Coating processes – Solid particles or fibers applied
Reexamination Certificate
2001-08-02
2003-09-23
Cameron, Erma (Department: 1762)
Coating processes
Solid particles or fibers applied
C427S207100, C427S385500
Reexamination Certificate
active
06623795
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a one-pack type urethane sealing material for a car body, and more particularly, to a one-pack type urethane sealing material for a car body which material cures by both factors of moisture and heating. The present invention also relates to a method for sealing a car body with such a urethane sealing material.
2. Description of the Related Art
A car body is fitted at its panel joint portions with a sealing material for watertightness, corrosion protection, and airtightness. In a car assembly line, after a sealing material is fitted to joint portions of a car body panel or part, a paint is coated on the sealing member, and the coated sealing member is directly sent to a paint baking step, where the paint is baked in a baking oven at about 140° C. Because of this procedure, vinyl chloride based sol compositions have hitherto been used for a sealing material for a car body since they can maintain their shape until they enter the baking oven and are of the heat curing type.
Under high temperature and high humidity conditions as in summer seasons, when a sealing material made of a vinyl chloride based sol composition is subjected to a high temperature and high humidity environment after it is fitted to the joint portions, the sealing material absorbs moisture. In this case, afterwards when the sealing material passes the baking oven the moisture contained in the sealing material vaporizes abruptly to form foams in the sealing material. As a result cracks occur in the paint coated on the sealing material. To remove the moisture in the sealing material, a preliminary drying oven must be provided in order to dry the sealing material at a temperature around 100° C. before it can be passed through the paint baking oven.
On the other hand, in recent years, substitutes for vinyl chloride based sol compositions have been desired from the viewpoint of environment protection. However, on the other side of the coin such a substitution requires change of order of operations in automobile assembly line by shifting the step of fitting of a sealing material to after the steps of coating and baking. Such a change in the assembly line is practically impossible from the viewpoint of costs and the like.
Therefore, development of a car body sealing material that does not form foams under high temperature and high humidity conditions and even in a paint baking oven and of a car body sealing method using such a sealing material has been keenly demanded.
Meanwhile, the technology of using a moisture curing one-pack type urethane composition as a sealing material for roofs, walls and the like has been known.
However, when such a moisture curing one-pack type urethane sealing material is used as a sealing material for a car body, the sealing material does not cure after the baking step.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve the problem of the prior art as described above and provide a sealing material that has a shape maintaining ability and can cure without causing any foaming in a high temperature and high humidity environment as in summer seasons even in a high temperature baking oven.
Another object of the present invention is to provide a method for sealing a car body with such a sealing material.
The present inventors have made extensive study with a view to solving the problems described above and as a result they have found that use of a moisture curing one-pack type urethane sealing material as a sealing material in order to prevent foaming due to vaporization of moisture and addition of a precipitated calcium carbonate treated with a fatty acid alkali metal salt thereto can afford a one-pack type urethane sealing material that can cure by heating. The present invention is based on this discovery.
That is, the one-pack type urethane sealing material for a car body of the present invention contains precipitated calcium carbonate treated with a fatty acid alkali metal salt, wherein the sealing material cures by both factors of moisture and heating.
Further, a car body sealing method of the present invention comprises using the one-pack urethane sealing material for a car body described above as a car body sealing material.
The one-pack type urethane sealing material for a car body of the present invention has shape maintaining ability (thixotropy) and can be cured by heating and causes no foaming upon heating in a high temperature and high humidity environment such as summer seasons, so that it can be used advantageously as a sealing material for a car body.
According to the car body sealing method of the present invention, because of use of the one-pack type urethane sealing material as described above, it can be advantageously incorporated into a car assembly line that performs the baking step in a heating oven after fitting the sealing material and that does not require a drying step in a preliminary drying oven as in the conventional technique so that the assembly line can be made simpler.
DETAILED DESCRIPTION OF THE INVENTION
First, the one-pack type urethane sealing material for a car body of the present invention will be explained hereinbelow.
The one-pack type urethane sealing material for a car body of the present invention contains a urethane prepolymer. The urethane prepolymer is not particularly limited and generally any urethane prepolymer may be used as far as it is produced from a polyol compound, i.e., a kind of polyhydroxyl compounds, and a polyisocyanate compound.
The polyol compound is a generic name for alcohols derived from hydrocarbons by substituting a plurality of hydrogen atoms thereof for hydroxyl groups and includes polyether polyols, polyolefin polyols, polyester polyols, other polyols than the above and mixtures of two or more of these polyols.
Examples of the polyether polyol include polyols obtained by adding one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, and styrene oxide to one or more of dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 4,4′-dihydroxyphenylpropane, and 4,4′-dihydroxyphenylmethane; polyhydric alcohols such as glycerol, 1,1,1-trimethylolpropane, and 1,2,5-hexanetriol, pentaerythritol; diamines such as ethylenediamine, aromatic diamines; one or more sugars such as sorbitol; and polyoxytetramethylene oxide and the like.
Examples of the polyester polyol include condensation polymers obtained from one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanedimethanol, glycerol, 1,1,1-trimethylolpropane, or other low molecular weight polyols, and one or more of glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, dimeric acid, or other low molecular weight carboxylic acids; ring open polymers such as propionolactone and valerolactone, and the like.
Suitable examples of the polyols other than the above include polyols whose main chain is composed of carbon—carbon bond, for example, acrylic polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, low molecular weight polyols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, and hexanediol.
These polyols may be used singly or two or more of them may be used in combination. Preferred polyols have a weight average molecular weight of about 1,000 to about 10,000, more preferably about 3,000 to about 7,000.
The polyisocyanate compound includes various types usually used in preparing polyurethane resins. Specific examples thereof include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, and modified preparations thereof, 1,5-naphthalene diisocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, triphenylmethane triisocyanate and the like. These poly
Yamada Atsushi
Yokouchi Keiichi
Cameron Erma
Finnegan Henderson Farabow Garrett & Dunner LLP
The Yokohama Rubber Co. Ltd.
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