Formaldehyde-free stiff water-absorbing rayon sand barrier and preparation method thereof

Abstract

The invention discloses a formaldehyde-free stiff water-absorbing rayon sand barrier and a preparation method thereof, the rayon sand barrier comprises rayon and an acrylic acid-acrylamide resin prepolymer, the acrylic acid-acrylamide resin prepolymer is baked and crosslinked on the rayon to form a three-dimensional network structure, wherein the acrylic acid-acrylamide resin prepolymer is crosslinked with-OH on the rayon material. The water absorption rate of the rayon sand barrier can reach 60 g / g, and the bending length of the sand barrier is 13 cm. The processing technology is simple, the cost is low, and mass production can be realized.

Description

Technical Field

[0001] This invention relates to the fields of chemistry and materials science, specifically to a formaldehyde-free, stiff, absorbent rayon sand barrier. Background Technology

[0002] Desertification is one of the world's most serious ecological problems. With economic development and population growth, human destruction of the ecological environment is inevitably increasing. This desertification, in turn, affects human survival and the sustainable development of the ecological environment.

[0003] Using sand barriers is a crucial method for combating desertification, primarily serving to prevent wind erosion and reduce further damage to vegetation from strong winds and sand. Rayon sand barriers are breathable and moisture-wicking, making them suitable for hot climates; they are also affordable and cost-effective. However, traditional stiffening agents such as GQ-800HH are often aldehyde-containing stiffening agents, which can harm the environment with long-term use.

[0004] Therefore, there is an urgent need for an environmentally friendly, biodegradable sand barrier that also has good water absorption, water retention, and rigidity. Summary of the Invention

[0005] Objectives of the invention: The first objective of this invention is to provide a formaldehyde-free, stiff, absorbent rayon sandal that combines stiffness, absorbency, and moisture retention; the second objective of this invention is to provide a method for preparing a formaldehyde-free, stiff, absorbent rayon sandal.

[0006] To achieve the first objective mentioned above, the technical solution for the formaldehyde-free, stiff, absorbent rayon sand barrier provided by this invention is as follows: This invention provides a formaldehyde-free, stiff, absorbent rayon sand barrier, which comprises rayon and acrylic-acrylamide resin prepolymer. The acrylic-acrylamide resin prepolymer is baked and cross-linked on the rayon to form a three-dimensional network structure, wherein the acrylic-acrylamide resin prepolymer is cross-linked with the -OH groups on the rayon material.

[0007] The chemical structure of the rayon sand barrier obtained by crosslinking acrylic-acrylamide resin prepolymer with rayon material is as follows:

[0008] To achieve the second objective mentioned above, the technical solution for the preparation method of formaldehyde-free, stiff, absorbent rayon sand barriers provided by this invention is as follows: This invention provides a method for preparing a formaldehyde-free, stiff, absorbent rayon sand barrier. An acrylic-acrylamide resin prepolymer, polyethylene glycol, and sodium hypophosphite are mixed to form a finishing solution. Rayon is immersed in the finishing solution, and the prepolymer is combined with the rayon through a rolling and baking process to prepare a formaldehyde-free, stiff rayon sand barrier.

[0009] The preparation method of acrylic acid-acrylamide resin prepolymer includes the following steps: adding acrylamide to acrylic acid neutralization solution to obtain a mixture; adding an initiator to the above mixture and stirring continuously to prepare a reaction stock solution; reacting in a water bath to polymerize the reaction stock solution to form acrylic acid-acrylamide resin prepolymer.

[0010] In the acrylic acid neutralization solution, the degree of neutralization of acrylic acid is 40-80%.

[0011] The concentration of acrylic acid-acrylamide resin prepolymer in the finishing solution is 300-500 g / L.

[0012] In the rolling baking process, the baking conditions are 150~170℃×90~180s.

[0013] The initiator is ammonium persulfate.

[0014] Preferably, the present invention provides a method for preparing a formaldehyde-free, stiff, absorbent rayon sand barrier, comprising the following steps: (1) Under ice-water bath conditions, acrylic acid solution is added dropwise to NaOH solution to prepare acrylic acid neutralized solution, the degree of neutralization of acrylic acid neutralized solution is 40-80%; (2) Add acrylamide to the acrylic acid neutralization solution to obtain a mixed solution; (3) Add the initiator to the mixed solution in step (2) and stir continuously to prepare the reaction stock solution. React in a water bath to polymerize the reaction stock solution to form an acrylic acid-acrylamide superabsorbent resin prepolymer. (5) Polyethylene glycol 1000 and sodium hypophosphite were added to the acrylic acid-acrylamide superabsorbent resin prepolymer to prepare a finishing solution; (6) The rayon is immersed in the finishing solution and the pacing and baking process is adopted. Under the condition of two immersions and two pacings, formaldehyde-free stiff and absorbent rayon sand barrier is obtained.

