Thermo-sensitive-PH dual-response environment-friendly color fixing agent for hemp as well as preparation method and application of color fixing agent

Abstract

The invention relates to a temperature-sensitive-pH dual-response environment-friendly color fixing agent for hemp as well as a preparation method and application of the color fixing agent. The color fixing agent is prepared from the following raw materials: chitosan, N-isopropylacrylamide, a sodium hydroxide solution, ammonium persulfate, 2, 3-epoxypropyltrimethylammonium chloride, sodium chloroacetate, a dispersing agent and pure water. Chitosan is used as a base material, carboxymethyl, N-isopropylacrylamide chain segments and cationic quaternary ammonium salt groups are sequentially introduced through graft polymerization and chemical modification, a dispersing agent is compounded, and the color fixing agent is prepared and has the temperature and pH dual response characteristics, specifically, when the temperature is higher than the low critical solution temperature, the temperature-sensitive chain segments shrink, and dye is physically coated; under the acidic condition, the cationic group and the anionic dye generate electrostatic adsorption, the two mechanisms have a synergistic effect, the color fixing agent is applied to bast fiber to remarkably improve the color fixing effect, the raw materials of the color fixing agent are environment-friendly, and the preparation process is simple.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of chemical auxiliaries, and particularly relates to a warm-sensitive and pH double-response environment-friendly fixing agent for hemp and a preparation method and application thereof. BACKGROUND

[0002] Hemp fibers are known as the "queen of natural fibers", and their natural antibacterial, green and sustainable, and multi-purpose functions are increasingly favored by people and are widely used in textile, papermaking, home decoration and other fields, and are in short supply. However, the poor color fastness of hemp fibers in the dyeing process is a difficult problem in the printing and dyeing industry, mainly reflected in poor washing fastness and substandard wet rubbing fastness.

[0003] The reasons for the poor color fastness of hemp fibers are mainly related to the following factors: (1) fiber characteristics limit, flax belongs to cellulose fiber, but the crystallinity is higher than that of cotton, and the surface structure is relatively rough, which makes it difficult for active dye molecules to penetrate and react, and the adhesion of the dye on the fiber is naturally weak. Even if the dye concentration is sufficient during dyeing, the problem of color bleeding or insufficient color fastness may occur, and the fixing rate is relatively low. At the same time, the surface of hemp fibers is smooth, and even after pretreatment, it still contains pectin and lignin, which hinders the effective contact between the fixing agent and the fiber; at the same time, the wet rubbing fastness is challenging, and the un-fixed hydrolyzed dye is easily migrated from the inside of the fiber to the surface in the wet state. (2) improper dyeing process, combined with the actual market situation, active dyes are generally used for hemp fiber dyeing, but if the dye has insufficient affinity with the fiber, the fixing agent is insufficient, or the dyeing temperature / time is insufficient, it will lead to substandard color fastness; if the temperature rising curve is too fast, the bath ratio is unreasonable, or the fixing stage temperature / time is insufficient during dyeing, it will lead to insufficient fixing of the dye, and harsh strong acid and strong alkali environment is more likely to damage the strength of flax fibers.

[0004] In order to solve the problem of poor color fastness of hemp fibers, the industry has long relied on post-fixing treatment. Traditional fixing agents are mainly divided into two categories: cationic resin type fixing agents (such as polyamine, quaternary ammonium salt polymer) and reaction crosslinking type fixing agents (such as formaldehyde condensate, multi-functional epoxy crosslinking agent). The former "locks" the dye through the electrostatic combination of cation and anion dye; the latter forms a covalent crosslinked structure between the dye, the fiber and the fixing agent. Although these traditional methods improve the fastness to a certain extent, they have problems such as environmental unfriendliness (containing formaldehyde, heavy metals), hard hand feeling, and color change. SUMMARY

[0005] The purpose of the present application is to provide a warm-sensitive and pH double-response environment-friendly fixing agent for hemp, which has both warm-sensitive and pH double-response mechanisms, good fixing effect and environmental friendliness.

