MXPA96002605A - Polyester resins that have rheological properties improves - Google Patents

Abstract

the present invention relates to: Polyester resins particularly suitable for extrusion blow molding containing from 20 to 100 ppm of an aromatic tetracarboxylic acid dianhydride and showing values of age increase of not less than 45%; are obtained by solid state polycondensation of the resin having intrinsic viscosity lower than 0.7 dl / g, added with an aromatic tetracarboxylic acid dianhydride in an amount of 0.002 and 0.1% in pe

Description

RESINS OF PQLIESTERES THAT HAVE IMPROVED REOLOSTCAS PROPERTIES DESCRIPTION The present invention relates to polyester resins with improved rheological properties, useful in particular for applications using blow molding techniques by extrusion and injection blow molding. The aromatic polyester resins obtained from aromatic bicarboxylic acids and from diols are suitable for the manufacture of fiber and film, although they do not have sufficient resistance to casting to allow their use in the manufacture of products by means of a molding technique. blown by extrusion. To increase the intrinsic viscosity and to improve its rheological characteristics, the resins are subjected to polycondensation reactions (SSP) of solid state in the presence of polyfunctional compounds that can act as branching agents or as chain extensors. These compounds, apart from improving the rheological characteristics of the polymer, accelerate the kinetics of the SSP reaction. Polyfunctional compounds containing at least 3 groups can react with the end groups of the resin, as branching agents. The rf-present compounds are polyhydric alcohol such as pentaerythrol and trimethylolpropane. Instead, the omptestos that work preferably as chain extenders are tetrahydric acid dichhydrides. The pyro elitic dianhydride (PMDA) is the representative compound. The branching agents generally cause the formation of gels that limit the use. It has been proposed < US-A - * + é > 16,579) use the branching agents in association with the chain terminating agents in order to reduce the formation of gels. Using this process in the manufacture of bottles from polyethylene terephthalate (PET) by means of extrusion blow molding, the thicker sections of the bottle wall, ie the neck, tend to have opacity that is not acceptable in the field of containers for beverages and cosmetics that also have to satisfy previous aesthetic requirements. The disadvantage could be eliminated extruyends, instead of PET, copolymers of polyethylene terephthalate to a content of up to 15% of the isophthalic acid unit (US-A- 234 579). Branching agents and chain extenders are generally used in amounts greater than 0.1 by weight, preferably between 0.1 and 0.3% by weight. W0-A-93 / 23- +, it is known to use for injection blow molding applications of limited amounts of polyhydric alcohol, such as peptaer itrol, comprised between 0.007 and 0.0% mole equal 0.005 / 0.057% by weight , if it refers to the molecular weight of pentaer itrol. HE used with the intention of limiting the formation of gels. Despite the low amounts used, the solid state polycondensation rate is still significant. However, the melting strength of the resin does not increase. Larger amounts cause an increase in the resistance to fusion, although they correspondingly increase the formation of infusions. In addition, the phenomena of induced crystallization are observed with the appearance of opaque areas that are not acceptable for beverage containers. The chain extenders, such dicarboxylic acid, aromatic dianhydrides, in particular pyromellitic dianhydride, are used in amounts of at least 0.1% by weight. The kinetics of the solid state polycalendensa ion increase appreciably (EP-A l +? 2 2? 2). PET blends in the molten state make it possible to obtain bottles by extrusion blow molding. The chain extenders of type PMDA, if on the one hand they cause an increase in the resistance to the function of the resin, on the other hand they determine the excessive increase of the elasticity of the molten polymer. This involves a significant reduction of the extrusion blow molding operations due to the excessive volume increase of the resin at the mold outlet (increase in die volume). It has been found unexpectedly now that, using the solid state polycondensation reaction, amounts of aromatic tetracarboxylic acid dianhydride lower than the minimum value of 0.1% by weight used in the processes of the known art, it is still possible to obtain significant increases not only in the kinetics of the solid state polycondensation , but also in the resistance to the function of the polymer as such or to allow intermediate stability, although at the same time it does not cause too high a level in the die volume increase vanes. It has also been found, and this represents a further aspect of the invention, that the use of limited amounts of aromatic tetracarbaxylic acid dianhydride also allows for significant improvement in mechanical characteristics (resistance to compression and explosion, etc.). and barrier properties of the containers obtained by the techniques of blow molding by ipjección. The average crystallinity in the PET bottle walls modified with PMDA is higher than that of the comparison bottles without PMDA. In the house of bottles and film obtained from PET modified with 4.5 moles of isophthalic acid or 7.5 mole% of 2,6-naphthalene dicarboxylic acid and 0.05% by weight of PMDA a crystal of up to 60% can be achieved in the side walls of the bottles and in the film by fixing by heating the bottles and the film at a temperature of 160 ° to 215 ° C.

