CN116397450A - Method for decoloring black waste cotton blended fabric and preparing cellulose dissolving pulp - Google Patents
Method for decoloring black waste cotton blended fabric and preparing cellulose dissolving pulp Download PDFInfo
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- CN116397450A CN116397450A CN202310381479.7A CN202310381479A CN116397450A CN 116397450 A CN116397450 A CN 116397450A CN 202310381479 A CN202310381479 A CN 202310381479A CN 116397450 A CN116397450 A CN 116397450A
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- 229920000742 Cotton Polymers 0.000 title claims abstract description 113
- 239000004744 fabric Substances 0.000 title claims abstract description 113
- 239000002699 waste material Substances 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 59
- 229920000875 Dissolving pulp Polymers 0.000 title claims abstract description 48
- 229920002678 cellulose Polymers 0.000 title claims abstract description 46
- 239000001913 cellulose Substances 0.000 title claims abstract description 46
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 63
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 38
- 238000010411 cooking Methods 0.000 claims abstract description 33
- 238000001035 drying Methods 0.000 claims abstract description 29
- 238000004537 pulping Methods 0.000 claims abstract description 24
- 238000004061 bleaching Methods 0.000 claims abstract description 18
- 239000011259 mixed solution Substances 0.000 claims abstract description 15
- RYYXDZDBXNUPOG-UHFFFAOYSA-N 4,5,6,7-tetrahydro-1,3-benzothiazole-2,6-diamine;dihydrochloride Chemical compound Cl.Cl.C1C(N)CCC2=C1SC(N)=N2 RYYXDZDBXNUPOG-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000005406 washing Methods 0.000 claims abstract description 13
- 239000003381 stabilizer Substances 0.000 claims abstract description 8
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 4
- 230000003213 activating effect Effects 0.000 claims abstract description 3
- 229920000728 polyester Polymers 0.000 claims description 22
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims description 16
- 238000004140 cleaning Methods 0.000 claims description 14
- 239000008367 deionised water Substances 0.000 claims description 11
- 229910021641 deionized water Inorganic materials 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 239000004115 Sodium Silicate Substances 0.000 claims description 9
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 9
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 9
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims description 8
- 235000019341 magnesium sulphate Nutrition 0.000 claims description 8
- 229940051841 polyoxyethylene ether Drugs 0.000 claims description 8
- 229920000056 polyoxyethylene ether Polymers 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 8
- FRPJTGXMTIIFIT-UHFFFAOYSA-N tetraacetylethylenediamine Chemical group CC(=O)C(N)(C(C)=O)C(N)(C(C)=O)C(C)=O FRPJTGXMTIIFIT-UHFFFAOYSA-N 0.000 claims description 8
- 150000002191 fatty alcohols Chemical class 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 4
- 239000004094 surface-active agent Substances 0.000 claims description 4
- 239000012190 activator Substances 0.000 claims description 2
- 239000013543 active substance Substances 0.000 claims description 2
- 239000012634 fragment Substances 0.000 claims description 2
- 238000004042 decolorization Methods 0.000 abstract description 7
- 238000011084 recovery Methods 0.000 abstract description 4
- 238000002791 soaking Methods 0.000 abstract description 4
- 239000000203 mixture Substances 0.000 abstract description 3
- 239000007788 liquid Substances 0.000 description 17
- 230000007935 neutral effect Effects 0.000 description 10
- 239000004698 Polyethylene Substances 0.000 description 8
- -1 polyethylene Polymers 0.000 description 8
- 229920000573 polyethylene Polymers 0.000 description 8
- 230000000694 effects Effects 0.000 description 6
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 4
- 230000029087 digestion Effects 0.000 description 4
- 238000010025 steaming Methods 0.000 description 4
- 239000004753 textile Substances 0.000 description 4
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 239000000975 dye Substances 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 238000004043 dyeing Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 206010042674 Swelling Diseases 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000009264 composting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000000986 disperse dye Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000985 reactive dye Substances 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
Images
Classifications
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- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06P—DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM
- D06P5/00—Other features in dyeing or printing textiles, or dyeing leather, furs, or solid macromolecular substances in any form
- D06P5/13—Fugitive dyeing or stripping dyes
