CA2262534A1 - Multilayered coloured plate made of a crystallising thermoplastic material, process for producing the same and its use - Google Patents

Abstract

An amorphous, coloured, multilayered plate with 1 to 20 mm thickness contains a crystallising thermoplastic material as its main component and at least one inorganic and/or organic pigment as dye in at least one of the layers. Other additives, such as UV stabilisers, antioxidants and soluble dyes may also be contained therein.

Description

WO 98/05499 ~ PCT/EP97/03855 Multilayered, colored sheet of a crystallizable thermoplastic, a process for its production and its use.

The invention relates to an amorphous, colored sheet of a crystallizable thermoplastic, the thickness of which is in the range from 1 to 20 mm. The invention furthemmore relates to a process for the production of this sheet and to its use.

Multilayered sheets of plastics materials are known per se.

Such sheets of branched polycarbonates are described in EP-A-0 247 480, EP-A-320 632 and US-A 5,108,835.

UV-stabilized polycarbonate shaped articles which are built up from polydiorganosiloxane-polycarbonate block copolymers are known from DE-A-34 14 116 and US-A 4,600,632.

Multilayered sheets of plastic with layers of polydiorganosiloxane-polycarbonate block copolymers which comprise UV absorbers are known from US-A 5,137,949. UV-stabilized, branched polycarbonates from specific diphenols are known from EP-A-0 416 404. It is mentioned that such polycarbonates can be employed for the production of sheets or multiwall sheets.
All these sheets are made of polycarbonate, an amorphous thermoplastic which cannot be crystallized. Polycarbonate sheets have the disadvantage that they often lead to blooming in the form of white specks and surface deposits, especially in the UV-stabilized embodiment (cf. EP-A-0 649 724).
According to EP-A-0 649 724, for example, evaporative loss of the UV
absorber is linked to a high degree to the average molecular weight.

These PC sheets, furthermore, are readily flammable and therefore CA 02262~34 1999-01-29 require the addition of flameproofing agents so that they can be employed for certain purposes, such as for interior applications. Tedious predrying times and relativeiy long processing times at high temperatures are necessary for further processing of these sheets to moldings. Devolatilizing 5 extruders must furthermore be used during sheet production for the purpose of withdrawing moisture, which means that the additives added to the raw material can also be removed at the same time, especially if low molecular weight, relatively volatile additives are employed.

10 Single-layered, colored amorphous sheets having a thickness in the range from 1 to 20 mm which comprise, as the main constituent, a crystallizable thermoplastic, such as, for example, polyethylene terephthalate, and an organic and/or inorganic pigment as a colorant have already been described by the Applicant (German Patent Applications No. 19519577.9, 19522119. 2 and 19528333.3). These sheets can have a standard viscosity of 800-6000 and comprise a UV stabilizer.
EP-A-0 471 528 describes a process for shaping an object from a polyethylene terephthalate (PET) sheet. The PET sheet is heat-treated on both sides in a thermoforming mold in a temperature range between the 20 glass transition temperature and the melting temperature. The shaped PET
sheet is removed from the mold when the extent of crystallization of the shaped PET sheet is in the range from 25 to 50%. The PET sheets disclosed in EP-A-0 471 528 have a thickness of 1 to 10 mm. Since the thermoformed shaped article produced from this PET sheet is partly 25 crystalline and therefore no longer transparent and the surface properties of the shaped article are determined by the thermoforming process and the temperatures and shapes given by this, the optical properties (for example gloss, clouding and light transmission) of the PET sheets employed are unimportant. As a rule, the optical properties of these sheets are poor and 30 in need of optimization. These polyethylene terephthalate sheets also have a single-layer construction and are not colored.

AMENDED SHEET
CA 02262~34 1999-01-29 -~ -re~ui~ ~he addition of f!ameproofin~ agents so that they can h~ l~mp~oy for certain purposes, such as for interior applications. Tedious predrying times and relatively long processing times at high temperatures are necessary for further processing of these sheets to moldings. Devolatilizing 5 extruders must furthermore be used during sheet production for,the purpose of withdrawing moisture, which means that the additi~es added to the raw material can also be removed at the same time, es~Decially if low molecular weight, relatively volatile additives are employefd.

!' 10 Single-layered, colored amorphous sheets having afthickness in the range from 1 to 20 mm which comprise, as the main co,nstituent, a crystallizable thermoplastic, such as, for example, polyethyle~e terephthalate, and an organic and/or inorganic pigment as a colora~t have already been described by the Applicant (German Patent Applications No.19519577.9, 19522116. 2 and 19528333.3). These s~eets can have a standard viscosity of 800-6000 and comprise a UV stabilizer.

EP-A-0 471 528 describes a process for shaping an object from a polyethylene terephthalate (PET) sheet. The PET sheet is heat-treated on 20 both sides in a thermoforming mold in a temperature range between the glass transition temperature and the melting temperature. The shaped PET
sheet is removed from the mold when the extent of crystallization of the shaped PET sheet is,in the range from 25 to 50%. The PET sheets disclosed in EP-A-0 471 528 have a thickness of 1 to 10 mm. Since the 25 thermoformed s~aped article produced from this PET sheet is partly crystalline an~therefore no longer transparent and the surface properties of the shap~d article are determined by the thermoforming process and the temperat~res and shapes given by this, the optical properties (for example gloss,~louding and light transmission) of the PET sheets employed are 30 uni~portant. As a rule, the optical properties of these sheets are poor and i~/need of optimization. These polyethylene terephthalate sheets also have fa single-layer construction and are not cQIored.

US-A-3 496 143 describes vacuum thermoforming of a 3 mm thick PET
CA 02262~34 1999-01-29 sheet, the crystallization of which should be in the range from 5 to 25%.
The crystallinity of the themmoformed shaped article is greater than 25%.
On these PET sheets also, no requirements are imposed in respect of optical properties. Since the crystallinity of the sheets employed is already 5 between 5% and 25%, these sheets are cloudy and nontransparent. These partly crystalline PET sheets are also single-layered.

Austrian Patent Specification No. 304 086 describes a process for the production of transparent shaped articles by the thermoforming process, a 10 PET sheet or film having a degree of crystallinity of less than 5% being employed as the starting material.
The sheet or film used as the starting material is single-layered and has been produced from a PET having a crystallization temperature of at least 1 60~C. From this relatively high crystallization temperature it follows that 15 the PET here is not a PET homopolymer but a glycol-modified PET, called PET-G for short, which is a PET copolymer. In contrast to pure PET, PET-G shows an extremely low tendency toward crystallization and is usually present in the amorphous state because of the glycol units additionally incorporated .
The object of the present invention is to provide a multilayered, amorphous, colored sheet having a thickness of 1 to 20 mm which is distinguished by good mechanical and homogeneous optical properties.

25 The homogeneous optical properties include, for example, a homogeneous light transmission and a high surface gloss.

The good mechanical properties include, inter alia, a high impact strength and a high fracture strength.
Furthermore, the sheet according to the invention should be recyclable, in particular without loss of the mechanical properties, and poorly combustible, so that, for example, it can also be used for interior applications and in exhibition construction.
CA 02262~34 1999-01-29 This object is achieved by a multilayered, colored amorphous sheet having a thickness of 1 to 20 mm which comprises, as the main constituent, at least one crystallizable thermoplastic, wherein the sheet has at least one core layer and at least one covering layer, the standard viscosity of the 5 cryst~lli7~hle thermoplastic of the core layer being higher than the standard viscosity of the crystallizable themmoplastic of the covering layer, and wherein at least one layer comprises at least one organic and/or inorganic pigment as a colorant.

10 Amorphous sheet in the context of the present invention is understood as meaning those sheets which are noncrystalline, although the crystallizable thermoplastic employed has a crystallinity of between 5 and 65%.
Noncrystalline, i.e. essentially amorphous, means that the degree of crystallinity is in general below 5%, preferably below 2%, and particularly 15 preferably is 0%, and that the sheet essentially shows no orientation.

According to the invention, crystallizable thermoplastic is understood as meaning - crystallizable homopolymers, 20 - crystallizable copolymers, - crystallizable compounds, - crystallizable recycled material and - other variations of crystallizable thermoplastics.