[0015] In step (6), the total mass of acrylic acid-acrylamide superabsorbent resin prepolymer, polyethylene glycol 1000 and sodium hypophosphite in each liter of finishing solution is 300-500g.

[0016] In step (6), the liquid content of the rayon is controlled to be 180% under the conditions of two dips and two nips.

[0017] Invention Principle: This invention uses NaOH and ammonia to partially neutralize acrylic acid, then adds acrylamide, heats the neutralized solution, and adds ammonium persulfate as an initiator under certain temperature conditions to synthesize a highly absorbent prepolymer. The prepolymer is then combined with rayon through a baking process to prepare a formaldehyde-free, stiff rayon sash. The three-dimensional network structure formed by the cross-linking of the resin prepolymer on the rayon during baking gives the fabric excellent water absorption and retention properties. Therefore, the resin also acts as a water absorbent and water retainer in this invention, enabling the rayon sash to achieve a three-in-one effect of stiffness, water absorption, and water retention.

[0018] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: 1) The polyacrylic acid resin not only acts as a formaldehyde-free stiffening agent, but also, the three-dimensional network structure formed by the cross-linking of the resin prepolymer on rayon during baking gives the fabric excellent water absorption properties. Therefore, the resin also acts as a water absorbent and water-retaining agent in this project, achieving a three-in-one effect of stiffness, water absorption, and water retention. In the process of combating desertification, rayon sand barriers can not only play a role in windbreak and sand fixation, but also take advantage of the large diurnal temperature range in the desert. At night, the temperature is low, and the sand barriers absorb and retain water; during the day, the desert temperature is high, and the sand barriers release water, thus conserving soil and water. The preparation process of this product is pollution-free, and the reaction and processing conditions are mild, making it green and environmentally friendly.

[0019] 2) The resin prepolymer in this project not only forms a three-dimensional network structure through cross-linking agent PEG-1000, but also utilizes the -OH group of rayon itself to enable the prepolymer to self-crosslink, thereby improving the bonding force between the resin and rayon material and increasing the durability of the formaldehyde-free, stiff, and absorbent rayon sand barrier.

[0020] 3) A mixed alkali is used to neutralize acrylic acid: NaOH neutralizes acrylic acid and introduces -COONa, which improves the water absorption of the rayon sand barrier. Ammonia water neutralizes acrylic acid and introduces -COONH4 to improve the pH value of the polyacrylic acid neutralizing solution, thereby increasing the degree of polymerization of the prepolymer, which is beneficial to subsequent experiments. In addition, during pre-drying, -COONH4 is converted into -COOH, which provides crosslinking points for the esterification and crosslinking reaction of the prepolymer and the crosslinking agent PEG-1000, and controls the degree of crosslinking of the resin.

[0021] 4) This project adjusts the stiffness of rayon quilts by controlling the amount of polyacrylic acid resin prepolymer and the degree of resin crosslinking. When the prepolymer dosage is 300-500 g / L, the rayon quilts exhibit good stiffness performance. In contrast, traditional stiffening finishing agents typically require 600-800 g / L. Therefore, this project effectively saves energy and aligns with the theme of green dyeing and finishing.

[0022] 5) NaH2PO2 is used as a catalyst to promote the esterification reaction between -COOH in the polyacrylic acid prepolymer and PEG-1000. At the same time, NaH2PO2 inhibits the oxidation of -COOH through its reducing properties, thus protecting the fiber strength. In addition, NaH2PO2 can lower the baking temperature of the esterification crosslinking reaction, making the reaction conditions milder, which can effectively save energy and is in line with the theme of green dyeing and finishing.

[0023] 6) The "pad-dry-bake" finishing process replaces the traditional coating and lamination processes to combine resin with rayon, resulting in a more uniform distribution of resin on the rayon and eliminating powder shedding. In addition, the "pad-dry-bake" finishing process has milder reaction conditions, achieving effective energy saving. Attached Figure Description

[0024] Figure 1 Electron micrograph of rayon fabric; Figure 2 Electron micrograph of the formaldehyde-free stiff rayon sand barrier prepared in Example 19. Detailed Implementation

[0025] To better illustrate the objectives, technical solutions, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples.

