WO2001053083A1 - Transparent, biaxially oriented, uv-stabilized barrier film, production method and utilization thereof - Google Patents

Abstract

The invention concerns a transparent, biaxially oriented, UV-stabilized barrier film made of cristallizable thermoplastic material, whose thickness ranges from 10 to 500 mu m. The film contains at least one UV stabilizer as light protective agent and at least one barrier layer to reduce gas and aroma permeability. Said film is characterized by good stretchability and by very good optical and mechanical properties. The invention further relates to a method for the production of said film and to the utilization thereof.

Description

Transparent, biaxially oriented, UV-stabilized barrier film, process for its production and its use

The invention relates to a transparent, biaxially oriented, UV-stabilized barrier film made of a crystallizable thermoplastic, the thickness of which is in the range from 10 to 500 μm. The film contains at least one UV stabilizer as a light stabilizer, at least one barrier or barrier layer to reduce gas and aroma permeability and is characterized by good stretchability and very good optical and mechanical properties. The invention further relates to a method for producing this film and its use.

Transparent films made of crystallizable thermoplastics with a thickness between 10 and 500 μm are well known.

These films do not contain any UV stabilizers as light stabilizers, so that neither the films nor the articles made from them are suitable for outdoor use. In outdoor applications, these films show yellowing and deterioration of the mechanical properties after a short time due to photooxidative degradation by sunlight.

EP-A-0620245 describes films which are improved with regard to their thermal stability. These films contain antioxidants which are suitable for trapping radicals formed in the film and for degrading the peroxide formed. However, this document does not give any suggestion of how the UV stability of such films could be improved.

The object of the present invention was to provide a transparent film with a thickness in

To provide range from 10 to 500 microns, which in addition to good stretchability and good mechanical and optical properties, above all, high UV stability and a high and effective barrier effect against the passage of gas and aroma. The invention therefore relates to a transparent, biaxially oriented, UV-stabilized film with a thickness in the range from 10 to 500 μm, which contains a crystallizable thermoplastic as the main constituent and which is characterized in that it additionally comprises at least one UV- soluble in the thermoplastic. Contains absorber and is provided with at least one barrier or barrier layer against the passage of gases or aromas and that it is stretched in the longitudinal and transverse directions.

It was thus possible to provide a transparent film with a thickness of 10 to 500 μm which, in addition to good stretchability, good mechanical and optical properties, above all UV absorption and high UV stability, a high barrier or barrier effect against gases having.

A high UV stability means that the film is not or only slightly damaged by sunlight or other UV radiation, so that the film is suitable for outdoor applications and / or critical indoor applications. In particular, the film should not yellow when used outdoors for several years, should not show embrittlement or cracking of the surface, and should also not show any deterioration in the mechanical properties. High UV stability means that the film absorbs the UV light and only lets light pass through in the visible area. The film thus has a barrier against the short-wave, aggressive UV light in the wavelength range of <380 nm. This means that the film completely absorbs the aggressive short-wave radiation, which is responsible, for example, for fat oxidation in foods, in the wavelength range <380 nm.

Good optical properties include, for example, high light transmission (> 74%), high surface gloss (> 120), extremely low haze (<20%) and low yellowness index (YID <10). The good mechanical properties include a high modulus of elasticity (E _MD > 3200 N / mm ² ; E _TD > 3500 N / mm ² ) and good tensile strength values (in MD> 100 N / mm ² ; in TD> 130 N) / mm ² ).

A good barrier effect against the passage of gas and aroma means that the oxygen permeability is <15 cm ³ / (m ^{2 •} 24h - bar).

Good stretchability includes the fact that the film can be oriented excellently in both the longitudinal and transverse directions and without tears.

The film according to the invention contains a crystallizable thermoplastic as the main component. Suitable crystallizable or partially crystalline thermoplastics are, for example, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, with polyethylene terephthalate being preferred.

According to the invention, a crystallizable thermoplastic is understood to mean crystallizable homopolymers, crystallizable copolymers, crystallizable compounds (mixtures), crystallizable recyclate and other variations of crystallizable thermoplastics.

The film according to the invention is generally one layer, but it can also be multi-layer. It can also be coated with various copolyesters or adhesion promoters.

