CN114441259A - Method for evaluating cellulose pulp reaction performance and application thereof - Google Patents
Method for evaluating cellulose pulp reaction performance and application thereof Download PDFInfo
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- CN114441259A CN114441259A CN202210001170.6A CN202210001170A CN114441259A CN 114441259 A CN114441259 A CN 114441259A CN 202210001170 A CN202210001170 A CN 202210001170A CN 114441259 A CN114441259 A CN 114441259A
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- 229920002678 cellulose Polymers 0.000 title claims abstract description 135
- 239000001913 cellulose Substances 0.000 title claims abstract description 135
- 238000000034 method Methods 0.000 title claims abstract description 46
- 238000006243 chemical reaction Methods 0.000 title abstract description 41
- LFTLOKWAGJYHHR-UHFFFAOYSA-N N-methylmorpholine N-oxide Chemical compound CN1(=O)CCOCC1 LFTLOKWAGJYHHR-UHFFFAOYSA-N 0.000 claims abstract description 142
- 229920000433 Lyocell Polymers 0.000 claims abstract description 42
- 239000004627 regenerated cellulose Substances 0.000 claims abstract description 30
- 229920003043 Cellulose fiber Polymers 0.000 claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 claims abstract description 19
- 238000011156 evaluation Methods 0.000 claims abstract description 8
- 238000009826 distribution Methods 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 111
- 239000007864 aqueous solution Substances 0.000 claims description 98
- 229920001131 Pulp (paper) Polymers 0.000 claims description 65
- 238000003756 stirring Methods 0.000 claims description 61
- 239000000243 solution Substances 0.000 claims description 50
- 229920000742 Cotton Polymers 0.000 claims description 36
- 239000007788 liquid Substances 0.000 claims description 36
- 235000017166 Bambusa arundinacea Nutrition 0.000 claims description 33
- 235000017491 Bambusa tulda Nutrition 0.000 claims description 33
- 241001330002 Bambuseae Species 0.000 claims description 33
- 235000015334 Phyllostachys viridis Nutrition 0.000 claims description 33
- 239000011425 bamboo Substances 0.000 claims description 33
- 239000006185 dispersion Substances 0.000 claims description 32
- 238000005406 washing Methods 0.000 claims description 29
- 230000008961 swelling Effects 0.000 claims description 27
- 238000001914 filtration Methods 0.000 claims description 22
- 238000002791 soaking Methods 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 15
- 238000005303 weighing Methods 0.000 claims description 13
- 230000009257 reactivity Effects 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 10
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 4
- 239000002904 solvent Substances 0.000 abstract description 33
- 238000012360 testing method Methods 0.000 abstract description 20
- 229920000297 Rayon Polymers 0.000 abstract description 17
- 239000000835 fiber Substances 0.000 abstract description 15
- 239000002994 raw material Substances 0.000 abstract description 14
- 230000006399 behavior Effects 0.000 abstract description 5
- 238000012216 screening Methods 0.000 abstract description 4
- 239000002023 wood Substances 0.000 description 36
- 239000011259 mixed solution Substances 0.000 description 26
- 206010042674 Swelling Diseases 0.000 description 25
- 235000011837 pasties Nutrition 0.000 description 16
- 239000012634 fragment Substances 0.000 description 15
- 238000009987 spinning Methods 0.000 description 12
- 230000008569 process Effects 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 230000001112 coagulating effect Effects 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 238000004090 dissolution Methods 0.000 description 8
- 238000010998 test method Methods 0.000 description 8
- 238000002360 preparation method Methods 0.000 description 7
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 6
- 239000011122 softwood Substances 0.000 description 6
- 230000015271 coagulation Effects 0.000 description 5
- 238000005345 coagulation Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 5
- 239000012535 impurity Substances 0.000 description 4
- 239000003960 organic solvent Substances 0.000 description 4
- QGJOPFRUJISHPQ-UHFFFAOYSA-N Carbon disulfide Chemical compound S=C=S QGJOPFRUJISHPQ-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- ZSXLAJUILPSSLE-UHFFFAOYSA-N amino(trimethyl)azanium Chemical compound C[N+](C)(C)N ZSXLAJUILPSSLE-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000007380 fibre production Methods 0.000 description 3
- 239000003513 alkali Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- ZOOODBUHSVUZEM-UHFFFAOYSA-N ethoxymethanedithioic acid Chemical compound CCOC(S)=S ZOOODBUHSVUZEM-UHFFFAOYSA-N 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000011550 stock solution Substances 0.000 description 2
- 239000012991 xanthate Substances 0.000 description 2
- 229920000875 Dissolving pulp Polymers 0.000 description 1
- 241000196324 Embryophyta Species 0.000 description 1
- BAVYZALUXZFZLV-UHFFFAOYSA-O Methylammonium ion Chemical compound [NH3+]C BAVYZALUXZFZLV-UHFFFAOYSA-O 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000011121 hardwood Substances 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000002655 kraft paper Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/30—Staining; Impregnating ; Fixation; Dehydration; Multistep processes for preparing samples of tissue, cell or nucleic acid material and the like for analysis
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/34—Purifying; Cleaning
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/38—Diluting, dispersing or mixing samples
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder
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- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
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Abstract
The invention discloses a method for evaluating the reaction performance of cellulose pulp and application thereof, the method provided by the invention calculates the percentage of soluble components of different types of cellulose pulp in the total mass of the cellulose pulp by testing the dissolving behaviors of the cellulose pulp in a low-concentration NMMO solvent and a high-concentration NMMO solvent respectively, can more intuitively and effectively evaluate the purity, the molecular weight distribution and the low molecular weight cellulose content of the pulp, and in the production process of regenerated cellulose fiber, especially Lyocell fiber, the reaction performance of cellulose pulp can be effectively evaluated, the dependence of the prior art on a pulp measuring method for viscose fiber is broken through, the blank of the pulp evaluation method for Lyocell fiber is filled, a more pertinent pulp evaluation system for Lyocell fiber is formed, the method has positive significance for screening the special pulp for the Lyocell fiber, reducing the cost of the pulp and solving the problem of raw material limitation of the Lyocell fiber industry.