[0026] The method for preparing the rayon sand barrier substrate used in this embodiment of the invention is as follows: rayon fiber monofilaments are twisted into yarn, and then the rayon sand barrier material is prepared by weaving. The main specifications are shown below:

[0027] The method for preparing the formaldehyde-free, stiff, absorbent rayon styrofoam styrofoam according to embodiments of the present invention involves partially neutralizing acrylic acid with NaOH and ammonia, then adding acrylamide, heating the neutralized solution, and adding ammonium persulfate as an initiator under certain temperature conditions to synthesize a highly absorbent prepolymer. The prepolymer is then combined with rayon through a padding and baking process to prepare the formaldehyde-free, stiff rayon styrofoam styrofoam. The initiator used in each embodiment of the present invention is ammonium persulfate.

[0028] The reaction equations involved in the formaldehyde-free, stiff, absorbent rayon sand barrier are as follows:

[0029] Formula 1,2: NaOH and ammonia water neutralize acrylic acid

[0030] Polymerization of polyacrylic acid prepolymers (Formula 3)

[0031] Equation 4 -COON is converted to -COOH

[0032] Formula 5 Esterification and crosslinking reaction of polyacrylic acid prepolymer with crosslinking agent

[0033] Formula 6 Esterification and crosslinking reaction of polyacrylic acid prepolymer with -OH groups on rayon material The specific steps of the preparation method of the formaldehyde-free, stiff, absorbent rayon sand barrier provided in this embodiment of the invention are as follows: (1) Weigh a certain amount of NaOH and dissolve it in a beaker. Add 20 ml of acrylic acid solution in an ice-water bath to prepare a neutralized acrylic acid solution with a degree of neutralization of 40-80%.

[0034] (2) Add acrylamide to the acrylic acid neutralization solution to prepare a mixed solution with an acrylic acid to acrylamide ratio of 1:1 to 5:1.

[0035] (3) Add a certain amount of water to the mixed solution so that the content of acrylic acid in the mixed solution is 10-30%.

[0036] (4) Add 0.2 to 0.5 g of initiator ammonium persulfate to the mixed solution in step (3), stir continuously to prepare the reaction stock solution, put it into a water bath at an initial temperature of 65 to 75°C and react for 2 to 5 hours to polymerize the reaction stock solution to form acrylic acid-acrylamide superabsorbent resin prepolymer.

[0037] (5) Add 1-5g of polyethylene glycol 1000 and 0.1-0.5g of sodium hypophosphite to the acrylic acid-acrylamide superabsorbent resin prepolymer to prepare a finishing solution.

[0038] (6) The rayon is immersed in the finishing solution and then subjected to a padding and baking process. When the resin content in the finishing solution is 300-500 g / L, the rayon liquid content is controlled to be 180% under the conditions of two dips and two pads. The drying conditions are 110-120℃×2-3 min and baking conditions are 150-170℃×90-180 s. Formaldehyde-free, stiff, and absorbent rayon sand barriers are obtained.

[0039] Example 1

[0040] (1) Weigh a certain amount of NaOH and dissolve it in a beaker. Add 20 ml of acrylic acid solution in an ice-water bath to make the degree of neutralization of acrylic acid 40%.

[0041] (2) Add acrylamide to the neutralization solution to prepare finishing solution 1 with an acrylic acid to acrylamide ratio of 4:1; (3) Add a certain amount of water to finishing solution 1 so that the amount of acrylic acid is 15% to obtain finishing solution 2; (4) Add 0.3g of initiator to finishing liquid 2 and stir continuously to prepare reaction stock solution. Place it in a water bath with an initial temperature of 70℃ and react for 4h to polymerize the reaction stock solution to form acrylic acid-acrylamide superabsorbent resin prepolymer.

[0042] (5) Add 2g of polyethylene glycol 1000 and 0.2g of sodium hypophosphite to the prepolymer to prepare finishing solution 3.

[0043] (6) The rayon was immersed in finishing solution 3 and a padding and baking process was adopted. When the resin content in finishing solution 3 was 300 g / L, the rayon liquid carrying rate was controlled at 180% under the conditions of two dips and two pads. The drying conditions were 120℃×3 min and the baking conditions were 160℃×120 s. Formaldehyde-free stiff and absorbent rayon sand barrier-1 was obtained. The resin content in finishing solution 3 refers to the total mass of acrylic acid-acrylamide superabsorbent resin prepolymer, polyethylene glycol 1000 and sodium hypophosphite contained in each liter of finishing solution.

[0044] Example 2

[0045] Replace “resin content 300g / L in finishing liquid 3” in (6) of Example 1 with “resin content 400g / L in finishing liquid 3”. The remaining steps are exactly the same as in Example 1. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-2.

[0046] Example 3

[0047] Replace “resin content 300g / L in finishing liquid 3” in (6) of Example 1 with “resin content 500g / L in finishing liquid 3”. The remaining steps are exactly the same as in Example 1. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-3.

