DE102005058907A1 - Matte, one-side sealable, biaxially oriented polyester film for use in packaging comprises a base layer with sealable cover layer on one side and a matte cover layer on the other - Google Patents

Abstract

A multilayer matte, one-side sealable, biaxially oriented polyester film with (a) a base layer, (b) a sealable cover layer on one side of (a) and (c) a matte cover layer on the other side of (a) is such that layer (b) contains less than 0.01 wt.% external particles based on its total weight; and #layer (c) contains (i) a polyester containing 6-30 mol.% of isophthalic acid based on total amount of polyester in this layer and (ii) a pigment having an average particle diameter (d50) of 2-10 mu , a particle size distribution as determined using Span 98 (RTM) of 1.2-2 and a concentration of 1.0-7.0 wt.% based on total weight of layer (c).

Description

The The invention relates to a one-sided matte, one-sided sealable biaxial oriented polyester film consisting of a base layer (B) and cover layers applied on both sides of this base layer (A) and (C), wherein the cover layer (A) is sealable and the cover layer (C) has a characteristic dull appearance. The invention further relates to a process for the production of the film and their use.

unilaterally matt, biaxially oriented polyester films, at least on one Side sealable are known.

In EP-A 1 219 413 a coextruded, one-sided matte and one-side sealable polyester film is described. The sealable layer of this film consists essentially of isophthalic and terephthalic acid containing copolyesters. Their surface is described by a certain topography. The opposite side of this page is matte and filled with anti-blocking agent (inert particles). In the preferred embodiment, the concentration of inert particles in this layer is between 1.0 and 18% by weight. The polymer used for this layer is polyethylene terephthalate, preferably a mixture of polyethylene terephthalate and a copolyester (component I). The copolyester contains isophthalic acid, an aliphatic acid and a sulfomonomer. The film according to this invention is characterized by a desirable high transparency, but can be produced only at high cost. Due to the high concentration of inert particles used in polyethylene terephthalate, or in the mixture, to obtain a polymer having a high crosslinking density, in which the stretching forces are significantly higher than in a polymer, without the inert particles (see. 1 ). The consequence of this are comparatively many tears in the production of the film, which are undesirable. Comparative Example 1 describes a film in which the sealing layer is pigment-free. The film according to the comparative example has unacceptable handling and performance, and it can not be produced by commercial standards.

EP-A 1 442 875 describes a coextruded and one-sided matte polyester film which has at least one base layer (B) and at least one matte covering layer (A), the matte covering layer (A) containing particles having an average particle diameter d ₅₀ from 2 to 10 μm and a SPAN98 of less than or equal to 2. The cover layer (A) contains a polyester which preferably has from 4 to 30 mol% of isophthalic acid units, based on the total amount of acid of the polyester in this layer. The matte outer layer (A) contains particles in a concentration of 1.0 to 7.0%. The film can be produced well, but is not or only insufficient.

• • eine verbesserte Siegelfähigkeit gegenüber sich selbst, gegenüber Substraten aus APET, A/CPET, CPET oder Metallen
• • verbesserte optische Eigenschaften (Trübung, Mattgrad)
• • eine gute Herstellbarkeit (Streckbarkeit) und
• • eine verbesserte Wickelung und verbessertes Verarbeitungsverhalten

auszeichnet.
(APET = amorphes Polyethylenterephthalat (PET); CPET = kristallines PET; A/CPET = zweischichtiges Laminat, innen APET, außen CPET (bei einer Schale))The object of the present invention was therefore to provide a one-sided matte, sealable, biaxially oriented polyester film which does not have the disadvantages of the prior art films and in particular by

• • an improved sealability to itself over substrates made of APET, A / CPET, CPET or metals
• • improved optical properties (haze, matt degree)
• • good manufacturability (ductility) and
• • improved winding and improved processing behavior

distinguished.
(APET = amorphous polyethylene terephthalate (PET); CPET = crystalline PET; A / CPET = two-layer laminate, inside APET, outside CPET (in one shell))

Improved sealability means a minimum sealing temperature of the outer layer A relative to itself of <110 ° C, preferably <108 ° C and more preferably <106 ° C and a sealed seam strength of this outer layer A to itself from 1.5 to 10 N / 15 mm, preferably from 1.6 to 10 N / 15 mm and more preferably from 1.7 to 10 N / 15 mm. Against an APET substrate, the minimum sealing temperature of the cover layer A should be <140 ° C., preferably <139 ° C. and more preferably <138 ° C., and the seal seam strength of this cover layer A should be 1.5 to 10 N / 15, compared to an A / CPET substrate mm, preferably from 1.6 to 10 N / 15 mm and particularly preferably from 1.7 to 10 N / 15 mm. A particular concern of the present invention was to improve the sealing of the film against metals, such as steel or aluminum, with lacquer-coated steel, chrome-plated, galvanized or tinned steel (tinplate). In addition, care should be taken to ensure that the film is well windable and can be processed on high-speed machines. In the production of the film should also be ensured that resulting waste material as a regenerate in an amount of preferably up to 60 wt .-%, based on the Gesamtge weight of the film, can be returned to the manufacturing process, without thereby affecting the physical and optical properties of the film are adversely affected.