[0006] The technical solution adopted by this invention to solve the above problems is: a temperature-sensitive and pH-responsive environmentally friendly color-fixing agent for anesthesia, comprising the following raw materials in parts by weight: 8-10 parts chitosan N-Isopropylacrylamide (NIPAM) 6-10 parts 5-8 parts of sodium hydroxide solution Ammonium persulfate (APS) 0.1-0.3 parts 3-5 parts of 2,3-epoxypropyltrimethylammonium chloride (GTA) Sodium chloroacetate (NaCH2COOCl) 1-3 parts 3-5 parts dispersant Pure water 58.7-73.9 parts Preferably, the degree of deacetylation of the chitosan is ≥80%, and the molecular weight is between 30kDa and 200kDa.

[0007] Preferably, the sodium hydroxide solution is a 30% sodium hydroxide aqueous solution by mass.

[0008] Preferably, the dispersant is a tallow-based surfactant.

[0009] Another object of the present invention is to provide a method for preparing a thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp, comprising the following steps: (1) Add chitosan to 1% dilute acetic acid solution and stir until a transparent viscous liquid is obtained. Adjust the pH to 10-11 using sodium hydroxide solution. (2) Add sodium chloroacetate slowly to the solution obtained in step (1), heat to 50-70℃ and stir to react. After the reaction, adjust the pH to 6-7 to obtain carboxymethyl chitosan CMCS solution. (3) Add N-isopropylacrylamide and ammonium persulfate initiator to the carboxymethyl chitosan CMCS solution obtained in step (2), purge with nitrogen, heat to 70°C, stir to react, and obtain the graft copolymer CMCS-g-PNIPAM solution. (4) Cool the system of step (3) to 60°C, slowly add 2,3-epoxypropyltrimethylammonium chloride, stir the reaction in the dark, and after the reaction is completed, cool, dialyze and purify, and freeze dry to obtain solid powder; (5) Dissolve the solid powder obtained in step (4) in water, add a dispersant, and ultrasonically disperse to obtain a temperature-sensitive-pH dual-response environmentally friendly color-fixing agent.

[0010] Preferably, the mass ratio of chitosan to 1% dilute acetic acid solution is 1:15-30.

[0011] Preferably, the stirring reaction time in step (2) is 2-3 hours, the stirring reaction time in step (3) is 4-5 hours, and the stirring reaction time in step (4) is 5-6 hours.

[0012] Preferably, the ultrasonic dispersion time in step (5) is 30-40 min.

[0013] Preferably, the dropping rate of sodium chloroacetate in step (2) is controlled at 5%-10% of its total mass per minute.

[0014] Preferably, the dropping rate of 2,3-epoxypropyltrimethylammonium chloride in step (4) is controlled at 3%-8% of its total mass per minute.

[0015] Another objective of this invention is to provide an environmentally friendly color-fixing agent for hemp that is both temperature-sensitive and pH-responsive, used in the color-fixing process of flax dyeing.

[0016] The structure and mechanism of action of the color-fixing agent of this invention: The thermo-pH dual-responsive environmentally friendly color-fixing agent of the present invention is a chitosan-based amphiphilic block copolymer that has undergone multiple chemical modifications. Its schematic structure and the functions of each part are as follows:

[0017] (1) Main chain: Using natural high-molecular-weight chitosan as the backbone, carboxymethyl groups (-CH2COOH) are introduced through sodium chloroacetate modification to form carboxymethyl chitosan, which improves the water solubility of chitosan, enabling it to be used in a wider pH range. At the same time, the carboxyl group itself can also serve as an active site for subsequent reactions to enhance the affinity of anionic dyes.

[0018] (2) Temperature-sensitive response unit: Poly(N-isopropylacrylamide) segments are chemically bonded to the CMCS backbone through graft copolymerization, forming a CMCS-g-PNIPAM structure. The PNIPAM segments, acting as temperature-sensitive responsive units, determine the temperature response behavior of the entire molecule: when the processing temperature exceeds its lower critical solution temperature (LCST, approximately 32°C), the PNIPAM segments transition from a hydrophilic extended state to a hydrophobic contractile state, undergoing phase separation and aggregation. This results in a strong physical coating and "capture" effect on dye molecules on the fiber surface, significantly improving colorfastness, especially wet fastness.

