Water-soluble adhesive and application thereof in non-woven fabric

Abstract

The invention relates to the technical field of adhesives, and particularly discloses a water-soluble adhesive and application thereof in non-woven fabric. The water-soluble adhesive comprises the following raw materials in parts by weight: 10-20 parts of starch; 5 to 10 parts of PVA; 100 parts of water; wherein the starch comprises cationic starch and glycidyl methacrylate modified starch. The adhesive disclosed by the invention can be applied to the fields of non-woven fabrics, packing material bonding, wood bonding and the like, has an excellent bonding effect, and can be used for effectively improving the bonding effect and mechanical strength of the non-woven fabrics by utilizing hydrogen bond bonding between positive ions and a bonded material; and glycidyl methacrylate can also be utilized to improve the water resistance effect of the adhesive, so that the non-woven fabric also has an excellent bonding effect in a humid environment, and the treatment effect on the saccharin sodium waste is improved.

Description

Technical Field

[0001] This application relates to the technical field of adhesives, and more specifically, to a water-soluble adhesive and its application in nonwoven fabrics. Background Technology

[0002] Wet-laid nonwoven fabrics are characterized by high production speed, lightweight products, and excellent fiber uniformity, leading to a wide range of applications. They can be used in battery separators, seedling fabrics, surgical gowns, masks, clothing linings, and dustproof clothing. Wet-laid nonwoven fabric production typically uses water as a medium. Fiber raw materials are added to water to create a suspension, which is then formed into a web using a web-forming mechanism and dried to produce the nonwoven fabric. Adhesives are usually required to bond the fibers in nonwoven fabrics. Adhesives typically include solvent-based adhesives and water-soluble adhesives. Because solvent-based adhesives are more prone to releasing harmful volatile substances, water-soluble adhesives have become the main research focus in recent years.

[0003] Because water-soluble adhesives have good hydrophilicity, they are more prone to failure in humid environments, which leads to a deterioration in the performance of nonwoven fabrics stored in humid environments. Therefore, further improvements are needed. Summary of the Invention

[0004] To improve the water resistance of water-soluble adhesives, this application provides a water-soluble adhesive and its application in nonwoven fabrics, employing the following technical solution: In a first aspect, a water-soluble adhesive comprises the following raw materials in parts by weight: 10-20 parts starch; 5-10 portions of PVA; 100 parts water; The starch includes cationic starch and glycidyl methacrylate modified starch.

[0005] By adopting the above technical solution, polyvinyl alcohol (PVA) and starch are preferably used as the adhesive. Polyvinyl alcohol has excellent adhesion and high surface activity, which can enhance the inter-fiber bonding strength of nonwoven fabrics, but its economic cost is relatively high. Starch also has excellent adhesion and is less expensive. Therefore, by combining a large amount of starch with a small amount of PVA, the excellent adhesion of the adhesive can be effectively maintained, while also reducing costs and improving economic efficiency, and reducing the environmental degradation pressure of PVA.

[0006] The preferred method is to combine cationic starch with glycidyl methacrylate-modified starch. Cationic starch adds cationic groups to the starch, which can connect with the fiber surface groups in the nonwoven fabric through hydrogen bonds. This increases the number of hydrogen bonds between fibers, improving the strength of the nonwoven fabric while also strengthening the bonds between fibers and reducing voids, thus enhancing the fabric's moisture resistance. Introducing glycidyl methacrylate into the starch utilizes the hydrophobic ester bonds in glycidyl methacrylate to improve the starch's hydrophobic properties. By reducing voids in the nonwoven fabric and increasing the number of hydrophobic groups, the water resistance of the adhesive is effectively improved, extending the service life and performance of the nonwoven fabric in humid environments.

[0007] Optionally, the preparation of the glycidyl methacrylate modified starch is as follows: the starch is dried to remove the water, the starch is mixed with water to obtain a suspension, acid is added and the reaction is continued, alkali solution is added to adjust the pH, and then ammonium persulfate and glycidyl methacrylate are added and stirred continuously to obtain glycidyl methacrylate modified starch.

