Grapevine powder bio-based polyurethane foam as well as preparation method and application thereof

Abstract

The invention discloses grapevine powder bio-based polyurethane foam as well as a preparation method and application thereof, and belongs to the field of grapevine heat-preservation and cold-proof materials. The invention aims to solve the technical problem of low resource utilization efficiency of wastes after grape branches are cut. The grape vine powder bio-based polyurethane foam (BPUF) is prepared by polymerizing polyethylene glycol-400 (PEG-400), glycerol (glycerol) and an alcohol-based compound obtained by liquefying grape vine powder. The heat-preservation cold-proof material is applied to wrapping grape branches, effective heat-preservation cold-proof measures and technical guidance are provided for the grape planting industry in vast areas to the north of the north latitude of 35 degrees, and sustainable development of the local grape industry is promoted.

Description

Technical Field

[0001] The invention belongs to the field of grapevine heat-insulating and cold-proof materials, and specifically relates to a grapevine powder bio-based polyurethane foam, a preparation method and application thereof. Background Art

[0002] Grapes (Vitis vinifera L.), a prominent member of the Vitaceae family, are widely cultivated in China and are considered the country's second-largest cultivated fruit tree. Their importance is self-evident. Grapes possess both ornamental and edible value, with their fruit being used in a variety of processes, including winemaking, raw consumption, juice extraction, and raisin production. These uses have made grapes an indispensable part of human life, satisfying both palate and nutritional needs in diverse forms.

[0003] Overwintering frost damage is a common winter phenomenon for plants. Prolonged exposure to low temperatures causes plants to lose their ability to function normally, resulting in severe damage or even death. In cold winter conditions, low-temperature stress severely impacts plants, inhibiting physiological activity within their cells and affecting their normal growth and development. In recent years, with climate change, the expansion of fruit production, and the increasing randomness of extreme low-temperature events, overwintering frost damage to fruit trees has become increasingly severe.

[0004] When studying the causes of winter frost damage in grapevines, climate conditions are crucial. Climate differences between regions directly impact the susceptibility of vineyards to frost damage. Generally speaking, low temperatures and dry climates are more likely to lead to frost damage, while humid climates are less likely. Furthermore, factors such as altitude, topography, and vegetation cover also influence winter frost damage, requiring targeted research and analysis. In addition to climate, the physiological characteristics of the grapevine itself are also a significant factor in frost damage. The cold resistance of grapevines varies depending on the variety, growth stage, and environmental conditions. Some varieties may be more susceptible to low temperatures, while others are better able to withstand cold weather. Understanding the physiological characteristics of grapevines in winter can help select grape varieties suited to local climate conditions, thereby reducing the risk of frost damage. Furthermore, vineyard management and cultivation techniques also play a crucial role in the occurrence of winter frost damage. Proper pruning, fertilization, and irrigation management can enhance the growth and disease resistance of grapevines, thereby reducing the severity of frost damage. Furthermore, techniques such as mulching, artificial heating, and ventilation can also, to a certain extent, prevent or mitigate winter frost damage. These studies provide a scientific basis for developing effective protective measures and cultivation management strategies, and are of great significance to the sustainable development of the grape industry.

[0005] my country is a major grape-growing country, with wine grapes primarily planted in northern regions like Xinjiang, Ningxia, Inner Mongolia, Gansu, Shaanxi, Shandong, and Heilongjiang. During the cold northern winters, burying vines in the ground or covering them with materials is crucial for keeping grapes safe over the winter. Thermal blankets and cold-weather blankets offer superior insulation compared to traditional plastic film and burying them in the ground. Wine grapes have a weak tolerance for cold weather, making wintering a significant challenge in the vast areas north of 35°N.

[0006] Warm temperate monsoon climate regions boast abundant rainfall, fertile soil, and flat terrain, making them ideal for grape cultivation and facilitating mechanized planting, greatly improving production efficiency. However, the impact of winter weather presents a major challenge for growers. Winters are cold and dry, with frequent bouts of severe cold weather. These frigid conditions impact the normal growth and development of grapes, requiring growers to implement a range of countermeasures. Currently, methods such as soil burial, covering with film or insulation blankets, or a combination of soil burial and insulation film, are widely used to protect grapevines from the cold during the winter in northern China. While some of these methods offer some promising results, the materials involved are all non-degradable, petroleum-based.