25 Examples of suitable thermoplastics are polyalkylene terephthalates with a C1 to C1 2-alkylene radical, such as polyethylene terephthalate and polybutylene terephthalate, polyalkylene naphthalate with a C1 to C12-alkylene radical, such as polyethylene naphthalate and polybutylene naphthalate, and crystallizable cycloolefin polymers and cycloolefin 30 copolymers, it being possible for the thermoplastic or thermoplastics for the core iayer(s) (also called the base layer) and the thermoplastic or thermoplastics for the covering layer(s) to be identical or different.

Polyolefins have also proved to be suitable for the covering layer.
CA 02262~34 1999-01-29 - Thermoplastics having a crystallite melting point Tm~ measured by DSC
(differential scanning calorimetry) with a heating-up rate of 10~C/minute, of 220~C to 260~C, preferably 230~C to 250~C, a crystallization temperature range Tc of between 75~C and 260~C, a glass transition temperature Tg of 5 between 65~C and 90~C and a density, measured in accordance with DIN
53479, of 1.30 to 1.45 g/cm3 and a crystallinity of between 5% and 65%
are preferred polymers for the core layer and the covering layer as starting materials for production of the sheet.

10 A thermoplastic having a cold (after-)crystallization temperature TCC of 120 to 158~C, in particular 130 to 158~C, is particularly preferred for the purpose according to the invention.

The bulk density, measured in accordance with DIN 53466, is preferably between 0.75 kg/dm3 and 1.0 kg/dm3, and particularly preferably between 0.80 kg/dm3 and 0.,90 kg/dm3.

The polydispersity MW/Mn of the thermoplastic, measured by means of GPC, is preferably between 1.5 and 6.0, and particularly preferably 20 between 2.0 and 5Ø

A particularly preferred crystallizable thermoplastic for the core layer(s) and the covering layer(s) is polyethylene terephthalate. The polyethylene terephthalate preferably used according to the invention essentially 25 comprises monomer units of the following formula O O
ECH2-CH2-O C~C O3 30 It is essential to the invention that the themmoplastic or thermoplastics of the core layer(s) has or have a higher standard viscosity than the thermoplastic OrllhC~ O~d~nCS Ot Ille ~ rin~ ~y~r~s) The~ st~a,J
viscosilies ~f th~ th~rmoplastics ~f ~ari~us cor~ af.d/or ~vel n ~y ~ayers of a~multila~crccl pl~tc 3an d~er.
CA 02262~34 1999-01-29 thermoplastics of the covering layer(s). The standard viscosities of the thermoplastics of various core and/or covering layers of a multilayered plate can differ.

AMENDED SHEET

The standard viscosity SV (DCA) of the crystallizable thermoplastic of the core layer or base layer, measured in dichloroacetic acid in accordance with DIN 53728, is preferably between 800 and 5000, and particularly preferably between 1000 and 4500.

The standard viscosity SV (DCA) of the crystallizable thermoplastic of the covering layer, measured in dichloroacetic acid in accordance with DIN
53728, is preferably between 500 and 4500, and particularly preferably between 700 and 4000.
The intrinsic viscosity IV (DCA) can be calculated from the standard viscosity SV (DCA) as follows:
IV (DCA) = 6.67 x 10-4 SV (DCA) + 0.118 The amorphous, multilayered sheet according to the invention furthermore comprises at least one organic and/or inorganic pigment. The pigment or also a mixture of pigments can be added to one or more of the layers. The concentration of the colorant is preferably in the range from 0.1 to 30% by weight, based on the weight of the thermoplastic in the layer treated with pigment.

Organic and inorganic pigments which are suitable for the invention are described in the abovementioned German Patent Applications No.
195 195 77.9, 195 221 19.2 and 195 283 33.3. By citation, these Applications are valid as belonging to the disclosure of the present Application .
When considering colorants, a distinction is made in accordance with DIN
55944 between dyestuffs and pigments. Pigments are virtually insoluble in the polymer under the respective processing conditions, whereas dyestuffs are soluble (DIN 55949).

AMENDED SHEET
CA 02262~34 1999-01-29 Th_ ~Id"darJ ~ ;usty ~V ~DCA) ef Ih~: ~,ly~lalllzable thermoplastic a~he core layer or base layer, measured in dichloroacetic acid in accorda,7ce with DIN 53728, is preferably between 800 and 5000, and particu,~rly preferably between 1000 and 4500.
The standard viscosity SV (DCA) of the crystallizable thermf~plastic of the covering layer, measured in dichloroacetic acid in accord~nce with DIN
53728, is preferably between 500 and 4500, and parti~fiarly preferably between 700 and 4000.
The intrinsic viscosity IV (DCA) can be calculate~from the standard viscosity SV (DCA) as follows: /

IV (DCA) = 6.67 x 10-4 SV (DCA) + 0.118/
The amorphous, multilayered sheet af~cording to the invention furthemmore comprises at least one organic and)6r inorganic pigment. The pigment or also a mixture of pigments can bfl'added to one or more of the layers. The concentration of the colorant i~fpreferably in the range from 0.1 to 30% by weight, based on the weight~6f the thermoplastic in the layer treated with pigment.

Organic and inorgan~/pigments which are suitable for the invention are described in the a)7~ovementioned German Patent Applications No.
195 195 77.9,1~5 221 19.2 and 195 283 33.3. By citation, these Applications~e valid as belonging to the disclosure of the present Applicatio~

When/~onsidering colorants, a distinction is made in accordance with DIN
559~4 between dyestuffs and pigments. Pigments are virtually insoluble in th,~ polymer under the respective processing conditions, whereas dyestuffs e s~l~o (DIN 55Dq9~¦ The coloring action of the pigments is brought about by the particles themselves. The term pigment is generally linked to a particle size of 0.01 to 1.0,um. According to DIN 53206, when defining CA 02262~34 l999-0l-29 pigment particles a distinction is made between primary particles, aggregates and agglomerates.

Primary particles such as are generally obtained in the preparation 5 possess a pronounced tendency to aggregate as a result of their extremely small particle size. This produces, by areal aggregation of the primary particles, the aggregates, which thus have a smaller surface area than that corresponding to the sum of the surface areas of their primary particles. As a result of the agglomeration of primary particles and/or aggregates at 10 comers and edges, agglomerates are formed, the total surface areas of which differ only little from the sum of the individual areas. If pigment particle size is referred to - without more detailed indications - this refers to the aggregates such as are essentially present after coloration.

15 In pulverulent pigments, the aggregates have always come together to forrn agglomerates, which, during coloration, must be divided up, wetted by the polymer and homogeneously distributed. These simultaneously occurring processes are called dispersion. In the case of coloring with dyestuffs, on the other hand, the process is a solution process, as a result 20 of which the dye is present in molecularly dissolved form.

In contrast to the inorganic pigments, in the case of individual organic pigments there is no complete insolubility, especially not in the case of pigments of simple composition having low molecular weights.
Dyestuffs are adequately described by their chemical structure. Pigments which are in each case of identical chemical composition, however, can be prepared in and exist in different crystal modifications. A typical example of this is the white pigment titanium dioxide, which can exist in the rutile form 30 and in the anatase foml.

In the case of pigments, it is possible by coating, i.e. by aftertreatment of the pigment particle surface, using organic or inorganic agents, to achieve an improvement in the use properties. This improvement lies in particular CA 02262~34 1999-01-29 in facilitating dispersion and in raising the light stability and resistance to weathering and chemicals. Typical coating agents for pigments are, for example, fatty acids, fatty acid amides, siloxanes and aluminum oxides.

5 Examples of suitable inorganic pigments are the white pigments titanium dioxide, zinc sulfide and tin sulfide, which may be coated with organic and/or inorganic substances.

The titanium dioxide particles can comprise anatase or rutile, but 10 preferably rutile, which, in comparison to anatase, has a higher covering power. In a preferred embodiment, at least 95% by weight of the titanium dioxide particles consist of rutile. They can be prepared by a customary process, for example by the chloride or the sulfate process. The mean particle size is relatively low and is preferably in the range from 0.10 to 0.30 ~m.

