Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2001-07-30
2003-08-19
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C521S155000, C521S159000, C521S128000, C521S130000, C521S170000, C521S174000, C528S068000, C528S085000
Reexamination Certificate
active
06608160
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a one-pack type curable composition for production of cover packing, as well as to a method for producing a cover packing superior in properties, etc. using the composition.
(2) Related Prior Art
Polyurethane elastomer molded articles have been known to have excellent physical properties such as high tensile strength, fatigue resistance, good low-temperature flexibility, abrasion resistance and the like.
Owing to these properties, they have been produced extensively as rolls, packings, various machine parts, automobile parts, electronic appliance parts, etc.
For production of a polyurethane resin, there is generally known, for example, a method of reacting a high-molecular polyhydroxyl compound, a low-molecular polyhydroxyl compound as a chain extender and an organic diisocyanate compound in the presence or absence of a catalyst.
This method is largely classified into two methods, i.e. a one-shot method of casting the above three components simultaneously and giving rise to a reaction among them, and a method of first synthesizing an isocyanate group-terminated urethane prepolymer from the high-molecular polyhydroxyl compound and the organic diisocyanate compound and then allowing the low-molecular polyhydroxyl compound to act on the isocyanate group-terminated urethane prepolymer for crosslinking reaction.
In, for example, JP-A-63-8685 is disclosed a method for obtaining a polyurethane elastomer having a JIS-A hardness of 78 to 80 by a reacting an isocyanate group-terminated urethane prepolymer (a main material) obtained from a polyester polyol and diphenylmethane diisocyanate, with a mixture (a crosslinking agent) of 1,4-butanediol and trimethylolpropane and conducting post-curing at 140° C. The polyurethane elastomer obtained by this method is superior in mechanical strength and is well balanced particularly as a cleaning blade for electronic photocopier.
As an example of the application of a polyurethane resin to a cover packing for container such as pail, open drum or the like, there is a technique described in JP-A-61-9481. In this technique, a first liquid containing a urethane prepolymer as a main component and a second liquid containing a polyol as a main component are mixed and, at that time, the viscosity of the mixture (for reaction) is controlled at 200 to 20,000 mPa·s at 0 to 60° C.
In a casting operation using an industrial machine, a tank for main material component and a tank for curing agent component are prepared separately; the two components are transferred from the respective tanks into a mixing apparatus in given proportions, using a metering pump. Mixing is conducted by mechanical stirring or high-pressure collision; the resultant mixture is cast into a mold; and a heat treatment is conducted for a given length of time to obtain an elastomer molded article.
Mechanical stirring is conducted generally at ordinary pressure; therefore, in the mechanical stirring, there is needed a flowing time for the mixture of the main material component and the curing agent component to be cast into the mold and there has been a limit in order to obtain a shorten curing time. In mixing by high-pressure collision, a high-performance high-pressure pump and a mold of good sealing are necessary.
Spraying is used in covering of a material of large area such as floor material or the like. This method is not applicable to molding of a shaped article such as cover packing intended in the present invention.
When a mixture for reaction, which may be any of a two-pack type composition such as described in JP-A-61-9481 and a one-pack type composition comprising a blocked isocyanate and a polyhydroxyl compound, is heated to high temperatures for curing or for acceleration of decomposition (of blocked isocyanate) and reaction, the viscosity of the mixture generally decreases before the reaction and curing take place. As a result, there have been a problem that when a cover near a discharging port is moved, the packing formed comes to have a non-uniform thickness owing to the movement of the cover and further the reaction mixture flowing out of the groove of the cover stains a production line inside a heating furnace, and a problem that when the reaction mixture shows dripping at the completion of discharging, cover portions other than the groove are stained (discharging should be made only to the groove).
OBJECTS AND SUMMARY OF THE INVENTION
The object of the present invention lies in solving the above-mentioned problems of the known prior art and providing (1) a composition for production of cover packing which is a one-pack type, curable composition requiring no apparatus for compounding two or three liquids [a main material(s) and a curing agent] and which, when heated, causes dissociation of blocking agent and completion of reaction simultaneously and gives a cured material superior in mechanical strength, etc. and (2) a method for producing a packing for cover using the above composition. Other object of the present invention lies in providing a composition for production of cover packing, which requires no high-performance high-pressure pump or no mold of good sealing, is cured in several minutes after the mixing at a mold temperature to give a cured material releasable from the mold despite of the low hardness, and is superior in dischargeability, lining ability and driplessness, and a method for producing a packing for cover using the above composition.
The present inventors made a study and found out that the above objects could be achieved by using a blocked isocyanate, an active hydrogen group-containing compound, an organic substance powder and an inorganic substance powder. The finding has led to the completion of the present invention.
The present invention lies in the following (1) and (2).
(1) A composition for production of cover packing, comprising:
(A) a blocked isocyanate,
(B) an active hydrogen group-containing compound having average two or more functional groups,
(C) an organic substance powder having an average particle diameter of 40 to 250 &mgr;m, and
(D) an inorganic substance powder having an average particle diameter of less than 40 &mgr;m.
(2) A method for producing a packing for cover, which comprises subjecting the above composition for production of cover packing to heat-curing at 100 to 250° C.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
The blocked isocyanate (A) used in the present invention is a compound obtained by reacting an isocyanate (e.g. an aromatic polyisocyanate, an aliphatic polyisocyanate, an alicyclic polyisocyanate, or a modification thereof) with a blocking agent to block the isocyanate group.
As specific examples of the above isocyanate, there can be mentioned aromatic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, xylylene-1,2-diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4′-diisocyanate, 2,2′-diphenylpropane-4,4′-diisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, 4,4′-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3′-dimethoxydiphenyl-4,4′-diisocyanate, tetramethylxylylene diisocyanate and the like; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate and the like; alicyclic diisocyanates such as hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylylene diisocyanate, isophorone diisocyanate and the like; urethane bond-containing polyisocyanates derived from the above organic diisocyanates, allophanate bond-containing polyisocyanate
Nii Sumito
Takata Osamu
Yokota Hiroei
Browdy and Neimark , P.L.L.C.
Cooney Jr. John M.
Nippon Polyurethane Industry Co., Ltd.
LandOfFree
Composition for production of cover packing and process for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composition for production of cover packing and process for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composition for production of cover packing and process for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3121809