Figure 1: UV Irradiation of Regalite R1125 Hydrogenated Hydrocarbon Resin Emission Spectrum

Figure 1 displays typical absorption/emission spectra from Regalite R1125 hydrocarbon resin. The resin was irradiated with UV radiation with a wave length of 360nm. The emission peak at 420nm would be seen as a violet-colored fluorescence, but the emission intensity is very low and thus fluorescence is not significantly observed.

Tables 1–3 display the fluorescence emission and relative intensity of a variety of Regalite hydrogenated hydrocarbon resins and competitive hydrogenated hydrocarbon resins. All resin samples have been UV irradiated with a wave length of 360nm. The emission maximum peak wave lengths indicate the color of the fluorescence (see Figure 1) while the maximum intensity values indicate the "brightness" of the fluorescence.

All samples tested, both Eastman and the competition, fluoresce to varying degrees. Thus, when any of these resins are used in hot melt adhesive formulations additional UV absorbing chemicals would need to be added.

Table 1: Regalite, Regalrez, and Competitive Partially Hydrogenated Resins for Use in SBS Block Copolymers

Table 2: Regalite and Competitive Fully Hydrogenated Resins for Use in SIS Block Copolymers

Table 3: Hydrogenated Hydrocarbon Resins Intended for SBS Block Copolymer Based Hot Melt Adhesives in Asian Markets

As shown in the above data, partially hydrogenated hydrocarbon resins suitable for styrene-butadiene-styrene (SBS) tackification always fluoresce more than fully hydrogenated resins. Also, the competitive hydrogenated hydrocarbon resins, intended for SBS, have significant fluorescence emission intensity requiring the use of UV absorbers in the hot melt adhesive.

Partially Hydrogenated Hydrocarbon Resins with Very Low Fluorescence
Regalrez 3102 is a partially hydrogenated hydrocarbon resin with approximately 30% hydrogenation. It is ideally suited for SBS tackification and has a lower fluorescence emission intensity than most fully hydrogenated hydrocarbon resins. The molecular structure is flexible due to the specific feedstock selection for the pre-cursor resin. When hydrogenated, even to a low degree, the molecule remains flexible, therefore, Regalrez 3102 and other resins in the Regalrez product line have exceptionally low fluorescence.