Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-02-25
2002-04-02
Le, Hoa T. (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S403000, C428S407000, C525S534000, C525S537000, C528S388000
Reexamination Certificate
active
06365274
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to European Application no. 98301492.9, filed Feb. 27, 1998.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a material used for thermal spraying made from, or preferably, incorporating a particular high temperature polymer, and to a process of forming a coating from such material by thermal spraying.
2. Description on the Related Art
Thermal spraying is a generic term describing established engineering processes whereby a material is formed into a coating by projecting particles in a stream of hot gases onto a surface. The invention relates primarily to thermal spray processes in which the material to be deposited is in powder form, but it also includes thermal spray processes where the material to be deposited is in the form of a rod or strand, or fabricated structure comprising for example a tube filled with compacted powder, or any other form in which it can be fed into thermal spray equipment. The invention relates to all types of thermal spray processes including the following specific examples:
Plasma flame spraying including
Conventional plasma spraying in natural atmosphere known as Atmosphere Plasma Spraying (APS);
Plasma spraying in a controlled atmosphere such as an inert gas, known as Controlled Atmosphere Plasma Spraying (CAPS), this includes but is not limited to the atmosphere being controlled by enclosing the process in a chamber containing the desired gas or gas combination, or by flooding the plasma stream by the desired gas or gas combination;
Plasma spraying in a partial or complete vacuum known as Vacuum Plasma Spraying (VPS).
Combustion thermal spray processes including
A conventional combustion flame, normally resulting from the combustion of a fuel gas such as acetylene in the presence of oxygen.
A high velocity stream of hot gases resulting from the combustion of a fuel, which may be gaseous or liquid, in the presence of oxygen and the expansion of the hot gasses being controlled and channelled through an exit nozzle. This process is well known and recognized by the description, high velocity oxy fuel (HVOF);
A process as described above but the combustion is supported by air instead of oxygen and is known and recognized by the description high velocity oxy air (HVAF).
And Electric arc thermal spray processes where the heat source is derived from an electric arc struck between a cathode and anode where either or both may comprise the material being sprayed.
Powders for thermal spraying typically comprise metals and/or carbides and/or ceramics although they can also comprise high temperature polymers and mixtures of high temperature polymers and metals to which the British patent specification GB 1 356 017 refers. In particular, GB 1 356 017 discloses high temperature polyimide, polyamide imide, polyester imide and aromatic polyester plastics suitable for flame spraying processes. Although these high temperature polymers, in particular aromatic polyester plastics, are used in a number of technically important applications, their physical properties, e.g. the resistance against corrosion through salt containing steam, are limited.
So far, oxidized polyarylene sulfides are used as additives to other polymers such as fluorocarbon polymers (EP-A-0 633 290 and EP-A-0 633 291) where they act as fillers, or they are processed into molded or functional parts for applications where resistance to high temperatures is required (EP-B-0 623 639 and EP-A-0 623 640).
It has now surprisingly been discovered that oxidized polyarylene sulfides are very suitable for use in thermal spraying and thereby form coatings having a strong chemical and mechanical resistance and high dimensional stability when exposed to high and low temperatures.
The invention provides a thermal spray powder comprising from 1 to 99% by weight, preferably from 5 to 60% by weight, and particular preferably from 20 to 45% by weight of oxidized polyarylene sulfide and from 1 to 99% by weight, preferably from 40 to 95% by weight, and particular preferably from 55 to 80% by weight of a metal powder.
The invention also provides a process of forming a thermal spray powder comprising or essentially consisting of oxidized polyarylene sulfide into a coating by thermal spraying, and a coating produced from a thermal spray powder comprising or essentially consisting of oxidized polyarylene sulfide.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
Thermal spray powders comprising oxidized polyarylene sulfide exhibit improved flow and trickle properties compared with conventionally used thermal spray powders comprising high temperature polymers. This enhanced property is particularly important for the processing of the powder by thermal spraying.
Further, coatings obtained by thermal spraying powders comprising oxidized polyarylene sulfide are extremely resistant against corrosion through hot and salt containing steam.
Polymers which can be used for the thermal spray powder according to the invention are linear and branched polyarylenes whose recurring units contain at least one SO
2
or SO group as bridge and which have a heat resistance which is adequate for the thermal spraying applications and processing. Favorable polyarylenes have the formula (I)
—[(Ar
1
)
d
—X]
e
—[(Ar
2
)
i
—Y]
j
—[(Ar
3
)
k
—Z]
l
—[(Ar
4
)
o
—W]
p
— (I)
in which each Ar
1
, Ar
2
, Ar
3
, Ar
4
, W, X, Y and Z, independently of the others, is identical to or different from the others. The indices d, e, i, j, k, l, o and p are, independently of one another, zero or integers 1, 2, 3, or 4, where at least one of the indices d, i, k and o and at least one of the indices e, j, l and p must be 1. Ar
1
, Ar
2
, Ar
3
and Ar
4
in the formula (I) are simple or directly para-, meta- or ortho-linked arylene systems having 6 to 18 carbon atoms, W, X, Y and Z are linking groups selected from —SO
2
—, —S—, —SO—, —CO—, —COO—, alkylene or alkylidene groups, each having 1-6 carbon atoms, and —NR
1
—groups where R
1
is an alkyl or alkylidene group having 1-6 carbon atoms, with the proviso that at least one of the linking groups W, X, Y and Z in formular (I) is —SO— or —SO
2
—.
Particularly suitable polymers are polyaryienes containing recurring units of the formula (II)
[—(S—E)
a
—(SO—E)
b
—(SO
2
—E)
c
—] (II)
in which each E, independently of the others, is phenylene, naphthylene or biphenylene, b and c, independently of one another, have values of from 0 to 1 and a has values of from 0 to less than 1, with the proviso that the sum a+b+c is equal to 1 and at least one of the indices is greater than zero and if any sulfur links (—S—) are present, at least further —SO
2
— or —SO— links are also present.
Particularly preferred oxidized polyarylene sulfides are linear or branched polyarylene sulfones, polyarylene sulfide sulfones, polyarylene sulfoxide sulfones, or polyarylene sulfide sulfoxide sulfones.
Polymers which can be specifically employed are those containing recurring units of formulae (III)-(VI)
and oxidized polyphenylene sulfides containing recurring units of the formula (VII)
where the degree of oxidation is at least 50% based on 100% of the theoretically possible uptake of oxygen (100% sulfone groups).
The oxidized polyarylene sulfides can be prepared by the processes described in German patent applications: DE 43 14 738, DE 43 14 737, DE 43 14 736, DE 43 14 735, DE 44 40 010, P 195 31 163.9, DE 196 36 692.5, DE 196 37 845.1, DE 197 16 016 and DE 197 51 239.9, which are expressly incorporated herein by way of reference.
Subsequent references in this specification to “the polymer” in the singular includes reference to each and all of the oxidized polyarylene sulfides described above.
In principle, the polymer can be used for thermal spraying without adding any further components and/or additives. Thermal sprayed coatin
Scheckenbach DI. Helmut
Smith Christopher William
Frommer & Lawrence & Haug LLP
Le Hoa T.
Ticona GmbH
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