MXPA00005445A - Method for producing surface-hardened pmma films which are highly glossy on both sides, free of gel bodies and can be manipulated in the"film-insert-moulding"method - Google Patents

Abstract

An impact resistant provided PMMA moulding material according to DE 195 44 563 is processed into a surface-hardened film which is highly glossy, essentially free of gel bodies and can be processed in the"in-mould-film-decoration"method. The melted mass is generated by means of an extruder and fed to the inventive glazing rolls via a flexible lip nozzle, said rolls being configured in order to generate an especially high locking pressure in the roll slit. The smoothing rolls are cambered. The films are used for decorating surfaces of high-value thermoplastic moulded parts.

Description

PROCEDURE FOR THE PRODUCTION OF PMMA SHEETS OF HARD SURFACE, EXEMPTIONS OF BODIES OF GEL, HIGH BRIGHTNESS BY BOTH SIDES, MANEJABLES IN THE PROCEDURE OF "FILM -_ * '5 INSERT-MOLDING" If you want to decorate injection molded parts with printed polymethyl methacrylate (PMMA) sheets, in order to achieve a certain effect of "depth" of the PMMA sheets with a thickness in the range of 80 to 300 microns are used. For the decoration, either pre-molded and printed PMMA sheets, pre-laminated and laminated to thermoplastic carriers, are placed in the injection molding tool and injected, or the printed PMMA sheet is passed as a roll product through an injection molding tool and injected further. The subsequent injection takes place on the printed side, so that the impression is protected by the PMMA sheet that contains ultraviolet absorbers. For subsequent injection, for example, the following thermoplastics and polymer blends can be used: ABS, PC / ABS, PVC, PC, PC / ASA, PP, PP mixtures. To decorate, either, molded pieces of sheet are placed printed (optionally pre-molded) in the injection molding tool and are subsequently injected, or the printed PMMA sheet is passed, as a roll product, by the injection molding tool and is subsequently injected, or, the PMMA sheet is laminated onto a thermoplastic carrier and (optionally pre-molded) is placed in the injection molding tool and injected further. As carriers that are laminated with the sheet according to the invention and printed, they can find application, for example, the following thermoplastics: ABS, polycarbonate-ABS blends, ASA (acryl-styrene-acrylonitrile copolymers), polycarbonate-ASA blends, polyolefins such as polyethylene, polypropylene, PVC and mixtures containing polyphenylene. All thermoplastic materials can be reinforced with fiberglass or mineral fillers. The PMMA sheet assumes the function of a protective lacquer. Unlike injection molding parts protected with protective lacquer or printed directly or printed with the transfer process (thermal transfer, aqueous transfer), the decoration of surfaces with printed PMMA sheets offers the following advantages: a considerable cost reduction (the surface finish and decoration are done in one step); - solvent-free processes; - costly investments are not required or environmental charges are not covered; - Easy change of print design; - high design freedom. The decoration of thermoplastic molded parts with printed sheets, together with the injection molding process, is generally referred to as "In-Mold-Film-Decoration". The best known form of this procedure is "Insert-Molding". In it, to reinforce the printed decorative PMMA sheet, it is bonded with a thermoplastic carrier. For this, ABS, ASA, PC, PVC, PP, PPE, as well as mixtures thereof are preferably used. The laminate is molded to the desired shape and stamped by a thermoforming process. The parts to be molded are then taken to the subsequent molding process for obtaining the molded part itself. For this, the parts to be molded are placed in the molding tool, usually automatically, and thermoplastics are injected. Preferably ABS, ASA, PC, PVC, PP, PPE, as well as mixtures thereof are used for further molding. If the carrier is used with sufficient thickness, subsequent molding can be saved and the molded, stamped or cut laminate can be used directly as a molded part.

