WO1998005496A1

WO1998005496A1 - Multilayered crystallizable thermoplastic plate, process for its production and use thereof

Info

Publication number: WO1998005496A1
Application number: PCT/EP1997/003856
Authority: WO
Inventors: Ursula Murschall; Rainer Brunow
Original assignee: Aventis Research & Technologies Gmbh & Co Kg; Hostaglas Ltd.
Priority date: 1996-07-31
Filing date: 1997-07-18
Publication date: 1998-02-12
Also published as: DE19630597A1; EP0915756A1; AU4010997A; CA2262543A1

Abstract

A multilayered transparent amorphous thermoplastic plate with at least one central layer and at least one outer layer which are mainly composed of crystallizable thermoplastic. The thermoplastic of the central layer has a higher standard viscosity than the outer layer. The invention also relates to a method of manufacture for the above-mentioned plate as well as to its use. According to the invention the plate can also contain at least one additive such as ultra violet stabilizers, antioxidant agents and/or one anti-scratch coating on at least one side.

Description

Multi-layer sheet made of a crystallizable thermoplastic, process for its production and use

The invention relates to an amorphous, transparent, multilayer plate made of a crystallizable thermoplastic, the thickness of which is in the range from 1 to 20 mm. The invention further relates to a method for producing this plate and its use.

Multi-layer plates made of plastic materials are known per se.

Such plates made of branched polycarbonates are described in EP-A-0 247 480, EP-A-320 632 and US Pat. No. 5,108,835.

From DE-A-34 14 1 1 6 and US Pat. No. 4,600,632, UV-stabilized polycarbonate moldings are known which are composed of polydiorganosiloxane-polycarbonate block copolymers.

Multilayer plastic sheets are known from US Pat. No. 5,137,949, with layers of polydiorganosiloxane-polycarbonate block copolymers which contain UV absorbers. EP-A-0 416 404 discloses UV-stabilized, branched polycarbonates made from special diphenols. It is mentioned that such polycarbonates can be used for the production of plates or multi-wall sheets.

All of these plates are made of polycarbonate, an amorphous thermoplastic that cannot be crystallized. Polycarbonate sheets have the disadvantage that they often show efflorescence in the form of white spots and surface coverings, especially in the UV-stabilized embodiment (cf. EP-A-0 649 724). According to EP-A-0 649 724, for example, UV absorber evaporation is strongly linked to the average molecular weight. Furthermore, these PC boards are easily flammable and therefore require the addition of flame retardants in order to be used for certain purposes such as for indoor applications. In the further processing of these plates into molded parts, protracted pre-drying times and relatively long processing times at high temperatures are required. In addition, degassing extruders must be used in the manufacture of plates for the purpose of moisture removal, as a result of which the additives added to the raw material can also be removed, in particular if low-molecular, volatile additives are used.

The applicant has already described single-layer, transparent, amorphous plates with a thickness in the range from 1 to 20 mm, the main constituent of which is a crystallizable thermoplastic such as e.g. Contain polyethylene terephthalate (German Patent Application Nos. 19519579.5, 195221 18.4 and 19528336.8). These plates can have a standard viscosity of 800-6000 and contain a UV stabilizer.

EP-A-0 471 528 describes a method for molding an article from a polyethylene terephthalate (PET) plate. The PET sheet is heat-treated on both sides in a deep-drawing mold in a temperature range between the glass transition temperature and the melting temperature. The molded PET sheet is taken out of the mold when the degree of crystallization of the molded PET sheet is in the range of 25 to 50%. The PET sheets disclosed in EP-A-0 471 528 have a thickness of 1 to 10 mm. Since the deep-drawn molded article made from this PET sheet is partially crystalline and therefore no longer transparent and the surface properties of the molded article are determined by the deep-drawing process, the temperatures and shapes given, it is immaterial which optical properties (e.g. gloss, cloudiness and Light transmission) have the PET plates used. As a rule, they are optical properties of these plates poor and in need of optimization. These polyethylene terephthalate plates also have a single-layer structure.

US-A-3 496 143 describes the vacuum deep drawing of a 3 mm thick PET sheet, the crystallization of which is said to be in the range from 5 to 25%. The crystallinity of the deep-drawn molded body is greater than 25%. No demands are made on the optical properties of these PET sheets either. Since the crystallinity of the plates used is already between 5 and 25%, these plates are cloudy and opaque. These semi-crystalline PET sheets are also single-layer.

In Austrian Patent No. 304 086 a method for

Production of transparent moldings described by the deep-drawing process, using a PET plate or film with a as the starting material

Degree of crystallinity below 5% is used.

The plate or film used as the starting material has been produced from a PET with a crystallization temperature of at least 160 ° C. It follows from this relatively high crystallization temperature that this is not a PET homopolymer, but a glycol-modified PET, PET for short.

Called G, which is a PET copolymer.

In contrast to pure PET, PET-G shows due to the additional built-in

Glycol units have an extremely low tendency to crystallize and is usually in the amorphous state.

The object of the present invention is to provide a multilayer, amorphous, transparent plate with a thickness of 1 mm to 20 mm, which is characterized by good mechanical and optical properties.

Good optical properties include, for example, high light transmission, high surface gloss, extremely low haze and high image sharpness (clarity). The good mechanical properties include high impact strength and high breaking strength.

In addition, the plate according to the invention should be recyclable, in particular without loss of the mechanical properties, and also difficult to burn, so that it can also be used, for example, for interior applications and in trade fair construction.

This object is achieved by a multilayer, transparent, amorphous plate with a thickness of 1 to 20 mm, which contains a crystallizable thermoplastic as the main component, which is characterized in that the plate has at least one core layer and at least one cover layer and that the standard viscosity of the crystallizable thermoplastic of the core layer is higher than the standard viscosity of the crystallizable thermoplastic of the outer layer.

