Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-01-07
2001-09-18
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, C528S322000, C528S332000, C528S339000, C524S397000, C524S447000, C524S449000, C524S451000, C524S494000, C524S496000, C524S606000
Reexamination Certificate
active
06291633
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polyamide resin compositions excellent in not only mechanical properties and moldability but weld strength. These resin compositions are used as molding materials for automotive parts and electrical/electronic parts.
BACKGROUND OF THE INVENTION
Filler-reinforced polyamides are extensively used as industrial materials because of their high strength and rigidity. However, reinforced polyamides in which the resin consists of one or more crystalline polyamides alone have insufficient weld strength and, hence, there are cases where applications thereof are limited. This is because molded parts thereof having many welds or molded parts or products thereof in which the welds are required to have a high safety factor have problems, for example, that they break or crack at welds or suffer considerable deterioration at welds in a high-temperature or high-humidity atmosphere or under high load.
On the other hand, in the case of reinforced polyamides in which the resin consists of one or more noncrystalline polyamides alone, molded objects obtained therefrom have sufficient weld strength. However, applications of these reinforced polyamides also are limited because they require a long molding time.
A known technique for eliminating the above problems is to improve weld strength by using a copolymer having a low melting point, such as, e.g., polyamide 6/66. However, this technique has a drawback that the composition not only has insufficient absolute strength but is reduced in heat and chemical resistance.
JP-A-5-112672 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposes a technique for weld strength improvement which comprises adding a specific acicular filler to a thermoplastic resin such as a polyamide. However, molded parts of this composition have insufficient strength in parts other than welds, i.e., have insufficient base material strength, although the weld strength is improved in some degree. This background art composition is hence unusable as structural parts required to have high base material strength.
JP-A-7-149947 proposes a technique for weld strength improvement which comprises adding a silicone rubber to a thermoplastic resin reinforced with a fibrous filler. However, this composition is reduced in rigidity and heat resistance although improved in weld strength.
JP-A-55-62959 and JP-A-6-172643 each proposes a technique which comprises adding an aromaticpolyamide. However, the technique disclosed in JP-A-55-62959 necessitates the addition of a large amount of an aromatic polyamide and is hence unable to give an inexpensive composition. In addition, this background art is intended to improve surface gloss and there is no description therein to the effect that weld strength is improved. The technique disclosed in JP-A-6-172643 is insufficient in weld strength improvement because an aromatic dicarboxylic acid is used as crystallinity-imparting monomer in producing the aromatic polyamide.
SUMMARY OF THE INVENTION
An object of the present invention is to provide molding polyamide resin compositions which have suitability for fast-cycle molding and retain calcium chloride resistance and high weld strength even in a high-temperature high-humidity atmosphere, under high load, etc., to thereby eliminate the above-described drawbacks of background art techniques.
The present inventors made intensive investigations in order to overcome the problems described above. As a result, they have found that the above object can be accomplished by adding a polyamide resin formed from a xylylenediamine and an aliphatic dicarboxylic acid to a crystalline polyamide. The present invention has thus been achieved.
The present inventors have further found that the above object can be accomplished also by adding a noncrystalline polyamide having a specific structure to a crystalline polyamide. The present invention has thus been achieved.
The present invention provides a molding polyamide resin composition with excellent weld strength which comprises:
100 parts by weight of a polyamide resin comprising
(A-1) a crystalline, partly aromatic copolyamide resin containing one kind of aromatic monomer units and/or
(A-2) a crystalline aliphatic polyamide resin 95-55 wt %
and
(B-1) a polyamide resin comprising units derived from a xylylenediamine and units derived from an aliphatic dicarboxylic acid 5-45 wt %;
and
from 5 to 200 parts by weight of (C) an inorganic filler.
The present invention further provides a molding polyamide resin composition with excellent weld strength which comprises:
100 parts by weight of a polyamide resin comprising
(A-1) a crystalline, partly aromatic copolyamide resin containing one kind of aromatic monomer units and/or
(A-2) a crystalline aliphatic polyamide resin 95-55 wt %
and
(B-2) a noncrystalline, partly aromatic copolyamide resin containing at least two kinds of aromatic monomer units 5-45 wt %;
and
from 5 to 200 parts by weight of (C) an inorganic filler.
In the present invention, polymers which show a distinct peak in DSC (differential scanning calorimetry) are defined as “crystalline” polymers, while polymers not showing a distinct peak in DSC are defined as “noncrystalline” polymers.
DETAILED DESCRIPTION OF THE INVENTION
The crystalline, partly aromatic copolyamide resin containing one kind of aromatic monomer units used as ingredient (A-1) in the present invention is a copolyamide containing one kind of aromatic monomer units, e.g., units derived from an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, or naphthalenedicarboxylic acid. Ingredient (A-1) is preferably a crystalline, partly aromatic copolyamide resin containing one kind of aromatic monomer units and having a melting point of from 260 to 320° C., excluding 320° C., and is more preferably a crystalline, partly aromatic copolyamide resin containing one kind of aromatic monomer units and having a melting point of from 290 to 316° C., excluding 316° C.
A monomer combination for the preferred, crystalline, partly aromatic copolyamide resin containing one kind of aromatic monomer units, ingredient (A-1), comprises an equimolar salt of an aliphatic diamine with an aliphatic dicarboxylic acid, and an equimolar salt of an aliphatic diamine with an aromatic dicarboxylic acid, and optionally at least one monomer forming an aliphatic polyamide.
Examples of the aliphatic diamine include those having 4 to 12 carbon atoms, such as tetramethylenediamine, hexamethylenediamine, octamethylenediamine, nonamethylenediamine, undecamethylenediamine, and dodecamethylenediamine.
Examples of the aliphatic dicarboxylic acid include those having 6 to 12 carbon atoms, such as adipic acid, heptanedicarboxylic acid, octanedicarboxylic acid, nonanedicarboxylic acid, undecanedicarboxylic acid, and dodecanedicarboxylic acid.
Preferred is an equimolar salt of hexamethylenediamine with adipic acid.
Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Preferred is an equimolar salt of hexamethylenediamine with terephthalic acid.
Examples of the monomer forming an aliphatic polyamide include aminocarboxylic acids having 6 to 12 carbon atoms and lactams having 6 to 12 carbon atoms. Specific examples thereof include 6-aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, &agr;-pyrrolidone, &egr;-caprolactam, laurolactam, and &egr;-enantholactam. Preferred of these are 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, &egr;-caprolactam, and laurolactam. Such monomers forming an aliphatic polyamide may be used either alone or as a mixture of two or more thereof.
The use amounts of the equimolar salt of hexamethylenediamine with adipic acid, the equimolar salt of hexamethylenediamine with terephthalic acid, and the monomer forming an aliphatic polyamide are generally from 30 to 70 wt %, from 70 to 30 wt %, and from 0 to 15 wt %, respectively, and are preferably from 35 to 55 wt %, from 65 to 45 w
Akin Gump Strauss Hauer & Feld L.L.P.
Hampton-Hightower P.
Ube Industries, Inc.
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