The "In-Mold-Decoration", thanks to its very rational processing and the possibility of rapid design change, offers processors and molded parts manufacturers the possibility of replacing costly traditional processes. For example, PMMA sheets printed with transparent and elastic lacquers, subsequently injected with transparent thermoplastics, can be used very rationally for the manufacture of automotive taillight coatings. Preferred transparent thermoplastics are preferably PMMA, SAN, molding compositions of polystyrene, polycarbonate and PMMA / SAN mixtures. This procedure offers the possibility of a rapid design change without having to build new and expensive multi-component injection tools. In addition, costly dyeing of expensive PMMA molding materials for the injection molding of various components is avoided. The "In-Mold-Decoration" allows in this field of application the production of complete external parts of the car bodies, which can optionally contain the coating of the taillights as a function surface. Optionally, in this application, to increase the rigidity in order to protect the paint from the melt under high pressure of the thermoplastic material used for the subsequent injection, the sheet of PMMA printed with elastic and transparent lacquers can be injected further before the production process of the molded part. A special realization, which works in a very economical way, of the "In-Mold-Film-Decoration", uses combined tools of subsequent injection-molding, with which, in a process based on printed sheets as a roll product, it carries out both the molding of the sheet and the subsequent injection. This procedure is generally referred to as "Film-Insert-Molding". When using PMMA sheets for the decoration of injection molded parts using the "In-Mold-Film-Decoration", high requirements are established for the material of the PMMA sheet: - good handling in the printing process, ie , enough elasticity; - a high surface hardness (at least Pencil-Hardness HB) in order to avoid scratching the molded parts decorated with PMMA sheet; - high surface brightness (measuring procedure according to DIN 67530) > 120; - little clouding under the action of moisture < 2 percent vapor mist according to the method described on page 17; low surface clouding < 1.5 percent; - number of extremely low gel bodies, maximum 1 gel body / 200 cm2; high resistance to weathering; comparable with that of the standard PMMA; - sufficient absorption of ultraviolet light; absorption of ultraviolet light in the range of 290 to 370 nm < 1 percent German Patent DE 38 42 796 (Rohm GmbH) describes PMMA sheets based on PMMA molding compositions with small elastomer particle sizes and a high proportion of elastomer. The sheet according to the invention can not be produced with these molding compositions in terms of the appearance of "surface hardness". WO 96/30435 and EP 763 560 (Mitsubishi Rayon) describe the production of PMMA sheets with a thickness of up to 0.3 mm, based on a certain composition of PMMA: a modifier of impact toughness based on polybutylacrylate with a determined particle diameter as well as the PMMA III matrix polymer and the addition (optional) of a melt strength modifier (polymer I).

