Polyethylene glycol grafted low-temperature-resistant acrylate pressure-sensitive adhesive and preparation method thereof

Abstract

The invention discloses a polyethylene glycol grafted low-temperature-resistant acrylate pressure-sensitive adhesive and a preparation method thereof, and relates to a low-temperature-resistant acrylate pressure-sensitive adhesive and a preparation method thereof. The invention aims to solve the problems that when an acrylate pressure-sensitive adhesive with a traditional formula faces a low-temperature application environment, an adhesive layer can be converted from a high-elastic state to a glass state, so that a colloid becomes hard and brittle, and necessary flexibility and initial viscosity are lost. The polyethylene glycol-grafted low-temperature-resistant acrylate pressure-sensitive adhesive is prepared from the following components in parts by mass: 10 to 50 parts of hydroxyl-terminated polyethylene glycol, 50 to 90 parts of acrylate monomer, 1 to 5 parts of vinyl silicon monomer, 1 to 5 parts of thermal initiator, 1 to 5 parts of oxidant, 1 to 5 parts of weak base, 1 to 5 parts of solvent and 1 to 5 parts of cross-linking agent. The adhesive comprises the following components in parts by weight: 0.1-0.5 part of a thermal initiator, 1-5 parts of an oxidizing agent, 0.01-1 part of weak base, 150-300 parts of a solvent and 0.01-0.05 part of a cross-linking agent. The invention belongs to the technical field of pressure-sensitive adhesive preparation.

Description

Technical Field

[0001] This invention relates to a low-temperature resistant acrylic pressure-sensitive adhesive and its preparation method, belonging to the field of pressure-sensitive adhesive preparation technology. Background Technology

[0002] Pressure-sensitive adhesives are special adhesives that can instantly adhere to the surface of the substrate with only slight pressure and can be easily peeled off without leaving any residue after use. The performance of acrylic pressure-sensitive adhesives mainly depends on the glass transition temperature of their polymer chains. Typically, the initial tack, peel strength, and cohesive strength are balanced by adjusting the ratio of soft monomers, hard monomers, polar monomers, and crosslinking monomers. However, traditionally formulated acrylic pressure-sensitive adhesives exhibit significant limitations in low-temperature applications. At room temperature, their polymer chains have sufficient mobility to effectively wet the adhered surface, resulting in good tack. But when the ambient temperature drops below 0°C, especially in frigid environments of -20°C to -40°C, the mobility of the polymer chains decreases sharply. When the ambient temperature approaches or falls below their designed glass transition temperature, the adhesive layer transitions from a highly elastic state to a glassy state, causing the adhesive to harden and become brittle, losing its necessary flexibility and initial tack. Its specific defects include: significant loss of initial tack; sharp decline in peel strength; deterioration of holding power; and risk of physical damage. With the development of science and industry, more stringent requirements are being placed on the application scenarios of pressure-sensitive adhesives. For example, outdoor advertising and signage in cold regions, winter logistics packaging, refrigerated packaging labels for frozen foods, wiring harness fixing and internal component bonding in automobiles in frigid environments, and applications in aerospace vehicles at high altitudes and low temperatures all urgently require an acrylic pressure-sensitive adhesive that can maintain reliable bonding performance under ultra-low temperature conditions. Summary of the Invention

[0003] This invention addresses the problem that traditional acrylic pressure-sensitive adhesives, when faced with low-temperature application environments, will transform from a highly elastic state to a glassy state, causing the adhesive to harden and become brittle, losing necessary flexibility and initial tack. Therefore, this invention proposes a low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method.

[0004] The technical solution adopted by the present invention to solve the above problems is as follows: The low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol of the present invention is composed of hydroxyl-terminated polyethylene glycol, acrylate monomer, vinyl silicone monomer, thermal initiator, oxidant, weak alkali, solvent and crosslinking agent, wherein the mass parts of each component are: 10-50 parts of hydroxyl-terminated polyethylene glycol, 50-90 parts of acrylate monomer, 1-5 parts of vinyl silicone monomer, 0.1-0.5 parts of thermal initiator, 1-5 parts of oxidant, 0.01-1 part of weak alkali, 150-300 parts of solvent and 0.01-0.05 parts of crosslinking agent.