The increase in mechanical and barrier properties allows the manufacture of containers with thinner walls to use therefore smaller amounts of resins. The amounts of dianhydrids used are less than 0.1% by weight and comprise between 0.1 and 0.015%, preferably between 0.05 and 0.02% by weight of the resin. The dianhydrides are added in the preparation phase of the resin by cast polycondensation as well as to the polymer obtained after this phase. L. intrinsic viscosity of the resin after the melting state melting state is generally lower than 0. 7 dl / g; is carried to a desirable level between 0. 7 and 1.5 dl / g by means of solid state polycondensation. The preferred dianhydride is pyromellitic dianhydride. Other anhydrides used are dianhydride: from the following acids: 2,2-bisO, 1-dicarboxyphenyl) pro-anus acid; 3.35B, L », l + L + -bepzophenone-tetracarboxylic, ether bisO, 1 * -dicarbo-ifenylic); 2,2-bis (3,4-dicarboxy phenyl); hexaf luoro propane 2,3,6,7-tetracarboxylic acid; 1.2, 5, tetracarboxylic naphthalene acid; sulfoxide < 3,4-dicarboxy phenyl). Addition compounds containing two groups of phthalic anhydride obtained by reacting 2 moles of dianhydride also belong to this category of dianhydride. of aromatic tetracarboxylic acid with one mol of alkyl glycol or polyalkylene glycol in particular ethylene glycol and polyethylene glycol or of another composition containing at least two hydroxyl terminal groups. The temperature of solid state polycondensation is generally between 150 ° and 220 ° C. Preferred temperatures are between 1 &0 ° C and 220 ° C. In the case of copolyesters in which parts of the terephthalic acid units are replaced by units deriving from other aromatic dicarboxylic acids, for example isobutyl acid, the reaction temperature in the solid state could be comprised in a scale lower than those mentioned above. L DS dianhydrides are present in the final polymer, after SSP, in combined form. The resins subjected to the polycondensation reaction of solid states are obtained according to known procedures by polycondensation of a diol containing from 2 to 12 carbon atoms with an aromatic dicarboxylic acid or its own ester. The representative diols are ethylene glycal, 1-3 propylene glycol, butylene glycol, dimethylocyclohexane. Terephthalic acid, isophthalic acid and dicarboxylic acid (2,6 and 2,7-naphthalene dicarboxylic acid) are preferred. Preferred resins include polyethylene terephthalate and its copolymers in which part of the terephthalic acid units are replaced by units of 1 or more dicarbo acids? lieos de which isophthalic acid and / or the naphthalene dicarboxylic acids used in amounts up to 20 mole% terephthalic acid. The most preferred resins are PET-ter polymers with 2 to 10% isaphthalic acid and 2 to 10% naphthalene dicarboxylic acids. The resins thus obtained are subjected to SSP treatments. Before this treatment, the resins undergo a crystallization treatment, in accordance with known procedures to eventually reach the values of level of crystallinity sufficiently high to avoid the phenomena of packing and / or adhesion of the polymer granules on the walls of the SSP reactor. . The equipment and methods used are disclosed, for example, in EP-1-222 714, EP-A-373 664, US-A-4 064 112, US-A-4 161 576 and EP-A-712 703, the descriptions of which are incorporated herein by reference. The SSP treatment is also carried out in the equipment in accordance with known techniques. For example, the wash gases used in the process are purified according to the procedure of WG-A-95 02 446, the description of which is also incorporated by reference. As indicated, the tetracarboxylic acid dianhydride is incorporated both during the preparation phase of the resin by melt state polycondensation as well as to the resin already formed. In the first case, it dissolves in the glycols used for the reaction; in the second case it is added to extruder to the molten resin. The second alternative is the preferred one. Preferably a double worm extruder is used without non-spinning with an average dwell time in the extruder of less than 100 seconds. The granules thus obtained are subjected to crystallization and then to polycondensation of soldered state. The additives normally used for polyester resins such as stabilizers, colorants, nucleants and others can be added to the resin. The following examples provide to illustrate although for na to limit the invention.