The manufacture of the sheet is carried out by a roller process (the so-called Chill-Roll melting process), in which during the cooling and solidification process, the thermoplastic melt comes into contact and cools with a single metal roller. It is expressly emphasized that the melt of thermoplastic can not be molded between two metal rollers to obtain sheets in the range of claimed thickness. This process has considerable disadvantages with respect to the two-roll process, which have a decisive influence on the quality of the sheets. The bodies of gel, to whose formation the PMMA molding compositions modified in terms of impact toughness have a tendency in principle, in the molding in the single Chill-Roll, unlike the process of (smoothing with) two rollers , they are not pressed under the surface of the sheet and remain visible as an optical defect. This has a particularly disadvantageous effect on the subsequent printing process for the production of decorative films, in which clearly visible defects are observed in the area of the gel bodies. In addition, unlike the case of the Chill-Roll, the surface of the sheets that are cooled freely in the air, presents a marked surface clouding, which results from the different volume contraction of the elastomer particles and the PMMA matrix . In this way, a marked surface structure type "mountain and valley" is generated, which diffuses the light and, thus, produces a disadvantageous clouding effect. German Patent DE 195 44 563 (Rohm GmbH) describes the impact-resistant PMMA molding compositions used to obtain the films according to the invention. German Patent DE 40 18 530 (Rohm GmbH) describes a process for the manufacture of whole sheets or sheets with less than 1 mm in thickness, starting from a thermoplastic with a glass transition temperature > 50 ° C. Smoothing is achieved by passing the sheet through an endless band. The plates or sheets obtained are practically free of cuts and double refractions. European Patent EP 659 829 (Rohm GmbH) describes a sheet of protection against the weather and molded bodies coated therewith. The sheet, in addition to the protection against the weather, has the task of absorbing the ultraviolet rays. It consists of a hard phase of PMMA and a tenacious phase, with the ultraviolet absorber in the hard phase. European Patent EP 391 193 (Bayer AG) describes a process for the production of glossy extruded sheets on both sides, optically isotropic, with a thickness less than 0.6 mm, which, either: 1. are manufactured by extrusion and subsequent calendering between a varnished elastic roller and a high-gloss steel roller, or 2. they are molded in two steps of extrusion, wherein in the first step a high-gloss sheet is obtained on one side and matte on the other, by extrusion and subsequent calendering between a polished elastic roll and a high-gloss steel roller. In a second extrusion step, the sheet obtained in the first step is coated on the matte side with the melt of the same thermoplastic, this coated sheet which is obtained is re-calendered between a high-gloss steel roll and a polished elastic roll. , the high gloss side of the coated sheet being directed towards the roll of polished elastic material. Both procedures, which are linked both with a complicated technology and with very high production costs, are in accordance with the current state of the art, which, due to the extremely high and difficult to control delamination forces, considers as unrealistic the production of glossy sheets on both sides between two high-gloss steel rollers.

