U.S. patent application number 16/314319 was filed with the patent office on 2020-06-04 for method for producing acetate grade dissolving pulp from poplar residual slabs.
This patent application is currently assigned to QILU UNIVERSITY OF TECHNOLOGY. The applicant listed for this patent is QILU UNIVERSITY OF TECHNOLOGY. Invention is credited to Ronggang LI, Chaojun WU, Dongmei YU.
Application Number | 20200173103 16/314319 |
Document ID | / |
Family ID | 65468610 |
Filed Date | 2020-06-04 |
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United States Patent
Application |
20200173103 |
Kind Code |
A1 |
WU; Chaojun ; et
al. |
June 4, 2020 |
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.
Inventors: |
WU; Chaojun; (Jinan, CN)
; YU; Dongmei; (Jinan, CN) ; LI; Ronggang;
(Jinan, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QILU UNIVERSITY OF TECHNOLOGY |
Jinan |
|
CN |
|
|
Assignee: |
QILU UNIVERSITY OF
TECHNOLOGY
Jinan
CN
|
Family ID: |
65468610 |
Appl. No.: |
16/314319 |
Filed: |
November 8, 2018 |
PCT Filed: |
November 8, 2018 |
PCT NO: |
PCT/CN2018/114525 |
371 Date: |
December 28, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21C 3/003 20130101;
D21C 3/022 20130101; D21C 3/006 20130101; D21C 5/005 20130101; D21C
1/02 20130101; D21C 3/22 20130101; D21C 9/1005 20130101 |
International
Class: |
D21C 5/00 20060101
D21C005/00; D21C 9/10 20060101 D21C009/10; D21C 3/00 20060101
D21C003/00; D21C 1/02 20060101 D21C001/02; D21C 3/02 20060101
D21C003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2018 |
CN |
201811228170.X |
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:(4.about.10), the addition
amount of a hydrolysis auxiliary agent is 0.1.about.2.0% of the
mass of oven dry poplar residual slab, a hydrolysis temperature is
80.about.170.degree. C., preservation time is 10.about.180 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 2.about.10%, the temperature is
30.about.50.degree. C., treatment time is 60 min, pH=4.0.about.7.0,
the amount of polyaspartic acid is 0.01%.about.1.0% of the mass of
oven dry pulp, the amount of OP-13 is 0.001.about.0.01% of the mass
of oven dry pulp, the amount of OP-15 is 0.001.about.0.01% of the
mass of oven dry pulp, the amount of endoglucanase is 0.1.about.0.6
IU/gpulp, the amount of xylanase is 2.about.4 XU/gpulp, and the
amount of pectase is 0.1.about.10 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 5.about.15% of the mass of oven dry pulp based on
Na.sub.2O, a liquid ratio is 1:(3.about.8), the amount of magnesium
hydroxide is 0.5% of the mass of oven dry pulp, the amount of
sodium sulfite is 1.0.about.10.0% of the mass of oven dry pulp, the
amount of AQ is 0.05% of the mass of oven dry pulp, the temperature
is 80.about.120.degree. C., and preservation time is 10.about.180
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 5.about.25% 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 1.0.about.10.0% of
the mass of oven dry pulp, a liquid ratio is 1:(3.about.10), the
amount of AQ is 0.05% of the mass of oven dry pulp, the temperature
is 140.about.180.degree. C., and preservation time is 10.about.240
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 0.4.about.0.6 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 1.0.about.3.0% of
the mass of oven dry pulp, the amount of H.sub.2O.sub.2 is
0.5.about.3.0% of the mass of oven dry pulp, the temperature is
70.about.110.degree. 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 10.about.120 minutes,
T=30.+-.2.degree. C., the concentration of pulp is 2.about.8%,
pH=1.about.3, the amount of sodium chlorite is 0.2.about.6.0% of
the mass of oven dry pulp, and the amount of IDS is 0.01.about.1.0%
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 30.about.180 min, the
amount of MgSO.sub.4is 1.0.about.5.0% of the mass of oven dry pulp,
the amount of NaOH is 0.5.about.5.0% of the mass of oven dry pulp,
the amount of H.sub.2O.sub.2 is 1.0.about.5.0% of the mass of oven
dry pulp, the amount of IDS is 0.01.about.1.0% of the mass of oven
dry pulp, the concentration of pulp is 8%, and the temperature is
70.about.95.degree. 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 60.about.180 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 1.0.about.5.0% of
the mass of oven dry pulp, the concentration of pulp is 10%, and
the temperature is 80.about.95.degree. 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.degree. 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.degree. C..+-.2.degree. 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.degree. 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.degree. C., and preservation time is 60 min; the
reaction time of the Q.sub.D bleaching process is 60 minutes,
T=30.+-.2.degree. 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.degree. 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.degree. C.; and (5) performing enzyme coprocessing: the
concentration of pulp is 5%, the temperature is 40.degree. 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 10.about.30 mm in length, the content
of pentosan is 22.3.about.24.3%, and the content of
.alpha.-cellulose is 43.0.about.45.0%.
