CN104017090B - A kind of method adopting hydrogen peroxide to prepare carboxycellulose - Google Patents

Abstract

The invention relates to a method for preparing carboxy cellulose by using hydrogen peroxide. The method comprises the following steps: taking 20 parts by mass of cellulose and soaking in a pretreatment solution with a mass fraction of 5% to 40%, washing with distilled water after soaking for 1 to 48 hours, suction filtering to neutrality, adding 10 ~80 parts by mass of oxidant, and catalysts accounting for 0.01%~5% of the mass of cellulose, stirred with a magnetic stirrer for 0.5~96 hours, followed by solid-liquid separation, and the solid product was washed with distilled water until the pH was 7.0, and the obtained solid sample was placed in Drying in an oven at a temperature of 40°C to 80°C for 4 to 12 hours to obtain oxidized cellulose with different degrees of oxidation. The invention has relatively mild reaction conditions, simple process, high yield, no special requirements on equipment technology, convenient industrial application, low preparation cost and no harmful by-products. The method is environmentally friendly and does not cause any harm or pollution to the environment.

Description

A kind of method adopting hydrogen peroxide to prepare carboxy cellulose

technical field

The invention belongs to the technical field of carboxy cellulose, in particular to a method for preparing carboxy cellulose by using hydrogen peroxide.

Background technique

Cellulose is a macromolecular polysaccharide composed of D-glucopyranose with β-1,4-glucosidic bonds, with a molecular weight of about 50,000 to 2,500,000, equivalent to 300 to 15,000 glucosyl groups, and is the most widely distributed and most abundant in nature. Natural polymers, derived from the photosynthesis of plants, are cheap and widely used in various fields.

Oxidized cellulose (OxidizedCellulose) is a derivative of cellulose, which has the characteristics of good biocompatibility, biodegradability, environmental friendliness and non-toxicity, so it is widely used in many fields. The performance of oxidized cellulose with high carboxyl content is greatly improved compared with natural cellulose after chemical modification. In particular, the carboxyl group has a good chelating effect on heavy metal ions, and can be widely used in the adsorption of metal ions, purification of industrial wastewater, antibacterial and other aspects. Zhang Shenghong et al. used NaOH solution to modify natural cellulose to improve its oxidizing ability, and used TEMPO-NaOCl-NaBr system as oxidant to selectively oxidize the primary hydroxyl group of cellulose glucosyl ring into carboxyl group. A fiber prepared by this technology Su-based heavy metal adsorption materials can be placed in the regulating tank of biological aerated filter to pretreat heavy metal ions such as Cu ²⁺ and Cd ²⁺ (Zhang Shenghong, Chen Jihua, Research on deep purification of organic wastewater by biological aerated filter, 2006) . Wang Fengchuan et al. used oxidized cellulose as a matrix, made a solution, and prepared copper ion-loaded cellulose-based nanoparticles through magnetic stirring, high-speed centrifugation, and drying, which increased the contact probability between antibacterial agents and bacteria, and improved antibacterial performance (Wang Fengchuan , Chen Yanmo, preparation and characterization of carboxylated polysaccharide-based nanomaterials loaded with metal ions, 2006). The Chinese patent with publication number CN1O2776594A discloses a cellulose fiber-loaded nano-silver antibacterial material and a preparation method thereof. In this invention, the cellulose fiber is chemically pretreated, and then TEMPO is selectively oxidized, and it is combined with silver nitrate aqueous solution without adding any reducing agent, and the nano-silver particles with small diameters are prepared by microwave heating for a short time. , The cellulose fiber with uniform structure supports nano-silver antibacterial material, which realizes the in-situ reduction and growth of nano-silver on the carboxylated cellulose fiber carrier. In addition, oxidized cellulose containing carboxyl groups is an important class of degradable polymers. In the medical field, it is mostly in the form of powder and non-woven fabrics, used for hemostasis during surgery and to prevent the formation of tissue adhesions after surgery. The medical absorbable hemostatic gauze sold on the market is all imported products, which cannot be produced in China, so the price is expensive. And the method for preparing oxidized cellulose hemostatic product in the domestic public report has: the method that the patent that publication number is CN1O201899A adopts is that viscose filament fabric is starting raw material, adopts organic oxidation solvent system to carry out viscose filament fabric Oxidation, after the oxidation reaction is completed, the oxidized cellulose hemostatic product is made by washing and drying. The carboxyl content of the product can reach 15% to 24%. The organic oxidation solvent used is cyclohexane or methylcyclohexane. The patent with the publication number CN1531976A provides a method for preparing a hemostatic wound dressing, which uses a fibrous fabric base made of carboxylated oxidized cellulose, and this fabric base contains a first surface and a second surface opposite to the first surface. On the surface, the fabric substrate has the flexibility, strength and porosity required for use as a hemostat. The patent with the publication number WO2012128671-A1 first oxidizes polypropylene at 180°C to 240°C for 4 to 6 hours, then dissolves it in tetrachlorethylene, and then dissolves the cellulose material in a saturated solution containing 0.4 %～0.5% oxidized polypropylene solution, drain it after dissolving, and then evaporate to dryness and condense by hot air, the obtained dry cellulose can not only be used to remove oil stains on the surface of water, but also can be used for industrial drainage cleaning. The excellent properties of oxidized cellulose can also be used in the tobacco industry as a substitute for natural tobacco, as an ion exchange material for photographic paper, and as a raw material for preparing activated carbon. U.S. Patent No. 6,627,749 B1 discloses a method of oxidizing cellulose by using a mixed liquid of sodium nitrite, phosphoric acid, and nitric acid to prepare oxidized cellulose with a carboxyl content lower than 24.5%, which can be used in the fields of medicine, chemical industry, and medical polymers. U.S. Patent No. 6120554-A discloses a method of oxidizing cellulose by using an alkyl quaternary ammonium salt as a catalyst and hydrogen peroxide as an oxidant to prepare oxidized cellulose, but the degree of oxidation is very low and the oxidation efficiency is poor. It is difficult to be widely used at a higher temperature. Japanese Patent No. 2011057749A reports the use of polar oxidants to oxidize hydroxyl groups on cellulose _C6 into aldehyde groups and carboxyl groups, wherein the carboxyl group content in the obtained oxidized cellulose is 0.6-2.2 mmol/g. German patent DE102010034782 reports a method for preparing cellulose with an oxidation degree of 5% to 50%. The method uses an oxidizing agent such as sodium hypochlorite for oxidation treatment at a reaction temperature of 20°C to 160°C.