[0008] Optionally, the amount of glycidyl methacrylate added is 15-20%.

[0009] By employing the above technical solution, a grafting reaction occurs between glycidyl methacrylate and starch under the initiation of ammonium persulfate, giving the starch hydrophobic groups and improving the water resistance of the adhesive. The amount of glycidyl methacrylate added was optimized; a suitable amount results in a moderate viscosity and good tackiness in the adhesive.

[0010] Optionally, the preparation of the glycidyl methacrylate modified starch is as follows: the starch is dried to remove the water, the starch is mixed with water to obtain a suspension, acid is added and the reaction is continued, alkali solution is added to adjust the pH, then ammonium persulfate and glycidyl methacrylate are added and stirred continuously, sodium metaphosphate, urea and sodium dodecyl sulfate are added and the reaction is continued to obtain glycidyl methacrylate modified starch.

[0011] By adopting the above technical solution, it is preferable to add sodium metaphosphate to the modified starch. The introduction of sodium metaphosphate can cause cross-linking between starches, increase the cohesive strength of the adhesive, form a cross-linked network structure, reduce the content of hydrophilic groups, and further improve the water resistance of the adhesive and the mechanical strength of the nonwoven fabric.

[0012] Optionally, the PVA includes PVA modified with silk fibroin.

[0013] By adopting the above technical solution, it is preferable to use silk fibroin to modify PVA. The polar groups such as hydroxyl and amino groups on silk fibroin can interact and cross-link with PVA through hydrogen bonds, which can simultaneously improve the bonding effect of PVA and enhance the bonding strength between nonwoven fibers.

[0014] Optionally, the starch may also include tannin-modified starch.

[0015] By employing the above technical solution, starch is modified using tannic acid. Tannic acid interacts with starch through hydrogen bonds, inhibiting the slippage of starch molecular chains and thus improving the mechanical strength and viscosity of starch. Simultaneously, tannic acid can bind with silk fibroin through hydrogen bonds, forming a PVA-silk fibroin-tannic acid-starch composite structure. The combination of tannic acid and silk fibroin results in excellent water resistance, further enhancing the crosslinking effect and water resistance of the adhesive.

[0016] Optionally, the starch may also include succinate-modified starch.

[0017] By adopting the above technical solution, starch is prone to peeling after drying due to its high internal rigidity. By modifying starch with succinate, polar groups are added to the starch, reducing the association of hydroxyl groups in the starch, enhancing the steric hindrance effect, improving the toughness of the starch, and reducing the occurrence of starch peeling after drying. At the same time, ester groups are introduced into the starch to further improve the hydrophobic effect of the starch.

[0018] Optionally, the succinate-modified starch is an amphiphilic modified starch, and the preparation method of the amphiphilic modified starch is as follows: starch is mixed with water to obtain a starch emulsion; the starch emulsion is mixed with acid, stirred and reacted, neutralized with alkali to obtain enzymatically hydrolyzed starch; the enzymatically hydrolyzed starch is mixed with an alkaline ethanol solution, monochloroacetic acid is added, and stirred and reacted to obtain carboxymethyl starch; the carboxymethyl starch is mixed with water, heated, ethanol and octenyl succinic anhydride are added, the reaction is continued, dried, pulverized, and sieved to obtain amphiphilic modified starch.

[0019] By adopting the above technical solution, starch is modified by hydroxymethyl and octenyl succinic anhydride at the same time, so that hydrophilic and hydrophobic groups are grafted onto the starch simultaneously. While maintaining the water solubility of the adhesive, it gives the adhesive excellent water resistance.

[0020] Optionally, the PVA is a PVA modified with KH560 or KH550.

[0021] By adopting the above technical solution and modifying PVA with silane coupling agent, the dispersion effect of PVA can be effectively improved, thereby enabling the adhesive to uniformly bond the fibers of the nonwoven fabric, so that the nonwoven fabric can obtain uniform strength and water resistance.

[0022] Optionally, the adhesive may also include 2-3 parts of carboxymethyl cellulose.

