BE1026675B1 - PROCESS FOR THE PRODUCTION OF ACETATE QUALITY DISSOLVING PASTE FROM RESIDUAL POPLAR SLABS - Google Patents

Abstract

The invention relates to the technical field of the preparation of dissolving paste and in particular to a process for producing acetate grade dissolving paste from residual poplar slabs, comprising: a prehydrolysis with the addition of auxiliary agent, a segment I baking soda / AQ; a Soda / AQ cooking segment II; OPQDEpP bleaching; a collaborative enzyme-based treatment. High-purity, high reactivity acetate grade dissolving paste from residual poplar slabs is produced; the chemicals used are clean, and the production process is clean.

Description

PROCESS FOR THE PRODUCTION OF ACETATE QUALITY DISSOLVING PASTE FROM RESIDUAL POPLAR SLABS TECHNICAL AREA

The invention relates to the technical field of the preparation of paste to dissolve, and in particular to a method of producing acetate grade paste to dissolve from residual poplar slabs.

DESCRIPTION OF THE PRIOR ART

[0002] At present, the production of cellulose acetate in the world is about one million tons, and that of cellulose acetate is nearly 400,000 tons in China. About 300,000 tonnes of acetate grade dissolving paste are consumed annually, mainly used for the preparation of cellulose triacetate and cellulose diacetate.

The hydroxyl groups at positions 2, 3, 6 of an anhydroglucose unit (AGU) in cellulose are almost completely acetylated in the paste to be dissolved to obtain cellulose triacetate (degree of substitution> 2.7), the cellulose triacetate is hydrolyzed to obtain cellulose diacetate (degree of substitution is 2.4-2.6), and the reaction process is as shown in a following formula.

[0003] OH HG DR HO OH> te. RO OR R = H or CH, CO

Cellulose triacetate is widely applied to films, polarizer films for liquid crystal display, reverse osmosis membranes and the like, and cellulose diacetate is widely applied to cigarette filters, plastic and similar products. Cellulose acetate has high requirements for acetate grade dissolving paste raw material, which is high purity and high reactivity. At present, only acetate grade cotton pulp can be prepared in China, and acetate grade wood dissolving pulp with high purity and high reactivity mainly depends on imports.

[0005] At home and abroad, acetate grade dissolving pulp is prepared using wood as a raw material, and the process generally adopts prehydrolysis, sulfate baking, ECF bleaching or acid sulfite baking, ECF bleaching and cold alkaline extraction. In order to improve the removal of hemicellulose in the prehydrolysis process, an inorganic acid or an organic acid is usually added, which increases the corrosivity of the equipment. In addition to improving the rate of delignification, some researchers have opted for high sulfidity KP firing technology. However, high sulfidity easily causes generation of the stinking gas such as methyl mercaptan and dimethyl sulfide. In order to reduce the ash content of dissolving pulp, a dissolving pulp production company should carry out acid treatment after pulp bleaching, but low pH value has a tendency to cause acid hydrolysis of cellulose. in the paste to be dissolved, leading to a decrease in polymerization. In order to improve the α-cellulose content in acetate grade dissolving paste, some researchers use cold alkaline extraction, but this greatly reduces the reactivity of acetate grade dissolving paste and acetic anhydride. Some researchers in Egypt are adopting microwave radiation and high concentration zinc chloride to process acetate grade dissolving paste to improve its reactivity, however, the technology is not mature. A US patent indicates that the strong acid is used to treat acetate-grade dissolving paste to improve its purity, but this technology has a high pollution degree and a high cost. Several universities in China are also carrying out research and technological development activities in this field, including South China University of Technology, Beijing Forestry University, Donghua University and other departments that have advanced in research. and the development of this technology, focusing primarily on the preparation of acetate grade dissolving paste made from eucalyptus, acacia and pine.