The process 1 has the disadvantage that it can not be carried out on a large scale, since the lacquer layers on the rubber rollers disintegrate very rapidly under the effect of the high melting temperature. To avoid this influence, the lacquered rubber rollers can be cooled in a water bath, however, the humidity has a disadvantageous effect on the surface quality of the sheet. The process 2 presents a particularly unfavorable performance, since the production of the sheets must be carried out in two extrusion steps. In addition, the extrusion coating of a sheet with melt and the subsequent calendering, especially in the case of the thickness range claimed, produce unsuitable surface properties. European Patent EP 195 075 (Exxon) describes a process for the production of a sheet of 10 to 85 weight percent of an elastomer and 90 to 15 weight percent of a polyolefin, in which the extrusion strip is made move to a temperature above its softening point, through the groove between rollers that rotate in opposite directions. One roller is a high-gloss cooling roller and the other a roller with a high-gloss rubber surface, the sheet cooling. The sheets obtained in this manner have a thickness of between 25 and 250 Micron (10"6) No closing pressures are described, the disadvantages indicated in the discussion of the European Patent EP 391 193 still exist here. EP 212 355 (Bayer AG) describes a polycarbonate sheet, which is optionally printed with an adhesive-free polyurethane layer The sheets are matt on the one hand or structured on the one hand, by passing them on a matt or structured cooling roller The sheets obtained in this way are printed and injected further.An acrylonitrile, butadiene and styrene copolymer is used as plastic for the subsequent injection The European Patent EP 294 705 (Rohm GmbH) describes a process for the manufacture of sheets smoothed on both sides, which uses as a smoothing element an already smoothed sheet, which was previously generated in the process and is fed back in. A. Huerner (Ku nststoffe, 87 (1997), 10, p. 1351 et seq.) Discusses the advantages and disadvantages of smoothing mechanisms, as does H. Gross in Kunststoffe 87 (1997), 5, p. 564. Huerner states that "the tests with a high line pressure have failed, since in this way neither the dwell time in the groove of the rollers nor the relaxation time in the polymer is modified". The measurements described by Huerner (correct ratio of nozzle exit velocity and extraction speed) are not enough to obtain sheets with a high surface quality. To smooth the surface, as Huerner says, as little line pressure as possible is required in the groove between rollers, but as much as possible. Thus, there was a need to provide a method of economical manufacture and large-scale application for sheets with thicknesses < 0.3 mm of PMMA mold masses resistant to impact, which, in addition, guarantees a surface quality on both sides of high gloss, almost free of gel bodies, with a surface hardness sufficient for decorative applications. Also, the sheet must be able to handle safely and economically both in the printing process and during the process "In-Mold-Film-Decoration", so it must have sufficient elasticity. Thus, the appropriate choice of the PMMA component should be given great importance, especially with regard to the balance between surface hardness and elasticity. The PMMA sheet properties presented below, necessary for surface decoration applications, can only be achieved if: impact resistant, weather resistant, polybutylacrylate-based modifiers are used; - the impact toughness modifier used has a certain minimum particle size of the active elastomeric phase (particle size range); - the impact tenacity modifier used, thanks to a favorable morphological configuration (clear separation of tenacious phase and elastomeric phase, an elastomeric portion of greater possible activity, a particle size as large as possible) can be used in a relatively strong dilution and , with this, the necessary minimum surface hardness is guaranteed; - For the production of the raw material of the sheet, a special molding compound preparation process is used, which, thanks to the coagulation technique of the integral impact toughness modifier, allows a sufficient separation of soluble polymerization aids. in water of the production of the modifier of the tenacity to the impact, and in this way, a tendency to the only reduced clouding of the sheet under the action of water vapor is guaranteed; - good handling in the printing process (for the "Film-Insert-Molding" PMMA sheets are usually used decoratively stamped), that is, a sufficient elasticity; - a high surface hardness (at least Pencil-Hardness HB) to avoid scratching of the molded pieces decorated with PMMA sheet; - A high surface brightness (measuring procedure according to DIN 67530> 120) - little cloudiness under the action of moisture <2 percent vapor mist according to the method described on page 17 - low turbidity surface < 1.5 percent; - extremely low number of gel bodies, maximum 1 gel body / 200 cm2; high weather resistance; comparable with that of standard PMMA; sufficient ultraviolet light absorption; ultraviolet light absorption in the range from 290 to 370 nm <1 percent The production of impact-resistant PMMA molding compositions used is described in German Patent DE 195 44 563 (Rohm GmbH), also, to ensure high quality sheet (number of gel bodies extremely reduced, high surface gloss, high weather resistance, reduced surface clouding), the molding process of the lamp is required ina in accordance with the invention. The combination of properties presented above is not possible with the Chill-Roll procedure normally used in the production of sheets with the thickness range claimed. The production of the sheet according to the invention is carried out with a special molding process, based on the smoothing mechanism technique, using a special pressure system and a pair of steel rollers, especially domed and polished to a gloss specular, in whose groove between rollers the molding of the sheets according to the invention is carried out. In the smoothing mechanism technique, hitherto only markedly thicker sheets were produced (d> 0.3 mm, see "Folien für thermogeformte Verpac ungen", VDI-Verlag, 1992). For the production of the sheets according to the invention (thickness range of 80 to 300 micrometers, preferably 95 to 250 micrometers, especially preferred of 105 to 250 micrometers) extremely high closing pressures are required in the groove between rolls, which could not be done with the constructions used so far (articulated lever clamping, see Figure 1, or conventional hydraulic clamping). A hydraulic clamping that seeks to approach this high closing pressure, is more expensive from the construction aspect than the solution according to the invention. Surprisingly, the generation of high closing pressures is achieved by the construction according to the invention: a smoothing mechanism is fixed immovably to the rollers forming the smoothing groove. The second mobile roller is positioned by means of two drives (electric or hydraulic) arranged in parallel with helical gear, attached to push rods at the points of support of the rollers (Figure 2). In this way, for the desired groove between the rollers, the opening of the groove of the rollers produced by the pressure generated by the melt is avoided. The maximum closing pressure that can be reached in this way is thus 1500 N / cm. The melt produced by a single or double helical extruder (to ensure the constancy of the melt flow rate can optionally be used melt pumps) is fed to the molding process according to the invention through a nozzle designed for extrusion of plates. The melt is dimensioned in the defined roller groove and is smoothed and cooled through the surface of the hardened and polished rollers to specular gloss (roughness depth RA 0.002 - 0.006, RT = 0.02 - 0.04, measured according to the standard DIN 4768). In the foregoing, the geometrical shape of one of the two rollers is polished in a bulged manner, unlike the cylindrical shape. The bulge is 0.1 to 0.2 mm, referred to the diameter of the roller. The bulge is of crucial importance for a homogeneous thickness distribution over the entire width of the sheet. Definition of "bulge": Parabolic increase in the diameter of the roller edges toward the center. Bibliography: Hensen, Knappe, Patent, Kunststoff-Extrusionstechnik II, Extrusionsanlagen, Hanser-Verlag, 1986. The bending must be adjusted to the thickness and width of sheet desired - (ie, there is no bulge that can be used universally ). Alternatively, to ensure a homogeneous distribution of thickness, the following constructive measures can be taken: - crossing of axes of roller ("ax-crossing"); - roll flexing ("roll -bending"). These two methods are not usual in the smoothing mechanisms, since, in this case, they involve a high construction cost. They are normally used in calendering equipment. As a result of the process according to the invention, a high gloss sheet is obtained on both sides, almost free of gel bodies, with excellent surface properties. The process according to the invention can also be applied in the production of polycarbonate sheets with excellent surface properties. In the two-roll process, the elastomer-modified PMMA melt is molded between two hardened steel rolls; the surface temperature thereof is below the glass temperature of the PMMA matrix polymers used. In this way, a preferential orientation of the PMMA matrix molecules (which compared to the elastomeric phase has a markedly greater solidification strength) results in the metal or sheet surface, which results in a high-foil surface. gloss with a low negligible surface clouding. The two-roll process also ensures a markedly better weathering behavior, since a smooth sheet surface behaves less sensitive to the erosion caused by ultraviolet light. Certainly, by the choice of the modifying component, extremely small particle sizes (as described in German Patent DE 38 472 796), also by means of a Chill-Roll process, a high-gloss sheet surface can be made on both sides . However, this presents the formation of gel bodies typical for the PMMA sheets produced by the Chill-Roll process and disadvantageous for surface decoration. Furthermore, with a decreasing size of the elastomer particles in order to guarantee a sufficient elasticity of the sheet, a higher concentration of elastomer is required, which again acts negatively on the surface hardness essential for decoration applications ( the minimum requirement is Pencil-Hardness "HB", preferably at least "H", particularly at least "2H"). The optimum temperature range for the molding of non-crystalline thermoplastics is located in various ways between the freezing temperature (TC) and the plastic-viscous flow range. To achieve a high surface gloss, in the smoothing process the surface temperatures of the smoothing molding rolls must be set lower than the glass temperature. Accordingly, sheets of thermoplastic materials are more difficult to mold to thin layers, the greater the temperature difference between the roll temperature (must be less than TG) and the optimum temperature range for hot forming.