By using titanium dioxide of the type described, no vacuoles form within the polymer matrix during production of sheets.

20 The titanium dioxide particles can have a coating of inorganic oxides as is usually employed as a coating for TiO2 white pigment in papers or coating compositions, to improve the light fastness. TiO2 is known to be photoactive. Under the action of UV rays, free radicals form on the surface of the particles. These free radicals may migrate to the film-forming 25 constituents of the coating composition, leading to degradation reactions and yellowing. Particularly suitable oxides include the oxides of aluminum, silicon, zinc or magnesium, or mixtures of two or more of these compounds. TiO2 particles having a coating of several of these compounds are described, for example, in EP-A-0 044 515 and EP-A-0 078 633. The 30 coating can also comprise organic compounds having polar and nonpolar groups. During production of the sheet by extrusion of the polymer melt, the organic compounds must be of sufficient heat stability. Examples of polar groups are -OH, -OR and -COOX (X = R, H or Na, R = alkyl having 1 to 34 carbon atoms). Preferred organic compounds are alkanols and fatty CA 02262~34 1999-01-29 acids having 8 to 30 carbon atoms in the alkyl group, in particular fatty acids and primary n-alkanols having 12 to 24 carbon atoms, and also polydiorganosiloxanes and/or polyorganohydridosiloxanes, such as, for example, polydimethylsiloxane and polymethylhydridosiloxane.

The coating on the titanium dioxide particles usually comprises 1 to 12, in particular 2 to 6 g of inorganic oxides and 0.5 to 3, in particular 0.7 to 1.5 gof organic compound, based on 100 g of titanium dioxide particles. The coating is applied to the particles in aqueous suspension. The inorganic 10 oxides are precipitated in the aqueous suspension from water-soluble compounds, for example alkali metal, in particular sodium, aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate, sodium silicate (water-glass) or silicic acid.

15 Inorganic oxides, such as Al2O3 and SiO2, are also to be understood as meaning the hydroxides or various dehydration stages thereof, such as, for example, oxide hydrates, without the precise composition and structure thereof being known. The oxide hydrates, for example of aluminum and/or silicon, are precipitated onto the TiO2 pigment after calcining and grinding 20 in aqueous suspension, and the pigments are then washed and dried. This precipitation can therefore take place directly in a suspension as is obtained in the preparation process following calcining and the subsequent wet grinding. The precipitation of the oxides and/or oxide hydrates of the respective metals takes place from the water-soluble metal salts within the 25 known pH range; for aluminum, for example, aluminum sulfate in aqueous solution (pH less than 4) is employed, and the oxide hydrate is precipitated by addition of aqueous ammonia solution or sodium hydroxide solution in the pH range between 5 and 9, preferably between 7 and 8.5. If a water-glass or alkali metal aluminate solution is used as the starting substance, 30 the pH of the initially introduced TiO2 suspension should be in the strongly alkaline range (pH greater than 8). The precipitation is then extracted by addition of mineral acid, such as sulfuric acid, in the pH range from 5 to 8.
After precipitation of the metal oxides, the suspension is stirred for a further15 minutes to about 2 hours, during which the precipitated layers undergo CA 02262~34 1999-01-29 ageing. The coated product is separated off from the aqueous dispersion and, after washing, is dried at elevated temperature, in particular at 70 to 1 1 O~C.

5 Typical inorganic black pigments are carbon black modifications, which may likewise be coated, carbon pigments which differ from the carbon black pigments by a higher ash content, and black oxide pigments, such as iron oxide black and copper, chromium and iron oxide mixtures (mixed phase pigments).
Suitable inorganic colored pigments are colored oxide pigments, hydroxyl-containing pigments, sulfide pigments and chromates.

Examples of colored oxide pigments are iron oxide red, titanium dioxide-15 nickel oxide-antimony oxide mixed phase pigments, titanium dioxide-chromium oxide-antimony oxide mixed phase pigments, mixtures of oxides of iron, zinc and titanium, chromium oxide-iron oxide brown, spinels of the system cobalt-aluminum-titanium-nickel-zinc oxide, and mixed phase pigments based on other metal oxides.
Examples of typical hydroxyl-containing pigments are oxide hydroxides of trivalent iron, such as FeOOH.

Examples of sulfide pigments are calcium sulfide selenides, cadmium-zinc 25 sulfides, and sodium aluminum silicate containing sulfur bonded in a polysulfide form in the lattice.

Examples of chromates are the lead chromates, which can exist in the crystal forms monoclinic, rhombic and tetragonal.
All colored pigments, like the white and black pigments, can be either uncoated or coated with inorganic and/or organic substances.

The organic colored pigments are as a rule divided into azo pigments and CA 02262~34 1999-01-29 so-called non-azo pigments.

The characteristic feature of the azo pigments is the azo (-N=N-) group.
Azo pigments can be monoazo pigments, diazo pigments, diazo 5 condensation pigments, salts of azo dye acids and mixtures of the azo pigments.

In specific embodiments, the amorphous, multilayered sheet can also comprise mixtures of inorganic and/or organic pigments and additionally 10 soluble dyestuffs in the core layer and/or covering layer.

The concentration of the soluble dyestuff here is preferably in the range from 0.01 to 20% by weight, particularly preferably in the range from 0.5 to 10% by weight, based on the weight of the crystallizable thermoplastic.
Among the soluble dyestuffs, those dyestuffs which are soluble in fats and aromatic substances are preferred. These are azo and anthraquinone dyestuffs.

20 Suitable soluble dyestuffs for the present invention are mentioned in German Patent Applications No.195 195 78.7,195 221 20.6 and 195 283 34.1. By citation, these Applications belong to the disclosure content of the present application.
The crystallizable thermoplastics used according to the invention can be 25 obtained by customary processes known to the expert. In general, thermoplastics such as are used according to the invention can be obtained by polycondensation in the melt or by a two-stage polycondensation. The first step here is carried out up to a moderate molecular weight - corresponding to a moderate intrinsic viscosity IV of 30 about 0.5 to 0.7 - in the melt, and the further condensation is carried out by means of solid condensation. The polycondensation is usually carried out in the presence of known polycondensation catalysts or catalyst systems.
In the solid condensation, chips of the thermoplastic are heated at temperatures in the range from 180 to 320~C under reduced pressure or CA 02262~34 1999-01-29 under an inert gas until the desired molecular weight is reached.

For example, the preparation 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-60-139 717, DE-C-2 429 087, DE-A-27 07 491, DE-A-23 19 089, DE-A-16 94 461, JP-63-41 528, JP-62-39 621, DE-A-41 17 825, DE-A-42 26 737, JP-60-141 715, DE-A-27 21 501 and US-A-5 296 586.

Polyethylene terephthalates having particularly high molecular weights can be prepared, for example, by polycondensation of dicarboxylic acid-diol precondensates (oligomers) at elevated temperature in a liquid heat transfer medium in the presence of customary polycondensation catalysts and, if appropriate, cocondensable modifying agents, if the liquid heat transfer medium is inert and free from aromatic structural groups and has a boiling point in the range from 200 to 320~C, a weight ratio of dicarboxylic acid-diol precondensate (oligomer) employed to liquid heat transfer medium is in the range from 20:80 to 80:20, and the polycondensation is carried out in a boiling reaction mixture in the presence of a dispersion stabilizer.

The multilayered, colored, amorphous sheets according to the invention can furthermore be treated with suitable additives, if desired. These additives can be added, as required, to one or more layers of the sheet individually or as a mixture, it also being possible for the layers to be those with a colorant.
Examples of suitable additives are UV stabilizers and antioxidants, such as are described in German Patent Application No.195 221 19.2 and Application by the same Applicant, attached at the same time, entitled 'Polyethylene terephthalate sheet of improved stability to hydrolysis'. By citation, these applications are valid as a constituent of the disclosure content of the present application.

As stated above, the multilayered, colored, amorphous sheet can CA 02262~34 1999-01-29 additionally comprise at least one UV stabilizer as a light stabilizer in the covering layer(s) and/or the core layer(s).

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

Inhibition of these photooxidative degradation processes is of considerable industrial and economic importance, since otherwise the possible uses of numerous thermoplastics are limited drastically.

