A degradable water-based acrylic pressure-sensitive adhesive, a degradable adhesive tape and a preparation method thereof

Abstract

The invention discloses a degradable water-based acrylic pressure-sensitive adhesive, which is mainly composed of 65-75 parts of soft monomers, 7-12 parts of hard monomers, 5-10 parts of functional monomers, 10-15 parts of degradable oligomer monomers, 1-3 parts of emulsifiers, 0.3-0.5 parts of initiators and 120-135 parts of deionized water by mass; the degradable oligomer monomer is ε-caprolactone-modified hydroxyethyl methacrylate monomer, and / or hydroxy-terminated polylactide is modified by isocyanate to modify hydroxyethyl methacrylate monomer. The degradable water-based acrylic pressure-sensitive adhesive is environmentally friendly and pollution-free, and the degradable oligomer monomer participates in chemical crosslinking, and the obtained water-based acrylic pressure-sensitive adhesive has degradability.

Description

Technical Field

[0001] The invention relates to the technical field of pressure-sensitive adhesives, and in particular to a degradable water-based acrylate pressure-sensitive adhesive, a degradable adhesive tape and a preparation method thereof. Background Art

[0002] As people's environmental awareness increases, in order to achieve green development of packaging and packaging and reduce white pollution, the degradable performance of products is of great significance. The tape used for packaging auxiliary is composed of a base layer and an adhesive layer. The base material of the tape is mostly polyester film, biaxially oriented polypropylene film or polyvinyl chloride film; the adhesive layer material of the tape is mostly acrylic or ethylene-vinyl acetate copolymer adhesive. The base material and adhesive layer material of conventional tapes are non-degradable materials, which are easy to cause white pollution.

[0003] The existing technologies all use polylactic acid or polyvinyl alcohol to make the base layer, and the glue layer uses plant adhesives and other methods to solve the degradation problem. Although the disclosed technical solutions have their advantages, plant adhesives do not have the properties of pressure-sensitive adhesives, and the gluing process is complicated. Therefore, there are limitations in use and promotion.

[0004] CN114479697A discloses a degradable pressure-sensitive adhesive tape, wherein the substrate layer is made of a polylactic acid-based material and the adhesive layer is a water-based acrylic pressure-sensitive adhesive. Although the water-based acrylic pressure-sensitive adhesive is environmentally friendly, the adhesive layer obtained by polymerization and curing is still not degradable. Summary of the invention

[0005] One of the purposes of the present invention is to overcome the defects in the prior art and provide a degradable water-based acrylate pressure-sensitive adhesive which is environmentally friendly and pollution-free. The degradable oligomers participate in chemical crosslinking, and the obtained water-based acrylate pressure-sensitive adhesive is degradable.

[0006] In order to achieve the above-mentioned process effect, the technical scheme of the present invention is: a degradable water-based acrylic pressure-sensitive adhesive, wherein the main components of the degradable water-based acrylic pressure-sensitive adhesive are 65-75 parts of soft monomer, 7-12 parts of hard monomer, 5-10 parts of functional monomer, 10-15 parts of degradable oligomer monomer, 1-3 parts of emulsifier, 0.3-0.5 parts of initiator and 120-135 parts of deionized water in parts by weight;

[0007] The degradable oligomer monomer is ε-caprolactone modified hydroxyethyl methacrylate monomer, and / or hydroxyl-terminated polylactide modified hydroxyethyl methacrylate monomer by isocyanate.

[0008] The preferred technical solution is: the emulsion synthesis method of the degradable water-based acrylic pressure-sensitive adhesive is a core-shell synthesis method or a seed emulsion polymerization method;

[0009] The core-shell synthesis method comprises core emulsion synthesis and shell emulsion synthesis. The core emulsion comprises hydroxyethyl methacrylate monomer modified by isocyanate with terminal hydroxyl polylactide; and the shell emulsion comprises hydroxyethyl methacrylate monomer modified by ε-caprolactone.