As can be seen in Figure 99 on page 166 of H. Saechtling, Kunststoff -Taschenbuch, 21. Auflage (1979), due to the previously described behavior, the hot molding of thin sheets with high gloss surfaces, is in the Polycarbonate case markedly more difficult than in the case of polymethyl methacrylate. Accordingly, with the smoothing process employed in the extrusion of polycarbonate, as a minor thickness approximately 120 microns can be achieved, in the case of PMMA about 100 microns. With a smaller thickness the necessary closing pressures are increased exponentially. In addition, the molding of sheets with the smoothing method claimed in the case of thermoplastic materials, can be formed more simply the longer the temperature range for the optimum hot molding is. Since a high temperature gradient is set in the melt film to be molded, the thermoplastic to be molded must have a sufficiently large hot-melt temperature intercalation when passing through the straightening groove. Consequently, there is almost no opportunity to process thermoplastics such as PP or PE to the laminations claimed. The modulus E, the tensile strength and the elongation at break were tested according to ISO 527-3, the free length between jaws was 60 mm, the test speed 50 mm / min. The Pencil-Hardness was tested according to ASTM D 3363-92 a. The brightness was measured at 60 ° according to the DIN norm 67530. The vapor mist was measured according to ASTM D 1003. With respect to the calculation of the surface vapor mist, the clouding of the sheet, after the treatment on both sides with silicone oil, was removed from the turbidity measured in the untreated state. The determination of the number of gel bodies constitutes an internal method of Rohm (quality assurance work instructions 1/021/220). The bodies are particles that can be observed amplifying, intermittent in a dark / clear way when moving up and down the sample. They are mainly caused by portions of high molecular weight that do not open during the melting process or, as for example in the case of PMMA modified to the impact toughness, by the addition of elastomeric particles of the modifier component of the impact toughness. The counting of the gel bodies on a sheet surface of 200 cm2 is carried out by means of a particle counter "Copea CP-3" of "Agfa Gaevert".