A high UV stability means that the sheet is not damaged or is damaged only extremely little by sunlight or other UV radiation, so that the sheet is suitable for exterior applications and/or critical interior applications, and shows no or only slight yellowing even after several years of external use.

Polyethylene terephthalates, for example, already start to absorb UV light below 360 nm, and 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, chiefly chain splitting reactions but no crosslinking reactions are observed here. Carbon monoxide, carbon dioxide and carboxylic acid are the predominant photooxidation products in terms of amount. In addition to direct photolysis of the ester groups, oxidation reactions which likewise result in the formation of carbon dioxide via peroxide radicals must also be taken into consideration.
The photooxidation of polyethylene terephthalates can also lead, via splitting off of hydrogen in the ~-position of the ester groups, to hydroperoxides and decomposition products thereof and to associated chain splitting reactions (H. Day, D. M. Wiles: J. Appl. Polym. Sci 16,1972, page 203).

CA 02262~34 1999-01-29 UV stabilizers, also called light stabilizers or UV absorbers, are chemical compounds which can intervene in the physical and chemical processes of light-induced degradation.

5 Certain pigments, such as, for example, carbon black, can also partly have the effect of light protection. However, these substances are unsuitable for the colored sheets according to the invention, since they lead to discoloration or a change in color. Only those UV stabilizers, for example, from the class of organic and organometallic compounds which bring about 10 very, very little or no color or change in color in the themmoplastic to be stabilized are expediently used for the amorphous sheets according to the nventlon.

Examples of UV stabilizers which are suitable for the present invention are 15 2-hydroxybenzophenones, 2-hydroxybenzotriazoles, organonickel compounds, salicylic acid esters, cinnamic acid ester derivatives, resorcinol monobenzoate, oxalic acid anilides, hydroxybenzoic acid esters, sterically hindered amines and triazines, 2-hydroxybenzotriazoles and triazines being preferred.
20 Mixtures of several UV stabilizers can also be employed.

The UV stabilizer is expediently present in a layer in a concentration of 0.01% by weight to 8% by weight, preferably 0.01 to 5% by weight, based on the weight of the themmoplastic in the layer treated with the stabilizer.
25 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 treated with the stabilizer is in general sufficient.
According to the invention, several layers can be treated simultaneously 30 with UV stabilizer. In general, however, it is sufficient for the layer on which the UV radiation impinges to be treated.

The core layer(s) can be treated in order to prevent UV radiation impairing the underlying core layer in the event of possible damage to the covering CA 02262~34 1999-01-29 layer.

In a particularly preferred embodiment, the colored, amorphous sheet according to the invention comprises, as the main constituent, a 5 crystallizable polyethylene terephthalate for the core layer and covering layer and 0.01% by weight 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'-methylenebis(6-(2H-benzotriazol-2-yl)-4-(1 ,1 ,3,3-tetramethylbutyl)phenol in the covering layer.
10 A mixture of these compounds and a mixture of at least one of these compounds with at least one other UV stabilizer can of course also be used.

The sheet according to the invention can also be treated with at least one 1 5 antioxidant.
Antioxidants are chemical compounds which can delay the oxidation and hydrolysis phenomena and the resulting aging.

Antioxidants which are suitable for the sheet according to the invention can 20 be classified as follows:

Additive group Substance class Primary antioxidants Sterically hindered phenols and/or secondar,v aromatic amines Secondary antioxidants Phosphites and phosphonites, thioethers, carbodiimides, zinc dibutyl-dithiocarbamate Mixtures of primary and secondary antioxidants and/or mixtures of secondary and/or primary antioxidants with UV stabilizers can furthermore be used. It has been found, surprisingly, that such mixtures show a synergistic effect.
In a preferred embodiment, the amorphous sheet according to the CA 02262~34 1999-01-29 invention comprises a phosphite and/or a phosphonite and/or a carbodiimide as a hydrolysis and oxidation stabiliser.

Examples of antioxidants used according to the invention are 2-[(2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxa-phosphepin-6-yl]oxy)-ethyl]ethanamine 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 treated with 1 0 this.

The thickness of the multilayered sheet according to the invention varies between 1 mm and 20 mm, it being possible for the thickness of the covering layer(s) to be between 10 ~m and 1 mm, depending on the sheet thickness. The covering layers preferably each have a thickness of between 400 and 500 ~m.

As already stated, the sheet according to the invention can have several core and covering layers which are laid one on top of the other like a sandwich. However, the sheet can also consist of only one covering layer and one core layer.

A structure having two covering layers and a core layer Iying between the covering layers is particularly preferred according to the invention.
The individual covering and core layers can comprise different or identical crystallizable themmoplastics as the main constituents, as long as the thermoplastic of a core layer has a higher standard viscosity than the thermoplastic of the covering layers directly adjacent to this core layer. A
layer can also comprise a mixture of crystallizable thermoplastics.

If desired, the colored, amorphous, multilayered sheet according to the invention, which optionally comprises one or more additives, can be provided with a scratch-resistant surface on one side or several sides.
CA 02262~34 1999-01-29 Possible coating systems and materials for the scratch-resistant surface (coating) are all the systems and materials known to the expert.
Suitable coating systems and materials are described, in particular, in German Patent Application No. 196 255 34.1, to the full contents of which 5 reference is made for the present invention.

From the large number of possible coating systems and materials, some are mentioned as examples below.

(1) US-A-4822828 discloses aqueous, radiation-curable coating compositions which comprise, in each case based on the weight of the dispersion, (A) from 50 to 85% of a silane having vinyl groups, (B) from 15 to 50% of a multifunctional acrylate and, if appropriate, (C) 1 to 3% of a photoinitiator.
(2) Inorganic/organic polymers, so-called ormocers (organically modified ceramics), which combine the properties of ceramic materials and polymers, are also known. Ormocers are employed, in particular, as hard and/or scratch-resistant coatings on polymethyl methacrylate (PMMA) and 20 polycarbonate (PC). The hard coatings are bonded on the basis of Al2O3, ZrO2, TiO2 or SiO2 as network formers and epoxide or methacrylate groups with Si by --Si-C- compounds.

(3) Coating compositions for acrylic resin plastics and polycarbonate 25 based on silicone resins in aqueous-organic solution which have a particularly high storage stability are described, for example, in EP-A-0 073 362 and EP-A-0 073 911. This technique uses the condensation products of partly hydrolyzed organosilicon compounds as coating compositions, above all for glass, and in particular for acrylic resin plastics and PC.

(4) Acrylic-containing coatings are also known, such as, for example, the Uvecryl coatings from UCB Chemicals. One example is Uvecryl 29203, which is cured with UV light. This material comprises a mixture of urethane acrylate oligomers with monomers and additives. Constituents are about CA 02262~34 1999-01-29 81% of acrylate oligomer and 19% of hexanediol diacrylate. These coatings are likewise described for PC and PMMA.

(5) CVD or PVD coating technologies with the aid of a polymerizing 5 plasma and diamond-like coatings are also described in the literature (Dunnschichttechnologie [Thin-layer technology], edited by Dr.Hartmut Frey and Dr. Gerhard Kienel, VDI Verlag, Dusseldorf, 1987~. These technologies are used here in particular for metals, PC and PMMA.

10 Other commercially obtainable coatings are, for example, Peeraguard from Peerless, Clearlite and Filtalite from Charvo, coating types such as, for example, the UVHC series from GE Silicones, Vuegard such as the 900 series from TEC Electrical Components, Highlink OG series from Société
Francaise Hoechst, PPZ~ products marketed by Siber Hegner (produced 15 by Idemitsu) and coating materials from Vianova Resins, Toagoshi, Toshiba or Mitsubishi. These coatings are also described for PC and PMMA.

Coating processes known from the literature are, for example, offset 20 printing, pouring on, dipping processes, flow-coating processes, spray processes or atomizing processes, knife-coating or rolling.

Coatings applied by the processes described are then cured, for example by means of UV radiation and/or heat. For the coating processes, it may be 25 advantageous to treat the surface to be coated with a primer, for example based on acrylate or an acrylic latex, before application of the coating.