EXAMPLE OF COMPARISON 1 Bis (2-h idroxe i 1) terephthalate (BHET) was prepared from terephthalic acid (TPA) also including a predetermined amount of isaphthalic acid (IPA) and ethyleneglieol (F6) using the FG / TPA ratio of 1.35. A catalyst based on antimony triacetate and cobalt diacetate was used. In a pressure reactor equipped with stirrer and condenser, the following was charged: TPA-4202 g, IPA-121 6 (26 moles in total); EG - 2176 g (35 moles) added three times respectively EGa. = 966g, EGa. = - 605 g, E & 3 = 605 g Fl catalyst was used in amounts of 2.72 g of Sb and 0.663 g of Co. The reagents were heated using the agitator between 250 ° and 270 ° C under pressure of 1 bar ca. Fl BHET obtained has a content of diethylene glycol (DEG) of 1.7 - 1.6% by weight and IPA from 2.0 to 2.4% by weight, without corresponding both to the desired values. Therefore, a second esterification is carried out using 30.46 cm of 40% by weight (2 kg of BHET as obtained above) the difference consisting of the monomers. BHET - 2000 g; TPA = 2610 g; IPA - 126 g; Sb = 1.59 g; Co = 0.45; FG = 1361 g added in three intervals; > EGA = 614 g; EGg, = 364 g; EG3 = 364 g The content of DEG obtained in this second esterification was 1.39 / 1.42% by weight; IPA was 3.00% by weight. The BHET obtained in this manner was polycondensed by adding phosphoric acid (0.415 g) equivalent to approximately 20 ppm of phosphorus on the final polymer. The duration of the polycondensation was 4 hours operating with an oil temperature of 290 ° C and a pressure in the reactor of 2.66 mbar. The polymer was extruded in a water bath and cut into wafers. The characteristics of the wafers are reported in the Table 1 TABLE 1 IV (dl / g) = 0.557 COOH (eq / t) = 16.25 SD (% by weight) = 1.5 IPA (% by weight) = 3.1 SB (ppm) = 209 Co (ppm) = 30 P (ppm) = 15 The solid state polycondensation was run at 215 ° C. (203 ° C inside the reactor) under stirring and in a stream of nitrogen for a period sufficient to reach an intrinsic viscosity of the polymer of 1076 dl / g. The values of melt stre (MS) and the volume increase of the die (DS) of the wafers are reported next together with the IV values and the natural logarithm of the kinetic constant of polycondensation Kin delta IV / h: Kin delta I / h = 9.9 E-3 IV dl / g = 1.076 DS at 1000 s - 1 = 16% M.S. (s) at 20s- * = 13 EXAMPLES 1-2 The comparison example 1 was repeated using also pyrolitic dianhydride (PMDA) dissolved in EG used for esterification.

In Example 1 the amount by weight of PMDA in the polymer was 0.01% and 0.005% in Example 2. The polycondensation time was about 4 hours with an oil temperature of 290 ° C. The obtained granules were subjected to solid state polycondensation as in comparative example 1 using a period such that an IV of 1.1J2 dl / g was obtained in example 1 and 1.096 in example 2. The data of the characteristics of nulls before and after SSP are reported in table 2.