• a) die siegelfähige Deckschicht (A) weniger als 0,01 Gew.-% externe Partikel enthält (bezogen auf das Gesamtgewicht der Deckschicht (A)) und
• b) die matte Deckschicht (C) i. einen Polyester enthält, der 6 bis 30 Mol-% Isophthalsäureeinheiten aufweist (bezogen auf die Gesamtsäuremenge des Polyesters in dieser Schicht), und ii. ein Pigment enthält, das durch die folgenden Merkmale gekennzeichnet ist: • der mittlere Durchmesser der Partikel (d₅₀-Wert) liegt im Bereich von 2 bis 10 μm, • die Streuung der Partikelgrößenverteilung, ausgedrückt durch den SPAN 98, liegt im Bereich von 1,2 bis 2, und • die Konzentration der Partikel liegt im Bereich von 1,0 bis 7,0 Gew.-%, bezogen auf das Gesamtgewicht der Deckschicht (C).

The object is achieved by providing a one-sided matte, one-side sealable, biaxially oriented polyester film with a base layer (B), a sealable cover layer (A) and a cover layer (C), wherein

• a) the sealable outer layer (A) contains less than 0.01 wt .-% external particles (based on the total weight of the outer layer (A)) and
• b) the matte topcoat (C) i. a polyester containing from 6 to 30 mol% of isophthalic acid units (based on the total amount of acid of the polyester in this layer), and ii. contains a pigment characterized by the following features: the average diameter of the particles (d ₅₀ value) is in the range of 2 to 10 μm, the dispersion of the particle size distribution, expressed by the SPAN 98, is in the range of 1 , 2 to 2, and • the concentration of the particles is in the range of 1.0 to 7.0 wt .-%, based on the total weight of the outer layer (C).

pigment also means antiblocking agent, filler, called external or inert particles, which by the mentioned Characteristics are characterized. Typical pigments are inorganic and / or organic particles, for example calcium carbonate, amorphous silica, talc, Magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, Lithium phosphate, calcium phosphate, magnesium phosphate, alumina, LiF, calcium, barium, zinc or manganese salts of the used dicarboxylic acids, Titanium dioxide, kaolin or cross-linked polystyrene or acrylate particles.

A matt film according to the invention has gloss values on the matt surface of the film of <70, preferably <60 and particularly preferably <50 (at a measuring angle of 60 °). The average roughness R _{a of} this surface is 150-1000 nm, preferably 175-950 nm and particularly preferably 200-900 nm.

According to the invention At least three layers of film and comprises the base layer (B), the sealable Topcoat (A) and the matte topcoat (C).

Material for the base layer (B)

The Base layer (B) of the film is preferably at least 90% by weight made of a thermoplastic polyester. Suitable for this are polyester Ethylene glycol and terephthalic acid (= Polyethylene terephthalate, PET), from ethylene glycol and naphthalene-2,6-dicarboxylic acid (= polyethylene 2,6-naphthalate, PEN), 1,4-bis-hydroxymethyl-cyclohexane and terephthalic acid (= poly (1,4-cyclohexanedimethylene terephthalate, PCDT) and ethylene glycol, naphthalene-2,6-dicarboxylic acid and Biphenyl-4,4'-dicarboxylic acid (= polyethylene-2,6-naphthalate bibenzoate, PENBB). Particularly preferred are polyesters which are at least 90 Mol%, preferably at least 95 mol%, of ethylene glycol and terephthalic acid units or consist of ethylene glycol and naphthalene-2,6-dicarboxylic acid units. The remaining monomer units are derived from other aliphatic, cycloaliphatic or aromatic diols or dicarboxylic acids.

Suitable other aliphatic diols are, for example, diethylene glycol, triethylene glycol, aliphatic glycols of the general formula HO- (CH ₂ ) _n -OH, where n is an integer from 3 to 6 (in particular propane-1,3-diol, butane-1,4 -diol, pentane-1,5-diol and hexane-1,6-diol) or branched aliphatic glycols having up to 6 carbon atoms. Of the cycloaliphatic diols, mention may be made of cyclohexanediols (in particular cyclohexane-1,4-diol). Suitable other aromatic diols correspond for example to the formula HO-C ₆ H ₄ -XC ₆ H ₄ -OH, where X is -CH ₂ -, -C (CH ₃ ) ₂ -, -C (CF ₃ ) ₂ -, -O -, -S- or -SO ₂ - stands. In addition, bisphenols of the formula HO-C ₆ H ₄ -C ₆ H ₄ -OH are also very suitable.