For the purposes of the present invention, amorphous plate is understood to mean plates which, although the crystallizable thermoplastic used preferably has a crystallinity of between 5 and 65%, are not crystalline. Not crystalline, i.e. essentially amorphous means that the degree of crystallinity is generally below 5%, preferably below 2% and particularly preferably 0% and that the plate has essentially no orientation.

According to the invention, crystallizable thermoplastic is understood to mean crystallizable homopolymers, crystallizable copolymers, crystallizable compounds, crystallizable recyclate and other variations of crystallizable thermoplastics. Examples of suitable thermoplastics are polyalkylene terephthalates with C1 to C1 2-alkylene radical, such as polyethylene terephthalate and polybutylene terephthalate, polyalkylene naphthalates with C1 to C12 alkylene radical, such as polyethylene naphthalate and polybutylene naphthalate, crystallizable cycloolefin polymers and cycloolefin copolymers, with the thermoplastic and the thermoplastic or the thermoplastic (en) or thermoplastic the thermoplastic or the thermoplastics for the cover layer (s) can be the same or different. Polyolefins have also proven suitable for the top layer.

Thermoplastics with a crystallite melting point T _m , measured with DSC (differential scanning calorimetry) with a heating rate of 10 ° C / min, from 220 ° C to 260 ° C, preferably from 230 ° C to 250 ° C, with a crystallization temperature range T _c between 75 ° C and 260 ° C, a glass transition temperature T _g between 65 ° C and 90 ° C and with a density, measured according to DIN 53479, of 1.30 to 1.45 g / cm ³ and a crystallinity between 5% and 65 % are preferred starting materials for the manufacture of the plate, polymers for the core layer and the top layer. For the purposes of the invention, a thermoplastic with a cold (post) crystallization temperature T _CN of 1 20 to 158 ° C, in particular 130 to 1 58 ° C, particularly preferred.

The bulk density, measured according to DIN 53466, is preferably between 0.75 kg / dm ³ and 1.0 kg / dm ³ , and particularly preferably between 0.80 kg / dm ³ and 0.90 kg / dm ³ .

The polydispersity of the thermoplastic M _w / M _n , measured by means of GPC, is preferably between 1.5 and 6.0 and particularly preferably between 2.0 and 5.0.

A particularly preferred crystallizable thermoplastic for the core layer (s) or the cover layer (s) is polyethylene terephthalate. The invention preferred polyethylene terephthalate consists essentially of monomer units of the following formula

It is essential to the invention that the thermoplastic or the thermoplastic of the core layer (s) has a higher standard viscosity than the thermoplastic or the thermoplastic of the outer layer (s). The standard viscosities of different core and / or outer layers of a multilayer plate can be different.

The standard viscosity SV (DCE) of the crystallizable thermoplastic of the core layer, measured in dichloroacetic acid according to DIN 53728, is preferably between 800 and 5000 and particularly preferably between 1000 and 4500.

The standard viscosity SV (DCE) of the crystallizable thermoplastic of the top layer, measured in dichloroacetic acid according to DIN 53728, is preferably between 500 and 4500 and particularly preferably between 700 and 4000.

The intrinsic viscosity IV (DCE) can be calculated from the standard viscosity SV (DCE) as follows:

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

The crystallizable thermoplastics used according to the invention can be obtained by customary processes known to the person skilled in the art.

In general, thermoplastics as used in the invention be obtained by melt polycondensation or by a two-stage polycondensation. The first step is carried out up to an average molecular weight - corresponding to an average intrinsic viscosity IV of about 0.5 to 0.7 - in the melt and the further condensation by means of solid condensation. The polycondensation is usually carried out in the presence of known polycondensation catalysts or catalyst systems. In solid condensation, chips made of the thermoplastic are heated to temperatures in the range from 180 to 320 ° C. under reduced pressure or under protective gas until the desired molecular weight is reached.

For example, the production of polyethylene terephthalate, which is particularly preferred according to the invention, is described in detail in a large number of patent applications, as in JP-A-60-139 71 7, DE-C-2 429 087, DE-A-27 07 491, DE-A-23 19 089, DE-A-1 6 94 461, JP-63-41 528, JP-62-39 621, DE-A-41 1 7 825, DE-A-42 26 737, JP- 60-141 715, DE-A-27 21 501 and US-A-5 296 586.

Polyethylene terephthalates with particularly high molecular weights can be e.g. by polycondensation of dicarboxylic acid diol precondensates (oligomers) at elevated temperature in a liquid heat transfer medium in the presence of conventional polycondensation catalysts and, if necessary, co-condensable modifiers if the liquid heat transfer medium is inert and free of aromatic components and a boiling point in the range from 200 to 320 ° C has, the weight ratio of dicarboxylic acid diol precondensate (oligomers) to liquid heat transfer medium is in the range from 20:80 to 80:20, and the polycondensation is carried out in the boiling reaction mixture in the presence of a dispersion stabilizer.

The multilayer, transparent, amorphous plate according to the invention can, if desired, also be equipped with suitable additives. This Additives can be added individually or as a mixture to one or more layers of the plate, as required.

Examples of suitable additives are UV stabilizers and antioxidants as described in German Patent Application No. 195 221 18.4 and the copending application by the same applicant with the title 'Polyethylene terephthalate plate with improved hydrolysis stability'. These applications are cited as part of the disclosure content of the present application.

As stated above, the multilayer, transparent, amorphous plate can additionally contain at least one UV stabilizer as light stabilizer in the top layer (s) and / or the core layer (s).

Light, especially the ultraviolet portion of solar radiation, i.e. the wavelength range from 280 to 400 nm initiate degradation processes in thermoplastics, as a result of which not only the visual appearance 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.

A high UV stability means that the plate is not or only slightly damaged by sunlight or other UV radiation, so that the plate is suitable for outdoor applications and / or critical indoor applications and shows little or no yellowing even after several years of outdoor use.