[0005] Furthermore, the hydroxyl-terminated polyethylene glycol is one or more of the following: hydroxy-polyethylene glycol-carboxyl, hydroxy-polyethylene glycol-amino, hydroxy-polyethylene glycol-succinic acid, hydroxy-polyethylene glycol-hydroxy, and polyethylene glycol monododecyl ether.

[0006] Furthermore, the hydroxyl-terminated polyethylene glycol is composed of one or more of the following: hydroxyl-terminated polyethylene glycol with a molecular weight of 400, 1000, 2000, 4000, 6000, and 8000.

[0007] Furthermore, the acrylate monomer is one or more of butyl methacrylate, isooctyl methacrylate, methyl methacrylate, alkyl octadecyl acrylate, hydroxyethyl methacrylate, alkyl dodecyl acrylate, butyl acrylate, isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate.

[0008] Furthermore, the vinylsilane monomer is one or more of triethylvinylsilane, diethylmethylvinylsilane, diethoxymethylvinylsilane, and 3-chloropropyldimethylvinylsilane.

[0009] Furthermore, the thermal initiator is one or more of benzoyl peroxide, tert-butyl peroxide, tert-butyl peroxide-2-ethylhexanoate, and diacyl peroxide.

[0010] Furthermore, the weak base is one or more of pyridine and triethylamine.

[0011] Furthermore, the oxidant is thionyl chloride; The solvent is one or more of ethyl acetate, butyl acetate, propyl acetate, toluene, and xylene.

[0012] Furthermore, the crosslinking agent is one or more of toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0013] The steps of the method for preparing a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol according to the present invention include: Step 1: Weigh the acrylate monomer, thermal initiator and part of the solvent and put them into the reaction vessel. Stir and heat to the set temperature to uniformly disperse the acrylate monomer. Keep warm for 2-4 hours. The set temperature is 70-95℃. Step 2: Add the solvent and thionyl chloride dropwise into the reaction vessel and stir to perform acyl chlorination on the acrylate segments. The wetting time is 0.5 h and the temperature is set at 30 °C. Step 3: Add the chlorine dioxide and hydrogen chloride produced by the acylation reaction to the weak base reaction vessel dropwise, and stir for 0.5 hours. Step 4: Add hydroxyl-terminated polyethylene glycol and the remaining solvent and continue the reaction at 70°C for 1 hour. Step 5: Cool to room temperature and discharge.

[0014] Step 6: Add crosslinking agent, heat and stir for 0.5 hours, then cure at room temperature for 24 hours; set the temperature to 80~100℃; In steps 1 to 6, the stirring rate is 100~200 r / min.

[0015] The beneficial effects of this invention are as follows: The main technical principle of this invention is to graft polyethylene glycol into an acrylate polymer system. By maintaining the mobility of the cross-linked polymer system through long side chains, the influence of low temperature on acrylate pressure-sensitive adhesives can be greatly improved. The side chain length can be adjusted by changing the molecular weight of polyethylene glycol, and the degree of cross-linking can be adjusted by changing the type and amount of cross-linking agent to meet the application requirements of low-temperature pressure-sensitive adhesives or coatings.

[0016] This invention improves the harsh and difficult conditions of carboxyl and hydroxyl esterification processes by converting carboxylic acids into acyl chlorides and then reacting them with hydroxyl groups. By maintaining the mobility of the crosslinked polymer system through long side chains, the influence of low temperature on acrylate pressure-sensitive adhesives can be greatly reduced. The side chain length can be adjusted by changing the molecular weight of polyethylene glycol, and the degree of crosslinking can be adjusted by changing the type and amount of crosslinking agent to meet the application requirements of low-temperature pressure-sensitive adhesives or coatings.

[0017] Example Example 1: This embodiment discloses a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method, including the following steps: Weigh 30g of isooctyl acrylate, 10g of methyl methacrylate, 5g of acrylic acid, 5g of alkyl octadecyl acrylate, 5g of 3-chloropropyl dimethylvinylsilane, 0.1g of benzoyl peroxide, and 100g of xylene and place them in a reaction vessel. Probe with N2 for protection, stir at 150 r / min, and heat to 85℃ for 2.5 h. Add 1g of thionyl chloride dropwise to the reaction vessel at 30℃ and stir continuously for 0.5 h to acyl chlorinate the acrylate segments; then add 0.05g of triethylamine and stir for 0.5 h; finally, add 10g of hydroxyl-polyethylene glycol-hydroxyl (Mn=8000) and 50g of xylene and continue the reaction at 60℃ and 100 r / min for 1 h; after the reaction is complete, lower the temperature to room temperature and cool before discharging. Add 0.01g of hexamethylene diisocyanate, heat to 80℃, stir at 100 r / min, and then cure at room temperature for 24h.

