CN108708219B - Method for deacidifying paper material by using subcritical fluid containing nano calcium hydroxide - Google Patents
Method for deacidifying paper material by using subcritical fluid containing nano calcium hydroxide Download PDFInfo
- Publication number
- CN108708219B CN108708219B CN201810557943.2A CN201810557943A CN108708219B CN 108708219 B CN108708219 B CN 108708219B CN 201810557943 A CN201810557943 A CN 201810557943A CN 108708219 B CN108708219 B CN 108708219B
- Authority
- CN
- China
- Prior art keywords
- paper
- calcium hydroxide
- deacidification
- nano calcium
- subcritical fluid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 title claims abstract description 83
- 239000000920 calcium hydroxide Substances 0.000 title claims abstract description 83
- 229910001861 calcium hydroxide Inorganic materials 0.000 title claims abstract description 83
- 239000012530 fluid Substances 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 31
- 239000000463 material Substances 0.000 title claims abstract description 22
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 45
- 238000000605 extraction Methods 0.000 claims abstract description 33
- 238000004140 cleaning Methods 0.000 claims abstract description 32
- 230000003068 static effect Effects 0.000 claims description 29
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 14
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 8
- 239000007822 coupling agent Substances 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 4
- LVGUZGTVOIAKKC-UHFFFAOYSA-N 1,1,1,2-tetrafluoroethane Chemical compound FCC(F)(F)F LVGUZGTVOIAKKC-UHFFFAOYSA-N 0.000 claims description 3
- 238000010924 continuous production Methods 0.000 claims description 2
- 239000012467 final product Substances 0.000 claims 1
- 239000001913 cellulose Substances 0.000 abstract description 7
- 229920002678 cellulose Polymers 0.000 abstract description 7
- 238000009792 diffusion process Methods 0.000 abstract description 3
- 238000005516 engineering process Methods 0.000 abstract description 3
- 239000002904 solvent Substances 0.000 abstract description 3
- 239000012466 permeate Substances 0.000 abstract description 2
- 230000032683 aging Effects 0.000 description 48
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 27
- 238000011068 loading method Methods 0.000 description 24
- 238000005086 pumping Methods 0.000 description 24
- 239000003513 alkali Substances 0.000 description 23
- 230000008859 change Effects 0.000 description 18
- 238000003860 storage Methods 0.000 description 11
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 7
- 230000008569 process Effects 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 230000002378 acidificating effect Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000000725 suspension Substances 0.000 description 5
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 238000001914 filtration Methods 0.000 description 3
- 230000007062 hydrolysis Effects 0.000 description 3
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000002572 peristaltic effect Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000008439 repair process Effects 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000009210 therapy by ultrasound Methods 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- DDMOUSALMHHKOS-UHFFFAOYSA-N 1,2-dichloro-1,1,2,2-tetrafluoroethane Chemical compound FC(F)(Cl)C(F)(F)Cl DDMOUSALMHHKOS-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 239000004338 Dichlorodifluoromethane Substances 0.000 description 1
- 229920002488 Hemicellulose Polymers 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 125000003172 aldehyde group Chemical group 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 239000001273 butane Substances 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- AFYPFACVUDMOHA-UHFFFAOYSA-N chlorotrifluoromethane Chemical compound FC(F)(F)Cl AFYPFACVUDMOHA-UHFFFAOYSA-N 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- PXBRQCKWGAHEHS-UHFFFAOYSA-N dichlorodifluoromethane Chemical compound FC(F)(Cl)Cl PXBRQCKWGAHEHS-UHFFFAOYSA-N 0.000 description 1
- 235000019404 dichlorodifluoromethane Nutrition 0.000 description 1
- UMNKXPULIDJLSU-UHFFFAOYSA-N dichlorofluoromethane Chemical compound FC(Cl)Cl UMNKXPULIDJLSU-UHFFFAOYSA-N 0.000 description 1
- 229940099364 dichlorofluoromethane Drugs 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000001282 iso-butane Substances 0.000 description 1
- 229920005610 lignin Polymers 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 231100000957 no side effect Toxicity 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- CYRMSUTZVYGINF-UHFFFAOYSA-N trichlorofluoromethane Chemical compound FC(Cl)(Cl)Cl CYRMSUTZVYGINF-UHFFFAOYSA-N 0.000 description 1
