METHOD FOR PRODUCING ACETATE GRADE DISSOLVING PULP FROM POPLAR RESIDUAL SLABS

Abstract

The disclosure relates to the technical field of dissolving pulp preparation, and particularly relates to a method for producing acetate grade dissolving pulp utilizing poplar residual slabs. The method comprises the following steps: adding an auxiliary agent for prehydrolysis, performing a Soda/AQ cooking I segment, performing a Soda/AQ cooking II segment, performing OpD.sub.QE.sub.PP bleaching and performing enzyme coprocessing, thereby preparing high-purity high-reactivity poplar residual slab acetate grade dissolving pulp. In the method, used chemicals are clean and environmental friendly, and production process is clean.

Claims

1. A method for producing acetate grade dissolving pulp utilizing poplar residual slabs, comprising: (1) adding an auxiliary agent for prehydrolysis: a liquid ratio is 1:(410), the addition amount of a hydrolysis auxiliary agent is 0.12.0% of the mass of oven dry poplar residual slab, a hydrolysis temperature is 80170 C., preservation time is 10180 minutes, the hydrolysis auxiliary agent is a mixture obtained by mixing sodium borate, magnesium sulfate, nonylphenol polyoxyethylene ether phosphate and tetrasodium iminodisuccinate in a mass ratio of 1:1:1:1; (2) performing a Soda/AQ cooking I segment; (3) performing a Soda/AQ cooking II segment; (4) performing O.sub.pD.sub.QE.sub.PP bleaching; and (5) performing enzyme coprocessing: the concentration of pulp is 210%, the temperature is 3050 C., treatment time is 60 min, pH=4.07.0, the amount of polyaspartic acid is 0.01%1.0% of the mass of oven dry pulp, the amount of OP-13 is 0.0010.01% of the mass of oven dry pulp, the amount of OP-15 is 0.0010.01% of the mass of oven dry pulp, the amount of endoglucanase is 0.10.6 IU/gpulp, the amount of xylanase is 24 XU/gpulp, and the amount of pectase is 0.110 IU/gpulp.

2. The method according to claim 1, wherein, the process conditions of the Soda/AQ cooking I segment are as follows: the amount of alkali is 515% of the mass of oven dry pulp based on Na.sub.2O, a liquid ratio is 1:(38), the amount of magnesium hydroxide is 0.5% of the mass of oven dry pulp, the amount of sodium sulfite is 1.010.0% of the mass of oven dry pulp, the amount of AQ is 0.05% of the mass of oven dry pulp, the temperature is 80120 C., and preservation time is 10180 minutes.

3. The method according to claim 1, wherein, the process conditions of the Soda/AQ cooking II segment are as follows: the amount of alkali is 525% of the mass of oven dry pulp based on Na.sub.2O, the amount of magnesium hydroxide is 0.5% of the mass of oven dry pulp, the amount of sodium sulfite is 1.010.0% of the mass of oven dry pulp, a liquid ratio is 1:(310), the amount of AQ is 0.05% of the mass of oven dry pulp, the temperature is 140180 C., and preservation time is 10240 minutes.

4. The method according to claim 1, wherein, the process conditions of O.sub.pD.sub.QE.sub.PP bleaching are as follows: the oxygen pressure of O.sub.p bleaching is 0.40.6 Mpa, the concentration of pulp is 10%, the amount of MgSO.sub.4 is 0.6% of the mass of oven dry pulp, the amount of NaOH is 1.03.0% of the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is 0.53.0% of the mass of oven dry pulp, the temperature is 70110 C., and preservation time is 60 min.

5. The method according to claim 1, wherein, the process conditions of O.sub.pD.sub.QE.sub.PP bleaching are as follows: the reaction time of Q.sub.D bleaching process is 10120 minutes, T=302 C., the concentration of pulp is 28%, pH=13, the amount of sodium chlorite is 0.26.0% of the mass of oven dry pulp, and the amount of IDS is 0.011.0% of the mass of oven dry pulp.