At least one surface side of the film according to the invention is coated with SiO _x , ethylene-vinyl alcohol copolymer, PVDC (polyvinylidene dichloride), EVOH (ethylene vinyl alcohol) or PVOH (polyvinyl alcohol). The thickness of this coating is generally in the range from 10 to 8000 nm, preferably from 30 to 4000 nm. A low oxygen permeability is achieved, for example, if the stoichiometric factor of SiO _x is x = 1.2 to 1.9. If x is greater than 2.0, the locking effect deteriorates.

The SiO _x coating can, for example, by electron beam evaporation or by conventional evaporation in a high vacuum, as in a conventional one

Metallization done.

In electron beam evaporation, silicon dioxide (Si0 ₂ ), which is in the form of granules or in pieces, is brought to red heat and evaporated by means of a guided electron beam, which happens in a very short time due to the high energy of the beams.

With conventional vapor deposition in a high vacuum, the Si0 _{2 is brought} to a high temperature in a melting tank. The temperature is around 1400 ° C. In both methods, the Si0 ₂ sublimes and condenses on the film surface - depending on the 0 ₂ content of the atmosphere - as SiO _x .

Evaporation of the thermoplastic surface with SiO _x results in a transparent layer with good adhesion to the polar polyester surface. In a preferred embodiment, the polyester surface may have been corona-treated prior to deposition.

It can be seen that the coating has already significantly reduced the oxygen permeability without the SiO _x layer being protected.

It also shows that the SiO _x layer in the composite, ie when it is covered by a second transparent film, has an oxygen permeability which is reduced again by a factor of 5 to 10. Portions of SiO _x , the film according to the invention can also be coated with ethylene-vinyl alcohol copolymer, PVDC, EVOH or PVOH.

The barrier layer serves as a gas, in particular oxygen, or aroma barrier and has an oxygen permeability of <15 cm ³ / (m ^{2 ■} 24h ^■ bar).

Since the barrier layer according to the embodiment of the invention just described is a layer of essentially silicon dioxide, the film according to the invention can be easily recycled. Silicon dioxide is often used as an antiblocking agent in the production of polyester films, which is why there is a single-raw material composite.

Light, especially the ultraviolet portion of solar radiation, i.e. the wavelength range from 280 to 400 nm generally initiates degradation processes in thermoplastics, as a result of which not only the visual appearance adversely changes as a result of color change or yellowing, but also the mechanical-physical properties are adversely affected.

The inhibition of these photooxidative degradation processes is of considerable technical and economic importance, since otherwise the application possibilities of numerous thermoplastics are drastically restricted.

Polyethylene terephthalates, for example, begin to absorb UV light below 360 nm, their absorption increases considerably below 320 nm and is very pronounced below 300 nm. The maximum absorption is between 280 and 300 nm.

In the presence of oxygen, mainly chain cleavages are observed, but no cross-links. Carbon monoxide, carbon dioxide and carboxylic acids are the amount of predominantly photooxidation products. In addition to the direct photoysis of the ester groups, oxidation reactions must also be considered, which also result in the formation of carbon dioxide via peroxide radicals.

The photooxidation of polyethylene terephthalates can also lead to hydroperoxides and their decomposition products and to associated chain cleavages via hydrogen elimination in the α-position of the ester groups (H. Day, D. M. Wiles: J. Appl. Polym. Sei 16, 1972, page 203).

UV stabilizers or UV absorbers as light stabilizers are chemical compounds that can intervene in the physical and chemical processes of light-induced degradation. Soot and other pigments can partially protect against light. However, these substances are unsuitable for transparent films because they lead to discoloration or color change. For transparent, matt films, only organic and organometallic compounds are suitable which give the thermoplastic to be stabilized no or only an extremely small color or color change, i.e. H. which are soluble in the thermoplastic.