So far, there have been reports on the preparation of carboxylated oxidized cellulose at home and abroad, but the preparation process is complicated and the conditions are harsh, and it must be prepared in a strongly acidic or alkaline medium. The selected oxidizing agent is not only destructive to cellulose itself, but also has by-products left over, which has a certain impact on the environment. During the reaction process, the molecular weight of cellulose will be reduced to a certain extent, the oxidation and degradation are not uniform, and the degradation is too severe and other defects, which limit the wide application of oxidized cellulose.

Contents of the invention

The present invention overcomes the shortcoming of prior art, provides a kind of method that adopts hydrogen peroxide to prepare carboxy cellulose, comprises the steps:

Weigh 20 parts by mass of cellulose and soak in a pretreatment solution with a mass fraction of 5% to 40%, wash with distilled water after soaking for 1 to 48 hours, and filter until neutral, and add 10 to 80 parts by mass of an oxidizing agent , and a catalyst that accounts for 0.01% to 5% of the cellulose mass, and after stirring with a magnetic stirrer for 0.5 to 96 hours at a temperature of 10 to 60° C., solid-liquid separation is carried out, and the solid product is washed with distilled water until the pH is 7.0, and the obtained The solid sample is dried in an oven at a temperature of 40° C. to 80° C. for 4 to 12 hours to obtain oxidized cellulose with different degrees of oxidation, namely carboxylated cellulose; the degree of oxidation is 1% to 10%.

In the above method, the solvent in the pretreatment solution described in step (1) includes more than one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, thiourea or urea; The solid-liquid separation method used includes any one or a combination of centrifugal separation, mechanical filtration or vacuum suction filtration.

In the above method, the catalyst described in step (1) includes a mixed solution of one or more of sulfate, chloride, bromide or iodide; the catalyst consumption is 0.01% to 5% of the cellulose mass .

In the above method, the oxidizing agent is hydrogen peroxide, its mass percentage concentration is 5%-35%, and its dosage is 0.5-4 times of the cellulose fraction.

In the above method, the sulfates include ferric sulfate, copper sulfate, cobalt sulfate, manganese sulfate or zinc sulfate; the chlorides include zinc chloride, cobalt chloride, cuprous chloride, ferrous chloride, ferric chloride or copper chloride; said bromide includes zinc bromide, cobalt bromide, ferrous bromide, ferric bromide or copper bromide.