[0007] Grape branches are a natural lignin-based fiber, containing cellulose, hemicellulose, and lignin, which are rich in hydroxyl groups. These chemical components can be converted into polyols through catalytic degradation, which serve as building blocks for chemical and industrial applications. However, the current resource utilization efficiency of grape branch waste is low, with the waste typically being incinerated or discarded in rural areas, failing to realize its full potential. Summary of the Invention

[0008] The present invention aims to solve the technical problem of low resource utilization efficiency of waste after grape branch cutting, and provides a grapevine powder bio-based polyurethane foam and a preparation method and application thereof.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] The object of the present invention is to provide a method for preparing grapevine powder bio-based polyurethane foam, comprising the following steps:

[0011] Step 1: clean the grape branches with water, air-dry them, and then dry them to a constant weight. Then, crush them and sieve them to obtain grape branch chips.

[0012] Step 2: Mix grapevine branch chips with polyethylene glycol 400 and glycerol, heat to 150°C under mechanical stirring, slowly add concentrated sulfuric acid, continue to stir at constant temperature for liquefaction, quickly cool to room temperature, and vacuum filter;

[0013] Step 3, adding a chain extender, a foam stabilizer, a catalyst and stannous octoate to the filtrate obtained in step 2, stirring until uniform, adding grape branch chips, continuing to stir, quickly adding a foaming agent, continuing to stir, and evenly pouring into a mold, allowing free foaming at room temperature, and ripening at room temperature to obtain the foam;

[0014] It is further defined that in step 1, the product is passed through a 60-mesh sieve.

[0015] It is further defined that in step 2, the liquefaction treatment time is 60 minutes.

[0016] It is further defined that in step 2, the mass ratio of polyethylene glycol 400, glycerol and grape tree branches and cuttings is (4-12):2:1, preferably, the mass ratio of polyethylene glycol 400, glycerol and grape tree branches and cuttings is 8:2:1.

[0017] It is further defined that in step 2, the amount of concentrated sulfuric acid added is 3 wt% to 9 wt%; preferably, the amount of concentrated sulfuric acid added is 5 wt%.

[0018] It is further defined that in step 2, ethylene glycol is used instead of glycerol.

[0019] It is further defined that in step 3, the catalyst is triethylenediamine A33.

[0020] It is further defined that in step 3, the chain extender is 1,4-butanediol (BDO).

[0021] It is further defined that in step 3, the foam stabilizer is silicone oil L-580.

[0022] It is further defined that in step 3, the foaming agent is polymeric MDI.

[0023] It is further defined that in step 3, the mass ratio of the filtrate to the chain extender, foam stabilizer, catalyst, and stannous octoate is 100:(3-4):2:0.3:0.5, and preferably, the mass ratio of the filtrate to the chain extender, foam stabilizer, catalyst, and stannous octoate is 100:3:2:0.3:0.5.

[0024] It is further defined that in step 3, the isocyanate index is controlled at 0.95-1.05, preferably at 1.05.

[0025] It is further defined that in step 3, the amount of grape branch chips added is 15 wt% to 20 wt%.

[0026] It is further defined that the ripening treatment time is 24 hours.

[0027] The present invention provides a grapevine powder bio-based polyurethane foam prepared by any of the above methods.

[0028] A heat-insulating and cold-proof material prepared by any of the above methods for wrapping grape branches, or the above grapevine powder bio-based polyurethane foam for wrapping grape branches.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] Since the BPUF in the present invention is polymerized from polyethylene glycol-400 (PEG-400), glycerin (glycerol), and liquefied grapevine powder, if foaming is performed simply according to the rigid polyurethane foaming method, the foaming and gelling processes will not be coordinated and balanced, resulting in collapse in the later stages of foaming and failing to achieve the desired foaming effect.