[0010] The preferred technical solution is: the emulsifier includes allyloxy nonylphenol polyoxyethylene ether ammonium sulfate and allyloxy nonylphenol polyoxyethylene ether, and the mass ratio of allyloxy nonylphenol polyoxyethylene ether ammonium sulfate and allyloxy nonylphenol polyoxyethylene ether is (1-1.6):1.

[0011] The preferred technical solution is: the initiator is sodium persulfate and / or ammonium persulfate.

[0012] The preferred technical solution is: the soft monomer is isooctyl acrylate and butyl acrylate; the hard monomer is methyl methacrylate; the functional monomer is β-carboxyethyl acrylate. Furthermore, the mass ratio of isooctyl acrylate to butyl acrylate is 1:(5-9).

[0013] The preferred technical scheme is: the ε-caprolactone modified hydroxyethyl methacrylate monomer is prepared by reactants ε-caprolactone and hydroxyethyl methacrylate in a molar ratio of (2-4):1, 1.2%-1.6% of stannous isooctanoate catalyst and 0.1% of p-hydroxyanisole inhibitor in the total mass of the reactants;

[0014] The hydroxyl-terminated polylactide is prepared by reacting lactide and 1,4-butanediol with a molar ratio of (8-12):1 with isocyanate-modified hydroxyethyl methacrylate monomer, and initiating ring-opening polymerization of lactide with 1,4-butanediol under the action of 0.3%-0.5% of the total mass of the reactants as a stannous octoate catalyst to obtain the hydroxyl-terminated polylactide; then, the hydroxyl-terminated polylactide and isophorone diisocyanate (IPDI) with a molar ratio of 1:2 are reacted with dibutyltin dimethicone catalyst to obtain an isocyanate-terminated polyamine prepolymer, which is then reacted with hydroxyethyl methacrylate to obtain a double-bond-terminated oligomer.

[0015] The second object of the present invention is to overcome the defects in the prior art and provide a degradable adhesive tape, comprising a degradable substrate layer and an adhesive layer, wherein the adhesive layer is made of the above-mentioned degradable water-based acrylate pressure-sensitive adhesive.

[0016] The third object of the present invention is to overcome the defects existing in the prior art and provide a method for preparing a degradable adhesive tape, comprising the following steps:

[0017] S1: configuring a degradable substrate layer;

[0018] S2: preparing the above-mentioned degradable water-based acrylate pressure-sensitive adhesive;

[0019] S3: diluting the degradable water-based acrylic pressure-sensitive adhesive and spraying it on the surface of the release film to form an uncured adhesive layer;

[0020] S4: drying and preliminarily curing the adhesive layer, and aging;

[0021] S5: The adhesive layer is compounded with the degradable substrate layer to obtain the degradable adhesive tape.

[0022] The preferred technical solution is: in S3, the stirring speed of diluting the degradable water-based acrylic pressure-sensitive adhesive is 500-800 r / min, the time is 20-30 min, and the dilution is performed to a solid content of 25-35%.

[0023] The preferred technical solution is: in S4, the continuous drying temperatures are set to: 60±5°C, 100±5°C, 130±5°C, 130±5°C, 110±5°C, 90±5°C, the aging temperature is 45-50°C, and the aging time is more than 72 hours.

[0024] The advantages and beneficial effects of the present invention are:

[0025] The degradable water-based acrylic pressure-sensitive adhesive is environmentally friendly and pollution-free. The degradable oligomers participate in chemical cross-linking, and the obtained water-based acrylic pressure-sensitive adhesive is degradable.

[0026] The obtained degradable water-based acrylic pressure-sensitive adhesive has good water resistance and weather resistance;

[0027] The obtained degradable water-based acrylic pressure-sensitive adhesive has good biocompatibility. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of the present invention.

