Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2000-04-11
2002-07-16
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C411S001000, C024S564000
Reexamination Certificate
active
06420035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a metal material subjected to a treatment for seizure prevention, as well as to a method for producing such a metal material.
2. Description of the Prior Art
In cold or hot working of a metal, when the metal to be worked causes seizure onto a rolling roller or tool, the seizure is printed on a metal of later working, allowing the latter metal to have surface flaw. In such a case, the rolling roller or tool is subjected to surface grinding, or is disposed as scrap in some cases; as a result, the productivity or workability is reduced and the rolling roll or tool has a shorter life.
In metal-made clamping materials such as bolts, nuts, washers and the like, local metal-to-metal friction is generated during the clamping (sliding) and, as no insertion is used which, even when a large load has been applied between metals, is not broken and can prevent metal-to-metal fusion bonding, seizure appears during the clamping and no intended axial force can be achieved. Consequently, the clamping becomes insufficient, which invites leakage at a site where a liquid passes or gives a structure of insufficient strength.
In metal-made clamping materials such as bolts, nuts, washers and the like, seizure appears not only during the clamping but also during the removal (dismantling) often for the same reason. In the latter case, a bolt is required to be removed by melting or cutting, which has posed great danger depending upon the working environment or has reduced working efficiency significantly, in some cases.
Further, clamping materials such as mentioned above have often caused seizure during the removal owing to the deterioration caused by heat, corrosion, etc.
The flaw on a metal product caused by the above-mentioned seizure is a serious problem in cold or hot plastic working (e.g. plate rolling, tube rolling, bar steel rolling, wire rolling, extrusion, drawing or forging) of:
(A) a metal material having a passivated film on the surface, such as stainless steel, titanium or its steel alloy, aluminum or its steel alloy, or the like,
(B) a metal material of low hardness, low thermal conductivity and high thermal expansion coefficient, or
(C) a thin metal.
The following techniques are mainly known as solutions for the above problem.
(1) Lubrication by liquid or oil film of machine oil, grease or the like.
(2) Use of solid lubricant such as iron oxide powder (JP-A-63-254195 and JP-A-64-83309), graphite (JP-A-1-167396), calcium sulfate or potassium sulfate (JP-A-54-123105), fluorinated graphite, molybdenum disulfide, tungsten disulfide or highly basic metal sulfonate (JP-A-5-306397 or JP-A-5-306399), highly basic metal phenate; or phosphonic acid ester (JP-9-40983) or fluororesin powder (JP-A-62-250054).
(3) Polymer film or fluorine film (JP-A-5-180383)
The above techniques, however, still have the following drawbacks.
Technique (1)
A liquid or oil film is easily broken by sliding and loses its effect; the kind of liquid or oil must be selected so as to match the material to which the film is applied; working environment is easily stained with the liquid or oil.
Technique (2)
An iron oxide powder, calcium sulfate and potassium sulfate are insufficient for prevention of seizure or wear; graphite, etc. have too low a friction coefficient and invites, during rolling, insufficient biting of to-be-rolled material and slippage; solid lubricants are broken as well at a sliding site and lose the effect and, in particular, polymer materials are easily broken for the softness.
Technique (3)
A polymer film has low adhesion to metal and finds limited application; moreover, the film has a limitation in thermal resistance.
SUMMARY OF THE INVENTION
The present invention aims at providing a metal material subjected to a treatment for seizure prevention, which can alleviate the problems of the prior art and which when processed into a clamping material used for land or marine structures, etc., can prevent seizure (which may occur in initial clamping or repeated clamping) and enables clamping and removal (dismantling) a plurality of times; and a method for producing such a metal material.
The present invention provides:
a metal material subjected to a treatment for seizure prevention, comprising a metal base material and a film formed thereon, composed of a carbodiimide group-containing resin obtained from an aromatic polyisocyanate or of a mixture of said carbodiimide group-containing resin and a lubricant; and
a method for producing a metal material subjected to a treatment for seizure prevention, which method comprises coating, on a metal base material, a carbodiimide group-containing resin obtained from an aromatic polyisocyanate or a mixture of a lubricant and said carbodiimide group-containing resin, and then subjecting the coated metal base material to a heat treatment at a temperature of 120° C. or higher.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The “carbodiimide group-containing resin obtained from an aromatic polyisocyanate” used in the present invention includes not only a polycarbodiimide resin obtained from an aromatic polyisocyanate but also its mixture with other appropriate resin, and can be any resin containing carbodiimide group.
As to the content of carbodiimide group in “carbodiimide group-containing resin obtained from an aromatic polyisocyanate”, there is no particular restriction. However, when the content is too low, there is a fear that no film is formed when such a resin is coated on a metal base material and subjected to a heat treatment.
The polycarbodiimide obtained from an aromatic polyisocyanate is known per se and is synthesized generally by decarboxylation and condensation of polyisocyanate in the presence of a catalyst, as shown in the following reaction formula. In the following formula, n refers to an average polymerization degree and is an integer of 2 or more.
The polycarbodiimide resin obtained from an aromatic polyisocyanate can specifically be produced, for example, by a method disclosed in JP-A-51-61599, a method by L. M. Alberin et al. [J. Appl. Polym. Sci., 21, 1999 (1997)], or a method disclosed in JP-A-2-292316. That is, it can be produced from an organic polyisocyanate in the presence of a catalyst which promotes the carbodiimidization of isocyanate.
As the organic polyisocyanate, there can be mentioned, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, crude tolylene diisocyanate, crude methylene diphenyl diisocyanate, 4,4′,4″-triphenylmethylene triisocyanate, xylene diisocyanate, m-phenylene diisocyanate, naphtylene-1,5-diisocyanate, 4,4′-biphenylene diisocyanate, diphenylmethane-4,4′-diisocyaante, 3,3′-dimethoxybiphenyl diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, and mixtures thereof.
The above organic polyisocyanates are all aromatic polyisocyanates. In the present invention, there are used a polycarbodiimide resin obtained from an aromatic polyisocyanate, because such a polycarbodiimide becomes a film when its varnish is subjected to solvent removal, and is highly reactive and, when heated, gives rise to crosslinking between carbodiimide groups.
The above polycarbodiimide may be one produced with the molecular weight being controlled by blocking the terminal with, for example, at least one kind of monoisocyanate to stop polycondensation of aromatic polyisocyanate at a certain stage. The monoisocyanate used to block the terminal of polycarbodiimide and control its molecular weight can be exemplified by phenyl isocyanate, o-, m- or p-tolyl isocyanate, dimethyl phenyl isocyanate, cyclohexyl isocyanate and methyl isocyanate.
As is easily inferred, the terminal-blocking agent may also be a compound having a terminal such as —OH, —NH
2
, —COOH, —SH or —NH-alkyl.
As the catalyst which promotes the carbodiimidization of isocyanate, used in the present invention, there can be ment
Amano Satoshi
Kuroyama Shoji
Nakamura Norimasa
Kubovcik & Kubovcik
Nisshinbo Industries Inc.
Paulraj Christopher
Thibodeau Paul
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