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
2000-04-12
2001-11-13
Woodward, Ana (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C252S500000, C524S514000, C524S538000, C525S066000, C525S09200D, C525S133000
Reexamination Certificate
active
06316551
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to polyphenylene ether-polyamide blends, and more particularly to the preparation of such blends without the use of compatibilizing compounds.
Blends of polyphenylene ethers and polyamides, in which the polyamide is generally the continuous phase, are in wide commercial use in applications requiring a combination of such properties as temperature stability, impact resistance and solvent resistance, as illustrated by the fabrication of such articles as exterior body parts for automobiles. It has long been known, however, that such blends are difficult to prepare because of the incompatibility of polyphenylene ethers with polyamides. As a result of this incompatibility, such blends typically undergo phase separation and delamination and contain large, incompletely dispersed polyphenylene ether particles and no phase interaction between the two resin phases. Molded parts made from such blends are, as a result, usually characterized by extremely low impact strength, brittleness, delamination and the like.
One strategy which has been employed to improve the properties of polyphenylene ether-polyamide blends is to introduce compatibilizing compounds which facilitate copolymer formation between the two resins. Typical compatibilizing compounds contain such functional groups as olefinic, carboxylic acid, ortho ester, epoxide and chlorotriazine groups; illustrative compounds of this type are maleic anhydride, fumaric acid, trimellitic anhydride acid chloride and 2-chloro-4-(2,4,6-trimethylphenoxy)-6-glycidoxy-1,3,5-triazine. The use of such compounds is disclosed in many U.S. patents, including U.S. Pat. Nos. 4,315,086, 4,600,741, 4,732,937, 4,873,286, 5,100,961, 5,089,567 and 5,115,042.
In a typical blending method which includes the use of compatibilizing compounds, a twin screw extruder configured to provide severe mixing intensity is employed. The feed throat of the extruder is charged with polyphenylene ether, compatibilizing compound, a suitable impact modifier as detailed hereinafter, any required stabilizers and a portion of the polyamide. The polyamide is present to protect the impact modifier, often an unsaturated rubbery polymer, from degradation caused by friction-generated heat in the upstream portion of the extruder.
Extrusion in the upstream region is at a temperature high enough to cause reaction of the compatibilizing compound with the polyphenylene ether, said temperature typically being up to about 290° C. Atmospheric venting of the extruder is employed upstream. The remainder of the polyamide is introduced downstream with vacuum venting, at a temperature typically in the range of about 290-300° C.
The use of such compatibilizing compounds and conditions is, however, often accompanied by disadvantages. For example, the compatibilizing compound can also react to link polyamide molecules, causing chain lengthening or crosslinking which may impair the flow properties of the blend. Depending on their chemical nature, they can further cause corrosion of blending equipment such as extruder screws and shafts and present environmental hazards. It goes without saying that they also add to the material costs of the blending process.
The preparation of uncompatibilized polyphenylene ether-polyamide blends is disclosed in U.S. Pat. No. 3,379,792. Because of the incompatibility of the resin phases, however, such blends are disclosed as having inferior physical properties if the polyamide is present in greater amount than 20% by weight. In such blends, the polyamide serves only as a flow modifier for the polyphenylene ether. Clearly, there is no opportunity for the polyamide to constitute the continuous phase or to contribute significantly to the properties of the composition.
It is desirable, therefore, to develop new methods for compatibilization of polyphenylene ether-polyamide blends which do not require the use of compatibilizing compounds which degrade blend properties. It is especially desirable to prepare compatible blends in which the polyamide is the continuous phase.
SUMMARY OF THE INVENTION
The present invention provides compatible polyphenylene ether-polyamide blends without the use of extraneous compatibilizing compounds. That is what the word “uncompatibilized” means in the title; said blends are compatible though no compatibilizing compounds are employed in their preparation.
Said blends can contain polyamide as the external phase and have excellent physical properties, generally at least equivalent to those of known blends made with the use of such compounds. In addition, they unexpectedly demonstrate good properties regardless of whether they are subjected to short or long molding cycles.
The invention includes polyphenylene ether-polyamide compositions and a method for their preparation. Said method comprises intimately melt blending, at an apparatus temperature maintained no lower than about 295° C. and a pressure maintained below about 200 torr, a mixture comprising (A) at least one polymer having an amine end group concentration of at least about 35 microequivalents per gram and (B) at least one polyphenylene ether, said mixture being free from compatibilizing compounds reactive with both of components A and B and having a weight ratio of component A to component B greater than 1:1; at least about 15% by weight of component A being present at the initiation of the blending operation and any remainder of said component A being subsequently added during said blending operation.
The compositions of the invention ordinarily comprise copolymers of components A and B and are characterized by a weight ratio of component A to component B greater than 1:1 and the absence of any compatibilizing compounds as described above.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
For the sake of brevity, each constituent of the compositions of this invention is designated “component” irrespective of whether it undergoes reaction with another constituent. Thus, the compositions of the invention may comprise the named components and any reaction products thereof.
Any polymer (other than a polyphenylene ether) containing amine end groups may be employed as component A in the present invention. Polyamides are particularly preferred, and will be referred to hereinafter for convenience; it should be understood, however, that other amine-terminated polymers may be employed when appropriate.
Included are polyamides prepared by the polymerization of a monoamino-monocarboxylic acid or a lactam thereof having at least 2 carbon atoms between the amino and carboxylic acid group, of substantially equimolar proportions of a diamine which contains at least 2 carbon atoms between the amino groups and a dicarboxylic acid, and of a monoaminocarboxylic acid or a lactam thereof as defined above together with substantially equimolar proportions of a diamine and a dicarboxylic acid. (The term “substantially equimolar” proportions includes both strictly equimolar proportions and slight departures therefrom which are involved in conventional techniques for stabilizing the viscosity of the resultant polyamides.) The dicarboxylic acid may be used in the form of a functional derivative thereof, for example, an ester or acid chloride.
Examples of the aforementioned monoamino-monocarboxylic acids or lactams thereof which are useful in preparing the polyamides include those compounds containing 2-16 carbon atoms between the amino and carboxylic acid groups, said carbon atoms forming a ring containing the —CO—NH— group in the case of a lactam. As particular examples of aminocarboxylic acids and lactams there may be mentioned &egr;-aminocaproic acid, butyrolactam, pivalolactam, &egr;-caprolactam, capryllactam, enantholactam, undecanolactam, dodecanolactam and 3- and 4-aminobenzoic acids.
Diamines suitable for use in the preparation of the polyamides include the straight chain and branched chain alkyl, aryl and alkaryl diamines. Illustrative diamines are trimethylenediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, hexamethylenediamine (
Giammattei Mark Howard
Silvi Norberto
Bennett Bernadette M.
General Electric Company
Johnson Noreen C.
Woodward Ana
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