Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
1998-09-28
2002-08-13
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S422000, C428S515000, C428S518000, C428S520000
Reexamination Certificate
active
06432542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to multicomponent structures; and more particularly to multicomponent structures having improved adhesion.
2. Description of the Prior Art
It is known in the art to produce multicomponent structures to take advantage of different properties exhibited by the various components in the structure. Typical of multicomponent structures are multilayer films in which different layers have specific characteristics.
For example, in packaging applications, it is desirable to use fluoropolymers which are known for their inertness to most chemicals and resistance to high temperatures as well as low coefficients of friction. Polychlorotrifluoroethylene (“PCTFE”) homopolymers and copolymers, and ethylene-chlorotrifluoroethylene (“ECTFE”) alternating copolymers, are particularly advantageous due to their excellent barrier properties. However, use of such fluoropolymers is restricted to specialty packaging applications due to their relatively high cost.
A suitable means of reducing the cost of a packaging material fabricated from a costly polymer is to form multilayer structures in which the polymer layer is either coextruded or laminated with other, less costly, polymer layers. This approach is particularly desirable for fluoropolymer packaging applications since a thin layer of the fluoropolymer is often all that is needed to take advantage of the desirable properties of the fluoropolymers while minimizing the cost. However, fluoropolymers do not adhere strongly to most other polymers; in fact, most fluoropolymers are known for their non-stick characteristics.
Use of functionalized polyolefins as the adhesive layer in multicomponent structures has been described; see for example U.S. Pat. Nos. 4,677,017 and 5,139,878, the disclosure of which is expressly incorporated herein by reference. While these multilayer structures exhibit excellent moisture and barrier properties, in many instances, they lack sufficient adhesive strength to have any significant use. As a result, there are not yet any commercially available coextruded halopolymer films. It would therefore be desirable to provide an improved adhesive resin in order to provide superior multicomponent structures suitable for a wide variety of applications.
SUMMARY OF THE INVENTION
In accordance with this invention, there is provided a multicomponent structure comprising at least one halopolymer layer and at least one adhesive layer wherein the adhesive layer is a soft, modified polymer comprising a base polymer having at least one functional moiety selected from the group consisting of unsaturated acids and anhydrides thereof, amines and epoxy compounds, wherein said adhesive layer has an ASTM D-2240 shore hardness number of less than about 25 in the D scale and less than about 75 in the A scale. Preferably, the shore hardness number is less than about 20 in the D scale and less than about 72 in the A scale. It is also preferable that the adhesive be highly modified with the functional moiety. Adhesives which are modified with maleic anhydride are particularly advantageous in the practice of this invention. In a preferred embodiment, the multilayer structure is a three layer structure which, most preferably, is a three layer film.
It has unexpectedly been found that when soft polymers with a high degree of modification are used as the adhesive layer in halopolymer-containing multicomponent structures, a high degree of adhesion between the halopolymer and the soft, modified polymer exists.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The adhesive layer of the present invention is formed from a base polymer having a functional moiety, and has an ASTM D-2240 shore hardness number of less than about 25 in the D scale and less than about 75 in the A scale, which polymer has been modified with an unsaturated acid, anhydride, amine or epoxy moiety in an amount of from about 0.1% to about 20% by weight based on the total weight of the polymer. In a preferred embodiment, the shore hardness number is less than about 20 in the D scale and less than about 72 in the A scale. Shore hardness number is measured by the American Standard Test Method (ASTM) D-2240 which is well known to those skilled in the art. As used herein, shore hardness number is determined by the shore hardness test and is based on the penetration of a specific type of indentor when forced into specific materials under specific conditions. Shore hardness number is an inverse function of indentor extension which is dependent on the elastic modulus and viscoelastic behavior of the material. Thus, the softer a material, the lower shore hardness number. There are different types of durometers used in shore hardness tests, among which Type A and Type D are commonly reported. The difference of these two types are based on the shape of the indentor and the applied force. For example, an indentor of a Type D Durometer has a sharper point (i.e., 0.100±0.012 mm R) than a Type A Durometer (i.e., 0.79±0.03 mm R).
The functional moiety of the adhesive layer comprises from about 0.2% to about 15%, preferably from about 0.5% to about 10%, and most preferably from about 1% to about 5% by weight based on the total weight of the polymer. Any unsaturated acid or anhydride may be used as the functional moiety in this invention. Suitable acids include unsaturated carboxylic acids such as maleic acid, fumaric acid, crotonic acid, citraconic acid and itaconic acid. Suitable anhydrides include anhydrides of any of the foregoing. Of these, the most preferred is maleic anhydride. Suitable amines include aliphatic or aromatic, primary, secondary and tertiary amines. Specific examples include: 2,4,6-tribromoaniline, methylamine, ethylamine, propylamine, dimethylamine-N-methylanaline, ethylmethylamine, 2-(N-methylamine)heptane, sec-butyldimethylamine, N-ethyl-N-methylaniline, trimethylamine, and N,N-dimethylanaline. Suitable epoxy compounds are those having from about 2 to about 20 carbon atoms. In a particularly preferred embodiment, the adhesive layer comprises about 1% to about 5% of maleic anhydride.
Base polymers which are useful in the preparation of the adhesive layer include, but are not limited to, poly(&agr;-olefin) homopolymers, copolymers, and mixtures thereof, and thermoplastic elastomers including styrenic block copolymers, olefinic elastomers, elastomeric alloys, thermoplastic polyurethanes, elastomeric polyesters and elastomeric polyamides.
Poly(&agr;-olefin) homopolymers can be prepared from &agr;-olefins having from about 2 to about 10 and preferably from about 2 to about 6 carbon atoms, and include polyethylene (including ultra low density, low density, linear low density, medium density, high and ultra high density), polypropylene, polybutylene, polybutene-1, polypentene-1, poly-3-methylbutane-1, poly-4-methylpentene-1, and polyhexene. Copolymers of two or more of the foregoing &agr;-olefins or &agr;-olefins and other monomers such as alkyl esters of &agr;,&bgr;-ethylenically unsaturated carboxylic acids are useful in the practice of this invention, see for example, U.S. Pat. No. 5,139,878, the disclosure of which is expressly incorporated herein by reference.
Styrene block copolymers may be linear or branched and include styrene and butadiene (SBS), styrene and isoprene, styrene and ethylene-butylene (SEBS), and styrene and ethylene-propylene.
Suitable olefinic thermoplastic elastomers include ethylene propylene diene (EPDM) and ethylene propylene rubber.
Suitable elastomeric alloys include melt processable rubbers, thermoplastic vulcanizates, such as ethylene propylene rubber or nitrile rubber and polyolefin in which vulcanized rubber is intimately dispersed in the polyolefin matrix, and ethylene interpolymers, such as polyethylene alloyed with polypropylene or polyethylene where the polyethylene is crosslinked.
Suitable elastomeric polyesters include copolymers of polyester and polyether. Suitable polyesters include poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT) and PET/PBT copol
Allied-Signal Inc.
Criss Roger H.
Jackson Monique R.
Thibodeau Paul
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