Civil nitrifying bacterial cellulose and preparation method thereof

Abstract

The invention discloses civil nitrifying bacterial cellulose and a preparation method thereof, and belongs to the field of nitrocotton manufacturing. The preparation method of the civil nitrifying bacterial cellulose comprises the following steps: mixing bacterial cellulose with mixed acid, carrying out nitration reaction to obtain an acid cotton mixture, carrying out acid cotton separation and washing on the acid cotton mixture, boiling and washing, and finally dehydrating to obtain the civil nitrifying bacterial cellulose. The boiling and washing are continuously boiling with acid water and are divided into two stages: in the first stage, the boiling and washing time is 1-2 hours, the temperature is 100-110 DEG C, the acidity is 6-8 g / L, and the pressure is 0.05-0.10 Mpa; in the second stage, the boiling and washing time is 0.5-1 hour, the temperature is 120-130 DEG C, and the pressure is 0.05-0.10 Mpa. The nitrogen content of the prepared civil nitrifying bacterial cellulose is 10.7-12.2%, the whiteness is 80-88%, the viscosity is 11.5-29 mpa.s, the light transmittance is 75-85%, and the prepared civil nitrifying bacterial cellulose is subjected to a heat resistance test at 80 DEG C for 20-30 min.

Description

Technical Field

[0001] The invention belongs to the field of nitrocellulose manufacturing, and specifically relates to civilian nitrated bacterial cellulose and a preparation method thereof. Background Art

[0002] Nitrocellulose (NC) is prepared from plant fibers through a nitration reaction in a two-phase medium of a crystalline region and an amorphous region. Usually, due to the inadequate nitration process, the nitrogen content of NC generally has the disadvantage of uneven nitrogen content distribution, which results in different degrees of insoluble "colloid particles" existing in the dissolution process of NC. At the same time, since plant cellulose contains a small amount of lignin, hemicellulose, protein, etc., the nitrocellulose prepared from plant cellulose contains a small amount of impurities. These impurities generate unstable nitrate esters during the reaction, thereby reducing the stability of the nitrocellulose. In the subsequent stability treatment stage, these impurities react with each other to generate unstable nitrate esters, which also reduces the stability of the product. The preparation of nitrocellulose with uniform nitrogen distribution and high solubility has been a long-term concern.

[0003] The uses of civilian nitrocellulose mainly include the production of paints, inks, celluloid products, adhesives, leather oil, nail polish and other products. The industry standards WJ / T 9015-1993 "Nitrocellulose for Celluloid" and WJ 9028-2005 "Nitrocellulose Specification for Coatings" set requirements for the nitrogen content, whiteness, viscosity and other aspects of civilian nitrocellulose products. Currently, civilian nitrocellulose is usually produced by a series of processes such as esterification reaction, acid washing, boiling and washing, bleaching, dehydration / water driving, etc. of refined cotton, wood (cotton) pulp raw materials and mixed acid; among them, the bleaching process requires the use of bleaching agents and increases energy consumption and production time, resulting in high production costs and low efficiency.

[0004] Cotton and wood cellulose are the basic raw materials of NC. In view of the limited cotton growth conditions and the necessity of protecting existing forests, finding NC raw material sources other than cotton fiber or wood cellulose has received extensive attention, among which bacterial cellulose is the most important one. CN116284457A discloses a military bacterial nitrocellulose and a preparation method thereof, comprising: mixing bacterial cellulose with mixed acid for nitration reaction, obtaining an acid-cotton mixture after the reaction, separating the acid-cotton and washing, and then boiling, washing, finely cutting, fine washing, and dehydrating to obtain bacterial nitrocellulose. The method is mainly used for the preparation of energetic nitrocellulose. Its preparation process, technology and parameters are significantly different from those of civilian nitrocellulose. At the same time, the evaluation system of energetic nitrocellulose indicators is completely inconsistent with that of civilian nitrocellulose.

