Preparation method of cellulose ester and water-soluble paper
By preparing a mixture of low-substituted cellulose esters and plant fibers, the problem of poor solubility in water-soluble paper was solved, resulting in water-soluble paper with high efficiency and excellent mechanical properties, suitable for industrial applications.
Patent Information
- Application Number
- CN202511013016.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-22
- Publication Date
- 2025-12-16
AI Technical Summary
Existing water-soluble paper has poor solubility and cannot meet the requirements for high water solubility, resulting in high cost and low efficiency in industrial applications.
Cellulose esters were prepared through alkalization, etherification, and purification steps. They were then reacted with an acid solution and mixed with plant fibers. Water-soluble paper was prepared by pulping, screening, and papermaking, with the degree of substitution of cellulose esters controlled between 0.45 and 0.83.
It improves the water solubility and mechanical properties of water-soluble paper, reduces production costs, and makes it suitable for industrial production.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of special paper, in particular to a preparation method of cellulose ester and water-soluble paper. BACKGROUND
[0002] Water-soluble paper brings revolutionary improvements in the field of pipe welding technology. In the welding process, in order to ensure the welding quality, it is necessary to achieve comprehensive and efficient gas protection. Traditional methods such as inflatable rubber airbags, rubber pads or circular paper boards often have to be placed at a distance from the welding point, resulting in the need for more inert gas (such as argon) to form an effective protection layer in the welding area, thereby causing a large amount of gas waste and significantly increasing the cost. Water-soluble paper can be placed in close proximity to the welding point, thereby achieving precise gas control, and only a small amount of gas is needed to achieve the desired protection effect, greatly reducing the cost. Its unique characteristics enable water-soluble paper to dissolve rapidly and completely in most liquids, especially when welding steel and aluminum alloy pipes, effectively assisting in the control of argon and helium. After the welding is completed, only water or steam cleaning of the inside of the pipe is required to ensure that there is no water-soluble paper residue, and the gas is quickly dispersed, achieving further cost optimization.
[0003] In addition, water-soluble paper can be used as the base material of "water-soluble labels", and its base paper and adhesive can be completely dissolved and dispersed in water. With the increase of temperature, its dissolution speed is significantly accelerated, and it is suitable for labels and seals on glass, plastic, ceramic, aluminum, copper, stainless steel and other recyclable containers that can be cleaned with cold or hot water.
[0004] In the prior art, the production of water-soluble paper is mainly through the hanging pulp treatment of paper made by wet papermaking with polyvinyl alcohol solution, and then through the processes of vacuum dewatering, drying, and polishing to prepare. Although this papermaking process is relatively simple and requires less equipment investment, the water-soluble paper prepared has poor dissolution performance and cannot meet the application fields with high water-solubility requirements.
[0005] Therefore, how to improve the water-solubility of water-soluble paper and optimize the reaction conditions so that it is suitable for industrial production has become a technical problem to be solved. In view of the above, there is an urgent need in the field for a preparation method of water-soluble paper to solve the above technical problems.
[0006] In view of this, the present application is proposed. SUMMARY
[0007] The purpose of the present application is to provide a preparation method of cellulose ester and water-soluble paper to solve at least one technical problem mentioned in the background art.
[0008] In a first aspect of the present application, a preparation method of cellulose ester is provided, comprising the steps of:
[0009] alkalization step, the cellulose raw material is mixed with an organic solvent and an alkali solution to perform an alkalization reaction to obtain alkali cellulose; the mass fraction of the organic solution is 50-95%, the mass fraction of the alkali solution is 20-60%, the mass ratio of cellulose: alkali solution: organic solvent is 1:1.0-4.0:1.5-3.2, the reaction time is 0.5-4h, and the reaction temperature is controlled at 30-70℃;
[0010] etherification step, an etherification agent and an organic solvent are added into the mixed solution obtained in the alkalization step, the mass fraction of the organic solution is 50-95%, the mass ratio of the mixed solution: etherification agent: organic solvent is 1:0.5-3.0:0.3-2.0, the temperature of the etherification reaction is gradually increased, the reaction temperature is controlled at 60-80℃, and the reaction time is 1-4h; after a period of reaction, a viscosity reducer is added to reduce viscosity;
[0011] purification step, the solution obtained in the etherification step is cooled to 40-60℃, washed with an organic solvent, dried after removing the salt produced in the reaction, and the cellulose esterification product is obtained.