For example, polyethylene terephthalates start below 360 nm Absorbing UV light, its 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 acid are the predominant quantities of photo-oxidation products. In addition to the direct photolysis 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 splitting in the α-position of the ester groups (H. Day, D. M. Wiles: J. Appl. Polym. Sei 16, 1972, page 203).

UV stabilizers, also called light stabilizers or UV absorbers, are chemical compounds that can intervene in the physical and chemical processes of light-induced degradation.

Certain pigments such as Soot can partially protect against light. However, these substances are unsuitable for the transparent plates according to the invention, since they lead to discoloration or color change. For the amorphous plates according to the invention, only such UV stabilizers, e.g. from the class of organic and organometallic compounds used, which cause no or only an extremely small color or color change in the thermoplastic to be stabilized.

Examples of UV stabilizers suitable for the present invention are 2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organo-nickel compounds, salicylic acid esters, cinnamic acid ester derivatives, resorcinol monobenzoates, oxalic acid anilides, hydroxybenzoic acid esters, sterically hindered amines and triazines, with 2-hydroxybenzotriazoles and triazines being preferred.

Mixtures of several UV stabilizers can also be used.

The UV stabilizer is expediently present in a cover layer in a concentration of 0.01% by weight to 8% by weight, based on the weight of the thermoplastic in the cover layer provided with the stabilizer. However, the UV stabilizer can also be added to a core layer. In this case, a concentration of 0.01% by weight to 1% by weight, based on the weight of the thermoplastic in the core layer provided with the stabilizer, is sufficient.

According to the invention, several layers can be equipped with a UV stabilizer at the same time. In general, however, it is sufficient if the layer on which the UV radiation occurs is equipped.

The core layer (s) can be equipped in order to prevent UV radiation which occurs in the event of possible damage to the outer layer from affecting the underlying core layer.

In a particularly preferred embodiment, the transparent, amorphous plate according to the invention contains, as the main constituent, a crystallizable polyethylene terephthalate for the core layer and top layer and 0.01% to 8.0% by weight of 2- (4,6-diphenyl-1,3 , 5-triazin-2-yl) -5- (hexyl) oxyphenol or 0.01% by weight to 8.0% by weight of 2,2'-methylene-bis (6- (2H-benzotriazole- 2-yl) -4- (1, 1, 3,3-tetramethylbutyD-phenol in the top layer.

Of course, a mixture of these compounds and a mixture of at least one of these compounds with at least one other UV stabilizer can also be used.

The plate according to the invention can also be equipped with at least one antioxidant. Antioxidants are chemical compounds that can delay the signs of oxidation and hydrolysis and the resulting aging.

Antioxidants suitable for the plate according to the invention can be divided as follows:

Additive group Substance class primary antioxidants sterically hindered phenols and / or secondary, aromatic amines secondary antioxidants phosphites and phosphonites, thioethers, carbondiimides, zinc dibutyl dithiocarbamate

Mixtures of primary and secondary antioxidants and / or mixtures of secondary and / or primary antioxidants with UV stabilizers can also be used. Surprisingly, it has been found that such mixtures show a synergistic effect.

In a preferred embodiment, the amorphous plate according to the invention contains a phosphite and / or a phosphonite and / or a carbodiimide as a hydrolysis and oxidation stabilizer.

Examples of antioxidants used according to the invention are 2 - [(2, 4.8, 10-tetrakis (1, 1 -dimethylethyl) dibenzo [d, f] [1, 3.2] dioxaphosphepin-6-yl] oxy) - ethyljethanamine and Tris (2,4-di-tert-butylphenyl) phosphite.

The antioxidant is usually present in a concentration of 0.01 to 6% by weight, based on the weight of the thermoplastic of the layer provided with it. The thickness of the multilayer plate according to the invention varies between 1 mm and 20 mm, the thickness of the cover layer (s) depending on the plate thickness being between 10 μm and 1 mm. The cover layers preferably each have a thickness between 400 to 500 μm.

As already stated, the plate according to the invention can have a plurality of core and cover layers which are stacked on top of one another in a sandwich. However, the plate can also consist of only one cover layer and one core layer.

According to the invention, a structure with two cover layers and a core layer lying between the cover layers is particularly preferred.

The individual cover and core layers can contain different or identical crystallizable thermoplastics as main components, as long as the thermoplastic of a core layer has a higher standard viscosity than the thermoplastics of the cover layers directly adjacent to this core layer.

If desired, the transparent, amorphous, multilayer plate, which optionally contains one or more additives, can be provided on one or more sides with a scratch-resistant surface.

All systems and materials known to the person skilled in the art are suitable as coating systems and materials for the scratch-resistant surface (coating).

Suitable coating systems and materials are described in particular in the applicant's German Patent Application No. 196 255 34.1, to which reference is made in full for the present invention.

Some of the large number of possible coating systems and materials are mentioned below. (1) US-A-4822828 discloses aqueous radiation-curable coating compositions which, each based on the weight of the dispersion, (A) from 50 to 85% of a silane with vinyl groups, (B) from 15 to 50% of a multifunctional Acrylates and optionally (C) 1 to 3% of a photoinitiator.

(2) Also known are inorganic / organic polymers, so-called Ormocere (Organically Modified Ceramics), which combine properties of ceramic materials and polymers. Ormocers are used in particular as hard and / or scratch-resistant coatings on polymethyl methacrylate (PMMA) and polycarbonate (PC). The hard coatings are bound on the basis of Al ₂ O ₃ , ZrO ₂ , TiO ₂ or SiO ₂ as network formers and epoxy or methacrylate groups with Si through ≡Si-C≡ connections.

