Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1998-10-02
2001-07-31
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S423100, C528S044000
Reexamination Certificate
active
06268057
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a polyurethane material and a molded product of polyurethanes molded by a reaction injection molding (RIM) which uses the same material.
2. Description of the Related Art
The applicant developed an invention covering a process for manufacturing a two-colored molded product of polyurethanes by RIM techniques which comprises injecting a small amount of a surface-forming polyurethane material containing a mold release agent, a coloring agent and a catalyst into a mold cavity having a reduced pressure so that it may adhere to the whole surface of the wall of the cavity and form the surface portion of a molded product. Then another polyurethane material is injected into the cavity to form its inner portion (see Japanese Patent Application Laid-open Specification No. 6-143340). This process has made it possible to eliminate the steps of applying the mold release agent and the in-mold coating material to the cavity wall before starting the molding step, and overcomes the problem of a burr formed by the in-mold coating material.
There has, however, been a problem facing the new process, since no polyurethane material that can be considered optimum has been found for use in forming the surface portion of a molded product. The applicant, therefore, further developed an invention covering a process for forming a surface portion from a non-yellowing polyurethane material containing a hexamethylene diisocyanate (HDI) trimer (see Japanese Patent Application No. 9-92930, which is not laid-opened yet). Since an HDI trimer has a ring structure, a polyurethane material using the same shows an improved wear resistance and is able to accelerate the urethane reaction by using a specific catalyst. However, since the molecular chain of the HDI trimer is not straight, there remains a problem that a polyurethane material using a generally available HDI trimer is low in breaking elongation, inferior in flexural resistance, and subject to cracks or breaking.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a polyurethane material which is high in breaking elongation, superior in flexural resistance, and not subject to cracks or breaking, and to provide a molded product of polyurethanes molded by RIM techniques which uses the same material.
In a generally available HDI trimer, content of oligomer, which is equal to or higher than a pentamer and which exists in the trimer as impurities, exceeds 50% by weight for 100% by weight of the HDI trimer. The present inventors thought a large amount of the oligomer to be the factor which lowers breaking elongation. And a result of various investigations and examinations, the inventors have completed the present invention.
A polyurethane material of the present invention comprises an HDI trimer and a polyol, wherein content of oligomer, which is equal to or higher than a pentamer, in said HDI trimer is restricted to 0 to 50% by weight, and 3 to 10% by weight of monool is added to said HDI trimer for 100% by weight of said HDI trimer.
A molded product of polyurethanes of the present invention is molded from a polyurethane material by RIM, said polyurethane material comprising an HDI trimer and a polyol, wherein content of oligomer, which is equal to or higher than a pentamer, in said HDI trimer is restricted to 0 to 50% by weight, and 3 to 10% by weight of monool is added to said HDI trimer.
A two-colored molded product of polyurethanes molded by RIM of the present invention comprises: a surface portion 15 formed by injecting a small amount of a surface-forming polyurethane material into a mold cavity under reduced pressure, said material comprising an HDI trimer and a polyol, wherein content of oligomer, which is equal to or higher than a pentamer, in said HDI trimer is restricted to 0 to 50% by weight, and 3 to 10% by weight of monool is added to said HDI trimer; and an optional inner portion formed by injecting an inner-forming polyurethane material into said cavity under reduced pressure.
In the above inventions, “oligomer, which is equal to or higher than a pentamer,” means that the number of monomeric units bound in the oligomer is equal or more than the number of monomeric units bound in a pentamer.
The reason why the content of oligomer, which is equal to or higher than a pentamer, is restricted to 0 to 50% by weight is that its content more than 50% by weight lowers breaking elongation of the molded product. The reason why 3 to 10% by weight of monool is added is that its addition less than 3% by weight is insufficient to decrease the number of functional groups, which lowers breaking elongation of the molded product, while its addition more than 10% by weight decreases the network structure, which lowers the wear resistance. It is more preferable to add 4 to 8% by weight of monool.
Monool is not limited to a specific one. For example, it may be at least one selected from the group consisting of 2-ethylhexyl alcohol, n-butanol, isopropanol, ethanol, isobutanol, n-propanol and n-pentanol.
The polyol component can be any of those which are commonly used for RIM, including the polyether and polyester polyols. More specifically, the polyol component may be selected from the group consisting of:
bifunctional, trifunctional or tetrafunctional polyols obtained by reacting cyclic ethers, such as ethylene oxide, propylene oxide, butylene oxide and styrene oxide, with low-molecular polyols, such as ethylene glycol, diethylene glycol, glycerol, trimethylolpropane and bisphenol A, and polymer polyols obtained by the graft polymerization thereof with e.g. vinyl monomers; and
polyesters obtained by reacting dicarboxylic acids, such as succinic, glutaric, adipic and piperic acids, with an excess of diols, such as ethylene glycol, polyoxyethylene glycol, dipropylene glycol and polyoxypropylene glycol.
It is preferable to add an organic bismuth catalyst or the following mixed catalyst, which acts specifically on the material using an HDI trimer, to the polyol. The mixed catalyst is a mixture of a first catalyst having the chemical formula
and a second catalyst represented by the chemical formula
where M stands for an alkali metal or an alkaline earth metal, and R stands for hydrogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl or alkynyl group having 2 to 20 carbon atoms (any of these groups being of the straight or branched chain type, and optionally replaced by one carboxyl group, or one or more halogens), a cycloalkyl group having 3 to 6 carbon atoms [this group being unsubstituted, or replaced by one carboxyl group, or one or more alkyl groups having 1 to 6 carbon atoms, or alkenyl or alkynyl groups having 2 to 6 carbon atoms (any of these groups being of the straight or branched chain type)], or an aryl group [this group being unsubstituted, or replaced by one or more halogens, or one or more alkyl groups having 1 to 8 carbon atoms, or alkenyl or alkynyl groups having 2 to 8 carbon atoms (any of these groups being of the straight or branched chain type), or one aryl group or one carboxyl group] (see U.S. Pat. No. 4,025,466). The organic bismuth catalyst is not limited to a specific one, and it may be at least one selected from the group consisting of bismuth neodecanoate, bismuth isodecanoate and bismuth octylate.
A mold release agent may be added to the polyol as a third component. It is also possible to add a coloring agent to the HDI trimer or the polyol as a third component.
Further objects of this invention will become evident upon an understanding of the illustrative embodiments described below. Various advantages not specifically referred to herein but within the scope of the instant invention will occur to one skilled in the art upon practice of the presently disclosed invention. The following examples and embodiments are illustrative and not seen to limit the scope of the invention.
REFERENCES:
patent: 5208334 (1993-05-01), Potter et al.
patent: 5691440 (1997-11-01), Katz et al.
patent: 5962142 (1999-10-01), Tachi
Mizuno Hisashi
Ono Satoru
Yamada Takahiro
Nakarani D. S.
Paulraj Christopher
Pillsbury & Winthrop LLP
Toyoda Gosei Co,., Ltd.
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