Preparation method of degradable cotton-soft towel and cotton-soft towel

Abstract

This invention discloses a method for preparing a biodegradable cotton towel and the cotton towel itself, specifically relating to the field of fiber composite materials technology. The preparation method includes: melt-condensing trans-aconitic acid and xylitol under a catalyst to obtain a biodegradable polyester prepolymer; pulverizing the prepolymer and dispersing it with sodium bicarbonate particles treated with stearic acid hydrophobicity and a crosslinking agent in a weakly buffered neutral aqueous phase; then, performing reverse-phase suspension crosslinking and curing to form microspheres; finally, loading the microspheres onto a nonwoven fabric substrate and drying and curing to obtain the finished product. This invention improves the degradation rate and absorbency of the cotton towel by decomposing sodium bicarbonate particles to form a porous structure, balancing biodegradability and usability, and solving the problem of difficulty in achieving both and limited functionality in existing technologies. It is suitable for personal care, daily cleaning, and other scenarios.

Description

Technical Field

[0001] This invention relates to the field of fiber composite materials technology, and in particular to a method for preparing a biodegradable cotton towel and the cotton towel itself. Background Technology

[0002] Biodegradable cotton wipes, with their unique natural, environmentally friendly, and biodegradable properties, have demonstrated broad application potential in various fields such as personal care, daily cleaning, and medical care, with market demand showing a continuous growth trend. In the personal care sector, biodegradable cotton wipes are widely used in daily products such as makeup removal, facial cleansing, and facial care. Their soft, skin-friendly, and lint-free properties provide a gentle and safe cleaning option for sensitive skin, infants, and other special groups, effectively avoiding the skin irritation caused by traditional cleaning products. With the increasing public awareness of environmental protection, the application of biodegradable cotton wipes in daily cleaning is becoming increasingly widespread, such as in household cleaning, hand wiping, and pet care. Their biodegradable properties significantly reduce the pollution of the environment caused by discarded cleaning products, creating a greener and more environmentally friendly living environment for consumers. Furthermore, in the medical care sector, biodegradable cotton wipes can be used for wound wiping and instrument cleaning. Their natural, non-irritating, and biodegradable advantages ensure the safety of the care process and reduce the environmental pressure of medical waste. Traditionally, biodegradable cotton wipes are mainly made from natural renewable cellulose as the main raw material, combined with biodegradable polymer materials and natural additives such as chitosan, and are prepared through special processes.

[0003] In existing technologies, the natural fiber raw materials used in the preparation of biodegradable cotton soft towels often suffer from problems such as high density, numerous impurities, and coarse fibers. These require complex pretreatment processes to meet processing requirements, increasing the complexity of the production process. Furthermore, it is difficult to simultaneously achieve biodegradability and performance during the preparation process. Products made from a single natural fiber are prone to brittleness, breakage, and poor water absorption, affecting the user experience. In addition, the pretreatment and molding processes are challenging, and improper control of process parameters can easily affect the product's core properties such as breathability and softness. Moreover, most preparation processes fail to achieve additional functions such as antibacterial and absorbent properties, limiting their application scope due to their limited functionality. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing a biodegradable cotton towel and the cotton towel itself, which can effectively solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a biodegradable cotton towel, comprising the following steps: S1: Trans-aconitic acid and xylitol are melt-polymerized in the presence of a catalyst to obtain a biodegradable polyester prepolymer; after cooling and pulverizing the prepolymer, it is dispersed together with sodium bicarbonate particles and a crosslinking agent in a weakly buffered neutral aqueous phase, and microspheres are formed by reverse-phase suspension crosslinking and solidification. S2: Microspheres are loaded onto a nonwoven fabric substrate, dried, and cured to obtain a biodegradable cotton towel. Preferably, the weakly buffered neutral aqueous phase is a phosphate buffer with a pH of 7.0-7.2 and a buffer concentration of 0.05-0.1 mol / L.

[0006] Preferably, the sodium bicarbonate particles used in step S1 are pre-treated with stearic acid to make them hydrophobic.

[0007] Preferably, the specific method for hydrophobicating stearic acid is as follows: add sodium bicarbonate particles to a stearic acid ethanol solution with a mass fraction of 5%-10%, stir and soak for 30-60 minutes, filter, and dry at 80-90℃ to constant weight.