Other known processes are, for example:
CVD processes and vacuum plasma processes, such as, for example, 30 vacuum plasma polymerization, PVD processes, such as coating with electron beam vaporization, resistance-heated vaporizer sources or coating by conventional processes under a high vacuum, such as in the case of a conventional metallization.

CA 02262~34 1999-01-29 Literature on CVD and PVD is, for example: Modeme Beschichtungsverfahren [Modern coating processes] by H.-D. Steffens and W. Brandl. DGM Infomlationsgesellschaft Verlag Oberursel. Other literature on coatings: Thin Film Technology by L. Maissel, R. Glang, 5 McGraw-Hill, New York (1983).

Coating systems which are particularly suitable for the purpose of the present invention are systems (1), (2), (4) and (5), coating system (4) being particularly preferred.
Suitable coating processes are, for example, also the pouring, the spraying, the atomizing, the dipping and the offset process, the atomizing process being preferred for coating system (4).

15 For coating the amorphous sheets, curing with UV radiation and/or at temperatures which preferably do not exceed 80~C can be carried out, UV
curing being preferred.

The coating according to system (4) has the advantage that no 20 crystallization which could cause clouding occurs. Furthermore, the coating shows an outstanding adhesion, outstanding optical properties and a very good resistance to chemicals and causes no impairment of the intrinsic color.

25 The thickness of the scratch-resistant coating is in general between 1 and 50 ,um.

The amorphous sheet according to the invention, which comprises a crystallizable thermoplstic, such as, for example, PET, as the main 30 constituent, has outstanding mechanical and optical properties. Thus, when the impact strength an according to Charpy (measured in accordance with ISO 179/1 D) is measured on the sheet, preferably no fracture occurs.
Furthermore, the notched impact strength ak according to Izod (measured in accordance with ISO 180/1A) of the plate is preferably in the range from CA 02262~34 1999-01-29 2.0 to 8.0 kJ/m2, particularly preferably in the range from 4.0 to 6.0 kJ/m2.

The surface gloss, measured in accordance with DIN 67530 (measurment angle 20~) is preferably greater than 100, and the light transmission, measured in accordance with ASTM D 1003, is preferably less than 60%.

Weathering tests have shown that even after 5 to 7 years of exterior use, the UV-stabilized sheets according to the invention show no visible yellowing and no visible loss of gloss, as well as no visible surface defects.
Furthermore, the sheet according to the invention is poorly flammable and produces non-buming drips with very little evolution of smoke, so that it is also particularly suitable for interior applications and in exhibition construction.
The sheet according to the invention furthermore can recycled without problems, without pollution of the environment and without loss in the mechanical properties, which means that it is suitable, for example, for the production of short-lived advertising signs or other advertising articles.
Outstanding and economical thermoforming properties (heat forming and vacuum forming properties) have in addition completely unexpectedly been found. Surprisingly, in contrast to polycarbonate sheets, it is not necessary to predry the sheet according to the invention before thermoforming. For 25 example, polycarbonate sheets must be predried at about 1 25~C for 3 to 50 hours before thermoforming, depending on the sheet thickness.

Furthermore, the sheet according to the invention can be obtained with very low thermoforming cycle times and at low temperatures during the 30 thermoforming. On the basis of these properties, shaped articles can be produced economically and with a high productivity from the sheet according to the invention on customary thermoforming machines.

The production of the multilayered, colored, amorphous sheet according to CA 02262~34 1999-01-29 the invention, which has been treated, if appropriate, with one or more additives, can be carried out, for example, by the coextrusion process known per se in an extrusion line.

5 Coextrusion as such is known from the literature (cf., for example, EP-1 10 221 and EP-1 10 238, which are expressly referred to here).

In this case, an extruder for plasticizing and producing the core layer and a further extruder per covering layer are each connected to a coextruder 10 adapter. The adapter is constructed such that the melts which form the covering layers are applied as thin layers adhesively to the melt of the core layer. The multilayered melt strand thus produced is then shaped in the downstream die and sized, polished and cooled in the polishing stack, before the sheet is cut to size.
The process for the production of the sheets according to the invention is described generally below.

If necessary, the thermoplastic polymer can be dried before the coextrusion.
Drying can expediently be carried out at temperatures in the range from 1 10 to 1 90~C over a period of 1 to 7 hours. The main drier is associated with the main extruder, and, per covering layer, a drier is associated with a coextruder.
Thereafter, the thermoplastic or the thermoplastics for the core layer(s) and the covering layer(s) are melted in the main extruder and in the coextruders. The temperature of the melt is preferably in the range from 230 to 330~C, it then being possible for the temperature of the melt to be 30 established essentially both by the temperature of the extruder and by the residence time of the melt in the extruder.

If polyethylene terephthalate, which is preferred according to the invention as the thermoplastic, is used, drying is usually carried out at 160 to 1 80~C
CA 02262~34 1999-01-29 for 4 to 6 hours and the temperature of the melt is established in the range from 250 to 320~C.

The colorant and, if appropriate, the additive, such as a UV stabilizer 5 and/or an antioxidant, can be metered into the themmoplastic of the corresponding layer by the actual manufacturer of the raw material, or can be metered into the extruder during sheet production.
Addition of the colorant and the additives via masterbatch technology or via the solid pigment preparation is particularly preferred. In this case, the 10 colorant and, if appropriate, the additives are dispersed completely in a solid carrier material. Possible carrier materials are certain resins, the thermoplastic itself, or else other polymers which are sufficiently compatible with the thermoplastic.

15 It is important that the particle size and bulk density of the masterbatch are similar to the particle size and bulk density of the therrnoplastic, so that homogeneous distribution and thus a homogeneous effect of the colorant and additives, such as, for example, homogeneous coloration and stabilization to UV and hydrolysis, can be achieved.
As already stated, the main extruder for producing the core layer and the coextruder(s) are connected to a coextruder adapter such that the melts forming the covering layers are applied as thin layers adhesively to the melt of the core layer. The multilayered melt strand thus produced is 25 shaped in a die connected to the line. This die is preferably a slot die.

The multilayered melt strand shaped by a slot die is then sized by polishing calender rolls, i.e. cooled intensively and polished. The calender rolls used can be arranged, for example, in an 1-, F-, L- or S-shape.
The material can then be after-cooled on a roller conveyor, trimmed to size at the edges, cut to length and stacked.

The thickness of the resulting sheet is essentially determined by the take-CA 02262~34 1999-01-29 off, which is positioned at the end of the cooling zone, by the cooling (polishing) rolls coupled to this in temms of speed, and by 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 employed as the extruders.

The slot die preferably comprises the dismountable die body, the lips and 10 the restrictor bar for flow regulation via the width. For this, the restrictor bar can be bent by tension and pressure screws. The thickness is set by adjusting the lips. It is important to ensure that the multilayered melt strand and the lip have a uniform temperature, since otherwise the melt strand flows out in different thicknesses as a result of the different flow paths.
The sizing die, i.e. the polishing calender, gives the melt strand the shape and the dimensions. This is effected by freezing to below the glass transition temperature by means of cooling and polishing. Shaping should no longer take place in this state, since otherwise surface defects would 20 form because of the cooling which has taken place. For this reason, the calender rolls are preferably driven jointly. 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 preferably leaves the slot die with a temperature of 240 to 300~C. The first polishing/cooling roll has a 25 temperature between 50~C and 80~C, depending on the output and sheet thickness. The second, somewhat cooler roll cools the second or other surface.

To obtain a uniform thickness in the range from 1 to 20 mm, with good 30 optical properties, it is essential for the temperature of the first polishing roll to be 50 to 80~C.

While the sizing device freezes the surfaces of the sheet as smoothly as possible and cools the profile to the extent that it is dimensionally stable, CA 02262~34 1999-01-29 the after-cooling device lowers the temperature of the sheet to virtually room temperature. After-cooling can take place on a roller board.

The speed of the take-off should be coordinated precisely with the speed 5 of the calender rolls in order to avoid defects and variations in thickness.

As additional devices, the extrusion line for production of the sheets according to the invention can comprise a separating saw as a device for cutting to length, the edge trimmer, the stacking unit and a control station.
10 The edge or margin trimmer is advantageous, since under certain circumstances the thickness in the margin region may be nonuniform. The thickness and visual properties of the sheet are measured at the control station.

