Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
2001-01-05
2004-08-03
Woodward, Ana L. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamide
C428S473500, C442S059000, C442S098000, C524S514000, C525S131000, C525S166000, C525S167000, C525S178000, C525S179000, C525S180000, C525S183000
Reexamination Certificate
active
06770378
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the fields of chemistry, mechanical engineering, and materials engineering and concerns compounds of polyamide and perfluoralkyl substance(s) and mixtures of these compounds with additional polymer substances which can be used, for example, as a compact substance, as surface modification components, as a filler or as an additive in sliding bearing materials, in anti-frictional films, in lubricating varnishes, in oleophobic and/or hydrophobic partial or compact materials or partial or compact materials equipped therewith, in mouldings, in textile thread, fleece, and/or other textile surface structures, in membrane materials, as a lacquer additive, or as a lacquer substance, as well as a process for the production and use thereof.
In search for polymer materials appropriate for building nuclear reactors, it was determined that polytetrafluoroethylene (PTFE), in contrast to its high chemical and Thermal stability, is extraordinarily sensitive to radiation. Under inert conditions as well as in the present of oxygen, it even decomposes at low absorbed doses, becomes brittle even at 0.2 to 0.3 kGy and crumbly at <100 kGy.
Beginning at approximately 360° C., the purely radiochemical decomposition is noticeably overlaid by a thermal decomposition.
Due to the stochastic progression of the radiochemical decomposition, reaction products form with a wide spectrum of chain lengths.
If PTFE is irradiated in the presence of oxygen, peroxy and alkoxy radicals are formed from the perfluoralkyl radicals that initially formed.
In the course of the intermediate stage of the formation of the alkoxy radical, the perfluoralkyl radical end group is decomposed in stages by shortening the chains and formation of carbonyldifluoride.
In contrast, perfluoralkanic acid fluorides and perfuoralkyl radical end groups form from the alkoxy radical side groups.
Perfluorized diacids are also formed in very small quantities because two radical center side groups can also form on a perfluorcarbon chain. Unsintered and unpressed PTFE emulsion and suspension polymerizates am of a fibrous-felted character. A transfer, for example, of the anti-adhesive and sliding characteristics of PTFE to other media by integration into aqueous or organic dispersions, polymers, dyes, lacquers, resins, or coatings is not possible because this PTFE cannot be homogenized, but rather tends to form clumps, agglomerates, floods, or settles.
By means of the effect of high-energy radiation with an absorbed dose of approximately 100 kGy, a pourable fine powder is attained from the fibrous-felted polymerizates as a result of the partial decomposition of the polymer chains. This powder still contains loose agglomerates that can be easily separated into primary particles with a particle diameter of <5 &mgr;m. In the case of irradiation in the presence of reactants, functional groups are formed into the polymers. If the irradiation occurs in air, then according to Eq. (9.22) (and subsequent hydrolysis of the —COF groups by means of moisture in the air), carboxyl groups result. If, before irradiation, (NH
4
)
2
SO
3
is mixed in, then groups containing S are to be attained. These functional groups reduce the hydrophobia and organophobia of the PTFE so substantially that the resulting fine powder can be easily homogenized with other media. The positive characteristics of PTFE, such as its excellent anti-frictional, separating, and dry lubrication characteristics as well as its high chemical and thermal stability, are maintained. Carboxyl and sulfonic acid groups to which perfluorized chains are connected also have a high degree of chemical inertness.
Because of the insolubility of tie PTFE and its decomposition products (with the exception of the very submolecular products), the conventional methods of determining molar mass cannot be used. The determination of molar mass must occur in an indirect manner.”
The incompatibility with other materials often has a negative effect. By chemically activating PTFE using known methods with (0.1) sodium amide in liquid ammonia and (2.) alkali alkyl and alkali aromatic compounds in aprotic inert solvents, a modification can be achieved. By means of these modifications, boundary surface interactions can be achieved that are reactive or even only improved by adsorptive forces.
Recycling of the products of PTFE decomposition occurs in various fields of use, also as an additive to plastics for the purpose of achieving sliding or antiahesive characteristics. The fine powder substances are more or less finely dispersed as filler components in a matrix In releasing the matrix components, the PTFE fine powder can be eliminated and/or is recovered
Although, in the areas of use of PTFE fine powder, an improvement of the characteristics is achieved as compared to the commercial fluorocarbon-free additives, the incompatibility, the insolubility, the loose coupling, and also heterogeneous distribution is disadvantageous for many areas of use.
SUMMARY OF THE INVENTION
The present invention relates to the improvement of the homogenization of perfluoralkyl substances in polyamide melts.
In one aspect, the present invention is directed to a compound comprising at least one modified perfuoralkyl substance homogenized with at least one polyamide in a melt by reactive transformation, and can comprise at least one additional polymeric substance.
The at least one modified perfluoralkyl substance can have functional groups, such as at least one of at least one carboxylic acid group, at least one carboxylic acid halogenide group, and at least one perfluorallylene group.
The at least one modified perfluoralkyl substance can be present at a concentration of 0.01 to 90 weight percent of the compound, preferably 1 to 70 weight percent of the compound.
The present invention is also directed to a process for producing a compound comprising at least one modified perfluoralkyl substance homogenized with at least one polyamide in a melt by reactive transformation, comprising compounding in a melt at least one modified perfluoralkyl substance and at least one polyamide, wherein the at least one polyamide comprises at least one of at least one of aliphatic and partially aromatic homopolyamides, at least one of copolyamides, at least one of polyester amides, at least one of polyether amides, at least one or polyesterether amides, at least one of polyimide amides, and at least one of polyamide amides, and reactively transforming said at least one modified perfluoralkyl substance and said at least polyamide.
The compounding can comprise single-level compounding or multi-level compounding.
The reactive transforming can occur during the compounding, or subsequent to the compounding.
At least one additional polymeric substance can be included. The at least one additional polymeric substance can comprise at least one of at least one polyolefin at least one polyvinyl component, at least one polycondensate, and at least one of polyaddition component. The at least one additional polymeric substance can be added to at least one of the at least one modified perfluoralkyl substance and the at least one polyamide prior to compounding, during compounding or subsequent to compounding.
The at least one polycondensate can comprise at least one of polyesters and polycarbonates, and the at least one polyaddition component can comprise polyurethane.
The at least one polyamide can comprise at least one of polyamide 6, polyamide 6,6 and polyamide 12.
The at least one polyamide can be in pure form or at least one of filled and reinforced materials.
The compounding can be performed in at least one of at least one of a single- and double-screw extruder, a kneader, and in a plasticizing unit of an injection molder.
The reactively transforming can be performed in a melt, with transformation being performed at temperatures at least over the melting point of the at least one polyamide component The temperature can be greater than 200° C.
At least one of before, during and after reactive transformation, reactive mas
Greenblum & Bernstein P.L.C.
Institut fur Polymerforschung E.V. Dresden
Woodward Ana L.
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