[0012] Preferably, in the alkalization step, the mass fraction of the organic solution is 90%, the mass fraction of the alkali solution is 22-45%, and / or the mass ratio of cellulose: alkali solution: organic solvent is 1:2.8-4.0:2.0-3.2, and / or the reaction time is 2-2.5h, and the reaction temperature is controlled at 30-40℃.
[0013] Preferably, in the etherification step, the mass fraction of the organic solution is 90-95%, and / or the mass ratio of the mixed solution: etherification agent: organic solvent is 1:0.88-2.2:0.5-1.1, and / or the temperature of the etherification reaction is gradually increased, the reaction temperature is controlled at 75℃, and the reaction time is 2-3h.
[0014] Preferably, in the alkalization step, a kneader is used for kneading reaction.
[0015] Preferably, in the etherification step, the organic solvent is one or more of methanol, ethanol, toluene and isopropanol.
[0016] Preferably, in the etherification step, the viscosity reducer is hydrogen peroxide.
[0017] Preferably, in the purification step, the solution obtained in the etherification step is cooled to 40℃, washed with an ethanol solvent, dried at 80℃ for 6h after removing the salt produced in the reaction, and the cellulose esterification product is obtained.
[0018] Preferably, the degree of substitution of the cellulose esterification product is 0.45-0.83.
[0019] In a second aspect of the present application, a method for preparing water-soluble paper is provided, comprising the steps of:
[0020] an acidification step, wherein the cellulose esterification product prepared in the first aspect of the present application is mixed with an acid solution at a mass ratio of 1:6-40, and the acid solution has a mass fraction of 2.5%-30%, and after acidification, the cellulose ester is washed with water until the pH is between 6.5 and 7.5;
[0021] a refining and screening step, wherein the product of the acidification step is subjected to refining and screening;
[0022] a papermaking step, wherein the cellulose ester obtained in the refining and screening step is mixed with plant fibers to obtain a mixed pulp, and after dewatering, forming, pressing and drying, a water-soluble paper base paper is prepared, and after alkali treatment, a water-soluble paper product is obtained.
[0023] Preferably, in the acidification step, the acid solution is a 10-25% sulfuric acid solution; and / or, the cellulose esterification product is mixed with the acid solution at a mass ratio of 1:8-20; and / or, in the acidification step, the reaction temperature is 25-30°C, and the reaction time is 2-4h.
[0024] Preferably, in the refining and screening step, the pulp can pass through a 0.15mm fine gap screening plate, and the refining is performed using a KRK refiner with a gap width of 0.2mm.
[0025] Preferably, the mixed pulp comprises plant fibers, cellulose ester, fillers and filler retention aids, and the mass percentage of plant fibers in the mixed pulp is 20%-80%, the mass percentage of cellulose ester in the mixed pulp is 15%-75%, and the mass percentage of fillers in the mixed pulp is 5%-25%, the beating degree of the plant fiber pulp is 12°-50°SR, and the addition amount of the filler retention aid is 0.01%-2.0% of the dry fibers.
[0026] Preferably, the mass percentage of plant fibers in the mixed pulp is 40-50%, the mass percentage of cellulose ester in the mixed pulp is 25-45%, and the mass percentage of fillers in the mixed pulp is 15%-25%, and the addition amount of the filler retention aid is 0.05-0.06% of the dry fibers.
[0027] Preferably, the plant fiber pulp is one or more of coniferous wood pulp, broadleaf wood pulp, hemp pulp, bamboo pulp, grass pulp, reed pulp and cotton pulp. More preferably, the plant fiber pulp is selected from broadleaf wood pulp with a beating degree of 15-55°SR, and / or coniferous wood pulp with a beating degree of 10-50°SR.
[0028] Preferably, the fillers are one or more of calcium carbonate, diatomite, talc and titanium dioxide.
[0029] Preferably, the filler retention aid is one or more of cationic polyacrylamide (CPAM), polyaluminum chloride, aluminum sulfate.
[0030] Preferably, the basis weight of the water-soluble paper base paper is 15-200 g / m 2 , more preferably 60-100 g / m 2 .
[0031] Preferably, in the papermaking step, the pressure of the dewatering press is 200-400 kPa, and the time is controlled to be 0.2-5 min; more preferably, the pressure of the dewatering press is 200-300 kPa, and the time is controlled to be 30-60 s.