Description
Technical Field
The invention belongs to the technical field of cellulose pulp detection, and particularly relates to a method for evaluating the reaction performance of cellulose pulp and application thereof.
Background
The Lyocell fiber is a novel renewable cellulose fiber which is produced by taking natural cellulose as a raw material and N-methylmorpholine-N-oxide (NMMO for short) as a solvent without a chemical reaction, and is widely concerned by the market due to excellent environmental protection characteristic and outstanding product performance, so that the Lyocell fiber is a new industry with wide prospect and rapid development. However, advanced Lyocell fiber dissolution techniques, harsh NMMO solvent systems place very high demands on the quality of the cellulose pulp feedstock and the cellulose pulp dissolution conditions. Most of raw material pulp used in the field of Lyocell fiber in China depends on import, the evaluation of the reaction performance of the raw material pulp follows the performance index and detection method of the viscose fiber industry, and a specific raw material pulp detection method and related national standards suitable for the field of producing Lyocell fiber by using organic solvent are not formed and formulated. Because the production processes of the Lyocell fiber and the viscose fiber are completely different, the requirements of the two fiber varieties on the quality index and the performance of the raw material pulp are not completely the same, and the pulp performance index in the field of the currently used viscose fiber cannot completely reflect the real internal quality of the cellulose pulp raw material and the applicability of the cellulose pulp raw material in the production process of the Lyocell fiber.
For example, the reaction performance of the pulp is an index for evaluating the capability of the pulp to react with reactants, and the index is an important reference in the preparation process of regenerated cellulose fibers, and currently, the viscose filtration method and the Fock test method are most widely applied in the fiber industry. The two methods are that a pulp sample is dissolved in a mixed solution of NaOH and carbon disulfide to form viscose, and the reaction performance of the pulp is further judged. For example, the content of impurities such as pentosan in pulp is an important index for detecting pulp for viscose, and for viscose pulp, pentosan affects the preparation of alkali cellulose and xanthate, and the content thereof needs to be strictly controlled, that is, for viscose, the content of impurities such as pentosan in the required cellulose pulp raw material is preferably as small as possible. However, for Lyocell fibers, the influence of the existence of pentosan on the production process is not clear, and the restriction of Lyocell fiber pulp by directly adopting a viscose pulp testing method is unreasonable by combining the high content of impurities such as Lyocell pulp, pentosan and the like in the prior art and the stability of the fiber production process and quality.
The current ideal Lyocell fiber process design is as follows: uniformly dipping low-concentration NMMO and regenerated cellulose pulp to form a mixed solution, then dissolving cellulose in a high-concentration NMMO solvent by evaporating water to form a liquid for spinning, extruding the liquid through a spinneret under certain pressure, and entering a coagulating bath to form regenerated cellulose fibers. By combining the production process of the Lyocell fiber, if the quality and the reaction performance of the cellulose pulp raw material are poor, on one hand, partial cellulose is dissolved in advance in the mixing and swelling stage, so that the fiber pores are blocked, the further diffusion of the NMMO solvent is influenced, colloidal particles are generated, and the high-quality uniform spinning solution is difficult to form. On the other hand, during the regeneration and formation process of the fiber tows in the coagulating bath, part of cellulose can be separated out, the product yield is reduced, and the solvent recovery is influenced. Therefore, what kind of method can be used to evaluate which kind of cellulose pulp raw material has better quality and reaction performance, so that the production quality and product yield of the regenerated cellulose fiber can be improved, and the production cost of the regenerated cellulose fiber can be reduced is a problem to be solved in the field.
The present invention has been made in view of this situation.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method for evaluating the reaction performance of cellulose pulp and application thereof.
In order to solve the technical problems, the invention adopts the technical scheme that:
the invention provides a method for evaluating the reaction performance of cellulose pulp, which comprises the following steps:
(1) mixing and infiltrating the flaky cellulose pulp and the low-concentration NMMO aqueous solution, uniformly stirring to obtain a dispersion liquid, standing the dispersion liquid for a first preset time period in a constant-temperature water bath at 10-30 ℃, and reacting to obtain a soaking liquid;
the mass ratio of the low-concentration NMMO aqueous solution to the cellulose pulp is (2-50): 1, the mass ratio of water to NMMO in the low-concentration NMMO aqueous solution is (7-9): (1-3);
or mixing and infiltrating the flaky cellulose pulp and the high-concentration NMMO aqueous solution, uniformly stirring to obtain a dispersion liquid, standing the dispersion liquid for a first preset time period in a constant-temperature water bath at 70-90 ℃, and reacting to obtain a swelling solution;
the mass ratio of the high-concentration NMMO aqueous solution to the cellulose pulp is (2-50): 1, the mass ratio of water to NMMO in the high-concentration NMMO aqueous solution is (1-2): (3-4);
(2) and filtering the soaking solution or the swelling solution, washing and drying to obtain filter residues, weighing the mass of the filter residues, calculating the mass of the soluble components of the cellulose pulp according to the total mass of the cellulose pulp, and further calculating the percentage of the soluble components of the cellulose pulp in the total mass of the cellulose pulp.
