Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-06-28
2002-05-07
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S170000, C528S176000, C528S272000, C528S288000, C528S302000, C528S303000, C528S308600, C528S312000, C528S317000, C528S322000, C528S332000, C528S335000, C528S336000, C528S339000
Reexamination Certificate
active
06384181
ABSTRACT:
This application is based on Japanese Patent Application Nos. 11-184156 filed Jun. 29, 1999 and 11-185770 filed Jun. 30, 1999, the contents of which are incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a method of producing a polyamide resin, in particular, a linear polyamide resin by using a polyester resin.
2. Discussion of Related Art
Nylon 66, 46, 6T and an aramide resin have been mass-produced as a heat-resistant polyamide resin which exhibits excellent mechanical, chemical and physical properties. In general, these nylon 66, 46, 6T and etc. are produced by dehydration and polycondensation of a nylon salt which is obtained by reaction of an organic dicarboxylic acid and an organic diamine. However, this method requires cumbersome process steps, and the polycondensation needs to be effected at a high temperature for a long period of time. In producing the aramide resin, there are some problems: use of expensive organic dicarboxylic dihalide; corrosion of the reaction device due to halogen; difficulty in recycling the material; and contamination of the environment.
The inventor of the present invention proposed novel methods of producing a linear polyamide resin by using a polyester resin in JP-A-9-324037, JP-A-11-106504, JP-A-2000-119391 and Japanese Patent Application Nos. 11-60267 and 11-119859. These methods are totally different from the above-indicated conventional method of producing the polyamide resin by polycondensation. Explained in detail, according to the proposed methods, the conventionally used organic dicarboxylic acid is replaced with the polyester resin. The polyester resin reacts with, in a predetermined solvent as a reaction medium, a diamine compound whose molar ratio is determined to be in a specified range for the polyester resin. According to the proposed methods, the polyamide resin having a high molecular weight can be obtained in a simplified manner in a relatively short period of time.
When the aramide resin is produced by using the aromatic diamine as the diamine compound according to the above methods, the obtained aramide resin is likely to have a undesirably low degree of yield. Further, it has been found that the polyamide resin tends to be gel or decomposed due to heat applied thereto during polycondensation in a solid state or molten state (i.e., solid-polycondensation or melt-polycondensation), which polycondensation is effected on the polyamide resin obtained after the reaction of the polyester resin and the diamine compound in an attempt to increase the molecular weight of the obtained polyamide resin.
As a result of an extensive study by the inventor, it has been found that addition of a suitable carboxylic acid-activator (i.e., an agent for activating a carboxylic acid) and/or an inorganic salt to the reaction system of the polyester resin and the diamine compound permits the polyamide resin to be obtained by the reaction of the polyester resin and the diamine compound to have a significantly high degree of yield while avoiding or minimizing gelation and decomposition of the obtained polyamide resin even after the polyamide resin has been subjected to the solid-polycondensation or melt-polycondensation. Further, it has been found that the polyamide resin to be obtained has a considerably high molecular weight as well as a sufficiently high degree of yield without suffering from gelation and decomposition, by adding a suitable carboxylic acid-activator and/or an inorganic salt to a reaction product obtained by the reaction of the polyester resin and the diamine compound, and then effecting the solid- or melt-polycondensation on the reaction product to which the carboxylic acid-activator and/or inorganic salt has/have been added.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of producing a polyamide resin by using a polyester resin, which polyamide resin has a high molecular weight suitable for practical use as well as a high degree of yield, while preventing or minimizing gelation and decomposition of the polyamide resin.
The above-indicated object of the present invention may be attained according to a first aspect of the invention, which provides a method of producing a polyamide resin by reacting with at least one diamine compound, at least one linear polyester resin consisting of at least one dicarboxylic acid component and at least one diol component and having an intrinsic viscosity of not less than 0.2 dl/g, so that the at least one diol component of the linear polyester resin is substituted by the diamine compound, resulting in the polyamide resin as a reaction product, wherein the improvement comprises: at least one of a carboxylic acid-activator and an inorganic salt being present in a reaction system of the linear polyester resin and the diamine compound.
In the method according to the above first aspect of the present invention, the carboxylic acid-activator and/or the inorganic salt is/are present in a reaction system of the predetermined linear polyester resin and the diamine compound which are used in respectively determined amounts, whereby the polyamide resin to be obtained has a significantly high molecular weight and a significantly high degree of yield. Further, the thus obtained polyamide resin is not likely to suffer from gelation or decomposition even after the polyamide resin has been subjected to the solid- or melt-polycondensation for increasing its molecular weight.
In a first preferred form of the above first aspect of the invention, the linear polyester resin reacts with the diamine compound in a reaction medium comprising at least one solvent selected from aprotic solvents.
In a second preferred form of the above first aspect of the invention, the method further comprises a step of effecting polycondensation in a solid state or molten state on the reaction product. By effecting the solid- or melt-polycondensation on the polyamide resin obtained by the reaction, the polymerization degree of the polyamide resin is sufficiently increased, whereby the polyamide resin has an industrially effectively high molecular weight. In addition, the polyamide resin produced according to the present invention is not likely to suffer from gelation and decomposition after it has been subjected to the solid- or melt-polycondensation, so that the produced polyamide resin can be employed for a considerably wide variety of applications.
In a third preferred form of the above first aspect of the present invention, the carboxylic acid-activator is used in an amount of 0.01-0.5 mol per 1 mol of the linear polyester resin as calculated in the repeating unit thereof.
In a fourth preferred form of the above first aspect of the present invention, the inorganic salt is used in an amount of 0.1-30 parts by weight per 100 parts by weight of the aprotic solvent.
In a fifth preferred form of the above first aspect of the invention, the method further comprises a step of melting and kneading reaction materials which include the linear polyester resin, the diamine compound, and the at least one of the carboxylic acid-activator and the inorganic salt.
According to this arrangement, the linear polyester resin and the diamine compound react with high efficiency without using a specific solvent as a reaction medium, so that the polyamide resin to be obtained has a molecular weight which is equal to or even higher than that of the polyamide resin obtained by using the reaction medium. This arrangement reduces a cost for producing the polyamide resin, and eliminates a problem of environmental contamination which would be caused by leakage of the solvent from the reaction equipment, for instance.
In a preferred arrangement of the above fifth form of the first aspect of the invention, the diamine compound is used in an amount of 0.05-1.5 mol per 1 mol of the linear polyester resin as calculated in the repeating unit thereof This arrangement advantageously permits production of the polyamide resin having a high molecu
Burr & Brown
Hampton-Hightower P.
M & S Research and Development Co., Ltd.
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