[0006] As a residue from wood treatment, a poplar residual slab has a low cost and a sufficient amount as a raw material. The amount of wood processing residue produced in China is reported to be around 50 million tons per year. The residual poplar slab has a holocellulose content of about 82%, with an a-cellulose content of about 44%. If a high reactivity acetate grade dissolving paste is produced with the residual poplar slab as a raw material, the development of acetate grade dissolving paste as a raw material will be greatly facilitated. However, there are no reports of the preparation of acetate grade dissolving paste using the residual poplar slab at home and abroad.

SUMMARY OF THE INVENTION

In order to solve the technical problem of the prior art that there is no preparation of acetate grade dissolving paste from residual poplar slabs, the present application describes a process for producing dissolving paste from acetate quality from residual poplar slabs.

[0008] Using a prehydrolysis technology with the addition of an auxiliary agent, the cellulose is selectively protected while eliminating the hemicellulose in the residual slabs of the poplar and the fibrous cells are swollen, then the lignin and the hemicellulose are selectively eliminated by adopting segmented firing and the decrease in cellulose polymerization is controlled; after baking, the dough is subjected to oxygen delignification enhanced by hydrogen peroxide / chlorine dioxide bleaching with addition of chelating agent / hot alkaline extraction with addition of hydrogen peroxide / bleaching with hydrogen peroxide (OpDoEpP) to remove residual lignin and hemicellulose, so that the pulp is improved and the degree of polymerization of the pulp to be dissolved is regulated, then the bleached pulp is subjected to a collaborative treatment at biological enzyme base to further improve its acetifying reaction value (PV value), reduce ash content and dichloromethane extract (DCM) content. After using this method, the purity and reactivity of the acetate grade dissolving paste is improved.

The invention is obtained by the following steps:

The invention provides a method of producing acetate grade dissolving paste from residual poplar slabs, comprising the following steps: (1) prehydrolysis with addition of auxiliary agent: the liquid ratio being 1: (4-10), the amount of auxiliary hydrolysis agent added being 0.1% -2.0% of the amount of residual dry poplar slabs, the hydrolysis temperature being 80-170 ° C, the maintenance time at the temperature being 10-180 minutes, the auxiliary hydrolysis agent being a mixture obtained by mixing sodium borate, magnesium sulfate, nonylphenol and polyoxyethylene ether phosphate and tetrasodium iminodisuccinate in a mass ratio of 1: 1: 1: 1; (2) a Soda / AQ cooking segment I; (3) a Soda / AQ cooking segment II; (4) OpQpEpP bleaching;

(5) a collaborative enzyme-based treatment: the paste concentration being 2-10%, the temperature being 30-50 ° C, the treatment time being 60 minutes, pH = 4.0-7.0, the used amount of polyaspartic acid being 0.01-1.0% of the amount of oven dry dough, the used amount of OP-13 being 0.001-0.01% of the amount of oven dry dough, the amount of OP-15 used being 0.001-0.01% of the amount of oven-dry dough, the amount of cellulase incision enzyme used being 0.1-0.61 IU / g of paste, the amount of xylanase used being 2-4 XU / g of paste and the amount of pectase being 0.1-10 IU / g of paste.

Preferably, the process conditions of the Soda / AQ baking segment I are as follows: the used amount of Na: O as alkali being 5-15% of the amount of the oven dry dough, the liquid ratio being 1: (3-8), the amount of magnesium hydroxide used being 0.5% of the amount of oven dry dough, the amount of sodium sulfite being 1.0-10, 0% of the amount of oven dry dough, the used amount of AQ being 0.05% of the amount of oven dry dough, the temperature being 80-120 ° C and the maintenance time at temperature being 10-180 minutes.

[0012] Preferably, the process conditions of the Soda / AQ baking segment II are as follows: the amount of Na: O used as alkali being 5-25% of the amount of the oven dry dough, the used amount of magnesium hydroxide being 0.5% of the amount of the oven dry dough, the used amount of sodium sulfite being 1.0-10.0% of the amount of the oven dry dough, the liquid ratio being 1: (3-10), the used amount of AQ being 0.05% of the amount of oven dry dough, the temperature being 140-180 ° C and the maintenance time at temperature being 10-240 minutes.