- D06P5/135—Fugitive dyeing or stripping dyes with combined acids or bases + oxidants + reductants means
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
- C08J11/16—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with inorganic material
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J11/00—Recovery or working-up of waste materials
- C08J11/04—Recovery or working-up of waste materials of polymers
- C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
- C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
- C08J11/28—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic compounds containing nitrogen, sulfur or phosphorus
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/02—Cellulose; Modified cellulose
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2467/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/64—Paper recycling
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- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Paper (AREA)
Abstract
A method for decoloring black waste cotton blended fabrics and preparing cellulose dissolving pulp comprises the following steps of: drying the cotton blended fabric in an oven to constant weight, immersing the cotton blended fabric in a thiourea dioxide and NaOH mixed solution, and decoloring at 90-100 ℃ for the first time; washing and drying the waste cotton blended fabric after the first step of decolorization; immersing the dried fabric into hydrogen peroxide solution containing a stabilizer for carrying out a second step of decoloring, washing and drying: mixing the fabric decolorized in the second step with cooking liquor, placing the mixture into a cooking pot, and cooking after soaking at 145-155 ℃; pulping and dehydrating the steamed fabric to obtain cellulose dissolving pulp; the cellulose dissolving pulp is soaked into hydrogen peroxide solution containing an activating agent for bleaching. The decoloring rate of the two-step method can reach about 90%, the whiteness of the finally obtained cellulose dissolving pulp can reach more than 70%, and the method realizes the full recovery of waste cotton blended fabrics, is environment-friendly and can be utilized in a high value.
Description
Technical Field
The invention relates to the technical field of waste fabric recovery, in particular to a method for decoloring black waste cotton blended fabric and preparing cellulose dissolving pulp.
Background
With the continuous growth of global population and the rapid development of economy, the demands of people on textile products are gradually increased, and a series of problems such as shortened service cycle, difficult cleaning and recycling, low added value and the like are caused. Waste textiles in China are mostly used as industrial application or filling materials, such as wall heat insulation materials, air conditioner shells and the like, but cannot be reused, the waste textiles are treated by simple means of composting, burning, crushing and the like, and meanwhile, dyes and other impurities on the surfaces of the textiles can generate methane, hydrogen sulfide and other room gases in the degradation process, so that the environment is greatly polluted.
Polyester fiber and cotton fiber in the polyester-cotton blended fabric are dyed by a two-bath method generally due to different physical and chemical properties, namely, the polyester fiber is dyed in a disperse dye acid bath, and the cotton fiber is dyed in a reactive dye alkaline bath. It has also appeared that the dyeing bath is maintained in neutral condition by the same bath dyeing of polyester and cotton in neutral bath, so that the polyester-cotton blended fabric requires a complex method to achieve true decolorization. Patent CN103603194B discloses a stripping method for polyester-cotton blended fabrics, namely, firstly, swelling treatment is carried out by using N, N-dimethylformamide at high temperature, then dispersing treatment is carried out in dimethyl sulfoxide, and finally reduction is carried out in aqueous solution of sodium hydroxide and thiourea dioxide.
At present, the main methods for separating and recycling the waste cotton blended fabrics in China are as follows: firstly, the cotton fiber is dissolved by the corresponding solvent, so as to separate the polyester cotton. Chinese patent CN201510458505.7 discloses a method for preparing terephthalic acid by using waste polyester cotton, in which the cotton component is carbonized at high temperature, and the method aims at preparing terephthalic acid without high-efficiency recovery of cotton fiber and harsh conditions; and secondly, dissolving polyester by using a corresponding solvent so as to separate polyester cotton. Patent CN112608513B discloses a method for preparing cellulose dissolving pulp from waste cotton-polyester blend, which adopts the procedures of enzyme treatment, digestion pulping, metal ion removal, bleaching and the like to prepare cellulose dissolving pulp and regenerated polyester, but does not study on black waste cotton blend fabrics and other fabrics with complex dye components.