Other aromatic dicarboxylic acids are preferably benzene dicarboxylic acids, naphthalene dicarboxylic acids, for example naphthalene-1,4- or 1,6-dicarboxylic acid, biphenyl-x, x'-dicarboxylic acids, in particular biphenyl-4,4'-dicarboxylic acid, diphenylacetylene-x, x'-dicarboxylic acids , in particular diphenylacetylene-4,4'-dicarboxylic acid, or stilbene-x, x'-dicarboxylic acids. Of the cycloaliphatic dicarboxylic acids, mention may be made of cyclohexanedicarboxylic acids, in particular cyclohexane-1,4-dicarboxylic acid. Of the aliphatic dicarboxylic acids, the (C ₃ to C ₁₉ ) alkanedioic acids are particularly suitable, it being possible for the alkane part to be straight-chain or branched.

The Preparation of the polyesters may e.g. after the transesterification process respectively. It is based on dicarboxylic acid esters and diols, the with the usual Transesterification catalysts, such as zinc, calcium, lithium, magnesium and manganese salts, to be implemented. The intermediates will be then generally more common in the presence Polycondensation catalysts, such as antimony trioxide or titanium salts, polycondensed. The production can be just as good after the direct esterification process in the presence of polycondensation catalysts. there starting directly from the dicarboxylic acids and diols. Polyester according to the invention are available as commercial products.

Sealable topcoat (A)

The sealable overcoat applied to the base layer (B) by coextrusion (A) preferably consists essentially of copolyesters, predominantly from isophthalic and terephthalic acid units and composed of ethylene glycol units. The remaining Monomer units are derived from other aliphatic, cycloaliphatic or aromatic diols or dicarboxylic acids, as in the base layer can happen. The preferred copolyesters that have the desired sealing properties are those prepared from ethylene terephthalate and ethylene isophthalate units are constructed. The proportion of ethylene terephthalate is preferred 60 to 95 mol% and the corresponding proportion of ethylene isophthalate 40 to 5 mol%. Also preferred are copolyesters in which the Proportion of ethylene terephthalate 65 to 90 mol% and the corresponding Proportion of ethylene isophthalate is 35 to 10 mol%, and most preferred are copolyesters in which the proportion of ethylene terephthalate 70 to 85 mol% and the corresponding proportion of ethylene isophthalate Is 30 to 15 mol%.

The sealable Cover layer (A) contains less than 0.01%, preferably no external particles. In this Case is the seal opposite yourself and opposite the above materials best. Between the sealing layer (A) and the substrate form no bubbles and the seal is the entire surface. Otherwise, e.g. through the tips of the pigments cavities which worsen the seal and lead to optical defects in the lead on laminated film.

Sealing properties of the sealable Cover layer (A)

The desired Sealing properties of the top layer (A) are believed to be from the Combination of the chemical composition of the copolyester used, the top layer thickness and the topography.

The sealable Cover layer (A) has opposite itself a sealing temperature of less than 110 ° C and a Seal seam strength (measured at 23 ° C) of at least 1.5 N / 15 now foil width, opposite a substrate of APET a sealing temperature of less 140 ° C and a seal strength (measured at 140 ° C) of at least 1.5 N / 15 mm film width. (The best sealing properties of the film receives one, if the copolyester no further additives, in particular no inorganic or organic fillers are added. For this Case gets for a given copolyester and given layer thickness the lowest seal initiation temperature and highest seal strength.) If the sealable Cover layer (A) small amounts (<0.01 %) are added to antiblocking agents, it has proved to be beneficial to use the same antiblocking agents as for the topcoat (C).

Matte topcoat (C)

The by coextrusion on the base layer (B) applied matte topcoat (C) is preferably predominant built on the basis of polyester. According to the invention, the matt covering layer (C) contains a polyester containing 6 to 30 mol% of isophthalic acid, preferably 8 to 28 mol% of isophthalic acid and particularly preferably 10 to 26 mol% of isophthalic acid, based on the total amount of acid of the polyester in this layer. The remaining monomer units come from other aliphatic, cycloaliphatic or aromatic dicarboxylic acids or diols, as they can also occur in the base layer and have already been described there. Those described for the base layer (B) Thus, polyesters are basically after appropriate modification also suitable for the outer layer (C).

Of the Raw material for leaves the cover layer (C) For example, about Copolymerization of the individual monomers or on masterbatches different Produce individual polymers as a mixture or as a blend. Prefers is the production over Masterbatches of various individual polymers as a mixture or as Blend.

In a preferred embodiment of the invention the matte topcoat (C) a copolyester consisting of terephthalate and isophthalate units and composed of ethylene glycol units is. The proportion of terephthalate units in this copolyester, based on the total amount of acid, is preferably 70 to 94 mol% and the corresponding proportion of isophthalate units 30 to 6 mol%. Particularly preferred among these are copolyesters, in which the proportion of terephthalate units 72 to 92 mol% and the corresponding proportion of isophthalate units 28 to 8 mol% is. Very preferred are those copolyesters in which the proportion of Terephthalate units 74 to 90 mol% and the corresponding proportion of isophthalate units is 26 to 10 mol%.

If be available for the remaining proportion of the polymers present in the cover layer (C) in principle used the same polymers as previously described for the base layer (B) were.

surprisingly It has been shown that when using the previously described Raw materials for the cover layer (C) receives a film with a particularly low haze.