Description
TECHNICAL FIELD
[0001] The disclosure pertains to the technical field of dissolving
pulp preparation, and specifically pertains to a method for
producing acetate grade dissolving pulp utilizing poplar residual
slabs.
BACKGROUND
[0002] At present, the yield of cellulose acetate is approximately
one million tons in the world, and the yield of cellulose acetate
is almost 400 thousand tons in China, about 300 thousand tons of
acetate grade dissolving pulp is consumed yearly, the acetate grade
dissolving pulp is mainly used for preparing cellulose triacetate
and cellulose diacetate, hydroxyl groups at 2, 3, 6 positions of an
anhydroglucose unit (AGU) in cellulose are almost completely
acetylated in the dissolving pulp to obtain cellulose triacetate
(substitution degree >2.7), cellulose triacetate is hydrolyzed
to obtain cellulose diacetate (substitution degree is 2.4-2.6), and
the reaction process is as shown in a formula as follows.
##STR00001##
[0003] Cellulose triacetate is widely applied to films, liquid
display polarizer films, reverse osmosis membranes and the like,
and cellulose diacetate is widely applied to cigarette filters,
plastic products and the like. Cellulose acetate has high
requirements on its raw material-acetate grade dissolving pulp,
namely, high purity and high reactivity. At present, acetate grade
cotton pulp can only be prepared in China, and high-purity
high-reactivity acetate grade wood dissolving pulp mainly depends
on imports.
[0004] At home and abroad, acetate grade dissolving pulp is
prepared using woods as a raw material, and a process typically
adopts prehydrolysis, sulfate cooking, ECF bleaching or acidic
sulfite cooking, ECF bleaching and cold alkali extraction. In order
to improve the removal of hemicellulose in the prehydrolysis
process, inorganic acid or organic acid is typically added, which
increases corrosivity of equipment. In order to improve a
delignification rate, some researchers adopt a high-sulfidity KP
cooking technology, however, high sulfidity easily causes
generation of odors such as methyl mercaptan and dimethylsulfide;
in order to reduce the ash content of the dissolving pulp, a
dissolving pulp production enterprise need to perform acidic
treatment after pulp is bleached, however, a low pH value easily
causes polymerization decrease of partial celluloses in the
dissolving pulp due to acidic hylydrosis; in order to improve the
content of .alpha.-cellulose in the acetate grade dissolving pulp,
some scholars adopt cold alkali extraction, but it severely reduces
the reactivity of the acetate grade dissolving pulp and acetic
anhydride, and some scholars in Egypt adopt microwave radiation and
high-concentration zinc chloride to treat the acetate dissolving
pulp so as to improve its reactivity, however, the technology is
not matured; a U.S. patent reports that strong acid is used to
treat the acetate dissolving pulp so as to improve its purity, but
this technology is high in pollution degree and high in cost.
Several institutions in China are researching and developing this
technology, mainly including South China University of Technology,
Beijing Forestry University and other departments which have gained
some progresses in research and development of this technology,
mainly focusing on preparation of acetate grade dissolving pulp
using eucalyptus, acacia and pine.
