pH value responsive self-adhesive heat and moisture preserving blanket and preparation method thereof

Abstract

The application discloses a pH value responsive self-adhesive heat and moisture preservation blanket and a preparation method and application thereof, and belongs to the technical field of composite materials. The heat and moisture preservation blanket is a multilayer composite structure, and from outside to inside, the heat and moisture preservation blanket is sequentially provided with a flame-retardant canvas, an aluminum foil rubber plastic plate, a composite geotextile and a sticky felt hydrogel layer. The sticky felt hydrogel layer is formed by dipping a sticky felt into a hydrogel precursor solution and then performing thermal crosslinking. The hydrogel precursor solution comprises, in parts by weight, 50-80 parts of methacrylate polyethylene imine, 20-40 parts of carboxymethyl cellulose, 10-30 parts of polyethylene glycol diglycidyl ether and 18-30 parts of 1,4-chloropropanol-piperazine. The heat and moisture preservation blanket with the pH value responsive sticky felt hydrogel layer has the characteristics of simple operation and good heat and moisture preservation effect.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a pH-responsive self-adhesive heat-insulating and moisture-retaining blanket and its preparation method. Background Technology

[0002] With rapid economic development, large-volume concrete is increasingly being used in key components such as the main structure of ship locks, the foundation slabs of large public buildings, and pile foundation caps. Considering factors such as crack control, strength, and cost, large-volume three-grade concrete is extensively used in the main structure of ship locks. The loads borne by large-volume concrete structures are mainly divided into two types: external loads, including dead loads and live loads under normal service conditions, acceleration loads generated by seismic waves during earthquakes, and wind loads. Another type is creep caused by the structure over time or stress caused during the pouring process. For large-volume concrete, the temperature stress generated by the hydration reaction is particularly important. The temperature stress in large-volume concrete structures is mainly due to the fact that during construction, in order to ensure the continuity of the structure, a large amount of concrete is poured at once. Before the heat generated by the hydration reaction of the concrete has a chance to dissipate, the newly poured concrete covers it. In addition, the concrete itself has poor thermal conductivity, and a large amount of hydration heat accumulates together, generating a large temperature stress. In addition, the uneven distribution of the concrete mix creates concentrated stress, which leads to local cracking. Such cracks are common in large-volume concrete structures and are prone to developing into larger through cracks, endangering structural safety.

[0003] For crack control in large-volume concrete, it is generally achieved by controlling the concrete materials and mix proportions, and controlling the temperature difference between the inside and outside of the concrete. Methods for controlling the temperature difference typically include external cooling by spraying water on the outer surface of the large-volume concrete, and covering the surface with a protective material. Especially during winter or summer construction, it is necessary to consider the possibility of excessive temperature differences between the inside and outside when the concrete curing temperature is low, or the risk of cracking due to sun exposure in summer. Therefore, it is essential to maintain appropriate humidity and temperature during the curing process to reduce surface cracking. However, existing curing materials have the following problems: insufficient moisture retention (<24h), causing humidity fluctuations and failing to effectively maintain the concrete surface moisture, requiring frequent water replenishment; high thermal conductivity (0.3–0.5 W / (m·K)) and poor temperature control performance, leading to thermal stress cracking; and a lack of self-healing function, making them unable to address micro-crack issues. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention provides a pH-responsive self-adhesive heat-insulating and moisturizing blanket and its preparation method, which uses an adhesive felt as a skeleton, impregnates it with a hydrogel precursor solution, and then forms an adhesive felt hydrogel layer structure through thermal cross-linking, wherein the hydrogel is a pH-responsive self-adhesive hydrogel layer.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] A pH-responsive self-adhesive thermal insulation blanket, wherein the thermal insulation blanket has a multi-layer composite structure, consisting of flame-retardant canvas, aluminum foil rubber-plastic board, composite geotextile, and a felt hydrogel layer from the outside to the inside; the felt hydrogel layer is formed by impregnating a hydrogel precursor solution with a felt as the skeleton, and then forming the felt hydrogel layer through thermal cross-linking; the hydrogel precursor solution, by weight, includes 50-80 parts of methacrylated polyethyleneimine, 20-40 parts of carboxymethyl cellulose, 10-30 parts of polyethylene glycol diglycidyl ether, and 18-30 parts of 1,4-chloropropanol-piperazine.