[0029] supplier

[0030] Isooctyl acrylate was purchased from Shanghai Huayi Company;

[0031] Butyl acrylate was purchased from Shanghai Huayi Company;

[0032] Methyl methacrylate was purchased from Formosa Plastics Group, Taiwan, China;

[0033] Hydroxyethyl acrylate was purchased from LG Group Co., Ltd. of South Korea;

[0034] β-Carboxyethyl acrylate was purchased from Guangzhou Lijun New Materials Co., Ltd.

[0035] Functional monomer

[0036] It is β-carboxyethyl acrylate, and the prepared acrylate pressure-sensitive adhesive emulsion has good stability. It is cross-linked with the hydroxyl groups of the degradable oligomer monomers, further improving the stability and cohesion of the acrylate pressure-sensitive adhesive emulsion and improving the water resistance of the degradable water-based acrylate pressure-sensitive adhesive.

[0037] Emulsifier

[0038] Including allyloxy nonylphenol polyoxyethylene ether ammonium sulfate (DNS-86) and allyloxy nonylphenol polyoxyethylene ether (ANPEO10), through the double bond of the emulsifier and the double bond of the monomer polymerization, the migration of the emulsifier during film formation is effectively solved, which has adverse effects on the adhesion, water resistance and mechanical properties of the adhesive layer. The emulsifier compounded with DNS-86 and ANPEO10 has good stability and no stratification; the film-forming property of the adhesive layer is also good.

[0039] Degradable oligomer monomer

[0040] (1) Preparation of ε-caprolactone-modified hydroxyethyl methacrylate monomer: The reactants ε-caprolactone and hydroxyethyl methacrylate were prepared in a molar ratio of 3:1. The reactor was filled with N2 for protection. Hydroxyethyl methacrylate was first added into the reactor containing 30% ethyl acetate solution of the total mass of the reactants. Then, 1.5% of the total mass of the reactants, stannous isooctanoate, and 0.1% of p-hydroxyanisole as an inhibitor were added. The temperature was raised to 120°C and kept warm. Then, ε-caprolactone was added dropwise one by one and the reaction was allowed to fully react for 6 hours.

[0041] (2) Preparation of terminal hydroxyl polylactide by isocyanate-modified hydroxyethyl methacrylate monomer: The reactor is filled with N2 for protection, and the reactants lactide and 1,4-butanediol are prepared in a molar ratio of 10:1. The 1,4-butanediol initiates the ring-opening polymerization of lactide in the presence of 0.4% stannous octoate catalyst of the total mass of the reactants. The reaction is kept at 150°C, and the product is dissolved in chloroform and precipitated with anhydrous ethanol, and dried in a vacuum environment at 50°C for 24 hours to obtain terminal hydroxyl polylactide; The terminal hydroxyl polylactide, isophorone diisocyanate (IPDI) and hydroxyethyl methacrylate are prepared in a ratio of 1:2:2. The terminal hydroxyl polylactide and 80% IPDI toluene solution are used as a dibutyltin disilicate catalyst to prepare an isocyanate-terminated polyamine prepolymer, and the reaction is maintained at 80±1°C for 2.5 hours. The temperature is lowered and hydroxyethyl methacrylate is added. The reaction is maintained at 70±1°C for 2.5 hours. The product is centrifuged in ether and precipitated. The product is dried under vacuum at 50°C for 24 hours.

[0042] Seeded emulsion polymerization method

[0043] Preparation of pre-emulsion: The emulsifier is dispersed in deionized water. After uniform dispersion, a mixture of soft monomers, hard monomers, functional monomers and degradable oligomer monomers is slowly added, and the addition of the mixed monomers is completed within 5 minutes. Stir thoroughly within 30 minutes to make the emulsion milky white. When standing, it does not stratify, and the preparation of the pre-emulsion is completed.

[0044] First, mix deionized water, sodium bicarbonate powder and emulsifier, and mix them evenly at a stirring speed of 180r / min, and heat them to 80°C, add the first part of initiator and pre-emulsion (8%), and react until the emulsion emits blue light and there is basically no reflux on the condenser tube, then add the second part of initiator and pre-emulsion dropwise for 3 hours. After the addition of the reactants is completed, heat to 85°C, keep the reaction warm for 2 hours, then cool to below 40°C, add ammonia water, and adjust the pH value of the emulsion to 7-8.

