Abstract: In order to replace the non-degradable polyvinyl alcohol (PVA) slurry, hemp stalk cellulose ether-hydroxypropyl methylcellulose was prepared from agricultural waste hemp stalks, and mixed with specific starch to prepare the slurry. Polyester-cotton blended yarn T/C65/35 14.7 tex was sized and its sizing performance was tested. The optimal production process of hydroxypropyl methylcellulose was as follows: the mass fraction of lye was 35%; the compression ratio of alkali cellulose was 2.4; The liquid volume ratio of methane and propylene oxide is 7 : 3 ; dilute with isopropanol ; the reaction pressure is 2 . 0MPa. The size prepared by mixing hydroxypropyl methylcellulose and specific starch has lower COD and is more environmentally friendly, and all sizing indicators can replace PVA size.
Key words: hemp stalk; hemp stalk cellulose ether; polyvinyl alcohol; cellulose ether sizing
0.Preface
China is one of the countries with relatively rich straw resources. The crop output is more than 700 million tons, and the utilization rate of straw is only 3% every year. A large amount of straw resources have not been utilized. Straw is a rich natural lignocellulosic raw material, which can be used in feed, fertilizer, cellulose derivatives and other products.
At present, desizing wastewater pollution in the textile production process has become one of the largest pollution sources. The chemical oxygen demand of PVA is very high. After the industrial wastewater produced by PVA in the printing and dyeing process is discharged into the river, it will inhibit or even destroy the respiration of aquatic organisms. Moreover, PVA aggravates the release and migration of heavy metals in sediments in water bodies, causing more serious environmental problems. To carry out research on replacing PVA with green slurry, it is necessary not only to meet the requirements of the sizing process, but also to minimize the pollution of water and air during the sizing process.
In this study, hemp stalk cellulose ether-hydroxypropyl methylcellulose (HPMC) was prepared from agricultural waste hemp stalks, and its production process was discussed. And mix hydroxypropyl methylcellulose and specific starch size as size for sizing, compare with PVA size, and discuss its sizing performance.
1. Experiment
1 . 1 Materials and instruments
Hemp stalk, Heilongjiang; polyester-cotton blended yarn T/C65/3514.7 tex; self-made hemp stalk cellulose ether-hydroxypropyl methylcellulose; FS-101, modified starch, PVA-1799, PVA-0588, Liaoning Zhongze Group Chaoyang Textile Co., Ltd.; propanol, premium grade; propylene oxide, glacial acetic acid, sodium hydroxide, isopropanol, analytically pure; methyl chloride, high-purity nitrogen.
GSH-3L reaction kettle, JRA-6 digital display magnetic stirring water bath, DHG-9079A electric heating constant temperature drying oven, IKARW-20 overhead mechanical agitator, ESS-1000 sample sizing machine, YG 061/PC electronic single yarn strength meter , LFY-109B computerized yarn abrasion tester.
1.2 Preparation of hydroxypropyl methylcellulose
1. 2. 1 Preparation of alkali fiber
Split the hemp stalk, crush it to 20 meshes with a pulverizer, add the hemp stalk powder to 35% NaOH aqueous solution, and soak it at room temperature for 1 . 5 ~ 2 . 0 h. Squeeze the impregnated alkali fiber so that the mass ratio of alkali, cellulose, and water is 1. 2:1. 2:1.
1. 2. 2 Etherification reaction
Throw the prepared alkali cellulose into the reaction kettle, add 100 mL of isopropanol as diluent, add liquid 140 mL of methyl chloride and 60 mL of propylene oxide, vacuumize, and pressurize to 2 . 0 MPa, slowly raise the temperature to 45°C for 1-2 hours, and react at 75°C for 1-2 hours to prepare hydroxypropyl methylcellulose.
1. 2. 3 Post-processing
Adjust the pH of the etherified cellulose ether with glacial acetic acid to 6 . 5 ~ 7 . 5, washed with propanol three times, and dried in an oven at 85°C.