[0008] Preferably, the catalyst in step S1 is selected from at least one of p-toluenesulfonic acid, methanesulfonic acid, citric acid, and tartaric acid, and the amount of catalyst added is 0.2 to 1.5 wt%; the crosslinking agent used is at least one of ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether, and the amount of crosslinking agent added is 1.5 to 7.0 wt%.

[0009] Preferably, the mass ratio of trans-aconitic acid to xylitol added in step S1 is 1:(1.1~1.3).

[0010] Preferably, the temperature of the melt polycondensation reaction in step S1 is 130–160°C, the pressure is 0.01–0.05 MPa, and the time is 1–3 h.

[0011] Preferably, the microspheres in step S1 are spherical particles with a particle size of 50 to 300 μm.

[0012] Preferably, the nonwoven fabric substrate used in step S2 is one of cotton spunlace nonwoven fabric and bamboo fiber spunlace nonwoven fabric; the drying and curing temperature is 100-130℃ and the time is 1-3 minutes.

[0013] Preferably, in step S1, the oil phase of the reverse suspension crosslinking curing system is either liquid paraffin or vegetable oil, the emulsifier is either Span-80 or Span-85, the reaction temperature is 80–105°C, and the reaction time is 2–4 hours.

[0014] Preferably, the loading in step S2 is achieved by spraying, and the microspheres are fixed with an adhesive, wherein the adhesive is either a modified starch aqueous solution or triethyl citrate. After spraying, the microspheres are dried and cured in stages at temperatures of 80–95°C and 100–120°C, respectively.

[0015] Preferably, the modified starch aqueous solution has a mass fraction of 5%-10%, the modified starch is hydroxypropyl starch, and the purity of triethyl citrate is ≥99%.

[0016] A biodegradable cotton towel prepared by the method described in any one of claims 1-9.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes a melt polycondensation reaction of trans-aconitic acid and xylitol to form a polyester prepolymer, which is then in-situ molded into absorbent microspheres via a reverse-phase suspension crosslinking and curing process. These microspheres are then loaded onto a nonwoven fabric substrate to prepare a biodegradable cotton towel. The absorbent microspheres are based on polyester, forming a stable three-dimensional crosslinked polymer framework through the crosslinking action of a crosslinking agent. A porous, through-structure is constructed within the framework, while sodium bicarbonate particles are uniformly dispersed within the framework after hydrophobic treatment, resulting in a microstructure that combines structural stability and functional activity.

[0018] 2. This invention utilizes the three-dimensional cross-linked network and porous structure of the microspheres to achieve excellent adsorption properties, enabling the adsorption of various impurities and secretions during the cleaning process, thus improving cleaning effectiveness. Simultaneously, the sodium bicarbonate particles dispersed within the microspheres react with the carboxyl groups in the framework during water absorption, releasing gas and enhancing penetration during cleaning. The porous structure of the microspheres also possesses a certain loading capacity, allowing for the loading of functional ingredients such as antibacterial agents, enriching the product's additional functions and making it suitable for a wider range of applications.

[0019] 3. The biodegradable cotton towel prepared by this invention contains absorbent microspheres with a specific structure. The three-dimensional cross-linked polymer backbone of the microspheres is composed of covalent bonds. The polyhydroxy structure of xylitol endows the polymer molecular chains with good flexibility. The porous through-structure inside the three-dimensional cross-linked network, combined with the active groups on the surface of the microspheres, can improve the absorbency of the product and alleviate the defects of poor absorbency in traditional products. The polyester backbone of the microspheres contains a large number of easily hydrolyzed ester bonds. Under the action of moisture and microorganisms in the natural environment, the ester bonds can gradually undergo hydrolysis and breakage to form small molecular fragments. These small molecular fragments can be further decomposed by microorganisms, thereby achieving the biodegradability of the product. To a certain extent, this reduces the pollution of the environment by waste products, achieving a synergistic improvement in biodegradability and performance, and improving the current situation where it is difficult to achieve both in the existing technology. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0021] A method for preparing a biodegradable cotton towel, the specific steps of which are as follows: S1: Weigh 100g of trans-aconitic acid and 110g of xylitol, and add 0.24g of p-toluenesulfonic acid catalyst; add the above materials to a reaction vessel and perform melt polycondensation for 1 hour at a temperature of 130℃ and a pressure of 0.01MPa to obtain a biodegradable polyester prepolymer; cool the prepolymer to room temperature and then pulverize it; take 50g of the pulverized prepolymer and mix it with 5g of sodium bicarbonate particles treated with stearic acid hydrophobicity (hydrophobicity treatment: take 10g of sodium bicarbonate particles and add 200mL of 5% stearic acid solution). Acid ethanol solution, stirred and soaked for 30 min, filtered and dried at 80℃ to constant weight for later use; 0.75 g crosslinking agent ethylene glycol diglycidyl ether, were dispersed together in 1000 mL of pH 7.0, 0.05 mol / L phosphate buffer; in the reverse suspension crosslinking curing system, 2000 mL of liquid paraffin and 10 mL of Span-80 were added, and the mixture was stirred at 80℃ for 2 h to form spherical microspheres with a particle size of 50-100 μm, which were then filtered, dried and used for later use.