Therefore, a method for decoloring black waste cotton blended fabrics and preparing cellulose dissolving pulp is necessary to be researched, and the waste cotton blended fabrics can be efficiently recovered and utilized in a high value.
Disclosure of Invention
Based on the method, the invention provides a method for decoloring black waste cotton blended fabrics and preparing cellulose dissolving pulp so as to realize recovery of the waste cotton blended fabrics.
In order to achieve the above purpose, the invention provides a method for decoloring black waste cotton blended fabric and preparing cellulose dissolving pulp, which comprises the following steps:
(1) Preparing a mixed solution A of thiourea dioxide and sodium hydroxide, drying the waste cotton blended fabric to be treated to constant weight, putting the waste cotton blended fabric into the mixed solution according to the mass ratio of the waste cotton blended fabric to the mixed solution A of 1:15-1:30, performing first-step decoloring treatment at 90-100 ℃, and then cleaning and drying;
(2) Putting the fabric treated in the step (1) into hydrogen peroxide solution containing a stabilizer and a surfactant, performing a second-step decoloring treatment at 90-100 ℃, and then cleaning and drying, wherein the stabilizer and the surfactant comprise: sodium silicate, magnesium sulfate and fatty alcohol-polyoxyethylene ether;
(3) Immersing the fabric treated in the step (2) into cooking liquor, immersing for 0.5-1h, and cooking, wherein the mass ratio (solid-liquid ratio) of the fabric to the cooking liquor is 1:6, the cooking liquor is sodium hydroxide solution, and the alkali consumption of the cooking liquor is less than 100%;
(4) Pulping and dewatering the fabric treated in the step (3) to obtain cellulose dissolving pulp; the cellulose dissolving pulp is immersed in hydrogen peroxide solution containing active agent, and bleaching treatment is carried out at 70-90 ℃.
As a further preferable technical scheme of the invention, the polyester content of the waste cotton blended fabric to be treated is 10 percent by weight.
As a further preferable technical scheme of the invention, the step (1) further comprises the following steps:
the waste cotton blended fabric to be treated is cut or polished into fragments. The waste cotton blended fabric can be cut into pieces of 3cm multiplied by 3cm, or the waste cotton blended fabric is ground into irregular chip shapes by a disc grinder; the aim of shearing the waste cotton blended fabric is to enable the subsequent treatment fluid to fully contact the fabric, if the waste cotton blended fabric is not treated, the length of the polyester cotton fabric is too long (about half a meter), the waste cotton blended fabric can be wound into a group, and in the subsequent treatment process, the surface of the polyester cotton part cannot fully contact the treatment fluid, so that the treatment time is increased, and the decoloring effect is reduced.
As a further preferable technical scheme of the invention, in the step (1), the concentration of thiourea dioxide in the mixed solution A is 10-20g/L, the concentration of sodium hydroxide is 5-10g/L, and the first-step decoloring treatment time is 90min. So that the decolorization process keeps the solution alkaline, and the decolorizer fully reduces the dye, thereby achieving the purpose of decolorization. Specifically, the dosage of thiourea dioxide is too low, the decoloring effect is poor, the dosage of thiourea dioxide is too high, the decoloring effect is slowly increased when reaching a certain value, and the cost is too high.
As a further preferable technical scheme of the invention, the mass ratio of the waste cotton blended fabric to the mixed liquor A in the first step of decoloring treatment is 1:15-1:30, preferably 1:20-1:30, wherein the dosage of the decoloring agent is far greater than the weight of the waste polyester cotton blended fabric so as to ensure that the decoloring effect reaches the expected value.
As a further preferable technical scheme of the invention, in the second step of decoloring treatment, the concentration of hydrogen peroxide is 3-5% and the decoloring time is 90-120min according to the weight percentage of the waste cotton blended fabric. Preferably, the hydrogen peroxide concentration is 5% and the decolorization time is 90min. The pH of the hydrogen peroxide solution is 9-11, and the hydrogen peroxide solution is slightly alkaline, so that the effect of the oxidant is fully exerted.
