Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
  • B29C43/22—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of indefinite length
  • B29C43/24—Calendering

Definitions

• the invention relates to a process for the production of vinyl chloride polymer films by processing vinyl polymers according to the Luvitherm process.
• the Luvitherm process for the production of rigid films from vinyl chloride polymers is known. It is described, for example, in the plastics handbook, volume II, Carl-Hanser-Verlag Kunststoff, 1963, polyvinyl chloride, part 1, pages 240 to 244.
• polyvinyl chloride powder is first mixed with additives, in particular lubricants and stabilizers, and pre-plasticized. This preplasticated mixture of polymer and additives is then, that is pressed in a first stage at relatively low temperatures, generally in the range of about 150 to 190 0, calendered through rolls to a film. Calenders with 4 or 5 rolls in an I or L arrangement are generally used for this purpose.
• the brittle films removed from the calender are sintered on rollers in a second process step to improve their mechanical strength by brief treatment at higher temperatures, at which the films have only a low dimensional stability.
• This short-term treatment for higher Temperatures at which the foils only have a low dimensional stability are sintered on rollers.
• This brief treatment at higher temperatures (luvithermizing), which is carried out without pressure, is generally carried out in a temperature range from about 200 to 280 ° C.
• the film can then be stretched in a further stage to improve the mechanical strength.
• the Luvitherm process generally processes fine-grain vinyl chloride polymers which have been obtained by polymerizing the monomers in aqueous emulsion to give rigid films.
• Suitable lubricants must be added to the vinyl chloride polymer in amounts of up to about 4 percent by weight in order to improve the flow of the polyvinyl chloride particles and to enable the film to be detached from the hot rollers.
• External lubricants such as montan waxes, polyethylene waxes or metal soaps of higher fatty acids are used in particular as lubricants.
• the previously known methods of carrying out the Luvitherm process have the disadvantage that it is only possible to work at relatively low processing speeds, since otherwise the plastic mass does not flow sufficiently and thus does not result in films of satisfactory quality and surface quality.
• the calendering speed is generally limited by inhomogeneous strips, so-called primary or calender strips, surface structure of the film and loss of transparency of the film. Strong streakiness can lead to a local reduction in mechanical strength. Such defects are mostly caused by excess material in the nip, which passes through the nip and is incorporated into the film, without being sufficiently compressed and tempered.
• the aim is for the Luvitherm process to be carried out at the highest possible calendering speeds without the quality of the films being impaired.
• special lubricants and processing aids to the vinyl chloride polymers before processing or to use larger amounts of external lubricants.
• special lubricants and processing aids in the Luvitherm process has so far only led to partial success in the problem of increasing the calendering speed.
• the use of large amounts of external lubricants is uneconomical and disadvantageous insofar as it is known that the amount of additives should be kept as low as possible because of the influence of these additives on the mechanical properties of the films. In addition, you can only work at limited calendering speeds.
• the present invention was therefore based on the object of demonstrating a process of the type described at the outset for producing hard films from vinyl chloride polymers, according to which it is possible to increase the calendering speed when processing the vinyl chloride polymers by the Luvitherm process and at the same time to improve the quality of the film, in particular to improve their surface quality and transparency, but at least not significantly impair them.
• this object is achieved in that when the Luvitherm process is carried out, a lubricant is applied at least to the last calender roll in the product flow direction.
• the present invention accordingly relates to a process for the production of rigid vinyl chloride polymer films by the Luvitherm process by calendering the pre-plastified vinyl chloride polymers, which che conventional additives can contain, at temperatures' in the range from about 150 to about 190 ° C, Luvithermizing the brittle film thus obtained at temperatures in the range from about 200 to about 280 ° C and optionally stretching the Luvithermized film, which is characterized in that that during calendering a lubricant in the form of a thin, uniform layer is continuously applied over the entire length of the calender roll at least to the last calender roll in the direction of product flow.
• Vinyl chloride polymers in the sense of the invention are to be understood as meaning both the homo- and copolymers of vinyl chloride.
• the homopolymers of vinyl chloride should preferably have a K value (according to DIN 53 726) of 70 to 85, in particular 75 to 83.
• the copolymers of vinyl chloride can contain up to 30 percent by weight, preferably up to 15 percent by weight, of other monomers copolymerizable with vinyl chloride.