[0019] (3) pH response and permanent cation fixation unit: A quaternary ammonium salt cationic group is introduced by ring-opening reaction of the remaining hydroxyl or amino groups on the polymer chain with 2,3-epoxypropyltrimethylammonium chloride. This group not only has pH-responsive properties, but the quaternary ammonium salt also has a permanently positive charge (N). +(CH3)3), unaffected by solution pH, can generate strong electrostatic adsorption with anionic dyes over a wide range from acidic to alkaline, which is the most direct and efficient chemical fixing power; it also enhances solubility and dispersibility: the strongly hydrophilic quaternary ammonium salt groups further improve the solubility and stability of the entire polymer in water, especially when it forms an amphiphilic structure with the hydrophobic PNIPAM segments, which helps it to form uniformly dispersed micelles or aggregates in water, which is a prerequisite for its application as a highly efficient fixing agent.

[0020] Compared with the prior art, the advantages of the present invention are as follows: (1) The color-fixing agent of the present invention uses chitosan as the base material. Through graft polymerization and chemical modification, carboxymethyl, N-isopropylacrylamide segments and cationic quaternary ammonium salt groups are introduced in sequence, and finally compounded with a dispersant. The color-fixing agent of the present invention integrates the dual intelligent response mechanism of "temperature-sensitive physical encapsulation" and "pH / electrostatic chemical adsorption". Under conditions higher than the low critical dissolution temperature (LCST, 32°C) of PNIPAM segments, the hydrophobic shrinkage PNIPAM segments can form a dense physical coating on the dye. At the same time, the permanent quaternary ammonium salt cations carried on the polymer backbone can generate strong electrostatic binding with anionic dyes in a wide pH range from acidic to weakly alkaline. The synergistic effect of physical and chemical color-fixing forces makes the treated linen fabric exhibit high color fastness, especially wet rubbing fastness and soaping fastness.

[0021] (2) The temperature-sensitive and pH-responsive environmentally friendly color-fixing agent for hemp in this invention is based on natural and renewable chitosan as raw material. The entire synthesis process does not involve toxic and harmful substances such as formaldehyde, phenol, and heavy metals.

[0022] (3) The present invention achieves color fixation through physical coating of intelligent polymer chains and molecular-level electrostatic effect, which hardly affects the original hand feel of the fabric. The treated linen fabric can still maintain its inherent softness, breathability and drape, and the color change is minimal, which can truly restore the dyed color. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments. Example 1

[0024] A thermosensitive and pH-responsive environmentally friendly color-fixing agent for hemp, comprising the following raw materials in parts by weight: 10 parts chitosan 6 parts of N-isopropylacrylamide 6.8 parts of sodium hydroxide solution 0.1 parts ammonium persulfate 4.5 parts of 2,3-epoxypropyltrimethylammonium chloride Sodium chloroacetate 1.5 parts 5 parts dispersant 66.1 parts pure water Among them, chitosan has a degree of deacetylation ≥80% and a molecular weight of 100 kDa.

[0025] The dispersant is VABAASE. TM HTFE, dispersant VABASE TM HTFE is a tallow-based surfactant provided by Shanghai Zimei Chemical Institute. It is a highly efficient modified cationic surfactant, which is different from conventional anionic nonionic dispersants such as Pingpingjia. It not only has excellent dispersion effect and can stabilize the color-fixing agent system, but also effectively disperses and suspends floating color under high temperature conditions, preventing floating color from re-adhering to the fabric, and forms a protective film on the surface of the cleaned object, further improving the color-fixing effect.