[0022] S2: 100g of all-cotton spunlace nonwoven fabric was selected as the substrate. The above-mentioned prepared microspheres were loaded onto the surface of the substrate by spraying. The microspheres were fixed with 50mL of 5% hydroxypropyl starch aqueous solution. After spraying, the microspheres were dried and cured in stages. First, they were dried at 80℃ for 30s, and then cured at 100℃ for 30s. The total drying and curing time was 1min. After cooling to room temperature, the microspheres were cut into finished products with a specification of 15cm×10cm to obtain biodegradable cotton soft towels. Example 2

[0023] A method for preparing a biodegradable cotton towel, the specific steps of which are as follows: S1: Weigh 100g of trans-aconitic acid and 120g of xylitol, and add 1.76g of citric acid catalyst; add the above materials to a reaction vessel and perform melt polycondensation for 2 hours at a temperature of 145℃ and a pressure of 0.03MPa to obtain a biodegradable polyester prepolymer; cool the prepolymer to room temperature and then pulverize it; take 50g of the pulverized prepolymer and mix it with 6g of sodium bicarbonate particles treated with stearic acid hydrophobicity (hydrophobicity treatment: take 10g of sodium bicarbonate particles and add 200mL of 7.5% stearic acid solution). Acid ethanol solution, stirred and soaked for 45 min, filtered and dried at 85℃ to constant weight for later use; 2.1 g of crosslinking agent propylene glycol diglycidyl ether, were dispersed together in 1000 mL of pH 7.1, 0.075 mol / L phosphate buffer; in the reverse suspension crosslinking curing system, 2000 mL of vegetable oil and 12 mL of Lpan-85 were added, and the mixture was stirred at 92℃ for 3 h to form spherical microspheres with a particle size of 150-200 μm, which were then filtered, dried and used for later use.

[0024] S2: 100g of bamboo fiber spunlace nonwoven fabric was selected as the substrate. The above-mentioned microspheres were loaded onto the surface of the substrate by spraying. 30mL of triethyl citrate (adhesive) with a purity of ≥99% was used to fix the microspheres. After spraying, the microspheres were dried and cured in stages. First, they were dried at 88℃ for 1min, and then cured at 110℃ for 1min. The total drying and curing time was 2min. After cooling to room temperature, the microspheres were cut into finished products with a specification of 15cm×10cm to obtain biodegradable cotton towels. Example 3

[0025] A method for preparing a biodegradable cotton towel, the specific steps of which are as follows: S1: Weigh 100g of trans-aconitic acid and 130g of xylitol, and add 3.45g of tartaric acid catalyst; add the above materials to a reaction vessel and perform melt polycondensation for 3 hours at a temperature of 160℃ and a pressure of 0.05MPa to obtain a biodegradable polyester prepolymer; cool the prepolymer to room temperature and then pulverize it; take 50g of the pulverized prepolymer and mix it with 7g of sodium bicarbonate particles treated with stearic acid hydrophobicity (hydrophobicity treatment: take 10g of sodium bicarbonate particles and add 200mL of 10% stearic acid). Ethanol solution, stirred and soaked for 60 min, filtered and dried at 90℃ to constant weight for later use; 3.5 g of crosslinking agent polyethylene glycol diglycidyl ether, were dispersed together in 1000 mL of pH 7.2, 0.1 mol / L phosphate buffer; 2000 mL of liquid paraffin and 15 mL of Span-80 were added to the reverse suspension crosslinking curing system, and the mixture was stirred at 105℃ for 4 h to form spherical microspheres with a particle size of 200-300 μm, which were then filtered, dried and used for later use.