TABLE 2 Before SSP Example Example 2 IV (dl / g) 0.604 0.607 C00H (eq / t) 16.06 16.1 SDR (% by weight) 1.65 1.7 IPA (% by weight) 2.6 2.7 Sb (ppm) 245 235 Co (ppm) 30 30 P (ppm) 37 40 After SSP Kin delta IV / h 1.71 E-02 1.50 E-02 IV dl / g 1,112 1,096 D.S. at lOOOs - * - 35 25 M.S. (s) to 20s - 1 26 24 Maximum Enthalpy J / g 3.2 EXAMPLES 3-4 Example 3 was repeated by preparing a polymer containing 0.02 weight percent PMDA added with EG, and a polymer without the addition of PMDA. The polymer containing no PMDA was mixed in the dry state with 0.02% by weight of PMDA and successively in the melting state in the double worm extruder. The two polymers were subjected to SSP at 215 ° C under agitation in nitrogen stream for a sufficient time to obtain the desired intrinsic viscosity. The polymer that results before and after SSP is reported in table 3. TABLE 3 E emolo 3 E ..iemo. What 4 Before SSP IV (dl / g 0. 636 0., 556 C00H (ea / t) 2C> .31 35.6 DFG (% by weight) 1. 55 1. 55 IPA (% by weight) 2. 75 2. 75 After SSP Kin delta IV / h 1.74 E-02 1.69 E-02 IV (dl / g) 1,066 1,099 DS at 1000s-A 40% 36% MS (s) at 20s ~ * 31 23 EXAMPLE OF COMPARISON 2 Only 20 kg / h of PET (IV = 0.57 dl / g) were fed from the molten polycondensation section of a pilot plant to a double worm extruder without intertamisation against rotation with a degassing system. The conditions of the test were: Worm velocity = 500 RFM worm L / D ratio = 46 cylinder temperature = 2A2 ° C melting temperature = 296-302 ° C average dwell temperature = 35.50 sec.

The product was produced in the form of wafers with a diameter of 5 mm and 5 mm in length with IV = 0.62 dl / g. The granules were then subjected to SSP in a continuous pilot plant that operates as follows: wafer yield = 50 kg / h average temperature of the wafers in the reactor = 203 ° C weight ratio of gas / wafers in the reactor = 1: 1 final intrinsic viscosity = 0.606 dl / g Kin delta IV / h = 5.65 E-4 EXAMPLE 5 The comparison example 2 was repeated with the difference that PMDA was fed in 20% by weight of the mixture with crystalline PET with a capacity of 40 g / h equivalent to a PMDA content in the polymer of 0.04% by weight. The polymer IV after the SSP treatment under the conditions of example 5 but using a time of 11.5 hours was 0.627 dl / g.

EXAMPLE OF COMPARISON 3 The polymer obtained according to the comparison example having an IV = 0.606 dl / g was converted, after drying, into preforms using an injection molding machine BMB 270 in accordance with the following procedure. mold = with 16 cavities preform weight = 46.9 g cycle time = 21 sec worm temperature = 273 * C feeding time = 10 sec injection time = 5 sec cooling water temperature = 3 ° C.

The preforms thus obtained were blown into bottles in a Krupp blow machine.

The conditions were the following: bottle production = 6000 bottles / h temperature of heating elements = 100 ° C blowing pressure = 35 bar bottle volume = 1500 ce The following measurements were made on the bottles: deformation = 4.67% low burst test = 33 kg vertical top load burst pressure = 11 kg / cma compressive strength = 32 N oxygen barrier / pack / day = 0.61 at 25 ° C. COa = 7.3 at 25 ° C average side wall crystallinity = 24.5% EXAMPLE 6 The polymer in Example 5 was transformed into bottles according to the modalities in comparison example 3.

The bottles had the following characteristics! deformation = 3. 5% low burst test = 36 kg vertical top load burst test = 14 kg / cm3 compressive strength = 36 N oxygen barrier / day = 0. 55 ai 25 ° C C0a 6. 2 at 25ßC average side wall crystallinity = 26.% MEASUREMENT AND ANALYTICAL DETERMINATION DEFORMATION The bottles were filled with water and placed in a suitable device to operate under pressure and connected to a graduated cylinder. The cylinder was filled with water and placed under pressure of 5 bar for 2 minutes. The water level in the cylinder was then measured and the percentage variation of the bottle was calculated.

PROOF OF SCREENING A bottle was placed in an appliance in order to pressurize it. The pressure needed to blow up the bottle was measured.

VERTICAL LOAD TEST A bottle was placed between a fixed plate and a mobile one (25 mm / min). Then the required force applied to the movable plate is measured in order to crush the bottle.

COMPRESSION TEST The first load at which an increase in deflection occurs without increasing the load is measured.