In the prior art, the testing method of viscose industry is still adopted for evaluating the applicability of the pulp for the regenerated cellulose fiber. For viscose, impurities such as pentosan in pulp can affect the preparation of alkali cellulose and xanthate, so in the detection index of the pulp applicability of viscose, the less the pentosan content in the pulp is detected, the better the quality of the produced viscose is. In other words, in the detection index of the applicability of the pulp for regenerated cellulose fibers, the quality of the produced regenerated cellulose fibers is not better when the content of the pentosan in the pulp is lower, so that the test method of the viscose industry is not accurate when the test method is directly applied to the regenerated cellulose fiber industry for testing.
It was found by examining the production process of regenerated cellulose fibers that, regardless of the content of components such as pentosan in pulp, regenerated cellulose fibers having good quality can be produced by dissolving most of the components such as pentosan in the dissolving stage after the swelling stage as long as the mass of the components such as pentosan dissolved in the swelling stage after mixing cellulose pulp with the NMMO aqueous solution is small. In the whole production process of the regenerated cellulose fiber, the cellulose in the cellulose pulp is ensured to have a narrow region and a normal molecular weight distribution, and the content of the low-molecular-weight cellulose needs to be controlled within a certain range.
Therefore, in the scheme, the dissolving behaviors of the cellulose pulp in the low-concentration NMMO solvent and the high-concentration NMMO solvent are respectively detected, namely the soluble components of different types of pulp are calculated to account for the percentage of the total mass of the pulp, so that on one hand, the capacity of the cellulose pulp for forming uniform and stable spinning stock solution in the preparation process of the regenerated cellulose fiber can be effectively represented, and the redissolution behavior of fiber tows in a coagulating bath in the spinning forming process is simulated, so that the loss of the regenerated cellulose fiber is calculated, and the product yield of the regenerated cellulose fiber is further obtained; on the other hand, the method can also evaluate the purity, the molecular weight distribution and the low molecular weight cellulose content of the cellulose pulp more intuitively and effectively, can effectively evaluate the reaction performance of the pulp in the production process of regenerated cellulose fibers, particularly Lyocell fibers, breaks through the dependence of the prior art on a pulp measuring method for viscose fibers, fills the blank of the pulp evaluating method for Lyocell fibers, forms a more targeted pulp evaluating system for Lyocell fibers, and has important significance for screening the special pulp for Lyocell fibers, reducing the cost of the pulp and solving the problem of raw material limitation of the Lyocell fiber industry.
In general, the production process of the regenerated cellulose fiber needs to pass through a swelling stage, a dissolving stage and a coagulating bath forming stage, the low concentration NMMO aqueous solution is the organic solvent concentration required for simulating the coagulating bath forming stage, the high concentration NMMO aqueous solution is the organic solvent concentration required for simulating the swelling stage, and the organic solvent concentration required for the dissolving stage is higher than the high concentration NMMO aqueous solution. When low molecular weight cellulose in pulp is dissolved in advance in a swelling stage, the pore diameter of the cellulose is blocked, the mobility of an NMMO solvent is reduced, the further diffusion of the NMMO solvent is influenced, colloidal particles are generated in a dissolving solution in a later stage dissolving stage, and a high-quality uniform spinning solution is difficult to form, so that the spinning stability is influenced; when the cellulose in the pulp has a large mass loss in the low-concentration NMMO solvent, it means that part of the components of the fiber tows are dissolved in the coagulating bath during the forming process of the coagulating bath, and the dissolved components can be remained in the coagulating bath and do not participate in the subsequent forming process of the product, which can cause the reduction of the product yield.
In some embodiments, step (1) is preceded by a pretreatment step comprising equilibrating moisture after drying the flaked cellulose pulp to constant weight and pre-equilibrating the low concentration aqueous NMMO solution and the high concentration aqueous NMMO solution in a thermostatic water bath;
preferably, the cellulose pulp in flake form is uniform in size; more preferably, the cellulose pulp in chip form is 5 x 5mm in size.
In the scheme, the sizes of the cellulose pulp fragments participating in the reaction are uniform and consistent by strictly controlling the sizes of the cellulose pulp, and factors influencing the shape of the cellulose pulp can be eliminated so as to ensure that the test effect of the test method is more accurate.
In some embodiments, in the step (1), the temperature of the mixing infiltration of the flake-shaped cellulose pulp and the low-concentration aqueous NMMO solution is 10-30 ℃, and the infiltration time is 10-60 s;
or the mixing and infiltrating temperature of the flake-shaped cellulose pulp and the high-concentration NMMO aqueous solution is 70-90 ℃, and the infiltrating time is 10-60 s.
In the scheme, the soaking time is controlled within the range, so that the cellulose pulp fragments can be ensured to be fully contacted with the NMMO aqueous solution, and the accuracy of the test effect is ensured.
In some embodiments, in step (1), after stirring for a second predetermined period of time, adding the aqueous NMMO solution and continuing to stir for a third predetermined period of time to obtain the dispersion;
preferably, the stirring temperature of the flake-shaped cellulose pulp and the low-concentration NMMO aqueous solution is 10-30 ℃, and the second preset time period and the third preset time period are respectively 1-5 min; the mass ratio of the added NMMO aqueous solution is (7-9): (1-3);
or the stirring temperature of the flake-shaped cellulose pulp and the high-concentration NMMO aqueous solution is 70-90 ℃, and the second preset time period and the third preset time period are respectively 1-5 min; the mass ratio of the added NMMO aqueous solution is (1-2): (3-4);
more preferably, the stirring is performed by using a magnetic stirrer at the rotation speed of 500-.