UV stabilizers suitable as light stabilizers for the purposes of the present invention are UV stabilizers which absorb at least 70%, preferably 80%, particularly preferably 90%, of the UV light in the wavelength range from 180 nm to 380 nm, preferably 280 to 350 nm. These are particularly suitable if they are thermally stable in the temperature range from 260 to 300 ° C, ie they do not decompose and do not lead to outgassing. Suitable UV stabilizers as light stabilizers are, for example, 2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organic nickel compounds, salicylic acid esters, cinnamic acid ester derivatives, resorcinol monobenzoates, oxalic acid anilides, hydroxybenzoic acid esters, sterically hindered amines and triazines, the 2-hydroxybenzotriazoles being preferred. The film according to the invention contains at least one UV stabilizer as light stabilizer, the concentration of the UV stabilizer preferably in the range from 0.01% by weight to 5.0% by weight, in particular in the range from 0.1%. -% to 3 wt .-%, based on the weight of the layer of crystallizable thermoplastic. The UV stabilizer can expediently be metered in directly during film production using the so-called masterbatch technology.

It is completely surprising that the use of the above-mentioned UV stabilizers in films leads to the desired result. If an attempt is made to achieve a certain UV stability via an antioxidant, the film quickly turns yellow after weathering.

If commercially available UV stabilizers are used which absorb the UV light and thus generally offer protection, it is found that the UV stabilizer has a poor thermal stability and decomposes or outgasses at temperatures between 200 ° C. and 240 ° C. Large amounts (approx. 10 to 15% by weight) of UV stabilizer have to be incorporated so that the UV light is absorbed and the film is not damaged.

At these high concentrations, the film already has a yellow appearance after production, with yellowness index differences (YID) around 25. Furthermore, the mechanical properties are adversely affected. Unusual problems such as stretching occur

Demolition due to lack of strength, i.e. E-modulus too low nozzle deposits, which leads to profile fluctuations - roller deposits from the UV stabilizer, which adversely affects the optical

Properties (poor cloudiness, adhesive defects, inhomogeneous surface) lead to deposits in stretching or fixing frames that drip onto the film.

It was therefore more than surprising that even with low concentrations of the excellent UV protection is achieved in accordance with the invention.

It is very surprising that with this excellent UV protection the yellowness index of the film does not change compared to an unstabilized film within the scope of the measurement accuracy; - No outgassing, no nozzle deposits, no frame evaporation set, so that the film has an excellent appearance and an excellent profile and flatness; The UV-stabilized film is characterized by excellent stretchability, so that it can be produced reliably and reliably on high speed film lines up to speeds of 420 m / min.

The film according to the invention is therefore also economically viable.

It was also very surprising that the film absorbs the aggressive, short-wave light in the wavelength range up to 380 nm, preferably up to 360 nm, i.e. does not let pass.

Furthermore, it is very surprising that the regrind can also be used again without negatively affecting the yellowness index of the film.

In a very particularly preferred embodiment, the film according to the invention contains 0.01% by weight to 5.0% by weight of 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- ( hexyl) oxy-phenol of the formula

oder 0,01 Gew.-% bis 5,0 Gew.-% 2,2-Methylen-bis(6-(2H-benzotriazol-2-yl)-4-(1 , 1 ,3,3- tetramethylbutyl)-phenol der Formel

or 0.01 wt% to 5.0 wt% 2,2-methylene-bis (6- (2H-benzotriazol-2-yl) -4- (1, 1, 3,3-tetramethylbutyl) - phenol of the formula

In a preferred embodiment, mixtures of these two UV stabilizers or mixtures of at least one of these two UV stabilizers with other UV stabilizers can also be used, the total concentration of light stabilizer preferably being between 0.01% by weight and 5.0% by weight. -%, based on the weight of crystallizable polyethylene terephthalate.

At least one surface is vapor-coated with ethylene-vinyl alcohol copolymer, EVOH, PVOH, PVDC or SiO _x , with SiO _{x being} preferred and with x being in the range from 1.2 to 1.9.

The surface gloss of the non-vaporized surface, measured according to DIN 67530 (measuring angle = 20 °), is greater than 80, preferably greater than 100, the light transmission L *, measured according to ASTM D 1003, is more than 74%, preferably more than 76% and the haze of the film, measured according to ASTM D 1003, is less than 20%, preferably less than 15%, which is surprisingly good for the UV stability achieved in combination with the barrier layer and the sealing layer.