[0005] As a wood processing residue, an poplar residual slab is low
in cost and sufficient in raw material. It is reported that the
production amount of wood processing residue is about 50 million
tons yearly in China. As one of wood processing residues, the
poplar residual slab has holocellulose content of about 82%, among
them, the content of .alpha.-cellulose is about 44%. If
high-reactivity acetate grade dissolving pulp is produced with the
poplar residual slab as a raw material, development of the raw
material of the acetate grade dissolving pulp will be greatly
facilitated. However, there are no any reports about preparation of
the acetate grade dissolving pulp using the poplar residual slab at
home and abroad.
SUMMARY
[0006] In order to solve the technical blank of the prior art that
preparation of acetate grade dissolving pulp using poplar residual
slabs is not present, the present application discloses a method
for producing acetate grade dissolving pulp using poplar residual
slabs.
[0007] By utilizing a prehydrolysis technology in which an
auxiliary agent is added, cellulose is selectively protected while
removing hemicellulose in the poplar residual slab raw material and
fiber cells are swelled; then lignin and hemicellulose are
selectively removed adopting segmented cooking, and polymerization
decrease of cellulose is controlled; after cooking, pulp is
subjected to oxygen delignification enhanced with hydrogen
peroxide/chlorine dioxide bleaching with addition of a chelating
agent/hot alkali extraction with addition of hydrogen
peroxide/residual lignin and hemicellulose removal via hydrogen
peroxide bleaching (O.sub.pD.sub.QE.sub.PP), the brightness of the
pulp is improved and the degree of polymerization of the dissolving
pulp is regulated, and then the bleached pulp is subjected to
biological enzyme coprocessing to further improve its acetifying
reaction value (PV value), reduce ash content and dichloromethane
(DCM) extract content. After using this process, the purity and
reactivity of the acetate grade dissolving pulp are improved.
[0008] The disclosure is obtained by the following steps:
[0009] Provided is a method for producing acetate grade dissolving
pulp utilizing poplar residual slabs, comprising the following
steps:
[0010] (1) adding an auxiliary agent for prehydrolysis: a liquid
ratio is 1:(4.about.10), the addition amount of a hydrolysis
auxiliary agent is 0.1.about.2.0% of the mass of dry poplar
residual slab, the hydrolysis temperature is 80.about.170.degree.
C., preservation time is 10.about.180 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;
[0011] (2) performing a Soda/AQ cooking I segment;
[0012] (3) performing a Soda/AQ cooking II segment;
[0013] (4) performing O.sub.pD.sub.QE.sub.PP bleaching; and
[0014] (5) performing enzyme coprocessing: the concentration of
pulp is 2.about.10%, the temperature is 30.about.50.degree. C.,
treatment time is 60 min, pH=4.0.about.7.0, the amount of
polyaspartic acid is 0.01%.about.1.0% of the mass of oven dry pulp,
the amount of OP-13 is 0.001.about.0.01% of the mass of oven dry
pulp, the amount of OP-15 is 0.001.about.0.01% of the mass of oven
dry pulp, the amount of endoglucanase is 0.1.about.0.6 IU/gpulp,
the amount of xylanase is 2.about.4 XU/gpulp, and the amount of
pectase is 0.1.about.10 IU/gpulp.
[0015] The preferred process conditions of the Soda/AQ cooking I
segment are as follows: the amount of alkali is 5.about.15% of the
mass of oven dry pulp based on Na.sub.2O, a liquid ratio is 1:
(3.about.8), the amount of magnesium hydroxide is 0.5% of the mass
of oven dry pulp, the amount of sodium sulfite is 1.0.about.10.0%
of the mass of oven dry pulp, the amount of AQ is 0.05% of the mass
of oven dry pulp, the temperature is 80.about.120.degree. C., and
preservation time is 10.about.180 minutes.
[0016] The preferred process conditions of the Soda/AQ cooking II
segment are as follows: the amount of alkali is 5.about.25% 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 1.0.about.10.0% of the mass of oven dry pulp, a liquid
ratio is 1:(3.about.10), the amount of AQ is 0.05% of the mass of
oven dry pulp, the temperature is 140.about.180.degree. C., and
preservation time is 10.about.240 minutes.