- 229940029284 trichlorofluoromethane Drugs 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
- D21H25/18—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00 of old paper as in books, documents, e.g. restoring
Landscapes
- Paper (AREA)
Abstract
The invention discloses a method for deacidifying a paper material. The method comprises the following steps: 1) putting paper to be treated into a high-pressure-resistant extraction kettle, and cleaning the paper by using subcritical fluid under the conditions of 5.0-12.0 MPa and 30-50 ℃; 2) and maintaining the conditions, adding a nano calcium hydroxide deacidification agent into the high-pressure resistant extraction kettle in the presence of the subcritical fluid, and carrying out deacidification treatment on the paper by utilizing the subcritical fluid and the deacidification agent together. The subcritical fluid technology is applied to deacidification of the paper material, the deacidification agent can effectively permeate into a cellulose structure of the paper material, no solvent is left, and the treated paper material has no phenomena of tilting, deformation, adhesion, ink shading, color diffusion and the like. The method has uniform deacidification and is suitable for deacidification of various paper materials.
Description
Technical Field
The invention belongs to the field of preservation and repair of paper materials, and particularly relates to a method for deacidifying a paper material by using subcritical fluid containing nano calcium hydroxide.
Background
The stability of cellulose, which is the main component of paper (in addition to very small amounts of lignin and hemicellulose in paper), directly determines the durability of paper. Cellulose is stable under neutral or slightly alkaline conditions, but the rate of hydrolysis is significantly increased under acidic conditions. Since the cellulose molecule has an oxidizing functional group such as an aldehyde group or a carboxyl group, the hydrolysis reaction is accompanied by the oxidation reaction. Hydrolysis and oxidation of cellulose leads to a decrease in the degree of polymerization of cellulose, directly affecting the mechanical strength and durability of the paper. Deacidification of paper is recognized as the most effective method for rescuing acidified paper materials. As the name suggests, deacidification of paper refers to neutralization of acidic substances in paper by using alkaline or slightly alkaline chemical substances, and meanwhile, a certain amount of residual alkali is remained on the surface of the paper, so that further hydrolysis of cellulose is inhibited, corrosion of acidic media possibly existing in a storage environment to the surface of the paper is prevented or delayed, and the softness and mechanical properties of the paper are maintained as much as possible. In general, deacidification agents are required to be non-toxic, harmless and environment-friendly, have no side effects on paper to be treated (do not affect writing, pigments and physicochemical properties of paper), and the deacidified paper does not pose a hazard to current and future users. Before and after deacidification, the color difference of paper is not obviously changed, the deacidification process is stable in writing, no redundant chemical substances or odor is left, and the alkali storage (alkali residual quantity) is distributed as uniformly as possible. This has been explored and studied for many years, and various deacidification methods have been studied.
R134a (1,1,1, 2-tetrafluoroethane) is a refrigerant which cannot damage the ozone layer, R134a is inert, nonflammable and stable to acid and alkali, and when R134a exists in a subcritical fluid state, special properties such as low viscosity, enhanced diffusion performance, accelerated mass transfer speed and remarkably improved permeability and dissolving capacity to nonpolar substances are shown. And CO2In contrast, R134a has a lower critical pressure, higher polarity, and better solvent performance in the liquid state and near the critical point. Currently, research is mainly focused on the basic properties of R134a and on extraction. The subcritical fluid has the advantages of supercritical fluid, and the defects of small volume, high manufacturing cost, large energy consumption and unsuitability for large-scale industrial production of supercritical fluid equipment are overcome. Therefore, the subcritical fluid has wide application practice and development prospects.