The standard viscosity SV (DCE) of the thermoplastic, measured in dichloroacetic acid according to DIN 53728, is between 600 and 1000, preferably between 700 and 900. The film according to the invention can be either single-layer or multi-layer.

In the multilayer embodiment, the film is composed of at least one core layer and at least one cover layer, a three-layer ABA or ABC structure being preferred in particular. In the multilayer embodiment, the UV stabilizer is preferably contained in the cover layer or layers. However, the core layer can also be equipped with UV stabilizers as required.

The concentration of the stabilizer or stabilizers here relates to the weight of the thermoplastics in the layer equipped with UV stabilizer (s).

Surprisingly, weathering tests according to the test specification ISO 4892 with the Atlas CI65 WeatherOmeter have shown that in the case of a three-layer base film, it is quite sufficient to equip the 0.5 to 2 μm thick top layers with UV stabilizers in order to achieve improved UV stability ,

As a result, the UV-stabilized, multi-layer films produced with a known coextrusion technology become economically interesting in comparison to the completely UV-stabilized monofilms, since significantly less UV stabilizer is required for comparable UV stability.

The thermoplastic film can also be provided on at least one side with a copolyester or with an adhesion promoter. Preferably the surface is provided with a copolyester or an adhesion promoter to which the heat seal layer is applied.

Weathering tests have shown that the films according to the invention, even in weathering tests after an extrapolated 5 to 7 years of outdoor use, generally have no yellowing, no embrittlement, no loss of gloss on the surface, no cracking on the surface and have no deterioration in mechanical properties.

During the production of the film it was found that the UV-stabilized film can be oriented excellently in the longitudinal and transverse directions without tears. Furthermore, no outgassing of the UV stabilizer was found in the production process, which is essential to the invention, since most UV stabilizers show disruptive, unpleasant outgassing at extrusion temperatures above 260 ° C. and are therefore unsuitable.

Furthermore, the barrier film according to the invention can be easily recycled without polluting the environment, which makes it suitable, for example, for use as a short-lived article.

Since the film absorbs not only the particularly low oxygen permeability but also the short-wave UV light in the wave range from 260 nm to 380 nm, in particular up to 360 nm, the film also offers a barrier against the aggressive short-wave light which, for. B. causes the dreaded fat oxidation in food. Consequently, the film according to the invention is outstandingly suitable as packaging film for sensitive goods on packaging machines in the vertical and horizontal range (vFFs and hFFs machines).

Furthermore, the film can also be used as a composite film, the composite of the film according to the invention, i.e. with the barrier coating, and a second film. This second film can also be a UV-stable thermoplastic film or a standard thermoplastic film or a polyolefin film. This second film is preferably applied to the barrier side of the film according to the invention.

The second film can have one or more layers and, like the first UV-stable film, can have been oriented by stretching and can have at least one sealing layer to have. The second film can be bonded to the first barrier film according to the invention with or without adhesive.

The thickness of this second film is generally between 10 and 100 microns.

The films, in particular the composite films, are generally obtained by laminating or laminating the films used, with or without an intermediate adhesive layer, by passing them between rollers heated to 30 to 90 ° C.

However, it is also possible, for example, to apply the coating (s) by in-line coating (melt extrusion onto an existing layer).

If adhesives are used, they are applied to a film surface by known methods, in particular by application from solutions or dispersions in water or organic solvents. The solutions usually have an adhesive concentration of 5.0 to 40.0% by weight in order to give an amount of adhesive on the film of 1.0 to 10.0 g / m ² .

Adhesives made from thermoplastic resins, such as cellulose esters and ethers, alkyl and acrylic esters, polyimides, polyurethanes or polyesters, or from thermosetting resins, such as epoxy resins, urea / formaldehyde, phenyl / formaldehyde or melamine / - Formaldehyde resins, or consist of synthetic rubbers.

Suitable solvents for the adhesive are e.g. Hydrocarbons such as ligroin and toluene, esters such as ethyl acetate or ketones such as acetone and methyl ethyl ketone.

The production of the film according to the invention can, for example, according to known Extrusion processes take place in an extrusion line. The thermoplastic film is first produced, then stretched and the surfaces provided with the barrier layer.

