US007 112632B2 (12) United States Patent (10) Patent No.: US 7,112,632 B2 Viola et al. (45) Date of Patent: Sep. 26, 2006 (54) PROCESS FOR THE PREPARATION OF 5,567,784. A 10, 1996 Wieder et al. LOW BRANCH CONTENT POLYBUTADIENE 5,681,886 A * 10/1997 Fuchs et al. ................ 524,493 6,090,926 A 7/2000 Keyer et al. (75) Inventors: Gian Tommaso Viola, Cervia (IT): 2005, 0182213 A1 8, 2005 Viola et al. Fabio Bacchelli, Ravenna (IT): Silvia FOREIGN PATENT DOCUMENTS Valenti, Ravenna (IT) EP O 957 115 A1 11, 1999 (73) Assignee: Polimeri Europa S.p.A., Brindisi (IT) EP 1 O99 71.0 A1 5, 2001 OTHER PUBLICATIONS (*) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 R. P. Quirk, et al., “Butadiene polymerization using neodymium U.S.C. 154(b) by 0 days. versatate-based catalysts: catalyst optimization and effects of water and excess versatic acid”, Polymer, Elsevier Science Publishers (21) Appl. No.: 11/250,383 B.V. GB, vol. 41, No. 15, Jul. 2000, pp. 5903-5908. * cited by examiner (22) Filed: Oct. 17, 2005 Primary Examiner Fred Teskin (65) Prior Publication Data (74) Attorney, Agent, or Firm Oblon, Spivak, McClelland, US 2006/0089472 A1 Apr. 27, 2006 Maier & Neustadt, P.C. (30) Foreign Application Priority Data (57) ABSTRACT A process for the preparation of low branch content polyb Oct. 25, 2004 (IT) .......................... MI2OO4A2O22 utadiene comprising: (51) Int. Cl. (a) a first butadiene polymerisation stage; CSF 8/08 (2006.01) (b) treatment of the polymer solution obtained upon CSF I36/06 (2006.01) completion of stage (a) with a coupling agent selected from: (52) U.S. Cl. ...................... 525/193; 525/232; 525/237; (i) polyunsaturated natural oils; 525/269; 525/285; 525/286; 525/302:525/333.2: (ii) butadiene and/or isoprene oligomers; 526/164; 526/340.4; 524/572 (iii) butadiene and/or isoprene co-polymers with viny (58) Field of Classification Search ................ 525/193, larene monomers; 525/232,237,269,285, 286, 302,333.2: the unsaturations present in compounds (i)–(iii) being at 526/164, 340.4; 524/572 least partially substituted with groups selected from See application file for complete search history. epoxides, anhydrides and esters; (56) References Cited (c) recovery of the low branch content polybutadiene obtained upon completion of stage (b). U.S. PATENT DOCUMENTS 4,990,573 A * 2/1991 Andreussi et al. ....... 525,332.3 23 Claims, 2 Drawing Sheets U.S. Patent Sep. 26, 2006 Sheet 1 of 2 US 7,112,632 B2 Fig. 1 a After...yrn 3' in the mixer BEFOREMIXING To or 10, 1o 1o 10 Freq rad/s) Fig. 1b After 3' in the mixer se? V Freq rad/s) U.S. Patent Sep. 26, 2006 Sheet 2 of 2 US 7,112,632 B2 1Of 10' 10 Fred rad/s) US 7,112,632 B2 1. 2 PROCESS FOR THE PREPARATION OF polymer, Such as polybutadiene, synthesised using Nd and LOW BRANCH CONTENT POLYBUTADIENE alkyl aluminium based catalytic systems, the elasticity required during processing is provided by the high molecu The present invention relates to a process for the prepa lar weight fractions. It is known that an excessively wide ration of low branch content, highly cis polybutadiene. The molecular weight distribution, i.e. containing both high polybutadiene thus obtained, displays an optimal balance molecular weight fractions (e.g. >10), and also those with between viscosity and elastic properties, which translates low molecular weights (e.g. <5.10), is not suited to pro into a definite improvement in workability. cessing using traditional (short) mixing cycles in order to The present invention also describes sulphur Vulcanisable provide a Vulcanised product with Sufficiently good techno mixtures, wherein the elastomeric component comprises the 10 logical characteristics. The high molecular weight fraction, low branching content, highly cis polybutadiene, prepared necessary for transmission of the work energy, is excessive, according to the process of the present invention. resulting in reduced process yield, in that the material has a It is known that the introduction of branching into a linear tendency to break up, hence reducing the shear force, during polymeric structure conveys a series of applicational advan the mixing stage. Thus, the high molecular weight frag tages, foremost among which being an improvement in 15 ments, whilst on the one hand favouring dispersion, on the workability. other hand, necessitate a longer incorporation (wetting) The workability of an elastomeric material is a very stage, and consequently, increased mixing times. important parameter in the transformation industry which Once the high molecular weight variable limits have been adds various fillers to the rubber, foremost amongst which established in practice, it follows that it is not possible to being reinforcing fillers (for example silica and carbon eliminate Such fraction without simultaneously eliminating black), using closed mixing devices with defined internal the complimentary low molecular weight fraction: it should geometries. When the user has the aim of maximising plant