Turbidity after the action of moisture: The sheets are placed 96 hours on water at 60 ° C (90% humidity). The vapor mist is then measured according to ASTM D 1003.

EXAMPLES The production of the impact-resistant molding compositions used and their composition is described in German Patent DE 195 44 563 (Rohm GmbH).

Raw materials used Latex dispersion as a modifier component of impact toughness: Emulsion polymerized in three levels with the following composition: level: copolymerized methylmethacrylate / ethylacrylate / allylmethacrylate = 95.7 / 4.0 / 0.3 (parts by weight) 2nd level : copolymerized butylacrylate / styrene / allyl methacrylate = 82/17/1 (parts by weight) 3rd level: copolymerized methyl methacrylate / ethylacrylate = 96/4. The mass proportion of the 3rd level is 23/40/30 (parts by weight). The latex dispersion has a solids content of 45 percent (by weight). Matrix polymer 1: obtained by continuous polymerization of substance, with a molecular weight (weight average) = 110,000 Dalton. Copolymer of 96 weight percent methyl methacrylate and 4 weight percent methylacrylate. Matrix polymer 2: obtained by batch polymerization, copolymer of 80 weight percent methyl methacrylate and 20 weight percent butylacrylate. Molecular weight (average): 270 '00 Dalton. Matrix polymer 3: obtained by continuous polymerization of substance. Average molecular weight (average) = 110,000 Dalton. Copolymer of 99 percent by weight of methylmethacrylate and 1 percent by weight of methylacrylate.

Obtaining the impact-resistant PMMA molding compositions on which the examples 1, 2 and 4 are based The production of the impact-resistant PMMA molding compositions on which examples 1, 2 and 4 are based is carried out in Two steps. In the first, an intermediate stage of molding mass is obtained by means of a combined coagulation / mixer equipment. In the second step, this intermediate molding mass stage is mixed in a double helical mixer with the "matrix polymer 2" to obtain the final sheet raw material; the mixing ratio of the intermediate stage of molding mass to matrix polymer 2 is 1: 1; during mixing 0.3 percent by weight of Tinuvin P (benztriazole-based ultraviolet absorber, manufacturer: Ciba-Geigy) is added. Step 1 is carried out in a device consisting of two successively connected extruders, where in the first extruder the latex dispersion is drained and mixed with a partial quantity of the "matrix polymer 1", which is added as a melt . In the second extruder, which functions as a mixing and degassing extruder, the addition of the main amount of the matrix polymer 1 takes place via a side feed. At the end of the degassing zones the addition is made through the master batch of blue tornado agents and a stabilizer of yellowing. Referring to the intermediate stage of the molding mass produced, 4 ppm of ultramarine blue 31, 14 ppm of ultramarine violet 11 are added and, as stabilizer of yellowing, 40 ppm of sodium phosphite. The weight ratio of the dispersion to the matrix polymer is from 82 to 63 parts.

