阅读说明：本技术 一种制造纤维素硝酸酯用棉浆粕生产工艺 (Production process of cotton pulp for preparing cellulose nitrate ) 是由 陈忠国 曹知朋 马伟良 唐逢 郑春友 吕兴华 李宗臻 孙海龙 于 2019-10-10 设计创作，主要内容包括：本发明公开了一种制造纤维素硝酸酯用棉浆粕生产工艺,该棉浆粕具有以下指标：聚合度930～980；白度≥88%；铁质≤15ppm；灰份≤0.08%；纤维长度23～32%；甲纤≥97.5%；水分6～9%；小尘埃≤15mm2/500g；B类尘埃≤2mm2/500g,本发明采用上述方法制得的纤维素硝酸酯用棉浆粕,纤维帚化程度高、强度好,并且甲纤含量高,聚合度稳定,尘埃少,能够更好的用于医药新型填充剂～微晶纤维素和炸药硝化棉以及高级硝基漆和建筑涂料等行业的生产。(The invention discloses a production process of cotton pulp for manufacturing cellulose nitrate, which has the following indexes: the polymerization degree is 930-980; the whiteness is more than or equal to 88 percent; iron is less than or equal to 15 ppm; ash content is less than or equal to 0.08 percent; the fiber length is 23-32%; alpha fiber is more than or equal to 97.5 percent; 6-9% of water; small dust is less than or equal to 15 mm/500 g; the B-type dust is not more than 2 mm/500 g, and the cellulose nitrate cotton pulp prepared by the method has the advantages of high fiber fibrillation degree, high strength, high methylcellulose content, stable polymerization degree and less dust, and can be better used for the production of novel pharmaceutical fillers, namely microcrystalline cellulose, explosive nitrocotton, high-grade nitrolacquer, building coatings and other industries.)

1. A production process of cotton pulp for manufacturing cellulose nitrate is characterized in that: the cotton pulp has the following indexes: the polymerization degree is 930-980; the whiteness is more than or equal to 88 percent; iron is less than or equal to 15 ppm; ash content is less than or equal to 0.08 percent; the fiber length is 23-32%; alpha fiber is more than or equal to 97.5 percent; 6-9% of water; small dust is less than or equal to 15 mm/500 g; the class B dust is less than or equal to 2.

2. The process for producing cotton pulp for cellulose nitrate according to claim 1, wherein: the process comprises the following steps: the method comprises the following steps of pre-processing, middle-stage processing and post-processing, wherein the pre-processing step comprises the following steps:

1) selecting materials, opening cotton, and removing impurities by a dry method: selecting 100% of second-class cotton linters with primary maturity of 79-81%, tearing the cotton linters by using a cotton opener, and selecting and removing impurities by using an impurity remover;

2) alkali preparation and impregnation: preparing alkali at normal temperature, wherein the prepared alkali liquor has the concentration of 44 +/-2 g/L, and the ratio of the prepared alkali liquor to the alkali liquor is 1: 3.6-4, and fully permeating and mixing the alkali liquor and the cotton linters during screw extrusion;

3) and (3) injection aid: the auxiliary agent is H₂O₂And adding H in an amount of 500 +/-100 Kg/ball₂O₂And putting into a rotary spherical digester.

3. The process for producing cotton pulp for cellulose nitrate according to claim 1, wherein: the intermediate treatment step includes the steps of:

1) and (3) cooking: and (3) cooking the materials to a polymerization degree DP by using a spherical digester: 1250 to 1300;

2) pre-desanding: mixing the materials with water to prepare slurry, and feeding the slurry into a heavy desander;

3) pre-pulping: pulping by using three large-taper refiners connected in series until the fiber length is 32-36%;

4) chloric basification: feeding the slurry prepared in the step into a chlorination tower, and chlorinating by using HCLO solution until the pH value of the solution in the chlorination tower is 11.5-13.5;

5) bleaching: and (3) sending the slurry prepared in the chloralkalization step into a bleaching pool with a slurry inlet amount of 2 pools/balls, wherein the chlorine content of the slurry in the bleaching pool is as follows: 0.35-0.40 g/L, bleaching temperature: bleaching at 45-50 ℃ for: 10-30 min, adding hydrogen peroxide after bleaching, adding SMA500 g/pool during bleaching, and dechlorinating for: not less than 20min, index: residual chlorine is removed completely, and starch potassium iodide is used for indicating that the residual chlorine is not changed into blue;

6) acid treatment: adding acid liquor into the bleached pulp in an amount of 100-120L/tank for acid treatment, wherein the acid treatment time is as follows: and (3) 30min, adding an iron removing agent, wherein the adding amount of the iron removing agent is 3 +/-2 measuring cups/pools, and washing with water for 10min after the acid treatment is finished.

