Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/16—Dicarboxylic acids and dihydroxy compounds
  • C08G63/20—Polyesters having been prepared in the presence of compounds having one reactive group or more than two reactive groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/16—Dicarboxylic acids and dihydroxy compounds
  • C08G63/18—Dicarboxylic acids and dihydroxy compounds the acids or hydroxy compounds containing carbocyclic rings
  • C08G63/181—Acids containing aromatic rings
  • C08G63/183—Terephthalic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/78—Preparation processes
  • C08G63/80—Solid-state polycondensation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
  • Y10T428/1397—Single layer [continuous layer]

Definitions

• the present invention relates to polyester resins, more particularly polyethylene terephthalate resins used in the manufacture of hollow containers, such as bottles for packaging liquid materials, in particular carbonated drinks, natural or mineral waters.
• polyester more particularly polyethylene terephthalate, better known by the abbreviation PET, has found an increasingly important application in the field of manufacturing hollow containers and more particularly bottles.
• acetaldehyde is a product resulting from the degradation of the polyester which is formed at high temperature during the manufacture of the polyester and of the process for manufacturing the bottles, in particular during the step of injecting the preforms.
• Numerous patents have described various methods for obtaining either a polyester with a low acetaldehyde content or methods for limiting the formation thereof during the shaping processes.
• One of the techniques used industrially and in particular described in European patent 41035 consists in carrying out a polycondensation of the polyester in a molten medium to a limited degree of polymerization to avoid the formation of large quantities of degradation products generally generating acetaldehyde when the polyester is heated to temperatures for example above 200 ° C.
• the polyester thus obtained is subjected to a new solid phase polymerization, generally called solid phase post-condensation, carried out at a lower temperature of the order of 200 to 220 ° C. generally under a nitrogen atmosphere.
• the polyester is polycondensed to a sufficiently high degree of polycondensation or intrinsic viscosity to obtain the desired mechanical properties and above all acetaldehyde formed during polycondensation in a molten medium as well as the degradation products are eliminated in their great majority.
• polyester resins containing less than 2 ppm, or even less than 1 ppm of acetaldehyde it is possible to obtain polyester resins containing less than 2 ppm, or even less than 1 ppm of acetaldehyde.
• this solid phase polycondensation step requires special equipment and consumes energy.
• the use of polyester resins of high intrinsic viscosity, therefore of fluidity in a low molten medium penalizes the injection cycles (duration between the start of the injection and the ejection of the part from the mold).
• One of the main aims of the present invention is to remedy these drawbacks by proposing a polyester resin with a low degree of polycondensation and a low acetaldehyde content, making it possible to obtain suitable bottles, in particular for packaging liquid foodstuffs such as carbonated drinks. , natural or mineral waters, aerated or not.
• the invention provides a polyester comprising at least 92.5% by number of repeating units derived from terephthalic acid from aliphatic diols, characterized in that it has an intrinsic viscosity of between 0.45 dl / g and 0.70 dl / g, and an acetaldehyde content of less than 3 ppm, preferably less than 1.5 ppm.
• the polyester is advantageously crystallized to prevent the polyester from being tacky or sticky at a temperature below about 200 ° C.
• the polyester can be treated to obtain a crystallization rate advantageously greater than 15%.
• the intrinsic viscosity of the polymer is between 0.45 dl / g and 0.65 dl / g.
• intrinsic viscosity (VI) is meant the viscosity of a zero concentration polymer solution.
• polyester is obtained from terephthalic acid, its esters or a mixture of these and aliphatic diols such as ethylene glycol , 1, 3-propanediol or 1, 4-butanediol.
• the preferred monomers are terephthalic acid and ethylene glycol leading to polyethylene terephthalate better known under the abbreviation PET as indicated above.
• PET covers both a homopolymer obtained only from terephthalic acid monomers or its esters such as dimethyl terephthalate and ethylene glycol as well as copolymers comprising at least 92.5% by number of repeating units of ethylene terephthalate.
