EP0915757A1

EP0915757A1 - Multilayered, transparent coloured plate made of a crystallising thermoplastic material, process for producing the same and its use

Info

Publication number: EP0915757A1
Application number: EP97934486A
Authority: EP
Inventors: Ursula Murschall; Rainer Brunow
Original assignee: Hostaglas Ltd
Current assignee: Hostaglas Ltd
Priority date: 1996-07-31
Filing date: 1997-07-18
Publication date: 1999-05-19
Also published as: WO1998005498A1; DE19630598A1; CA2261716A1; AU3768197A

Abstract

A multilayered, transparent coloured amorphous plate with 1 to 20 mm thickness contains a crystallising thermoplastic material as its main component and a dye which is soluble in the thermoplastic material. The plate consists of at least one covering layer and at least one core layer, the standard viscosity of the thermoplastic material of which the core layer is made being higher than that of the thermoplastic material of the adjacent covering layer(s).

Description

Multi-layer, transparent colored plate made of a crystallizable thermoplastic, process for its production and use

The invention relates to an amorphous, transparently colored 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 sheets of branched polycarbonates are described in EP-A-0 247 480, EP-A-320 632 and US Pat. No. 5,108,835.

DE-A-34 14 116 and US Pat. No. 4,600,632 disclose UV-stabilized polycarbonate moldings which are composed of polydiorganosiloxane-polycarbonate block copolymers.

Multilayer plastic sheets are known from US Pat. No. 5,137,949, with layers of polydiorganosiioxane-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-0649 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 sheets into molded parts, lengthy 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, transparently colored 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 and at least one dye soluble in this thermoplastic (German Patent Application Nos. 19519578.7, 19522120.6 and 19528334.1). These plates can have a standard viscosity of 800-6000 and contain a UV stabilizer. It goes without saying that the plates, starting materials, additives and processes described there can in principle also be used for the present invention, so that these applications belong to the disclosure content of the present application by quotation.

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-0471 528 have a thickness of 1 to 10 mm. Since the deep-drawn molded article made from this PET sheet is semi-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, haze and light transmission) ) have the PET sheets used. Usually the optical properties of these plates are poor and need to be optimized. These polyethylene terephthalate plates also have a single-layer structure and are also not colored.

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.

The Austrian patent specification No. 304 086 describes a process for the production of transparent moldings by the deep-drawing process, a PET plate or film with a degree of crystallinity below 5% being used as the starting material.

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 rather a glycol-modified PET, or PET-G for short, which is a PET copolymer.

In contrast to pure PET, PET-G shows an extremely low tendency to crystallize due to the additional built-in glycol units and is usually in the amorphous state.

The object of the present invention is to provide a multilayer, amorphous, transparently colored 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 colored 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 that the standard viscosity of the crystallizable thermoplastic of the core layer is higher than the standard viscosity of the thermoplastic of the top layer and that at least one layer of the plate contains at least one dye which is soluble in the thermoplastic of this 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 C12 alkylene radical, such as polyethylene terephthalate and polybutylene terephthalate, Polyalkylene naphthalates with C1 to C12 alkylene radical, crystallizable cycloolefin polymers and cycloolefin copolymers, it being possible for the thermoplastic or the thermoplastics for the core layer (s) and the thermoplastic or the thermoplastics for the cover layer (s) to be the same or different.

It has been shown that a polyolefin is also suitable for the cover layer.

Thermoplastics with a Kristaliitschmelzpunkt T _m, as measured by DSC (differential scanning calorimetry) at a heating rate of 10 ° C / min, from 220 ° C to 260 ^β C, preferably from 230 ° C to 250 ° C, with a crystallization temperature T _c between 75 ° C and 260 ° C, a glass transition temperature T_ 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% represent preferred polymers for the core layer and the cover layer as starting materials for the production of the plate. For the purposes of the invention, a thermoplastic with a cold (post) crystallization temperature T _CN of 120 to 158 ° C., in particular 130 to 158 ° 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 ^ M ,, measured by 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 or the cover layer (s) is polyethylene terephthalate. The polyethylene terephthalate preferably used according to the invention essentially consists of monomer units of the following formula