15 As a result of the surprisingly large number of excellent properties, the colored, amorphous sheet according to the invention is outstandingly suitable for a large number of various uses, for example for interior panelling, for exhibition construction and exhibition articles, as displays, forsigns, in the illumination sector, in shopfitting and shelf construction, as 20 advertising articles, as menu stands, as basketball target boards, as room dividers, as aquaria, as information boards, as brochure and magazine stands, and also for external applications, such as, for example, greenhouses, roofing, exterior paneling, coverings, for applications in the building sector, illuminated advertising profiles, balcony paneling and roof 25 patios.

The invention is illustrated in more detail in the following with the aid of embodiment examples, without being limited by these.

30 Measurement of the individual propeties is carried out here in accordance with the following standards or methods.

CA 02262~34 1999-01-29 Measurement methods Surface gloss:

5 The surface gloss is determined in accordance with DIN 67 530. The reflector value is measured as the optical parameter for the surface of a sheet. In accordance with the standards ASTM-D 523-78 and ISO 2813 the angle of incidence was set at 20~. Under the angle of incidence set, a ray of light strikes the flat test surface and is reflected or scattered by it.
10 The rays of light incident on the photoelectronic receiver are indicated as aproportional electrical value. The measurement value is dimensionless and must be stated together with the angle of incidence.

Whiteness The whiteness is detemmined with the aid of the electrical remission photometer"ELREPHO" from Zeiss, Oberkochem (DE), standard light source C, 2~ normal observer. The whiteness is defined as W = RY + 3RZ - 3RX.

W = whiteness, RY, RZ, RX = corresponding reflexion factors when using Y-, Z- and X-color measurement filter. The white standard used is a compression molding of barium sulfate (DIN 5033, Part 9).
Surface defects:
The surface defects are determined visually.

Charpy impact strength an:
30 This value is determined in accordance with ISO 179/1 D.

Izod impact strength ak:
The Izod notched impact strength or resistance ak is measured in accordance with ISO 180/1A.

Density:
The density is determined in accordance with DIN 53479.

SV (DCA), IV (DCA):
5 The standard viscosity SV (DCA) is measured in dichloroacetic acid in accordance with DIN 53728.

The intrinsic viscosity is calculated as follows from the standard viscosity IV (DCA) = 6.67 x 10-4 SV (DCA) + 0.118 Themmal properties:
The thermal properties, such as crystallite melting point Tm~ crystallization temperature range Tc, (after-(cold)crystallization temperature TCC and 15 glass transition temperature Tg are measured by means of differential scanning calorimetry (DSC) at a heating-up rate of 10~C/minute.

Molecular weight, polydispersity:
The molecular weights Mw and Mn and the resulting polydispersity MW/Mn 20 are measured by means of gel permeation chromatography.

Weathering (both sides), UV stability:
The UV stability is tested as follows in accordance with test specification Test apparatus : Atlas Ci 65 Weather Ometer Test conditions : ISO 4892, i.e. simulated weathering lu~ v~ e ; 1000 h~ r5 (C-ersi-Irradiati~ : 0.5 W/m2, 340 nm 30 Temperature \: 63~C
Relative atmospheric hum~ %
Xenon lamp : int~xternal filter of borosilicate Irradiation cycles : 102 minutes U~ liy~,t, th~n 1~ minutes UV light ~ith ~r~yinS~ t~f th~ 3~6im CA 02262~34 1999-01-29 s ~

1o I rradiation time : 1 000 hou rs (per side) Irradiation : 0.5 Wlm2, 340 nm Temperature : 63~C
Relative atmospheric humidity: 50 %
Xenon lamp : internal and external filter of borosilicate Irradiation cycles : 102 minutes UV light, then 18 minutes UV light with spraying of the specimens AMENDED SHEET
CA 02262~34 1999-01-29 with water, then 102 minutes UV light again and so on.

In the following examples and comparison examples, the sheets are in 5 each case colored sheets of different thickness produced on the extrusion line described.

Example 1:
A 4 mm thick, multilayered, colored, amorphous polyethylene terephthalate 10 sheet having the layer sequence A-B-A is produced by the coextrusion process described, B representing the base layer and A the covering layer.
The base layer B is 3.5 mm thick and the two covering layers, which coat the base layer, are each 0.250 mm thick.

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

SV (DCA) : 1100 IV (DCA) 0.85 dl/g Density : 1.38 g/cm3 Crystallinity 44 %
Crystallite melting point Tm : 245~C
Crystallization temperature range Tc : 82 to 245~C
After-(cold)crystallization temperature range TCG : 152~C
Polydispersity MW/Mn : 2.02 Glasstransition temperature : 82~C
~ ~~
I

AMENDED SHEET
CA 02262~34 1999-01-29 with water, then 102 minutes UV light again and so on.

I;i~f~ following exampies and comparison examples, the shee~re in 5 each case colored sheets of different thickness produced o,~e extrusion line described. f Example 1: ~
A 4 mm thick, multilayered, colored, amorpho~polyethylene terephthalate 10 sheet having the layer sequence A-B-A is ~oduced by the coextrusion process described, B representing the ~se layer and A the covering layer.
The base layer B is 3.5 mm thick and~the two covering layers, which coat the base layer, are each 250 mmt~thick.

15 The polyethylene terephtha~e employed for the base layer B has the following properties:

~r~
SV (DCA) ff : 1100 IV (DCA) ,tAf 0.85 dl/g Density ~ : 1.38 g/cm3 Crystallinity/ : 44 %
Crystallitymelting pointTm : 245~C
Crysta~tzation temperature range Tc : 82to 245~C
Afte~(cold)crystallization temperature range TCC : 152~C
P~ydispersity M~NJMn : 2.02 s t~nsiti~n tel~p~r~lur~ : 8~C

The base layer comprises the polyethylene terephthalate described, as the main constituent, and 8% by weight of titanium dioxide.
The titanium dioxide is of the rutile type and is coated with an inorganic coating of Al2O3 and with an organic coating of polydimethylsilane. The titanium dioxide has an average particle diameter of 0.2 ~m.

The titanium dioxide is added in the form of a masterbatch. The masterbatch is composed of 40% by weight of the titanium dioxide described, as the active compound component, and 60% by weight of the polyethylene terephthalate described, as the carrier material.

The polyethylene terephthalate from which the covering layers are produced has a standard viscosity SV (DCA) of 1010, which corresponds to an intrinsic viscosity IV (DCA) of 0.79 dl/g. The moisture content is ~ 0.2% and the density (DIN 53479) is 1.41 g/cm3. The crystallinity is 59%, 10 the crystallite melting point, according to DSC measurements, being 258~C. The crystallization temperature range Tc is between 83~C and 258~C, the after-crystallization temperature (also the cold crystallization temperature) TCC being 144~C. The polydispersity MW/Mn of the polyethylene terephthalate polymer is 2.14.
15 The glass transition temperature is 83~C.

Before the coextrusion, 80% by weight of the polyethylene terephthalate for the base layer and 20% by weight of the masterbatch are mixed and the mixture is dried at 170~C for 5 hours in the main dryer, which is 20 associated with the main extruder.

The polyethylene terephthalate for the base or core layer and the masterbatch are melted in the main extruder and the polyethylene terephthalate for the covering layers is melted in the coextruders. The 25 extrusion temperature of the main extruder for the core layer is 281 ~C.

The extrusion temperatures of the two coextruders for the covering layers are 294~C. The main extruder and the two coextruders are connected to a coextruder adapter, which is constructed such that the melts which form 30 the covering layers are applied as thin layers adhesively to the melt of the core layer. The multilayered melt strand thus produced is shaped in the slot die, connected to the line, and polished on a polishing calender, the rolls of which are arranged in an S-shape, to give a three-layered sheet 4 mm thick.
CA 02262~34 1999-01-29 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 take-off is 4.2 m/minute.

5 After the after-cooling, the three-layered colored sheet is trimmed at the edges with separating saws, cut to length and stacked.

