Super-stable water-based foam containing nanocellulose as well as preparation method and application of super-stable water-based foam

Abstract

The invention belongs to the field of chemical engineering, and discloses nano-cellulose-containing super-stable water-based foam and a preparation method and application thereof.The nano-cellulose-containing super-stable water-based foam is prepared from, by mass, 0.1-2.0 parts of nano-cellulose hydrogel, 0.5-5.0 parts of lauryl sodium sulfate, 1.0-5.0 parts of tetradecanol, 0.1-3.0 parts of polyvinyl alcohol and the balance water on the basis that the total mass of compound water-based foam is 100 parts; the components are stirred at a high speed to generate foam, and the super-stable water-based foam containing the nanocellulose is prepared. According to the super-stable foam mulching film disclosed by the invention, the processes of drainage, coalescence and disproportionation can be effectively slowed down after the nano cellulose, the tetradecanol and the polyvinyl alcohol are added, so that the foam has super-long service life and can be stabilized for more than 20 days. The water-based foam has good environmental adaptability and renewability, a multi-layer foam system is more stable than foam of a single-layer film, and the water-based foam is used as a foam mulching film and has better water retention, humidification and heat preservation effects.

Description

Technical Field

[0001] The invention belongs to the field of chemical industry, and specifically relates to an ultra-stable water-based foam containing nanocellulose, and a preparation method and application thereof. Background Art

[0002] Foam systems are widely used in many fields such as daily chemicals, fire protection, mineral flotation, petrochemicals, and oil production (such as foam flooding of oil reservoirs). However, foams are usually unstable systems because film drainage, bubble aggregation and disproportionation will definitely occur, thereby reducing the free energy of the entire system. For better foam stability, surfactants, polymers, proteins, or surface-active solid particles are usually added to the foam system. However, despite the easy and rapid movement to the gas-liquid interface by adding surfactants, the high viscosity of the foam film when adding proteins and polymers, or the elastic layer formed by the aggregation of surface-active solid particles, these additives cannot effectively prevent the decay of bubbles; the space occupied by the foam liquid film will spontaneously decrease to reduce the overall surface free energy of the system and maintain its own stability. From a long-term perspective, the collapse of the foam is irreversible. The instability of the foam system has always been a key factor restricting its application. Current foam stabilizers mainly include high molecular polymers and solid-phase nanomaterials, but there are still problems such as poor material performance, high cost and limited sources.

[0003] In modern agricultural production, mulching technology is widely used to increase soil temperature, maintain soil moisture, inhibit weed growth and improve the crop growth environment. Traditional mulch materials mainly include plastic films such as polyethylene and polyvinyl chloride. While these materials play a role, they also bring a series of environmental and ecological problems. Plastic mulch is not easy to degrade. Long-term residue in the soil will cause soil structure damage and microplastic pollution, which will have a negative impact on crops and the ecological environment.

[0004] To solve this problem, degradable mulch has received extensive attention. A liquid foam mulch with soil improvement function was prepared by emulsification method, which can be used as a sprayable green substitute for petroleum-based plastic mulch and a soil remediator for degraded soil. At present, there is no report on the use of water-based foam as foam mulch. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide an ultra-stable water-based foamed mulch containing nanocellulose and a preparation method thereof. The water-based foamed mulch prepared by the present invention has high foaming property, strong stability, simple preparation process, and is easy to mass produce.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] The invention discloses an ultra-stable water-based foam containing nanocellulose, which comprises the following components by mass fraction: based on 100 parts of the total mass of the composite water-based foam, 0.1-2.0 parts of nanocellulose hydrogel, 0.5-5.0 parts of sodium dodecyl sulfate (SDS), 1.0-5.0 parts of tetradecanol (TDA), 0.1-3.0 parts of polyvinyl alcohol (PVA), and the balance is water; the above components are stirred at high speed to generate foam, so as to prepare the ultra-stable water-based foam.

[0008] Preferably, the nanocellulose contained in the nanocellulose hydrogel has a length of 500-1000 nm and a diameter of 3-5 nm.

[0009] Preferably, the alcoholysis degree of the polyvinyl alcohol is 88%-100%.