[0048] Example 4

[0049] Replace “resin content 300g / L in finishing liquid 3” in (6) of Example 1 with “resin content 600g / L in finishing liquid 3”. The remaining steps are exactly the same as in Example 1. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-4.

[0050] Example 5

[0051] Replace “resin content 300g / L in finishing liquid 3” in (6) of Example 1 with “resin content 700g / L in finishing liquid 3”. The remaining steps are exactly the same as in Example 1. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-5.

[0052] Example 6

[0053] (1) Weigh a certain amount of NaOH and dissolve it in a beaker. Add 20 ml of acrylic acid solution in an ice-water bath to make the degree of neutralization of acrylic acid 50%.

[0054] (2) Add acrylamide to the neutralization solution to prepare finishing solution 1 with an acrylic acid to acrylamide ratio of 4:1; (3) Add a certain amount of water to the finishing solution so that the amount of acrylic acid is 15% to obtain finishing solution 2; (4) Add 0.3g of initiator to finishing solution 2 and stir continuously to prepare reaction stock solution. Place it in a water bath with an initial temperature of 70℃ and react for 4h to polymerize the reaction stock solution to form acrylic acid-acrylamide superabsorbent resin prepolymer.

[0055] (5) Add 2g of polyethylene glycol 1000 and 0.2g of sodium hypophosphite to the prepolymer to prepare finishing solution 3.

[0056] (6) The rayon was immersed in finishing solution 3 and a padding and baking process was adopted. When the resin content in finishing solution 3 was 600 g / L, the rayon liquid carrying rate was controlled at 180% under the conditions of two dips and two pads. The drying conditions were 120℃×3 min and the baking conditions were 160℃×120 s. Formaldehyde-free stiff and absorbent rayon sand barrier-6 was obtained. The resin content in finishing solution 3 refers to the total mass of acrylic acid-acrylamide superabsorbent resin prepolymer, polyethylene glycol 1000 and sodium hypophosphite contained in each liter of finishing solution.

[0057] Example 7

[0058] Replace “50% acrylic acid neutralization” in (1) of Example 6 with “60% acrylic acid neutralization”, and the remaining steps are exactly the same as in Example 6. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-7.

[0059] Example 8

[0060] Replace “50% acrylic acid neutralization” in (1) of Example 6 with “70% acrylic acid neutralization”, and the remaining steps are exactly the same as in Example 6. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-8.

[0061] Example 9

[0062] Replace “50% acrylic acid neutralization” in (1) of Example 6 with “80% acrylic acid neutralization”, and the remaining steps are exactly the same as in Example 6. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-9.

[0063] Example 10

[0064] (1) Weigh a certain amount of NaOH and dissolve it in a beaker. Add 20 ml of acrylic acid solution in an ice-water bath to make the degree of neutralization of acrylic acid 40%.

[0065] (2) Add acrylamide to the neutralization solution to prepare finishing solution 1 with an acrylic acid to acrylamide ratio of 4:1. (3) Add a certain amount of water to finishing solution 1 so that the amount of acrylic acid used is 15%. (4) Add 0.3g of initiator to finishing solution 2 and stir continuously to prepare reaction stock solution. Place it in a water bath with an initial temperature of 70℃ and react for 4h to polymerize the reaction stock solution to form acrylic acid-acrylamide superabsorbent resin prepolymer.

[0066] (5) Add 1g of polyethylene glycol 1000 and 0.2g of sodium hypophosphite to the prepolymer to prepare finishing solution 3.

[0067] (6) The rayon was immersed in finishing solution 3 and a padding and baking process was adopted. When the resin content in finishing solution 3 was 600 g / L, the rayon liquid carrying rate was controlled at 180% under the conditions of two dips and two pads. The drying conditions were 120℃×3min and the baking conditions were 160℃×120s. Formaldehyde-free stiff and absorbent rayon Shazhang-10 was obtained. The resin content in finishing solution 3 refers to the total mass of acrylic acid-acrylamide superabsorbent resin prepolymer, polyethylene glycol 1000 and sodium hypophosphite contained in each liter of finishing solution.

[0068] Example 11

[0069] Replace “1g of polyethylene glycol 1000” in (5) of Example 10 with “3g of polyethylene glycol 1000”, and the remaining steps are exactly the same as in Example 10. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-11.

[0070] Example 12

[0071] Replace “1g of polyethylene glycol 1000” in (5) of Example 10 with “4g of polyethylene glycol 1000”, and the remaining steps are exactly the same as in Example 10. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-12.

