Synthesis of Crosslinked Acrylate Pressure-Sensitive Adhesives

1 Introduction

Since the pressure sensitive adhesive was used in large quantities in the 1980s, due to its special use performance and effects, it has been widely used in various fields of industry, agriculture and daily life. For example: various sealing tapes, labels, protective tapes, decorative plates, insulation layers, etc. With the increase in the number and scope of use of pressure-sensitive adhesives, the variety of pressure-sensitive adhesives has also increased continuously. At present, industrialized varieties are mainly classified into rubber type, acrylate type, and silicone type from the type of compound; and there are solvent type, emulsion type (water dispersion type), and hot melt type, etc. from the type of formulation. From the perspective of long-term development, water-based emulsions and solvent-free hot melts are undoubtedly the direction of development.

At present, the solvent-based acrylate pressure-sensitive adhesive still occupies a leading position on the comprehensive performance index of pressure-sensitive adhesives and the requirements for some special properties and the environmental protection devices for solvent recovery. Therefore, the high-performance solvent-based acrylic pressure The study of sensitive glue still has its important significance.

2 Experimental studies

2.1 Test materials

Butyl acrylate BA, purity 99.9%; isooctyl acrylate 2-EHA, purity 99.8%; hydroxyethyl acrylate 2-HEA, purity 98.5%; methyl methacrylate MMA, purity 99.9%; ethyl acetate EtAc, purity 99.82%; toluene, purity 99.91%; benzoyl peroxide, purity 99.1%; petroleum resin grade NP-S;

2.2 Synthetic process

In a four-necked flask equipped with a stirring, reflux condenser, thermometer, and N2 tube, the above-mentioned various raw materials were metered in, N2 was passed, stirred, and the temperature was raised. When the temperature was raised to 78°C, the polymerization reaction started. At this temperature Under the refluxing reaction for 5 hours, then part of the initiator was added. The temperature of the reactants was increased to 85° C. and then reacted for 1 hour. After the unreacted monomers were further reacted, they were cooled. When the temperature dropped to 30° C., the tackifier resin was added. After dissolution is uniform, the solvent-type acrylate pressure-sensitive adhesive is filtered.

2.3 Performance Test Methods

Since this test was made during the course of studying in Japan, the method of testing was the adoption of Japanese Industrial Standards (JIS). 2.3.1 Fabrication of specimens Manufactured according to the JIS-1008 standard.
2.3.2 180o peeling test according to JIS-1009 standard.
2.3.3 Tack force Tested in accordance with JIS-1010.
2.3.4 Fast adhesion force Tested in accordance with JIS-1011.

3 Results and Discussion

3.1 Effect of Solvent on Adhesive Viscosity

As we all know, there are many factors that affect the viscosity of polymers, such as monomer concentration, polymerization time, polymerization temperature, initiator concentration, and stirring state. In this experiment, we studied the effect of neglected solvents on the viscosity of adhesives. After fixing other conditions, only the proportion of toluene and ethyl acetate in the solvent was changed, and adhesives with different viscosities were obtained.

From the test results in Table 1, it can be seen that, in the case of the same monomer ratio, the change of the solvent ratio has a great influence on the viscosity of the adhesive. Acrylate pressure-sensitive adhesives suitable for coating performance can be designed by varying the ratio of toluene to ethyl acetate.

3.2 Effect of Crosslinking Agent on Adhesive Bonding Performance

We use the above-mentioned synthetic C formula to divide the adhesive and add different proportions of cross-linking agents. The test results are shown in Table 2. From the test results in Table 2, it can be seen that as the amount of crosslinker increases, the fast viscosity decreases because of the increase in the internal crosslink density. The stickiness when the cross-linking agent is less than 1.0 or less does not completely fall off after a predetermined time, and the amount of the cross-linking agent exceeds 1.0 after which the binder lattice is held because the adhesive strength of the adhesive is low when the cross-linking agent is insufficient. In terms of peeling, although the strength was the highest at 1.0, glue remained on the test plate, indicating that the cohesive force of the adhesive was insufficient. Judging from the comprehensive data balance, the optimum amount of crosslinker is 2.0%.

3.3 Effect of Tackifier Resin on Adhesive Bonding Properties

In this test, Adhesive C was used, the amount of cross-linking agent was 2.0%, and the tackifying resin was Nippon Oil Resin NPS. The influence of the addition amount of different tackifying resins on the adhesive performance is shown in Table 3.

From the above results, it can be seen that the addition of the tackifying resin has no effect on the tack retention, while the rapid tack decreases with the increase of the resin amount, and the peel strength increases with the increase of the amount of the resin. At the same time, in practical applications, the amount of tackifier resin can be determined based on the balance of its overall performance.

4 Conclusion

(1) Under the same conditions of solid content and glass transition temperature, changing the ratio of toluene and ethyl acetate can change the viscosity of the adhesive, that is, it increases with the increase of ethyl acetate.

(2) The cross-linking agent can improve the cohesion of the pressure-sensitive adhesive and improve its adhesive performance. The optimum dosage is 2.0%.
(3) The tackifier resin can increase the peel strength of the pressure-sensitive adhesive, but it is preferably from 15% to 30% in view of the balance of properties.

Source: 21st Century Fine Network