[0031] The grapevine powder bio-based polyurethane foam (BPUF) prepared by the method of the present invention has a certain cold-proof effect, and when the addition amount of the grapevine powder is 20%, the cold-proof effect of the BPUF is the best.

[0032] The method of the invention provides effective heat preservation and cold prevention measures and technical guidance for the grape planting industry in a large area north of 35° north latitude, thereby promoting the sustainable development of the local grape industry.

[0033] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the accompanying drawings. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Scanning electron micrographs of grape branch powder-filled composite BPUFs: (a) sample without grape branch powder; (b) sample with 15% grape branch powder addition; (c) sample with 20% grape branch powder addition.

[0035] Figure 2 is the change of electrical conductivity of grape branches under low temperature stress;

[0036] Figure 3 It is the change of soluble sugar in grape branches under low temperature stress;

[0037] Figure 4 It is the change of soluble protein in grape branches under low temperature stress;

[0038] Figure 5 is the change of MDA in grape branches under low temperature stress;

[0039] Figure 6 is the change of CAT in grape branches under low temperature stress;

[0040] Figure 7It is the change of POD of grape branches under low temperature stress. DETAILED DESCRIPTION

[0041] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art further understand the present invention and are not intended to limit the present invention in any way. It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention. These modifications and improvements are all within the scope of protection of the present invention.

[0042] Example 1: The method for preparing grapevine powder bio-based polyurethane foam in this example comprises the following steps:

[0043] Step 1: Rinse the grape branches thoroughly with tap water, dry them in an electric blast drying oven, and dry them to a constant weight. Use a grinder to crush the dried grape branches into powder, and then pass it through a 60-mesh sieve to obtain grape branch chips.

[0044] Step 2: Mix grapevine branches with polyethylene glycol 400 and glycerol, raise the temperature to 150° C. while mechanically stirring, slowly add concentrated sulfuric acid (concentration of 98.3 wt.%), continue to liquefy at constant temperature and stirring after adding concentrated sulfuric acid for 1 hour, quickly cool to room temperature, and vacuum filter at 0.1 MPa;

[0045] The mass ratio of polyethylene glycol 400, glycerol and grape shavings is 8:2:1, and the amount of concentrated sulfuric acid accounts for 5wt% of the total amount of polyethylene glycol 400, glycerol and grape shavings.

[0046] Step 3: Add chain extender, foam stabilizer, catalyst and stannous octoate to the filtrate obtained in step 2 in a mass ratio of 100:3:2:0.3:0.5, and heat at 800 r min. -1 The mixture was stirred with an electric stirrer at a speed of 800 r·min until uniform, and the grape branch chips obtained in step 1 (the addition amount was 20wt%) were added. -1 At a speed of 800 r·min, stir continuously with an electric stirrer for 1 minute, quickly add the foaming agent, and stir at 800 r·min -1 The mixture was stirred continuously for 1 minute with an electric stirrer at a speed of 1000 nm, poured evenly into a mold, foamed freely at room temperature, and matured at room temperature for 24 hours to obtain the foam (BPUF);

[0047] In step 3, the catalyst is triethylenediamine A33, the chain extender is 1,4-butanediol (BDO), the foam stabilizer is silicone oil L-580, and the foaming agent is polymerized MDI.

[0048] The density of the foamed BPUF obtained in this example is 62.37 / kg·m -3 .

[0049] The following experiments were used to verify the effect of the invention

[0050] The field experiment was conducted in the Shigezhuang experimental field in Changli District, Qinhuangdao City, Hebei Province from October 2022 to August 2023, and the indoor experiment was conducted in the laboratory of Hebei Science and Technology Normal University.

[0051] On October 20, 22, and 24, 2022, three visits were made to the base to collect test samples. The number of branches collected each time was 48, and four one-year-old branches with a length of about 30 cm were cut from each plant, with more than three full buds on each branch. The sampling branches were required to be uniform in thickness, well-grown, and free of mechanical damage or pests and diseases. Each plant was divided into three parts, with 16 branches in each part. Vaseline was applied to the end of each branch, and then wrapped with plastic film to prevent moisture loss. It was then placed in a ziplock bag, marked, and finally placed in an insulated box and taken back to the laboratory for subsequent testing.