I ~ CH, CH, - O - CC - 0 3 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 thermoplastics of different core and / or cover 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 • IQ ^" 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 according to the invention can 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, such as in JP-A-60-139717, DE-C-2 429087, DE-A-27 07 491, DE-A -23 19 089, DE-A-16 94461, JP-63-41 528, JP-62-39621, DE-A-41 17 825, DE-A-42 26737, JP-60-141 715, DE-A -27 21 501 and US-A-5296 586.

Polyethylene terephthalates with particularly high molecular weights can be produced, for example, 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 appropriate, co-condensable modifiers, if the liquid heat transfer medium is inert and free of aromatic components and one Boiling point in the range of 200 to 320 ^β C, the weight ratio of dicarboxylic acid diol precondensate (oligomers) to liquid heat transfer medium is in the range of 20:80 to 80:20, and the polycondensation is carried out in the boiling reaction mixture in the presence of a dispersion stabilizer .

It is essential to the invention that the amorphous, multilayer plate contains at least one thermoplastic-soluble dye in at least one of the layers. The concentration of the soluble dye is preferably in the range from 0.001% by weight to 20% by weight, based on the weight of the thermoplastic of the layer provided with it.

Soluble dyes are substances that are molecularly dissolved in the polymer (DIN 55949).

The color change as a result of the coloring of the amorphous plate is based on the wavelength-dependent absorption and / or scattering of the light. Dyes can only absorb light, not scatter, since the physical requirement for scattering is a certain minimum particle size.

Coloring with dyes is a solution process. As The result of this solution process is that the dye is molecularly dissolved, for example, in the PET polymer. Such coloring is referred to as transparent or translucent or translucent or opal.

Of the various classes of soluble dyes, the fat and aromatic soluble dyes are particularly preferred. These are, for example, azo and anthraquinone dyes. They are particularly suitable for coloring PET because the migration of the dye is restricted due to the high glass transition temperature of PET.

(Literature J. Koerner: Soluble dyes in the plastics industry in the VDI Society for Plastics Technology: Coloring plastics, VDI-Verlag, Düsseldorf 1975).

Suitable soluble dyes are, for example: solvent yellow 93 a pyrazolone derivative, solvent yellow 16 a fat-soluble azo dye, fluorole green gold a fluorescent polycyclic dye, solvent red 1 an azo dye, azo dyes such as thermoplastic red BS, Sudan red BB, solvent red 138 an anthraquinone derivative, and fluorescent fluorophenane fluorophores such as fluorophenane GK, solvent blue 35 an anthraquinone dye, solvent blue a phthalocyanine dye and many others.

Mixtures of two or more of these soluble dyes are also suitable.

The multilayered, transparently colored, amorphous plate according to the invention can, if desired, also be equipped with other suitable additives. Depending on requirements, these additives can be added individually or as a mixture to one or more layers of the plate. These additives can also be mixed with the layer (s) with the dye.

Examples of such additives are UV stabilizers and antioxidants as described in German Patent Application No. 195 221 20.6 and the copending application by the same applicant with the title 'Polyethylene terephthalate plate with improved hydrolysis stability'. These registrations apply by quotation as part of the disclosure content of the present application.

As stated above, the multilayer, transparently colored, 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 no or only slight yellowing even after several years of outdoor use.

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

In the presence of oxygen, mainly chain cleavages are observed, but no cross-links. Carbon monoxide, carbon dioxide and carboxylic acids are the predominant quantities of photooxidation 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, DM 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 transparently colored plates according to the invention, since they lead to discoloration or color change. For amorphous plates, 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 being preferred. Mixtures of several UV stabilizers can also be used.

The UV stabilizer is expediently present in a layer in a concentration of 0.01% by weight to 8% by weight, based on the weight of the thermoplastic in the layer provided with the stabilizer.