[0072] Example 13

[0073] Replace “1g of polyethylene glycol 1000” in (5) of Example 10 with “5g of polyethylene glycol 1000”, and the remaining steps are exactly the same as in Example 10. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-13.

[0074] Example 14

[0075] (1) Weigh a certain amount of NaOH and dissolve it in a beaker. Add 20 ml of acrylic acid solution in an ice-water bath to make the degree of neutralization of acrylic acid 40%.

[0076] (2) Add acrylamide to the neutralization solution to prepare finishing solution 1 with an acrylic acid to acrylamide ratio of 4:1; (3) Add a certain amount of water to finishing solution 1 so that the amount of acrylic acid is 15% to obtain finishing solution 2; (4) Add 0.3% initiator to finishing solution 2 and stir continuously to prepare reaction stock solution. Place it in a water bath with an initial temperature of 70℃ and react for 4 hours to polymerize the reaction stock solution to form acrylic acid-acrylamide superabsorbent resin prepolymer.

[0077] (5) Add 3g of polyethylene glycol 1000 and 0.2g of sodium hypophosphite to the prepolymer to prepare finishing solution 3.

[0078] (6) The rayon was immersed in finishing solution 3 and a padding and baking process was adopted. When the resin content in finishing solution 3 was 600 g / L, the rayon liquid carrying rate was controlled at 180% under the conditions of two dips and two pads. The drying conditions were 120℃×3 min and the baking conditions were 150℃×120 s. Formaldehyde-free stiff and absorbent rayon Shazhang-14 was obtained. The resin content in finishing solution 3 refers to the total mass of acrylic acid-acrylamide superabsorbent resin prepolymer, polyethylene glycol 1000 and sodium hypophosphite contained in each liter of finishing solution.

[0079] Example 15

[0080] Replace “baking conditions 150℃×120s” in (6) of Example 14 with “baking conditions 170℃×120s”, and the remaining steps are exactly the same as in Example 14. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-15.

[0081] Example 16

[0082] Replace “baking conditions 150℃×120s” in (6) of Example 14 with “baking conditions 180℃×120s”, and the remaining steps are exactly the same as in Example 14. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-16.

[0083] Example 17

[0084] Replace “baking conditions 150℃×120s” in (6) of Example 14 with “baking conditions 190℃×120s”, and the remaining steps are exactly the same as in Example 14. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-17.

[0085] Example 18

[0086] Replace “baking conditions 170℃×120s” in (6) of Example 15 with “baking conditions 170℃×90s”, and the remaining steps are exactly the same as in Example 15. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-18.

[0087] Example 19

[0088] Replace “baking conditions 170℃×120s” in (6) of Example 15 with “baking conditions 170℃×150s”, and the remaining steps are exactly the same as in Example 15. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-19.

[0089] like Figure 1-2 As shown, comparing the scanning electron microscope images of the rayon gauze before and after treatment, there are a large number of gaps between the fibers of the rayon gauze before treatment, while the gaps between the fibers of the rayon gauze after treatment are filled with resin, indicating that the absorbent resin has been combined with the fabric.

[0090] Example 20

[0091] Replace “baking conditions 170℃×120s” in (6) of Example 15 with “baking conditions 170℃×180s”, and the remaining steps are exactly the same as in Example 15. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-20.

[0092] Example 21

[0093] Replace “baking conditions 170℃×120s” in (6) of Example 15 with “baking conditions 170℃×210s”, and the remaining steps are exactly the same as in Example 15. The resulting composite material is formaldehyde-free stiff absorbent rayon sand barrier-21.

[0094] Comparative Example 1 Referring to patent CN116926955A, straw fibers separated from straw are liquefied and dissolved into a high-viscosity liquid, which is then spun and solidified into fibers and spun into sand barrier materials. Acrylic acid neutralization liquid is prepared by neutralizing acrylic acid monomers with sodium hydroxide solution to a certain degree of neutralization in an ice-water bath. Acrylamide, potassium persulfate initiator, and NN methylenebisacrylamide crosslinking agent are then added to the neutralization liquid in sequence and stirred until viscous to obtain a resin finishing liquid. The resin finishing liquid and coating are compounded onto the straw sand barrier material through a padding process, with the padding rate controlled at 200%. The material is pre-dried at 100℃ for 5 min and then baked at 150 min for 2 min to obtain Comparative Example 1 - Superabsorbent Colored Sand Barrier.