[0023] By adopting the above technical solution, the introduction of carboxymethyl cellulose can increase the negative charge content in the adhesive. Utilizing the principle of mutual repulsion between charged particles, the fibers in the nonwoven fabric are evenly dispersed. Furthermore, it can synergize with cationic starch to ensure a moderate amount of negative charge in the adhesive, thereby allowing the fibers to disperse effectively and preventing the formation of large voids.

[0024] Secondly, this application provides an application of a water-soluble adhesive in nonwoven fabrics, employing the following technical solution: The application of a water-soluble adhesive in nonwoven fabrics involves adding the aforementioned water-soluble adhesive after the nonwoven fabric fibers have been web-formed.

[0025] In summary, this application has the following beneficial effects: 1. This application preferably uses a combination of cationic starch and glycidyl methacrylate-modified starch. The cationic starch adds cationic groups to the starch, which can connect with the fiber surface groups in the nonwoven fabric through hydrogen bonds. This increases the number of hydrogen bonds between fibers, improving the strength of the nonwoven fabric while also strengthening the bonds between fibers and reducing gaps, thus enhancing the moisture resistance of the nonwoven fabric. Introducing glycidyl methacrylate into the starch utilizes the hydrophobic ester bonds in glycidyl methacrylate to improve the hydrophobic effect of the starch. By reducing the porosity of the nonwoven fabric and increasing the number of hydrophobic groups, the water resistance of the adhesive is effectively improved, extending the service life and performance of the nonwoven fabric in humid environments.

[0026] 2. In this application, tannic acid is used to modify starch. Tannic acid can interact with starch through hydrogen bonds. The addition of tannic acid can inhibit the sliding of starch molecular chains, thereby improving the mechanical strength and viscosity of starch. At the same time, tannic acid can bind with silk fibroin through hydrogen bonds, thus forming a PVA-silk fibroin-tannic acid-starch composite structure. After tannic acid combines with silk fibroin, it achieves excellent water resistance, further improving the crosslinking effect and water resistance of the adhesive.

[0027] 3. In this application, because the internal structure of starch is relatively rigid, it is easy to peel off after drying. By modifying starch with succinate, polar groups are added to starch, reducing the association of hydroxyl groups in starch, enhancing the steric hindrance effect, improving the toughness of starch, and reducing the occurrence of starch peeling after drying. At the same time, ester groups are introduced into starch to further improve the hydrophobic effect of starch. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the embodiments.

[0029] Preparation Example Example of preparation of starch modified with glycidyl methacrylate Preparation Example 1 Corn starch was first dried in a vacuum oven at 80°C for 5 hours to remove moisture. Corn starch (20.00 g) and distilled water (37.14 g) were added to a container and stirred at 50°C for 10 minutes to obtain a suspension with a starch content of 35% wt. After uniform dispersion, 0.8 mL of concentrated hydrochloric acid (4% of the starch mass) was added, and the mixture was kept at 50°C for 2 hours. Then, NaOH solution (25% wt) was added to adjust the pH to 5.5-6. 0.5 g of ammonium persulfate (APS) (2.5% of the starch mass) was added, and the reaction was continued for 1 hour. After oxidation, 4 mL of glycidyl methacrylate was added, and the mixture was reacted for a period of time to obtain glycidyl methacrylate-modified starch.

[0030] Preparation Example 2 Corn starch was first dried in a vacuum oven at 80°C for 5 hours to remove moisture. 20.00 g of corn starch and 37.14 g of distilled water were added to a container and stirred at 50°C for 10 minutes to obtain a suspension with a starch content of 35% wt. After uniform dispersion, 0.8 mL of concentrated hydrochloric acid (4% of the starch mass) was added, and the mixture was kept at 50°C for 2 hours. Then, 25% wt NaOH solution was added to adjust the pH to 5.5-6. 0.5 g of ammonium persulfate (APS) (2.5% of the starch mass) was added, and the reaction was continued for 1 hour. After oxidation, 4 mL of glycidyl methacrylate was added, and the mixture was reacted for a period of time to obtain an intermediate. After cross-linking with 4% sodium metaphosphate for a period of time, 0.5 g of urea and 0.7 g of sodium dodecyl sulfate were added, and the mixture was heated to 90°C and reacted for 30 minutes to obtain glycidyl methacrylate-modified starch.

