Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-12-30
2001-08-07
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S589000, C528S044000, C528S049000
Reexamination Certificate
active
06271304
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sealing material, and more specifically, it relates to a sealing material suitable for filling up a clearance between a coated steel plate and a component forming a gasket in a flange part of a trunk lid of an automobile or the like.
2. Description of the Prior Art
A sealing material, which is employed in various fields, fills up a clearance between a coated steel plate and a component forming a gasket in a flange part of a trunk lid of an automobile, for example, for sealing and rust prevention.
FIG. 1
is a sectional view showing such a flange part A hollow-sealing member
2
for sealing a trunk room when closing a trunk lid is integrally formed with a gasket
4
. A sealing member
6
fills an inner part of the gasket
4
, which is engaged with a coated steel plate
8
of the trunk lid for dipping the forward end of the coated steel plate
8
into the sealing material
6
.
The material for the gasket
4
has been mainly prepared from a rubber material such as PVC (polyvinyl chloride), SBR (styrene-butadiene rubber), NR (natural rubber) or CR (chloroprene rubber). Furthemore, EPDM (ethylene-propylene rubber) is generally employed particularly in recent years, while thermoplastic elastomer such as TPO (olefinic elastomer) is regarded as a promising advanced material.
The coated steel plate
8
of the flange part is formed by a baked coated steel plate of melamine, acrylic or melamine acrylic.
The sealing material
6
for filling up the inner part of the gasket
4
must have the following characteristics:
(1) To hold viscosity over a long period after filling up the inner part of the gasket
4
;
(2) to have less swelling action of the gasket
4
of synthetic resin or synthetic rubber,
(3) to minimize contamination or swelling of the coated steel plate
8
;
(4) to have less self-volume shrinkage factor;
(5) to have no self-foaming or swelling,
(6) to be readily engaged with the coated steel plate
8
of the flange part after filling the inner part of the gasket
4
; and
(7) not to ooze out from the gasket
4
.
A sealing material for filling a clearance between a coated steel plate and a part forming a gasket in a flange part of an automobile is mainly prepared from a polybutene material or a butyl rubber material. The polybutene sealing material is a composite prepared by blending an adhesive component of polybutene resin with an oil extender which includes a plasticizer, process oil, polypropylene glycol having a hydroxyl group on one or each end and a solvent, and a powder filler.
The butyl rubber sealing material is prepared by dissolving butyl rubber in process oil or a solvent and blending the same with the aforementioned oil extender and a powder filler.
However, when employing the polybutene sealing material, the polybutene itself, and the plasticizer, the process oil, or the solvent which are contained in the oil extender, disadvantageously swells the gasket Furthermore, the plasticizer or the process oil, which are contained in the oil extender, erodes the coated steel plate to swell or contaminate the same. In addition, the sealing material remarkably shrinks due to evaporation of the oil extender or the solvent.
On the other hand, in the butyl rubber sealing material,, the viscosity of the composite increases due to volatilization of the solvent in addition to the aforementioned action of swelling the gasket Thus, the sealing material cannot be readily engaged with the coated steel plate of the flange part Furthermore, the sealing material disadvantageously shrinks due to volatilization of the oil extender or the solvent.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a sealing material, which can maintain its viscosity over a long period without swelling a component of synthetic resin or synthetic rubber.
The inventors have studied deeply to discover that a novel composite, which is absolutely different from the aforementioned general sealing material of polybutene or butyl rubber, solves the aforementioned problems, and were able to complete the present invention. In order to attain the aforementioned object, a non-swelling sealing material according to the present invention is mainly composed of a viscous liquid compound having at least two alkyl ether end groups having a carbon number of 1 to 30 in one molecule and having a urethane bond in its principal chain, and contains a powder filler for compounding.
The inventive sealing material has the maximum technical significance in a point requiring no oil extender swelling a gasket due to employment of the viscous liquid compound having the aforementioned specific chemical structure as the main component
The compound forming the main component of the sealing material can maintain viscosity over a long period itself. Furthermore, the sealing material mainly composed of this compound may not be blended with an oil extender required by the conventional sealing material, and the compound itself does not swell a gasket.
According to the present invention, the viscous liquid compound forming the main component of the sealing material has alkyl ether groups on molecular ends with a urethane bond in its principal chain. Such a compound is generally synthesized by urethane bond forming reaction by addition of a compound having an isocyanate group and a monoalcohol compound.
In order to suppress foaming of the sealing material, it is necessary to blend hydroxyl groups to be at least equimolar with the isocyanate groups so that no free isocyanate groups are substantially present in the obtained compound. If isocyanate groups are present in this compound, the sealing material may react with moisture contained in the air to foam. Even if the material composition is so set in the synthesizing process that the hydroxyl groups are in excess of the isocyanate groups, unreacted isocyanate groups may remain in the compound. The aforementioned expression “no free isocyanate groups are substantially present” means that some isocyanate groups may remain in the compound if swelling of the sealing material itself causes no problem by foaming.
Presence of unreacted hydroxyl groups is allowed so far as the sealing material obtained from the compound does not swell a gasket This means that the monoalcohol compound reacted with the compound having the isocyanate groups can be employed in excess of the equimolar state.
A first method of preparing a non-swelling sealing material according to the present invention reacts a low molecular weight polyisocyanate compound having at least two isocyanate groups in one molecule with polyalkylene oxide monoether having a hydroxyl group only on one end in such a molar ratio that the hydroxyl groups are equimolar with or slightly in excess of the isocyanate groups for synthesizing a compound, and thereafter blends the synthesized compound with a powder filler.
The low molecular weight polyisocyanate compound having at least two isocyanate groups in one molecule can be prepared from aliphatic, aromatic or alicyclic low molecular weight polyisocyanate having molecular weight of less than 500.
Such low molecular weight polyisocyanate compound can be prepared from diisocyanate such as 4,4′-diphenylmethane diisocyanate, polyphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, m-xylylene diisocyanate, naphthalene diisocyanate, cyclohexanel, 4-diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate or dicyclohexylmethane diisocyanate, or triisocyanate such as triphenylmethane triisocyanate or tris(isocyanatephenyl)thiophosphate.
The polyalkylene oxide monoether having a hydroxyl group only on one end can be prepared from a compound having a polyalkylene oxide part of its principal chain part consisting of polyether such as polyethylene oxide, polypropylene oxide, polyethylene oxide/polypropylene oxide random copolymer or polytetramethylene oxide, and another ether end gro
Fujimoto Sukehide
Nakano Yoshinori
Armstrong Westerman Hattori McLeland & Naughton LLP
Niland Patrick D.
Sunrise MSI Corporation
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