[0026] S2: 100g of all-cotton spunlace nonwoven fabric was selected as the substrate. The above-mentioned prepared microspheres were loaded onto the surface of the substrate by spraying. The microspheres were fixed with 50mL of 10% hydroxypropyl starch aqueous solution. After spraying, the microspheres were dried and cured in stages. First, they were dried at 95℃ for 1.5min, and then cured at 120℃ for 1.5min. The total drying and curing time was 3min. After cooling to room temperature, the microspheres were cut into finished products with a specification of 15cm×10cm to obtain biodegradable cotton soft towels.

[0027] Comparative Example 1 The difference between this comparative example and Example 1 is that the sodium bicarbonate particles in S1 are removed, while the other steps are the same as in Example 1.

[0028] The biodegradable cotton towels prepared in Examples 1-3 and Comparative Example 1 were subjected to the following performance tests: First, take the cotton towels prepared in Example 1, Example 2, Example 3, and Comparative Example 1, cut 10 pieces of each, and each piece is uniformly 15cm×10cm in size. They are numbered as Sample 1-4 respectively. All samples are placed in a dry and clean petri dish and left to stand for 2 hours at room temperature of 25℃±2℃ and relative humidity of 50%±5% for later use.

[0029] 1. Degradability Test: Take four identical petri dishes and add 100g of simulated soil (pre-mixed with humus and river sand in a 3:1 ratio and sterilized) to each dish. Spray deionized water with a dropper while stirring to adjust the soil moisture to 60% (the soil should clump together when squeezed but crumble easily when released). Spread the four pre-treated samples evenly on the soil surface of the corresponding petri dishes, ensuring each sample is flat and without folds or overlaps. Cover each petri dish with a 5cm layer of the simulated soil and gently compact it with sterile forceps. Mark the corresponding sample number on the outer wall of the petri dishes. Place all petri dishes in a constant temperature incubator. The culture chamber was set at a temperature of 25℃ and a humidity of 70% to maintain constant temperature and humidity. On days 7, 14, 21, and 28 of culture, three corresponding samples were removed from each culture dish using sterile forceps. The soil adhering to the sample surface was gently rinsed with deionized water until no obvious soil residue was left. The surface moisture of the sample was gently blotted with absorbent paper, and the damage and decomposition of the sample were observed. The remaining mass of each sample was then weighed using an electronic balance with an accuracy of 0.01g, and the degradation rate of each group of samples was calculated (degradation rate = (initial mass of sample - remaining mass) / initial mass of sample × 100%). The three samples in each group were measured in parallel, and the average value was recorded.

[0030] 2. Water absorption performance test: Weigh the initial mass of each sample in the four groups of pretreated samples using an electronic balance with an accuracy of 0.01g (recorded as m1). The measurements were performed in parallel for three samples in each group, and the average value was recorded. Take four 50mL beakers and add 40mL of deionized water to each beaker. Use tweezers to completely immerse the four groups of samples in the deionized water in the corresponding beakers, ensuring that the samples are completely submerged and do not float or fold. Start the timer and soak for 10min. After 10min, gently remove the samples with tweezers, suspend the samples vertically, and let them stand for 30s. When there are no water droplets on the sample surface, weigh the mass of each sample after water absorption using an electronic balance (recorded as m2). Calculate the water absorption ratio of each group of samples (water absorption ratio = (m2-m1) / m1×100%). The measurements were performed in parallel for three samples in each group, and the average value was recorded.

[0031] Table 1: Performance Test Results of Biodegradable Cotton Soft Towels

[0032] Examples 1-3: Sodium bicarbonate particles treated with stearic acid hydrophobicity were added during the preparation process. In a constant temperature and humidity culture environment, sodium bicarbonate gradually decomposes to produce carbon dioxide gas. This process creates numerous tiny pores and channels inside and on the surface of the cotton towel, increasing the contact area between soil microorganisms and the cotton towel material. This makes it easier for microorganisms to attach to and penetrate the material, accelerating its decomposition. Simultaneously, these pores and channels also facilitate the penetration of water and nutrients from the soil into the material, providing a more favorable environment for microbial growth and metabolism, thus promoting the degradation process of the cotton towel. This resulted in relatively high degradation rates in Examples 1-3 at different time points, with the degradation rate gradually increasing significantly with prolonged culture time.