[0005] Therefore, it is necessary to study a method for producing civilian nitrocellulose with high efficiency and low cost by using cellulose materials other than cotton fiber or wood cellulose as raw materials. Summary of the invention

[0006] The technical problem to be solved by the present invention is to broaden the raw materials for preparing civilian nitrocellulose and simplify the process flow, so as to provide a new idea for realizing continuous automation of boiling and washing and thus improving production efficiency.

[0007] The technical solution adopted by the present invention to solve its technical problem is:

[0008] In a first aspect, the present invention provides a method for preparing civilian nitrated bacterial cellulose: bacterial cellulose is mixed with mixed acid to undergo nitration reaction to obtain an acid-cotton mixture, the acid-cotton mixture is boiled and washed after acid-cotton separation and washing, and finally dehydrated to obtain civilian nitrated bacterial cellulose.

[0009] The preparation method of civilian nitrified bacterial cellulose specifically comprises the following steps:

[0010] a. Nitration: Mix bacterial cellulose with mixed acid to undergo nitration reaction to obtain an acid-cotton mixture;

[0011] b. Boiling and washing: The acid-cotton mixture is boiled and washed after acid-cotton separation and washing. The boiling and washing is a continuous boiling of acid water, which is divided into two stages:

[0012] The first stage of boiling and washing time is 1 to 2 hours, the boiling and washing temperature is 100 to 110°C, the boiling and washing acidity is 6 to 8 g / L, and the boiling and washing pressure is 0.05 to 0.10 MPa;

[0013] The second stage of boiling and washing time is 0.5 to 1 hour, the boiling and washing temperature is 120 to 130°C, and the boiling and washing pressure is 0.05 to 0.10Mpa;

[0014] c. Dehydration to obtain civilian nitrified bacterial cellulose.

[0015] In step a of the above preparation method, the α-cellulose content in the bacterial cellulose is ≥97.0%, the ash content is ≤0.15%, and the sulfuric acid insoluble matter is ≤0.25%.

[0016] In step a of the above preparation method, the viscosity of the bacterial cellulose is 10-20 mPa.s higher than the viscosity of the civilian nitrocellulose product, and the whiteness is ≥88%.

[0017] In step a of the above preparation method, the mixed acid is a mixture of nitric acid, sulfuric acid and water; wherein the nitric acid content is 18% to 25%, the water content is 16% to 21%, and the rest is sulfuric acid.

[0018] The mass concentration of nitric acid in the above preparation method is 98%, and the mass concentration of sulfuric acid is 98%.

[0019] In step a of the above preparation method, the mass ratio of the mixed acid to the bacterial cellulose is (40-45):1, and the mass of the bacterial cellulose refers to the absolute dry weight, which refers to the mass of the bacterial cellulose when the water content is 0.

[0020] In step a of the above preparation method, the nitration reaction temperature is 25-55°C.

[0021] In step a of the above preparation method, the nitration reaction time is 30 to 40 minutes.

[0022] In a second aspect, the present invention provides civilian nitrified bacterial cellulose produced by the above-mentioned preparation method.

[0023] Furthermore, the above-mentioned civilian nitrified bacterial cellulose has a nitrogen content of 10.7-12.2%, a whiteness of 80-88%, a viscosity of 11.5-29mPa.s, a light transmittance of 75-85%, and a heat resistance test of 80°C for 20-30min.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention uses bacterial cellulose as a raw material to prepare civilian nitrocellulose, which broadens the raw materials for preparing civilian nitrocellulose. The bacterial cellulose raw material used in the present invention is in the form of small flakes of uniform size, which is conducive to sufficient reaction during the nitrification process, so that the nitrogen content of the prepared civilian nitrocellulose is evenly distributed, and the solubility performance is improved to a certain extent; in addition, based on the small and uniform shape of bacterial cellulose, it can be ensured that it is transported smoothly in the pipeline, which is conducive to the automatic and continuous development of boiling and washing.

[0026] (2) This invention provides a new process flow for preparing nitrocellulose for civil use. By controlling the degree of polymerization and whiteness of bacterial cellulose, the boiling and washing time is reduced in the preparation process of nitrocellulose for civil use, and the bleaching process is omitted, thereby reducing the energy consumption of producing nitrocellulose for civil use and improving production efficiency.