4. The process for producing cotton pulp for cellulose nitrate according to claim 1, wherein: the post-processing step comprises the steps of:

1) and (3) after-desanding: desanding by using a light desander, wherein the desanding pressure is 0.28-0.30 MPa, and the final stage of tail slurry is concentrated: 0.5-1 per mill, and concentrating through a rotary screen after sand removal;

2) post pulping: one or two back large taper refiners are used, and the current of the refiners is set as follows: 300-400A, and grinding the pulp by a disc mill, wherein the power of the disc mill is as follows: 180-220 KW;

3) pulping: and (5) making the pulp by a pulp making machine, and drying to obtain a finished product.

5. The process for producing cotton pulp for cellulose nitrate according to claim 4, wherein: in the cooking step, before temperature rise, the rotary spherical digester is cooled for a period of time, wherein the cooling time is as follows: and (3) heating for 10-15 min, wherein the heating time is as follows: 40-60 min, the temperature is 156 +/-5 ℃, and the heat preservation time is as follows: and (3) discharging steam after the heat preservation is finished for 20 +/-20 min, wherein the steam discharging time is 20-30 min.

6. The process for producing cotton pulp for cellulose nitrate according to claim 5, wherein: in the preceding desanding step: the sand removing time is 80 +/-10 minutes per ball, the sand removing pressure is 0.28-0.30 MPa, and the final stage of tail slurry is concentrated: 1 to 1.5 per mill.

7. The process for producing cotton pulp for cellulose nitrate according to claim 6, wherein: in the preceding beating step, the refiner current is set to: 280-340A, pulping time: 80 plus or minus 10 minutes per ball, washing by a filter press after pulping, and then sending into a bleaching pool for bleaching.

8. The process for producing cotton pulp for cellulose nitrate according to claim 7, wherein: in the chloralkali step, the chlorination time: 30min, chlorine content: 0.15 to 0.25 g/L.

9. The process for producing cotton pulp for cellulose nitrate according to claim 8, wherein: in the bleaching step, the DP measured after the end of bleaching: 950 to 1000.

10. The process for producing cotton pulp for cellulose nitrate according to claim 9, wherein: in the post-beating step, the fiber length is measured after the post-beating is finished: 23 to 32 percent.

Technical Field

The invention relates to a cotton pulp production process, in particular to a cotton pulp production process for manufacturing cellulose nitrate, which is used for producing celluloid, motion picture films, nitro-lacquer films, explosives and the like in various colors, spray paint in various colors, typewriting wax paper, lacquer cloth, bottle opening sleeves and the like, and belongs to the technical field of cotton pulp.

Background

In recent years, explosives with strong explosive force and large acting force and medicines used as vasodilators are manufactured in markets at home and abroad and prepared into 0.3 percent nitroglycerin tablets for sublingual administration, and the effect is rapid and transient and is extremely strong. The demand for nitrocellulose products is also increasing, and development of this cotton pulp variety is a favorable condition.

China is a big cotton-producing country and has rich cotton linter resources. In high-quality cotton production areas such as Xinjiang, Hebei, Shandong, Jiangsu and the like, sufficient and high-quality raw materials are ensured.

In the bleaching process of the existing common cotton pulp production process, sodium hypochlorite and chlorine are used for carrying out multi-stage bleaching on cotton pulp, so that fiber is damaged, and the strength of the fiber is reduced. And the COD of the digestion black liquor is about 45000mg/L, so that the problem of high pollution waste water which is difficult to treat exists.

Chinese patent, application No. CN200810016759.3, entitled "a method for producing cotton pulp", wherein cotton linters are used as raw materials to produce nitration grade cotton pulp, but the cooking process and the bleaching process are too complicated, which is not favorable for controlling the whole body and maximizing the product benefit.

Therefore, further improvements are still needed.

Disclosure of Invention

The invention aims to solve the main technical problem of providing a production process of cotton pulp for manufacturing cellulose nitrate, which aims to solve the problems in the background technology.

In order to solve the technical problems, the invention provides the following technical scheme:

a process for producing a cotton pulp for cellulose nitrate production, the cotton pulp having the following indices: the polymerization degree is 930-980; the whiteness is more than or equal to 88 percent; iron is less than or equal to 15 ppm; ash content is less than or equal to 0.08 percent; the fiber length is 23-32%; alpha fiber is more than or equal to 97.5 percent; 6-9% of water; small dust is less than or equal to 15 mm/500 g; class B dust is less than or equal to 2 mm/500 g.