[0018] Example 2: This embodiment discloses a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method, including the following steps: Weigh 5g of alkyl icosate, 2g of hydroxyethyl methacrylate, 30g of butyl acrylate, 40g of isooctyl acrylate, 5g of acrylic acid, 1g of diethylmethyl vinylsilane, 0.1g of tert-butyl peroxide, and 100g of toluene into a reaction vessel, purge with N2 for protection, stir at 150 r / min, and heat to 100℃ for 3 h. Add 2g of thionyl chloride dropwise to the reaction vessel, and stir continuously at 30℃ for 0.5 h. Then add 0.05g of pyridine dropwise, and stir for 0.5 h. Finally, add 10g of hydroxyl-polyethylene glycol-amino (Mn=2000) and 50g of toluene to continue the reaction at 70℃ for 1 h. After the reaction is complete, lower the temperature to room temperature and cool before discharging. Add 0.05g of isophorone diisocyanate, heat to 90℃, stir at 100 r / min, and then cure at room temperature for 24h.

[0019] Example 3: This embodiment discloses a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method, including the following steps: Weigh 25g of butyl acrylate, 50g of isooctyl acrylate, 5g of alkyl octadecyl acrylate, 5g of acrylic acid, 5g of hydroxyethyl acrylate, 1g of ethoxymethyl vinylsilane, 2g of 3-chloropropyl dimethyl vinylsilane, 0.4g of tert-butyl peroxide-2-ethylhexanoate, 140g of propyl acetate and 60g of toluene and place them in a reaction vessel, introduce N2 for protection, stir at 150 r / min, heat to 105℃, and keep at that temperature for 2 h. Add 5g of thionyl chloride dropwise to the reaction vessel at 30℃ and stir continuously for 0.5 h; then add 0.05g of triethylamine and stir for another 0.5 h; finally, add 50g of hydroxyl-polyethylene glycol-hydroxyl (Mn=2000), 70g of propyl acetate, and 30g of toluene and continue the reaction at 70℃ for 1 h; after the reaction is complete, lower the temperature to room temperature and cool the material before discharging. Add 0.03g of toluene diisocyanate and heat to 80℃, stirring at 100 r / min, then cure at room temperature for 24 h.

[0020] Example 4: This embodiment discloses a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method, including the following steps: Weigh 45g of butyl methacrylate, 20g of isooctyl methacrylate, 5g of acrylic acid, 5g of hydroxyethyl methacrylate, 15g of docosyl acrylate, 2g of ethoxymethyl vinyl silane, 3g of 3-chloropropyl dimethyl vinyl silane, 0.5g of tert-butyl peroxide-2-ethylhexanoate, 80g of propyl acetate, and 120g of xylene and place them in a reaction vessel. Probe N2 is introduced for protection, the mixture is stirred at 150 r / min, heated to 95℃, and held at that temperature for 4 h. Add 5g of thionyl chloride dropwise to the reaction vessel and stir continuously for 0.5h to induce acyl chlorination of the acrylate segments at 30℃. Then add 1g of triethylamine and stir for 0.5h. Finally, add hydroxyl-polyethylene glycol-carboxyl (Mn=1000), 40g of propyl acetate, and 60g of xylene and continue the reaction at 70℃ for 1h. After the reaction is complete, lower the temperature to room temperature and cool the material before discharging. Add 0.05g of hexamethylene diisocyanate and heat to 90℃, stirring at 100 r / min, then cure at room temperature for 24h.

[0021] Example 5: This embodiment discloses a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method, including the following steps: Weigh 20g butyl methacrylate, 5g methyl methacrylate, 5g acrylic acid, 20g alkyl octadecyl acrylate, 1g triethylvinylsilane, 1g diethylmethylvinylsilane, 0.3g benzoyl peroxide, and 100g ethyl acetate into a reaction vessel, purge with nitrogen for protection, stir at 150 r / min, heat to 70℃, and maintain the temperature for 4 h. Add 3g thionyl chloride dropwise to the reaction vessel, stir continuously for 0.5 h at 30℃; then add 1g pyridine dropwise, stirring for 0.5 h; finally, add 30g polyethylene glycol monododecyl ether (Mn=400) and 50g ethyl acetate to continue the reaction at 70℃ for 1 h; after the reaction is complete, lower the temperature to room temperature and cool before discharging. Add 0.04g of isophorone diisocyanate, heat to 100℃, stir at 100 r / min, and cure at room temperature for 24h.