In particular, it has surprisingly been found that when using the raw materials described above for the outer layer (C) receives a film that can be produced process-safe. The number of film breaks is now comparable to that in the production of standard polyester film, in which the proportion of pigments in this layer is significantly lower. Due to the special selection of the raw material in this layer, the stretching forces have become significantly lower (cf. 2 ).

• a) Die matte Deckschicht (C) enthält Partikel mit einem Partikeldurchmesser d₅₀ von 2,0 bis 10 μm. Es hat sich als besonders vorteilhaft erwiesen, Teilchen mit einem mittleren Partikeldurchmesser d₅₀ von 2,2 bis 9 μm, bevorzugt von 2,4 bis 8 μm und besonders bevorzugt von 2,6 bis 7 μm, zu verwenden. Bei der Verwendung von Teilchen mit einem Durchmesser, der unterhalb 2,0 μm liegt, stellt sich (bei vergleichbaren Konzentrationen) eine erhöhte Trübung ein. Teilchen mit einem Durchmesser größer als 10 μm verursachen in der Regel Filterprobleme.
• b) Die matte Deckschicht (C) enthält Partikel, deren Durchmesser eine Streuung aufweisen, die durch einen SPAN98 ≤ 2,0 beschrieben wird (Definition des SPAN98, siehe Messvorschrift). Bevorzugt ist der SPAN98 ≤ 1,9 und besonders bevorzugt ist der SPAN98 < 1,8. Enthält die Deckschicht (C) der Folie dagegen ein Partikelsystem, bei dem der SPAN98 größer als 2,0 ist, so wird der Glanz der Deckschicht (C) höher, was unerwünscht ist. Ist der SPAN98 kleiner als 1,2, so wird die Wickelung der Folie schlechter, sie neigt beispielsweise zum ,Verblocken'.
• c) Erfindungsgemäß enthält die Deckschicht (C) Partikel in einer Konzentration von 1,0 bis 7,0 Gew.-%, bezogen auf das Gesamtgewicht dieser Schicht. Bevorzugt beträgt die Konzentration der Partikel 1,5 bis 6,5 Gew.-% und besonders bevorzugt 2,0 bis 6,0 Gew.-%. Enthält die Deckschicht (C) der Folie dagegen ein Partikelsystem, bei dem die Partikel in einer Konzentration von weniger als 1,0 Gew.-% vorliegen, so ist sie für eine Anwendung als Mattfolie weniger geeignet, der Glanz ist zu hoch. Enthält dagegen die Deckschicht (C) der Folie ein Partikelsystem, bei dem die Partikel in einer Konzentration von mehr als 7,0 Gew.-% vorliegen, so wird die Trübung der Folie zu groß.

To achieve the desired mattness / desired degree of matting, the topcoat (C) additionally contains a particle system characterized by the following set of parameters:

• a) The matte outer layer (C) contains particles with a particle diameter d ₅₀ from 2.0 to 10 microns. It has proved to be particularly advantageous to use particles having a mean particle diameter d ₅₀ of 2.2 to 9 .mu.m, preferably from 2.4 to 8 microns and more preferably from 2.6 to 7 microns. Using particles with a diameter below 2.0 μm results in increased turbidity (at comparable concentrations). Particles with a diameter greater than 10 microns usually cause filter problems.
• b) The matt top layer (C) contains particles whose diameters have a scattering which is described by a SPAN98 ≤ 2.0 (definition of the SPAN98, see measuring instructions). Preferably, the SPAN98 is ≦ 1.9 and more preferably the SPAN98 is <1.8. In contrast, if the cover layer (C) of the film contains a particle system in which the SPAN98 is greater than 2.0, the gloss of the cover layer (C) becomes higher, which is undesirable. If the SPAN98 is less than 1.2, the winding of the film will be worse, for example, it tends to 'block'.
• c) According to the invention, the cover layer (C) contains particles in a concentration of 1.0 to 7.0 wt .-%, based on the total weight of this layer. The concentration of the particles is preferably from 1.5 to 6.5% by weight and more preferably from 2.0 to 6.0% by weight. On the other hand, if the covering layer (C) of the film contains a particle system in which the particles are present in a concentration of less than 1.0% by weight, it is less suitable for use as a matt film and the gloss is too high. If, on the other hand, the cover layer (C) of the film contains a particle system in which the particles are present in a concentration of more than 7.0% by weight, the haze of the film becomes too large.

typical favoring the degree of matting of the film and thus preferred particle systems are inorganic and / or organic particles, for example calcium carbonate, amorphous silica, talc, Magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, Lithium phosphate, calcium phosphate, magnesium phosphate, alumina, Lithium fluoride, calcium, barium, zinc or manganese salts of the used dicarboxylic acids, Carbon black, titanium dioxide, Kaolin or crosslinked polymer particles, e.g. Polystyrene or acrylate particles.

In addition, other pigments, but with a smaller d ₅₀ value than the main pigment system, may additionally be incorporated into the cover layer C. However, if the d ₅₀ values and / or SPAN98 values of the main pigment deviate from the abovementioned values or if such a pigment is not present, the disadvantages described above arise.

