Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2001-11-28
2004-02-10
Mulcahy, Peter D. (Department: 1713)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C524S482000, C525S370000, C525S329700, C525S330200, C525S330300
Reexamination Certificate
active
06689483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for removing residual acids including acetic acid and acrylic or methacrylic acids from ethylene copolymers such as ethylene vinyl acetate or ethylene acrylic acid or ethylene methacrylic acid or ionomers thereof. The process is also directed to the removal of residual monomeric alkyl acrylates which may be present in the ethylene copolymers.
2. Description of Related Art
Residual acids or monomeric alkyl acrylates formed during the production process of ethylene copolymers have presented a continual technical problem, especially if the packaging material or wire and cable material or other fabricated material is utilized to package or contain acid or monomeric alkyl acrylate sensitive contents or material.
The use of a certain kind of zeolite to remove offensive odors or flavors is known. For example, WO 95/20624 published on Aug. 3, 1995 describes the use of an adsorption agent which is added to films made from ethylene/acid copolymers to absorb odors. The siliceous material described therein is selected from those molecular sieves having a framework of tetrahedral oxide units, in which at least 90% of the tetrahedral oxide units are SiO tetrahedral, have a pore diameter greater than 5.5 Angstroms (preferably at least 6.0 Angstroms) and have a sorption capacity for water of less than 10% by weight at 25° C. and 4.6 Torr (preferably less than 6% by weight). The preferred sieves are also described as having a framework SiO
2
/Al
2
O
3
molar ratio of greater than 35, more preferably 200-500. This invention is also described in U.S. application Ser. No. 08/676,237. These molecular sieves are known to be hydrophobic in that they sorb less than 10 wt. % water at 25° C. and 4.6 Torr pressure.
The present invention, on the other hand, is directed to the use of a completely different molecular sieve for a particular purpose-the scavenging or removal or unwanted acid from ethylene copolymeric material which is utilized to contain or package acid or monomeric acrylate sensitive material. The recited molecular sieves utilized in this invention are hydrophilic in nature (e.g., absorb greater than 10% water at 25° C. and 4.6 Torr pressure) and are thus different than that described and used in the above patent publication.
BRIEF SUMMARY OF THE INVENTION
The present invention broadly relates to a process for removing unwanted acid or monomeric acrylate from an ethylene/acid copolymer comprising,
i) preparing a thermoplastic composition comprising an ethylene/acid copolymer or ionomer thereof or an ethylene/acid/acrylate terpolymer or ionomer thereof or an ethylene/vinyl acetate copolymer wherein the composition contains residual acid, and
ii) adding to the composition an acid scavenging agent selected from a hydrophilic molecular sieve which comprises a sodium aluminosilicate containing less than 5 wt. % of magnesium oxide and having a silica/alumina ratio of less than 100 and having a nominal pore diameter of 8-10 Angstroms. The preferred ratio is less than 35 and most preferred ratio is less than 3.0.
The invention further relates to a process as described above wherein the molecular sieve preferentially absorbs acetic acid over water.
The present invention also relates to a method for packaging or containing an acid sensitive material comprising,
i) preparing a film or material comprising a thermoplastic composition comprising an ethylene/acid copolymer or ionomer thereof or an ethylene/acid/acrylate terpolymer or ionomer thereof or an ethylene/vinyl acetate copolymer and an acid scavenging agent selected from a hydrophilic molecular sieve which comprises a sodium aluminosilicate containing less than 5 wt. % of magnesium oxide and having a silica/alumina ratio of less than 100 (or less than 5 35 or less than 3.0) and having a nominal pore diameter of 8-10 Angstroms and
ii) packaging said film or material with the acid sensitive material. The material to be packaged, such as surgical sutures, can be packaged in such a way that the packaged material does not actually contact the packaging surface but, the packaged material may still be exposed to fumes of acid which would come from the packaging material if the zeolite was not present.
The present invention also relates to a thermoplastic composition comprising an ethylene/acid copolymer or ionomer thereof or an ethylene/acid/acrylate terpolymer or ionomer thereof or an ethylene/vinyl acetate copolymer and an acid scavenging agent selected from a hydrophilic molecular sieve which comprises a sodium aluminosilicate containing less than 5 wt. % of magnesium oxide and having a silica/alumina ratio of less than 100 (or less than 35 or less than 3.0) and having a nominal pore diameter of 8-10 Angstroms. The invention also relates to a peelable seal composition comprising (a) a zeolite concentrate which comprises an ethylene acid copolymer or ionomer thereof and a hydrophilic molecular sieve which comprises a sodium aluminosilicate containing less than 5 wt. % of magnesium oxide and having a silica/alumina ratio of less than 100 (or less than 35 or less than 3.0) and having a nominal pore diameter of 8-10 Angstroms and (b) a blend of (i) an ethylene acid copolymer or ionomer thereof and (ii) a polyolefin resin selected from a homopolymer or copolymer of polybutylene or blends of such polymers with polypropylene; or a homopolymer or copolymer of polypropylene and further to this peelable composition coated onto an aluminum surface or a primed aluminum surface wherein the primer is selected from a mixture of ethylene acid copolymer or ionomer thereof and the above zeolite. The invention further relates to a composition as recited above wherein the molecular sieve preferentially absorbs acetic acid over water upon exposure of said composition to an aqueous/acetic acid environment.
The present invention additionally relates to a multilayer packaging structure comprising,
(a) an innermost layer comprising a thermoplastic ethylene copolymeric composition comprising an ethylene copolymer and a zeolite selected from a molecular sieve which comprises a sodium aluminosilicate containing less than 5 wt. % of magnesium oxide and having a silica/alumina ratio of less than 100 (or less than 35 or less than 3.0) and having a nominal pore diameter of
8-10 Angstroms; and
(b) at least one additional polymeric, metallic or non-metallic layer. This additional polymeric layer may be selected from the same generic material as the inner layer (a) (e.g. both layers do not have to be but may be identical) or may be selected from a layer containing an ethylene copolymeric packaging material which is, for example, an ethylene/acid copolymer or ionomer containing film which does not have the molecular sieve contained therein or from a polyester or other common packaging material. Such materials are sold under the trade names NUCREL® (ethylene acid copolymer) or SURLYN® (ethylene acid ionomer). The metallic layer may be selected from a common packaging material such as aluminum. The multilayer structure can include additional layers as necessary to form the desired package provided that at least one of the layers is (a). The peelable seal composition described above can be extrusion coated onto a single layer or multilayer structure to form the multilayer structure containing said composition as a layer. The peelable seal composition can also be coextrusion coated onto an aluminum surface of a multilayer aluminum substrate wherein a tie layer having a tie composition is the coextrusion component and actually contacts the surface of the aluminum. The tie layer can comprise an ethylene acid copolymer/zeolite concentrate wherein the zeolite is type 13X.
DETAILED DESCRIPTION
As summarized above, the present invention relates to a thermoplastic ethylene copolymeric composition comprising an ethylene copolymer and a zeolite selected from a molecular sieve which comprises a sodium aluminosilicate containing less than 5 wt. % of magnesium oxide and having a silica/alumina ratio of
Corbin David Richard
Hoh George Lok Kwong
Oblath Deborah T.
Oblath Steven B.
Dobson Kevin S.
E. I. du Pont de Nemours and Company
Mulcahy Peter D.
Oblath Deborah T.
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