Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1997-04-28
2001-02-27
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S397000, C524S398000, C524S399000, C524S400000
Reexamination Certificate
active
06194504
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to metal acrylates which are useful as processing aids for elastomers.
Elastomers such as polybutadiene, hydrogenated nitrile rubber, etc., are usually processed in a two roll mill or a Banbury type internal mixer, with a combination of additives which are added in order to provide the proper curing and physical property characteristics. For peroxide cure systems, metal salts, especially acrylates, are commonly used to improve the efficiency of the cure process. Additional ingredients added to the compound include peroxides, fillers such as zinc oxide, plasticizers, additional coagents, and pigments.
In typical processing of such elastomers, there is a tendency for build-up to occur on the rolls, sides of the mixer, and/or on the rotors. This build-up, if left over several cycles, reduces the heat transfer of the equipment and undesirably lengthens the cycle time. Also, fragments from the build-up can enter subsequent batches and result in non-uniform properties and out-of-specification product. In such cases, it may become necessary to shut down and either run clean-out batches until the equipment is clean, or to mechanically clean the mixer.
Metal acrylates and their interaction with the peroxide and elastomer are frequently a major contributor to the undesirable build-up (also known as plate-out process).
Various methods have been tried in an effort to minimize the tendency for the metal acrylates to plate-out. One such method involves the ordering of the addition of the formulation ingredients. Normally, most of the ingredients are added together to the elastomer with the peroxide being added last. Under these conditions, plate-out is very bad. By adding the metal acrylate first, it is possible to partially encapsulate and minimize the contact of metal acrylate with the ingredients causing the plate-out. This technique has the disadvantage of lengthening the mixing cycle and only partially reducing plate-out.
An alternate technique is surface treating of the metal acrylate particle surface prior to addition to the mixer. Leo, et al., U.S. Pat. No. 4,092,285 assigned to Wyrough and Loser, Inc., discloses the encapsulation of “critical chemical” rubber additives with a mixture of a liquid compatible with the rubber or a wax with a melting point of 55-80° C., and a high molecular weight polymer with molecular weight greater than 50,000. This mixture produces a non-tacky gel below 53° C. which can be coated onto the particle surface. Johansson, et al., U.S. Pat. No. 4,397,992, also assigned to Wyrough and Loser, Inc., discloses the incorporation of a vulcanizing agent or coagent into a polymeric binder composition comprising a major amount of multi-stage graft copolymer along with a high molecular weight hydrocarbon polymer and free radical polymerization inhibitor. This composition results in a non-bleeding homogeneous solid which can be readily dispersed in a rubber or plastic stock by mechanically mixing. However, in the case of metal acrylates, neither the Leo, et al., nor Johansson, et al., processes provide surface treatment of encapsulated metal acrylates which function effectively to prevent plate-out in elastomer processing. Neither of these patents suggests a method which provides an efficient method of coating or treating the metal acrylate particles prior to their incorporation into elastomers.
Metal acrylates, as normally produced, are typically dusty products (approximately 10 microns in diameter) causing odor and inhalation problems when transferred because of dust. In addition, metal acrylates are usually extremely difficult to process on mixing equipment, such that they tend to stick to the mixer metal surfaces (plate-out) resulting in poor dispersion of the metal acrylates in the rubber or elastomer. An additional disadvantage of prior art metal acrylates is the slowness with which they mix into many rubbers due to the polar nature of the particles and charge build-up on the particle surface.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide improved metal acrylate cure additives for elastomers which do not cause plate-out or build up in the processing of the elastomers.
It is a further object to provide a method of preparing such improved metal acrylate cure additives, and to methods of processing elastomers with such improved metal acrylate cure additives.
These objects, and others which will become apparent from the following disclosure, are achieved by the present invention which comprises, in one aspect, a method of making MA
n
salt in particulate form having improved dispersibility in elastomers, wherein M is a metal selected from zinc, calcium, magnesium, potassium, lithium, aluminum, cobalt, zirconium, sodium, iron, barium, bismuth, etc., A is acrylate or methacrylate, and n is 1, 2, 3 or 4, comprising contacting said salt with a solution of polymer in organic solvent, and then removing the solvent, thereby encapsulating the salt with the polymer.
In another aspect, the invention comprises a composition comprising the resultant MA
n
salt in particulate form having improved dispersibility in elastomers, and the improved elastomers themselves.
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
As mentioned, one aspect of the invention is the method of making MA
n
salt in particulate form having improved dispersibility in elastomers, wherein M is a metal selected from zinc, calcium, and magnesium and other metals, A is acrylate or methacrylate, and n is 1, 2, 3 or 4, comprising contacting said salt with a solution of polymer in organic solvent, and then removing the solvent, thereby effecting a surface treatment of said salt with said polymer.
Among the metals, M, zinc is the most typical for the type of cure additives most useful for elastomers. Other suitable metals are calcium, magnesium, potassium, lithium, aluminum, cobalt, zirconium, sodium, iron, barium, bismuth, etc., and the like.
The acrylate can be acrylate, methacrylate, ethacryate, and the like, with acrylate itself being most typical. The value for n is most typically 2, so that zinc diacrylate (ZDA) is the most typical of the metal acrylate salts.
The polymer which is used to treat the surface of the metal salt is preferably selected from the group consisting of polybutadiene, EPDM (saturated and unsaturated), hydroxy-terminated polybutadiene, polybutadiene diacrylate, mineral oil, ethylene-butylene diacrylate, natural rubber, polybutene, and the like. The preferred polymer is the one most closely related to the elastomer in which the metal salt will be incorporated as cure additive.
Suitable treatment polymers include, for example, liquid EPDM, e.g., Uniroyal Trilenes, especially CP20, hydroxy terminated liquid polybutadiene e.g., Elf Atochem R45HT, Sartomer CN-301 PEG 500 diacrylate, mineral oil, Ethylene butylene diacrylate, liquid natural rubber e.g., Hammond DPR, liquid polybutadiene, Amoco polybutene, and the like.
The surface treatment of the metal acrylate is accomplished by dissolving the treating polymer in organic solvent and then slurrying the metal salt particles for a short time in the resultant solution. The treatment process can be carried out in the same reactor as is used to prepare the metal acrylate after the metal acrylate reaction is completed, or following removal of the metal acrylate after it is prepared from the reactor in a secondary step.
Improved speed of processing is achieved with treatment according to the invention, as the treating polymer acts as a bridge between the particle and the elastomer.
Heptane is the preferred solvent for the treatment polymer because heptane is the conventional solvent used to prepare the metal acrylate, but other solvents can alternatively be used, if desired. Other suitable solvents include hexane, octane, nonene, toluene, and the like.
The treatment polymer can be incorporated in the solvent at varying concentrations, but a concentration of about 1-5, preferably 2-5 percent on the metal salt appears optimum. Lower concentrations d
Ceska Gary W.
Costin C. Richard
Nagel Walter R.
Cozen & O'Connor
Fein Michael B.
Mulcahy Peter D.
Sartomer Technologies Inc.
LandOfFree
Process for compounding metal salts in elastomers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for compounding metal salts in elastomers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for compounding metal salts in elastomers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2565335