be remembered that the material has a reasonably symmetri yield, it is necessary that the rheological characteristics of cal molecular weight distribution around a central molecular the material be such as to make incorporation of the filler weight, and that its Mooney viscosity is typically equal to possible in the shortest possible time. 25 40–50; hence it is obvious that with a wide molecular weight Optimum distribution of the latter is demonstrated in the distribution, we would have both low and high molecular improved mechanical and dynamic characteristics of the weights, where the former would act as plasticisers (viscous Vulcanised product. Filler dispersion is correlated with component) and the latter, as already mentioned, as elastic parameters which are measured using a variety of tech components. The reduction or elimination of the high and niques; amongst which being electrical conductivity, in the 30 low molecular weight fractions, ideally bringing us towards case of carbon black mixtures, the Payne effect, or more a Poisson distribution, would give rise to a polymer without practically, Mooney viscosity, before and after incorpora any internal plasticisers, hence during processing, display tion. Generally, aside from degradative phenomena, which ing the behaviour defined in the art as "cheesy' or “dry” as should be avoided, the Mooney viscosity of the mixture is a function of molecular weight; another negative character greater than that of the starting polymer, but the increase 35 istic of such material types is the appearance of the so-called must be restrained. “cold flow” phenomenon, in which the rubber bales have the The principal macromolecular parameters, on which it is tendency to flow during their typical storage times, and possible to intervene in order to improve filler dispersion hence become deformed, making it impossible to use them within the rubber, are molecular weight distribution and the in automated transformation line feeding systems. presence of branched chains. 40 The problem of obtaining a material with sufficient elas In absolutely general terms, globally applicable to rubbers ticity, but with the latter not deriving from the presence of and their processing, it should be emphasised that the high linear molecular weights, correlated with a wide introduction of a solid material into a rubbery matrix using molecular weight distribution (for example Mw/Mn>3.5), machinery requires the necessary transfer of work from the may be overcome by the introduction of a sufficient number machinery itself to the material through shear forces; hence 45 of branches into the molecular chain. it is necessary that the material responds in a viscoelastic manner in order to transfer such work from the volume area Branching of a naturally linear polymer may only be immediately adjacent to the mechanically active parts achieved through a postmodification operation: herein, by towards the inner areas, acting on the filler particles which the definition “naturally linear is meant a macrostructure, must first be incorporated and then more homogeneously 50 the reference catalytic system of which being incapable of dispersed. It is a requisite that the polymeric material has producing branches during kinetic chain propagation. sufficient elasticity in order to be able to perform the work Aside from the techniques for introducing branches into a transfer function from the machinery to the rubber, but an molecular chain, which we will see below, it is clear that, excess of this quality is not allowed since excessive elas since we are dealing with a postmodification, the modifica ticity would indeed make incorporation difficult: in this 55 tions must be made to a polymer having a suitable molecular respect, the working of Vulcanised rubber is considered architecture in order to achieve the goal of obtaining a impossible since it represents the conceptual reference of an processable material, from which to obtain a Vulcanised (almost) purely elastic material. rubber having good dynamic characteristics. In other words, Thus the objective to be pursued is the correct compro to induce branching (and hence elasticity) into a high mise between viscosity and elasticity: the attribute “correct 60 molecular weight distribution polymer (and hence already is used in purely qualitative terms since there is no satis elastic due to the high molecular weight fractions) besides factory experimental basis for the identification of any being useless, would become detrimental. qualitative correlation between the damping factors of the A method for achieving the aforementioned post-modifi material and the shear applied in the mixer. By reducing the cation of polydienes is reported in U.S. Pat. No. 5,567,784, question to macromolecular terms, a material is required 65 in which the polybutadiene is treated with a sulphur com with sufficient elasticity, the latter property deriving from the pound selected from SC1, SC1, SOCl, preferably SC1.