[0010] Preferably, the mass ratio of sodium dodecyl sulfate, tetradecanol, polyvinyl alcohol and nanocellulose hydrogel is (2.5-5.0):2.0:(0.5-2.0):(0.5-1.5).

[0011] The method for preparing the ultra-stable water-based foam comprises the following steps:

[0012] (1) mixing sodium dodecyl sulfate and tetradecanol in water and heating to uniformly disperse all the solutes, cooling and stirring at high speed to obtain an SDS / TDA foam system;

[0013] (2) adding polyvinyl alcohol to the above foam system, dissolving it completely, and stirring at high speed;

[0014] (3) Adding the nanocellulose hydrogel to the foam system of step (2), mixing evenly, and stirring at high speed to obtain an ultra-stable water-based foam containing nanocellulose.

[0015] Preferably, the high-speed stirring conditions in steps (1) to (3) are all mechanical stirring, with a rotation speed of 1000-1500 rpm and a time of 5-10 min.

[0016] Preferably, the heating condition in step (1) is heating at 60±10°C for 20±10 min.

[0017] Application of the ultra-stable water-based foam containing nanocellulose in foam mulch.

[0018] Preferably, the ultra-stable water-based foam can be sprayed onto the soil or water surface by high-pressure spraying to form a foam mulch.

[0019] The ultra-stable water-based foam containing nanocellulose is formed by multi-layer foam. The present invention evenly disperses nanocellulose in a water-based foam system, significantly improving the poor stability and low foaming rate of the foam. This is because nanocellulose has a very high specific surface area, which can provide a large number of adsorption sites, promote the effective adsorption of surfactant molecules, thereby reducing the surface tension of the liquid, which is conducive to the formation and stability of the foam. In addition, when nanocellulose is dispersed in a liquid medium, they can be intertwined to form a three-dimensional network structure. This structure provides additional mechanical strength for the foam, preventing the foam from easily breaking when subjected to external forces. The hydroxyl groups on the surface of nanocellulose give it a good affinity with water molecules, which can enhance the liquid film strength in the foam, reduce the discharge speed of the liquid, and thus extend the life of the foam. The multi-layer foam system of the present invention is more stable than the foam of a single-layer film, because the multi-layer foam can usually withstand a higher threshold of air pressure fluctuations. And even if one layer of the film breaks, the other layers can become stable while the foam structure remains unchanged, thereby forming an ultra-stable system.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) The ultra-stable foam mulch of the present invention can effectively slow down the drainage, aggregation and disproportionation processes by adding nanocellulose (NCF), tetradecyl alcohol (TDA) and polyvinyl alcohol (PVA), so that the foam has an ultra-long life and can be stable for more than 20 days.

[0022] (2) Nanocellulose is abundant in sources and completely biodegradable. Adding a small amount can improve foam stability and foaming rate, while reducing the amount of chemical emulsifiers used, which is beneficial to ecological environmental protection.

[0023] (3) The water-based foam of the present invention has good environmental adaptability and renewability. Gas, such as CO2 gas fertilizer, can be added to the foam film at a later stage, and the foam film can also float in paddy fields. The multi-layer foam system of the present invention is more stable than the foam of a single-layer film. When used as a foam mulch, the composition ratio can be adjusted according to the plant growth cycle to regulate the degradation cycle of the foam mulch, and the foam mulch has better water retention, humidification and heat preservation effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a macroscopic photograph of the foam prepared in Example 1-3 after being left to stand for 2 hours.

[0025] Figure 2 This is a macroscopic photograph of the foam obtained in Example 4-6 after being left to stand for 2 hours.

[0026] Figure 3 This is a macroscopic photograph of the foam prepared in Comparative Example 1 after being left to stand for 2 hours.

[0027] Figure 4 These are macroscopic photographs of the foam prepared in Example 4 after standing for 0 h (a), 24 h (b), 158 h (c), and 501 h (d).

[0028] Figure 5 is macroscopic photographs of the foam obtained in Example 5 after standing for 0 hours (a), 141 hours (b), 309 hours (c), 497 hours (d), and 640 hours (e), respectively; wherein the left picture is a picture of the overall state, and the right picture is an enlarged picture of the surface.