[0031] Example of PVA preparation modified with silk fibroin Preparation Example 3 Take silk fibroin and water, mix, stir, filter, and obtain a silk fibroin solution with a mass fraction of 2%. Mix PVA and water, dissolve, filter, and obtain a PVA solution with a mass fraction of 4%. Mix the silk fibroin solution and PVA solution at a mass ratio of 3:17, stir, obtain a mixture, dry, and obtain silk fibroin modified PVA.

[0032] Example of tannic acid modified starch preparation Preparation Example 4 Mix 4g starch, 1g tannic acid and 100mL water, stir and dry to obtain tannic acid modified starch.

[0033] Example of preparation of succinate-modified starch Preparation Example 5 Weigh 80g of raw corn starch (dry weight) on an electronic balance, add a certain amount of distilled water to prepare a 40% starch slurry, then transfer it to a container, stir and heat to 50℃, add 8.33mL of 2mol / L HCl solution, and continue the reaction for 5 hours. After the reaction is complete, neutralize with 3% NaOH solution, filter, disperse the filter cake in distilled water, wash and filter again, repeating 3-4 times until no Cl is found. - Ionization, drying, and sieving yielded enzymatically hydrolyzed starch. 30g of acid-hydrolyzed starch was weighed and added to 1440mL of ethanol containing 42g of NaOH. Alkalinization was carried out at 35℃ for 30min, followed by heating to 0℃. Monochloroacetic acid was dissolved in 60mL of ethanol and simultaneously added to the reaction system along with an equimolar amount of NaOH solution. The reaction was allowed to proceed for 3h. After the reaction, the pH was neutralized to 7. The mixture was filtered, washed 3-4 times, dried, pulverized, and sieved to obtain carboxymethyl starch. Carboxymethyl starch was then mixed with water to prepare a 35% starch slurry. The mixture was stirred at 35℃, and 20% ethanol solution was added. The pH was adjusted to 8.5 by adding 3% NaOH solution. The reaction was allowed to proceed for 3h, neutralized, vacuum filtered, and dried to obtain amphiphilic modified starch.

[0034] Example of silane-modified PVA preparation Preparation Example 6 PVA was dissolved at 90℃, cooled to room temperature, and silane coupling agent kH560 was added dropwise. The mass ratio of silane coupling agent to PVA was 1:5, thus obtaining silane-modified PVA.

[0035] Example Examples 1-3 On the one hand, this application provides a water-soluble adhesive comprising starch, PVA, carboxymethyl cellulose and water, the specific quantities of which are shown in the table below. The starch comprises cationic starch in a mass ratio of 2:1 and glycidyl methacrylate modified starch prepared in Preparation Example 1.

[0036] On the other hand, this application provides a nonwoven fabric in which the above-mentioned adhesive is used during the manufacturing process.

[0037] Table 1 Composition of Examples 1-4

[0038] Example 5 The difference from Example 3 is that the starch includes cationic starch in a mass ratio of 2:1 and glycidyl methacrylate modified starch prepared in Preparation Example 2, and the adhesive is prepared.

[0039] Example 6 The difference from Example 3 is that the starch includes cationic starch in a mass ratio of 2:1 and glycidyl methacrylate modified starch prepared in Preparation Example 1, and the PVA is silk fibroin modified PVA prepared in Preparation Example 3, and the adhesive is prepared.

[0040] Example 7 The difference from Example 3 is that the starch includes cationic starch in a mass ratio of 2:1:1, glycidyl methacrylate modified starch prepared in Preparation Example 1, and tannic acid modified starch prepared in Preparation Example 4, and the PVA is silk fibroin modified PVA prepared in Preparation Example 3, and the adhesive is prepared.

[0041] Example 8 The difference from Example 4 is that the starch includes cationic starch in a mass ratio of 2:1:1, glycidyl methacrylate modified starch prepared in Preparation Example 1, and tannic acid modified starch prepared in Preparation Example 4, and the PVA is silk fibroin modified PVA prepared in Preparation Example 3, and the adhesive is prepared.

