Polyvinyl alcohol gel and preparation method thereof
By configuring the polyvinyl alcohol aqueous solution at high temperature and adding acrylic acid, N’N-dimethacrylamide and ammonium persulfate for cross-linking reaction, the problem of long-term preparation and poor performance of existing polyvinyl alcohol gels is solved, and the rapid preparation of high-performance gels under a temperature-controlled environment is achieved.
Patent Information
- Application Number
- CN202510322270.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2025-06-03
AI Technical Summary
The existing polyvinyl alcohol gel preparation methods require strict freezing conditions, which consumes a long time and has poor mechanical properties and stability of the prepared gel, which limits its production application.
A polyvinyl alcohol gel and its preparation method are adopted. By placing an aqueous polyvinyl alcohol solution at a temperature of 90-95°C, and adding acrylic acid, N’N-dimethacrylamide and ammonium persulfate at the same temperature, the cross-linking reaction is carried out to form a gel. This method simplifies operation without the freezing and thawing steps.
Gel preparation can be completed in an environment of 40-90℃, and good mechanical strength and toughness are obtained, tensile strength can reach 5.1MPa, and elongation at break of 400%, which significantly improves the performance of the gel and reduces energy consumption and production costs.
Smart Images
Figure CN120081981A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of gel preparation, and particularly relates to a polyvinyl alcohol gel and a preparation method thereof. Background Art
[0002] Polyvinyl alcohol hydrogel has excellent properties such as high chemical stability, good biocompatibility, low toxicity, and strong water absorption, and is widely used in the fields of biomedicine, skin care products, agriculture, and environmental protection. At present, the most commonly used method for preparing polyvinyl alcohol gel is the freeze-thaw method. This method forms microcrystalline regions through repeated freeze-thaw cycles, uses the microcrystalline regions as cross-linking points, and forms a gel through physical cross-linking. However, the preparation conditions required by this method are relatively harsh, the freezing temperature must reach at least -20°C, and the entire process from freezing to thawing requires at least 3 cycles, with each cycle requiring at least 12 hours, which is time-consuming. Moreover, the mechanical properties and stability of the polyvinyl alcohol gel prepared by this method are poor, which limits the production and application of polyvinyl alcohol gel. Summary of the Invention
[0003] Object of the Invention: To provide a polyvinyl alcohol gel and a preparation method thereof, which solve the above problems existing in the prior art.
[0004] Technical Solution: A polyvinyl alcohol gel includes an aqueous polyvinyl alcohol solution, acrylic acid, an initiator N,N-dimethylacrylamide, and an ammonium persulfate cross-linking agent. Among them, the concentration of the aqueous polyvinyl alcohol solution is 4wt%-6wt%, the addition amount of acrylic acid is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid, the addition amount of N,N-dimethylacrylamide is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid, and the addition amount of ammonium persulfate is 0.6%-1% of the total amount of polyvinyl alcohol and acrylic acid.
[0005] Preferably, the polyvinyl alcohol is of type 1799, and the alcoholysis degree is 98%-99%.
[0006] A preparation method of a polyvinyl alcohol gel includes the following steps: S1. At a temperature of 90-95°C, use polyvinyl alcohol type 1799 to prepare an aqueous polyvinyl alcohol solution with a concentration of 4wt%-6wt%; S2. After obtaining the aqueous polyvinyl alcohol solution, at a temperature of 90-95°C, add acrylic acid to the aqueous polyvinyl alcohol solution, adjust the stirring speed to 1200 rmp, stir the solution for 2 hours, and at this time the solution shows a transparent and homogeneous state to obtain an acrylic acid mixed solution, where the addition amount of acrylic acid is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid; S3. Add initiator N,N-dimethylacrylamide to the acrylic acid mixed solution, adjust the stirring speed to 1000 rmp, and stir the solution for 1 hour. At this time, the added initiator N,N-dimethylacrylamide is completely dissolved in the acrylic acid mixed solution, and the whole solution changes from a semi-transparent state to a completely clear and transparent state, obtaining a dimethylacrylamide mixed solution. Among them, the addition amount of N,N-dimethylacrylamide is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid. S4. Add ammonium persulfate cross-linking agent to the dimethylacrylamide mixed solution, and stir and dissolve it until a clear cross-linked mixed solution is obtained. S5. Place the cross-linked mixed solution at multiple temperatures within the range of 40-90 °C for cross-linking reaction to obtain polyvinyl alcohol gel.