[0032] Preferably, in the papermaking step, the drying temperature of the water-soluble paper base paper is 60-110℃.
[0033] Preferably, in the papermaking step, the alkali species of the alkali treatment is sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and the alkali concentration is 2%-10%, more preferably 2%-4%.
[0034] Preferably, in the papermaking step, the alkali treatment of the base paper can be realized by impregnation, coating, etc. Further, the coating method is one or more of doctor blade, doctor bar, spraying, air knife, and roll coating.
[0035] Preferably, in the papermaking step, the drying method after the alkali treatment is one or more of hot air drying, oven drying, and infrared drying.
[0036] Preferably, in the papermaking step, the drying temperature of the alkali treatment is 70-120℃.
[0037] In summary, the present application has the following beneficial effects:
[0038] First, the cellulose ester preparation method provided by the present application has a simple preparation process, consumes less alkali agent and ether agent, has a low degree of substitution of the obtained cellulose ester, and can directly use the existing cellulose ester production equipment, which is conducive to the popularization and application in industry.
[0039] Second, the water-soluble paper preparation method provided by the present application obtains cellulose ester through acid treatment, grinding, screening, and compounding with plant fibers and fillers to obtain a water-soluble paper base paper, and the base paper is treated with alkali to obtain a water-soluble paper product. Compounding of plant fibers with a high beating degree can improve the strength of the paper, and the addition of cellulose ester can improve the water solubility of the paper. The combination of the two can be used to prepare water-soluble paper with good performance. The process is simple, the equipment energy consumption is low, and the cost is low, which is conducive to subsequent production. DETAILED DESCRIPTION
[0040] The exemplary embodiments will be described in detail below with reference to the attached drawings.
[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.
[0042] The present application will be described in detail below with reference to the following examples.
[0043] In the prior art, the production of water-soluble paper is mainly through the sizing treatment of a paper sheet made by a wet papermaking process with a polyvinyl alcohol solution, and then prepared by a process flow of vacuum dewatering, drying, and polishing. Although this papermaking process is relatively simple and the equipment investment is less, the prepared water-soluble paper performs poorly in the dissolving performance and cannot meet the application fields with high efficiency water-soluble requirements.
[0044] In view of this, in order to solve the technical problems existing in the background art, the inventive concept of the present application provides a preparation method of cellulose ester, comprising the steps of: an alkalization step, mixing cellulose raw material with an organic solution and an alkali solution to perform an alkalization reaction to obtain alkali cellulose; the mass fraction of the organic solution is 50-95%, the mass fraction of the alkali solution is 20-60%, the mass ratio of cellulose: alkali solution: organic solvent is 1:1.0-4.0:1.5-3.2, the reaction time is 0.5-4h, and the reaction temperature is controlled at 30-70°C; an etherification step, adding an etherification agent and an organic solvent into the mixed solution obtained in the alkalization step, the mass fraction of the organic solution is 50-95%, the mass ratio of the mixed solution: etherification agent: organic solvent is 1:0.5-3.0:0.3-2.0, the etherification reaction temperature is gradually increased and controlled at 60-80°C, and the reaction time is 1-4h; a viscosity reducer is added after a period of time for viscosity reduction; a purification step, cooling the solution obtained in the etherification step to 40-60°C, washing with an organic solvent, drying after removing the salt produced in the reaction, and obtaining a cellulose ester product.
[0045] According to the inventive concept, through the treatment of the alkalization, etherification, and purification steps of the cellulose raw material, the cellulose ester obtained has a low degree of substitution, and can be directly applied to the existing cellulose ester production equipment, which is beneficial to the popularization and application in industry.
[0046] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with specific embodiments, and those skilled in the art should understand that the reaction time, component feeding involved in the present application cannot be absolutely accurate in actual production process, but are within the allowable error range. For example, if a sample is desired to be heated for 30 minutes, the actual operation may be 30 minutes plus or minus 1 second; if a 30g sample is desired to be weighed, the actual weighing may be 30.001g or 29.998g.
[0047] Unless otherwise specified, all raw materials involved in the present application are commercially available products.