[0042] Example 9 The difference from Example 3 is that the starch includes cationic starch with a mass ratio of 2:1:1:0.5, glycidyl methacrylate modified starch prepared in Preparation Example 1, tannic acid modified starch prepared in Preparation Example 4, and succinate modified starch prepared in Preparation Example 5, and the PVA is silk fibroin modified PVA prepared in Preparation Example 3, and the adhesive is prepared.

[0043] Example 10 The difference from Example 3 is that the starch includes cationic starch in a mass ratio of 2:1:1:0.5, glycidyl methacrylate modified starch prepared in Preparation Example 1, tannic acid modified starch prepared in Preparation Example 4, and succinate modified starch prepared in Preparation Example 5. The PVA includes equal masses of silk fibroin modified PVA prepared in Preparation Example 3 and silane modified PVA prepared in Preparation Example 6. The adhesive is prepared.

[0044] Comparative Example Comparative Example 1 The difference between this comparative example and Example 3 is that cationic starch was not added in this comparative example to prepare the adhesive.

[0045] Comparative Example 2 The difference between this comparative example and Example 3 is that glycidyl methacrylate-modified starch was not added in this comparative example to prepare the adhesive.

[0046] Performance testing Nonwoven fabric preparation: Flax fibers are fed into a carding machine, and the flax strips are cut into 15mm pieces using a guillotine cutter to form a web, obtaining pretreated fibers; the pretreated fibers are then subjected to acid washing, cold water washing, scouring, hot water washing, and cold water washing to obtain degummed fibers; the degummed fibers are mixed with water, beaten for 5 minutes, and 1% surfactant and 1g / L NaCl are added, stirred, and a suspension with a suspension degree of 0.05% is prepared; the web is formed using an inclined wire mesh, and the single web weight is 150g / m². 2 Bonding process parameters: emulsified oil 0.004 kg / L; adhesive addition 15 g / L. A hot air dryer was used for drying, and the post-drying moisture regain was controlled at 8% to obtain the nonwoven fabric.

[0047] (1) Water resistance test: Immerse the nonwoven fabric in 60℃ warm water and record the time of fiber degumming.

[0048] (2) Mechanical property testing: Take 75mm and 63mm samples and place them in a tear tester to test the mechanical strength of the nonwoven fabric.

[0049] Table 2 Performance Testing

[0050] By comparing the performance test results in Table 2, we can find that: 1. Comparing Examples 1-3, Example 4, and Comparative Examples 1-2, it can be found that the adhesives prepared in Examples 1-3 have improved water resistance and strength of nonwoven fabrics. This indicates that cationic starch increases cationic groups in starch, which connect with the fiber surface groups in the nonwoven fabric through hydrogen bonds, increasing the number of hydrogen bonds between fibers. This not only improves the strength of the nonwoven fabric but also strengthens the connection between fibers, reducing gaps and improving the moisture resistance. Introducing glycidyl methacrylate into starch utilizes the hydrophobic ester bonds in glycidyl methacrylate to improve the hydrophobic effect of starch. By reducing nonwoven fabric porosity and increasing hydrophobic groups, the water resistance of the adhesive is effectively improved, extending the service life and performance of the nonwoven fabric in humid environments. The introduction of carboxymethyl cellulose increases the negative charge content in the adhesive. Utilizing the principle of mutual repulsion of charged particles, the fibers in the nonwoven fabric are evenly dispersed. Furthermore, it can synergize with cationic starch to ensure a moderate amount of negative charge in the adhesive, allowing for dispersion between fibers and preventing the formation of large gaps.

[0051] 2. A comparison between Example 5 and Example 3 reveals that the adhesive prepared in Example 5 exhibits improved water resistance and strength to the nonwoven fabric. This indicates that the addition of sodium metaphosphate to the modified starch in this application enables cross-linking between starches, increases the cohesive strength of the adhesive, forms a cross-linked network structure, and further improves the water resistance of the adhesive and the mechanical strength of the nonwoven fabric.