6. The method according to claim 1, wherein, the process conditions of O.sub.pD.sub.QE.sub.PP bleaching are as follows: the reaction time of the E.sub.p extraction process is 30180 min, the amount of MgSO.sub.4is 1.05.0% of the mass of oven dry pulp, the amount of NaOH is 0.55.0% of the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is 1.05.0% of the mass of oven dry pulp, the amount of IDS is 0.011.0% of the mass of oven dry pulp, the concentration of pulp is 8%, and the temperature is 7095 C.

7. The method according to claim 1, wherein, the process conditions of O.sub.pD.sub.QE.sub.PP bleaching are as follows: the reaction time of P bleaching is 60180 min, the amount of MgSO.sub.4 is 0.5% of the mass of oven dry pulp, the amount of NaOH is 0.4% of the mass of oven dry pulp, the amount of NaAC is 0.4% of the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is 1.05.0% of the mass of oven dry pulp, the concentration of pulp is 10%, and the temperature is 8095 C.

8. The method according to claim 1, comprising the following steps: (1) adding an auxiliary agent for prehydrolysis: a liquid ratio is 1:6, the addition amount of the auxiliary agent is 0.4% of the mass of oven dry pulp, the temperature is 160 C., preservation time is 60 minutes; (2) performing a Soda/AQ cooking I segment: the amount of alkali is 5% of the mass of oven dry pulp, a liquid ratio is 1:4, the amount of magnesium hydroxide is 0.5% of the mass of absolutely dry pulp, the amount of sodium sulfite is 5.0% of the mass of oven dry pulp, the amount of AQ is 0.05% of the mass of oven dry pulp, T.sub.max=100 C.2 C., and preservation time is 60 minutes; (3) performing a Soda/AQ cooking II segment: the amount of alkali is 18% of the mass of oven dry pulp, the amount of magnesium hydroxide is 0.5% of the mass of oven dry pulp, the amount of sodium sulfite is 3.0% of the mass of oven dry pulp, a liquid ratio is 1:7, the amount of AQ is 0.05% of the mass of oven dry pulp, the maximum temperature is 160 C., and preservation time is 120 minutes; (4) performing O.sub.pD.sub.QE.sub.PP bleaching: the oxygen pressure of O.sub.P bleaching is 0.5 Mpa, the concentration of pulp is 10%, the amount of MgSO.sub.4 is 0.6% of the mass of oven dry pulp, the amount of NaOH is 2.0% of the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is 1.0% of the mass of oven dry pulp, the temperature is 95 C., and preservation time is 60 min; the reaction time of the Q.sub.D bleaching process is 60 minutes, T=302 C., the concentration of pulp is 4.0%, pH=1.5, the amount of sodium chlorite is 3.0% of the mass of oven dry pulp, and the amount of IDS is 0.05% of the mass of oven dry pulp; the reaction time of the E.sub.p extraction process is 90 min, the amount of MgSO.sub.4 is 0.5% of the mass of oven dry pulp, the amount of NaOH is 3.0% of the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is 2.0% of the mass of oven dry pulp, the amount of IDS is 0.05% of the mass of oven dry pulp, the concentration of pulp is 8%, and the temperature is 85 C.; the reaction time of P bleaching is 120 min, the amount of MgSO.sub.4 is 0.5% of the mass of oven dry pulp, the amount of NaOH is 0.4% of the mass of oven dry pulp, the amount of NaAC is 0.4% of the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is 3.0% of the mass of oven dry pulp, the concentration of pulp is 10%, and the temperature is 90 C.; and (5) performing enzyme coprocessing: the concentration of pulp is 5%, the temperature is 40 C., treatment time is 60 min, pH=5.0, the amount of polyaspartic acid is 0.05% of the mass of oven dry pulp, the amount of OP-13 is 0.005% of the mass of oven dry pulp, the amount of OP-15 is 0.005% of the mass of oven dry pulp, the amount of endoglucanase is 0.2 IU/gpulp, the amount of xylanase is 3 XU/gpulp, and the amount of pectase is 3 IU/gpulp.

9. The method according to claim 1, wherein, in the step (1), the used poplar residual slab is 1030 mm in length, the content of pentosan is 22.324.3%, and the content of -cellulose is 43.045.0%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a process flowchart of acetate grade dissolving pulp produced by using poplar residual slab.