[0045] The composition of the seed emulsion by mass is shown in Table 1:

[0046]

[0047]

[0048] The first oligomer is ε-caprolactone modified hydroxyethyl methacrylate monomer; the second oligomer is hydroxyl-terminated polylactide modified hydroxyethyl methacrylate monomer by isocyanate.

[0049] Core-shell synthesis

[0050] Core emulsion synthesis: first, soft monomer, hard monomer, functional monomer, terminal hydroxyl polylactide modified by isocyanate hydroxyethyl methacrylate monomer, emulsifier and initiator are used as raw materials, and mixed evenly at a stirring speed of 500r / min to prepare a pre-emulsion; deionized water is added to the reactor, the temperature is raised to 85°C, the stirring speed is set to 150r / min, and then 10% of the first part of the pre-emulsion is dripped within 1 hour, and the reaction is kept warm for 30 minutes; then the second part of the pre-emulsion is dripped, the dripping time is 3 hours, and after the dripping of the reactants is completed, the reaction is kept warm for 1 hour, and finally the temperature is reduced and the material is discharged.

[0051] Shell emulsion synthesis: soft monomer, hard monomer, ε-caprolactone modified hydroxyethyl methacrylate monomer, emulsifier and initiator are used as raw materials, and mixed uniformly at a stirring speed of 1000r / min to prepare a pre-emulsion; deionized water, sodium bicarbonate powder and emulsifier are mixed in a reactor, the stirring speed is set to 200r / min, and the temperature is raised to 85°C, and then 5% of the first part of the pre-emulsion is added dropwise within 30min, and the reaction is kept warm for 30min; then 95% of the second part of the pre-emulsion is added dropwise, the addition time is 3h, and after the addition of the reactants is completed, the reaction is kept warm for 1h, and finally the temperature is lowered to room temperature.

[0052] Preparation of core-shell emulsion: The synthesized core emulsion and shell emulsion were pre-treated and shaken in an ultrasonic machine for 30 minutes, and then the core emulsion and shell emulsion were mixed in a mass ratio of 1: (0.6-0.9), and heated and stirred at 90°C for 1 hour.

[0053] The composition of the core emulsion by mass is shown in Table 2:

[0054]

[0055]

[0056] The composition of the core emulsion by mass is shown in Table 3:

[0057]

[0058] In the preparation of the core-shell emulsion, the core emulsion and the shell emulsion are as follows in Table 4 according to the mass ratio:

[0059] Nuclear Emulsion Shell Emulsion Sample 11 1 0.7 Sample 12 1 0.9

[0060] The dilution configurations of the degradable water-based acrylate pressure-sensitive adhesives of the embodiments and comparative examples are shown in Table 5 by weight:

[0061]

[0062]

[0063] The method for preparing a degradable adhesive tape comprises the following steps:

[0064] S1: A degradable substrate layer of 40 μm is provided, and the material of the substrate layer is polylactic acid;

[0065] S2: Examples 1 to 3 and Comparative Example 1 are provided with a degradable water-based acrylate pressure-sensitive adhesive according to Table 1;

[0066] S2': Example 4-5 is prepared according to Tables 2-4 with a degradable water-based acrylate pressure-sensitive adhesive;

[0067] S3: dilute the degradable water-based acrylic pressure-sensitive adhesive according to Table 5, and spray it on the surface of the release film to form an uncured adhesive layer; the stirring speed of the diluted degradable water-based acrylic pressure-sensitive adhesive is 600 r / min, and the time is 30 min.

[0068] S4: Dry and preliminarily cure the adhesive layer, and mature it; the continuous drying temperatures are set in sequence: 60°C, 100°C, 130°C, 130°C, 110°C, 90°C, the maturation temperature is 50°C, the maturation time is more than 72h, and the thickness of the adhesive layer is 20μm.

