraft pulp not only improves optical and bulk properties, but also maintains or improves tensile strength, even though the P-RC APMP pulp used has lower tensile than the kraft pulp.展开更多
Bleaching of poplar APMP with Formamidine sulphinic acid (FAS) was investigated in this paper. The effects of FAS charges, ratio of treatment on the brightness gain, color reduction and pulp strength were studied. A s...Bleaching of poplar APMP with Formamidine sulphinic acid (FAS) was investigated in this paper. The effects of FAS charges, ratio of treatment on the brightness gain, color reduction and pulp strength were studied. A single-stage FAS bleaching was optimized. Under the conditions of 10 % pulp consistency, 60 minutes time and 70℃ reaction temperature and 0.6 %, FAS (on 0.d.pulp), ratio of FAS to NaOH was 2, we produced a bleached pulp with a brightness of 62.3 %(SBD), a brightness gain of 9.2 units.展开更多
The paper is to study the TCF bleaching of high-yield chemical pulp of NS-AQ aspen(digester yield 63.7%, Kappa number 37.3, brightness 50.0%ISO, intrinsic viscosity 1,340ml/g). Under the suitable conditions(oxygen pre...The paper is to study the TCF bleaching of high-yield chemical pulp of NS-AQ aspen(digester yield 63.7%, Kappa number 37.3, brightness 50.0%ISO, intrinsic viscosity 1,340ml/g). Under the suitable conditions(oxygen pressure 0.6MPa, 85℃, 80min., NaOH 5%, MgSO4 0.3%, consistency 11%), oxygen delignification, can increase the brightness of pulp to 64.9%ISO, substantially decrease Kappa number to 9.11. Before the oxygen delignification pretreating pulp by acidic chelant(Qa)under conditions of pH 3.0, 30min, 40℃, DTPA 0.25%, consistency 15%, and after the Qa strengthening oxygen delignification by H2O2(Op, H2O2 2%)can increase the brightness of pulp to 77.1%ISO, decrease Kappa number and intrinsic viscosity to 6.36 and 984ml/g, respectively. After the Op, pretreat pulp by chelant once again(pH 6.0, 60℃, consistency 12%, other as the Qa), and following this pretreatment do bleach with 1% H2O2, namely using Qa-Op-Q-P bleaching sequence, resulting in the brightness 84.8%ISO, Kappa number 5.01, intrinsic viscosity 792ml/g, total bleaching loss 12.17% for bleached pulp.展开更多
文摘cDNA encoding caffeoyl CoA O-methyltransferase (CCoAOMT) from Chinese white poplar ( Populus tomentosa Carr.) was cloned by RT-PCR and sequenced. Northern analysis displayed that the CCoAOMT was expressed specifically in the developing secondary xylem and its expression was coincident with lignification. The antisense CCoAOMT cDNA was transformed into P. tremula x P. alba mediated by Agrobacterium tumefaciens ( Smith et Townsend) Conn. Transgenic plants were identified with PCR, PCR-Southern and Southern analysis. Lignin content in 5- to 6-month-old transgenic plants was measured. One of the transgenic lines had significant reduction of 17.9% in Klason lignin content as compared with that of untransformed poplar. The results demonstrate that antisense repression of CCoAOMT is an efficient way to reduce lignin content for improving pulping property in engineered trees.
文摘Substituting bleached CTMP (BCTMP) for chemical pulps, such as bleached hardwood kraft pulp in many paper grades is in rising demand for reducing cost and improving product performance. In this paper we investigated the effect of substituting aspen BCTMP for hardwood kraft pulp (varying from 10% to 30%) on product performance of light weight coated paper. The results show that the tensile index increases and other strength properties are essentially unchanged as the substitution level increases. With the increased BCTMP substitution level, the surface roughness of base sheets increases slightly, while coating coverage of base sheets is not affected significantly. The increased BCTMP substitution results in an increase in porosity of the base sheets, but does not change the average pore diameter. Increasing BCTMP substitution level leads to a slight decrease in gloss and an increase in surface roughness of the coated paper, however the latter can be compensated by a higher nip load calendering.
文摘In this investigation, two different grades of birch chemical mechanical (P-RC APMP) pulps and aspen market bleached kraft pulp were compared by low consistency refining of the pulps separately and in different combinations. In addition, the separately refined pulps were also combined to compare with the pulps from the co-refined pulp blend. The results showed that in both cases there were synergistic effects between the two types of pulps: adding the birch P-RC APMP pulp to the aspen kraft pulp improved pulp properties, and the resultant pulp blends had a higher fiber bonding strength (tensile and tensile energy absorption) than the sum of weighted contributions from the individual components. Understanding this synergistic effect between chemical mechanical (P-RC APMP) and kraft pulps can help to improve their applications and performances in various papermaking processes.The results also showed that introducing, at least up to certain percentage of, the birch P-RC APMP pulp into the aspen bleached kraft pulp not only improves optical and bulk properties, but also maintains or improves tensile strength, even though the P-RC APMP pulp used has lower tensile than the kraft pulp.
文摘Bleaching of poplar APMP with Formamidine sulphinic acid (FAS) was investigated in this paper. The effects of FAS charges, ratio of treatment on the brightness gain, color reduction and pulp strength were studied. A single-stage FAS bleaching was optimized. Under the conditions of 10 % pulp consistency, 60 minutes time and 70℃ reaction temperature and 0.6 %, FAS (on 0.d.pulp), ratio of FAS to NaOH was 2, we produced a bleached pulp with a brightness of 62.3 %(SBD), a brightness gain of 9.2 units.
文摘The paper is to study the TCF bleaching of high-yield chemical pulp of NS-AQ aspen(digester yield 63.7%, Kappa number 37.3, brightness 50.0%ISO, intrinsic viscosity 1,340ml/g). Under the suitable conditions(oxygen pressure 0.6MPa, 85℃, 80min., NaOH 5%, MgSO4 0.3%, consistency 11%), oxygen delignification, can increase the brightness of pulp to 64.9%ISO, substantially decrease Kappa number to 9.11. Before the oxygen delignification pretreating pulp by acidic chelant(Qa)under conditions of pH 3.0, 30min, 40℃, DTPA 0.25%, consistency 15%, and after the Qa strengthening oxygen delignification by H2O2(Op, H2O2 2%)can increase the brightness of pulp to 77.1%ISO, decrease Kappa number and intrinsic viscosity to 6.36 and 984ml/g, respectively. After the Op, pretreat pulp by chelant once again(pH 6.0, 60℃, consistency 12%, other as the Qa), and following this pretreatment do bleach with 1% H2O2, namely using Qa-Op-Q-P bleaching sequence, resulting in the brightness 84.8%ISO, Kappa number 5.01, intrinsic viscosity 792ml/g, total bleaching loss 12.17% for bleached pulp.