Disclosure of Invention
According to the method, the characteristics of low viscosity, strong diffusivity, low interfacial tension and strong extraction capability of subcritical fluid are utilized, acidic substances in the paper material to be treated are neutralized or extracted, and meanwhile, the nano calcium hydroxide of the deacidification agent is permeated into fiber structure gaps of the paper material, so that the paper retains certain deacidification agent residue (alkali storage), and further corrosion of the acidic medium possibly existing in a storage environment to the surface of the paper is delayed.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of deacidifying a paper material comprising the steps of:
1) putting paper to be treated into a high-pressure-resistant extraction kettle, and cleaning the paper by using subcritical fluid under the conditions of 5.0-12.0 MPa and 30-50 ℃;
2) and maintaining the conditions, adding a nano calcium hydroxide deacidification agent into the high-pressure resistant extraction kettle in the presence of the subcritical fluid, and carrying out deacidification treatment on the paper by utilizing the subcritical fluid and the deacidification agent together.
In the above method, the conditions in step 1) are preferably: 6.0-9.0 MPa, 35-45 ℃. The flow rate of the subcritical fluid may be 8.0 to 80.0 g/min. The cleaning may be static cleaning. The cleaning time can be 0.5-3.0 hours.
In the method, the nano calcium hydroxide deacidification agent in the step 2) consists of nano calcium hydroxide, isopropanol and a titanate coupling agent; wherein the proportion of the nano calcium hydroxide, the isopropanol and the titanate coupling agent is 1.0-6.0 g: 0.8-1.2L: 0.05-0.25 g, preferably 1.5 g: 1.0L: 0.05 g.
The nano calcium hydroxide deacidification agent is prepared by the following method: dispersing the nano calcium hydroxide into isopropanol, and adding a titanate coupling agent. The particle size of the nano calcium hydroxide is 50-120 nm.
The nano calcium hydroxide is prepared by the method comprising the following steps:
respectively preparing a calcium chloride solution and a sodium hydroxide solution; and dropwise adding the sodium hydroxide solution into the calcium chloride solution, and generating the nano calcium hydroxide through heterogeneous reaction.
The concentration of the calcium chloride solution can be 0.3-0.6 mol/L;
the concentration of the sodium hydroxide solution can be 0.5-0.9 mol/L;
the volume ratio of the calcium chloride solution to the sodium hydroxide solution can be 1: 1.
the sodium hydroxide solution can be dripped into the calcium chloride solution through a peristaltic pump, and the dripping speed is kept at 1.0-3.0 mL/min. Stirring was continued during the dropwise addition to allow the reaction to proceed sufficiently.
The reaction temperature can be 80-100 ℃.
And (4) after the sodium hydroxide solution is completely added, continuing to react for 8-20 minutes to obtain a suspension.
And filtering the prepared suspension while the suspension is hot to obtain white powder, dissolving the white powder by using deionized water, carrying out ultrasonic treatment for 15-45 minutes, then carrying out centrifugal separation for 8-12 minutes at 6000-10000 r/min, repeating the whole process for 5-8 times, and carrying out vacuum drying on the precipitate for 15-30 hours at 80-100 ℃ to obtain the nano calcium hydroxide with the particle size of 50-120 nanometers.
The concentration of the nano calcium hydroxide in the nano calcium hydroxide deacidification agent in the step 2) is 1.0-6.0 mg/mL;
the dosage of the nano calcium hydroxide deacidification agent is 70-150ml per square meter of paper to be treated.
The deacidification treatment time in the step 2) is 0.5-5 hours, and specifically can be 4 hours.
The deacidification treatment in step 2) may be a batch or continuous process. The deacidification treatment is static deacidification.
The paper material processed in the invention can be various paper materials, and can be single-page paper or multi-page books, files and the like.