However, if the UV stabilizer is added to a core layer, 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 generally 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 cover layer from affecting the underlying core layer.

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

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

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) -ethyethanamine 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.

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 shown that such mixtures have a synergistic effect.

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 sandwiched one above the other. However, the plate can only consist of a top layer and a 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 transparently colored, amorphous, multilayer plate 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 German Patent Application No. 196255 34.1 of the applicant, 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-Cs compounds.

(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-0 073 911. 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) Also known are acrylic coatings, such as 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. Components are about 81% acrylate oligomers and 19% hexanediol diacrylate. These coatings are also described for PC and PMMA.

(5) The literature also describes CVD or PVD coating technologies using a polymerizing plasma and diamond-like coatings (thin-film technology, published 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, for example, 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 Societe Francaise Hoechst Highlink OG series, PPZ ^® Products sold by Siber Hegner (manufactured by Idemitsu) and coating materials by 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, such as 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 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, crystallizable plates, curing with UV radiation and / or at temperatures which preferably do not exceed 80 ° C. can take place, with 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. For example, when measuring the impact strength a _n according to Charpy (measured according to ISO 179 / 1D), there is preferably no fracture on the plate. In addition, the notched impact strength a _k according to Izod (measured according to ISO 180 / 1A) 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 ^2nd The image sharpness of the plate, which is also called Clarity and is determined at an angle of less than 2.5 ° (ASTM D 1003), is preferably over 83% and particularly preferably over 84%.

The surface gloss, measured according to DIN 67530 (measuring angle 20 °), is greater than 100, preferably greater than 110, the light transmission, measured according to ASTM D 1003, is generally between 5 and 90%, preferably between 10 and 80%, and the Turbidity of the plate, measured according to ASTM D 1003, is in the range from 2 to 50, preferably from 10 to 35%.

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, the plate according to the invention can be used Manufacture moldings economically and with high productivity using conventional thermoforming machines.

The multilayer, transparently colored, amorphous plates according to the invention can be produced in an extrusion line, for example, by the coextrusion process known per se.

Coextrusion as such is known from the literature (see e.g. EP-110 221 and EP-110 238).

One extruder for plasticizing and producing the core layer and one additional extruder per cover layer are connected to each coextruder adapter. The adapter is constructed in such a way that the 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 1 to 7 hours. The main dryer is connected to the main extruder and one dryer is connected to one coextruder per top layer.

Then the thermoplastic or the thermoplastics for the core layer (s) and the cover layer (s) are melted in the main extruder and in the coextrude. The temperature of the melt is preferably in the range from 230 to 330 ° C, the temperature of the melt being set essentially both by the temperature of the extruder and the residence time of the melt in the extruder can.

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.

The dye and optionally the additives such as a UV stabilizer and / or an antioxidant can already be metered in at the raw material manufacturer or metered into the extruder during plate manufacture.

The addition of the dye and, if appropriate, the additives via masterbatch technology is particularly preferred. The dye and optionally 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 the bulk density of the masterbatch are similar to the grain size and the bulk density of the thermoplastic, so that a homogeneous distribution and thus a homogeneous effect of the dye and the additives such as e.g. homogeneous coloring, UV and hydrolysis stabilization can take place.

As already stated above, the main extruder for producing the core layer and the coextruder (s) are connected to a coextruder adapter in such a way that the melts forming the outer layers are adhered to the melt of the core layer as thin layers. 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 lower than the crystallite melting temperature in order to avoid sticking of the melt strand. The melt strand leaves the slot die preferably at a temperature of 240 to 300 ° C. Depending on the output and plate thickness, the first smoothing-cooling roller has a temperature between 50 ° C and 80 ^β C. The second, somewhat cooler roller cools the second or other surface.