In the above method, the cellulose is derived from cotton, hemp, wheat straw, rice straw, bagasse, coarse grains, bran, vegetables or beans.

Compared with the prior art, the present invention has the following advantages:

(1) Compared with other methods at present, the present invention oxidizes cellulose with cheap hydrogen peroxide as an oxidizing agent, introduces a large amount of carboxyl groups in the reaction process, reaches the purpose of controlling carboxyl group content by controlling the content of hydrogen peroxide, and reacts The conditions are relatively mild, the preparation is simple, there is no special requirement for equipment technology, it is convenient for industrial application, and the production cost is reduced;

(2) Since the method for preparing oxidized cellulose with high carboxyl content provided by the present invention is completed in a low-acidity environment, the reaction temperature is low, thereby avoiding the preparation of carboxylation oxidation in high temperature, high-concentration acid or alkaline medium. Cellulose causes a serious problem of molecular weight drop;

(3) The degree of oxidation of the carboxylated oxidized cellulose prepared by the method provided by the invention can be as high as 10.4%, and the oxidized cellulose with different carboxyl content can also be prepared by controlling the addition of hydrogen peroxide, so as to meet the requirements of different use occasions Require;

(4) prepare carboxylated oxidized cellulose with hydrogen peroxide provided by the present invention, the adsorption effect to heavy metal ions such as lead, copper ion is obvious, wherein the adsorption value to lead ion is improved more than 10 times than the adsorption value of pure cellulose, to copper ion The adsorption value is more than 3 times higher than that of pure cellulose;

(5) Due to the new method for preparing oxidized cellulose with low cost and high carboxyl content provided by the present invention, the product after the reaction is water without other by-products, which has the advantages of environmental protection and will not cause any environmental pollution problems.

Description of drawings:

Fig. 1 is the infrared spectrogram of comparative example 1, embodiment 4 and embodiment 6 products;

Fig. 2 is the solid carbon spectrogram of comparative example 1 product;

Fig. 3 is the solid carbon spectrogram of embodiment 6 product;

Fig. 4 is the SEM figure of pure cellulose;

Fig. 5 is the SEM figure of the oxidized cellulose of embodiment 2;

Fig. 6 is the SEM figure of the oxidized cellulose of embodiment 4;

Fig. 7 is the SEM figure of the oxidized cellulose of embodiment 6;

Fig. 8 is a standard curve diagram of the adsorption value of oxidized cellulose obtained in Comparative Example 1 and various examples for the adsorption capacity of Cu ²⁺ and Pb ²⁺ .

detailed description

Examples are given below and the present invention is further described.

In addition, it is worth noting that the parts of solid materials in the examples are parts by mass, and the parts of liquid materials are also parts by mass. There are many methods for the determination of carboxyl content in oxidized cellulose, according to the literature [Preparation and Research on Structure and Properties of Oxidized Cellulose, Wang Li, Xiang Bingren, Zou Qiaogen, Progress in Pharmacy, 2009, 33(8): 365-371 ] for titration, specifically as follows: Accurately weigh about 0.5 g of dried oxidized cellulose, cut into pieces, accurately weigh, completely immerse in 50 mL of 2% calcium acetate solution, and ultrasonically vibrate for 30 minutes. Titrate with 0.1M NaOH solution, use phenolphthalein as indicator, and pure cellulose as blank solution for calibration. The carboxyl content in the sample is calculated according to the formula (1), and the above experiment takes the average value of the titration results of 3 times.

In the above formula, C is the NaOH concentration (mol/L); V ₁ is the volume (L) that the sample solution to be tested consumes NaOH; V ₂ is the volume (L) that pure cellulose consumes NaOH; M is 45g/mol ( Carboxyl molar mass); W is the sample weight (g).

Embodiment Infrared spectrum analysis and solid-phase nuclear magnetic analysis adopt Vector33 (Germany Bruker company) and AVANCEDigital400MHzNMR (Germany Bruker company) to test respectively, and microscopic morphology analysis is after spraying gold to cellulose, adopts S-3700N (Japan Hitachi company) conduct. The experiment of lead ion and copper ion is as follows:

1, prepare the 1% dilute nitric acid solution of 2L with deionized water for subsequent use, prepare the stock solution of copper sulfate and lead nitrate solution of mass concentration 200mg/L, be used for adsorption experiment as mother liquor, measure copper, Lead working curve range, copper sulfate and lead nitrate solutions prepare standard solutions with a concentration of 0-5mg/L and 0.5-5mg/L respectively, and are used to measure absorbance by flame atomic absorption spectrophotometry (FTAS-990, Shimadzu Corporation of Japan), Draw the standard curves of Cu ²⁺ and Pb ²⁺ respectively.

