Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-03-18
2001-01-30
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S09200D
Reexamination Certificate
active
06180716
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of enhancing the surface appearance of articles made from an impact modified composition of a compatibilized polyphenylene ether-polyamide resin blend.
The invention also relates to the compositions and articles formed out of the compositions made by the method of the invention.
2. Brief Description of the Related Art
Poly(phenylene ether) resins (referred to hereafter as “PPE”) are commercially attractive materials because of their unique combination of physical, chemical, and electrical properties. Furthermore, the combination of these resins with polyamide resins into compatibilized blends results in additional overall properties such as chemical resistance, high strength, and high flow. Examples of such compatibilized blends can be found in U.S. Pat. Nos. 4,315,086 (Ueno, et al); 4,659,760 (van der Meer); and 4,732,938 (Grant, et al). The properties of these blends can be further enhanced by the addition of various additives such as impact modifiers, flame retardants, light stabilizers, processing stabilizers, heat stabilizers, antioxidants and fillers.
The physical properties of PPE/ polyamide blends make them attractive for a variety of end-use articles in the automotive market, especially for various exterior components. Many of these components are subjected to a variety of abuses such as impacts and as such require outstanding impact resistance and ductility. Moreover, many of these same articles are preferentially produced using conversion techniques involving extrusion of sheet and forming of the sheet into articles. With today's high gloss paint systems highlighting surface imperfections and consumer emphasis on quality and cost, body panels and moldings need to have extremely good surface appearance at the least possible cost. Articles made from conventional PPE/polyamide blends have inadequate surface appearance and require secondary sanding and/or special paints to achieve the desired surface appearance. These additional steps add cost to the article and reduce the overall benefits associated with PPE/polyamide blends for these applications.
It is therefore apparent that a need continues to exist for methods to improve the surface appearance of articles formed from sheet made from PPE/ polyamide compositions such that the need for sanding and/or special paints is reduced.
SUMMARY OF THE INVENTION
The needs discussed above have been generally satisfied by the discovery of an improved method for enhancing the surface appearance characteristics of articles formed from sheet made from a PPE/ polyamide composition, wherein the method comprises:
(a) melt-mixing in a first step, from about 5% to less than 50% by weight polyphenylene ether resin with from about 0.7% to about 1.1% by weight of citric acid or a hydrate of citric acid and from about 5% to about 15% by weight of an elastomeric block copolymer, wherein the elastomeric block copolymer is a di-block copolymer, tri-block copolymer, or a mixture of a di-block copolymer and tri-block copolymer, wherein the copolymer comprises a polyarylene block and a saturated or unsaturated rubber block, with from about 5% to about 93% by weight of a polyamide resin, and
(b) further melt mixing in a second step, from 0% to about 90% of a polyamide resin;
wherein the total weight of the polyamide resin is from about 45% to about 90% by weight based on the total weight of the composition; and wherein the amine endgroup to acid endgroup ratio (i.e., —NH
2
/—CO
2
H) is at least about 1.0 or greater.
In a preferred embodiment of the present invention, the PPE level is between about 35% and about 49% by weight, the citric acid level is between about 0.8% and about 1.0% by weight, the elastomeric block copolymer is present from about 8% to about 12% by weight, wherein elastomeric block copolymer contains a polystyrene-polybutadiene-polystyrene block copolymer, the polyamide is a nylon 6 resin present at a level between about 45% and about 55% by weight, wherein between about 10% and 15% of the nylon 6 is added with the PPE, the citric acid, and the elastomeric block copolymer with the remainder of the nylon 6 added in a second step; wherein all weight percentages are based on the total weight of the composition.
The description which follows provides further details regarding this invention.
DETAILED DESCRIPTION OF THE INVENTION
PPE, per se, are known polymers comprising a plurality of structural units of the formula (I):
wherein for each structural unit, each Q
1
is independently halogen, primary or secondary lower alkyl (e.g., alkyl containing up to 7 carbon atoms), phenyl, haloalkyl, aminoalkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at least two carbon atoms separate the halogen and oxygen atoms; and each Q
2
is independently hydrogen, halogen, primary or secondary lower alkyl, phenyl, haloalkyl, hydrocarbonoxy or halohydrocarbonoxy as defined for Q
1
. Preferably, each Q
1
is alkyl or phenyl, especially C
1-4
alkyl, and each Q
2
is hydrogen.
Both homopolymer and copolymer PPE are included. The is preferred homopolymers are those containing 2,6-dimethyl-1,4-phenylene ether units. Suitable copolymers include random copolymers containing, for example, such units in combination with 2,3,6-trimethyl-1,4-phenylene ether units. Also included are PPE containing moieties prepared by grafting vinyl monomers or polymers such as polystyrenes, as well as coupled PPE in which coupling agents such as low molecular weight polycarbonates, quinones, heterocycles and formals undergo reaction in known manner with the hydroxy groups of two PPE chains to produce a higher molecular weight polymer, provided a substantial proportion of free OH groups remains.
The PPE generally has a number average molecular weight within the range of about 3,000-40,000 and a weight average molecular weight within the range of about 20,000-80,000, as determined by gel permeation chromatography. Its intrinsic viscosity is most often in the range of about 0.15-0.6 dl./g., as measured in chloroform at 25° C.
The PPE are typically prepared by the oxidative coupling of at least one monohydroxyaromatic compound such as 2,6-xylenol or 2,3,6-trimethylphenol. Catalyst systems are generally employed for such coupling; they typically contain at least one heavy metal compound such as a copper, manganese or cobalt compound, usually in combination with various other materials.
Particularly useful PPE for many purposes are those which comprise molecules having at least one aminoalkyl-containing end group. The aminoalkyl radical is typically located in an ortho position to the hydroxy group. Products containing such end groups may be obtained by incorporating an appropriate primary or secondary monoamine such as di-n-butylamine or dimethylamine as one of the constituents of the oxidative coupling reaction mixture. Also frequently present are 4-hydroxybiphenyl end groups, typically obtained from reaction mixtures in which a by-product diphenoquinone is present, especially in a copper-halide-secondary or tertiary amine system. A substantial proportion of the polymer molecules, typically constituting as much as about 90% by weight of the polymer, may contain at least one of said aminoalkyl-containing and 4-hydroxybiphenyl end groups.
It will be apparent to those skilled in the art from the foregoing that the PPE contemplated for use in the present invention include all those presently known, irrespective of variations in structural units or ancillary chemical features.
The polyamide resins useful in the practice of the present invention are a generic family of resins known as nylons, characterized by the presence of an amide group (—C(O)NH—). Nylon-6 and nylon-6,6 are the generally preferred polyamides and are available from a variety of commercial sources. Other polyamides, however, such as nylon-4,6, nylon-12, nylon-6,10, nylon 6,9, nylon 6/6T and nylon 6,6/6T with triamine contents below about 0.5 weight percent as well as others, such as the amorphous nylons may be useful for parti
General Electric Company
Short Patricia A.
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