Hot polymerized emulsion styrene butadiene rubber

Non-crosslinked eSBR rubbers can be handled by most mixers, although the efficiency will depend on mixer design, solvent solubility parameters and order of addition. An exception is SBR 1012; because it is a high molecular-weight polymer it requires high-shear mixing. Because of their structure, crosslinked polymers usually require greater shear energy to achieve a satisfactory blend.

For this reason, mixers with high-shear impellers circulating with high peripheral speed are recommended; good agitation is achieved even in high-viscosity solutions. Using our crumb rubbers simplifies mixing. as the resin and solvent can be added directly to the mixer. Because of the large surface area of the crumbs, incorporation of rubber and other ingredients is faster with milled or ground bale rubber.

The same mixers can be used with bale rubber, however milling or grinding is usually required first.

Sample formulations for adhesives and sealants

The following starting formulations demonstrate the versatility of our polymers. The final choice of polymers is dependent on the end-use application and its property requirement. Additional information on our hot and cold SBR polymers can be obtained by calling +1 800 962 8324.

Mixing process

1) Load 90 percent of the solvent and mix well.
2) Add the antioxidant and stir until well mixed.
3) Add all the tackifier and mix using medium shear until completely dissolved.
4) Add half the rubber under shear; mix until it is well wetted and is starting to disperse.
5) Add the remaining rubber and mix under high shear until smooth.
6) Adjust the viscosity as desired using the remaining solvent.

a) SBR 1009 AF2 is a crosslinked crumb SBR with 23.5 percent bound styrene; this product contains between 3 to 5 wt % calcium carbonate as a partitioning agent to prevent the crumb blocking during storage and transport. The very high level of crosslinking in SBR 1009 AF2 makes this rubber particularly suited to aerosol spray applied adhesive formulations. The high gel content results in a clean cobweb-free spray pattern. SBR 4503 can also be substituted for 1009 AF if higher bond strength is required. The lower level of crosslinking in 4503 may also result in a greater tendency to cobweb when sprayed.

b) Pentalyn* H is a pentaerythritol ester based tackifier resin available with a ball and ring softening point of 94 to102 °C. If this is not available, then any pentaerythritol ester-based tackifier with a similar melting point should provide similar performance.

c) Pure n-hexane, free of cyclo-aliphatics, may not dissolve 1009 AF2 well. The best choice is a blend containing at least 10 percent cyclohexane

d) Irganox* 1520 is an antioxidant available from Ciba.