Antistatic molded article comprising a polyesteramide resin

Details Antistatic molded article comprising a polyesteramide resin Antistatic molded article comprising a polyesteramide resin

2003-06-11

2004-09-28

Hightower, P. Hampton (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From carboxylic acid or derivative thereof

C528S170000, C528S271000, C528S272000, C528S274000, C528S288000, C528S322000, C525S420000, C525S437000, C525S450000, C430S311000

Reexamination Certificate

active

06797804

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to an antistatic molded article comprising a polyesteramide resin, particularly a molded article comprising a resin prepared by copolymerizing a cyclic amide and a cyclic ester and/or a linear ester, and further a molded article comprising a polyesteramide resin prepared by reacting a chemical compound having at least two hydroxyl groups, together with the above monomers.
PRIOR ART
A molded resin article provided with an antistatic property is widely used in electric appliances and electronic instruments. Especially, this is used in various kinds of parts used in production lines of semiconductor-related products, such as carrier pallets, housings, bearings, guides, and rollers.
To provide an antistatic property to a polymer matrix, for example, thermoplastic resins, the following methods have been employed: to add an electrically conductive filler such as graphite, carbon black, carbon fibers, metal oxides, metal powder, and metal fibers; to add or apply an antistatic agent to the surface, such as a surface-active agent; or to add an electrically conductive polymer.
It is rather easy to decrease a surface conductivity by blending in an electrically conductive filler. However, the filler must be added usually in an amount of as much as about 20 wt % of the molded article, so that homogeneous dispersion is difficult. Further, there is a problem of high costs. When an electrically conductive carbon filler is used, a molded article gets black and therefore coloration is limited, and sometimes its application field may be limited because of contamination with carbon powder. Further, it is difficult to steadily attain a required resistivity range of an order of from 10
9
to 10
12
&OHgr;. If the resistivity is lower than this, in IC related parts, circuits in the IC may be damaged.
In the case where a surface-active agent is added to the polymerization system, the surface-active agent may inhibit the reaction or decompose at a high mold temperature; and even when the required resistivity is attained, the resistivity may change with time or a problem of ion extraction may arise, which problem is fatal in semiconductor production lines. In the case where a surface-active agent is applied on a surface of a molded article, there are problems that heat resistance is poor; the antistatic property degrades with time; and the surface-active agent adversely affects circuits in IC related parts.
The use of an electrically conductive polymer is better in that there is not the problem of ion extraction. However, the polymer is very expensive, and the molding temperature may be a limiting factor, like in the case of the use of a surface-active agent.
PROBLEM TO BE SOLVED BY THE INVENTION
The object of the present invention is to provide an antistatic molded article having a desired surface resistivity without using a substantive amount of an electrically conductive additive, which article can be obtained easily and economically.
MEANS TO SOLVE THE PROBLEM
To solve the above problems, the present inventor has had an idea of attaining using a substantive amount of an electrically conductive antistatic property only by molecular skeleton structure without using a substantive amount of an electrically conductive additive, and has completed the present invention.
Thus the present invention is an antistatic molded article comprising a polyesteramide resin, characterized in that said molded article is prepared by copolymerizing (a) a cyclic amide and at least one ester selected from the group consisting of (b
1
) a cyclic ester and (b
2
) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, said molded article having a surface resistivity of less than 10
13
&OHgr;.
Preferred embodiments of the above antistatic molded article comprising a polyesteramide resin are as follows:
the antistatic molded article comprising a polyesteramide resin, wherein the surface resistivity is in a range of from 10
9
to 10
12
&OHgr;;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by ring-opening copolymerizing the cyclic amide (a) and the cyclic ester (b
1
) in a weight ratio of (a) to (b
1
) of from 100:3 to 100:44;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the cyclic ester (b
1
) in a weight ratio of (a) to (b
1
) of from 100:3 to 100: less than 10, wherein an electrically conductive material is further provided;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by ring-opening copolymerizing the cyclic amide (a) and the cyclic ester (b
1
) in a weight ratio of (a) to (b
1
) of from 100:10 to 100:34;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b
2
), or a mixture of the linear ester (b
2
) and the cyclic ester (b
1
) in a weight ratio of (a) to (b
2
) or (a) to the mixture of (b
2
) and (b
1
) of from 100:2 to 100:50;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b
2
) or a mixture of the linear ester (b
2
) and the cyclic ester (b
1
), in a weight ratio of (a) to (b
2
) or (a) to the mixture of (b
2
) and (b
1
) of from 100:2 to 100: less than 5, wherein an electrically conductive material is further provided;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b
2
) or the mixture of the cyclic ester (b
1
) and the linear ester (b
2
), in a weight ratio of (a) to (b
2
) or (a) to the mixture of (b
2
) and (b
1
) of from 100:5 to 100:45;
the antistatic molded article comprising a polyesteramide resin, having a tensile strength, measured according to ASTM D-638, of at least 40 MPa;
the antistatic molded article comprising a polyesteramide resin, wherein the linear ester (b
2
) is polycaprolactonediol;
the antistatic molded article comprising a polyesteramide resin, wherein the cyclic ester (b
1
) is &egr;-caprolactone; and
the antistatic molded article comprising a polyesteramide resin, wherein the cyclic amide (a) is &egr;-caprolactam.
Further, the present invention relates to a polyesteramide resin prepared by reacting 100 parts by weight of (a) a cyclic amide, 5 to 50 parts by weight of (b
2
) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, or 5 to 50 parts by weight of a mixture of at least 5 parts by weight of the linear ester (b
2
) and (b
1
) a cyclic ester, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups, wherein said resin has a number average molecular weight, reduced from polystyrene, of from 4,000 to 100,000.
Preferred embodiments of the above polyesteramide resin are as follows:
the polyesteramide resin, wherein said polyesteramide resin has the surface resistivity of from 10
6
to 10
9
&OHgr;;
the polyesteramide resin, wherein said polyesteramide resin has a volume resistivity of from 10
4
to 10
7
&OHgr;.m.;
the polyesteramide resin, wherein the chemical compound (c) is used in such an amount that a molar ratio of the hydroxyl groups, defined by the following equation, is in a range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b
2
);
the polyesteramide resin, wherein the molar ratio of the hydroxyl groups is in the range of from 0.2 to 0.5;
the polyesteramide resin, wherein the chemical compound (c) has at least 3 hydroxyl groups;
the polyesteramide resin, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane or a m

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