The white-colored, amorphous three-layered PET sheet produced has the following properties profile:
- Layer build-up : A-B-A
- Totalthickness : 4 mm - Thickness of the base layer : 3.5 mm - Thickness of the covering layers : 0.25 mm each - Surface gloss 1 st side : 152 (Measurement angle 20~) 2nd side : 148 - Light transmission : o %
- Whiteness : 1 18 - Coloration : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the like) - Charpy impact strength an : no fracture - Izod notched impact strength ak : 5.1 kJ/m2 - Crystallinity : o %
- Roll deposits after 2 hours of production : none Example 2:
A three-layered colored sheet is produced analogousiy to Example 1, a 30 polyethylene terephthalate which has the following properties being used for the core layer:

SV (DCA) : 2717 IV (DCA) 1.9 dl/g CA 02262~34 1999-01-29 Density : 1.38 g/cm3 Crystallinity : 44 %
Crystallite melting point Tm : 245~C
Crystallization temperature range Tc : 82 to 245~C
Cold crystallization temperature TCC : 154 ~C
Mw : 175 640 g/mol Mn : 49 580 g/mol Polydispersity MW/Mn : 2.02 Glass transition temperature : 82~C
The titanium dioxide masterbatch is composed of 40% by weight of the titanium dioxide described under Example 1 and 60% by weight of the polyethylene terephthalate of this example.

15 The extrusion temperature is 280~C. The first calender roll has a temperature of 56~C and the subsequent rolls have a temperature of 50~C.
The speed of the take-off and of the calender rolls is 2.9 m/minute.

The three-layered PET sheet produced has the following properties:
- Layer build-up : A-B-A
- Total thickness : 6 mm - Thickness of the base layer : 5.5 mm - Thickness of the covering layers : 0.25 mm each - Surface gloss 1st side : 149 (Measurement angle 20~) 2nd side : 143 - Light transmission : 0 %
- Whiteness : 125 - Coloration : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the lime) - Charpy impact strength an : nofracture - Izod notched impactstrength ak : 5.2 kJ/m2 - Crystallinity : 0 %
CA 02262~34 1999-01-29 - Roll deposits after 2 hours of production : none Example 3:
5 A three-layered, white-colored PET sheet is produced analogously to Example 1. 50% by weight of the polyethylene terephthalate from Example 1 are mixed with 30% by weight of recycled material from the sheets of Example 1 and 20% by weight of the titanium dioxide masterbatch and the mixture is dried and coextruded analogously to Example 1.
The three-layered, colored PET sheet produced has the following properties:

- Layer build-up : A-B-A
- Total thickness : 4 mm - Thickness of the base layer : 3.5 mm - Thickness ofthe covering layers : 0.25 mm each - Surface gloss 1st side : 150 (measurement angle 20~) 2nd side : 144 - Lighttransmission : 0 %
- Whiteness : 127 - Coloration : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the like) 25 - Charpy impactstrength an : nofracture - Izod notched impact strength ak : 4.9 kJ/m2 - Crystallinity : 0%
- Roll deposits after 2 hours of production: none 30 Example 4:
A three-layered PET sheet is produced analogously to Example 1. The base layer comprises the polyethylene terephthalate described in Example 1, as the main constituent, and 1.0% by weight of the titanium dioxide from Example 1. The titanium dioxide is incorporated into the polyethylene CA 02262~34 1999-01-29 terephthalate for the base layer directly by the manufacturer of the raw material.

The two covering layers comprise the polyethylene terephthalate of the 5 covering layers from Example 1, as the main constituent, and 0.5% by weight of the titanium dioxide for the base layer. The titanium dioxide is metered in directly by the manufacturer of the raw material. Drying, coextrusion and sheet production are carried out analogously to Example 1.
The three-layered PET sheet produced has the following properties:

- Layer build-up : A-B-A
- Total thickness : 4 mm - Thicknessofthe base layer : 3.5 mm - Content of TiO2 in the base layer : 1.0% by weight - Thickness of the covering layers : 0.25 mm each - Content of TiO2 in the covering layers : 0.5% by weight - Surface gloss 1st side : 121 (measurement angle 20~) 2nd side : 118 - Lighttransmission : 36 %
- Coloration : opal, white - Surface defects : none (specks, bubbles, orange peel and the like) 25 - Charpyimpact strength an : no fracture - Izod notched impact strength ak : 4.8 kJ/m2 - Crystallinity : 0 %

Example 5:
30 A three-layered sheet is produced analogously to Example 2. The sheet is colored green, not white. The base layer comprises the polyethylene terephthalate from Example 2, as the main constituent, and 9% by weight of Pigment Green 17. Pigment Green 17 is a chromium oxide (Cr2O3) from BASF (C~9Sicopalgrun 9996).
CA 02262~34 1999-01-29 The chromium oxide is added in the form of a masterbatch. The masterbatch is composed of 45% by weight of chromium oxide and 55%
by weight of the polyethylene terephthalate from Example 2.

5 The two covering layers comprise the polyethylene terephthalate from Example 2, as the main constituent, and 2% by weight of chromium oxide, the chromium oxide being metered in directly by the manufacturer of the raw material.

10 Drying, coextrusion and sheet production are carried out analogously to Example 2.

The three-layered PET sheet produced has the following properties:

- Layer build-up : A-B-A
- Total thickness : 6 mm - Thickness of the base layer : 5.5 mm - Content of Cr2O3 in the base layer : 9% by weight - Thickness of the covering layers : 0.25 mm each - Content of Cr2O3 in the covering layers: 2% by weight - Surface gloss 1 st side : 1 16 (measurement angle 20~) 2nd side : 114 - Light transmission : 0 %
- Coloration : opaquegreen, homogeneous - Surfacedefects : none (steps, bubbles, orange peel and the like) - Charpyimpactstrength an : nofracture - Izod notched impact strength ak : 5.3 kJ/m2 30 - Crystallinity : 0%
- Roll deposits after 2 hours of production: none Example 6:
A three-layered, white-colored, amorphous PET sheet is produced CA 02262~34 1999-01-29 analogously to Example 2.

The two covering layers comprise the polyethylene terephthalate from Example 2, as the main constituent, and 2.5% by weight of the UV
stabilizer 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxyphenol ('9Tinuvin t577 from Ciba Geigy). Tinuvin 1577 has a melting point of 1 49~C and is stable to heat up to about 330~C.
2.5% by weight of the UV stabilizer are incorporated into the polyethylene terephthalate directly by the manufacturer of the raw material.
The drying, coextrusion and process parameters are chosen as in Example 2.

The three-layered PET sheet produced has the following properties:
- Layer build-up : A-B-A
- Total thickness : 6 mm - Thickness of the base layer : 5.5 mm - Thickness of the covering layers : 0.25 mm each - Surface gloss 1st side : 138 (measurement angle 20~) 2nd side : 134 - Lighttransmission : 0 %
- Whiteness : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the like) - Charpyimpactstrength an : nofracture - Izod notched impact strength ak : 5.1 kJ/m2 - Crystallinity : 0 %
- Roll deposits after 2 hours of production: none After 1000 hours of weathering on each side with the Atlas Ci 65 Weather Ometer, the PET sheet has the following properties:

- Surface gloss 1st side : 126 CA 02262~34 1999-01-29 (measurement angle 20~) 2nd side : 125 - Light transmission : 0 %
- Whiteness : 120 - Coloration : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the like) - Charpyimpact strength an : nofracture - Izod notched impact strength ak : 4.6 kJ/m2 - Crystallinity : o %
Example 7:
A three-layered sheet is produced analogously to Example 1.

The covering layers comprise 3.5% by weight of the UV stabilizer 2,2'-methylenebis(6-(2H-benzotriazol-2-yl)4-(1,1,3,3-tetramethylbutyl)-phenol (~DTinuvin 360 from Ciba Geigy), based on the weight of the covering layer.
Tinuvin 360 has a melting point of 195~C and is stable to heat up to about 250~C.
As in Example 6, 3.5% by weight of the UV stabilizer are incorporated directly into the polyethylene terephthalate by the manufacturer of the raw material.