Subcritical refers to a condition where one of the critical process parameters pressure and temperature of the fluid is above the critical point, while the other parameter is below the critical point. Subcritical fluid refers to a substance that exists as a fluid in a subcritical state. The present invention utilizes only the feature of subcritical fluid. The subcritical fluid of particular choice for the present invention is R134a (1,1,1, 2-tetrafluoroethane), but the process of the present invention is not limited to subcritical R134 a. The subcritical fluids propane, butane, isobutane, dichlorodifluoromethane, chlorotrifluoromethane, dichlorofluoromethane, trichlorofluoromethane, 1, 2-dichlorotetrafluoroethane and the like are also suitable for use in the present invention.
The method for deacidifying the paper material by using the subcritical fluid overcomes the defects of solvent pollution, reduced strength of the deacidified paper, paper warping, ink permeation and the like in the conventional deacidifying method.
The present invention uses 1920 and 1940 mechanical paper and 1962 daily reports of workers to deacidify paper materials, but the technology is not limited to deacidifying selected paper.
The invention has the following beneficial effects:
1. by utilizing the characteristics of small viscosity, strong diffusivity, low interfacial tension and strong extraction capability of subcritical fluid, the deacidification agent nano calcium hydroxide is easy to permeate into fiber structure gaps of paper materials, and the deacidification treatment of the whole book (no disassembly and assembly required during book assembly) is easy to realize. The treatment process is green, and R134a can be recycled.
2. The subcritical fluid is combined with the nano deacidification agent for deacidification, the advantages of the subcritical fluid and the nano technology are simultaneously played, and cleaning and deacidification are integrated, so that the paper material is more convenient to repair and protect. The deacidified paper is cleaner, has no deformation, color diffusion, ink leakage, adhesion and the like, and the mechanical property of the paper is improved, thereby being beneficial to long-term storage of paper materials.
Detailed Description
The method of the present invention is illustrated by the following specific examples, but the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included within the scope of the present invention.
The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The deacidification agent adopted in the following embodiment is prepared by dispersing nano calcium hydroxide into isopropanol and then adding a titanate coupling agent, wherein the concentration of the nano calcium hydroxide is 1.0mg/mL, and the addition amount of the titanate coupling agent is 2% of the mass of the nano calcium hydroxide powder.
Wherein the nano calcium hydroxide is prepared by the following method:
preparing calcium chloride solution with the concentration of 0.5mol/L and sodium hydroxide solution with the concentration of 0.7 mol/L. 500mL of sodium hydroxide solution is dripped into 500mL of calcium chloride solution by a peristaltic pump, the dripping speed is kept at 1.0mL/min, the reaction is fully carried out by stirring, and the reaction temperature is controlled at 90 ℃ by oil bath heating. And (5) after the sodium hydroxide solution is completely added, continuing to react for 10 minutes to obtain a suspension. The suspension obtained is filtered and during the filtration the temperature is maintained as much as possible, since the solubility of calcium hydroxide increases with decreasing temperature. Filtering to obtain white powder, dissolving with deionized water, performing ultrasonic treatment for 30min, centrifuging at 8000r/min, repeating the whole process for 5-8 times until no chloride ion is detected in silver nitrate test, and vacuum drying the precipitate at 100 deg.C for 24 hr to obtain nanometer calcium hydroxide with particle size of about 100 nm.
Example 1
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a (note: static deacidification of paper under a certain pressure), adding nano calcium hydroxide with the concentration of 1.0mg/mL, and performing static deacidification treatment for 4 hours. After the treatment, the pH was 7.8 and the average alkali storage reached 0.92 mol/kg. The average alkali reserve measured after ageing according to ISO5630-1:1991 is 0.82 mol/kg. The average alkali reserve measured after ageing according to ISO5630-3:1996 was 0.68 mol/kg.
Example 2
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. After the treatment, the pH was found to be 8.2 and the average alkali storage reached 1.16 mol/kg. The average alkali reserve measured after ageing according to ISO5630-1:1991 is 1.01 mol/kg. The average alkali reserve measured after ageing according to ISO5630-3:1996 was 0.87 mol/kg.