[0022] Example 6: This embodiment discloses a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol and its preparation method, including the following steps: Weigh 30g of butyl methacrylate, 40g of butyl acrylate, 5g of acrylic acid, 5g of alkyl octadecyl acrylate, 0.5g of benzoyl peroxide, and 150g of butyl acetate and place them in a reaction vessel. Probe N2 for protection, stir at 150 r / min, heat to 90℃, and maintain the temperature for 2 hours. Add 3g of thionyl chloride dropwise to the reaction vessel and stir continuously for 0.5 hours at 30℃. Then add 1g of pyridine and stir for 0.5 hours. Finally, add 40g of hydroxyl-polyethylene glycol-succinic acid (Mn=2000) and 100g of butyl acetate and continue the reaction at 70℃ for 1 hour. After the reaction is complete, lower the temperature to room temperature and cool the material. Add 4g of toluene diisocyanate and heat to 95℃, stirring at 100 r / min, then cure at room temperature for 24 hours.

[0023] Comparative Example 1 30g of isooctyl acrylate, 10g of methyl methacrylate, 5g of acrylic acid, 5g of alkyl octadecyl acrylate, 5g of 3-chloropropyl dimethylvinylsilane, 0.1g of benzoyl peroxide, and 100g of ethyl acetate were placed in a reaction vessel, protected with N2, stirred at 150 r / min, and heated to 85℃ for 2.5 h. Then, 0.01g of hexamethylene diisocyanate was added, the temperature was raised to 80℃, the stirring speed was 100 r / min, and the mixture was cured at room temperature for 24 h.

[0024] Comparative Example 2 20 g of n-butyl acrylate, 20 g of n-octyl acrylate, 30 g of methyl methacrylate, 4 g of acrylic acid, 80 g of ethyl acetate, and 20 g of toluene were added to a 500 ml four-necked flask. The mixture was kept at 85 °C under N2 protection, mechanically stirred at 150 r / min, and maintained at this temperature for 0.1 h. After the first stage of reflux stabilization, a mixture of 40 g of ethyl acetate, 10 g of toluene, and 0.3 g of benzoyl peroxide was added dropwise at 85 °C for 4 h at 150 r / min, and maintained for 1 h. Then, a mixture of 10 g of ethyl acetate, 6.25 g of toluene, and 0.1 g of benzoyl peroxide was added. The mixture was then added dropwise at 85 °C with mechanical stirring at 300 r / min for 0.1 h, maintained at this temperature for 0.5 h, and then cooled to room temperature before being discharged. After the reaction was complete, the temperature was lowered to room temperature, and the mixture was cooled before being discharged.

[0025] Comparative Example 3 35 g of n-butyl acrylate, 30 g of octyl acrylate, 15 g of benzyl acrylate, 4 g of acrylic acid, 40 g of propyl acetate, and 20 g of xylene were added to a 500 ml four-necked flask. The mixture was kept at 80 °C under nitrogen protection, mechanically stirred at 150 r / min, and maintained for 0.1 h. After the first stage of reflux stabilization, a mixture of 50 g of propyl acetate, 25 g of xylene, and 0.35 g of tert-butyl peroxide was added dropwise at 90 °C for 2 h at 150 r / min, and maintained for 1 h. Then, a mixture of 10 g of ethyl acetate, 6.25 g of toluene, and 0.05 g of tert-butyl peroxide was added. The mixture was then added dropwise at 90 °C with mechanical stirring at 150 r / min for 10 min, and maintained for 2 h before cooling to room temperature. Finally, add 10g of hydroxyl-polyethylene glycol-hydroxyl (Mn=2000) and 50g of propyl acetate to continue the reaction at 70℃ for 1 hour. After the reaction is complete, lower the temperature to room temperature and cool the material before discharging. Add 0.03g of toluene diisocyanate and heat to 80℃, stirring at 100 r / min, then cure at room temperature for 24 hours.