(3) Coating agents for acrylic resin plastics and polycarbonate based on silicone resin in aqueous-organic solution, which have a particularly high storage stability, are e.g. in EP-A-0 073 362 and EP-A-0 073 91 1. This technique uses the condensation products of partially hydrolyzed organosilicon compounds as coating agents, especially for glass and especially for acrylic resin plastics and PC.

(4) Acrylic coatings such as e.g. the Uvecryl products from UCB Chemicals. One example is the Uvecryl 29203, which is hardened with UV light. This material consists of a mixture of urethane acrylate oligomers with monomers and additives. Ingredients are approximately 81% acrylate oligomers and 19% hexanediol diacrylate. These coatings are also described for PC and PMMA.

(5) Also in the literature are CVD or PVD coating technologies with the help of a polymerizing plasma as well as diamond-like ones Coatings described (thin-film technology, edited by Dr. Hartmut Frey and Dr. Gerhard Kienel, VDI Verlag, Düsseldorf, 1987). These technologies are used here in particular for metals, PC and PMMA.

Other commercially available coatings are e.g. Peeraguard from Peerless, Clearlite and Filtalite from Charvo, coating types such as the UVHC series from GE Silicones, Vuegard such as the 900 series from TEC Electrical Components, from the Societέ Francaise Hoechst Highlink OG series, PPZ products sold by Siber Hegner (manufactured by Idemitsu) and coating materials from Vianova Resins, Toagoshi, Toshiba or Mitsubishi. These coatings are also described for PC and PMMA.

Coating methods known from the literature are e.g. Offset printing, pouring, dipping, flooding, spraying or spraying, knife coating or rolling.

Coatings applied by the described methods are then cured, for example by means of UV radiation and / or thermally. In the coating processes it may be advantageous to coat the surface to be coated with a primer, e.g. based on acrylate or acrylic latex.

Other known methods include:

CVD processes or vacuum plasma processes, e.g. Vacuum plasma polymerization, PVD processes, such as coating with electron beam evaporation, resistance-heated evaporator sources or coating by conventional processes in high vacuum, such as in a conventional metallization.

Literature on CVD and PVD is for example: Modern coating processes by H.-D. Steffens and W. Brandl. DGM Information Society Verlag Oberursel. Other literature on coatings: Thin Film Technology by L. Maissei, R. Glang, McGraw-Hill, New York (1983).

Coating systems which are particularly suitable for the purposes of the present invention are systems (1), (2), (4) and (5), with coating system (4) being particularly preferred.

Suitable coating processes are e.g. also the casting, the spraying, the spraying, the immersion and the offset method, the spraying method being preferred for the coating system (4).

When coating the amorphous plates, curing can take place with UV radiation and / or at temperatures which preferably do not exceed 80 ° C., UV curing being preferred.

The coating according to system (4) has the advantage that there is no crystallization which could cause turbidity. Furthermore, the coating shows excellent adhesion, excellent optical properties, very good chemical resistance and does not impair the intrinsic color.

The thickness of the scratch-resistant coating is generally between 1 and 50 μm.

The amorphous plate according to the invention, which contains a crystallizable thermoplastic such as PET as the main component, has excellent mechanical and optical properties. Thus, when measuring the impact strength a _n according to Charpy (measured according to ISO 179/1 D), preferably no breakage occurs on the plate. In addition, the notched impact strength a _k according to Izod (measured according to ISO 180/1 A) of the plate is preferably in the range from 2.0 to 8.0 kJ / m ² , particularly preferably in the range from 4.0 to 6.0 kJ / m ² . The image sharpness of the plate, which is also called Clarity and which is determined at an angle of less than 2.5 ° (ASTM D 1003), is preferably above 95% and particularly preferably above 96%.

The surface gloss, measured in accordance with DIN 67530 (measuring angle 20 °), is greater than 110, preferably greater than 120, the light transmission, measured in accordance with ASTM D 1003, is more than 80%, preferably more than 84%, and the turbidity of the plate, measured according to ASTM D 1003 is less than 15%, preferably less than 11%.

Weathering tests have shown that the UV-stabilized plate according to the invention has no visible yellowing and no visible loss of gloss and no visible surface defects even after 5 to 7 years of outdoor use.

In addition, the plate according to the invention is flame-retardant and does not drip off with very little smoke, so that it is also particularly suitable for indoor applications and trade fair construction.

Furthermore, the plate according to the invention can be easily recycled without any environmental pollution and loss of mechanical properties, which is why it is suitable, for example, for the production of short-lived advertising signs or other promotional items.

In addition, an excellent and economical thermoforming behavior (thermoforming and vacuum forming behavior) was found completely unexpectedly. Surprisingly, in contrast to polycarbonate sheets, it is not necessary to predry the sheet according to the invention before thermoforming. Polycarbonate sheets, for example, have to be pre-dried at approx. 125 ° C for 3 to 50 hours, depending on the sheet thickness, before thermoforming. In addition, the plate according to the invention can be obtained with very short thermoforming cycle times and at low temperatures during thermoforming. Because of these properties, moldings can be produced economically and with high productivity from the plate according to the invention on conventional thermoforming machines.

The multilayered, transparent, amorphous plate according to the invention, optionally equipped with one or more additives, can be produced in an extrusion line, for example, by the coextrusion process known per se.

An extruder for plasticizing and producing the core layer and an additional extruder per cover layer are connected to each coextruder adapter. The adapter is constructed in such a way that the, possibly UV-stabilized, melts forming the cover layers are adhered as thin layers to the melt of the core layer. The multilayer melt strand produced in this way is then shaped in the subsequently connected nozzle and calibrated, smoothed and cooled in the smoothing unit before the plate is cut to length.

The process for producing the plates according to the invention is explained in general below.

If necessary, the thermoplastic polymer can be dried before coextrusion.

The drying can expediently take place at temperatures in the range from 110 to 190 ° C. over a period of from 1 to 7 hours. The main dryer is connected to the main extruder and one dryer is connected to one coextruder per top layer.