Preferably, the process conditions of the OpDgEpP bleaching are as follows: the oxygen pressure of the Op bleaching being 0.4-0.6 MPa, the pulp concentration being 10%, the amount of MgSO4 used being 0 , 6% of the amount of the oven dry dough, the used amount of NaOH being 1.0-3.0% of the amount of the oven dry dough, the used amount of H, O, being 0, 5-3.0% of the amount of the dough dries in the oven, the temperature being 70-110 ° C and the maintenance time at temperature being 60 minutes.

Preferably, the process conditions of the OpDgEpP bleaching are as follows: the reaction time of the bleaching process Qp being 10-120 minutes, T = 30 + 2 ° C, the pulp concentration being 2-8%, pH = 1-3, the used amount of sodium chlorite being 0.2-6.0% of the amount of oven dry dough, the amount of IDS used being 0.01-1.0% of the amount dry dough in the oven.

[0015] Preferably, the process conditions of the OpDgEpP bleaching are the

° BE2019 / 5709: the reaction time of the extraction process Ep being 30-180 minutes, the quantity used of MgSO4 being 0.5% of the quantity of the dry paste in the oven, the quantity used of NaOH being 0.5-5.0% of the amount of oven dry dough, the amount of H, O being 1.0-5.0% of the amount of oven dry dough, the amount of used d IDS being 0.01-1.0% of the amount of oven dry dough, the dough concentration being 8%, and the temperature being 70-95 ° C.

Preferably, the process conditions of the OpDoEpP bleaching are as follows: the reaction time of the bleaching P being 60-180 minutes, the amount used of MgSO4 being 0.5% of the amount of the dry paste in the oven , the used amount of NaOH being 0.4% of the amount of oven dry dough, the used amount of NaAC being 0.4% of the amount of oven dry dough, the used amount of H, O; being 1.0-5.0% of the amount of the oven dry dough, the dough concentration being 10%, and the temperature being 80-95 ° C.

In summary, the hemicellulose in the acetate grade dissolving paste is selectively removed by adding an auxiliary agent during the prehydrolysis of residual poplar slabs, then a segmented baking of Soda / AQ with addition of agent auxiliary is carried out to remove lignin as much as possible and protect cellulose. The pulp is subjected to OpDoEpP bleaching after baking to further remove lignin and to regulate the degree of polymerization of the pulp to be dissolved, and finally, using a collaborative enzyme-based processing process, the purity of The dissolving paste is further improved and the reactivity of the dissolving paste is regulated, which results in a high purity acetate grade dissolving paste from residual poplar slab.

[0018] The invention has the following beneficial effects: (1) firstly, the hemicellulose in the residual poplar slabs is very selectively dissolved through the prehydrolysis with added auxiliaries, and then the paste is subjected to a collaborative enzyme-based treatment to further improve the purity and the acetifying reaction value (PV value) of the pulp of residual poplar slabs, and finally in a combination of Soda / AQ segmented firing and OpDgErP bleaching, the pulp to dissolve acetate grade of high purity and high reactivity from residual poplar slabs is produced; (2) By adopting the process of the invention to deal with the residual poplar slabs, the chemicals used are clean and environmentally friendly, and the production process is clean.

© BE2019 / 5709

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow diagram of the production process of acetate grade dissolving paste from residual poplar slabs.

DESCRIPTION OF PREFERENTIAL ACHIEVEMENTS

The invention will be better understood on reading the description given in combination with specific examples which will follow.

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

The percentage contents of the materials used in the different stages of the process are all percentage contents representing their mass of dry dough in the oven.

[0023] Example 1

Prehydrolysis with addition of auxiliary agent - segmented cooking of Soda / AQ with addition of auxiliary agent - OpQpEpP - collaborative enzyme-based treatment are adopted to treat the raw material of residual poplar slabs: 500g Residual poplar slabs from a factory were used, with a length of 10-30 mm, the pentosan content of which is 24.3% and the a-cellulose content of 43.0%.