[0007] The structural formula of the 1,4-chloropropanol-piperazine is shown in Formula 1:

[0008]

[0009] Using 1,4-chloropropanol-piperazine as a crosslinking agent can regulate the methacrylated polyethyleneimine to achieve maximum swelling at neutral pH, thus facilitating the maximum water absorption of the thermal insulation blanket; at alkaline pH, it deprotonates, the crosslinked network shrinks, and the stored water is released, thereby replenishing the large amount of water required in the early stage of concrete hardening.

[0010] Preferably, the adhesive felt is a hydrophilic adhesive felt, which is a water-absorbing needle-punched nonwoven fabric.

[0011] Preferably, the 1,4-chloropropanol-piperazine is prepared as follows: 1 equivalent of piperazine is dissolved in distilled water, 2 to 2.5 equivalents of epichlorohydrin are added at 25-35°C, and the mixture is stirred and reacted at 50-60°C for 12 to 24 hours to obtain the product.

[0012] Preferably, the method for preparing the methacrylated polyethyleneimine is as follows: polyethyleneimine is pre-dried under vacuum, dichloromethane and triethylamine are added under argon protection, the mixture is dissolved and activated for a period of time, methacrylic anhydride is added, and the mixture is continuously stirred at room temperature under argon protection for 12-20 hours. After purification, the mixture is dried to obtain the methacrylated polyethyleneimine. The molar amount of methacrylic anhydride added is 10-30 times the molar amount of polyethyleneimine.

[0013] It is important to note that methacrylated polyethyleneimine is only partially methacrylated polyethyleneimine. This is because polyethyleneimine itself contains a high density of amine groups, which readily protonate in water to form positively charged -NR3 groups. + This leads to strong electrostatic repulsion, hindering the tight stacking of chain segments. However, methacrylate esterification can partially neutralize the amine charge, balancing electrostatic repulsion and chain segment interactions. This makes it easier for polymer chains to form a loose porous network through hydrophobic interactions and hydrogen bonds, thereby accommodating more water molecules.

[0014] Preferably, the polyethyleneimine is branched polyethyleneimine with a weight-average molecular weight of 10,000 to 50,000 g / mol.

[0015] Preferably, the weight-average molecular weight of the polyethylene glycol diglycidyl ether is 400–600 g / mol.

[0016] This application also protects a method for preparing a pH-responsive self-adhesive thermal and moisture-retaining blanket, comprising the following steps:

[0017] (1) Carboxymethyl cellulose solution, methacrylated polyethyleneimine solution, polyethylene glycol diglycidyl ether and 1,4-chloropropanol-piperazine solution are premixed and stirred to obtain a hydrogel precursor solution. Then, the adhesive felt is completely immersed in the hydrogel precursor solution for a period of time to penetrate and adsorb. After being taken out and drained, it is transferred to an oven and crosslinked at 60-80℃ for 3-5 hours. After being taken out and cooled to room temperature.

[0018] (2) Flame-retardant canvas, aluminum foil rubber and plastic board, composite geotextile and adhesive felt hydrogel are bonded or sewn together in sequence, and then cut and sewn to obtain pH-responsive self-adhesive heat preservation and moisture retention blanket.

[0019] This application also protects the application of a pH-responsive self-adhesive thermal insulation blanket in agricultural irrigation, geological restoration, and building insulation.