[0026] A method for preparing a thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp includes the following steps: (1) Add chitosan to a 1% dilute acetic acid aqueous solution and stir until a transparent viscous liquid is obtained. Adjust the pH to 10 using a 30% sodium hydroxide aqueous solution. The mass ratio of chitosan to 1% dilute acetic acid aqueous solution is 1:20.

[0027] (2) Add sodium chloroacetate slowly (the dropping rate is controlled at 7% of its total mass per minute), heat to 60°C, stir for 3 hours, adjust the pH to 6 with dilute hydrochloric acid to obtain carboxymethyl chitosan solution.

[0028] (3) Add N-isopropylacrylamide, purge with nitrogen, heat to 70°C, stir for 4 hours to obtain the graft copolymer CMCS-g-PNIPAM solution.

[0029] (4) Cool down to 60°C, slowly add 2,3-epoxypropyltrimethylammonium chloride (the dropping rate is controlled at 4% of its total mass per minute), stir in the dark for 6 hours, cool and put into a dialysis bag with a molecular weight cutoff of 8000-14000, dialyze with deionized water for 3 days to remove small molecule impurities, and freeze dry to obtain solid powder.

[0030] (5) Dissolve the solid in water and add the dispersant VABAS. TM HTFE was ultrasonically dispersed for 30 minutes to obtain the target fixing agent. Example 2

[0031] A thermosensitive and pH-responsive environmentally friendly color-fixing agent for hemp, comprising the following raw materials in parts by weight: 8 parts chitosan 6 parts of N-isopropylacrylamide 6.1 parts sodium hydroxide solution 0.1 parts ammonium persulfate 3 parts of 2,3-epoxypropyltrimethylammonium chloride Sodium chloroacetate 1.1 parts dispersant VABASE TM 5 servings of HTFE 70.7 parts pure water A method for preparing a thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp includes the following steps: (1) Add chitosan to a 1% dilute acetic acid aqueous solution and stir until a transparent viscous liquid is obtained. Adjust the pH to 10 using a 30% sodium hydroxide aqueous solution. The mass ratio of chitosan to 1% dilute acetic acid aqueous solution is 1:25.

[0032] (2) Add sodium chloroacetate slowly (the dropping rate is controlled at 8% of its total mass per minute), heat to 60°C, stir for 2 hours, adjust the pH to 6 with dilute hydrochloric acid, and obtain carboxymethyl chitosan solution.

[0033] (3) Add N-isopropylacrylamide, purge with nitrogen, heat to 70°C, stir for 5 hours to obtain the graft copolymer CMCS-g-PNIPAM solution.

[0034] (4) Cool down to 60°C, slowly add 2,3-epoxypropyltrimethylammonium chloride (the dropping rate is controlled at 5% of its total mass per minute), stir in the dark for 5 hours, cool and put into a dialysis bag with a molecular weight cutoff of 8000-14000, dialyze with deionized water for 3 days to remove small molecule impurities, and freeze dry to obtain solid powder.

[0035] (5) Dissolve the solid in water and add the dispersant VABAS. TM HTFE was ultrasonically dispersed for 30 minutes to obtain the target fixing agent.

[0036] Comparative Example 1 The only difference from Example 1 is that 2,3-epoxypropyltrimethylammonium chloride is not added.

[0037] Comparative Example 2 Quaternary ammonium chitosan is used directly as a color-fixing agent. Quaternary ammonium chitosan, by weight, includes the following components: 10 parts chitosan, 18 parts glycidyltrimethylammonium chloride, 80 parts 1% dilute acetic acid solution, 50 parts isopropanol, 10 parts 30% sodium hydroxide solution, and 200 parts ethanol-acetone mixture. The preparation method of this fixing agent includes the following steps: (1) Add 10g of chitosan to 80g of 1% dilute acetic acid solution, control the pH to 3.0, stir at room temperature for 3 hours to form a transparent viscous liquid, filter to remove insoluble impurities, and put into a clean reaction vessel.

[0038] (2) Turn on the stirrer, add 10g of 30% sodium hydroxide aqueous solution dropwise while stirring, adjust the pH to 10.0, let stand for half an hour, filter, and put into a clean reaction vessel.