The conditions for controlling the process of the prehydrolysis addition of auxiliary agent are as follows: the liquid ratio is 1: 6, the content of auxiliary agent is 0.4%, the maximum temperature is 160 ° C, the maintenance time at temperature is 60 minutes, the pentosan content after hydrolysis is 8.6% and the hydrolysis yield is 80%;

The process conditions of a Soda / AQ baking segment I are as follows: the used amount of alkali is 5%, the liquid ratio is 1: 4, the content of magnesium hydroxide is 0.5 %, the content of sodium sulfite is 5.0%, the amount of AQ is 0.05%, Tmax = 100 ° C + 2 ° C, and the maintenance time at temperature is 60 minutes;

The process conditions of a Soda / AQ baking segment II are as follows: the used amount of alkali is 18%, the content of magnesium hydroxide is 0.5%, the content of sodium sulfite is 3.0%, the liquid ratio is 1: 7, the used amount of QA is 0.05%, the maximum temperature is 160 ° C, and the maintenance time at temperature is 120 minutes;

The oxygen pressure of the Op bleach is 0.5 MPa, the pulp concentration is

10%, the MgSO4 content is 0.6%, the NaOH content is 2.0%, the H, O, content is 1.0%, the temperature is 95 ° C, and the maintenance time at temperature is 60 minutes;

The reaction time of the bleaching process Qp is 60 minutes, T = 30 + 2 ° C, the paste concentration is 4.0%, pH = 1.5, the amount of sodium chlorite used is 3, 0% and the used amount of IDS is 0.05. %;

The reaction time of the Ep extraction process is 90 min, the content of MgSO4 is 0.5%, the content of NaOH is 3.0%, the content of H202 is 2.0%, the amount used IDS is 0.05%, the paste concentration is 8% and the temperature is 85 ° C;

The reaction time of the bleaching P is 120 minutes, the content of MgSOa: is 0.5%, the content of NaOH is 0.4%, the content of NaAC is 0.4%, the content of H, O, is 3.0%, the paste concentration is 10% and the temperature is 90 ° C;

The conditions of the collaborative enzyme-based treatment are as follows: the paste concentration is 5%, the temperature is 40 ° C, the treatment time is 60 minutes, pH = 5.0, the amount used d polyaspartic acid is 0.05%, used amount of OP-13 is 0.005%, used amount of OP-15 is 0.005%, used amount of cellulase incision enzyme is 0.2 IU / g of paste, the amount of xylanase used is 3 XU / g of paste and the amount of pectase used is 3 IU / g of paste;

The acetate grade dissolving paste obtained from residual poplar slabs has an a-cellulose content of 97%, a pentosan content of 2.6%, a degree of polymerization of 1250, a gloss of 89 % ISO, an ash content of 0.01%, a DCM extract content of 0.03% and an acetification reaction value (PV value) of 800.

[0034] The acetate grade dissolving paste obtained from residual poplar slabs has good detection indices and can be used to produce high quality cellulose acetate products.

[0035] Example 2

[0036] Prehydrolysis with addition of auxiliary agent - segmented cooking of Soda / AQ with addition of auxiliary agent - OpQpEpP - collaborative enzyme-based treatment are adopted to treat the raw material of the residual poplar slabs; the residual poplar slabs have a pentosan content of 22.3% and an α-cellulose content of 45%, and the process conditions are the same as in Example 1. The acetate grade dissolving paste obtained from residual poplar slabs has an a-cellulose content of 97%, a pentosan content of 2.2%, a degree of polymerization of 1280, a gloss of

90% ISO, an ash content of 0.01%, a DCM extract content of 0.02% and an acetification reaction value (PV value) of 820.

[0037] Acetate grade dissolving paste obtained from residual poplar slabs has good detection indices and can be used to produce high quality cellulose acetate products.