[0020] Beneficial effects

[0021] This invention offers the following beneficial effects: It provides a pH-responsive self-adhesive thermal insulation and moisture-retaining blanket with a multi-layered composite structure and a pH-responsive self-adhesive hydrogel layer. Before use, the blanket is soaked in water to absorb water and swell. Then, through the adhesion between the hydrogel and concrete, it is directly applied to the concrete surface requiring curing. In the early stages of concrete curing on a highly alkaline surface, the amine matrix of the methacrylated polyethyleneimine in the hydrogel undergoes amine maturation, causing the hydrogel network to shrink and release stored water to the concrete surface. Simultaneously, the deprotonation of the carboxymethyl cellulose carboxylic acid groups absorbs some free water, preventing the moisture in the blanket from being lost all at once and exceeding the absorption limit of the concrete hydration reaction. As the concrete hardens and the pH decreases, the free water stored in the carboxymethyl cellulose in the hydrogel layer is slowly released, continuously replenishing moisture for the slow hydration reaction on the concrete surface, ensuring a suitable humidity environment. Through the self-healing effect of concrete hydration, crack formation is reduced. When the water in the adhesive hydrogel layer of the thermal insulation blanket is almost completely consumed, the adhesion between the thermal insulation blanket and the concrete interface decreases, resulting in detachment or loosening. At this time, the thermal insulation blanket can be reused after being soaked in clean water to absorb water and swell. It has the characteristics of simple operation and good thermal insulation effect. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the synthesis steps and structure of 1,4-chloropropanol-piperazine.

[0023] Figure 2 The NMR spectrum of 1,4-chloropropanol-piperazine is shown.

[0024] Figure 3 This is the infrared spectrum of methacrylated polyethyleneimine. Detailed Implementation

[0025] The technical solutions 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0027] The raw materials and equipment used in the embodiments and comparative examples are described below:

[0028] Piperazine: 99%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0029] Epichlorohydrin: 99%, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0030] Carboxymethyl cellulose: Industrial grade, Hubei Zhonglong Kangcheng Fine Chemical Co., Ltd.;

[0031] Polyethylene glycol diglycidyl ether: molecular weight 400 g / mol, purchased from Tianjin Xiens Biochemical Technology Co., Ltd.;

[0032] Polyethyleneimine: Branched polyethyleneimine, average Mw ~ 25000, Shanghai Yuanye Biotechnology Co., Ltd.;

[0033] Methacrylic anhydride: 94%, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0034] Aluminum foil rubber-plastic sheet: thermal conductivity <0.034W / (m·K), Hebei Aomeisi Rubber & Plastic Insulation Materials Co., Ltd.

[0035] Composite geotextile: Polyester filament composite geotextile, 1mm thick, Shandong Xingzhao Environmental Technology Co., Ltd.

[0036] Flame-retardant canvas: 0.8mm thick, purchased from Angyang Refractory Materials Factory, Dacheng County.

[0037] Adhesive felt: absorbent needle-punched nonwoven fabric, 5mm thick, Weixian Runhua Felt Products Sales Co., Ltd.; 1m×1m;

[0038] 1,4-Chloropropanol-piperazine: 0.023 mol piperazine was dissolved in 18.2 ml of distilled water. The temperature was maintained at 25-35 °C using a water-ice bath. 0.046 mol epichlorohydrin was slowly added, and the mixture was stirred for 20 min. The water-ice bath was then removed, and the reaction was continued at 50 °C with stirring for 12 h to obtain 1,4-chloropropanol-piperazine. The 1H NMR spectrum is shown below. Figure 2 As shown.

[0039] Methacrylated polyethyleneimine 1: 4 mmol of vacuum-dried polyethyleneimine was added to a round-bottom flask and purged with argon for 30 min. Under argon protection, 300 mL of dichloromethane and 1 mL of triethylamine were added, and the mixture was stirred for 5 min to activate the primary and secondary amine groups of the polyethyleneimine. 0.1 mol of methacrylic anhydride was added, and the mixture was stirred continuously at room temperature under argon protection for 18 h. The mixture was then vacuum-dried for 12 h to remove residual dichloromethane. Unreacted methacrylic anhydride and triethylamine were removed by washing with deionized water and ethanol. After vacuum drying for 48 h, methacrylated polyethyleneimine 1 was obtained. The infrared spectrum is as follows: Figure 3 As shown, 1106cm -1 The CN stretching vibration corresponding to the secondary amine is 1307 cm⁻¹. -1 The corresponding CN stretching vibration and CH bending vibration of the primary amine, 1468 cm.-1 The corresponding NH bending vibration and CH2 shear vibration of the secondary amine are 1654 cm⁻¹. -1 and 1620cm -1 The peak at 1548 cm⁻¹ represents the stretching vibration of the C=O group in the amide group, confirming the formation of the amide group. -1 The peak at that point corresponds to the stretching vibration of CN. Furthermore, the peak at 3600-3200 cm⁻¹... -1 The broad absorption band in the range originates from the OH stretching vibrations of intramolecular and intermolecular hydrogen bonds, while the 2959-2825 cm⁻¹ range... -1 The vibrational bands between them correspond to the CH stretching vibrations of alkyl groups.