[0069] S5: The adhesive layer is compounded with the degradable substrate layer to obtain a degradable adhesive tape.

[0070] Performance test of biodegradable tape:

[0071] (1) Peel strength: According to the standard GB / T2792-2014, a standard tape (25 mm*200 mm) was attached to a stainless steel plate wiped clean with alcohol, and pressed back and forth with a 2 kg roller. After being left at room temperature for a period of time, it was tested by a peel strength tester. The results were measured more than three times and the average value was calculated.

[0072] (2) Adhesion retention: According to the standard GB / T4851-2014, a standard tape (25 mm wide and 100 mm long) was attached to a stainless steel plate, with the upper end aligned with the standard line and the excess portion at the lower end cut off. The plate was pressed back and forth three times with a 2 kg roller and then placed at room temperature for 30 min. The stainless steel plate with the sample was vertically hung on the test frame and kept stationary. A weight of 500 g was hung below. The time it took for the tape to fall represented the adhesion retention of the pressure-sensitive adhesive.

[0073] (3) Aging resistance: The tape was placed in a constant temperature and humidity aging box at 70°C and 95% humidity for 72 hours, and then the peel strength was measured.

[0074] (4) Degradability: Cut the adhesive tapes of the embodiment and comparative example into 5 samples of each with a size of 20 cm in length and 5 cm in width. First weigh the mass m0 before degradation. Bury the sample in soil with a pH of about 6 for 1 month, and then weigh the mass m1 after burying. The decomposition rate = (m0-m1) / m0*100%. The larger the m0, the better the degradability of the tape.

[0075] The performance test results of the degradable water-based acrylic pressure-sensitive adhesives of the embodiments and comparative examples are shown in Table 6:

[0076]

[0077] Excellent degradable tape meets the following requirements: adhesion retention greater than 24 hours; aging resistance, the peel strength change after aging compared to before aging is plus or minus 0.5N / 25mm; decomposition rate is greater than 85%.

[0078] Compared with Example 1, the degradable oligomer monomer in Example 2 contains only ε-caprolactone modified hydroxyethyl methacrylate monomer, and the degradable performance does not change much. However, due to the reduced crosslinking density, the peel strength increases, and the cohesive force decreases, which has a negative effect on the adhesion. Moreover, it does not contain polyurethane modification, which has a negative effect on the aging resistance.

[0079] Compared with Example 1, the degradable oligomer monomer in Example 3 only contains terminal hydroxyl polylactide modified with hydroxyethyl methacrylate monomer by isocyanate, and the degradable performance does not change much. However, due to the reduced crosslinking density, increased peel strength, and decreased cohesion, the adhesion and aging resistance properties are negatively affected.

[0080] Compared with Example 4, in Example 5, due to the increased ratio of shell emulsion to core emulsion, more cross-linking points of β-carboxyethyl acrylate and ε-caprolactone-modified hydroxyethyl methacrylate monomers are formed, the cohesive force is greater, the viscosity is reduced, and the peel strength is reduced. However, after the aging test, the difference in peel strength change is smaller.

[0081] Compared with Example 1, in Comparative Example 1, no degradable oligomer monomer was added, the adhesive layer was not decomposed, and only the base material layer of the polylactic acid material was decomposed.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A degradable water-based acrylic pressure-sensitive adhesive, characterized in that: The main components of the degradable water-based acrylate pressure-sensitive adhesive are, by weight, 65-75 parts of soft monomers, 7-12 parts of hard monomers, 5-10 parts of functional monomers, 10-15 parts of degradable oligomer monomers, 1-3 parts of emulsifiers, 0.3-0.5 parts of initiators, and 120-135 parts of deionized water. The degradable oligomer monomer is ε-caprolactone modified hydroxyethyl methacrylate monomer, and / or hydroxyl-terminated polylactide modified hydroxyethyl methacrylate monomer by isocyanate; The emulsion synthesis method of the degradable water-based acrylic pressure-sensitive adhesive is a core-shell synthesis method or a seed emulsion polymerization method; The core-shell synthesis method comprises core emulsion synthesis and shell emulsion synthesis. The core emulsion comprises hydroxyethyl methacrylate monomer modified by isocyanate with terminal hydroxyl polylactide; and the shell emulsion comprises hydroxyethyl methacrylate monomer modified by ε-caprolactone.