[0027] (3) The civilian nitrified bacterial cellulose prepared by the method of the present invention has high purity, high whiteness, high light transmittance, good heat resistance, good solubility and good nitrogen uniformity; the preparation process has low cost and high efficiency, and has obvious advantages over traditional nitrocellulose. The technical solution of the present invention has high promotion and application value and is of great significance to the production of nitrocellulose in my country. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the process flow for preparing traditional civilian nitrocellulose;

[0029] Figure 2 This is the process flow for preparing civilian nitrified bacterial cellulose of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention can be specifically implemented in the following manner.

[0031] The present invention conducts in-depth analysis and research on the basic properties of raw materials and finds that bacterial cellulose can be used for the preparation of civilian nitrocellulose. At the same time, the preparation process of civilian nitrocellulose can also be optimized and designed. Based on this, a new idea for preparing civilian nitrocellulose with excellent comprehensive performance at low cost and high efficiency is provided: bacterial cellulose is mixed with mixed acid for nitration reaction, and an acid-cotton mixture is obtained after the reaction. After the acid-cotton mixture is separated and washed, it is boiled and washed (boiled with acid and water continuously), and finally dehydrated to obtain civilian bacterial cellulose. Figure 1 This is the current process flow for preparing nitrocellulose for civilian use. Figure 2 This is the preparation process flow of the civilian bacterial cellulose of the present invention. As can be seen from the figure, the preparation process of the present invention can omit the bleaching step compared with the prior art, simplify the process flow, and thus reduce energy consumption and improve production efficiency.

[0032] Bacterial cellulose has an ultra-fine network structure. Bacterial cellulose fibers are composed of microfibrils with a diameter of 3 to 4 nanometers combined into fiber bundles with a thickness of 40 to 60 nanometers, which are interwoven to form a developed ultra-fine network structure. Its elastic modulus is several to ten times that of general plant fibers, and it has high tensile strength. Its mechanical properties (tensile strength, material brittleness, etc.) have obvious advantages over traditional nitrocellulose. The bacterial cellulose used in the method of the present invention has an alpha-cellulose content of ≥97.0%, an ash content of ≤0.15%, sulfuric acid insolubles of ≤0.25%, a viscosity that is 10-20 MPa.s higher than the viscosity of civil nitrocellulose products, and a whiteness of ≥88%. The various indicators of the prepared civil nitrated bacterial cellulose are equivalent to the various indicators of the current industrial civil nitrocellulose, while also achieving reduced energy consumption, simplified process flow, and improved production efficiency; at the same time, the raw material of the bacterial cellulose is in the form of small flakes of uniform size, and the reaction is sufficient during the nitration process, so the prepared civil nitrocellulose has a uniform nitrogen content distribution and a certain improvement in solubility; in addition, it can be smoothly transported in a pipeline, which is conducive to the automatic and continuous boiling and washing in the future.

[0033] The technical solution and effects of the present invention are further illustrated below through practical examples.

[0034] Example

[0035] The present invention provides two groups of Examples 1 and 2 for preparing civilian nitrocellulose using the method of the present invention; wherein the raw materials used in Examples 1 and 2 are shown in Table 1.

[0036] Table 1 Raw materials

[0037]

[0038] The preparation method of civilian nitrified bacterial cellulose specifically comprises the following steps:

[0039] 1. Nitration: The bacterial cellulose is mixed with mixed acid for nitration reaction to obtain an acid-cotton mixture. The nitration process parameters are shown in Table 2; wherein the mass of the bacterial cellulose in the mass ratio refers to the absolute dry weight, and the absolute dry weight refers to the mass of cellulose when the water content is 0.

[0040] Table 2 Nitration process parameters

[0041] Mass ratio of mixed acid to bacterial cellulose Nitration reaction temperature Nitration reaction time Example 1 42:1 36℃ 35min Example 2 42:1 36℃ 35min

[0042] 2. Boiling and washing: The acid-cotton mixture is boiled and washed after acid-cotton separation and washing. The boiling and washing is a continuous boiling with acid water. The specific process is shown in Table 3.