Thereafter, the thermal load for the core layer (s) and the Cover layer (s) melted in the main extruder and in the coextrudes. The temperature of the melt is preferably in the range from 230 to 330 ° C, the temperature of the melt being able to be set essentially both by the temperature of the extruder and by the residence time of the melt in the extruder.

If the polyethylene terephthalate preferred according to the invention as the thermoplastic is used, it is usually dried for 4 to 6 hours at 160 to 180 ° C. and the temperature of the melt is set in the range from 250 to 320 ° C.

If an additive such as a UV stabilizer and / or an antioxidant is used, these can be metered in at the raw material manufacturer or metered into the extruder during plate production.

Addition via masterbatch technology is particularly preferred. The additives are fully dispersed in a solid carrier material. Suitable carrier materials are certain resins, the thermoplastic itself or other polymers which are sufficiently compatible with the thermoplastic.

It is important that the grain size and bulk density of the masterbatch are similar to the grain size and bulk density of the thermoplastic, so that a homogeneous distribution and thus a homogeneous effect of the additives, e.g. UV and hydrolysis stabilization can take place.

As already stated above, the main extruder for producing the core layer and the co-extruder or co-extruders are connected to a co-extruder adapter in such a way that the melts forming the outer layers are adhered as thin layers to the melt of the core layer. The multilayer melt strand thus produced is shaped in a connected nozzle. This nozzle is preferably a slot die. The multi-layer melt strand formed by a slot die is then calibrated by smoothing calender rolls, ie intensively cooled and smoothed. The calender rolls used can, for example, be arranged in an I, F, L or S shape.

The material can then be cooled on a roller conveyor, cut to the side, cut to length and stacked.

The thickness of the plate obtained is essentially determined by the take-off which is arranged at the end of the cooling zone, the cooling (smoothing) rolls coupled to it in terms of speed and the conveying speed of the extruder on the one hand and the distance between the rolls on the other hand.

Both single-screw and twin-screw extruders can be used as extruders.

The slot die preferably consists of the dismantled tool body, the lips and the control bar for flow regulation across the width. To do this, the control bar can be bent using tension and compression screws. The thickness is adjusted by adjusting the lips. It is important to ensure that the temperature of the multilayer melt strand and the lip is uniform, otherwise the melt strand will flow out to different thicknesses through the different flow paths.

The calibration tool, ie the smoothing calender, gives the melt strand the shape and dimensions. This is done by freezing below the glass transition temperature by cooling and smoothing. In this state, no more deformation should take place, as otherwise surface defects would occur due to the cooling. For this reason, the calender rolls are preferably driven together. The temperature of the calender rolls must be avoided to prevent the melt strand from sticking be less than the crystallite melting temperature. The melt strand leaves the slot die preferably at a temperature of 240 to 300 ° C. The first smoothing-cooling roller has a temperature between 50 ° C and 80 ° C depending on the output and plate thickness. The second, somewhat cooler roller cools the second or other surface.

In order to obtain a uniform thickness in the range from 1 to 20 mm with good optical properties, it is essential that the temperature of the first smoothing roll is 50 to 80 ° C.

While the calibration device freezes the surfaces of the plate as smoothly as possible and cools the profile to such an extent that it is dimensionally stable, the post-cooling device lowers the temperature of the plate to almost room temperature. After-cooling can be done on a roller board.

The speed of the take-off should be exactly matched to the speed of the calender rolls in order to avoid defects and thickness fluctuations.

A separating saw as a cutting device, the side trimming, the stacking system and a control point can be located in the extrusion line for producing the plates according to the invention as additional devices. The side or edge trimming is advantageous because the thickness in the edge area can be uneven under certain circumstances. The thickness and appearance of the plate are measured at the control point.

Due to the surprising number of excellent properties, the transparent, amorphous plate according to the invention is excellently suitable for a variety of different applications, for example for interior cladding, for trade fair construction and trade fair items, as displays, for signs, in the lighting sector, in shop and shelf construction, as promotional items, as Menu card stand, as Basketball goal boards, as room dividers, as aquariums, as information boards, as brochure and newspaper stands as well as for outdoor applications such as greenhouses, canopies, outer cladding, covers, for applications in the construction sector, illuminated advertising profiles, balcony cladding and roof hatches.

The invention is explained in more detail below on the basis of exemplary embodiments, without being restricted thereby.

The individual properties are measured according to the following standards and procedures.

Measurement methods

Surface gloss:

The surface gloss is measured at a measuring angle of 20 ° according to DIN 67530. The reflector value is measured as an optical parameter for the surface of a plate. Based on the standards ASTM-D 523-78 and ISO 2813, the angle of incidence was set at 20 °. A light beam hits the flat test surface at the set angle of incidence and is reflected or scattered by it. The light rays striking the photoelectronic receiver are displayed as a proportional electrical quantity. The measured value is dimensional and must be specified together with the angle of incidence.

Light transmission:

Under the light transmission is the ratio of the total let through

To understand light to the incident amount of light.

The light transmission is measured with the "Hazegard plus" measuring device in accordance with ASTM D 1003. Turbidity and Clarity:

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 and clarity are measured using the "Hazegard plus" measuring device in accordance with ASTM D 1003.

Surface defects:

The surface defects are determined visually.

Charpy impact strength a _n:

This size is determined according to ISO 179/1 D.

Notched impact strength a _k according to Izod:

The impact strength or strength a _k according to Izod is measured according to ISO 1 80/1 A.

Density:

The density is determined according to DIN 53479.

SV (DCE), IV (DCE):

The standard viscosity SV (DCE) is based on DIN 53728 in

Dichloroacetic acid measured.