Obtaining the impact-resistant PMMA molding compositions on which the example 3 is based Obtaining the impact-resistant PMMA molding compositions on which the example 3 is based is carried out by means of a combined coagulation / mixer equipment consists of two extruders connected successively. In the first step the latex dispersion is drained and mixed with a partial amount of the "matrix polymer 2", which is added as a melt. In the second extruder, which functions as a mixing and degassing extruder,. the addition of the residual amount of matrix polymer 2 through a side feed takes place. At the end of the degassing zones, the addition through the master batch of blue tornado agents, a yellowing stabilizer and the ultraviolet absorber is performed. Referring to the intermediate stage of the molding mass produced, 4 ppm ultramarine blue 31, 14 ppm ultramarine violet 11, 40 ppm sodium phosphite, as well as 0.5 weight percent Mark LA 31 (ultraviolet absorber a) are added. Benztriazole base, manufacturer: Asahi-Denka). The weight ratio of the dispersion to the matrix polymer is 42/81 parts.

Obtaining the sheets of examples 1 and 3 (according to the invention) The melt is generated by a simple helical extruder of 120 mm in diameter and is fed to the smoothing mechanism according to the invention through a nozzle of flexible lips designed for the extrusion of sheets (1500 mm wide). The pre-adjustment of the lips of the nozzle is 0.8 mm. The smoothing mechanism is designed according to the invention, by means of the special construction, for the generation of high closing pressures in the groove between rollers (see Figure 2). Of the rollers that make up the groove, one is fixed immovably to the calendering frame. The displaced roller is positioned at the points of support of the rollers by means of two electric drives arranged in parallel, with helical gears, attached to push rods. In this way, by means of the closing pressure generated of 1'500 N / cm, the opening of the groove between rollers is avoided during the manufacture of the 0.125 mm thick sheet, due to the pressure produced by the cooled melt. The melt is sized in the groove between rollers and is smoothed and cooled by the surface of the polished rollers to a high specular gloss, tempered below the glass temperature of the PMMA matrix polymer (roughness depth RA = 0.004). In this, one of the two rollers is domed. The bulge is 0.1 mm. As a result, a high gloss sheet is obtained on both sides, free of gel bodies, with very low surface clouding. The sheets are stamped with the desired design, and then, by means of the "In-Mold-Film-Decoration", the desired decorated molding piece is processed.

Obtaining the sheet of Example 2 (comparative example, Chill-Roll method analogous to the aforementioned Mitsubishi Patent, No. EP 763 560) The melt is generated by a simple helical extruder of 120 mm in diameter and is fed into the mechanism of molding of Chill-Roll sheets through a flexible lip nozzle designed for the extrusion of sheet with 1500 mm width. The pre-adjustment of the nozzle lip groove is 0.8 mm. The melt film is placed and cooled on the surface of the cold Chill-Roll. As a result, a sheet is obtained which, compared to the sheets obtained according to the invention, has a relatively low surface gloss, a high number of gel bodies, low gloss and a significant surface clouding (see Table 1). ).

Obtaining the sheet of example 4 (comparative example, smoothing mechanism with articulated lever closure, see Figure No. 1) The melt is generated by a simple helical extruder of 120 mm in diameter and fed to a smoothing mechanism provided with articulated lever closure through a flexible lip nozzle designed for sheet extrusion with 1500 mm width. The pre-adjustment of the nozzle lip groove is 0.8 mm. As a result, a product matching the surface properties of the sheets of Examples 1 and 3 is obtained. However, with the hinged lever closing system the intended sheet thickness of < 300 micrometers Due to the articulation necessarily not completely stretched (a fully stretched articulation under load, requires an immensely high opening force), this closing system does not present in the closed state the rigidity necessary to produce the extremely high closing pressure that is required . The above is of decisive relevance in the case of the high counterforce (exerted by the thin film of the melt in the production of the sheet).