To a uniform thickness in the range of 1 to 20 mm with good optical To obtain properties, it is essential that the temperature of the first smooth roller 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 transparently colored, amorphous plate according to the invention is outstandingly suitable for a large number of different applications, for example for interior cladding, for trade fair construction and trade fair articles, as displays, for signs, in the lighting sector, in shop and shelf construction, as promotional articles, as a menu card stand, as a basketball goal board, as a room divider, as aquariums, as information boards, as a brochure and newspaper stand and also for outdoor applications, such as Greenhouses, roofing, external 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 in accordance with 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 dimensionless and must be specified together with the angle of incidence.

Light transmission:

Under the light transmission is the ratio of the total transmitted

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 / D. Notched impact strength a _k according to Izod:

The impact strength or strength a _k according to Izod is measured according to ISO 180 / 1A.

Density:

The density is determined according to DIN 53479.

SV (DCE), IV (DCE):

The standard viscosity SV (DCE) is measured based on DIN 53728 in dichloroacetic acid.

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

IV (DCE) = 6.67 • 10 ^" SV (DCE) + 0.18

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 M .. are measured by means of gel permeation chromatography (GPC).

Example 1 :

According to the coextrusion process described, a 4 mm thick, multi-layer, transparently colored, amorphous polyethylene terephthalate plate with the layer sequence A-B-A, is produced, B representing the base layer and A the top layer. The base layer B is 3.5 mm thick and the two cover layers which cover the base layer are each 250 μm thick.

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

SV (DCE) 1100

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 ^β C to 245 ° C

Post (cold) crystallization temperature T _CN 152 ° C

Polydispersity MM ₂ 2.02

Glass transition temperature 82 ° C

The main component of the base layer is the polyethylene terephthalate described and 2% by weight of the soluble dye Solventrot 138, an anthraquinone derivative from BASF (© Thermoplast G).

The soluble dye Solventrot 138 is added in the form of a masterbatch. The masterbatch is composed of 20% by weight of the dye Solventrot 138 as the active ingredient and 80% by weight of the above-described polyethylene terephthalate polymer as the carrier material.

The polyethylene terephthalate from which the cover layers are made has a standard viscosity SV (DCE) 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 is 258 ° C. The crystallization temperature range T _c is between 83 ° C and 258 ^β C, the post-crystallization temperature (also cold crystallization temperature) T _CN at 144 ° C. The polydispersity MM _{π of} the polyethylene terephthalate is 2.14. The glass transition temperature is 83 ° C

Before the coextrusion, 90% by weight of the polyethylene terephthalate for the base layer and 10% by weight of the masterbatch are mixed and dried for 5 hours at 170 ° C. in the main dryer which is connected to the main extruder.

The polyethylene terephthalate for the top layer is also dried in two smaller dryers, which are connected to the two coextrusions, at 170 ° C. for 5 hours.

The polyethylene terephthalate for the base or core layer and the masterbatch are melted in the main extruder and the polyethylene terephthalate for the cover layers are melted in the coextruder. The extrusion temperature of the main extruder for the core layer is 281 ^β C.

The extrusion temperatures of the two coextruders for the cover layers are 294 ° C. The main extruder and the two coextruders are connected to a coextruder adapter which is constructed in such a way that the melts forming the outer layers are adhered to the melt of the core layer as a thin layer. The multilayer melt strand produced in this way is shaped in the connected slot die and smoothed on a smoothing calender, the rollers of which are arranged in an S-shape, to form a three-layer, 4 mm thick plate.

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 added Cutting saws hemmed, cut to length and stacked at the edges.

The transparently colored, amorphous, three-layer PET sheet has the following property profile

Layer structure A-B-A

Overall thickness 4 mm

Base layer thickness 3.5 mm

Thickness of the outer layers each 0.25 mm

Color red-transparent

Surface gloss 1st page 160

(Measuring angle 20 °) 2nd page 153

Light transmission 36.9%

Clarity 99.0%

Turbidity 3.8%

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 4.9 kJ / m2

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm3

Calender roll coverings after 2 hours of production none

Example 2:

Analogously to Example 1, a three-layer, red-transparent, amorphous

Plate made.