[0095] Comparative Example 2 Acrylic acid neutralized solution was prepared by neutralizing acrylic acid monomers with sodium hydroxide solution in an ice-water bath until the neutralization degree reached 80%. Acrylamide (40% by weight of acrylic acid) and potassium persulfate (0.12g initiator) were added sequentially to the neutralized solution. The liquid was stirred uniformly at 65℃ until viscous to obtain a resin prepolymer finishing solution. GH-710 adhesive (0.3% by weight of total acrylic acid and acrylamide) and aluminum hydroxide crosslinking agent were added to the prepolymer and stirred until homogeneous. This solution was then loaded onto rayon sand barrier material using a two-dip, two-nip process, controlling the liquid content at 200%. The sand barrier material was dried in an oven at 80℃ until dry to obtain superabsorbent rayon sand barrier material – Comparative Example 2. Test method: Fabric absorbency ratio: After weighing the sand barrier material sample, it was absorbed with water for 1 hour. After removing excess water, it was weighed again. The water absorption ratio of the resin loaded on the fabric was calculated according to formula (1).

[0096] In the formula: Q represents the water absorption ratio of the resin loaded on the fabric, in g / g. m is the dry mass of the original fabric, g m1 is the dry mass of the sample, in g m2 is the mass of the sample after absorbing water, in grams. Fabric water retention properties: The mass m of the sand barrier sample was measured, and then the sample was left to stand in distilled water for 1 hour to remove excess water. The mass m3 was then measured. The mass m4 of the fabric was measured at intervals thereafter. The water retention rate R was determined by formula (2) to measure the water retention performance of the sand barrier sample.

[0097]

[0098] Bending stiffness: The weft bending length of the fabric was tested according to GB / T 1831—2001 "Textiles - Determination of Fabric Bending Length".

[0099] Fracture strength: The test was conducted according to GB / T 3923.1—2013 "Textiles - Tensile Properties of Fabrics - Part 1: Breaking Strength and Elongation at Break (Strip Method)".

[0100] Analysis of the water absorption and stiffness properties of sand barrier materials (1) Table 1 shows the test results of water absorption and stiffness of the formaldehyde-free stiff rayon sand barriers in Examples 1 to 5: Table 1. Test results of water absorption and stiffness properties of Examples 1-5 Sample Example 1 Example 2 Example 3 Example 4 Example 5 Q / (g / g) 87 89 63 44 40 Bending length / cm 8 10 11 11.5 12 The water absorption and stiffness properties of sand barrier materials show a trend of first increasing and then decreasing, and then gradually increasing, respectively, with the increase of resin content. This is because as the amount of resin loaded on the sand barrier increases, the three-dimensional network structure inside the resin becomes more compact, which increases the binding effect on water molecules after water absorption, thus improving the water absorption performance of the sand barrier. If the amount of resin is further increased, the structure becomes too compact, which restricts the water from entering the interior of the resin, and the water absorption performance decreases. At the same time, the increasingly compact three-dimensional network structure of the resin restricts the relative slippage of the molecular chain segments of the sand barrier material, and the stiffness property of the sand barrier material shows a continuous increasing trend.

[0101] (2) Table 2 shows the test results of water absorption and stiffness of the formaldehyde-free stiff rayon sand barriers in Examples 4 and 6-9: Table 2. Test results of water absorption and stiffness properties of Examples 4 and 6-9 Sample Example 4 Example 6 Example 7 Example 8 Example 9 Q / (g / g) 44 48 55 58 50 Bending length / cm 11.5 11 10.3 10 8.9 The water absorption capacity of sand barrier materials initially increases and then decreases with increasing neutralization degree. This is because increased neutralization degree leads to an increase in the number of -COONa groups dissociating in water, causing the polymer molecular chains to expand and thus absorbing more water, thereby improving the water absorption capacity of the sand barrier material. Further increasing the neutralization degree results in an excessive amount of COOH in the solution, creating a shielding effect that causes the polymer molecular chains to contract, thus decreasing the water absorption capacity. The stiffness also decreases with increasing neutralization degree. As COOH is converted to COOH, the groups generate electrostatic repulsion, causing the molecular chain segments to fully extend. This results in a lower network modulus of the resin, making it more flexible.

[0102] (3) Table 3 shows the test results of water absorption and stiffness of the formaldehyde-free stiff rayon sand barriers in Examples 4 and 10-13: Table 3. Test results of water absorption and stiffness properties in Examples 4 and 10-13 Sample Example 10 Example 4 Example 11 Example 12 Example 13 Q / (g / g) 31 44 45 36 34 Bending length / cm 10.4 11.5 11.9 12.2 12.4 As the amount of crosslinking agent polyethylene glycol 1000 (PEG-1000) increases, the water absorption performance of the sand barrier improves because the increase of crosslinking agent makes the three-dimensional network structure of the resin more compact. In Example 11, the water absorption ratio reaches its peak. If the amount of PEG-1000 is further increased, the three-dimensional network structure becomes too compact, which restricts the entry of water molecules and the water absorption performance decreases. The stiffness performance continues to improve with the increase of crosslinking agent because after the resin macromolecular chain segments are crosslinked, the relative slippage between the molecular chain segments is weakened, and the stiffness performance gradually improves.