[0029] Figure 6 These are macroscopic photographs of the foam prepared in Comparative Example 1 after standing for 0 hour (left) and one week (right). DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0031] If no specific conditions are specified in the examples and comparative examples of the present invention, the reactions were carried out according to conventional conditions or conditions recommended by the manufacturer.

[0032] All raw materials, reagents, etc., whose manufacturers are not specified, are conventional products that can be purchased commercially. The nanocellulose hydrogel in the examples was purchased from Henan Kegao Radiation Chemical Technology Co., Ltd., specifically nanocellulose fiber hydrogel (concentration of 2wt%), tetradecanol (TDA, purity>99%), sodium dodecyl sulfate (SDS, purity>99%) and polyvinyl alcohol (PVA-1799, degree of polymerization 1700, degree of alcoholysis: 99.8-100%) were purchased from Aladdin Company.

[0033] Example 1

[0034] (1) Weigh 0.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60°C for 20 min to ensure that all solutes are evenly dispersed; after cooling, the solution is rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0035] (2) 0.5 parts of PVA was added to the SDS / TDA foam system. After the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 min at 25° C. by mechanical stirring to generate foam.

[0036] (3) Accurately weigh 0.5 parts of nanocellulose hydrogel and add it to the above mixed solution, and quickly stir the solution at a speed of 1500 rpm at 25° C. for 10 minutes by mechanical stirring to obtain an ultra-stable water-based foam containing nanocellulose.

[0037] According to experimental determination, the foaming rate of the water-based foam prepared in Example 1 is 84%.

[0038] Example 2

[0039] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60°C for 20 min to ensure that all solutes are evenly dispersed; after cooling, the solution is rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0040] (2) 0.5 parts of PVA was added to the SDS / TDA foam system. After the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 min at 25° C. by mechanical stirring to generate foam.

[0041] (3) Accurately weigh 0.5 parts of nanocellulose hydrogel and add it to the above mixed solution, and quickly stir the solution at a speed of 1500 rpm at 25° C. for 10 minutes by mechanical stirring to obtain an ultra-stable water-based foam containing nanocellulose.

[0042] According to experimental determination, the foaming rate of the water-based foam prepared in Example 1 is 89%.

[0043] Example 3

[0044] (1) 5.0 parts of SDS and 2.0 parts of TDA were weighed into deionized water and heated at 60°C for 20 min to ensure that all solutes were evenly dispersed; after cooling, the solution was rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0045] (2) 0.5 parts of PVA was added to the SDS / TDA foam system. After the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 min at 25° C. by mechanical stirring to generate foam.

[0046] (3) Accurately weigh 0.5 parts of nanocellulose hydrogel and add it to the above mixed solution, and quickly stir the solution at a speed of 1500 rpm at 25° C. for 10 minutes by mechanical stirring to obtain an ultra-stable water-based foam containing nanocellulose.

[0047] According to experimental determination, the foaming rate of the water-based foam prepared in Example 1 is 92%.

[0048] Example 4

[0049] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60°C for 20 min to ensure that all solutes are evenly dispersed; after cooling, the solution is rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0050] (2) 0.5 parts of PVA was added to the SDS / TDA foam system. After the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 min at 25° C. by mechanical stirring to generate foam.

[0051] (3) Accurately weigh 1.0 part of nanocellulose hydrogel and add it to the above mixed solution. Rapidly stir the solution at a speed of 1500 rpm at 25° C. for 10 min by mechanical stirring to obtain an ultra-stable water-based foam containing nanocellulose.

[0052] According to experimental determination, the foaming rate of the water-based foam prepared in Example 1 is 90%.

[0053] Example 5

[0054] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60°C for 20 min to ensure that all solutes are evenly dispersed; after cooling, the solution is rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0055] (2) 0.5 parts of PVA was added to the SDS / TDA foam system. After the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 min at 25° C. by mechanical stirring to generate foam.

[0056] (3) Accurately weigh 1.5 parts of nanocellulose hydrogel and add it to the above mixed solution. Rapidly stir the solution at a speed of 1500 rpm at 25° C. for 10 min by mechanical stirring to obtain an ultra-stable water-based foam containing nanocellulose.