Preferred particles are synthetically produced SiO ₂ particles (in colloidal form). These particles are very well integrated into the polymer matrix and produce only few vacuoles (cavities). Vacuoles are formed on the particles in the biaxial orientation, generally causing turbidity, and are therefore not very suitable for the present invention. For the (synthetic) preparation of the SiO ₂ particles (also called silica gel), first sulfuric acid and sodium silicate are mixed together under controlled conditions to form hydrosol. This eventually forms into a hard, transparent mass, which as Hydrogel is known. After segregation of the by-produced sodium sulfate by a washing process, it can be dried and further processed. By controlling the wash water pH and the drying conditions, the important physical parameters such as pore volume, pore size and the size of the surface of the resulting silica gel can be varied. The desired particle size (eg the d ₅₀ value) and particle size distribution (SPAN98) are obtained by suitable grinding of the silica gel (eg mechanically or hydromechanically). Manufacturers of such particles are, for example, the companies Grace (USA), Fuji (Japan), Degussa (Germany) or Ineos (Great Britain).

The matte topcoat (C) is further characterized in a preferred embodiment by the following set of parameters:
The roughness of the matte side of the film, expressed by its R _a , is in the range from 150 to 1000 nm, preferably from 175 to 950 nm, more preferably from 200 to 900 nm. Lower values than 150 nm have negative effects on the Dullness of the surface, larger than 1000 nm affect the optical properties of the film.

Of the Coefficient of friction (COF) of the matte side of the film (against itself itself) is less than 0.45, preferably less than 0.40 and especially preferably less than 0.35.

The Base layer (B) may additionally contain conventional additives such as stabilizers and / or particles (= filler) included. As stabilizers, for example, phosphorus compounds are advantageous such as phosphoric acid ester used.

typical Particles (filler or pigments) for the base layer (B) are for the outer layer (C) indicated inorganic and / or organic Particles, for example calcium carbonate, amorphous silica, talc, Magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, Lithium phosphate, calcium phosphate, magnesium phosphate, alumina, Lithium fluoride, calcium, barium, zinc or manganese salts of the used dicarboxylic acids, Titanium dioxide, kaolin or cross-linked polystyrene or acrylate particles.

In a particularly advantageous embodiment contains the base layer no or just the over the regenerated pigment introduced. This will make a slide with very low turbidity receive.

Summarized the film of the invention is characterized in particular by a low gloss of the film surface (C), by a comparatively low turbidity and a high transparency out. Furthermore it has a good wrapping and processing behavior.

Of the Gloss of the film surface (C) (at a measuring angle of 60 °) is lower than 70. In a preferred embodiment, the gloss is this page is less than 60 and in a particularly preferred embodiment less than 50. This film surface thus provides a particularly high advertising effective character and is therefore particularly suitable as outboard surface with a lamination with steel. Due to the high transparency of the Film will not falsify underlying colors and will not turn gray.

The cloudiness the film is less than 45%. In a preferred embodiment is the cloudiness of the Film less than 40% and in a particularly preferred embodiment less than 35%. The transparency of the film is greater than 80%. In a preferred embodiment is Transparency of the film more than 84% and in a particularly preferred embodiment more than 88%. Due to the comparatively low turbidity and high transparency of the film (compared to a matt monofilm, see comparative example), the film according to the invention can e.g. in counter pressure be printed, the pressure is very easy to recognize.

at The thickness of the cover layer (C) is generally greater than that of the film 0.4 μm and is preferably in the range of 0.5 to 10.0 .mu.m, in particular in the range of 0.8 to 9.0 μm and more preferably in the range of 1.0 to 8.0 μm.

at The thickness of the cover layer (A) is generally greater than that of the film 0.4 μm and is preferably in the range of 0.5 to 10.0 .mu.m, in particular in the range of 0.8 to 9.0 μm and more preferably in the range of 1.0 to 8.0 μm.

The total thickness of the polyester film of the invention can vary within wide limits. It is preferably 5 to 100 .mu.m, in particular 6 to 90 .mu.m, preferably 7 to 80 .mu.m, wherein the layer B has a proportion of preferably 5 to 90% of the total thickness.

production method

The The invention also relates to a process for the preparation of the polyester film according to the invention according to the known from the literature coextrusion.

in the Under this procedure, the procedure is that the individual Layers (A), (B) and (C) of the film corresponding to melts a flat nozzle coextruded, the resulting film for solidification one or more rolls is withdrawn, the film then biaxially stretched, the biaxially stretched film heat-set and optionally corona treated on the surface layer intended for the treatment becomes.

The Biaxial stretching (orientation) generally becomes consecutive carried out, the successive biaxial stretching, at first along (in Machine direction) and then across (perpendicular to the machine direction) is stretched, is preferred.