The polyethylene terephthalate used for the base or core layer B has the following properties: SV (DCE) 3173

IV (DCE) 2.23 dl / g

Density 1.34 g / cm ³

Crystallinity 12%

Crystallite melting point T _m 240 ° C

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

Cold crystallization temperature T _CN 156 ° C

Polydispersity M ^ M ,, 3.66

Glass transition temperature 82 ^β C

M, 204,660 g / mol

M, 55,952 g / mol

As in Example 1, the soluble dye Solventrot 138 is added using masterbatch technology. The base layer contains only 1.0% by weight of the solvent red 138 dye, i.e. only 5% by weight of the masterbatch is metered into the polyethylene terephthalate of the base layer.

The extrusion temperature is 274 C. The first calender roll ^β 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 each 0.4 mm

Base layer thickness 5.2 mm

Overall thickness 6 mm

Color red-transparent

Surface gloss 1st page 162

(Measuring angle 20 °) 2nd page 159

Light transmission 68.4%

Clarity 99.1% Turbidity 3.2%

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 5.1 kJ / m ²

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

Calender roll coverings after 2 hours none

Example 3

Analogously to Example 1, a transparently colored, three-layer, amorphous plate is produced. The base layer of the plate contains 4% by weight of the soluble dye

Solventblau 35, a fat-soluble anthraquinone dye from BASF

The 4 wt .-% of the dye solvent blue 35 are also in the form of a

Masterbatches added, the masterbatch from 20 wt .-% of

Dye solvent blue 35 and 80% of the polyethylene terephthalate polymer

Base layer composed of Example 1. 80 wt .-% of

Polyethylene terephthalate polymers of the base layer from Example 1 are 20

% By weight of the masterbatch used.

The blue-transparent colored plate produced has the following property profile:

Layer structure A-B-A

Overall thickness 4 mm

Base layer thickness 3.5 mm

Thickness of the outer layers each 0.25 mm

Color blue transparent

Surface gloss 1st page 163

(Measuring angle 20 °) 2nd page 158 Light transmission 30.6%

Clarity 99.0%

Turbidity 4.7%

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 4.9 kJ / m ²

Cold formability good, no defects

Crystallinity 0%

Density 1.33 g / cm ³

Calender roll coverings after 2 hours none

Comparative Example 1:

Analogously to example 1, a transparent colored plate is produced. The outer layers are analogous to the outer layers from Example 1. The polyethylene terephthalate used in the base layer has a standard viscosity SV (DCE) of 760, which corresponds to an intrinsic viscosity IV (DCE) of 0.62 dl / g. The other properties are identical to the properties of the polyethylene terephthalate from Example 1 within the scope of the measurement accuracy. The masterbatch used is identical to the masterbatch from example 1. The process parameters and the temperature were chosen as in Example 1. Due to the low viscosity of the base layer, plate production is not possible. The three-layer melt strand shows a large number of flow disorders. The meltdown rate is insufficient.

Comparative Example 2

Analogously to Example 2, a transparently colored, translucent plate is produced, polyethylene terephthalate and masterbatch from Example 2 also being used. The first calender roll has a temperature of 93 ° C. and the subsequent rolls each have a temperature of 87 ° C.

The plate produced is extremely cloudy and almost opaque Light transmission, clarity and gloss are significantly reduced. The plate shows surface defects such as blisters, orange peel or blotchy structures. The optics are unacceptable for a transparent colored application.

The plate produced has the following property profile:

Thickness 6 mm

Surface gloss 1st side non-homogeneous 70 to 80

(Measuring angle 20 °) 2nd side non-homogeneous 70 to 90

Light transmission approx. 8% to 10%

Clarity is not measurable

Turbidity cannot be measured

Surface defects per m ² blisters, orange peel,

stains

(Specks, orange peel, blisters, etc.)

Charpy impact strength a _n no break

Notched impact strength a _k according to Izod 3.2 kJ / m ²

Cold formability good

Crystallinity approx. 8% to 10%

Density 1.34 g / cm ³

Claims

claims

1. Multilayer, transparently colored, 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 of the in the core layer containing thermoplastics is greater than the standard viscosity of the thermoplastic contained in the cover layer, and has at least one layer with at least one dye soluble in the thermoplastic of the layer.