In the scheme, the mass ratio of water to NMMO in the aqueous NMMO solution is (7-9): (1-3) or (1-2): and (3) in the step (4), the corresponding reaction stirring temperature is 10-30 ℃ or 70-90 ℃, and the conditions are matched with the coagulation bath forming conditions and swelling stage conditions involved in the Lyocell fiber preparation process, so that the test method has practical operability and effectiveness. In addition, the cellulose pulp fragments can be dispersed more uniformly in the aqueous NMMO solution by adding the aqueous NMMO solution in portions and stirring with a magnetic stirrer.
In some embodiments, in the step (1), the first preset time period is 30-120 min.
In some embodiments, in the step (2), washing is first performed with an aqueous NMMO solution having a mass ratio of water to NMMO of (4: 19) -1, and then washing is performed with pure water.
In some embodiments, ultrasonically dispersing is performed for a fourth preset time period during the washing process; preferably, the fourth preset time period is 30-40 min.
In the scheme, a better washing effect can be generated by adopting a washing mode combining low-concentration solvent-pure water-ultrasonic dispersion.
In some embodiments, the percentage of the soluble component of the cellulose pulp to the total mass of the cellulose pulp is calculated in step (2) using the following formula (I):
formula (I)
In the formula (I), SN is the percentage of the soluble component of the cellulose pulp to the total mass of the cellulose pulp; m is0Is the total mass of the cellulose pulp; m is1The mass of the filter residue of the cellulose pulp is shown.
In the scheme, the loss amount of the soluble components of the cellulose pulp is accurately calculated to obtain the percentage of the soluble components in the total mass of the cellulose pulp sample, and the loss amount can be used for evaluating the reaction performance of the cellulose pulp with a high-concentration solvent and the precipitation amount of the cellulose pulp in a low-concentration solvent, effectively evaluating the reaction performance and the product yield of the pulp and an NMMO solvent, and serving as the standard for evaluating the applicability of the regenerated cellulose pulp for Lyocell fiber production.
In some embodiments, the cellulose pulp comprises at least one of cotton pulp, wood pulp, bamboo pulp.
The invention also provides an application of the method for evaluating the reaction performance of the cellulose pulp in producing the regenerated cellulose fiber, wherein according to the calculated percentage of the soluble components of the cellulose pulp in the total mass of the cellulose pulp, the purity, the molecular weight distribution and the content of low-molecular-weight cellulose of the cellulose pulp are evaluated, and the product yield of the regenerated cellulose fiber is evaluated;
preferably, the regenerated cellulose fibers are Lyocell fibers.
After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:
according to the method for evaluating the reaction performance of the cellulose pulp, provided by the invention, the dissolving behaviors of the cellulose pulp in a low-concentration NMMO solvent and a high-concentration NMMO solvent are respectively detected, namely, according to the percentage of soluble components of different types of pulp to the total mass of the pulp, which is obtained through calculation, on one hand, the capacity of the cellulose pulp for forming uniform and stable spinning stock solution in the preparation process of regenerated cellulose fibers can be effectively represented, and the redissolution behavior of fiber tows in a coagulating bath in the spinning forming process is simulated, so that the loss amount of the regenerated cellulose fibers is calculated, and the product yield of the regenerated cellulose fibers is further obtained; on the other hand, the method can also evaluate the purity, the molecular weight distribution and the low molecular weight cellulose content of the cellulose pulp more intuitively and effectively, can effectively evaluate the reaction performance of the pulp in the production process of regenerated cellulose fibers, particularly Lyocell fibers, breaks through the dependence of the prior art on a pulp measuring method for viscose fibers, fills the blank of the pulp evaluating method for Lyocell fibers, forms a more targeted pulp evaluating system for Lyocell fibers, and has important significance for screening the special pulp for Lyocell fibers, reducing the cost of the pulp and solving the problem of raw material limitation of the Lyocell fiber industry.
The invention provides a method for evaluating the reaction performance of cellulose pulp, when the mass ratio of water to NMMO in an NMMO aqueous solution is (7-9): (1-3) or (1-2): and (3) in the step (4), the corresponding reaction stirring temperature is 10-30 ℃ or 70-90 ℃, and the conditions are matched with the coagulation bath forming conditions and swelling stage conditions involved in the Lyocell fiber preparation process, so that the test method has practical operability and effectiveness.
The method for evaluating the reaction performance of the cellulose pulp can be used for screening the special pulp for the Lyocell fiber and improving the quality of the pulp, so that the high quality and high performance of a fiber finished product are ensured. Is beneficial to the pulp manufacturers to pertinently produce the pulp for the Lyocell fiber, and eliminates unnecessary quality indexes, thereby giving consideration to the product quality and the production cost. The pulp for the Lyocell fiber is diversified, and the problem of raw material limitation of the Lyocell fiber industry is solved.
According to the method for evaluating the reaction performance of the cellulose pulp, the loss amount of the soluble components of the cellulose pulp is accurately calculated to obtain the percentage of the soluble components in the total mass of a cellulose pulp sample, the method can be used for evaluating the reaction performance of the cellulose pulp with a high-concentration solvent and the precipitation amount of the cellulose pulp in a low-concentration solvent, and effectively evaluating the reaction performance and the product yield of pulp and an NMMO solvent, and the method is used as a standard for evaluating the applicability of regenerated cellulose pulp in Lyocell fiber production.
The following describes in further detail embodiments of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments are clearly and completely described below, and the following embodiments are used for illustrating the present invention and are not used for limiting the scope of the present invention.
Example 1
In this example, the specific steps for evaluating the reaction properties of cellulose pulp (a sulfite softwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 1: 4 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 80 ℃.