First, be as usual in the coextrusion process the polymer or the polymer mixtures for the individual layers in an extruder compressed and liquefied, with the optionally as additives provided additives already in the polymer or in the polymer mixture may be included. The melts are then pressed simultaneously through a flat die (slot die), and the extruded multi-layer melt is on or withdrawn several take-off rolls, wherein the melt cools and solidifies into a prefilm.

The Biaxial stretching is generally performed sequentially. there Preferably, the prefilm is first longitudinally (i.e., in the machine direction = MD direction) and then in the transverse direction (i.e., perpendicular to the machine direction = TD direction) stretched. this leads to to a spatial Orientation (orientation) of the polymer chains. The stretching in the longitudinal direction let yourself with the help of two different according to the desired stretch ratio fast rotating rollers. Used for cross stretching you generally have a corresponding clip frame in which the film on both edges clamped and then at elevated Temperature is drawn to both sides.

The Temperature at which the stretching is carried out can be done in a relative huge Range vary and depends on the desired properties of the film. In general, the longitudinal stretching is at a temperature in the range of 80 to 130 ° C and the transverse extent in the range from 90 to 150 ° C carried out. The longitudinal stretching ratio is generally in the range of 2.5: 1 to 6: 1, preferably 3.0: 1 to 5.5: 1st The transverse stretch ratio is generally in the range of 3.0: 1 to 5.0: 1, preferably 3.5: 1 to 4.5: 1.

at the subsequent heat setting is the film over a Duration of about 0.1 to 10 seconds at a temperature of about 150 up to 250 ° C held. Subsequently The film is in the usual Wrapped up way.

to Setting further desired Properties can add the foil in addition be coated. Typical coatings are adhesion-promoting, antistatic, slip-improving or dehesive layers. It lends itself to this extra Layers over In-line coating by means of aqueous Dispersions before the stretching step in the transverse direction on the film applied.

Advantages of the invention

The according to the invention, one-sided sealable and one-sided matte film is characterized by a superb Sealability, a very good winding, a very good processing behavior and by a very good look. The sealable outer layer (A) seals against itself, against the matte topcoat (C) and against substrates made of APET or metal (e.g., aluminum, steel, painted steel, chromed or tinned steel) and the film is thus in many areas can be used such. B. as a cover sheet for (menu) shells, bags or as a cover layer on sheet metal or glass fiber reinforced Plates.

Also impressive the film through an advertising effective, matte surface (C) with high transparency. In addition, in the production of the film ensures that the waste material (Regenerat) in an amount in the range of up to 60 wt .-%, based on the total weight of the film, re-fed to the extrusion can, without losing the physical properties of the film are significantly negatively affected, especially their optical Appearance.

The Film is also very suitable for use in flexible packaging, especially where theirs excellent sealing properties and their good processability comes to fruition. This is especially their use on high-speed Packaging machines.

The The table below (Table 1) summarizes the most important film properties according to the invention once together.

For the characterization of the raw materials and the films were in the context of the present invention uses the following measurement methods:

Measurement of the mean particle diameter d ₅₀

The determination of the mean particle diameter d ₅₀ was carried out by laser on a Master Sizer (Malvern Instruments, UK) according to the standard method (other measuring devices are eg Horiba LA 500 (Horiba Ltd., Japan) or Helos (Sympatec GmbH, Germany), which is the use the same measuring principle). The samples were placed in a cuvette with water and then placed in the meter. The measuring process is automatic and includes the mathematical determination of the d ₅₀ value. By definition, the d ₅₀ value is determined from the (relative) cumulative curve of the particle size distribution: the point of intersection of the 50% ordinate value with the cumulative curve gives the desired d ₅₀ value on the abscissa axis (cf. 3 ).

Measurement of the SPAN 98

The determination of the SPAN 98 was carried out with the same measuring device as described in the determination of the mean diameter d ₅₀ . The SPAN 98 is defined as follows:

For the determination of d ₉₈ and d ₁₀ again the cumulative curve of the particle size distribution is used. The point of intersection of the 98% ordinate value with the cumulative curve gives the desired d ₉₈ value on the abscissa axis, and the point of intersection of the 10% ordinate value with the cumulative curve gives the desired d ₁₀ value on the abscissa axis (cf. 4 ).

Sealing seam strength (compared to APET)

To determine the seal seam strength, a foil strip (100 mm long x 15 mm wide) is placed on the APET side of a corresponding strip of a menu shell and at the set temperature of 140 ° C, a sealing time of 0.5 s and a sealing pressure of approx. 3 bar (sealing device HSG / ET from Bragger, Germany, both sides heated sealing jaw sealed). Corresponding 5 the sealed strips are clamped in the tensile testing machine (eg universal testing machine TC-FR1.0TH.D09 from Zwick, Germany) and the 180 ° seal strength, ie the force required to separate the test strips, with a take-off speed of 200 mm / min and a Test temperature of 23 ° C determined. The seal seam strength is given in N per 15 mm foil strip (eg 2 N / 15 mm).