According to the invention, the light stabilizer can already be metered in at the thermoplastic raw material manufacturer or metered into the extruder during film production.

It is preferred to add the light stabilizer via masterbatch technology. The additive is first fully dispersed in a carrier material. The thermoplastic itself comes as a carrier material, e.g. polyethylene terephthalate or other polymers that are compatible with the thermoplastic, in question. After metering into the thermoplastic for film production, the components of the masterbatch melt during the extrusion and are thus dissolved in the thermoplastic.

The concentration of the UV absorber in addition to the thermoplastic in the masterbatch is 2.0 to 50.0% by weight, preferably 5.0 to 30.0% by weight, the sum of the constituents always being 100% by weight.

It is important with masterbatch technology that the grain size and bulk density of the masterbatch are similar to the grain size and bulk density of the thermoplastic, so that homogeneous distribution and thus homogeneous UV stabilization can take place.

The films can be made from a thermoplastic raw material, optionally with further raw materials and the UV stabilizer and / or other conventional additives, in a conventional amount of 0.1 to a maximum of 10.0% by weight, both as monofilms and as multi-layered, optionally coextruded Films with the same or differently shaped surfaces are produced, one surface being pigmented, for example, and the other surface containing no pigment. As well one or both surfaces of the film can be provided with a conventional functional coating by known methods.

In the preferred extrusion process for producing the thermoplastic film, the melted material is extruded through a slot die and quenched as a largely amorphous pre-film on a chill roll. This film is then heated again and stretched in the longitudinal and transverse directions or in the transverse and longitudinal directions or in the longitudinal, transverse and again in the longitudinal direction and / or transverse direction. The stretching temperatures are generally T _g + 10 ° C to T _g + 60 ° C (T _g = glass temperature), the stretching ratio of the longitudinal stretching is usually 2 to 6, in particular 3 to 4.5, that of the transverse stretching is 2 to 5, in particular at 3 to 4.5, and that of the second longitudinal stretching which may be carried out at 1, 1 to 3. The first longitudinal stretching can optionally be carried out simultaneously with the transverse stretching (simultaneous stretching). The film is then heat-set at oven temperatures of 180 to 260 ° C, in particular at 220 to 250 ° C. The film is then cooled and wound up.

A surface layer is coated with ethylene-vinyl alcohol copolymer, EVOH, PVOH or PVDC, the thickness of the coating being between 0.5 and 8.0 μm or being vaporized with SiO _x on an electron beam system, where x is between 1, 2 and 1 , 9 lies. The SiO _x layer has a thickness in the range from 10 nm to 200 nm. On the other surface side is a 10 μm to 100 μm thick LDPE film, which may contain 0.1 to 3% by weight of light stabilizer is equipped and contains the other usual additives, laminated.

Due to the surprising combination of excellent properties, the film according to the invention is outstandingly suitable for a large number of different applications, for example for interior cladding, for trade fair construction and trade fair articles, as displays, for signs, for protective glazing of machines and vehicles, in lighting sector, in shop and shelf construction, as promotional items, laminating medium, for thermal applications of all kinds, as packaging film for sensitive products.

Due to the good UV stability, the film is also suitable for outdoor applications, e.g. B. for greenhouses, in the advertising sector, roofing, external cladding, covers, applications in the construction sector and illuminated advertising profiles.

In the following exemplary embodiments, the individual properties are measured in accordance with the following standards or methods.

measurement methods

surface gloss

The surface gloss is measured at a measuring angle of 20 ° according to DIN 67530.

light transmission

The light transmission is the ratio of the total transmitted light to the amount of incident light.

The light transmission is measured with the measuring device "® Hazegard plus" according to ASTM D 1003.

cloudiness

Haze is the percentage of the transmitted light that deviates by more than 2.5 ° on average from the incident light beam. The image sharpness is determined at an angle of less than 2.5 °.

The haze is measured using the "Hazegard plus" measuring device in accordance with ASTM D 1003. Oberfiächendefekte

The surface defects are determined visually.

Mechanical properties

The modulus of elasticity, tensile strength and elongation at break are measured in the longitudinal and transverse directions according to ISO 527-1-2.