EXAMPLE 5 Lamination with a thermoplastic carrier of the PMMA sheets obtained in accordance with the invention in Examples 1 and 3 By means of a simple helical extruder with a diameter of 90 mm, a film of melt is generated.

ABS and is fed through a wide slot nozzle to a smoothing mechanism. The pre-adjustment of the nozzle lip groove is 1.2 mm. In the smoothing groove, the PMMA sheet according to the invention, stamped, for example, with a so-called "Carbon-Design" and a covering lacquer that produces the adhesion to ABS, is laminated with the ABS melt film. at 240 ° C. The PMMA sheet according to the invention is suspended from a braking winding shaft. In order to ensure an entry free of creases, or a suitable laminate, the plexilglass sheet according to the invention is passed through a so-called "wide path roller". The resulting laminate has a total thickness of 0.50 mm, of which 125 micrometers are formed by the PMMA layer. The pulling speed of the smoothing mechanism is 5 m / min. The composite sheet serves for the decoration of. surface of pieces molded by injection through the so-called "Insert-Molding" process. The resulting injection molding parts have an attractive surface design thanks to the decorative printing used. Due to its valuable surface properties, the PMMA sheet is the ideal substrate for high-value lacquer systems.

Table 1 * in accordance with the invention References Figure 1 100 Flexible lip nozzle 110 Fixed roller 120 Mobile roller 130 Joint lever 140 Pneumatic cylinder 150 Plate Fiqura 2 200 Flexible lip nozzle 210 Fixed roller 220 Mobile roller 230 Push rod 240 Helical gear 250 Pressure gauge 260 Blade Fiqura 3 310 Roller of the smoothing mechanism 320 Roll of the smoothing mechanism 330 Roll of the smoothing mechanism 340 Sheet of PMMA 350 Roll of wide path 360 Sheet

Claims (12)

1. A process for the production of high gloss sheets on both sides, of thermoplastics, in the thickness range of 80 to 300 micrometers, by a special process of smoothing rolls, characterized in that the smoothing mechanism is designed for high closing pressures in the groove between rollers.

2. A process for the production of high gloss sheets on both sides, of thermoplastics, in the thickness range of 80 to 300 micrometers, by a special process of smoothing rolls, according to claim 1, characterized in that the interval The temperature of the plastics for the optimal hot molding is at least 15 K.

3. A process for the production of high-gloss sheets on both sides, of thermoplastics, in the thickness range of 80 to 300 micrometers, by a special process of smoothing rolls, according to claim 1, characterized in that the difference in temperature between the freezing temperature and the temperature range for the optimum hot molding is of maximum 50 K.

4. The production of high sheets gloss on both sides, of thermoplastics, in the thickness range of 80 to 300 micrometers, by means of a special process of smoothing rollers nto, characterized in that the thermoplastics are polymethylmethacrylate or polycarbonate.

5. The production of high gloss sheets on both sides, of thermoplastics, in the thickness range of 80 to 300 micrometers, by means of a special process of smoothing rolls, according to claim 1, characterized in that the thermoplastic is PMMA.

6. A method according to claim 1, characterized in that the roller is domed. The use of the sheet produced according to the method according to claims 1 to 6, as a decorative sheet for injection molded parts. 8. An object of injection molded thermoplastic molding compositions, characterized in that it is decorated with a sheet produced according to the method according to claims 1 to 6. 9. An object according to the claim 8, characterized in that the thermoplastic molding composition is a transparent molding composition. 10. An object according to claims 7 to 9, characterized in that the sheet produced according to claims 1 to 6, before being used as a decorative sheet for injection molding parts, is laminated with a thermoplastic carrier. 11. The use of the sheet produced according to the method according to claims 1 to 6, as a decorative sheet for extruded molded parts. 12. The use of the sheet produced according to the process according to claims 1 to 6, as a decorative sheet for extruded molded remoulded pieces.