[0048] Example 1
[0049] A high-efficiency water-soluble paper, the preparation method comprising the steps of:
[0050] S100, preparing cellulose ester:
[0051] S101, alkalization step: after the needle pulp raw material is defibrated and dried, it reacts with an alkali solution, the reaction occurs in an ethanol solution; the mass ratio of the needle pulp raw material: alkali solution: ethanol solution is 1:2.8:2.0, the kneader kneading reaction time is 2.5h, and the reaction temperature is controlled at 40℃;
[0052] Among them, the mass fraction of the ethanol solution is 90%, and the alkali solution is a sodium hydroxide solution with a mass fraction of 45%.
[0053] S102, etherification step: adding etherifying agent chloroacetic acid and ethanol solution to the mixture after the alkalization step, the mass fraction of the ethanol solution is 95%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:0.94:0.55, the etherification temperature is 75℃, and the reaction time is 2h;
[0054] After the reaction is completed, hydrogen peroxide is added, and the mass ratio of cellulose: hydrogen peroxide is 10:1.
[0055] S103, purification step: after cooling to 40℃, washing with ethanol solution for 5 times, removing the salt produced in the reaction, and drying in an 80℃ oven for 6h, the cellulose esterification product is obtained, and the degree of substitution is detected to be 0.45.
[0056] S200, preparing water-soluble paper:
[0057] S201, acidification step, the cellulose esterification product is treated by acidification to obtain flocculent fibers, 25% sulfuric acid is selected as the acidification reagent, the mass ratio of cellulose esterification product: 25% sulfuric acid is 1:8, the reaction temperature is 30℃, the reaction time is 3h, and the product is washed to pH=7 after the reaction.
[0058] S202, refining and screening step, the product obtained in the acidification step is screened and refined so that it can pass through a 0.15 mm slit screen plate, and the refining is performed using a KRK refiner with a slit width of 0.2 mm.
[0059] S203, papermaking step, the papermaking is performed at a basis weight of 60 g / m 2 , 50% of softwood pulp is beaten to a degree of 30°SR, the cellulose esterification product obtained in step S202 is added at an amount of 35%, and calcium carbonate is added as a filler at an amount of 15%, and 0.05% of CPAM is further added in the pulp with respect to the above-mentioned dry fiber, the press pressure and time are 200 kPa and 60 s, and the paper drying temperature is 105°C.
[0060] The base paper is impregnated with 2% sodium hydroxide solution, the roller pressure is 10 N / m, and the paper drying method is cylinder drying at a temperature of 105°C.
[0061] Example 2
[0062] A method for preparing a high-efficiency water-soluble paper includes the steps of:
[0063] S100, preparing cellulose ester:
[0064] S101, alkalization step: the cotton pulp raw material is reacted with an alkali solution after being defibrated and dried, and the reaction occurs in an ethanol solution; the mass ratio of the cotton pulp raw material: alkali solution: ethanol solution is 1:3:2.2, the kneader kneading reaction time is 2.5 h, and the reaction temperature is controlled at 40°C.
[0065] The mass fraction of the ethanol solution is 90%, and the alkali solution is a sodium hydroxide solution with a mass fraction of 40%.
[0066] S102, etherification step: an etherification agent chloroacetic acid and an ethanol solution are added to the mixture after the alkalization step, the mass fraction of the ethanol solution is 95%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:0.94:0.55, the etherification temperature is 75°C, and the reaction time is 3 h.
[0067] After the reaction is completed, hydrogen peroxide is added, and the mass ratio of cellulose: hydrogen peroxide is 10:1.
[0068] S103, purification step: after being cooled to 40°C, the mixture is washed 5 times with an ethanol solution to remove the salt produced in the reaction, and then dried in an oven at 80°C for 6 h to obtain a cellulose esterification product, which is detected to have a degree of substitution of 0.70.
[0069] S200, preparing water-soluble paper:
[0070] S201, acidification step, the cellulose esterification product is treated by acidification to obtain flocculent fiber, 15% sulfuric acid is selected as acidification reagent, the mass ratio of cellulose esterification product: 15% sulfuric acid is 1:13, the reaction temperature is 25°C, and the reaction time is 2h, and the product is washed to pH=7 after reaction.
[0071] S202, grinding and screening step, the product obtained in the acidification step is subjected to screening and grinding, so that it can pass through a 0.15mm fine gap screening plate, the grinding is performed by using a KRK grinder, and the gap width is set to 0.2mm.