[0017] The preferred process conditions of O.sub.pD.sub.QE.sub.PP
bleaching are as follows: the oxygen pressure of O.sub.p bleaching
is 0.4.about.0.6 Mpa, the concentration of pulp is 10%, the amount
of MgSO4 is 0.6% of the mass of oven dry pulp, the amount of NaOH
is 1.0.about.3.0% of the mass of oven dry pulp, the amount of
H.sub.2O.sub.2 is 0.5.about.3.0% of the mass of oven dry pulp, the
temperature is 70.about.110.degree. C., and preservation time is 60
min.
[0018] The preferred process conditions of O.sub.pD.sub.QE.sub.PP
bleaching are as follows: the reaction time of a Q.sub.D bleaching
process is 10.about.120 minutes, T=30.+-.2.degree. C., the
concentration of pulp is 2.about.8%, pH=1.about.3, the amount of
sodium chlorite is 0.2.about.6.0% of the mass of oven dry pulp, and
the amount of IDS is 0.01.about.1.0% of the mass of oven dry
pulp.
[0019] The preferred 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 30.about.180 min, the amount of MgSO.sub.4 is
0.5% of the mass of oven dry pulp, the amount of NaOH is
0.5.about.5.0% of the mass of oven dry pulp, the amount of
H.sub.2O.sub.2 is 1.0.about.5.0% of the mass of oven dry pulp, the
amount of IDS is 0.01.about.1.0% of the mass of oven dry pulp, the
concentration of pulp is 8%, and the temperature is
70.about.95.degree. C.
[0020] The preferred process conditions of O.sub.pD.sub.QE.sub.PP
bleaching are as follows: the reaction time of P bleaching is
60.about.180 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 1.0.about.5.0% of the mass of oven dry
pulp, the concentration of pulp is 10%, and the temperature is
80.about.95.degree. C.
[0021] In summary, hemicellulose in the acetate grade dissolving
pulp is selectively removed by adding an auxiliary agent when
poplar residual slabs are prehydrolyzed, then Soda/AQ segmented
cooking with addition of the auxiliary agent is carried out to
remove lignin to the greatest extent so as to protect cellulose,
the pulp is subjected to O.sub.pD.sub.QE.sub.PP bleaching after
being cooked to further remove lignin and regulate the degree of
polymerization of the dissolving pulp, and finally, by using an
enzyme coprocessing process, the purity of the dissolving pulp is
further improved and the reactivity of the dissolving pulp is
regulated, thereby obtaining high-purity high-reactivity poplar
residual slab acetate grade dissolving pulp.
[0022] The disclosure has the beneficial effects:
[0023] (1) at first, hemicellulose in the poplar residual slab is
greatly selectively dissolved out by virtue of prehydrolysis with
addition of an auxiliary agent, and finally the purity and the
acetifying reaction value of the poplar residual slab pulp are
improved using enzyme coprocessing, and then high-purity
high-reactivity poplar residual slab acetate grade dissolving pulp
is prepared by combining with Soda/AQ segmented cooking and
O.sub.pD.sub.QE.sub.PP bleaching;
[0024] (2) the poplar residual slab is treated adopting the process
of the disclosure, the used chemicals are clean and environmental
friendly, and the production process is clean.
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 10.about.30 mm, pentosan content of 24.3% and
.alpha.-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.degree. 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.degree. C..+-.2.degree. 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.degree. 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.degree. C., and
preservation time is 60 min.
[0034] The reaction time of the Q.sub.D bleaching process is 60
minutes, T=30.+-.2.degree. 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.degree. 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.degree.
C.
[0037] The conditions of enzyme coprocessing are as follows: the
concentration of pulp is 5%, the temperature is 40.degree. 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 .alpha.-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 .alpha.-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 .alpha.-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 .alpha.-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
.alpha.-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 .alpha.-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.degree. C..+-.2.degree. C., and preservation time is
60 minutes; then thermal preservation is performed for 120 minutes
at 160.degree. C., and other processes are the same as those in
Example 1. The finally obtained poplar residual slab acetate grade
dissolving pulp has .alpha.-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.
* * * * *