• the polyester comprises at least one crystallization retarder allowing, in particular during the cooling of the molded or injected article such as a preform, to slow down or delay the crystallization of the polyester so as to obtain a crystallization into very small crystals, avoiding spherulitic crystallization and being able to manufacture a transparent article, the walls of which do not exhibit haze or "haze", with acceptable mechanical properties.
• crystallization retarding agents are difunctional compounds such as diacids and / or diols added to the mixture of monomers before or during the polymerization of the polyester.
• crystallization retarding agent of examples of diacids, isophthalic acid, naphthalenedicarboxylic acid, cyclohexane dicarboxylic acid, cyclohexane diacetic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and as examples of diols, there may be mentioned aliphatic diols comprising from 3 to 20 carbon atoms, cycloaliphatic diols from 6 to 20 carbon atoms, diols aromatics comprising from 6 to 14 carbon atoms and their mixtures such as di-ethylene glycol, tri-ethylene glycol, isomers of 1,4-cyclohexane di-methanol, 1, 3-propane diol, 1, 4- butane diol, 1,5-pentane diol, (2,4) -3 methylpentanediol, (1,4) -2 methylpentanediol
• Diethylene glycol is often present in polyesters inherently because it is formed during the synthesis by condensation of two molecules of ethylene glycol. Depending on the desired concentration in repeating units comprising a residue of diethylene glycol (DEG) in the final polyester, either diethylene glycol is added to the monomer mixtures, or the polyester synthesis conditions are controlled to limit the formation of diethylene glycol.
• DEG diethylene glycol
• the molar concentration of diethylene glycol in the polyester relative to the numbers of moles of diacid monomers is less than 3.5%, preferably less than 2 mol%.
• the molar concentration relative to the number of moles of all of the diacids in the mixture of monomers and therefore in the polyester obtained is advantageously less than 7.5%, with the condition that the DEG content must be deducted from this value if it is present.
• the total molar concentration of crystallization retardant must be less than 7.5% as indicated in European Patent No. 41035.
• the polyester may comprise a mixture of agents for retarding crystallization of the acid and / or diol type. If the processes for injecting preforms and blowing hollow containers make it possible to control in particular the cooling rates to avoid spherulitic crystallization of the resin or in the case where the bottles to be produced are not translucent such as milk bottles by
• the total concentration of crystallization retarder can be very low, for example of the order of 1%, or even zero with the exception of the DEG formed during the synthesis of the polyester.
• the polyester of the invention advantageously comprises less than 4% of isophthalic acid and less than 3.5% of diethylene glycol, content expressed in% of moles of crystallization retarder relative to the number of moles of all the diacid monomers.
• the invention also relates to a process for manufacturing a polyester in accordance with the invention. This process comprises a first step consisting in manufacturing a polyester by a polymerization process in a molten medium to obtain a resin having an intrinsic viscosity advantageously between 0.45 and 0.8 dl / g and preferably between 0.45 and 0.75 dl / g. In a second step, the polyester is formed into granules, by any suitable process known in the technical field of manufacturing polymers.
• These granules are subjected to a crystallization stage making it possible to prevent the granules from agglomerating together when they are brought to a temperature below 200 ° C., by example between 130 ° C and 200 ° C.
• the crystallization stage must make it possible to form at least one skin or an external surface sufficiently crystallized to avoid any tackiness when the granules are brought to a temperature of the order of 200 ° C.
• This step can be carried out by keeping the granules at a temperature between 120 ° C and 170 ° C or by treating them with hot water, for example with boiling water, at a temperature between 80 ° C and 100 ° C or any other suitable means to obtain the above result.
• the polyester granules are subjected to a heat treatment by maintaining at a temperature between 130 ° C and 200 ° C, advantageously between 150 ° C and 180 ° C to lower the concentration of acetaldehyde to a value below 3 ppm and obtain a polyester having an intrinsic viscosity of less than 0.70 dl / g.
• the heat treatment is carried out in the presence of a gas, preferably by scanning a gas through the mass of granules, said gas having a dew point greater than -60 ° C., advantageously between -60 ° C and 20 ° C, and in a preferred embodiment, between - 10 D C and 20 ° C.