[0072] S203, papermaking step, the papermaking paper has a basis weight of 60g / m 2 , the cotton pulp has a beating degree of 40°SR, the cellulose esterification product obtained in step S202 is added in an amount of 35%, the filler diatomite is added in an amount of 20%, and 0.05% of CPAM is further added in the pulp relative to the amount of the above dry fiber, the pressing pressure and time are 300kPa and 50s respectively, and the paper drying temperature is 105°C.
[0073] A 3% sodium carbonate solution is selected to impregnate the base paper, the roller pressure is 10N / m, and the paper drying method is cylinder drying, and the temperature is 105°C.
[0074] Example 3
[0075] A high-efficiency water-soluble paper, the preparation method comprises the steps of:
[0076] S100, preparing cellulose ester:
[0077] S101, alkali treatment step: the bamboo pulp raw material is reacted with an alkali solution after being defibrated and dried, and the reaction occurs in an ethanol solution; the mass ratio of bamboo pulp raw material: alkali solution: ethanol solution is 1:3:2, the kneader kneading reaction time is 2h, and the reaction temperature is controlled at 40°C.
[0078] The mass fraction of the ethanol solution is 90%, and the alkali solution is a sodium hydroxide solution with a mass fraction of 35%.
[0079] S102, etherification step: the etherification agent chloroacetic acid and the ethanol solution are added to the mixture after the alkali treatment step, the mass fraction of the ethanol solution is 90%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:1:0.5, the etherification temperature is 75°C, and the reaction time is 2h.
[0080] After the reaction is completed, hydrogen peroxide is added, and the mass ratio of cellulose: hydrogen peroxide is 10:1.
[0081] S103, purification step: after cooling to 40℃, washing with ethanol solution 5 times, removing the salt produced in the reaction, drying in 80℃ oven for 6h, obtaining the cellulose esterification product, which is detected to have a degree of substitution of 0.75.
[0082] S200, preparing water-soluble paper:
[0083] S201, acidification step: the cellulose esterification product is treated by acidification to obtain flocculent fibers, 25% sulfuric acid is selected as the acidification reagent, the mass ratio of cellulose esterification product to 25% sulfuric acid is 1:8, the reaction temperature is 30℃, and the reaction time is 3h, and the product is washed to pH=7 after the reaction.
[0084] S202, pulp refining and screening step: the product obtained in the acidification step is subjected to screening and refining, so that it can pass through a 0.15mm fine gap screening plate, and the KRK refiner is used for refining, and the gap width is set to 0.2mm.
[0085] S203, papermaking step: the papermaking paper has a basis weight of 60g / m 2 , the beating degree of 20% bamboo pulp is 30°SR, the cellulose esterification product obtained in step S202 is added in an amount of 25%, the filler talc is added in an amount of 25%, and 0.06% of CPAM is further added in the pulp relative to the amount of the above dry fibers, the pressing pressure and time are 250kPa and 60s, and the paper drying temperature is 105℃.
[0086] A 4% sodium carbonate solution is selected for impregnating the base paper, the roller pressure is 10N / m, and the paper drying method is oven drying at a temperature of 105℃.
[0087] Example 4
[0088] A high-efficiency water-soluble paper, the preparation method comprising the steps of:
[0089] S100, preparing cellulose ester:
[0090] S101, alkalization step: the broadleaf pulp raw material is defibrated and dried, and then reacts with an alkali solution, the reaction occurs in an ethanol solution; the mass ratio of broadleaf pulp raw material: alkali solution: ethanol solution is 1:4.0:3.2, the kneader kneading reaction time is 2h, and the reaction temperature is controlled at 30℃;
[0091] The mass fraction of the ethanol solution is 90%, and the alkali solution is a sodium hydroxide solution with a mass fraction of 32%.
[0092] S102, etherification step: an etherification agent chloroacetic acid and an ethanol solution are added to the mixture after the alkalization step, the mass fraction of the ethanol solution is 95%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:0.88:0.60, the etherification temperature is 75℃, and the reaction time is 2h.
[0093] After the reaction, hydrogen peroxide is added, and the mass ratio of cellulose to hydrogen peroxide is 10:1.
[0094] S103, purification step: after cooling to 40℃, the product is washed with ethanol solution for 5 times, and then dried in an oven at 80℃ for 6h after removing the salt produced in the reaction to obtain the cellulose esterification product, and the degree of substitution of which is 0.78.
