Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-01-20
2001-10-23
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S104000, C525S192000, C525S194000, C525S197000, C525S232000, C525S233000, C525S239000, C525S329300
Reexamination Certificate
active
06306971
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of polymers and more particularly to compositions comprising at least one fluorinated polymer comprising units deriving from vinylidene fluoride (VF2) and at least one nitrile rubber.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,095,072 has described thermoplastic blends of PVDF and of rubber of nitrile or acrylate type in the gel form. The gelling of the rubber is obtained by addition of multifunctional monomers or by high-temperature polymerization and not by vulcanization. The gelled rubber is then mixed with the PVDF; it is found that the gelled rubber is distributed crudely and unevenly in the PVDF and that the blends obtained exhibit no tensile, flexural or impact-resistant properties, which generally characterizes heterogeneous mixtures of polymers.
EP 714,944 has provided thermoplastic compositions comprising a poly(vinylidene fluoride) (PVDF) matrix in which are dispersed nodules of essentially non-fluorinated vulcanized rubber which exhibit improved mechanical properties in comparison with the blends described in U.S. Pat. No. 5,095,072. In order to improve the multiaxial impact strength, EP 714,944 recommends the addition of a compatibilizing agent chosen from optionally grafted aliphatic polyesters, optionally imidized poly(methyl methacrylate) (PMMA) or polyolefins grafted with methyl methacrylate. These compatibilizing agents often have mediocre chemical and mechanical properties, which has a harmful influence on the compositions onto which they are introduced.
SUMMARY OF THE INVENTION
The compositions according to the invention simultaneously exhibit good mechanical and thermo-mechanical properties as well as good chemical resistance, in particular good impermeability to hydrocarbons, and do not require a compatibilizing agent. They are characterized in that they comprise a mixture composed of 5 to 95% by weight of at least one thermoplastic fluorinated polymer and of 95 to 5% by weight of at least one nitrile elastomer and in that the overall percentage of acrylonitrile in the nitrile elastomer or elastomers is greater than or equal to 30%.
The compositions according to the invention are generally thermoplastic compositions, that is to say that they can be processed by the technologies used for thermoplastics, such as extrusion or calendering. They can also exhibit, depending on the amount of elastomer(s) employed, an elastomeric nature.
In the present invention, fluorinated polymer denotes polymers possessing at least 50 mol % of VF
2
residues. Preference is given to VF2 homopolymers (PVDF) and/or to copolymers comprising units derived from VF2 and from hexafluoropropylene (HFP).
Nitrile elastomer within the meaning of the present invention is understood to mean copolymers of butadiene and of acrylonitrile which are optionally partially or completely hydrogenated. The preferred compositions according to the invention are those which contain at least one nitrile elastomer containing at least 35% by weight of acrylonitrile.
The nitrile elastomer or elastomers may or may not be crosslinked.
The vulcanization systems used are well known to the person skilled in the art and the invention is not limited to one specific type of system. Mention may be made of four types of vulcanization systems:
Sulphur systems composed of sulphur in combination with conventional accelerators, such as metal salts of dithiocarbamates (zinc dimethyl-dithiocarbamate, tellurium dimethyldithiocarbamate, and the like), thiuram disulphides (tetramethylthiuram disulphide and the like), sulphenamides, and the like.
These systems can also contain zinc oxide in combination with stearic acid.
Sulphur-donor systems in which most of the sulphur used for the bridgings originates from sulphur-containing molecules such as the abovementioned organosulphur compounds.
Phenolic resin systems composed of difunctional phenol-formaldehyde resins, which may be halogenated, in combination with accelerators, such as stannous chloride or zinc oxide.
Peroxide systems. They make it possible to have a product which is more stable to heat, and white, not yellow, as in the case of sulphur-donor systems. All free-radical donors can be used (dicumyl peroxide and the like) in combination with zinc oxide and stearic acid.
The nitrile elastomer can be functionalized, for example with carboxylic acid radicals or anhydrides, salts or esters of the said carboxylic acids, with epoxide or amino groups and/or with halogens. The above rubbers which are not functionalized can be functionalized, for example by grafting with radicals in a known way or by mixing with already functionalized elastomers, such as acrylic elastomers or carboxylated NBRs (X-NBRs).
It is also possible to add already vulcanized rubber (for example by recycling milled material). It would not be departing from the scope of the invention to use an elastomer mixture containing a small proporion of fluorinated rubbers, for example up to 5% by weight of the amount of nitrile elastomer.
The compositions according to the invention can be modified for certain specific properties (improvement in the mechanical properties, for example) by the addition of fillers, such as carbon black, silica, kaolin, clay, talc, chalk, and the like. These fillers can be surface treated with silanes, polyethylene glycols or any other coupling molecule. The level by weight of fillers is generally between 5 and 100 per 100 parts of elastomer.
In addition, the compositions can be rendered flexible by plasticizers, such as mineral oils derived from oil, esters of phthalic acid or of sebacic acid, liquid polymer plasticizers, such as optionally carboxylated low-mass polybutadiene, and other plasticizers well known to the person skilled in the art.
It is generally the nitrile elastomers employed which are formulated, that is to say which have added to them inorganic fillers, plasticizer and optionally a crosslinking system (sulphur or peroxide-based system).
The invention also relates to a process for the preparation of these compositions.
The compositions of the invention can be prepared by mixing:
(i) the nitrile elastomer(s), which has or have optionally been formulated beforehand with a sufficient amount of crosslinking agent, with fillers and with plasticizers,
(ii) with the fluorinated polymer(s) at a temperature sufficient to cause the fluorinated polymer(s) to melt and for a period of time sufficient for the nitrile elastomer(s) to be intimately mixed with the fluorinated polymer(s).
When the nitrile elastomer or elastomers are crosslinked, it is preferable to carry out the dynamic vulcanization at a temperature greater than the melting temperature of the thermoplastics and less than 300° C. or better still 250° C., so as to prevent degradation of the elastomers and other additives in the formulation. The duration of the dynamic vulcanization will preferably be sufficient to reach at least the t
90
of the formulation (time taken to achieve 90% vulcanization of the elastomer or elastomers).
The equipment used to carry out this operation can be a kneader or cokneader, an internal mixer or alternatively a twin-screw extruder.
It is also possible to introduce the fluorinated polymer or polymers, the elastomer or elastomers and the premixed additives together in the plastic state onto a roller or into a mixer, the optional vulcanization system being introduced at the same time (or later when the thermoplastics are in the molten state), and then to increase the temperature to a temperature greater than the melting temperature of the thermoplastics, in order to carry out the dynamic vulcanization.
The vulcanization agent combinations are such that they must make it possible for the elastomer or elastomers to be crosslinked.
The mixing time in order to prepare the compositions of the invention can be between 2 and 20 minutes and advantageously between 2 and 10 minutes.
The compositions of the invention exist in the form of a matrix of fluorinated polymer(s) containing nodules of nitrile elastomer(s), when the amount of nitri
Betremieux Isabelle
Dousson Christian
Atofina
Millen White Zelano & Branigan P.C.
Zitomer Fred
LandOfFree
Compositions based on a fluorinated polymer comprising... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compositions based on a fluorinated polymer comprising..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compositions based on a fluorinated polymer comprising... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2611676