[0057] According to experimental determination, the foaming rate of the water-based foam prepared in Example 1 is 95%.

[0058] Example 6

[0059] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60°C for 20 min to ensure that all solutes are evenly dispersed; after cooling, the solution is rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0060] (2) 2.0 parts of PVA was added to the SDS / TDA foam system. After the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 min at 25° C. by mechanical stirring to generate foam.

[0061] (3) Accurately weigh 1.5 parts of nanocellulose hydrogel and add it to the above mixed solution. Rapidly stir the solution at a speed of 1500 rpm at 25° C. for 10 min by mechanical stirring to obtain an ultra-stable water-based foam containing nanocellulose.

[0062] According to experimental determination, the foaming rate of the water-based foam prepared in Example 1 is 88%.

[0063] Comparative Example 1

[0064] (1) Weigh 2.5 parts of SDS and 2.0 parts of TDA in deionized water and heat at 60°C for 20 min to ensure that all solutes are evenly dispersed; after cooling, the solution is rapidly stirred at 1200 rpm at 25°C for 5 min to generate foam, thereby obtaining an SDS / TDA foam system.

[0065] (2) 0.5 parts of PVA was added to the SDS / TDA foam system, and after the PVA was completely dissolved, the solution was rapidly stirred at 1200 rpm for 5 minutes at 25° C. by mechanical stirring to generate foam. Thus, a water-based foam without nanocellulose was obtained.

[0066] According to experimental determination, the foaming rate of the water-based foam prepared in Comparative Example 1 is ˜65%.

[0067] The water-based foams prepared in Examples 1-6 and Comparative Example 1 were analyzed and measured by the following methods: (1) Determination of foam foaming rate: The foaming rate was calculated by the following equation:

[0068] Overrun = (V f -V s ) / V s

[0069] Among them, V f and V s represent the volume of foam after stirring and the initial volume respectively.

[0070] Short-term drainage rate: Short-term drainage rate refers to the percentage of liquid volume discharged within 2 hours after foaming to the initial volume after foaming.

[0071] Short-term drainage rate ε=V / V1*100, where V is the drainage volume and V1 is the foam volume.

[0072] The stability of the foam is measured by the short-term drainage rate of the foam. A drainage rate of less than 8% (volume ratio) indicates "very good" stability, a drainage rate of 8%-10% (volume ratio) indicates "very good" stability, a drainage rate of 10%-12% (volume ratio) indicates "good" stability, and a drainage rate greater than 15% (volume ratio) indicates "poor" stability.

[0073] Table 1

[0074]

[0075] According to the data in Table 1, by Examples 3-5 (combined Figure 1 and Figure 2 ) It can be seen that with the increase of NCF addition, the foaming rate of the foam continues to increase. This is because nanocellulose has a high specific surface area, which can provide a large number of adsorption sites, promote the effective adsorption of surfactant molecules, reduce the surface tension of the liquid, and is conducive to the formation and stability of foam. According to Example 4-5 ( Figure 2 ) and Comparative Example 1 ( Figure 3 ) results show that the addition of nanocellulose is beneficial to improving the stability and density of the foam. This is because nanocellulose can reduce the surface tension of the liquid, promote the formation and stability of bubbles, and the adsorption effect on the gas-liquid interface helps to stabilize the bubbles and prevent them from merging or bursting too quickly. In addition, the surface of nanocellulose contains a large number of hydroxyl groups, which are easy to combine with water, which can increase the viscosity of the foam and make the formed foam dense. According to Examples 3 and 4 ( Figure 1 and Figure 2 ) results show that the addition of nanocellulose can reduce the amount of emulsifier SDS used without affecting the stability of the foam.

[0076] In order to test the long-term stability of the foam, experiments were conducted using Examples 4 and 5 and Comparative Example 1 as examples. The experimental results are as follows:

[0077] Macroscopic photos of the foam were taken with a Sony TX-10 camera after 0 hours (a), 24 hours (b), 158 hours (c), and 501 hours (d). Figure 4 (Example 4) The foam just prepared is about 1400 ml of foam, which is fine and evenly distributed in a milkshake-like state (a). One day later, a foam layer with a larger pore size is observed on the surface, which is about 0.1 cm thick and has no water leakage (b). After 158 hours, the foam is still stable, with 100 ml of thin foam on the upper layer and the rest of the foam dense (c). After 501 hours, 600 ml of thin foam is still left (d). It can be seen that the foam prepared by the present invention can be stable for more than 20 days.