DESCRIPTION OF THE EMBODIMENTS

[0026] In order to better understand the disclosure, the disclosure will be further described in combination with specific examples next.

[0027] In the following examples, a hydrolysis auxiliary agent is a mixture obtained by mixing sodium borate, magnesium sulfate, nonylphenol polyoxyethylene ether phosphate and tetrasodium iminodisuccinate in a mass ratio of 1:1:1:1.

[0028] Percentage contents of materials used in various process stages are all percentage contents accounting for their oven dry pulp mass.

Example 1

[0029] A prehydrolysis with addition of an auxiliary agent-Soda/AQ segmented cooking-O.sub.pD.sub.QE.sub.PP-enzyme coprocessing process is adopted to treat a poplar residual slab raw material: 500 g of poplar residual slab chips from a factory were taken, with a length of 1030 mm, pentosan content of 24.3% and -cellulose content of 43.0%.

[0030] The process conditions of prehydrolysis with addition of an auxiliary agent are as follows: a liquid ratio is 1:6, the auxiliary agent is 0.4%, the maximum temperature is 160 C., preservation time is 60 minutes, the content of pentosan after hydrolysis is 8.6%, and the hydrolysis yield is 80%.

[0031] The process conditions of a Soda/AQ cooking I segment are as follows: the amount of alkali is 5%, a liquid ratio is 1:4, magnesium hydroxide is 0.5%, sodium sulfite is 5.0%, the amount of AQ is 0.05%, T.sub.max=100 C.2 C., and preservation time is 60 minutes.

[0032] The process conditions of a Soda/AQ cooking II segment are as follows: the amount of alkali is 18%, magnesium hydroxide is 0.5%, sodium sulfite is 3.0%, a liquid ratio is 1:7, the amount of AQ is 0.05%, the maximum temperature is 160 C., and preservation time is 120 minutes.

[0033] The oxygen pressure of O.sub.P bleaching is 0.5 Mpa, the concentration of pulp is 10%, MgSO.sub.4 is 0.6%, NaOH is 2.0%, H.sub.2O.sub.2 is 1.0%, the temperature is 95 C., and preservation time is 60 min.

[0034] The reaction time of the Q.sub.D bleaching process is 60 minutes, T=302 C., the concentration of pulp is 4.0%, pH=1.5, the amount of sodium chlorite is 3.0%, and the amount of IDS is 0.05%.

[0035] The reaction time of the E.sub.p extraction process is 90 min, MgSO.sub.4 is 0.5%, NaOH is 3.0%, H.sub.2O.sub.2 is 2.0%, the amount of IDS is 0.05%, the concentration of pulp is 8%, and the temperature is 85 C.

[0036] The reaction time of P bleaching is 120 min, MgSO.sub.4 is 0.5%, NaOH is 0.4%, NaAC is 0.4%, H.sub.2O.sub.2 is 3.0%, the concentration of pulp is 10%, and the temperature is 90 C.

[0037] The conditions of enzyme coprocessing are as follows: the concentration of pulp is 5%, the temperature is 40 C., treatment time is 60 min, pH=5.0, the amount of polyaspartic acid is 0.05%, the amount of OP-13 is 0.005%, the amount of OP-15 is 0.005%, the amount of endoglucanase is 0.2 IU/gpulp, the amount of xylanase is 3 XU/gpulp, and the amount of pectase is 3 IU/gpulp.

[0038] The obtained poplar residual slab acetate grade dissolving pulp has -cellulose content of 97%, pentosan content of 2.6%, a degree of polymerization of 1250, a brightness of 89% ISO, an ash content of 0.01%, DCM extract content of 0.03% and an acetifying reaction value (PV value) of 800.

[0039] The poplar residual slab acetate grade dissolving pulp is good in various detection indexes, and can be used for producing a high-grade cellulose acetate product.