Step (1): immersing 1g of the wood pulp fragments in 10g of the NMMO aqueous solution, immersing the wood pulp fragments in a water bath at the temperature of 80 ℃ for 10s to obtain a mixed solution of wood pulp-NMMO aqueous solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 80 ℃ for 2min, and then adding 10g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 1: and 4, adjusting the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 80 ℃ to obtain pasty dispersion liquid of the wood pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the wood pulp-NMMO aqueous solution in a constant-temperature water bath kettle at the temperature of 80 ℃ for 30min, and reacting to obtain the wood pulp-NMMO swelling solution.
Step (2): taking out the wood pulp-NMMO swelling solution, firstly filtering and washing for 3 times by using a low-concentration 20% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the mass ratio of the wood pulp to NMMO (N-methyl-amino-methyl-N-methyl-ammonium) to be 1: 4, the percentage of soluble components accounting for the total mass of the wood pulp is 2.69 percent when the mixture reacts for 30min in the NMMO aqueous solution.
Example 2
In this example, the specific steps for evaluating the reaction properties of cellulose pulp (a sulfite softwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 1: 3 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 80 ℃.
Step (1): immersing 1g of the wood pulp chips in 25g of the NMMO aqueous solution, immersing the wood pulp chips in a water bath at 90 ℃ for 30s to obtain a wood pulp-NMMO aqueous solution mixed solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 90 ℃ for 2min, and then adding 25g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 1: and 3, adjusting the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 90 ℃ to obtain the pasty dispersion liquid of the wood pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the wood pulp-NMMO aqueous solution in a constant-temperature water bath kettle at 90 ℃ for 60min, and reacting to obtain the wood pulp-NMMO swelling liquid.
Step (2): taking out the wood pulp-NMMO swelling solution, firstly filtering and washing for 3 times by using a low-concentration 20% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the mass ratio of the wood pulp to NMMO (N-methyl-ammonium) to be 1: 3, the percentage of the soluble components in the total mass of the wood pulp is 3.54 percent when the NMMO aqueous solution reacts for 60 min.
Example 3
In this example, the specific steps for evaluating the reactivity of cellulose pulp (a sulfite hardwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 1: 4 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 80 ℃.
Step (1): immersing 1g of the wood pulp fragments in 10g of the NMMO aqueous solution, immersing the wood pulp fragments in a water bath at the temperature of 80 ℃ for 10s to obtain a mixed solution of wood pulp-NMMO aqueous solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 80 ℃ for 2min, and then adding 10g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 1: and 4, adjusting the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 80 ℃ to obtain pasty dispersion liquid of the wood pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the wood pulp-NMMO aqueous solution in a constant-temperature water bath kettle at the temperature of 80 ℃ for 30min, and reacting to obtain the wood pulp-NMMO swelling solution.
Step (2): taking out the wood pulp-NMMO swelling solution, firstly filtering and washing for 3 times by using a low-concentration 20% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the mass ratio of the wood pulp to NMMO (N-methyl-amino-methyl-N-methyl-ammonium) to be 1: 4, the percentage of the soluble components in the total mass of the wood pulp is 5.21 percent when the mixture reacts for 30min in the NMMO aqueous solution.
Example 4
In this example, the specific steps for evaluating the reactivity of cellulose pulp (a kraft softwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 1: 4 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 80 ℃.
Step (1): immersing 1g of the wood pulp fragments in 10g of the NMMO aqueous solution, immersing the wood pulp fragments in a water bath at the temperature of 80 ℃ for 10s to obtain a mixed solution of wood pulp-NMMO aqueous solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 80 ℃ for 2min, and then adding 10g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 1: and 4, adjusting the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 80 ℃ to obtain pasty dispersion liquid of the wood pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the wood pulp-NMMO aqueous solution in a constant-temperature water bath kettle at the temperature of 80 ℃ for 30min, and reacting to obtain the wood pulp-NMMO swelling solution.
Step (2): taking out the wood pulp-NMMO swelling solution, firstly filtering and washing for 3 times by using a low-concentration 20% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the mass ratio of the wood pulp to NMMO (N-methyl-amino-methyl-N-methyl-ammonium) to be 1: 4 the percentage of the soluble components in the total mass of the wood pulp is 7.34 percent when the NMMO aqueous solution reacts for 30 min.
Example 5
In this example, the specific steps for evaluating the reaction properties of cellulose pulp (a sulfite softwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 4: 1 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 25 ℃.
Step (1): immersing 1g of the wood pulp chips in 10g of the NMMO aqueous solution, immersing the wood pulp chips in a water bath at 25 ℃ for 10s to obtain a wood pulp-NMMO aqueous solution mixed solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 25 ℃ for 2min, and then adding 10g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 4: 1, regulating the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 25 ℃ to obtain pasty dispersion liquid of the wood pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the wood pulp-NMMO aqueous solution in a constant-temperature water bath kettle at the temperature of 25 ℃ for 30min, and reacting to obtain a wood pulp-NMMO soaking solution.
Step (2): taking out the wood pulp-NMMO soaking swelling solution, firstly filtering and washing for 3 times by using a low-concentration 5% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed clean and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the mass ratio of the wood pulp in water to NMMO to be 4: 1, the percentage of soluble components in the total mass of the wood pulp is 0.37 percent when the solution reacts for 30 min.
Example 6
In this example, the specific steps for evaluating the reaction properties of cellulose pulp (a sulfite softwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mass ratio of water to NMMO of 7: 3 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 30 ℃.
Step (1): taking 1g of the wood pulp fragments to be immersed in 25g of the NMMO aqueous solution, placing the wood pulp fragments in a water bath at 30 ℃ to be immersed for 30s to obtain a wood pulp-NMMO aqueous solution mixed solution, placing a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 30 ℃ for 2min, then adding 25g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 7: and 3, adjusting the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 30 ℃ to obtain the pasty dispersion liquid of the wood pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the wood pulp-NMMO aqueous solution in a constant-temperature water bath kettle at the temperature of 30 ℃ for 60min, and reacting to obtain a wood pulp-NMMO soaking solution.