• monomers polymerizable with vinyl chloride are vinylidene chloride, vinyl esters, preferably vinyl acetate and vinyl propionate, acrylic and methacrylic acid alkyl esters, acrylonitrile, styrene and olefins, in particular ethylene and propylene.
• the homopolymers of vinyl chloride are generally preferred.
• Vinyl chloride polymers which have been obtained by aqueous emulsion polymerization are preferably used.
• the processes for emulsion polymerization of vinyl chloride and the various auxiliaries and catalysts used for this purpose are described in detail in the monograph by H. Kainer, polyvinyl chloride and vinyl chloride copolymers, Springer-Verlag (1965), pages 34 to 59, to which reference is made for further details shall be.
• the vinyl chloride polymers are processed into hard films by the Luvitherm process, as described at the beginning.
• the powdery vinyl chloride polymers are first mixed with the usual and known additives.
• External lubricants, other processing agents and stabilizers are particularly suitable as additives; fillers, pigments and dyes can also be added.
• the individual additives are mixed into the vinyl chloride polymer in the usual and known proportions.
• Suitable lubricants which are generally used in amounts of 2 to 4 percent by weight, based on the vinyl chloride polymer, are, for example, montan waxes, polyethylene waxes or metal salts of higher fatty acids.
• graft copolymers of methyl methacrylate and / or styrene, optionally in a mixture with acrylonitrile, on a rubber-like diene polymer (the so-called ABS, MBS, AMBS polymers) in amounts of 0.5 to 5 percent by weight, preferably 2 to 3 percent by weight, based on the vinyl chloride polymer, serve as described in patent application P 26 24 656.0.
• ABS, MBS, AMBS polymers graft copolymers of methyl methacrylate and / or styrene, optionally in a mixture with acrylonitrile, on a rubber-like diene polymer
• ABS, MBS, AMBS polymers graft copolymers of methyl methacrylate and / or styrene, optionally in a mixture with acrylonitrile, on a rubber-like diene polymer
• the additives are added to the vinyl chloride polymers either directly after the polymerization in the dispersion has ended
• the pre-plasticized mixture of the vinyl chloride polymer and the additives is then processed in a manner known per se in a multi-roll calender to give an initially brittle film with low mechanical strength.
• the pre-plasticized polymer mixture is introduced into the nip at one end of the calender and the film is pulled off at the other end of the calender.
• the processing of vinyl chloride polymers is carried out on the calender to the film rolls at relatively low temperatures, generally in the range of about 150 to about 190 o C, preferably from about 150 to about 175 ° C.
• a lubricant is now applied to this calendering at least on the last calender roll in the product flow direction.
• the lubricant can also be applied to several of the calender rolls, for example the penultimate and last calender roll, or all of the calender rolls. However, it has proven to be completely sufficient if the lubricant is applied at least to the last calender roll in the product flow direction.
• Lubricants which are applied to the calender roll are understood in the sense of the invention to be all additives which facilitate and improve the processing of the vinyl chloride polymers.
• Suitable lubricants for application to the calender rolls are all known and customary lubricants known in the production of polyvinyl chloride calender foils, such as partial fatty acid esters, epoxidized soybean oil or montan wax.
• other additives such as stabilizers, which are known to cause a sliding effect, can also be used for this purpose.
• Liquid lubricants such as fatty acid esters can be applied directly to the calender rolls. Solid lubricants must be atomized, melted or otherwise liquefied before they can be applied to the calender rolls.
• the lubricants can be applied to the calender rollers using any suitable application device, provided that it is only guaranteed that the application takes place evenly over the entire length of the roller.
• the lubricants can be applied to the calender rolls, for example by spraying or dusting. Liquid lubricants are best applied using a roll of felt or a strip of felt soaked in them, lying evenly on the roll over the entire roll length. The applicator is most conveniently placed on the upper vertex of the last calender roll in the commonly used vertical I or L-shaped calenders.
• liquid lubricants are advantageously applied continuously to the calender rolls.
• liquid lubricants can advantageously be continuously applied to the calender rolls by pushing a felt jacket over a hollow metal roller, the metal jacket of which has previously been provided with many small holes.
• the continuous supply of the liquid lubricant then takes place from a storage container into the hollow metal roller, from where the liquid lubricant penetrates through the holes in the metal jacket of the roller into the felt jacket and soaks it uniformly.
• the felt jacket of the application roll lies evenly over the entire length on the calender roll, so that the lubricant penetrating the felt jacket is applied to the calender roll.
• the hollow metal roll covered with the felt jacket is expediently driven separately from the calender rolls and generally runs much more slowly than the latter.
• the lubricant only needs to be very thin Apply a layer to the calender rolls, provided that the rolls are only covered evenly. Accordingly, the amount of lubricant that is applied to the calender roll is extremely small. It is sufficient if the lubricant is applied in amounts of only about 0.03 percent by weight, based on the total vinyl chloride polymer mixture. In general, the amounts of lubricant that are applied according to the invention to the calender rolls and mostly pass into the product via them are in the range from 0.01 to 0.1 percent by weight, preferably in the range from 0.03 to 0.05 percent by weight on the vinyl chloride polymer.
• the calendering speed depends on the product and is generally 20 to 25 m / min. When using the procedure according to the invention, it can, depending on the polymer mixture to be processed, be increased to values of 50 m / min without the quality of the film being adversely affected thereby.
• the film removed from the calender is sintered in a subsequent step in the manner known and known for the Luvitherm process by brief treatment at higher temperatures, generally in the range from about 200 to about 280 ° C., on rollers without pressure, i.e. luvithermized. the film can then additionally be stretched to further improve the mechanical strength.
• the further details for carrying out the Luvitherm process, in particular for Luvithermizing the calender film and, if appropriate, for stretching the film are well known to the person skilled in the art; in this regard, reference is also made to the relevant specialist literature.
• the process according to the invention allows the calendering speed in the processing of vinyl chloride polymer to be significantly increased by the Luvitherm process increase. It has been shown that the increase in the processing speed does not impair the properties of the film obtained, in particular its transparency and surface quality. It has even been found, surprisingly, that despite the increase in the calendering speed, films with improved surface quality are produced when the procedure according to the invention is used.
• the films obtained according to the invention are practically free of calender strips and air bubbles and their transparency is better than those of films which have been produced in a conventional manner.
• Another advantage of the method according to the invention is that the total amount of lubricant required for processing can be reduced. By applying the small amounts of lubricant to the last calender roll, it is possible to significantly reduce the amount of lubricants and processing aids that are usually added to the vinyl chloride polymer before calendering, for example by 1/3 or 1/2.
• the films produced by the process according to the invention generally have thicknesses between 25 and 200 / u.
• they can be used in the adhesive tape sector or for tapes.
• emulsion polyvinyl chloride with a K value of 78 100 parts of emulsion polyvinyl chloride with a K value of 78, which is already manufactured with 2 parts of a montanic acid ester (e-wax) as a lubricant and 0.15 part of diphenylthiourea as a thermal stabilizer was equipped, were mixed intensively with a further 2 parts of e-wax and a further 0.2 parts of diphinylthiourea in a high-speed mixer.
• the powder mixture was then pre-plasticized in a known manner with a planetary roller extruder at 160 ° C. and then rolled out on an I-shaped 4-roller calender.
• the calender rolls had a length of 800 mm and a diameter of 400 mm.
• the roll temperatures from roll 1 (bottom roll) to roll 4 (top roll) were: 172 ° C, 168 ° C, 165 ° C and 160 ° C.
• Coming from the calender 125 / u thick film was then passed through a fuser roll and there luvitherminstrument at a roll temperature of 265 0 C.
• the film was then removed and stretched in a conventional manner in a ratio of 1: 3 at 110 ° C.
• the thickness of the final film was 40 / u.
• the calendering speed speed of the last calender roll was varied between 15 m / min and 50 m / min.
• the surface quality of the calender film and the number of matt strips in the calender films were taken into account.
• the Luvithermization could not be taken into account in the assessment because the Luvitherm behavior largely depends on the quality of the calender film.
• the test was carried out as stated in the general description of the test. At a calendering speed of 18 m / min, a calender film was obtained which was good in terms of surface and rigidity. It had about 8 to 10 calender strips across the width of 70 cm. Increasing the calendering speed to 20 m / min worsened the film quality is noticeable. The calender strips in the FoL lie became wider and their number increased to approx. 14 to 16 pieces over the width of 70 cm. The film surface became inhomogeneous.

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• Engineering & Computer Science (AREA)
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• Casting Or Compression Moulding Of Plastics Or The Like (AREA)

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Cited By (1)

Citations (3)

• 1977
  • 1977-06-14 DE DE19772726658 patent/DE2726658A1/de not_active Ceased
• 1978
  • 1978-06-01 DE DE7878100042T patent/DE2860160D1/de not_active Expired
  • 1978-06-01 EP EP78100042A patent/EP0000027B1/fr not_active Expired
  • 1978-06-13 IT IT49843/78A patent/IT1105495B/it active

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