[0103] (4) Table 4 shows the test results of water absorption and stiffness of the formaldehyde-free stiff rayon sand barriers in Examples 11 and 14-17: Table 4. Test results of water absorption and stiffness properties in Examples 11 and 14-17. Sample Example 14 Example 11 Example 15 Example 16 Example 17 Q / (g / g) 31 45 51 40 23 Bending length / cm 10.6 11.9 12.3 12.5 13 As the baking temperature increases, the esterification reaction between the -COOH groups on the resin and the -OH groups in the crosslinking agent tends to be complete, and the three-dimensional network structure of the resin becomes more compact, enhancing the water absorption capacity of the sand barrier material. However, further increasing the temperature leads to an excessively compact three-dimensional network structure, and the fibers of the sand barrier material will yellow and become damaged at excessively high temperatures, reducing the bonding force with the loaded resin. After absorbing water, the resin will fall off the sand barrier, thus decreasing the water absorption capacity. Conversely, with increasing temperature, the tight crosslinking of the resin's three-dimensional network structure when not absorbing water greatly restricts the slippage of molecular chain segments, thus improving the stiffness of the sand barrier.

[0104] (5) Table 5 shows the test results of water absorption and stiffness of the formaldehyde-free stiff rayon sand barriers in Examples 15 and 18-21: Table 5. Test results of water absorption and stiffness properties of Examples 15 and 18-21 Sample Example 18 Example 15 Example 19 Example 20 Example 21 Q / (g / g) 46 51 60 45 30 Bending length / cm 12.1 12.3 13 13.3 13.6 As the baking time increases, the esterification reaction between the -COOH groups on the resin and the -OH groups in the crosslinking agent tends to be more complete, and the three-dimensional network structure of the resin tends to be more compact. The water absorption and stiffness of the sand barrier material gradually improve. However, if the baking time is too long, the resin network structure becomes too compact, making it difficult for water to enter the interior of the resin, and the water absorption performance decreases.

[0105] Table 6 shows the test results of water absorption and stiffness properties of the sand barrier materials in Example 19 and Comparative Examples 1-2.

[0106] Table 6. Test results of water absorption and stiffness of Example 19 and Comparative Examples 1-2 Sample Example 19 Comparative Example 1 Comparative Example 2 Q / (g / g) 60 27 180 Bending length / cm 13 10 7 In Comparative Example 1, water-absorbing sand barrier material was prepared using fibers extracted from straw as the base material. This material had a complex composition and was rich in impurities, making it difficult for the -OH groups on the fibers to be fully exposed. These impurities hindered the grafting and cross-linking reactions of the resin, thus affecting the resin's water absorption, stiffness, and the bonding strength between the resin and the sand barrier material. The results in the table show that the water absorption ratio of the sand barrier material in Comparative Example 1 was only 27 g / g, and the bending stiffness was 10 cm, indicating unsatisfactory water absorption performance. In Comparative Example 2, sand barrier materials were prepared using aluminum hydroxide as a cross-linking agent and polyvinyl acetate GH-710 as a binder. The cross-linking points were mainly formed by the physical filling of aluminum ions. This bonding force was weak, and in long-term alternating wet and dry environments, the resin easily dissociated, leading to network collapse, softening the sand barrier material, and reducing its water absorption and stiffness. Furthermore, aluminum hydroxide, as an inorganic substance, has poor compatibility with the resin. After water absorption, the resin easily agglomerated locally, affecting the uniformity of the sand barrier material. Water-absorbing sand barrier materials utilize resin simultaneously as a water absorbent, stiffener, and water-retaining / releasing agent. A balance among these three properties is necessary. In Comparative Example 2, the water absorption performance of the sand barrier is the primary characteristic. Its water absorption ratio is excessively high at 180 g / g. After the resin absorbs water and forms a gel, the gel becomes too thick and heavy, causing the sand barrier structure to collapse and affecting its durability. The flexural stiffness of the water-absorbing sand barrier material is 7 cm. Because the physical cross-linking method using aluminum hydroxide as a cross-linking agent imposes relatively little restriction on the movement of resin molecular chains, the stiffness of the sand barrier material is generally average.