Determination of minimum sealing temperature (across from APET)

With the sealing device HSG / ET from Bragger become, as before, in the measurement of the seal seam strength described, heat-sealed Samples (sealed seam 15 mm x 100 mm) are produced, with the film at different temperatures with the help of two heated sealing jaws at a sealing pressure of 3 bar and a sealing time of 0.5 s is sealed. The 180 ° seal strength was measured as in the determination of the seal seam strength. The minimum sealing temperature is the temperature at which a sealed seam strength of at least 0.5 N / 15 mm is reached (= sealing temperature).

Sealing seam strength against itself self (= FIN-seal)

to Determination of the seal seam strength two 15 mm wide film strips were superimposed and at 130 ° C, a sealing time of 0.5 s and a sealing pressure of 2 bar (device: Brugger Type NDS, one side heated sealing jaw) sealed. The seal seam strength was determined by the T-Peel method at 23 ° C = 2 x 90 °).

Determination of minimum sealing temperature across from oneself

With the sealing device HSG / ET from Brugger become heat-sealed samples (sealed seam 20 now × 100 mm), the film at different temperatures with the help of two heated sealing jaws at a sealing pressure of 2 bar and a sealing time of 0.5 s is sealed. From the sealed samples were test strips cut 15 mm wide. The T-seal strength was like measured in the determination of the seal strength. The minimum sealing temperature is the temperature at which a sealed seam strength of at least 0.5 N / 15 is reached now.

cloudiness

The cloudiness becomes according to ASTM D 1003 - 52 certainly.

shine

Of the Gloss is determined according to DIN 67530. The reflector value is measured as an optical parameter for the surface of a Foil. Based on the standards ASTM-D 523 - 78 and ISO 2813, the Beam angle with 20 ° (for glossy surfaces) or 60 ° (for matt Surfaces) set.

SV value (standard Viscosity)

The standard viscosity SV (DCE), based on DIN 53726, is measured at 25 ° C. in dichloroacetic acid. The intrinsic viscosity (IV) of polyethylene terephthalate is calculated from the standard viscosity as follows IV = [η] = 6.907 x 10 -4 SV (DCE) + 0.063096 [dl / g]

friction

The Friction was determined according to DIN 53 375. The sliding friction coefficient was Measured 14 days after production.

processing behavior the foil

+:

Das Verhalten der Folie ist einwandfrei. Es wurden z.B. keine Falten und keinen Blasen festgestellt.

-:

Das Verarbeitungsverhalten der Folie ist fehlerbehaftet. Es wurde mindestens einer der folgenden Fehler beobachtet: Falten oder Blasen.

The behavior of the film was visually evaluated by lamination on steel sheets.

+:

The behavior of the film is flawless. For example, no wrinkles and no bubbles were detected.

-:

The processing behavior of the film is faulty. At least one of the following errors was observed: wrinkles or blisters.

Tears in the film production

The Number of foil breaks per unit of time in production is compared with that in the production of foil according to the prior art and the percentage deviation is detected.

example 1

crisps of polyethylene terephthalate were at a temperature of 150 ° C to a Residual moisture dried below 100 ppm and the extruder for the base layer (B) supplied. Also chips were made of a polyester and polyethylene terephthalate containing silica particles dried as a pigment and the extruder for the matt top layer (C) fed.

Besides chips were made from a linear polyester, which consists of a amorphous copolyester with 78 mole% ethylene terephthalate and 22 mole% Ethylene isophthalate (prepared via the transesterification process with Mn as transesterification catalyst, Mn concentration: 100 ppm). The copolyester was at a temperature of 100 ° C to a residual moisture of below 200 ppm dried and the extruder for the sealable topcoat (A) supplied.

Then was by coextrusion and subsequent gradual orientation in longitudinal and transverse, a transparent, three-layer film with ABC structure and a total thickness of 25 μm produced. The thickness of the respective cover layers is the table 2 to remove.

Cover layer (A): 100.0% by weight Copolyester with an SV value of 800

Base layer (B): 100.0% by weight Polyethylene terephthalate with an SV value of 800

Cover layer (C): 70% by weight Copolyester (from 78 mol% terephthalic acid, 22 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia Fa. Fuji / Japan) with a d ₅₀ value of 3.4 microns and a SPAN 98 of 1.6 and a SV of 800. 30% by weight Polyethylene terephthalate 4023 from Invista, Germany with an SV value of 800

The production conditions in the individual process steps were:

The Film had the required low gloss, low haze and the good sealing properties. Furthermore, the film can be easily, i.e. without an increased Make number of breaks. The foil shows the desired handling and the desired one Processing performance. The film structure and the properties achieved thus produced films are shown in Tables 2 and 3.

Example 2

in the Compared to Example 1, the top layer thickness of the sealable layer (A) from 1.5 to 2.0 μm otherwise identical film structure and identical manufacturing method raised.

The Sealing properties have improved as a result, in particular the seal seam strength has become significantly larger.

Example 3

in the Compared to Example 1, the top layer thickness of the sealable layer (A) to 2.5 microns and that of the matte layer (C) raised to 2.0 microns. The sealing properties have thereby further improved, in particular, the seal seam strength become much bigger. The degree of matting of the film has tend to improve.