1.3 Production process of hydroxypropyl methylcellulose
1. 3. 1 The influence of rotational speed on the preparation of cellulose ether
Usually the etherification reaction is a heterogeneous reaction from the inside to the inside. If there is no external power, it is difficult for the etherification agent to enter the crystallization of the cellulose, so it is necessary to fully combine the etherification agent with the cellulose by means of stirring. In this study, a high-pressure stirred reactor was used. After repeated experiments and demonstrations, the selected rotational speed was 240-350 r/min.
1. 3. 2 The effect of alkali concentration on the preparation of cellulose ether
Alkali can destroy the compact structure of cellulose to make it swell, and when the swelling of the amorphous region and the crystalline region tend to be consistent, the etherification proceeds smoothly. In the production process of cellulose ether, the amount of alkali used in the cellulose alkalization process has a great influence on the etherification efficiency of etherification products and the degree of substitution of groups. In the preparation process of hydroxypropyl methylcellulose, as the concentration of lye increases, the content of methoxyl groups also increases; conversely, when the concentration of lye decreases, the hydroxypropyl methylcellulose The base content is larger. The content of methoxy group is directly proportional to the concentration of lye; the content of hydroxypropyl is inversely proportional to the concentration of lye. The mass fraction of NaOH was selected as 35% after repeated tests.
1. 3. 3 The effect of alkali cellulose pressing ratio on the preparation of cellulose ether
The purpose of pressing alkali fiber is to control the water content of alkali cellulose. When the pressing ratio is too small, the water content increases, the concentration of lye decreases, the etherification rate decreases, and the etherification agent is hydrolyzed and side reactions increase. , the etherification efficiency is greatly reduced. When the pressing ratio is too large, the water content decreases, the cellulose cannot be swollen, and has no reactivity, and the etherification agent cannot fully contact with the alkali cellulose, and the reaction is uneven. After many tests and pressing comparisons, it was determined that the mass ratio of alkali, water and cellulose was 1. 2:1. 2:1.
1. 3. 4 Effect of temperature on the preparation of cellulose ether
In the process of preparing hydroxypropyl methylcellulose, first control the temperature at 50-60 °C and keep it at a constant temperature for 2 hours. The hydroxypropylation reaction can be carried out at about 30 ℃, and the hydroxypropylation reaction rate increases greatly at 50 ℃; slowly raise the temperature to 75 ℃, and control the temperature for 2 hours. At 50°C, the methylation reaction hardly reacts, at 60°C, the reaction rate is slow, and at 75°C, the methylation reaction rate is greatly accelerated.
The preparation of hydroxypropyl methylcellulose with multi-stage temperature control can not only control the balance of methoxyl and hydroxypropyl groups, but also help reduce side reactions and post-treatment, and obtain products with reasonable structure.
1. 3. 5 Effect of etherification agent dosage ratio on the preparation of cellulose ether
Since hydroxypropyl methylcellulose is a typical non-ionic mixed ether, the methyl and hydroxypropyl groups are substituted on different hydroxypropyl methylcellulose macromolecular chains, that is, different C in each glucose ring position. On the other hand, the distribution ratio of methyl and hydroxypropyl has greater dispersion and randomness. The water solubility of HPMC is related to the content of methoxy group. When the content of methoxy group is low, it can be dissolved in strong alkali. As the methoxyl content increases, it becomes more sensitive to water swelling. The higher the methoxy content, the better the water solubility, and it can be formulated into slurry.
The amount of etherifying agent methyl chloride and propylene oxide has a direct impact on the content of methoxyl and hydroxypropyl. In order to prepare hydroxypropyl methylcellulose with good water solubility, the liquid volume ratio of methyl chloride and propylene oxide was selected as 7:3.