[0107] The table shows the test results of the water retention / release performance of the sand barrier materials in Example 19 and Comparative Examples 1-2: Table 7. Water retention / release performance test results of Example 19 and Comparative Examples 1-2 Time / h 1 2 5 8 10 15 Example 19 Water retention rate / % 93 88 83 71 58 50 Comparative Example 1: Water Retention Rate / % 100 80 30 24 22 17 Comparative Example 2: Water Retention Rate / % 97 93 89 83 81 64 In practical applications, water-absorbing sand barrier materials utilize the large temperature difference between day and night in the desert environment. At night, when temperatures are low, the sand barrier material absorbs moisture from the air and has a certain water retention capacity to lock in moisture. During the day, when the climate is hot and dry, the sand barrier material has a certain water release capacity, which can release moisture in a timely manner to maintain soil and water conservation. Therefore, the water retention capacity of sand barrier materials should not be too high or too low.

[0108] As shown in the table, Comparative Example 1 exhibited the worst water retention performance, while Comparative Example 2 showed the best. In Comparative Example 1, a water-absorbing sand barrier was prepared using straw fiber as the substrate. The impurities in the straw fiber affected the resin composite, resulting in poor water absorption. During water release, the limited amount of water encapsulated by the resin was quickly released, leading to unsatisfactory water retention. Comparative Example 2, on the other hand, primarily characterized the sand barrier's water absorption ratio. After water absorption, the resin-formed gel was too thick, resulting in slow water release and difficulty in timely drainage, thus leading to excessively high water retention. In Example 19, after 15 hours, the water retention rate of the sand barrier was 50% of its original value, indicating a more balanced water retention / release performance. The sand barrier exhibited a certain degree of water retention after absorption, and the water was released promptly. In conclusion, Example 19 demonstrated more ideal water retention / release performance than Comparative Examples 1 and 2.

Claims

1. A formaldehyde-free, stiff, absorbent rayon sand barrier, characterized in that, The rayon sand barrier includes rayon and acrylic-acrylamide resin prepolymer. The acrylic-acrylamide resin prepolymer is baked and cross-linked on the rayon to form a three-dimensional network structure, wherein the acrylic-acrylamide resin prepolymer is cross-linked with the -OH groups on the rayon material.

2. A method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 1, characterized in that, A finishing solution is prepared by mixing acrylic-acrylamide resin prepolymer, polyethylene glycol, and sodium hypophosphite. Formaldehyde-free, stiff rayon sand barriers are prepared by immersing rayon in finishing solution and then combining the prepolymer with rayon through a rolling and baking process.

3. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 2, characterized in that, The preparation method of acrylic acid-acrylamide resin prepolymer includes the following steps: adding acrylamide to acrylic acid neutralization solution to obtain a mixture; adding an initiator to the above mixture and stirring continuously to prepare a reaction stock solution; reacting in a water bath to polymerize the reaction stock solution to form acrylic acid-acrylamide resin prepolymer.

4. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 3, characterized in that, In the acrylic acid neutralization solution, the degree of neutralization of acrylic acid is 40-80%.

5. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 2, characterized in that, The concentration of acrylic acid-acrylamide resin prepolymer in the finishing solution is 300-500 g / L.

6. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 3, characterized in that, In the rolling baking process, the baking conditions are 150~170℃×90~180s.

7. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 3, characterized in that, The initiator is ammonium persulfate.

8. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 2, characterized in that, Includes the following steps: (1) Under ice-water bath conditions, acrylic acid solution is added dropwise to NaOH solution to prepare acrylic acid neutralized solution, the degree of neutralization of acrylic acid neutralized solution is 40-80%; (2) Add acrylamide to the acrylic acid neutralization solution to obtain a mixed solution; (3) Add the initiator to the mixed solution in step (2) and stir continuously to prepare the reaction stock solution. React in a water bath to polymerize the reaction stock solution to form an acrylic acid-acrylamide superabsorbent resin prepolymer. (5) Polyethylene glycol 1000 and sodium hypophosphite were added to the acrylic acid-acrylamide superabsorbent resin prepolymer to prepare a finishing solution; (6) The rayon is immersed in the finishing solution and the pacing and baking process is adopted. Under the condition of two immersions and two pacings, formaldehyde-free stiff and absorbent rayon sand barrier is obtained.

9. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 8, characterized in that, In step (6), the total mass of acrylic acid-acrylamide superabsorbent resin prepolymer, polyethylene glycol 1000 and sodium hypophosphite in each liter of finishing solution is 300-500g.

10. The method for preparing the formaldehyde-free, stiff, absorbent rayon sand barrier according to claim 8, characterized in that, In step (6), the liquid content of the rayon is controlled to be 180% under the conditions of two dips and two nips.

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