Example 3
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. After the treatment, the pH was found to be 8.0 and the average alkali storage reached 1.08 mol/kg. The average alkali reserve measured after ageing according to ISO5630-1:1991 is 0.90 mol/kg. The average alkali reserve measured after ageing according to ISO5630-3:1996 was 0.77 mol/kg.
Example 4
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. After the treatment, the pH was found to be 8.0 and the average alkali storage reached 0.94 mol/kg. The average alkali reserve measured after ageing according to ISO5630-1:1991 is 0.80 mol/kg. The average alkali reserve measured after ageing according to ISO5630-3:1996 was 0.69 mol/kg.
Example 5
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. After the treatment, the pH was found to be 8.3 and the average alkali storage reached 1.21 mol/kg. The average alkali reserve measured after ageing according to ISO5630-1:1991 is 1.01 mol/kg. The average alkali reserve measured after ageing according to ISO5630-3:1996 was 0.91 mol/kg.
Example 6
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. After the treatment, the pH was found to be 8.1 and the average alkali storage reached 1.10 mol/kg. The average alkali reserve measured after ageing according to ISO5630-1:1991 is 0.94 mol/kg. The average alkali reserve measured after ageing according to ISO5630-3:1996 was 0.84 mol/kg.
Example 7
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Color difference change value delta L measured before and after treatment*＝-0.56，Δb*＝0.45，Δa*＝0.40,ΔE＝0.82。
Example 8
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Color difference change value delta L measured before and after treatment*＝-0.14，Δb*＝0.60，Δa*＝0.11,ΔE＝0.63。
Example 9
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Color difference change value delta L measured before and after treatment*＝-0.85，Δb*＝-0.47Δa*＝0.19,ΔE＝0.99。
Example 10
Loading pH 2.6 mechanical paper (1920 years) of 7cm × 7cm into high-pressure extraction kettle, and extracting at 40 deg.C under 6.0MPa with subcritical R134a (flow rate of 10.0 g/min)) Static cleaning is carried out for 30 minutes; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Color difference change value delta L measured before and after treatment*＝-0.60，Δb*＝0.35，Δa*＝0.42,ΔE＝0.81。
Example 11
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Color difference change value delta L measured before and after treatment*＝-0.22，Δb*＝0.40，Δa*＝0.18,ΔE＝0.49。
Example 12
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Color difference change value delta L measured before and after treatment*＝-0.75，Δb*＝-0.52Δa*＝0.29,ΔE＝0.96。
Example 13
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was aged according to ISO5630-1:1991, and the change in color difference Δ L before and after aging of the untreated paper was measured*＝-1.20，Δb*＝4.06，Δa*0.36. Color difference change measured before and after aging of treated paperValue Δ L*＝-1.43，Δb*＝4.59，Δa*＝0.48。
Example 14
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was aged according to ISO5630-1:1991, and the change in color difference Δ L before and after aging of the untreated paper was measured*＝-1.32，Δb*＝3.66，Δa*0.38. Color difference change value delta L measured before and after aging of treated paper*＝-1.46，Δb*＝4.12，Δa*＝0.44。
Example 15
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was aged according to ISO5630-1:1991, and the change in color difference Δ L before and after aging of the untreated paper was measured*＝-2.12，Δb*＝4.51，Δa*0.57. Color difference change value delta L measured before and after aging of treated paper*＝-2.28，Δb*＝4.64，Δa*＝0.68。
Example 16
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Paper was aged according to ISO5630-3:1996, and the change in color difference Δ L before and after aging of untreated paper was measured*＝-1.98，Δb*＝4.54，Δa*0.42. Color difference change value delta L measured before and after aging of treated paper*＝-2.23，Δb*＝4.89，Δa*＝0.78。
Example 17
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Paper was aged according to ISO5630-3:1996, and the change in color difference Δ L before and after aging of untreated paper was measured*＝-1.78，Δb*＝3.91，Δa*0.42. Color difference change value delta L measured before and after aging of treated paper*＝-2.16，Δb*＝3.98，Δa*＝0.62。
Example 18
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. Paper was aged according to ISO5630-3:1996, and the change in color difference Δ L before and after aging of untreated paper was measured*＝-1.90，Δb*＝4.82，Δa*0.89. Color difference change value delta L measured before and after aging of treated paper*＝-2.32，Δb*＝4.72，Δa*＝0.88。
Example 19
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was tested for tensile strength according to ISO 1924-2: 2008. The tensile strength of the untreated paper was 1.20KN/m, the tensile strength of the untreated paper was 1.05KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the untreated paper was 0.75KN/m measured after aging according to ISO5630-3: 1996; the tensile strength of the paper after deacidification was 1.52KN/m, the tensile strength of the paper after deacidification was 1.40KN/m measured after ageing according to ISO5630-1:1991 and the tensile strength of the paper after deacidification was 1.05KN/m measured after ageing according to ISO5630-3: 1996.