• the scanning of the gas is carried out either through a fixed bed of the granules, or through a fluidized bed of the granules, the scanning gas being advantageously the fluidizing gas of the granules.
• the sweeping gas has a dew point of between -10 ° C and 20 ° C (limits included).
• the treatment method of the invention can comprise two successive stages consisting of a first stage of treatment with a gas with high humidity, even water vapor to cause a rapid decrease in the intrinsic viscosity, followed by sweeping with dry gas to remove acetaldehyde while limiting the variation in intrinsic viscosity.
• the gas suitable for the invention is advantageously air, nitrogen, carbon dioxide or any other gas which is not degrading for the polyester.
• the polyester obtained by polycondensation in a molten medium has a low intrinsic viscosity, for example between 0.45 and 0.65 dl / g
• the heat treatment can be carried out with a gas having a low dew point, for example between -60 ° C and 0 ° C.
• the intrinsic viscosity (VI) may increase slightly but advantageously remain at a value less than 0.70 dl / g, preferably less than 0.65 dl / g.
• this heat treatment is carried out at a temperature between 130 ° C and 200 ° C for a period of a few hours to several tens hours. The duration of the treatment is determined to obtain the desired acetaldehyde content and intrinsic viscosity.
• the treated polyester is obtained by polycondensation processes in the melt phase, generally in the melt phase under reduced pressure, as described in the literature for more than fifty years.
• Such a method comprises a first step of esterification or transesterification in the presence or absence of catalyst.
• the hydrolyzate or esteriate obtained is then polycondensed under reduced pressure in the presence of catalysts such as antimony, titanium or germanium compounds, for example.
• catalysts such as antimony, titanium or germanium compounds, for example.
• alcohol or water is removed to allow advancement of the polycondensation reaction.
• this polycondensation is stopped when the degree of polycondensation or the intrinsic viscosity has reached the desired value, less than 0.8 dl / g, preferably less than 0.75 dl / g.
• the polyester obtained is poured into dies making it possible to obtain rods which are then transformed into granules by cutting.
• the polyester must advantageously have a sufficient intrinsic viscosity, for example greater than 0.45 dl / g.
• the polyester may comprise a monofunctional monomer, preferably a monoacid.
• the molar content of monofunctional monomer is between 0.5% by mole and 3% relative to the total of the diacid monomers.
• the monoacids suitable for the invention are, for example, benzoic acid, naphthalenic acid, aliphatic acids having a boiling point compatible with the process for the synthesis of polyester, that is to say advantageously at less higher than that of ethylene glycol or their esters or alcohols such as cyclohexanol or aliphatic alcohols also advantageously having a boiling point higher than that of ethylene glycol.
• the granules with a low acetaldehyde content obtained according to the process of the invention and having an acetaldehyde content and an intrinsic viscosity in accordance with the invention are preferably used as raw materials for the manufacture of hollow containers, such as bottles.
• polyesters of the invention can be added to the polyesters of the invention either in the polymerization step or in the polyester melted before injection, various additives such as brighteners, dyes or other additives stabilizing light, heat or antioxidants, for example.
• additives such as brighteners, dyes or other additives stabilizing light, heat or antioxidants, for example.
• These granules are advantageously dried to obtain a moisture content of less than 50 ppm, preferably less than 20 ppm. This drying step is not compulsory if the moisture content of the polyester is sufficiently low.
• the granules are then introduced into injection-blowing processes for the manufacture of hollow containers such as bottles.
• the preforms are obtained, for example, by melting the resin in a single or double screw injection press, also making it possible to obtain a plasticization of the polyester and to supply it under pressure in a distributor provided with heated nozzles and obturators , for example at a temperature between 260 ° C and 285 ° C.
• the resin is injected into at least one mold of the preform provided with cooling means adapted to control the cooling rate of the latter and thus avoid spherulitic crystallization making it possible to obtain, preferably if this result is desired, a preform does not with no haze in the walls or opaque walls.
• the preform is ejected and cooled to room temperature or introduced directly, without cooling in a blowing installation as described below.