[0078] As can be seen from Figure 5 (Example 5), after 0 hours of storage, the foam is fine and yogurt-like, 1250 ml (a). After 141 hours, it was stored for about six days, and there was a slightly dry foam film on the upper layer, 1250 ml (b). After 309 hours, it was stored for about 13 days, and the upper film was slightly concave, and the thickness became a little wider, 1250 ml (c). After 497 hours, about 20 days, it was relatively stable as a whole, and the upper film was broken (d). After 640 hours, about 26 days, only 600 ml of dense foam remained, the film was separated from the foam, and there was about 80 ml of thin foam on the upper layer (e). The upper film was very strong, which may be caused by air drying in contact with air.

[0079] from Figure 6 (Comparative Example 1) It can be seen that the foam stability is poor. After standing for a week, the water output is relatively high, there is a film on the surface, and the foam is small and relatively dispersed.

[0080] In summary, in the SDS / DDA / PVA / NCF system, the addition of NCF / PVA strengthens the hydrogen bonds between water and solvent molecules, and the distribution intensity of bound water near the sulfur atom and sodium ion of the sulfonic acid group of SDS increases significantly. In addition, the addition of NCF can enhance the gas-liquid interface and improve the density of molecules in the network. This leads to a decrease in the gas diffusion rate and stabilizes the foam system. At the same time, compared with the single-layer film foam structure formed by SDS emulsified foam, the multi-layer film structure is conducive to the balance of air pressure between the air layers in the system, and has a higher fluctuation threshold than the single-layer film structure, which is conducive to the formation of ultra-stable foam.

[0081] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An ultra-stable water-based foam containing nanocellulose, characterized in that: The invention comprises the following components by mass fraction: based on 100 parts of the total mass of the composite water-based foam, 0.1-2.0 parts of nanocellulose hydrogel, 0.5-5.0 parts of sodium lauryl sulfate, 1.0-5.0 parts of tetradecanol, 0.1-3.0 parts of polyvinyl alcohol, and the balance is water; the above components are stirred at high speed to generate foam, so as to obtain ultra-stable water-based foam containing nanocellulose.

2. The ultra-stable water-based foam according to claim 1, characterized in that The nanocellulose contained in the nanocellulose hydrogel has a length of 500-1000 nm and a diameter of 3-5 nm.

3. The ultra-stable water-based foam according to claim 1, characterized in that The alcoholysis degree of the polyvinyl alcohol is 88%-100%.

4. The ultrastable water-based foam according to claim 1, 2 or 3, characterized in that: The mass ratio of the sodium dodecyl sulfate, tetradecanol, polyvinyl alcohol and nanocellulose hydrogel is (2.5-5.0):2.0:(0.5-2.0):(0.5-1.5).

5. The method for preparing the ultrastable water-based foam according to any one of claims 1 to 4, characterized in that: The steps include: (1) mixing sodium dodecyl sulfate and tetradecanol in water and heating to uniformly disperse all the solutes, cooling and stirring at high speed to obtain an SDS / TDA foam system; (2) adding polyvinyl alcohol to the above foam system, dissolving it completely, and stirring at high speed; (3) Adding the nanocellulose hydrogel to the foam system of step (2), mixing evenly, and stirring at high speed to obtain an ultra-stable water-based foam containing nanocellulose.

6. The preparation method according to claim 5, characterized in that: The high-speed stirring conditions in steps (1) to (3) are all mechanical stirring, with a rotation speed of 1000-1500 rpm and a time of 5-10 min.

7. The preparation method according to claim 5 or 6, characterized in that: The heating condition of step (1) is heating at 60±10°C for 20±10min.

8. Use of the ultra-stable water-based foam containing nanocellulose according to any one of claims 1 to 4 in foam mulch.

9. The use according to claim 8, characterized in that: Ultra-stable water-based foam is sprayed onto the soil or water surface through high-pressure spray to form a foam film.

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