[0052] Branches wrapped in different insulation materials were cryogenically frozen using a low-temperature freezer. The experiment employed a gradient of low-temperature treatments, including -5°C, -10°C, -15°C, -20°C, and -25°C. Each cooling step was reduced in increments of 5°C, gradually decreasing from 4°C to the preset treatment temperature. After reaching the target temperature, the branch samples were maintained at that temperature for 24 hours to simulate the low-temperature stress that can occur in a real-world environment.

[0053] The scanning electron microscopy image of BPUF prepared in this example is as follows Figure 1 As shown, from Figure 1 It can be seen that the overall porous structure is supported by the porous structure composed of the polymer wall membrane, and its performance depends on the size, uniformity and morphology of the porous structure. Figure 1 As can be seen, the cell shapes of all three samples are approximately round or hexagonal, with a relatively regular structure and relatively uniform pore size. The product containing grape branch powder exhibits a higher closed-cell ratio. During the BPUF reaction, the addition of grape branch powder solids results in a higher number of bubbles trapped within the foam due to the heat absorption effect during foaming. As the amount of grape branch powder added increases, the bubbles become finer and more uniform. This indirectly adjusts the internal temperature and pressure during the reaction, effectively preventing large-scale cell wall breakage. However, without the addition of grape branch powder, the temperature and pressure within the foam rise too quickly, damaging the foam walls and creating numerous holes, making insulation ineffective. Therefore, composite BPUF materials containing grape branch powder can be used to protect grapevines from the cold during winter.

[0054] Changes in electrical conductivity of grape branches under low temperature stress Figure 2 As shown, from Figure 2 As can be seen from the data, during the cooling process from -5 to -25°C, the relative conductivity of all treated branches showed an overall upward trend. Throughout the cooling process, the relative conductivity increases of the three types of branches varied. The conductivity increases were smaller for branches wrapped with 20% filler material and 15% filler material, while the conductivity increase was greatest for branches wrapped with no filler material. The conductivity increases for the three different treatments (no filler material wrapping, 20% filler material wrapping, and 15% filler material wrapping) were 29.59%, 22.64%, and 25.10%, respectively.

[0055] The accumulation of soluble sugars in grape tissues can prevent damage to the plants caused by low temperatures. Figure 3 As shown, under low temperature stress, the soluble sugar content in grape branches under various treatments showed significant changes. As the temperature gradually decreased from -5°C to -25°C, the soluble sugar content in all treatments experienced an initial increase followed by a decrease. Notably, the peak temperatures reached by the different treatments varied significantly, and the soluble sugar content varied significantly among the treatments. Previous studies have shown that plants with high cold tolerance experience relatively small increases in soluble sugar content under low temperature conditions. This is consistent with the data in this study, indicating that treatments with smaller increases in soluble sugar content exhibited greater cold tolerance. Branches wrapped with 20% filler material showed the smallest increase in soluble sugar content under low temperature stress, at 0.2261 mg / g. Branches wrapped with 15% filler material showed an intermediate increase, at 0.2563 mg / g. The unwrapped treatment showed the largest increase, at 0.2875 mg / g.

[0056] Under low temperature stress, plants will increase the water content of cells by adjusting protein content, thereby increasing the plant's cold resistance. Figure 4 As shown, as the temperature dropped, the soluble protein content of all samples showed a trend of first increasing and then decreasing, or a trend of increasing continuously; among them, the soluble protein content of the samples wrapped with 20% filling material reached a peak at -20℃ treatment, and the samples wrapped with ordinary treatment and 15% filling material showed a roughly stable upward trend, reaching a peak at -25℃ treatment. At the initial temperature, the soluble protein content of the three samples was basically the same, but as the temperature continued to drop, the soluble protein content showed a large difference. Under low temperature stress, the branches wrapped with 20% filling material had the smallest increase, with an increase of 1.144μg / g. -1 The increase in branches treated with 15% filler material was 3 μg / g -1, which is at an intermediate level; the content of ordinary unwrapped treatment increased the most, which was 4.432μg / g -1 .