Step (2): taking out the wood pulp-NMMO soaking solution, firstly filtering and washing for 3 times by using a low-concentration 5% NMMO solvent, then filtering and washing for 3 times by using pure water, and carrying out ultrasonic dispersion for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the mass ratio of the wood pulp in water to NMMO to be 7: 3, the percentage of the soluble components in the total mass of the wood pulp is 0.48 percent when the NMMO aqueous solution reacts for 60 min.
Example 7
In this example, the specific steps for evaluating the reaction performance of cellulose pulp (bamboo pulp) are as follows:
a pretreatment step: tearing the bamboo pulp for testing into pieces of 5mm multiplied by 5mm, drying at 105 ℃ to constant weight, and balancing water in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 1: 3 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 90 ℃.
Step (1): soaking 1g of the bamboo pulp chips in 25g of the NMMO aqueous solution, placing the bamboo pulp chips in a water bath at 90 ℃ for 30s to obtain a wood pulp-NMMO aqueous solution mixed solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 90 ℃ for 2min, then adding 25g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 1: 3, regulating the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 90 ℃ to obtain the pasty dispersion liquid of the bamboo pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the bamboo pulp-NMMO aqueous solution in a constant-temperature water bath kettle at 90 ℃ for 60min, and reacting to obtain the bamboo pulp-NMMO swelling solution.
Step (2): taking out the bamboo pulp-NMMO swelling solution, firstly filtering and washing for 3 times by using a low-concentration 20% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the bamboo pulp by adopting a formula (I) according to the total mass of the bamboo pulp, and further calculating the mass ratio of the bamboo pulp in water to NMMO to be 1: 3, when the NMMO aqueous solution reacts for 60min, the percentage of the soluble components in the total mass of the bamboo pulp is 4.94 percent.
Example 8
In this example, the specific steps for evaluating the reaction performance of cellulose pulp (cotton pulp) were as follows:
a pretreatment step: tearing the cotton pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; preparing a mixture of water and NMMO with a mass ratio of 1: 3 in aqueous NMMO, pre-equilibrated in a thermostatic water bath at 90 ℃.
Step (1): immersing 1g of the cotton pulp fragments in 25g of the NMMO aqueous solution, immersing the cotton pulp fragments in a water bath at 90 ℃ for 30s to obtain a mixed solution of cotton pulp-NMMO aqueous solution, adding a magnetic rotor into the mixed solution, adjusting the rotating speed to be 1000r/min, stirring the mixed solution at the stirring temperature of 90 ℃ for 2min, and then adding 25g of the NMMO aqueous solution, wherein the mass ratio of water to NMMO in the NMMO aqueous solution is 1: and 3, adjusting the rotating speed to 1500r/min, and continuously stirring for 2min at the stirring temperature of 90 ℃ to obtain pasty dispersion liquid of the cotton pulp-NMMO aqueous solution. And (3) standing the pasty dispersion liquid of the cotton pulp-NMMO aqueous solution in a constant-temperature water bath kettle at 90 ℃ for 60min, and reacting to obtain the cotton pulp-NMMO swelling liquid.
Step (2): taking out the cotton pulp-NMMO swelling solution, firstly filtering and washing for 3 times by using a low-concentration 20% NMMO solvent, then filtering and washing for 3 times by using pure water, and ultrasonically dispersing for 30min until the solution is washed cleanly and separated to obtain filter residues. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the cotton pulp by adopting a formula (I) according to the total mass of the cotton pulp, and further calculating the mass ratio of the cotton pulp to NMMO (N-methyl-amino-methyl-N-methyl-ethyl) to obtain the mass ratio of the water to the mass of the filter residue is 1: 3, the percentage of the soluble components in the total mass of the cotton pulp is 1.82 percent when the NMMO aqueous solution reacts for 60 min.
Comparative example 1
In this comparative example, the specific steps for evaluating the reaction performance of cellulose pulp (a sulfite softwood pulp) were as follows:
a pretreatment step: tearing the wood pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; the water was pre-equilibrated in a thermostatic water bath at 90 ℃.
Step (1): immersing 1g of the wood pulp chips in 25g of the water, immersing the wood pulp chips in a water bath at 90 ℃ for 30s to obtain a wood pulp aqueous solution, adding a magnetic rotor into the wood pulp aqueous solution, adjusting the rotating speed to be 1000r/min, stirring the wood pulp aqueous solution at the stirring temperature of 90 ℃ for 2min, then adding 25g of water, adjusting the rotating speed to be 1500r/min, and continuously stirring the wood pulp aqueous solution at the stirring temperature of 90 ℃ for 2min to obtain a wood pulp-water dispersion liquid. And (3) placing the wood pulp-water dispersion liquid in a constant-temperature water bath kettle at the temperature of 90 ℃ for standing for 60min, and reacting to obtain a wood pulp-water soaking liquid.
Step (2): taking out the wood pulp-water soaking solution, filtering and washing for 6 times by using pure water, and performing ultrasonic dispersion for 30min until the wood pulp-water soaking solution is washed cleanly and separated to obtain filter residues. And (3) weighing the mass of the filter residue, calculating the loss amount of the soluble components of the wood pulp by adopting a formula (I) according to the total mass of the wood pulp, and further calculating the percentage of the soluble components in the total mass of the wood pulp to be 0.02% when the wood pulp reacts in water for 60 min.
