Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-12-17
2001-02-20
Yoon, Tae (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S606000
Reexamination Certificate
active
06191207
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polyamide resin composition which is excellent in surface smoothness, mechanical properties and weatherability, and to a molded article thereof.
BACKGROUND OF THE INVENTION
Polyamide resins are widely, used in various application fields because they have excellent mechanical properties and can be improved remarkably in their strength and rigidity by reinforcement with glass fiber. However, polyamide compositions containing glass fiber at a relatively higher content for the improvement of the strength and rigidity have problems, for example, such that articles molded by injection molding have poor appearance owing to emergence of the glass fiber on the molded article surface.
To solve such problems, a composition is disclosed which employs a polyamide having a relatively low crystallization temperature among polyamide resins such as those derived by copolymerization of adipic acid and m-xylylenediamine (hereinafter referred to as “nylon MXD6”) or by copolymerization of adipic acid, isophthalic acid and hexamethylenediamine (hereinafter referred to as “nylon 66/6I copolymer”), and which polyamide is reinforced by glass fiber.
As other methods for improving the appearance of the molded articles, for example, JP-A-56-30460, and JP-A-63-156856 (The term “JP-A” as used herein means an “unexamined published Japanese patent application.) disclose resin compositions composed of a polyester resin or a nylon 46 resin and glass fiber incorporated therein, in which the glass fiber length is regulated for improving the balance between external appearance and mechanical properties. The aforementioned fiber-reinforced resin compositions produce molded articles having good appearance by preventing emergence of glass fiber out of the article surface to a certain extent. However, such compositions are not yet satisfactory for uses requiring more excellent appearance such as surface smoothness free from periodic roughness of about 1 to 5 mm period generated on a molded article surface (hereinafter referred to as “waviness”), and do not give sufficient mechanical properties of the resulting molded articles. In particular, nylon 46 has a crystallization temperature as high as 250° C. and does not produce a molded article having satisfactory appearance. Moreover, nylon 46 cannot be readily molded owing to the narrow range of the applicable molding conditions.
To solve the above problems, the inventors of the present invention paid attention to the glass fiber in the glass fiber-reinforced polyamide resin. They found that the polyamide resin composition is improved in the surface smoothness and the balance of mechanical properties by regulating the average aspect ratio of the glass fiber and the content of a fraction having a high aspect ratio in the glass fiber. Thus, an application has been filed for the invention as disclosed in JP-A-10-120900.
The aforementioned polyamide composition, however, is not satisfactory yet for use in application fields which require higher mechanical strength, especially higher level of impact strength, more excellent appearance (gloss and surface smoothness), and higher weatherability (especially, resistance to phenomena that articles under conditions where they are used are deteriorated by exposure to ultraviolet light and rain (water) to cause emergence of the glass fiber on the article surface, thereby whitening the article with loss of gloss).
SUMMARY OF THE INVENTION
The present invention is to solve the above described problems of the conventional polyamide composition.
Accordingly, an object of the present invention is to provide a polyamide resin composition which is capable of providing a molded article excellent in mechanical properties (especially, impact resistance), weatherability, surface gloss and surface smoothness.
Another object of the present invention is to provide a molded article produced from the polyamide resin composition.
Other objects and effects of the present invention will become apparent from the following description.
To solve the above problems, the inventors of the present invention further studied comprehensively polyamide resin compositions and constituting components thereof. As the results, the inventors found a polyamide resin molded article having more excellent appearance and being superior in impact strength and weatherability.
In particular, the inventors of the present invention found surprisingly that the impact resistance (notched Izod characteristics) and weatherability are remarkably improved by use of glass fiber having a larger diameter than conventional ones. Consequently, the inventors have accomplished the present invention.
That is, the above described objects of the present invention have been achieved by providing the following polyamide resin compositions and polyamide resin molded articles.
1) A polyamide resin composition comprising:
from 30 to 70% by weight of a polyamide resin having a crystallization temperature not higher than 210° C.; and
from 70 to 30% by weight of glass fiber having an average aspect ratio of from 10 to 20, and an average fiber diameter of from 15 to 30 &mgr;m.
2) The polyamide resin composition according to the above 1, wherein the content of a fraction having an aspect ratio of not more than 5 in said glass fiber is not more than 15% by weight based on the weight of said glass fiber.
3) The polyamide resin composition according to the above 1), wherein said polyamide resin is a copolymer comprising:
(a) from 70 to 95% by weight of a hexamethylene adipamide component obtained from adipic acid and hexamethylenediamine; and
(b) from 30 to 5% by weight of a hexamethylene isophthalamide component obtained from isophthalic acid and hexamethylenediamine.
4) The polyamide resin composition according to the above 2), wherein said polyamide resin is a copolymer comprising:
(a) from 70 to 95% by weight of a hexamethylene adipamide component obtained from adipic acid and hexamethylenediamine; and
(b) from 30 to 5% by weight of a hexamethylene isophthalamide component obtained from isophthalic acid and hexamethylenediamine.
5) A polyamide resin molded article comprising:
from 30 to 70% by weight of a polyamide resin having a crystallization temperature not higher than 210° C.; and
from 70 to 30% by weight of glass fiber having an average aspect ratio of from 9 to 18, and an average fiber diameter of from 15 to 30 &mgr;m.
6) The polyamide resin molded article according to the above 5), wherein the content of a fraction having an aspect ratio of not more than 5 in said glass fiber is not more than 15% by weight based on the weight of said glass fiber.
7) The polyamide resin molded article according to the above 5), wherein said polyamide resin is a copolymer comprising:
(a) from 70 to 95% by weight of a hexamethylene adipamide component obtained from adipic acid and hexamethylenediamine; and
(b) from 30 to 5% by weight of a hexamethylene isophthalamide component obtained from isophthalic acid and hexamethylenediamine.
8) The polyamide resin molded article according to the above 6), wherein said polyamide resin is a copolymer comprising:
(a) from 70 to 95% by weight of a hexamethylene adipamide component obtained from adipic acid and hexamethylenediamine; and
(b) from 30 to 5% by weight of a hexamethylene isophthalamide component obtained from isophthalic acid and hexamethylenediamine.
9) The polyamide resin molded article according to the above 5), wherein said molded article is an injection-molded article.
10) The polyamide resin molded article according to the above 6), wherein said molded article is an injection-molded article.
11) The polyamide resin molded article according to the above 7), wherein said molded article is an injection-molded article.
12) The polyamide resin molded article according to the above 8), wherein said molded article is an injection-molded article.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described below in detail.
The polyamide resin composition of the present invention comprises a polyami
Fujii Osamu
Watanabe Harumi
Asahi Kasei Kogyo Kabushiki Kaisha
Birch Stewart Kolach & Birch LLP
Yoon Tae
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