[0057] After the winter simulated low temperature test, the MDA content changes as follows Figure 5 As shown in the figure, the MDA content of the three samples showed an increasing trend. The MDA content of the branches under the ordinary treatment was significantly higher than that of the branches wrapped with 20% filling material and 15% filling material at all times. The MDA content of the three samples at -25℃ was as follows: the MDA content of the branches under the ordinary treatment was 8.326 μmol·g -1 The MDA content of the branches wrapped with 20% filler material was 7.366 μmol·g -1 The MDA content of the branches wrapped with 15% filler material was 8.046 μmol·g -1 The increase in MDA content of the three samples under the cooling treatment from -4℃ to -25℃ was as follows: the MDA content of branches under the ordinary treatment was 4.55μmol·g -1 The MDA content of the dendrites wrapped with 20% filler material was 4.03 μmol·g -1 The MDA content of the branches wrapped with 15% filler material was 5.05 μmol·g -1 .

[0058] The effects of different filling materials on CAT activity in grape branches under low temperature are as follows Figure 6 This study shows changes in CAT activity in grapevine branches treated with different filler materials under low temperature stress. As the temperature dropped from -5°C to -25°C, CAT activity in the branches of each treatment initially increased, then decreased, and then increased again. Within the -5°C to -10°C range, CAT activity varied relatively steadily, increasing rapidly at -15°C before slowing down as the temperature continued to decrease. Maximum CAT activity was reached at -25°C for all three treatments. The CAT activity in branches under the standard treatment was 32.5656 nmol / g, 20.5315 nmol / g for branches covered with 20% filler material, and 18.1027 nmol / g for branches covered with 15% filler material. The increases in CAT activity in the three samples from -4°C to -25°C were 26.1033 nmol / g for the standard treatment, 14.6675 nmol / g for branches covered with 20% filler material, and 11.7694 nmol / g for branches covered with 15% filler material.

[0059] Peroxidase (POD) is an enzyme that uses H2O2 as an electron acceptor to catalyze substrate oxidation. It is a peroxisome in the cytoplasm that neutralizes the toxicity of hydrogen peroxide. Figure 7Low temperatures significantly affected POD activity in grapevine branches. Within the -5 to -25°C temperature range, POD activity in all treatments showed an initial increase followed by a decrease. POD activity in branches treated with conventional treatment and those wrapped with 15% filler material both peaked at -15°C, reaching 0.2421 mU / g and 0.2474 mU / g, respectively. POD activity in branches wrapped with 20% filler material peaked at -20°C, reaching 0.2008 mU / g. The increases in POD activity across the three samples from -4°C to -25°C were: 0.089 mU / g for conventional treatment, 0.057 mU / g for 20% filler material, and 0.085 mU / g for 15% filler material. The largest increase occurred in the conventional treatment, followed by the 15% filler material treatment, with similar increases. The smallest increase occurred in the 20% filler material-wrapped branches.

[0060] As the temperature decreased, the conductivity of the samples treated with the three different insulation treatments gradually increased. The semi-lethal temperatures of the three samples were (normally treated branches: -12.08°C, branches wrapped with 15% filler: -14.14°C, and branches wrapped with 20% filler: -15.44°C). The branches wrapped with 20% filler had the lowest semi-lethal temperature. This addition of bio-based polyurethane foam achieved the best insulation performance in terms of both conductivity and lethal temperature.

[0061] The soluble sugar content generally showed an upward and then downward trend, but the peak temperatures were different. The soluble sugar content peaked at -15°C, -15°C, and -20°C for the three samples (normal treatment, 15% filler wrapped treatment, and 20% filler wrapped treatment). The branches wrapped with 20% filler showed the smallest increase in soluble sugar content under low temperature stress, at 0.2261 mg / g. The branches wrapped with 15% filler saw an intermediate increase of 0.2563 mg / g. The normal treatment showed the largest increase in soluble sugar, at 0.2875 mg / g. Based on the changes in soluble protein content, the 20% filler bio-based polyurethane foam demonstrated superior thermal insulation performance.

