Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-26
2001-09-11
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S460000
Reexamination Certificate
active
06288145
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to high-melting polyamide resin compositions having improved mechanical properties. More specifically, it relates to polyamide resin compositions in which the mechanical properties have been enhanced while maintaining the reflow heat temperature resistance of the high-melting polyamide, and also to molded articles for electrical and electronic components made of the same.
BACKGROUND OF THE INVENTION
Electrical and electronic components such as connectors have recently been undergoing dramatic increases in performance. This trend is especially striking in connectors used in surface-mount technology (SMT), where molding materials with high flame retardance, high flowability, high melt stability, high mechanical properties, and a high reflow heat temperature resistance are required.
Thermoplastic resins which have hitherto been used to mold SMT connectors include aromatic polyamides, polytetra-methylene adipamide, a polymer of tetramethylene diamine and adipic acid (“nylon 46”), polyphenylene sulfide and liquid crystal polymers. However, in the case of aromatic polyamides and nylon 46, it is generally necessary to carry out flame-retarding treatment in order to achieve the high flame retardance required, which means attaining a UL 94 rating of V-0. Various methods exist for carrying out flame-retarding treatment, although polyamides are generally flame-retarded by a method involving the addition of a flame retardant. However, when a low-molecular-weight flame retardant is used and a flowability enhancer such as a wax is also added to elicit a high flowability, the mechanical properties intrinsic to the polyamide are lost. Also, the reflow heat temperature resistance decreases by adding a low-molecular-weight flame retardant. Therefore, polyamide resin compositions endowed with the high flame retardance, high flowability, high melt stability, high functional properties, and high reflow heat temperature resistance required of SMT connector molding materials have yet to achieved.
The use of epoxy group-containing compounds, such as glycidyl isocyanurate and novolak-epoxy resins, as binders in paints is well known, but these compounds have not often been used as additives for enhancing the properties of resins. One case in which they have been used as resin additives is in methods for the stabilization of flame-retarded resin compositions characterized by the use of glycidyl isocyanurate, either alone or in combination with other compounds, as the heat stabilizer in resin composites of styrene resin and carbonate resins that have been flame-retarded using brominated flame retardants (Japanese Unexamined Patent Application Disclosure [Kokai] Nos. 2-279,763 (1990) and 4-266,956 (1992)). However, because general-purpose resin composites of styrene and carbonate resins such as this have a heat resistance that is far inferior to that of polyamides, they cannot be used as the molding materials for electrical and electronic components such as SMT connectors.
SUMMARY OF THE INVENTION
This invention provides a polyamide resin composition comprising a polyamide having a melting point of 280 to 340° C. and an epoxy group-containing compound. The epoxy group-containing compound is preferably glycidyl isocyanurate, novolak-epoxy resin, or mixtures thereof.
The polyamide is preferably an aromatic polyamide.
The resin composition may additionally comprise an inorganic filler, and also (a) a brominated flame retardant and (b) a co-flame retardant which is antimony-based or zinc borate-based.
The flame retarding resin composition may further comprise hydrotalcite.
This invention also provides molded articles for electrical and electronic components made with such compositions.
DETAILED DESCRIPTION OF THE INVENTION
The polyamide used in the present invention has a melting point of 280° C. to 340° C. and can be used in injection molding. Examples include:
(1) polyamides obtained by the polycondensation of diamine constituents and dicarboxylic acid constituents, the former being at least one diamine selected from the group consisting of aliphatic alkylenediamines, aromatic diamines and alicyclic diamines, and the latter being at least one dicarboxylic acid selected from the group consisting of aliphatic dicarboxylic acids and aromatic dicarboxylic acids;
(2) polyamides obtained by ring opening polymerization from lactam;
(3) polyamides obtained by the polycondensation of an aminocarboxylic acid; and
(4) blends thereof.
The aliphatic alkylenediamines in (1) may be straight-chained or branched, and may be used alone or as combinations of two or more thereof. Specific examples of these aliphatic alkylenediamines are ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,7-diamino-heptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 2-methylpenta-methylenediamine and 2-ethyltetramethylenediamine.
The aromatic diamines in (1) may be used alone or as a combination of two or more thereof. Specific examples include para-phenylenediamine, ortho-phenylenediamine, meta-phenylenediamine, para-xylylenediamine and meta-xylylene-diamine.
The alicyclic alkylenediamine in (1) may be used alone or as a combination of two or more thereof. Specific examples include 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, 4,4′-diamino-3,3′-dimethyldicyclohexylmethane, isophoronediamine and piperazine.
The aliphatic dicarboxylic acid in (1) may be used singly or as a combination of two or more thereof. Specific examples include adipic acid, sebacic acid, azelaic acid and dodecanedioic acid.
The aromatic dicarboxylic acid in (1) may be used singly or as a combination of two or more thereof. Specific examples include terephthalic acid, isophthalic acid, phthalic acid, 2-methylterephthalic acid and naphthalenedicarboxylic acid.
The lactam in (1) may be used singly or as a combination of two or more thereof. Specific examples include butyl lactam, pivalolactam, caprolactam, capryl lactam, enantholactam, undecanolactam and dodecanolactam.
Examples of (3) are polymerizable &ohgr;-amino acids, which may be used singly or as a combination of two or more thereof. Specific examples include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid.
The high-melting polyamides used in the present invention may include aromatic polyamides and nylon 46, with melting points of 280° C. to 340° C. They are particularly suitable as resins which have the heat resistance and mechanical properties required of the molded articles, as well as excellent thermal stability during molding, and which are suitable also from the standpoint of cost. Examples of aromatic polyamides include injection-moldable aromatic polyamides, blends of two or more aromatic polyamides, and blends of an aromatic polyamide with another polyamide. Aromatic polyamides which are composed of hexamethylenediamine, terephthalic acid and adipic acid, and in which decreased rigidity and dimensional changes do not occur with moisture absorption, are especially desirable.
When epoxy group-containing compounds are blended with those high-melting polyamides, the mechanical properties of the resin composition are enhanced, while maintaining the reflow heat temperature resistance. Specific examples of these epoxy group-containing compounds are glycidyl isocyanurates and novolak-epoxy resins. These may be used alone or as combinations of two or more thereof.
Examples of glycidyl isocyanurates include monoglycidyl isocyanurate, diglycidyl isocyanurate and triglycidyl isocyanurate. Triglycidyl isocyanurate is especially preferred.
“Novolak-epoxy resin” is a generic name for compounds in which the hydroxyl groups of phenols that have been condensed using an acid catalyst are substituted with epoxy groups. Examples of the phenol include unsubstituted phenol and cresol, with cresol-novolak resin being especiall
Aylward D.
Dawson Robert
E. I. Du Pont de Nemours and Company
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