SV (DCE), IV (DCE)

The standard viscosity SV (DCE) is measured based on DIN 53726 in dichloroacetic acid.

The intrinsic viscosity (IV) is calculated as follows from the standard viscosity (SV)

IV (DCE) = 6.67 ^• 10 ^"4 SV (DCE) + 0.118

Weathering, UV stability

The UV stability is tested according to the test specification ISO 4892 as follows

Atlas Ci 65 Weather Ometer test device

Test conditions ISO 4892, i.e. H. artificial weathering irradiation time 1000 hours (per side)

Irradiation 0.5 W / m ² , 340 nm

Temperature 63 ° C

Relative humidity 50%

Xenon lamp inner and outer filter made of borosilicate irradiation cycles 102 minutes of UV light, then 18 minutes of UV light with

Water spraying the samples, then 102 again

Minutes of UV light etc. oxygen barrier

The oxygen permeability is measured according to DIN 53380.

Yellowness index: The yellowness index G (YID) is the deviation from the colorlessness in the "yellow" direction and is measured in accordance with DIN 6167. Yellowness values of <5 are not visually visible.

Examples

The examples below and the comparative example are each transparent films of different thicknesses which are produced on the extrusion line described.

All films were weathered according to the test specification ISO 4892 for 1000 hours with the Atlas Ci 65 Weather Ometer from Atlas and then checked for discoloration, surface defects, haze and gloss.

example 1

A 50 μm thick, transparent film is produced, the main component of which is polyethylene terephthalate 0.3% by weight © Sylobloc and 1.0% by weight of the UV stabilizer 2- (4,6-diphenyl-1,3,5 -triazin-2-yl) -5- (hexyl) oxyphenol ( ^® Tinuvin 1577 from Ciba-Geigy).

Tinuvin 1577 has a melting point of 149 ° C and is thermally stable up to approx. 330 ° C.

For the purpose of homogeneous distribution, 0.3% by weight of Sylobloc and 1.0% by weight of the UV stabilizer are incorporated into the polyethylene terephthalate.

The polyethylene terephthalate from which the transparent film is made has a standard viscosity SV (DCE) of 810, which means an intrinsic viscosity IV (DCE) of Corresponds to 0.658 dl / g.

A surface layer is sputtered with SiO _x on an electron beam system from Leybold, the SiO _x layer (x = 1, 6) having a thickness of 50 nm.

Example 2

A transparent film is produced analogously to Example 1, the UV stabilizer being 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- (hexyl) -oxyphenol (Tinuvin 1577) in the form of a Masterbatches is metered. The masterbatch is composed of 5% by weight of Tinuvin 1577 as the active ingredient and 95% by weight of the polyethylene terephthalate from Example 1.

Before the extrusion, 90% by weight of the polyethylene terephthalate from Example 1 with 10% by weight of the masterbatch are dried at 170 ° C. for 5 hours. The extrusion, the film production and the SiO _x coating are carried out analogously to Example 1.

Example 3

Analogously to Example 2, a transparent 350 μm thick UV-stabilized PET film is produced. One surface side is coated with SiO _x analogously to Example 1.

Example 4

Coextrusion technology is used to produce a 50 m thick multilayer PET film with the layer sequence A-B-A, where B represents the core layer and A the top layers. The core layer B is 48 m thick and the two outer layers, which cover the core layer, are each 1 m thick.

The polyethylene terephthalate used for the core layer B is identical to that from the example, but contains no sylobloc. The polyethylene terephthalate of the outer layers A is identical to the polyethylene terephthalate from Example 2, ie the outer layer raw material is equipped with 0.3% by weight of Sylobloc.

Analogously to Example 2, the 5% by weight Tinuvin 1577 masterbatch is used, but only 20% by weight of the masterbatch is metered into the 1 μm thick outer layers using the masterbatch technology.

A cover layer A is coated with SiO _x as in Example 1.

The films from Examples 1 to 4 absorb the UV light in the wavelength range up to 390 nm, ie they only let the radiation through from 390 nm and show an oxygen barrier of <5 cm ³ / (m ^{2 ■} 24 h - bar) at 23 ° C.

