Liquid carboxylated nitrile rubber

Bhattacharjee et al. [79] introduced another new catalyst based on a Pd complex containing both acetate and benzoyl pyridine ligands (Table 6). This was developed to hydrogenate liquid carboxylated nitrile rubber (L-XNBR) [80]. Selective hydrogenation of C=C in L-... 

Later, in 1974, amine reactive versions of the liquid nitrile polymers (ATBN) were issued, thereby offering another way to introduce rubbery segments into a cured epoxy resin network. References are cited which provide detailed discussions of nitrile rubber, carboxylic nitrile rubber and both carboxyl- and amine-terminated nitrile liquid polymers (1-4). Table I illustrates CTBN and ATBN products structurally. Table II provides properties for typical solid carboxylic nitrile elastomers. 

One of the first approaches was to use a blend of liquid reactive rubbers and the much higher molecular weight elastomer (carboxylated nitrile rubber). This led to a bimodal distribution of the precipitated secondary phase, which was seen as a distinct improvement over either the elastomer or the RLP on its own. 

Another example of a structural adhesive is a two-part solventless liquid system. One part contains carboxylated nitrile rubber, methyl methacrylate, and cobalt naphthenate. The second part is composed of carboxylated nitrile rubber, methyl methacrylate, and cumene hydroperoxide. In this example the carboxylated nitrile rubber used was Hycar 1072." ... 

Other nitrile rubber epoxy adhesives have been described for rubber to rubber and rubber to metal bonds. Liquid carboxylated nitrile materials have been found useful in a number of applications. An adhesive comprised of carboxylated nitrile rubber, epoxy resins, imidazole, or tertiary amine and an organic peroxide has been described for bonding metals, paper, plastics, and inorganic materials. 

One of the largest areas of use of nitrile rubber modified epoxy systems is in the printed circuit board area. A number of systems have been described that are composed of carboxyl-containing nitrile rubber such as Hycar 1072 mixed with epoxy resin. " The low molecular weight functionally terminated nitrile rubbers have also found significant application in this area. Other workers have found useful a system that combines a high molecular weight nitrile rubber with the liquid functionally terminated materials. Finally, other references describe the use of non carboxylated nitrile rubbers in circuit board applications. 2 ... 

Low molecular weight liquid nitrile rubbers with vinyl, carboxyl or mercaptan reactive end groups have been used with acrylic adhesives, epoxide resins and polyesters. Japanese workers have produced interesting butadiene-acrylonitrile alternating copolymers using Ziegler-Natta-type catalysts that are capable of some degree of ciystallisation. 

Flexibilized epoxy resins are important structural adhesives [69]. Liquid functionally terminated nitrile rubbers are excellent flexibilizing agents for epoxy resins. This liquid nitrile rubber can be reacted into the epoxy matrix if it contains carboxylated terminated functionalities or by adding an amine terminated rubber. The main effects produced by addition of liquid nitrile rubber in epoxy formulations is the increase in T-peel strength and in low-temperature lap shear strength, without reducing the elevated temperature lap shear. 

Liquid diglycidyl ether of bisphenol A Carboxyl-terminated nitrile rubber... 

It is these solid carboxylic nitrile elastomers which began to show utility in the modification of epoxy resins. Processing needs for solid elastomer Inclusion, particularly in liquid epoxy resins, have not always been advantageous. Associated problems include gel, viscosity threshold limitations and achieving desired rubber levels in excess of 5-6 phr. Sometimes processing must be carried out in selected solvents, not always a desirable or tolerable step. 

Carboxylic nitrile liquid and solid elastomers are used to prepare elastomer-modified epoxy liquid and solid resins when it is desirable to have the modifier in the epoxy portion of the system. This is effected through alkyl-hydroxy esterification reactions. This is covered in the literature for uncatalyzed liquid resins (9), for tert-amine catalyzed systems (10), for tert-phosphine catalyzed systems (11), for low molecular weight solid resins advanced from the liquid state (12) and for liquid and solid resins where an additional rubber vulcanization step is carried out in addition to the alkylhydroxy ester adducting step (13). Such adduct preparations offer formulation stability with a wide range of hardener types amines, anhydrides, catalytic, Lewis acids/bases. 

C-H from vinyl group as (CH2=CH-) C-H pendant vinyl group of the 1,2 unit for liquid carboxylated poly(acrylonitrile-co-butadiene) [or nitrile rubber (NBR)] C-H from vinyl-associated group... 

Because of the speed of data acquisition of NIR instrumentation with nonmoving parts, opportunities arise to study reaction rates and mechanisms. One example includes the crosslinking reaction of liquid carboxylated poly(acrylonitrile-Co-butadiene) or nitrile rubber (NBR) with dicumyl peroxide (DCPO). This reaction was studied by electron spin resonance (ESR) spectroscopy and the crosslinking reaction was followed in situ in dioxane by monitoring of the disappearance of the pendant vinyl double bond with Fourier transform NIR (FT-NIR). The overall activation energy and rate equation of the reaction were able to be determined and provided insight into the reaction mechanism [42]. 

The liquid nitrile rubbers can be reacted into the epoxy matrix in one of two ways. If a carboxyl terminated material is used it is normally adducted or prepolymerized with an epoxy resin prior to formulating. The resulting epoxy adduct is then placed in the epoxy component of the composition. A second method of incorporating liquid nitrile materials would be to use an amine terminated rubber. In this case the material contributes amine reactivity and functions as a part of the hardener system. These materials were primarily developed to form stable admixes with amine containing epoxy hardeners. 

Liquid nitrile rubber provided by Zeon Chemicals is illustrated in Table 2.12. JSR also produces a liquid NBR. The Nipol 1312 series comes in two viscosity levels. Due to the tackiness in this form, many plants elect to use these as dry liquid concentrates. Other uses are in PVC plastisols, where lower volatility is an asset. The liquid, carboxylated Nipol DN601 is reactive, hence finds its primary application modifying thermosetting resins. 

Numata and Kinjo (52) have shown rubber-modified isocyanurate-oxazolidone resins may be effectively modified with carboxyl-reactive nitrile liquids. The viscoelastic behavior of models using a polyglycidyl ether of phenol-formaldehyde novolac resin and di-phenylmethane-4,4 -diisocyanate is discussed. Such resins have suggested utility in thin films as electrical varnishes. 

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