[0007] Preferably, the degree of alcoholysis of the polyvinyl alcohol in step S1 is 98%-99%.
[0008] Preferably, the addition amount of acrylic acid in S2 is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid.
[0009] Preferably, the addition amount of N,N-dimethylacrylamide in S3 is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid.
[0010] Preferably, the addition amount of ammonium persulfate in S4 is 0.6%-1% of the total amount of polyvinyl alcohol and acrylic acid.
[0011] Beneficial effects: The present invention relates to a polyvinyl alcohol gel and its preparation method. In an environment of 40-90 °C, the preparation of polyvinyl alcohol gel can be completed, without the need for complex freezing and thawing steps, and without low-temperature freezing equipment. A gel with good mechanical strength and toughness can be obtained, with a tensile strength of up to 5.1 MPa and an elongation at break of 400%, which is much higher than that of gels prepared by traditional methods. It not only reduces the operation difficulty, lowers the requirements for equipment and environment, but also reduces energy consumption and production costs, and improves economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 is the preparation flow chart of the present invention; Figure 2 is the reaction time curve in Example 1 of the present invention; Figure 3 is the reaction time curve in Example 2 of the present invention; Figure 4 is the reaction time curve in Example 3 of the present invention; Figure 5 is the reaction time curve in Example 4 of the present invention; Figure 6 is the tensile stress-strain curve of the present invention; Figure 7 This is the tensile stress-strain curve of the freeze-thaw method of the present invention. Detailed implementation mode
[0013] As Figures 1 to 7 shown, the present invention provides a technical solution: a polyvinyl alcohol gel, including an aqueous solution of polyvinyl alcohol, acrylic acid, an initiator N,N-dimethylacrylamide, and an ammonium persulfate cross-linking agent. Among them, the concentration of the aqueous solution of polyvinyl alcohol is 4wt%-6wt%, the addition amount of acrylic acid is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid, the addition amount of N,N-dimethylacrylamide is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid, and the addition amount of ammonium persulfate is 0.6%-1% of the total amount of polyvinyl alcohol and acrylic acid. Among them, the polyvinyl alcohol is of type 1799, and the degree of alcoholysis is 98%-99%.
[0014] A preparation method of a polyvinyl alcohol gel includes the following steps: Step 1: At a temperature of 90-95°C, use polyvinyl alcohol of type 1799 to prepare an aqueous solution of polyvinyl alcohol with a concentration of 4wt%-6wt%. Among them, the degree of alcoholysis of polyvinyl alcohol is 98%-99%; Step 2: After obtaining the aqueous solution of polyvinyl alcohol, at a temperature of 90-95°C, add acrylic acid to the aqueous solution of polyvinyl alcohol, adjust the stirring speed to 1200rmp, and stir the solution for 2 hours. At this time, the solution shows a transparent and homogeneous state, and an acrylic acid mixed solution is obtained. Among them, the addition amount of acrylic acid is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid; Step 3: Add the initiator N,N-dimethylacrylamide to the acrylic acid mixed solution, adjust the stirring speed to 1000rmp, and stir the solution for 1 hour. At this time, the added initiator N,N-dimethylacrylamide is completely dissolved in the acrylic acid mixed solution, and at this time the whole solution completely changes from a semi-transparent state to a clear and transparent state, and a dimethylacrylamide mixed solution is obtained. Among them, the addition amount of N,N-dimethylacrylamide is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid; Step 4: Add the ammonium persulfate cross-linking agent to the dimethylacrylamide mixed solution, and stir and dissolve it into a clear cross-linked mixed solution. Among them, the addition amount of ammonium persulfate is 0.6%-1% of the total amount of polyvinyl alcohol and acrylic acid; Step 5: Place the cross-linked mixed solution at multiple temperatures within the range of 40-90 degrees Celsius for cross-linking reaction to obtain a polyvinyl alcohol gel.