• the polyester is melted at a temperature of the order of 280 ° C., for example between 270 and 285 ° C., then injected into molds.
• the lowest possible injection temperature will be used to limit the formation of acetaldehyde, in particular to reduce the rate of formation of acetaldehyde.
• the process for manufacturing the preform preferably uses a pressure for injecting the molten resin into the mold (s) of between 2.5 ⁇ 10 7 Pa (250 bars) and 5.10 7 Pa (500 bars) for a temperature between 260 ° C and 270 ° C.
• This pressure range is lower than that used for polyester resins having a higher intrinsic viscosity, namely greater than 0.70 dl / g.
• the molds it is advantageous for the molds to be cooled to a temperature between 0 ° C and 10 ° C.
• This cooling is obtained by using any suitable cooling fluid such as, for example, glycol water.
• the injection and cooling cycle is of the order of 10 seconds to 20 seconds.
• the polyester forming the wall of the preform obtained according to this process has an intrinsic viscosity of between 0.45 dl / g and 0.70 dl / g, advantageously between 0.45 dl / g and 0.65 dl / g.
• the acetaldehyde content in the preform is less than 10 ppm, preferably less than 6 ppm.
• the preforms thus obtained are generally used in blowing processes for the manufacture of bottles. These blowing methods are also widespread and described in numerous publications.
• They generally consist in introducing the preform into a blowing installation, with or without over-stretching comprising heating means.
• the preform is heated at least above the Tg (glass transition temperature) of the polymer and then pre-blown by injection of a gas under pressure at a first pressure during a first period.
• a second injection of a gas at a second pressure makes it possible to obtain the final shape of the bottle before it is ejected after cooling.
• the heating temperature of the preform is between 80 ° C and 100 ° C.
• This heating is carried out by any suitable means, for example by infrared rays directed towards the external surface of the preform.
• the pre-blowing of the preform takes place at a first pressure of between 4.10 5 Pa and 10.10 5 Pa (4 bars and 10 bars) for a period of between 0.15 and 0.6 seconds.
• the second blowing is carried out under a second pressure between 3.10 6 Pa and 4.10 a Pa (30 and 40 bars) for a second period between 0.3 and 2 seconds.
• a drawing rod can also be introduced into the preform during the pre-blowing and / or blowing operations to partially stretch the preform.
• an object of the invention resides in bottles whose polyester forming the walls has an intrinsic viscosity of between 0.45 and 0.70 dl / g and an acetaldehyde content of less than 6 ppm.
• this material allows the manufacture of bottles of identical capacity, with mechanical properties at least equivalent to those obtained with a polyester of higher intrinsic viscosity.
• the invention also relates to hollow containers such as bottles, obtained with a polyester according to the invention and according to the injection-blowing methods described in the present application.
• the bottles of the invention are used for packaging any liquid product, more particularly for packaging liquid foodstuffs such as carbonated or non-carbonated sweet drinks, known under the general name "Soda", the various natural waters, from sources or minerals, gaseous or not.
• liquid foodstuffs such as carbonated or non-carbonated sweet drinks, known under the general name "Soda"
• Soda the various natural waters, from sources or minerals, gaseous or not.
• a sample of granules (approximately 4 g) is ground in a cryogenic mill under liquid nitrogen to obtain a powder passing through a mesh screen of 800 ⁇ m
• This "head-space" tube is placed in an analyzer by vapor phase chromatography ("head-space”: Perkin Elmer HS 40 and chromatograph: VARIAN 3500 with a PORAPLOTQ column and a carrier gas consisting of helium at a flow rate of 5 ml / min) and a temperature varying from 60 ° C to 230 ° C (with a rise speed of + 10 ° C / min).
• head-space Perkin Elmer HS 40 and chromatograph: VARIAN 3500 with a PORAPLOTQ column and a carrier gas consisting of helium at a flow rate of 5 ml / min) and a temperature varying from 60 ° C to 230 ° C (with a rise speed of + 10 ° C / min).
• the “head-space” tube is kept for 90 minutes at 145 ° C.