2. Weigh 0.02g of different samples, add them into 100mL Erlenmeyer flask with stopper and 25mL of copper sulfate and lead nitrate solution of known concentration, shake on a rotary oscillator at room temperature for 2h, let it stand still for 30min, and take the supernatant to measure Absorbance.

3. Use formula (1) to calculate the adsorption capacity of 10 samples to copper and lead respectively.

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; W</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them: Q _e , C ₀ , V, W are the adsorption capacity of the adsorbent, mg/L; the initial concentration of copper or lead before adsorption, mg/L; the equilibrium mass concentration of copper or lead after adsorption, mg/L; Solution volume of copper or lead, mL; sample mass, g.

In the following examples, the cellulose used in Comparative Example 1 is cotton, the cellulose used in Example 1 is straw, the cellulose used in Example 2 is cotton, the cellulose used in Example 3 is wheat straw, and the cellulose used in Example 4 is straw. The cellulose used is bagasse, the cellulose used in embodiment 5 is bran, and the cellulose used in embodiment 6 is cotton.

Comparative example 1

Take 20 parts by mass parts of cellulose and soak in 18% sodium hydroxide solution, wash with distilled water after soaking for 12 hours, filter to neutrality, then add 30 parts of hydrogen peroxide, at a temperature of Stir with a magnetic stirrer at 45°C for 48 hours. After oxidation, the sample was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at 60°C for 4 hours. After drying, it was ground into powder and then dissolved and titrated. The carboxyl content was measured to be 0.7%.

Example 1

Take 20 parts by mass of cellulose and soak it in a potassium carbonate solution with a mass fraction of 24%, wash it with distilled water after soaking for 2 hours, and filter it to neutrality, then add 14 parts of hydrogen peroxide and 100 parts of water , and cobalt sulfate accounting for 0.025% of the cellulose mass, stirred with a magnetic stirrer for 24 hours at a temperature of 20°C. After oxidation, it was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at 55°C for 8 hours to obtain oxidized cellulose with high carboxyl content, which was ground into powder and then dissolved and titrated, and the carboxyl content was measured as 6.3%.

Example 2

Weigh 20 parts by mass of cellulose and soak it in 18% sodium hydroxide solution, wash with distilled water after soaking for 12 hours, and filter it to neutrality, then add 30 parts of hydrogen peroxide and 100 parts of cellulose Water, and iron sulfate accounting for 0.075% of the mass of cellulose were stirred with a magnetic stirrer for 48 hours at a temperature of 15°C. After oxidation, it was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at 60°C for 6 hours. After drying, it was ground into powder and then dissolved and titrated. The carboxyl content was found to be 6.7%.

Example 3

Take 20 parts by mass parts of cellulose and soak it in a potassium hydroxide solution with a mass fraction of 30%, wash it with distilled water after soaking for 8 hours, and filter it to neutrality, then add 28 parts of hydrogen peroxide and 100 parts of Water and cobalt sulfate accounting for 1% of the cellulose mass were stirred with a magnetic stirrer for 75 hours at a temperature of 25°C. After oxidation, the sample was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at 60°C for 7 hours. After drying, it was ground into powder and then dissolved and titrated. The carboxyl content was found to be 6.6%.

Example 4

Take 20 parts by mass parts of cellulose and soak it in the potassium bicarbonate solution whose mass fraction is 40%, wash with distilled water after soaking for 48 hours, suction filter to neutrality, then add 56 parts of hydrogen peroxide and 100 parts of Water, and nickel chloride accounting for 0.5% of the cellulose mass were stirred with a magnetic stirrer for 86 hours at a temperature of 50°C. After oxidation, it was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at a temperature of 50°C for 9 hours. After drying, it was ground into powder and then dissolved and titrated. The carboxyl content was measured to be 9.2%.

Example 5

Take 20 parts by mass parts of cellulose and soak in 24% sodium bicarbonate solution in mass fraction, wash with distilled water after soaking for 6 hours, filter to neutrality, then add 36 parts of hydrogen peroxide and 100 parts of Water, and zinc chloride accounting for 3% of the cellulose mass, were stirred with a magnetic stirrer for 50 hours at a temperature of 30°C. After oxidation, it was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at 60°C for 4 hours. After drying, it was ground into powder and then dissolved and titrated. The carboxyl content was measured to be 8.5%.