[0040] Methacrylated polyethyleneimine 2: Compared with methacrylated polyethyleneimine 1, the difference is that 0.1 mol of methacrylic anhydride is replaced with 0.04 mol of methacrylic anhydride;

[0041] Methacrylated polyethyleneimine 3: Compared with methacrylated polyethyleneimine 1, the difference is that 0.1 mol of methacrylic anhydride is replaced with 0.15 mol of methacrylic anhydride;

[0042] Methacrylated polyethyleneimine 4: Compared with methacrylated polyethyleneimine 1, the difference is that 0.1 mol of methacrylic anhydride is replaced with 0.02 mol of methacrylic anhydride;

[0043] Examples and Comparative Examples

[0044] A pH-responsive self-adhesive heat-insulating and moisture-retaining blanket, the preparation method includes the following steps.

[0045] (1) Dissolve carboxymethyl cellulose in 1.0M KOH alkaline solution to prepare a carboxymethyl cellulose solution with a concentration of 0.3 g / mL; dissolve methacrylated polyethyleneimine in distilled water to prepare a solution with a concentration of 0.1 g / mL; mix polyethylene glycol diglycidyl ether with 1,4-chloropropanol-piperazine solution;

[0046] (2) Carboxymethyl cellulose solution, methacrylated polyethyleneimine solution and crosslinking agent solution are premixed and stirred for 30 minutes to obtain hydrogel precursor solution. Then, the adhesive felt is completely immersed in the hydrogel precursor solution for 30 minutes for permeation and adsorption. After being taken out and drained, it is transferred to an oven and crosslinked at 80°C for 3 hours. After being taken out and cooled to room temperature.

[0047] (3) Flame-retardant canvas, aluminum foil rubber and plastic board, composite geotextile and adhesive felt hydrogel are bonded or sewn together in sequence, and then cut and sewed to obtain pH-responsive self-adhesive heat preservation and moisture retention blanket.

[0048] The composition and proportions of the hydrogel precursor solutions used in each embodiment and comparative example are shown in Table 1:

[0049] Table 1. Composition and number of parts (by weight) of the hydrogel precursor solution.

[0050]

[0051]

[0052] The following are the test methods for the performance parameters involved in this invention, and the test results are shown in Table 2:

[0053] 1. Water absorption and swelling capacity of the adhesive hydrogel layer: The adhesive hydrogel layer was soaked in buffer solutions with pH values ​​of 7 and 12 for 2 days to absorb water and swell. The surface moisture was removed with a paper towel, and the sample was weighed W1. Then, the sample was dried in an oven at 110℃ for 15 hours, and the dried sample was weighed W2. The water absorption and swelling capacity was calculated as SC=(W1-W2) / W2×100%.

[0054] 2. Moisturizing performance: The heat-insulating and moisturizing blankets prepared in the examples and comparative examples were soaked in water and swelled for 12 hours, then covered on concrete test blocks. The temperature was kept constant at 20±2℃. Three high-precision humidity sensors were evenly arranged on the surface of the concrete test blocks, and humidity data was recorded every 30 minutes for 7 days. The relative humidity on day 1, day 3 and day 7 was recorded.

[0055] 3. Crack condition of concrete: Use standard point line gauges, film rulers, comparison cards, and feeler gauges to measure the crack condition on day 7, and record the total length of the crack, the average length of the crack, and the maximum width of the crack.

[0056] Table 2 Performance tests of the examples and comparative examples

[0057]

[0058]

[0059] As can be seen from Examples 3-6 and Comparative Example 1, the water absorption and swelling capacity of polyethyleneimine after methacrylic acid esterification is significantly enhanced. However, excessive methacrylic acid modification can affect the crosslinking density of polyethyleneimine, thereby reducing the water absorption and swelling capacity of the adhesive hydrogel layer. The optimal water absorption and swelling effect can be achieved when the molar amount of methacrylic anhydride added is 10 to 30 times the molar amount of polyethyleneimine.