The films from Examples 1 to 4 are weathered on the uncoated side for 1000 hours with the Atlas CI 65 Weather Ometer. The films show excellent UV resistance. The films show no cracks or embrittlement. The yellowness index of the film does not change.

The films from Examples 1 to 4 are weathered on the side coated with SiO _{x for} 1000 hours with the Atlas CI 65 Weather Ometer. The films show no cracks or embrittlement. The yellowness index of the film does not change.

Comparative Example 1

Analogously to example 1, a 50 μm thick PET monofilm is produced. In contrast to Example 1, the film contains no UV stabilizer and no barrier layer.

The film lets the UV radiation through from 280 nm. After weathering one side with Atlas CI 65 Weather Ometer for 1000 hours, the film shows cracks and embrittlement on this surface. A precise property profile - especially that mechanical properties - can therefore no longer be measured. The film also shows a visually visible yellow color. The oxygen barrier of the film is> 15 cm ³ / (m ^{2 ■} 24h ^■ bar) at 23 ° C.

The film is completely unsuitable for packaging sensitive packaged goods that have to be protected from the aggressive, short-wave light and that require an oxygen barrier.

Claims

Patent claims 1. Transparent, biaxially oriented, UV-stabilized film with a thickness in the range from 10 to 500 μm, which contains a crystallizable thermoplastic as the main component, characterized in that it additionally contains at least one im Thermoplastics contain soluble UV absorbers and are provided with at least one barrier layer against gases and stretched in the longitudinal and transverse directions. 2. Film according to claim 1, characterized in that the crystallized thermoplastic is a polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate or mixtures thereof, preferably polyethylene terephthalate. 3. Film according to claim 1 or 2, characterized in that the concentration of the UV absorber is in the range from 0.01% by weight to 5.0% by weight, preferably 0.1% by weight. % to 3% by weight, based on the weight of the crystallizable thermoplastic. 4. Film according to one or more of claims 1 to 3, characterized in that it contains, as UV absorbers, 2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organo-nickel compounds, salicylic acid esters, cinnamic acid ester derivatives, resorcinol monobenzoates, oxalic anilides, hydroxybenzoic acid esters, sterically hindered amines and/or or triazines, preferably 2-hydroxybenzotriazoles and triazines and in particular 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxy-phenol or 2,2'-methylene-bis( 6-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol contains. 5. Film according to one or more of claims 1 to 4, characterized in that the barrier layer is based on SiO _x , an ethylene-vinyl alcohol copolymer, polyvinyl alcohol or polyvinylidene dichloride, preferably SiO _x , where x = 1.2 to 1, 9 or an ethylene-vinyl alcohol copolymer with an ethylene content of 15 - 60 mol% and one Degree of saponification of at least 90 mol%, preferably greater than 96 mol%, in particular greater than 99 mol%. 6. Film according to one or more of claims 1 to 5, characterized in that the regrind is used. 7. A process for producing a transparent, biaxially oriented, UV-stabilized barrier film made of a crystallizable thermoplastic, the thickness of which is in the range from 10 to 500 μm, characterized in that a thermoplastic is mixed with at least one UV absorber, then after a Extrusion process is formed into a melt film, drawn off via a take-off roller and solidified as an amorphous pre-film, then stretched in the longitudinal and transverse directions, heat-set and provided with a barrier layer. 8. The method according to claim 7, characterized in that the UV absorber is metered into the extruder at the thermoplastic raw material manufacturer or during film production, with addition via masterbatch technology being preferred. 9. The method according to claim 8, characterized in that the material batch contains, in addition to the thermoplastic, 2.0 to 50.0% by weight, preferably 5.0 to 30.0% by weight, of UV absorbers, the sum of the components is always 100% by weight. 10. Use of the film according to one or more of claims 1 to 6 for indoor and/or outdoor use. 2.3 - 11. Use according to claim 10 in the interior for interior cladding, for trade fair construction and trade fair items, as displays, for signs, for protective glazing of machines and vehicles, in the lighting sector, in shop and shelf construction, as promotional items, laminating medium, for thermal applications of all kinds, as packaging film for sensitive and advertising products and outdoors for greenhouses, in the advertising sector, roofing, external cladding, covers in the construction sector and illuminated advertising profiles.