As a further preferable technical scheme of the invention, in the step (2), the concentration of sodium silicate is 5-10g/L, the concentration of magnesium sulfate is 0.1-0.25g/L, and the concentration of fatty alcohol polyoxyethylene ether is 1-1.5g/L. Preferably, the concentration of sodium silicate is 10g/L, the concentration of magnesium sulfate is 0.2-0.25g/L, and the concentration of fatty alcohol-polyoxyethylene ether is 1.5g/L. Wherein the addition of sodium silicate slows down the decomposition of hydrogen peroxide.
As a further preferred technical scheme of the invention, the cooking process parameters of the step (3) are as follows: the cooking temperature is 145-155 ℃, the concentration of sodium hydroxide is 35-45g/L, and the cooking time is 90-150min. Preferably, the concentration of sodium hydroxide is 40-45g/L, and the cooking time is 120-150min.
As a further preferable embodiment of the present invention, in the step (4), the pulping and dewatering process is as follows: washing the steamed fabric with deionized water, pulping in a pulping machine for 1-30min, dehydrating after pulping, and drying.
As a further preferable embodiment of the present invention, in the step (4), the bleaching step is: immersing the pulped cotton pulp into hydrogen peroxide solution containing an activating agent for 60-120min at 70-90 ℃.
As a further preferred embodiment of the present invention, the activator is tetraacetylethylene diamine (TAED) at a concentration of 10-20g/L. Preferably 15-20g/L
The method for decoloring the black waste cotton blended fabric and preparing the cellulose dissolving pulp uses the black waste cotton blended fabric as a raw material, the black waste cotton blended fabric is firstly decolored, the decoloring rate reaches about 90%, and then the cellulose dissolving pulp is prepared, so that the whiteness of the dissolving pulp is improved, and cotton fibers in the waste cotton blended fabric are recycled.
Compared with the prior art, the method has the advantages of simple decoloring step, mild condition, low cost, good decoloring effect and environmental friendliness on the black waste cotton blended fabric, and the whiteness of the finally obtained cellulose dissolving pulp can reach about 70.
In the process of preparing cellulose dissolving pulp by using waste cotton blended fabrics, the digestion liquid is sodium hydroxide solution, polyester is hydrolyzed in alkali liquor, and the complete hydrolysis of the polyester in the alkali liquor can be completed in one step by adjusting the digestion process.
Drawings
The invention will be described in further detail with reference to the drawings and the detailed description.
FIG. 1 is a flow chart of the preparation of cellulose dissolving pulp in example 1.
FIG. 2 is a two-step decolorization flow chart of example 1.
FIG. 3 is an infrared spectrum of the fiber before and after high temperature steaming in example 1.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
Unless defined otherwise, technical terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which the inventive concepts pertain. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
Example 1
The method for decoloring the black waste cotton blended fabric and preparing the cellulose dissolving pulp comprises the following steps of: two-step decoloring pretreatment, pre-soaking, steaming, pulping and bleaching, as shown in figure 1, the specific steps are as follows:
(1) Cutting the waste cotton blended fabric (polyester/cotton ratio is 10/90, weight ratio) into pieces of 3cm x 3 cm.
(2) The two-step decoloring pretreatment process is as follows (see FIG. 2):
preparing 150g of mixed solution of thiourea dioxide and sodium hydroxide according to a solid-to-liquid ratio of 1:15, wherein the dosage of thiourea dioxide is 10g/L, the dosage of sodium hydroxide is 5g/L, putting 10g of sheared waste cotton blended fabric into a baking oven, drying to constant weight, putting into the prepared mixed solution, and carrying out first-step decoloring treatment at 90 ℃ for 90min; then carrying out first cleaning treatment and drying on the waste cotton blended fabric subjected to the first-step decoloring treatment;
putting the waste cotton blended fabric subjected to the first cleaning treatment and drying into a hydrogen peroxide solution containing a stabilizer, and carrying out a second-step decoloring treatment at 99 ℃; carrying out second cleaning treatment on the waste cotton blended fabric subjected to the second-step decoloring treatment and drying; wherein the concentration of hydrogen peroxide is 3 percent (accounting for the proportion of the waste cotton blended fabric), the solid-liquid ratio is 5 percent, the dosage of sodium silicate is 10g/L, the dosage of magnesium sulfate is 0.25g/L, and the dosage of fatty alcohol polyoxyethylene ether is 1.5g/L.