[0039] (3) Heat to 50°C, add 50g isopropanol, stir for 40 minutes, heat to 60°C, add 18g glycidyltrimethylammonium chloride (GTMAC) in three portions, each time adding one-third of the total amount of glycidyltrimethylammonium chloride (GTMAC), stirring while adding, and continue the reaction for 24 hours to obtain a pale yellow transparent liquid.

[0040] (4) Pour the obtained pale yellow transparent liquid into a reaction vessel containing 100g of ethanol-acetone mixture in a mass ratio of 1:1, and turn on the stirrer at the same time. A pale yellow flocculent precipitate will be precipitated. Collect the precipitate by filtration, and dry the precipitate in a vacuum drying oven at 80°C for 48 hours to obtain the crude product. (5) Dissolve the crude product in 20g of water and pour it into a reaction vessel containing 100g of a 1:1 mixture of ethanol and acetone. Let it precipitate again, filter and collect the precipitate, and place the precipitate in a vacuum drying oven at 50°C for 12 hours to obtain refined quaternized chitosan HACC.

[0041] Comparative Example 3 The product uses a common hemp color-fixing agent available on the market, which, by weight, includes the following components: 660 parts of dimethyl diallyl ammonium chloride, 30 parts of diallylamine hydrochloride, 0.5 parts of soda ash, 1.2 parts of ammonium persulfate, 0.8 parts of sodium sulfite, 0.8 parts of hydrochloric acid, and 320 parts of pure water.

[0042] The preparation method of this color-fixing agent for hemp includes the following steps: At room temperature, first add dimethyl diallyl ammonium chloride, diallylamine hydrochloride, 250 parts of pure water and soda ash into a clean reaction vessel and stir for 20 minutes.

[0043] Heat to 60°C, then slowly add 30 parts of a homogeneous mixture of pure water and ammonium persulfate in four separate additions, stirring for 15 minutes after each addition. Continue to slowly add 30 parts of a homogeneous mixture of pure water and sodium sulfite in four separate additions, stirring for 15 minutes after each addition.

[0044] Heat to 70℃, keep warm and stir for 6 hours, then cool to 50℃, add the remaining pure water and hydrochloric acid to adjust the pH to 6 to obtain the finished product.

[0045] The fixing agents in the examples and comparative examples were tested for the following properties: (1) Rubbing fastness test: The test is conducted in accordance with the "Test for color fastness of textiles - color fastness to rubbing" (GB / T 3920-1997) and evaluated according to the "Test for color fastness of textiles - gray scale for staining" (GB / T 251-2008). The higher the grade, the better the rubbing fastness.

[0046] (2) Wash fastness test: The test shall be conducted in accordance with the "Textile Color Fastness Test: Wash Fastness" (GB / T 3921-2008). The higher the grade, the better the wash fastness.

[0047] (3) Using a MACBETH 7000A colorimeter, the larger the ΔE, the greater the color difference from the original fabric.

[0048] (4) The LCST (low critical solution temperature) of the prepared fixing agent was tested by differential scanning calorimetry (DSC) and recorded.

[0049] (5) Test the Zeta potential of the prepared fixing agent (which is the potential difference between the sliding surface of the colloidal particles and the dispersion medium) using electrophoretic light scattering method, and record it.

[0050] The color-fixing agents prepared in the examples and comparative examples were subjected to various fastness tests under the same conditions and with the same solid content. The calculation method for solid content was in accordance with industry standard HG / T*4266-2011. Fastness was tested on bright red pure linen fabric. The color-fixing agent dosage was specified as 1% (owf), the fixing time was 50℃×20min, and the drying temperature was 130℃×2min.