[0026] Performance test results of the acrylic pressure-sensitive adhesives obtained in Examples 1 to 6 and Comparative Examples 1 to 3:

[0027] Molecular weight determination: Weigh 3-5 mg of sample and dissolve it in tetrahydrofuran as solvent. Perform molecular weight determination using gel permeation chromatography. The test temperature is 25℃, the solution concentration is 3 mg / L, and the flow rate is 1 mL / min.

[0028] Glass transition temperature test: The sample was tested by differential calorimetry under N2 atmosphere. The test temperature was from -50℃ to 50℃ and the heating rate was 5℃ / min.

[0029] Low-temperature peel strength test: Tested in accordance with GB / T 2792-2014 at an ambient temperature of -40℃. The results in the table above show that the prepared low-temperature resistant acrylic pressure-sensitive adhesive exhibits good dispersion stability, with a wide adjustable range for both the glass transition temperature and content of polyacrylate. This invention provides a new preparation process for the application of low-temperature resistant acrylic pressure-sensitive adhesives. The prepared acrylic pressure-sensitive adhesive can meet the requirements for low-temperature bonding, thus expanding the application fields of acrylic pressure-sensitive adhesives.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol, characterized in that, The pressure-sensitive adhesive is composed of hydroxyl-terminated polyethylene glycol, acrylate monomers, vinyl silicone monomers, thermal initiator, oxidant, weak alkali, solvent, and crosslinking agent. The mass percentages of each component are as follows: hydroxyl-terminated polyethylene glycol 10-50 parts, acrylate monomers 50-90 parts, vinyl silicone monomers 1-5 parts, thermal initiator 0.1-0.5 parts, oxidant 1-5 parts, weak alkali 0.01-1 part, solvent 150-300 parts, and crosslinking agent 0.01-0.05 parts.

2. The low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The hydroxyl-terminated polyethylene glycol is one or more of the following: hydroxy-polyethylene glycol-carboxyl, hydroxy-polyethylene glycol-amino, hydroxy-polyethylene glycol-succinic acid, hydroxy-polyethylene glycol-hydroxy, and polyethylene glycol monododecyl ether.

3. The low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The hydroxyl-terminated polyethylene glycol is composed of one or more of the following: hydroxyl-terminated polyethylene glycol with a molecular weight of 400, 1000, 2000, 4000, 6000, and 8000.

4. The low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The acrylate monomer is one or more of butyl methacrylate, isooctyl methacrylate, methyl methacrylate, alkyl octadecyl acrylate, hydroxyethyl methacrylate, alkyl dodecyl acrylate, butyl acrylate, isooctyl acrylate, acrylic acid, and hydroxyethyl acrylate.

5. The low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The vinylsilane monomer is one or more of triethylvinylsilane, diethylmethylvinylsilane, diethoxymethylvinylsilane, and 3-chloropropyldimethylvinylsilane.

6. The low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The thermal initiator is one or more of benzoyl peroxide, tert-butyl peroxide, tert-butyl peroxide-2-ethylhexanoate, and diacyl peroxide.

7. The low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The weak base is one or more of pyridine and triethylamine.

8. The low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The oxidant is thionyl chloride; The solvent is one or more of ethyl acetate, butyl acetate, propyl acetate, toluene, and xylene.

9. The low-temperature resistant acrylic pressure-sensitive adhesive grafted with polyethylene glycol according to claim 1, characterized in that, The crosslinking agent is one or more of toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

10. A method for preparing a low-temperature resistant acrylate pressure-sensitive adhesive grafted with polyethylene glycol, characterized in that, The specific steps include: Step 1: Weigh the acrylate monomer, thermal initiator and part of the solvent and put them into the reaction vessel. Stir and heat to the set temperature to uniformly disperse the acrylate monomer. Keep warm for 2-4 hours. The set temperature is 70-95℃. Step 2: Add the solvent and thionyl chloride dropwise into the reaction vessel and stir to perform acyl chlorination on the acrylate segments. The wetting time is 0.5 h and the temperature is set at 30 °C. Step 3: Add the chlorine dioxide and hydrogen chloride produced by the acylation reaction to the weak base reaction vessel dropwise, and stir for 0.5 hours. Step 4: Add hydroxyl-terminated polyethylene glycol and the remaining solvent and continue the reaction at 70°C for 1 hour. Step 5: Cool to room temperature and discharge. Step 6: Add crosslinking agent, heat and stir for 0.5 hours, then cure at room temperature for 24 hours; set the temperature to 80~100℃; In steps 1 to 6, the stirring rate is 100~200 r / min.

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