Example 2

[0040] A prehydrolysis with addition of an auxiliary agent-Soda/AQ segmented cooking-O.sub.pD.sub.QE.sub.PP-enzyme coprocessing process is adopted to treat a poplar residual slab raw material, the taken poplar residual slab has a pentosan content of 22.3% and a -cellulose content of 45.0%, and the process conditions are the same as those in Example 1. The obtained poplar residual slab acetate grade dissolving pulp has -cellulose content of 97%, pentosan content of 2.2%, a degree of polymerization of 1280, a brightness of 90% ISO, ash content of 0.01%, a DCM extract content of 0.02% and an acetifying reaction value (PV value) of 820.

[0041] The poplar residual slab acetate grade dissolving pulp is good in various detection indexes, and can be used for producing a high-grade cellulose acetate product.

Example 3

[0042] A prehydrolysis with addition of an auxiliary agent-Soda/AQ segmented cooking-O.sub.pD.sub.QE.sub.PP-enzyme coprocessing process is adopted to treat a poplar residual slab raw material, and the taken poplar residual slab is the same as that in Example 1. The preservation time of prehydrolysis is only changed as 120 minutes, the content of pentosan after hydrolysis is 8.5%, the hydrolysis yield is 79%, and other processes are unchanged. The finally obtained poplar residual slab acetate grade dissolving pulp has -cellulose content of 97% and pentosan content of 2.2%, a degree of polymerization of 1200, a brightness of 89% ISO, ash content of 0.01%, DCM extract content of 0.02% and an acetifying reaction value (PV value) of 780.

Example 4

[0043] A prehydrolysis with addition of an auxiliary agent-Soda/AQ segmented cooking-O.sub.pD.sub.QE.sub.PP-enzyme coprocessing process is adopted to treat a poplar residual slab raw material, and the taken poplar residual slab is the same as that in Example 1. The cooking liquid ratio of the Soda/AQ cooking II segment is only changed as 1:4 and other processes are unchanged. The finally obtained poplar residual slab acetate grade dissolving pulp has -cellulose content of 97%, pentosan content of 2.5%, a degree of polymerization of 1600, a brightness of 90% ISO, ash content of 0.01%, DCM extract content of 0.02% and an acetifying reaction value (PV value) of 730.

[0044] The poplar residual slab acetate grade dissolving pulp is good in various detection indexes, and can be used for producing a high-grade cellulose acetate product.

Example 5

[0045] A prehydrolysis with addition of an auxiliary agent-Soda/AQ segmented cooking-O.sub.pD.sub.QE.sub.PP-enzyme coprocessing process is adopted to treat a poplar residual slab raw material, and the taken poplar residual slab is the same as that in Example 1. Prehydrolysis with addition of an auxiliary agent in the steps are removed, a liquid ratio is 1:6, and other processes are the same as those in Example 1. The finally obtained poplar residual slab acetate grade dissolving pulp has -cellulose content of 95%, pentosan content of 3.6%, a degree of polymerization of 1200, brightness of 88% ISO, ash content of 0.015%, DCM extract content of 0.025% and an acetifying reaction value (PV value) of 680.

Example 6

[0046] A prehydrolysis with addition of an auxiliary agent-Soda/AQ segmented cooking-O.sub.pD.sub.QE.sub.PP-enzyme coprocessing process is adopted to treat a poplar residual slab raw material, and the taken poplar residual slab is the same as that in Example 1. Two segments of cooking in steps (2) and (3) are combined into one segment of cooking, alkali, magnesium hydrate, sodium sulfite and AQ used in two segments are added once, a liquid ratio is 1:6, T.sub.max=100 C.2 C., and preservation time is 60 minutes; then thermal preservation is performed for 120 minutes at 160 C., and other processes are the same as those in Example 1. The finally obtained poplar residual slab acetate grade dissolving pulp has -cellulose content of 96% and pentosan content of 2.7%, a degree of polymerization of 1000, a brightness of 89% ISO, ash content of 0.01%, DCM extract content of 0.02% and an acetifying reaction value (PV value) of 700.

[0047] The above examples are preferred embodiments of the disclosure, but embodiments of the disclosure are not limited by the examples, and other any changes, modifications, combinations, substitutions and simplifications made without departing from the spirit and principle of the disclosure are all equivalent substitution modes, and are all included within the protective scope of the disclosure.