[0015] Example 1 Under the condition of 90 °C, 5 g of polyvinyl alcohol was added to 90 g of deionized water. By heating and stirring, the polyvinyl alcohol was completely dissolved in water to obtain an aqueous polyvinyl alcohol solution. 5 g of acrylic acid was added to this polyvinyl alcohol solution and stirred for 1 h to dissolve, obtaining an acrylic acid mixed solution. Then the temperature was lowered to 60 °C. First, 0.3 g of N,N-dimethylacrylamide was added to this mixed solution and stirred to dissolve. Then 0.1 g of ammonium persulfate was continuously added and stirred until a clear crosslinked mixed solution was obtained. Then this crosslinked mixed solution was placed under the conditions of 90 °C, 80 °C, 70 °C, 60 °C, 50 °C, and 40 °C respectively for crosslinking reaction. When the crosslinked mixed solution lost fluidity, polyvinyl alcohol gel was formed. The gel times were recorded as 5 min, 20 min, 30 min, 55 min, 100 min, and 115 min respectively. The corresponding graph of the temperature at which the crosslinked mixed solution was placed and the gel time is as Figure 2 shown.
[0016] Example 2 Under the condition of 90 °C, 4 g of polyvinyl alcohol was added to 90 g of deionized water. By heating and stirring, the polyvinyl alcohol was completely dissolved in water to obtain an aqueous polyvinyl alcohol solution. 6 g of acrylic acid was added to this polyvinyl alcohol solution and stirred for 1 h to dissolve, obtaining an acrylic acid mixed solution. Then the temperature was lowered to 60 °C. First, 0.2 g of N,N-dimethylacrylamide was added to this mixed solution and stirred to dissolve. Then 0.08 g of ammonium persulfate was continuously added and stirred until a clear crosslinked mixed solution was obtained. Then this mixed solution was placed under the conditions of 90 °C, 80 °C, 70 °C, 60 °C, 50 °C, and 40 °C respectively for crosslinking reaction. When the crosslinked mixed solution lost fluidity, polyvinyl alcohol gel was formed. The gel times were recorded as 6 min, 23 min, 32 min, 58 min, 105 min, and 118 min respectively. The corresponding graph of the temperature at which the crosslinked mixed solution was placed and the gel time is as Figure 3 shown.
[0017] Example 3 Under the condition of 90 °C, 6 g of polyvinyl alcohol was added to 90 g of deionized water. By heating and stirring, the polyvinyl alcohol was completely dissolved in the water to obtain an aqueous polyvinyl alcohol solution. 10 g of acrylic acid was added to the polyvinyl alcohol solution and stirred for 1 h to dissolve, obtaining an acrylic acid mixed solution. Then, the temperature was lowered to 60 °C. First, 0.4 g of N,N-dimethylacrylamide was added to the mixed solution and stirred to dissolve. Then, 0.1 g of ammonium persulfate was continuously added and stirred until a clear cross-linked mixed solution was obtained. Then, the mixed solution was placed under the conditions of 90 °C, 80 °C, 70 °C, 60 °C, 50 °C, and 40 °C for cross-linking reaction. When the cross-linked mixed solution lost fluidity, polyvinyl alcohol gel was formed. The gel times were recorded as 4 min, 18 min, 27 min, 53 min, 98 min, and 113 min respectively. The corresponding graph of the temperature at which the cross-linked mixed solution was placed and the gel time is as Figure 4 shown.
[0018] Example 4 Under the condition of 90 °C, 5 g of polyvinyl alcohol was added to 90 g of deionized water. By heating and stirring, the polyvinyl alcohol was completely dissolved in the water to obtain an aqueous polyvinyl alcohol solution. 6 g of acrylic acid was added to the polyvinyl alcohol solution and stirred for 1 h to dissolve, obtaining an acrylic acid mixed solution. Then, the temperature was lowered to 55 °C. First, 0.18 g of N,N-dimethylacrylamide was added to the mixed solution and stirred to dissolve. Then, 0.08 g of ammonium persulfate was continuously added and stirred until a clear cross-linked mixed solution was obtained. Then, the mixed solution was placed under the conditions of 90 °C, 80 °C, 70 °C, 60 °C, 50 °C, and 40 °C for cross-linking reaction. When the cross-linked mixed solution lost fluidity, polyvinyl alcohol gel was formed. The gel times were recorded as 7 min, 25 min, 35 min, 60 min, 107 min, and 120 min respectively. The corresponding graph of the temperature at which the cross-linked mixed solution was placed and the gel time is as Figure 5 shown.