[0038] Example 3

A prehydrolysis with the addition of auxiliary agent - a segmented cooking of Soda / AQ with the addition of auxiliary agent - OpQpEpP - a collaborative enzyme-based treatment are adopted to treat the raw material of the residual poplar slabs, and the residual poplar slabs used are the same as those in Example 1. The maintenance time at the prehydrolysis temperature is modified to 120 minutes, the pentosan content after the prehydrolysis is 8.5%, the yield of hydrolysis is 79%, and the rest of the process remains unchanged. The acetate grade dissolving paste obtained from residual poplar slabs has an α-cellulose content of 97%, a pentosan content of 2.2%, a degree of polymerization of 1200, a gloss of ISO 89%, an ash content of 0.01%, a DCM extract content of 0.02% and an acetification reaction value (PV value) of

780.

[0040] Example 4

A prehydrolysis with the addition of auxiliary agent - a segmented cooking of sodium hydroxide / AQ with the addition of auxiliary agent - OpQpEpP - a collaborative enzyme-based treatment are adopted to treat the raw material of the residual poplar slabs, and the residual poplar slabs used are the same as in Example 1. The ratio of baking liquid in baking segment II Soda / AQ is changed to 1: 4, and the rest of the process remains unchanged. The acetate grade dissolving paste obtained from residual poplar slabs has an a-cellulose content of 97%, a pentosan content of 2.5%, a degree of polymerization of 1060, a gloss of 90% ISO, an ash content of 0.01%, a DCM extract content of 0.02% and an acetification reaction value (PV value) of

730.

[0042] Acetate grade dissolving paste obtained from residual poplar slabs has good detection indices and can be used to produce high quality cellulose acetate products.

[0043] Example 5

[0044] The segmented cooking of Soda / AQ with the addition of auxiliary agent - OpQpEpP - the collaborative enzyme-based treatment are adopted to treat a raw material of the residual poplar slabs, and the residual poplar slabs used are the same than those in Example 1. The prehydrolysis step with addition of auxiliary agent is omitted, the liquid ratio is 1: 6, and the rest of the process remains unchanged. The acetate grade dissolving paste obtained from residual poplar slabs has an a-cellulose content of 95%, a pentosan content of 3.6%, a degree of polymerization of 1200, a gloss of 88% ISO, an ash content of 0.015%, a DCM extract content of 0.025% and an acetification reaction value (PV value) of 680.

[0045] Example 6

Prehydrolysis with addition of auxiliary agent - segmented cooking of Soda / AQ with addition of auxiliary agent - OpQpEpP - collaborative enzyme-based treatment are adopted to treat the raw material of residual poplar slabs, and the residual poplar slabs used are the same as those in Example 1. The two cooking segments in steps (2) and (3) are combined with one cooking segment. Of alkali, magnesium hydrate, sodium sulfite and AQ used in the two cooking segments are added all together, the liquid ratio is 1: 6, Tmax = 100 ° C + 2 ° C and the duration of maintenance at temperature is 60 minutes; the maintenance time at the temperature of 160 ° C is 120 minutes, and the rest of the process is the same as that of Example 1. The acetate grade dissolving paste obtained from residual poplar slabs has a content of a-cellulose of 96%, a pentosan content of 2.7%, a degree of polymerization of 1000, a gloss of ISO 89%, an ash content of 0.01%, an extract content of DCM of 0, 02% and an acetification reaction value (PV value) of 700.

[0047] The above examples are preferred embodiments of the invention, but the embodiments in the description are not limited by these examples, and other equivalent substitution modes such as variants, modifications, combinations , substitutions and simplifications made without departing from the spirit and principle of the invention are all included within the scope of protection of the invention.