Comparative example 2
In this comparative example, the specific steps for evaluating the reaction performance of cellulose pulp (bamboo pulp) were as follows:
a pretreatment step: tearing the bamboo pulp for testing into pieces of 5mm multiplied by 5mm, drying at 105 ℃ to constant weight, and balancing water in a dryer for later use; the water was pre-equilibrated in a thermostatic water bath at 90 ℃.
Step (1): soaking 1g of the bamboo pulp chips in 25g of the water, placing the bamboo pulp chips in a water bath at 90 ℃ for 30s to obtain a bamboo pulp aqueous solution, adding a magnetic rotor into the bamboo pulp aqueous solution, adjusting the rotating speed to be 1000r/min, stirring at the stirring temperature of 90 ℃ for 2min, then adding 25g of water, adjusting the rotating speed to be 1500r/min, and continuously stirring at the stirring temperature of 90 ℃ for 2min to obtain a bamboo pulp-water dispersion liquid. Standing the bamboo pulp-water dispersion in a constant temperature water bath at 90 deg.C for 60min, and reacting to obtain bamboo pulp-water soaking solution.
Step (2): taking out the bamboo pulp-water soaking solution, filtering and washing with pure water for 6 times, and ultrasonically dispersing for 30min until the solution is washed clean and separated to obtain filter residue. Weighing the mass of the filter residue, calculating the loss amount of the soluble components of the bamboo pulp by adopting a formula (I) according to the total mass of the bamboo pulp, and further calculating the percentage of the soluble components in the total mass of the bamboo pulp to be 0.04% when the bamboo pulp reacts in water for 60 min.
Comparative example 3
In this comparative example, the specific steps for evaluating the reaction properties of cellulose pulp (cotton pulp) were as follows:
a pretreatment step: tearing the cotton pulp for testing into pieces of 5mm multiplied by 5mm, drying the pieces to constant weight at the temperature of 105 ℃, and balancing the moisture in a dryer for later use; the water was pre-equilibrated in a thermostatic water bath at 90 ℃.
Step (1): immersing 1g of the cotton pulp fragments in 25g of the water, immersing the cotton pulp fragments in a water bath at 90 ℃ for 30s to obtain a cotton pulp aqueous solution, adding a magnetic rotor into the cotton pulp aqueous solution, adjusting the rotating speed to be 1000r/min, stirring the cotton pulp aqueous solution at the stirring temperature of 90 ℃ for 2min, then adding 25g of the water, adjusting the rotating speed to be 1500r/min, and continuously stirring the cotton pulp aqueous solution at the stirring temperature of 90 ℃ for 2min to obtain a cotton pulp-water dispersion liquid. Placing the cotton pulp-water dispersion in a constant temperature water bath kettle at 90 deg.C, standing for 60min, and reacting to obtain cotton pulp-water soaking solution.
Step (2): taking out the cotton pulp-water soaking solution, filtering and washing with pure water for 6 times, and ultrasonically dispersing for 30min until the cotton pulp-water soaking solution is washed clean and separated to obtain filter residue. And (3) weighing the mass of the filter residue, calculating the loss amount of the soluble components of the cotton pulp by adopting a formula (I) according to the total mass of the cotton pulp, and further calculating the percentage of the soluble components in the total mass of the cotton pulp to be 0.01% when the cotton pulp reacts in water for 60 min.
The test results of the above data are summarized in Table 1
TABLE 1
As can be seen from the data of examples 2, 7 and 8 in Table 1, the soluble components of wood pulp, bamboo pulp and cotton pulp in the same condition account for different percentages of the total mass of the pulp, which shows that the test method provided by the invention can effectively reflect the reaction performance of different types of pulp and NMMO solvent. The loss of mass of bamboo pulp is the greatest and the loss of mass of cotton pulp is the least, which is related to the difference in cellulose content among different types of plants. The chemical composition of the cotton pulp is mainly high molecular weight cellulose, and the molecular weight distribution is concentrated, so that the dissolved cellulose is less in the swelling stage, and the fiber prepared from the cotton pulp has better quality; the content of the pentosan with low molecular weight in the bamboo pulp is much higher than that of the wood pulp, and in the swelling process of the reaction with the NMMO solvent, the components such as the pentosan with low molecular weight and the like are dissolved in advance in the reaction with the NMMO solvent, so that the mass loss is large, the contact of the NMMO solvent and the cellulose in the bamboo pulp in the subsequent reaction dissolving stage is hindered, the dissolution is influenced, and the dissolution condition of the bamboo pulp is harsh and the spinning condition is unstable by combining the spinning condition analysis of Lyocell fibers, so that the test result of the invention is verified.
As can be seen by comparing the data of examples 1, 3 and 4 in Table 1, the percentage of soluble components obtained in different wood pulps under the same reaction conditions are different. For the wood pulp of the embodiment 1, when the vacuum degree is 8KPa, the complete dissolution is realized within 30min, and the formed finished Lyocell fiber product is obtained after spinning. While the dissolution conditions of the wood pulp are more severe due to the increased soluble components of the pulp in examples 3 and 4, the complete dissolution time is extended by 50% under the same vacuum conditions as the wood pulp in example 3, resulting in 1/3 decreased production efficiency of the Lyocell fiber. The wood pulp of example 4 had a complete dissolution time 2 times longer than that of the wood pulp of example 1 under the same vacuum condition, and the production efficiency was reduced 1/2. The reduction of the production efficiency means the increase of the production cost, so that the wood pulp meeting the requirement that the percentage of the soluble component is less than 4 percent can take both the product quality and the production cost into consideration. By analyzing the data of examples 5 and 6, it was demonstrated that there was a certain amount of mass loss in wood pulp during the simulated coagulation bath spin forming process, resulting in a decrease in yield of Lyocell fiber product. This is because some low molecular weight cellulose in pulp is easily dissolved in the coagulation bath in a low concentration, and these dissolved components remain in the coagulation bath and do not participate in the subsequent product forming process, thereby reducing the yield of the Lyocell fiber product. The testing method provided by the invention can effectively reflect the product yield in the spinning process.