The following is a further optimization of the above technical solution of the present invention:

further optimization: the process comprises the following steps: the method comprises the following steps of pre-processing, middle-stage processing and post-processing, wherein the pre-processing step comprises the following steps:

1) selecting materials, opening cotton, and removing impurities by a dry method: selecting 100% of second-class cotton linters with primary maturity of 79-81%, tearing the cotton linters by using a cotton opener, and selecting and removing impurities by using an impurity remover;

2) alkali preparation and impregnation: preparing alkali at normal temperature, wherein the prepared alkali liquor has the concentration of 44 +/-2 g/L, and the ratio of the prepared alkali liquor to the alkali liquor is 1: 3.6-4, and fully permeating and mixing the alkali liquor and the cotton linters during screw extrusion;

3) and (3) injection aid: the auxiliary agent is H₂O₂And adding H in an amount of 500 +/-100 Kg/ball₂O₂And putting into a rotary spherical digester.

Further optimization: the intermediate treatment step includes the steps of:

1) and (3) cooking: and (3) cooking the materials to a polymerization degree DP by using a spherical digester: 1250 to 1300;

2) pre-desanding: mixing the materials with water to prepare slurry, and feeding the slurry into a heavy desander;

3) pre-pulping: pulping by using three large-taper refiners connected in series until the fiber length is 32-36%;

4) chloric basification: feeding the slurry prepared in the step into a chlorination tower, and chlorinating by using HCLO solution until the pH value of the solution in the chlorination tower is 11.5-13.5;

5) bleaching: and (3) sending the slurry prepared in the chloralkalization step into a bleaching pool with a slurry inlet amount of 2 pools/balls, wherein the chlorine content of the slurry in the bleaching pool is as follows: 0.35-0.40 g/L, bleaching temperature: bleaching at 45-50 ℃ for: 10-30 min, adding hydrogen peroxide after bleaching, adding SMA500 g/pool during bleaching, and dechlorinating for: not less than 20min, index: residual chlorine is removed completely, and starch potassium iodide is used for indicating that the residual chlorine is not changed into blue;

6) acid treatment: adding acid liquor into the bleached pulp in an amount of 100-120L/tank for acid treatment, wherein the acid treatment time is as follows: and (3) 30min, adding an iron removing agent, wherein the adding amount of the iron removing agent is 3 +/-2 measuring cups/pools, and washing with water for 10min after the acid treatment is finished.

Further optimization: the post-processing step comprises the steps of:

1) and (3) after-desanding: desanding by using a light desander, wherein the desanding pressure is 0.28-0.30 MPa, and the final stage of tail slurry is concentrated: 0.5-1 per mill, and concentrating through a rotary screen after sand removal;

2) post pulping: one or two back large taper refiners are used, and the current of the refiners is set as follows: 300-400A, and grinding the pulp by a disc mill, wherein the power of the disc mill is as follows: 180-220 KW;

3) pulping: and (5) making the pulp by a pulp making machine, and drying to obtain a finished product.

Further optimization: in the cooking step, before temperature rise, the rotary spherical digester is cooled for a period of time, wherein the cooling time is as follows: and (3) heating for 10-15 min, wherein the heating time is as follows: 40-60 min, the temperature is 156 +/-5 ℃, and the heat preservation time is as follows: and (3) discharging steam after the heat preservation is finished for 20 +/-20 min, wherein the steam discharging time is 20-30 min.

Further optimization: in the preceding desanding step: the sand removing time is 80 +/-10 minutes per ball, the sand removing pressure is 0.28-0.30 MPa, and the final stage of tail slurry is concentrated: 1 to 1.5 per mill.

Further optimization: in the preceding beating step, the refiner current is set to: 280-340A, pulping time: 80 plus or minus 10 minutes per ball, washing by a filter press after pulping, and then sending into a bleaching pool for bleaching.

Further optimization: in the chloralkali step, the chlorination time: 30min, chlorine content: 0.15 to 0.25 g/L.

Further optimization: in the bleaching step, the DP measured after the end of bleaching: 950 to 1000.

Further optimization: in the post-beating step, the fiber length is measured after the post-beating is finished: 23 to 32 percent.

According to the technical scheme, the process of adding hydrogen peroxide in the cooking section is adopted, the subsequent bleaching process is weakened, the cotton linters are used as raw materials, the COD (chemical oxygen demand) of the cooking black liquor is 25000-28000 mg/l, the pollution to the environment is reduced, three large conical degrees of the front beating are matched in series, then the large conical degrees of the beating and the disc mill are adopted, the length of cotton pulp fibers is effectively controlled, the fiber fibrillation degree is high, the strength is good, the content of alpha-cellulose is high, the polymerization degree is stable, the dust is less, and the method can be better used for the production of industries such as novel pharmaceutical fillers, namely microcrystalline cellulose, nitrocotton explosive, high-grade nitrolacquer and building coating.

The present invention will be further described with reference to the following examples.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.