[0043] Table 3 Boil-wash process parameters

[0044]

[0045] 3. Dehydration to obtain civilian nitrified bacterial cellulose;

[0046] The civilian nitrified bacterial cellulose prepared in Example 1 has a nitrogen content of 11.20%, a whiteness of 82%, a viscosity of 21.8 mpa.s, a light transmittance of 78%, and a heat resistance test of 80°C for 25 min, which meets the technical requirements of WJ / T9015;

[0047] The civilian nitrified bacterial cellulose prepared in Example 2 has a nitrogen content of 11.00%, a whiteness of 83%, a viscosity of 23.8 mPa.s, a light transmittance of 77%, and a heat resistance test of 80°C for 23 min, which meets the technical requirements of WJ / T9015.

[0048] Based on the above, it can be seen that bacterial cellulose can be used as a raw material for the preparation of civilian nitrocellulose; compared with the boiling and washing time (≥4h) of the current civilian nitrocellulose production line, the boiling and washing time in the preparation method of the present invention is significantly shortened; at the same time, the process flow is further simplified, providing a new idea for the preparation of civilian nitrocellulose.

Claims

1. A method for preparing civilian nitrified bacterial cellulose, characterized in that: The specific steps include: a. Nitration: Mix bacterial cellulose with mixed acid to undergo nitration reaction to obtain an acid-cotton mixture; b. Boiling and washing: The acid-cotton mixture is boiled and washed after acid-cotton separation and washing. The boiling and washing is a continuous boiling of acid water, which is divided into two stages: The first stage of boiling and washing time is 1 to 2 hours, the boiling and washing temperature is 100 to 110°C, the boiling and washing acidity is 6 to 8 g / L, and the boiling and washing pressure is 0.05 to 0.10 MPa; The second stage of boiling and washing time is 0.5 to 1 hour, the boiling and washing temperature is 120 to 130°C, and the boiling and washing pressure is 0.05 to 0.10Mpa; c. Dehydration to obtain civilian nitrified bacterial cellulose.

2. The method for preparing civilian nitrified bacterial cellulose according to claim 1, characterized in that: In step a, the α-cellulose content in the bacterial cellulose is ≥97.0%, the ash content is ≤0.15%, and the sulfuric acid insoluble matter is ≤0.25%.

3. The method for preparing civilian nitrified bacterial cellulose according to claim 1, characterized in that: In step a, the viscosity of the bacterial cellulose is 10-20 MPa.s higher than the viscosity of the civilian nitrocellulose product, and the whiteness is ≥88%.

4. The method for preparing civilian nitrified bacterial cellulose according to claim 1, characterized in that: In step a, the mixed acid is a mixture of nitric acid, sulfuric acid and water; wherein the nitric acid content is 18% to 25%, the water content is 16% to 21%, and the rest is sulfuric acid.

5. The method for preparing civilian nitrified bacterial cellulose according to claim 4, characterized in that: The mass concentration of nitric acid is 98%, and the mass concentration of sulfuric acid is 98%.

6. The method for preparing civilian nitrified bacterial cellulose according to claim 1, characterized in that: In step a, the mass ratio of the mixed acid to the bacterial cellulose is (40-45):1, and the mass of the bacterial cellulose refers to the absolute dry weight, which refers to the mass of the bacterial cellulose when the water content is 0.

7. The method for preparing civilian nitrified bacterial cellulose according to claim 1, characterized in that: In step a, the nitration reaction temperature is 25-55°C.

8. The method for preparing civilian nitrified bacterial cellulose according to claim 1, characterized in that: In step a, the nitration reaction time is 30 to 40 minutes.

9. Civilian nitrified bacterial cellulose, characterized by: The method is prepared according to any one of claims 1 to 8.

10. The civilian nitrified bacterial cellulose according to claim 9, characterized in that: The nitrogen content is 10.7-12.2%, the whiteness is 80-88%, the viscosity is 11.5-29mPa.s, the light transmittance is 75-85%, and the heat resistance test is 80℃ for 20-30min.

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