• the polycondensation is stopped when the intrinsic viscosity of the polyester is 0.48 dl / g and contains 3.4 mol% of DEG relative to the number of moles of diacid monomers.
• the polymer is formed into granules by extrusion in the form of rods which are cut to give granules of average mass 13 mg per granule.
• the residual acetaldehyde content in the amorphous granules determined according to the above method is 140 ppm.
• the granules are subjected to crystallization in an oven for 30 minutes at 160 ° C. and then placed in a column. A flow of dry air (dew point below -60 ° C) is sent through the column at a rate of 0.39 Nm 3 / h for 8 hours, the temperature of the granules being maintained at 180 ° C. After a treatment time of 8 hours, the polyester has an intrinsic viscosity of 0.56 dl / g and an acetaldehyde content of 0.75 ppm. This polyester is called Polyester A.
• Examples 2 to 5 A polyester comprising 2.3 mol% of isophthalic acid was produced according to a procedure identical to that of Example 1. However, the polycondensation was stopped when the intrinsic viscosity was equal to 0.64 dl / g.
• the amorphous granules have an acetaldehyde content equal to 45 ppm and
• the polymers B to E obtained in these examples have an improved coloration. This improvement results in a decrease in the yellowness index.
• the presence of moisture makes it possible to limit the degradation of the yellowness index of the polyester.
• a homopolyester was produced by adding 2.6 mol% of benzoic acid relative to the terephthalic acid according to the procedure described in Example 1.
• the polycondensation was stopped when the intrinsic viscosity was equal to 0.47 dl / g.
• the polymer obtained contains 70 ppm of acetaldehyde and 3.5 mol% of DEG.
• the granules After crystallization and treatment with dry air (dew temperature - 60 ° C) at 180 ° C for 8 hours according to the procedure of Example 1, the granules have an intrinsic viscosity of 0.53 dl / g and an acetaldehyde content of 1.6 ppm.
• This polymer will be called polymer F.
• polyesters obtained according to the above examples were used for the manufacture of bottles according to the process described below:
• the polyester granules are melted in an endless single screw with a barrel temperature of 285 ° C.
• the molten polyester is fed into a preform injection device sold under the name "HUSKY 48 imprint XL 300 press" with an injection temperature between 262 ° C and 266 ° C and a pressure of 450 bars.
• the preforms are cooled by circulating water at a temperature of 8.5 ° C.
• the overall cycle time for injection is 15.7 s.
• the preforms After the preforms have cooled, they are supplied to a blowing installation for the manufacture of bottles with a capacity of 0.51 having a neck with a shape referenced by the standardized designation 28 PCO and a bottom with a petaioid shape with 5 petals.
• This installation is marketed under the name "SIDEL SBO 1 F2 Lab”.
• the preforms are heated to a temperature indicated in the table below. Pre-blowing is carried out for 0.19 s under a blowing pressure of 8.5 bars. The blowing is carried out for 1.78 s under a blowing pressure of 38 bars.
• the speed of the stretch rod is 1, 2 m / s.
• the viscosity of the polyester forming the walls of the bottle is of the order of that of the polyesters used.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Polyesters Or Polycarbonates (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
• Containers Having Bodies Formed In One Piece (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

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• 2001
  • 2001-07-31 FR FR0110279A patent/FR2828199A1/fr not_active Withdrawn
• 2002
  • 2002-07-11 MX MXPA04000900A patent/MXPA04000900A/es not_active Application Discontinuation
  • 2002-07-11 EP EP02791496A patent/EP1417247A1/de not_active Withdrawn
  • 2002-07-11 BR BR0211689-8A patent/BR0211689A/pt not_active IP Right Cessation
  • 2002-07-11 WO PCT/FR2002/002463 patent/WO2003011940A1/fr not_active Application Discontinuation
  • 2002-07-11 CN CNA028186125A patent/CN1556821A/zh active Pending
  • 2002-07-11 US US10/485,552 patent/US7189441B2/en not_active Expired - Fee Related
  • 2002-07-31 AR ARP020102899A patent/AR034951A1/es unknown

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