And (3) using a color measuring and matching instrument to characterize the decoloring rate of the waste cotton blended fabric decolored by the two-step method, wherein the decoloring rate is 88.5%.
As a comparison experiment, in the two-step decoloring pretreatment step, only the first decoloring is carried out on the black waste cotton blended fabric, and the decoloring rate is only 36%. Thus, a two-step decolorization pretreatment is necessary.
(3) The pre-dipping and stewing steps are as follows:
immersing the waste cotton blended fabric subjected to the decoloring treatment by a two-step method into a cooking liquid according to a solid-to-liquid ratio of 1:6, wherein the sodium hydroxide content in the cooking liquid is 40g/L, and then cooking the waste cotton blended fabric for 1h at a cooking temperature of 150 ℃ for 120min; washing the steamed fabric with deionized water until the pH value is neutral;
as shown in FIG. 3, 1715cm can be seen from the infrared spectra before and after cooking -1 The characteristic peak of the polyester is disappeared after the boiling, and the polyester on the surface is completely removed.
(4) Pulping:
and (3) repeatedly washing and drying the washed neutral fabric with deionized water to pulp and dewater to obtain cellulose dissolving pulp, wherein the pulping time is 13min.
(5) Bleaching:
drying the pulped cellulose dissolving pulp to constant weight for bleaching treatment: immersing cellulose dissolving pulp into hydrogen peroxide solution containing TAED (total active ingredients) in an amount of 20g/L, bleaching the pulp at 90 ℃ for 90min at a hydrogen peroxide concentration of 5% (which is a proportion of waste cotton blended fabrics), opening the polyethylene bag every 20min, stirring, transferring cotton pulp in the polyethylene bag into a 100-mesh pulp bag, and washing the cotton pulp with deionized water to neutrality;
whiteness test was performed on the bleached cellulose dissolved pulp to determine the diffuse reflectance (%) of pulp to blue light of dominant wavelength 457nm as whiteness value. The bleached cellulose dissolving pulp was characterized by whiteness of 69 by a whiteness meter.
Example 2
The method for decoloring the black waste cotton blended fabric and preparing the cellulose dissolving pulp comprises the following steps of: two-step decoloring pretreatment, pre-soaking, steaming, pulping and bleaching. The method comprises the following specific steps:
(1) Cutting the waste cotton blended fabric (polyester/cotton ratio is 10/90, weight ratio) into pieces of 3cm x 3 cm.
(2) The two-step decoloring pretreatment process comprises the following steps:
preparing 150g of mixed solution of thiourea dioxide and sodium hydroxide according to a solid-to-liquid ratio of 1:20, wherein the dosage of thiourea dioxide is 20g/L, the dosage of sodium hydroxide is 10g/L, putting 10g of chopped cotton blended fabric into a baking oven, drying to constant weight, putting into the prepared mixed solution, and carrying out first-step decoloring treatment at 99 ℃ for 90min; then carrying out first cleaning treatment and drying on the waste cotton blended fabric subjected to the first-step decoloring treatment;
putting the waste cotton blended fabric subjected to the first cleaning treatment and drying into a hydrogen peroxide solution containing a stabilizer, wherein the concentration of hydrogen peroxide is 5% (accounting for the proportion of the waste cotton blended fabric), the solid-liquid ratio is 5wt%, the sodium silicate dosage is 8g/L, the magnesium sulfate dosage is 0.2g/L, the fatty alcohol polyoxyethylene ether dosage is 1.5g/L, and carrying out a second step of decoloring treatment at 90 ℃; carrying out second cleaning treatment on the waste cotton blended fabric subjected to the second-step decoloring treatment and drying;
and (3) characterizing the decoloring rate of the waste cotton blended fabric decolored by a two-step method by using a spectrophotometer, wherein the decoloring rate is 89.19%.