[0033] The cotton towel in Comparative Example 1 lacked the pores and channels created by the decomposition of sodium bicarbonate. The relatively small contact area between soil microorganisms and the material made it difficult for them to penetrate and decompose the material. The penetration of water and nutrients was also limited, hindering microbial growth and metabolic activities. Therefore, the degradation rate was slower, and the degradation rate at different time points was significantly lower than that in Examples 1-3.

[0034] Examples 1-3: Due to the addition of sodium bicarbonate particles treated with stearic acid hydrophobicity, a rich porous structure is formed inside the cotton towel. These pores act like tiny "water containers," capable of holding more water. When the cotton towel is immersed in water, the water can quickly penetrate into these pores and be adsorbed and retained by the surface tension of the pores, thereby greatly improving the water absorption capacity of the cotton towel, resulting in a high water absorption ratio in Examples 1-3. Moreover, as the amount of sodium bicarbonate particles gradually increases in the examples (5g in Example 1, 6g in Example 2, and 7g in Example 3), the formed porous structure may become richer and more complete, so the water absorption ratio also shows a gradually increasing trend.

[0035] Comparative Example 1, lacking the porous structure formed by sodium bicarbonate particles, has a relatively dense fiber structure, limiting the space for moisture penetration and retention. When immersed in water, it can absorb and retain relatively less moisture, resulting in a significantly lower absorbency rate compared to Examples 1-3.

[0036] In summary, sodium bicarbonate particles treated with stearic acid hydrophobicity play a key role in the preparation of biodegradable cotton towels. By decomposing and generating a porous structure, they significantly improve the degradation rate and water absorption rate of the cotton towels.

[0037] In the description of this specification, the terms "preparation example," "example," "various examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that example or preparation example, which are included in at least one example or preparation example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same example or preparation example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more examples or preparation examples.

[0038] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a biodegradable cotton towel, characterized in that, Prepared by the following steps: S1: Trans-aconitic acid and xylitol are melt-polymerized in the presence of a catalyst to obtain a biodegradable polyester prepolymer; after cooling and pulverizing the prepolymer, it is dispersed together with sodium bicarbonate particles and a crosslinking agent in a weakly buffered neutral aqueous phase, and microspheres are formed by reverse-phase suspension crosslinking and solidification. S2: Microspheres are loaded onto a nonwoven fabric substrate, dried, and cured to obtain a biodegradable cotton towel.

2. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, The sodium bicarbonate particles used in step S1 are pre-treated with stearic acid to make them hydrophobic.

3. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, The catalyst in step S1 is selected from at least one of p-toluenesulfonic acid, methanesulfonic acid, citric acid, and tartaric acid; the crosslinking agent used is at least one of ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether.

4. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, The mass ratio of trans-aconitic acid to xylitol added in step S1 is 1:(1.1~1.3).

5. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, In step S1, the temperature of the melt polycondensation reaction is 130–160°C, the pressure is 0.01–0.05 MPa, and the time is 1–3 h.

6. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, The microspheres in step S1 are spherical particles with a diameter of 50–300 μm.

7. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, The nonwoven fabric substrate used in step S2 is either all-cotton spunlace nonwoven fabric or bamboo fiber spunlace nonwoven fabric; the loading method used is either impregnation, spraying or mixed web forming; the drying and curing temperature is 100-130℃ and the time is 1-3 minutes.

8. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, In step S1, the oil phase of the reverse suspension crosslinking curing system is either liquid paraffin or vegetable oil, the emulsifier is either Span-80 or Span-85, the reaction temperature is 80-105℃, and the reaction time is 2-4 hours.

9. The method for preparing the biodegradable cotton towel according to claim 1, characterized in that, The loading in step S2 is achieved by spraying, and the microspheres are fixed with an adhesive. The adhesive is either a modified starch aqueous solution or triethyl citrate. After spraying, the microspheres are dried and cured in stages at temperatures of 80–95°C and 100–120°C, respectively.

10. A biodegradable cotton towel prepared by the preparation method according to any one of claims 1-9.

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