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SBR latex polymers with improved auto-adhesion

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Continuously decreasing availability and increasing costs create incentives to identify suitable alternatives to natural rubber. Adhesive formulators have blended natural rubber latex with small amounts of styrene-butadiene latex, albeit with a negative impact on adhesive performance. For some pressure sensitive adhesive applications natural rubber has been hard to replace because of its superior auto-adhesion characteristics, low tack and good compatibility with tackifiers. Newly engineered SBR latexes might enable adhesive formulators to substantially substitute SBR for NR. Such latexes offer improved auto-adhesion through molecular architecture and polymer characteristics. These new SBRs are fully miscible up to 20 percent with NR, and the homogeneous blends show the same or better autohesion properties as natural rubber in a certain ratio. The autohesion characteristics are gradually changing with increasing SBR concentration higher than 20 percent. This paper discusses the design of new synthetic SBR which can be blended in with NR at high concentrations without sacrificing adhesive performance for cold seal, tamper evidence and similar applications. The SBR latexes are fully miscible up to 20 percent with NR and the homogeneous blends showing the same or better (90/10 NR/SBR) autohesion properties as natural rubber. Autohesion gradually deteriorates with an increasing SBR concentration over 20 percent. However, natural rubber’s low tack is preserved over a wide range of SBR.