[0052] 3. A comparison of Examples 6, 7, and 8 with Example 3 reveals that the adhesives prepared in Examples 6-8 exhibit improved water resistance and strength of the nonwoven fabric. This indicates that silk fibroin in this application can enhance the crosslinking degree of PVA through hydrogen bonds, thereby increasing the adhesive's viscosity. Tannic acid can inhibit starch molecular chain migration through hydrogen bonds, improving the adhesive's viscosity and strength. Furthermore, tannic acid and silk fibroin can also combine through hydrogen bonds to form a multi-composite structure. The combination of tannic acid and silk fibroin results in excellent water resistance, further enhancing the adhesive's water resistance. In addition, silk fibroin can also combine with carboxymethyl cellulose, further improving the adhesive's viscosity, i.e., increasing the strength of the nonwoven fabric.

[0053] 4. A comparison of Examples 9 and 10 with Example 3 reveals that the adhesives prepared in Examples 9-10 exhibit improved water resistance and strength to the nonwoven fabric. This indicates that the present application simultaneously modifies starch with hydroxymethyl and octenyl succinic anhydride, grafting both hydrophilic and hydrophobic groups onto the starch. This maintains the water solubility of the adhesive while imparting excellent water resistance. Furthermore, the introduction of the silane coupling agent effectively improves the dispersion of PVA, thereby enabling the adhesive to uniformly bond the fibers of the nonwoven fabric.

[0054] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A water-soluble adhesive, characterized in that, Including the following parts by weight of raw materials: 10-20 parts starch; 5-10 portions of PVA; 100 parts water; The starch includes cationic starch and glycidyl methacrylate modified starch.

2. The water-soluble adhesive according to claim 1, characterized in that: The preparation of the glycidyl methacrylate modified starch is as follows: the starch is dried to remove the water, the starch is mixed with water to obtain a suspension, acid is added and the reaction is continued, alkali solution is added to adjust the pH, and then ammonium persulfate and glycidyl methacrylate are added and stirred continuously to obtain glycidyl methacrylate modified starch.

3. The water-soluble adhesive according to claim 1, characterized in that: The preparation of the glycidyl methacrylate modified starch is as follows: the starch is dried to remove the water, the starch is mixed with water to obtain a suspension, acid is added and the reaction is continued, alkali solution is added to adjust the pH, then ammonium persulfate and glycidyl methacrylate are added and stirred continuously, sodium metaphosphate, urea and sodium dodecyl sulfate are added and the reaction is continued to obtain glycidyl methacrylate modified starch.

4. The water-soluble adhesive according to claim 1, characterized in that: The PVA includes PVA modified with silk fibroin.

5. The water-soluble adhesive according to claim 4, characterized in that: The starch also includes tannic acid-modified starch.

6. The water-soluble adhesive according to claim 1, characterized in that: The starch also includes succinate-modified starch.

7. The water-soluble adhesive according to claim 1, characterized in that: The succinate-modified starch is an amphiphilic modified starch. The preparation method of the amphiphilic modified starch is as follows: starch is mixed with water to obtain a starch emulsion; the starch emulsion is mixed with acid, stirred and reacted, and neutralized with alkali to obtain enzymatically hydrolyzed starch; the enzymatically hydrolyzed starch is mixed with an alkaline ethanol solution, monochloroacetic acid is added, and stirred and reacted to obtain carboxymethyl starch; the carboxymethyl starch is mixed with water, heated, ethanol and octenyl succinic anhydride are added, the reaction is continued, dried, pulverized, and sieved to obtain amphiphilic modified starch.

8. The water-soluble adhesive according to claim 1, characterized in that: The PVA is a PVA modified with KH560 or KH550.

9. The water-soluble adhesive according to claim 1, characterized in that: The adhesive also includes 2-3 parts of carboxymethyl cellulose.

10. The application of a water-soluble adhesive in nonwoven fabrics, characterized in that: A water-soluble adhesive as described in any one of claims 1-9 is added after the nonwoven fabric fibers are webbed.

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