Synthesis and Properties of BA-St-MMA Pressure-Sensitive Adhesives

At present, compared with developed countries, China's acrylic ester pressure-sensitive adhesives have a relatively large gap in technical level. The pressure sensitive adhesives are only acrylate emulsions, while developed countries are solvent-based, emulsion-based, and hot melt-based. Variety of competing development [1-4]. Therefore, the development of solvent-based pressure-sensitive adhesives in our country is of great significance. This article describes the preparation of solvent-borne acrylate pressures using azobisisobutyronitrile as an initiator and ternary copolymerization of butyl acrylate (BA), styrene (St), and methyl methacrylate (MMA) in toluene solvent. Sensitive adhesive process, and explore the reaction conditions to find the best reaction conditions.

1 Experiment part 1

1.1 The main raw materials and reagents

Azobisisobutyronitrile, AR; Toluene, CP; St, industrial grade, produced by Yueyang Chemical Plant; MMA, CP; BA, AR.

1.2 Preparation of Pressure Sensitive Adhesives

In a 250 mL three-necked flask, a portion of toluene dissolved in azobisisobutyronitrile and a predetermined amount of BA, St, and MMA distilled under reduced pressure were previously introduced, and N2 was introduced to replace the air in the flask and then heated in a water bath. To the reaction temperature, after the reaction for 2 hours, the remaining toluene solution of azobisisobutyronitrile was added, the reaction was incubated for 5 hours, and the temperature was gradually lowered. After the mixture was completely cooled, a copolymerized pressure-sensitive adhesive was obtained.

1.3 Performance Test

180° Peel Strength A 25mm×200mm polyester film and a 1.5mm×120mm×40mm aluminum sheet were carefully wiped with absolute ethanol, and the pressure-sensitive adhesive solution was adjusted to a proper viscosity with toluene and applied to the aluminum sheet and the polyester. On the membrane, air dry at room temperature and apply the adhesive surface. The peel strength was measured on a CSS-1101 electronic tensile tester according to GB2792-81. Solid content Weigh 1～1.5g of pressure sensitive glue solution, place it in a dry and clear glass watch glass of known quality, and put it into a drying oven at 110°C. After drying for 2 hours, remove it into a desiccator and cool to room temperature. Weigh, and then put it in a drying oven at 110 °C heat drying 30min, removed into a desiccator, cooled to room temperature weighing. The operation was repeated until the difference between the two weighing qualities was less than 0.01 g. The solid content of the pressure-sensitive adhesive is thus calculated. The sticking force and the initial sticking force are determined according to GB4851-84, and the initial sticking force is measured according to GB4852-84.

2 Results and Discussion

2.1 Effect of Reaction Temperature on Adhesive Properties

Take toluene 70mL, St30mL, MMA20mL, BA35mL, control azobisisobutyronitrile 30mmol L, change the reaction temperature, obtained a series of adhesive, measured the peel strength and solid content, the results are shown in Table 1.

When the thermal decomposition initiator is used, a certain temperature initiator must be reached to decompose to generate a sufficient amount of free radicals to initiate polymerization of the monomer, and too high a temperature will cause the initiator to decompose too quickly, affecting the relative molecular weight of the copolymer. . From Table 1, we can see that the peel strength and solid content of pressure-sensitive adhesives increase with temperature before 65°C, decrease with increasing temperature after 65°C, and are highest at 65°C, so the optimal reaction temperature It is 65°C. 2.2 The effect of MMA amount on adhesive performance Take toluene 70mL, St30mL, BA35mL, control azobisisobutyronitrile to 30mmol L, the reaction temperature is 65°C, change the amount of MMA, obtain a series of adhesives, determine its peel strength and solid Content, results are shown in Table 2.

In the terpolymer system, MMA is a hard monomer, because its side chain has a certain polarity, can give pressure-sensitive adhesive cohesion and adhesive properties. From Table 2, it can be seen that as the amount of MMA increases, the peel strength of the adhesive increases, and when the amount of MMA exceeds 20 mL, the glass transition temperature Tg of the copolymer may increase excessively, and the rigidity of the molecular chain becomes large, so that the peel strength decreases. . At this point, the solid content increased with the increase of MMA level first and then decreased. When the dosage was 20 mL, the solid content was the largest, and the monomer ratio of the copolymerization was reasonable, which resulted in the maximum solid content. 2.3 The impact of St content on the performance of the adhesive Toluene 70mL, MMA20mL, BA35mL, control azobisisobutyronitrile to 30mmol L, the reaction temperature is 65 °C, change the amount of St, a series of adhesives were prepared to determine the peel strength and solid Content, results are shown in Table 3.

The addition of St is beneficial to increase the Tg of the copolymer, which can increase the peel strength of the adhesive. However, the benzene ring in the side chain of St is large in rigidity and the amount is too much, which adversely affects the performance of the adhesive. As can be seen from Table 3, when the amount of St is 30 mL, the effect is good. And the effect of St content on solid content is similar to that of MMA, but the effect is less than that of MMA. In summary, the optimal reaction conditions of the BA-St-MMA ternary copolymerized acrylate pressure-sensitive adhesive are as follows: 70 mL of toluene, 30 mmol of azobisisobutyronitrile, 20 mL of MMA, 30 mL of St, and 35 mL of BA, copolymerization temperature of 65°C.

3 Pressure-sensitive Adhesive Properties <br><br> Comparative Experiments Solvent-based three-component copolyacrylate pressure-sensitive adhesives were prepared according to the above optimal reaction conditions, and their properties were tested, and they were subjected to commercial solvent-based acrylic pressures produced by Wenzhou Taichang Adhesive Products Co., Ltd. Sensitive adhesives were compared and the results are shown in Table 4.

From Table 4, it can be seen that the performance of the ternary copolymer adhesive has higher peel strength, better stickiness and initial tackiness than the commercial pressure-sensitive adhesive, and the adhesive has good transparency.

4 Conclusion

The optimal reaction conditions for the preparation of acrylate pressure-sensitive adhesives by terpolymerization of BA-St-MMA were as follows: 70 mL of toluene, 30 mmol of azobisisobutyronitrile, 20 mL of MMA, 30 mL of St, and 35 mL of BA. The copolymerization temperature was 65°C. Under this condition, the synthesized pressure-sensitive adhesive can achieve a peel strength of 13 (25mm) N and a solids content of 63.9%. Compared with commercial pressure-sensitive adhesives, it has higher peel strength, better tack retention and initial tackiness. Adhesive transparency is good.