25 The three-layered PET sheet produced has the following properties:

- Layer build-up : A-B-A
- Totalthickness : 4 mm - Thickness of the base layer : 3.5 mm - Thickness of the covering layers : 0.25 mm each - Surface gloss 1st side : 146 (measurement angle 20~) 2nd side : 142 - Lighttransmission : 0 %
- Whiteness : 116 CA 02262~34 1999-01-29 - Coloration : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the like) - Charpy impactstrength an : no fracture 5 - Izod notched impact strength ak : 4.9 kJ/m2 - Crystallinity : 0 %

After 1000 hours of weathering on each side of the Atlas Ci 65 Weather Ometer, the PET sheet has the following properties:
- Surface gloss 1st side : 138 (Measurement angle 20~) 2nd side : 134 - Lighttransmission : o %
- Whiteness : 1 13 - Coloration: : white, homogeneous - Surface defects : none (specks, bubbles, orange peel and the like) - Charpy impact strength an : nofracture - Izod notched impact strength ak : 4.6 kJ/m2 20 - Crystallinity : 0 %

Comparison Example A colored sheet is produced analogously to Example 1. The polyethylene 25 terephthalate employed for the core layer has a standard viscosity SV
(DCA) of 760, which corresponds to an intrinsic viscosity IV (DCA) of 0.62 dVg. The other properties are identical to the properties of the polyethylene terephthalate from Example 1 in the context of measurement accuracy. The titanium dioxide masterbatch, the covering layers, the 3~ process parameters and the temperature are chosen as in Example 1.
Because of the low viscosity, no sheet production is possible. The stability of the melt is inadequate. The emerging melt strand shows a number of flow streams and inhomogeneities.

CA 02262~34 1999-01-29

Claims (37)

Claims

1. A multilayered, colored amorphous sheet having a thickness in the range from 1 to 20 mm which comprises, as the main constituent, a crystallizable thermoplastic, wherein the sheet has a multilayered build-up of at least one core layer and at least one covering layer, the standard viscosity of the thermoplastic contained in the core layer being greater than the standard viscosity of the thermoplastic contained in the covering layer, and at least one layer of the sheet comprising at least one colorant chosen from organic and inorganic pigments.

2. The sheet as claimed in claim 1, wherein the standard viscosity of the thermoplastic of the core layer, of which at least one is present, is in the range from 800 to 5000 and that of the thermoplastic of the covering layer, of which at least one is present, is in the range from 500 to 4500.

3. The sheet as claimed in claim 1 or 2, wherein the sheet has two covering layers and a core layer lying between the covering layers.

4. The sheet as claimed in one of the preceding claims, wherein the concentration of the pigments is in the range from 0.5 to 30% by weight, based on the weight of the crystallizable thermoplastic of the layer treated with this.

5. The sheet as claimed in one of the preceding claims, wherein the sheet additionally comprises a soluble dyestuff.

6. The sheet as claimed in one of the preceding claims, wherein at least one of the core and/or covering layer(s) is treated with at least one UV stabilizer.

7. The sheet as claimed in Claim 6, wherein the concentration of the UV stabilizer in the layer, of which at least one is present, is 0.01 to 8% by weight, based on the weight of the thermoplastic of the layer comprising the UV stabilizer.

8. The sheet as claimed in claim 6 or 7, wherein the concentration of the UV stabilizer in the core layer, of which at least one is present, is 0.01 to 1% by weight, based on the weight of the thermoplastic of the core layer comprising the UV stabilizer.

9. The sheet as claimed in one of claims 6 to 8, wherein the UV
stabilizer is chosen from 2-hydroxybenzotriazoles, triazines and mixtures thereof.

10. The sheet as claimed in claim 9, wherein the UV stabilizer is chosen from 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyl)oxyphenol and 2,2-methylenebis(6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethyl-butyl)phenol.

11. The sheet as claimed in one of the preceding claims, wherein at least one of the core and/or covering layers is treated with at least one antioxidant.

12. The sheet as claimed in 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 treated with this.

13. The sheet as claimed in claim 11 or 12, wherein the antioxidant, of which at least one is present, is chosen from sterically hindered phenols, secondary aromatic amines, phosphites, phosphonites, thioethers, carbodiimides and zinc dibutyldiothiocarbamate.

14. The sheet as claimed in claim 13, wherein the antioxidant is 2-[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]-dioxaphosphepin-6-yl]oxy)-ethyl]ethanamine and/or tris(2,4-di-tert-butylphenyl) phosphite.

15. The sheet as claimed in one of the preceding claims, wherein the crystallizable thermoplastic for the core layer is chosen from a polyalkylene terephthalate with a C1 to C12-alkylene radical, a polyalkylenenaphthalate with a C1 to C12-alkylene radical, a cycloolefin polymer and a cycloolefin copolymer.

16. The sheet as claimed in one of the preceding claims, wherein the crystallizable thermoplastic for the covering layer is chosen from a polyalkylene terephthalate with a C1 to C12-alkylene radical, a polyalkylene naphthalate with a C1 to C12-alkylene radical, a polyolefin, a cycloolefin polymer and a cycloolefin copolymer.

17. The sheet as claimed in claim 15 or 16, wherein the alkylene radical is ethylene or butylene.

18. The sheet as claimed in one of the preceding claims, wherein the thermoplastic is the same for the core layer and the covering layer.

19. The sheet as claimed in one of claims 15 to 18, wherein the thermoplastic is polyethylene terephthalate.

20. The sheet as claimed in one of claims 15 to 19, wherein the thermoplastic is recycled material of the thermoplastic.

21. The sheet as claimed in one of the preceding claims, wherein the thermoplastic has a crystallite melting point, measured by DSC with a heating-up rate of 10°C/minute, in the range from 220 to 280°C.

22. The sheet as claimed in one of the preceding claims, wherein the thermoplastic has a crystallization temperature, measured by DSC with a heating-up rate of 10°C/minute, in the range from 75 to 280°C.

23. The sheet as claimed in one of the preceding claims, wherein the thermoplastic employed has a crystallinity which is in the range from 5 to 65.

24. The sheet as claimed in one of the preceding claims, wherein the thermoplastic employed has a cold (after-)crystallization temperature T CC
in a range from 120 to 158°C.

25. The sheet as claimed in one of the preceding claims, wherein the sheet has a surface gloss, measured in accordance with DIN 67530 (measurement angle 20°), of greater than 110.

26. The sheet as claimed in one of the preceding claims, wherein the sheet has a light transmission, measured in accordance with ASTM D
1003, of less than 60%.

27. The sheet as claimed in one of the preceding claims, wherein no fracture occurs during measurement of the Charpy impact strength a n, measured in accordance with ISO 179/1D.

28. The sheet as claimed in one of the preceding claims, wherein the sheet has an Izod notched impact strength a k, measured in accordance with ISO 180/1A, in the range from 2.0 to 8.0 kJ/m2.

29. The sheet as claimed in one of the preceding claims, wherein the sheet has a scratch-resistant coating on at least one side.

30. The sheet as claimed in claim 29, wherein the scratch-resistant coating comprises silicon and/or acrylic.

31. A process for the production of a multilayered, colored, amorphous sheet as claimed in one of the preceding claims, wherein the thermoplastic for the core layer, of which at least one is present, in a main extruder, and the thermoplastic for the covering layer, of which at least one is present, is melted in a coextruder, the melts are layered one on top of the other and the layers fed together are shaped by a die and subsequently sized, polished and cooled in a polishing stack having at least two rolls, the temperature of the first roll of the polishing stack being in a range from 50 to 80°C and the colorant being melted together with the thermoplastic of the layer(s) which comprise(s) the colorant.

32. The process as claimed in claim 31, wherein at least one additive is melted together with the thermoplastic of the layer to be treated with the additive.

33. The process as claimed in claim 31 or 32, wherein the thermoplastic is a polyalkylene terephthalate or polyalkylene naphthalate.

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

35. The process as claimed in 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 process as claimed in one of claims 31 to 35, wherein the colorant, of which at least one is present, and if appropriate the additive, of which at least one is present, are added via masterbatch technology.

37. The use of a multilayered, colored, amorphous sheet as claimed in one of the preceding claims 1 to 30 for the exterior and interior sector.