(3) The pre-dipping and stewing steps are as follows:
immersing the waste cotton blended fabric subjected to the decoloring treatment by a two-step method into cooking liquid according to a solid-to-liquid ratio of 1:6, wherein the sodium hydroxide content in the cooking liquid is 35g/L, and then cooking the waste cotton blended fabric for 1h at a cooking temperature of 150 ℃ for 120min; and washing the steamed fabric with deionized water until the pH value is neutral.
(4) Pulping:
pulping and dewatering the washed neutral fabric, and repeatedly washing and drying with deionized water to obtain cellulose dissolving pulp, wherein the pulping time is 13min.
(5) Bleaching:
drying the pulped cellulose dissolving pulp to constant weight for bleaching treatment: immersing the dissolving pulp into hydrogen peroxide solution containing TAED, placing the solution into a polyethylene bag, bleaching the solution at 90 ℃ for 90 minutes with the TAED dosage of 20g/L and the hydrogen peroxide concentration of 5% (accounting for the proportion of waste cotton blended fabrics), opening the polyethylene bag every 20 minutes, stirring, transferring cotton pulp in the polyethylene bag into a 100-mesh pulp bag, and washing the cotton pulp with deionized water to be neutral.
The bleached cellulose dissolving pulp is subjected to whiteness characterization by adopting a whiteness instrument, and the whiteness is 72.
Example 3
The method for decoloring the black waste cotton blended fabric and preparing the cellulose dissolving pulp comprises the following steps of: two-step decoloring pretreatment, pre-soaking, steaming, pulping and bleaching. The method comprises the following specific steps:
(1) Cutting the waste cotton blended fabric (polyester/cotton ratio is 10/90, weight ratio) into pieces of 3cm x 3 cm.
(2) The two-step decoloring pretreatment process comprises the following steps:
preparing 150g of mixed solution of thiourea dioxide and sodium hydroxide according to a solid-to-liquid ratio of 1:30, wherein the dosage of thiourea dioxide is 20g/L, the dosage of sodium hydroxide is 10g/L, putting 10g of chopped cotton blended fabric into a baking oven, drying to constant weight, putting into the prepared mixed solution, and carrying out first-step decoloring treatment at 99 ℃ for 90min; then carrying out first cleaning treatment and drying on the waste cotton blended fabric subjected to the first-step decoloring treatment;
putting the waste cotton blended fabric subjected to the first cleaning treatment and drying into a hydrogen peroxide solution containing a stabilizer, wherein the concentration of hydrogen peroxide is 5% (accounting for the proportion of the waste cotton blended fabric), the solid-liquid ratio is 5wt%, the sodium silicate dosage is 10g/L, the magnesium sulfate dosage is 0.2g/L, the fatty alcohol polyoxyethylene ether dosage is 1.5g/L, and carrying out a second step of decoloring treatment at 99 ℃; carrying out second cleaning treatment on the waste cotton blended fabric subjected to the second-step decoloring treatment and drying;
and (3) characterizing the decoloring rate of the waste cotton blended fabric decolored by a two-step method by using a spectrophotometer, wherein the decoloring rate is 90.3%.
(3) The pre-dipping and stewing steps are as follows:
immersing the waste cotton blended fabric subjected to the decoloring treatment by a two-step method into cooking liquid according to a solid-to-liquid ratio of 1:6, wherein the sodium hydroxide content in the cooking liquid is 40g/L, and then cooking the waste cotton blended fabric for 1h at a cooking temperature of 155 ℃ for 120min; and washing the steamed fabric with deionized water until the pH value is neutral.
(4) Pulping:
pulping and dewatering the washed neutral fabric, and repeatedly washing and drying with deionized water to obtain cellulose dissolving pulp, wherein the pulping time is 13min.
(5) Bleaching:
drying the pulped cellulose dissolving pulp to constant weight for bleaching treatment: immersing the dissolving pulp into hydrogen peroxide solution containing TAED, placing the solution into a polyethylene bag, bleaching the solution at 90 ℃ for 90 minutes with the TAED with the hydrogen peroxide concentration of 5% (accounting for the proportion of waste cotton blended fabrics), opening the polyethylene bag every 20 minutes, stirring, transferring cotton pulp in the polyethylene bag into a 100-mesh pulp bag, and washing the cotton pulp with deionized water to be neutral;
the bleached cellulose dissolving pulp is subjected to whiteness characterization by a whiteness instrument, and the whiteness is 76.
