Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-12-11
2003-09-09
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S480000, C428S332000, C428S336000, C428S337000, C428S343000, C428S3550RA, C427S299000, C427S385500, C264S290200
Reexamination Certificate
active
06617035
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a hot-sterilizable, biaxially oriented polyester film with at least a base layer B containing a minimum of 80% by weight of thermoplastic polyester and at least an adhesive layer containing a mixture of the two components I and II. The invention also relates to a process for the production and to the use of this film.
EP-A-0 144 978 describes a self-supporting, oriented film made from a thermoplastic synthetic material, where the film has a continuous polyester coating on at least one of its two surfaces, which is applied to the film in the form of an aqueous dispersion before the final orientation step is done. The polyester coating consists of a condensation product of various derivatives capable of forming polyesters, such as isophthalic acid, aliphatic dicarboxilic acid, sulfonomers and aliphatic or cycloaliphatic glycol. The film has good metal adhesion, it is, however, not sterilizable due to a lack of steam resistance.
EP-A-0 144 978 describes a self-supporting, oriented film made from a thermoplastic synthetic material, where the film has, on at least one of its two surfaces, a continuous, cross-linked, acrylate-containing coating, which may also be applied to the film in the form of an aqueous dispersion before the final orientation step is done. The acrylate-containing coating consists of copolymers with at least 50% by weight of acrylic and/or methacrylic monomers, 1 to 15% by weight of monomers containing a functional group capable of forming intermolecular cross-linkings, when in a copolymerised state and under the influence of elevated temperatures, and of up to 49% by weight of one or several mono ethylenically unsaturated monomer, free of halogene, wherein the percentages are based on the total weight of the copolymers forming the adhesive layer. The film has good sterilizing properties, but poor metal adhesion.
It was the object of the present invention to provide a hot-sterilizable, especially a steam-sterilizable, biaxially-oriented polyester film with an adhesive layer with good adhesion properties to metal. A special object of this invention was to set the metal adhesion of the film such that the metallized film can be simultaneously sterilized when treated with steam. Moreover, the film according to the invention shall be processable on high-speed processing machines. It was another object that during film production up to 60% by weight of the waste material resulting from the film production can be reused as regrind for extrusion, without negatively affecting the physical properties of the film so produced.
BRIEF SUMMARY OF THE INVENTION
This object has been achieved by providing a hot-sterilizable, biaxially oriented polyester film of the kind previously mentioned, wherein the adhesive layer contains a mixture, respectively a blend of the two components I and II, with component I being a copolyester and component II being an acrylically and/or methacrylically cross-linked copolymer, described below in more details.
Surprisingly, by using a mixture, respectively a blend of components I and II the desired combination of good metal adhesion and sterilizability could be achieved. The weight ratio of the used components to one another is I:II=5:95 to I:II=95:5, preferably I:II=10:90 to I:II=90:10 and especially preferred I:II=15:85 to I:II=85:15.
DETAILED DESCRIPTION OF THE INVENTION
Mixtures within the scope of the present invention are mechanical mixtures made from the individual components. In general the individual components are initially combined for this purpose in the form of pressed molded articles of small size, e.g. lenticular or spherical granulate, mechanically mixed thereafter using a suitable vibrating device and then dissolved in water. Another way of producing the mixture is to initially dissolve the granulated components I and II, each individually, to obtain an aqueous solution, and then mix the aqueous solutions before applying them to the film.
A blend in the sense of the present invention is an alloy-like combination of the individual components I and II which can no longer be decomposed into its original components. A blend has the same properties as a homogeneous material and can be characterised accordingly by suitable parameters.
According to the invention the film has at least a base layer B. A preferred embodiment of the invention has a three-layered structure and has in addition to base layer B the cover layers A and C. Moreover, additional intermediate layers can be present between base layer B and cover layers A and C.
Base layer B contains a minimum of 90% by weight of thermoplastic polyester. Suitable polyesters are made from ethylene glycol and terephthalic acid (=polyethylene terephthalate, PET), from ethylene glycol and naphthalene-2,6-dicarboxilic acid (=polyethylene-2,6-naphthalate, PEN), from 1,4-bis-hydroxymethyl-cyclohexane and terephthalicacid [=poly(1,4-cyclohexanedimethylene terephthalate), PCDT] as well as from ethylene glycol, naphthalene-2,6-dicarboxilic acid and biphenyl-4,4′-dicarboxilic acid (polyethylene-2,6-naphthalatebibenzoate, PENBB). Special preference is given to polyesters consisting of at least 90 mol %, preferably of at least 95 mol % of ethylene glycol and terephthalic acid units or of ethylene glycol and naphthalene-2,6-dicarboxilic acid units. The remaining monomer units may be selected from other aliphatic, cycloaliphatic or aromatic diols, respectively dicarboxilic acids, which may also be present in cover layer A (or cover layer C).
Other suitable aliphatic diols are, as an example, diethylene glycol, triethylene glycol, aliphatic glycols with the general formula HO—(CH
2
)
n
—OH, with n being an integer from 3 to 6 (propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol and hexane-1,6-diol) or branched aliphatic glycols with up to 6 carbon atoms. Among the group of cycloaliphatic diols, cyclohexanediols (especially cyclohexane-1,4-diol) are worth mentioning. Other suitable aromatic diols, for example, correspond to the formula HO—C
6
H
4
—X—C
6
H
4
—OH, where X represents —CH
2
—, —C(CH
3
)
2
—, —C(CF
3
)
2
—, —O—, —S— or —SO
2
—. Along with that, bisphenols of the formula HO—C
6
H
4
—C
6
H
4
—OH are well suited.
Other dicarboxilic acids are preferably benzene dicarboxilic acids, naphthalene dicarboxilic acids (for example naphthalene-1,4′- or 1,6-dicarboxilic acid), biphenyl-x,x′-dicarboxilic acids (especially biphenyl-4,4′-dicarboxilic acid), diphenylacetylene-x,x′-dicarboxilic acids (especially diphenylacetylene-4,4′-dicarboxilic acid) or stilbene-x,x′-dicarboxilic acids. Among the cycloaliphatic dicarboxilic acids, cyclohexanedicarboxilic acids (especially cyclohexane-1,4-dicarboxilic acid) are worth mentioning. Among the aliphatic dicarboxilic acids, the (C
3
-C
19
) alkane diacids are especially suitable, wherein the alkane portion can be linear or branched.
The polyesters can be produced, e.g., according to the ester interchange process. This is based on the use of dicarboxilic acid esters and diols, which are reacted with conventional ester interchange catalysts, such as zinc-, calcium-, lithium-, magnesium- and manganese salts. The intermediate products are then polycondensated in the presence of customary polycondensation catalysts, such as antimontrioxide or titanium salts. These may just as well be produced according to the ester interchange process in the presence of polycondensation catalysts, where dicarboxilic acids and diols directly react with each other.
For the intermediate layers and for cover layers A and C basically the same polymers can be used as for base layer B. At the same time cover layers A and C may also contain different materials, wherein the cover layers then preferably consist of polyesters, which in turn contain ethylene-2,6-naphthalate units and ethylene terephthalate units. Up to 30 mol % of the polymers may consist of additional comonomers. In a preferred embodiment of the invention the coat
Bartsch Stefan
Davis Richard Lee
Peiffer Herbert
Dawson Robert
Feely Michael J
Mitsubishi Polyester Film GmbH
ProPat L.L.C.
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