[0095] S200, preparation of water-soluble paper:
[0096] S201, acidification step: the cellulose esterification product is treated by acidification to obtain flocculent fibers, and 25% sulfuric acid is selected as the acidification reagent, the mass ratio of cellulose esterification product to 25% sulfuric acid is 1:8, the reaction temperature is 30℃, and the reaction time is 3h, and then the product is washed to pH=7 after the reaction.
[0097] S202, pulp refining and screening step: the product obtained in the acidification step is subjected to screening and refining so that it can pass through a 0.15mm fine gap screen plate, and the KRK refiner is used for refining, and the gap width is set to 0.2mm.
[0098] S203, papermaking step: the basis weight of the paper to be made is 80g / m 2 , the beating degree of 40% broadleaf wood pulp is 30°SR, the addition amount of the cellulose esterification product obtained in step S202 is 45%, the addition amount of the filler calcium carbonate is 15%, 0.05% CPAM is further added in the pulp relative to the amount of the above dry fibers, the pressing pressure and time are 300kPa and 40s respectively, and the paper drying temperature is 105℃.
[0099] The base paper is treated by immersion with 2% potassium hydroxide solution, the roller pressure is 10N / m, and the paper drying method is cylinder drying at a temperature of 105℃.
[0100] Example 5
[0101] A high-efficiency water-soluble paper, the preparation method comprising the steps of:
[0102] S100, preparation of cellulose ester:
[0103] S101, alkalization step: the needle pulp raw material is disintegrated and dried, and then reacts with an alkali solution in an ethanol solution; the mass ratio of needle pulp raw material to alkali solution to ethanol solution is 1:3.0:2.2, the kneader kneading reaction time is 2.5h, and the reaction temperature is controlled at 40℃.
[0104] The mass fraction of the ethanol solution is 90%, and the alkali solution is sodium hydroxide solution with a mass fraction of 22%.
[0105] S102, etherification step: after the reaction of the alkalization step, an etherification agent, chloroacetic acid and an ethanol solution, is added to the mixture, the mass fraction of the ethanol solution is 95%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:2.2:1.1, the etherification temperature is 75°C, and the reaction time is 2h;
[0106] After the reaction is completed, hydrogen peroxide is added, and the mass ratio of cellulose: hydrogen peroxide is 10:1.
[0107] S103, purification step: after cooling to 40°C, the product is washed with an ethanol solution for 5 times, and then dried in an oven at 80°C for 6h after removing the salt produced in the reaction to obtain a cellulose esterification product, and the degree of substitution of the product is 0.83.
[0108] S200, preparation of water-soluble paper:
[0109] S201, acidification step: the cellulose esterification product is treated by acidification to obtain flocculent fibers, 10% sulfuric acid is selected as the acidification reagent, the mass ratio of cellulose esterification product: 10% sulfuric acid is 1:20, the reaction temperature is 30°C, the reaction time is 4h, and the product is washed to pH=7 after the reaction.
[0110] S202, refining and screening step: the product obtained in the acidification step is subjected to screening and refining so that it can pass through a 0.15mm fine gap screening plate, and the KRK refiner is used for refining, and the gap width is set to 0.2mm.
[0111] S203, papermaking step: the basis weight of the paper to be made is 100g / m 2 , the beating degree of 50% softwood pulp is 40°SR, the addition amount of the cellulose esterification product obtained in step S202 is 35%, the addition amount of the filler calcium carbonate is 15%, 0.05% CPAM is further added in the pulp relative to the amount of the above dry fibers, the pressing pressure and time are 300kPa and 30s, and the paper drying temperature is 105°C.
[0112] The base paper is treated by immersion with 2% sodium hydroxide solution, the roller pressure is 10N / m, and the paper drying method is cylinder drying at a temperature of 105°C.
[0113] Comparative Example 1
[0114] A water-soluble paper, the preparation method of which comprises the steps of:
[0115] S100, preparation of cellulose ester:
[0116] S101, alkalization step: after the needle pulp raw material is defibrated and dried, it is reacted with an alkali solution in an ethanol solution; the mass ratio of needle pulp raw material: alkali solution: ethanol solution is 1:3.0:2.2, the kneader kneading reaction time is 3.5h, and the reaction temperature is controlled at 40°C;
[0117] The mass fraction of the ethanol solution is 90%, and the alkali solution is a sodium hydroxide solution with a mass fraction of 22%.
