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
2002-05-22
2004-03-23
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S805000
Reexamination Certificate
active
06710132
ABSTRACT:
The present invention relates to (per)fluoroelastomeric compositions consisting essentially of a perfluoroelastomer and of a semi-crystalline fluoropolymer, having improved chemical, thermal, sealing resistance, lower fluid permeability, in particular hydrocarbons, combined with good mechanical properties and usable in the preparation of sealing manufactured articles, in particular for electronic, optical, pharmaceutical and oil industry.
Specifically, the present invention relates to (per)fluoroelastomeric compositions comprising a perfluoroelastomeric matrix which incorporates semi-crystalline fluoropolymer particles, wherein the semi-crystalline fluoropolymer is coated by a semi-crystalline fluoropolymer shell containing bromine and/or iodine in the polymer chain, said compositions characterized by improved-mechanical and sealing properties combined with improved surface aspect (absence of roughnesses).
It is known from the European patent application EP 1,031,606 to prepare (per)fluoroelastomeric compositions obtained by incorporation under the latex form of a semi-crystalline fluoropolymer containing iodine and/or bromine atoms, in a (per)fluoroelastomer to improve the mechanical properties with respect to a (per)fluoroelastomer filled with PTFE powder. The particles of the semi-crystalline fluoropolymer latex have sizes comprised between 10 and 100 nm. In said patent application it is stated that the use of a semi-crystalline fluoropolymer latex containing iodine and/or bromine allows to improve the mechanical properties with respect to the case of absence of iodine and/or bromine. In the Examples the introduction of iodine atoms by using iodinated transfer agents is reported. In said patent application it is stated that iodine and/or bromine can be introduced by using comonomers containing iodine and/or bromine in the preparation of the semi-crystalline fluoropolymer. The comonomer content in the final compound results lower than 2 moles per 100 moles of the other monomeric units of the semi-crystalline fluoropolymer. No Examples of compositions containing semi-crystalline fluoropolymers having iodinated and/or brominated comonomers are reported.
The need was felt to have available (per)fluoroelastomeric compositions having a better combination of properties:
improved mechanical properties, preferably combined with an improved compression set;
homogeneity of the mechanical properties on the whole manufactured article;
improved chemical and thermal resistance;
excellent surface aspect, roughnesses free;
working easiness in equipments conventionally used in the fluoroelastomer field, without using complicated technologies for incorporation of fluoropolymer.
lower permeability to fluids, in particular hydrocarbons.
The Applicant has unexpectedly and surprisingly found that it is possible to obtain the improved combination of the above properties by using the specific compositions defined hereunder.
An object of the present invention are therefore (per)fluoroelastomeric compositions comprising:
A) a perfluoroelastomeric matrix based on tetrafluoroethylene (TFE);
B) a semi-crystalline fluoropolymer, in an amount from 2 to 90% by weight based on the total of A)+B), comprising a semi-crystalline fluoropolymer core coated by a semi-crystalline fluoropolymer shell containing bromine and/or iodine in the polymer chain, the amount of brominated and/or iodinated comonomer being from >2% to 10% by moles per 100 moles of the other basic monomeric units of the semi-crystalline fluoropolymer B) core+shell; the fluoroelastomer A) incorporates the fluoropolymer B), the fluoropolymer B) being formed by tetrafluoroethylene (TFE) homopolymers, or TFE by copolymers with one or more monomers containing at least one unsaturation of ethylene type, in an amount from 0.01% to 10% by moles, preferably from 0.05% to 7% by moles; the core and the shell of the fluoropolymer B) can be of a different composition between each other, the average sizes of the particles of the semi-crystalline fluoropolymer being from 10 to 100 nm, preferably from 10 to 60 nm.
The (per)fluoroelastomeric compositions of the invention are obtainable by mixing the latex of the semi-crystalline fluoropolymer B) with the latex of the perfluoroelastomer A) and subsequent coagulation.
Alternatively to the latex mixing, the (per)fluoroelastomeric compositions of the invention can be obtained in the same reactor, using two subsequent steps: in the first step the semi-crystalline fluoropolymer B) having the above nanometric sizes is polymerized, while in the second step the perfluoroelastomer A) is polymerized. By operating in this way the perfluoroelastomer A) covers the latex particles of semi-crystalline fluoropolymer B) allowing to obtain a very good disperdibility of the latter in the perfluoroelastomer.
The semi-crystalline fluoroelastomer B) amount incorporated in the (per)fluoroelastomeric matrix is preferably from 5% to 80% by weight based on the total weight of the polymer mixture, more preferably from 10 to 70% by weight.
The semi-crystalline fluoropolymer B) particles having the mentioned nanometric sizes are obtainable for example by polymerization in aqueous microemulsion of perfluoropolyoxyalkylenes as described for example in the European patent application 969,027 in the name of the Applicant, herein incorporated by reference. Polymerization techniques in microemulsion wherein the oil phase is formed by polymerizable unsaturated monomers can also be used, as described in U.S. Pat. Nos. 5,523,346 and 5,616,648.
The Applicant has found that in order to obtain the results of the invention it is essential that the semi-crystalline fluoropolymer B) has the mentioned nanometric sizes, while the size of the perfluoroelastomer A) particles to be mixed with the fluoropolymer is not critical.
The semi-crystalline fluoropolymers of the present invention comprise a semi-crystalline fluoropolymer core shelled by a semi-crystalline fluoropolymer containing in the polymer chain bromine and/or iodine atoms. The introduction of said bromine and/or iodine atoms can be carried out by addition in the polymerization mixture of the (co)monomers forming the fluoropolymer B), of brominated and/or iodinated comonomers, such as bromo- and/or iodo-olefins having from 2 to 10 carbon atoms, as described for example in U.S. Pat. Nos. 4,035,565 and 4,694,045, 5,625,019, or bromo and/or iodo fluoroalkylvinylethers, as described in U.S. Pat. Nos. 4,745,165, 4,564,662 and EP 199,138, in such amounts whereby the content of brominated and/or iodinated comonomers in the final polymer B) is generally from >2 to 10% by moles per 100 moles of the other basic monomeric units as above said, preferably from 2.5 to 6%.
Optionally, in combination with said comonomers, it is possible to introduce bromine and/or iodine end atoms by addition to the reaction mixture of brominated and/or iodinated polymer chain transfer agents, as for example described in U.S. Pat. Nos. 4,243,770 and 4,943,622, 5,173,553.
It has been unexpectedly found by the Applicant, see the comparative Examples, that the combination of properties of the invention compositions is obtainable only if the semicrystalline fluoropolymer B) is prepared by using on the fluoropolymer shell a brominated and/or iodinated comonomer in an amount higher than 2% by moles with respect to the other basic monomeric units as above said. Tests carried out by the Applicant have shown that by operating under the conditions reported in the Examples of European patent application 1,031,606, wherein the semi-crystalline fluoropolymer does not contain bromine and/or iodine in the polymer chain but only on the polymer chain end groups, the improved combination of the above properties is not obtained.
By semi-crystalline fluoropolymer a fluoropolymer is meant which shows, besides the glass trnsition temperature Tg, at least one melting temperature.
The preparation of the perfluoroelastomers A) of the composition of the present invention can be carried out by copolymerization of the monomers in aqueous emu
Albano Margherita
Apostolo Marco
Arrigoni Stefano
Arent Fox Kintner & Plotkin & Kahn, PLLC
Ausimont S.p.A.
Nutter Nathan M.
LandOfFree
Fluoroelastomeric compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fluoroelastomeric compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fluoroelastomeric compositions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3288234