Example 20
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was tested for tensile strength according to ISO 1924-2: 2008. The tensile strength of the untreated paper was 1.30KN/m, the tensile strength of the untreated paper was 1.10KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the untreated paper was 0.81KN/m measured after aging according to ISO5630-3: 1996; the tensile strength of the paper after deacidification was 1.78KN/m, the tensile strength of the paper after deacidification was 1.51KN/m after aging according to ISO5630-1:1991, and the tensile strength of the paper after deacidification was 1.25KN/m after aging according to ISO5630-3: 1996.
Example 21
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 8.0MPa for 30 min; maintaining the conditions, pumping 1.0mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was tested for tensile strength according to ISO 1924-2: 2008. The tensile strength of the untreated paper was 1.10KN/m, the tensile strength of the untreated paper was 0.80KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the untreated paper was 0.69KN/m measured after aging according to ISO5630-3: 1996; the tensile strength of the paper after deacidification was 1.38KN/m, the tensile strength of the paper after deacidification was 1.22KN/m after aging according to ISO5630-1:1991 and the tensile strength of the paper after deacidification was 0.90KN/m after aging according to ISO5630-3: 1996.
Example 22
Loading 7cm × 7cm mechanical paper (1920 years) with pH of 2.6 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was tested for tensile strength according to ISO 1924-2: 2008. The tensile strength of the untreated paper was 1.20KN/m, the tensile strength of the untreated paper was 1.05KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the untreated paper was 0.75KN/m measured after aging according to ISO5630-3: 1996; the tensile strength of the paper after deacidification was 1.55KN/m, the tensile strength of the paper after deacidification was 1.43KN/m measured after ageing according to ISO5630-1:1991 and the tensile strength of the paper after deacidification was 1.02KN/m measured after ageing according to ISO5630-3: 1996.
Example 23
Loading 7cm × 7cm mechanical paper (1940) with pH of 3.5 into high pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was tested for tensile strength according to ISO 1924-2: 2008. The tensile strength of the untreated paper was 1.30KN/m, the tensile strength of the untreated paper was 1.10KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the untreated paper was 0.81KN/m measured after aging according to ISO5630-3: 1996; the tensile strength of the paper after deacidification was 1.78KN/m, the tensile strength of the paper after deacidification was 1.49KN/m after aging according to ISO5630-1:1991, and the tensile strength of the paper after deacidification was 1.10KN/m after aging according to ISO5630-3: 1996.