Example 4

in the Comparison to Example 1 now became the pigmentation of the matte Layer (C) changed and the top layer thickness of the matte layer (C) is raised to 2.0 μm. The degree of matting of the film has improved.

Cover layer (C): 80% by weight Copolyester (from 78 mol% terephthalic acid, 22 mol% isophthalic acid and 100 mol% ethylene glycol) and 5 wt .-% silica particles (Sylysia 430 from Fuji / Japan) with a d ₅₀ value of 3.4 microns and a SPAN 98 of 1.6 20% by weight Polyethylene terephthalate from Invista, Germany with an SV value of 800 and 5% by weight of silica particles (Sylysia 430 from Fuji / Japan) with a d ₅₀ value of 3.4 μm and a SPAN 98 of 1, 6

Comparative Example 1

Compared to Example 1, the sealable topcoat (A) has now been pigmented as follows: 80% by weight Copolyester with an SV value of 800 20% by weight Masterbatch of 99 wt .-% copolyester and 1.0 wt .-% Sylobloc 44 H (synthetic SiO ₂ from Grace)

The Winding and the processing properties of the film have become by this measure marginally improved, however, are the sealing properties and the Optics of the film have become significantly worse.

Comparative Example 2

It Example 1 from EP-A-0 035 835 was worked up. The sealing behavior, the appearance, the handling and the processing behavior of the film are worse than in the inventive examples.

Comparative Example 3

It Example 1 from EP-A-1 219 413 A1 was worked up. The sealing behavior, the appearance and the tear-off behavior during the production of the film is significantly worse than in the inventive examples become.

The The most important properties of the films thus produced are in the Tables 2 and 3 summarized below.

Claims (14)

A multi-layer, matte, single-side sealable, biaxially oriented polyester film having a base layer (B), a sealable top layer (A) which is on one surface of the base layer B, and a matte top layer (C) which overlies the other surface of the base layer B, wherein a) the sealable outer layer (A) contains less than 0.01% by weight of external particles (based on the total weight of the outer layer (A)) and b) the matt outer layer (C) has an i. Polyester containing from 6 to 30 mol% of isophthalic acid units (based on the total amount of acid of the polyester in this layer), and ii. contains a pigment characterized by the following features: the average diameter of the particles (d ₅₀ value) is in the range of 2 to 10 μm, the dispersion of the particle size distribution, expressed by the SPAN 98, is in the range of 1 , 2 to 2, and • the concentration of the particles is in the range of 1.0 to 7.0 wt .-% (based on the total weight of the outer layer (C)). Polyester film according to claim 1, characterized that the film is a cloudiness of less than 45%. Polyester film according to claim 1 or 2, characterized the base layer (B) contains a thermoplastic polyester Polyester film according to one or more of claims 1 to 3, characterized in that the polyester of the base layer (B) at least 90 mole% ethylene glycol and terephthalic acid units or ethylene glycol and naphthalene-2,6-dicarboxylic acid units. Polyester film according to one or more of claims 1 to 4, characterized in that as polyester of the base layer (B) Polyethylene terephthalate is used Polyester film according to one or more of claims 1 to 5, characterized in that the sealable cover layer (A) has a Contains copolyester, composed of ethylene terephthalate and ethylene euchphthalate units is. Polyester film according to one or more of claims 1 to 6, characterized in that the copolyester of the sealable cover layer (A) 60-95 Mole percent of ethylene terephthalate and 40-5 mole percent of ethylene anophthalate units having. Polyester film according to one or more of claims 1 to 7, characterized in that the pigment of the cover layer (C) SiO ₂ particles. Polyester film according to one or more of claims 1 to 8, characterized in that the sealable outer layer (A) no contains added particles. Polyester film according to one or more of claims 1 to 9, characterized in that the cover layer (A) has a thickness of 0.5 to 10 μm having. Polyester film according to one or more of claims 1 to 10, characterized in that the minimum sealing temperature of Covering layer (A) against an APET substrate 140 ° C or less. Polyester film according to one or more of claims 1 to 11, characterized in that the cover layer (A) has a gloss from bigger than 130 (measuring angle 20 °). A process for producing a polyester film according to one or more of claims 1 to 12, comprising the steps of a) producing a multilayer film by coextrusion, b) biaxially stretching the film and c) thermosetting the stretched film, wherein the polymer for the sealable top layer (A ) contains less than 0.01% by weight of external particles (based on the total weight of the outer layer (A)) and the matte outer layer (C) contains a polyester which 6 to 30 mol% of isophthalic acid units (based on the total amount of acid of the polyester in this layer) and contains a pigment system which is characterized by the following features: the average diameter of the particles (d ₅₀ value) is in the range from 2 to 10 μm, • the dispersion of the particle size distribution, expressed by the SPAN 98, is in the range of 1.2 to 2, and • the concentration of the particles is in the range of 1.0 to 7.0 wt .-% (based on the Total weight of the outer layer (C)). Use of a polyester film after one or several of the claims 1 to 12 as packaging film or laminating film against APET, CPET and metals.