2. Plate according to 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 outer 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 claim 1, wherein the concentration of the soluble dye is in the range of 0.001 to 20 wt .-%, based on the weight of the crystallizable thermoplastic of the layer equipped with dye.

5. Plate according to one of the preceding claims, wherein the soluble dye is a fat- and aromatic-soluble azo or anthraquinone dye.

6. 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.

7. Plate according to claim 6, wherein the concentration of the UV stabilizer in the at least one layer is 0.01 to 8 wt .-%, based on the weight of the Thermoplastics of the layer containing the UV stabilizer.

8. Plate according to claim 6 or 7, 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.

9. Plate according to one of claims 6 to 8, wherein the UV stabilizer is selected from 2-hydroxybenzotriazoles, triazines and mixtures thereof.

10. Plate according to claim 9, 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-y I) -4- (1, 1,3, 3-tetramethylbutyl) phenol.

11. 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.

12. The plate of claim 11, 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.

13. Plate according to claim 11 or 12, wherein the at least one antioxidant is selected from sterically hindered phenols, secondary, aromatic amines, phosphites, phosphonites, thioethers, carbondiimides and zinc dibutyldithiocarbamate.

14. The plate of claim 13, wherein the antioxidant 2- [2,4,8,10-tetrakis (1,1-dimethytethyl) dibenzo [d, f] [1,3,2] dioxaphosphepine-yl] oxy) -ethyl] ethanamine and / or tris (2,4-di-tert-butylphenyl) phosphite.

15. Plate according to 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 C12 alkylene radical, one Cycloolefin polymer and a cycloolefin copolymer.

16. The plate of claim 15, wherein the alkylene radical is ethylene or butylene.

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

18. The plate of claim 15 to 17, wherein the thermoplastic contains a recyclate of the thermoplastic.

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

20. 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 ^β C.

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

22. Plate according to one of the preceding claims, wherein the thermoplastic used has a cold (post) crystallization temperature T _CN in a range from 120 to 158 ° C.

23. Plate according to one of the preceding claims, wherein the surface gloss, measured according to DIN 67530 (measuring angle 20 °), is greater than 100.

24. Plate according to one of the preceding claims, wherein the light transmission, measured according to ASTM D 1003, is in the range from 5 to 90%.

25. Plate according to one of the preceding claims, wherein the haze, measured according to ASTM D 1003, is in the range of 2 to 50%.

26. 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.

27. 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 / 1A, in the range from 2.0 to 8.0 kJ / m ² .

28. Plate according to one of the preceding claims, wherein the plate has an image sharpness, measured according to ASTM D 1003 at an angle smaller than 2.5 °, is over 83%.

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

30. The plate of claim 29, wherein the scratch-resistant coating contains silicon and / or acrylic.

31. A method for producing a multilayer, transparent, amorphous plate according to any one of the preceding claims, wherein the thermoplastic for the at least one core layer in a main extruder and the thermoplastic for the at least one cover layer are melted in a coextruder, the melts are stacked on top of one another and the merged Layers are formed by 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. and the at least one soluble dye together with the thermoplastic of the layer (s) that are equipped with it are melted.

32. The method according to claim 31, wherein at least one additive is melted together with the thermoplastic of the layer to be treated with additive.

33. The method of claim 31 or 32, wherein the thermoplastic is a polyalkylene terephthalate or polyalkylene naphthalate.

34. The method of claim 33, wherein the polyalkylene terephthalate or polyalkylene naphthalate is dried at 160 to 180 ° C for 4 to 6 hours before extrusion.

35. The method according to any one of claims 33 or 34, wherein the temperature of the polyalkylene terephthalate or polyalkylene naphthalate melt is in the range from 250 to 320 ° C.

36. The method according to any one of claims 31 to 35, wherein the dye and optionally the at least one additive are added via the masterbatch technology.

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