Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-19
2002-06-04
Woodward, Ana (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S136000, C524S139000, C524S414000
Reexamination Certificate
active
06399684
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates polymer/polyamide blend systems also having a morphology controlling reagent selected from a class of phosphorous containing compounds.
2. Description of Related Art
The inventor has previously found that certain blends of polyamides and neutralized ethylene acid copolymers provide compositions that are particularly useful in applications such as molded parts where a combination of toughness, high gloss, abrasion/scratch resistance, UV resistance, high temperature properties and stiffness are needed. These blends previously discovered specifically relate to compositions having 40 to 60 weight percent polyamide and 60 to 40 relative weight percent neutralized ethylene acid copolymer. The polyamide in these blends forms a continuous or co-continuous phase and the neutralized ethylene acid copolymer is dispersed there between in particle form. A multitude of other excipients, including thermal stabilizers such as organophosphorous compounds, were utilized in these compositions.
While these blends at the stated percentages achieve a balance of physical properties that are useful in molded parts applications, blends having less than 40 wt. % polyamide heretofore did not have an adequate balance of physical properties to provide useful compositions. This inventor has now found that the addition of phosphorous containing salts such as sodium hypophosphite (NaH2PO2) to a blend having less than 40 wt. % polyamide relative to a remaining portion of neutralized ethylene acid copolymer provides a composition with significantly enhanced morphological and mechanical properties. This discovery permits a broad spectrum of utility in molded part applications for polyamide
eutralized ethylene copolymer blends. In addition, the inventor has discovered that addition of the hypophosphite excipient to the blend also provides unexpected advantages to blends having 40% or greater polyamide relative to the neutralized alpha-olefin/alpha, beta-unsaturated carboxylic acid copolymer or terpolymer.
Heretofore, several prior art references have disclosed compositions or blends having both ethylene copolymers containing an unsaturated monocarboxylic acid and polyamides that are useful in a range of molding, coating or adhesive applications. For example, U.S. Pat. No. 5,091,478 teaches blends of thermoplastic resins including polyamides with ethylene copolymers including ethylene acid copolymers which may be neutralized with a metal ion along with a polymeric grafting agent selected from epoxides, isocyanates, aziridine, silanes, alkylating agents. These grafting reagents react with the acid-containing moieties of the ethylene acid copolymer and additionally react with a reactive graft site on the thermoplastic resin to form partially grafted flexible thermoplastic compositions having a specific quantity of reactive groups. There is no description in this disclosure of the use of a hypophosphite salt or phosphorous containing salt in the composition.
Similarly, EPO 574 532 B1 and the art cited therein discloses polyamide/ethylene copolymer blends. In particular, this reference discloses thermoplastic molding compositions having above zero to 50 wt. % of a polyamide; between 1 and 49 wt. % of at least one modified ethylene/propylene copolymer and between 1 and 49 wt. % of an ionomer of at least one olefinic acid copolymer having units derived from an alpha-olefin and an alpha, beta ethylenically unsaturated carboxlyic acid which is 10-100% neutralized. Again, as the in prior teaching, there is no disclosure or suggestion of the use of an inorganic phosphorous containing compound in the composition(s).
BRIEF SUMMARY OF THE INVENTION
The present invention broadly relates to a composition comprising or consisting essentially of a polyamide, a neutralized or partially neutralized alpha-olefin/alpha, beta unsaturated carboxylic acid copolymer or terpolymer or other neutralized acid-containing polymer or other polyamide polymer and an organic or inorganic phosphorous containing salt such as sodium, lithium or potassium hypophosphite (MH2PO2).
Additional polymeric or non-polymeric components may also be added to this composition. For example, the additional polymeric components may be selected from modified elastomeric copolymers such as those described in U.S. Pat. No. 5,420,206, hereby incorporated by reference. Suitable non-polymeric components include UV stabilizers, antioxidants, thermal stabilizers, processing aids, pigments and the like.
The present invention preferably comprises blends as described above having less than 40 wt. % polyamide relative to the neutralized ethylene copolymer. These blends, with the hypophosphite additive, provide significant enhancement to high temperature tensile strength and to Vicat softening points while retaining the properties associated with continuous or co-continuous polyamide domains with particles of neutralized ethylene copolymers dispersed there between.
DETAILED DESCRIPTION
As summarized above, the present invention relates to polyamide/ethylene copolymer blends having an additional morphological enhancing excipient. This morphology enhancing reagent permits blends having less than 40 wt. % polyamide relative to a neutralized alpha-olefin/alpha-beta-unsaturated carboxylic acid to retain the requisite physical and mechanical properties necessary for certain molded and fabricated parts. In addition, the morphology enhancing reagent enhances the physical properties of polyamide/alpha-olefin copolymer blends having 40 wt. % or greater polyamide.
The polyamide in the blends may be selected from semi-crystalline polyamides or blends of semi-crystalline polyamides and amorphous polyamides. The alpha-olefin based copolymer in the blends may be selected from copolymers having a carboxylic acid or derivative or precursor thereof as either part of the copolymer chain (e.g. in or within the backbone) or grafted onto the polymer or copolymer chain (e.g. grafted onto the backbone) or blends thereof. For example, an alpha-olefin such as ethylene can be copolymerized with an alpha, beta-unsaturated carboxylic acid such as acrylic acid or methacrylic acid and “neutralized”, which in the present invention can mean either partial or complete neutralization of the acid moiety to form a metal salt of the acid-containing polymer, alternately referred to herein as a neutralized acid copolymer, a neutralized ethylene acid copolymer, a neutralized alpha-olefin based polymer, a neutralized acid-containing polymer, or more simply as a neutralized copolymer. This neutralized copolymer, having varying percentages of ethylene and the acid moiety or neutralized versions thereof, is then combined with the polyamide and the hypophosphite salt to form compositions of the invention.
Additionally, the alpha-olefin based polymer may be selected from, for example, EPDM that is grafted with a carboxyl containing molecule such as maleic anhydride or, for example, a non-metallocene or metallocene produced polymer or copolymer that is grafted with a polar carboxylic acid containing moiety. This grafted polymer is then blended with a polyamide and the hypophosphite salt to form a composition of the invention. Blends of grafted copolymers and copolymers having a carboxylic acid moiety in the polymer backbone chain may also be combined with a polyamide and a hypophosphite salt to form a composition of the invention. In all cases, the compositions are suitable for processing into fabricated parts such as molded automobile bumpers or the like. The preferred composition is selected from a blend of a semi-crystalline polyamide such as nylon-6, a neutralized ethylene acid copolymer and sodium hypophosphite.
The present invention particularly relates to compositions comprising blends of:
(a) 40 to 75 wt. % neutralized alpha-olefin based polymer and
(b) 60 to 25 wt. % polyamide based upon the combined weight of (a) plus (b) and
(c) a hypophosphite salt.
The preferred composition has less than 3 wt. % of component (c) based upon the c
Dobson Kevin S.
E. I. du Pont de Nemours & Company
Woodward Ana
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