2. The degradable water-based acrylate pressure-sensitive adhesive according to claim 1, characterized in that: The emulsifier comprises allyloxy nonylphenol polyoxyethylene ether ammonium sulfate and allyloxy nonylphenol polyoxyethylene ether, and the mass ratio of allyloxy nonylphenol polyoxyethylene ether ammonium sulfate and allyloxy nonylphenol polyoxyethylene ether is (1-1.6):

1.

3. The degradable water-based acrylate pressure-sensitive adhesive according to claim 1, characterized in that: The initiator is sodium persulfate and / or ammonium persulfate.

4. The degradable water-based acrylate pressure-sensitive adhesive according to claim 1, characterized in that: The soft monomer is isooctyl acrylate and butyl acrylate; the hard monomer is methyl methacrylate; and the functional monomer is beta-carboxyethyl acrylate.

5. The degradable water-based acrylate pressure-sensitive adhesive according to claim 1, characterized in that: The ε-caprolactone modified hydroxyethyl methacrylate monomer is prepared by reacting ε-caprolactone and hydroxyethyl methacrylate in a molar ratio of (2-4):1, 1.2%-1.6% of the total mass of the reactants, a stannous isooctanoate catalyst, and 0.1% of a p-hydroxyanisole inhibitor; The hydroxyl-terminated polylactide is prepared by reacting lactide and 1,4-butanediol with a molar ratio of (8-12):1 with isocyanate-modified hydroxyethyl methacrylate monomer, and initiating ring-opening polymerization of lactide with 1,4-butanediol under the action of stannous octoate catalyst with a total mass of 0.3%-0.5% of the total mass of the reactants to obtain the hydroxyl-terminated polylactide; then, the hydroxyl-terminated polylactide and isophorone diisocyanate (IPDI) with a molar ratio of 1:2 are reacted with dibutyltin disilicic acid catalyst to obtain an isocyanate-terminated polyamine prepolymer, which is then reacted with hydroxyethyl methacrylate to obtain a double-bond-terminated oligomer.

6. A degradable adhesive tape comprising a degradable substrate layer and an adhesive layer, characterized in that: The adhesive layer is made of the degradable water-based acrylate pressure-sensitive adhesive according to any one of claims 1 to 5.

7. A method for preparing a degradable adhesive tape, characterized in that: The following steps are involved: S1: configuring a degradable substrate layer; S2: preparing the degradable water-based acrylate pressure-sensitive adhesive according to any one of claims 1 to 5; S3: diluting the degradable water-based acrylic pressure-sensitive adhesive and spraying it on the surface of the release film to form an uncured adhesive layer; S4: drying and preliminarily curing the adhesive layer, and aging; S5: The adhesive layer is compounded with the degradable substrate layer to obtain the degradable adhesive tape.

8. The degradable water-based acrylate pressure-sensitive adhesive according to claim 7, characterized in that: In S3, the stirring speed of diluting the degradable water-based acrylic pressure-sensitive adhesive is 500-800 r / min, the time is 20-30 min, and the dilution is performed to a solid content of 25-35%.

9. The degradable water-based acrylate pressure-sensitive adhesive according to claim 7, characterized in that: In S4, the continuous drying temperatures are sequentially set to: 60±5°C, 100±5°C, 130±5°C, 130±5°C, 110±5°C, 90±5°C, the aging temperature is 45-50°C, and the aging time is more than 72 hours.

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