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

IV (DCE) = 6.67 -10 ^"4 SV (DCE) + 0, 1 1 8

Thermal properties: The thermal properties such as crystallite melting point T _m , crystallization temperature range T _c , post- (cold) crystallization temperature T _CN and glass transition temperature T _g are measured by differential scanning calorimetry (DSC) at a heating rate of 10 ° C / min.

Molecular weight, polydispersity:

The molecular weights M _w and M _n and the resulting polydispersity M _w / M _n are measured by means of gel permeation chromatography (GPC).

Weathering (both sides), 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. 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 again 102 minutes of UV light, etc.

Color change:

The color change of the samples after artificial weathering is measured with a spectrophotometer according to DIN 5033.

The following applies:

ΔL: difference in brightness

+ ΔL: The sample is lighter than the standard -ΔL: The sample is darker than the standard

ΔA: difference in the red-green area

+ ΔA: The sample is redder than the standard -ΔA: The sample is greener than the standard

ΔB: difference in the blue-yellow range

+ ΔB: The sample is yellower than the standard -ΔB: The sample is bluer than the standard

ΔE: total color change

The greater the numerical deviation from the standard, the greater the

Color difference.

Numerical values of ≤ 0.3 are negligible and mean that there is no significant color change.

Yellowness index:

The yellowness index G is the deviation from the colorlessness in the "yellow" direction and is measured in accordance with DIN 6167. Yellow value G values of ≤ 5 are not visually visible.

The examples and comparative examples below are each transparent sheets of different thicknesses which are produced on the extrusion line described. Example 1 :

A 4 mm thick, multilayer, transparent, amorphous polyethylene terephthalate plate with the layer sequence ABA is produced by the described coextrusion process, B representing the core layer and A the top layer. The core layer B is 3.5 mm thick and the two outer layers that cover the core layer are each 250

thick.

The polyethylene terephthalate used for the core layer B has the following properties:

SV (DCE) 1 100

IV (DCE) 0.85 dl / g

Density 1.38 g / cm ³

Crystallinity 44%

Crystallite melting point T _m 245 ° C

Crystallization temperature range T _c 82 ° C to 245 ° C

Post (cold) crystallization temperature T _CN 1 52 ° C

Polydispersity M _w / M ₂ 2.02

Glass transition temperature 82 ° C

The main layers A contain polyethylene terephthalate and 3.0 wt .-% of the UV stabilizer 2- (4,6-diphenyl-1, 3,5-triazin-2-yl) -5- (hexyloxyphenol ( ^® Tinuvin 1577 or Ciba-Geigy).

Tinuvin 1577 has a melting point of 140 ° C and is thermally stable up to approx. 330 ° C.

In order to ensure a homogeneous distribution, 3.0% by weight of the UV stabilizer is incorporated into the polyethylene terephthalate directly at the raw material manufacturer. The polyethylene terephthalate from which the outer layers are made has a standard viscosity SV (DCE) of 1010, which corresponds to an intrinsic viscosity IV (DCE) of 0.79 dl / g. The moisture content is <0.2% and the density (DIN 53479) is 1.41 g / cm ³ . The crystallinity is 59%, the crystallite melting point according to DSC measurements being 259 ° C. The crystallization temperature range T _c is between 83 ° C and 258 ° C, the post-crystallization temperature (also cold crystallization temperature) T _CN at 144 ° C. The polydispersity M _w / M _{n of} the polyethylene terephthalate is 2.14. The glass transition temperature is 83 ° C.

Before coextrusion, the polyethylene terephthalate for the core layer and the UV-stabilized polyethylene terephthalate for the outer layers are each dried in a dryer at 170 ° C. for 5 hours and then coextruded through a slot die onto a smoothing calender, the rollers of which are arranged in an S-shape, and into one three-layer, 4 mm thick plate smoothed.

The extrusion temperature of the main extruder for the core layer is 282 ° C. The extrusion temperatures of the two coextruders for the cover layers are 294 ° C. The first calender roll has a temperature of 65 ° C and the subsequent rolls each have a temperature of 58 ° C. The speed of the trigger is 4.2 m / min.

Following the after-cooling, the three-layer transparent plate is lined with cut-off saws on the edges, cut to length and stacked.

The transparent, amorphous, three-layer PET sheet obtained has the following property profile

Layer structure A-B-A

Overall thickness 4 mm

Core layer thickness 3.5 mm Thickness of the outer layer each 0.25 mm

Surface gloss 1. Page 1 85

(Measuring angle 20 °) 2nd page 183

Light transmission 93.6%

Clarity 100%

Turbidity 0.7%

Surface defects per m ² none

(Specks, orange peel, blisters, etc.)

Charpy impact strength a _n no break

Notched impact strength a _k according to Izod good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

After 1000 hours of weathering per side with the Atlas Ci 65 Weather Ometer, the PET plate shows the following properties:

Overall thickness 4 mm

Surface gloss 1. Page 1 66 (measuring angle 20 °) 2. Page 1 64 Light transmission 91, 1% Clarity 100% turbidity 1, 2%

Total discoloration ΔE 0.22 Dark discoloration ΔL -0, 18 red-green discoloration ΔA -0.08 Blue-yellow discoloration ΔB 0, 10 surface defects none (cracks, embrittlement) yellowness index G Example 2:

Analogously to Example 1, a 4 mm thick, transparent, three-layer PET sheet is produced.

The core layer B consists of 50% of the polyethylene terephthalate

Example 1 and from 50% recycled plate from Example 1 together.

The transparent PET sheet obtained has the following property profile:

Overall thickness 4 mm

Surface gloss 1. Page 172

(Measuring angle 20 °) 2nd page 1 70

Light transmission 92.1%

Clarity 99.8%

Turbidity 2.0%

Surface defects per m ² none

(Specks, orange peel, blisters, etc.)