[0051]

[0052] It is evident that the thermo-pH dual-response environmentally friendly color-fixing agent for linen of the present invention exhibits superior overall performance. A comparison of Example 1 and Comparative Example 1 shows that Comparative Example 1, which does not contain 2,3-epoxypropyltrimethylammonium chloride, shows a decrease in both wet and dry rubbing fastness and washing fastness. This is because 2,3-epoxypropyltrimethylammonium chloride retains the high reactivity of epoxy groups and possesses a quaternary ammonium structure, achieving cross-linking and cationization in one step, significantly improving the color-fixing effect of the fabric. Comparative Example 2, which contains quaternized chitosan, has a relatively simple composition, resulting in a decrease in both wet and dry rubbing fastness and washing fastness. Comparative Example 3, a common color-fixing agent on the market, shows a higher color change than Example 1, but slightly lower wet and dry rubbing fastness and washing fastness. Therefore, the present invention achieves color fixation through the physical coating of intelligent polymer chains and molecular-level electrostatic interaction, with minimal color change, truly restoring the dyed color.

[0053] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for anesthesia, characterized in that: The ingredients include the following parts by weight: 8-10 parts chitosan N-Isopropylacrylamide (NIPAM) 6-10 parts 5-8 parts of sodium hydroxide solution Ammonium persulfate (APS) 0.1-0.3 parts 3-5 parts of 2,3-epoxypropyltrimethylammonium chloride (GTA) Sodium chloroacetate (NaCH2COOCl) 1-3 parts 3-5 parts dispersant Pure water 58.7-73.9 parts.

2. The environmentally friendly color-fixing agent for anesthesia with temperature-sensitive and pH-responsive properties according to claim 1, characterized in that: The sodium hydroxide solution is a 30% sodium hydroxide aqueous solution by mass.

3. The environmentally friendly color-fixing agent for anesthesia with temperature-sensitive and pH-responsive properties according to claim 1, characterized in that: The dispersant is a tallow-based surfactant.

4. A method for preparing a thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp according to any one of claims 1-3, characterized in that: Includes the following steps: (1) Add chitosan to 1% dilute acetic acid solution and stir until a transparent viscous liquid is obtained. Adjust the pH to 10-11 using sodium hydroxide solution. (2) Add sodium chloroacetate slowly to the solution obtained in step (1), heat to 50-70℃ and stir to react. After the reaction, adjust the pH to 6-7 to obtain carboxymethyl chitosan CMCS solution. (3) Add N-isopropylacrylamide and ammonium persulfate initiator to the carboxymethyl chitosan CMCS solution obtained in step (2), purge with nitrogen, heat to 70°C, stir to react, and obtain the graft copolymer CMCS-g-PNIPAM solution. (4) Cool the system of step (3) to 60°C, slowly add 2,3-epoxypropyltrimethylammonium chloride, stir the reaction in the dark, and after the reaction is completed, cool, dialyze and purify, and freeze dry to obtain solid powder; (5) Dissolve the solid powder obtained in step (4) in water, add a dispersant, and ultrasonically disperse to obtain a temperature-sensitive-pH dual-response environmentally friendly color-fixing agent.

5. The preparation method of the thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp according to claim 4, characterized in that: The mass ratio of chitosan to 1% dilute acetic acid solution is 1:15-30.

6. The preparation method of the thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp according to claim 4, characterized in that: The stirring reaction time in step (2) is 2-3 hours, the stirring reaction time in step (3) is 4-5 hours, and the stirring reaction time in step (4) is 5-6 hours.

7. The preparation method of the thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp according to claim 4, characterized in that: The ultrasonic dispersion time in step (5) is 30-40 min.

8. The preparation method of the thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp according to claim 4, characterized in that: The dropping rate of sodium chloroacetate in step (2) is controlled at 5%-10% of its total mass per minute.

9. The preparation method of the thermosensitive-pH dual-responsive environmentally friendly color-fixing agent for hemp according to claim 4, characterized in that: The dropping rate of 2,3-epoxypropyltrimethylammonium chloride in step (4) is controlled at 3%-8% of its total mass per minute.

10. The application of a temperature-sensitive and pH-responsive environmentally friendly color-fixing agent for flax according to any one of claims 1-3 in the flax dyeing and color-fixing process.

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