By comparing example 2 with comparative example 1, example 7 with comparative example 2, example 8 with comparative example 3, respectively, it is demonstrated that when the NMMO solvent is not added and is completely replaced by pure water, the mass loss of the pulp sample is very little and almost negligible, and the interference of water in the experimental process can be eliminated, thus proving that the test method provided by the invention has feasibility.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method of evaluating the reactivity of cellulose pulp, comprising the steps of:
(1) mixing and infiltrating the flaky cellulose pulp and the low-concentration NMMO aqueous solution, uniformly stirring to obtain a dispersion liquid, standing the dispersion liquid for a first preset time period in a constant-temperature water bath at 10-30 ℃, and reacting to obtain a soaking liquid;
the mass ratio of the low-concentration NMMO aqueous solution to the cellulose pulp is (2-50): 1, the mass ratio of water to NMMO in the low-concentration NMMO aqueous solution is (7-9): (1-3);
or mixing and infiltrating the flaky cellulose pulp and the high-concentration NMMO aqueous solution, uniformly stirring to obtain a dispersion liquid, standing the dispersion liquid for a first preset time period in a constant-temperature water bath at 70-90 ℃, and reacting to obtain a swelling solution;
the mass ratio of the high-concentration NMMO aqueous solution to the cellulose pulp is (2-50): 1, the mass ratio of water to NMMO in the high-concentration NMMO aqueous solution is (1-2): (3-4);
(2) and filtering the soaking solution or the swelling solution, washing and drying to obtain filter residues, weighing the mass of the filter residues, calculating the mass of the soluble components of the cellulose pulp according to the total mass of the cellulose pulp, and further calculating the percentage of the soluble components of the cellulose pulp in the total mass of the cellulose pulp.
2. The method of claim 1, wherein the evaluation of the reactivity of the cellulose pulp comprises:
before the step (1), a pretreatment step is also included, which comprises the steps of drying the cellulose pulp in a flake shape to constant weight, balancing moisture, and placing the low-concentration NMMO aqueous solution and the high-concentration NMMO aqueous solution in a thermostatic water bath for pre-balancing;
preferably, the shredded cellulose pulp is uniform in size; more preferably, the cellulose pulp in chip form is 5 x 5mm in size.
3. The method of claim 1, wherein the evaluation of the reactivity of the cellulose pulp comprises:
in the step (1), the temperature for mixing and infiltrating the flaky cellulose pulp and the low-concentration NMMO aqueous solution is 10-30 ℃, and the infiltrating time is 10-60 s;
or the mixing and infiltrating temperature of the flake-shaped cellulose pulp and the high-concentration NMMO aqueous solution is 70-90 ℃, and the infiltrating time is 10-60 s.
4. A method of evaluating the reactivity of cellulose pulp according to claim 1 or 3, wherein:
in the step (1), after stirring for a second preset time period, adding an NMMO aqueous solution and continuously stirring for a third preset time period to obtain the dispersion liquid;
preferably, the stirring temperature of the flake-shaped cellulose pulp and the low-concentration NMMO aqueous solution is 10-30 ℃, and the second preset time period and the third preset time period are respectively 1-5 min; the mass ratio of the added NMMO aqueous solution is (7-9): (1-3);
or the stirring temperature of the flake-shaped cellulose pulp and the high-concentration NMMO aqueous solution is 70-90 ℃, and the second preset time period and the third preset time period are respectively 1-5 min; the mass ratio of the added NMMO aqueous solution is (1-2): (3-4);
more preferably, the stirring is performed by using a magnetic stirrer at the rotation speed of 500-.
5. The method of claim 1, wherein the evaluation of the reactivity of the cellulose pulp comprises:
in the step (1), the first preset time period is 30-120 min.
6. The method of claim 1, wherein the evaluation of the reactivity of the cellulose pulp comprises:
in the step (2), firstly, washing is carried out by adopting an NMMO aqueous solution with the mass ratio of water to NMMO being (4: 19) -1, and then washing is carried out by adopting pure water.
7. The method of evaluating the reactivity of cellulose pulp according to claim 1 or 6, wherein:
performing ultrasonic dispersion for a fourth preset time period in the washing process; preferably, the fourth preset time period is 30-40 min.
8. The method of claim 1, wherein the evaluation of the reactivity of the cellulose pulp comprises:
in the step (2), the percentage of the soluble components of the cellulose pulp to the total mass of the cellulose pulp is calculated by the following formula (I):
in the formula (I), SN is the percentage of the soluble component of the cellulose pulp to the total mass of the cellulose pulp; m is0Is the total mass of the cellulose pulp; m is1The mass of the filter residue of the cellulose pulp is shown.
9. A method for evaluating the reactivity of cellulose pulp according to any one of claims 1-8, wherein:
the cellulose pulp comprises at least one of cotton pulp, wood pulp and bamboo pulp.
10. Use of a method of assessing the reactivity of cellulose pulp according to any one of claims 1 to 9 in the production of regenerated cellulose fibers, wherein:
according to the calculated percentage of the soluble components of the cellulose pulp to the total mass of the cellulose pulp, evaluating the purity, the molecular weight distribution and the content of low molecular weight cellulose of the cellulose pulp and evaluating the product yield of regenerated cellulose fibers;
preferably, the regenerated cellulose fibers are Lyocell fibers.
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