Charpy impact strength a _n no break

Notched impact strength a _k according to Izod 4.6 kJ / m ²

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

After 1000 hours of weathering with Atlas Ci 65 Weather Ometer, the PET panel shows the following properties:

Overall thickness 4 mm

Surface gloss 1. Page 1 58

(Measuring angle 20 °) 2nd page 1 54

Light transmission 91.1%

Clarity 99.4%

Turbidity 2.9% Total discoloration ΔE 0.24 dark discoloration ΔL -0, 19 red-green discoloration ΔA -0.08 blue-yellow discoloration ΔB 0.1 2 surface defects no yellowness index G 4

Example 3:

Analogous to Example I, a three-layer, transparent, amorphous 6 mm thick

Plate made.

The cover layers contain 3.5% by weight of the UV stabilizer 2,2'-methylene-bis- (6- (2H-benzotriazol-2-yl) -4- (1, 1, 3,3-tetramethylbutyl) - phenol ( ^® Tinuvin 360 from Ciby-Geigy), based on the weight of the thermoplastic

Top layers.

Tinuvin 360 has a melting point of 195 ° C and is thermally stable up to approx. 250 ° C.

As in Example 1, 3.5% by weight of the UV stabilizer is incorporated directly into the polyethylene terephthalate at the raw material manufacturer.

The first calender roll has a temperature of 59 ° C and the subsequent rolls have a temperature of 51 ° C. The speed of the trigger is 2.5 m / min.

The transparent PET sheet obtained has the following property profile:

Layer structure A-B-A

Thickness of the outer layers each 0.4 mm

Core layer thickness 5.2 mm

Overall thickness 6 mm Surface gloss 1. Page 1 65

(Measuring angle 20 °) 2nd page 163

Light transmission 89.1%

Clarity 99.6%

Turbidity 2.4%

Surface defects per m ² none

(Specks, orange peel, blisters, etc.)

Impact strength a _π according to Charpy no break

Notched impact strength a _k according to Izod 4.9 U / m ²

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

Thickness 6 mm

Surface gloss 1. Page 1 51 (measuring angle 20 °) 2. Page 150 Light transmission 88.3% Clarity 99.5% Haze 3.1%

Total discoloration ΔE 0.56 dark discoloration ΔL -0.21 red-green discoloration ΔA -0.1 1 blue-yellow discoloration ΔB + 0.51 surface defects none (cracks, embrittlement) yellowness index G Example 4:

Analogously to example 1, a three-layer, transparent PET sheet is produced. As in Example 3, the top layers contain 3.5% by weight of Tinuvin 360 as UV stabilizer, based on the weight of the thermoplastic of the top layer, which has been incorporated directly at the raw material manufacturer. The polyethylene terephthalate used for the core layer has the following properties:

SV (DCE) 3173

IV (DCE) 2.23 dl / g

Density 1.34 g / cm ³

Crystallinity 1 1 2%

Crystallite melting point T _m 240 ° C

Crystallization temperature range T _c 82 ° C to 240 ° C

After (-cold) crystallization temperature T _CN 1 56 ° C

Polydispersity M _w / M _n 3.66

Glass transition temperature 82 ° C

Mw 204 660 g / mol M "55 952 g / mol

The polyethylene terephthalate for the top layers is the same as in Example 1. The extrusion temperature is 274 ° C. The first calender roll has a temperature of 50 ° C and the subsequent rolls have a temperature of 45 ° C. The speed of the take-off and the calender rolls is 2.4 m / min.

The plate produced has the following property profile:

Layer structure A-B-A

Thickness of the outer layers 0.4 mm

Core layer thickness 5.2 mm

Overall thickness 6 mm Surface gloss 1. Page 162

(Measuring angle 20 °) 2nd page 1 59

Light transmission 89.3%

Clarity 99.3%

Turbidity 2.2%

Surface defects per m ² none

(Specks, orange peel, blisters, etc.)

Charpy impact strength a _n no break

Notched impact strength a _k acc. To Izod 5, 1 kJ / m ²

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

After 1000 hours of weathering with the Atlas Ci 65 Weather Ometer, the PET panel shows the following properties:

Thickness 6 mm

Surface gloss 1. Page 1 50 (measuring angle 20 °) 2. Page 149 Light transmission 86.2% Clarity 99, 1% haze 3.2%

Total discoloration ΔE 0.47 Dark discoloration ΔL -0, 18 red-green discoloration ΔA -0.09 Blue-yellow discoloration ΔB + 0.42 Surface defects none (cracks, embrittlement) yellowness index G Comparative example:

Analogous to example 1, a transparent, amorphous plate is produced. In contrast to example 1, the plate contains no UV stabilizer. The polyethylene terephthalate used, the extrusion parameters, the process parameters and the temperatures are chosen as in Example 1.

The transparent, amorphous, three-layer board produced has the following property profile:

Layer structure A-B-A

Base layer thickness 3.5 mm

Thickness of the outer layers each 0.25 mm

Overall thickness 4 mm

Surface gloss 1. Page 189

(Measuring angle 20 °) 2nd page 185

Light transmission 93.8%

Clarity 100%

Turbidity 0.8%

Surface defects per m ² none

(Specks, orange peel, blisters, etc.)

Charpy impact strength a _n no break

Notched impact strength a _k according to Izod 4.6 kJ / m ²

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

Total thickness 4 mm surface gloss 1. Page 98 (Measuring angle 20 °) 2nd side 95 light transmission 79.5% Clarity 81, 2% haze 7.8%

Total discoloration ΔE 3.41 dark discoloration ΔL -0.29 red-green discoloration ΔA -0.87 blue-yellow discoloration ΔB + 3.29 surface defects embrittlement (cracks, embrittlement) yellowness index G 1 7

Claims

claims

1 . Multilayer, transparent, amorphous plate with a thickness in the range from 1 to 20 mm, which contains a crystallizable thermoplastic as the main component, characterized in that it has a multilayer structure comprising at least one core layer and at least one top layer, the standard viscosity being that in the core layer containing thermoplastics is greater than the standard viscosity of the thermoplastic contained in the cover layer.