[0019] Comparative Example 1 Under the condition of 90 °C, 10 g of polyvinyl alcohol was added to 90 g of deionized water. By heating and stirring, the polyvinyl alcohol was completely dissolved in the water to obtain an aqueous polyvinyl alcohol solution. After the polyvinyl alcohol solution had no bubbles, it was placed at -20 °C for 12 hours for freezing, and then thawed for 3 hours. The freezing-thawing cycle was repeated three times to obtain polyvinyl alcohol gel.
[0020] Figure 6 and Figure 7 are the tensile stress-strain curves of the gels, where Figure 6 is the polyvinyl alcohol gel prepared according to the present invention, Figure 7 is the gel prepared by the freezing-thawing method. From Figure 6It can be seen that the tensile strength of the polyvinyl alcohol gel prepared by the preparation method of the present application can reach 5.1 MPa, which is more than 7 times the gel strength (0.7 MPa) prepared by the freeze-thaw method. The elongation at break of the gel prepared by the present invention reaches 400%, which is also much higher than that of the gel prepared by the freeze-thaw method. It proves that the gel prepared by the present invention has good strength and toughness.
[0021] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.
Claims
1. A polyvinyl alcohol gel, characterized in that: The invention comprises a polyvinyl alcohol aqueous solution, acrylic acid, an initiator N'N-dimethylacrylamide and an ammonium persulfate crosslinking agent, wherein the concentration of the polyvinyl alcohol aqueous solution is 4wt%-6wt%, the amount of acrylic acid added is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid, the amount of N'N-dimethylacrylamide added is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid, and the amount of ammonium persulfate added is 0.6%-1% of the total amount of polyvinyl alcohol and acrylic acid.
2. A polyvinyl alcohol gel according to claim 1, characterized in that: The polyvinyl alcohol is of type 1799, and the alcoholysis degree is 98%-99%.
3. A method for preparing a polyvinyl alcohol gel, used for preparing a polyvinyl alcohol gel as claimed in claim 1 or 2, characterized in that: The following steps are involved: S1. At a temperature of 90-95°C, using polyvinyl alcohol 1799 to prepare a polyvinyl alcohol aqueous solution with a concentration of 4wt%-6wt%, wherein the alcoholysis degree of the polyvinyl alcohol is 98%-99%; S2. After obtaining the polyvinyl alcohol aqueous solution, acrylic acid is added to the polyvinyl alcohol aqueous solution at a temperature of 90-95° C., and the stirring speed is adjusted to 1200 rpm. After stirring the solution for 2 hours, the solution is transparent and uniform, and an acrylic acid mixed solution is obtained, wherein the amount of acrylic acid added is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid; S3, adding initiator N'N-dimethylacrylamide to the acrylic acid mixed solution, adjusting the stirring speed to 1000rmp, stirring the solution for 1 hour, at which time the added initiator N'N-dimethylacrylamide is completely dissolved in the acrylic acid mixed solution, and at this time the whole solution changes from a translucent state to a clear and transparent state, to obtain a dimethylacrylamide mixed solution, wherein the amount of N'N-dimethylacrylamide added is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid; S4, adding ammonium persulfate crosslinking agent to the dimethyl acrylamide mixed solution, stirring and dissolving to obtain a clear crosslinked mixed solution; S5. placing the cross-linked mixed solution at multiple temperatures within the range of 40-90 degrees Celsius to perform a cross-linking reaction to obtain a polyvinyl alcohol gel.
4. The method for preparing a polyvinyl alcohol gel according to claim 3, characterized in that: The alcoholysis degree of the polyvinyl alcohol in step S1 is 98%-99%.
5. The method for preparing a polyvinyl alcohol gel according to claim 4, characterized in that: The amount of acrylic acid added in S2 is 50%-70% of the total amount of polyvinyl alcohol and acrylic acid.
6. The method for preparing a polyvinyl alcohol gel according to claim 4, characterized in that: The amount of N'N-dimethylacrylamide added in S3 is 1%-3% of the total amount of polyvinyl alcohol and acrylic acid.
7. The method for preparing polyvinyl alcohol gel according to claim 4, characterized in that: The amount of ammonium persulfate added in S4 is 0.6%-1% of the total amount of polyvinyl alcohol and acrylic acid.