Example 24
Loading a 7cm × 7cm worker daily newspaper (1962) with pH of 3.0 into a high-pressure extraction kettle, and statically cleaning with subcritical R134a (flow rate of 10.0 g/min) at 40 deg.C under 6.0MPa for 30 min; maintaining the conditions, pumping 1.6mL of deacidification agent nano calcium hydroxide in the presence of subcritical fluid R134a, wherein the concentration of the added nano calcium hydroxide is 1.0mg/mL, and the static treatment time is 4 hours. The paper was tested for tensile strength according to ISO 1924-2: 2008. The tensile strength of the untreated paper was 1.10KN/m, the tensile strength of the untreated paper was 0.80KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the untreated paper was 0.69KN/m measured after aging according to ISO5630-3: 1996; the tensile strength of the paper after deacidification was 1.36KN/m, the tensile strength of the paper after deacidification was 1.19KN/m measured after aging according to ISO5630-1:1991, and the tensile strength of the paper after deacidification was 0.96KN/m measured after aging according to ISO5630-3: 1996.
Claims (5)
1. A method of deacidifying a paper material comprising the steps of:
1) putting paper to be treated into a high-pressure-resistant extraction kettle, and cleaning the paper by using subcritical fluid under the conditions of 5.0-12.0 MPa and 30-50 ℃;
2) maintaining the condition, adding a nano calcium hydroxide deacidification agent into the high-pressure resistant extraction kettle in the presence of the subcritical fluid, and carrying out deacidification treatment on the paper by utilizing the subcritical fluid and the deacidification agent together;
the nano calcium hydroxide deacidification agent consists of nano calcium hydroxide, isopropanol and a titanate coupling agent; wherein the proportion of the nano calcium hydroxide, the isopropanol and the titanate coupling agent is 1.0-6.0 g: 0.8-1.2L: 0.05-0.25 g;
the subcritical fluid is selected from 1,1,1, 2-tetrafluoroethane;
the flow rate of the subcritical fluid is 8.0-80.0 g/min;
the cleaning time in the step 1) is 0.5-3.0 hours;
the particle size of the nano calcium hydroxide is 50-120 nanometers;
the concentration of the nano calcium hydroxide in the nano calcium hydroxide deacidification agent in the step 2) is 1.0-6.0 mg/mL;
the dosage of the nano calcium hydroxide deacidification agent is 70-150ml per square meter of paper to be treated;
the time of the deacidification treatment in the step 2) is 0.5-5 hours.
2. The method of claim 1, wherein: the conditions in step 1) are as follows: 6.0-9.0 MPa, 35-45 ℃.
3. The method of claim 1, wherein: the nano calcium hydroxide deacidification agent is prepared by the following method: dispersing nanometer calcium hydroxide into isopropanol, and adding titanate coupling agent to obtain the final product.
4. The method of claim 1, wherein: in the step 2), the deacidification treatment is an intermittent or continuous process.
5. The method of claim 1, wherein: the deacidification treatment is static deacidification.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810557943.2A CN108708219B (en) | 2018-06-01 | 2018-06-01 | Method for deacidifying paper material by using subcritical fluid containing nano calcium hydroxide |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810557943.2A CN108708219B (en) | 2018-06-01 | 2018-06-01 | Method for deacidifying paper material by using subcritical fluid containing nano calcium hydroxide |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108708219A CN108708219A (en) | 2018-10-26 |
| CN108708219B true CN108708219B (en) | 2020-11-17 |
Family
ID=63871011
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810557943.2A Expired - Fee Related CN108708219B (en) | 2018-06-01 | 2018-06-01 | Method for deacidifying paper material by using subcritical fluid containing nano calcium hydroxide |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108708219B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113026420B (en) * | 2021-03-26 | 2022-05-17 | 南京大学 | Cellulose water-resistant paper and preparation method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4202320A1 (en) * | 1992-01-29 | 1993-08-05 | Dierk Dr Knittel | Impregnating substrate by contact with supercritical fluid contg. impregnant - followed by conversion of fluid to subcritical state |