Claims (9)

BE2019 / 5709 claims 1. A method of producing acetate grade dissolving paste from residual poplar slabs, characterized by comprising: (1) prehydrolysis with addition of auxiliary agent: the liquid ratio being 1: (4-10) , the amount of auxiliary hydrolysis agent added being 0.1% -2.0% of the amount of residual dry poplar slabs, the hydrolysis temperature being 80-170 ° C, the maintenance time at the temperature being 10-180 minutes, the auxiliary hydrolysis agent being a mixture obtained by mixing sodium borate, magnesium sulfate, nonylphenol and polyoxyethylene ether phosphate and tetrasodium iminodisuccinate in a mass ratio of 1: 1: 1: 1; (2) a Soda / AQ cooking segment I; (3) a Soda / AQ cooking segment II; (4) OpQpEpP bleaching; (5) a collaborative enzyme-based treatment: the paste concentration being 2-10%, the temperature being 30-50 ° C, the treatment time being 60 minutes, pH = 4.0-7.0, the used amount of polyaspartic acid being 0.01-1.0% of the amount of oven dry dough, the used amount of OP-13 being 0.001-0.01% of the amount of oven dry dough, the used amount of OP-15 being 0.001-0.01% of the amount of the oven-dry dough, the used amount of cellulase incision enzyme being 0.1-0.61 IU / g of dough, the used amount of xylanase being 2-4 XU / g of paste and the amount of pectase being 0.1-10 IU / g of paste. 2. The process according to claim 1, characterized in that the process conditions of the Soda / AQ baking segment I are as follows: the used amount of Na: O as alkali being 5-15% of the amount. oven-dry dough, the liquid ratio being 1: (3-8), the amount of magnesium hydroxide used being 0.5% of the amount of the oven-dry dough, the amount of sodium sulfite used being 1.0-10.0% of the amount of oven-dry dough, the amount of AQ used being 0.05% of the amount of oven-dry dough, the temperature being 80-120 ° C and the maintenance time at temperature being 10-180 minutes. 3. The method according to claim 1, characterized in that the process conditions of the & BE2019 / 5709 Soda / AQ baking segment II are as follows: the used amount of Na: O as alkali being 5-25% of the amount of oven dry dough, the used amount of sodium hydroxide magnesium being 0.5% of the amount of oven dry dough, the amount of sodium sulfite used being 1.0-10.0% of the amount of oven dry dough, the liquid ratio being 1 :( 3-10), the amount of AQ used being 0.05% of the amount of oven dry dough, the temperature being 140-180 ° C and the maintenance time at temperature being 10-240 minutes. 4. The process according to claim 1, characterized in that the process conditions of the OpDoEpP bleaching are as follows: the oxygen pressure of the Op bleach being 0.4-0.6 MPa, the pulp concentration being 10%, the used amount of MgSO4 being 0.6% of the amount of oven dry dough, the used amount of NaOH being 1.0-3.0% of the amount of oven dry dough, the amount used d 'H, O' being 0.5-3.0% of the amount of the dough dry in the oven, the temperature being 70-110 ° C and the maintenance time at temperature being 60 minutes. 5. The process according to claim 1, characterized in that the process conditions of the OpDoErP bleaching are as follows: the reaction time of the bleaching process Qp being 10-120 minutes, T = 30 + 2 ° C, the concentration of dough being 2-8%, pH = 1-3, the used amount of sodium chlorite being 0.2-6.0% of the amount of oven dry dough, the used amount of IDS being 0.01- 1.0% of the amount of dough dry in the oven. 6. The process according to claim 1, characterized in that the process conditions of the OpDoEpP bleaching are as follows: the reaction time of the extraction process Ep being 30-180 minutes, the amount used of MgSO4 being 0.5 % of the amount of oven dry dough, the used amount of NaOH being 0.5-5.0% of the amount of oven dry dough, the used amount of H; O; being 1.0-5.0% of the amount of oven dry dough, the amount of IDS used being 0.01-1.0% of the amount of oven dry dough, the dough concentration being 8 %, and the temperature being 70-95 ° C. 7. The process according to claim 