In conclusion, the decoloring method of the waste polyester-cotton blended fabric has the advantages of simple process, low cost and no environmental pollution, and the decoloring rate of the black polyester-cotton blended fabric reaches about 90% under different processes, so that the method is an ideal composite decoloring method of the polyester-cotton blended fabric; the digestion pulping method is adopted to separate polyester cotton fabrics to recycle cotton fibers, and the whiteness of the obtained cellulose dissolving pulp reaches about 70.
While particular embodiments of the present invention have been described above, it will be appreciated by those skilled in the art that these are merely illustrative, and that many variations or modifications may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined only by the appended claims.
Claims (10)
1. The method for decoloring the black waste cotton blended fabric and preparing the cellulose dissolving pulp is characterized by comprising the following steps of:
(1) Preparing a mixed solution A of thiourea dioxide and sodium hydroxide, drying the waste cotton blended fabric to be treated to constant weight, putting the waste cotton blended fabric into the mixed solution according to the mass ratio of the waste cotton blended fabric to the mixed solution A of 1:15-1:30, performing first-step decoloring treatment at 90-100 ℃, and then cleaning and drying;
(2) Putting the fabric treated in the step (1) into hydrogen peroxide solution containing a stabilizer and a surfactant, performing a second-step decoloring treatment at 90-100 ℃, and then cleaning and drying, wherein the stabilizer and the surfactant comprise: sodium silicate, magnesium sulfate and fatty alcohol-polyoxyethylene ether;
(3) Immersing the fabric treated in the step (2) into cooking liquor, immersing for 0.5-1h, and cooking, wherein the mass ratio of the fabric to the cooking liquor is 1:6-1:8, the cooking liquor is sodium hydroxide solution, and the alkali consumption of the cooking liquor is less than 100%;
(4) Pulping and dewatering the fabric treated in the step (3) to obtain cellulose dissolving pulp; the cellulose dissolving pulp is immersed in hydrogen peroxide solution containing active agent, and bleaching treatment is carried out at 70-90 ℃.
2. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein the content of polyester in the waste cotton blended fabric to be treated is 10% by weight.
3. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein the step (1) is preceded by the steps of:
the waste cotton blended fabric to be treated is cut or polished into fragments.
4. The method for decoloring and preparing cellulose dissolving pulp for black waste cotton blended fabrics according to claim 1, wherein in the step (1), the concentration of thiourea dioxide in the mixed solution A is 10-20g/L, the concentration of sodium hydroxide is 5-10g/L, and the first decoloring treatment time is 90min.
5. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein in the step (2), the concentration of hydrogen peroxide is 3-5% calculated by the weight percentage of hydrogen peroxide in the fabric.
6. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein in the step (2), the concentration of sodium silicate is 5-10g/L, the concentration of magnesium sulfate is 0.1-0.25g/L, and the concentration of fatty alcohol polyoxyethylene ether is 1-1.5g/L.
7. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein the cooking process parameters of the step (3) are as follows: the cooking temperature is 145-155 ℃, the concentration of sodium hydroxide is 35-45g/L, and the cooking time is 90-150min.
8. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein in the step (4), the pulping and dewatering process is as follows: washing the steamed fabric with deionized water, pulping in a pulping machine for 1-30min, dehydrating after pulping, and drying.
9. The method for decoloring and preparing cellulose dissolving pulp for a black waste cotton blended fabric according to claim 1, wherein in the step (4), the bleaching process is as follows: immersing the pulped cotton pulp into hydrogen peroxide solution containing an activating agent for 60-120min at 70-90 ℃.
10. The method for decoloring and preparing cellulose dissolving pulp according to any one of claims 1 to 9, wherein the activator is tetraacetylethylene diamine with a concentration of 10-20g/L.
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