ANALYTICAL MEASUREMENTS The intrinsic viscosity is measured in a solution of 0.5 g of polymer in 100 c 3 of a mixture of 60/40 in weight of phenol and tetrachloroethane at 5 5 ° C in accordance with ASTM 4603.66. The rheological determination was carried out using a 2003 Gottfert capillary rheometer operating on nitrogen at 270 ° C. The samples were dried for 24 hours under vacuum at 140 ° C. The die volume increase measurements were made by cooling the molten polymer leaving the capillary apparatus in cold water at a shear rate of lOOOs- *. The diameter of the polymer chain was compared with the diameter of the capillary apparatus. The ratio is considered to be the index of volume increase of the die. The resistance to the casting was evaluated by measuring the time the chain used to reach a predetermined length (55 cm). This method provides an indirect measurement of the casting resistance and simulates the volume increase of the actual situation when the material is processed by blow molding. The curing characteristics were determined using an accelerated process consisting of cooling the polymer granules from the molten state and maintaining it at 60 ° C for different times up to 4 days. The samples then supported a DSC determination with a heating rate of 10 ° C / min on the scale of the glass transition region. The resulting peak is considered afterwards (enthalpy of connection). The determination of pyromellitic anhydride was carried out in accordance with the method described in US 5 340 646, the description of which is incorporated by reference. According to this method, 0.5 g of polymer is added to 20 cm3 of dimethylsulfoxide (DM30) in which 5 cm3 of 5N sodium hydroxide in methanol is then added. The mixture was refluxed for 1/2 ih. He cooled; 50 cm3 of deionized water was added to the solution. The determination of the PMDA concentration was made through high performance liquid chromatography (HPLC) eluting a portion of the sample neutralized through a high pressure liquid chromatography (HPLC) system using a mobile phase at a gradient concentration formed of acetonitrile and water. The method is calibrated using the normal concentration in known amounts of PMDA. According to a variant, PMD determination as pyramitic acid is carried out through HPLC chromatography using a calibration scale with solutions of 10 mg of pyromellitic acid in 100 ml of a 20/5/75 solution of DMSO / CHaOH / Ha.0. According to another method, the PMDA concentration is determined by the extraction of the polymer with ethanol in soxhlet for 24 hacas.

Claims (7)

NOVELTY OF THE INVENTION CLAIMS

1. - The aromatic polyester resins having intrinsic viscosity greater than 0.7 dl / g and containing in combination a quantity of anhydride of an aromatic tetracarboxylic acid, less than 100 ppm and comprised between 200 and 1000 ppm. 2.- The resins in accordance with the claim 1, also characterized because the dianhydro is dianhydro pyro elitico. 3. The resins according to claims 1 and 2, further characterized in that the intrinsic viscosity is between 0.7 and 1.5 dl / g. 4. The resins according to claim 1, 2 or 3, further characterized in that the pyromellitic dianhydride is comprised between 300 and 500 ppm. 5. The resin according to claim 1, 2, 3 or 4, further characterized in that the resin is polyethylene terephthalate. 6. The resin according to claim 1, 2, 3 or 4, in which the resin is a copolyethylene terephthalate in which up to 20% by mole of unit that are derived from terephthalic acid are replaced with units which are derived from dicarboxylic acid aromatic. 7. The resins according to claim 6, further characterized in that the aromatic dicarboxylic acid is isophthalic acid. 6. The resins according to the preceding claims, further characterized in that the aromatic acid is formed of a mixture of isophthalic acid and a naphthalenedicarboxylic acid. 9. The resins according to claim 6, further characterized in that the isophthalic acid is present in amounts of up to 10% by mole and the naphthalenedicarboxylic acid is the 2,6-naph alendicarboxylic acid present in amounts of up to 10% in moles 10. The containers obtained from the resins of the previous claims. 11. The bottles obtained by blow molding by extrusion of the resins of the previous claims. 12.- The bottles obtained by blow molding by injection of the resins of the previous claims. 13.- The bottles obtained by blow molding by extrusion or blow molding by injection of the resins of claims 5, 6, 7 or 6 14. The process for the preparation of the resins of the previous claims, wherein a resin of aromatic polyester with intrinsic viscosity less than 0.7 dl / g added with a dianhydride of an aromatic tetracarboxylic acid in amounts of 0.002 to 0.1% by weight is subjected to solid state polycalendensation until a value of intrinsic viscosity greater than 0.7 dl / g is reached. 15. The process according to claim 14, further characterized in that the dianhydride is pyromellitic dianhydride and the solid state polycondensation is carried out at a temperature between 150 ° C and 230 ° C.