1.3.6 The optimal production process of hydroxypropyl methylcellulose
The reaction equipment is a high-pressure stirred reactor; the rotation speed is 240-350 r/min; the mass fraction of lye is 35%; the compression ratio of alkali cellulose is 2. 4; Hydroxypropoxylation at 50°C for 2 hours, methoxylation at 75°C for 2 hours; etherification agent methyl chloride and propylene oxide liquid volume ratio 7:3; vacuum; pressure 2 . 0 MPa; diluent is isopropanol.
2. Detection and application
2.1 SEM of hemp cellulose and alkali cellulose
Comparing the untreated hemp cellulose and the hemp cellulose treated with 35% NaOH, it can be clearly found that the alkalized cellulose has more surface cracks, larger surface area, higher activity and easier etherification reaction.
2.2 Infrared Spectroscopy Determination
The cellulose extracted from hemp stalks after treatment and the infrared spectrum of HPMC prepared from hemp stalk cellulose. Among them, the strong and wide absorption band at 3295 cm -1 is the stretching vibration absorption band of HPMC association hydroxyl group, the absorption band at 1250 ~ 1460 cm -1 is the absorption band of CH, CH2 and CH3, and the absorption band at 1600 cm -1 is the absorption band of water in the polymer absorption band. The absorption band at 1025cm -1 is the absorption band of C — O — C in the polymer.
2.3 Viscosity determination
Take the prepared cannabis stalk cellulose ether sample and add it to a beaker to prepare a 2% aqueous solution, stir it thoroughly, measure its viscosity and viscosity stability with a viscometer, and measure the average viscosity for 3 times. The viscosity of the prepared cannabis stalk cellulose ether sample was 11 . 8 mPa·s.
2.4 Sizing application
2.4.1 Slurry configuration
The slurry was prepared into 1000mL of a slurry with a mass fraction of 3.5%, stirred evenly with a mixer, and then placed in a water bath and heated to 95°C for 1 h. At the same time, note that the pulp cooking container should be sealed well to prevent the concentration of the slurry from increasing due to water evaporation.
2.4.2 Slurry formulation pH, miscibility and COD
Mix hydroxypropyl methyl cellulose and specific starch size to prepare slurry (1#~4#), and compare with PVA formula slurry (0#) to analyze pH, miscibility and COD. The polyester-cotton blended yarn T/C65/3514.7 tex was sized on the ESS1000 sample sizing machine, and its sizing performance was analyzed.
It can be seen that the homemade hemp stalk cellulose ether and specific starch size 3 # are the optimal size formulation: 25% hemp stalk cellulose ether, 65% modified starch and 10% FS-101.
All sizing data are comparable to the sizing data of PVA size, indicating that the mixed size of hydroxypropyl methylcellulose and specific starch has good sizing performance; its pH is closer to neutral; hydroxypropyl methylcellulose and specific starch The COD (17459.2 mg/L) of the specific starch mixed size was significantly lower than that of the PVA size (26448.0 mg/L), and the environmental protection performance was good.
3. Conclusion
The optimal production process for preparing hemp stalk cellulose ether-hydroxypropyl methylcellulose for sizing is as follows: a high-pressure stirred reactor with a rotation speed of 240-350 r/min, a mass fraction of lye of 35%, and a compression ratio of alkali cellulose 2.4, the methylation temperature is 75 ℃, and the hydroxypropylation temperature is 50 ℃, each maintained for 2 hours, the liquid volume ratio of methyl chloride and propylene oxide is 7:3, vacuum, the reaction pressure is 2.0 MPa, isopropanol is the diluent .
Hemp stalk cellulose ether was used to replace PVA size for sizing, and the optimal size ratio was: 25% hemp stalk cellulose ether, 65% modified starch and 10% FS‐101. The pH of the slurry is 6.5 and the COD (17459.2 mg/L) is significantly lower than that of the PVA slurry (26448.0 mg/L), showing good environmental performance.
Hemp stalk cellulose ether was used for sizing instead of PVA size to sizing the polyester-cotton blended yarn T/C 65/3514.7tex. The sizing index is equivalent. The new hemp stalk cellulose ether and modified starch mixed size can replace PVA size.