Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2002-07-18
2004-05-04
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S213000, C428S215000, C428S216000, C428S336000, C428S430000, C428S446000, C428S458000, C428S480000, C428S483000, C428S910000, C525S437000, C525S444000, C264S288400, C264S290200, C264S173120, C264S173150, C106S015050, C106S018140, C106S018180, C106S018310
Reexamination Certificate
active
06730406
ABSTRACT:
The invention relates to a biaxially oriented polyester film with a base layer composed of at least 70% by weight of a thermoplastic polyester and comprising at least one UV stabilizer and one flame retardant, and with at least one matt outer layer which comprises a mixture or, respectively, a blend made from two components I and II. The invention further relates to the use of the film and to a process for its production.
Component I of the mixture or blend is a polyethylene terephthalate homopolymer or polyethylene terephthalate copolymer, or a mixture of polyethylene terephthalate homo- or copolymers.
Component II of the mixture or blend is a polyethylene terephthalate copolymer which is composed of the condensation product of the following monomers or, respectively, of their derivatives capable of forming polyesters: isophthalic acid, aliphatic dicarboxylic acid, sulfomonomer which contains a metal sulfonate group on the aromatic moiety of an aromatic dicarboxylic acid, and aliphatic or cycloaliphatic glycol.
The outer layer of the invention has a characteristic matt surface or appearance and is very suitable for use in constructing exhibition stands, in greenhouses, or for industrial applications, in particular where a requirement is UV resistance or impermeability to UV light and flame retardancy to DIN 4102 Part 2, construction materials class B2 and B1.
BACKGROUND OF THE INVENTION
There is high industrial demand for transparent, high-gloss plastic films, e.g. biaxially oriented propylene films or biaxially oriented polyester films. There is also an increasing demand for transparent films of this type which are flame retardant to DIN 4102 and which have at least one surface layer which is not high-gloss but has a characteristic matt appearance and therefore, for example, provides the application with an appearance which is particularly attractive and therefore effective for promotional purposes, and provides protection from UV radiation while also providing flame retardancy.
U.S. Pat. No. 4,399,179 describes a coextruded biaxially oriented polyester film which is composed of a transparent base layer and of at least one matt layer which essentially consists of a certain polyethylene terephthalate copolymer and also comprises inert particles with a diameter of from 0.3 to 20 &mgr;m at a concentration of from 3 to 40%. The specific copolymer is a processing aid which reduces the viscosity of the melt comprising the inert particles, thus permitting satisfactory extrusion of that layer. The mattness of the film is achieved by adding the inert particles to the appropriate layer.
EP 0 144 978 describes a self-supporting oriented film made from thermoplastic and, on at least one of its two surfaces, bearing a continuous polyester coating which is applied as aqueous dispersion to the film prior to the final stretching step. The polyester coating is composed of a condensation product of various monomers which are capable of forming polyesters, such as isophthalic acid, aliphatic dicarboxylic acid, sulfomonomers, and aliphatic or cycloaliphatic glycols.
EP-A-0 620 245 describes films with improved heat resistance. These films comprise antioxidants which are suitable for scavenging free radicals formed in the film and degrading any peroxide formed. However, that specification gives no proposal as to how the UV resistance of films of that type might be improved.
DE-A 2346 787 describes a flame-retardant, phospholane-modified polymer. Besides the polymer, the use of the polymer to give films and fibers is also claimed. When films were produced from this phospholane-modified polymer the following shortcomings were apparent:
The polymer is very susceptible to hydrolysis and has to be very effectively predried. When the polymer is dried with prior art dryers it cakes, and production of a film is therefore possible only under very difficult conditions.
The films produced, under extreme and uneconomic conditions, also embrittle at high temperatures. The associated decline in mechanical properties is so severe as to make the film unusable. This embrittlement occurs after as little as 48 hours of exposure to heat.
The instances described give no indication as to how at least one surface of the film can be provided with low gloss while retaining high film transparency, or how the film is to absorb UV light, or how the film is to be provided with high UV resistance and also flame retardancy.
It was therefore an object of the present invention to provide a coextruded biaxially oriented and transparent polyester film which has at least one matt outer layer and whose production is simple and cost-effective, and which has the good physical properties of known films, causes no disposal problems, and in particular absorbs UV light and has high UV resistance, and also is flame-retardant to DIN 4102, and does not embrittle on exposure to heat.
BRIEF DESCRIPTIONS OF THE INVENTION
This object is achieved by means of a coextruded and biaxially oriented polyester film of the generic type mentioned at the outset, the characterizing features of which are that the film comprises at least one UV stabilizer and at least one flame retardant, the flame retardant and, where appropriate, the UV stabilizer being fed by way of masterbatch technology, and has a matt outer layer which comprises a mixture or, respectively, a blend made from two components I and II.
DETAILED DESCRIPTION OF THE INVENTION
Component I of the mixture or blend is a polyethylene terephthalate homopolymer or polyethylene terephthalate copolymer, or a mixture made from polyethylene terephthalate homo- or copolymers.
Component II of the copolymer or of the mixture or blend is a polymer containing at least one sulfonate group, in particular a condensation product of the following monomers or of their derivatives capable of forming polyesters:
A) from 65 to 95 mol % of isophthalic acid;
B) from 0 to 30 mol % of at least one aliphatic dicarboxylic acid with the formula
HOOC(CH
2
)
n
COOH
where
n is from 1 to 11;
C) from 5 to 15 mol % of at least one sulfomonomer containing an alkali metal sulfonate group on the aromatic moiety of a dicarboxylic acid;
D) a copolymerizable aliphatic or cycloaliphatic glycol having from 2 to 11 carbon atoms, in the stoichiometric amount necessary to form 100 mol % of condensate;
where each of the percentages given is based on the total amount of the monomers forming component II.
High UV resistance means that sunlight or other UV radiation causes no, or only extremely little, damage to the films, and that the films are therefore suitable for outdoor applications and/or critical indoor applications. In particular, the films should not yellow after a number of years of outdoor use, nor display any embrittlement or cracking of the surface, nor should their mechanical properties deteriorate. High UV resistance therefore means that the film absorbs UV light and does not transmit light until the visible region has been reached.
The good mechanical properties include high modulus of elasticity (E
MD
>3200 N/mm
2
; E
TD
>3500 N/mm
2
) and also good values for tensile strength at break (in MD>100 N/mm
2
; in TD>130 N/mm
2
).
Good orientability includes the capability of the film to give excellent orientation both longitudinally and transversely during its production, without break-offs.
Cost-effective production includes the capability of the raw materials or raw material components needed for producing the flame-retardant film to be dried using conventional industrial dryers. It is important that the raw materials do not cake or undergo thermal degradation. These prior art industrial dryers include vacuum dryers, fluidized-bed dryers, and fixed-bed dryers (tower dryers). These dryers operate at temperatures from 100 to 170° C., at which polymers provided with flame retardancy by conventional methods cake and eventually have to be removed by force, making film production impossible. In the case of the vacuum dryer, which has the gentlest drying action, the raw material usually passes through a range of temperatur
Crass Guenther
Hilkert Gottfried
Kern Ulrich
Murschall Ursula
Chen Vivian
Mitsubishi Polyester Film GmbH
ProPat L.L.C.
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