Thickening acrylic adhesive

Acrylic adhesives are known to be used, including heat melt adhesives, heat activation adhesives, and pressure sensitive adhesives to bond on a variety of substrates such as metals, painted surfaces, plastics, etc. Acrylic adhesives, especially acrylic pressure-sensitive adhesives are known for their transparency and excellent aging properties.

The preparation of acrylic pressure-sensitive adhesives has been reported in a number of literature, including, for example, US patents Re24,906(Ulrich), 4,181,752(Martens et al.), 4,952,650(Young et al.), and 4.569.960(Blake). Although acrylic adhesives are versatile, they do not bond well on some substrates, such as certain types of automotive paints and low-energy olefin surfaces commonly used in acrylic adhesives. Improving the adhesion of acrylic adhesives on these types of surfaces (i.e., increasing dry viscosity) has been investigated, usually by increasing the adhesion of base acrylic polymers. Various types of tackifying resins include phenol-modified alkenes, hydrocarbon resins (such as polyvinylcyclohexane and polytert-butylstyrene), and rosin resins (such as rosin glycerol vinegar and rosin pentaerythritol).

Due to the high solubility parameters of most acrylic pressure-sensitive adhesives and the particular potential interactions that exist between these adhesives and many viscosities resins, the options available to formulation designers for viscosifier resins are limited. As a class of resins, hydrocarbon base viscosifier resins, especially hydrogenated hydrocarbon resins, are not suitable for the preparation of polar acrylic binders because of their non-polar properties.

Among various acrylic pressure-sensitive binders, rosin base viscosifying resins and selected phenol-modified ene and A-delay resins show good performance. However, there are still some problems with the limited range of these viscosifying resins used in acrylic adhesives. Viscosifying acrylic pressure-sensitive adhesives preparations often turn discolored or yellow. The yellowing appearance of these viscosifying acrylic pressure-sensitive adhesives is a direct consequence of the particular yellow tint inherent in many of these viscosifying resins, which can become quite noticeable through aging and exposure to light even with lighter color grades. Acrylic adhesives without viscosities often have excellent aging properties.