2. The plate of claim 1, wherein the standard viscosity of the thermoplastic of the at least one core layer is in the range from 800 to 5000 and that of the thermoplastic of the at least one cover layer is in the range from 500 to 4500.

3. Plate according to claim 1 or 2, wherein the plate has two cover layers and a core layer lying between the cover layers.

4. Plate according to one of the preceding claims, wherein at least one of the core and / or cover layer (s) is equipped with at least one UV stabilizer.

5. Plate according to claim 4, wherein the concentration of the UV stabilizer in a layer is 0.01 to 8 wt .-%, based on the weight of the thermoplastic of the layer containing the UV stabilizer.

6. Plate according to claim 4 or 5, wherein the concentration of the UV stabilizer in the at least one core layer is 0.01 to 1 wt .-%, based on the weight of the thermoplastic of the core layer containing the UV stabilizer.

7. Plate according to one of claims 4 to 6, wherein the UV stabilizer is selected from 2-hydroxybenzotriazoles, triazines and mixtures thereof.

8. Plate according to claim 7, wherein the UV stabilizer is selected from 2- (4,6-diphenyl-1, 3,5-triazin-2-yl) -5- (hexyl) oxyphenol and 2,2'-methylene -bis (6- (2H-benzotriazol-2-yl) -4- (1, 1, 3,3-tetramethylbutyl) phenol.

9. Plate according to one of the preceding claims, wherein at least one of the core and / or outer layers is equipped with at least one antioxidant.

10. Plate according to claim 9, wherein the antioxidant is present in a concentration of 0.1 to 6% by weight, based on the weight of the thermoplastic of the layer provided with it.

1 1. Plate according to claim 9 or 10, wherein the at least one antioxidant is selected from sterically hindered phenols, secondary, aromatic amines, phosphites, phosphonites, thioethers, carbondiimides and zinc dibutyldithiocarbamate.

1 2. plate according to claim 1 1, wherein the antioxidant 2- [2, 4,8,10- tetrakis (1, 1 -dimethylethyl) dibenzo [d, f] I1, 3,2] dioxaphosphepin-6-yl] oxy ) - ethyljethanamine and / or tris (2,4-di-tert-butylphenyl) phosphite.

1 3. plate according to any one of the preceding claims, wherein the crystallizable thermoplastic is selected from polyalkylene terephthalate with C1 to C12 alkylene radical, polyalkylene naphthalate with C1 to C1 2 alkylene radical, a cycloolefin polymer and a cycloolefin copolymer.

14. The plate of claim 13, wherein the alkylene radical is ethylene or butylene.

15. The plate of claim 13, wherein the thermoplastic is polyethylene terephthalate.

16. The plate of claim 13 to 1 5, wherein the thermoplastic contains a recyclate of the thermoplastic.

17. Plate according to one of the preceding claims, wherein the thermoplastic has a crystallite melting point, measured with DSC at a heating rate of 10 ° C / min. , in the range of 220 to 280 ° C.

18. Plate according to one of the preceding claims, wherein the thermoplastic has a crystallization temperature, measured by DSC with a heating rate of 10 ° C / min., In the range from 75 to 280 ° C.

19. Plate according to one of the preceding claims, wherein the thermoplastic used has a crystallinity which is in the range from 5 to 65.

20. Plate according to one of the preceding claims, wherein the thermoplastic used has a cold (post) crystallization temperature T _CN in a range from 1 20 to 1 58 ° C.

21. Plate according to one of the preceding claims, wherein the plate has a surface gloss, measured according to DIN 67530 (measuring angle 20 °), of greater than 1 10.

A plate according to any one of the preceding claims, wherein the plate has a light transmission, measured according to ASTM D 1003, of more than 80%.

23. Plate according to one of the preceding claims, wherein the haze of the plate, measured according to ASTM D 1003, is less than 15%.

24. Plate according to one of the preceding claims, wherein no fracture occurs when measuring the impact strength according to Charpy a _n , measured according to ISO 179/1 D.

25. Plate according to one of the preceding claims, wherein the plate has a notched impact strength a _k according to Izod, measured according to ISO 180/1 A, in the range from 2.0 to 8.0 / m ² .

26. Plate according to one of the preceding claims, wherein the plate has an image sharpness, measured according to ASTM D 1003 at an angle less than 2.5 °, is over 95%.

27. Plate according to one of the preceding claims, wherein the plate has a scratch-resistant coating on at least one side.

28. The plate of claim 27, wherein the scratch-resistant coating contains silicon and / or acrylic.

29. A method for producing a multilayer, transparent, amorphous plate according to one of the preceding claims, wherein the thermoplastic for the at least one core layer is melted in a main extruder and the thermoplastic for the at least one cover layer in a coextruder, the melts are stacked on top of one another and the merged Layers are formed through a nozzle and then calibrated, smoothed and cooled in the smoothing unit with at least two rollers, the temperature of the first roller of the smoothing unit being in a range of 50-80 ° C.

30. The method according to claim 29, wherein at least one additive is melted together with the thermoplastic of the layer to be treated with additive.

31 The method of claim 29 or 30, wherein the thermoplastic is a polyalkylene terephthalate or polyalkylene naphthalate.

32. The method of claim 31, wherein the polyalkylene terephthalate or polyalkylene naphthalate is dried for 4 to 6 hours at 160 to 180 ° C before extrusion.

33. The method according to any one of claims 31 or 32, wherein the temperature of the polyalkylene terephthalate or polyalkylene naphthalate melt is in the range of 250 to 320 ° C.

34. The method according to any one of claims 29 to 33, wherein the at least one additive is added via the masterbatch technology.

35. Use of a multi-layer, transparent, amorphous plate according to one of the preceding claims for outdoor and indoor use