[0118] S102, etherification step: an etherifying agent, chloroacetic acid, and an ethanol solution are added to the mixture after the alkalization step; the mass fraction of the ethanol solution is 95%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:3.2:1.1; the etherification temperature is 75°C; and the reaction time is 3h.
[0119] After the reaction is completed, hydrogen peroxide is added; the mass ratio of cellulose: hydrogen peroxide is 10:1.
[0120] S103, purification step: after being cooled to 40°C, the mixture is washed with an ethanol solution for 5 times; after the salts produced in the reaction are removed, the mixture is dried in an oven at 80°C for 6h to obtain a cellulose esterification product; and the degree of substitution of the cellulose esterification product is 0.92.
[0121] S200, the process of preparing the water-soluble paper is the same as that in Example 1.
[0122] Comparative Example 2
[0123] A water-soluble paper, the preparation method of which comprises the following steps:
[0124] S100, preparation of cellulose ester:
[0125] S101, alkalization step: after being defibrated and dried, a conifer pulp raw material is reacted with an alkali solution in an ethanol solution; the mass ratio of the conifer pulp raw material: alkali solution: ethanol solution is 1:1.8:2.0; the kneader kneading reaction time is 1.5h; and the reaction temperature is controlled at 40°C.
[0126] The mass fraction of the ethanol solution is 90%, and the alkali solution is a sodium hydroxide solution with a mass fraction of 45%.
[0127] S102, etherification step: an etherifying agent, chloroacetic acid, and an ethanol solution are added to the mixture after the alkalization step; the mass fraction of the ethanol solution is 95%; the mass ratio of cellulose: chloroacetic acid: ethanol solution is 1:0.56:0.55; the etherification temperature is 55°C; and the reaction time is 1h.
[0128] After the reaction is completed, hydrogen peroxide is added; the mass ratio of cellulose: hydrogen peroxide is 10:1.
[0129] S103, purification step: after being cooled to 40°C, the mixture is washed with an ethanol solution for 5 times; after the salts produced in the reaction are removed, the mixture is dried in an oven at 80°C for 6h to obtain a cellulose esterification product; and the degree of substitution of the cellulose esterification product is 0.25.
[0130] S200, the process of preparing the water-soluble paper is the same as that in Example 1.
[0131] Example 6
[0132] The water-soluble time, longitudinal tensile force, basis weight and tightness data of the water-soluble paper obtained in Examples 1-5 were detected according to the detection method in the art, and the detection results are shown in Table 1.
[0133] Table 1, comparison of detection results of examples with target values
[0134]
[0135] The performance indicators of the water-soluble paper produced by the above-mentioned embodiments all meet the requirements of the target values, indicating that the high-efficiency water-soluble paper obtained by using the preparation method has a shorter water-soluble time, excellent longitudinal tensile force, and can achieve good water-solubility and mechanical properties.
[0136] According to the experimental results in Table 1, those skilled in the art can understand that:
[0137] First, the water-soluble paper produced by the preparation method provided in the present application meets the requirements of the target values, indicating that the high-efficiency water-soluble paper obtained by using the preparation method has a shorter water-soluble time, excellent longitudinal tensile force, and can achieve good water-solubility and mechanical properties. Based on the dissociation mechanism of the hydrogen bond network in cellulose material, the present application proposes a carboxymethylated cellulose composite paper with water-responsive dissociation function. The mechanical strength of traditional paper is mainly derived from the three-dimensional network structure of hydrogen bonds formed between cellulose molecules. This combination makes it difficult for the formed paper to spontaneously depolymerize into single fibers in water. The innovation of this study lies in the preparation of paper materials by compounding carboxymethylated cellulose with ordinary cellulose fibers. The strong hydrophilicity and swelling properties of carboxymethylated cellulose in water environment generate sufficient intermolecular forces to break the hydrogen bond connection between adjacent ordinary cellulose fibers, thereby realizing the spontaneous dissociation of paper materials in water medium and restoring them to single fiber state.
[0138] Second, when the degree of substitution of the cellulose ester obtained by preparation is too low or too high, it will affect the water-solubility of the paper, therefore the degree of substitution of the cellulose ester product should be controlled in the range of greater than 0.25 and less than 0.92, preferably in the range of 0.45-0.83.