| RU2243309C1 (en) * | 2003-11-17 | 2004-12-27 | Федеральное государственное учреждение Российская национальная библиотека | Method of neutralizing acidity of paper |
| CN101538816A (en) * | 2009-04-27 | 2009-09-23 | 广东工业大学 | Paper deacidification method |
-
2018
- 2018-06-01 CN CN201810557943.2A patent/CN108708219B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4202320A1 (en) * | 1992-01-29 | 1993-08-05 | Dierk Dr Knittel | Impregnating substrate by contact with supercritical fluid contg. impregnant - followed by conversion of fluid to subcritical state |
| RU2243309C1 (en) * | 2003-11-17 | 2004-12-27 | Федеральное государственное учреждение Российская национальная библиотека | Method of neutralizing acidity of paper |
| CN101538816A (en) * | 2009-04-27 | 2009-09-23 | 广东工业大学 | Paper deacidification method |
Non-Patent Citations (2)
| Title |
|---|
| Deacidification of paper using dispersions of Ca(OH)2 nanoparticles in isopropanol. Study of efficiency;S. Sequeira, etal.;《Journal of Cultural Heritage》;20061231;第264页右栏第14-18行 * |
| 纳米颗粒的化学改性方法研究现状;陈云华等;《中国表面工程》;20051231(第2期);第5页引言，第7页1.6节 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN108708219A (en) | 2018-10-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2860956C (en) | Method and apparatus for processing fibril cellulose and fibril cellulose product | |
| Lee et al. | Fouling of reverse osmosis membranes by hydrophilic organic matter: implications for water reuse | |
| CN104888620B (en) | High flux high efficiency nano tunica fibrosa and preparation method thereof | |
| CN105617882B (en) | A kind of compound forward osmosis membrane of chitosan-modified stannic oxide/graphene nano and preparation method thereof | |
| CN101732998B (en) | Preparation method for cross-linking polyvinyl alcohol furfural nanofiltration membrane | |
| CN108409981A (en) | A kind of preparation method of modified metal organic frame and composite nanometer filtering film | |
| KR950017739A (en) | Titanium Dioxide Slurry and Manufacturing Method Thereof | |
| CN109260970B (en) | Preparation method of high-strength inorganic doped calcium alginate hydrogel filtering membrane | |
| CN109342382B (en) | Preparation method of deacidification functional paper with pH response fluorescent probe | |
| CN108708219B (en) | Method for deacidifying paper material by using subcritical fluid containing nano calcium hydroxide | |
| CN112915816A (en) | MXene separation membrane capable of simultaneously separating oil and dye and preparation method and application thereof | |
| CN109695182A (en) | A kind of method depickling enhancing treatment fluid and aging paper is handled | |
| CN103157388A (en) | Hydrophilic reverse osmosis composite membrane and preparation method thereof | |
| CN105148750A (en) | Method for modifying surface of polyamide composite film | |
| CN104150787B (en) | A kind of Induced by Dopamine sol-gal process prepares the method for modifying of high hydrophiling coating | |
| Wang et al. | Facile construction of multifunctional bio-aerogel for efficient separation of surfactant-stabilized oil-in-water emulsions and co-existing organic pollutant | |
| CN107574717B (en) | Layer-by-layer self-assembly paper document repairing equipment assisted with vacuum infiltration | |
| CN108164606A (en) | Preparation method of amphoteric cellulose ether for drilling fluid | |
| CN104492283B (en) | A kind of nano micro crystal cellulose enhanced polyethylene alcohol forward osmosis membrane and preparation and application | |
| Zhuang et al. | Desalination and lignin concentration in a lignin aqueous solution by nano-filtration process: Advanced γ-Al2O3 film-coated porous α-Al2O3 hollow fiber membrane | |
| CN108484984A (en) | A kind of preparation method of high strength fibre element based coextruded film | |
| Li et al. | Biomimetic stable cellulose based superhydrophobic Janus paper sheets engineered with industrial lignin residues/nano-silica for efficient oil-water separation | |
| Pan et al. | A fully degradable flexible membrane via green synthesis for highly effective separation of oil–water emulsions | |
| CN115287052B (en) | Carbon point compound oil displacement system based on interface regulation and control and preparation method and application thereof | |
| CN117106427A (en) | Ag/Fe 3 O 4 Nanocomposite and method of making |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20201117 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |