Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
  • G03C1/795—Photosensitive materials characterised by the base or auxiliary layers the base being of macromolecular substances
  • G03C1/7954—Polyesters

Definitions

• the present invention relates to a method of manufacturing a photographic reflective support, more in particular to a method of manufacturing polyester comprising units of ethylene terephthalate as the main repeating units suitable for being melt-extruded, biaxially stretched and annealed according to common means to produce a photographic reflective support.
• a reflective photographic material means a photographic material wherein an opaque material is used as support and a photographic layer is provided thereon and the photographic image formed in the photographic layer is seen directly by means of reflected light.
• a paper support more in particular a polyethylene (PE)-coated paper wherein a layer of polyethylene in which white pigments are kneaded is provided on a base paper made from pulp.
• PE polyethylene
• Such reflective photographic supports based on PE-coated paper have various disadvantages. During processing developing liquid permeate the base paper through its cut edges resulting in a detrimental influence on the photographic image obtained.
• PETP-films are disclosed wherein barium sulfate is added to the polyester resin as finely divided inorganic particles.
• thermoplastic resin essentially comprised of polyester resin and preferably PETP, containing white pigment, made up for 90 % by weight or more of surface-treated titanium oxide meeting a well-defined particle size distribution.
• polyester and in particular polyethylene terephthalate is an important raw material for the manufacture of i.a. filaments and films, packaging films as well as photographic films, the processes for manufacturing PETP-granulate and converting said PETP-granulate to film are well known to those skilled in the art.
• Film materials are generally obtained by melt-extrusion of the polyester through an extruder, rapidly cooling the melt-extruded sheet on the surface of a cooling drum and then biaxially orienting the solidified material in longitudinal and transverse direction.
• the polyester which is melt extruded can be prepared according to two main methods.
• a first method there is an ester exchange reaction between dimethyl terephthalate (DMT) and ethylene glycol (EG) to form bis( ⁇ -hydroxyethyl-terephthalate (BHET) whereupon polycondensation takes place.
• DMT dimethyl terephthalate
• EG ethylene glycol
• BHET bis( ⁇ -hydroxyethyl-terephthalate
• Both in the ester exchange reaction and in the polycondensation reaction catalysts are used : e.g. a zinc, magnesium, manganese, or cobalt salt or mixtures thereof in particular manganese acetate as ester exchange catalyst, and antimony compounds and/or germanium compounds (such as antimony and/or germanium dioxide) as polycondensation catalyst, and stabilisers such as e.g. phosphorus compounds.
• the BHET is obtained by direct esterification of terephthalic acid (PTA) with ethylene glycol (EG).
• PTA terephthalic acid
• EG ethylene glycol
• Antimony trioxide and/or germanium dioxide are also added as polycondensation catalyst and a phosphorus compound may be added as stabilizer.
• PETP starting from PETP-granulate may be found in GB-A-1 269 127, GB-1-1 312 263 and EU-A- 0 022 278.
• PETP-film production process One of the most critical factors in the above described PETP-film production process is the extrusion of the PETP-film through the extrusion die onto the moving cooling or quenching surface, constituted by a cooled drum or belt.
• the PETP-film should be sufficiently cooled to solidify it, and said cooling should take place sufficiently fast so as to become a substantially amorphous film.
• a solidified film with too high a degree of crystallinity causes problems during the subsequent longitudinal and transverse stretching stages.
• PETP polymer incorporating a substantial amount of finely divided inert inorganic filler such as barium sulfate, silica or titanium dioxide has to be melt-extruded and biaxially stretched so as to obtain a PETP-film sheet suitable as support for a reflective photographic material.
• the numerous finely divided inert inorganic filler material act as crystallisation nuclei in the PETP-polymer and hence it is very difficult to melt-extrude such PETP-polymer through a slot-like orifice so as to obtain a substantially amorphous film on the moving quenching member.
• the biaxial stretching process comprising stretching the PETP-film material lengthwise and then widthwise or in the converse order, has a serious drawback in that the material is ruptured particularly in the second, transverse stretching step.
• Some techniques of simultaneously biaxial stretching also have a similar drawback of rupture.
• a solution is proposed being a particular method of manufacturing a photographic reflective support overcoming the above-mentioned drawbacks of rupture, said method comprising : heat-treating chips and/or resin scraps composed of a thermoplastic resin mainly comprising a polyester resin and containing a white inorganic pigment in an amount of not less than 10 % by weight, at a temperature of from 180°C to 245°C for a period of not shorter than 3 hours in a vacuum of not more than 20 mm Hg; feeding said heat-treated chips and/or resin scraps into an extruder to be melted and then extruded in the form of a sheet out of the die of the extruder; cooling and solidifying the resulting sheet on a cooled casting drum; stretching said cooled and solidified sheet 6 to 16 times in terms of area, lengthwise and then widthwise or vice versa, or biaxially at the same time, at a temperature within the range of from a temperature not lower than the glass transition point of said thermoplastic resin to a temperature not higher
• PETP-films used as photographic support are transparant, clear film materials and the demand for opaque photographic supports is substantially lower.
• opaque PETP-supports should (temporarily) be manufactured according to the above described process, most if not all of the process parameters must be changed, the latter giving rise to substantial material losses during the switch from clear to opaque PETP support-manufacture, and later during the switch again from opaque to clear PETP support-manufacture.
• an opaque polyester copolymer support for reflective photographic materials comprising an inorganic inert pigment preferably in an amount of at least 10%, said polyester comprising units of ethylene terephthalate as the main repeating units, said method comprising the following steps in the order given :
• the polyester copolymer is the polycondensation reaction product of ethylene glycol and either terephthalic acid, the latter being replaced by isophthalic acid for up to a maximum of 20 mol percent, or dimethyl terephthalate, replaced by dimethyl isophthalate, for up to a maximum of 20 mol percent.
• Opaque thermoplastic film sheets for use as support of reflective photographic materials made up of copolymers according to our invention, are produced according to the per se known polyester chips production methods and polyester film extrusion process, except the composition of the raw materials for the polyester chips production and certain precautions preferably taken in the polyester film extrusion process.
• the polyester chips production process according to the direct esterification method up to 20 mol percent of the ethylene glycol is replaced by another diol such as 1,3-propanediol 1,4-butanediol , neopenthylglycol or 1,4-cyclohexanedimethanol , and/or up to 20 mol percent of the terephthalic acid is replaced by another aromatic dicarboxylic acid such as isophthalic, phthalic, 2,5-, 2,6- and 2,7-napthalene dicarboxylic acid, diphenyl dicarboxylic acid or hexahydroterephthalic acid.
• another diol such as 1,3-propanediol 1,4-butanediol , neopenthylglycol or 1,4-cyclohexanedimethanol
• another aromatic dicarboxylic acid such as isophthalic, phthalic, 2,5-, 2,6- and 2,7-napthal
• the terephthalic acid could also be replaced up to a maximum of 20 mol percent by another dicarboxylic aliphatic acid such as succinic acid, sebacic acid, adipic acid, azelaic acid or the like.
• another dicarboxylic aliphatic acid such as succinic acid, sebacic acid, adipic acid, azelaic acid or the like.
• the substitution of the terephthalic acid by another dicarboxylic aromatic acid is preferred in view of the mechanical strength comprising i.a. dimensional stability, of the resulting thermoplastic film support.
• ester-exchange or transesterification reaction method when the so-called ester-exchange or transesterification reaction method is used for the production of polyester, in particular ethylene terephthalate, up to 20 mol percent of the ethylene glycol is replaced by one of the diols above mentioned, and/or up to 20 mol percent of the dimethylterephthalate is replaced by the dimethylester of one of the aromatic dicarboxylic acids above mentioned.
• the copolyester resin After direct esterification, resp. transesterification, and polycondensation, the copolyester resin has an intrinsic viscosity of 0.5-0.6 which is determined according to the procedure set forth hereinafter.
• the finely divided inert inorganic pigment used in the thermoplastic opaque support of our invention may be selected from titanium oxide, barium sulfate, calcium carbonate, silica, talc, zinc sulfide and clay as well as certain combinations hereof.
• the white inorganic pigment is prefereably not larger than 20 um, especially not larger than 10 um in its average particle size.
• the amount of the white inorganic pigment dispersed into the thermoplastic opaque support of our invention depends to some extent on the type of pigment, but is essentially at least not less than 10 parts by weight and preferably not more than 30 parts by weight per 100 parts by weight of pigment plus resin.
• Chips composed of the copolyester resin as aforementioned containing more than 10 weight % of the dispersed white inorganic pigment can be manufactured with varied methods including the method in which the pigment is added to and dispersed into a glycolic compound such as ethylene glycol to form a slurry which is in turn polymerized, and then dried and chipped; and the method in which the pigment is mixed and dispersed, with the use of a Banbury mixer or a twin screw extruder, into the copolyester resin as aforementioned which is then chipped.
• a glycolic compound such as ethylene glycol
• the copolymer resin comprising the white inorganic inert pigment can be produced according to a so-called batch or discontinuous production process or according to a continuous process.
• the copolymer resin of the thermoplastic opaque support of our invention may be produced according to the ester-exchange or transesterification method or according to the direct esterification method, in both instances followed by polycondensation and chips cutting.
• the discontinuous process for the production of polyester as well as suitable apparatus for the performance of said process, are disclosed in US-P-4,008,048.
• the substitute diol and/or substitute dicarboxylic acid or dimethylester thereof, and the white finely divided inorganic pigment such as preferably BaSO4 and TiO2
• various other additives are required or preferred for producing chips suitable for being melt-extruded to the opaque thermoplastic film support of our invention.
• Such additives include e.g. transesterification and polycondensation catalysts, stabilisers, electro-conductivity enhancing additives, as well as optical brighteners and dyestuffs.
• transesterification catalysts include e.g. a zinc, magnesium, manganese, or cobalt salt or mixtures thereof, in particular manganese acetate. These compounds are usually added as a solution in ethylene glycol well before the start of the esterification reaction.
• electroconductivity enhancing additives are usually provided to the oligomer reaction mixture obtained after the performance of the direct esterification reaction.
• Such additives are e.g. the transesterification catalysts cited above.
• one of the known polycondensation catalysts such as e.g. GeO2 and/or Sb2O3, should be added as a solution in ethylene glycol before the start of the polycondensation reaction.
• polyester resin preferably contains a stabiliser selected from a.o. a phosphorous compound, e.g. phosphoric acid, phosphorous acid, phosphonic acid and/or esters of these acids, in particular e.g. triphenyl or trimethylphosphate, dimethyl phosphite.
• a stabiliser selected from a.o. a phosphorous compound, e.g. phosphoric acid, phosphorous acid, phosphonic acid and/or esters of these acids, in particular e.g. triphenyl or trimethylphosphate, dimethyl phosphite.
• Optical brighteners may be included as solutions in ethylene glycol added to the oligomer reaction mixture, or subsequently, prior to the film extrusion operation, e.g. by injection during extrusion. These compounds should be present in amounts up to 1500, preferably 500 ppm on the polyester.
• a suitable example is the brightener commercially available undere the trade name "Leucopur", marketed by Sandoz N.V., Haachtsesteenweg 226-234, B - 1030 Brussels, Belgium.
• dyestuff may be incorporated in the polyester so as to slightly modify its color.
• a suitable example is Ceresblau, marketed by Bayer AG.
• copolyester resin so obtained may then be further melt-extruded according to per se conventional means to the thermoplastic opaque support of our invention except for certain precautions to be preferably taken during the cooling of the melt-extruded resin on the moving quenching member, usually constituted by a rotating drum.
• the conventional process of extruding polyester granulate to film comprises, as set forth supra, drying the polyester granulate, followed by melt extrusion upon a quenching drum, stretching the polyester film first in the longitudinal direction, subsequently in transverse direction, finally followed by heat setting the biaxially stretched film.
• the molten polymer is extruded through a slot-like orifice and the extruded polymer is received on a quenching drum or drums on which the temperature of the extruded film is lowered sufficiently rapidly through the softening range of the polymer to obtain a substantially amorphous film.
• the cooling capacity of the quenching drum, along with the cooling of the molten polyester film by air-blowing is a critical factor in obtaining a substantially amorphous film.
• the process and apparatus as described in US-P-4,310,294 is preferably employed.
• the process for melt-extruding a polyester film comprises extruding the polyester in the form of a continuous film from the extrusion die onto a moving quenching drum, maintaining an electrical potential difference between said quenching drum and the extrusion die, the magnitude of such potential difference being sufficient to improve the adherence of said film to said quenching drum, and finally withdrawing the solidified film from the quenching drum, for further treatment, including longitudinal and transverse stretching. Further particulars about this preferred method of electrostatic adherence are described in said specification.
• the film By stretching the quenched film longitudinally and transversely while the polymer is at the lower end of the softening range. above the second order transition temperature of the polymer, the film can be subjected to molecular orientation leading to an improvement in various physical properties of the film, notably the tensile strength.
• the longitudinal stretching of the film is usually achieved by passing the film first around a series of slowly rotating rollers and then around a series of rollers which are rotated more rapidly, and by heating the film between the two series of rollers to a temperature such that the film undergoes plastic elongation under the traction forces imposed on it due to the different speeds of the two series of rollers.
• the heating of the film to the desired stretching temperature occurs in two stages in the conventional methods.
• the first stage the film is heated to a temperature that is somewhat higher than the second order transition temperature (hereinafter called Tg) of the film.
• Tg the second order transition temperature
• said first stage heating usually heats the film to a temperature between 78° and 80°C.
• This first stage heating is effected by heating the first series of rollers.
• the first stage heating temperature should not exceed 82°C because at temperatures higher than 82°C the film starts to stick to the roller surfaces.
• the second heating stage the film is heated to the stretching temperature by means of IR radiation.
• a common stretching temperature of the film is within the range 85° to 95°C.
• the cooling of the film after stretching is effected by cooling the more rapidly rotating rollers to a temperature well below the Tg of the film but above the dew point of the atmosphere in order to avoid condensation effects.
• the described steps of heating, cooling and stretching a film are disclosed in US-A-4093695 to a process for making polymeric film.
• This process comprises longitudinally stretching a substantially amorphous polyethylene terephthalate film during its longitudinal conveyance by exerting longitudinal stretching forces on the film by first and second traction means located at spaced positions along the path of conveyance of the film, while heating the film between said first and second traction means by means of infrared radiation to a temperature such that the film undergoes plastic elongation under said stretching forces, and cooling the stretched film.
• the temperature of the first traction means is not higher than 65°C
• the said heating is achieved by directly and symmetrically exposing both sides of the film first to diffused IR-radiation which causes the film temperature to increase but insufficiently for plastic elongation to occur thereby preheating the film, and then to concentrated infrared radiation which heats the film to a temperature between 100° and 120°C whereby rapid plastic elongation of the film occurs under said stretching forces, and whereby the film is rapidly cooled to below its second order transition temperature, before it reaches the second traction means. Then the film is immersed in a bath of cooling liquid which is continuously renewed at the region where the film enters the bath, and wherein the liquid surface at that region is kept quiescent.
• drying of the liquid-cooled film may occur by means of squeezing means and heaters.
• a typical stretch ratio of the PETP-film in longitudinal direction is 3.3:1, while the film is kept at a temperature of approx. 100°C.
• the typical stretch ratio of the PETP-film in transverse direction is also 3.3:1.
• the biaxially stretched film should finally be heat-set at a temperature of approx. 205°C.
• Heat-setting or heat-relaxing biaxially oriented polyester film involves holding the film at a reduced longitudinal tension while it is heated.
• Such heat-relaxed or annealed biaxially oriented polymer film exhibits a high degree of dimensional stability and resistance to shrinkage at elevated temperatures up to the heat-relaxing temperature.
• the principle of heat-relaxing and heat-relaxing devices are described in e.g. US-2,779,684, US-4,160,799 and US-3,632,726.
• the film should be kept at a temperature between the glass transition temperature and the melt temperature of the polymer, while the film is prevented from shrinking, so as to increase the crystallinity of the film.
• Such an enhanced crystallinity offers the heat-relaxed film its higher mechanical strength, inclusive of its improved dimensional stability.
• the amount of diol substituting the ethylene glycol or the amount of dicarboxylic aromatic acid substituting the terephthalic acid or the amount of dimethylester of such aromatic acid substituting the dimethyl terephthalate in the polyethylene terephthalate chain should be limited to maximum 20 and preferably 15 % mol percent.
• Polyethylene terephthalate was produced in a laboratory reactor according to the discontinuous transesterification and polycondensation reaction process, more in particular according to the process described in the already cited US-P-4,008,048.
• the production capacity of one batch amounted to 20 kg of PETP-polymer, starting from the following raw materials : dimethylterephthalate 19.4 kg ethylene glycol 12.4 kg Mn(OAc)2 7.95 g DeO2, 1.05 g Sb2O3 and 2.92 g diethylphosphite 4.14 g
• the manganese acetate was used as transesterification catalyst. This catalyst was added as a solution of Mn(OAc)2 in ethylene glycol , said solution being added at the beginning of the transesterification reaction.
• the mixture of GeO2/Sb2O3 was used as polycondensation catalyst.
• This catalyst mixture was added as a solution of GeO2/Sb2O3 in ethylene glycol, said solution being added at the end of the transesterification reaction.
• the diethylphosphite compound was added also as a solution in ethylene glycol , acting as stabiliser for the PETP obtained.
• the intrinsic viscosity of the PETP produced amounted to 0,65 dl/g and its crystalline melting point was 264°C.
• the intrinsic viscosity was measured on a solution of 0.5 g of PETP in 100 ml of a mixture of 40 parts by weight of phenol and 60 parts by weight of 1,2-dichloorbenzene, in the way as described in ISO 1628/1 and ISO 1628/5 standards.
• Polyethylene terephthalate was produced in a commercial scale reactor system according to the discontinuous transesterification and polycondensation reaction process, as described in the already cited US-P-4,068,048.
• the production capacity of one batch amounted to 1820 kg of polymer, starting from the following raw materials : dimethylterephthalate 1467 kg dimethylisophthalate 33 kg ethylene glycol 869 kg Mn(OAc)2 568 g GeO2 81 g Sb2O3 225 g diethylphosphite 427 g BaSO4 293 kg TiO2 32.6 kg Leucopur 350 g Ceresblau 0.35 g
• the manganese acetate was used as esterification catalyst; this catalyst was added as a solution of Mn(OAc)2 in ethylene glycol , said solution being added at the begin of the transesterification reaction.
• the mixture of GeO2/Sb2O3 was used as polycondensation catalyst. This catalyst mixture was added as a solution of GeO2/Sb2O3 in ethylene glycol , said solution being added at the end of the transesterification reaction.
• the BaSO4, TiO2, Leucopur and Ceresblau compounds were added as a suspension in 1048 kg of ethylene glycol to the oligomer mixture at the end of the transesterification reaction so as to become an opaque white copolymer.
• the concentration of BaSO4, TiO2 and isophthalate in the copolymer produced amounted to 16.7, resp. 1.8, resp. 1.7, expressed in weight percent of the total copolymer weight.
• the intrinsic viscosity of the copolymer produced measured as set forth above amounted to 0,65 dl/g, its crystalline melting point was 260°C.
• the concentration of BaSO4 and isophthalate in the copolymer produced amounted to 16,9, resp.1,7, expressed in weight percent of the total copolymer weight.
• the intrinsic viscosity of the copolymer produced measured as set forth above amounted to 0,65 dl/g, its crystalline melting point was 260°C.
• the white inorganic copolyester polymers produced according to the Examples 1 to 4 were steadily converted by a conventional film-extrusion process and apparatus to opaque film sheets suitable as support for white photographic materials.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• General Physics & Mathematics (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Polyesters Or Polycarbonates (AREA)
• Shaping By String And By Release Of Stress In Plastics And The Like (AREA)

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Cited By (4)

Citations (6)

• 1993
  • 1993-01-12 EP EP93200065A patent/EP0606663A1/de not_active Withdrawn

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