[0139] In summary, the present method prepares cellulose ester with lower degree of substitution through alkalization, etherification, purification and other steps, which can significantly improve the water-solubility of water-soluble paper when used in the preparation of water-soluble paper, solves the technical problem of poor solubility of water-soluble paper in the prior art, realizes the preparation of higher quality water-soluble paper, and has good industrial application prospect.
[0140] It should be noted that the technical features in the above embodiments can be freely combined for the person of ordinary skill in the art, and the technical solutions formed also belong to the embodiments disclosed in the present application.
[0141] Further, the present application can be modified and improved in several ways without departing from the principles of the present application, and these modifications and improvements also fall within the scope of protection of the claims of the present application.
Claims
1. A method for preparing a cellulose ester, characterized in that: Including the following steps: The alkalization step involves mixing cellulose raw material with an organic solvent and an alkaline solution to undergo an alkalization reaction to obtain alkali cellulose. The organic solution has a mass fraction of 50-95%, the alkaline solution has a mass fraction of 20-60%, the mass ratio of cellulose:alkaline solution:organic solvent is 1:1.0-4.0:1.5-3.2, the reaction time is 0.5-4 hours, and the reaction temperature is controlled at 30-70℃. In the etherification step, the etherifying agent and organic solvent are added to the mixture obtained in the alkalization step. The organic solvent has a mass fraction of 50-95%, and the mass ratio of the mixture to the etherifying agent to the organic solvent is 1:0.5-3.0:0.3-2.
0. The temperature of the etherification reaction is gradually increased and controlled at 60-80℃, and the reaction time is 1-4 hours. After reacting for a period of time, a viscosity reducer is added to reduce viscosity. In the purification step, the solution obtained in the etherification step is cooled to 40-60℃, washed with an organic solvent to remove the salt produced in the reaction, and then dried to obtain the cellulose esterification product.
2. The method for preparing cellulose ester according to claim 1, characterized in that: In the alkalization step and / or etherification step, the organic solvent is one or more of methanol, ethanol, toluene, and isopropanol.
3. The method for preparing cellulose ester according to claim 1, characterized in that: In the etherification step, the viscosity reducer is hydrogen peroxide.
4. The method for preparing cellulose ester according to any one of claims 1-3, characterized in that: The degree of substitution of the cellulose ester is 0.45-0.
83.
5. A method for preparing water-soluble paper, characterized in that: Including the following steps: The acidification step involves preparing an acid solution by mixing the cellulose esterification product according to any one of claims 1-4 with an acid solution at a mass ratio of 1:6-40, wherein the mass fraction of the acid solution is 2.5%-30%. After acidification, the cellulose esters are washed with water until the pH is between 6.5 and 7.
5. The pulping and screening steps, and the products of the acidification step are subjected to pulp screening and pulping treatment; In the papermaking process, the cellulose ester obtained from the pulping and screening steps is mixed with plant fibers to obtain a mixed pulp. After dehydration, forming, pressing, and drying, water-soluble paper base paper is obtained. The base paper is then treated with alkali to obtain the finished water-soluble paper.
6. The method for preparing water-soluble paper according to claim 5, characterized in that: In the acidification step, the acid solution is a 25% sulfuric acid solution; in the acidification step, the reaction temperature is 25-30℃, and the reaction time is 2-4h.
7. The method for preparing water-soluble paper according to claim 5, characterized in that: The mixed pulp comprises plant fiber, cellulose ester, filler, and filler retention aid. The plant fiber accounts for 20%-80% of the mass of the mixed pulp, the cellulose ester accounts for 15%-75% of the mass of the mixed pulp, the filler accounts for 5%-25% of the mass of the mixed pulp, the freeness of the plant fiber pulp is 12°-50°SR, and the amount of filler retention aid added is 0.01% to 2.0% of the oven-dry fiber.
8. The method for preparing water-soluble paper according to claim 7, characterized in that: The plant fiber pulp is one or more of the following: softwood pulp, hardwood pulp, hemp pulp, bamboo pulp, grass pulp, reed pulp, and cotton pulp.
9. The method for preparing water-soluble paper according to claim 7, characterized in that: The filler is one or more of calcium carbonate, diatomaceous earth, talc, and titanium dioxide; the filler retention aid is one or more of cationic polyacrylamide, polyaluminum chloride, and aluminum sulfate.
10. The method for preparing water-soluble paper according to any one of claims 5-9, characterized in that: The basis weight of the water-soluble paper base is 15-200 g / m³. 2 .