[0062] The soluble protein content showed a trend of first increasing and then decreasing or continuously increasing. The soluble protein content of the samples wrapped with 20% filler material reached its peak at -20°C. The samples wrapped with ordinary treatment and 15% filler material showed a generally stable upward trend, reaching its peak at -25°C. The branches wrapped with 20% filler material had the smallest increase, reaching 1.144μg / g. -1 The increase in branches treated with 15% filler material was 3 μg / g -1, which is at an intermediate level; the increase in ordinary treatment is the largest, which is 4.432μg / g -1 .

[0063] The MDA content showed a continuous upward trend. The MDA content of branches treated with the standard treatment was significantly higher than that of branches treated with 20% filler material and 15% filler material at all times. The MDA content of the three samples at -25°C (standard treatment, 15% filler material treatment, and 20% filler material treatment) was 8.326 μmol·g -1 , 8.046 μmol·g -1 , 7.366 μmol·g -1 The increase in MDA content of the three samples under the cooling treatment from -4℃ to -25℃ (normal treatment, 15% filling material wrapping treatment, 20% filling material wrapping treatment) is: 4.55μmol·g -1 , 5.05 μmol·g -1 , 4.03 μmol·g -1 .

[0064] In plant cold stress experiments, protective enzyme activity showed a trend of continuous increase, or an initial increase followed by a decrease and then a subsequent increase, with prolonged stress. Samples with good insulation showed a small increase in protective enzyme activity, only 0.057 mU / g, while samples with poor insulation showed a rapid and significant increase. MDA content showed similar changes to protective enzyme activity, with samples with good insulation showing a small increase and samples with poor insulation showing a significant increase.

[0065] The above describes the specific embodiments of the present invention. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing grapevine powder bio-based polyurethane foam, characterized in that: The following steps are involved: Step 1: clean the grape branches with water, air-dry them, and then dry them to a constant weight. Then, crush them and sieve them to obtain grape branch chips. Step 2: Mix grapevine branch chips with polyethylene glycol 400 and glycerol, heat to 150°C under mechanical stirring, slowly add concentrated sulfuric acid, continue to stir at constant temperature for liquefaction, quickly cool to room temperature, and vacuum filter; Step 3: Add a chain extender, a foam stabilizer, a catalyst and stannous octoate to the filtrate obtained in step 2, stir until uniform, add grape branch chips, continue stirring, quickly add a foaming agent, continue stirring, evenly pour into a mold, foam freely at room temperature, and mature at room temperature to obtain the foam.

2. The method according to claim 1, characterized in that Step 1: Pass through a 60-mesh sieve.

3. The method according to claim 1, characterized in that In step 2, the liquefaction treatment time is 60 minutes.

4. The method according to claim 1, characterized in that In step 2, the mass ratio of polyethylene glycol 400, glycerol and grape branch cuttings is (4-12):2:1, the amount of concentrated sulfuric acid added is 3wt% to 9wt%, and ethylene glycol is used to replace glycerol. Preferably, the amount of concentrated sulfuric acid added in the 8:2:1 ratio is 5 wt%.

5. The method according to claim 1, characterized in that: In step 3, the catalyst is triethylenediamine A33, the chain extender is 1,4-butanediol (BDO), the foam stabilizer is silicone oil L-580, and the foaming agent is polymerized MDI.

6. The method according to claim 5, characterized in that In step 3, the mass ratio of the filtrate to the chain extender, foam stabilizer, catalyst, and stannous octoate is 100:(3-4):2:0.3:0.5, and the isocyanate index is controlled at 0.95-1.

05.

7. The method according to claim 1, characterized in that: In step 3, the amount of grape branch chips added is 15 wt% to 20 wt%.

8. The method according to claim 1, characterized in that: The ripening time is 24h.

9. A grapevine powder bio-based polyurethane foam prepared by the method according to any one of claims 1 to 8.

10. A grapevine powder bio-based polyurethane foam prepared by the method according to any one of claims 1 to 8 or according to claim 9, used as a heat-insulating and cold-proof material for wrapping grape branches.

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