1, characterized in that the process conditions of the OpDgEpP bleaching are as follows: the reaction time of the P bleaching being 60-180 minutes, the amount used of MgSO4 being 0.5% of the amount of oven dry dough, the used amount of NaOH being 0.4% of the amount of oven dry dough, the used amount of NaAC being 0.4% of the amount of oven dry dough, used amount of H 2 O being 1.0-5.0% of the amount of oven dry dough, the dough concentration being 10%, and the temperature being 80-95 ° C. 8. The process according to claim 1, characterized in that the process comprises the following steps: (1) prehydrolysis with addition of auxiliary agent: the liquid ratio being 1: 6, the amount used of auxiliary agent being 0 , 4% of the amount of the dough dry in the oven, the temperature being 160 ° C, the maintenance time at the temperature being 60 minutes; (2) Soda / AQ baking segment I: the used amount of alkali being 5% of the amount of dough dry in the oven, the liquid ratio is 1: 4, the used amount of magnesium hydroxide alkali being 0.5% of the amount of oven dry dough, the amount of sodium sulfite used being 5.0% of the amount of oven dry dough, the amount of AQ used being 0.05% of the amount of the dough dry in the oven, Tmax = 100 ° C + 2 ° C and the maintenance time at temperature being 60 minutes; (3) Soda / AQ baking segment II: the amount of alkali used being 18% of the amount of oven-dry dough, the amount of alkali magnesium hydroxide used being 0.5% of the amount of the oven dry dough, the used amount of sodium sulfite being 3.0% of the amount of the oven dry dough, the liquid ratio is 1: 7, the used amount of AQ being 0.05% of the amount of the dough dry in the oven, the maximum temperature being 160 ° C. and the maintenance time at the temperature being 120 minutes; (4) OpDQErP bleaching: the oxygen pressure of the Op bleaching being 0.5 MPa, the pulp concentration being 10%, the amount of MgSO4 used being 0.6% of the amount of the oven-dry pulp, the used amount of NaOH being 2.0% of the amount of oven dry dough, the used amount of H, Oz being 1.0% of the amount of oven dry dough, the temperature being 95 ° C and the maintenance time at temperature being 60 minutes; the reaction time of the bleaching process Qp being 60 minutes, T = 30 + 2 ° C, the pulp concentration being 4.0%, pH = 1.5, the amount of sodium chlorite used being 3.0% of the amount of the oven dry dough and the used amount of IDS being 0.05% of the amount of the oven dry dough; the reaction time of the extraction process Ep being 90 minutes, the amount of MgSO4 used being 0.5% of the amount of the dough dry in the oven, the amount of NaOH being 3.0% of the amount of oven-dry dough, the amount of H; 0; being 2.0% of the amount of oven dry dough, the amount of IDS used being 0.05% of the amount of oven dry dough, the dough concentration being 8% and the temperature being 85 ° VS ; the reaction time of the bleaching P being 120 minutes, the amount of MgSO used being 0.5% of the amount of the dough dry in the oven, the amount of NaOH being 0.4% of the amount of the paste oven dry, the amount of NaAC used being 0.4% of the amount of the oven dry dough, the amount of H, O ”being 3.0% of the amount of the oven dry dough, the paste concentration being 10% and the temperature being 90 ° C; (5) collaborative enzyme-based treatment: the paste concentration being 5%, the temperature being 40 ° C, the treatment time being 60 minutes, pH = 5.0, the amount of polyaspartic acid used being 0 , 05% of the amount of oven dry dough, the amount of OP-13 used being 0.005% of the amount of the oven dry dough, the amount of OP-15 being 0.005% of the amount of oven-dry paste, the used amount of cellulase incision enzyme being 0.2 IU / g of paste, the amount of xylanase used being 3 XU / g of paste and the amount of pectase used being 3 IU / g of paste . 9. The process according to claim 1, characterized in that the residual poplar slabs have a length of 10-30mm, the polypentose content is 22.3-24.3% and the α-cellulose content is 43.0. -45.0%.