Example 6

Weigh 20 parts by mass of cellulose and soak it in 18% sodium bicarbonate solution, wash with distilled water after soaking for 48 hours, filter to neutrality, then add 65 parts of hydrogen peroxide and 100 parts of Water and manganese sulfate accounting for 5% of the cellulose mass were stirred with a magnetic stirrer for 48 hours at a temperature of 50°C. After oxidation, it was washed with distilled water until the pH was 7, and the obtained sample was dried in an oven at a temperature of 40°C for 4 hours. After drying, it was ground into powder and then dissolved and titrated. The carboxyl content was measured to be 10.2%.

Fig. 1 is the infrared spectrogram of comparative example 1, embodiment 4 and embodiment 6 product, as can be seen from (b) and (c) curve among Fig. 1, very strong absorption peak appears at 1724cm ^-1 , and this peak is The hydroxyl group on _C6 is oxidized to the carboxyl absorption peak of carboxyl group, showing that cellulose is successfully oxidized; Fig. 2 is the solid carbon spectrogram of comparative example 1, and Fig. 3 is the solid carbon spectrogram of the product of embodiment 6, as can be seen from the figure It can be seen that compared with Figure 2, the response signal of carboxyl carbon atoms appears in Figure 3 at 170ppm-180ppm, suggesting that the hydroxyl group at the _C6 position in the cellulose structure is oxidized to carboxyl, which also shows that the cellulose is successfully oxidized. Figure 4-Figure 7 is the SEM image of cellulose and oxidized cellulose (magnification 10 times, the minimum scale of the icon size is 50um), it can be seen from Figure 4-Figure 7 that the appearance of oxidized cellulose is still smooth, No obvious fiber breakage was seen, so it can be explained that the oxidation process used in the present invention has little damage to cellulose. Fig. 8 is a standard curve diagram of the adsorption value of oxidized cellulose obtained in Comparative Example 1 and each embodiment to Cu ²⁺ , Pb ²⁺ adsorption capacity, wherein 0 in the abscissa represents Comparative Example 1, and 1-6 represent Example 1 respectively -6. It can be seen from the figure that the oxidized cellulose prepared by hydrogen peroxide has obvious adsorption effect on Cu ²⁺ and Pb ²⁺ heavy metal ions, and the adsorption value of lead ion is more than 10 times higher than that of pure cellulose. Copper ion adsorption is more than 3 times higher than that of pure cellulose.

The above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in different forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the claims of the present invention.

Claims (3)

1. a method adopting hydrogen peroxide to prepare carboxy cellulose, is characterized in that, comprises the following steps: Weigh 20 parts by mass of cellulose and soak it in a pretreatment solution with a mass fraction of 5% to 40%. After soaking for 1 to 48 hours, wash with distilled water, filter until neutral, and add 10 to 80 parts by mass of oxidizing agent , and a catalyst accounting for 0.01% to 5% of the cellulose mass, stirred with a magnetic stirrer at a temperature of 10 to 60°C for 0.5 to 96 hours, then separated from the solid and liquid, and the solid product was washed with distilled water until the pH was 7.0, and the obtained The solid sample is dried in an oven at a temperature of 40°C to 80°C for 4 to 12 hours to obtain oxidized cellulose with different degrees of oxidation, that is, carboxylated cellulose; the solvent in the pretreatment solution includes sodium carbonate, sodium bicarbonate, More than one of potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, thiourea or urea; the solid-liquid separation method used includes any one or several methods of centrifugal separation, mechanical filtration or vacuum filtration combination; the catalyst includes one or more mixed solutions of sulfate, chloride, bromide or iodide; the amount of the catalyst is 0.01% to 5% of the cellulose mass; Hydrogen, its mass percent concentration is 5%~35%, and its dosage is 0.5~4 times of the cellulose part. 2. The method for preparing carboxy cellulose by hydrogen peroxide according to claim 1, wherein the cellulose is derived from cotton, hemp, wheat straw, straw, bagasse, coarse grains, bran, vegetables or beans . 3. adopt hydrogen peroxide to prepare the method for carboxy cellulose according to claim 1, it is characterized in that, described sulfate comprises ferric sulfate, cupric sulfate, cobalt sulfate, manganese sulfate or zinc sulfate; Described chloride comprises chlorinated Zinc, cobalt chloride, cuprous chloride, ferrous chloride, ferric chloride or cupric chloride; said bromide includes zinc bromide, cobalt bromide, ferrous bromide, ferric bromide or copper bromide.