[0060] Examples 1-3 show that the ratio of methacrylated polyethyleneimine and carboxymethyl cellulose needs to be controlled at a certain level. At this ratio, the pH response of the thermal insulation blanket to absorb / dehydrate water matches the water requirements of the concrete hydration reaction, resulting in better thermal insulation and moisture retention. Comparative Example 3 shows that without the use of 1,4-chloropropanol-piperazine, the water absorption and swelling capacity and moisture retention performance of Comparative Example 3 are significantly reduced, and the concrete cracks are severe. This may be because the crosslinking network density is insufficient when only polyethylene glycol diglycidyl ether is used as a crosslinking agent, affecting the water absorption and retention capacity of the hydrogel.

[0061] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A pH value responsive self-adhesive heat-retaining and moisture-retaining blanket, characterized by, The heat and moisture preservation blanket is a multi-layer composite structure, from outside to inside, in turn is flame-retardant canvas, aluminum foil rubber plastic plate, composite geotextile and adhesive felt hydrogel layer;The adhesive felt hydrogel layer is a structure formed by impregnating the adhesive felt with a hydrogel precursor solution and then crosslinking it by heat, the hydrogel precursor solution comprises, by weight, 50-80 parts of methacrylated polyethyleneimine, 20-40 parts of carboxymethyl cellulose, 10-30 parts of polyethylene glycol diglycidyl ether, and 18-30 parts of 1,4-chloropropanol-piperazine, and the structural formula of the 1,4-chloropropanol-piperazine is shown as formula 1: Formula 1; The preparation method of the methacrylated polyethyleneimine is as follows: the polyethyleneimine is pre-dried in vacuum, dichloromethane and triethylamine are added under argon protection, the polyethyleneimine is dissolved and activated for a period of time, methacrylic anhydride is added, and the mixture is continuously stirred at room temperature for 12-20 hours under argon protection, and then the methacrylated polyethyleneimine is obtained after purification and drying, the molar amount of the methacrylic anhydride added is 10-30 times the molar amount of the polyethyleneimine, and the polyethyleneimine is branched polyethyleneimine with a weight average molecular weight of 10,000-50,000 g / mol.

2. The pH-responsive self-adhesive thermal and moisture retention blanket according to claim 1, wherein, The adhesive felt is a hydrophilic adhesive felt, and the hydrophilic adhesive felt is a water-absorbing needle-punched non-woven fabric.

3. The self-adhesive temperature and moisture retaining blanket according to claim 1, wherein the adhesive layer is a pH responsive adhesive layer. The preparation method of the 1,4-chloropropanol-piperazine is as follows: 1 equivalent of piperazine is dissolved in distilled water, 2-2.2 equivalents of epichlorohydrin are added at 25-35℃, and the mixture is continuously stirred at 50-60℃ for 12-24 hours to obtain the product.

4. The pH-responsive self-adhesive thermal and moisture retention blanket of claim 1, wherein, The polyethylene glycol diglycidyl ether has a weight average molecular weight of 400-600 g / mol.

5. The preparation method of the pH value responsive self-adhesive thermal and moisture retention blanket according to any one of claims 1-4, characterized in that, The method comprises the following steps: (1) mixing the carboxymethyl cellulose solution, the methacrylated polyethyleneimine solution, the polyethylene glycol diglycidyl ether, and the 1,4-chloropropanol-piperazine solution to obtain a hydrogel precursor solution, then completely immersing the adhesive felt in the hydrogel precursor solution for a period of time, draining the solution after taking out the adhesive felt, and then transferring the adhesive felt to an oven for crosslinking reaction at 60-80℃ for 3-5 hours, and then taking out the adhesive felt and cooling it to room temperature; (2) sequentially bonding or sewing the flame-retardant canvas, the aluminum foil rubber plastic plate, the composite geotextile, and the adhesive felt hydrogel, and then cutting and hemming to obtain the pH value responsive self-adhesive heat and moisture preservation blanket.

6. The pH value responsive self-adhesive heat and moisture preservation blanket according to any one of claims 1-4 is used in agricultural irrigation, geological remediation, and building heat preservation.

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